• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 추계학술대회 논문집
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• pp.173-176
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• 2007

The characteristics of the tool system give many effects into the costs and qualities for the finished components. This study proposes a new method for manufacturing of high manufacturing productivity, production process reduction and low cost through back pressure forming. The Lock-up hub is manufactured through many processes, such as upsetting($1^{st}$ Forming), piercing, direct extrusion($2^{nd}$ Forming), final sizing process($3^{rd}$ Forming). In this study, process design for closed-die forging of a Lock-up hub used for a component of automobile transmission was made using three-dimensional finite element simulations, and the strain distributions and velocity distributions are investigated through the post processor. The rigid-plastic finite-element method for back pressure forging has been used in order to reduce development time and die cost. Using the FEM simulation, we found the optimum value of back pressure. The prototypes of Lock-up hub parts were forged into the net-shape. In the experiment, lead precision of tooth are measured by the CCMM(Contact Coordinate Measuring Machine). The dimensional accuracy of forged part was improved up to the 40% when back press was applied.

• 대한기계학회논문집A
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• 제30권10호
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• pp.1209-1218
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• 2006

Precision servomechanisms are widely used in machine tool, semiconductor and flat panel display industries. It is important to improve contouring accuracy in high-precision servomechanisms. In order to improve the contouring accuracy, cross-coupled control systems have been proposed. However, it is very difficult to select the controller parameters because cross-coupled control systems are multivariable, nonlinear and time-varying systems. In this paper, in order to improve contouring accuracy of a biaxial servomechanism, a cross-coupled controller is adopted and an optimal tuning procedure based on an integrated design concept is proposed. Strict mathematical modeling and identification process of a servomechanism are performed. An optimal tuning problem is formulated as a nonlinear constrained optimization problem including the relevant controller parameters of the servomechanism. The objective of the optimal tuning procedure is to minimize both the contour error and the settling time while satisfying constraints such as the relative stability and maximum overshoot conditions, etc. The effectiveness of the proposed optimal tuning procedure is verified through experiments.

• International Journal of Precision Engineering and Manufacturing
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• 제6권4호
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• pp.8-13
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• 2005

Interoperability has been the problem of CAD/CAM systems. Starting from 1980's, national and international organizations have addressed the issue through development and release of standards for the exchange of geometric and nongeometric design data. To CAD/CAM vendors, the task of interpreting and implementing these standards falls into their products. This task is a balancing action between users' needs, available development resources, and the technical specifications of standards. This paper explores an area of CAD/CAM systems development, particularly the implementation of the effective exchange files translators'. A new approach is introduced, which proposes to enclose all the translation operations concerning each exchange format to a separate DLL, thus making a 'plug-in.' Then, this plug-in could be used together with the CAD/CAM system or with specialized translation software. This approach allows to create new translators rapidly and to gain the reliable, high-efficiency, and reusable program code. The second part of the paper concerns the possible problems of translators' development. These difficulties often come from the exchange standards' misunderstanding or ambiguity in standards. All examples come from the authors' practice experiences of dealing with CAD/CAM systems.

• Design & Manufacturing
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• 제1권1호
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• pp.51-56
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• 2007

As various manufacturing technology of optical glass is developed, the aspheric lenses are supplied to many fields. Electronic or measuring instruments equipped with aspheric lens have recently been used since aspheric lens is more effective than spheric one. However, it is still difficult manufacture glass lens because of high cost and the short life of core. The demands of the aspheric glass lenses increase since it is difficult to obtain the desirable performance in the plastic lens. For the mass production of aspheric lens, specific molds with precisely machined cores should be prepared. In order to obtain competitiveness in the field of industrial manufacturing, a reduction in the development period for the batch machining of products is required. It is essential to analyze the stress distribution and deformations of machining system which is used for manufacturing the aspheric lens using FEM software ANSYS. Finite element simulations have been performed in order to study the influence of machining system which is developed in this study on structures. It is very important to understand the structural behavior of machining system. This paper investigated the static analysis and dynamic analysis of machining system for aspheric lens to predict the damage due to loading.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 춘계학술대회논문집 - 한국공작기계학회
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• pp.411-416
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• 2000

Cutting process has been automated by progress of CNC and CAD/CAM, but polishing process has been depended on only experiential knowledge of expert. To automate the polishing process, a polishing robot with w degrees of freedom which is attached to a machining center with 3 degrees of freedom has been developed. This automatic polishing robot is able to keep the polishing tool normal on the curved surface of die to improve a performance of polishing. Polishing task for a curved surface die demands repetitive operation and high precision, but conventional control algorithm can not cope with the problem of disturbance such as a change of load. In this research, a new sliding mode control algorithm is applied to the robot. The signal compression method is used to identify polishing robot system. to obtain an effect of 5 degrees of freedom motion, a synchronization between the machining center and polishing robot is accomplished by using M code of machining center. And also a trajectory for polishing the curved surface die by 5 degrees of freedom motion, a synchronization between the machining center and polishing robot is accomplished by using M code of machining center. And also a trajectory for polishing the curved surface die by 5 axes machining center is divided into data of two types for 3 axes machining center and 2 axes polishing robot. To evaluate polishing performance of the robot. various experiments are carried out.

