Influence Of Free Surface Curvature Of A Liquid Layer On The Critical Marangoni Convection

The Pearson instability was suggested to discuss the onset of Marangoni convection in a liquid layer of large Prandtl number under an applied temperature difference perpendicular to the free surface in the microgravity environment. In this case, the temperature distribution on the curved free surface is nonuniform, and the thermocapillary convection is induced and coupled with the Marangoni convection. In the present paper the effect of volume ratio of the liquid layer on the critical Marangoni convection and the corresponding spatial variation of the convection structure in zero-gravity condition were numerically investigated by two-dimensional model. (C) 2008 Elsevier Ltd. All rights reserved.

Computer Simulation Of Random Sphere Packing In An Arbitrarily Shaped Container

Most simulations of random sphere packing concern a cubic or cylindric container with periodic boundary, containers of other shapes are rarely studied. In this paper, a new relaxation algorithm with pre-expanding procedure for random sphere packing in an arbitrarily shaped container is presented. Boundaries of the container are simulated by overlapping spheres which covers the boundary surface of the container. We find 0.4 similar to 0.6 of the overlap rate is a proper value for boundary spheres. The algorithm begins with a random distribution of small internal spheres. Then the expansion and relaxation procedures are performed alternately to increase the packing density. The pre-expanding procedure stops when the packing density of internal spheres reaches a preset value. Following the pre-expanding procedure, the relaxation and shrinking iterations are carried out alternately to reduce the overlaps of internal spheres. The pre-expanding procedure avoids the overflow problem and gives a uniform distribution of initial spheres. Efficiency of the algorithm is increased with the cubic cell background system and double link data structure. Examples show the packing results agree well with both computational and experimental results. Packing density about 0.63 is obtained by the algorithm for random sphere packing in containers of various shapes.

Attractor crisis and bursting in a fluid flow with two no-slip directions

Characteristic burtsing behavior is observed in a driven, two-dimensional viscous flow, confined to a square domain and subject to no-slip boundaries. Passing a critical parameter value, an existing chaotic attractor undergoes a crisis, after which the flow initially enters a transient bursting regime. Bursting is caused by ejections from and return to a limited subdomain of the phase space, whereas the precrisis chaotic set forms the asymptotic attractor of the flow. For increasing values of the control parameter the length of the bursting regime increases progressively. Passing another critical parameter value, a second crisis leads to the appearance of a secondary type of bursting, of very large dynamical range. Within the bursting regime the flow then switches in irregular intervals from the primary to the secondary type of bursting. Peak enstrophy levels for both types of bursting are associated to the collapse of a primary vortex into a quadrupolar state.

The role of cell-surface-bound phosphatases in species competition within natural phytoplankton assemblage: an in situ experiment

Despite it is widely acknowledged that the ability to hydrolyze dissolved organic matter using extracellular phosphatases is diverse in fresh water phytoplankton, the competition within single species related to presence and quantity of cell-surface-bound phosphatases has not been examined in natural conditions yet. Here, we studied phytoplankton species competition in a freshwater reservoir during an in situ experiment. A natural plankton community, with the exclusion of large zooplankton, was enclosed in permeable dialysis bags inside two large containers of different bioavailable phosphate concentrations. Phytoplankton species biomass and the abundance of bacteria were determined in purpose to compare the development of enclosed microbial communities. Total and cell-surface-bound phosphatase activities in the phytoplankton were investigated using the Fluorescently Labelled Enzyme Activity (FLEA) technique that allows for direct microscopic detection of phosphatase-positive cells and, with image cytometry, enables quantification of phosphatase hydrolytic capacity. Production of extracellular phosphatases was not completely inhibited or stopped in the phosphate-enriched environment, phytoplankton cells only showed the activity less often. Under the phosphate-nonenriched conditions, the production of phosphatases was enhanced, but active species did not proliferate amongst phytoplankton assemblage. Further, specific growth rates of the phosphatase-positive species in the non-enriched environment were lower than the same phosphatase-positive species in phosphate-enriched environment. Interestingly, the phosphatase-positive cells of Ankyra ancora increased their size in both treatments equally, although the population in phosphate-enriched environment grew much faster and the cell-specific phosphatase activity was lower. We hypothesize that brand new daughter cells had sufficient phosphorus reserves and therefore did not employ extracellular phosphatases until they matured and needed extra bioavailable phosphorus to support their metabolism before cell division. Based on presented in situ experiment, we propose that the ability to hydrolyze organic polymers and particles with cell-surface-hound phosphatases is advantageous for longer persistence of given population in a phosphate-scarce environment; although phosphatase-positive species cannot dominate the reservoir phytoplankton solely because of specific phosphorus-scavenging strategy.

