Use of laser scanning technology for perimeter protection

The Police Scientific Branch (PSDB) is part of the Crime Reduction and Community Safety Group (CRCSG) of the Home Office. Part of PSDB's work includes evaluating and assessing new technologies for perimeter intrusion detection. Laser scanning technology has been used for some time in a range of industrial and commercial applications. These span from detecting hands when they are close to dangerous machinery to preventing collisions at container ports and monitoring manufacturing processes. Laser scanners are non-contact measurement systems and scan their surroundings two-dimensionally. This describes the application of laser scanning to physical security, including modifications to such systems for their use as perimeter intrusion detection systems (PIDS). In these systems, motion detection is provided by a pulsed laser beam by measuring the propagation time for the reflected beam to return to its source. Using this information, a contour plot of the surrounding area is built up. Once this contour information has been obtained, the detector can recognise the addition of an object to its field of view through a change in the programmed surroundings. Consequently, the size, shape, and direction of targets moving in the frame can be assessed and an alarm output given, if required. This explains the main operating principles of the systems, including mechanisms for the detection of a potential intruder and the handling of false alarms. Detection capabilities and the potential for low false alarm rates will be described, along with configurations for operational deployment.     

Fiber optic fence sensor developments

Many detection technologies have been employed for perimeter detection, to sensitize a barrier. These outdoor perimeter fence detection sensors must reliably detect intruders attempting to cut or climb the barrier, while ignoring the effects of environmental noise, including nearby activity. In recent conference proceedings, the new IntelliFIBER/spl trade/ fiber optic based product was introduced and compared with previous technologies. IntelliFIBER is designed to provide the advantages of a nonconductive "dielectric" cable sensor, e.g., resistance to electromagnetic interference and the ability to provide longer cable zones. It utilizes the proven processor of the Intelli-FLEX/spl trade/ triboelectric cable fence sensor, which provides relay or bidirectional networked serial communications and is compatible with its calibration module. IntelliFIBER also capitalizes on the Intelli-FLEX's adaptive detection algorithms that were developed through extensive field-testing, to provide exceptional immunity to environmental alarms while still detecting the skilled intruder.     

多相材料结构拓扑优化的周长控制方法研究

针对多相材料结构的拓扑优化出现的棋盘格问题,研究了周长约束控制方法。根据多相材料组分情况下结构有限单元密度变量的定义特点,拓展了周长约束的原始定义概念并提出了相应的4种周长控制约束新格式。以结构最大刚度优化设计问题为例,结合凸规划对偶求解方法验证了4种格式的有效性。计算结果表明:独立控制各类变量周长的方式能更有效地实现多相材料结构的拓扑优化设计,获得消除棋盘格和中间变量值的清晰结果。     

Security applications of computer vision

In an age which bears witness to a proliferation of Closed Circuit Television (CCTV) cameras for security and surveillance monitoring, the use of image processing and computer vision techniques which were provided as top end bespoke solutions can now be realised using desktop PC processing. Commercial Video Motion Detection (VMD) and Intelligent Scene Monitoring (ISM) systems are becoming increasingly sophisticated, aided, in no small way, by a technology transfer from previously exclusively military research sectors. Image processing is traditionally concerned with pre-processing operations such as Fourier filtering, edge detection and morphological operations. Computer vision extends the image processing paradigm to include understanding of scene content, tracking and object classification. Examples of computer vision applications include Automatic Number Plate Recognition (ANPR), people and vehicle tracking, crowd analysis and model based vision. Often image processing and computer vision techniques are developed with highly specific applications in mind and the goal of a more global understanding computer vision system remains, at least for now, outside the bounds of present technology. This paper will review some of the most recent developments in computer vision and image processing for challenging outdoor perimeter security applications. It also describes the efforts of development teams to integrate some of these advanced ideas into coherent prototype development systems     

Model-based vision for automatic alarm interpretation

The further development of a previously reported knowledge-based vision recognition system for automating the interpretation of alarm events resulting from a perimeter intrusion detection system (PIDS) is reported. Measurements extracted over a sequence of digitized images are analyzed to identify the cause of the alarm. Models are maintained for alarm causes, and the scene and the measurements are matched with the models to derive an appropriate classification of the event. An overview of the initial classification system is provided, and modifications to the system are described. The results of applying the system to a range of real alarm events are presented, and further improvements are discussed     

