• Journal of The Korean Society of Integrative Medicine
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• v.8 no.3
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• pp.11-20
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• 2020

Purpose : The purpose of this study was to determine the correlation between smartphone use, body composition, posture and muscle properties of elementary school students. Methods : A total of 22 healthy elementary school students in Daejeon, South Korea, participated in this study with informed consent. Smartphone use was evaluated with Smartphone addiction self-report scale (S-scale) for youth. Body composition (BMI, percent body fat, body fat mass, and skeletal muscle mass) was measured using Inbody. To assess posture, forward head posture and round shoulder posture were measured using Dartfish motion analysis. Muscle properties (muscle tone, stiffness, and elasticity) were measured on the upper trapezius, splenius capitis and sternocleidomastoid muscles using Myoton. To investigate the correlation between the main variables, Pearson correlation analysis was performed. Results : Disturbance of adaptive function, which is one of sub-component of S-scale, had a weak positive correlations with BMI (r=.538, p<.01), and body fat mass (r=.453, p<.05). However, scores of S-scale showed no correlation with posture and muscle properties. The correlation between posture and muscle properties was analyzed, and round shoulder posture revealed a weak positive correlation with respect to stiffness (r=.418, p<.05) and elasticity (r=.502, p<.05) of the sternocleidomastoid muscle. Conclusion : Scores of S-scale demonstrated a weak correlation with body composition (BMI) among elementary school students, whereas S-scale scores were not correlated with the posture and muscle properties. Further research is needed to identify and focus on potential high-risk user groups of elementary students who are more dependent upon smartphones.

• Journal of the Korean Applied Science and Technology
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• v.34 no.4
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• pp.899-907
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• 2017

The purpose of this study is to investigate effects of floor exercise on senior fitness test, blood lipids and arterial stiffness in elderly women with metabolic syndrome. Forty one elderly women with metabolic syndrome were randomly assigned to a exercsie group(n=23) or control goup(n=18). The exercise group performed floor exercise for 12 weeks, 3times per week. Exercise intensity was increased gradually from 30%-60% of heart rate reserve. Senior fitness, blood lipids profile and arterial stiffness were measured pre and post the 12 weeks intervention. Senior fitness(lower body strength, upper body strength, flexibility, aerobic capacity and body composition(%fat, LBM, WC)), Blood lipids(TC, TG, HDL-C and LDL-C) and Arterial stiffness(PWV) were significantly improved in the exercise group after floor exercise, however no changes were confirmed in the control group. These findings indicates that 12 weeks of floor exercise improves senior fitness, blood lipids and arterial stiffness in elderly women with metabolic syndrome. Thus, this study provides evidence that floor exercise is important methods to improve metabolic syndrome health. And it can reduce metabolic syndrome symptoms risk in elderly women with metabolic syndrome.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.2
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• pp.131-140
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• 2022

Installing Continuous Welded Rail (CWR) is one of the economical ways to resolve the challenges of noise, vibration, and the open-deck steel railway bridge impact, and the SSF method using the interlocking sleeper fastener has recently been developed. In this study, the method employed for determining the optimum vertical stiffness of the sleeper pad installed under the bridge sleeper, which is utilized to adjust the rail height and absorb shock when the train passes when the interlocking sleeper fastener is applied, is presented. To determine the optimal vertical stiffness of the sleeper pad, related existing design codes are reviewed, and, running safety, ride comfort, track safety, and bridge vibration according to the change in the vertical stiffness of the sleeper pad are estimated via flexible multi-body dynamic analysis,. The flexible multi-body dynamic analysis is performed using commercial programs ABAQUS and VI-Rail. The numerical analysis is conducted using the bridge model for a 30m-long plate girder bridge, and the response is calculated when passing ITX Saemaeul and KTX vehicles and freight wagon when the vertical stiffness of the sleeper pad is altered from 7.5 kN/mm to 240 kN/mm. The optimum stiffness of the sleeper pad is calculated as 200 kN/mm under the conditions of the track components applied to the numerical analysis.

