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Volume 29 Issue 1
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Symmetry and Period-Adding Windows in a Modified Optical Injection Semiconductor Laser Model
LI Xian-Feng**, Andrew Y. -T. Leung, CHU Yan-Dong
Chin. Phys. Lett. 2012, 29 (1): 010201 .   DOI: 10.1088/0256-307X/29/1/010201
Abstract   PDF(pc) (1954KB) ( 618 )
Hierarchical structural symmetry of periodic islands embedded in the chaotic region of modified optical injection semiconductor lasers (MOISLs) is expounded upon in phase diagrams. The onset of the bifurcation cascade shows remarkable accumulation horizons. Each cascade follows a specific period-adding route. Self-similarities and infinite spiral nestings shrinking beyond a certain point of the periodic hub are revealed to affirm the existence of self-organized distribution of periodicity and chaos in phase diagrams.
Note on the Lax Pair of a Coupled Hybrid System
LIU Ping**, FU Pei-Kai
Chin. Phys. Lett. 2012, 29 (1): 010202 .   DOI: 10.1088/0256-307X/29/1/010202
Abstract   PDF(pc) (395KB) ( 440 )
The hybrid lattice, known as a discrete Korteweg-de Vries (KdV) equation, is found to be a discrete modified Korteweg-de Vries (mKdV) equation. The coupled hybrid lattice, which is pointed out to be a discrete coupled KdV system, is also found to be a discrete form of a coupled mKdV system. New lax pairs for the single and coupled discrete hybrid systems are proposed as a different study from previous ones.
Inhomogeneous Quantum Invariance Group of Multi-Dimensional Multi-parameter Deformed Boson Algebra
Azmi Ali Altintas, Metin Arik, Ali Serdar Arikan, Emre Dil**
Chin. Phys. Lett. 2012, 29 (1): 010203 .   DOI: 10.1088/0256-307X/29/1/010203
Abstract   PDF(pc) (379KB) ( 318 )
We investigate the inhomogeneous invariance quantum group of the d−dimensional d−parameter deformed boson algebra. It is found that the homogeneous part of this quantum group is given by the d−parameter deformed general linear group. We construct the R-matrix which collects all information about the non-commuting structure of the quantum group for the two-dimensional case.
New View of Ping-Pong Protocol Security
Piotr Zawadzki**
Chin. Phys. Lett. 2012, 29 (1): 010301 .   DOI: 10.1088/0256-307X/29/1/010301
Abstract   PDF(pc) (376KB) ( 418 )
The ping-pong protocol offers confidential transmission of classic information without a prior key agreement. It is believed that it is quasi secure in lossless quantum channels. Serious doubts related to the analysis paradigm which has been used so far are presented in the study. The security of the protocol is reconsidered.
Exact Propagator for the Anisotropic Two-Dimensional Charged Harmonic Oscillator in a Constant Magnetic Field and an Arbitrary Electric Field
ZHAI Zhi-Yuan, YANG Tao, PAN Xiao-Yin**
Chin. Phys. Lett. 2012, 29 (1): 010302 .   DOI: 10.1088/0256-307X/29/1/010302
Abstract   PDF(pc) (402KB) ( 697 )
The propagator for an anisotropic two-dimension charged harmonic oscillator in the presence of a constant external magnetic field and a time-dependent electric field is exactly evaluated. Various special cases appearing in the literature can be obtained by properly setting the values of the parameters in our results.
Repeater-Assisted Zeno Effect in Classical Stochastic Processes
GU Shi-Jian**, WANG Li-Gang, WANG Zhi-Guo, LIN Hai-Qing
Chin. Phys. Lett. 2012, 29 (1): 010303 .   DOI: 10.1088/0256-307X/29/1/010303
Abstract   PDF(pc) (1002KB) ( 400 )
We address the possibility of the classical Zeno effect in classical stochastic processes as sampled by transferring a digitized image through a classical channel with surrounding noise. It is shown that the the classical state of the image decays inevitably with the distance of the channel due to the interference of the surroundings. However, if there are enough repeaters, which can both check and recover the state's information, the classical state's decay rate will be significantly suppressed, then a classical Zeno effect might occur.
Chiral Fermion Conductivity in Graphene-Like Samples Subjected to Orthogonal Fields
Ciprian Dariescu, Marina-Aura Dariescu**
Chin. Phys. Lett. 2012, 29 (1): 010304 .   DOI: 10.1088/0256-307X/29/1/010304
Abstract   PDF(pc) (425KB) ( 359 )
Starting with the U(1)−gauge covariant four-dimensional Dirac equation, we derive the analytic solutions describing the chiral massless fermions evolving in static orthogonal magnetic and electric fields. Working in cylindric coordinates, we compute the electric current density essential component and the off-diagonal conductivities. By summing up the conductivities of the two distinct species of electrons connected to the orientation of spin, the well-known 4n-quantization law is restored.
Randomly Generating Four Mixed Bell-Diagonal States with a Concurrences Sum to Unity
S. P. Toh**, Hishamuddin Zainuddin, Kim Eng Foo,
Chin. Phys. Lett. 2012, 29 (1): 010305 .   DOI: 10.1088/0256-307X/29/1/010305
Abstract   PDF(pc) (438KB) ( 376 )
A two-qubit system in quantum information theory is the simplest bipartite quantum system and its concurrence for pure and mixed states is well known. As a subset of two-qubit systems, Bell-diagonal states can be depicted by a very simple geometrical representation of a tetrahedron with sides of length 22. Based on this geometric representation, we propose a simple approach to randomly generate four mixed Bell decomposable states in which the sum of their concurrence is equal to one.
Phantom Energy Accretion by a Stringy Charged Black Hole
M. Sharif**, G. Abbas
Chin. Phys. Lett. 2012, 29 (1): 010401 .   DOI: 10.1088/0256-307X/29/1/010401
Abstract   PDF(pc) (366KB) ( 347 )
We investigate the dynamical behavior of phantom energy near a stringy magnetically charged black hole. For this purpose, we derive equations of motion for steady-state spherically symmetric flow of phantom energy onto the stringy magnetically charged black hole. It is found that phantom energy accreting onto a black hole decreases its mass. Further, the location of the critical points of accretion is explored, which yields a mass to charge ratio. This ratio implies that accretion process cannot transform a black hole into an extremal black hole or a naked singularity, hence cosmic censorship hypothesis remains valid here.
Propagation and Evolution of a Scalar Field in Einstein–Power–Maxwell Spacetime
LIU Yan, JING Ji-Liang**
Chin. Phys. Lett. 2012, 29 (1): 010402 .   DOI: 10.1088/0256-307X/29/1/010402
Abstract   PDF(pc) (493KB) ( 399 )
The propagation and dynamical evolution of a scalar field in the background of a (2+1)-dimensional Einstein–Power–Maxwell (EPM) black hole are studied. We obtain an analytical expression for the greybody factor, which shows that the greybody factor increases as the electric charge increases and approaches unity for large frequencies. We also find the quasinormal modes of the black hole, which tell us that the EPM spacetime is very stable.
LRS Bianchi Type-II Cosmological Model with a Decaying Lambda Term
R. K. Tiwari**, D. Tiwari, Pratibha Shukla
Chin. Phys. Lett. 2012, 29 (1): 010403 .   DOI: 10.1088/0256-307X/29/1/010403
Abstract   PDF(pc) (431KB) ( 475 )
We consider a locally rotationally symmetric (LRS) Bianchi type-II spacetime with a perfect fluid and a variable cosmological constant Λ. To solve the Einstein field equations we consider the cosmological term Λ to be proportional to R−m with R being the scale factor and m a constant [Phys. Rev. D 58 (1998) 043506]. In this model we obtain Λ∼H2, Λ∼R"/R and Lambda ∼t−2, in agreement with the main dynamical laws for the decay of Λ. The physical significance of the cosmological model is also discussed.
Evaluation of an Asymmetric Bistable System for Signal Detection under Lévy Stable Noise
HUANG Jia-Min, TAO Wei-Ming**, XU Bo-Hou
Chin. Phys. Lett. 2012, 29 (1): 010501 .   DOI: 10.1088/0256-307X/29/1/010501
Abstract   PDF(pc) (473KB) ( 373 )
We evaluate the performance of a typical asymmetric bistable system for detecting aperiodic signal under Lévy stable noise. A Grünwald–Letnikov implicit finite difference method is employed to solve the fractional Fokker–Planck equation numerically. The noise-induced stochastic resonance (SR) and the parameter-induced SR both exist in the asymmetric bistable systems. The increase of the skewness parameter γ may deteriorate the system performance. However, by tuning the system parameters, the effects of asymmetry on the system performance can be reduced.
Relationship between the Permeation-Diffusion Parameters of a Single-File Channel
LIU Jian, FAN Jian-Fen**
Chin. Phys. Lett. 2012, 29 (1): 010502 .   DOI: 10.1088/0256-307X/29/1/010502
Abstract   PDF(pc) (758KB) ( 413 )
Two sets of widely used parameters can describe the molecular permeation through a nanochannel. One is permeation rate j and its diffusion Dn, and the other is flow and net flux. We establish a relationship between the two sets for a single-file nanochannel, as well as its dependence on the temperature and pressure difference between the two ends of a single-file channel, based on the Brownian motion theories and verified with molecular dynamics simulations for the water diffusion in a transmembrane (6,6) armchair carbon nanotube. Simulation results are in excellent agreement with our predictions.
Size Segregation in Rapid Flows of Inelastic Particles with Continuous Size Distributions
LI Rui**, ZHANG Duan-Ming, LI Zhi-Hao
Chin. Phys. Lett. 2012, 29 (1): 010503 .   DOI: 10.1088/0256-307X/29/1/010503
Abstract   PDF(pc) (683KB) ( 317 )
Two-dimensional numerical simulations are employed to gain insight into the segregation behavior of granular mixtures with a power-law particle size distribution in the presence of a granular temperature gradient. It is found that particles of all sizes move toward regions of low granular temperature. Species segregation is also observed. Large particles demonstrate a higher affinity for the low-temperature regions and accumulate in these cool regions to a greater extent than their smaller counterparts. Furthermore, the local particle size distribution maintains the same form as the overall (including all particles) size distribution.
