Matrix pencil method for simultaneously estimating azimuth and elevation angles of arrival along with the frequency of the incoming signals

In this paper we describe a method for simultaneously estimating the direction of arrival (DOA) of the signal along with its unknown frequency. In a typical DOA estimation problem it is often assumed that all the signals are arriving at the antenna array at the same frequency which is assumed to be known. The antenna elements in the array are then placed half wavelength apart at the frequency of operation. However, in practice seldom all the signals arrive at the antenna array at a single pre-specified frequency, but at different frequencies. The question then is what to do when there are signals at multiple frequencies, which are unknown. This paper presents an extension of the matrix pencil method to simultaneously estimate the DOA along with the operating frequency of each of the signals. This novel approach involves approximating the voltages that are induced in a three-dimensional antenna array, by a sum of complex exponentials by jointly estimating the direction of arrival (both azimuth and elevation angles) along with the carrier frequencies of multiple far-field sources impinging on the array by using the three-dimensional matrix pencil method. The matrix pencil method is a direct data domain method for approximating a function by a sum of complex exponentials in the presence of noise. The variances of the estimates computed by the matrix pencil method are quite close to the Cramer–Rao bound. Finally, we illustrate how to carry out the broadband DOA estimation procedure using realistic antenna elements located in a conformal array. Some numerical examples are presented to illustrate the applicability of this methodology in the presence of noise. It is shown that the variance decreases as the SNR increases. The Cramer–Rao bound for the estimators are also provided to illustrate the accuracy and the computational efficiency of this new methodology.     

Estimation of skew angles for scanned documents based on piecewise covering by parallelograms

We propose a fast and robust skew estimation method for scanned documents that estimates skew angles based on piecewise covering of objects, such as textlines, figures, forms, or tables. The method first divides a document image into a number of non-overlapping slabs in which each object is covered by parallelograms. It then estimates the skew angle based on these parallelograms or, equivalently, their complementary regions. Putting our method to a systematic test and comparing it with some alternatives, we find that it yields favorable results in terms of accuracy, sensitivity to non-textual objects, effectiveness in dealing with documents of unspecified reading order, and computational efficiency. Some work is also conducted to find an effective way to further shorten its computation time at the expense of an extremely small loss of accuracy.     

A satellite selection criterion incorporating the effect of elevation angle in GPS positioning

When positioning by global positioning systems, geometric dilution of precision is generally used as a satellite selection criterion. While it takes account of only geometric effects, there are other factors causing positioning error, such as ionospheric delay, tropospheric delay, and multipath. In this paper, a new criterion for satellite selection, which considers the effect of these errors, is proposed and the effectiveness of the proposed criterion is shown.     

LORES: Low resolution shape program for the calculation of small angle scattering profiles for biological macromolecules in solution

A program for determining the low resolution shape of biological macromolecules, based on the optimization of a small angle neutron scattering profile to experimental data, is presented. This program, termed LORES, relies on a Monte Carlo optimization procedure and will allow for multiple scattering length densities of complex structures. It is therefore more versatile than utilizing a form factor approach to produce low resolution structural models. LORES is easy to compile and use, and allows for structural modeling of biological samples in real time. To illustrate the effectiveness and versatility of the program, we present four specific biological examples, Apoferritin (shell model), Ribonuclease S (ellipsoidal model), a 10-mer dsDNA (duplex helix) and a construct of a 10-mer DNA/PNA duplex helix (heterogeneous structure). These examples are taken from protein and nucleic acid SANS studies, of both large and small scale structures. We find, in general, that our program will accurately reproduce the geometric shape of a given macromolecule, when compared with the known crystallographic structures. We also present results to illustrate the lower limit of the experimental resolution which the LORES program is capable of modeling.

Program summary

Title of program:LORESCatalogue identifier: ADVCProgram summary URL:http://cpc.cs.qub.ac.uk/summaries/ADVCProgram obtainable from: CPC Program Library, Queen's University of Belfast, N. IrelandComputer:SGI Origin200, SGI Octane, SGI Linux, Intel Pentium PCOperating systems:UNIX64 6.5 and LINUX 2.4.7Programming language used:CMemory required to execute with typical data:8 MBNo. of lines in distributed program, including test data, etc.:2270No. of bytes in distributed program, including test data, etc.:13 302Distribution format:tar.gzExternal subprograms used:The entire code must be linked with the MATH library     

