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Volume 30 Issue 9
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GENERAL
Acceleration of the Stochastic Analytic Continuation Method via an Orthogonal Polynomial Representation of the Spectral Function
WU Quan-Sheng, WANG Yi-Lin, FANG Zhong, DAI Xi
Chin. Phys. Lett. 2013, 30 (9): 090201 .   DOI: 10.1088/0256-307X/30/9/090201
Abstract   PDF(pc) (601KB) ( 681 )
Stochastic analytic continuation is an excellent numerical method for analytically continuing Green's functions from imaginary frequencies to real frequencies, although it requires significantly more computational time than the traditional MaxEnt method. We develop an alternate implementation of stochastic analytic continuation which expands the dimensionless field n(x) introduced by Beach using orthogonal polynomials. We use the kernel polynomial method (KPM) to control the Gibbs oscillations associated with truncation of the expansion in orthogonal polynomials. Our KPM variant of stochastic analytic continuation delivers improved precision at a significantly reduced computational cost.
Synchronization of Colored Networks via Discrete Control
SUN Mei, LI Dan-Dan, HAN Dun, JIA Qiang
Chin. Phys. Lett. 2013, 30 (9): 090202 .   DOI: 10.1088/0256-307X/30/9/090202
Abstract   PDF(pc) (472KB) ( 454 )
We investigate the synchronization problem of two colored networks via discrete control based on the Lyapunov stability theory. First, intermittent control is adopted to synchronize two edge-colored networks, and the sufficient condition connecting the control width, control period and the network topology is established for reaching synchronization. Then, an impulsive controller is designed to ensure two general colored networks in synchronization, and the relation among the impulsive interval, impulsive gain and the network topology for synchronization is also discovered. Finally, two numerical examples are provided to demonstrate and verify the theoretical results.
A Bidirectional Quantum Secure Direct Communication Protocol Based on Five-Particle Cluster State
CHANG Yan, ZHANG Shi-Bin, YAN Li-Li
Chin. Phys. Lett. 2013, 30 (9): 090301 .   DOI: 10.1088/0256-307X/30/9/090301
Abstract   PDF(pc) (408KB) ( 533 )
To transmit a message safely, five-particle cluster state particles are used to construct a bidirectional quantum secure direct communication protocol. Five-particle cluster state particles are used for both detecting eavesdroppers and transmitting secret messages. All of the five-particle cluster states' photons for detection are mixed to the sending sequence to detect eavesdroppers. The detection rate approaches 88% per qubit. The five-particle cluster states needed are only one fifth of the photons in the sending sequence. In this protocol, there is no photon carrying secret information transmitting in quantum channel, and the classical XOR operation which serves as a one-time-pad is used to ensure the security of the protocol. Compared with three photons of each five-particle cluster state as detection photons, the five photons in this study will decrease the five-particle cluster states needed for detection greatly.
Quantum Discord-Breaking Channels
YAO Chun-Mei, HE Zhi, CHEN Zhi-Hua, NIE Jian-Jun
Chin. Phys. Lett. 2013, 30 (9): 090302 .   DOI: 10.1088/0256-307X/30/9/090302
Abstract   PDF(pc) (434KB) ( 439 )
Through comparisons with an entanglement breaking (EB) channel, we characterize the local quantum channels that destroy quantum correlations, especially for quantum discord, and give a detailed description of a discord-breaking (DB) channel. We prove that the quantum discord can be broken if and only if the local quantum channel is a commutativity-creating (CoC) channel. Then we show which kind of channels is a CoC channel, and address the relation between EB and DB channels. Furthermore we apply our results to three typical noise channels.
Separability of Generalized Graph Product States
ZHAO Hui, FAN Jiao
Chin. Phys. Lett. 2013, 30 (9): 090303 .   DOI: 10.1088/0256-307X/30/9/090303
Abstract   PDF(pc) (441KB) ( 349 )

We construct two classes of generalized graph product states and study the entanglement of these states. It is first presented that the density matrices of complex edge-weighted digraphs associated with the generalized graph product in mn systems are positive partial transformation and separable states. Then we prove that the density matrices of the vertex-weighted digraphs associated with another generalized graph product are entangled states.

Damping Law of Photocount Distribution in a Dissipative Channel
FAN Hong-Yi, LOU Sen-Yue, HU Li-Yun
Chin. Phys. Lett. 2013, 30 (9): 090304 .   DOI: 10.1088/0256-307X/30/9/090304
Abstract   PDF(pc) (449KB) ( 259 )
For a dissipative channel governed by the master equation of the density operator describing the photon loss, we find that the photocount distribution formula at time t can be related to the initial photocount distribution by replacing the efficiency of the detector ξ with ξe?2κt, as if the quantum efficiency ξ of the detector becomes ξe?2κt. This law greatly simplifies the theoretical study of the photocount distribution for quantum optical fields.
The Energy Distribution of a Noncommutative Reissner–Nordström Black Hole
Kourosh Nozari, A. Yazdani
Chin. Phys. Lett. 2013, 30 (9): 090401 .   DOI: 10.1088/0256-307X/30/9/090401
Abstract   PDF(pc) (685KB) ( 326 )
We study the energy distribution of a noncommutative Reissner–Nordstr?m black hole. We consider both Einstein and M?ller prescriptions, and compare our results with the corresponding results obtained recently for a Schwarzschild black hole.
The Thermodynamical Behaviors of Kerr–Newman AdS Black Holes
A. Belhaj, M. Chabab, H. El Moumni, L. Medari, M. B. Sedra
Chin. Phys. Lett. 2013, 30 (9): 090402 .   DOI: 10.1088/0256-307X/30/9/090402
Abstract   PDF(pc) (502KB) ( 294 )
We reconsider the study of critical behaviors of Kerr–Newman Anti-de Sitter (AdS) black holes in four dimensions. The study is made in terms of the moduli space parameterized by the charge Q and the rotation parameter a, relating the mass M of the black hole and its angular momentum J via the relation a =J/M. Specifically, we discuss such thermodynamical behaviors in the presence of a positive cosmological constant considered as a thermodynamic pressure and its conjugate quantity as a thermodynamic volume. The equation of state for a charged Reissner–Nordstrom AdS black hole predicts a critical universal number depending on the (Q,a) moduli space. In the vanishing limit of the a parameter, this prediction recovers the usual universal number in four dimensions. Then, we find the bounded region of the moduli space allowing the consistency of the model with real thermodynamical variables.
