Removal of nutrients and organic pollutants from domestic wastewater treatment by sponge-based moving bed biofilm reactor

Huynh Tan Nhut,Nguyen Tri Quang Hung,Tran Cong Sac,Nguyen Huynh Khanh Bang,Tran Quang Tri,Nguyen Trung Hiep,Nguyen Minh Ky 대한환경공학회 2020 Environmental Engineering Research Vol.25 No.5

This study evaluates the efficiency of domestic wastewater treatment via Sponge-Based Moving Bed Biofilm Reactor (S-MBBR). The laboratory-based treatment plan uses polyurethane sponge with a specific surface area was 260 ㎡/㎥ as a carrier. The treatment plan operated under four different organic load rate: OLR1 = 0.4 ㎏ BOD/㎥.day; OLR2 = 0.6 ㎏ BOD/㎥.day; OLR3 = 0.8 ㎏ BOD/㎥.day; and OLR4 = 1.0 ㎏ BOD/㎥.day. During 80 d of the experiment, the highest treatment efficiency was at the organic load rate of 0.4 ㎏ BOD/㎥.day, with COD, SS, TN and TP were found to be 85.0 ± 12.9%, 85.7 ± 5.3%, 68.9 ± 1.7%, and 40.3 ± 0.2%, respectively. In which, the influent SS concentration were from 117.3 to 126.0 ㎎/L, the effluent concentration were in ranged 18.0 to 34.22 ㎎/L, respectively. The values of influent and effluent COD were 298.8 ± 12.88 and 44.8 ± 3.78 ㎎/L in turn. The OLR1 influent TN, TP concentrations were respectively 47.9 ± 2.11 and 3.6 ± 0.15 ㎎/L; the effluent TN, TP concentration were 14.9 ± 0.18 and 2.2 ± 0.06 ㎎/L, respectively. The study suggests that the effluent is within the allowable limits of National technical regulation on domestic wastewater (Column B1), indicating the applicability of S-MBBR for the domestic wastewater treatment plant.

A study on emission and fuel consumption of motorcycles in idle mode and the impacts on air quality in Hanoi, Vietnam

Yen-Lien T. Nguyen,Anh-Tuan Le,Khanh Nguyen Duc,Vinh Nguyen Duy,Cong Doan Nguyen 서울시립대학교 도시과학연구원 2021 도시과학국제저널 Vol.25 No.4

This study aims to develop the models of emission and fuel consumption during idling of motorcycles (MCs) in Hanoi, including the unsteady and steady idling stages. Five MC models commonly used in Hanoi were selected to measure the instantaneous emission and fuel consumption rates under the controlled conditions at the laboratory conditions. The instantaneous emission and fuel consumption models during idling were developed for the test MCs in the unsteady idling stage. The R2 of obtained models are higher than 0.9. The average emission and fuel consumption rates in the steady idling stages were determined. The average idling emissions of pollutants CO, CO2, HC and NOx were 60.9, 534.3, 10.3 and 1.8 g/h, respectively. The average fuel loss during idling is around 180 g/h. The emission released from the MC fleet in Hanoi during idling was estimated for the year 2018. The total idling emissions from the MC fleet of 3.9 million vehicles in the year 2018 of CO, CO2, HC and NOx were 6.5, 57.1, 1.1 and 0.2 kt, respectively. The total fuel loss during idling of the MC fleet in 2018 was ∼19.3 kt. The air pollutants eliminated in the idle mode as CO, CO2, HC and NOx contributed 2.23%, 3.19%, 1.14% and 1.03%, respectively, of the total emission from the MC fleet in Hanoi.

