纵向涡发生器作用下矩形通道内流动换热性能研究

对渐缩式纵向涡发生器与椭圆支柱共同作用下矩形通道内的流动换热性能进行了研究,与渐缩式纵向涡发生器、渐扩式纵向涡发生器和光通道的流动换热性能进行了对比,并利用场协同原理对其换热机理进行了分析。结果表明：纵向涡发生器可增强换热,有利于降低加热板的表面温度,从而提高反应堆堆芯的CHF值。采用JF因子对各矩形通道的综合流动换热性能进行了比较,结果表明,渐缩式纵向涡发生器与椭圆支柱组合结构能以较小的阻力代价得到较大的换热效果,是一种理想的强化换热方式。     

带周期性分布纵向涡发生器的矩形狭窄通道内传热流动的数值模拟

在换热表面上周期性地安装粗糙元,可以使流动区域产生漩涡从而增强换热.本文采用数值分析的方法,以水作为工作介质,以带有纵向涡发生器狭窄矩形通道为研究对象,研究不同排列方式纵向涡发生器的传热性能,分析不同的纵向涡发生器入射角度β、不同流向、不同纵向涡间距对换热和流动特性的影响.结果表明,纵向涡发生器能够强化换热,当入射角度β=50°时,换热效果最佳.     

脉动流通道内带纵向涡发生器动态特性研究

对单侧带有周期性分布纵向涡发生器通道内的流动与传热动态特性进行了非稳态三维数值模拟;通过数值仿真的方法研究了带纵向涡发生器通道在进口流速呈正弦波周期性脉动扰动下出口平均温度的响应特性;分析了进口脉动流脉动频率对纵向涡发生器传热通道动态特性的影响规律.结果表明:在脉动流动的影响下纵向涡发生器的传热能力得到了强化,随着脉动频率的增加传热强化程度得到了进一步加强.     

纵向涡对窄间隙矩形通道内流动边界层作用特性研究

利用纵向涡发生器(LVG)产生纵向涡(LV)强化传热的机理主要是基于对边界层的削薄和破坏。由于LV作用距离远,结构简单,安装高度低,对于具有窄间隙通道的换热结构,LV强化传热有着较强的应用价值。本文应用相位多普勒粒径分析仪对LV作用下的窄间隙矩形通道内速度场分布进行了测量。实验结果表明,LV可以有效地削薄和破坏流动边界层厚度;LV对边界层的削薄和破坏可以对传热起到强化的作用;CFD数值模拟结果表明,剪切应力模型(SST)以对LV作用下窄间隙矩形通道内的速度场进行有效地模拟。     

窄间隙矩形通道单相水纵向涡可视化实验研究

在窄间隙矩形通道内设置4对周期性分布的矩形块纵向涡发生器(LVG),应用相位多普勒粒子图像分析仪技术(PDPA)对该通道内单相流动的速度场进行可视化测量.通道内单相层流和湍流的主流速度分布表明:当流动经过LVG时,将会产生以二次流动为特征的纵向涡(LV);LV使得流动边界层的发展受到抑制或破坏作用,强化通道内部流动的横...     

CFD在纵向涡强化两相传热模拟中的应用

利用纵向涡发生器在窄间隙矩形通道内产生的纵向涡可以起到强化传热的作用.运用CFD商业软件CFX10.0对带纵向涡发生器的窄间隙矩形通道内的汽液两相介质进行了模拟计算.结果表明,产生和纵向涡能有效地降低窄间隙矩形通道的边角处热量集中,提高中央主流区流速,进而明显提高加热板上的热流密度;LV也能加强通道内冷热流体交混,起到强化传热的作用.在本文参数范围内,相对于光滑通道而言,带LVG的窄间隙矩形通道在适当增加流动阻力的基础上,能明显提高传热效率.     

纵向涡作用下窄缝矩形通道外壁温可视化研究

在窄缝矩形通道内设置4对周期性分布的矩形块纵向涡(LV)发生器作为强化换热措施,应用红外热成像测温技术对该通道加热板外壁面温度场进行可视化测量.测量结果表明,LV以一定作用距离和相对强度对温度场进行重构,形成了窄缝矩形通道内加热板外壁温交替下降和上升的类周期性变化过程,提高了通道内整体对流传热能力.     

窄间隙矩形通道单相水纵向涡强化传热实验

在窄间隙矩形通道内设置4对周期性分布的矩形块纵向涡发事器(LVG),研究该类通道和光通道内单相水介质流动阻力特性和对流传热特性.在雷诺数Re为310-4220范围内,纵向涡(LV)使得通道内流动提前由层流向紊流转化.在层流区,LV强化传热可达100.9%,摩擦阻力增大仅11.4%;在紊流区,LV强化传热可超过87.1%...     

翅管式换热器中采用环形和三角形小翼涡发生器的流动可视化研究

研究了翅管式换热器带放大尺寸的两种涡发生器和不带涡发生器的一种平翅片的流动可视化和摩擦结果，并进行了实验。当心为500时，管排在平翅片上产生的马蹄涡不显著；当流过第二排管时，马蹄涡分成了两股，使其旋转强度下降。在以前报道的研究中，这种低忍区域的现象称之为“最大现象”。采用环形涡发生器时，可以看到在管后形成了一对纵向涡。相对旋转的漩涡强度随环形高度的增加而增强。纵向涡的强度也足够强，可能随着马蹄涡和其它流动而旋转。在小翼高度相同时，三角形小翼比环形小翼展现出更强的旋转趋势和流动不稳定，形成的混和现象更好。在相同心时，三角形小翼对应的压降比环形的低。在平直翅片上采用涡发生器所造成的压降损耗与忍的变化关联不大。     

液态金属在堆芯子通道内的湍流换热

采用Speziale-Sarkar-Gatski(SSG)雷诺应力模型对液态金属在堆芯子通道内的流动、传热过程进行计算流体动力学(Computational Fluid Dynamics,CFD)模拟,研究雷诺数(Re)、分子普朗特数(Pr)、格拉晓夫数(Gr)、节径比(P/D)等无量纲参数对湍流换热的影响。比较无量纲对流换热系数(Nu)可以看出,CFD预测值与实验值及经验关系式符合得较好。对各种不同无量纲参数下的计算结果进行分析发现:在P/D和Re数相同条件下,三角形子通道的壁面温度分布比方形更均匀,换热情况更好;提高Re数,增大P/D,选用Pr数大的冷却剂,可有效改善温度和换热的周向分布不均情况;在Re数大于10 000的条件下,浮力对液态金属换热的影响可忽略不计。     

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.     

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.     

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。     

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.     

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.     

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.     

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.     

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.     

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.