A calibration method for fully polarimetric microwave radiometers

A technique for absolute end-to-end calibration of a fully polarimetric microwave radiometer is presented. The technique is based on the tripolarimetric calibration technique of Gasiewski and Kunkee, but is extended to provide a means of calibrating all four Stokes parameters. The extension is facilitated using a biaxial phase-retarding microwave plate to provide a precisely known fourth Stokes signal from the Gasiewski-Kunkee (GK) linearly polarized standard. The relations needed to determine the Stokes vector produced by the augmented standard are presented, and the effects of nonidealities in the various components are discussed. The application of the extended standard to determining the complete set of radiometer constants (the calibration matrix elements) for the National Oceanic and Atmospheric Administration Polarimetric Scanning Radiometer in a laboratory environment is illustrated. A calibration matrix inversion technique and error analysis are described, as well. The uncertainties associated with practical implementation of the fully polarimetric standard for spaceborne wind vector measurements are discussed relative to error thresholds anticipated for wind vector retrieval from the U.S. National Polar-Orbiting Environmental Satellite System.     

A fully automated method for lung nodule detection from postero-anterior chest radiographs

In the past decades, a great deal of research work has been devoted to the development of systems that could improve radiologists' accuracy in detecting lung nodules. Despite the great efforts, the problem is still open. In this paper, we present a fully automated system processing digital postero-anterior (PA) chest radiographs, that starts by producing an accurate segmentation of the lung field area. The segmented lung area includes even those parts of the lungs hidden behind the heart, the spine, and the diaphragm, which are usually excluded from the methods presented in the literature. This decision is motivated by the fact that lung nodules may be found also in these areas. The segmented area is processed with a simple multiscale method that enhances the visibility of the nodules, and an extraction scheme is then applied to select potential nodules. To reduce the high number of false positives extracted, cost-sensitive support vector machines (SVMs) are trained to recognize the true nodules. Different learning experiments were performed on two different data sets, created by means of feature selection, and employing Gaussian and polynomial SVMs trained with different parameters; the results are reported and compared. With the best SVM models, we obtain about 1.5 false positives per image (fp/image) when sensitivity is approximately equal to 0.71; this number increases to about 2.5 and 4 fp/image when sensitivity is = 0.78 and = 0.85, respectively. For the highest sensitivity (= 0.92 and 1.0), we get 7 or 8 fp/image.     

A head-mounted operating binocular for augmented reality visualization in medicine--design and initial evaluation

Computer-aided surgery (CAS), the intraoperative application of biomedical visualization techniques, appears to be one of the most promising fields of application for augmented reality (AR), the display of additional computer-generated graphics over a real-world scene. Typically a device such as a head-mounted display (HMD) is used for AR. However, considerable technical problems connected with AR have limited the intraoperative application of HMDs up to now. One of the difficulties in using HMDs is the requirement for a common optical focal plane for both the realworld scene and the computer-generated image, and acceptance of the HMD by the user in a surgical environment. In order to increase the clinical acceptance of AR, we have adapted the Varioscope (Life Optics, Vienna), a miniature, cost-effective head-mounted operating binocular, for AR. In this paper, we present the basic design of the modified HMD, and the method and results of an extensive laboratory study for photogrammetric calibration of the Varioscope's computer displays to a real-world scene. In a series of 16 calibrations with varying zoom factors and object distances, mean calibration error was found to be 1.24 +/- 0.38 pixels or 0.12 +/- 0.05 mm for a 640 x 480 display. Maximum error accounted for 3.33 +/- 1.04 pixels or 0.33 +/- 0.12 mm. The location of a position measurement probe of an optical tracking system was transformed to the display with an error of less than 1 mm in the real world in 56% of all cases. For the remaining cases, error was below 2 mm. We conclude that the accuracy achieved in our experiments is sufficient for a wide range of CAS applications.     

