You are invited to attend a lecture

By

Dr. Alex Ruderman, Associate Professor

Department of Electrical and Electronic Engineering, School of Engineering, Nazarbayev University Kabanbay Batyr Ave 53 Astana, Kazakhstan 010000.

Phone +7-7172-709146

Email alexander.ruderman@nu.edu.kz

On the subject:

Time Domain Analysis of Multilevel Converter Voltage and Current Quality

Today power electronics community is biased towards frequency domain analysis of PWM phenomena. The seminar goal is to show that time domain averaging methods are more adequate for certain integral problems that don't require a specific knowledge of individual harmonics. The power of time domain analysis is demonstrated while elaborating voltage and current quality in multilevel inverters for PWM and staircase (step) modulation. For relatively high frequency PWM, the solution is obtained under the asymptotic assumption – a switching frequency is supposed much higher than a fundamental one. The closed-form asymptotic solution for an arbitrary voltage level count involves only elementary functions and, in fact, presents voltage quality upper bound for nearest level PWM. The asymptotic solution is practically very accurate for relatively high switching-to-fundamental frequency ratios (>25-30). For staircase modulation, voltage and current optimal quality (minimal Total Harmonic Distortion - THD) problems are formulated in time domain as constrained optimization ones. Optimal switching angles that minimize voltage and current THD accounting for all switching harmonics are found using numerical optimization for different inverter level counts and the whole modulation index range 0<M<1. Suggested are simple voltage and current THD ripple-free approximations for arbitrary level counts and modulation indices. While these simple hyperbolic formulas accurately approximate the average trend, local maxima and minima of voltage and current THD may be addressed on separate. The obtained current THD is actually frequency weighted THD that assumes inductance dominated RL-load. For grid-connected applications, normalized current fundamental harmonic is smaller than voltage modulation index and current THD will be larger than frequency weighted voltage one.

1 January 2014, at 15:00,

Room 011, Kitot Building

You are invited to attend a lecture

By

Dr. Ido Kaminer, MIT

On the subject:

Quantum Theory of Čerenkov Radiation, 

Spectral Cutoff and Resonances

When a charged particle travels faster than the phase velocity of light in a medium, it produces Čerenkov radiation. We show that the Čerenkov Effect contains new phenomena arising from the quantum nature of a charged particle. Specifically, with proper design of particle wavepacket, we predict the traditional Čerenkov radiation angle splits into two distinctive cones of photonic shockwaves. One of the shockwaves can move along a backward cone, otherwise considered impossible for Čerenkov radiation in ordinary matter. More importantly, and more generally, the spectral response reveals an upper frequency cutoff at which the photon emission rate is diverging – manifesting a new resonant light-matter interaction. The origins of the major deviations from the known understanding of the Čerenkov effect are the nonlinear nature of the interaction, and its spatial extent that exceeds the wavelength of the emitted radiation. Importantly, our findings are observable for electron beams with realistic parameters, offering new applications including coherent x-ray sources and open a new realm for Čerenkov detectors.

25 December 2014, at 15:00,

Room 011, Kitot Building

School of Mechanical Engineering Seminar
Wednesday, January 14, 2014 at 15:00
Wolfson Building of Mechanical Engineering, Room 206

MicroRobotics and NanoMedicine

Prof. Brad Nelson

Institute of Robotics and Intelligent Systems

ETH Zurich

Switzerland

While the futuristic vision of micro and nanorobotics is of intelligent machines that navigate throughout our bodies searching for and destroying disease, we have a long way to go to get there. Progress is being made, though, and the past decade has seen impressive advances in the fabrication, powering, and control of tiny motile devices. Much of our work focuses on creating systems for controlling micro and nanorobots as well as pursuing applications of these devices. As systems such as these enter clinical trials, and as commercial applications of this new technology are realized, radically new therapies and uses will result that have yet to be envisioned.

About the speaker:

Brad Nelson received mechanical engineering degrees from the University of Illinois (B.S. 1984) and the University of Minnesota (M.S. 1987), and a Ph.D. in Robotics (School of Computer Science) from Carnegie Mellon University (1995). He has been the Professor of Robotics and Intelligent Systems at ETH Zürich since 2002 and has received a number of awards for his work in robotics, nanotechnology, and biomedicine. He serves on the advisory boards of a number of academic departments and research institutes across North America, Europe, and Asia and is on the editorial boards of several academic journals.

Prof. Nelson has been the Department Head of Mechanical and Process Engineering at ETH, Chairman of the ETH Electron Microscopy Center, and is a member of the Research Council of the Swiss National Science Foundation. He is a member of the board of directors of three Swiss companies.

Before moving to Europe, Prof. Nelson worked as an engineer at Honeywell and Motorola and served as a United States Peace Corps Volunteer in Botswana, Africa. He has also been a professor at the University of Minnesota and the University of Illinois at Chicago.