• 한국농공학회지
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• 제27권4호
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• pp.42-52
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• 1985

This study was attempted to derivate empirical formulas for the runoff: ratio during ilood. season at three watersheds of Dan Yang, Chung Ju, and Yeo Ju are located at upper, middle, and lower portion of Nam Han river basin, respectively. Obtained formulas for flood runoff ratio can be applied as an element for the estimation, peak discharge for the design of various hydraulics structures which can be concidented with meteorological and topographical condition. The obtained through this study were analyzed as follows. 1.It was found that the magnitude of runoff ratio depends on the amount of rainfall for all studying basins. 2.Empirical formulas 'for the runoff' ratio were derivated as 1- 2,707 Rt0.345, 1-1.691 Rt0.242 and 1-1.807 Rt0.227 at Dan Yang, Chung Ju and Yeo Ju watershed, respectively. 3.The magnitude of runoff ratio was appeared in the order of Dan Yang, Chung Ju, and Yeo Ju are located at upper, middle and lower portion of Nam Han rivet basin, respectively. 4.It was assumed that in general the more it rains, the lesser becomes the ratio of loss rainfall. Especially, the ratio of loss rainfall for Dan Yang, upper portion of river basin was shown as the lowest among three watersheds. Besides, the magnitude of that was appeared in the order of Chung Ju and Yeo Ju watershed located at middle, and lower part of river basin, respectively. 5.Relative and standard errors of runoff ratio calculated by empirical formulas were shown to be within ten percent to the observed runoff ratio in all watersheds. 6.It is urgently essential that the effect of antecedent rainfall have an influence on the next coming flood should be studied in near future.

• Journal of Positioning, Navigation, and Timing
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• 제11권4호
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• pp.287-295
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• 2022

The GNSS coordinate time series is used as important data for geophysical analysis such as terrestrial reference frame establishment, crustal deformation, Earth orientation parameter estimation, etc. However, various factors may cause discontinuity in the coordinate time series, which may lead to errors in the interpretation. In this paper, we describe the discontinuity in the coordinate time series due to the equipment replacement for domestic GNSS stations and discuss the change in movement magnitude and velocity vector difference in each direction before and after discontinuity correction. To do this, we used three years (2017-2019) of data from 40 GNSS stations. The average magnitude of the velocity vector in the north-south, east-west, and vertical directions before correction is -12.9±1.5, 28.0±1.9, and 4.2±7.6 mm/yr, respectively. After correction, the average moving speed in each direction was -13.0±1.0, 28.2±0.8, and 0.7±2.1 mm/yr, respectively. The average magnitudes of the horizontal GNSS velocity vectors before and after discontinuous correction was similar, but the deviation in movement size of stations decreased after correction. After equipment replacement, the change in the vertical movement occurred more than the horizontal movement variation. Moreover, the change in the magnitude of movement in each direction may also cause a change in the velocity vector, which may lead to errors in geophysical analysis.

• 한국자동차공학회논문집
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• 제15권2호
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• pp.50-57
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• 2007

Shocks are excited by impulsive forces and cause discomfort in vehicles. Current standards define means of evaluating shocks and predicting their discomfort, but the methods are based on research with a restricted range of shocks. This experimental study was designed to investigate the discomfort of seated subjects exposed to a wide range of vertical shocks. Shocks were produced from the responses of one degree-of-freedom models, with 16 natural frequencies (from 0.5 to 16 Hz) and four damping ratios (0.05 0.1, 0.2 and 0.4), to a hanning-windowed half-sine force inputs. Each type of shock was presented at five vibration dose values in the range $0.35\;ms^{-1.75}$ to $2.89\;ms^{-1.75}$. Fifteen subjects used magnitude estimation method to judge the discomfort of all shocks. The exponent in Stevens' power law, indicating the rate of growth in discomfort with shock magnitude, decreased with increasing fundamental frequency of the shocks. At all magnitudes, the equivalent comfort contours showed greatest sensitivity to shocks having fundamental frequencies in the range 4 to 12.5 Hz. At low magnitudes the variations in discomfort with the shock fundamental frequency were similar to the frequency weighting $W_b$ in BS 6841, but low frequency high magnitudes shocks produced greater discomfort than predicted by this weighting. At some frequencies, for the same unweighted vibration dose value, there were small but significant differences in discomfort caused by shocks having different damping ratios. The rate of increase in discomfort with increasing shock magnitude depends on the fundamental frequency of the shock. In consequence, the frequency-dependence of discomfort produced by vertical shocks depends on shock magnitude. For shocks of low and moderate discomfort, the current methods seem reasonable, but the response to higher magnitude shocks needs further investigation.

