Automatic system for dimension recording and high accuracy metrology of plane pieces without contact

The image processing system described has been designed for two main purposes: (1) automatic non-contact dimension recording of plane workpieces, and (2) high accuracy metrology. The method of image acquisition, and the data processing are detailed for the control of a laser cutting robot.     

Quantum metrology with two-mode squeezed thermal state: Parity detection and phase sensitivity

Based on the Wigner-function method, we investigate the parity detection and phase sensitivity in a Mach–Zehnder interferometer(MZI) with two-mode squeezed thermal state(TMSTS). Using the classical transformation relation of the MZI, we derive the input–output Wigner functions and then obtain the explicit expressions of parity and phase sensitivity.The results from the numerical calculation show that supersensitivity can be reached only if the input TMSTS have a large number photons.     

一种提高双CCD图像拼接精度的方法

利用一对光楔间距变化时,通过它的成像光束的像点会产生微小偏移这一特性,在双CCD图像拼接探测器中增加了光楔调整机构,该光楔调整机构包含两对光楔,一对光楔用于CCD水平方向的图像调整;另一对用于垂直方向的图像调整。通过设计、制作,光楔调整机构最终应用于双CCD图像拼接探测器的装调。装调过程显示:加装光楔调整机构对原有光学系统没有任何影响,可以实现精度高于0.001 mm的图像移动量,有效降低了双CCD图像拼接探测器的装调难度,提高了拼接图像质量,降低了生产成本。     

青铜时代人类改进时钟精度之设计

开发精确、稳定的计时装置是物理学研究的基本组成部分。从改善卫星导航到理解植物的日常生命周期,准确的时钟“滴答”声都是必不可少的。但我们今天使用的时钟(钟摆时钟)仍然是属于相对较新的发明,距今只运转了365个年头,仅仅是现代人类在这个星球上漫步的30万年中的一小部分。在共振原子、盘旋齿轮和重力摆之前,人类先用水,然后利用太阳来测量时间的流逝。现在,三位考古学家和物理学家表示,他们已经辨认了第一个例子：组合使用水和太阳两种元素制作古代时钟。研究人员假设我们的前辈采用联合设计,是旨在提高守时准确性的早期努力。     

小波降噪提高时延估计精度的研究

为了估计两个在空间上分离的传感器所接收信号之间的时间延迟,结合小波降噪的特点,提出了一种基于小波降噪的广义相关时延估计算法.鉴于传统阈值降噪的不足,对小波阙值的选取进行改进,研究出一种新的小波阈值降噪技术.该算法克服了传统广义相关法需要信号和噪声先验知识的局限性,放宽了直接互相关法对信号和噪声的假设条件.仿真和实验结果...     

Improving the accuracy of aerosol extinction coefficient inversion

This paper considers the relationship between the accuracy of aerosol extinction inversion and the boundary value, and derives a theoretical high-accuracy aerosol extinction coefficient inversion. Aerosol extinction coefficient profiles depend on the boundary value. The relationship function of the differential extinction coefficient and differential boundary value is expressed by a maximum value. The smaller the differential boundary value, the smaller the differential extinction coefficient. The clean atmosphere layer is easily found from the lidar range-corrected signal, and the extinction coefficient of the clean atmosphere layer can be obtained using the slope method. By relating the extinction coefficient of the clean atmosphere layer to the extinction coefficient profiles at different boundary values, an accurate aerosol extinction coefficient profile can be obtained.     

Improving accuracy of acoustic source localization in anisotropic plates

The acoustic source localization technique for anisotropic plates proposed by the authors in an earlier publication ([1] Kundu et al., 2012) is improved in this paper by adopting some modifications. The improvements are experimentally verified on anisotropic flat and curved composite plates. Difficulties associated with the original technique were first investigated before making any modification. It was noted that the accuracy of this technique depends strongly on the accuracy of the measured time difference of arrivals (TDOA) at different receiving sensors placed in close proximity in a sensor cluster. The sensor cluster is needed to obtain the direction of the acoustic source without knowing the material properties of the plate. Two modifications are proposed to obtain the accurate TDOA. The first one is to replace the recorded full time histories by only their initial parts – the first dip and peak – for the subsequent signal processing. The second modification is to place the sensors in the sensor cluster as close as possible. It is shown that the predictions are improved significantly with these modifications. These modifications are then applied to another sensor cluster based technique called the beamforming technique, to see if similar improvements are achieved for that technique also with these modifications.     

提高锁相放大器测量交流磁化率精度的方法

在交流磁化率的测量实验中,互感法是常用方法,通常是利用线圈绕组和锁相放大器组合来测量样品在线圈中引起的电感变化.但这种方法其背景信号随绕组的增加而增大.本文采用2对线圈绕组并把两初级线圈反绕、两次级线圈同向绕的设计,减小背景信号,实际使用证明,经改进后测量灵敏度和测试精度都有很大提高.     

Increasing the sensitivity and accuracy of zinc determination in atomic absorption spectrometry

We have studied the effect of the nature and concentration of surfactants on the analytical signal of zinc. We show that of all the studied surfactants, sodium dodecylbenzenesulfonate increases the sensitivity and selectivity of the zinc determination the most. We have designed a method for atomic absorption determination of zinc in food products using sodium dodecylsulfate as a modifier. The detection limit for zinc according to the proposed procedure is C_min = 0.003 μg/mL. Report given at the International Congress of Analytical Sciences, ICAS-2006, 20–30 June 2006, Moscow, Russia. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 2, pp. 269–273, March–April, 2008.     

