SPOT BEAM JUDGEMENT ALGORITHM IN LEO SATELLITE BASED ON OPNET

Low earth orbit（LEO）satellite constellation networks have a predominance of global coverage with low propagation delays.A new spot beam judgement algorithm is presented in LEO satellite constellation.At first,judgement of central spot beam is considered.Then the judgement of outlying spot beam is achieved by two algorithms.One is 2-D space judgement algorithm and the other is 3-D space judgement algorithm.Based on these algorithms,an Iridium model implemented on OPNET with dynamic topology nodes and network layer protocols is presented and simulation results are obtained.The simulation results show that the satellite serving time has obviously increased through the method of longest visible time criterion and the equal beam width model is validated.

Consistency of the directionality of partially coherent beams in turbulence expressed in terms of the angular spread and the far-field average intensity

Under the quadratic approximation of the Rytov＇s phase structure function, this paper derives the general closed-form expressions for the mean-squared width and the angular spread of partially coherent beams in turbulence. It finds that under a certain condition different types of partially coherent beams may have the same directionality as a fully coherent Gaussian beam in free space and also in atmospheric turbulence if the angular spread is chosen as the characteristic parameter of beam directionality. On the other hand, it shows that generally, the directionality of partially coherent beams expressed in terms of the angular spread is not consistent with that in terms of the normalized far-field average intensity distribution in free space, but the consistency can be achieved due to turbulence.

Spot beam handover trigger and channel allocation scheme in GEO mobile satellite communication

An effective spot beam handover trigger and channel allocation scheme is proposed for GEO mobile satellite communication based on its characteristic and application. By using both signal strength and terminal location information, necessary handover is triggered promptly and accurately to reduce the negative effect of long signaling delay. Then handover decision is made with the handover queuing and channel allocation strategy. An adaptive channel resource allocation scheme is considered to optimize resource utilization with guarantee of emergency communication, which is significant for emergency rescue and disaster relief. Simulation results show that the proposed scheme prevents unnecessary handover effectively and has favorable adaptability to emergent requirement of satellite communication.

Creation of Multiple Subwavelength Focal Spot Segments Using Phase Modulated Radially Polarized Multi Gaussian Beam

Based on the vector diffraction theory, the effect of complex phase filters on intensity distribution of a radially polarized multi Gaussian beam in the focal region of high NA lens is theoretically investigated. It is observed that a properly designed multi belt complex phase filter can generate subwavelength novel focal patterns including splitting of focal spots and generation of multiple focal spot segments such as eight, six and four focal spots along the optical axis are obtained. We expect that such an investigation is useful for optical manipulation and material processing, multiple high refractive index particle trapping technologies.

多路激光集束的焦斑测试技术

为了实现多路激光集束焦斑测量,给出其时间和空间分辨的特性,搭建了基于成像系统、光电管结合示波器、条纹相机和科学CCD等主要部件组成的焦斑光学测试平台。实验之前,对科学CCD的灵敏度和动态范围及条纹相机增益系数、狭缝宽度、扫描时间等性能参数进行离线测试标定。采用CCD测试多路激光时间积分的集束焦斑空间分布;采用光电管结合示波器及条纹相机对多路激光到达靶点的时间同步进行测试;开展高质量集束焦斑的时间分辨特性测试,获得了光谱色散匀滑光束焦斑精细的时空演化图像。多路激光集束焦斑形态及多路光束时间同步测试为提升高功率激光装置焦斑测试技术和方法提供了支撑。

GPS的现代化进展及启示

目前的全球定位系统(GPS)相关信息内容多,良莠不齐,导致出现一些二手信息误导读者的问题。该文以GPS官方机构近些年公开发布的相关技术文件为依据,梳理了GPS的现代化发展历程,阐述了导航卫星上新增加的民用信号及军用信号、新一代运行控制系统、新型GPS BlockⅢ/IIIF卫星的特点,介绍了GPS Block IIIF上使用的点波束技术,并提出了几点启示。GPS是世界上第一个建成的全球卫星导航系统(GNSS),全球覆盖程度、软件应用、全球用户数量等指标都处于领先地位,它的很多技术发展方向代表当前的主流趋势。GPS建设过程中的经验教训值得我们借鉴,GPS的发展方向值得我们学习和参考。本文内容可供卫星导航行业相关人员参考。

