• 한국해안·해양공학회논문집
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• 제28권6호
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• pp.383-396
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• 2016

본 연구에서는 파랑과 흐름이 공존하는 해역에서 수위변화 및 흐름효과 고려 유무에 대하여 파랑모델을 수행하여 그 결과를 비교하였다. 해수유동장은 RIAMOM 모델 결과를 적용하였으며 파랑모델은 SWAN모델을 적용하였다. 바람자료는 ECMWF, NCEP 및 JMA의 3가지에 대하여 관측자료를 비교적 잘 재현하는 JMA 자료를 적용하였다. 수치모의는 2016년 1월~8월까지 8개월간 수행하였으며, 각 경우에 대하여 관측자료와의 비교를 위하여 2.5 m이상의 고파랑 기간에 대해 파고변화를 검토하였다. 분석결과, 수심이 깊은 파랑관측부이 정점에서는 수위/흐름효과를 고려할 경우 파고변화가 크지 않게 나타났으나, 수심이 얕은 비교 정점에서는 수위/흐름효과의 고려 여부에 따라 5~10%의 유의미한 파고변화가 나타났다.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2003년도 춘계공동학술대회논문집
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• pp.157-164
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• 2003

복잡한 수심을 가진 연안해역에서 조석, 바람과 파에 의해 발생된 흐름의 영향까지를 고려한 파랑모델의 도입은 대부분의 해안공학 설계나 방재 문제에 매우 중요한 요소이다. 근해역에서 수심변화에 의한 굴절 및 천수효과, 흐름에 의해 유발되는 굴절효과, 파형경사에 따른 쇄파, 회절, 바람에 의한 파의 성장, 파랑 상호간의 간섭 및 에너지 재분포 등을 다를 수 있다는 점에서 정상상태 스펙트럼 모델의 현장 적용은 지금까지 여러 모델이 다루지 못한 부분을 해소하게 될 것이다. 본 연구에서는 부만 신항만 건설이 이루어지고 있는 가덕인접의 및은 수역에 대해 파랑의 변환과정을 보다 합리적으로 해석하기 위해 스펙트럼 모델을 적용하고 기존의 모델 결과와 비교 분석하는 것을 골자로 하고 있다. 이러한 시도가 가까운 장래에 항만설계 및 방재시스템 분야에서 보다 안전하고 널리 스펙트럼 모델을 적용하게 하는 계기가 되도록 의도하였다.

• 한국해안·해양공학회논문집
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• 제32권5호
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• pp.351-362
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• 2020

2003년 남해안에 내습한 태풍 매미에 의해 발생한 폭풍해일과 파랑을 JMA-MSM 예보기상자료, NCEP-CFSR 재분석 기상자료, ECMWF-ERA5 재분석 기상자료, JTWC의 최적경로를 이용한 기상자료를 이용하여 수치모의하고, 계산된 해일고를 전국 해안의 항만에서 관측된 폭풍해일 시계열 자료와 비교하였다. 폭풍해일과 동시에 발생하는 파랑에 대해서는 계산된 유의파고를 관측 자료와 비교하였다. 이 비교를 통해 태풍 매미에 대한 각종 기상장의 신뢰도를 평가하였다. 그 결과 JMA-MSM 기상자료가 가장 신뢰도가 높았고, JTWC의 최적경로를 이용한 기상자료도 상당히 우수하게 나타났다. ECMWF-ERA5 기상자료는 전반적으로 해일고나 파고의 크기가 작게 나타났으며, NCEP-CFSR 기상자료는 태풍 매미의 특정 경우에 대해 신뢰도가 가장 낮게 나타났다. 이 연구를 통하여 폭풍해일과 파랑을 추산하기 위해 신뢰도 높은 기상장이 필수적임을 알 수 있었다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.296-300
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• 2003

The autopilot system targets decreasing labor, working environment improvement, service safety security and elevation of service efficiency. Ultimate purpose is minimizing number of crew for guarantee economical efficiency of shipping service. Recently, being achieving research about Course Keeping Control, Track Keeping Control, Roll-Rudder Stabilization. Dynamic Ship Positioning and Automatic Mooring Control etc. which compensate nonlinear characteristic using optimizing control technique. And application research is progressing using real ship on actual field. Relation of Rudder angle which adjusted by Steering Machine and ship-heading angle are non-linear. And Load Condition of ship as non-linear element that influence to Parameter of ship. Also, because the speed of a current and direction of waves, velocity and quantity of wind etc. that is disturbance act in non-linear from, become factor who make serv ice of shipping painfully. Therefore, service system of shipping requires robust control algorithm that can overcome nonlinearity. In this paper, Using fuzzy algorithm ,Design autopilot system of ship that could overcome the non-linear factor of ship and disturbance and examined result through simulation.

• International Journal of Internet, Broadcasting and Communication
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• 제12권3호
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• pp.156-162
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• 2020

Wireless Sensor Network (WSN) field is mainly studied to monitor and characterize large-scale physical environments to track various environmental or physical conditions, such as temperature, pressure, wind speed and humidity. WSN can be used in various applications such as wild surveillance, military target tracking and monitoring, dangerous environmental exploration and natural disaster relief. We design probabilistic mobile models that apply to mobile ad hoc network mobile environments. A probabilistic shift model proposed by dividing the number of moving nodes and the distance of travel into two categories to express node movement characteristics. The proposed model of movement through simulation was compared with the existing random movement model, ensuring that the width and variation rate of the first node node node node (FND) was stable regardless of the node movement rate. In addition, when the proposed mobile model is applied to the routing protocol, the superiority of network life can be verified from measured FND values. We overcame the limitations of the existing random movement model, showing excellent characteristics in terms of energy efficiency and stable in terms of changes in node movement.

