bluuebunny/crossref_metadata_2025 huggingface dataset:
Sóng trụ trong môi trường đàn hồi phi tuyến với biến dạng ban đầu thuần nhất
Authors: Oanh Pham Thi
Published: April 2018

None
On vibration of hanging pendulum in hammer crusher
Authors: Dao Nguyen Van
Published: April 2018

In- this article the vibration of hanging pendulum in hammer crusher is investigated in case when the ratio p2 /l2 is not very small in comparison with 1. It turned out that the suitable parameters in this case are 33% larger than that in the case p2 /l2 <<1 [1]. Because there is the friction the pendulum vibrates not around straight line OA but around A' with an angle x0 determined by  (4.3), (4.4 ).
On the motion of mechanical systems with unilateral constraints
Authors: Sanh Do
Published: April 2018

The motion of the system with unilateral constraints being imposed may be divised into positions, so that in certain positions the constraint is taut and the motion occurs as if the constraint was bilateral and in other positions the constraint is not taut and the motion occurs as if there was no such constraint. In the present paper two problems are discussed : 1. To determine the constant of time along with the positions and the velocities of the system when the system has just been released from the constraint. 2. To write the equations of motion of the system when the system has been released from the constraint.
Về định lý tồn tại nghiệm bài toán biên của lý thuyết dẻo đối với quá trình biến dạng có độ cong trung bình
Authors: Bich Dao Huy
Published: April 2018

None
Cấu trúc toán học của các vật thể đàn hồi. I. Trạng thái đàn hồi riêng
Authors: J Rychlewski
Published: April 2018

None
Về một cách tham số hóa lớp biên tà áp dừng của khí quyển
Authors: Quang Le Dinh
Published: April 2018

None
Self- excited oscillation under the influence of non - linear frictions
Authors: Dao Nguyen Van
Published: April 2018

In this article the influence of friction R1, R2 on Van der Pol oscillator is considered. It turned out that the mentioned frictions decrease the amplitude of self – excited oscillations and they stabilize the equilibrium position of the self – excited system.
Tính toán một số đặc trưng cơ bản của rối trong các bài toán ứng dụng của lý thuyết lớp biên khí quyển
Authors: Quang Le Dinh
Published: April 2018

None
The mass transfer in the capillary- porous materials
Authors: Chanh Truong Minh
Published: April 2018

In the paper the Mass transfers in capillary-porous plate, circular cylinder are, considered within the framework of the linear isothermal generalized - diffusive theory of the homogenous fluid mixtures. Solutions are obtained by the method of laplacces integral transformation.
Tính ứng suất phẳng trong tấm có gờ
Authors: Lang Vu Manh
Published: April 2018

None
On a bending problem of thick laminated composite plates
Authors: Khoa Ngo Nhu , Thinh Ngo Ich
Published: April 2018

A high-order displacement field in quadrilateral element with nine nodes and twelve-degrees-of-freedom per node is developed for bending analysis of thick arbitrary layered composite plates under transverse loads. Results for plate deformations, internal stress-resultants and stresses for selected examples are shown to compare well with the closed-form and other finite element solutions.
A numerical investigation of non-rotational, rigid spherical particle sedimentation problem in viscous fluid
Authors: Phan Nguyen Hong , Diep Nguyen Van
Published: April 2018

This paper can be considered as continuous part of [1], where the generalized diffusion theory of rigid spherical particle sedimentation in viscous fluid was investigated. Here a numerical solution of non-stationary sedimentation process is obtained by using the explicit finite difference method. The obtained results show that this model can be used for qualitative study of physical phenomenon of sedimentation problem.
Extension of method of moment equation to nonlinear deterministic vibrations
Authors: Anh Nguyen Dong , Hai Ninh Quang
Published: April 2018

The paper present the so-called "an extended averaged equation approach" to the investigation of nonlinear vibration problems. The numerical results in analysing the vibration systems with weak, middle and strong non-linearity show the advantages of the method.
Hygrothermo-mechanical behaviour of layered composite plates
Authors: Thinh Tran Ich
Published: April 2018

In this paper, a hygrothermo-mechanical behaviour of simply supported, composite layered rectangular plates is presented. The analysis is based on use of the Finite Element (FE) method and the full third-order displacement theory. Numerical examples are presented for symmetrically in-axis (0° /90° /90° /0°) and off-axis ( 45° / - 45° / -45° / 45°) layered rectangular plates.
Numerical model of three phase-three dimensional flow in porous media for reservoir simulation
Authors: Hai Duong Ngoc , Ba Dang The
Published: April 2018

The paper presents the results of simulation and study of mixture - oil, gas and water - flows in porous medium using three-phase, three dimensional "Black oil" model. For discretizing the system of mathematical equations, the finite volume difference method was used. To solve numerically the system of discretized equations the IMPES and iterative methods were chosen. The numerical results are compared with a number of analytical solution, experimental measurement and calculation results of the other authors and they shown a good agreement. The model can be developed, adapted and used for study and simulation of mixture - oil, gas and water - flow in different experimental and real field conditions.
Non-linear analysis of laminated plates
Authors: Bich Dao Huy
Published: April 2018

