The structure and properties of Ag(Nb0.8Ta0.2)O3 ceramic doped with MnNb2O6

The influences of doping of MnNb2O6 on the structure and dielectric properties of Ag(Nb0.8Ta0.2)O3 were illustrated. Ag(Nb0.8Ta0.2)O3 samples doped with different amount of preformed MnNb2O6 (1 mol%, 2 mol%, 3 mol%, 4 mol%, 6 mol%, 8 mol%) were prepared by traditional solid-state reaction method and characterized by XRD, SEM and EDS, and the dielectric properties of samples were compared. The experiment results indicated that when the doping amount of MnNb2O6 was greater than 3 mol%, second phase appeared because of the solid solution limit. The permittivity of the Ag(Nb0.8Ta0.2)O3 samples doped with MnNb2O6 firstly increased and then decreased with the sintering temperature, while the dielectric loss decreased first, and then increased slightly. 1 100 ℃ seems to be the most proper sintering temperature for most of the samples. When the amount of MnNb2O6 is about 3 mol%, the samples have the best dielectric properties, larger permittivity and smaller dielectric loss.     

Preparation and characterization of carboxylterminated poly (butadiene-co-acrylonitrile) -epoxy resin prepolymers for fusion-bonded-epoxy powder coating

Liquid carboxyl-terminated poly(butadiene-co-acrylonitrile)(CTBN)-epoxy resin(EP) prepolymers were prepared with different contents of CTBN.The chemical reactions between EP and CTBN were characterized by Fourier ransform infrared(FTIR) spectroscopy and gel permeation chromatography(GPC).The scanning electron micrograph(SEM) and dynamic mechanical analysis(DMA) of curing films showed phase separation,and the rubber particles were finely dispersed in the epoxy matrix.Mechanical properties analysis of curing films showed that impact strength and elongation at break increased significantly upon the addition of CTBN,indicating good toughness of the modified epoxy resins.Thermogravimetric analysis(TGA) showed that the incorporation of CTBN had little effect on the thermal stability of EP.Fusion-bonded-epoxy(FBE) powder coatings modified with CTBN-EP prepolymers were prepared.The experimental results demonstrate the ability of CTBN-EP prepolymers,toughening technology to dramatically enhance the flexibility and impact resistance of FBE coatings without compromising other key properties such as corrosion protection.     

中空纤维支撑液膜萃取技术及其在药物残留检测中的应用

中空纤维支撑液膜是一种萃取新技术,具有选择性好、重现性好、节省有机溶剂等优点。介绍中空纤维支撑液膜的工作原理、结构以及萃取影响因素,就该技术在药物残留检测方面的应用进行综述。     

低相噪频率合成器的设计与仿真

为了获得低相位噪声和高集成度频率源,设计了基于锁相环的频率合成器。利用ADS射频仿真软件,对锁定时间和相位噪声进行仿真,确定设计满足指标要求。用集成VCO的锁相环芯片ADF4360-7进行硬件测试,锁定频率在434MHz,功率达到1dBm,相位噪声为-87dBc/Hz@10kHz。此频率源指标满足大多数测量和通信系统要求,可在射频电路中推广使用。     

工业季戊四醇结晶成长速度

针对传统流化床结晶器中工业季戊四醇结晶成长速度低及产品质量和产率不稳定的问题,在新型撞击流结晶器中开展了工业季戊四醇结晶成长速度的研究实验,采用阿伦尼乌斯公式拟合了结晶器中结晶成长速度系数同温度之间的关系,将撞击流结晶器和传统流化床结晶器中工业季戊四醇结晶成长速度进行了对比.研究结果表明:撞击流结晶器中结晶成长速度系数高于流化床中结晶成长速度系数;撞击流结晶器和流化床结晶器中的结晶成长速度系数都随温度的升高而增大;实验结果支持撞击流中强烈的微观混合和压力波动促进结晶成长动力学过程的理论推测.     

地铁盾构隧道小净距穿越高架桥桩基数值模拟分析

针对南京地铁3号线部分路段小净距穿越高架桥桩基问题,适当简化后建立了隧道、管片及桩基的三维数值模型。模拟结果表明,地铁盾构小净距穿越高架桥对地表和桩基的受力和变形将会带来影响,地表最大变形量大于桩基顶部变形量,隧道右帮下侧管片出现应力集中。通过与现场监测结果对比,现场监测值与数值模拟结果吻合,建议今后施工时控制好施工参数,加强跟踪监测,必要时进行跟踪注浆加固。研究结果为本工程的顺利实施提供了参考。     

Development of a compact filament-discharge multi-cusp H- ion source

A 14 MeV medical cyclotron with the external ion source has been designed and is being constructed at China Institute of Atomic Energy. The H(-) ion will be accelerated by this machine and the proton beam will be extracted by carbon strippers in dual opposite direction. The compact multi-cusp H(-) ion source has been developed for the cyclotron. The 79.5 mm long ion source is 48 mm in diameter, which is consisting of a special shape filament, ten columns of permanent magnets providing a multi-cusp field, and a three-electrode extraction system. So far, the 3 mA∕25 keV H(-) beam with an emittance of 0.3 π mm mrad has been obtained from the ion source. The paper gives the design details and the beam test results. Further experimental study is under way and an extracted beam of 5 mA is expected.     

复杂文本网数据的主题建模进展

文中介绍了大规模文本网数据的主题建模研究的特点和近年来的重要进展.主题建模方法吸引了世界范围的广泛兴趣,并且促进了许多重要的数据挖掘、计算机视觉和计算生物应用系统的发展,包括文本自动摘要、信息检索、信息推荐、主题检测和追踪、自然场景理解、人体动作识别以及微阵列基因表达分析等.文中重点介绍文本网数据的4个主要特点以及对应的主题模型.文本网数据含有动态、高阶、多通路及分布式的结构,而之前的主题模型仅对部分的结构进行建模.而文中讨论了在三维马尔可夫模型的框架下统一对文本网数据的4个结构特点进行建模,并分析了结合三维马尔可夫模型和二型模糊系统对分布式单词计算和主题建模应用的可能性.除了对文本网数据的结构建模之外,还讨论了一些对三维马尔可夫模型能量最小化的机器学习算法.     

基于WiFi的体温监测系统设计与实现

为实现住院患者体温的非接触式实时采集和监测,减少感染机率,设计了基于WiFi的体温实时监测系统。本系统主要由数据采集单元和监控中心组成,数据采集单元由温度传感器和低功耗WiFi芯片GS1010组成,完成数据采集和发送功能。监控中心通过无线AP点(Access Point)接收,解析和实时显示数据。实验结果表明,该系统性能可靠,能够快速完成温度显示,具有一定的应用价值。     

Contextual correlation based thread detection in short text message streams

Short text message streams are produced by Instant Messaging and Short Message Service which are wildly used nowadays. Each stream contains more than one thread usually. Detecting threads in the streams is helpful to various applications, such as business intelligence, investigation of crime and public opinion analysis. Existing works which are mainly based on text similarity encounter many challenges including the sparse eigenvector and anomaly of short text message. This paper introduces a novel concept of contextual correlation instead of the traditional text similarity into single-pass clustering algorithm to cover the challenges of thread detection. We firstly analyze the contextually correlative nature of conversations in short text message streams, and then propose an unsupervised method to compute the correlative degree. As a reference, a single-pass algorithm employing the contextual correlation is developed to detect threads in massive short text stream. Experiments on large real-life online chat logs show that our approach improves the performance by 11% when compared with the best similarity-based algorithm in terms of F1 measure.