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Search Results: 1 - 10 of 120223 matches for " WANG Liwei "
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Text Classification Using Support Vector Machine with Mixture of Kernel  [PDF]
Liwei Wei, Bo Wei, Bin Wang
Journal of Software Engineering and Applications (JSEA) , 2012, DOI: 10.4236/jsea.2012.512B012
Abstract: Recent studies have revealed that emerging modern machine learning techniques are advantageous to statistical models for text classification, such as SVM. In this study, we discuss the applications of the support vector machine with mixture of kernel (SVM-MK) to design a text classification system. Differing from the standard SVM, the SVM-MK uses the 1-norm based object function and adopts the convex combinations of single feature basic kernels. Only a linear programming problem needs to be resolved and it greatly reduces the computational costs. More important, it is a transparent model and the optimal feature subset can be obtained automatically. A real Chinese corpus from FudanUniversityis used to demonstrate the good performance of the SVM- MK.
Channel Simulation of Non-imaging Optical MIMO Communication  [PDF]
Jiao Feng, Liwei Ding, Yongjin Wang
Optics and Photonics Journal (OPJ) , 2013, DOI: 10.4236/opj.2013.32B050

This paper reports a channel simulation of an indoor optical wireless multiple-input-multiple-output (MIMO) system with non-imaging receivers. The system consists of a 2×2 array of white light-emitting diodes (LEDs) and 2×2 array of PDs. An overview of the model specifications, channel impulse response and channel capacity are demonstrated in this paper. The distribution of the first reflection is analyzed. The effect of SNR and the location of receivers on non-imaging optical MIMO communications are investigated. In addition, by moving the receivers, the optimal location of the communication is found.

Adsorption refrigeration-green cooling driven by low grade thermal energy
Ruzhu Wang,Liwei Wang
Chinese Science Bulletin , 2005, DOI: 10.1007/BF02897526
Abstract: As a type of environmental benign refrigeration technology powered by low grade thermal energy, adsorption refrigeration have aroused more and more attention in recent years. In this paper, the research frontiers of adsorption refrigeration, including adsorbent, adsorption theory, heat recovery process, technology of adsorber, the research achievements, and the development achievements, are summarized. Typical systems for adsorption refrigeration research facing to applications in the recent years are presented. Future applications of adsorption refrigeration are analysed.
The Effect of Transition Metal on the Optical Properties and Photoactivity of Nano-particulate Titanium Dioxide
Liwei Wang,Terry Egerton
Journal of Materials Science Research , 2012, DOI: 10.5539/jmsr.v1n4p19
Abstract: Transition metal (vanadium, chromium, iron) doped TiO2 was synthesised by co-precipitation or by surface-deposition. The specimens were characterised by XRD and reflectance spectroscopy. In terms of the structure, the surface doped samples are same as those made by co-precipitation nor did the presence of metal ions change the structure. The presence of transition metal induced a shift of light absorption of the doped TiO2 to visible wavelengths. The introduction of transition metal ions into TiO2 significantly affected the photoactivity, which was determined by the oxidation of IPA and photogreying. As a general trend, an optimum dopant appeared which gave the maximum photoactivity. It was found that the photoactivity of co-precipitated samples was lower than that of surface-doped. The photoactivity of doped TiO2 is a function of many parameters, such as the dopant content, energy level of dopant, the d electronic configuration of dopant ions and the distribution of dopant. These factors influence IPA photo-oxidation and photogreying to different extents.
Numerical Method for Solving Matrix Coefficient Elliptic Equation on Irregular Domains with Sharp-Edged Boundaries
Liqun Wang,Liwei Shi
Advances in Numerical Analysis , 2013, DOI: 10.1155/2013/967342
Abstract: We present a new second-order accurate numerical method for solving matrix coefficient elliptic equation on irregular domains with sharp-edged boundaries. Nontraditional finite element method with non-body-fitting grids is implemented on a fictitious domain in which the irregular domains are embedded. First we set the function and coefficient in the fictitious part, and the nonsmooth boundary is then treated as an interface. The emphasis is on the construction of jump conditions on the interface; a special position for the ghost point is chosen so that the method is more accurate. The test function basis is chosen to be the standard finite element basis independent of the interface, and the solution basis is chosen to be piecewise linear satisfying the jump conditions across the interface. This is an efficient method for dealing with elliptic equations in irregular domains with non-smooth boundaries, and it is able to treat the general case of matrix coefficient. The complexity and computational expense in mesh generation is highly decreased, especially for moving boundaries, while robustness, efficiency, and accuracy are promised. Extensive numerical experiments indicate that this method is second-order accurate in the norm in both two and three dimensions and numerically very stable. 1. Introduction Let ( ) be an open-bounded domain with a Lipschitz continuous boundary . We consider the variable coefficient elliptic equation where refers to the spatial variable, is the gradient operator, and the right-hand side is assumed to lie in . The coefficient is a matrix that is uniformly elliptic, and its entries are continuously differentiable on . For a given function on the boundary , the Dirichlet boundary condition is prescribed as Elliptic partial differential equations are often used to construct models of the most basic theories underlying physics and engineering, such as electromagnetism, material science, and fluid dynamics. Different kinds of boundary conditions arise with the wide range of applications, such as Dirichlet boundary condition, Neumann boundary condition, and Robin boundary condition. Elliptic equation on irregular domains has been studied by many researchers and several techniques have been developed. Finite element methods use a mesh triangulation to capture the boundary [1–4]. However, in many situations, such as when the boundary is moving, the mesh generation may be both computational expensive and challenging. A more preferred method is to combine the Cartesian grid method with level-set approach [5–7] to capture the boundary.
Pairwise Constraint Propagation on Multi-View Data
Zhiwu Lu,Liwei Wang
Computer Science , 2015,
Abstract: This paper presents a graph-based learning approach to pairwise constraint propagation on multi-view data. Although pairwise constraint propagation has been studied extensively, pairwise constraints are usually defined over pairs of data points from a single view, i.e., only intra-view constraint propagation is considered for multi-view tasks. In fact, very little attention has been paid to inter-view constraint propagation, which is more challenging since pairwise constraints are now defined over pairs of data points from different views. In this paper, we propose to decompose the challenging inter-view constraint propagation problem into semi-supervised learning subproblems so that they can be efficiently solved based on graph-based label propagation. To the best of our knowledge, this is the first attempt to give an efficient solution to inter-view constraint propagation from a semi-supervised learning viewpoint. Moreover, since graph-based label propagation has been adopted for basic optimization, we develop two constrained graph construction methods for interview constraint propagation, which only differ in how the intra-view pairwise constraints are exploited. The experimental results in cross-view retrieval have shown the promising performance of our inter-view constraint propagation.
Real-time Audio & Video Transmission System Based on Visible Light Communication  [PDF]
Yingjie He, Liwei Ding, Yuxian Gong, Yongjin Wang
Optics and Photonics Journal (OPJ) , 2013, DOI: 10.4236/opj.2013.32B037

