数字化多道中双指数脉冲梯形成形算法研究

本文在双指数脉冲梯形滤波成形算法原理基础上,从理论上分析了算法的滤波特性和弹道亏损特性。通过MATLAB仿真和基于FPGA的实验验证,证明了该算法的梯形上升沿时间越长滤波效果越好,修复弹道亏损所需梯形平顶长度小于探测器电荷收集时间。在设计数字化多道时可根据上述特性对梯形参数进行优化调整,从而最大限度地减少系统脉冲成形时间,降低脉冲堆积概率,提高多道脉冲幅度分析系统的脉冲通过率。     

核信号高斯与梯形数字成形方法仿真及其评价

针对理想单脉冲负指数衰减核信号,建立了数值递推法的高斯核脉冲成形模型和Z变换法的梯形核脉冲成形模型,在MATLAB/Simulink环境下,运用DSP Builder系统级模型开发工具搭建了梯形核脉冲成形平台。通过改变脉冲成形参数,获得了脉宽、半高宽、峰高等信号特征量,并对高斯与梯形成形方法进行了仿真对比分析及其评价。结果表明,改进后的梯形成形方法成形速度快、灵敏度高、抗噪能力强,最终在FPGA板级测试验证了梯形成形方法的正确性,取得了较好的效果。     

数字多道中梯形成形算法的FPGA实现

针对数字多道核谱仪系统,研究并实现了数字滤波梯形成形算法。从数学理论上对算法可行性进行论证,并利用Matlab仿真验证;采用FPGA技术对该算法建模及Modelsim仿真分析,完成了数字多道的研制。通过NaI(TI)探测器进行55Fe源能谱实测结果表明,该算法能够达到最佳滤波成形效果,改善了数字多道的各方面性能,在自主研制的多道分析器中得到了成功应用。     

基于LabVIEW语言的PCI总线数据传输系统

介绍了一种基于LabVIEW的针对FPGA的数据开发接口平台。该系统核心硬件由FPGA组成,可提供数据处理、数据IO等多种功能,并通过PC104对外提供PCI接口实现通信。该系统可兼容NI(美国国家仪器公司)CRIO机箱。它不同于传统的用HDL语言对FPGA的开发流程,这样一个系统的所有软件代码,包括FPGA代码都可以由LabVIEW语言实现。借助于图形化的LabVIEW语言,它大大降低了实验人员对于FPGA的开发要求,是一种通用的数据处理和数据接口平台。给出了平台的结构组成,并着重介绍了平台数据传输部分的实现和测试。     

反应堆FPGA保护子系统开发与验证

验证与确认(VV)方法是FPGA在核安全级仪控系统中应用所面临的关键问题之一。本研究以CPR1000核电机组一次冷却剂流量和ΔT保护系统为对象,进行基于FPGA的系统开发和VV研究,提出了FPGA仪控系统的开发、VV过程和方法。采用通用验证方法学(UVM)和第三方仿真工具确保硬件描述语言(HDL)代码获得100%的测试覆盖率,借助核电厂原理模拟机开展集成测试。研究结果为FPGA反应堆保护系统的开发、VV和评审提供了理论和技术参考。     

数字化能谱获取中梯形成形研究

在数字化能谱采集系统中,往往需要添加适当的脉冲成形算法对数字化核信号进行处理,以提升系统能量分辨率等指标。梯形成形算法因具有实现简单、成形脉冲窄等诸多优势而得到广泛的应用。从探测器输出的脉冲信号进行数学模型建立及简化出发,对信号模型的梯形成形算法进行分析讨论,并利用Simulink在现场可编程逻辑门阵列(Field-Programmable Gate Array,FPGA)上实现并改进梯形成形算法,通过实验测试了成形算法的可行性及其在能谱测量过程中对能量分辨率的提升。     

梯形成形算法中成形参数与成形脉冲波形关系研究

在梯形成形算法理论基础上,利用模拟和实测核脉冲信号研究了梯形成形算法中衰减时间常数(τ_(trap))、达峰时间(n_a)与成形脉冲波形、滤波效果的关系,以及nb在分离堆积脉冲时的取值选择。研究表明,当且仅当τ_(trap)等于输入信号衰减时间常数时,成形脉冲对称;n_a值越大,滤波效果越好,脉冲宽度增加;n_b小于两个核脉冲信号发生的时间间隔时,采用梯形成形算法可分离堆积脉冲。     

新型数字BPM信号处理器研制进展

介绍了采用Arm微处理器技术、FPGA数字信号处理技术、高速带通欠采样技术的新型BPM信号处理器研制进展情况;对两类主要的原理样机进行了评估测试.信号处理算法评估样机基于商业评估板搭建,用于测试包含数字下变频、低通滤波、抽取降速等信号处理算法功能模块.自主开发的硬件评估样机用于测试不同硬件功能模块及整机集成后的硬件性能...     

