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  • 1
    Online Resource
    Online Resource
    Changes in Precipitation Extremes across Vietnam and Its Relationships with Teleconnection Patterns of the Northern Hemisphere
    MDPI AG ; 2020
    In:  Water Vol. 12, No. 6 ( 2020-06-08), p. 1646-
    Details
    In: Water, MDPI AG, Vol. 12, No. 6 ( 2020-06-08), p. 1646-
    Abstract: Understanding changes in precipitation extremes is critical for designing mitigation measures for the potential implications of a warming climate. This study assessed changes in the magnitude and frequency of precipitation extremes over Vietnam using high-quality gridded daily precipitation observations from 1980 to 2010. The annual maxima precipitation was analyzed to detect historical changes in the magnitude of precipitation extremes, while the number of heavy precipitation events, defined using the peak-over-threshold approach, was used to assess changes in the frequency of precipitation extremes. We found a strong signal of changes in the frequency of heavy precipitation, with 28.3% of Vietnam’s landmass exhibiting significant increasing trends. The magnitude of annual maxima precipitation shows a mixed pattern of changes, with less than 10% of Vietnam’s landmass exhibiting significant (both increasing and decreasing) trends. To identify possible mechanisms driving changes in precipitation, we assessed the relationship between inter-annual variations in precipitation extremes and climate variability represented by the teleconnection patterns of the Northern Hemisphere. Using five climate indices, we found that teleconnections across the Indian and Pacific Oceans have implied large control over the characteristics of precipitation extremes across Vietnam, with up to 30% of Vietnam’s landmass exhibiting a significant relationship.
    Type of Medium: Online Resource
    ISSN: 2073-4441
    URL: Article
    DOI: 10.3390/w12061646
    Language: English
    Publisher: MDPI AG
    Publication Date: 2020
    detail.hit.zdb_id: 2521238-2
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  • 2
    Online Resource
    Online Resource
    Future Changes in Hydro-Climatic Extremes across Vietnam: Evidence from a Semi-Distributed Hydrological Model Forced by Downscaled CMIP6 Climate Data
    MDPI AG ; 2024
    In:  Water Vol. 16, No. 5 ( 2024-02-25), p. 674-
    Details
    In: Water, MDPI AG, Vol. 16, No. 5 ( 2024-02-25), p. 674-
    Abstract: Flood hazards have led to substantial fatalities and economic loss in the last five decades, making it essential to understand flood dynamics in a warming climate. This study reports the first comprehensive assessment of projected flood hazards across Vietnam. We used downscaled climate data from the CMIP6 initiative, involving a total of 20 climate models, and streamflow projection simulated using a semi-distributed hydrological model. The assessment covers seven near-natural catchments, each representing a climate zone of the country. To evaluate climate change impacts on floods, the study simultaneously analyzes changes in three indices: (i) the annual hottest day temperature, to represent temperature extremes; (ii) the maximum daily rainfall amount, to represent rainfall extremes; and (iii) the discharge value exceeding 5% in a year, to assess streamflow extremes. Changes in the selected indices (relative to the reference period from 1985 to 2014) are assessed under four emission scenarios (SSP1–2.6, SSP2–4.5, SSP3–7.0, and SSP5–8.5) and two future time slices (2036–2065 and 2070–2099). Although the robustness (as indicated by multi-model agreement) and significance (identified through the statistical test) of the changes vary substantially, depending on the selected indices and assessed time slices, an overall increase is consistently identified across all of the assessed hydro-climatic extremes (up to 4.8 °C for temperature extremes, 43 mm for rainfall extremes, and 31% for streamflow extremes). The findings suggest a potential increase in flood risk across Vietnam in a warming climate, highlighting the urgent need for improved flood preparedness and investment to reduce economic loss and mortality in an uncertain future.
