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Huynh Van Thao,Bui Thi Chuyen,Pham Van Toan,Tran Sy Nam,Nguyen Van Cong 환경독성보건학회 2023 환경독성보건학회지 Vol.38 No.4
Fenobucarb is one of most common insecticides applied to rice crops in the Vietnamese Mekong Delta. Paddy fields are preferred habitats for snakehead fish (Channa striata). Therefore, the probability of exposure risks and growth effects is highly. This paper aimed to examine the effects of using fenobucarb based – Excel Basa 50EC on the brain cholinesterase (ChE) of snakehead fish. Two rice fields, in which a single dose of Excel Basa 50EC was applied to one field, whilst the other acted as a control. Each field was subdivided into three plots by earthen dikes. In each plot, one fish cage (1.2 m x 1.2 m x 1.2 m) was installed that was stocked with 20 snakehead fish. The Excel Basa 50EC was applied once at the indication dose. The results highlighted that the concentration of fenobucarb in water at 1 hr after application was 116.72 ppb ± 12.64, which decreased to 23.96 ± 6.61 ppb after d and then to below detection limits (0.02 ppb). For fish living in this field, no mortality was seen, but ChE was significantly inhibited for 31 % on the first day and recovery following 7 days of exposure. Residues of fenobucarb in soil and fish should also be investigated furthermore.
Thang Phan,Ha Phan Ai Nguyen,Cao Khoa Dang,Minh Tri Phan,Vu Thanh Nguyen,Van Tuan Le,Binh Thang Tran,Chinh Van Dang,Tinh Huu Ho,Minh Tu Nguyen,Thang Van Dinh,Van Trong Phan,Binh Thai Dang,Huynh Ho Ngo The Korean Society for Preventive Medicine 2023 예방의학회지 Vol.56 No.4
Objectives: The coronavirus disease 2019 (COVID-19) pandemic has increased the workload of healthcare workers (HCWs), impacting their health. This study aimed to assess sleep quality using the Pittsburgh Sleep Quality Index (PSQI) and identify factors associated with poor sleep among HCWs in Vietnam during the COVID-19 pandemic. Methods: In this cross-sectional study, 1000 frontline HCWs were recruited from various healthcare facilities in Vietnam between October 2021 and November 2021. Data were collected using a 3-part self-administered questionnaire, which covered demographics, sleep quality, and factors related to poor sleep. Poor sleep quality was defined as a total PSQI score of 5 or higher. Results: Participants' mean age was 33.20±6.81 years (range, 20.0-61.0), and 63.0% were women. The median work experience was 8.54±6.30 years. Approximately 6.3% had chronic comorbidities, such as hypertension and diabetes mellitus. About 59.5% were directly responsible for patient care and treatment, while 7.1% worked in tracing and sampling. A total of 73.8% reported poor sleep quality. Multivariate logistic regression revealed significant associations between poor sleep quality and the presence of chronic comorbidities (odds ratio [OR], 2.34; 95% confidence interval [CI], 1.17 to 5.24), being a frontline HCW directly involved in patient care and treatment (OR, 1.59; 95% CI, 1.16 to 2.16), increased working hours (OR, 1.84; 95% CI,1.37 to 2.48), and a higher frequency of encountering critically ill and dying patients (OR, 1.42; 95% CI, 1.03 to 1.95). Conclusions: The high prevalence of poor sleep among HCWs in Vietnam during the COVID-19 pandemic was similar to that in other countries. Working conditions should be adjusted to improve sleep quality among this population.
Huynh Ngoc-Diem,Jana Jayasmita,Nivetha Ravi,Van Phuc Tran,정진석,허승현 한국물리학회 2022 Current Applied Physics Vol.44 No.-
The activity of NiO/Co3O4 for the hydrogen evolution reaction (HER) during water splitting was increased by depositing these metal oxides on siloxene multi-sheets. The improvement in active sites due to siloxene was used to increase the catalytic activity. The hierarchical structure of the composite with the synergistic effect of metal oxides helped enhance the catalytic activity to show a low overpotential of 110 mV at 10 mA/cm2 in 1 M KOH and stability at 10 mA/cm2 over 20 h without an obvious change in voltage. The as-prepared catalyst can be a promising electrocatalyst for the HER owing to the low cost of transition metal oxides, the abundance of silicon on Earth, and the simplicity of the synthesis process.
