Experimental study of enhanced emission of the laser-ablated plume in backing gas

The effects of background gases on the optical emission of the excimer-laser-ablated plume from a brass target have been studied experimentally. It is found that the plume emission can be enhanced significantly in a proper gas ambient. In hydrogen, the highest peak intensity is detected, and in argon, there is a distinctive difference in the pressure-dependent emission between in He and in the other three gases, Ar, N₂ and H₂. Moreover, the monitored line peak intensity remains unchanged in Ar and N₂ and increases in H₂ within a distance above the target surface; but in He, the observed peak intensity decreases with distance like in vacuum. Furthermore, the emissions of several more atomic lines of Cu and Zn atoms from the plume are also found to be enhanced in the same manner in gas ambient. Some physical processes involved in the plume expansion and the possible mechanisms for the enhanced emission of the plume in backing gas are discussed.     

SMAP／INDI／1单重休假随机服务系统的MSP方法

本文借助于马尔可夫骨架过程(MSP)方法研究了SMAP/INID/1单重休假随机服务系统的队长及等待时间等指标的瞬时分布.     

对称正定问题多搜索方向共轭梯度法的收敛性理论

In this paper, we give the convergence and consistence theory of multiple search direction conjugate gradient method (see [10]) and give some upper bound estimations of iterative value and error of our method.     

Fluorescence feedback control of a diode pumped solid state laser

We implement active feedback control in a Q-switched diode-pumped Nd:YVO₄ laser by monitoring the fluorescence intensity from the laser crystal. When the initial inversion level indicated by the detected fluorescence has reached a predetermined value, Q-switching is initiated. The Q-switched pulse energy is stabler with our feedback scheme based on the fluorescence intensity than that with the conventional Q-switching when pumping source is not stable.     

Self-assembly of monodisperse spheres on substrates with different wettability

A new method was developed to fabricate colloidal crystals with controllable shapes by taking advantage of the self-assembly of monodisperse spheres at a solid/gas interface. Different shapes such as ring, hemisphere and crater were derived via a control of the substrate wettability and the suspension concentration. PACS 82.70.Dd; 81.16.Dn; 42.70.Qs; 42.25.Fx     

低温液体流动沸腾数值计算中的相间传热模型

采用双流体模型预测了液氮在垂直管内的流动沸腾过程,着重考察和评价了五个常用的相间传热模型对数值计算结果的影响,找出了最优的相间传热模型;同时,研究还发现相间传热模型对流动压降的预测并无明显影响.     

反应等离子喷涂纳米TiN涂层的显微硬度及微观结构研究

阐述了反应等离子喷涂(RPS)方法的基本思想.利用气体隧道等离子喷枪，通过RPS方法在Q23 5钢基底上成功制备了氮化钛涂层.检测了TiN涂层在不同载荷下的显微硬度，结果显示TiN涂层具有明显的硬度压痕尺寸效应，在高载荷下加工硬化效应较弱.XRD,TEM及HRTEM等分析 表明,通过RPS方法制备得到了纳米TiN涂层，涂层由直径约为50—70nm的TiN晶粒及非晶Ti N所组成. 关键词： 反应等离子喷涂 纳米 氮化钛 微观结构     

Analysis of a statistical multiplexer with generalized periodic sources

We provide solution techniques for the analysis of multiplexers with periodic arrival streams, which accurately account for the effects of active and idle periods and of gradual arrival. In the models considered in this paper, it is assumed that each source alternates (periodically) between active and idle periods of fixed durations. Incoming packets are transmitted on the network link and excess information is stored in the multiplexing buffer when the aggregate input rate exceeds the capacity of the link. We are interested in the probability distribution of the buffer content for a given network link speed as a function of the number of sources and their characteristics, i.e., rate and duration of idle and active periods. We derive this distribution from two models: discrete time and continuous time systems. Discrete time systems operate in a slotted fashion, with a slot defining the base unit for data generation and transmission. In particular, in each slot the link is capable of transmitting one data unit and conversely an active source generates one data unit in that time. The continuous time model of the paper falls in the category of fluid models. Compared to previous works we allow a more general model for the periodic packet arrival process of each source. In discrete time, this means that the active period of a source can now extend over several consecutive slots instead of a single slot as in previous models. In continuous time, packet arrivals are not required to be instantaneous, but rather the data generation process can now take place over the entire duration of the active period. In both cases, these generalizations allow us to account for the progressive arrival of source data as a function of both the source speed and the amount of data it generates in an active period.This work was done while at the IBM T.J. Watson Research Center.This work was done while at the IBM T.J. Watson Research Center.Part of the work was done while visiting the IBM T.J. Watson Research Center.     

Computer generation of character tables of generalized wreath product groups

Algorithms and computer codes in FORTRAN 77 are developed for the computation of characters of generalized wreath product groups through generating function methods. Characters of generalized wreath product groups of symmetric groups are computed in terms of the characters of much smaller composing groups using plethysms of S-functions. The developed codes were tested for many generalized wreath product groups. The character tables of generalized wreath products, S₂[S₃, S₂, S₂] (NMR group of hexane) and S₄[S₃] containing 576 and 31,104 elements, respectively, were constructed as examples.