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  • Electronic Resource  (776)
  • 1990-1994  (776)
  • 1991  (776)
  • Engineering General  (564)
  • Industrial Chemistry and Chemical Engineering  (212)
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  • Electronic Resource  (776)
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  • 1990-1994  (776)
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  • 101
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 14 (1991), S. 73-78 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In the study of the possible coke removal from zeolite catalysts, the solubility of polyaromates in supercritical fluids (SCF) was determined, showing that it becomes drastically reduced with increasing molar mass. Experiments with supercritical ethyl benzene and benzene showed that only coke precursors can be dissolved and, therefore, complete coke removal by SCF is impossible but it has been confirmed that, under supercritical conditions, deactivation of the catalyst could be slowed down.
    Additional Material: 6 Ill.
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  • 102
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 14 (1991), S. 101-104 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An improved method is presented for the design of a complex flow network system. The method employs head loss and flow rate in the iteration process for the determination of flow rates and/or pressure drop. This represents a major departure from the conventional approach which uses only the flow rate. The two-step iteration method proposed here drastically improves both the convergence rate and iteration stability. Tests on different examples have shown that, for most design applications, three iterations are sufficient to yield an accurate final solution, regardless of the initial guess.
    Additional Material: 5 Ill.
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  • 103
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 14 (1991), S. 96-100 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Oxidation of methanol to formaldehyde, using a mixture of ferric and molybdenum oxides as catalyst, has been studied in a fixed bed integral reactor, 150 mm long, 25 mm o.d. and 10 mm i.d. The catalyst was prepared by reaction between aqueous solutions of ammonium heptamolybdate and ferric chloride. It has been shown that, under experimental conditions similar to those employed in industry, neither external nor internal diffusion had been effective in the process and isothermal conditions prevailed in both gas and solid phases. A two-step mechanism has been put forward for the oxidation of methanol. According to such a mechanism, methanol is first oxidized to formaldehyde, accepting an oxygen molecule from the catalyst and changing the latter into a reduced form. In the second step, the reduced catalyst is transformed into the original form on obtaining an oxygen molecule from the gas phase. Based on this scheme, a rate model has been derived and verified by experimental results.
    Additional Material: 5 Ill.
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  • 104
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 14 (1991), S. 118-121 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effects of impeller speed, air flow rate, cell concentration, agitator size and cell volume on the recovery of aluminium particles have been studied in a KHD Humboldt Wedge AG machine, using alkyl benzene sodium sulphonate paste as collector and pine oil as frother. The recovery yield increased with increasing impeller speed, air flow rate, cell concentration and cell volume, up to a certain range, whereafter it decreased. A decrease in the recovery yield was observed on increasing the agitator size. A mathematical model has been developed to correlate percentage recovery with the above variables.
    Additional Material: 6 Ill.
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  • 105
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 14 (1991), S. 248-252 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Conventional vacuum stripping to reduce the oxygen content of injection water for secondary recovery of oil is carried out in packed columns with the released gases and water flowing countercurrently; hence large column diameters (normal liquid load circa 100 m3/(m2h)) and foaming that requires the addition of defoaming agents. Measurements with cocurrent and countercurrent flow at the same flow rate produced practically identical mass transfer coefficients. With flooding excluded in cocurrent flow, columns can be operated with higher liquid loads than in countercurrent flow. In addition, nitrogen released in the top part of the packing is better utilized as stripping gas, and foam is withdrawn as soon as it increases the pressure drop.
    Additional Material: 5 Ill.
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  • 106
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 14 (1991), S. 270-274 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper presents laboratory-scale measurements on the absorption of nitric oxide in dilute nitric acid. The NO concentration in the gas feed varied from 250 to 10 000 ppm. Nitrogen was used as carrier gas. The concentration of nitric acid was between 30 and 60 mass-%. Temperature during the measurements was set at 25 °C. In order to determine mass flow rates, experiments were performed in a double-stirred cell. This type of absorber has a defined gas/liquid interface as the mass transfer area. The liquid phase is introduced periodically and the gas phase continuously. A well-known model was used to describe the phenomenon of NO absorption. Several balance equations were established and solved. The calculated mass transfer rates were compared with those obtained experimentally. The empirical and theoretical data are in satisfactory agreement.
    Additional Material: 7 Ill.
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  • 107
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 14 (1991), S. 287-293 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A study of mass transfer to regular packings by the electrochemical technique is presented in this paper. The excellent properties of radial mixing were verified and the correlation for mass transfer rate was also obtained. It was found that the energy efficiency, which is represented by the LeGoff number, is higher than that of other packings due to the low pressure drop shown by these arrangements.
    Additional Material: 9 Ill.
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  • 108
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Dynamic behaviour of a stirred liquid-liquid extraction column was studied experimentally. Various input variables of the column were varied stepwise and the resulting variations in the system and output variables were measured. In addition to experimental work, a computer model was developed on the basis of the dispersion model to simulate the dynamic behaviour of the extractor. This model forms a component program of the dynamic process simulator DIVA, developed at the TU Stuttgart. The experiments showed that the hydrodynamic parameters exhibit no significant dynamic behaviour of their own. Therefore, changes occurring in these parameters closely follow variations in input and system variables. As a result, steady-state relationships for the calculation of flow parameters could be used in the simulation program. The simulator satisfactorily reproduced the experimental results for a number of disturbances. However, this was not always the case. As shown in the following, the model did not take into account the column level controller which, under certain conditions, exerts a very strong influence on the column's dynamic behaviour. As a result, larger differences occurred between experimental and simulated data. This influence on the extractor's dynamic behaviour can, however, be eliminated by a simple modification of the level controller arrangement.
    Additional Material: 6 Ill.
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  • 109
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 14 (1991), S. 333-347 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Power consumption (Part I) and liquid phase mixing time (Part II) were measured in 0.57, 1.0 and 1.5 m i.d. vessels. A pitched blade downflow impeller (PTD) was used. Design details of the PTD impeller such as diameter (0.22T to 0.5T), blade width (0.25D to 0.4D) and blade thickness (2.8, 4.3 and 6.4 mm) were studied. The effect of sparger type and geometry on power consumption has been investigated. For this purpose, pipe, ring, conical and concentric ring sparger were employed. Design details of the ring sparger such as ring diameter, number of holes and hole size were also studied in depth. Sparger location with respect to the impeller was found to be the most important parameter and was therefore varied for nearly all the spargers studied. A correlation for the power consumption has been developed.
    Additional Material: 24 Ill.
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  • 110
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 14 (1991), S. 414-420 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper presents a study on modelling and simulation of transient operational characteristics in multitubular fixed-bed reactors. The dynamic model of the reactor is based on a “porous body” approach which regards the intertubular space as a pseudo-homogeneous environment. Such an approach permits to take into account most factors in the geometrical design of the unit and thus to study the influence of various shell-side geometrical and operational parameters on the reactor behaviour. Based on the model, the dynamic responses of the two most common industrial reactor designs, i.e. the parallel flow unit with distributing plates and the crossflow reactor with disk-and-doughnut baffles have been investigated and compared. In addition, some problems of correct space discretization and use of time-dependent regridding procedures, are discussed.
    Additional Material: 8 Ill.
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  • 111
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 8 (1991), S. 35-39 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: There are a limited number of phenomena occuring with aerosol particles that depend only on physical quantities. Examples of new developments in aerosol particle characterization in situ that make use of such phenomena are briefly reviewed. They concern electrophoretic size classification, inertial size analysis and shape characterization of agglomerates. In addition to deriving basic descriptors, measurements of composite quantities can be performed and developed into sensors. Examples of sensors responding to relevant complex aerosol quantities are explained.
    Additional Material: 9 Ill.
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  • 112
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Based on physical assumptions, simple equations have been derived for the probability of breakage of particles, for the dependence of fragmentation energy on particle size and for the fragment size distributions as a function of mass-specific energy. The particles were considered as spheres, and Hertz theory of the stress distribution at the contact between a sphere of brittle material and a flat surface was applied in combination with Weibull statistics of failure. The predicted dependence of the probability of breakage on particle size and mass-specific energy agrees well with experimentally obtained data for single-particle experiments, even if the particles were not spherical. The resulting fragment size distribution could be predicted by the application of fracture mechanics. The theory can also be applied to rock drilling, where the breaking material is considered as a flat surface and the drilling tool as being of spherical shape. In both comminution and drilling, the experimental results agree fairly well with the theory.
    Additional Material: 14 Ill.
