On high-frequency noise scattering by aerofoils in flow

Abstract A theoretical model is developed for the sound scattered when a sound wave is incident on a cambered aerofoil at non-zero angle of attack. The model is based on the linearization of the Euler equations about a steady subsonic flow, and is an adaptation of previous work which considered incident vortical disturbances. Only high-frequency sound waves are considered. The aerofoil thickness, camber and angle of attack are restricted such that the steady flow past the aerofoil is a small perturbation to a uniform flow. The singular perturbation analysis identifies asymptotic regions around the aerofoil; local 'inner' regions, which scale on the incident wavelength, at the leading and trailing edges of the aerofoil; Fresnel regions emanating from the leading and trailing edges of the aerofoil due to the coalescence of singularities and points of stationary phase; a wake transition region downstream of the aerofoil leading and trailing edge; and an outer region far from the aerofoil and wake. An acoustic boundary layer on the aerofoil surface and within the transition region accounts for the effects of curvature. The final result is a uniformly-valid solution for the far-field sound; the effects of angle of attack, camber and thickness are investigated. © 2013 Cambridge University Press.

Improving intermediate pressure turbine performance by using a nonorthogonal stator

Intermediate pressure (IP) turbines in high bypass ratio civil aeroengines are characterized by a significant increase in radius and a low aspect ratio stator. Conventional aerodynamic designs for the IP turbine stator have had leading and trailing edges orthogonal to the hub and casing end walls. The IP turbine rotor, however, is stacked radially due to stress limits. These choices inevitably lead to a substantial gap between the IP stator and rotor at the outer diameter in a duct that is generally diffusing the flow due to the increasing radius. In this low Mach number study, the IP stator is redesigned, incorporating compound sweep so that the leading and trailing edges are no longer orthogonal to the end walls. Computational investigations showed that the nonorthogonal stator reduces the flow diffusion between the stator and rotor, which yields two benefits: The stator trailing edge velocity was reduced, as was the boundary layer growth on the casing end wall within the gap. Experimental measurements confirm that the turbine with the nonorthogonal stator has an increased efficiency by 0.49%, while also increasing the work output by 4.6%, at the design point. © 2014 by ASME.

基于神经网络的机器人视觉伺服控制

视觉伺服可以应用于机器人初始定位自动导引、自动避障、轨线跟踪和运动目标跟踪等控制系统中。传统的视觉伺服系统在运行时包括工作空间定位和动力学逆运算两个过程,需要实时计算视觉雅可比矩阵和机器人逆雅可比矩阵,计算量大,系统结构复杂。本文分析了基于图像的机器人视觉伺服的基本原理,使用BP神经网络来确定达到指定位姿所需要的关节角度,将视觉信息直接融入伺服过程,在保证伺服精度的情况下大大简化了控制算法。文中针对Puma560工业机器人的模型进行了仿真实验,结果验证了该方法的有效性。

基于对称极多项式曲线的移动机器人平滑路径生成

详细分析了对称极多项式曲线作为移动机器人跟踪路径所具有的各种优异的几何特性,并将对称极多项式曲线应用于移动机器人的平滑路径生成,提高了移动机器人的灵活性,同时将有助于改善移动机器人的路径跟踪精度,扩展移动机器人的应用领域.

一种面向无线传感器网络协同任务分配的动态联盟更新机制

在面向目标追踪等应用的无线传感器网络研究中,协同任务分配机制的研究是很重要的。基于动态联盟机制的协同任务分配方法是事件触发的,适用于任务出现频率相对较低的大规模无线传感器网络。本文在基于动态联盟机制研究的基础上,首先引入了联盟覆盖范围和休眠盟员的概念,进一步消除针对同一任务的检测传感器节点的冗余,降低系统的能量消耗;而后又给出了一种动态联盟的更新机制,以保证动态联盟执行任务时的连续性,在一定程度上保证网络的检测性能。最后通过仿真,从系统总能耗、目标捕获率和检测误差标准差等方面检验了算法的性能,并给出了缓冲带宽度等参数对能耗和网络检测性能的影响。

基于双目视觉的运动物体实时跟踪与测距

利用双目视觉信息系统实现三维空间中运动物体实时跟踪与测距。当运动目标超出视野范围时,可通过控制摄像机云台转动搜索目标。此外,还研究了在摄像头运动情况下,无需重新标定,即可实现运动物体测距的算法。这里,自适应背景建模法与CamShift算法用于实现运动物体的辨识与跟踪。实验结果证明了所提出的算法能够有效地追踪物体,并同时准确地测量它的三维位置。

大射电望远镜精调Stewart平台工作空间分析

针对大射电望远镜精调Stewart平台的五自由度运动特性,采用快速极坐标搜索法确定了五自由度大射电望远镜精调Stewart平台的工作空间.通过实例分析验证了所提出的工作空间分析方法的有效性.为大射电望远镜馈源轨迹跟踪实现和精调Stewart平台的设计奠定了坚实的基础.

