Ju Feng

Biography of Ju Feng

Dr. Ju Feng is an Associate Professor at the School of Mechanical and Electrical Engineering, Nanjing University of Aeronautics and Astronautics. He earned his Ph.D. from Nanyang Technological University, Singapore, and his Bachelor’s and Master’s degrees from Southeast University. He previously served as a researcher at NIDEC Singapore Research Center. His primary research focuses on bio-inspired soft robotics and their applications in surgical robots, industrial non-destructive testing, and related fields. Dr. Ju has led multiple research projects, including three grants from the National Natural Science Foundation of China, a project from the Jiangsu Natural Science Foundation, and the Jiangsu Entrepreneurship and Innovation Program. He has also participated in key national and international projects, such as the National Key R&D Program of China on Intelligent Robotics, the Royal Society International Exchange Program (UK), and the Jiangsu Major Scientific and Technological Achievements Transformation Program. He has published over 30 SCI-indexed papers and holds more than 10 authorized Chinese patents, as well as 2 U.S. patents and 2 Japanese patents. Dr. Ju is a member of the Medical Engineering Equipment Committee of the Chinese Mechanical Engineering Society, a member of the Chinese Aeronautical Society, the Jiangsu Association for Artificial Intelligence, and IEEE, and has been recognized as a Talent under the Jiangsu/Gusu/Kunshan Entrepreneurship and Innovation Programs.

Inverse Characterization of The Spatial-Domain Distribution of Acoustic Parameters

in Heterogeneous Structures

Xi Ze

Irregular heterogeneous structures, represented by dissimilar steel welds, are widely employed in energy industries and other fields. After experiencing extreme service conditions, the nondestructive characterization of internal heterogeneous material properties and interface morphology in such structures has become an important research topic. Ultrasonic arrays stand out as one of the most viable techniques for online nondestructive evaluation due to their flexible beamforming capabilities. However, the complex internal interfaces and inhomogeneity make it difficult for existing methods to accurately obtain material property distributions. To address the above challenges, this study introduces the concept of spatial-domain reconstruction and develops a quantitative spatial-domain reconstruction model for macroscopic acoustic parameters and interface morphology characterization. First, the tensor projection transformation relationship between acoustic parameter tensors (e.g., attenuation coefficient and sound velocity) and beamforming is extracted with forward model of wave propagation in heterogeneous structures, and a spatial-domain regularized reconstruction model for key acoustic parameters is constructed. Subsequently, by combining multi-angle plane wave beamforming, image correlation, and registration techniques, the relative amplitude ratio and relative measurement time-difference matrix are extracted. Based on total variation regularization theory, the ill-posed nature of the inversion model is resolved, enabling quantitative reconstruction of macroscopic acoustic parameters and irregular interfaces under the coupling effect of complex interfaces and weak acoustic impedance ratios. Simulation and experimental verification demonstrate that the proposed method can accurately reconstruct the spatial distribution of attenuation coefficient and sound velocity in dissimilar steel weld specimen. This approach provides theoretical support for characterizing macro/micro material properties, grain size, and mechanical performance, while laying a technical foundation for reliability assessment of equipment under extreme service conditions and multi-dimensional, multi-parameter online measurements.

Biography of Xi Ze

Dr. Xi Ze is an Assistant Researcher at the Institute of Nuclear and New Energy Technology, Tsinghua University. He received his Ph.D. in Nuclear Science and Technology from Tsinghua University in 2023. His long-term research focuses on acoustic theory in complex structures, array ultrasonic imaging, and risk-informed optimization of in-service inspection for nuclear power equipment. Recently, his work has centered on acoustic parameter inversion in multi-layered complex interface media and data-driven optimization of array ultrasonic inspection, aiming to address practical engineering challenges. In recent years, as a key member, he has contributed to major national research projects, including the National Key Science and Technology Program for High-Temperature Gas-Cooled Reactors and the National Natural Science Foundation of China. Over the past five years, he has authored more than 10 SCI/EI-indexed papers published in top-tier journals such as NDT&E International, IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, and Ultrasonics. His research achievements have earned multiple honors, including a cover feature in IEEE Transactions, the Excellent Paper Award at the Far East NDT Forum (FENDT 2025), and the Best Paper Award at the International Conference on Nuclear Engineering (ICONE 31).