• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.12
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• pp.1395-1401
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• 2014

In an effort to develop and implement an inertial balance with high performance, the response characteristics of a load cell, which are some of the critical parameters for optimal system design, were evaluated using a sample object of approximately 100 g under microgravity conditions. To this end, a 15-m drop-tower was used to produce microgravity conditions, and the response characteristics of the load cell were investigated in terms of the variations in the magnitude of the deceleration of the sample object, noting that the mass of a living animal should be determined in microgravity. An analysis of the ratio of the inertial forces clearly demonstrated that the average velocity of a load cell plate should be higher than 0.5 m/s to meet the design requirements.

• The Journal of the Korea Contents Association
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• v.10 no.5
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• pp.267-276
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• 2010

The purpose of this study was to investigate the variations in gait parameters according to arm slings used in healthy adults. Twenty healthy adults (9 males, 11 females) participated in this study and walked at self-selected speeds on a GAITRite-instrumented carpet. They were randomly assigned conditions: without an arm sling, a care sling, a Harris hemi arm sling, a CVA sling, and a Rolyan humeral cuff sling. The following gait parameters were analyzed: the temporo-spatial parameters of gait velocity, swing phase, single support, cadence. In the comparison of parameters in each trial, step length was statistically significantly changed(p=.002). The right step length was significantly decreased in the Harris hemi arm sling and increased in the Rolyan humeral cuff sling when compared with no sling. This study found that several different types arm slings varied gait pattern in healthy adults.

• The Journal of the Korea Contents Association
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• v.13 no.2
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• pp.498-504
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• 2013

Recently, the frequency of typhoons have increased due to the effects of climate change. As a result, in mountain streams, it has caused streamflow increase upstream and frequent water surface elevation downstream. This study analyzed the effects of the heavy rainfalls caused by Typhoon Sanba, which had a direct impact on Korea between September 17 and 18, on the water level variations downstream in mountainous streams. In addition, the drainage basin of Samcheok Oship stream was chosen as the object of this study. This study analyzed the flood level by applying HEC-RAS model. The observed water level measured in 2012 and the water level simulated by HEC-RAS model showed similar results. In addition, the simulation results showed the maximum flood level was 5.32m the mean flow velocity was 2.33m/sec and the maximum channel water depth was 7.51m. The analysis showed that the heavy rainfalls caused by Typhoon Sanba had an impact on the water surface elevation in Oship stream. The final results from this study will give a reasonable and important data to perform the Design of Hydraulic Structure.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.2
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• pp.85-91
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• 2017

A wind tunnel test for 1/86 scaled down model of the NREL 5 MW offshore wind turbine was conducted to investigate the wake and flow fields. Deficit of flow speed in the wake region and variations of the turbulence intensity were measured using a hot wire anemometer at rated tip speed ratio of 11.4 m/s and a rotational speed of 1,045 rpm. According to the test results, velocity deficits along both of lateral and vertical directions were recovered within 2 rotor radii downstream from the rotating disc plane. The tip vortices effect was negligible after 5 rotor radii downstream from the rotating plane. Turbulence intensities showed maximum value around the blade tip, and decreased rapidly after one radius apart from the rotating plane, and those values were preserved until 6 rotor radii downstream.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.2
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• pp.244-251
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• 2011

Pipe rolling process using the planetary rolling mill for AISI 304 stainless steel has been studied by using finite element method. Mannesmann method using three-roll is applied to this rolling process. Commonly, rolling process has started from the cold working and finished to the hot working. This rolling process has more advantage that make reduction of process and cost than existing extrusion process. This process includes various and complex process parameters. Each of the process parameters affects forming result. Therefore, all of the process parameters should be considered in FEA. In this study, possibility and productivity of forming pipe for AISI 304 stainless steel had been investigated. Also, preheating process and variations of rotation velocity and product thickness were considered in FEA. Rolling process for AISI 304 stainless steel pipe was successfully simulated and it should be useful to determine optimal rolling condition.

• Journal of Mechanical Science and Technology
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• v.14 no.10
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• pp.1131-1142
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• 2000

