Hydrophones' effective diameter measurements as a quasi-continuous function of frequency

The spatial averaging effect is strongly dependent on the active aperture of the hydrophone probes used to measure ultrasound fields. An experimental method was developed to determine the effective diameter of the probes as a quasi-continuous function of frequency. The implementation of the method utilizes the time delay spectrometry (TDS) technique and a set of focused acoustic sources. The use of focused sources ensured plane wave conditions for the whole frequency range and TDS eliminated all the reflections from the water tank boundaries. This approach allows effective diameter of circular aperture hydrophones to be determined as a quasi-continuous function of frequency up to 40 MHz. The measurements were performed for both needles and membrane designs having nominal diameters ranging from 50 to 500 microm. The results were successfully employed in the development of spatial averaging correction algorithms. Current efforts are being focused on extension of the frequency range up to 60 MHz by using a novel measurement technique termed time gating frequency analysis.     

Approximation by circles

We derive algorithms which permit the inspection of plane hole patterns for their position tolerance. The entire hole pattern is measured by a coordinate measuring machine and then is fitted into the nominal pattern in such a way as to minimize the maximum of the distances between the nominal and the actual positions.

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Zusammenfassung Wir entwickeln Algorithmen, mit deren Hilfe die Einhaltung der Positionstoleranzen ebener Lochbilder untersucht werden kann. Die Gruppe der Ist-Zentren wird dabei gegenüber der Gruppe der Soll-Zentren so eingepaßt, daß der maximale Abstand zwischen den Soll- und den Ist-Werten minimal ausfällt.

     

相位恢复测量长焦距镜面

针对长焦距光学镜面检测中测量光路长,振动干扰较大,不容易用干涉仪进行面形检测的难题,提出了一种基于相位恢复技术的测量方法.该方法用相干点光源照射被测镜,采集一系列焦点附近的衍射光强图像,然后运用相位恢复算法得到镜面面形误差分布.利用衍射光学理论建立了测量模型,并用基于Gerchberg-Saxton算法的迭代算法求解模型.然后仿真验证了光场传播模型的可靠性和测量算法的有效性,并用该方法测量了一块曲率半径8 700 mm,口径145 mm的球面镜.通过对光强图像位置进行优化,并选择适当离焦位置的图像,最终恢复出了镜面面形.相位恢复测量的结果与动态干涉仪测量结果基本一致,并且测量装置简单,对环境要求低.     

基于X射线掠射法的纳米薄膜厚度计量与量值溯源研究

为了实现纳米薄膜厚度的高精度计量,研制了可供台阶仪、扫描探针显微镜等接触测量的纳米薄膜样片,研究了X射线掠射法测量该纳米薄膜样片厚度的基本原理和计算方法,导出了基于Kiessig厚度干涉条纹计算膜层厚度的线性拟合公式,并提出了一种可溯源至单晶硅原子晶格间距和角度计量标准的纳米膜厚量值溯源方法,同时给出了相应的不确定度评定方法.实验证明:该纳米薄膜厚度H测量相对扩展不确定度达到U=0.3 nm+1.5%H,包含因子k=2.从而建立了一套纳米薄膜厚度计量方法和溯源体系.     

Nano-scale sensing transducer using entangled photon walk-off compensation

We propose a new concept of a nano-sensing transducer system using a nano-waveguide. The small change in physical quantity affects to the change in device parameters such as refractive index or length which is relatively absorbed and observed by the resonant signals. In principle, the stored light pulse at the specified wavelength is generated by using a soliton propagating within the ring resonators, whereas a resonant signals can be stored within the nano-waveguide, i.e. a sensing transducer, which is formed by the sensing ring device. The induced change in the resonant signals by the surrounded environment is occurred, and can be detected by using the optical/quantum processor. Such a proposed device is namely suitable to perform the measurements in the nano-scale regime such as force, stress and temperature.     

气控钠热管特性的实验研究

为了研究气控钠热管的传热性能,中国计量科学研究院自主研制了气控钠热管系统。包括:气控钠热管、热管加热炉及温控系统、高温真空除气系统、压力控制系统和高精密温度测量系统。在此基础上开展了气控钠热管温度稳定性与温度场均匀性实验研究。实验结果表明:在热管内温度655℃、压力动态控制在7840 Pa条件下,气控钠热管温度计阱15min内温度稳定性为士0.84 mK。     

原子运动速度对激光驻波场作用下纳米光栅沉积特性的影响

利用近共振激光驻波场操纵中性原子实现纳米光栅的沉积是一种新型的研制纳米结构方法,处于激光驻波场中的原子运动速度特性对最终纳米光栅的沉积特性有着重要的影响.利用半经典理论,基于4阶Runge-Kutta算法进行了不同铬原子纵向和横向运动速度条件下纳米光栅结构沉积的仿真研究.研究表明,铬原子纵向速度为最大概率速度960 m/s时,所形成的纳米光栅的半高宽为1.49 nm,对比度为62.1 ∶1,当铬原子的纵向速度为半最大概率速度480 m/s时,纳米光栅的半高宽为5.35 nm,对比度下降为25.6 ∶1.同 关键词： 原子光刻 纳米计量 激光驻波场 纳米光栅结构     

标准白场仪及视角测量方法的研究

 针对目前主流彩色电视与平板显示器,建立了能够溯源到国家光谱辐射度、光度与色度基准的标准白场仪装置,可用于显示器光色特性参数测量。对该装置进行了定标,提供了标准白场仪光谱、稳定性以及光色参数。应用该标准装置对主流的液晶显示器进行了视角研究,主要考虑了测量过程中所忽略的被测发光面积因素对视角特性的影响。结果表明,基于绝对亮度的视角阈值方法,差别可达8%以上,是测量过程中需要考虑和避免的。     

Fabrication and measurement of traceable pitch standard with a big area at trans-scale

Atom lithography with chromium can be utilized to fabricate a pitch standard,which is directly traceable to the wavelength of the laser standing waves. The result of a calibrated commercial AFM measurement demonstrates that the pitch standard is(212.8±0.1) nm with a peak-to-valley-height(PTVH) better than 20 nm. The measurement results show the high period accuracy of traceability with the standing laser wavelength(λ /2 = 212.78 nm). The Cr nano-grating covers a 1000 μm×500 μm area, with a PTVH better than 10 nm. The feature width broadening of the Cr nanostructure has been experimentally observed along the direction of the standing waves. The PTVH along the Gaussian laser direction is similar to a Gaussian distribution. Highly uniform periodic nanostructures with a big area at the millimeter scale, and the surface growth uniformity of the Cr nano-grating, show its great potential in the application of a traceable pitch standard at trans-scales.     

某型装备便携式计量校准系统的设计与实现

运用基于Windows 2000 SP4/Windows XP SP2操作系统的Microsoft Access 2003数据库管理系统,设计了某型装备的便携式计量校准系统。该系统由校准通用平台、通用校准装置、专用校准装置和系统软件组成。阐述了该系统的总体设计组成,重点介绍了专用校准装置;实际应用表明,该系统能够完成初始射高、射角、射向、温度等参数的精确计量,能够保证射击精度要求,而且能够提高现场检测效率。