Rate of Phonon Excitation and Conditions for Phonon Generation in Rectangular Quantum Wires

Tran Cong PHONG,Dinh Quoc VUONG,Le DINH,Nguyen Quang BAU 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.49 No.III

Phonon generation via the Cerenkov eect in rectangular quantum wires is theoretically studied based on the quantum kinetic equation for the phonon population operator. Analytical expressions for the rate of change of the phonon population and conditions for phonon generation are obtained. Numerical results for the speci.c rectangular quantum wires show that the amplitude of the laser .eld must satisfy additional conditions that are dierent in comparison with those of the other works. The dierences between the generation of acoustic phonon and optical phonon are considered.

Calculation of the Nonlinear Absorption Coefficient of an Intense Electromagnetic Wave Caused by Confined Electrons in Doped Semiconductor Superlattices

Tran Cong Phong,Vo Thanh Lam,Bui Dinh Hoi 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.57 No.5

General analytic expressions for the absorption coefficient (ACF) of an intense electromagnetic wave (IEW) caused by confined electrons in doped semiconductor superlattices (DSSL) are obtained by using the quantum kinetic equation (QKE) for electrons in the case of electron-optical phonon scattering. A second-order multiphoton process is included in the result. The dependence of the ACF on the amplitude E0 and the photon energy hΩof an IEW, the plasma frequency ωp and the temperature T for a specific DSSL of n-GaAs/p-GaAs is achieved by using a numerical method. The computational results show that the dependence of ACF on the photon energy can be applied to optically detect the electric subbands in a DSSL.

Parametric Resonance of Acoustic and Optical Phonons in a Quantum Well

Tran Cong Phong,Nguyen Quang Bau 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.5

The parametric resonance of acoustic and optical phonons in a quantum well in the presence of an external electromagnetic eld is theoretically predicted by using a set of quantum transport equations for the phonons. Dispersions of the resonant phonon frequency and the threshold amplitude of the field for parametric amplication of the acoustic phonons are obtained. If they are obtained, then they are also estimated for realistic semiconductor models.

Influence of Phonon Confinement on the Optically-detected Electrophonon Resonance Linewidth in Rectangular Quantum Wires

Tran Cong Phong,Le Thi Thu Phuong,Huynh Vinh Phuc,Pham Tuan Vinh 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.2

We investigate the influence of phonon confinement on the optically-detected electrophonon resonance (ODEPR) effect and ODEPR linewidth in rectangular quantum wires (RQW). The ODEPR conditions as functions of the wire’s size and the photon energy are also obtained. The splittings of ODEPR peaks caused by the confined phonon are discussed. The numerical result for a specific RQW shows that in the two cases of confined and bulk phonons, the linewidth decreases with increasing wire size and increases with increasing temperature. Furthermore, in the small range of the wire’s size (<i>L</i> ≤ 40 nm), phonon confinement plays an important role and cannot be neglected in reaching the ODEPR linewidth.

Parametric Resonance of Acoustic and Optical Phonons in a Doped Semiconductor Superlattice

Tran Cong Phong,Luong Van Tung,Nguyen Quang Bau 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.4

The parametric resonance of acoustic and optical phonons in a doped superlattice with a nondegenerative electron gas in the presence of a laser field is theoretically predicted by using a set of quantum transport equations for the phonons. Dispersions of the resonant phonon frequency and the threshold amplitude of the field for parametric amplification of the acoustic phonons are obtained. The amplitude is also estimated for realistic semiconductor models

Absorption Coefficient of Weak Electromagnetic Waves Caused by Confined Electrons in Quantum Wires

Nguyen Quang BAu,Tran Cong PHONG,Le DINH 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.51 No.II

The quantum theory of the absorption of weak electromagnetic waves (EMWs) caused by confined electrons in quantum wires has been studied based on Kubo's linear response theory and Mori's projection operator method. Analytical expressions for the absorption coefficients of weak EMWs in quantum wires with electron-acoustic phonon and electron-optical phonon scattering mechanisms are obtained. The dependence of the absorption coefficient of a weak EMW on its frequency $\omega$ as system temperature $T$, and the parameters charactering the sample are analyzed. Numerical calculations have been done, and the results are discussed for a typical wire of GaAs/GaAsAl.

