中国上市公司资本结构影响因素之实证研究

资本结构不仅是财务理论研究中的热点及难点,也日益成为公司理财决策的关键问题.本文从影响因素角度对资本结构进行实证研究.文中以深沪两市部分非金融类上市公司为样本,利用本世纪最初三年的企业财务数据,选取可能影响企业资本结构的多个指标为解释变量,利用单因素方差分析、主成分分析、逐步回归分析找出了主要影响因素及其影响方式,试图为国内上市公司资本结构决定因素提供最新实证研究证据,并为企业财务决策提供支持.     

The phase diagram of a single polymer chain: New insights from a new simulation method

We present simulation results for the phase behavior of a single chain for a flexible lattice polymer model using the Wang-Landau sampling idea. Applying this new algorithm to the problem of the homopolymer collapse allows us to investigate not only the high temperature coil–globule transition but also an ensuing crystallization at lower temperature. Performing a finite size scaling analysis on the two transitions, we show that they coincide for our model in the thermodynamic limit corresponding to a direct collapse of the random coil into the crystal without intermediate coil–globule transition. As a consequence, also the many chain phase diagram of this model can be predicted to consist only of gas and crystal phase in the limit of infinite chain length. This behavior is in agreement with findings on the phase behavior of hard-sphere systems with a relatively short-ranged attractive square well. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2542–2555, 2006     

Proton and alpha evaporation spectra in low energy 12C and 16O induced reactions

Proton and alpha particle spectra have been measured in the ¹²C+⁹³Nb and ¹²C+⁵⁸Ni reactions at E(¹²C)=40 and 50 MeV and in the ¹⁶O + ⁹³Nb reaction at E(¹⁶O) =75 MeV. The spectra are compared with the statistical model calculations. The shapes of the calculated spectra are in agreement with experimental data except for the alpha spectrum in the ¹²C + ⁹³Nb reaction at 40 MeV. The observed evaporation bump is at ∼2 MeV lower energy compared to the calculated one. This discrepancy could imply alpha particle emission from a deformed configuration before compound nucleus formation at this near Coulomb barrier beam energy.     

Degeneracy in NLP and the development of results motivated by its presence

We study notions of nondegeneracy and several levels of increasing degeneracy from the perspective of the local behavior of a local solution of a nonlinear program when problem parameters are slightly perturbed. Ideal nondegeneracy at a local minimizer is taken to mean satisfaction of second order sufficient conditions, linear independence and strict complimentary slackness. Following a brief exploration of the relationship of these conditions with the classical definition of nondegeneracy in linear programming, we recall a number of optimality and regularity conditions used to attempt to resolve degeneracy and survey results of Fiacco, McCormick, Robinson, Kojima, Gauvin and Janin, Shapiro, Kyparisis and Liu. This overview may be viewed as a structured survey of sensitivity and stability results: the focus is on progressive levels of degeneracy. We note connections of nondegeneracy with the convergence of algorithms and observe the striking parallel between the effects of nondegeneracy and degeneracy on optimality conditions, stability analysis and algorithmic convergence behavior. Although our orientation here is primarily interpretive and noncritical, we conclude that more effort is needed to unify optimality, stability and convergence theory and more results are needed in all three areas for radically degenerate problems.Research supported by National Science Foundation Grant ECS 90-00560 and Grant N00014-89-J-1537 Office of Naval Research     

饱和水蒸汽与水的焓与熵参数的新关联式

饱和水蒸汽与水的焓与熵参数的新关联式李斯特，马润梅，吴冷（北京化工大学机械工程系北京１０００２９）关键词统计力学，剩余函数，焓与熵１引言本文根据统计力学与热力学剩余函数原理，结合本课题组曾已建立的饱和水蒸汽与水的新简明状态方程模型，经推导出一则适合于...     

双参数变形玻色湮没算符高次幂的本征态及其量子统计性质

本文构造了双参数变形玻色湮没算符高次幂a^'k(k≥3)的k个正交归一木征态的数学结构,发现它们能构成一个完备的Hilbert空间,并且讨论了它们的量子统计性质.     

Statistical mechanics of probabilistic cellular automata

We investigate the behavior of discrete-time probabilistic cellular automata (PCA), which are Markov processes on spin configurations on ad-dimensional lattice, from a rigorous statistical mechanics point of view. In particular, we exploit, whenever possible, the correspondence between stationary measures on the space-time histories of PCAs on ^d and translation-invariant Gibbs states for a related Hamiltonian on ( ^d+1). This leads to a simple large-deviation formula for the space-time histories of the PCA and a proof that in a high-temperature regime the stationary states of the PCA are Gibbsian. We also obtain results about entropy, fluctuations, and correlation inequalities, and demonstrate uniqueness of the invariant state and exponential decay of correlations in a high-noise regime. We discuss phase transitions in the low-noise (or low-temperature) regime and review Toom's proof of nonergodicity of a certain class of PCAs.     

碳原子簇的结构与质谱的关联（Ⅱ）

根据出现在质谱中的各种大小的碳原子簇的相对丰度,分析了由激光产生的碳原子簇离子的统计分布,研究了这些统计分布与碳原子簇结构的关联。研究结果表明：相同构型的原子簇的相对丰度可以由同一条对数正态分布曲线来描述,由此能够获得碳原子簇构型的变化情况。质谱中分布曲线的数目对应于具有不同构型或不同结构稳定性的原子簇的数目。如果某些簇离子的谱峰明显地高出分布曲线,它们的结构应特别稳定,其成簇原子数就是所谓的“奇幻数”（ｍａｇｉｃｎｕｍｂｅｒ）,例如在石墨质谱中的Ｃ＿（６０）就属于这种情况。原子簇的统计分布还与它们的生成过程有关,由此可能揭示出原子簇的产生机理。     

Statistical replacement for systems with delta-correlated fluctuations

Nonlinear systems with stochastic parameters are approximated by simpler systems using a method that we call statistical replacement. This method is an extension of the previously developed AGREE which was restricted to systems with additive fluctuations. Statistical replacement incorporates the distinctions between globally stable thermodynamically closed systems and thermodynamically open systems that can be unstable.     

不同交联度的杜仲胶的红外光谱研究

研究了不同交联度的杜仲胶在室温及加热后红外光谱的变化规律．发现在室温下测定的样品红外光谱在低波数内对应链段变形振动的几个特征峰、加热后会消失或弥散，而交联度的改变对其影响不大，即使材料中结晶完全消失而变成高弹态．因此，推测这些特微峰的存在，应该和杜仲胶弹性网络中交联点间链段存在着明显的构象规整性有关．