The variable property grain model applied to the zinc oxide-hydrogen sulfide reaction

The variable property grain model, including the effect of grain diffusion resistance, has been applied to experimental results from the reaction of hydrogen sulfide with zinc oxide. Grain radius is assumed to vary under the combined effects of sintering and extent of reaction. Property variations are correlated by the specific surface area, an easily measured quantity. All model parameters with the exception of the grain diffusion coefficient have been evaluated by literature correlations or independent experimental measurements. Significant improvement in the match with experimental data, as compared to the constant property grain model, has been achieved.     

网站数据相关内容提取功能的设计与研究

本文根据内容提取的相关知识,以及它们在用户浏览信息时的应用,提出了内容匹配的高效算法,重点研究提取信息时如何提高匹配精度。通过这种算法,系统预测用户可能感兴趣的文章,并按感兴趣的程度向用户提供内容导航,得到一个个性化的相关信息显示页面。     

The use of a mixing-sensitive chemical reaction for the study of pulp fibre suspension mixing

The competitive, consecutive chemical reactions between 1-naphthol and diazotized sulfanilic acid were utilized to study the mixing of a pulp fibre suspension in a 22 L stirred tank reactor. Mixing quality was determined from the distribution between the mono and bis substituted reaction products once a correlation was made for the adsorption of the product dyes onto the suspended fibres. The technique was found to be adequate for assessing micromixing and turbulence intensity within a fibre suspension provided the measured product distribution, Xs, was between 0.4 and 0.01. Thus the mixing conditions that could be assessed depended on both the energy dissipation within the mixer and the amount of the fibre present. For the experimental conditions chosen for this study energy dissipation rates would typically have to be less than 80 W/kg and the suspension mass concentration less than 2.5%. When compared with water, a reduction in turbulence levels at both the impeller zone and a remote zone in the stirred vessel was observed for fibre mass concentrations as low as 0.5%. The turbulence decreased as the suspension mass concentration was increased. This decrease is attributed to energy dissipation by friction at fibre-fibre contact points as the fibres move relative to one another in the flow. This sink removes energy from the turbulence cascade which never shows up as small-scale fluid deformations leading to better mixing.     

Theory and experiment on the three-dimensional motion of a freely suspended spherical particle at the entrance to a pore at low Reynolds number

This paper examines the three dimensional approach of a neutrally buoyant sphere of any size to a circular hole in a plane wall at very low Reynolds number. The analysis differs from previous studies, largely applied to the multipore filter, in that the authors investigate the three dimensional hydrodynamic interaction of the sphere with the entrance geometry of the pore in the limit of zero inertia. The problem is first exactly formulated as the linear superposition of fundamental Stokes flows for rotation and translation of the sphere and flow past a stationary sphere. Approximate solutions are then obtained for the deviation of sphere trajectories from fluid stream lines and the results compared with laboratory model experiments in a low Reynolds number settling tank. The theory and experiment show that because of the hydrodynamic interaction sphere trajectories and fluid streamlines deviate significantly as the opening is approached, that all spheres eventually enter the pore regardless of their initial position, but that a non-uniform concentration profile develops with large increases in concentration near the walls of the orifice in the vicinity of the opening. The results provide a basic mechanism to explain the onset of Fahraeus phenomenon for red cells entering small blood vessels and glass tubes.     

Optimal production of intermediate for zero—first and first—first order reaction sequences in fluidised bed reactors1

An analysis of zero—first and first—first order reaction schemes has been carried out in a fluidised bed with a view to optimising the production of intermediate R for a given bubble diameter. For the zero—first order reaction sequence, the gas residence time at which the maximum concentration of R occurs is shown to be fixed and independent of bubble size in the bed. On the other hand, for a first—first order reaction scheme, an optimum gas residence time exists for the concentration maximum to occur at the bed exit. This interaction between bubble diameter, gas residence time and maximum concentration of intermediate is resolved by recourse to a three dimensional diagram which optimises the production of intermediate for any given value of bubble diameter or gas residence time.     

Particle-fluid heat transfer and dispersion in fluidised beds

The dynamic response of a gas fluidised bed has been measured for a range of particle sizes of lead glass ballotini and a range of particle Reynolds numbers. A dispersion model has been formulated that includes the effects of gas and particle mixing, fluid-to-particle heat transfer and intraparticle thermal conductivity, and the dynamic thermal response in theory has been found by solving the partial differential equations in the Laplace transform domain. The coefficient of thermal dispersion, the particle-to-fluid heat transfer coefficient and the intraparticle thermal conductivity have been found for the experimental response by non-linear regression. The coefficient of axial dispersion was found to be large and the particle to fluid heat transfer coefficients agreed with an established correlation for fixed and fluidised beds. The intraparticle thermal conductivity agreed with literature values for lead glass, the estimates showed no trend with flowrate, and the standard deviation of the estimate was three times smaller than the deviation found from similar experiments in fixed beds.     

