线性相邻k/n(F)不可修系统的可靠性分析

线性相邻的表决系统k/n(F)在电讯系统和石油输通管道中广泛存在。对该类型的不可修系统的可靠性进行系统分析和讨论,假定每一个部件的工作时间服从负指数分布,且相互独立。先对特殊情况下的几种系统进行分析,在此基础上,根据n与k的关系分3种情况进行讨论,求得一般系统的可靠度表达式,为工程上进行可靠性分析以及相应的系统可靠性优化提供参考。     

Si3N4-TiN纳米复相陶瓷的制备与性能研究

采用热压烧结方法制备了Si3N4-TiN纳米复相陶瓷,研究了纳米TiN颗粒的添加对Si3N4陶瓷组织、力学性能和抗热震性能的影响.研究结果表明:Si3N4-TiN纳米复相陶瓷的显微组织由粒径为100 nm左右的晶粒构成,TiN以独立颗粒的形式存在;纳米TiN颗粒的添加可以提高纳米Si3N4陶瓷的断裂韧性和抗弯强度,但对硬度影响不大;适量TiN颗粒的添加能改善纳米Si3N4陶瓷的抗热震性.     

氮化硅对注凝成型熔融石英陶瓷性能影响的研究

以丙烯酰胺(AM)为有机单体,N,N'-亚甲基丙稀酰胺(MBAM)为交联剂,过硫酸铵(APS)为引发剂,pH=3.5,温度为1190 ℃保温5 h的条件下,采用注凝成型方法制备熔融石英陶瓷;以氮化硅为添加剂,通过XRD、SEM等分析不同氮化硅添加量对熔融石英陶瓷的影响,结果表明,氮化硅促进石英陶瓷的烧结,不会导致方石英出现;试样常温抗折强度、体积密度随氮化硅添加量的增加而增大,而显气孔率随氮化硅添加量的增加而减小.当氮化硅添加量为2%时,试样常温抗折强度为37.13 MPa,体积密度为1.96 g/cm3 ,显气孔率为10%.     

负热膨胀系数材料的研究现状与展望

本文从负热膨胀材料的发展概况、负热膨胀产生机理、负热膨胀材料分类出发,着重介绍了化学通式为A2M3O12的负热膨胀材料.通过几种A2M3O12型负热膨胀材料的性质、制备方法和晶体结构的归纳和总结,对这一系列的负热膨胀材料未来研究方向进行了展望.     

乳液聚合方法研究进展

乳液聚合方法具有各方面的优点和广泛的应用范围,因此,受到人们的广泛关注。本文介绍了乳液聚合的优缺点,并着重介绍了一些新的乳液聚合方法及其原理、特点、应用以及中外最新的一些研究成果。     

Unscented Kalman filtering in the additive noise case

The unscented Kalman filter(UKF) has four implementations in the additive noise case,according to whether the state is augmented with noise vectors and whether a new set of sigma points is redrawn from the predicted state(which is so-called resampling) for the observation prediction.This paper concerns the differences of performances for those implementations,such as accuracy,adaptability,computational complexity,etc.The conditionally equivalent relationships between the augmented and non-augmented unscente...     

Research on forecasting model of sandstone deformation rate during sine wave loading segment under the lag effect

To reduce data variance caused by individual differences of different samples,a new experimental method is proposed by loading and unloading the axial forces with different frequencies and different waves of a certain load amplitude to the same rock sample without damaging it.Lag time segments are defined and fractionized into segments I and Ⅱ.Criterions for seg-mentation,definitions of relevant parameters and empirical analysis are also offered afterwards.In the course of sinusoidal loading,the serious pea...     

论城市品格的塑造——以镇江为例

城市品格是城市无形层面里最本质的部分。城市品格的塑造需要渗入人文精神和城市特色,这样才能使人们生活得更美好。对镇江而言,要塑造城市品格,就需要立足镇江的历史与现实,结合镇江民众的思考,从功利与超功利的角度进行具体的探索。     

四方相BaTiO3薄膜的自组装制备与表征

以(NH₄)₂TiF₆、 Ba(NO₃)₂ 和H₃BO₃为主要原料, 采用自组装单层膜(SAMs)技术, 以三氯十八烷基硅烷(octadecyl-trichloro-silane, OTS)为模版, 在玻璃基片上制备了四方相钛酸钡晶态薄膜. 改性基板的亲水性测定与原子力显微镜（AFM）测试表明, 紫外光照射使基板由疏水转变为亲水, 能够对OTS-SAM起到修饰作用. 金相显微镜观察结果显示,OTS单分子膜指导沉积的薄膜样品表面均匀, 表明OTSSAM对钛酸钡薄膜的沉积具有诱导作用; X射线衍射（XRD）与扫描电镜（SEM）表征显示, 空气中600℃下保温2h实现了薄膜由非晶态向四方相BaTiO₃晶态薄膜的转化过程, 制备的钛酸钡薄膜在基板表面呈纳米线状生长, 线长约在500～1000nm之间, 相互连接的晶粒大小约为100nm. 文章同时对自组装单层膜和钛酸钡薄膜的形成机理进行了探讨.     

In situ study on dendrite growth of metallic alloy by a synchrotron radiation imaging technology

This study was trying to observe the real-time dendrite growth of Sn-Bi and Sn-Pb binary alloys by a synchrotron radiation imaging technology.The imaging system includes an intense and high brightness synchrotron radiation source,a high-resolution and fast-readout charge coupled device camera,an alloy sample and a Bridgman solidification system.The imaging experiments were done at Beijing Synchrotron Radiation Facility with an updated synchrotron radiation imaging technique,diffraction-enhanced imaging,whic...