המחלקה למדע והנדסה של חומרים | אוניברסיטת תל אביב

סמינר מחלקתי Shai Ly Shohat and Barak Even Hen

18 בנובמבר 2015, 15:00

וולפסון 206

סמינר מחלקתי Shai Ly Shohat and Barak Even Hen

School of Mechanical Engineering Seminar
Wednesday, November 18, 2015 at 15:00
Wolfson Building of Mechanical Engineering, Room 206

THE EFFECT OF AORTIC VALVE REPLACEMENT ON THE CORONARY PERFUSION - COMPUTATIONAL FLUID-STRUCTURE INTERACTION MODELING AND ANALYSIS

Shaily Wald Shohat

MSc Student of Prof. Alex Liberzon & Prof. Idit Avrahami

In this study, we examine the impact of replacement valve on the coronary perfusion and on the pressure changes in the aortic root, compared with an intact valve. The numerical models include 2D computational fluid-structure interaction (FSI) simulation of the aortic root including the valve's leaflets and coronary arteries, using the commercial finite-element package of ADINA.

The study considered healthy, stenosed and TAVI valves. Pressure and flow patterns at different cardiac output (flow rate) and heart rates (beats per minute) were studied in details. It is found that aortic valve replacement leads to a significant improve in coronary perfusion pressure as well as in the cardiac cycle time. This could be explained by two potential mechanisms: (1) increase of the pressure gradient across the sinus due to induced diastolic vortical flow patterns, and (2) the high velocity ejection of blood into the aorta is reduced, thus reducing any existing Venturi effect on pressures in the sinus. The results may shed light on the dynamic mechanisms that affect coronary perfusion due to TAVI.

School of Mechanical Engineering Seminar
Wednesday, November 18, 2015 at 15:00
Wolfson Building of Mechanical Engineering, Room 206

THE EFFECT OF AORTIC VALVE REPLACEMENT

ON THE CORONARY PERFUSION - EXPERIMENTAL STUDY

Barak Even Chen

MSc Student of Prof. Alex Liberzon & Prof. Idit Avrahami

Transcatheter aortic valve implantation (TAVI) is an alternative treatment to conventional surgical aortic valve replacement for patients with aortic stenosis. Patients with severe aortic stenosis suffer also from diastolic dysfunction and reduced coronary flow (perfusion). The coronary perfusion depends on the pressure gradient between the myocardial tissue during diastole and the coronary origin located at the aortic root (sinuses of Valsalva), and thus subjected to changes in diastolic flow field near the closing valve's leaflets. Coronary perfusion can be influenced by the valve size and design as well as diastolic time. It is suggested that TAVI improves coronary perfusion pressure and increases coronary flow-rate by two potential mechanisms: (1) increase of the pressure gradient across the sinus due to induced diastolic vortical flow patterns, and (2) the high velocity ejection of blood into the aorta is reduced, thus reducing any existing Venturi effect on pressures in the sinus.

In this experimental study, we examine the impact of replacement valve on the coronary perfusion and on the pressure changes in the aortic root, compared with an intact valve. The method is based on flow visualization in a transparent flexible model of the aortic root, along with the pressure and flowrate measurements to coronary arteries. The flow is driven by hemodynamic pump using pulse duplicator, and contains a synchronized controlled resistance in the coronary arteries.

The study considered healthy, stenosed and TAVI valves. Pressure and flow patterns at different cardiac output (flow rate) and heart rates (beats per minute) were investigated. The experimental results confirm that aortic valve replacement leads to normalization of coronary flow, although at slightly different rate as compared to the reference healthy case.

EE Seminar: Fronthaul Compression for Cloud Radio Access Networks: An Information Theoretic View

~~(The talk will be given in English)

Speaker: Prof. Shlomo Shamai
EE, Technion

Monday, November 9th, 2015
15:00 - 16:00
Room 011, Kitot Bldg., Faculty of Engineering
Fronthaul Compression for Cloud Radio Access Networks: An Information Theoretic View
Abstract
Cloud radio access networks (C-RANs) emerge as appealing architectures for next-generation wireless/cellular systems whereby the processing/decoding is migrated from the local base-stations/radio units (RU) to a control/central units (CU) in the "cloud".
This is facilitated by fronthaul links connecting the RUs to the managing CUs. We focus on oblivious processing at the RU, and hence the fronthaul links carry digital information about the baseband signals, in the uplink from the RUs to the CU and vice versa in the downlink. The high data rate service demands in C-RANs, imply that even with fast (optical) fronthauls, let alone for heterogeneous fronhauls, efficient compression of the basedand signals is essential.
In this talk we focus on advanced robust signal processing solutions, emerging by network information theoretic concepts, and review also the basic approaches to this cloud network.
Multi-hop fronthaul topologies are also discussed.
Analysis and numerical results illustrate the considerable
performance gains to be expected for different cellular models.
Some interesting theoretical directions conclude the presentation.
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Joint work with S.-H. Park, O. Simeone (NJIT), and O. Sahin (InterDigital)