Multi-Scale Permutation Entropy: A Complexity Measure for Discriminating Two-Phase Flow Dynamics
FAN Chun-Ling, JIN Ning-De, CHEN Xiu-Ting, GAO Zhong-Ke
Chin. Phys. Lett. 2013, 30 (9): 090501 .   DOI: 10.1088/0256-307X/30/9/090501
Abstract   PDF(pc) (1086KB) ( 713 )
We propose an improved permutation entropy method, i.e., multi-scale permutation entropy (MSPE), for discriminating two-phase flow dynamics. We first take the signals from different typical dynamical systems as examples to demonstrate the effectiveness of the methods. In particular, we compute the MSPE values of sinusoidal signal, logistic, Lorenz and Chen chaotic signals and their signals with white Gaussian noise added. We find that the MSPE method can be an effective tool for analyzing the time series with distinct dynamics. We finally calculate the multi-scale permutation entropy and rate of MSPE from 66 groups of conductance fluctuating signals and find that these two measures can be used to identify different flow patterns and further explore dynamical characteristics of gas-liquid flow patterns. These results suggest that the MSPE can potentially be a useful tool for revealing the dynamical complexity of two-phase flow on different scales.
THE PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
J/ψ Production Associated with the W-Boson at the 7 TeV Large Hadron Collider
SONG Mao, LI Gang, MA Wen-Gan, ZHANG Ren-You, GUO Lei, GUO Jian-You
Chin. Phys. Lett. 2013, 30 (9): 091201 .   DOI: 10.1088/0256-307X/30/9/091201
Abstract   PDF(pc) (677KB) ( 256 )
We calculate the complete next-to-leading order (NLO) QCD corrections to J/ψ+W associated production within the factorization formalism of nonrelativistic QCD at the 7 TeV Large Hadron Collider. We provide the numerical results for the leading-order (LO), NLO QCD corrected differential cross sections of the J/ψ transverse momentum by adopting the event selection criteria requested by the ATLAS experiment. It is found that the differential cross section at the LO is significantly enhanced by the NLO QCD corrections.
Influence of Quark Current Mass on Quark Condensate at Finite Temperature
LU Chang-Fang, LÜ Xiao-Fu
Chin. Phys. Lett. 2013, 30 (9): 091202 .   DOI: 10.1088/0256-307X/30/9/091202
Abstract   PDF(pc) (598KB) ( 310 )
Using the Dyson–Schwinger equation and perturbation theory, we define the quark condensate with the quark current mass at finite temperature, and compare the quark condensate at finite temperature for the quark current mass m=0 and m≠0, respectively. The results show that the two-quark condensates have significantly different behaviors from the quark condensate in the chiral limit, and the quark current mass has a very important influence over the solution of the non-perturbative term.
NUCLEAR PHYSICS
Nuclear Symmetry Energy from a Relativistic Mean Field Theory
OUYANG Fei, LIU Bei-Bei, CHEN Wei
Chin. Phys. Lett. 2013, 30 (9): 092101 .   DOI: 10.1088/0256-307X/30/9/092101
Abstract   PDF(pc) (772KB) ( 309 )
We discuss the density dependence and coupling-constant dependence of the nuclear symmetry energy in the relativistic mean field approximation of the σ?ω?ρ model. An extremely stiff density dependence of symmetry energy is obtained. At the same time, we find that the coupling constants gσ and gω have greater effect on the nuclear symmetry energy than the self-coupling constants c and d. In particular, gω and gσ determine the slope L and curvature Ksym of nuclear symmetry energy at saturation density, respectively.
Scaling Behavior of Anisotropic Flows in Intermediate Energy Heavy Ion Collisions
YAN Ting-Zhi
Chin. Phys. Lett. 2013, 30 (9): 092501 .   DOI: 10.1088/0256-307X/30/9/092501
Abstract   PDF(pc) (510KB) ( 388 )
Number of nucleons scaling for elliptic flows of light charged particles (LCPs) (A ≤4) is studied for 40 and 200 MeV/A197Au+197Au collisions at impact parameter of 6–12 fm by the isospin-dependent quantum molecular dynamics model. The transverse-momentum-dependent ratios of v4/v22 and v3/(v1v2) are also found to be scaled for different LCPs from the two different energy collisions, and approximately equal to 0.5 and 0.55, respectively. All the above description can be seen as the result of nucleonic coalescence mechanism.
ATOMIC AND MOLECULAR PHYSICS
Generation and Measurement of Isolated 160-Attosecond XUV Laser Pulses at 82 eV
ZHAN Min-Jie, YE Peng, TENG Hao, HE Xin-Kui, ZHANG Wei, ZHONG Shi-Yang, WANG Li-Feng, YUN Chen-Xia, WEI Zhi-Yi
Chin. Phys. Lett. 2013, 30 (9): 093201 .   DOI: 10.1088/0256-307X/30/9/093201
Abstract   PDF(pc) (1210KB) ( 332 )
Isolated attosecond extreme-ultraviolate (XUV) pulses are generated based on high-harmonic-generation from a neon gas cell driven by carrier-envelope phase stabilized sub-5-fs Ti:sapphire laser pulses at repetition rate of 1 kHz. Temporal characterization of isolated attosecond XUV pulses is demonstrated to be 160-attosecond by attosecond streaking spectroscopy. The development of attosecond source and streaking spectroscopy will allow scientists to explore the electron dynamics in matter.
FUNDAMENTAL AREAS OF PHENOMENOLOGY(INCLUDING APPLICATIONS)
A Compact and Wavelength-Tunable PPLN Electro-optics Q-Switched Laser with Intra-Cavity Optical Parametric Generation
CHIANG An-Chung, LIN Yen-Yin
Chin. Phys. Lett. 2013, 30 (9): 094201 .   DOI: 10.1088/0256-307X/30/9/094201
Abstract   PDF(pc) (443KB) ( 461 )
We report a compact and wavelength-tunable periodically poled lithium niobate (PPLN) Q-switched laser with intra-cavity optical parametric generation, producing 8-ns, 10-μJ pulses at 10-kHz repetition rate when pumped with a 10-W diode laser at 808 nm. The output wavelength can be tuned from 1450 nm to 1600 nm. Multiple-pulse generation was observed in the experiment.