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  • 113
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 8 (1991), S. 79-85 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The evaporation rates of particles of solid KBr or NH4Cl suspended in argon were studied under high-temperature conditions behind incident shock waves. The mass-transfer process during particle evaporation was observed by two optical techniques allowing the measurement of scattered light from a particle ensemble and also from individual particles. The scattered light flux signals were interpreted on the basis of the Mie theory, resulting in values for the time-dependent particle size and for the refractive index of particle materials. The experiments were performed in the gas-phase temperature ranges TG = 1070-1300K (KBr) and 525-650K (NH4Cl). The initial size of the suspended particles ranged between 0.6 and 1.0 μm. From the measured decrease in the particle size during the mass-transfer process the evaporation coefficients of both materials were determined as a function of the gas-phase temperature. They depend on the vapour pressure and the diffusion coefficient for vapour into gas. Typical parameters (àKBr, m) describing the diffusion coefficient of KBr vapour in argon and the vapour pressure of NH4Cl could be determined.
    Additional Material: 11 Ill.
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  • 114
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 8 (1991), S. 72-78 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A combined experimental and theoretical study of the droplet deposition and mist supercooling in a turbulent channel flow has been performed. The measurement of droplet deposition on the unheated and heated channel wall was carried out using a particle-sizing two-dimensional reference-mode laser-Doppler anemomentry technique in a 41 mm × 41 mm vertical square channel at Re = 1.0 × 104 - 6.05 × 104. The dimensionless deposition coefficient kd/uZ. H. Yang Prof. S. L. Lee Department of Mechanical Engineering, State University of New York at Stony Brook, Stony Brook, NY 11794 (USA) is analyzed theoretically based on a new unified theoretical approach for the entire transverse flow region from the turbulent core to the quasi-laminar region next to the boundary wall. The proposed analytical model shows satisfactory agreement with the results of present experimental measurement. In the mist supercooling, the heated surface is cooled by the evaporation on the outside surface of an extra thin continuous liquid film which is maintained by the continuous deposition of extremely small droplets of an optimal size determined by a selection process on the droplets transverse migration due to the dynamic interaction between the phases in a parallel turbulent mist flow. The heat transfer enhancement coefficient depends on droplet deposition rate, droplet size, concentration and the Reynolds number.
    Additional Material: 11 Ill.
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  • 115
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 8 (1991), S. 90-94 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Some parameters which affect the explosibility of dusts have been investigated. Important parameters are particle size, dust concentration, pore size and chemical composition. The dust explosion index measurements illustrate the importance of pore size and particle size. The reaction mechanism occurring is also important. Particles which burn at the solid surface and form gaseous products tend to react completely whereas other materials show a limited transport of the reactants.
    Additional Material: 9 Ill.
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  • 116
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 8 (1991), S. 136-141 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An optical instrument for simultaneous on-line measurements of the droplet size and droplet velocity of periodically generated droplets is described. This instrument is suitable for studying basic phenomena such as the evaporation or combustion of small droplets and the mutual interaction of neighbouring droplets. For the study of evaporation and combustion rates it is important to have precisely defined initial and boundary conditions. A vibrating-orifice generator is used to produce monodisperse droplet streams which are characterized by their highly coherent structure. The droplets all have the same size, the same spacing and the same initial velocity. These characteristic parameters of the droplet stream can be adjusted over a wide range as required for the specific experiment. The droplet size is measured with a sizing method of very high accuracy, which evaluates the intensity distribution of the light scattered by the droplets. The droplet diameter ranges from 10 to 150 μm. The droplet velocity is measured by a particle image displacement velocimeter and is compared with conventional LDV measurements. The results of the two methods agree very well. Typical droplet velocities lie in the range from 10 to 20 m/s. Some exemplary experimental results are presented for burning droplet streams, which show the influence of a finite spacing between the droplets on the burning rate.
    Additional Material: 10 Ill.
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  • 117
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 8 (1991), S. 151-158 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A Lagrangian approach is presented for the prediction of 3D dispersion in turbulent flows. A brief description of the main characteristics of the code PALAS (Particle Lagrangian Simulation) is given and the different methods for the simulation of either a fluid particle trajectory or a discrete particle trajectory are outlined. Comparisons with experimental results for particle 3D dispersion in grid turbulence with a nonhomogeneous force field are presented and proved to be very satisfactory in most instances.
    Additional Material: 16 Ill.
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  • 118
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 8 (1991), S. 159-163 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Experiments with a purpose built cylindrical capacitor are used to determine the sensitivity of low frequency impedance measurements to changes in the coatings of four different industrial powders. It is demonstrated that the technique should be suitable for off-line quality control.
    Additional Material: 2 Ill.
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  • 119
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The possibilities and limitations of Photon Correlation Spectroscopy as a practical tool for particle sizing are revisited. In a first step, well characterized monodisperse polystyrene latices with particle sizes ranging from about 30 nm to about 2 μm were examined in five different industrial and academic laboratories. Particular attention was paid to the effect of particle concentration and scattering angle. It turned out that for a particle diameter less than 0.5 μm reliable particle sizes can be obtained. In the range of 0.5 to 1 μm this was only possible within a very narrow range of concentration of dispersed material. For the largest size investigated (about 2 μm) the PCS measurements were less reliable which was reflected in a considerable variation of the results.
    Additional Material: 3 Ill.
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  • 120
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 8 (1991), S. 222-228 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new-generation velocimeter/sizemeter is described. Size measurement is based on the top-hat beam technique. Velocity measurement is carried out by using laser Doppler velocimetry. Advantages and limitations of the top-hat beam technique are discussed and compared with other techniques (pedestal, visibility, phase Doppler). Bubble diagnosis in a turbulent pipe flow is reported.
    Additional Material: 15 Ill.
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  • 121
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    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 8 (1991), S. 233-236 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper presents the results of a systematic study to measure the exposure to asbestos fiber concentrations associated with occupational use of asbestos-containing floor tile. Specifically, air measurements were made during floor tile installation, maintenance and removal. The procedures for these tests are outlined and the results of the air sampling and analysis are discussed.
    Additional Material: 7 Tab.
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  • 122
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 8 (1991), S. 229-232 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper presents the results of experimental tests designed to determine the amount of airborne asbestos, if any, released from vinyl-asbestos floor tile due to pedestrian trafficking. These tests involved the use of several human subjects to continuously walk on vinyl-asbestos floor tile in a controlled environment for an extended period of time. Similar trafficking tests were conducted on a non-asbestos, all-vinyl floor covering for comparison purposes. During the trafficking tests, continuous air sampling was performed through high efficiency filters for later analysis. The collected samples were then subjected to extensive analysis to characterize the collected particulate matter. Use of the optical microscope, scanning electron microscope (SEM) and transmission electron microscopy (TEM) allowed a detailed description of the collected material to be made.
    Additional Material: 1 Tab.
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  • 123
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    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 8 (1991), S. 242-242 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
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  • 124
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    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 8 (1991), S. 237-241 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In the science of particulate systems, existing nomenclature systems are not always consistent with each other. The same is true for their physical relevance. A coherent nomenclature system for denoting mean particle diameters is recommended and its physical relevance demonstrated. Comments have been made on a nomenclature for particle-size distributions to support the proposed nomenclature for mean particle diameters. This nomenclature system does not contain any ambiguities and clearly conveys the physical meanings of mean particle diameters.
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  • 125
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    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 8 (1991), S. 243-243 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 126
    Electronic Resource
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    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 8 (1991), S. 243-244 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 127
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    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 32 (1991), S. 275-293 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The performance of multiplier algorithms for structural optimization has been significantly improved by using trust regions. The trust regions are constructed using analytical second order sensitivity, and within this region, the augmented Lagrangian φ is minimized subject to bounds. Evaluation of first and second derivatives of φ by the adjoint method does not require derivations of individual (implicit) constraint functions, which makes the method economical. Eight test problems are considered and a vast improvement over previously used multiplier algorithms has been noted. Also, the algorithm is robust with respect to scaling, input parameters and starting designs.
    Additional Material: 7 Ill.
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  • 128
    Electronic Resource
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 32 (1991), S. 223-253 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A new class of predictor/corrector algorithms is proposed to solve the complex system of differential equations that arises from a Galerkin spatial discretization of the equations of motion in a recent formulation of dynamic vehicle/structure interaction. The applicability of the concept of a building-block vehicle/structure interaction model developed in our previous work - where the vehicle nominal motion is not prescribed a priori, but is part of the unknown motion of the system - is demonstrated through the construction of a simple vehicle model. In the new algorithms, the presence of the accelerations of the vehicle component is eliminated in the predictor structural equations, making these equations different from the corrector structural equations. The special treatment of the predicted axial motion that provides an artificial damping to eliminate unstable oscillations in the numerical results as proposed in the old algorithms is avoided. Accurate results from numerical simulations using the new algorithms are obtained, and there are no unstable oscillations that were observed in some other predictor/corrector schemes. The system energy balance is also better preserved compared with the old algorithms.
