• Annals of Geriatric Medicine and Research
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• v.21 no.1
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• pp.17-23
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• 2017

Background: In at-risk older adults, gait speed is an important factor associated with quality of life and falling risk. In this study, we assessed whether therapeutic exercise could improve gait speed. Methods: We conducted a meta-analysis to evaluate the 'best' therapeutic exercise method by analyzing each exercise in terms of intensity, type, and several gait speed indices. For the analysis, we gathered 122 papers through a database search and selected 9 (n=627) that were appropriate for the meta-analysis. Results: In 8 of the 9 included papers, gait speed improved with therapeutic exercise. Usual gait speed (n=246) improved more than maximal gait speed (n=574). A resistance program was more effective than a nonresistance program for improving maximal, but not usual, gait speed. We also found that the effects of therapeutic exercise were greater in noncommunity than in community-dwelling elderly people. Conclusion: In conclusion, therapeutic exercise was effective in improving gait speed.

• Proceedings of the KSR Conference
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• 2005.05a
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• pp.467-472
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• 2005

The characteristics of dynamic vibration are generally analyzed by an acceleration of a car body of high speed train and the acceleration can be applied to evaluation of running safety. The test of process and the analysis method about it are well explained on UIC Code 518 OR which is the spacial international standard about running safety and dynamic behavior on the line test for railway vehicle. Korean High Speed Train designed to operate at speed 350km/h has been tested on high speed line since it was developed in 2002 and it recorded the highest speed 352.4km/h at the 16th Dec. 2004 in Korea. This paper includes the analysis of running behavior of this train at speed 350km/h and also the analysis of dynamic safety is presented in it, extending to the range of high speed while the UIC 518 limit the speed below 200km/h.

• International Journal of Railway
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• v.6 no.2
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• pp.64-68
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• 2013

In recent years, the speed of a train has been recognized as one of the important factors to determine the competitiveness as a mean of transportation. In line with this, infrastructure improvements and enhancements are being made with increases in the speed of train. Accordingly, there is a need to establish plans for infrastructure improvements through a comprehensive analysis of signals, track/civil engineering, catenary and environment, etc. to improve the speed of a train of high-speed train service sections in Korea. This study proposes improvement plans for catenary systems by investigating the possibility of improvements through performance analysis of catenary equipment by speed increase based on the analysis on catenary systems in Gyeongbu high-speed line, and analysis the applicability of catenary improvements and economic feasibility.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.8
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• pp.11-16
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• 1998

Recently, the motor-integrated spindle systems have been used to simplify the machine tool structure, to improve the motion flexibility of machine tool, and to perform the high-speed machining. In this study, a static and dynamic analysis system for motor-integrated high-speed spindle systems is developed based on Timoshenko theory, finite element method and windows programming techniques. Since the system has various analysis modules related to static deformation analysis, modal analysis, frequency response analysis, unbalance response analysis and so on, it is useful in performing systematically the design and evaluation processes of motor-integrated high-speed spindle systems under windows GUI environment.

• Journal of the Korean Society for Precision Engineering
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• v.34 no.3
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• pp.205-210
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• 2017

Critical speed analysis was conducted for a active steering bogie prototype, developed to improve the curving performance of railway vehicles. The critical speed for the design concept was about 169.2k m/h. To validate the analysis result, we performed a critical speed test for the prototype bogie using a roller-rig tester. The test results showed that the critical speed for the prototype bogie was about 165 km/h. From the analysis and test results, The critical speed for the prototype bogie was determined to be 165 km/h. Considering the maximum operating speed of the test vehicle is 100 km/h, the prototype bogie is considered stable.

• Journal of Drive and Control
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• v.19 no.4
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• pp.1-9
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• 2022

The structure and operating principle of the 2-speed shift reducer were explained, the allowable bending stress value of the material was compared with the analysis result through FM structural analysis program, and the average stress distribution value of von Mises was performed on the gear root atmosphere. The structural safety of the 2-speed planetary gear reducer was verified through FM structural analysis. The natural frequency was calculated by applying the specifications of the planetary gears of the 2-speed gearbox, and the critical speed of resonance was calculated by calculating the natural frequency and the transmission error of the engaged gear pair. As a result of analyzing the critical speed, since it is formed higher than the actual operating speed range, it is considered safe because there is no resonance problem due to the suggested specifications of the planetary gears of the 2-speed shift reduction.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.1056-1061
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• 2004