Optical Isolation by Time-Dependent Sinusoidal-Shaped Structures
XU Ye-Long, FENG Liang, LU Ming-Hui, CHEN Yan-Feng
Chin. Phys. Lett. 2013, 30 (9): 094202 .   DOI: 10.1088/0256-307X/30/9/094202
Abstract   PDF(pc) (501KB) ( 258 )
Design of nonmagnetic optical isolators integrated with silicon waveguides is important for rapidly growing silicon photonics in optical communications. We introduce a silicon waveguide consisting of an array of complex sinusoidal-shaped structures that create the designed time-dependent modulation of refractive indices. These time-dependent sinusoidal-shaped structures are engineered to have in-phase mode conversion only in one direction, thus leading to asymmetric optical mode conversion in the silicon waveguide and one-way light transmission with high contrast ratios, confirmed by numerically simulated field maps and calculated transmission at the wavelength of 1550 nm. Our design may offer another practical design to the compact chip-scale optical isolators in silicon waveguides.
Nonreciprocal Magneto-Plasmonic Waveguide with Compact Metal-Sandwiched Structure
JIN Yi-Chang, XU Chao, QIU Hui-Ye, XIANG Le-Qiang, YANG Jian-Yi, JIANG Xiao-Qing
Chin. Phys. Lett. 2013, 30 (9): 094203 .   DOI: 10.1088/0256-307X/30/9/094203
Abstract   PDF(pc) (648KB) ( 378 )
A magneto-optical (MO) metal-sandwiched multilayered structure composed of metal, MO medium and dielectric buffer layers is presented and investigated by finite-element-method-based-mode solver and perturbation theory. The results show that this structure exhibits large nonreciprocal phase shift, strong mode confinement in the narrow buffer layers as well as very low propagation loss. The propagation length with 1 dB loss is much longer than the required length of π/2 nonreciprocal phase shifts in this structure. The modal area is smaller than half of the conventional MO waveguides. This phenomenon can be used to achieve a compact plasmonic isolator based on the Mach–Zehnder interferometer.
Self-Starting Harmonic Mode-Locked Thulium-Doped Fiber Laser with Carbon Nanotubes Saturable Absorber
S. W. Harun, N. Saidin, D. I. M. Zen, N. M. Ali, H. Ahmad, F. Ahmad, K. Dimyati
Chin. Phys. Lett. 2013, 30 (9): 094204 .   DOI: 10.1088/0256-307X/30/9/094204
Abstract   PDF(pc) (405KB) ( 386 )
We report a ring cavity passively harmonic mode-locked thulium-doped fiber laser (TDFL) using a newly developed single-wall carbon nanotube-based saturable absorber. The TDFL generates the 25th harmonic mode-locked stretched pulse train with a high repetition rate of 213 MHz and a pulse duration of 710 fs. The laser operates at 1901.6 nm with an average power of 1.89 mW, which corresponds to the pulse energy of 0.008 nJ, at 1552 nm pump power of 719 mW. The peak-to-background ratio is measured to be 60 dB, which indicates the stability of the laser.
Phase-Shift Extraction and Wavefront Reconstruction in Generalized Phase-Shifting Interferometry with a Standard Phase Object
LI Jie, WANG Yu-Rong, MENG Xiang-Feng, YANG Xiu-Lun, WANG Qing-Pu
Chin. Phys. Lett. 2013, 30 (9): 094205 .   DOI: 10.1088/0256-307X/30/9/094205
Abstract   PDF(pc) (528KB) ( 299 )
A method to extract phase shifts and reconstruct the object wave in generalized phase-shifting interferometry (GPSI) is proposed. The phase distribution of a standard phase object and the least-square method are used to extract phase shifts over a wide range from 0 to π. Consequently, the tested object wave can be further reconstructed with the extracted phase shifts. It is accurate and applicable for GPSI of any frame number N (N≥2). Computer simulation has verified its feasibility and validity.
Band Compression of Plasmonic Filters
LIN Yuan-Hai, ZHAI Tian-Rui, LIU Hong-Mei, ZHANG Xin-Ping
Chin. Phys. Lett. 2013, 30 (9): 094206 .   DOI: 10.1088/0256-307X/30/9/094206
Abstract   PDF(pc) (903KB) ( 476 )
We demonstrate theoretically and experimentally the difference between the band compression mechanisms of plasmonic gratings and plasmonic heterogratings. The plasmonic grating can pick out a fixed polarization bandwidth with changing the incidence angle, while the plasmonic heterograting composed of two different nanogratings can pick out a tunable bandwidth with changing the incidence angle and the period ratio of two gratings. The range of the plasmonic resonances of the heterograting is about 30% wider than that of a conventional grating. Thus, the plasmonic heterograting can work efficiently in a wider wavelength range. Moreover, high polarization extinction ratio is achieved in these plasmonic devices. This gives more insights into the mechanisms in plasmonic filters and is helpful to promote the actual applications.
Shear Banding Driven by Electric Field and Shear Flow
ZHENG Jie, FU Wei-Juan, ZHOU Lu-Wei
Chin. Phys. Lett. 2013, 30 (9): 094701 .   DOI: 10.1088/0256-307X/30/9/094701
Abstract   PDF(pc) (622KB) ( 374 )
The shear banding is explored in a granular suspension driven by electric field and shear flow. We find that, given an imposed electric field, there is a critical shear rate determining whether shear banding emerges. A phase diagram of shear banding and fluidization is constructed by using the present experimental data. The evolution in different shear banding phases constitutes an apparent shear thinning phenomenon, probably reflecting an underlying perspective of shear banding. Using the two-phase model, combining with mean field approach and the Onsager least dissipation principle, we give a qualitative explanation of our experimental findings. The results suggest that the stress heterogeneity plays a crucial role for the physical origin of shear banding in this system.
Experimental Investigation of the Induced Airflow of Corona Discharge
HUANG Yong, ZHANG Xin, WANG Xun-Nian, WANG Wan-Bo, HUANG Zong-Bo, LI Hua-Xing
Chin. Phys. Lett. 2013, 30 (9): 094702 .   DOI: 10.1088/0256-307X/30/9/094702
Abstract   PDF(pc) (682KB) ( 291 )
In order to improve the acceleration effect of corona discharge acting on air, we present an experimental study on the induced airflow produced by corona discharge between two parallel electrodes. The parameters investigated are the type of electrodes, actuation voltage and the distance in the absence of free airflow. The induced flow velocity is measured directly in the accelerated region using the particle image velocimetry technology. The results show that if corona discharge is not developed into arc discharge, the induced airflow velocity increases nearly linearly with the applied voltage and the maximum induced airflow velocity near the needle electrode reaches 36 m/s. It is expected that in the future, the result can be referred to in the research about effect of active flow control to reach much higher induced airflow speed.