With the increasing popularity of solid sate lighting devices, Visible Light Communication (VLC) is globally recognized as an advanced and promising technology to realize short-range, high speed as well as large capacity wireless data transmission. In this paper, we propose a prototype of real-time audio and video broadcast system using inexpensive commercially available light emitting diode (LED) lamps. Experimental results show that real-time high quality audio and video with the maximum distance of 3 m can be achieved through proper layout of LED sources and improvement of concentration effects. Lighting model within room environment is designed and simulated which indicates close relationship between layout of light sources and distribution of illuminance.

Design of Wireless Optical Access System using LED  [PDF]
Liwei Ding, Fang Liu, Yingjie He, Hongbo Zhu, Yongjin Wang
Optics and Photonics Journal (OPJ) , 2013, DOI: 10.4236/opj.2013.32B036

This paper develops a prototype to demonstrate a full-duplex wireless visible light communication (VLC) system based on Universal Serial Bus (USB) port. Combing with a USB 2.0 port on one board, it can achieve up to 2 Mbps bit rates error free, which is mainly limited to the USB bridge circuit, between two computers for data transmission, such as text, audio and video. Hyper Terminal and self-written software are used to allow setting the transmission data rate, control bits, check bits and achieve real-time transmission between any two mobile devices with a USB port. The work is based on the research of VLC local access network. This paper also shows the experimental results and the relationship between system transmission eye diagram and bit rate.

A Knowledge Maturity Model for Aerospace Product Development  [PDF]
Qian Jia, Jingyuan Bi, Jingyuan Bi, Liwei Wang, Yukun Yang
Open Journal of Social Sciences (JSS) , 2014, DOI: 10.4236/jss.2014.29026

At present, China's aerospace product development mission are characterized by mammoth task and high responsibility, in which situation, the role of knowledge in business process is particularly prominent. Although we have realized the importance of the problem, and embarked on the accumulation job, the problem faced is that we lack the criteria to judge our harvest, which spontaneously caused that we cannot define the quality and practical value of accumulated knowledge. Focusing of above problems, the paper puts forward a knowledge maturity model for aerospace product development, which divides knowledge maturity into 6 levels according to development process. Criteria of each level as well as translation condition to next grade is elaborated, assessment note is specially stated, aiming at offering enterprises a potent method for knowledge system construction and evaluation.

High-efficient thermochemical sorption refrigeration driven by low-grade thermal energy
TingXian Li,RuZhu Wang,LiWei Wang
Chinese Science Bulletin , 2009, DOI: 10.1007/s11434-009-0117-3
Abstract: Thermochemical sorption refrigeration powered by low-grade thermal energy is one of the energy-saving and environment friendly green refrigeration technologies. The operation principle of sorption refrigeration system is based on the thermal effects of reversible physicochemical reaction processes between sorbents and refrigerants. This paper presents the developing study on the different thermochemical sorption refrigeration cycles, and some representative high-efficient thermochemical sorption refrigeration cycles were evaluated and analyzed based on the conventional single-effect sorption cycle. These advanced sorption refrigeration cycles mainly include the heat and mass recovery sorption cycle, double-effect sorption cycle, multi-effect sorption cycle, combined double-way sorption cycle, and double-effect and double-way sorption cycle with internal heat recovery. Moreover, the developing tendency of the thermochemical sorption refrigeration is also predicted in this paper.
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