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Point Spread Function Estimation for a Turbulence-Degenerated Image Based on Àtrous Wavelet Transform
CHEN Bo, GENG Ze-Xun, SHEN Jun, YANG Yang
Chin. Phys. Lett. 2009, 26 (4):
040701
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DOI: 10.1088/0256-307X/26/4/040701
The observed object images are seriously blurred because of the influence of atmospheric turbulence. The restoration is required for the reconstruction of turbulence degraded images. Point spread function (PSF) estimation, an essential part of image restoration, has no accurate estimation algorithm at present. Based on the àtrous wavelet, we deduce a novel PSF estimation algorithm. First, the àtrous wavelet at varying scales is transformed. Then, on the basis of the relation among the local maxima of the modulus of the wavelet coefficients at different scales, the Lipschitz exponent of the wavelet coefficients is computed, thus the variance of a PSF is estimated. From this estimated variance, one is able to obtain the PSF. Consequently, the object image can be restored. Experimental results show that the proposed method is highly effective with good performance.
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A Light-Cone QCD Inspired Effective Hamiltonian Model with SU(3) Flavor Mixing
GUO Xiao-Bo, TAO Jun, LI Lei, ZHOU Shan-Gui, WANG Shun-Jin,
Chin. Phys. Lett. 2009, 26 (4):
041201
.
DOI: 10.1088/0256-307X/26/4/041201
The effective light-cone Hamiltonian is extended to include the SU(3) flavor mixing interaction besides the confining potential. Solving the coupled J=0 mass eigen equations for the up, down, and strange quark components numerically, the masses of π0 and η, their radial wave functions, and rms radii are obtained in agreement with the experimental data.
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Effect of Anode Floating Voltage and its Applications in Characterizing Silicon Drift Detectors
WU Guang-Guo, LI Hong-Ri, LIANG Kun, YANG Ru, CAO Xue-Lei, WANGHuan-Yu, AN Jun-Ming, HU Xiong-Wei, HAN De-Jun
Chin. Phys. Lett. 2009, 26 (4):
042901
.
DOI: 10.1088/0256-307X/26/4/042901
Anode floating voltage is predicted and investigated for silicon drift detectors (SDDs) with an active area of 5mm2 fabricated by a double-side parallel technology. It is demonstrated that the anode floating voltage increases with the increasing inner ring voltage, and is almost unchanged with the external ring voltage. The anode floating voltage will not be affected by the back electrode biased voltage until it reaches the full-depleted voltage (-50V) of the SDD. Theoretical analysis and experimental results show that the anode floating voltage is equal to the sum of the inner ring voltage and the built-in potential between the p+ inner ring and the n+ anode. A fast checking method before detector encapsulation is proposed by employing the anode floating voltage along with checking the leakage current, potential distribution and drift properties.
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Effect of Electron Correlations and Breit Interactions on Ground-State Fine-Structures along the Nitrogen-Like Isoelectronic Sequence
WANG Xiao-Lu, LU Wen-Lai, GAO Xiang, LI Jia-Ming,
Chin. Phys. Lett. 2009, 26 (4):
043101
.
DOI: 10.1088/0256-307X/26/4/043101
The accurate atomic data of nitrogen and nitrogen-like ions have an importance role in fusion plasma studies and astrophysics studies. The recise calculation of fine-structures is required to obtain such atomic data. Along the whole nitrogen isoelectronic sequence, the contributions of the
electron correlations, the Breit interactions and the quantum electrodynamics corrections on the ground-state fine-structures are elucidated. When Z is low, the electron correlations are important, and the Breit interactions, which cannot be neglected cause interesting anomalous fine-structure splittings. When Z is high, the electron correlations are less important, and the Breit interactions are important in addit
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Coherent Beam Combination of Three Fiber Amplifiers with Multi-dithering Technique
MA Yan-Xing, LIU Ze-Jin, ZHOU Pu, WANG Xiao-Lin, MA Hao-Tong, LI Xiao, XU Xiao-Jun, SI Lei
Chin. Phys. Lett. 2009, 26 (4):
044204
.
