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Publication Open Access A new RIS architecture with a single power amplifier: energy efficiency and error performance analysis(Institute of Electrical and Electronics Engineers (IEEE), 2022) Alexandropoulos, George C.; Department of Electrical and Electronics Engineering; Başar, Ertuğrul; Taşçı, Recep Akif; Kılınç, Fatih; Faculty Member; Master Student; Researcher; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; 149116; N/A; N/AMany electrochemical devices are based on the fundamental process of ion migration and accumulation on surfaces. Complex interplay of molecular properties of ions and device dimensions control the entire process and define the overall dynamics of the system. Particularly, for ionic liquid-based electrolytes it is often not clear which property, and to what extent, contributes to the overall performance of the device. Herein we use X-ray photoelectron spectroscopy (XPS) while the device is under electrical bias. Such a procedure reveals localized electrical potential developments, through binding energy shifts of the atomic core levels, in a chemically specific fashion. Combining it with square-wave AC modulation, the information can also be extended to time domain, and we investigate devices configured as a coplanar capacitor, with an ionic liquid as the electrolyte, in macro-dimensions. Our analysis reveals that a nonlinear voltage profile across the device emerges from spatially non-uniform electrical double layer formation on electrode surfaces. Interestingly the coplanar capacitor has an extremely slow time response which is particularly controlled by IL film thickness. XPS measurements can capture the ion dynamics in the tens of seconds to microseconds range, and reveal that ionic motion is all over the device, including on metallic electrode regions. This behavior can only be attributed to motion in more than one dimension. The ion dynamics can also be faithfully simulated by using a modified PNP equation, taking into account steric effects, and device dimensions. XPS measurements on two devices with different dimensions corroborated and validated the simulation results. The present results propose a new experimental approach and provide new insights into the dynamics of ions across electrochemical devices.Publication Open Access A queueing-theoretical delay analysis for intra-body nervous nanonetwork(Elsevier, 2015) Department of Electrical and Electronics Engineering; Abbasi, Naveed Ahmed; Akan, Özgür Barış; Faculty Member; Department of Electrical and Electronics Engineering; College of EngineeringNanonetworks is an emerging field of study where nanomachines communicate to work beyond their individual limited processing capabilities and perform complicated tasks. The human body is an example of a very large nanoscale communication network, where individual constituents communicate by means of molecular nanonetworks. Amongst the various intra-body networks, the nervous system forms the largest and the most complex network. In this paper, we introduce a queueing theory based delay analysis model for neuro-spike communication between two neurons. Using standard queueing model blocks such as servers, queues and fork-join networks, impulse reception and processing through the nervous system is modeled as arrival and service processes in queues. Simulations show that the response time characteristics of the model are comparable to those of the biological neurons.
Publication Metadata only A reliable and efficient procedure for oscillator PPV computation, with phase noise macromodeling applications(IEEE-Inst Electrical Electronics Engineers Inc, 2003) Roychowdhury, J; Department of Electrical and Electronics Engineering; Demir, Alper; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 3756The main effort in oscillator phase noise calculation and macromodeling lies in computing a vector function called the perturbation projection vector (PPV). Current techniques for PPV calculation use time-domain numerics to generate the system's monodromy matrix, followed by full or partial eigenanalysis. We present superior methods that find the PPV using only a single linear solution of the oscillator's time- or frequency-domain steady-state Jacobian matrix. The new methods are better suited for implementation in existing tools with harmonic balance or shooting capabilities (especially those incorporating "fast" variants), and can also be more accurate than explicit eigenanalysis. A key advantage is that they dispense with the need to select the correct one eigenfunction from amongst a potentially large set of choices, an issue that explicit eigencalculation-based methods have to face. We illustrate the new methods in detail using LC and ring oscillators.Publication Open Access A silicon photonic data link with a monolithic erbium-doped laser(Nature Publishing Group (NPG), 2020) Li, Nanxi; Xin, Ming; Su, Zhan; Singh, Neetesh; Notaros, Jelena; Timurdoğan, Erman; Purnawirman, Purnawirman; Bradley, Jonathan D.B.; Watts, Michael R.; Department of Electrical and Electronics Engineering; Mağden, Emir Salih; Department of Electrical and Electronics Engineering; College of Engineering; 276368To meet the increasing demand for data communication bandwidth and overcome the limits of electrical interconnects, silicon photonic technology has been extensively studied, with various photonics devices and optical links being demonstrated. All of the optical data links previously demonstrated have used either heterogeneously integrated lasers or external laser sources. This work presents the first silicon photonic data link using a monolithic rare-earth-ion-doped laser, a silicon microdisk modulator, and a germanium photodetector integrated on a single chip. The fabrication is CMOS compatible, demonstrating data transmission as a proof-of-concept at kHz speed level, and potential data rate of more than 1 Gbps. This work provides a solution for the monolithic integration of laser sources on the silicon photonic platform, which is fully compatible with the CMOS fabrication line, and has potential applications such as free-space communication and integrated LIDAR.Publication Metadata only A tree-weighting approach to sequential decision problems with multiplicative loss(Elsevier, 2011) Singer, Andrew C.; Bean, Andrew J; Department of Electrical and Electronics Engineering; Kozat, Süleyman Serdar; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 177972In this paper, we consider sequential decision problems in which the decision at each time is taken as a convex-combination of observations and whose performance metric is multiplicatively compounded over time. Such sequential decision problems arise in gambling, investing and in a host of signal processing applications from statistical language modeling to mixed-modality multimedia signal processing. Using a competitive algorithm framework, we construct