The governing equations of laminates plates taking into account the transverse shear deformation effects for large deformation are given. The formulation of Ritsz method and finite element method for non-linear analysis of this problem is presented
On some numerical methods for solving the 1-D Saint-Venant equations of general flow regime. Part 1: Numerical methods
Authors: Hanh Nguyen Van , Diep Nguyen Van , Can Ngo Huy
Published: April 2018

Development of methods for numerical simulation of dike- or dam-break flood is one of essential problems of Fluid Mechanics at the present time. Many numerical methods for solving the 1-D Saint-Venant equations have been proposed. However, the analysis, the evaluation and the selection of appropriate and efficient methods are interest of many research groups and institutions in the world. The purpose of this paper is to introduce and to evaluate four numerical methods for solving the 1-D homogenous Saint-Venant equations in combination with three approaches of processing source terms. The evaluation is based on the test problems, proposed by European Hydraulic Research Laboratories. The Part 1of the paper presents some modern numerical methods for solving the 1-D Saint-Venant equations of general Bow regime, where the Bow may be mixed between sub­ critical and supercritical. The homogenous part of the system of equations is numerically solved by "shock capturing methods" for conservation laws: the Lax-Friedrichs, the self adjusting hybrid, the Roe's approximation and the Nessyahu-Tedmor methods. The source terms play an important role and are discretized by the pointwise, upwind or mixed approaches. In the second part of this paper the above methods are verified by a set of test problems, covering all of three flow regimes: subcritical, supercritical, transcritical. The re­sults show that the mixed approach of processing source terms is better than the pointwise one. The Roe approximation method with the mixed discretization of source terms is then applied for a preliminary evaluation of the Son La - Hoa Binh dam-break problem.
On the elasto-plastic stability problem of shells of revolution
Authors: Bich Dao Huy
Published: April 2018

This paper deals with the elasto-plastic stability problems of shells of revolution subjected to complex loading process. The governing equations were derived and were solved by using the Bubnov-Galerkin method and the loading parameter method. Some examples were considered.
On some numerical methods for solving the 1-D Saint-Venant equations of general flow regime. Part 2: Verification and application
Authors: Hanh Nguyen Van , Diep Nguyen Van , Can Ngo Huy
Published: April 2018

In the Part 1 of this paper [1], some numerical methods for solving the 1-D Saint-Venant equations of general flow regime have been described. This Part of the paper presents the results of verification by various test problems, covering all of three flow regimes: sub-, trans-, and super-critical. The results show that the mixed approach (between pointwise and upwind) for source terms is better than the pointwise one and any mathematical transformation of source terms must be careful, since that can lead to nonphysical solutions. The Roe's approximation with the mixed technique for the source terms is used for a preliminary evaluation of the Son La - Hoa Binh dambreak problem
Long shore sediment transport computation for Hai Hau beach-Nam Dinh province
Authors: Hung Nguyen Manh
Published: April 2018

Several stretches of shore line in the Red River Delta (RRD) are suffering from severe erosion, especially an area between too large river mouths Balat in the North and Day in the South, known as Hai Hau beach. Several different hypothesis have been put forward to explain this erosion. The cut off of the Ha Lan river mouth (in 1955) which discharged sediment at the upstream end of the beach, possibly affects Hai Hau beach. Also, the construction of Hoa Binh dam in the upstream part of Red river has reduced the sediment supply to the area. In this study, it is shown that the prevailing wave climate in connection with the complex topography of Balat river mouth and Hai Hau beach promotes erosion along the coastal line. A two dimensional random wave transformation model was used with 20-year time series of hindcast waves to compute the long shore sediment transport along the study beach.
Application of numerical water force to a small sport boat running on a lake
Authors: Tran H.T. , Bikowski S. , Wolf C. D. , Maiber P.
Published: April 2018

In this paper the motion of a small sport boat running on a lake is simulated using alaska tools. External forces and torques from water during movement have been taken into account. Using results from measurements the simulation has been validated.
A two dimension numerical model for waves induced currents in the coastal zone
Authors: Hoan Le Xuan , Hung Nguyen Manh
Published: April 2018

In this paper, the results of two dimension numerical model for waves induced currents in the coastal zone are presented. The model was adjusted and verified at Phan Ri-Binh Thuan zone. The results of the testing show a good agreement between the observed and computed values. Then the model is applied to calculation of the distribution of waves induced currents in Ly Hoa area.
Frequency of a Vanderpol oscillator with large cubic restoring nonlinearity
Authors: Dinh Nguyen Van , Tri Tran Duong
Published: April 2018

In [2], a modified Poincare method has been presented and applied to evaluate the period (frequency) of free oscillation in an undamped Duffing oscillator with large cubic restoring nonlinearity. There, the system examined is supposed to be near certain linear one with unknown (to be evaluated) frequency.
Large deflection analysis of frames by elements containing higher-order terms
Authors: Kien Nguyen Dinh , Quang Do Quoc
Published: April 2018

In this paper, the beam elements using higher-order terms for large deflection analysis of elastic frames are discussed. The elements based on the co-rotational method are derived using the strain energy and effective strains. The arc-length method is employed as numerical algorithm to compute the equilibrium paths. A number of numerical examples are studied to verify and compare the developed formulations. The obtained results show that while the inclusion of second-order local rotation contributes to some improvement in the accuracy, the higher-order axial strain hardly improves the numerical results. With the employment of the higher-order term elements, the accuracy in numerical analysis may be attained at coarser meshes.
Ảnh hưởng của lõi đất dưới đáy móng đối với sư phân bố ứng suất trong nền đất
Authors: An Le Quy
Published: April 2018