Directed Dynamic Small-World Network Model for Worm Epidemics in Mobile ad hoc Networks
ZHU Chen-Ping, **, WANG Li, LIU Xiao-Ting, YAN Zhi-Jun
Chin. Phys. Lett. 2012, 29 (1): 010504 .   DOI: 10.1088/0256-307X/29/1/010504
Abstract   PDF(pc) (544KB) ( 4386 )
We investigate the worm spreading process in mobile ad hoc networks with a susceptible-infected-recovered model on a two-dimensional plane. A medium access control mechanism operates within it, inhibiting transmission and relaying a message by using other nodes inside the node's transmitting circle during speaking. We measure the rewiring probability p with the transmitting range r and the average relative velocity v of the moving nodes, and map the problem into a directed dynamic small-world network. A new scaling relation for the recovered portion of the nodes reveals the effect caused by geometric distance, which has been ignored by previous models.
Torsional Vibrations of a Cantilever with Lateral Friction in a Resonance Friction Microscope
CHEN Jian-Song, GE Yun**, ZHANG Hui**
Chin. Phys. Lett. 2012, 29 (1): 010701 .   DOI: 10.1088/0256-307X/29/1/010701
Abstract   PDF(pc) (832KB) ( 482 )
A model of fundamental torsional vibration of a cantilever with lateral friction is presented by using the harmonic balance method. The model demonstrates that the torsional vibration has close relations with the lateral friction threshold, the lateral contact stiffness and the torsional vibration amplitude of the cantilever. When the threshold is larger than a product of the stiffness and the vibration amplitude, the lateral friction is a linear force with the amplitude. If the lateral friction threshold is less than the product, the motions of the tip on the sample can be stick-slip or slip motions. The results are useful to optimize and to manipulate the fundamental flexural vibration of the piezo-cantilever, and give an insight into the tribological characterization of the interface in a resonance friction microscope.
Second-Order Contribution of the Incompressibility in Asymmetric Nuclear Matter
LI Zeng-Hua, **, ZHANG Da-Peng, SCHULZE Hans-Josef, ZUO Wei
Chin. Phys. Lett. 2012, 29 (1): 012101 .   DOI: 10.1088/0256-307X/29/1/012101
Abstract   PDF(pc) (504KB) ( 412 )
With the complementarity of the nucleonic three-body force, we present the saturation points of symmetric nuclear matter with different interactions adopted within the Brueckner–Hartree–Fock scheme, and a more accurate empirical parameterization function for the equation of state of symmetric nuclear matter and pure neutron matter. On the basis of this fit formula, the symmetry energy and its derivatives are investigated, and ultimately the higher-order coefficient of the isobaric incompressibility for isospin asymmetric nuclear matter is predicted.
Single-Particle Properties of Isospin Asymmetric Nuclear Matter
LI Zeng-Hua, **, ZUO Wei, GUO Wen-Jun
Chin. Phys. Lett. 2012, 29 (1): 012102 .   DOI: 10.1088/0256-307X/29/1/012102
Abstract   PDF(pc) (630KB) ( 364 )
The single-particle potentials in isospin asymmetric nuclear matter is investigated in the framework of the Brueckner theory by adopting the realistic Bonn B two-body interaction in combination with a consistent microscopic three-body force. The rearrangement contribution induced by the ground state correlations to single-nucleon potentials is calculated in terms of the hole-line expansion of the mass operator. With the modification of this rearrangement term the symmetry potential is discussed as a function of momentum for several isospin asymmetries.
Thermal Annealing Behavior of Helium in Ti Films Deposited by Magnetron Sputtering
ZHANG Lei, HE Zhi-Jiang, LIU Chao-Zhuo, WANG Xu-Fei, SHI Li-Qun**
Chin. Phys. Lett. 2012, 29 (1): 012501 .   DOI: 10.1088/0256-307X/29/1/012501
Abstract   PDF(pc) (768KB) ( 372 )
Helium contents of up to 30at.% are prepared in sputter-deposited Ti films. Isochronal annealing behaviors of helium including the depth profiles and the evolution of helium bubbles in the films at different temperatures are examined by ion beam analysis including Rutherford backscattering spectrometry (RBS) and elastic recoil detection analysis (ERDA), as well as thermal helium desorption spectroscopy (THDS). It is found that the energy spreading induced by structural inhomogeneities in the spectra of RBS and ERDA as well as the increment in the width of spectra occurs, which corresponds to the change of stopping cross-section of helium atoms in the Ti film due to the change of physical-state of helium in the evolution of helium bubble. The ion beam analysis on the helium evolution is consistent with the THDS measurement. Ion beam technique opens interesting possibilities in the characterizing on the growth of helium bubbles.
Observation of the Superheavy Nuclide 271Ds
ZHANG Zhi-Yuan, GAN Zai-Guo**, MA Long, HUANG Ming-Hui, HUANG Tian-Heng, WU Xiao-Lei, JIA Guo-Bin, LI Guang-Shun, YU Lin, REN Zhong-Zhou, ZHOU Shan-Gui, ZHANG Yu-Hu, ZHOU Xiao-Hong, XU Hu-Shan, ZHANG Huan-Qiao, XIAO Guo-Qing, ZHAN Wen-Long
Chin. Phys. Lett. 2012, 29 (1): 012502 .   DOI: 10.1088/0256-307X/29/1/012502
Abstract   PDF(pc) (607KB) ( 489 )
With the recent commissioning of a gas-filled recoil separator at Institute of Modern Physics (IMP) in Lanzhou, the decay properties of 271Ds (Z=110) were studied via the 208Pb(64Ni, n) reaction at a beam energy of 313.3 MeV. Based on the separator coupled with a position sensitive silicon strip detector, we carried out the energy−position-time correlation measurements for the implanted nucleus and its subsequent decay α's. One α−decay chain for 271Ds was established. The α energy and decay time of the 271Ds nucleus were measured to be 10.644 MeV and 96.8 ms, which are consistent with the values reported in the literature.
Anomalously High Isotope Ratio 3He/4He and Tritium in Deuterium-Loaded Metal: Evidence for Nuclear Reaction in Metal Hydrides at Low Temperature
JIANG Song-Sheng**, HE Ming, WU Shao-Yong, QI Bu-Jia
Chin. Phys. Lett. 2012, 29 (1): 012503 .   DOI: 10.1088/0256-307X/29/1/012503
Abstract   PDF(pc) (521KB) ( 373 )
Anomalous 3He/4He ratios in deuterium−loaded titanium samples are observed to be about 1– 4×10−1, much greater than the values (≤10−4) in natural objects. Control experiments with the deuterium-unloaded titanium sample and original industrial deuterium gas are also carried out, but no anomalous 3He/4He values are observed. In addition, anomalous tritium in deuterium−loaded titanium samples are also observed. To explain the excess 3He and tritium in the deuterium-loaded titanium samples, it is required that the deuteron-induced nuclear reaction occurs in the samples at low temperature.
A Cosmic-Ray Muon Hodoscope Based on Up-down THGEM Detectors
PANG Hong-Chao, LIU Hong-Bang, **, CHEN Shi, MIN Jian, ZHENG Yang-Heng, XIE Yi-Gang, TANG Ai-Song, YANG Ya-Dan, DONG Yang, LI Min
Chin. Phys. Lett. 2012, 29 (1): 012901 .   DOI: 10.1088/0256-307X/29/1/012901
Abstract   PDF(pc) (1255KB) ( 705 )
Thick gas electron multipliers (THGEMs) are new types of gas detectors with merits such as a high counting rate, anti-radiation, high gain, robustness and relatively low cost. We establish an up-down THGEM detector hodoscope system for detecting and displaying muon tracks. Muon tracks can be well observed with the detectors and the present study lays an important technological foundation for the domestic and mass production of THGEMs.
Narrow Near-Threshold Resonance in e+–He+ Scattering
LIU Min-Min, , HAN Hui-Li**, GU Si-Hong, SHI Ting-Yun
Chin. Phys. Lett. 2012, 29 (1): 013101 .   DOI: 10.1088/0256-307X/29/1/013101
Abstract   PDF(pc) (662KB) ( 307 )
An independent alternative calculation is performed for narrow near-threshold resonances in the e+–He+ system using the stabilization method in the framework of hyperspherical coordinates (HSSM). A narrow resonance at Er=−0.249995 with width Γ=1.9×10−5, associated with the He2+–Ps (n =1) threshold is confirmed. The resonances around the energies −0.365 and −0.195, predicted by Bhatia and Drachman [Phys. Rev. A 42 (1990) 5117] and confirmed by Ho [Phys. Rev. A 53 (1996) 3165], do not appear in our calculations.
First-Principles Study of Hydrogen Impact on the Formation and Migration of Helium Interstitial Defects in hcp Titanium
LU Yong-Fang, SHI Li-Qun**, DING Wei, LONG Xing-Gui
Chin. Phys. Lett. 2012, 29 (1): 013102 .   DOI: 10.1088/0256-307X/29/1/013102
Abstract   PDF(pc) (729KB) ( 372 )
We present a first-principles study of the effects of hydrogen on helium behavior in hcp titanium. The calculation indicates that the dissolved H atoms in hcp Ti change the formation energy of the interstitial He atom, but they do not change the energetically favorable occupying site of the He atom, i.e., the tetrahedral site is more favorable than the octahedral site. The impacts of H on the formation of interstitial He defects are directly related to the atomic environment around H atoms and their positions relative to interstitial He atoms as well. For He diffusion, a tetrahedral interstitial He atom can more easily migrate along the indirect tetrahedron-octahedron-tetrahedron path than the direct path of tetrahedron-tetrahedron. When a H atom exists in the first neighbor octahedral site from the He, the activation energy for He atom diffusion is 0.46 eV, which is higher than that of the He atom diffusion in perfect crystal, 0.41 eV. Increasing the number of H atoms to two, He diffusion needs much higher activation energy. This suggests that the H atoms around interstitial He may impede the migration of interstitial He atom in hcp Ti.
