On the amplifiction of sound (acoustic phonons) by absorption of laser radiation in cylindrical quantum wires with parabolic potential in the presence of magnetic field

Authors:	Nguyen, Quoc Hung Nguyen, Quang Bau
Keywords:	amplifiction of sound;acoustic phonons;laser radiation;cylindrical quantum wires;parabolic potential;magnetic field
Issue Date:	2002
Publisher:	H. : ĐHQGHN
Series/Report no.:	Vol. 18;No. 3 (2002)
Abstract:	Based on the quantum kinetic equation for phonon, the amplification of sound (acoustic phonons) due to the absorption of laser radiation in cylindrical quantum wires with parabolic potential in the presence of m agnetic field is studied. Analytical expressions for the rate of acoustic phonons excitations, the conditions for the amplification of sound and the momentum conditions for electron to participate in the amplification of sound are obtained for the two cases: singlephoton absorption process and multiphoton absorption process. The differences between the two cases of singlephoton absorption and m ultiphoton absorption are discussed; the numerical computations and plots are carried out for a GaAs/GaAsAl quantum wire. The results are compared with bulk semiconductors and quantum wells.
Description:	p. 10-16
URI:	http://repository.vnu.edu.vn/handle/VNU_123/58424
ISSN:	2588-1124
Appears in Collections:	Mathematics and Physics

Nghiệp vụ RED-PLATE: Phân tích phê bình về sự phát triển nghiệp vụ của các cán bộ thư viện ở Inđônêxia

Authors:	Sanjaya Pendit, Putu Laxman
Keywords:	Thư viện;Cán bộ Thư viện;Nghiệp vụ RED-PLATE;Inđônêxia
Issue Date:	2009
Publisher:	Đại học Quốc gia Hà Nội
Description:	tr. 452-466 Kỷ yếu đại hội cán bộ thư viện các nước Đông Nam Á lần thứ 14
URI:	http://repository.vnu.edu.vn/handle/VNU_123/31283
Appears in Collections:	Kỷ yếu Hội nghị - Hội thảo (LIC)

Tái lập Hội Thư viện: Kinh nghiệm ở In-đô-nê-xia

Authors:	Gani, Fuad Zen, Zulfikar
Keywords:	Thông tin thư viện;Hiệp hội thư viện;Inđônêxia
Issue Date:	2009
Publisher:	Đại học Quốc gia Hà Nội
Description:	tr. 467-475 Kỷ yếu đại hội cán bộ thư viện các nước Đông Nam Á lần thứ 14
URI:	http://repository.vnu.edu.vn/handle/VNU_123/31286
Appears in Collections:	Kỷ yếu Hội nghị - Hội thảo (LIC)

Các lý thuyết kinh tế trong bối cảnh khủng hoảng kinh tế toàn cầu và thực tiễn Việt Nam

Keywords:	Kinh tế học;Lý thuyết kinh tế
Issue Date:	2010
Publisher:	H. : ĐHQGHN
Description:	442 tr.
URI:	http://repository.vnu.edu.vn/handle/VNU_123/34214
Appears in Collections:	Kỷ yếu Hội nghị - Hội thảo (LIC)

Study of self-diffusion in semiconductors by statistical moment method

Authors:	Vu, Van Hung Nguyen, Quang Hoc Phan, Thi Thanh Hong
Keywords:	self-diffusion;statistical moment method
Issue Date:	2004
Publisher:	H. : ĐHQGHN
Series/Report no.:	Vol. 20;No. 1 (2004)
Abstract:	Using the statistical moment method, self-diffusion in semiconductors is studied including the anharmonic effects of lattice vibrations. The interaction energies between atoms in semiconductors are estimated by applying many-body potential. The activation energy Q and pre-exponential factor D{) of the self-diffusion coefficient are given in closed forms. The values of Q and D0 are calculated for Si and GaAs at high temperature region near the melting temperatures and they shown to be in good agreement with the experimental data.
Description:	p. 23-30
URI:	http://repository.vnu.edu.vn/handle/VNU_123/57889
ISSN:	2588-1124
Appears in Collections:	Mathematics and Physics

Thermodynamic and correlation effects in atomic vibration of bcc crystals containing dopant atom

