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( Nguyen Van Tuyen ),( Tran Hung Thuan ),( Chu Xuan Quang ),( Nhat Minh Dang ) 한국공업화학회 2023 공업화학 Vol.34 No.5
The effect of temperature and influent alkalinity/ammonia (K/A) ratio on the start-up of the partial nitrification (PN) process for an activated sludge-based domestic wastewater treatment was studied. Two different sequence batch reactors (SBR) were operated at 26 °C and 32 °C. The relationship between temperature and the concentration of free ammonia (FA) and free acid nitrite (FNA) was investigated. A stable PN process was achieved in the 32 °C reactor when the influent ammonium concentration was lower than 150 mg-N/L. In contrast, the PN process in the 26 °C reactor had a higher nitrite accumulation rate (NAR) and ammonium removal efficiency (ARE) when the influent ammonia concentration was increased to more than 150 mg-N/L. Then three different ranges of the K/A ratio were applied to an SBR reactor. In the K/A range of 2.48~1.65, the SBR reactor achieved the highest NAR ratio (75.78%). This ratio helps to achieve the appropriate level of alkalinity to maintain a stable pH and provide a sufficient amount of inorganic carbon source for the activity of microorganisms. At the same time, FA and FNA values also reached the threshold to inhibit nitrite-oxidizing bacteria (NOB) without a significant effect on ammonia-oxidizing bacteria (AOB). Results showed that the control of temperature and K/A ratio during the start-up period may be important in establishing a stable and steady PN process for the treatment of domestic wastewater.
The manufacturing of sintered bricks from clay and red mud derived from the alumina processing plant
Ngoc Tuyen Tran,Duc Vu Quyen Nguyen,Van Minh Hai Ho,Xuan Tin Dang,Ngoc Quang Tran 한양대학교 청정에너지연구소 2017 Journal of Ceramic Processing Research Vol.18 No.5
In this study, the manufacturing of sintered bricks from clay and red mud was presented. The initial materials and obtainedbricks were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope(TEM), X-ray fluorescence (XRF), and differential scanning calorimetry-thermal gravimetry (DSC-TG). The compressivestrength, water absorption, bulk density and sintering shrinkage of sintered bricks were performed. The effects of componentsof raw materials, sintering temperature and time on physico-mechanical properties of the products was investigated. Theresults showed that the bricks prepared at 1000 oC for 1 hr with raw material containing up to 50% of red mud providedexcellent physico-mechanical properties. The obtained brick met the Vietnam standard VS1451-1998 and was satisfied theconstruction material requirements that were safe to human’s health and friendly with environment in terms of alkalineleaching and radioactivity indexes.
Dynamic stability of cholesterol and desmosterol in human milk from four asian countries
김지은,My Tuyen Thi Nguyen,김용기,정지아,Dan Li,Mai Xuan Hong To,Huynh Khanh Trang Nguyen,Beenish Israr,Thanh Van Le,안현주,김재한 한국식품과학회 2022 Food Science and Biotechnology Vol.31 No.12
Cholesterol is one of the functional nutrients in human milk, which is indispensable for infant growth. In this study, the concentration of cholesterol and desmosterol in human milk from four Asian countries (n = 578), including Korea, China, Vietnam, and Pakistan, were investigated. The average cholesterol concentrations of Korea and China were similar ranging between 90.2–91.6 mg/L, but those from Vietnam and Pakistan were higher at 113.8 and 175.7 mg/L, respectively. The relative standard deviations were 31–36%, except for Pakistan (51%), showing a broad distribution of 48 to 612 mg/L. Desmosterol concentrations were similar, ranging between 11.2 and 12.8 mg/L except for Pakistan, which was lower than other countries at 9.4 mg/L. In addition, the cholesterol and desmosterol concentrations during the lactation periods were not significantly different in all four Asian countries. Mothers’ BMI did not significantly impact the cholesterol and desmosterol concentration in maternal milk within the same country.
