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Volume 27 Issue 11
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GENERAL
A Simple Method for Generating Discrete Multi-Component Integrable Hierarchy
YAO Yu-Qin**, ZENG Yun-Bo
Chin. Phys. Lett. 2010, 27 (11): 110201 .   DOI: 10.1088/0256-307X/27/11/110201
Abstract   PDF(pc) (436KB) ( 504 )
For M×N spectral matrix, a kind of operation ʘ which satisfies combination law (aʘb)ʘc=aʘ(bʘc) is introduced. The discrete multi−component zero-curvature equation is deduced by using the new operation ʘ, and a simple method for constructing discrete multi-component integrable hierarchy is proposed. As its application, the multi-component Toda hierarchy and its two kinds of integrable couplings are worked out.
Liquid Film on Unsteady Stretching Sheet with General Surface Temperature and Viscous Dissipation
R. C. Aziz, I. Hashim**
Chin. Phys. Lett. 2010, 27 (11): 110202 .   DOI: 10.1088/0256-307X/27/11/110202
Abstract   PDF(pc) (435KB) ( 971 )
We study the effects of viscous dissipation on flow and heat transfer in a thin liquid film on an unsteady stretching sheet. A general surface temperature is taken into consideration. The velocity and temperature fields are solved using the homotopy analysis method. The results show that the increasing values of the Eckert number can increase temperature distribution and the heat transfer rate.
Analytical Solutions of the Manning-Rosen Potential In the Tridiagonal Program
ZHANG Min-Cang**, AN Bo
Chin. Phys. Lett. 2010, 27 (11): 110301 .   DOI: 10.1088/0256-307X/27/11/110301
Abstract   PDF(pc) (399KB) ( 420 )
The Schrödinger equation with the Manning-Rosen potential is studied by working in a complete square integrable basis that carries a tridiagonal matrix representation of the wave operator. In this program, solving the Schrödinger equation is translated into finding solutions of the resulting three-term recursion relation for the expansion coefficients of the wavefunction. The discrete spectrum of the bound states is obtained by diagonalization of the recursion relation with special choice of the parameters and the wavefunctions is expressed in terms of the Jocobi polynomial.
Evolution of a Thermo Vacuum State in a Single-Mode Amplitude Dissipative Channel
WANG Chang-Chun**, FAN Hong-Yi,
Chin. Phys. Lett. 2010, 27 (11): 110302 .   DOI: 10.1088/0256-307X/27/11/110302
Abstract   PDF(pc) (394KB) ( 426 )
We investigate how an initial thermo vacuum state, in the context of thermo field dynamics, evolves in a single-mode amplitude dissipative channel, and find that in this process the thermo squeezing effect decreases while the fictitious-mode vacuum becomes chaotic.
Six-State Quantum Key Distribution Using Photons with Orbital Angular Momentum
LI Jun-Lin**, WANG Chuan
Chin. Phys. Lett. 2010, 27 (11): 110303 .   DOI: 10.1088/0256-307X/27/11/110303
Abstract   PDF(pc) (452KB) ( 879 )
A new implementation of high-dimensional quantum key distribution (QKD) protocol is discussed. Using three mutual unbiased bases, we present a d−level six-state QKD protocol that exploits the orbital angular momentum with the spatial mode of the light beam. The protocol shows that the feature of a high capacity since keys are encoded using photon modes in d-level Hilbert space. The devices for state preparation and measurement are also discussed. This protocol has high security and the alignment of shared reference frames is not needed between sender and receiver.
Bound and Resonant States of the Hulthén Potential Investigated by Using the Complex Scaling Method with the Oscillator Basis
FENG Jun-Sheng**, LIU Zheng, GUO Jian-You
Chin. Phys. Lett. 2010, 27 (11): 110304 .   DOI: 10.1088/0256-307X/27/11/110304
Abstract   PDF(pc) (476KB) ( 425 )
Bound and resonant states of the Hulthén potential are studied. The complex scaling method is used to achieve the energy spectrum. The oscillator basis is used to expand the radial wave function. Conforming to the standard feature of the complex scaling method, the bound energies do not change and the continuums change with the rotational angle. With tables and graphs, the interesting properties of the energy spectrum for various physical parameters are presented. The Gauss quadrature integral approximation is used to deal with the potential integral term.
A New Scheme to Projective Synchronization of Fractional-Order Chaotic Systems
WANG Jun-Wei**, CHEN Ai-Min,
Chin. Phys. Lett. 2010, 27 (11): 110501 .   DOI: 10.1088/0256-307X/27/11/110501
Abstract   PDF(pc) (532KB) ( 542 )
We demonstrate that the projective synchronization can be observed in coupled fractional-order chaotic systems. A new systematic and powerful coupling scheme is developed to investigate the projective synchronization via the open-plus-closed-loop control, which allows us to arbitrarily manipulate the scaling factor of projective synchronization. The proposed scheme is proved analytically on the basis of the stability theorem of the fractional differential equations. Numerical simulations on the fraction-order chaotic Chen system are presented to justify the theoretical analysis.
Progress in AMS Measurement of 182Hf at CIAE
DONG Ke-Jun, HE Ming, LI Zhen-Yu, WANG Xiang-Gao, LI Chao-Li, YOU Qu-Bo, BAO Yi-Wen, WU Shao-Yong, SHEN Hong-Tao, GUAN Yong-Jing, ZHANG Wei, FAN Jin-Long, YANG Lei, SUN Hong-Qing, DING You-Qian, HE Guo-Zhu, LI Shi-Zhuo, GONG Jie, HE Xian-Wen, LU Li-Yan, WANG Wei, HU Yue-Ming, YUAN Jian, ZHANG Sheng-Dong, CHANG Yong-Fu, JIANG Shan**
Chin. Phys. Lett. 2010, 27 (11): 110701 .   DOI: 10.1088/0256-307X/27/11/110701
Abstract   PDF(pc) (1195KB) ( 390 )
Accelerator mass spectrometry (AMS) is one of the most promising methods to detect minute amounts of 182Hf. However, the sensitivity of 5×10−11 for 182Hf/180Hf obtained previously by the AMS method at China Institute of Atomic Energy (CIAE) cannot meet the requirement of some applications. We present some new improvements of measurement method for AMS measurement of 182Hf at the CIAE HI−13 tandem accelerator system. As a result, a sensitivity of 1.0×10-11 for 182Hf/180Hf is achieved.
NUCLEAR PHYSICS
Band Interaction between Chiral Doublet Bands
QI Bin, ZHANG Shuang-Quan, WANG Shou-Yu, MENG Jie, ,
Chin. Phys. Lett. 2010, 27 (11): 112101 .   DOI: 10.1088/0256-307X/27/11/112101
Abstract   PDF(pc) (589KB) ( 399 )
Band interaction between the chiral doublet bands based on πh11/2⊗νh−111/2 configuration is investigated in the particle rotor model with different triaxial deformation γ. The variation of chiral partner states with γ values is understood qualitatively based on the basic picture of two interaction levels, which is confirmed further by the calculated overlap integral of wave functions at different γ values. It is found that the interaction strengths of chiral partner states are obviously different for odd spins and even ones.
