Vietnam Academy of Science and Technology: Journals Online
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PLASMONIC PHOTOTHERMAL HEATING OF GOLD NANOSHELL SOLUTIONS
No full textWe present a theoretical approach to theoretically investigate how gold core-shellnanoparticles dispersed in water thermally respond to near-infrared-regime laser illumination. First, the absorption cross section of gold nanostructures is calculated using Mie theory. Second, we determine the absorbed power density when the solution is exposed by the laser light. Here, the solution of nanostructures is assumed to be uniform and homogenous. Third, we analytically solve the transient bioheat equation to calculate time-dependent temperature increase. Our theoretical calculations quantitatively agree with previous experiments without any adjustable parameter.This approach would provide a reliable tool to understand photothermal effects in unexplored structures
LARGE DEFLECTION OF CANTILEVER FUNCTIONALLY GRADED SANDWICH BEAM UNDER END FORCES BASED ON A TOTAL LAGRANGE FORMULATION
Get PDFA two-node beam element for large deflection analysis of cantilever functionally graded sandwich (FGSW) beams subjected to end forces is formulated in the context of total Lagrange formulation. The beams consist of three layers, a homogeneous core and two functionally graded layers with material properties varying in the thickness direction by a power gradation law. Linear functions are adopted to interpolate the displacement field and reduced integral technique is applied to evaluate the element formulation. Newton-Raphson based iterative algorithm is employed in combination with arc-length control method to compute equilibrium paths of the beams. Numerical investigations are given for the beam under a transverse point load and a moment to show the accuracy of the element and to illustrate the effects of material inhomogeneity and the layer thickness ratio on the large deflection behavior of the FGSW beams
Some Characteristics And Allopurinol Release Of Carrageenan/ Allopurinol Films Using Polyethylene Oxide As A Dispersion Aid Agent
Get PDFThis paper presents the effect of carrageenan (CG) on some characteristics and drug release of allopurinol in the presence of polyethylene oxide (PEO) as a dispersion aid agent. The samples were prepared in film shape by solution method, in which, the content of PEO was changed from 1 wt.% to 5 wt.% and the content of allopurinol was fixed at 10 wt.% in comparison with carrageenan weight. FTIR , FESEM, UV-Vis methods were used to evaluate characterizations and morphology of CG/PEO/allopurinol films
Assessment of impacts of utilization on water resources in the basin of trans-boundary Red river system
Get PDFThe Red river system is the large trans-boundary river system, there has been no united system of hydrology stations as well as integrated plan for the water use and management in the whole basin. The trend of water resources change in the Red river system basin has been assessed on the basic of statistic analyses of data observed during the studies, especially in the time when the exploitation of water resources has been intensified for the multisectoral development. This paper shows some of the results from considerations of the water use in the highlands that is influential in water resources in the Red river system basin and the planned reservoirs which are built in the basin of Red river system. The results include the assessment of the state and trend of water resources in the Red river system basin, the trend of water level lowering in the lowlands and its impacts
Landslide susceptibility mapping using Forest by Penalizing Attributes (FPA) algorithm based machine learning approach
No full textLandslide susceptibility mapping is a helpful tool for assessment and management of landslides of an area. In this study, we have applied first time Forest by Penalizing Attributes (FPA) algorithm-based Machine Learning (ML) approach for mapping of landslide susceptibility at Muong Lay district (Vietnam). For this aim, 217 historical landslides locations were identified and analyzed for the development of FPA model and generation of susceptibility map. Nine landslide topographical and geo-environmental conditioning factors (curvature, geology/lithology, aspect, distance from faults, rivers and roads, weathering crust, slope, and deep division) were utilized to construct the training and validating datasets for landslide modeling. Different quantitative statistical indices including Area Under the Receiver Operating Characteristic (ROC) curve (AUC) were used to evaluate the performance of the model. The results indicate that the predictive capability of the FPA is very good for landslide susceptibility mapping on both training (AUC = 0.935) and validating (AUC = 0.882) datasets. Thus, the novel FPA based ML model can be utilized for the development of accurate landslide susceptibility map of the study area and this approach can also be applied in other landslide prone areas
Feature Properties of Photonic Crystal Fiber with Hollow Core Filled Nitrobenzene
