用于气象观测的阵列式温度传感器流体动力学分析与实验研究

传统百叶箱和防辐射罩内部的温度传感器受到太阳辐射会导致其温度高于大气真实温度, 升温量可达0.8 K甚至更高. 为提高大气温度观测精度, 本文设计了一种阵列式温度传感器. 利用计算流体动力学方法分析计算该传感器在不同环境条件下的辐射升温量, 采用遗传算法对计算结果进行拟合, 获得辐射升温量修正方程. 为验证阵列式温度传感器的实际性能, 研制了强制通风温度测量平台. 将阵列式温度传感器、配有传统防辐射罩的温度传感器和强制通风温度测量平台置于相同环境下, 进行大气温度观测比对实验. 配有传统防辐射罩的温度传感器辐射升温量平均值为0.409 K; 与前者相比, 阵列式温度传感器的辐射升温量仅为0.027 K. 这种阵列式温度传感器可将辐射升温引起的误差降低约93%. 辐射升温量实验测量值与修正方程修正值之间的平均偏移量为0.0174 K, 均方根误差为0.0215 K, 该结果验证了计算流体动力学方法与遗传算法的准确性. 如果配合计算流体动力学方法与遗传算法, 温度测量精度有进一步提高的潜力.     

Development and implementation of an angle detector using nanoporous silicon-based photovoltaic sensor

The present work deals with the design, development, and implementation of an angle detector using n-ATO/p-PSi photovoltaic sensor. Nanoporous structures have been developed over p-type porous silicon wafers by anodization technique under optimized conditions. Photoluminescence studies of porous silicon show emission between 700 and 702 nm for the constant excitation at 350 nm, which illustrates that the band gap can be tuned according to the HF:H₂O:C₂H₅OH ratio. n-ATO/p-PSi O heterojunction photovoltaic sensor has been developed by cost-effective Spray pyrolysis method. I–V characteristics under dark and different illumination intensities have been investigated, and the results are discussed. The fabricated sensor is employed for sensitive angle detection of a light source. The sensor is attached to a DC motor, which rotates at 30 rpm. When the light is from the source incident on the light sensor, a dc voltage has been produced, which in turn is amplified, and the signal has been used to stop the motor. The motor is coupled to a rotary transducer, which is calibrated to read or display 0–3.60 V for 0–360°. Paper presented at the Third International Conference on Ionic Devices (ICID 2006), Chennai, Tamilnadu, India, Dec. 7–9, 2006.     

大孔径声全息密集阵列的阵元数量去冗余方法

大孔径密集声全息阵列是实现对非平稳噪声成像的有效手段,通过现场快速成像可以掌握声场分布的动态特征。增加声阵列的孔径和阵元密度是提高近场声全息成像性能的主要措施,但随着声阵列阵元数量的增加,声压采集数据量增大,全息运算速度降低,全息成像动态性能下降,不利于现场即时成像分析。研究表明,在一定信噪比条件下,盲目增加阵元数量并不一定能提高近场声全息性能,为此,本文针对密集声全息阵列的阵元数量冗余问题进行研究,提出最优阵元数量估算方法,并采取去冗余处理。本文仿真和实验验证表明:针对一定信噪比条件下的密集阵列去冗余方法实际有效,可以在不降低近场声全息成像性能的前提下,降低运算量,提高全息成像速度,对于非平稳噪声的现场声全息成像测试具有实用意义。     

一种强指向性基阵的设计及声场计算

提出了一种新的基阵:将90个小圆环分布于半径不同的5个同心圆周上,对每个小圆环采用了抛物型的振速加权。通过改变阵元尺寸、间距等参数研究了声场特征的变化。计算结果表明,该基阵模型具有非常高的指向性和抑制旁瓣的能力。通过优化阵元组合方式和参数,可获得最佳的声压分布效果。     

微分Haar-Gaussian小波变换在大景深物体边缘测量中的应用

提出了微分Haar_Gaussian小波变换算法并将其应用于边缘检测,在空域和频域中进行变换,并应用带宽匹配方法和远心测量光学系统,提高了运算速度,通过对实际大景深物体离焦像的边缘测量,得到了准确的结果。     

Modeling and design of an optimized patterned electrode liquid crystal microlens array with dielectric slab

To eliminate the occurrence of disclination lines in the hole patterned electrode liquid crystal microlens array (LC MLA), inserting an ultrathin dielectric slab was proved to be an effective method. The thickness of the dielectric slab played an important role in effecting the optical performance of the liquid crystal microlens array device, including the dynamic focal range, focus diameter and symmetry of phase profile. In this paper, we studied the effect of dielectric slab thickness on the optical performance of the liquid crystal microlens array by numerical simulation. It is indicated that the optical performance of the device could be improved by reducing the dielectric slab thickness, assuming that the dielectric slab thickness was larger than the threshold thickness. The dependence of the threshold thickness on some key parameters was investigated and the associated effect on the optical performance by changing these key parameters was also studied. In the end, the approaches to enhance the optical performance, namely the dynamic focal range of the liquid crystal microlens array was proposed and proved to be in effect by numerical simulation results.     

