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Quasi-angle-preserving mesh deformation using the least-squares approach 基于最小二乘法的准保角网格变形
Pub Date : 2014-09-01 DOI: 10.1631/jzus.C1400103
Gang Xu, Lishan Deng, Wenbing Ge, K. Hui, Guozhen Wang, Yi-gang Wang
We propose an angle-based mesh representation, which is invariant under translation, rotation, and uniform scaling, to encode the geometric details of a triangular mesh. Angle-based mesh representation consists of angle quantities defined on the mesh, from which the mesh can be reconstructed uniquely up to translation, rotation, and uniform scaling. The reconstruction process requires solving three sparse linear systems: the first system encodes the length of edges between vertices on the mesh, the second system encodes the relationship of local frames between two adjacent vertices on the mesh, and the third system defines the position of the vertices via the edge length and the local frames. From this angle-based mesh representation, we propose a quasi-angle-preserving mesh deformation system with the least-squares approach via handle translation, rotation, and uniform scaling. Several detail-preserving mesh editing examples are presented to demonstrate the effectiveness of the proposed method.
我们提出了一种基于角度的网格表示,它在平移、旋转和均匀缩放下是不变的,以编码三角形网格的几何细节。基于角度的网格表示由定义在网格上的角度量组成,从这些角度量可以唯一地重构网格,直至平移、旋转和均匀缩放。重构过程需要求解三个稀疏线性系统:第一个系统对网格上顶点之间的边长度进行编码,第二个系统对网格上两个相邻顶点之间的局部帧关系进行编码,第三个系统通过边缘长度和局部帧定义顶点的位置。基于这种基于角度的网格表示,我们提出了一种基于最小二乘方法的准角度保持网格变形系统,该系统通过手柄平移、旋转和均匀缩放。最后给出了若干保持细节的网格编辑实例,验证了该方法的有效性。
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引用次数: 0
Image anti-aliasing techniques for Internet visual media processing: a review 网络视觉媒体处理中的图像抗混叠技术综述
Pub Date : 2014-09-01 DOI: 10.1631/jzus.C1400100
Xu-dong Jiang, Bin Sheng, Weiyao Lin, Wei Lu, Lizhuang Ma
Anti-aliasing is a well-established technique in computer graphics that reduces the blocky or stair-wise appearance of pixels. This paper provides a comprehensive overview of the anti-aliasing techniques used in computer graphics, which can be classified into two categories: post-filtering based anti-aliasing and pre-filtering based anti-aliasing. We discuss post-filtering based anti-aliasing algorithms through classifying them into hardware anti-aliasing techniques and post-process techniques for deferred rendering. Comparisons are made among different methods to illustrate the strengths and weaknesses of every category. We also review the utilization of anti-aliasing techniques from the first category in different graphic processing units, i.e., different NVIDIA and AMD series. This review provides a guide that should allow researchers to position their work in this important research area, and new research problems are identified.
