Sand-throwing behaviour in pit-building antlion larvae: insights from finite-element modelling

Sandy pitfall traps of antlions are elaborate constructions to capture prey. Antlions exploit the interactions between the particles in their habitat and build a stable trap. This trap is close to the unstable state; prey items will slide towards the centre—where the antlion ambushes—when entering the trap. This is efficient but requires permanent maintenance. According to the present knowledge, antlions throw sand, mainly to cause sandslides towards the centre of the pit. We hypothesized that: (i) sand-throwing causes sandslides towards the centre of the pit and (ii) sand-throwing constantly maintains the pitfall trap and thus keeps its efficiency high. Using laboratory experiments, as well as finite-element analysis, we tested these hypotheses. We show, experimentally and numerically, that sand that accumulates at the centre of the pit will be removed continuously by sand-throwing, this maintenance is leading to slope condition close to an unstable state. This keeps the slope angle steep and the efficiency of the trap constant. Furthermore, the resulting sandslides can relocate the trapped prey towards the centre of the pit. This study adds further insights from specific mechanical properties of a granular medium into the behavioural context of hunting antlion larvae.     

无向双环网络的容错路由研究

在节点出现故障的情况下,如何保证网络节点之间的路由是一个重要的问题。将无向双环网络的节点按照最短路径访问方式映射到直角坐标系形成最优路由构图[CG(N;±r,±s)];基于该构图根据源节点和目的节点是否位于坐标轴上以及它们周围的故障节点数,提出故障节点封闭区和逃逸区的概念;存在故障逃逸区的情况下,源、目的节点之间仍然可以进行最优路由,针对出现故障节点封闭区而无法进行最优路由的情况下,增加等价节点形成扩展路由构图[ECG(N;±r,±s)],从而寻找容错路由;给出最优路由构图、扩展路由构图和容错路由的算法,并编程仿真了这些算法。     

内蒙古某电厂逃逸氨浓度测试与灰分影响分析

燃煤电厂选择性催化还原（SCR）脱硝系统氨逃逸问题普遍存在,为良好控制逃逸氨浓度,采用靛酚蓝分光光度法在现场对烟气中氨浓度进行了测试。以内蒙古某200 MW级燃煤机组氨逃逸性能试验为例,详述了靛酚蓝分光光度法现场测试的操作方法与流程,并将试验结果与现场在线仪表数据进行了比较,同时分析了烟气中飞灰对该方法测试结果的影响。结果表明,现场测试可获得不同取样点逃逸氨的浓度,对喷氨控制有利;样品中灰分的存在会大幅提升吸光度值,使测试结果偏高,采样过程中需严防灰分进入样品,以便获得正确的分析结果。     

基于三维多项式映射的广义Julia集表示与绘制

研究了基于三维多项式映射的三维广义Julia集表示方法.从理论上分析并证明了三维多项式映射满足等变的条件,精确地给出了关于正四面体群和正八面体群具有旋转不变对称性的两类三维等变映射的具体公式,在此基础上讨论并证明了三维多项式映射的广义Julia集所具有的性质.提出了基于逃选距离色彩调配的光线跟踪体绘制算法,对给定三维空间中属于Julia集的离散点根据其逃逸距离赋予颜色和不透明度,并采用光线跟踪法进行体绘制.实验结果表明,利用三维多项式映射来构造三维Julia集,不仅可以根据映射的性质预知Julia集的总体结构特征,并且能够通过调控映射的参数来获得多种具有不同旋转对称结构的Julia集,因而有效地克服了现有三维分形集生成方法所构造的分形集包含信息量少、形状结构单一和分形形状无法预测等缺陷.进一步地,三维多项式映射可以应用于其他三维分形的构造,从而为三维分形的生成提供一个新的有效途径.     

基于捕食搜索策略的粒子群算法在输电网络扩展规划中的应用

针对标准粒子群算法粒子维数要求过高和收敛困难易陷入局部最优的缺点,提出一种基于捕食搜索策略的粒子群算法,并将其应用于输电网络扩展规划。捕食搜索在较差的区域进行全局搜索以找到较好的区域,然后在较好的区域进行集中地局域搜索以使解得到迅速改善。通过限制的调节,控制粒子群搜索空间的增大和减小,从而平衡探索能力和开发能力。局域搜索大大降低了粒子数的要求,全局搜索有效地避免陷入局部最优。算例分析证明了算法的有效性和正确性。     

