片状放大器泵浦腔屋脊形反射器性能分析

 用蒙特卡洛光线追迹法模拟和比较屋脊形截面反射器与平板反射器的光传输性能 ,分析反射器构型对泵浦腔性能的影响。三维光线追迹结果显示：在本文设定的腔体构型条件下, 屋脊形反射器腔的光传输效率可达63％,优于平板反射器腔的传输效率(η≤56%)。     

经典分形集测度上估的计算机搜索Ⅱ──对典型例子Sierpinski垫片计数技术和格点跟踪技术的剖析

相同生标题的文献山,通过编码技术导出了义献问给出的Sierninski垫片Hausdorff测度＊”（S的L方估值函数…X）．本文的第一个目的,是利用计数技术,推导出更好的上方估值函数“一及其可计算的过剩近似值。N（）的数学表达式其中l二0．lllZ…2n…,t二k·2－N二0．tltZ…iN,（二0f122··＜N是二进制小数,ZI—…二打．1二0,。三2满足！1＋…十认．1二！。l＝1,＊表示l的整数部分,unitx二1,若xZ地否则unitx二队尽管op00的上述表达式把人们从看图作业和手工计算的状态中解脱出来,但其计算复杂性却仍然是指数爆炸的,对大如10的N…     

共轴抛物镜线聚焦性能的2维分析

 掠入射泵浦方式作为一种全新的X射线激光泵浦方式,采用了共轴抛物镜作为线聚焦器件。利用2维光路追踪程序,计算了高斯光束从5°掠入射角增加到7°时入射到共轴抛物镜上的线聚焦效果。研究发现,掠入射角从5°增加到7°过程中,线聚焦的尺寸随着掠入射角变大,线聚焦长度从6 mm逐渐变长到12 mm,线聚焦宽度从150 μm变到40 μm;掠入射角6.5°～7°可以实现符合实验要求的线聚焦效果,线聚焦尺寸约10 mm×20 μm(最小线聚焦宽度),7°掠入射可以实现较好的线聚焦,基本满足实验的要求。     

A full wave model of high-harmonic EMIC wave propagation in sheared magnetic fields

ABSTRACT

A new dispersion relation, with finite Larmor orbit effects, for oblique propagating electromagnetic ion cyclotron (EMIC) waves in a magnetized plasma medium, is derived including the magnetic shear effect. The approximate, yet accurate, dispersion relation is used to implement the ray tracing model. A parabolic magnetic field is considered to model the geomagnetic field in the magnetosphere. Energetic protons are also considered as resonant particles. The propagation characteristics of EMIC waves in the vicinity of the ion cyclotron resonances are investigated in some detail. The results reveal adiabatic oscillating motion for wave and magnetic field fluctuations where high harmonics limit the wave damping and confines the magnetic fluctuations. For inward propagating EMIC waves we find (1) turning points which depend on the wave launch position, and (2) wave trapped areas playing a role in quasi-coherent wave-particle interaction in agreement with the observational and theoretical studies. This wave trapping is an effective process for particle acceleration in the context of space plasmas.     

Numerical estimation of the influence of joint stiffness on free vibrations of frame structures via the scattering of waves at elastic joints

In the structural design of mechanical products, natural frequencies must be controlled to reduce noise and vibration. In particular, the stiffness of the joints which assemble the structural components affects the natural frequencies. Therefore, it is important to predict the influence of joint stiffness on natural frequencies. Generally, these effects are determined by iterative finite element analyses of assembled structural models. Because this results in high computational costs, the sensitivity of natural frequencies to joint stiffness should be determined by a different approach to make the structural design process more efficient. Therefore, this paper proposes the use of reflection and transmission coefficients of elastic joints to predict the dependency of natural frequencies on joint stiffness. First, we formulate the reflection and transmission coefficients of joint stiffness, and then organize the coefficients using a ray tracing method. These formulations enable us to discuss the mechanisms which determine the natural frequency of a structure based on a wave approach using the phase-closure principle. Therefore, by applying the phase-closure principle to the frame structure, we investigate the formation of bending modes, which suggests that the effects of joint stiffness on natural frequencies correspond to the dependence of the reflection and transmission coefficients on joint stiffness. Therefore, these coefficients are useful indicators for estimating the influence of joint stiffness.     