    Type of Medium: Online Resource
    ISSN: 2073-4441
    URL: Article
    DOI: 10.3390/w16050674
    Language: English
    Publisher: MDPI AG
    Publication Date: 2024
    detail.hit.zdb_id: 2521238-2
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  • 3
    Online Resource
    Online Resource
    Impacts of Solar Radiation Management on Hydro-Climatic Extremes in Southeast Asia
    MDPI AG ; 2023
    In:  Water Vol. 15, No. 6 ( 2023-03-13), p. 1089-
    Details
    In: Water, MDPI AG, Vol. 15, No. 6 ( 2023-03-13), p. 1089-
    Abstract: Solar radiation management (SRM), or solar geoengineering, reduces the earth’s temperature by reflecting more sunlight back to space. However, the impacts of SRM remain unclear, making it difficult to project the benefits as well as consequences should this approach be adopted to combat climate change. To provide novel insight into the SRM impact on hydro-climatic extremes in Southeast Asia, this study conducts a simulation experiment for the Kelantan River Basin (KRB) in Malaysia by incorporating three bias-corrected Stratospheric Aerosol Geoengineering Large Ensemble (GLENS) members into the Soil and Water Assessment Tool Plus (SWAT+) model. The study found that SRM practices could generate substantial cooling effects on regional temperatures, leading to a reduction in projected annual precipitation and monthly precipitation during the flooding season (from November to mid-January) under SRM relative to the Representative Concentration Pathway 8.5 (RCP8.5) scenario. In addition, SRM could reduce the number of days with heavy precipitation as well as the intensity of maximum daily precipitation as compared to RCP8.5, during the 2045–2064 and 2065–2084 periods, leading to a reduction in high flows. Nevertheless, under SRM impacts, the driest months from February to May would experience comparable decreases in monthly precipitation and streamflow.
    Type of Medium: Online Resource
    ISSN: 2073-4441
    URL: Article
    DOI: 10.3390/w15061089
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2521238-2
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  • 4
    Online Resource
    Online Resource
    Scenarios for a Scaling-up System for Organic Cassava Production in the Mekong River Basin: A Foresight Approach
    MDPI AG ; 2024
    In:  Agriculture Vol. 14, No. 4 ( 2024-04-10), p. 600-
    Details
    In: Agriculture, MDPI AG, Vol. 14, No. 4 ( 2024-04-10), p. 600-
    Abstract: Organic cassava flour and products are in high demand. However, the expansion of organic cassava (OCS) production is rather slow. To increase OCS production, extension workers, cassava flour mills, farmers, and researchers have been collaborating to support the farmers, but the planted areas have remained limited. This research aimed at understanding the current issues in scaling up the organic cassava production. The findings were subsequently used to formulate scenarios and recommendations for the collaborative scale-up of organic cassava production in the Mekong River Basin (MRB). We carried out a six-step foresight process with leaders of organic cassava farmers, the staff of organic cassava flour mills and factories, extension workers, the staff of research agencies, and local policy makers in Thailand. The results revealed two key factors or drivers of changes, namely, the degree of collaboration among stakeholders using multiple-view scenarios or a single-view situation and the degree of learning and communication about OCS that future stakeholders are likely to experience. Four possible scenarios for a scaling-up system of OCS production in the MRB were developed. The foresight process allowed for recognizing multiple views and opinions about the OCS production scaling-up process, considered as a whole system. The system was found to consist of various interdependent components. The process highlighted the need to increase the capacity and opportunities for productive collaboration in research and development. We concluded that the MRB members should issue a policy formulating a joint task force to coordinate the existing institutions’ plans and resources towards an actionable OCS production scaling-up system for the MRB in 2030.
    Type of Medium: Online Resource
    ISSN: 2077-0472
    URL: Article
    DOI: 10.3390/agriculture14040600
    Language: English
    Publisher: MDPI AG
    Publication Date: 2024
    detail.hit.zdb_id: 2651678-0
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  • 5
    Online Resource
    Online Resource
    Assimilation of SMAP Products for Improving Streamflow Simulations over Tropical Climate Region—Is Spatial Information More Important Than Temporal Information?
