• 한국정보통신학회논문지
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• 제6권2호
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• pp.300-308
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• 2002

본 논문은 네트웍을 이용하여 원격 제어가 가능한 사족보행로봇의 구현에 대하여 다루고 있다. 로봇이 평탄하지 않은 지면에서 작업하거나 인간 친화적인 요소를 부여하기 위해서는 인간이나 곤충과 같이 다리를 가지는 보행이 필수적이다. 제작된 사족 보행로봇은 장착된 센서와 구동부를 이용하여 기본적인 동작을 수행하는 동시에 유선알고리즘을 이용해 만들어진 진보된 걸음새를 가지고 있다. 또한 웹브라우저를 이용하여 로봇의 명령을 만들고 현재의 상태를 모니터링 하는 등의 원격 동작을 수행하기 위해 네트웍을 통해 제어를 수행할 수 있게 하였다. 본 논문에서는 제작된 로봇의 기구적인 해석 결과를 다루었고 해석된 결과를 모의 실험과 더불어 실제 구현하여 제시된 방법의 유용성을 제시하였다.

• 대한인간공학회지
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• 제29권3호
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• pp.375-382
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• 2010

The purpose of this study was to analyze the risk factors of the musculoskeletal workload of mid-old-age food preparation workers by identifying the differences in the complaints of subjective symptoms between mid-old-age housewives and mid-old-age food preparation workers. This study was carried out on a total of 83 subjects from April 2009 through July 2009: 43 food preparation workers at the catering department of general hospital A, with a high rate of mid-old-age food preparation staff, and 40 full-time housewives (40~59 years old). The analysis of the relationship between the rates of the subjective symptoms of the two groups showed that the mid-old-age food preparation workers had a 7.8-fold higher risk of developing musculoskeletal diseases than the full-time housewives. The musculoskeletal workload of the mid-old-age food preparation workers included repetitive motions, uncomfortable postures, and heavy lifting. It is hoped that this study will help provide mid-old-age people with opportunities for appropriate economic activity and labor and will help improve their work postures and methods as well as their environmental-risk factors.

• Journal of Mechanical Science and Technology
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• 제20권7호
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• pp.1019-1029
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• 2006

The ballistic range has long been employed in a variety of engineering fields such as high-velocity impact engineering, projectile aerodynamics, creation of new materials, etc, since it can create an extremely high-pressure state in very short time. Of many different types of ballistic ranges developed to date, two-stage light gas gun is being employed most extensively. In the present study, a theoretical work has been made to develop a new type of ballistic range which can easily simulate a flying projectile. The present ballistic range consists of high-pressure tube, piston, pump tube, shock tube and launch tube. The effect of adding a shock tube in between the pump tube and launch tube is investigated. This improvement is identified as the reduction in pressures in the high pressure tube and pump tube while maintaining the projectile velocity. Equations of motions of piston and projectile are solved using Runge-Kutta methods. Dependence of projectile velocity on various design factors such as high pressure tube pressure, piston mass, projectile mass, area ratio of pump tube to launch tube and type of driver gas in the pump tube are also analyzed. Effect of various gas combinations is also investigated. Calculations show that projectile velocities of the order 8 km/sec could be achieved with the present ballistic range.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1995년도 Proceedings of the Korea Automation Control Conference, 10th (KACC); Seoul, Korea; 23-25 Oct. 1995
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• pp.464-467
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• 1995

Autonomous Mobile Robot(AMR) is a field of study which is under active research along with rapid development of the engineering technology. The main reasons for the high interest in AMR are because of its ability to change work space freely and its capability to replace human being for difficult and dangerous jobs. Also the fact that AMR provides a variety of research fields, such as path planning, navigation algorithm, sensor fusion, image processing, and controller design is part of the reason for its popularity. But relatively few researches are concerned with controller. So in this paper, a control strategy of mobile robot with nonholonomic constraint for tracking ordered discontinuous motion is proposed. The proposed control strategy has been designed as a state feedback shape to allow the AMR to obtain continuous velocity and track the path which is composed of discontinuous motions. In order to design such controller, 3 states have been reduced to 2 states through coordinate projection. These ideas are tested for validity through simulation and simulation result is compared with experiments result.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2006년도 정기 학술대회 논문집
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• pp.451-458
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• 2006

The goal of many researchers in the field of structural engineering is to reduce both damage to building structures and discomfort of their inhabitants during strong motion seismic events. The present paper reports on analytical work conducted with this aim in mind as a prior research of experimental study. A four-story, 6.4 m tall, laboratory model of a building is employed as a example structure. The laboratory structure has graphite epoxy columns and each floor is equipped with a chevron brace that serves to resist inter-story drift with the installation of a magnetorheological (MR) damper. An artificial excitation has been generated with a robust range of seismic characteristics. A series of numerical simulations demonstrates that an optimized fuzzy controller is capable of robust performance for a variety of seismic base motions. Optimization of the fuzzy controller is achieved using multi-objective genetic algorithm(MOGA), i.e. NSGA-II. Multiple objective functions are used in order to reduce both peak and root-means-squared displacement and accelerations at the floor levels of the building.

