• Journal of Wind Energy
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• v.4 no.1
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• pp.46-52
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• 2013

The wind generally includes turbulence characteristics in nature. So the yaw errors between wind turbine direction and wind direction occur due to turbulence fluctuation. The yaw errors affect the fatigue load of wind turbine system and power reduction. The components of turbulence intensity are different from those of each site where the wind turbines are installed. We studied that the fatigue load and power efficiency are improved by controlling yaw motions. In this study, we controlled the averaged yaw error time according to site conditions by turbulence intensity.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.60 no.1
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• pp.37-46
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• 2024

This study was conducted to provide the basic information on environment effects on appearance of ichthyoplankton in the Yeongsan River Estuary in Spring and Summer from 2018 to 2020. Data were obtain from the database of 'Coastal Ecosystem' in "National Survey of Marine Ecosystem." Among the abundance ichthyoplankton species, the Gobiidae spp. dominated, accounting for 85% of the total abundances with the secondary dominant species being the Parablennius yatabei, representing 3% of the abundances. Cluster analysis results revealed a composition differentiated between spring and summer. The Yeongsan River Estuary is known to be significantly influenced by the opening and closing of estuarine gates. In this study, the fluctuation in the number of occurrence groups and abundance among the years and season is attributed to the phenomenon of high water temperature period and the freshwater discharge.

• Journal of Environmental Science International
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• v.13 no.5
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• pp.449-467
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• 2004

Interannual and decadal scale changes in body size of Pacific saury, catch and catch per unit effort were examined to investigate the environmental effects on the stock structure and abundance in the Tsushima Warm Current region. Interannual changes in thermal conditions are responsible for the different occurrence (catch) rates of sized group of the fish. Changes in body size due to environmental variables lead the stock to be homogeneous during the period of high abundance, while one of the reminder cohorts supports the stock during the period of low level of abundance. Migration circuits of two cohorts of saury stock are hypothesized on the basis of short life span and spatio-temporal changes of the stock structure in normal environmental conditions. Changes in upper ocean structure and production cycles by the decadal scale climate changes lead changes in stock structure and recruitment, resulting in the fluctuation of saury abundance. Hypothesized mechanism of the effects of climate changes on stock structure and abundance is illustrated on the basis of changes in thermal regime and production cycle.

• Journal of Advanced Marine Engineering and Technology
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• v.10 no.3
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• pp.94-106
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• 1986

Since the oil shock of '70s the engine makers have developed new types of diesel engine with low fuel consumption. There is an obvious tendency towards the use of poorer quality fuels, such as the residual oil from chemical processes of refinery. The shaft driving generators is also widely adopted on behalf of the auxiliary diesel engines, which are driving on the expensive diesel oil and have high fuel oil consumption rates, and some mania propulsion diesel engines are equipped with reduction gear systems to get better propulsive efficiency by slower propeller revolutions. The propulsion shafting system equipped with the shaft driving generator or the geared diesel engine shafting system has flexible couplings, and it requires extensive investigations of the torsional vibration and torque fluctuation in order to ensure the acceptable operation range in service. The characteristics of misfiring must be especially examined for the high viscosity fuels to be used. Both torsional vibration and fluctuating torque resulted from misfiring, should be examined for thier effects on the flexible coupling and propulsion shafting system. This paper is to investigate and solve the above mentioned problems which must be predicted on the design-stage of marine propulsion shafting system. A computer program is developed to calculate the indicated diagram, fluctating torque and torsional vibration for both normal and misfiring conditions.

• Microbiology and Biotechnology Letters
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• v.47 no.4
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• pp.614-620
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• 2019

Microalgae have been explored as potential host species for biofuel production. Environmental factors affect algal growth and cellular composition. The effects of several key environmental factors, such as temperature, light, and pH of the medium on the growth and biochemical composition of Scenedesmus obliquus were investigated in this study. The highest growth rate of microalgae was observed at an optimal temperature of 25℃, 150 μmol/(m²·s) light intensity, and pH 10.0. The biochemical composition analysis revealed that the carbohydrate content decreased at lower (20℃) or higher temperature (35℃), whereas the protein and lipid contents increase at these temperatures. The fluctuation of light intensity significantly affected the contents of protein, carbohydrate, and lipid. The protein levels varied greatly when the pH of the medium was below 7.0. The carbohydrate and lipid contents significantly increased at pH above 7.0.

• Journal of Korean Physical Therapy Science
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• v.25 no.2
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• pp.15-23
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• 2018

Purpose: The purpose of this study was to investigate the effects of Interferential current stimulation therapy(ICT) on pain, balance, and walking ability of elderly patients with chronic low back pain. Methods: Twenty participants were randomly assigned to ICT group (2 males and 8 females) and placebo ICT group (3 males and 7 females). Participants were ICT and placebo ICT for 20 minutes, and the pre- and post-VAS, TUG and postural balance were measured. Results: The ICT group showed significantly decreased pain scores in the elderly patients with chronic low back pain (p<.05) than the placebo ICT group. The postural fluctuation with eyes opened and closed was significantly lower than the placebo ICT group(p<.05), and the ICT group showed remarkable improvement (p<.05). Conclusion: ICT was expected to improve decrease pain, improve postureal sway and walking ability remarkably. Therefore, It was expected that the application or ICT would be an effective method for elderly patients with Chronic Low Back Pain.