Half-Lives of Proton Emitters With a Deformed Density-Dependent Model
QIAN Yi-Bin**, REN Zhong-Zhou, , NI Dong-Dong, SHENG Zong-Qiang
Chin. Phys. Lett. 2010, 27 (11): 112301 .   DOI: 10.1088/0256-307X/27/11/112301
Abstract   PDF(pc) (440KB) ( 424 )
Half-lives of proton radioactivity are investigated with a deformed density-dependent model. The single folding potential which is dependent on deformation and orientation is employed to calculate the proton decay width through the deformed potential barrier. In addition, the spectroscopic factor is taken into account in the calculation, which is obtained in the relativistic mean field theory with NL3. The calculated results of semi-spherical nuclei are found to be in good agreement with the experimental data, and the results of well-deformed nuclei are also satisfactory. Moreover, a formula for the spherical proton emission half-life based on the Gamow quantum tunneling theory is presented.
Study of Fusion Dynamics Using Skyrme Energy Density Formalism with Different Surface Corrections
Ishwar Dutt**, Narinder K. Dhiman
Chin. Phys. Lett. 2010, 27 (11): 112401 .   DOI: 10.1088/0256-307X/27/11/112401
Abstract   PDF(pc) (1050KB) ( 432 )
Within the framework of Skyrme energy density formalism, we investigate the role of surface corrections on the fusion of colliding nuclei. The coefficient of surface correction is varied between 1/36 and 4/36, and its impact is studied on about 180 reactions. The detailed investigations indicate a linear relationship between the fusion barrier heights and strength of the surface corrections. Our analysis of the fusion barriers advocate the strength of surface correction of 1/36.
A Modified Proximity Approach in the Fusion of Heavy Ions
Ishwar Dutt**, Rajni Bansal
Chin. Phys. Lett. 2010, 27 (11): 112402 .   DOI: 10.1088/0256-307X/27/11/112402
Abstract   PDF(pc) (763KB) ( 537 )
By using a suitable set of the surface energy coefficient, nuclear radius, and universal function, the original proximity potential 1977 is modified. The overestimate of the data by 4% reported in the literature is significantly reduced. Our modified proximity potential reproduces the experimental data nicely compared to its older versions.
Theoretical Design of a 104MHz Ladder Type IH-RFQ Accelerator
NIE Yuan-Cun, LU Yuan-Rong**, CHEN Jia-Er, YAN Xue-Qing, GAO Shu-Li, ZHU Kun, LIU Ke-Xin, GUO Zhi-Yu
Chin. Phys. Lett. 2010, 27 (11): 112901 .   DOI: 10.1088/0256-307X/27/11/112901
Abstract   PDF(pc) (710KB) ( 503 )
Beam dynamics and rf designs of a 104 MHz ladder type IH-RFQ (L-IH-RFQ) accelerator are finished at Peking University for the acceleration of 14C+ from 40 keV to 500 keV. As a specific feature, the output beam energy spread is as low as 0.6% achieved with the internal discrete bunching method, which makes potential applications of RFQ feasible, such as accelerator mass spectrometry and ion implantation. Tolerances of the beam dynamics design are studied by means of changing the input beam parameters, and the results are quite satisfying. On the other hand, the L-IH-RFQ structure is employed, taking advantage of its mechanical stability and the absence of inter-electrode voltage asymmetry. Radio-frequency properties are studied and optimized for reducing power loss with Microwave Studio (MWS). Tuning of the field flatness and frequency is investigated in principle.
ATOMIC AND MOLECULAR PHYSICS
Coherent Population Trapping-Ramsey Interference in Cold Atoms
CHEN Xi, , YANG Guo-Qing, , WANG Jin, **, ZHAN Ming-Sheng,
Chin. Phys. Lett. 2010, 27 (11): 113201 .   DOI: 10.1088/0256-307X/27/11/113201
Abstract   PDF(pc) (532KB) ( 680 )
We demonstrate an experimental observation of coherent population trapping-Ramsey interference in cold 87Rb atoms by employing the time-domain separated oscillatory fields' method. The interference fringe with line width of 80 Hz is obtained. We propose a novel method to measure the cold atom number. The measurement is insensitive to the pump beam intensity, the single photon detuning and even the initial state population. We use this method to normalize the interference signal and to improve the signal-to-noise ratio significantly.
Time-Resolved Measurement of Radiatively Heated Iron 2p-3d Transmission Spectra
ZHAO Yang**, SHANG Wan-Li, XIONG Gang, JIN Feng-Tao, HU Zhi-Min, WEI Min-Xi, YANG Guo-Hong, ZHANG Ji-Yan, YANG Jia-Min
Chin. Phys. Lett. 2010, 27 (11): 113202 .   DOI: 10.1088/0256-307X/27/11/113202
Abstract   PDF(pc) (624KB) ( 413 )
An experimental measurement of radiatively heated iron plasma transmission spectra was performed on Shenguang II laser facility. In the measurement, the self−emission spectrum, the backlighting spectrum, and the absorption spectrum were imaged with a flat filed grating and recorded on a gated micro channel plate detector to obtain the time-resolved transmission spectra in the range 10-20 Å (approximately 0.6-1.3 keV). Experimental results are compared with the calculation results of an unsolved transition array (UTA) code. The time-dependent relative shift in the positions of the 2p-3d transmission array is interpreted in terms of the plasma temperature variations.
Optically Forbidden Transition of A'3Δu ← X3Σg-in Oxygen
ZHU Lin-Fan**, XU Wei-Qing, SUN Jian-Min***, ZHANG Wen-Yao
Chin. Phys. Lett. 2010, 27 (11): 113301 .   DOI: 10.1088/0256-307X/27/11/113301
Abstract   PDF(pc) (630KB) ( 396 )
The electron energy loss spectra for the valence-shell excitations of oxygen are measured at an incident electron energy of 2500 eV and at scattering angles from 4° to 8.5°. The dipole−forbidden and octupole-allowed transition of the A'3Δu ←X3Σg- is observed from the measured spectra, and it is found that the peak profile of the A'3Δu ←X3Σg excitation can be well represented by a Gaussin function. The energy position of 6.007±0.008 eV and Franck−Condon linewidth of 1.312±0.020 eV of the A'3Δu ←X3Σg, which are independent of the scattering condition, have been determined for the first time. The peak profiles of the A'3Δu ←X3Σg determined in this work provide a possibility to realize the spectral decomposition method of unfolding the Herzberg pseudocontinuum proposed by Campbell ıt et al. [Phys. Rev. A 61 (2000) 022706]
Differential and Integral Cross Sections for Electron Impact Excitation of Lithium
YANG Ning-Xuan**, JIANG Jun, DONG Chen-Zhong,
Chin. Phys. Lett. 2010, 27 (11): 113401 .   DOI: 10.1088/0256-307X/27/11/113401
Abstract   PDF(pc) (600KB) ( 423 )
The differential and integral cross sections for electron impact excitation of lithium from the ground state 1s22s to excited states 1s22p, 1s23l (l=s, p, d) and 1s24l (l=s, p, d, f)at incident energies ranging from 5 eV to 25 eV are calculated by using a full relativistic distorted wave method. The target state wavefunctions are calculated by using the Grasp92 code. The continuum orbitals are computed in the distorted-wave approximation, in which the direct and exchange potentials among all the electrons are included. A part of the cross sections are compared with the available experimental data and with the previous theoretical values. It is found that, for the integral cross sections, the present calculations are in good agreement with the time-independent distorted wave method calculation, for differential cross sections, our results agree with the experimental data very well.
