318 results on '"Changsoo Lee"'
Search Results
202. Mycelial cultivation of Phellinus linteus using cheese-processing waste and optimization of bioconversion conditions
- Author
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Seungyong Lee, Seokhwan Hwang, Kyungjin Cho, and Changsoo Lee
- Subjects
Environmental Engineering ,Bioconversion ,Bioengineering ,Waste Disposal, Fluid ,Microbiology ,chemistry.chemical_compound ,Cheese ,Botany ,Environmental Chemistry ,Growth rate ,Lactose ,Growth medium ,Mycelium ,Sewage ,biology ,Basidiomycota ,Temperature ,Substrate (chemistry) ,Hydrogen-Ion Concentration ,Biodegradation ,biology.organism_classification ,Pollution ,Culture Media ,Phellinus linteus ,chemistry ,Waste disposal ,Nuclear chemistry - Abstract
A medicinal mushroom, Phellinus linteus, was successfully cultivated using a cheese-processing waste, whey, and the optimal bioconversion conditions for the maximum mycelial growth rate was also estimated through solid-state cultivation experiments. Response surface analysis with a face-centered design (center point replication = 5) was applied to statistically approximate the simultaneous effects of the three variables, i.e., substrate concentration (10–30 g lactose l−1), temperature (20–30°C), and pH (4–6), on the mycelial growth rate of P. linteus. The following is a partial cubic model where η is the mycelial growth rate (K r ) and x k is the corresponding variable term (k = substrate concentration, temperature, and pH in order): η = −23.8 + 8.67 × 10−2 x 1 + 1.48x 2 + 1.77x 3 + 8.00 × 10−4 x 1 x 2 + 7.25 × 10−2 x 1 x 3 + 5.13 × 10−2 x 2 x 3 −1.28 × 10−2 x 1 2 –3.18 × 10−2 x 2 2 . −2.64 × 10−1 x 3 2 −3.28 × 10−3 x 1 x 2 x 3 + 4.68 × 10−4 x 1 2 x 2. The produced response surface model proved to be significant (r 2 > 0.99, P-value
- Published
- 2010
203. Photocatalytic activities of TiO2 thin films prepared on Galvanized Iron substrate by plasma-enhanced atomic layer deposition
- Author
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Jungwon Kim, Du Hwan Jo, Changsoo Lee, Wonyong Choi, Hyungjun Kim, Gil Ho Gu, and Chan Gyung Park
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Anatase ,Materials science ,business.industry ,Metals and Alloys ,chemistry.chemical_element ,Surfaces and Interfaces ,Substrate (electronics) ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,Atomic layer deposition ,Optics ,Chemical engineering ,chemistry ,Superhydrophilicity ,Titanium dioxide ,Materials Chemistry ,Photocatalysis ,Thin film ,business ,Titanium - Abstract
Titanium dioxide (TiO 2 ) thin films were prepared on Galvanized Iron (GI) substrate by plasma-enhanced atomic layer deposition (PE-ALD) using tetrakis-dimethylamido titanium and O 2 plasma to investigate the photocatalytic activities. The PE-ALD TiO 2 thin films exhibited relatively high growth rate and the crystal structures of TiO 2 thin films depended on the growth temperatures. TiO 2 thin films deposited at 200 °C have amorphous phase, whereas those with anatase phase and bandgap energy about 3.2 eV were deposited at growth temperature of 250 °C and 300 °C. From contact angles measurement of water droplet, TiO 2 thin films with anatase phase and Activ™ glass exhibited superhydrophilic surfaces after UV light exposure. And from photo-induced degradation test of organic solution, anatase TiO 2 thin films and Activ™ glass decomposed organic solution under UV illumination. The anatase TiO 2 thin film on GI substrate showed higher photocatalytic efficiency than Activ™ glass after 5 h UV light exposure. Thus, we suggest that the anatase phase in TiO 2 thin film contributes to both superhydrophilicity and photocatalytic decomposition of 4-chlorophenol solution and anatase TiO 2 thin films are suitable for self-cleaning applications.
- Published
- 2010
204. Quantitative and qualitative transitions of methanogen community structure during the batch anaerobic digestion of cheese-processing wastewater
- Author
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Seokhwan Hwang, Changsoo Lee, Vincent O'Flaherty, Seung Gu Shin, and Jaai Kim
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DNA, Bacterial ,Molecular Sequence Data ,Population ,Industrial Waste ,Acetates ,Nucleic Acid Denaturation ,DNA, Ribosomal ,Polymerase Chain Reaction ,Applied Microbiology and Biotechnology ,Water Purification ,Biogas ,Cheese ,RNA, Ribosomal, 16S ,Cluster Analysis ,Food Industry ,Anaerobiosis ,Food science ,education ,Phylogeny ,Methanosarcinaceae ,education.field_of_study ,Chromatography ,Bacteria ,biology ,Fatty Acids ,Biodiversity ,Sequence Analysis, DNA ,General Medicine ,biology.organism_classification ,Methanogen ,Anaerobic digestion ,Microbial population biology ,Electrophoresis, Polyacrylamide Gel ,Methanomicrobiales ,Methane ,Temperature gradient gel electrophoresis ,Biotechnology - Abstract
Qualitative and quantitative shifts in methanogen community structure, associated with process performance data, were investigated during the batch anaerobic digestion of a cheese-processing wastewater, whey permeate. Denaturing gradient gel electrophoresis (DGGE) and real-time PCR techniques were applied to obtain qualitative and quantitative microbial data sets, respectively, based on methanogen 16S rRNA genes. Throughout the operation, dynamic variations in both qualitative and quantitative community structures were observed, with repeated shifts in dominance between the aceticlastic Methanosarcinaceae (suggested mainly by the detection of a Methanosarcina-like population) and the hydrogenotrophic Methanomicrobiales (suggested mainly by the detection of a Methanofollis-like population). This trend corresponded well to the diauxic utilization of acetate and longer-chain fatty acids (C(3)-C(6)), mainly propionate. Joint-plot non-metric multidimensional scaling (NMS) analysis demonstrated that the qualitative and quantitative community shifts had significant correlations with the composition of residual organic acids and the methane production rate, respectively. This suggests the potential use of microbial community shift analysis as an indicative tool for diagnosing anaerobic digestion processes. The results suggest that more attention should be directed to quantitative, as well as qualitative, approaches for a better understanding of anaerobic digestion, particularly in terms of biogas production efficiency, under dynamic and transitional conditions.
- Published
- 2010
205. Solar Water Splitting: Directly Assembled 3D Molybdenum Disulfide on Silicon Wafer for Efficient Photoelectrochemical Water Reduction (Adv. Sustainable Syst. 3/2018)
- Author
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Changyeon Kim, Woonbae Sohn, Sungwoo Kang, Jun Min Suh, Seokhoon Choi, Moon-Ho Jo, Dinsefa Mensur Andoshe, Cheon Woo Moon, Seunghee Lee, Seungwu Han, Gangtae Jin, Ki Chang Kwon, Jong Kyu Kim, Jaehyun Park, Ho Won Jang, Hoseok Heo, and Changsoo Lee
- Subjects
Reduction (complexity) ,chemistry.chemical_compound ,Materials science ,chemistry ,Chemical engineering ,Renewable Energy, Sustainability and the Environment ,Wafer ,Molybdenum disulfide ,General Environmental Science ,Solar water - Published
- 2018
206. Investigation of Water Quality and Hydrological Characteristic When Red Tide Develop in the Mouth of Hyeongsan River
- Author
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Changsoo Lee
- Subjects
Hydrology ,Water area ,Red tide ,Environmental science ,Stage (hydrology) ,Water quality ,Precipitation ,Surface runoff - Abstract
To investigate the influence of water area calmness on the red tide development, runoff phenomena due to antecedent precipitation of red tide development day were analyzed. There were examined the water quality variation properties at about the same time of the red tide develop. The red tide was developed when the stage and discharge nearly had not changed. It was estimated that the stability of particle behavior in the mouth of river effected on the red tide develop. Also, the concentrations of were increased about 241~629% when the red tide developed.
- Published
- 2009
207. Quantitative and qualitative analysis of methanogenic communities in mesophilically and psychrophilically cultivated anaerobic granular biofilims
- Author
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Fabio Alexandre Chinalia, Joe O’Reilly, Vincent O'Flaherty, Changsoo Lee, Thérèse Mahony, and Gavin Collins
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Electrophoresis ,Environmental Engineering ,Methanogenesis ,Methanogenic community ,Biology ,Bioreactors ,Biogas ,RNA, Ribosomal, 16S ,Bioreactor ,Anaerobiosis ,DGGE ,Waste Management and Disposal ,Phylogeny ,Water Science and Technology ,Civil and Structural Engineering ,Low-temperature anaerobic digestion ,Granular biofilm ,Ecological Modeling ,Environmental engineering ,Pulp and paper industry ,Quantitative real-time PCR ,Archaea ,Pollution ,Cold Temperature ,Oxygen ,Anaerobic digestion ,Wastewater ,Biofilms ,Sewage treatment ,Methane ,Anaerobic exercise ,Mesophile - Abstract
Anaerobic granulation describes the self-immobilisation of methanogenic consortia into dense, particulate biofilms. This procedure underpins the operation of several categories of high-rate anaerobic wastewater treatment system. Full-scale anaerobic granular sludge plants have been generally operated in the mesophilic (20-45 degrees C) or thermophilic (45-65 degrees C) temperature range. On the other hand, recent studies highlighted the economic advantages of treating wastewaters at their discharge temperatures (mostly under 18 degrees C), removing a costly heating process and increasing net biogas yield. However, as yet, relatively little information is available about the microbial behaviour and interactions in anaerobic granular sludge formed under psychrophilic conditions. To this end, and in order to provide a microbial insight into low-temperature anaerobic granulation, we monitored the changes in methanogenic community structure, associated with the changes in process performance. Three, laboratory-scale, expanded granular sludge bed (EGSB) bioreactors treating a synthetic glucose wastewater were tested at two temperatures of 37+/-1 degrees C (R1) and 15+/-1 degrees C (R2 and 3). Quantitative real-time PCR and specific methanogenic activity assays highlighted a community shift towards hydrogenotrophic methanogens, particularly the order Methanomicrobiales in the low-temperature bioreactors. Corresponding to this, denaturing gradient gel electrophoresis (DGGE) analysis identified the emergence and maintenance of a Methanocorpusculum-like organism. Our results indicate that hydrogenotrophic methanogens, particularly the Methanomicrobiales-related populations, are likely to play important roles in low-temperature anaerobic granular sludge systems. This suggests that the process efficiency could be improved by facilitating the growth and retention of this group.
