• 한국항해학회지
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• 제18권4호
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• pp.137-146
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• 1994

In this paper, a new algorithm to measure the ultrasonic travel time is proposed, which is fundamental to estimate distance depth and volume in several media. Pulse wave has been used to measure travel time of transmitted signal. However, due to the characteristic of transducer and propagation, the received signal is so distorted that it is difficult to measure travel time, which is propagation, the received signal is so distorted that it is difficult to measure travel time, which is to be time difference between transmitted and received signals. In this proposed method, transmitted and received signal are transformed respectively into norm phase newly designed by this paper and displayed on phase-time curve. And travel time is simply determined by the arithmetic numerical mean of time difference at the identical norm phase on the phase-time curves of transmitted and received signals. This method has several features; firstly, travel time is calculated analytically with high accuracy by least square error method, secondly, it is useful to compare the difference of signal magnitude for time information, thirdly, noise and discrete errors are relatively small, finally, the measurement accuracy is not influenced by D.C. bias. In particular, this method is useful and applicable to measuring very short distance and sound speed with high accuracy.

• 대한교통학회:학술대회논문집
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• 대한교통학회 1996년도 제3회 한-중 국제학술회의
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• pp.95-128
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• 1996

Dipped track profiles between rail transit stations can significantly reduce propulsive energy, braking energy and travel times. This work quantifies their potential benefits for circumstances reflected in various values for dips, speed and acceleration limits, station spacings, and available power. A deterministic simulation model has been developed to precisely estimate train motions and performance using basic equations for kinematics, resistance, power and braking. For a dip of 1% of station spacing, in which gradients never exceed 4%, our results show savings (compared with level tracks) exceeding 9% for propulsive energy, 15% for braking energy and 5% for travel time between stations.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1997년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Fall 1997
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• pp.70-81
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• 1997

The intesity survery on the 26 June 1997 Kyeongju Earthquake whose magnitude is 4.3, has been made for 316 locations throughout southen park of Korean Peninsula, then we have investigated the intensities distribution of the earthquake. Because the earthquake was occurred during night time (03:50:23.19), the most people who live farather than about 200km from the epicenter did not feel the earthquake. Therefore, the intensities are estimated only from IV to V in this study. The iso-seismal intensity map shows that the shape of iso-seismal intensity is similar to the boundary of the Kyeongsang Basin. This phenomenon may indicates that the energy of the earthquake is trapped within the Kyeongsang Basin due to low velocity within the basin compared with the velocity outside of the basin. The travel time curves with 10 possible phases are used to identify the earquake records. The Pg and Sg phases are crearly shown in the records whose epicental distance is less than 60 km. The records of MUN and PCH stations located outside of the Kyiongsang Basin show different frequency compared with that of the other stations located within the Kyeongsang Basin.

• 천문학논총
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• 제30권2호
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• pp.211-214
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• 2015

We investigated the period variation for 79 eclipsing binary systems using 20 years (1990-2009) of EROS, Macho, and OGLE survey observations. We discovered 9 apsidal motions, 8 mass transfers, 5 period increasing and decreasing systems, 12 light-travel-time effects, 5 eccentric systems and 40 other systems showing no period variations. We select 3 representative eclipsing binary systems; EROS 1052 for apsidal motion, EROS 1056 for mass transfer, and EROS 1037 for the light-travel-time effect. We determine the period variation rate (dP/dt), orbital parameters of the 3rd body (e3, ${\omega}_3$, $f(m_3)$, $P_3$, $T_3$), apsidal motion parameters ($d{\omega}/dt$, U, Ps, Pa, e) and apsidal motion period by analyzing the light curves and O-C diagrams.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 1997년도 총회 및 춘계 학술발표회 논문집
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• pp.25-29
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• 1997

In many solute transport studies, either flux or resident concentration has been used. Choice of the concentration mode was dependent on the monitoring device in solute displacement experiments. It would be questionable, however. to accept the equivalency in the solute transport parameters between flux and resident concentrations in structured soils exhibiting preferential movement of solute. In this study, we investigate how they differ in the monitored breakthrough curves (BTCs) and transport parameters for a given boundary and flow condition by performing solute displacement experiments on a number of undisturbed soil columns. Both flux and resident concentrations have been simultaneously obtained by monitoring the effluent and resistance of the Horizontally-positioned TDR probes. The study reveals that soil columns having relatively high flux densities exhibited great differences in the degree of peak concentration and travel time of peak between flux and resident concentrations. The peak concentration in flux mode was several times higher than that in resident one. This was mainly due to the bypassing of solute through soil macropores.

• International Journal of Railway
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• 제5권3호
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• pp.103-113
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• 2012

Infrastructure costs could be greatly reduced if the need for bridges and tunnels was reduced, or if the line could be shortened. Tilting trains might be a less costly alternative to building new tracks with large curve radii, because tilting trains can negotiate tighter curves without having to decrease their speeds. Tracks built for tilting trains would be cheaper, as they require fewer bridges and tunnels. This paper compares the construction costs of two different options for the new Dodam-Yeoncheong section on the Central line, which includes 148.65 km of new electrified double-track with a design speed of 250 km/h. The first option is to straighten the high-speed line. The second option is to build a line with small radii curves and run tilting trains on the line. In the first option, tunnels would account for about 51% of the new section. In comparison, the second option would have shorter curves and fewer tunnels and bridges which would reduce construction costs. Furthermore, alignment modifications could be made to several segments on the straight line, making the most of the existing roadbed. The analysis concluded that the line suited to tilting trains would be 95.7 million USD cheaper to build the straight route. That is a savings of 2.8% of the total project cost. However, this option would increase the total travel time of the route by 1.2 minutes, which means it is not necessarily the best choice.

