Array configuration of multiple-input multiple-output （MIMO） radar with non-uniform linear array （NLA） is proposed. Unlike a standard phased-array radar where NLA is used to generate thinner beam patterns, in MIMO...Array configuration of multiple-input multiple-output （MIMO） radar with non-uniform linear array （NLA） is proposed. Unlike a standard phased-array radar where NLA is used to generate thinner beam patterns, in MIMO radar the property of NLA is exploited to get more distinct virtual array elements so as to improve pa- rameter identifiability, which means the maximum number of targets that can be uniquely identified by the radar. A class of NLA called minimum redundancy linear array （MRLA） is employed and a new method to construct large MRLAs is descrihed. The numerical results verify that compared to uniform linear array （ULA） MIMO radars, NLA MIMO radars can retain the same parameter identifiability with fewer physical antennas and achieve larger aperture length and lower Cramer-Rao bound with the same number of the physical antennas.展开更多
The structure of the Si3Ox （x =2, 3） cluster is investigated; we find that the geometry of Si3O2 is similar to that of Si3O3 except for the oxygen-deficient defect structure （Si-Si band） which exists only in the S...The structure of the Si3Ox （x =2, 3） cluster is investigated; we find that the geometry of Si3O2 is similar to that of Si3O3 except for the oxygen-deficient defect structure （Si-Si band） which exists only in the Si3O2 cluster. It is known that oxygen-deficient defects are used to explain visible luminescence （especially blue, purple and ultraviolet light） from silicon-based materials, which are directly bound up with the excited states of the molecules. Therefore the excitation properties of the two clusters are also studied. Our results show that the absorption spectrum of Si3O2 is concentrated in the visible light region. In contrast, the absorption spectrum of Si3O3 is mainly located in the ultraviolet light region. The calculations are perfectly consistent with experimental data and also support the theory of oxygen-deficient defects.展开更多
A series of hydrogenated silicon thin films with varying silane concentrations have been deposited by using very high frequency plasma enhanced chemical vapor deposition （VHF-PECVD） method. The deposition process an...A series of hydrogenated silicon thin films with varying silane concentrations have been deposited by using very high frequency plasma enhanced chemical vapor deposition （VHF-PECVD） method. The deposition process and the silicon thin films are studied by using optical emission spectroscopy （OES） and Fourier transfer infrared （FTIR） spectroscopy, respectively. The results show that when the silane concentration changes from 10% to 1%, the peak frequency of the Si-H stretching mode shifts from 2000 cm-1 to 2100 cm-1, while the peak frequency of the Si-H wagging-rocking mode shifts from 650 cm-1 to 620 cm-1. At the same time the SiH^＊/Ha intensity ratio in the plasma decreases gradually. The evolution of the infrared spectra and the optical emission spectra demonstrates a morphological phase transition from amorphous silicon （a-Si：H） to microcrystalline silicon （μc-Si：H）. The structural evolution and the p-c-SiH formation have been analyzed based on the variation of Ha and SiH^＊ intensities in the plasma. The role of oxygen impurity during the plasma process and in the silicon films is also discussed in this study.展开更多
The basic configuration of step up converter usually used in photovoltaic solar systems to increase the DC voltage generated at their outputs suffers from some drawbacks just like high ripple in the output voltage,gre...The basic configuration of step up converter usually used in photovoltaic solar systems to increase the DC voltage generated at their outputs suffers from some drawbacks just like high ripple in the output voltage,greater losses in the system and unstable dynamic behavior.To eliminate these drawbacks,this paper introduces a two-phase connection of step up converter with uncoupled smoothing reactors.Detailed analysis,simulation and control strategy have been proposed in this paper to investigate the advantages of using such connection with uncoupled reactors.This paper is intended to prove that two-phase connection with uncoupled reactors helps increasing the output power of the converter,minimizing its output ripple and making its control easier and more efficient.It also increases the converter chopping frequency and consequently decreases the size of smoothing reactors and filters used in the system.Concerning the design of such converters,it requires a long working period of time with a significant cost and specific technical tests at nominal operating points.Therefore,simulation can essentially decrease economic and development costs.Using modulation and simulation software techniques(Simplorer,Simulink,and Matlab)throughout this paper helped simulation of very fast the converter behavior and accurate determination of its dynamic characteristics.Moreover,the paper deals with modulation of voltage control technique using Matlab and Simplorer,thus regulating the converter output current and voltage.Simulation results show that this control technique provides robust output current and voltage of step up converters and is more feasible for their chopper up conversion technique.展开更多
基金Supported by the Aeronautic Science Foundation of China(2008ZC52026)the Innovation Foundation of Nanjing University of Aeronautics and Astronautics~~
文摘Array configuration of multiple-input multiple-output （MIMO） radar with non-uniform linear array （NLA） is proposed. Unlike a standard phased-array radar where NLA is used to generate thinner beam patterns, in MIMO radar the property of NLA is exploited to get more distinct virtual array elements so as to improve pa- rameter identifiability, which means the maximum number of targets that can be uniquely identified by the radar. A class of NLA called minimum redundancy linear array （MRLA） is employed and a new method to construct large MRLAs is descrihed. The numerical results verify that compared to uniform linear array （ULA） MIMO radars, NLA MIMO radars can retain the same parameter identifiability with fewer physical antennas and achieve larger aperture length and lower Cramer-Rao bound with the same number of the physical antennas.