- Published
- 2009
208. Unusual bacterial populations observed in a full-scale municipal sludge digester affected by intermittent seawater inputs
- Author
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Fabio Alexandre Chinalia, Jaai Kim, Changsoo Lee, Seung Gu Shin, and Seokhwan Hwang
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Bacteria ,Sewage ,biology ,Library ,Molecular Sequence Data ,Zoology ,Bacteroidetes ,Bioengineering ,16S ribosomal RNA ,biology.organism_classification ,Applied Microbiology and Biotechnology ,Microbiology ,Anaerobic digestion ,Thermotogae ,Seawater ,Seasons ,Proteobacteria ,Anaerobic exercise ,Phylogeny ,Biotechnology - Abstract
This study investigated the bacterial community of a full-scale anaerobic digester, which suffers from intermittent seawater contaminations, using 16S rRNA gene clone analysis over different seasons. Bacteroidetes, Proteobacteria, and unclassifiable bacteria were the three major bacterial groups within the clone library (a total of 290 clones). A significant portion of the total clones (29.3%) was not affiliated to any previously reported phylum, and 55.3% of the unclassifiable clones (16.9% of the total clones) showed potential relations to the species of Thermotogae, rarely present under normal mesophilic anaerobic conditions. These results suggested that the novel populations may have the potential to play an important role in anaerobic processes, particularly under abnormal environmental conditions. Additionally, statistical analysis supported that seasonal variations in influent characteristics, and potential competitions among different populations, may be related to the unusual bacterial diversity and community dynamics observed over the study period.
- Published
- 2009
209. Biodegradable meniscus screw fixation of thin flap lesion of osteochondritis dissecans
- Author
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Myungsang Moon, Chulhyung Lee, Hyunyoon Jeong, Hyeonseok Jeong, Changsoo Lee, and Jegyun Chon
- Subjects
medicine.medical_specialty ,business.industry ,Thin flap ,Right knee ,equipment and supplies ,medicine.disease ,Osteochondritis dissecans ,Surgery ,Screw fixation ,Classical type ,Lesion ,Fixation (surgical) ,medicine ,Orthopedics and Sports Medicine ,medicine.symptom ,business - Abstract
Authors reported a young adult with Guhl’s arthroscopic stage III unstable thin bony backing flap lesion (Aichroth’s extended classical type) of osteochondritis dissecans in the right knee which was successfully treated with fixation of the unstable OCD fragment utilizing the biodegradable meniscus screws, and simultaneous multiple drilling of fixated fragment. Based on the result, it is thought that the preservation of thin bony backing fragment lesion among the unstable OCD without extraction is possible by the above surgical procedure.
- Published
- 2009
210. An investigation of the excavation damaged zone at the KAERI underground research tunnel
- Author
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Sumin Jeon, Won-Jin Cho, Sangki Kwon, Changsoo Lee, and S.J. Cho
- Subjects
Empirical equations ,Engineering ,Deformation (mechanics) ,business.industry ,Radioactive waste ,Excavation ,Building and Construction ,In situ stress ,Geotechnical Engineering and Engineering Geology ,Borehole radar ,Sensitivity (explosives) ,Stress redistribution ,Geotechnical engineering ,business - Abstract
The disturbance of a rock due to a blasting impact or stress redistribution can significantly influence the overall performance of an underground excavation. In order to investigate the characteristics of the EDZ (Excavation Damaged Zone) developed during the construction of the KAERI underground research tunnel in Korea (KURT), which is an underground research tunnel for a Korean high-level radioactive waste disposal program, various in situ and laboratory tests were carried out. A Goodman jack test showed that the deformation modules were influenced by a blasting to a depth of 1.5–2 m. With empirical equations, the EDZ could be predicted as 0.3–2.3 m. The average RQD from the rock cores at 0–2 m, where the blasting impact was significant, was 17% lower than that from the deeper regions. From the laboratory tests, the EDZ size could be estimated to be around 0.9–1.5 m. The elastic modules in the EDZ were decreased by about 56%. From a borehole radar reflection survey and a subtracting technique, it was possible to detect the new reflectors generated by a tunnel blasting. By using the determined EDZ size and the properties from the laboratory and in situ tests, a sensitivity analysis was performed. From the sensitivity analysis with seven parameters, it was possible to determine that the in situ stress ratio, Young’s modules, and EDZ size were the three main parameters.
- Published
- 2009
211. Quantitative analysis of methanogenic community dynamics in three anaerobic batch digesters treating different wastewaters
- Author
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Kwanghyun Hwang, Jaai Kim, Seokhwan Hwang, Vincent O'Flaherty, and Changsoo Lee
- Subjects
Time Factors ,Environmental Engineering ,Anaerobic respiration ,Biology ,Waste Disposal, Fluid ,Water Purification ,Bioreactors ,RNA, Ribosomal, 16S ,Bioreactor ,Anaerobiosis ,Waste Management and Disposal ,Water Science and Technology ,Civil and Structural Engineering ,Bacteria ,Ecological Modeling ,Environmental engineering ,Pulp and paper industry ,biology.organism_classification ,Pollution ,Waste treatment ,Anaerobic digestion ,Biodegradation, Environmental ,Wastewater ,Sewage treatment ,Methanomicrobiales ,Methane ,Sludge - Abstract
Quantitative changes in methanogenic community structures, associated with performance data, were investigated in three anaerobic batch digesters treating synthetic glucose medium, whey permeate, and liquefied sewage sludge. All digesters were initially seeded with anaerobic sludge obtained from a local municipal wastewater treatment plant. Dynamics of methanogenic populations were monitored, at order and family levels, using real-time PCR based on the 16S rRNA gene. The molecular monitoring revealed that, in each digester, the quantitative structure of methanogenic community varied continuously over treatment time and the variation corresponded well to the changes in chemical profiles. Biphasic production of methane, associated with successive increases in aceticlastic (mainly Methanosarcinaceae) and hydrogenotrophic (mainly Methanomicrobiales) methanogenic groups, was observed in each digester. This corresponded to the diauxic utilization of acetate and longer-chain volatile fatty acids (C(3)-C(6)), mainly propionate. Additionally, the non-metric multidimensional scaling (NMDS) analysis of the quantification results demonstrated that the community shift patterns in three digesters were totally different from each other. Considering that the operating conditions in all trials were identical except substrates, the differences in quantitative shift profiles were suggested to be due to the different substrate compositions. This implied that the composition of wastewater could affect the evolution of quantitative methanogenic community structure in an anaerobic process. Overall, our results suggested that more attention to quantitative as well as qualitative approaches on microbial communities is needed for fundamental understanding of anaerobic processes, particularly under dynamic or transitional conditions.
- Published
- 2009
212. Influence of the Point Source Inflow on the Water Quality Variation in the Downstream of Hyeongsan River
- Author
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Changsoo Lee
- Subjects
Wet season ,Pollutant ,Hydrology ,Downstream (manufacturing) ,Point source ,Dry season ,medicine ,Environmental science ,Water quality ,Inflow ,Seasonality ,medicine.disease - Abstract
The influence of the point source inflow on the water quality variation in the downstream of Hyeongsan River was investigated. As the results of seasonal variation, the pollutant concentrations of dry season were 1.5-4 times higher than those of wet season. The increase rate of , , T-N, T-P due to point source were ranged to , and as the inflow of P1, P2 and P3, respectively. After P1, P2 and P3 inflow, the accumulated increase rate were 64.3%, 32.6%, 93.1% and 258.9% in , , T-N, T-P, respectively. It was found that the influence of point source inflow on the water quality in the downstream of Hyeongsan River is severe.
- Published
- 2008
213. Monitoring bacterial and archaeal community shifts in a mesophilic anaerobic batch reactor treating a high-strength organic wastewater
- Author
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Jaai Kim, Seung Gu Shin, Seokhwan Hwang, and Changsoo Lee
- Subjects
Ecology ,biology ,Ethanol fermentation ,biology.organism_classification ,Applied Microbiology and Biotechnology ,Microbiology ,Anaerobic digestion ,Clostridium ,Carbohydrate fermentation ,Fermentation ,Food science ,Bacteria ,Temperature gradient gel electrophoresis ,Mesophile - Abstract
Shifts in bacterial and archaeal communities, associated with changes in chemical profiles, were investigated in an anaerobic batch reactor treating dairy-processing wastewater prepared with whey permeate powder. The dynamics of bacterial and archaeal populations were monitored by quantitative real-time PCR and showed good agreement with the process data. A rapid increase in bacterial populations and a high rate of substrate fermentation were observed during the initial period. Growth and regrowth of archaeal populations occurred with biphasic production of methane, corresponding to the diauxic consumption of acetate and propionate. Bacterial community structure was examined by denaturing gel gradient electrophoresis (DGGE) targeting 16S rRNA genes. An Aeromonas-like organism was suggested to be mainly responsible for the rapid fermentation of carbohydrate during the initial period. Several band sequences closely related to the Clostridium species, capable of carbohydrate fermentation, lactate or ethanol fermentation, and/or homoacetogenesis, were also detected. Statistical analyses of the DGGE profiles showed that the bacterial community structure, as well as the process performance, varied with the incubation time. Our results demonstrated that the bacterial community shifted, reflecting the performance changes and, particularly, that a significant community shift corresponded to a considerable process event. This suggested that the diagnosis of an anaerobic digestion process could be possible by monitoring bacterial community shifts.