    Additional Material: 9 Ill.
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  • 129
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 32 (1991), S. 295-311 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This paper presents a new method for the direct and accurate evaluation of strongly singular integrals in the sense of Cauchy principal values and weakly singular integrals over quadratic boundary elements in three-dimensional stress analysis and quadratic internal cells in two-dimensional elastoplastic analysis by the boundary element method. A quadratic triangle polar co-ordinate transformation technique is applied to reduce the order of singularity of the singular integrals. Next, a form of Stokes' theorem is introduced in order to remove the singularity in the Cauchy principal value integrals; therefore, the evaluation of these integrals can be carried out by standard Gaussian quadrature. Numerical examples of 2-D elastoplastic problems and a 3-D elastic problem show the effectiveness and efficiency of the method.
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    International Journal for Numerical Methods in Engineering 32 (1991), S. 363-383 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A numerical method for the solution of inverse heat conduction problems in two-dimensional rectangular domains is established and its performance is demonstrated by computational results. The present method extends Beck's8 method to two spatial dimensions and also utilizes future times in order to stabilize the ill-posedness of the underlying problems. The approach relies on a line approximation of the elliptic part of the parabolic differential equation leading to a system of one-dimensional problems which can be decoupled.
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    International Journal for Numerical Methods in Engineering 32 (1991), S. 439-439 
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    Keywords: Engineering ; Engineering General
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  • 132
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    International Journal for Numerical Methods in Engineering 32 (1991), S. 921-937 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Methods are described for adapting a structured grid in response to a numerical solution, so that grid nodes become clustered where ‘solution activity’ is high, the aim being to reduce solution truncation errors without increasing the number of grid nodes employed, or modifying their connectivity. After introducing the concept of ‘equidistribution’, and discussing options for the measurement of solution activity, the paper concentrates mainly on two alternative techniques for producing smooth, regular grids which apply constraints on this equidistribution. The first technique described is based on a spring analogy, and is demonstrated here with examples of two- and three-dimensional inviscid flows, and with two-dimensional viscous flows. The second technique employs a Poisson grid generator with adaptive terms included in the control functions, and is demonstrated with a two-dimensional inviscid flow. A third method is then introduced, termed the LPE method, which allows a compromise to be chosen between grids generated by solving Laplace equations, Poisson equations and equidistribution equations. Since this method is still being developed, results are currently limited and tentative.
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    International Journal for Numerical Methods in Engineering 32 (1991), S. 957-967 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Bounds on eigenvalues of various finite element systems are analysed by using an element eigenvalue theorem together with the Global Eigenvalue Theorem. Both two dimensional continuum dynamics and heat conduction problems are considered. These bounds provide stable time steps for explict time integration schemes. A reduced eigenproblem at element quadrature point level, with all zero eigenvalues suppressed, is also presented in this paper. The simplified eigenproblem results in simple formulas for calculating the eigenvalues.
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    International Journal for Numerical Methods in Engineering 32 (1991), S. 1041-1055 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Based on the assumed element strain fields and the interrelated displacement-rotation interpolations, a four-node (12 dof) quadrilateral C0 finite element, designated as QCCP-2, for the analysis of thick/thin plates is developed in this paper. The four-node C0 plate element presented here possesses a linear bending strain field, and the element stiffness matrices are given explicitly. Therefore, the present four-node C0 plate element is more efficient and accurate than the existing four-node C0 plate elements where the constant strain stiffness matrices are obtained by numerical integration. By the use of the interrelated displacement-rotation interpolations, QCCP-2 is capable of automatically satisfying the Kirchhoff assumption for the case of thin plates. Consequently, QCCP-2 is not only free of shear locking, but also free from the numerical ill-conditioning. Furthermore, QCCP-2 passes the patch test of thin plates. The four-node quadrilateral C0 elements presented here can automatically reduce to the corresponding three-node triangular elements. Several numerical examples are given to demonstrate the efficiency and accuracy of the C0 plate bending element QCCP-2.
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  • 135
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    International Journal for Numerical Methods in Engineering 31 (1991), S. 1249-1252 
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    Keywords: Engineering ; Engineering General
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  • 136
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    International Journal for Numerical Methods in Engineering 32 (1991), S. 1189-1203 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The severe restrictions of the Babuška-Brezzi stability criteria permit only a limited number of interpolations for velocities (displacements) and pressure to be used for incompressible behaviour. These restrictions preclude the use of many useful elements. We show in this paper how such difficulties can be side-stepped by seeking the steady state solution through the use of various time marching schemes. This permits a simple iterative approach to incompressible (or nearly incompressible) problems of fluid mechanics or solid mechanics and provides a stimulus for the use of such procedures in metal forming flow, etc.
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  • 137
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    International Journal for Numerical Methods in Engineering 32 (1991), S. 1165-1187 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A control-augmented structural synthesis methodology is presented in which actuator and sensor placement is treated in terms of (0, 1) variables. Structural member sizes and control variables are treated simultaneously as design variables. A multiobjective utopian approach is used to obtain a compromise solution for inherently conflicting objective functions such as structural mass, control effort and number of actuators. Constraints are imposed on natural frequencies, peak transient displacements and accelerations, peak actuator forces and dynamic stability as well as controllability and observability of the system. The combinatorial aspects of the mixed (0, 1)-continuous variable design optimization problem are made tractable by combining approximation concepts with branch and bound techniques. Some numerical results for example problems are presented to illustrate the efficacy of the design procedure set forth.
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  • 138
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    International Journal for Numerical Methods in Engineering 31 (1991), S. 1497-1509 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The lateral hulls of multi-shelled ships such as Catamarans or Trimarans can be considered as rigid solids, or compared to thin walled beams in multi-layered materials for the global statical or dynamical behaviour of the ship. Unfortunately this approximation no longer hold after a detailed study of the hulls.Working in these problems we proceed to a fine analysis of the stress field at the neighbourhood of the linkage shell-arm or of the holes for access input to the hull itself. Analysis with a beam model is inadequate and the shell theory must be more appropriate. Numerous papers have been devoted to shell elements, see References 1 to 8 to mention just a few. Some of them require a reduced or selective integration scheme.9-12 We choose to start from the Ahmad element, 13, 14 which is suitable for moderate thick shells.15.16 The final aim of this paper is to explain how to build up a multi-layered equivalent homogeneous shell element which is both economical and accurate. Some examples will be given and compared with those obtained with the Ahmad finite element.
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    International Journal for Numerical Methods in Engineering 31 (1991), S. 1477-1495 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The stiffness matrix in the finite element method for multi-layered materials is generally computed by expressing the strain energy in each layer and adding them together. In order to lower the computing time, which may be prohibitive if the number of layers is high, and to get accurate information on the stresses, especially on transverse shear stresses, we present a new finite element using the Reissner principle. In the first part the case of plates will be detailed: extensions to shell problems will be presented in the second part. The efficiency of the method is tested on a special analytic solution, and some examples are given.
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    International Journal for Numerical Methods in Engineering 31 (1991), S. 1511-1536 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Iterative techniques for the solution of the algebraic equations associated with the direct boundary element analysis (BEA) method are discussed. Continuum structural response analysis problems are considered, employing single- and multi-zone boundary element models with and without zone condensation. The impact on convergence rate and computer resource requirements associated with the sparse and blocked matrices, resulting in multi-zone BEA, is studied. Both conjugate gradient and generalized minimum residual preconditioned iterative solvers are applied for these problems and the performance of these algorithms is reported. Included is a quantification of the impact of the preconditioning utilized to render the boundary element matrices solvable by the respective iterative methods in a time competitive with direct methods. To characterize the potential of these iterative techniques, we discuss accuracy, storage and timing statistics in comparison with analogous information from direct, sparse blocked matrix factorization procedures. Matrix populations that experience block fill-in during the direct decomposition process are included. With different degrees of preconditioning, iterative equation solving is shown to be competitive with direct methods for the problems considered.
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    International Journal for Numerical Methods in Engineering 31 (1991), S. 1553-1566 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A Newton method for solution of frictionless contact problems is presented. A finite element discretization is performed and the contact constraints are given as complementarity conditions. The resulting equations, which represent the equilibrium of the system, are formulated as a generalized equation. Generalized equations, from the discipline of Mathematical Programming, are a way of writing multi-valued relations, such as complementarity conditions, in a way that is similar to ordinary equations. Newton's method is then used, in a straightforward way, to solve the present non-linear generalized equation, resulting in a sequence of Linear Complementarity Problems (LCP's).
