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SCHOOL OF MECHANICAL ENGINEERING SEMINAR
Wednesday, November 20, 2019 at 14:00
Wolfson Building of Mechanical Engineering, Room 206

Co-evolving rationalizable strategies in multi-objective games

Erella Eisenstadt-Matalon
PhD student of Ami Moshaiov

The vast majority of game-theoretic studies are on Single Objective Games (SOG), also known as single payoff games. The area of Multi-Objective Games (MOGs), which are also termed as multi payoff, multi criteria or vector payoff games, has received lesser attention. Yet, in many practical problems, in economics and engineering, the players must cope with multiple objectives or payoffs.
The considered MOGs are static, non-cooperative, two-persons, zero-sum games with pure strategies, in which each player has self-conflicting objectives and none of the players has a-priori objective preferences. Yet, each player knows all the available strategies of the opponent and all the payoff vectors that result from all possible interactions between the player's strategies and those of the opponent. Here, common knowledge of rationality is assumed. Namely, it is assumed that each player is rational, and that each player knows it, and so on.
The common approach to deal with MOGs is to assume that the objective preferences of the players are known a-priori. In such a case a utility function is employed which transforms the MOG into a surrogate SOG (usually by a weighted-sum approach). However, players may have doubts when trying to a-priori make a rational decision on their objective preferences. Moreover, existing solution techniques, such as by equilibrium or by a MiniMax approach, suffer from not considering the performance trade-offs. In contrast, here it is assumed that in general, decision-makers should take into account performance trade-offs when making a decision. In view of this assertion and of the state-of-the-art, a novel solution concept to MOGs is suggested, which is based on the idea of rationalizability.
The proposed mutual-rationalizability solution concept for solving MOGs involves two-stages. In the first stage, a Set of Rationalizable Strategies (SRS) and their associated payoff vectors are sought for each of the players. This is done using Pareto-based best replies of the opponent, under the assumptions of common knowledge of rationality and undecided objective preferences by the players. The proposed approach results with trade-off information at the end of the first stage. In the second stage, Multi-Criteria Decision Analysis (MCDA) techniques are used to select a strategy out of the obtained SRSs based on the trade-off information that is revealed in the first stage. To realize the proposed two-stage solution approach, a multi-objective co-evolutionary algorithm is devised, which co-evolve the players’ strategies and finds approximated SRS for each of them.
To demonstrate the proposed approach, a novel MOG version of the Traveling Salesperson Problem (TSP) is suggested. It amalgamates two known versions of the TSP including the competing TSP and the selective TSP. The demonstration shows the capabilities of the proposed search algorithm and the significance of the proposed solution approach.

You are invited to attend a lecture
Evidence of absorption dominating over scattering in light attenuation by nanodiamonds
By:
Sergei Koniakhin

Researcher, Université Clermont Auvergne, Institut Pascal, Photon-N2, France
Senior Researcher, Zhores Alferov St. Petersburg Academic University, Russia

Abstract
We show an experimental evidence of the domination of absorption over scattering in absorbance spectra of detonation nanodiamonds. We perform the absorbance measurements on the UV-Vis spectrophotometer equipped with integrating sphere and compare them with conventional absorbance spectra. Additionally, we measure the scattering light intensity at the cuvette side wall (scattering at 90 degrees angle). The obtained experimental data were interpreted using the simulations of photon random walk in turbid media and Kubelka-Munk approach. The scattering cross sections and indicatrices were obtained by Mie theory.
 We discover that despite being very close to -4 power law (like Rayleigh scattering) the light extinction by the primary 4 nm diamond crystallites is due to absorption only and scattering can be neglected. That is the reason why previously absorption and scattering contributions were confused. The scattering is governed only by the agglomerates of 100 nm and larger in size remaining in the hydrosols and their fraction can be effectively controlled by centrifugation. Only Mie theory reproduces correctly the close to -2 scattering by the agglomerates accounting for the weird interplay between their size, fractal dimension, and dielectric properties. Finally, using the obtained absorbance spectra we estimate the fraction of non diamond phase in nanodiamonds and their agglomerates.

On Tuesday, Nov 12, 2019, 15:00
Room 011, Kitot building

בתאריך 4.11.2019 יתקיים הטקס השנתי של הקרן לאלקטרואופטיקה. פרופ' עמנואל מרום ז"ל יזם את הקמת הקרן וניהל אותה במשך שנים רבות. מוזמנים לטקס בני משפחה וסטודנטים מהעבר, ופרופ' אשר פריזם ממכון ויצמן הוזמן להרצות באירוע זה, יחד עם הזוכים בתחרות הסטודנטים השנה.

הזוכים בתחרות הסטודנטים הם:

• מר עופר בר און, סטודנט לתואר שלישי בהנחיית פרופ' קובי שויער  3D Integrated photonic devices using non-conventional soluble materials
• מר רועי כהן, סטודנט לתואר שלישי בהנחייתם של פרופ' שלמה רושין וד"ר עופר עמרני Response shaping with a silicon ring resonator via double injection
• מר שי קרן צור, סטודנט לתואר שלישי בהנחיית פרופ' טל אלנבוגן Generation of spatiotemporally tailored terahertz wavepackets by nonlinear metasurfaces

כמו כן, הקרן החליטה לתמוך בפעילות תא הסטודנטים של SPIE באוניברסיטת תל-אביב.

לו"ז הטקס

15:00-15:10 התכנסות

15:10-15:20 פתיחה וברכות

15:20-15:30 עמנואל – מדען, מנחה וחבר (פרופ' דוד מנדלוביץ)

15:30-15:35 טקס חלוקת המלגות (פרופ' עדי אריה)

15:35-15:55 הרצאות הזוכים

15:55-16:05 תא הסטודנטים

16:05-16:15 לנצח את הדיפרקציה – שי אלמלם, תלמידו האחרון של עמנואל

16:15-16:45 פרופ' אשר פריזם

16:45-17:00 נציג המשפחה