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  • 1
    Digitale Medien
    Digitale Medien
    Kinetically balanced geometric Gaussian basis sets for relativistic atoms (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 1829-1833 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: We present Dirac–Hartree–Fock (DHF) atomic structure results for many-electron atoms (Z=2–86) using kinetically balanced geometric basis sets of Gaussian functions. There is no "variational collapse'' or bound failure if we impose the condition of kinetic balance between the large and the small component spinors along with proper boundary conditions for bound state orbitals. Furthermore, with a finite-size nucleus model, the DHF total energy for atoms converges more rapidly to the numerical Dirac–Fock (DF) limit with a smaller number of basis functions than those calculations where a point nucleus is assumed. By systematically extending the geometric basis sets, we have obtained the DHF total energies for all atoms(up to Z=86) within a few millihartrees of the numerical (DF) limit, with smooth convergence from above.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.459110
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  • 2
    Digitale Medien
    Digitale Medien
    Modelling of small-angle X-ray scattering data using Hermite polynomials (2001)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 34 (2001), S. 510-518 
    Details
    ISSN: 1600-5767
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Geologie und Paläontologie , Physik
    Notizen: A new algorithm, called the term-selection algorithm (TSA), is derived to treat small-angle X-ray scattering (SAXS) data by fitting models to the scattering intensity using weighted Hermite polynomials. This algorithm exploits the orthogonal property of the Hermite polynomials and introduces an error-reduction ratio test to select the correct model terms or to determine which polynomials are to be included in the model and to estimate the associated unknown coefficients. With no a priori information about particle sizes, it is possible to evaluate the real-space distribution function as well as three- and one-dimensional correlation functions directly from the models fitted to raw experimental data. The success of this algorithm depends on the choice of a scale factor and the accuracy of orthogonality of the Hermite polynomials over a finite range of SAXS data. An algorithm to select a weighted orthogonal term is therefore derived to overcome the disadvantages of the TSA. This algorithm combines the properties and advantages of both weighted and orthogonal least-squares algorithms and is numerically more robust for the estimation of the parameters of the Hermite polynomial models. The weighting feature of the algorithm provides an additional degree of freedom to control the effects of noise and the orthogonal feature enables the reorthogonalization of the Hermite polynomials with respect to the weighting matrix. This considerably reduces the error in orthogonality of the Hermite polynomials. The performance of the algorithm has been demonstrated considering both simulated data and experimental data from SAXS measurements of dewaxed cotton fibre at different temperatures.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1107/S0021889801006951
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  • 3
    Digitale Medien
    Digitale Medien
    Characterization of several modified jute fibers using zeta-potential measurements (2000)
    Springer
    Colloid & polymer science 278 (2000), S. 229-235 
    Details
    ISSN: 1435-1536
    Schlagwort(e): Key words Jute fiber ; Surface modification ; Zeta-potential
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract  ζ-potential measurements using the streaming potential method were performed on several differently modified jute fibers. The time dependence of the ζ-potential measured in 1 × 10−3 M KCl solution offers the possibility to characterize the water-uptake behavior and the velocity constant of this process for almost all the jute fibers investigated. All the jute fibers contain, as expected, dissociable acidic surface functional groups as could be verified by measuring the pH dependence of the ζ-potential. Remarkably a peak (increase in the negative ζ-potential values) was detected while measuring the ζ–pH dependency. The origin of this peak is still questionable; however, it could be observed that this peak is a function of the degree of surface coverage of additional components, such as fats, waxes or grafted polymers, i.e. the accessibility of ether functions in the jute fiber surface.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s003960050036
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  • 4
    Digitale Medien
    Digitale Medien
    Heat transfer from a circular cylinder rotating about an orthogonal axis in quiescent air (1991)
    Springer
    Experiments in fluids 10 (1991), S. 267-272 
    Details
    ISSN: 1432-1114
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Direct measurements of local heat flux and temperature from rotating cylinders have been carried out using Gardon type foil heat flux sensors and a power supply cum instrumentation slip ring set up. The local and average heat transfer results are presented covering a rotational Reynolds number range of 2 × 104 to 6.2 x 104 corresponding to the speeds varying from 400 to 1,400 rpm. A correlation has been derived for peripherally averaged values of Nusselt numbers: $$\overline {Nu_r } = 0.55Re_r^{0.661} $$ . The values of surface average Nusselt number for the cylinder under the present rotating conditions are found to be higher than for a stationary cylinder in crossflow and for a cylinder rotating about its own axis, in the range of present experiments.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00202459
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  • 5
    Digitale Medien
