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41.
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低比特率时,基于块离散余弦变换(BDCT)的图像压缩方法常常会引起块效应。量化约束集(QCS)作为关于编码模型的重要先验信息在块效应消除方法中被广泛地采用。利用量化误差的统计特性,提出了一种改进的量化约束集(MQCS)。实验结果表明当在现有的基于凸集投影(POCS)的去块算法中以新的约束集代替传统量化约束集,峰值信噪比(PSNR)和主观图像质量有不同程度的提高,性能与窄量化约束集(NQCS)相当。 相似文献
43.
提出了一种计算海量平面点集凸壳的快速近似算法——点集坐标旋转法(PSCR)。该算法采用点集不断旋转并求X(Y)坐标极值的方法得到平面点集的近似凸壳。它充分利用了成熟的数据库技术,能够在比较短的时间内计算出海量平面点集的近似凸壳。它不需要空间索引的支持,并能获得比较理想的近似效果。 相似文献
44.
论二维点集或线段集凸壳生成算法改进与优化的同构化方向 总被引:8,自引:6,他引:2
本文指出了迄今为止的现行二维点集或线段集(包括:多边形、封闭折线、半封闭折线、开放线段集等)凸壳生成算法的共同弱点;提出了可改进与优化凸壳算法的同构化凸壳构造基本定理。进而,基于同构化凸壳构造基本定理,阐明了有限二维点集或线段集凸壳生成算法改进与优化的同构化方向,应当是:第一,使凸壳极点(或称顶点)分布域极小化,即让包含凸壳极点的判定区域尽可能小;使极点判定对象直接化,即让所判定对象尽可能接近当前所寻极点。第二,尽力对有可改造潜力的优秀串行凸壳算法施以并行化改造和创新。 相似文献
45.
基于最大基线倾角智能逼近的凸壳新算法 总被引:7,自引:7,他引:0
本文评述了有代表性的折半分治递归凸壳算法,并利用同构化凸壳基本定理提出效率更高的最大倾角智能逼近凸壳新算法。本新算法的同构化特点是:1)找出给定二维点集最外点(指最左、最右、最高、最低点),即其X轴、Y轴坐标值最大、最小的四个初始极点;2)用该初始极点,把原二维点集分布域划分为四个子分布域;3)分别在这四个子分布域中,各基于自身最新所得极点依次动态构造其基线倾角最大的当前极点,并用这些极点作凸边,来逐步智能逼近和最终生成该给定二维点集的凸壳。 相似文献
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47.
In this paper, the problem of optimal sizing of a series PHEV is studied by formulating a convex program that minimizes the sum of operational and component costs. The solution gives the optimal sizes of the main powertrain components, simultaneously with the vehicle's optimal energy management. Investigations are performed on driving cycles generated stochastically from real data using Markov chains, with different driving distance distributions and charging patterns. The results show that the optimal component sizing is affected more from the driving distances between charging opportunities, than the speed profile of the driving. With anticipated future battery and petroleum prices, larger battery sizes are obtained. 相似文献
48.
Classic linear dimensionality reduction (LDR) methods, such as principal component analysis (PCA) and linear discriminant analysis (LDA), are known not to be robust against outliers. Following a systematic analysis of the multi-class LDR problem in a unified framework, we propose a new algorithm, called minimal distance maximization (MDM), to address the non-robustness issue. The principle behind MDM is to maximize the minimal between-class distance in the output space. MDM is formulated as a semi-definite program (SDP), and its dual problem reveals a close connection to “weighted” LDR methods. A soft version of MDM, in which LDA is subsumed as a special case, is also developed to deal with overlapping centroids. Finally, we drop the homoscedastic Gaussian assumption made in MDM by extending it in a non-parametric way, along with a gradient-based convex approximation algorithm to significantly reduce the complexity of the original SDP. The effectiveness of our proposed methods are validated on two UCI datasets and two face datasets. 相似文献
49.
One of the most important aspects of the (statistical) analysis of imprecise data is the usage of a suitable distance on the family of all compact, convex fuzzy sets, which is not too hard to calculate and which reflects the intuitive meaning of fuzzy sets. On the basis of expressing the metric of Bertoluzza et al. [C. Bertoluzza, N. Corral, A. Salas, On a new class of distances between fuzzy numbers, Mathware Soft Comput. 2 (1995) 71-84] in terms of the mid points and spreads of the corresponding intervals we construct new families of metrics on the family of all d-dimensional compact convex sets as well as on the family of all d-dimensional compact convex fuzzy sets. It is shown that these metrics not only fulfill many good properties, but also that they are easy to calculate and easy to manage for statistical purposes, and therefore, useful from the practical point of view. 相似文献
50.
Coverage path planning for UAVs based on enhanced exact cellular decomposition method 总被引:3,自引:0,他引:3
In this paper, an enhanced exact cellular decomposition method to plan the coverage path of UAVs in a polygon area is proposed. To be more specific, the contributions of the paper are: firstly, the turning motion of UAVs is shown to be less efficient from the viewpoints of route length, duration and energy. Secondly, the problem of coverage Path Planning (CPP) in a convex polygon area is transformed to width calculation of the convex polygon, and a novel algorithm to calculate the widths of convex polygons with time complexity of O(n) is developed. The path of the least number of turns for an UAV based on the widths of convex polygons is devised. Thirdly, a convex decomposition algorithm for minimum width sum based on the greedy recursive method which revolves around decomposing the concave area into convex subregions is developed. It is proved that the algorithm is a polynomial time algorithm. To avoid unnecessary back and forth motion, some entirely adjacent subregions are combined. Finally, comparing different weights of two joint-points, a subregion connection algorithm based on minimum traversal of weighted undirected graph is proposed to connect the coverage paths of the subregions. Simulation results show that the proposed method is feasible and effective. 相似文献