הנכם מוזמנים להשתתף ביריד תעסוקה שיתקיים ביום שלישי, 18.12.2018, בין השעות 15:00-18:00 ברחבת הלובי של הבניין הרב תחומי,  אוניברסיטת תל-אביב.

כזכור, בשנה שעברה התקיים היריד הראשון מסוגו ונחל הצלחה רבה הן בתעשייה והן בקרב הסטודנטים והבוגרים. ביריד ישתתפו גם הפעם חברות בתחום הביו-רפואה וחברות ממגזרי היי-טק אחרים.

לרישום ליריד תעסוקה, מענה לשאלות ואישור השתתפות אנא פנו ליערית רחמים אברוצקי – מנהלת קשרי תעשיה של ארגון ה - IAP,

טלפון: 03-6405532;

אי-מייל:  yaaritr@tauex.tau.ac.il

You are invited to attend a lecture

Beam-Based Local Tomographic Inverse Scattering

:By

Ram Tuvi

(Ph.D. student Under the joint supervision of Prof. Ehud Heyman of the Faculty of Engineering, TAU, and Prof. Timor Melamed of the Electrical and Computer Engineering Dept, BGU)

Abstract

We present a novel strategy for local-tomographic inverse scattering using of beam-wave processing. We actually formulate two self-consistent inversion schemes: a multi-frequency scheme which is used if the scattering data is given as a function of frequency over a wide frequency band, and a time domain scheme which used if the data is given in the short-pulse time domain. 

The frequency domain scheme utilizes a phase-space set of iso-diffracting Gaussian beams (ID-GB) while the time domain scheme utilizes a phase-space set of iso-diffracting pulsed beams (ID-PB). The term iso-diffracting implies that the propagation parameters of these beams are frequency independent and need to be calculated only once and then used for all frequencies.

The theory is structured upon frame theory: It is shown that both the ID-GB set and the ID-PB set constitute frames everywhere in the propagation domain, and thus can be used for local expansion of fields or sources, as an alternative to the conventional plane-wave transforms. They also generalize the standard window Fourier transform frames and the windowed Radon transforms frames.

In the inversion schemes, these "beam frames" are utilized for local phase-space pre-processing of the scattering data, and then for local "filtered-backpropagation" and medium reconstruction. A cogent physical interpretation of these operations is obtained via asymptotic analysis. The efficacy and accuracy of these beam formulations are explored via numerical examples.

 On Thursday, Dec 6th, 2018, 15:00

Room 011, Kitot building

You are invited to attend a lecture

Lightning-fast solution of scattering problems in nanophotonics: an effortless modal approach

:By

Parry Yu Chen

Unit of electro-optics Engineering, Ben-Gurion University

Abstract

Nanophotonic structures are capable of generating field hotspots, which can enhance quantum light-matter interactions by many orders of magnitude. However, numerical simulations for applications such as radiative heat transfer, electron energy loss spectroscopy, van der Waals forces, Purcell factor throughout a volume, and many others are challenging and often computationally prohibitive. Common to these simulations is that the Green’s function or local photonic density of states must be known at each point across a volume of space, necessitating the solution of Maxwell’s equations perhaps many thousands of times.

We propose a modal solution, which requires just a single simulation to find the modes of the nanophotonic system, from which we immediately obtain the Green’s function everywhere in space. This not only reduces simulation time by approximately 2 orders of magnitude, but also offers ready physical insight into the spatial variation of Green’s function. Modal methods have long been used for closed systems, where the formulation is exceedingly simple. We have generalized modal methods to open systems while maintaining this simplicity, catering to the explosion of research interest in nanophotonics. We furthermore present a highly-efficient exponentially-convergent method of generating the modes themselves

On Thursday, November 29, 2018, 15:00

Room 011, Kitot building

School of Mechanical Engineering Seminar
Wednesday, December 05, 2018 at 14.00
Wolfson Building of Mechanical Engineering, Room 206

The Parametric HFGMC Micromechanics for Nonlinear and Damage Modeling of Multiphase Materials

Aviad Levi Sasson

 Ph.D. student of Prof. Rami Haj-Ali and Prof. Jacob Aboudi

This study expands the parametric HFGMC capabilities to model and solve engineering problems. New condensed formulation is proposed and proved to yield good results for the effective thermo-mechanical properties and the spatial elastic fields in terms of computing time. For the first time, the parametric HFGMC is extended to predict the effective thermal properties of composite material: coefficients of thermal expansion, effective thermal conductivity and heat capacity at constant pressure and constant volume.

A continuum damage model has been integrated with the parametric HFGMC. This damage model was originated from the principal of energy dissipation proposed by Marigo (1981) model and was coupled with Ledeveze-Lemaitre (1984) model. The Marigo damage model was revised in the current work to eliminate nonphysical behavior under shear loading conditions. The corrected damage model is implemented at the subcell level so each subcell can detect failure due to its local stress state. Material softening behavior due to damage is implemented as well. The isotropic damage law and its evolution generates both an effective anisotropic damage behavior in the global (composite) level and global nonlinear stress-strain response. Several material systems were used to demonstrate the new damage and failure prediction capabilities of the parametric HFGMC. The obtained failure envelops from the parametric HFGMC were compared with experimental results and showed very good agreement. For the first time, micromechanical based failure envelops are matched with new analytical-mathematical expressions for future design and analysis and to reduced computational effort during analyses.

Multiscale analysis of laminated composite structures is proposed by integrating the parametric HFGMC with the classical FE. The multiscale analysis is compared with the experimental results for the cases of notched laminated composite coupons that are subjected to tension and compression loading. In additions, the parametric HFGMC is used to model the mechanical behavior of a Dyneema based soft composite. The new capacities of the parametric HFGMC are shown again to succeed with the prediction of stress-strain curves of soft composite. New experimental tests for the soft composite are designed and proposed in the framework of this study in order to compare the periodic HFGMC prediction with some measurements. The parametric HFGMC shows good agreement with the measured elastic properties.  This talk will conclude by discussing potential future extensions of the proposed micromechanical framework.