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901.
在新装备测试指标选取过程中,由于列装时间短,测试样本少,测试条件不足,通常选取工作无据可依。通过分析层次分析法、Dijkstra法、粗糙集法的优缺点,提出一种基于层次分析法、群组G1法和信息熵理论的指标多准则选取方法,将指标按几个基本准则两两比较获得原始数据,用群组G1法通过专家评判和信息熵法分析原始数据来确定评价准则的权值,最后对原始数据进行加权来对指标进行权重判断。文章结尾给出一个实际算例。方法依赖于两两比较数据,具有一定客观性,且无需进行样本测试,简化了指标选取工作。 相似文献
902.
The studies of conductivity behavior of composite polymeric electrolytes (CPE) have been widely realized for about 15 years. There is, however, a lack of a versatile and efficient model of conductivity in these systems. The effective medium approach was introduced to predict the conductivity of systems according to some previously defined mixing rules. The main limitation of this method, however, is the fact that each new composite microstructure forces a new mixing rule development. This paper presents the random resistor network approach as an alternative method to the effective medium theory based approach. The presented comparison of both methods is based on both dc and ac simulated conductivity data. Some experimental data are introduced to compare the models with the conductivity values obtained for real samples. 相似文献
903.
An analytical expression for the thermal efficiency of evaporative heat loss and heat transfer for a open- and closed-cycle systems of floating tilted wick solar stills in terms of system design and climatic parameters has been derived. The expression for open- and closed-cycle systems was validated by performing experiments for both systems. Optimization of the design of the still for evaporative cooling (open cycle) and the distillation unit (closed cycle) was obtained using the derived analytical expression for large-scale installation. Numerical calculations were also carried out for a typical summer day at the Sri Ramakrishna Mission Vidyalaya College of Arts and Science, Coimbatore, India, to predict the performance of the still. 相似文献
904.
A new procedure has been developed for the determination of specific filter cake resistance from experimental filtration data. Unlike the conventional procedure which treats constant-pressure filtration data through the t/V vs. V plot and yields a single value of the average specific cake resistance (αav) from a given experiment, this new procedure allows the establishment of the relationship of αav vs. the cake compressive stress (ps) over a range of ps values. Results from the new procedures were compared with those obtained from the procedure based on the t/V vs. V plot as well as those from compression-permeability (C-P) measurements. Discussions on the possible improvement of the new procedure are also presented. 相似文献
905.
Examines the equilibration theory of Piaget (learning vs development, stage transitions) to make more explicit the methodological foundations of B. Inhelder et al (1974). In this connection, the "problem-solving" learning method used by these authors is analyzed by means of the new concept of "learning loops." Similarly, the successful equilibration learning method used by M. Lefebvre and A. Pinard (1974) is analyzed and shown to involve executive facilitation and chunking (coordination) of 2 crucial schemes. A process-structural model of conservation acquisition previously developed by the present author, and its empirical tests by R. Case (1975) and by G. M. Parkinson (1975), are used to illustrate and to empirically support the process-structural differences theoretically found between these 2 equilibration methods. (54 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
906.
协调作为一个重要的概念广泛地出现在多个学科和社会经济领域,成为广大学者共同关注的一个研究课题。目前对于协调问题中依赖关系及协调策略的研究,多是做定性的表述,给出的一般都是非形式化的描述,这样不利于协调问题在计算机上的表述,难以实现协调问题的计算机求解。针对这一问题,利用形式化和图形化的建模工具Petri Nets对协调问题中的依赖关系进行研究,提出任务之间的依赖关系可以分为两类,基于资源的依赖关系和基于时间的依赖关系,并用Petri Nets对这些依赖关系进行了表述,为协调问题的可计算描述提供了一种新的思考角度。 相似文献
907.
基于模糊灰色理论液压压桩机工作可靠性评价方法 总被引:1,自引:0,他引:1
液压静力压桩机是一种大型桩基础施工设备,其工作可靠性问题十分重要,由于其各影响因素之间存在灰色模糊特征,传统评价方法很难对其进行正确的评价。本文利用模糊灰色理论,构建了基于模糊灰色理论静力压桩机工作评价可靠性模型,经过试验研究证明利用该方法对静力压桩机进行评价,其评价精度、可靠性较传统方法显著提高。 相似文献
908.
909.
薄壁箱型结构位移参数的动态Bayes随机估计 总被引:3,自引:0,他引:3
应用薄壁箱型结构的有限条控制方程,建立了薄壁箱型结构位移参数的动态B ayes误差函数和相应的动态B ayes均值及方差表达式.利用迭代步长的一维自动寻优方案,结合共轭梯度法研究了薄壁箱型结构位移参数的动态B ayes估计方法.通过典型算例分析,获得薄壁箱型结构位移参数先验信息准确性判定方法及结构位移参数动态B ayes随机估计的相关结论. 相似文献
910.
Ümit Sönmez 《International Journal of Mechanics and Materials in Design》2006,3(4):347-360
Buckling dynamics of a pinned-pinned flexible imperfect beam attached to a sliding mass is investigated using nonlinear Elastica
theory. Initially straight flexible buckling beam having pinned end boundary conditions loaded at one of its end with curved
imperfection is considered. Large deflection analysis of flexible beam is studied using nonlinear Elastica theory. Imperfection
analysis of the flexible beam is investigated considering the imperfection as an initial curvature. The governing differential
equations are expressed in terms of nonlinear functions that are typical of flexible beams, generally leading to highly implicit
relationships involving elliptic integrals and functions. Dynamic simulation of the flexible beam is studied using numerical
simulation procedures with various types of loading (step, ramp, and sinusoidal) assuming this member buckles in its first
mode. Dynamic response of the imperfect buckling Elastica has been obtained by using numerical Runge-Kutta methods. Load deflection
characteristics of flexible beams are presented in polynomial curve fits. The polynomial curve fits obtained from nonlinear
inextensible exact beam theory may then be used as the nonlinear lumped system stiffness. The buckling Elastica may find applications
in compliant mechanism design. The motivation behind this research is not only to present the dynamic behavior of the buckling
beam considering the magnitude of the imperfection but also to provide a tool to design new types of compliant mechanisms.
Original compliant mechanism designs are presented demonstrating where the buckling dynamics of imperfect Elastica or flexible
curved beams might be needed in mechanism design and synthesis. 相似文献