• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.1525-1530
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• 2008

최근의 기상이변 및 집중호우 등에 대응하기 위해 기존 다목적댐 상류지역에 대한 홍수를 저감시키고, 용수공급, 퇴사 및 탁수저감, 부유물 차단 및 레크레이션 등 기존댐의 효용 증진과 그 가치를 제고하기 위하여 다목적댐 상류에 소규모댐 설치 필요성이 커지고 있다. 따라서 본 연구에서는 소양강, 충주, 횡성, 안동, 임하, 합천, 남강, 밀양, 대청, 용담, 섬진강, 주암(본,조), 부안, 보령, 장흥 등 전국의 다목적댐 15개소의 상류 하천 및 유역을 대상으로 국내외 사례를 조사하여 소규모댐의 정의, 역할, 기능 및 효과를 제시하고 소규모댐의 필요성 및 사업의 타당성을 정립하며, 상류 소규모댐 개발 가능지점 선정을 위하여 댐별 특성을 고려한 수문현황, 환경기초현황 등의 문헌조사와 이를 토대로 도상검토 및 현장조사를 통한 홍수조절, 상류 용수공급, 퇴사, 탁수, 부유물, 레크레이션 등의 소규모댐의 필요성을 제시하여 지자체 및 지역의견 수렴후 개발지점을 선정하는 것이다. 개발지점 선정을 위하여 이수부문 및 치수부문으로 조사목적을 구분하였으며, 이수부분은 인구 현황 및 상수도 이용실태 등을 각 댐별 관련보고서 및 현황 자료를 조사 분석하여 개발의 필요성 및 지점을 결정하였고, 치수부분은 홍수피해액, 수해상습지 및 재해위험지구 등을, 소규모댐의 설치 목적별로 지표들을 핵함수를 이용한 비매개변수적 확률밀도함수법으로 지수화하여 우선순위를 결정하였다.

• Journal of Broadcast Engineering
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• v.18 no.4
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• pp.543-549
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• 2013

Motion artifacts of central and autonomic nervous system signals degrades the performance of the bio-signal based human factor analysis. Firstly, we propose a defining method of motion artifact section by analyzing successive image frames. Motion artifact section is defined when the amount of motion is greater than the pre-defined threshold. In here, the amount of motion is estimated by first derivation of image frames at temporal domain. Secondly, we propose another defining method of motion artifact section through designing 2D Gaussian probability density function model by analyzing feature vectors of one cycle of signal such as length and amplitude. The defined motion artifact sections are interpolated on the basis of 1D Gaussian function. At result of applying the method into photoplethysmography signal, we confirmed that the calculated heartbeat rate from the restored photoplethysmography came up to the one from electrocardiography. Also, we found that the video based method generated relatively more false acceptance of motion artifact section and the probability density function based method generated relatively more false rejection of motion artifact section.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.7
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• pp.665-670
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• 2010

The effect of a particle's spin is investigated numerically by taking into account the effect of lift forces originating due to difference between the rotations of a particle and of a fluid, such as the Saffman and Magnus lift forces. These lift forces have been ignored in many previous studies on particle-laden turbulence. The trajectory of the particles can be changed by the lift forces, resulting in a significant modification of the stochastic characteristics of heavy particles. Probability density functions and autocorrelations are evaluated from the velocity of solid particle, acceleration of solid particles, and acceleration of fluid at the position of solid particle. Changes in velocity statistics are negligible but statistics related with acceleration are affected by the rotation of particle. When a laden particle encounters coherent structures during its motion, the particle's rotation might significantly affects the motion due to intermittently large fluid acceleration near the coherent structures.

• Science of Emotion and Sensibility
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• v.17 no.2
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• pp.63-76
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• 2014

Although most behavioral reaction times (RTs) for cognitive tasks exhibit positively skewed distributions, the majority of studies primarily rely on a measure of central tendency (e.g. mean) which can cause misinterpretations of data's underlying property. The purpose of current study is to introduce procedures for describing characteristics of RT distributions, thereby effectively examine the influence of experimental manipulations. On the basis of assumption that RT distribution can be represented as a convolution of Gaussian and exponential variables, we fitted the ex-Gaussian function under a maximum-likelihood method. The ex-Gaussian function provides quantitative parameters of distributional properties and the probability density functions. Here we exemplified distributional analysis by using empirical RT data from two conventional visual search tasks, and attempted theoretical interpretation for setsize effect leading proportional mean RT delays. We believe that distributional RT analysis with a mathematical function beyond the central tendency estimates could provide insights into various theoretical and individual difference studies.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.2 no.3
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• pp.119-127
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• 1990

