纳构件加工后的力学特性

"采用分子动力学模拟的方法,运用镶嵌原子模型,研究了经过刻划后的单晶铜纳构件在不同拉伸速度条件下的力学行为. 通过原子位图、缺陷原子透视图、径向分布函数及应力-应变关系研究加工后纳构件在拉伸负载作用下的变化特性,并与理想单晶铜纳构件进行对比分析．模拟结果表明,加工后的纳构件的屈服强度较理想纳构件的屈服强度有明显下降,屈服强度随着刻槽深度的增加而下降,而且屈服强度对刻槽方向和拉伸速度敏感;纳结构在拉伸负载作用下,其应力应变关系出现了双峰形式,即工作硬化现象,二次屈服后表现为Z字形逐波下降形式．刻划深度、刻划     

Study of high-coercivity sintered NdFeB magnets

Magnetic powders for sintered NdFeB magnets have been prepared by using an advanced processing method including strip casting, hydrogen decrepitation, jet milling and rubber isotropic press. The effects of Dy, Ga and Co addition on the microstructure and magnetic properties of sintered magnets have been investigated. By adopting a suitable component ratio and adjusting proper technological parameters, we have prepared high-coercivity sintered NdFeB magnets with hard magnetic properties of _jH_c=25.6 kOe, B_r=13.2 kG and (BH)_max=39.9 MGOe. The temperature coefficient of coercivity of the magnets (between 20 and 150 °C) is –0.53%/°C. The magnetic properties at high temperature satisfy the needs of permanent magnet motors.     

Renal Clearable Luminescent WSe2 for Radioprotection of Nontargeted Tissues during Radiotherapy

High‐energy ionizing radiation is widely used in medical diagnosis and cancer radiation therapy. However, high‐energy radiation can also impose significant damages in healthy tissues during medical treatments via direct DNA damages and indirect damages from production of reactive oxygen species (ROS). Therefore, it is urgent to develop highly effective radioprotectants with low toxicities that can meet the increasing needs for alleviating the adverse effects from cancer radiation therapy and nuclear emergency. In this work, strongly catalytic ultrasmall (sub‐5 nm) cysteine‐protected WSe₂ dots are employed to protect healthy tissues against radiation via diminishing radiation‐induced free radicals. The WSe₂ dots with high surface activities can recover radiation‐induced DNA damages and eliminate the excessive ROS generated from radiation. In vivo experiments confirm that the survival rate of mice treated with WSe₂ dots is significantly elevated with radiation damages postponed under exposure to high‐dose ionizing radiation. Furthermore, the free radicals in major organs and hematological system can be appreciably omitted, suggesting their unique role as free radical scavengers. These WSe₂ dots in ultrasmall size show rapid renal clearance of ≈74% injection dose via urine excretion in 24 h and do not cause any apparent toxicity in vivo for up to 30 d.     

碳纳米纤维吸附储氢性能分析

文中综合碳纳米纤维微观结构的表征结果以及氢吸脱附等温线的实验测量结果,对碳纳米纤维的吸附储氢性能进行了综合分析,分析发现:比表面积和中孔容积均与氢吸附量成线性关系;微孔容积对材料吸附性能影响较大,微孔容积与氢吸附量成抛物线关系;氢在常温左右以及77K下的吸附等温线呈现超临界气体的吸附特征,氢在273K和353K下的吸脱附等温线也基本重合,呈现的是物理吸附的特征。实验结果还说明:常温左右,甚至是77K下,碳纳米纤维均不适合于氢的吸附储存。     

微通道板固定图案噪声及测试研究

叙述微通道板的噪声,着重介绍微通道板固定图案噪声及其简便新颖而又实用的一种测试方法,给出测试结果并进行分析。     

螺线管场下强流相对论电子束焦斑尺寸的限制

 分析了螺线管场下影响强流相对论电子束聚焦的主要因素,并给出了各影响因素所限制的最小焦斑。计算结果表明,当发射度和能散度的值分别控制在0.397mm× rad和1%以内, 单个螺线管磁轴的偏心不大于0.54mrad,初始注入束偏心不大于1mrad时,对于20MeV、3kA的电子束和15MeV、2.5kA的电子束,最终打靶束焦斑均可小于1.5mm。     

双反射镜式光电经纬仪测角误差的分析(轴系部分)

双反射镜式光电经纬仪由于采用了反射镜跟踪头,轴系误差对测角精度的影响不同于典型光电经纬仪。本文从建立经纬仪三维直角坐标系入手,建立了该类型经纬仪轴系误差引起测角误差的数学模型,为精度分析和误差修正提供了依据。     

Asymptotic behavior of positive solutions of semilinear elliptic equations in ℝ n , II

In this paper, we will analyze further to obtain a finer asymptotic behavior of positive solutions of semilinear elliptic equations in R^n by employing the Li＇s method of energy function.     

Transitive Novikov Algebras on Four-Dimensional Nilpotent Lie Algebras

Novikov algebras were introduced in connection with the Poisson brackets (of hydrodynamic type) and Hamiltonian operators in the formal variational calculus. The commutator of a Novikov algebra is a Lie algebra, and the radical of a finite-dimensional Novikov algebra is transitive. In this paper, we give a classification of transitive Novikov algebras on four-dimensional nilpotent Lie algebras based on Kim (1986, Journal of Differential Geometry 24, 373–394).     

用微机处理冷却实验数据

利用微机研究金属冷却规律。