一类非完整约束动力学系统的人工场导向控制

对于一类具有轮式移动机构的非完整动力学系统，本文通过建立人工场的方法来实现其位姿镇定、轨迹跟踪和路径跟踪等控制问题。人工场用于导向和控制方向角，而通过辅助的线速度控制以获取最佳收敛路径。控制器设计中同时兼顾动力学扰动及实际系统速度和输出力矩的饱和限制，所得控制器对于跟踪问题仅需知道期望位姿，而且结构简单、鲁棒性强、便于实现。

非完整约束轮式移动机器人人工场导向控制研究

导向控制在非完整约束轮式移动机器人的运动控制中具有重要作用，该文通过建立人工场的方法来引导和控制方向角，通过辅助的线速度控制前进或后退，以获得最佳收敛路径；同时考虑到实际系统速度饱和限制，从而设计出一种新的非连续位姿镇定律，并将该结果扩展，使得平面内任意点-点镇定、轨迹跟踪和路径跟踪问题均可得以实现，且对于跟踪问题仅需知道期望位姿，所得控制器不权设计简单，鲁棒性强，收敛速度快，还具有一定的普遍性。

基于模型扰动抑制的直线伺服系统设计

针对高精度、微进给永磁直线交流同步电机 (PMLSM )驱动系统 ,采用基于模型的扰动抑制 (MBDA)方法 ,对诸如摩擦力、切削力、负载变动之类的扰动进行抑制。MBDA是利用一个与系统并行的标称模型 ,通过输出反馈 ,将系统输出与标称模型输出进行比较 ,得出误差信号 ,并通过设计一个补偿器将误差信号反馈给被控对象的输入端 ,从而实现扰动抑制。同时 ,针对速度环设计了积分 -比例 (IP)控制器 ,以满足系统快速跟踪指令的要求 ,并且其具有较强的抗扰动能力。仿真结果表明 ,该控制方法响应速度快 ,抗干扰能力强

浮动信号的自动跟踪与检测

在工业生产和科学研究中，对浮动信号的自动跟踪与检测是经常遇到的一个问题。本文给出一种新的信号跟踪与检测电路，它不但可以在直流电平或缓慢浮动的电平下检测到脉冲信号，在浮动电平变化速度较快（如１ｋＨｚ）的情况下，也能准确地检测出脉冲信号。

开展高技术情报跟踪与服务的几点做法

开展高技术情报跟踪与服务是科技情报工作的重要任务之一,结合完成国家科委、科学院和国家863等高技术情报研究项目的多年实践,叙述了为我国高技术研究创造良好的文献情报支撑环境,主动为高技术研究服务的几点做法。

智能相机在激光焊缝跟踪检测系统中的应用研究

本文以中国科学院知识创新工程重要方向项目“全自动激光拼焊成套装备关键技术研究与示范应用”及沈阳市科技攻关项目“激光视觉焊缝自动跟踪与质量检测系统”为依托，针对激光焊接这个难点问题，在广泛调研国内外研究现状的基础上，研究开发了一套激光视觉焊缝跟踪检测原理样机。本文主要包括以下四方面的工作：1焊缝跟踪系统的系统结构搭建；2图像处理方法研究；3图像处理方法在FPGA中的实现；4基于工业机器人的激光焊接实验 及结果分析。具体工作如下： 本文首先论述了应用于焊缝跟踪的线结构光视觉传感器检测原理，建立了激光焊缝跟踪检测系统实验平台。该平台由图像采集与处理模块、上位机系统、DSP控制器、伺服电机驱动器、伺服电机等五部分组成。 激光拼焊焊缝跟踪图像的处理方法是关键技术之一，直接影响系统的实时性，根据激光拼焊焊缝跟踪图像的特点设计了相应的图像处理算法，分析研究了基于数学形态学的焊缝跟踪结构光条纹图像增强算法，并根据本课题的特点提出了一种基于模板的边缘提取方法，能简洁快速地提取出单像素边缘，然后研究了结构光中心线提取算法以及焊缝特征点识别算法，最后通过仿真实验验证了该图像处理流程的有效性。 论文的重点在于图像处理方法在智能相机中的实时实现。跟踪系统对图像处理的实时性要求很高，传统的处理方法主要是在DSP中以软件编程的方式实现，速度难以进一步提高，本课题中通过在智能相机中的FPGA中构建一个SOPC系统，将基于硬件描述语言VHDL完成的图像预处理模块和基于Xilinx公司的microblaze软核的特征点提取模块集成在单片芯片上，实现了激光条纹特征点的实时提取，系统具有高度的灵活性与出色的功能。 最后对搭建的跟踪系统平台进行了实验研究，用实验验证了焊缝跟踪系统的性能，保证了该套系统能够满足实时跟踪的要求，可以达到预期的设计目标。

交通监控系统中运动目标分类和跟踪研究

文章讲述了交通监控系统中应用视频图像流来跟踪运动目标并对目标进行分类的具体过程和原则.基于目标检测提出了双差分的目标检测算法,目标分类应用到了连续时间限制和最大可能性估计的原则,目标跟踪则结合检测到的运动目标图像和当前模板进行相关匹配.实验结果表明,该过程能够很好地探测和分类目标,去除背景信息的干扰,并能够在运动目标部分被遮挡、外观改变和运动停止等情况下连续地跟踪目标.