Efficiency improvement and spectral shift of an organic light-emitting device with a square-based microlens array

In this paper, we present and analyze the influences of the fill factor and the height ratio of square-based microlens arrays on the optical characteristics of an organic light-emitting device (OLED). These properties include spectral shift, CIE coordinates, viewing-angle dependence, luminous current efficiency and luminous power efficiency. Both the luminous current efficiency and luminous power efficiency of the OLED were found to increase linearly with increasing the fill factor of microlenses. It is also found that the full width at half maximum (FWHM) of the OLED spectra and CIE coordinate decreased linearly with increasing the fill factor of the microlenses. Besides, the efficiency improvement of the OLED increased with the height ratio of attached microlenses. Compared to the OLED, the luminous current efficiency and luminous power efficiency of the device can be enhanced by 42% and 47%, respectively, by attaching the microlens array having a fill factor of 90% and a height ratio of 0.57. We also observed blue shifts at different viewing angles when microlens arrays were attached to the OLED, which is the evidence that the waveguiding modes are being extracted. In our planar OLED, the peak wavelength blue shifted and the FWHM decreased with increasing the viewing angles due to the microcavity effect.     

薄板挠曲型光纤Bragg光栅土压力传感器设计与分析

根据土压力传感器与土介质的匹配原则,设计了一种圆平膜片薄板挠曲型FBG土压力传感器。通过在圆膜片上设计一组对称的光栅固定柱,有效避免了传感器在使用过程中产生谱峰分裂。同时,利用光栅固定柱张角引起的应变效应,大幅度地提高了传感器的压力灵敏度。理论分析了该结构的增敏机理并给出传感器灵敏度公式,计算结果表明,传感器的压力灵敏度可达1 374.3 pm/MPa。使用ANSYS建立薄板挠曲的有限元模型,通过提取固定柱中心点处在光纤方向上的位移,获得了有限元模型的压力灵敏度为1 360.8 pm/MPa。有限元分析和理论设计结果的相对误差为0.98%,具有很高的一致度,验证了理论设计和分析的正确性。     

由各向异性海森伯自旋环链组成的量子位及其通用量子逻辑门

研究了各向异性耦合的三粒子海森伯自旋环链团簇在随时间变化的磁场中的运动.该系统的哈密顿量具有SU(2)代数结构.用代数动力学方法对此系统进行求解，得到了严格的解析解.基于严格解, 可以构造一位量子逻辑门.通过调节磁场强度和频率, 就可以控制该量子逻辑门, 实现一位量子逻辑门的任何操作. 关键词： 代数动力学 自旋环链团簇 一位量子逻辑门     

窗口可变滑动相关分析方法在激光诱导击穿光谱谱线自动识别中的应用

激光诱导击穿光谱(LIBS)谱线具有很窄的展宽,且光谱仪因外界温度条件的变化存在波长漂移,光谱数据为离散数字信号,受噪声、谱线重叠及连续背景的影响,信号存在失真和变形。而目前光谱仪自带谱线识别分析软件主要以"就近原则"为主,错误率较高,必须依赖于人眼的观察对比。针对这个问题,在研究LIBS光谱特性的基础上,提出了一种窗口可变滑动相关分析方法(CAASW),用于激光诱导击穿光谱谱线自动识别。以土壤标准物质为样品,对该方法进行了实验分析和评价,与光谱仪自带分析识别软件相比,CAASW明显提高了识别准确率和识别速度,最终实现了谱线的自动识别。     

Contrast reversal and enhancement of phase spot array/grid with an intensity-dependent refractive index medium as phase filter

We report on a complete contrast reversal and contrast enhancement of a holographically recorded phase spot array/grid achieved by phase filtering, using an intensity-dependent refractive index medium, zinc tetraphenyl porphyrin as phase filter placed in the Fourier plane of the 4-f imaging system. We show that the contrast enhancement is robust and insensitive to local errors in the phase array and can be used to repair a damaged portion of the input phase array.     

