• International Journal of Naval Architecture and Ocean Engineering
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• v.5 no.2
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• pp.313-323
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• 2013

Offshore floating structures have so-called moonpool in the centre area for the purpose of drilling, installation of subsea structures, recovery of Remotely-Operated Vehicle (ROV) and divers. However, this vertical opening has an effect on the operating performance of floating offshore structure in the vicinity of moonpool resonance frequency; piston mode and sloshing mode. Experimental study based on model test was carried out. Moonpool resonance of floating offshore structure on fixed condition and motion free condition were investigated. And, the effect of cofferdam which is representative inner structure inside moonpool was examined. Model test results showed that Molin's theoretical formula can predict moonpool resonance on fixed condition quite accurately. However, motion free condition has higher resonance frequency when it is compared with that of motion fixed. The installation of cofferdam moves resonance frequency to higher region and also generates secondary resonance at lower frequency. Furthermore, it was found that cofferdam was the cause of generating waves in the longitudinal direction when the vessel was in beam sea.

• Journal of the Korean Society of Propulsion Engineers
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• v.13 no.3
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• pp.41-49
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• 2009

The present paper describes a mathematical modeling and simulation of the separation of a solid rocket booster from an air breathing engine vehicle. The vehicle and booster are considered as a multi-connected body and the booster is assumed to move only along the axial direction of the vehicle. The dynamic motion of the vehicle and the booster were modeled by using Kane's method. The aerodynamic forces on the whole system along various positions of booster were calculated by using DATCOM software and the internal pressure force acting on the effective surface during separation was simply calculated with gas dynamics and Taylor MacColl equation. Numerical simulation was done by using Mathworks-Matlab. From the result, the variation of Mach number and angle of attack are not large during the separation, so the variation of pitch angle and the characteristics of inlet flow for varying the Mach number and angle of attack during the separation test can be identified as neglectable values.

• International Journal of Ocean System Engineering
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• v.1 no.2
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• pp.60-67
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• 2011

This paper presents an in-situ correction method to compensate for the position error of an autonomous underwater vehicle (AUV) near the sea floor. AUVs generally have an inertial navigation system assisted with auxiliary navigational sensors. Since the inertial navigation system shows drift in position without the bottom reflection of a Doppler velocity log, external acoustic positioning systems, such as an ultra short baseline (USBL), are needed to set the position without surfacing the AUV. The main concept of the correction method is as follows: when the AUV arrives near the sea floor, the vehicle moves around horizontally in a circular mode, while the USBL transceiver installed on a surface vessel measures the AUV's position. After acquiring one data set, a least-square curve fitting method is adopted to find the center of the AUV's circular motion, which is transferred to the AUV via an acoustic telemetry modem (ATM). The proposed method is robust for the outlier of USBL, and it is independent of the time delay for the data transfer of the USBL position with the ATM. The proposed method also reduces the intrinsic position error of the USBL, and is applicable to the in-situ calibration as well as the initialization of the AUVs' position. Monte Carlo simulation was conducted to verify the effectiveness of the method.

• Smart Media Journal
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• v.11 no.5
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• pp.75-81
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• 2022

In order to respond to carbon neutrality and climate change in agriculture, agricultural machinery, which has been developed centered on internal combustion engines, needs to be converted to an electric-based technology that does not emit greenhouse gases. In this study, simulations for electric UTV suspension design were performed to reduce vibration and shock of electric UTV for agricultural use and to improve driving stability and control performance of the vehicle. The simulation was performed by dividing the tolerance load of the vehicle body and the loaded load state. The range of motion of the suspension spring of UTV is within 30% of the range of motion under condition B under tolerance, the displacement of the UTV suspension with full load is reduced from 264mm to 121mm, and the damping speed is 260mm/s to 300mm/s that it can be seen that the range of motion is within 60%. Suspension design of electric UTV for multi-purpose agricultural work is a very important factor for maintaining agricultural work ability in towing work such as tillage as well as driving and terrain adaptation. The results of this study can be usefully used to determine the spring parameters with the appropriate damping range so that the electric UTV can be used for various agricultural tasks.