erent Phase Control in e-Ar Scattering in a Bichromatic Laser Field in the Second Born Approximation
ZHOU Bin**, LI Shu-Min,
Chin. Phys. Lett. 2010, 27 (11): 113402 .   DOI: 10.1088/0256-307X/27/11/113402
Abstract   PDF(pc) (519KB) ( 352 )
We study the elastic scattering of atomic argon by an electron in the presence of a bichromatic laser field in the second Born approximation. The target atom is approximated by a simple screening potential. We explore the dependences of the differential cross sections on the relative phase φ between the two components of the radiation field and discuss the influence of the number of photons exchanged on the phase-dependence effect. Moreover, for different scattering angles and incident electron energies, the differential cross sections are notably different.
Proton Inelastic Mean Free Path in a Group of Organic Materials in 0.05-10MeV Range
TAN Zhen-Yu**, XIA Yue-Yuan, ZHAO Ming-Wen, LIU Xiang-Dong
Chin. Phys. Lett. 2010, 27 (11): 113403 .   DOI: 10.1088/0256-307X/27/11/113403
Abstract   PDF(pc) (456KB) ( 542 )
Inelastic mean free paths (MFPs) of 0.05-10 MeV protons in a group of 10 organic compounds are systematically calculated. The calculations are based on the method newly derived from the Ashley optical-data model and from the higher-order correction terms in stopping power calculations. Especially, in this method the new and empirical Bloch correction for the inelastic MFP is given. An evaluation for the optical energy loss function is incorporated into the present calculations because of the lack of available experimental optical data for the considered organic compounds expect for kapton. The proton inelastic MFPs for these 10 organic compounds in the energy range from 0.05 to 10 MeV are presented here for the first time, and the combination of these inelastic MFP data and our previous data of stopping power calculation for these bioorganic compounds may form a useful database for Monte Carlo track-structure studies of various radiation effects on these materials.
Single-Electron Detachment for Ti-, Fe-, Co-, Ni-, and Cu-, in Collision with Ar
BAI Xue, ZHAO Jun, WEI Bao-Ren, ZHANG Xue-Mei, **
Chin. Phys. Lett. 2010, 27 (11): 113404 .   DOI: 10.1088/0256-307X/27/11/113404
Abstract   PDF(pc) (482KB) ( 352 )
By using the micro-channel plate position sensitive detector with the delay-line anode we measure the single electron detachment cross sections for some transition elements in collision with Ar in the energy region 10-30 keV. These single electron detachment cross sections perform as velocity and electron affinity dependences. The experiments are carried out using the growth rate method.
FUNDAMENTAL AREAS OF PHENOMENOLOGY(INCLUDING APPLICATIONS)
(2+1)-Dimensional Envelope Solitons in Nonlinear Magnetic Metamaterials
CUI Wei-Na, ZHU Yong-Yuan**, LI Hong-Xia, LIU Su-Mei
Chin. Phys. Lett. 2010, 27 (11): 114101 .   DOI: 10.1088/0256-307X/27/11/114101
Abstract   PDF(pc) (385KB) ( 326 )
The dynamics of nonlinear magnetoinductive waves in a two-dimensional monoatomic lattice of Split ring resonators (SRRs) with Kerr nonlinear interaction between nearest neighbors is studied analytically. The soliton excitation genuine of the discreteness and nonlinearity in such a system based on an extended quasidiscreteness approach are obtained.
High Characteristic Temperature InGaAsP/InP Tunnel Injection Multiple-Quantum-Well Lasers
WANG Yang**, QIU Ying-Ping, PAN Jiao-Qing, ZHAO Ling-Juan, ZHU Hong-Liang, WANG Wei
Chin. Phys. Lett. 2010, 27 (11): 114201 .   DOI: 10.1088/0256-307X/27/11/114201
Abstract   PDF(pc) (541KB) ( 772 )
We fabricate 1.5 μm InGaAsP/InP tunnel injection multiple−quantum-well (TI-MQW) Fabry-Perot (F-P) ridge lasers. The laser heterostructures, including an inner cladding layer and an InP tunnel barrier layer, are grown by metal-organic chemical-vapor deposition (MOCVD). Characteristic temperature T0 of 160 K at 20°C is obtained for 500−μm−long lasers. T0 is measured as high as 88 K in the temperature range of 15−75°C. Cavity length dependence of T0 is investigated.
High Power Continuous-Wave Actively Mode-Locked Diode-Pumped Nd:YAG Laser
LING Wei-Jun, **, ZHANG Shao-Gang, ZHANG Ming-Xia, DONG Zhong, LI Ke, ZUO Yin-Yan, GUO Xiao-Hua, JIA Yu-Lei
Chin. Phys. Lett. 2010, 27 (11): 114202 .   DOI: 10.1088/0256-307X/27/11/114202
Abstract   PDF(pc) (565KB) ( 413 )
We demonstrate a diode-pumped cw mode-locked Nd:YAG by an acousto-optic mode locker. A mode-locked pulse with duration of 345 ps and output power of 12 W is obtained. The resonator design shows three advantages: a larger mode volume, high stability against thermal lens fluctuations, and excellent beam quality with TE00 mode. Different from previous active mode locking designs, we employ a frequency stabilizer and a phase-lock loop circuit to ensure the mode locking stable operation.
LD Side-Pumped Passive Mode-Locked TEM_00 Nd:YAG Laser Based on SESAM
ZHANG Ling**, GUO Lin, XIONG Bo, YU Hai-Juan, SUN Lu, HOU Wei, LIN Xue-Chun, LI Jin-Min
Chin. Phys. Lett. 2010, 27 (11): 114203 .   DOI: 10.1088/0256-307X/27/11/114203
Abstract   PDF(pc) (711KB) ( 701 )
We report an LD side-pumped continuous-wave passive mode-locked Nd:YAG laser with a Z-type folded cavity based on a semiconductor saturable absorber mirror (SESAM). The average output power 2.95 W of mode-locked laser with electro-optical conversion efficiency of 1.3% and high beam quality (Mx2=1.25 and My2=1.22) is achieved. The repetition rate of mode-locked pulse of 88 MHz with pulse energy of 34 nJ is obtained.