• 자원환경지질
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• 제51권6호
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• pp.589-593
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• 2018

북한은 대한민국 지역시간으로 2017년 9월 3일 12시 30분 함경북도 길주군 풍계리 핵실험장에서 6차 지하핵실험을 실시하였다. 북한 6차 핵실험의 실체파 규모 측정에 있어서 미국지질조사국은 $m_b$ 6.3으로 발표한 반면 UN 산하 포괄적핵실험금지조약기구는 $m_b$ 6.1로 발표하여 상이한 값을 제시하였다. 본 연구에서는 이러한 규모의 차이를 규명하고 규모계산을 검증하고자 하였다. 이를 위해 진앙이 200 m 상호 이격된 5차 핵실험과 6차 핵실험의 지진원 상대비율을 30개 광대역 지진관측소 자료를 이용하여 측정하였다. 지진원 상대비율 측정을 통해 5차 핵실험에 대비한 6차 핵실험의 진폭변화가 주파수 영역에서 어떠한 양상을 보이는지 분석하고 실체파 규모 계산의 기준이 되는 1 Hz에서의 실체파 규모 $m_b$의 증가량을 계산하였고 이를 미국지질조사국과 포괄적핵실험금지조약기구에서 발표한 북한 5차 핵실험 대비 6차 핵실험의 실체파 규모 증가량과 비교하였다.

• 인터넷정보학회논문지
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• 제8권4호
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• pp.105-117
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• 2007

프로젝트 관리자는 입찰 또는 개발을 성공하기 위해 비용과 일정을 프로젝트 초기 단계에서 보다 정확히 추정해야만 한다. 평균적으로 대부분의 프로젝트들이 수행하고 있는 명목상의 개발기간은 경험법칙, 선형함수 추정경험 또는 개략적 일정 추정표로부터 유도할 수 있다. 명목상 개발기간에는 다양한 경험법칙이 존재하며, 선형함수 모델은 충분한 정보를 제공하지 못하여 특정 규모의 프로젝트에 적합한 개발노력과 일정을 결정하기 어렵다. 본 논문은 개략적 일정 추정표로부터 개발노력과 일정을 유도하는 통계적 회귀분석 모델을 제시하였다. 먼저, 개략적 일정 추정표에서 제시하고 있는 최대 단축기간, 효율적 개발기간과 명목상 개발기간을 재정의 하였다. 다음으로 개발노력과 기간과의 관계를 고찰하고, 개략적 일정추정표에 제시되지 않은 특정 규모의 소프트웨어에 대한 개발노력 추정 모델과 개발노력에 따른 일정을 보다 정확히 추정할 수 있는 모델을 제시하였다. 제시된 회귀분석 모델은 기존의 방법들과 비교하여 상대오차를 최대 2%까지 줄이는 효과를 얻었다. 또한, 특정 규모의 소프트웨어에 대해서도 개발노력과 일정을 추정할 수 있었다.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2009년도 정기 학술발표대회
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• pp.43-50
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• 2009

Strong ground motion attenuation relationship represents a comprehensive trend of ground shakings at sites with distances from the source, geology, local soil conditions, and others. It is necessary to develop an attenuation relationship with careful considerations of characteristics of the target area for reliable seismic hazard/risk assessments. In the study, observed ground motions from the January 2007 magnitude 4.9 Odaesan earthquake and the events occurring in the Gyeongsang provinces are compared with the previously proposed ground attenuation relationships in the Korean Peninsula to select most appropriate one. In the meantime, a few strong ground motion attenuation relationships are proposed and introduced in HAZUS, which have been designed for the Western United States and the Central and Eastern United States. The selected relationship from the ones for the Korean Peninsula has been compared with attenuation relationships available in HAZUS. Then, the attenuation relation for the Western United States proposed by Sadigh et al. (1997) for the Site Class B has been selected for this study. Reliability of the assessment will be improved by using an appropriate attenuation relation. It has been used for the earthquake loss estimation of the Gyeongju area located in southeast Korea using the deterministic method in HAZUS with a scenario earthquake (M=6.7). Our preliminary estimates show 15.6% damage of houses, shelter needs for about three thousands residents, and 75 life losses in the study area for the scenario events occurring at 2 A.M. Approximately 96% of hospitals will be in normal operation in 24 hours from the proposed event. Losses related to houses will be more than 114 million US dollars. Application of the improved methodology for loss estimation in Korea will help decision makers for planning disaster responses and hazard mitigation.

