• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.05a
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• pp.577-580
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• 2010

This paper proposes a new algorithm for flicker reduction. Flicker is defined as unwanted luminance fluctuation in the image sequences. As the flicker degrades the performance of motion estimation or segmentation of the objects, it should be corrected before further processing. In this paper, we model the flicker effects as a linear system with gain and offset parameter and propose the new algorithm for flicker reduction. The proposed algorithm considers gain and offset parameter separately, and stabilizes the luminance fluctuation based on these parameters. We show the performance of the proposed method by testing on the sequence with artificially added luminance flicker and real sequence with object motion.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.139-139
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• 2017

우리나라 수자원의 잠재적 문제점중 하나는 단일 하천 혹은 댐에 대한 의존도가 매우 높다는 것이다. 이러한 현상은 한반도의 지형, 기상, 경제성 등의 요인에 의해 야기된 결과이기도 하지만, 지하수 수자원의 불확실성과 적정 관리의 어려움에서 기인하였다. 지하수는 유속이 매우 느리며 눈에 보이지 않기 때문에 지하수 과잉개발 및 오염 등에 취약하다는 단점이 있는 것이 사실이다. 그러나 지하수자원을 활용하지 않고 무작정 보존하기 보다는 많은 연구개발을 통하여 지속가능한 수자원으로 활용하는 것이 더 바람직하다. 해안에 위치한 지하수개발관정의 경우 바닷물이 대수층을 통해 침투하여 지하수관정을 오염시키는 경우가 발생한다. 해안지하수의 주된 오염 원인은 과잉양수로 해수침투를 야기한 결과이다. 이러한 경우 수질을 회복하기까지 수년이 걸리게 되며, 그동안 취수원으로서의 가치를 상실하게 된다. 또한 최근에는 기후변화의 영향으로 해수면상승에 따른 해수침투길이가 길어져 기존의 해안지역 지하수의 오염위험성이 더욱 증가할 것으로 전망된다. 이러한 이유로 국내외에서 해안지하수 개발에 대한 많은 연구가 진행되고 있다. 많은 해안지하수 수치해석연구에서는 해안경계에 평균해수면(MSL)이 적용된다. 본 연구에서는 조위변화가 지하수위 및 해수침투에 끼치는 영향에 대해 연구하였다.

• Proceedings of the Optical Society of Korea Conference
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• 1995.06a
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• pp.127-137
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• 1995

Anomalously large real space charge transfer through thick barries in GaAs asymmetric double quantum wells is studied by photoluminesence exitation. This inter-well excitonic transfer is very large when the barrier is the Al0.3Ga0.7As alloy, but disappears when the barrier is GaAs/AlAs digital alloy with an equivalent Al concentration of 0.28. These resilts combined with observed x and barrier thickness depence suggest that the spatial fluctuation of the atomic arrangment of Ga and Al in the alloy may be responsible for this transfer. This picture is supported by the quantum mechanical calculation in three dimensions which takes into account the side fluctuation effects.

• Journal of the Korean Society of Physical Medicine
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• v.15 no.1
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• pp.65-76
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• 2020

PURPOSE: The purpose of this study were to determine an intervention that involves proprioceptive exercises combined with cognitive task completion for adults with chronic ankle instability and to investigate the effects of the exercises on the static balance, dynamic balance, and ankle function of such individuals. METHODS: A total of 30 adults suffering from the aforementioned condition were randomly divided into experimental (n=15) and control (n=15) groups. The experimental group performed proprioceptive exercises in combination with cognitive tasks for 15 minutes in each session that was held three times a week for four 4 weeks, whereas the control group carried out only proprioceptive exercises. A Wii Balance Board, which enables examining the fluctuation area distance, and speed, was used to determine static balance; a Y-balance test kit was employed to measure dynamic balance; and the side hop, figure-of-8 hop, and square hop tests were conducted to ascertain ankle function. RESULTS: The results showed that the static balance, dynamic balance, and ankle function of both the experimental and control groups significantly improved. The participants were instructed to perform one-leg postural exercises with and without vision blocking for the affected leg. The experimental group showed more significant improvement than did the controls in terms of the fluctuation distance, speed, and area of static balance. CONCLUSION: In conclusion, although combined proprioceptive exercises and cognitive tasks were insufficient to enhance all types of balance among the subjects, it effectively reinforced their static balance.

