Microstructural Evolution in Directionally Solidified Ni-Base Superalloy IN792+Hf

Microstructural evolution during directional solidification （DS） of Ni-base superalloy IN792＋Hf has been investigated with an emphasis on theγ′precipitates and MC-type carbides.The quantitative image analyses revealed that the increase in the solidification rate up to 100μm/s at constant thermal gradient of 178 K/cm resulted in a fine and uniform distribution ofγ′precipitates.The relationship between the as-castγ′size and cooling rate was also determined for DS IN792＋Hf.In the mean time,the MC carbide size was found to be dependent both on the solidification rate and the S/L interface morphology while the area fraction of MC carbide was significantly influenced by the S/L interface morphology.     

瞬发伽玛活化分析中3种探测器性能比较

利用中国先进研究堆(CARR)热中子束流孔道首次开展了瞬发伽玛中子活化分析(PGNAA)实验。对NH4Cl、Si、Fe、Al等4种样品进行了辐照,同时采用HPGe、LaBr_3、BGO 3种探测器对样品进行实时测量,在瞬发伽玛射线的能量为0.002~10 MeV范围内研究了3种探测器在宽能区的能量线性、能量分辨率、探测效率等性能。     

The natural radioactivity in the bricks used for the construction of the dwelling in Tehran areas of Iran

This paper presents the finding of a study undertaken to determine the natural radioactivity present in bricks in Tehran. A total of 45 samples of commonly used bricks were collected from various manufacturers and suppliers and analyzed using a shielded HPGe gamma ray spectrometer. The specific activities of (226) Ra, (232) Th, and (40) K were measured in all brick samples, and results ranged from minimum values of 26, 24, and 524 Bq kg(-1) to maximum values of 38, 36, and 820 Bq kg(-1) with mean values of 33, 30, and 700 Bq kg(-1) ,respectively. In general, these activities were comparable to the results of similar studies undertaken in another countries. These activities would suggest that the use of such bricks in construction of dwellings or work places in Tehran is unlikely to give rise to any significant radiation exposure to the occupants.     

含Gd环境友好型射线柔性综合屏蔽体研究

针对核辐射 n-γ 混合场,研制了一种以 Gd 为核心屏蔽粒子, SEBS 为基体的环境友好型射线柔性综合屏蔽体,该材料具有绿色环保、生产节能、综合防护、柔性可塑、可回收使用等特点。扫描电镜结果表明 Gd2O3 粉末呈颗粒状均匀分布,在基体中有良好的分散性; X 射线衍射和红外光谱结果表明 Gd2O3 和基体本质上属于物理机械混合,不涉及化学键变化; γ 射线和热中子屏蔽性能验证表明,随着 Gd 面密度的提高, γ 射线和热中子透射率吸收遵从指数衰减规律;当 Gd 面密度为0.018 4 ~ 0.291 3 g/cm2时,材料在39 keV、59 keV和122 keV下 γ 射线透射率为83.73%~11.48%,75.43%~2.73%和93.03%~51.64%;当 Gd 面密度为0.018 9 ~ 0.070 9 g/cm2时,材料中子透射率为45.74%~35.78%。该柔性射线综合屏蔽体有效弥补了传统防护材料的弊端,在未来舰船生物屏蔽、核医学诊疗、安全检测等领域具有潜在应用价值。     

致密砂岩气藏水平井测井评价——以鄂尔多斯盆地大牛地气田X井区为例

致密气藏中有相当一部分水平井测井系列少、评价难度大,如何利用有限的测井资料有效开展水平井测井评价,对气藏高效开发具有重要意义。以鄂尔多斯盆地大牛地气田X井区为例,结合地质和生产动态等资料,利用水平井仅有的随钻伽马测井和气测录井资料开展测井评价研究,形成了基于伽马峰值和全烃有效指示因子的双参数水平井产能评价方法,有效提高了水平井产能评价精度,为同类气藏水平井测井评价提供了借鉴。研究认为,基于随钻伽马峰值分析能够有效对储层进行评价,大牛地X井区山西组和下石盒子组高产井目的层段随钻伽马值的分布均表现出了明显的单峰特征,而低产井则表现为双峰或不具有明显的峰值特征,主要与水平井钻遇砂体的稳定性有关。利用X井区气测录井资料,构建了基于全烃有效指示因子用于评价单井产能,并建立了山西组和下石盒子组水平井经济产能的气测录井指标。综合上述两种方法,形成双参数水平井产能评价方法,准确评价了X井区水平井单井产能。     

