VNU Journal of Science

Xem 1-20 trên 172 kết quả VNU Journal of Science
  • Centre for Applied Research in Remote Sensing and GIS, College of Science, VNU 2 Norwegian Mapping Authority, Norway. 3 University of Social and Human Sciences of Ho Chi Minh City 4 Earth Remote Sensing Data Analysis Centre, Tokyo, Japan. 5 VTGEO, Institute of Geology, Vietnam Academy of Science and Technology ABSTRACT. The Mekong Delta in the south of Vietnam is a highly dynamic landscape with rapid changes in land use. Costal forests of mangrove (Rhizophoraceae, Sonneratiaceae and Avicenniaceae) and the more inland Melaleuca forests are changed into shrimp ponds and rice fields.

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  • This paper provides almost complete review on DLTS, focusing on the main three approaches widely used today. We also summarize the development of this method in the Faculty of Physics, VNU University of Science.

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  • VNU Journal of Science, Natural Sciences and Technology 24 (2008) 280-286 In this study, primarily treating waste sludge rich of Cr, Ni, Fe,…generated from electroplating wastewater treatment plant and experimentally methods of utilizing wastes as inorganic pigment in production of bricks were carried out. Economic, technical and environmental efficiency and feasibility, bases to apply to practical conditions were evaluated. The results show that water accounts for about 70% of sludge. Contents of Ni, Cr and Fe are relatively high (20, 4.5 and 2.5%, respectively). ...

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  • The water quality of lakes in Hanoi has been declining. In that, eutrophycation is the most popular. One of the effective tools for its accessing and predicting is the use of mathematical models. This paper used the Vollenweider model, Empirical watershed model and Jorgensen model to determine the eutrophycation of West Lake by Phosphorous concentration in the lake water. The results given by the models show that the ability of Eutrophication of West Lake is very high, because the content of Phosphorous in the lake exceed allowable value of standard (0.03mg/l) many times.

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  • Digital Elevation Model (DEM) is an important component of GIS applications in many socio-economic areas. Especially, DEM has a very important role in monitoring and managing natural resources, preventing natural hazards, and supporting spatial decision making. Usually, DEM is built by interpolation from a limited set of sample points. Thus, the accuracy of the DEM is depended on the used interpolation method.

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  • The system of three-dimensional hydrodynamic-environmental models could simulate full advection and dispersion processes of the dissolved and particulate matter as suspended sediment and all oil phases in the realistic marine conditions. The hydrodynamic model provides temperature, salinity and current structure and water level. These variables will be used in the environmental model simulating the advection and diffusion processes for suspended matter concentration, bottom sediment thickness and all oil spill phases in the water and bottom sediment.

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  • Eastern Sea of Vietnam is the world's largest semi-open sea and is bounded by archipelagos, islands, mainland and connected partially with Pacific and Indian Ocean. Its total water surface area is about 2,974,600km2. Vietnamese and foreign geoscientists have researched, got samples and mapped the geological map of Eastern Sea since 1960s but no guidance or right method was carried out to map, especially in presenting geological units on geological map.

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  • In this research, remote sensing technology was used to evaluate urban development and its thermal characteristics through mapping impervious surfaces and evaluating thermal infrared images. The study is carried out in the northern part of Ho Chi Minh City, which is experienced an accelerated urban development since the end of 1980s. Landsat and Aster images were used to calculate the variation in urban impervious surfaces from 1989 to 2006. Thermal bands were processed to obtain land surface temperatures for investigating the urban heat island effect...

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  • Biological solution using strain Lipomyces starkeyi 7.1, which can produce viscous membranes to improve dry soil is considered to be sustainable for slope land improvement. The results of research on Lipomycin M ability to keep effective water in the soil of Me Linh District, Vinh Phuc Province show that in the soil samples cultivated traditional medicinal trees, the total amounts of effective water in the soil fertilized Lipomycin M (taken out under pressure pF 2.5-4.

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  • Coastal zone of Cuu Long estuary is a place through which Mekong River flows into the Eastern Sea with 8 estuaries. is the zone is formed under the influences in the interaction between river and sea. Geologically, coastal zone of Mekong delta is characterised by the predominat of clay and silt formations. These two factors makes the shoreline sensitive to exogenous processes such assedimentation and erosion.. This paper presents an application of satellite remote sensing technology to detect and analyze the spatial changes as well as quantify the shoreline change in Cuu Long estuary.

