Effect of Ce addition on hot tearing behavior of AZ91 alloy

A small amount of cerium (below 1.0 wt%) addition to AZ91 alloy have been investigated on the hot tearing susceptibility (HTS) at a cooling rate of 1.5Ks^?1. The HTS increased to a maximum value with a cerium addition of 0.6 wt% and then decreased to a stable status as cerium was gradually added. Due to high chemical activity, cerium into the melts can react with aluminum to form an Al₁₁Ce₃ intermetallic compound. X–ray diffraction results also confirmed the existence of Al₁₁Ce₃. The Al₁₁Ce₃ increased with the presence of the needle-like and block morphology. As cerium levels increased, the amount of Mg₁₇Al₁₂ decreased. The variations between Mg₁₇Al₁₂ and Al₁₁Ce₃ resulted in a similar normal distribution of the HTS in AZ91 alloy. The findings were further verified through the microstructure evolution and the surface morphology of fracture.     

Progenesis as a principle in meiofauna evolution

The interstitial meiofaunal taxa may have evolved in very different ways, which are shortly discussed and schematically represented. Several taxa reveal the possibility of an evolutionary pathway by early maturation of larvae or juvenile stages of large size species with a pelago-benthic life-cycle. This presumed progenetic (= neotenic) evolution can be sustantiated in, for example, various Polychaeta and Crustacea by larval or juvenile morphological features. The progenetic origin of several of these taxa is also strongly supported by morphological series, of which species conforming well with typical larvae form the endpoint. The monophyletic origin of similar progenetic taxa, however, is only proved with difficulties. The theoretical available phylogenetic reconstructions for a series of progenetic taxa are discussed. It is emphasized that progenetic evolution is not regressive or degenerate but novel morphological features like derived reproductive organs are characteristic indications of the progenetic origin of a species. In general, progenesis may have a significant role in the evolution of higher taxa in the interstitial habitat.     

《皇明条法事类纂》所见明成弘间“讲读律令”教育实践

明成化、弘治年间《皇明条法事类篡》＂讲读律令＂通过条例的形式将其予以细化和定制,给我们展示出了这一时期＂讲读律令＂丰富的条例背景、法源以及在官员、士子讲读律令条例规文中的各项具体安排与演变,大大弥补了《大明律》＂讲读律令＂条相关信息缺失的局限,有助于加深我们对于明代前中期推行＂讲读律令＂教育的了解。     

Evolution in leptolid life-cycles (Cnidaria: Hydroida)

The medusae of many hydroids remain attached to the colony, often in a vestigial state. Evolutionary origins are sometimes thus obscured. Some authorities have considered these derived hydroid life-cycles as paedomorphic; and regarded the hydroid stage as a prolonged larva. In some genera, for example in the familiar but unusual Obelia, a re-evolution of the medusa stage has been proposed.

These theories are evaluated. Primitively, the larval stage throughout the Cnidaria is the planula. Some possible processes in the re-evolution of the medusa are discussed but the hypothesis is discounted. The origin of medusoid coelenterates is taken to be wholly polypoid, medusae being evolved later as modified and released reproductive polyps. The subsequent evolutionary retention and suppression of the medusa stage is discussed and some physiological processes perhaps leading to it are considered. This direction of evolution is related to the advantages of perennation in large, iterated colonies and consequent larval philopatry. Certain confusing terminology is clarified. The term ‘leptolids’ is rescued from disuse, with the original meaning ‘hydroids and/or hydromedusae’ but implicitly including the planula stage as well, to fill a tiresome gap.     

DELLA基因家族在被子植物中的系统演化关系

基于被子植物各主要分支代表类群的DELLA氨基酸序列，开展它们在被子植物中演化关系的系统发育分析.DELLA基因家族在双子叶植物早期演化阶段经历了一次复制事件，形成2大分支，每支都包含相应的蔷薇类和菊类；单子叶植物没有经历早期的复制事件，所有的DELLA基因聚在一起形成单一的支系.另外，证实了在被子植物的双子叶植物中存在第3个DELLA基因支系.     

基于规则提升的 Agent 系统异常处理方法

基于进化计算理论中的重组思想, 提出一种基于规则提升的Agent系统异常处理方法, 处理Agent系统中违背执行规则的异常. 该方法根据规则间的相互触发和执行情况分析得到规则处于异常状态的原因, 重组处于异常状态的规则, 提升规则向适应环境的方向进化. 实验结果表明, 该方法能处理规则的异常状态, 增强了规则的触发条件, 保证了规则达到预期的后置条件, 提高了Agent系统在开放环境下的异常处理能力.     

面向OD客流的高速列车开行方案的优化

满足旅客出行需求的列车开行方案能够更好地吸引客流，提高高速铁路的核心竞争力.以最大化经济收益和最小化出行费用为目标函数，以高速铁路开行方案为研究对象，以旅客出行需求等作为约束条件，将列车开行方案与OD客流量结合起来，同时考虑旅客的购票心理和列车购票的时效性，建立了一种基于动态客流的列车开行方案的多目标优化模型，并设计一种基于个体信息和改进变异算子的多目标差分(SG-MOSaDE)算法进行求解.以广州市某线路为例进行实验，结果表明，优化后的开行方案不仅最大化满足了旅客出行需求，而且在提高铁路部门经济收益的同时降低了旅客的出行花费，并且优化后的列车总停站次数较原来有所下降，停站方案更加均衡.     

基于沉积数值模拟的辫状河心滩演化

选取黄骅坳陷新近系典型辫状河沉积解剖区,利用密井网区动静态资料相结合识别和刻画心滩及其内部结构,在此基础上通过沉积数值模拟探究研究区心滩形成过程,并建立研究区心滩顺流迁移和横向迁移演化模式。结果表明:顺流加积、垂向加积、侧向加积和侵蚀作用共同塑造心滩的形态和内部结构;滩头侵蚀、滩尾顺流加积和垂向加积形成了心滩的顺流生长和垂向生长;侧向加积与侵蚀作用控制心滩的不对称侧向生长过程。     

基于游客类型的旅游企业自愿环境行动演化模型

基于游客类型的企业自愿环境行动演化模型表明,当景区有更高比例的生态游客和较高的资源环境自净能力时,就会有更多的旅游企业实施自愿环境行动。景区游客总数量、企业总数量对旅游企业实施自愿环境行动的影响具有不确定性。     

抽象半线性发展方程正解的存在性

利用线性算子半群理论和抽象锥上的不动点定理 ,在合适的条件下建立了偏序Banach空间中半线性发展方程全局正解的存在性结果