- Published
- 2008
214. Use of order-specific primers to investigate the methanogenic diversity in acetate enrichment system
- Author
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Kwanghyun Hwang, Johng-Hwa Ahn, Seung Gu Shin, Seokhwan Hwang, and Changsoo Lee
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Methanogenesis ,Molecular Sequence Data ,Population ,Bioengineering ,Methanobacteriales ,Acetates ,Euryarchaeota ,Polymerase Chain Reaction ,Applied Microbiology and Biotechnology ,Microbiology ,law.invention ,Bioreactors ,Species Specificity ,law ,Food science ,education ,Phylogeny ,Polymerase chain reaction ,DNA Primers ,education.field_of_study ,biology ,Biodiversity ,16S ribosomal RNA ,biology.organism_classification ,DNA, Archaeal ,Microbial population biology ,Electrophoresis, Polyacrylamide Gel ,Methanomicrobiales ,Temperature gradient gel electrophoresis ,Biotechnology - Abstract
The applicability of order-specific primers in minimizing the possible underestimation of microbial diversity was evaluated via denaturing gradient gel electrophoresis (DGGE) analysis of a lab-scale anaerobic digester. Initially, a population analysis with real-time quantitative PCR demonstrated the existence of three methanogenic orders--Methanobacteriales, Methanomicrobiales, and Methanosarcinales--throughout the reaction period. DGGE analyses with three pairs of order-specific primers yielded eight operational taxonomic units (OTUs), whereas DGGE analysis with two independent Archaea-specific primers identified only five. Moreover, the order-specific primers amplified at least one OTU affiliated with each order, whereas no members of Methanobacteriales or Methanomicrobiales were identified with Archaea-specific primers in most samples. These findings provide evidence that order-specific analysis can detect the diversity of methanogens in greater detail than conventional Archaea-specific analysis.
- Published
- 2008
215. In-Situ Doping during ZnO Atomic Layer Deposition
- Author
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Soon-Ju Kwon, Changsoo Lee, Sung Kyun Lee, Hyungjun Kim, S. J. Lim, and Minho Jo
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Atomic layer deposition ,In situ doping ,Materials science ,General Physics and Astronomy ,Nanotechnology ,Thin film ,Pulsed laser deposition - Published
- 2008
216. Influence of Precipitation Characteristic on the Rainfall Water Quality
- Author
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Changsoo Lee
- Subjects
Hydrology ,Asian Dust ,Environmental science ,Water quality ,Precipitation ,Turbidity ,Rainwater harvesting - Abstract
The purpose of this study was to invesitigate relationship between rainfall water quality and precipitation characteristic during the accumulated rainfall and rainless period. As the results of the analysis, rainfall water quality was improved in the rainfall duration. Correlation coefficients between rainwater quality and accumulated rainfall were except . and that between rainless period and initial rainfall water quality were . During the Asian dust event, concentration of the turbidity, BOD and electric conductivity were high. Therefore, it shows that the rainfall water quality is effected by atmospheric conditions before the rainfall events.
- Published
- 2007
217. Correlation of microbial mass with ATP and DNA concentrations in acidogenesis of whey permeate
- Author
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Changsoo Lee, Seung Gu Shin, Seokhwan Hwang, and Jaai Kim
- Subjects
Acidogenesis ,Environmental Engineering ,Microorganism ,Population ,Industrial Waste ,Bioengineering ,Waste Disposal, Fluid ,Microbiology ,chemistry.chemical_compound ,Adenosine Triphosphate ,Bioreactors ,Cheese ,Environmental Chemistry ,Mass concentration (chemistry) ,education ,Incubation ,education.field_of_study ,Chromatography ,DNA ,Biodegradation ,Milk Proteins ,Pollution ,Biodegradation, Environmental ,Whey Proteins ,Wastewater ,chemistry - Abstract
In this paper, we examine variations in the contents of ATP and DNA per unit microbial mass in an acidogenesis of whey permeate. We also introduce a novel approach to estimate microbial mass by measuring ATP and DNA when the ratios of ATP and DNA to microbial mass vary. Acidogenic experiments were performed at 35°C and pH 6.0 in batch mode. The amounts of ATP and DNA per unit microbial mass were not consistent during the incubation except during the post-decay phase. Especially within the exponential phase, each showed a 10-fold difference between maximal and minimal values. In this case, the conventional method which converts ATP or DNA concentration into microbial mass using a fixed conversion factor can give inaccurate results. While the constant ratios of 0.74 mg ATP/g VSS and 1.96 mg DNA/g VSS were determined for the post-decay phase, the ATP and DNA concentrations showed strong linear relationships with the microbial mass (r 2 = 0.99) within the ranges of 0.039–1.078 mg ATP/l and 0.075–2.080 mg DNA/l, respectively. The linear regression equations are as follows: (1) microbial mass concentration (mg/l) = 478.5 × ATP concentration (mg/l) + 293.5, (2) microbial mass concentration (mg/l) = 257.2 × DNA concentration (mg/l) + 250.4. Therefore, changes in the mass of the acidogenic population should be monitored by the combined use of the regression equations obtained in the exponential phase and the constant ratios determined in the post-decay phase. This procedure should be widely applicable to the acidogenesis of dairy processing wastewaters, especially of a highly suspended organic wastewater such as whey.
- Published
- 2007
218. GeSbTe deposition for the PRAM application
- Author
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Sangjoon Choi, Changsoo Lee, Yoonho Kang, Junghyun Lee, and Daeil Kim
- Subjects
Materials science ,Scanning electron microscope ,Annealing (metallurgy) ,Chalcogenide ,General Physics and Astronomy ,Surfaces and Interfaces ,General Chemistry ,Chemical vapor deposition ,GeSbTe ,Condensed Matter Physics ,Surfaces, Coatings and Films ,chemistry.chemical_compound ,Crystallography ,Atomic layer deposition ,chemistry ,Transmission electron microscopy ,Thin film - Abstract
GeSbTe (GST) chalcogenide thin films for the phase-change random access memory (PRAM) were deposited by an atomic layer deposition (ALD) process. New precursors for GST thin films made with an ALD process were synthesized. Among the synthesized precursors, Ge(N(CH 3 ) 2 ) 4 , Sb(N(CH 3 ) 2 ) 4 , and Te( i -Pr) 2 ( i -Pr = iso -propyl) were selected. Using the above precursors, GST thin films were deposited using an H 2 plasma-assisted ALD process. Film resistivity abruptly changed after an N 2 annealing process above a temperature of 350 °C. Cross-sectional scanning electron microscope (SEM) photographs of the GST films on the patterned substrate with aspect ratio of 7 shows that the step coverage is about 90%.
- Published
- 2007
219. Bioaugmentation of anaerobic sludge digestion with iron-reducing bacteria: process and microbial responses to variations in hydraulic retention time
- Author
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Gahyun Baek, Seung Gu Shin, Jaai Kim, and Changsoo Lee
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0301 basic medicine ,Bioaugmentation ,Hydraulic retention time ,Iron ,Microbial Consortia ,010501 environmental sciences ,Wastewater ,01 natural sciences ,Applied Microbiology and Biotechnology ,Waste Disposal, Fluid ,Biostimulation ,03 medical and health sciences ,Iron bacteria ,Bioreactors ,Food science ,Anaerobiosis ,0105 earth and related environmental sciences ,Biological Oxygen Demand Analysis ,Bacteria ,Sewage ,Chemistry ,Ecology ,Denaturing Gradient Gel Electrophoresis ,General Medicine ,Microbial consortium ,Spirochaetaceae ,Anaerobic digestion ,030104 developmental biology ,Activated sludge ,Anaerobic exercise ,Biotechnology - Abstract
Although anaerobic digestion (AD) is a widely used option to manage waste activated sludge (WAS), there are some drawbacks related to its slow reaction rate and low energy productivity. This study examined an anaerobic WAS digester, augmented with an iron-reducing microbial consortium, relative to changes in microbial community structure and process performance at decreasing hydraulic retention times (HRTs) of 20 to 10 days. The enhanced methanation performance (approximately 40 % increase in methane yield) by the bioaugmentation was sustained until the HRT was decreased to 12.5 days, under Fe(3+)-rich conditions (ferric oxyhydroxide, 20 mM Fe). Enhanced iron-reducing activity was evidenced by the increased Fe(2+) to total Fe ratio maintained above 50 % during the stable operational phases. A further decrease in HRT to 10 days resulted in a significant performance deterioration, along with a drop in the Fe(2+) to total Fe ratio to35 %, after four turnovers of operation. Prevailing existence of putative iron-reducing bacteria (IRBs) was identified by denaturing gradient gel electrophoresis (DGGE), with Spirochaetaceae- and Thauera-related organisms being dominant members, and clear dominance shifts among them with respect to decrease in HRT were observed. Lowering HRT led to evident shifts in bacterial community structure likely associated with washout of IRBs, leading to decreases in iron respiration activity and AD performance at a lower HRT. The bacterial community structure shifted dynamically over phases, and the community transitions correlated well with the changes in process performance. Overall, the combined biostimulation and bioaugmentation investigated in this study proved effective for enhanced methane recovery from anaerobic WAS digestion, which suggests an interesting potential for high-rate AD.