Effects of Job Satisfaction on Organizational Commitment and Turnover Intention Among Vietnamese Employees in Foreign Direct Investment Enterprises

Thi Phuong Diu TRAN(Thi Phuong Diu TRAN ),Thi Van Khanh NGUYEN(Thi Van Khanh NGUYEN ),Thanh Quang DO3(Thanh Quang DO3 ),Cong Nghiep NGUYEN(Cong Nghiep NGUYEN ),Thu Thuy LUONG(Thu Thuy LUONG ) 한국유통과학회 2022 유통과학연구 Vol.20 No.10

Purpose: This article focuses on exploring the associations between job satisfaction, organizational commitment, and turnover intention. Specifically, this study estimates the impacts of Vietnamese employees’ job satisfaction on their organizational commitment and turnover intention in FDI enterprises. Research design, data and methodology: The measures are adapted from previous studies to develop a questionnaire with a seven-point Likert scale. The dataset is directly collected from 227 respondents who are employees at FDI enterprises situated in the North of Vietnam. The dataset is analyzed by quantitative approaches using SPSS 24.0 and AMOS 24.0. Results: The results show that while turnover intention is positively correlated with monthly income, it is negatively correlated with job satisfaction and organizational commitment. Also, organizational commitment is positively associated with job satisfaction among employees at FDI enterprises in Vietnam. Conclusions: The findings of this study will serve as useful references for administrators of FDI enterprises and policymakers to promote employees’ job satisfaction and retain skilled employees.

Understanding the COVID-19 Infodemic: Analyzing User-Generated Online Information During a COVID-19 Outbreak in Vietnam

Ha-Linh Quach,Thai Quang Pham,Ngoc-Anh Hoang,Dinh Cong Phung,Viet-Cuong Nguyen,Son Hong Le,Thanh Cong Le,Dang Hai Le,Anh Duc Dang,Duong Nhu Tran,Nghia Duy Ngu,Florian Vogt,Cong-Khanh Nguyen 대한의료정보학회 2022 Healthcare Informatics Research Vol.28 No.4

Objectives: Online misinformation has reached unprecedented levels during the coronavirus disease 2019 (COVID-19) pandemic. This study analyzed the magnitude and sentiment dynamics of misinformation and unverified information about public health interventions during a COVID-19 outbreak in Da Nang, Vietnam, between July and September 2020. Methods: We analyzed user-generated online information about five public health interventions during the Da Nang outbreak. We compared the volume, source, sentiment polarity, and engagements of online posts before, during, and after the outbreak using negative binomial and logistic regression, and assessed the content validity of the 500 most influential posts. Results: Most of the 54,528 online posts included were generated during the outbreak (n = 46,035; 84.42%) and by online newspapers (n = 32,034; 58.75%). Among the 500 most influential posts, 316 (63.20%) contained genuine information, 10 (2.00%) contained misinformation, 152 (30.40%) were non-factual opinions, and 22 (4.40%) contained unverifiable information. All misinformation posts were made during the outbreak, mostly on social media, and were predominantly negative. Higher levels of engagement were observed for information that was unverifiable (incidence relative risk [IRR] = 2.83; 95% confidence interval [CI], 1.33–0.62), posted during the outbreak (before: IRR = 0.15; 95% CI, 0.07–0.35; after: IRR = 0.46; 95% CI, 0.34-0.63), and with negative sentiment (IRR = 1.84; 95% CI, 1.23–2.75). Negatively toned posts were more likely to be misinformation (odds ratio [OR] = 9.59; 95% CI, 1.20–76.70) or unverified (OR = 5.03; 95% CI, 1.66–15.24). Conclusions: Misinformation and unverified information during the outbreak showed clustering, with social media being particularly affected. This indepth assessment demonstrates the value of analyzing online “infodemics” to inform public health responses.

Biodegradable oligo(amidoamine/β-amino ester) hydrogels for controlled insulin delivery

Nguyen, Minh Khanh,Huynh, Cong Truc,Gao, Guang Hui,Kim, Ji Hyun,Huynh, Dai Phu,Chae, Su Young,Lee, Kang Choon,Lee, Doo Sung The Royal Society of Chemistry 2011 Soft matter Vol.7 No.6

