הפקולטה להנדסה ע"ש איבי ואלדר פליישמן

8.2.15

08 בפברואר 2015, 15:00

Kitot 011

Physical Electronics Dept. SEMINAR

***** Seminar *****

You are invited to attend a lecture

Nir Atzmon

(Msc. student under the supervision of Prof. Eshel Ben-Jacob and Prof. Avraham Gover)

School of Electrical Engineering, Tel-Aviv University, Tel-Aviv 69978, Israel

Real-Time feedback stimulator for investigating neuroplasticity in cultured networks

In-vitro neuronal cultures offer exciting possibilities for studying neuronal information coding and processing. A network level approach is necessary to fully understand information processing in the brain, as every function in the human brain employs correlated activities of large populations of neurons. It was shown that synaptic plasticity plays a crucial role in the synchronized behavior of the network, and therefore investigating neuroplasticity in cultured networks may yield new insight as to the functions of neuronal circuits in the brain. While much is known on the cellular mechanism underlying synaptic plasticity, making the leap from the cellular level to the network level is far from trivial. Previous studies aimed at uncovering the dynamics governing network plasticity have used open-loop assays to study the response of neuronal networks to external stimulation by combining electrical stimulation of cultured networks on multi-electrode arrays, in conjunction with extracellular recording.

In this work we developed a closed-loop assay for investigating neuroplasticity in cultured networks. The assay makes use of a real-time feedback stimulator (RTFS) that responds to network activity within a few milliseconds and is both generic and easily modified to suit different experimental setups. In order to demonstrate the potential of such a system in the study of network plasticity, we used the RTFS to generate electrical stimulation to the network based on real-time detection of spontaneous burst patterns and were able to show a decrease in inter-burst correlation, indicating attenuation of the synchronized activity of the network. These findings imply that similar closed loop assays can be used in the study of network-level plasticity, and a generic system, such as the one presented here, can open up a wide range of research possibilities, for example in the study of epilepsy.

Sunday, February 8, 2015, at 15:00

Room 011, EE- KITOT building

EE Seminar: Guy Nadav

~~
Guy Nadav,
M.Sc. student under the supervision of Prof. Nahum Kiryati and Dr. Dafna Ben-Bashat

Monday, February 16, 2015 at 15:00
Room 011, Kitot Bldg., Faculty of Engineering

Pharmacokinetics Parameters Estimation from MRI

Abstract

We consider the problem of estimating the underlying anatomical structure and dynamics in brain pathologies from a set of 3-D images of the brain following the injection of a contrast agent, acquired using a Magnetic Resonance Imaging (MRI) method. The goal is to produce quantitative clinically relevant maps of the brain that can help in the assessment of neurological pathologies such as disruption of the Blood-Brain-Barrier (BBB) in a tumor, decrease of blood flow in a stroke etc.
To do that, a contrast agent (Gadolinium) is injected to a subject and temporal tracing of its concentration in the brain is conducted. Dynamic contrast-enhanced MRI (DCE-MRI) is a functional MRI method that enables temporal tracing, where -weighted MR images are acquired dynamically after bolus injection of a contrast agent. The brain tissue effect on the measured contrast agent concentration over time (concentration-time-curve), is modelled as an Impulse Response Function (IRF). The IRF is parameterized by Pharmacokinetics (PK) parameters that represent physiological characteristics, and explain the change in the concentration-time-curve from artery to tissue voxel.
This work describes the entire process of deriving pharmacokinetics parameters from an MRI signal, and suggests novel techniques for handling estimation issues originating from the problem of accurately measuring concentration-time-curve in every voxel of the brain. We first present a few possible brain models, then describe the work that has been previously done and continue by suggesting improvements to the pharmacokinetics parameters estimation. The estimation process was tested in simulation and on data acquired from patients.
The proposed optimization method, denoted ACoPeD (AIF-Corrected-Perfusion-DCE-MRI), showed significant correlation (r=0.46, p<0.001) between flow parameter extracted from DCE-MRI and DSC-MRI (a commonly used perfusion MRI method) in patients, and is applicable in clinical settings.
In conclusion, this study proposes an optimized method, ACoPeD for tissue perfusion and permeability estimation using DCE-MRI, which is applicable in clinical settings, and includes recommendations for DCE-MRI data acquisition and analysis.