- Published
- 2015
220. Understanding the light soaking effect of ZnMgO buffer in CIGS solar cells
- Author
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Byung Tae Ahn, Suncheul Kim, Essam A. Al-Ammar, Seungtae Kim, Changsoo Lee, and R.B.V. Chalapathy
- Subjects
inorganic chemicals ,Materials science ,Passivation ,business.industry ,Open-circuit voltage ,Doping ,General Physics and Astronomy ,Copper indium gallium selenide solar cells ,Atomic layer deposition ,X-ray photoelectron spectroscopy ,Interstitial defect ,Optoelectronics ,Physical and Theoretical Chemistry ,business ,Layer (electronics) - Abstract
This study investigated the mechanism underlying the light soaking effect of a ZnMgO buffer in Cu(In,Ga)Se2 (CIGS) solar cells, where the cell efficiency increased with an increase of light soaking time. The ZnMgO buffer layer was deposited by an atomic layer deposition method. With light soaking, the cell efficiency of ZnMgO/CIGS cells increased mainly by the increase of the fill factor and partly by the increase of the open-circuit voltage. With light soaking, the electron carrier concentration of the ZnMgO layer increased and the XPS intensity of the hydroxyl bond in the ZnMgO layer decreased. Based on the above results and the comparison of other buffers in literature, we assumed that the hydrogen atoms broken away from the hydroxyl bond by photon irradiation occupied the interstitial sites of the ZnMgO layer as a donor atom and also passivated the defects at the ZnMgO/CIGS interface. The increase of the fill factor and open circuit voltage was explained based on H doping in the ZnMgO layer and H passivation at the ZnO/CIGS interface.
- Published
- 2015
221. Anaerobic treatment of rice winery wastewater in an upflow filter packed with steel slag under different hydraulic loading conditions
- Author
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Seokhwan Hwang, Jaai Kim, Yeadam Jo, and Changsoo Lee
- Subjects
Environmental Engineering ,Materials science ,Bioengineering ,Wine ,Euryarchaeota ,Wastewater ,Waste Disposal, Fluid ,Bioreactors ,Anaerobic treatment ,Anaerobiosis ,Drainage ,Waste Management and Disposal ,Biological Oxygen Demand Analysis ,Waste management ,Sewage ,Renewable Energy, Sustainability and the Environment ,Chemical oxygen demand ,Slag ,Oryza ,General Medicine ,Models, Theoretical ,Winery ,Filter (aquarium) ,Kinetics ,Ground granulated blast-furnace slag ,Steel ,visual_art ,Biofilms ,visual_art.visual_art_medium ,Methane - Abstract
Rice-washing drainage (RWD), a strong organic wastewater, was anaerobically treated using an upflow filter filled with blast-furnace slag. The continuous performance of the reactor was examined at varying hydraulic retention times (HRTs). The reactor achieved 91.7% chemical oxygen demand removal (CODr) for a 10-day HRT (0.6 g COD/Ld organic loading rate) and maintained fairly stable performance until the HRT was shortened to 2.2 days (CODr84%). Further decreases in HRT caused process deterioration (CODr50% and pH5.5 for a 0.7-day HRT). The methane production rate increased with decreasing HRT to reach the peak level for a 1.3-day HRT, whereas the yield was significantly greater for 3.4-day or longer HRTs. The substrate removal and methane production kinetics were successfully evaluated, and the generated kinetic models produced good performance predictions. The methanogenic activity of the reactor likely relies on the filter biofilm, with Methanosaeta being the main driver.
- Published
- 2015
222. Static and dynamic behaviour of ECAPed copper alloy.
- Author
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Yerim Lee, Keunho Lee, Sanghyun Woo, Changsoo Lee, and Leeju Park
- Subjects
COPPER alloys ,MATERIAL plasticity ,TENSILE tests ,STRAIN rate ,HOPKINSON bars (Testing) ,YIELD strength (Engineering) ,GRAIN size ,HYDRODYNAMICS - Abstract
The equal channel angular processing (ECAP) is a severe plastic deformation technique which can produce ultrafine-grained (UFG) alloy. This paper investigate the static and dynamic behaviour of ECAPed OFHC-Cu to evaluate possibility of its application to defence industries. Tensile tests were carried out at two different strain rate (10-3/s, 1/s) using digital image correlation (DIC) technique. High strain rate experiments were conducted using the split Hopkinson pressure bar (SHPB). The results were compared with forged OFHC-Cu and additional heat treated OFHC-Cu after processed by ECAP. Flow stress and strain sensitivity of ECAPed OFHC-Copper were increased compare to forged OFHC-Copper. After ECAPed copper heat treatment, the yield strength decreased with increasing of the average grain size. And numerical simulation of ECAPed copper shaped charge was performed using Autodyn hydrodynamic code. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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223. Absolute and relative QPCR quantification of plasmid copy number in Escherichia coli
- Author
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Changsoo Lee, Seokhwan Hwang, Seung Gu Shin, and Jaai Kim
- Subjects
DNA, Bacterial ,Molecular Sequence Data ,Gene Dosage ,Cloning vector ,Bioengineering ,Biology ,medicine.disease_cause ,Applied Microbiology and Biotechnology ,law.invention ,Plasmid ,law ,Escherichia coli ,medicine ,Polymerase chain reaction ,Southern blot ,Genetics ,Base Sequence ,Reverse Transcriptase Polymerase Chain Reaction ,Sequence Analysis, DNA ,General Medicine ,Molecular biology ,PBR322 ,Recombinant DNA ,Primer (molecular biology) ,Sequence Alignment ,Algorithms ,Plasmids ,Biotechnology - Abstract
Real-time QPCR based methods for determination of plasmid copy number in recombinant Escherichia coli cultures are presented. Two compatible methods based on absolute and relative analyses were tested with recombinant E. coli DH5α harboring pBR322, which is a common bacterial cloning vector. The separate detection of the plasmid and the host chromosomal DNA was achieved using two separate primer sets, specific for the plasmid β-lactamase gene ( bla ) and for the chromosomal d -1-deoxyxylulose 5-phosphate synthase gene ( dxs ), respectively. Since both bla and dxs are single-copy genes of pBR322 and E. coli chromosomal DNA, respectively, the plasmid copy number can be determined as the copy ratio of bla to dxs . These methods were successfully applied to determine the plasmid copy number of pBR322 of E. coli host cells. The results of the absolute and relative analyses were identical and highly reproducible with coefficient of variation (CV) values of 2.8–3.9% and 4.7–5.4%, respectively. The results corresponded to the previously reported values of pBR322 copy number within E. coli host cells, 15–20. The methods introduced in this study are convenient to perform and cost-effective compared to the traditionally used Southern blot method. The primer sets designed in this study can be used to determine plasmid copy number of any recombinant E. coli with a plasmid vector having bla gene.
- Published
- 2006
224. A feasible strategy to prepare quantum dotincorporated carbon nanofibers as free-standing platforms.
- Author
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Taeyoung Song, Jun Young Cheong, Ji Yong Choi, Cheolmin Park, Chulhee Lee, Changsoo Lee, Hyuck Mo Lee, Sung-Yool Choi, Hyunjoon Song, Il-Doo Kim, and Duk Young Jeon
- Published
- 2019
- Full Text
- View/download PDF
225. Group-specific primer and probe sets to detect methanogenic communities using quantitative real-time polymerase chain reaction
- Author
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Jaai Kim, Youngseob Yu, Seokhwan Hwang, and Changsoo Lee
- Subjects
Genetics ,biology ,Bioengineering ,Euryarchaeota ,biology.organism_classification ,16S ribosomal RNA ,Polymerase Chain Reaction ,Applied Microbiology and Biotechnology ,law.invention ,law ,Methanosarcinales ,TaqMan ,Primer (molecular biology) ,DNA Probes ,Molecular probe ,Methane ,Methanosaetaceae ,Polymerase chain reaction ,DNA Primers ,Biotechnology ,Methanosarcinaceae - Abstract
Real-time polymerase chain reaction (PCR) is a highly sensitive method that can be used for the detection and quantification of microbial populations without cultivating them in anaerobic processes and environmental samples. This work was conducted to design primer and probe sets for the detection of methanogens using a real-time PCR with the TaqMan system. Six group-specific methanogenic primer and probe sets were designed. These sets separately detect four orders (Methanococcales, Methanobacteriales, Methanomicrobiales, and Methanosarcinales) along with two families (Methanosarcinaceae and Methanosaetaceae) of the order Methanosarcinales. We also designed the universal primer and probe sets that specifically detect the 16S rDNA of prokaryotes and of the domain Bacteria and Archaea, and which are fully compatible with the TaqMan real-time PCR system. Target-group specificity of each primer and probe set was empirically verified by testing DNA isolated from 28 archaeal cultures and by analyzing potential false results. In general, each primer and probe set was very specific to the target group. The primer and probe sets designed in this study can be used to detect and quantify the order-level (family-level in the case of Methanosarcinales) methanogenic groups in anaerobic biological processes and various environments.
- Published
- 2005
226. [Untitled]
- Author
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Jinsoo Chang, Seokhwan Hwang, Changsoo Lee, and Jaai Kim
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Bacillus (shape) ,Klebsiella ,Environmental Engineering ,biology ,Thiocyanate ,Bacillus cereus ,Bioengineering ,Bacillus mycoides ,biology.organism_classification ,Pollution ,Microbiology ,chemistry.chemical_compound ,chemistry ,Environmental Chemistry ,Brevibacterium epidermidis ,Bacillus licheniformis ,Ribosomal DNA - Abstract
A mixed bacterial culture capable of growing in potassium-thiocyanate containing medium (200 mg KSCN) has been isolated from bacterial suspensions of soil samples collected near gold mines in Kumjung (Korea). The isolates were initially characterized by metabolic profile analysis and were identified as Bacillus thermoglucosidasius, Bacillus cereus, Bacillus licheniformis, Bacillus mycoides, Brevibacterium epidermidis, Brevibacterium otitidis ,a ndCorynebacterium nitrilophilus. One of the seven isolates was initially characterized as Brevibacterium epidermidis, which is not known to degrade thiocyanate. However, using 16S rDNA sequencing, this strain was identified as a member of Klebsiella. The strain shows high similarity values (95.8 to 96.4%) with Klebsiella species, and the closest known relative was found to be K. ornithinolytica ATCC 31898. The result indicates that species of the genus Klebsiella were the closest phylogenetic relatives of the investigated strain. This is the first known report of a member of Klebsiella that is capable of utilizing thiocyanate as sole source of carbon and nitrogen.
