Characterization of EPDM Vulcanizates Modified with Gamma Irradiation and Trichloroisocyanuric Acid and Their Adhesion Behavior with Natural Rubber

The adhesion strength between surface-modified vulcanized ethylene propylene diene methylene (EPDM) rubber and unmodified natural rubber (NR) was investigated by a 180° peel test. Surface modification of EPDM vulcanizate was carried out by two different techniques: (a) irradiation of the surface by gamma radiation in the presence and absence of trimethylol propane triacrylate (TMPTA) as a sensitizer and (b) chemical treatment of the surface with trichloroisocyanuric acid (TCICA). The modified EPDM surface was thoroughly characterized by attenuated total reflection infrared spectroscopy (ATR-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive X-ray sulfur mapping (EDX), surface energy measurements, and free sulfur and gel content analysis. The joint between the modified vulcanized EPDM and the unmodified unvulcanized NR was prepared by a co-curing method. The adhesion strength between these two surfaces was found to depend on the nature of oxidation, roughness of the joining surfaces, and extent of blooming of sulfur on the modified surface. Surface modification of EPDM sample with 1 kGy of gamma irradiation in the presence of 10 wt% TMPTA resulted in a good increase in the adhesion strength between EPDM and NR (～76% improvement over the untreated sample). On the other hand, for the trichloroisocyanuric acid modified sample, maximum improvement of adhesion strength was observed at 0.5 wt% of TCICA (～29% improvement in comparison with the untreated sample).     

EPR study of radical annihilation kinetics of γ-ray-irradiated acrylic (PMMA) at elevated temperatures

High-energy irradiations of polymers may cause bond cleavage or crosslinking and change the structures and physical properties of the polymers, which may offer various applications. Despite wide investigation, relationship between the kinetics and mechanism of annihilation after irradiations and the structure and some physical properties of irradiated polymers is still poorly established. We have been exploring such possible relationship and report herein investigation of the kinetics of radical annihilation of γ-ray irradiated acrylic, i.e., poly(methylmethacrylate) or PMMA, at elevated temperatures with EPR spectroscopy. The EPR spectra consist of three components, a quintet Ra, a quartet Rb, and a broad singlet Rc. Ra and Rb follow second-order annihilation kinetics, while the decay of the radical Rc is comprised of at least two parallel kinetic processes, a slow second-order pathway and a fast pathway which can be equally well fitted to first- or second-order kinetics. The kinetics is analogous to that for the radical decays in irradiated 2-hydroxyethyl methacrylate copolymer. On the basis of the large hyperfine coupling constant of 2.3 mT, Ra may be assigned to a radical adjacent to two groups of protons, such as a doublet of quartet with similar coupling constants due to an anti-methylene proton and a methyl group; the Rb signal, possibly a methyl radical; and the broad singlet Rc, a magnetically coupled combination species. Alternative assignments of the radicals have also been suggested. The rate constant increases with increasing dose for each radical at a given temperature, possibly due to increase in radical concentrations at higher doses. The rate constants satisfy the Arrhenius equation, suggesting a single mechanistic pathway for the annihilation process in the temperature range; wherein the activation energy decreases with increasing dose for all radicals, possibly due to higher concentrations of free radicals in close proximity produced at higher doses.     

Radiological characteristics of pulverized fly ashes produced in Turkish coal-burning thermal power plants

The objective of this study is to determine radiological characteristics of pulverized fly ash (PFA) collected from the 15 coal-burning thermal power plants (TPPs) in operation by means of gamma spectrometric technique and to assess the radiological impacts from the utilization of PFA samples examined as filling and cover material in earthwork applications. Also, the annual effective doses received by workers handling PFA and members of the public living in a house near the PFA pile/landfill were estimated using methods specified in the Radiation Protection 122. The activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K measured in PFA samples were tabulated for each TPP. The activity results show that Turkish PFA may have relatively high natural radioactivity content, depending on its origin reaching in the case of Kangal PFA 2720 Bq kg⁻¹ of ²²⁶Ra. The values of external exposure indexes (radium equivalent activity index and gamma index) calculated for PFA samples are within the recommended safety limits. As well, the highest mean total annual effective doses estimated as 7.3 × 10⁻⁵ Sv y⁻¹ for workers and 1.5 × 10⁻⁴ Sv y⁻¹ for members of the public are significantly lower than the annual limit of 1.0 × 10⁻³ Sv y⁻¹.     

福岛核事故期间浙江地区环境γ辐射剂量率监测

福岛核事故期间,浙江省辐射环境监测站在秦山核电基地周围、杭州和舟山等地区开展了环境γ辐射剂量率的连续监测和瞬时巡测工作.连续监测和瞬时巡测结果表明,日本地震引发的核泄漏事故对浙江地区的环境γ辐射剂量率水平未造成可监测到的影响.     

Change of the properties of nanostructured MoO3 thin films using gamma-ray irradiation

Thin films of Molybdenum trioxide (MoO₃) were deposited on glass substrates by the spray pyrolysis at 500?°C and the samples were then exposed to gamma γ radiation doses by ⁶⁰Co radioisotope at different doses (0.1, 10 and 50 kGy). The effects of gamma irradiation on the properties of MoO3 thin films were investigated. The XRD pattern and Raman spectroscopy of as-deposited MoO₃ samples show an orthorhombic structure related to α-MoO₃ with (0k0) preferred orientations. Uv‐vis spectra were studied to investigate the transmission measurements of MoO₃ films. The optical energy band gap and Urbach energy were found to be gamma-dose dependent. Photoluminescence measurements at room temperature using 300?nm wavelength excitation were investigated. SEM images indicate the formation of α-MoO₃ nanorods.     

