德摩根商拓扑代数的拓扑性质

探讨了德摩根商拓扑代数的连通性，可分性等一些拓扑性质，并建立了德摩根商拓扑代数为Ｔ１的一个充分必要条件。     

近30年来典型山地城市建设用地蔓延的时空特征分析

作为典型的山地城市,重庆市自改革开放的近30 a内,区域建设用地的数量发生了很大变化,因此对其建设用地蔓延情况进行详细的了解十分必要。通过构建拓扑关系指数区分建设用地蔓延类型,分析了1978—2007年不同研究时段、不同区域的建设用地在平面和立面的蔓延特征。结果表明,研究区建设用地从5 885.69 hm²增加到29 347.47 hm²;跳跃型发展是建设用地主要的蔓延类型;建设用地的蔓延使得区域建设用地的重心在竖向方向上由1978年的250.40 m升高到2007年的284.61 m。近30 a来重庆城区的建设用地增长迅速,建设用地的重心不断抬升,可能会影响到区域的生态安全,因此需从规划的角度对城市扩展进行科学合理的指导。     

约束对应的图像拓扑下拟变分不等式解的稳定性

以往关于拟变分不等式解的稳定性的研究,都采用约束映射之间的一致度量.现采用约束映射图像之间的Hausdorff度量,并在此弱图像拓扑下,得到了拟变分不等式解的稳定性,即在Baire分类的意义下,大多数的拟变分不等式的解均是本质的.     

电子交易市场实时拍卖系统分析及设计

电子交易市场实时拍卖系统是一种基于Internet的第三方大宗商品电子交易平台。它以电子拍卖形式进行交易,涵盖了货款支付、货物交收及市场管理业务。系统采用了C／S与B／S相结合的混合体系架构,兼顾了系统的实时性与协同商务流程的灵活性。本文介绍了该实时拍卖模式,对其运营系统的运行时TOP架构、实时数据处理、实时通讯及系统安全进行了分析与设计。     

基于权重优化的液压机械无级变速器箱体的轻量化设计

为了优化自主研发的六轴式三行星排液压机械无级变速器(HMCVT)箱体的结构性能,提高材料的利用率,减轻箱体质量,对HMCVT箱体进行拓扑优化设计。考虑HMCVT箱体所受载荷的复杂性,基于虚拟样机技术,建立变速器虚拟样机模型,结合拖拉机地面振动测试,获取单行星排工作、双行星排工作和三行星排工作3种不同载荷传递工况下变速器轴承孔动载荷;以应力、体积比为约束,基于折衷规划法建立包含3种载荷传递工况下刚度和箱体前三阶固有频率的综合目标函数;考虑子目标权重的影响,基于代理模型和遗传算法获取最佳权重并与层次分析法进行对比分析;最后,利用Hypermesh对HMCVT箱体进行拓扑优化求解。优化结果表明,优化后的箱体最大应力减小了13.6%,最大变形减小了0.5%,箱体的刚度和强度基本不变或略有提升,质量减轻10.9%,实现了变速器箱体轻量化目标。     

冗余铺丝机械手逆运动学的拓扑流形分析

针对优化的梯度投影算法在冗余铺丝机械手逆运动学求解问题中不一定存在最优解的问题,提出了一种拓扑流形算法。将冗余铺丝机械手的位形空间看作一个光滑流形,对耦合的位置逆解和姿态逆解进行解耦,然后分别针对位置子流形和姿态子流形进行仿真分析得到其相应的仿真拓扑流形。该方法可以将铺丝机械手的运动学问题抽象为数学中的曲面拓扑流形来研究,为铺丝机械手运动学在流形上分析提供了理论基础,同时也为后续铺丝机械手的最优化自运动控制提供了一种新的方法。最后以飞机S形进气道为例进行仿真,验证了所提方法的正确性。     

4-TPT与其变拓扑结构并联机构的特性

给出了并联机构具体可行的变拓扑结构途径.以4-TPT并联机构为例,以其串联分支为基础,依据螺旋理论研究了其中一种变拓扑实现形式,得到了数量众多的对称型与非对称型变拓扑结构并联机构.通过对该类变拓扑结构并联机构特性进行的分析、研究和对比,表明变拓扑结构并联机构的工作空间与灵巧度性能指标有了显著提高.     

