Development of the ERS-1 active radar calibration unit

The development of a microwave active radar calibration unit (ARC) to be used as a ground calibration reference standard for the European Remote Sensing Satellite ERS-1 imaging synthetic aperture radar is described. Three such units are placed across the radar swath, giving point target returns with a known signal strength, and are used to calibrate the radar image. The units have been designed for maximum stability with temperature (<0.1 dB over the temperature range of -15°C to +35°C). For absolute calibration the ARC is referenced to a flat plate using a novel technique of multiple transmission in its self-calibration mode, achieving an absolute calibration error of <0.14 dB     

The development and first results from the ESTEC ERS-1 active radarcalibration unit

The specification and development of a microwave active radar calibration unit (ARC) used as a ground calibration reference standard for the European Remote Sensing Satellite ERS-1 imaging synthetic aperture radar are described. The first results obtained from its use as a calibration standard from the processed satellite image are given. Three such units are placed across the swath giving point target returns with a known radar return. The units have been designed for maximum stability with temperature (<0.1 dB), for absolute calibration the ARC is referenced to a flat plate using a novel technique of multiple transmission in its self-calibration mode, achieving an absolute calibration error of <0.14 dB. First results obtained from the calibration validation exercise are presented and discussed     

Development of an active radar calibrator for the TRMMprecipitation radar

An active radar calibrator (ARC) was developed for the calibration of the first spaceborne Precipitation Radar (PR) onboard the Tropical Rainfall Measuring Mission (TRMM) satellite. The ARC has three functions of the radar receiver, beacon-signal transmitter, and delayed-transponder. A ground-based measurement using a prototype ARC and a bread-board model of the TRMM-PR demonstrated the ARC's capability for the on-orbit TRMM-PR calibration     

机载杂波测量雷达的有源绝对校准技术研究

雷达系统的精确校准是保证地海杂波测量数据可靠性的关键问题.本文利用地面有源雷达校准器(ARC)对L波段HH极化机载杂波测量雷达进行绝对校准,通过ARC设计、目标提取以及坐标系变换技术,充分考虑了校准场地背景杂波、载机姿态和GPS误差等因素对雷达系统常数、时延和天线方向图的影响.分析结果证明了这一技术的有效性.     

Defying hard times [semiconductor intellectual property business]

The article discusses the challenges facing the semiconductor intellectual property business from the perspective of ARC International. ARC has been working hard to strengthen its position as a one-stop-shop SIP supplier with a highly distinctive processor technology. It is operating in a crowded and highly competitive market. ARC gains an edge on its rivals by virtue of its Tangent reconfigurable processor and by positioning itself as a supplier of integrated system solutions. Using the ARChitect point-and-click configuration tool, customers can fine-tune the parameters of their processor, for example by selecting the size of the data and instruction caches. There is also the opportunity to make customer-specific additions to the instruction set, an option taken up in around 20% of designs. Following a programme of acquisitions, ARC now complements its processor cores with a range of application-specific SIP products supporting USB, Ethernet and 802.11 wireless LANs.     

The gridded trihedral: a new polarimetric SAR calibration reflector

The characteristics of the gridded trihedral used to calibrate polarimetric synthetic-aperture radar (SAR) systems are considered. The gridded trihedral is a normal trihedral with one of the conducting faces replaced with a grid of closely spaced (relative to a wavelength) parallel conductors over a layer of microwave absorber. This grid changes the incident wave's polarization and results in a calibration target with a significant cross-polarized reflection. The advantages of the gridded trihedral are that it has a broad backscatter beamwidth (unlike the dihedral), and that it is passive and simple to construct (unlike the active radar calibrator, or ARC). The performance characteristics of the gridded trihedral reflector are reviewed, using basic theoretical models and calibrated P-3 SAR imagery     

Adaptive rate-controlled scheduling for multimedia applications

We present a framework for integrated scheduling of continuous media (CM) and other applications. The framework, called ARC scheduling, consists of a rate-controlled on-line CPU scheduler, an admission control interface, a monitoring module, and a rate adaptation interface. ARC scheduling allows threads to reserve CPU time for guaranteed progress. It provides firewall protection between threads such that the progress guarantee to a thread is independent of how other threads actually make scheduling requests. Rate adaptation allows a CM application to adapt its rate to changes in its execution environment. We have implemented the framework as an extension to Solaris 2.3. We present experimental results which show that ARC scheduling is highly effective for integrated scheduling of CM and other applications in a general purpose workstation environment. ARC scheduling is a key component of an end system architecture we have designed and implemented to support networking with quality of service guarantees. In particular, it enables protocol threads to make guaranteed progress     

