School of Mechanical Engineering Seminar
Wednesday June 21.6.2023

Wolfson Building of Mechanical Engineering, Room 206

Biomechanics of Calcified Aortic Valves:  Predictive Growth Models and Mechanical Analysis of TAVI Repair

Omer Tal

M.Sc. research under the supervision of Prof. Rami Haj-Ali Tel Aviv University, Department of Mechanical Engineering

The aortic valve (AV) is one of four heart valves and is the final one encountered by oxygenated blood as it leaves the heart. It is responsible for preventing the backflow of oxygen-rich blood from the aorta into the left ventricle during diastole. Aortic stenosis (AS) is the most prevalent of all valvular heart diseases in developed countries. Roughly 25% of people over 65 have AV thickening and 3% over 75 have severe stenosis. AV calcification refers to the inflammation and remodeling of the extracellular matrix, resulting in the formation of bone-like structures on the valve. Calcified AS is the leading cause of valve replacement in developed nations. More than 50% of patients diagnosed with AS have bicuspid aortic valves (BAV), and their disease progression rate is accelerated compared to patients with a tricuspid aortic valve (TAV). Transcatheter Aortic Valve Implantation (TAVI) is a minimally invasive procedure used to replace a damaged AV without open-heart surgery. Since its introduction in 2002, TAVI has become an increasingly preferred alternative to surgical aortic valve replacement.

This study presents a validation and extension of the theoretical framework of the Reversed Calcification Technique (RCT) previously proposed in our Lab. RCT enables the reconstruction of patient-specific aortic valve calcification progression, aiming to encompass the timeline from initiation to the current state. Notably, this study incorporates a time scale into the RCT theory, transforming it into a robust quantitative method capable of reconstructing calcification morphology and quantifying calcification volume at any relevant time in the past. Two approaches are introduced and rigorously validated. The RCT is utilized to provide a clinically relevant and realistic simulation of calcification growth in bicuspid aortic valves. To assess the impact of calcification distribution on valve biomechanics and transcatheter aortic valve implantation (TAVI) outcomes, finite element analyses are conducted by integrating RCT with a group-specific calcification modeling technique. By dividing the bicuspid aortic valve calcification into regional calcification, precise control over calcification distribution is achieved by manipulating regional calcification growth stages. Multiple valve calcification distributions are simulated with critical parameters, including pre-and post-TAVI valve area, maximal stresses on the valve, and anchoring forces. The extended RCT method is quantitative and capable of predicting the total volume growth of different TAV and BAV patents (n=14) with an average error of 15% from multiple CT over a maximum time interval of 5 years. Combining RCT in BAV to perform TAVI simulations at different calcification stages can serve in the patient-specific design of future repair therapy. This study advances our understanding of calcified bicuspid aortic valves and offers valuable insights for optimizing TAVI procedures.

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סטודנטים.ות להנדסת חשמל, מכונות ותעשיה וניהול חברת SolarEdge מגיעה כדי לפגוש אתכם.ן ביום זרקור מהנה.

SolarEdge הינה חברה ישראלית ציבורית, מובילה עולמית בטכנולוגיית אנרגיה חכמה, הנסחרת בנאסד"ק בארה"ב. החברה מייצרת מוצרים ושירותים בתחום האנרגיה המתחדשת כגון: מערכות סולאריות ביתיות ומסחריות המאפשרות ניצול מקסימאלי של אנרגיה, רכבים חשמליים, סוללות נטענות, ניהול בית חכם ועוד… המערכות של SolarEdge נמכרות בלמעלה מ- 130 מדינות ברחבי העולם, ומאפשרות למאות אלפים ליהנות יום יום מייצור אנרגיה נקיה וירוקה. 

רוצים.ות לשמוע על אפשרויות התעסוקה בחברה? איך ניתן להשתלב ובאילו תפקידים? 

בואו לפגוש את צוות החברה!

מתי? : יום שני ה08.05.23

שעה?: 12:00-14:00

איפה?: שדרת הדקלים, בפקולטה להנדסה.

נתראה!

School of Mechanical Engineering Seminar
wednesday May 24.5.2023 at 14:00

Wolfson Building of Mechanical Engineering, Room 206

Acoustic-Gravity Waves – a focus on nonlinear triad interaction

Usama Kadri

senior lecturer, Cardiff University, UK

In linear water wave theory, acoustic (compression) waves are virtually decoupled from free-surface (gravity) waves, since the speed of sound in water far exceeds the maximum phase speed of gravity waves. Nevertheless, we argue theoretically that these two types of wave motion could exchange energy via nonlinear resonant triad interactions. There are two cases of interest this talk focuses on: (I) two gravity waves interacting with an acoustic mode of a comparable timescale; and (II) two acoustic modes interacting with a gravity wave of a comparable lengthscale. Using multiscale analysis cubic nonlinear Schrödinger-type evolution equations are derived. For finely tuned monochromatic waves almost all energy initially stored in the gravity waves transfers into the acoustic mode, whereas for wavepackets energy transfer becomes much less efficient. 

