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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/3
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Publication Metadata only A physical channel model for nanoscale neuro-spike communications(IEEE-Inst Electrical Electronics Engineers Inc, 2013) Balevi, eren; Department of Electrical and Electronics Engineering; Akan, Özgür Barış; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 6647Nanoscale communications is an appealing domain in nanotechnology. Novel nanoscale communications techniques are currently being devised inspired by some naturally existing phenomena such as the molecular communications governing cellular signaling mechanisms. Among these, neuro-spike communications, which governs the communications between neurons, is a vastly unexplored area. The ultimate goal of this paper is to accurately investigate nanoscale neuro-spike communications characteristics through the development of a realistic physical channel model between two neurons. The neuro-spike communications channel is analyzed based on the probability of error and delay in spike detection at the output. The derived communication theoretical channel model may help designing novel artificial nanoscale communications methods for the realization of future practical nanonetworks, which are the interconnections of nanomachines.Publication Metadata only Second language tutoring using social robots: a large-scale study(Institute of Electrical and Electronics Engineers (IEEE), 2019) Vogt, Paul; van den Berghe, Rianne; de Haas, Mirjam; Hoffman, Laura; Montanier, Jean-Marc; Oudgenoeg-Paz, Ora; Garcia, Daniel Hernandez; Papadopoulos, Fotios; Schodde, Thorsten; Verhagen, Josje; Wallbridge, Christopher D.; Willemsen, Bram; de Wit, Jan; Belpaeme, Tony; Kopp, Stefan; Krahmer, Emiel; Leseman, Paul; Pandey, Amit Kumar; Department of Psychology; Department of Psychology; Department of Psychology; Department of Psychology; Department of Psychology; Göksun, Tilbe; Kanero, Junko; Küntay, Aylin C.; Mamuş, Ayşe Ezgi; Oranç, Cansu; Faculty Member; Researcher; Faculty Member; Researcher; Researcher; Department of Psychology; College of Social Sciences and Humanities; College of Social Sciences and Humanities; College of Social Sciences and Humanities; College of Social Sciences and Humanities; College of Social Sciences and Humanities; 47278; N/A; 178879; N/A; N/AWe present a large-scale study of a series of seven lessons designed to help young children learn English vocabulary as a foreign language using a social robot. The experiment was designed to investigate 1) the effectiveness of a social robot teaching children new words over the course of multiple interactions (supported by a tablet), 2) the added benefit of a robot's iconic gestures on word learning and retention, and 3) the effect of learning from a robot tutor accompanied by a tablet versus learning from a tablet application alone. For reasons of transparency, the research questions, hypotheses and methods were preregistered. With a sample size of 194 children, our study was statistically well-powered. Our findings demonstrate that children are able to acquire and retain English vocabulary words taught by a robot tutor to a similar extent as when they are taught by a tablet application. In addition, we found no beneficial effect of a robot's iconic gestures on learning gains.Publication Metadata only Guest editorial special issue on toward securing Internet of Connected Vehicles (IoV) from virtual vehicle hijacking(Institute of Electrical and Electronics Engineers (IEEE), 2019) Cao, Yue; Kaiwartya, Omprakash; Song, Houbing; Lloret, Jaime; Ahmad, Naveed; Department of Electrical and Electronics Engineering; Ergen, Sinem Çöleri; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 7211N/APublication Metadata only Analysis and optimization of duty-cycle in preamble-based random access networks(Springer, 2013) Fischione, C.; Park, P.; Department of Electrical and Electronics Engineering; Ergen, Sinem Çöleri; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 7211Duty-cycling has been proposed as an effective mechanism for reducing the energy consumption in wireless sensor networks (WSNs). Asynchronous duty-cycle protocols where the receiver wakes up periodically to check whether there is a transmission and the sender transmits preambles to check if the receiver is awake are widely used in WSNs due to the elimination of complex control mechanisms for topology discovery and synchronization. However, the intrinsic simplicity of the asynchronous mechanism has the drawback of smaller energy saving potential that requires the optimization of the duty cycle parameters. In this paper, we propose a novel method for the optimization of the duty-cycle parameters in preamble-based random access networks based on the accurate modeling of delay, reliability and energy consumption as a function of listen time, sleep time, traffic rate and medium access control (MAC) protocol parameters. The challenges for modeling are the random access MAC and the sleep policy of the receivers, which make it impossible to determine the exact time of data packet transmissions, and thus difficult to investigate the performance indicators given by the delay, reliability and energy consumption to successfully receive packets. An analysis of these indicators is developed as a function of the relevant parameters of the network and it is used in the minimization of the energy consumption subject to delay and reliability requirements. The optimization provides significant reduction of the energy consumption compared to the previously proposed protocols in the literature.Publication Metadata only A deformation-based approach to tuning of magnetic micromechanical resonators(2018) Yalçınkaya, Arda D.; Department of Mechanical Engineering; N/A; Department of Mechanical Engineering; Biçer, Mahmut; Esfahani, Mohammad Nasr; Alaca, Burhanettin Erdem; Researcher; PhD Student; Faculty Member; Department of Mechanical Engineering; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); College of Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; 115108Resonance frequency tuning in magnetic micromechanical resonators remains a primary field of study for frequency reference applications. The use of magnetic micromechanical resonators for innovative timing, oscillator and sensing applications necessitates a platform for the precise control of the resonance frequency. The present work addresses a deformation based technique for tuning the resonance frequency of nickel micromechanical resonators. Frequency response is measured through magnetic actuation and optical readout. The tuning approach is based on a combination of flexural deformation