• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2008년도 학술발표회 논문집
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• pp.67-74
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• 2008

The regional-scale transient groundwater-river interaction model is developed to gain a better understanding of the regional-scale relationships and interactions between groundwater and river system and quantify the residual river flow after groundwater abstraction from the aquifers with climate variability in the Waimea Plains, New Zealand. The effect of groundwater abstraction and climate variability on river flows is evaluated by calculating river flows at the downstream area for three different drought years (a 1 in 10 drought year, 1 in 20 drought year, and 1 in 24 drought year) and an average year with metered water abstraction data. The effect of future water demand (50 year projection) on river flows is also evaluated. A significant increase in the occurrence of zero flow, or very low flow of 100 L/sec at the downstream area is predicted due to large groundwater abstraction increase with climate variability. Modeling results shows the necessity of establishing dynamic cutback scenarios of water usage to users over the period of drought conditions considering different climate variability from current allocation limit to reduce the occurrence of low flow conditions at the downstream area.

• 대한한의진단학회지
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• 제12권2호
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• pp.96-106
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• 2008

Background and purpose : Health is characterized by variability and a loss variability is associated with aging and disease. Normal healthy respiratory patterns are characterized by breath to breath variability. Cold-Heat score are quantified indices in Korean Medicine. The aim of this study is to analyze relations between 9 respiratory indices (including breath to breath variability) and cold-heat score by questionnaire. Method : Respiratory data were measured during 15 minutes and transferred to text file. We calculated 9 respiratory parameters in use of MATLAB7.1. After then we did correlation analysis of 9 respiratory indices and cold-heat score Results and conclusion : EIratio is showed significant correlation with Cold score and weighted Heat score.

• 천문학회보
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• 제45권1호
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• pp.60.1-60.1
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• 2020

We present optical variability of nearby luminous active galactic nucleus (AGN). We use the multi-epoch data of 46 AGNs obtained from 2015 to 2019 through SNU AGN Monitoring Project (SAMP), which was carried out for the reverberation mapping of luminous AGNs. We estimated variability amplitudes and time scales using the various types of analytic function, such as structure function and damped random work. We present the comparisons between physical properties of AGNs and optical variability in order to unveil the origin of the variability of AGNs.

• 천문학회보
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• 제42권1호
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• pp.45.1-45.1
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• 2017

Optical variability is one way to probe the nature of the central engine of AGN at smaller linear scales, and previous studies have shown that optical variability of AGN is more prevalent at longer timescales and at shorter wavelengths. To understand the properties and physical mechanism of variability, we are performing the KMTNet Active Nuclei Variability Survey (KANVaS). Especially, we investigated intra-night variability of AGN with KMTNet data which observed COSMOS field during 3 separate nights from 2015 to 2016 in B, V, R, and I bands. Each night was composed of 5, 9, and 11 epochs with 20-30 min cadence. To find AGN in the COSMOS field, we applied multi-wavelength selection methods. Using X-ray, mid-infrared, and radio selection methods, 50-60, 130-220, 20-40 number of AGN are detected, respectively. Achieving photometric uncertainty ~0.01mag by differential photometry, we employed a standard time-series analysis tool to identify variable AGN, chi-square test. Preliminary results indicate that there is no evidence of intra-night optical variability of AGN. It is possible that previous studies discovered intra-night variability used inappropriate photometric error. However, main reason seems that our targets have fainter magnitude (higher photometric error) than that of previous studies. To discover variability of AGN, we will investigate longer timescale variability of AGN.

• 한국운동역학회지
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• 제17권4호
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• pp.1-8
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• 2007

The purpose of this study was to investigate the difference in the stride-to-stride variability between two treadmill conditions; traditional treadmill and special treadmill whose speed can be adjusted automatically by subject's walking speed. Eight male subjects (25.1 years, 172.7 cm, 66.6 kg) were participated in treadmill walking experiment. First, preferred walking speed (PWS) of each subject was determined. Second, each subject performed walking experiment with fixed PWS condition and with free PWS condition for 10 minutes. 3D motion capture system (Motion analysis Corp., USA) with 6 cameras was used to collect motion data with sampling frequency of 120Hz. Temporal and spatial variables for stride-to-stride variability were calculated. Coefficient of variance (CV) which quantifies the amount of variability and Detrended Fluctuation Analysis (DFA) which explains the structure (self-similarity) of the variability were used for analysis. Results showed that the amount of variability during free PWS condition was greater than that of fixed PWS condition. DFA results showed that there was a statistical difference between two treadmill conditions for the variables of step length, stance time, and double support time. From these results, it is possible that traditional treadmill study might give incorrect conclusion about gait variability study. Further study is necessary to clarify these matters by considering the number of subjects, experimental time, and gait variables for the study of stride-to-stride variability.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2001년도 추계종합학술대회
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• pp.300-303
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• 2001

The first 7 years of altimeter data from the TOPEX/POSEIDON (T/P) were analyzed to study the surface circulation and its variability in the East Asian Marginal Seas. Long term averaged T/P sea level time series data where compared with in situ sea level measurements from a float-operated type tide gauge around of south Korea and Japan. T/P data are a large contaminated by 60-day tidal aliasing effect, very near the alias periods of M2 and S2. When this 60-day effect is removed, the data agree well with the tide gauge data with 4.6 cm averaged RMS difference. The T/P derived sea level variability reveals clearly the well-known, strong current-topography such as Kuroshio. The T/P mean sea level of North Pacific (NP) was higher than Yellow Sea (YS) and East Sea (ES). The T/P sea level valibility, with strong eddy and meandaring, was the largest in eastern part of Japan and this variability was mainly due to the influence of bottom topography in Kuroshio Extention area.

