• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.9
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• pp.1071-1076
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• 2011

NC machines are generally used for machining operations because of their position accuracy, path accuracy, and machining reaction force. However, some NC machines require a very large space and are expensive. Recently, industrial articulated robot arms with large handling capability and wrist torque have been developed and the corresponding sensor technology has been improved. A machining robot for three-dimensional large curved objects was developed on the basis of an automatic-path-generation method. A self-position-compensation method with a laser displacement sensor was adopted for the six-axis robot developed, because the large articulated robot arms had poor position accuracy. An automatic-path-generation method using specific points was adopted to reduce the number of teaching points and time. In order to determine the proper machining conditions, various machining conditions such as tool rotation speed, cutting angle, cutting depth, and tool moving speed, were evaluated.

• Journal of the Korean Society of Radiology
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• v.4 no.1
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• pp.19-24
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• 2010

A cone-beam computed tomography (CT) system for a small animal has been widely used in the bio-medical application. This paper introduced simple methods for evaluating a cone-beam CT system using a simple tungsten wire phantom of 10{$\mu}m$ diameter and a water phantom. Slice images and three-dimensional tomography images were obtained through 360 projection views per one sample rotation under stable X-ray tube conditions for a long running time. The cone-beam CT system at a position of a 1.07 magnification showed a spatial frequency of 13.78 lp/mm ($36.2{\mu}m$ spatial resolution) and gave a CNR of 10.33 and a S/N of 5.87 under a tube voltage of 80kV.

• Journal of The Korean Society of Integrative Medicine
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• v.2 no.1
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• pp.63-76
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• 2014

Purpose : The purpose of this study was to ascertain the effects of scapular stabilization exercise before rotator cuff surgery on pain and range of motion of middle-aged women. Method : 20 subjects who agreed on this experiment and were diagnosed with rotator cuff rupture participated in this study. Experimental groups were treated while 40 minutes a day, 5 times per week, for 2 weeks before surgery. The effects of scapular stabilization exercise were evaluated on VAS and range of motion. Collected data were analyzed with SPSS for windows ver. 20.0 program. One-way repeated ANOVA was used to examine a significance of each variable by time. Two-way repeated ANOVA was applied to examine a significance of the experimental group against the control group. In all statistical tests, the significance level was set by ${\alpha}=.05$. Result : The results of this study are as follows: 1) In both control and experimental groups, VASs were decreased significantly according to intervention period. There was no significant difference between VASs of two groups. 2) In both control and experimental groups, ROMs of shoulder, flexion, abduction and external rotation were increased significantly according to intervention period. In these three flexibility measurement variables, there were significant differences between ROMs of two groups. Conclusion : In view of all the results in this study, scapular stabilization exercise on before rotator cuff surgery proved to be effective in improving their pain, range of motion after surgery. It will be sufficient data to perform with their own exercise program.

• Geomechanics and Engineering
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• v.22 no.5
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• pp.449-460
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• 2020

The double-lane arrangement model is frequently used in underground coal mines because it is beneficial to improve the mining efficiency of the working face. When the double-lane arrangement is used, the service time of the reserved roadway increases by twice, which causes several difficulties for the maintenance of the roadway. Given the severe non-uniform deformation of the reserved roadway in the Buertai Coal Mine, the stress distribution law in the mining area, the failure characteristics of roadway and the control effect of support resistance (SR) were systematically studied through on-site monitoring, FLAC 3D numerical simulation, mechanical model analysis. The research shows that the deformation and failure of the reserved roadway mainly manifested as asymmetrical roof sag and floor heave in the region behind the working face, and the roof dripping phenomenon occurred in the severe roof sag area. After the coal is mined out, the stress adjustment around goaf will happen to some extent. For example, the magnitude, direction, and confining pressure ratio of the principal stress at different positions will change. Under the influence of high-stress rotation, the plastic zone of the weak surrounding rock is expanded asymmetrically, which finally leads to the asymmetric failure of roadway. The existing roadway support has a limited effect on the control of the stress field and plastic zone, i.e., the anchor cable reinforcement cannot fully control the roadway deformation under given conditions. Based on obtained results, using roadway grouting and advanced hydraulic support during the secondary mining of the panel 22205 is proposed to ensure roadway safety. This study provides a reference for the stability control of roadway with similar geological conditions.