None
Về một điều kiện ổn định
Authors: Dinh Nguyen Van
Published: April 2018

None
Concentration distribution of particles in pipe flow
Authors: Chanh Truong Minh
Published: April 2018

This paper deals with the construction of a generalized diffusive theory of micro-fluid polar mixtures. The results of the problem on the concentration distribution of particles in pipe flow are given. These results are obtained in arcordance with the experimental values.
Về độ cứng hình trụ của bản hai lớp
Authors: Lap Nguyen Van
Published: April 2018

None
Control of a pointer located on a vibrating system
Authors: Casciati F. , Faraveli L. , Anh Nguyen Dong
Published: April 2018

In this paper, the problem of controlling a bar supporting, at one end a pointer and hinged, at the other end, to a structural system vibrating under any extern excitation is investigated. The problem is to maintain the pointer toward the target with a prescribed tolerance. Emphasis is put on the uncertainty, which characterizes the problem and a simple fuzzy controller approach is discussed. Some numerical simulations are presented.
A numerical model for the tidal oscillation and current in the Gulf of Tonkin
Authors: Ngoc Duyet Tran Thi , Ninh Pham Van , Quynh Do Ngoc
Published: April 2018

in this paper results of a numerical model, based on the TIDEFLOW-2DSoftware, for the tidal oscillation and current in the Gulf of Tonkin (GT) are presented. The model was tested as follows: i) the observed values of the four main tidal constituents M2, S2, K1, 01 at the 44 coastal stations and islands were compared with computed ones; ii). the computed tidal levels were compared with the correlative ones in the Tide Tables at the six stations: Hon Gai, Cua Ong, Hon Dau, Cua Hoi, Cua Gianh and Cua Tung in many monthly periods; iii) the results of computed tidal levels and currents were compared with the observed data. The results of testing show a good agreement between the available data and computed values, therefore we can use this model for simulation t ide level and current of GT. The results of using this model in GT: distribution of the major harmonic constituents; the tidal elevation and current patterns; the extremal values of the tidal level and current,... will be published later.
On the relations between kinetic energy and linear momentum, angular momentum of the particle and of the rigid body
Authors: Khang Nguyen Van
Published: April 2018

Using the definition for the partial derivative of a scalar in respect to the vector, this paper presents the relations between kinetic energy and linear momentum, angular momentum of the particle and of the rigid body. The obtained results are useful for the investigation of the dynamics of multibody systems
Elastoplastic stability of thin rectangular plates under complex and impure loading
Authors: Ham Vu Cong
Published: April 2018

This paper deals with investigation of the elastoplastic stability of thin rectangular plates. The plate considered herein is subjected to the biaxial compressive forces which are assumed to be linearly distributed along every its edge.The governing equations of the problem are formulated with applying the elastoplastic process theory whereas Bubnov - Galerkin method is used to calculate the critical forces.In the paper the author proposes a new method to determine the elements of the matrix concerned with the instability moment of the structure and applies the Gaussian quadric method for integral calculation. Some results of numerical calculations are also presented in the paper.
Transition length of two stationary random functions in investigation of railway stability
Authors: Nam Nguyen Duong
Published: April 2018

In this paper the scientific justification for determination of transition length of two stationary random functions is presented on the basis of the weight function and properties of stationary random function in wide sense. The application of the results for practice gives the transition lengths of straight and curved railway, which it is necessary to throw away in measurement of initial horizontal displacement of railway in its stability estimation under action of longitudinal compression load.
The bifurcation theorem on the problem of thermal convection and contaminant transport in underground water
Authors: Can Ngo Huy , Ha Tran Thu
Published: April 2018

In the paper the bifurcation theorem on the problem of thermal convection and contaminant transport in underground water is proven.
IDV model for suspended sand transport under waves in ripple regime
Authors: Chung Dang Huu
Published: April 2018

In this paper the results of theoretical studies on suspended sand transport under irregular waves in the ripple regime are presented. The results from the lDV model, which simulates the instantaneous velocity and sand concentration from close to the bed up to higher in the water column are obtained. The model is based on the classical diffusion approach taking both the turbulence-related and the effective wave related diffusion into account. It shows that the time-averaged sand concentrations can be simulated reasonably well in the ripple regime using calibrated equations. Especially, the proposed formula for the diffusion coefficient by wave, considerably improved the behavior of vertical distribution of upended sediment concentration. Finally, the wave related suspended sediment transport in depth-integration is computed and compared with the measured data. The accuracy of the suspended transport was found to be strongly dependent on using measured data or predictive formula for concentration at the bed boundary.
Shock adiabat analysis for the mixture of liquid and gas of two components
Authors: Hai Duong Ngoc , Tuan Nguyen Van
Published: April 2018

The liquid and gas mixture is met in many natural and industrial processes. In the paper, the investigation results of shock waves, propagated in the liquid and two-component gas (one component is neutral, the other is condensed) mixture, are presented. The influence of the relative gas ratios, initial gas volume, wave intensity etc. on the main wave characteristics, is analyzed and illustrated as examples for two mixtures. The first is a mixture of water and gas (air and water vapor). The second is a mixture of crude oil and gas (one component is soluble, the other is insoluble).
Experimental results on sand transport under waves in large-scale wave flume
Authors: Chung Dang Huu
Published: April 2018