• 대한조선학회논문집
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• 제45권5호
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• pp.523-529
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• 2008

The course stability performance for tankers is evaluated by computational fluid dynamics. In the present work, a Reynolds averaged Navier-Stokes (RANS) code is applied to a maneuvering problem covering the pure drift and yaw motions. The purposes of this study are to evaluate the hydrodynamic force in the bare hull (AFRAMAX) in pure drift and yaw motion and to provide information about the trends in the forces and moments when the rudder angles are varied. The flow simulation is performed by FLUENT. The CFD code is examined to find the optimistic computational condition such as size of grid, turbulence model and initial condition. The hydrodynamic derivatives in drift and pure yaw motion are estimated by the numerical simulation, and then the stability levers are calculated. It is confirmed that the computations show the superiority and inferiority of course stability performance according to the hull forms. Finally, the CFD code is applied to the estimation of the rudder forces when the rudder angles are varied. The propeller effect expressed by the body force distribution is also included.

• 한국정밀공학회지
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• 제22권11호
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• pp.111-117
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• 2005

The vibration problems associated with gear coupled rotors have been the focus of much engineering work. These systems are complex and difficult to analyze in that they have the problems associated with conventional rotors plus those additional problems associated with the gear couplings. This paper examines the problems peculiar to the gear mesh. Because of the meshing action of gears, the elasticity of the gear teeth introduces time-varying stiffness coefficients into the governing equations of motion. This means that system response must be thought of in terms of Mathieu-type equations, where multiple-frequency response occur due to the periodic coefficients. The meshing action of the gears also couples the lateral and torsional gear motions. Gear errors, such as tooth profile and spacing errors, produce forces and torque that excite the system at multiple frequencies, some of which are much higher than shaft rotational speed. To investigate how to the time-varying stiffness in the gear teeth and the gear errors act one the dynamic response of the gear coupled rotors, a three-dimensional dynamic model with lateral-tortional oscillation is developed. The harmonic balance technique is employed to solve this mathieu-type problem.

• 천문학회보
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• 제43권1호
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• pp.46.3-47
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• 2018

We present a general N-body exasolar system simulator in anticipation of upcoming searches for exoplanets and even exomoons by next generation telescopes such as James Webb Space Telescope. For habitable zones, traditionally defined by temperature, we here address the essential problem of dynamical stability of planetary orbits. Illustrative examples are presented on P-type orbits in stellar binary systems, that should be fairly common as in Kepler 16b. Specific attention is paid to reduced orbital lifetimes of exoplanets in the habitable zone by the stellar binary, that is propoesed by Maurice van Putten (2017). Especially, we focused on a classic work of complex three-body problem that is well known by Dvorak(1986). We charge his elliptic restricted three-body problem to extend unrestricted three-body problem to look into dynamical motions in view of circumbinary planet, furthermore, we suggest that opposite angular orientation of the planet is relative to the stability of orbits. In here, counter-rotation case is relatively more faster than co-rotation case for being stable. As a result, we find that various initial conditions and thresholds to approach dynamical stability and unstability with unexpectable isolated islands over enormous parameter space. Even, superkeplerian effect of binary is important to habitability of the exoplanet and we can verify that superfaster binary doesn't effect on th planet and increases survivality of planet around the binary.

• 제어로봇시스템학회논문지
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• 제13권1호
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• pp.65-71
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• 2007

Adjustable autonomy architecture provides various ways for a human operator to participate as a member of a human-robot team in improving the performance of the team by resolving issues that the robots cannot deal with or performing tasks that the robots alone would unable to do. According to the level of involvement of the human operator, the robots have to adjust their level of autonomy and, in consequence, the operation mode of the overall system shifts. This paper deals with the implementation issues of seamless switching when the level of autonomy of the human-robot team shifts from one level to another. Especially, we focus on developing reliable methods for monitoring the task progress and maximizing the system flexibility by coping with the detailed differences between humans and robots in their characteristics of motions and their choices of positions, paths, and sequences of sub-goals to achieve a given task. To test and motivate the proposed methods, we have assembled three heterogeneous robots which work together to dock both ends of a suspended beam into stanchions.

• Ocean Systems Engineering
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• 제8권3호
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• pp.329-343
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• 2018

The inclination of seabed profile (sloped seabed) is one of the known topographic features which can be observed at different seabed level in the large offshore basin. A mooring system connected between the platform and global seabed is an integral part of the floating structure which tries to keep the floating platform settled in its own position against hostile sea environment. This paper deals with an investigation of the motion responses of an FPSO platform moored on the sloped seabed under the combined action of wave, wind and current loads. A three-dimensional panel discretization method has been used to model the floating body. To introduce the connection of multi-segmented non-linear elastic catenary mooring cables with the sloped seabed, a quasi-static composite catenary model is employed. The model and analysis have been completed by using hydrodynamic diffraction code AQWA. Validation of the numerical model has been successfully carried out with an experimental work published in the latest literature. The analysis procedure in this study has been followed time domain analysis. The study involves an objective oriented investigation on platform motions, in order to identify the effects of the slopped seabed, the action of the wave, wind and current loads and the presence of riser system. In the end, an effective analysis has been performed to identify a stable mooring model in demand of reducing structural responses of the FPSO.