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Ghim, Sa-Youl Korean Society of Life Science 2001 Journal of Life Science Vol.11 No.2
The pyrR gene of the pyrimidine biosynthesis (pyr) operon of the thermophile Bacillus caldolyticus, encoding a uracil phosphoribosyltransferase (UPRTase), turned to rely as a pyr operon regulator. It has been proposed that PyrR mediates transcriptional termination-antitermination at three intercistronic regions of the par operon (S.-Y Ghim and J. Neuhard, J. Bacteriol.,176, 3698-3707, 1994). In this research, a plasmid carrying the pyrR region of B. caldolyticus could restore a pyrimidine regulation in a pyrR mutant of B. subtilis. Expression of pyrR was found to increase 6-7 fold during pyrimidine starvation. Additionally, a highly conserved nucleotide sequence which may constitute the binding site for a PyrR protein (PyrR-binding loop) in transcript was staggested. Alternative antiterminator and terminator structures involving three conserved motifs in front of the pyrR, pyrP and pyrB genes, respectively, are proposed to account for the observed regulation pattern.
Condensation heat transfer of low GWP ORC working fluids in a horizontal smooth tube
Ghim, G.,Lee, J. Pergamon Press ; Elsevier Science Ltd 2017 INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER - Vol.104 No.-
The objective of the current study is to conduct an experimental investigation of condensation heat transfer for the ORC (organic Rankine cycle) working fluids R245fa, Novec®649 and HFE-7000 over a wide range of parameters. Quasi-local condensation heat transfer coefficients are measured in a straight horizontal 7.75-mm-ID smooth tube with flow conditions at mass flux G=150-700kg (m<SUP>2</SUP>-s)<SUP>-1</SUP>, local equilibrium quality x=0.05-0.95, and reduced pressure, P<SUB>r</SUB>=0.05-0.15. Test data reveal that the environmentally friendly fluids have lower condensation heat transfer coefficients when compared to R245fa. The 141 measured condensation heat transfer coefficients are compared to six well-known correlations. Among the six correlations verified with test data, the Shah correlation shows the best predictive performance for the three fluids tested.
Dry Deposition of Reactive Nitrogen and Sulfur Compounds in the Greater Seoul Area
Ghim, Young Sung,Kim, Jin Young 한국화학공학회 2002 Korean Journal of Chemical Engineering Vol.19 No.1
While deposition is a removal process of pollutants from the atmosphere, it is an intake process of such pollutants into the ground. It is suggested that surface waters in the Greater Seoul Area, used as a source of drinking water, have been affected by severe air pollution. In this work, the dry deposition of reactive nitrogen and sulfur species was estimated for three typical days in each season for the year of 1997. The CIT (California Institute of Technology) photochemical model incorporated with a gaseous oxidation reaction of SO_2 was used. The study revealed that reactive nitrogen deposition was the largest in summer and sulfur deposition was the largest in winter. Most of the reactive nitrogen was deposited in the form of HNO_3 and NO_2, but HNO_3 deposition is highly dependent on the season according to the extent of photochemical production. On the other hand, the contribution of sulfate to the total deposition of sulfur was minimal partly because of low deposition velocity and of the neglect of possible inflow from the boundaries. Approximately 53% of the reactive nitrogen and 30% of the sulfur emitted in the study area was deposited in the ground in the dry form on an annual basis.
ADVANCED TREATMENT OF LEACHATE BY MEMBRANE PROCESSES
GHIM, Shijun,OZAKI, Hiroaki,TERASHIMA, Yutaka 嶺南大學校 環境問題硏究所 1996 環境硏究 Vol.16 No.1
AbstractIn this research, we present the treatment results ofleachates from landfill sites of municipal solid wastes or artificial incineration ash leachate by the process of ASMF (activated sludge process with microfiltiation membrane) combined with LPRO (low pressure reverse osmosis membrane). The LPRO showed a high removal of recaldttant substances and inorganic salts. However, this process is not appropriate fer the direct leachate treatment. Thus, the ASMF using ceramic membrane of the pore size of 0.1 fim was applied as a pretreatment process.As the result of experiments, it was found that these processes could effectively remove both recalcitrant substances and inorganic salts of leachates. For example, the treatment efficiencies of artificial. incineration ash leachate by ASMF combined with LPRO were 99 % ofCODcr, 55 %ofT-N, 70 % of calcium, and 53 % of sodium. Therefere, it was confirmed that the process of ASMF combined with LPRO can become an alternative to the physico-chemical process in conventional leachate treatment plant. In this research, we present the treatment results of leachates from landfill sites of municipal solid wastes or artificial incineration ash leachate by the process of ASMF (activated sludge process with microfiltration membrane) combined with LPRO (low pressure reverse osmosis membrane). The LPRO showed a high removal of recalcitrant substances and inorganic salts. However, this process is not appropriate for the direct leachate treatment. Thus, the ASMF using ceramic membrane of the pore size of 0.1㎛ was applied as a pretreatment process. As the result of experiments, it was found that these processes could effectively remove both recalcitrant substances and inorganic salts of leachates. For example, the treatment efficiencies of artificial incineration ash leachate by ASMF combined with LPRO were 99% of COD_cr, 55% of T-N, 70% of calcium, and 53% of sodium. Therefore, it was confirmed that the process of ASMF combined with LPRO can become an alternative to the physico-chemical process in conventional leachate treatment plant.
Ghim, G.,Lee, J. Pergamon ; Elsevier Science Ltd 2016 Applied thermal engineering Vol.106 No.-
The existence of temperature gliding in non-azeotropic mixture working fluids provides a promising opportunity for greatly improved resource utilization in organic Rankine cycle (ORC) systems for geothermal applications. The condensation heat transfer degradation associated with working fluid mixtures is an unavoidable penalty that may reduce the utilization and system benefits by necessitating larger heat exchangers. The objective of the current study is an experimental investigation of condensation heat transfer for R245fa, n-pentane, and a composition of their mixture. Quasi-local condensation heat transfer coefficients are measured in a straight horizontal smooth tube with flow conditions at mass flux G=100 and 150kg(m<SUP>2</SUP>s)<SUP>-1</SUP>, local equilibrium quality x=0.05-0.80, and reduced pressures P<SUB>r</SUB>=0.05-0.15. The reduced condensation heat transfer coefficients from the test are compared with the predictions from already established mixture correction methods in the literature. Pure components R245fa and n-pentane condensation heat transfer data are well predicted by Shah (1979) correlations for all test conditions. However, their non-azeotropic mixture condensation heat transfer data require additional correction parameter to account for the heat transfer degradation. This correction parameter is correlated by the temperature gliding gradient of mixture fluids. Test data with mixture working fluids from current study are reasonably well predicted by the corrected in-tube correlation.