The paper presents some results of a study based on the experiment carried out in Delta Flume of Delft Hydraulics. The analysis of time-series of sand concentration and velocity are implemented for regular and irregular waves with different conditions on wave and grain size. From measured concentrations and velocities the suspended transport components are calculated and some interesting information is obtained. At the same time some formulae for calculations of suspended sediment transport have been proposed and verified. A general evaluation on the total sediment transport rate over the water depth has been given on the basis of incorporating measurement, extrapolation and bed load prediction.
A three dimensional non-hydrostatic model for turbulent air flow
Authors: Hai Duong Ngoc , Duc Nguyen The
Published: April 2018

A finite-volume code is developed to compute the turbulent airflow over small- scale complex terrain. A pressure-correction algorithm is used to solve the three-dimensional non-hydrostatic flow equations. The turbulent transport is simulated by the k- € model using some modifications suitable for atmospheric boundary-layer application. As an example, the model is used to simulate the flow-field around a cubical building. The same flow as a towing-tank experiment of USEPA was simulated using our code. These simulations show that, the model was capable of simulating recirculation zones behind the building. The results of calculation are also compared with available measurement data.
Spectral analysis of vibration in weakly non-linear systems
Authors: Khiem Nguyen Tien
Published: April 2018

The weakly nonlinear systems subjected to deterministic excitations have been fully and deeply studied by use of the well developed asymptotic methods [1-4]. The systems excited by a random load have been investigated mostly using the Fokker-Plank-Kolmogorov equation technique combined with the asymptotic methods [5-8]. However, the last approach in most successful cases allows to obtain only a stationary single point probability density function, that contains no information about the correlation nor' consequently, the spectral structure of the response. The linearization technique [9, 10] in general permits the spectral density of the response to be determined, but the spectral function obtained by this method because of the linearization eliminates the effect of the nonlinearity. Thus, spectral structure of response of weakly nonlinear systems to random excitation, to the author's knowledge, has not been studied enough. This paper deals with the above mentioned problem. The main idea of this work is the use of an analytical simulation of random excitation given by its spectral density function and afterward application of the well known procedure of the asymptotic method to obtain an asymptotic expression of the response spectral density function. The obtained spectral relationship covers the linear system case and especially emphasizes the nonlinear effect on the spectral density of response. The theory will be illustrated by an example and at the end of this paper there will be a discussion about the obtained results.
An identification algorithm for feedback active control
Authors: Anh Nguyen Dong
Published: April 2018

The aim of the paper is to present a control law for feedback active controlled structures in which a control algorithm is proposed to identify the external excitation with a time delay. The time duration in which the external excitation acts on the structure is devised into subintervals. In each subinterval the external excitation is identified and is then selected with the opposite sign as the control force for the next subinterval. The realization of the identification control algorithm in the practical application mainly depends on the computing capacity of the involved computer. and requires an investigation with respect to its robustness and stabilization.
Combination of collocation and factorization methods applied to numerical solutions of bubble-inside drop system dynamics
Authors: Hai Duong Ngoc
Published: April 2018

In the paper the combination of collocation and factorization methods applied to numerical investigation of bubble-inside drop system dynamics is presented. Initially assumed bubble and drop have ellipsoidal forms. The initial relative location of the drop in the bubble is determined by equilibrium condition between drop weight and lift-force due to pressure distribution in gas/vapor. Calculations are implemented for the case of spherical bubble, drop without and with vaporization (thermal effect) and for the experimental case [6] with alumina drop in water in pressure waves.
Study of prestrain influence for the prediction of the necking occurrence
Authors: Thang Nguyen Nhat
Published: April 2018

This paper contains experimental results for mechanical characteristics of a mild steel sheet. The determination of the forming limit stress curve for solicitation along two direction is drawn. Study of pestraint influence from the limit stress diagram is presented.
An algorithm for simultaneous determination of pressure and temperature distribution in oil-producing tube flow and the counter flow in gas-lift annulus
Authors: Hien Ha Ngoc , Diep Nguyen Van , Hai Duong Ngoc , Canh Nguyen Van
Published: April 2018

An algorithm for simultaneous determination of pressure and temperature distribution in oil-producing tube flow and the counter flow in gas-lift annulus has been proposed. The algorithm is based on a double loop iterative procedure and shooting method. The two-phase flow calculation for pressure Used in the algorithm is based on improved methods of Beggs and Brills, Orkissewski or Hagedorn and Brown. The numerical implementation for an example is presented to assure the applicability of proposed algorithm.
An implicit algorithm for computation of overflow in flood plains
Authors: Dac Nguyen Tat
Published: April 2018

None
Identifying the resonance curve of a system subjected to linear and quadratic parametric excitations (case with damping)
Authors: Dinh Nguyen Van , Chi Tran Kim
Published: April 2018

In [3], a quasi linear oscillating system simultaneously subjected to linear and cubic parametric excitations has been studied. In the present paper, we examine the case in which the linear and quadratic parametric excitations are present. The asymptotic method [ 1] is applied. We are interested in the method of identifying the resonance curve. The results obtained show that the "associated" equations can be used.
Associated equations and their corresponding resonance curve
Authors: Dinh Nguyen Van
Published: April 2018

