https://vjol.info.vn/index.php/cip <p><strong>Tạp chí của Viện Hàn lâm Khoa học và Công nghệ Việt Nam</strong></p> Vietnamese Academy of Science and Technology en-US Communications in Physics 0868-3166 https://vjol.info.vn/index.php/cip/article/view/2006 We 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. Hoang Manh Tien Nguyen Hai Chau Phan Thi Kim Loan Copyright (c) 2009-05-27 2009-05-27 19 1 1 8 https://vjol.info.vn/index.php/cip/article/view/2007 A 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. V. V. Kulish I. V. Gubanov Le Huu Dien Nguyen Ai Viet O. V. Lysenko Copyright (c) 2009-05-27 2009-05-27 19 1 9 18 https://vjol.info.vn/index.php/cip/article/view/2008 In 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. Pham Hoai Linh Tran Dang Thanh Do Hung Manh Nguyen Chi Thuan Le Van Hong Nguyen Xuan Phuc Copyright (c) 2009-05-27 2009-05-27 19 1 19 25 https://vjol.info.vn/index.php/cip/article/view/2009 The 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. Pho Thi Nguyet Hang Pham Thuy Dung Copyright (c) 2009-05-27 2009-05-27 19 1 26 32 https://vjol.info.vn/index.php/cip/article/view/2010 ZnS: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. Tran Minh Thi Copyright (c) 2009-05-27 2009-05-27 19 1 33 38 https://vjol.info.vn/index.php/cip/article/view/2011 Based 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. Mai Van Luu Dinh Xuan Khoa Vu Ngoc Sau Ho Quang Quy Copyright (c) 2009-05-27 2009-05-27 19 1 39 44 https://vjol.info.vn/index.php/cip/article/view/2012 When 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. Truong Thi Hong Loan Dang Nguyen Phuong Do Pham Huu Phong Tran Ai Khanh Copyright (c) 2009-05-27 2009-05-27 19 1 45 52 https://vjol.info.vn/index.php/cip/article/view/2013 The 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. Nguyen Tuan Khai Tran Duc Thiep Truong Thi An Phan Viet Cuong Nguyen The Vinh Copyright (c) 2009-05-27 2009-05-27 19 1 53 58 https://vjol.info.vn/index.php/cip/article/view/2014 This 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. Vo Van Thuan Copyright (c) 2009-05-27 2009-05-27 19 1 59 64