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991.
Kapil Hari Paranjape 《Proceedings Mathematical Sciences》2002,112(3):383-391
A result of Belyi can be stated as follows. Every curve defined over a number field can be expressed as a cover of the projective
line with branch locus contained in a rigid divisor. We define the notion of geometrically rigid divisors in surfaces and
then show that every surface defined over a number field can be expressed as a cover of the projective plane with branch locus
contained in a geometrically rigid divisor in the plane. The main result is the characterization of arithmetically defined
divisors in the plane as geometrically rigid divisors in the plane. 相似文献
992.
Mark S. Ashbaugh Carmen C. Chicone Richard H. Cushman 《Journal of Dynamics and Differential Equations》1991,3(1):67-85
This paper describes, analyzes, and explains a novel twisting phenomenon which occurs in a triaxial rigid body (such as a tennis racket) when it is rotating about an axis initially near its unstable intermediate principal axis. 相似文献
993.
A series of lithium and sodium salts of sulfonated polyethylene oxide (PEO) polyurethane ionomers in different levels of ionization were prepared. It has been found that this material is a new type of ionic conductive polymer, characterized by a single-ion transport mechanism and good mechanical properties. The ionization level significantly influences the ionic conductivity of the samples. When the mole ratio of the metal ion and ether oxygen atom is about 0.05, the ionomers exhibit maximum cationic conductivity. An optimal cationic conductivity of 1.0 × 10?5 S/cm is obtained at about 70°C without any addition of organic plasticizer. The conductivity increases apparently when propylene carbonate and low MW PEO are added to the polyurethane ionomer. © 1995 John Wiley & Sons, Inc. 相似文献
994.
Rigid finite element and its applications in engineering 总被引:1,自引:0,他引:1
Rigid Finite Element Method (RFEM) was proposed to simulate the mechanical behavior of discontinuous structures such as rock
and soil structures. The authors' work on the theory and applications of RFEM is summarized in this paper. Based on the theory
of RFEM, the Elastic Body-Seams Model (EBSM) is proposed to take the deformation and damage of rock masses into account. 相似文献
995.
In this work, the following problem is considered. A rigid body is moving immersed in a fluid of infinite depth. Its goal is to hit another body which floats on the surface of the fluid. Using stochastic control methods, a sequence of subproblems concerning the guidance and control of the immersed rigid body are dealt with. 相似文献
996.
阳离子型水性聚氨酯制备和应用 总被引:2,自引:0,他引:2
阳离子型水性聚氨酯制备和应用台会文,王农跃,张留成(河北工学院化工系天津300130)关键词聚氨酯,乳液,织物整理剂水性聚氨酯能赋予织物柔软、丰满的手感,改善织物耐磨性、抗皱性、防缩性、回弹性、通透性等。它还能与多种乳液树脂及助剂配合使用,是一类很有... 相似文献
997.
本文研究了以二元酸与二元醉在酸性催化荆存在下进行熔融缩聚反应的规律,合成了己二破系和已二酸/芳香二酸系两个系列的策韶二醉,考查了原料配比、催化剂种类、反应温度等工艺条件对缩琅反应和产品质f的影响。用化学分析、vPO,nsc,wAxn等手段对聚命进行了表征.讨论了聚酸的化学组成与结构对获自型聚氮幽的结晶性、粘结性、耐热性的影响,从而找出了适合于聚氮偏胶粘剂用豪留的组成结构和合成工艺. 相似文献
998.
Summary Three conservation laws are associated with the dynamics of Hamiltonian systems with symmetry: The total energy, the momentum
map associated with the symmetry group, and the symplectic structure are invariant under the flow. Discrete time approximations
of Hamiltonian flows typically do not share these properties unless specifically designed to do so. We develop explicit conservation
conditions for a general class of algorithms on Lie groups. For the rigid body these conditions lead to a single-step algorithm
that exactly preserves the energy, spatial momentum, and symplectic form. For homogeneous nonlinear elasticity, we find algorithms
that conserve angular momentum and either the energy or the symplectic form. 相似文献
999.
In [6], O. C. García and W. Taylor asked if the breadth of the lattice of interpretability types of varieties is uncountable.
The present paper solves the problem by two different constructions. Both of them show that any cardinal number is the cardinality
of an antichain in the named lattice and that the existence of a proper class antichain is equivalent to the negation of Vopěnka's
principle. The first construction gives in a way a minimal solution of the problem, whereas the second one gives stronger
results about the category of clones.
Received November 12, 1999; accepted in final form June 19, 2001. 相似文献
1000.
Yong‐Ming Guo Kenji Nakanishi Yasuto Yokouchi 《Numerical Methods for Partial Differential Equations》2002,18(6):726-737
A rigid‐plastic hybrid element method (HEM) for simulation of metal forming is developed. This method is a mixed approach of the rigid‐plastic domain‐BEM and the rigid‐plastic FEM based on the theory of compressible plasticity. Because the compatibilities of not only velocity but also velocity's derivative between the adjoining boundary elements and finite elements can be met, the velocities and the derivatives of the velocity can be calculated with the same precision for the rigid‐plastic HEM. Then, it is considered that the rigid‐plastic HEM is a more precise method in formulation than the conventional rigid‐plastic FEMs for which the compatibilities of velocity's derivative cannot be met. The plane strain upsetting processes with two friction factors are analyzed by the rigid‐plastic HEM in this article. © 2002 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 18: 726–737, 2002; Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/num.10031. 相似文献