共形阵机载雷达杂波非平稳特性及抑制方法研究

分析了共形阵机载雷达的杂波非平稳特性,并结合该特性提出了一种非平稳杂波环境下的Doppler补偿方法.不同于传统的线阵天线,共形阵天线的三维空间结构决定了应在四维频域研究其杂波分布.针对这个特点,对共形阵机载雷达的杂波非平稳特性进行了理论分析,揭示了共形阵杂波非平稳现象的本质机理,并得出在任意摆放姿态下共形阵机载雷达均存在杂波非平稳现象这一结论.在此基础上,提出了在四维频域对主杂波进行联合补偿的空时自适应处理(space-time adaptive processing,STAP)方法.经仿真验证,在共形阵机载雷达非平稳杂波环境下,利用本文所提STAP方法的杂波抑制性能显著优于传统的Doppler补偿STAP方法.     

The Translator’s Extended Mind

The rapid development of natural language processing in the last three decades has drastically changed the way professional translators do their work. Nowadays most of them use computer-assisted translation (CAT) or translation memory (TM) tools whose evolution has been overshadowed by the much more sensational development of machine translation (MT) systems, with which TM tools are sometimes confused. These two language technologies now interact in mutually enhancing ways, and their increasing role in human translation has become a subject of behavioral studies. Philosophers and linguists, however, have been slow in coming to grips with these important developments. The present paper seeks to fill in this lacuna. I focus on the semantic aspects of the highly distributed human–computer interaction in the CAT process which presents an interesting case of an extended cognitive system involving a human translator, a TM tool, an MT engine, and sometimes other human translators or editors. Considered as a whole, such a system is engaged in representing the linguistic meaning of the source document in the target language. But the roles played by its various components, natural as well as artificial, are far from trivial, and the division of linguistic labor between them throws new light on the familiar notions that were initially inspired by rather different phenomena in the philosophy of language, mind, and cognitive science.

     

An optimal circular antenna array design considering mutual coupling using heuristic approaches

This article shows the design of a non‐uniformly excited single ring circular antenna array (CAA) for the synthesis of optimal far‐field radiation characteristics. A recently proposed meta‐heuristic based optimization algorithm called gray wolf optimization (GWO) and state‐of‐the‐art swarm intelligence based evolutionary optimization technique known as particle swarm optimization with a distribution based update mechanism (PSOd) are individually applied to determine the optimum set of current excitation amplitude weights and the inter‐element spacing among the array elements to reduce the side lobe level and 3‐dB beamwidth considering the mutual coupling. The results obtained by employing PSOd and GWO are compared to those of the uniform radiation pattern and the recently published results of state‐of‐the‐art literature having equal sets of elements to show the superiority of employed approaches. Three different design examples of 8, 10, and 12 elements CAA are reported in this article to study the performances of PSOd and GWO algorithm‐based results over the results of other recently reported literature.     

Design of a PCB stator coreless axial flux permanent magnet synchronous motor based on a novel topology Halbach array

A novel topology Halbach permanent magnet array is proposed and applied to the design of a printed circuit board (PCB) axial flux permanent magnet (AFPM) motor. Compared with the traditional coreless AFPM motor, this novel topology for a Halbach permanent magnet array PCB stator AFPM motor has larger air-gap magnetic flux density and air-gap flux per pole. The magnetic flux leakage is effectively reduced, and the air-gap magnetic density is close to the sine wave. Results of the finite element analysis and prototype experiments verify the feasibility and effectiveness of the novel Halbach permanent magnet array PCB stator motor. A reference basis and practical value for the design of the PCB AFPM motor are provided.

     

An evaluation of optical profilometry techniques for CMUT characterization

Accurate characterization of thin films and geometric features including the cavities during and after the fabrication process is crucial for proper CMUT operation, reliability, consistent array operation, and improved yield. Three different optical profilometry techniques: white light interferometry, laser confocal microscopy, and structural grid illumination microscopy have been reviewed in this paper with a focus on characterization of various thin films and geometric features during different CMUT fabrication stages and post processing. The relative merits of each technique have been investigated experimentally in the context of CMUT fabrication for better characterization and process development. The surface roughness and diaphragm deformation results have also been compared with AFM data. From the review, it appears that characterization needs of CMUTs are unique and a combination of complex diversified characterization tools is necessary to generate sufficient data for design verification and functional optimization.

