<i>In situ</i> growth of flower-like V₂O₅ arrays on graphene@nickel foam as high-performance electrode for supercapacitors

Van Hoa, Nguyen,Quyen, Tran Thi Hoang,Nghia, Nguyen Huu,Van Hieu, Nguyen,Shim, Jae-Jin Elsevier 2017 Journal of alloys and compounds Vol.702 No.-

<P><B>Abstract</B></P> <P>Hierarchical flower-like V<SUB>2</SUB>O<SUB>5</SUB> growth on graphene and nickel foam electrodes was fabricated by using chemical vapor deposition and hydrothermal methods for electrochemical capacitors. Taking advantages of the high conductivity of graphene, high capacitance of well-defined V<SUB>2</SUB>O<SUB>5</SUB> flower-like structure and open framework of three-dimensional nickel foam, the resulting electrodes exhibited rapid electron and ion transport, large electroactive surface area, and excellent structural stability. The specific capacitance was as high as 1235 F g<SUP>−1</SUP> at a current density of 2 A g<SUP>-1</SUP>, suggesting its potential as a high performance electrode for supercapacitors.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Hierarchical flower-like V2O5/graphene/nickel foam electrodes was fabricated. </LI> <LI> The electrodes exhibited rapid electron and ion transport, large electroactive surface area. </LI> <LI> The specific capacitance was as high as 1235 A g−1 at a current density of 2 A g−1. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Excellent detection of H₂S gas at ppb concentrations using ZnFe₂O₄ nanofibers loaded with reduced graphene oxide

Van Hoang, Nguyen,Hung, Chu Manh,Hoa, Nguyen Duc,Van Duy, Nguyen,Park, Inkyu,Van Hieu, Nguyen Elsevier Sequoia 2019 Sensors and actuators. B Chemical Vol.282 No.-

<P><B>Abstract</B></P> <P>Cost-effective fabrication of sensors and detection of ultralow concentrations of toxic gases are important concerns for environmental monitoring. In this study, the reduced graphene oxide (RGO)-loaded ZnFe<SUB>2</SUB>O<SUB>4</SUB> nanofibers (ZFO-NFs) were fabricated by facile on-chip electrospinning method and subsequent heat treatment. The multi-porous NFs with single-phase cubic spinel structure and typical spider-net morphology were directly assembled on Pt-interdigitated electrodes. The diameters of the RGO-loaded ZFO-NFs were approximately 50–100 nm with many nanograins. The responses to H<SUB>2</SUB>S gas showed a bell-shaped behaviour with respect to RGO contents and annealing temperatures. The optimal values of the RGO contents and the annealing temperatures were found to be about 1.0 wt% and 600 °C, respectively. The response of the RGO-loaded ZnFe<SUB>2</SUB>O<SUB>4</SUB> NFs to 1 ppm H<SUB>2</SUB>S gas was as high as 147 at 350°C while their cross-gas responses to SO<SUB>2</SUB> (10 ppm), NH<SUB>3</SUB> (100 ppm), H<SUB>2</SUB> (250 ppm), C<SUB>3</SUB>H<SUB>6</SUB>O (1000 ppm), and C<SUB>2</SUB>H<SUB>5</SUB>OH (1000 ppm) were rather low (1.8−5.6). The high sensor response was attributed to formation of a heterojunction between RGO and ZnFe<SUB>2</SUB>O<SUB>4</SUB> and due to the fact that NFs consisted of many nanograins which resulted in multi-porous structure and formation of potential barriers at grain boundaries.</P> <P><B>Highlights</B></P> <P> <UL> <LI> rGO-loaded ZnFe<SUB>2</SUB>O<SUB>4</SUB> nanofibers have simply prepared by electrospinning. </LI> <LI> rGO-loaded ZnFe<SUB>2</SUB>O<SUB>4</SUB> nanofiber sensors can detect H<SUB>2</SUB>S gas down to ppb level. </LI> <LI> The loading rGO can result in an enhancement of H<SUB>2</SUB>S gas ensing performance. </LI> </UL> </P>

An online Indigenous Knowledge Database on Climate Change Adaptation of Farmers in the Vietnam Mekong Delta

Van Hoa Nguyen,Thi Mai Phung Bui,Thanh Phong Le,Hoang Tung Nguyen,Minh Tuyen Truong,Minh Nhut Do,Van Nha Duong 인간식물환경학회 2022 인간식물환경학회지 Vol.25 No.6

Background and objective: For countries vulnerable to climate change as Vietnam, indigenous knowledge (IK) might assist in revealing the values of local people's adaptations to environmental stresses and potentially support decision-making. Despite IK can provide the adaptive capacity of local people's activities within environmental contexts, but it is rapidly vanishing. This study aimed to describe the documentation of IK associated with climate change adaptation of farmers in the Vietnam Mekong Delta (VMD). Methods: We focused on collecting and establishing online access to IK documents through collaboration between IK holders, public sector, collecting institutions, and researchers in the five agro-ecological zones of the VMD. An online IK database for storing IK documents has been designed and implemented based on the web application schema. Results: Through interviews, we gathered IK from farming practices that are well-adapted to climate risks such as floods, droughts, and saltwater intrusions as well as traditional knowledge being used to forecast weather, flood, and saltwater intrusion. The database for storing IK documents has been successfully deployed using free and open-source software. The database currently contains more than 260 IK documents, with their location on agro-ecological zones displayed on a web-based map. Conclusion: We have captured and provided an online access to IK on climate change adaptation of the farmers in the VMD. This research is expected as an initial strategy for long-term sustainable development of the agriculture system in this region.