抗锯齿是计算机图形学中一项成熟的技术,它可以减少像素的块状或阶梯状外观。本文全面概述了计算机图形学中使用的抗混叠技术,可分为两类:基于后滤波的抗混叠和基于预滤波的抗混叠。我们讨论了基于后滤波的抗混叠算法,通过将它们分类为硬件抗混叠技术和延迟渲染的后处理技术。在不同的方法之间进行比较,以说明每一类的优点和缺点。我们还回顾了第一类抗混叠技术在不同图形处理单元(即不同的NVIDIA和AMD系列)中的应用。这篇综述提供了一个指南,应该允许研究人员在这个重要的研究领域定位他们的工作,并确定新的研究问题。
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引用次数: 5
Exploring optimal combination of a file system and an I/O scheduler for underlying solid state disks 探索用于底层固态磁盘的文件系统和I/O调度器的最佳组合
Pub Date : 2014-08-01 DOI: 10.1631/jzus.C1300314
Hui Sun, Xiao-Lin Qin, Chang-sheng Xie
Performance and energy consumption of a solid state disk (SSD) highly depend on file systems and I/O schedulers in operating systems. To find an optimal combination of a file system and an I/O scheduler for SSDs, we use a metric called the aggregative indicator (AI), which is the ratio of SSD performance value (e.g., data transfer rate in MB/s or throughput in IOPS) to that of energy consumption for an SSD. This metric aims to evaluate SSD performance per energy consumption and to study the SSD which delivers high performance at low energy consumption in a combination of a file system and an I/O scheduler. We also propose a metric called Cemp to study the changes of energy consumption and mean performance for an Intel SSD (SSD-I) when it provides the largest AI, lowest power, and highest performance, respectively. Using Cemp, we attempt to find the combination of a file system and an I/O scheduler to make SSD-I deliver a smooth change in energy consumption. We employ Filebench as a workload generator to simulate a wide range of workloads (i.e., varmail, fileserver, and webserver), and explore optimal combinations of file systems and I/O schedulers (i.e., optimal values of AI) for tested SSDs under different workloads. Experimental results reveal that the proposed aggregative indicator is comprehensive for exploring the optimal combination of a file system and an I/O scheduler for SSDs, compared with an individual metric.
SSD的性能和能耗在很大程度上取决于操作系统中的文件系统和I/O调度器。为了找到SSD的文件系统和I/O调度器的最佳组合,我们使用了一个称为聚合指标(AI)的度量,它是SSD性能值(例如,以MB/s为单位的数据传输速率或以IOPS为单位的吞吐量)与SSD能耗的比率。该指标旨在评估SSD的每能耗性能,并研究在文件系统和I/O调度器的组合中提供低能耗高性能的SSD。我们还提出了一个名为Cemp的指标来研究英特尔SSD (SSD- i)在提供最大AI、最低功耗和最高性能时的能耗和平均性能的变化。使用Cemp,我们试图找到文件系统和I/O调度器的组合,以使SSD-I在能耗方面实现平稳的变化。我们使用Filebench作为工作负载生成器来模拟各种工作负载(即,varmail, fileserver和webserver),并为不同工作负载下的测试ssd探索文件系统和I/O调度器的最佳组合(即,AI的最佳值)。实验结果表明,与单个指标相比,所提出的聚合指标在探索文件系统和ssd I/O调度器的最佳组合方面是全面的。
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引用次数: 2
Adaptive contourlet-wavelet iterative shrinkage/thresholding for remote sensing image restoration 自适应contourlet-小波迭代收缩/阈值复原遥感图像
Pub Date : 2014-08-01 DOI: 10.1631/jzus.C1300377
Nu Wen, Shi-Zhi Yang, C. Zhu, Sheng-cheng Cui
In this paper, we present an adaptive two-step contourlet-wavelet iterative shrinkage/thresholding (TcwIST) algorithm for remote sensing image restoration. This algorithm can be used to deal with various linear inverse problems (LIPs), including image deconvolution and reconstruction. This algorithm is a new version of the famous two-step iterative shrinkage/thresholding (TwIST) algorithm. First, we use the split Bregman Rudin-Osher-Fatemi (ROF) model, based on a sparse dictionary, to decompose the image into cartoon and texture parts, which are represented by wavelet and contourlet, respectively. Second, we use an adaptive method to estimate the regularization parameter and the shrinkage threshold. Finally, we use a linear search method to find a step length and a fast method to accelerate convergence. Results show that our method can achieve a signal-to-noise ratio improvement (ISNR) for image restoration and high convergence speed.