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    International Journal for Numerical Methods in Engineering 31 (1991), S. 1537-1552 
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    Notes: The present study is concerned with the physical explanations of the linear and the cubic finite elements for beams and axisymmetric shells through comparisons of their strain energy approximations with those of the Rigid Bodies-Spring Models which are discrete elements suitable for plastic collapse analysis using the concepts of plastic hinges and hinge lines. The established conditions for the equivalence between these two modellings, which are given as the relations between the locations of the numerical integration points and those of the occurrence of plastic hinges, can be conveniently used in the economical plastic collapse analysis of framed structures and axisymmetric shells where the locations of plastic hinge formations are controlled by the movement of numerical integration points. Some numerical results are shown in order to prove numerically the obtained relations and to verify the validity of the proposed shifting technique of numerical integration points, which is identified as ‘the shifted integration technique’ in the present paper.
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    International Journal for Numerical Methods in Engineering 32 (1991), S. 595-607 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The paper deals with the development of a numerical method for determining Weight Functions in two-dimensional problems. After a short review of some recent numerical techniques an original approach is presented. The method is based on Finite Element calculations with coarse meshes and on the knowledge of some values of the Stress Intensity Factor for one reference loading condition. The validity of the method is demonstrated for a theoretical case and its accuracy and suitability are discussed with reference to practical applications.
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    International Journal for Numerical Methods in Engineering 32 (1991), S. 571-594 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A general computational technique is developed for the accurate analysis of forced non-synchronous harmonic vibration of linear structures rotating with constant speed about a fixed axis in the inertial space. The structures studied are built up from piecewise uniform straight Rayleigh-Timoshenko beam members having coinciding cross-sectional centres of geometry, shear and mass, and vibrating in coupled tension, torsion, bending and shearing. Hysteretic and viscous dampings in the beam material and in a Winkler-type ambient medium are considered. Rigid bodies and modal bodies and also discrete masses, springs and dampers can be included in the structure. The six coupled scalar partial linear differential equations governing the motion of a loaded beam are established in a corotating local co-ordinate system. A transcendentally frequency-dependent non-symmetric complex-valued 12 × 12 stiffness matrix is derived, over a state-space analogy and an associated eigenproblem, for a harmonically vibrating beam member non-synchronously excited at its ends. This matrix is exact in the sense that no assumed shape functions and no lumped masses are used. The general computational technique is here applied to a simple beam rotating about (1) its longitudinal axis and (2) about a transverse axis. The study clarifies the influence of gyroscopic effects and of material and support dampings on the dynamical behaviour of the beam at different rotational speeds and forcing frequencies. Resonance frequencies are found. Frequency response functions and frequency maps are plotted.
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    International Journal for Numerical Methods in Engineering 32 (1991), S. 609-621 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A direct boundary element formulation which produces equilibrium satisfaction in the numerical solutions is presented. It consistently originates from the standard boundary integral equation with a simple modification in the fundamental solution and can be applied to general potential and elasticity problems. Since boundary equilibrium is guaranteed for any problem discretization, the procedure is also found useful to generate improved stiffness matrices, which permits combination with finite elements.Some elastostatic examples are included to demonstrate the applicability of the formulation.
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    International Journal for Numerical Methods in Engineering 32 (1991), S. 645-646 
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    International Journal for Numerical Methods in Engineering 32 (1991), S. 647-649 
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    International Journal for Numerical Methods in Engineering 32 (1991), S. 623-643 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A new finite element model for the contact/impact problem is presented, and both its static and dynamic implementations are described. In this geometrical non-linear formulation, contact (from node to surface) is simulated through fictitious equivalent pressure along the boundary. Contrary to most existing models, this formulation entails relatively few matrix decompositions and thus is computationally inexpensive. The model is first assessed through some classical contact problems, and is subsequently applied to the fracture mechanics based analysis of a cracked dam under seismic excitation.
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    International Journal for Numerical Methods in Engineering 31 (1991), S. 19-52 
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    Notes: We show that, for rigid body dynamics, the mid-point rule formulated in body co-ordinates exactly conserves energy and the norm of the angular momentum for incremental force-free motions, but fails to conserve the direction of the angular momentum vector. Further, we show that the mid-point rule formulated in the spatial representation is, in general, physically and geometrically meaningless. An alternative algorithm is developed which exactly preserves energy, and the total spatial angular momentum in incremental force-free motions. The implicit version of this algorithm is unconditionally stable and second order accurate. The explicit version conserves exactly angular momentum in incremental force-free motions. Numerical simulations are presented which illustrate the excellent performance of the proposed procedure, even for incremental rotations over 65 degrees. The procedure is directly applicable to transient dynamic calculations of geometrically exact rods and shells.
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    International Journal for Numerical Methods in Engineering 31 (1991), S. 127-150 
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    Notes: The paper presents a shell formulation based on the ‘degenerated solid approach’. The theory employs covariant strains and performs explicit integration through the shell thickness. The rigid body motion is exactly represented. The consistent tangent stiffness matrix is evaluated for the four node quadrilateral. It is shown, in the final part, that this type of element, which distinguishes itself by a very simple and easily understandable theory, gives good answers for linear as well as non-linear applications.
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    International Journal for Numerical Methods in Engineering 31 (1991), S. 113-126 
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    Keywords: Engineering ; Engineering General
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    Notes: A method to connect momentum Navier-Stokes equations with the universal law of the wall using the finite element method is developed for turbulent wall flows. This method is based on a domain decomposition of the fluid into subdomains near a solid boundary where the law of the wall is valid. A transmission formulation is introduced to match these regions and a new class of boundary finite element is used. This finite element takes into account the near-wall profile of the velocity and the transmission conditions. Computational results are presented for Poiseuille flow and flow over a backward-facing step.
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    International Journal for Numerical Methods in Engineering 31 (1991), S. 265-285 
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    Notes: We consider large eigenvalue problems for skeletal structures with symmetry. We present an algorithm, based upon a novel combination of group-theoretic ideas and substructuring techniques, that block-diagonalizes such systems exactly and efficiently. The procedure requires only the structural matrices of a repeating substructure, together with the symmetry modes, which are obtained from symmetry considerations alone. We first present a simple paradigmatic example and then follow with several non-trivial applications involving large lattice structures.
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    International Journal for Numerical Methods in Engineering 31 (1991), S. 307-317 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 154
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    Notes: Two different methods of assuming independent strain fields are examined for the nine node degenerate solid shell element. In the first case, the assumed strain field is chosen for the local orthogonal co-ordinate systems defined at the Gaussian integration points. In the second case, the independent strain is assumed for a local orthogonal co-ordinate system defined at the origin of the parent co-ordinates. The results of numerical tests involving simple example problems demonstrate that the second method is capable of exactly representing constant stress or moment states even when element geometries are distorted. In addition, both methods lead to a finite element model which is free of locking.
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    International Journal for Numerical Methods in Engineering 31 (1991), S. 319-343 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A new numerical technique for large deflection elasto-plastic analysis of stiffened plates is presented. The method uses super finite elements which are macro elements having analytical as well as the usual finite element shape functions, specially designed so that only one plate element per bay and one beam element per span are needed. The large deflection theory by von Karman and the von Mises yield criterion and associated flow rule are employed. The governing equations are derived using the principle of virtual work, integrated numerically using Gauss quadrature and solved by Newton-Raphson iteration. Numerical solutions are presented for simple beams and plates, and plates stiffened in one or two mutually perpendicular directions. Good approximations are obtained with only one-element representations of each plate bay or beam span with significant savings in computing time, costs and storage requirements as compared with using regular finite elements.
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    International Journal for Numerical Methods in Engineering 31 (1991), S. 427-446 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A numerical method is presented for the solution of two dimensional crack problems including the effects of crack kinks and frictional contact between crack faces. The metod is based on an integral equation for the resultant forces along a crack. Coulomb friction between contacting crack surfaces is taken into account. The numerical implementation is demonstrated by considerations of surface and sub-surface piece-wise straight line cracks in a half-plane. Numerical results are presented to illustrate the efficiency and the reliability of the presented method.