A novel stopping method for induction motors operating from variable frequency drives

Many applications involving induction motors that are controlled using variable frequency drives require the ability to stop quickly. These applications include emergency stops, quick stopping of fans, centrifuges, presses, etc. The technique that is widely accepted in the industry for achieving quick stopping makes use of brake resistors in series with a power semiconductor switch. The switch-resistor combination (brake-unit) is applied across the dc bus. The fastest decelerating time achievable depends on the size of the resistors and the switch employed. In this paper, the authors propose a novel method of achieving quick stopping times without the use of any brake-unit. The stopping times achievable depend on the inverter rating, motor parameters, and the inertia of the load. The proposed method uses the concept of achieving large slip condition between the rotating motor and the commanded drive output frequency. Control of current through the motor during the process of stopping is achieved by modifying the V/f pattern. Experimental test results with and without this method on a large inertia motor-load combination show that the proposed stopping method is able to reduce the stopping time significantly compared to normal decelerated stop without the need for a braking unit.     

A new method for enhancing focus latitude in optical lithography: FLEX

A new concept for enhancing the focus latitude in optical lithography is proposed that makes it possible to overcome the Rayleigh optical limit in the depth of focus. The method, called focus-latitude enhancement exposure (FLEX), uses multiple exposures in several different focal planes to extend the image contrast of the mask pattern along the light axis. It is confirmed both in simulations and experiments that the focus latitude for patterns with a feature size of about a half-micrometer can be increased by more than two times using FLEX, compared with the conventional method. FLEX is especially effective when applied to small isolated transparent patterns like contact holes.     

A monolithic, standard CMOS, fully differential optical receiver with an integrated MSM photodetector

This paper presents a realization of a silicon-based standard CMOS, fully differential optoelectronic inte grated receiver based on a metal-semiconductor-metal light detector (MSM photodetector). In the optical receiver, two MSM photodetectors are integrated to convert the incident light signal into a pair of fully differential photo generated currents. The optoelectronic integrated receiver was designed and implemented in a chartered 0.35 μm, 3.3 V standard CMOS process. For 850 nm wavelength, it achieves a 1 GHz 3 dB bandwidth due to the MSM pho todetector's low capacitance and high intrinsic bandwidth. In addition, it has a transimpedance gain of 98.75 dBΩ, and an equivalent input integrated referred noise current of 283 nA from 1 Hz up to -3 dB frequency.     

一种集成MSM光电探测器的单片标准CMOS全差分光接收机

This paper presents a realization of a silicon-based standard CMOS,fully differential optoelectronic integrated receiver based on a metal–semiconductor–metal light detector（MSM photodetector）.In the optical receiver, two MSM photodetectors are integrated to convert the incident light signal into a pair of fully differential photogenerated currents.The optoelectronic integrated receiver was designed and implemented in a chartered 0.35μm, 3.3 V standard CMOS process.For 850 nm wavelength,it achieves a 1 GHz 3 dB bandwidth due to the MSM photodetector’s low capacitance and high intrinsic bandwidth.In addition,it has a transimpedance gain of 98.75 dBΩ, and an equivalent input integrated referred noise current of 283 nA from 1 Hz up to–3 dB frequency.     

A fully automated recurrent neural network for unknown dynamic system identification and control

This paper presents a fully automated recurrent neural network (FARNN) that is capable of self-structuring its network in a minimal representation with satisfactory performance for unknown dynamic system identification and control. A novel recurrent network, consisting of a fully-connected single-layer neural network and a feedback interconnected dynamic network, was developed to describe an unknown dynamic system as a state-space representation. Next, a fully automated construction algorithm was devised to construct a minimal state-space representation with the essential dynamics captured from the input-output measurements of the unknown system. The construction algorithm integrates the methods of minimal model determination, parameter initialization and performance optimization into a systematic framework that totally exempt trial-and-error processes on the selections of network sizes and parameters. Computer simulations on benchmark examples of unknown nonlinear dynamic system identification and control have successfully validated the effectiveness of the proposed FARNN in constructing a parsimonious network with superior performance.     

