上升流式生物流化床反应器膨胀行为的数学建模与分析

基于Richardson—Zaki液固流态化方程,运用数值模拟分析的方法针对上升流式生物流化床反应器的膨胀行为展开了研究,并建立了相应数学模型．同时以厌氧膨胀颗粒污泥床反应器为例进行了数值模拟研究,数值模拟研究结果很好反映了该反应器的特点且两次相关实验结果的平均相对误差分别为4．74％和8．3％．所得结果显示所建模型以及所采用的数值模拟分析方法基本可行．     

磷矿堆场多目标优化配矿模型

以磷矿浮选场堆场配矿过程为研究对象,选取人选原矿品质指标及低品质矿石利用量为主要目标,增加资源量约束及决策变量非负约束,构建了堆场多目标优化配矿模型.同时应用Matlab优化工具箱中多目标规划解算函数,对算例及实际配矿模型求解验证,并与现场混配结果进行比较,配矿效果明显.研究结果表明:磷矿多目标优化配矿模型实现了磷矿堆场配矿工艺及过程的简单、直观、较完整描述,Matlab优化工具箱多目标规划相关函数,对求解磷矿堆场多目标优化配矿模型是简便、有效的.     

Bias in bacteriophage morphological classification by transmission electron microscopy due to breakage or loss of tail structures

Virtually every study that has used transmission electron microscopy (TEM) to estimate viral diversity has acknowledged that loss of phage tails during sample preparation may have biased the results. However, the magnitude of this potential bias has yet to be constrained. To characterize biases in virus morphological diversity due to tail loss, six phage strains representing the order Caudovirales were inoculated into sterile sediments and soils. Phage particles were then extracted using standard methods. Morphologies of extracted phage particles were compared to those of unmanipulated control samples to determine the extent of tail breakage incurred by extraction procedures. Podoviruses exhibited the smallest frequency of tail loss during extraction (1.2-14%), myoviruses were moderately susceptible to tail breakage (15-40%), and siphoviruses were highly susceptible (32-76%). Thus, TEM assessments of viral diversity in soils or sediments by distribution of tail morphologies may be biased toward podoviruses and virions lacking tails, while simultaneously underestimating the abundance of siphoviruses. However, since the majority of viral capsids observed under TEM were intact, estimates of viral diversity based on the distribution of capsid diameters may provide a more reliable basis for morphological comparisons within and across ecosystems.     

冲积河流滩槽定量划分方法及应用

通过理论分析与数值计算,研究了冲积河流漫滩水流水力因子的变化特性。结果表明,断面平均流速在漫滩瞬间迅速减小,然后逐渐增大;断面综合动能修正系数、动量修正系数均随水深而缓慢增加,在漫滩瞬间迅速增大,随即快速减小。根据漫滩水流水力因子沿水深的变化特性,提出采用断面横向平均流速为判别因子以定量划分复式断面的滩与槽。此外,文中将其应用于黄河下游漫滩水流的水沙数值模拟,其结果与实际情况符合较好。     

黄河上中游流域泥沙优化配置研究

针对流域水土流失的灾害性、泥沙利用现状及泥沙优化配置的必要性,基于大系统分解-协调思想的流域泥沙优化配置原理与流域各子系统的泥沙多目标优化配置方法,构建了流域泥沙优化配置理论框架。进而建立了黄河上中游流域泥沙优化配置数学模型,该模型包括相互联系的各子系统、各分区和大系统三级泥沙优化配置数学模型,开展了不同水沙条件的黄河上中游流域泥沙优化配置方案计算,对计算结果进行了评价并提出了建议方案,为黄河上中游流域泥沙的科学治理提供了参考依据。     

Covering a convex 3D polytope by a minimal number of congruent spheres

The problem of covering a convex 3D polytope by the minimal number of congruent spheres is reduced to a sequence of problems of minimising sphere radius when fixing the number of the spheres. We form a mathematical model of the problem using the Voronoi polytopes. Characteristics of the model are investigated. Extrema are attained at the vertices of the Voronoi polytopes constructed for sphere centres. To search for local minima, a modification of the Zoutendijk feasible directions method in a combination with random search is developed. Some numerical results for a cube and a non-regular octahedron are obtained.     

