Vietnam Academy of Science and Technology: Journals Online
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Research on fabrication of non-calcined geopolymer ceramics from kaolin Tung Ba, Vi Xuyen, Ha Giang
No full textThe mineral component of kaolin clay in Tung Ba commune analyzed by X-ray diffraction is composed mainly of kaolinite (24–27%), illite (26–30%) and quartz (40–44%). Chemical composition (wt%) of Tung Ba kaolin determined by X-ray fluorescence (XRF) shows SiO2 at 59.92–64.98, Al2O3: 18.95–20.82, Fe2O3: 2.28–3.95, SO3: 2.47–4.66, CaO: 0.12–0.36, MgO: 1.72–2.13 and TiO2 at 0.75–1,08. To fabricate geopolymer ceramic, kaolin clay was transformed into metakaolin with the optimal parameters of calcination: the temperature at 750°C and heating time of 120 min. Obtained metakaolin is mixed with mixtures of NaOH/Na2SiO3 (40%wt) with ratios of 0.2, 0.25, 0.33, 0.5 and NaOH molarities are 10M, 12M, 14M. Testing geopolymer ceramics after 28 days had a compressive strength of 40–196 KG/cm2, water absorption of 15.25–17.98% and density of 1.54–1.69 g/cm3, totally satisfied the Vietnamese standard for construction bricks and ceramics
Exact receptance function and receptance curvature of a clamped-clamped continuous cracked beam
No full textThe receptance function has been studied and applied widely since it interrelates the harmonic excitation and the response of a structure in the frequency domain. This paper presents the derivation of the exact receptance function of continuous cracked beams and its application for crack detection. The receptance curvature is defined as the second derivative of the receptance. The influence of the crack on the receptance and receptance curvature is investigated. It is concluded that when there are cracks the receptance curvature has sharp changes at the crack positions. This can be applied for the crack detection purpose. In this paper, the numerical simulations are provided
Effects of nano mineral-supplemented diet on sow productivity
Get PDFThis study aimed to evaluate the effects of nano mineral-supplemented diet on sow productivity. The data were estimated by several parameters consisting of piglet live ratio at newborn stage and weaning stage, piglet weight at newborn stage and weaning stage, metal content in piglet livers. The results showed that live ratio of newborn piglets in group III was highest (93.44 ± 2.83%) comparing with other groups. However, there was no significant difference of live ratio in piglets at weaning stage between nano mineral-supplemented groups with control. The birth weight of piglets in nano mineral-supplemented groups was similar to control group. The birth weight of piglets in nano mineral-supplemented groups was ranged from 1,361.61 ± 47.37 grams (group II) to 1,410.48 ± 44.28 grams (group I). However, the average weight of weaned pigs in groups III and IV was higher than other groups (6,772.92 ± 105.47 grams and 6,818.87 ± 89.59 grams). Moreover, the amount of Fe, Cu, Zn, Mn in piglet liver from nano mineral-supplemented groups have been found to be lower than those in control group. These results revealed that the supplement of nano minerals for sows promoted the reproductive performance of sows and reduced mineral content in the liver of piglets.
Evaluating the shoreline and bottom terrain variations in the naval port of zone 5, Phu Quoc, Kien Giang by using multi - temporal remote sensing images
Get PDFIn this study, the authors aim to study two major contents: (1) Evaluating the shoreline variation in the naval port of zone 5 (in the years of 1999, 2006, 2009 and 2016); (2) Evaluating the bottom terrain variation in the naval port of zone 5 (in the years of 2007 and 2010). Three main research methodologies were applied: (i) Band rationing method for the shoreline extraction; (ii) Shoreline change analysis method using GPS data; (iii) Digital elevation model integrated with bottom terrain analysis method. The most obvious change in shoreline is in the An Thoi port from Mui Den to Mui Ong Doi. In the shoreline from Mui Den to Mui Con Duong, a backward shoreline evolution (erosion) mainly occurred with an average width of about 40–50 m, while some other places had a forward shoreline evolution (accumulation), especially in Mui Con Duong with a width of 60 m. These sediment materials are sent to conductor and accumulation, making the bottom terrain raised. As on the sections AA’, BB’, CC’, DD’, we could see that the bottom terrain at the channel of naval port of zone 5 has the depth variation only from 2 m to 4 m. The accumulation rate is up to 1 m/year in this period
Research on marine environment and coral distribution on Nam Yet island using VNRedsat-1 and QuickBird images