海上无线SDMA接入的波束指向切换技术研究

针对海上用户稀疏且呈现独立动态小型局域网分布特点的通信场景,提出了一种基于相控阵天线的海上无线通信系统,其反向链路基于中心站相控阵天线单个点波束动态波束指向切换实现小站在特定空间方向的波束覆盖,从而实现SDMA接入,具有覆盖范围广、组网灵活等特点,适合于海上动态稀疏的通信场景。主要研究了实现SDMA接入的波束指向切换技术,提出了基于位置信息和时隙分配的波束指向切换方法,该方法根据中心站和小站的实时位置信息解算出波束指向信息并在每个时隙的起始时刻调整波束指向。基于系统级现场可编程门阵列芯片实现了该方法,并通过测试证明了基于位置信息可实现点波束指向对准,且所提方法可在1μs内完成波束指向切换并实现多路高速业务同时回传。

笔形束质子放疗系统质控中束斑大小测量方法对比研究

目的 研究对比笔形束质子放疗系统质控中束斑大小的测量方法。方法 使用Matrixx One二维平面电离室矩阵、Lynx-PT平面闪烁体探测器及XRV-124锥形闪烁体探测器-三种不同种类、不同形状的探测器对质子放疗系统中不同能量的质子束斑大小进行测量,并将测量结果与加速器验收时束斑大小结果进行对比。结果 Matrixx One的束斑大小测量结果与验收结果相比偏差较大,其中230 MeV时的最大偏差达到41.25%。而Lynx-PT和XRV-124的束斑测量结果与验收结果相比,最大偏差分别为-7.35%和3.69%,Lynx-PT测量结果相较于验收结果系统性偏小。结论 Lynx-PT和XRV-124均适用于质子放疗系统束斑大小的测量,Matrixx One适用于束斑尺寸较大的质子放疗系统,相较于Lynx-PT和Matrixx One, XRV-124在旋转治疗室单能单点束斑尺寸测量中更有优势。

基于磁透镜结构参数的电子枪磁聚焦特性分析

磁透镜是电子枪的重要组成部分,其结构会影响磁聚焦性能,从而影响束斑直径与电子束焊接质量。文章以国产ZD-VEBW系列高压电子束焊接设备电子枪为研究对象,构建电子枪束源与电磁聚焦结构的物理模型,并借助CST平台,仿真分析了球差影响下的束斑形貌和不同聚焦电流下磁透镜铁壳内径、铁壳开口对束斑直径的影响。设计环形挡板实现了磁透镜铁壳内径、铁壳开口参数的调整,并进行聚焦电流变化下的焊接实验研究。实验结果表明:磁透镜结构参数的合理设计可以达到更优的磁聚焦特性、更小束斑直径与更大的焊缝深宽比,实验验证了仿真结果的正确性,文章的研究对国产ZD-VEBW系列高压电子枪磁透镜结构的设计和该系列电子枪焊接质量的提升提供了理论和实验指导。

板-梁耦合结构振动功率流与声辐射特性研究

针对车身低频结构噪声控制问题,首先以车身典型板-梁耦合结构简化模型为研究对象,推导出一种以CBAR焊点单元轴向位移响应和速度响应为计算参数的净功率流简化计算公式。然后以振动净功率流和等效辐射声功率(ERP)为评价参数,研究了板-梁耦合结构振动辐射噪声产生机理,从中可知不可忽视焊点对板、梁之间功率流传递的影响,而且合理设计焊点布局有利于提高辐射噪声水平。最后,基于净功率流简化计算公式,提出了一种焊点布局拓扑优化方法,结合板-梁耦合结构振动辐射噪声控制算例验证了其有效性。上述研究成果可为车身NVH品质的提高提供一种新的思路和方法,具有良好的工程实用价值和应用前景。

济南市庆祝中国共产党成立100周年大型文艺演出灯光舞美设计实施

本文详细介绍了济南市庆祝中国共产党成立100周年大型文艺演出灯光舞美设计思路、设计方案、设计特点及艺术处理。舞台集独唱、合唱、话剧、舞蹈、戏曲、杂技等多种艺术形式于一体,融合了声、光、电、虚拟植入等技术手段,呈现出一幅建党百年,波澜壮阔的历史画卷。