Polarizability of helium and gas metrology

Using a quasispherical, microwave cavity resonator, we measured the refractive index of helium to deduce its molar polarizability A(epsilon) in the limit of zero density. We obtained (A(epsilon,meas) - A(epsilon,theory))/A(epsilon) = (-1.8 +/- 9.1) x 10(-6), where the standard uncertainty (9.1 ppm) is a factor of 3.3 smaller than that of the best previous measurement. If the theoretical value of A(epsilon) is accepted, these data determine a value for the Boltzmann constant that is only 1.8 +/- 9.1 ppm larger than the accepted value. Our techniques will enable a helium-based pressure standard and measurements of thermodynamic temperatures.     

Engineering and metrology of epitaxial graphene

Here we review the concepts and technologies, in particular photochemical gating, which contributed to the recent progress in quantum Hall resistance metrology based on large scale epitaxial graphene on silicon carbide.     

当代计量学的现状和发展②——20世纪的度量衡,21世纪的量子计量学

介绍了新中国成立以来我国计量科学技术的发展和新取得的成就，并对21世纪的量子计量学作了展望和阐述。     

Improving accuracy by subpixel smoothing in the finite-difference time domain

Finite-difference time-domain (FDTD) methods suffer from reduced accuracy when modeling discontinuous dielectric materials, due to the inhererent discretization (pixelization). We show that accuracy can be significantly improved by using a subpixel smoothing of the dielectric function, but only if the smoothing scheme is properly designed. We develop such a scheme based on a simple criterion taken from perturbation theory and compare it with other published FDTD smoothing methods. In addition to consistently achieving the smallest errors, our scheme is the only one that attains quadratic convergence with resolution for arbitrarily sloped interfaces. Finally, we discuss additional difficulties that arise for sharp dielectric corners.     

Improving excitation and inversion accuracy by optimized RF pulse using genetic algorithm

In this study, a Genetic Algorithm (GA) is introduced to optimize the multidimensional spatial selective RF pulse to reduce the passband and stopband errors of excitation profile while limiting the transition width. This method is also used to diminish the nonlinearity effect of the Bloch equation for large tip angle excitation pulse design. The RF pulse is first designed by the k-space method and then coded into float strings to form an initial population. GA operators are then applied to this population to perform evolution, which is an optimization process. In this process, an evaluation function defined as the sum of the reciprocal of passband and stopband errors is used to assess the fitness value of each individual, so as to find the best individual in current generation. It is possible to optimize the RF pulse after a number of iterations. Simulation results of the Bloch equation show that in a 90 degrees excitation pulse design, compared with the k-space method, a GA-optimized RF pulse can reduce the passband and stopband error by 12% and 3%, respectively, while maintaining the transition width within 2 cm (about 12% of the whole 32 cm FOV). In a 180 degrees inversion pulse design, the passband error can be reduced by 43%, while the transition is also kept at 2 cm in a whole 32 cm FOV.     

Inverse perturbation analysis: Improving the accuracy of potential energy curves

The equation for the first-order energy correction is used inversely to find the perturbation responsible for the energy correction. In the specific application to the calculation of a potential energy curve from the spectroscopic term values, the sought perturbation is a correction to an approximate potential curve. Consequently, an approximate potential curve (e.g. an RKR (Rydberg-Klein-Rees) curve) can be improved until the eigenvalues calculated for this curve agree with the spectroscopic term values within the experimental uncertainty. Results are given for the X²Σ⁺ state of HgH.     

Improving the accuracy of laser particle sizer with Mie scattering theory

Using the classical Mie scattering theory and Fraunhofer diffraction theory,adetailed analysis of the differences of the light energy distribution falling on the multi-elementconcentric photo-detector of a diffraction based laser particle sizer is given.Numerical calcula-tions and computer simulation are carried out. Experimental studies are also made with latexspheres as Standard Reference Material.Our research shows that when the classical Mie scat-tering theory is used,the accuracy of the particle sizer can be essentially improved not only inthe small size range,but also for large paticles.At the same time the time needed for data re-duction in both cases is almost the same.     

基于多级组合棱镜提高激光中心波长检测精度的研究

为了在保证抗干扰能力不下降的条件下提高对激光中心波长的检测精度,设计了多级组合棱镜系统,并提出了多级组合棱镜的干涉条纹拼接处理方法及相位耦合的计算公式.通过计算多级组合棱镜的干涉图强度、光程差函数及光谱分辨率,分析了采用三块子棱镜的组合结构的光谱获取,给出了用于分段干涉条纹拼接的处理方法及步骤,最终光谱分辨率可达2.8...     

时间序列散斑干涉技术研究及应用

当用相干激光照射在一个连续位移或变形的漫射物体表面时,在与参考光形成干涉的接收面上即产生一随时间变化的散斑干涉场通过对这一干涉场的时间域进行分析,可实现时变位移场的定量检测本文介绍了基本时间序列散斑干涉场的扫描相位方法和时间序列相位法的相位函数解调原理,探讨了它们的计量特性,并将其用于火箭固体燃料性能的检测.     

Improving NMR sensitivity in room temperature and cooled probes with dipolar ions

The response of inverse triple resonance cold and conventional probes to ionic strength has been compared under a variety of conditions relevant to protein NMR. Increasing the salt concentration degrades probe performance in terms of sensitivity, and the effect is more severe for cold probes and with increasing magnetic field strength. This is especially noticeable for experiments that involve a spin lock or decoupling, where sensitivity losses compared with pure water can be more than 2-fold. We have investigated the use of glycine as a substitute for salt as a supporting solute for proteins, and we show that it has a minimal effect on probe tuning or performance. Readily available d5-Gly is a useful co-solute for protein NMR, especially at high magnetic field strengths and on cold probes, as it maintains solubility while not degrading probe performance.