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Hybrid ants-like search algorithms for P2P media streaming distribution in ad hoc networks
ZUO Dong-hong, DU Xu, YANG Zong-kai
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2007, 8(8): 1191-1198.
https://doi.org/10.1631/jzus.2007.A1191
Media streaming delivery in wireless ad hoc networks is challenging due to the stringent resource restrictions, potential high loss rate and the decentralized architecture. To support long and high-quality streams, one viable approach is that a media stream is partitioned into segments, and then the segments are replicated in a network and served in a peer-to-peer (P2P) fashion. However, the searching strategy for segments is one key problem with the approach. This paper proposes a hybrid ants-like search algorithm (HASA) for P2P media streaming distribution in ad hoc networks. It takes the advantages of random walks and ants-like algorithms for searching in unstructured P2P networks, such as low transmitting latency, less jitter times, and low unnecessary traffic. We quantify the performance of our scheme in terms of response time, jitter times, and network messages for media streaming distribution. Simulation results showed that it can effectively improve the search efficiency for P2P media streaming distribution in ad hoc networks.
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A new algorithm for computing the convex hull of a planar point set
LIU Guang-hui, CHEN Chuan-bo
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2007, 8(8): 1210-1217.
https://doi.org/10.1631/jzus.2007.A1210
When the edges of a convex polygon are traversed along one direction, the interior of the convex polygon is always on the same side of the edges. Based on this characteristic of convex polygons, a new algorithm for computing the convex hull of a simple polygon is proposed in this paper, which is then extended to a new algorithm for computing the convex hull of a planar point set. First, the extreme points of the planar point set are found, and the subsets of point candidate for vertex of the convex hull between extreme points are obtained. Then, the ordered convex hull point sequences between extreme points are constructed separately and concatenated by removing redundant extreme points to get the convex hull. The time complexity of the new planar convex hull algorithm is O(nlogh), which is equal to the time complexity of the best output-sensitive planar convex hull algorithms. Compared with the algorithm having the same complexity, the new algorithm is much faster.
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Iris recognition: a biometric method after refractive surgery
YUAN Xiao-yan, ZHOU Hao, SHI Peng-fei
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2007, 8(8): 1227-1231.
https://doi.org/10.1631/jzus.2007.A1227
Iris recognition, as a biometric method, outperforms others because of its high accuracy. Iris is the visible internal organ of human, so it is stable and very difficult to be altered. But if an eye surgery must be made to some individuals, it may be rejected by iris recognition system as imposters after the surgery, because the iris pattern was altered or damaged somewhat during surgery and cannot match the iris template stored before the surgery. In this paper, we originally discuss whether refractive surgery for vision correction (LASIK surgery) would influence the performance of iris recognition. And experiments are designed and tested on iris images captured especially for this research from patients before and after refractive surgery. Experiments showed that refractive surgery has little influence on iris recognition.
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Fruit shape detection by level set
GUI Jiang-sheng, RAO Xiu-qin, YING Yi-bin
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2007, 8(8): 1232-1236.
https://doi.org/10.1631/jzus.2007.A1232
A novel approach for fruit shape detection in RGB space was proposed, which was based on fast level set and Chan-Vese model named as Modified Chan-Vese model (MCV). This new algorithm is fast and suitable for fruit sorting because it does not need re-initializing. MCV has three advantages compared to the traditional methods. First, it provides a unified framework for detecting fruit shape boundary, and does not need any preprocessing even though the raw image is noisy or blurred. Second, if the fruit has different colors at the edges, it can detect perfect boundary. Third, it processed directly in color space without any transformations that may lose much information. The proposed method has been applied to fruit shape detection with promising result.
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Joint application of feature extraction based on EMD-AR strategy and multi-class classifier based on LS-SVM in EMG motion classification
YAN Zhi-guo, WANG Zhi-zhong, REN Xiao-mei
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2007, 8(8): 1246-1255.
https://doi.org/10.1631/jzus.2007.A1246
This paper presents an effective and efficient combination of feature extraction and multi-class classifier for motion classification by analyzing the surface electromyografic (sEMG) signals. In contrast to the existing methods, considering the non-stationary and nonlinear characteristics of EMG signals, to get the more separable feature set, we introduce the empirical mode decomposition (EMD) to decompose the original EMG signals into several intrinsic mode functions (IMFs) and then compute the coefficients of autoregressive models of each IMF to form the feature set. Based on the least squares support vector machines (LS-SVMs), the multi-class classifier is designed and constructed to classify various motions. The results of contrastive experiments showed that the accuracy of motion recognition is improved with the described classification scheme. Furthermore, compared with other classifiers using different features, the excellent performance indicated the potential of the SVM techniques embedding the EMD-AR kernel in motion classification.
