9—46keV电子引直怕Ni的K壳层电离截面

用Ｓｉ（Ｌｉ）探测器测量薄Ｎｉ靶在９－４６ｋｅＶ的电子轰击下产生的Ｋ壳层特征Ｘ射线，以确定其Ｋ壳层电子的电离截面。测量结果与前人的实验和理论计算以及经验公式的计算结果作了比较。     

9—28keV电子引起的Cu的K壳层电子电离截面

用高分辨的Ｓｔ（Ｌｉ）探测器测量Ｃｕ靶在９—２８ｋｅＶ的电子轰击下产生的Ｋ壳层特征Ｘ射线，以确定其Ｋ壳层电子的电离截面。运用用电子输运双群模型对衬底的反射对电离的贡献进行了修正。测量结果与前人的实验和经验公式计算结果作了比较。     

用虚量子理论研究重离子束—靶相互作用

本文将虚量了理论用于重离子束与靶相互作用过程中靶原子的Ｋ壳层电子的离子化以及入射重离子的Ｋ壳层电子的激发与离化，这一简单模型所提供的理论结果与实验符合得很好。     

电子引起的钛和锰的K壳层电离截面测量

报道了电子引起的钛,锰原子的Ｋ壳层电离截面实验值。实验中,采用了薄靶厚衬底技术,并将衬底中反射的电子对测量值的影响进行了修正。实验结果与其他文献报道的测量结果相吻合。最后,还将实验结果与Ｃａｓｎａｔｉ等人的经验公式进行了比较。     

一氟三氯甲烷(CFCl3)3a1轨道电子动量分布测量

利用电子动量谱仪测量了一氟三氯甲烷外价壳层的电离能谱和电子动量分布, 并与B3LYP/6-31 G的计算结果进行了比较.     

Measurement of Titanium and Manganese K -shell Ionization Cross Sections by Electron Impact

报道了电子引起的钛、锰原子的Ｋ壳层电离截面实验值。实验中,采用了薄靶厚衬底技术,并将衬底中反射的电子对测量值的影响进行了修正。实验结果与其他文献报道的测量结果相吻合。最后,还将实验结果与Ｃａｓｎａｔｉ等人的经验公式进行了比较。     

Nb,Ag原子的K壳层和L壳层电离截面的理论计算

电子离子碰撞电离截面是模拟激光等离子体的超热电子的能谱和产额的主要过程之一.基于相对论性的电子离子碰撞的K壳层电离截面理论,计算了Nb、Ag的K壳层和L壳层电子碰撞电离截面,结果和最近的文献实验数值和其它理论数值进行了比较,计算结果比其它模型更加准确,与最近的实验结果也吻合较好,该结果可用来模拟激光等离子体的超热电子能谱和产额.     

准旋一角动量标量算子本征值与j壳浊合态的完全分类计算

应用二次量子化和不可约张量理论,由４个产生一湮灭算子耦合成准旋一角动量标量算子Ｚ（Ｋ）,Ｋ为参数。计算表明：Ｚ（Ｋ）的本片值有很强的分类功能,能对ｊ≤１５／２壳层准旋一角动量耦记完全分类（用准旋和角努量只能对ｊ≤７／２壳层耦合态完全分类）讨论Ｚ（Ｋ）的构造和它的本片值的计算方法,给出ｊ≤１５／２壳层耦合态的完全分类。     

Al,Ti,Cu,Mo原子的K壳层电离截面的理论计算

 电子离子碰撞过程是模拟激光等离子体的超热电子的能谱和产额的主要过程之一。基于相对论性的电子离子碰撞的K壳层的电离截面理论,计算了Al,Ti,Cu,Mo原子的K壳层的电子离子碰撞截面,结果和最近的文献实验数值和其它理论数值进行了比较,计算结果可用来模拟激光等离子体的超热电子能谱和产额。     

