In the last 30 days

• Open/close Development of a new atmospheric pressure cold plasma jet generator and application in sterilization

  Cheng Cheng et al 2006 Chinese Phys. 15 1544 Tag this article

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  This paper reports that a new plasma generator at atmospheric pressure, which is composed of two homocentric cylindrical all-metal tubes, successfully generates a cold plasma jet. The inside tube electrode is connected to ground, the outside tube electrode is connected to a high-voltage power supply, and a dielectric layer is covered on the outside tube electrode. When the reactor is operated by low-frequency (6 kHz–20 kHz) AC supply in atmospheric pressure and argon is steadily fed as a discharge gas through inside tube electrode, a cold plasma jet is blown out into air and the plasma gas temperature is only 25–30°C. The electric character of the discharge is studied by using digital real-time oscilloscope (TDS 200-Series), and the discharge is capacitive. Preliminary results are presented on the decontamination of E.colis bacteria and Bacillus subtilis bacteria by this plasma jet, and an optical emission analysis of the plasma jet is presented in this paper. The ozone concentration generated by the plasma jet is 1.0×10 ¹⁶cm ⁻³ which is acquired by using the ultraviolet absorption spectroscopy.

• Open/close AlGaInP thin-film LED with omni-directionally reflector and ITO transparent conducting n-type contact

  Zhang Jian-Ming et al 2007 Chinese Phys. 16 3498 Tag this article

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  In this paper a novel AlGaInP thin-film light-emitting diode (LED) with omni-directionally reflector (ODR) and transparent conducting indium tin oxide (ITO) n-type contact structure is proposed, and fabrication process is developed. This reflector is realized with the combination of a low-refractive-index dielectric layer and a high reflectivity metal layer. This allows the light emitted or internally reflected downwardly towards the GaAs substrate at any angle of incidence to be reflected towards the top surface of the chip. ITO n-type contact is used for anti-reflection and current spreading layers on the ODR-LED with ITO. The sheet resistance of the ITO films (95 nm) deposited on n-ohmic contact of ODR-LED is of the order 23.5Ω/□ with up to 90% transmittance (above 92% for 590–770 nm) in the visible region of the spectrum. The optical and electrical characteristics of the ODR-LED with ITO are presented and compared to conventional AS-LED and ODR-LED without ITO. It is shown that the light output from the ODR-LED with ITO at forward current 20 mA exceeds that of AS-LED and ODR-LED without ITO by about a factor of 1.63 and 0.16, respectively. A favourable luminous intensity of 218.3 mcd from the ODR-LED with ITO (peak wavelength 620 nm) could be obtained under 20 mA injection, which is 2.63 times and 1.21 times higher than that of AS-LED and ODR-LED without ITO, respectively.

• Open/close Non-equilibrium extrapolation method for velocity and pressure boundary conditions in the lattice Boltzmann method

  Guo Zhao-Li et al 2002 Chinese Phys. 11 366 Tag this article

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  In this paper, we propose a new approach to implementing boundary conditions in the lattice Boltzmann method (LBM). The basic idea is to decompose the distribution function at the boundary node into its equilibrium and non-equilibrium parts and then to approximate the non-equilibrium part with a first-order extrapolation of the non-equilibrium part of the distribution at the neighbouring fluid node. Schemes for velocity and pressure boundary conditions are constructed based on this method. The resulting schemes are of second-order accuracy. Numerical tests show that the numerical solutions of the LBM together with the present boundary schemes are in excellent agreement with the analytical solutions. Second-order convergence is also verified from the results. It is also found that the numerical stability of the present schemes is much better than that of the original extrapolation schemes proposed by Chen et al. (1996 Phys. Fluids 8 2527).

• Open/close Adaptive split-step Fourier method for simulating ultrashort laser pulse propagation in photonic crystal fibres

  Li Shu-Guang et al 2006 Chinese Phys. 15 437 Tag this article

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  In this paper, the generalized nonlinear Schrödinger equation (GNLSE) is solved by an adaptive split-step Fourier method (ASSFM). It is found that ASSFM must be used to solve GNLSE to ensure precision when the soliton self-frequency shift is remarkable and the photonic crystal fibre (PCF) parameters vary with the frequency considerably. The precision of numerical simulation by using ASSFM is higher than that by using split-step Fourier method in the process of laser pulse propagation in PCFs due to the fact that the variation of fibre parameters with the peak frequency in the pulse spectrum can be taken into account fully.

• Open/close Formation of graphene on Ru(0001) surface

  Pan Yi et al 2007 Chinese Phys. 16 3151 Tag this article

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  We report on the formation of a graphene monolayer on a Ru(0001) surface by annealing the Ru(0001) crystal. The samples are characterized by scanning tunnelling microscopy (STM) and Auger electron spectroscopy (AES). STM images show that the Moiré pattern is caused by the graphene layer mismatched with the underlying Ru(0001) surface and has an N × N superlattice. It is further found that the graphene monolayer on a Ru(0001) surface is very stable at high temperatures. Our results provide a simple and convenient method to produce a graphene monolayer on the Ru(0001) surface, which is used as a template for fabricating functional nanostructures needed in future nano devices and catalysis.

