Junchao Wei

Ph.D. in Engineering - Auburn University - University of Pittsburgh

Journal Publications

  • Wei, J., Hua, Y., Yang, B., Wang, B., Schmitt, S. E., Wang, B., … & Sigal, I. A. (2022). Comparing Acute IOP-Induced Lamina Cribrosa Deformations Premortem and Postmortem. Translational Vision Science & Technology, 11(12), 1-1.[LINK]

       

eCover of Translational Vision Science and Technology

  • Introduction: Lamina cribrosa (LC) deformations caused by elevated intraocular pressure (IOP) are believed to contribute to glaucomatous neuropathy and have therefore been extensively studied, in many conditions, from in vivo to ex vivo. We compare acute IOP-induced global and local LC deformations immediately before (premortem) and after (postmortem) sacrifice by exsanguination.
  • Methods: The optic nerve heads of three healthy monkeys 12 to 15 years old were imaged with spectral-domain optical coherence tomography under controlled IOP premortem and postmortem. Volume scans were acquired at baseline IOP (8–10 mm Hg) and at 15, 30, and 40 mm Hg IOP. A digital volume correlation technique was used to determine the IOP-induced three-dimensional LC deformations (strains) in regions visible premortem and postmortem.
  • Results: Both conditions exhibited similar nonlinear relationships between IOP increases and LC deformations. Median effective and shear strains were, on average, over all eyes and pressures, smaller postmortem than premortem, by 14% and 11%, respectively (P’s< 0.001). Locally, however, the differences in LC deformation between conditions were variable. Some regions were subjected premortem to triple the strains observed postmortem, and others suffered smaller deformations premortem than postmortem.
  • Conclusions: Increasing IOP acutely caused nonlinear LC deformations with an overall smaller effect postmortem than premortem. Locally, deformations premortem and postmortem were sometimes substantially different. We suggest that the differences may be due to weakened mechanical support.

       

Before(Left)&After(Right) the Registration:Ref.(Green),Def.(Red),Aligned(Yellow)

  • Sibony, P. A., Wei, J., & Sigal, I. A. (2018). Gaze-Evoked Deformations in Optic Nerve Head Drusen: Repetitive Shearing as a Potential Factor in the Visual and Vascular Complications. Ophthalmology, 125(6), 929-937. Impact Factor: 13.1 [LINK]

Introduction: Axial rasters of the optic nerve from a spectral-domain optical coherence tomography(SD-OCT) [Cirrus 5000. Zeiss Meditch] were used to analyze the shape of the peripapillary basement membrane-layer (ppBM-layer) in 20 confirmed cases of ONHD. We compared registered images obtained two eye positions: 10-15° in adduction and 30-40° degrees in abduction. Geometric Morphometrics was used to analyze the shape of the ppBM-layer defined by placing 10 equidistant landmarks extending 2500 microns on both sides of the basement membrane opening. We also adapted an image strain tracking technique to measure regional intrapapillary strains in six of our patients. Using manually placed “nodes” on the reference image (in adduction), an iterative, block-matching algorithm is used to determine local displacements between the reference and its paired image in abduction. Displacement vectors were used to calculate the mean shear and effective strain(%change)

       

  • Lall, P., & Wei, J. (2015). Prediction of L70 life and assessment of color shift for solid-state lighting using Kalman filter and extended Kalman filter-based models. IEEE Transactions on Device and Materials Reliability, 15(1), 54-68. [LINK]

  • Introduction: Kalman filter (KF) and extended Kalman Filters (EKF) have been used to develop a 70% Lumen Maintenance Life Prediction Model for LEDs used in SSL luminaires. Ten-thousand-hour LM-80 test data for various LEDs have been used for model development. System state at each future time has been computed based on the state space at preceding time step, system dynamics matrix, control vector, control matrix, measurement matrix, measured vector, process noise, and measurement noise. The future state of the lumen depreciation has been estimated based on a second-order Kalman Filter model and a Bayesian Framework. The measured state variable has been related to the underlying damage using physics-based models. Life prediction of L70 life for the LEDs used in SSL luminaires from KF- and EKF-based models have been compared with the TM-21 model predictions and experimental data.

       

  • Lall, P., Wei, J., & Sakalaukus, P. Life Prediction and Classification of Fault-Modes in Solid State Lamps Using Bayesian Probabilistic Models. IEEE Reliability Digest, 2 (2014):7-18 [LINK]

  • Yang, B., Brazile, B., Jan, N. J., Hua, Y., Wei, J., & Sigal, I. A. (2018). Structured polarized light microscopy for collagen fiber structure and orientation quantification in thick ocular tissues. Journal of biomedical optics, 23(10), 106001.

Book Chapter

  • Wei, J., “Artificial Intelligence and LED degradation” in Reliability of organic compounds in microelectronics and optoelectronics. Springer, Feb.2022. [LINK] [CONTENTS]

Introduction: Artificial Intelligence (AI) is intelligence performed by designed algorithms. Recently, there are many advancements in the AI field that benefited by the improvements in computational power from the hardware. Meanwhile, there is easy access and availability of data from various platforms. AI technologies with data science can help solve many industrial problems like tracking Solid-state Lighting (SSL) system degradation, classifying LED failures, and predicting Remaining Useful Life (RUL) for the system. The modern AI technologies and fields include Deep Learning (DL) and Computer Vision (CV). Deep Convolutional Neural Network (CNN) and Recurrent Neural Network (RNN) is the fundamental network that can be easily adapted to the imaging system for material degradation analysis in the LEDs. In this chapter, firstly, it introduces representative supervised learning algorithms for LED degradation monitoring.