- Published
- 2003
227. Flow Characteristics of Steam and Gas Push in the Presence of Heat Thief Zones Overlying Oil Sands Deposits
- Author
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Changhyup Park, Changsoo Lee, and Soobin Park
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Mass flux ,oil sands ,Thermal efficiency ,020209 energy ,Flow (psychology) ,chemistry.chemical_element ,Aquifer ,02 engineering and technology ,lcsh:Technology ,lcsh:Chemistry ,020401 chemical engineering ,0202 electrical engineering, electronic engineering, information engineering ,General Materials Science ,steam and gas push ,thermal efficiency ,0204 chemical engineering ,lcsh:QH301-705.5 ,Instrumentation ,Fluid Flow and Transfer Processes ,geography ,aquifer ,geography.geographical_feature_category ,Gas oil ratio ,Petroleum engineering ,lcsh:T ,Process Chemistry and Technology ,non condensable gas ,thief zone ,General Engineering ,Nitrogen ,lcsh:QC1-999 ,Computer Science Applications ,lcsh:Biology (General) ,lcsh:QD1-999 ,chemistry ,lcsh:TA1-2040 ,Asphalt ,Oil sands ,Environmental science ,lcsh:Engineering (General). Civil engineering (General) ,lcsh:Physics - Abstract
This paper presents the effects of the top water-bearing zone on the performance of the steam and gas push, i.e., nitrogen as a non-condensable gas injected with steam into an oil sands deposit. The flow characteristics of fluid mixtures are examined in the presence of different-sized water-bearing formations overlying oil sands deposits, i.e., a finite aquifer with no-flow boundaries and an infinite aquifer with continuous mass flux. The performance efficiency is investigated by respectively implementing the cumulative steam to oil ratio, a simple thermal efficiency parameter, and the oil production on the surface. The top water-bearing area serves as a heat thief zone and negatively impacts bitumen recovery; furthermore, it increases the cumulative steam to oil ratio while decreasing the simple thermal efficiency parameter, as well as the oil production rate. When the steam chamber encounters the top aquifer, a severe heat loss occurs. As increasing mol % of nitrogen, the producing time with energy efficiency increases but the chamber growth is limited. The specific operational conditions would be possible for the finite-sized aquifer, while the continuous water influx and the significant heat loss obstructs the thermal processes for the infinite aquifer.
- Published
- 2017
228. Response of a continuous biomethanation process to transient organic shock loads under controlled and uncontrolled pH conditions
- Author
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Changsoo Lee and Jaai Kim
- Subjects
Environmental Engineering ,Biology ,Wastewater ,Waste Disposal, Fluid ,Bioreactors ,Biogas ,Cheese ,Bioreactor ,Organic Chemicals ,Waste Management and Disposal ,Water Science and Technology ,Civil and Structural Engineering ,Bacteria ,Ecological Modeling ,Microbiota ,Environmental engineering ,Hydrogen-Ion Concentration ,Pulp and paper industry ,Pollution ,Archaea ,Shock (mechanics) ,Anaerobic digestion ,Waste treatment ,Anaerobic exercise ,Methane ,Water Pollutants, Chemical ,Mesophile - Abstract
The organic loading rate (OLR) is a critical factor that controls the treatment efficiency and biogas production in anaerobic digestion (AD). Therefore, organic shock loads may cause significant process imbalances accompanied by a drop in pH and acid accumulation or even failure. This study investigated the response of a continuous mesophilic anaerobic bioreactor to a series of transient organic shock loads of the substrate whey permeate, a high-strength organic wastewater from cheese making. The reactor was subjected to organic shock loads of increasing magnitude (a one-day pulse of elevated feed organic concentration) under controlled (near 7) and uncontrolled pH conditions at a fixed HRT of 10 days. The reactor was resilient to up to a shock load of up to 8.0 g SCOD/L·d under controlled pH conditions but failed to recover from the serious imbalance caused by a 3.0-g SCOD/L·d shock load, thus indicating the critical effect of pH on system resilience. The acidified reactor was not restored by interrupted feeding under the acidic conditions that were formed (pH ≤ 4.5) but was successfully restored after pH adjustment to 7. The reactor subsequently reverted to continuous mode without pH control and showed a performance comparable to the stable performance at the design OLR of 1.0 g SCOD/L·d. The bacterial community structure shifted dynamically in association with disturbances in the reactor conditions, whereas the archaeal community structure remained simple and less variable during the shock loading experiments. The structural shifts of the bacterial community were well correlated with the process performance changes, and performance recovery was generally accompanied by recovery of the bacterial community structure. The overall results suggest that the reactor pH, rather than simply acting as an accumulation of organic acids, had a crucial effect on the resilience and robustness of the microbial community and thus on the reactor performance under organic shock loads.
- Published
- 2014
229. Effect of mild-temperature H2O2 oxidation on solubilization and anaerobic digestion of waste activated sludge
- Author
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Seungyong Lee, Jaai Kim, Heejung Jung, and Changsoo Lee
- Subjects
Models, Statistical ,Waste management ,Sewage ,Chemical oxygen demand ,Temperature ,General Medicine ,Hydrogen Peroxide ,Pulp and paper industry ,Anaerobic digestion ,chemistry.chemical_compound ,Activated sludge ,Wastewater ,chemistry ,Biogas ,Bioenergy ,Biofuels ,Environmental Chemistry ,Sewage treatment ,Anaerobiosis ,Hydrogen peroxide ,Waste Management and Disposal ,Oxidation-Reduction ,Water Science and Technology - Abstract
Efficient sludge management is among the most challenging issues in wastewater treatment today, and anaerobic digestion is regarded as a viable solution. Mild-temperature H202 oxidation was examined for enhanced solubilization and biogas production of waste activated sludge (WAS). The effects of pretreatment factors (i.e. temperature and H202 concentration) on the degree of WAS disintegration (DD) and biogas yield (BY) were assessed by response surface analysis within the design space of 60-90 degrees C and 0-200mM H202. Significant sludge disintegration (up to 23.0% DD) and visibly enhanced BY (up to 26.9%) were shown in the pretreatment trials. Two response surface models to describe how DD and BY respond to changes in the pretreatment conditions were successfully constructed (R20.95, p0.05). The models showed totally different response surface shapes, indicating the DD and BY were influenced by pretreatment conditions in very different ways. DD was dominantly affected by temperature and showed higher model responses at the high-temperature region, while the BY response peaked in the low-temperature and mid-level H2O2 region. This observation implies that the enhanced solubilization of WAS was not directly translated into an increase in biogas production. Our results showed that WAS can be efficiently disintegrated by H202 oxidation under mild-temperature conditions for enhanced anaerobic digestibility. Within the explored region of pretreatment conditions, the maximum BY was estimated to be 82.1 mL/gCODadded (32.8% greater than the untreated control) at (60.0 degrees C, 74.2 mM H2O2).
- Published
- 2014
230. Influence of ferric oxyhydroxide addition on biomethanation of waste activated sludge in a continuous reactor
- Author
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Changsoo Lee, Gahyun Baek, and Jaai Kim
- Subjects
Bioaugmentation ,Environmental Engineering ,Waste management ,Sewage ,Renewable Energy, Sustainability and the Environment ,Chemistry ,Continuous reactor ,Bioengineering ,General Medicine ,Pulp and paper industry ,Ferric Compounds ,Biostimulation ,Waste treatment ,Anaerobic digestion ,Bacteria, Anaerobic ,Activated sludge ,Iron bacteria ,Bioreactors ,Waste Management ,Waste Management and Disposal ,Anaerobic exercise ,Methane - Abstract
This study investigated the potential of enhancing the activity of iron-reducing bacteria (IRBs) to increase the biomethanation rate of waste activate sludge (WAS). The effects of biostimulation by ferric oxyhydroxide (Phase 2) and bioaugmentation with an enriched IRB consortium (Phase 3) were examined in a continuous anaerobic reactor treating WAS. Compared to the control operation (Phase 1), significant rises in methane yield (10.8–59.4%) and production rate (24.5–52.9%) were demonstrated by the biostimulation and bioaugmentation treatments. Visible structural changes were observed in bacterial community with the phases while not in archaeal community. Acinetobacter- and Spirochaetales-related populations were likely the major players driving anaerobic iron respiration and thus leading to enhanced biomethanation performance, in Phases 2 and 3, respectively. Our results suggest an interesting new potential for enhancing biomethanation of WAS.
- Published
- 2014
231. Science Walden: Exploring the Convergence of Environmental Technologies with Design and Art
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Gi-Hyoug Cho, Chang Ha Lee, Hyun-Kyung Lee, Changsoo Lee, Yongwon Seo, Kyong-Mi Paek, Jaeweon Cho, Young-Nam Kwon, Kyung Hwa Cho, and Huiyuhl Yi
- Subjects
Engineering ,Theory of Forms ,Geography, Planning and Development ,Water source ,TJ807-830 ,Pavilion ,feces standard money (FSM) ,010501 environmental sciences ,Management, Monitoring, Policy and Law ,Humanism ,TD194-195 ,010402 general chemistry ,01 natural sciences ,Renewable energy sources ,GE1-350 ,collaboration of science & ,art ,0105 earth and related environmental sciences ,Environmental effects of industries and plants ,Renewable Energy, Sustainability and the Environment ,business.industry ,collaboration of science & art ,sustainableenergy production ,0104 chemical sciences ,Sustainable energy ,Environmental sciences ,Aesthetics ,sustainable energy production ,Convergence (relationship) ,business - Abstract
Science Walden, which is inspired by two prominent literary works, namely, Walden by Henry David Thoreau (1817–1862) and Walden Two by Burrhus Frederic Skinner (1904–1990), is aimed at establishing a community that embodies humanistic values while embracing scientific advancement to produce renewable energy and water sources. This study attempts to capitalize on feces standard money (FSM) and artistic collaboration between scientists and artists as a means of achieving the forms of life depicted in Walden and Walden Two. On our campus, we designed and built a pavilion that serves as a laboratory where scientific advantages, design, and art are merged. In the pavilion, feces are processed in reactors and facilities for sustainable energy production, and rainwater is harvested and treated for use in daily life. Our application of design and art contributes to easing interaction between the general public and scientists because it visualizes an ambiguous theory and concretizes it into an understandable image.