土壤样品γ谱分析自吸收校正技术研究

用点源实验方法,表征了探测器晶体的结构参数,以此为基础利用蒙卡模拟计算了不同质量样品对各种能量γ射线的线衰减系数和探测效率,进而建立了75 mm×25 mm样品自吸收校正因子F(μ)的关系式;使用标准面源模拟体源不同高度的薄层,通过γ能谱测量得到体源不同高度薄层的探测效率与其高度的函数关系式ε(h),积分获得体源探测效率,进而建立75 mm×25 mm样品自吸收校正因子随γ射线线衰减系数的变化关系F(μ),面源实验建立的F(μ)关系式与蒙卡计算得到的F(μ)关系式趋于一致。以蒙卡计算模型为依据,拓展计算了75 mm×75 mm盒装土壤样品的F(μ)函数关系,并实验验证了计算结果的有效性。利用建立的F(μ)函数关系对取自某污染场址的多个土壤样品进行测量结果自吸收校正,建立了样品质量和自吸收校正因子的函数关系F(m),并给出土壤样品自吸收校正的技术方法。     

伽玛刀治疗计划系统中一种新的图像轮廓提取算法

在伽玛刀治疗计划系统中,为了给三维重建提供汽观的参考依据,要求准确地对体表、病灶和其他组织进行轮廓提取。针对目前该系统中以手工轮廓提取为主的现状,本文提出并实现了一种新的图像轮廓提取算法。该方法利用初始轮廓逐步逼近最佳轮廓,不仅将图像灰度变化的微分信息作为边缘提取的依据,旧时以图像轮廓的整体几何信息作为指导,从而在满足边缘检测精度要求的前提下,一定程度上解决丁噪声对轮廓特征提取的影响。     

Partially hydrolyzed polyacrylamide–poly(N-vinylpyrrolidone) copolymers as superabsorbents synthesized by gamma irradiation

Partially hydrolyzed polyacrylamide-co-poly(n-vinyl pyrrolidone) used as a superabsorbent was prepared from acrylamide monomers exposed to γ-rays to become polyacrylamide that was subsequently partially hydrolyzed and was then copolymerized with n-vinylpyrrolidone to obtain a terpolymeric superabsorbent with a water retention value of 1100 times its dried weight. The total dose and dose rate along with the appropriate degree of hydrolysis were investigated for percentage conversion in each polymerization and the extent of water absorption. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68:191–203, 1998     

四氯化碳协同γ射线辐射去除噻吩型含硫化合物的研究

随着环保要求的不断提高,对各类燃油中含硫化合物的含量所制定的限制标准将越来越严格。常规的加氢脱硫方法存在工艺复杂、运行成本高等问题。本文探索了利用四氯化碳协同γ射线辐射去除油品中噻吩型硫的新方法。利用十二烷模拟油品,以噻吩、二甲基噻吩、苯并噻吩和二苯并噻吩为研究对象,考察了其辐射去除效果。结果表明,四氯化碳对噻吩型硫的辐解有着明显的促进作用;在高剂量率时的能量效率更高;绝大部分含硫化合物和氯化物会从反应体系中逸出。     

Understanding E. coli internalization in lettuce leaves for optimization of irradiation treatment

Irradiation penetrates food tissues and effectively reduces the number of food microorganisms in fresh produce, but the efficacy of the process against internalized bacteria is unknown. The objective of this study was to understand the mechanisms of pathogen colonization of plants relative to lettuce leaf structures so that radiation treatment of fresh leafy vegetables can be optimized. Leaves of iceberg, Boston, green leaf, and red leaf lettuces were cut into pieces, submerged in a cocktail mixture of two isolates of Escherichia coli (Rifampicin resistant), and subjected to a vacuum perfusion process to force the bacterial cells into the intercellular spaces in the leaves. Sixty bags containing 20 g of lettuce each were tested. The inoculated leaves were gamma irradiated (Lanthanum-140, 0.16 kGy/h) at 0.25–1.0-kGy (surface dose values), with increments of 0.25 kGy at 15 °C. Microbial analysis was performed right after irradiation, including non-irradiated leaf pieces (controls). A dose uniformity ratio (max/min dose) of 2.8 was set to confirm the effect of non-uniform dose distribution. Calculated D₁₀-values varied between 48 and 62% based on the dose distribution from the entrance dose. However, despite the subtle differences in composition and structure among the four lettuce varieties, the D₁₀-values were not significantly different. Irradiation up to 1.0-kGy resulted in 3–4-log reduction of internalized E. coli on the lettuce leaves. The SEM images suggest that the contamination sites of pathogens in leafy vegetables are mainly localized on crevices and into the stomata. This study shows that irradiation effectively reduces viable E. coli cells internalized in lettuce, and decontamination is not influenced by lettuce variety. Ionizing irradiation effectively reduced the population of internalized pathogen in a dose-dependent manner and could be used as an effective killing step to mitigate the risk of foodborne disease outbreaks.