Sound propagation in ducts with spatially variant parameters

The one-dimensional theory of sound propagation in ducts is generalized and investigated in this paper . It can be assumed that any duct system consists of two kinds of elementary structures : One is the piped structure in which the characteristics , such as the acoustical parameter on the interior surface of the wall , the cross-section area and the aerodynamic parameters of the flow , etc., will vary continuously and slowly with distance along the axis of the duct . The other is the local structure with discontinuity in which the characteristics will change abruptly. The acoustical properties of both structures are analysed in general cases based upon the fundamental equations of aerodynamics , and their transmission matrixes are derived and discussed respectively . Two typical examples are analysed and discussed .

Time variant multi-objective linear fractional interval-valued transportation problem

This paper studies a time-variant multi-objective linear fractional transportation problem. In reality, transported goods should reach in destinations within a specific time. Considering the importance of time, a time-variant multi-objective linear fractional transportation problem is formulated here. We take into account the parameters as cost, supply and demand are interval valued that involved in the proposed model, so we treat the model as a multi-objective linear fractional interval transportation problem. To solve the formulated model, we first convert it into a deterministic form using a new transformation technique and then apply fuzzy programming to solve it. The applicability of our proposed method is shown by considering two numerical examples. At last, conclusions and future research directions regarding our study is included.

A Novel CAPP System Based on SML for Variant Design of Process Planning

The production model of“multi-specification and low-quantity”is becoming the main trend of manufacturing industry.As a key activity in the manufacturing chain,traditional computer aided process planning(CAPP)system fails to adapt to the production model of customization.Therefore,a novel method for variant design of process planning was proposed to develop CAPP system based on Tabular Layouts of Article Characteristics(Sach-Merk Leisten in German and SML for short). With the support of standard database of master process planning documents which are developed by parameterization technique, and instance process planning for special product(instance product)can be generated automatically by the sub-system of variant de- sign of process planning.Finally,a CAPP system was developed for process design of rotor of steam turbine to validate the feasibil- ity and applicability of the method.

基于参数化的机床产品快速变型设计

在产品的概念设计过程中,融入参数化技术,实现大规模定制化产品的快速设计。针对机床产品,以UG为软件平台,结合VC++和SQLServer数据库开发机床产品参数化变型系统,并讨论从功能需求到结构参数模型的映射过程、主要结构特征尺寸参数化等关键技术,通过参数化实现产品级的机床快速变型设计。

基于参数化的产品变形设计建模研究与实现

通过对产品级的装配件产品的CAD模型进行层次性的分解和简化,对零部件的参数类型、参数取值范围、参数间的关联等进行分析,然后层次性地构建产品的变形设计模型,以数据库表保存变形设计模型参数,利用SolidEdge、SQLSever数据库和VC++开发了基于SolidEdge的变形设计系统。

基于时变可靠性的桥式起重机主梁参数化设计

为提高我国起重机产品的安全可靠性水平,根据桥式起重机的工作特点,针对静态可靠性方法在评估结构可靠度时没有考虑金属结构抗力和载荷效应随时间变化的情况,采用时变可靠性分析理论,结合Visual C++6.0开发环境中的MFC,集成ANSYS二次开发语言APDL,研发了桥式起重机主梁参数化建模设计软件,为桥式起重机主梁结构时变可靠性分析提供了一种可行的方法。经验证,时变模型能更好地反映结构的实际可靠度,同时也证明了时变模型的合理性。

基于SML的产品参数化工艺变型设计研究

为了满足市场产品多样化、客户个性化的要求,以及缩短产品设计和制造周期,提高产品设计效率和企业的市场竞争力,提出了基于SML的零件参数化工艺变型设计方法,引入减料几何特性与加工分步特征等概念,分析了基于SML的产品工艺变型设计技术及其实施方案,实践证明,研究结果达到了预期效果。

Uncertainty Assessment of Soil Erosion Model Using Particle Filtering

Recent advances in computer with geographic information system(GIS) technologies have allowed modelers to develop physics-based models for modeling soil erosion processes in time and space.However, it has been widely recognized that the effect of uncertainties on model predictions may be more significant when modelers apply such models for their own modeling purposes.Sources of uncertainty involved in modeling include data, model structural, and parameter uncertainty.To deal with the uncertain parameters of a catchment-scale soil erosion model(CSEM) and assess simulation uncertainties in soil erosion, particle filtering modeling(PF) is introduced in the CSEM.The proposed method, CSEM-PF, estimates parameters of non-linear and non-Gaussian systems, such as a physics-based soil erosion model by assimilating observation data such as discharge and sediment discharge sequences at outlets.PF provides timevarying feasible parameter sets as well as uncertainty bounds of outputs while traditional automatic calibration techniques result in a time-invariant global optimal parameter set.CSEM-PF was applied to a small mountainous catchment of the Yongdamdam in Korea for soil erosion modeling and uncertainty assessment for three historical typhoon events.Finally, the most optimal parameter sets and uncertainty bounds of simulation of both discharge and sediment discharge at each time step of the study events are provided.

高压开关产品3D零部件库系统的设计与开发

为了有效快捷地管理、重用零部件,并进行相应的信息集成和变形设计,笔者以GW-126型户外高压隔离开关为例,针对企业设计部门,研究并开发了基于C/S架构的多属性映射的零部件库系统,实现对零部件的有效分类、动态管理、信息集成及重用和变形设计。同时结合二次开发技术实现该系统与Inventor2008设计软件的无缝集成,提高系统的运行效率,大大提高了设计效率,缩短了产品开发周期。

机械产品参数化变型设计的工程图调优技术

针对模型参数化后自动生成的工程图视图布局较差、比例不合理、尺寸标注不整洁、线条繁杂、注释容易错位等缺点,根据企业给定的工程图模板及相应标准,研究了工程图模板创建与保存方法,视图遍历的方法,模型驱动后工程图视图布局、比例、特征尺寸、焊接符号、零件序号的调整方法。

自动渲染系统的变型设计研究

针对零部件手动渲染工作量大,工作时间长,且效率低;同时手动渲染时,对计算机的性能要求较高等问题,通过对三维模型结构树中特征成型的特点进行分析,提出了基于特征遍历的零部件自动渲染方法。集成变型设计中的参数化技术、模块化技术,开发了自动渲染系统。将系统应用于桥式起重机设计中,实现了桥式起重机的快速设计和自动渲染。

基于模型分析的汽车变速箱参数化变型设计方法

针对目前国内汽车变速箱变型研究存在的箱体结构复杂难以变型的问题,为了实现汽车变速箱的变型设计,提高企业生产效率,进行了汽车变速箱箱体的变型分析研究。通过结合特征模块化思想对汽车变速箱模型进行模块划分,对模块之间的位置关联以及变型参数进行分析研究,给出了汽车变速箱模型的分析方法,并系统地提出了基于模型分析的汽车变速箱参数化变型设计方法,实现了汽车变速箱的变型设计。通过实例应用表明此方法能有效实现汽车变速箱的变型设计,可为其他复杂零部件变型研究提供新思路。