结构性零和零膨胀模型(英文)

在社会心理学和行为学的研究中,记录某些健康或行为结果发生频率的计数中(如在一段时间内无防护措施的性行为的次数)往往含有大量的零,这是因为当某些对象对于某种研究行为没有危险时就会产生"结构性零"。不像随机零(结果可以是大于零,但是也可能由于样本变异性而成为零),结构性零在统计和临床上通常是非常不同的。如果两种类型零的差异被忽略,就可能会导致对结果和研究发现的错误解释。然而在实践中,结构性零经常会没有被观察到而这种潜在性使数据分析复杂化了。在这篇文章中,我们专注于一种模式,即通常用于解决零膨胀数据的零膨胀泊松(Zero-inflated Poisson,ZIP)回归模型。首先,我们对结构性零和ZIP模型做一个简要概述。然后我们以一项青春期少女艾滋病高危性行为的研究数据来阐述ZIP模型。文中还附有SAS和Stata的示例代码,以帮助运行和解释ZIP分析。

In-Plane and Out-of-Plane Mechanical Properties of Zero Poisson’s Ratio Cellular Structures for Morphing Application

Intelligent structures like zero Poisson’s ratio(ZPR)cellular structures have been widely applied to the engineering fields such as morphing wings in recent decades,owing to their outstanding characteristics including light weight and low effective modulus. In-plane and out-of-plane mechanical properties of ZPR cellular structures are investigated in this paper. A theoretical method for calculating in-plane tensile modulus,in-plane shear modulus and out-of-plane bending modulus of ZPR cellular structures is proposed,and the impacts of the unit cell geometrical configurations on in-plane tensile modulus,in-plane shear modulus and out-of-plane bending modulus are studied systematically based on finite element(FE)simulation. Experimental tests validate the feasibility and effectiveness of the theoretical and FE analysis. And the results show that the in-plane and out-of-plane mechanical properties of ZPR cellular structures can be manipulated by designing cell geometrical parameters.

On SS-quasinormal subgroups and the structure of finite groups

A subgroup H of a finite group G is said to be an SS-quasinormal subgroup of G if there is a subgroup B of G such that G = HB and H permutes with every Sylow subgroup of B. In this paper, we investigate the structure of a group under the assumption that every subgroup with order pm of a Sylow p-subgroup P of G is SS-quasinormal in G for a fixed positive integer m. Some interesting results related to the p-nilpotency and supersolvability of a finite group are obtained. For example, we prove that G is p-nilpotent if there is a subgroup D of P with 1 < |D| < |P| such that every subgroup of P with order |D| or 2|D| whenever p = 2 and |D| = 2 is SS-quasinormal in G, where p is the smallest prime dividing the order of G and P is a Sylow p-subgroup of G.

A CONSTITUTIVE EQUATION SATISFYING THE NULL CONDITION FOR NONLINEAR COMPRESSIBLE ELASTICITY

This paper constructs a polyconvex stored energy function, satisfying the null condition, for isotropic compressible elastic materials with given Lame constants. The difference between this stored energy function and St Venant-Kirchhoff's is a three order term.

Loop Algebras and Bi-integrable Couplings

A class of non-semisimple matrix loop algebras consisting of triangular block matrices is introduced and used to generate bi-integrable couplings of soliton equations from zero curvature equations.The variational identities under non-degenerate,symmetric and ad-invariant bilinear forms are used to furnish Hamiltonian structures of the resulting bi-integrable couplings.A special case of the suggested loop algebras yields nonlinear bi-integrable Hamiltonian couplings for the AKNS soliton hierarchy.

Algebraic Structure of Discrete Zero Curvature Equations and Master Symmetries of Discrete Evolution Equations

In this paper, based on a discrete spectral problem and the corresponding zero curvature representation,the isospectral and nonisospectral lattice hierarchies are proposed. An algebraic structure of discrete zero curvature equations is then established for such integrable systems. the commutation relations of Lax operators corresponding to the isospectral and non-isospectral lattice flows are worked out, the master symmetries of each lattice equation in the isospectral hierarchyand are generated, thus a τ-symmetry algebra for the lattice integrable systems is engendered from this theory.