• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.275-282
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• 2007

In this study, a fluid-structure interaction (FSI) analysis system has been developed in order to evaluate the turbine cascade performance with blade structural deformation effect. Relative movement of the rotor with respect to stator is reflected by modeling independent two computational domains. To consider the deformed position of rotor airfoil, dynamic moving grid method is applied. Reynolds-averaged Navier-Stokes equations with one equation Spalart-Allmaras and two-equation SST $k-{\varepsilon}$ turbulence models are solved to predict unsteady fluid dynamic loads. A fully implicit time marching scheme based on the Newmark direct integration method with high artificial damping is used to compute the fluid-structure interaction problem. Cascade performance evaluations for different elastic axis positions are presented and compared each other. It is importantly shown that the predicted aerodynamic performance considering structural deformation effect of blade can show some deviations compared to the data generally computed from rigid blade configurations and the position of elastic axis also tend to give sensitive effect.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1994.04a
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• pp.375-384
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• 1994

Depending upon the eye and head movement, the visual field is often classified into three categories; stationary field, eye field and head field. To investigate the effect of background condition on the size of stationary field, an experiment was conducted, in which the subject was instructed to search a target with distinct orientations. In each trial, a single target was presented on the rear-view screen projected by the two-field tachistoscope, with the visual angle subtended 4.3.deg. vertically and horizontally. Density, meridian and subject showed a significant effect on stationary field at .alpha.=0.01, where density was inversely proportional to the size of stationary field. The size of the stationary field on horizontal axis was larger than that on vertical axis, and that on right and below meridian also larger than on left and lower meridian. The shape was found to be horizontally oriented oval and statistically asymmetric with respect to horizontal and vertical axes. The regression equation to predict stationary field on the given background condition was suggested. These results were expected to be used as a designing guideline when arranging displays and controls on panels such as automobile display panels, cockpits, etc. In addition, it can be inferred from the results that eye field and head field are also subjected to the influence of background condition.

• Journal of the Korean Institute of Landscape Architecture
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• v.26 no.2
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• pp.101-109
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• 1998

Recently, improvement of the quality of urban riverscape environment has been emphasized not only by landscape architectural field but also by various professionals in planning and ecology. Regarding to this current movement, the aim of this paper is to highlight major visual elements of riverscape axis as a case study of Shinchon River in Taegu City to suggest some basic guidelines for arranging riverscape in urban area. The study was mainly based on Repertory Grid Development method which was developed in Japan. The method is consist of three steps such as decision of element landscape in study area for slide photos, selection of evaluation items for interview and obstraction of proper evaluation factors. The major findings through this study are as follows; 1) The 12 major visual elements which possibly improve riverscape, based on abstraction of proper evaluation factors, are Dunchi, surface of the water,, equipment of river, buildings near riverside, river vertical and horizontal facilities like bridge, fine view, riverbed, water plant, naturalness, water's edge line, harmony and street trees by order. 2) Total numbers of adjective which describe 12 common factors are 25, such as clean, open, stable, quiet, comfortable, friendly, bright, natural etc. In addition, Dunchi was described 337 times by various adjectives, surface of the water was 200 times and arrangement of river was 146 times which is similar result with the order of 12 influential common factors. 3) Therefore, Dunchi, surface of the water and equipment of river are three most important factors which could create better riverscape. These three factors implies us how we supply good quality of urban river environment for the urban residents.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.5 no.1
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• pp.87-93
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• 2011

This paper proposes a method for extraction of the gaze point on display using EOG(Electrooculography) signal. Based on the linear property of EOG signal, the proposed method corrects scaling difference, rotation difference and origin difference between coordinate of using EOG signal and coordinate on display, without adjustment using the head movement. The performance of the proposed method was evaluated by measuring the difference between extracted gaze point and displayed circle point on the monitor with 1680*1050 resolution. Experimental results show that the average distance errors at the gaze points are 3%(56pixel) on x-axis, 4%(47pixel) on y-axis, respectively. This method can be used to human computer interface of pointing device for general paralysis patients or HCI for VR game application.

• Journal of the Ergonomics Society of Korea
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• v.14 no.1
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• pp.59-67
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• 1995

Depending upon the eye and head movement, the visual field is often classified into three categories ; stationary field, eye field and head and eye field. To investigate the effect of background condition on the size of the visual field, an experiment was conducted, in which the subject was instructed to search a target with distinct orientations. In each trial, a single target was presented on the perimeter modified to cover the range of 330 .deg. around the fixation point, with the visual angle subtended 1.4 .deg. vertically and horizontally. Nontarget density, meridian, size contrast and subject showed a significant effect on the visual field at .alpha. =0.01, where density was inversely proportional to the size of the visual field, and size contrast linearly proportional to the size of the visual field. The size of the visual field on horizontal axis was larger than that on vertical axis, and that on right and upper meridian was also larger than on left and lower meridian. The shape was found to be horizontally oriented oval and statistically asymmetric with respect to horizontal and vertical axes. In addition, the regression equations to predict the visual field on the given background condition were suggested. These results were expected to be used as a design guideline when arranging displays and controls on panels such as automobile display panels, cockpits, etc.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.49 no.8
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• pp.459-466
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• 2000