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    International Journal for Numerical Methods in Engineering 31 (1991), S. 447-462 
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    Notes: In this paper, a new procedure for solving 3-D dynamic problems of unbounded foundations in the frequency domain by using BEM is studied. For simulations of wave propagations due to far field effects, a type of infinite boundary element (IBEM) is presented for modelling a 3-D regular or irregular half space. The wave type considered could be compressional, shear or a combination of the two. Through the analysis of the asymptotic behaviour of 3-D fundamental solutions for elasto dynamics, a rather feasible technique for obtaining singular integral coefficients for dynamic problems has been developed. Through the analysis of the dynamic response for a 3-D square foundation under a uniform load distribution, excellent accuracy has been achieved in agreement with previous numerical solutions. Another example-analysis of the dynamic compliance of a rigid square plate on a half space-has also shown very good results. The development of this infinite boundary element provides a powerful tool for dealing with 3-D structure foundation interaction or wave propagation problems for irregular foundations such as arch dam canyons.
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    International Journal for Numerical Methods in Engineering 31 (1991), S. 493-507 
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    Notes: A perturbation analysis is developed for 1-D shallow water flow over a curved bed for applications such as spillways. The perturbation approach leads to a new formulation of the problem with associated weak integral statement and approximation using finite elements. The flow may exhibit a hydraulic jump in the downstream regime. An artificial dissipation technique is introduced to stabilize the non-linear problem and suppress numerical oscillations. Numerical results demonstrate the performance of the model and compare it with the steep-slope shallow water formulation corresponding to the model with zero curvature.
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    International Journal for Numerical Methods in Engineering 31 (1991), S. 509-524 
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    Notes: For the analysis of deformation processes the Eulerian approach is usually formulated in material velocities. To describe the die compaction of compressible media, this paper presents an Eulerian simulation method, basically expressed in displacements. The material behaviour is modelled by the theory of elastoplasticity. Frictional interaction with the surroundings is included. As a spatially fixed finite element mesh is applied, rezoning is governed by the process specification and not, as in the Lagrangian approach, by the mesh distortion. The solution scheme, using a Newton-Raphson algorithm, is considered in detail. A consistent iteration procedure is derived. Examples demonstrate the merits of the method developed.
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    International Journal for Numerical Methods in Engineering 31 (1991), S. 525-545 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A method is described to determine contact stresses and deformation using a combination of the finite element method and a surface integral form of the Bousinesq solution. Numerical examples of contacting hypoid gears are presented.
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  • 161
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    International Journal for Numerical Methods in Engineering 31 (1991), S. 547-572 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Contact-impact algorithms, which are sometimes called slideline algorithms, are a computationally time-consuming part of many explicit simulations of non-linear problems because they involve many branches, so they are not amenable to vectorization, which is essential for speed on supercomputers. The pinball algorithm is a simplified slideline algorithm which is readily vectorized. Its major idea is to embed pinballs in surface elements and to enforce the impenetrability condition only to pinballs. It can be implemented in either a Lagrange multiplier or penalty method. It is shown that, in any Lagrange multiplier method, no iterations are needed to define the contact surface. Examples of solutions and running times are given.
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    International Journal for Numerical Methods in Engineering 31 (1991), S. 611-614 
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    Keywords: Engineering ; Engineering General
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  • 163
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    International Journal for Numerical Methods in Engineering 31 (1991), S. 573-592 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This is the first of a two part paper on three-dimensional finite elements with rotational degrees of freedom (DOF). Part I introduces an 8-node solid hexahedron element having three translational and three rotational DOF per node. The corner rotations are introduced by transformation of the midside translational DOF of a 20-node hexahedron element. The new element produces a much smaller effective band width of the global system equations than does the 20-node hexahedron element having midside nodes.A small penalty stiffness is introduced to augment the usual element stiffness so that no spurious zero energy modes are present. The new element passes the patch test and demonstrates greatly improved performance over elements of identical shape but having only translational DOF at the corner nodes.
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    International Journal for Numerical Methods in Engineering 31 (1991), S. 615-618 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 165
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    International Journal for Numerical Methods in Engineering 31 (1991), S. 593-610 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This is the second part of a two part paper on three-dimensional finite elements with rotational degrees of freedom (DOF). Part II introduces a solid tetrahedron element having 3 translational and 3 rotational DOF per node. The corner rotations are introduced by transformation of the midside translational DOF of a 10-node tetrahedron element. To further enhance the element performance a least squares strain extraction technique is also implemented to develop the stiffness matrix with a desired field. The strain smoothing improves performance without causing a loss in generality.As with the hexahedron in Part I, the element stiffness is augmented with a small penalty stiffness to eliminate any possible spurious zero energy modes. The new tetrahedron element passes the patch test and demonstrates much improved performance over the 4-node translational DOF only (constant strain) tetrahedron element.
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  • 166
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    International Journal for Numerical Methods in Engineering 31 (1991), S. 859-878 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This paper presents the development of a design algorithm for epicyclic gear systems. The criterion on which the design performance is assessed is the maximum tensile stress induced in the fillets of the sun, planet and annulus gears. From an initial set of prescribed real and integer design parameters the finite element method is used to determine the maximum tensile fillet stresses in each gear. An objective function is formulated to represent the total stress in the system by combining the maximum fillet stresses in each component. A sequential procedure is then used to minimize the objective function subject to equality, inequality and integer function constraints.The finite element method is used to evaluate the stresses in the gear teeth and iterative application of the analysis and optimization stages converges to produce a design vector such that the maximum stress produced in all components of the system is minimized.Since the effectiveness of each design is assessed using the finite element method, the factorized stiffness matrix is reused to calculate the design derivatives. This makes the processes very efficient in its use of computer resources.
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  • 167
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    International Journal for Numerical Methods in Engineering 31 (1991), S. 895-907 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: By using cubic B-spline approximations, reasonably accurate solutions are obtained for line-loaded shallow spherical shells with a centre hole within a wide range of values of the geometrical parameter K (0 ≤ K ≤ 400, \documentclass{article}\pagestyle{empty}\begin{document}$ K = \sqrt {12(1 - v^2)} 2f/h $\end{document}, f = shell rise, h = shell thickness). It was found that the buckling loads Pc as well as the buckling threshold of the geometrical parameter Kc increase monotonically as the radius of the centre hole β increases if the hole edge is reinforced with a rigid ring and the outer edge of the shell is simply supported. However, the effect of the centre hole on Pc decreases rapidly as K increases and becomes negligible for K ≥ 45 and β ≤ 0.4.
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  • 168
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    International Journal for Numerical Methods in Engineering 31 (1991), S. 909-926 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The following paper describes the incorporation of different constraints into a finite element system by means of matrix operators in conjunction with consecutive corresponding transformations. Instead of increasing the number of equations-as e.g. the Lagrange Multiplier Method10, 14 does-the Matrix Operator Method yields a set of reduced magnitude which can be solved more efficiently. The method will be developed for two classes of constraints: (i) stiff coupling of previously known subdomains and (ii) contact problem between two bodies. The assembly rules to obtain the system matrices are deduced. An application is given by a three-dimensional example of structural analysis in mechanical engineering.
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  • 169
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    International Journal for Numerical Methods in Engineering 31 (1991), S. 927-947 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The need for adding to the many existing rectangular plate elements is justified and the inclusion of the twist parameter, in the degrees of freedom selected, is shown to be essential. Using a rational choice of parameters to form the deflection functions for a simply supported plate element, a constant term, sixteen degrees of freedom rectangular element is developed which is shown to predict exactly the first mode frequency and mode shape when used in whole plate modelling. The properties of this ‘dynamic’ element are combined with the properties of an existing ‘static’ element to obtain the frequency dependent properties of a ‘blended’ element. It is demonstrated that in order to obtain high accuracy in eigenvalue determination it is necessary to use three separate modellings of the plate using a square element and two rectangular elements which are oriented orthogonally. From 3 × 3 and 2 × 5 modelling, it is shown that the frequencies of the first 20 modes of a simply supported square plate, resulting from matrix eigenvalue determinations are obtainable within one per cent of the exact values. Modes 11 and 18 are determined exactly. Mode shape distortions associated with frequency errors are examined and shown to be minimal for the first 20 modes.
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  • 170
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    International Journal for Numerical Methods in Engineering 31 (1991), S. 949-966 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A new methodology of evaluation of C0 beam elements is presented. It is shown that, knowing the stiffness matrix of an arbitrary type of element, it is possible to create equivalent equilibrium conditions expressed in the form of one difference equation for a regular beam discretized by these elements. The study of the convergence of one difference equation gives an interpretation of the source of troubles occurring in low-order bending elements which is more convincing than the usually applied consideration of the conditioning of element stiffness matrices. A careful examination of quadratic Mindlin elements provides a very clear explanation of the shear locking essence in the Timoshenko beam. The presented method enables one to identify errors that appear also in the reduced integrated or constrained elements. For each type of analysed quadratic element an adequate difference equation is derived and compared with the exact one. Based on this comparison a simple method of corrections is proposed that completely eliminates the errors associated with the application of C0 bending elements.
