• 한국음향학회지
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• 제36권6호
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• pp.378-386
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• 2017

해양무기체계 연구개발 과정에 있어서 정량적 시험평가를 수행하기 위해 수중에서 기동하는 표적과 계측 장비간의 거리측정이 요구된다. 일반적으로 정확하게 동기화된 송 수신기 사이의 전송 시간차를 측정하는 단방향 ToA(Time of Arrival) 기법을 이용하여 목표물의 거리를 측정한다. 하지만 수신된 신호는 다중경로의 영향으로 왜곡되어 거리 추정 성능을 저하시킨다. 본 논문에서는 음선 기반의 블라인드 디컨볼루션 기법을 사용하여 수신된 각 데이터 프레임으로부터 시변하는 복합 수중 채널 함수를 추정하고 추정된 시변 전달 함수를 시역전하여 다중경로 현상을 제거한다. 제안된 기법으로 시뮬레이션 및 해상실험을 진행하였을 때, 기존의 ToA 기법보다 거리 추정 성능이 향상되는 결과를 확인하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 심포지엄 논문집 정보 및 제어부문
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• pp.266-268
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• 2005

Recently, the ability of sensing obstacles by oneself and creating suitable moving path in mobile robots are required to provide various kinds automation services. Therefore, in this paper, we studied the avoidance behavior of mobile robots from dynamic obstacles using potential function that minimizes distance and time. We examined the performance of the proposed algorithm by comparing the method of based on the geometrical experience in simulations.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 춘계학술대회논문집 - 한국공작기계학회
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• pp.667-672
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• 2000

This article presents a new acceleration/deceleration method for real-time control of autonomous mobile robots. In this method, a function which produces the table of acceleration/deceleration in real-time is proposed. This function, while satisfying the basic concept of mechanics, can choose both various ranges of velocity and distance ranges for the selected velocities. Moreover it can control motors with real time. This function is convenient to be realized by programming. and it is faster than other functions because it can be made by assembly language.

• Communications for Statistical Applications and Methods
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• 제6권3호
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• pp.729-748
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• 1999

In this paper we present combined estimator of capture-recapture and line transect model using bivariate detection function and detection probability according to objects being in cluster population. Here bivariate detection function use distance and cluster size. The simulation shows that combined estimator approaches the more true value the larger size parameter. Therefore this estimator using the bivariate detection function is more efficient in estimate the population size and density by size parameter.

• 한국군사과학기술학회지
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• 제12권2호
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• pp.213-221
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• 2009

An aircraft collision accident is a disaster that causes great losses of inventories and lives. Though a collision avoidance warning function is provided automatically to pilots in the aircrafts by the enhancement of the aircraft capability, achieving fast decision-making to escape a collision situation is a complex and dangerous work for pilots. If an in-flight collision situation is controlled by the air traffic control system which monitors all airplanes in the air, it would be more efficient to prevent in-flight collisions because it can handle the emergency before the pilot's action. In this paper, we develop the collision avoidance warning function in the air traffic control system. Specifically, we design and implement the five stages of the collision avoidance function, and propose a visualization method which could effectively provide the operators with the trajectories and altitudes of the aircrafts in a collision situation. By developing an in-flight collision warning function in the air traffic control system that visualizes flight patterns through the state transition data of in-flight aircrafts on the flight path lines, it can effectively prevent in-flight collisions with traffic alerts. The developed function allows operators to effectively select and control the aircraft in a collision situation by providing the operators with the expected collision time, the relative distance, and the relative altitude while assessing the level of alert, and visualizing the alert information which includes the Attention-Warning-Alert phase via embodying the TCAS standard. With the developed function the air traffic control system could sense an in-flight collision situation before the pilot's decision-making moment.

