Kang-neung, South Korea
Kang-neung, South Korea

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Lee J.-W.,University of California at Davis | Kim J.-W.,Gangwon Provincial College | De Riu N.,University of Sassari | Moniello G.,University of Sassari | Hung S.S.O.,University of California at Davis
Aquatic Toxicology | Year: 2012

Triplicate groups of juvenile green and white sturgeon (average weight of 30 ± 2. g) were exposed to one of four concentrations of dietary methylmercury (MeHg; 0, 25, 50, and 100. mg MeHg/kg diet) for 8 weeks to determine and compare the sensitivity of the two sturgeon species from a histopathological perspective. After 4- and 8-week exposure, histological changes were examined in the kidney, liver, gill, skeletal muscle, and heart muscle of both species using light microscopy. Marked abnormalities were observed in the kidney and liver of both sturgeon species after each exposure period; the abnormalities showed progressive histological alterations in severity with increasing doses and duration of exposure. Renal lesions included tubular epithelium degeneration and necrosis, renal corpuscular disintegration, and interstitial tissue degeneration. The changes observed in the livers of both sturgeon species were glycogen depletion and vacuolar degeneration. In the gill and skeletal and heart muscle of green and white sturgeon fed MeHg-added diets, mild histological changes were observed but did not show pronounced difference between the two species. Although the lowest observed effect concentration in both species was the 25. mg MeHg/kg diet, the histological changes in the kidney and liver were more pronounced at all treatments groups of green sturgeon than those of white sturgeon. The current results on structural changes of kidney and liver (i.e., more severe glycogen depletion and tubular epithelium degeneration in green sturgeon) confirmed our previous results, in that green sturgeon exhibited a higher mortality, lower growth rate, and lower protein, lipid, and energy contents in their whole body than white sturgeon under the same MeHg exposures. © 2011 Elsevier B.V..

Yim H.-B.,Gangwon Provincial College | Lee S.-R.,Mokpo Maritime University
International Journal of Multimedia and Ubiquitous Engineering | Year: 2016

The compensation effects of number of fiber spans and the residual dispersion per span (RDPS) in the combining of dispersion management (DM) and the midway optical phase conjugation on the optical transmission link consisted of the long fiber spans with 94 km of SMF length and -160 ps/nm/km of the dispersion-compensating fiber’s dispersion coefficient for 24 channels x 40 Gbps wavelength division multiplexed (WDM) signals. We confirm that the combining technique of DM and the midway optical phase conjugation is still effective to compensate for the distorted WDM signals through the optical link consisted of the long fiber spans. It is also confirmed that the compensation effect on the distorted WDM channels is more increased as the portion of the concentrated compensation is more increased than the portion of in-line compensation. © 2016 SERSC.

Yim H.-B.,Gangwon Provincial College | Lee S.-R.,Mokpo Maritime University
International Journal of Information and Communication Technology | Year: 2016

In high-capacity and long-haul optical communication systems, signal distortion is induced by the group velocity dispersion (GVD) and nonlinear Kerr effects of optical fibres. Different techniques to compensate for the signal distortion in the optical links, by using an optical phase conjugator (OPC), have been proposed in the literature. However, compensation by the use of an OPC is limited by the asymmetry of the signal power. Dispersion management (DM) combined with an OPC is one of the various techniques for overcoming this drawback. The system performance improvement in these optical links has been reported; however, the fixed residual dispersion per span (RDPS) usually used in the optical links with an OPC and DM restricts flexible link configuration. In this paper, OPC links combined with DM of randomly distributed RDPS is proposed for implementing a flexible optical transmission network. We confirm that the proposed links are effective for our purpose, if the averaged RDPS of the fibre span was selected to be non-zero and low. © 2016 Inderscience Enterprises Ltd.

Park J.,University of Arkansas at Pine Bluff | Kim P.-K.,Gangwon Provincial College | Lim T.,Ministry of Agriculture, Fisheries and Food | Daniels H.V.,North Carolina State University
Aquacultural Engineering | Year: 2013

A 44-day production trial was done in three identically configured pilot-scale seawater recirculating aquaculture systems (RAS) to evaluate the effects of two different ozonation levels on solids, bacteria, water clarity, and color variables. The control system (CS) was not ozonated, while the treatment systems received ozone at either 20gO3/kgfeedday-1 (T 20) or 40gO3/kgfeedday-1(T 40).Solids concentrations in the two treatments receiving ozone were lower and less variable than the concentrations in the CS. Ozonation reduced suspended solids (SS) and volatile suspended solid (VSS) concentrations by 42.0-52.5% and dissolved organic carbon (DOC) by 29.3-30.6%. The ratios of DOC to SS and to VSS decreased significantly (. P<. 0.05). In addition, the amount of solid removed from the radial flow settler increased 27.1% in both ozone-treatment systems. Bacteria counts on different culture media (Marine, TCBS and MacConkey agars) varied considerably during the study period, but were generally lower in the treatments receiving ozone than the CS. Differences in bacteria abundance between two treatments, T 20 and T 40, were not significant (. P>. 0.05). Based on 24-h sampling, bacteria counts in CS gradually increased after feeding during the daytime and declined during the night. Counts of Vibrio spp. in T 20 fluctuated daily in a similar pattern to the Vibrio spp. in the CS, while overall bacteria counts in T 40 remained low throughout the 24-h sampling period.Turbidity fluctuated greatly in all treatments; there were no significant differences between any of the treatments (. P>. 0.05). Apparent water color (AC) and true water color (TC) in the treatment were reduced 70% compared to the CS, but there was no significant difference (. P>. 0.05) between the two ozone treatments.Based on the variables measured, the higher dose of ozone (40gO3/kgfeedday-1) did not improve solid concentrations, bacterial counts or water colors beyond the values found in the T 20 treatment. Thus, the use of ozone at 20gO3/kgfeedday-1 in a seawater RAS appears to be sufficient to improve water quality of these systems without adversely affecting black sea bream (Acanthopagrus schlegelii) growth. © 2013 Elsevier B.V.

