• 한국ITS학회 논문지
• /
• 제18권4호
• /
• pp.44-57
• /
• 2019

여러 대도시에서 교통 혼잡 문제를 해결하기 위해 정확한 교통 흐름을 예측하는 다양한 연구가 진행되었다. 대부분의 연구가 과거의 교통 흐름 패턴이 미래에도 반복될 것이라는 가정하에 예측 모델을 개발하였으나 교통사고 등과 같은 뜻하지 않은 비반복적 교통 패턴을 예측하는 데에는 신뢰성이 낮게 나타났다. 이런 문제를 해결하기 위한 대안으로 지능형 교통 시스템(ITS)을 통해 얻은 빅데이터와 인공지능을 접목한 교통 흐름 예측 연구가 진행되어 왔다. 하지만 시계열 분석에 일반적으로 사용되는 알고리즘인 RNN의 경우, 단기 예측에 최적화되어 장기 예측 정확도가 낮다는 단점을 가지고 있다. 이런 문제를 해결하기 위해 본 논문에서는 기온과 강수량 등의 기상 정보 외에도 각종 외부 요인들을 고려하여 장기적 시점에서 교통 혼잡도를 예측하는 '심층 인공 신경망 모델'을 제안하였다. TOPIS 자료를 이용한 사례 연구 결과 서울시 주요 도로 링크의 교통 혼잡도를 90%에 가까운 정확도로 예측이 가능하였다. 추후 교통사고나 도로 공사와 같은 도로에 영향을 미치는 이벤트 데이터를 추가로 확보할 수 있다면 정확도는 더욱 높아질 것으로 예상된다.

• Ocean and Polar Research
• /
• 제25권1호
• /
• pp.63-74
• /
• 2003

The build-up of the heat field in shallow coastal water due to a point source has been investigated using an analytical solution of a time-integral form derived by extending the solutions by Holley(1969) and also presented in Harleman (1971). The uniform water depth is assumed with non-isotropic turbulent dispersion. The alongshore-flow is assumed to be uni-directional, spatially uniform and oscillatory. Due to the presence of the oscillatory alongshore-flow, the heat build-up occurs in an oscillatory manner, and the excess temperature thereby fluctuates in that course and even in the quasi-steady state. A series of calculations reveal that proper choices of the decay coefficient as well as dispersion coefficients are critical to the reliable prediction of the excess temperature field. The dispersion coefficients determine the absolute values of the excess temperature and characterize the shoreline profile, particularly within the tidal excursion distance, while the decay coefficient determines the absolute value of the excess temperature and the convergence rate to that of the quasi-steady state. Within the e-folding time scale $1/k_d$ (where $k_d$ is the heat decay coefficient), heat build-up occurs more than 90% of the quasi-steady state values in a region within a tidal excursion distance (L), while occurs increasingly less the farther we go to the downstream direction (about 80% at 1.25L, and 70% at 1.5L). Calculations with onshore and offshore discharges indicate that thermal spreading in the direction of the shoreline is reduced as the shoreline constraint which controls the lateral mixing is reduced. The importance of collecting long-term records of in situ meteorological conditions and clarifying the definition of the heat loss coefficient is addressed. Interactive use of analytical and numerical modeling is recommended as a desirable way to obtain a reliable estimate of the far-field excess temperature along with extensive field measurements.

• 대한의용생체공학회:의공학회지
• /
• 제14권1호
• /
• pp.89-96
• /
• 1993

During high frequency ventilation (HFV), mean alveolar pressure has been measured to increase with mean airway opening pressure controlled at a constant level in both humans and experimental animals. Since this phenomenon could potentiate barotrauma limiting advantages of HFV, the present study theoretically predicted the difference between menu alveolar and airway opening pressures ($MP_{alv}$). In a Weibel's trumpet airway model, approximated formula for $MP_{alv}$ was derived based on momentum conservation assuming a uniform velocity profile. The prediction, equation was a func pion of gas density($\rho$), mean flow rate(Q), and diameter of the airway opening where the pressure measurement was made($D_0$) : $MP_{alv}=4{\rho}(Q/D_0^{2})^2$. This was a result of the difference in crosssectional area between the alveoli and the airway opening. A simple aireway model experiment was performed and the results well fitted to the prediction, which demonstrated the validity of the present analysis. Previously reported $MP_{alv}$ data from anesthetized dogs in supine position were comparable to the predicted values, indicating that the observed dissociation between mean alveolar and airway opening pressures during HFV can be explained by this innate geometric (or cross-sectional area) asymmetry of the airways. In lateral position, however, the prediction substantially underestimated the measurements suggesting involvement of other important physiological mechanisms.

