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Search Results: 1 - 10 of 42566 matches for " Renbo Xu "
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An Improved Non-isolated LED Converter with Power Factor Correction and Average Current Mode Control  [PDF]
Renbo Xu, Hongjian Li, Yongzhi Li, Changqian Zhang
Circuits and Systems (CS) , 2011, DOI: 10.4236/cs.2011.23034
Abstract: A new type of high power LED drivers is proposed by adopting an improved two-stages non-isolated configuration. In order to improve power factor and achieve accurate average current control under universal input voltages ranging from 100 Vrms to 240 Vrms, the power factor correction and average current mode control methods operating in continuous current conduction mode are designed and implemented. With the LUMILEDS emitter type LEDs, a laboratory prototype is built and measured. And from the measured results, it could be concluded that the proposed driver has many better performances such as high power factor, low current harmonic, accurate average current control and switch protection.
Research on a High-Efficiency LED Driving Circuit Based on Buck Topology  [PDF]
Renbo Xu, Hongjian Li, Yongzhi Li, Xiaomao Hou
Circuits and Systems (CS) , 2011, DOI: 10.4236/cs.2011.24048
Abstract: A high efficiency LED(Light Emitting Diode) driver based on Buck converter, which could operate under a wide AC input voltage range(85V~265V) and drive a series of high power LEDs, is presented in this paper. The operation principles, power loss factors of the LED driver in this study are analyzed and discussed in detail and some effective ways to improve efficiency are proposed through system design considerations. To verify the feasibility, a laboratory prototype is also designed and tested for an LED lamp which consists of 16 LUMILEDS LEDs in series. Experimental results show that a high efficiency of 92% at I0=350mA can be achieved and the studied driver might be practical for driving high power LEDs. In the last, the overall efficiency over 90% is gained through some experiments under variable input and output voltages and verifies the validity of the designed driver.
Research of an Efficient LED Lighting Driver Based on Boost-Buck Converter  [PDF]
Renbo Xu, Yongzhi Li, Lixin Zhong, Jiaming Liu
Circuits and Systems (CS) , 2014, DOI: 10.4236/cs.2014.56017

Boost-Buck converter is widely used in LED lighting drivers. In this paper, Boost-Buck main circuit related characteristics are firstly discussed, and then a new Boost-Buck high power efficient double loop control strategy is built by adopting error amplifier and integrator control method. It is demonstrated that the new system has many advantages such as high efficiency, fast response, strong anti-interference, good stability after analyses and simulations of its working dynamic characteristics.

Parallelism and Optimization of Numerical Ocean Forecasting Model Parallelism and Optimization of Numerical Ocean Forecasting Model
XU Jianliang,PANG Renbo,TENG Junhua,LIANG Hongtao,YANG Dandan
- , 2016,
Abstract: According to the characteristics of Chinese marginal seas, the Marginal Sea Model of China(MSMC) has been developed independently in China. Because the model requires long simulation time, as a routine forecasting model, the parallelism of MSMC becomes necessary to be introduced to improve the performance of it. However, some methods used in MSMC, such as Successive Over Relaxation(SOR) algorithm, are not suitable for parallelism. In this paper, methods are developedto solve the parallel problem of the SOR algorithm following the steps as below. First, based on a 3D computing grid system, an automatic data partition method is implemented to dynamically divide the computing grid according to computing resources. Next, based on the characteristics of the numerical forecasting model, a parallel method is designed to solve the parallel problem of the SOR algorithm. Lastly, a communication optimization method is provided to avoid the cost of communication. In the communication optimization method, the non-blocking communication of Message Passing Interface(MPI) is used to implement the parallelism of MSMC with complex physical equations, and the process of communication is overlapped with the computations for improving the performance of parallel MSMC. The experiments show that the parallel MSMC runs 97.2 times faster than the serial MSMC, and root mean square error between the parallel MSMC and the serial MSMC is less than 0.01 for a 30-day simulation(172800 time steps), which meets the requirements of timeliness and accuracy for numerical ocean forecasting products
Discriminative Supervised Neighborhood Preserving Embedding Feature Extraction for Hyperspectral-image Classification
Renbo Luo,Wenzhi Liao,Youguo Pi
TELKOMNIKA : Indonesian Journal of Electrical Engineering , 2012, DOI: 10.11591/telkomnika.v10i5.1346
Abstract: A novel discriminative supervised neighborhood preserving embedding (DSNPE) method is proposed for feature extraction in classifying hyperspectral remote sensing imagery. DSNPE can preserve the local manifold structure and the neighborhood structure. What’s more, for each data point, DSNPE aims at pulling the neighboring points with the same class label towards it as near as possible, while simultaneously pushing the neighboring points with different labels apart from it as far as possible. Experimental results on two real hyperspectral image datasets are reported to illustrate the performance of DSNPE and to compare it with a few competing methods.
Solid State Synthesis and Thermoelectric Properties of Mg-Si-Ge System
Renbo SONG,Yazheng LIU,Tatsuhiko AIZAWA,

材料科学技术学报 , 2005,
Abstract: Thermoelectric materials, Mg2Si1-xGex (x=0, 0.2, 0.4, 0.6, 0.8, 1), have been prepared by bulk mechanical alloying (BMA) and hot pressing (HP). The electrical conductivity, Seebeck coefficient and thermal conductivity were measured from room temperature up to about 700 K. The electrical conductivity of all the samples increases with increasing temperature, while the Seebeck coefficient and thermal conductivity decrease with increasing temperature.Mg2Si and Mg2Si0.8Ge0.2 possess negative type of conductivity, while for other compounds it is positive. At the same time, the effect of hot processing condition on thermoelectric properties was also investigated. The maximum figure of merit of Mg2Si0.6Ge0.4 was obtained with the processing parameter of BMA at 600 cycles and hot pressing at 773 K and 1 GPa for 1 h.

