层板复合材料疲劳性能的唯象学研究模型及其应用

介绍了层板复合材料在疲劳载荷作用下的剩余强度衰退模型、剩余刚度衰退模型及剩余强度和剩余刚度的关系模型 ,给出了模型的实验验证实例 ,讨论了这些模型的应用范围及需要进一步研究的问题     

带市场选择的联合库存选址模型

假设存在一个有供应能力限制的供应商和一个需求量和收益都不确定的潜在需求市场集.选择进行服务的需求市场,然后根据风险分摊的效益原理,确定将哪些需求市场建立为配送中心,如何分配这些配送中心对其他被选择的需求市场进行服务.其目标为使损失的总收益、配送中心的建立成本、运输成本和库存成本之和最小.所以,构建了一个非线性的整数规划模型.由于该模型属于NP-Hard问题,因此提出了一种基于拉格朗日松弛和子梯度法的启发式算法,并通过算例对该算法进行了研究,得到的最优解的上下界相对误差最大不超过5%,大多数小于l%.     

重力式自动装料衡器检定方法的选择及误差计算

重力式自动装料衡器的应用已十分广泛,检定依据的规程是JJG 564—2002《重力式自动装料衡器》。规程的条款比其它衡器规程要多,检定记录和误差的计算相对复杂。     

如何选用数字电压表检定直流电位差计

本文分析了运用数字电压表检定直流电位差计基本误差的可行性，对提高检定工作效率起了积极的作用。     

线性回归模型的Boosting变量选择方法

针对线性回归模型的变量选择问题,本文基于遗传算法提出了一种新的Boosting学习方法.该方法对每一训练个体赋予权重,以遗传算法作为Boosting的基学习算法,将带有权重分布的训练集作为遗传算法的输入进行变量选择.同时,根据前一次变量选择效果的好坏更新训练集上的权重分布.重复上述步骤多次,最后以加权融合方式合并多次变量选择的结果.基于模拟和实际数据的试验结果表明,本文新提出的Boosting方法能显著提高传统遗传算法用于变量选择的质量,准确识别出与响应变量相关的协变量,这为线性回归模型的变量选择提供了一种有效的新方法.     

极值分布下联合位置与散度模型的变量选择?

极值分布在地震、洪灾和其它自然灾害的预测中是非常有用的.在许多应用方面,很有必要对散度建模.本文推广经典极值回归模型,研究了联合位置与散度模型,并提出了一种同时对位置模型和散度模型的变量选择方法.同时证明了惩罚极大似然估计具有相合性和 oracle 性质,通过随机模拟研究了所提出方法的有限样本性质.     

A Feature Selection Algorithm for the Regularization of Neuron Models

This paper presents a novel training method for estimating the parameters of retina models, such as integrate-and-fire (IF) or Poisson based. The presented models are constructed using a set of linear and nonlinear filters, which are described by basis functions and Taylor polynomials, respectively. This approach allows for the identification of a set of features that can be used for reproducing retina responses. By using the Bayesian-Laplace feature selection algorithm herein proposed, an efficient model with a reduced set of parameters is achieved. Experimental results show that the proposed algorithm is able to remove unimportant features while still accurately reproducing retina responses. These results also show that the IF model is able to mimic the retina visual processing system using less parameters than the Poisson-based model.     

Phenomenological Theory of Pyroelectricity

In pyroelectric materials there is a spontaneous dielectric polarization.When raising the temperature,then a voltage appears in the system.In the present manusc...     

三峡工程水电站压力管道和蜗壳技术结构型式的选择及论证

长江三峡水利枢纽工程建设中重大技术问题的决策是建立在大量科学试验和专家论证的基础上，三峡工程水电站压力管道和蜗壳技术结构型式的选择不仅是重大的技术经济问题，也是关系水电站长期运行问题，文章介绍了三峡工程水电站压力管道和蜗壳技术型式选择及决策。     

纵向数据下部分线性EV模型的变量选择

本文考虑了纵向数据下部分线性EV模型的变量选择问题,采用SCAD惩罚方法提出了一个变量选择过程.通过选择适当的惩罚参数,证明了该变量选择过程可以相合地识别出真实模型,并且所得的正则估计具有Orcale性质.最后模拟研究了所提出方法的有限样本性质.     

Phenomenological features of diaphragm discharge

Flame formations of relatively little-studied diaphragm discharge in water at low energy of discharge (up to 10 J) are investigated. Its particular features show up in the fundamental difference in shape between the anode and cathode flames on both sides of the diaphragm, in the difference in variation of their shape and size with the variation of electrical conductivity of the medium, in polar development of flames from the diaphragm to their electrodes, in the possibility of existence of “half-breakdowns”, and in the difference between them depending on polarity, in a special form of cathode breakdown.     

Phenomenological theory of elastic semiconductors

A conceptually simple but nonetheless nonlinear, rotationally invariant and thermodynamically admissible, phenomenological theory of elastic semiconductors is presented. The primitive nonlinearity is essential in that it guarantees the obtaining of a consistent set of linearized equations about a bias state, a fact overlooked practically by all previous authors. Nonlinear representations are obtained for all effects of importance in elastic semiconductors (elasticity, electromechanical couplings, galvanomagnetic, thermoelectric and thermomagnetic effects, elastoresistance and magnetoresistance). In particular, generalized Ohm's and Fourier's laws are obtained in which gradients of the chemical potential associated with charge carriers and the conduction current play a crucial role. Upon linearizing the nonlinear field and constitutive equations about a rigid-body stationary solution (which is nonetheless endowed with initial electromagnetic fields and internal stresses) by means of the so-called Lagrangian variation, a complete set of bulk and surface electroacoustic equations is obtained for elastic piezoelectric semiconductors in which the influence of the initial electric and magnetic fields is duly recognized. In particular, these fields greatly complicate the picture (stiffening of material coefficients, breaking of material symmetry, allowance for further electromechanical couplings, etc.) although, for the sake of simplicity, they are assumed to vary much more slowly over space than the small dynamical fields superimposed on them. The equations thus obtained provide a general framework for the study of the coupling and excitation of both bulk and surface displacement and charge modes which can be controlled through the intensity and direction, as also through the frequency, of the bias fields.     

Phenomenological model of contact slip

Summary A constitutive model of the contact zone is proposed, accounting for dilatancy, elastic compliance, hardening and softening phenomena, and also hysteresis effects. Some model predictions are discussed in view of available experimental data.     

JJG 882-2019《压力变送器》检定规程对标准器的要求及选择

压力变送器是将压力变量转换为可传输的标准信号进行传输的仪表.能够将现场作业的压力模拟量转换为长距离传输便于观测控制的数字量,在生产企业中有着广泛的使用,具有不可代替的优势.JJG 882-2004压力变送器检定规程编写至今已经有16年了,[1]因时代发展和技术进步,很多内容已经不适应当前市场环境的要求,新规程在压力变送...