DOI: 10.1088/0256-307X/26/4/044204
Coherent beam combination of three W-level fiber amplifiers with multi-dithering technique is demonstrated. The multi-dithering technique is used for phase control in two channels. In the experiment, two channels are modulated by sine wave with 70kHz and 100kHz respectively, and two regular commercial DSP lock-in amplifiers and an industrial computer are used for electric signal processing in the feedback loop. The fringe contrast is advanced from 12% to 81%, and 78% coherent combination efficiency is obtained when the feedback loop is closed.
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An Array of One-Dimensional Porous Silicon Photonic Crystal Reflector Islands for a Far-Infrared Image Detector
MIAO Feng-Juan, ZHANG Jie, XU Shao-Hui, WANG Lian-Wei, CHU Jun-Hao, CAO Zhi-Shen, ZHAN Peng, WANG Zhen-Lin
Chin. Phys. Lett. 2009, 26 (4):
044207
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DOI: 10.1088/0256-307X/26/4/044207
With the aid of photolithography, an array of one-dimensional porous silicon photonic crystal reflector islands for a far infrared image detector ranging from 10μm to 14μm is successfully fabricated. Silicon nitride formed by low pressure chemical vapor deposition (LPCVD) was used as the masking layer for the island array formation. After etching, the microstructures were examined by a scanning electron microscope and the optical properties were studied by Fourier transform infrared spectroscopy, the result indicates that the multilayer structure could be obtained in the perpendicular direction via periodically alternative etching current in each pre-pattern. At the same time, the island array has a well-proportioned lateral etching effect, which is very useful for the thermal isolation in lateral orientation of the application in devices. It is concluded that regardless of the absorption of the deposition layer on the substrate, the localized photonic crystalline islands have higher reflectivity. The designed islands structure not only prevents the cracking of the porous silicon layers but is also useful for the application in the cold part for the sensor devices and the interconnection of each pixel.
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Identification of Acceptor States in Li-N Dual-Doped p-Type ZnO Thin Films
ZHANG Yin-Zhu, LU Jian-Guo, YE Zhi-Zhen, HE Hai-Ping, CHEN Lan-Lan, ZHAO Bing-Hui
Chin. Phys. Lett. 2009, 26 (4):
046103
.
DOI: 10.1088/0256-307X/26/4/046103
Li-N dual-doped p-type ZnO (ZnO:(Li,N)) thin films are prepared by pulsed laser deposition. The optical properties are studied using temperature-dependent photoluminescence. The LiZn-NO complex acceptor with an energy level of 138meV is identified from the free-to-neutral-acceptor (e, A0) emission. The Haynes factor is about 0.087 for the LiZn-NO complex acceptor, with the acceptor bound-exciton binding energy of 12meV. Another deeper acceptor state located at 248meV, also identified from the (e, A0) emission, is attributed to zinc vacancy acceptor. The two acceptor states might both contribute to the observed p-type conductivity in ZnO:(Li,N).
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Theoretical Study of Elastic Properties of Tungsten Disilicide
XU Guo-Liang, ZHANG Dong-Ling, XIA Yao-Zheng, LIU Xue-Feng, LIU Yu-Fang, ZHANG Xian-Zhou
Chin. Phys. Lett. 2009, 26 (4):
046302
.
DOI: 10.1088/0256-307X/26/4/046302
The plane-wave pseudopotential method using the generalized gradient approximation within the framework of density functional theory is applied to analyse the lattice parameters, elastic constants, bulk moduli, shear moduli and Young's moduli of WSi2. The quasi-harmonic Debye model, using a set of total energy versus cell volume obtained with the plane-wave pseudopotential method, is applied to the study of the elastic properties and vibrational effects. The athermal elastic constants of WSi2 are calculated as a function of pressure up to 35GPa. The relationship between bulk modulus and temperature up to 1200K is also obtained. Moreover, the Debye temperature is determined from the non-equilibrium Gibbs function. The calculated results are in good agreement with the experimental data.
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Phase Transition and EOS of Cinnabar (α-HgS) at High Pressure and High Temperature
FAN Da-Wei, ZHOU Wen-Ge, LIU Cong-Qiang, WAN Fang, XING Yin-Suo, LIU Jing, LI Yan-Chun, XIE Hong-Sen
Chin. Phys. Lett. 2009, 26 (4):
046402
.