• 전기학회논문지
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• 제58권8호
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• pp.1512-1518
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• 2009

Recently, new dispersed power sources such as photovoltaics, wind power, fuel cell etc. are energetically interconnected and operated in the distribution systems, as one of the national projects for alternative energy. This paper deals with the optimal countermeasures for the mal-function of protective devices at primary feeder in distribution systems when new power sources like photovoltaic (PV) systems are interconnected, based on the symmetrical components of short circuit studies. When new power sources are considered to be interconnected to distribution systems, bi-directional power flow and interconnection transformer connection of new power sources may cause the operation problems of protective devices (mainly re-closer), since new power sources can change typical characteristics of distribution systems. Therefore, this paper shows an analysis skill of the mal-functional mechanism of protective relay and proposes the optimal solution for the mal-function problem using the symmetrical components of fault analysis. And, this paper also shows the effectiveness of proposed method by the simulation at the field distribution systems.

• 한국대기환경학회지
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• 제18권2호
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• pp.67-83
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• 2002

The coupled model (SMART) of dynamic meteorology model and particle dispersion model was developed. The numerical experiment on the relationship between change of land use and diffusion behavior in complex terrain was carried out using this model. It tried to investigate the change of particle diffusion behavior and local weather under the condition in which land-land breeze and sea breeze and mountain breeze intermingled. The numerical experiment results are as follows; 1) The more complicated local circulation field of the interaction of sea breeze, mountain breeze and Land -land breeze is formed. Then, the region circulation in which the urbanization is specific by location of the region is strengthened and is weakened. 2) Though in the region with dominant sea breeze, Land-land breeze does not appear directly, the progress of the sea wind to the inland is affected. 3) In the prediction of the air diffusion, emission high quality and accurate information of the emission site are important. That is to say, the dispersion predicting result which emission high quality and small error of the site perfectly vary for Land - land breeze in the effect may be brought about.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2003년도 The Fifth Asian Computational Fluid Dynamics Conference
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• pp.253-254
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• 2003

Computations of the mean and turbulence flows over three-dimensional hill of conical shape have implemented. Beside the standard ${\kappa}-{\varepsilon}$ , two other modifications proposed by Detering & Etling and Duynkerke for atmospheric applications were also considered. These predictions were compared with the data of a wind tunnel experiment. From the comparison, it was concluded that all three models predict the mean flow velocities equally well while only the Duynkerke's model accurately predicts the turbulence data statistics. It also concluded that there are large discrepancies between model predictions and the measurements near the ground surface. The flow field, which was obtained by using the Duynkerke's modification, was used to simulate gas dispersion from an upwind source. The calculation results are verified based on the measurement data. Modifications of the turbulent Schmidt number were carried out in order to match the measured results. The code was used to investigate the influence of the recirculation zone behind a building of cubical shape on the transport and dispersion of pollutant. For a stack behind and near the obstacle, some conclusions about the effect of the stack height and stack location were derived.

• Wind and Structures
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• 제29권6호
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• pp.371-387
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• 2019

In the present paper, a simple refined nth-higher-order shear deformation theory is applied for the free vibration analysis of laminated composite plates. The proposed displacement field is based on a novel kinematic in which include the undetermined integral terms and contains only four unknowns, as against five or more in case of other higher-order theories. The present theory accounts for adequate distribution of the transverse shear strains through the plate thickness and satisfies the shear stress-free boundary conditions on the top and bottom surfaces of the plate, therefore, it does not require problem dependent shear correction factor. The governing equations of motion are derived from Hamilton's principle and solved via Navier-type to obtain closed form solutions. The numerical results of non-dimensional natural frequencies obtained by using the present theory are presented and compared with those of other theories available in the literature to verify the validity of present solutions. It can be concluded that the present refined theory is accurate and efficient in predicting the natural frequencies of isotropic, orthotropic and laminated composite plates.

• International Journal of Railway
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• 제5권2호
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• pp.55-64
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• 2012

Subject of the paper is a particular configuration of overhead line, in which noise barrier structure is used as supports of the catenary instead of standard poles. This configuration is foreseen in case the noise barrier position is in conflict with the poles location. If the catenary is supported by the noise barrier, the motion that the latter undergo due to wave pressure associated to train transit is transmitted to the overhead line, so that potentially it influences the interaction between the catenary itself and the pantograph of the passing train. The paper focuses on the influence of such peculiar configuration on the quality of the current collection of high speed pantograph, for single and double current collection. The study has been carried out first with an experimental investigation on the pressure distribution on noise barrier, both in wind tunnel and with in-field tests. Subsequently a numerical analysis of the dynamics of the barrier subjected to the wave pressure due to train transit has been carried out, and the output of such analysis has been used as input data for the simulation of the pantograph-dynamic interaction at different speeds and with front or rear pantograph in operation. Consideration of structural modifications was then highlighted, in order to reduce the influence on the contact loss percentage.