16 בפברואר 2015, 15:00

חדר 011, בניין כיתות-חשמל

EE Seminar: Mor Cohen

~~
Mor Cohen,
M.Sc. student under the supervision of Prof. Yoel Shkonisky and Prof. Arie Yeredor

Monday, February 16, 2015 at 15:30
Room 011, Kitot Bldg., Faculty of Engineering

Detecting Common Lines In Cryo-EM Images Using Maximum Likelihood

Abstract

The reconstruction of three dimensional structures from Cryo-EM images is often based on the “Angular Reconstitution” method in which a coordinate system is established from three projections, and the orientation of the particle in each image is deduced from common lines shared among the images. Detecting these common lines is usually performed by first denoising the images, which takes advantage of the large number of available images to improve their SNR, followed by computing correlations between radial lines in the images. This work presents a maximum likelihood (ML) algorithm for detecting common lines that takes advantage of the highly redundant data in a different way. The algorithm is based on a global iterative detector in which we jointly estimate and classify common lines using the data from all projection images. We demonstrate by simulations that the algorithm improves the detection rate of common lines compared to state of the art methods, and operates well even with non-white imaging noise.

16 בפברואר 2015, 15:30

חדר 011, בניין כיתות-חשמל

Seminar 1.2.15

01 בפברואר 2015, 14:00

Room 101, Computer and Software Engineering building

You are invited to attend a lecture

Lihi Shiloh

(MSc. student under the supervision of Prof. Avishay Eyal)

School of Electrical Engineering, Tel-Aviv University, Tel-Aviv 69978, Israel

Optical fiber sensing via Optical Fractional Fourier transform Reflectometry (OFFR)

Fiber-optic sensing is a highly promising technology for a variety of applications, ranging from biomedical sensing to structural health monitoring. In the field of Distributed Acoustic Sensing (DAS) there is a growing demand for a fiber optic sensing system that can provide fast scan rates over long distances with high spatial resolution and high sensitivity. Among the various approaches for implementing DAS, methods based on Rayleigh backscattering standout as practical and affordable solutions due to the use of a conventional communication fiber as the sensing element and the simplicity of the interrogation scheme. There are two main approaches: The first approach is Optical Time Domain Reflectometry (OTDR) in which the interrogation waveform is a short pulse and the detected light is analyzed in the time domain. The second approach is Optical Frequency Domain Reflectometry (OFDR) where the interrogation waveform is linearly chirped and the received reflections are mixed with a reference and analyzed in the frequency domain.

Recently we introduced a new interrogation method, the Optical Fractional Fourier transform Reflectometry (OFFR). It enables interrogation of distant sections of the fiber with a high scan rate and enhanced spatial resolution. It is similar to OFDR but the frequency sweep period has both positive and negative slopes. Under certain conditions the frequency variations of the backscattered light from distant reflectors and the reference light have opposite slopes. In such cases the beat signal at the receiver output will have a component whose instantaneous frequency varies linearly in time. There is a variety of methods to detect such a linearly chirped signal buried in measured data. Here we describe the use of the Fractional Fourier Transform (FrFT) to that end. We present theoretical formulation of the method and its limitations, numerical simulation of its performance in comparison with OFDR and a static, as well as dynamic, experimental results.

