面向大规模定制的产品设计的一种模型

 大规模定制 (MassCustomization)环境下对产品设计的基本要求是模块化,通过模块化构件重组快速设计个性化产品,这对传统的产品设计方式提出了挑战。给出一种大规模定制环境下的产品设计模型,通过逐层分解产品的物料清单 (BOM)和工序集,动态计算个性化产品的最终物料清单、工艺路线以及对相应生产资源的需要,并且这种产品设计模型符合适合准时制 (JustInTime)生产方式的需要。     

基于气/固耦合非定常流动的叶栅颤振分析

采用二维N-S方程／结构振动方程组耦合数值方法，分析计算了二维非定常气动力强迫振动条件下振动能量及气动力对叶栅所做的功，分别根据振动能量和气动力做功分析了叶栅的颤振特性。NACA0012和PROF叶栅在不同折合频率下气动参数随时间的变化表明，折合频率是影响叶栅颤振的重要因素。气固耦合方法得到的NA-CA0012叶栅颤振折合频率比非耦合的结果高，而对PROF叶栅则相反。这表明叶栅结构动力参数对其发生颤振时的折合频率影响很大且很复杂，要准确预测颤振应该考虑叶栅结构动力与气动力的耦合因素。     

WTO背景下中国证券市场国际化

证券市场国际化是20世纪80年代以来世界金融市场的一大发展趋势,是生产国际化和资本国际化发展的必然结果,也是国际融资证券化趋势的必然要求.但是我国的证券市场国际化存在着诸多障碍,特别是我国加入WTO后更是面临严峻的挑战.然而机遇与挑战同在,我们应该抓住机遇,在坚持循序渐进地开放证券市场的原则下,大力发展我国证券市场,加速证券市场国际化.文章以我国证券市场的发展为主线,对WTO背景下我国证券市场国际化问题进行了探析.     

房地产调控的政策导向及其市场走势

2006年是我国房地产宏观调控政策出台最多和调控力度最大的一年，文章就调控后的房地产业的政策环境、市场情况、价格走势和消费心态等进行了深入的研究并对我国2007年房地产走势进行了相关分析，认为随着国家对土地资源的严格控制，土地出让制度的逐步规范，房地产市场供需矛盾出现两极分化态势；房地产宏观调控也会对自住者、投资者、中介、银行和开发商产生不同的影响，中国房产市场将在调控中稳定、持续、健康发展。     

甲烷点火燃烧的简化化学反应动力学模型

1引言超燃发动机的燃烧室是整个超燃发动机研究的关键所在,有效缩短碳氢燃料的点火延迟时间,提高点火性能,对于缩短发动机长度、减轻发动机重量、提高其性能具有极其重要的意义[1]。碳氢化合物的燃烧是一个很复杂的化学过程,以甲烷为例[2],描述其详细燃烧反应机理的GR I-Mech化     

飞机结构健康监测与管理技术研究进展和展望

飞机结构是飞机平台的基础,是确保飞机安全、长寿命使用的最重要的承力架构.随着航空技术的不断发展,飞机设计思想不断演变发展,对飞机机体结构性能也不断提出更高的要求.严酷的使用环境和严格的功能/性能综合要求,使得结构完整性面临重大挑战.飞机结构健康监测与管理技术具有实时性、在线性等优势,是保证结构安全性、降低维护费用的重要...     

基于闭环电流平均值法的永磁同步电机谐波抑制方法

由于逆变器的非线性及永磁同步电机(PMSM)的气隙磁场畸变,在运行过程中PMSM定子电流中含有大量的谐波分量,导致电流波形发生畸变,从而引起较大的转矩脉动。针对传统谐波抑制方法采用低通滤波器(LPF)提取5、7次谐波分量,动态响应时间长,稳态误差大的问题,提出了闭环电流平均值法提取谐波分量。仿真结果表明,闭环电流平均值法可以提高系统的快速性和稳定性。将电流平均值法应用于PMSM谐波抑制系统,仿真结果表明:基于闭环电流平均值法的谐波电压注入法可以降低电流波形的畸变率及5、7次谐波含量。     

A new error-controllable method for smoothing the G01 commands

In real machining, the tool paths are composed of a series of short line segments, which constitute groups of sharp corners correspondingly leading to geometry discontinuity in tangent. As a result, high acceleration with high fluctuation usually occurs. If these kinds of tool paths are directly used for machining, the feedrate and quality will be greatly reduced. Thus, generating continuous tool paths is strongly desired. This paper presents a new error-controllable method for generating continuous tool path. Different from the traditional method focusing on fitting the cutter locations, the proposed method realizes globally smoothing the tool path in an error-controllable way. Concretely, it does the smoothing by approaching the newly produced curve to the linear tool path by taking the tolerance requirement as a constraint. That is, the error between the desired tool path and the G01 commands are taken as a boundary condition to ensure the finally smoothed curve being within the given tolerance. Besides, to improve the smoothing ability in case of small corner angle, an improved local smoothing method is also proposed by symmetrically assigning the control points to the two adjacent linear segments with the constrains of tolerance and G3 continuity. Experiments on an open five-axis machine are developed to verify the advantages of the proposed methods.     

低温推进剂集成管理技术的发展与启示

低温推进剂集成管理技术(IVF)是实现上面级等航天器长期在轨的新技术思路。通过将液氢液氧长期在轨产生的蒸汽与内燃机技术结合,实现贮箱增压、排气、姿控、沉底、发电功能一体化,减小航天器系统质量,增强任务灵活性。回顾了IVF模块设计的发展过程,探讨了IVF的技术优势,与燃料电池技术、蒸发量控制技术对比分析了IVF技术的使用范围及不足,提出了研究气氢气氧内燃机技术、IVF模块方案设计、系统仿真等关键技术的建议,并展望了其应用前景。     

An Elasticity Model Considering Grain Boundaries and Tensile Orientations for Directionally Solidified Superalloys

In order to investigate the elastic properties of directionally solidified(DS)superalloys,an elasticity model called boundaries elastic model(GBE model),considering grain boundaries and tensile orientations,is proposed in this paper. Two assumptions are adopted in the GBE model:(1)The displacement of grains,which moves along the perpendicular direction,is restricted by the grain boundaries;(2) Grain boundaries influence region(GBIR) is formed around the grain boundaries. Based on the single crystal(SC)calculation method of elastic properties,the GBE model can well predict macroscopic equivalent elastic modulus(Young's modulus)of DS superalloys under different tensile orientations effectively. To demonstrate the correctness of the GBE model,3 D finite element simulation is adopted and tensile experiments on a Ni3 Al-base DS superalloy(IC10)along five tensile orientations are carried out. Meanwhile,the grain boundaries are observed by light microscopy and transmission electron microscope(TEM). Therefore,the GBE model is proved to be feasible by comparing the simulated results with the experiments.