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Search Results: 1 - 10 of 73775 matches for " WU Zhi-Mei "
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Temperature Insensitivity of Optical Properties of InAs/GaAs Quantum Dots due to a Pregrown InGaAs Quantum Well

LIANG Zhi-Mei,JIN Can,JIN Peng,WU Ju,WANG Zhan-Guo,

中国物理快报 , 2009,
Abstract: Both the peak position and linewidth in the photoluminescence spectrum of the InAs/GaAs quantum dots usually vary in an anomalous way with increasing temperature. Such anomalous optical behaviour is eliminated by inserting an In0.2Ga0.8As quantum well below the quantum dot layer in molecular beam epitaxy. The insensitivity of the photoluminescence spectra to temperature is explained in terms of the effective carrier redistribution between quantum dots through the In0.2Ga0.8As quantum well.
Reliable Multicast for Real-Time Continuous-Media Streams over Switch Ethernet

WANG Jun,WU Zhi-Mei,

软件学报 , 2004,
Abstract: A reliable multicast protocol for real-time continuous-media streams on switch Ethernet after research of the LANs special features for reliable multicast is proposed. The recovery of this protocol begins with the receivers detection of packet loss by packets number, and the second step of it is the NAK (negative acknowledgment) suppression procedure, and then the sender will retransmit the lost packet by the received NAK, and finally the receiver will discard or accept the recovered packet based on the limit of the real-time playback. The experimental results and the analysis of performance demonstrate the effectiveness and reliability of the approach.
Traffic Control in Linux-Based Routers

ZHANG Huan-Qiang,WU Zhi-Mei,

软件学报 , 2005,
Abstract: Linux is widely adopted in routers nowadays, and traffic control is one of the most important functions for this kind of network-oriented operating systems. This paper studies the traffic control mechanism of Linux system and shows that the packet scheduling based traffic control mechanism adopted by current Linux kernel lacks a global view of system bandwidth, and is also short of efficient ingress scheduling. This can result in unnecessary CPU time wasting. To address this problem, a novel traffic control scheme is proposed, which is based on the CPU scheduling of the network protocol processing. By transplanting packet scheduling from the egress point of network interfaces to the soft interrupt handler that processes incoming packets, the new method can eliminate disadvantages of the old traffic control scheme without introducing any additional demerits. An implementation of the new traffic control scheme is given, and comparative experimental results show that the new mechanism has fewer overload than the old traffic control scheme in Linux, and can maintain the efficiency of traffic isolation and traffic policing while avoiding the CPU time wasting.
Multicast Protocol over Switch Ethernet

WANG Jun,WU Zhi-Mei,

软件学报 , 2003,
Abstract: Many services, including video conference, whiteboard and video broadcasting, have been running over LANs. However, most of LANs, such as Ethernet, treat multicast just as broadcast, and they all have few supports for multicast. In this paper, a multicast protocol in an LAN switch, named IGMP snooping, is implemented based on VLAN and IGMP. IGMP snooping will be applied to the IP multicast stream control on the switch Ethernet. The basic idea, syntax and semantics of this protocol are given in this paper, and the verification and test procedure is also provided.
Adaptive Hurst Index Estimator Based on Wavelet

HONG Fei,WU Zhi-Mei,

软件学报 , 2005,
Abstract: The measurement studies show that the burstiness of packet traffic in LAN as well as WAN is associated with self-similar and long-range dependency, and Hurst index is the key value of this model representing the burstiness of traffic. With the analysis in discrete wavelet domain, the nature of the wavelet coefficients and their statistical properties are proposed. Then an adaptive, efficient unbiased estimator of Hurst index based on multiresolution wavelet analysis and weighted regression is presented. Simulation results based on fractal Gaussian noise and real traffic data reveal the proposed approach shows more adaptiveness, accuracy and robustness than traditional estimators which has only O(N) computation. Thus this estimator can be applied to the application of traffic management and real-time control in high-speed networks.
A Comparative Study: Offering Multi-Service of the Generic Broadband Residential Access Techniques