基于软核的数字化多道脉冲幅度分析器

介绍了一种数字化多道脉冲幅度分析器(DMCA),该系统采用数字梯形滤波成形等数字信号处理方法进行核脉冲信号处理,采用NOISII软核处理器进行数据处理,所有数字功能均在单片FPGA中实现。测试表明,该系统转换增益可达4 096道,最大脉冲通过率可达200 kcps以上。     

基于ARM与FPGA的运动控制平台研究

介绍了基于ARM与FPGA的实时束流截面测量的嵌入式平台,讨论了电机控制器子系统的硬件接口设计,通过ARM的外围总线实现了ARM与FPGA的接口,并采用Linux操作系统对FPGA设备进行驱动开发。自主开发的硬件接口板用于测试ARM与FPGA实现方案以及整机集成后的硬件性能。实验测试表明,硬件接口板能有效实现电动控制,原运动控制器定位精度为1μm,现平台定位精度达2μm,数量级上满足要求,可用于后续FEL设备升级。     

Preparation of Zn/TiO2 powder and its photocatalytic performance for oxidation of P-nitrophenol

Zn-doped TiO2 catalysts were prepared using a sol-gel method and characterized by XPS,UV-Vis, BET, XRD in this study. Under the irradiation of simulant sunlight, the photocatalytic activity for the degradation of p-nitrophenol was studied too. After irradiation for 2.5 h, the degradation percentage of p-nitrophenol could rise to more than 80 %. The results showed that the spectrum absorption band edge of Zn/TiO2 powder does not broaden obviously comparing with pure TiO2 powder. Zinc exists as Zn （11）. When calcined at 973 K, there is a new phase as ZnTiO3 in Zn/TiO2 catalyst. The order of photocatalytic activity of Zn/TiO2 catalysts calcined at different temperatures for p-nitrophenol is 773 K 〉 673 K 〉 873 K 〉 573 K 〉 973 K and the photocatalytic activity of Zn/TiO2 catalyst calcined at 773 K is better than TiO2 catalysts heated at the same temperature, and outclasses that of commercial TiO2 catalyst. It also showed that the photocatalytic degradation of p-nitrophenol follows first-order kinetics under the irradiation of simulant sunlight.     

Current status of radiation therapy for prostate cancer

Radiotherapy for the treatment of prostate cancer has been extensively explored in the past. Along with the comprehensive understanding of the biology of prostate cancer and rapid advances in terms of technology, the out- come of treatment for the patients with prostate cancer has improved. The authors review radiotherapy as the primary treatment for the disease, with particular emphasis on the technological advances from both the radiobiological and radiophysics aspects. Nonconventional fractionated irradiation like hyper- or hypo-fractionation has been imple- mented in the clinic, the final results still need to be confirmed in the future. Technological advances like IMRT, IGRT, in the last two decades have significantly improved the delivery of external radiotherapy to the prostate. This has re- sulted in an overall increase in the total dose that can be safely delivered to the prostate, which has led to modest im- provements in the biochemical outcome. However, establishing the standard therapy for prostate cancer remains con- troversial. It is hoped that the next decades will bring continued advances in the development of biologicals that will further improve current clinical outcomes.     

The control system for SSRF injection and extraction

This paper introduces the injection and extraction control system design for SSRF,which is a distributed control system aimed at stability and reliability of the pulse power supplies,PPS(Personnel Protection System)and MPS(Machine Protection System).The hardware environment is mainly based on PLC(Programmable Logic Con- troller),and ARM(Advanced RISC Machine)is also applied for studying stability of the power supplies.WinCC and EPICS(Experimental Physics and Industrial Control System)have been selected as the platforms of SCADA(Super- visory Control and Data Acquisition).For unifying the interfacing to the control computer,all front-end equipments are connected via Industrial Ethemet.     

