• 소성∙가공
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• 제23권3호
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• pp.164-170
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• 2014

To predict the deformation and fracture during tube expansion using the finite element (FE) method, a material model is considered that incorporates the damage evolution due to the deformation. In the current study, a Rice-Tracey model was used as the damage model with inclusion of the hydrostatic stress term. Since OFHC Cu is not significantly affected by strain rate, a Hollomon flow stress model was used. The material parameters in each model were obtained by using an optimization method. The objective function was defined as the difference between the experimental measurements and FE simulation results. The parameters were determined by minimizing the objective function. To verify the validity of the FE modeling, cross-verification was conducted through a tube expansion test. The simulation results show reasonable agreement with the experiments. The design for a minimum diameter of expansion tube using the FE modeling was verified by a simplified tube expansion test and simulation results.

• 한국융합학회논문지
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• 제9권7호
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• pp.251-257
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• 2018

타로카드는 사람들의 재미와 호기심을 주는 하나의 놀이문화로 자리 잡고 있으므로 뷰티타로카드로 재미와 뷰티에 더 깊은 관심을 가질 수 있는 계기를 마련해 주고자 한다. 이에 선행연구를 바탕으로 타로카드의 기본이 되는 유니버셜웨이트 타로카드의 핵심요소인 메이저 아르카나카드를 중심으로 카발라를 적용하여 뷰티타로카드를 해석하였다. 유니버셜타로카드의 기본상징인 불 물 공기 땅 4원소를 뷰티와 관련된 상징으로 브러쉬, 파운데이션, 눈썹칼, 섀도우로 변경하여 뷰티타로카드를 메이저 아르카나 22장에 디자인을 적용하여 뷰티타로카드 점을 상담방법으로써 활용 할 수 있는 도구를 제작하였다. 제작된 뷰티타로카드는 타로 리더나 관련 종사자가 직접 활용하여 타로카드에 흥미를 가지고 있는 사람들에게 뷰티와 관련된 상담을 유용하게 할 수 있을 것으로 사료된다. 앞으로 뷰티타로카드에 대한 연구 관심도를 높이고 흥미를 이끌어 내고 메이크업, 헤어, 피부, 네일아트 등 다양한 미용영역에 알맞은 타로카드의 제작을 기대한다.

• 센서학회지
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• 제29권1호
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• pp.33-39
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• 2020

Typically, photoacoustic images are obtained in water or gelatin because the impedance of these mediums is similar to that of the human body. However, these acoustic mediums can have an additional mass effect that changes the resonance frequency of the transducer. The acoustic radiation impedance in air is negligible because it is very small compared to that of the transducer. However, the high acoustic impedance of mediums such as the human body and water is quite large compared to that of air, making it difficult to ignore. Specifically, in a case where the equivalent mass is very small, such as with a micro-machined ultrasound transducer, the additional mass effects of the acoustic medium should be considered for an accurate resonance frequency design. In this study, a piezoelectric micro-machined ultrasonic transducer (pMUT) was designed to have a resonance frequency of 10 MHz in the acoustic medium of water, which has similar impedance as the human body. At that time, the resonance frequency of the pMUT in air was calculated at 15.2 MHz. When measuring the center displacement of the manufactured pMUT using a laser vibrometer, the resonance frequencies were measured as 14.3-15.1 MHz, which is consistent with the finite element method (FEM) simulation results. Finally, photoacoustic images of human hair samples were successfully obtained using the fabricated pMUT.