Authors:	Nguyen, Van Hung Ho, Khac Hieu Nguyen, Cong Toan
Keywords:	Thermodynamic effects;correlation effects;atomic vibration;dopant atom
Issue Date:	2006
Publisher:	H. : ĐHQGHN
Series/Report no.:	Vol. 22;No. 1 (2006)
Abstract:	A new procedure for calculation and analysis of thermodynamic and correlation effects of bcc crystals under in fluence of dopant atom in the X-ray Absorption Fine Structure (XAFS) has been developed. Analytical expression for the Displacement-displacement Correlation Function (DCF) CR has been derived based on the derived Mean Square Relative Displacement (MSRD) 2 Ơ2 and Mean Square Displacement (MSD) u of bcc crystals containing dopant atom. Numerical calculations have been carried out for Fe doped by w and by Cr atom. They are found to be in good agreement with experiment.
Description:	p. 26-32
URI:	http://repository.vnu.edu.vn/handle/VNU_123/57779
ISSN:	2588-1124
Appears in Collections:	Mathematics and Physics

Image and video compression for wireless networks

Authors:	Ho, Anh Tuy Nguyen, Vinh An
Keywords:	video compression;Image compression;wireless networks
Issue Date:	2006
Publisher:	H. : ĐHQGHN
Series/Report no.:	Vol. 22;No. 1 (2006)
Abstract:	The demands for transmission of image, video and multimedia over wireless networks are increasing very rapidly. The inherently characteristics of wireless medium as bandwidth narrowing, interferences and fading are big challenges. The traditional compression techniques can not adapt to this changes. In this paper, we will discuss of issues of using wavelet compression for image and video over wireless networks. This paper also introduces some change of wavelet parameters in order to improve quality of transmission image and video over wireless network conditions.
Description:	p. 33-46
URI:	http://repository.vnu.edu.vn/handle/VNU_123/57780
ISSN:	2588-1124
Appears in Collections:	Mathematics and Physics

Electronic Structure of a Molecular Magnet from Salicylate Based Copper Complex

Authors:	Nguyen, Duc Tho Nguyen, Thuy Trang Hoang, Nam Nhat
Keywords:	Molecular magnet;DFT;Electronic structure
Issue Date:	2012
Publisher:	H. : ĐHQGHN
Series/Report no.:	Vol. 28;No. 1 (2012)
Abstract:	The electronic structure of the metallo-organic compound Cu(SA)2(2-PM)2 (2-PM is 2-pyridylmethanol) is presented. The calculation was performed using the Density Functional Theory with unrestricted spin polarized model and large wave function basis sets which include the polarized and diffuse functions. The single point energy calculation for the isolated molecule gave the HOMO-LUMO separation of 3.8 eV and the LDA+U band structure calculation showed the band gap of only 0.38 eV. The calculated magnetic moment per molecule is comparable to the experimentally observed value.
Description:	p. 26-31
URI:	http://repository.vnu.edu.vn/handle/VNU_123/56354
ISSN:	2588-1124
Appears in Collections:	Mathematics and Physics

Dynamics and mechanism diffusion in silica liquid: Insight from simulation

Authors:	Nguyen, Thi Thanh Ha Nguyen, Quang Bau Pham, Khac Hung
Keywords:	silica liquid;Dynamics;mechanism
Issue Date:	2012
Publisher:	H. : ĐHQGHN
Series/Report no.:	Vol. 28;No. 1 (2012)
Abstract:	In this paper, we numerically study the diffusion mechanism at atomic level in silica liquid via molecular dynamics simulation. The model consisting of 1998 particles and using the BKS potential has been constructed at the temperature from 2600 to 4500 K. Furthermore, we track the evolution of network units with x=4, 5 and 6 over different time. The simulation shows that the diffusivity depends strongly not only on the rate of the exchanging the coordinated oxygens, but also on the correlation effect. This effect is caused by the specific distribution of the exchanging coordinated oxygens (ECO) through the space which leads to spatially heterogeneous dynamics in the liquid. Analyzing the temperature dependence of the correlation coefficient F we found that the slowdown in dynamics near glass transition point is ascribed from percolation of the domains where high frequent exchanging coordinated oxygens occurs.
Description:	p. 32-38
URI:	http://repository.vnu.edu.vn/handle/VNU_123/56358
ISSN:	2588-1124
Appears in Collections:	Mathematics and Physics