基于Word2Vec模型特征扩展的Web搜索结果聚类性能的改进

对于用户泛化和模糊的查询，将Web搜索引擎返回的列表内容聚类处理，便于用户有效查找感兴趣的内容。由于返回的列表由称为片段（snippet）的短文本组成，而传统的单词频率-逆文档频率（TF-IDF）特征选择模型不能适用于稀疏的短文本，使得聚类性能下降。一个有效的方法就是通过一个外部的知识库对短文本进行扩展。受到基于神经网络词表示方法的启发，提出了通过词嵌入技术的Word2Vec模型对短文本扩展，即采用Word2Vec模型的TopN个最相似的单词用于对片段（snippet）的扩展，扩展文档使得TF-IDF模型特征选择得到聚类性能的提高。同时考虑到通用性单词造成的噪声引入，对扩展文档的TF-IDF矩阵进行了词频权重修正。实验在两个公开数据集ODP239和SearchSnippets上完成，将所提方法和纯snippet无扩展的方法、基于Wordnet的特征扩展方法和基于Wikipedia的特征扩展方法进行了对比。实验结果表明，所提方法在聚类性能方面优于对比方法。     

保健食品中格列本脲含量测定的能力验证研究

目的设计组织保健食品中格列本脲含量测定能力验证项目,评价实验室检测保健食品中格列本脲的技术能力和水平。方法对考核样品通过实施能力验证计划,来自27个省(自治区)、直辖市80家实验室的测定结果进行稳健统计分析,通过稳健Z比分数评价实验室检测能力。结果考核样品中的格列本脲在P0.05显著水平时是均匀的,且在整个计划周期内稳定,满足能力验证的要求。在80家参加实验室中,满意结果数为68家,满意率为85.0%;可疑结果数为6家,可疑率为7.5%;不满意结果数为6家,不满意率为7.5%。结论多数参加的实验室检测能力结果满意,表明保健食品中格列本脲检测水平总体良好。     

Interval analysis of mode shapes to identify damage in beam structures

Various damage detection methods have been proposed by several researchers in the past few decades. Amongst them, the efficiency of mode shapes in detecting damage has been demonstrated by many researchers when further processed. In most cases, the processing involves expansion or reduction of the mode shape data. However, vital information that are damage-prints are often lost during processing of the mode shape data. In addition, most of these processes involve long and complex computation, thus, leading to inaccurate damage identification. In this study, a simple and fast damage identification technique is proposed to identify damage in beam structures. Interval analysis is applied to the mode shapes of a beam structure in the damaged and undamaged states. The interval situations of each of the beam's segment via mode shape are derived to obtain the upper and lower bounds and the derived bounds are compared. To establish a relationship for identify the damaged point, a possibility of damage existence is defined for each segment of the beam structure. The mode shape increment is defined as the increase in the mode shape value. Furthermore, a damage measure index that provide enhance damage information is obtained as the product of the possibility of damage existence and mode shape increment. A numerical model of a simply supported steel beam is applied to demonstrate this method by imposing damage through thickness reduction of elements in segments. In addition, a parametric analysis is carried out to evaluate noise effect by considering varying damage severities and different noise levels. The results showed that this method is simple and provides considerable accurate results.     

Qualitative analysis of thermal explosion of sodium droplet with variable thermophysical properties and thermal radiations

There are many coolants frequently used in the industry for controlling not only heat transfer, but also temperature distribution in a confined domain. However, little is known on the thermal properties of sodium droplets. The qualitative analysis of differential equations that model the thermal explosion, nonlinear dynamic of sodium droplet with variable thermophysical properties when thermal radiations are considered as suggested by Cogley et al, Sohrab et al, and P‐1 approximation Sazhin et al is deliberated upon in this study. The governing equations, first‐order nonlinear ordinary differential equations, are nondimensionalized using the appropriate similarity variables. The existence and uniqueness of the solutions, concavity, and convexity of the temperature distribution, and positivity nature of the solutions of the dimensionless governing equations are established. It is concluded that there exists a solution for a certain range of the admissible parameters and when the reduced activation energy is negative and temperature distribution fits concavity. More so, the major criteria to obtain a positive solution are outlined in this study.     

基于双向耦合的东安513型发动机整机多物理场研究

以东安513型汽油发动机整机为例,基于ANSYS有限元分析软件对其进行流体场、瞬态温度场以及瞬态结构场的多物理场双向耦合研究,实现了对发动机实际工况下的有限元分析。研究了发动机整机在实际工况下的受力以及密封情况,并对现有发动机组合结构存在的密封缺陷进行优化调整。文中详细阐述了在分析过程中涉及到的关键技术和要点,并最终获得了发动机整机实际工作状态下的多个结果云图。根据分析结果云图可以发现,发动机在热载荷、螺栓预紧力以及爆破压力的共同影响下,会使整机发生一定的形变,这种变形会影响其工作状况下的密封性能。通过对分析结果的研究,最终选择调整螺栓预紧力的大小和分布来提高发动机密封性能。     

水泥回转窑系统固相中硫、碱分布特性研究

采用XRF、XRD与EPMA分析方法对取自某水泥厂生产线的几种试样(入预热器生料、入窑热生料、烟室结皮、窑皮、熟料)进行测试分析,研究硫、碱在水泥回转窑系统内固相中的分布特性.结果表明:回转窑内入窑热生料、烟室结皮以及过渡带区域窑皮中,硫、碱含量较高;且不同试样中硫、碱的存在形式也不一样,其中烟室结皮最为复杂.不同粒径大小的熟料,将硫、碱带出回转窑系统的情况存在着差异,大粒径熟料带出的钾、硫含量较小粒径熟料高出许多,但是钠含量相差不大,而且后者的晶体发育程度较好.     

无氰镀银自动生产线电流控制故障的排除

通过QC(质量控制)活动分析了无氰电镀银自动生产线电流控制故障产生的原因。通过编写单周期响应程序避免RLO(逻辑运算结果)正跳沿指令失效,通过改变数据移库时机解决了上下料在同一工位时数据移库错误,增加程序模块提高电流控制准确性。采用以上措施可彻底消除电流控制故障。     

影响塑料制品拉伸试验结果的因素

分析了影响塑料拉伸试验结果的因素,除塑料的组成、分子结构和内部缺陷等因素直接影响拉伸性能外,试验仪器、试样制备、试样装夹、试验环境、拉伸速率、数据处理、操作人员等因素亦影响试验结果。这些外部因素对试验结果的影响,经过认真操作和严格控制是可以降低或避免的,从而可提高试验结果的准确性。     

振冲碎石桩复合地基处理应用及效果

通过软基处理工程实例分析,探讨了振冲碎石桩设计中的取值,设计与施工实践的关系,施工中的主要技术措施。     

五里亭立交桥设计及存在的问题

本文叙述了五里亭立交桥设计概况,主要技术指标及营运效果,并对立交存在的问题进行探讨。