基于奇偶性的大容量医学图像可逆水印算法

本文提出了一种针对医学图像的基于奇偶性的大容量可逆水印算法。相比一般图像医学图像拥有更多接近0 值的像素点,在嵌入过程中容易溢出。通过测试选择像素中嵌入水印信息不会引起溢出的像素携带水印信息。本算法充分利用了医学图像中所有有能力携带水印信息的像素,提高了医学图像的嵌入率。为保证水印信息提取端图像像素的正确分类和算法的可逆性,本算法基于像素预测误差的奇偶性改进了提取端的测试算法。实验分析表明,本算法不仅保证了含水印医学图像的视觉效果,同时提高了医学图像的水印嵌入容量。对于一般图像,在水印嵌入量和视觉效果方面也有一定的提升。     

Assessing the influence of repeated exposures and mental stress on human wayfinding performance in indoor environments using virtual reality technology

This study aimed to examine the effect of repeated exposures to indoor environments on people’s indoor wayfinding performance, both under normal condition and during fire emergency which could induce significant mental stress. Indoor wayfinding experiments were conducted in an immersive virtual museum developed using virtual reality technologies. Participants of the experiments were divided into three groups, who participated in one, two and three trials, respectively. Those who participated in more than one trial were given an interval of two weeks between two consecutive trials. Each trial of the experiment included a treasure hunting task and an egress task. Participants were presented with a virtual fire emergency during the egress task of their last trial. Data of wayfinding performance measures of the participants, as well as their physiological and emotional responses, sense of direction, wayfinding anxiety and simulator sickness were collected and analyzed. The results revealed significant positive impact of repeated exposure on participants’ wayfinding performance, which resulted in a decrease in the time needed to complete the treasure hunting task. The results also revealed significant negative impact of mental stressed caused by the fire emergency on participants’ wayfinding performance, which led to increased travel time and distance during egress. Such negative impact of stress, however, could be noticeably diminished by the repeated exposures, showing significant interaction effect between these two factors.     

建筑供热负荷预报与预测控制策略研究

基于建筑供热节能需要和供热对象的特点,提出了供热负荷预报及对供热过程施加预测控制策略.根据时间序列分析原理,对供热负荷进行节能预报并作为预测控制的设定值.为满足实时性的要求,根据供热对象的特性对预测模型进行简化,给出了用预报误差校正代替误差校正的预测控制算法.最后对供热系统进行相关算法的仿真,其结果证明了该方法的有效性.     

A model of (en)action to approach embodiment: a cornerstone for the design of virtual environments for learning

This paper presents a model of (en)action from a conceptual and theoretical point of view. This model is used to provide solid bases to overcome the complexity of designing virtual environments for learning (VEL). It provides a common grounding for trans-disciplinary collaborations where embodiment can be perceived as the cornerstone of the project. Where virtual environments are concerned, both computer scientists and educationalists have to deal with the learner/user’s body; therefore the model provides tools with which to approach both human actions and learning processes within a threefold model. It is mainly based on neuroscientific research, including enaction and the neurophysiology of action.     

基于虚拟仪器的远程校准系统软件--远程校准技术初探(之二)

介绍了虚拟仪器和DataSocket的有关概念及其在远程校准编程中的应用，并通过对基于Internet的远程相关测速装置的实际编程考察了远程校准的可行性。     

基于改进灰色模型的ATS测试仪器校准周期确定

针对自动测试系统ATS中测试仪器校准周期的确定问题,提出了改进的灰色GM(1,1)模型预测方法。首先从GM(1,1)模型出发对模型本身进行改进,然后建立等维新息模型,并确定其最佳维数,递补动态更新预测信息,为进一步提高预测精度,提出了残差修正预测模型,并引入马尔可夫过程解决其修正残差的符号问题。实例结果表明,改进的模型预测方法比单独的模型预测具有更高的精度,可以应用于测试仪器校准周期的预测过程。     

提高T-DMB系统纠错能力的方法

通过对手机电视地面数字多媒体广播（T-DMB）系统外部编码方式的分析,利用TS流中填充字节为固定值的特性,在RS译码前首先检测填充字节区域并预先纠正该区域内的误码;在此基础上,利用解交织前后码元符号间的位置对应关系,对常规纠错RS译码不可译的TS包进行错误位置预测,利用预测结果进行纠错纠删RS译码。实验结果表明,该算法与常规RS码纠错算法相比,能进一步提高系统的纠错能力,改善视音频的播放质量。     

A Virtual Environment for the Design and Simulated Construction of Prefabricated Buildings