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    International Journal for Numerical Methods in Engineering 31 (1991), S. 967-985 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The dynamic substructure method is extended to linear and non-linear coupling systems. Only those master co-ordinates with non-linear nature (non-linear co-ordinates) are retained. Other slave co-ordinates relating to the linear part (linear co-ordinates) are eliminated by the dynamic substructure method. The dynamic flexibility matrix associated with the linear co-ordinates is first expanded in terms of the fixed interface natural modes. The condensed dynamic stiffness-matrix associated with the non-linear co-ordinates is formed subsequently. The convergence of the condensed dynamic stiffness matrix with respect to the natural modes can be improved by means of matrix manipulations and Taylor series expansion. To find the steady state solutions, the non-linear responses are expanded into a Fourier series. Responses of the linear co-ordinates are related to the non-linear co-ordinates analytically. To solve for the unknown Fourier coefficients, the harmonic balance method gives a set of non-linear algebraic equations relating the vibrating frequency and the nodal displacement coefficients. A Newtonian algorithm is adopted to solve for the unknown Fourier coefficients iteratively. The computational cost of a non-linear analysis depends heavily on the number of degrees of freedom encountered. In the method, the number of degrees of freedom is kept to a minimum and the computational cost is greatly reduced.
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  • 172
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    International Journal for Numerical Methods in Engineering 31 (1991), S. 1055-1068 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Boundary integral formulations for the 2D Helmholtz equation involve kernels in the form of modified Bessel functions. Accurate schemes for evaluating integrals of the kernels and their derivatives are presented. Special attention is paid to integrals involving singular and near singular kernels. Both boundary and domain integrals are considered. It is shown that, with the use of series expansion functions for the modified Bessel functions, the boundary integrals can be evaluated analytically in the neighbourhood of the singularity. For domain integrals, the behaviour of the kernels in the vicinity of the singularity is used to construct accurate numerical quadrature schemes. A transient heat conduction problem is formulated as a Helmholtz equation, solved, and compared against analytic solution to demonstrate the effectiveness of these schemes in relation to traditional methods. References are made to previous work to advocate the utility of the boundary integral method for non-linear and time-transient problems.
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  • 173
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    International Journal for Numerical Methods in Engineering 31 (1991), S. 1069-1086 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A variational higher-order theory involving all transverse strain and stress components is proposed for the analysis of laminated composite plates. Derived from three-dimensional elasticity with emphasis on developing a viable computational methodology, the theory is well suited for finite element approximations as it incorporates both C0 and C-1 continuous kinematic fields and Poisson boundary conditions. From the theory, a simple three-node stretching-bending finite element is developed and applied to the problem of cylindrical bending of a symmetric carbon/epoxy laminate for which an exact solution is available. Both the analytic and finite element results were found to be in excellent agreement with the exact solution for a wide range of the length-to-thickness ratio. The proposed higher-order theory has the same computational advantages as first-order shear-deformable theories. The present methodology, however, provides greater predictive capabilities, especially, for thick-section composites.
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  • 174
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    International Journal for Numerical Methods in Engineering 31 (1991), S. 1135-1149 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A new Petrov-Galerkin method for the incompressible Navier-Stokes equations is presented. The use of the so-called ‘optimal upwind’ parameter in multidimensions is justified by a time-scale analysis of the relevant physical processes. The resulting procedure circumvents the Babuška-Brezzi condition and allows equal order interpolation for velocity and pressure to be used.
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  • 175
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    International Journal for Numerical Methods in Engineering 31 (1991), S. 1121-1133 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Given a list of points defining a domain boundary, a three-stage process is often used to triangulate a domain. First, an appropriate distribution of interior points is generated. Next the points are connected to form triangles. And, finally, the connectivity data are used to reposition the interior points using the Laplacian smoothing technique, thereby usually improving the shapes of the shapes of the triangles. This paper describes a new techniques for mesh improvement - adjusting the connection structure during the second stage of this process. The new scheme, which we call mesh relaxation, consists of a procedure for iteratively making the mesh topology more regular by edge swapping. For each interior edge, a relaxation index is computed that depends on the degrees of its end points and adjacent points. Any edge for which this index exceed a prescribed threshold will be swapped, i.e. replaced by a new edge connecting the adjacent points of the original edge. After all edge swaps are completed, Laplacian smoothing is applied to the mesh. Example show that, when the mesh point density varies smoothly and due care is taken in the vicinity of the boundary, mesh relaxation can dramatically increase the regularity of the mesh and produce improve triangle shapes.
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  • 176
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    International Journal for Numerical Methods in Engineering 32 (1991) 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 177
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    International Journal for Numerical Methods in Engineering 32 (1991), S. 1371-1387 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This paper discusses an application of a boundary integral equation method (BIEM) to an inverse problem of determining the shape and the location of cracks by boundary measurements. Suppose that a given body contains an interior crack, the shape and the location of which are unknown. On the exterior boundary of this body one carries out measurements which are interpreted mathematically as prescribing Dirichlet data and measuring the corresponding Neumann data, or vice versa, for a field governed by Laplace's equation. The inverse problem considered here attempts to determine the geometry of the crack from these experimental data. We propose to solve this problem by minimizing the error of a certain boundary integral equation (BIE). The process of this minimization, however, is shown to require solutions of certain are proposed. Several 2D and 3D numerical examples are given in order to test the performance of the present method.
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  • 178
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    International Journal for Numerical Methods in Engineering 32 (1991), S. 1389-1409 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An explicit expression for the stiffness matrix is worked out for a triangular plate bending element considering the effect of transverse shear deformation. The element has twelve nodes on the sides and four nodes internal to it. The formulation is displacement type and the use of area co-ordinates makes it possible to obtain the shape functions explicitly. Separate polynomials are assumed for transverse displacement and rotations. To obtain the element stiffness matrix no matrix inversion or numerical integration need be carried out and only a few matrix multiplications of low order are necessary. The element, which is initially of thirty five degrees of freedom, can be reduced to a thirty degrees of freedom one by condensation of the internal nodes. An interesting feature of the element developed is that the values of nodal moments computed at a node point, considering different elements surrounding the node, do not vary significantly. Thus the nodal moments can be obtained directly at node points. Also, the element does not give rise to any inconvenience like locking, even for very thin plates. The straightforward approach in formation of the element stiffness will cut down the storage space considerably and will also call for less CPU time, thus making the use of the element well suited to low capacity computers. A number of plate bending problems have been worked out using the present element for different thickness to side ratios and a comparison has been made with the available results. Good accuracy has been observed in all cases, even for a small number of elements.
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    International Journal for Numerical Methods in Engineering 32 (1991), S. 1411-1439 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The non-linear response of soft hydrated tissues under physiologically relevant levels of mechanical loading can be represented by a two-phase continuum model based on the theory of mixtures. The governing equations for a biphasic soft tissue, consisting of an incompressible solid and an incompressible, inviscid fluid, under finite deformation are presented and a finite element formulation of this highly non-linear problem is developed. The solid phase is assumed to be hyperelastic, and the stress-strain relations for the solid phase are defined in terms of the free energy function. A finite element model is formulated via the Galerkin weighted residual method coupled with a penalty treatment of the continuity equation for the mixture. Using a total Lagrangian formulation, the non-linear weighted residual statement, expressed with respect to the reference configuration, leads to a coupled non-linear system of first order differential equations. The non-linear constitutive equation for the solid phase elasticity is incrementally linearized in terms of the second Piola-Kirchhoff stress and the corresponding Lagrangian strain. A tangent stiffness matrix is defined in terms of the free energy function; this matrix definition can be applied to any free energy function, and will yield a symmetric matrix when the free energy function is convex. An unconditionally stable implicit predictor-corrector algorithm is used to obtain the temporal response histories. The confined compression mechanical test of soft tissue in stress relaxation is used as an example problem. Results are presented for moderate and rapid rates of loading, as well as small and large applied strains. Comparison of the finite element solution with an independent finite difference solution demonstrates the accuracy of the formulation.
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    International Journal for Numerical Methods in Engineering 32 (1991), S. 1531-1542 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A simple approach to the numerical simulation of mechanical systems consisting of rigid and flexible bodies is presented. The mechanical system may consist of rigid bodies, different types of flexible bodies, joints and actuators and may have arbitrary topological structure with kinematical loops. The equations of motion are formulated as a large sparse system of equations in absolute co-ordinates as well as relative co-ordinates. These equations are numerically integrated as a system of differential-algebraic equations using modern numerical methods.