水平管内含空气蒸汽强制对流冷凝换热模型研究

为研究含空气蒸汽在水平管内强制对流冷凝换热特性,基于对传热传质过程的分析,建立了管内为环状流与波状流条件下的流动冷凝换热模型。从潜热、显热和液膜3个环节对整个换热过程进行建模,最终得到计算局部冷凝换热系数的理论关系式。模型预测结果与实验数据的对比表明,二者相对偏差在±20%以内,验证了该换热模型的准确性与适用性。通过进一步的研究发现：从换热管入口至出口,随着冷凝的进行,管内换热主要热阻由液膜热阻向气液界面的凝结热阻转变;主流气体对流换热过程基本可忽略。     

Investigations on landmine detection by BF3 detector

Experiments were carried out to investigate the possible use of neutron backscattering for the detection of polyethylene (PE) sample buried in the soil. In detection of landmine by neutrons, the neutron detector and its shield play an important role. In this paper, the effects of graphite, heavy water, polyethylene and boric acid moderators on the flux of back scattered neutrons were investigated. We have also experimentally verified the effect of BF3 detector shield and obtained good agreement with theory.     

Web Services interface of SSRF archive data analysis system

Accelerator database stores various static parameters and real-time data of accelerator. SSRF (Shanghai Synchrotron Radiation Facility) adopts relational database to save the data. We developed a data retrieval system based on XML Web Services for accessing the archive data. It includes a bottom layer interface and an interface applicable for accelerator physics. Client samples exemplifying how to consume the interface are given. The users can browse, retrieve and plot data by the client samples. Also, we give a method to test its stability. The test result and performance are described.     

有效探测面积大于1000 cm2的正比计数器测量系统性能测试

为对自制的活性面积高达1 000 cm²的大面积源进行表面发射率定值,同时作为现有2πα、2πβ表面发射率标准装置能力的扩充,研制了一套内置式大面积2π多丝正比计数器测量系统,并利用活性区直径为8 mm的²⁴¹Am点源及活性区面积为10 cm×15 cm的大面积²⁴¹Am和⁹⁰Sr-⁹⁰Y源对其进行计量学性能测试。结果表明：计数器内计数响应均匀性优于±0.4%,有效探测面积达1 400 cm²;所得²⁴¹Am源高压坪曲线的坪长为1 400 V,坪斜为0.27%/100 V,坪区内计数变化为0.87%;⁹⁰Sr-⁹⁰Y源高压坪曲线的坪长为300 V,坪斜为0.75%/100 V,坪区内计数变化为0.80%;10次测量重复性好于0.4%,8 h内短期稳定性好于0.3%,1 a内长期稳定性好于0.8%。     

Assessment of radioactivity levels in some oil samples from the western desert, Egypt

Distributions of natural gamma-emitting radionuclides were determined in 93 oil samples collected from some petroleum fields in the western desert of Egypt. The radioisotope activities in the area under investigation lay in the range of (21 ± 4) to (38 ± 13) Bq?L-1 for 226Ra, (9 ± 2) to (15 ± 5) Bq?L-1 for 232Th, and (154 ± 28) to (303 ± 54) Bq?L-1 for 40K. The mean values were 27, 12, and 201 Bq?L-1, respectively. Among oils, variations in radionuclide ac- tivities could be on account of differences in TDS, HCO3, and Ba, with high or low pH. In this environment, oil prop- erties differently affected the mobilization of natural radionuclides. The range of 226Ra variation had been compared with available data from other countries. The calculated absorbed dose rate ranged from 22.33 to 32.66 nGy?h-1 in lo- cation (B) and (E) respectively, which was less than the accepted value.     

Preparation and properties of 117m Sn(IV)-TTHMP in in-vitro and in small animals

In this work,TTHMP was synthesized and labelled with 117m Sn.The preparation conditions,stability and lipophilicity of 117m Sn(IV)-TTHMP were investigated.Biodistribution of the complex in rabbits and mice was studied.It was found that the quantity of TTHMP and pH value of the prepararion solution had vital effects on the labeling yield of 117m Sn(IV)-TTHMP.It was also found that 117m Sn(IV)-TTHMP was hydrophilic and stable at room temperature and 37℃ in open air 117m Sn(IV)-TTHMP showed unexpectedly high bone uptake and bone-to-blood ratio in the animals.This made it potentially useful as an reagent for skeletal scintigraphy and radiotherapy of bone tumors.     

The role of AGFA high-energy CR in the calibration and quality control of multileaf collimators （MLC）

Linear accelerators equipped with multileaf collimators （MLC） are becoming more common and are widely used in the intensity-modulated radiotherapy （IMRT）. There is an imperative need to ensure the commissioning specification of the linear accelerators for the sake of quality assurance （QA） and quality control （QC）. This paper is aimed to investigate the role of AGFA high-energy CR （Computed Radiography） in calibrating dynamic multileaf collimators and evaluating the accuracy of the leaf position. The result shows that AGFA high-energy CR can easily and conveniently be used to calibrate MLC and verify its position. Hence, the application of AGFA high-energy CR is proved to be an accurate and time-saving method for routine MLC QC, especially when MLC calibration adjustments are required.