A New Extrapolation Treatment for Boundary Conditions in Lattice Boltzmann Method
WANG Zheng-Dao, YANG Jian-Fei, WEI Yi-Kun, QIAN Yue-Hong
Chin. Phys. Lett. 2013, 30 (9): 094703 .   DOI: 10.1088/0256-307X/30/9/094703
Abstract   PDF(pc) (1768KB) ( 435 )
The lattice Boltzmann method is widely used in solving hydrodynamics for various systems. The accuracy of the extrapolation method for boundary conditions and Mei's method for curved boundary is not high enough. We propose a modified extrapolation method for boundary conditions. Numerical simulations conform the higher accuracy and stability compared with the other methods.
CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES
X-Ray Diffraction Pattern of Graphite Oxide
MU Shi-Jia, SU Yu-Chang, XIAO Li-Hua, LIU Si-Dong, HU Te, TANG Hong-Bo
Chin. Phys. Lett. 2013, 30 (9): 096101 .   DOI: 10.1088/0256-307X/30/9/096101
Abstract   PDF(pc) (633KB) ( 3234 )
X-ray diffraction patterns of graphite oxide (GO) are theoretically simulated as a function of the displacements of carbon atoms using the Debye–Waller factor in terms of the Warren–Bodenstein equation. The results demonstrate that GO has the turbostratically stacked structure. The high order (00l) peaks gradually disappear with the increase in atomic thermal vibrations along c-axis while the (hk0) ones weaken for the vibrations along a-axis. When the displacement deviation ua=0.015 nm and uc=0.100 nm the computed result is consistent with the experimental measurements.
Electronic Band Structure of Carbon Nanotubes with Kekule Structure
Nguyen Ngoc Hieu, Le Cong Nhan
Chin. Phys. Lett. 2013, 30 (9): 096102 .   DOI: 10.1088/0256-307X/30/9/096102
Abstract   PDF(pc) (505KB) ( 323 )
Electronic band structure of carbon nanotubes with the Kekule structure is studied by the tight-binding approximation. We give a complete geometrical approach to structural properties of carbon nanotubes with bond alternation, including chiral and achiral tubes. When the Kekule is introduced, all carbon nanotubes become semiconducting with a small band gap at the Fermi level. The band gap of the carbon nanotubes depends only on the difference between C–C bond lengths or the resonance integrals.
Wake Effects in Ion Transport through Carbon Nanotubes
ZHANG Ying-Ying, ZHAO Dan, YOU Shu-Yan, SONG Yuan-Hong, WANG You-Nian
Chin. Phys. Lett. 2013, 30 (9): 096103 .   DOI: 10.1088/0256-307X/30/9/096103
Abstract   PDF(pc) (1331KB) ( 281 )
A semiclassical kinetic model is explored to investigate the wake effects in the transport of charged particles through single-walled (SWCNT) and double-walled (2WCNTs) carbon nanotubes, with the introduction of electron band structure effect. The analytical expressions of the induced electron density at nanotube surface and the induced potential around the nanotube walls are obtained. The simulation results indicate that a bell-like distribution appears for the induced electron density when the incident particle speed is below a threshold value, otherwise wake-like oscillation can be seen behind the particle in the axial distribution. Dependencies of the amplitude and frequency of oscillations on the incident particle speed are also discussed. Meanwhile, we notice that the valence electrons on the outer wall of 2WCNTs tend to be easily excited by the polarized electrons on the inner wall, compared with that by the incident particle without the inner wall in SWCNTs. Finally, the induced potential trailing the incident particle also exhibits remarkable oscillations, not only along the axial direction but also in the lateral region, with evident extrema at the nanotube walls.
Excellent Glass Forming Ability and Refrigeration Capacity of a Gd55Al20Ni12Co10Mn3 Bulk Metallic Glass
DING Ding, WANG Peng, GUAN Quan, TANG Mei-Bo, XIA Lei
Chin. Phys. Lett. 2013, 30 (9): 096104 .   DOI: 10.1088/0256-307X/30/9/096104
Abstract   PDF(pc) (810KB) ( 323 )
We investigate an excellent refrigeration capacity Rc of Gd55Al20Ni12Co10Mn3 bulk metallic glass (BMG). The Gd55Al20Ni12Co10Mn3 glassy rod is subjected to Cu mold suction-casting to prepare bulky metallic glasses, with a diameter of 3 mm. The glass forming ability as well as the magnetic properties of the BMG is investigated. The BMG exhibits a rather high glass formation ability with critical diameter of about 5.6 mm. The peak value of magnetic entropy change of about 8 J?kg?1K?1 is obtained in this alloy. This BMG alloy also exhibits excellent magnetic refrigerant capacity of about 880 J?kg?1 under the field of 5 T and 35% larger than that of other alloys reported previously, supposed to be closely related to the high effective moment (7.3μB) of the Gd55Al20Ni12Co10Mn3 BMG.
Characterization of Obtuse Triangular Defects on 4H-SiC 4° off-Axis Epitaxial Wafers
DONG Lin, SUN Guo-Sheng, YU Jun, ZHENG Liu, LIU Xing-Fang, ZHANG Feng, YAN Guo-Guo, LI Xi-Guang, WANG Zhan-Guo, YANG Fei
Chin. Phys. Lett. 2013, 30 (9): 096105 .   DOI: 10.1088/0256-307X/30/9/096105
Abstract   PDF(pc) (1018KB) ( 375 )
We investigate the triangular defects with different structural features on 4H-SiC epilayers by a Nomarski microscope, a Candela optical surface analyzer and ultraviolet photoluminescence (UV-PL) imaging. Both the foreign particles and the substrate scratches can cause the formation of the obtuse triangular defects. The central area of some obtuse triangular defects can have the spatially confined core, in which the in-grown stacking faults can be observed under the UV-PL imaging. In contrast, the obtuse triangular defects induced by the scratches appear in the form of band-like defects, of which the width depends on the scratch direction and reaches the maximum when the scratch direction is parallel to the step flow direction. The formation mechanisms of these obtuse triangular defects are discussed.
