• Journal of the Korean Society for Precision Engineering
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• v.22 no.3 s.168
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• pp.29-37
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• 2005

In this study, the control of the free surface deformation of a magnetic fluid for the change in electromagnetic force is discussed. The free surface of magnetic fluid is formed by the balance of surface force, gravity, pressure difference, magnetic normal pressure and magnetic body force. Magnetic fluid in characteristics of fluid adjusted to the opposite direction of the gravity direction. Thus, the device of a magnetic fluid proposed the complete zero-leakage sealing, oscillator for surface control, boundary layer control, MHD, flow control, flow using magnetic levitation system and surface actuator. This study show the deformation of surface rise due to the intensity of the magnetic field and possibility of two-dimensional control of magnetic fluid through the feedback data of hall sensor.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.09a
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• pp.75-82
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• 2002

The Mononobe-Okabe method is generally used to evaluate the dynamic earth force for the seismic design of retaining walls. However, the Mononobe-Okabe method does not consider the effects of the dynamic interactions between the backfill soil and the wall. In fact, a phase difference exists between the inertia force and the seismic earth pressure. In this study, shaking table tests were peformed on gravity walls retaining dry backfill sand to analyze the influence of several parameters (the unit weight of the wall, the input acceleration and base friction) on the development of the seismic earth pressure. The experiments revealed that the magnitude of the inertia force mobilized during seismic loading affected the seismic earth pressure. The difference in the phase angles between the inertia force and the seismic earth pressure was retained at 180 degrees before the wall failed but its magnitude changed significantly as the wall began to fail.

• Journal of Korean Institute of Industrial Engineers
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• v.11 no.2
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• pp.87-99
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• 1985

The purpose of this study is to analyze the changes in centers-of-gravity (COG), acceleration and body posture and their associated effects both on EMG and on the maximum capability of weight lifting during Clean & Jerk and Snatch motions. Displacement, velocity, acceleration of joints were obtained from film analysis. Also levels of exertions on 11 major muscle groups were obtained from EMG analysis during a lifting cycle. The EMG data were measured from Telemetry System which is useful in field experiments. Magnitude and direction of force, change in center-of-gravity were extracted from COG data which were measured from force platform. The results of this study can be to be useful both to coaches and to athletes in weight-lifting.

• International Journal of Aerospace System Engineering
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• v.7 no.1
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• pp.1-6
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• 2020

A deployment mechanism is designed to stow into a small volume efficiently. The panels are fabricated by carbon fiber reinforced plastics (CFRPs). The parameters for the deployment are determined by considering the number of panels, the folding/twisting angles, and the driving force for a deployment device. In addition, a surface accuracy of the manufactured reflector is measured through a photogrammetry methodology. The deployment behavior of CFRP reflector is observed by using the zero-gravity device which compensates the gravity effect during the deployment. The zero-gravity device is constructed wire, motor, controller and loadcell. During the deployment of the reflector panel, the wire and motor compensate for its weight by the feedback process of the controller. Tests result show that a zero-gravity device compensates for the weight of the panel during the deployment of the CFRP reflector.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.267-272
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• 2000

The modeling on uplift pressure on the foundation of a dam on which it was constructed, and on the interface between the dam and foundation is a critical aspect in the analysis of concrete gravity dams. The evaluation of stress intensity factor at the crack tip of concrete gravity dam due to uplift pressure effect by surface integral method is performed in this study. The effects of body force, overtopping pressure and water pressure on the crack-face are also considered in this study.