Shrinkage of Gobiocypris rarus, Procypris rabaudi, and Sinilabeo rendahli preserved in formalin

Length measurements of preserved fishes are necessary in many types of fish surveys because logistics often do not allow for fish measurement immediately after catch. If the fixative causes significant shrinkage, then the preserved lengths cannot be directly used to indicate accurate live lengths. The objective of this study was to determine how preservation in formalin affects standard length of Gobiocypris rarus larvae (24-day-old and newly hatched), larval Procypris rabaudi (4-day-old), and larval Sinilabeo rendahli (12-day-old). Fishes were measured (to nearest 0.01 mm) and individually fixed in the appropriate formalin solution (2.5% or 5.0% formalin), then re-measured at 0.5, 1, 3, 7, 14, 30, 45 and 75 days after preservation to follow the time course of shrinkage. Most of the shrinkage occurred within the first half day after preservation. The 5.0% formalin caused a higher relative shrinkage rate than did the 2.5% solution; however, the difference was not statistically significant. In G. rarus, initial shrinkage of newly hatched larvae was higher than that of 24-day-old larvae.

Analysis of expression of the binary toxin genes from Bacillus sphaericus in Anabaena and the potential in mosquito control

Anabaena strains expressing the binary toxin genes of Bacillus sphaericus produce high larvicidal activity with living cells. Western blot analysis showed that the 51-kDa and 42-kDa toxin proteins were stable in Anabaena. When a DNA fragment upstream of the 51-kDa protein gene was deleted, the toxicity was reduced by over a hundred-fold, whereas deletions at the coding regions showed that the cooperation of the two proteins expressed in Anabaena is essential for the larvicidal activity. Outdoor tests showed that the genetically altered Anabaena could keep containers with natural water from being inhabited by Culex larvae for over 2 months.

基于产品线工程的组件容器开发方法研究

近年来，随着Internet规模的增长，分布式组件技术快速发展，新的组件模型不断涌现，现有的组件模型也持续更新。组件容器为组件及组件应用提供部署和运行环境，是基于组件分布式应用开发的核心。组件模型的多样化和快速演化要求组件容器的开发方法将研究范围扩大到整个领域。产品线工程是基于软件核心资产构建软件产品系列的工程方法，将产品线工程方法应用于组件容器领域可以促进组件容器的系统化复用，获得更高的生产效率和产品质量。 由于组件容器领域的特点，应用过程中现有的产品线工程方法体现出一些不足。产品线工程包括领域工程和应用工程，其中领域工程又由领域分析、领域设计和领域实现构成。组件模型是组件容器需求的主要来源，但目前缺乏对组件模型的统一认识和详细分析；领域分析建模要求领域模型有效地刻画领域需求的组织结构、相互关系和变化性，并提供具体的建模过程指导，现有的面向特征、基于用例等领域建模方法存在语义模糊、粒度不当、缺乏具体流程指导等不足。 针对上述问题，论文按照软件开发流程顺序，从需求分析、领域建模、领域设计等方面，对组件容器设计和开发的若干关键问题进行了重点研究，包括组件模型分析、基于原子需求的领域建模方法、组件容器产品线体系结构等。 首先，由于组件模型是组件容器需求的主要来源，针对现有的组件模型分析方法粒度较大的问题，通过分析相关软件实体可能具有的各种约束，选择从语法、部署和交互三个方面，得到构成组件模型的模型元素，提出了一个细粒度的组件模型分析框架。将该分析框架应用于目前有代表性的分布式组件模型，基于分析结果提炼了分布式组件模型的主要公共特征，并与其他分析方法做了对比。 另一方面给出了基于原子需求的领域建模方法。以原子需求概念为基础，提出了一个多层次的领域需求描述模型，从用例、原子需求等多个层次刻画领域需求，并基于变化点建立独立的变化性描述机制。介绍了相应的领域建模过程，包括其建模步骤、建模原则和描述规范，为领域分析人员提供具体指导。并结合领域实例探讨了领域建模的过程。 基于以上工作，本文设计了组件容器产品线体系结构PLACE。首先将基于软件实体的组件模型分析框架与基于原子需求的领域建模方法相结合，建立组件容器领域模型，进而提出了组件容器产品线体系结构PLACE，从体系结构、模块功能、变化性设计和变化性管理等方面介绍了其设计。具体组件容器的设计实例表明，PLACE通过在组件模型和体系结构间建立直接的对应关系，有效促进了组件容器领域内的系统化复用。 最后，我们将上述方法应用于网驰平台中组件容器产品系列包括Web容器、EJB容器、BPEL容器和Portlet容器等的设计。实验结果证实了基于PLACE的开发方法在保证产品功能正确性的同时，提高了组件容器领域内的结构复用性，获得了更高的生产效率和产品质量。