本文提出了一种用于遥感图像恢复的自适应两步contourlet-wavelet迭代收缩/阈值(tcist)算法。该算法可用于处理各种线性逆问题,包括图像反卷积和重建。该算法是著名的两步迭代收缩/阈值(TwIST)算法的新版本。首先,采用基于稀疏字典的分割Bregman Rudin-Osher-Fatemi (ROF)模型,将图像分解为卡通部分和纹理部分,分别用小波和contourlet表示。其次,我们使用自适应方法估计正则化参数和收缩阈值。最后,我们用线性搜索法求出步长,用快速方法加速收敛。实验结果表明,该方法能够有效地提高图像恢复的信噪比,收敛速度快。
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引用次数: 2
Designing a location update strategy for free-moving and network-constrained objects with varying velocity 变速度自由运动和网络约束物体的位置更新策略设计
Pub Date : 2014-08-01 DOI: 10.1631/jzus.C1300337
Yuan-Ko Huang, Lien-Fa Lin
Spatio-temporal databases aim at appropriately managing moving objects so as to support various types of queries. While much research has been conducted on developing query processing techniques, less effort has been made to address the issue of when and how to update location information of moving objects. Previous work shifts the workload of processing updates to each object which usually has limited CPU and battery capacities. This results in a tremendous processing overhead for each moving object. In this paper, we focus on designing efficient update strategies for two important types of moving objects, free-moving objects (FMOs) and network-constrained objects (NCOs), which are classified based on object movement models. For FMOs, we develop a novel update strategy, namely the FMO update strategy (FMOUS), to explicitly indicate a time point at which the object needs to update location information. As each object knows in advance when to update (meaning that it does not have to continuously check), the processing overhead can be greatly reduced. In addition, the FMO update procedure (FMOUP) is designed to efficiently process the updates issued from moving objects. Similarly, for NCOs, we propose the NCO update strategy (NCOUS) and the NCO update procedure (NCOUP) to inform each object when and how to update location information. Extensive experiments are conducted to demonstrate the effectiveness and efficiency of the proposed update strategies.
时空数据库旨在对运动对象进行适当的管理,以支持各种类型的查询。虽然在开发查询处理技术方面进行了大量的研究,但在解决何时以及如何更新运动对象的位置信息的问题上却做得很少。以前的工作将处理更新的工作量转移到每个对象,这些对象通常具有有限的CPU和电池容量。这将导致每个移动对象的巨大处理开销。本文主要针对自由运动目标(FMOs)和网络约束目标(nco)这两种重要的运动目标,设计了基于目标运动模型的有效更新策略。对于FMO,我们开发了一种新的更新策略,即FMO更新策略(FMOUS),以明确地指出对象需要更新位置信息的时间点。由于每个对象都提前知道何时更新(这意味着它不必连续检查),因此可以大大降低处理开销。此外,设计了FMO更新过程(FMOUP),以有效地处理来自运动对象的更新。同样,对于NCO,我们提出了NCO更新策略(NCOUS)和NCO更新过程(NCOUP)来通知每个对象何时以及如何更新位置信息。大量的实验证明了所提出的更新策略的有效性和效率。
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引用次数: 1
Development of a monocular vision system for robotic drilling 机器人钻孔单目视觉系统的研制
Pub Date : 2014-08-01 DOI: 10.1631/jzus.C1300379
Wei-dong Zhu, Biao Mei, Guo-Rui Yan, Y. Ke
Robotic drilling for aerospace structures demands a high positioning accuracy of the robot, which is usually achieved through error measurement and compensation. In this paper, we report the development of a practical monocular vision system for measurement of the relative error between the drill tool center point (TCP) and the reference hole. First, the principle of relative error measurement with the vision system is explained, followed by a detailed discussion on the hardware components, software components, and system integration. The elliptical contour extraction algorithm is presented for accurate and robust reference hole detection. System calibration is of key importance to the measurement accuracy of a vision system. A new method is proposed for the simultaneous calibration of camera internal parameters and hand-eye relationship with a dedicated calibration board. Extensive measurement experiments have been performed on a robotic drilling system. Experimental results show that the measurement accuracy of the developed vision system is higher than 0.15 mm, which meets the requirement of robotic drilling for aircraft structures.
