• 터널과지하공간
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• 제21권5호
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• pp.349-358
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• 2011

본 연구에서는 방사성폐기물처분장에서 발생하는 탄성파와 같이 낮은 신호 대 잡음비로 인하여 P파의 식별이 어려운 신호에 적합한 P파 도달시간 결정 알고리즘에 대한 연구를 수행하였다. 사용된 알고리즘은 임계 전압법, Akaike Information Criterion(AIC), Two step AIC, Hinkley criterion이며 샤프심 압절법에 의하여 생성된 탄성파 신호에 white noise를 적용하여 신호 대 잡음비를 낮추었다. 실험결과 임계전압, AIC, Hinkley criterion 알고리즘의 경우 배경잡음 수준이 증가함에 따라 P파 도달시간의 정확성은 감소하였으나 Two step AIC 알고리즘의 경우 1차적으로 결정된 P파의 도달시간 주변의 신호를 중심으로 특성함수와 AIC 알고리즘을 반복적으로 적용함에 따라 배경잡음 수준에 관계없이 정확한 결과를 나타냈다.

• Structural Monitoring and Maintenance
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• 제1권4호
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• pp.411-425
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• 2014

A relatively low frequency Lamb wave-based damage identification method called damage imaging method for rectangular composite plate is presented. A damage index (DI) is generated from the delay matrix of the Lamb wave response signals, and it is used to indicate the location and approximate area of the damage. The viability of this method is demonstrated by analyzing the numerical and experimental Lamb wave response signals from rectangular composite plates. The technique only requires the response signals from the plate after damage, and it is capable of performing near real time damage identification. This study sheds some light on the application of Lamb wave-based damage detection algorithm for plate-type structures by using the relatively low frequency (e.g., in the neighborhood of 100 kHz, more suitable for the best capability of the existing fiber optic sensor interrogator system with the sampling frequency of 500 kHz) Lamb wave response and a reference-free damage detection technique.

• 한국해양공학회지
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• 제22권1호
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• pp.1-5
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• 2008

A 2-D Fluent-based numerical wave tank(FBNWT) capable of simulating wave propagating and overtopping is presented. The FBNWT model is based on the Reynolds averaged Naiver-Stokes equations and VOF free surface tracking method. The piston wave maker system is realized by dynamic mesh technology(DMT) and user defined function(UDF). The non-iteration time advancement(NITA) PISO algorithm is employed for the velocity and pressure coupling. The FBNWT numerical solutions of linear wave propagation have been validated by analytical solutions. Several overtopping problems are simulated and the prediction results show good agreements with the experimental data, which demonstrates that the present model can be utilized in the corresponding analysis.

• 해양환경안전학회지
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• 제27권7호
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• pp.1023-1030
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• 2021

중앙해양안전심판원(2019)에서 발표한 최근 5년의 해양사고통계자료에 따르면 충돌사고의 대부분은 20톤 미만의 어선에서 발생하고 있으며 전방 부주의, 경계 소홀 등의 운항과실로 인한 사고가 주요 원인으로 나타나고 있다. 이러한 사고 방지를 위해 운항자를 대상으로 훈련 및 교육을 강화하고 있지만 충돌사고는 빈번히 발생되고 있으며 충돌 사고를 줄이기 위한 기술적인 방안 또한 지속적으로 개발중에 있다. 본 연구에서는 고속 활주형 소형 선박에 WAVE 통신 기술을 적용하여 선박 간 거리, 속도, 방위에 기반한 조우 상황을 고려하여 충돌 회피 동작이 가능한 제어 알고리즘을 개발하였으며, WAVE 통신-제어기를 결합하여 충돌 회피 시스템을 구축하였다. 그리고 충돌 회피 동작의 검증을 위해 두 소형 선박간의 정면, 추월, 교차의 3가지의 조우 시나리오에 대해서 시뮬레이션을 수행하고 실선 시험을 통해서 충돌 회피 알고리즘을 검증하였다.