• Steel and Composite Structures
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• v.45 no.5
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• pp.697-713
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• 2022

In the context of the finite elements method, the dynamic behavior of porous functionally graded double wishbone vehicle suspension structural system incorporating joints flexibility constraints under road bump excitation is studied and analyzed. The functionally graded material properties distribution through the thickness direction is simulated by the power law including the porosity effect. To explore the porosity effects, both classical and adopted porosity models are considered based on even porosity distribution pattern. The dynamic equations of motion are derived based on the Hamiltonian principle. Closed forms of the inertia and material stiffness components are derived. Based on the plane frame isoparametric Timoshenko beam element, the dynamic finite elements equations are developed incorporating joint flexibilities constraints. The Newmark's implicit direct integration methodology is utilized to obtain the transient vibration time response under road bump excitation. The presented procedure is validated by comparing the computational model results with the available numerical solutions and an excellent agreement is observed. Obtained results show that the decrease of porosity percentage and material graduation tends to decrease the deflection as well as the resulting stresses of the control arms thus improving the dynamic performance and increasing the service lifetime of the control arms.

• Proceedings of the Korean Society of Computer Information Conference
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• 2020.07a
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• pp.71-72
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• 2020

본 논문에서는 자동차 블랙박스를 사용하여 촬영된 비디오에서 자동차 사고 발생 여부를 판단하는 방법을 제안한다. 제안한 방법은 우선 객체 추적 과정에서 구한 조감도 좌표를 사용하여 각 차량 사이의 거리에 기반을 두고 교통사고 여부를 판단한다. 그런데 거리만을 사용하여 사고 여부를 판단하는 경우 자동차가 밀집된 주·정차 환경에서는 오검출의 확률이 높아질 수 있다. 이를 위해 각 차량에 대한 움직임 벡터를 계산하고 벡터 간의 정보(사잇각과 크기 등)를 사용하여 차량의 주·정차 여부를 판단한 후 사고 검출 대상에서 배제할 수 있도록 한다. 주·정차 판단 여부를 통해 사고 검출의 정확도를 향상할 수 있는 것을 실험적으로 확인하였다.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.92-94
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• 1997

A stabilizing system of EOTS is constructed. This system has two major parts. One of them is for detecting the moving motion of a vehicle with electronic gyroscope. The other is for driving of two axes of the platform where the sensor is attached. The controller used in this paper is DSP(TMS320c31) and two BLDC DD motor are used.

• Cartoon and Animation Studies
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• s.15
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• pp.251-265
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• 2009

Motion Graphics are a great effective vehicle for precise communication between customers in various media and formats. The important thing in the expression of Motion Graphics is to deliver messages clearly. Some current Motion Graphics which are focused on only attracting attention or sensational expressions more than narrative are evaluated lower. This study aims to utilize easy and positive Motion Graphics to deliver messages by applying their utility to production of Motion Graphics, omitting time spent on delivering effective messages and analyzing their suggestive expression methods because of the nature of producing Motion Graphics. This thesis is to study several theoretical backgrounds of omission and implicated expressions mentioned in the similar studies from the view of Motion Graphics, and to search applied examples and functional things using the expression methods in some film title sequence. Excellent Motion Graphics use planned omission and implicated methods rather than to use entire narratives or complicated descriptions. Especially, a film title sequence should focus on symbolic visual expressions. They are necessary to attract the audience's interest. To overcome the limitation of time and space deliver a huge amount of information quickly and powerfully, Motion Graphics should properly use omission of image and time and suggestive expressions through symbols and metaphors. Then they will have a role to level up their current values and discussions.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.3
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• pp.462-468
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• 2010

A new course keeping controller for RIB(Rigid Inflatable Boat)-type USV(Unmanned Surface Vehicle) is developed using pilot's steering pattern. A pilot's simple steering pattern is found out from various course change tests. It is used to course keeping algorithm, suitable for large course change more than 60 degrees. To validate the course keeping controller, sea trial tests are conducted. From sea trial test, new course keeping controller shows good performance with less overshoot, maximum roll angle less than $20^{\circ}$, which makes it possible that fast course changes without slip motion of USV.

• Journal of Ocean Engineering and Technology
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• v.23 no.2
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• pp.58-68
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• 2009

The increased use of unmanned underwater vehicles (UUV) has led to the development of alternative navigational methods that do not employ acoustic beacons and dead reckoning sensors. This paper describes a simultaneous localization and mapping (SLAM) scheme that uses range sonars mounted on a small UUV. A SLAM scheme is an alternative navigation method for measuring the environment through which the vehicle is passing and providing the relative position of the UUV. A technique for a SLAM algorithm that uses several ranging sonars is presented. This technique utilizes an unscented Kalman filter to estimate the locations of the UUV and surrounding objects. In order to work efficiently, the nearest neighbor standard filter is introduced as the data association algorithm in the SLAM for associating the stored targets returned by the sonar at each time step. The proposed SLAM algorithm was tested by experiments under various three degrees of freedom motion conditions. The results of these experiments showed that the proposed SLAM algorithm was capable of estimating the position of the UUV and the surrounding objects and demonstrated that the algorithm will perform well in various environments.