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.
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
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.
Le D.-A.,Hanoi National University of Education
Modern Physics Letters B | Year: 2014
At zero temperature, the Kotliar-Ruckenstein slave boson mean-field approach is applied to the dynamic Hubbard model. In this paper, the influences of the dynamics of the auxiliary boson field on the Mott transition are investigated. At finite boson frequency, the Mott-type features of the Hubbard model is found to be enhanced by increasing the pseudospin coupling parameter g. For sufficiently large pseudospin coupling g, the Mott transition occurs even for modest values of the bare Hubbard interaction U. The lack of electron-hole symmetry is highlighted through the quasiparticle weight. Our results are in good agreement with the ones obtained by two-site dynamical mean-field theory and determinant quantum Monte Carlo simulation. © 2014 World Scientific Publishing Company.
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.
Hien L.V.,Hanoi National University of Education
International Journal of Systems Science | Year: 2010
This article presents new exponential stability and stabilisation conditions for Takagi-Sugeno fuzzy time-varying delay systems. Based on an improved Lyapunov-Krasovskii functional, the exponential stability and stabilisation conditions are derived in terms of linear matrix inequalities, which allows one to compute simultaneously the two bounds that characterise the exponential stability rate of the solution. Finally, some numerical examples are given to illustrate the effectiveness of the proposed conditions. © 2010 Taylor & Francis.
Van Hien L.,Hanoi National University of Education
Journal of Biological Dynamics | Year: 2014
This paper addresses the global existence and global asymptotic behaviour of positive solutions to a non-autonomous Nicholson's blowflies model with delays. By using a novel approach, sufficient conditions are derived for the existence and global exponential convergence of positive solutions of the model without any restriction on uniform positiveness of the per capita dead rate. Numerical examples are provided to illustrate the effectiveness of the obtained results. © 2014 The Author(s). Published by Taylor & Francis.
Minh N.V.,Hanoi National University of Education |
Thang D.V.,Hanoi National University of Education
Journal of Alloys and Compounds | Year: 2010
Multiferroic Bi1-xYxFeO3 (x = 0.00, 0.05, 0.1, 0.15, 0.2) ceramics were prepared by conventional solid-state-reaction method. X-ray diffraction measurement was carried out to characterize the crystal structure and to detect the impurities existing in these ceramics. The substitution of rare earth Y for Bi was found to decrease the impurity phase in BiFeO3 ceramics. There is strong evidence that both lattice constants a and c of the unit cell unusually change at Y content of about x = 0.10. The effect of introducing Y3+ is shown to increase the optical band gap for doped sample Bi1-xYxFeO3. Additionally, the Raman measurement performed for the lattice dynamics study of Bi 1-xYxFeO3 samples reveals a strong band centered at around 1150-1350 cm-1 which is associated with the resonant enhancement of two-phonon Raman scattering in the multiferroic Bi 1-xYxFeO3 samples. The impedance spectroscopy indicates that, the Y dopant has improved the grain impedance. The enhancement of magnetization was observed in Y-doped samples compared to pure BiFeO 3. © 2010 Elsevier B.V.All rights reserved.
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.