The construction industry has acknowledged that its current working practices are in need of substantial improvements in quality and efficiency and has identified that computer modelling techniques and the use of prefabricated components can help reduce times, costs, and minimise defects and problems of on-site construction. This paper describes a virtual environment to support the design and construction processes of buildings from prefabricated components and the simulation of their construction sequence according to a project schedule. The design environment can import a library of 3-D models of prefabricated modules that can be used to interactively design a building. Using Microsoft Project, the construction schedule of the designed building can be altered, with this information feeding back to the construction simulation environment. Within this environment the order of construction can be visualised using virtual machines. Novel aspects of the system are that it provides a single 3-D environment where the user can construct their design with minimal user interaction through automatic constraint recognition and view the real-time simulation of the construction process within the environment. This takes this area of research a step forward from other systems that only allow the planner to view the construction at certain stages, and do not provide an animated view of the construction process.     

倾角仪特性研究及其测量误差补偿

为了减轻非线性因素和环境温度的变化对倾角仪测量的影响,在充分研究倾角仪测量特性的基础上,采用多项式拟合方法研究了倾角仪非线性误差和温度漂移误差的软件补偿技术.建立了测量误差与非线性输出的多项式模型,拟合求出了多项式模型的各个系数与环境温度的关系函数,得到了倾角仪在一定倾角范围和温度范围内的测量误差的计算公式.实验证明了...     

基于VRML的虚拟现实协同实验系统的研究

讨论了VRML技术与Java等技术相结合来提高Internet下协同环境的交互性。在此基础上，给出了一个虚拟现实协同实验系统的设计，系统基于B／S模式。重点分析了虚拟协同实验系统中的数据一致性处理和交互协同处理机制。     

On the development of a haptic system for rapid product development

This paper presents a system development that extends haptic modeling to a number of key aspects in product development. Since haptic modeling has been developed based on physical laws, it is anticipated that a natural link between the virtual world and practical applications can be established based on haptic interaction. In the proposed system, a haptic device is used as the central mechanism for reverse engineering, shape modeling, real time mechanical property analysis, machining tool path planning and coordinate measuring machine (CMM) tolerance inspection path planning. With all these features in a single haptic system, it is possible to construct a three dimensional part by either haptic shape modeling or reverse engineering, then performing real-time mechanical property analysis in which the stiffness of a part can be felt and intuitively evaluated by the user, or generating collision free cutter tool path and CMM tolerance inspection path. Due to the force feed back in all of the above activities, the product development process is more intuitive, efficient and user-friendly. A prototype system has been developed to demonstrate the proposed capabilities.     

On calculation of the power indices with allowance for the agent preferences

In the general case, complexity of the algorithm to calculate the power indices grows exponentially with the number of voting agents. Yet the volume of calculations may be reduced dramatically if many coalitions have equal numbers of votes. The well-known algorithm for calculation of the Banzhaf and Shapley-Shubik indices was generalized, which enables fast calculation of the power indices where entry of the voting agent into a coalition depends on its preferences over the set of the rest of agents.     

VPN技术的研究与应用现状及发展趋势

文章探讨VPN技术的研究与应用现状及发展趋势。首先,对主流VPN技术内核或标准的发展现状与趋势进行了分析,并简单介绍了商品化VPN产品;其次,阐述了VPN市场现状和发展趋势,并对现有厂商的VPN解决方案作了比较;最后,提出了典型企业VPN系统的应用模式,并对下一代VPN技术的发展趋势进行了展望。     

室内定位航位推测算法的研究与实现

针对室内定位的个人航位推测(PDR)中漂移导致定位误差累积的问题,提出一种微机电系统传感器整合的PDR算法.根据典型计步器原理及步长估算获取位移信息,在计步算法中加入动态时间窗口及动态加速度阈值,以得到更精确的计步结果.利用捷联航向角校正磁航向角得到校正后的航向角,以修正定位中的累积误差.实验结果表明,室内定位精度距离误差可控制在5％以内,计步结果精度高,易于求得航向角,又能在一定程度上校正长时间漂移等因素带来的位置误差.     

对预警探测雷达模拟器目标分辨率模型的校验方法的研究

预警探测雷达模拟器目标分辨率设置会影响目标数量的探测,分辨率错误会产生与实体雷达不一致的虚警和漏警,影响预警探测雷达模拟器的逼真度。本文首先从理论上分析了对目标分辨率模型进行校核应该注意的几个方面,然后研究了用来测试验证目标分辨率模型的空情想定的设计方法,通过对预警探测雷达模拟器目标分辨率模型进行校验,可以有效提高模型的仿真效果。