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February 15,2014
Volume 7,Issue 3
Pages -
Subject Area:Fluid Mechanics,Computational Physics,High-energy Physics,Condensed Matter Physics,Heat Transfer

Title: Simulation of the damage and fracture in particle reinforced composites based on digital image

Authors: BAI Xiaoming, GUO Licheng, SHEN Rilin
PP: 285-290
Abstract: This paper describes a finite element modeling method based on digital image filter and boundary smoothing algorithm. Different cohesive finite elements are utilized to describe the damage process in mesoscale. Using this model, the damage process in polymer bonded explosive (PBX) under tension is investigated. The results show that the damage initiates at the matrix-particle interface, then the macrocrack initiates under tension, whith leads to the material to be invalid.
Keywords: solid mechanics; particle reinforced composite; damage evolution; cohesive model

Title: Aerodynamic force of insect in downward flight

Authors: LIANG Bin, SUN Mao
PP: 277-284
Abstract: The effects of wake on the aerodynamic force production of model insect wings in stroking motion were investigated when the insect hovering and downward flight, using the method of numerically solving the Navier-Stokes (N-S) equations over moving overset grids. Various speeds of downward flight were considered (the nondimensional speed of downward flight is 0.1, 0.2 and 0.5). The main results were as the following: the force coefficients varied slightly when the insect hovering and having small speed of downward flight, the change of the force coefficients and moment of force coefficient generally was less than 2%; when the insect having large speed of downward flight, the effect of wake was relatively large, which resulted in the oscillation of the average force coefficients and moment of force coefficient, but it had only minor effects on the insect stable flight. Results of the paper would have important academic value and engineering significance in study of the insect flight and design of micro air vehicle (MAV).
Keywords: fluid mechanics; insect; downward flight; aerodynamic force; flight stability

Title: Return probability of one-dimensional quantum random walk

Authors: ZHANG Xiaokun, WEI Chenyang, XU Xinping
PP: 273-276
Abstract: In this paper, we investigate the return probability for discrete-time quantum random walk on the line. Using the stationary phase approximation (SPA), we derive approximate analytical expression of return probability for the first time. It is found that the return probability of one-dimensional quantum walk exhibits a power law behavior with exponent -1, where the exponent is twice the exponent of the corresponding classical random walk, indicating that the quantum walk displays a faster decay behavior. In addition, the effect of “coin” and initial state parameters on the return probability is discussed, and it is evident that the “coin” and initial state parameters of quantum walk has no influence on the scaling behavior of the return probablity.
Keywords: theoretical physics; statistical physics and complex system; random walk; quantum random walk; complex network

Title: Charging simulation of particulates in low temperature plasma based on PIC-MCC method

Authors: QIAN Zhong, YANG Fan
PP: 269-272
Abstract: Charging of particulates in low temperature plasma is instantaneously finished and the process is complicated. The motion and trapping of the particulates are directly determined by the charges of themselves. Here, a numerical model based on particle-in-cell(PIC) and Monte-Carlo collision (MCC) hybrid method was developed to study the charging characteristics of fine particles immersed in low temperature argon plasma. The net charge of a fine particulate was evaluated by counting the number charged particles reaching the surface of the particulate. Meanwhile, the profiles of electric potential and particle number density were obtained. For the particulate with a radius of 15 μm in the plasma, the charge is approximately -1.24×10-14 C and the electric potential of the surface is about -7.56 V. Also the potential quickly increased to 0 within 100 μm. In the sheath, the ion number density was always greater than that of the electron. Ion density quickly raised to the background plasma density, however, the electron density relatively slowly enlarged to the background value. The charge of a particulate tended to be proportional to its diameter.
Keywords: computational physics; plasma; particulates; charging; particle-in-cell; Monte-Carlo collision

Title: Morphology study of titanium film deposited on silicon macropores by magnetron sputtering

Authors: ZHAN Changyong, JIANG Wen, ZOU Yu, REN Ding, WU Jianchun, YANG Bin, HUANG Ningkang
PP: 262-268
Abstract: Titanium films were deposited on silicon macropores with pore diameters of 2.5, 12, 15 μm and random etched size. Morphologies of titanium films deposited at different bias voltages are presented and the effects of etched morphology on titanium film are discussed. The results indicate that, without applying bias voltages, titanium film grows as columnar crystals and island growth mode on pore wall and a shadow effect is due to the gathering of titanium atoms on the etched bulges and edges of silicon, which makes the film uneven. The gathering of titanium atoms on the bulges and edges is reduced due to sputtering of the ions accelerated by bias voltages. The titanium thickness difference of surface and bottom is decreased by bias voltages. The deposition depth of titanium film in the macropores can reach more than 55 μm. It is clear that the morphologies of silicon macropores surface and pore wall also play an important role in the deposition of titanium film. Smooth wall is superior to rough wall. This work provides the fabricating method and formation study of film in pore for future application of silicon macropores in energy conversion and detection of energetic particle.
Keywords: thin film physics; silicon macropores; magnetron sputtering; bias voltage; titanium film