Line Impedance Estimation Based Adaptive Droop Control Method for Parallel Inverters
Le, Phuong Minh,Pham, Xuan Hoa Thi,Nguyen, Huy Minh,Hoang, Duc Duy Vo,Nguyen, Tuyen Dinh,Vo, Dieu Ngoc The Korean Institute of Power Electronics 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.1
This paper presents a new load sharing control for use between paralleled three-phase inverters in an islanded microgrid based on the online line impedance estimation by the use of a Kalman filter. In this study, the mismatch of power sharing when the line impedance changes due to temperature, frequency, significant differences in line parameters and the requirements of the Plug-and-Play mode for inverters connected to a microgrid has been solved. In addition, this paper also presents a new droop control method working with the line impedance that is different from the traditional droop algorithm when the line impedance is assumed to be pure resistance or pure inductance. In this paper, the line impedance estimation for parallel inverters uses the minimum square method combined with a Kalman filter. In addition, the secondary control loops are designed to restore the voltage amplitude and frequency of a microgrid by using a combined nominal value SOGI-PLL with a generalized integral block and phase lock loop to monitor the exact voltage magnitude and frequency phase at the PCC. A control model has been simulated in Matlab/Simulink with three voltage source inverters connected in parallel for different ratios of power sharing. The simulation results demonstrate the accuracy of the proposed control method.
Line Impedance Estimation Based Adaptive Droop Control Method for Parallel Inverters
Phuong Minh Le,Xuan Hoa Thi Pham,Huy Minh Nguyen,Duc Duy Vo Hoang,Tuyen Dinh Nguyen,Dieu Ngoc Vo 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.1
This paper presents a new load sharing control for use between paralleled three-phase inverters in an islanded microgrid based on the online line impedance estimation by the use of a Kalman filter. In this study, the mismatch of power sharing when the line impedance changes due to temperature, frequency, significant differences in line parameters and the requirements of the Plug-and-Play mode for inverters connected to a microgrid has been solved. In addition, this paper also presents a new droop control method working with the line impedance that is different from the traditional droop algorithm when the line impedance is assumed to be pure resistance or pure inductance. In this paper, the line impedance estimation for parallel inverters uses the minimum square method combined with a Kalman filter. In addition, the secondary control loops are designed to restore the voltage amplitude and frequency of a microgrid by using a combined nominal value SOGI-PLL with a generalized integral block and phase lock loop to monitor the exact voltage magnitude and frequency phase at the PCC. A control model has been simulated in Matlab/Simulink with three voltage source inverters connected in parallel for different ratios of power sharing. The simulation results demonstrate the accuracy of the proposed control method.
Han Thi Vo,Tien Duc Dao,Tuyen Van Duong,Tan Thanh Nguyen,Binh Nhu Do,Tinh Xuan Do,Khue Minh Pham,Vinh Hai Vu,Linh Van Pham,Lien Thi Hong Nguyen,Lan Thi Huong Le,Hoang Cong Nguyen,Nga Hoang Dang,Trung 질병관리청 2024 Osong Public Health and Research Persptectives Vol.15 No.1
Objectives: The incidence of posttraumatic stress disorder (PTSD) has increased, particularly among individuals who have recovered from coronavirus disease 2019 (COVID-19) infection. Health literacy is considered a “social vaccine” that helps people respond effectively to the pandemic. We aimed to investigate the association between long COVID-19 and PTSD, and to examine the modifying role of health literacy in this association.Methods: A cross-sectional study was conducted at 18 hospitals and health centers in Vietnam from December 2021 to October 2022. We recruited 4,463 individuals who had recovered from COVID-19 infection for at least 4 weeks. Participants provided information about their sociodemographics, clinical parameters, health-related behaviors, health literacy (using the 12-item short-form health literacy scale), long COVID-19 symptoms and PTSD (Impact Event Scale-Revised score of 33 or higher). Logistic regression models were used to examine associations and interactions.Results: Out of the study sample, 55.9% had long COVID-19 symptoms, and 49.6% had PTSD. Individuals with long COVID-19 symptoms had a higher likelihood of PTSD (odds ratio [OR], 1.68; 95% confidence interval [CI], 1.63–2.12; p<0.001). Higher health literacy was associated with a lower likelihood of PTSD (OR, 0.98; 95% CI, 0.97–0.99; p=0.001). Compared to those with long COVID-19 symptoms and the lowest health literacy score, those with long COVID-19 symptoms and a 1-point health literacy increment had a 3% lower likelihood of PTSD (OR, 0.97; 95% CI, 0.96–0.99; p=0.001).Conclusion: Health literacy was found to be a protective factor against PTSD and modified the negative impact of long COVID-19 symptoms on PTSD.