Vietnam Academy of Science and Technology: Journals Online
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Adsorption of arsenic and heavy metals from solutions by modified iron ore sludge
No full textWater pollution with arsenic (As) and heavy metals has been a major considering issue because of their negative impact on ecosystems and human health. This study was conducted to evaluate the adsorption behavior of As and heavy metals by iron ore sludge modified by the addition of 10% sodium silicate solution and heating at 400°C (SBC2-400-10S) in both batches and fixed–bed column experiments. The kinetics showed that the removal of As and heavy metals by the adsorbent is a pseudo-second-order reaction. The adsorption data fitted well with Langmuir isotherm and provided Langmuir monolayer capacity (mg/g) of As and heavy metals in the following order: Pb (2.379) Cd (2.008) Zn (1.915) Mn (1.692) As (0.452). The column adsorption data were fairly well described by Thomas model, with the order of Thomas adsorption capacity following a similar trend as in the batch study. The results of this study indicated that SBC2-400-10S was a potential adsorbent for removal of As and heavy metals from solutions
Constraints on the Model from the Process
No full textWe study the process in the model. The production cross-section times branching ratio is determined. We use the LHC data to derive constraint on the new physical scale, , and the elements of right-handed quarks mixing matrix
Tunable Cloaking of Mexican-hat Confined States in Bilayer Silicene
Get PDFWe present the ballistic quantum transport of a p-n-p bilayer silicene junction in the presence of spin-orbit coupling and electric field using a four-band model in combination with the transfer-matrix approach. A Mexican-hat shape of low-energy spectrum is observed similarly to bilayer graphene under an interalayer bias. We show that while bilayer silicene shares some physics with bilayer graphene, it has many intriguing phenomena that have not been reported for the latter. First, the confined state producing a significantly non-zero transmission in Mexican hat. Second, the cloaking of the Mexican-hat confined state is found. Third, we observe that the Mexican-hat cloaking results in a strong oscillation of conductance when the incident energy is below the potential height. Finally, unlike monolayer silicene, the conductance at large interlayer distances increases with the rise of electric field when the incident energy is above the potential height.
Facile synthesis and electrical characteristics of n-SnO2/p-NiO nanowire heterojunctions
Get PDFIn the current work, we report a facile synthesis of n-SnO2/p-NiO nanowire heterojunctions by a drop-coating approach. The pure SnO2 and NiO nanowires (NWs) were grown by chemical vapor deposition (CVD) and hydrothermal methods, respectively. Morphology, composition and crystal structures of the NWs and heterojunctions were investigated by means of field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD), respectively. The data showed that SnO2 NWs were grown with their average diameter of 200 nm and length of about 10 mm. The NiO NWs were also synthesized with a shorter average length and smaller average diameter compared to those of the SnO2 NWs. The EDS results indicated no impurity present in both SnO2 and NiO NWs. The XRD patterns pointed out the tetragonal rutile and cubic structures of SnO2 and NiO, respectively. Interestingly, electrical properties of the NWs and heterojunctions were studied through the Keithley 2602A sourcemeter-based I-V characterizations. The results confirm the nature of the metal semiconducting oxides. The formation of the n-SnO2/p-NiO heterojunctions was certified through the rectifying behavior of the I-V curves with the rectification ratio of about 5 at ± 3V and 350 oC. The potential energy barrier between the NWs was also estimated to be about 1.16 eV. The band energy structure was also proposed to get insight into characteristics of the n-SnO2/p-NiO heterojunction
CHẤT LƯỢNG NƯỚC KHU VỰC BIỂN VEN BỜ TỈNH NINH BÌNH
No full textThis paper presents the results of investigation on water quality in Ninh Binh coastal area in 2015. The results show that the risk quotient of water quality of the area was 0.34, indicating the water was safe for aquatic life. However, for individual water quality parameter, the coastal water of Ninh Binh was contaminated by TSS, ammonium and arsenic; water faced the risk of deficiency of dissolved oxygen. The remaining water quality parameters (nitrite, phosphate, cyanide, oil and grease, coliform, Cu, Pb, Zn, Cd, Hg and organochlorinated pesticides) are safe for aquatic life. As spatial distribution, the concentration of pollutants in water is lower at depth 15 m. In the rainy season, the water quality tends to decrease compared to the dry season.Vùng biển Ninh Bình có chiều dài 15 km với hàng nghìn hecta bãi bồi cửa sông. Số liệu về chất lượng nước vùng nước ven bờ của Ninh Bình hầu như chưa được công bố. Bài báo này trình bày kết quả điều tra, khảo sát về chất lượng nước vùng ven biển Ninh Bình năm 2015. Kết quả cho thấy hệ số tai biến chất lượng nước toàn vùng có giá trị là 0,37 nên nước an toàn đối với các sinh vật thủy sinh. Tuy nhiên, tính từng thông số thì nước đã bị ô nhiễm bởi 3 thông số là TSS, amoni và asen; nước có nguy cơ ô nhiễm bởi chlorrophyll a (gây phú dưỡng) và có nguy cơ thiếu hụt oxy hòa tan. Các thông số còn lại an toàn với sinh vật thủy sinh
Simulation of spatial variation of plankton communities in the South Central Vietnam sea by ROMS model