     

Synthesis of linear antenna array using flower pollination algorithm

Linear antenna array (LAA) design is a classical electromagnetic problem. It has been extensively dealt by number of researchers in the past, and different optimization algorithms have been applied for the synthesis of LAA. This paper presents a relatively new optimization technique, namely flower pollination algorithm (FPA) for the design of LAA for reducing the maximum side lobe level (SLL) and null control. The desired antenna is achieved by controlling only amplitudes or positions of the array elements. FPA is a novel meta-heuristic optimization method based on the process of pollination of flowers. The effectiveness and capability of FPA have been proved by taking difficult instances of antenna array design with single and multiple objectives. It is found that FPA is able to provide SLL reduction and steering the nulls in the undesired interference directions. Numerical results of FPA are also compared with the available results in the literature of state-of-the-art algorithms like genetic algorithm, particle swarm optimization, cuckoo search, tabu search, biogeography based optimization (BBO) and others which also proves the better performance of the proposed method. Moreover, FPA is more consistent in giving optimum results as compared to BBO method reported recently in the literature.

     

Frameworks for designing and implementing dependable systems using Coordinated Atomic Actions: A comparative study

This paper¹ presents ways of implementing dependable distributed applications designed using the Coordinated Atomic Action (CAA) paradigm. CAAs provide a coherent set of concepts adapted to fault tolerant distributed system design that includes structured transactions, distribution, cooperation, competition, and forward and backward error recovery mechanisms triggered by exceptions. DRIP (Dependable Remote Interacting Processes) is an efficient Java implementation framework which provides support for implementing Dependable Multiparty Interactions (DMI). As DMIs have a softer exception handling semantics compared with the CAA semantics, a CAA design can be implemented using the DRIP framework. A new framework called CAA-DRIP allows programmers to exclusively implement the semantics of CAAs using the same terminology and concepts at the design and implementation levels. The new framework not only simplifies the implementation phase, but also reduces the final system size as it requires less number of instances for creating a CAA at runtime. The paper analyses both implementation frameworks in great detail, drawing a systematic comparison of the two. The CAAs behaviour is described in terms of Statecharts to better understand the differences between the two frameworks. Based on the results of the comparison, we use one of the frameworks to implement a case study belonging to the e-health domain.     

Designing and using integrated data collection and analysis tools: challenges and considerations

Abstract

This paper describes the design and evolution of mi integrated set of computer-aided usability engineering (CAUSE) tools for data collection and analysis. The tools were designed to collect and analyse observational, video, and system event data in both the usability laboratory and in the field. Three generations of tools are described and the problems with each generation are discussed. Solutions to the problems arc presented, where available. Conclusions about the strengths and weaknesses of particular types of data, CAUSE tool design, and the importance of multiple data sources are drawn. An agenda for future work is also outlined.     

Ergonomics action research II: a framework for integrating HF into work system design

This paper presents a conceptual framework that can support efforts to integrate human factors (HF) into the work system design process, where improved and cost-effective application of HF is possible. The framework advocates strategies of broad stakeholder participation, linking of performance and health goals, and process focussed change tools that can help practitioners engage in improvements to embed HF into a firm's work system design process. Recommended tools include business process mapping of the design process, implementing design criteria, using cognitive mapping to connect to managers’ strategic goals, tactical use of training and adopting virtual HF (VHF) tools to support the integration effort. Consistent with organisational change research, the framework provides guidance but does not suggest a strict set of steps. This allows more adaptability for the practitioner who must navigate within a particular organisational context to secure support for embedding HF into the design process for improved operator wellbeing and system performance.

Practitioner Summary: There has been little scientific literature about how a practitioner might integrate HF into a company's work system design process. This paper proposes a framework for this effort by presenting a coherent conceptual framework, process tools, design tools and procedural advice that can be adapted for a target organisation.     

A comparison of SPOT and Landsat-TM data for use in conducting inventories of forest resources

Abstract

SPOT multispectral (XS) and Landsat Thematic Mapper (TM) digital data were studied in an attempt to evaluate the use of this data in detailed assessments of forest conditions. Forest type, basal area, and age class information were collected from 256 sample sites within an intensively managed 80000acre experimental forest in North Carolina, U.S.A. A comparison of the SPOT and TM data with the sample site information showed that XS3, the near-infrared waveband, and TM bands 2, 3, 4, 5, and 7 were significantly correlated with basal area. Age class was not found to be significantly correlated with any of the three SPOT XS wavebands. TM bands 2, 3, 4, 5, and 7 were, however, shown to be significantly correlated with age class. Although significant, the correlation coefficients between the TM or SPOT waveband data and basal area or age class were low (<0.65).

Six forest cover types, and an additional water category, were selected as the basis of a land cover classification system for use with the TM and SPOT data. Verification of the classification of the seven cover types using the SPOT XS waveband data resulted in an estimated accuracy of 74.4 per cent. Classification accuracy was slightly reduced (70.8 per cent) when the TM wavebands corresponding to the SPOT XS bands were used as inputs to the classifier. When each of the six visible and reflective infrared TM wavebands were included in the classification process overall accuracy increased to 885 per cent.     