- Published
- 2016
232. Modeling of Permeable Groundwater Treatment Wall using Zero-Valent Iron
- Author
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Changsoo Lee, Negishi Masanori, Satoshi Imamura, and Masanori Shimomura
- Subjects
Chemistry - Published
- 1998
233. Retardation due to Sorption of the Gaseous Volatile Organic Compounds to Unsaturated Soil
- Author
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Kohji Muraoka, Yoshihiro Ishii, and Changsoo Lee
- Subjects
Waste management ,Retardation coefficient ,Chemistry ,Environmental chemistry ,Organic Chemistry ,Sorption ,Biochemistry - Published
- 1997
234. New Introduction: Search Method for Similar Images from Representative Video Frame Images
- Author
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Changsoo Lee and Daewon Jung
- Subjects
Motion compensation ,business.industry ,Computer science ,Frame (networking) ,ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION ,Image processing ,Video compression picture types ,Feature (computer vision) ,Video tracking ,Key frame ,Computer vision ,Artificial intelligence ,business ,Block-matching algorithm - Abstract
With rapid advances in computer and communications technology, the internet and video information is being used in a variety of areas?and the amount of this information is increasing exponentially. However, existing information analysis systems mainly depend on text, so it is not easy to differentiate video information. In order to solve this problem, we propose an algorithm that efficiently analyzes large amounts of video information and searches for similar images. We extract representative frames from a video via histogram analysis of the video information through low computational complexity of frame intervals. Then, we search for images with high similarity using information about colors and shapes. For obtaining color feature information in images and shape feature information, we use both hue?saturation?intensity and moment invariants.
- Published
- 2013
235. Thermo-alkaline pretreatment of waste activated sludge at low-temperatures: effects on sludge disintegration, methane production, and methanogen community structure
- Author
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Changsoo Lee, Youngseob Yu, and Jaai Kim
- Subjects
Environmental Engineering ,Molecular Sequence Data ,Bioengineering ,Alkalies ,Waste Disposal, Fluid ,Methanosaeta ,RNA, Ribosomal, 16S ,Sodium Hydroxide ,Methane production ,Waste Management and Disposal ,Phylogeny ,biology ,Bacteria ,Base Sequence ,Sewage ,Renewable Energy, Sustainability and the Environment ,Chemistry ,Denaturing Gradient Gel Electrophoresis ,Environmental engineering ,General Medicine ,Methanosarcina ,Models, Theoretical ,biology.organism_classification ,Methanogen ,Cold Temperature ,Anaerobic digestion ,Activated sludge ,Biodegradation, Environmental ,Methane ,Nuclear chemistry - Abstract
Low-temperature thermo-alkaline pretreatment of waste activated sludge (WAS) was studied, within the region of 0-0.2 M NaOH and 60-90°C, for the effects of NaOH concentration and temperature on sludge degradability in anaerobic digestion (AD). Significant disintegration of sludge solids (up to 75.6%) and an increase in methane production (up to 70.6%) were observed in the pretreatment trials. Two quadratic models were successfully generated by response surface analysis (R(2)>0.9, p
- Published
- 2013
236. THM analysis for an in situ experiment using FLAC3D-TOUGH2 and an artificial neural network.
- Author
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Sangki Kwon and Changsoo Lee
- Subjects
- *
RADIOACTIVE waste repositories , *BOUNDARY value problems , *ARTIFICIAL neural networks , *HYDRAULIC fracturing - Abstract
The evaluation of Thermo-Hydro-Mechanical (THM) coupling behavior is important for the development of underground space for various purposes. For a high-level radioactive waste repository excavated in a deep underground rock mass, the accurate prediction of the complex THM behavior is essential for the long-term safety and stability assessment. In order to develop reliable THM analysis techniques effectively, an international cooperation project, Development of Coupled models and their Validation against Experiments (DECOVALEX), was carried out. In DECOVALEX-2015 Task B2, the in situ THM experiment that was conducted at Horonobe Underground Research Laboratory(URL) by Japan Atomic Energy Agency (JAEA), was modeled by the research teams from the participating countries. In this study, a THM coupling technique that combined TOUGH2 and FLAC3D was developed and applied to the THM analysis for the in situ experiment, in which rock, buffer, backfill, sand, and heater were installed. With the assistance of an artificial neural network, the boundary conditions for the experiment could be adequately implemented in the modeling. The thermal, hydraulic, and mechanical results from the modeling were compared with the measurements from the in situ THM experiment. The predicted buffer temperature from the THM modelling was about 10 °C higher than measurement near by the overpack. At the other locations far from the overpack, modelling predicted slightly lower temperature than measurement. Even though the magnitude of pressure from the modeling was different from the measurements, the general trends of the variation with time were found to be similar. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
237. Research on Real-Time Localization and Environmental Monitoring Using Sensors and ZigBee for Cold Chain System
- Author
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Keun-Wang Lee, Changsoo Lee, and Daewon Jung
- Subjects
Article Subject ,Computer Networks and Communications ,business.industry ,Computer science ,media_common.quotation_subject ,General Engineering ,ComputerApplications_COMPUTERSINOTHERSYSTEMS ,Computer security ,computer.software_genre ,lcsh:QA75.5-76.95 ,Environmental monitoring ,Ready to use ,Quality (business) ,lcsh:Electronic computers. Computer science ,Cold chain ,Telecommunications ,business ,Wireless sensor network ,computer ,media_common - Abstract
As consumers increase the level of quality requirements for foods due to the spread of well-being culture, the demands for safe cold chain have been continuously increased. However, as we can see from the food poisoning incidents that have recently occurred, important issues are how to keep the items (foods) and manage them. Although many people are aware that these issues are important, development and investment for keeping and managing foods are not enough at present. In the existing cold chain system, it is seen that the technologies of ubiquitous sensor networks (USNs), GPS, and CDMA have been used. However, this is only applied to a particular area, and the refrigeration/freezing level is the same as the existing one. In this paper, in order to increase the utilization of the cold chain system, we use both the commercial technologies of sensors and ZigBee for environmental measurements and cellular phone or smart phone with GPS for real-time localization and date transmissions. It is expected that our implementation system that is instantly ready to use leads to the expansion of cold chain system to various fields and the development of USN technologies.
- Published
- 2013
- Full Text
- View/download PDF
238. Tuning Molecular Interactions for Highly Reproducible and Efficient Formamidinium Perovskite Solar Cells via Adduct Approach.
- Author
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Jin-Wook Lee, Zhenghong Dai, Changsoo Lee, Hyuck Mo Lee, Tae-Hee Han, De Marco, Nicholas, Lin, Oliver, Choi, Christopher S., Dunn, Bruce, Jaekyung Koh, Di Carlo, Dino, Jeong Hoon Ko, Maynard, Heather D., and Yang Yang
- Published
- 2018
- Full Text
- View/download PDF
239. Dislocation structure associated with deformation behavior of Fe3Al alloys
- Author
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H.C. Jung, Chan Gyung Park, and Changsoo Lee
- Subjects
Materials science ,Mechanical Engineering ,Metallurgy ,Alloy ,Metals and Alloys ,Intermetallic ,engineering.material ,Condensed Matter Physics ,Hot working ,Mechanics of Materials ,Ultimate tensile strength ,engineering ,General Materials Science ,Dislocation ,Deformation (engineering) ,Composite material ,Ductility ,Yield strength anomaly - Abstract
The aim of the present investigation is to correlate the change of tensile yield strength with the dislocation structure of Fe-23Al and Fe-30Al alloys tested at room and high temperatures. The results showed that the yield strength of Fe-23Al alloy increased with increasing the quench and test temperatures. This was mainly attributed to the increase in the partition of imperfect superdislocations, leaving NNN and NN type APB trails behind during the deformation. In Fe-30Al alloy, the yield strength increased with increasing the test temperature, but decreased with increasing the quench temperature. The lower yield strength of the specimen quenched at 500 ° C was thought to be due to relatively lower NNN APB energy. It is considered that the yield strength of Fe-30Al alloy is governed by two competing factors; the partition of perfect and imperfect variants of dislocations and the shear stress required for the dislocation movement.
- Published
- 1996
240. Reduction of Concentration in Volatile Organic Compound Solution flowing in Saturated Porus Media
- Author
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Changsoo Lee, Michiaki Tamura, Kohji Muraoka, and Yoshibiro Ishii
- Subjects
Hydrology ,Mass transfer coefficient ,chemistry.chemical_classification ,Materials science ,Organic Chemistry ,Groundwater remediation ,Evaporation ,Biochemistry ,Physics::Geophysics ,Physics::Fluid Dynamics ,Chemical engineering ,chemistry ,Vaporization ,Vadose zone ,Volatile organic compound ,Porosity ,Groundwater - Abstract
The reduction of concentration of groundwater contaminated by volatile organic compounds is based on two phenomena. One is the convection-diffusion in the liquid zone with flow. The other is the vaporization from surface of groundwater to unsaturated zone, and the transportation from liquid phase to gas phase. Some experiments were carried outin the laboratory. Observing the change of gas concentration in porous. media, the mass transfer coefficient from liquid phase to gas phase and vapor rate are researched. Consequently, the behavior of gaseous volatile organic compounds is chased down by utilizing vapor rate on the groundwater surface.