No full textIn this paper, a photonic crystal fiber (PCF) with core infiltrated with Nitrobenzene is proposed and investigated. Its feature properties as the effective refractive index, effective mode area, chromatic dispersion, and confinement loss have been numerically simulated. The obtained results show that characteristic quantities of PCF with core infiltrated with Nitrobenzene (PCF-N) having some advantages in comparison to PCF with core infiltrated with Toluene (PCF-T) at 1.55μm wavelength. For the purpose of supercontinuum generation, two optimal structures with lattice constants 2.0μm and 2.5μm with filling factors d/Ʌ = 0.3 are identified
Efficient Generation of Coherent Stokes Field in Hydrogen Gas-Filled Hollow Core Photonic Crystal Fibres
Get PDFIn this paper, we study of the coherent Stokes generation in a transient Raman regime by Hydrogen gas-filled hollow-core photonic crystal fibres (HC-PCFs) configuration. The temporal and spatial evolution of the pump and Stokes field envelopes as well as the coherence and population inversion is numerically observed. The influence of the pump pulse width and gas pressure on the energy exchange along fiber and Stokes generation efficiency is investigated
Effect of Sm and Mn Co-doping on the Crystal Structure and Magnetic Properties of Polycrystalline Ceramics
No full textThe crystal structure, phonon vibration, microstructure, and magnetic properties have been investigated in multiferroics Bi0.9Sm0.1Fe1-xMnxO3 for . The structural analysis by XRD and Rietveld refinement suggest that Mn doping compounds crystallize in the polar R3c rhombohedral symmetry (isostructural with BiFeO3). Raman analysis confirms no structural transformation but the change of line widths and peak intensities reveal the lattice distortion in Mn-substitution samples. The study of microstructure shows no obvious change of grain size and shape. The magnetic properties of the as-prepared samples show the linear magnetic field dependence of magnetization, suggesting the antiferromagnetic feature of polycrystalline ceramics. The field dependence of magnetization measured after two-years synthesis and after applying an electric field reveal a decrease of maximum magnetization but the hysteresis loops retain the antiferromagnetic behavior. The implication of these results is that the magnetic properties of single structural phase compound, including coercivity and remanent magnetization, do not show the aging behavior as observed in the morphotropic phase boundary systems
Fish distribution in the Ba Che and Tien Yen rivers
Get PDFThe ichthyo-fauna in the Ba Che and Tien Yen rivers, northern Vietnam is highly diverse, with a total of 245 species determined. However, data on the distribution of fish species are not sufficiently provided for the whole area. This study was conducted from 2008 to 2011 at 27 stations from the Ba Che and Tien Yen river basins to determine the distribution of fish species according to different sections of the rivers, water bodies, seasons, and salinity levels. The results show that fish species are distributed mainly in the river (with 210 species), concentrated in the downstream area (with 213 species). Fishes are mainly collected in the dry season when the salinity level of river is high, due to seawater intrusion which also brings in 160 species of marine fish. This shows that fish distribution in the research areas is mainly dominated by the presence of marine species. While for freshwater fish, it is clearly affected by the mountainous features. Apart from the common characteristics sharing between the two river basins, but the number of both freshwater and marine fish species in the Tien Yen river are larger than those of Ba Che river, which is related to fresh water surface, river morphology, the width and location of the estuary to the sea. The downstream area is home to the fish species recorded in the Red Data Book of Vietnam and the complementary species for Vietnam, while the middle and upstream of the rivers may offer a high potential of biodiversity, with many possibly new species for science. These are important data for the conservation and sustainable development of fish resources in the Ba Che and Tien Yen river basins.
Polymorphism at variable regions (VRs) of porA gene from Neisseria meningitidis strains isolated in Northern Vietnam
No full textMeningococcal bacterium Neisseria meningitidis is one of the major causes of meningitis worldwide. Currently in Vietnam, N. meningitidis B and C are the most prevalent invasive serogroups. N. meningitidis expresses two major transmembrane proteins, PorA and PorB, of which PorA showed high levels of polymorphism among strains and has been studied as one component of vaccines against N. meningitidis B. Polymorphisms in porA gene clustered into three variable regions VR1, VR2 and VR3. In this study, we sequenced the entired porA gene of 19 N. meningitidis strains isolated from military units in northern Vietnam during the period 2008 – 2017 in order to: (1) evaluate the polymorphism of porA gene at nucleotide level and predict its immuno-reactivity from annotated amino acide sequences; and (2) compare porA variants of Vietnamese strains with known strains worldwide. Our results showed a high level of polymorphisms among Vietnamese strains, with the highest polymorphism found in VR1, followed by VR2 and VR3. Notably, 5/19 strains in this study showed novel variants at VR2 with unknown immunological reactivity. This result suggested potential novel immunological characteristics of meningococcal strains from Vietnam