33 research outputs found

    Assessing the impact of urbanization on urban climate by remote satellite perspective: a case study in Danang city, Vietnam

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    Urban climate, one of the challenges of human being in 21 century, is known as the results of land use/cover transformation. Its characteristics are distinguished by different varieties of climatic conditions in comparison with those of less built-up areas. The alterations lead to “Urban Heat Island”, in which temperature in urban places is higher than surrounding environment. This happens not only in mega cities but also in less urbanized sites. The results determine the change of land use/cover and land surface temperature in Danang city by using multi-temporal Landsat and ASTER data for the period of 1990-2009. Based on the supervised classification method of maximum likelihood algorithm, satellite images in 1990, 2003, 2009 were classified into five classes: water, forest, shrub, agriculture, barren land and built-up area. For accuracy assessment, the error metric tabulations of mapped classes and reference classes were made. The Kappa statistics, derived from error matrices, were over 80% for all of land use maps. An comparison change detection algorithm was made in three intervals, 1990-2003, 2003-2009 and 1990-2009. The results showed that built-up area increased from 8.95% to 17.87% between 1990 and 2009, while agriculture, shrub and barren decreased from 12.98% to 7.53%, 15.72% to 9.89% and 3.88% to 1.77% due to urbanization that resulted from increasing of urban population and economic development, respectively. Land surface temperature (LST) maps were retrieved from thermal infrared bands of Landsat and ASTER data. The result indicated that the temperature in study area increased from 39oC to 41oC for the period of 1990-2009. Our analysis showed that built-up area had the highest LST values, whereas water bodies had the least LST. This study is expected to be useful for decision makers to make an appropriate land use planning which can mitigate the effect to urban climate

    Invited review. Natural rubber nanocomposites.

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    Natural rubber (NR) is a valuable and important polymer material that has wide and various applications. Therefore the investigations for NR improvement, particularly for special applications are in continuous development. In this trend, preparation of NR nanocomposites using nanofillers of both organic and inorganic origination is one of leading directions. In this paper, NR nanocomposites with the most popular and promising nanofillers were reviewed. These nanofillers are nanosilica and layered silicate as the most important fillers for NR industry after carbon black, and nanocellulose as a new abundant and environmental friendly filler. Methods of NR nanocomposites preparation were briefly summarized. The main attention was paid to the establishment of nanostructures in NR composites. Based on limited (about 80) references, mostly in recent 15 years, the improvement of NR nanocomposite properties was analyzed in connection with their nanostructure. Keywords. Natural rubber, nanocellulose, nanosilica, nanoclay, nanocomposite

    ỨNG DỤNG VIỄN THÁM VÀ GIS TRONG NGHIÊN CỨU BIẾN ĐỘNG TRẠNG THÁI RỪNG KHỘP TẠI VƯỜN QUỐC GIA YOK DON

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    This study was conducted in the Yok Don National Park with the GIS and remote sensing technology to assess the dipterocarp forest area fluctuation. The maps of the current status and changes of dipterocarp forest status were developed for the 2001–2010, 2010–2020, and 2001–2020 periods with the Kappa coefficient from 0,76 to 0,82, the User’s Accuracy and the Producer’s Accuracy reaching over 70%. Analysis data show that from 2001 to 2020, the area of ​​dipterocarp forest decreased from 104,239.74 ha in 2001 to 102,062.53 ha in 2010 and 95,955.23 ha in 2020. The impoverished dipterocarp forest decreased by 2,692.16 ha; the medium and rich dipterocarp forests decreased by 8,805.99 ha; the poor dipterocarp forest increased by 3,213.64 ha. The primary causes of the changes include the management and protection of the park, the recovery of forest over time, the illegal exploitation of forest products, and the impacts of living, working and production activities of people in the core and buffer zones areas.Nghiên cứu này được thực hiện tại Vườn quốc gia Yok Don để đánh giá biến động trạng thái rừng khộp bằng công nghệ GIS và viễn thám. Các bản đồ về hiện trạng, biến động trạng thái rừng khộp các giai đoạn 2001–2010, 2010–2020 và 2001–2020 với hệ số Kappa từ 0,76 đến 0,82, User’s Accuracy và Producer’s Accuracy đạt trên 70% đã được vẽ. Dữ liệu phân tích cho thấy từ 2001 đến 2020, diện tích rừng khộp giảm từ 10.4239,74 ha vào năm 2001 xuống 102.062,53 ha năm 2010 và 95.955,23 ha năm 2020. Trong đó, rừng khộp nghèo kiệt giảm 2.692,16 ha; rừng khộp trung bình và giàu giảm 8.805,99 ha; rừng khộp nghèo tăng 3213,64 ha. Những nguyên nhân chính dẫn đến biến động trạng thái rừng khộp bao gồm công tác quản lý và bảo vệ, sự phục hồi của các trạng thái rừng theo thời gian, hoạt động khai thác lâm sản trái phép và tác động từ hoạt động sinh sống, lao động và sản xuất của dân cư vùng lõi và vùng đệm

