The boundary contour method for two-dimensional Stokes flow and incompressible elastic materials

 A variant of the boundary element method, called the boundary contour method (BCM), offers a further reduction in dimensionality. Consequently, boundary contour analysis of two-dimensional (2-D) problems does not require any numerical integration at all. While the method has enjoyed many successful applications in linear elasticity, the above advantage has not been exploited for Stokes flow problems and incompressible media. In order to extend the BCM to these materials, this paper presents a development of the method based on the equations of Stokes flow and its 2-D kernel tensors. Potential functions are derived for quadratic boundary elements. Numerical solutions for some well-known examples are compared with the analytical ones to validate the development. Received 28 August 2001 / Accepted 15 January 2002     

涡流管类比逆流换热器方法的研究

结合Scheper，Lewins和Bejan的理论模型，对涡流管类比逆流换热器模型进行了深入地分析，得出了冷流分量对温度分离效应的函数关系式，为了解涡流管机理和实验中强化涡流管温度分离效应提供了理论依据。     

正交曲线坐标下三维代数应力通量模型

针对弯曲及不规则明渠的水动力及物质输运特性，本文建立了曲线坐标系下的三维代数应力通量数学模型，对平面上弯曲及不规则复杂边界情形，采用Poisson方程进行正交曲线坐标变换，各向异性的湍流代数应力通量模型被引用于本文的模拟计算中，以体现复杂边界条件引起的水动力及物质输运特性的变化。通过180度强弯曲明渠水槽及贵溪电厂不规则边界河段物理模型试验两个实例计算表明，实测值与计算吻合良好，效果令人满意。     

关于混联梯级水电站经济调度的研究

提出采用具有附加线性约束的网络规划法，可把混联梯级水电站分解为几个子网络，简化了每个子网络的求解计算，从而加速大电网复杂的经济调度的计算速度。     

Mathematical modelling of a reverse flow reactor with catalytic surface dynamics

This paper studies a system of partial differential equations modelling the behaviour of a reverse flow reactor. For the parameters appropriate for the oxidation of ammonia on a Pt/Al₂O₃ catalyst in a typical laboratory set-up, the reactor may be split into regions where approximate formulas that determine its behaviour are deduced. Numerical calculations are presented and can be used to compare with the analytical formulas. The physical insight gained from the asymptotic analysis suggests a new switching strategy which is the subject of numerical experiments. The switching strategy is found to be efficient at minimising the ammonia exiting the reactor after reversal.     

填料萃取塔的操作性能及设计计算

系统地介绍了填料抽提塔的两相流动及传质特性，设计计算，对填料塔的设计和操作有一定指导意义。     

Effect of Channel Changes in the St. Clair River During the Present Century

Periodic man-made changes in the outlet of Lake Huron through the St. Clair River date back to the middle of the last century. These artificial channel changes have been well documented during the present century. They consist of dredging for commercial gravel removal in the upper river during 1908–25 and uncompensated navigation improvements for the 7.6-m (25-ft) and 8.2-m (27-ft) projects completed in 1933 and 1962, respectively. The total effect of these changes on the levels of Lakes Michigan and Huron (hydraulically one lake) and on the upper St. Clair River profile was determined with dynamic flow models. The ultimate effect of the above dredging was a permanent lowering of the Lake Michigan-Huron levels 0.27 m (0.89 ft), which represents a tremendous loss of freshwater resource [32 km³ (7.7 mi³)].     

Split and collectorless flotation to medium coking coal fines for multi-product zero waste concept

The medium coking coal fines of − 0.5 mm from Jharia coal field were taken for this investigation. The release analysis of the composite coal reveals that yield is very low at 10.0% ash, about 25% at 14% ash and 50% at 17% ash level. The low yield is caused by the presence of high ash finer fraction. The size-wise ash analysis of − 0.5 mm coal indicated that − 0.5 + 0.15 mm fraction contains less ash than − 0.15 mm fraction. Thus, the composite feed was split into − 0.5 + 0.15 mm and − 0.15 mm fractions and subjected to flotation separately. The low ash bearing fraction (− 0.5 + 0.15 mm) was subjected to two stages collectorless flotation to achieve the concentrate with 10% ash. The cleaner concentrate (18.9%) with 10% ash was recovered which has an application in metallurgical industries. The concentrate of 30.2% yield with 12.5% ash could be achieved in one stage collectorless flotation which is suitable for use in coke making as sweetener. As the − 0.15 mm fraction contains relatively high ash, collector aided flotation using sodium silicate was performed to get a concentrate of 23.6% yield with about 17% ash. The blending of this product with cleaner tail obtained from − 0.5 + 0.15 mm produces about 35.0% yield with 17% ash and that can be utilized for coke making. The reject from the two fractions can be used for conventional thermal power plant or cement industries using a 23.5% ash after one stage collector aided flotation and the final tailings produced content ash of 61.6% can be used for fluidization combustion bed (FBC). This eventually leads to complete utilization of coal.     

低渗透油藏生产井关井测压时间的计算与应用

低渗透油藏的生产井压裂后，在单井试油试采过程中，压力恢复测试关井时间不同，其中有些井压力恢复曲线不能出现边界反应段，渗流不能反映地层中真实流动特征。针对这种情况，基于长庆绥靖油田塞39井区长：低渗透油藏大量试井和实际生产资料，利用现代试井解释理论，研究合理关井时间的界限及其计算方法。结果表明，当油井关井测压时间达到3倍地层径向流开始出现的时间后，利用此时的压力数据解释地层参数和地层压力，其结果的误差小于5％，同时能较准确地判断边界类型。计算的理论曲线和霍纳法解释值非常接近，对于塞39井区，若预先知道某生产井地层有效渗透率值，可从理论曲线查出压力恢复试井的关井时间，否则，建议按照该井区地层有效渗透率（大约在6mD左右），将不稳定试井测试时间控制在25d以上为宜。图4表3参14     

Yeast exo-β-glucanases can be used as efficient and readily detectable reporter genes in Saccharomyces cerevisiae

Yeast exo-1,3-β-glucanases are secretable proteins whose function is basically trophic and may also be involved in cell wall glucan hydrolytic processes. Since fluorescein di(β-D -glucopyranoside) is a fluorogenic substrate detectable and quantifiable by flow cytometry, it was used for testing the ability of the EXG1 gene product of Saccharomyces cerevisiae and its homologous gene in Candida albicans to function as reporter genes. These open reading frames were coupled to different promoters in multicopy plasmids, and exoglucanase activity quantified at flow cytometry. Exoglucanases were found to be useful tools for the study of promoter regions in S. cerevisiae. This technique has the advantage over other reporter gene systems—such as β-galactosidase fusions—that it does not require permeabilization of yeast cells and therefore it allows the recovery of viable cells—by sorting—after flow cytometry analysis.