γ射线辐照对聚砜结构与性能的影响

应用力学性能测试、傅立叶变换红外光谱分析、扫描电镜断口形貌分析、差示扫描量热分析、凝胶渗透色谱分析、X射线光电子能谱分析等多种手段从多个角度研究了聚砜材料在γ射线辐照下的老化行为,并研究了吸收剂量对材料结构和性能的影响.结果表明,聚砜材料的拉伸强度、弯曲强度、冲击强度、玻璃化温度、数均分子量、峰值分子量和数均聚合度等均随吸收剂量的增加而下降;化学结构在辐照过程中基本上没有变化;其断口表面的光滑程度随辐射剂量的增加而增大;弯曲强度、冲击强度和重均分子量随吸收剂量变化曲线的上升段表明,在低吸收剂量下聚砜材料内部交联反应占优势;这些曲线的下降段表明,在中高吸收剂量下聚砜内部降解反应占优势.动力学分析表明,聚砜在化学上的降解属于无规降解类型,间接证明了聚砜在低吸收剂量下交联反应占优势,在中高吸收剂量下降解反应占优势.     

γ-辐照对高密度聚乙烯-尼龙-6共混物结构和性能的影响

用熔融共混的方法制备出高密度聚乙烯(HDPE)和尼龙-6(PA-6)的共混物，研究了共混物经γ射线辐照后结构与性能的改变。扫描电镜(SEM)观察结果表明，γ射线辐照会影响共混物的相态结构；辐照4h后，共混物样品的吸收剂量为15.84kGy；PA-6和HDPE的界面粘结力增强，两相之间有明显的界面过渡层的存在，材料的相容性增加；随着辐照时间延长，材料结构破坏。经γ射线辐照后，共混材料的冲击强度下降，拉伸强度与断裂伸长率增加，其中断裂伸长率增加明显。共混材料经辐照后对二甲苯的吸收减小。     

聚碳酸酯材料的辐射老化

应用拉伸强度测试(Tensile strength testing,TST)、扫描电镜(Scanning electronic micrograph,SEM)断口形貌分析、差示扫描量热分析(Differential scanning calorimetry,DSC)、富立叶变换红外光谱(Fourier transform infrared absorbption spectroscopy,FTIAS)、凝胶渗透色谱(Gel permeation chromatography,GPC)、X射线光电子能谱(X-Ray photoelectron spectroscopy,X-RPS)等多种手段研究了聚碳酸酯材料在γ射线辐照下的老化行为.结果表明,聚碳酸酯材料的力学性能、玻璃化温度、分子量和数均聚合度均随吸收剂量的增加而下降;其断口表面的光滑程度随吸收剂量的增加而增大;只观察到结构上微小的变化;动力学分析表明其辐射降解属于无规降解类型.间接证明了聚碳酸酯在0-12MGy剂量范围内辐射降解机理占优势.     

γ辐射对氮化硼/环氧树脂复合材料性能的影响

环氧树脂及其复合材料具有良好的电气绝缘性能,在核工业领域得到了广泛应用。本工作将六方氮化硼粉末(h-BN)与四氢邻苯二甲酸二缩水甘油酯、固化剂甲基四氢邻苯二甲酸酐和促进剂2,4,6-三(二甲氨基甲基)苯酚共混,并热固化成型,制备了氮化硼/环氧树脂(h-BN/EP)复合材料。在空气和通氮限氧气氛及一定吸收剂量率下(60 Gy/min),研究了h-BN粉末和h-BN/EP复合材料经60Coγ射线辐照后结构和性能(力学性能、导热性能和热稳定性等)的变化情况。结果表明,两种气氛中,h-BN粉末都具有良好的γ射线辐照稳定性,吸收剂量达到380 kGy时,化学结构和热稳定性均未发生变化。但h-BN/EP复合材料经γ射线辐照后,玻璃化转变温度和初始热分解温度的下降程度都较纯EP基体明显。γ射线辐照对复合材料力学性能的影响与h-BN含量和吸收剂量相关。对于低h-BN含量(质量分数0.52%)的复合材料,其拉伸强度在吸收剂量较低(≤180 k Gy)时即显著下降;而高h-BN含量(质量分数≥0.52%)的复合材料,其拉伸强度在较低剂量(≤180 k Gy)时反而明显上升。当吸收剂量达1 000 kGy时,辐照后不同h-BN含量的复合材料以及纯EP的拉伸强度基本为同一水平,即吸收剂量高于1 000 kGy时,添加h-BN对EP的拉伸强度基本无影响。当吸收剂量为180 kGy时,γ射线辐射使得h-BN/EP复合材料的导热系数显著增加。     

甲基乙烯基硅泡沫材料在复合条件下的辐射效应研究

为考察甲基乙烯基硅泡沫材料在不同条件下的辐射效应,开展了受压状态下材料经⁶⁰Co γ射线辐照后的热老化和湿热老化实验。采用扫描电镜、傅里叶转换红外光谱仪、固体核磁共振仪、万能材料试验机和蠕变松弛试验机等手段剖析了材料微观结构和宏观性能。结果表明,不同条件下老化后甲基乙烯基硅泡沫材料的泡孔有减小的趋势。²⁹Si交叉极化的NMR分析发现材料中有机硅链段峰的强度随吸收剂量的增大而升高,¹³C交叉极化的NMR分析表明γ射线辐照后材料的结构规整性有所降低。辐射后热老化样品的拉伸强度总比辐射后湿热老化样品的低,辐射老化和湿热老化的协同作用对材料的应力松弛率影响非常明显。     

