二次损失下带线性等式约束的多元线性模型中线性预测的可容许性

本文在二次损失下研究了带线性等式约束条件的多元线性模型中条件线性可预测变量的可容许线性预测,并分别在齐次线性预测和非齐次线性预测类中得到了条件线性可预测变量的一个线性预测是可容线性预测的若干充要条件.     

带线性不等式约束的线性模型中线性预测的可容许性

本文刻画了线性模型在线性不等式约束条件下的线性预测的可容许性。我们给出了条件线性可预测变量和线性不等式约束条件下可容许预测的定义,在二次损失函数下,讨论了齐次和非齐次线性预测可容许性的关系,得到了条件线性可预测变量的线性预测是可容许线性预测的充要条件。     

线性隐写码的性质与构造

本文从隐写术的安全性需求出发抽象出一个新的编码问题,称之为隐写码。利用线性空间的直和分解得到了一种线性隐写码的构造方法。通过引入线性空间t阶维数的概念将线性隐写码问题转化成了一个代数问题,从而得到了线性隐写码长度的上界,并由此定义了最大长度可嵌入码。证明了线性最大长度可嵌入码与线性完备纠错码有1-1对应关系。     

制冷线性压缩机关键技术及发展现状

随着技术的发展,线性压缩机技术的应用逐渐从军工、航天、生物医药领域转向民用领域,应用范围扩大,技术研发增强。为了使科研人员对线性压缩机关键技术和发展现状有所了解,介绍了线性压缩机直线电机技术、线性压缩机润滑技术、线性压缩机控制技术和线性压缩机活塞及阀门布局四大技术,详细分析比较了线性压缩机直线电机的三种结构、线性压缩机有油润滑和无油润滑的优缺点、线性压缩机各种控制技术的特点、线性压缩机活塞单双侧布局和阀门三种布局的结构方式,并对线性压缩机的性能、发展现状进行了简要论述。     

矩阵损失下线性混合模型中的局部线性Minimax估计

本文研究了一般线性混合模型中固定效应和随机效应的线性组合的Minimax估计问题.在矩阵损失函数下,考虑了这个组合的线性估计在线性估计类中的局部极小极大性.关于适当的假设,得到了线性可估函数的唯一局部线性Minimax估计.     

周期二元序列的线性复杂度及其稳定性分析

密码学意义上强的序列不仅应该具有高的线性复杂度而且其线性复杂度必须稳定,k-错线性复杂度用来反应线性复杂度的稳定性。本文基于x~(p~(m_2~n))-1在GF(2)上具有明确的分解式,研究了p~(m_2~n)-周期二元序列的线性复杂度和k-错线性复杂度之间的关系,然后说明了同时使得线性复杂度和k-错线性复杂度都达到最大值的p~(m_2~n)-周期二元序列是存在的。这里p是一个奇素数,2是模p~2的本原根。     

一般增长曲线模型中随机回归系数线性估计的可容许性

本文在矩阵损失下研究了一般增长曲线模型中随机回归系数线性估计的可容许性。分别在齐次线性估计类和非齐次线性估计类中得到了随机回归系数的一个线性估计是可容许的充要条件。     

泛论线性声源阵列扬声器系统与应用（1）

根据目前社会上针对线性声源阵列扬声器系统的一些问题,从线性声源阵列扬声器起源开始,对于线性声源阵列扬声器系统的译名与定义;线性声源阵列扬声器系统的基本特性;线性声源阵列扬声器的应用等方面展开讨论,希望能够通过广泛的探讨。辨析线性声源和线性声源阵列扬声器系统的真实原意。本文不过分专注理论推导,只是选用部分有关测试数据和实用经验展开分析。力求减少一些片面的宣传和误导的影响,对实际应用和扬声器制造提供一些有限的帮助。     

形状记忆合金线性回复性能及其计算机辅助测试系统

提出了形状记忆合金线性回复行为的新概念,定义了评价线性回复行为的性能指标.介绍了形状记忆合金弹簧线性回复性能的计算机辅助测试系统.简略介绍了采用常规热处理和稀土表面化学热处理的方法,对TiNi形状记忆合金线性回复性能的影响.     

输入存贮线性有限自动机积的讨论

本文刻画了输入存贮线性有限自动机本身结构矩阵的特点,证明了两个输入存贮线性有限自动机作积(后并、全直积、化合)之后仍然是输入存贮线性有限自动机,给出了两个输入存贮线性有限自动机作积之后的结构矩阵、自由响应生成矩阵、传输函数矩阵和原来两个输入存贮线性有限自动机的结构矩阵、自由响应生成矩阵、传输函数矩阵的关系.得出线性有限自动机M具有r阶输入存贮的等价命题.     

采用压痕实验确定线性强化弹塑性材料的弹性模量

利用有限元分析,该文尝试将双锥形压头压痕实验确定幂强化材料力学特性的方法应用于线性强化材料弹性模量的识别。研究发现,得到的弹性模量的误差与弹性模量和屈服极限的比值及线性强化参数m之间有密切的关系:弹性模量与屈服极限的比值小于45.4时,弹性模量的识别误差很小,可以认为识别结果不受材料线性强化特性的影响;弹性模量与屈服极限的比值大于45.4时,在线性强化参数m满足文中给定的条件时,可以认为识别结果不受材料线性强化特性的影响。     

Fluid–structure interaction modeling of a patient-specific cerebral aneurysm: influence of structural modeling

Fluid–structure interaction (FSI) simulations of a cerebral aneurysm with the linearly elastic and hyper-elastic wall constitutive models are carried out to investigate the influence of the wall-structure model on patient-specific FSI simulations. The maximum displacement computed with the hyper-elastic model is 36% smaller compared to the linearly elastic material model, but the displacement patterns such as the site of local maxima are not sensitive to the wall models. The blood near the apex of an aneurysm is likely to be stagnant, which causes very low wall shear stress and is a factor in rupture by degrading the aneurysmal wall. In this study, however, relatively high flow velocities due to the interaction between the blood flow and aneurysmal wall are seen to be independent of the wall model. The present results indicate that both linearly elastic and hyper-elastic models can be useful to investigate aneurysm FSI.     

