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RISS 인기검색어
- 검색키워드
- 저자 : SALAH EDDINE, EZAHEDI (검색결과 2 건)
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SALAH EDDINE, EZAHEDI 忠南大學校 大學院 2023 국내석사
최근 리튬이온배터리(Lithium-ion battery; LIB) 기반 전기차(Electrical vehicle; EV)의 화재사고가 증가하고 있다. 이러한 화재를 예방하기 위해서는 열폭주에 대한 사전 진단이 필수적이다. 이에 따라 EV 팩을 구성하는 모든 배터리의 진단을 위해 단일 셀 수준의 정밀한 온도 모니터링이 필요하다. 전기화학적 임피던스 분광법 (Electrochemical impedance spectroscopy; EIS)는 센서리스 온도 추정을 위한 배터리의 내부 온도(Tint)와 밀접하게 연관되어 있지만 셀 간 변동에 따른 EIS 임피던스 차이로 인해 다중 셀 사용에 제한이 있습니다. 본 논문은 다중 LIB 온도 추정을 위해 EIS와 가우시안 프로세스 회귀(Gaussian process regression; GPR) 기계 학습을 결합한 프레임워크를 제안한다. 서로 다른 주파수에서 배터리의 임피던스 특성과 함께 온도, 충전 상태 및 온도 감도 사이의 본질적인 관계를 조사한다. 51개의 주파수에서 10Hz의 단일 지점 주파수 측정값이 온도 추정 모델에 적합하며, 해당 주파수의 데이터 빈도는 이후에 GPR 모델을 훈련하는 데 활용된다. 5개의 커널 기능이 실험적으로 연구, 훈련 및 검증되었으며, 가장 정확한 커널에 대한 평균 제곱근 오차 (Root means square error; RMSE)는 0.2°C이다. 또한 새로운 셀 추정을 위한 테스트 RMSE는 0.79°C로 높은 모델 정확도를 도출하였다. Recently, fire incidents due to electrical vehicle (EV) lithium-ion battery (LIB)-based energy storage devices have been increasingly occurring. Preemptive diagnosis of the thermal runaway is essential for preventing such fires. However, precise and accurate temperature monitoring at the single cell level is required for all the batteries present in the EV pack. Electrochemical impedance spectroscopy (EIS) closely correlates with the battery's internal temperature (Tint) for sensorless temperature estimation, but is limited for multi-cell use because of the impact of cell-to-cell variations on the EIS impedance values, causing inaccuracies in the use case of predefined models. This study developed a framework combining the EIS method with Gaussian process regression (GPR) machine learning for multiple LIBs cell temperature estimation. The intrinsic relationship between the temperature, state of charge, and temperature sensitivity with the impedance properties of the batteries at different frequencies was investigated. The results showed that from 51 extracted frequencies only single-point frequency measurements at 10Hz were necessary to develop the temperature estimation model. The data at this frequency was subsequently utilized to train the GPR model. Five kernel functions were studied, trained, and validated experimentally. The root means square error (RMSE) for the most accurate kernel was 0.2°C at the validation step, and the test RMSE for the estimation of a new cell was 0.79°C, confirming the high accuracy of the model.
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Micromachined piezoelectric ultrasonic imaging transducer
Mohamed, Hisham Salah Eddin Aly University of Minnesota 2000 해외박사(DDOD)
소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.
Four different sizes of MEMS based piezoelectric ultrasonic transducers have been successfully fabricated at the University of Minnesota Micro-technology laboratory. The transducers operate at their fundamental resonance frequencies for maximum sensitivity. The ultrasonic transducer elements consist of square silicon nitride membranes. A capacitor structure of piezoelectric material, lead zirconium titanate (PZT), was deposited on the top of the supporting nitride structure. The PZT structure enables the actuation and the sensing of the ultrasonic waves. The thin film PZT for this work was spin-coated onto the device using a metalorganic deposition method, resulting in a PZT thickness of 0.4μ<italic> m</italic>. The average remanent polarization (+<italic>P<sub>r</sub></italic>) of the PZT thin film was measured at 23.5μ<italic>C</italic>\<italic>cm </italic><super>2</super> with an average dielectric constant (<italic>K</italic>) of 1552. The membrane elements were individually released free by a deep reactive ion etching (DRIE) of the back of the silicon substrate, resulting in a structure with minimal cross talk between the different elements when fabricated in two dimensional arrays. The transducers were also tested for impedance characteristics, average fundamental resonance modes were found at 15.6<italic>MHz</italic>, 9.52<italic> MHz</italic>, 8.8<italic>MHz</italic>, and 8.7<italic>MHz</italic>, with the highest frequency registered for the smallest membrane size. Finally, the transducers were pulsed in per-fluorocarbon high dielectric strength solution and ethos were received from an air-solution interface. Mechanical and electrical models were used to study the transducers behavior, simulations results agree well with the measured data suggesting that these models can be further used for optimizing future generations of transducers. This thesis also suggests a novel ultrasonic micro-imaging system based on the integration of the transducer elements with micro-pumps for local contrast agent deployment. This method will overcome the toxicity, and absorption in circulation associated with the use of contrast agents.
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