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High-Resolution Simulations for Vietnam - Methodology and Evaluation of Current Climate
Jack Katzfey,Kim Nguyen,John McGregor,Peter Hoffmann,Suppiah Ramasamy,Hiep Van Nguyen,Mai Van Khiem,Thang Van Nguyen,Kien Ba Truong,Thang Van Vu,Hien Thuan Nguyen,Tran Thuc,Doan Ha Phong,Bang Thanh Ng 한국기상학회 2016 Asia-Pacific Journal of Atmospheric Sciences Vol.52 No.2
To assist the government of Vietnam in its efforts to better understand the impacts of climate change and prioritise its adaptation measures, dynamically downscaled climate change projections were produced across Vietnam. Two Regional Climate Models (RCMs) were used: CSIRO’s variable-resolution Conformal-Cubic Atmospheric Model (CCAM) and the limited-area model Regional Climate Model system version 4.2 (RegCM4.2). First, global CCAM simulations were completed using bias- and variance-corrected sea surface temperatures as well as sea ice concentrations from six Coupled Model Intercomparison Project Phase 5 (CMIP5) global climate models. This approach is different from other downscaling approaches as it does not use any atmospheric fields from the GCMs. The global CCAM simulations were then further downscaled to 10 km using CCAM and to 20 km using RegCM4.2. Evaluations of temperature and precipitation for the current climate (1980-2000) were completed using station data as well as various gridded observational datasets. The RCMs were able to reproduce reasonably well most of the important characteristics of observed spatial patterns and annual cycles of temperature. Average and minimum temperatures were well simulated (biases generally less than 1oC), while maximum temperatures had biases of around 1oC. For precipitation, although the RCMs captured the annual cycle, RegCM4.2 was too dry in Oct.-Nov. (−60% bias), while CCAM was too wet in Dec.- Mar. (130% bias). Both models were too dry in summer and too wet in winter (especially in northern Vietnam). The ability of the ensemble simulations to capture current climate increases confidence in the simulations of future climate.
Nguyen, Duc Ba,Nguyen, Van Toan,Heo, Il Jeong,Mok, Young Sun Elsevier 2019 Journal of industrial and engineering chemistry Vol.72 No.-
<P><B>Abstract</B></P> <P>The hydrocarbon selective catalytic reduction (HC-SCR) of nitrogen oxides (NO<SUB>x</SUB>) over Ag/α–Al<SUB>2</SUB>O<SUB>3</SUB> with temperature fluctuation in the range of 150–350°C was investigated in a packed-bed dielectric barrier discharge plasma reactor. The results revealed that the HC-SCR coupled with plasma maintained high NO<SUB>x</SUB> reduction efficiency around 74% regardless of the temperature variations in the range from 150 to 350°C (10–40°C/min). In comparison, the NO<SUB>x</SUB> reduction efficiency of the HC-SCR-alone process was varied from 37.6 to 63.4%, depending on the reaction temperature fluctuations. Consequently, the strong temperature dependence of catalytic activity can be resolved by integrating plasma and catalysis.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Improvement of unsteady state behavior of NOx removal by HC-SCR coupled with plasma. </LI> <LI> High NO<SUB>x</SUB> reduction under the temperature fluctuating conditions by plasma. </LI> <LI> Conversion of HC reductant at low temperatures in the presence of plasma. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Nguyen Ba Tiến,Hoai-Nam Nguyen,Hoang-Ha Le,Tran Thu Trang,Chau Van Dinh,Ha-Nam Nguyen,Gyoo Seok Choi 한국인터넷방송통신학회 2023 International Journal of Internet, Broadcasting an Vol.15 No.2
A common approach to the problem of predicting student test scores is based on the student's previous educational history. In this study, high school transcripts of about two thousand candidates, who took the High-school Student Assessment (HSA) were collected. The data were estimated through building a regression model - Random Forest and optimizing the model's parameters based on Genetic Algorithm (GA) to predict the HSA scores. The RMSE (Root Mean Square Error) measure of the predictive models was used to evaluate the model’s performance.
