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Spring 2011

January 21, 2011Benjamin Braaten

Title: High Frequency Amplifier Circuit Modeling

Abstract: This presentation will address small signal and large signal modeling of SiGe Heterojunction Bipolar Transistor (SiGe HBT) based microwave amplifier, to be used for phase noise characterization in the frequency range of 10MHz → 6GHz. The large signal model includes high frequency models of passive components, microstrip and SMA connector. The predictive model’s capabilities were validated with measured and simulated output power and S-Parameters. The results indicated that large signal amplifier model was successfully developed in Ansoft Designer (AD). The AD model can be used for analyzing additive phase noise (phase and thermal) at various input power to the microwave amplifier operating under a large-signal condition. With this model the measured and simulated phase noise can be compared for various DC bias, RF input signal frequency and power level.

February 4, 2011Dr. Anne Denton, guest of Samee Khan

Title: Data Mining of Complex Scientific Data

Abstract: Data Mining has established itself as a discipline for analyzing data that are too complex and / or too large for conventional statistics or machine learning techniques. While many data mining algorithms have been developed that use ad hoc measures of interestingness, science and engineering applications require that results can be justified based on rigorous statistical measures. This presentation will focus on work to identify patterns between sets of continuous attributes and one or more binary attributes. These patterns are, for example, of interest in combinatorial chemistry experiments, in which binary attributes can be used to characterize sample composition, and multiple experimental observations are recorded for each sample. Other applications include experiments on gene deletion mutants in microbiology. The presentation will conclude with an overview of other work on data mining of complex data performed in my research group.

Speaker bio: Anne Denton is Associate Professor in the Computer Science Department at North Dakota State University (NDSU). She received her Ph.D. in Physics from the Johannes Gutenberg University, Mainz, Germany, in 1996 and a M.S. in Computer Science from NDSU in 2003. Her research interests are in data mining of diverse scientific data sets that are too complex to be analyzed using classical statistics or machine learning techniques, and for which rigorous significance evaluations are required. She works with collaborators in plant sciences, microbiology, and the chemistry of coatings.

March 4, 2011Cristinel Ababei

Title: Energy- and reliability-aware mapping for Networks-on-Chip

Abstract: The problem of energy consumption and reliability oriented application mapping on regular Network-on-Chip topologies is formulated. A novel branch-and-bound based algorithm to solve this problem is proposed. Reliability is estimated by an efficient Monte Carlo algorithm based on the destruction spectrum of the network. Simulation results demonstrate that network reliability can be improved without sacrificing much of energy consumption.

March 25, 2011Ravi Thapa, guest of Rajesh Kavasseri

Title: Damping intr area oscillations in power systems with DFIGs

Abstract: With rapid depletion of fossil fuels and increasing environmental concerns, the trend to capture renewable energy, especially through wind energy resources is increasing. Doubly fed induction generator (DFIG) is the most widely used generator for wind energy conversion because of its various advantages over other types of generators. In a DFIG, the rotor is fed through back to back converters via slip rings. The converters enable the generation control. This control property can be used to support the reliable operation of a network system.

Inter-area oscillations have been a major factor in limiting power transfers in interconnected power systems. Poorly damped modes can trigger oscillatory instability potentially leading to cascading blackouts in such systems. We consider a two-area system where DFIG based wind generation is integrated with conventional synchronous generators. A simple controller is proposed for DFIG to improve the damping of inter-area oscillations. To support the proposition case studies are conducted in Matlab/Simulink. The effectiveness of the proposed controller is then analyzed by eigen-value analysis and verified with time domain simulation results. The results show that a properly tuned controller can increase the damping of the dominant oscillatory mode by nearly 5% while improving the area transfer by about 300 MW.

April 1, 2011Dr. Cosme Rubio, Visiting Faculty

Title: The Finite Element Method in Photonic

Abstract: In recent years, advances in the fields of near-field optics, nanoscale manufacturing, transportation and confinement of light in regions smaller than the wavelength has resulted in the emergence of new areas of research in nanophotonics and plasmonics. The numerical technique of the 2D Finite Element Method (2D-FEM) is introduced with differential equations that govern electromagnetic waves propagation in Photonic Structures. To demonstrate the applicability the method, several numerical examples are presented.