Sunday, February 1, 2015, at 14:00

Room 101, Computer and Software Engineering building

EE Seminar: Gilad Kahala

~~Gilad Kahala
M.Sc. student under the supervision of Dr. Hedva Spitzer and Prof. Shai Avidan

Wednesday, March 4, 2015 at 15:00
Room 011, Kitot Bldg., Faculty of Engineering

Multi Scale Blood Vessels Detection and Segmentation in Breast MRI

A method is proposed to perform segmentation of blood vessels in 3D breast MRI. The blood vessels play an essential role as an additional tool to detect tumors. Radiologists use a maximum intensity projection for the understanding of vasculature. The breast is a challenging organ in detecting vascular structures, because of noise and fat tissues. There are several existing algorithms for the detection of blood vessels in MRI images, but these usually prove insufficient when it comes to the breast. Our algorithm provided a 3-dimensional model of the blood vessels by utilizing texture enhancement followed by hessian-based methods. In addition to this, we tackled blood vessel completion by employing center line tracking, where the seeds are the end points of detached blood vessels found through skeletonizing. The results were compared to the manually segmented golden models defined by radiologist in 20 different patients, which yielded an 88.73% match to the ground truth with 13.63% false positives. It appears that with the application of mass detection as the last step, our algorithm provides a helpful tool for tumor enhancement and an automated detection of breast cancer.

04 במרץ 2015, 15:00

חדר 011, בניין כיתות-חשמל

Seminar 29.1.14

29 בינואר 2015, 14:00

Kitot 011

Physical Electronics Dept. SEMINAR

***** Seminar *****

You are invited to attend a lecture by:

Prof. Nader Engheta

H. Nedwill Ramsey Professor

University of Pennsylvania

Philadelphia, PA 19104, USA

On the subject:

Metastructures for Manipulating Light-Matter Interaction

Abstract

In this talk, I will give an overview of some of our ongoing research activities in the areas of metamaterials, metasystems, and nanoscale optics. I will discuss some of the following topics: (a) the extreme-parameter nanophotonics, (b) nanomaterials that perform mathematical operations (nanoscale analog computers), (c) nonreciprocal nanostructures for unusual flow of photons, (d) metamaterial “bits” and “bytes” as building blocks for digital metamaterials, and (e) graphene photonics, to name a few. In my group we are exploring new classes of phenomena and potential applications in engineering functional metastructures. I will present our latest results, and forecast future directions and possibilities.

Thursday, 29 January 2015 at 14:00

Room 011, Kitot Build.

29.1.15

29 בינואר 2015, 15:00

011 Kitot

Paul C. McIntyre

Professor and Department Chair, Materials Science and Engineering, Stanford University, Stanford, CA

On the subject:

Nanoscale Photonic and Photo-Electrochemical Behavior of Group IV Semiconductor Structures

This talk will summarize recent work from our group on two topics 1) photo-generated carrier dynamics in single crystal germanium nanowire arrays, and 2) the application of atomic layer deposition to protect silicon absorbers from corrosion during water splitting, while simultaneously provided good electrical connection to an overlying catalyst layer. The first topic is related to future application of germanium nanostructures in integrated photonics. The second has applications in renewable synthesis of fuels and chemicals.

Thursday, 29 January 2015 at 15:00

Room 011, Kitot Build.

פרוייקטים שנה ד' הנדסת תעשיה

קרא עוד אודות פרוייקטים שנה ד' הנדסת תעשיה

EE Seminar: Gilboa Levy

~~Gilboa Levy,
M.Sc. student under the supervision of Prof. Shai Avidan

Wednesday, March 11, 2015 at 15:00
Room 011, Kitot Bldg., Faculty of Engineering

Predicting Trajectories in Video Sequences by Motion Regularity

Abstract

We address the problem of object tracking in video sequences. We explore the regularity in the world to provide context for object tracking in video sequences. Many motions are repetitive and we would like to use this prior knowledge to improve our tracker. Our approach builds a database of tracklets - short tracking segments over time - and uses it to generate a prior for the tracking process. Specifically, we use the current tracklet (i.e., the track over the last few frames) as a query into a database of tracklets and use the top matches to predict where the object should move to next. This extends existing methods for adding context to tracking that only use tracklets that occur at the same time as the query tracklet. In our formulation, every tracklet that was ever recorded can be used to help predict the motion of the current object. We demonstrate the proposed method on several sequences.