• 신재생에너지
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• 제19권4호
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• pp.98-107
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• 2023

A study was conducted to analyze data from 1981 to 2020 for understanding the impact of climate on solar energy generation. A significant increase of 104.6 kWhm^-2 was observed in the annual cumulative solar radiation over this period. Notably, the distribution of solar radiation shifted, with the solar radiation in Busan rising from the seventh place in 1981 to the second place in 2020 in South Korea. This study also examined the correlation between long-term temperature trends and solar radiation. Areas with the highest solar radiation in 2020, such as Busan, Gwangju, Daegu, and Jinju, exhibited strong positive correlations, suggesting that increased solar radiation contributed to higher temperatures. Conversely, regions like Seosan and Mokpo showed lower temperature increases due to factors such as reduced cloud cover. To evaluate the impact on solar energy production, simulations were conducted using climate data from both years. The results revealed that relying solely on historical data for solar energy predictions could lead to overestimations in some areas, including Seosan or Jinju, and underestimations in others such as Busan. Hence, considering long-term climate variability is vital for accurate solar energy forecasting and ensuring the economic feasibility of solar projects.

• 한국정보통신학회논문지
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• 제5권6호
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• pp.1190-1194
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• 2001

TOPEX/POSEIDON(T/P) 위성의 7년 간 고도계자료를 사용하여 동북아시아지역에서의 해수면 순환과 해수면 변화에 대하여 연구하였다. 헌장 조위자료와 고도계자료간의 비교에서, 고도계에 포함되어 있는 60일의 tidal aliasing(M$_2$ 및 S$_2$의 해양조석 성분)의 영향을 제거한 후 순수 해수면 성분을 구하였다. 해수면 변동을 보면 쿠로시오 해류가 사행을 하면서 강하게 흘러가는 일본 동남부해역에서 뚜렷한 와류의 형성과 함께 높은 해수면 변화 값을 보였다. 이것은 쿠로시오의 확장과 해저지형의 영향과 기인하다. 평균해수면은 황해 및 동해에 비해서 북태평양해역에서 높게 나타났다.

• 대한원격탐사학회지
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• 제23권4호
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• pp.257-272
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• 2007

이 논문에서는 촬영 시기 및 촬영 모드(주파수, 편파, 입사각)에 있어서 여러 가지 조건을 가지는 다양한 SAR 자료로부터 특징을 추출하여 토지 피복 항목과의 상호 연관성을 분석하였다. 현재까지 가용한 인공위성 SAR 영상의 촬영 조건을 고려하여 다음의 두 가지 경우로 구분하여 특징을 추출하였다. 첫째, 단일 모드로 다중 시기에 얻어진 SAR 자료로부터 긴밀도, 시간적 변이도, 주성분 변환에 의한 특징들을 추출하였다. C-밴드인 ERS-1/2, ENVISAT SAR, Radarsat-1 자료와 L-밴드인 JERS-1 SAR 자료를 대상으로 이러한 특징들을 각각 추출하였으며, 일반적인 토지 피복 항목과의 연관성 분석을 통해 다중 센서의 특성 차이를 비교 분석하였다. 여러 특징들 중에서 Tandem 긴밀도는 대체적으로 토지 피복 항목간 구별력이 가장 좋게 나타났다. C-밴드 SAR 자료의 장기간 긴밀도에서는 도심 지역의 구분이 용이하였으며, 시간적 변이도에서는 모든 센서 자료에서 논 지역이 가장 높은 값을 나타내었다. 또한 시계열 후방 산란 계수와 긴밀도의 주성분 변환에 기반한 특징들에서는 토지 피복과 관련된 부가 정보 추출이 가능하였다. 둘째, 다중모드(편파, 입사각)로 비슷한 시기에 얻어진 SAR 자료로부터 편파비와 다중 채널 변이도를 주요 특징으로 추출하여 토지 피복 항목별로 비교하였다. 그 결과, VH/VV 편파비로부터 산림과 밭 항목의 구분력이 향상되는 것으로 나타났다. 이 연구의 분석 결과는 향후 다양한 모드의 시계열적 SAR 자료 및 지상 산란계 실험을 통한 다양한 사례 연구 결과와 결합된다면, SAR 자료를 이용한 토지 피복 분류의 정확도 향상을 위한 기초 정보로 활용될 수 있을 것으로 기대된다.

• 대한토목학회논문집
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• 제26권4B호
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• pp.329-334
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• 2006

Southern Great Plain 1999 실험을 통하여 획득된 L-band와 C-band 토양수분 측정치의 공간 변화 양상을 분석하였다. L-band 토양수분 측정치의 스펙트럼은 관측 스케일의 변화와 함께 토양수분의 공간 변화 양상이 변화됨을 보여주었고, 이러한 변화 양상은 모래함유비와 같은 토양 특성의 공간 변화 양상과 일치함을 보여주었다. 그리고 C-band 토양수분 측정치의 공간 변화 양상은 관측 스케일의 변화와 상관없이 일정한 변화도를 가지는 것으로 나타났다. 이는 식생피복의 공간 변화 양상과 동일함을 보여주는 것이다. 이러한 결과는 AMSR기기를 이용하여 현재 진행되고 있는 토양수분의 전 지구 관측치의 downscaling시 고려되어야 할 것이다.