Laser-Diode End-Pumped Nd:YVO4 Slab Laser under Direct Pumping into the Emitting Level
CUI Li, ZHANG Heng-Li**, XU Liu, LI Jing, YAN Ying, DUAN Can, SHA Peng-Fei, XIN Jian-Guo
Chin. Phys. Lett. 2010, 27 (11): 114204 .   DOI: 10.1088/0256-307X/27/11/114204
Abstract   PDF(pc) (529KB) ( 1314 )
We present an 880-nm laser-diode partially end-pumped Nd:YVO4 slab cw laser with output 126.7 W by using a hybrid resonator. The slop efficiency and optical-to-optical efficiency with respect to absorbed pumping power are 73.2% and 58.7%, respectively. At the output power of 100 W, the beam propagation M2 factors are 1.1 in the unstable direction and 1.15 in the stable direction.
Laser Damage Mechanisms of Amorphous Ta2O5 Films at 1064, 532 and 355nm in One-on-One Regime
XU Cheng**, QIANG Ying-Huai, ZHU Ya-Bo, GUO Li-Tong, SHAO Jian-Da, FAN Zheng-Xiu
Chin. Phys. Lett. 2010, 27 (11): 114205 .   DOI: 10.1088/0256-307X/27/11/114205
Abstract   PDF(pc) (736KB) ( 582 )
Ta2O5 films are deposited on fused silica substrates by conventional e−beam evaporation. Surface topography and chemical composition are examined by atomic force microscopy (AFM) and x-ray photoelectron spectroscopy (XPS). The calculation of electron structures of Ta2O5 and Ta2O5−x is attempted using a first-principle pseudopotential method within the local density approximation. The laser-induced damage threshold (LIDT) is performed at 1064, 532 and 355 nm in 1-on-1 regime, respectively. The results show that the LIDT increases with the wavelength increasing, which is in agreement with the wavelength effect. However, the LIDT results are not consistent with the empirical equation (I(λ)=aλm), which may be attributed to the intrinsic absorption of Ta2O5 at the wavelengths of 532 or/and 355 nm. Moreover, different damage morphologies are observed when the films are irradiated at different wavelengths. It is concluded that the laser damage at 1064 nm is the defect dominant mechanism and at 355 nm it is the intrinsic absorption dominant mechanism, whereas at 532 nm it is the combined defect and intrinsic absorption dominant mechanism.
Electrical Property of Infrared-Sensitive InAs Solar Cells
DENG Hui-Yong**, WANG Qi-Wei, TAO Jun-Chao, WU Jie, HU Shu-Hong, CHEN Xin, DAI Ning***
Chin. Phys. Lett. 2010, 27 (11): 114206 .   DOI: 10.1088/0256-307X/27/11/114206
Abstract   PDF(pc) (632KB) ( 428 )
InAs infrared-sensitive solar cells are fabricated by using the films grown by the liquid phase epitaxy technique. The film microstructures are characterized by x-ray diffraction and scanning electronic microscopy. The current-voltage characteristics of the solar cells in the dark and under AM1.5 illumination at 300 K and 77 K are discussed. The conversion efficiency of p-InAs/n-sub InAs cells decreases when the thickness of the p-type film changes from 1.7 μm to 3.5 μm, which is caused by the reduced effective photons near p−n junction. The p-InAs/n-InAs/n-sub InAs solar cell with the conversion efficiency of 7.43% in 1-2.5 μm under AM1.5 at 77 K is obtained. The short circuit current density increases dramatically with decreasing temperature due to the weakened effect of phonon scattering.
Analysis of Detectors and Transmission Curve Correction of Mobile Rayleigh Doppler Wind Lidar
TANG Lei**, WANG Yong-Tao, SHU Zhi-Feng, DONG Ji-Hui, WANG Guo-Cheng, XU Wen-Jing, HU Dong-Dong, CHEN Ting-Di, DOU Xian-Kang, SUN Dong-Song, CHA Hyunki
Chin. Phys. Lett. 2010, 27 (11): 114207 .   DOI: 10.1088/0256-307X/27/11/114207
Abstract   PDF(pc) (761KB) ( 450 )
A mobile molecular Doppler wind lidar (DWL) based on double-edge technique is presented for wind measurement at altitudes from 10 km to 40 km. A triple Fabry-Perot etalon is employed as a frequency discriminator to determine the Doppler shift proportional to the wind velocity. The lidar operates at 355 nm with a 45-cm aperture telescope and a matching azimuth-over-elevation scanner that can provide full hemispherical pointing. In order to guarantee the wind accuracy, different forms of calibration function of detectors in different count rates response range would be especially valuable. The accuracy of wind velocity iteration is improved greatly because of application of the calibration function of linearity at the ultra low light intensity especially at altitudes from 10 km to 40 km. The calibration functions of nonlinearity make the transmission of edge channel 1 and edge channel 2 increase 38.9% and 27.7% at about 1 M count rates, respectively. The dynamic range of wind field measurement may also be extended because of consideration of the response function of detectors in their all possible operating range.
A Novel Ce3+/Tb3+ Codoped Phosphate Glass as Down-Shifting Materials for Enhancing Efficiency of Solar Cells
HE Dong-Bing, **, YU Chun-Lei, CHENG Ji-Meng, LI Shun-Guang, HU Li-Li
Chin. Phys. Lett. 2010, 27 (11): 114208 .   DOI: 10.1088/0256-307X/27/11/114208
Abstract   PDF(pc) (526KB) ( 575 )
For the purpose of improving conversion efficiency of solar cells by applying the effect of the wavelength conversion of rare earth ions, photo-luminescence and excitation spectrums of Ce3+−Tb3+ doped phosphate glass are investigated. Results show that incorporating Ce3+ ions to Tb3+−doped phosphate glass can greatly increase the absorption coefficient in the range 300-400 nm and then the energy transfer (ET) from Ce3+ to Tb3+ occurs. In addition, increasing Tb3+ concentration in Ce3+/Tb3+ co−doped phosphate glass can greatly enhance the ET efficiency and 545 nm emission intensity. This shows that Ce3+/Tb3+ co-doped phosphate glass would be a promising down-shifting material for enhancing the efficiency of solar cells.
Giant Enhancement of Second Harmonic Generation at Photonic Band Gap Edges
MA Dong-Li, REN Ming-Liang, DOU Jun-Hong, LI Zhi-Yuan**
Chin. Phys. Lett. 2010, 27 (11): 114209 .   DOI: 10.1088/0256-307X/27/11/114209
Abstract   PDF(pc) (554KB) ( 438 )
Second harmonic generation (SHG) in one-dimensional nonlinear photonic crystals made from periodically alternating ferroelectric and dielectric layers is investigated by means of the transfer matrix method. When tuned at the photonic band gap (PBG) edges, the fundamental wave and second harmonic wave slow down, and the filed enhancement takes place within the nonlinear photonic crystal. The phase mismatching can be compensated for to some extent and the second harmonic process will be enhanced. Numerical results show that the enhancement of SHG in the PBG structure can be up to four orders of magnitude compared with the traditional quasi-phase-matching structure.