In the theory of nonlinear oscillations, in order to identify the resonance curve we usually try to eliminate the diphase Ѳ in the equations of stationary oscillations. We obtain thus a certain frequency-amplitude relationship. In simple cases when the mentioned equations contain only and linearly the first harmonics (sin Ѳ, cos Ѳ) the elimination of Ѳ is elementary, by using the trigono-metrical identity sin2 Ѳ+ cos2 Ѳ = 1. In general, high harmonics (sin2 Ѳ, cos2 Ѳ, etc.) are present. Consequently the expressions of sin Ѳ, cos Ѳ are cumbersome or do not exist and the analytical elimination of Ѳ is quite inconvenient or impossible. For this reason, to identify the resonance curve of complicated systems, we use the numerical method. Below, intending to develop the analytical method, we shall propose a procedure enabling us to transform the "original" complicated equations of stationary oscillations into the so-called associated ones, only and linearly containing sin Ѳ, cos Ѳ. The equivalence of the original and associated equations will be treated and the associated resonance 'curve-that is determined by the associated equations-will be analyzed The discussion will be restricted to a simple practical case in which, beside sin Ѳ and cos Ѳ, only sin2 Ѳ and cos2 Ѳ are present. Nevertheless, the method proposed and the results obtained can be generalized.
A physico-mathematical model for solute transport in groundwater
Authors: Khu Nguyen Phi
Published: April 2018

In this paper a model for solute transport in groundwater, including physic-co-mathematical basis, numerical method some simple example simulations is briefly presented. This model has been gradually improved in both simulation and methodology.
Some initial experimental results on the conditions of free water layer formation in horizontal pipes
Authors: Thien Nguyen Duy , Diep Nguyen Van , Hai Duong Ngoc , Phan Nguyen Hong
Published: April 2018

This paper presents an experimental facility conducted in Hanoi Institute of Mechanics to investigate multiphase How pattern in the pipes. First and foremost, it is used to define the conditions of water layer formation in the horizontal pipe.Experimental results have been obtained in stainless steel pipes of three different diameters (24.6mm; 30.8mm and 40.5mm) with white spindle oil N° 10 and water. They have been shown in the form of water layer maps.
A New Approach to the Theory of Hierarchic Wave-oscillation Dynamic Systems
Authors: Kulish V. V. , Gubanov I. V. , Dien Le Huu , Viet Nguyen Ai , Lysenko O. V.
Published: April 2018

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.
Fabrication and Magnetic Properties of Mn1 - xZnxFe2O4 (0 ≤ x ≤ 0.8) Nanoparticles
Authors: Linh Pham Hoai , Thanh Tran Dang , Manh Do Hung , Thuan Nguyen Chi , Hong Le Van , Phuc Nguyen Xuan
Published: April 2018

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.
Transverse Distribution of Pump Power in the Diode-laser Side-pumped Solid-state Laser Rod
Authors: Luu Mai Van , Khoa Dinh Xuan , Sau Vu Ngoc , Quy Ho Quang
Published: April 2018

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.
A Superluminal Formalism for Majorana-like Lepton
Authors: Thuan Vo Van
Published: April 2018

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.
Orbital Oscillator Commutation Relations and Mass Shifting for Superstring
Authors: Loan Nguyen Thi Ha , Ha Nguyen Hong
Published: April 2018

In this work we extend the results obtained in [5] on mass shifting for bosonic string to the case of superstring. The modified anomaly terms of superstring superalgebras are shown and the corresponding BRST charge is used.
Multipartite Disentanglement Dynamics Due Simultaneously to Amplitude Damping and Phase Damping
Authors: An Nguyen Ba
Published: April 2018

We present a detailed analysis on disentanglement dynamics of multiqubit GHZ-type states whose qubits are remotely located in absence of any mutual interactions. The dynamics is thus induced by independent local environments surrounding each qubit. It has recently been known that if each qubit is subjected solely to the phase damping then the state's entanglement vanishes asymptotically in time and if only the amplitude damping is active then the state's entanglement may vanish suddenly in certain parameter subspace. In this paper, we shall show that a combined action of both the phase damping and the amplitude damping will force the state's entanglement to always vanish suddenly in the entire parameter space. Furthermore, we shall prove that by proper local operations such a finite-time disentanglement can be avoided for whatever state's parameters, no matter the phase damping and the amplitude damping act severally or in combination.
Electrical and Optical Properties of the Hybrid TiO\(_{2}\) Nanocrystals - MEH-PPV Thin Films
Authors: Chi Le Ha
Published: April 2018