11 במרץ 2015, 15:00

סמינר מחלקתי Mark Baevsky and Ofir Gilad

25 במרץ 2015, 15:00

וולפסון 206

סמינר מחלקתי Mark Baevsky and Ofir Gilad

School of Mechanical Engineering Seminar

Wednesday, March 25, 2015 at 15:00
Wolfson Building of Mechanical Engineering, Room 206

Evolution of a turbulent patch in dilute polymer solutions

Baevsky Mark

M.Sc. Student of Prof. Alex Liberzon

Drag reduction effect by dilute polymer solutions was discovered in 1946 by Toms, but the basic mechanisms by which polymers modify the turbulent flow have not been understood thoroughly, despite the progress in understanding the drag reduction in pipes or channels. One of the main problems is relatively poor understanding of dilute polymer solutions and inter-scale transfer of energy in turbulent flows. The problem intensifies in the case of turbulent entrainment across turbulent/non-turbulent interfaces on the boundaries of turbulent jets, wakes or mixing layers. The polymer is sought to alter this region of flow significantly due to the large gradients at the interface and strong interaction of multiple scales - large scales that deflect the interface and the small scales that diffuse the vorticity and strain. There is however no detailed experimental studies devoted to the interfaces and the numerical simulations that use polymer models (such as Oldroyd-B or FENE-P) require a solid empirical background for comparison.

An experimental study has been performed to characterize the basic mechanisms of turbulent entrainment in water - poly(ethylene oxide) solutions, alongside the benchmark case of the fresh water. A new experimental setup was developed to create a spherical localized turbulent patch, thus isolating the polymer effect far from the boundaries with negligible wall friction effects, as opposed to the previously utilized 2D space-filling planar oscillating grids. The setup enables a direct comparison of the results with the direct numerical simulations. We performed a large set of particle image velocimetry (PIV) measurements. The patch life cycle comprises of three phases: initial growth, a steady state and the decay phase after the forcing have ceased. The direct polymer effect is in every stage, from a reduced growth rate, to monotonically decreasing energy levels at steady state and a reduced decay rate, with increasing polymer concentration (0 ppm is a freshwater benchmark case).

From enstrophy fields we could deduce the position of the sharp interface between the turbulent patch and its surrounding fluid. We observe a smaller patch, much smoother interface and the depletion of the length scales separation. An algorithm for patch interface detection is proposed and successfully applied to the PIV measurements, revealing the change in energy transfer towards and across the interface, along with additional physical measures of the patch evolution. The results will be used in developing an improved models of turbulent entrainment and possibly implemented in the applications that require a precise control of localized mixing rates.

School of Mechanical Engineering Seminar
Wednesday, March 25, 2015 at 15:00
Wolfson Building of Mechanical Engineering, Room 206

A Hyperelastic Micromechanical Model for Biocomposite Material:

Collagen Fiber in Alginate Matrix

Ofir Gilad

MSc Student of Prof. Rami Haj-Ali and Prof. Yehuda Benayahu

Soft tissues are biocomposite materials formed by biological matrix and fibers. Developing novel Biocomposite that will provide appropriate mimic of native tissues can have many practical uses in medicine. Tailoring the mechanical properties of the developed biocomposite for a certain use requires an accurate material model.

The purpose of this research is to find a material model for a biocomposite system of Alginate hydrogel matrix reinforced with Collagen fibers of coral origin.

The material model is a hyperplasic micromechanical one which describes the strain energy density of the system as a function of the volume fracture of the fibers.

In order to find the model for the system, the mechanical properties of the fibers in tension were characterized by conducting tensile experiments. The stress strain curve from the experiments was used for adjusting a hyperelastic model for the fibers. Tensile experiments for the matrix, taken from other research, were used for adjusting both linear and hyperelastic models for the matrix.

These material models for the fiber and matrix were implemented in final element model of unit cell in order to characterize the behavior of the material as a homorganic material in tension. Such unit cells, in deferent volume fracture of the fiber were modeled and the stress strain curve from each one was recorded

For every curve, a hyperelastic model was adjusted and the constants of the models were generalized in order to get to general models for the bio-composite material as a function of the fibers volume fracture. The two models show good agreement with experimental results of tensile tests conducted on the biocomposite.

עמודים