Numerical Simulation of 3D Atmospheric Flow Around a Bluff Body of CAARC Standard High Rise Building Model

Based on Reynolds Averaged Navier Stokes Equations(RANS)standard k ε model, realizable k ε model, RNG k ε model and SST k ε model, the 3D steady wind flow field around standard high building CAARC in atmospheric boundary layer was numerically simulated with software Fluent 6.3. And upon the comparison with those from wind tunnel test, it was found that numerical simulation was a feasible way to study the wind flow around high building and the distribution of wind pressure in the building’s surface. The four proposed models can reach the accuracy from the actual demand. Furthermore, it was also shown that, the numerical results were approximate to those from wind tunnel tests in the windward while between those from NPL and TJ 2 tests in the side and leeward. The pressure on the windward surface was positive with the maximum at 2/3 height and the minimum on the sides and the bottom. The pressures on the leeward surface and two sides were negative. There were little differences among the results of the four models.     

An Improved Grey Relation Model of Safety Evaluations of Evacuation from High rise Building Fires

Based on a study of the time process of individual evacuees in high rise building fires, we found that the low security influencing factor will affect the possibility of successful evacuation severely. The traditional grey relational grade cannot reflect the effect of the grey relational coefficient fluctuation. Moreover, the single weight calculation with a subjective or objective weight will also directly affect the evaluation result of safe evacuation during high rise building fires. Based on these analyses, the grey Euclid relative grade was applied to indicate the effect of the grey relational coefficient fluctuation. The Spearman correlative rating coefficient was used to combine the subjective and objective weights to eliminate the deficiency of the single weight case. We discuss the possibility of applying the improved grey relational evaluation. Comparing the evaluation results, we found that the weight combination and grey Euclid relation applied in a safety evaluation model can improve evaluation result accuracy. The evaluation model thus corresponds to the characteristics of high rise building fires and the weight set substantially affects the evaluation result.     

基于跑车升角和摩擦卷筒传动的驱动机功率计算

利用跑车运行升角和摩擦卷筒传动理论,提出基于牵引和运输计算驱动机功率的方法.从得到的计算结果取较大者表示缆索起重运输机所需驱动功率.     

Near-future sea level impacts on coastal dune landscapes

Very little attention has been paid to the impact of global warming, especially sea level rise, on coastal dunescapes, despite the fact that these provide natural protection along many of the world's shorelines. This paper reviews likely responses given the IPCC climate change predictions to 2030AD, which include sea level rise in the order of 0.09 to 0.29m. It is envisaged that coastal dunes will react in a variety of ways dependent both on regional and local factors. Rising water levels will increase susceptibility to erosion, but the fate of released sediment, particularly the onshore/offshore partitioning, must depend on morphodynamic antecedence, and the propensity for periodic domain shifts. The release of material at the shoreline may allow construction of coastal dunes, to the point of progradation in some zones. The response of dune vegetation to a warmer, wetter climate is uncertain. Most of the main temperate dune species are C3 plants which given favourable conditions would respond positively to CO₂ enhancement. However local factors may offset such potential gains.     

The possible influence of sea level rise on the precarious dunes of Devesa del Saler Beach,Valencia, Spain

The Saler Beach dune field in Spain was partially destroyed between 1970 and 1973 due to building development. Presently great efforts to restore some dunes has begun. The possible consequence of a sea level rise for the Saler dune field is discussed according to different scenarios.     

浅谈高层建筑结构设计的重点和难点

由于我国人口数量的增多,为解决住房等问题需要发展建筑行业,尤其是要发展高层建筑行业。随着建筑高度的不断增加,建筑的形式和结构功能也变得复杂多样,因此,高层建筑的结构设计工作便成为建筑工程师在设计过程中的重点和难点。本文着重对高层建筑结构设计过程中应注意的问题进行分析。     

周礼对鲁国兴衰的影响

周礼曾使西周初期鲁国国内政局相对稳定,社会和谐,经济发展,成为当时众多诸侯国的精神领袖,其国家政治地位高,综合实力也足以与当时的东方强国齐国相比肩,但后期的鲁国面对不可阻挡的历史洪流,不思进取,仍一味地固守周礼,最终导致亡国的命运。     

夹砂层土体构型毛管水上升的实验研究

针对西北地区土壤剖面多呈层状和春季强烈返盐季节土壤多处于裸露状态的特点，通过室内土柱实验，研究了有地下水位条件下夹砂层剖面的土壤蒸发问题。结果表明，砂层会影响毛管水上升的高度和速度，毛管水到达土表的时间随砂层厚度的增加、层位的升高以及级配的变差而延长，但砂层级配对于水分的阻滞作用最大。砂层影响各层土壤含水量的分布，在水分达到平衡状态时，砂层以下土壤含水量大于均质土，而砂层以上土壤含水量则小于或近似于均质土。砂层能明显降低地下水的蒸发量，但夹砂层土柱的蒸发量随砂层厚度的增加而降低，而表砂层土柱的蒸发量则随砂层厚度的增加而增强。在蒸发阶段，砂层层位的作用表现更为显著。     

剥皮机挤压揉搓机构中曲沟球轴承的试制及其承载能力

为了满足剥皮机的挤压揉搓作业效果,简化机械结构,设计了一种曲沟球轴承。建立曲沟球轴承受力分析模型,分析了不同加载力下滚动体与外圈滚道的峰顶到谷底之间5个接触点的接触应力,得到滚动体与外圈之间的接触应力从峰顶到谷底逐渐减小、随着加载力的增大而增加的趋势;在此基础上,试制了外圈为三维正弦曲线环形圆弧滚道,内圈为定点窝眼滚珠结构的曲沟球轴承,用自制的试验台对试制的曲沟球轴承进行了测试。结果表明:加载力增大,轴承外圈的温升幅度增高,温升速度加快,经过10 min后,温升曲线趋于平缓,基本达到了热平衡状态。研究成果为曲沟球轴承的结构优化、定型生产及后续的推广应用提供了参考。     

架空炕与传统落地炕热性能对比试验

为了解架空炕与落地火炕升温特性、热效率等方面的特性,依据国家相关标准,对甘肃省临洮县传统落地火炕与2016年新推广的架空炕进行了热性能的对比试验,研究了炕面温度分布、炕面升温降温速率、排放烟气温度、炕温对室内温度的影响以及架空炕的节能减排等性能,研究结果表明:架空炕和落地火炕炕面平均升温速率分别为2.2和0.9℃/h;烟气热量能被架空炕充分地吸收利用,架空炕烟气排放平均温度较落地火炕烟气排放平均温度低36.1℃;架空炕和落地火炕的热效率分别为66.8%和37.1%,相比传统炕架空炕节柴率达到45%;有架空炕和落地火炕室内日平均温度分别为12.6和10.8℃,架空炕对室内有较好的增温效果;与落地火坑相比,架空炕有明显的节能减排效果,每铺架空炕每年节省945 kg薪柴,减排CO21 069.17 kg,减排SO20.45 kg,减排NOx 1.01 kg,减排PM107.4 kg,减排PM2.5为6.8 kg,架空炕的推广应用对中国农村节能减排具有重要意义。