Recently, the conjugated polymer -- inorganic nanocomposites have been increasingly studied because of their enhanced optical and electronic properties as well as their potential application in developing optoelectronic devices. In this study nanocomposite materials thin films based on poly [2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) and nanocrystalline TiO\(_{2}\) (nc-TiO\(_{2}\)) have been fabricated. The photoluminescence (PL) spectra of pure MEH-PPV and nanohybrid films have shown that the excitation at a 377 nm wavelength leads to the strongly enhanced performance in photoluminescent intensity due to the compositions of TiO\(_{2}\) component. Current-voltage (I-V) characteristics of multi-layer device Al//MEH-PPV:nc-TiO\(_{2}\)//PEDOT: PSS//ITO//glass were investigated. The results show that the hybrid MEH-PPV:nc-TiO\(_{2}\) materials with high concentrations of TiO\(_{2}\) (>25%) can be expected to be a good candidate for photovoltaic solar cell applications whereas those with lower concentrations of TiO\(_{2}\) are more suitable for organic light-emitting diodes (OLEDs).
Test
Authors: Giao Nguyen Xuan
Published: April 2018

Test
Complexes of SiH\(_2^{2+}\) with Carbodiphosphorane and Analogues {E(PPh\(_3\))\(_2\)} (E = C – Pb) in Unusual Bonding Mode
Authors: Pham Tat Van
Published: April 2018

Quantum chemical calculations at the BP86 level with various basis sets (SVP, TZVPP) were carried out for complexes of carbodiphosphorane analogues E(PPh3)2 with E = C–Pb. The equilibrium geometries of the complexes [SiH22+–{E(PPh3)2}] (Si2+-1E) possess the carbodiphosphorane ligand 1C is slightly bonded in a tilted way to SiH22+ in the complex Si2+-1C, whereas the heavier group-14 ligands E(PPh3)2 (E = Si – Pb) in the complexes Si2+-1Si – Si2+-1Pb are strongly bonded in side-on fashions. The surprising structures SiH22+-tetrylone complexes possess a strong Si-C1 bond between the Si atom of the SiH22+ fragment and atom C1 of the phenyl group. The trend of the BDEs for the Si-E bond in the Si2+-1E complexes is Si2+-1C ~ Si2+-1Si < Si2+-1Ge < Si2+-1Sn < Si2+-1Pb. Bonding analysis of the complexes shows that the Si-E bonds have a significant contribution from H2Si2+←E(PPh3)2 π-donation.
Transport Properties of A Quasi-two-dimensional Electron Gas in InP/In\(_{1 - x}\)Ga\(_{x}\)As/InP Quantum Wells : Correlation and Magnetic Field Effects
Authors: Khanh Nguyen Quoc , Huyen Mai Thanh
Published: April 2018

We investigate correlation and magnetic field effects on the mobility and resistivity of a quasi-two-dimensional electron gas in an InP/In\(_{1 - x}\)Ga\(_{x}\)As/InP quantum well at arbitrary temperatures. We study the dependence of the mobility and resistivity on the carrier density, magnetic field, layer thickness and temperature for alloy disorder and impurity scattering using different approximations for the local-field correction. Multiple scattering effects and discuss the possibility of a metal-insulator transition, which might happen at low density for unpolarized and fully polarized electron gas are also considered.
Challenges in particle physics and 3-3-1 models
Authors: Long Hoang Ngoc
Published: April 2018

At present,   particle physics faces problems related with disparity in diphoton decay of Higgs boson,  discrepancybetween theory and experiment of about $3.6 \si$ in anomalous magnetic moment of the muon and neutrino physics.Moreover, the existence of   Dark Matter and the Matter-Antimatter Asymmetry are challenges for any physical model.In this review I present some solutions  in the framework  of  the 3-3-1 models. The  simple (by Higgs sector) models contain the hybrid inflationary scenario and the first-order phase transitions, from which  leptogenesis needed for BAUis followed.By these considerations, some bounds on model parameters are derived.
Influence of ASE Noise on Performance of DWDM Networks Using Low-power Pumped Raman Amplifiers
Authors: Ninh Bui Trung , Tuan Nguyen Quoc , Hung Ta Viet , Anh Nguyen The , Hoi Pham Van
Published: April 2018

We present the results of investigation  for  influence of amplified spontaneous emission (ASE) noise, noise figure (NF) and  chromatic dispersion on the performance of middle-distance Dense-wavelength-division-multiplexing (DWDM) networks using low-power pumped distributed Raman amplifiers (DRAs) in two different pump configurations, i.e., forward and backward pumping. We found that the pumping configurations, ASE noise, and dispersion play an important role for improving network performance by decrease of noise figure and bit error rate (BER) of the system. Simulation results show that the lowest bit error rate and low noise figure were obtained, when using forward pumping configuration. Moreover, we have also compared ASE noise powers of the simulation with these of the experiment. These results conclude that DRA with low pump power  ($<1$~W) is the promising key technology for short-- and/or middle-distance DWDM transmission networks.
Gauge Bosons in the 3-3-1 Model with Three Neutrino Singlets
Authors: Long Hoang Ngoc , Huy Lam Phu An , Thuy Tran Thanh , Tran Ly Thi Tu , Yen Vu Thi Hoang
Published: April 2018

We show that the mass matrix of electrically neutral gauge bosons in the recent proposed  model based on \(\mathrm{SU}(3)_C\otimes \mathrm{SU}(3)_L\otimes \mathrm{U}(1)_X\) group with three neutrino singlets [9] has two exact eigenvalues and corresponding eigenvectors. Hence the neutral non-Hermitian gauge boson \(X^0_\mu\) is properly determined.With extra vacuum expectation values of the Higgs fields, there are mixings among charged gauge bosons \(W^\pm\) and \(Y^\pm\) as well as amongneutral gauge bosons \(Z, Z'\) and \(X^0\). From the $W$ boson decay width, we get lower bound on  scale of the model about few TeVs.
\(\gamma e^{-} \rightarrow h e^{-}\) Collision in Randall - Sundrum Model
Authors: Giang Bui Thi Ha , Thuy Dao Thi Le
Published: April 2018