• 한국통신학회논문지
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• 제27권6A호
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• pp.610-617
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• 2002

본 논문에서는 적응적 변이추정 기법을 이용한 새로운 중간시점영상합성 방법을 제시하였다. 즉, 스테레오 입력 영상으로부터 특징값을 추출하고, 설정된 임계값과 비교하여 특징값의 크기를 결정한 다음, 특징값의 크기에 따라 정합창의 크기를 적응적으로 선택하여 정합함으로써 중간시점의 영상을 합성하는 새로운 기법을 제안하였다. 제안된 기법에서는 배경과 같인 특징값이 작은 영역에서는 비교적 큰 정합창에 의한 블록정합이 이루어지고 물체의 윤곽선과 같이 특징값이 큰 영역에서는 상대적으로 작은 정합창에 의한 미세한 정합이 적응적으로 수행되기 때문에 전체적인 정합성능의 개선뿐만 아니라 기존의 기법에서 나타나는 오정합이나 블록화 현상등의 문제점 해결의 가능성을 제시하였다. 또한, 'Parts' 및 'Piano' 영상을 사용한 실험결과 본 논문에서 새로이 제안한 중간시점 영상합성 방법은 기존의 방식에 비해 평균적으로 PSNR은 약 2.32∼4.16dB가 향상되었고, 수행시간은 약 39.34∼65.58% 감소됨을 확인하였다.

• Ocean and Polar Research
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• 제42권1호
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• pp.21-31
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• 2020

Shorebirds migrating along the East Asian-Australasian Flyway (EAAF) have been drastically decreasing due to continuous area loss and quality degradation of intertidal mudflats in the Yellow Sea. Evaluating the current habitat quality by means of habitat carrying capacity estimation could be effective in predicting the magnitude of impacts caused by habitat loss and provide better understanding to improve management strategies. In this study, we estimated the total biomass of Macrophthalmus japonicus, a main prey item of curlews in the Korea peninsular as habitat carrying capacity of the southern intertidal mudflat of Ganghwa Island, one of the key stopover sites for curlews in the EAAF. The result of the estimation took into account spatial differences of prey biomass and the available foraging time by tide patterns. Accordingly, it was found that curlew populations account for 30.26% of the habitat carrying capacity. When we calculated the mean biomass of the area and extrapolated it to the whole area to calculate the total biomass, it was found that the curlews have consumed 10.92% of the total biomass. The results show that the habitat carrying capacity of the southern intertidal mudflat of Ganghwa Island has decreased by 7.8% compared to a study conducted twenty years ago employing the same method. This study shows that there can be considerable differences in the results of habitat carrying capacity estimation between different methods, indicating that various environmental factors that affect the estimation results of habitat carrying capacity must be considered to achieve a more precise analysis and assessment.

• Journal of Power Electronics
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• 제18권1호
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• pp.234-250
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• 2018

This paper presents a new load sharing control for use between paralleled three-phase inverters in an islanded microgrid based on the online line impedance estimation by the use of a Kalman filter. In this study, the mismatch of power sharing when the line impedance changes due to temperature, frequency, significant differences in line parameters and the requirements of the Plug-and-Play mode for inverters connected to a microgrid has been solved. In addition, this paper also presents a new droop control method working with the line impedance that is different from the traditional droop algorithm when the line impedance is assumed to be pure resistance or pure inductance. In this paper, the line impedance estimation for parallel inverters uses the minimum square method combined with a Kalman filter. In addition, the secondary control loops are designed to restore the voltage amplitude and frequency of a microgrid by using a combined nominal value SOGI-PLL with a generalized integral block and phase lock loop to monitor the exact voltage magnitude and frequency phase at the PCC. A control model has been simulated in Matlab/Simulink with three voltage source inverters connected in parallel for different ratios of power sharing. The simulation results demonstrate the accuracy of the proposed control method.

• 조명전기설비학회논문지
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• 제26권2호
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• pp.34-43
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• 2012

This paper describes system modeling and controller design method in the measured signal by discrete Fourier transform. Transfer function of the second order system is estimated by the dominant parameter which is computed in the magnitude and the phase of Fourier spectrum of the measured signal. In addition, the controller was designed by the estimated transfer function, and the results were compared. The proposed estimation method of transfer function contains only a very simple mathematical process. Therefore, it is effective to design the controller in the measured signal when the output of the system contains the characteristics of complex exponential functions case. The proposed method was applied on Op-Amp system to verify the efficiency and the reliability. The results show that the proposed algorithms are highly applicable to the system modeling and controller design in the measured data.