A moored underwater energy conservation system for profiling measurement

There is a need to obtain the hydrologic data including ocean current, wave, temperature and so on in the South China Sea. A new profiling instrument which does not suffer from the damage due to nature forces or incidents caused by passing ships, is under development to acquire data from this area. This device is based on a taut single point mid-water mooring system. It incorporates a small, instrumented vertically profiling float attached via an electromechanical cable to a winch integral with the main subsurface flotation. On a pre-set schedule, the instrument float with sensors is winched up to the surface if there is no strip passing by, which is defined by an on-board miniature sonar. And it can be immediately winched down to a certain depth if the sonar sensor finds something is coming. Since, because Of logistics, the area can only be visited once for a long time and a minimum of 10 times per day profiles are desired, energy demands are severe. To respond to these concerns, the system has been designed to conserve a substantial portion of the potential energy lost during the ascent phase of each profile and subsequently use this energy to pull the instrument down. Compared with the previous single-point layered measuring mode, it is advanced and economical. At last the paper introduces the test in the South China Sea.

逆向物流流量不确定闭环供应链鲁棒运作策略设计

考虑一类同时具有再分销、再制造和再利用的闭环供应链在逆向物流流量不确定环境下的运作问题.采用具有已知概率的离散情景描述逆向物流流量的不确定性,利用基于情景分析的鲁棒线性优化方法建立该闭环供应链的多目标运作模型.设计了一个数值算例,其结果验证了运作策略的鲁棒性.在该算例基础上,分析了逆向物流流量的大小对闭环供应链系统运作性能的影响.

供应链中物流及信息流管理

供应链管理使企业在变化的市场环境中有效地与其它企业合作 ,取得集体竞争优势。本文首先讨论了后勤学与供应链管理的定义和之间的关系。本文认为供应链管理的核心是物流与信息流的控制。物流控制决策主要包括操作层次的库存补充和运输路径规划 ,以及战略层次的设施地点规划。信息流管理跨越部门与企业的界限将相关的应用集成起来。动态联盟协调各企业内部的生产经营活动 ,战略性地决定物流与信息流的构形。

STL格式文件拓扑重建及快速切片算法研究

建立三角面片之间拓扑关系是提高分层切片效率的关键因素之一,提出基于标准模板库set容器的拓扑关系重建算法及快速切片算法,有效地去除了STL文件大量冗余数据,简化了数据的存储,该算法每一个三角面片在每一切平面内只求一次交点,切片完成后可直接得到封闭轮廓环,以减少在切片过程中对三角面片的遍历次数、排序次数及求交点计算量,简化了轮廓环的构造过程,从而有效地提高了算法的效率。

基于整车配送的多仓库开路VRPTW问题的研究与实现

以整车销售物流为背景,探讨多仓库带时窗约束的车辆路线安排问题的解决方法.提出了更为复杂的基于现实的细节性要求的多配送中心开路VRPTW问题模型,并将遗传算法产生部分解和评估完整解的优化解决方法和涌现交叉算子MX1引入到带时窗的多仓库VRP问题优化中,实现了快速全局优化.提出的开路混合配送方法有利于提高车辆满载率,降低回程空载率.同时实现了运输资源的优化配置,提高车辆利用率.计算机仿真实验证明了算法的可行性.