Measurement of the Absolute Photoionization Cross Section for the 5P3/2 State of 87Rb in a Vapor Cell Magneto-optic Trap
HUANG Wei, RUAN Ya-Ping, JIA Feng-Dong, ZHONG Yin-Peng, LIU Long-Wei, DAI Xing-Can, XUE Ping, XU Xiang-Yuan, ZHONG Zhi-Ping**
Chin. Phys. Lett. 2012, 29 (1): 013201 .   DOI: 10.1088/0256-307X/29/1/013201
Abstract   PDF(pc) (704KB) ( 384 )
We report the measurement of the absolute photoionization cross section for the 5P3/2 state of 87Rb at wavelength of 473 nm, which results in the photoelectron energies of 33 meV above the ionization threshold, using cold atoms confined in a vapor−loaded magneto-optical trap. The 87Rb 5P3/2 photoionization cross section at 473 nm is determined to be σPI=10.5±2.2 Mb. Considering the spatial distribution of the trapped atoms, the average intensity IPI of the ionization laser seen by an atom in the MOT instead of ionizing laser intensity IPI is used in our calculations for the photoionization cross sections. The excited state fraction is also accurately estimated using the latest experimental result.
Photodetachment of H near a Hard Spherical Surface
M. Haneef, Iftikhar Ahmad**, A. Afaq, A. Rahman
Chin. Phys. Lett. 2012, 29 (1): 013202 .   DOI: 10.1088/0256-307X/29/1/013202
Abstract   PDF(pc) (444KB) ( 475 )
The photodetachment of a hydrogen negative ion (H) near a hard spherical surface is investigated by using the theoretical imaging method. The surface is oriented in such a fashion that the laser polarization direction is perpendicular to the principal axis of the spherical surface. Analytical expressions are derived for the detached-electron flux and photodetachment cross section. Strong interference patterns are observed in the detached-electron flux, while no visible oscillations are found in the photodetachment cross section.
Local Field Distributions in Systems with Dipolar Interaction
YAN Yue, WU Biao**
Chin. Phys. Lett. 2012, 29 (1): 013203 .   DOI: 10.1088/0256-307X/29/1/013203
Abstract   PDF(pc) (637KB) ( 312 )
We investigate systematically the local field distribution functions of up-spins for systems of dipolar interaction, with particular emphasis on Ising-type lattice systems. It is found that as the fraction increases, the shape of the distribution function changes from Lorentzian to Gaussian. In addition, sub-peaks can be induced in the distribution function by non-cubic lattice structures. This is in stark contrast with a dilute gas system, where the distribution has only one Lorentzian peak for any up-spin fraction.
Measurements of the Spectrum of Singly Ionized Argon between 320 and 520 nm
YANG Zhao-Rui, YUAN Ping**, SONG Zhang-Yong, XU Qiu-Mei, YANG Zhi-Hu
Chin. Phys. Lett. 2012, 29 (1): 013204 .   DOI: 10.1088/0256-307X/29/1/013204
Abstract   PDF(pc) (508KB) ( 381 )
We report beam-foil measurements of the spectrum for Ar II. Totally 56 lines are measured. Most of them are mainly ascribed to 3d–4p, 4s–4p, 4p–4d and 4p–5s resonance transitions. These spectral lines are identified, among which 16 lines are new and accurately measured. Analyses of the spectra are based on a comparison with the other experimental results and calculated values.
Second-Order Born Effect in Single Ionization of Argon by Electron Impact
WANG Yang**, ZHOU Ya-Jun, JIAO Li-Guang
Chin. Phys. Lett. 2012, 29 (1): 013401 .   DOI: 10.1088/0256-307X/29/1/013401
Abstract   PDF(pc) (603KB) ( 393 )
We extend the standard distorted wave Born approximation (DWBA) to include the second-order Born amplitude in order to describe the multiple interactions between a projectile and an atomic target. Both the first- and second-order DWBA models are used to calculate triply differential cross sections (TDCS) of coplanar (e, 2e) on atomic argon with the scattered electron energy fixed at 500 eV, the scattering angle at 6° and the ejected electron energies at 37, 74 and 205 eV. Overall agreements with experimental measurements have been obtained in shape, and the second-order DWBA model improves the calculations as expected, especially for recoil peak of TDCS.
Compact Dual-Band Zeroth-Order Resonance Antenna
XU He-Xiu**, WANG Guang-Ming, GONG Jian-Qiang
Chin. Phys. Lett. 2012, 29 (1): 014101 .   DOI: 10.1088/0256-307X/29/1/014101
Abstract   PDF(pc) (1946KB) ( 1937 )
A novel microstrip zeroth-order resonator (ZOR) antenna and its equivalent circuit model are exploited with two zeroth-order resonances. It is constructed based on a resonant-type composite right/left handed transmission line (CRLH TL) using a Wunderlich-shaped extended complementary single split ring resonator pair (W-ECSSRRP) and a series capacitive gap. The gap either can be utilized for double negative (DNG) ZOR antenna or be removed to engineer a simplified elision-negative ZOR (ENG) antenna. For verification, a DNG ZOR antenna sample is fabricated and measured. Numerical and experimental results agree well with each other, indicating that the omnidirectional radiations occur at two frequency bands which are accounted for by two shunt branches in the circuit model. The size of the antenna is 49% more compact than its previous counterpart. The superiority of W-ECSSRRP over CSSRRP lies in the lower fundamental resonance of the antenna by 38.2% and the introduction of a higher zeroth-order resonance.
Concealing a Passive Sensing System with Single-Negative Layers
ZHU Xue-Feng, ZOU Xin-Ye, ZHOU Xiao-Wei, LIANG Bin, CHENG Jian-Chun**
Chin. Phys. Lett. 2012, 29 (1): 014102 .   DOI: 10.1088/0256-307X/29/1/014102
Abstract   PDF(pc) (752KB) ( 808 )
We propose a multi-layer structure for concealing an electromagnetic sensing system (a sensor is wrapped with a transparent protective layer), using single-negative (SNG) materials whose material parameters are completely independent of those of the host matrix as well as the concealed system. The numerical results show that only three different kinds of SNG materials are sufficient to yield the cloaking effect even in the presence of weak loss. This may significantly facilitate the experimental realization of a well-performing sensor-cloaking device.
Ultraviolet Continuum Generation in the Fundamental Mode of Photonic Crystal Fibers
HAN Ying, **, HOU Lan-Tian, YUAN Jin-Hui, XIA Chang-Ming, ZHOU Gui-Yao,
Chin. Phys. Lett. 2012, 29 (1): 014201 .   DOI: 10.1088/0256-307X/29/1/014201
Abstract   PDF(pc) (586KB) ( 421 )
The ultraviolet continuum generation in the fundamental mode of photonic crystal fibers designed and fabricated in our lab are experimentally demonstrated. When the pump works in the normal dispersion regions of 780 nm and 830 nm, and the average powers increase from 100 to 500 mW, anti-Stokes signals can be efficiently generated based on the phase-matched degenerate four-wave mixing. The cross-phase modulation between the pump and the generated anti-Stokes signals can effectively extend the continuum into the ultraviolet wavelength range. This can provide an efficient light source for ultraviolet photonics and spectroscopy.
Comparison of the Noise Properties of Squeezed Probe Light in Optically Thick and Thin Quantum Coherence Media for Weak and Strong Coupling Lights
LI Zhong-Hua, LI Yuan, DOU Ya-Fang, GAO Jiang-Rui, ZHANG Jun-Xiang**
Chin. Phys. Lett. 2012, 29 (1): 014202 .   DOI: 10.1088/0256-307X/29/1/014202
Abstract   PDF(pc) (553KB) ( 375 )
The output amplitude noises of one squeezed probe light which is at resonance throughout different optical depths media in strong- and weak-coupling-field regimes are investigated theoretically. By comparing the output quantum noises for different Rabi frequencies of coupling field and also for different optical depths, it is found that the optimal squeezing preservation of the probe light occurs in an optically thin medium with strong-coupling-field, where we can obtain the output squeezing close to the input one at nonzero detection frequency.
All-Optical Temporal Differentiator Using a High Resolution Optical Arbitrary Waveform Shaper
DONG Jian-Ji**, LUO Bo-Wen, ZHANG Yin, LEI Lei, HUANG De-Xiu, ZHANG Xin-Liang
Chin. Phys. Lett. 2012, 29 (1): 014203 .   DOI: 10.1088/0256-307X/29/1/014203
Abstract   PDF(pc) (502KB) ( 484 )
We experimentally demonstrate an all-optical temporal differentiator using a high resolution optical arbitrary waveform shaper, which is based on liquid crystal on silicon switching elements, and both amplitude and phase of the spectrum are programmable. By designing specific transfer functions with the optical waveform shaper, we obtain first-, second-, and third-order differentiators for periodic pulses with small average errors. We also theoretically analyze the bandwidth limitation of optical waveform shaper on the differentiator.
Influence of Multi-Cascaded Semiconductor Optical Amplifiers on the Signal in an Energy-Efficient System
CHEN Xiao-Yong, SHENG Xin-Zhi**, WU Chong-Qing
Chin. Phys. Lett. 2012, 29 (1): 014204 .   DOI: 10.1088/0256-307X/29/1/014204
Abstract   PDF(pc) (868KB) ( 482 )
Signal impairment is experimentally studied by using the extinction ratio (ER), error bit rate (BER) and optical spectrum in a three-cascaded semiconductor optical amplifier (SOA) setup. The signal with the ER of 13 dB and BER of <10−9 is achieved after the signal passing through the cascaded SOAs. With the results obtained from the experiment, we confirm that the three-cascaded SOAs used to compensate for power in the optical transmission can be accepted. This experimental result also offers the possibility of achieving a higher throughput of multi-plane architecture by exploiting three switching domains instead of two switching domains in the energy-efficient design of a scalable optical multi-plane interconnection architecture. The space switches in output ports of multi-plane interconnection architecture can be improved to N=32×32×32=32768.