• Journal of agriculture & life science
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• v.46 no.4
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• pp.101-111
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• 2012

Soybean cyst nematode(SCN) (Heterodera glycines Ichinohe) causes the greatest yield loss to soybean compared to any other pest worldwide. Yield loss due to SCN is estimated 7.6 million megagrams in the USA and nearly 9 million worldwide. SCN causes yield reductions by feeding on plant nutrients, retarding root growth, and inhibiting Bradyrhizpbium japonicum(Kirchner) Buchanan nodulation. The primary methods for controlling SCN include planting resistant cultivars and rotation with nonhost crops. Genetically diverse field populations of SCN combined with the limited germplasm base of commercial soybean for resistance could potentially leads to population shifts over time, and this makes controlling H. glycines more difficult. This paper reviewed the importance of soybean, soybean cyst nematode, researches on resistance to SCN, and prospects. Tremendous effort must still be endeavored for elucidating resistance mechanisms and managing H. glycines in the soybean field.

• Steel and Composite Structures
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• v.9 no.4
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• pp.381-395
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• 2009

This paper presents the details of an advanced Finite Element (FE) analysis of a plane steel portal frame with semi-rigid beam-to-column connections subjected cyclic loading. In spite of several component models on cyclic behaviour of connections presented in the literature, works on numerical investigations on cyclic behaviour of full scale frames are rather scarce. This paper presents the evolution of an FE model which deals comprehensively with the issues related to cyclic behaviour of full scale steel frames using ABAQUS software. In the material modeling, combined kinematic/isotropic hardening model and isotropic hardening model along with Von Mises criteria are used. Connection non-linearity is also considered in the analysis. The bolt slip which happens in friction grip connection is modeled. The bolt load variation during loading, which is a pivotal issue in reality, has been taken care in the present model. This aspect, according to the knowledge of the authors, has been first time reported in the literature. The numerically predicted results using the methodology evolved in the present study, for the cyclic behaviour of a cantilever beam and a rigid frame, are validated with experimental results available in the literature. The moment-rotation and deflection responses of the evolved model, match well with experimental results. This proves that the methodology for evolving the steel frame and connection model presented in this paper is closer to real frame behaviour as evident from the good comparison and hence paves the way for further parametric studies on cyclic behaviour of flexibly connected frames.

• Journal of Ocean Engineering and Technology
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• v.35 no.5
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• pp.347-359
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• 2021

This study aims to evaluate the dynamic responses of the jacket-type offshore wind turbine using FAST software (Fatigue, Aerodynamics, Structures, and Turbulence). A systematic series of simulation cases of a 5 MW jacket-type offshore wind turbine, including wind-only, wave-only, wind & wave load cases are conducted. The dynamic responses of the wind turbine structure are obtained, including the structure displacement, rotor speed, thrust force, nacelle acceleration, bending moment at the tower bottom, and shear force on the jacket leg. The calculated time-domain results are transformed to frequency domain results using FFT and the environmental load with more impact on each dynamic response is identified. It is confirmed that the dynamic displacements of the wind turbine are dominant in the wave frequency under the incident wave alone condition, and the rotor thrust, nacelle acceleration, and bending moment at the bottom of the tower exhibit high responses in the natural frequency band of the wind turbine. In the wind only condition, all responses except the vertical displacement of the wind turbine are dominant at three times the rotor rotation frequency (considering the number of blades) generated by the wind. In a combined external force with wind and waves, it was observed that the horizontal displacement is dominant by the wind load. Additionally, the bending moment on the tower base is highly affected by the wind. The shear force of the jacket leg is basically influenced by the wave loads, but it can be affected by both the wind and wave loads especially under the turbulent wind and irregular wave conditions.

