阵列误差校正的综合校正补偿法

本文提出一种阵列误差的有源校正方法一综合校正补偿法。文中通过对我们研制的水下高分辨阵列处理实验系统中各种误差产生来源进行深入分析,有针对性地解决产生误差的主要因素;阵元性能不一致性、阵列误差的方向性,并提出把空域平滑技术应用到误差校正中,在不增加运算量的情况下,解相干与误差校正一次完成。水池实验表明该方法效果良好。     

Uncertainty analysis of the standard delay-and-sum beamformer and array calibration

Beamforming has become an ubiquitous task in aeroacoustic noise measurements for source localization and power estimation. The standard delay-and-sum (DAS) beamformer is the most commonly used beamforming algorithm due to its simplicity and robustness and also serves as the basis for more sophisticated algorithms, such as the deconvolution approach for the mapping of acoustic sources (DAMAS). The DAS data reduction equation is a function of many parameters including the microphone locations, microphone transfer functions, temperature and the cross-spectral matrix (CSM), where each one of these parameters has a unique uncertainty associated with it. This paper provides a systematic uncertainty analysis of the DAS beamformer and Dougherty's widely used calibration procedure under the assumption that the underlying mathematical model of incoherent, monopole sources is correct. An analytical multivariate method based on a first-order Taylor series expansion and a numerical Monte-Carlo method based on assumed uncertainty distributions for the input variables are considered. The uncertainty of calibration is analyzed using the Monte-Carlo method, whereas the uncertainty of the DAS beamformer is analyzed using both the complex multivariate and the Monte-Carlo methods. It is shown that the multivariate uncertainty analysis method fails when the perturbations are relatively large and/or the output distribution is non-Gaussian, and therefore the Monte-Carlo analysis should be used in the general case. The calibration procedure is shown to greatly reduce the uncertainties in the DAS power estimates. In particular, 95 percent confidence intervals for the DAS power estimates are presented with simulated data for various scenarios. Moreover, the 95 percent confidence intervals for the integrated DAS levels at different frequencies are computed using experimental data. It is shown that with experimental data, the 95 percent confidence intervals for the integrated power levels are within of the mean levels when the component uncertainties are set at low but achievable values.     

点阵列标定模板图像特征点提取方法

在摄像机标定过程中,提取标定模板图像特征点的精度是影响摄像机内外参数标定精度的重要因素。本文根据条纹投影三维轮廓测量实验系统的要求制作了点阵列标定模板,在图像处理边缘理论的基础上,以圆的解析特性为依据,采用坐标转换思想,引进圆系描述点、圆对应关系,运用统计学理论,提出提取点阵列标定模板图像特征点的新方法,并通过实验验证了该方法的正确性和可行性。为下一步的摄像机内外参数求解做了铺垫。     

Optical sorting using an array of optical vortices with fractional topological charge

An array of optical vortices with fractional topological charge is generated using a phase-only Talbot array illuminator and used to sort microparticles. Our theoretical analysis and experimental results reveal that when a particle passes through a fractional vortex array, it will be driven by two forces, intensity-gradient force and phase-gradient force, and the cooperation of these two forces can improve its ability in optical sorting because of the special intensity and phase distribution of the fractional optical vortex array. Larger angle separation could be obtained with moderate laser power.     

Timing-error-difference calibration of a two-dimensional array imaging system using the overlapping-subaperture algorithm

Timing errors in the transmitting and receiving electronic channels of an imaging system can generate different transmission and reception phase-aberration profiles. To decide if these two profiles need to be measured separately, an overlapping-subaperture algorithm has been proposed in a previous paper to measure the difference between timing errors in transmitting and receiving channels connected to each element in a two-dimensional array. This algorithm has been used to calibrate a custom built imaging system with a curved linear two-dimensional array, and the results are presented in this paper. The experimental results have demonstrated that the overlapping-subaperture algorithm is capable of calibrating the timing-error-difference profile of this imaging system with a standard deviation of only a few nanoseconds. Experimental results have also shown that the time-error-difference profile of this imaging system is smaller than one tenth of a wavelength and there is no need to measure the transmission and reception phase-aberration profiles separately. The derived average phase-aberration profile using the near-field signal-redundancy algorithm can be used to correct phase aberrations for both transmission and reception.     