Flame transfer function measurements were performed in a turbulent premixed lean combustor with various blends of hydrogen and natural gas. The fuel mixture was completely premixed with air upstream of a choked inlet to the combustor to avoid equivalence ratio fluctuations. A variable speed siren was used to modulate fluctuations in the inlet velocity, which was measured using a hot wire anemometer as an input parameter of the flame transfer function. Heat release oscillations as an output function were determined using chemiluminescence measurements from whole flames. Stable flame images were captured to understand general flame behavior over a range of operating conditions and fuel blends. Experimental results showed that the stable flames' COMs (centers of mass) laid along a common path in a 2-D plane for all of the operating conditions and tested fuel compositions at a given injector geometry, and that variations in the stable flame shape could be characterized by the location of the common path of the flame's COM. It was also shown that changes in the fuels significantly affected the flame shape; as a result, flame dynamics varied with changes in flame geometry. Accordingly, flames that were close together on the characteristic flame COM curve were shown to have similar forced flame responses. © 2010 Elsevier Ltd. All rights reserved.

Kim D.,Gangwon Provincial College | Park S.W.,Hanyang University
Fuel Processing Technology | Year: 2010

An experimental study of the flame response in a premixed gas turbine combustor has been conducted at room temperature and under atmospheric pressure inlet conditions using natural gas. The fuel is premixed with the air upstream of a choked inlet to avoid equivalence ratio fluctuations. Therefore the observed flame response is only the result of the imposed velocity fluctuations, which are produced using a variable-speed siren. Also, a variable length combustor is designed for investigating characteristics of self-excited instabilities. Measurements are made of the velocity fluctuation in the mixing section using hot wire anemometry and of the heat release fluctuation in the combustor using chemiluminescence emission. The results are analyzed to determine the phase and gain of the flame transfer function. The results show that the gain of flame transfer function is closely associated both with inlet flow forcing conditions such as frequency and amplitude of modulation as well as the operating conditions such as equivalence ratio. In order to predict the operating conditions where the combustor goes stable or unstable at given combustor and nozzle designs, time-lag analysis was tried using convection time delay measured from the phase information of the transfer function. The model prediction was in very good agreement with the self-excited instability measurement. However, spatial heat release distribution became more significant in long flames than in short flames and also had an important influence on the system damping procedure. © 2010 Elsevier B.V. All rights reserved.

Kim J.,University of Wisconsin - Madison | Reitz R.D.,University of Wisconsin - Madison | Park S.W.,Hanyang University | Sung K.,Gangwon Provincial College
Journal of Engineering for Gas Turbines and Power | Year: 2010

Experimental and numerical studies were performed to investigate the simultaneous reduction in NOx and CO for stoichiometric diesel combustion with a three-way catalyst. A single-cylinder engine was used for the experiments and KIVA simulations were used in order to characterize the combustion efficiency and emissions of throttled stoichiometric diesel combustion at 0.7 bar boost pressure and 90 MPa injection pressure. In addition, the efficiency of emission conversion with three-way catalysts in stoichiometric diesel combustion was investigated experimentally. The results showed CO and NOx emissions can be controlled with the three-way catalyst in spite of the fact that CO increases more at high equivalence ratios compared with conventional diesel combustion (i.e., lean combustion). At a stoichiometric operation, the three-way catalyst reduced CO and NOx emissions by up to 95%, which achieves lower emissions compared with conventional diesel combustion or low temperature diesel combustion, while keeping better fuel consumption than a comparable gasoline engine. Copyright © 2010 by ASME.