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    International Journal for Numerical Methods in Engineering 32 (1991), S. 1543-1563 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A formulation for the dynamic analysis of flexible systems, composed of slender bodies that can be accurately modelled by beams is presented in this paper. A new set of state variables, composed of Cartesian co-ordinates of points and unit vectors, is introduced to define the beam with respect to an inertial frame. A non-linear Timoshenko beam finite element capable of handling finite displacements with small linear elastic strains is developed. This allows relative displacements between material points of a single beam to be arbitrarily large. Since deformations are not explicit variables, there is no need to define a moving reference frame attached to each flexible body. Instead, deformations are obtained through a displacement-deformation relation based on finite-displacement beam theory. The differential equations of motion are obtained using the Lagrange equations. A symmetric, constant and sparse mass matrix is obtained in the inertial frame. Constraints are introduced with a penalty formulation and the resulting set of ordinary differential equations is integrated with Newmark's family of methods. The whole formulation is extremely simple and the results demonstrate the capabilities and efficiency of the proposed method for dynamic simulation, even when relative displacements are finite in a single beam or coupling effects are significant.
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    International Journal for Numerical Methods in Engineering 32 (1991), S. 1669-1689 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An extended kinematic graph concept and a variational-vector calculus approach are employed to develop a new recursive formulation for the dynamic analysis of flexible multibody systems. The extended graph concept introduced defines frames and transformations between frames as nodes and edges, respectively, rather than the more traditional body and joint convention. Kinematic relationships between adjacent flexible bodies are derived, using joint relative co-ordinates and a state vector notation that represents both translational and rotational components of velocity. Deformation kinematics are formulated in terms of modal co-ordinates, under small deformation assumptions. Joint relative co-ordinates are decoupled from deformation modal co-ordinates in both kinematic relations and in the recursive dynamics algorithm, leading to a significant reduction in the dimension of matrices that must be inverted. Dynamic analysis of a flexible closed-loop spatial robot is performed to illustrate the efficiency of the algorithm.
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    International Journal for Numerical Methods in Engineering 32 (1991), S. 1799-1812 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This paper presents a systematic method for deriving the minimum number of equations of motion for spatial flexible multibody systems. Relative kinematics are developed using relative joint co-ordinates and relative joint velocities to formulate a minimum number of equations of motion. The present method takes advantage of the simplicity of the absolute co-ordinate formulation and computational efficiency of the relative joint co-ordinate formulation. The system equations of motion are first formulated in terms of a coupled set of absolute reference co-ordinates and elastic modal co-ordinates. These equations are transformed to the joint co-ordinate space by use of a velocity transformation matrix including the elastic modal velocities. A computer algorithm is proposed and extended to closed loop mechanisms. One example of a flexible vehicle is presented and the results are discussed to illustrate the computational efficiency of the method.
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    International Journal for Numerical Methods in Engineering 32 (1991), S. 1813-1831 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In this paper, issues related to the dynamic modelling of constrained deformable bodies that undergo large rigid body displacements are discussed. Particular attention is focused on finite element formulations. It is shown that the use of nodal co-ordinates and shape functions to describe the finite rotation of some of the commonly used finite elements leads to a linearization of the kinematics and dynamic relationships. The structure of the non-linear dynamic equations that govern the motion of deformable bodies that undergo large displacements is examined. Comments on the finite element formulation of the invariants of motion, the definition of the generalized forces and moments in flexible body dynamics and the computational strategy used for the automatic generation of the equations of motion are made. The computer formulation of the joint constraints between deformable bodies as well as the numerical algorithms currently used in many of the general purpose computer programs that are based on the augmented formulation are discussed. A decoupled joint-elastic acceleration recursive formulation is also presented. This formulation leads to a small system of acceleration equations whose dimensions are independent of the number of the elastic degrees of freedom of the system. In this paper, the coupling between the displacements of the deformable bodies is classified as kinematic, inertia and elastic. In view of this classification, comments on the validity of using the updated finite element Lagrangian formulation and the 4 × 4 transformation matrix in the dynamic analysis of flexible multibody systems are made. The coupling between the finite rotation and the wave motion in constrained deformable bodies is also discussed.
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    International Journal for Numerical Methods in Engineering 32 (1991), S. 1851-1852 
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    Keywords: Engineering ; Engineering General
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  • 186
    ISSN: 0268-2605
    Keywords: Zirconocene ; benzyne ; chalcogen (S, Se) ; zirconacycle ; 1H NMR ; mass spectrometry ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The para-substituted diphenylzirconocenes [(t-BuCp)2Zr(p-C6H4R)2; R = Br, NMe2] (A) were easily obtained from the reaction of the appropriate organolithium reagent with bis(t-butylcyclopentadienyl)zirconium dichloride. Elimination of bromobenzene or N,N-dimethylaminobenzene from A by slight heating led to arynezirconocenes into which were inserted two equivalents of elementary chalcogens. As a result dichalcogenated zirconacycles [(t-BuCp)2ZrY2C6H3R; Y = S, Se] (B) were obtained. Complexes B constitute useful potential synthons in organic synthesis and a large family of new functionalized dichalcogenated benzenic compounds was prepared by reacting electrophiles.The structure of complexes B as well as related benzenic derivatives has been confirmed by microanalysis, 1H NMR and mass spectrometry.
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    Applied Organometallic Chemistry 5 (1991), S. 79-82 
    ISSN: 0268-2605
    Keywords: Siloxanes (silicones) ; lead-210 ; inductively coupled plasma spectrophotometer ; environment ; sediment deposition ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A Puget Sound sediment core has been quantitatively analyzed for organic silicon content, as derived from post-1945 release of poly(organo)-siloxanes (silicones). The sedimentary silicone data record and preserve at depth, a smeared event horizon, or first appearance of silicone in the sediment column. Core samples older than 50 years showed no detectable silicone as measured by a new procedure utilizing inductively coupled plasma (ICP) emission spectroscopy after solvent extraction to collect the silicone from gram-sized sediment core samples.
    Additional Material: 4 Ill.
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  • 188
    ISSN: 0268-2605
    Keywords: heterocyclic thiosemicarbazones ; Dimethylsilicon complexes ; antifungicidal activity ; antibacterial activity ; antifertility activity ; 1H NMR spectra ; 13C NMR spectra ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthetic, structural and biological aspects of trigonal-bipyramidal, Me2Si(NS)Cl and octahedral, Me2Si(NS)2 types of organosilicon (IV) complexes of heterocyclic thiosemicarbazones (N—SH) have been described. The complexes were characterized by elemental analysis, molecular weight determination, conductance measurements and electronic, infrared, 1H and 13C NMR spectral studies. Some ligands and their corresponding dimethylsilicon (IV) complexes have been tested for their effects on several pathogenic fungi and bacteria. Two representative complexes have also been found to act as sterilizing agents by reducing the production of sperm in male mice.
    Additional Material: 7 Tab.
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  • 189
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    Applied Organometallic Chemistry 5 (1991), S. 167-172 
    ISSN: 0268-2605
    Keywords: Catalysis ; ethylation ; organosodium ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Study of the catalytic ethylation of p-t-butyltoluene in the presence of organosodium compounds, and of toluene in the presence of organopotassium compounds, was carried out at an ethylene pressure of 40 bar.Various yields of different products were obtained after 23 h of reaction in the presence of different tertiary polyamines used to complex and solubilize the organoalkali compounds.A higher initial ethylation rate was observed in the presence of organosodium than in the presence of organopotassium species. However, the thermal stability of organopotassium species being higher, much higher yields were observed in their presence in catalytic ethylation reactions than those observed previously.The results obtained concerning metallation or ethylation of hindered alkylaromatics may be interpreted by an anionic mechanism and the activation by a steric effect.
    Additional Material: 3 Ill.
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  • 190
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    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 5 (1991), S. 57-64 
    ISSN: 0268-2605
    Keywords: Laser evaporation ; deposition ; polysilane ; poly(sila-alkene) ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Continuous wave (cw) CO2 laser irradiation of some organosilicon polymers composed of -Me2Si-, -Me2SiMe2SiCH2-, RMeSi- and RMeSiMe2SiCH2CH2- units (where R = methyl, adamantyl, phenyl and hydrogen) leads to the evaporation of the polymer and is dominated by the formation of a solid deposit that has a continuous structure. It is assumed that chemical changes occur prior to the transfer of ejected material to the gas phase and that these consist mainly of the formation of high molecular biradicals or 1,2-disilacyclobutane monomer that both re-polymerize spontaneously upon their deposition onto a nearby cold surface. The mechanism of these specific decompositions of the polymers is assessed on the basis of the IR spectra of the deposits and, for the minor gaseous products, identification by GC MS techniques.