sequential strategies that asymptotically achieve the performance of the best piecewise-convex strategy that could have been chosen by observing the entire sequence of outcomes in advance. Using the notion of context-trees, a mixture approach is able to asymptotically achieve the performance of the best choice of both the partitioning of the space of past observations and convex strategies within each region, for every sequence of outcomes. This performance is achieved with linear complexity in the depth of the context-tree, per decision. For the application of sequential investment, we also investigate transaction costs incurred for each decision. An explicit algorithmic description and examples demonstrating the performance of the algorithms are given. Our methods can be used to sequentially combine probability distributions produced by different statistical language models used in speech recognition or natural language processing and by different modalities in multimedia signal processing.Publication Metadata only Accurate prediction of random telegraph noise effects in srams and drams(IEEE-Inst Electrical Electronics Engineers Inc, 2013) Aadithya, Karthik V.; Venugopalan, Sriramkumar; Roychowdhury, Jaijeet; Department of Electrical and Electronics Engineering; Demir, Alper; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 3756With aggressive technology scaling and heightened variability, circuits such as SRAMs and DRAMs have become vulnerable to random telegraph noise (RTN). The bias dependence (i.e., non-stationarity), bi-directional coupling, and high inter-device variability of RTN present significant challenges to understanding its circuit-level effects. In this paper, we present two computer-aided design (CAD) tools, SAMURAI and MUSTARD, for accurately estimating the impact of non-stationary RTN on SRAMs and DRAMs. While traditional (stationary) analysis is often overly pessimistic (e. g., it overestimates RTN-induced SRAM failure rates), the predictions made by SAMURAI and MUSTARD are more reliable by virtue of non-stationary analysis.Publication Metadata only Active control of focal length and beam deflection in a metallic nanoslit array lens with multiple sources(Optical Soc Amer, 2010) Department of Electrical and Electronics Engineering; Department of Physics; Department of Physics; Çetin, Arif Engin; Güven, Kaan; Müstecaplıoğlu, Özgür Esat; Master Student; Faculty Member; Faculty Member; Department of Electrical and Electronics Engineering; Department of Physics; College of Engineering; College of Sciences; College of Sciences; N/A; 52290; 1674We propose an all-optical method to actively control the transmission of nanoslit arrays for scanning and lensing applications. We show that by utilizing two lateral control slits, the transmitted beam can be actively steered. (C) 2010 Optical Society of AmericaPublication Metadata only Adaptation strategies for MGS scalable video streaming(Elsevier, 2012) N/A; Department of Electrical and Electronics Engineering; Görkemli, Burak; Tekalp, Ahmet Murat; N/A; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; College of Engineering; N/A; 26207An adaptive streaming framework consists of a video codec that can produce video encoded at a variety of rates, a transport protocol that supports an effective rate/congestion control mechanism, and an adaptation strategy in order to match the video source rate to the available network throughput. The main parameters of the adaptation strategy are encoder configuration, video extraction method, determination of video extraction rate, send rate control, retransmission of lost packets, decoder buffer status, and packetization method. This paper proposes optimal adaptation strategies, in terms of received video quality and used network resources, at the codec and network levels using a medium grain scalable (MGS) video codec and two transport protocols with built-in congestion control, TCP and DCCP. Key recommendations are presented to obtain the best results in adaptive video streaming using TCP or DCCP based on extensive experimental results over the Internet. (c) 2012 Elsevier B.V. All rights reserved.Publication Metadata only Adaptive streaming of multi-view video over P2P networks(Elsevier, 2012) Ekmekçioğlu, Erhan; Worrall, Stewart; Kondoz, Ahmet; N/A; N/A; Department of Electrical and Electronics Engineering; Savaş, Saadet Sedef; Gürler, Cihat Göktuğ; Tekalp, Ahmet Murat; PhD Student; PhD Student; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; 26207In this paper, we propose a novel solution for the adaptive streaming of 3D representations in the form of multi-view video by utilizing P2P overlay networks to assist the media delivery and minimize the bandwidth requirement at the server side. Adaptation to diverse network conditions is performed regarding the features of human perception to maximize the perceived 3D. We have performed subjective tests to characterize these features and determined the best adaptation method to achieve the highest possible perceived quality. Moreover, we provide a novel method for mapping from scalable video elementary stream to torrent-like data chunks for adaptive video streaming and provide an optimized windowing mechanism that ensures timely delivery of the content over yanlis gibi. The paper also describes techniques generating scalable video chunks and methods for determining system parameters such as chunk size and window length.Publication Open Access Adaptive time resolved mass spectrometry with nanomechanical resonant sensors(Institute of Electrical and Electronics Engineers (IEEE), 2021) Department of Electrical and Electronics Engineering; Demir, Alper; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 3756Nanomechanical resonant sensors that are based on detecting and tracking the resonance frequency deviations due to events of interest are being advocated for a variety of applications. All sensor schemes currently in use are subject to a basic trade-off between accuracy and speed, while there is great interest in improving both in order to enable unprecedented and widespread applications. Based on a thorough understanding of the characteristics of current resonant sensor architectures, we propose adaptive and flexible sensor schemes. Unlike recently proposed time-resolved mechanical detection methods, the proposed schemes do not require ensemble averaging of the resonator response for many independent identical stimuli. Distinct one-time events can be detected in real-time with high time resolution with an accuracy that then improves considerably with elapsed time. While the proposed adaptive schemes also need to abide by the fundamental speed versus accuracy trade-off, we show that there is still "some room at the bottom" for improvement with sensor architecture innovations. Pareto optimal performance that reaches a bound that is imposed by the fundamental thermomechanical noise can be achieved.