• 한국방재학회 논문집
• /
• 제8권3호
• /
• pp.23-27
• /
• 2008

대규모 육지수문모형(Land Surface Model, LSM)에서 종합적인 육지 물흐름 및 에너지흐름의 예측을 위해 새로운 지표면-지표하 연계 물흐름 모형이 지표하 물흐름 모의를 위한 3차원 체적평균 토양수분 이송방정식(Volume Averaged Soil-moisture Transpor, VAST)을 지표수 흐름모의를 위한 1차원 확산방정식과 연계하여 개발되었다. 각 흐름특성에 맞는 복합적인 수치해석법이 적용되어, 시간분할 방법에 의해 3차원 VAST 방정식의 종방향 흐름이 완전음해법에 의해 해석된 후, 횡방향 흐름이 양해법으로 구해지며, 그 후에 1차원 확산방정식은 MacCormack 유한차분법으로 계산한다. 이 새로운 흐름연계모형은 최신의 육지수문모형인 CLM(Common Land Model)내의 기존 1차원 수리수문계산부분을 대체하게 된다. CLM과 결합된 새로운 연계흐름모형은 오하이오 계곡부근의 시험유역에 적용되었으며, 모의결과는 지표면-지표하 물흐름 상호작용의 모의와 지표수 흐름추적방법을 사용한 새로운 모형의 유출예측이 실측치에 더 근접함을 보여준다. 이 개선된 육지수문모형은 지역적, 대륙적, 그리고 지구전체를 다루는 수문기상연구와 기후변화로 인한 재해예방을 위하여 기상모형인 CWRF(Climate extension of the next-generation Weather Research and Forecasting)와 연계될 예정이다.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
• /
• pp.687-692
• /
• 2004

For the prediction of sloshing in the propellant tank of rocket vehicle utilized in RVT (reusable rocket vehicle testing) conducted by ISAS/JAXA, the flow field in the propellant tank during the ballistic flight was experimentally reproduced with the sub-scale model of it. The lateral acceleration as large as about 0.8 G was provided with a mechanical exciter and the deformation of liquid surface in the vessel was visualized with a high-speed camera. The several con-figurations of damping devices were installed and tested in the vessel, which should keep the ullage gas away from the outlet port. It was consequently suggested that the combination of a baffle plate and a perforated cylinder could be effective against the gas suction before the re-ignition of the engine. The sloshing phenomena were also simulated with the CFD code, called CIP-LSM. The numerical results showed good agreement with the corresponding data obtained in the experiment.

• Water Engineering Research
• /
• 제2권2호
• /
• pp.113-121
• /
• 2001

The objective of this study is to develop a prediction mode for a flood forecasting system in the downstream of the Nakdong river basin. Ranging from the gauging station at Jindong to the Nakdong estuary barrage, the hydraulic flood routing model(DWOPER) based on the Saint Venant equation was calibrated by comparing the calculated river stage with the observed river stages using four different flood events recorded. The upstream boundary condition was specified by the measured river stage data at Jindong station and the downstream boundary condition was given according to the tide level data observed at he Nakdong estuary barrage. The lateral inflow from tributaries were estimated by the rainfall-runoff model. In the calibration process, the optimum roughness coefficients for proper functions of channel reach and discharge were determined by minimizing the sum of the differences between the observed and the computed stage. In addition, the forecasting lead time on the basis of each gauging station was determined by a numerical simulation technique. Also, we suggested a model structure for a real-time flood forecasting system and tested it on the basis of past flood events. The testing results of the developed system showed close agreement between the forecasted and observed stages. Therefore, it is expected that the flood forecasting system we developed can improve the accuracy of flood forecasting on the Nakdong river.

• 소성∙가공
• /
• 제23권7호
• /
• pp.425-430
• /
• 2014

The aim of the current study was to predict the plastic deformation behavior of a heated slab during hot rough rolling. FE-simulations were performed to investigate the metal flow and to locate the position of surface material from the slab through the rough rolling and onto the strip, using a material point tracking technique. In addition, experimental hot rolling trials were conducted where artificial defects were impressed onto a heated slab in order to validate the FE-simulation results. The simulated results show the same tendency of deformation behavior as the experimental measurements. The movement of slab defects from the side surface towards the strip center is directly linked to the extent of lateral spread during the rolling.

