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  • 1
    Electronic Resource
    Electronic Resource
    On the validity of conforming BEM algorithms for hypersingular boundary integral equations (1997)
    Springer
    Computational mechanics 20 (1997), S. 213-220 
    Details
    ISSN: 1432-0924
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The widely held notion that the use of standard conforming isoparametric boundary elements may not be used in the solution of hypersingular integral equations is investigated. It is demonstrated that for points on the boundary where the underlying field is C 1,α continuous, a class of rigorous nonsingular conforming BEM algorithms may be applied. The justification for this class of algorithms is interpreted in terms of some recent criticism. It is shown that the numerical integration in these conforming BEM algorithms using relaxed regularization represents a finite approximation to the standard two-sided Hadamard finite part interpretation of hypersingular integrals. It is also shown that the integration schemes in this class of algorithms are not based upon one-sided finite part interpretations. As a result, the attendant ambiguities associated with the incorrect use of the one-sided interpretations in boundary integral equations pose no problem for this class of algorithms. Additionally, the distinction is made between the analytic discontinuities in the field which place limitations on the applicability of the conforming BEM and the discontinuities resulting from the use of piece-wise C 1,α interpolations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004660050241
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  • 2
    Electronic Resource
    Electronic Resource
    Characterisation of Epoxy Resins for Microstereolithographic Rapid Prototyping (1999)
    Springer
    The international journal of advanced manufacturing technology 15 (1999), S. 281-286 
    Details
    ISSN: 1433-3015
    Keywords: Key words.Diffractive optics; Four-wave mixing; Microstereo-lithography; Optoelectronics; Photochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Two epoxy resins are investigated using non-degenerate fourwave mixing. The materials assessed are optimised for use with a UV argon-ion laser. The holographic gratings were written at a wavelength of l= 351.1 nm for an irradiance range 0.5–3.0 W/cm 2 and read at l= 632.8 nm in order to compare the reactivity, curing speed, shrinkage and resolution of the resins. These experiments were carried out to prove the suitability of the photopolymerisation systems for use with a new microstereolithographic technique. This new technique exploits a spatial light modulator to create 3D components using a completely planer, layer-by-layer, process of exposure which is described herein. With this procedure it is possible to build components with dimensions in the range of 50 mm to 50 μm, and feature sizes as small as 5 μm with a resolution of 1 μm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001700050067
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Bedside percutaneous endoscopic gastrostomy (1997)
    Springer
    Surgical endoscopy and other interventional techniques 11 (1997), S. 1068-1071 
    Details
    ISSN: 1432-2218
    Keywords: Key words: Percutaneous endoscopic gastrostomy (PEG) — Nutrition — Trauma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Background: Percutaneous endoscopic gastrostomy (PEG) is a good alternative that provides long-term nutritional support and is associated with minimal morbidity. Methods: During a 24-month period, we studied 54 critically injured patients who underwent early PEG to provide enteral nutritional support. Patients were selected due to the inability to tolerate intake by mouth secondary to multiple associated injuries, especially to the central nervous system. Results: All patients sustained multiple injuries with an average Injury Severity Score of 27. The mean Glasgow Coma Scale at the time of admission was 7 and at the time of the PEG was 10. Eleven patients (20%) had an intracranial pressure (ICP) device, and there was no significant increase in the mean ICP before, during, or after the procedure. In 63% of patients, tube feedings were interrupted for a variety of problems in the 72 h preceding the PEG, and in 70% of patients an average of five radiographs were obtained to document tube position. In 95% of patients, the nutritional goal was achieved within 48 h of PEG placement. There were one immediate and two delayed complications after PEG placement. There were two deaths, neither related to the PEG placement. Conclusions: Early PEG in critically injured patients is a safe and effective method of providing access to the GI tract for nutritional support. In patients with significant brain injuries, adequate sedation and the presence of an ICP monitor help to minimize secondary insults to the brain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004649900531
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  • 4
    Electronic Resource
    Electronic Resource
    Voyager observations of the magnetic field, interstellar pickup ions and solar wind in the distant heliosphere (1996)
    Springer
    Space science reviews 78 (1996), S. 33-42 
    Details
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Voyagers 1 and 2 are now observing the latitudinal structure of the heliospheric magnetic field in the distant heliosphere (the legion between ∼- 30 AU and the termination shock). Voyager 2 is observing the influence of the interstellar medium on the solar wind. The pressure of the interstellar pickup protons, measured by their contribution to pressure balanced structures, is greater than or equal to the magnetic pressure and much greater than the thermal pressures of the solar wind protons and electrons in the distant heliosphere. The solar wind speed is observed to decrease and the proton temperature increase with increasing distance from the sun. This may result from the production of pickup ions by the charge exchange process with the interstellar neutrals. The introduction of the pickup ions into the dynamics of the magnetized solar wind plasma appears to be an important new process which must be considered in future theoretical studies of the termination shock and boundary with the local interstellar medium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00170790
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  • 5
    Electronic Resource
    Electronic Resource
    Voyager 2 Solar Wind Observations in the Outer Heliosphere (1998)
    Springer
    Space science reviews 83 (1998), S. 87-92 
    Details
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We discuss the solar wind parameters measured in the distant heliosphere from the Voyager 2 spacecraft. Periodic variations in the speed of the wind observed at roughly the solar rotation period may correspond to interaction regions between slower and faster streams of wind. Since the interplanetary magnetic field is enhanced in such regions, they are important for the study of modulation of cosmic rays. Unfortunately, direct observation of the enhanced magnetic field from Voyager 2 has been made difficult by spacecraft-associated noise since 1989.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005021412128
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    NON-SINGULAR SOMIGLIANA STRESS IDENTITIES IN ELASTICITY (1996)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 39 (1996), S. 3273-3304 
    Details
    ISSN: 0029-5981
    Keywords: elasticity ; boundary integral equations ; hypersingular ; continuity ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The paper presents two fully equivalent and regular forms of the hypersingular Somigliana stress identity in elasticity that are appropriate for problems in which the displacement field (and resulting stresses) is C1,α continuous. Each form is found as the result of a single decomposition process on the kernels of the Somigliana stress identity in three dimensions. The results show that the use of a simple stress state for regularization arises in a direct manner from the Somigliana stress identity, just as the use of a constant displacement state regularization arose naturally for the Somigliana displacement identity. The results also show that the same construction leads naturally to a finite part form of the same identity. While various indirect constructions of the equivalents to these findings are published, none of the earlier forms address the fundamental issue of the usual discontinuities of boundary data in the hypersingular Somigliana stress identity that arise at corners and edges. These new findings specifically focus on the corner problem and establish that the previous requirements for continuity on the densities in the hypersingular Somigliana stress identity are replaced by a sole requirement on displacement field continuity.The resulting regularized and finite part forms of the Somigliana stress identity leads to a regularized form of the stress boundary integral equation (stress-BIE). The regularized stress-BIE is shown to properly allow piecewise discontinuity of the boundary data subject only to C1,α continuity of the underlying displacement field. The importance of the findings is in their application to boundary element modeling of the hypersingular problem. The piecewise discontinuity derivation for corners is found to provide a rigorous and non-singular basis for collocation of the discontinuous boundary data for both the regularized and finite part forms of the stress-BIE. The boundary stress solution for both forms is found to be an average of the computed stresses at collocation points at the vertices of boundary element meshes. Collocation at these points is shown to be without any unbounded terms in the formulation thereby eliminating the use of non-conforming elements for the hypersingular equations. The analytical findings in this paper confirm the correct use of both regularized and finite part forms of the stress-BIE that have been the basis of boundary element analysis previously published by the first author of the current paper.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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