Influence of Temperature and Stress on Near-Surface Cascades in Alpha-Zirconium Revealed by Molecular Dynamics Simulation
WU Tian-Yu, PENG Meng-Meng, LUO Xiao-Feng, LAI Wen-Sheng
Chin. Phys. Lett. 2013, 30 (9): 096106 .   DOI: 10.1088/0256-307X/30/9/096106
Abstract   PDF(pc) (464KB) ( 226 )
Molecular dynamics simulations are used to study cascades near the surface in hcp Zr. The influences of several factors, namely the primary knock-on atom (PKA) in different layers, angle of incidence, temperature and stress, on the number and type of defects are considered. Compared to bulk cascades, near-surface cascades show different characteristics in defect type and quantity when the PKA is in different layers. Low angle incidences create surface sputtering while the effects of high angle incidences are similar to those of bulk cascades. The effect of temperature is mainly focused on the number of sputtered atoms, with little influence on the total number of surviving defects. Stress helps to create more defects and the influence of compressive stress is more prominent than tensile stress.
Surface Plasmons and Optical Properties of TiO2/X(X = Au and Ag) Nanostructure Thin Films
A. Zolanvari, H. Sadeghi, R. Norouzi, A. Ranjgar
Chin. Phys. Lett. 2013, 30 (9): 096201 .   DOI: 10.1088/0256-307X/30/9/096201
Abstract   PDF(pc) (777KB) ( 520 )
TiO2/X(X = Au and Ag) nanolayers are fabricated by depositing TiO2 films using rf magnetron sputtering on thin quartz substrates embedded with Au and Ag nanoparticles. Enhancement of light absorption of the nanostructural layers is observed. These plasmonic and non-plasmonic materials are ordered in geometric arrangements with dimensions that are fractions of the wavelength of light. The light absorption enhancement of synthesized structure in comparison to TiO2 is originated from near-field enhancement caused by the plasmonic effect of metallic nanoparticles, which can be demonstrated by the optical absorption spectra. We show that plasmon modes can exist for the infrared region of the optical spectrum. Also, we analyze the optical properties of the metal-insulator films, in order to clarify the role of metal inclusions in the TiO2 dielectric matrix. Optical band gaps of the nanolayer films are calculated by using Tauc's relation, and the n values of optical band gaps with the variation composition are found from 1.80 to 3.69 eV. Band gap narrowing and absorption in the visible spectral region induced by the incorporation of TiO2/X(X=Au and Ag) nanolayers enable the design of nanostructured thin films to be achieved for photocatalysts and solar energy converters.
Propagation of Shear Horizontal Waves in Laminated Composites Based on Differently Orientated Poled 0.72Pb(Mg1/3Nb2/3)O3-0.28PbTiO3 Single Crystals
WANG Yu-Ling, ZHANG Rui, SUN En-Wei, SONG Wei, CAO Wen-Wu
Chin. Phys. Lett. 2013, 30 (9): 096301 .   DOI: 10.1088/0256-307X/30/9/096301
Abstract   PDF(pc) (629KB) ( 369 )
The propagation characteristics of shear horizontal waves in [001]c, [011]c and [111]c direction polarized 0.72Pb (Mg1/3Nb2/3)O3-0.28PbTiO3 (PMN-0.28PT) piezoelectric single crystals/polymer periodic laminated composites are studied by using the global matrix method. The numerical results show that the piezoelectric effect has a significant influence on the bandgap width of the composite structure containing [011]c and [111]c poled PMN-0.28PT, but little effect on the band structure of the system containing [001]c poled single crystal. In addition, the first bandgap (FBG) width of the composite structure depends strongly on the poling directions when the filling fraction of PMN-0.28PT is larger than 0.5, and its FBG starting frequency displays no distinct difference among the three polarization directions at all filling fractions. The reported results provide valuable guidelines for designing filters and transducers made of composite structures containing relaxor-based ferroelectric single crystals.
Simultaneous Formation of AlB2-Type and ThSi2-Type Nanoislands of Er Silicide by Using a Prepatterned Si(001) Substrate
LIU Bei-Bei, CAI Qun
Chin. Phys. Lett. 2013, 30 (9): 096801 .   DOI: 10.1088/0256-307X/30/9/096801
Abstract   PDF(pc) (437KB) ( 268 )
We report the simultaneous growth of hexagonal AlB2-phase and tetragonal ThSi2-phase nanoislands of erbium silicide on the same silicon substrate. As a new technique, the patterned Si(001) surface with pits in a reverse-pyramid shape and {111} sidewalls is taken as the substrate template. The distribution of nanoislands reveals that the upward diffusion over surface steps plays an influential role on the location of islands. Si {111} facets on the pit sidewalls actually provide growth symmetry for the hexagonal islands. This work paves the way for exploring the intrinsic electrical transport properties of metal-semiconductor nanocontacts.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES
First Principle Calculations of the Ground and Excited State Properties of RbPbF3
Hayatullah, G. Murtaza, R. Khenata, S. Naeem, M. N. Khalid, S. Mohammad
Chin. Phys. Lett. 2013, 30 (9): 097101 .   DOI: 10.1088/0256-307X/30/9/097101
Abstract   PDF(pc) (522KB) ( 409 )
Structural, elastic, electronic, chemical bonding and optical properties of the cubic RbPbF3 compound under pressure are studied using a highly accurate state-of-the-art full potential linearized augmented plane wave method. The exchange correlation effects are included through the generalized gradient and modified Becke–Johnson exchange potential. The lattice constant and band gap of the cubic RbPbF3 decreases with enhanced pressure. RbPbF3 is brittle, elastically anisotropic, and a direct bandgap material. Its optical properties such as refractive index n(ω), extinction coefficient k(ω), reflectivity R(ω), and optical conductivity σ(ω) are predicted.
