散裂靶中质子束窗的散射效应

 质子束窗是在高功率靶区中的一个分界窗,它将质子输运线上高真空区域和氦容器中的氦环境分开。在其他散裂中子源中质子束窗的热效应以及机械问题都已经被研究过了,但质子束在该窗中散射效应的研究却很少被报导,然而在靶设计中如果没有处理好质子束窗的散射效应会有很大的问题。报导了质子束窗散射效应的模拟计算结果,包括不同质子束窗的材料和结构选择,并以中国散裂中子源（CSNS）为例,介绍了在CSNS一期和二期中质子束窗采用周边水冷的铝合金单层结构,CSNS三期采用中间水冷的铝合金夹层结构。文中给出了不同结构的质子束窗和不同的与靶距离散射效应对靶上经非线性磁铁均匀化的束流分布的影响的模拟计算结果。模拟结果显示质子窗的散射效应对束流损失和靶上的束流分布有重要的影响。     

基于单孔洞近似的高纯铝部分层裂实验的数值模拟研究

基于单孔洞近似,对不同撞击速度下高纯铝的部分层裂实验进行了数值模拟研究,讨论了微孔洞长大对波传播的影响及其在自由面速度波剖面上的表现. 通过分析微孔洞周围的应力场变化,认识到实测自由面速度波剖面出现"回跳"特征并不能说明材料发生完全层裂,其直接原因是样品内部微孔洞长大所引起的局部卸载效应. 将计算得到的自由面速度波剖面和微孔洞相对体积与实验结果进行了对比分析,发现两者均符合很好,表明采用单孔洞增长来近似描述部分层裂样品中随机损伤发展及其对波传播的影响是可行的. 关键词： 层裂 孔洞增长 自由面速度波剖面 微孔洞相对体积     

Cascade-exciton model analysis of level density parameter dependence in proton induced fission cross sections of some sub-actinide nuclei

Fission cross sections strongly depend on the ratio of the level density parameter in fission to neutron emission, a_f/a_n. In this work, a cascade-exciton model implemented in the code CEM95 has been used to observe this effect for proton induced fission cross sections of tungsten, lead and bismuth. The method was employed using different level density parameter ratios for each fission cross section calculation. The calculated fission cross sections are compared with the available experimental data in the literature. It has been observed that a change of the ratio of the level density parameter, a_f/a_n, is necessary with the incident energy of the proton, to best estimate the fission cross sections in CEM95.     

Study on induced radioactivity of China Spallation Neutron Source

China Spallation Neutron Source (CSNS) is the first High Energy Intense Proton Accelerator planned to be constructed in China during the State Eleventh Five-Year Plan period, whose induced radioactivity is very important for occupational disease hazard assessment and environmental impact assessment. Adopting the FLUKA code, the authors have constructed a cylinder-tunnel geometric model and a line-source sampling physical model, deduced proper formulas to calculate air activation, and analyzed various issues with regard to the activation of different tunnel parts. The results show that the environmental impact resulting from induced activation is negligible, whereas the residual radiation in the tunnels has a great influence on maintenance personnel, so strict measures should be adopted.     

Preliminary shielding analysis in support of the CSNS target station shutter neutron beam stop design

The construction of China Spallation Neutron Source (CSNS) has been initiated in Dongguan, Guangdong, China. Thus a detailed radiation transport analysis of the shutter neutron beam stop is of vital importance. The analyses are performed using the coupled Monte Carlo and multi-dimensional discrete ordinates method. The target of calculations is to optimize the neutron beamline shielding design to guarantee personal safety and minimize cost. Successful elimination of the primary ray effects via the two-dimensional uncollided flux and the first collision source methodology is also illustrated. Two-dimensional dose distribution is calculated. The dose at the end of the neutron beam line is less than 2.5 μSv/h. The models have ensured that the doses received by the hall staff members are below the standard limit required.     

巧构常数列解两类数列求和问题

数列求和问题,一直都是高考考查的热点,相关题型千变万化,精彩纷呈,让人目不暇接,其中利用＂错位相减法＂与＂裂项相消法＂求解的两类求和问题尤为突出.但利用错位相减法求解时,繁琐运算有时总使人望而却步;利用裂项相消法求解时,剩余若干项有时常叫人丢三落四.结合2013年的高考题介绍＂构造常数列＂的办法,来解决这两类问题,以藉读者.     

一种钨合金含损伤本构的唯象模型

利用多压阻传感器拉氏实验分析方法对受冲击90w钨合金材料中形成的应力波场进行了测试，并利用拉格朗日分析方法获得的结果建立了合金的不含损伤的本构关系．然后以动态层裂试验获得的层裂参数曲线和数据为依据．提出了一种考虑材料内部损伤成核，成长及汇合效应的唯象本构模型，并通过对层裂实验曲线进行数值模拟，确定了该合金的含损伤本构的参数．     

不锈钢(00Cr18Ni9)动态累积损伤研究

用一级压缩气体炮加载技术和可变平板电容传感技术，对不锈钢（００Ｃｒ１８Ｎｉ９） 动态累积损伤进行了实验研究，给出了层裂累积损伤连续度量的经验关系式，并对损伤度与动载历史的相互关系进行分析、讨论。     

诱导效应指数与XSiRxH3—x的标准生成热

诱导效应指数与ＸＳｉＲｘＨ３－ｘ的标准生成热张秀利（河北轻化工学院基础部石家庄０５００１８）关键词诱导效应指数标准生成热键裂能烷基硅衍生物对于含硅有机物的标准生成热大多未见报导［１－２］，本文将利用诱导效应指数Ｉ［３，４］，作为参数，建立一套简单而准...     

孔洞增长与汇合的数值模拟

在研究延性材料的层裂过程中，微孔洞的成核、增长与汇合是主要问题。在二维平面条件下，应用二维拉氏有限元弹塑性流体力学程序(LTZ-2D)，在动态拉伸作用下，对多种形状的孔洞增长、相互作用和汇合进行了数值模拟。结果表明，初始非圆形孔洞在动态拉伸作用下，经过了一定时间后，孔洞的增长均趋近于圆形。如果在孔洞周围允许材料损伤断裂的话，当孔洞继续长大到一定程度时，将产生破裂并且汇合。以铜材料为例，