09 בנובמבר 2015, 15:00

חדר 011, בניין כיתות חשמל

EE Seminar: Coding Theory and some String Duplication Systems

~~ (The talk will be given in English)

Speaker: Prof. Moshe Schwartz
Ben Gurion University

Monday, October 26th, 2015
15:00 - 16:00
Room 011, Kitot Bldg., Faculty of Engineering
Coding Theory and some String Duplication Systems
Abstract
Amazingly, the majority of the human genome is made up of repeated sequences. Repetitions were shown to be connected with diseases such as as cancer, myotonic dystrophy, Huntington's disease, and important phenomena such as chromosome fragility, expansion diseases, silencing genes, and rapid morphological variation. Repetitions are common in other species as well, and are claimed to be a major evolutionary force during vertebrate evolution.

In this work we mathematically model string duplication, and ask several coding-theoretic questions:
1. Is there new information created strictly by duplication? What is the capacity of such systems?
2. Can string duplication account for diversity? Can we reach every possible substring?

We also mention other results concerning probabilistic models, and error-correcting codes. The talk is based on joint works with Ohad Elishco, Farzad Farnoud, Siddharth Jain, and Jehoshua Bruck.

26 באוקטובר 2015, 16:00

חדר 011, בניין כיתות חשמל

EE Seminar: Polar Coded Modulation

~~
Speaker: Peer Berger,
M.Sc. student under the supervision of Prof. Simon Litsyn

Wednesday, October 21, 2015 at 15:30
Room 011, Kitot Bldg., Faculty of Engineering

Polar Coded Modulation

Abstract

Polar codes are the first provably capacity achieving codes for the class of binary-input symmetric discrete memoryless channels with low encoding and decoding complexity.

It is clear that polar codes are very attractive, but up until now most researches considered only the BPSK scenario. Unlike in the BPSK case - where code construction is the major concern, one can divide the general polar coded modulation problem into three major parts - code construction, constellation choosing and decoder choosing. Moreover, in the polar coded modulation case, performance refers to much more than BLER/BER.

This seminar will deal with aspects related to polar coded modulation. It will provide a set of tools and observations that improves the design of currently used polar coded modulation schemes (code construction for a certain constellation, kernel and decoder) that meets ones requirements (error probability, complexity and PAPR). We will do so by answering all three questions above, presenting new ideas, developing new criterions, using new modifications, and most important achieving better performance than known results.

In this seminar, two new labeling choosing criterions will be presented for arbitrary constellation, kernel and decoder, named Genie-Aided Gaussian-Approximation Union-Bound Criterion and Genie-Aided Single-Constellation-Polar-Code Criterion. A significant BLER performance improvement will be shown using those criterions. An error probability and PAPR reduction will be shown using different constellation sizes, APSK schemes and multi-dimensional constellations schemes. A PAPR reduction using APSK schemes, and an error probability and PAPR reduction using multi-dimensional constellations schemes will be presented. A new SCL-SC MLPC decoder that gives similar results to the SCL MLPC decoder with less complexity and a new Mixed-Kernels-MLPC scheme are being used in order to attain a better performance-complexity tradeoff. Finally, a new BIMLPCM decoder concept that potentially has better results than the capacity achieving MLPC decoder will be presented.

21 באוקטובר 2015, 15:30

חדר 011, בניין כיתות חשמל

EE Seminar: Polar Codes Constructing over Binary and Non-Binary Kernels

~~
Speaker: Michael Milkov,
M.Sc. student under the supervision of Prof. Simon Litsyn

Wednesday, October 21, 2015 at 15:00
Room 011, Kitot Bldg., Faculty of Engineering

Polar Codes Constructing over Binary and Non-Binary Kernels

Abstract

Polar codes is a family of codes which was discovered by Arikan. This family is an encoding and decoding scheme that provably achieves channel capacity over the binary symmetric memoryless channels.

This thesis deals with the subject of polar codes constructing.
First of all, we describe the problem. Then, we investigate several methods for constructing polar codes using binary kernels when our focus is on the channel degrading and upgrading approximations proposed by Tal and Vardy. With several modifications we decrease the amount of calculations needed for these algorithms while maintaining their performance.
In addition, lower bounds on bit-error probability were derived as a complementary research to the upper bounds derived by Arikan.