Optimization strategy for planing hull design
Tran Thai Gia,Van Huynh Quang,김현철 대한조선학회 2022 International Journal of Naval Architecture and Oc Vol.14 No.1
The planing hull optimization has always been a difficult problem due to the trim changes caused by lift force and complex hydrodynamic interactions at high speeds. In this paper, a strategy is presented to optimize a planing hull design, starting from using dimensional analysis to establish a resistance objective function depending on three dimensionless hull form parameters, then using CFD or Savitsky method to predict resistance for each hull variant formed by changing each pair of hull form parameters in the resistance objective function, and finally, determining an optimal hull formvariant with minimum resistance based on the combination of the Kriging surrogate model and Neldel-Mead optimization algorithm. In addition, our modified Savitsky computational procedure and suitable inputs for the CFD solver are also applied to improve the accuracy of planing hull resistance predictions. For practicality, the proposed strategy was applied to evaluate the design of a high-speed vessel, named K88, which was model tested but did not achieve the expected performance. As a result, this vessel can be optimally redesigned with the ability to reduce total resistance by about 11.3% when simultaneously correcting deadrise angle and breadth, and by about 19.4% when simultaneously correcting deadrise angle and chine height at the bow.
Optimal design method of bulbous bow for fishing vessels
Tran Thai Gia,Van Huynh Chinh,Kim Hyun Cheol 대한조선학회 2021 International Journal of Naval Architecture and Oc Vol.13 No.1
Although widely used, the design of the bulbous bow for ships has been difficult due to the complex interference between the wave system generated by the bulb and the wave system of the ship hull. Until now, a bulbous bow has been often designed using Kracht charts, which were established based on model test data, but these charts apply only to ships with a block coefficient CB ¼ 0.56-0.82, Froude number Fn ¼ 0.20-0.40, and the obtained bulb sizes are only close to optimal. This paper presents a new method for the optimal design of bulbous bow, starting from the design of an initial bulb using Kracht charts for ships with any block coefficient or Froude number, then resizing this initial bulb to define the optimal bulb sizes based on a multi-objective function of the required power reduction, and a combined solution of Computation Fluid Dynamics (CFD) analysis and surrogate models. This study was applied to a fishing vessel FAO 75, which has been model tested and used to design steel fishing vessels in Vietnam recently. The obtained quantitative results showed the same trend as the theory and practice, with a reduction of the ship’s required power by about 14%.
Do Van Cong,Nguyen Thi Thu Trang,Nguyen Vu Giang,Tran Huu Trung,Nguyen Thuy Chinh,Mai Duc Huynh,Thai Hoang,Jun Seo Park(박준서) 한국고분자학회 2016 폴리머 Vol.40 No.3
This study describes the preparation and characterization of nanocomposites obtained by melt-mixing of poly (ethylene-co-vinyl acetate) (EVA), polylactic acid (PLA), and TiO₂ nanoparticles (TNPs) via three different methods of direct mixing, one-step, and two-step methods. Vinyltrimethoxysilane was used as a surface modifier for the TNPs. The one-step method showed the best suitability for the preparation of EVA/PLA/TiO₂ nanocomposites. The increase in torque and the adhesion of the TNPs with EVA/PLA matrix in these nanocomposites showed enhanced interfacial interactions between EVA, PLA chains, and TNPs. The tensile strength, Young’s modulus, dynamic storage modulus, and thermooxidative stability of the one-step prepared nanocomposites were higher than those of two other nanocomposites and that of the EVA/PLA blend, reaching maximum values at 2.0 wt% of TNPs.
Effect of composition on the ability to form SiC/SiO2-C composite from rice husk and silica gel
Do Quang Minh,Tran Van Khai,Huynh Ngoc Minh,Nguyen Vu Uyen Nhi,Kieu Do Trung Kien 한양대학교 세라믹연구소 2021 Journal of Ceramic Processing Research Vol.22 No.2
Rice husk is a waste product of agricultural production of rice. Every year, the agricultural production of Vietnam emits about10 million tons of rice husks. Rice husks are usually treated by burning method or discharged into rivers, causing manynegative impacts on the environment. In this study, the rice husk/silica gel ratio components were investigated to form SiC/SiO2-C composite in a CO2 environment at 1000 oC for 60 min. The products after pyrolysis were determined SiC, SiO2, andfree C contents according to ISO 21068-2: 2008 standards. The functional groups and mineral composition of composites wereanalyzed by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The microstructure and elementdistribution of them were observed by scanning electron microscope (SEM) and Energy-dispersive X-ray (EDX) mapping. Theresults showed that the optimum rice husk/silica gel ratio to form SiC/SiO2-C was 1.4/1. The sample after pyrolysis hadchemical composition including 14% SiC, 63% SiO2, 23% free C (%wt.) and the phase composition including amorphouscarbon, β-SiC, 6H-SiC, 4H-SiC, cristobalite. Composite SiC/SiO2-C can apply to advanced friction systems. This can be seenas an effective method to treat rice husk waste and improved the economic value of rice plants.