电磁脉冲对带孔腔体耦合的频域分析

利用时域有限差分法研究了电磁脉冲对带孔腔体的耦合效应,将时域计算结果变换到频域。利用现有的频域解析结果对该问题进行分析:时域中耦合电场的强弱关系在频域中有所改变;电磁脉冲在腔内激起的谐振与同尺寸谐振腔的谐振模式吻合;与孔外沿作用后的脉冲电场,通过孔的过程可近似看作通过波导的过程;不同脉冲标准入射时,孔和腔内不同位置的频域幅值的比例关系相同。     

UWB电磁脉冲圆孔耦合计算及试验研究

采用电磁场数值计算软件CST计算了前沿为400 ps的UWB电磁脉冲辐射场通过不同直径的圆形孔耦合到金属屏蔽腔体内的电场,对相同尺寸的带圆孔的金属屏蔽腔体在UWB辐射模拟源上进行了验证试验.通过理论计算和试验测试得到的电场衰减系数符合较好,证明采用的UWB电磁脉冲圆孔耦合计算及试验的方法是可行、正确的.     

环形窄缝通道单相流动特性研究

对环形窄缝通道内单相流动特性进行了分析，提出了理论模型预测环形窄缝通道内单相流动阻力特性。根据该模型，对窄缝宽度分别为1.0、1.5、2.0mm环形通道内单相湍流流动摩擦阻力系数进行了理论计算，并与实验结果进行了比较。理论预测值与实验结果符合较好，且窄缝间隙大小对环形窄缝通道内流动特性有着重要影响，随着间隙的减小，摩擦阻力系数相应减小。间隙对流动阻力系数的影响还依赖于Re大小，其影响随Re的减小而降低。     

环形窄通道内过冷沸腾起始点的实验研究

在1.0-4．5MPa的压力范围内研究了1．2mm间隙环形窄缝通道内过冷沸腾起始点．分析了部分热工参量对沸腾起始点的影响。引入双面加热影响因子．对环形窄缝内过冷沸腾起始点的数据进行回归分析,得出了适用于环形窄缝过冷沸腾起始点的实验关系式     

小尺度环形通道流体阻力特性实验研究

为确定小尺度环形流道间隙尺寸对流体阻力特性的影响,以水为工质,分别在滞流区和湍流区对间隙为0.540～2.685 mm的水平环形通道单相流体摩擦阻力特性进行实验研究。结果表明,小尺度环形通道的流体阻力特性与理论分析有明显的差异。摩擦系数随环形流道间隙的减小而减小,且流态转捩点较常规尺寸提前。当环形通道间隙大于2.5 mm时流体的流动特性符合常规尺寸的特性。依据实验结果,给出了窄缝环形通道的流体阻力预测式。     

窄缝环形通道内流动阻力特性的实验研究

分别在换热和冷态条件下,对水平、竖直向上和竖直向下3个流动方向的窄缝环形通道进行了流动摩擦阻力实验研究.实验发现窄缝通道内流态转变点比普通流道有所提前.将实验结果与传统的阻力计算公式进行对比,分析了换热温差及流动方向对摩擦阻力的影响,对窄缝环形通道内阻力特性进行了探讨.     

同心环形管内沸腾两相流动与传热实验研究

对窄缝为2．1mm的同心环形管，试验研究了外管加热条件下水的沸腾两相流动阻力与传热特性，得到了以下结果：窄缝环形管内两相流动的阻力较普通圆管内大，沸腾换热得到了较明显的强化，换热系数弓压力、热平衡干度、工质流量、加热负荷均有关系，且与缝隙宽度和加热方式有关；提出了环形管强化传热的微液膜蒸发机理与汽泡扰动机理的物理解释；得到了环形管内流动摩擦阻力系数与传热系数的实验关联式。     

电磁脉冲对双层屏蔽腔的孔洞耦合特性研究

用时域有限差分(FDTD)法对电磁脉冲与双层屏蔽腔上孔洞的耦合特性进行了研究,计算了不同类型的孔阵对腔体内电场耦合系数的影响.计算结果表明,采用双层屏蔽使得腔体的屏蔽性能大大提高;另外,在双层屏蔽腔体上开孔洞方向垂直的长方形孔阵可以在任意极化方向上改善腔体的屏蔽性能,并且纵横比较大时效果较好.     

