复合材料迭层板铺层可靠性优化设计

飞机复合材料结构的壁板主要承受轴力和剪力。这两种外载之间存在一定的比例关系,因而是一个广义外载。文中以某一小展弦比复合材料多墙式翼面结构为例,据轴力和剪力的不同比值,对根部蒙皮的迭层板进行铺层可靠性优化设计。采用加速收敛梯度法得到广义外载作用下满足结构系统可靠度指标 R_s~*的主要约束条件和次要约束条件(最小层数比约束条件、±45°层均衡对称约束条件等)迭层板总重最小时的最优分层比例。通过算例证明本文提出的复合材料迭层板可靠性基础上的铺层优化设计方法是十分有效的。     

机床主轴箱多公比传动系统设计

为了在既不改变极限传动比又不增加结构复杂性的条件下,设计扩大主轴变速范围的主轴箱传动系统,本文对对称型和非对称型多公比传动系统的形成原理进行了详细论述,并给出了其数学公式,以供机床设计人员参考.     

子波分析在声辐射和声散射中的应用

文章提出将子波分析用于求解声学中的边界积分方程,能提高现有边界元方法解决工程问题的能力。在子波分析于声辐射和声散射的应用研究中,提出了把积分核函数用级数展开,建立频率响应函数计算的频率迭代技术,大大提高了频率响应函数的计算效率。讨论了子波分析在声学工程数值计算中的研究前景。     

Method of Prevention of Fracture of Welded Metal Structural Elements Subjected to Single Dynamic Loading

We propose a method for the assessment of the fracture toughness of structural materials and their welded joints under conditions of single dynamic loading, which is based on the criterion of nonlinear fracture mechanics _cr ^D . The regularities of the loading rate effect defined by the parameter ' (the rate of the crack tip opening displacement) on the fracture toughness have been established. A procedure is recommended for prevention of fracture of welded structure elements under conditions of high strain-rate deformation.     

Does Classicism Explain Universality?

One of the hallmarks of human cognition is the capacity to generalize over arbitrary constituents. Recently, Marcus (1998, 1998a, b; Cognition 66, p. 153; Cognitive Psychology 37, p. 243) argued that this capacity, called universal generalization (universality), is not supported by Connectionist models. Instead, universality is best explained by Classical symbol systems, with Connectionism as its implementation. Here it is argued that universality is also a problem for Classicism in that the syntax-sensitive rules that are supposed to provide causal explanations of mental processes are either too strict, precluding possible generalizations; or too lax, providing no information as to the appropriate alternative. Consequently, universality is not explained by a Classical theory.     

A Component-Based Debugging Approach for Detecting Structural Inconsistencies in Declarative Equation Based Models

Object-oriented modeling with declarative equation based languages often unconsciously leads to structural inconsistencies. Component-based debugging is a new structural analysis approach that addresses this problem by analyzing the structure of each component in a model to separately locate faulty components. The analysis procedure is performed recursively based on the depth-first rule. It first generates fictitious equations for a component to establish a debugging environment, and then detects structural defects by using graph theoretical approaches to analyzing the structure of the system of equations resulting from the component. The proposed method can automatically locate components that cause the structural inconsistencies, and show the user detailed error messages. This information can be a great help in finding and localizing structural inconsistencies, and in some cases pinpoints them immediately.     

A model of stage of change to recommend colonoscopy among urban primary care physicians.

Theory is little used in the prediction of physician cancer screening stage of change. Structural equation modeling was used to evaluate the theoretical predictors of stage of change to recommend colonoscopy among 235 urban physicians. Constructs from the theory of planned behavior, social-cognitive theory, and the transtheoretical model were systematically tested. As predicted, contextual factors, such as the physicians' ages, their race-ethnicities, patient race-ethnicity, and office-related barriers to preventive care were associated with stage of change through self-efficacy, normative beliefs, and negative behavioral beliefs. The findings demonstrate the relevance of these models to studying the behavior of physicians and support the development of interventions that are tailored to normative beliefs and specific physician cognitions for colonoscopy recommendation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Causal ordering of physical self-concept and exercise behavior: Reciprocal effects model and the influence of physical education teachers.

Does prior physical self-concept influence subsequent exercise behavior? On the basis of a large sample of physical education classes (2,786 students, 200 classes, 67 teachers) collected early (Time 1) and late (Time 2) in the school year, findings support a reciprocal effects model in which prior physical self-concept and exercise behavior both influence subsequent physical self-concept and exercise behavior. Whereas variables from the theory of planned behavior (TOPB; behavioral intentions, perceived behavioral control, exercise attitudes) also contributed to the prediction of subsequent exercise behavior, the effect of prior physical self-concept was significant for subsequent outcomes after controlling these variables, suggesting that the TOPB should be supplemented with self-concept measures. On the basis of multilevel models, there were systematic differences in these variables for students taught by different teachers that generalized over time and across different classes taught by the same teacher. Support for the reciprocal effects model was robust. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Planned missing data designs in psychological research.

The authors describe 2 efficiency (planned missing data) designs for measurement: the 3-form design and the 2-method measurement design. The 3-form design, a kind of matrix sampling, allows researchers to leverage limited resources to collect data for 33% more survey questions than can be answered by any 1 respondent. Power tables for estimating correlation effects illustrate the benefit of this design. The 2-method measurement design involves a relatively cheap, less valid measure of a construct and an expensive, more valid measure of the same construct. The cost effectiveness of this design stems from the fact that few cases have both measures, and many cases have just the cheap measure. With 3 brief simulations involving structural equation models, the authors show that compared with the same-cost complete cases design, a 2-method measurement design yields lower standard errors and a higher effective sample size for testing important study parameters. With a large cost differential between cheap and expensive measures and small effect sizes, the benefits of the design can be enormous. Strategies for using these 2 designs are suggested. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

BP人工神经网络隐层结构设计的研究进展

指出BP人工神经网络隐层结构的确定,尤其是隐层神经元数目的选择历来是研究的热点。针对目前解决这一问题尚缺乏严格的理论依据,设计者多凭经验而定,介绍了用来优化设计隐层结构的可行方法,纵览了现有多种设计研究成果,从而探讨了新的设计方向。分析了网络隐层结构优化问题的产生及其理论依据,对各种设计方法进行了详细的分类综述, 探讨各自的优势与不足,并对神经网络结构优化问题的研究和发展做了评述与展望。