• Korean Journal of Organic Agriculture
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• v.29 no.1
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• pp.51-73
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• 2021

This study is intended to derive the key issues on vitalization of the governance of rural area development for 6 cities and counties in Chungcheongnam-do where privately entrusted intermediary support organizations have been established and to present their improvement plans of policy. The findings of the study have shown the governance for the case regions is still being characterized with a very formal governance being dominated by the strong administrative initiative and expediency. What have been presented as the improvement plans of policy are as follows: First, core provisions of the ordinances must be strengthened to mandatory regulations, and some ways to check and supplement such as monitoring, policy forums by public-private partnership, etc. are required for the sake of the effective operation of the ordinances. Second, in relation to the bases of competence according to the roles of core governance players, it is necessary to overcome the limitations of job rotation system, align the administrative support systems, expand the functions of a policy committee based on public-private cooperation and operate it effectively in the case of administration, and to strengthen a footing of a civilian community and the perspectives of political incubation in administration and provide support projects contributing to the growth of the corporations in the case of the entrusted corporation, and to align the operating systems of the centers, review the introduction of a system with a full-time center head, continuously provide specialized education and improve the working environment in the case of the support centers.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.15 no.1
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• pp.62-70
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• 2019

The APR1400 reactor may be operated for a long time under high temperature and pressure conditions, causing damage to the stud holes and causing stud bolts and holes to stick. The present practice is to manually remove the anti-sticking agent and foreign matter remaining in the APR1400 reactor stud hole and to visually check the surface condition of the thread to check the damage status of the threads. In the case of the APR1400 reactor stud holes, manually cleaning the threads increases the risk of radiation exposure and operator's fatigue. To avoid this, the autonomous mobile robot is used to automatically clean the reactor stud holes. The purpose of this study is to optimize the cleaning performance of the mobile robot by looking at the behavior of the surface roughness of the stud surface cleaned by the brush attached to the mobile robot due to changes in brush material, thickness of wire, and rotation speed. A microscopic approach to the surface roughness of the flank is needed to investigate the effects of the newly proposed brush of the autonomous mobile robot on the thread holes. According to this experiment, it is reasonable to use STS brush rather than Carbon one. Optimal operating conditions are derived and the safety of APR1400 reactor stud holes maintenance can be improved.

• Journal of The Korean Astronomical Society
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• v.51 no.6
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• pp.207-214
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• 2018

A coelostat is often used for solar observations, because it corrects the image rotation automatically by guiding sunlight into a fixed telescope with two plane mirrors. For the purposes of education and spectroscopic observation, the solar group at Seoul National University (SNU) plans to develop the SNU coelostat (SNUC) and install it in the SNU Astronomical Observatory (SAO). Requirements of the SNUC are < 1" positioning accuracy with 30 cm beam size on the entrance pupil in the compact dome. To allow for installation in the small dome, we design a compact slope type coelostat with a 45 cm primary plane mirror and a 39 cm secondary plane mirror. The motion of the SNUC is minimized by fixing the position of the slope frame. Numerical simulations of the available observational time of the designed coelostat shows that the sun can be observed ay all times from June to early August and at least three hours in other months. Since the high accuracy driving motors installed in the SNUC can be affected by external environment factors such as humidity and temperature variations, we design a prototype to test the significance of these effects. The prototype consists of a 20 cm primary plane mirror, a 1 m slope rail, a direct drive motor, a ballscrew, a linear motion guide, an AC servo motor, a reduction gear and a linear encoder. We plan to control and test the accuracy of the prototype with varying atmospheric conditions in early 2019. After testing the prototype, the SNUC will be manufactured and installed in SAO by 2020.