基于重复补偿控制的交流伺服系统的PID控制

针对精密机床采用的交流伺服系统中,输出快速无超调地跟踪输入指令,控制精度高的要求,利用重复补偿控制的优点,将其与PID控制相结合形成一种基于重复补偿的PID控制结构,用于精密机床中交流伺服系统的位置控制,并在此基础上着重讨论了滤波器对控制效果的影响.从仿真结果可以看出,该控制方法提高了交流伺服系统对周期信号的跟踪精度....     

On the design of compensator for quantization-caused input-output deviation

This paper considers the design of compensators for systems with quantized inputs in order to reduce the influence of quantization.For systems with (vector) relative degrees,we propose a kind of compensators which can compensate for the accumulated output deviation completely caused by quantization.The proposed compensators are capable of keeping the differences of the input-output responses between the systems with quantized inputs and the original systems without considering quantization within certain sm...     

经济型补偿柜调试仪

介绍了一种使用三相工频电源,利用2个小功率变压器和若干开关组成的补偿柜调试仪,与传统继保仪相比具有极高的经济性,能够较好地满足补偿柜的调试需要。     

基于网络检测平台应对网络灾害探讨

网络灾害作为互联网给人类社会带来的各种潜在风险和负面效应之一,正在影响着社会各个行业。除了在网络安全技术、网络道德和相关法律等方面开展研究外,网络检测平台通过检测网络拓扑结构和其他网络动态属性,构建网络地图,可以为网络灾害的预防和控制提供相关依据。     

Topological active volumes: A topology-adaptive deformable model for volume segmentation

This paper proposes a generic methodology for segmentation and reconstruction of volumetric datasets based on a deformable model, the topological active volumes (TAV). This model, based on a polyhedral mesh, integrates features of region-based and boundary-based segmentation methods in order to fit the contours of the objects and model its inner topology. Moreover, it implements automatic procedures, the so-called topological changes, that alter the mesh structure and allow the segmentation of complex features such as pronounced curvatures or holes, as well as the detection of several objects in the scene. This work presents the TAV model and the segmentation methodology and explains how the changes in the TAV structure can improve the adjustment process. In particular, it is focused on the increase of the mesh density in complex image areas in order to improve the adjustment to object surfaces. The suitability of the mesh structure and the segmentation methodology is analyzed and the accuracy of the proposed model is proved with both synthetic and real images.     

Series feature aggregation for content-based image retrieval

Feature aggregation is a critical technique in content-based image retrieval (CBIR) systems that employs multiple visual features to characterize image content. Most previous feature aggregation schemes apply parallel topology, e.g., the linear combination scheme, which suffer from two problems. First, the function of individual visual feature is limited since the ranks of the retrieved images are determined only by the combined similarity. Second, the irrelevant images seriously affect the retrieval performance of feature aggregation scheme since all images in a collection will be ranked. To address these problems, we propose a new feature aggregation scheme, series feature aggregation (SFA). SFA selects relevant images using visual features one by one in series from the images highly ranked by the previous visual feature. The irrelevant images will be effectively filtered out by individual visual features in each stage, and the remaining images are collectively described by all visual features. Experiments, conducted with IAPR TC-12 benchmark image collection (ImageCLEF2006) that contains over 20,000 photographic images and defined queries, have shown that the proposed SFA can outperform conventional parallel feature aggregation schemes.     

无线传感器网络的一种可调节的拓扑控制算法

在无线传感器网络的拓扑控制问题中,保持节点能耗最低路径和低节点度之间存在一种平衡.最佳的平衡点与具体的应用和网络状态有关.文中提出一种新的拓扑控制算法,使所构造的拓扑能在这两个不一致的目标之间进行调节.该算法所构造的拓扑结构在一极能保持所有能耗最低路径,另一极能使平均节点度逼近理论最小值.仿真结果证实新算法在比已有方案更真实的能量消耗模型下可以保持所有能耗最低路径,同时也显示新算法对节点度有更大的调节范围.     

拓扑结构对动态增长的复杂网络的影响

研究在网络增长和外部目标的双重作用下,拓扑结构对复杂网络的演化产生的影响。在经典的布尔网络模型上应用进化算法进行大量仿真计算,考察在2种不同的增长规则作用下,网络向预先设定的目标函数演化时表现出的演化性能。仿真结果显示,Scale-Free网络表现出明显优于随机网络的的演化能力,而且不同的度分布对网络的演化性能有重要的影响。     

基于价值密度的替代与事务优先级分派策略

针对基于替代/补偿的实时事务模型中的优先级分派问题,提出基于价值密度的替代与事务优先级分派策略PBAC。在PBAC中,替代优先级基于替代的价值密度,并与替代的执行时间和紧迫性相关,事务优先级继承自替代的优先级,并受事务执行度的影响。仿真实验结果证明,该策略使系统可以更好地对基于替代/补偿的事务模型进行调度。     

基于XvMC的MPEG-2硬件解码的研究与实现

研究了如何利用GPU来加速视频解码,概述了MPEG-2视频解码的系统框架,论述了MPEG-2视频解码在Linux下以XvMC(X video motion compensation)为API并基于通用可编程GPU的实现过程,重点讨论了MPEG-2视频解码中IDCT(inverse discrete cosine transform)和运动补偿的实现,提出了新的优化算法.MPEG-2视频解码算法具有一定的通用性,实验结果表明,与传统的解码方式相比,该解码器不仅能加速视频解码,还能有效降低CPU的利用率和电脑的功耗.