一维介观结链中电荷孤子的控制

研究了一维介观结链中的电势分布随各岛上门电压和电子数分布的变化关系,并发现在一个岛上加一个门电压会产生一个静电势孤子.通过调节门电压可以较好地控制静电势孤子的形状及其位置,从而达到对电荷孤子的有效控制. 关键词： 电荷孤子 介观结 单电荷隧穿     

传声器阵列声压级在线校准*

在户外环境中对某一目标噪声源进行声压级测量时,由于单个传声器不能在多声源干扰情况下有效监测目标信号,为了有效抑制非目标信号的干扰,通常利用传声器阵列进行波束形成从而对目标信号进行增强。MEMS传声器阵列由于体积小,价格低等优点而得到广泛使用,为了解决在户外进行噪声监测时,MEMS然而MEMS传声器阵列器件的工艺误差和灵敏度退化问题会导致波束形成滤波器的性能下降存在由器件工艺误差和老化所导致的声压级测量不准确问题,从而影响声压级的测量结果。为了解决这一问题,本文介绍了一种通过比较补偿参考传声器与传声器阵列之间的测量声压级之偏差进行从而实时在线校准的方法。该方法利用TDOA多声源定位方法在时频点上对实时采集的信号对所采集的信号在时频点上挑选有效目标信号进行有效挑选,并利用参考传声器的标准频响特性去修正阵列的声压级测量误差值。为了验证方法的可行性,本文通过实验比较了不同环境噪声干扰下的测量声压级差与无干扰条件下的测量声压级差的一致性,结果证明该校准方法在具有较好高的精确性和鲁棒性,并且可推广于任意一种阵型的传声器阵列声源定位装置噪声监测装置。     

Three-dimensional focus engineering using dipole array radiation pattern

A systematic three-dimensional focus engineering method based on the dipole-array radiation pattern is proposed. High numerical aperture focusing of generalized cylindrical vector beam is interpreted as the reversing of the radiation from electrically small dipole arrays. Required pupil plane illumination can be found for the desired focal field with specific characteristics. Magnetic-dipole array radiation is utilized to create ultra-long (~ 8λ) diffraction limited three-dimensional optical tube with maximal uniformity. Combined with a recently reported optical needle field generation with the help of electric dipole array radiation, ultra-long (~ 8λ) three-dimensional flattop focus that has top hat profiles in both transversal and longitudinal directions can be realized with the help of radiations pattern from co-located magnetic and electric dipole arrays.     

Light source system for high-precision flat-field correction and the calibration of an array detector

Signal distortion due to the non-uniform response of the detector degrades the measurement accuracy of most metrology instruments. In this Letter, we report a newly developed calibration source system for reference-based non-uniformity correction using a laser source, a fiber, and a diffusive module. By applying the Monte Carlo simulation, we show that the transmittance of the system highly depends on the cavity reflection of the diffusive module. We also demonstrate the use of this system to achieve a flat field at a very low non-uniformity(less than 0.2%) with proper illumination intensity, which most costly commercial integrating sphere systems traditionally cannot provide.     

强多途环境下水听器阵列位置近场有源校正方法

针对水听器阵列近场强多途环境下的校正需求, 提出了一种高精度的多辅助源阵列位置校正方法.综合近场点源非平面波模型和泰勒近似原理, 构建了近场阵元位置二维误差模型, 进而获得信号特征向量与阵元位置误差的线性映射关系.推导并计算了校正模型的克拉美罗界(CRB).研究了多途对阵元位置校正的影响, 将多途干扰视为位置已知的相干源, 提出了多途补偿策略.理论及仿真结果表明, 近场多辅助源阵列位置校正方法具有较高的精度, 在低信噪比时接近CRB, 对于辅助源位置等误差具有一定的容忍度, 且适用于强多途环境.湖试验证了方法结论的正确性.     

一种单线阵CCD立靶系统参数的标定方法

单线阵CCD立靶相对其它立靶方法而言具有结构简单、成本低等优势,而系统参数的准确标定是测量精度的保证。针对该立靶测量系统,通过建立标定模型确定了影响测量精度的各系统参数,包括镜头主点,激光器位置,相机的倾角、焦距和原向反射膜高度。将整个系统参数看做一个黑盒模型并进行整体标定,只需考虑黑盒的输入和输出端,根据CCD相机所接收到弹丸双投影点的位置计算弹丸的坐标。实验结果表明在靶面大小1m×1m时,理论计算值与实际放置模拟弹丸之间的偏差小于5mm。     

Effects of Coulomb interaction on charge transport in a silicon-based nanocluster array

The effects of Coulomb interaction on charge transport in a model of light emission from an array of silicon nanoclusters are studied by Monte Carlo simulations. The array is sandwiched between a p-type and an n-type doped silicon crystals and electrons and holes are driven into the array by an applied electric field. Radiative recombinations of electrons and holes take place near the center of the array producing the emission of red light, and the total emission power is approximately proportional to the current injected into the system. It is found that the carrier-carrier interaction plays a crucial role in charge transport. Specifically, the self-interaction of charges inside each nanocluster is found to be the dominant interaction term for the semiclassical Hamiltonian considered. In addition, it drastically limits the current in the device giving rise to a strong non-linear relation between current and density of free carriers in the doped silicon crystals.     

