Study of liquid injection impact on the performance of new refrigerant mixtures

In this paper, the test results of liquid injection impact on the performance of new alternative refrigerant mixtures such as: R-410A, R-507, R-407C and R-404A are discussed, analysed and presented. The test results were obtained using an air-source heat pump set-up with enhanced surface tubing under various liquid injection ratios. Performance tests were conducted according to the ARI/ASHRAE standards. The performance data demonstrated that as liquid injection ratio increases, compressor head pressure and discharge temperature decrease. This has a positive effect in protecting the compressor. The effect of liquid injection on mixture behaviour varies from one mixture to another depending upon the mixture's composition. Furthermore, liquid injection appears to have a significant influence on R-410A behaviour compared to the other mixtures in question. Copyright © 2002 John Wiley & Sons, Ltd.     

Flow stress of high density polyethylene and nylon 66 at high rates of strain

Measurement of the flow stress of high density polyethylene (HDPE) and nylon 66 at strain rates of 10³ s^?1 using a split Hopkinson pressure bar technique is discussed. The flow stress at a strain of 10% has been determined for both polymers at 20°C. The intrinsic errors involved in this technique are briefly reviewed. The results indicate that the flow stress of HDPE and nylon 66 were 50MPa and 150MPa, respectively, at strain rates of about 10³s^?1.     

Study on phase behavior–impact strength relationship of unsaturated polyester/polyurethane hybrid polymer network

The phase behavior of a hybrid polymer network (HPN) composed of poly[(propylene glycol maleate)-co-(propylene glycol phthalate)] crosslinked with styrene and polyester–urethane crosslinked with methylene-bis-ortho-chloroaniline was examined. The correlation between phase separation and impact strength of the HPNs is discussed. The composition of HPNs has an effect on their properties.     

Synfuel development impacts— econometric modelling and policy analysis

The prospects for rapid near-term development of a synfuel industry in the USA have decreased, due to depressed world oil prices, synfuel project cost overruns, and the lukewarm support of the Reagan administration. Nonetheless, socioeconomic and environmental impact analysis studies can provide valuable information for determining the regional welfare effects of proposed projects. The author discusses the results of a regional econometric analysis of the synfuel projects planned for Western Kentucky, which focuses on environmental impacts, and reveals the inevitable trade-offs that would accompany synfuel development. Some policy issues are briefly reviewed, especially that of efficient energy pricing.     

提高高铬白口铸铁磨球冲击抗力的技术关键

当高铬白口铸铁含铬量为18%～28%,Cr/C值是8￣9,铸铁的显微组织是回火马氏体 少量残余奥氏体(<5%) M7C3碳化物,则磨球具有高的冲击韧性和断裂韧性K1C,具有高的冲击抗力,表现出低的冲击剥落量。     

民间传统御寒器具——火桶设计研究

＂火桶＂是南方传统的御寒器物,它具有造型简单,取材方便,功能实用多样的特点,凝聚了民间朴素造物的思想。同时,火桶所具有着深厚的人文特点和文化内涵。文章以黔东南镇远地区民间火桶为例,分析其形态、结构、功能及人机关系等内容,探究民间造物的设计巧思。     

如何设定品牌标志的设计标准

品牌设计师通过知觉联想可以将文字语言转化为直接、可见的视觉图形传达给社会大众,这种语言上的转换是设计师发掘人们想象不到或想象不全面的一种表现方式,是艺术创造。同时,在没有限制,具有广泛可能性的创意、设计中,要把企业理念和目标等文字语言浓缩、整合出适合创意、设计的关键语,这一个个关键语就是品牌标志设计的依据和标准。有了这样的设计标准就会提高设计效率和准确性,减少在标志设计过程中的矛盾与摩擦,起到指引方向和检验最终方案的作用。     

浅议视觉传达设计中的“空白”

空白,也称为"虚空间",指被其他要素包围的空间。空白部分运用的好,有时则会成为设计中最突出、最令人瞩目的部分。本文就针对空白在视觉设计中的一些作用做相关的探讨。     

城市街区空间引导系统的设计思考

城市街区空间引导系统与人们的日常生活息息相关,为人们的出行提供了便捷的标识引导,同时它也是城市形象的重要组成部分之一。本文分析总结了该系统的设计原则,并从视觉传达学科入手分析其视觉元素的设计。为了设计无语言障碍和有个性、地域化的城市街区空间引导系统,从符号、文字、色彩三方面对其进行设计思考。     

Dynamic Response Calculation of Spatial Elastic Multibody Systems with High-Frequency Excitation

The objective of this paper is to establish a computationalscheme for dynamic response calculations of a three-dimensionalmultibody mechanical system with impulsive forces, which give rise tohigh-frequency excitations. The finite-element method is employed torepresent the local deformations of three-dimensional beam-like elasticcomponents by either a finite set of nodal coordinates or a truncatedset of modal coordinates. A reduced-order model is obtained by invokinga modal transformation. Both planar and complex modal reduction schemesare established. The developed formulation is implemented into amultibody simulation program that assembles the equations of motion andproceeds with its solution. The computational scheme permits a change inthe basis of the modal space in order to regulate the admittance ofhigher frequencies and to accommodate any change in the kinematicconfiguration. Numerical examples are presented to demonstrate theapplicability of the developed computational scheme.