Theoretical Study on a Cluster-Seven-Core Photonic Crystal Fiber with High Nonlinearity and High-Power Endurance
CHENG Tong-Lei, CHAI Lu**, HU Ming-Lie, LI Yan-Feng, WANG Ching-Yue
Chin. Phys. Lett. 2010, 27 (11): 114210 .   DOI: 10.1088/0256-307X/27/11/114210
Abstract   PDF(pc) (533KB) ( 528 )
We present a novel cluster-seven-core photonic crystal fiber which possesses high nonlinearity and supports the high-power pumping. Its nonlinearity coefficient and effective mode area are calculated by the full vector multipole method. Compared with the single core PCF, the cluster-seven-core photonic crystal fiber can support high-power beam transmitting in the core, and simultaneously has high nonlinearity. This kind of photonic crystal fiber can be applied to the photoelectron-device field.
A Novel Photonic Quasicrystal Fiber with Broadband Large Negative Dispersion
LI Yu-He, FAN Wan-De**, SHENG Qiu-Qin
Chin. Phys. Lett. 2010, 27 (11): 114211 .   DOI: 10.1088/0256-307X/27/11/114211
Abstract   PDF(pc) (489KB) ( 617 )
A broadband highly dispersive fiber based on a dual-concentric-core photonic quasicrystal fiber (PQF) is designed for chromatic dispersion compensation. The fiber is composed of pure silica background and air-holes without doping. The fundamental supermode has a large negative dispersion value of about 9600 psnm−1km−1 over an optical communication band around 1550 nm and a full width at half maximum (FWHM) of 40 nm. By adjusting the structural parameters, a dispersion of 2250 psnm−1km−1 around 1550 nm with the FWHM exceeding 280 nm is obtained and the dispersion-bandwidth product can reach 630 GHz−1km−1, which is the highest value of dispersion-bandwidth product from pure silica fibers reported so far.
Time-Domain Measurement of Optical True-Time Delay in Two-Dimensional Photonic Crystal Waveguides
ZHANG Geng-Yan, ZHOU Qiang, CUI Kai-Yu, ZHANG Wei, HUANG Yi-Dong**
Chin. Phys. Lett. 2010, 27 (11): 114212 .   DOI: 10.1088/0256-307X/27/11/114212
Abstract   PDF(pc) (542KB) ( 543 )
We report on the realization of optical true-time delay (TTD) by a two-dimensional photonic crystal waveguide (PCWG). Design and fabrication of the PCWG are investigated. The spectral dependence of the group delay is measured by detecting the phase shifts of a 10 GHz modulating signal, and a maximum delay of 25±2.5 ps is obtained.
A Clock Enhanced Loop for Simultaneous Error-Free Demultiplexing and Clock Recovery of 160Gb/s OTDM Signal Single-Channel Transmission over 100km
JIA Nan**, LI Tang-Jun, ZHONG Kang-Ping, WANG Mu-Guang, CHEN Ming, LI Jing, CHI Jian-Feng
Chin. Phys. Lett. 2010, 27 (11): 114213 .   DOI: 10.1088/0256-307X/27/11/114213
Abstract   PDF(pc) (972KB) ( 435 )
A simple clock enhanced loop of cascaded electro-absorption modulators (EAMs) and 10 GHz clock recovery modules is presented. The intensity of harmonic of clock-frequency component is analyzed theoretically and verified experimentally in a 160 Gb/s OTDM 100 km transmission system. The 10 GHz clock component is enhanced obviously before launching into the clock recovery module and the recovered clock signal exhibits low rms jitter of <400 fs. Moreover, completely error−free (10-12) transmission is observed for more than two hours without using forward error correction technology. The power penalty is about 3.6 dB. The proposed loop has merits of enhancing base clock component, simultaneously de-multiplexing and clock recovery, which make the performance of this loop more stable and high suppression of non-target channels.
Surface Emitting Distributed Feedback Quantum Cascade Laser around 8.3 μm
GUO Wan-Hong, LIU Jun-Qi**, LU Quan-Yong, ZHANG Wei, JIANG Yu-Chao, LI Lu, WANG Li-Jun, LIU Feng-Qi, WANG Zhan-Guo
Chin. Phys. Lett. 2010, 27 (11): 114214 .   DOI: 10.1088/0256-307X/27/11/114214
Abstract   PDF(pc) (690KB) ( 508 )
We demonstrate surface emitting distributed feedback quantum cascade lasers emitting at wavelengths from 8.1 μm at 90 K to 8.4 μm at 210 K. The second−order metalized grating is carefully designed using a modified coupled-mode theory and fabricated by contact lithography. The devices show single mode behavior with a side mode suppression ratio above 18 dB at all working temperatures. At 90 K, the device emits an optical power of 101 mW from the surface and 199 mW from the edge. In addition, a double-lobe far-field pattern with a separation of 2.2° is obtained in the direction along the waveguide.
Theoretical and Experimental Investigation of Flexural Wave Propagating in a Periodic Pipe with Fluid-Filled Loading
WEN Ji-Hong**, SHEN Hui-Jie, YU Dian-Long, WEN Xi-Sen
Chin. Phys. Lett. 2010, 27 (11): 114301 .   DOI: 10.1088/0256-307X/27/11/114301
Abstract   PDF(pc) (639KB) ( 1364 )
Based on the Bragg scattering mechanism of phononic crystals (PCs), a periodic composite material pipe with fluid loading is designed and studied. The band structure of the flexural wave in the periodic pipe is calculated with the transfer matrix (TM) method. A periodic piping experimental system is designed, and the vibration experiment is performed to validate the attenuation ability of the periodic pipe structure. Finally, a finite-element pipe model is constructed using the MSC-Actran software, and the calculated results match well with the vibration experiment. The errors between the theoretical calculation results and the vibration experimental results are analyzed.
Three-Dimensional Mode Coupling around a Conical Seamount and the Use of Random Discretization
LUO Wen-Yu**, SCHMIDT Henrik
Chin. Phys. Lett. 2010, 27 (11): 114302 .   DOI: 10.1088/0256-307X/27/11/114302
Abstract   PDF(pc) (596KB) ( 359 )
Three-dimensional mode coupling around a conical seamount in an ocean waveguide is studied. It is shown that strong mode coupling occurs at the edge of a conical seamount for the incident normal modes with significant amplitudes below the top of the seamount. Therefore, mode coupling is critical for the investigation of the acoustic field around a seamount. In addition, we suggest the use of random discretization for representing smoothly varying bathymetry. For the use of uniform discretization, when the horizontal step size is greater than half of the wavelength, artificial diffraction lobes appear due to coherent backscatter. However, by using the random discretization scheme instead, such artificial diffraction lobes are diffused, resulting in a faster convergence rate.
Matched Bearing Processing for Airborne Source Localization by an Underwater Horizontal Line Array
PENG Zhao-Hui**, LI Zheng-Lin, WANG Guang-Xu,
Chin. Phys. Lett. 2010, 27 (11): 114303 .   DOI: 10.1088/0256-307X/27/11/114303
Abstract   PDF(pc) (1218KB) ( 465 )
Location of an airborne source is estimated from signals measured by a horizontal line array (HLA), based on the fact that a signal transmitted by an airborne source will reach a underwater hydrophone in different ways: via a direct refracted path, via one or more bottom and surface reflections, via the so-called lateral wave. As a result, when an HLA near the airborne source is used for beamforming, several peaks at different bearing angles will appear. By matching the experimental beamforming outputs with the predicted outputs for all source locations, the most likely location is the one which gives minimum difference. An experiment is conducted for airborne source localization in the Yellow Sea in October 2008. An HLA was laid on the sea bottom at the depth of 30m. A high-power loudspeaker was hung on a research ship floating near the HLA and sent out LFM pulses. The estimated location of the loudspeaker is in agreement well with the GPS measurements.
