http://tainguyenso.vnu.edu.vn/jspui/handle/123456789/98 2026-05-17T21:45:56Z http://tainguyenso.vnu.edu.vn/jspui/handle/123456789/901 Congestion control of Wavelet image compression over wireless networks Ho, Anh Tuy; Nguyen, Vinh An The demand of transmission of images and video is increasing quickly recently and researchers are trying to invest good solutions to improve the quality of these over wireless networks. There are still challenges due to the different characteristics and quality of images between wired and wireless channels. An important issue is congestion control to ensure network stability and achieve a reasonably fair distribution of the network resources among the users. The paper will present a model of congestion control by combining Wavelet image compression at the source with applying Fuzzy logic technique to control traffics. The simulation shows a good result, the transmission rate can be adjusted to adapt the changes of wireless channel, the buffer of intermediate devices will not be swung from idle to overflow or vice versa so that the cell loss rate is small. VNU Journal of Science, Mathematics - Physics. Vol. 23 (2007), No 1 (M.P), P. 55-62 2007-01-01T00:00:00Z http://tainguyenso.vnu.edu.vn/jspui/handle/123456789/894 Influence of intradot Coulomb interaction on transport properties of an Aharonov-Bohm interferometer Do, Ngoc Son; Bach, Thanh Cong Using Greens function method and the equation of motion approach, we have investigated the electronic transport properties of an Aharonov-Bohm (AB) ring in the presence of a magnetic field with a quantum dot inserted in one arm of the ring. In particular, we consider the electron-electron Coulomb interaction within the quantum dot. We find that the current through the system is dependent on the magnetic flux via the AB phase and the Coulomb interaction within the quantum dot, in agreement with experiments. Furthermore, the intradot Coulomb interaction induces dephasing. VNU Journal of Science, Mathematics - Physics. Vol. 23 (2007), No 1 (M.P), P. 47-54 2007-01-01T00:00:00Z http://tainguyenso.vnu.edu.vn/jspui/handle/123456789/888 Applying probabilistic model for ranking Webs in multi-context Le, Trung Kien; Tran, Loc Hung; Le, Anh Vu The PageRank algorithm, used in the Google search engine, greatly improves the results of Web search by applying probabilistic model on the link structure of Webs to evaluate the “importance” of Webs. In PageRank probabilistic model, the links and webs are uniform, so the rank score of webs are quite independent from their content. In practice, the researchers often hope that the web results can be ranked by their proposed topics. Moreover, when computer’s techniques solve given problems ineffectively, it’s necessary to do better research in theoretical problems. From this judgement, in this paper, we introduce and describe the MPageRank based on a new probabilistic model supporting multi-context for ranking Webs. A Web now has different ranking scores, which depends on the given multi topics. The basic idea in establishing the new MPageRank model is that partition our Web graph into smaller-size sub Web graph. As a consequence of evaluation and rejection about pages influence weakly to other pages, the rank score of pages of the original Web graph can be approximated from the rank score of pages in the new partition Web graph. Similar to the PageRank, the multi ranking scores in the MPageRank are pre-computed and reflect the hyperlink of Web environment. VNU Journal of Science, Mathematics - Physics. Vol. 23 (2007), No 1 (M.P), P. 35-46 2007-01-01T00:00:00Z http://tainguyenso.vnu.edu.vn/jspui/handle/123456789/884 Anharmonic effective potential and XAFS cumulants for hcp crystals containing dopant atom Nguyen, Van Hung; Le, Thi Thuy Hau; Tong, Sy Tien A new procedure for calculation and analysis of XAFS (X-ray Absorption Fine Structure) cumulants of hcp crystals containing dopant atom has been derived based on quantum statistical theory with generalized anharmonic correlated Einstein model. Analytical expressions for effective local force constants, correlated Einstein frequency and temperature, first cumulant or net thermal expansion, second cumulant or Debye Waller factor and third cumulant of hcp crystals containing dopant atom have been derived. Morse potential parameters of pure crystals and those with dopant included in the derived expressions have been calculated. Numerical results for Zn doped by Cd are found to be in good agreement with experiment. VNU Journal of Science, Mathematics - Physics. Vol. 23 (2007), No 1 (M.P), P. 28-34 2007-01-01T00:00:00Z