Low-discrepancy sampling for approximate dynamic programming with local approximators

Approximate dynamic programming (ADP) relies, in the continuous-state case, on both a flexible class of models for the approximation of the value functions and a smart sampling of the state space for the numerical solution of the recursive Bellman equations. In this paper, low-discrepancy sequences, commonly employed for number-theoretic methods, are investigated as a sampling scheme in the ADP context when local models, such as the Nadaraya–Watson (NW) ones, are employed for the approximation of the value function. The analysis is carried out both from a theoretical and a practical point of view. In particular, it is shown that the combined use of low-discrepancy sequences and NW models enables the convergence of the ADP procedure. Then, the regular structure of the low-discrepancy sampling is exploited to derive a method for automatic selection of the bandwidth of NW models, which yields a significant saving in the computational effort with respect to the standard cross validation approach. Simulation results concerning an inventory management problem are presented to show the effectiveness of the proposed techniques.     

Self‐similarity for accurate compression of point sampled surfaces

Most surfaces, be it from a fine‐art artifact or a mechanical object, are characterized by a strong self‐similarity. This property finds its source in the natural structures of objects but also in the fabrication processes: regularity of the sculpting technique, or machine tool. In this paper, we propose to exploit the self‐similarity of the underlying shapes for compressing point cloud surfaces which can contain millions of points at a very high precision. Our approach locally resamples the point cloud in order to highlight the self‐similarity of the shape, while remaining consistent with the original shape and the scanner precision. It then uses this self‐similarity to create an ad hoc dictionary on which the local neighborhoods will be sparsely represented, thus allowing for a light‐weight representation of the total surface. We demonstrate the validity of our approach on several point clouds from fine‐arts and mechanical objects, as well as a urban scene. In addition, we show that our approach also achieves a filtering of noise whose magnitude is smaller than the scanner precision.     

基于语义的智能信息处理技术的研究

智能信息处理是模拟人或者自然界其他生物处理各种信息的行为,是当前信息处理技术向多样化、集成化与智能化方向的发展,具有很高的理论研究和应用价值.经过多年的研究和探索,智能信息处理技术已经取得较大的发展,但在实际应用中还存在许多问题需要解决和完善.分析了基于概念图的语义研究在智能信息处理中的应用,并设计与实现了一个基于概念图的智能答疑系统CGQAS,通过实验结果验证了基于概念图的智能信息处理的可行性和有效性.     

基于图形处理器的形态学重建系统

形态学重建是医学图像处理中非常基础和重要的操作。它根据掩膜图像的特征对标记图像反复进行膨胀操作，直到标记图像中的像素值不再变化为止。对于传统基于中央处理器（CPU）的形态学重建系统计算效率不高的问题，提出了使用图形处理器（GPU）来加速形态学重建。首先，设计了适合GPU处理的数据结构：并行堆集群；然后，基于并行堆集群，设计和实现了一套基于GPU的形态学重建系统。实验结果表明，相比传统基于CPU的形态学重建系统，基于GPU的形态学重建系统可以获取超过20倍的加速比。基于GPU的形态学重建系统展示了如何把基于复杂数据结构的软件系统高效地移植到GPU上。     

An Approach to Synthesize Diverse Underwater Image Dataset

Images that are taken underwater mostly present color shift with hazy effects due to the special property of water.Underwater image enhancement methods are prop...     

Probabilistic enhancement of approximate indexing in metric spaces

Some approximate indexing schemes have been recently proposed in metric spaces which sort the objects in the database according to pseudo-scores. It is known that (1) some of them provide a very good trade-off between response time and accuracy, and (2) probability-based pseudo-scores can provide an optimal trade-off in range queries if the probabilities are correctly estimated. Based on these facts, we propose a probabilistic enhancement scheme which can be applied to any pseudo-score based scheme. Our scheme computes probability-based pseudo-scores using pseudo-scores obtained from a pseudo-score based scheme. In order to estimate the probability-based pseudo-scores, we use the object-specific parameters in logistic regression and learn the parameters using MAP (Maximum a Posteriori) estimation and the empirical Bayes method. We also propose a technique which speeds up learning the parameters using pseudo-scores. We applied our scheme to the two state-of-the-art schemes: the standard pivot-based scheme and the permutation-based scheme, and evaluated them using various kinds of datasets from the Metric Space Library. The results showed that our scheme outperformed the conventional schemes, with regard to both the number of distance computations and the CPU time, in all the datasets.     

动态目标移动数据管理技术研究

日益发展的预警监控技术的应用，在信息系统中积累了海量的动态目标运动信息，而这些数据并没有得到很好的管理和利用。本文提出采用移动对象数据库技术对动态目标移动数据进行有效的管理。     

Windows GDI的图形图像处理技术应用

在对Windows GDI的图形图像处理技术进行论述的基础上,分析了其主要功能及相关新技术.同时探讨了其在图形图像处理中的应用.     

Characterization of stainless steel parts by Laser Metal Deposition Shaping

Laser Metal Deposition Shaping (LMDS) is a new rapid manufacturing technology, which can build fully-dense metal components directly from the information transferred from a computer file by depositing metal powders layer by layer with neither mould nor tool. Typically, performed with stainless steel (SS) 316 powder, the orthogonal experiments combining with the ideal overlapping model were applied to ascertain the optimal processing parameters. Then the characteristics of microstructure, composition and phase of as-deposited cladding layers were analyzed through Scanning Electron Microscope (SEM) and X-ray diffraction (XRD), as well as relative model. Furthermore, the cooling rate and the solidification velocity during LMDS were evaluated based on empirical method. With the optimal parameters, some parts were fabricated without obvious defects, and then the mechanical properties of them were tested. Finally, the influencing regularities of critical parameters on microstructure and properties were concluded by comparison. The results prove that the microstructure of SS 316 deposits is composed of the slender dendrites growing epitaxially from the substrate, the mechanical properties are favorable and anisotropic, and the composition is uniform. Besides, the microstructure morphology and the mechanical properties are affected by the varied processing parameters at different degrees. Among them, the scanning speed shows the most remarkable effects on microstructure morphology, characteristic microscale, mechanical properties, as well as geometric shape of as-deposited parts.     

GAG型复合片材的挤出生产工艺

本文介绍了几种常见聚酯树脂的性能特点及应用情况。介绍了GAG复合片材的成型设备和加工工艺。分析了加工过程的关键问题和解决方案。