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Search Results: 1 - 10 of 78942 matches for " Zhigang Chen "
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Partial Feedback Based Orthogonal Space-Time Block Coding With Flexible Feedback Bits  [PDF]
Lei Wang, Zhigang Chen
Communications and Network (CN) , 2013, DOI: 10.4236/cn.2013.53B2024
Abstract: The conventional orthogonal space-time block code (OSTBC) with limited feedback has fixed p-1 feedback bits for the specific ntp transmit antennas. A new partial feedback based OSTBC which provides flexible feedback bits is proposed in this paper. The proposed scheme inherits the properties of having a simple decoder and the full diversity of OSTBC, moreover, preserves full data rate. Simulation results show that for ntp transmit antennas, the proposed scheme has the similar performance with the conventional one by using p-1 feedback bits, whereas has the better performance with more feedback bits.
A Voice Coil Powered Controllable Micro-Jet Injection System  [PDF]
Kai Chen, Laiwu Miao, Zhigang Feng
Journal of Biomedical Science and Engineering (JBiSE) , 2015, DOI: 10.4236/jbise.2015.89059
Abstract: A medical device of micro-jet injection for drug delivery is described in this paper. The device is powered by a Lorentz force driver (or voice coil motor, VCM) and is able to perform pulsed injection through controlling the direction of the current passing through the device. The driving force and the resulting injection pressure are also controllable through control of the current intensity of the VCM. A physical model was established by combining the existing jet injection model with the relationship of the driving force obtained from a finite-element-method (FEM) analysis, and was verified by experimental measurements. The numerical calculation of the physical model reveals the relationship between the injection pressure and the current intensity of VCM under system conditions. In normal cases, the injection dose can be varied. Thus the relationship between the current intensity of VCM and the dose value was numerically obtained under the condition for the maximum injection pressure to be above a threshold value. These results can be used for optimization of the device.
Simple and Selective Colorimetric Detection of Oxytetracycline Based on Fe(III) Ion-3,3’,5,5’-Tetramethylbenzidine  [PDF]
Wenshu Yang, Zhigang Chen, Huaming Li
Materials Sciences and Applications (MSA) , 2018, DOI: 10.4236/msa.2018.913076
Abstract: Oxytetracycline (OTC) is a common antibacterial agent used for the control of animal diseases. OTC abuse can seriously affect human health. Herein, based on the Fe(III)-3,3’,5,5’-tetramethylbenzidine (Fe(III)-TMB) system, a facile and rapid colorimetricassay for oxytetracycline (OTC) was successfully developed. The addition of OTC could remarkably enhance the Fe(III)-oxidized TMB reaction and the absorbance increase of Fe(III)-TMB solution is proportional to the added OTC. The linear range of proposed sensor for OTC was from 20 nM to 1000 nM with the detection limit of 7.97 nM. The high sensitivity for OTC detection was successfully achieved under optimal conditions. For real sample analysis, recoveries of 89.93% to 100.02% was obtained. This is the first report for detecting OTC based on the nonenzymatic colorimetric reaction using the intrinsic oxidized activity of OTC/Fe3+ complex. The present simple, low-cost and visualized sensor has great potential for OTC detection in food.
The Role of Session Border Controllers in the DMZ of Voice over IP(VoIP) Networks
Huihong Chen,Zhigang Chen
Computer and Information Science , 2009, DOI: 10.5539/cis.v1n3p27
Abstract: SBCs usually sit between two service provider networks in a peering environment, or between an access network and a backbone network to provide service to residential and/or enterprise customers. They provide a variety of functions to enable or enhance session-based multi-media services (e.g., Voice over IP). This thesis analyzes the internet structure of SBC and shows single-box and dual-box SBCs in the DMZ and introduces firewalls and network address translation. And then explain how the SBC cooperates with the firewalls to ensure that VoIP signaling and media traverses the DMZ without compromising the security of the
Asymptotic Stability Results for Nonlinear Fractional Difference Equations
Fulai Chen,Zhigang Liu
Journal of Applied Mathematics , 2012, DOI: 10.1155/2012/879657
Abstract: We present some results for the asymptotic stability of solutions for nonlinear fractional difference equations involvingRiemann-Liouville-likedifference operator. The results are obtained by using Krasnoselskii's fixed point theorem and discrete Arzela-Ascoli's theorem. Three examples are also provided to illustrate our main results.