离子碰撞过程中电荷转移的理论研究

用经典轨道蒙托卡罗(CTMC)方法计算离子与氢原子碰撞过程电荷转移截面,并计算俘获电子的n(n为主量子数)壳层分布。对于多电荷离子的碰撞过程,利用约化变量得到了截面的q标度规律。计算结果与实验测量符合得很好。     

Impact load identification of composite structure using genetic algorithms

For structural health monitoring of composite structure, it is important to quickly and accurately identify the impact load whenever an impact event occurs. This paper proposes a genetic algorithms (GA)-based approach for impact load identification, which can identify the impact location and reconstruct the impact force history simultaneously. In this study, impact load is represented by a set of parameters, thus the impact load identification problem in both space (impact location) and time (impact force history) domains is transformed to a parameter identification problem. A forward model characterizes the dynamic response of the structure subject to a known impact force is incorporated in the identification procedure. By minimizing the difference between the analytical responses given by the forward model and the measured ones, GA adaptively identify the impact location and force history with its global search capability. This new impact identification approach is applied to a stiffened composite panel. The stiffened composite panel is modeled as an equivalent laminate with varying properties and the forward response is obtained by using an assumed modes approach. To improve the computational efficiency, micro-GA (μGA) is employed to perform the identification task. Numerical simulation studies are conducted to demonstrate the effectiveness and applicability of the proposed method.     

Residual microstructure associated with impact crater in Ti-6Al-4V meshes reinforced 5A06Al alloy matrix composite

In this paper, TC4(m)/5A06Al composite was hypervelocity impacted by 2024 aluminium projectile with the diameter of 2mm and with the impact velocity of 3.5 km/s. The residual microstructure was observed by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HREM). The TC4-Al interface before impact was composed of TiAl(3) phase and Ti(3)Al phase. Near the pithead, separation of TC4 fibers and Al matrix occurred along the impact direction. Around the middle of the crater, TC4 fibers were sheared into several sections. Near the bottom of crater, adiabatic shear band (ASB) occurred in TC4 fiber, while the angle between shear plane and cross section was 45°. The crack propagated along TC4-Ti(3)Al interface during impact and some Ti(3)Al phase at the TC4-Al interface transformed to amorphous with few nanocrystals after hypervelocity impact.     

Residual microstructure associated with impact craters in TiB2/2024Al composite

Residual microstructures associated with hypervelocity impact craters in 55 vol.% TiB(2)/2024Al composite were investigated by transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). TiB(2)-Al interface, TiB(2) particles and Al matrix before and after hypervelocity impact were compared to discuss the effect of hypervelocity impact. A new Al(x)O(1-x) phase with the fcc structure and the crystal parameter of 0.69 nm was formed at TiB(2)-Al interface. Stacking fault with width of 10-20 nm was formed along the (001) plane of TiB(2) particle. Formation of nanograins (≈ 100 nm) was observed within Al matrix, moreover, lamellar S' phase was transformed into lenticular or spherical S phase after hypervelocity impact.     

Wheel/rail noise—Part III: Impact noise generation by wheel and rail discontinuities

This paper is part of a series of publications dealing with wheel/rail noise [1–4]. Except for comparing the relative importance of impact noise with rolling noise, this paper concerns itself exclusively with the impact noise generated by such discontinuities as rail joints, frogs, switches, and wheel flats.Studies show that above a certain critical train speed the wheel separates from the rail when the interface encounters certain types of discontinuities. This critical train speed is an important acoustical parameter, because the noise generation process obeys completely different laws in the speed ranges below and above it. From the geometry, the kinematics, and the dynamics of the wheel/rail system, analytical models have been developed to identify the major variables controlling the generation of impact noise. The validity of these models has been confirmed by both scale-model and full-scale experiments.The results of the study show the following: (1) at rail joints, the height difference—and not the width of the gap—is the controlling parameter; (2) below critical train speed, impact noise increases with increasing train speed and does not depend on the direction of travel; (3) above critical train speed, the intensity of impact noise increases with increasing train speed for travel in the step-up direction but is independent of the train speed for travel in the step-down direction; (4) in generating impact noise, wheel flats are equivalent to step-down rail joints, provided flat height equals height difference at the joint; (5) both the magnitude and spectrum of impact noise produced by wheel and rail discontinuities can be predicted from a simple wheel drop test. With the knowledge gained from both the analytical and the experimental studies, we have been able to identify feasible measures for the control of impact noise.     