Title: Channel-coupling effects of nonstrange quarkonia

Authors: ZOU Jing, PING Jialun
PP: 254-261
Abstract: Meson not only includes the component of quark-antiquark, but multi-quarkand gluon components as well. Based on the framework of chiral quark model, the quark-antiquark meson pectrum is calculated by Gaussian expansion method. Then the masses and wave functions of uark-antiquark clusters are employed to calculate the mass shifts of the quark-antiquark lusters due to the coupling with the four-quark components according to 3P0 model. The results show that the mass shifts are rather large for nonstrange mesons. The effect of the contribution for high Fock cannot be ignored, although the most of the effects can be absorbed by re-adjusting the model parameters. Further study of ulti-quark components are needed.
Keywords: high energy physics; constituent quark model; Gaussian expansion method; 3P0 model; mass shift

Title: Red light sensitive heterojunction organic field-effect transistors based on neodymium phthalocyanine as photosensitive layer

Authors: LIU Jinfeng, LUO Xiao, PENG Yingquan
PP: 247-253
Abstract: A metal phthalocyanine light-sensitive material, neodymium phthalocyanine (NdPc2), which has high absorption coefficient(~1.7 05 cm-1) was synthesized. The highest absorption peak in visible region of NdPc2 film is centered at 638 nm which is near the commonly used wavelength of red light (650-670 nm). NdPc2 and C60 were used in heterojunction photoresponsive organic field-effect transistors (photOFETs). In this device, NdPc2 was used as photosensitive layer, and n-type high mobility ratio material C60 was used as the carrier transport layer. Compared with single-layer NdPc2 photOFETs (NdPc2-photOFETs), C60/NdPc2 heterojunction photOFETs (C60/NdPc2-photOFETs) showed a better performance. The maximum photoresponsivity of C60/NdPc2-photOFETs is 0.8 A/W with the incident light intensity of 1.41 mW/cm2, which is approximately 62 times larger than that of NdPc2-photOFETs at the same condition. It is concluded that the synthesized NdPc2 with high absorption coefficient can be used as photosensitive material and C60/NdPc2-photOFETs are very suited for detecting red light.
Keywords: semiconductor physics; NdPc2/C60 heterojunction; photoresponsive organic field-effect transistors; photoresponsivity; neodymium phthalocyanine

Title: Preparation of urchin-like ZnO/In2O3 nanocomposite structure and its optical property

Authors: LÜ Shanshan, FANG Fang, ZHAO Haifeng, WANG Xujie, WANG Xing, CHU Xueying, LI Jinhua, FANG Xuan, WEI Zhipeng, WANG Xiaohua
PP: 242-246
Abstract: Through an electrochemical deposition process, urchin-like ZnO/In2O3 nanocomposite structure was prepared. The surface morphological analysis was carried out by scanning electron microscopy (SEM), the phase and structural analysis was studied by X-ray diffraction (XRD), and the optical property was characterized by photoluminescence (PL). The research results showed that this was a kind of ZnO nanowires coated In2O3 core, which showing an urchin-like ZnO/In2O3 nanocomposite structure. After annealing, the crystallinity of composite materials was improved and ultraviolet emission had enhanced, while the emission peak related to the interface of ZnO/In2O3 nanocomposite structure was observed at 443 nm. The synthesized ZnO/In2O3 nanocomposite structure has a novel morphology and excellent optical property. We believe such urchin-like ZnO/In2O3 nanocomposite structure would have broad application prospects in new photoelectric materials.
Keywords: condensed matter physics; electrochemical deposition method; urchin-like; ZnO/In2O3 nanocomposite structure; optical property

Title: Negative differential resistance of n-ZnO nanorods/p-diamond heterojunction

Authors: SANG Dandan, CHENG Shaoheng, WANG Qiliang, PEI Xiaoqiang, LIU Junsong, LI Hongdon
PP: 236-241
Abstract: By thermal vapor transport method, ZnO nanorods (NRs) were grown on boron-doped chemical vapor deposited (CVD) polycrystalline diamond films. The n-ZnO NRs/p-diamond heterojunctions were constructed and show typical rectifying current-voltage behavior for lightly boron-doped diamond. When the p-type diamond is degenerated with heavily boron doping, a negative differential resistance phenomenon is presented for the heterojunctions. The origin of the NDR is attributed to the tunneling current occurred in the hybrid structure.
Keywords: condensed matter physics; ZnO nanorods; B-doped chemical vapor deposited diamond; n-ZnO nanorods/p-diamond heterojunction; negative differential resistance

Title: Analysis of temperature distribution based on ANSYS on the surface of glass heated by moving laser