Factors Affecting Night-Time Economic Development: Research in Hanoi, Vietnam

Ngoc Son NGUYEN(Ngoc Son NGUYEN ),Vu Hiep HOANG(Vu Hiep HOANG ),Quoc Dung NGO(Quoc Dung NGO ),Van Hoa HOANG(Van Hoa HOANG ) 한국유통과학회 2023 Asian Journal of Business Environment (AJBE) Vol.13 No.2

Purpose: The purpose of the study is to explore the factors which influence the night-time economic development in Hanoi, Vietnam. The results can help policymakers achieve a scientific basis to plan the development of night-time economy in Hanoi. Research design, data and methodology: The research model is developed from literature review with 7 independent variables, including natural conditions and resources, infrastructure, safety, environmental issues, promotion and international integration, development of sharing economy, and institution and policy. This model is then adjusted by exploratory factors analysis to have 4 new variables: Institution and environment, Infrastructure and safety, Promotion and sharing, and Nature and resources. The model is regressed based on the data of 463 observations of night-time economy in Hanoi, Vietnam. Results: Consistent with the current literature addressing night-time economy, the results show positive impacts of all of the independent variables studied. Conclusions: It is recommended for the local authorities to strengthen advertising and promoting investment for NTE development in Hanoi city and also enhance the role of state management in NTE activities by raising awareness of the state management apparatus towards a more open-minded multi-dimensional view of the NTE, developing the NTE to overcome the barrier of thinking “if it cannot be managed, it is forbidden” in state management agencies, and defining responsibilities and authority among state management agencies in the management of NTE activities and strengthening decentralization and decentralization of powers for localities in the management and development of NTE.

Bank Capital and Lending Behavior of Vietnamese Commercial Banks

DANG, Van Dan,LE, Thi Tuyet Hoa,LE, Dinh Hac,NGUYEN, Hoang Dieu Hien Korea Distribution Science Association 2021 The Journal of Asian Finance, Economics and Busine Vol.8 No.2

The objective of the study is to empirically investigate the impact of bank capital on the lending behavior of Vietnamese commercial banks from 2007 to 2019. Lending behavior is captured by two dimensions, including the quantity (loan growth) and quality (credit risk) of loans. Instead of investigating loan growth and credit risk separately, we combine these two aspects in our study and further develop the interaction term between capital buffers and credit risk to capture the asymmetric impact. We apply the dynamic model (regressed by the generalized method of moments) and the static models (regressed using the fixed effects, random effects, and the pooled regression approach) to perform regressions. The results show that banks with higher capital ratios tend to expand lending more, while the risk of credit portfolios is controlled at lower levels at these banks. Further analysis reveals that credit risk mitigates some aspects of the relationship between bank capital and loan expansion. The patterns remain robust across alternative measures and econometric techniques. The study provides insightful policy implications for bank managers and regulators in the process of upgrading capital resources to ensure the safety and soundness of the banking industry in an emerging country.

New Phenylpropanoid Esters of Sucrose from Polygonum hydropiper and Their Antioxidant Activity

Phan Van Kiem,Nguyen Xuan Nhiem,Nguyen Xuan Cuong,Tran Quynh Hoa,Le Mai Huong,Chua Van Minh,Hoang Thanh Huong,김영호 대한약학회 2008 Archives of Pharmacal Research Vol.31 No.11

By various chromatographic methods, two new phenylpropanoid esters of sucrose named hidropiperosides A (1) and B (2), and three known compounds as vanicosides A (3), B (4), and E (5) were isolated from the methanolic extract of the whole plant of Polygonum hydropiper L. (Polygonaceae). Their structures were elucidated by extensive spectroscopic methods including 1D- and 2D-NMR experiments, as well as ESI-MS analysis. All the isolated compounds were tested for their antioxidant activity in the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay system. Among them, compounds 2 and 3 showed significant antioxidant activity with their SC50 values of 23.4 and 26.7 μg/mL, respectively.

New Phenylpropanoid Esters of Sucrose from Polygonum hydropiper and Their Antioxidant Activity

Kiem, Phan Van,Nhiem, Nguyen Xuan,Cuong, Nguyen Xuan,Hoa, Tran Quynh,Huong, Hoang Thanh,Huong, Le Mai,Minh, Chau Van,Kim, Young-Ho 대한약학회 2008 Archives of Pharmacal Research Vol.31 No.11

By various chromatographic methods, two new phenylpropanoid esters of sucrose named hidropiperosides A (1) and B (2), and three known compounds as vanicosides A (3), B (4), and E (5) were isolated from the methanolic extract of the whole plant of Polygonum hydropiper L. (Polygonaceae). Their structures were elucidated by extensive spectroscopic methods including 1D- and 2D-NMR experiments, as well as ESI-MS analysis. All the isolated compounds were tested for their antioxidant activity in the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay system. Among them, compounds 2 and 3 showed significant antioxidant activity with their $SC_{50}$ values of 23.4 and $26.7{\mu}g/mL$, respectively.

