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Search Results: 1 - 10 of 127421 matches for " PengFei Li "
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Dalian High-Tech SMEs Growth Evaluation Based on Catastrophe and Principal Component Projection Method  [PDF]
Lin LI, Pengfei ZHOU, Zhenghe LI
Journal of Service Science and Management (JSSM) , 2009, DOI: 10.4236/jssm.2009.24034
Abstract: In the course of rapid economic development, high-tech small and medium enterprises (SMEs) are gradually playing an important role, which become important support to regional economic growth and science and technology development. So SMEs growth becomes a universal problem. And how to evaluate the SMEs growth becomes an important step, especially to high-tech SMEs growth. In this paper, catastrophe theory and improved principal components projection method are used and a mutation series of high-tech SMEs growth evaluation index system is built. Taking Dalian high-tech SMEs as an example, high-tech SMEs growth is evaluated, which contributes to high-tech SMEs growth forecast and government to formulate policies to support high-tech SMEs development.
The Clinical Anatomy of the Cavernous Sinus  [PDF]
Pengfei Zhang, Huanjiu Xi, Wenhui Li
Forensic Medicine and Anatomy Research (FMAR) , 2015, DOI: 10.4236/fmar.2015.32012
Abstract: Introduction: The cavernous sinus (CS) is a very important concept because it is not only interesting to anatomical theory but also useful to clinical medicine, especially in the field of surgery. This paper described the microsurgical anatomy of the CS with special attention to its concept that the CS was really venous sinus or plexus. Materials and Methods: Fifty CSs from 25 Chinese adult cadaver heads fixed in 10% methanal, whose artery and vein were injected with red and blue latex, respectively, dissected stepwise under the operating microscope. Results: Asymmetric and nonintegral blue latex distributed in the cavity of the CS to form a retina with various diameters and repeatedly diverged and converged were observed under the surgical microscope with magnification 5 - 25, after the lateral wall of the CS was opened by maxillary approach. Measurement of sinus included length, diameter and triangular structure of the CS. It is very important to understand the microsurgical anatomy of the CS for neurosurgeons. Conclusion: The CS was venous plexus rather than sinus. The lateral wall of the sinus had two layers, and the lateral cavity of the sinus really did exist even though it was very small. The triangles where maxillary approach passed were more important for neurosurgeons.
Driving Style Recognition Based on Driver Behavior Questionnaire  [PDF]
Pengfei Li, Jianjun Shi, Xiaoming Liu
Open Journal of Applied Sciences (OJAppS) , 2017, DOI: 10.4236/ojapps.2017.74010
Abstract: The ability to classify driver behavior lays the foundation for more advanced driver assistance systems. The present study aims to research driver pattern and classification feature. Driver behavior self-reported investigation was conducted with standardized driver behavior questionnaire (DBQ) by 225 nonprofessional drivers on the internet in Beijing. Questionnaire’s reliability was verified by statistics analysis. Confirmatory factor analysis (CFA) was used to analyze the underlying factor structure. Speed advantage, space occupation, the contend right of way and the contend space advantage were extracted from the ques-tionnaire results to quantify driver characteristics. Based on fuzzy C-means (FCM) algorithm and taking the four factors as pattern features, the number of driver classification distribution was discussed. Then the number of driver classification was determined by statistical indices. The comparison of classification results with the survey finding on whether the driver occurred in traffic accidents within five years shows that the classification result is the same as the actual driving conditions. Finally, correlation between the demographic and types of driving behavior has been analyzed. Female were more likely than male to careful driving, and the older the driver and the less driving experience, the more careful and moderate driving behavior is.
Clustering Network Topology Control Method Based on Responsibility Transmission  [PDF]
Zhihua Li, Pengfei Li, Xi Yin, Kexiang Cui
International Journal of Intelligence Science (IJIS) , 2012, DOI: 10.4236/ijis.2012.224017
Abstract: The topology control is an effective approach which can improve the quality of wireless sensor network at all sides. Through studying the mechanism of sensor network data transmission, the nature of data transmission in wireless sensor network is concluded as a kind of responsibility transmission. By redefining the responsibility and availability of nodes, the strategy for cluster head selection is studied, the responsibility and availability is determined by the combination of the residual energy, location and current flow of nodes. Based on the above, new clustering network topology control algorithm based on responsibility transmission CNTCABRT and hierarchical multi-hop CNTCABRT is presented in this paper, whose algorithm structure is along the famous LEACH algorithm. Experimental result demonstrates its promising performance over the famous LEACH algorithm in the cluster head selection, the size of cluster, the deployment of nodes and the lifetime of nodes, and several innovative conclusions are proposed finally.