<P>An injectable biodegradable hydrogel system based on oligo(amidoamine/β-amino ester) (OAAAE) was designed and synthesized for controlled release of insulin under the physiological conditions. OAAAE was prepared in one step <I>via</I> the Michael-addition oligomerization of the secondary aminegroups of 4,4-trimethylene dipiperidine (TMDP) with the vinyl groups of 1,8-octylene diacrylamide (ODA) and 1,6-hexane diol diacrylate (HDA). The formed oligomer was characterized by <SUP>1</SUP>H NMR and gel permeation chromatography (GPC). OAAAE in aqueous solution (20 wt%) underwent a gel–sol transition in the pH range of 6.8–7.4. A complex hydrogel was formed when mixinginsulin with the oligomer solution followed by increasing pH and temperature. Degradation of the hydrogel, influence of insulin on gel phase and gel strength, <I>in vitro</I> cytotoxicity of OAAAE, <I>in vitro</I> and <I>in vivo</I> release of insulin from the complex hydrogel were investigated. Furthermore, the <I>in vivo</I> release profile of insulin from the complex hydrogel was compared with that from the neutral hydrogel.</P> <P>Graphic Abstract</P><P>Controlled protein release using injectable and biodegradable oligomer hydrogel. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c0sm01285h'> </P>

Sustained delivery of doxorubicin using biodegradable pH/temperature-sensitive poly(ethylene glycol)-poly(β-amino ester urethane) multiblock copolymer hydrogels

Huynh, Cong Truc,Nguyen, Minh Khanh,Kim, Ji Hyun,Kang, Seong Woo,Kim, Bong Sup,Lee, Doo Sung Royal Society of Chemistry 2011 Soft matter Vol.7 No.10

<P>Polymers containing amino urethane groups have great potential as polymeric hydrogel carriers for the delivery of drugs/proteins because of their non-toxicity and ability to form hydrogen bonds and ionic interactions with biomolecules. However, the reported gels have high molecular weights and/or are non-biodegradable or showed fast degradation. This study examined a series of low molecular weight, biodegradable pH/temperature-sensitive multiblock copolymer hydrogels composed of poly(ethylene glycol) (PEG) and poly(β-amino ester urethane) (PAEU) and their potential appication for drug sustained release. The copolymers were synthesized and characterized by <SUP>1</SUP>H and <SUP>13</SUP>C NMR, Fourier transform infrared spectroscopy and gel permeation chromatography. Aqueous solutions of the copolymer showed a gel-to-sol phase transition as a function of temperature in the pH range of 6.8–7.6. The gel window covered the physiological conditions (37 °C, pH 7.4). The gel region could be controlled by changing PEG/PAEU ratio, copolymer solution concentration and PEG molecular weight. A gel formed rapidly <I>in situ</I> after injecting the copolymer solution subcutaneously into SD rats. The non-cytotoxicity of this hydrogel was confirmed by <I>in vitro</I> cytotoxicity test and the <I>in vitro</I> release of doxorubicin from this hydrogel was sustained for more than 5 weeks. This novel injectable biodegradable pH/temperature-sensitive hydrogels can be a potential candidate for drugs carrier.</P> <P>Graphic Abstract</P><P>A series of poly(β-amino ester urethane)-based copolymer hydrogel was synthesized and examined as a non-cytotoxic, injectable, biodegradable and pH/temperature-sensitive system for long-term sustained release of doxorubicin. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c1sm05080j'> </P>

Dually cationic and anionic pH/temperature-sensitive injectable hydrogels and potential application as a protein carrier

Huynh, Cong Truc,Nguyen, Minh Khanh,Lee, Doo Sung The Royal Society of Chemistry 2012 Chemical communications Vol.48 No.89

<P>Novel copolymers containing both anionic and cationic pH-sensitive moieties were reported. These amphoteric copolymers exhibited special closed-loop reversible sol–gel–sol phase transitions in response to both pH and temperature.</P> <P>Graphic Abstract</P><P>Biodegradable amphoteric PUASM block copolymers exhibited specific closed-loop reversible sol–gel–sol phase transition in response to temperature and pH. The copolymer aqueous solutions exist at both mildly acidic (A) and basic (B) pH but turn into a gel at neutral pH (C). <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2cc36134e'> </P>

