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1.
2.
Jaedong Cho John Blackwell Sergei N. Chvalun Morton Litt Yuan Wang 《Journal of Polymer Science.Polymer Physics》2004,42(13):2576-2585
As‐cast films of poly(2,5‐benzimidazole) exhibit uniplanar orientation in which the planes of the aromatic rings lie parallel to the film surface. Upon doping with phosphoric acid, the original crystalline order is lost, but the doped film can be stretched to produce films with uniaxial orientation. After thermal annealing at 540 °C, nine Bragg reflections are resolved in the fiber diagram, and these are indexed by an orthorhombic unit cell with the dimensions a = 18.1 Å, b = 3.5 Å, and c = 11.4 Å, containing four monomer units of two chains. The absence of odd‐order 00l reflections points to a 21 chain conformation, which is probably planar so that the aromatic units can be stacked along the b axis. The water and phosphoric acid contents of the crystalline structure cannot be determined exactly because of the presence of extensive amorphous regions that probably have different solvation. The best agreement between the observed and calculated intensities is for an idealized structure containing two phosphoric acids and two water molecules per unit cell. However, the phosphoric acid is probably present mainly in the form of pyrophosphoric acid and its higher oligomers. In addition, the X‐ray data are consistent with a more disordered structure containing chains with random (up and down) polarity and a lack of c‐axis registry. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2576–2585, 2004 相似文献
3.
N. I. Alekseev V. B. Kaplan A. M. Martsinovskii I. I. Stolyarov 《Technical Physics》1997,42(6):599-605
Results are presented from a systematic investigation of the conditions under which anomalously high rates of plasma generation
are observed in the anode region of a low-voltage Knudsen arc in grid plasma switch elements. The phenomenon develops over
a wide range of currents and switched voltages under conditions for which the plasma density in the cathode-grid region is
noticeably higher than the density in the anode region. and its onset is characterized by a pronounced pressure threshold
of ∼2×10−2 Torr. The results are analyzed from the standpoint of the possible mechanisms for anomalous plasma generation — collisional
nonresonance diffusion of electrons in velocity space, leading to enrichment of the distribution function in fast particles,
and the collapse of Langmuir waves in the gap at the high energies of the beam produced when the wires of the grid are bridged
by the quenching pulse and and the current is blocked.
Zh. Tekh. Fiz. 67, 15–21 (June 1997) 相似文献
4.
R. H. Enns D. E. Edmundson S. S. Rangnekar A. E. Kaplan 《Optical and Quantum Electronics》1992,24(11):S1295-S1314
In this paper we summarize what is currently known about optical switching between bright bistable soliton states in one and higher dimensions. A guideline to selecting media with appropriate intensity-dependent refractive indices to support bistable solitary waves is presented. The stability criterion for robustness of the solitary waves is discussed. Finally, some methods and numerical examples of optical switching are presented. 相似文献
5.
Let G be a finite group. A complete Sylow product of G is a product of Sylow subgroups of G, one for each prime divisor of |G|. We shall call G a Sylow factorizable group if it is equal to at least one of its complete Sylow products. We prove that if G is a Sylow factorizable group then the
intersection of all complete Sylow products of G is equal to the solvable radical of G. We generalize the concepts and the result to Sylow products which involve an arbitrary subset of the prime divisors of |G|.
Received: 26 January 2005 相似文献
6.
We determine the minimal domain structure for the equilibrium thickness of stripes as well as for the minimal energy of the domain configuration in ultrathin films of ferromagnetically coupled spins, where the easy direction of magnetization is perpendicular to the film. It is found that the equilibrium thickness of stripes and walls depend on the exchange energy. The normalized anisotropy, f, depends on interplay between the magnetic and anisotropy energies and is almost independent of the exchange energy inside the wall. The results are compared with the experimental data for thin Ag/Fe/Ag (0 0 1) films and a good coincidence is obtained between both results. 相似文献
7.
T. A. Kaplan 《Journal of statistical physics》2006,122(6):1237-1260
The definition of the fundamental quantity, the chemical potential, is badly confused in the literature: there are at least
three distinct definitions in various books and papers. While they all give the same result in the thermodynamic limit, major
differences between them can occur for finite systems, in anomalous cases even for finite systems as large as a cm3. We resolve the situation by arguing that the chemical potential defined as the symbol μ conventionally appearing in the
grand canonical density operator is the uniquely correct definition valid for all finite systems, the grand canonical ensemble
being the only one of the various ensembles usually discussed (microcanonical, canonical, Gibbs, grand canonical) that is
appropriate for statistical thermodynamics, whenever the chemical potential is physically relevant. The zero–temperature limit
of this μ was derived by Perdew et al. for finite systems involving electrons, generally allowing for electron–electron interactions;
we extend this derivation and, for semiconductors, we also consider the zero–T limit taken after the thermodynamic limit.
The enormous finite size corrections (in macroscopic samples, e.g. 1 cm3) for one rather common definition of the c.p., found recently by Shegelski within the standard effective mass model of an
ideal intrinsic semiconductor, are discussed. Also, two very–small–system examples are given, including a quantum dot. 相似文献
8.
In contrast to stochastic differential equation models used for the calculation of the term structure of interest rates, we
develop an approach based on linear dynamical systems under non-stochastic uncertainty with perturbations. The uncertainty
is described in terms of known feasible sets of varying parameters. Observations are used in order to estimate these parameters
by minimizing the maximum of the absolute value of measurement errors, which leads to a linear or nonlinear semi-infinite
programming problem. A regularized logarithmic barrier method for solving (ill-posed) convex semi-infinite programming problems
is suggested. In this method a multi-step proximal regularization is coupled with an adaptive discretization strategy in the
framework of an interior point approach. A special deleting rule permits one to use only a part of the constraints of the
discretized problems. Convergence of the method and its stability with respect to data perturbations in the cone of convexC
1-functions are studied. On the basis of the solutions of the semi-infinite programming problems a technical trading system
for future contracts of the German DAX is suggested and developed.
Supported by the Stiftung Rheinland/Pfalz für Innovation, No. 8312-386261/307. 相似文献
9.
S. De Nicola A. E. Kaplan S. Martellucci P. Mormile G. Pierattini J. Quartieri 《Applied physics. B, Lasers and optics》1989,49(5):441-444
We have observed a hysteretic (bistable) reflection of a Gaussian laser beam at the interface between glass and a liquid solution of polystyrene microspheres as nonlinear medium with both branches of the hysteretic curve being stable, in contrast to the results of previous experiments. 相似文献
10.
A cubic (trivalent) graph is said to be 4-arc-transitive ifits automorphism group acts transitively on the 4-arcs of (wherea 4-arc is a sequence v0, v1, ... v4 of vertices of such thatvi1 is adjacent to vi for 1 i 4, and vi1 vi+1for 1 i < 4). In his investigations into graphs of thissort, Biggs defined a family of groups 4+(am), for m = 3,4,5...,each presented in terms of generators and relations under theadditional assumption that the vertices of a circuit of lengthm are cyclically permuted by some automorphism. In this paperit is shown that whenever m is a proper multiple of 6, the group4+(am) is infinite. The proof is obtained by constructing transitivepermutation representations of arbitrarily large degree. 相似文献