R410A冷凝器性能的仿真

以往通过经验公式法对空调器性能进行仿真,只在局部范围内精度较高,本文通过分段多项式法对替代工质R410A进行了物性计算.仿真结果精度较高,误差小于2%,且适用范围广.     

Design and analysis of a class of redundant collaborative manipulators with 2D large rotational angles

The parallel spindle heads with high rotational capability are demanded in the area of multi-axis machine tools and 3D printers. This paper focuses on designing a class of 2R1T (R: Rotation; T: Translation) parallel spindle heads and the corresponding collaborative 5-axis manipulators with 2-dimension (2D) large rotational angles. In order to construct 2D rotational degrees of freedom (DOFs), a platform with 2D revolute joints is proposed first. Based on the constraint screw theory, the feasible limbs that can be connected in the platform are synthesized. In order to provide constant rotational axis for the platform, a class of redundant limbs are designed. A class of redundant 2R1T parallel spindle heads is obtained by connecting the redundant limbs with the platform and the redundant characteristics are verified by the modified Grübler-Kutzbach criterion. The corresponding 5-axis collaborative manipulators are presented by constructing a 2-DOF series translational bottom moving platform. The inverse kinematics and the orientation workspace as well as the decoupling characteristics of this type of 2R1T parallel spindle heads are analyzed. The results show that these manipulators have large 2D rotational angles than the traditional A3/Z3 heads and can be potentially used in the application of multi-axis machine tools and the 3D printers.     

Ti-50.8%Ni形状记忆合金R相区力学性能研究

对Ti-50．8％Ni形状记忆合金丝进行了不同预变形量处理和不同温度的时效，研究了合金力学性能和预变形量、时效温度之间的关系。结果表明：时效温度和预变形量对NiTi合金的强度影响很大，经适当的预变形和时效后NiTi合金的屈服强度降低，抗拉强度增大。测试表明10％预变形 500℃时效的合金丝室温组织为R相。     

在Auto CAD R14中创建标准件图形库

利用 Auto CAD R14绘图软件将机械工程中常用的标准件 ,如螺钉、螺母、垫圈等制做成标准图形 ,并集成一个图形文件库。然后制做成图标菜单或工具条 ,以解决工程技术人员在制图中重复性绘图造成的浪费 ,提高其绘图的工作效率     

基于ObjectARX的产品参数化设计与绘图

提出了面向功能的产品参数化设计思想 ,利用 Auto CAD的二次开发工具Object ARX实现设计与绘图的一体化 ,并成功地应用于锅炉水冷壁参数化设计绘图中。     

多因素作用下钢筋混凝土构件氯离子扩散系数模型

通过对钢筋混凝土氯离子侵蚀机理的分析,在Fick第二扩散定律基础上,建立了综合考虑水灰比、湿度、时间、温度、混凝土材料对氯离子结合作用等多因素作用下的氯离子侵蚀模型,并给出了考虑边界条件的侵蚀模型数学解.通过对长期现场暴露试验数据分析,验证了该侵蚀模型的有效性和可靠性.与传统的Fick第二扩散定律模型对比并分析得:该模...     

河南省民政厅综合办公楼数码多联空调工程设计

本文着重介绍了数码涡旋技术在商用办公楼的设计及应用,该工程能在一年四季提供稳定的制冷和制热,充分体现数码涡旋技术的广泛适用性、节能可靠性、控制便利及精确性,具有安装和后期维护简单方便等突出优点。     

奥宇钢框胶合板模板开发与工程应用

介绍了北京奥宇模板有限公司开发的钢框木胶合板模板的技术特点,并对该模板体系在国家体育场工程和哈萨克斯坦国MAG工程中的应用情况进行了简要介绍。     

Performance studies of R433A in a direct expansion solar-assisted heat pump

ABSTRACT

Energy assessment of a simple direct expansion solar-assisted heat pump system has been experimentally assessed with R433A as a possible alternative to R22. An artificial neural network integrated genetic algorithm model was developed to assess the performance system. The data obtained from the experimentation at different ambient conditions are used as the training data for the ANN network. The back propagation learning mechanism with variants Lavenberg-Maguardt with 20 neurons in the hidden layer were used in modelling of ANN. The values obtained from the analysis using ANN are optimised further by integrating the ANN procedure with GA. The results indicated that R433A has 6.4% and 1% lower instantaneous compressor power consumption and heating capacity compared to R22. Energy performance ratio of R433A was found to be about 5.67% higher compared to R22. The results confirmed that R433A can be used as a possible alternative to R22 DX-SAHP systems.     

Alternative approaches to trip distribution modelling: A retrospective review and suggestions for combining different approaches

Abstract.  Various alternative approaches are available in the literature for modelling trip distribution. The objective of this paper is to provide a review of this literature with the view of summarising the general nature of the current state of practise and what is now available for practical modelling work. Both aggregate and disaggregate destination choice models are considered, a classification of them will be proposed and suggestions for further research will be given as well. One outcome of this review is that significant contributions are emerging from mixed models (e.g., gravity-opportunity, random utility, intervening opportunities models, etc). In particular, the review will highlight the benefit of integrating different approaches like the introduction of intervening opportunities factors within random utility models.