Computational fluid dynamics for dense gas-solid fluidized beds

Many computational fluid dynamics (CFD) models for describing the hydrodynamics of dense gas-solid flows in fluidized beds have been put forward in the past few decades. These models treat the solid phase as continuum or discrete particles, which leads to Eulerian-Eulerian or Eulerian-Lagrangian formulations, respectively. Different governing equations and closure relations essentially result from an insufficient understanding of the complex gas?particle and particle?particle interactions for gas?solid flows. The current status of these models is discussed briefly in this paper. All the approaches in the literature modify only the solid phase momentum balance equation introducing various forms of the solid phase stress tensor and the solid phase pressure drop in the Eulerian-Eulerian models. Taking them into consideration, a new model for predicting the fluid behavior of dense gas?solid flows in fluidized beds has been developed, which contains new terms in both the particle and gas phase momentum balance equations and requires only the use of an experimental drag force correlation. Several results are shown to verify the model’s reliability, which include the homogeneous fluidization of Geldart type A particles, the bubbling and jetting fluidization of Geldart type B particles in rectangular beds, and fluid dynamics in a complicated geometry for a bubbling?bed of a fast internally circulating fluidized?bed biomass gasifier.     

The fate of injectant coal in blast furnaces: The origin of extractable materials of high molecular mass in blast furnace carryover dusts

The aim of the work was to investigate the fate of injectant coal in blast furnaces and the origin of extractable materials in blast furnace carryover dusts. Two sets of samples including injectant coal and the corresponding carryover dusts from a full sized blast furnace and a pilot scale rig have been examined. The samples were extracted using 1-methyl-2-pyrrolidinone (NMP) solvent and the extracts studied by size exclusion chromatography (SEC). The blast furnace carryover dust extracts contained high molecular weight carbonaceous material, of apparent mass corresponding to 10⁷?10⁸ u, by polystyrene calibration. In contrast, the feed coke and char prepared in a wire mesh reactor under high temperature conditions did not give any extractable material. Meanwhile, controlled combustion experiments in a high-pressure wire mesh reactor suggest that the extent of combustion of injectant coal in the blast furnace tuyeres and raceways is limited by time of exposure and very low oxygen concentration. It is thus likely that the extractable, soot-like material in the blast furnace dust originated in tars is released by the injectant coal. Our results suggest that the unburned tars were thermally altered during the upward path within the furnace, giving rise to the formation of heavy molecular weight (soot-like) materials.     

环抱式接骨板内固定治疗尺桡骨骨不连

我院2000年6月～2004年5月利用环抱式接骨板内固定治疗尺桡骨骨不连取得了较好的效果，现报告如下。     

固定期限劳动合同之分析

《劳动法》对固定期限劳动合同之期限采取的是一种放任主义的态度，因而不可避免地影响了劳动者的职业安全与稳定，限制了劳动者的合理流动，也使固定期限劳动合同之期限立法与世界通行立法相左。要克服这一现象，我国固定期限的劳动合同立法应与国际接轨，对期限与续签次数进行严格的法律规范。     

来自河南华灵微循环医学研究所的报告

<正> 纵观几千年人类科学的发展史,每前进一步都要经过大胆地创造、创新和反复的实践。人们将每一次被实践证明是正确的东西称之为科学。科学每前进一步,都会推动社会的发展与进步。人们的生产实践缔造了科学,反过来科学又给人类发展提出了极为苛刻的规范和要求。科学之所以被称为科学,就是它必须是指导人们进行社会实践的真理,任何失误和差错都会给人们带来惨烈的教训和沉重的代价。尤其是医学科学的发展,更须慎之又慎,因它是一门与人的生命息息相关的科学。     

桥本病合并甲状腺功能亢进临床分析

为探讨桥本病合并甲状腺功能亢进的临床特征及其诊断、治疗、预后，对1985～2002年间收治的桥本病176例进行回顾性分析。结果表明，桥本病合并甲状腺功能亢进的发病率为5．1％，桥本病一过性甲状腺功能亢进的发病率16．5％，手术治疗24例，低功5例，提示临床医师应重视桥本病、桥本病一过性甲状腺功能亢进及合并甲状腺功能亢进疾病的认识。诊断性用药、细针穿刺活检、T3、T4及吸碘率的测定对于明确诊断有重要意义，术中直视观察有助于甲状腺功能低下的预防，对一些一过性功能亢进而有呼吸道压迫症状的病人，术中尽量保留正常的甲状腺组织。     

激光皮肤治疗技术研究

利用激光对病损组织进行修复的皮肤整形过程,激光对皮肤的治疗,不仅可治愈各种胎记,也能治疗雀斑、纹身、眼眉色斑及鲜红斑痣等多种皮肤病,可为不同年龄的患者,包括老年人与婴儿作治疗.能够解决色素增生类和血管类皮肤病,改善或恢复先天造成的容貌和外表缺陷.激光对皮肤的治疗技术与传统的疗法相比具有出血少、痛苦小、手术质量高、手术时间短、疤痕少和复发率少等优点,是一种科学、快速、安全有效的美容方法.     

在.NET框架下用活动目录实现对WEB用户的认证

如何认证访问Web的用户 ,是网络安全的重要组成部分。在对用户进行认证的过程中 ,通过使用活动目录认证取代自定义方式认证 ,将极大地提高认证过程的安全性和认证效率。文章结合微软的活动目录及 .NETFramework技术并集成IIS、NTFSACL多种安全措施实现安全认证的网站 ,并用微软的C #语言实现编程     

P-拉普拉斯方程正解和多解的存在性

研究在RN中的一般形式的P-拉普拉斯方程-div(|Du|p-2Du)=f(x,u)(N>P>1).在一定的条件下得到正确和多解.首先建立相应的变分范函,利用H lder和Sobolev不等式证明此范函满足Palais-Smale条件,然后利用爬山原理证明了解的存在性.最后利用严格最大值原理证明了正解的存在性.