Van Thanh, Nguyen,Jang, Hyun-Jae,Vinh, Le Ba,Linh, Kieu Thi Phuong,Huong, Phan Thi Thanh,Cuong, Nguyen Xuan,Nam, Nguyen Hoai,Van Minh, Chau,Kim, Young Ho,Yang, Seo Young Elsevier 2019 Bioorganic chemistry Vol.88 No.-
<P><B>Abstract</B></P> <P>In a search for anti-inflammatory activity in resources from Vietnamese mangroves, we found that a methanolic extract from the leaves of <I>Calophyllum inophyllum</I> (CIL) showed significant anti-inflammatory effects <I>in vitro</I>. Using various chromatographic techniques, we subsequently isolated 12 compounds (<B>1</B>–<B>12</B>) from a methanolic extract of CIL, including two novel compounds (<B>1</B>–<B>2</B>). The inhibitory effects of these compounds on lipopolysaccharide-induced nitric oxide (NO) production in RAW264.7 cells were also evaluated. Compound <B>1</B> significantly suppressed NO production (IC<SUB>50</SUB> = 2.44 ± 0.88 µM), the secretion of pro-inflammatory cytokines (including interleukin-1 beta and tumor necrosis factor alpha), and the expression of inducible nitric oxide synthase through downregulation of nuclear factor-kappa-B signaling cascades. These results suggest that <I>C. inophyllum</I> leaves might be a useful resource for the development of drugs for the treatment of inflammation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Twelve compounds were isolated from Vietnamese mangrove <I>Calophyllum inophyllum</I>. </LI> <LI> Two new compounds <B>1</B> and <B>2</B> were determined by spectroscopic methods. </LI> <LI> Compound <B>1</B> showed significant anti-inflammatory activity. </LI> <LI> These results suggested that <I>C. inophyllum</I> might useful as the anti-inflammation drug. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
( Nguyen Van Toan ),( Nguyen Duc Ba ),목영선 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.0
At low operating temperatures (≤ 300 °C), the NOx removal efficiency in exhaust gases is generally low, due to plasma-catalyst is mainly oxidize NO to NO<sub>2</sub>. In this work, a dielectric barrier discharge (DBD) reactor coupled with the ZSM-5-supported bimetallic catalysts (Co-ZSM-5 and Ag-ZSM-5) was investigated to improve NO<sub>x</sub> reduction efficiency under low operation temperature condition. Aiming at finding out suitable catalyst materials and understanding the interaction between plasma and catalyst in NOx reduction process. The effect of the reaction temperature and the energy density on the NO<sub>x</sub> reduction was examined and discussed. The result showed that the presence of the elements (Co and Ag) in the catalysts significantly improved the adsorption of NO<sub>2</sub> at low temperatures, so that the performance of catalytic NO<sub>x</sub> reduction could be kept high over a wide temperature range.
Ba, Nguyen Xuan,Van, Nguyen Huu,Ngoan, Le Duc,Leddin, Clare M.,Doyle, Peter T. Asian Australasian Association of Animal Productio 2008 Animal Bioscience Vol.21 No.8
An experiment was conducted in Vietnam to test the hypothesis that supplementation with cassava powder up to 2% of live weight (LW)/d (DM basis) would linearly increase digestible organic matter intake and LW gain of Laisind cattle. There were five treatments: a basal diet of elephant grass fed at 1.25% of LW and rice straw fed ad libitum or this diet supplemented with cassava powder, containing 2% urea, at about 0.3, 0.7, 1.3 or 2.0% LW. The cattle fed cassava powder at about 2.0% LW did not consume all of the supplement, with actual intake similar to the 1.3% LW treatment. Organic matter, digestible organic matter and digestible energy intakes increased (p<0.001) curvilinearly with increased consumption of cassava powder. Rice straw intake declined curvilinearly with increasing intake of cassava powder (p<0.001), and there was a small linear decline (p = 0.01) in grass intake. The substitution rate of cassava powder for forage was between 0.5 and 0.7 kg DM reduction in forage intake per kg DM supplement consumed, with no difference between treatments. Apparent digestibility of organic matter increased (p<0.001) in a curvilinear manner, while digestibility of neutral detergent fibre declined (p<0.001) in a curvilinear manner with increased consumption of cassava powder. Live weight gain increased (p<0.01) linearly with increased consumption of supplement. It was concluded that the amount of cassava powder fed should be limited to between 0.7 and 1.0% LW.
