New developments in CdTe and CdZnTe detectors for X and γ-ray applications

There has been considerable recent progress in II-VI semiconductor material and in methods for improving performance of the associated radiation detectors. New high resistivity CdZnTe material, new contact technologies, new detector structures, new electronic correction methods have opened the field of nuclear and x-ray imaging for industrial and medical applications. The purpose of this paper is to review new developments in several of these fields. In addition, we will present some recent results at LETI concerning first the CdTe 2-D imaging system (20 × 30 mm² with 400 × 600 pixels) for dental radiology and second the CdZnTe fast pulse correction method applied to a 5 × 5 × 5 mm³ CdZnTe detector (energy resolution = 5% for detection efficiency of 85% at 122 keV) for medical imaging.     

JETS,PLUMES AND BUOYANT JETS IN STATIC ENVIRONMENT

Turbulence represents an essential aspect in atmospheric and oceanic circulations.In particu-lar,it is a preponderant factor in the dispersion of pollutants of artificial or natural origin.Thevertical turbulent jets,plumes and buoyant jets discharging into static environment is one of themost important and basic flow patterns related with the environment pollution.These flows havenumerous important applications,for example,thrust augmentors,waste disposal plumes fromstacks and combustion systems,and significant problems of turbulent diffusion.     

ETR Ⅱ-30调速器液压控制系统

ETRⅠ-30调速器是瑞士爱舍维斯工厂生产的具有PID调节规律的电液调速器。本文对其液压控制系统作了较详细的介绍,供有关人员参考。     

异质谷间转移电子器件的计算机模拟

使用弛豫时间近似求出了描述两能谷间电子交换的方程。在此基础上建立了双能谷电子的连续性方程和油松方程。对具体的ＧａＡｓ／ＡｌｘＧａ１－ｘＡｓ异质谷间转移电子器件结构求解了这些方程组，得到了直流工作时器件内的电场分布、双能谷中载流子的布居以及两个能谷的电流分布。这些结果正好和常规Ｇｕｎｎ器件相反，说明了两种器件的不同工作机理。最后通过对低Ａｌ组份势垒结构的计算说明了Ｘ谷电子注入对器件工作的重要作用。     

CIMSCLASS─—面向CIM的零件分类软件开发工具

介绍了一个能为工厂设置零件编码系统和开发零件分类系统的工具系统。该系统能适应用户的具体环境，能对零件的特征信息做较详细的描述和建立相应目标的零件分类系统，从而能在ＧＴ（成组技术）基础上为机械加工零件开发ＣＡＤ／ＣＡＰＰ／ＣＡＭ集成系统提供支持，以满足ＣＩＭＳ的需要。     

Electrical/electronic effects of titanium and iron impurities in EFG and FZ solar cell silicon: SPV/EBIC analysis

In this paper results on surface photovoltage (SPV) and electron beam induced conductivity (EBIC) studies of edge-defined film-fed growth (EFG) and floating zone (FZ) silicon solar cell materials (both p-type) are presented. A systematic comparison based on minority carrier diffusion length and carrier recombination is made between: (i) samples contaminated with Ti and/or Fe, (ii) samples gettered by phosphorous diffusion, and (iii) as-received samples. Deep level transient spectroscopy (DLTS) measurements, together with the iron-boron (FeB) pairing kinetics [1] have successfully been used to detect the presence of Fe in the samples. Even though this process is effective in revealing Fe impurities in p-type FZ silicon it is evidently not suitable for Fe identification in p-type EFG silicon. Ti, like Fe, is found to be a prominent lifetime-limiting metallic impurity in both EFG and FZ silicon. Phosphorous diffusion is proven to be an effective external gettering technique for fast-diffusing impurities such as Fe, but not for Ti.     

Computer analysis,design and simulation of horizontal ground heat exchangers

This paper presents a new computerized procedure for dealing with the design of horizontal ground heat exchangers (HGHE). The computer program is based on the transient model of coupled nonlinear partial differential equations governing heat and mass flow in soils. The model is two-dimensional and delineates the operation of ground heat storage with the HGHE and such phenomena as freezing/thawing and drying/rewetting of soil moisture. Comprehensive climatological data, such as ambient temperature, solar radiation, wind velocity, rainfall, snowfall, snow characterstics, and water vapour pressure is used to simulate conditions at the ground surface over any required length of time. The package can be applied to any geographical location by changing climatic and soil data input. The designer has the possibility of selecting any of 12 types of soils from sand to clay, 12 commercial heat pumps, nine different configurations of the HGHE, 16 plastic pipes for ground coils, and 13 ground coil fluids. The program, however, does not calculate the length of the HGHE but it evaluates the thermodynamic performance of a ground heat pump system and provides comprehensive data on thermal and hydraulic conditions in ground heat storage. The length of the ground heat exchanger is obtained from a line source theory model or from site dimensions and pipe spacing. Computed results for ground heat exchanger operation correlate fairly well with experimental data. Simulation of temperature and moisture content in the ground for natural conditions (no heat extraction/deposition) showed a fair agreement with field data. The entire computer program is user-friendly, interactive, menu-driven, and written in FORTRAN 77.     

A portable cryo-storage system for low-temperature scanning electron microscopy,suitable for international transport of cryo-specimens

A cryo-specimen storage system for low-temperature scanning electron microscopy (LTSEM) specimens is described, which: liberates multi-specimen experiments from sampling restrictions imposed by the rate at which LTSEM specimens can be examined in the SEM; provides security against experiment loss resulting from breakdown of the SEM or cryo-system; enables collection of specimens in the field or in laboratories remote from the SEM laboratory; and facilitates international air transport of LTSEM specimens. The components of the system, which has a capacity of 98 stub-mounted specimens, are readily made in a laboratory workshop. The details of the design may be altered to suit particular specimen types or experimental approaches.     

The pickup and delivery problem: Faces and branch-and-cut algorithm

This paper formulates the pickup and delivery problem, also known as the dial-a-ride problem, as an integer program. Its polyhedral structure is explored and four classes of valid inequalities developed. The results of a branch-and-cut algorithm based on these constraints are presented.     

WC对Cu/WC_P复合材料性能及组织的影响

通过ＷＣ含量对ＷＣ／Ｃｕ复合材料性能的影响，确定了冷压－烧结法制备Ｃｕ／ＷＣ材料的适宜ＷＣ含量为１０ｖｏｌ％左右。并就ＷＣ对该材料组织和再结晶行为的影响进行了有益的探讨。