一种副反射面为椭球面的天线反射体测量技术

针对副反射面为非对称椭球面形式的多馈源、多频段天线反射体,需要对天线主反射面表面准确度、副反射面表面准确度及主反射面电轴、副反射面电轴和馈源系统中心轴的同轴度进行精确的测量和调整。应用数字工业摄影测量系统,以副反射面六杆联动机构的旋转中心轴为基准,对副反射面表面准确度进行精密测量和调整;在天线俯仰35°位置,以馈源系统中心轴为基准对主反射面表面准确度和副反射面姿态进行精密测量和调整。主反射面表面准确度优于±0.30 mm;副反射面表面准确度优于±0.11 mm;副反射面电轴和主反射面电轴的同轴度优于0.5 mm时,测试天线系统接收S频段和X频段信号的方向图,综合电气性能满足指标要求。     

天线反射体的空间几何关系精密测量

采用数字工业摄影测量技术对天线反射体的空间几何关系进行精密测量和调整,并应用公共点坐标转换方法统一测量和调整过程中的坐标系。公共点坐标转换准确度可达±0.1 mm。天线主反射面表面准确度优于±0.26 mm,副反射面中心位置准确度优于0.7 mm,高度位置准确度优于0.5 mm时,某13 m口径抛物面天线接收和发送频率为f=19.6 GHz的Ka频段电磁波信号,天线反射体的电性能测试满足指标需求。与传统的天线反射体测量和调整方式相比,省去通过天线接收卫星信号扫描方向图调整副反射面姿态的大量工作,具有高准确度、高效、高可靠性等特点。     

65米射电望远镜主面精度及主、副面位置关系测量

65米射电望远镜是目前亚洲口径最大、精度最高的天线,其最高工作频率为43GHz,因此,如何保证天线主反射面精度以及正确的主、副面位置关系是天线实现高精度工作的关键所在。工程实践中采用了数字近景摄影测量系统（以下简称摄影系统）对天线主反射面精度和主、副面位置关系进行测量,并以测量结果为依据调整主面精度及主、副面位置关系,取得了良好的效果。     

飞行器RCS计算中曲面剖分技术研究与实现

飞行器RCS预估计算是隐身技术研究中的重要研究内容。论述了利用飞行器外形的特点,在满足飞行器设计误差的前提下使用平面和柱面对飞行器的整机作NURBS曲面逼近,然后用柱面和平面剖分代替曲面的剖分。实现了飞行器整机模型的指定边长的三角剖分。这种方法不同于有限元计算的网格剖分,具有网格单元与曲面曲率无关和剖分速度快等特点。     

结构型雷达吸波材料的性能特点及其应用进展

<正>隐身技术是通过弱化目标信号特征,最大限度地降低探测系统发现和识别目标能力的技术。雷达隐身技术是研究较早和发展最快的现代隐身技术。隐身技术中最重要的环节是隐身材料。因此,隐身材料的研究受到世界各国的高度重视,是在武器系统的使用和设计过程中,降低其目标特征的材料。在现代战争中,雷达是探测武器特别是飞行器的最可靠方法。一、雷达隐身的基本原理雷达是利用电磁波发现目标并测     

上海65 m射电望远镜太阳辐射作用分析

利用 ANSYS 热分析模块分别对天线主副反射面板结构和天线的杆系结构建立有限元模型, 计算夏季7月15 日晴天无云这一最不利气候之一的天气各时刻的空气对流换热、太阳辐射、环境长波辐射换热以及阴影遮挡等各种边界条件, 研究分析了主面板、副面板在日照作用下的温度场分布, 特别是由于主面板反射太阳辐射热量并聚焦于副面板从而使副面板温度剧增的“太阳灶”现象;同时为获取天线结构在日照下指向误差变化规律, 还对天线杆系结构进行了日照非均匀热变形分析, 给出日照下主反射面型面精度随时间的变化规律。结果表明:主副面板之间存在的“太阳灶”效应使的副面板最高温度达135℃, 由于日照非均匀温度场的作用, 杆系结构中最大温差达到10.8℃。太阳照射引起的阴阳面造成主反射面不均匀热变形, 在俯仰角90°工况下导致RMS(反射面表面各点误差平方和均方根)最大增加0.35mm。这些数据为下一步结构的施工、传感器的布设以及局部温度控制措施提供了参考信息。     

导电高分子材料在隐身技术中的应用

隐身技术是一项跨学科的综合技术，它涉及到电磁、材料、能量转换、信息处理等学科和技术。本文简单介绍了材料隐身的隐身机理及材料隐身技术对材料的要求，说明了导电高分子材料是隐身材料的优选材料之一，综述了导电高分子材料在雷达隐身、红外隐身技术中的应用。     

纳米材料在隐身技术中的应用研究进展

近年来纳米材料的应用已经成为隐身技术领域中的一个研究热点,纳米材料由于其独特的理化性能及优良的电磁吸收特性,成为最具潜力的功能型隐身材料。分析了纳米材料的隐身作用机理,概述了近年来纳米材料在可见光、红外、雷达、激光、声波及多波段隐身技术中的应用现状,并展望了纳米材料在隐身技术中的发展方向。     

智能雷达隐身材料研究现状

概述了雷达隐身技术的基本原理、智能雷达隐身技术与材料实现功能的结构平台以及智能雷达隐身材料研究的主要方向,结合智能雷达隐身材料实现可控的主要机理综述了导电高分子材料、液晶材料、可电控超材料在智能雷达隐身材料中的研究现状.     

卡西尼卵形贴片的电磁微波吸收研究

简单介绍了卡西尼卵形线的形成和卵形线族，提出了基于卡西尼卵形线的新型贴片电磁结构，并采用商业软件HFSS对雷达散射截面（RCS）随入射频率与随视角的变化进行了仿真计算。得到：在频率4-8GHz范围内，卡西尼贴片的RCS小于-8dBm，明显优于矩形贴片，约小2．2dBm。在频率6GHz，Φ=90°时，RCS随视角口的变化也优于矩形贴片。通过与相同面积的矩形贴片RCS的结果对比与简单分析，得出卡西尼卵形线贴片结构用于电磁隐身将优于相同面积的矩形贴片的结论。最后指出了卡西尼卵形线新型贴片结构在电磁隐身、天线设计等方面可能具有潜在的应用前景。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...