• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.7
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• pp.21-27
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• 2022

This study was conducted to evaluate the structural stability of a CNC automatic lathe structure and avoid resonance. The analysis conditions were analyzed by applying the weight of the upper assembly. From the structural analysis, the stress and deformation were low, and the safety factor was high. From the dynamic characteristic analysis, it was determined that resonance does not occur because the natural frequency is outside the driving range. The error between the dynamic characteristic analysis and vibration test results is very low; thus, the reliability of the analysis results can be secured.

• Journal of the Korean Society of Physical Medicine
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• v.7 no.4
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• pp.501-507
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• 2012

PURPOSE: This study aims to examine the effects of trunk flexion on the kinetic characteristics of the lumbar according to the degree of hamstring flexibility. METHODS: This study has as its subjects 29 young adults and divides them into the group (NSRTG, n=15) with the normal length of hamstrings according to SRT and the group (SSRTG, n=14) tending to have shortened hamstrings. Sit and Reach Test was conducted to evaluate the degree of hamstring flexibility. And to examine the kinetic difference of the lumbar at the trunk flexion, it was compared and analyzed by using the picture archiving and communication system (PACS). RESULTS: SSRTG showed more significant difference than NSRTG in the analysis on the trunk flexion of NSRTG and SSRTG. CONCLUSION: According to the analysis, the shortening of hamstrings is the factor that affects the dynamic stability of the lower lumbar through the reduction of the pelvic anterior tilt at the trunk flexion.

• Korean Journal of Materials Research
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• v.29 no.6
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• pp.343-348
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• 2019

Structural and mechanical effects of the dynamical precipitation in two copper-base alloys have been investigated over a wide range of deformation temperatures. Basing upon the information gained during the experiment, also some general conclusion may be formulated. A one concerns the nature of dynamic precipitation(DP). Under this term it is commonly understood decomposition of a supersaturated solid solution during plastic straining. The process may, however, proceed in two different ways. It may be a homogeneous one from the point of view of distribution and morphological aspect of particles or it may lead to substantial difference in shape, size and particles distribution. The effect is controlled by the mode of deformation. Hence it seems to be reasonable to distinguish DP during homogeneous deformation from that which takes place in heterogeneously deformed alloy. In the first case the process can be analyzed solely in terms of particle-dislocation-particle interrelation. Much more complex problem we are facing in heterogeneously deforming alloy. Deformation bands and specific arrangement of dislocations in form of pile-ups at grain boundaries generate additional driving force and additional nucleation sites for precipitation. Along with heterogeneous precipitation, there is a homogeneous precipitation in areas between bands of coarse slip which also deform but at much smaller rate. This form of decomposition is responsible for a specially high hardening rate during high temperature straining and for thermally stable product of the decomposition of alloy.