8 mm二次谐波回旋速调管放大器双阳极磁控注入电子枪的设计

 计算了8 mm二次谐波回旋速调管双阳极电子枪的设计参数，根据这些参数，采用EGUN软件进行模拟和优化，设计出了一只双阳极磁控注入电子枪，该枪的电子束纵横速度比为1.45，速度零散为5.4%，并讨论了电极形状、磁场分布、电流、控制极电压和第二阳极电压对电子注性能的影响，结果发现电子注对这些影响因子非常敏感，设计中应对它们进行充分优化。     

二极管泵浦Nd:YAG棒双通放大器技术

二极管泵浦NdYAG棒双通放大器采用两个峰值功率6.5 kW激光泵浦模块作为泵浦源.每个激光泵浦模块由81个二极管激光器组成,NdYAG棒直径为6 mm,Nd掺杂质量分数1%.在两个封装方式和结构一致的激光泵浦模块之间采用光学像传递和插入90°石英旋转片进行退偏补偿.在重复频率400 Hz,谐振腔输出单脉冲能量6 mJ时,双通输出400 mJ,激光器光-光转换效率为12.3%,光束质量4.6,脉宽15 ns.     

掺镱双包层光纤放大器分布泵浦方式下的优化算法

 利用平均反转率迭代算法计算掺镱双包层光纤放大器分布泵浦方式下的稳态速率方程组，并采用遗传算法对分布泵浦功率的大小和每段光纤长度同时进行优化。评估函数中引入了每段光纤中最高温度的标准方差，以确保每段光纤中的最高工作温度是相同的。通过优化，7段泵浦的最高温度和标准方差分别为126.34 ℃和1.95 ℃ ，8段泵浦条件下的最高温度和标准方差分别为119.76 ℃和2.12 ℃。而未经优化的7段泵浦的最高温度和标准方差分别为147.12 ℃和21.37 ℃，8段泵浦条件下的最高温度和标准方差分别为139.95 ℃和20.83 ℃。计算结果表明：泵浦方式的优化降低了最高温度和标准方差，实现了光纤中温度分布的均匀性，并且通过增加泵浦段数可以进一步降低最高温度和平坦温度分布。     

Noise performance analysis of bi-directionally pumped distributed fiber Raman amplifiers with consideration of fiber nonlinearity and its impact on EDFA output OSNR

Under small-signal assumption, equivalent noise figure normalized by fiber nonlinearities (NENF) of bi-directionally pumped distributed fiber Raman amplifiers (BiDFRA) is derived. Amplified spontaneous Raman scattering noise and double Rayleigh scattering noise are both included. The relation between NENF and Raman gain, forward Raman gain percentage is investigated under different polarization factor and Rayleigh scattering coefficient. It agrees well with numerical simulation results. Based on the analytical expression, the optical signal-to-nose ratio (OSNR) improvement of hybrid pre-BiDFRA/erbium-doped fiber amplifier (EDFA) compared with sole EDFA is studied. It is shown that there is an optimum Raman gain and forward Raman gain percentage to maximize the OSNR improvement. Finally, some guidelines on BiDFRA design are proposed.     

Periodic maintenance and repair rate control in stochastic manufacturing systems

In this paper, we consider a periodic preventive maintenance, repair, and production model of a flexible manufacturing system with failure-prone machines, where the control variables are the repair rate and production rate. We use periodic preventive maintenance to reduce the machine failure rates and improve the productivity of the system. One of the distinct features of the model is that the repair rate is adjustable. Our objective is to choose a control process that minimizes the total cost of inventory/shortage, production, repair, and maintenance. Under suitable conditions, we show that the value function is locally Lipschitz and satisfies an Hamilton-Jacobi-Bellman equation. A sufficient condition for optimal control is obtained. Since analytic solutions are rarely available, we design an algorithm to approximate the optimal control problem. To demonstrate the performance of the numerical method, an example is presented.Research of this author was supported by the Natural Sciences and Engineering Research Council of Canada, Grant OGP0036444.Research of this author was supported in part by the University of Georgia.Research of this author was supported in part by the National Science Foundation, Grant DMS-92-24372.     

Novel formulations of vitamins and insulin by nanoengineering of polyelectrolyte multilayers around microcrystals

Microcapsules loaded with vitamin K3 (VK3), biotin, or insulin were prepared by using a novel coating technology based on the layer-by-layer (LbL) deposition of oppositely charged polyelectrolytes onto microcrystal templates. This produced multilayered, polymeric shells of varying thickness around the crystalline cores. Dissolution of the core material (VK3 with ethanol, biotin with basic solution, and insulin with acidic solution), resulted in its release through the shells. Microelectrophoresis was employed to monitor the microcrystal coating process; confocal laser scanning microscopy (CLSM) and atomic force microscopy (AFM) were used to verify multilayer coating and the formation of hollow polymer shells following removal of the microcrystal templates. The release rates of both VK3 and insulin decreased as the wall thickness (the number of polyelectrolyte layers deposited onto the microcrystal cores), increased. The release time could be varied by a factor of more than ten, depending on the number of polyelectrolyte layers applied. Following the addition of 70 mass % ethanol, the solubility of VK3 increased by as much as 170-fold, resulting in an increased rate of VK3 release. By selecting appropriate polymer materials for the shells, and by controlling the number of polyelectrolyte layers applied, shells of various thickness, stiffness, aqueous solubility, dispersibility, biocompatibility, and permeability can be constructed.     

Calculation of the Electron Efficiency for a Two-Cavity Gyroklystron Amplifier by Using a Self-Consistent Code

The beam-wave interaction in a Ka-band, two-cavity fundamental gyroklystron amplifier is studied by using a self-consistent nonlinear simulation code. The electron efficiency for this gyroklystron amplifier is calculated, and the effect of various parameters, such as beam voltage, beam current, electron guiding center radius, velocity pitch ratio and drift tube length on the electron efficiency is discussed in detail.     

Continuous-Time Controlled Markov Chains with Discounted Rewards

This paper studies denumerable state continuous-time controlled Markov chains with the discounted reward criterion and a Borel action space. The reward and transition rates are unbounded, and the reward rates are allowed to take positive or negative values. First, we present new conditions for a nonhomogeneous Q(t)-process to be regular. Then, using these conditions, we give a new set of mild hypotheses that ensure the existence of -optimal (0) stationary policies. We also present a martingale characterization of an optimal stationary policy. Our results are illustrated with controlled birth and death processes.     

Controlled Wild Algebras

The controlled wild algebra is introduced, a covering criterionfor a finite-dimensional algebra to be controlled wild is given,and this criterion is applied to the algebras with radical squarezero, algebras with zero relations, local algebras and finitep-group algebras. 2000 Mathematical Subject Classification:16G20, 16G60.     

Noise Stability of SIS Receivers

There is a strong interest in the submillimeter astronomy community to increase the IF bandwidth of SIS receivers in order to better facilitate broad spectral linewidth and continuum observations of extragalactic sources. However, with an increase in receiver IF bandwidth there is a decrease in the mixer stability. This in turn effects the integration efficiency and quality of the measurement. In order to better understand the noise mechanisms responsible for reducing the receiver stability, we employed a technique first described by D.W. Allan and later elaborated upon by Schieder et al. In this paper we address a variety of factors that degrade the noise stability of SIS receivers. The goal of this exercise is to make recommendations aimed at maximizing SIS receiver stability.