• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.4
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• pp.281-289
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• 2016

Accurate prediction of the trajectory and time of a time-varying mass parachute system remains essential in the mission requiring a precision airdrop to the ground. In this study, we investigate the altitude-varying behavior of a cross-type parachute system designed to deliver a time-varying mass object like flare. The dynamics of the descending parachute system was analyzed based on the Runge-Kutta method of the ordinary differential system. The drag coefficients of the cross-type parachute and flare were calculated by a CFD code based on the incompressible Navier-Stokes equation. Finally, by using a simplified gust wind model in troposphere, the combined effects of gust wind and time-varying mass were examined in detail.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.11
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• pp.1741-1747
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• 2010

This work presents a study on the design of an economic service robot hand for tele-presence manipulators. The conceptual design of new robot hand is derived from biomimetics approach. Guided by the analysis of human arm' musculoskeletal structure, the fingers are actuated by cables and actuators in the forearm. High tension in the cables is achieved by screw-nut mechanism driven by DC motors. A set of combination springs is incorporated in each of the screw-nut mechanism for easy control of gripping force. The first prototype revealed difficulties with finger control and coupling problem between gripping force and wrist movement. The solutions to these problems have been derived from the contradiction analysis of TRIZ. The second design has been verified by tests on various objects with different weight and shape for full range of wrist motion.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.46 no.6
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• pp.73-79
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• 2009

For the shake of control for movement object, control theory like neural network, nonlinear model predictive control(NMPC) is realized on digital high speed computer. Predictor of flight control system(FCS) based nonlinear model predictive control has to be satisfied with response for hard real-time to perform applications on each module in the FCS. Simultaneously, It gives a serious consideration accuracy to give full play to FCS's performance. Error of mathematical aspect affects realization of whole algorithm. But factors of bring mathematical error is not considered to calculate final accuracy on parameter of predictor. In this paper, Predictor was made using load control model on the digital computer for design FCS at hard real-time and is shown response time on realization algorithm. And is shown realization algorithm of high effective predictor over the accuracy. The predictor was realized on the load control model using Euler method, Heun method, Runge-Kutta and Taylor method.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.48 no.4
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• pp.86-93
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• 2011

The ship movement implies current position, wave, wind, and its other factors. We need to know exactly the location and the shape of the ship and control its motion because of these effects. In order to control the small ship according to the movement of the large ship, the position and shape of the ship should be given first. In this paper we propose the method with which we know the current status of the ship without dynamic equations of the ship. There are several methods to track the system such as optical, radio frequency, radar, camera, and infrared light. We propose the movement of the ship using the GPS absolute axis. But, the genuine error by the GPS itself and the movement of the ship cause the result of the GPS of not being accurate. This paper reduces the error of the location and the shape of the ship and gives the exact values of the ship movements even if the GPS implies some error itself.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.22 no.6
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• pp.423-428
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• 2010

This study is aiming to find one of reasonable guidelines to select a proper berthing ship at Kwang Yang harbors for loading/unloading for the POSCO(Pohang Steel Co. Ltd.). For dynamic analysis for the moored ships, the selection of subjected vessels has to be given the priority, so that the motion characteristics are figured out. The calculation of the dynamic fluid forces and wave, wind and current forces in time domain are followed. Then, the dynamic mooring analyses are performed. This study might contribute to make a new guideline by which the proper sized and loaded ships could be moored safety at the berths of Kwang Yang Harbor.

• Journal of Korean Philosophical Society
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• v.144
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• pp.235-256
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• 2017

This essay considers Leibniz-Clark correspondence on the nature of space and hole argument. The ontology of space had been debated under the name of substantivalism-relationism controversy. The debates between the two parties are concerned with the nature of existence of parts of space-time. Substantivalism claims that the point of space-time has existence analogous to that of material substance. Relationism argues that space-time should be understood as the framework of possible spatio-temporal relations between bodies. Although these two approaches attempt to respect theoretical context, it seems that the problems of these two interpretive schemes stems from the lack of understanding of the structure of space-time theories, especially how space-time is connected with the laws of motion. In order to appreciate the substance-relation controversy without deviating from the context of space-time theories, it is necessary then to capture how space-time theories are constituted. This essay offers the clear connection of ontology of space-time with present practices of theoretical physicists.

• Journal of the Society of Naval Architects of Korea
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• v.31 no.3
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• pp.47-58
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• 1994

Theoretical calculations are carried out for the estimation of linear maneuvering coefficients of a ship moving in shallow water region. Hydrodynamic forces and moments acting on a maneuvering ship are modelled based on a slender body theory, from which integro-differential equation for the unknown inner stream velocity is derived. Numerical algorithms fur solving this equation are described in detail. By considering water depth effects in the mathematical model, variations of maneuvering coefficients with water depth are studied. Programs are developed according to this method and calculations are done for Mariner, Series 60 and Wigley hull forms. For the verification of the programs, calculated results are compared with some analytic solutions and with published experimental results, which show good agreements in spite of many assumptions included in the mathematical model. It is expected that this method can be used as a preliminary tool for the estimation of maneuverability coefficients of a ship in shallow water region at its initial design stage.

• Journal of Aerospace System Engineering
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• v.12 no.1
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• pp.1-9
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• 2018

In this study, a hybrid control method that adjusts for the existing force control technique has been presented for consideration. The proposed hybrid control technique does away with the chattering phenomenon occurring in existing force control technique and provides high shock absorption efficiency. In order to design the controller for the landing gear with MR damper, the equation of motion of the landing gear was derived. The hybrid controller was designed after constructing a simulation model using Recur-Dyne, multi-body dynamic analysis software. The hybrid controller can reduce the maximum strut force and displacement based on the skyhook controller, and is able to get the high efficiency by making it work for the additional force control technique. In addition, an effective switching control technique and input shaping technique was applied to prevent the chattering in the drop simulation. Finally, the performance of the landing characteristics was evaluated throughout the various drop simulations.

• Journal of the Korea Convergence Society
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• v.10 no.10
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• pp.117-122
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• 2019

In the field of fluid dynamics, the sloshing effects are most common and significant problem. It is usually appeared in the tank filled with fluid which is on the main structure, thus, sloshing effects and its impact load may affect to entire system. For the sloshing effects analysis, impact loads due to tank motion is generally investigated theocratically, experimentally and numerically. The difficulty of sloshing phenomenon is non-linearity induced by large deformation at the free-surface. In this regard, it is well known issue that the repeatability on the sloshing problems is very low. In this study, moving particle semi-implicit method was employed to simulate sloshing problem and then the results were compared with corresponding experiments captured by high accuracy high speed camera. The results from numerical simulation was compared to experimental results.

• Journal of Advanced Navigation Technology
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• v.27 no.1
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• pp.43-49
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• 2023

Object tracking is being studied with various techniques such as Kalman filter and Luenberger tracker. Even in situations, such as the one in which the system model is not well specified, to which existing signal processing techniques are not successfully applicable, it is possible to design artificial neural networks to track objects. In this paper, we propose an artificial neural network, which we call 'maximum-likelihood weighted-average neural network', to continuously track unpredictably moving objects. This neural network does not directly estimate the locations of an object but obtains location estimates by making weighted average combining various results of maximum likelihood tracking with different data lengths. We compare the performance of the proposed system with those of Kalman filter and maximum likelihood object trackers and show that the proposed scheme exhibits excellent performance well adapting the change of object moving characteristics.