令牌多环网性能—可靠性综合评价

网络的性能与可靠性已分别得到广泛的研究,然而,怎样分析具有容错机制的环网的性能仍属有待开拓的研究领域,本文提出了一种分析具有自修复机制的多环网络系统的方法,并给出了报文传输时间分布的拉氏变换式,平均等待时间及平均队列长度公式,分析结果可用于评估故障与修复过程对实时令牌环网的实时响应特性的影响,对基于LAN的分布式实时系统设计具有指导意义。     

碱性氰化物防渗碳光亮镀铜工艺的研究

本文介绍了一种高效率，高韧性，防渗碳底铜工艺，可以大辐度提高镀层的沉积速度，降低铜层孔隙率，提高产品合格率，具有显著的经济效益和社会效益。     

新取代苯基荧光酮试剂的合成及其性质的研究Ⅱ．新型取代苯基荧光酮与金属离子显色反应的研究

研究了３，５－二溴－４－氨基苯基荧光酮、３，５－二溴－４－偶氮变色酸等８种苯基荧光酮在酸性介质中与高价金属离子Ｚｒ（Ⅳ）、Ｍｏ（Ⅵ）、Ｗ（Ⅵ）、Ａｌ（Ⅲ）、Ｇａ（Ⅲ）等的显色反应。３，５－位二溴取代的试剂的灵敏度高于未取代的灵敏度，摩尔吸光系数绝大多数在１０５Ｌ·ｍｏｌ－１·ｃｍ－１以上。     

Reliability and performance analysis of time – space – time switching networks with multiple separated space switches

Since electronic switching systems usually require very strict reliability requirements as well as good performance objectives, we need to jointly analyse the performance and reliability of switching systems. In this paper, we compare conventional time–space–time switches with single space switches with those with multiple separated space switches, from the viewpoints of reliability and performance. We consider time–space–time switching networks which consist of N incoming time switches, i.e. one NxN space switch, two (N/2)x(N/2) space switches, and four (N/4)x(N/4) space switches. We introduce a Markov reliability model to study the effect of failures and analyse the reliability and performance of three different types of switching networks in terms of average blocking probability and the mean time to unreliable operation, as we vary the offered traffic. As a result, T–S–T switching networks with multiple separated space switches exhibit better performance and reliability than those with single space switches.     

Pullout tests of epoxy-coated reinforcement in concrete

The bond strength and slip of epoxy-coated reinforcing bars in concrete have been evaluated by carrying out single pullout and double pullout tests. In extended single pullout tests, slip measurements were made while tensile force was applied to reinforcing bars embedded in concrete. In double pullout tests, 20 cycles of load were applied at levels of steel stress between zero and 0·5 times characteristic steel strength. Strains were measured by electrical resistance strain gauges glued inside the bars. Both epoxy-coated and uncoated bars were used in the investigation, to obtain comparative results. The strain gradient along the bar was found to be less for the coated reinforcement. In general, the epoxy coating was found to increase slip in bond and thereby reduce the bond performance of coated bars.     

Li2O在保护渣中的作用

采用在不同玻璃性的两种基渣中加入Ｌｉ２Ｏ为研究Ｌｉ２Ｏ对保护渣粘度，熔化温度及玻璃性能的影响，并对Ｌｉ２Ｏ改善保护渣玻璃性的机理进行了探讨，提出了寻找高速连铸保护渣中Ｌｉ２Ｏ的代用物的一种方法。     

伺服元件的生产应用及发展趋势

本文概括地介绍了我国自70年代以来伺服元件的生产发展状况、元件的性能特点和应用情况，并分析了今后发展的趋势。     

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.     

Impact of uncertainties on estimations of heat pump cycle performance

Sensitivity analysis is used to show how uncertainties in basic factors, such as heat transfer, pressure drop, compressor efficiency, and thermophysical properties, influence the result of heat pump cycle performance estimations. By comparing the results of this analysis with uncertainty levels of estimations and experimental determinations, it is established to what extent improvements in accuracy are needed. The investigation was carried out for several different applications and, as working fluids, both pure substances and non-azeotropic mixtures were examined. It was found that evaporation heat transfer and compressor efficiency are two areas where improvements are needed. It is also shown that estimates using very accurate, substance-specific, equations of state differ from those using more general types by up to 1 % for COP and 2% for capacity.