A coated pixel device TimePix with micron spatial resolution for UCN detection

A position sensitive detector for ultra-cold neutrons (UCNs) has been developed. Here we present the first experimental results and compare them with Monte-Carlo simulations. The silicon pixel device “TimePix” with a spatial resolution below 1 μm for strongly ionizing particles has been coated with a conversion layer of ⁶LiF for the detection of UCN. A spatial resolution of 5.3 μm has been measured for UCN. An optimized setup with 10B as conversion layer can achieve a spatial resolution below 3 μm.     

基于半像素运动估计的DCVS残差重建算法

针对分布式视频压缩感知中非关键帧重建质量较差的问题进行了研究,提出了一种基于半像素插值技术的残差多假设块迭代重建算法。该算法先对重建后的相邻关键帧进行半像素插值运动估计生成当前非关键帧的边信息;然后,在测量域内对非关键帧与边信息求残差并对残差进行多假设重建;最后,将重建的残差与边信息进行融合得到重建的非关键帧。仿真结果表明,基于半像素插值的改进残差多假设块迭代重建算法比多假设迭代重建算法重建质量平均提高了0.3~1.4dB,提高了非关键帧的重建质量。     

Reversible data hiding with contrast enhancement using adaptive histogram shifting and pixel value ordering

Existing image-based reversible data hiding (RDH) methods tend to focus on increasing embedding capacity, but few consider keeping or improving visual image quality. Wu et al. proposed a new RDH method with contrast enhancement (RDH-CE) by pair-wisely expanding the histogram to the lower end and upper end. RDH-CE is especially valuable in exploiting the details of poorly illustrated images for which the visibility of image details is more important than just keeping PSNR high. However, obvious visual image distortion appears when embedding level gets high, and embedding capacity is relatively low when embedding level is small. In this paper, Wu et al.'s work is improved from three perspectives, namely image contrast enhancement, visual distortion reduction, and embedding capacity increment. The image contrast is improved by making the histogram shifting process adaptive to the histogram distribution characteristics, the image visual distortion is reduced by cutting off half the modification range of pixels induced in histogram pre-shifting, and the embedding capacity is increased by exploiting the pixel value ordering technique at the early stage of data embedment. Experimental result proves that the proposed work is effective in improving image contrast, reducing visual image distortion, and increasing embedding capacity.     

Efficient visual object detection with spatially global Gaussian mixture models and uncertainties

In this paper, we deal with the problem of visual detection of moving objects using innovative Gaussian mixture models (GMM). The proposed method, the Spatially Global Gaussian Mixture Model (SGGMM) uses RGB and pixel uncertainty for background modelling. The SGGMM with colours only is used for scenes with moderate illumination changes. When combined with pixel uncertainty statistics, the method can deal efficiently with dynamic backgrounds and scene backgrounds with fast change in luminosity. Experimental evaluation in indoor and outdoor environments shows the performance of the foreground segmentation with the proposed SGGMM model using solely RGB colour or in combination with pixel uncertainties. These experimental scenarios take into account changes in the background within the scene. They are also used to compare the proposed technique with other state-of-the-art segmentation approaches in terms of accuracy and execution time performance. Further, our solution is implemented and tested in embedded camera sensor network nodes.     

Optimized high speed pixel sorting and its application in watershed based image segmentation

Efficient sorting of image pixels based on their grayscale value is traditionally implemented using an algorithm based on distribution or counting sort methods. We show that an elegant alternative can be used which outperforms the traditional method both in terms of processing speed and main memory access. We discuss both theoretically analyzed and real-life performance results, and demonstrate the improvements that can be obtained when our algorithm is combined with a well-known watershed image segmentation method.     

单壁碳纳米管与稀土螯合物的磁性-荧光复合体系的制备及其多模成像应用研究

利用共价连结和非共价修饰相结合的方法,成功地制备了基于单壁碳纳米管与铕、钆螯合物的复合体系（SWNT—Eu—Gd）,并采用层层自组装的方法在单壁碳纳米管表面修饰多层高分子电解质作为隔离层,有效地克服了铕螯合物与单壁碳纳米管直接接触的荧光淬灭问题。SWNT—Eu—Gd复合体系除具有铕的特征荧光之外,还可以作为T1加权核磁共振造影剂,在纳米生物医学多模成像上具有潜在的应用。     

Maximizing revenue with allocation of multiple advertisements on a Web banner

The problem addressed in this paper is the allocation of multiple advertisements on a Web banner, in order to maximize the revenue of the allocated advertisements. It is essentially a two-dimensional, single, orthogonal, knapsack problem, applied to pixel advertisement. As this problem is known to be NP-hard, and due to the temporal constraints that Web applications need to fulfill, we propose several heuristic algorithms for generating allocation patterns. The heuristic algorithms presented in this paper are the left justified algorithm, the orthogonal algorithm, the GRASP constructive algorithm, and the greedy stripping algorithm. We set out an experimental design using standard banner sizes, and primary and secondary sorting criteria for the set of advertisements. We run two simulations, the first simulation compares the heuristics with an optimal solution found using brute force search, and the second simulation compares the heuristic algorithms to gain a better insight into their performance. Finding a suitable pattern generating algorithm is a trade-off between effectiveness and efficiency. Results indicate that allocating advertisements with the orthogonal algorithm is the most effective. In contrast, allocating advertisements using the greedy stripping algorithm is the most efficient. Furthermore, the best settings per algorithm for each banner size are given.     

Automated segmentation of optic disc region on retinal fundus photographs: Comparison of contour modeling and pixel classification methods

The automatic determination of the optic disc area in retinal fundus images can be useful for calculation of the cup-to-disc (CD) ratio in the glaucoma screening. We compared three different methods that employed active contour model (ACM), fuzzy c-mean (FCM) clustering, and artificial neural network (ANN) for the segmentation of the optic disc regions. The results of these methods were evaluated using new databases that included the images captured by different camera systems. The average measures of overlap between the disc regions determined by an ophthalmologist and by using the ACM (0.88 and 0.87 for two test datasets) and ANN (0.88 and 0.89) methods were slightly higher than that by using FCM (0.86 and 0.86) method. These results on the unknown datasets were comparable with those of the resubstitution test; this indicates the generalizability of these methods. The differences in the vertical diameters, which are often used for CD ratio calculation, determined by the proposed methods and based on the ophthalmologist's outlines were even smaller than those in the case of the measure of overlap. The proposed methods can be useful for automatic determination of CD ratios.     

First results in micromapping the sensitivity to SEE of an electronic device in a SOI technology at the LNL IEEM

In this paper we review on radiation tolerance studies on a Monolithic Pixels Detector fabricated in a commercial Silicon On Insulator (SOI) technology and we report on the first application of Ion Electron Emission Microscopy to obtain a micrometric map of its sensitivity to Single Event Upset.     

基于图像区域像素二阶中心矩的集成电路芯片图像拼接技术

在集成电路芯片光学检测中,完整而准确地获取芯片形貌的图像非常重要.针对集成电路芯片表面形貌图像获取的要求,首先讨论集成电路芯片图像放大采集系统构成及工作原理,并研究图像拼接在精密芯片图像检测中的必要性及重要性,针对集成芯片的微观表面图像特征处理的要求,提出集成电路芯片的区域像素二阶中心矩图像拼接技术,通过建立图像区域像素的二阶中心矩进行匹配点的准确搜索,随后进行芯片精密显微图像的拼接.编程实验证明,采用本方法可获得集成电路芯片表面的清晰图像,并使芯片的微观形貌和细小缺陷等细节能得到很好的展现.