Optical interferometry for measurement of the geometric dimensions of industrial parts

We describe an instrument for the measurement of surface flatness, parallelism, and size (thickness) of plane-parallel parts in a single measurement to 1sigma gauge capability of 0.02, 0.03, and 0.06 microm, respectively. A low-coherence IR profiler viewing both sides of the part simultaneously, believed to be novel, accommodates a wide variety of industrial surface finishes, including machined, ground, or lapped parts, with a 75-mm field of view and 15,000 pixels per side. A heterodyne laser displacement gauge together with an integrated zeroing system allows for a range of part sizes from 0 to 100 mm.     

空气中雷达波速测量校准方法的探讨

随着工程技术的高速发展,地质雷达近几年被广泛使用.开展地质雷达的校准工作,可有效保证其量值的准确可靠.目前针对地质雷达的国家计量技术规范尚未制定,仅制定相关的行业计量技术规范,其测量方法不尽相同,各有特点.在此基础上针对空气中雷达波速测量校准方法进行探讨.实验结果表明,优先采用垂直方向测量间距,且测量间距的选取应不小于...     

Goniofluorometer for characterization of fluorescent materials

A goniofluorometer has been built that is capable of measuring in various viewing angles ranging from 10 degrees to 90 degrees . The incident angle can be varied from 0 degrees to 8 degrees . The goniofluorometer can measure bispectral luminescent radiance factors in the wavelength range of 250-800 nm. To our knowledge, there are no other reported results of similar devices capable of spectral measurements in various measurement geometries.     

多孔材料和微穿孔板复合吸声结构研究

主要研究如何利用多孔材料拓宽微穿孔板的吸声频带,微穿孔板用来吸收低频噪声,同时加入吸声材料来提高中高频的吸声。给出复合结构吸声系数的计算方法,并在阻抗管内进行实验验证,测量结果和计算结果取得很好的一致性。研究结果表明,多孔吸声材料置于微穿孔板之前,并且二者之间有一定的空气层时,可以显著改善微穿孔板的吸声性能。     

Analysis and compensation of the measurement error in a lock-in amplifier used for wavelength shift measurements in optical sensing application

The phase measurement error in an interferometric wavelength shift measurement scheme, such as that used in association with in-fiber Bragg grating sensors, has been investigated experimentally with appropriate underpinning analytical theory. It has been shown that when a lock-in amplifier is used to detect the phase shift generated by the Bragg wavelength shift, a pseudoperiodical measurement error can be introduced owing to the difference between the amplitude of the optical path difference ramp and the value of the Bragg wavelength. If the initial ramp deviation equals 20 nm, the measurement error may be as large as +/-2.5% of the total measurement range. With a double-phase lock-in amplifier approach to measure the ac strain, the measurement error can be decreased to 0.4% of the total measurement range. With the real-time measured period that corresponds to the Bragg wavelength with the distorted carrier signal of the interferometer as the reference period of a digital lock-in amplifier, the effect of the initial ramp deviation can be principally avoided, and the measurement error can be kept to an acceptably low level, about 0.1% of the total measurement range.     

多功能压力综合校准装置研究

为了解决飞机地面试验中压力测量设备需校准的数量多、量程分散、介质种类特殊且繁多等问题,对压力测量设备校准原理及方式进行理论分析,设计一种集成了多通道、多量程范围、多介质于一体的压力综合校准装置,该装置具有全自动控制、数据采集及处理功能。经过多个飞机型号研制过程的应用验证,该装置设计合理,切实解决了飞机地面试验压力测量设备的校准需求,提高了校准效率,取得了较好的应用效果。     

过滤器清洗对地铁站空调效果影响的实测分析

首先对过滤器运行存在的问题进行了分析,结合南京某地铁站空调系统过滤器清洗前、后各个房间的风量和空气温、湿度实测结果,分析了过滤器对地铁空调系统冷量的影响.实测结果表明,当空调系统冷量减小时,对过滤器进行清洗会显著增大空调系统的风量和冷量、提高空调的换热效率、有效提高了冷量的传输,并且节能效果明显.     

