Power levels and packet lengths in random multiple access with multiple-packet reception capability

This paper extends our earlier results. We assume that the receiver has the capability of capturing multiple packets so long as the signal-to-interference-plus-noise ratio (SINR) of each packet is above a designed threshold T throughout its transmission period. We prove that, compared with a multiple-power-level system, the single-power-level system in which all nodes transmit at the maximum allowable power level achieves optimal throughput, under a condition that T exceeds the value 3.33. Given a minimum throughput requirement, under the same condition on T, the single-power-level system also achieves the maximum average packet capture probability as well as the optimum energy usage efficiency. If the multiple-power-level systems are constrained such that higher power levels always have shorter packet lengths, then the above results hold for T greater than 2.     

中温炻器天目油滴釉的研制及影响因素的探讨

详细介绍了中温炻器辊遭窑烧成天目油滴釉的研制情况，对该产品的釉料组成，主要工艺参数，形成机理及影响因素进行了探讨分析，并指出该釉面产品具有广阔的市场前景。     

A comparison of lightness contrast effects in CRT and surface colours

The simultaneous contrast effect is investigated in this article. A total of 174 and 154 test/induction combinations were studied for CRT and surface colours respectively. Each combination was assessed by nine observers using a matching technique. The test and induction colours used for CRT colours were similar to surface colours using fabric samples. The results indicated a strong lightness contrast effect for both CRT and surface media; that is, the lightness of a test colour surrounded by a lighter induction colour was reduced for both CRT and surface colours. However, the effect in CRT medium was more pronounced than in the surface medium. © 2004 Wiley Periodicals, Inc. Col Res Appl, 30, 13–20, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20074     

液氨装置工艺计算及改造总结

介绍我公司液氯装置由活塞式氨气压缩机氨-CaCl2盐水系统改为带经济器的螺杆式氯气液化机组的工艺计算,新建装置特点以及改造后的装置在我公司运行情况和使用效果。经改造后的液氯装置每年可节约电费73万余元,同时提高了装置的安全可靠性。     

准噶尔盆地三台-北三台地区第三系勘探潜力分析

从沉积及储层组合、油气运移系统等方面全面剖析了准噶尔盆地三台-北三台地区第三系油气成藏条件，建立了成藏模式，对未钻探区勘探潜力进行了预测；通过分析，认为该区第三系储层物性主体差，断裂更多地表现为封闭性，导致沟通深部油气源的运移体系不畅，致使第三系圈闭不能有效捕获和储集油气。圈闭又比较匮乏，主体勘探潜力不大。北25井西背斜紧邻多期活动的甘诃子北断裂，第三系可能发育较好的储层，相对有利，北25井西背斜应是钻探第三系的首选目标。     

大港渣油掺兑催化油浆氧化沥青的研究

重油催化裂化外甩油浆中富含芳烃，可望在国产原油生产优质道路沥青上发挥作用。对大港环烷基渣油中掺兑一定比例的油浆后氧化改善道路沥青性质的可能性进行了研究，结果表明：渣油掺兑油浆氧化，不仅可以有效改善沥青延度，同时也为油浆的合理利用开辟了一条新途径。     

高速列车风量控制式通风系统的探讨

介绍了能够减轻乘坐高速列车时产生的耳朵不适感的风量控制式通风系统，该系统通过检测车内外的压力来控制进排气量，并且由模拟计算证实，该系统能够控制车内压力的波动，满足高速列车的舒适性需要。     

Effects of process-control agents on mechanical alloying of nanostructured aluminum alloys

The effects of the process-control agents (PCAs) stearic acid and methanol on the mechanical alloying (MA) of a nanostructured aluminum alloy (Al₉₃Fe₃Ti₂Cr₂) have been investigated. The dependency of the powder-particle sizes, grain sizes, atomic-level strains, lattice parameters, formation of solid solutions, and microstructural evolution of the aluminum alloy on the types of PCAs and their concentrations have been studied using a variety of analytical instruments including X-ray diffraction scanning electron microscopy, and transmission electron microscopy. The results clearly indicate that prevention of excessive cold welding of Al particles can be achieved by the addition of a PCA at the expense of reductions in the grain size, formation rate of solid solutions, and rate of microstructural refinement, all of which are desired in MA of the Al alloy. Furthermore, a PCA that is more effective in preventing excessive cold welding will also impose more hindrance to the MA process. These phenomena have been discussed in the light of the adsorption of the PCA on the metal surface and the lubricating function of the PCA.     

Quantification of the layer dispersion degree in polymer layered silicate nanocomposites by transmission electron microscopy

As the performance of polymer layered silicate nanocomposites strongly depends on their interior layer dispersion, quantification of the layer dispersion degree is needed. In this work, a new methodology was developed to determine the dispersion parameter D_0.1, based on the measurement of the free-path spacing distance between the single clay sheets from the transmission electron microscopy (TEM) images. Several examples of exfoliated, intercalated, and immiscible composites were studied. It was found that the exfoliated composites had D_0.1 over 8%, while that of intercalated composites were between 4 and 8%. In the case of intercalation, a high frequency peak appeared at a short spacing distance in the histogram, which was a characteristic of the intercalation, distinct from the exfoliation. The main utility of this TEM methodology is for the quantification of exfoliated or intercalated samples with small number of layers with stacks. The dispersion parameter D_0.1 below 4% was suggested to classify as immiscible. A unique advantage of the TEM measurement is that the dispersion degree of different fillers can be counted individually.