• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.2
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• pp.348-355
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• 1992

Casting structures and properties are determined by the solidification speed in the metal mold. The heat transfer characteristics of the interface between the mold and the casting is one of the major factors that control the solidification speed. According to Sully's research, the thermal resistance exists due to the air-gap formation at the mold-casting interface during the freezing process and the interface heat transfer coefficient is used to describe the degree of it. In this study, one-dimensional Stefan problem with air-gap resistance in the cylindrical geometry is considered and heat transfer characteristics is numerically examined. The temperature distribution and solidification speed are obtained by using the modified variable time step method. And the effects of the major parameters such as mold geometry, thermal conductivity, heat transfer coefficient and initial temperature of casting on the thermal characteristics are investigated.

• Journal of The Korean Society of Integrative Medicine
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• v.10 no.1
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• pp.49-60
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• 2022

Purpose : The purpose of this study was to identify whether gym-ball exercise in standing position was an effective intervention for improving muscle strength, balance, gait, and fall efficacy in stroke patients. Methods : Twenty-four stroke patients were randomized into three groups: experimental group 1 (n=8), experimental group 2 (n=8), and control group (n=8). Experimental groups 1, 2 and the control group performed the gym-ball exercise in standing position, same exercise without a gym-ball, and general physical therapy for 4 weeks, five times a week in 30-minute sessions. Muscle strength, balance, gait, and fall efficacy were assessed using a handheld dynamometer, the Berg Balance Scale (BBS), the wearable BTS G-WALK® sensor, and the Korean version of the Falls Efficacy Scale (K-FES), before and after training, respectively. Comparisons within and between groups were analyzed using the Wilcoxon signed rank test, Kruskal Wallis H test, and Mann-Whitney U test. Bonferroni correction was performed when significant differences between groups were identified (p<.017, .05/3). Results : Regarding muscle strength, BBS score, cadence and FES-K were significantly improved after intervention in all three groups. The weight bearing rate, gait speed and step length in experimental group 1 and 2 were significantly improved after the intervention. The stride length in experimental group 1 were significantly improved after the intervention. Experimental group 1 had significantly improved BBS score and stride length after intervention than experimental group 2 and control group. Experimental group 1 and 2 improved muscle strength, weight bearing rate, and FES-K score more than the control group. Experimental group 1 showed significant improvement in cadence, gait speed, and step length after the intervention than control group. Conclusion : This study showed that exercise with gym-ball in standing position can be an effective intervention to improve balance and gait in stroke patients than the same exercise without gym-ball.

• Journal of the Korean Society of Industry Convergence
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• v.22 no.4
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• pp.459-465
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• 2019

There is an increasing interest in health and research on methods for measuring human body information. The importance of continuously observing information such as the step change and the walking speed is increasing. At a person's gait, information about the disease and the currently weakened area can be known. In this paper, gait is measured using wearable walking module built in shoes. We want to make continuous measurement possible by simplifying gait measurement method. This module is designed to receive information of gyro sensor and acceleration sensor. The designed module is capable of WiFi communication and the collected walking information is stored in the server. The information stored in the server is corrected by integrating the acceleration sensor and the gyro sensor value. A band-pass filter was used to reduce the error. This data is categorized by the Gait Finder into walking and waiting states. When walking, each step is divided and stored separately for analysis.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.1
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• pp.119-130
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• 1996

This paper is the part I of the full study about improved structure of fully interconnected ATM switch to develop the small sized switch element and practical implemention of switch network. This part I paper describes about proposed switch structure, performance evaluations and some of considerations to practical implementation. The proposed structure is constructed of two step buffering scheme in a filtered multiplexer. First step buffering is carried out by small sized dedicated buffers located at each input port. And second step buffering is provided by a large sized common buffer at the output port. To control bursty traffic, we use speed up factor in multiplexing and priority polling according to the levels of buffer occupancy. Proposed structure was evaluated by computer simulation with two evaluation points. One is comparision of multiplexing discipline between hub polling and priority polling. The ogher is overall which should be considered to improve the practical implementation.

• Proceedings of the KIEE Conference
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• 1997.07f
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• pp.2101-2103
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• 1997

In this paper, micro step driving method is used for a high performance motion control and minimizing of vibration in a industrial X-Y table. By using a mathmetical analysis method of 2 phase Hybrid-type step motor, each phase current can be optimized about unit speed and torque. We can improve the electrical and mechnical driving charicteristic of machine by applying this proposed driver to the real plant using microprocessor.

