A fast digital Radon transform—An efficient means for evaluating the Hough transform

A fast digital Radon transform based on recursively defined digital straight lines is described, which has the sequential complexity of N² log N additions for an N × N image. This transform can be used to evaluate the Hough transform to detect straight lines in a digital image. Whilst a parallel implementation of the Hough transform algorithm is difficult because of global memory access requirements, the fast digital Radon transform is vectorizable and therefore well suited for parallel computation. The structure of the fast algorithm is shown to be quite similar to the FFT algorithm for decimation in frequency. It is demonstrated that even for sequential computation the fast Radon transform is an attractive alternative to the classical Hough transform algorithm.     

Concealed weapon detection and visualization in a synthesized image

Images acquired by heterogeneous image sensors may provide complementary information about the scene, for instance, the visual image can provide personal identification information like the facial pattern while the infrared (IR) or millimeter wave image can detect the suspicious regions of concealed weapons. Usually, a technique, namely multiresolution pixel-level image fusion is applied to integrate the information from multi-sensor images. However, when the images are significantly different, the performance of the multiresolution fusion algorithms is not always satisfactory. In this study, a new strategy consisting of two steps is proposed. The first step is to use an unsupervised fuzzy k-means clustering to detect the concealed weapon from the IR image. The detected region is embedded in the visual image in the second step and this process is implemented with a multiresolution mosaic technique. Therefore, the synthesized image retains the quality comparable to the visual image while the region of the concealed weapon is highlighted and enhanced. The experimental results indicate the efficiency of the proposed approach.This material is based on part of the work carried out at the SPCR laboratory of Lehigh University and the work is partially supported by the U. S. Army Research Office under grant number DAAD19-00-1-0431. The content of the information does not necessarily reflect the position or the policy of the federal government, and no official endorsement should be inferred.     

石匣小流域坡地水土流失监测系统的建立及应用

以石匣小流域为坡地水土流失监测试点,以遥感及地理信息系统技术为手段,以坡地径流小区定位观测为依据,建立石匣小流域坡地水土流失监测系统,定位、定性、定量监测各种坡地类型的水土流失量、污染物流失量,为水土流失监测预报提供数据,为全市山区水土流失监测预报工作提供经验及方法,为制定水土流失防治方针政策及水土流失生态环境建设提供依据.     

Two years of operational use of Subpixel Automatic Navigation of AVHRR scheme: accuracy assessment and validation

Automated techniques for satellite imagery navigation and co-location are especially required for environmental monitoring activities intensively using satellite data. In this work are presented the results obtained after 2 years of operational use of the Subpixel Automatic Navigation of AVHRR (SANA) scheme. An automatic method for accuracy assessment of satellite navigation techniques, which permits a preliminary evaluation of their performances, dealing with a large collection of test images is also proposed. The navigation accuracy assessment, performed by using a selection of small islands as reference points, is discussed.Results achieved over more than 400 Advanced Very-High-Resolution Radiometer (AVHRR) scenes confirm that the SANA scheme is a very accurate one (computed mean navigation error is generally about one AVHRR pixel). Furthermore, because of its high processing speed, it can be considered a suitable tool for intensive satellite data processing in multitemporal analyses, especially required for environmental studies as well as for operational monitoring purposes.     

A review of the effects of water transfers in the La Grande Hydroelectric Complex (Québec,Canada)

Construction of the La Grande Complex in Eastern Canada called for complete or partial diversion of six rivers, the mean annual discharge of which varied from 60 to 1600 m³ s^?1, and the transfer of water from two adjoining watersheds (1586m³ s^?1) into La Grande Rivière. Three of these rivers with reduced flow, Eastmain (from 700 to 95m³ s^?1), Opinaca (from 260 to 35m³ s^?1), and Caniapiscau (from 1708 to 960m³ s^?1) and the waterways with increased flows, Boyd-Sakami (from 1 to 811m³ s^?1) and La Grande Rivière (from 1760 to 3400m³ s^?1) were intensively monitored from 1978 to 1988, while the others were surveyed sporadically. Very few modifications were observed, compared to previous conditions, in banks stability, water quality, and aquatic fauna of the affected rivers: those which appeared can be explained by the water level fluctuations, the water quality of the tributaries of the residual drainage basin, and/or by the direct influence of the reservoirs. In James Bay, the areal extent of the Eastmain River and La Grand Rivière plumes varied with discharge in an exponential relation, mostly under ice cover; resources from the coastal environment had not yet undergone any major changes. Because of the very small population dwelling in the area, less than 3000 inhabitants, modifications in the hydrological regime of these rivers did cause relatively few impacts, the main being greater banks instability in specific locations, reduction of the thickness and ice cover on La Grande Rivière, enhancement of navigation constraints on Eastmain River, and higher mercury levels in fish related to operation of the reservoirs.     

新疆叶尔羌河中游渠首工程地基处理设计

叶尔羌河洪水动态规律极为复杂,以其极高的起涨速率、异常的高洪峰值闻名于世。中游渠首地基是粘粒极少、极松散的粉细沙层。针对其特点,采用振冲挤密砂石桩、防渗防冲连续墙、抗冲柔性土工布金属网格石笼等综合处理措施进行设计。     

高炉炉缸内铁水环流与内衬侵蚀

从分析中心焦柱在炉缸内的受力出发，计算了１０００￣５５８０ｍ＾３高炉大喷煤前后中心焦柱在炉缸铁水内的沉入深度，分析了炉缸内铁水环流的产生与炉缸内衬侵的关系，分析表明大喷煤有得利抑制铁水环流对缸内补的冲刷，提出了降低铁水环流对炉缸内衬侵蚀的途径。     

Image segmentation towards new image representation methods

Very low bit-rate video coding has recently become one of the most important areas of image communication and a large variety of applications have already been identified. Since conventional approaches are reaching a saturation point, in terms of coding efficiency, a new generation of video coding techniques, aiming at a deeper “understanding” of the image, is being studied. In this context, image analysis, particularly the identification of objects or regions in images (segmentation), is a very important step. This paper describes a segmentation algorithm based on split and merge. Images are first simplified using mathematical morphology operators, which eliminate perceptually less relevant details. The simplified image is then split according to a quad tree structure and the resulting regions are finally merged in three steps: merge, elimination of small regions and control of the number of regions.     

DPCM编码在图像压缩中的应用

DPCM编码（差分脉冲编码调制）是一种线性预测编码。在二维图像中,由于相邻像素间的相关性很强,所以图像数据的冗余度都很大。对于瞬时斜率比较大和传输速度要求比较高的信号场合,为了使相邻像素间的相关性减小,通常采用DPCM编码技术对图像进行压缩。通过MATLAB仿真,表明DPCM编码能有效地对图像进行压缩。     

基于森林火灾平台的红外图像识别技术研究

森林火灾探测一直是森林资源保护工作中的老大难问题。早期的火灾探测技术多是基于火灾的烟雾和温度特征的,但其判别标准过于单一,误报率较高。随着计算机技术的发展和红外探测器的发明,出现了基于红外图像处理的森林火灾防护技术,该技术主要对红外探测器获得的森林现场的红外图像进行一定的处理后识别图像中是否有火灾出现。本文的主要工作是进行红外图像增强算法的研究,通过对各种算法的描述和仿真实验结果分析,提出一种相对较适合森林背景红外图像的处理算法一将基于频域处理的提升小波变换与直方图修正结合起来的红外图像增强算法。