• Korean Journal of Optics and Photonics
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• v.19 no.6
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• pp.422-428
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• 2008

The pitch tool provides superior surface roughness compared to other types of polishing tool. However, because of difficulty in handling the pitch tool, pitch tool polishing has rarely been analysed, which led many craftsman to eliminate the pitch tool from their experiences. We found that it was possible to use a pitch tool in the well-determined material removal after the completion of computer simulation and experiment. We could simulate the TIF of the pitch tool with 79% accuracy. Also, after five successive simulations of polishing process on a 280 mm optical flat, the surface p-v error was found to be reduced from $1{\mu}m$ to 168 nm.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.3
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• pp.167-172
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• 2016

The computer controlled optical surfacing (CCOS) technique provides superior fabrication performance for optical mirrors when compared to the conventional method, which relies heavily on the skill of the optician. The CCOS technique provides improvements in terms of mass production, low cost, and short polishing time, and are achieved by estimating and controlling the moving speed of the tool and toolpath through a numerical analysis of the tool influence function (TIF). Hence, the exact estimation of various TIFs is critical for high convergence rates and high form accuracy in the CCOS process. In this paper, we suggest a new model for TIFs, which can be applied for various tool shapes, different velocity distributions, and non-uniform tool pressure distributions. Our proposed TIFs were also verified by comparisons with experimental results. We anticipate that these new TIFs will have a major role in improving the form accuracy and shortening the polishing time by increasing the accuracy of the material removal rate.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.4 no.2
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• pp.46-53
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• 1995

In this study, Wear of a ceramic cutting tool for hardened STD11 steel was investigated. Under the finish machining condition. DOC notch wear of a ceramic cutting tool was mostly occurred earlier than flank and crater wear were proceeded. The relations of DOC notch wear, which was characteristically produced at the beginning of cutting. to cutting speed, feed, depth of cut, and nose radius of a ceramic cutting tool were examined. Effective approach angle, which is a function of cutting conditions, and boundary area were suggested, and then the influence of those was investigated, The following conclusions were obtained: (1)as cutting speed was increasing. DOC notch wear was decreasing (2) the cutting condition that magnitude of slendermess ratio was made small, was favorable for DOC notch wear, (3) as depth of cut was smaller, the influence of feed on DOC notch wear was also smaller, (4) DOC notch wear was mainly influenced by effective approach angle, but by boundary area in the range of low feed.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.1 s.94
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• pp.174-181
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• 1999

In this paper the technique to predict tool wear theoretically in shearing process is suggested. The tool wear in the process affects the tolerances of final pans, metal flows and costs of processes. In order to predict the tool wear the deformation of workpiece during the process is analyzed by using non-isothermal finite element program. The ductile fracture criterion and the element kill method are also used to estimate if and where a fracture will occur and to investigate the features of the sheared surface in shearing process. Results obtained from finite element simulation, such as nodal velocities and nodal forces, are transformed into sliding velocity and normal pressure on tool monitoring points respectively. The monitoring points are automatically generated and the wear rates on these points are accumulated during the process. It is assumed that the wear depth on the tool surface is linear function of the lot sizes based upon the known experimental results. The influence of clearance between die and punch upon tool wear is also discussed.

• Smart Structures and Systems
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• v.16 no.3
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• pp.401-414
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• 2015

A developed hybrid method for crack identification of beams is presented. Based on the Euler-Bernouli beam theory and concepts of fracture mechanics, governing equation of the cracked beams is reformulated. Finite element (FE) method as a powerful numerical tool is used to discritize the equation in space domain. After transferring the equations from time domain to frequency domain, frequencies and mode shapes of the beam are obtained. Efficiency of the governed equation for free vibration analysis of the beams is shown by comparing the results with those available in literature and via ANSYS software. The used equation yields to move the influence of cracks from the stiffness matrix to the mass matrix. For crack identification measured data are produced by applying random error to the calculated frequencies and mode shapes. An objective function is prepared as root mean square error between measured and calculated data. To minimize the function, hybrid genetic algorithms (GAs) and particle swarm optimization (PSO) technique is introduced. Efficiency, Robustness, applicability and usefulness of the mixed optimization numerical tool in conjunction with the finite element method for identification of cracks locations and depths are shown via solving different examples.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.805-810
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• 1997

In this paper the technique to predict tool were theoretically in the sheet metal shearing process is suggested. The were in sheet metal tool affects the tolerances of final parts, metal flows and costs of processes. In order to predict the tool were the deformation of workpiece during the process is analyzed by using non-isothermal finite element program. The ductile fracture criterion and the element kill method are also used to estimate if and where a fracture will occur and to investigate the features of the sheared surface in shearing process. Results obtained form finite element simulation such as node velocities and node forces are transformed into sliding velocity and normal pressure on tool monitoring points respectively. The monitoring points are automatically generated and the were rates on these points are accumulated during a process. It is assumed that the wear depth on the tool surface are linear function of the lot sizes based upon the known experimental results. The influence of clearance between die and punch upon tool wear is were is also discussed during the process.

