向服务业务模式转型——中国企业的可持续发展之路

<正>通向差异化竞争和可持续发展的新道路面对产品同质化、利润率不断下降、消费者需求日益严苛等难题,中国制造企业重生产轻服务的模式将难以维持。2008年开始的席卷全球的金融风暴引发了一系列的实体经济危机,制造企业急需走出一条通向差异化和可持续发展的新路。     

The oxidation of bituminous coal—I Development of a mathematical model

A general rate expression based on a proposed dual-path reaction model is developed for the oxidation of coal under mild conditions such as are useful in pretreatment for gasification. The effects on the oxidation rate of mass transfer, particle surface, oxygen partial pressure, and temperature have been considered and incorporated into the derived rate expression.     

The mixing aspects of NiMo and CoMo hydrotreating catalysts in ebullated-bed reactors

Recently, the Shuaiba Refinery of Kuwait National Petroleum Company (KNPC) conducted a test run using mixed NiMo/CoMo catalysts in one of the H–Oil reactors to verify the specifications of a CoMo catalyst. However, reduced unit performance and unstable operation were experienced. This led to the unit shut-down and process time loss. To search the causes for the different reactor behaviours, a research work was undertaken in the Petroleum Technology Department at Kuwait Institute for Scientific Research (KISR). It had found that the hydrodynamics of the mixed NiMo/CoMo and CoMo catalysts in a cold flow ebullated-bed reactor (EBR) were very different than NiMo catalyst alone.     

Performance of Differentially Detected DPSK Over Nonselective Rayleigh Fading Channels With Maximal Ratio Combining and Multiple Cochannel Interferers

In this paper, we investigate the performance of differentially detected differential phase-shift keying (DPSK) modulation with postdetection maximal ratio combining, in nonselective Rayleigh fading channels with multiple asynchronous cochannel interferers. The approach is based on an analytical technique we have presented earlier in the literature. Exact bit-error probability (BEP) results for binary DPSK and quaternary DPSK are derived. More specifically, we look into the effects of symbol-timing offsets between the interfering signals and the desired signal on the error performance. Our results show that when all the interfering signals are synchronous with the desired signal, the impairment caused by the cochannel interference to the desired user is maximum. On the other hand, when all the interfering signals are half-symbol-duration-delayed with respect to the desired user, they introduce the minimum impairment. Based on these findings, upper and lower bounds on the BEP are derived in simple closed form. Our explicit BEP results also show that the error probabilities of different transmitted symbols of the desired user are affected differently by the interfering signal