济阳地区深部结构与含油气性讨论

Oil and gas exploration of marine strata in China's Pre-Cenozoic residual basins is regarded as a worldwide puzzle because of existent problems and cruxes. Objectively speaking, the subsurface geologic structure is complicated, and the surface conditions of some areas are tough. On the other hand, there are still many problems to be solved in oil and gas exploration technologies of Pre-Cenozoic marine fades, and theoretic cognition about petroleum geology is not profound yet. Therefore, it is principal to explore integrated geophysical research ways of Pre-Cenozoic residual basins. Seismic prospecting and geophysical integrated interpretation technologies aimed at middle Paleozoic marine facies with deeper burial and complicated geologic conditions have not formed due to bad quality of deep strata data. Pre-Cenozoic strata, and especially extension, thickness and internal structure of Paleozoic strata can not be recognized from seismic profiles, so it is hard to systematically cognize structural features and oil-gas resources prospect of Pre-Cenozoic basins. To further investigation of fabric and structural features, basin prototype, formation and evolution pattern of Pre-Cenozoic basins, and also their control over formation, migration and aggregation of oil and gas, will play a guiding and promotive role in developing new surveying areas, selecting advantageous zones and predicting oil-gas resources.This paper follows the modem macrocontrol theory of "Region constrains local, deep strata controls shallow ones", and uses the integrated geophysical method of "One guide, two hinges, three combinations and multi feedbacks'*. Based on several years of geological and geophysical results of the Shengli Oilfield, and 14 newly-joint regional seismic profiles, deep structure and oil-gas bearing capacity of the Jiyang area are discussed and new cognitions are drawn as below.Seismic identification marks Tr, Tg, Tgl and Tg2 are established for importantPre-Cenozoic geological interfaces, and promoted to the whole Jiyang area.Through area-wide tracking and clogging of important seismic reflection marker,the isochronic framework of pre-Tertiary basin is set up in the Jiyang area for the firsttime, which is vital for basin research.Integrated with geological and geophysical research results, the Jiyang area isdivided into four first-order tectonic sequences- basement, lower tectonic layer,upper tectonic layer, and top tectonic layer. The basement and lower tectonic sequence which are related to Pre-Cenozoic are studied with emphasis.Through the research of regional seismic profiles, the point of view is given thatthe Kongdian Formation of Jiyang is structural transition period. The top-bottomunconformable interface of the Kongdian Formation is found out for the first time,and the basin model is determined primarily, which lay a basis for prototype basinresearch of the Jiyang Kongdian Formation.The distribution status of Middle-Paleozoic is delineated in the Jiyang area.The maximum thickness of Paleozoic lies in the top of the south declivity of half-graben. The thickness gets thinner towards the center of Mesozoic and Cenozoic half-graben basin, and even disappears. Structural action in the west-north affects the distribution of Paleozoic residual strata.6. The features of second-order tectonic sequence of the Jiyang depression isstudied and its evolution history of is rebuilt.Combined with the 5-stage evolution history of the China continent and structure evolution features of the Jiyang area, the structure sedimentary process since Paleozoic is divided into 5 periods - basement forming , Indosinian orogenic, Yanshan negative reversal, Himalayan extension and Neogene subsidence period.Combined with the research results of gravity, magnetic surveying and regionalprofiles, this paper brings forward the idea for the first time that the western boundaryof the Jiyang depression is the Ningjin-Yangpan fracture zone, and forms aside-column assemblage with the Wudi fracture zone.The opinion that under Middle-Cenozoic basins in the middle Jiyang area theremight superimpose an old residual basin is given for the first time. And if it is provedto be true, a new exploration space will be pioneered for Jiyang and even north China.There exists many types of tectonic-stratigraphic traps formed under piezotropy,extension and compound action in Pre-Cenozoic Jiyang. Therein all kinds of burialhills are the most important oil-gas trap type of Pre-Cenozoic, which should besurveyed layeredly according to the layout of oil sources.As such a new challenging project and field, the paper systematically analyses different geophysical responses of the Jiyang area, frames the deep structure of the area, and preliminarily recognizes the Pre-Cenozoic residual basins. It breaks through to a certain extent in both theory and practice, and is expected to provide new geophysical and geotectonic clues for deep exploration in Shengli.