基于基础结构法的柔顺机构可靠性拓扑优化

为了减少因制造和使用过程中的不确定性因素而导致的机构性能下降现象,提出一种新的基于基础结构法的柔顺机构可靠性拓扑优化方法。框架单元能够包含弯曲模式,因此采用它的集合来表示设计域。将作用载荷和结构几何尺寸视为随机变量,把机构的失效模式视为应变能和互应变能的串联系统。采用一次可靠度方法计算串联系统的失效概率。建立柔顺机构可靠性拓扑优化设计对偶数学模型,采用对偶算法对优化问题进行迭代求解。数值算例结果表明,提出的方法是正确和有效的;基于可靠性拓扑优化所得机构比确定性拓扑优化所得机构具有更好的性能。

基于基础结构法的柔顺机构动力学拓扑优化

提出一种新的在简谐激励作用下,基于基础结构法的柔顺机构动力学拓扑优化方法。框架单元能够包含弯曲模式,因此采用它的集合表示设计域。以动力放大系数最大化与应变能的最小化加权函数为目标,满足在动态条件下柔顺机构具有足够柔度和刚度;并且规一化目标函数避免不同性质目标函数的量级差异。目标函数的敏度采用伴随矩阵法求解,用移动近似算法对优化问题进行迭代求解。通过数值算例对不同外激励频率和不同输出刚度的拓扑优化结构进行分析讨论。结果表明,该方法在柔顺机构动力学拓扑优化设计中是正确的和有效的。

Hazard degree identification of goafs based on scale effect of structure by RS-TOPSIS method

In order to precisely predict the hazard degree of goaf(HDG), the RS-TOPSIS model was built based on the results of expert investigation. To evaluate the HDG in the underground mine, five structure size factors, i.e. goaf span, exposed area, goaf height, goaf depth, and pillar width, were selected as the evaluation indexes. And based on rough dependability in rough set(RS)theory, the weights of evaluation indexes were identified by calculating rough dependability between evaluation indexes and evaluation results. Fourty goafs in some mines of western China, whose indexes parameters were measured by cavity monitoring system(CMS), were taken as evaluation objects. In addition, the characteristic parameters of five grades' typical goafs were built according to the interval limits value of single index evaluation. Then, using the technique for order preference by similarity to ideal solution(TOPSIS), five-category classification of HDG was realized based on closeness degree, and the HDG was also identified.Results show that the five-category identification of mine goafs could be realized by RS-TOPSIS method, based on the structure-scale-effect. The classification results are consistent with those of numerical simulation based on stress and displacement,while the coincidence rate is up to 92.5%. Furthermore, the results are more conservative to safety evaluation than numerical simulation, thus demonstrating that the proposed method is more easier, reasonable and more definite for HDG identification.

Perception of the People of Tepoztlfin About Employment Since the Denomination of Magic Town

This article aims to describe the perception of the residents of Tepoztlan Morelos regarding the level of employment since their designation as Magic Town. Tepoztlan is a municipality in the northern part of the State of Morelos, located in the South-Central of Mexico. It is a magical town situated on the slopes of the Tepozteco Mountain. It is recognized as one of the most attractive places in the aforementioned state. Its relative proximity to Mexico City makes this town an attractive tourist destination for visitors. The importance of this issue lies mainly in the fact that tourism is one of the largest sources of income and employment generation for the country, so it is essential to strengthen the tourism infrastructure through federal programs of social participation, which promotes the development from the bottom to top. With that objective, the Mexican government created a federal program primarily with the purpose of contributing to the development of rural tourism. So, the ＂Magic Towns＂ program emerged as a strategy to generate resources for certain communities and increase the tourist offer. Tepoztlan was one of the first towns to enter the program, so it is relevant to analyze if the benefits generated by this program related to employment are perceived by the population. That is to say, to know the opinion of the settlers on the increase and the conditions of the employment that tourism generates and how the denomination of magical town influences this. Regarding the method used, we can say that it is a research with a quantitative approach, a questionnaire was designed as an instrument for data collection. The sample was obtained by the sampling method called： simple random probabilistic sampling. The results presented here correspond to a sample of 119 inhabitants of Tepoztlan. In summary, the research on this subject allows us to conclude that there is an increase in the generation of jobs in Tepoztl/m since its denomination as Magical Town; however, the working conditions and remuneration generated by tourism are perceived as low and far from the expectations of the population.

Constructions on Approximately Mutually Unbiased Bases by Galois Rings

Several new series of approximately mutually unbiased bases are constructed by using Gauss sums and Jacobi sums over Galois rings GR(p2, r), and the tensor method.

A composite insulation structure for silicon-based planar neuroprobes

Silicon-based planar neuroprobes are composed of silicon substrate,conducting layer,and insulation layers of SiO 2 or SiN membrane.The insulation layer is very important because it affects many key parameters of neuprobes,like impedance,SNR(signal noise ratio),reliability,etc.Monolayer membrane of SiO 2 or SiN are not good choices for insulation layer,since defects and residual stress in these layers can induce bad passivation.In this paper a composite insulation structure is studied,with thermal SiO 2 as the lower insulation layer and with multilayer membrane composed of PECVD SiO 2 and SiN as the upper insulation layer.This structure not only solves the problem of residual stress but also ensures a good probe passivation.So it's a good choice for insulation layer of neuroprobes.

Compliant mechanisms design based on pairs of curves

The success of compliant mechanism design by structural topology optimization approach depends,to a large extent,on its structural geometry representation scheme.In this work,a novel representation scheme based on pairs of curves is presented.In the representation,the structure is characterized by a set of input/output(I/O) regions.While it is still unknown how the rest of the design space will be occupied by the structure,the I/O regions must exist somewhere because any structure must have parts which interact with its surroundings by way of at least one loading region,one support region,and one output region.For a valid structural design,pairs of Bezier curves are used to connect I/O regions in order to form one single connected load-bearing structure.The boundary is explicitly described,so the need for smoothening of the blurred and jagged edges can be avoided by developing such a representation scheme to directly generate smooth boundary structures.With the scheme,shape and topology can be optimized simultaneously,and the obtained topology solutions have no check-board phenomena nor intermediate zones.A multi-objective genetic algorithm is then applied to couple with the representation scheme for defining and encoding the structural geometry in the form of graph.The solution framework is integrated with a nonlinear fixed grid finite element method(FG-FEM) code for large-displacement analyses of the compliant structures.Simulation results from a displacement inverter indicated that the proposed representation scheme is appropriate.