• 한국통신학회논문지
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• 제38C권2호
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• pp.165-171
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• 2013

차량 통신 프로토콜은 IEEE 802.11 WG과 P1609에서 진행하고 있는 WAVE(Wireless Access in Vehicular Environments)가 대표적이며, 보안 등을 제외한 MAC과 PHY에 대한 부분은 표준으로 제정되었다. 이러한 차량통신을 이용하여 운전자들의 안전과 전체 교통 흐름의 원활한 통제를 위해 국내외에서 많은 프로젝트가 진행되고 있다. 따라서 본 논문에서는 교차로에서 좌회전 시도 시에 위험 상황이 예상되면 운전자에게 알려주기 위한 차량간 통신 기반 안전서비스 알고리즘을 설계하였고, 이를 실제 구현하였다. 제안하는 알고리즘은 자차와 반대편에서의 접근차량에 대한 모델을 구성하고 충돌 위험이 있을 경우 운전자에게 HMI(Human Machine Interface)를 통해 경고를 주게 된다. 본 안전 서비스의 성능 테스트를 위해 테스트 차량을 이용하여 알고리즘을 시스템에 탑재하였으며, 테스트 케이스를 구성하여 성능 시험장에서 검증하였다. 테스트 결과로써, 우수한 성능을 나타냈으며, 앞으로 차량 통신 인프라가 설치된다면 V2I(Vehicle to Infrastructure) 통신을 이용하여 본 알고리즘을 보다 정밀하게 보완해야 할 것이다.

• 한국군사과학기술학회지
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• 제17권6호
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• pp.800-809
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• 2014

The gridded environmental data is usually provided by the numerical simulation coupled with a data assimilation technique and various inter- or extrapolation algorithms, both of which are based on the observation spanning from simple equipments to satellites. But it is difficult to represent the natural phenomenon such as sea mount, internal-wave, warm eddy in modeling or observation because of increase in the complexity of model. This paper introduces the algorithm artificially representing the natural phenomenon and the techniques applying it to the gridded volume data and smoothing for natural effects. Moreover, the inserted results are analyzed by use of graphical tool. The results can be used for the battle simulation or acoustic model.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 학술대회 논문집 정보 및 제어부문
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• pp.117-119
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• 2004

In order to successfully exploit underwater resources, the first step would be a marine environmental research and exploration on the seafloor. Traditionally one sets up a long-term underwater experimental unit on the seafloor and retrieves the unit later after a certain period time. Essential to these applications is the reliable teleoperation and telemetering of the unit. This study presents ultrasonic-wave remote control system and an underwater sound recognition algorithm that can identify the sound signal without the influence of disturbances due to underwater environmental changes. The proposed method provides a means suitable for units which require low power dissipation and long-time underwater operation. We demonstrate its ability of securing stability and fast sound recognition through experimental methods.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 D
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• pp.2347-2349
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• 2004

The iron loss in electric machines takes large part of machine losses and the reduction of iron loss brings the increase of the efficiency. In the rotating machines, however it is very difficult to calculate result because the measuring processes are very complex and laborious. As is well known, the relation between the flux density B and the magnetic field intensity H relation is not linear. For the iron loss, B and H must be measured and usually B becomes the reference wave(sine wave) and the following H is measured using H-coil. To make the B as sine wave, B is controlled by some devices. The error is controlled to become zero by the proposed algorithm which uses the bisection algorithm. The experiments are compared with the simulation results, and they show acceptable agreements.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1995년도 창립기념학술대회
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• pp.30-36
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• 1995

An axisymmetric flow induced by a train moving into a tunnel is numerically simulated. The effect of train shape on wavefront of a compression wave created by a train is investigated parametrically using several model trains having the same nose shape but different blockage. The zonal method combined with the Fortified Solution Algorithm (FSA) is employed as a numerical algorithm to solve this moving body problem. The computational result is compared with the experimental data. Good agreement is obtained, which justifies the present computational approach. The compression waves created by the model trains are compared and the result shows that the pressure gradient of the wavefront of the compression wave becomes small in the case of small blockage even though the nose shape is same. The wavefront is not determined solely by the cross-sectional area distribution of the train nose.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권7호
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• pp.3050-3065
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• 2016

Neural networks (NNs) are extensively used in applications requiring signal classification and regression analysis. In this paper, a NN based threshold selection algorithm for 60 GHz millimeter wave (MMW) time of arrival (TOA) estimation using an energy detector (ED) is proposed which is based on the skewness, kurtosis, and curl of the received energy block values. The best normalized threshold for a given signal-to-noise ratio (SNR) is determined, and the influence of the integration period and channel on the performance is investigated. Results are presented which show that the proposed NN based algorithm provides superior precision and better robustness than other ED based algorithms over a wide range of SNR values. Further, it is independent of the integration period and channel model.