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Digitale Medien

Chemical modification in mass spectrometry IV - 2-alkenyl-4,4-dimethyloxazolines as derivatives for the double bond location of long-chain olefinic acids (1988)

Zhang, J. Y. ; Yu, Q. T. ; Liu, B. N. ; [weitere]

Chichester : Wiley-Blackwell

Biological Mass Spectrometry 15 (1988), S. 33-44

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ISSN: 0887-6134

Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Long-chain unsaturated fatty acids (UFA) can easily be converted on a microgram scale to the corresponding 2-alkenyl-4,4-dimethyloxazolines by condensation with 2-amino-2-methylpropanol (AMP). These modified molecules with a ‘hidden’ carboxyl group have been proved to be a class of useful derivatives for gas chromatography/mass spectrometry (GC/MS) of UFA mixtures. While possessing very good GC characteristics, the title compounds show regular, well-recognizable diagnostic ion peaks of the double bond position in the chain. Detailed description of the method as well as electron impact (E1) mass spectra of derivatives resulting from mono-, di and polyenoic (maximally containing six double bonds) acids are presented.

Zusätzliches Material: 5 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/bms.1200150106

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Digitale Medien

A semi-analytic method for dynamic response analysis based on Gurtin's variational principle (1995)

Peng, J. S. ; Lewis, R. W. ; Zhang, J. Y.

Chichester : Wiley-Blackwell

Communications in Numerical Methods in Engineering 11 (1995), S. 297-306

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ISSN: 1069-8299

Schlagwort(e): semi-analytic method ; dynamic response ; convolution ; variational principle ; series ; finite element method ; Engineering ; Engineering General

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Mathematik , Technik allgemein

Notizen: In the paper a semi-analytic approach for solving dynamic response problems is developed which is based on Gurtin's convolution-type variational principle. A finite element discretization in the space domain and a series representation in the time domain are considered. This approach overcomes the shortcomings of existing methods yet utilizes their advantages for solving dynamic response problems. The example of a beam shows that this new approach is a very effective method in obtaining solutions for dynamic response problems. The paper also concentrates on utilizing time domain series for various boundary conditions, so that solutions calculated by this approach have a very high accuracy and efficiency.

Zusätzliches Material: 1 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/cnm.1640110403

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Numerical modelling of crack propagation using multi-variable and breakable finite elements (1990)

Zhang, J. Y. ; Hsu, T. R. ; Wang, I. Q.

New York, NY [u.a.] : Wiley-Blackwell

Communications in Applied Numerical Methods 6 (1990), S. 215-222

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ISSN: 0748-8025

Schlagwort(e): Engineering ; Engineering General

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Mathematik , Technik allgemein

Notizen: In this study, the advantage of the multi-variable finite-element model based on the generalized virtual work principle is described. The model has been applied to the elasto-plastic fracture analysis with finite deformations. Using the multi-variable finite-element model with a‘breakable finite-element’ concept, the authors proposed an algorithm which can more accurately simulate the crack growth. Numerical examples illustrate that the algorithm presented can be successfully used to predict whether the crack growth is stable or unstable. The rupture effective strain is considered as a fracture criterion, and some comparisons between various criteria are also provided.

Zusätzliches Material: 5 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/cnm.1630060308

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