• Open/close Production of recoil ions Heⁱ⁺ accompanied by single electron loss of 0.2–7 MeV C^q+ and 0.25–5 MeV O^q+ (q = 1 – 4) ions

  Chen Xi-Meng et al 2007 Chinese Phys. 16 2384 Tag this article

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  Target ionization accompanied with projectile electron loss is investigated for 0.2–7 MeV C ^q+ ( q = 1 – 4) with He and 0.25–5 MeV O ^q+ ( q = 1 – 4) with He collisions. For projectile single-electron loss channel, the He double-to-single ionization ratio R is nearly independent of projectile charge state but dependent on the nuclear charge of projectile Z _p. The results are analysed with atomic structure qualitatively. So far there have not existed the experimental data comparable with our results, to our knowledge. The ratio R is interpreted in terms of the two-step mechanism. This analysis agrees well with similar experiments in the literature.

• Open/close Ab initio calculations of electronic structure of anatase TiO₂

  Chen Qiang and Cao Hong-Hong 2004 Chinese Phys. 13 2121 Tag this article

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  This paper presents the results of the self-consistent calculations on the electronic structure of anatase phase of TiO ₂. The calculations were performed using the full potential-linearized augmented plane wave method (FP-LAPW) in the framework of the density functional theory (DFT) with the generalized gradient approximation (GGA). The fully optimized structure, obtained by minimizing the total energy and atomic forces, is in good agreement with experiment. We also calculated the band structure and the density of states. In particular, the calculated band structure prefers an indirect transition between valence and conduction bands of anatase TiO ₂, which may be helpful for clarifying the ambiguity in other theoretical works.

• Open/close Lattice Boltzmann method for three-dimensional moving particles in a Newtonian fluid

  Fang Hai-Ping and Chen Shi-Yi 2004 Chinese Phys. 13 47 Tag this article

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  A lattice Boltzmann method is developed to simulate three-dimensional solid particle motions in fluids. In the present model, a uniform grid is used and the exact spatial location of the physical boundary of the suspended particles is determined using an interpolation scheme. The numerical accuracy and efficiency of the proposed lattice Boltzmann method is demonstrated by simulating the sedimentation of a single sphere in a square cylinder. Highly accurate simulation results can be achieved with few meshes, compared with the previous lattice Boltzmann methods. The present method is expected to find applications on the flow systems with moving boundaries, such as the blood flow in distensible vessels, the particle–flow interaction and the solidification of alloys.

• Open/close A modified split-step Fourier method for optical pulse propagation with polarization mode dispersion

  Rao Min et al 2003 Chinese Phys. 12 502 Tag this article

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  A modified split-step Fourier method (SSFM) is presented to solve the coupled nonlinear Schrödinger equation (CNLS) that can be used to model high-speed pulse propagation in optical fibres with polarization mode dispersion (PMD). We compare our approach with the SSFM and demonstrate that our approach is much faster with no loss of accuracy. We discuss the pulse distortion and system Q-factor of non-return-to-zero (NRZ), return-to-zero (RZ) and pre-chirped RZ (CRZ) formats in the presence of high PMD through this approach. The simulation results show that CRZ pulses are the most tolerant to high PMD values and the extinct ratio has a great impact on the transmission performance.

• Open/close Fabrication and optical properties of platinum nanowire arrays on anodic aluminium oxide templates

  Gao Tie-Ren et al 2002 Chinese Phys. 11 1307 Tag this article

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  Arrays of Pt nanowires, fabricated by electrodepositing Pt metal into nanoporous anodic aluminium oxide (AAO) templates, exhibit a preferable optical absorption band in the ultraviolet-visible (UV-VIS) spectra and present a blueshift as the wire aspect ratio increases or its radius decreases. This type of optical property of Pt nanowire/porous alumina composites has been theoretically explored using Maxwell-Garnett (MG) effective medium theory. The MG theory, however, is only applicable to nanowires with an infinitesimally small radius relative to the wavelength of an incident light. The nanowire radius is controlled by the pore radius of the host alumina, which depends on anodizing conditions such as the selected electrolyte, anodizing time, temperature and voltage. The nanowire aspect ratios depend on the amount of Pt deposited into the nanopores of AAO films. The optical absorption properties of the arrays of Pt nanowires with diameters of 24, 55 and 90 nm have been investigated by the UV-VIS spectra, which show that the extinction maximum (λ _max ) shifts to shorter wavelength side as the wire aspect ratio increases or its radius decreases. The results are qualitatively consistent with those calculated based on the MG theory.