带虚设层的抗反射结构导模共振滤波器设计与分析

提出带虚设层的抗反射导模共振滤波器结构及设计方法,该方法适用于任意角度入射带虚设层的抗反射结构导模共振滤波器设计与分析.得到带虚设层的导模共振滤波器抗反射结构所满足的关系式.指出在维持虚设层光学厚度不变的情况下,可以通过不同选材,在低反射旁带中实现等带宽不同波长的选择.此外,由于结构的抗反射特性在低角范围内具有较大的角度容差,改变入射角,可以实现滤波波长及光谱带宽在宽光谱范围内的准线性可调谐.     

Analysis of input functions from different arterial branches with gamma variate functions and cluster analysis for quantitative blood volume measurements

Regional cerebral blood volume (rCBV) provides valuable information about the nature and progress of diseases of the central nervous system. While relative rCBV maps can be derived directly from dynamic susceptibility contrast data, the arterial input function (AIF) has to be measured for absolute rCBV quantification. For determination of the AIF pixels located completely within a feeding artery must be selected. However, by using a region-of-interest (ROI) based selection some confounding effects can occur, especially if single shot echo planar imaging (EPI) with low spatial resolution is used. In this study we analyzed the influence of partial volume effects and spatial misregistration due to frequency shifts induced by paramagnetic contrast agents. We analyzed AIFs from the internal carotid artery (ICA), the vertebral artery (VA) and the middle cerebral artery (MCA) using gamma variate function based parameterization. The concentration time curves (CTC) of several pixels which were selected on the basis of strong signal drop appeared distorted during the bolus passage. Moreover, the amplitudes of input functions derived from the MCA were smaller by a factor of three as compared to those of the ICA and VA. Simulations revealed that these effects can be attributed to a spatial shift of the vessel along phase-encoding direction during the passage of the bolus. We therefore developed a procedure for a pixel selection based on cluster analysis which classifies pixels according to the parameters of the fitted gamma variate functions. This approach accounted for misregistration of the vessel and yielded very consistent results for a group of normal subjects.     

Detection of Static and Mobile Targets by an Autonomous Agent with Deep Q-Learning Abilities

This paper addresses the problem of detecting multiple static and mobile targets by an autonomous mobile agent acting under uncertainty. It is assumed that the agent is able to detect targets at different distances and that the detection includes errors of the first and second types. The goal of the agent is to plan and follow a trajectory that results in the detection of the targets in a minimal time. The suggested solution implements the approach of deep Q-learning applied to maximize the cumulative information gain regarding the targets’ locations and minimize the trajectory length on the map with a predefined detection probability. The Q-learning process is based on a neural network that receives the agent location and current probability map and results in the preferred move of the agent. The presented procedure is compared with the previously developed techniques of sequential decision making, and it is demonstrated that the suggested novel algorithm strongly outperforms the existing methods.     

An analysis of the simulated acoustic emission sources with different propagation distances,types and depths for rail defect detection

Acoustic Emission (AE) technique is an effective nondestructive detecting method, and has a promising application for rail defect detection. So far, little attention has been paid to propagation distances, types, and depths of AE sources, which are important for rail defect detection accurately. This paper presents an experimental study on the simulated AE sources with different propagation distances, types and depths for rail defect detection. Three simulated AE sources with different frequencies are seeded on the cross section of rail, and the depths of AE sources are changed in the vertical direction. After receiving AE signals, wavelet transform and Rayleigh–Lamb equations are utilized to extract time–frequency features and modes. Based on the wavelet transform with corresponding group-velocity curves, the influences of different propagation distances, the features of different source types and the rules of different source depths are examined. It is concluded that the features of AE sources with different propagation distances, types and depths can be obtained by AE technique for rail defect detection. It is very useful to analyze and detect defects in rail defect detection.     

Dynamic analysis and synchronization control of an unusual chaotic system with exponential term and coexisting attractors

This paper reports a new four-dimensional chaotic system consisting of an exponential nonlinear term, two quadratic nonlinear terms and five linear terms. The system has only one equilibrium and performs stability, periodicity and chaos with the variation of the parameters. It losses its stability with the occurrence of Hopf bifurcation and goes into chaos via period-doubling bifurcation. One more interesting feature of the system is that it can generate multiple coexisting attractors for different initial conditions, such as two strange attractors with one limit cycle, one strange attractor with two limit cycles, etc. The dynamic properties of the system are presented by numerical simulation includes bifurcation diagrams, Lyapunov exponent spectrum and phase portraits. An electronic circuit is constructed to implement the chaotic attractor of the system. Based on the linear quadratic regulator (LQR) method, the synchronization control of the system is investigated.     

