纵向风作用下竖井自然排烟对隧道内烟气逆流长度的影响

为了研究纵向风作用下隧道内竖井自然排烟对烟气逆流长度的影响,采用数值模拟的方法,建立了不同竖井高度的全尺寸隧道模型。并选取无竖井排烟的工况作为对照组,模拟不同火源功率下,改变竖井与火源纵向距离时竖井自然排烟对烟气逆流长度的影响和竖井排烟失效临界风速的变化。结果表明：当纵向风风速较小时,竖井对烟气逆流起抑制作用;随着风速增大,烟气逆流被控制在竖井近域范围内,竖井对烟气逆流的抑制作用减弱;当风速足够大时,烟气逆流将被完全限制在竖井下游,此时竖井排烟作用失效,且对纵向通风气流起到分流作用,烟气逆流长度反而变长。在此基础上,提出了竖井排烟失效临界风速的概念,竖井排烟失效临界风速随竖井高度增加而增大。     

淀山湖水生态系统的物质循环

为了解淀山湖水生态系统中氮、磷的循环过程与特征,于1990～1995年间在全湖布设的25个样点上调查、测定了淀山湖水生态系统中各营养级的种类组成、生物量、生产力,以及水质和底质情况;并估算了淀山湖氮、磷的主要输入与输出途径和数量。根据湖中生物体内氮、磷的含量建立了淀山湖水生态系统内氮、磷循环模式。氮、磷输入、输出统计表明,磷基本平衡,氮每年约有117.72t积累在湖中。淀山湖目前仍以有机污染为主,处在中营养向富营养湖泊的过渡阶段。各类水生生物对于维持淀山湖水生态系统的物质平衡具有重要作用。     

沙漠环境特点及其对工程装备的影响

介绍了国内典型沙漠环境的特点,分析了其对工程装备的主要影响和危害,从装备论证、研制、设计定型和使用等全寿命周期提出了增强工程装备沙漠环境适应性所需要采取的措施。     

商用车铝合金与钢制轮辋生命周期环境影响评价对比分析

基于生命周期评价(LCA)理论,运用Ga Bi软件建模,采用EDIP 2003评价体系,对某款商用车铝合金轮辋和钢制轮辋的生命周期环境影响进行了评价和对比分析.结果表明:在原材料获取阶段铝合金轮辋对环境的影响要远远大于钢制轮辋;制造阶段两种轮辋对环境的影响相差不大;使用阶段钢制轮辋对环境的影响大于铝合金轮辋;综合所有阶段来看,当车辆总行驶里程低于11.6万km时,铝合金轮辋对环境的影响更大,超过11.6万km后,钢制轮辋对环境的影响更大.     

我国热带地区胶-茶-鸡农林复合系统物质循环研究

以海南省文昌市典型的胶-茶-鸡农林复合模式为研究对象 ,以单作胶园、胶茶间作园为对照 ,采用定量研究与定性分析相结合的方法 ,研究其物质循环规律。结果表明 ,胶-茶-鸡农林复合系统的氮、磷输入、输出量最大 ,系统外物质投入率比另两系统明显减少 ,系统内养分循环量增加 ,因此 ,该系统具有较合理的物质循环结构。     

The Information Content of a Scalar Plume – A Plume Tracing Perspective

The ability of many animals and insects to track a plume to its source is a particularly impressive feat when the fluid dynamics is considered. Inspired by this observation this research seeks to identify the information in a passive scalar plume suitable for developing robust and efficient plume tracing algorithms. The subject of this study is a scalar plume emanating from a point source in a turbulent boundary layer which has been modeled in a laboratory facility built specifically for this purpose. A coupled PIV-LIF technique is used to measure the velocity and scalar field in a time resolved fashion. This data set is analyzed and the convergence rates of five single-point statistics, suitable as kernels of plume tracing algorithms, are investigated. The experimental data shows that the scalar fluctuations over long downstream distances from the source are characterized by filamentary structures that lead to relatively slow convergence rates for any statistic that is based on mean concentrations. The scalar intermittency, however, converges rapidly toward its true value, in fact converging to a testable hypothesis for source location direction faster than the time scale of the larger scale plume meander.     

产品生命周期评价在固体废弃物管理中的应用

产品生命周期评价应用到固体废弃物的管理 ,可以改变传统的管理方法 ,为固体废弃物管理从产品设计、生产到废弃、处置全过程 ,提供系统的全过程管理概念     

Food (miles) for Thought - Energy Balance for Locally-grown versus Imported Apple Fruit (3 pp)

- This commentary compares the primary energy requirement for apples (cultivar ‘Braeburn’), which were either imported or locally-grown in Meckenheim, Germany. Imported apples of the same cultivar were grown in a Southern hemisphere winter in Nelson, Southland, New Zealand, and were picked at the end of March with subsequent 28 d transport by sea for sale in April in Germany. Locally-grown apples (cultivar ‘Braeburn’) were picked in mid-October and required a primary energy of nearly 6 MJ/kg of fruit including 0.8 MJoule/kg for five months CA storage at 1°C during a Northern hemisphere winter until mid-March. This compared favourably with 7.5 MJoule/kg for overseas shipment from New Zealand, i.e. a ca. 27% greater energy requirement for these imported fruits. Overall, the primary energy requirement of regional produce, stored several months on-site, partially compensated for the larger energy required to import fresh fruit from overseas. This result is in marked contrast to reported overestimates of a reported up to 8-fold energy requirement for domestic versus imported apple juice concentrate [7]. Our own findings of less primary energy required for domestic apple fruit is discussed with respect to providing local employment, fruit orchards preserving the countryside, quality assurance systems for local fruit such as QS and EUREP-GAP, networking and other factors favouring regional production.     

问歇曝气周期对低C/N比污水生物脱氮的影响

研究了间歇曝气生物脱氮工艺中,曝气周期和污水的c/N比对脱氮效率的影响,以及氧化还原电位(ORP)变化规律.中试试验结果表明,TN污泥负荷为0.05 kg/(kg MLVSS.d)时,间歇曝气系统的硝化反应所需曝气时间与总反应时间比至少要在0.5以上,一周期内搅拌时间不宜超过1 h;反硝化过程中难以找到ORP曲线突变点,因此,在低c/N比污水生物脱氮中ORP难以作为工程控制参数;由于原水的碳氮比太低,TN去除率只有35%～40%左右,为提高脱氮效率有必要投入外加碳源.     

快速成形技术的优势及其前景展望

基于快速成形技术的基本原理,比较了传统加工制造过程与快速成形过程的差异;并就涉及产品生命周期的几个核心环节如设计、制造、销售和用户等分析了快速成形技术的优势,展示了快速成形技术的广泛应用前景。