- Published
- 1996
241. Surface modification of oleylamine-capped Ag–Cu nanoparticles to fabricate low-temperature-sinterable Ag–Cu nanoink
- Author
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Hyuck Mo Lee, Na Rae Kim, Jahyun Koo, Changsoo Lee, and Yung Jong Lee
- Subjects
Materials science ,Nanoparticle ,Sintering ,Bioengineering ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,chemistry.chemical_compound ,Oleylamine ,General Materials Science ,Electrical and Electronic Engineering ,Thin film ,chemistry.chemical_classification ,Tetramethylammonium hydroxide ,Mechanical Engineering ,Thermal decomposition ,General Chemistry ,Polymer ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,chemistry ,Chemical engineering ,Mechanics of Materials ,Surface modification ,0210 nano-technology - Abstract
By treating oleylamine (OA)-capped Ag-Cu nanoparticles with tetramethylammonium hydroxide (TMAH), we obtained metal nanoparticles that are suspended in polar solvents and sinterable at low temperatures. The simple process with ultra sonication enables synthesis of monodispersed and high purity nanoparticles in an organic base, where the resulting nanoparticles are dispersible in polar solvents such as ethanol and isopropyl alcohol. To investigate the surface characteristics, we conducted Fourier-transform infrared and zeta-potential analyses. After thermal sintering at 200 °C, which is approximately 150 °C lower than the thermal decomposition temperature of OA, an electrically conductive thin film was obtained. Electrical resistivity measurements of the TMAH-treated ink demonstrate that surface modified nanoparticles have a low resistivity of 13.7 × 10(-6) Ω cm. These results confirm the prospects of using low-temperature sinterable nanoparticles as the electrode layer for flexible printed electronics without damaging other stacked polymer layers.
- Published
- 2016
242. Comparative study of changes in reaction profile and microbial community structure in two anaerobic repeated-batch reactors started up with different seed sludges
- Author
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Jaai Kim, Seungyong Lee, and Changsoo Lee
- Subjects
Acidogenesis ,animal structures ,Environmental Engineering ,Waste management ,biology ,Sewage ,Renewable Energy, Sustainability and the Environment ,Methanogenesis ,Microorganism ,Microbial Consortia ,Community structure ,Bioengineering ,General Medicine ,Equipment Design ,Pulp and paper industry ,biology.organism_classification ,Methanogen ,Equipment Failure Analysis ,Anaerobic digestion ,Bacteria, Anaerobic ,Microbial population biology ,Batch Cell Culture Techniques ,Waste Management and Disposal ,Anaerobic exercise - Abstract
Microbial community structure and dynamics were examined in two anaerobic reactors run in repeated-batch mode to treat whey permeate. Despite being started up using different seeding sources, the reactors showed generally similar reaction patterns and performances. During the repeated-batch operation for three cycles, the overall reaction rate increased with the increase in the initial population size of both bacteria and methanogens over cycles. Clostridium- and Methanospirillum-related microorganisms were likely the main acidogenic and methanogenic populations, respectively, in both reactors. Bacterial community structure shifted dynamically over cycles, while little change was observed in methanogen community structure throughout the operation. This means that the changes in bacterial community structure changes had little influence on the formation and evolution of methanogen community structure in the reactors. The increased methanogenesis rate with cycles seemed therefore more likely due to the effect of the increase in methanogen abundance rather than the alteration of community structure.
- Published
- 2012
243. Effects of temperature and pH on the biokinetic properties of thiocyanate biodegradation under autotrophic conditions
- Author
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Kyungjin Cho, Changsoo Lee, Jaai Kim, Gyuseong Han, and Seokhwan Hwang
- Subjects
Specific growth ,Autotrophic Processes ,Environmental Engineering ,Thiocyanate ,Bacteria ,Ecological Modeling ,Inorganic chemistry ,Temperature ,Substrate (chemistry) ,Biodegradation ,Hydrogen-Ion Concentration ,Ph changes ,Pollution ,chemistry.chemical_compound ,Biodegradation, Environmental ,chemistry ,Kinetic coefficient ,Autotroph ,Saturation (chemistry) ,Waste Management and Disposal ,Thiocyanates ,Water Science and Technology ,Civil and Structural Engineering - Abstract
The simultaneous effects of temperature and pH on the biokinetic properties of thiocyanate biodegradation under mixed-culture, autotrophic conditions were investigated using response surface analysis (RSA) combined with biokinetic modeling. A partial cubic model, based on substrate inhibition biokinetics, was constructed for each kinetic coefficient in Andrew model (i.e., maximum specific growth rate (μ(m)), saturation coefficient (K(S)), and substrate inhibition coefficient (K(SI))). Each model proved statistically reliable to approximate the responses of the kinetic coefficients to temperature and pH changes (r(2)0.8, p0.05). The response surface plots demonstrated that the biokinetic coefficients change with respect to temperature and pH significantly and in different ways. The model response surfaces were substantially different to each other, indicating distinct correlations between the independent (temperature and pH) and dependent (model response) variables in the models. Based on the estimated response surface models, temperature was shown to have significant effects on all biokinetic coefficients tested. A dominant influence of temperature on μ(m) response was observed while the interdependence of temperature and pH was apparent in the K(S) and K(SI) models. Specific growth rate (μ) versus substrate (i.e., thiocyanate) concentration plots simulating using the obtained response surface models confirmed the significant effects of temperature and pH on the microbial growth rate and therefore on the thiocyanate degradation rate. Overall, the response surface models able to describe the biokinetic effects of temperature and pH on thiocyanate biodegradation within the explored region (20-30 °C and pH 6.0-9.0) were successfully constructed and validated, providing fundamental information for better process control in thiocyanate treatment.
- Published
- 2012
244. Design of energy band alignment at the Zn(1-x)Mg(x)O/Cu(In,Ga)Se2 interface for Cd-free Cu(In,Ga)Se2 solar cells
- Author
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Byung Tae Ahn, Changsoo Lee, Liudmila L. Larina, Young Min Shin, and Essam A. Al-Ammar
- Subjects
Band bending ,Materials science ,Band gap ,Analytical chemistry ,General Physics and Astronomy ,Heterojunction ,Physical and Theoretical Chemistry ,Electronic band structure ,Copper indium gallium selenide solar cells ,Semimetal ,Band offset ,Ultraviolet photoelectron spectroscopy - Abstract
The electronic band structure at the Zn(1-x)Mg(x)O/Cu(In(0.7)Ga(0.3))Se(2) interface was investigated for its potential application in Cd-free Cu(In,Ga)Se(2) thin film solar cells. Zn(1-x)Mg(x)O thin films with various Mg contents were grown by atomic layer deposition on Cu(In(0.7)Ga(0.3))Se(2) absorbers, which were deposited by the co-evaporation of Cu, In, Ga, and Se elemental sources. The electron emissions from the valence band and core levels were measured by a depth profile technique using X-ray and ultraviolet photoelectron spectroscopy. The valence band maximum positions are around 3.17 eV for both Zn(0.9)Mg(0.1)O and Zn(0.8)Mg(0.2)O films, while the valence band maximum value for CIGS is 0.48 eV. As a result, the valence band offset value between the bulk Zn(1-x)Mg(x)O (x = 0.1 and x = 0.2) region and the bulk CIGS region was 2.69 eV. The valence band offset value at the Zn(1-x)Mg(x)O/CIGS interface was found to be 2.55 eV after considering a small band bending in the interface region. The bandgap energy of Zn(1-x)Mg(x)O films increased from 3.25 to 3.76 eV as the Mg content increased from 0% to 25%. The combination of the valence band offset values and the bandgap energy of Zn(1-x)Mg(x)O films results in the flat (0 eV) and cliff (-0.23 eV) conduction band alignments at the Zn(0.8)Mg(0.2)O/Cu(In(0.7)Ga(0.3))Se(2) and Zn(0.9)Mg(0.1)O/Cu(In(0.7)Ga(0.3))Se(2) interfaces, respectively. The experimental results suggest that the bandgap energy of Zn(1-x)Mg(x)O films is the main factor that determines the conduction band offset at the Zn(1-x)Mg(x)O/Cu(In(0.7)Ga(0.3))Se(2) interface. Based on these results, we conclude that a Zn(1-x)Mg(x)O film with a relatively high bandgap energy is necessary to create a suitable conduction band offset at the Zn(1-x)Mg(x)O/CIGS interface to obtain a robust heterojunction. Also, ALD Zn(1-x)Mg(x)O films can be considered as a promising alternative buffer material to replace the toxic CdS for environmental safety.
- Published
- 2012
245. Performance of methanogenic reactors in temperature phased two-stage anaerobic digestion of swine wastewater
- Author
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Seung Gu Shin, Woong Kim, Kyungjin Cho, Seokhwan Hwang, and Changsoo Lee
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Acidogenesis ,animal structures ,Swine ,Bioengineering ,Protein degradation ,Biology ,Wastewater ,Applied Microbiology and Biotechnology ,Microbiology ,Hydrolysis ,Bioreactors ,Animals ,Food science ,Anaerobiosis ,Sewage ,Thermophile ,Temperature ,Hydrogen-Ion Concentration ,Anaerobic digestion ,Swine wastewater ,Proteolysis ,Gradual increase ,Acids ,Methane ,Biotechnology ,Mesophile - Abstract
The present study investigated the shifts in the chemical profiles of a two-phase anaerobic digestion system in methanogenic and acidogenic reactors for the treatment of swine wastewater. Acidogenic and methanogenic digesters were used with overall HRTs ranging from 27 to 6 d. In the optimized thermophilic/acidogenic phase throughout the entire experimental period, VS was reduced by 13.8% (1.6%); however, COD hardly decreased because of the thermophilic hydrolysis of organic materials, such as carbohydrates, proteins, and lipids, without any significant consumption of volatile fatty acids. In the methanogenic/mesophilic phase, COD was reduced by 65.8 (1.1)% compared to a 47.4 (2.9)% reduction in VS reduction efficiency with the gradual increase in methane production during a methanogenic HRT between 25 and 10 d. A high protein degradation rate was observed in the optimized acidogenic phase, which is assumed to be due to the low content of carbohydrates in raw swine wastewater as well as the readily thermophilic hydrolysis of proteins. Two-phase systems of anaerobic digestion consisting of optimized thermophilic and mesophilic methanogenic digesters showed a stable performance with respect to VS reduction efficiency with OLRs less than 3 g VS/L·d, in other words, more than 10 days of methanogenic HRT in this study.