    Application of Ordinary Kriging and Regression Kriging Method for Soil Properties Mapping in Hilly Region of Central Vietnam

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    Soil property maps are essential resources for agricultural land use. However, soil properties mapping is costly and time-consuming, especially in the regions with complicated topographic conditions. This study was conducted in a hilly region of Central Vietnam with the following objectives: (i) to evaluate the best environmental variables to estimate soil organic carbon (SOC), total nitrogen (TN), and soil reaction (pH) with a regression kriging (RK) model, and (ii) to compare the accuracy of the ordinary kriging (OK) and RK methods. SOC, TN, and soil pH data were measured at 155 locations within the research area with a sampling grid of 2 km × 2 km for a soil layer from 0 to 30 cm depth. From these samples, 117 were used for interpolation, and the 38 randomly remaining samples were used for evaluating accuracy. The chosen environmental variables are land use type (LUT), topographic wetness index (TWI), and transformed soil adjusted vegetation index (TSAVI). The results indicate that the LUT variable is more effective than TWI and TSAVI for determining TN and pH when using the RK method, with a variance of 7.00% and 18.40%, respectively. In contrast, a combination of the LUT and TWI variables is the best for SOC mapping with the RK method, with a variance of 14.98%. The OK method seemed more accurate than the RK method for SOC mapping by 3.33% and for TN mapping by 10% but the RK method was found more precise than the OK method for soil pH mapping by 1.81%. Further selection of auxiliary variables and higher sampling density should be considered to improve the accuracy of the RK method

    Accessing land cover change in Bo Trach district, Quang Binh province based on highresolution satellite imagery based on objectoriented perspective

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    This paper aims to assess land cover change by high-resolution remote satellite images in Bo Trach district, Quang Binh province. The study used eCognition Developer 9.1 to classify SPOT and Sentinal-2 images of the study area. Objects on the images are characterized by values of Channels, including Red, Green, Blue, NIR, Brightness, NDVI, and RIV. Since then, maps of land cover status in the year of 2005, 2010, and 2017 were created with high accuracy 92.22%, 91.28%, 94.22%, respectively. Overlaid three land cover maps to develop the land cover change maps of two periods 2005-2010 (period 1) and 2010-2017 (period 2). The results show that there is a variation in the area of land cover types, especially agriculture and forest land. Of which, agrarian land increased by 7.7% in period 1 and 9.95% in period 2. Whereas, forest land decreased by 0.6% in period 1 and 1.5% in period 2.Bài báo này nhằm mục đích đánh giá biến động sử dụng đất bằng viễn thám độ phân giải cao tại huyện Bố Trạch, tỉnh Quảng Bình. Nghiên cứu sử dụng phần mềm eCognition Developer 9.1để phân loại ảnh ảnh SPOT và Sentinal-2 trên địa bàn nghiên cứu. Các đặc trưng của đối tượng trên ảnh được xác định dựa trên giá trị độ sáng các Kênh 1, Kênh 2, Kênh 3, Kênh 4, giá trị độ sáng trung bình (Brightness), chỉ số khác biệt thực vật (NDVI) và tỷ số thực vật (RIV). Từ đó xây dựng được các bản đồ lớp phủ mặt đất các năm 2005, 2010, 2017 với độ chính xác lần lượt là 92,22%, 91,28%, 94.22%. Chồng ghép các bản đồ lớp phủ mặt đất, xây dựng bản đồ biến động sử dụng đất giữa hai thời kỳ 2005-2010 và 2010-2017. Kết quả nghiên cứu cho thấy có sự thay đổi giữa các loại hình lớp phủ gồm: đất nông nghiệp tăng khoảng 7,7% giai đoạn 1 và 9,95% giai đoạn 2. Đất lâm nghiệp giảm khoảng 0,6% giai đoạn 1 và 1,5% giai đoạn 2