Active Mixing in a Microchannel
GUO Chun-Hai**, TAN Jun-Jie***, REN Deng-Feng, ZHANG Yu-Cheng, WANG Fu-Hua
Chin. Phys. Lett. 2010, 27 (11): 114701 .   DOI: 10.1088/0256-307X/27/11/114701
Abstract   PDF(pc) (586KB) ( 608 )
We investigate a minute magneto hydro-dynamic mixer with relatively rapid mixing enhancement experimentally and analytically. The mixer is fabricated with brass and polymethyl methacrylate (PMMA) layers. A secondary flow is generated by using the Lorentz force in the fluids. The efficiency of mixing is greatly improved due to the large increase of the contact area between two mixing fluids. The micro particle image velocimetry technique is employed to measure the fluid flow characteristics in the micro-channel. Numerical simulation is performed based on the theoretical model of the computational fluid dynamics and the electromagnetic field theory. The experimental results are in good agreement with the numerical results, which indicates that the mixing area is enlarged by the driving of Lorentz force and the mixing can be enhanced.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES
Numerical Studies of s-Polarized Surface Plasmon Polaritons at the Interface Associated with Metamaterial
YAN Bao-Rong, LV Jian-Hong, KONG Ling-Hua, HU Xi-Wei**
Chin. Phys. Lett. 2010, 27 (11): 115101 .   DOI: 10.1088/0256-307X/27/11/115101
Abstract   PDF(pc) (533KB) ( 418 )
The s-polarized surface plasmon polaritons (SPPs) at the interface between dielectric and metamaterial are studied, and the dispersion relations of SPPs are also presented. Using the prism coupling mechanism, we obtain the attenuated total reflection (ATR) spectra in the frequency regime based on the Otto configuration. It is found that the thickness of the dielectric in the configuration and the small damping of the metamaterial affect the coupling strength significantly without changing the coupling frequency. Furthermore, the optimized thickness of the dielectric decreases with a larger damping, and the coefficient F of the metamaterial also determines the coupling frequency and strength.
Structures and Dynamics of Two-Dimensional Dust Lattices with and without Coulomb Molecules in Plasmas
HUANG Feng**, LIU Yan-Hong, YE Mao-Fu, WANG Xue-Jin, WANG Long
Chin. Phys. Lett. 2010, 27 (11): 115201 .   DOI: 10.1088/0256-307X/27/11/115201
Abstract   PDF(pc) (779KB) ( 356 )
Structures and dynamics of two-dimensional dust lattices with and without Coulomb molecules in plasmas are investigated. The experimental results show that the lattices have the crystal-like hexagonal structures, i.e. most particles have six nearest-neighboring particles. However, the lattice points can be occupied by the individual particles or by a pair of particles called Coulomb molecules. The pair correlation function is used to compare the structures between the lattices with or without the Coulomb molecules. In the experiments, the Coulomb molecules can also decompose and recombine with another individual particle to form a new molecule.
CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES
Fragile-to-Strong Transition in Al-Ni-M (M=La, Pr, Nd) Metallic Glasses
ZHANG Chun-Zhi, HU Li-Na**, BIAN Xiu-Fang, YUE Yuan-Zheng,
Chin. Phys. Lett. 2010, 27 (11): 116401 .   DOI: 10.1088/0256-307X/27/11/116401
Abstract   PDF(pc) (503KB) ( 484 )
We study the dynamic behavior of marginal metallic glass-forming liquids Al-Ni-M (M=La, Pr, Nd) in terms of liquid fragility in high and low temperature regions. The liquids are extremely fragile above the liquidus temperature T liq, but become rather strong near the glass transition temperature Tg. The strength of the transition is inversely correlated with the fragility index at Tg. This relation is discussed in terms of potential energy landscape.
Production of ZnO Nanobelts and Meso-Scale Study of Mechanical Properties
NI Heng-Kan, ZOU Qiang**, FU Xing, WU Sen, WANG Hui, XUE Tao
Chin. Phys. Lett. 2010, 27 (11): 116801 .   DOI: 10.1088/0256-307X/27/11/116801
Abstract   PDF(pc) (774KB) ( 467 )
We investigate a peculiar phenomenon by processing ZnO nanobelts with an atomic force microscope (AFM). In the contact mode of AFM, peculiar bending occurs in meso-scale when the nanobelt is applied with force in lateral direction. We study the mechanical properties of ZnO nanobelts under the influence of small size effect, with finite element analysis and mathematical analysis by means of Matlab. Based on this abnormal effect, a novel measuring method is proposed, which allows the surface morphology and surface properties to be characterized at the same time.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
Effect of Dopant Properties on the Microstructures and Electrical Characteristics of Poly(3-Hexylthiophene) Thin Films
MA Liang**
Chin. Phys. Lett. 2010, 27 (11): 117301 .   DOI: 10.1088/0256-307X/27/11/117301
Abstract   PDF(pc) (676KB) ( 480 )
Effects of dopant properties on microstructures and the electrical characteristics of poly (3-hexylthiophene) (P3HT) films are studied by doping 0.1 wt% 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4−TCNQ), 6,6-phenyl-C61butyric acid methyl ester (PCBM) and N,N'−Diphenyl-N,N'-(m-tolyl)-benzidine (TPD) into P3HT, respectively. The introductions of various dopants in small quantities increase the field-effect mobility and the I on/Ioff ratio of P3HT thin-film transistors. However, each of dopants shows various effects on the crystalline order and the molecular orientation of P3HT films and the performance of P3HT thin-film transistors. These can be attributed to the various size, shape and energy-level properties of the dopants.
Enhancement of Critical Current Density and Flux Pinning in Acetone and La2O3 Codoped MgB2 Tapes
GAO Zhao-Shun, MA Yan-Wei**, WANG Dong-Liang, ZHANG Xian-Ping, AWAJI Satoshi, WATANABE Kazuo
Chin. Phys. Lett. 2010, 27 (11): 117401 .   DOI: 10.1088/0256-307X/27/11/117401
Abstract   PDF(pc) (786KB) ( 331 )
MgB2 tape samples with simultaneous additions of acetone and La2O3 were prepared by an in−situ processed powder-in-tube method. Compared to the pure and single doped tapes, both transport Jc and fluxing pinning are greatly improved by acetone and La2O3 codoping. Acetone supplies carbon into the MgB2 crystal lattice and increases the upper critical field, while the La2O3 reacts with B to form LaB6 nanoparticles as effective flux pining centers. The improvement of the superconducting properties in codoped tapes can be attributed to the combined effects of improvement in Hc2 and flux pinning.