DOI: 10.1088/0256-307X/26/4/046402
Phase relations and equation of state (EOS) of natural cinnabar (α-HgS) are investigated by high-pressure and high-temperature synchrotron x-ray powder diffraction. The unambiguous cinnabar-rocksalt structure phase boundaries are determined to be Plower(GPa)=15.54-0.014T°C and Pupper(GPa)=23.84-0.014T(°C) at 300-623K. With K' fixed at 4, we obtain K0= 37(4)GPa, (∂K/∂ T)P=-0.025(2)GPaK-1, and α_{0}=3.79(20)×10-5K-1 for the cinnabar phase of α-HgS. The (K/∂T)P and α0 of cinnabar phase are obtained for the first time. A nearly isotropic compression of cinnabar phase is observed by linear regressions.
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Fabrication and Characterization of Si Nanocrystals Synthesized by Electron Beam Evaporation of Si and SiO2 Mixture
LI Wei-Long, JIA Rui, LIU Ming, CHEN Chen, XIE Chang-Qing, ZHU Chen-Xin, LI Hao-Feng, ZHANG Pei-Wen, YE Tian-Chun
Chin. Phys. Lett. 2009, 26 (4):
046801
.
DOI: 10.1088/0256-307X/26/4/046801
Silicon nanocrystals synthesized by electron beam (e-beam) evaporation of Si and SiO2 mixture are studied. Rutherford backscattering spectrometry of the as-deposited Si-rich silicon dioxide or oxide (SRO) thin film shows that after evaporation, the Si and SiO2 concentration is well kept, indicating that the e-beam evaporation is suitable for evaporating mixtures of Si and SiO2. The SRO thin films are annealed at different temperatures for two hours to synthesize silicon nanocrystals. For the sample annealed at 1050°C, silicon nanocrystals with different sizes and the mean diameter of 4.5nm are evidently observed by high resolution transmission electron microscopy (HRTEM). Then the Raman scattering and photoluminescence spectra arising from silicon nanocrystals are further confirmed the above results
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Ferroelectric Properties of Bi3.25La0.75Ti3O12 Thin Films Crystallized inDifferent N2/O2 Ambients
LI Jian-Jun, YU Jun, LI Jia, YANG Wei-Ming, ZHOU Bin, GAO Jun-Xiong, WANG Yun-Bo
Chin. Phys. Lett. 2009, 26 (4):
047702
.
DOI: 10.1088/0256-307X/26/4/047702
Bi3.25La0.75Ti3O12 (BLT) ferroelectric thin films are deposited by sol-gel method and annealed for crystallizaion in total 1sccm N2/O2 mixed gas with various ratio at 750°C for 30min. The effect of crystallization ambient on the structural and ferroelectric properties of the BLT films is studied. The growth direction and grain size of BLT film are revealed to affect ferroelectric properties. After the BLT film is annealed in 20% O2, the largest Pr value is obtained, which is ascribed to an increase of random orientation and large grain size. The fatigue property is improved with the concentration of oxygen in the ambient increasing, which is ascribed to annealing in the ambient with high concentrated oxygen adequately decreasing the defects related to lack of oxygen.
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Luminescent Characteristics of LiSrBO3:Eu3+ Phosphor for White Light Emitting Diode
LI Pan-Lai, WANG Zhi-Jun, YANG Zhi-Ping, GUO Qing-Lin
Chin. Phys. Lett. 2009, 26 (4):
047801
.
DOI: 10.1088/0256-307X/26/4/047801
LiSrBO3:Eu3+ phosphor is synthesized by a high solid-state reaction method, and its luminescent characteristics are investigated. The emission and excitation spectra of LiSrBO3:Eu3+ phosphors exhibit that the phosphors can be effectively excited by near ultraviolet (401nm) and blue (471nm) light, and emit 615nm red light. The effect of Eu3+ concentration on the emission spectrum of LiSrBO3:Eu3+ phosphor is studied; the results show that the emission intensity increases with increasing Eu3+ concentration, and then decreases because of concentration quenching. It reaches the maximum at 3mol%, and the concentration self-quenching mechanism is the dipole-dipole interaction according to the Dexter theory. Under the conditions of charge compensation Li+, Na+ or K+ incorporated in LiSrBO3, the luminescent intensities of LiSrBO3:Eu3+ phosphor are enhanced.
