对合成孔径雷达压制干扰效果分析

合成孔径雷达是一种高性能成像雷达,能全天候、实时地获取地面图像。干扰效果是衡量干扰设备能力的一个综合性的指标,干扰效果的定量评估与检测是雷达对抗中的重要课题。分析了SAR雷达压制干扰的成像原理,引用了保护距离的概念,建立压制干扰的数学模型,进行了参数的选择,并对SAR的干扰效果进行了计算机仿真,通过结果的输出,验证了通过保护距离进行压制干扰效果定量评估方法的正确性和可行性。     

紫荆关引水枢纽防沙工程研究及运行效果

紫荆关枢纽是一座跨流域引水工程，1973年扩建成枢纽，由于设施简陋，泥沙问题严重。1988年按模型试验的布置形式进行了改建，五年来运行情况良好，利用导流、束水攻沙、侧面泄洪等措施，有效地扭转了闸首的不利形势，取得了少进沙少淤积多进水多发电的效果，改建后五年间，年均引水量，比改建前增加42％左右，年均发电量比改建前翻 番。工程实践证明，合理的工程和正确的运行方式对工程效果的发挥是至关重要的。     

雷达在阻塞干扰下的无源测距及其仿真

探讨了雷达在面对阻塞式干扰时进行无源测距的必要性,主要讲述了角速率测距法和三角形测距法测距的原理及其适用情况,并用M atlab对无源测距算法进行了仿真,给出了各种条件下的仿真结果,最后简述了无源测距的其他一些方法。     

The effects of a Severn Barrage on wave conditions in the Bristol Channel

The study investigates the impact that construction of a Severn Barrage in the Severn Estuary, on the west coast of the UK, might have on local wave conditions. Implementation of a barrage will impact on tidal currents and water elevations in the wider region. There is strong tidal modulation of wave conditions under the natural regime and therefore barrage-induced changes to tidal conditions could affect wave modulation in the region. This paper uses Swan, an open source 3rd generation spectral wave model, to investigate the possible impacts of construction of a barrage on tidal modulation of the wave conditions. It is found that current variations, rather than water level variations, are the dominant factor in tidal modulation of wave conditions. Barrage implementation does not substantially change the modulation of the wave period or direction. However, barrage implementation does affect the tidal modulation of wave heights in the area of interest. The tidal modulation of the wave heights is generally reduced compared to the natural case; the peaks in the wave heights on an incoming tide are slightly lowered and there is lesser attenuation in wave heights on the outgoing tide. This modulation leads to net changes in the wave heights over one tidal cycle. For all of the tested wave conditions, this net change is small for the majority of the tested domain, namely to within ±5% of the no barrage case. There are some areas of greater change, most notably larger net increases in the wave heights near the North Somerset coast where the post-construction net wave height increase over a tidal cycle approach 20% of the pre-construction conditions. These changes do not impact coastal flooding because the wave height increase is not co-incident with high tide. Importantly, the maximum wave height is not increased and thus the likelihood of extreme events is not increased. The area of greatest reduction is between Swansea and Porthcawl. Changes over a neap tidal cycle show similar patterns of net change, but the modulation over the tidal cycle is different; primarily the magnitude of modulation is half that for the spring tide case and the shape is altered in some locations.     

MPEG-4中的视频对象检测技术研究

MPEG 4标准中 ,如何从视频图像分割出视频对象是一个要解决的重要问题。本文依据视频图像的特点 ,提出了一种新的视频对象检测方法 ,他能有效抑制视频图像边缘检测中噪声干扰、控制图像外轮廓检测范围和检测精细度 ,使断裂的外轮廓有效闭合。该方法具有对噪声不敏感、分割准确、外轮廓完整、运算速度快等优点。最后 ,给出了实验验证。     

基于微动调制的FMCW SAR无源压制干扰方法

调频连续波(FMCW)合成孔径雷达(SAR)体积小、重量轻、成本低、功耗低等优点,在无人机等小型飞行平台中具有较大的应用潜力,对FMCW SAR的干扰也将成为目前干扰技术研究的重点;在构建旋转微动目标回波模型的基础上,分析了FMCW SAR旋转微动目标的干扰特性,并进一步提出了一种基于微动调制的FMCW SAR无源压制干扰方法;该方法利用旋转角反射器在距离向和方位向上形成的二维干扰条带,能够实现对被掩护目标的有效保护;文章详细分析了对FMCW SAR实施干扰时旋转角反射器的参数选择方法,并利用仿真实验验证了理论分析与所提无源压制干扰方法的有效性。     

楠溪江供水工程设计综述

楠溪江供水工程是浙江省水资源配置的大型长距离供水工程,由拦河闸取水枢纽、输水线路等建筑物组成。工程设计很好地解决了在风景区河道、感潮河道末端复杂地质条件下拦河闸的布置、基础处理、洄游鱼道等技术问题。输水系统采用运行管理方便、节能的有压重力输水方式。工程经过多年运行实践,设计技术成熟可靠,运行管理方便。本文系统介绍了工程设计的方案比选及关键设计技术问题,可为类似工程设计提供参考。     

基于种子词和数据集的垃圾弹幕屏蔽词典的自动构建

随着弹幕视频的流行,弹幕已经成为了互联网时代青年互动交流的一种形式,但随着弹幕数量的增多,如何屏蔽垃圾弹幕成为一个问题。在各类视频网站提出的关键词屏蔽法的基础上,提出了分别基于种子词和数据集的2类屏蔽词典自动构建方法。第1类方法主要采用Google的自然语言处理工具word2vec和PMI,寻找与种子词相似性较大或共现次数较多的词添加到屏蔽词典中去;第2类方法主要采用TF-IDF、LDA主题模型和信息增益IG的方法,从垃圾弹幕数据集中提取关键词来构建屏蔽词典。最后,对所构建的屏蔽词典进行评测,实验结果表明,词典规模在400~500时,弹幕屏蔽效果最好。同时,还考察了LDA主题数和数据集规模等因素对弹幕屏蔽效果的影响。     

The optimization design of collision detection for barrage games

The collision detection is of great importance in almost every game, whether among the objects or between the object and the scene .If the author don＇t detect collisions, objects will intersect each other or object will intersect the scene. In this paper, the author present two algorithms that high-speed detects the collision detection between moving bullet and role with unknown trajectories in 2D environment. The objects for collision detection are bounded by the axis-aligned rectangles or circles. The known information such as world coordinate system, collision object coordinate system and collision detection area coordinate system etc, are stored in the data files in advance. The data control systems load those information into the collision detection module to handle the collision among the roles and bullets. We set coordinate values of rectangular center and four vertexes or the center point of a circle and use the distance between two points or the distance from a point to a line to see whether the object＇s vertexes are enclosed in the other object. If it is true, there is a collision occurring. We improved the algorithm to make the player share the scene of running through the bullet cluster with skill and ease while avoiding being shot.     

逆合成孔径雷达成像干扰仿真研究

在介绍逆合成孔径雷达(ISAR)运动补偿及成像原理的基础上,重点对ISAR的抗压制干扰能力进行了分析和仿真,并将ISAR与普通脉压雷达、合成孔径雷达的抗压制干扰能力进行了对比。研究结果表明,由于ISAR成像必须经过运动补偿处理,这一弱点使其抗压制干扰能力相对较差。