用声透射损失测气一水混相介质中的含气量

本文利用超声检测中的穿透法,用频率为０．５ ＭＨｚ、 １ＭＨｚ、 １．２５ＭＨｚ、 ２ＭＨｚ、 ２．５ＭＨｚ的声波,测量了气一水混相介质中的声速比值和声透射损失。结果表明：在气泡大小、分布一定的情况下,可能用声透射损失来确定混相介质中的含气量,但不宜用声速比值．     

用声透射损失测气一水混相介质中的含气量

本文利用超声检测中的穿透法,用频率为０．５ＭＨｚ、１ＭＨｚ、１．２５ＭＨｚ、２ＭＨｚ、２．５ＭＨｚ的声波,测量了气－水混相介质听声速比值和声透射损失,结果表明,在气泡大小,分布一定的情况下,可能用声透射损失来确定混相介质中的含量量,但不宜用声速比值。     

用来激励高频超声换能器的电激励源

讨论了超声换能器的几种激励方法，分析了三种常用激励方法在激励高频超声换能器时的特点及其同局限性，我们雪崩ＭＡＲＸ电路制作的单极窄脉冲能地激励率高达１００ＭＨｚ的换能器并取得了较好的结果。     

反常声电光偏转器

本文介绍的新型声光偏转器可提高传统光偏转器的带宽，制作了一个ＬＮ反常声电光偏转器，中心频率为６０ＭＨｚ测试结果表明，带宽由原来的２６ＭＨｚ提高到３７ＭＨｚ。     

二极管激光泵浦固体激光器和稳频研究

用调制法布里－珀罗干涉仪方法稳定二极管激光泵浦的ＮｄＹＶＯ４单频激光器的频率。在锁定情形下，激光频从自由运行慢漂移１．４３ＭＨｚ／ｓ和抖动±２．５ＭＨｚ分别改善到７５．７５ｋＨｚ／ｓ和±１ＭＨｚ     

中国人参的核磁共振研究Ⅰ．人参皂甙Re的二维核磁共振谱研究

用４００ＭＨｚ和５００ＭＨｚ超导核磁共振谱仪测定了具有生理活性的达玛烷型人参皂甙Ｒｅ的同核、异核二维化学位移相关谱和相敏双量子滤波二维相关谱，由此归属了人参皂甙Ｒｅ的氢谱，测定了Ｒｅ的质子偶合常数。     

频率对双频超声辐照声化学产额增强效应的影响

本文采用电学法研究了２８ｋＨｚ分别与０．８７ＭＨｚ、１ＭＨｚ、１．７ＭＨｚ组成的双频超声辐照的声化学效应。结果表明，双频辐照增强声化学产额具有明显的频率效率。     

用于远红外FEL的直线加速器物理模拟计算

波长在２００μｍ附近的自由电子激光对电子束品质有特别要求，不仅要求较长的束流微脉冲，而且对流强、能散度以及束流参数对加速器噪声的稳定性等都有很高的要求。我们采用ＰＡＲＭＥＬＡ程序，对一台由１０８ＭＨｚ分频预聚束器、９腔１３００ＭＨｚ聚束加速段和９腔１３００ＭＨｚ加速段组成的加速器进行了大量模拟计算，得到了满足ＦＥＬ要求的物理设计方案和对加速器各部件稳定性的要求指标。     

300MHz激光扫描声学显微镜

本文对激光扫描声学显微镜（ＳＬＡＭ）的刀口理论以及利用谐波技术提高其工作频率的方法进行了研究．实验上实现了使基波频率为１００ＭＨｚ的ＳＬＡＭ工作于３００ＭＨｚ三次谐波上．最后给出了一些样品在３００ＭＨｚＳＬＡＭ系统上较清晰的声学图像．     

射频激励层叠式波导CO2激光器

提出一种射频激励层叠式波导ＣＯ２激光器技术，在两个波导空间尺寸均为１×１４．５×２００ｍｍ３、射频电源频率为９９ＭＨｚ的条件下，获得最大输出功率为７５Ｗ、最大电光转换效率为１０．８％的实验结果，并在远场得到单峰分布的一维压窄光斑     

高频环行器打火原因的分析

合肥光源(HLS)储存环高频系统环行器在工作中出现了两种形式的打火——谐波打火和束流丢失打火. 谐波打火的原因已经找到并予以解决, 但丢束打火的机制尚未明确. 文中描述了丢束后高频系统的响应过程, 分析了一些可能造成环行器打火的因素. 为了防止环行器打火受损, 建立了快速联锁保护电路, 该电路在历次打火中成功地保护了环行器.     

低场永磁体磁共振射频场映像

射频场映像是通过一定算法对磁共振射频线圈的发射场进行重建的方法.高场下的射频场经过生物组织时会发生明显变化,在其基础上可以反演生物组织体内电特性,进而对癌症等疾病进行早期诊断,是对生物组织的磁共振结构成像的有力补充.目前为止,射频场映像和电特性研究都以高场鸟笼线圈为主,对低场下的相控阵研究较少.本文主要研究了低场永磁体磁共振射频场的均匀度.有限元仿真和实验验证了在17.8 MHz激励下,射频场在空载和负载下均匀度均发生较大变化.射频场均匀度在负载下的改变在一定程度上可以反映负载生物组织的电特性,对磁共振电特性实用化研究提供了一定的参考价值.     