• Journal of Ocean Engineering and Technology
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• v.11 no.4
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• pp.213-220
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• 1997

In this study, a design for a shape of centrifugal pump impeller has been performed using a p.c. under a Windows environment. Interaction between a user and a computer has been easily established using the Visual Basic. In determining an outer diameter of an impeller, steps are divided into two, a basic computational step and a refinment step. In this way user can enter his/her experience at the refinment step and hence can expect to lessen the nonlinear nature inherent to the design. In determining a shape of a side view of an impeller, the Bezier cubic curve has been used, and it can be seen that the Bezier cubic curves are well suited in the shape design under a Windows environment. By simply manipulating the four control points, one can generate various cubic curves among which one is selected. Also, a simple method, which can determine the curved position of an impeller vane, has been developed. These data can be used for final CAD drawings.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.967-968
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• 2007

This report is the study for laser scanning. Scanning control of $CO_2$ laser, He-Ne laser, used for the treatment of body skin, has relatively low band about hundered Hz. It could be used as a substitiute for expensive galvanometer that is the established scan method, which operates the number of KHz movement by using step motor when it operates low speed. To increase the accuracy of step motor's the angle of rotation, We could materialize 100Hz low band by using open loop, closed loop method with microprocessor. This causes it to be stable even direction by attaching electric capacity sensor. Therefore, We could expect to reduce the cost by manufacturing low band scanner rather than costly feedback galvanometer.

• Journal of Korean Biological Nursing Science
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• v.4 no.1
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• pp.5-23
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• 2002

Purpose: To determine the effect of the Fall Prevention Program(EPP) on gait, balance and muscle strength in elderly women at a nursing home. Method: The subjects of this consisted of 38 elderly women between the ages of 70 to 89 years living at a nursing home located in Seoul. Each of the experimental group and control group was composed of 19 subjects. The subjects in experimental group have participated in FPP for the 8 weeks which consisted of exercise, education and foot care. They started to exercise for 40 minutes per session, 3 sessions a week during the 1st week at 40% of age adjusted maximum heart rate. From the 2nd week to the 4th week, they increased the duration of exercise to 50 minutes per session and the intensity to 60% of age-adjusted maximum heart rate. They participated in 50 minutes at 60% of age-adjusted maximum heart rate from the 5th week to the 8th week. Each exercise session consisted of 10 minutes of warming-up exercise, 30 minutes of conditioning exercise and 10 minutes of cooling-down exercise. They participated in education for 20 minutes per week from the 1st week to the 4th week. Then they participated in a 30-minute foot care program per week from the 5th week to the 8th week. Gait, balance and muscle strength for each subject were measured before and after FPP. Gait was evaluated by step length, step width, gait speed and walking distance. Balance was measured by the duration of standing on one leg with their eyes closed and open each, and a get-up and go test. Grip strength was measured by hand dynamometer. Hip extensor and flexor strength, knee extensor and flexor strength and ankle plantarflexor and dorsiflexor strength were measured by manual muscle tester. Data was analyzed using SPSS form Windows. t-test and Chi square test were utilized as a homogeneity test. Repeated measure ANOVA was used to test the effect of FPP. Result: 1) Step width significantly decreased, and step length, gait speed and walking distance significantly increased in the experimental group compared with the control group after FPP(p<0.005). 2) There was no significant change in standing time on one leg with their eyes closed after FPP. The standing time on leg with their eyes open and the time of "get-up and go" significantly decreased in the experimental group compared with the control group after FPP(p<0.005). 3) Muscle strength-grip strength, hip extensor and flexor strength-significantly increased in the experimental group compared with the control group after FPP(p<0.005). 4) There was no significant difference of frequency of fall between the experimental group and control group during the period of FPP. Conclusion: These results suggest that FPP can increase gait, balance and muscle strength of elderly women at a nursing home.

• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.6
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• pp.389-395
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• 2019

This paper presents the sensorless position control of an auxiliary scaffolding step system for vehicles using DC motors. The designed auxiliary scaffolding step has a mechanical protector at the stop position. At this position, the scaffolding is forcibly stopped by the mechanical protector, and the motor current is dramatically increased to the stall current of the DC motor, thereby increasing the electrical damage. In this study, the estimated back EMF- and current model-based observers are proposed to estimate the motor speed and stop position. A simple V/F acceleration voltage pattern is used to operate the auxiliary scaffolding system. The estimated moving position is adopted to determine the stop position of the DC motor with the load current state. The operating current of the DC motor can be reduced by the estimated moving position and V/F acceleration pattern. At the stop position, the proposed sensorless position controller can smoothly stop the DC motor with the estimated moving position and reduced load current without any mechanical and electrical stress from the stall current from the mechanical protector. The proposed control scheme is verified by the comparison of simulations and experiments.

• Journal of Biosystems Engineering
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• v.13 no.3
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• pp.20-31
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• 1988

This study was undertaken to investigate the load characteristics of the head-feed thresher, which may be affected by various factors such as physical properties of grain, thresher design parameters and its operational condition. The study was conducted at an initial step toward developing an automatic feed-rate control system of the head-feed thresher. A microcomputer-based data acquisition system for the load-speed characteristic of the thresher-shaft and the rail-deflection of the feeding device in accordance with a varied feeding thickness was developed. The sensors being developed and used for sensing the torque and speed of the cylinder and the power-input-shaft and the feeding thickness showed a high accuracy. A microcomputer-based data acquisition system developed in this study was assessed as adequate for a rapid acquisition and analysis of data. The effect of the feed-rate on the torque and speed of the thresher shaft, when fed intermittently by bundles, affected not by the rice varieties but by the dryness of threshing material tested. When fed by the continuous constant thickness, the torque and speed of the cylinder due to the increase of the feed-rate or feeding thickness were given by the relation by the second order parabola.