航天结构的机器人钻孔对机器人的定位精度要求很高,通常通过误差测量和补偿来实现。在本文中,我们报告了一种实用的单目视觉系统的开发,用于测量钻具中心点(TCP)与参考孔之间的相对误差。首先阐述了视觉系统相对误差测量的原理,然后对硬件组成、软件组成和系统集成进行了详细的讨论。提出了一种精确、鲁棒的参考孔检测椭圆轮廓提取算法。系统标定对视觉系统的测量精度至关重要。提出了一种利用专用标定板同时标定摄像机内部参数和手眼关系的新方法。在机器人钻井系统上进行了大量的测量实验。实验结果表明,所开发的视觉系统测量精度高于0.15 mm,满足飞机结构机器人钻孔的要求。
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引用次数: 7
Motion synchronization of dual-cylinder pneumatic servo systems with integration of adaptive robust control and cross-coupling approach 自适应鲁棒控制与交叉耦合相结合的双缸气动伺服系统运动同步
Pub Date : 2014-08-01 DOI: 10.1631/jzus.C1300360
De-yuan Meng, G. Tao, Aimin Li, Wei Li
We investigate motion synchronization of dual-cylinder pneumatic servo systems and develop an adaptive robust synchronization controller. The proposed controller incorporates the cross-coupling technology into the integrated direct/indirect adaptive robust control (DIARC) architecture by feeding back the coupled position errors, which are formed by the trajectory tracking errors of two cylinders and the synchronization error between them. The controller employs an online recursive least squares estimation algorithm to obtain accurate estimates of model parameters for reducing the extent of parametric uncertainties, and uses a robust control law to attenuate the effects of parameter estimation errors, unmodeled dynamics, and disturbances. Therefore, asymptotic convergence to zero of both trajectory tracking and synchronization errors can be guaranteed. Experimental results verify the effectiveness of the proposed controller.
研究了双缸气动伺服系统的运动同步问题,开发了一种自适应鲁棒同步控制器。该控制器将交叉耦合技术引入直接/间接自适应鲁棒综合控制(DIARC)体系结构中,对两缸轨迹跟踪误差及其同步误差形成的耦合位置误差进行反馈。控制器采用在线递归最小二乘估计算法来获得模型参数的准确估计,以减小参数不确定性的程度,并使用鲁棒控制律来减弱参数估计误差、未建模动力学和干扰的影响。因此,可以保证轨迹跟踪误差和同步误差都渐近收敛于零。实验结果验证了该控制器的有效性。
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引用次数: 7
Knowledge modeling based on interval-valued fuzzy rough set and similarity inference: prediction of welding distortion 基于区间模糊粗糙集和相似性推理的知识建模:焊接变形预测
Pub Date : 2014-08-01 DOI: 10.1631/jzus.C1300370
Zhi-qiang Feng, Cun-Gen Liu, Hu Huang
Knowledge-based modeling is a trend in complex system modeling technology. To extract the process knowledge from an information system, an approach of knowledge modeling based on interval-valued fuzzy rough set is presented in this paper, in which attribute reduction is a key to obtain the simplified knowledge model. Through defining dependency and inclusion functions, algorithms for attribute reduction and rule extraction are obtained. The approximation inference plays an important role in the development of the fuzzy system. To improve the inference mechanism, we provide a method of similarity-based inference in an interval-valued fuzzy environment. Combining the conventional compositional rule of inference with similarity based approximate reasoning, an inference result is deduced via rule translation, similarity matching, relation modification, and projection operation. This approach is applied to the problem of predicting welding distortion in marine structures, and the experimental results validate the effectiveness of the proposed methods of knowledge modeling and similarity-based inference.