Optical properties of randomly distributed soot: improved polarimetric and intensity scattering functions

Reference scattering curves for polarization and intensity produced by aggregates and agglomerates of ethylene and kerosene soot are obtained for scattering angles in the 10-170 degrees range. The polarization measurements were obtained with the Propriétés Optiques des Grains Astronomiques et Atmosphériques instrument for particles that levitate in microgravity during parabolic flights and on the ground by an air draught technique. The intensity measurements were obtained also on the ground with a Laboratoire de Metéorologie Physique nephelometer. The maximum polarization is of the order of 80% at a scattering angle of 80 degrees at lambda = 632.8 nm and approximately 75% at an angle of 90 degrees at lambda = 543.5 nm. The polarization increases by approximately 10% when the size of the agglomerate increases from 10 microm to a few hundred micrometers. The intensity curve exhibits a strong increase at small scattering angles. These reference curves will be used in the near future for the detection of stratospheric soot by remote-sensing measurement techniques.     

论地对空雷达干扰系统在局部战争中的作用及其发展

文章介绍了从地对空干扰机的发展概况,从单一干扰轰炸瞄准雷达,发展成地对空干扰系统和系列,可以干扰空载作战飞机雷达、导弹制导雷达、精密制导雷达、预警机雷达、星载探测雷达等,分析了这些雷达的干扰原理、干扰方法和干扰机的布局。文章对新体制雷达的干扰压制系数进行了分析,导出各类新体制雷达的干扰压制系数表达式,并提供了计算机仿真和实际试验的结果。文章分析了90年代以来两次现代化局部战争,地对空干扰系统若能发挥作用,将使被入侵国家的损失率下降,使入侵者的损失率升高。地对空干扰系统具有攻防兼备的立体干扰系列功能,需要经费较低,很适合于第三世界国家的需求,具有广泛的发展前景。     

氮化钛镀层的表面颜色研究

一般情况下，测色工作者在测色时，按CIE（国际照明委员会）标准色度学系统，在CIE推荐的四种标准照明及观测条件下进行。在实践的基础上，提出用0／t或0／0照明和观测条件对具有镜面反射光的物体进行测色，取得了良好的结果。     

基于二进制电抗分流器实现热电变换器共地测量

相比于传统的串联连接方式,提出了一种基于二进制电抗分流器实现热电转换器共地比较测量的方法,通过串联连接的方式实现交流电流量程扩展。二进制电抗分流器产生两路共地可自校的电流输出,为热电转换器之间进行相互比较提供已知关系的1:1电流比例;该方法可以减少电流泄漏和三通连接器串联连接的影响。基于这种共地测量方法,热电变换器结合100 mA和1 A分流器进行了实验分析,测量频率范围1~200 kHz,同时在串联模式下进行换臂测量。实验结果表明基于二进制电抗分流器和换臂法可以很好地消除泄露电流所引起的测量误差,且两种不同方法在200 kHz频率下一致性优于3 μA/A。3种不同热电变换器和分流器组合在10 mA~1 A测量电流下交流转换误差一致性优于6 μA/A。     

Hazardous ranges of laser beams and their reflections from targets

The hazardous range of laser beams and their reflections from surfaces must be known when one uses lasers outdoors in areas where individuals could be exposed above the applicable exposure limits. In this paper, we describe formulas that can be used to calculate these hazardous ranges, and a few experimental data are presented that indicate the validity of the formulas and the underlying assumptions. The hazardous range depends on the laser parameters, the exposure limit, the atmospheric attenuation, the distance between the laser and reflector, the dimensions of the reflector, the angle of incidence on the reflector, and the surface parameters such as the reflection coefficient and flatness of the surface. The hazardous range of some commonly used lasers by the U.S. Army extends from 5 to 25 km for unaided viewing.     