The vibration of rotor systems is caused by various factors, such as misalignment, unbalance, gear meshing, error of assembly, etc. Modal test and TDA/ODS analysis were done. The dynamic analysis of the armature was done with SAMCEF which is a commercial software for finite element and kinematic analysis. The transient response of the armature is calculated by the SAMCEF with the consideration of magnetic force and bearing stiffness, which are the essential elements for the design of high speed cutter. Main frequency of the vibration is due to the unbalance of the armature. The FEM analysis model considering unbalance and the high speed cutter have same vibration properties. The vibration sources of the high speed cutter is proved to be unbalance.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.984-988
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• 2010

In Korea, the next generation high-speed train, whose target is maximum speed of 400km/h and operating speed of 370km/h, has been developed since 2007. In this paper, the safety of the next generation high-speed train is compared UIC 518OR under the malfunctioning situation of the suspension system. The bogie of the next generation high-speed train has two suspensions. Two different vehicle models of the next generation high-speed train are created by using VAMPIRE and ADAMS/Rail, which are specialized to design railway vehicle. And Those models are showed same dynamic properties. First of all, the sensitivity analysis of ModelCenter is performed using model of VAMPIRE. One suspension element which has significant effects on the safety are selected by result of the sensitivity analysis. And then, the dynamic analysis when the suspension element is broken is performed using ADAMS/Rail. The 30km track between Pungsegyo and Biryong tunnel in Gyeongbu High-speed Line was used at the dynamic analysis. The estimated value is found by using the normal method of UIC 518OR. The estimated values on the normal/fault state and the limit values of UIC 518OR are compared. Finally, the safety of the next generation high-speed train is verified.

• Journal of ILASS-Korea
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• v.16 no.3
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• pp.126-133
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• 2011

In HCCI Engine, combustion is affected by change of compression speed corresponding to engine speed. The purpose of this study is to investigate the mechanism of influence of engine speed on HCCI combustion characteristics by using numerical analysis. At first, the influence of engine speed was shown. And then, in order to clarify the mechanism of influence of engine speed, results of kinetics computations were analyzed to investigate the elementary reaction path for heat release at transient temperatures by using contribution matrix. In results, as engine speed increased, in-cylinder gas temperature and pressure at ignition start increased. And ignition start timing was retarded and combustion duration was lengthened on crank angle basis. On time basis, ignition start timing was advanced and combustion duration was shortened. High engine speed showed higher robustness to change of initial temperature than low engine speed. Because of its high robustness, selecting high engine speed was efficient for keeping stable operation in real engine which include variation of initial temperature by various factors. The variation of engine speed did not change the reaction path. But, as engine speed increased, the temperature that each elementary reaction would be active became high and reaction speed quicken. Rising the in-cylinder gas temperature of combustion start was caused by these gaps of temperature.

• Journal of the Korean Institute of Landscape Architecture
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• v.29 no.4
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• pp.91-99
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• 2001

This study was carried out to investigate the effects of mowing height, rolling, N-fertilizing, and season on green speed(i.e., ball-roll distance) for developing and implementing a program of increasing green speed in Korean golf courses. Data were subjected to multi-regression analysis using SPSSWIN(Statistical Package for the Social Science), which collected from Yong-Pyong golf course greens selected to investigate. The results was as follows. 1) The multi-regression analysis of mowing height, rolling times, and N-fertilizer application rates on spring green speed was as follows; $Y_1$(spring green speed)=4.287+0.155X$_1$(rolling times)-0.131X$_2$(the amount of N-fertilizing)-0.251X$_3$(mowing height). 2) The multi-regression analysis of mowing height, rolling times, and N-fertilizer application rates on summer green speed was as follows; $Y_2$(summer green speed)=4.833-0.423X$_3$(mowing height)+0.146X$_1$(rolling times)-0.107X$_2$(the amount of N-fertilizing). 3) The multi-regression analysis of mowing height, rolling times, and N-fertilizer application rates on fall green speed was as follows; $Y_3$(fall green speed)=4.651-0.383X$_3$(mowing height)+0.142X$_1$(rolling times)-0.103X$_2$(the amount of N-fertilizing). 4) As mowing height was lowered by 1mm, green speed increased by 0.251~0.423m. As rolling times increased by 1(one), green speed increased by0.142~0.15m. As the amount of N-fertilizing increased by 1g/$m^2$, green speed decreased by 0.103~0.131m. The season also affected green speed. In comparison with spring green speed, summer green speed decreased by 0.145m and fall green speed decreased by 0.144m.