Two-Detector Arbitrary Nth-Order HBT-Type Ghost Diffraction
CAO Bin**, ZHANG Chun-Xi, OU Pan, LIN Zhi-Li, SUN Ming-Jie
Chin. Phys. Lett. 2012, 29 (1): 014205 .   DOI: 10.1088/0256-307X/29/1/014205
Abstract   PDF(pc) (574KB) ( 394 )
The imaging quality using two-detector arbitrary Nth−order intensity correlation in optics is investigated. It is theoretically demonstrated that with the order of intensity correlation N increases, the visibility of the retrieved image enhances promptly; and different n−fold intensity on one arm of the intensity correlation leads to different visibility, whereas the resolution is independent of N and n. The numerical simulation results are shown to be consistent with our theoretical analysis results. Furthermore, a particular imaging system of the two−detector Nth-order Hanbury–Brown–Twiss (HBT) type ghost diffraction is conceived by using a slit as the object, the image quality by this type of ghost diffraction is investigated. The experimental results coincide with our theoretical analysis.
Optically Controlled Coherent Backscattering from a Water Suspension of Positive Uniaxial Microcrystals
SHI Fan, LI Wei, WANG Pi-Dong, LI Jun, WU Qiang, WANG Zhen-Hua, ZHANG Xin-Zheng**
Chin. Phys. Lett. 2012, 29 (1): 014206 .   DOI: 10.1088/0256-307X/29/1/014206
Abstract   PDF(pc) (479KB) ( 346 )
Coherent backscattering of light from a water suspension of zirconium silicate microcrystals is experimentally studied. Optically controlled weak localization of photons is realized, which is due to the reorientation behaviors of positive uniaxial microcrystals induced by a linearly polarized pump beam. Because zirconium silicate particles are positive uniaxial microcrystals, their reorientation behaviors are contrary to negative ones. Our work widely extends the materials used in the light-controllable weak localization of photons.
THz-Wave Difference Frequency Generation by Phase-Matching in GaAs/AlxGa1−xAs Asymmetric Quantum Well
CAO Xiao-Long, WANG Yu-Ye, XU De-Gang, **, ZHONG Kai, LI Jing-Hui, LI Zhong-Yang, ZHU Neng-Nian, YAO Jian-Quan,
Chin. Phys. Lett. 2012, 29 (1): 014207 .   DOI: 10.1088/0256-307X/29/1/014207
Abstract   PDF(pc) (1425KB) ( 407 )
An asymmetric quantum well (AQW) is designed to emit a terahertz (THz) wave by using difference frequency generation (DFG) with the structure of GaAs/Al0.2Ga0.8As/Al0.5Ga0.5As under a doubly resonant condition. It is found that the second−order nonlinear susceptibility χ(2) varies with the two pump wavelengths, and it can reach the peak value of 1.61 µm/V when the wavelengths are given as λp1=9.756 µm and λp2=10.96 µm, respectively. The numerical results show that the refractive index of one pump wave in the AQW is concerned with not only its own wavelength but also the other wavelength. Phase-matching inside the AQW can be obtained through the tuning of the two pump wavelengths.
The Spectrum in Qubit-Oscillator Systems in the Ultrastrong Coupling Regime
CHEN Qing-Hu, **, LI Lei, LIU Tao, WANG Ke-Lin
Chin. Phys. Lett. 2012, 29 (1): 014208 .   DOI: 10.1088/0256-307X/29/1/014208
Abstract   PDF(pc) (504KB) ( 429 )
Recent measurement on an LC resonator magnetically coupled to a superconducting qubit [Phys. Rev. Lett. 105 (2010) 237001] shows that the system operates in the ultra-strong coupling regime and crosses the limit of validity for the rotating-wave approximation of the Jaynes–Cummings model. By using extended bosonic coherent states, we solve the Jaynes–Cummings model exactly without using the rotating-wave approximation. Our numerically exact results for the spectrum of the flux qubit coupled to the LC resonator are fully consistent with the experimental observations. The smallest Bloch–Siegert shift obtained is consistent with that observed in this experiment. In addition, the Bloch–Siegert shifts in arbitrary level transitions and for arbitrary coupling constants are predicted.
A 100-TW Ti:Sapphire Laser System at a Repetition Rate of 0.1 Hz
TENG Hao, MA Jing-Long, WANG Zhao-Hua, ZHENG Yi, GE Xu-Lei, ZHANG Wei, WEI Zhi-Yi**, LI Yu-Tong, ZHANG Jie,
Chin. Phys. Lett. 2012, 29 (1): 014209 .   DOI: 10.1088/0256-307X/29/1/014209
Abstract   PDF(pc) (520KB) ( 391 )
We demonstrate a 100-TW-class femtosecond Ti:sapphire laser running at a repetition rate of 0.1 Hz based on a 20 TW/10 Hz laser facility (XL-II). Pumping the new stage amplifier with a 25J green Nd:glass laser, we successfully improve the laser energy to 3.4 J with duration of 29 fs, corresponding to a peak power of 117 TW.
Polarization Beam Splitter Based on a Self-Collimation Michelson Interferometer in a Silicon Photonic Crystal
CHEN Xi-Yao**, LIN Gui-Min, LI Jun-Jun, XU Xiao-Fu, JIANG Jun-Zhen, QIANG Ze-Xuan, QIU Yi-Shen, LI Hui
Chin. Phys. Lett. 2012, 29 (1): 014210 .   DOI: 10.1088/0256-307X/29/1/014210
Abstract   PDF(pc) (2888KB) ( 416 )
A polarization beam splitter based on a self-collimation Michelson interferometer (SMI) in a hole-type silicon photonic crystal is proposed and numerically demonstrated. Utilizing the polarization dependence of the transmission spectra of the SMI and polarization peak matching method, the SMI can work as a polarization beam splitter (PBS) by selecting an appropriate path length difference in the structure. Based on its novel polarization beam splitting mechanics, the polarization extinction ratios (PERs) for TM and TE modes are as high as 18.4 dB and 24.3 dB, respectively. Since its dimensions are only several operating wavelengths, the PBS may have practical applications in photonic integrated circuits.
Frequency Modulation Induced by using the Linear Phase Modulation Method used in a Resonator Micro-optic Gyro
HONG Ling-Fei**, ZHANG Chun-Xi, FENG Li-Shuang, YU Huai-Yong, LEI Ming
Chin. Phys. Lett. 2012, 29 (1): 014211 .   DOI: 10.1088/0256-307X/29/1/014211
Abstract   PDF(pc) (547KB) ( 590 )
Resonator micro-optic gyro (R-MOG) sensing rotation angular-velocity is based on Sagnac effect. We present a frequency modulation (FM) induced by the analog triangle-waveform phase modulation (ATAW-PM) technique in an R-MOG. Compared with the traditional serrodyne phase modulation or digital phase modulation methods, the proposed modulation technique has the intrinsic advantage in free of sweeping-back or step-effect induced pulse noise. The influence on dynamic range and resolution of the R-MOG by the parameters of analog triangle-waveform is theoretically analyzed. Experiments are carried out on an R-MOG composed of an integrated optic resonator with a free spectral range (FSR) and a fitness (F) of 1.6 GHz and 61, respectively. Dynamic range of ±500 deg/s and bias drift of 0.6 deg/s over 1 h and 0.05 deg/s for 60 s are reliably obtained.
Polymer Electro-optic Modulator Linear Bias Using the Thermo-optic Effect
SUN Xiao-Qiang, CHEN Chang-Ming, LI Xiao-Dong, WANG Xi-Bin, YANG Tian-Fu, ZHANG Da-Ming, WANG Fei**, XIE Zhi-Yuan**
Chin. Phys. Lett. 2012, 29 (1): 014212 .   DOI: 10.1088/0256-307X/29/1/014212
Abstract   PDF(pc) (786KB) ( 496 )
A quasi-rectangular waveguide polymer Mach–Zehnder (M-Z) electro-optic (EO) modulator based on an organic/inorganic hybrid material with thermal bias control is fabricated and demonstrated. Linear bias for the modulator is obtained through thermo-optic effect. The optical output is adjusted by changing phase difference between the two arms of the M-Z interferometer. A power consumption of 16.1 mW for π phase change is observed owing to the application of silica cladding. This approach is proved to be effective to suppress direct current drift in polymer EO modulators.
Rayleigh Doppler Lidar for Higher Tropospheric and Stratospheric Wind Observation
TANG Lei**, WANG Cong-Rong, WU Hai-Bin, DONG Ji-Hui
Chin. Phys. Lett. 2012, 29 (1): 014213 .   DOI: 10.1088/0256-307X/29/1/014213
Abstract   PDF(pc) (1443KB) ( 401 )
A mobile molecular Doppler wind lidar (DWL) based on the double-edge technique is described for wind measurement from 10 km to 40 km altitude. Two edge filters located in the wings of the thermally broadened molecular backscattered signal spectrum at 355 nm are 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. Intercomparison experiments of the lidar wind profile measurement are performed with collocated pilot balloon. The results show that the standard deviation of wind speed and direction are less than 10 m/s and 30° in the 5–40 km altitude range, respectively. The small mean difference and normal distribution between DWL and pilot balloon data and the transient eddy of the west-wind jet observed demonstrate that the DWL consistently measures the wind with acceptable random errors.
The Measurement of Displacement and Optical Force in Multi-Optical Tweezers
LING Lin, GUO Hong-Lian**, HUANG Lu, QU E, LI Zhao-Lin, LI Zhi-Yuan
Chin. Phys. Lett. 2012, 29 (1): 014214 .   DOI: 10.1088/0256-307X/29/1/014214
Abstract   PDF(pc) (731KB) ( 532 )
We set up a system of multiple optical tweezers based on a spatial light modulator, and measured the displacement and optical force of the trapped particles simultaneously. All of the trapped particles can be clearly imaged in three dimensions by several CCDs. The displacement is obtained by calculating the gray weighted centroid in the trapped particle's image. The stiffness of the trapped particles in the optical traps is measured by oscillating the sample stage in a triangular wave based on Stokes fluid dynamics. The optical force of each trapped particle can be calculated by the measured displacement and stiffness.
