https://vjol.info.vn/index.php/cip/issue/feedCommunications in Physics2012-08-02T11:19:30+07:00Nguyen Xuan Giaocip@vjs.ac.vnOpen Journal Systems<p><strong>Tạp chí của Viện Hàn lâm Khoa học và Công nghệ Việt Nam</strong></p>https://vjol.info.vn/index.php/cip/article/view/2006Tight-binding Calculations of Band Structure and Conductance in Graphene Nano-ribbons2012-08-02T11:19:29+07:00Hoang Manh Tienphysics70thd@yahoo.com.vnNguyen Hai Chauphysics70thd@yahoo.com.vnPhan Thi Kim Loanphysics70thd@yahoo.com.vnWe suggest a general approach based on the nearest-neighbor tight-binding approximation (TB) to investigate the band structure and conductance of a quasi-one dimensional system. Numerical calculations carried out for Graphene nanoribbons (GNRs) with different widths and edge conditions (zigzag and armchair) reveal the well-known results that the electronic properties of GNRs depend strongly on the size and geometry of the sample.2009-05-27T17:27:43+07:00Copyright (c) https://vjol.info.vn/index.php/cip/article/view/2007A New Approach to the Theory of Hierarchic Wave-oscillation Dynamic Systems2012-08-02T11:19:29+07:00V. V. Kulishphysics70thd@yahoo.com.vnI. V. Gubanovphysics70thd@yahoo.com.vnLe Huu Dienphysics70thd@yahoo.com.vnNguyen Ai Vietphysics70thd@yahoo.com.vnO. V. Lysenkophysics70thd@yahoo.com.vnA set of new ideas and concepts (which the authors treat as a new version of the theory of hierarchic dynamic systems) are set forth in the article. In turn, the set of hierarchic principles is put in the methodological basis of this theory. It is shows, a peculiar version of the theory of hierarchic waves and oscillations can be developed on the basis of proposed general theory.2009-05-27T18:27:07+07:00Copyright (c) https://vjol.info.vn/index.php/cip/article/view/2008Fabrication and Magnetic Properties of Mn1 - xZnxFe2O4 (0 ≤ x ≤ 0.8) Nanoparticles2012-08-02T11:19:29+07:00Pham Hoai Linhphysics70thd@yahoo.com.vnTran Dang Thanhphysics70thd@yahoo.com.vnDo Hung Manhphysics70thd@yahoo.com.vnNguyen Chi Thuanphysics70thd@yahoo.com.vnLe Van Hongphysics70thd@yahoo.com.vnNguyen Xuan Phucphysics70thd@yahoo.com.vnIn this paper, we report results on the fabrication and magnetic properties of spinel ferrite Mn1-xZnxFe2O4 (0 ≤ x ≤ 0.8) nanoparticles. The nanoparticles were synthesized by a co-precipitation method. The effects of substituting Zn for Mn on the magnetic properties and particles size were focused. It was found that the phase-formation temperature is 90OC and the average particle size decreases from 40 nm to 10 nm when increased Zn concentration from zero to 0.8. The Curie temperature TC strongly decreases from 585 K (x = 0) to 320 K (x = 0.8) concomitantly with a decrease of the saturation magnetization MS. With a TC of 320 K and MS of 17 emu/g, the x=0.8 sample could be a promising candidate for some biomedical applications.2009-05-27T18:32:34+07:00Copyright (c) https://vjol.info.vn/index.php/cip/article/view/2009The Propagation of the Electromagnetic Wave in Multilayers Structures Composed from Cholesteric Liquid Crystals under the Influence of the External Electric Field2012-08-02T11:19:29+07:00Pho Thi Nguyet Hangphysics70thd@yahoo.com.vnPham Thuy Dungphysics70thd@yahoo.com.vnThe tensor solution for the electromagnetic wave being in quadrature with the surface of the cholesteric liquid crystal under the influence of the external electric field along axis of swing of crystal, has been found. Description of the reflection, transmission of the electromagnetic wave in multilayer structures composed from cholesteric liquid crystals have been shown. Futher the dependence of the reflection spectrum on the polarization of the incident beam and magnitude of the external electric field are determined.2009-05-27T18:36:28+07:00Copyright (c) https://vjol.info.vn/index.php/cip/article/view/2010Influence of Mn<SUP>2+</SUP> Concentration and