Wavevector Filtering through Monolayer and Bilayer Graphene Superlattices
F. Sattari, E. Faizabadi
Chin. Phys. Lett. 2013, 30 (9): 097201 .   DOI: 10.1088/0256-307X/30/9/097201
Abstract   PDF(pc) (613KB) ( 349 )
We investigate the transport properties through monolayer and bilayer graphene superlattices modulated by an in-plane homogeneous electric field based on the transfer matrix method. It is found that the angular range of the transmission probability through a graphene superlattice can be effectively controlled by the number of barriers and this results in the structure having efficient wavevector filters. As the number of barriers increases, this range shrinks. It is also shown that the conductance of the systems has an oscillatory behavior with respect to the barrier height and it decreases with the increasing number of barriers.
An All-Optical Diode Based on Plasmonic Attenuation and Nonlinear Frequency Conversion
REN Ming-Liang, ZHONG Xiao-Lan, CHEN Bao-Qin, LI Zhi-Yuan
Chin. Phys. Lett. 2013, 30 (9): 097301 .   DOI: 10.1088/0256-307X/30/9/097301
Abstract   PDF(pc) (1130KB) ( 267 )
We present the design of an all-optical diode in a metal-dielectric structure where plasmonic attenuation and quasi-phase-matching are harnessed to greatly improve its performance. Due to the asymmetric design of the second-order nonlinear coefficient, different incident directions will ignite different plasmonic nonlinear processes, which compensate or accelerate plasmonic attenuation. As a result, a unidirectional output of plasmonic signal is achieved. This designed all-optical diode shows advantages of low power consumption, short sample length, high isolation contrast, wide acceptance of structural and initial conditions, and tunable unidirectionality, and becomes of practical interest.
The Application of a New Simulation Approach to Ferrimagnetic Nanowires
LIU Zhao-Sen, YANG Cui-Hong, GU Bin, MA Rong, LI Qing-Fang
Chin. Phys. Lett. 2013, 30 (9): 097302 .   DOI: 10.1088/0256-307X/30/9/097302
Abstract   PDF(pc) (632KB) ( 251 )
The quantum simulation model and the self-consistent computational algorithm we proposed two years ago are utilized to investigate the physical properties of a magnetic nanowire consisting of 3d ions which are coupled antiferromagnetically. In the absence of the external magnetic field, all simulations are started from a spin configuration with all moments in the nanosample randomly oriented and performed from a temperature above the magnetic transition temperature TM down to very low temperature as carried out by previous researchers using the Monte Carlo method, and such obtained results are all physically reasonable, verifying the correctness of the simulation model and computing algorithm. In addition, our calculated results suggest that increasing the surface anisotropy enables an increase in the magnetic transition temperature, although less effectively than by enhancing the Heisenberg exchange strength directly.
Improved Breakdown Voltage in AlGaN/GaN High Electron Mobility Transistors by Employing Polyimide/Chromium Composite Thin Films as Surface Passivation and High-Permittivity Field Plates
CHU Fu-Tong, CHEN Chao, ZHOU Wei, LIU Xing-Zhao
Chin. Phys. Lett. 2013, 30 (9): 097303 .   DOI: 10.1088/0256-307X/30/9/097303
Abstract   PDF(pc) (870KB) ( 449 )
The breakdown voltage of AlGaN/GaN high electron mobility transistors (HEMTs) is enhanced by employing metal chromium (Cr) nanoparticle-embedded polyimide (PI) as a high-permittivity (high-K) dielectric covering both the source-gate and gate-drain regions. The PI/Cr composite high-K dielectrics acting as a field plate prevent the occurrence of strong electric fields produced at the drain side edge of the gate electrode to obtain an optimum lateral electric flux of HEMTs. The breakdown voltage is improved by approximately 35% when using the PI/Cr thin film dielectric field plate while maintaining high performance, a high transconductance value of 122.4 mS/mm, and a large saturated drain-current value of 748 mA/mm.
Non-UV Photoelectric Properties of the Ni/n-Si/N+-SiC Isotype Heterostructure Schottky Barrier Photodiode
LI Lian-Bi, CHEN Zhi-Ming, REN Zhan-Qiang, GAO Zhan-Jun
Chin. Phys. Lett. 2013, 30 (9): 097304 .   DOI: 10.1088/0256-307X/30/9/097304
Abstract   PDF(pc) (631KB) ( 284 )
The energy-band structure and non-ultraviolet photoelectric properties of a Ni/n-Si/N+-SiC isotype heterostructure Schottky photodiode are simulated by using Silvaco-Atlas. There are energy offsets in the conduction and valance band of the heterojunction, which are about 0.09 eV and 1.79 eV, respectively. The non-UV photodiode with this structure is fabricated on a 6H-SiC(0001) substrate. JV measurements indicate that the device has good rectifying behavior with a rectification ratio up to 200 at 5 V, and the turn-on voltage is about 0.7 V. Under non-ultraviolet illumination of 0.6 W/cm2, the device demonstrates a significant photoelectric response with a photocurrent density of 2.9 mA/cm2 and an open-circuit voltage of 63.0 mV. Non-ultraviolet operation of the SiC-based photoelectric device is initially realized.
The Impact Induced Demagnetization Mechanism in NdFeB Permanent Magnets
LI Yan-Feng, ZHU Ming-Gang, LI Wei, ZHOU Dong, LU Feng, CHEN Lang, WU Jun-Ying, QI Yan, DU An
Chin. Phys. Lett. 2013, 30 (9): 097501 .   DOI: 10.1088/0256-307X/30/9/097501
Abstract   PDF(pc) (956KB) ( 964 )
Compression of unmagnetized Nd2Fe14B permanent magnets is executed by using shock waves with different pressures in a one-stage light gas gun system. The microstructure, crystal structure, and magnetic properties of the magnets are examined with scanning electronic microscopy, x-ray diffraction, hysteresis loop instruments, and a vibrating sample magnetometer, respectively. The NdFeB magnets display a demagnetization phenomenon after shock wave compression. The coercivity dropped from about 21.4 kOe to 3.2 kOe. The critical pressure of irreversible demagnetization of NdFeB magnets should be less than 4.92 GPa. The coercivity of the NdFeB magnets compressed by shock waves could be recovered after annealing at 900°C and 520°C for 2 h, sequentially. The chaotic orientation of Nd2Fe14B grains in the compressed magnets is the source of demagnetization.