轻质材料与结构的一体化设计

针对多孔材料微结构构型的可设计性,基于材料多尺度均匀化计算理论,提出以宏观结构最大刚度为目标,材料微结构构型为变量的材料与结构一体化设计新方法,实现了材料宏观布局设计与材料微结构精细设计的统一。采用凸规划对偶优化求解技术与二次型周长约束格式相结合的途径,实现了快速求解与材料分布棋盘格效应的控制。数值计算结果表明,在材料用量一定的情况下,本方法能有效地实现蜂窝结构及夹层结构的拓扑优化设计,为满足极端环境下航空航天结构的设计需求提供了新的设计思想。     

Fence vibrations [intruder detection]

Many Perimeter Intrusion Detection Systems (PIDS) use microphonic sensors mounted on fences to detect intruder attacks. Vibrations in the fence are detected and analysed to determine whether they represent an intrusion attempt. The signals from the fence are processed to filter out as many false alarms as possible. It is important that the output from the sensors is linear along the fence, to ensure that there is no point on the perimeter less sensitive to intruder attack. The investigation reported in this paper aims to discover whether the performance of acoustic detection systems could be improved through research into fence acoustics. Using models of fence vibrations, sensors could be positioned to obtain a more linear response. In addition, through knowledge of the fence vibrations produced by both real attacks and the typical causes of false alarms, a system could be designed which could better distinguish between them, giving a lower false alarm rate and increased detection performance. Characteristic profiles were found for the different forms of attack to the fence. Although the investigation is still in its early stages, these attack profiles suggest that a new type of detection system could be designed based on profile recognition     

Intelli-FIELDTM: the next generation electrostatic fielddisturbance sensor

Outdoor perimeter volumetric field disturbance sensors must reliably detect perturbations to the field caused by an intruder, while rejecting noise and environmental changes that may be orders of magnitude greater than the target response. Currently, E-Field(R) systems are widely deployed in nuclear, correctional, and industrial sites to provide perimeter security. These systems are effective in rejecting the majority of noise and environmental stimuli through combined fixed attribute threshold comparison techniques. However, some environmental stimuli closely mimic target stimuli, so improved discrimination techniques have been sought. We describe the results of current studies and investigations of electrostatic sensor system response to targets and to various environmental changes. Fundamental principles in the character of sensor response to these varied stimuli are discussed. Techniques and methods that may be used to exploit the difference between intruder and environmental responses, while using cost-effective discrimination methods, are described. We show how the new Intelli-FIELD system was created, using currently available technologies, to provide both excellent detection properties, and an extremely low nuisance alarm rate, while, at the same time, greatly simplifying installation, calibration, and maintenance. The details of the new system hardware components and test results from initial field installations are described. A comparison of field performance with the previous E-Field product is provided to indicate the advantages of this new sensor technology     

民航订座系统PNR容量扩容

对民航订座系统中的旅客记录编号容量扩容、PNR位数升级等进行了研究;提出了PNR位数升级“5／6位并存”的平缓过渡方案。提出了两个“控制开关”的设计方案,即为降低程序上线与投产风险所设计的系统切换开关;为应对其他外航系统不能及时兼容系统升级而设计的外航交互开关。方案已运用于中国民航订座系统的改造,不仅实现了PNR容量扩容,同时保障了系统运行稳定,并最大程度降低了对周边系统的影响。     

多相多孔材料/结构的集成优化设计

采用均匀化方法,以宏观结构柔顺度为优化目标,开展了多相多孔材料/结构的集成优化设计。借鉴仿生思想,提出两尺度材料/结构构成模型,归纳出微结构精细设计的选择判据。结合伪密度法和周长控制消除了多相材料分布的棋盘格。采用分层优化方法并结合算例研究了实体材料模量相对比值、材料组分变化对优化结果的影响。计算结果说明所提出的结构构成模型能有效地应用于多相多孔材料/结构的优化设计,为新型多功能材料/结构的设计拓宽了思路。     