Get PDFBased on the processing of VNRedsat-1 and QuickBird images in the area of Truong Sa archipelago, the research results showed the efficiency of assessing marine environmental characteristics in surroundings of these islands. In this paper, we presented the research results on Nam Yet island and adjacent area. The marine parameters in this research include sea surface temperature (SST) and chlorophyll-a concentration in the surface layer as well as in the deep layers of 20m and 40m, the distributions of the ground objects such as coral shelf, sand accumulation, coral reef combined with seagrass and seaweed. The accuracy of assessment of supervised and unsupervised classified results is approximate of 87.8%. The research results allowed assessing the environmental characteristics, warning of the risk of erosion and coastal line change in the study area
Research on deep geological structure and forecasting of some areas with petroleum prospects in the Red river delta coastal strip according to geophysical data
Get PDFThe coastal areas of the Red River Delta are the transition areas from the continent to the sea and have great mineral prospects, especially petroleum prospects. In this area, a lot of topics and projects in geology and geophysics have been conducted for many different purposes such as studying the deep structure, tectonic - geological features, seismic reflection - refraction to identify petroleum traps in the Cenozoic sediments... However there are very few studies on deep structure features, using the results of processing and meta-analysis of gravity, magnetotelluric, tectonic - geological data to detect the direct and indirect relations to the formation of structures with petroleum potential. The authors have researched, tested and applied an appropriate methodology of processing and analysis, to overcome the shortfall of gravity data as well as the nonhomogeneity in details of seismic and geophysical surveys. The obtained results are semi-quantitative and qualitative characteristics of structure of deep boundary surfaces, structural characteristics of fault systems and their distribution in the study area, calculation of the average rock density of pre-Cenozoic basement... From these results, the authors established the zoning map of the areas with petroleum potential in the Red river delta coastal strip according to geophysical data
The influence of foundation mass on dynamic response of track-vehicle interaction
Get PDFThe influence of foundation mass on the dynamic response of track-vehicle interaction is studied in this paper. The moving vehicle is modeled as a two-axle mass-spring-damper four-degrees-of-freedom system. A new dynamic foundation model, called "Dynamic foundation model" including linear elastic spring, shear layer, viscous damping and foundation mass parameter, is used to analyze the dynamic response of the track-vehicle interaction. The railway track on the new dynamic foundation model subjected to a moving vehicle is regarded as an integrated system. By means of the finite element method and dynamic balance principle, the governing equation of motion for railway track-vehicle-foundation interaction is derived and solved by the step-by-step integration method. The accuracy of the algorithm is verified by comparing the numerical results with the other numerical results in the literature. The influence of foundation mass parameter on the dynamic response of railway track-vehicle interaction is investigated. The numerical results show that with the new dynamic foundation model the foundation mass effects more significantly on the dynamic response of track-vehicle interaction. The study shows that the new dynamic foundation model describes the true behavior of soil in the analysis of dynamic response of structures on the foundation
Simulation for Optimizing the Design of Cryogenic Stopping Cell for the IGISOL Facility at ELI-NP
Get PDFThe production of the exotic neutron-rich ion beams from photofission of the actinide targets in an IGISOL facility will be studied via an experimental program that will take place at the Extreme Light Infrastructure - Nuclear Physics (ELI-NP) facility. Geant4 simulation toolkit was used for optimizing the target configuration in order to maximize the rate of released photofission fragments from targets placed in a cell filled with He gas
On the classification of the genera Labyrinthula, Schizochytrium and Thraustochytrium (Labyrinthulids and Thraustochytrids)
Get PDFSpecies of the genera Labyrinthula, Schizochytrium, Thraustochytrium and related organisms have recently attracted attention in biotechnology, and here is a short note on how to classify these rather special organisms
INVESTIGATION OF COUPLED EFFECTS OF TEMPERATURE AND RELATIVE HUMIDITY ON DYNAMIC PERFORMANCE OF MEMS CANTILEVER RESONATORS IN GAS RAREFACTION
No full textThe modified molecular gas lubrication (MMGL) equation with the effective viscosity of moist air is utilized to solve for the squeeze film damping (SFD) problem on the dynamic performance of MEMS cantilever resonators. Thus, the coupled effects of temperature and relative humidity are discussed on the Q-factors of MEMS cantilever resonators in a wide range of gas rarefaction (pressure, p and accommodation coefficients, ACs) and resonant mode of vibration. The results showed that the Q-factor of moist air decreases more significantly as temperature and relative humidity increase at higher gas rarefaction (lower p, and ACs) conditions.