YAG：Nd激光照射犬气管粘膜的实验研究

An experimental study for the pathologic changes of the canine tracheal mucosa under YAG:Nd laser ablation was performed in order to master the appropriate parameters for the clinical treatment of YAG:Nd laser. 6 male and female Mongolia dogs weighing 13-18 kg were received 20W YAG:Nd laser treatment and their pathologic changes were examined instantly and 3, 7, 14 and 28 days after ablation.     

固定波形时间保护间隔OFDM系统循环卷积特性研究

针对固定波形时间保护间隔OFDM系统接收端OFDM信息符号和信道冲击响应之间不具有循环卷积特性的系统特点,本文提出一种简单有效的信号处理算法对该系统接收端OFDM信息符号和信道冲击响应之间的循环卷积特性进行恢复。理论分析和计算机仿真表明,该算法能够恢复接收端此循环卷积特性;在时延扩展和AWGN信道条件下,系统误符号性能受到的影响微弱。     

CDMA位置服务系统的本地定位平台建设

移动位置业务是移动通信网络的一项特色增值业务．将成为今后几年的业务增长亮点之一。中国联通总部的增值业务部于2002年采用集中设置方案，进行了CDMA位置服务系统一期工程的建设。本地定位平台建立于中国联通CDMA位置服务系统基础之上．其功能由以下的一项或多项组合而成：门户功能、中间件功能、GIS系统的的功能和对本地的CP进行管理和计费的功能。     

Measurements of total and positronium-formation cross sections for the scattering of positrons by alkali atoms

We present a review of our recent measurements of total cross sections (Q _T's) for the scattering of positrons by Na, K, and Rb, and positronium-formation cross sections (Q _Ps's) for Na and K. For our total cross section measurements, a beam transmission technique has been used. For ourQ _Ps measurements, our approach involves setting upper and lower limits onQ _Ps using a combination of (1) measuring the transmission of the positron beam with the angular discrimination of the apparatus made as poor as possible, and (2) measuring the 511 keV annihilation gamma rays in coincidence produced by the decay of para-Ps formed in the scattering cell. Comparison with theoretical calculations shows that our measuredQ _T's andQ _Ps's for Na and K agree reasonably well with a close coupling approximation (CCA) calculation which takes into account the formation of Ps in then=1 andn=2 states. In the 3–10 eV energy range, this calculation predicts a peak in theQ _T's andQ _Ps's for K which also appears in our measurements. The absence of such a peak in our measuredQ _T's andQ _Ps's (preliminary) for Na in this energy range is also consistent with the same theory. Comparisons with five-state CCA calculations ofQ _T which do not take Ps-formation into account also show good agreement with our positron-Na, K, and RbQ _T measurements for energies above 20 eV, but show dramatic departures from our measurements below 10 eV for K and Rb.     

Field emission mechanism from nanocrystalline cubic boron nitride films

An electron-emission theoretical model integrating the change in the grain size of nanocrystalline cubic boron nitride (c-BN) thin films was established. To understand better the essence of field emission, an accurate numerical scheme, the transfer matrix method, that can be used to compute the tunneling coefficients of the actual surface barrier, was also adopted. The present results show that the emission current from nanocrystalline grain films is far larger than that from regular grain films or bulk c-BN.     

Effect of Stress State on Growth of Interfacial Intermetallic Compounds Between Sn-Ag-Cu Solder and Cu Substrates Coated with Electroless Ni Immersion Au

Excessive intermetallic compound (IMC) growth in solder joints will significantly decrease the reliability of the joints. IMC growth is known to be influenced by numerous factors during the component fabrication process and in service. It is reported that, other than temperature and holding time, stress can also influence the IMC growth behavior. However, no existing method can be used to study the effect of stress state on IMC growth in a controlled manner. This paper presents a novel method to study the effect of stress on interfacial IMC growth between Sn-Ag-Cu solder and a Cu substrate coated with electroless Ni immersion Au (ENIG). A C-ring was used and in-plane bending induced tensile and compressive stresses were applied by tightening the C-ring. Results revealed that in-plane compressive stress led to faster IMC growth as compared with in-plane tensile stress.     

微型网状结构支架的力学性能研究

冠状动脉支架为圆柱形微型网状结构，直径1mm，厚度0．1mm，长度10～16mm。在经皮冠状动脉介入PCI治疗中由球囊充气撑开到直径为2．5～3．5mm的支架，在血管内承受血管壁回弹压力。为了保持血液流通支架必须保持其几何圆形。这是一个结构弹塑性稳定性问题。但是目前国际上对于支架的力学性能质量指标主要以强度性能评定而不涉及支架屈曲性能是不妥的。本文对于支架的强度和屈曲性能进行了全面的理论分析和实验研究，自行研制了智能式电子检测仪成功地对微型网状结构支架的强度和屈曲性能实现了实测实验研究。由于微型支架的离散型网状结构的特点，在实验中出现一些特殊的屈曲现象。本文研究结果对于支架的形状与性能设计的改进和力学性能质量标准规范的制订具有重要意义。     

旋转带电体磁矩计算的若干法则与算例

本文在文献 [1]、[2 ]等的基础上给出关于旋转带电体的磁矩计算的若干法则 ,均以定理形式表达 ,并列表枚举其相关算例     

一类非线性弹簧振子的周期性振动

本文用数值计算的方法讨论了一类非线性弹簧振子的周期性振动及其特点．     

FDTD Method in the Analysis of Lithium Niobate Modulator

The Mach-Zehnder traveling-wave lithium niobate modulator is simulated by time domain finite difference (FDTD)method for different device geometry. The result is comparable to the reported value by finite element method.