掺Yb3+光纤激光器的特性与设计

 从速率方程出发，对波长为980nm的激光泵浦掺Yb^{3+光纤激光器进行数值模拟，全面分析激光器阈值功率、输出激光功率、增益等重要参数与泵浦功率、光纤长度、腔镜反射率、掺杂浓度等参量之间的关系。采用高浓度掺Yb3+光纤对环形光纤激光器做了初步实验研究，所得结论与实验模拟结果基本一致。}     

A flux-based modified method of characteristics

A flux-based modified method of characteristics (MMOC) methodology in 1D is described which has the following properties: unconditional stability (though explicit), exact answers for integer CFL (Courant) numbers, completely conservative (locally and globally) and able to utilize various flux limiters and various characteristic- (trajectory-) tracking algorithms. The use of characteristics based on cell-wise constant characteristic velocities results in considerable code simplification, and Van Leer's MUSCL is an accurate and cost-effective flux limiter. For CFL≥1 the flux limiter is applied only to the non-integer part of CFL, whereas the integer part is exact for constant velocities; therefore accuracy improves with larger CFL. It is not a cheap algorithm, although explicit, because the operation count per time step increases with the integer part of CFL, but it is much more accurate than the commonly used implicit upstream differencing. This flux-based MMOC method is well suited for groundwater flow calculations in which large local Courant numbers arise owing to grid clustering.     

“强光一号”预脉冲气体开关特性研究

 对“强光一号”加速器预脉冲气体开关特性进行了初步研究，估算开关固有电容等电气参数，给出了开关的直流自击穿特性。在此基础上，针对“强光一号”加速器预脉冲的特点，选取加速器中的预脉冲开关的工作间距及工作气压，在开关间距为24mm，气压为6.0×10⁵Pa时，成功的抑制了预脉冲。     

A MIXED FINITE ELEMENT METHOD FOR THE TRANSIENT BEHAVIOR OF A SEMICONDUCTOR DEVICE

The transient behavior of a semiconductor device is described by a system of three quasilinear partial differential equations. One is elliptic in form for the electric potential and the other two are parabolic in form for the conservation of electron and hole concentrations. The electric potential equation is discretized by a mixed finite element method. The electron and hole density equations are treated by a Galerkin method that applies a variant of the method of characteristics to the transport terms. Optimal order convergence analysis in L2 is given for the proposed method.     

The Dependence of Gliding Arc Gas Discharge Characteristics on Reactor Geometrical Configuration

The dependence of gliding arc gas discharge characteristics, including gas flow field, arc column motion and volatile organic compounds (VOCs) decomposition performance, on reactor configuration parameters was investigated based on numerical simulation and laboratory experimental findings. For a given supply voltage (10 kV) and a certain nozzle outlet diameter (1.5 mm), increasing the electrodes gap (1–4 mm) or decreasing vertical distance between electrode throat and nozzle outlet (25–10 mm) will increase the gas flow rate through the electrode throat, the gas velocity in the plasma region, the arc column velocity, the maximum attainable position of the arc column and the electrical power consumption, also, higher VOCs decomposition rate and lower specific energy requirement are observed according to the n-butane and toluene decomposition experiments.     

浙江遂昌好川墓地五件出土绿松石珠的科技分析

目前现代测试技术发展较快,为古代玉器的加工技术、产源研究提供了无损研究手段.利用红外光谱和能量色散X射线荧光光谱技术(EDXRF),对浙江省遂昌县好川墓地中M52号墓出土的五件绿松石珠进行无损测试,期望判断其可能的产地来源.红外谱学特征显示,3468和3514 cm-1处可见红外吸收锐谱带,是由于ν(O H)伸缩振动所...     

黄土边坡剥落病害的发育特征及其发育程度评价

黄土边坡剥落病害影响黄土边坡的坡面稳定及环保美观。以黄延高速公路黄土路堑边坡剥落病害为背景,采用现场调查结合理论分析的方法,研究了黄土边坡剥落病害的发育特征; 将发育特征与可拓工程方法相结合,实现了黄土边坡剥落病害发育程度的评价。研究结果表明:(1)黄土中节理裂隙分布密度大于6条 ·m^-1 时,极易发生剥落,小于2条 ·m^-1 时,基本不发生剥落。黏粒含量大于15%时,剥落病害越易发生,小于5%时,不易发生剥落。黄土边坡开挖量越大、剥落产生的厚度越大。黄土边坡坡体节理裂隙促使剥落病害的发生。当黄土边坡单级坡高大于10m、坡度大于60°时,容易出现重力型剥落病害; 而单极坡高小于4m、坡度小于50°时,边坡坡面很少出现剥落病害。(2)针对影响黄土边坡剥落病害发育因素的复杂性和模糊性,重视实践中的经验,将可拓工程方法与黄土边坡剥落发育程度评价相结合,提出了黄土边坡剥落发育程度的物元关联函数及物元关联度的计算方法。建立了适合可拓学理论的黄土边坡剥落发育程度的分类标准,实现了定性与定量评价结合。     

R600a/R23两级自动复叠制冷系统降温特性研究

以R600 a/R23两级自动复叠制冷系统为例,研究了不同配比条件下,制冷系统中的特征点温度在降温过程中变化特性。试验表明混合制冷剂的配比是自动复叠制冷系统关键问题,通过控制关键点的温度可以判断混合制冷剂的最佳配比。     

木质素改性高分子材料研究进展

木质素改性高分子材料的基础研究和应用开发极为活跃.在材料中引入木质素,不仅可提高材料的性能,还能降低成本,产生可观的经济效益.本文综述了木质素改性高分子材料的最新研究成果,并由此归纳出木质素结构与材料性能之间的关系,提出了基于控制木质素多级结构的材料设计和性能优化的思路.     

不可压核废料污染问题沿特征线的混合有限元方法

本文对具有分子弥散项的不可压核废料污染问题提出了沿特征方向的混合元离散格式，即对流动方程采用混合元格式，而对浓度方程和传热方程沿特征方向有限元离散。我们的论证表明：该格式具有最优收敛精度；时间步长△ｔ的前置常数仅依赖二阶方向导数；对△ｔ的限制由标准元方法中的△ｔ＝ｏ（ｈ）＾［２］减弱为△ｔ＝Ｏ（ｈ）。