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Fe-Doped Polycrystalline CeO2 as Terahertz Optical Material
WEN Qi-Ye, ZHANG Huai-Wu, YANG Qing-Hui, LI Sheng, XU De-Gang, YAOJian-Quan
Chin. Phys. Lett. 2009, 26 (4):
047803
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DOI: 10.1088/0256-307X/26/4/047803
Fe-doped CeO2 is synthesized by ceramic method and the effects of Fe doping on the structure and properties are characterized by ordinary methods and terahertz-time domain spectrometer (THz-TDS) technique. Our results show that pure CeO2 only has a small dielectric constant ε of 4, while a small amount of Fe (0.9at.%) doping into CeO2 promotes densification and induces a large ε of 23. From the THz spectroscopy, it is found that for undoped CeO2 both the power absorption and the index of refraction increase with frequency, while for Fe-doped CeO2 we measure a remarkable transparency together with a flat index curve. The absorption coefficient of Fe-doped CeO2 at frequency ranging from 0.2 to 1.8THz is less than 0.35cm-1, implying that Fe-doped CeO2 is a potential THz optical material.
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Impurity Activation in MBE-Grown As-Doped HgCdTe by Modulated Photoluminescence Spectra
YUE Fang-Yu, CHEN Lu, WU Jun, HU Zhi-Gao, LI Ya-Wei, YANG Ping-Xiong, CHU Jun-Hao,
Chin. Phys. Lett. 2009, 26 (4):
047804
.
DOI: 10.1088/0256-307X/26/4/047804
Modulated photoluminescence spectra have been performed to investigate the impurity activation in MBE-grown As-doped Hg1-xCdxTe (x≈0.3). The results show that the doped As mainly acting as donors in the as-grown samples can be fully activated as AsTe by two-stage anneals of 285°C/16h + 240°C/48h, of which the ionization energy has been determined to be about 10.5meV, slightly smaller than that of intrinsic VHg (about 14.5meV). However, the higher activation temperature (e.g. 400°C) at the first-stage can produce large numbers of excessive VHg and seriously deteriorate the quality of epilayers. This could give a brief guideline for preparing extrinsic
p-type HgCdTe materials or devices.
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Structural and Thermodynamic Properties of M3W3N (M=Fe, Co, Ni)
CHEN Yi, SHEN Jiang, CHEN Nan-Xian
Chin. Phys. Lett. 2009, 26 (4):
048101
.
DOI: 10.1088/0256-307X/26/4/048101
Ternary transition metal nitrides, Fe3W3N, Co3W3N, and Ni3W3N, are studied by the use of interatomic potentials acquired from lattice inversion. The study indicates that Fe3W3N would be more stable than the other compounds in the family of intermetallic tungsten nitrides. The investigation of phonon density of states indicates that the lower frequency modes are mostly excited by the metal atoms, and the higher frequency modes are mostly excited by the nitrogen atoms. A qualitative analysis is carried out with the relevant potentials for the phase stability and vibrational modes.
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HPHT Synthesis of Different Shape Coarse-Grain Diamond Single Crystals
ZHOU Sheng-Guo, ZANG Chuan-Yi, MA Hong-An, HU Qiang, LI Xiao-Lei, LI Shang-Sheng, ZHANG He-Min, JIA Xiao-Peng,
Chin. Phys. Lett. 2009, 26 (4):
048102
.
DOI: 10.1088/0256-307X/26/4/048102
Synthesis of coarse-grain diamond crystals is studied in a China-type SPD6×1670T cubic high-pressure apparatus with high exact control system. To
synthesize high quality coarse-grain diamond crystals, advanced indirect heat assembly, powder catalyst technology and optimized synthesis craft are used. At last, three kinds of coarse-grain diamond (about 0.85mm) single crystals with hexahedron, hex-octahedron and octahedron are synthesized successfully under HPHT (about 5.4GPa, 1300-1450°). The growth characters
of different shape crystals are discussed. The results and techniques might be useful for the production of coarse-grain diamonds.
