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Search Results: 1 - 10 of 38083 matches for " Zhongwei Lin "
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Optimum Setting Strategy for WTGS by Using an Adaptive Neuro-Fuzzy Inference System  [PDF]
Yang Hu, Jizhen Liu, Zhongwei Lin
Energy and Power Engineering (EPE) , 2013, DOI: 10.4236/epe.2013.54B078
Abstract: With the popularization of wind energy, the further reduction of power generation cost became the critical problem. As to improve the efficiency of control for variable speed Wind Turbine Generation System (WTGS), the data-driven Adaptive Neuro-Fuzzy Inference System (ANFIS) was used to establish a sensorless wind speed estimator. Moreover, based on the Supervisory Control and Data Acquisition (SCADA) System, the optimum setting strategy for the maximum energy capture was proposed for the practical operation process. Finally, the simulation was executed which suggested the effectiveness of the approaches.
State-feedback H2/H-infinity controller design with D-stability constraints for stochastic systems

Zhongwei LIN,Weihai ZHANG,

控制理论与应用 , 2007,
Abstract: This paper addresses the state-feedback H2/H-infinity controller design that satisfies D-stability constraints for stochastic systems. Firstly, the concept of regional stability for stochastic systems is defined in linear matrix inequality(LMI) regions; Secondly, the characterization about stochastic D-stability is presented. This paper introduces a new technique to solve the regional stability problem for stochastic systems, which is different from the pole placement technique ever used in deterministic systems. Based on this, in the state-feedback case, mixed H2/H-infinity synthesis with D-stability constraints is discussed via LMI optimization.
Increased Dependence of Humans on Ecosystem Services and Biodiversity
Zhongwei Guo,Lin Zhang,Yiming Li
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0013113
Abstract: Humans have altered ecosystems more rapidly and extensively than ever, largely to meet rapidly growing demands for resources along with economic development. These demands have been considered important drivers of ecosystem degradation and biodiversity loss. Are humans becoming less dependent on ecosystem services and biodiversity following economic development? Here, we used roundwood production, hydroelectricity generation and tourism investment in 92 biodiversity hotspot and 60 non-hotspot countries as cases to seek the answer. In 1980–2005, annual growth rates of roundwood production, hydroelectricity generation and tourism investment were higher in hotspot countries (5.2, 9.1 and 7.5%) than in non-hotspot countries (3.4, 5.9 and 5.6%), when GDP grew more rapidly in hotspot countries than non-hotspot countries. Annual growth rates of per capita hydropower and per capita tourism investment were higher in hotspot countries (5.3% and 6.1%) than in non-hotspot countries (3.5% and 4.3%); however, the annual growth rate of per capita roundwood production in hotspot countries (1%) was lower than in non-hotspot countries (1.4%). The dependence of humans on cultural services has increased more rapidly than on regulating services, while the dependence on provisioning services has reduced. This pattern is projected to continue during 2005–2020. Our preliminary results show that economic growth has actually made humans more dependent upon ecosystem services and biodiversity. As a consequence, the policies and implementations of both economic development and ecosystems/biodiversity conservation should be formulated and carried out in the context of the increased dependence of humans on ecosystem services along with economic development.
Robust Passivity and Feedback Design for Nonlinear Stochastic Systems with Structural Uncertainty
Zhongwei Lin,Jizhen Liu,Yuguang Niu
Mathematical Problems in Engineering , 2013, DOI: 10.1155/2013/460348
Abstract:
Homogenization of Elliptic Systems with Neumann Boundary Conditions
Carlos E. Kenig,Fanghua Lin,Zhongwei Shen
Mathematics , 2010,
Abstract: The main purpose of this work is to study uniform regularity estimates for a family of elliptic operators $\{\mathcal{L}_\varepsilon, \varepsilon>0\}$, arising in the theory of homogenization, with rapidly oscillating periodic coefficients. We establish sharp $W^{1,p}$ estimates, Lipschitz estimates, and nontangential maximal function estimates, which are uniform in the parameter $\varepsilon$, on solutions with Neumann boundary conditions in $C^{1,\alpha}$ domains.
Estimates of Eigenvalues and Eigenfunctions in Periodic Homogenization
Carlos E. Kenig,Fanghua Lin,Zhongwei Shen
Mathematics , 2012,
Abstract: For a family of elliptic operators with rapidly oscillating periodic coefficients, we study the convergence rates for Dirichlet eigenvalues and bounds of the normal derivatives of Dirichlet eigenfunctions. The results rely on an $O(\epsilon)$ estimate in $H^1$ for solutions with Dirichlet condition.
