• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.5
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• pp.1087-1095
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• 1994

Chain drive power transmission system was developed for a low head hydro-turbine which generates power by energy transformation on the turbine blades attached to chains. Also, experimental and theoretical analysis for the sprocket wheel tooth load distribution were performed. The tooth load was measured by the specially designed load sensor. It was found that the tooth load distribution for the steady state operation was in good accordance with the quasi-static state results showing the peak load at the final meshing tooth. The trend of the experimental results agreed with the theoretical results based on the spring model analysis and difference in the magnitude of the maximum tooth load was considered to be the effect of the variable spring constant due to the moving contact point between the roller and sprocket wheel tooth.

• Journal of the Korean Society of Propulsion Engineers
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• v.5 no.2
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• pp.59-64
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• 2001

The purpose of this work is to investigate the static strength, the stress distribution, and the failure process of quasi-isotropic composite laminates made of two different matrices when loading directions are changed. We carried out static tests of $[0/-60/+60]_s$ and $[+30/-30/90]_s$ laminates. Two types of matrices used are AS4/epoxy and AS4/PEEK. The damage mechanisms of the quasi-isotropic laminate, $[0/-60/+60]_s$, strongly depend on the load direction applied to the laminate.

• Journal of Ocean Engineering and Technology
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• v.31 no.4
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• pp.274-280
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• 2017

Generally, global performance analysis in offshore platforms is performed using potential-based numerical tools, which neglect hydrodynamic viscous effects. In comparison with the potential theory, computational fluid dynamics (CFD) methods can take into account the viscous effects by solving the Navier-Stokes equation using the finite-volume method. The open-source field operation and manipulation (OpenFOAM) C++ libraries are employed for a finite volume method (FVM) numerical analysis. In this study, in order to apply CFD to the global performance analysis of a hull-mooring coupled system, we developed a numerical wave basin to analyze the global performance problem of a floating body with a catenary mooring system under regular wave conditions. The mooring system was modeled using a catenary equation and solved in a quasi-static condition, which excluded the dynamics of the mooring lines such as the inertia and drag effects. To demonstrate the capability of the numerical basin, the global performance of a barge with four mooring lines was simulated under regular wave conditions. The simulation results were compared to the analysis results from a commercial mooring analysis program, Orcaflex. The comparison included the motion of the barge, catenary shape, and tension in the mooring lines. The study found good agreement between the results from the developed CFD-based numerical calculation and commercial software.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.12
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• pp.1730-1738
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• 2001

This paper presents an overview of testing and analyzing field performance of a centrifugal chiller which has a rated capacity of 200 RT(703 kW). Field data of a chiller installed in the cleanroom research building of KIST has been collected far performance analysis. The operating data included start-up, shut-down, and quasi-static state where cooling capacity and compressor power consumption varied cyclically. It was found that the steady-state thermodynamic model could be applied to relate the cooling capacity and COP under quasi-static conditions. The results led to finding the required cooling load pattern and a possible energy saving method. This study provides a method of evaluating performance of a large capacity centrifugal chiller in which field test is necessary.

• Structural Engineering and Mechanics
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• v.19 no.3
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• pp.281-295
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• 2005

An analytical method is presented to solve the elastodynamic problem of finitely long hollow cylinder subjected to torsional impact often occurs in engineering mechanics. The analytical solution is composed of a solution of quasi-static equation satisfied with the non-homogeneous boundary condition and a solution of dynamic equation satisfied with homogeneous boundary condition. The quasi-static solution is obtained directly by solving the quasi-static equation satisfied with the non-homogeneous boundary condition. The solution of the non-homogeneous dynamic equation is obtained by means of finite Hankel transform on the radial variable, r, Laplace transform on time variable, t, and finite Fourier transform on axial variable, z. Thus, the solution for finitely long, hollow cylinder subjected to torsion impact is obtained. In the calculating examples, the response histories and distributions of shear stress in the finitely long hollow cylinder subjected to an exponential decay torsion load are obtained, and the results have been analyzed and discussed. Finally, a dynamic finite element for the same problem is carried out by using ABAQUS finite element analysis. Comparing the analytical solution with the finite element solution, it can be found that two kinds of results obtained by means of two different methods agree well. Therefore, it is further concluded that the analytical method and computing process presented in the paper are effective and accurate.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.2
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• pp.129-136
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• 2005

