电子成像均匀约束磁场的产生及测试分析

为增加离子与原子碰撞成像系统中探测电子的立体角，设计了一约束电子的复合型亥姆霍兹线圈装置.对复合型亥姆霍兹线圈的磁场分布进行了理论计算和分析，并对制作的复合型亥姆赫兹线圈产生的磁场进行了实验测量，得出磁场的均匀性好于±0.6%. 关键词： 亥姆霍兹线圈 磁场分布 磁场均匀性     

工业X射线机的射束均匀性检验

在与法国某公司的合作项目中,对射线机的性能做了充分的评估,针对工业X射线机射束均匀性的检验给出了实验内容、过程和结果分析。实验所用射线机分别为ISOVOLT320/13与XYD-225/10,两台设备的实验结果均符合该公司质控文件规定,满足黑度差不超过0.3的要求。定期对射线机进行射束均匀性检验,将有利于监测射线机的工作状态,以保证检测工作的准确性和一致性。     

新型低损耗1×3光分路器的优化设计

针对传统Y分支光分路器损耗较大的缺陷，采用直锥形波导代替传统的直波导来减小器件的尺寸，并且采用激模波导结构设计1×3分支波导。设计中，利用辐射模和本征基模的叠加来修正光波场，通过改善模匹配来降低分支耦合损耗，并通过对对称输出弯曲分支波导的优化来降低弯曲损耗，最后在1×3光分路器中的两弯曲波导的输入端加入过渡锥形波导来降低损耗和优化分路器的输出均匀性，并用有限差分光束传播法对该1×3分支波导进行数值模拟。模拟结果表明，该结构具有均匀性好、器件尺寸小、损耗小和结构简单等优点，有利于器件的进一步集成。     

Urea co-inclusion compounds of glipizide for the improvement of dissolution profile

In the present study, urea, a well-known adductor for linear compounds was successfully utilized for inclusion of glipizide—a highly substituted cyclic organic compound through a modified technique. Formation of glipizide co-inclusion compounds in urea was confirmed by FTIR, DSC and XRD. The minimum proportion of rapidly adductible endocyte (RAE) required for adduction of glipizide in urea was estimated by a modified Zimmerschied calorimetric method. Urea–GLP–RAE inclusion compounds containing varying proportions of guests were prepared and their thermal behaviour studied by DSC. The co-inclusion compounds were found to exhibit good content uniformity. Through the formation of co-inclusion compounds of urea, it was possible to achieve steep improvement in the dissolution efficiency of glipizide, which is a BCS class II drug.     

任意凸多面体上布点均匀性的度量

均匀性度量是构作均匀设计的基础,本文从距离概念出发,通过对称的方法,得到一种新的距离函数-势函数,并将势函数作为衡量任意凸多面体上布点均匀性好坏的准则.数值例子和多变量Kendall 协和系数检验表明,当试验区域限制在单位立方体上时,势函数与目前常用的两种偏差-中心化L_2-偏差和可卷L_2.偏差在度量布点均匀性方面结论一致.     

Estimation of DUR and source utilization efficiency for changing product dimensions and source activities in gamma irradiator

This paper discusses the application of the developed analytical method (Reji George, Jain, Pradhan, A.S., 2008. Theoretical evaluation of dose distribution in product in radiation processing plants. Radiat. Phys. Chem. 77, 186–191), for determining the activity loading pattern in a radiation processing plant to get the desired dose uniformity ratio (DUR) for processing mangoes and how the method was used to evaluate the expected source utilization efficiency for the redesigned source–product configuration.     