    MDPI AG ; 2022
    In:  Remote Sensing Vol. 14, No. 7 ( 2022-03-28), p. 1607-
    Details
    In: Remote Sensing, MDPI AG, Vol. 14, No. 7 ( 2022-03-28), p. 1607-
    Abstract: Streamflow is one of the key variables in the hydrological cycle. Simulation and forecasting of streamflow are challenging tasks for hydrologists, especially in sparsely gauged areas. Coarse spatial resolution remote sensing soil moisture products (equal to or larger than 9 km) are often assimilated into hydrological models to improve streamflow simulation in large catchments. This study uses the Ensemble Kalman Filter (EnKF) technique to assimilate SMAP soil moisture products at the coarse spatial resolution of 9 km (SMAP 9 km), and downscaled SMAP soil moisture product at the higher spatial resolution of 1 km (SMAP 1 km), into the Soil and Water Assessment Tool (SWAT) to investigate the usefulness of different spatial and temporal resolutions of remotely sensed soil moisture products in streamflow simulation and forecasting. The experiment was set up for eight catchments across the tropical climate of Vietnam, with varying catchment areas from 267 to 6430 km2 during the period 2017–2019. We comprehensively evaluated the EnKF-based SWAT model in simulating streamflow at low, average, and high flow. Our results indicated that high-spatial resolution of downscaled SMAP 1 km is more beneficial in the data assimilation framework in aiding the accuracy of streamflow simulation, as compared to that of SMAP 9 km, especially for the small catchments. Our analysis on the impact of observation resolution also indicates that the improvement in the streamflow simulation with data assimilation is more significant at catchments where downscaled SMAP 1 km has fewer missing observations. This study is helpful for adding more understanding of performances of soil moisture data assimilation based hydrological modelling over the tropical climate region, and exhibits the potential use of remote sensing data assimilation in hydrology.
    Type of Medium: Online Resource
    ISSN: 2072-4292
    URL: Article
    DOI: 10.3390/rs14071607
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2513863-7
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  • 6
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    Online Resource
    Synthesis and Characterization of Broccoli-like Ag/Cu2O Nanostructures on ZnO Nanowires Using the Plasma–Liquid Interaction Method
    MDPI AG ; 2024
    In:  Inorganics Vol. 12, No. 3 ( 2024-03-06), p. 80-
    Details
    In: Inorganics, MDPI AG, Vol. 12, No. 3 ( 2024-03-06), p. 80-
    Abstract: We have designed an excellent visible-light-driven and high-performance photocatalyst with a Ag-Cu2O-ZnO nanowire heterostructure in our work by combining the hydrothermal approach with plasma–liquid technology. The structural and morphological characteristics and optical properties of the samples were evaluated using X-ray diffraction, field-emission scanning electron microscopy, and spectrophotometry, respectively. The results show that the Ag nanoparticles are mainly positioned on the Cu2O nanoclusters compared with the ZnO nanowire surface, forming broccoli-like Ag-Cu2O nanoclusters during the Ar gas plasma treatment process in an aqueous solution. The diameter of the Ag/Cu2O nanoclusters ranges from 150 to 180 nm. The Ag-Cu2O-ZnO nanowires exhibited improved photocatalytic performance, decomposing approximately 98% methyl orange dye in 30 min. This is a consequence of the synergistic interactions between the p-n heterojunction formed at the Cu2O-ZnO interfaces and the localized surface plasmon resonance (LSPR) effect of the Ag nanoparticles, which broaden the visible light absorption range and effectively separate the photogenerated charge carriers.
