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Search Results: 1 - 10 of 104233 matches for " Meixia Zhang "
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The Research on Neutral Grounding Scheme of Fengxian 35kV and 10 kV Power Grid  [PDF]
Siming Hua, Hua Zhang, Feng Qian, Chunjie Chen, Meixia Zhang
Energy and Power Engineering (EPE) , 2013, DOI: 10.4236/epe.2013.54B172
Abstract:

Combined with actual situation of Fengxian power Supply Company, the neutral grounding modes of Fengxian 35 kV and 10 kV power grid are studied in the paper. The different frequencies injected method is used to measure the capacitive current of Fengxian 28 substations, and the neutral grounding modes of the 28 substations are determined based on the measured values of capacitive current.

Resource Allocation with Subcarrier Pairing in OFDMA Two-Way Relay Networks
Hao Zhang,Yuan Liu,Meixia Tao
Mathematics , 2011,
Abstract: This study considers an orthogonal frequency-division multiple-access (OFDMA)-based multi-user two-way relay network where multiple mobile stations (MSs) communicate with a common base station (BS) via multiple relay stations (RSs). We study the joint optimization problem of subcarrier-pairing based relay-power allocation, relay selection, and subcarrier assignment. The problem is formulated as a mixed integer programming problem. By using the dual method, we propose an efficient algorithm to solve the problem in an asymptotically optimal manner. Simulation results show that the proposed method can improve system performance significantly over the conventional methods.
A New SLNR-based Linear Precoding for Downlink Multi-User Multi-Stream MIMO Systems
Peng Cheng,Meixia Tao,Wenjun Zhang
Mathematics , 2010,
Abstract: Signal-to-leakage-and-noise ratio (SLNR) is a promising criterion for linear precoder design in multi-user (MU) multiple-input multiple-output (MIMO) systems. It decouples the precoder design problem and makes closed-form solution available. In this letter, we present a new linear precoding scheme by slightly relaxing the SLNR maximization for MU-MIMO systems with multiple data streams per user. The precoding matrices are obtained by a general form of simultaneous diagonalization of two Hermitian matrices. The new scheme reduces the gap between the per-stream effective channel gains, an inherent limitation in the original SLNR precoding scheme. Simulation results demonstrate that the proposed precoding achieves considerable gains in error performance over the original one for multi-stream transmission while maintaining almost the same achievable sum-rate.
Utility-Based Wireless Resource Allocation for Variable Rate Transmission
Xiaolu Zhang,Meixia Tao,Chun Sum Ng
Computer Science , 2007,
Abstract: For most wireless services with variable rate transmission, both average rate and rate oscillation are important performance metrics. The traditional performance criterion, utility of average transmission rate, boosts the average rate but also results in high rate oscillations. We introduce a utility function of instantaneous transmission rates. It is capable of facilitating the resource allocation with flexible combinations of average rate and rate oscillation. Based on the new utility, we consider the time and power allocation in a time-shared wireless network. Two adaptation policies are developed, namely, time sharing (TS) and joint time sharing and power control (JTPC). An extension to quantized time sharing with limited channel feedback (QTSL) for practical systems is also discussed. Simulation results show that by controlling the concavity of the utility function, a tradeoff between the average rate and rate oscillation can be easily made.
New Model for L2 Norm Flow  [PDF]
Jiaojiao Li, Meixia Dou
Journal of Applied Mathematics and Physics (JAMP) , 2015, DOI: 10.4236/jamp.2015.37089
Abstract:

We introduce a new L2 norm preserving heat flow in matrix geometry. We show that this flow exists globally and preserves the positivity property of Hermitian matrices.

