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In-situ Removal of Nitrogen and Phosphorus for the Prevention of Harmful Algal Blooms in River
( Dang Thanh Loan ),이철균 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.1
Harmful algal blooms (HABs) due to water eutrophication are becoming more serious in Korean rivers. There are many attempts to prevent HABs and the most effective method is to reduce nitrogen and phosphorus load from point and non-point source. However, this method is hard to apply in large area and is very expensive. On the other hand, microalgae have been utilized in wastewater treatment to reduce nitrogen and phosphorus level. In this study, ability to remove nitrogen and phosphorus in artificial river water by Euglena gracilis in permeable reactor was investigated. Permeable reactor keeps microalgae cells inside while let nutrients in artificial river water diffuse in for the growth of Euglena. The highest growth rate of Euglena in permeable reactor is 1 d-1at day 3. It is concluded that cultivating microalgae in permeable reactor could be an effective method to reduce nitrogen and phosphorus levels in river water.
Using glycerol in mixotrophic culture of tetraselmis sp. To increase lipid productivity
( Dang Thanh Loan ),박한울,이철균 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.0
Some microalgae can grow in mixotrophic condition with higher growth rate and lipid productivity compared with photoautotrophic condition. However, mixotrophic cultures are often not cost effective. In biodiesel production via transesterification, glycerol is produced along with fatty acid methyl ester. Using glycerol from transesterification for microalgae cultivation could be a way to reduce cultivation cost. In the present study, the effect of glycerol addition on the algal biomass and fatty acids productivity in Tetraselmis sp. MBEyh04Gc, was investigated. Addition of glycerol increased biomass and lipid productivity by 36% and 56%, respectively, compared with photoautotrophic cultures. The results suggest that glycerol can be used as a supplement in the culture of Tetraselmis sp., but further studies on the effects of quality and quantity of glycerol need to be conducted for optimization of mixotrophic cultivation.
Enhancing biomass and lipid productivity of a marine microalga tetraselmis sp. With glycerol
( Dang Thanh Loan ),김필한,박한울,이철균 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.0
Microalgae are one of the promising feedstocks for biodiesel production.During biodiesel production process from microalgae, glycerol is produced as a by-product from transesterification. As biodiesel production expands, global production of glycerol will continue to increase as well,which would reduce the price of glycerol to the point when selling glycerol is not profitable. In such case, utilization of glycerol for improved microalgal biomass and fatty acid production could be a solution. In this study, glycerol was added as a supplement to cultures of a marine microalga, Tetraselmis sp. KCT12432BP to investigate its effects on algal biomass and fatty acid production, Addition of glycerol improved biomass and fatty acid productivities by 36% and 56%, respectively. In the present study, microalgae could not consume all of the glycerol provided, and as the further study, the proper amount of glycerol supplement for efficient carbon utilization and improving biomass and fatty acids productivities will be investigated.
신영숙,박한울,( Dang Thanh Loan ),이철균 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.0
Algal cultures undergo dark cycles at nights in which energy storage biochemical are consumed for respiration, resulting in loss of biomass. In this study, the effect of duration of the first photoperiod on algal biomass productivity in Tetraselmis sp. MBEyh01L was investigated. On the day of inoculation, microalgae were inoculated at three different times so that each culture would have 12, 6, and 0 hours of first light periods before the first dark cycle. Compared to the culture with 12 hours of initial light period, the algal biomass productivity was reduced by 35% when the culture began with a dark period while similar biomass productivity was obtained with 6 hour of initial photoperiod. The results of this study suggest that the exposure to light on the inoculation day can be a significant factor impacting the overall biomass productivity in algal cultivation. Therefore, the time for inoculation/harvest should be carefully determined to achieve high algal biomass productivity.
Critical Factors of Subcontractor Evaluation and Selection: A Case Study in Vietnam
VO, Khoa Dang,PHAM, Cuong Phu,PHAN, Phuong Thanh,VU, Ngoc Bich,DUONG, My Tien Ha,LE, Loan Phuc,NGUYEN, Quyen Le Hoang Thuy To Korea Distribution Science Association 2021 The Journal of Asian Finance, Economics and Busine Vol.8 No.3
A contractor or a main contractor is a company with full capacity to construct all project's works for the owner. A subcontractor is an organization that works with the main contractor to execute and complete work packages for the project. Selecting an effective subcontractor will help the efficiency and success of any projects in the construction industry. Therefore, this study identified subcontractor evaluation factors in Vietnam by collecting questionnaire survey data from engineers and staffs in the construction industry project environment. An exploratory factor analysis (EFA) was then performed to identify the critical factors when evaluating and selecting the subcontractor in construction projects. Moreover, when considering the impact level in terms of the average value, the research results showed that the most critical concern was the subcontractor's reputation. Furthermore, the top five factors affecting the sub-contractor evaluation and selection are (i) reputation, (ii) price, (iii) construction techniques, (iv) ability to implement projects according to commitments, and (v) subcontractor competence (the team of workers, technician staff, engineers with full capacity according to regulations). These research results provide an overall perspective that will help main contractors develop suitable subcontractors' evaluation and selection factors in their projects in the construction industry.
Chien Minh Tran,Ngoc Thi‑Thanh Nguyen,Minh Hieu Ho,Vinh Khanh Doan,Khanh Loan Ly,Nhi Ngoc‑Thao Dang,Nam Minh‑Phuong Tran,Hoai Thi‑Thu Nguyen,Long Phuoc Truong,Thai Minh Do,Quyen Ngoc Tran,Hien Quoc Ng 한국섬유공학회 2023 Fibers and polymers Vol.24 No.1
In this study, we proposed a straightforward electrospun polycaprolactone (PCL) loaded with silver nanoparticles (SNPs)membrane fabrication process, in which SNPs were directly synthesized from silver nitrate (AgNO3) in PCL–acetone mixtureby gamma irradiation. The insolubility of AgNO3in PCL solution was solved using an auxiliary dimethyl sulfoxide solvent. As a physical approach, gamma rays readily converted silver ions into SNPs without the addition of harmful reductionagents, which reduced the cytotoxicity of the synthesized material. By avoiding some processes such as purification, solventremoval, or redispersion of SNPs, this method was more time-saving compared to other related studies. SNPs formation wasconfirmed by both UV–Visible spectrum (UV–Vis) and X-ray diffraction analysis. Scanning electron microscopy (SEM)revealed that the addition of SNPs significantly reduced the fiber diameter of PCL–Ag membranes compared to that of rawPCL. Uniform spherical-shaped SNPs incorporated in PCL fibers were observed under transmission electron microscopy(TEM). The tensile test showed that the electrospun PCL–Ag membranes exhibited good mechanical characteristics. Moistureeasily penetrated the porous microstructure of PCL–Ag, facilitating wound humidity regulation. Inductively coupledplasma-mass spectroscopy (ICP-MS) was employed to study the release profiles of SNPs at different time intervals. Overall,the PCL–Ag 500 ppm sample exerted excellent antibacterial activity against Pseudomonas aeruginosa and Staphylococcusaureus strains and low in vitro cytotoxicity.