SYSTEMATIC SYNTHESIS OF PARALLEL ARCHITECTURES FOR THE REAL-TIME ESTIMATION OF HIGHER ORDER STATISTICAL MOMENTS

Abstract

The Higher Order Statistics, such as the Higher Order Moments, Cumulants and Polyspectra, have been recognized as important tools in modem time series analysis since they overcome well-known limitations of the autocorrelation/power spectrum second order methods. The systematic synthesis of parallel algorithms and architectures for the real-time estimation of moments up to any desirable maximal order k > 3 is presented. First, a design methodology is developed which can take into account the desirable characteristics of the targeted parallel architecture and used to construct an optimal locally recursive form of the algorithm amenable to efficient parallelization. The design methodology is then used to synthesize a family of algorithms and minimum latency, low granularity, processor array architectures that can compute all lags of Higher Order Moments, from the samples of the incoming data sequence in real-time.     

Systolic Array Synthesis using SFG Representations

One of the important design problems in systolic array processing is the development of a systematic methodology for transforming an algorithm represented in some high level constructs into a systolic architecture specified by the timing of data movement and the interconnection of processing elements such that the design requirements are satisfied. In this paper a method using the SFG (signal flow graph) of a given algorithm to design systolic arrays through graphic mapping and retiming is presented. An algorithm is first represented by a DG (dependence graph). Then the DG is mapped into an SFG by a graph projection. Cut-set retiming procedures are then applied to derive a regular localised SFG from which a systolic array design can be obtained for the given matrix examples i.e. LU and QR decompositions.     

Behavioural synthesis of SGD using the CCC framework: a simple XOR-solving MLP

Behavioural synthesis enables the automation of the design process by generating task-specific hardware configured for either FPGA and SoC platforms or custom silicon devices such as ASICs. Relevant commercial tools’ flows can bring significant benefits for software developers with no hardware design expertise. Our Custom Coprocessor Compilations (CCC) high level synthesis tool is leveraged in this work to synthesize a FPGA design for stochastic gradient descent (SGD), a cornerstone optimization approach into today’s modern deep neural networks. A simple 3-input-XOR-solving, multilayer perceptron (MLP) is implemented and transformed into a Register Transfer Level (RTL) VHDL hardware microarchitecture using the CCC hardware synthesizer. The produced VHDL is subsequently verified for correct functionality in GNU Ada. Results validate our motivation for accelerated performance, targeted to low-powered, autonomous devices.

     

Designing accessible visual programming tools for children with autism spectrum condition

Visual programming tools allow users to create interactive media projects such as games and animations using visual representations of programming concepts. Although these tools have been shown to have huge potential for teaching children, research has shown that they may not be accessible for children with cognitive impairments, including those with autism spectrum condition. Therefore, this study proposes a set of recommendations for the design of accessible visual programming tools for children with autism spectrum condition. Semi-structured interviews with experts (\(n=7\)) were conducted and thematically analysed to identify initial recommendations. A second set of semi-structured interviews with a subset of the initial experts (\(n=3\)) were then conducted to validate and produce a final set of recommendations.

     

Caractérisation de formations végétales mediterranéennes à partir de données ‘Thematic Mapper’ Une étude de cas en Andalousie (Espagne)

Abstract

The study is focused on the characterization of vegetation formations in a Mediterranean area (943 km²) located in southern Spain: herbaceous canopies (rangelands), shrubby vegetation (‘matorral’) and complex woody/herbaceous formations (‘dehesa’). Vegetation formations (physiognomical units) have been characterized by their spectral responses in the six reflective TM channels and by vegetation indices. From the ratio index TM4/TM3 there has been derived a map displaying seven classes (water, bare soil and five biomass levels reflecting the hierarchy of vegetation formations). Channels TM3, TM4 and TM5 have been considered for a supervised classification into nine land-cover categories (seven vegetation formations, bare soil and water). The proportion of correct classification of vegetation formations is about 78 per cent when considering test areas. Classification made from three principal components gives similar results.     

MEMS design and modelling based on resonant gate transistor for cochlear biomimetical application

The electromechanical behaviour and frequency response of the human cochlear have been described to be mimicked using an array of resonant gate transistors (RGT). Presented in this paper are the mathematical model, geometrical analysis and novel design of RGT, employed for the physical model development of the cochlea. In an array of RGTs, the aluminium bridge gate structures with length of 0.57–1.62 mm transduce the sound input signal into mechanical vibrations at audible frequency range of 1–8 kHz. The channels underneath the bridge gates transduce the mechanical vibrations into small signal drain currents with reasonable estimated sensitivity of 4–17 nA/Pa. The gain amplification and resonant frequency reduction of RGT with respect to the voltage applied onto the bridge gate structure highlight the adaptive characteristics of a human cochlear. The proposed modelling approach can aid the fabrication design of RGT for cochlear model.