Authors: LIU Caifei, FENG Guoying, WU Changshun, SONG Min
PP: 229-235
Abstract: Based on the theoretical model, this paper first simulates the temperature field on the surface of glass heated by static laser source, which is compared with the experiment results to verify the correctness of the model. Then, based on that, it studies the temperature distribution on the surface of glass heated by moving laser source and the influence of laser power, scanning rate and spot radius on that. It turns out that the temperature field changes with movement of laser source, whose shape presents the comet with tail. The node temperature increases with the increase of laser power. However, it decreases with the increase of scanning rate and spot radius. The above research provides the basis for studying the mechanism of laser cutting glass and cutting glass more precisely in practice, which is of great significance.
Keywords: physical electronics; ANSYS; temperature field; laser power; scanning rate; spot radius

Title: Effect of anodic SiO2 oxide’s annealing treatment on the minority carrier recombination in silicon

Authors: WEN Duzi, LIU Weifeng, LUO Yinglin, QIAO Jiankun
PP: 224-228
Abstract: SiO2 films were fabricated on textured Si wafers by anodic oxidation, and the Si wafers were annealed at different temperatures and time. The products were characterized by capacitance-voltage (C-V) and surface photovoltage (SPV) measurement. It was found that surface states and positive fixed charges changed with annealing temperatures. When the annealing temperature was low, just positive fixed charges were decreased, so minority carriers' recombination velocity was increased. Both surface states and positive fixed charges decreased when the annealing temperature arrived at 500℃, but the surface states were decreased significantly. Then minority carriers’recombination velocity was decreased.
Keywords: microelectronics and solid state electronics; SiO2; anodic oxidation; annealing

Title: Effects of pressure on the Mg doped GaN layers

Authors: ZHU Ming, LIANG Hongwei, SHEN Rensheng, ZHANG Kexiong, XIA Xiaochuan, SONG Shiwei, LIU Yang, DU Guotong
PP: 219-223
Abstract: A series of Mg doped GaN were grown with four different pressures using metal-organic chemical vapor deposition (MOCVD) in an Aixtron CCS close-coupled showerhead reactor. The four pressures for samples were 150, 250, 400, 600 mbar respectively. The quality of samples was characterized by X-ray diffraction(XRD). The results showed that, with the increasing pressure, the growth rate of Mg doped GaN decreased but the dislocation density was deteriorated simultaneously. These results indicate that higher growth pressure leads to a lower Mg incorporation in the p-GaN layer
Keywords: microelectronics and solid state electronics; p-GaN; pressure adjusting; Mg doped GaN

Title: Refraction of the Gaussian beam and its propagation

Authors: ZHANG Qiuchang, CHEN Ping, ZHENG Danyang
PP: 211-218
Abstract: An analytical expression of the refracted field of a Gaussian beam obliquely incident on a planar interface is derived on the basis of the Fresnel-Kirchhoff diffraction integral and under paraxial approximation. Numerical analysis shows that, while a TEM00 Gaussian beam propagates obliquely through a planar interface between materials of mismatched refractive indices, the refracted beam is an elliptical Gaussian beam. The beam waist radius in the direction perpendicular to the incident plane keeps unchanged while the one in the direction within the incident plane is different from that of the incident beam and their locations shift differently, which leads to a separation in space.
Keywords: optics; diffraction; Gaussian beam; scalar filed; diffraction theory

Title: Investigation of the time-resolved optical emission spectrum of the ejected material during femtosecond laser ablation of the highly oriented pyrolytic graphite

Authors: ZHANG Nan, FENG Peipei
PP: 206-210
Abstract: In this paper, 50 fs laser pulses with single pulse energy of 0.44 mJ are used to ablate the highly oriented pyrolytic graphite target in ambient air. And the ultrafast temporal evolution of the optical emission spectrum of the ejected material generated by the ablation is studied. It is found that in the early time after the striking of the femtosecond laser pulses with a laser fluence of 100 J/cm2, the optical emission spectrum of the ejected material is continuum ranging from 380 nm to 760 nm, which can be mainly attributed to the carbon plasma’s spectrum generated through the bremsstrahlung. As time elapses, several distinctive narrow spectral bands appear on the top of the continuum. These narrow bands with a bandwidth of 10-40 nm（full width at half maximum）are mainly generated by the carbon dimer. When time delay reaches several microseconds, the continuum disappears firstly, and only the narrow bands are left.
Keywords: optics; time-resolved optical emission spectrum; femtosecond laser ablation; highly oriented pyrolytic graphite

Title: Passively Q-switched Tm3+:BaY2F8 pulse laser

Authors: ZHAO Yongguang, YU Haohai
PP: 203-205
Abstract: In this paper, with a Cr2+:ZnS as saturable absorber, z-cut Tm:BYF (8% atom fraction, Tm3+:BaY2F8) as laser gain material, passively Q-switched pulse laser at 1 918.6 nm was demonstrated. L-cavity was adopted to enlange the light spot, and prevent damage to the Cr2+:ZnS. At the absorbed pump power of 1.58 W, the maximum average output power is 207 mW, the maximum pulse energy, the shortest pulse width and the largest peak power are 382 μJ, 28.6 ns and 13.3 kW, respectively, at the pulse repetition rate of 543 Hz.
Keywords: optics; 2 μm laser; passive Q-switching; Tm3+:BaY2F8 crystal; pulse laser

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