Slepian simulation of distributions of plastic displacements of earthquake excited shear frames with a large number of stories

The object of this study is a stationary Gaussian white noise excited plane multistory shear frame with a large number of rigid traverses. All the traverse-connecting columns have finite symmetrical yield limits except the columns in one or more of the bottom floors. The columns behave linearly elastic within the yield limits and ideally plastic outside these without accumulating eigenstresses. Within the elastic domain, the frame is modeled as a linearly damped oscillator. The white noise excitation acts on the mass of the first floor making the movement of the elastic bottom floors simulate a ground motion that interacts with the structure above the bottom floors. As in a recent work by the authors, the paper is about application of the so-called Slepian model simulation, but in this paper supplemented by a simplification principle that allows a manageable calculation for the considered type of elasto-plastic oscillator also when it has a large number of elasto-plastic columns.     

The anti-plane shear problem of debonding of two solids made of power law hardening materials

Debonding of two different solids made of power law hardening materials is studied for the case of anti-plane shear loading mode by using an interface crack model. The stresses and the stress intensity factor at the interface crack are determined analytically. Using these analytical results, the constitutive equations by Hencky–Ilyushin and the general equation of energy in the neighborhood of the crack tip, the adhesion energy for the loading mode under consideration is found analytically. It can be observed that for the particular case of two linearly elastic materials and a homogeneous linearly elastic material the solution found here is in excellent agreement with the solutions found in the literature.     

A theory for physically nonlinear elastic fiber-reinforced composites

A three-dimensional constitutive relationship for the fiber-reinforced composite with a nonlinearly elastic matrix material is derived. The composite is modeled by a medium consisting of thin nonlinear matrix layers alternating with effective linearly elastic fibrous layers. Shear wave propagations are investigated. The formation of shock wave, its stability and growth behaviors are discussed.     

Universal theorems for total energy of the dynamics of linearly elastic heterogeneous solids

In this paper we consider a sample of a linearly elastic heterogeneous composite in elastodynamic equilibrium and present universal theorems which provide lower bounds for the total elastic strain energy plus the kinetic energy, and the total complementary elastic energy plus the kinetic energy. For a general heterogeneous sample which undergoes harmonic motion at a single frequency, we show that, among all consistent boundary data which produce the same average strain, the uniform-stress boundary data render the total elastic strain energy plus the kinetic energy an absolute minimum. We also show that, among all consistent boundary data which produce the same average momentum in the sample, the uniform velocity boundary data render the total complementary elastic energy plus the kinetic energy an absolute minimum. We do not assume statistical homogeneity or material isotropy in our treatment, although they are not excluded. These universal theorems are the dynamic equivalent of the universal theorems already known for the static case [Nemat-Nasser and Hori, 1993] and [Nemat-Nasser and Hori, 1995]. It is envisaged that the bounds on the total energy presented in this paper will be used to formulate computable bounds on the overall dynamic properties of linearly elastic heterogeneous composites with arbitrary microstructures.     

A theory of acoustic measurement of the elastic constants of a general anisotropic solid

An acoustic wave approach is presented for the measurement of the twenty-one independent elastic constants of the most general linearly elastic anisotropic solid. The method requires that one be able to measure the density of the material, the velocities of the three modes of wave propagation in each of six directions, and the particle displacements associated with each of those modes.     

Manganese contributions to the elastic constants of face centred cubic Fe-Cr-Ni stainless steel

We determined experimentally the effect of manganese on the elastic constants of face centred cubic Fe-Cr-Ni alloys with chemical compositions near 304-type stainless steel. By a pulse-echo-overlap method, longitudinal and transverse soundwave velocities were determined in ten alloys containing up to 6% manganese. All the elastic stiffnesses decrease linearly with increasing manganese. The bulk modulus decreases most strongly. Poisson's ratio changes least. We consider what the elastic constants reveal concerning changes in chemical bonding, caused by manganese additions.     

Strength and elastic modulus of a porous brittle solid: An acousto-ultrasonic study

The strength and elastic modulus of a porous brittle solid such as gypsum have been studied using an acousto-ultrasonic technique. Acousto-ultrasonics has been found to be a sensitive indicator of strength and porosity which are linearly related to some powers of a stress wave factor. New equations for porosity dependence of ultrasonic velocity, elastic modulus and strength of brittle solids have been proposed.     

Convergence problems in the theory of random elastic media

A main result of the rigorous theory of random, linearly elastic media consists in the representation of the tensor of effective elastic moduli as a Neumann type infinite series which contains the infinite set of correlation functions of the distribution of the local elastic moduli. Under the restriction to statistically homogeneous and isotropic finite media it is proved that convergent series can always be obtained provided the local elastic moduli remain finite everywhere in the medium. This means that the mentioned theory cannot be applied in the above mentioned form to media with pores and/or rigid inclusions. It also means that the theory is not restricted to media with small fluctuations of the elastic parameter.