Effects of low-frequency electromagnetic field on the surface quality of 7050 aluminum alloy ingots during the hot-top casting process

To improve the quality of 7050 aluminum alloy ingots, low-frequency electromagnetic (LFE) field was applied during the conventional hot-top casting process. Macrostructures and microstructures of the ingots by the conventional and LFE hot-top casting processes were studied. The experimental results show that when the LFE field is turn off during the hot-top casting process, cold folding appears, and the as-cast structure becomes very coarse. Additionally, the thickness of the shell zone is much thinner during the low-frequency electromagnetic hot-top casting process than that during the conventional hot-top casting process. Some reasons for low-frequency electromagnetic field improving the surface quality, refining the structure of the ingot, and minimizing the thickness of the shell zone have been studied.     

The spring soil moisture and the summer rainfall in eastern China

The relation between the soil moisture in spring and the rainfall in summer in eastern China is investi- gated. Results show that the summer rainfall in eastern China is closely related to the spring soil moisture in the area from North China to the lower reaches of Yangtze River (NCYR). When spring soil moisture anomalies over NCYR are positive, the summer precipitation exhibits positive anomalies in Northeast China and the lower reaches of Yangtze River, and negative anomalies in southern China and North China. The higher soil moisture over NCYR cools land surface and reduces the land-sea tem- perature gradient, which weakens East Asian summer monsoon. The western Pacific Subtropical High (WPSH) is located to the south and shifts westward, resulting in more rainfall in the lower reaches of Yangtze River and less in southern China and North China.     

合金钢的退火不软化行为

某些合金经热处理后产生退火不软化问题．作者对W18Cr4V和18Cr2Ni4WA2种合金钢进行了锻后软化退火试验,对退火组织进行了SEM分析,对合金钢的退火不软化原因进行了探讨,提出钢的退火必须根据等温转变C曲线（即TTT图）,以确定其方法与工艺,从而获得最佳的切削加工性能．实验结果表明W18Cr4V钢经普通退火处理,硬度偏高（269～286HBS）;采用等温退火方法,软化效果好,满足了切削加工对硬度的一般要求（＜255HBS）;无论采用何种退火方法,18Cr2Ni4WA合金钢的硬度均不能满足要求,只有采用高温回火的办法,方可使其软化．     

不同工况下各种材质高炉冷却壁温度场数值模拟

建立高炉冷却壁稳态传热模型,模拟球墨铸铁、铸钢和铜3种材质的冷却壁在热面镶砖、裸露和挂渣等工况下的温度场分布。结果表明,相同工况条件下,铜冷却壁导热性能优于铸钢冷却壁导热性能,铸钢冷却壁导热性能优于球墨铸铁冷却壁导热性能;铸钢冷却壁热面温度远低于球墨铸铁冷却壁热面温度;渣皮的存在,对冷却壁体起温度降低和保护作用,从而延长冷却器及高炉寿命。     

高炉冷却壁冷却能力影响因素分析

通过对某厂生产的高炉铸铁冷却壁进行热阻分析,计算不同参数条件下冷却壁本体与冷却水之间的综合换热系数,从而探讨冷却水速、水垢厚度、涂层厚度、气隙厚度等因素对高炉冷却壁冷却能力的影响。结果表明,提高冷却水速、减少水垢、减小涂层厚度均可提高冷却壁本体与冷却水之间的综合换热系数;气隙热阻占总热阻的71.6%以上,是影响冷却壁冷却能力的限制性环节,减小气隙厚度可以明显提高综合换热系数。冷却壁本体与冷却水之间的综合换热系数在121.5~343.8 W/(m2·℃)范围内。     

IL-2与猪瘟病毒E_2基因真核双表达载体的构建及其免疫增强作用的研究

应用DNA重组技术构建了猪瘟病毒E2 基因与IL 2基因的双表达真核表达载体 ,观察其表达水平 ,并对其免疫增强效果进行了观察。结果是构建了猪瘟病毒E2 基因与白细胞介素 2的真核表达质粒pIRSTIL 2。将质粒转染BHK 2 1细胞 ,可在体外表达E2 和有生物活性IL 2。pIRSTIL 2质粒能诱导产生CSFV的特异性免疫反应。pIRSTIL 2所诱导的免疫应答反应比使用单表达质粒pIRST强。实验表明 :IL 2与猪瘟病毒E2 基因构建的双表达基因疫苗能有效提高基因疫苗的免疫效果     

A Way to Find All the Optimal Solutions in Linear Programming

1.INTRoDUCTIoNIngeneral,theoptimalsolutionsformedinactualbusinessmanagementsituationsprovidethebesteoforcemelltplansinthegivenpracticalproblems.Whenthereismoretha-noneoptimalsolutioninlinearprogramming,thereekistsunlimitednumberofoptimalsolutions.Tofindthemultipleoptimalsolutionsinlinearprogradringisaverysignificantwork,becausethedecisionmakercanbegivenmoreoptimalplanstochoosefrom.Sofar,therehavebeenmanypaPersdiscussingthesituationofunliIintedoptimalsolutions.However,therearendstthesandde…     

两个钆吸附在Z型石墨烯纳米带上的第一性原理研究

巨大的Rashba效应对于自旋电子学的应用至关重要,但很少涉及一维磁性体系,为了探究一维磁性体系Rashba效应的特征和强度,提出了两个钆原子吸附在Z型石墨烯纳米带上的一维磁性结构,通过第一性原理计算方法分析了不同磁态下不同磁化轴方向的Rashba效应以及体系的磁各向异性。结果表明,反铁磁基态下的体系具有很强的Rashba强度和面外磁各向异性能。磁性体系中的Rashba效应需要考虑磁性原子的自旋磁矩。这项工作对设计一维磁性Rashba体系具有重要的意义。     

ERT网络计算分析之补充

为解决PERT网络中可能有多于一条关键线路或次关键线路时 ,在特定计划工期下对工程完工概率的影响问题 ,从分析进度网络结构入手 ,在分清这些线路是相关的还是相互独立线路的基础上 ,针对各种情况 ,给出分析计算方法与算例 .此外 ,为了修订工程工期 ,对活动持续时间的压缩提出一种简便的方案 .