谈形位公差新国际

本文着重介绍了形位公差新旧国际的异同，并谈及了对新国际的初步理解。     

平尺直线度公差值计算式的研究

分析比较了世界主要工业国家平尺工作面直线度公差值的计算式，得出我国际准采用的计算式确定的分差值倨于我国国家检定规程规定值和各国际准给出值。文中建议国家规程修订时采用国家标准确定值，以利平尺使用精度的提高。     

螺母的形状和位置公差标准探讨

根据螺母形状和位置公差标准现状，对标准进行分析与对比，以便大家能够更加方便的使用标准。     

线性尺寸未注公差标准演变及应用

从实际应用的角度出发，阐述了线性尺寸未注公差各标准的演变和主要特点，并提出了在机械加工应用中具有简明、省时、质优等特点。     

谈形位公差新国标

本文着重介绍了形位公差新旧国际的异同，并谈及了对新国标的初步理解。     

浅谈在新产品上贯彻重要基础新标准的做法

国家标准《公差与配合》、《形状和位置公差》、《公差原则》、《一般公差》等是重要的基础标准，在我公司贯彻实施已近20年了。为适应空军装备的更新和第三代、第四代飞机的使用，在新产品上贯彻《极限与配合》(GB／T1800．1-1997、GB／T1800．2～1800．3-1998、GB／T1800．4-1999、GB／T1801-1999)；     

基于《产品几何技术规范(GPS)》的最新变动

如何正确理解《产品几何技术规范(GPS)》的最新国家标准,只有将其重要的定义、概念、名称等与之相对应的旧国标对照,才可以做到心中有数,才能将这最重要的基础性标准了解清楚,从而更好、更准确地掌握和应用它。     

平行孔系中心距公差坐标换算

通过对平面尺寸链分析，应用马克劳林公式作近似计算和全微分近似全增量方法，导出了孔距公差坐标换算公式．最后通过实例对其换算结果进行了验证．完全符合设计要求。公式简明、实用、易掌握。可供设计、工艺和操作人员在相应的平行孔系中心距公差坐标计算中采用。具有一定的实际应用价值。     

基于HB/Z 103-86的标准验证飞机水平测量点位置度研究

以HB/Z 103-86《飞机水平测量公差》要求为前提，对飞机水平测量点位置度开展研究，同时以某中型Ⅰ级飞机为例开展水平测量点位置度设计，最后指出现代化飞机高精度要求有必要在相关标准中增加位置度要求，提出在标准规定暂缺的情况下水平测量点位置度要结合标准公差及飞机机体结构、工艺特点、制造能力以及经济性等建设性意见。     

标准化服务于生产——中俄螺纹标准的公差转换

通过对GB普通螺纹标准和ГОСТ普通螺纹标准的对比分析 ,简要介绍了两种标准的主要特点和差异 ;通过对两种标准中的 5H6H公差带的具体分析和对照 ,得出了某型号工程产品设计图样和工艺规程中ГОСТ标准要求的 5H6H公差带 ,可用GB普通螺纹的 5H6H公差带替代的结论。     

Research and development version of computer-aided system of aircraft and rocket-space equipment vibration tests

In this paper, a research and development version of the computer-aided system of mass tensometry (SMT) for conduction of aircraft and rocket-space equipment vibration tests is considered. A technique of the system design and development that combines the advantages of the system and process approaches when using the modern element base around the high-performance integral microcircuits is a distinctive feature in this research and development problem solution. We describe the architecture and structure of the advanced computer-aided SMTs and present data on its basic components desigtn. Also determined are the list and functional parameters of ratio-measuring network modules as well as the scheme of their connection to the test object and the local computer network of the enterprise.     

GB/T 3364中异形截面纤维当量直径计算方法的研究

GB/T 3364碳纤维直径和当量直径试验方法中,异形截面纤维当量直径的计算方法较为复杂.经过计算公式的数学推导,使得异形截面纤维当量直径的计算和测量步骤有了较大的简化,并通过实验验证了简化方法的有效性.     

Modified Difference Change Detector for Small Targets in SAR Imagery

One of the most straightforward techniques for detecting changes in an image involves forming the difference between a test image and a reference image. Unfortunately, such a technique can give rise to a large number of false alarms due to the statistical variability of the underlying pixel values, as has been well established within the radar community over the years. One method for dealing with this large number of false alarms involves forming the ratio, rather than the difference, of two synthetic aperture radar (SAR) images. We introduce a modified version of the standard differencing technique to overcome problems associated with pixel value variability. The new (modified) differencing approach utilizes assumptions about the statistics of the image background and the object being sought (target) to reduce the number of false alarms due to highly variable background (clutter) regions, and it includes the standard ratio test as a special case. In fact, we find that the modified difference approach can also be viewed as a modified version of the ratio test with a threshold that varies as a function of the background clutter radar cross section (RCS). We also present an abridged, albeit suboptimal, version of this approach that eliminates assumptions regarding the target's probability distribution, and we analyze both of the approaches. We then compare these results with those obtained with a standard ratio test, and illustrate how the modified difference test reduces to the ratio test under certain operating conditions. The abridged version of the modified approach is applied to high resolution synthetic aperture radar imagery and compared with results obtained with the classical differencing technique, and following this, the modified difference technique is compared with the standard ratio test. Results suggest that under appropriate conditions the abridged, modified technique can successfully detect changes without the need for any image segmentation.     