AMETHYST: automatic alarm assessment becoming a reality

The aim of the AMETHYST (AutoMatic Event auTHentication SYSTems) project is to encourage the development of a high performance perimeter detection system which combines Video Motion Detection (VMD) technology with another type of Perimeter Intrusion Detection System (PIDS). AMETHYST will automatically assess the cause of PIDS alarms and pass to an operator those alarms likely to be caused by an intruder. It will filter out alarms not likely to have a human cause. A previous paper explaining and exploring the AMETHYST concept was presented at the 1995 Carnahan Conference. Since then PSDB has produced a single channel AMETHYST demonstrator and placed a contract for the development of an eight channel prototype AMETHYST system. This updated paper gives details of the hardware and software used with these two systems. Also described is PSDB's approach to the development of AMETHYST's automatic assessment algorithms. These will combine current expertise from Video Motion Detection (VMD) and Intelligent Scene Monitoring (ISM) systems with the unique AMETHYST approach. AMETHYST analyses picture sequences from before and after an alarm instead of continuously analysing live video. Sequences are provided by a Loop Framestore, either connected to or part of the AMETHYST system. The algorithms will be assessed and developed using PSDB's growing collection of over 150 alarm sequences     

Envelope Threshold Detection in a Class of Non-Gaussian Interference

This paper considers the detection of a sinusoidal or chirp signal imbedded in wideband FM interference (as might be generated by some types of active jamming), such that after pulse compression or other integration, the interference can be approximated by a sum of sinusoids of independent phase. The detection probability in such non-Gaussian noise is compared to that for Gaussian noise, with the Gaussian result approached, as required, in the limit that the number of sinusoids in the sum increases without bound. For detection using a comparison of the envelope with a threshold which yields a given false-alarm probability (CFAR detection), the detection probability is improved over the case of Gaussian noise, so that the usual approach basing the design on Gaussian noise would be conservative. Using a threshold determined from the envelope mean, the FM interference yields a lower false-alarm probability than for Gaussian noise, with detection probability only slightly degraded.     

智能检测技术在靶场测控设备中的应用及前景

综合运用先进的GPS授时技术和数字仿真、虚拟仪器结构、可视化编程等计算机软件技术，构建新一代靶场智能型检测系统，解决对野外分散站点上测控设备进行检测、标校、监控和测控网通信联试等技术问题。着重阐述智能化检测技术在靶场的应用及发展趋势，为技术人员开发测试软件提供参考。     

Adaptive Rectification Filter for Detecting Small IR Targets

Clutter suppression is one of the most important subjects in the field of small target detection under infrared (IR) strong clutter background. While removing the clutter background, however, such methods may reverse the relative energy distribution of target and noise in the clutter suppressed image, and disturb the subsequent target segmentation and detection. This paper analyzes the causation of such problems, does research on the relationship between target energy characteristics and detection probability, and presents a novel filter of energy distribution adaptive rectification (EDARF). Based on the EDARF, an improved framework of dim small target detection is proposed to rectify the energy distribution in the clutter-suppressed images by conventional adaptive filters. The proposed EDARF's performance is estimated by experimental comparisons of three linear/nonlinear filters before and after using EDARF. Extensive experimental results show that the proposed EDARF improves efficiently the performance of detecting dim small targets against strong undulant cloud-cluttered backgrounds.     

半固态金属材料EMS法制备过程中的微观组织相场法模拟

利用相场法模拟了电磁搅拌法(EMS法)制备半固态金属材料(Al-4Cu-Mg合金)过程中微观组织的演变,分析和讨论了宏微观因素,如扰动强度、各向异性强度、固液相中扩散系数比等对微观组织演变的影响。结果表明:界面层厚度的减小,使得固相颗粒的外形轮廓更接近于圆形;固相中扩散系数增加,可以减少微观偏论析的程度;扰动强度越大,初生相的微粒越细,其形态越趋向于球形。     