Variable spot size optical system for a dual-wavelength laser therapy device

The majority of existing high-power laser therapeutic instruments employ a single wavelength for a single target;thus,they do not meet the requirements for clinical treatment.Therefore,this study designs an optical system for a dual-wavelength high-power laser therapeutic device with a variable spot size.The waist of the short arm of the optical cavity and the G1G2 parameter(G-parameter equivalent cavity method)is calculated using MATLAB software,the spot size and divergence angle on the lens are calculated using an ABCD matrix,and the distance between the treatment spot at different spot sizes and the transformation lens is calculated in order to design the treatment handpiece.Experiments are conducted to analyze the stability at an output power of 532 nm before beam combination and the power loss after beam combination.The results show that the output power stability of the 532-nm beam varies by less than 2%over 150 min,and the loss of both wavelengths is less than 20%,which meets the clinical requirements of the system.The safety performance can meet the requirements of national general standards for medical electrical safety.The proposed dual-wavelength laser therapy instrument has both visible wave and near-infrared wave characteristics;thus,it can accurately target both superficial vessels and vessels with a larger diameter and deeper position.This therapeutic device has the advantages of simple operation,stable and reliable laser output,high security and strong anti-interference ability,and meets the comprehensive clinical treat-ment demands of vascular diseases.

SIMULATION OF THE SPOT SIZE AT DISPLAY TUBE SCREEN

Based on a description of several methods of how to determine the resolutionat display tube screen,and the transfer relation between them,this paper lays emphasis ondiscussing the spot size at display screen by way of the electronic optic CAD.A set of pre-cise and reasonable calculation models are presented,and thomputcr simulation ismade.It is shown that the calculation results coincide with the experimental ones.

The Progress of a Microbeam Facility in the Institute of Plasma Physics

The progress of a microbeam facility in the Institute of Plasma Physics was discussed in this paper. This kind of equipment can supply single-particle beam which may be implanted into cells in micrometer-radius and measured by a new outstanding detector among global microbeam systems. Measurements by some plain targets showed that the highest current after the accelerator tube can be larger than 20 /μA, the H_2^+ current before the second bending magnet is near 0.9 /μA, the current after the second bending magnet is near 0.8 μA, and the current of the beam line (after a 2-mm diameter aperture) is near 0.25 nA which is enough for the single-particle microbeam experiment. It took scientists 3 months to do their microbeam experiment after setting up the accelerator beam line and get the microbeam from this equipment. Two pre-collimators were installed between the 2-mm diameter aperture and the collimator to survey the beam. Tracks on the CR39 film etched in the solution of NaOH showed that the beam can go through the collimator including a 10 μm diameter aperture and the 3.5 μm thick vacuum sealing film (Mylar). A new method, which is called optimization of the beam quality, was put forward in this paper, in order to get smaller diameter of beam-spot in microbeam system.

Algorithm of far-field centre estimation based on phase-only matched filter

Estimation of the far-field centre is carried out in beam auto-alignment. In this paper, the features of the far-field of a square beam are presented. Based on these features, a phase-only matched filter is designed, and the algorithm of centre estimation is developed. Using the simulated images with different kinds of noise and the 40 test images that are taken in sequence, the accuracy of this algorithm is estimated. Results show that the error is no more than one pixel for simulated noise images with a 99% probability, and the stability is restricted within one pixel for test images. Using the improved algorithm, the consumed time is reduced to 0.049 s.

挑臂式钢箱梁面板-中纵梁构造细节疲劳性能研究及构造参数分析

为研究挑臂式面板-中纵梁构造细节的疲劳特性,运用大型通用有限元软件ANSYS建立精细化分析模型,结合热点应力法、Palmgren-Miner线性累积损伤理论及雨流计数法对该构造细节进行横纵向疲劳车加载应力结果计算分析,并开展构造参数影响研究。研究结果表明,轮载作用下该细节经历多次应力循环,应力影响线具有明显的轴重识别效果,采用横向应力/竖向应力研究其疲劳特性是合适的;该细节面板焊趾较腹板焊趾应力水平高,更易发生疲劳开裂,而腹板处焊趾具有无限寿命;面板厚度从12 mm增加到20 mm,面板焊趾和腹板焊趾热点应力分别降低55%和40%,中纵梁腹板与附近U肋的间距从250 mm增加到400 mm,面板焊趾和腹板焊趾热点应力增幅达61%和58%,而中纵梁腹板厚度从12 mm变化到20 mm,面板焊趾处和腹板焊趾处的热点应力基本不变,维持在53 MPa和22 MPa左右。建议在充分考虑安全性和经济性的情况下,合理选择面板厚度及中纵梁腹板与附近U肋的间距以提高面板-中纵梁构造细节的疲劳寿命。