Wear Characteristics of Zirconia Toughened Ceramic Drawing Dies
Zhigang CHEN,

材料科学技术学报 , 1995,
Abstract: Wear resistance of several zirconia toughened ceramics in comparison with a metal-ceramic CoWC has been studied in drawing wire field test. Result indicates that the harder the ceramic die, the longer the service life. Excellent wear resistance of ceramic die is obtained with a very high hardness (19 GPa). The service life is nearly three times that of Co-WC die. SEM observation on wear surfaces showed that material removal is mainly caused by plastic flow and ploughing process. But when the ceramic is composed of zirconia, alumina and some titanium carbide, micro-chipping and tribochemical reaction take place, and wear rate increases. Wear and friction induced martensite was detected by XRD. The T-M (tetragonal to monoclinic) phase transformation has a contribution to inhibiting microfracture.
The Design and Implementation of Single Sign-on Based on Hybrid Architecture
Zhigang Liang,Yuhai Chen
Journal of Networks , 2012, DOI: 10.4304/jnw.7.1.165-172
Abstract: For the purpose of solving the problems of user repeated logon from various kinds of Application which based on hybrid architecture and in different domains, single sign-on architecture is proposed. On the basis of analyzing the advantages and disadvantages of existing single sign-on models, combined with the key technology like Web Service, Applet and reverse proxy, two core problems such as single sign-on architecture mix B/S and C/S structure applications and cross-domain single sign-on are resolved. Meanwhile, the security and performance of this architecture are well protected since the reverse proxy and related encryption technology are adopted. The results show that this architecture is high performance and it is widely applicable, and it will be applied to practical application soon.
Can Large Extra Dimensions Solve the Proton Radius Puzzle?
Zhigang Li,Xuelei Chen
Physics , 2013,
Abstract: The proton charge radius extracted from the recent muonic hydrogen spectroscopy [Antognini et al. 2013; Pohl et al. 2010] differs from the CODATA 2010 recommended value [Mohr et al. 2012] by more than 4% or $4.4 \sigma$. This discrepancy, dubbed as the "Proton Radius Puzzle", is a big challenge to the Standard Model of particle physics, and has triggered a number of works on the quantum electrodynamic calculations recently. The proton radius puzzle may indicate the presence of an extra correction which enlarges the 2S-2P energy gap in muonic hydrogen. Here we explore the possibility of large extra dimensions which could modify the Newtonian gravity at small scales and lower the 2S state energy while leaving the 2P state nearly unchanged. We find that such effect could be produced by four or more large extra dimensions which are allowed by the current constraints from low energy physics.
Comparative Study on Electromagnetic and Electrome-chanical Transient Model for Grid-connected Photovoltaic Power System  [PDF]
Man Zhang, Hao Sun, Zhigang Chen, Xiaorong Xie, Qirong Jiang
Energy and Power Engineering (EPE) , 2013, DOI: 10.4236/epe.2013.54B048
Abstract: With the development of new energy technology, there are increasing applications of grid-connected photovoltaic power generation system. However, there is little research on development of electromechanical model of large scale photovoltaic power station. The computational speed will be very slow if electromagnetic transient model is used for stability study because of its complexity. Therefore, study on electromechanical transient model of grid-connected photovoltaic power generation system is of great meaning. In this paper, electromagnetic transient model of photovoltaic power generation system is introduced first, and then a general electromechanical transient model is proposed. These two kinds of simulation model are set up in PSCAD. By comparing the simulation results of two models, the correctness and validity of the electromechanical transient model is verified. It provides reference model for efficient simulation and modeling of grid-connected photovoltaic power station in large-scale power systems.
Adaptive Rate Control for Multi-Antenna Multicast in OFDM Systems  [PDF]
Qinghe Du, Pinyi Ren, Yi Jia, Zhigang Chen
Communications and Network (CN) , 2013, DOI: 10.4236/cn.2013.53B2029
Abstract: We propose two rate control schemes for multi-antenna multicast in OFDM systems, which aim to maximize the minimum average rate over all users in a multicast group. In our system, we do not require all multicast users to successfully recover the signals received on each subcarrier. In contrast, we allow certain loss for multicast users, such that the multicast transmission rate can be increased. We assume that the loss-repairing can be completed at upper protocol layers via advanced fountain codes. Following this principle, we formulate the rate control problem via beamforming in multi-antenna multicast to optimize the minimum achievable rate for all multicast users. While the computation complexity to solve for the optimal beamformer is prohibitively high, we propose a suboptimal iterative rate control scheme. Moreover, we modify the above optimization problem by selecting a ?xed proportion of users on each subcarrier. The beamformer searching process will then be performed only based on the selected users on each subcarrier, such that the complexity can be further reduced. We also solve this new problem with a low complexity approach. Theoretical analyses and simulation results show that our proposed two rate control schemes can have higher minimum average rate than the baseline scheme without rate control, while achieving low complexity.
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