R12在水平管内流动沸腾换热实验研究

本文对R12在水平管内流动沸腾换热特性作了实验研究。实验结果表明,管内流动沸腾换热与单相对流换热一样,存在热进口效应,国外早期的实验数据由于未能考虑热进口效应而偏大。实验结果还表明,水平流动沸腾周向不均匀换热主要受流动结构影响;截面平均换热系数则与质量流速、热流密度、质量干度和蒸发压力密切相关。分析实验数据证实,流动沸腾换热是由气泡产生而引起的流动充分发展核态沸腾和双相对流蒸发两部分组成的。本文的实验数据与国外已有的换热关系式能较好吻合。     

用干簧管进行液位测量的方法探讨

本文介绍了液位测量中开发应用干簧管作浮子式液位计传感器件的工作原理和几个关键技术问题的处理方法。对于物位测量和其它领域也有参考意义和学术价值。     

ZnO/AlN复合压电薄膜的研制

各种超高频电子整机需要高性能的表声波压电器件。介绍了新的压电薄膜——ZnO/AIN复合压电薄膜的制速、结构和性能,并给出主要研制结果。     

资产证券化交易过程中的会计和税务问题探讨

资产证券化是世界上最先进的金融工具之一。就目前我国来讲 ,资产证券化的发展还处于起步阶段 ,缺乏实践经验 ,因此在会计和税务制度等方面尚难以对资产证券化形成支持 ,这将成为我国开展资产证券化的障碍。在借鉴发达国家运用证券化融资的成功经验的基础上 ,着重讨论了资产证券化过程中的会计和税务问题 ,并结合资产证券化本身的特性 ,提出了相应的解决建议     

恒流管的非稳系数和改进系数

引入非稳系数和改进系数分析了四种恒流管充电式扫描电路的非线性系数和电源利用系数 ,并提出了改进恒流管充电式扫描电路性能的具体方法 .     

Cloud manufacturing system for sheet metal processing

Abstract

Cloud computing is changing the way industries and enterprises run their businesses. Cloud manufacturing is emerging as an approach to transform the traditional manufacturing business model, while helping the manufacturer to align production efficiency with its business strategy, and creating intelligent factory networks that enable collaboration across the whole enterprise. Many production planning and control (PPC) problems are essentially optimisation problems, where the objective is to develop a plan that meets the demand at minimum cost or maximum profit. Because the underlying optimisation problem will vary in the different business and operation phases, it is important to think about optimisation in a dynamic mechanism and in a number of interlinked sub-problems at the same time. Cloud manufacturing has the potential to offer decision support as a service and medium of communication in PPC. To solve these problems and produce collaboration across the supply chain, this paper provides an overview of the state of the art in cloud manufacturing and presents a model of cloud-based production planning and production system for sheet metal processing.     

超长钢板桩围堰合理内支撑施工方案

钢板桩围堰合理的内支撑施工方案对施工安全、工期长短、成本大小均有一定的影响。以阜阳至六安铁路颍河特大桥深水基础超长钢板桩围堰施工实践为例，通过建立钢板桩、内支撑和土层相互作用的三维整体有限元模型，根据封底混凝土施工时机的不同，选择4种施工方案，对超长钢板桩围堰内支撑施工方案进行了探讨。结果表明：封底混凝土施工越早，对围堰结构的整体安全越有利；实际采用的施工方案要根据桥址处工程地质条件，结合实际工程情况，经方案比选和分析论证以后确定。     

介电可调薄膜材料及压控微波器件研究

利用介电可调薄膜材料的调谐特性研制的介质压控微波器件高频特性好、功率容量大、响应速度快,还有易集成、功耗小、成本低、可靠性高的特点,相比半导体管、铁氧体以及MEMS器件有明显的优势。该文系统介绍了近年来国内外介电可调薄膜材料及压控微波器件的研究进展,并结合作者的工作评述了介电可调薄膜材料和压控微波器件的应用情况。除研究最为集中的钛酸锶钡BaxSr1-xTiO3(BST)材料,还介绍了具有较高调谐率的铋基焦绿石铌酸铋镁Bi1.5MgNb1.5O7(BMN)薄膜材料,该材料介电损耗低(约0.002),介电常数适中(约86),温度系数小,是一种极具发展前景的微波介电可调材料。     

Statistical techniques in stereology

Stereology typically concerns estimation of properties of a geometric structure from plane section information. This paperprovides a brief review of some statistical aspects of this rapidly developing field, with some reference to applications in the earth sciences. After an introductory discussion of the scope of stereology, section 2 briefly mentions results applicable when no assumptions can be made about the stochastic nature of the sampled matrix, statistical considerations then arising solelyfrom the ‘randomness’ of the plane section. The next two sections postulate embedded particles of specific shapes, the particular case of spheres being discussed in some detail.

References are made to results for ‘thin slices’ and other prob-ing mechanisms. Randomly located convex particles, of otherwise arbitrary shape, are discussed in section 5 and the review concludes with a specific application of stereological ideas to some data on neolithic mining.     

北京地名管理中的片区地名问题

随着城市的发展,大量沿街商铺的涌现,门牌设置出现了同一座楼房楼下为道路门牌系统,楼上为小区门牌系统的混乱状况,如何处理片区地名的命名成为地名规划工作中的棘手问题。本文指出城市片区地名起到的作用、引发的问题,深入剖析其中原因,并提出建议,为今后地名规划工作和城市生活提供帮助。