Biodegradable star-shaped poly(ethylene glycol)-poly(β-amino ester) cationic pH/temperature-sensitive copolymer hydrogels

Huynh, Cong Truc,Nguyen, Minh Khanh,Huynh, Dai Phu,Lee, Doo Sung Springer-Verlag 2011 Colloid and polymer science Vol.289 No.3

pH- and Temperature-Sensitive PCL-Grafted Poly(β-amino ester)- Poly(ethylene glycol)-Poly(β-amino ester) Copolymer Hydrogels

Yongtai Zheng,Minh Khanh Nguyen,Chaoliang He,Cong Truc Huynh,이두성 한국고분자학회 2010 Macromolecular Research Vol.18 No.11

A series of poly(ε-caprolactone)-grafted poly(β-amino ester)-poly(ethylene glycol)-poly(β-amino ester)((PAE-g-PCL)-PEG-(PAE-g-PCL)) copolymers were designed and synthesized for use in injectable pH- and temperature-sensitive hydrogels. First, PEG diacrylate was synthesized and used as a macroinitiator, and the chain was extended by 4,4 trimethylene dipiperidine (TMDP), 3-amino-1-propanol and diacrylate monomers (1,4-butanediol diacrylate (BDA), and 1,6-hexanediol diacrylate (HDA)) to obtain the triblock copolymers (PAE-PEG-PAE). Poly (ε-caprolactone) was then grafted to the pendant OH groups of the resulting PAE-PEG-PAE by ring opening polymerization. The PAE-PEG-PAE and (PAE-g-PCL)-PEG-(PAE-g-PCL) copolymers were characterized by 1H nuclear magnetic resonance (NMR) spectroscopy and gel permeation chromatography. The phase diagram was measured using the tube inverting method. At pH 6.6 or higher, the (PAE-g-PCL)-PEG-(PAE-g-PCL) copolymer solutions (30 wt%) displayed sol-gel-sol transitions with increasing temperature. The viscosity of the graft copolymer solutions was determined as a function of temperature by dynamic mechanical analysis. In addition, after the subcutaneous injection of the polymer solution (30 wt%, pH 6.4) into a rat, a gel formed within a short time, suggesting biomedical applications.

Investigation of Extruded Endwall on Heat Transfer Characteristics of Channel with Staggering Pin-fins

Van-Hoang Tran,Thanh-Huan Nguyen,Frédéric Plourde,Khanh-Duy Cong Do,Duy-Hung Chung,Cong-Truong Dinh,Gia-Diem Pham 한국유체기계학회 2023 International journal of fluid machinery and syste Vol.16 No.2

In order to increase turbine efficiency while retaining structural integrity, modern jet engines need an effective cooling system. Pin-fin arrays play a significant role in the internal cooling system of the turbine blade. In examining the efficacy of cooling techniques using pin-fins, the other papers focus on pin-fin configurations. In contrast, the current study is a step toward optimizing cooling cascade endwalls for better maneuvering and reservation of vortices, which leads to more considerable heat transfer near the endwalls. This study examines the flow field and heat transfer of roughed endwall in the pin-fin channel, including varieties with flat endwall and extruded endwall. The heat transfer of the channel and pressure drop properties of the extruded endwall case are quantitatively assessed to contrast with those of the flat endwalls scenario for an intake Reynolds number range of 7400 to 36000. The leading and trailing surfaces of the channel are divided into five streamwise regions to understand better how well the pin-fins and endwalls transmit heat. The results show that the new endwall construction significantly increases the high heat transfer zones around the pin-fins compared to the flat endwall scenario. In the meantime, the heat transfer of the channel to the pin-fins is enhanced by the modified endwall configuration. The redesigned endwall outperformed the basic case regarding the HTEI, rising by 15.9%. It is found that the friction factor of the new design is increased due to the narrowing channel. However, due to their much higher heat transfer capacity, the HTEI of extruded endwall is up to 41.5% higher than the HTEI of the channel with flat endwalls. These results demonstrate that the heat transfer properties of pin-fins can be significantly improved by optimizing endwall design.