近来的局部战争对陆基防空雷达的需求

从近来的局部战争陆基防空雷达面临的任务出发,简要阐述了近来出现的各种目标的特点以及防空雷达所处的作战环境与电子对抗环境。分析了陆基中低空防空系统在现代防空中的作用和地位。陆基中低空防空系统在现在的防空中是可以发挥它的重要作用的,尤其是在对付巡航导弹、武装直升机、低空飞机（含隐身飞机）、反辐射导弹等目标时,该系统是属于比较优选的武器;归纳了对陆基中低空防空雷达的新的要求,主要是强的抗干扰性能,好的低空特性,满足武器系统需要的探测小目标的能力,快速的搜捕截获目标的能力等;同时也简要分析了这些要求在陆基中低空防空雷达中的技术可实现性。     

风量罩测试试验台的开发与应用

首先介绍了风量罩的测试原理及方法,风量罩测试试验台的设计原理及使用方法。本试验台的流量测量方法是采用多喷嘴流量测量方法。多喷嘴流量法具有测量流量大,耐磨损、使用范围广的特点。其次,介绍了风量罩测试试验台的组成、设计主要参数及选用的各种仪器,并结合具体工程案例说明了试验台的组成及使用方法,在所设计的试验台上进行了风量罩的测试工作,并给出了测试报告,达到了比较满意的使用效果,能为今后的工程实践提供有力的理论支持,为风量罩的年度校准提供了保障,并希望能为我国风量罩标准的制定提供参考。     

Near-threshold fatigue propagation of physically through-thickness short and long cracks in a low alloy steel

In this paper, the near-threshold fatigue behavior of physically through-thickness short cracks and of long cracks in a low alloy steel is investigated by experiments in ambient air. Physically through-thickness short fatigue cracks are created by gradually removing the plastic wake of long cracks in compact tension specimens. The crack closure is systematically measured using the compliance variation technique with numerical data acquisition and filtering for accurate detection of the stress intensity factor (SIF) at the crack opening. Based on the experimental results, the nominal threshold SIF range is shown to be dependent on the crack length and the characteristic of the crack wake which is strongly dependent on the loading history. The effective threshold SIF range and the relation between the crack propagation rate and the effective SIF range after the crack closure correction are shown to be independent on crack length and loading history. The shielding effect of the crack closure is shown to be related to the wake length and load history. The effective threshold SIF range and the relationship between the crack growth rate and the effective SIF range appear to be unique for this material in ambient air. These properties can be considered as specific fatigue properties of the couple material/ambient air environment.     

Debris slopes ventilation in the periglacial zone of the Tatra Mountains (Poland and Slovakia): The indicators

This paper examines environmental indicators of debris slopes ventilation in the periglacial zone of the Tatra Mountains. Geomorphological and meteorological influences on ground surface temperature anomaly, hoarfrost, air ventilation funnels and snow melt windows, were analyzed as well as locations of long-lying snow and permafrost patches. The results show that debris slope ventilation is a common phenomenon occurring in different periods of the year. Its range is influenced mainly by substratum porosity (ground and snow cover), and the difference between the pressure inside and outside this medium (pore and atmospheric air temperature/dense; wind velocity). The height of the slope (‘chimney’) is less important. Some phenomena assumed to be evidences of slope ventilation are often connected with other factors influencing the thermal balance of the ground and the size of snow accumulation.     

Prelaunch characterization of the Ozone Monitoring Instrument transfer function in the spectral domain

A method and an experimental measurement setup to accurately characterize the instrument transfer function in the spectral domain for hyperspectral spectrometers in the ultraviolet-visible wavelength range are described. The application to the on-ground calibration of the Ozone Monitoring Instrument (OMI) on board the Earth Observing System Aura satellite is presented and discussed. With this method and setup, based on an echelle grating, a sampling of the instrument transfer function in the spectral domain can be selected and is not limited by the spectral resolution and sampling of the spectrometer that is being characterized. The importance of accurately knowing the OMI instrument transfer functions in the spectral domain for in-flight differential optical absorption spectroscopy retrievals and wavelength calibration is discussed. The analysis of the OMI measurement data is presented and shows that the instrument transfer functions in the spectral domain as a function of wavelength and viewing angle can be determined with high accuracy.     