Single differential and total ionization cross section of the helium atom by positron impact

Single differential (SDCS) and total (TCS) cross sections are calculated for the single ionization process of a helium atom by positron impact in the intermediate and high energy range (50–300 eV). To study the charge asymmetry, cross sections for electron impact ionization are also presented for comparison with the positron data. The TCS results for positron impact have been compared with existing measurements. A good agreement is noted in the high energy regime ( 100–300 eV).     

超高速碰撞LY12铝靶产生闪光辐射的速度及角度效应

为了研究超高速碰撞产生闪光辐射的速度及角度效应,利用建立的瞬态光纤高温计测量系统结合二级轻气炮加载系统,进行了6种实验条件下的超高速碰撞实验。每组实验使用一组光纤探头,基于实验所获原始数据结合标定,通过Matlab编程处理得到了给定实验条件及光纤探头安装条件下,超高速碰撞LY12铝靶产生的闪光辐射与碰撞速度和弹丸入射角度的关系。实验结果表明,超高速碰撞LY12铝靶产生的闪光辐射在温度峰值出现前近似与碰撞速度和弹丸入射角度(弹道与靶板平面的夹角)正弦乘积的平方成正比;碰撞闪光辐射在温度峰值出现后近似与碰撞速度和弹丸入射角度正弦乘积的0.75次幂成正比,与理论推导结果基本吻合。     

Triple differential cross-sections for the fast electron/positron impact ionization of hydrogen and helium in the Glauber approximation

Triple differential cross-section for electron and positron impact ionization of hydrogen and helium are calculated by using the Glauber approximation along with post-collision interaction effects which are estimated classically. The present results are compared with the recent absolute data of Ehrhardt, Jung and coworkers for the electron impact case. The positron impact case is found to lead to a larger binary to recoil peak maxima ratio (compared to the electron impact case) which further increases when post-collision interaction effects are included.     

Study on Impact Property and Fracture Morphology of Injection-molded Optical-grade Polycarbonate

The low-velocity, low-energy impact response of optical-grade polycarbonate (PC) was characterized by the Izod impact testing at ambient temperature. The following factors affecting impact response were investigated: mold temperatures (80, 90, 100, 110, and 120°C) and annealing treatment (120°C for 12 h). The results showed that the annealing treatment remarkably reduced the impact strength. The maximum impact strength was obtained when the mold temperature was 100°C for both unannealed samples and annealed ones. Moreover, the annealing treatment changed the failure mode of specimens from ductile failure to brittle failure, which was confirmed by fracture morphology analysis using scanning electron microscopy (SEM). The ductile failure was attributed to shearing behavior, and the fracture surfaces were rough and irregular with many river-shaped striations. The brittle fracture was caused by a craze failure mechanism. The brittle fracture sections could be divided into three regions: fracture origin, mist region, and end-wall banded region.     

Weak avalanche multiplication in SiGe heterojunction bipolar transistors on thin film silicon-on-insulator

In this paper, we propose an analytical avalanche multiplication model for the next generation of SiGe silicon-on-insulator (SOI) heterojunction bipolar transistors (HBTs) and consider their vertical and lateral impact ionizations for the first time. Supported by experimental data, the analytical model predicts that the avalanche multiplication governed by impact ionization shows kinks and the impact ionization effect is small compared with that of the bulk HBT, resulting in a larger base-collector breakdown voltage. The model presented in the paper is significant and has useful applications in the design and simulation of the next generation of SiGe SOI BiCMOS technology.