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Belloni F Himbert J Marzocchi O Romanello V 《Journal of environmental radioactivity》2011,102(9):852-862
Most of the surface explosions in nuclear tests have released radioactivity to the environment in the form of bulk glassy materials originating from the melting of sandy soil in the neighbourhood of ground zero. In view of clarifying issues concerning the mechanism of formation and the radiological impact of these materials, we investigated incorporation and volume distribution of radionuclides in a typical fragment of trinitite, the glassy substance generated following the first nuclear test (Trinity Site, New Mexico, 1945). Specific activities were determined by γ-spectrometry for the most significant fission and activation products. In particular, 152Eu activity was used to estimate the original point of collection of the sample with respect to ground zero. After embedding in an epoxy resin, the sample was then sliced to perform cross-sectional β- and α-autoradiograph. α-spectrometry was also carried out on a fine powder obtained by surface abrasion. In the β-autoradiography, hot spots were distinguishable in the proximity of the blast side, over a 1000 times less intense background of sand activation products. Also α-contamination (from 239+240Pu and 241Am) was mostly concentrated within the superficial layer, in a fraction of only 20% of the overall volume of the sample, exhibiting a discontinuous, droplet-like distribution. This evidence would partially support a recent hypothesis on trinitite formation according to which most of the glass layer was formed not on the ground but by a rain of material injected into the fireball that melted, fell back, and collected on a bed of already fused sand. 相似文献
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目的获取舰载飞机弹射过程中冲击动载荷在结构上的响应规律,以及前起落架和与其连接的机体主传力结构的动响应特性。方法基于多体系统动力学理论,建立描述舰载机弹射过程的刚柔耦合多体系统动力学模型,对弹射过程进行仿真分析。同时开展地面模拟弹射冲击试验,通过仿真和试验对照,重点研究牵制载荷突卸瞬间结构的动态响应规律。结果仿真和试验得到结构传力路径各点的加速度和应力响应数据,试验测得机体结构加速度峰值达到255g,而同位置的应力峰值为85 MPa,仿真和试验数据的趋势一致。结论牵制载荷突卸形成的冲击动响应峰值沿着结构传力路径衰减。航向加速度和应力响应峰值随着牵制释放载荷的增加而增加。虽然瞬态加速度峰值达到较高水平,但是瞬态作用机体结构的应力峰值不高,不足以造成结构失效。结构设计应重点关注弹射冲击响应峰值和振动疲劳的影响。 相似文献
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Vacuum sealing drainage has excellent therapeutic effects on the complex injuries. There is no relevant report on seawater-immersed sulfur mustard injury. The treatment effects were examined with miniature pigs. Injuries were performed on their back followed by vacuum sealing drainage at various pressures for nine days. Injured tissues were sampled up to 30 d after treatment and healing rates, levels of interleukin-6, tumor necrosis factor α, and vascular endothelial growth factor were recorded. Vacuum sealing drainage enhances the healing of sulfur mustard wounds significantly, reduces the interleukin-6 and tumor necrosis factor α levels in the wound, and increases the vascular endothelial growth factor expression. Pressure reduction by 180 mmHg is the most suitable condition for vacuum treatment. 相似文献
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导弹核武器核事故应急有关问题研究 总被引:1,自引:0,他引:1
对导弹核武器核事故应急的主要任务、特点、组织指挥以及力量运用等问题进行了探讨 ,导弹核武器核事故的应急问题是一项涉及体制、人员、装备、技术、科学理论等方面的复杂系统工程 ,笔者结合实际 ,有针对性的研究了事故应急有关的问题 ,可为导弹核武器核事故应急提供理论指导 相似文献
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目的研究导弹武器系统使用可用度评估问题,方法通过基于故障数据的使用可用度评估,提出一种基于灰色模型GM(1,1)的径向基函数(RBF—Radial Basis Function)神经网络组合模型。结果该模型克服了灰色理论的长时间序列预估误差大和神经网络的训练样本需求量大、输入变量选取困难等缺点。结论仿真结果表明,GM—RBF神经网络对导弹武器系统使用可用度评估具有评估误差小、精度高等优点。 相似文献
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