高铁弓网电弧对飞机进近着陆的电磁干扰影响

为了研究高铁弓网离线电弧对飞机进近着陆的电磁干扰（EMI）影响,选取高速铁路弓网离线现象发生频繁的电分相处,对高速铁路列车发生弓网离线电弧时的电磁辐射强度进行了实际测试。根据电波传播理论和GB 6364-2013的相关要求,数值计算得到了高铁下穿角、电分相位置以及飞机着陆高度对机载接收信号的影响规律：机载接收信号信干比（SIR）随着高铁下穿角增大逐渐增大;电分相距离机场跑道口越近机载接收信号的信干比越小;随着飞机进近着陆高度的减小,机载接收信号信干比先减小后增大。以高速铁路45°角下穿机场跑道中心时,以飞机受干扰最强的位置分析了弓网离线电弧电磁干扰对仪表着陆系统（ILS）信标台的影响：飞机接收到的航向信标台信号信干比为12.92 dB,小于GB 6364-2013规定最小20 dB的防护率要求;下滑信标台信号信干比为29.08 dB,符合国标要求;指点信标台信号信干比为16.64 dB,小于国标规定的最低23 dB的防护率要求。本文研究为民航与高速铁路的电磁兼容性研究提供了理论依据和技术方法,可以为机场选址和高速铁路选线规划提供支持。     

The extra-galactic background light: A modern version of Olbers' paradox

A non-technical discussion is given of the energy density E of the extra-galactic background light. The fact that E is small means that the space between galaxies is dark, which is a modern version of a classical problem in astronomy known as Olbers' paradox. It is seen that the order of magnitude of E is fixed by the order of magnitude of the lifetime of the galaxies, as pointed out by Harrison; but that the expansion of the Universe can affect E by a smaller factor, typically about 2. These comments should help to end persistent confusion about the effects of the lifetime of the galaxies and the expansion of the Universe on the darkness of the night sky. It is hoped that Olbers' so-called paradox can now rest in peace.     

某民用机场航空噪声影响计算分析

根据《机场周围飞机噪声环境标准（GB9660—88）》，以计权等效连续感觉噪声级￡删为评价量，同时参照ICAO（国际民航组织）和SAE（汽车工程师协会）的计算方法，借助FAA（美国联邦航空局）的INM（综合噪声模型）对某机场的航空噪声影响进行了详细分析，比较详细地考虑了机型组合、飞行架次、起降方向、时间分布和飞行程序等因素对机场噪声的强度、分布区域形状和分布区域面积的影响。提出一套先进的机场航空噪声影响计算与分析方法，可为今后机场作航空噪声环境影响评价提供借鉴。     

六自由度舰面模拟平台的数学建模与仿真

建立了一种六自由度运动平台的数学模型;按国家标准(GB/T14410-93)定义的坐标系,导出了液压动作筒长度与平台六自由度位移之间的关系;最后根据液压动作筒的极限行程,采用数值仿真确定了平台单自由度运动时的幅值,对平台的多自由度组合运动也进行了仿真计算,为设计六自由度舰面模拟运动平台提供了理论依据。     

Theoretical Aspects of Dark Matter Detection

Direct and indirect dark matter detection relies on the scattering of the dark matter candidate on nucleons or nuclei. Here, attention is focused on dark matter candidates (neutralinos) predicted in the minimal supersymmetric standard model and its constrained version with universal input soft supersymmetry-breaking masses. Current expectations for elastic scattering cross sections for neutralinos on protons are discussed with particular attention to satisfying all current accelerator constraints as well as insuring a sufficient cosmological relic density to account for the dark matter in the universe.     

Next generation digital GPS receiver

The architecture and technology features of the next-generation (NGR) digital GPS (Global Positioning System) receiver manufactured by Collin are described. The project's objective was to develop an advanced GPS receiver chipset with high antijam capabilities. The program, initiated in 1985, has provided the technology for miniature receiver products for both unmanned and manned vehicle applications. A two-channel version of the receiver is in full-scale development for tactical missile applications. A five-channel version is being tested and evaluated as a drop-in replacement for RCVR-3A, the US Department of Defense standard high dynamic receiver. The NGR design started with the digital signal processing architecture developed for the Defense Advanced Research Project Agency (DARPA) hand-held GPS receiver. Enhancements were made to improve the antijam and signal acquisition performance. Producible, qualifiable and cost-effective silicon monolithic microwave integrated circuits and semicustom digital technologies were used to develop the core GPS chipset. A system design approach was established to permit reuse of mature and validated GPS software     

基于三维的波纹管CAD/CAPP集成系统开发

针对企业提高波纹管产品设计效率和减少设计差错的需要,基于SolidWorks用VisualBa-sic6.0开发了波纹管CAD/CAPP集成系统,采用Access数据库存储所需要的工艺数据。该系统能够根据EJMA和GB12777标准设计波纹管参数,根据设计结果自动生成波纹管三维模型、工程图纸和波纹管工艺卡。所形成的图纸和工艺卡可以用交互方式进行修改以满足具体需要。