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Admittance 기반 압전체 센서 자가진단절차의 영향인자 파악 및 실험적 고찰
조혜진(HyeJin Jo),박통일(Tong-il Park),박규해(Gyuhae Park) 대한기계학회 2015 大韓機械學會論文集A Vol.39 No.1
압전소자(Piezoelectric transducer, PZT)는 구조물의 안정성 평가를 목적으로 하는 구조 건전성 모니터링 기법(Structural Health Monitoring, SHM)의 센서(sensor) 및 구동기(actuator)로 많이 활용되고 있다. 사용되는 센서 및 구동기의 성능을 사전에 파악하고, 잔존수명 및 결함을 탐지하는 센서 자가 진단법은 안정적인 SHM의 결과를 얻기 위해 매우 중요한 절차이다. 본 연구에서는 Admittance 값을 기반으로 한 센서 자가 진단절차를 통하여 압전체 센서의 결함을 탐지하였으며, 센서 진단과정에 영향을 줄 수 있는 접합층 및 온도 등의 영향인자에 대해 실험적 분석을 실시하였다. 분석 결과 Admittance와 온도 및 접착제의 상관관계를 파악할 수 있었으며, admittance를 기반으로 한 센서 자가 진단 절차를 통해 센서의 접착상태와 접착제의 성능평가가 가능함을 검증하였다. Structural health monitoring (SHM) techniques based on the use of active-sensing piezoelectric (PZT) materials have received considerable attention. The validation of the PZT functionality during SHM operation is critical to successfully implementing a reliable SHM system. In this study, we investigated several parameters that affect the admittance-based sensor diagnostic process. We experimentally identified the temperature dependency of the active-sensor diagnostic process. We found that the admittance-based sensor diagnostic process can differentiate the adhesion conditions of bonding materials that are used to install a PZT on a structure, which is important when designing a sensor diagnostic process for an SHM system.
다양한 온도조건에서 압전체 센서 자가진단법의 실험적 고찰
조혜진(HyeJin Jo),김은강(EunKang Kim),공예슬(YeSeul Kong),김지민(JiMin Kim),박제운(JeWoon Park),이경이(KyoungLee Lee),이지현(JiHyeon Lee),박규해(Gyuhae Park) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.11
An active sensor diagnostics procedure, where the sensors/actuators are confirmed to be functioning properly during operation, is a critical component to successfully complete the structural health monitoring (SHM) process. The impedance-based piezoelectric sensor diagnostics process tracks the changes in the capacitive value of piezoelectric materials, which shows up in measured admittance. A change in the capacitive value indicates changes in sensor conditions, including sensor fracture and de-bonding. The effect of temperature variations in the high temperatures and cryogenic range on the performance of the impedance-based piezoelectric sensor diagnostics, along with the sensing capability of piezoelectric active-sensors, was experimentally studied. The results of this study indicate that the impedance-based sensor diagnostic processes is capable of detecting faulty sensors even at the high temperatures and cryogenic temperatures, thereby allowing piezoelectric sensors to be effectively used for dynamics and SHM sensing at high temperature and cryogenic temperature ranges.
온도 변화에 따른 압전체 센서 자가진단법 및 접합제의 영향에 대한 실험적 고찰
조혜진(HyeJin Jo),박통일(Tong-il Park),박규해(Gyuhae Park) 한국소음진동공학회 2013 한국소음진동공학회 학술대회논문집 Vol.2013 No.10
The sensor/actuator active sensor diagnostics procedure, where the sensors/actuators are confirmed to be functioning properly during operation, is a critical component to successfully complete the structural health monitoring (SHM) process with large numbers of active sensors typically installed in a structure. The basis of this process is to track the changes in the capacitive value of piezoelectric materials, which shows up in measured admittance. Due to the temperature dependent nature of piezoelectric materials, we investigated the effects of temperature variations on sensor diagnostic process. The effect of temperature variations found to be remarkable, modifying the measured capacitive values significantly. In addition we analyzed the effect of bonding agents between a PZT patch and a host structure. This paper summarizes considerations needed to develop such sensor diagnostic processes, experimental procedures and results, and additional issues that can be used as guidelines for future investigations.
디지털 맘모 디텍터 성능평가를 위한 몬테카를로용 산란선 제거 그리드 작성에 관한 연구
김예지(Yeji Kim),조혜진(Hyejin Jo),윤용수(Yongsu Yoon) 대한방사선과학회(구 대한방사선기술학회) 2024 방사선기술과학 Vol.47 No.1
In Recent years, there has been a noticeable increase in the global incidence of breast cancer, with approximately 2.3 million cases of female breast cancer reported worldwide in 2020. Numerous studies are currently underway to enhance the accuracy of breast cancer diagnosis through the development of digital mammography detectors. This study aims to create Monte Carlo simulation-based mammographic anti-scatter grids and investigate their utility in evaluating the performance of digital mammography detector. Two types of mammographic anti-scatter grids, MAM-CP and Senographe 600T HF, were created using Monte Carlo simulation software (MCNPX 2.7.0), with grid ratios of 3.7 : 1 and 5 : 1, respectively. The grid physical characteristics (sensitivity, exposure factor, contrast improvement ratio) were calculated based on the KS C IEC60627 in the simulations using two X-ray qualities, RQA-M2 (28 kVp) and MW4 (35 kVp). As the X-ray tube voltage increased from 28 kVp to 35 kVp, sensitivity and exposure factor exhibited a decreasing trend, while contrast improvement ratio demonstrated an increasing trend. With an increase in grid ratio from 3.7 : 1 to 5 : 1, all physical characteristics showed an upward trend. Our results were consistent with a previous study that conducted measurements of physical properties using a real phantom. However, the pattern of change in the contrast improvement ratio with X-ray tube voltage differed from the previous study.
이소시아네이트 경화제 종류에 따른 PU 난연도료의 도막물성 및 난연효과
박홍수(Park HongSoo),심일우(Shim IlWoo),조혜진(Jo HyeJin),함현식(Hahm HyunSik),김영근(Kim YoungGeun) 한국유화학회 2006 한국응용과학기술학회지 Vol.23 No.3
PU type flame-retardant coatings (TBAO/L-75, TBAOL ; TBAO/N-100, TBAON) were prepared by blending bromine-containing modified polyester (TBAO) which was synthesized in our earlier work. with two kinds of isocyanate curing agents, Desmodur L-75 and Desmodur N-100. Physical properties of the prepared flame-retardant coatings were tested. TBAOL shows better hardness than TBAON, while TBAON shows better viscosity, accelerated weathering resistance, yellowness index and lightness index difference than TBAOL. There were no remarkable differences in fineness of grind, 60^{circ} specular gloss, cross-hatch adhesion, and abrasion resistance of TBAOL and TBAON. There was no discernable difference in flame-retardancy between the two flame-retardant coatings, TBAOL and TBAON. When the content of tribromo acetic acid, which is flame-retarding component, was 30wt% the LOI value was in a range of 29{sim}30%, which indicates that the two coatings are good flame-retardant coatings.