液晶空间光调制器Gamma曲线的线性化调试算法及其对光束整形的影响

在惯性约束聚变(ICF)驱动装置中利用液晶空间光调制器进行激光束的实时、可调控光束空间整形时,Gamma曲线呈线性变化有着重要意义。针对现有调整Gamma曲线呈线性变化的方法费时费力、效果不理想的现状,提出了一种新的调整方法,即依靠Lagrange插值将横坐标为灰度值、纵坐标为功率值的离散点拟合得到曲线方程,然后利用Bolzano二分法求得该曲线方程上与目标Gamma曲线中灰度间隔为1的功率值对应的新灰度值,将新、旧灰度值逐点替换使Gamma曲线呈线性变化。将其应用到大型高能量激光放大装置的光束整形中,得到近场调制度较低且长时间保持稳定的超高斯平顶光束。     

基于“伽马地图”分析的藏传佛教建筑空间组织形式研究--以内蒙古呼和浩特乌素图召为例

内蒙古地区藏传佛教的大雄宝殿是按照某种即成规定的方式,将汉式、藏式两种建筑语汇组合成一个完整的建筑。正是这种“即成规定”的组合形式表达了藏传佛教的宗教含义,并给予信徒特殊的宗教体验。本文以呼和浩特市乌素图召建造于不同年代、现在保存完好的三座寺庙的大雄宝殿为研究对象,进行对比分析,将三个建筑的空间秩序简化成抽象规则,阐释大雄宝殿为达到特殊的宗教体验的组织形式。     

Effects of gamma radiation on the growth of Alternaria alternata and on the production of alternariol and alternariol monomethyl ether in sunflower seeds

The objective of the present study was to evaluate the effects of different gamma radiation doses on the growth of Alternaria alternata and on the production of toxins alternariol (AOH), and alternariol monomethyl ether (AME) in sunflower seed samples. After irradiation with 2, 5 and 7 kGy, the spore mass was resuspended in sterile distilled water and the suspension was inoculated into sunflower seeds. The number of colony-forming units per gram (CFU/g) was determined after culture on Dichloran Rose Bengal Chloramphenicol and Dichloran Chloramphenicol Malt Extract Agar. The presence of AOH and AME was investigated by liquid chromatography coupled to mass spectrometry. The radiation doses used resulted in a reduction of the number of A. alternata CFU/g and of AOH and AME levels when compared to the nonirradiated control group. Maximum reduction of the fungus (98.5%) and toxins (99.9%) was observed at a dose of 7 and 5 kGy, respectively. Under the present conditions, gamma radiation was found to be an alternative for the control of A. alternata and, consequently, of AOH and AME production in sunflower seeds.     

A Study on Two-dimensional Spectrum Analysis System of Energy and Time

Proposed is a two-dimensional (2D) spectrum analysis system for acquiring the statistical information of ra-dioactive particles on two dimensions, i.e. energy and time. Based on pulse width modulation readout circuit, such a system with 4-channels is designed, which converts the radiation signal into a rectangular pulse signal with pulse width modulated. The pulse width, occurrence time, and pulse count of the rectangular pulses are measured simultaneously with digital counters, so that the 2D spectra on energy and time of the radioactive particles can be obtained efficiently based on bi-parameter statistical analysis. A prototype of this 2D system is tested with gamma rays from 241Am isotopes, from which both the correlated 2D spectra and the independent spectra on energy and time are obtained. The energy spectra of four channels shows all characteristic peaks of 241Am gamma rays, among which the full-energy peak at 59.5keV exhibits energy resolution of about 5-6%, suggesting a good energy resolution and channel uniformity of the system. The regression of the time spectra of the characteristic peaks can give the time constants of each characteristic peak, revealing the time characteristics of the nuclear reactions in the radiative source.     

The role of PbO/Bi2O3 insertion on the shielding characteristics of novel borate glasses

Impacts of lead and bismuth oxides insertion on a novel glass system of P₂O₅, B₂O₃, Li₂O, Al₂O₃ according the formula 25B₂O₃–25P₂O₅–10Li₂O–5Al₂O₃–5ZnO-xPbO+ (30-x)Bi₂O₃, x = 5,10, 15, 20, 25 mol%. The mass attenuation coefficient (μ_m = μ/ρ) simulated between 0.015 and 15 MeV using MCNP and calculated theoretically using Phy-X/PSD program. Based on the simulated μ_m, other significant parameters such as linear attenuation coefficient (LAC), half and tenth value layer (HVL, TVL), mean free path (MFP), and effective atomic number (Z_eff) were calculated for fabricated glasses. The G-P fitting methods were used to calculate the exposure and energy absorption buildup factors (EBF and EABF) for fabricated glasses. Furthermore, fast neutron removal cross sections (Σ_R) were calculated theoretically for fabricated glasses. The prepared glasses were effective shielding material which can reduce fast neutrons as well as gamma rays.