Get PDFThis study preliminarily applies the Regional Ocean Modeling System (ROMS) in the two major monsoon seasons (Northeast and Southwest monsoons) for the South Central Vietnam sea (9–14.5oN, 105–112oE), in which the hydrodynamic and ecological modules are coupled. The results show that the plankton only develop in 200 m water on the top, concentrated mainly in the 0–70 m layer and in maximum biomass of 15–40 m layer. In the Northeast monsoon season, the plankton are concentrated mainly in the northern part and open seas of the area, while in the Southwest monsoon season, they are concentrated in the upwelling and adjacent southern areas. These results correctly reflect the basic law of the development of plankton communities in the sea area.This study preliminarily applies the Regional Ocean Modeling System (ROMS) in the two major monsoon seasons (Northeast and Southwest monsoons) for the South Central Vietnam sea (9–14.5oN, 105–112oE), in which the hydrodynamic and ecological modules are coupled. The results show that the plankton only develop in 200 m water on the top, concentrated mainly in the 0–70 m layer and in maximum biomass of 15–40 m layer. In the Northeast monsoon season, the plankton are concentrated mainly in the northern part and open seas of the area, while in the Southwest monsoon season, they are concentrated in the upwelling and adjacent southern areas. These results correctly reflect the basic law of the development of plankton communities in the sea area
SIR-DL: AN ARCHITECTURE OF SEMANTIC-BASED IMAGE RETRIEVAL USING DEEP LEARNING TECHNIQUE AND RDF TRIPLE LANGUAGE
Get PDFThe problem of finding and identifying semantics of images is applied in multimedia applications of many different fields such as Hospital Information System, Geographic Information System, Digital Library System, etc. In this paper, we propose the semantic-based image retrieval (SBIR) system based on the deep learning technique; this system is called as SIR-DL that generates visual semantics based on classifying image contents. At the same time we identify the semantics of similar images on Ontology, which describes semantics of visual features of images. Firstly, the color and spatial features of segmented images are we extracted and these visual feature vectors are trained on the deep neural network to obtain visual words vectors. The process of image retrieval is executed rely on semantic classification of SIR-DL according to the visual feature vector of the query image from which it produces a visual word vector. Then, we retrieve it on Ontology to provide the identities and the semantics of similar images corresponds to a similarity measure. In order to carry out SIR-DL, the algorithms and diagram of this image retrieval system are proposed after that we implement them on ImageCLEF@IAPR, which has 20,000 images. On the base of the experimental results, the effectiveness of our method is evaluated by the accuracy, precision, recall, and F-measure; these results are compared with some of works recently published on the same image dataset. It shows that SIR-DL effectively solves the problem of semantic-based image retrieval and can be used to build multimedia systems in many different fields
CORROSION PROTECTION OF CARBON STEEL USING ZIRCONIUM OXIDE/SILANE PRETREATMENT AND POWDER COATING
Get PDFSurface pretreatment plays important role in improvement of corrosion resistance and adhesion of organic coatings. A new generation of metal pretreatments based on nanosize zirconium oxide or ogranosilane film has been investigated recently as an alternative method to phosphatation. In this paper, ZrO2/silane composite film on carbon steel was prepared and characterised by field emission scanning electron microscopy, energy dispersive X-ray spectrum and electrochemical measurements. The effect of ZrO2/silane surface treatment on the protection properties of powder coating was studied by salt spray test and adhesion measurement. The results obtained showed that ZrO2 was rapidly precipitated on the steel surface after first 1 minute immersion and ZrO2/silane film formed after 4 minutes immersion give best protective properties. Powder coating on carbon steel with ZrO2/silane pretreatement has equivalent protection performance like powder coating with phosphate pretreatment
FLAVONOIDS ISOLATED FROM THE FLOWERS OF CAMELLIA CHRYSANTHA
Get PDFCamellia chrysantha (the golden camellia, golden tea) is a species of evergreen shrub or small tree belonging to the family Theaceae. The flowers and the leaves of this plant are used as tea and drank for its health benefits. The aim of this study was to investigate the chemical constituents of the flowers of Camellia chrysantha. Five flavonoids were isolated from the flowers of Camellia chrysantha (Theaceae), including (+)-catechin (1), (-)-epicatechin (2), quercetin (3), quercetin-3-O-methyl ether (4) and kaempferol (5). Their chemical structures were elucidated by spectroscopic data analysis and by comparison with those reported in the literature. Among five compounds, compounds 4 was isolated for the first time from this species
THE SHELF-LIFE OF BLACK TIGER SHRIMP (PENAEUS MONODON) TREATED WITH THE DIFFERENT CONDITIONS
Get PDFThis study examines the chemical and microbiological changes and the sensory attributes of black tiger shrimp (Penaeus monodon) when stored at the temperature of 0 ºC. Sodium propionate and sodium lactate were used to treat shrimps before storage. Vacuum packaging was also carefully investigated. Throughout storage, the quality indicates including TVB-N, TMA-N, histamine, quality index (QI) and total viable count (TVC) were used to evaluate the quality changes of shrimp. The results show that though with different rates, the increase in quality indicators caused the decrease in the quality of shrimp during storage. The quality of shrimps treated with salts of organic acids or those packed in the vacuum bags was significantly higher than that of the control. In particular, the shelf-life of the sample packed in the vacuum packages was twelve days, which was four days longer than that of the control