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Fabrication and Frequency Response Characteristics of AlN-Based Solidly Mounted Resonator
XIONG Juan, GU Hao-Shuang, HU Kuan, HU Ming-Zhe
Chin. Phys. Lett. 2009, 26 (4):
048104
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DOI: 10.1088/0256-307X/26/4/048104
Film bulk acoustic resonator (FBAR) with solidly mounted resonator (SMR)-type is carried out by rf magnetic sputtering. To fabricate SMR-type FBAR, alternative high and low acoustic impedance layers, Mo/Ti multilayer, are adopted as Bragg reflector deposited by dc magnetron sputtering. The influences of sputtering pressure, substrate temperature and sputtering power on the surface roughness of Bragg reflector layer are discussed. From the atom force microscopy (AFM) analysis, the surface roughness of the Bragg reflector is improved remarkably by controlling deposition conditions. Under the appropriate sputtering condition, AlN thin films with highly c-axis-preferred orientation are deposited by rf magnetron sputtering. The performance of fabricated Mo/Ti SMR shows that the electromechanical coupling coefficient is 3.89%, the series and parallel resonant frequencies appear at 2.49 and 2.53GHz, with their quality factors 134.2 and 97.6, respectively.
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Lattice Boltzmann Simulations of Particle-Particle Interaction in Steady Poiseuille Flow
YI Hou-Hui, FAN Li-Juan, YANG Xiao-Feng, LI Hua-Bing
Chin. Phys. Lett. 2009, 26 (4):
048701
.
DOI: 10.1088/0256-307X/26/4/048701
The moving behaviour of two- and three-particles in a pressure-driven flow is studied by the lattice Boltzmann simulation in two dimensions. The time-dependent values, including particles' radial positions, translational velocities, angular velocities, and the x-directional distance between the particles are analysed extensively. The effect of flow Reynolds number on particle motion is also investigated numerically. The simulation results show that the leading particle equilibrium position is closer to the channel centre while the trailing particle equilibrium position is closer to the channel wall. If Reynolds number Re is less than 85.30, the larger flow Reynolds number results in the smaller x-directional equilibrium distance, otherwise the x-directional distance increases almost linearly with the increase of time and the particles separate finally. The simulation results are helpful to understand the particle-particle
interaction in suspensions with swarms of particles.
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Contribution from the Earth's Bow Shock to Region 1 Current under Low Alfvén Mach Numbers
PENG Zhong, HU You-Qiu
Chin. Phys. Lett. 2009, 26 (4):
049401
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DOI: 10.1088/0256-307X/26/4/049401
Using global MHD simulations of the solar wind-magnetosphere-ionosphere system, we investigate the dependence of the contribution from the Earth's bow shock (I1bs) to ionospheric region 1 field aligned current (FAC) (I1). It is found that I1bs increases with increasing southward interplanetary magnetic field (IMF) strength Bs, if the Alfvén Mach number MA of the solar wind exceeds 2, a similar result as obtained by previous authors. However, if MA becomes close to or falls below 2, I1bs will decrease with Bs in both magnitude and percentage (i.e., I1bs}/I1) because of the resultant reduction of the bow shock strength. Both the surface current density Jbs at the nose of the bow shock and the total bow shock current Ibs share nearly the same relationship with MA, and vary non-monotonically with MA or Bs. The maximum point is found to be located at MA = 2.7. Three conclusions are then made as follows: (1) The surface current density at the nose, which is much easier to be evaluated, may be used to largely describe the behaviour of the bow shock instead of the total bow shock current. (2) The peak of the total bow shock current is reached at about MA = 2.7 when only Bs is adjusted. (3) The non-monotonic variation of the bow shock current with MA causes a similar variation of its contribution to region 1 FAC. The turning point for such contribution is found to be nearly MA= 2. The implication of these conclusions to the saturation of the ionospheric transpolar potential is briefly discussed
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76 articles
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