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91.
Herbert E. Scarf 《Mathematical Programming》1997,79(1-3):355-368
In this paper I discuss various properties of the simplicial complex of maximal lattice free bodies associated with a matrixA. If the matrix satisfies some mild conditions, and isgeneric, the edges of the complex form the minimal test set for the family of integer programs obtained by selecting a particular
row ofA as the objective function, and using the remaining rows to impose constraints on the integer variables. 相似文献
92.
Peter G. Thompson Larry T. Taylor Bruce E. Richter Neil L. Porter John L. Ezzell 《Journal of separation science》1993,16(12):713-716
A polarity test mix consisting of acetophenone, N, N-dimethylaniline, naphthalene, decanoic acid, 2-naphthol, and n-tetracosane was spiked onto sand, and extracted with supercritical carbon dioxide, to evaluate the collection efficiency of various solvents and solvent mixtures. Nine single collection solvent systems and four mixed collection solvent systems were studied. When one-component collection solvents were employed, quantitative (above 90%) recovery of all analytes was not possible. With mixed collection solvents, recoveries of 90% or better with all analytes studied were possible. 相似文献
93.
94.
The dynamic behavior of two parallel symmetric cracks in a piezoelectric strip under harmonic anti-plane shear waves is studied
using the Schmidt method for permeable crack surface conditions. The cracks are parallel to the edge of the strip. By means
of the Fourier transform, the problem can be solved with the help of two pairs of dual integral equations. These equations
are solved using the schmidt method. The results show that the stress and the electric displacement intensity factors depend
on the geometry of the cracks, the frequency of incident waves, the distance between cracks and the thickness of the strip.
It is also found that the electric displacement intensity factors for the permeable crack surface conditions are much smaller
than those for the impermeable crack surface conditions.
Project supported by the Post Doctoral Science Foundation of Heilongjiang Province, the Natural Science Foundation of Heilongjiang
Province, the National Science Foundation with the Excellent Young Investigator Award (No. 19725209) and the Scientific Research
Foundation of Harbin Institute of Technology (HIT.2000.30). 相似文献
95.
96.
Christian Tischler Thomas R. Kratochvilla Heinz Muschik Heinz Dragaun 《Macromolecular Symposia》2010,296(1):626-631
It is known, that the lifetime of polyethylene pipes is essentially limited by slow crack growth (SCG). For state of the art PE materials common SCG testing methods have reached their limits with respect to extension of testing times. A comparatively new method is the Notched Ring Test (NRT) as developed by Choi et al.[1] Pipe rings notched at the inner wall are used. The test is carried out in 80 °C water under constant bending load. The arrangement of the notch at the inner wall reduces testing times using the residual stress of extruded pipes. A disadvantage of this method is that there is no clearly defined failure time because SCG takes place between two phases of creeping. The output of this test is an “on-set slow cracking time” (crack initiation), obtained by analysis of the displacement curve. In this work it has been shown that the NRT method yields to brittle fracture within acceptable time frames.[2] Methods for data analysis are presented. This test could be very useful applied in research and development for resin evaluation and as a tool in quality control in pipe production for evaluating the process conditions. 相似文献
97.
98.
99.
Zeynep Özkurt 《代数通讯》2013,41(8):3534-3544
Let F be the free Leibniz algebra of rank two over a field K of characteristic zero freely generated by x 1 and x 2. In this article we show that an endomorphism of F which preserves the orbit of a nontrivial element of F is an automorphism. Using this result, we determine some test elements of F. 相似文献
100.
近二十年来,我国高等教育规模不断扩大,高校在校生数不断增加,其中武汉市位居全国前列.为了研究高校在校生数对当地经济发展的影响,本文利用武汉市1992—2012年在校大学生人数数据,通过建立合适的模型,来定量探讨武汉市在校大学生数与经济增长的内在关系.结果表明,武汉市经济增长与武汉在校大学生人数模型之间存在着长期均衡关系且互为格兰杰因果关系. 相似文献