SONG Renbo,XIANG Jianying,HOU Dongpo,REN Peidong,

金属学报 , 2010,
Abstract: The characteristics of hot work-hardening for 316L stainless steel have been systematically studied through high temperature compression tests on the Gleeble-1500 thermal simulation testing machine. According to Ludwik true stress-strain model, the experimental data has been regressed by using nonlinear fitting method, and the $n$ value in Ludwik model, a comprehensive index which reflects the competitive result between work-hardening and softening, has been calculated with Crussard-Jaoul method. The dynamic recrystallization and twinning were observed by OM and TEM. The experiments reveal that 316L stainless steel is easy to work-hardening during hot deformation, and deformation rate can effect nC-J-ε curves and variation law; There is no peak stress on its true stress-strain curves, but partial dynamic recrystallization has occurred during hot working process. This incomplete softening mechanism can't counteract the effect of hot work-hardening, so the true stress-strain curves still rise with deformation increasing; In addition, twinning occurred during hot working is one of the major mechanisms of hot work-hardening.

QUE Renbo,WANG Kuihua,

岩石力学与工程学报 , 2007,
Abstract: Modeling soil as a 3D axisymmetric continuum and taking its 3D wave effect into account,the interaction between soil layer and pile with viscoelastic bottom boundary undergoing arbitrary vertical load is theoretically investigated.The investigation will be of significance for dynamic test of pile.The pile is assumed to be vertical,elastic and of uniform cross-section,and the soil is considered as a linear viscoelastic layer with viscous damping.With Laplace transforms,the question can be solved in Laplace domain.With the aid of two potentials,the displacement of soil is decomposed and the dynamic equilibrium equation of soil layer is uncoupled and solved first.Thus the vibration modes of the soil layer are obtained to analyze the pile response.By considering the interaction between the soil layer and the pile with boundary condition of continuity of displacement and equilibrium of force at their interface,the dynamic equilibrium equation of pile is solved and an analytical solution for the displacement function in Laplace domain is yielded,so are the corresponding analytical solutions for the mobility at the level of the pile head in frequency domain.With the convolution theorem and inverse Fourier transform,a semi-analytical solution of velocity response in time-domain subjected to a semi-sine exciting force is derived.Based on the solutions proposed herein,a parametric study of the effect of some governing dimensionless parameters on mobility curves and velocity reflection wave curves is conducted to illustrate the main features of longitudinal vibration of pile.
Investigation of the Microstructure of Rolled Semi-Solid Steel
Investigation of the Microstructure of Rolled Semi—Solid Steel

Renbo SONG,Yonglin KANG,Jianlin SUN,Xiongfei YANG,Aimin ZHAO,Weimin MAO,

材料科学技术学报 , 2002,
Abstract: In this paper, spring steel-60Si2Mn and stainless steel-1Cr18Ni9Ti were rolled one pass in the semi-solid state. The microstructural evolution during rolling of the steels with different solid fraction was investigated. The experimental results showed that the manner of liquid and solid phases flowing and deforming was different. During rolling, most of solid phases remained in the center of the rolled specimens, while liquid phase flowed to the edge, which resulted in the macrosegregation of liquid and solid phases. Only the amount of solid fraction reached a certain value, were the solid phases deformed and flattened.
Research on crystal growth and properties of a new nonlinear optical crystal: Bismuth borate BiB3O6
Bing Teng,Jiyang Wang,Zhengping Wang,Huaidong Jiang,Renbo Song,Hong Liu,Xiaobo Hu,Yaogang Liu,Jingqian Wei,Zongshu Shao
Chinese Science Bulletin , 2001, DOI: 10.1007/BF02900549
Abstract: BiB3O6 (BIBO) single crystals with sizes of 44 mm × 24 mm × 10 mm and weight of 24.7 g have been successfully grown by the top-seeded method. In this note, the preparation of seed, the growth of crystal and some problems encountered are reported. The lattice parameters of BIBO area =7.1203(7) ,b = 4.9948(7) ,c = 6.5077(7) ,β= 105.586(8) ?,V=222.93(5) 3, which were determined by BRUKER-P4 four-circle diffractometer. BIBO is biaxial crystal and the relative orientation of (X, Y, Z) with regard to (a, b, c) is:X // b, (Y, c) =47.2°, (Z, a) = 31.6°, determined by the X-ray analysis combined with polarized microscopy. The second-harmonic-generation (SHG) conversion efficiency of the sample for 1.064 μm light is up to 67.7%. We have also obtained the third harmonic generation (THG) of 1.064 μm, namely, 1.064 μm + 0.532 μm →0.355 μm. BIBO crystal is free of moisture and hygroscopy.
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