• 정보처리학회논문지D
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• 제14D권2호
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• pp.169-180
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• 2007

본 논문은 함수 변환(Function Transform)과 FFT(Fast Fourier Transform)를 사용하는 새로운 XML 문서 클리스터링 기법에 대하여 논한다. 본 문서 클러스터링 기법은 조정자 없이 점진적으로 수행된다. XML 문서는 엘리먼트의 계층적인 구조에 기반하여 이산 함수로 변환된다. 이산 함수는 FFT를 사용하여 벡터로 변환된다. 문서를 나타내는 벡터는 가중치 유클리디안 거리 메트릭을 사용하여 비교된다. 비교 결과가 미리 정의된 값보다 작을 때에는 비교되는 두 개의 문서는 구조적으로 비슷한 것으로 간주되어 동일한 그룹으로 분류된다. XML 문서 클리스터링은 XML 문서의 저장과 검색에 유용하게 사용될 수 있다. 800개의 합서 문서와 520개의 실제 문서를 사용하여 실험하였다. 실험 결과는 함수변환과 FFT는 XML 문서를 엘리먼트의 구조를 기반으로 하여 점진적으로 조정자 없이 효과적으로 분류하는 것을 보여주었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 추계학술대회 논문집 전기물성,응용부문
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• pp.62-64
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• 2005

Indium Tim Oxide(ITO) thin film was prepared for TOLEDs by Facing Targets Sputtering(FTS) apparatus which can suppress the damage of organic layer due to the collisions of high energetic particles. In particular, ITO thin film was prepared with changing the distance between two targets for reduced the bombardment by high energetic particles such as ${\gamma}-electron$ or negative oxygen ions. The electrical and optical properties of ITO thin films as a function of distance of between two targets were measured. Additionally, the ITO thin films were prepared on the cell (cell : MgAg/LiF/EML/HTL/ bottom electrode) with distance of between two targets. And the I-V characteristics of ITO/cell was investigated.

• Current Applied Physics
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• 제18권11호
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• pp.1393-1398
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• 2018

We have investigated Bernal-stacked tetralayer graphene as a function of interlayer distance and perpendicular electric field by using density functional theory calculations. The low-energy band structure was found to be very sensitive to the interlayer distance, undergoing a metal-insulator transition. It can be attributed to the nearest-layer coupling that is more sensitive to the interlayer distance than are the next-nearest-layer couplings. Under a perpendicular electric field above a critical field, six electric-field-induced Dirac cones with mass gaps predicted in tight-binding models were confirmed, however, our density functional theory calculations demonstrate a phase transition to a quantum valley Hall insulator, contrasting to the tight-binding model prediction of an ordinary insulator.

• Geomechanics and Engineering
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• 제22권2호
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• pp.187-196
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• 2020

The changeable stress environment directly affect the propagation law of a stress wave. Stress wave propagation tests in sandstone with different axial stresses were carried using a modified split Hopkinson Pressure bar (SHPB) assuming the sandstone has a uniform pore distribution. Then the waveform and stress wave energy dissipation were analyzed. The results show that the stress wave exhibits the double peak phenomenon. With increasing axial stress, the intensity difference decreases exponentially and experiences first a dramatic decrease and then gentle development. The demarcation stress is σ/σ_c=30%, indicating that the closer to the incident end, the faster the intensity difference attenuates. Under the same axial stress, the intensity difference decreases linearly with propagation distance and its attenuation intensity factor displays a quadratic function with axial stress. With increasing propagation distance, the time difference decays linearly and its delay coefficient reflects the damage degree. The stress wave energy attenuates exponentially with propagation distance, and the relations between attenuation rate, attenuation coefficient and axial stress can be represented by the quadratic function.

• Journal of Mechanical Science and Technology
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• 제18권8호
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• pp.1288-1296
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• 2004

Wall-following control problem for a mobile robot is to move it along a wall at a constant speed and keep a specified distance to the wall. This paper proposes wall-following controllers based on Lyapunov function candidate for a two-wheeled mobile robot (MR) to follow an unknown wall. The mobile robot is considered in terms of kinematic model in Cartesian coordinate system. Two wall-following feedback controllers are designed: full state feedback controller and observer-based controller. To design the former controller, the errors of distance and orientation of the mobile robot to the wall are defined, and the feedback controller based on Lyapunov function candidate is designed to guarantee that the errors converge to zero asymptotically. The latter controller is designed based on Busawon's observer as only the distance error is measured. Additionally, the simulation and experimental results are included to illustrate the effectiveness of the proposed controllers.