Sensitivity metric approach for retrieval of aerosol properties from multiangular and multispectral polarized radiances

Linearly polarized radiation is sensitive to the microphysical properties of aerosols, namely, to the particle-size distribution and refractive index. The discriminating power of polarized radiation increases strongly with the increasing range of scattering angles and the addition of multiple wavelengths. The polarization and directionality of the Earth's reflectances (POLDER) missions demonstrate that some aerosol properties can be successfully derived from spaceborne polarimetric, multiangular measurements at two visible wavelengths. We extend the concept to analyze the retrieval capabilities of a spaceborne instrument with six polarimetric channels at 412, 445, 555, 865, 1250, and 2250 nm, measuring approximately 100 scattering angles covering a range between 50 and 150 deg. Our focus is development of an analysis methodology that can help quantify the benefits of such multiangular and multispectral polarimetric measurements. To that goal we employ a sensitivity metric approach in a framework of the principal-component analysis. The radiances and noise used to construct the sensitivity metric are calculated with the realistic solar flux for representative orbital viewing geometries, accounting for surface reflection from the ground, and statistical and calibration errors of a notional instrument. Spherical aerosol particles covering a range of representative microphysical properties (effective radius, effective variance, real and imaginary parts of the refractive index, single-scattering albedo) are considered in the calculations. We find that there is a limiting threshold for the effective size (approximately 0.7 microm), below which the weak scattering intensity results in a decreased signal-to-noise ratio and minimal polarization sensitivity, precluding reliable aerosol retrievals. For such small particles, close to the Rayleigh scattering limit, the total intensity provides a much stronger aerosol signature than the linear polarization, inspiring retrieval when the combined signals of intensities and the polarization fraction are used. We also find a strong correlation between aerosol parameters, in particular between the effective size and the variance, which forces one to simultaneously retrieve at least these two parameters.     

Development of a laser-scattering-based probe for on-line measurement of surface roughness

The design and properties of an optical probe for on-line measurement of surface roughness are discussed. Based on light scattering, a probe that consists of a laser diode, a measuring lens, and a linear photodiode array was designed to detect surface roughness, in which the light scattered from a test surface at a relatively large scattering angle phi (=28 degrees) can be collected to enhance measuring range and repeatability. A coaxial design that incorporates a dual-laser probe and compressed air makes the proposed system insensitive to the position of the test surface and to surface conditions such as the presence of debris, vibration, and lubricants that result from machining. The results from measurements of several sets of specimens have demonstrated the feasibility of measuring surface roughness by using light scattering. On-line measurement on a diamond-turning lathe has shown that the proposed technique is stable and compact enough to be applicable to on-line measurement of surface roughness of an engineering surface.     

Influence of barrier on partial discharge activity by a conducting particle in liquid nitrogen under AC voltages adopting UHF technique

The UHF signals are generated due to PD formed by particle movement in liquid nitrogen under AC voltages. The levitation voltage of a particle in liquid nitrogen measured through UHF technique and by conventional PD measurement technique is the same, confirming the sensitivity of UHF technique for identification of PD activity. The frequency content of UHF signal generated due to particle movement in liquid nitrogen, under AC voltages, lies in the range 0.5–1.5 GHz. The characteristics of UHF signal generated due to particle movement between the barrier and high voltage/ground electrode is much similar to the signal generated by particle movement in clean electrode gap. Pseudo resonance phenomena can occur in liquid nitrogen due to particle movement. It is also observed that the partial discharge magnitude, in general, be high when the particle moves between the barrier and high voltage electrode when compared to the barrier and the ground electrode. Percentage of clay in epoxy nanocomposites has not altered the levitation voltage of the particle in the electrode gap. Zero span analysis clearly indicates that pseudo resonance occurs when particle moves (in a short gap) between the barrier and high voltage/ground electrode.