强激光系统光束质量的非线性退化及补偿研究

为了在强激光非线性传输仿真中综合考虑系统像差等因素,提出了一种基于光线追迹的非线性介质光追方法,并编程实现了线性介质与非线性介质的混合建模。以三片式聚焦系统为例,在系统中加入KDP晶体作为非线性介质,仿真分析了不同激光功率密度下KDP晶体的非线性效应对光束质量的影响。仿真结果表明,当激光功率密度达到1.62×1010 W/cm2时,非线性效应会导致光束质量明显下降。在该仿真结果的基础上提出了在不改变焦面位置的情况下,将元件间隔作为补偿器进行系统优化的方法。优化结果表明,焦斑尺寸较优化前减小2.8μm,规范尺寸下的环围能量提高了16.2%,焦面处的光束质量得到显著改善。     

Aspherical lens shapes for focusing synchrotron beams

Aspherical surfaces required for focusing collimated and divergent synchrotron beams using a single refractive element (lens) are reviewed. The Cartesian oval, a lens shape that produces perfect point‐to‐point focusing for monochromatic radiation, is studied in the context of X‐ray beamlines. Optical surfaces that approximate ideal shapes are compared. Results are supported by ray‐tracing simulations. Elliptical lenses, rather than parabolic, are preferred for nanofocusing X‐rays because of the higher peak and lower tails in the intensity distribution. Cartesian ovals will improve the gain when using high‐demagnification lenses of high numerical aperture.     

基于潮流追踪的电网同步性能优化及鲁棒性分析

采用二阶类Kuramoto模型对电网进行合理建模，分别应用临界同步耦合强度和平均同步误差来描述电网的同步能力和鲁棒性.研究发现，发电机的功率分配对线路的传输功率影响较大，而电网中高负荷线路越多，网络越难同步.基于这一发现，首先在发电机功率均匀分配（EG）方式下，计算出每条线路的传输功率，然后基于潮流追踪算法提出一种发电机功率非均匀分配（TG）方式，即在发电总量不变的情况下，增大枢纽发电机节点的功率，减小边缘发电机节点的功率.该发电机功率分配策略可以在一定程度上降低网络的临界同步耦合强度，减小平均同步误差，改善电网的同步性能和鲁棒性.     

Sulfur‐33 Isotope Tracing of the Hydrodesulfurization Process: Insights into the Reaction Mechanism,Catalyst Characterization and Improvement

The novel approach based on ³³S isotope tracing is proposed for the elucidation of hydrodesulfurization (HDS) mechanisms and characterization of molybdenum sulfide catalysts. The technique involves sulfidation of the catalyst with ³³S‐isotope‐labeled dihydrogen sulfide, followed by monitoring the fate of the ³³S isotope in the course of the hydrodesulfurization reaction by online mass spectrometry and characterization of the catalyst after the reaction by temperature‐programmed oxidation with mass spectrometry (TPO‐MS). The results point to different pathways of thiophene transformation over Co or Ni‐promoted and unpromoted molybdenum sulfide catalysts, provide information on the role of promoter and give a key for the design of new efficient HDS catalysts.     

沙丘粗糙面的二次极化电磁散射

研究了新月形沙丘粗糙面的二次极化电磁散射. 结合射线追踪理论, 由一次散射面元的反射场照射到二次散射面元, 采用基尔霍夫近似推导了二次散射面元的二次极化散射场. 计算结果表明二次极化散射结果在特定的角度和类型范围内有显著影响. 在电磁波射向背风坡时可以发现其同极化散射截面在入射角较大时大于其他入射方向的结果, 入射角在休止角附近时的交叉极化散射截面出现峰值, 以及前后狭长沙丘之间的二次极化散射特别突出. 本文结果可用于反演分析沙漠地区的风场信息. 关键词： 新月形沙丘 二次极化散射 射线追踪 休止角