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EXISTENCE OF WEAK SOLUTIONS TO A DEGENERATE STEAD-STATE SEMICONDUCTOR EQUATIONS

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Acta Mathematica Scientia 2011年第3期31卷 960-968页

作者：吴斌 College of mathematics and physics nanjing university of information science and technology

In this paper, we consider a degenerate steady-state drift-diffusion model for semiconductors. The pressure function used in this paper is （）（s） = s~α（α 〉 1）. We present existence results for general nonlin... 详细信息

关键词： steady-state degenerate semiconductor equations drift-diffusion model

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Basin filling algorithm for the circular packing problem with equilibrium behavioral constraints

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science china(information sciences) 2010年第5期53卷 885-895页

作者： LIU JingFa1& LI Gang2 1school of Computer and Software, nanjing university of information science & technology, nanjing 210044, china 2school of mathematics and physics, nanjing university of information science & technology, nanjing 210044, china school of Computer and Software Nanjing University of Information Science & Technology Nanjing China school of mathematics and physics Nanjing University of Information Science & Technology Nanjing China

With the background of the satellite module layout design, the circular packing problem with equilibrium behavioral constraints is a layout optimization problem and NP-hard problem in math. For lack of a powerful optimization method, this problem is hard to solve. The energy landscape paving (ELP) method is a class of stochastic global optimization algorithms based on the Monte Carlo sampling. Based on the quasiphysical strategy and the penalty function method, the problem is converted into an unconstrained optimization problem. Here by combining the improved ELP method, the gradient method based on local search and the heuristic configuration update mechanism, a new global search algorithm, basin filling algorithm, is put forward. The numerical results show that the proposed algorithm is effective to solving the circular packing problem with equilibrium behavioral constraints, and is easy to be popularized to other layout optimization problems.

关键词： equilibrium behavioral constraints packing problem layout optimization

Research into a theoretical mode of coherent structures in the wall region of a turbulent boundary layer induced by a wall local disturbance

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Progress in Natural science:Materials International 2009年第9期19卷 1119-1124页

作者： Changgen Lua,*, Qinjuan Qi b a College of Atmospheric sciences, nanjing university of information science & technology, nanjing 210044, china b College of Public Management, nanjing university of information science & technology, nanjing 210044, china College of Atmospheric sciences Nanjing University of Information Science & Technology Nanjing 210044 China College of Public Management Nanjing University of Information Science & Technology Nanjing 210044 China

The idea of applying direct numerical simulation (DNS), a theoretical mode of coherent structures in the wall region of a turbulent boundary layer, has been discussed in the literature. The various aspects of the formation mechanism of the coherent structures agree well with both DNS and experimental results. In addition, a close relationship has been found between the evolutional characteristics and factors such as the magnitude and structural distribution of the wall local impulse disturbance, and the amount of energy a local disturbance introduces into the wall region. Moreover, these parameters play key roles in the formation of coherent structures near the wall region of a turbulent boundary layer. Therefore, the wall local impulse disturbance provides a theoretical model for triggering the formation of coherent structures in the wall region of a turbulent boundary layer.

关键词： Turbulent boundary layer Wall region Coherent structure Local disturbance

A Note on the Completeness of an Exponential Type Sequence

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Chinese Annals of mathematics,Series B 2011年第4期32卷 527-532页

作者： Jinhui FANG Department of mathematics Nanjing University of Information Science and Technology Nanjing 210044 China

For any given coprime integers p and q greater than 1, in 1959, B. J. Birch proved that all sufficiently large integers can be expressed as a sum of pairwise distinct terms of the form p a q b . As Davenport observed, Birch's proof can be modified to show that the exponent b can be bounded in terms of p and q. In 2000, N. Hegyvari gave an effective version of this bound. The author improves this bound.

关键词：指数型整性序列有效版本整数证明互质

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Tsallis model-based separation of overlapped peak signals

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science china(information sciences) 2010年第4期53卷 823-832页

作者： LI YuanLu*, ZHANG YingChao & TANG HuiQiang College of information and Control, nanjing university of information science & technology, nanjing 210044, china College of information and Control Nanjing University of Information Science & Technology Nanjing China

A simple scheme for separating overlapped peak signals (OPS) is proposed, with the Tsallis distribution as the model for OPS processing and fractional-order differentiation as tool for the signal analysis, the relationships of the maxima and zero-crossing values of the Tsallis peak signal, separately, to the order of differentiation are established, leading to two types of parameter estimators, which are utilized, by adjusting the peak-shape parameter, to calculate the parameters of position, height and width of the Gaussian, Lorentzian and Tsallis distribution. The obtained characteristic parameters can be employed to fit the peak signals to be treated, thereby fulfilling the OPS decomposition.

关键词： fractional differentials filter overlapped peak signal Tsallis model separation of overlapped peak signals

Influence of mesoscale topography on vortex intensity

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Progress in Natural science:Materials International 2008年第1期18卷 71-78页

作者： Zhexian Luo*,Yun Gao Remote Sensing College,nanjing university of information science and technology,Najing 210044,china Remote Sensing College Nanjing University of Information Science and Technology Najing 210044 China

The effect of mesoscale topography on multi-vortex self-organization is investigated numerically in this paper using a barotropic prim- itive equation model with topographic *** the initial field there are one DeMaria major vortex with the maximum wind radius rm of 80 km at the center of the computational domain,and four meso-b vortices in the vicinity of rm to the east of the major vortex center. When there is no topography present,the initial vortices self-organize into a quasi-final state flow pattern,i.e.a quasi-axisymmetric vor- tex whose intensity is close to that of the initial major ***,when a mesoscale topography is incorporated,the spatial scale of the quasi-final state vortex reduces,and the relative vorticity at the center of the vortex and the local maximum wind speed remarkably *** possible mechanism for the enhancement of the quasi-final state vortex might be that the negative relative vorticity lump, generated above the mesoscale topography because of the constraint of absolute vorticity conservation,squeezes the center of positive vorticity towards the mountain slope area,and thus reduces the spatial range of the major ***,because the total kinetic energy is basically conservative,the squeezing directly leads to the concentration of the energy in a smaller area,*** strengthening of the vortex.