In an effort to illustrate the global variation of SMD (Sauter mean diameter, or $D_{32}$) and AMD (Arithmetic mean diameter, or $D_{10}$) at five axial downstream locations (i. e., at Z=30, 50, 80, 120, and 170 mm) under the different experimental conditions, the radial coordinate is normalized by the spray half-width. Experimental data to analyze the atomization characteristics concerning with an internal mixing type have been obtained using a PDPA(Phase Doppler Particle Analyzer). The air injection pressure was varied from 40 kPa to 120 kPa. In this study, counterflowing internal mixing nozzles manufactured at an angle of $15^{\circ}$with axi-symmetric tangential-drilled four holes have been considered. By comparing the results, it is clearly possible to discern the effects of increasing air pressure, suggesting that the disintegration process is enhanced and finer spray droplets can be obtained under higher air assist. The variations in $D_{32}$ are attributed to the characteristic feature of internal mixing nozzle in which the droplets are preferentially ejected downward with strong axial momentum, and dispersed with the larger droplets which are detected in the spray centerline at the near stations and smaller ones are generated due to further subsequent breakup by higher shear stresses at farther axial locations. The poor atomization around the centre close to the nozzle exit is attributed to the fact that the relatively lower rates of spherical particles are detected and these drops are not subject to instantaneous breakup in spite of the strong axial momentum. However, substantial increases in SMD from the central part toward the edge of the spray as they go farther downstream are mainly due to the fact that the relative velocity of droplet is too low to cause any subsequent disintegration.

• KIPS Transactions on Software and Data Engineering
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• v.4 no.7
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• pp.297-300
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• 2015

In medical ultrasonography, transit time and contrast enhancement patterns are considered as important parameters to analyze liver diseases. In many recent researches, time-intensity curves(TIC) have been used for calculating the transit time of the contrast agents. However, the intensity curve may include the variations which are caused by the micro-bubble effect of contrast agents. In this paper, we propose a complementary approach to diagnostic parameter extraction which utilizes a density information as well as the intensity data. The proposed technique improves the accuracy in extraction of the transit time and velocity of contrast agents for detection and characterization of focal liver lesions. Through the experiments using a set of clinical data, we show that the proposed methods can improve the reliability of the parametric image data.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.12
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• pp.1653-1661
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• 2012

In this study, the pressure drop changes and structural characteristics of a SMART rod bundle under the effect of a coolant were investigated. The turbulence model of the BSL Reynolds stress model was used to model the coolant flow, and a fluid solid interaction simulation was conducted. First, fuel rod vibration analysis was performed to confirm the natural frequency of the fuel rod, which was supported by spacer grid assemblies, and this was compared with experimental results. From the experimental results, the natural frequency was found to be 48 Hz, and the error compared with the simulation results was 2%. The pressure drop at the rod bundle was calculated and compared with the experimental data; it showed an error of 8%, demonstrating the simulation accuracy. In the flow analysis, the flow velocity and secondary flow at different domains were calculated, and vortex generation was also observed. Finally, through the fluid solid interaction analysis, the fuel rod displacements caused by flow-induced vibrations were calculated. Then, calculated displacement PSD at maximum displacement happed point.

• Journal of KSNVE
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• v.9 no.6
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• pp.1173-1179
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• 1999

A study was made on crack developments of the nearly building due to rock blasting for road construction at the 623 Common Block near the rear side of the Gamchun Habor. The gelogy of the study area is composed of andesite, which belongs to the Kyungsang System of the Cretaceous Period. For 3 months of blasting events, the vibration velocity data were measured at the site just in front of the K freezing factory. The data were divided into 4 groups according to the period of blasting(i.e, DATA 1, DATA 2, DATA 3 and DATA 4), for deriving K and n values. As a result, DATA 1 shows that K and n were 83.3756 and -0.848, respectively, and then K and n were progressively increased in absolute values for the follow-up groups and the last DATA 4 shows K and n were 2980.4898 and -1.502, respectively. Such differences in K and n values may be due to partly : 1) variations geological characteristics, from the upper rather weathered, fisssuring soft rocks at the earlier stage less weathered and fissuring hard rocks at the later stage of blasting events, and 2) the geometry between the blasting and detecting points.Among the total count of 225 blasting events, the number exceeding the safety limits of 0.5cm/sec was 20(8.9% of the total), the maximum displacement detected at the crack gage was 0.25mm, the level of which is far less to cause the occurrence and development of any cracks to the K factory. Therefore, it was confirmed that there were no damages such as structural failure or safety problem to the building.

• Journal of Korea Water Resources Association
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• v.31 no.1
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• pp.85-93
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• 1998

This study is to analyze and predict the contaminant transport based on the hydrauli characteristics using 2-dimensional finite element model. The dynamic wate quality model. RMA-4. is used to predict the contaminant transport using the hydrulic characteristics obtained from RMA-2v model. The study region is from downstream of Cham-sil weir to upstream of Shin-Kok weir. From the results of contaminant transport analysis. it is shown that the variations of discharge and velocity give quite large effect to the transport and dispersion of contaminant material. and that the water qualities of Joong-Rang and Tan streams play an important role to the downstream also. when the incidental contaminant accident occurs and contaminant material moves to the downstream. it is resulted the decreasing of the maximum COD and the increasing of the duration time to be affected by contaminant. Finally. 2-dimensional analysis is required in the case of large river like Han River. since the large difference of contaminant concentration has been investigated in the left and right bank.