Trapping Behavior of He in Ti Revisited by ab initio Calculations

We report a detailed ab initio study of the trapping behavior of interstitial helium atoms （IHAs） in hcp Ti. The tetrahedral interstitial site for one He is confirmed to be the most stable IHA configuration, but the most favorable interstitial site comprises two adjacent octahedral sites for two helium atoms. The octahedral IHA can trap another IHA regardless of the site where it is initially located, whereas the tetrahedral IHA cannot. Hybridization among the different states is responsible for the stable order, which has significant implications for He clustering and bubble nucleation that can affect material performance in future fusion reactors. These results provide the basis for the development of improved atomistic models.     

Characterization of zirconium thin films deposited by pulsed laser deposition

Zirconium(Zr) thin films deposited on Si(100) by pulsed laser deposition(PLD) at different pulse repetition rates are investigated. The deposited Zr films exhibit a polycrystalline structure, and the X-ray diffraction(XRD) patterns of the films show the α Zr phase. Due to the morphology variation of the target and the laser–plasma interaction, the deposition rate significantly decreases from 0.0431 /pulse at 2 Hz to 0.0189 /pulse at 20 Hz. The presence of droplets on the surface of the deposited film, which is one of the main disadvantages of the PLD, is observed at various pulse repetition rates. Statistical results show that the dimension and the density of the droplets increase with an increasing pulse repetition rate. We find that the source of droplets is the liquid layer formed under the target surface. The dense nanoparticles covered on the film surface are observed through atomic force microscopy(AFM). The root mean square(RMS) roughness caused by valleys and islands on the film surface initially increases and then decreases with the increasing pulse repetition rate.The results of our investigation will be useful to optimize the synthesis conditions of the Zr films.     

软件无线接收数字前端的实现

基于软件无线电(SDR)基本思想,提出数字前端概念,对数字前端的组成、功能和基于CORDIC算法的数字下变频、多速率滤波等关键技术进行了介绍。设计了一种软件无线电接收系统,实验表明该设计方案扩展性和移植性好,技术性能达到要求。仿照GSM接收系统技术参数,设计了多速率滤波器,仿真表明,数字前端采用多速率滤波器,能节省成本。对SDR的发展进行了展望。     

红霉素肟合成反应研究

采用盐酸羟胺三乙胺乙酸体系将红霉素转化为红霉素肟,利用薄层色谱（TCL）及高效液相色谱法（HPLC）对反应结果进行纯度测定,重点考察了酸度对反应的影响,在最佳反应条件下红霉素肟的收率为97％,纯度达87．9％。     

数字电视机的发展

本文阐述了数字电视机的发展趋势,数字电视机由模拟／数字混合型向标准数字、高清（HDTV）发展的三个阶段。     

反相高效液相色谱分析克拉霉素合成工艺中区域选择性甲基化的关键中间体

采用反相高效液相色谱法对克拉霉素合成工艺中关键中间体E-2′,4″-双(三甲基硅)-红霉素A-9-(1-异丙氧环己基)肟、Z-2′,4″-双(三甲基硅)-红霉素A-9-(1-异丙氧环己基)肟和E-2′,4″-双(三甲基硅)-6-甲基红霉素A-9-(1-异丙氧环己基)肟、Z-2′,4″-双(三甲基硅)- 6-甲基红霉素A-9-(1-异丙氧环己基)肟及其相关的6种工艺杂质进行了分离、定性和定量分析。色谱柱为DIKMA公司的Inertsil ODS-3(150 mm×4.6 mm i.d., 5 μm);流动相     

二车异地电视直播方案

随着广播电视事业的发展,大型演播活动中异地、多车电视直播应用越来越多。我台进行了几次二车异地大型活动电视直播,取得了圆满成功,得到了较好的社会反响。下面介绍一下我台二车异地电视直播方案。     

UWB无线网络QoS跨层联合优化的研究

为了更好地实现无线办公室组网,无线家庭组网,必须对UWB无线网络的QoS进行优化.对UWB无线网络MAC协议--IEEE 802.15.3进行了分析,介绍了基于跨层设计的DCC-MAC算法.在NS2.29环境下进行了仿真,测试表明:即使节点数增多,干扰增强,采用DCC-MAC协议的UWB无线网络能保持比较高的平均吞吐量,当节点的总个数从2到60变化时,系统吞吐量约为250Mbit/s.     

2',4″-O-双(三甲基硅)-6-O-甲基红霉素A9-O-(1-甲氧基环己基)肟的区域选择性合成机理及其晶体结构

克拉霉素(Clarithromycin)是第二代十四元大环内酯抗生素, 其合成是保护技术应用和区域选择性研究的一次集中体现[1,2].目前, 美国雅培实验室和日本大正公司是以2′,4″-O-双(三甲基硅)红霉素A 9-O-(1-异丙氧环己基)肟(1)作为区域选择性前体制备的[1,3]; 而中国和印度制药企业多采用2′,4″-O-双(三甲基硅)红霉素A 9-O-(1-甲氧基-1-甲基乙基)肟(2)作为关键中间体[4,5].后者的主要杂质为6,11-O-双甲基红霉素A[6].对大环内酯的区域选择性进行了大量的研究后, 发现2′,4″-O-双(三甲基硅)红霉素A 9-O-(1-甲氧基环己基)肟(3)的区域选择性远低于空间结构差异不大的化合物1[7], 却与空间结构差异较大的化合物2一样, 易生成大量的6,11-O-双甲基化产物.     

碱性去活柱反相高效液相色谱法分析红霉素肟及相关化合物

采用碱性去活(BDS)C18柱分离测定了红霉素肟及相关化合物。以0.02 mol/L 磷酸氢二钾(用磷酸调pH 7.2)-乙腈-甲醇(体积比为50∶40∶10)为流动相,检测波长为210 nm,柱温为35 ℃。红霉素肟E、Z异构体及相关化合物红霉素A、红霉素A 8,9-脱水-6,9-半缩酮和红霉素A 6,9-9,12-螺缩酮五种组分分离完全,检测限(S/N=3)为6.0～24.0 ng,线性关系良好,方法准确可靠,用于实际样品分析时取得较好的效果。