Magnetic Properties of Ni-Zn Ferrite Prepared with the Layered Precursor Method
ZHOU Xin, HOU Zhi-Ling, LI Feng, QI Xin**
Chin. Phys. Lett. 2010, 27 (11): 117501 .   DOI: 10.1088/0256-307X/27/11/117501
Abstract   PDF(pc) (554KB) ( 751 )
We prepare NiZnFe2O4 soft magnetic ferrites with different molar ratios with the layered precursor method and investigate their magnetic properties. In the layered precursor, metal ions are scattered on the layer plate in a certain way on account of the effect of lowest lattice energy and lattice orientation. After high temperature calcinations, spinel ferrites with uniform structural component and single magnetic domain can be obtained, and the magnetic property is improved greatly. NiZnFe2O4 ferrites prepared have the best specific saturation magnetization of 79.15 emug−1, higher than that of 68 emug−1 prepared by the chemical co-precipitation method and that of 59 emug−1prepared by the emulsion-gel method. Meanwhile the coercivity of NiZnFe2O4 ferrites prepared by layered precursor method is 14 kAm−1, lower than that of 50 emug−1 prepared by the co-precipitation method and that of 59 emug−1 prepared by the emulsion-gel method.
Excellent Magnetocaloric Effect in Er60Al18Co22 Bulk Metallic Glass
HUI Xi-Dong**, XU Zhi-Yi, WANG En-Rui, CHEN Guo-Liang, LU Zhao-Ping
Chin. Phys. Lett. 2010, 27 (11): 117502 .   DOI: 10.1088/0256-307X/27/11/117502
Abstract   PDF(pc) (773KB) ( 399 )
Excellent magnetocaloric effect with a maximum entropy change and refrigeration capacity of 17.6 Jkg−1⋅K−1 and 546 Jkg−1, respectively, has been discovered in the Er60Al18Co22 bulk metallic glass under the field of 50 kOe in the temperature range of helium liquefaction. This MCE results from the second-order magnetic transition from the paramagnetic to the ferromagnetic state. Our analysis based on mean-field theory suggests that the excellent MCE is attributed to the strong exchange of magnetic moment in the glassy structure.
Evolution of Structural and Magnetic Properties of BaFe12O19 with B2O3 Addition
Ugur Topal**
Chin. Phys. Lett. 2010, 27 (11): 117503 .   DOI: 10.1088/0256-307X/27/11/117503
Abstract   PDF(pc) (885KB) ( 924 )
We investigate the effects of B2O3 addition on structural and magnetic properties of hard magnetic BaFe12O19 particles. The conventional solid state reaction method is used as the synthesis route. Single phase BaFe12O19 could be synthesized with very small amounts of B2O3 addition and with calcination at low temperatures (850°C) in short times (1 h). B2O3 addition also improves the magnetic parameters significantly. Remanence magnetization and specific magnetization at 1.5 T increase by ∼40% in magnitude although no significant variations on coercivity is observed.
Inverted Bottom-Emission Organic Light Emitting Diode Using Two n-Doped Layers for the Enhanced Performance
CHENG Cui-Ran, CHEN Yu-Huan, QIN Da-Shan**, QUAN Wei, LIU Jin-Suo
Chin. Phys. Lett. 2010, 27 (11): 117801 .   DOI: 10.1088/0256-307X/27/11/117801
Abstract   PDF(pc) (556KB) ( 597 )
We fabricate an inverted bottom-emission organic light emitting diode (IBOLED) employing two n-doped layers, i.e., 5 nm lithium carbonate doped PTCDA (1:2 Li2CO3:PTCDA) with 5 nm Li2CO3 doped BCP (1:4 Li2CO3:BCP) on top, where PTCDA and BCP stand for 3, 4, 9, 10 perylenetetracarboxylic dianhydride and bathcuporine, respectively. Compared to the IBOED using a layer of 10 nm 1:4 Li2CO3:BCP, the one utilizing the two-layer combination of 5 nm 1:2 Li2CO3:PTCDA and 5 nm 1:4 Li2CO3:BCP shows decreasing operation voltage and thereby increasing power efficiency, mainly attributed to the higher electron conductivity of 1:2 Li2CO3:PTCDA than that of 1:4 Li2CO3:BCP. The mechanism of the electron transport through the interface of 1:2 Li2CO3:PTCDA and 1:4 Li2CO3:BCP is also discussed. We provide a simply and effective structure to enhance the current conduction for IBOLEDs.
Planar Metamaterial Absorber Based on Lumped Elements
GU Chao, QU Shao-Bo, **, PEI Zhi-Bin, ZHOU Hang, XU Zhuo, BAI Peng, PENG Wei-Dong, LIN Bao-Qin
Chin. Phys. Lett. 2010, 27 (11): 117802 .   DOI: 10.1088/0256-307X/27/11/117802
Abstract   PDF(pc) (1112KB) ( 675 )
We present the design of a planar metamaterial absorber based on lumped elements, which shows a wide-band polarization-insensitive and wide-angle strong absorption. This absorber consists of metal electric resonators, the dielectric substrate, the metal film and lumped elements. The simulated absorbances under two different loss conditions indicate that high absorbance in the absorption band is mainly due to lumped resistances. The simulated absorbances under three different load conditions indicate that the local resonance circuit (lumped resistance and capacitance) could boost up the resonance of the whole RLC circuit. The simulated voltage in lumped elements indicates that the transformation efficiency from electromagnetic energy to electric energy in the absorption band is high, and electric energy is subsequently consumed by lumped resistances. This absorber may have potential applications in many military fields.
CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY
Effect of In Composition on Two-Dimensional Electron Gas in Wurtzite AlGaN/InGaN Heterostructures
KIM Bong-Hwan**, PARK Seoung-Hwan***, LEE Jung-Hee, MOON Yong-Tae
Chin. Phys. Lett. 2010, 27 (11): 118501 .   DOI: 10.1088/0256-307X/27/11/118501
Abstract   PDF(pc) (534KB) ( 507 )
The effect of In composition on two-dimensional electron gas in wurtzite AlGaN/InGaN heterostructures is theoretically investigated. The sheet carrier density is shown to increase nearly linearly with In mole fraction x, due to the increase in the polarization charge at the AlGaN/InGaN interface. The electron sheet density is enhanced with the doping in the AlGaN layer. The sheet carrier density is as high as 3.7×1013 cm−2 at the donor density of 10×1018 cm−3 for the HEMT structure with x=0.3. The contribution of additional donor density on the electron sheet density is nearly independent of the In mole fraction.