• Computers and Concrete
• /
• 제1권3호
• /
• pp.325-354
• /
• 2004

Slabs in buildings and bridge decks, which are restrained against lateral displacements at the edges, have ultimate strengths far in excess of those predicted by analytical methods based on yield line theory. The increase in strength has been attributed to membrane action, which is due to the in-plane forces developed at the supports. The benefits of compressive membrane action are usually not taken into account in currently available design methods developed based on plastic flow theories assuming concrete to be a rigid-plastic material. By extending the existing knowledge of compressive membrane action, it is possible to design slabs in building and bridge structures economically with less than normal reinforcement. Recent research on building and bridge structures reflects the importance of membrane action in design. This paper describes the finite element modelling of membrane action in reinforced concrete slabs through optimisation of a simple concrete model. Through a series of parametric studies using the simple concrete model in the finite element simulation of eight fully clamped concrete slabs with significant membrane action, a set of fixed numerical model parameter values is identified and computational conditions established, which would guarantee reliable strength prediction of arbitrary slabs. The reliability of the identified values to simulate membrane action (for prediction purposes) is further verified by the direct simulation of 42 other slabs, which gave an average value of 0.9698 for the ratio of experimental to predicted strengths and a standard deviation of 0.117. A 'deflection factor' is also established for the slabs, relating the predicted peak deflection to experimental values, which, (for the same level of fixity at the supports), can be used for accurate displacement determination. The proposed optimised concrete model and finite element procedure can be used as a tool to simulate membrane action in slabs in building and bridge structures having variable support and loading conditions including fire. Other practical applications of the developed finite element procedure and design process are also discussed.

• 콘크리트학회논문집
• /
• 제27권5호
• /
• pp.489-499
• /
• 2015

내진 보강 공법의 보강효과 파악을 위해선 이에 대한 이론적 규명이 필요하다. 이에 본 연구는 단부에 기둥 부재를 증타한 단근 배근된 전단벽체를 대상으로 해 보강되는 기둥의 상세와 일체화 거동을 고려한 전단강도 모델을 제안했다. 이 모델은 증타된 기둥부재의 전단변형이 집중되는 길이를 가정해 이를 일체화된 벽체 내에 발생하는 스트럿 두께 산정에 이용했다. 뿐만 아니라 이 길이 내에 집중 발생하는 전단변형률을 유도, 이를 일체화 거동을 고려한 적합성 조건을 기존 전단벽체의 해석 알고리즘에 도입함으로써 증타 보강된 벽체의 해석 알고리즘을 새로이 제안했다. 또한 제안된 알고리즘을 통해 계산된 전단강도로 횡력 저항 메커니즘을 단일 스트럿 화 시켜줌으로써 보강부재의 초기강성을 제안하였다. 본 연구에서 제안한 방법의 타당성을 확인하기 위해 해석 결과 값을 본 연구에서 수행한 증타 보강된 벽체를 대상으로 한 실험뿐만 아니라 기존 RC 골조 내에 RC 전단벽체를 신설해 보강한 실험의 결과와 비교해 본 결과, 기둥부재의 상세를 고려하면서 동시에 기존 기준들에 비해 실험결과에 가깝게 예측할 수 있음을 확인했다.

• 한국수자원학회논문집
• /
• 제54권7호
• /
• pp.495-507
• /
• 2021

최근 도시와 산업의 발달과 함께 하천, 호소 등 수환경에서의 수질 오염사고가 빈번하게 일어나고 있어 어류폐사, 취수중단, 친수활동 저해 등 심각한 수생태계 및 사회경제적 피해가 발생하고 있다. 따라서 이에 대한 대응책으로 수질모델링을 통한 오염물질의 이동 및 확산에 대한 사전 예측이 필요하다. 본 연구에서는 2차원 하천흐름/수질해석 프로그램인 RAMS+의 현장 적용성 및 예측 정확도를 검증하기 위해 만곡하천인 섬강에서 현장실험을 수행하였다. 모의결과 흐름해석모형 HDM-2Di와 수질해석모형 CTM-2D-TX는 현장실험에서 관측된 2차원 흐름 특성과 오염물질의 거동 및 혼합 양상을 정확하게 재현하였다. 특히 하천의 양안과 만곡부에서 국부적으로 발생하는 저유속 흐름에 의해 오염물질의 거동이 지체되는 저장대 효과를 정확하게 모의하였다. 나아가서 하천 만곡부에서 이차류가 야기하는 오염물질 3차원적 혼합 양상을 2차원 분산계수를 통해 효과적으로 재현하였다. 오염물질의 위험농도 체류시간은 취수중단 기간을 결정하는데 있어 매우 중요한 요소이다. 본 연구에서는 CTM-2D-TX 모의결과를 기반으로 오염물질 위험농도 체류시간을 계산하였고, 위험농도 체류시간의 공간적 분포가 하폭방향으로 큰 편차를 지니고 있음을 확인하였다. 이러한 오염물질의 2차원적 체류 특성은 1차원 수질모형을 통해서는 예측이 불가능하기 때문에 효율적이고 정확한 수질사고대응을 위해 2차원 수질모형의 활용이 필요함을 본 연구의 결과는 시사하고 있다.