应用捕食搜索策略的改进多态蚁群算法

结合捕食搜索策略对多态蚁群算法进行改良。该算法引入以下机制：在人工蚁选择路径阶段，设置侦查素路径为优先，为非侦查素路径设置惩罚因子；利用权值在侦查素和非侦查素路径都施加信息素，通过该机制避免多态蚁群算法陷入停滞；在每轮人工蚁最优结果的邻域应用捕食搜索策略，并通过竞争机制选择最优解更新信息素。通过TSP的仿真实验结果表明，提出的融合算法可以有目的地指导信息素分布，加快算法向最优解的收敛速度及提高最优解质量，克服传统多态蚁群算法的缺陷。     

Development of chemically mediated prey-search response in postlarval lobsters (Homarus americanus) through feeding experience

Postlarval lobsters were fed live amphipods (Gammarus oceanicus), soft clam spat (Mya arenaria), or frozen brine shrimp (Artemia salina) for five weeks in order to determine by behavioral bioassay if chemically mediated prey-search behavior is established by feeding experience. Chemosensory responses of predatorily naive lobsters to live clam and amphipod metabolites were low and erratic. After five weeks, amphipod-fed lobsters had developed strong responses towards amphipod metabolites but not clam metabolites. In contrast, clam-fed lobsters did not develop responses to either prey. Chemical fractionation of amphipod metabolites indicated that attractants were confined to the same fraction as for prey extracts, i.e., polar, low-molecular-weight compounds. Survival (80–90%) was similar for each diet group; growth was greatest for amphipod-fed lobsters (100%), followed by clam-fed lobsters (72%) and brine shrimp-fed lobsters (18%); and feeding rates increased for amphipod-fed lobsters and decreased for clam-fed lobsters. Coloration of lobsters indicated that only amphipod diet provided desirable pigments. Differences in ingestive conditioning results between clamfed and amphipod-fed lobsters may have been related to (1) clam metabolites being qualitatively or quantitatively less attractive than amphipod metabolites or (2) differences in the predisposition of lobsters to show ingestive conditioning to different prey and their associated metabolites as a function of quality of prey as a diet.     

Herbivory induces systemic production of plant volatiles that attract predators of the herbivore: Extraction of endogenous elicitor

It was previously shown that in response to infestation by spider mites (Tetranychus urticae), lima bean plants produce a volatile herbivoreinduced synomone that attracts phytoseiid mites (Phytoseiulus persimilis) that are predators of the spider mites. The production of predator-attracting infochemicals was established to occur systemically throughout the spider mitein-fested plant. Here we describe the extraction of a water-soluble endogenous elicitor from spider mite-infested lima bean leaves. This elicitor was shown to be transported out of infested leaves and was collected in water in which the petiole of the infested leaf was placed. When the petioles of uninfested lima bean leaves were placed in water in which infested leaves had been present for the previous seven days, these uninfested lima bean leaves became highly attractive to predatory mites in an olfactometer when an appropriate control of uninfested lima bean leaves was offered as alternative. The strength of this effect was dependent on the number of spider mites infesting the elicitor-producing leaves. Higher numbers of spider mites resulted in an elicitor solution with a stronger effect. In addition, spider mite density was important. The elicitor obtained from one leaf with 50 spider mites had a stronger effect on the attractiveness of uninfested leaves than the elicitor obtained from three leaves with 17 spider mites each. This suggests that the stress intensity imposed on a plant is an important determinant of the elicitor quantity. While the elicitor has a strong effect on the attractiveness of uninfested leaves, spider mite-infested leaves are still much more attractive to predatory mites than elicitor-exposed leaves. The data are discussed in the context of systemic effects in plant defense and the biosynthesis of herbivore-induced terpenoids in plants.     

焊缝中氢的扩散行为及影响因素

 扩散氢会在焊缝中引起氢脆、延迟裂纹等,导致结构产生低应力断裂。为了研究氢的扩散行为,采用水银法和气相色谱法测定了逸出的扩散氢量,并采用真空抽取法测试了不同温度下残余氢的释放量。试验表明,扩散氢量不受焊道数量的影响,它的逸出时间随焊道数的增多而增长,逸出速度随合金含量的增多而降低。随着焊后冷速的降低,冷却过程中逸出的氢增多,测定出的扩散氢量减少;测氢试样在100~200℃保温时,逸出氢的总量变化不大,但逸出时间随温度的升高而明显缩短。残余氢量与扩散氢量的多少无关,它与焊缝的含氧量、组织和硬度等有关系。     

车辆路径问题的捕食搜索算法研究

针对车辆路径问题存在的NP难题,设计了一种模仿动物捕食策略的捕食搜索算法进行求解。该算法利用搜索空间限制的大小,定义算法的局域搜索和全局搜索,并通过调节搜索空间的限制,以实现局域搜索和全局搜索之间的转换,它具有较好的局部集中搜索和跳出局部最优的能力。通过测试实例的计算,并与已有相关算法进行比较,结果表明该算法简洁而行之有效,是求解车辆路径问题的一个较好方法。