一对一遭遇时飞机生存力-探测时间解析模型

 考虑探测事件的发生时间对开火、击中以及杀伤事件的影响,分析飞机与威胁的一对一遭遇情形,推导出飞机遭遇打击的次数的概率分布以及特定打击次数下飞机的生存概率,最后得到了一对一遭遇飞机生存力 探测时间的解析求解公式。该解析模型精确考虑了威胁与飞机遭遇的全过程,包括：探测,跟踪、开火以及重新装弹、开火等。根据该模型,不仅可以计算一对一遭遇飞机生存概率,而且可以方便地绘制生存力随平均发现时间、一次打击杀伤概率等参数变化的曲线。算例和分析结果表明该模型计算简便、合理有效。     

一种变信噪比条件下的恒虚警野值检测方法

野值检测又称异常值检测,是模式识别、机器智能和知识发现等领域经常面临的一个问题。当出现环境失配,数据信噪比（SNR）发生变化时,测试样本和训练样本所含噪声会有不同方差,以往的野值检测方法在虚警控制方面将会失效。针对这一问题,提出一种基于归一化残差（NR）的野值检测方法。该方法首先根据所需虚警概率和噪声方差变化情况确定野值检测门限,其次基于训练样本计算待考查模式的NR值,再比较NR值与检测门限的相对大小,从而判断待考查模式是否为野值。这一方法所依赖的检测门限对所需虚警率和噪声方差变化具有适应能力,因此可以在变信噪比条件下实现恒虚警（CFAR）野值检测。仿真实验验证了所提方法在虚警控制和野值检测方面的优越性能。     

高经济性静音中航程民机设计方法讨论

 人们已愈来愈重视工业产品对环境的影响。人们直接感受民机对环境的影响首先是机场周边的噪声。静音飞机预案的研究目标是设计一种飞机,在机场周边听不见其响声,且油耗和排污指标优于现有的和正在设计的其他飞机。通过介绍SAX（Silent Aircraft eXperiment）三代概念机的研究进程,讨论了静音飞机设计的方法和使用的关键技术,包括具有一定准确度的快速翼身融合体准三维设计方法;具有最佳中央体外形的融合体气动外形设计;可平滑下弯的外翼前缘和后缘刷;分布、埋入式多风扇可吞吸边界层的发动机组;喷口截面可变的推力矢量喷管;先进的隔音衬管;整流的起落架等。最终的概念机SAX-40实现了在机场周边的最大噪声计算值为61 dBA,接近于稠密居民区的背景噪声,且使机场周边的人们不易感觉到飞机的起飞/进场。其油耗经济性亦达到了124座 哩/加仑的优异指标。     

Application of frequency correlation function to radar target detection

Analysis of high-resolution 35 GHz synthetic aperture radar (SAR) imagery of terrain reveals that when point targets, such as vehicles, are viewed at angles close to grazing incidence, they are often difficult to distinguish from tree trunks because the radar cross section (RCS) intensities of the vehicles are comparable to the upper end of the RCS exhibited by tree trunks. To resolve the point target/tree trunk ambiguity problem, a detailed study was conducted to evaluate the use of new detection features based on the complex frequency correlation function (FCF). This paper presents an analytical examination of FCF and its physical meaning, the results of a numerical simulation study conducted to evaluate the performance of a detection algorithm that uses FCF, and the corroboration of theory with experimental observations conducted at 35 and 95 GHz. The FCF-based detection algorithm was found to correctly identify tree trunks as such in over 90% of the cases, while exhibiting a false alarm rate of only 3%.     

频率直方图法在复合材料检测中的应用

飞行器中复合材料结构的无损检测大多采用超声波检测方法。在实际检测过程中，类似碳纤维复合材料这样的特殊材料组织的结构比较复杂，所得到的超声波回波信号经常受到较强的结构噪声的干扰，信噪比较低，影响缺陷信号的识别。利用分离谱技术中最小值法，考虑结构噪声幅度对频率变化的敏感性，应用频率统计直方图法，对窄带信号的采样点进行统计、比较，选择绝对值最小的采样点信号作为输出信号，得到最佳频率检测带，对这些频带采用带通滤波器进行滤波，从而较好地将目标回波和结构噪声区分开，更准确地对复合材料构件讲行无损检测。