       

Ph.D. Dissertation

  • Wei, J. (2017). In-situ Electronics Measurement Using X-ray Micro-Computed Tomography System and Data Driven Prognostic Health Management. [LINK]

Conference Papers

  • Wei, J., Yang, B., Voorhees, A. P., Tran, H., Brazile, B., Wang, B., … & Sigal, I. A. (2018, February). Measuring in-vivo and in-situ ex-vivo the 3D deformation of the lamina cribrosa microstructure under elevated intraocular pressure. In Optical Elastography and Tissue Biomechanics V (Vol. 10496, p. 1049611). International Society for Optics and Photonics.

  • Wei, J., Lall, P. (2017, May). X-ray micro-CT and DVC based analysis of strains in metallization of flexible electronics. In Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm), 2017 16th IEEE Intersociety Conference on (pp. 1253-1261). IEEE.

  • Wei, J., Lall, P. (2016, May). Remaining Useful Life Assessment of Field Deployed Electronics Using X-Ray Micro-CT Based Digital Volume Correlation and Finite-Element Analysis. In Electronic Components and Technology Conference (ECTC), 2016 IEEE 66th (pp. 1583-1592). IEEE.

  • Wei, J., Lall, P. (2016, May). PBGA package Finite Element Analysis based on the physical geometry modeling using X-ray micro-CT digital volume reconstruction. In Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm), 2016 15th IEEE Intersociety Conference on (pp. 285-294). IEEE.

  • Wei, J., Lall, P. (2015, July). LED Chip Deformation Measurement During the Operation Using the X-Ray CT Digital Volume Correlation. In ASME 2015 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems collocated with the ASME 2015 13th International Conference on Nanochannels, Microchannels, and Minichannels (pp. V002T01A011-V002T01A011). American Society of Mechanical Engineers.

  • Wei, J., Lall, P. (2015, May). X-ray micro-CT and digital-volume correlation based three-dimensional measurements of deformation and strain in operational electronics. In Electronic Components and Technology Conference (ECTC), 2015 IEEE 65th (pp. 406-416). IEEE.

  • Wei, J., Lall, P. & Sakalaukus, P. (2015, April). Bayesian models for life prediction and fault-mode classification in solid state lamps. In Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems (EuroSimE), 2015 16th International Conference on (pp. 1-13). IEEE.

  • Wei, J., Lall, P. & Sakalaukus, P. (2014, November). Fault-Mode Classification of Solid State Luminaires Using Bayesian Probabilistic Models. In ASME 2014 International Mechanical Engineering Congress and Exposition (pp. V010T13A079-V010T13A079). American Society of Mechanical Engineers.

  • Wei, J., Lall, P. & Sakalaukus, P. (2014, June). Bayesian probabilistic model for life prediction and fault mode classification of solid state luminaires. In Prognostics and Health Management (PHM), 2014 IEEE Conference on (pp. 1-10). IEEE.

  • Wei, J., Lall, P. & Sakalaukus, P. (2014, May). Life prediction and classification of failure modes in solid state luminaires using Bayesian Probabilistic Models. In Electronic Components and Technology Conference (ECTC), 2014 IEEE 64th (pp. 2053-2062). IEEE.

  • Wei, J., Lall, P. & Davis, L. (2013, September). Prediction of L70 lumen maintenance and chromaticity for LEDs using extended Kalman filter models. In LED-based Illumination Systems (Vol. 8835, p. 88350M). International Society for Optics and Photonics.

  • Wei, J., Lall, P. & Davis, L. (2013, July). Solid state lighting life prediction using extended kalman filter. In ASME 2013 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems (pp. V001T05A016-V001T05A016). American Society of Mechanical Engineers.

  • Wei, J., Lall, P. & Davis, L. (2013, June). Prediction of lumen output and chromaticity shift in LEDs using Kalman Filter and Extended Kalman Filter based models. In Prognostics and Health Management (PHM), 2013 IEEE Conference on (pp. 1-14). IEEE.

  • Wei, J., Lall, P. & Davis, L. (2013, May). L70 life prediction for solid state lighting using Kalman Filter and Extended Kalman Filter based models. In Electronic Components and Technology Conference (ECTC), 2013 IEEE 63rd (pp. 1452-1465). IEEE.

  • Wei, J., Lall, P. & Goebel, K. (2012, May). Comparison of Lalman-filter and extended Kalman-filter for prognostics health management of electronics. In Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm), 2012 13th IEEE Intersociety Conference on (pp. 1281-1291). IEEE.

  • Lall, P., Dornala, K., Wei, J., Lowe, R., & Foley, J. (2015, June). Prognostication of solder-joint reliability of 0.4 mm and 0.5 mm pitch bgas subjected to mechanical shocks up to 10,000 G. In Prognostics and Health Management (PHM), 2015 IEEE Conference on (pp. 1-14). IEEE.

  • Lall, P., Deshpande, S., Wei, J., & Suhling, J. (2014, May). Non-destructive crack and defect detection in SAC solder interconnects using cross-sectioning and X-ray micro-CT. In 2014 IEEE 64th Electronic Components and Technology Conference (ECTC) (pp. 1449-1456). IEEE.

  • Wei, J., Lall, P., Sakalaukus, P. & Davis, L. (2014, May). SSL and LED life prediction and assessment of CCT shift. In Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm), 2014 IEEE Intersociety Conference on (pp. 1179-1185). IEEE.