基于Unity 3D的船舶压缩空气系统的虚拟设计

针对目前船舶空气压缩仿真训练系统大多采用半物理仿真与二维软件界面仿真相结合方式训练效果不佳的问题,将虚拟现实技术引入到船舶压缩空气系统的仿真设计;设计一套基于Unity 3D的船舶压缩空气系统,实现虚拟仿真程序和三维虚拟场景的实时交互,生成一个逼真的三维视觉、听觉、触觉的感官世界,加强培训人员的沉浸感,从而获得一种置身于真实环境中的感受;系统可供学员无限制反复训练,节省系统的维护费用,规避实物操作设备中可能出现的各种风险,提高训练效果。     

基于虚拟仪器技术和网络的综合实验控制系统设计

为实现大型物理实验现场复杂多样的仪器控制,分析了物理实验的特点、过程、环境及仪器控制功能需求,利用虚拟仪器技术、计算机网络技术和数据库技术,建立了一套集成硬件和软件的综合控制管理信息系统,实现记录系统中示波器状态远程批量设置及波形数据自动采集、控制探测系统的高压电源并发加压或退压、保障各测试项目间测试仪器之间时间关联、监控UPS电量和远端现场图片或视频状态。给出了系统的关键的设计思路,列举了某型示波器控制的通用控制代码。结果表明,系统达到了一人总控或多人分权控制实验过程中多种多台仪器的目标,方便快捷地实现不同品牌不同类型示波器的相同功能。     

On the performance of a virtual user pairing scheme to efficiently utilize the spectrum of unpaired users in NOMA

This paper evaluates the performance of a virtual user pairing scheme that efficiently utilizes the spectrum of unpaired users in non-orthogonal multiple access (NOMA), termed as VP-NOMA. The scheme aims at utilizing the frequency bands of those users which remain unpaired due to the non-uniform distribution of users in a cellular area. We consider a case where the cell edge users are more than the cell center users, so that complete one-to-one correspondence does not exist between all cell center and cell edge users to be accommodated/paired using conventional NOMA (C-NOMA) user pairing. Thus, some cell edge users remain unpaired, and are served using conventional multiple access (OMA) schemes. In such scenario, VP-NOMA pairs a single cell center user with two or more clustered (closely located) cell edge users over non-overlapping frequency bands, thus enabling the cell center user to efficiently use the frequency bands of these previously unpaired cell edge users. Performance of VP-NOMA in terms of ergodic sum capacity (ESC), outage probability (OP), and outage sum capacity (OSC), is analyzed through comprehensive mathematical derivations and simulations for a generalized system model. Moreover, the mathematical analysis is validated through close concordance between analytical and simulation results of ESC, OP, and OSC.     

Linearized iterative method for determining effects of vessel attitude error on single-beacon localization

Single-beacon localization is an advanced (and relatively new) acoustic localization technique. The traditional single-beacon uses non-linear trajectories to localize underwater vessels, which has notable drawbacks in actual underwater operations. To mitigate the limitations associated with non-linear trajectories, we developed an innovative single-beacon localization with linear trajectories. The traditional linearized least square method is not suited to linear trajectories, so we developed a linearized iterative method that includes a virtual long baseline array to analyze the effects of vessel attitude error on single-beacon localization results. We simulated the forward velocity, number of beacons, distance measurement period, and vessel heading impact on horizontal localization. The results showed that according to the proposed analysis method, localization precision is strongly dependent on vessel attitude error.     

Simple laser vision sensor calibration for surface profiling applications

Due to the relatively large structures in the Oil and Gas industry, original equipment manufacturers (OEMs) have been implementing custom-designed laser vision sensor (LVS) surface profiling systems as part of quality control in their manufacturing processes. The rough manufacturing environment and the continuous movement and misalignment of these custom-designed tools adversely affect the accuracy of laser-based vision surface profiling applications. Accordingly, Oil and Gas businesses have been raising the demand from the OEMs to implement practical and robust LVS calibration techniques prior to running any visual inspections. This effort introduces an LVS calibration technique representing a simplified version of two known calibration techniques, which are commonly implemented to obtain a calibrated LVS system for surface profiling applications. Both calibration techniques are implemented virtually and experimentally to scan simulated and three-dimensional (3D) printed features of known profiles, respectively. Scanned data is transformed from the camera frame to points in the world coordinate system and compared with the input profiles to validate the introduced calibration technique capability against the more complex approach and preliminarily assess the measurement technique for weld profiling applications. Moreover, the sensitivity to stand-off distances is analyzed to illustrate the practicality of the presented technique.     

