掺氟Bi-Ph-Sr-Ca-Cu-O大块超导体的磁通蠕动

实验研究了掺氟的Bi-Pb-Sr-Ca-Cu-O块状超导体的磁化和磁通蠕动,结果表明存在一些新的行为:当100Oe150Oe时,U_0(H)∝H~(-α),且α=3/2。     

掺氟Bi-Ph-Sr-Ca-Cu-O大块超导体的磁通蠕动(英文)

实验研究了掺氟的Bi-Pb-Sr-Ca-Cu-O块状超导体的磁化和磁通蠕动,结果表明存在一些新的行为:当100Oe150Oe时,U_0(H)∝H~(-α),且α=3/2。     

两种变截面的高压纳秒电阻分压器

文章介绍了一种具有完全横向电容补偿功能的特殊结构的电阻分压器——扇形分压器,以及另一种同时具有横向电容补偿和减小趋肤效应功能的锥形薄壁分压器,用于测量纳秒上升沿的脉冲高电压。简述了它们的补偿原理和结构。刻度表明,它们具有良好的响应特性,并给出了它们在脉冲加速器上测到的电压波形。     

250千伏双同轴电容分压器

本电容分压器是为了测量速调管电源——脉冲调制器的输出脉冲高压而设计的。该分压器是双同轴结构,它具有耐压高、体积小、输入阻抗高、波形畸变小、结构紧凑简单、加工和使用方便等特点。经长期使用,性能良好,满足了工作的需要。     

КАКТУС型微伦仪用电离室的不饱和特性

КАКТУС型微伦仪在与ЛИГ-5电离室配套使用时,一般认为对微伦仪的五个量程都应在饱和状态下工作,才能保证仪器的测量误差和刻度线性要求。这不仅在微伦仪的技术说明书中有明确规定,而且扎别林(Забелин)更具体地指出:假定U_0为ДИГ-5电离室的饱和电压,则在其电极上加的电压为U_0的45%时,收集到的电流即可达饱和电流的95%。并指出,在20000微伦/秒(第五量程上限)的剂量率下,ДИГ-5电离室的U_0等于200伏。这样,根据     

铈掺杂诱导U3O8晶型变化

铈是核反应的重要裂变元素,其氧化物CeO_2容易与UO_2燃料形成U_(1-x)Ce_xO_2固溶体。铀铈固溶体会因为U4+发生氧化而生成(U_(1-x)Ce_x)3O_(8-δ)混合氧化物。Ce在U_3O_8中的存在会改变U_3O_8母体的局域结构,影响着(U_(1-x)Ce_x)3O_(8-δ)产物的物理化学性质。研究铀铈混合氧化物的局域结构,可以帮助理解处于苛刻环境中乏燃料的性状。使用共沉淀方法制备了铈掺杂的U_3O_8混合氧化物样品,即(U_(1-y)Ce_y)3O_(8-δ)(y=0,0.05,0.20),利用粉末X射线衍射(X-ray Diffraction,XRD)获取其物相信息,借助同步辐射X射线吸收精细结构(X-ray Absorption Fine Structure,XAFS)技术来获取(U_(1-y)Ce_y)3O_(8-δ)中铀和铈的局域结构。结果表明:与掺杂前的U_3O_8具有C2mm空间群不同,掺入Ce后的(U_(1-y)Ce_y)3O_(8-δ)转变成了与U_3O_8的P62m空间群一样的晶型,Ce的存在还导致铀的平均价态升高,层内最近邻Ce-U(Ce)的原子距离减小。     

时间型和增益型光电倍增管分压系统的比较研究

介绍了光电倍增管分压器的工作原理,在此基础上讨论了分压器和输出信号(增益、线性和时间响应等)的关系。根据这些原理,按照实际实验需求设计分压器,进行了实验比较分析。     

U_3Si_2热稳定性与防护研究

叙述了用热分析方法研究U_3Si_2在Ar、N_2和空气中的热稳定性,以及U_3Si_2/Al、U_3Si_2/Zr间的相互反应。实验结果表明,U_3Si_2/Al弥散体生坯在空气中加热时,生坯中Al基体并不能完全防止U_3Si_2的氧化;U_3Si_2颗粒在钢瓶N_2气(99.95％)中加热时,在689℃时有一放热峰,经X射线鉴定,U_3Si_2与N_2反应生成UN_2;U_3Si_2颗粒在钢瓶Ar气(99.95％)中加热到1000℃时,无任何反应。U_3Si_2/Zr弥散体冷压块,在瞬态温度加热过程中,929℃时有可测得的反应。根据热分析结果,对U_3Si_2-Al弥散型燃料板生产中的各工序防护措施进行了改进。生产实践证明,这些改进后的防护措施有效地保证了安全生产及产品质量,并降低了成本。     

U_3Si_2热稳定性与防护研究

叙述了用热分析方法研究U_3Si_2在Ar、N_2和空气中的热稳定性,以及U_3Si_2/Al、U_3Si_2/Zr间的相互反应。实验结果表明,U_3Si_2/Al弥散体生坯在空气中加热时,生坯中Al基体并不能完全防止U_3Si_2的氧化;U_3Si_2颗粒在钢瓶N_2气(99.95％)中加热时,在689℃时有一放热峰,经X射线鉴定,U_3Si_2与N_2反应生成UN_2;U_3Si_2颗粒在钢瓶Ar气(99.95％)中加热到1000℃时,无任何反应。U_3Si_2/Zr弥散体冷压块,在瞬态温度加热过程中,929℃时有可测得的反应。根据热分析结果,对U_3Si_2-Al弥散型燃料板生产中的各工序防护措施进行了改进。生产实践证明,这些改进后的防护措施有效地保证了安全生产及产品质量,并降低了成本。     

关于统计检验的一点意见

和其他数理统计方法一样,统计检验也大量地引用到放射性物探工作中来。在运用中感到存在某些问题,特提出供商榷。一、问题的提出在任何统计检验中都少不了差异显著性水平α。α也叫信度,其可信程度为1—α。由统计检验可知,一种检验的肯定域均随α的减小而增大。如对正态分布N(μ,σ~2)进行U检验时,对应α的U值为U_α,若测量次数为m,均值为X,则肯定域: (1) 式(1)中因U_α随α的减小而增大(α→0时U_2→∞),使得肯定域值可信程度的加大而增大。事情象是两全其美的,把握程度越大越容易被肯定。比如说:“某地一年之内会下     

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。     

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%。     

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.     

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.     

Gamma radiation levels in the ambient environment of the QNPP Base

Monitoring results of gamma dose rate level in 1992～2004 in the ambient environment of the Qinshan Nuclear Power Plants(QNPP)Base,the northeast of Zhejiang Province,are reported in this paper.It is shown that the gamma dose rate of five monitoring sites of 2.5 km to QNPP Base is 84～113 nGy/h,with an average of 96 nGy/h in the 13 years.The average value is close to the background level of 93 nGy/h prior to operation of the QNPP Base,and is lower than the monitoring result of 101 nGy/h at the reference site in Hangzhou City.Within 50 km from the QNPP Base,the cumulative dose rate of the thermoluminescent dosimeter(TLD)is 90 nGy/h,which is lower than the back- ground level of 111 nGy/h.