关键词： Mesoscale topography Vortex Self-organization Intensity change

A Raw Signal Simulator for Bistatic SAR

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Chinese Journal of Aeronautics 2009年第4期22卷 434-443页

作者： Xia Weijie,Zhou Jianjiang College of information science and technology,nanjing university of Aeronautics and Astronautics,nanjing 210016,china College of information science and technology Nanjing University of Aeronautics and Astronautics Nanjing 210016 China

This article proposes a new efficient raw signal simulator for the bistatic synthetic aperture radar （SAR） based on 2D fast Fourier transform （FFT） to deal with cases of both ideal trajectory and trajectory deviation. It begins with analyzing the geometric configuration and the range history of the bistatic SAR in side-looking and squint modes of ideal trajectory as well as trajectory deviation. Then a detailed and mathematical study is conducted on the equivalence relation of bistatic-to-monostatic applications （BTMA） in the case of ideal trajectory and trajectory deviation. Also a set of formulas are derived for the equivalence relation between bistatic SAR and monostatic SAR on some reasonable assumptions. Therefore, the application of the simulation method based on the 2D FFT for the monostatic SAR can be extended to the case of bistatic SAR. Finally, the simulation results prove the validity of this method. By comparing the efficiency of the proposed method with that of the time domain method, it is shown that the former is a few orders of magnitude higher.

关键词： bistatic synthetic aperture radar raw signal simulation fast Fourier transform

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Characteristics of fMRI BOLD signal and its neurophysiological mechanism

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Progress in Natural science:Materials International 2007年第6期17卷 630-638页

作者： Zhao Xiaohu1,2, Wu Yigen3 and Guo Shengli3(1. College of Life sciences, Zhejiang university, Hangzhou 310058, china 2. Imaging Department of Tongji Hospital of Tongji university, Shanghai 200065, china 3. College of mathematics and physics, nanjing university of information science and technology, nanjing 210044, china) College of Life sciences Zhejiang University Hangzhou 310058 China Imaging Department Tongji Hospital Tongji University Shanghai 200065 China College of mathematics and physics Nanjing University of Information Science and Technology Nanjing 210044 China

The functional magnetic resonance imaging (fMRI) based on blood oxygen level dependent (BOLD) contrast has emerged as one of the most potent noninvasive tools for mapping brain function and has been widely used to explore physiological, pathological changes and mental activity in the brain. Exploring the nature and property of BOLD signal has recently attracted more attentions. Despite that great progress has been made in investigation of the characteristics and neurophysiological basis, the exact nature of BOLD signal remains unclear. In this paper we discuss the characteristics of BOLD signals, the nonlinear BOLD response to external stimuli and the relation between BOLD signals and neural electrophysiological recordings. Furthermore, we develop our new opinions regarding nonlinear BOLD response and make some perspectives on future study.

关键词： functional magnetic resonance imaging blood oxygen level dependent nonlinear response neural electrophysiological activity.

A new parameterization scheme for sea surface aerodynamic roughness

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Progress in Natural science:Materials International 2008年第11期18卷 1365-1373页

作者： Yuping Pan~(a,b) Wenyu Sha~c Shouxian Zhu~c Sufang Ge~(a,*) a nanjing university of information science and technology,nanjing 210044,china b Air Force Meteorological Center of the nanjing Military Region,nanjing 210018,china c Meteorology College,The PLA university of information science and technology,nanjing 211101,china nanjing university of information science and technology Nanjing 210044 China Air Force Meteorological Center of the nanjing Military Region Nanjing 210018 China Meteorology College The PLA University of Information Science and Technology Nanjing 211101 China

The dimensionless roughness length derived from dimensional analysis bears a relation to wave age,and the dimensionless form of roughness length can be expressed with the relation with a significant wave *** on six experiments(HEXMAX,RASEX,BIO steady platform,Lake Ontario data analysis FETCH,CBLAST low wind),we verified that the Charnock parameter,Zch,and dimension- less roughness length,z0/Hs,are dependent on wave age,u*/***,we constructed a new scheme for roughness length,and explored its sensitivity to friction velocity and wave *** the newly developed parameterization scheme(PS07)with COARE (Coupled Ocean-Atmosphere Response Experiment V.3.0)algorithm,we calculated the data from the North Sea Platform experiment in December,1985,and made an attempt to validate the suitability of the PS07 compared to the other three schemes of *** found that the calculated results based on the PS07 are close to the *** also conducted an experiment in which the PS07 was combined with the nested model of waves coupling in datasets of 3 typhoons that occurred at the Zhanjiang *** comparison results between the calculated and observed waves around the Naozhou Island indicate that the new parameterization scheme(PS07)has a good applicability.

关键词： Sea surface roughness Parameterization scheme Significant wave height Wave age COARE algorithm