Adaptive audio streaming in mobile ad hoc networks using neural networks

We design a transport protocol that uses artificial neural networks (ANNs) to adapt the audio transmission rate to changing conditions in a mobile ad hoc network. The response variables of throughput, end-to-end delay, and jitter are examined. For each, statistically significant factors and interactions are identified and used in the ANN design. The efficacy of different ANN topologies are evaluated for their predictive accuracy. The Audio Rate Cognition (ARC) protocol incorporates the ANN topology that appears to be the most effective into the end-points of a (multi-hop) flow, using it to adapt its transmission rate. Compared to competing protocols for media streaming, ARC achieves a significant reduction in packet loss and increased goodput while satisfying the requirements of end-to-end delay and jitter. While the average throughput of ARC is less than that of TFRC, its average goodput is much higher. As a result, ARC transmits higher quality audio, minimizing root mean square and Itakura–Saito spectral distances, as well as several parametric distance measures. In particular, ARC minimizes linear predictive coding cepstral (sic) distance, which closely correlates to subjective audio measures.     

Packet combining with adaptive retransmission control in DS-CDMA random access networks

Packet combining with adaptive retransmission control (ARC) in DS-CDMA random access networks has been investigated. The proposed system uses diversity packet combining while adaptively adjusting the retransmission probability of backlog users to optimize packet retransmissions. A soft decision DS-CDMA analysis is used to derive the optimum channel input for ARC. Simulation results show that packet combining with ARC can significantly increase the throughput and maintain the performance very close to its optimum in the high traffic region.     

ARC网格中间件的研究与实现

首先将arc和现有的使用最为广泛的globus做了简单的比较,深入探讨的arc的性能优点以及各个组件之间的逻辑联系,并进一步的分析arc的实现要点以及在系统的运行过程中的注意事项,文章最后给出了arc目前还没有解决的问题,并提出了自己的看法和改进的意见。     

Use of porous silicon antireflection coating in multicrystallinesilicon solar cell processing

The latest results on the use of porous silicon (PS) as an antireflection coating (ARC) in simplified processing for multicrystalline silicon solar cells are presented. The optimization of a PS selective emitter formation results in a 14.1% efficiency multicrystalline (5×5 cm²) Si cell with evaporated contacts processed without texturization, surface passivation, or additional ARC deposition. Specific attention is given to the implementation of a PS ARC into an industrially compatible screen-printed solar cell process. Both the chemical and electrochemical PS ARC formation method are used in different solar cell processes, as well as on different multicrystalline silicon materials. Efficiencies between 12.1 and 13.2% are achieved on large-area (up to 164 cm² ) commercial Si solar cells     

雷达威力检测中替代等效推算方法研究

介绍了替代等效推算方法,讨论了替代等效推算方法在雷达检飞试验中的应用。以目标χ^2分布起伏统计模型来定义的五类典型的雷达目标,设计了雷达威力检测的模型,给出了雷达威力试验中不同飞行合作目标间替代等效推算关系,并对其应用进行了分析,为替代等效推算方法在靶场雷达检飞中的应用奠定了理论基础,在雷达检飞试验中具有一定的实际意义。     

The next-generation ARC middleware

The Advanced Resource Connector (ARC) is a light-weight, non-intrusive, simple yet powerful Grid middleware capable of connecting highly heterogeneous computing and storage resources. ARC aims at providing general purpose, flexible, collaborative computing environments suitable for a range of uses, both in science and business. The server side offers the fundamental job execution management, information and data capabilities required for a Grid. Users are provided with an easy to install and use client which provides a basic toolbox for job- and data management. The KnowARC project developed the next-generation ARC middleware, implemented as Web Services with the aim of standard-compliant interoperability.     