Eye pupil detection system using an ensemble of regression forest and fast radial symmetry transform with a near infrared camera

In this paper, we focus on pupil center detection in various video sequences that include head poses and changes in illumination. To detect the pupil center, we first find four eye landmarks in each eye by using cascade local regression based on a regression forest. Based on the rough location of the pupil, a fast radial symmetric transform is applied using the previously found pupil location to rearrange the fine pupil center. As the final step, the pupil displacement is estimated between the previous frame and the current frame to maintain the level of accuracy against a false locating result occurring in a particular frame. We generated a new face dataset, called Keimyung University pupil detection (KMUPD), with infrared camera. The proposed method was successfully applied to the KMUPD dataset, and the results indicate that its pupil center detection capability is better than that of other methods and with a shorter processing time.     

Mechanical properties of silicon nanobeams with an undercut evaluated by combining the dynamic resonance test and finite element analysis

Mechanical properties of silicon nanobeams are of prime importance in nanoelectromechanical system applications.A numerical experimental method of determining resonant frequencies and Young’s modulus of nanobeams by combining finite element analysis and frequency response tests based on an electrostatic excitation and visual detection by using a laser Doppler vibrometer is presented in this paper.Silicon nanobeam test structures are fabricated from silicon-oninsulator wafers by using a standard lithography and anisotropic wet etching release process,which inevitably generates the undercut of the nanobeam clamping.In conjunction with three-dimensional finite element numerical simulations incorporating the geometric undercut,dynamic resonance tests reveal that the undercut significantly reduces resonant frequencies of nanobeams due to the fact that it effectively increases the nanobeam length by a correct value △L,which is a key parameter that is correlated with deviations in the resonant frequencies predicted from the ideal Euler-Bernoulli beam theory and experimentally measured data.By using a least-square fit expression including △L,we finally extract Young’s modulus from the measured resonance frequency versus effective length dependency and find that Young’s modulus of a silicon nanobeam with 200-nm thickness is close to that of bulk silicon.This result supports that the finite size effect due to the surface effect does not play a role in the mechanical elastic behaviour of silicon nanobeams with thickness larger than 200 nm.     

Mechanical properties an undercut evaluated resonance test and of silicon nanobeams with by combining the dynamic finite element analysis

Mechanical properties of silicon nanobeams are of prime importance in nanoelectromechanical system applications. A numerical experimental method of determining resonant frequencies and Young＇s modulus of nanobeams by combining finite element analysis and frequency response tests based on an electrostatic excitation and visual detection by using a laser Doppler vibrometer is presented in this paper. Silicon nanobeam test structures are fabricated from silicon-oninsulator wafers by using a standard lithography and anisotropic wet etching release process, which inevitably generates the undercut of the nanobeam clamping. In conjunction with three-dimensional finite element numerical simulations incorporating the geometric undercut, dynamic resonance tests reveal that the undercut significantly reduces resonant frequencies of nanobeams due to the fact that it effectively increases the nanobeam length by a correct value △L, which is a key parameter that is correlated with deviations in the resonant frequencies predicted from the ideal Euler-Bernoulli beam theory and experimentally measured data. By using a least-square fit expression including △L, we finally extract Young＇s modulus from the measured resonance frequency versus effective length dependency and find that Young＇s modulus of a silicon nanobeam with 200-nm thickness is close to that of bulk silicon. This result supports that the finite size effect due to the surface effect does not play a role in the mechanical elastic behaviour of silicon nanobeams with thickness larger than 200 nm.     

Amplitude modulation and soliton formation of an intense laser beam interacting with dense quantum plasma: Symbolic simulation analysis

In this theoretical study, we investigate the amplitude modulation and envelop soliton formation in a dense plasma when such a plasma interacts with a strong laser beam. We have made use of the symbolic simulation technique to find the modulation instability of an electrostatic wave with higher orders of non-linearity. We identified the range of wavenumber in which such non-linearity is important. Furthermore, we have analysed the formation of envelope soliton of waves localized in space. The results obtained here will be helpful in interpreting different phenomena that arise in laser plasma interaction. The importance of the relativistic contribution of streaming particles is discussed alongside the parametric influences experienced by the plasma particles.