Performance Evaluation and Effectiveness of the Reverberation Room

This research presents a thorough evaluation of the reverberation room at Acoustics Laboratory in National Institute of Standards (NIS) according to the related international standards. The evaluation aims at examining the room performance and exploring its effectiveness in the frequency range from 125 Hz to 10000 Hz according to the international standard requirements. The room, which was designed and built several years ago, is an irregular rectangular shape free from diffusers. Its volume is about 158.84 m³, which meets the requirement of the ISO 354 standard L_max < 1.9V^1/3. Cut-off frequencies of one and one-third octave are 63 Hz and 100 Hz respectively; however Schroder frequency is 400 Hz. Calculations of cut-off frequency and modal density showed adequate modes that give acceptable uniformity starting comfortably from frequency of 125 Hz. The room has a reverberation time that is suitable for its size over the frequency range of interest. The room sound absorption surface area and its sound absorption coefficient satisfy the criteria given in ISO 3741 and ISO 354. There is an accepted diffuse sound field inside the room due to the standard deviation of measured sound level, which is less than 1.5 dB over all the frequency range. The only exception was 125 Hz which may be due to a lack of diffusivity of the sound field at this frequency. The evaluation proves that the NIS reverberation room is in full agreement with the international standards, which in turns qualifies the room to host measurements inside without concerns.     

Uniformity analysis of temperature distribution in an industrial MOCVD reactor

Three‐dimensional models, coupling fluid flow and heat transfer, have been adopted to analyze influences of the process parameters on the temperature uniformity in an industrial MOCVD reactor. Important factors, such as the inlet gas flow, the susceptor rotation, the heater power, the distance between the heat shield and the susceptor (d₁), as well as the distance between the heater and the susceptor (d₂), have been investigated carefully. The system heating condition is characterized by temperature uniformity denoted as the standard deviation of temperature, and by thermal efficiency expressed as a combination parameter of the dissipated energy. The results reveal that decrease of the gas flow and the rotation rate, as well as increase of the distance d₁, could monotonically enhance the temperature uniformity. The results also show that decrease of the above three parameters could improve the thermal efficiency. Furthermore, increase of the distance d₂ enhances the temperature uniformity, and reduces the thermal efficiency slightly. The influences of the parameters on the uniformity vary at the different locations of the susceptor as divided into Zone A, Zone B and Zone C. The conclusions help the growth engineer optimize the system design and process conditions of the reactor.     

Uniformity investigation of MOCVD‐grown LED layers

Doped or undoped gallium nitride compounds (GaN/InGaN), usually grown by metal‐organic chemical vapor deposition (MOCVD) method, are at the heart of blue and green light emitting diodes (LEDs). Growth uniformities, such as the excited wavelength, luminous intensity and film thickness, critically influence their application in LED devices. In this paper, growth of GaN compounds in a MOCVD reactor, capable of a one‐time production of 36 × 2” wafers of nitrides, has been investigated. To examine growth uniformity across the wafer and from wafer to wafer, the reactor is divided into Zone A, Zone B and Zone C according to distance to the center of the graphite susceptor. Comparative analysis of each zone offers a straightforward view of the mean excitation wavelength, luminous intensity, film thickness and their standard deviations. Conformity of the growth uniformity in each zone is further checked comprehensively through averaging across‐wafer and wafer‐to‐wafer variables and their standard deviations. Zone B is found to retain excellent wavelength uniformity, since it is located at the middle of the susceptor with weaker effects of the susceptor edge and of the inlet gas flow. Zone A, at the center of the reactor, has the best mean intensity and thickness uniformities due to a well control of the infrared temperature measurement during the growth. And Zone C is worst in all uniformities and should be the main focus when optimizing the reactor. The above experimental analysis reveals the principles common to the MOCVD technique, and provides a basic for further optimization of the process window to improve the cycles with considerable reduction of the costs.     

LED显示屏质量提升的探讨

近年来LED显示屏被广泛应用于室内外显示领域。文章主要依据信息产业部标准SJ/T11141-2003《LED显示屏通用规范》和SJ/T11281-2007《发光二极管（LED）显示屏测试方法》,针对LED显示屏的一些重要考核指标如亮度、均匀性、视角和安全等,探讨如何提升LED显示屏的质量。