双基地雷达的主要性能分析与试验方法研究

双基地雷达的主要性能指标均与收/发两站的布站方式及目标所处的空间位置有关,这与单基地雷达有很大的差异,不能直接采用单基地雷达的试验方法来检验双基地雷达的主要性能指标。为解决双基地雷达的试验与性能评估问题,重点围绕双基地雷达的探测范围、测量精度、分辨力等主要性能进行了理论分析与计算,据此提出了合理可行的双基地雷达主要性能试验方法,有关研究成果已经在一个实用双基地雷达中得到了成功的应用。     

Low-Dropout Regulators With Adaptive Reference Control and Dynamic Push–Pull Techniques for Enhancing Transient Performance

An adaptive reference control (ARC) technique is proposed for minimizing overshoot/undershoot voltage and settling time of low-dropout regulators. Linear operation provided by the ARC technique can dynamically and smoothly adjust the reference voltage so as to increase the slew rate of error amplifier thus forcing the output voltage back to its steady-state value rapidly. The amount of transient revision is proportional to transient state output voltage variation and load condition. In addition, a dynamic push-pull technique is used to enhance transient response. Experimental results demonstrate that the undershoot voltage, settling time, and load regulation are improved by 31%, 68.5%, and 70%, respectively, when load current changes between 1 and 100 mA.     

红外增透薄膜新进展述评

本文综述了红外增透薄膜研究的一些新进展,其中包括宽带增透薄膜的多种设计和制备方法及具有优异性能的增透膜新材料的研究。     

High-performance robust motion control of machine tools: an adaptive robust control approach and comparative experiments

This paper studies the high-performance robust motion control of machine tools. The newly proposed adaptive robust control (ARC) is applied to make the resulting closed-loop system robust to model uncertainties, instead of the disturbance observer (DOB) design previously tested by many researchers. Compared to DOB, the proposed ARC has a better tracking performance and transient in the presence of discontinuous disturbances, such as Coulomb friction, and it is of a lower order. As a result, time-consuming and costly rigorous friction identification and compensation is alleviated, and overall tracking performance is improved. The ARC design can also handle large parameter variations and is flexible in introducing extra nonlinear robust control terms and parameter adaptations to further improve the transient response and tracking performance. An anti-integration windup mechanism is inherently built in the ARC and, thus, the problem of control saturation is alleviated. Extensive comparative experimental tests are performed, and the results show the improved performance of the proposed ARC.     

高分辨率条件下延时有源定标器SAR成像质量分析与校正

延时有源定标器是合成孔径雷达(Synthetic Aperture Radar, SAR)图像质量评估和辐射定标的关键设备,有源定标器延时技术的采用可以降低本地杂波的影响,提高测量精度。但其点目标成像质量不可避免地会受到延时的影响,尤其在高分辨率条件下更为严重。该文建立了高分辨率条件下延时对有源定标器点目标成像质量影响分析模型,定量地分析了不同延时对有源定标器点目标响应峰值功率、主瓣3 dB宽度、峰值旁瓣比和积分旁瓣比的影响程度,通过研究提出了一种延时影响的校正方法,仿真实验验证了该方法的正确性。     

SAR辐射定标的融合算法研究

针对机载SAR辐射定标外场试验可重复性较差的问题,提出了一种结合内场仿真信息进行辐射定标的参数估计新算法:首先建立机载SAR定标成像模型,在进行模型有效性检验之后,利用定标成像模型得到SAR线性动态范围内定标体RCS的渐进经验分布,然后结合定标试验实测数据进行辐射定标参数的融合估计。仿真表明该算法可以减小估计结果的误差方差,提高定标精度。     

激光雷达截面在系统设计评价中的应用分析

讨论分析了激光雷达截面在激光测量系统设计评价中的应用.分析了激光雷达截面的物理意义,给出了目标激光雷达截面的计算、测量原理与方法,从激光雷达截面的理论定义出发,推导出普遍适用于各类激光测量系统和各种散射特性目标的基本测量方程,该方程利用激光雷达截面表征目标的激光散射特性.通过典型实例说明了该方程在激光测量系统设计评价中的应用.与其他用于表征目标激光散射特性的指标相比,激光雷达截面更容易通过计算或测量得到,且更适用于复杂散射特性目标,因此,在激光测量系统的设计评价中应采用由目标激光雷达截面表述的激光测量方程.