     

A drainage system analysis evaluation of,and comparison between,Landsat-3 RBV,Landsat-5 TM and SPOT PA imageries covering the Central Macedonia district,Greece

Abstract

Landsat-3 RBV, Landsat-5 TM imageries and SPOT PA stereopair diapositives were visually interpreted for the purpose of finding the accuracy of certain morphometric variables of three drainage basin sample areas in Central Macedonia, North Greece, drawn separately from each of the above three types of satellite imageries and comparisons were made between the efficiency of drainage systems drawn from each of the above imageries and the drainage systems extracted from the available topographic maps of 1:50000 scale.

The main findings were the following: (1) SPOT PA stereopair diapositives of 1:200000 scale can be used to map drainage systems to an order of magnitude slightly more than TM imagery of 1:125000 scale, but significantly more than RBV imagery of 1:125000 scale. This slight superiority of SPOT imagery over TM imagery implies that the greater spectral range of TM, compared with the shorter range of SPOT imageries, vastly outweighs the advantage of SPOT'S superior resolution, but not the superiority of stereoscopic view; (2) TM imagery can be used to map drainage systems to an order of magnitude significantly more than RBV imagery; and (3) RBV imagery can be used to map drainage systems to an order of magnitude less than topographic maps of 1:50000 scale but better than topographic maps of 1:100000 scale.     

Reflectance relations in row crop scenes

Abstract

Models that relate composite reflectance to its components are useful for inferring crop growth information from measured scene reflectance. Radiation measurements in Thematic Mapper bands (TM1, TM2, TM3, and TM4) were made from cotton, soybean, sunflower and grain sorghum at three stages of growth and used to evaluate three reflectance models. Two models, AIRM1 and AIRM2, assumed that scene components contribute in an additive independent manner to composite reflectance. The third model, TRIM, assumes that radiation transmitted through the canopy interacts with bare soil in two scene components. The AIRM2 and TRIM models divide the composite reflectance into canopy, bare soil, and shadow components, but AIRM1 considers only canopy and bare soil. Ranking of models in order of decreasing accuracy for predicting composite reflectance in bands TM3 and TM4 was AIRM2, TRIM, and AIRM1. The AIRM1 and AIRM2 models estimated average TM3 reflectance at full plant cover between 1 and 4 per cent for all crops. Their estimations in band TM4 were 60 per cent for cotton, soybean, and sunflower with grain sorghum being 50 percent.

Measured canopy and composite reflectances were graphically compared at the lowest and highest levels of canopy cover observed in each crop. Measured band TM3 canopy reflectance did not change with solar zenith angle, composite reflectance decreased with increasing zenith angle at the lowest canopy cover levels but was invariant at the highest canopy cover levels. Measured band TM4 canopy reflectance increased linearly with increasing solar zenith angle in all crops, but for composite reflectance this pattern was observed only at the highest canopy cover levels of cotton and soybean. The absence of a uniform pattern between band TM4 composite reflectance and solar zenith angle in grain sorghum is presumably due to large horizontal leaf angles and in sunflower to long vertical spacings between leaves. Predicted compared to measured band TM3 and TM4 composite reflectances of the AIRM1 and AIRM2 models were insensitive but the TRIM model was overly sensitive to zenith angle.     

Polarization independent quad‐bandpass frequency selective surfaces with wide‐band ratio

A single layer polarization independent quad‐bandpass frequency selective surface (FSS) with wide‐band ratio is demonstrated theoretically as well as experimentally. The proposed structure passes four frequency bands with wide band ratio. The proposed FSS design is implemented by incorporating alternate arrangement of four units which are rotated 90° clockwise to form a unit cell of metal over a FR4 substrate. The geometrical dimensions of proposed unit cell are optimized and arranged in such a way that the structure possesses the quad bandpass characteristic and aspect dimensions of one unit is 0.11λ × 0.11λ with respect to first resonant frequency. This FSS provides stable response for different angle of incidence in transverse electric (TE) mode and transverse magnetic (TM) mode. To validate the results proposed FSS array has been fabricated and measured in free space environment. The measured results are in good agreement with the simulated results. Excellent stability is also observed for different incident angle.     

Integrating Physical and Digital Interactions on Walls for Fluid Design Collaboration

ABSTRACT

Web designers use pens, paper, walls, and tables for explaining, developing, and communicating ideas during the early phases of design. These practices inspired The Designers' Outpost. With Outpost, users collaboratively author Web site information architectures on an electronic whiteboard using physical media (sticky notes and images), structuring and annotating that information with electronic pens. This interaction is enabled by a touch-sensitive electronic whiteboard augmented with a computer vision system. The Designers' Outpost integrates wall-scale, paper-based design practices with novel electronic tools to better support collaboration during early-phase design. Our studies with professional designers showed this integration to be especially helpful for fluidly transitioning to other design tools, access and exploration of design history, and remote collaboration.