In this paper, we propose an attitude controller for an unstructured object using CMG(Control Moment of Gyro) subsystem, which has a stabilizer function. The CMG subsystem consists of one motor for spinning the wheel and the other motor for turning the outer gimbal. While the wheel of CMG subsystem is spinning at high speed, applying force to the spin axis of the wheel leads the torque about the vertical axis. We utilize the torque to control the attitude of object in this study. For the stabilizer function, in additiion, holding the load at the current position, the power applied to the gimbal motor of CMG will be cut, which result in the braking force to stop the load by gyro effect. However, due to the gear reduction connected to outer gimbal, slow load motion cannot generate the braking force. Thus, in this study, we are willing to make a holding force by applying control power to the gimbal motor from the signal of piezoelectric gyroscopic sensor that detected the angular velocity of the load. These two features are demonstrated in experiment, carrying a beam with crane. As a result, load was started to rotate by controlling gimbal positiion and was stopped by turning off the gimbal power. Moreover, slow movement of the load was also rejected by additional control with gyroscopic sensor.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.10
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• pp.45-52
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• 1999

The online realtime positioning error compensation system 'SKY-PACS' is developed to correct geometric errors, thermal errors and tool deflection errors induced by cutting forces on the vertical machining center. 'SKY-PACS' communicates position commands and position compensation signals with the CNC controller at 100Hz, which is CNC control frequency. So the compensation procedure can be applied during axis movement. Using 'SKY-PACS', Maximum 1 axis positioning accuracy was corrected from 5{\mu}m$ to 2{\mu}m$and the squareness error of X-Y table was corrected from 51{\mu}m$/m to below 4{\mu}m$/m. The error compensation under the cutting condition is carried out by ISO10791-7. And the measurement of test-pieces shows that the roundness is corrected rom 8{\mu}m$ to below 5{\mu}m$.

• Journal of Institute of Control, Robotics and Systems
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• v.21 no.7
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• pp.677-683
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• 2015

This paper proposes a helicopter direction adjustment system using barycenter shift. Most conventional methods for direction adjustment of uniaxial helicopters rely on the angle of inclination of the main rotor. However, the inherent burden of the bearing of the main rotor and serious abrasion of the helicopter using the above methods may results in loss of balance. To decrease abrasion and enhance the barycenter stability, the proposed method was used to shift the barycenter of the helicopter instead of the main rotor for direction adjustment. We set a biaxial ARM on a uniaxial helicopter to adjust the direction of ARM pointing as well as to realize stable direction control when the helicopter loses its balance. The method may enhance the landing safety of helicopters in emergencies. Uniaxial helicopters can be controlled under any environment by adjusting the motor parameters of the ARM which is dependent on the center of mass using neural network. The experiment results show that the helicopter can return to the starting position quickly under the external disturbance.

• Korean Journal of Applied Biomechanics
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• v.33 no.1
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• pp.34-44
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• 2023

Objective: The purpose of this study was to examine the effects of increasing running speed on human stability by comparing the Lyapunov Exponent (LyE) and Coefficient of Variation (CV) methods, with the goal of identifying key variables and uncovering new insights. Method: Fourteen adult males (age: 24.7 ± 6.4 yrs, height: 176.9 ± 4.6 cm, weight: 74.7 ± 10.9 kg) participated in this study. Results: In the CV method, significant differences were observed in ankle (flexion-inversion/eversion; p < .05) and hip joint (internal-external rotation; p < .05) movements, while the center of mass (COM) variable in the coronal axis movements showed a significant difference at the p < .001 level. In the LyE method, statistical differences were observed at the p < .05 level in knee (flexion-extension), hip joint (internal-external rotation) movements, and COM across all three directions (sagittal, coronal, and transverse axis). Conclusion: Our results revealed that the stability of the human body is affected at faster running speeds. The movement of the COM and ankle joint were identified as the most critical factors influencing stability. This suggests that LyE, a nonlinear time series analysis, should be actively introduced to better understand human stabilization strategies.

• The Journal of Korean Academy of Prosthodontics
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• v.32 no.2
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• pp.281-295
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• 1994

It is very important for the ideal restorations of anterior openbite patients to record the mandibular movement and to harmonize mandibular movement with other organs in stomatognathic systems. This study was designed to compare the mandibular movement of anterior openbite patients with that of normal bite(Angle Class I) patients, to ascertain which components of mandibular movement have differences between two groups, and to use for occlusal treatment of mandibular movement. Saphon Visi-trainer Model 3(Tokyo Shizaisha Co. Japan) and Denar Pantronic(Denar Corp.,U.S.A.) were used to record mandibular movement. Pantronic survey was peformed by using an arbitrary hinge axis according to manufacturer's direction. Twenty-eight adult who have physiologically normal occlusion(Angle Class I) and are free of TM dysfunction were selected as a control group(Group 1). Fifteen adult who are anterior openbite patient and have not anterior guidance function and have posterior interference at protrusion were selected as a experimental group(Group 2). The results are as follows : 1. There was no statistically significant difference between the average immediate and progressive side shift of anterior openbite patients(0.54mm, $7.57^{\circ}$) and those of normal group(0.49mm, $5.96^{\circ}$). 2. The average protrusive and orbiting condylar inclination of anterior openbite patient$(30.87^{\circ},\;32.27^{\circ})$ were significantly lower than those of normal group$(36.11^{\circ},\;39.04^{\circ})$ (P<0.05). 3. In the results of Visi-trainer recordings, the mean for the maximum protrusion, the maximum laterotrusion, the angle of laterotrusion and the angle of protrusion in the horizontal trajectory between group 1 and 2 did not differ significantly. 4. The mean for the angle of protrusion, the maximum opening in the frontal trajectory, the ICP-RCP(A-P) distance and the angle of protrusion in the sagittal trajectory differ significantly(P<0.05). 5. The significant correlation was found between orbiting condylar inclination and protrusive condylar inclination.