Propagation of Shear Waves Generated by Acoustic Radiation Force in Nondissipative Inhomogeneous Media
LU Ming-Zhu, LIU Xue-Jin, SHI Yu, KANG Yan-Ni, GUAN Yu-Bo, WAN Ming-Xi**
Chin. Phys. Lett. 2012, 29 (1): 014301 .   DOI: 10.1088/0256-307X/29/1/014301
Abstract   PDF(pc) (1505KB) ( 372 )
We concentrate on the nondissipative mechanism induced shear wave in inhomogenous tissue. The shear wave equation of radiation force in inhomogeneous media is solved numerically with a finite-difference time-domain method. A rarely studied nondissipative mechanism of shear displacement due to a smooth medium inhomogeneity is evaluated. It is noted that unlike the dissipative effect, the nondissipative action on a localized inhomogeneity with its hardness parameter changing smoothly along the beam axis, compresses or stretches the focus area. The shear waves in nondissipative inhomogeneous media remain the property of sharp turn with 100% peak positive displacement and 64% peak negative displacement. This action is useful in discerning the water-like lesion.
Generalized Coupled-Mode Formulation for Sound Propagation in Range-Dependent Waveguides
LUO Wen-Yu**, YANG Chun-Mei, ZHANG Ren-He
Chin. Phys. Lett. 2012, 29 (1): 014302 .   DOI: 10.1088/0256-307X/29/1/014302
Abstract   PDF(pc) (985KB) ( 339 )
An accurate and numerically stable method based on the coupled-mode theory is presented. By applying the direct global matrix approach to obtain the modal expansion coefficients, this method is numerically stable. In addition, appropriately normalized range solutions are introduced, which resolves the overflow problem entirely. Furthermore, we put forward source conditions appropriate for the line-source problem in plane geometry. As a result, this method is capable of dealing with the scenario where a line source is located inside the region of a deformation. Closed-form expressions for coupling matrices are provided for ideal waveguides. Numerical results indicate that the present method is accurate and numerically stable. Consequently, this model can serve as a benchmark in range-dependent propagation modeling.
Two Kinds of Localized Oscillating Modes in Strongly Nonlinear Hertzian Chains with Defect
CHEN Qiong, YANG Xian-Qing**, WANG Zhen-Hui, ZHAO Xin-Yin
Chin. Phys. Lett. 2012, 29 (1): 014501 .   DOI: 10.1088/0256-307X/29/1/014501
Abstract   PDF(pc) (526KB) ( 341 )
We study mechanical energy localization, which has been experimentally observed by Job [Phys. Rev. E 80 (2009) 025602(R)], using computer simulations and the binary-collision approximation. We find interactions of a solitary wave with a light intruder exciting two kinds of localized modes. One is visible in the tail of the incident impulse, and the other is observed when the defect is loaded by the solitary wave. The frequency of localized oscillations is analytically obtained and is in excellent agreement with the numerical results.
Shedding Phenomenon of Ventilated Partial Cavitation around an Underwater Projectile
WANG Yi-Wei, HUANG Chen-Guang, DU Te-Zhuan, WU Xian-Qian, FANG Xin, LIANG Nai-Gang, WEI Yan-Peng**
Chin. Phys. Lett. 2012, 29 (1): 014601 .   DOI: 10.1088/0256-307X/29/1/014601
Abstract   PDF(pc) (801KB) ( 552 )
A new shedding phenomenon of ventilated partial cavitations is observed around an axisymmetric projectile in a horizontal launching experiment. The experiment system is established based on SHPB launching and high speed photography. A numerical simulation is carried out based on the homogeneous mixture approach, and its predicted evolutions of cavities are compared with the experimental results. The cavity breaks off by the interaction between the gas injection and the re-entry jet at the middle location of the projectile, which is obviously different from natural cavitation. The mechanism of cavity breaking and shedding is investigated, and the influences of important factors are also discussed.
Exact Solutions of Chemically Reactive Solute Distribution in MHD Boundary Layer Flow over a Shrinking Surface
Chandaneswar Midya*
Chin. Phys. Lett. 2012, 29 (1): 014701 .   DOI: 10.1088/0256-307X/29/1/014701
Abstract   PDF(pc) (453KB) ( 339 )
An analytical study of the distribution of a reactant solute undergoing a first-order chemical reaction in the boundary layer flow of an electrically conducting incompressible fluid over a linearly shrinking surface is presented. The flow is permeated by an externally applied magnetic field normal to the plane of the flow. The equations governing the flow and concentration field are reduced into a set of nonlinear ordinary differential equations using similarity variables. Closed form exact solutions of the reduced concentration equation are obtained for both prescribed power-law surface concentration (PSC) and power-law wall mass flux (PMF) as boundary conditions. The study reveals that the concentration over a shrinking sheet is significantly different from that of a stretching surface. It is found that the solute boundary layer thickness is enhanced with the increasing values of the Schmidt number and the power-law index parameter, but decreases with enhanced values of magnetic and reaction rate parameters for the PSC case. For the PMF case, the solute boundary layer thickness decreases with the increase of the Schmidt number, magnetic and reaction rate parameter for power-law index parameter n=0. Negative solute boundary layer thickness is observed for the PMF case when n=1 and 2, and these facts may not be realized in real-world applications.
Numerical Simulation of Cavitation in a Centrifugal Pump at Low Flow Rate
TAN Lei, CAO Shu-Liang**, WANG Yu-Ming, ZHU Bao-Shan
Chin. Phys. Lett. 2012, 29 (1): 014702 .   DOI: 10.1088/0256-307X/29/1/014702
Abstract   PDF(pc) (1278KB) ( 1778 )
Based on the full cavitation model which adopts homogeneous flow supposition and considering the compressibility effect on cavitation flow to modify the re-normalization group kϵ turbulence model by the density function, a computational model is developed to simulate cavitation flow of a centrifugal pump at low flow rate. The Navier–Stokes equation is solved with the SIMPLEC algorithm. The calculated curves of net positive suction head available (NPSHa) HNPSHa agree well with the experimental data. The critical point of cavitation in centrifugal pump can be predicted precisely, and the NPSH critical values derived from simulation are consistent with the experimental data. Thus the veracity and reliability of this computational model are verified. Based on the result of numerical simulation, the distribution of vapor volume fraction in the impeller and pressure at the impeller inlet are analyzed. Cavities first appear on the suction side of the blade head near the front shroud. A large number of cavities block the impeller channels, which leads to the sudden drop of head at the cavitation critical point. With the reduction of NPSHa, the distribution of pressure at the impeller inlet is more uniform.
Stimulated Raman Backscattering Amplification Using Multiple Pump Pulses
GE Zhe-Yi, YIN Yan**, CHEN De-Peng, ZHUO Hong-Bin, MA Yan-Yun, SHAO Fu-Qiu
Chin. Phys. Lett. 2012, 29 (1): 015201 .   DOI: 10.1088/0256-307X/29/1/015201
Abstract   PDF(pc) (542KB) ( 306 )
A multiple-pump-pulses-stimulated Raman backscattering amplification (m-SRA) scheme is proposed and examined using 1D PIC simulations. Compared with the SRA using a single long pump pulse, higher energy conversion efficiency can be obtained with the same output laser intensity by employing the m-SRA scheme. Unwanted Raman forward scattering can be suppressed in the m-SRA case. Favorable pulse envelope and frequency characteristics of the seed pulse after amplification are obtained by using the m-SRA scheme.
Single-Shot Measurement of Broad Bandwidth Terahertz Pulses
ZHOU Mu-Lin, LIU Feng, LI Chun, DU Fei, LI Yu-Tong**, WANG Wei-Min, SHENG Zheng-Ming, , CHEN Li-Ming, MA Jing-Long, LU Xin, DONG Quan-Li, ZHANG Jie, **
Chin. Phys. Lett. 2012, 29 (1): 015202 .   DOI: 10.1088/0256-307X/29/1/015202
Abstract   PDF(pc) (1125KB) ( 513 )
We propose a new single-shot method for measuring terahertz pulses using a linearly chirped optical pulse interferogram. Modulated frequency domain phase information can be extracted by the interferogram recorded on imaging spectrographs. The terahertz pulse waveform is obtained from the phase information. We overcome the energy fluctuation problem by using the phase information, making a reference shot unnecessary and the terahertz detection more flexible and convincing.
Hysteresis Loops and Phase Diagrams of the Spin-1 Ising Model in a Transverse Crystal Field
S. Bouhou, I. Essaoudi, A. Ainane, M. Saber, J. J. de Miguel, M. Kerouad
Chin. Phys. Lett. 2012, 29 (1): 016101 .   DOI: 10.1088/0256-307X/29/1/016101
Abstract   PDF(pc) (1079KB) ( 602 )
Within the framework of the effective-field theory with a probability distribution technique, which accounts for the self-spin correlation functions, the ferromagnetic spin-1 Ising model with a transverse crystal field on honeycomb, square and simple cubic lattices is studied. We have investigated the effect of the transverse crystal field on the phase diagrams, magnetization, hysteresis loops and χz,h of the system. A number of interesting phenomena of the system are discussed.
Cavitating Flow over a Mini Hydrofoil
LUO Xian-Wu**, JI Bin, ZHANG Yao, XU Hong-Yuan
Chin. Phys. Lett. 2012, 29 (1): 016401 .   DOI: 10.1088/0256-307X/29/1/016401
Abstract   PDF(pc) (566KB) ( 826 )
We consider a cavitating flow over a mini hydrofoil (foil profile: Clark-Y-11.7) having a 14 mm chord length in a cavitation tunnel at various cavitation numbers. Experimental observations show that cavitating flows over a miniature hydrofoil display several types of cavitation behavior, such as cavitation inception, sheet cavitation, cloud cavitation and super cavitation with the decreasing cavitation number. Under the same cavitation conditions, cavitation over a mini hydrofoil would be suppressed in comparison to cavitation over an ordinary hydrofoil. This cavitation scale effect is suspected to be caused by the Reynolds number.