相对标定电荷交换复合谱及束发射谱测量杂质浓度的方法研究

采用数值模拟方法计算了HL-2A装置上电荷交换复合谱和束发射谱的强度,并根据两种光谱的比值得到碳和氦杂质的浓度,与初始假设对比后验证了该方法理论上的可靠性。实验上采用一台三光栅光谱仪系统,利用同一视线、同时测量了碳(CⅥ)、氦(HeⅡ)的电荷交换复合谱及中性束发射谱,首次在HL-2A装置上同步获得了C6+、He2+离子的绝对浓度剖面。该方法采用了相对强度标定而非复杂的绝对强度标定,并且避免了中性束衰减计算。     

Method of array shape calibration based on time delay estimation using two auxiliary sources

As for a flexible horizontal array deployed in the sea, it is difficult to obtain each sensor's precise relative position. Therefore a method of array shape calibration is proposed. The method is described as follows. Firstly two separate auxiliary sources are deployed. Secondly tune delay of each sensor's received signal is estimated. Finally, with the aid of GPS location of the sources and the horizontal array, relative sensor positions of the horizontal array can be determined. The estimation of relative sensor positions is unbiased. Simultaneously, simulation analysis has been done to estimate its standard variance, and the optimal flare angle of the two sources has been derived. Data of 2001 Asian Sea International Experiment have been used to validate the method. After array calibration, measured source azimuth angle agrees with the real one, and measured array gain agrees with the theoretical gain. In conclusion, the theoretical and experimental results both show that the method can determine each sensor's relative position precisely.     

A study of space charge measurement

At present, there is no appropriate measurement techniques for space charge. In this paper, a U-shaped cavity device is developed as the space charge measurement device, which can be applied to transmission lines. Its design principle and calculation techniques of design parameter are also introduced. To test the space charge measurement accuracy of the U-shaped cavity device, a space charge generator is developed specifically for this experiment. The test results are excellent and show that the U-shaped cavity device can meet the design requirements. This technique is suitable for space charge measurement under transmission line normally charged work condition.     

Electric charge systems moving with the velocity of light and associated with charge creation

A discussion is given of certain electromagnetic fields associated with charges moving with the velocity of light which are associated with zero magnetic field, and the creation of charge. The stress energy tensor associated with charge creation is also discussed and it is shown that the stress energy tensor includes a term which may be interpreted as a shear.     

Spectroscopic study of polyphenylquinolines—materials with efficient intramolecular charge transfer

The energy structure and nature of intramolecular charge transfer have been determined for a series of synthesized 2,6-polyphenylquinolines (PPQs) containing resorcinol, oxygen, and phenylamine bridging groups between phenylquinoline cycles and possessing an arylene radical in the form of alkylated derivatives of carbazole or indolo[3,2-b]carbazole, as well as arylated derivatives of carbazole with nitro- and fluorine substituents. The analysis was based on data on their absorption spectra, photosensitivity, carrier photogeneration quantum efficiency, and luminescence. It is shown that the PPQ monomeric unit is a composite intramolecular charge-transfer complex (ICTC) between the donor arylene fragment and the acceptor quinoline cycle; the latter, in turn, is an ICTC between the donor bridging group and quinoline ring (when acceptor fluorine or nitro substituents are introduced into the carbazole structure, the complex becomes ternary), and the narrowest band gap (2.3 eV) corresponds to the PPQ having a phenylamine bridging group and a fragment of indolo[3,2-b]carbazole.     

利用恒星辐射测量整层大气透过率的多目标星定标

介绍了整层大气透过率测量仪及其测量原理和Langley-Plot定标方法,提出了基于恒星整层大气透过率仪测量大气透过率的多目标星定标方法,并分别进行了K,A光谱类型恒星定标试验,得到了基于K,A两种光谱类型恒星辐射的定标值。对多目标星定标方法与单颗恒星的Langley-Plot定标方法进行了对比实验,验证了多目标星定标方法的合理性与准确性。当实时测量同类型的恒星辐射整层大气透过率时,就可以根据对应的定标参数进行测量研究。     

一种基于时延估计的双辅助声源阵形校准方法

布放柔性水平阵列时,各阵元的相对位置很难精确知道,为了解决这一问题,提出了一种阵形校准方法。首先布设两个成一定张角的校准声源,利用它们估计各阵元信号的时延关系,利用声源和接收阵的GPS位置,确定各阵元的相对位置。得到的位置估计是无偏估计,给出了位置估计标准差的数值模拟结果,得出了两校准声源的最佳角度关系。利用2001年亚洲海国际实验的数据对该方法进行了验证,用校准后的阵形得到的测量声源方位角和实际角度一致,实测的阵增益也和理论值相符合。理论及实验分析结果表明,该方法能够准确定出各阵元的相对位置。