    Type of Medium: Online Resource
    ISSN: 2304-6740
    URL: Article
    DOI: 10.3390/inorganics12030080
    Language: English
    Publisher: MDPI AG
    Publication Date: 2024
    detail.hit.zdb_id: 2735043-5
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  • 7
    Online Resource
    Online Resource
    Coverage of Health Information by Different Sources in Communities: Implication for COVID-19 Epidemic Response
    MDPI AG ; 2020
    In:  International Journal of Environmental Research and Public Health Vol. 17, No. 10 ( 2020-05-20), p. 3577-
    Details
    In: International Journal of Environmental Research and Public Health, MDPI AG, Vol. 17, No. 10 ( 2020-05-20), p. 3577-
    Abstract: Health personnel and community workers are at the front line of the COVID-19 emergency response and need to be equipped with adequate knowledge related to epidemics for an effective response. This study aimed to identify the coverage of COVID-19 health information via different sources accessed by health workers and community workers in Vietnam. A cross-sectional study using a web-based survey was carried out from January to February 2020 in Vietnam. Respondent-driven sampling (RDS) was used for recruiting participants. We utilized the exploratory factor analysis (EFA) to examine the construct validity of the questionnaire. A higher percentage of participants knew about “Clinical and pathogen characteristics of COVID-19”, compared to “Regulations and policies related to COVID-19”. The percentage of participants accessing the information on “Guidelines and policies on prevention and control of COVID-19” was the lowest, especially among medical students. “Mass media and peer-educators” channels had a higher score of accessing COVID-19 information, compared to “Organizations/ agencies/ associations” sources. Participants consumed most of their COVID-19 information via “Internet, online newspapers, social networks”. Our findings indicate an urgency to re-design training programs and communication activities for a more effective dissemination of information related to the COVID-19 epidemic or epidemics in general.
    Type of Medium: Online Resource
    ISSN: 1660-4601
    URL: Article
    DOI: 10.3390/ijerph17103577
    Language: English
    Publisher: MDPI AG
    Publication Date: 2020
    detail.hit.zdb_id: 2175195-X
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  • 8
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    Online Resource
    Methadone Maintenance Treatment Reduces the Vulnerability of Drug Users on HIV/AIDS in Vietnamese Remote Settings: Assessing the Changes in HIV Knowledge, Perceived Risk, and Testing Uptake after a 12-Month Follow-Up
    MDPI AG ; 2018
    In:  International Journal of Environmental Research and Public Health Vol. 15, No. 11 ( 2018-11-16), p. 2567-
    Details
    In: International Journal of Environmental Research and Public Health, MDPI AG, Vol. 15, No. 11 ( 2018-11-16), p. 2567-
    Abstract: Methadone Maintenance Treatment (MMT) program has been considered a medium through which human immunodeficiency virus (HIV) risks assessment and prevention on drug use/HIV-infected population can be effectively conducted. Studies concerning the implementation of such idea on patients in remote, under-developed areas, however, have been limited. Having the clinics established in three mountainous provinces of Vietnam, this study aimed to evaluate the changes in knowledge of HIV, perceived risk, and HIV testing uptake of the patients. A longitudinal study was conducted at six MMT clinics in three provinces with a pre- and post-assessments among 300 patients. Outcomes of interest were compared between baseline and after 12 months. The magnitude of changes was extrapolated. The proportion of participants reporting that their HIV knowledge was not good fell by 4.4% (61.3% at the baseline vs. 56.8% at 12 months). The significant improvement seen was in the knowledge that needle sharing was a mode of transmission (82.7% vs. 89.6%). Nevertheless, the majority of participants reportedly considered mosquitoes/insect and eating with the HIV-infected patient were the route of transmission at both time points (84.7% vs. 89.1%, 92.2% vs. 93.3%, respectively). This study found a limited improvement in HIV knowledge and testing uptake among MMT patients following a 12-month period. It also highlighted some shortcomings in the knowledge, attitudes and practices (KAP) of these patients, in particular, incorrect identification of HIV transmission routes, among patients both at program initiation and follow-up. The findings lent support to the argument for enhancing education and counseling efforts at MMT clinics regarding HIV, as well as for improving access to preventive and health care services through the integration of MMT/HIV services.
