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Mechanical Property of Hierarchically Porous PDMS according to Mixing Conditions
S. Lee(이상민),J. Lim(임종경),T. Yoon(윤태운),J. H. Bae(배재현) Korean Society for Precision Engineering 2021 한국정밀공학회 학술발표대회 논문집 Vol.2021 No.11월
A PDMS (Polydimethylsiloxane) material has been widely used in a lab-on-a-chip, an optical device, a wearable device, etc., because of chemical resistance, flexibility, high biocompatibility, and good optical transparency. When such a PDMS material is manufactured in a porous form, it can have a low density and a large surface area to volume ratio, so many studies are being actively conducted to apply it to an oil absorbent, a flexible pressure sensor with high sensitivity, and a scaffold in bio and tissue engineering field. In this study, a hierarchically porous PDMS using a sieved commercial salt (Sodium Chloride) was fabricated, and changes in mechanical properties of porous PDMS according to the size of salt particle (Adjusted according to Sieve Size) were analyzed. A test sample in the form of a cylinder was prepared according to the size of salt particle, the compressive modulus was measured, and the change of the elastic modulus was comparatively analyzed.
노연우(Yeonwoo Noh),지정환(Jeonghwan Chi),배재현(Jaehyun Bae),오정소(Jeongso Oh),주종화(Jong Wha J. Joo) 한국정보기술학회 2020 Proceedings of KIIT Conference Vol.2020 No.10
본 논문에서는 한국 인구의 고령화에 따라 노인의 낙상에 대비할 수 있는 스마트폰 낙상감지 애플리케이션을 제안한다. 스마트폰에 내장된 3축 가속도 센서와 자이로스코프 센서를 통해 수집된 데이터를 가공해 낙상감지 알고리즘에 적용하여, 스마트폰을 소지 중인 사용자의 낙상사고에 대비한다. 낙상사고 발생 시 등록된 보호자 연락처와 응급시설에 연락을 취하게 하여 신속한 대처를 통해 피해를 최소화하고, 사용자의 느낄 낙상사고에 대한 부담감을 감소시킨다. 추후에 다양한 센서를 추가하여 알고리즘의 낙상감지확률을 높이고 스마트폰 이외의 디바이스에 적용하여 낙상감지시스템이 확장될 기반이 될 것으로 기대한다. Our thesis represents the propose of smartphone fall detection application that can prevent and prepare for the falls of the elderly as it is aging era in Korea. The data collected through the 3-axis accleration sensor and the gyroscope sensor that are in the smartphone are processed and applied to the fall detection algorithm, which prepare for a fall accident of a user with a smartphone. Registered guardians contact information and emergency facilities are called when a fall accident occurs, therefore we could minimize harm and concern of falling from the user by taking rapid response. We are planning to add various sensors to increase the fall detection probability of the algorithm and expecting of fall detection system expanded by applying it to devices other than smartphones.
압축성 기저 유동에 대한 GEKO 모델 계수의 불확실성 정량화 연구
정영기(Y.K. Jung),장경식(K. Chang),배재현(J.H. Bae) 한국전산유체공학회 2021 한국전산유체공학회지 Vol.26 No.1
The present work, supersonic flow over an axisymmetric base is simulated using Generalized k-ω (GEKO) model which is proposed by Menter. GEKO two-equation model based on the k-ω formulation provides free model coefficients which can be adjusted by user depending on the specified flow type. Uncertainty Quantification analysis (UQ) is adopted to quantify the uncertainty of the model coefficients and to calibrate the coefficients for the flow. Latin Hypercube Sampling (LHS) method is used for sampling input parameters which are independent as a uniform distribution. Surrogate model is constructed by using ordinary least-squares (OLS). In order to characterize the posterior via Markov Chain Monte Carlo sampling, Affine Invariant Ensemble Algorithm (AIES) is selected. Through Forward problem, the most effective coefficient among the coefficients of GEKO model is figured out (Sensitivity analysis). Calibrated model coefficients are obtained through Bayesian inference. The results obtained using the calibrated coefficients by UQ to the base flow shows better agreement with available experimental measurements than the results obtained using default model coefficients.