缓倾斜厚煤层瓦斯渗流非线性模型及抽采钻孔优化设计

为了消除缓倾斜厚煤层布置的11501综放长壁工作面回采时瓦斯急剧涌出的安全隐患,降低传统的瓦斯线性模型分析的误差。在充分考虑瓦斯吸附/解吸动态过程的影响基础上,对瓦斯渗流特性模型进行了相应的修正,依据修正模型进行了工作面开采时瓦斯运移的数值模拟,并在现场实施了高位钻孔抽采瓦斯的效果考察。结果表明：优化后的高位钻孔抽采综放工作面瓦斯量提高了50.1%,煤层瓦斯含量降低了40.6%。     

基于产品生命周期的供应链选择研究

回顾了供应链类型以及影响供应链类型选择的需求变量,提出产品生命周期内的供应链匹配关系,并给出产品生命周期内供应链选择的决策过程,对生命周期不同阶段供应链的转换进行了探讨.     

“万象更新壶”的造型特征、创新路径及装饰寓意解析

“万象更新壶”以“象”的形态为塑形依据,以“还原法”为创新路径,以“琢砂地”的装饰技法寄托“吉”的情缘,整器造型与装饰浑然一体,营造出宽广的审美空间。     

天然气换热式转化制合成气催化剂的选用

论述了制合成气过程催化剂的选择及重要性,转化催化剂要求有较好的低温活性和抗积炭性能,中变催化剂考虑催化剂本体含硫量,低变催化剂要从活性、热稳定性、堆积密度、还原后体积收缩率、烧失重和自由水含量等方面衡量,甲烷化催化剂的选用要根据设备状况满足工艺要求方面考虑。催化剂的使用寿命既与合理选用催化剂有重要关系,也与工业应用过程中的正确使用和维护有关。     

泡菜货架期研究

研究了泡菜自然发酵的工艺及其货架期,结果表明,泡菜自然发酵的最佳条件为:6%的加盐量,发酵温度20℃,加入0.05?Cl2,发酵8~10 d。采用真空包装加冷藏后的泡菜保质期可达1年以上,加入0.05%的防腐剂可以延长保质期和改善产品质量。     

单长链烷基酸性磷酸酯对锆的萃取和保留

本文研究了在30％TBP-单长链烷基酸性磷酸酯(MLCAP)-煤油-HNO_3和MLCAP-煤油-HNO_3两个体系中,萃取剂浓度、水相中H~+、总NO_3~-、稳定锆和铀的浓度及温度等因素对Zr的萃取行为和酸、碱洗涤后Zr的保留行为的影响。还对萃取反应机制进行了初步探讨。结果表明,在实验条件下,MLCAP与Zr生成组成为2:1的萃合物;当MLCAP存在于30％TBP-煤油中时,会使Zr的萃取明显增加并易产生界面物;在用Na_2CO_3洗涤有机相时,不能将Zr有效洗脱并易产生乳化现象,使溶剂质量变坏和造成分相困难。乳化生成的程度与体系中稳定锆的浓度和MLCAP的存在量有关。     

涤纶长丝纺丝组件更换周期探索

通过生产实践和统计分析 ,提出涤纶长丝纺丝组件的使用周期可从原 3个月延长至 5～ 6个月。生产不同品种组件使用周期可通过上机试验来确认     

Behavior of bridge girders with corrugated webs under monotonic and cyclic loading

The focus of this study is to investigate the behavior of plate girders with trapezoidally corrugated webs under fatigue loading. Six girders were tested under both monotonic and cyclic four-point loading arrangements. A relationship between the stress range, F_r, and the number of cycles to failure, N, was developed for the girders. The results from the fatigue tests were related to the current AASHTO specifications and compared with the test results of different types of girders carried out by others. Nonlinear finite element analyses were conducted to study the effects of the different geometrical parameters of this type of girders on the stress concentrations at different locations and to explain the findings of the experimental study. Two sources of stress concentration leading to fatigue cracking were isolated and evaluated; one is dependent on the radius of curvature between the web folds and the other depends on the inclination angle of the inclined fold. An analytical technique based on fracture mechanics is also proposed to enable designers to determine the fatigue life of corrugated web steel girders.     

Semiparametric Inference in Seasonal and Cyclical Long Memory Processes

Several semiparametric estimates of the memory parameter in standard long memory time series are now available. They consider only local behaviour of the spectrum near zero frequency, about which the spectrum is symmetric. However long-range dependence can appear as a spectral pole at any Nyqvist frequency (reflecting seasonal or cyclical long-memory), where the spectrum need display no such symmetry. We introduce Seasonal/Cyclical Asymmetric Long Memory (SCALM) processes that allow differing rates of increase on either side of such a pole. To estimate the two consequent memory parameters we extend two semiparametric methods that were proposed for the standard case of a spectrum diverging at the origin, namely the log-periodogram and Gaussian or Whittle methods. We also provide three tests of symmetry. Monte Carlo analysis of finite sample behaviour and an empirical application to UK inflation data are included. Our models and methods allow also for the possibility of negative dependence, described by a possibly asymmetric spectral zero.     

Short‐term and long‐term performance of thermosets exposed to water at elevated temperatures

The water‐transport, mechanical, and chemical‐structure changes in various vinyl ester, novolac, and urethane‐modified vinyl ester thermosets exposed to water at 50 to 95°C for times up to 1000 days have been studied within the framework of a larger study of osmotic blistering in fiber reinforced plastics (FRP) process components. The water sorption saturation concentration did not reach a steady‐state value but gradually increased in many cases upon long‐term exposure. The diffusion coefficient was not significantly affected. Infrared spectroscopy and gas chromatography‐mass spectrometry indicated that the net mass loss from the thermosets on immersion in water was due to the leaching of non‐reacted styrene, monomer, and additives. It is suggested that this, together with polymer relaxation processes (as measured on specimens under tension in water at 80°C), is the primary reason for the time‐dependent increase in the water saturation concentration. Infrared spectroscopy indicated that, even at the highest temperatures, hydrolysis of the polymer ester groups was small. Correlations were found between the styrene content in the uncured thermosets, the estimated solubility parameters, and the sorption and diffusion coefficients. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010