Wave directional spectrum estimation methods for irregular waves were considered in this study. Until now, the Longuet-Higgins Method (LHM) initiated by Longuet-Higgins et al. (1963) has been widely used, but resolutions of the estimation were found to be low. Kobune's Maximum Entropy Method (MEM) for the estimation of wave directional spectrum, bas-ed on the entropy Principle showed higher resolutions comparing with the LHM . If the wave directional spectrum is of Delta functions, the MEM is exact in its estimation. It was also found that for a unimodal spectrum, if the Mitsuyasu's spreading coefficient is above 5, the estimation resolutions were high. In bimodal spectrum, as the angle difference between the two peaks increased, the resolution improved. The energy seems to transfer to the smoother peak in the smoothing of peak's peakedness. LHM has a tendency to estimate bimodal spectrum as a unimodal spectrum ； thus, except for its computational speed, the resolution of LHM falls far below that of MEM.

• 한국지구과학회:학술대회논문집
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• 2010.04a
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• pp.79-79
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• 2010

이 연구는 북한지역의 풍력 자원을 조사하기 위한 사전 연구로 30년간의 북한 지역의 27개 지상 관측소의 풍속 (고도 10 m)을 수집하였다. 이 풍속을 고도 50 m로 환산하였으며, 풍속의 확률밀도함수를 Weibull 함수로 가정하여 분석하였다. 30년 동안의 지상 관측 자료를 바탕으로 볼 때, 대체적으로 황해도 해안지역과 개마고원지역에서 평균 풍속이 북한 전역에서의 평균 풍속 4.0 m/s 보다 큰 지역이 나타났다. 따라서, 해안지역에서 바람 자원이 풍부함을 알 수 있었다. 지역의 차이는 있으나, 봄철 동안의 주풍은 북서풍과 남풍계열이 대등하게 나타나고 있으며, 여름은 남풍계열의 바람이 주풍으로 변하며, 가을과 겨울 동안 북서풍 계열이 주된 바람이었다. 고도 80 m 에서 풍속이 5 m/s 이상 지속되는 기간이 연간 30% 이상인 주요 6지점 중 장진을 제외한 나머지 네 곳은 해안에 위치함을 알 수 있다. 북한 지역 내륙의 중심부인 장진에서 연간 평균풍속 4.7 m/s 이상으로 관측 되었다. 이 지역은 개마고원 일대로 낭림산맥과 함경산맥의 두줄기가 만나는 곳으로 산맥에 의해 뒤쪽이 막혀있어 바람이 집중되어 높은 풍속을 나타낸 것으로 보인다. 또한 이 지역은 고원지대에 위치하여 북쪽에서 고도 1 km 이상에서 강하게 불어오는 북서풍의 영향으로 풍속이 높게 나타나는 것으로 보인다. 이 연구에서 사용한 관측자료는 단순히 지상의 풍속과 풍력으로만 분석한 것이므로 몇 가지 제약성을 가지고 있어 추후 보강이 필요하다. 관측지점의 지리적 위치나 주변의 환경에 따라 풍황의 변화가 크게 달라질 수 있으므로, 북한의 지형적인 요인을 고려한 정확한 실측을 통해 정확도를 높이는 풍력 자원 조사가 뒷받침 되어야 한다. 이 연구의 가치는 30년간의 바람 자료를 이용하였기 때문에 북한 지역에서의 풍황을 보는데 중요한 정성적 자료로 쓰여질 수 있으리라 본다. 또한, 이 자료를 바탕으로 풍력에너지 발전의 후보지 선정에 유용하게 활용되기를 기대하며, 더 나아가 두 나라 간에 에너지 교류가 활발히 이루어지기를 바란다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.4
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• pp.383-389
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• 2011

In this paper, a statistical calibration method is proposed in order to identify the variability of complex modulus for a rubber material due to operational temperature and experimental/model errors. To describe temperature- and frequency-dependent material properties, a fractional derivative model and a shift factor relationship are used. A likelihood function is defined as a product of the probability density functions where experimental values lie on the model. The variation of the fractional derivative model parameters is obtained by maximizing the likelihood function. Using the proposed method, the variability of a synthetic rubber material is estimated and applied to a rubber mount problem. The dynamic characteristics of the rubber mount are calculated using a finite element model of which material properties are sampled from Monte Carlo simulation. The calculated dynamic stiffnesses show very large variation.

• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.1
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• pp.73-80
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• 2010

The optimal design of water distribution system have started with the least cost design of single objective function using fixed hydraulic variables, eg. fixed water demand and pipe roughness. However, more adequate design is accomplished with considering uncertainties laid on water distribution system such as uncertain future water demands, resulting in successful estimation of real network's behaviors. So, many researchers have suggested a variety of approaches to consider uncertainties in water distribution system using uncertainties quantification methods and the optimal design of multi-objective function is also studied. This paper suggests the new approach of a multi-objective optimization seeking the minimum cost and maximum robustness of the network based on two uncertain variables, nodal demands and pipe roughness uncertainties. Total design procedure consists of two folds: least cost design and final optimal design under uncertainties. The uncertainties of demands and roughness are considered with Latin Hypercube sampling technique with beta probability density functions and multi-objective genetic algorithms (MOGA) is used for the optimization process. The suggested approach is tested in a case study of real network named the New York Tunnels and the applicability of new approach is checked. As the computation time passes, we can check that initial populations, one solution of solutions of multi-objective genetic algorithm, spread to lower right section on the solution space and yield Pareto Optimum solutions building Pareto Front.

• Korean Journal of Agricultural and Forest Meteorology
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• v.19 no.3
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• pp.130-139
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• 2017

The crop damage caused by strong wind was predicted using the wind speed data available from Korean Meteorological Administration (KMA). Wind speed data measured at 19 automatic weather stations in 2012 were compared with wind data available from the KMA's digital forecast. Linear regression equations were derived using the maximum value of wind speed measurements for the three-hour period prior to a given hour and the digital forecasts at the three-hour interval. Estimates of daily maximum wind speed were obtained from the regression equation finding the greatest value among the maximum wind speed at the three-hour interval. The estimation error for the daily maximum wind speed was expressed using normal distribution and Weibull distribution probability density function. The daily maximum wind speed was compared with the critical wind speed that could cause crop damage to determine the level of stages for wind damage, e.g., "watch" or "warning." Spatial interpolation of the regression coefficient for the maximum wind speed, the standard deviation of the estimation error at the automated weather stations, the parameters of Weibull distribution was performed. These interpolated values at the four synoptic weather stations including Suncheon, Namwon, Imsil, and Jangsu were used to estimate the daily maximum wind speed in 2012. The wind damage risk was determined using the critical wind speed of 10m/s under the assumption that the fruit of a pear variety Mansamgil would begin to drop at 10 m/s. The results indicated that the Weibull distribution was more effective than the normal distribution for the estimation error probability distribution for assessing wind damage risk.

• Clean Technology
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• v.28 no.3
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• pp.210-217
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• 2022

Boron(B) is a rare resource used for various purposes such as glass, semiconductor materials, gunpowder, rocket fuel, etc. However, Korea depends entirely on imports for boron. Considering the global boron reserves and its current production rate, boron will be depleted on earth in 50 years. Thus, a process including proper adsorbent materials recovering boron from seawater is demanded. This research proposed carbonized nanofibers prepared from electrospun PAN(polyacrylonitrile) mats as promising materials to adsorb boron in aqueous solution. First, the mechanism of boron adsorption on carbonized nanofibers was investigated by DFT(density functional method)-based molecular modeling and the calculated energetics demonstrated that the boron chemisorption on the nitrogen-doped graphene surface by a two-step dehydration is possible with viable activation energies. Then, the electrospun PAN mats were stabilized in air and then carbonized in an argon atmosphere before being immersed in the boric acid aqueous solution. Analytically, SEM(scanning electron microscopy) and Raman measurements were employed to confirm whether the electrospinning and carbonization of PAN mats proceeded successfully. Then, XPS(X-ray photoelectron spectroscopy) peak analysis showed whether the intended nitrogen-doped carbon nanofiber surface was formed and boron was properly adsorbed on nanofibers. Those results demonstrated that the carbonized nanofibers prepared from electrospun PAN mats could be feasible adsorbents for boron recovery in seawater.