Beyond synthesis: re-presenting heterogeneous research literature

This article examines the nature, role and function of the literature review in academic discourse. Researchers in information systems (IS) are often advised to espouse a neutral viewpoint and adapt the goal of synthesising previous literature when conducting a literature review. However, since research literature in many areas of IS is diverse and heterogeneous, this synthesis is not value neutral, but is a construction of the researchers. We suggest that other goals and viewpoints for reviewing and presenting previous literature are possible, and in some cases, desirable. Using the example of service quality literature, we use a lens of historical discourse, and techniques of soft systems analysis and rich pictures, to present previous research literature on ServQual-related research in IS and electronic commerce. We identify seven ‘stories’ from service quality research literature and analyse the clients, actors, transformations, world-view (weltanschauung), owners and environment in each story. We conclude that alternative presentations of research literature can offer fresh insights, especially in areas where the research literature is diffuse, contradictory and heterogeneous.     

真空-堆载联合预压法在软土路基处理中的应用

以苏州市工业园区桑田岛河湖相软土地基为研究背景,介绍了真空-堆载联合预压法的加固机理和桑田岛软土地基的工程地质条件,经过现场踏勘和室内土工试验的分析拟采用真空-堆载联合预压法对该软土地基进行处理。通过对真空预压试验段的地表沉降、水平位移的监测分析,对路基加固效果进行了评价,认为本试验段采用真空-堆载联合预压法处理是成功的,有效的提高了软土地基的物理力学性质及承载能力,在类似工程中推广应用是可行的。     

太阳能飞机工作条件对太阳能电池性能的影响

太阳能飞机能源系统的核心部件是太阳能电池,性能受外界环境影响动态变化,准确预测其性能是飞机方案设计的重要基础工作。文章以光伏发电模型为基础,通过模拟太阳辐射和太阳能电池温度的逐时变化,预测了太阳能电池在飞行时间、速度和高度等工作条件变化时的性能。研究结果表明,受一天内太阳辐射和环境温度的变化影响,飞行时间是太阳能电池性能最大的影响因素,性能指标以太阳时12点为中心左右基本对称变化。飞行高度的改变伴随太阳辐射和环境温度变化,每升高1 km,开路电压提高1.52%,短路电流提高1.49%,最大功率提高3.65%。飞行速度的改变使得太阳能电池温度变化,每加速10 km/h,开路电压提高3.90%,短路电流降低0.31%,最大功率提高5.32%。以上研究,预测了太阳能电池在不同工作条件下的变化情况,为正确选择和改进能源系统方案奠定了理论基础。     

滨海吹填土固结蠕变特性试验研究

围海造陆形成的吹填土地基与天然形成地基的工程特性存在诸多差异,为了保证吹填土地基的长期稳定性和安全性,有必要揭示吹填土与天然土工程特性的差异。利用单向固结仪,开展了不同加荷方式下滨海典型软土和围海造陆吹填土的蠕变特性试验对比研究,得到了不同试验条件下土体的应变、应力和时间的关系,对比分析两种软弱土蠕变性状的差异和影响因素,同时给出次固结系数的变化规律。试验结果表明,分级加载下两种滨海软土均具有明显的非线性蠕变特性,高应力水平下经排水加固的吹填土最终变形量明显低于软黏土,而次固结变形较大;吹填土的一维固结蠕变特性受加荷比和试样高度影响,加荷比越大、高度越高土样最终蠕变量越大;次固结系数与加荷比和荷载等级有关,表现为次固结系数随荷载增大先增大后减小,峰值随加荷比增大而减小。