基金supported by the Natural Science Foundation of Henan Province of China (Grant No. 092300410249)the Natural Science Foundation of the Education Bureau of Henan Province of China (Grant No. 2010A140008)the Foundation for University Young Core Instructors of Henan Province, China (Grant No. 2009GGJS-044)
文摘The structure of the Si3Ox （x =2, 3） cluster is investigated; we find that the geometry of Si3O2 is similar to that of Si3O3 except for the oxygen-deficient defect structure （Si-Si band） which exists only in the Si3O2 cluster. It is known that oxygen-deficient defects are used to explain visible luminescence （especially blue, purple and ultraviolet light） from silicon-based materials, which are directly bound up with the excited states of the molecules. Therefore the excitation properties of the two clusters are also studied. Our results show that the absorption spectrum of Si3O2 is concentrated in the visible light region. In contrast, the absorption spectrum of Si3O3 is mainly located in the ultraviolet light region. The calculations are perfectly consistent with experimental data and also support the theory of oxygen-deficient defects.
基金Project supported by the National High Technology Research and Development Program of China (Grant No. 2009AA050602)the International Cooperation Project between China-Greece Government (Grant No. 2009DFA62580)the National Basic Research Program of China (Grant Nos. 2011CBA00705, 2011CBA00706, and 2011CBA00707)
文摘A series of hydrogenated silicon thin films with varying silane concentrations have been deposited by using very high frequency plasma enhanced chemical vapor deposition （VHF-PECVD） method. The deposition process and the silicon thin films are studied by using optical emission spectroscopy （OES） and Fourier transfer infrared （FTIR） spectroscopy, respectively. The results show that when the silane concentration changes from 10% to 1%, the peak frequency of the Si-H stretching mode shifts from 2000 cm-1 to 2100 cm-1, while the peak frequency of the Si-H wagging-rocking mode shifts from 650 cm-1 to 620 cm-1. At the same time the SiH^＊/Ha intensity ratio in the plasma decreases gradually. The evolution of the infrared spectra and the optical emission spectra demonstrates a morphological phase transition from amorphous silicon （a-Si：H） to microcrystalline silicon （μc-Si：H）. The structural evolution and the p-c-SiH formation have been analyzed based on the variation of Ha and SiH^＊ intensities in the plasma. The role of oxygen impurity during the plasma process and in the silicon films is also discussed in this study.
文摘The basic configuration of step up converter usually used in photovoltaic solar systems to increase the DC voltage generated at their outputs suffers from some drawbacks just like high ripple in the output voltage,greater losses in the system and unstable dynamic behavior.To eliminate these drawbacks,this paper introduces a two-phase connection of step up converter with uncoupled smoothing reactors.Detailed analysis,simulation and control strategy have been proposed in this paper to investigate the advantages of using such connection with uncoupled reactors.This paper is intended to prove that two-phase connection with uncoupled reactors helps increasing the output power of the converter,minimizing its output ripple and making its control easier and more efficient.It also increases the converter chopping frequency and consequently decreases the size of smoothing reactors and filters used in the system.Concerning the design of such converters,it requires a long working period of time with a significant cost and specific technical tests at nominal operating points.Therefore,simulation can essentially decrease economic and development costs.Using modulation and simulation software techniques(Simplorer,Simulink,and Matlab)throughout this paper helped simulation of very fast the converter behavior and accurate determination of its dynamic characteristics.Moreover,the paper deals with modulation of voltage control technique using Matlab and Simplorer,thus regulating the converter output current and voltage.Simulation results show that this control technique provides robust output current and voltage of step up converters and is more feasible for their chopper up conversion technique.