环形窄缝通道内干涸后摩擦倍增因子的试验研究

在间隙为1.1和1.6mm的环形窄缝通道内，通过内外管双面通电加热流体，进行环形窄缝通道内的干涸后弥散流区压强的试验研究，通过试验得出环形窄缝通道内干涸后弥散流区全汽相摩擦倍增因子的计算式，该式能够较好地预测环形窄缝通道内干涸后弥散流区的两相摩擦压降。     

在垂直环形窄缝流道中的沸腾传热特性研究

为了弄清在窄缝环形流道中气泡的形成、聚合和变形的特性 ,以及气泡在聚合变形之后对传热特性的影响 ,在常压下用蒸馏水对窄缝间隙为 0 75mm的垂直环形流道 ,进行了可视化的流动沸腾传热实验研究 ;实验段的有效加热长度为 90 0mm ,其加热方式为单面内侧加热 ,实验的流量变化范围为 1 667× 1 0 - 5m3/s至 5 833× 1 0 - 5m3/s。实验得到了在不同质量流密度和热流密度下窄缝流道中的沸腾传热系数随干度变化的分布。通过与常规流道中的沸腾传热系数的比较 ,得到了在窄缝环形流道中沸腾传热系数比常规流道中的沸腾传热系数约高 1 5 %的结论。另外通过用高速摄像机对可视化的垂直环形流道中的流型进行的拍摄研究 ,分清了存在在窄缝环形流道中的四种流型     

Identification of radiation treatment of wheat （Triticum aestivum. L）and rice （Oryza sativa. L） samples using thermoluminescence of contaminating minerals

Food irradiation is gaining popularity worldwide and this technology is important to improve quality and reduce the post harvest losses of food. Because of the rapid commercialization of irradiated foods throughout the world, compliance of different regulations relating to use of technology in different countries and demand of consumers for clear labelling of irradiated foods, there is need for the development of analytical methods to detect radiation treatment of food. Among several methods studied so far, thermoluminescence （TL） is an important method that can be used to find out the irradiation history of food that contain even a very minute amount of dust particles. In this study, the irradiated and unirradiated wheat and rice samples were analyzed using the TL method. The samples were purchased from the local market of Peshawar and irradiated to radiation doses of 0.5 and 1.0 kGy using Co-60 gamma irradiator at the Nuclear Institute for Food and Agriculture （NIFA）, Peshawar. The mineral contaminants were isolated by jet water, ultrasonic treatment, and density gradient. TL glow curves of the isolated minerals from irradiated and unirradiated samples were recorded between the temperature ranges of 50-500℃ using a TL reader. Generally, the glow curves for irradiated samples showed much higher TL intensities （TL1） than the unirradiated samples. The results were normalized by rerradiation of mineral samples to gamma-ray dose of 1.0 kGy followed by determination of the second glow curves （TL2）. The ratio of the area of first glow curve to that of second glow curve （TL1/TL2） was calculated for selected temperature intervals and compared with the recommended values for unirradiated and irradiated samples. Finally, the shapes of the glow curves for irradiated and unirradiated samples were also analyzed. On the basis of these results （comparison of TL-intensities, TL1/TL2 ratios and shapes of the glow curves）, all the irradiated and unirradiated samples of wheat and rice were unequivocally identified.     

The preclinical pharmacological study of dopamine transporter imaging agent 18F-FP-β-CIT

The paper is to study pharmacologic characteristics of 18F-FP-β-CIT (18F-N-(3-fluoropropyl)-2β- carbomethoxy-3β- (4-iodophenyl)nortropane) as an imaging agent for dopamine transporter. The radiochemical purity of 18F-FP-β-CIT in aqueous solution was over 95% after standing at room temperature for 4h. Biodistribution displayed rapid uptake in rat brain (1.375 %ID/organ at 5min and 0.100 %ID/organ at 180 min) and the striatal uptake was 1.444,0.731, 0.397, 0.230 and 0.146 %ID/g at 5, 30, 60, 120 and 180 min, respectively. The values of striatum/cerebellum,striatum/frontal cortex and striatum / hippocampus in rat's brain at 30 min were 3.38, 2.17 and 2.40 respectively. The uptake in striatum can be blocked by β-CFT, suggesting that 18F-FP-β-CIT binds to DAT peculiarly. The compound was rapidly cleared from monkey's blood. The striatal uptake was bilaterally decreased in the left-sided lesioned PD rats, compared with normal control. Brain PET imaging studies in normal monkey showed that 18F-FP-β-CIT was concentrated in striatum. The test of undue toxicity showed that the dose received by mice was 1250 times as by human, which indicates that 18F-FP-β-CIT is very safe. So 18F-FP-β-CIT is a promising PET imaging agent for DAT with safety and validity.     

PLASMA SCIENCE AND TECHNOLOGY AUTHOR INDEX TO VOLUME 16(2014)

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Radioactivity levels in soil of salt field area,Kelambakkam,Tamilnadu,India

Soil samples in and around salt field area have been analyzed for natural radioactivity concentration using gamma ray spectrometer.The activity concentration for ~(232)Th,~(238)U and ~(40)K are ranged from 27.88 to 45.27 Bq/kg, from BDL to 13.30 Bq/kg,and from 135.54 to 381.28 Bq/kg,respectively.The measured activity concentrations for these radionuclides were compared with world average activity of soil.The average activity concentration of ~(232)Th in the present study is 1.19 times higher than world median value while the activity of ~(238)U and ~(40)K is found to be lower. The absorbed dose rates due to these radionuclides were calculated.The average absorbed gamma dose rate due to the presence of ~(232)Th,~(238)U and ~(40)K in soil samples is 36.99 nGy·h~(-1).These results indicate no radiological anomaly. The data presented in this study will serve as a base line survey for primordial radionuclides concentration in the study area.     