• 대한토목학회논문집
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• 제12권2호
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• pp.87-99
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• 1992

댐 붕괴의 유형을 순간적 붕괴와 점진적 붕괴로 구분하였고 각 경우에 대하여 첨두유량의 산정식을 Metric 단위로 환산하여 유도하였다. 기존의 SMPDBK 모형에서 사용된 거리 매개변수의 개념을 도입하고 국내 댐 및 저수지의 자료를 기초로 한 새로운 무차원 홍수추적곡선을 유도하였다. 새로운 추적곡선은 기존의 모형에서 다루지 않은 사류(射流)상태의 경우도 포함하고 있으므로, 산지하천이 많은 국내유역에 적용시킬 수 있도록 하였다. 본 연구에서 유도된 무차원 홍수추적곡선은 Froude 수가 증가됨에 따라 유량감쇠비(流量減衰比)도 증가하고 있는 경향을 보여주었으며, 그 증가율은 Froude 수가 증가함에 따라 감소하고 있었다. 특히, 사류의 경우에서는 Froude 수가 커짐에 따라 그 증가율이 비교적 작게 나타나는 특성을 보이고 있었다. 효기(孝基) 댐 붕괴의 경우에 대하여 본 연구에서 유도한 무차원 홍수추적곡선을 적용한 결과를 실측치 및 동역학적 모형에 의한 계산결과치와 비교할 때, 댐 붕괴 지점에서의 첨두유량, 최고수위 및 홍수파의 도달시간 등에 있어 비교적 잘 일치되었다. 본 연구결과는 국내의 중소 댐에 경제적으로 활용될 수 있을 것으로 기대된다.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1997년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Fall 1997
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• pp.67-76
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• 1997

The seismic records of the main shock and two after shocks of the Yeongwol Earthquake are studied based on the phsase analysis. The travel time curves with 12 different possible phases are constructed to analysis the phases of the records. which were provided by KIGAM seismic network. The results of phase analysis show that 1) The main shock (Ms=4.5) shows clear Pn phase but two after shocks (Ms=4 and Ms=2.5) do not show Pn phase. 2) The Pg or PmP phases look as first arrival phase in the after shock records whose edicental distance is smaller or larger than 150 km. 3) It is very difficult to identity the phases related to the Conrad discontinuity even if the Conrad discontiuity arrival exists. 4) The record of GRE station located outside of the Kueongsan Basin shows different arrival time of Pn phase, P-S duration time and frequency compared with those of the other stations located within the Kyeongsan Basin.

• 자원환경지질
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• 제29권6호
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• pp.713-724
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• 1996

현장에서의 주요 운송 메카니즘을 연구하기 위하여 시간별 잔존수 농도분포곡선 자료를 이용하였다. 운송개념을 대표하는 모델로서 2개의 상반된 가설에 근기한 모델, 즉 CDE와 CLT모델을 사용하였으며 파라미터 추정을 위하여 깊이별 평균농도자료에 최적화기법을 적용하였으며 잔존수 농도의 도달시간을 나타내는 확율밀도함수를 이용하여 모멘트해석도 시행되었다. 모멘트 해석결과 잔존수농도의 1차 및 2차 시간 모멘트는 침출수농도의 것들보다 크게 나타났다. 또한 시간 모멘트를 이용하여 오염물질 운송시간의 변이도와 확산 파라미터도 도출되었다. 변이도 및 확산계수와 운송거리간의 상관관계는 침출수농도 및 잔존수농도에 대해서 동일하게 나타났다. 이러한 관계를 이용하여 2가지 모델을 검정하였으나 운송거리에 따른 운송파라미터의 불규칙한 변화로 확정적 결론을 얻을 수 없었다. 따라서 첫 번째 깊이에서 얻은 파라미터를 이용하여 다른 깊이에서의 오염물질 운송 방식을 예측하여 실측자료와 비교하여 각 모델을 검정하였다. 그 결과 CLT 모델이 CDE 모델보다 현장실측자료에 근접하였다. 이는 오염물질이 이동함에 따라 완전한 혼합이 발생하는 것이 아니라 상관흐름 즉, "오염물질이 각 층을 통과할 때 빠른 물질은 빠르게 느린 물질은 지속적으로 느리게 움직인다"는 사실을 뒷받침한다고 볼 수 있다. 특히 첨두농도에 대한 CDE 모델의 과대예측은 오염물질 확산의 과소평가에 기인하는 것으로 나타났다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2002년도 춘계학술대회 논문집
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• pp.303-311
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• 2002

A first evaluation of the possibilities of high speed trains in conventional railway in Korea have been investigated. The radius of curvature was considered the major problem with high-speed trains in Korea. If KNR(Korea National railway) likes to increase the speed, is then whether KNR shall construct straigthen the track or develop a train that can reduce travel time in curves The research concerns structural design of train car-body is to reduce heavy stress concentration. Using 3D solid modeling, Finite Element analysis and shape optimization combined with powerful postprocessing, graphical display and animation to achieve complete and accurate design and performance will be carried out further project Main purpose of this project is to provide korean tilting train car body's conceptional design. Based on first year research results, the design of car-body will be performed by train manufacture.