Si-Nanocrystals with Bimodal Size Distribution in Evenly Annealed SiO Revealed with Raman Scattering
KE Wei-Wei, FENG Xue**, HUANG Yi-Dong
Chin. Phys. Lett. 2012, 29 (1): 016402 .   DOI: 10.1088/0256-307X/29/1/016402
Abstract   PDF(pc) (913KB) ( 402 )
The size distribution of Si-nanocrystals (Si-ncs) in evenly annealed SiO is investigated with transmission electron microscopy (TEM), x-ray diffraction (XRD), and Raman scattering. Two groups of Si-ncs with very different most probable diameters are identified, where one is >6 nm and the other one is < 2 nm. Both of them increase gradually with increasing annealing temperature. Such a phenomenon is observed directly by TEM for samples with larger Si−ncs (>10 nm) and it can be revealed clearly for all samples by Raman spectra with two components (∼500 cm−1 and ∼520 cm−1). The results of XRD show the average effect. The experimental results indicate that the common assumption of Si-nc size distribution with single most probable diameter is not always proper and the possible mechanisms are briefly discussed.
Amphiphilic Bio-molecules/ZnO Interface: Enhancement of Bio-affinity and Dispersibility
MENG Xiu-Qing**, FANG Yun-Zhang, WU Feng-Min
Chin. Phys. Lett. 2012, 29 (1): 016801 .   DOI: 10.1088/0256-307X/29/1/016801
Abstract   PDF(pc) (897KB) ( 340 )
The dispersibility of bio-molecules such as lecithins on the surface of ZnO nanowires are investigated for biosensor applications. Lecithins can be absorbed on an as-synthesized ZnO nanowire surface in the form of sub-micro sized clusters, while scattering well on those annealed under oxygen atmosphere. Wettability analysis reveals that the as-synthesized ZnO nanowires bear a super-hydrophobic surface, which convents to superhydrophilic after oxygen annealing. First-principles calculations indicate that the adsorption energy of ZnO with water is about 0.2 eV at a distance of 2 Å when it is superhydrophilic, suggesting that lecithin can be absorbed on the hydrophilic surface stably at this distance and the bio-affinity can be enhanced under this condition.
Reddish Orange Long-Lasting Phosphorescence in KY3F10:Sm3+ for X-Ray or Cathode Ray Tubes
ZHANG Jin-Su, ZHONG Hai-Yang, SUN Jia-Shi, CHENG Li-Hong, LI Xiang-Ping, CHEN Bao-Jiu**
Chin. Phys. Lett. 2012, 29 (1): 017101 .   DOI: 10.1088/0256-307X/29/1/017101
Abstract   PDF(pc) (850KB) ( 474 )
We report a reddish orange long-lasting phosphor of KY3F10:Sm3+ synthesized by a solid−state reaction for applications in x-ray or cathode-ray tubes. The spectrum contains a group of reddish orange emission lines originating from 4G5/2 6HJ transitions of Sm3+. The Judd–Ofelt theory is introduced to analyze the optical transitions of the Sm3+ ions. Moreover, phosphorescence characteristics are discussed. The energy charging and release processes of the phosphor are measured and the phosphorescence decay time with 10% of initial intensity is about 40.7 seconds. The order of kinetics and the activation energy are obtained according to the thermoluminescence curve. The phosphorescence mechanism is proposed based on structural analysis and thermoluminescence glow curve measurement.
Metal-Insulator Transition of Plutonium Hydrides: DFT+U Calculations in the FPLAPW Basis
AO Bing-Yun**, AI Juan-Juan, GAO Tao**, WANG Xiao-Lin, SHI Peng, CHEN Pi-Heng, YE Xiao-Qiu
Chin. Phys. Lett. 2012, 29 (1): 017102 .   DOI: 10.1088/0256-307X/29/1/017102
Abstract   PDF(pc) (776KB) ( 373 )
We report on the first-principles calculations of the electronic structure of face-centered cubic PuH2 and hexagonal PuH3 combining the full potential linearized augmented plane−wave basis with the density functional theory plus a Hubbard parameter U for considering the strong Coulomb correlation between localized Pu 5f electrons. Most importantly, the findings provide evidence for the first time that a spectacular metal−insulator transition occurs on the phase transformation from PuH2 to PuH3.
Charge Transport and Electrical Properties in Poly(3-hexylthiophene) Polymer Layers
WANG Li-Guo**, ZHANG Huai-Wu, TANG Xiao-Li, LI Yuan-Xun, ZHONG Zhi-Yong
Chin. Phys. Lett. 2012, 29 (1): 017201 .   DOI: 10.1088/0256-307X/29/1/017201
Abstract   PDF(pc) (514KB) ( 393 )
A systematic study of the charge transport and electrical properties in poly(3-hexylthiophene) (P3HT) polymer layers is performed. We demonstrate that the temperature-dependent current-voltage J(V,T) characteristics of hole−only devices based on P3HT can be accurately described using the recently introduced extended Gaussian disorder model (EGDM). A particular numerical method adopting the uneven discretization and Newton iteration method is used to solve the coupled equations describing the space-charge limited (SCL) current in conjugated polymers. For the polymer studied, we find the width of the density of states σ=0.1 eV and the lattice constant a=1.15 nm. Based on the numerical method and EGDM, we further calculate and analyze some important electrical properties for P3HT in detail, including the variation of current-voltage characteristics with the boundary carrier density and the distribution of charge-carrier density and electric field with the distance from interface.
Formation of Low-Resistant and Thermally Stable Nonalloyed Ohmic Contact to N-Face n-GaN
ZENG Chang, ZHANG Shu-Ming**, WANG Hui, LIU Jian-Ping, WANG Huai-Bing, LI Zeng-Cheng, FENG Mei-Xin, ZHAO De-Gang, LIU Zong-Shun, JIANG De-Sheng, YANG Hui
Chin. Phys. Lett. 2012, 29 (1): 017301 .   DOI: 10.1088/0256-307X/29/1/017301
Abstract   PDF(pc) (615KB) ( 1611 )
We report on the formation of Ohmic contacts with low resistance and high thermal stability to N-face n-GaN for vertical structure light emitters using a Ti(50nm)/Pt(50nm)/Au(50nm) metal scheme, where the Pt layer is introduced as a blocking layer to suppress the diffusion of Au onto the N-face n-GaN surface. It is shown that unlike the conventional Ti/Al/Ti/Au contacts, the Ti/Pt/Au contacts exhibit an Ohmic behavior with a relatively low specific contact resistivity of 1.1×10−4 Ω⋅cm2 even after annealing at 350 °C. X-ray diffraction (XRD) measurements by synchrotron radiation and Auger electron spectroscopy (AES) examination are performed to understand the effects of heat treatment.
Effect of Substrate Temperature on the Structural and Raman Properties of Ag-Doped ZnO Films
WANG Li-Na, HU Li-Zhong, ZHANG He-Qiu, **, QIU Yu, LANG Ye, LIU Guo-Qiang, QU Guang-Wei, JI Jiu-Yu, MA Jin-Xue,
Chin. Phys. Lett. 2012, 29 (1): 017302 .   DOI: 10.1088/0256-307X/29/1/017302
Abstract   PDF(pc) (527KB) ( 729 )
Ag-doped ZnO (ZnO:Ag) films are prepared on c-plane sapphire substrates by pulsed laser deposition at different substrate temperatures. The effect of substrate temperature on the ZnO:Ag film is studied in detail by EDX, XRD and Raman spectroscopy. The results reveal that raising the substrate temperature is beneficial for incorporating Ag into ZnO:Ag films in the range of our experimental temperatures and a number of Ag atoms incorporation into ZnO:Ag films may cause the (002) peak positions of the XRD spectra shift to a lower angle direction, but hardly affect the c−axis orientation of the films. The (002) peak shift ought to be due to the increase of lattice constant in the c−axis direction caused by the partial substitution of Zn2+ ions by Ag+ ions. In addition, a local vibrational mode (LVM) at 492 cm−1 induced by doping Ag occurred in the Raman spectra of all the ZnO:Ag films and its peak position hardly shifted with increasing substrate temperature. It means that the LVM can act as an indication of Ag incorporation into ZnO:Ag film.
Structural, Electronic and Optical Properties of KTa0.5Nb0.5O3 Surface: A First-Principles Study
SUN Hong-Guo**, ZHOU Zhong-Xiang, YUAN Cheng-Xun, YANG Wen-Long, WANG He
Chin. Phys. Lett. 2012, 29 (1): 017303 .   DOI: 10.1088/0256-307X/29/1/017303
Abstract   PDF(pc) (523KB) ( 505 )
The crystal surface properties of potassium tantalite niobate, KTa0.5Nb0.5O3 (KTN), are studied with first−principles calculation based on the density functional theory (DFT). Generalized gradient approximation (GGA) functional analysis is also employed by using CASTEP software. The explanations for the differences of the ferroelectric and piezoelectric properties between the bulk and surface of the material are provided. The DFT with GGA is used to determine the structure and to calculate the electronic and optical properties of the chemically ordered KTa0.5Nb0.5O3 crystal (100), (110) and (111) surfaces. The results show that the surface properties are different from the bulk properties. The data obtained agree with the expected values and can serve as guidance for future experimental studies in the fields of photorefraction and nonlinear optics.
Terahertz Current Oscillation in Wurtzite InN
FENG Wei**
Chin. Phys. Lett. 2012, 29 (1): 017304 .   DOI: 10.1088/0256-307X/29/1/017304
Abstract   PDF(pc) (560KB) ( 370 )
Current self-oscillation in doped n+nn+ wurtzite InN diodes driven by a dc electric field is theoretically investigated by solving the time−dependent drift-diffusion model. Current self-oscillation is associated with the negative differential mobility effect in the highly non-parabolic conduction band of InN. A detailed analysis of the dependence of current oscillations on the doping concentration and the applied electric field is presented. The current oscillation frequencies can reach up to the terahertz (THz) region. The n+nn+ InN self-oscillating diode may be a promising candidate for THz generation, and the calculation results may guide the design of the devices.
The Theoretical Investigation and Analysis of High-Performance ZnO Double-Gate Double-Layer Insulator Thin-Film Transistors
GAO Hai-Xia**, HU Rong, YANG Yin-Tang
Chin. Phys. Lett. 2012, 29 (1): 017305 .   DOI: 10.1088/0256-307X/29/1/017305
Abstract   PDF(pc) (752KB) ( 876 )
A novel structure of a ZnO thin-film transistor with a double-gate and double-layer insulator is proposed to improve device performance. Compared with the conventional ZnO thin-film transistor structure, the novel thin-film transistor has a higher on-state current, steeper sub-threshold characteristics and a lower threshold voltage, owing to the double-gate and high-k dielectric. Based on two-dimensional simulation, the potential channel distribution and the reasons for the improvement in performance are investigated.