组合式三相逆变器同步控制方法

为实现组合式三相逆变器输出电压的同步控制,该文以三台单相储能逆变器Y/△连接为例,对其离网模式及离并网预同步过程时的同步控制方法进行研究。该文在离网模式下采用基于CAN(controller area network)总线通信的基准时间同步与相位调整同步的主从同步控制方法;在此基础上,针对离并网预同步过程,该文提出了一种基于改进的二阶广义积分锁相环的频率调整同步控制方法,引入了逻辑判断控制器,实现了三相逆变器电压输出相位差时刻满足120°,保证了离网模式及离并网预同步过程时输出电压的同步,为离并网无冲击切换打下基础。最后,实际试验验证了该方法的可靠性和实用性。     

Effects of environmental factors on growth and mortality of Parashorea macrophylla (Dipterocarpaceae) planted on slopes and valleys in a degraded tropical secondary forest in Sarawak,Malaysia

Enrichment planting with climax trees such as dipterocarps is required to rehabilitate degraded tropical forests in Southeast Asia, because these forests have been damaged by various anthropogenic activities. Severely degraded tropical secondary forests are the most important targets for enrichment planting in the region, because secondary forest trees potentially provide moderate conditions for planted seedlings by preventing strong sunlight and high temperatures. In an enrichment planting site located in Sarawak, Malaysia, we explored how variation in secondary forest structure (biomass and stand density) and soil (nutrient and water) conditions influenced the mortality and growth rates of planted dipterocarp seedlings (Parashorea macrophylla, Wyatt-Sm. ex P.S. Ashton) over the period from 2000–2007. Experimental plots were set up on different topographical features (slopes and valleys). Using the data collected, we demonstrated the ways in which environmental factors, such as soil nitrogen content, relate to climax tree seedling growth and mortality in degraded tropical secondary forests dominated by the genera Macaranga, Ficus, and Glochidion. Stand density and total aboveground biomass of secondary forest trees were significantly lower in the valley plots than on the slopes, whereas soil total nitrogen and water contents were significantly higher in valley plots. Over seven years, the total biomass of trees increased, whereas the density of secondary forest trees decreased in all plots. Nutrient stocks (nitrogen, phosphorus, potassium, calcium, and magnesium) in the soil (0–5?cm) also decreased over seven years in all plots. Height, diameter, and mortality of planted seedlings were higher in the valley plots than on slopes. Multiple stepwise regression demonstrated significant positive effects of total soil nitrogen and water content on the relative growth rate of seedlings over seven years. There were no significant relationships between seedling mortality and any of the environmental factors measured, including soil conditions. We conclude that (1) seedling growth was enhanced by soil total nitrogen rather than by available phosphorus or potassium, and (2) planted seedlings grew faster and died more often in the valley plots than on the slopes.     

Root Architecture Plasticity of Citrus Rootstocks in Response to Nitrate Availability

Under nutrient heterogeneous soil conditions, the ability of plants to compete for resource acquisition was closely related to the plasticity of root architecture, intended as a change of topology and geometry.

Root architecture variations in response to different nitrate supplies of co-generic citrus rootstocks, ‘Rough Lemon’ (Citrus jambhiri Lush), ‘Sweet Orange’ (Citrus sinensis (L) Osbeck), ‘Cleopatra Mandarin’ (Citrus reshni Hort ex Tan.), and ‘Sour Orange’ (Citrus aurantium L.) are reported here. Root architecture was gauged by an image-specific analysis system (WinRHIZO).

Based on the topological index, root topology of citrus rootstocks varied in response to nitrate treatments. In terms of root geometry, external-external and, to a lesser degree, internal-internal links of all rootstocks changed in response to nitrate supply. Among the rootstocks, ‘Cleopatra Mandarin’, both in terms of root topology (high TI) and root geometry (high length of exterior and interior link), could be considered less competitive owing to resource acquisition compared to the other rootstocks.