    Type of Medium: Online Resource
    ISSN: 1660-4601
    URL: Article
    DOI: 10.3390/ijerph15112567
    Language: English
    Publisher: MDPI AG
    Publication Date: 2018
    detail.hit.zdb_id: 2175195-X
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  • 9
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    Online Resource
    Decorating of Ag and CuO on ZnO Nanowires by Plasma Electrolyte Oxidation Method for Enhanced Photocatalytic Efficiency
    MDPI AG ; 2022
    In:  Catalysts Vol. 12, No. 7 ( 2022-07-21), p. 801-
    Details
    In: Catalysts, MDPI AG, Vol. 12, No. 7 ( 2022-07-21), p. 801-
    Abstract: In this work, photocatalytic performance is divulged in the ternary CuO-Ag-ZnO nanowire synthesized via a two-step approach. The decoration of Ag and CuO nanostructures onto the surface of ZnO nanowires was simply carried out by using the plasma electrolytic oxidation method in a short time. The structure, size, morphology, and optical properties of as-prepared samples were characterized by X-ray diffraction, field-emission scanning electron microscopy, and spectrophotometry measurements. The diameters of Ag nanoparticles and ZnO nanoflowers are in the range of 5–20 nm and 20–60 nm, respectively. Within the first 15 min, methyl orange was decolorized 96.3 and 82.8% in the CuO-Ag-ZnO and Ag-ZnO, respectively, and there is only about 46.7% of that decomposed in pure ZnO. The CuO-Ag-ZnO shows a higher rate constant k = 0.2007 min−1 and a lower half-life time t = 6.1 min compared to Ag-ZnO and bare ZnO nanowires. The photo-reusability of the ternary nanostructures was estimated to be much outweighed compared to ZnO nanowires. Interestingly, the synergic incorporation between noble metal–semiconductor or semiconductor–semiconductor in the interfaces of Ag-CuO, Ag-ZnO, and CuO-ZnO expands the visible light absorption range and eliminates the photogenerated electron–hole recombination, resulting in a superior visible-light-driven photocatalyst.
    Type of Medium: Online Resource
    ISSN: 2073-4344
    URL: Article
    DOI: 10.3390/catal12070801
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2662126-5
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  • 10
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    Robust Fault Estimation Using the Intermediate Observer: Application to the Quadcopter
    MDPI AG ; 2020
    In:  Sensors Vol. 20, No. 17 ( 2020-08-31), p. 4917-
    Details
    In: Sensors, MDPI AG, Vol. 20, No. 17 ( 2020-08-31), p. 4917-
    Abstract: In this paper, an actuator fault estimation technique is proposed for quadcopters under uncertainties. In previous studies, matching conditions were required for the observer design, but they were found to be complex for solving linear matrix inequalities (LMIs). To overcome these limitations, in this study, an improved intermediate estimator algorithm was applied to the quadcopter model, which can be used to estimate actuator faults and system states. The system stability was validated using Lyapunov theory. It was shown that system errors are uniformly ultimately bounded. To increase the accuracy of the proposed fault estimation algorithm, a magnitude order balance method was applied. Experiments were verified with four scenarios to show the effectiveness of the proposed algorithm. Two first scenarios were compared to show the effectiveness of the magnitude order balance method. The remaining scenarios were described to test the reliability of the presented method in the presence of multiple actuator faults. Different from previous studies on observer-based fault estimation, this proposal not only can estimate the fault magnitude of the roll, pitch, yaw, and thrust channel, but also can estimate the loss of control effectiveness of each actuator under uncertainties.
    Type of Medium: Online Resource
    ISSN: 1424-8220
    URL: Article
    DOI: 10.3390/s20174917
    Language: English
    Publisher: MDPI AG
    Publication Date: 2020
    detail.hit.zdb_id: 2052857-7
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