@article{kim_balagopal_kerrigan_garcia_chow_bourham_fang_jiang_2023, title={Noninvasive liquid level sensing with laser generated ultrasonic waves}, volume={130}, ISSN={0041-624X}, url={http://dx.doi.org/10.1016/j.ultras.2023.106926}, DOI={10.1016/j.ultras.2023.106926}, abstractNote={This article proposes a noninvasive liquid level sensing technique using laser-generated ultrasound waves for nuclear power plant applications. Liquid level sensors play an important role of managing the coolant system safely and stably in the plant structure. Current sensing techniques are mostly intrusive, performing inside the fluidic structure, which is disadvantageous in terms of the regular maintenance of the plant system. Furthermore, typical intrusive sensors do not perform stably under varying environmental conditions such as temperature and radiation. In this study, sensing units are attached to the outer surface of a liquid vessel to capture guided ultrasound waves in a nonintrusive manner. The signal intensity of the guided wave dissipates when the signal interacts with the internal liquid media. The sensing mechanism is mathematically expressed as an index value to correlate the liquid level with the sensor signal. For the acoustic wave generation, laser-generated ultrasound was adopted instead of using typical contact type transducers. Following the simulation validation of the proposed concept, the performance of the developed sensor was confirmed through experimental results under elevated liquid temperature conditions. The nonlinear multivariable regression exhibited the best-fit to the datasets measured under the variable liquid level and temperature conditions.}, journal={Ultrasonics}, publisher={Elsevier BV}, author={Kim, Howuk and Balagopal, Bharat and Kerrigan, Sean and Garcia, Nicholas and Chow, Mo-Yuen and Bourham, Mohamed and Fang, Tiegang and Jiang, Xiaoning}, year={2023}, month={Apr}, pages={106926} }
 @article{kim_kerrigan_bourham_jiang_2021, title={AlN Single Crystal Accelerometer for Nuclear Power Plants}, volume={68}, ISSN={["1557-9948"]}, url={https://doi.org/10.1109/TIE.2020.2992002}, DOI={10.1109/TIE.2020.2992002}, abstractNote={Reliable vibration sensing is essential to the immediate detection of unusual vibrations, ensuring the safety of nuclear power plant structures. For nuclear power plant applications, the sensor element must endure the harsh environment while retaining reliable performance. Aluminum nitride (AlN) single crystal is considered a promising candidate for the sensing unit due to its robustness to high temperature (HT) and irradiation conditions. However, there are few efforts in developing industrial accelerometers using AlN bulk-machined materials. This article aims to develop a shear-type accelerometer with AlN single crystal plates. The accelerometer's design is based on the numerical simulation results, followed by the fabrication of the sensor and the extensive validation under HT (∼1000 °C). The sensitivity of the accelerometer was about 9.2 pC/g. The prototype sensor showed stable performance at varying temperatures from room temperature to 1000 °C. Furthermore, the sensitivity of the accelerometer was successfully sustained for 10 h under HT exposure of 1000 °C, and no obvious mechanical damage was detected after the test. After gamma irradiation for 1 month, the sensor performed stably, without any significant change in sensitivity. The developed AlN accelerometer can be a promising option to monitor the structural integrity of nuclear power plant structures.}, number={6}, journal={IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Kim, Howuk and Kerrigan, Sean and Bourham, Mohamed and Jiang, Xiaoning}, year={2021}, month={Jun}, pages={5346–5354} }