Assessing forest cover changes in Dak Lak province (Central Highlands of Vietnam) from multi-temporal Landsat data and machine learning techniques

Dak Lak is a province in the Central Highlands region of Vietnam, with a large area of forests and forestry land. However, the forest cover has changed dramatically in recent times due to the influence of human activities and climate change. This article presents the results of assessing forest cover changes in Dak Lak province from Landsat satellite image data for the period 2000 – 2020. Three Landsat satellite image scenes, including Landsat 5 TM images taken in March 2000 and February 2010 and Landsat 8 OLI image taken in February 2020 are used to classify forest cover. Three common machine learning techniques, including Random Forest (RF), Support Vector Machine (SVM), Classification and Regression Tree (CART) and the traditional maximum likelihood classification algorithm are used to classify forest cover in the study area, thereby choosing the method with the highest accuracy. The results show that the RF algorithm has the highest accuracy in classifying forest cover from multi-temporal Landsat images by comparing the overall accuracy value and the Kappa coefficient. The obtained results are used to build forest cover change maps in the period 2000 - 2010, 2010 - 2020 and 2000 - 2020. The results received in the study provide information to help managers in monitoring and protecting forest resources

Evaluation of Asaoka and Hyperbolic Methods for Settlement Prediction of Vacuum Preloading Combined with Prefabricated Vertical Drains in Soft Ground Treatment

This study evaluated the use of the Asaoka and hyperbolic methods to estimate the ultimate settlement of soft ground treated by vacuum preloading combined with prefabricated vertical drains. For this aim, a large-scale physical laboratory model was constructed. The model was a reinforced-tempered glass box containing a soil mass with dimensions of 2.0 × 1.0 × 1.2 m (length × width × depth). Physical models of this scale for the same purpose are rare in the literature. The soil was taken from a typical coastal region in Dinh Vu Hai Phong, Vietnam. The surface settlement near and between the two drains was measured right after the vacuum preloading started. Important properties of the soil were tested to evaluate the effectiveness of the treatment method. The measured settlement was used in the Asaoka and hyperbolic methods to predict the potential ultimate settlement. The results showed the superiority of the vacuum consolidation approach in improving fundamental engineering properties of soft soil. Furthermore, the ultimate settlement predicted by both methods showed a good agreement with the measured value, proving that the Asaoka and hyperbolic methods are suitable for the estimation of the ultimate settlement of soft soil treated with vacuum consolidation

Status of the shore area from Tiengiang to Camau: causes of accumulation and erosion

The paper presents some results of the research programs which had been performed during 1996-1999 (“Studying of river-sea interaction in the mouth of Tien river” and KHCN.06.08). Based on these results the morphological schemes of the shore areas from Tiengiang to Camau were compiled; causes and mechanics of accumulation and erosion were also determined. These results may be used as scientific basis for forecasting the development of the shoreline, it will contribute to the management, protection and reasonable exploitation the shore areas

Determination of the relationship between Vietnam national coordinate reference system (VN-2000) and ITRS, WGS84 and PZ-90

In July 2000, Hanoi-72 reference system was replaced by the Vietnam reference system, namely as VN-2000 as an official geodetic background system in Vietnam. Ministry of Natural Resources and Environment of Vietnam has reported the transformation parameters between VN-2000 and WGS84. Nevertheless, there is a need to estimate a new transformation parameter set between VN-2000 and WGS84 because WGS84 has been updated. In addition, there is now a lack of an accurate published set of parameters for transformation from VN-2000 to not only the International Terrestrial Reference System ITRS but also PZ-90. In this study, coordinate transformation parameters between ITRS and VN-2000 are estimated through the use of a least square approach and the common points with known coordinates in both systems. These set of parameters was then deployed to determine the link between VN-2000 and WGS84 as well as PZ-90. The results denoted that the derived transformation parameters, on the basis of the results at the checkpoints, could generated station positions with the accuracy at several cm level for transformation from VN-2000 to the new realizations of ITRS, WGS84 and PZ90 and reversely. These achievements reveals that the set of parameters is great significance for many applications related to positioning in Vietnam

SOME RESULTS OF STUDY ON PRESENT SITUATION OF HOUSEHOLD SOLID WASTE IN HANOI, VIETNAM

This paper presents some results on the study of Solid waste generated by households (hereinafter referred to as HSW) in Hanoi city. Compositions of the waste generated from three typical communities and their relationship with family life-style of each community were investigated. Differences among compositions of HSW of three resident groups of different incomes, lifestyles were analyzed. Based on the study results, some measures for better management of HSW and maximum reuse and recycle of HSW were proposed. By this way, the amount of HSW transported to landfill could be reduced and stabilization phase of landfill sites could be shortened