Implications of the result are presented for a wide range of applications: from oceanic scale microseisms (faint earth tremors), wave energy harnessing and tsunami generation and mitigation, to lab-size time reversals, standing Faraday waves in an oscillating bath, and pilot-wave quantum analogues. The talk is concluded with a discussion over pushing the boundaries towards the derivation of general evolution equations. 

 Biography
I am an Aerospace Engineer, an Applied Mathematician, and a Science Communicator. My research focus lies in the area of fluid dynamics and nonlinear phenomena. Specifically, it is concerned with studying “acoustic–gravity waves”, which I employ to address most challenging questions with high impact on science and society. Recently I have focused on the early detection and mitigation of tsunami, in collaboration with the UNESCO; Covid-19; the missing Malaysian Airplane MH370; and Quantum Analogues. My approach is theoretical mathematical, combined with numerical modelling, lab experiments, and field-data analysis.

I obtained a B.Sc. and M.Sc. in Aerospace Engineering at the Technion, and a PhD in Applied Science at TU Delft (2009) under the supervision of Dist. Prof. and V. Rector R.F. Mudde, and Prof. R.V.A. Oliemans, where I also gave consultancy to oil & gas related industry (i.e., Shell, TNO), and spent some time at NTNU in Norway. I was a postdoc at CEE, Technion where I started working on acoustic-gravity waves with Prof. Micky Stiassnie (2010-2013), after which I was a Visiting Scholar at the Department of Mechanical & Aerospace Engineering, at UCSD (2013), where I met and worked with the legendary Prof. Walter Munk (Einstein of the Ocean). Then I became a Visiting Scientist & Research Fellow/postdoc, at the Department of Mechanical Engineering, MIT (2013-2015), where I worked with Prof. T.R. Akylas; and an Assistant Prof. at Haifa University and a Visiting Assistant Professor at the Department of Mathematics, MIT (2015-2016) hosted by Prof. John Bush and worked closely with Prof. C.C. Mei from CEE. I moved to the UK and joined Cardiff University’s School of Mathematics (tenured position) in 2016, keeping an honorary Research Affiliation at MIT (2016-2020). In 2018 I became a Visiting Assistant Professor at the School of Mechanical and Material Engineering, University College Dublin.  

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https://tau-ac-il.zoom.us/j/86497933118

You are invited to attend a lecture on Wednesday, May 3, 2023 at 12:00

Wolfson Engineering Building, Room 206

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https://tau-ac-il.zoom.us/j/83060796575

Overview of Electromagnetic Selective Structures

By:

Prof. Zhongxiang Shen

IEEE Antennas and Propagation Society Distinguished Lecturer

Nanyang Technological University

Singapore

Abstract

In this talk, we intend to provide a brief overview of electromagnetic selective surfaces/structures (EMSS). According to the properties of an incident electromagnetic wave, EMSS can be divided into four categories: frequency-selective structure (FSS), polarization-selective surface (PSS), angle-selective surface (ASS), and energy-selective surface (ESS). Recent developments and advances in the design of EMSS will also be briefly introduced. Finally, future opportunities in the areas of the design and analysis of EMSS will be suggested.

Biography

Zhongxiang Shen  received the B. Eng. degree from the University of Electronic Science and Technology of China, Chengdu, China, in 1987, the M. S. degree from Southeast University, Nanjing, China, in 1990, and the PhD degree from the University of Waterloo, Waterloo, Ontario, Canada, in 1997, all in electrical engineering.

From 1990 to 1994, he was with Nanjing University of Aeronautics and Astronautics, China. He was with Com Dev Ltd., Cambridge, Canada, as an Advanced Member of Technical Staff in 1997. He spent six months each in 1998, first with the Gordon McKay Laboratory, Harvard University, Cambridge, MA, and then with the Radiation Laboratory, the University of Michigan, Ann Arbor, MI, as a Postdoctoral Fellow. In Jan. 1999, he joined Nanyang Technological University, Singapore, as an assistant professor, where he is currently a full professor. Dr. Shen served as the Chair of the IEEE MTT/AP Singapore Chapter in 2009. From Jan. 2010 to Aug. 2014, he was the Chair of IEEE AP-S Chapter Activities Committee. From July 2014 to December 2018, he served as the Secretary of IEEE AP-S. He was an elected AdCom member of the IEEE AP-S from Jan. 2017 to Dec. 2019. He served as an Associate Editor of the IEEE Transactions on Antennas and Propagation from July 2016 to July 2022. From Jan. 2021 to Dec. 2023, he is a Distinguished Lecturer of the IEEE AP-S. Prof. Shen is currently the Editor-in-Chief of IEEE Open Journal of Antennas and Propagation.

Prof. Shen is an IEEE Fellow. His research interests include small and planar antennas for various wireless communication systems, analysis and design of frequency-selective structures and absorbers, hybrid numerical techniques for modeling RF/microwave components and antennas. He has authored more than 220 journal papers (among them 170 were published in IEEE Journals) and also presented nearly 200 papers at international conferences.