Ba, Nguyen Xuan,Van Huu, Nguyen,Ngoan, Le Duc,Leddin, Clare M.,Doyle, Peter T. Asian Australasian Association of Animal Productio 2008 Animal Bioscience Vol.21 No.12
Two experiments were conducted in central Vietnam to test the hypothesis that supplementation with a concentrate, comprising rice bran (45% fresh basis), maize (49%), fish meal (3%), urea (2%) and salt (1%), up to 2% of live weight (LW)/d (dry matter (DM) basis) would linearly increase digestible organic matter intake and LW gain of yellow cattle. In both experiments, there were five treatments, namely a basal diet of fresh grass fed at 1.25% of LW (experiment 1, elephant grass, Pennisetum purpureum; experiment 2, native grass) and rice straw (Oryza sativa) fed ad libitum or this diet supplemented with concentrate at about 0.3, 0.7, 1.3 or 2.0% LW. There were 4 male growing cattle per treatment in experiment 1 and 3 in experiment 2. Diets were fed for 44 (experiment 1) or 49 (experiment 2) days, with feed intake recorded daily, LW measured about weekly and digestibility measurements made over 7 days commencing on day 24 (experiment 1) or day 10 (experiment 2). The elephant grass and native grass had neutral detergent fibre (NDF) concentrations of 82 and 73% DM, and nitrogen concentrations of 1.3 and 1.8% DM, respectively. The rice straw used had a NDF concentration of 79-84% DM and nitrogen concentration of 0.8% DM. The concentrate had NDF and nitrogen concentrations of 33 and 2.8% DM. In both experiments, DM intake increased (p<0.001) linearly as the amount of concentrate consumed increased. Rice straw intake declined (p<0.001) (experiment 1: 1.24 to 0.48 kg DM/d; experiment 2: 0.95 to 0.50 kg DM/d) as concentrate intake increased. Grass intake was not significantly affected by concentrate intake in either experiment. The lowest amount of concentrate supplement increased forage intake, after which substitution rate increased as the amount of concentrate consumed increased. However, substitution rates at the highest amount of concentrate consumed were modest at 0.3 to 0.5 kg DM reduction in forage intake/kg DM supplement consumed. In both experiments, digestible organic matter intake increased linearly (p<0.001) (experiment 1: 1.16 to 2.38 kg/d; experiment 2: 1.30 to 2.49 kg/d) as the amount of supplement consumed increased, as did LW gain (experiment 1: 0.15 to 0.81 kg/d; experiment 2: 0.15 to 0.77 kg/d). This was associated with significant (p<0.01) linear increases in organic matter intake and apparent organic matter digestibility. Neutral detergent fibre digestibility declined as concentrate intake increased, but the effect was not significant (p = 0.051) in experiment 2. These results are discussed in relation to existing literature and potential to improve the profitability of cattle fattening in central Vietnam.
( Nguyen Duc Ba ),( Nguyen Van Toan ),목영선 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.0
Ag/Al<sub>2</sub>O<sub>3</sub> catalyst with hydrocarbons as a reduction agent is potential for selective catalyst reduction of NOx at a temperature above 300°C. However, NOx efficiency removal decreased sharply at an early state or low temperature, owing to the low activity of hydrocarbon reducing agent at low-temperatures (≤ 250°C). In order to expended temperature window, a combination of the catalyst with atmospheric-pressure plasma has been proposed, since plasma-catalyst enhanced partially oxidize hydrocarbons at low temperature and these hydrocarbon derivatives are more activity for NOx removal. In this work, several hydrocarbons such as C<sub>2</sub>H<sub>4</sub>, C<sub>3</sub>H<sub>8</sub>, and C<sub>7</sub>H<sub>16</sub> have been proposed as a reducing agent for the process. The effects will consider in terms of NOx efficiency removal, energy efficiency, and hydrocarbon consumption.