Application of meshless method to electromagnetic NDT

0 Introduction Finite element methods have been successfully pliedfor solving different kinds of problemsinelectrom netic NDT. The domain under study is divided into mesh of element inthis method.For complicated geom tries or in variable geometry problemsthe mesh present high computational cost due to the reevaluation of e newgeometry. Meshless methods are nowproven as a robust te nique to study field problems in which large geometri deformations areto be modeled,since such methods av the on…     

考虑氯离子侵蚀时变劣化效应的近海斜拉桥地震易损性分析

为研究氯离子侵蚀对近海大型桥梁地震易损性的时变影响规律,以某近海斜拉桥为对象,建立非线性数值模型并开展增量动力分析,获得主塔等构件及桥梁系统的时变易损性曲线.结果表明,材料腐蚀会导致构件及结构的损伤概率出现不同程度的增加.桥梁结构第1阶自振周期对应的谱加速度Sa(T1)为0.3g时,主塔严重损伤的概率在0、25、50、...     

哈特曼装置上粉尘浓度的测量

粉尘浓度和湍流速度对粉尘爆炸猛烈程度和粉尘云最小着火能的测试有很大影响.针对1.2 L哈特曼装置上的粉尘浓度进行了测量研究,并对测量数据进行了分析讨论,得到了1.2 L哈特曼管上不同位置高度的粉尘浓度随时间的变化曲线.粉尘浓度随哈特曼管高度位置分布很不均匀.对于哈特曼管电极位置高度,当点火延迟时间170 ms、计算浓度为500 g/m3时,其粉尘测量浓度近似等于计算浓度;当计算浓度低于500 g/m3时,其测量浓度高于计算浓度.当计算浓度大于500 g/m3时,测量浓度低于计算浓度.哈特曼管上粉尘浓度随高度分布的获得,为最小着火能在不同装置上的测试比较提供了数据,为粉尘爆炸数学模型的检验提供了...     

Is the valid species Synchaeta monopus Plate, 1889 (Rotifera: Monogononta) a product of preparation artefacts?

The morphology of soft-bodied rotifers, including those of Synchaeta spp, can be strongly affected by preparation artefacts including contraction and deformation. The long-standing, valid species Synchaeta monopus is known exclusively from ethanol- or formaldehyde-preserved material and no live specimens of it have ever been described. Although this alone is cause for concern, we could also reproduce unique characteristics diagnostic for this species (e.g. the swollen body and the rudimental foot) by subjecting specimens of Synchaeta pectinata to the preservation conditions under which it was first described. This proxy experiment and comparisons to other Synchaeta species indicate that literature occurrences of S. monopus likely represent preserved and deformed specimens of Synchaeta cecilia or other marine species of Synchaeta, thereby highlighting the importance of thorough morphological investigations of the habitus using live specimens and of features that are unaffected by preservation (e.g. the trophi). We therefore recommend that S. monopus be listed as a species inquirenda until topotypes are examined. Furthermore, in ecological studies including rotifers, where the examination of preserved material is often unavoidable, we stress that light-microscopical images of the habitus and trophi of the specimens minimally be included to facilitate independent verification of the species assignments.     

基于仿真驱动的高速公路主动限速效用评价与推荐

传统的路侧被动限速方式对于特定的惩处区域以外缺少管控,间接导致车辆行为在时空上的不一致性甚至突变,影响了交通的通行效率与安全性。从车侧主动限速方式入手,提出主动限速效用评价与推荐方法,结合道路线形、交通流量、车型比例,开展多情景主动、被动限速交通仿真,利用安全间接分析模型及交通流运行状态,从安全与效率2个层面提取效用评价指标及其权重,采用集成学习方法进行预测分析。结果显示：主动限速方式相较于被动限速方式更有利于提高安全性和调节效率,而在主动限速方面,GBDT(gradient boosting decision tree)回归模型的预测稳定性和准确率更高(R²=0.984)。     

基于协作式深度强化学习的火灾应急疏散仿真研究

火灾是威胁公共安全的主要灾害之一,火灾产生的高温和有毒有害烟气严重影响了疏散路径的选择。将深度强化学习引入到应急疏散仿真研究,针对多智能体环境提出了协作式双深度Q网络算法。建立随时间动态变化的火灾场景模型,为人员疏散提供实时的危险区域分布信息;对各自独立的智能体神经网络进行整合,建立多智能体统一的深度神经网络,实现所有智能体之间的神经网络和经验共享,提高整体协作疏散效率。结果表明：所提方法具有良好的稳定性和适应性,训练和学习效率得到提升,具有良好的应用价值。     

基于CPN的智能合约交易顺序依赖漏洞的验证

智能合约的形式化验证工作主要集中在编程语言层面的漏洞研究,而交易顺序依赖作为区块链层面的漏洞更不易被检测。基于着色Petri网对智能合约中潜在的交易顺序依赖漏洞进行形式化验证。以Decode悬赏合约为对象,分析合约中潜在的漏洞,自顶向下地对合约本身及其执行环境建立着色Petri网模型,并引入攻击者模型来考虑合约遭受攻击的情况。通过运行模型以验证合约存在交易顺序依赖漏洞,最后基于Remix平台在以太坊网络中证实结论的正确性。     

量子全加法器的修改和算法研究

通过与经典全加器的基本模型进行比较后,讨论了一个改进后的量子平面加法器的基本构型.对其原理、组件和算法进行了研究,比较了本加法器两个主要组件与一般量子加法器的不同.作为应用的例,设计了一个n比特量子全加法器的模型,对其具体运算过程和基本功能进行了说明.     

水溶性聚季铵盐修饰多壁碳纳米管的制备

采用聚季铵盐修饰的方法合成了水溶性的多壁碳纳米管(MWNTs)。用混酸(浓硫酸与浓硝酸,体积比为3∶1)对平均直径为20 nm的MWNTs进行氧化处理。红外光谱分析表明,氧化1 h~3 h可使MWNTs表面生成羧基,扫描电镜测试表明MWNTs被氧化为短管。氧化2 h的MWNTs经过与氯化亚枫的酰氯化及与聚季铵盐的脂化缩合两个反应步骤,合成了表面接枝聚季铵盐的MWNTs,红外光谱分析证明了该MWNTs的生成。透射电镜测试显示聚季铵盐修饰的MWNTs在乙醇中能够有效地克服团聚倾向;水溶性实验表明改性后的MWNTs在水中具有自分散性,并能够保持长时间的溶解能力。     

Diversity in enoyl-acyl carrier protein reductases

The enoyl-acyl carrier protein reductase (ENR) is the last enzyme in the fatty acid elongation cycle. Unlike most enzymes in this essential pathway, ENR displays an unusual diversity among organisms. The growing interest in ENRs is mainly due to the fact that a variety of both synthetic and natural antibacterial compounds are shown to specifically target their activity. The primary anti-tuberculosis drug, isoniazid, and the broadly used antibacterial compound, triclosan, both target this enzyme. In this review, we discuss the diversity of ENRs, and their inhibitors in the light of current research progress. Received 3 November 2008; received after revision 5 December 2008; accepted 8 December 2008