Effect of external magnetic field on critical current for the onset of virtual cathode oscillations in relativistic electron beams

In this Letter we research the space charge limiting current value at which the oscillating virtual cathode is formed in the relativistic electron beam as a function of the external magnetic field guiding the beam electrons. It is shown that the space charge limiting (critical) current decreases with growth of the external magnetic field, and that there is an optimal induction value of the magnetic field at which the critical current for the onset of virtual cathode oscillations in the electron beam is minimum. For the strong external magnetic field the space charge limiting current corresponds to the analytical relation derived under the assumption that the motion of the electron beam is one-dimensional [D.J. Sullivan, J.E. Walsh, E. Coutsias, in: V.L. Granatstein, I. Alexeff (Eds.), Virtual Cathode Oscillator (Vircator) Theory, in: High Power Microwave Sources, vol. 13, Artech House Microwave Library, 1987, Chapter 13]. Such behavior is explained by the characteristic features of the dynamics of electron space charge in the longitudinal and radial directions in the drift space at the different external magnetic fields.     

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在"星光Ⅱ"钕玻璃激光装置上,开展了脉宽约0.8ns、能量~70J的351nm激光在不同条件下辐照Au盘靶的实验,研究了激光光束质量对受激布里渊散射(SBS)谱的影响。SBS散射光谱测量结果表明,在激光束未匀滑条件下,SBS散射谱范围为352~360nm;在采用透镜列阵将激光束匀滑聚焦的条件下,激光等离子体密度变得更加均匀,SBS散射光谱范围变为351~351.5nm。实验数据为透镜列阵对光束的匀滑效果提供了直接支持。     

用于开口声辐射控制的虚拟声屏障实现 方法及机理研究*

建筑物通常留有开口以便人员物料的进出及室内的自然通风采光,但这些开口也是噪声传播的途径。传统被动噪声控制方法需要将开口封闭,且对低频噪声的控制效果不好,故引入有源噪声控制技术降低室内声源通过开口的声辐射。基于惠更斯原理,均布开口的次级源和误差传声器构成的平面型虚拟声屏障可以实现对开口声辐射的有效控制,数值仿真和实验已证明其有效性。将次级源安装在开口边界更有利于保留开口的功能且方便实际安装,但这样的单层边界虚拟声屏障降噪效果存在上限,仅能在低频段实现全局控制。和单层边界次级源相比,双层边界次级源可显著提高降噪量和有效降噪频率上限。该文回顾了开口声辐射有源控制的相关工作,并讨论了未来可能的研究方向。     

基于虚拟仪器的人体皮肤组织吸收光谱检测平台

本文运用光电无损检测技术,采用皮外反射式测量方法,通过光纤光谱仪和虚拟仪器构建人体皮肤组织吸收光谱检测平台.该平台适合于光子-组织相互作用基础研究及激光美容临床检测,可协助医师进行病理诊断和病变程度判别.文中给出几个吸收光谱的检测结果.     

基于虚拟样机与模糊可靠性的弹簧优化方法

智能塑壳断路器操作机构的驱动弹簧是极其重要的零件,对断路器的主要性能有很大影响,为了提高断路器的分断能力和使用寿命,提出一种虚拟样机与模糊可靠性相结合的弹簧优化方法。首先利用断路器操作机构虚拟样机参数化模型,以手柄操作力为约束条件,动触头主轴平均分断角速度最大为目标函数,优化弹簧刚度系数。然后以弹簧模糊可靠度为约束条件,弹簧质量最轻为目标函数,建立弹簧的模糊可靠性优化数学模型,优化弹簧的结构参数。优化后的弹簧疲劳强度可靠度为0.999 9,质量减轻13.33%,动触头分断速度提高20.81%。符合智能断路器的高可靠度、小型化和分断能力强的要求。