75As Nuclear Magnetic Resonance Studies on Ba(Fe1−xNix)2As2 Single Crystals under High Pressure
ZHANG Xiao-Dong, FAN Guo-Zhi, ZHANG Cheng-Lin, JING Xiu-Nian, LUO Jian-Lin**
Chin. Phys. Lett. 2012, 29 (1): 017401 .   DOI: 10.1088/0256-307X/29/1/017401
Abstract   PDF(pc) (770KB) ( 331 )
75As nuclear magnetic resonance (NMR) was measured for Ba(Fe1−xNix)2As2 single crystals with x=0.05 and x=0.1 under 0 and 1.5 GPa, respectively. For the optimal doped sample with x=0.05, the superconducting transition temperature, Tc, is strongly suppressed from 18 to 5 K, while for the over−doped sample with x=0.1, it is turned from a superconducting ground state to a disordered paramagnetic state under 1.5 GPa. Our experimental results show that the antiferromagnetic spin fluctuations, as well as Tc, are suppressed. The experimental results can be explained with the two-band model. As a result, the electronic band is shifted downwards with an increase in pressure, and the electrons become the dominant carriers in the system.
The Comprehensive Retrieval Method of Electromagnetic Parameters Using the Scattering Parameters of Metamaterials for Two Choices of Time-Dependent Factors
HOU Zhi-Ling**, KONG Ling-Bao, JIN Hai-Bo, CAO Mao-Sheng, LI Xiao, QI Xin
Chin. Phys. Lett. 2012, 29 (1): 017701 .   DOI: 10.1088/0256-307X/29/1/017701
Abstract   PDF(pc) (810KB) ( 531 )
The electromagnetic parameters (permittivity and permeability) method, retrieved from the reflection and transmission coefficients of a slab, is presented. Improvements over existing methods, including the determination of the permittivity, permeability and impedance of the slab, are expressed as explicit functions of the S parameters for both the time−dependent factors, eiωt and e−iωt (ω is the angular frequency of the incident electromagnetic wave), and the proper selection of the sign of impedance and the real part of the refractive index. Moreover, based on the retrieving method, the calculations of the electromagnetic parameters of the conventional−material teflon slab standard sample through the experimental data of the S parameters are performed, which confirm the validity of the technique for the retrieval of electromagnetic parameters.
Nanostructured Metal-Enhanced Photoluminescence of Micro-Sr2Si5N8:Eu2+ Phosphors
LIU Ling, XU Xiao-Liang**, LEI Jie-Mei, YIN Nai-Qiang
Chin. Phys. Lett. 2012, 29 (1): 017801 .   DOI: 10.1088/0256-307X/29/1/017801
Abstract   PDF(pc) (598KB) ( 512 )
The enhancement of the photoluminescence of micro-Sr2Si5N8:Eu2+ phosphors on the surface of Ag and Au nanoparticles is studied. Ag nanoparticles cause a considerable enhancement in the photoluminescence intensity of microsized Sr2Si5N8:Eu2+ phosphors. We further investigate the enhanced emission of self−assembled worm-like Au nanoparticles from Sr2Si5N8:Eu2+ phosphors. A brightness photoluminescence intensity enhanced by about six times is observed, and is due to the stronger scattering and higher numbers of hot spots in the Au worms. The luminescence efficiency of the microparticles is higher than the nanoparticles, and it is very difficult to enhance light emission. Therefore, the realization of microphosphor photoluminescence enhancement is a great breakthrough.
The Preparation and Photoluminescence Properties of Fluorosilicate Glass Ceramics Containing CeF3:Dy3+ Nanocrystals
WU Li-Ang, FU Heng-Yi, QIAN Jiang-Yun, ZHAO Da-Liang, LUO Qun, QIAO Xu-Sheng**, FAN Xian-Ping, ZHANG Xiang-Hua
Chin. Phys. Lett. 2012, 29 (1): 017802 .   DOI: 10.1088/0256-307X/29/1/017802
Abstract   PDF(pc) (1095KB) ( 498 )
Ce3+ and Dy3+ co−doped oxyfluoride glasses and glass ceramics containing CeF3 nanocrystals are prepared in a reducing atmosphere. XRD measurements and the calculated lattice parameters suggest that Dy3+ ions are incorporated with precipitated CeF3 nanocrystals along with a rise in the Dy3+ concentration or an increase in the annealing temperature. The glass ceramics emit white light close to the CIE coordinates of (0.3,0.3), derived from a combination of Ce3+ and Dy3+ emission. The CIE chromaticity coordinates of the Ce3+ and Dy3+ co−doped glass ceramics can be tuned by varying the ratio of Ce3+/Dy3+, while the luminescence intensity can be enhanced by heat treatment above 620°C.
Comparative Study of the Characteristics of the Basal Plane Stacking Faults of Nonpolar a−Plane and Semipolar (11
XU Sheng-Rui**, LIN Zhi-Yu, XUE Xiao-Yong, LIU Zi-Yang, MA Jun-Cai, JIANG Teng, MAO Wei, WANG Dang-Hui, ZHANG Jin-Cheng, HAO Yue
Chin. Phys. Lett. 2012, 29 (1): 017803 .   DOI: 10.1088/0256-307X/29/1/017803
Abstract   PDF(pc) (626KB) ( 520 )
Nonpolar (1120) and semipolar (1122) GaN are grown on r−plane and m−plane sapphire by MOCVD to investigate the characteristics of basal plane stacking faults (BSFs). Transmission electron microscopy reveals that the density of BSFs for the semipolar (1122) and nonpolar a−plane GaN template is 3×105 cm−1 and 8×105 cm−1, respectively. The semipolar (1122) GaN shows an arrowhead−like structure, and the nonpolar a−plane GaN has a much smoother morphology with a streak along the c−axis. Both nonpolar (1120) and semipolar (1122) GaN have very strong BSF luminescence due to the optically active character of the BSFs.
The Annealing-Induced Shape Deformation of Hydrothermal-Grown ZnO Nanorods
ZHENG Zhong-Kui, DUANMU Qing-Duo**, ZHAO Dong-Xu**, WANG Li-Dan, SHEN De-Zhen
Chin. Phys. Lett. 2012, 29 (1): 017804 .   DOI: 10.1088/0256-307X/29/1/017804
Abstract   PDF(pc) (1034KB) ( 500 )
The shape deformation of hydrothermal-grown ZnO nanorods is observed. After annealing at high temperature, hexagonal ZnO nanorods change to become cylinder-like ones. The adjacent nanorods tend to connect to each other to form one nanostructure. Photoluminescence measurements show that a sample annealed at 600°C has a strong ultraviolet emission with a very weak visible emission, and with increasing annealing temperature the visible emission becomes more intense. It can be concluded from analyses of the morphological changes that the surface reaction between the doped C and ZnO is the main reason for the shape deformation of the ZnO nanorods.
The Morphological Change of Silver Nanoparticles in Water
WANG Peng, WANG Rong-Yao**, JIN Jing-Yang, XU Le, SHI Qing-Fan**
Chin. Phys. Lett. 2012, 29 (1): 017805 .   DOI: 10.1088/0256-307X/29/1/017805
Abstract   PDF(pc) (474KB) ( 435 )
The solvent-induced morphological change of silver nanoparticles is studied with a combination of optical spectroscopy and atomic force microscopy (AFM). By using the local surface plasmon resonance (LSPR) spectroscopy arising from Ag nanoparticles, an in-situ investigation of the spectral changes is carried out before, during and after exposure of Ag island films to water. Combining with the morphological observations by AFM, we sort out the morphological and dielectric contributions to the water-induced LSPR changes. Our results demonstrate that a slight morphological change induced by water contact can result in an apparent blue shift of the LSPR spectral maximum. Furthermore, it is found that this structural change leads to a higher sensitivity of the Ag island films in response to the change in the external dielectric environment. This solvent-induced morphological change, and consequently the modification of the LSPR of the metal nanoparticles, may have significant impact in the applications of solvent-involved plasmon sensors, such as chemical/biological sensing and single-molecule spectroscopy.
The Growth of Semi-Polar ZnO (10
SANG Ling**, WANG Jun**, SHI Kai, WEI Hong-Yuan, JIAO Chun-Mei, LIU Xiang-Lin, YANG Shao-Yan, ZHU Qin-Sheng, WANG Zhan-Guo
Chin. Phys. Lett. 2012, 29 (1): 018101 .   DOI: 10.1088/0256-307X/29/1/018101
Abstract   PDF(pc) (2075KB) ( 317 )
Semi-polar ZnO (1011) epitaxial films are demonstrated using a methanol oxidant by metalorganic chemical vapor deposition on Si (111) substrates at 500°C. X−ray φ scanning indicates that there are six kinds of in−plane domain growths, with the ZnO [1012] parallel to the Si 〈112〉 direction families. The crystallographic orientation of ZnO is supposed to be caused by surface passivation. The methanol, as a polar molecule, may be adsorbed on the Si (111) surface to form a passivation layer, which inhibits the (0001) ZnO plane deposition on the substrate surface, and as a result the ZnO (1011) plane becomes preferred. The optical properties, examined by a room−temperature photoluminescence spectrum, exhibit a strong near-band-edge emission peak at 379 nm, indicating that the (1011) ZnO film has good crystal quality. These results are significant for research into and for the applications of semi-polar ZnO films.
A Study of GaN Grown on SiH4 Pre-Treated 6H-SiC Substrates
SONG Shi-Wei, LIANG Hong-Wei**, LIU Yang, XIA Xiao-Chuan, SHEN Ren-Sheng, LUO Ying-Min, DU Guo-Tong,
Chin. Phys. Lett. 2012, 29 (1): 018102 .   DOI: 10.1088/0256-307X/29/1/018102
Abstract   PDF(pc) (630KB) ( 420 )
GaN thin films are grown on Si-terminated (0001) 6H-SiC substrates pre-treated with SiH4 in a metal organic chemical vapor deposition system. The influence of the SiH4 pre−treatment conditions on the SiC surface is carefully investigated. It is found that SiH4 could react with the SiC surface oxide, which will change the surface termination. Moreover, our experiments demonstrate that SiH4 pre-treatment can distinctly influence the AlGaN nucleation layer and the basic characteristics of GaN.