基于知识的建模是复杂系统建模技术的发展趋势。为了从信息系统中提取过程知识,提出了一种基于区间值模糊粗糙集的知识建模方法,其中属性约简是获得简化知识模型的关键。通过定义依赖函数和包含函数,得到属性约简和规则提取算法。逼近推理在模糊系统的发展中起着重要的作用。为了改进推理机制,提出了一种区间值模糊环境下基于相似度的推理方法。将传统的推理组合规则与基于相似度的近似推理相结合,通过规则转换、相似度匹配、关系修改、投影运算等步骤推导出推理结果。将该方法应用于船舶结构焊接变形预测问题,实验结果验证了知识建模和基于相似度推理方法的有效性。
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引用次数: 2
Volterra filter modeling of a nonlinear discrete-time system based on a ranked differential evolution algorithm 基于分级差分进化算法的非线性离散系统Volterra滤波建模
Pub Date : 2014-08-01 DOI: 10.1631/jzus.C1300350
De-Xuan Zou, Li-qun Gao, Steven Li
This paper presents a ranked differential evolution (RDE) algorithm for solving the identification problem of non-linear discrete-time systems based on a Volterra filter model. In the improved method, a scale factor, generated by combining a sine function and randomness, effectively keeps a balance between the global search and the local search. Also, the mutation operation is modified after ranking all candidate solutions of the population to help avoid the occurrence of premature convergence. Finally, two examples including a highly nonlinear discrete-time rational system and a real heat exchanger are used to evaluate the performance of the RDE algorithm and five other approaches. Numerical experiments and comparisons demonstrate that the RDE algorithm performs better than the other approaches in most cases.
提出了一种基于Volterra滤波模型求解非线性离散系统辨识问题的分级差分进化算法。在改进的方法中,将正弦函数与随机性相结合产生尺度因子,有效地保持了全局搜索与局部搜索之间的平衡。同时,在对种群的所有候选解进行排序后,对突变操作进行修改,以避免过早收敛的发生。最后,以一个高度非线性离散有理系统和一个实际换热器为例,对RDE算法和其他五种方法的性能进行了评价。数值实验和比较表明,RDE算法在大多数情况下都优于其他方法。
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引用次数: 5
Automatic recovery from resource exhaustion exceptions by collecting leaked resources 通过收集泄漏的资源,从资源耗尽异常中自动恢复
Pub Date : 2014-08-01 DOI: 10.1631/jzus.C1300352
Ziying Dai, Xiaoguang Mao, Li-qian Chen, Yan Lei
Despite the availability of garbage collectors, programmers must manually manage non-memory finite system resources such as file descriptors. Resource leaks can gradually consume all available resources and cause programs to raise resource exhaustion exceptions. However, programmers commonly provide no effective recovery approach for resource exhaustion exceptions, which often causes programs to halt without completing their tasks. In this paper, we propose to automatically recover programs from resource exhaustion exceptions caused by resource leaks. We transform programs to catch resource exhaustion exceptions, collect leaked resources, and then retry the failure code. A resource collector is designed to identify leaked resources and safely release them. We implement our approach for Java programs. Experimental results show that our approach can successfully handle resource exhaustion exceptions caused by reported resource leaks and allow programs to complete their tasks with an average execution time increase of 2.52% and negligible bytecode size increase.
尽管有垃圾收集器的可用性,程序员必须手动管理非内存有限的系统资源,如文件描述符。资源泄漏会逐渐消耗所有可用资源,并导致程序引发资源耗尽异常。然而,程序员通常没有为资源耗尽异常提供有效的恢复方法,这通常会导致程序在没有完成任务的情况下停止。在本文中,我们提出了自动恢复程序从资源泄漏引起的资源耗尽异常。我们转换程序来捕获资源耗尽异常,收集泄漏的资源,然后重试失败代码。资源收集器设计用于识别泄漏的资源并安全地释放它们。我们在Java程序中实现了我们的方法。实验结果表明,该方法可以成功地处理由报告的资源泄漏引起的资源耗尽异常,并使程序在平均执行时间增加2.52%的情况下完成任务,而字节码大小的增加可以忽略不计。
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引用次数: 0
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Journal of Zhejiang University-Science C-Computers & Electronics
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