Hanoi National University of Education

Hanoi, Vietnam

The High School for Gifted Students, Hanoi National University of Education ) is a public magnate school in Hanoi, Vietnam. The school was founded in 1966 as a national educational institution to nurture Vietnamese students who excelled at mathematics. One of the three national gifted high schools in Hanoi, along with Foreign Language Specialized School and Natural Science Gifted High School, HNUE High School is the second oldest magnet high school in Vietnam.The school and HUS High School for Gifted Students are often interchangeably ranked the first in National Science Olympiads for high school students and National University Entrance Examinations. HNUE High School ranks second nationally in the 2012 Vietnam university admission ranking.Established as a school for mathematics talents, in recent years, HNUE high school's specialized education have spanned over other subjects such as physics, chemistry, biology, computer science, English and literature Wikipedia.

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Tinh B.D.,Hanoi National University of Education
Solid State Communications | Year: 2017

The time-dependent Ginzburg-Landau model with thermal noise is used to calculate the out of plane a.c. fluctuation conductivity of type-II superconductor under magnetic field. We assume that thermal fluctuations, represented by the Langevin white noise, are strong enough to melt the Abrikosov vortex lattice created by the magnetic field into a moving vortex liquid. The nonlinear interaction term in the time-dependent Ginzburg-Landau equation is treated within the self-consistent Gaussian approximation. The real and imaginary parts of the out of plane a.c. fluctuation conductivity formula are summation over all Landau levels to treat arbitrary magnetic fields. Our results indicate that high frequencies can be effectively used to suppress the out-of-plane a.c. fluctuation conductivity in high-temperature superconductors. The results also have refined analytical form and are fitted well to experimental data on high-Tc superconductor. The results in two-dimensional and three-dimensional limits are directly inferred from the corresponding result of the layered model. © 2017 Elsevier Ltd

Tinh B.D.,Hanoi National University of Education
European Physical Journal B | Year: 2017

The effect of a high electric field on the c-axis fluctuation conductivity in layered superconductors near the superconducting transition is investigated by the time-dependent Ginzburg-Landau equation. The c-axis fluctuation conductivity is calculated in self-consistent Gaussian approximation for an arbitrarily strong electric field and a magnetic field perpendicular to the layers. Our results include all Landau levels and have refined analytical form. The results in linear response are in good agreement with the experimental data in a wide region around Tc in high Tc superconductor. We also show that high electric fields can be effectively used to suppress the c-axis fluctuation conductivity in high-temperature superconductors. © 2017, EDP Sciences, SIF, Springer-Verlag GmbH Germany.

van Manh P.,Hanoi National University of Education
Numerical Algorithms | Year: 2017

We study the Hermite interpolation problem on the spaces of symmetric bivariate polynomials. We show that the multipoint Berzolari-Radon sets solve the problem. We also give a Newton formula for the interpolation polynomial and use it to prove a continuity property of the interpolation polynomial with respect to the interpolation points. © 2017 Springer Science+Business Media New York

Hien L.V.,Hanoi National University of Education
International Journal of Systems Science | Year: 2017

In this paper, the problems of full-order and reduced-order positive state estimations are developed for discrete-time positive Markov jump linear systems with delay. By establishing a positive time-delay system for 1-moment function of the state vector, delay-dependent necessary and sufficient exponential stability conditions are first derived based on a comparison technique for positive systems. Then, on the basis of the derived stability conditions, the problems of designing positive state observers in full-order and reduced-order for positive Markov jump systems with delay are addressed. The existence conditions of positive observers and the design schemes are formulated in terms of linear programming problems which can be effectively solved by various optimisation algorithms to obtain the observer parameters. Finally, three numerical examples with simulations are given to validate the analysis and design results. © 2017 Informa UK Limited, trading as Taylor & Francis Group

Khang N.C.,Hanoi National University of Education
Journal of Electronic Materials | Year: 2017

Hetero-photocatalysts TiO2/CuO were prepared by a wet impregnation process and their optical properties were characterized with a variety of techniques. The x-ray diffraction patterns corresponding to the anatase and the rutile phases of TiO2 were noticed for all the samples, but the peaks belonging to CuO crystals were observed only for samples with high CuO content (≥4 wt.%). The UV–Vis spectra show that absorption edges of the modified TiO2 were shifted toward longer wavelengths, indicating a reduction in the energy bandgap upon CuO. For photocatalytic application, the addition of CuO into TiO2 was found to increase the photodegradation of methylene blue and methylene orange with the highest photodegradation observed at CuO content of 3 wt.%. Moreover, using some extra experimental processes, we reveal how the CuO component affects the optical properties of the resulting materials. © 2017 The Minerals, Metals & Materials Society