    Digitale Medien
    Effect of chemical modification on the performance of biodegradable jute yarn-Biopol® composites (2000)
    Springer
    Journal of materials science 35 (2000), S. 2589-2595 
    Details
    ISSN: 1573-4803
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Jute yarn-Biopol® composites are prepared by hot-press moulding technique. Jute yarns of two varieties (7.36 lbs/spy and 11.86 lbs/spy) are used for composite fabrications. Effects of temperature, yarn amount, chemical modification like dewaxing (defatting), alkali treatment, graft copolymerization and orientation of yarn winding on the performance of resulting composites have been investigated. The mechanical properties like tensile strength, bending strength, impact strength and bending-E-modulus increased substantially in comparison to pure Biopol® as a result of reinforcement with jute yarns. The most remarkable observations of our present investigations include more than 150% enhancement in tensile strength, impact strength, bending-E-modulus and more than 50% enhancement in bending strength of the resulting composites as compared to pure Biopol® sheets. Amount of jute yarn, chemical modifications and measurement of mechanical properties on the direction of winding of yarns contribute significantly to the mechanical properties of resulting composites.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004723330799
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  • 6
    Digitale Medien
    Digitale Medien
    Graft polymerization of acrylonitrile onto chemically modified bleached jute fibers (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 225 (1995), S. 1-9 
    Details
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Acrylnitril wurde unter Verwendung des Redoxinitiatorpaares Peroxodisulfat-Eisen(II)-ammoniumsulfat auf Jutefasern gepfropft. Der Einfluß der Reaktionszeit, Temperatur, Menge an Jutefaser, Monomer-, Initiator- und Schwefelsäurekonzentration sowie verschiedener Lösungsmittel und Salze auf die Pfropfausbeute wurde untersucht. Die gepfropfte Jute wurde mittels IR-Spektroskopie charakterisiert. Die Pfropfung verbessert die Lichtechtheit von mit Rhodamin B gefärbter Jute.
    Notizen: The graft polymerization of acrylonitrile (AN) onto chemically modified bleached jute fibers has been studied using potassium peroxydisulfate-ferrous ammonium sulfate redox initiating system. The effects of time of reaction, variation in concentration of monomer, peroxydisulfate, ferrous ammonium sulfate and sulfuric acid on graft yield have been studied. The effects of temperature, amount of jute fibers, some inorganic salts and organic solvents on graft yield have also been investigated. Grafted jute has been characterized by IR spectra. Grafting has improved the light fastness of jute dyed with Rhodamine B dye.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/apmc.1995.052250101
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  • 7
    Digitale Medien
    Digitale Medien
    Vanadium-cyclohexanone-initiated graft copolymerization of methyl methacrylate onto jute fibers (1986)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 31 (1986), S. 1763-1769 
    Details
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Graft copolymerization of methyl methacrylate (MMA) was carried out on jute fibers using a V5+ -cyclohexanone redox initiator system. The effect of the concentration of acid, monomer, and V5+ on graft yield have been studied. In order to obtain optimum conditions of grafting, the effects of temperature, acid, reaction medium, solvent, and some inorganic salts on graft yield have been investigated. The most remarkable features of the investigation include the proposition of a mechanism and derivation of rate expression for the grafting process. More than 100% grafting could be achieved with the present system.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/app.1986.070310621
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  • 8
    Digitale Medien
    Digitale Medien
    Redox-initiated graft copolymerization onto modified jute fibers (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 34 (1987), S. 1325-1327 
    Details
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/app.1987.070340336
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  • 9
    Digitale Medien
    Digitale Medien
    Kinetics of retarded polymerization: Investigation of the retardation of V5+-thiourea initiated polymerization of methyl acrylate by phenol (1987)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 25 (1987), S. 2107-2116 
    Details
    ISSN: 0887-624X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The kinetics and mechanism of the retarding action of phenol on the V5+-thiourea initiated polymerization of methyl acrylate (MA) have been studied within the temperature range of 30-50°C. The effects of retarder (phenol), metal ion (V5+), monomer (MA), sulfuric acid, some organic solvents and inorganic salts on the percentage and rate of polymerization have been studied. The remarkable observation of the present study is the positive intercept obtained from the plot of [M]/Rp vs. 1/[M]. This type of observation is significantly different from previous studies on retarded polymerization. The values of composite rate constants k0kt/kikpkK have been calculated from plots of [M]/Rp vs. 1/[M]. On the basis of experimental findings a reaction mechanism has been suggested, and a suitable rate expression has been proposed and explained.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pola.1987.080250807
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  • 10
    Digitale Medien
    Digitale Medien
    Laminar flow in the entrance region of a parallel plate channel (1982)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 28 (1982), S. 830-833 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690280520
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