基于淘宝直通车的竞价决策系统的研究与设计

电子商务蓬勃发展的大环境下,广告主具有强烈的电商广告投放意愿,显然他们并未达到电商广告的核心业务SEM （搜索引擎营销优化）的专业要求。所以广告主希望借助第三方工具来进行搜索引擎广告投放的一站式服务来满足其业务需求。基于此,本文将提供一整套的竞价词托管式服务的解决方案。以淘宝直通车这一全新的搜索竞价模式作为研究对象,从语义抽取、关键词扩展、竞价词生成、模型化出价、广告效果正向反馈监控模型几方面进行分析和统计,为直通车广告主提供最优投放策略整体解决方案。第一阶段针对商品信息进行数据挖掘,实现关键词推荐引擎。第二阶段实现投放优化模块,实施定价策略,建立的点击量与PPC（“平均点击花费”）模型,实现在预算资金的约束下对不同竞价组合进行ROI（投入产出比）最大化的投资决策。以实际效果改善直通车竞价搜索用户体验。     

An analytical model for freeboard and in-bed limestone sulfation in fluidized-bed coal combustors

A new model, which combines in-bed and freeboard sulfation, significantly improves the ability to predict sulfur capture by limestone sorbents in fluidized-bed coal combustors. In this model, the in-bed hydrodynamics are described in terms of a bubble phase and an emulsion phase while the freeboard region has only a diluted emulsion phase. The solids, which are in the emulsion phases, are considered to be completely back-mixed; the gaseous bubble phase travels in plug-flow but exchanges with the emulsion phase. The sulfation reaction occurs principally in the emulsion phase and the reaction rate is a direct function of the sulfur dioxide concentration, the extent of the calcium oxide conversion (as measured by a thermogravimetric analyzer), and the amount of limestone present in the bed and in the freeboard. The amount present, or holdup, in the free-board is calculated from empirical correlations for elutriation and from particle-time trajectories as predicted from equations of motion.The model indicates that a significant amount of sulfur capture can occur in the freeboard region, especially with high superficial gas velocities and small particle sizes, both of which lead to increased freeboard holdup. For an overall sulfur retention of 90%, approximately 9% of the sulfur is predicted to be captured within the freeboard above a combustor bed 1.8 m by 1.8 m by 1.2 m high of 1200 μm diameter limestone particles that are fluidized at 2.4 m/s. The model also predicts that the sulfur captured by the entrained particles is negligible. These predictions compare favorably with the actual sulfur retentions experienced in similar sized pilot-scale combustors.     

两亲性共聚物P(MMA-co-AMPS)对聚偏氟乙烯超滤膜性能的影响

以2-丙烯酰胺基-2-甲基丙磺酸(AMPS)为亲水单体,甲基丙烯酸甲酯(MMA)为疏水单体,偶氮二异丁腈(AIBN)为引发剂,采用自由基共聚合法制得了两亲性共聚物P(AMPS-co-MMA);以两亲性共聚物P(AMPS-co-MMA)与聚偏氟乙烯(PVDF)共混,通过相转变法制备PVDF/P(MMA-co-AMPS)超滤膜。利用傅里叶变换红外光谱、热失重法表征无规共聚物的组成和热稳定性能。并通过扫描电子显微镜,傅里叶变换红外光谱、吸水率测试、表面润湿性测试,探讨了不同单体摩尔比对PVDF/P(MMA-co-AMPS)超滤膜的结构及性能的影响。结果表明,单体AMPS与MMA间发生自由基聚合生成两亲性共聚物P(AMPS-co-MMA)。PVDF/P(MMA-co-AMPS)超滤膜表面多孔,内部有大孔,存在相对致密皮层和多孔的支撑层。当2-丙烯酰胺基-2-甲基丙磺酸和甲基丙烯酸甲酯的摩尔比为2∶1时,PVDF/P(MMA-co-AMPS)超滤膜吸水率和表面润湿性能最好。     

Connectivity Infrastructure and Components for POCT Environments - Overall Infrastructure

Connectivity infrastructure, hardware and software components for point-of-care testing (POCT) environments at medium-to-large sized hospitals with expected number of POCT instruments in the order of hundreds or thousands are described. The instruments include both network-ready and non-network-ready devices. The latter are connected to the network by means of a hardware-based Instrument Network Adapter. Instrument messages are converted to standardized form and, depending on message content, are routed and delivered to appropriate destinations by a software-based Message Routing System consisting of a Message Router and a Delivery Agent. Target information systems consist of departmental and central information systems.