• Journal of fish pathology
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• v.15 no.2
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• pp.65-75
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• 2002

This study was performed to know the effects of stress induced by the daily fluctuation of water temperture from 18$^{\circ}C$ to 25$^{\circ}C$ up and down for 30 days on the defence mechanism of olive flounder. Puralichthys olivaceus. To make clear the temperature stress on the defense mechanism of the tested fish. several factors of immune response such as counting of leucocyte appearance in peripheral blood, phagocytic activity in whole blood cells, nitroblue tetrazolium(NBT) reduction, chemiluminescence(CL) response, and lysozyme activity were investigated at 28 days after giving the change of water temperature. The fish was controlled under the none feeding condition during experimental period. Mortality of the tested fish was rapidly increased up to 22% within the first one week of the experimental period without any additional stress factors. The number of neutrophil of peripheral blood in the tested group was significantly higher than the control group at the 2nd week. but the number of lymphocyte was significantly lower than the control group at the 1st and 3rd day of the experimental period. respectively. In the NBT reduction test, the activity of macrophage in the control group fish was the highest on the 7th day while that in the tested group was on the 3rd day. Also. the phagocytosis of tested group against formalin killed cells was retarded compared with the control. CL response of the tested group was significantly lower from 2nd to 5lh day of the experimental period than the control. 'The lysozyme activity of tested group was remained higher during the experimental period than the control. Even though the tested fish showed different results in some non-specific factors of immune respceses between tested and control group fish, olive flounder seems highly adaptable in repealed water temperature change in condition after one week under the given temperature fluctuation range.

• Journal of Environmental Science International
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• v.18 no.10
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• pp.1171-1179
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• 2009

The solitary ascidian, Halocynthia aurantium, which is commonly called the sea peach because of its coloration and general shape, is a valuable organism of benthic marine population in the northern region of the East Sea, Korea. It is seldom found at a depth of less than 10 meters and the sea peach is frequently observed in large populations between 20 and 100 meters. It appears to prefer attachment to vertical rocks faces and artificial cement blocks exposed to the currents. Mass mortality and reduction of resources in sea peach, H. aurantium, were occurred in the benthic area of the northern region of the East Sea because of the rapid fluctuation of environmental factors such as temperature and salinity due to mass rainfall in summer and going up north of a strong warm current in winter. Therefore, we examined the effects of temperature and salinity on embryonic development of fertilized eggs, tadpole larva to metamorphosis, and attachment to siphon development. Laboratory-raised larvae were studied using a two-factorial experimental design with four levels of temperature(8, 12, 16 and $20^{\circ}C$) and four levels of salinity(20, 25, 30 and 34 psu). The ascidian larvae of H. aurantium survived environmental conditions between temperature of $8{\sim}20^{\circ}C$ and salinity of 25~34 psu and exhibited positive growth at $8{\sim}16^{\circ}C$ and 30~34 psu. Fertilized eggs have not developed at lower salinity of 20 psu irrespective of temperature range tested and have showed an abnormal development at the salinity of 25 psu between higher temperatures of 20 and $24^{\circ}C$. This result suggests that temperature increase and salinity reduction depending on environmental fluctuation may have significant impacts on population variation of H. aurantium in the northern region of the East Sea.