Radio frequency field intensity mapping using a composite spin-echo sequence

A novel radio frequency (RF) field intensity mapping or imaging method using a composite NMR spin-echo sequence is proposed. A composite spin-echo RF pulse with 90 degrees y-180 degrees x-90 degrees y sequence makes phase change in the final image depending on the RF field intensity on the object. The resultant phase change or phase map can be used to obtain the actual RF flip-angle map for a given condition which includes the status of tuning and RF inhomogeneity, etc. Bloch equation has been solved numerically to obtain the effects of the RF field intensity as well as the main magnetic field inhomogeneity and the results are used for the mapping (imaging) of the RF field intensity. Phantom studies have been performed using a 1.5 Tesla whole body MRI system and the results are presented.     

重离子加速器冷却储存环高频腔体设计

 通过二维高频电磁场的计算，设计了兰州重离子加速器冷却储存环（HIRFL–CSR）的铁氧体加载腔，给出了高频系统主要参数及加速电场的分布。     

Physicochemical and Antioxidant Properties of Riboflavin in Dextran70/HSA Systems

Physicochemical properties of Riboflavin (Vitamin B₂) (RF), in Dextran 70 (Dx70) (a biological relevant glucidic type macromolecule) and Human Serum Albumin (HSA) (a carrier/transport protein) based system, have been studied by absorption, fluorescence, circular dichroism and electrochemistry. No significant changes on the fluorescence of RF in Dx70/HSA systems with and without the influence of temperature (30–60 °C range) were observed. No changes on the intrinsic Tryptophan fluorescence in Dx70/RF/HSA system, have been evidenced. HSA secondary structure when RF binds in Dx70/RF/HSA systems, with a renaturation effect of Dx70, was found. In Dx70/RF/HSA system the major process which RF undergoes is the proton transfer, E_red = ?0.43 V. Using the chemiluminescence method, an improvement of the antioxidant activity of RF into the Dx70/RF/HSA system, was also found. RF concentration in Dx70/RF/HSA systems is important in RF oxidative damages when it reacts with target molecules and thus promotes their oxidation. The results have relevance in the oxidative stress process and in pharmaceutical formulations containing RF.     

航天器多路射频频谱自动监测系统设计

设计了一种采用太阳能供电模式的无线户外环境监测系统。该系统由终端节点,ZigBee-GSM网关和上位机数据存储中心组成,集成ZigBee和GSM无线通信,根据用户发送的短信指令控制终端节点数据采集的通断,同时用户发送短信指令远程查询户外环境的重要信息。针对户外环境因子的特点,选用工业级、灵敏度高的传感器,对户外不同位置的PM2.5浓度和紫外线指数进行测量,测量结果既可在上位机实时显示和存储,也可以由ZigBee-GSM网关通过SIM900A模块发送至移动终端。户外测试结果表明,该系统运行稳定,数据传输可靠,能快速地实现远程遥测功能,为户外环境远程监测提供了一种技术手段。     

The influence of external parameters on the peculiarities of a hybrid low-pressure radio-frequency discharge

This paper deals with the experimental study of the patterns of the RF power input into the plasma of a hybrid RF discharge that was sustained by an RF power unit, which consisted of a spiral antenna connected in parallel with capacitor electrodes. At low values of RF generator power, RF power has been shown to be derived in the hybrid discharge through the capacitive channel; the role of the inductive channel becomes more significant at higher RF generator power as the power of the RF generator increases. It was demonstrated that at a low power of the RF generator the RF power occurs in the hybrid discharge essentially through the capacitive channel and then increases as the power of the RF generator increases. The larger the contribution of the inductive channel is, the smaller the value of the dividing capacity included in the capacitive discharge chain is.     

中国散裂中子源直线射频低电平远程控制软件研制

中国散裂中子源一期工程的直线加速器,共有8套数字化射频低电平控制单元,射频低电平的本地控制属于EPICS的异构系统,无法直接与EPICS客户端进行通信。通过在射频低电平本地控制上位机程序中嵌入一个C#类型的EPICS服务器程序,实现了使用EPICS客户端对射频低电平系统的远程控制, 从而把射频低电平控制系统接入基于EPICS框架的控制系统中。直线射频低电平远程控制投入在线运行以来,运行稳定可靠。     

BEPCⅡ直线加速器速调管的反射保护

为了使速调管陶瓷窗免受大功率微波反射信号的损伤,延长速调管使用寿命,要求当前反射信号功率超过阈值后,系统能够在下一个脉冲到达之前发出报警信号,进而切断触发信号,实现对速调管的保护。提出了3种较高性价比、易实施的方案,即PicoScope虚拟示波器的遮罩报警方案、基于自带检波和报警输出功能的芯片制作反射保护插件以及原功率计的升级改进。创新性地提出“3+1”反射保护响应时间测试法,并对上述3种方案进行详细测试。最终后两种方案取得较好的结果,综合考虑后,将改进型功率计作为最终实施方案。目前该改进型功率计已稳定可靠地上线运行超过1年。     

Supersonic CO2 laser excited by RF discharge in closed cycle

A supersonic gas flow having a Mach number of 2 has been realized in a closed-cycle radio-frequency (RF)-discharge-excited supersonic CO₂ laser system. Stable RF discharge at a high CO₂ gas concentration has become possible using supersonic gas flow and RF discharge generated between dielectric electrodes. As a result, high RF input power density has been obtained. In addition, a high small-signal gain has been obtained in the supersonic section through decreases in gas pressure and gas temperature due to supersonic gas flow.This revised version was published online in August 2005 with a corrected cover date.