Second-law-based thermodynamic analysis of two-stage and mechanical-subcooling refrigeration cycles

Thermodynamic analysis of HFC-134a vapor-compression refrigeration cycles is investigated by both the first and second laws of thermodynamics. Second-law analysis is carried out for both two-stage and mechanical-subcooling refrigeration cycles. The analysis is performed on each of the system components to determine their individual contribution to the overall system irreversible losses. It is found that most of the losses are due to a low compressor efficiency. Irreversibilities of expansion valves and condenser are also significant. In addition, it is shown that the optimum inter-stage pressure for two-stage and mechanical-subcooling refrigeration systems is very close to the saturation pressure corresponding to the arithmetic mean of the refrigerant condensation and evaporation temperatures. These results are compared with the existing practice in the industry. Furthermore, theoretical results of a two-stage refrigeration system performance are also compared with experimental values for a CFC-22 system.     

夏季面漆起泡的预防

面漆漆膜在夏季潮湿天气下成膜后3—5天，漆膜表面易形成米粒状的漆泡，针对漆泡的现象，寻找其形成的机理，根据起泡的机理采取预防面漆起泡的措施。     

浅谈书籍装帧设计

“佛靠金装，人靠衣装”。封面设计是书籍装帧设计的重要内容。封面设计要体现书的内容、性质、色彩要考虑读书对象、文化层次，装帧设计给人以美的感觉。     

Ti-6-22-22S合金步进轧制工艺加工棒材研究

采用步进轧制工艺制备了Ti-6-22-22S合金Ф50mm棒材，对加工、热处理、组织与性能的关系进行了分析。结果表明：在两相区上部温度960℃轧制获得细网篮组织，棒材性能较好且数据均匀；热处理后，得到双态组织，强度．塑性达到优良组合，而片层状组织强度较高，但塑性稍低。     

三江平原水利综合规划的重新编制问题

三江平原是我国重要的商品粮基地和粮食战略后备基地。原有规划距今已过30年，远不能适应现代发展要求。结合新的形势，提出了重新编制三江平原综合规划的现实意义、目标设想及主要修编内容。     

奥钢联板坯连铸计算机系统升级研究

某钢厂板坯连铸过程控制系统采用的奥钢联(VAI)技术,运行数年来,由于模型不透明,维护和调整困难,迫切需要升级改造。改造后的计算机系统充分考虑现有资源和需求,能够达到升级改造的目的。     

异构数据的管理方法及异构数据源的集成研究

工程应用中软件工具的多样性和设计活动的分散性形成了大量异构数据。本文分析了传统的异构数据管理方法的不足，提出使用数据库系统的文件系统结合的管理方法。针对此方法下所形成的异构数据源问题，给出了基于J2EE规范的数据访问对象抽象工厂解决方案。     

酸催化二甘醇脱水环化反应研究

以硫酸、磷钨酸、ZRP-5分子筛为催化剂,研究了二甘醇(DEG)脱水环化的反应规律。结果表明,DEG发生分子内脱水环化反应,生成1,4-二氧六环(DOX),DEG分子间脱水不仅可以生成四甘醇、六甘醇等,同时可生成三甘醇、五甘醇等一系列的多甘醇(PEG)。不仅DEG可以脱水环化生成DOX,在反应中生成的PEG也同样可以进行生成DOX的反应。对于二甘醇(DEG)脱水环化反应,硫酸是性能优良的催化剂,反应可以在较低的温度下进行,馏出产物中DOX选择性大于95％。     

历史中心区复兴中的地域性问题与对策

本文以上海思南路47～48街坊改造为例,探讨城市形态更新与居民外迁问题,并期待相关地域性社会对策的出现。     

Directional features in online handwriting recognition

The selection of valuable features is crucial in pattern recognition. In this paper we deal with the issue that part of features originate from directional instead of common linear data. Both for directional and linear data a theory for a statistical modeling exists. However, none of these theories gives an integrated solution to problems, where linear and directional variables are to be combined in a single, multivariate probability density function. We describe a general approach for a unified statistical modeling, given the constraint that variances of the circular variables are small. The method is practically evaluated in the context of our online handwriting recognition system frog on hand and the so-called tangent slope angle feature. Recognition results are compared with two alternative modeling approaches. The proposed solution gives significant improvements in recognition accuracy, computational speed and memory requirements.