• Journal of Korean Society on Water Environment
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• v.40 no.2
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• pp.79-88
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• 2024

This study employed field measurements and biogeochemical analysis to examine the effects of seasonal conditions (e.g., temperature and precipitation) and human intervention (e.g., dam or weir construction) on the chemical composition of dissolved organic matter, flocculation kinetics of suspended particulate matter, and formation of the fluid mud layer on riverbeds. The results indicated that a water environment with a substantial amount of biopolymers offered favorable conditions for flocculation kinetics during an algal bloom period in summer; a thick fluid mud layer was found to be predominated with cohesive materials during this period. However, after high rainfall, a substantial influx of terrigenous humic substances led to enhanced stabilization of the particulate matter, thereby decreasing flocculation and deposition, and the reduced biopolymer composition served to weaken the erosion resistance of the fluid mud on the riverbed. Moreover, a high-turbulence condition disaggregated the flocs and the fluid mud layer and resuspended the suspended particulate matter in the water column. This study demonstrates the mutual relationship that exists between biogeochemistry, flocculation kinetics, and the formation of the fluid mud layer on the riverine area during different seasons and under varying hydrological conditions. These findings are expected to eventually help inform the more optimal management of water resources, which is an urgent task in the face of anthropogenic stressors and climate change.

• Korean Journal of Clinical Laboratory Science
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• v.40 no.2
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• pp.75-79
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• 2008

86 clinical isolates of Acinetobacter baumannii and 116 clinical isolates of Pseudomonas aeruginosa strains isolated from clinical specimens were collected from a hospital in Daegu city area. We investigated the Antimicrobial susceptibility patterns of A. baumannii and P. aeruginosa isolated from sputum, urine, wound, blood, nasal swab, body fluid. The antimicrobial resistance of A. baumannii were shown 96% for piperacillin, carbenicillin 82%. cefotaxime 78%, ciprofloxacin 77%, sulfamethoxazole/trimethoprime 76%, ceftazidime 75%, tobramycin 72%. For P. aeruginosa, the resistance of cefotaxime and sulfamethoxazole/trimethoprime were 100%, carbenicillin 49%, piperacillin 47%, ticarcillin 45%, ticarcillin/ clavulanic acid 40%.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.05a
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• pp.251-256
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• 2002

Resistance performance of small size fishing vessel is experimentally investigated to find out the effect of fore-body shape and trim for the better hull form development. The tests are performed for four different cases in the high speed circulating water channel(CWC). Wave patterns are observed together to investigate the relation between the resistance performance and the wave characteristics.

• International Journal of Internet, Broadcasting and Communication
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• v.7 no.2
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• pp.161-167
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• 2015

The performance of high power LEDs highly depends on the junction temperature. Operating at high junction temperature causes elevation of the overall thermal resistance which causes degradation of light intensity and lifetime. Thus, appropriate thermal management is critical for LED packaging. The main goal of this research is to improve thermal resistance by optimizing and comparing nano-pore silicon-based thermal substrate to insulated metal substrate and direct bonded copper thermal substrate. The thermal resistance of the packages are evaluated using computation fluid dynamic approach for 1 W single chip LED module.

• Journal of Advanced Research in Ocean Engineering
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• v.2 no.2
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• pp.67-80
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• 2016

The resistance performance of an icebreaking cargo vessel with varied stem angles is investigated numerically and experimentally. Ship-ice interaction loads are numerically calculated based on the fluid structure interaction (FSI) method using the commercial FE package LS-DYNA. Test results obtained from model testing with synthetic ice at the Pusan National University towing tank and with refrigerated ice at the National Research Council's (NRC) ice tank are used to validate and benchmark the numerical simulations. The designed icebreaking cargo vessel with three stem angles ($20^{\circ}$, $25^{\circ}$, and $30^{\circ}$) is used as the target ship for three concentrations (90%, 80%, and 60%) of pack ice conditions. The comparisons between numerical and experimental results are shown and our main conclusions are given.

• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.70-77
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• 2004

Comprehensive investigation on the outlet's geometric shapes of a centrifugal blower with higher inlet resistance than an atmospheric pressure is carried out for improvements of its performance. Most unwanted behaviors of such blower are pulsating flows because of unbalance between inflows and outflows in a scroll casing. In order to reduce this undesirable phenomenon a triump is made for both the shape of outlet duct and an accessory structure inserted in the outlet port of the blower. The modification on the shape is concerned with the contraction of cross sectional area and the attached structure is for an intentional obstruction to cause a flow resistance. The details of the modification are examined for different cases and results. The methodologies for the work are performance evaluations including noise level and velocity measurements with PIV Consequently, the performance of improved system is close to that of the system operating with atmospheric pressure at the inlet.

• International Journal of Naval Architecture and Ocean Engineering
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• v.9 no.5
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• pp.537-551
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• 2017

In this paper, a two-phase flow solver $HiFoam^{(R)}$ has been developed based on the $OpenFOAM^{(R)}$ to predict resistance of a ship in calm water. The VOF method of $OpenFOAM^{(R)}$ was reviewed and a simple flux limiter was introduced to enhance the robustness of the solver. The procedure for predicting ship motion was modified by introducing Quasi-Steady Fluid-Body Interaction (QS-FBI) with least square regression to improve the efficiency. Other minor factors were considered as well in terms of the efficiency and robustness. The HiFoam was applied to KCS and JBC simulations to validate its efficiency and accuracy by comparing the results to experimental data and STAR-CCM+. The $HiFoam^{(R)}$ was also applied to various ships and it showed good agreements to the experimental data.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.9
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• pp.849-854
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• 2005

In this paper, the cooling performance of a microchannel heat sink with nano-particle-fluid suspensions ('nanofluids') is numerically investigated. By using theoretical models of thermal conductivity and viscosity of nanofluids that account for the fundamental role of Brownian motion respectively, we investigate the temperature contours and thermal resistance of a microchannel heat sink with nanofluids such as 6nm copper-in-water and 2nm diamond-in-water. The results show that a microchannel heat sink with nanofluids has high cooling performance compared with the cooling performance of that with water, the classical coolant. Nanofluids reduce both the thermal resistance and the temperature difference between the heated microchannel wall and the coolant.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.8 no.1
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• pp.13-25
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• 1996

The purpose of this paper is to study heat transfer characteristics of rotating heat pipe with tapered condensers by numerical analysis and experimental method. An experimental investigation has been carried out on thermal resistance between condenser wall and vapor region fo the rotating heat pipe with various taper 0, 1/11.4, 1/38. Heat transfer characteristics by analytical study were applied to describe various Nu numbers on the base of dimensionless condensate film, Re and Pr numbers in both condensers. Comparison between calculated results and experimental data showed qualitatively good agreement and the numerical analysis of this study can be utilized to predict the performance of a rotating heat pipe. The thermal resistance can be decreased by increasing the revolution per minute. Regardless of various dimensionless condensate film, Nu number was largely influenced by saturation temperatures of working fluid.

• Elastomers and Composites
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• v.17 no.2
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• pp.77-90
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• 1982

The purpose of this study is to get comparative results on the combined antioxidant systems comprised of MHPPD with IPPD, MHPPD with PBN and MHIPPD with MB when they are individually added to NR and SBR compound. Vulcanization characterstics and physical properties of the combined antioxidants have been studied by means of the Mooney viscometer, the Monsanto disc rheometer and so on. According to the test results, MHPPD with IPPD system has shown faster cure rate, better optimum cure time and shorter scorch time than other systems. The vulcanizate comprised of the MHPPD with IPPD antioxidant system has taken advantage of heat resistance, fluid resistance and antiozone resistance.