Inclusion-Induced Bilayer Deformation:An Effect of Surface Tension

Kong-Ju-Bock Lee,Tran Cong Phong 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.43 No.51

Hydrophobic interactions between an inclusion, such as a protein, and a lipid bilayer play an important role in conformational changes of the inclusion and the bilayer. We analyze a deformation energy related to a hydrophobic mismatch by using a continuum theory in which compression, tension, and bending energies are considered. Dierently from previous works in which the eect of surface tension was usually neglected, we concentrate on the eect of the tension on the membrane deformation. We solve the Euler-Lagrange equation of a local deformation prole by using modied boundary conditions and a nite-dierence approximation. With well-known information for three kinds of lipid bilayers, we numerically calculate the deformation energies with and without the surface tension. We nd that the contribution of the surface tension to the deformation energy cannot always be neglected, implying a strong dependence on the lipid composition. The surface tension plays a negligible role in the dimyristoyl phosphatidylcholine (DMPC) bilayer; however, it does not in the glycerolmonooleate(GMO) bilayer which has a longer hydrophobic length and relatively weaker compression and bending rigidities than the DMPC bilayer.

Application of Cost-Volume-Profit Analysis in Decision-Making by Public Universities in Vietnam

LE, Oanh Thi Tu,TRAN, Phong Thi Thu,TRAN, Thuan Van,NGUYEN, Cong Van Korea Distribution Science Association 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.6

This paper aims to examine the application of cost-volume-profit (CVP) analysis by public universities in Vietnam. In the context where Vietnam is gradually transferring financial autonomy to public universities, the conduct of a CVP analysis in relation to these public universities is particularly urgent. Research samples were collected in 2018 and 2019 by surveying Vietnamese public universities. After collection, the data is synthesized by excel file, conformity check, data cleansing and data analysis on SPSS software by tools such as Frequency statistics, price statistics, and means. The results show that: (1) universities used the CVP analysis in decision-making, (2) information related to the CVP analysis used for decision-making by administrators remained simplistic and lacked cost-control details, and (3) the application of the CVP analysis by university administrators for decision-making was neither comprehensive nor coordinated. The findings also show that, given the current conditions in Vietnam, increasing the governance in public universities is essential, as is contributing to reducing costs, increasing universities'income, providing the best service to students, and improving the quality of training. The study calls for the flexible application of the CVP analysis, which will provide information to help managers at Vietnamese public universities make the best decisions.

Cyclotron Resonance Linewidth in GaAs/AlAs Quantum Wires

Huynh Vinh Phuc,Le Dinh Quang,Tran Cong Phong 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.60 No.9

In this paper, we study cyclotron-resonance linewidths in an electron-phonon system with the presence of a z-directional triangular potential and a y-directional parabolic potential. A general analytical expression for the absorption power is obtained in the presence of an external static magnetic field applied to the sample along the z-axis. The dependence of the absorption power on the photon energy is numerically calculated and graphically plotted for a specific GaAs/AlAs quantum wire. From graphs of the absorption power, we identified the locations of the cyclotron resonance peaks and obtained the cyclotron resonance linewidth (CRLW) as profiles of the curves. The temperature and the magnetic field dependences of the CRLW have been investigated. The CRLW is shown to increase with increasing temperature and magnetic field. In this paper, we study cyclotron-resonance linewidths in an electron-phonon system with the presence of a z-directional triangular potential and a y-directional parabolic potential. A general analytical expression for the absorption power is obtained in the presence of an external static magnetic field applied to the sample along the z-axis. The dependence of the absorption power on the photon energy is numerically calculated and graphically plotted for a specific GaAs/AlAs quantum wire. From graphs of the absorption power, we identified the locations of the cyclotron resonance peaks and obtained the cyclotron resonance linewidth (CRLW) as profiles of the curves. The temperature and the magnetic field dependences of the CRLW have been investigated. The CRLW is shown to increase with increasing temperature and magnetic field.