We consider the Randall - Sundrum model, which solves the Higgs hierarchy problem. In this paper, we have calculated the cross - section of the \(\gamma e^{-} \rightarrow h e^{-}\) process with the polarization of the electron beams. Based on the results, we show that the reaction can give observable cross - section in future accelerators at the high degree of polarization.
Contents
Authors: - -
Published: April 2018

Contents, Vol. 26 No. 1 (2016)
UV Light Induced Thermoluminescence of Rare Earth doped Nanomaterials Y\(_2\)O\(_3\):Eu\(^{3+}\), Gd\(_2\)O\(_3\):Eu\(^{3+}\) and Gd\(_2\)O\(_3\):Er\(^{3+}\)
Authors: Hai Nguyen Thi Quy , Anh Tran Kim , Ha Vu Thi Thai , Chau Pham Thi Minh , Tuyen Ho Van , Thanh Nguyen Trong , Minh Le Quoc
Published: April 2018

Thermoluminescence  properties of ultraviolet irradiated Y2O3:Eu3+, Gd2O3:Eu3+ and Gd2O3:Er3+ nanophosphors have been reported. The materials were synthesized by gel- combustion method with EDTA- Na2 as organic agent. This method allows production of very fine white powder at low temperature with very high efficiency. XRD has been studied to determine the structure of the prepared nano powders. The obtained materials exhibit sufficient sensibility to UV radiation and may be useful in UV light measurements.
Influence of Temperature And Concentration of Ethanol on Properties of Borosilicate Glass Photonic Crystal Fiber Infiltrated by Water – Ethanol Mixture
Authors: Le Van Hieu , Nguyen Hue Thi , Ho Dinh Quang , Cao Long Van
Published: April 2018

In this paper, we present a numerical simulation of the properties of a photonic crystal fiber (PCF) made of borosilicate glass infiltrated by the water-ethanol mixture. We examine the influence of temperature and ethanol concentration for the refractive index, dispersion properties, effective mode area and confinement loss of the fundamental mode by a Lumerical simulation method. We also calculate the fundamental mode of the fiber infiltrated with a water-ethanol mixture with the concentration range of ethanol from 0% to 100% in the temperature range from 10°C to boiling point of ethanol. The results show that all fibers infiltrated with water-ethanol mixture have flat dispersion characteristics in the infrared range above 1.32. The best flatness exists for pure ethanol. Furthermore, it is possible to shift the zero-dispersion wavelength and modify fundamental properties of PCFs by both temperature and concentration of ethanol. The results obtained are important because of that we not only use their reasonable parameters for the design and manufacture but also use them in nonlinear phenomena and nonlinear applications of fibers as supercontinuum generation.
DNA barcodes and morphology of P. krempfi, P. mekongensis, and P. elongatus
Authors: Yên Dương Thúy , Kiệt Nguyễn , Nên Bùi Sơn , Thường Nguyễn Văn , Loan Nguyễn Bạch , Định Trần Đắc
Published: April 2018

Three Pangasius species including P. krempfi, P. elongatus and P. mekongensis, are economically important. They can be mis-identified due to similar external appreance at small sizes. This study aimed to distinguish these species based on their differences in DNA barcode, COI (cytochrome c oxidase subunit I) gene, and morphological characteristics. Fish with various sizes (>90 samples/species) were sampled at the lower Mekong delta region. Kimura-2 parameter genetic distances based on COI sequences of three species (15 samples, in which, 4 unique sequences were assigned Genbank accession numbers from KT289877 to KT289880) are relatively high, ranging 9.33 – 12.10 %. Morphological measurements show that coutanble traits including numbers of fin rays and the first gill rakers vary in similar ranges but ratios of metric traits are significantly different among three species (P<0.01). Principle component analysis using metric traits sets three species apart. P. elongatus is characterized by elongated body, long caudal preduncle, large eyes, and retangle palatine tooth plates. P. krempfi differs from P. mekongesis in characteristics on their head. The number of sections, shape and length of barbel are different among three species. Phylogenetic relationship of three species based on morphology and COI sequences indicate that P. krempfi is closer to P. mekongenis rather than P. elongatus, and that the distance between P. mekongenis and P. elongatus is the largest.
Expression analysis of GmNAC085 gene under dehydration and salt treatment in drought-tolerant DT51 and drought-sensitive MTD720 soybean cultivars
Authors: Hiếu Đoàn Ngọc , Thư Nguyễn Bình Anh , Xuân Hoàng Thị Lan , Uyên Nguyễn Phạm Kim , Thảo Nguyễn Phương
Published: April 2018