• Journal of Environmental Health Sciences
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• v.47 no.2
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• pp.175-181
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• 2021

Objectives: The correlation between the size of a leak hole, the volume of the leakage, and the range of influence was investigated for a hydrochloric acid tank-lorry. Methods: For the case of a tank-lorry chemical accident, KORA (Korea Off-site Risk Assessment Supporting Tool) was used to predict the leak rate and the range of influence according to the size of the leak hole. The correlation was studied using R. Results: As a result of analyzing the leak rate change according to the leak hole size in a 35% hydrochloric acid tank-lorry, as the size of the leak hole increased from 1 to 100 mm, the leak rate increased from 0.008 to 83.94 kg/sec, following the power function. As a result of calculating the range of influence under conditions ranging from 1 to 100 mm in size and 10 to 60 minutes of leakage time, it was found that the range spanned from a minimum of 5.4 m to a maximum of 307.9 m. As a result of multiple regression analysis using R, the quadratic function model best explained the correlation between the size of the leak hole, the leak time, and the range of influence with an adjected coefficient of determination of 0.97 and a root mean square error of 22.33. Conclusion: If a correlation database for the size of a leak hole is accumulated for various substances and under various conditions, the amount of leakage and the range of influence can easily be calculated, facilitating field response activities.

• Journal of Korean Physical Therapy Science
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• v.29 no.4
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• pp.1-16
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• 2022

Background: This study was conducted to examine the correlation of VDT, posture and shoulder function among each group divided by according to the neck pain disorder index (NDI) scores for female patients with neck pain. Design: Cross-sectional study. Methods: Fifty adult women with neck pain voluntarily participated in this study and the neck pain disorder index questionnaire, VDT syndrome assessment tool questionnaire, craniovertebral angle, thoracic kyphosis angle, round shoulder posture, pectoralis minor length, shoulder joint hypermobility, and serratus anterior strength tests were conducted respectively. Subjects were divided into two groups where 21 subjects were allocated to the mild pain group whom have rated below 14 points on the NDI scores, and 29 subjects were in the severe pain group, whom have rated above 15 on the NDI score. Results: The study found that in the mean difference between variables in each group, VDT syndrome showed a higher mean score in the severe pain group than the mild pain group (p<0.05). In the group correlation and regression analysis, the mild pain group showed a significant negative correlation between the craniovertebral angle and round shoulder posture (r=-0.467, p<0.05), and the round shoulder posture for craniovertebral angle was shown to have significant positive influence (B=10.162, p<0.05). The severe pain group showed that the NDI and the VDT syndrome had a significant amount of correlation (r=0.520, p<0.01), the VDT syndrome showed significant positive influence (B=0.330, p<0.05), and the craniovertebral angle showed significant negative influence (B=-0.809, p<0.05). It was also shown that shoulder joint hypermobility had a significant negative correlation with the serratus anterior strength (r=-0.437, p<0.01), and that serratus anterior strength had a significant negative influence on shoulder joint hypermobility (B=-4.175, p<0.05). Conclusion: This study is of clinical significance in that it presented variables that should be considered depending on the degree of neck pain in treating patients with neck pain and that it presented patients with not only posture but also the function of the shoulder joint as factors to consider.

• Structural Engineering and Mechanics
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• v.21 no.3
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• pp.315-332
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• 2005

The Element-free Galerkin Method has become a very popular tool for the simulation of mechanical problems with moving boundaries. The internally applied Moving Least Squares interpolation uses in general Gaussian or cubic weighting functions and has compact support. Due to the approximative character of this interpolation the obtained shape functions do not fulfill the interpolation conditions, which causes additional numerical effort for the application of the boundary conditions. In this paper a new weighting function is presented, which was designed for meshless shape functions to fulfill these essential conditions with very high accuracy without any additional effort. Furthermore this interpolation gives much more stable results for varying size of the influence radius and for strongly distorted nodal arrangements than existing weighting function types.

• Smart Structures and Systems
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• v.6 no.2
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• pp.167-182
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• 2010

An adaptronic strut for machine tools with parallel kinematics for compensation of the influence of geometric errors is introduced. Implemented within the strut is a piezoelectric sensor-actuator unit separated in function. In the first part of this contribution, the functional principle of the strut is presented. For use of one piezoelectric transducer as both, sensor and actuator as so-called self-sensing actuator, the acquisition of the sensing signal while actuating simultaneously using electrical bridge circuits as well as filter properties are examined. In the second part the control concept developed for the adaptronic strut is presented. A co-simulation model of the strut for simulating the controlled multi-body behavior of the strut is set-up. The control design for the strut as a stand-alone system is tested under various external loads. Finally, the strut is implemented into a model of the complete machine tool and the influence of the controlled strut onto the behavior of the machine tool is examined.