Inhibitors of mitogen-activated protein kinases differentially regulate costimulated T cell cytokine production and mouse airway eosinophilia
Ligia Chialda, Meixia Zhang, Kay Brune, Andreas Pahl
Respiratory Research , 2005, DOI: 10.1186/1465-9921-6-36
Abstract: Human primary CD4+ T cells from blood were activated by beads with defined combinations of surface receptor stimulating antibodies and costimulatory receptor ligands. Real-time RT-PCR was used for measuring the production of cytokines from activated T cells. Activation of mitogen activated protein kinase (MAPK) signaling pathways leading to cytokine synthesis were investigated by western blot analysis and by specific inhibitors. The effect of inhibitors in vivo was tested in a murine asthma model of late phase eosinophilia. Lung inflammation was assessed by differential cell count of the bronchoalveolar lavage, determination of serum IgE and lung histology.We showed in vitro that ICOS and CD28 are stimulatory members of an expanding family of co-receptors, whereas PD1 ligands failed to co-stimulate T cells. ICOS and CD28 activated different MAPK signaling cascades necessary for cytokine activation. By means of specific inhibitors we showed that p38 and ERK act downstream of CD28 and that ERK and JNK act downstream of ICOS leading to the induction of various T cell derived cytokines. Using a murine asthma model of late phase eosinophilia, we demonstrated that the ERK inhibitor U0126 and the JNK inhibitor SP600125 inhibited lung inflammation in vivo. This inhibition correlated with the inhibition of Th2 cytokines in the BAL fluid. Despite acting on different signaling cascades, we could not detect synergistic action of any combination of MAPK inhibitors. In contrast, we found that the p38 inhibitor SB203580 antagonizes the action of the ERK inhibitor U0126 in vitro and in vivo.These results demonstrate that the MAPKs ERK and JNK may be suitable targets for anti-inflammatory therapy of asthma, whereas inhibition of p38 seems to be an unlikely target.Asthma is a chronic inflammatory disease of the airways. The inflammation characterizing asthma is complex and involves multiple cells and mediators. The cells involved include well-recognized immune and inflammatory cells,
Replacements of Rare Herbs and Simplifications of Traditional Chinese Medicine Formulae Based on Attribute Similarities and Pathway Enrichment Analysis
Zhao Fang,Meixia Zhang,Zhenghui Yi,Chengping Wen
Evidence-Based Complementary and Alternative Medicine , 2013, DOI: 10.1155/2013/136732
Abstract:
Structural and Acoustic Responses of a Submerged Stiffened Conical Shell
Meixia Chen,Cong Zhang,Xiangfan Tao,Naiqi Deng
Shock and Vibration , 2014, DOI: 10.1155/2014/954253
Abstract: This paper studies the vibrational behavior and far-field sound radiation of a submerged stiffened conical shell at low frequencies. The solution for the dynamic response of the conical shell is presented in the form of a power series. A smeared approach is used to model the ring stiffeners. Fluid loading is taken into account by dividing the conical shell into narrow strips which are considered to be local cylindrical shells. The far-field sound pressure is solved by the Element Radiation Superposition Method. Excitations in two directions are considered to simulate the loading on the surface of the conical shell. These excitations are applied along the generator and normal to the surface of the conical shell. The contributions from the individual circumferential modes on the structural responses of the conical shell are studied. The effects of the external fluid loading and stiffeners are discussed. The results from the analytical models are validated by numerical results from a fully coupled finite element/boundary element model. 1. Introduction The reduction of noise emitted by maritime platforms is an important topic in naval research. A truncated cone is used to support the aft-shaft-bearing of the submarine propeller. The structural and acoustic responses of a conical shell are not as widely reported in literature as in the case of cylindrical shells. This is due to the increased mathematical complexity associated with the effect of the variation of the radius along the length of the cone on the elastic waves. Much of the earlier work on the equations of motion for conical shells and forms of solution with different boundary conditions has been summarized by Leissa [1]. The approximate locations of the natural frequencies have been found using the Rayleigh-Ritz method by several authors [2, 3]. Tong presented a procedure for the free vibration analysis of isotropic and orthotropic conical shells in the form of a power series [4]. Guo studied the propagation and radiation properties of elastic waves in a cone in vacuo [5]. For fluid loaded conical shells, Guo investigated fluid loading effects of waves on conical shells in which a perturbation technique is applied by introducing a small vertex angle parameter [6]. Caresta and Kessissoglou considered the fluid loading by dividing the conical shell into narrow strips and each of these strips is treated as a locally cylindrical shell [7]. Donnell-Mushtari and Flügge equations of motion were compared by Caresta and Kessissoglou [8]. It was shown that in order to use the Flügge equations of motion with
Resource Allocation for Delay Differentiated Traffic in Multiuser OFDM Systems
Meixia Tao,Ying-Chang Liang,Fan Zhang
Mathematics , 2007,
Abstract: Most existing work on adaptive allocation of subcarriers and power in multiuser orthogonal frequency division multiplexing (OFDM) systems has focused on homogeneous traffic consisting solely of either delay-constrained data (guaranteed service) or non-delay-constrained data (best-effort service). In this paper, we investigate the resource allocation problem in a heterogeneous multiuser OFDM system with both delay-constrained (DC) and non-delay-constrained (NDC) traffic. The objective is to maximize the sum-rate of all the users with NDC traffic while maintaining guaranteed rates for the users with DC traffic under a total transmit power constraint. Through our analysis we show that the optimal power allocation over subcarriers follows a multi-level water-filling principle; moreover, the valid candidates competing for each subcarrier include only one NDC user but all DC users. By converting this combinatorial problem with exponential complexity into a convex problem or showing that it can be solved in the dual domain, efficient iterative algorithms are proposed to find the optimal solutions. To further reduce the computational cost, a low-complexity suboptimal algorithm is also developed. Numerical studies are conducted to evaluate the performance the proposed algorithms in terms of service outage probability, achievable transmission rate pairs for DC and NDC traffic, and multiuser diversity.
End-to-End Outage Minimization in OFDM Based Linear Relay Networks
Xiaolu Zhang,Meixia Tao,Wenhua Jiao,Chun Sum Ng
Mathematics , 2009,
Abstract: Multi-hop relaying is an economically efficient architecture for coverage extension and throughput enhancement in future wireless networks. OFDM, on the other hand, is a spectrally efficient physical layer modulation technique for broadband transmission. As a natural consequence of combining OFDM with multi-hop relaying, the allocation of per-hop subcarrier power and per-hop transmission time is crucial in optimizing the network performance. This paper is concerned with the end-to-end information outage in an OFDM based linear relay network. Our goal is to find an optimal power and time adaptation policy to minimize the outage probability under a long-term total power constraint. We solve the problem in two steps. First, for any given channel realization, we derive the minimum short-term power required to meet a target transmission rate. We show that it can be obtained through two nested bisection loops. To reduce computational complexity and signalling overhead, we also propose a sub-optimal algorithm. In the second step, we determine a power threshold to control the transmission on-off so that the long-term total power constraint is satisfied. Numerical examples are provided to illustrate the performance of the proposed power and time adaptation schemes with respect to other resource adaptation schemes.
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