NAC transcription factors (NAC TFs) are important regulatory factors in plant response to drought and salt which are the two osmotic stresses seriously affecting plant production. In our previous studies, GmNAC085 was confirmed as a drought-responsive gene in shoots and roots of soybeans. In this study, expression of GmNAC085 under osmotic stresses was examined in drought-tolerant soybean DT51. 12-day-old plants were dehydrated or treated with salt for 0 h, 2 h and 10 h. Our results shown that under dehydration, the expression of GmNAC085 significantly increased in both shoots and roots, especially in shoots. More specifically, its expression was elevated 30-fold in shoots and 5-fold in roots at 2 h; at 10 h, its expression was elevated 260-fold in shoot and 8-fold in root of DT51; in MTD720, expression was elevated 15-fold and 28-fold in root, 499-fold and 494-fold in shoot tissues at 2h and 10h, respectively. Similarly, under salt treatment at 2h and 10h, the expression of GmNAC085 was up-regulated in both shoots and roots. The expression of GmNAC085 was elevated 35-fold and 656-fold in shoots, 2-fold and 14-fold in root of DT51, respectively; meanwhile, in MTD720, expression was elevated 10-fold and 377-fold in shoots, 5-fold and 26-fold in roots. Therefore, GmNAC085 was considered to be not only drought-responsive but also abiotic stress-responsive. GmNAC085 is a potential gene for genetic engineering to improve stress tolerance in soybean and other crops.
Perspectives of RNAi studies in plant pathogenic fungi
Authors: Quốc Nguyễn Bảo , Châu Nguyễn Ngọc Bảo
Published: April 2018

RNA silencing, the phenomenon known as RNA interference (RNAi), co-suppression or post-transcriptional gene silencing (PTGS) and quelling, has become more popular in studies of its intrinsic roles and applications in many organisms or of gene functions in a whole genomic scale. Since the discovery of RNA silencing more two decades ago, this powerful technology has demonstrated its applicability in developing RNAi-based drugs for various diseases in human. RNA silencing is also of interest in basic and applied studies in agriculture, especially in plant protection to create crop varieties that are resistant to biotic and abiotic stresses. This review provides an overview of RNA silencing studies in filamentous fungi, the molecular mechanisms of RNA silencing in fungi, and also describes potential applications in plant protection potentially important for the agricultural industry and for global food security.
Investigation of suitable conditions for the growth and producing biofilm of denitrifying bacteria
Authors: Hà Hoàng Phương , Huy Nguyễn Quang , Yến Hoàng Thị
Published: April 2018

Denitrification occurs under anaerobic conditions, utilizing organic substances such as a carbon source and nitrate as the terminal electron acceptor. Some bacteria strains that are capable of producing biofilm and are attached to the carrier for the applications of the nitrate contaminated water treatment. This process is done simultaneously with the process of nitrification, nitrifying bacteria on the biofilm surface (ocic zone), denitrifying bacteria under biofilm (anoxic zone). The selection of suitable conditions for the growth and production of biofilm of denitrifying bacteria is the target of this research. Two strains D10 and D32 are capable to reduce nitrate and created the best biofilm. Optimal conditions for the strain growth were: 37oC, pH 6.6 - 7. Supplementation of 0.006% M1, E2 (methanol, ethanol) increased the reducing N-NO3 to 80% and 100% respectively. Denitrification process still occured in aerobic condition but with lower efficiency (25.8%) byD32 strain. Based on 16S rRNA gene analysis, D10 strain was the closest relative with Bacillus fusiformis, D32 closest to Pseudomonas denitrifricans.
Table of contents (Volum 14 Number 2 (2016))
Authors: Biotechnology Journal Of
Published: April 2018

Volum 14 Number 2 (2016)
Genetic characterization of mitochondrial genome of the small intestinal fluke, Haplorchis taichui (Trematoda: Heterophyidae), Vietnamese sample
Authors: Hòa Lê Thanh , Khuê Nguyễn Thị , Nga Nguyễn Thị Bích , Roan Đỗ Thị , Dũng Đỗ Trung , Xuyến Lê Thị Kim , Hương Đoàn Thị Thanh
Published: April 2018

The small intestinal fluke, Haplorchis taichui Nishigori, 1924, belonging to genus Haplorchis (family Heterophyidae, class Trematoda, phylum Platyhelminthes), is a zoonotic pathogen causing disease in humans and animals. Complete mitochondrial genome (mtDNA) of H. taichui (strain HTAQT, collected from Quang Tri) was obtained and characterized for structural genomics providing valuable data for studies on epidemiology, species identification, diagnosis, classification, molecular phylogenetic relationships and prevention of the disease. The entire nucleotide mtDNA sequence of H. taichui (HTAQT) is 15.119 bp in length, containing 36 genes, including 12 protein-coding genes (cox1, cox2, cox3, nad1, nad2, nad3, nad4L, nad4, nad5, nad6, atp6 and cob); 2 ribosomal RNA genes, rrnL (16S) and rrnS (12S); 22 transfer RNA genes (tRNA or trn), and a non-coding region (NR), divided into two sub-regions of short non-coding (short, SNR) and long non-coding (long, LNR). LNR region, 1.692 bp in length, located between the position of trnG (transfer RNA-Glycine) and trnE (Glutamic acid), contains 6 tandem repeats (TR), arranged as TR1A, TR2A, TR1B, TR2B, TR3A, TR3B, respectively. Each protein coding gene (overall, 12 genes), ribosomal rRNA (2 genes) and tRNA (22 genes) were analyzed, in particular, protein-coding genes were defined in length, start and stop codons, and rRNA and tRNA genes for secondary structure.