• Structural Engineering and Mechanics
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• v.89 no.2
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• pp.155-170
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• 2024

Several types of column-beam connections are used in the design of steel structures. This situation causes different cross-section effects and, therefore, different displacements and deformations. In other words, connection elements such as welds, bolts, continuity plates, end plates, and stiffness plates used in steel column-beam connections directly affect the section effects. This matter reveals the necessity of knowing the steel column-beam connection behaviours. In this article, behaviours of bolted column-beam connection with end plate widely used in steel structures are investigated comparatively the effects of the stiffness plates added to the beam body, the change in the end plate thickness and bolt diameter. The results obtained reveal that the moment and force carrying capacity of the said connection increases with the increase in the end plate thickness and bolt diameter. In contrast, it causes the other elements to deform and lose their capacity. This matter shows that optimum dimensions are very important in steel column-beam connections. In addition, it has been seen that adding a stiffness plate to the beam body part positively contributes to the connection's moment-carrying capacity.

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.459-464
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• 2001

Vibration characteristics of a vehicle are mainly influenced by dynamic stiffness of the vehicle body structure and material and physical properties of the components attached to the vehicle body structure. In this paper, modeling techniques of the vehicle components are presented and the effects of the vehicle components on the vibration characteristics of the vehicle are investigated.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.4
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• pp.47-53
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• 2011

Firstly, FEM model for the body frame of a fuel cell vehicle was built up and design optimization results based on different schemes were exhibited. One scheme was to minimize weight while maintaining the normal mode frequencies and the other was to increase the frequencies without weight change. Next, for a rear frame model, shape parameter study on collapse characteristics such as peak resistance load and absorbed energy was carried out. Also, the stiffness of frame mounting brackets was predicted using inertance calculation and the durability of those mounting brackets for vehicle system loads was evaluated. Finally, for a representative mounting model, the influence on durability due to thickness change was analyzed.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.417-422
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• 2004

The vibration of a running vehicle can be classified on lateral, longitudinal and vertical motions. The important factor on the stability and ride quality of a railway vehicle is the lateral motion. The contact between wheel and rail with conicity influences strongly on the lateral motion. In this study, an experiment for the vibration of a running railway vehicle was performed using a small scale railway vehicle model. Also, the effects on the car body, bogie and wheelset were examined for the weight and the stiffness of the first and second suspension. The experimental results showed that the lateral vibration increases as the wheel conicity and stiffness of the second suspension increase. And the lateral vibration of the bogie increases as the mass ratio between car body and bogie increases. Also, the lateral vibration of the wheel becomes high at low speed, while the wheel of 1/20 conicity makes severe vibration at high speed running.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.800-805
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• 2004

In this paper, a numerical method for train/track/structure interaction analysis in frequency domain is developed. Track is modelled as continuous beams supported by elastomers. The motion of train is expressed by those of car body, bogies and unsprung masses supported by springs and dampers. The equation of motion for train and track interaction system is derived by applying compatibility condition at the contact points between wheels and rails. The Effects of rail pad stiffness on the behaviors of train and track are analyzed using the presented method.

• The Journal of Korea Robotics Society
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• v.14 no.4
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• pp.270-277
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• 2019

Inspired by small insects, which perform rapid and stable locomotion based on body softness and tripod gait, various milli-scale six-legged crawling robots were developed to move rapidly in harsh environment. In particular, cockroach's leg compliance was resembled to enhance the locomotion performance of the crawling robots. In this paper, we investigated the effects of changing leg compliance for the locomotion performance of the small light weight legged crawling robot under various payload condition. First, we developed robust milli-scale six-leg crawling robot which actuated by one motor and fabricated in SCM method with light and soft material. Using this robot platform, we measured the running velocity of the robot depending on the leg stiffness and payload. In result, there was optimal range of the leg stiffness enhancing the locomotion ability at each payload condition in the experiment. It suggests that the performance of the crawling robot can be improved by adjusting stiffness of the legs in given payload condition.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.4
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• pp.266-273
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• 2003

The purpose of this study is to obtain the effects of the parameters of the suspension system in railway rolling-stock for KT-23 type Passenger vehicle. According to the analysis and the small scale model car test. optimal condition was obtained for the stiffness ratio of secondary spring to primary spring of the suspension system and the mass ratio of the bogie frame to the car body. The analysis of the study shows that if the car body mass is increased or secondary stiffness Is lowered, the vertical vibration level is reduced and the passenger comfort can be improved. Especially, strong peaks are occurred in the frequencies corresponding to the rotational speed of driving axle and vehicle wheel. Hence, in order to obtain the dynamic characteristics through the small scale model car, the driving method of the vehicle on the test bench, rotational characteristics of the wheel and the natural modes of vehicle should be investigated and be modified.