• Journal of Institute of Control, Robotics and Systems
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• v.16 no.6
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• pp.532-538
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• 2010

SD (Smart Door) is a human friendly power-assisted door system initially targeted for passenger car doors. The Smart Door offers comfort and safety to passengers or/and drivers by supplying additional power. Amount of power supplied by the Smart Door system is depend on the environment where the automotive is situated. It realizes comfort, for example, when the force applied by the passenger to the door is expected to be abnormal, the SD system tries to compensate passenger's effort by supplying additional force. In this study, to enhance the ease of opening and closing the doors of the passenger vehicle, a Smart Door with a power assist mechanism consisting of a motor was developed and analysed. A power assist mechanism mounted within the vehicle's door is designed and modeled for simulation purpose. The required force necessary to control the designed mechanism during the vehicle's roll, pitch and the opening angle of the door has been considered. To this end, we propose a power-assisting control strategy called "gravity cancellation". The system is analysed by numerical simulation with the gravity cancellation control algorithm.

• Water for future
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• v.29 no.1
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• pp.163-179
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• 1996

Flood flow characteristics of the Han River (from Goan to Indo Bridge) are analyzed using 1-dimensional St. Venant equations. NETWORK, a finite difference model, is used to calculate each term (local acceleration term, convective acceleration term, pressure force term, gravity force term, and friction force term) of the momentum equation and to analyze the flow characteristics. By the result of the study, as the general characteristics of flow in a channel that acceleration terms are very small and the other three terms are much greater is presented, three terms(pressure force term, gravity force term, friction force term) are to be main terms which decide the characteristics of flow. Specially in this region the acceleration term is noted so large that it cannot be ignored according to the shape of hydrograph and the region.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.1019-1022
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• 2002

Pipe-cutting machines have been used in many fields. Recently, an automatic pipe-cutting machine that uses magnet has born developed. In this paper, a magnetic-type automatic pipe-cutting machine that attaches itself and performs unmanned cutting process is proposed. It is designed that there is a room at the bottom of its body to contain a magnet. And it uses magnetic force between the magnet and the pipe surface to prevent slip and to attach the machine to the pipe against gravity. Also the magnetic force is adjustable by changing the gap between the magnet and the pipe. This machine is, however, necessary to control cutting velocity for the elevation of work efficiency and the adjustable faculties. During pipe cutting process, the gravity acting on the pipe-cutting machine widely varies. That is, the cutting machine gets fast when moving from the top to the bottom of the pipe and slow when moving from the bottom to the top. Actually the system is kind of a non-linear system where the gravity is function of climbing angle of the cutting machine along the pipe. Especially jerking motion is critical. Therefore, authors design the non-linear controller that estimates the current position of the machine along the pipe and compensates the effect of gravity in this paper. It receives the feed back signal from the encoder.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.297-300
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• 2002

In this study, the deformation of the free surface motion of a magnetic fluid for the change in electromagnetic force is discussed and carried out theoretically and experimentally on the basis of Rosensweig Ferrohydrodynamic Bernoulli Equation. While applied magnetic fields are induced by 4$\times$4 electromagnet located under the magnetic fluid, the surface of the magnetic fluid is formed the balance of surface force, gravity, pressure difference, magnetic normal pressure and magnetic body farce. In case, magnetic fluid in characteristics of fluid adjusted to the opposite direction of the gravity direction. thus, the device of a magnetic fluid proposed the surface actuator. The device of surface deformation as well comparison between numerical simulation and experiments as will be presented.

• Wind and Structures
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• v.12 no.5
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• pp.425-439
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• 2009

The expediency of revising universal rules for the combination of gravity and lateral actions of wind force-resisting steel structures recommended by the Standards EN 1990 and ASCE/SEI 7-05 is discussed. Extreme wind forces, gravity actions and their combinations for the limit state design of structures are considered. The effect of statistical uncertainties of extreme wind pressure and steel yield strength on the structural safety of beam-column joints of wind force-resisting multistory steel frames designed by the partial factor design (PFD) and the load and resistance factor design (LRFD) methods is demonstrated. The limit state criterion and the performance process of steel frame joints are presented and considered. Their long-term survival probability analysis is based on the unsophisticated method of transformed conditional probabilities. A numerical example illustrates some discrepancies in international design standards and the necessity to revise the rule of universal combinations of loads in wind and structural engineering.