• Journal of ILASS-Korea
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• v.6 no.1
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• pp.25-34
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• 2001

Several efforts to meet the exhaust gas regulation have been undertaken by many researchers in recent years. Main researches are on development of design techniques of intake port and combustion chamber, atomisation of fuel and precise control of air-fuel ratio, post-treatment of exhaust gas and so on. Engine technology is changed from PFI to GDI to correspond with exhaust gas regulation. GDI technique makes it possible to preserve lean air-fuel ratio and control accurate air-fuel ratio. Nevertheless, It is not cleared that information of spray characteristics and atomization process are very dependent on fluctuation of pressure and change of temperature in intake stroke. In this study, a constant volume combustion chamber is manufactured to investigate various fluctuations of in-cylinder pressure for injection duration. It is taken photographs of injection process of conventional GDI injector using PMAS. Then, it was verified experimently that ambient conditions as temperature and pressure of combustion chamber have effects on process of spray growth and atomization of fuel.

• Proceedings of the Korean Aquaculture Society Conference
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• 2004.05a
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• pp.169-171
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• 2004

Interannual and decadal scale body size of Pacific saury, catch and catch per unit effort were examined to investigate the environmental effects on the stock structure and abundance in the Tsushima Warm Current region. Interannual changes in thermal conditions are responsible for the different occurrence (catch) rates of sized group of the fish. Changes in body size due to environmental variables lead the stock to be homogeneous during the period of high abundance, while one of the reminder cohorts supports the stock during the period of low level of abundance. Migration circuits of two cohorts of saury stock are hypothesized on the basis of short life span and spatio-temporal changes in stock structure in normal environmental conditions. Changes in upper ocean structure and production cycles by the decadal scale climate changes lead changes in stock structure and recruitment, resulting in the fluctuation of saury abundance. Hypothesized mechanism of the effects of climate changes on the stock structure and abundance is illustrated on the basis of changes in thermal regime and production cycle.

• JSTS:Journal of Semiconductor Technology and Science
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• v.13 no.5
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• pp.511-515
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• 2013

A Monte Carlo (MC) simulation study has been done in order to investigate the effects of line-edge-roughness (LER) induced by either 1P1E (single-patterning and single-etching) or 2P2E (double-patterning and double-etching) on fully-depleted silicon-on-insulator (FDSOI) tri-gate metal-oxide-semiconductor field-effect transistors (MOSFETs). Three parameters for characterizing the LER profile [i.e., root-mean square deviation (${\sigma}$), correlation length (${\zeta}$), and fractal dimension (D)] are extracted from the image-processed scanning electron microscopy (SEM) image for each photolithography method. It is experimentally verified that two parameters (i.e., ${\sigma}$ and D) are almost the same in each case, but the correlation length in the 2P2E case is longer than that in the 1P1E case. The 2P2E-LER-induced $V_TH$ variation in FDSOI tri-gate MOSFETs is smaller than the 1P1E-LER-induced $V_TH$ variation. The total random variation in $V_TH$, however, is very dependent on the other major random variation sources, such as random dopant fluctuation (RDF) and work-function variation (WFV).

• Journal of Technology Innovation
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• v.5 no.1
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• pp.181-205
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• 1997

There has been considerable controversy over the impacts of the tax credit on R&D expenditures in many countries. Korea has adopted various kinds of tax credit system to stimulate private firm' R&D expenditures. Korean government, Recently, is trying to reform tax system to reduce tax credit programmes according to Uruguay Round agreement and in line with OECD policy standards. The purpose of this paper is to analyze the effectiveness of current tax credit system on technology innovation in Korea and derive some policy implications over tax reform. In this paper, firstly, I investigate the size of tax reduction effects from each program in theoretical models and simulate the actual rate of individual tax incentive to a unit of R&D expenditure. I find that theoretically the reserve fund for technology development program has given the largest tax reduction effects to private firms irrespective of the R&D incentive system reform. Tax credit on R&D expenditure also has been very effective instrument to firm's tax reduction. Secondly, I try to measure the effectiveness of tax credit through the estimation of effective margianl tax rate between with the system and without the system of credit on R&D expenditure during the tax credit reform periods. I find that the tax credit on R&D has lowered firm's investment cost since the system introduced. I also have strong results that there has been a positive relation between the fluctuation of firm's R&D expenditure and the change of effective marginal tax rate. I suggest that it is better to sustain the system of tax credit on R&D for a while to increase firm's R&D expenditure.