Turbulent natural convection in an enclosure with localized heating from below

This study reports the results of a numerical investigation of turbulent natural convection in a square enclosure with localized heating from below and symmetrical cooling from the vertical side walls. The present study simulates the case of an accidental heat generation due to fire in a typical isolated building of a nuclear reactor or electronic components cabin. The source of fire is considered to be centrally located at the bottom wall with different heated widths, which is assumed to be either isothermal or with isoflux. For the purpose of the analysis, the source length is varied from 20 to 80% of the total width of the bottom wall. The top wall and the unheated portion of the bottom wall are considered to be adiabatic, whereas sidewalls are isothermal. Steady as well as transient forms of two-dimensional Reynolds–Averaged-Navier–Stokes equations and conservation equations of mass and energy, coupled with the Boussinesq approximation, are solved by the control volume based discretisation method employing the SIMPLE algorithm for pressure–velocity coupling. Turbulence is modeled using the standard k–ε model. Rayleigh number, Ra, based on the enclosure height is varied from 10⁸ to 10¹². Stream lines and isotherms are presented for various combinations of Ra and the heated width. A double cell flow pattern is observed with marginal loss in symmetry as Ra increases. The results are reported in the form of local and average Nusselt number on the heated floor. Correlations are developed to predict the heat transfer rates from the enclosure as a function of dimensionless heated width of the bottom wall and Ra, by least square linear regression analysis.     

J55钢HFW焊管管体的腐蚀电化学行为

采用电化学方法研究了J55钢HFW焊管管体在模拟长庆油田高矿化度油井水中的腐蚀行为,考察了矿化度和预腐蚀的影响。试验结果表明,随着溶液矿化度的增大,自腐蚀电位朝正的方向移动,但自腐蚀速率与矿化度呈非直线规律。当矿化度为23.204 g/L时,管体材料具有最大的腐蚀速率。随着预腐蚀时间的增长,极化电阻增大,发生一定程度的电阻极化,相应的腐蚀速率会有所降低。     

FT8—55燃压机组技术考察报告

文章综述了德国MGB公司生产制造燃压机组的情况。FT8－55燃压机组在德国输气管道Wingas和Werne天然气压气站的运行使用状况;对FT8燃机和MGB公司压缩机的特性,以及配套燃压机组的优势作了基本介绍。可供天然气长输管线压气站选择燃压机组作为参考。     

中碳J55钢HFW焊接油井管钩状裂纹缺陷分析

钩状裂纹缺陷是导致中碳J55钢超声波探伤不合格的主要原因。针对中碳J55钢HFW焊接过程中出现的不同钩状裂纹缺陷进行了分析,并提出了改进措施。研究结果表明,造成中碳J55钢HFW焊接钩状裂纹的主要原因为钢中的大颗粒夹杂物以及板厚1/4位置严重偏析,且现有的夹杂物及带状组织检验标准难以对J55钢的质量进行有效管控。通过减少单中包连浇炉次、增加铸坯头尾切废量以及改用直弧形连铸机等措施,钩状裂纹缺陷率可大幅降低。     

热浸镀55%Al-Zn后钢的拉伸性能和耐蚀性能研究

研究了热浸镀55%Al-Zn合金镀层钢的室温拉伸性能和耐蚀性能。结果表明：Q235钢板经热浸镀55%Al-Zn合金后的室温屈服强度和抗拉强度均高于Q235钢，而伸长率没有降低。经SEM观察，55%Al-Zn合金镀层钢的拉伸断口由钢基体的韧窝断口和Fe-Al-Zn-Si合金层的穿晶解理断口组成。腐蚀试验结果显示：热浸镀55%Al-Zn合金后钢的耐蚀性在盐雾中是镀锌钢的6倍，在盐水中是镀锌钢的3倍，并同样具有镀锌层对钢基体的电化学保护能力。     

石油套管用热轧钢带J55缺陷原因分析

对热轧钢带J55在制造石油套管时焊缝附近出现的细裂纹缺陷进行分析。结果显示,此类缺陷是由于连铸板坯原始缺陷经热轧轧制后形成的。     

A scenario-driven conceptual design information model and its formation

This study describes a scenario-driven conceptual design information model and its formation from the viewpoint of the designer55jbrv/xxlarge8217.gif" alt="rsquo" align="BASELINE" BORDER="0">s cognition, which is a fundamental part of practical design support tools. Four design meetings were observed in a company, at intervals of several weeks, in order to derive the model. The model consists of information elements generated through the cognitive design problem-solving process, which is a basic design process defined in this study. The study describes the relationship among these information elements, which illustrate the design information model and its formation. The model described in this study is based on scenarios, which promote the evolution of product design. Examples of designers55jbrv/xxlarge8217.gif" alt="rsquo" align="BASELINE" BORDER="0"> discourse in the design meetings are presented to validate the model.     

Digital fundamental group and Euler characteristic of a connected sum of digital closed surfaces

Unlike the connected sum in classical topology, its digital version is shown to have some intrinsic feature. In this paper, we study both the digital fundamental group and the Euler characteristic of a connected sum of digital closed k_i-surfaces, i∈{0,1}.     

镀55%铝锌板在冰箱后背板上的应用

镀55%铝锌钢卷的铝锌合金结构是由55%铝、43.4%锌与1.6%硅在600℃高温下固化而组成。其整体结构由铝、铁、硅、锌形成致密的四元结晶体,此结晶体在钢板上形成一层屏障,因此能有效地防止腐蚀因子穿透。     

溶瘤腺病毒ZD55-Mn-SOD联合TPL对骨髓瘤细胞的生长抑制效应

研究利用携带Mn-SOD的溶瘤腺病毒Ad-E1A-△E1B55Kd-Mn-SOD(ZD55-Mn-SOD)联合小分子化合物雷公藤内酯醇(Tnptolide,TPL)对骨髓瘤细胞株RPMI8226、U266生长的体外抑制效应,希望找到解决化疗药物在临床使用中所出现的疗效低及毒副作用大的方法.采用CCK-8比色分析方法表明100 MOI ZD55-Mn-SOD与TPL(2 ng/mL、4 ng/mL)联合处理后,RPMI 8226及U266的细胞存活率均显著低于单用ZD55-Mn-SOD或TPL(P＜0.05);用结晶紫染色法定性分析了ZD55-Mn-SOD联合TPL对两种骨髓瘤细胞的杀伤作用;最后Hoechst33342染色法观察细胞凋亡也显示联合应用ZD65-Mn-SOD与TPL处理组的细胞凋亡现象比二者单独使用均要显著.本研究初步证实ZD55-Mn-SOD与TPL联合具有协同作用,能有效地在体外抑制骨髓瘤细胞RPMI 8226和U 266的生长.