Non-FDG PET imaging of brain tumors

Due to relatively high uptake of glucose in the brain cortex, the use of FDG PET imaging is greatly limited in brain tumor imaging, especially for low-grade gliomas and some metastatic tumours. More and more tracers with higher specificity were developed lately for brain tumor imaging. There are 3 main types of non-FDG PET tracers： amino acid tracers, choline tracers and nucleic acid tracers. These tracers are now widely applied in many aspects of brain tumor imaging. This article summarized the general use of non-FDG PET in different aspects of brain tumor imaging.     

基于NPL-NMC系统的γ测量子系统的建模与优化

在军控核查中,核部件的质量、丰度、年龄属性需采用无损方法进行核查,NPL-NMC系统是一套利用中子多重性测量核部件质量属性的装置,为建立完善的属性测量系统,还需在NPL-NMC系统的基础上建立γ测量子系统。本文通过设计γ测量子系统在NPL-NMC系统上的布局及对中子屏蔽的优化,使系统能对铀部件的丰度、年龄属性进行测量。模拟计算结果表明,该γ测量子系统能很好地满足军控核查对铀部件丰度、年龄属性测量的要求。     

Improvement of carbon fiber surface properties using electron beam irradiation

Carbon fiber-reinforced advance composites have been used for structural applications,mainly on account of their mechanical properties.The main factor for a good mechanical performance of carbon fiber-reinforced com- posite is the interfacial interaction between its components,which are carbon fiber and polymeric matrix.The aim of this study is to improve the surface properties of the carbon fiber using ionizing radiation from an electron beam to obtain better adhesion properties in the resultant composite.EB radiation was applied on the carbon fiber itself before preparing test specimens for the mechanical tests.Experimental results showed that EB irradiation improved the ten- sile strength of carbon fiber samples.The maximum value in tensile strength was reached using doses of about 250 kGy.After breakage,the morphology aspect of the tensile specimens prepared with irradiated and non-irradiated car- bon fibers were evaluated.SEM micrographs showed modifications on the carbon fiber surface.     

Measurement system for SSRF pulsed magnets

This paper describes the magnetic field measurement system for pulsed magnets in SSRF.The system consists of magnetic probes,analog active integrator,oscilloscope,stepper motor and a controller.An application pro- gram based on LabVIEW has been developed as main control unit.After the magnetic field mapping of a septum magnet prototype,it is verified that the test results accord with the results of theoretical calculation and computer simulation.     

旁路阀调节对高温气冷堆闭式布雷顿循环瞬态特性影响研究

闭式布雷顿循环是第4代高温堆核能系统的关键技术之一,其典型的动态过程是旁路阀调节。为分析这一过程,建立了循环中关键部件的动态模型,其中压气机在径向平衡模型基础上耦合了对附面层发展的预测,兼顾了计算效率与准确性;换热部件模型基于双曲型守恒律方程,对工质的热物性和参数的快速变化有较好的适应性。在此基础上根据回路的质量守恒和压力平衡原则将各部件的模型耦合,建立了系统的动态模型。由于旁路阀调节是氦气透平发电系统主要的功率快速调节手段,瞬态效应较为显著,以模块式高温气冷堆（HTR-10GT）旁路阀开启后的过渡过程作为算例,分析了主要循环参数的响应特性,并通过分析,给出了降低输出功率的机制。计算结果表明：系统的容积惯性对旁路阀调节的响应速度影响较大,而阀门的开度则决定了系统在末态的输出功率;回热器的温度冲击现象可能发生在调节过程中,但可通过两旁路阀联动的方式缓解;反应堆出口温度变化幅度很小,因此反应堆模型的准确程度对结果基本无影响。     

CEFR 100%额定功率运行汽轮机发电能力分析

中国实验快堆(CEFR)首次100%额定功率发电运行中,实际电功率较设计值相差较多。为判断影响机组实际发电能力的主要原因,以现场采集的运行数据和汽轮机厂商提供的设计资料为基础,进行了相应的计算分析。对汽轮机内效率进行修正,绘制汽轮机近似热力过程曲线,并通过实测的各段抽汽压力,在热力过程曲线上获得抽汽焓值;利用换热器的能量守恒和流量守恒的基本方程进行除氧器和各加热器的热平衡计算,获得各段抽汽的流量;利用汽轮机的功率计算方程,得到汽轮机发电功率的计算值。通过计算值与实际值的比较分析,得出主蒸汽参数不达标是影响CEFR汽轮机发电能力的主要因素。