Dong P.V.,Vietnam Academy of Science and Technology | Nguyen T.P.,Can Tho University | Soa D.V.,Hanoi National University of Education
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

We show that the typical 3-3-1 models are only self-consistent if they contain interactions that explicitly violate the lepton number. The 3-3-1 model with right-handed neutrinos can by itself work as an economical 3-3-1 model as a natural recognition of the above criteria, while it also produces an inert scalar triplet (η) responsible for dark matter. This is ensured by a Z 2 symmetry (assigned so that only η is odd while all other multiplets which perform the economical 3-3-1 model are even), which is not broken by the vacuum. The minimal 3-3-1 model can provide dark matter by a similar realization. Taking the former into account, we show that the dark matter candidate (Hη) contained in η transforms as a singlet in the effective limit under the standard model symmetry and is naturally heavy. The Hη relic density and direct detection cross section will have the correct values when the mass of Hη is in TeV range, as expected. The model predicts the Hη mass mHη= λ5×2 TeV and the Hη-nucleon scattering cross section σHη-N=1.56×10-44 cm2, provided that the new neutral Higgs boson is much heavier than the dark matter. © 2013 American Physical Society.

Hien L.V.,Hanoi National University of Education | Trinh H.M.,Deakin University
Automatica | Year: 2014

In this note, the problem of state bounding for linear time-varying systems with delay and bounded disturbances input is considered for the first time. By using a novel approach which does not involve the Lyapunov-Krasovskii functional method, new explicit delay-independent conditions are derived for the existence of a ball such that all the state trajectories of the system converge exponentially within it. A numerical example is given to illustrate the effectiveness of the obtained result. © 2014 Elsevier Ltd. All rights reserved.

Van Minh N.,Hanoi National University of Education | Gia Quan N.,Hanoi National University of Education
Journal of Alloys and Compounds | Year: 2011

Bi1-xHoxFeO3 (x = 0.00, 0.05, 0.10, 0.15 and 0.20) polycrystalline ceramics were synthesized by a solid-state reaction and their structural, absorption, Raman scattering, impedance and magnetic properties were investigated. The substitution of rare earth Ho for Bi was found to decrease the impurity phase in BiFeO3 ceramics. There appears an anomalous change in the lattice constants, optical band gap as well as the impedance spectroscopy and magnetization of samples at x = 0.10, suggesting a limit of dissolubility of Ho doped ions in BiFeO3. Additionally, the Raman measurement performed for the lattice dynamics study of Bi 1-xHoxFeO3 samples reveals a band centered at around 1000-1300 cm-1 which is associated with the resonant enhancement of two-phonon Raman scattering in the multiferroic Bi 1-xHoxFeO3 samples. Ho-doped BiFeO3 also showed a ferromagnetic-like behavior with Mr = 1070 × 10-4 and Ms = 1.60 emu/g for optimum content x = 0.10, which is similar to the solid solution system of BiFeO3. © 2010 Elsevier B.V. All rights reserved.

Le D.A.,Hanoi National University of Education
Modern Physics Letters B | Year: 2013

Using the coherent potential approximation, we study zero-temperature Mott transition in the half-filled Hubbard model on the honeycomb lattice. Although a pseudogap is already present for the non-interacting case, the gap will not occur until the onsite Coulomb repulsion exceeds a critical value U ≈ 3.6t, where t is the hopping integral. When increasing U/t, the density of states at the Fermi energy first goes up gradually from zero and after reaching a maximum it goes down to zero again. Our calculated critical interaction UC/t is in very good agreement with the ones obtained by quantum Monte Carlo simulation and cluster dynamical mean-field theory. © 2013 World Scientific Publishing Company.

Si D.Q.,Hanoi National University of Education
Complex Analysis and Operator Theory | Year: 2013

In this article, we prove that two meromorphic functions f and g must be linked by a quasi-Möbius transformation if they share two pairs of small functions ignoring multiplicities and share other four small functions with multiplicities truncated by 2. We also show that two meromorphic functions which share seven pairs of small functions ignoring multiplicities are linked by a quasi-Möbius transformation. © 2012 Springer Basel AG.

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