Electron impact excitation of Ni XIX using theR-matrix method

Collision strengths for all the transitions between the 15 lowest states of neon-like Ni XIX have been calculated for electron impact in the 80–140 Ry energy range. Configuration-interaction wavefunctions have been used to represent the target states. The standardR-matrix code has been used to calculate the lower scattering partial waves (L≤9), while a no-exchange version of the same code has been used to compute efficiently the higher partial waves (L≥10). Effective collision strengths for 105 excitation transitions between the ground state 2s ²2p ^{6 1} S ^e and the 142s ²2p ⁵3l Rydberg states are tabulated for electron temperatures in the range logT=5.40 to logT=7.00, withT expressed in °K.     

Controlling the mechanical properties of poly(L‐lactide– ε‐caprolactone) monofilament sutures by an acetone/water treatment

For monofilament biodegradable sutures fabricated from the L ‐lactide–ε‐caprolactone (75/25) copolymer [P(LLA/CL)], there have been some concerns regarding their mechanical properties, such as the knot‐pull strength and stiffness. This article demonstrates the further potentiality of these sutures through improvements in those properties. With the aim of diminishing the molecular orientation, particularly in the suture surface region, we adopted an expedient method to treat P(LLA/CL) sutures with an acetone/water mixture, using different times and time patterns. The changes in the molecular orientation distributions across the suture cross sections were characterized by the specific index of birefringence measured with an interference microscope. The crystal orientations, knot‐pull strengths, tensile strengths, and bending rigidity were measured. The conformational changes in suture breaking during knot‐pull tests were analyzed with high‐speed‐video observations. Morphological analyses of the fractural surfaces were performed with scanning electron microscopy. The knot‐pull strength tended to rise, in comparison with that of untreated samples, up to a certain treatment time and was accompanied by a minimal decrement of the tensile strength. The knot‐pull strength did not show an increasing trend with further treatment, whereas the tensile strength declined remarkably. The birefringence, crystal orientation, bending rigidity, fractured surface analysis, and high‐speed‐video observations revealed molecular disorientation mainly in the filament outer layers for that particular treatment causing the sutures to be considerably softer. The suture softness played a role in changing the deformation behavior of the knot when a load was applied and caused the knot‐pull strength to rise. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2449–2462, 2002     

湿敏陶瓷感湿机理的新模型讨论

本讨论了湿敏陶瓷感湿机理比较接近于实际的“镶嵌模型”，对“镶嵌模型”的线性方程进行了求解，并对结果进行了分析，为各种多孔陶瓷湿敏元件的开发提供了新途径。     

LY—12铝高温屈服强度的测量

本文介绍LY-12铝合金在常温至400℃动载下(应变率为 10~3/秒),屈服强度的测试及研究。采用一维Hopkinson压杆实验装置及管式高温炉。利用一维应力波传播理论及应变片直接测量两种方法,得到了LY-12铝合金的屈服强度随温度变化的曲线。     

Multi-response optimization of CO2 laser-welding process of austenitic stainless steel

Recently, laser welding of austenitic stainless steel has received great attention in industry. This is due to its widespread application in petroleum refinement stations, power plants, the pharmaceutical industry and also in households. Therefore, mechanical properties should be controlled to obtain good welded joints. The welding process should be optimized by the proper mathematical models. In this research, the tensile strength and impact strength along with the joint-operating cost of laser-welded butt joints made of AISI304 was investigated.Design-expert software was used to establish the design matrix and to analyze the experimental data. The relationships between the laser-welding parameters (laser power, welding speed and focal point position) and the three responses (tensile strength, impact strength and joint-operating cost) were established. Also, the optimization capabilities in design-expert software were used to optimize the welding process.The developed mathematical models were tested for adequacy using analysis of variance and other adequacy measures. In this investigation, the optimal welding conditions were identified in order to increase the productivity and minimize the total operating cost. Overlay graphs were plotted by superimposing the contours for the various response surfaces. The process parameters effect was determined and the optimal welding combinations were tabulated.     

Picosecond excitonic luminescence in ZnO and other wide-gap semiconductors

Radiative lifetimes of free-atom transitions, scaled by ω³ for comparison at 368 nm, are not faster than about 6.9 ns. BaF₂ core-valence luminescence, scaled in the same way from 220 to 368 nm, corresponds to 4.1 ns. In contrast, excitonic transitions in wide-gap semiconductors display subnanosecond radiative lifetimes, and in particular ZnO has radiative lifetimes measured at 50–300 ps for D^o,X and 400–900 ps for free excitons. The “giant oscillator strength” corresponding to these lifetimes can be explained by theories developed initially for defect-bound excitons, then quantum wells, and nanoparticles. An exciton is a coherent array of N dipoles, where N is the number of sites covered by coherent translational motion of the exciton. This is not essentially a phenomenon of multiple excitons, but applies as well to single-exciton decay. It differs in that regard from the more familiar Dicke giant dipole of N coherently excited atoms lacking translational periodicity. The phenomenon suggests possibilities for achieving ultrafast scintillators and high light yield.     

光纤制导关键技术分析和研究

系统地讨论、分析和研究光纤制导中的关键技术，并对未来的发展提出了建议。     

类锂硅离子能级结构与振子强度的理论计算（相对论DF模型）

用相对论性的ＤＦ方法与非相对论性的ＨＦ方法分别计算了类锂硅离子能级结构及振子强度、跃迁概率，考查了计算精度，对数值结果进行了理论分析并与其它结果进行了比较。     

高强度均匀静磁场中氢原子能级的计算

采用一种简便的变分法，计算了在均匀高强度静磁场下氢原子的１１个低能态能级和平均半径，讨论了高强度磁场对能级和半径的影响。     

Beta decay rates for nuclei with 115<A<140 for r-process nucleosynthesis

For r-process nucleosynthesis the β-decay rates for a number of neutron-rich intermediate heavy nuclei are calculated. The model for the β-strength function is able to reproduce the observed half-lives quite well.