http://tainguyenso.vnu.edu.vn/jspui/handle/123456789/980 Kết quả nghiên cứu của Học giả Việt Nam tham gia Chương trình Giao lưu Học giả Quốc tế (ISEF) 2026-05-15T22:44:40Z http://tainguyenso.vnu.edu.vn/jspui/handle/123456789/1535 Land use change modelling based on Remote Sensing, GIS and Fractal analysis: a case study of Vietnamese coastal zone Nguyễn, An Thịnh The last decades has seen the emergence of landscape/land use change as one of the key driving forces in global changes, especially climate change, environmental change, and ecological economic change. This change, from landscape ecological perspective, has a tendency of altering landscape mosaic pattern which may well lead to ecosystem function change over time, and could be seen at global, regional and local scales altogether. By using multiscale approach, at regional scale, in addition to landscape change dynamic, almost of important impacts of climate change and sea level rise were completely analyzed throughout Vietnam coastal zone. At local scale, land use change, landscape dynamic, the correlation between spatial pattern and ecosystem function was particularly clarified over a selected case study area of Tien Lang district, a specific coastal area nearby Gulf of Tonkin, North of Vietnam. There were four main studying results obtained, including environmental impact assessment of sea level rise on Vietnamese coastal zone, reconstructing landscape changes since 1989 by using satellite remote sensing data, landscape change modelling and proposing scenarios of landscape ecological planning (LANDEP) for the case study area. A final report was designed with six chapters (in English), into which involved a key collection of 10 thematic maps by digital format and 3 papers submitted in international conferences/world congress. The results of this research, theoretically, pointed out the major problems of clarifying landscape pattern in the past, understanding trends of landscape change in the future, and analyzing dynamic of landscape change along transects. Practically, these not only helped detect such spatially explicit landscape patterns, but improved the ability of planners to integrate ecological and environmental considerations in territorial planning. 2010-01-01T00:00:00Z http://tainguyenso.vnu.edu.vn/jspui/handle/123456789/1527 Phonon-Assisted Electron Hopping Conduction in the Uranium Doped One-Dimensional Antiferromagnet Ca2CuO3 Phùng, Quốc Thanh The authors studied the conduction mechanism in an uranium doped low dimensional magnetic system Ca2CuO3. This system exhibits the S=1/2 quasi 1D antiferromagnetic chains of -Cu-O- with strong magnetic coupling, and demonstrates continuous semiconductor-like behavior with constant covalent insulator character. This paper identifies the conduction is due to thermally activated phonon-assisted electron hopping between dopant uranium sites. The parameter á, the characteristic for hopping probability, was determined to be 0.18 Å−1. This value manifests a relatively stronger hopping probability for Ca2CuO3 as compared with other uranium doped ceramics. 2008-01-01T00:00:00Z http://tainguyenso.vnu.edu.vn/jspui/handle/123456789/1522 Large Enhancement of the GMI E ect in Multi-Ferromagnetic Ribbons Phùng, Quốc Thanh A kind of composite material consisting of stacked magnetic ribbons, each isolated with thin plastic sheets, for high-performance sensor applications. Impedance measurements were conducted in the frequency range of 1-10 MHz for a varying dc magnetic field within 300 Oe. The giant magnetoimpedance (GMI) effect and its field sensitivity were achieved in these composite materials. The GMI effect was found increase strongly with increasing number of ferromagnetic ribbons. The GMI ratio and its field sensitivity reached the highest values of 220% and 25%/Oe for the composite containing five ribbons, which indicates that the newly developed composite material is very promising for high-performance GMI sensor applications. The increase in the GMI effect in the composite sample was shown to be attributable to a decrease in the electrical resistance and the increase of effective permeability 2009-01-01T00:00:00Z http://tainguyenso.vnu.edu.vn/jspui/handle/123456789/1506 Critical behavior and magnetic entropy change in La0.7Ca0.3Mn0.9Zn0.1O3 perovskite manganite Phùng, Quốc Thanh We studied the critical behavior and magnetic entropy change in a perovskite-manganite compound of La0.7Ca0.3Mn0.9Zn0.1O3 around its Curie temperature of TC ¼ 206.75 K. Experimental results revealed that the sample exhibited the second-order magnetic phase transition with the exponents b ¼ 0.474 and g ¼ 1.152 close to those expected from the mean-field theory (b ¼ 0.5 and g ¼ 1.0). In the vicinity of TC, the magnetic entropy change DSM reached maximum values of 1.1, 1.7, and 2.7 J/kg K under magneticfield variations of 10, 20, and 35 kOe, respectively. These DSM values are much lower than those reported previously on the parent compound of La0.7Ca0.3MnO3. The nature of this phenomenon is discussed by means of the characteristics of the magnetic phase transition, and critical exponents. 2011-01-01T00:00:00Z