• 한국컴퓨터정보학회논문지
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• 제29권5호
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• pp.11-20
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• 2024

최근 IT 기술의 발전과 더불어 금융 시장에서의 불확실성이 증대되는 상황에서 기업 신용등급 평가의 중요성을 인식하고, 이를 개선하기 위한 새로운 접근 방식으로 딥러닝 모델인 TabNet을 제안한다. 이에 본 연구에서는 TabNet을 활용하여 기업 신용등급을 예측하고, 이의 예측 성능을 기존 머신러닝 방법론과 상세하게 비교한다. 한국의 주요 증권시장에 상장된 기업들의 재무 데이터를 기반으로 TabNet 알고리즘을 적용하여 신용등급 예측 모델을 구축하고, 다양한 머신러닝 모델과의 성능을 비교 분석하였다. 실험 결과, TabNet 모델은 Precision 0.884, F1이 0.895로 기존의 머신러닝 모델들보다 우수한 성능을 보였으며, 고위험 기업을 저위험 기업으로 잘못 분류하는 경우가 다른 머신러닝 모델보다 적어 TabNet의 우수성을 확인하였다. 이는 TabNet이 기업 신용등급 예측에 있어 효과적인 도구로 활용될 수 있으며, 금융기관의 신용 위험 관리 및 의사 결정 과정을 지원할 수 있을 것으로 기대한다.

• 센서학회지
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• 제33권2호
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• pp.112-116
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• 2024

Gas-sensor technology for volatile organic compounds (VOC) biomarker detection offers significant advantages for noninvasive diagnostics, including rapid response time and low operational costs, exhibiting promising potential for disease diagnosis. Colorimetric gas sensors, which enable intuitive analysis of gas concentrations through changes in color, present additional benefits for the development of personal diagnostic kits. However, the traditional method of visually monitoring these sensors can limit quantitative analysis and consistency in detection threshold evaluation, potentially affecting diagnostic accuracy. To address this, we developed a machine vision platform based on metal-organic framework (MOF) for colorimetric gas sensor arrays, designed to accurately detect disease-related VOC biomarkers. This platform integrates a CMOS camera module, gas chamber, and colorimetric MOF sensor jig to quantitatively assess color changes. A specialized machine vision algorithm accurately identifies the color-change Region of Interest (ROI) from the captured images and monitors the color trends. Performance evaluation was conducted through experiments using a platform with four types of low-concentration standard gases. A limit-of-detection (LoD) at 100 ppb level was observed. This approach significantly enhances the potential for non-invasive and accurate disease diagnosis by detecting low-concentration VOC biomarkers and offers a novel diagnostic tool.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 춘계학술대회논문집 - 한국공작기계학회
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• pp.459-464
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• 2000

In this paper, it verifies the relationships between wheel velocity and surface roughness with the mirror surface grinding using electrolytic in-process dressing (ELID). In the general, as wheel velocity is high, surface roughness is better on the base of grinding theory. However, the relationships between wheel velocity and surface roughness is undefined due to the effect of electro-chemical dressing and the characteristics of materials. According to above relationships, ELID grinding experiment is carried out by following the change of wheel velocity. As the result of this study, it is found that surface roughness is not better as linearly as the increase of wheel velocity, but the limit of wheel velocity exists according to the characteristics of materials. Also, in contradiction to the present trend of high wheel velocity of manufacturing system for high surface integrity, it is able to expected to the base on the development of new ultra precision grinding method with the practicality of mirror surface grinding using ELID grinding method.

• 한국공작기계학회논문집
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• 제18권2호
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• pp.130-136
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• 2009

Semi-solid casting(SSC) of magnesium alloys is increasingly being used to produce high quality components. This process is similar to the injection molding of plastics and is called thixomolding. Using this process, higher strength, thinner wall sections and tighter tolerances without porosity are obtained. The high strength and low weight characteristics of magnesium alloys render the high-precision fabrication of thin-walled components with large surface areas. They are widely used for the IT, auto and consumer electronics industries. However, warpage of the thin-walled sections degrade quality of the parts produced in the SCC process. To produce thin-walled magnesium alloy parts, the geometry of gating system on the quality of the finished products should be clearly studied. In this paper, to minimize warpage of the thin-walled sections, Taguchi method is applied to the optimal design of the gate geometry in the thixomolding process. Width, height, length and angle of the gating system are selected for the robust design parameters. Effectiveness of the robust design is verified through the CAE software.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2005년도 춘계학술대회 논문집
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• pp.441-445
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• 2005

In the resent years, as the research and the development of micro and precision machinery become active, the interest of micro actuators using SMA(Shape Memory Alloy) has been increased. But, no detailed researches between the thermo-dynamic property in Nitinol alloy have been done yet. In this study, the thermal property of high temperature Nitinol shape memory alloy were evaluated using differential scanning calorimeter(DSC). The structure property was investigated using X-ray diffraction(XRD). A dynamic mechanical analyzer(DMA) with three point bending mode was used to study storage and loss modulus of shape memory alloy according to the thirteen frequencies in the temperature range between 30 and $200^{\circ}C$. The effects of the temperature heating/cooling rate, the frequency on the damping capacity have been systematically investigated. Such a frequency and temperature changes also influenced significantly to the damping behavior of the shape memory alloy. It was also found that Nitinol exhibited high damping capacity during phase transformation.