Temperature Dependence of the AlN E1(To) Phonon Decay, Thermal Expansion and Strain Effect in AlN/Sapphire by Infrared Reflection
ZHOU Shu-Tong, YU Chen-Hui, ZHANG Bo
Chin. Phys. Lett. 2013, 30 (9): 097701 .   DOI: 10.1088/0256-307X/30/9/097701
Abstract   PDF(pc) (660KB) ( 292 )
Infrared reflectivity measurement is carried out for AlN films on sapphire substrates. The frequencies of the symmetry optical phonon E1(TO) in the temperature range from 77 K to 500 K are reported by fitting the experimental reflectivity with the classical multi-oscillators model. Taking the lattice thermal expansion and Klemens process of the phonon decay into account, along with the strain effect introduced by thermal mismatch between the film and the substrate, the temperature effect on the frequency of the optical phonon E1(TO) is revealed. It is shown that the shift of frequency is mainly attributed to the decay process while the strain effect induced by thermal mismatch plays a non-negligible role in the outcomes of the strength and damping parameters.
Switching Plasmon Resonances by Polarization of the Incident Light in Metamolecules
LIU Jian-Qiang, CHEN Jing, WANG Dian-Yuan, ZHOU Yu-Xiu, CHEN Zhen-Hua, WANG Ling-Ling
Chin. Phys. Lett. 2013, 30 (9): 097801 .   DOI: 10.1088/0256-307X/30/9/097801
Abstract   PDF(pc) (949KB) ( 272 )
We numerically demonstrate the modulation of plasmon resonances in a metamolecule composed of metal bars and L-shaped nanoparticles by using the finite difference time domain method. Due to the dependence of electromagnetic coupling on polarization of the incident light, we show that the superradiant and subradiant states can be switched from ON and OFF resonantly. These two resonances are continuously adjustable as the polarization angle of incident wave changes. This feature reveals a possibility of dynamically switching the coupled plasmon resonances of an artificial microstructure and to construct functional metamaterials, which is helpful for nanophotonic devices such as filters and optical switches.
CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY
Stress Distribution in GaN Films grown on Patterned Si (111) Substrates and Its Effect on LED Performance
CHEN Dan-Yang, WANG Li, XIONG Chuan-Bing, ZHENG Chang-Da, MO Chun-Lan, JIANG Feng-Yi
Chin. Phys. Lett. 2013, 30 (9): 098101 .   DOI: 10.1088/0256-307X/30/9/098101
Abstract   PDF(pc) (451KB) ( 513 )
Crack free GaN films were grown on 1200×1200 μm2 patterned Si (111) substrates and 36 light emitting diodes (LEDs) were fabricated in each pattern unit. Spatial distribution of the tensile stress in the pattern units and its influence on the LED performance are studied by micro-Raman and electroluminescence (EL). The Raman shift of the GaN E2 mode shows that the tensile stress is the maximum at the center, partially relaxed at the edge, and further relaxed at the corner. With the stress relaxation, the EL wavelength has a significant blue shift and the luminous intensity shows a great enhancement.
Strain Distributions in Non-Polar a-Plane InxGa1−xN Epitaxial Layers on r-Plane Sapphire Extracted from X-Ray Diffraction
ZHAO Gui-Juan, YANG Shao-Yan, LIU Gui-Peng, LIU Chang-Bo, SANG Ling, GU Cheng-Yan, LIU Xiang-Lin, WEI Hong-Yuan, ZHU Qin-Sheng, WANG Zhan-Guo
Chin. Phys. Lett. 2013, 30 (9): 098102 .   DOI: 10.1088/0256-307X/30/9/098102
Abstract   PDF(pc) (618KB) ( 282 )
By using x-ray diffraction analysis, we investigate the major structural parameters such as strain state and crystal quality of non-polar a-plane InxGa1?xN thin films grown on r-sapphire substrates by metalorganic chemical vapour deposition. The results of the inplane grazing incidence diffraction technique are analyzed and compared with a complementary out-of-plane high resolution x-ray diffraction technique. When the indium composition is low, the a-plane InxGa1?xN layer is tensile strain in the growth direction (a-axis) and compressive strain in the two in-plane directions (m-axis and c-axis). The strain status becomes contrary when the indium composition is high. The stress in the m-axis direction σyy is larger than that in the c-axis direction σzz. Furthermore, strain in the two in-plane directions decrease and the crystal quality becomes better with the growing of the InxGa1?xN film.
Effect of Cations on the Chemical Mechanical Polishing of SiO2 Film
SONG Han, WANG Liang-Yong, LIU Wei-Li, SONG Zhi-Tang
Chin. Phys. Lett. 2013, 30 (9): 098103 .   DOI: 10.1088/0256-307X/30/9/098103
Abstract   PDF(pc) (718KB) ( 773 )
We investigate the effect of cations with different valences on the chemical mechanical polishing (CMP) of silicon dioxide films. The removal rate and surface roughness of the silicon-dioxide-film post-CMP are checked for the silica-based slurry with different cation salts (NaCl, CaCl2, AlCl3). Meanwhile, the particle size and size distribution of the slurries are characterized to test their lifetimes. The result shows that the three kinds of salts can improve the polishing removal rate from around 20 nm/min to 120 nm/min without affecting the surface roughness when the polishing slurry is stable. With increasing valence of cations, the polishing slurry requires less cation concentration to be added to improve the removal rate, while keeping a superior surface topography and maintaining a longer lifetime as well.
Preparation of Micropowder by a Combination of Jet-Milling and Electrostatic Dispersion
YIN Peng-Fei, ZHANG Rong, LIU Qian, HU Jian-Chang, LI Yin-Bing, LI Ning
Chin. Phys. Lett. 2013, 30 (9): 098104 .   DOI: 10.1088/0256-307X/30/9/098104
Abstract   PDF(pc) (785KB) ( 452 )
We develop a new method to prepare micropowders with a combination of jet-milling and electrostatic dispersion techniques. The dispersiveness of the powder can be obviously improved by charging the particles during the process of jet-milling. Calcium carbonate (CaCO3) powders with high dispersion are prepared by using this method from two different initial particle sizes (10.93 and 25.43 μm). The experimental studies and theoretical analysis about the effects of preparation parameter on dispersiveness of the powder are investigated, showing that the jet-milling/electrostatic dispersion (J/E) is a considerably effective way to prepare micropowder in ambient atmosphere. It is found that the strength of electrostatic field and particle radius of the raw powder strongly affect the dispersion. The average particle size of both powders decreases with the increase in charging voltage while the reduction of particle size is more obvious in the powder with larger initial particle size.