Study on the effect of carbon black, carbon nanotube on the properties of rubber blend acrylonitrile butadiene rubber (NBR)/polyvinyl chloride (PVC)

The effects of carbon nanotube (CNT) in combination with carbon black (CB) on the properties of acrylonitrile butadiene rubber (NBR)/polyvinyl chloride (PVC) (70/30) were investigated. The results reveal that the maximal tensile strength of the rubber blend was obtained by the fillers ratio of CB:CNT = 39:1. At this filler ratio, the thermal stability and heat conductivity of the rubber blend were also significantly improved. The analysis of FE-SEM images and DMA diagram indicate that the dispersion of filler as well as the interaction between fillers and rubber matrix was improved by the incorporation of CNT. Keywords. NBR/PVC blends, carbon nanotube (CNT), carbon black (CB), nanocomposites

Groundwater simulation in Dak Lak province based on MODFLOW model and climate change scenarios

Purpose – Groundwater plays a critical part in both natural and human existence. When surface water is scarce in arid climates, groundwater becomes an immensely valuable resource. Dak Lak is an area that frequently lacks water resources for everyday living and production, and the scarcity of water resources is exacerbated during the dry season. As a result, it is critical to do study and understand about groundwater to meet the region's water demand. This study aims to extend the use of the MODFLOW model for groundwater simulation and assess the overall groundwater reserves and water demand in the highland province Dak Lak. Design/methodology/approach – The MODFLOW model is used in this work to compute and analyze the flow, prospective reserves of groundwater from which to plan extraction and estimate groundwater variation in the future. Findings – The application of the MODFLOW model to Dak Lak province demonstrates that, despite limited data, particularly drilling hole data for subterranean water research, the model's calculation results have demonstrated its reliability and great potential for use in other similar places. The use of the model in conjunction with other data extraction modules is a useful input for creating underground flow module maps for various time periods. The large impact of recharge and evaporation on groundwater supplies and water balance in the research area is demonstrated by simulations of climate change scenarios RCP4.5 and RCP8.5. Originality/value – None of the studies has been done previously to analyze water resources of Dak Lak and the scarcity of water resources is exacerbated during the dry season. Therefore, this study will provide useful insights in the water resource management and the conservation of Dak Lak. The groundwater in Dak Lak can meet the area's water demand, according to the results obtained and water balance in the study area. However, the management of water resources and rigorous monitoring of groundwater extraction activities in the area should receive more attention

CSA: Thực hành nông nghiệp thông minh với khí hậu ở Việt Nam

During the last five years, Vietnam has been one of the countries most affected by climate change. Severe typhoons, flooding, cold spells, salinity intrusion, and drought have affected agriculture production across the country, from upland to lowland regions. Fortunately for Vietnam, continuous work in developing climate-smart agriculture has been occurring in research organizations and among innovative farmers and entrepreneurs. Application of various CSA practices and technologies to adapt to the impact of climate change in agriculture production have been expanding. However, there is a need to accelerate the scaling process of these practices and technologies in order to ensure growth of agriculture production and food security, increase income of farmers, make farming climate resilient, and contribute to global climate change mitigation. This book aims to provide basic information to researchers, managers, and technicians and extentionists at different levels on what CSA practices and technologies can be up scaled in different locations in Vietnam

Spatiotemporal evolution of SARS-CoV-2 Alpha and Delta variants during large nationwide outbreak of COVID-19, Vietnam, 2021

We analyzed 1,303 SARS-CoV-2 whole-genome sequences from Vietnam, and found the Alpha and Delta variants were responsible for a large nationwide outbreak of COVID-19 in 2021. The Delta variant was confined to the AY.57 lineage and caused >1.7 million infections and >32,000 deaths. Viral transmission was strongly affected by nonpharmaceutical interventions

Partial food systems baseline assessment at the Vietnam benchmark sites

Using data collected from a cross-sectional study in Moc Chau, Dong Anh and Cau Giay districts in Vietnam, this report aims to elucidate specific components of local Vietnamese food systems along a rural to urban transect focusing specifically on (i) diets, (ii) nutrition status (anthropometry), (iii) consumer behavior, (iv) food environment, and (v) food flows