The vehicle loading test under the strict traffic control is generally carried out as a present practice in an evaluation process of the bearing capacity of a bridge. The quasi-static load test is recently proposed to mitigate the traffic condition of test, and analyze the disturbed acceleration time-history data of free vibration due to the ambient traffic on the bridge by Fourier transform to calculate only the natural frequencies of the bridge. The calculated frequencies have some errors due to the analysis technique as well as the influence of ambient traffic loads, and in addition to it is cumbersome to obtain the free vibration data during a quasi-static load test. In this study, the wavelet transform technique using Morlet wavelet is used to analyze the acceleration data recorded during a quasi-static load test on a bridge and calculate the natural frequencies and the modal damping ratios of the bridge. The study results show that the wavelet transform technique is a reliable and reasonable method to analyze test data and obtain the natural frequencies and the modal damping ratios of a bridge regardless of the data types i.e. free or forced vibrations.

• Journal of International Academy of Physical Therapy Research
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• v.11 no.1
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• pp.1999-2004
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• 2020

Background: Although studies on physical motor learning through motor imagery training have been conducted in various fields, studies on its effectiveness are still considered insufficient. Objective: To investigate the effect of motor imagery training and balance training on static balance of asymptomatic adults in their 20s. Design: A quasi-experimental study. Methods: Thirty-six adults in their 20s who passed the tandem stance test were randomized to the motor imagery training group (MIG, n=12), motor imagery with balance training group (MIBG, n=12), and balance training group (BG, n=12). Each group underwent their respective interventions three times a week for four weeks, and changes in static balance were analyzed using multivariate analysis of variance. Results: Trace length was significantly lower in the MIBG than in the MIG and BG (P<.05), and a significant reduction in trace length in the MIBG was observed after the intervention as compared to the baseline (P<.05). Furthermore, a significantly lower velocity was observed in the MIBG than in the MIG and BG (P<.05), and a significant reduction of velocity in the MIBG was more observed after the intervention compared to the baseline (P<.05). Conclusion: These results suggest that motor imagery training enhance static balance in healthy college students.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.289-294
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• 2011

The purpose of this paper is to validate energy absorbing capacity that satisfies APTA SS-C&S-034-99, REV.2 with North America type Electric Multiple Units. The FE models for collision and corner post simulation were developed. Two type of simulation were conducted. One is quasi-static analysis for collision post and the other is quasi-static analysis for corner post. And the energy absorption capacity of the analytical model was verified.

• Structural Engineering and Mechanics
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• v.2 no.2
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• pp.211-225
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• 1994

Responses of asymmetrical multistorey buildings to earthquakes are obtained by quasi-static code approach and real time dynamic analysis, using two different structural models. In the first model, all vertical members are assumed to be restrained at the slab levels and hence their end rotations, about horizontal axes, are taken as zero. In the second model this restriction is removed and the rotation is assumed to be proportional to the lateral stiffness of the member. A simple microcomputer based procedure is used in the analyses, by both models. Numerical examples are presented where results obtained from both the models are given. Effects of modelling on the response of three buildings, each with a different type and degree of asymmetry, are studied. Results for deflections and shear forces are presented and the effects of the type of model on the response are discussed.

• International Journal of Air-Conditioning and Refrigeration
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• v.9 no.2
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• pp.44-50
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• 2001

The Sirocco fan performance and its three-dimensional flow characteristics are numerically prediction by STAR-CD. Turbulent flow computations are performed using approximately 500,000 mesh points, and the performance results of tow computational methods, transient and quasi-static flow analyses are compared with experimental data. In the present study, our attention is focused on the three-dimensional flow characteristics of the Sirocco fan blades and the secondary flow structure in the scroll. For a design optimization study, the scroll shape is titled by $10^\circ$ to modify the secondary flow structure, which yields some improvement of the fan performance.