Selective Deposition and Alignment of Single-Walled Carbon Nanotubes Assisted by Dielectrophoresis: From Thin Films to Individual Nanotubes
Li Pengfei,Xue Wei
Nanoscale Research Letters , 2010,
Abstract: Dielectrophoresis has been used in the controlled deposition of single-walled carbon nanotubes (SWNTs) with the focus on the alignment of nanotube thin films and their applications in the last decade. In this paper, we extend the research from the selective deposition of SWNT thin films to the alignment of small nanotube bundles and individual nanotubes. Electrodes with “teeth”-like patterns are fabricated to study the influence of the electrode width on the deposition and alignment of SWNTs. The entire fabrication process is compatible with optical lithography-based techniques. Therefore, the fabrication cost is low, and the resulting devices are inexpensive. A series of SWNT solutions is prepared with concentrations ranging from 0.0125 to 0.2 mg/ml. The alignment of SWNT thin films, small bundles, and individual nanotubes is achieved under the optimized experimental conditions. The electrical properties of these samples are characterized; the linear current–voltage plots prove that the aligned SWNTs are mainly metallic nanotubes. The microscopy inspection of the samples demonstrates that the alignment of small nanotube bundles and individual nanotubes can only be achieved using narrow electrodes and low-concentration solutions. Our investigation shows that it is possible to deposit a controlled amount of SWNTs in desirable locations using dielectrophoresis.
The quermassintegral inequalities for starshaped domains
Pengfei Guan,Junfang Li
Mathematics , 2007,
Abstract: We give a simple proof of the insoperimetric inequality for quermassintegrals of non-convex starshaped domains, using a reslut of Gerhardt \cite{G} and Urbas \cite{U} on an expanding geometric curvature flow.
The finite precision computation and the nonconvergence of difference scheme
Wang Pengfei,Li Jianping
Mathematics , 2008,
Abstract: The authors show that the round-off error can break the consistency which is the premise of using the difference equation to replace the original differential equations. We therefore proposed a theoretical approach to investigate this effect, and found that the difference scheme can not guarantee the convergence of the actual compute result to the analytical one. A conservation scheme experiment is applied to solve a simple linear differential equation satisfing the LAX equivalence theorem in a finite precision computer. The result of this experiment is not convergent when time step-size decreases trend to zero, which proves that even the stable scheme can't guarantee the numerical convergence in finite precision computer. Further the relative convergence concept is introduced.
A mean curvature type flow in space forms
Pengfei Guan,Junfang Li
Mathematics , 2013,
Abstract: In this article, we introduce a new type of mean curvature flow for bounded star-shaped domains in space forms and prove its longtime existence, exponential convergence without any curvature assumption. Along this flow, the enclosed volume is a constant and the surface area evolves monotonically. Moreover, for a bounded convex domain in R n+1, the quermassintegrals evolve monotonically along the flow which allows us to prove a class of Alexandrov-Fenchel inequalities of quermassintegrals.
On the relation between reliable computation time, float-point precision and the Lyapunov exponent in chaotic systems
PengFei Wang,JianPing Li
Computer Science , 2014,
Abstract: The relation among reliable computation time, Tc, float-point precision, K, and the Lyapunov exponent, {\lambda}, is obtained as Tc= (lnB/{\lambda})K+C, where B is the base of the float-point system and C is a constant dependent only on the chaotic equation. The equation shows good agreement with numerical experimental results, especially the scale factors.
Hypothesis test for normal mixture models: The EM approach
Jiahua Chen,Pengfei Li
Statistics , 2009, DOI: 10.1214/08-AOS651
Abstract: Normal mixture distributions are arguably the most important mixture models, and also the most technically challenging. The likelihood function of the normal mixture model is unbounded based on a set of random samples, unless an artificial bound is placed on its component variance parameter. Moreover, the model is not strongly identifiable so it is hard to differentiate between over dispersion caused by the presence of a mixture and that caused by a large variance, and it has infinite Fisher information with respect to mixing proportions. There has been extensive research on finite normal mixture models, but much of it addresses merely consistency of the point estimation or useful practical procedures, and many results require undesirable restrictions on the parameter space. We show that an EM-test for homogeneity is effective at overcoming many challenges in the context of finite normal mixtures. We find that the limiting distribution of the EM-test is a simple function of the $0.5\chi^2_0+0.5\chi^2_1$ and $\chi^2_1$ distributions when the mixing variances are equal but unknown and the $\chi^2_2$ when variances are unequal and unknown. Simulations show that the limiting distributions approximate the finite sample distribution satisfactorily. Two genetic examples are used to illustrate the application of the EM-test.
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