Design of a novel optically stimulated luminescent dosimeter using alkaline earth sulfides doped with SrS:Eu,Sm materials

Optically stimulated luminescence （OSL） is the luminescence emitted from an irradiated insulator or semiconductor during exposure to light. The OSL intensity is a function of the dose of radiation absorbed by the sample and thus can be used as the basis of a radiation dosimetry method. Alkaline earth sulfides doped with rare-earth elements such as Ce, Sm and Eu are OSL dosimeters having very high sensitivity, and the OSL with a short time constant is separated from the stimulated light. In this paper, a novel OSL dosimeter designed with SrS：Eu,Sm materials is described. The dosimeter takes advantage of the characteristics of charge trapping materials SrS：Eu,Sm that exhibit OSL. The measuring range of the dosimeter is from 0.01 to 100Gy. The equipment, which is relatively simple and small in size, is promising for applications in space exploration and high dose radiation dosimetry.     

《外国文学作品选读》双语教学的可行性研究

双语教学有利于帮助二语习得者实现母语正迁移,更好地适应时代发展的需要和自身素质的提高。作为提高高校学生素质的外国文学课程,有其独特的学科特征,有必要把双语教学作为一种独特的教育手段纳入课堂教学领域,使外国文学课堂教学更具特色。通过问卷调查的方式,认为双语教学不仅能激发学生学习兴趣,提高学生语言运用能力,而且有利于提高教师的业务水平。     

交流磁场下7075铝合金液相线和固相线温度变化

在7075铝合金凝固过程中施加频率为50Hz的交流磁场,磁场强度的变化范围为0 06T,0 09T,0 12T·运用双电桥法分别测定了上述凝固过程的电阻 温度曲线,确定了合金在不同磁场条件下凝固的液相线和固相线温度·实验结果表明:在交流磁场中凝固的合金,其液相线和固相线温度均明显提高,并且结晶温度间隔变小,磁场强度越大,这种变化越明显·与未加磁场的合金相比,经交变磁场处理后的合金,其液相线温度上升了7 5～12 5℃,固相线温度升高了10～20℃·交流磁场作用改变了固液界面前沿液相中的原子团簇向固相跳动时所需克服的势垒,最终导致合金熔点的改变·     

Body size variability and water balance: A comparison between mainland and island populations ofMastomys huberti (Rodentia: Muridae) in Senegal

Generally rodents are found to be larger on islands than on the mainland. However, there are some exceptions to this rule, and the aim of this paper is to examine one of them. On the mainland of Senegal,Mastomys huberti occupies humid habitats. However, it occurs also on dry and sandy islands (Saloum delta), where its representatives are dwarf. Since water availability appeared to be the limiting factor in these islands when compared to the mainland, we studied water turnover characteristics in relation to body size, in mainland and island populations at the end of the dry season, under both field and laboratory conditions. All populations were found to be water balanced in their natural habitats. They presented similar rates of water turnover, even though island animals were subjected to stronger constraints than mainland ones. Laboratory experiments suggested that the physiological plasticity of one of the island populations may be reduced. Island populations have a higher kidney size to body weight ratio than those from the mainland. We propose that smaller size in the islands allows the maintenance of water balance with a smaller amount of water, and that a higher ratio of kidney filtration surface to body size may helpMastomys huberti to survive in dry islands. We discuss the factors responsible for body size variability and variation in water exchange characteristics and conclude that different factors could explain body size variation among island populations, depending on the species considered and the ecological constraints met within the islands.     

图象压缩技术的分析与评价

视频图象压缩是多媒体系统中的关键技术，其原理是通过消除视频信号中的冗余信息来减少信息量。文中首先分析了图象压缩的基本技术，其中包括空间冗余信息的压缩和时间冗余信息的压缩，并对这些压缩方法的理论依据和实用效果加以探讨。以此为基础，还重点分析了通过集成基本压缩技术而建立的以混合编码系统，特别针对现有的图象压缩国际标准如ＪＰＥＧ，ＭＰＥＧ和Ｈ．２６１等作了较为深入的探讨，对其系统结构，适用范围及有效性进行了比较和分析。     

聚合物/层状硅酸盐纳米复合材料制备方法及性能的研究进展

聚合物 /层状硅酸盐纳米复合材料因其优异的性能是目前材料科学研究的热点。本文介绍了层状硅酸盐的结构、聚合物 /层状硅酸盐纳米复合材料的类型及微观结构 ,重点介绍了聚合物 /层状硅酸盐纳米复合材料制备方法及性能的研究进展 ,指出需根据不同的聚合物 ,寻求经济可行的制备方法     

宽带跳频通信系统频域均衡算法

针对差分跳频通信系统跳频带宽宽、瞬时带宽窄的信号特点,提出了一种差分跳频均衡算法--基于最小均方算法的多跳联合频域均衡算法。分析了最小均方误差准则频域均衡与单符号最小均方频域均衡对宽带差分跳频通信系统的不适用性,从而提出适用于差分跳频通信系统的多跳联合最小均方频域均衡算法,给出了算法详细的设计过程和结构。对算法性能在频率选择性衰落信道条件下进行仿真评估,结果表明本算法对差分跳频通信系统的信道均衡性能具有显著的作用,能提高差分跳频系统的解调误码性能。     

放电频率对DBD气动激励影响的数值分析

基于数值方法分析了DBD等离子体对翼型失速特征的改善效果,研究了不同放电频率对等离子体气动激励的影响.通过计算发现,采用DBD等离子体流动控制技术能够有效地抑制低雷诺数大攻角下翼型的动态失速特征.静止空气中,等离子体诱导速度随放电频率的增大先增大后减小,振荡频率的变化规律不明显,但在放电频率为无控制时翼型表面涡脱落频率的倍频和不是涡脱落倍频两种情况下,振荡频率分布随放电频率的增大而增大.采用等离子体抑制气动分离后,翼型升阻比随放电频率的增大先增大后趋于平缓,但不同放电频率下翼型气动力大小的变化很小;翼型气动力振荡频率随放电频率的变化较大,变化规律与静止空气中等离子体诱导速度的振荡频率相同.     

基于数据包重要性的低时延广播重传算法

 无线广播信道存在噪声和多径衰落,导致无线广播性能较差。传统的无线广播重传技术更多地考虑重传效率,而忽视了重要数据包优先重传的问题,使得一些特殊应用难以优先获得那些重要性较高的丢包。为提高无线广播重传的性能,同时满足对数据包重要性敏感应用的需求,本文在传统广播重传技术的基础上提出了一种基于数据包重要性的低时延广播重传算法。此算法在利用机会式网络编码方法编码重传包时,根据各终端所含丢包重要性的级别,分别对丢包进行编码优先权排序,在满足各终端能够及时译码的基础上优先编码终端中重要性高的丢包,权衡丢包重要性与参与编码丢包总的数量,使得一次编码重传中,参与编码的丢包数尽可能的多,并且使重要性级别靠前的丢包优先参与编码,如此不仅保持了一个较好的重传效率,降低了传输时延,同时又缩短终端获取高重要性丢包的时间。仿真结果表明,在典型的无线信道条件下,此算法不仅保持了现有的经典策略好的重传增益,同时突出了重要性高的丢包能够优先获得的优点,降低了传输时延。