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Study on spillover effect of copper futures between LME and SHFE using wavelet multiresolution analysis
WANG Su-nan, PAN Yun-he, YANG Jian-gang
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2007, 8(8): 1290-1295.
https://doi.org/10.1631/jzus.2007.A1290
Research on information spillover effects between financial markets remains active in the economic community. A Granger-type model has recently been used to investigate the spillover between London Metal Exchange (LME) and Shanghai Futures Exchange (SHFE), however, possible correlation between the future price and return on different time scales have been ignored. In this paper, wavelet multiresolution decomposition is used to investigate the spillover effects of copper future returns between the two markets. The daily return time series are decomposed on 2n (n=1, …, 6) frequency bands through wavelet multiresolution analysis. The correlation between the two markets is studied with decomposed data. It is shown that high frequency detail components represent much more energy than low-frequency smooth components. The relation between copper future daily returns in LME and that in SHFE are different on different time scales. The fluctuations of the copper future daily returns in LME have large effect on that in SHFE in 32-day scale, but small effect in high frequency scales. It also has evidence that strong effects exist between LME and SHFE for monthly responses of the copper futures but not for daily responses.
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Analysis of a new 5-phase bearingless induction motor
HUANG Jin, KANG Min, YANG Jia-qiang
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2007, 8(8): 1311-1319.
https://doi.org/10.1631/jzus.2007.A1311
This paper addresses the bearingless motor with a single set of multiphase windings. The interaction between M and M±1 pole-pair magnetic fields produces radial force. Based on this principle, a bearingless machine is obtained. Conventional bearingless machine has dual windings, levitation windings and torque windings, which produce the two magnetic fields. In the proposed bearingless motor, the two needed magnetic fields are produced by feeding two groups of currents to a single set of multiphase windings. Taking a 5-phase induction motor as example, the inductance matrices, considering air gap eccentricity, are calculated with the modified winding function method. The radial force analytical model is deduced by virtual displacement, and its results are validated by FEA. The mathematical model of the new bearingless machine is set up, and the simulation results verified the feasibility of this novel bearingless motor.
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New finding on out-of-step separation configuration of large-scale power systems
WANG Chao, GAO Peng, ZHANG Xue-song, SHAO Wei
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2007, 8(8): 1340-1345.
https://doi.org/10.1631/jzus.2007.A1340
In this paper, two new concepts—“main out-of-step mode” and “minor out-of-step mode”—are proposed for power system reliability analysis. Large-scale power system studies found that out-of-step generator groups may have characteristics of the main out-of-step mode and the minor out-of-step mode. The generator groups with main out-of-step modes can determine the out-of-step interface of the large-scale power system, while generators with the minor out-of-step modes cannot play such a role. Therefore, the method of capturing the out-of-step interface by seeking the lowest voltage point (the out-of-step center) can only group the generators with the main out-of-step modes, and may fail to combine the generators with the minor out-of-step modes into proper coherent generator groups. Thus, it is necessary in engineering applications to equip the generators that are likely to have the characteristics of the minor out-of-step modes with separation devices based on off-line simulation studies in order to reduce the risk of further accidents caused by these generators after system separation.
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A 155 Mbps laser diode driver with automatic power and extinction ratio control
CHEN Xiao-fei, ZOU Xue-cheng, LIN Shuang-xi, LIU Zheng-lin, JIN Hai
Journal of Zhejiang University-SCIENCE A (Applied Physics & Engineering), 2007, 8(8): 1346-1350.
https://doi.org/10.1631/jzus.2007.A1346
An integrated laser diode driver (LDD) driving an edge-emitting laser diode was designed and fabricated by 0.35 μm BiCMOS technology. This paper proposes a scheme which combines the automatic power control loop and temperature compensation for modulation current in order to maintain constant extinction ratio and average optical power. To implement temperature compensation for modulation current, a novel circuit which generates a PTAT current by using the injecting base current of a bipolar transistor in saturation region, and alternates the amplifier feedback loop (closed or not) to control the state of the current path is presented. Simulation results showed that programmed by choice of external resistors, the IC can provide modulation current from 5 mA to 85 mA with temperature compensation adjustments and independent bias current from 4 mA to 100 mA. Optical test results showed that clear eye-diagrams can be obtained at 155 Mbps, with the output optical power being nearly constant, and the variation of extinction ratio being lower than 0.7 dB.
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23 articles
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