The Field Emission Characteristics of Titanium-Doped Nano-Diamonds
YANG Yan-Ning, ZHANG Zhi-Yong**, ZHANG Fu-Chun, DONG Jun-Tang, ZHAO Wu, ZHAI Chun-Xue, ZHANG Wei-Hu
Chin. Phys. Lett. 2012, 29 (1): 018103 .   DOI: 10.1088/0256-307X/29/1/018103
Abstract   PDF(pc) (1210KB) ( 429 )
An electrophoresis solution, prepared in a specific ratio of titanium (Ti)-doped nano-diamond, is dispersed by ultrasound and the nano-diamond coating is then deposited on a polished Ti substrate by electrophoresis. After high-temperature vacuum annealing, the appearance of the surface and the microstructures of the coating are observed by a metallomicroscope, scanning electron microscopy and Raman spectroscopy. The field emission characteristics and luminescence features are also tested, and the mechanism of the field emission characteristics of the Ti-doped nano-diamond is analyzed. The experimental results show that under the same conditions, the diamond-coated surface (by deposition) is more uniform after doping with 5 mg of Ti powder. Compared with the undoped nano-diamond cathode, the turn-on fields decline from 6.95 to 5.95 V/µm. When the electric field strength is 13.80 V/µm, the field emission current density increases to 130.00 µA/cm2. Under the applied fields, the emission current is stable and the luminescence is at its best, while the field emission characteristics of the 10 mg Ti-doped coating become worse, as does the luminescence. The reason for this could be that an excessive amount of TiC is generated on the surface of the coating.
The Photovoltaic Properties of BiFeO3La0.7Sr0.3MnO3 Heterostructures
LUO Bing-Cheng, CHEN Chang-Le**, FAN Fei, JIN Ke-Xin
Chin. Phys. Lett. 2012, 29 (1): 018104 .   DOI: 10.1088/0256-307X/29/1/018104
Abstract   PDF(pc) (609KB) ( 599 )
An epitaxial BiFeO3/La0.7Sr0.3MnO3 (BFO/LSMO) multiferroic heterostructure is grown on an LaAlO3 (001) substrate by laser molecular beam epitaxy, and its photovoltaic properties are investigated. It is found that the photocurrent is significantly increased under illumination, and the short-circuit photocurrent has a linear relationship with the laser intensity. Furthermore, when the ferroelectric polarization of the BFO layer is switched, the short-circuit photocurrent and open-circuit voltage can be switched. These results are discussed by considering the contributions from the ferroelectric polarization and the electrode/film interface.
The Electric Mechanism of Surface Pretreatments for Dye-Sensitized Solar Cells Based on Internal Equivalent Resistance Analysis
XU Wei-Wei, HU Lin-Hua, LUO Xiang-Dong, LIU Pei-Sheng, DAI Song-Yuan**
Chin. Phys. Lett. 2012, 29 (1): 018401 .   DOI: 10.1088/0256-307X/29/1/018401
Abstract   PDF(pc) (842KB) ( 514 )
Based on the optimization of dye-sensitized solar cell (DSC) photoelectrodes pretreated with different methods such as electrodeposition, spin-coating and TiCl4 pretreatment, theoretical calculations are carried out to interpret the internal electric mechanism. The numerical values, including the series resistance Rs and the shunt resistance Rsh corresponding to the equivalent circuit model, are well evaluated and confirm that the DSC has good performance with a high Rsh and a low Rs due to good electrical contact and a low charge recombination after the different modifications. The IV curves are fitted in the case without series resistance, and account for the role of Rs in the output characteristics. It is found that when Rs tends to the infinitesimal, the short−circuit current Isc, the open−circuit voltage Voc and the fill factor can be improved by almost 0.8–1.4, 2.9 and 2.1–6.8%, respectively.
Reactive Radiofrequency Sputtering-Deposited Nanocrystalline ZnO Thin-Film Transistors
LI Shao-Juan, HE Xin, HAN De-Dong, SUN Lei, WANG Yi, HAN Ru-Qi, CHAN Man-Sun, ZHANG Sheng-Dong, **
Chin. Phys. Lett. 2012, 29 (1): 018501 .   DOI: 10.1088/0256-307X/29/1/018501
Abstract   PDF(pc) (1089KB) ( 584 )
The structural and electrical properties of ZnO films deposited by reactive radiofrequency sputtering with a metallic zinc target are systematically investigated. While the as-deposited ZnO film is in a poly-crystalline structure when the partial pressure of oxygen (pO2) is low, the grain size abruptly decreases to a few nanometers as pO2 increases to a critical value, and then becomes almost unchanged with a further increase in pO2. In addition, the resistivity of the ZnO films shows a non−monotonic dependence on pO2, including an abrupt transition of about seven orders of magnitude at the critical pO2. Thin−film transistors (TFTs) with the nanocrystalline ZnO films as channel layers have an on/off current ratio of more than 107, an off−current in the order of pA, a threshold voltage of about 4.5 V, and a carrier mobility of about 2 cm2/(V⋅s). The results show that radiofrequency sputtered ZnO with a zinc target is a promising candidate for high-performance ZnO TFTs.
Temporal Correlation-Based Spatial Filtering of Rician Noise for Functional MRIs
Amir. A. Khaliq*, I. M. Qureshi, Jawad. A. Shah
Chin. Phys. Lett. 2012, 29 (1): 018701 .   DOI: 10.1088/0256-307X/29/1/018701
Abstract   PDF(pc) (492KB) ( 408 )
A novel correlation-based filter is presented for de-noising functional magnetic resonance imaging (fMRI) data. Temporal correlation-based exponential weights are defined for spatial smoothing of the data, with bias reduction using estimated noise variance. The proposed scheme is tested on simulated and real fMRI data. Finally, the results are compared with conventional filters. The method is found to be effectively suppressing the Rician noise in fMRI data, while improving the SNR.
Intelligent Exit-Selection Behaviors during a Room Evacuation
Zarita Zainuddin, Lim Eng Aik**
Chin. Phys. Lett. 2012, 29 (1): 018901 .   DOI: 10.1088/0256-307X/29/1/018901
Abstract   PDF(pc) (411KB) ( 470 )
A modified version of the existing cellular automata (CA) model is proposed to simulate an evacuation procedure in a classroom with and without obstacles. Based on the numerous literature on the implementation of CA in modeling evacuation motions, it is notable that most of the published studies do not take into account the pedestrian's ability to select the exit route in their models. To resolve these issues, we develop a CA model incorporating a probabilistic neural network for determining the decision-making ability of the pedestrians, and simulate an exit-selection phenomenon in the simulation. Intelligent exit-selection behavior is observed in our model. From the simulation results, it is observed that occupants tend to select the exit closest to them when the density is low, but if the density is high they will go to an alternative exit so as to avoid a long wait. This reflects the fact that occupants may not fully utilize multiple exits during evacuation. The improvement in our proposed model is valuable for further study and for upgrading the safety aspects of building designs.
An Internal Heating Model to Elucidate the Shape of a Small Planetary Body
LI Gen, CHEN Chu-Xin**
Chin. Phys. Lett. 2012, 29 (1): 019601 .   DOI: 10.1088/0256-307X/29/1/019601
Abstract   PDF(pc) (524KB) ( 347 )
Small planetary bodies usually have irregular shapes. If they are large enough to be heated to a partial melting status, the deforming force of gravity could overcome the internal forces and make the shape transfigure from potato-like to spherical. We have developed a model to calculate the thermal history of a planetoid and apply the model to asteroids, since ample evidence has shown that many asteroids could have undergone differentiation. After revealing the relation between the shape and the ratio of the melt part, we also examine the surface roughness of these asteroids and suggest that 280 km would be a critical radius for an asteroid to develop a virtually globular contour.
Reanalysis of the Isotopic Mixture of Neutron-Capture Elements in the Metal-Poor Star HD 175305
ZHANG Jiang, **, WANG Bo, ZHANG Bo, HAN Zhan-Wen,
Chin. Phys. Lett. 2012, 29 (1): 019701 .   DOI: 10.1088/0256-307X/29/1/019701
Abstract   PDF(pc) (613KB) ( 331 )
The neutron-capture process is traditionally postulated to be responsible for the nucleosynthesis of heavy elements beyond Fe. Based on the least squares method and solar isotopic abundances from the classical model, we estimate the relative contributions of the s- and r-processes to the abundance of neutron-capture elements in the metal-poor star HD 175305 from the component coefficients. Applying the calculated component coefficients Cr and Cs, the model predicts the isotopic fractions of elements Nd, Sm and Eu to be f142+144=0.482, f152+154=0.525 and f151=0.450, respectively. As well as the observed abundances, the isotropic fractions are also consistent with the calculations. Finally, for the first time, we estimated the contribution percentage of the two neutron processes (the r− and s-processes) from the observed isotopic fractions of different elements in HD 175305, e.g. an r-process contribution of 67%-32%+21% from the 4604 Å line of Sm.
Erratum: Multilayer Antireflection Coating for Triple Junction Solar Cells [Chin. Phys. Lett. 28 (2011) 047802]
ZHAN Feng**, WANG Hai-Li, HE Ji-Fang, WANG Juan, HUANG She-Song, NI Hai-Qiao, NIU Zhi-Chuan
Chin. Phys. Lett. 2012, 29 (1): 019901 .   DOI: 10.1088/0256-307X/29/1/019901
Abstract   PDF(pc) (285KB) ( 286 )
Erratum: Dyadic Green Function for an Electromagnetic Medium Inspired by General Relativity [Chin. Phys. Lett. 23 (2006) 832]
Akhlesh Lakhtakia, Tom G. Mackay, *
Chin. Phys. Lett. 2012, 29 (1): 019902 .   DOI: 10.1088/0256-307X/29/1/019902
Abstract   PDF(pc) (234KB) ( 332 )
84 articles