Park J.,North Carolina State University | Kim Y.,Gangwon Provincial College | Kim P.-K.,Gangwon Provincial College | Daniels H.V.,North Carolina State University
Aquacultural Engineering | Year: 2011

Foam fractionators, with and without additional ozonation, were evaluated for their effect on solids removal (suspended solids, SS; volatile suspended solids, VSS; dissolved organic carbon, DOC), particle size distribution of the foam in seawater recirculating systems during a 44-day experimental period. The effect of ozone on heterotrophic bacteria was also quantified in the entire system. Three separate but identical recirculating systems (4.5m3 system volume) with foam fractionators (300mm in diameter, 3m in height) were used in this study. One system (Control: CS) did not receive ozone, while the other two systems were ozonated at a rate of either 20g ozone/day (T 20) or 40g ozone/day (T 40) per kg of feed applied, respectively. A total of 107kg of black sea bream Acanthopagrus schlegeli (Bleeker) with an average weight of 334.5g was stocked into each system. Daily feeding rate was 1% of total body weight. The solids enrichment factor (EF=Cc/Ci, where Cc=concentration in foam condensate, Ci=concentration in inlet water) in T 40 was 10 times more dilute than the factors in CS and T 20. However, due to the higher volume of the foam (>10 times) in T 40, the removal rates of SS, VSS and DOC were the highest in T 40, but were not significantly different from T 20 (P>0.05). The mean particle sizes at the 90% cumulative removal point decreased with ozonation, 71.2±15.9, 57.9±10.2 and 48.0±10.2μm in CS, T 20 and T 40, respectively. The overall mean particle diameter of solids in the foam decreased as ozonation increased, with values of 29.4±4.4, 23.9±3.8 and 20.5±3.7μm in CS, T 20 and T 40. Numbers of heterotrophic bacteria in the inlet were 6.21±4.93×105CFU/mL, 0.29±0.19×105CFU/mL and 0.30±0.29×105CFU/mL in CS, T 20 and T 40, declining sharply with the addition of ozonation. As the number of the bacteria in the inlet decreased, the bacteria in the foam and the removal rate greatly decreased with increasing ozonation. However, EFs in T 20 (76.4) and T 40 (14.5) were higher than that in CS (12.2), and the T 20 showed significantly higher EF (P<0.05). Therefore, based on the EF, ozonation improved the removal efficiency of heterotrophic bacteria, even at the lowest concentration. © 2010 Elsevier B.V.

Shin I.-S.,Bioscience Technology | Han J.-S.,Bioscience Technology | Choi K.-D.,Bioscience Technology | Chung D.-H.,Bioscience Technology | And 2 more authors.
Food Control | Year: 2010

The effects of isothiocyanates (ITCs) on microbiological, physicochemical, and sensory properties were investigated in tofu on days 0, 2, 4, 6, 8, and 10 of storage at 10 °C. When compared to the control (8.14 log CFU/g), the 200 ppm of ITCs (4.40 log CFU/g) effectively retarded the growth of microflora in tofu after 10 days of storage. The initial pH slightly declined after 10 days of storage, ranging between 5.81 and 6.14. The control showed significantly higher acid values over storage. Compared to the control, the preference to sensory attributes (color, taste, odor, chewiness, and over acceptance) of ITC-treated samples was highly rated after 10 days of storage. The ITCs can be used as an alternative for extending the shelf life and improving the safety of tofu. © 2010 Elsevier Ltd. All rights reserved.

Okorie O.E.,Pukyong National University | Bae J.Y.,Pukyong National University | Kim K.W.,South Korean National Fisheries Research and Development Institute | Son M.H.,South Korean National Fisheries Research and Development Institute | And 2 more authors.
Aquaculture Nutrition | Year: 2013

Two feeding trials were carried out to determine the optimum feeding rates in juvenile olive flounder, Paralichthys olivaceus, at the optimum rearing temperature. Fish averaging 5.0 ± 0.11 g (mean ± SD) in experiment 1 and 20.2 ± 0.54 g (mean ± SD) in experiment 2 were fed a commercial diet at the feeding rates of 0%, 3.0%, 4.0%, 4.25%, 4.5% and 4.75% body weight (BW) day-1 and satiation (5.52% BW day-1) in experiment 1 and 0%, 1.0%, 2.0%, 3.0% and 3.5% BW day-1 and satiation (4.12% BW day-1) in experiment 2 at 20 ± 1 °C. Both feeding trials lasted for 2 weeks. Results from experiment 1 indicated that weight gain (WG) and specific growth rate (SGR) of fish fed to satiation were significantly higher than those of fish fed at other feeding rates while feed efficiency (FE) and protein efficiency ratio (PER) of fish fed at 4.25% BW day-1 were significantly higher than those of fish fed to satiation and fish fed at 3.0% BW day-1 (P < 0.05). In experiment 2 WG, SGR and PER leveled out after the feeding rate of 3.5% BW day-1 whereas FE reached a plateau at 3.0% BW day-1. anova of FE indicated that the optimum feeding rates in 5.0 and 20 g juvenile olive flounder could be 4.25% and 3.0% BW day-1, respectively. Broken line analysis of WG suggested the optimum feeding rates of 5.17% and 3.47% BW day-1 in 5.0 and 20 g fish, respectively. Therefore, these results indicated that the optimum feeding rates could be >4.25 but <5.17% BW day-1 for 5.0 g, and it could be >3.0 but <3.47% BW day-1 for 20 g size of juvenile olive flounder at the optimum rearing temperature. © 2012 Blackwell Publishing Ltd.

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