UV Irradiation Time on the Luminescence Properties of Mn-doped ZnS Nanocrystals2012-08-02T11:19:30+07:00Tran Minh Thiphysics70thd@yahoo.com.vnZnS:Mn were prepared by wet chemical method with Mn doping concentration from 0 at% to 12 at%. The structure and particle size of the obtained powders were measured by X-ray diffraction (XRD) and scanning electron microscopy (SEM) and shown that all samples are single phase with sphalerite crystal structure and average particle size of about 5 - 7 nm. The dependence of Mn2+ ions doped concentration, and UV irradiation time on the luminescent intensity of ZnS:Mn nanocrystals was discussed.2009-05-27T18:40:21+07:00Copyright (c) https://vjol.info.vn/index.php/cip/article/view/2011Transverse Distribution of Pump Power in the Diode-laser Side-pumped Solid-state Laser Rod2012-08-02T11:19:30+07:00Mai Van Luuphysics70thd@yahoo.com.vnDinh Xuan Khoaphysics70thd@yahoo.com.vnVu Ngoc Sauphysics70thd@yahoo.com.vnHo Quang Quyphysics70thd@yahoo.com.vnBased on the assumption that Gaussian pump power of diode laser bar is the same at any cross-section along the laser rod and its curvated surface plays as thin lens, the expression describing the pump intensity distribution inside laser rod was obtained by transfer matrix. To have the cross-section of active volume or excited volume coincides with one of laser mode volume, the dependence of pump intensity distribution on location of outside pump beams is investigated by simulation.2009-05-27T18:45:17+07:00Copyright (c) https://vjol.info.vn/index.php/cip/article/view/2012Investigating the Effect of Matrices and Densities on the Efficiency of HPGe Gamma Spectroscopy Using MCNP2012-08-02T11:19:30+07:00Truong Thi Hong Loanphysics70thd@yahoo.com.vnDang Nguyen Phuongphysics70thd@yahoo.com.vnDo Pham Huu Phongphysics70thd@yahoo.com.vnTran Ai Khanhphysics70thd@yahoo.com.vnWhen determining radioactivities in environmental samples using low-level gamma spectroscopy, in order to raise detection limit, voluminous samples are used. It takes in account for the self-absorption (self-attenuation) of gamma rays in samples. The self-absorption effect is small or large depend on the sample shapes, matrices and densities. In this paper, we investigated the effect of some regular matrices such as water, soil, epoxy resin on the detector efficiency. Some analytical formulas for the correction of matrix and densities for soil sample was established and applied to calculate some activities from standard sample of IAEA-375.2009-05-27T18:50:08+07:00Copyright (c) https://vjol.info.vn/index.php/cip/article/view/2013Neutron Yield from (γ, n) and (γ, 2n) Reactions following 100 MeV Bremsstrahlung in a Tungsten Target2012-08-02T11:19:30+07:00Nguyen Tuan Khaintkhai@iop.vast.ac.vnTran Duc Thiepntkhai@iop.vast.ac.vnTruong Thi Anntkhai@iop.vast.ac.vnPhan Viet Cuongntkhai@iop.vast.ac.vnNguyen The Vinhntkhai@iop.vast.ac.vnThe photonuclear reactions of (γ, xn) or (γ, xnp) types can be used to produce high-intensity neutron sources for research and applied purposes. In this work a Monte-Carlo calculation has been used to evaluate the production yield of neutrons from the (γ, n) and (γ, 2n) reactions following the bremsstrahlung produced by a 100 MeV electron beam on a tungsten target.2009-05-27T18:54:47+07:00Copyright (c) https://vjol.info.vn/index.php/cip/article/view/2014A Superluminal Formalism for Majorana-like Lepton2012-08-02T11:19:30+07:00Vo Van Thuanvvthuan@mail.vaec.gov.vnThis work deals with the nature of Majorana particles by applying the time-like formalism of the superluminal Lorentz transformation (SLT). It is proposed that along with the SLT of the space-time coordinates, the Dirac equation should be treated simultaneously by a Majorana-like representation to be invariant. This formalism leads to a natural understanding of Majorana physics.2009-05-27T18:57:48+07:00Copyright (c)