~(90)Sr-~(90)Yβ源辐射场中轫致辐射剂量分量的理论计算和实验测量

对90 Sr 90 Y源半导体辐照效应在线测量系统中所用辐射源与周围物质相互作用所产生的轫致辐射剂量进行了理论计算和实验测量。采用聚乙烯薄膜作吸收材料 ,实现了 β与X射线辐射剂量的分离。给出了测量的吸收剂量中X射线辐射剂量的贡献 ,并对测量及理论计算中的误差进行了分析     

60Coγ射线辐照对PTMPS--DPS共聚物形态结构及性能的影响

采用两种催化体系制备了聚四甲基苯撑硅氧烷--二苯基硅氧烷(PTMPS--DPS)共聚物.用凝胶色谱分析、广角X光衍射分析、示差扫描量热分析(GPC、WAXD、DSC)等方法研究了60Coγ射线辐照对PTMPS--DPS共聚物形态结构及力学性能的影响.结果表明,经过8.5 105Gy大剂量辐照后,PTMPS--DPS共聚物的平均分子量、结晶度、拉伸强度及断裂伸长率等变化不大.使用非平衡催化体系可以进一步提高PTMPS--DPS共聚物的耐辐照性能.     

^90Sr—^90Yβ源辐射场中轫致辐射剂量分量的理论计算和实验测量

对^90Sr-^90Y源半导体辐照效应在线测量系统中所用辐射源与周围物质相互作用所产生的轫致辐射剂量进行了理论计算和实验测量。采用聚乙烯薄膜作吸收材料,实现了β与X射线辐射剂量的分离。给出了测量的吸收剂量中X射线辐射剂量的贡献,并对测量及理论计算中的误差进行了分析。     

米曲霉孢子对同步辐射C、N、O元素K吸收边附近软X射线的吸收剂量分布研究

以C、N、O元素的K吸收边附近能量的软X射线为辐射光源,通过模型分析,比较了米曲霉孢子不同部位对不同能量软X射线吸收剂量分布.同时利用合肥同步辐射软X射线显微术光束线准单色的软X射线对孢子进行辐照实验,对不同能量辐照存活率结果进行了比较.理论分析表明,由于C、N、O元素K吸收边效应以及孢子不同部位元素组成的不同,受照时孢子不同部位对软X射线的吸收剂量分布随能量变化存在差异.实验结果显示,3种元素K吸收边附近软X射线对米曲霉孢子均有很强的辐射失活效应,其中2.3nm波长的软X射线对孢子的辐射损伤效应要高于3.2nm和4.4nm波长的软X射线.     

γ辐射场中硅橡胶泡沫的辐射效应研究

研究了室温下空气、真空或惰性气氛中60 Coγ射线对柔性开孔型甲基乙烯基硅橡胶泡沫的辐射效应。采用傅立叶红外分析仪 (FTIR)、扫描电镜 (SEM )、裂解色谱 质谱联用仪 (PGC/MS)以及热失重分析仪 (TG)等对辐照前后的样品进行了分析 ,同时使用色质联用仪 (GC/MS)对辐照后产生的气体进行了分析 ,并且测定了空气中辐照试样的凝胶含量与吸收剂量的关系以及在室温下试样的压缩性能、应力松弛率与吸收剂量的关系。结果表明 :化学交联后的硅泡沫材料在低剂量 ( 2× 1 0 5Gy)下发生了第二次交联 ,但随剂量的进一步提高 ,则以辐射降解为主。经不同剂量辐照以后 ,试样的力学性能有所改变。     

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.     

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%。     

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.     

Interaction between uranium and humic acid (Ⅰ): Adsorption behaviors of U(Ⅵ) in soil humic acids

The adsorption behaviors of uranium on three soil humic acids (HAs), which were extracted from soils of different depths at the same site, were investigated under various experimental conditions. The adsorption results showed that U(Ⅵ) in solutions can be adsorbed by the three soil HAs, with the order of FHA (HA from 5 m depth of soil) ＞SHA (HA from the surface) ＞THA (HA from 10 m depth of soil) for adsorption efficiency in each desirable condition, and the adsorption reached equilibrium in about 240 min. Although the maximum adsorption efficiency was adsorption could be described with Langmiur isotherm or Freundlich isotherm equation. The L/S (liquid/solid, mL/g)ratio and pH were important factors influencing the adsorption in our adsorption system besides uranium concentration. The adsorption efficiency decreased with the increase of the L/S ratio and pH at the pH range of 2.0-3.0 for SHA and THA or 2.5 - 6.0 for FHA. However, no significant difference in adsorption of U(Ⅵ) was observed at the experimental temperature. All the results implied that humic substances have different characteristics in samples even collected at the same site.     

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。     

Information for authors

<正>1.NUCLEAR SCIENCE AND TECHNIQUES(NST),a bimonthly journal,is devoted to all aspects of nuclear science and technology,theoretical or experimental.Its special interest lies in the subjects of synchrotron radiation science and technology;low energy accelerators,radiation technology and applications;radiochemistry,radiopharmaceuticals and nuclear medicine;nuclear electronics and instrumen-     

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

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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.