The Effect of Technology Spillover on Business Efficiency: A Case Study in Vietnam

Mai Lan PHUNG,Vu Hiep HOANG,Thi Thanh Huyen NGUYEN,Thi Thanh Van PHAM,Viet Tien TRAN,Van Hoa HOANG 한국유통과학회 2021 The Journal of Asian Finance, Economics and Busine Vol.8 No.5

The main objective of this study is to examine the interactive effect of technology spillover channels on business efficiency within the case study of manufacturing industry of Vietnam during the period from 2012 to 2018. The research model was developed with business efficiency as dependent variable and the relevant factors affecting the technology spillover capacity as independent variables. With a sample of 2,776 cross-sectional enterprises, panel data analysis approach was adopted to estimate the impact of technology spillover issue. Different spillover channels were also included in the analysis to enhance the empirical result. The study reveals that technology spillovers positively influence manufacturing business efficiency, in which horizontal spillover channel produces negative impact and vertical spillover channel, creates positive impact. Several factors that negatively affect the technology spillover capacity of businesses could be mentioned such as limited skills and experiences of workers, methods of implementing R&D, and the existence of FDI enterprises. Meanwhile, the rise of other factors related to joint-venture activities can help to increase the technology spillover capacity of businesses. In addition, skill and experience transfer makes a partial impact since this variable only positively affect the vertical spillover channel and provide no evidence of impact regarding horizontal spillover channel model.

Left Pulmonary Artery Sling: Report of Five Cases on Multidetector Computed Tomography From Vietnamese Children

Phung Bao Ngoc,Nguyen Khoi Viet,Hoang Van Hoa,Nguyen Ngoc Trang,Le Thi Thuy Lien,Pham Minh Thong,Vu Dang Luu 아시아심장혈관영상의학회 2022 Cardiovascular Imaging Asia Vol.6 No.2

Left pulmonary artery sling (LPAS) is a rare congenital anomaly in which the left pulmonary artery (LPA) originates from the posterior aspect of the right pulmonary artery and courses between the trachea and esophagus to reach the left lung. This anomaly causes distal tracheal and/or right main stem bronchus compression. Most LPAS cases are associated with early symptom onset, around 2 month-old, and have severe respiratory distress within the first year of life. There are two major types of LPAS based on the location of LPA and abnormal bronchial branching. The diagnosis can be made by using various imaging modalities. Herein, we present the imaging characteristics on multidetector computed tomography of 5 LPAS cases with respiratory distress (2 months to 12 months).

Assessment of Left Ventricular Function and Regional Wall Motion by 256-Slice Dual-Source Coronary CT Angiography: A Comparison With 2D Transthoracic Echocardiography

Le Thi Thuy Lien,Nguyen Khoi Viet,Hoang Van Hoa,Phung Bao Ngoc,Nguyen Ngoc Trang,Vu Thi Kim Thoa,Nguyen Cong Tien,Phan Anh Phuong,Pham Minh Thong,Vu Dang Luu 아시아심장혈관영상의학회 2022 Cardiovascular Imaging Asia Vol.6 No.2

Objective: To compare left ventricular (LV) function, ejection fraction (EF), end-diastolic volume (EDV), end-systolic volume (ESV), and regional wall motion analyzed in 256-slice dualsource coronary CT angiography (DSCT) with 2D transthoracic echocardiography (TTE). Materials and Methods: One hundred twelve patients suspected of coronary artery disease underwent DSCT and 2D-TTE within one week for LVEF, EDV, and ESV. The correlation between DSCT and 2D-TTE measurements was analyzed through linear regression and Bland- Altman analysis. Regional wall motion was visually scored with a 3-point scale (1, normal; 2, hypokinesia; 3, dysphagia, akinesia). Results: Average LVEF at 66.45%±1.27% (range 23%–85%) as determined on DSCT compared with 66.09%±1.01% (range 25%–84%) on 2D-TTE. LVEF exhibited a good correlation between DSCT and 2D-TTE (r=0.715; p<0.001). Good correlations between DSCT and 2D-TTE were demonstrated for LVEDV (r=0.732; p<0.001) and LVESV (r=0.841; p<0.001). Mean differences (±SD) of 1.78±24.10 mL (p<0.05) and 0.77±13.70 mL (p<0.05) were observed between DSCT and 2D-TTE for LVEDV and LVESV, respectively. LVEF was slightly overestimated with DSCT (0.52%±9.59%; p<0.05). Although the LVEF values calculated by DSCT and 2D-TTE were similar, EDV and ESV from DSCT were statistically higher than those from 2D-TTE (p<0.05). Agreement between DSCT and 2D-TTE in regional wall motion was 96.4%, κ=0.840. Conclusion: DSCT can provide comparable results to those using 2D-TTE for LV function (EF, EDV, and ESV) and regional wall motion assessment in a heterogeneous population.