A method for rebroadcasting signals in an optical backplane bussystem

A guided-wave optical backplane bus system intended for use in high-performance board-to-board interconnects is described. Its multiplexed polymeric holograms can implement optical signal broadcast between boards so that all boards share common optical channels. By introducing an active coupler to the doubly multiplexed hologram at the center board, signals received from any board can be rebroadcast to all other boards. We describe the design concepts for a centralized optical backplane and the resulting performance and assembly advantages over previously developed guided-wave and free-space optical backplane bus systems used for broadcasting signals. These advantages include equalized fan-out power, increased interconnect distance, and simpler fabrication     

原生质体扫描电镜观察研究的一种新方法

常规方法制备原生质体扫描电镜样品容易造成原生质体变形和破裂,影响其电镜观测结果。本文工作中,通过选用适宜的固定剂对原生质体进行快速因定,然后将原生质体悬浮液滴在经过硅烷化处理而引入了胺基的玻片上,直接在玻片上进行原生质体洗涤、脱水、置换、临界点干燥、喷镀处理,避免了在制样过程中进行离心操作,从而有效地解决了原生质体变形和破裂的问题。     

Modeling and algorithm development for automated optical endpointing of an HBT emitter etch

This paper discusses the development of a high-accuracy endpointing algorithm for the emitter etch of a heterojunction bipolar transistor (HBT). Fabrication of high-performance HBTs using self-aligned base-emitter processes requires etching through the emitter layer and stopping with very high accuracy on the base layer. The lack of selectivity in dry etching coupled with the high etch rates possible in high density plasmas render the use of a standard timed overetch impractical, especially as device layers continue to become thinner. The etch process under study requires the complete removal of an AlInAs emitter while etching no more than 5 nm of the underlying GaInAs base layer. Etch products are monitored using optical emission spectroscopy (OES) to determine etch endpoint. The process under study relies on the intensity of the 417.2 nm Ga emission line. The detection of the Ga line indicates that the etch has reached the GaInAs layer. However, the presence of a time-varying Ga baseline signal before endpoint and significant noise in the OES signal necessitate more than a simple threshold scheme for critical endpoint detection. The algorithm presented here is based on a generalized likelihood ratio with a signature function. This algorithm is robust to variance in the optical gains of the measurement equipment and is applicable to other etch processes. Experimental results of automated endpointing using this algorithm are presented in the form of pre- and post-etch ex situ film thickness measurements.     

一种可靠的2D激光雷达和摄像机标定方法

维激光雷达和摄像机的最小解标定方法存在精度较差、解缺失等不足,为此,提出了一种新的可靠最小解标定方法。首先,利用透视相似三角形(perspective similar triangle,PST) 算法求解3个棋盘格构建的P3P(perspective three points,P3P) 问题,并通过多项式极值点获取缺失的解,提高了算法对噪声的抗干扰能力。其次,提出基于两类激光点约束的误差度量模型来评估多解的误差程度,从而更准确地从标定结果的多解中选取最优解。实验结果表明,该文算法相比于文献中的FRANCISCO算法和HU算法,能明显提高有效解概率和标定精度;在不同噪声水平下,该文算法的有效解概率提高了5%—20%和5%—13%,旋转矩阵精度提高了46%—63%和41%—47%,平移向量精度提高了170—430 mm和120—170 mm,性能提高明显。     

Development of an automated method for detecting mammographicmasses with a partial loss of region

Recently, we have been developing several automated algorithms for detecting masses on mammograms. For our algorithm, we devised an adaptive thresholding technique for detecting masses, but our system failed to detect masses with a partial loss of region that were located on the edge of the film. This is a common issue in all of the algorithms developed so far by other groups. In order to deal with this problem, we propose a new method in the present study. The partial loss masses are identified by their similarity to a sector-form model in the template matching process. To calculate the similarity, four features are applied: 1) average pixel value; 2) standard deviation of pixel values; 3) standard correlation coefficient defined by the sector-form model; and 4) concentration feature determined from the density gradient. After employing the new method to 335 digitized mammograms, the detection sensitivity for the partial loss masses jumped from 70% to 90% when the number of false positives was kept constant (0.2/image). Moreover, a combination of the existing method and the new method improved the true-positive rate up to 97%. Such results indicate that the new technique may improve the performance of our computer-aided diagnosis system for mammographic masses effectively.     