    Additional Material: 3 Ill.
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  • 191
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    Applied Organometallic Chemistry 5 (1991), S. i 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 192
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    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 5 (1991), S. 191-194 
    ISSN: 0268-2605
    Keywords: Carbon dioxide ; propylene oxide ; organozinc-oxygen compounds ; poly(;propylene carbonate) ; propylene carbonate ; copolymerization ; cyclization ; organozinc catalyst ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of carbon dioxide with propylene oxide in the presence of catalysts with condensed zinc species (;derived from diethylzinc and dihydric phenols, e.g. catechol o= C6H4(;OH)2 and saligenin 0= HOC6H4CH2OH) yields poly(;propylene carbonate) as well as propylene carbonate. The above reaction in the presence of catalysts with noncondensed zinc species (;derived from diethylzinc and phenol) yields propylene carbonate as the main product, but in relatively low yield. The mechanism of the linear and cyclic carbonate formation is discussed in terms of the nature of the catalyst's active sites for both types.
    Additional Material: 1 Tab.
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  • 193
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    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 5 (1991) 
    ISSN: 0268-2605
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 194
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    Applied Organometallic Chemistry 5 (1991), S. 203-206 
    ISSN: 0268-2605
    Keywords: X-ray photoelectron spectroscopy ; phthalocyanine sheet polymers ; metal-free ; nickel ; copper ; electrical conductivity ; pyrolysis ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The X-ray photoelectron spectroscopy (XPS) technique has been used to characterize metallophthalocyanine sheet polymers having peripheral carboxyl groups. A comparative analysis of the XPS and electrical conductivity data of metal-free, and nickel- and copper-containing, phthalocyanine sheet polymers has been described. Metallophthalocyanine sheet polymers exhibited a maximum conductivity of about 1 S cm-1 on pyrolysis.
    Additional Material: 1 Ill.
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  • 195
    ISSN: 0268-2605
    Keywords: dmit ; dmio ; metal complexes ; cyclopentadienyl ; cobalt(III) complex ; cyclic voltammetry ; controlled potential coulometry ; electron reservoir ; sulphur-rich organic electron donor ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Four novel cobalt(III) complexes with a cyclopentadienyl or pentamethylcyclopentadienyl ring and dmit or dmio ligands were synthesized, and their electrochemical behaviour was investigated. All these complexes exhibited three one-electron transfer steps: one reduction and two oxidation steps. In addition, a novel organosulphur compound was afforded by electrochemical oxidation of dmit cobalt complex. Thus, these complexes may have considerable synthetic potential as precursors for electron reservoirs and organosulphur compounds.
    Additional Material: 7 Ill.
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  • 196
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    Applied Organometallic Chemistry 5 (1991), S. 229-241 
    ISSN: 0268-2605
    Keywords: Synchrotron radiation ; photochemical reaction ; semiconductor process ; etching ; chemical vapor deposition ; epitaxial growth ; atomic layer epitaxial growth ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Recent results are reviewed on synchrotron radiation (SR)-excited photochemical reaction studies aimed at applications to semiconductor processes. Valence or core electronic excitations induced by SR irradiation and ensuing chemical reactions are classified and characterized by rate equations. Unique material selectivity in etching has been found. SiO2 has been found to evaporate by SR irradiation and this phenomenon can be applied to the low-temperature surface cleaning of silicon. In the epitaxial growth of Silicon by ultrahighvacuum chemical vapor deposition using Si2H6, SR irradiation significantly lowers growth temperature beyond the low-temperature limit of thermal reaction. Lowering of the operating temperature by SR irradiation is especially effective in applications to the atomic layer epitaxial growth of silicon. The layer-by-layer process has been successfully demonstrated, confirming self-limiting adsorption of SiH2Cl2 and ensuring surface reactivation by SR irradiation.
    Additional Material: 18 Ill.
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  • 197
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    Applied Organometallic Chemistry 5 (1991), S. 243-246 
    ISSN: 0268-2605
    Keywords: Photochemistry ; iron pentacarbonyl ; titanium dioxide ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The photolysis of iron carbonyl (Fe(CO)5) adsorbed on titanium dioxide (TiO2, anatase) was studied by FT-IR spectroscopy. When adsorbed Fe(CO)5 is illuminated by visible and near-UV light, the IR spectrum of its photolysis products is hardly observed, indicating that most of the Fe(CO)5 is photodecomposed to iron(0) or iron oxides on TiO2. The carbon monoxide (CO) evolution rate upon illumination depends on the wavelength of light; 433 nm light is more effective for CO evolution than 366 nm light. This result implies that the band-gap excitation of TiO2 has little effect on the photolysis of adsorbed Fe(CO)5, since the absorption edge of TiO2 (anatase) lies at around 400 nm. The effects of substrates on the photolysis of adsorbed Fe(CO)5 are discussed with reference to previous results obtained for aluminium oxide (Al2O3) and silicon dioxide (SiO2), on which the photolysis leads to the formation of Fe2(CO)9 or Fe3(CO)12.
    Additional Material: 3 Ill.
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  • 198
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    Applied Organometallic Chemistry 5 (1991), S. 247-255 
    ISSN: 0268-2605
    Keywords: Photodissociation ; organometallic ; time-of-flight ; translational energy ; dynamics ; photoejection ; excimer laser ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The photodissociation dynamics of organometallic compounds (tetramethyltin, trimethylgallium, trimethylindium and dimethylzinc) adsorbed on a quartz substrate at 100 K have been studied by time-of-flight mass spectrometry, detecting mainly CH3 photofragments. Shapes of the time-of-flight spectra depend on the flux of the dissociation laser at 193 nm and the thickness of multilayers of organometallic compounds. In thick layers, not only a low energy component but also a high energy component are observed in the time-of-flight spectrum of the CH3 photofragments. In thin layers, relaxation processes take place so quickly that the product time-of-flight profiles are characterized by a Maxwell-Boltzmann temperature profile.
    Additional Material: 10 Ill.
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  • 199
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    Applied Organometallic Chemistry 5 (1991), S. 261-268 
    ISSN: 0268-2605
    Keywords: Photochemistry ; silver alginate ; Ag-Au composite colloids ; metal particles ; extinction spectrum ; Mie scattering ; surface plasmon ; polyelectrolyte ; protective agent ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photochemical formation of colloidal silver, colloidal gold and silver-gold (Ag-Au) composite colloids under mild conditions has been studied. Irradiation of either aqueous AgCIO4 or HAuCI4 solution in the presence of sodium alginate (SA) with 253.7 nm light yielded colloidal silver or gold, whose particle diamter was 10-30 nm or 40-60 nm, respectively. The Ag-Au composite colloids consisting of mixtures of silver and gold domains (particle diameter 30-150 nm) have been prepared and their extinction spectra have been examined on the basis of a conventional Mie theory in combination with an effective medium theory to estimate the optical constants of these colloids. It has been shown that the extinction spectra of the Ag-Au composite colloids are completely different from those of Ag-Au alloy colloids, in that the former have two extinction maxima close to the colloidal extinction bands of pure silver and gold, in contrast to a single extinction maximum of the latter. The importance of natural, high-molecular carboxylic acids such as alginic acid in the photochemical formation of metal colloids and thin films has been stressed.
    Additional Material: 8 Ill.
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  • 200
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    Applied Organometallic Chemistry 5 (1991), S. 289-293 
    ISSN: 0268-2605
    Keywords: Photochemical vapor deposition (CVD) ; aluminum film ; deuterium lamp ; dimethylaluminum hydride ; wavelength dependence ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In photochemical vapor deposition of aluminum film on silicon using dimethylaluminum hydride, (CH3)2AlH, a surface reaction dominated below a (CH3)2AlH pressure of 0.3 m Torr at 200°C, which was induced only with the 160 nm band emitted from a deuterium lamp. A gas-phase reaction occurred above 0.3 mTorr at 200°C, which could be induced by both 160 nm and 240 nm emission bands from the lamp. To distinguish between surface ad gas-phase reactions, a thickness profile was used. At 240°C the surface reaction could be induced even by the 240 nm band, while the deposits formed under illumination of the two bands were thinner than those obtained with only the 240 nm band, indicating occurrence of vacuum ultraviolet (VUV)-enhanced desorption. The mechanism responsible for the observed wavelength dependence in unclear. The electrical resistivity of the films deposited at 200°C was 4.5 μΩ cm, which did not change with wavelength.
    Additional Material: 6 Ill.
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