InAlAs/InGaAs Pseudomorphic High Eelectron Mobility Transistors Grown by Molecular Beam Epitaxy on the InP Substrate
HUANG Jie, **, GUO Tian-Yi, ZHANG Hai-Ying, XU Jing-Bo, FU Xiao-Jun, YANG Hao, NIU Jie-Bin
Chin. Phys. Lett. 2010, 27 (11): 118502 .   DOI: 10.1088/0256-307X/27/11/118502
Abstract   PDF(pc) (624KB) ( 427 )
A novel PMMA/PMGI/ZEP520 trilayer resist electron beam lithograph (EBL) technology is successfully developed and used to fabricate the 150 nm gate-length In0.7Ga0.3As/In0.52Al0.48As Pseudomorphic HEMT on an InP substrate, of which the material structure is successfully designed and optimized. A perfect profile of T−gate is successfully obtained. These fabricated devices demonstrate excellent dc and rf characteristics: the transconductance Gm, maximum saturation drain−to-source current IDSS, threshold voltage VT, maximum current gain frequency fT derived from h21, maximum frequency of oscillation derived from maximum available power gain/maximum stable gain and from unilateral power−gain of metamorphic InGaAs/InAlAs high electron mobility transistors (HEMTs) are 470 mS/mm, 560 mA/mm, -1.0 V, 76 GHz, 135 GHz and 436 GHz, respectively. The excellent high frequency performances promise the possibility of metamorphic HEMTs for millimeter-wave applications.
Influences of Interface States on Resistive Switching Properties of TiOx with Different Electrodes
JIA Ze**, WANG Lin-Kai, REN Tian-Ling
Chin. Phys. Lett. 2010, 27 (11): 118503 .   DOI: 10.1088/0256-307X/27/11/118503
Abstract   PDF(pc) (652KB) ( 490 )
Different TiOx thin films prepared by graded or sufficient oxidization of Ti are applied with Pt or Ag electrode in metal−insulator-metal (MIM) structures for studying the properties and mechanisms of resistive switching. The differences on the mobile oxygen vacancies in TiOx films and different work functions of the electrode films result in different insulator-metal interface states, which are displayed as ohmic-like or non-ohmic contact. Based on the interface states, the electrical models for MIM devices are analyzed and extracted. The electrode-limited effect and the bulk-limited effect can be unified to explain the mechanisms for resistive switching behavior as the dominant effect respectively in various conditions. All the current-voltage curves of the four kinds of specimens measured in the experiments can be explained and proved in accordance with the theory.
Photon-Measurement Density Function of Fluorescence Molecular Tomography Based on Direct Method
QUAN Guo-Tao, GONG Hui, FU Jian-Wei, DENG Yong**
Chin. Phys. Lett. 2010, 27 (11): 118701 .   DOI: 10.1088/0256-307X/27/11/118701
Abstract   PDF(pc) (641KB) ( 321 )
Photon-measurement density function (PMDF), which is the kernel of fluorescence molecular tomography (FMT), largely determines the accuracy of reconstruction result of FMT. Based on the direct method, we propose an expression of PMDF in FMT, which is derived from the finite element method (FEM) solution of the diffusion equation. Compared with the traditional expression based on the perturbation method, the accuracy of expression based on the direct method is shown in theory. Lastly the reconstruction results of phantoms prove this accuracy in experiment.
An RNA Base Discrete State Model toward Tertiary Structure Prediction
ZHANG Jian**, ZHANG Yu-Jie, WANG Wei**
Chin. Phys. Lett. 2010, 27 (11): 118702 .   DOI: 10.1088/0256-307X/27/11/118702
Abstract   PDF(pc) (949KB) ( 327 )
We report a new ribonucleic acid (RNA) base discrete state model, which was first developed in our lab and designed to provide an efficient and accurate way of representing RNA structures toward RNA three-dimensional structure predictions. Since RNA free energy is largely determined by base pairs and base stackings instead of backbone trajectories, we directly model the RNA base configurations with respect to its previous one along the sequence. This is in sharp contrast with all previous works where the backbone trace was represented. To test how faithfully the discrete model can reproduce the chain trace in continuous space, we randomly select partial chains from the native structure of 23S ribosome RNA and re-grow them. The rms distance of the re-grown structures from the native ones is ∼1.7 Å for an optimized 16−state discrete model and gradually increases to ∼3.3 Å for long chains of length 50. The efficiency is also good, e.g. the program will finish within several tens of second for long loops of length 50. Our model may facilitate the RNA three-dimensional structure predictions in the near future when combined with appropriate free energy evaluation methods.
GEOPHYSICS, ASTRONOMY, AND ASTROPHYSICS
Is Low-Frequency-Peaked BL Lac Object OJ 287 a TeV Emitter?
CHEN Liang, **, BAI Jin-Ming,
Chin. Phys. Lett. 2010, 27 (11): 119501 .   DOI: 10.1088/0256-307X/27/11/119501
Abstract   PDF(pc) (507KB) ( 366 )
It is well known that there are only two low-frequency-peaked BL Lac objects (LBLs: BL Lacertae and S5 0716+714) and one flat spectrum radio quasar (FSRQ: 3C 279) among more than 30 active galactic nuclei (AGNs) with detected TeV emissions. We study the spectral energy distribution (SED) of a famous LBL OJ 287, whose light curve has a 12-y period. Using a homogeneous one-zone synchrotron + synchrotron-self Compton model, we model the quasi-simultaneous broad-band SED of OJ 287. With some reasonable assumptions, we extrapolate the model to the high state of OJ 287 and predict its γ−ray emissions. Taking into account the absorption of γ-ray by the extragalactic background light (EBL), we find that the TeV emission of OJ 287 in high state is slightly higher than the sensitivity of H.E.S.S. The study on SEDs of OJ 287 has implications to unveil the origin of jet activity during its 12-y period and the properties of EBL.
Model for Formation of Dunes at the North Martian Pole
ZHU Jie, CHEN Chu-Xin**
Chin. Phys. Lett. 2010, 27 (11): 119601 .   DOI: 10.1088/0256-307X/27/11/119601
Abstract   PDF(pc) (563KB) ( 358 )
The Mars Global Surveyor Mars Orbiter Camera (MOC) took images of a series of strange horseshoe-shaped dunes at the North Martian pole in 2004. These dunes would be formed due to the strong Martian winds whose pattern is different from that on the Earth. We study the cause of the formation of these dunes and make a model for them. In this model, wind speed near the north Martian pole can be evaluated based on the shape of the dunes. We also estimate the surpassing speed of dunes of different sizes.
Original Articles
Neutron Star Motion in the Disk Galaxy
WEI Ying-Chun, A. Taani**, PAN Yuan-Yue, WANG Jing, CAI Yan, LIU Gao-Chao, LUO A-Li, ZHANG Hong-Bo, ZHAO Yong-Heng
Chin. Phys. Lett. 2010, 27 (11): 119801 .   DOI: 10.1088/0256-307X/27/11/119801
Abstract   PDF(pc) (685KB) ( 432 )
The neutron star motions are based on the undisturbed finitely thick galactic disk gravitational potential model. Two initial conditions, i.e. the locations and velocities, are considered. The Monte Carlo method is employed to separate rich diversities of the orbits of neutron stars into several sorts. The Poincaré section has the potential to play an important role in the diagnosis of the neutron star motion. It has been observed that the increasing ratio of the motion range vertical to the galactic plane to that parallel to the galactic plane results in the irregularity of neutron star motion.
58 articles