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  • World Heritage National Park Phong Nha - Ke Bang has been and is being invested by the government in general and by Quang Binh province in particular to expand into a population with different types of tourism in order to invite domestic and foreign tourists. Since the 60s of 20th century, the Phong Nha - Ke Bang zone has been regarded as a tourism spot that attracts the most number of tourists among the tourism industry of Quang Binh province. However, since then this National Park has only exploited the exterior caves and has not, together with other...

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  • VNU Journal of Science, Natural Sciences and Technology 26 (2010) 161-164 Fresh leaves of Litsea glutinosa (Lour.) C. B. Rob. from Ha Tinh were steam distilled to produce an oil in 0.15% yield. The essential oil was analysis by a combination of capillary GC and GC/MS. Seventy eight compounds were detected in the oil, of which more than 95.18% were terpenoids. The major components were (E)-β-ocimene (13.35%), β-caryophyllene (27.20%) and bicyclogermacrene (18.16%).

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  • The mountainous area occupies three fourth of the total area of Binh Dinh Province. The potential of landuse is very large. However, under the influence of irrational exploitation and natural disasters in the past, the land resource has declined, thus leading to the decline of forest resource. Furthermore, the increase of unused land and bare hills along with the decrease in the cultivated area seriously influenced on the ecological environment as well as the socio-economic development.

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  • Public transport is a part of the contemporary urban model. In Vietnam, the bus system is re-established a few years ago. At the same time, some maps have been published for helping the bus passengers. But these maps are still lacked of rich contents and useful functionalities. With the aim to improving the effectiveness of Hanoi public transport system, the authors have applied GIS technology for developing an information system of Hanoi bus. A logical model of the bus network consisting of 2 sub-networks and 5 cost attributes has been designed. This model serves as a basis for developing...

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  • Mangroves play an important role in coastal zones in many aspects e.g. extremely essential habitats for many species, coastlines protection from natural hazards, and so on. However, in Vietnam, like in other developing countries, these mangrove areas have been destroyed and encroached as a consequence of a poorly planned economic development. The study has been conducted in Phu Long - Gia Luan region, which have the largest mangrove area in the Cat Ba Archipelago Biosphere Reserve, Hai Phong City, Vietnam. The aims of the study are to investigate existing land...

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  •  Ho Chi Minh City is a one of the biggest cities of Vietnam. Before 1945, there were about  400,000 inhabitants living in the city. During the last two decades, it became the biggest industrial  and commercial center of the country. According to the statistics in 2005, its population was about  6.2 million people. In the suburban areas of the city, particularly in the northern part, agricultural  activities  produce  the  main  income  of  these  local  residents.  Within  the  last  15  years,  due  to  urbanization  and  emigration ...

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  • In Eastern Sea (South China Sea), Jurassic - Cretaceous magmatic intrusives are discovered, they were cutting the Pre-Cenozoic sedimentaries. The Cenozoic volcanic basalts are strongly distributed together with Cenozoic sedimentaries. The paper concerns only the volcanic activities with description on their geology, chemistry, geochemistry, isotopic ages and their forming mechanism. In fact, the main topic of the paper is dealt with the forming mechanism of basalt in the dynamics of the opening of Eastern Sea in particular, and of South China Sea in general.

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  • Formations of endogenous ore deposits and mineralization are widely distributed in Vietnam. Detailed studies allow for distinguishing 30 ore formations representing 9 groups of mineral raw - materials: Cr, Ti, Fe, Sn - W, Mo, Pb - Zn, Au, Sb - Hg. Three of presented formations are of magmatic affiliation, one is pegmatitic, three others belong to skarn mineralization and the remaining ones are of hydrothermal - volcanic and controversial origin. Three metallogenic epochs can be distinguished: Proterozoic, Palaeozoic and Mesozoic - Cainozoic.

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  • The aim of the study was to reconstruct sedimentary environments of the MR1 core and investigate geotechnical properties of sedimentary facies through the piezocone penetration test (CPTU). A core at the Vinhlong province, Mekong River Delta (MRD), sufficiently presented the Holocene facies of the area. Eight facies were identified based upon sedimentary properties. Characteristics of the units showed

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  • Base on the results of the flow simulated by Mekong River Commission (MRC), combined with Sea Level Rise (SLR) and salinity scenarios by IMHEN, the paper presents impacts of CC on flooding and salinity intrusion in Cuu Long Delta. By 2050, the maximal flooded area which is more than 0.5 m depth can be up to 68.3% of the entire area of Cuu Long Delta. The maximum distance of salinity intrusion increases in the main rivers can reach by 10 km by the middle of the 21st century. The area affected by salinity intrusion at 4‰ occupies 41%...

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