April 15, 2011Kai Johnson, guest of Roger Green

Title: Accounting for Long Duration Transients

Abstract: Measuring impedance of an object can reveal a number of useful details about said object. However, when the object has a particularly large impedance it will also have a proportionally long transient. In the case where the transient exists for longer than the measurement duration the accuracy of the measurement is effected. This presentation will address a method that will minimize the effect of this transient has on the accuracy of the impedance measurement.

April 29, 2011Dr. David W. Matolak, guest of Hongxiang Li

Title: Modeling Wireless Channels: Some Basics, and New Results for Severe Fading and Statistical Non-Stationarity

Abstract: The wireless propagation channel is typically the most challenging element facing reliable communication in many communication systems today. Both large-scale propagation path loss, and small-scale (multipath) fading can render the received signal either too weak, or too distorted for reliable message transfer. Although wireless channels in various environments and in various frequency bands have been studied for decades, this is still an active area of research because of the growth (and breadth) of wireless applications [1]. A larger user population, higher data rates, and connectivity over larger areas all require that accurate models for the channel be available for system analysis, design, and development. In this talk, we first review some fundamentals of propagation, and the most common method for modeling wireless channels: linear, time-varying filters [2]. These models are nearly always stochastic, for two reasons: (1) the propagation environment for most terrestrial applications is too complex to efficiently model deterministically, particularly for mobile channels, and; (2) the random models have both theoretical and empirical support, and are relatively easy to use. We will present some common models for cellular and satellite communication to illustrate the use of such models. We then describe some recent findings that are being studied to produce even more accurate models for use in future system design. These findings include severe fading, and statistical non-stationarity [3]. Severe fading is any type of fading that yields amplitude statistics that are worse than Rayleigh statistics: in short, the probability of a deep fade is larger than if fading were Rayleigh. Statistical non-stationarity means that the channel’s statistics change over time (equivalently, over space), which, while seemingly obvious, has not been employed in channel modeling until recently [4]. We describe conditions for stationarity, and applications where non-stationarity must be modeled for sufficient accuracy. Finally, we also provide some recent results from our work with the National Institute of Standards & Technology, Boulder, Colorado, where we measured and modeled urban and indoor-outdoor channels in the public safety frequency bands, for use in future emergency responder communication systems.

[1] J. D. Parsons, The Mobile Radio Propagation Channel, 2nd ed., John Wiley & Sons, New York, NY, 2000.

[2] P. Bello, “Characterization of Random Time-Variant Linear Channels,” IEEE Trans. Comm., vol. 11, pp. 360-393, December 1963.

[3] D. W. Matolak, “Channel Modeling for Vehicle-to-Vehicle Communications,” IEEE Communications Magazine, vol. 46, no. 5, pp. 76-83, May 2008.

[4] G. Matz, "On Non-WSSUS Wireless Fading Channels," IEEE Trans Wireless Comm., vol. 4, no. 5, pp. 2465-2478, Sept. 2005.

Speaker bio: David W. Matolak is a professor in the School of Electrical Engineering and Computer Science at Ohio University, where he has been a faculty member since 1999. He has approximately 20 years of experience working on various types of communication systems, including work experience with private industry (AT&T Bell Laboratories, L3 Communications, and Lockheed Martin Telecommunications) federal government organizations (Rural Electrification Administration, MITRE Corp.), and academia. Dr. Matolak received the B.S. degree from The Pennsylvania State University in 1983, the M.S. degree from The University of Massachusetts in 1987, and the Ph.D. degree from The University of Virginia in 1995, all in electrical engineering. His areas of expertise and current interest are tatistically non-stationary wireless channel measurement and modeling, ad hoc networking, spread-spectrum and multicarrier wireless transmission, and aeronautical communications. While at Ohio University, he has conducted sponsored research for multiple organizations, including NASA, the NSF, the Air Force/DARPA, the NIST, and the FAA. He has also consulted for several industries, and was a guest researcher at the NIST Boulder Laboratories in summer 2009, and the University of Malaga, Spain, in June 2010. He has also given over a dozen invited presentations. Dr. Matolak is a member of Eta Kappa Nu and Sigma Xi. He has served on dozens of IEEE Conference Technical Program committees and was also Chair of the Geo Mobile Radio Standards group in the Telecommunications Industries Association’s (TIA’s) Satellite Communications Division. He has published several book chapters, more than 70 refereed articles, more than 50 technical reports and other conference papers, more than 45 industry technical reports, and has 8 patents. He is a Senior Member of IEEE and an Associate Editor for the IEEE Transactions on Vehicular Technology.

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