• International Commerce and Information Review
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• v.7 no.3
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• pp.269-286
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• 2005

The exchange rate volatility has been increased since the time when the floating exchange rate system was introduced in Korea. As a result, the increase of the exchange rate volatility raised the risk in international trades in Korea. The purpose of this study in to study the feature of exchange rate volatility and the main sources of its increase and to confirm whether the exchange rate volatility influence export volume and price of Korea. In the first place, I measured exchange rate volatility with two methods. The one is descriptive statistic method such as the width of daily exchange rate fluctuation and the rate of exchange rate devaluation. The other is the time varying conditional variance of exchange rate. Then, I studied the sources of exchange rate volatility. In the second place, I defined the exchange rate volatility as the time varying conditional variance and estimated it by using elastic a approach model which shows exchange rate is affected by itself and its conditional variance, I estimated its effects on export volumes and prices of electric home appliances, information & communication equal and semi-conductor. The result of this study is as follows. With presumed result EU and Korea because is not the goods which is to substantial competition relationship, The effect where the relative value change of presumed result expression anger and the dollar of import and export function goes mad to the import and export of Korea the income compared to is to export and it is appearing a lot. The EU goods is sold more expensively the Korean goods than from about length being caused by American market of the dollar and the balance of trade of Korea is visible like being visible the improvement of single breadth. Because the relationship of competition is weak but substantially there is to a short term and expression - the effect where the dollar rate fluctuation is big in Korean trade there is a possibility of saying that widely known it is not.

• Environmental and Resource Economics Review
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• v.26 no.3
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• pp.451-472
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• 2017

An OPEC production announcement is a major source of supply disruption that has a significant impact on the international crude oil market. In this study, the effects of OPEC's announcements are analyzed using event study methodology. Considering the oil price volatility and structural changes in the oil price, we divide the entire period into three periods and analyze the impact of OPEC's production quota announcements, including 'cut', 'hike', and 'maintain'. As a result of the analysis, we observe that the degree and direction of abnormal returns differ according to the announcements in each period. In addition, by subdividing oil price surge and plunge period into two sections, we analyze the effect of OPEC's 'maintain' announcements. During the oil price plunge period, the amount of abnormal returns was significant. This study provides policy implications for oil trading strategies and for the impact of OPEC announcements during periods of oil price fluctuation.

• Journal of Soil and Groundwater Environment
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• v.13 no.1
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• pp.43-51
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• 2008

Periodic fluctuation of water levels were analyzed for their causes and effects on groundwater movement. Groundwater levels were monitored from two shallow monitoring wells, G1 and G4, located at a headwater catchment in the Gwangneung Ecohydrological Research Site using pressure transducers with automatic data-loggers by five-minute interval from February to October, 2006. The water table fluctuates on a daily basis with a clear diurnal variation, and the fluctuation amplitude increases with time from the winter to the summer. Results from spectral analysis of water-level data show periodic variations in 24.38 hour and in 12.19 hour, indicating $P_1$ diurnal and $L_2$ semidiurnal tidal components, respectively. The diurnal component of the water level in summer has greater power than that in winter, implying that the water table is affected not only by earth tides, but also by evapotranspiration. Right after rain stops, the power of diurnal component of the water level decreases, indicating that evapotranspiration influences significantly diurnal periodicity. The effects of diurnal and semidiurnal components of the water level range from 0.4 to 4.2 cm and from 0.2 to 0.7 cm, respectively.

• Korean Journal of Applied Biomechanics
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• v.18 no.2
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• pp.49-58
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• 2008

The purpose of this study was to identify effects of walking speed and a cognitive task during treadmill walking on gait variability. Experiments consisted of 5 different walking speeds(80%, 90%, 100%, 110% and 120% of preferred walking speed) with/without a cognitive task. 3D motion analysis system was used to measure subject's kinematic data. Temporal/spatial variables were selected for this study; stride time, stance time, swing time, step time, double support time, stride length, step length and step width. Two parameters were used to compare stride-to-stride variability with/without cognitive task. One is the coefficient of variance which is used to describe the amount of variability. The other is the detrended fluctuation analysis which is used to infer self-similarity from fluctuation of aspects. Results showed that cognitive task may influence stride-to-stride variability during treadmill walking. Further study is necessary to clarify this result.