ZHAO Zhuang,LIU Qiong,WU Zhi-Mei,

软件学报 , 2003,
Abstract: Nowadays, the broadband residential access infrastructure remains one of the major research areas for NGN (next generation network). Apart from popular ADSL (asymmetrical digital subscriber loop), HFC (hybrid fiber-coax) and APON (ATM passive optical network), academic communities and industry are increasingly showing great concern about Ethernet technique in the subscriber access network. This paper investigates the substantial differences among the generic broadband residential access techniques and allows a comprehensive understanding of them. The authors survey the generic broadband residential access techniques and present a comparative study on the emerging residential Ethernet-based access solutions with the ADSL, HFC, and APON techniques based on multiplex methods and transport technologies in terms of network architecture, service and traffic models, and QoS (quality of service) provisioning. The comparative study is of benefit to research and implementation of the future broadband residential access infrastructure.
Discovering Layer-2 Topology in Bridged Local Area Networks

LI Tao SHI Zhi-Qiang WU Zhi-Mei,

计算机科学 , 2003,
Abstract: With the rapid development and the wide use of Bridged Local Area Networks, the importance of below-OSI-Layer-3 topology comes to be realized. Recent research work has demonstrated that active layer-2 topology can be determined using Address Forwarding Information. The large quantities of address forwarding entries in a typical BLAN, however, make their algorithms both time-consuming and bandwidth-consuming. In view of the above and the fact that transparent bridges are used preponderantly in real networks, we base our algorithm on information supported by Spanning Tree Protocol MIB group, which reduces the cost of acquiring and processing information, and improves the accuracy. Our algorithm relies on standard MIB information and can be used in heterogeneous environments.
A Hierarchy Reliable Mobile Multicast Algorithm Based on Mixed Acknowledgement Mechanism

SUN Li-Min,LIAO Yong,WU Zhi-Mei,

软件学报 , 2004,
Abstract: 由于移动主机位置的不断改变引起组播树的频繁重构,已有的可靠组播算法已不适用于主机移动的无线网络环境.首先提出了前向网络签署的移动组播机制,然后在基于区域的层次型网络结构中,集成前向网络签署和远程签署,采用ACK和NAK相结合的应答机制,在子网局部范围内使用组播恢复机制和应答抑制机制,提出了一个新的支持主机移动的可靠移动组播算法.在重传延迟、重传开销、协议开销和服务中断时间这些方面的模拟结果和分析显示,该算法是一个高效的、可扩展的可靠移动组播算法.
A Hierarchical Retrieval Method for MPEG Video

LIU Yang,XU Song-Tao,WU Zhi-Mei,

软件学报 , 2003,
Abstract: Video retrieval is a current hot research area. Most of the past algorithms are done in pixel domain, which need many decode calculations. What is more, the same matching algorithm is used to all the video clips in the same way, which wasts many unnecessary calculations. A new hierarchical retrieval method based on example video for MPEG video is proposed: firstly the dct_dc_size field in I frames is used to locate the suspected videos quickly, then the retrieval result scope can be further reduced by analyzing the spatiotemporal distribution of motion vector in B frames using tomography method, at last DC images precise matching analysis is used to validate the retrieval result. The experimental results show that this method needs a few calculations and has higher precision ratio.
Effects of 3,5-Dimethylpyrazole on Soil Urea-N Transformation and NO-N Leaching

SUN Zhi-mei,WU Zhi-jie,CHEN Li-jun,YU De-qing,

环境科学 , 2007,
Abstract: With the combination of incubation test and field experiment, the effects of the new nitrification inhibitor 3,5-dimethylpyrazole on urea-N transformation and NO3- leaching loss from corn field were studied. The results showed that DMP could temporally retard the hydrolysis of urea after its application, but strongly inhibit the process of ammonium oxidation for a longer time, and the inhibitory efficiency was enhanced with increasing DMP dose. Compared with CK, soil NH4+-N content in treatments DMP1 (0.0025 g/kg), DMP2 (0.01 g/kg) and DMP3 (0.025 g/kg) was increased by 5.17, 9.36 and 11.04 times on the 10th day of incubation, while soil NO3--N content was decreased by 33.30%, 61.19% and 73.72% on the 14th day, respectively. The application of DMP could also decrease soil NO2--N content by 95.77% ~ 96.13% on the 3rd day of incubation, increase soil microbial biomass N from 14d to 56d, and reduce the total amount of soil mineral-N significantly with increasing DMP dose after 10 days of incubation. The corn field experiment indicated that, compared with CK, the soil NO3--N content of 40 ~ 100 cm layer in treatment DMP was decreased by 28.77% and 44.70% in 2004 and 2005, respectively. DMP application might be an effective means for regulating urea-N transformation and mitigating nitrogen pollution.
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