Efficient Green Organic Light-Emitting Devices Based on a Solution-Processable Starburst Molecule
ZHANG Xin-Wen, WANG Jian-Yun, ZHAO Ling-Ling, GUO Xin, LAI Wen-Yong, HUANG Wei
Chin. Phys. Lett. 2013, 30 (9): 098501 .   DOI: 10.1088/0256-307X/30/9/098501
Abstract   PDF(pc) (615KB) ( 447 )
We develop high efficiency solution-processed pure green organic light-emitting devices using a starburst molecule 7,7',7"-(5,5,10,10,15,15-hexahexyl-10, 15-dihydro-5H-diindeno[1, 2-a:1', 2'-c]fluorene-2,7,12-triyl)tris(4-(4-(9H-carbazol-9-yl)phenyl)benzo[c][1,2,5]thiadiazole) (TRcz) doped 2-methyl-9,10-di(2-naphthyl)anthracene (MADN) as the emitting layers. The electroluminescence properties of the devices with different doping concentrations are investigated. With the increasing doping concentration from 0.5wt% to 5wt%, the maximum efficiency changes from 4.8 cd/A to 8.4 cd/A. Under the optimal concentration of 4wt%, the device shows pure green emission at 516 nm with a chromaticity coordinate of (0.30, 0.59) as well as a high brightness of 19900 cd/m2 and a high efficiency of 10.1 cd/A, which are better than 11490 cd/m2 and 4.2 cd/A obtained in the undoped device.
Enhanced Radiation Sensitivity in Short-Channel Partially Depleted Silicon-on-Insulator n-Type Metal-Oxide-Semiconductor Field Effect Transistors
PENG Chao, ZHANG Zheng-Xuan, HU Zhi-Yuan, HUANG Hui-Xiang, NING Bing-Xu, BI Da-Wei
Chin. Phys. Lett. 2013, 30 (9): 098502 .   DOI: 10.1088/0256-307X/30/9/098502
Abstract   PDF(pc) (728KB) ( 269 )
The total ionizing dose effects of partially depleted silicon-on-insulator (SOI) transistors in a 0.13 μm technology are studied by 60Co γ-ray irradiation. Radiation enhanced drain-induced barrier lowering (DIBL) under different bias conditions is related to the parasitic bipolar in the SOI transistor and oxide trapped charge in the buried oxide, and it is experimentally observed for short channel transistors. The enhanced DIBL effect manifests as the DIBL parameter increases with total dose. Body doping concentration is a key factor affecting the total ionizing dose effect of the transistor. The low body doping transistor exhibits not only significant front gate threshold voltage shift as a result of the coupling effect, but also great off-state leakage at high drain voltage due to the enhanced DIBL effect.
An Optimal Power-Law for Synchrony and Lognormally Synaptic Weighted Hub Networks
Yasuomi D. Sato
Chin. Phys. Lett. 2013, 30 (9): 098701 .   DOI: 10.1088/0256-307X/30/9/098701
Abstract   PDF(pc) (850KB) ( 279 )
Details about the structure of a network model are revealed at the spontaneous spike activity level, in which the power-law of synchrony is optimized to that observed in the CA3 hippocampal slice cultures. The network model is subject to spike noise with exponentially distributed interspike intervals. The excitatory (E) and/or inhibitory (I) neurons interact through synapses whose weights show a log-normal distribution. The spike behavior observed in the network model with the appropriate log-normal distributed synaptic weights fits best to that observed in the experiment. The best-fit is then achieved with high activities of I neurons having a hub-like structure, in which the I neurons, subject to optimized spike noise, are intensively projected from low active E neurons.
The Fluorescence Dynamics of Chlorophyll a and Sodium Magnesium Chlorophyllin
WANG Ya-Lan, ZHOU Zhang-Kai, PENG Xiao-Niu, ZHOU Li, HAO Zhong-Hua, WANG Qu-Quan
Chin. Phys. Lett. 2013, 30 (9): 098702 .   DOI: 10.1088/0256-307X/30/9/098702
Abstract   PDF(pc) (721KB) ( 347 )
The concentration dependence of the fluorescence spectra and lifetimes of chlorophyll a and sodium magnesium chlorophyllin are compared to explore the influences of intramolecular relaxation and intermolecular interaction of chlorophylls on the fluorescence dynamics. With different concentrations of chlorophyll a and sodium magnesium chlorophyllin in the suspensions, three different fluorescence emission bands are observed. Intermolecular interactions increase as the concentrations increase, which lead to redshifts in both fluorescence and lifetime spectra. Additionally, the lifetime is increased by re-absorption in the sodium magnesium chlorophyllin suspensions. These observations increase the understanding of the light harvesting and energy relaxation mechanisms of chlorophyll molecules.
GEOPHYSICS, ASTRONOMY, AND ASTROPHYSICS
Stochastic Resonance of a General Relativistic Accretion Disk
WANG Zhi-Yun, CHEN Pei-Jie, ZHANG Liang-Ying
Chin. Phys. Lett. 2013, 30 (9): 099801 .   DOI: 10.1088/0256-307X/30/9/099801
Abstract   PDF(pc) (576KB) ( 311 )
Based on a generalized Langevin equation, we consider a full general relativistic model to describe the vertical oscillations of particles in accretion disks around compact astrophysical objects, and calculate oscillating luminosity and power spectral density (PSD) of an accretion disk. The influences of the friction parameter ζ, spin parameter a? and mass M of the center compact object on the stochastic resonance (SR) in PSD curves are discussed. The results show that a large spin parameter a? can enhance the SR phenomenon, but the larger the ζ or M is, the weaker the SR phenomenon becomes. In addition, our simulated PSD curves of the output luminosity of stochastically oscillating disk have the same profile as the observed PSD of x-ray binaries, and the resonance peak in the PSD curve can interpret the quasi-periodic oscillations at the same time.
COMMENTS AND ERRATA
Erratum: The Decay Rate of J/ψ to Λc+Σ+ in and beyond the Standard Model [Chin. Phys. Lett. 28 (2011) 071301]
KE Hong-Wei, CHEN Ya-Zheng, LI Xue-Qian
Chin. Phys. Lett. 2013, 30 (9): 099901 .   DOI: 10.1088/0256-307X/30/9/099901
Abstract   PDF(pc) (254KB) ( 191 )
51 articles