Later, we modify the methods described for the binary case in order to perform code constructing for the non-binary Reed-Solomon 4 kernel. Again, we perform several modifications in order to decrease the amount of calculations while preserving performance. In addition, we formalize the Bhattacharyya parameter recursive relations of the symbol-channels and use them for ranking the quality the symbol-channels. This method also allows to upper bound the block error probability even when its value is too low to attain using a monte-carlo simulation and the degrading approximations.

Finally, we use the methods studied in this thesis for constructing polar codes for non-trivial constellations.

21 באוקטובר 2015, 15:00

חדר 011, בניין כיתות חשמל

Departmental Seminar

Integrated multi-disciplinary studies of applied transition metal oxide interfaces

Dr. Dorian Hanaor

Faculty of Engineering, University of Sydney

21 באוקטובר 2015, 16:00

כיתה 103, בניין וולפסון כיתות

Integrated multi-disciplinary studies of applied transition

סמינר מחלקתי Ariela Aizinshtat

30 בדצמבר 2015, 15:00

וולפסון 206

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סמינר מחלקתי Deborah Sills

28 בדצמבר 2015, 15:00

School of Mechanical Engineering Seminar
Monday, December 28, 2015 at 15:00
Wolfson Building of Mechanical Engineering, Room 206

Green crude or brown crud? Target cultivation and financing parameters for sustainable production of algal biofuel

Deborah Sills

Bucknell University

Production of economically competitive and environmentally sustainable algal biofuel faces technical challenges that are subject to high uncertainties. High operating costs and harmful environmental impacts result primarily from electricity consumption during cultivation of algae. Increases in algal productivity are needed to reduce electricity consumption and improve economic and environmental performances. Here we identify target values for algal productivity and financing conditions required to achieve a biofuel selling price of $5 per gallon gasoline equivalent (GGE) and beneficial environmental impacts. A modeling framework—combining process design, techno-economic analysis, life cycle assessment, and uncertainty analysis—was applied to two conversion pathways: (1) “fuel only”, using hydrothermal liquefaction to produce biofuel, heat and power, and (2) “fuel and feed”, using wet extraction to produce biofuel and defatted algae, which can substitute components of animal and aqua feeds. Our results suggest that with supporting policy incentives, the “fuel and feed” scenario will likely achieve a biofuel selling price of less than $5 per GGE at a productivity of 39 g/m²/day, versus 47 g/m²/day for the “fuel only” scenario. Furthermore, if defatted algae is used to replace fishmeal, the process has a 50 percent probability of reaching $5 per GGE with a base case productivity of 23 g/m²/day. Scenarios with improved economics were associated with beneficial environmental impacts for climate change, ecosystem quality, and resource depletion, but not for human health.

סמינר מחלקתי Prof. Sonia Mogilevskaya

14 בדצמבר 2015, 15:00

וולפסון 206

School of Mechanical Engineering Seminar
Monday, December 14, 2015 at 15:00
Wolfson Building of Mechanical Engineering, Room 206

Lost in Translation: Crack Problems in Different Languages

Sonia Mogilevskaya

Department of Civil Engineering

University of Minnesota

The feeling of “lost in translation” is familiar to everyone who stumbles on a relevant literature source written by someone with a different academic background. It may take a significant effort to “translate” the source and interpret its contents into a familiar “language.” This may happen in various research areas and analysis of crack problems is one of such examples. The methods of analytical or computational crack modeling vary with the academic background of the researcher and with specific applications. In addition, as typically happens in scientific research, the developments in the relevant areas take place simultaneously in different countries, and the results are literally described and published in different languages. Some of those publications are not even translated.

The talk examines major techniques for modeling elastostatic crack problems. The foundations of these techniques and fundamental papers that introduced, developed, and applied them are reviewed. The goal is to provide “translation” between different academic languages that describe the same problem.

Bio. Prof. Mogilevskaya received her PhD in Engineering Mechanics from the Scotchinsky Research Institute of Mining (Russian Academy of Sciences, Moscow) in 1987. She is currently a Research Professor and the Member of Graduate Faculty in the Department of Civil, Environmental, and Geo- Engineering at the University of Minnesota. She has published over 70 archival journal papers and coauthored a chapter in a book on complex hypersingular BEM in plane elasticity problems. She teaches a graduate course on the Boundary Element Methods.

הכינוס המחקרי ה-7 להנדסת תעשיה וניהול 23 לפברואר, 2016

שלוש שנים לאחר הכינוס המחקרי האחרון החלטנו לחזור ולקיימו במתכונתו המקורית, קרי באירוח אחד המוסדות האקדמיים. הכינוס המחקרי הקרוב יתקיים ביום שלישי, 23 בפברואר, 2016, באירוח המחלקה להנדסת תעשייה באוניברסיטת תל-אביב.

קרא עוד אודות הכינוס המחקרי ה-7 להנדסת תעשיה וניהול 23 לפברואר, 2016

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