基于分簇波束成形算法的MIMO-OFDM系统信道容量的分析

提出了一种在有限反馈条件下多输入多输出-正交频分复用(MIMO-OFDM)系统中基于信道容量的分簇波束成形算法。该算法针对MIMO-OFDM系统在高信噪、低信噪比等不同情况时选择不同的波束成形向量来提升系统的容量。根据簇间、各子簇间均存在一定的相关性,设计出了次优波束成形算法。通过对所提出的算法仿真可知,在高信噪比、低信噪比情况下针对系统容量采用分簇的波束成形算法能够在一定程度上提升MIMO-OFDM系统在确定性信道与随机性信道的信道容量。     

三对角M矩阵的Hadamard积的最小特征值下界估计式的研究

研究了三对角M矩阵B和三对角M矩阵A的逆矩阵A-1的Hadamard积的最小特征值q(B°A-1)界的估计问题,利用A-1的元素新的上界估计式给出了q(B°A-1)新的估计式.若A=B,得到q(A°A-1)新的估计式.     

Improving teaching and learning of basic maths and reading in Africa: Does teacher preparation count?

Teacher education has an important role in ensuring quality of learning especially for the poorest children. The article draws on a study of teacher preparation for the early primary grades in six African countries – Ghana, Kenya, Mali, Senegal, Tanzania and Uganda – in reading and mathematics. Initial teacher education had the strongest impact on newly qualified teachers but also induced misplaced confidence leading to standardised teacher-led approaches that failed to engage learners. Learning to read was divorced from meaning while mathematical activities were not linked to learning concepts. We suggest that teacher education is reconstructed as a study of classroom practice that places children's learning at its centre.     

完全图的循环图分解和4个Ramsey数的下界

研究素数阶完全图分解为循环图的方法,给出了计算它的子图的团数的一种算法,得到２个三色,２个四色Ｒａｍｓｅｙ数的新的下界：Ｒ（３,４,１７）≥４４４,Ｒ（３,６,１７）≥８１２,Ｒ（３,３,４,１４）≥６９２,Ｒ（３,３,５,１５）≥１０２２。     

经典Ramsey数R(4,23)的下界

本文构造了1个新的素数阶循环圈，从而得到了1个Ramsey数的下界：R（4，23）≥272。     

宋代知县、县令带兵职能研究

宋代的知县、县令,也有兼一县兵马的职责。朝官知县兼领一县兵马,被称为兵马都监;京官知县和幕职州县官县令兼领一县兵马,被称为兵马都监;畿县知县兼领一县兵马,称为签书兵马司公事。宋代知县、县令兼领兵马,一是镇压民间的反抗活动,二是抵制异族的进攻。宋代的知县、县令始于宋初;神宗革新,实行将兵法,专门别置教官训练军队,罢黜知县、县令兼领一县兵马之权;到南宋恢复知县、县令兼兵权,知县、县令带兵制几经变化……     

Lower extremity injuries in vehicle-pedestrian collisions using a legform impactor model

Though the bumper of a vehicle plays a major role in protecting the vehicle body against damage in low speed impacts, many bumpers, particularly in large vehicles, are too stiff for pedestrian protection. In designing a bumper for an automobile, pedestrian protection is as important as bumper energy absorption in low speed collisions. To prevent lower extremity injuries in car-pedestrian collisions, it is important to determine the loadings that car front structures impart on the lower extremities and the mechanisms by which injury is caused by these loadings. The present work was focused on gaining more insight into the injury mechanisms leading to both ligament damage and bone fracture during bumper-pedestrian collisions. The European Enhanced Vehicle-safety Committee （EEVC） legform impactor model was introduced and validated against EEVCAVG17 criteria. The collision mechanism between a bumper and this legform impactor was investigated numerically using LS-DYNA software. To identify the effect of the bumper beam material on leg injuries, four analyses were performed on bumpers that had the same assembly but were made from different materials.     

近40年来盛泽镇研究述评

自傅衣凌讨论江南市镇中的资本主义萌芽以来,盛泽镇一直被学界视为经典案例。近40年来,中国社会经济史学界从市镇的兴起、发展及其现代化、商品流通和以市镇为结点的市场体系、丝织品的专业化生产等方面,以盛泽为个案或为例进行了考察,并展开了更为深入的讨论。本文试就此作一回顾,以期为江南市镇研究的进一步展开提供参考。     

老年患者下呼吸道感染革兰阴性菌分布及耐药性分析

目的:探讨某院呼吸内科老年患者下呼吸道感染革兰阴性菌的分布及其耐药性,指导临床治疗。方法:回顾性分析2013年1月-2014年12月老年患者下呼吸道感染染革兰阴性菌的分布及其耐药性;采用法国生物梅里埃公司全自动细菌鉴定仪VITEK2 compact进行菌株鉴定,采用K-B法进行药敏试验,按美国临床实验室标准化委员会(CLSI)2014年标准判读结果。结果:分离出的217株病原菌中,革兰阴性菌有156株(71.9%),前4位为肺炎克雷伯菌、大肠埃希菌、铜绿假单胞菌、鲍曼不动杆菌。肺炎克雷伯菌对氨苄西林、庆大霉素及氨曲南的耐药率较高,分别为96.6%、88.1%、81.4%,对亚胺培南的耐药率为0。结论:老年患者下呼吸道感染以革兰阴性菌为主,临床上应根据药敏结果合理选用抗菌药物。     

下荆江蜿蜒河道分形弯曲的物理机制探讨--I．非线性机制

下荆江河流是一个耗散系统,其平面形态具有分形结构,这种分形结构形成的物理机制之一是河流系统内部诸因素之间（如河床与含沙水流）及河流内部与外部环境（如流域）因素之间存在复杂的非线性依存关系和非线性相互作用,系统外界的扰动如洞庭湖顶托或各种人类活动（如沿江围垸）等是下荆江河型突变的触发力量。