Convergence Rates in L^2 for Elliptic Homogenization Problems
Carlos E. Kenig,Fanghua Lin,Zhongwei Shen
Mathematics , 2011, DOI: 10.1007/s00205-011-0469-0
Abstract: We study rates of convergence of solutions in L^2 and H^{1/2} for a family of elliptic systems {L_\epsilon} with rapidly oscillating oscillating coefficients in Lipschitz domains with Dirichlet or Neumann boundary conditions. As a consequence, we obtain convergence rates for Dirichlet, Neumann, and Steklov eigenvalues of {L_\epsilon}. Most of our results, which rely on the recently established uniform estimates for the L^2 Dirichlet and Neumann problems in \cite{12,13}, are new even for smooth domains.
Homogenization of Green and Neumann Functions
Carlos E. Kenig,Fanghua Lin,Zhongwei Shen
Mathematics , 2012,
Abstract: For a family of second-order elliptic operators with rapidly oscillating periodic coefficients, we study the asymptotic behavior of the Green and Neumann functions, using Dirichlet and Neumann correctors. As a result we obtain asymptotic expansions of Poisson kernels and the Dirichlet-to-Neumann maps as well as near optimal convergence rates in $W^{1,p}$ for solutions with Dirichlet or Neumann boundary conditions.
Evaluation and Optimization of Gaussian Approximation for Polar Codes
Jincheng Dai,Kai Niu,Zhongwei Si,Jiaru Lin
Mathematics , 2015,
Abstract: Gaussian approximation (GA) is widely used to construct polar codes. But when the code length is sufficiently long, the subchannel selection inaccuracy due to calculation error of conventional approximate GA (AGA), which uses two-segment approximation function, will result in a catastrophic loss in performance. In this paper, we propose a new metric, named cumulative-logarithmic error (CLE), to evaluate the numeric error of subchannel capacity calculation in log-domain. Further, we derive the upper bound of CLE to simplify its calculation and find that the error of AGA will be amplified exponentially with the increment of polarization levels. Guided by CLE bound, we design new GA approximation function, which can efficiently reduce the capacity calculation error. Numeric and simulation results show that multi-segment AGA based on CLE bound is an efficient method to construct a high-performance polar code with a long length.
Modeling Transmission of Tuberculosis with MDR and Undetected Cases
Yongqi Liu,Zhendong Sun,Guiquan Sun,Qiu Zhong,Li Jiang,Lin Zhou,Yupeng Qiao,Zhongwei Jia
Discrete Dynamics in Nature and Society , 2011, DOI: 10.1155/2011/296905
Abstract: This paper presents a novel mathematical model with multidrug-resistant (MDR) and undetected TB cases. The theoretical analysis indicates that the disease-free equilibrium is globally asymptotically stable if ; otherwise, the system may exist a locally asymptotically stable endemic equilibrium. The model is also used to simulate and predict TB epidemic in Guangdong. The results imply that our model is in agreement with actual data and the undetected rate plays vital role in the TB trend. Our model also implies that TB cannot be eradicated from population if it continues to implement current TB control strategies. 1. Introduction China is among the highest TB burden countries in the world and is second only to India. The number of MDR-TB cases is about one third of that of the world [1, 2]. For an MDR-TB patient, the cost for the treatment is usually 10–100 times higher than that of a common TB patient [3]. Moreover, undetected TB patients pose threat to others, which plays a major role in mycobacterium transmission among the general population [4]. It is no doubt that the earlier the diagnosis and treatment, the better in attenuating the transmissions. Clearly, the understanding of the mechanism and contribution of undetected patients in transmission is important to conduct targeted interventions and control TB decease. Blower et al. proposed a transmission dynamics among the cases infected by drug-sensitive and the drug-resistant strains, respectively [5]. Many subsequent investigations focused on similar topics with various perspectives about the role of drug-resistant strain [3, 6–8]. However, these works failed to independently identify the role of the undetected patients in TB transmission. motivated by the previous work, we carefully divide the infectious cases into undetected cases and timely detected cases in this paper. This improved classification enables us to interpret the real situation in a better manner. To analyze the stability of the disease-free equilibrium in our transmission model, we introduce a novel Lyapunov function. We prove that the disease-free equilibrium is globally asymptotically stable when the basic reproduction number is less than one, and a forward (transcritical) bifurcation exists otherwise. While Guangdong is a developed province of China, the number of TB cases in Guangdong is about 10% of that of national TB cases. Mass migrants, MDR, and HIV/AIDS coinfections make the situation of TB transmission very complex in this region. We apply our model to describe the TB situation in Guangdong and simulate the distribution
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