- Published
- 2011
246. The high contrast ratio and fast response time of a liquid crystal display lit by a carbon nanotube field emission backlight unit
- Author
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Jong Hwan Park, Byong Gon Lee, Jong Woon Moon, Yun Hee Kim, Sang-Jin Lee, Changsoo Lee, Mun Seok Kang, Yong C. Kim, Su Kyung Lee, Ji Hong Lim, Ji-won Lee, Myung Ick Hwang, Young Chul Choi, Kyu-Won Jung, Il Hwan Kim, Hyung Rae Seon, and Hun Soo Kim
- Subjects
Liquid-crystal display ,Fabrication ,Materials science ,business.industry ,Mechanical Engineering ,Response time ,Bioengineering ,General Chemistry ,Carbon nanotube ,Backlight ,Luminance ,law.invention ,Field electron emission ,Optics ,Mechanics of Materials ,law ,General Materials Science ,Contrast ratio ,Electrical and Electronic Engineering ,business - Abstract
We report on the fabrication of a carbon nanotube field emission backlight unit (CNT-BLU) and its application for liquid crystal displays (LCD). The CNT-BLU was operated with locally controllable luminance and impulse-type scanning. The local luminance control, which is based on a very small block size of 1 cm 2 , consisted of local dimming and local brightening. This resulted in the contrast ratio of the LCD-TV to be as high as 300 000:1. A fast response time of ∼5.7 ms was also achieved from the LCD-TV lit by CNT-BLU, originating from the impulse-type scanning. In addition, the CNT-BLU showed long-term emission stability and high luminance uniformity.
- Published
- 2011
247. Cu2ZnSnS4 (CZTS) thin films grown by sulfurization of different precursor layers in sulfur atomsphere
- Author
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R.B.V. Chalapathy, Byung Tae Ahn, and Changsoo Lee
- Subjects
Materials science ,Annealing (metallurgy) ,Open-circuit voltage ,Alloy ,Metallurgy ,chemistry.chemical_element ,engineering.material ,Copper ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,Sputtering ,engineering ,Kesterite ,CZTS ,Thin film - Abstract
Cu 2 ZnSnS 4 (CZTS) thin films have been grown by two step process. Two different precursors; one is stacked layer consists of Cu/ZnSn/Cu and the other one is single layer from an alloy target of Cu-Zn-Sn were deposited onto Mo coated soda lime glass substrates kept at RT by Dc sputtering. The precursor layers were converted into CZTS films by annealing at 560°C for 6 min in sulfur atmosphere. The XRD pattern of the stacked precursor layer consists of Cu 3 Sn, CuZn, Cu 6 Sn 5 , Sn phases suggests that Cu diffuses into the ZnSn during the precursor deposition and forms binary phases. CZTS films grown with stacked precursors were single phase Kesterite with (112) orientation. The films exhibited dense morphology with submicron grain sizes and fine grains at the interface between CZTS and Mo. On the other hand the precursor grown with Cu poor and Zn rich alloy target showed peaks of corresponding to binary metallic phase Cu 6 Sn 5 . The CZTS films obtained at 560°C for 6 min showed non uniform surface with voids. The cross-sectional morphology of the films shows dense columnar grains. The solar cells fabricated with these films showed no performance due to porous and inhomogeneous surface morphology. We found that the CZTS films grown with stacked precursor layers deposited with Cu and ZnSn targets have shown better properties. Solar cells fabricated with this CZTS absorber showed an efficiency of 4.7% with an open circuit voltage of 632 mV, a short circuit current density of 15.80 mA/cm2 and fill factor 47.13% for an area of 0.44 cm2.
- Published
- 2011
248. Quantitative and qualitative analyses of methanogenic community development in high-rate anaerobic bioreactors
- Author
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Gavin Collins, Changsoo Lee, Vincent O'Flaherty, Jaai Kim, Katarzyna Bialek, and Thérèse Mahony
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0106 biological sciences ,Environmental Engineering ,Hydraulic retention time ,Population ,Methanobacteriales ,010501 environmental sciences ,Euryarchaeota ,01 natural sciences ,7. Clean energy ,Polymerase Chain Reaction ,Bioreactors ,010608 biotechnology ,RNA, Ribosomal, 16S ,Bioreactor ,Anaerobiosis ,education ,Waste Management and Disposal ,0105 earth and related environmental sciences ,Water Science and Technology ,Civil and Structural Engineering ,education.field_of_study ,biology ,Denaturing Gradient Gel Electrophoresis ,Ecological Modeling ,Environmental engineering ,biology.organism_classification ,Pulp and paper industry ,Pollution ,6. Clean water ,Anaerobic digestion ,Wastewater ,Fluidized bed ,Methane ,Temperature gradient gel electrophoresis - Abstract
Methanogenic community structure and population dynamics were investigated in two anaerobic reactors treating a dairy wastewater, an Inverted Fluidized Bed (IFB) and Expanded Granular Sludge Bed (EGSB). A combination of real-time PCR, denaturing gradient gel electrophoresis and statistical techniques was employed. Distinct methanogenic communities developed in the IFB and EGSB reactors reflecting step-wise reductions in the applied hydraulic retention time from 72 to 12 h during the 200-day trial. The aceticlastic family Methanosarcinaceae was only detected in the IFB and the order Methanomicrobiales was also much more abundant in this reactor, while the aceticlastic family Methanosaetaceae was more abundant in the EGSB. The hydrogenotrophic order, Methanobacteriales, predominated in both reactors under all applied operational conditions. Non-metric multidimensional scaling (NMS) and moving-window analyses, based on absolute and relative abundance quantification data, demonstrated that the methanogenic communities developed in a different manner in the IFB, compared to the EGSB reactor. In our study, relative abundance-based quantification by NMS and moving-window analysis appeared to be a valuable molecular approach that was more applicable to reflect the changes in the anaerobic digestion process than approaches based either on qualitative analysis, or solely on absolute quantification of the various methanogenic groups. The overall results and findings provided a comparative, quantitative and qualitative insight into anaerobic digestion processes, which could be helpful for better future reactor design and process control.
- Published
- 2010
249. A comprehensive microbial insight into two-stage anaerobic digestion of food waste-recycling wastewater
- Author
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Seung Gu Shin, Juntaek Lim, Changsoo Lee, Seokhwan Hwang, and Gyuseong Han
- Subjects
Acidogenesis ,Environmental Engineering ,Waste Disposal, Fluid ,Bioreactors ,RNA, Ribosomal, 16S ,Recycling ,Anaerobiosis ,Waste Management and Disposal ,Phylogeny ,Water Science and Technology ,Civil and Structural Engineering ,Waste Products ,Bacteria ,Chemistry ,Denaturing Gradient Gel Electrophoresis ,Ecological Modeling ,Chemical oxygen demand ,Environmental engineering ,Biodegradable waste ,Pulp and paper industry ,Pollution ,Food waste ,Anaerobic digestion ,Activated sludge ,Wastewater ,Microbial population biology ,Food - Abstract
Microbial community structures were assessed in a two-stage anaerobic digestion system treating food waste-recycling wastewater. The reactors were operated for 390 d at 10 different hydraulic retention times (HRTs) ranging from 25 to 4 d. Stable operation was achieved with the overall chemical oxygen demand (COD) removal efficiency of 73.0–85.9% at organic loading rate of up to 35.6 g COD/L·d. Performance of the acidogenic reactors, however, changed significantly during operation. This change coincided with transition of the bacterial community from one dominated by Aeriscardovia- and Lactobacillus amylovorus-related species to one dominated by Lactobacillus acetotolerans- and Lactobacillus kefiri-like organisms. In methanogenic reactors, the microbial community structures also changed at this stage along with the shift from Methanoculleus- to Methanosarcina-like organisms. This trend was confirmed by the non-metric multidimensional scaling joint plot of microbial shifts along with performance parameters. These results indicated that the overall process performance was relatively stable compared to the dynamic changes in the microbial structures and the acidogenic performance.
- Published
- 2010
250. Effect of the Yield Stress and r-value Distribution on the Earing Profile of Cup Drawing with Yld2000-2d Yield Function
- Author
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Yanshan Lou, Gihyun Bae, Changsoo Lee, Hoon Huh, F. Barlat, Y. H. Moon, and M. G. Lee
- Subjects
Stress (mechanics) ,Materials science ,Deformation (mechanics) ,Metallurgy ,Pseudoelasticity ,Earing ,Geometry ,Deep drawing ,Anisotropy ,Blank ,R-value (insulation) - Abstract
This paper deals with the effect of the yield stress and r‐value distribution on the earing in the cup drawing. The anisotropic yield function, Yld2000‐2d yield function, is selected to describe the anisotropy of two metal sheets, 719B and AA5182‐O. The tool dimension is referred from the Benchmark problem of NUMISHEET’2002. The Downhill Simplex method is applied to identify the anisotropic coefficients in Yld2000‐2d yield function. Simulations of the drawing process are performed to investigate the earing profile of two materials. The earing profiles obtained from simulations are compared with the analytical model developed by Hosford and Caddell. Simulations are conducted with respect to the change of the yield stress and r‐value distribution, respectively. The correlation between the anisotropy and the earing tendency is investigated based on simulation data. Finally, the earing mechanism is analyzed through the deformation process of the blank during the cup deep drawing. It can be concluded that ears locate at angular positions with lower yield stress and higher r‐value while the valleys appear at the angular position with higher yield stress and lower r‐value. The effect of the yield stress distribution is more important for the cup height distribution than that of the r‐value distribution.
- Published
- 2010
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