    Detailed Study on the Mechanical Properties and Activation Energy of Natural Rubber/Chloroprene Rubber Blends during Aging Processes

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    Selection of a suitable thermal aging process could render desirable mechanical properties of the rubbers or blended rubbers. In this work, the effect of the aging processes on the mechanical properties and activation energies of natural rubbers (NR) and NR/chloroprene rubbers (CR) blends with low CR contents (5–10%) was investigated. Three aging processes including heat aging (at 110°C for 22 hours), mechanical aging (under dynamic loading to 140% strain for 16000 cycles), and complex aging (heat and mechanical aging) were studied. The results revealed that the compatibility of CR in natural rubber matrix had a significant effect on the dynamic properties of the blended rubber and negligible effect on the static properties. The changes in activation energies of the blended rubber during aging processes were calculated using Arrhenius relation. The calculated changes (ΔUc, ΔUd, and ΔUT) in activation energies were consistent with the results of mechanical properties of the blended rubber. Interestingly, the change in activation energies using complex aging conditions (ΔUc) was mostly equal to the total changes in activation energies calculated separately from heat aging (ΔUT) and mechanical aging (ΔUd) conditions. This indicates that, in complex aging conditions, the heat and dynamic loading factors act independently on the properties of the blended rubber

    ỨNG DỤNG GIS ĐỂ XÂY DỰNG CƠ SỞ DỮ LIỆU ĐỊA LÝ PHỤC VỤ QUẢN LÝ ĐẤT ĐAI TẠI HUYỆN LÝ SƠN, TỈNH QUẢNG NGÃI

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    We use ArcGIS 10.3 software in building maps and updating geographic attribute data of the database belonging to the study area. The information on each land plot was updated and adjusted on the cadastral map. The high-resolution DEM SRTM (Shuttle Radar Topography Mission) data show that the topographic elevation of Ly Son district is 0–90 m with a slope below 5 degrees. The highest point is in the Thoi Loi mountain area. In addition, the research results enable us to build a detailed map for 107 accommodation establishments, including hotels, motels, homestays, 15 restaurants, and 16 attractions on the island.Chúng tôi sử dụng phần mềm ArcGIS 10.3 để xây dựng dữ liệu bản đồ và cập nhật dữ liệu thuộc tính của cơ sở dữ liệu địa lý thuộc khu vực nghiên cứu. Thông tin đến từng thửa đất trên nền bản đồ địa chính đã được cập nhật, chỉnh lý. Dữ liệu DEM SRTM (Shuttle Radar Topography Mission) với độ phân giải cao cho thấy độ cao địa hình huyện Lý Sơn là 0–90 m so với mực nước biển và độ dốc dưới 5°; trong đó, điểm cao nhất nằm ở khu vực núi Thới Lới. Ngoài ra, kết quả nghiên cứu còn cho phép xây dựng dữ liệu bản đồ chi tiết cho khoảng 107 cơ sở lưu trú gồm khách sạn, nhà nghỉ và homestay, 15 nhà hàng và 16 điểm tham quan trên đảo
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