基于数学形态学的小孔径高斯光束光斑半径测量方法

为减小现有的激光光束光斑半径测量方法的测量误差,设计基于数学形态学的小孔径高斯光束光斑半径测量方法。对小孔径光斑几何特征进行划分,计算探测误差,获取光斑能量在探测器光敏面上的均匀分布函数,得到质心点到光斑轮廓点的距离。建立高斯光束光斑轮廓模型,获取位置轮廓的灵敏度,并计算其在某光斑点位的能量值,通过质心点的误差函数,得到光斑点的轮廓函数。基于数学形态学设计光斑半径测量方法,计算不同方向与尺度元素在对角线上的梯度幅值,得到激光光束光斑的半径长度。分析光照强度与发射角对测量精度的影响,实验结果显示:在该激光光束下,光照强度为80且发射角度为1.8时,测量误差最小。对比4种测量方法的测量误差,由数据可知,数学形态学的测量方法误差最小,可见该方法优于其他测量方法。

基于遗传算法的低轨卫星点波束规划方法

针对低轨卫星“等通量”覆盖要求,提出了一种点波束规划方法。该方法结合遗传算法和逐层规划的思路,得出环形小区各层点波束最优的数目和大小,同时可以得到满足任意空间区域方向性覆盖要求的最优分层布局。以1000 km高度的低轨卫星为例进行分析,同典型的点波束规划方法相比,与理想“等通量”的误差由6 dB减小为0.2 dB,仿真结果表明该方法具有更高的满意度。

束斑直径和能量密度对锆石U-Pb定年准确度的影响研究

激光剥蚀电感耦合等离子体质谱(LA-ICP-MS)是锆石U-Pb定年常用的方法之一。应用LA-ICP-MS进行锆石U-Pb定年的过程中,束斑直径的大小和能量密度的高低是影响定年准确度的两个关键因素。本文开展了应用LA-ICP-MS在不同束斑直径和能量密度条件下对锆石标样91500和GJ-1 U-Pb定年结果准确度的对比研究,旨在优化LA-ICP-MS锆石U-Pb定年的方法,提高分析准确度,也为其他实验室开展类似的研究工作提供一定的借鉴。实验结果表明:在剥蚀频率、扫描速度、载气流速保持不变的前提下,当能量密度固定,随着剥蚀束斑直径从25μm增大至65μm的过程中,锆石91500和GJ-1在互为标样和盲样的条件下实测年龄结果与推荐值之间的相对误差(RE)不断减小(RE分别为0.61%、0.41%、0.13%和0.08%),即增加束斑直径降低了相对误差,提高了定年准确度。而当束斑直径固定时,能量密度≤3.5 J/cm^(2)时,随着能量密度不断增大,实测年龄结果与推荐值之间的相对误差逐渐减小(RE分别为8.69%、3.48%、3.95%、4.16%和0.41%),定年准确度逐渐增加;但是当能量密度大于3.5 J/cm^(2)时,能量密度增大导致剥蚀速率显著增大,在深度方向上的分馏效应明显增加,对比3.5 J/cm^(2)条件下,此时的实测年龄结果与推荐值之间的相对误差增大(RE分别为2.40%和0.83%),定年准确度降低。因此,在实际测试中,考虑到样品大小和尽可能少地对样品进行破坏,合理的能量密度和束斑大小可以有效提高定年的准确度。

管径渐缩式静电透镜束流动力学研究

电透镜是横向压缩带电粒子束的常用技术手段,在获得高空间分辨、高亮度等高品质聚焦电子束/离子束/正电子束方面发挥着重要作用。针对低能、大束斑带电粒子束的聚焦过程,本文设计了基于管径渐缩式简单电极结构的电透镜聚焦方法,采用SIMION模拟结合电子束实验的方式对该电透镜中涉及的关键技术进行了研究,研究了透镜聚焦效率及聚焦束斑等核心性能的影响因素及分布规律。结果显示:通过合理布局透镜结构和优化电压配置,能够实现对初始大口径电子束的有效压缩,同时确保聚焦效率达到80%以上。本文提出的这种简单电极结构电透镜聚焦方法,具有显著的横向压缩优势,在反应堆正电子源等多束流聚焦场景中具有广泛的应用前景。