A method of task allocation and automated negotiation for multi robots

A method of task allocation and automated negotiation for multi robots was proposed. Firstly, the principles of task allocation were described based on the real capability of robot. Secondly, the model of automated negotiation was constructed, in which Least-Squares Support Vector Regression (LSSVR) was improved to estimate the opponent??s negotiation utility and the robust controller of H ^?? output feedback was employed to optimize the utility performance indicators. Thirdly, the protocol of negotiation and reallocation was proposed to improve the real-time capability and task allocation. Finally, the validity of method was proved through experiments.     

A study on an active square-law combining method for apolarization-diversity coherent optical receiver

A polarization-diversity coherent optical receiver which realizes ideal square-law combining with active gain control is described. This receiver can suppress the additional power penalty due to the demodulator dynamic range limitation by equivalently expanding the demodulator dynamic range. A low-power penalty less than 1 dB was attained with a 400-Mb/s FSK (frequency-shift keyed) single-filter detection system. Throughout a 25-h 183-km transmission experiment, the stable operation of this receiver was confirmed     

A BJT translinear loop based optoelectronic integrated circuit with variable transimpedance for optical storage systems

A 0.35 μm SiGe BiCMOS optical receiver with voltage-controlled transimpedance is presented. A variable-gain current amplifier using a BJT translinear loop is applied. A transimpedance dynamic range of 1554 (63.8 dB) with the largest transimpedance of 2.84 MΩ, a bandwidth up to 379 MHz, and a transimpedance bandwidth product up to 168 TΩHz are achieved.     

A new test setup and method for the calibration of current clamps

Current probes are widely used to measure the common mode currents in electromagnetic compatibility (EMC) applications. Often, it is necessary to characterize the ratio of measured voltage to the common mode currents up to gigahertz (GHz) frequencies. Existing calibration methods for current probes suffer from the problem of not directly measuring the current within the current clamp. Instead they either reconstruct the current from measurements at other locations or they use assumptions regarding the geometry which allows them to use a current that is measured at a different location without applying a mathematical correction. For example, by maintaining a 50-/spl Omega/ transmission-line impedance the current can be determined with low uncertainty. The proposed method overcomes these disadvantages by directly measuring the current at the center of the current clamp. This way the mechanical dimensions of the test setup are not critical any more, i.e., one setup can be easily used to measure a large variety of clamps. The method is primarily applicable for current monitoring probes in the frequency domain.     

阵列幅度/相位误差的有源校正新方法

实际应用中的阵列存在幅度/相位响应误差,往往导致阵列高分辨算法性能的下降。对此本文给出一种阵列幅度/相位响应误差的有源校正新方法,它基于子空间正交理论,通过对误差建模,将阵列校正问题转换成误差参数估计问题,并利用经典的Lagrange乘子法方便地得到最优解。另外,此方法只需要一个已知方位的校正源,计算简便,无需迭代,可用于阵元位置已知的任意形状的阵列,因此更适用于实际阵列安装应用前的校正。通过半消声室实验对16-元圆环形声阵列进行了测试和校正,数据处理结果表明,本文所提的校正方法能够准确地估计出各阵元幅度/相位误差,且校正前后MVDR (Minimum Variance Distortionless Response) 波束形成的性能得到明显提高。      

椭圆波束变焦距环焦天线的设计方法

导出椭圆波束变焦距天线重要几何参数的求解方程。给出了这种天线的简便而有效的设计方法，并给出实例和理论的天线方向图。这种天线可以形成高效率的椭圆波束。