and uniaxial strain. The bending deformation is achieved by using a DC current through the microbeam. This magnetomotive mechanism reduces the resonance frequency by about 13% for a maximum DC current of 80 mA. A substrate bending method is used for applying uniaxial strain to increase the resonance frequency by about 8%. A bidirectional frequency modulation is thus demonstrated by utilizing both deformation techniques. The interpretation of results is carried out by finite element analysis and electromechanical analogy in an equivalent circuit. Using deformation techniques, this study provides a rigorous approach to control the resonance frequency of magnetic micromechanical resonators.Publication Metadata only Cross-subject continuous emotion recognition using speech and body motion in dyadic interactions(International Speech Communication Association ( ISCA), 2017) N/A; N/A; Department of Computer Engineering; Fatima, Syeda Narjis; Erzin, Engin; PhD Student; Faculty Member; Department of Computer Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 34503Dyadic interactions encapsulate rich emotional exchange between interlocutors suggesting a multimodal, cross-speaker and cross-dimensional continuous emotion dependency. This study explores the dynamic inter-attribute emotional dependency at the cross-subject level with implications to continuous emotion recognition based on speech and body motion cues. We propose a novel two-stage Gaussian Mixture Model mapping framework for the continuous emotion recognition problem. In the first stage, we perform continuous emotion recognition (CER) of both speakers from speech and body motion modalities to estimate activation, valence and dominance (AVD) attributes. In the second stage, we improve the first stage estimates by performing CER of the selected speaker using her/his speech and body motion modalities as well as using the estimated affective attribute(s) of the other speaker. Our experimental evaluations indicate that the second stage, cross-subject continuous emotion recognition (CSCER), provides complementary information to recognize the affective state, and delivers promising improvements for the continuous emotion recognition problem.Publication Metadata only Body area nanonetworks with molecular communications in nanomedicine(Institute of Electrical and Electronics Engineers (IEEE), 2012) Balasubramaniam, Sasitharan; N/A; Department of Electrical and Electronics Engineering; Atakan, Barış; Akan, Özgür Barış; PhD Student; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 6647Recent developments in nano and biotechnology enable promising therapeutic nanomachines (NMs) that operate on inter-or intracellular area of human body. The networks of such therapeutic NMs, body area nanonetworks (BAN(2)s), also empower sophisticated nanomedicine applications. In these applications, therapeutic NMs share information to perform computation and logic operations, and make decisions to treat complex diseases. Hence, one of the most challenging subjects for these sophisticated applications is the realization of BAN(2)s through a nanoscale communication paradigm. In this article, we introduce the concept of a BAN(2) with molecular communication, where messenger molecules are used as communication carrier from a sender to a receiver NM. The current state of the art of molecular communication and BAN(2) in nanomedicine applications is first presented. Then communication theoretical efforts are reviewed, and open research issues are given. The objective of this work is to introduce this novel and interdisciplinary research field and highlight major barriers toward its realization from the viewpoint of communication theory.Publication Metadata only Gain-matched output couplers (GMOCs) for efficient and Robust Kerr-Lens mode-locking of Cr:LiSAF lasers(Institute of Electrical and Electronics Engineers (IEEE), 2014) Chen, Li-Jin; Sumpf, Bernd; Erbert, Goetz; Leitenstorfer, Alfred; Kaertner, Franz X.; Demirbaş, Ümit; N/A; N/A; N/A; Department of Physics; Cihan, Can; Beyatlı, Ersen; Canbaz, Ferda; Sennaroğlu, Alphan; PhD Student; PhD Student; PhD Student; Faculty Member; Department of Physics; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; N/A; 229317; N/A; 23851We report efficient and robust Kerr-lens mode-locking of single-mode and tapered diode-pumped Cr:LiSAF lasers by using gain-matched output couplers. Sub-15-fs pulses were generated with peak powers above 60-kW and optical-to-optical conversion efficiencies up to 21%.Publication Metadata only Piezoresistive silicon nanowire resonators as embedded building blocks in thick SOI(Iop Publishing Ltd, 2018) Karakan, M. Çağatay; Orhan, Ezgi; Hanay, M. Selim; Leblebici, Yusuf; N/A; N/A; Department of Mechanical Engineering; Esfahani, Mohammad Nasr; Kılınç, Yasin; Alaca, Burhanettin Erdem; PhD Student; PhD Student; Faculty Member; Department of Mechanical Engineering; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; N/A; N/A; 115108The use of silicon nanowire resonators in nanoelectromechanical systems for new-generation sensing and communication devices faces integration challenges with higher-order structures. Monolithic and deterministic integration of such nanowires with the surrounding microscale architecture within the same thick crystal is a critical aspect for the improvement of throughput, reliability and device functionality. A monolithic and IC-compatible technology based on a tuned combination of etching and protection processes was recently introduced yielding silicon nanowires within a 10 mu m-thick device layer. Motivated by its success, the implications of the technology regarding the electromechanical resonance are studied within a particular setting, where the resonator is co-fabricated with all terminals and tuning electrodes. Frequency response is measured via piezoresistive readout with frequency down-mixing. Measurements indicate mechanical resonance with frequencies as high as 100 MHz exhibiting a Lorentzian behavior with proper transition to nonlinearity, while Allan deviation on the order of 3-8 ppm is achieved. Enabling the fabrication of silicon nanowires in thick silicon crystals using conventional semiconductor manufacturing, the present study thus demonstrates an alternative pathway to bottom-up and thin silicon-on-insulator approaches for silicon nanowire resonators.Publication Metadata only A simple geometric blind source separation method for bounded magnitude sources(IEEE-Inst Electrical Electronics Engineers Inc, 2006) Department of Electrical and Electronics Engineering; Erdoğan, Alper Tunga; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 41624A novel blind source separation approach and the corresponding adaptive algorithm is presented. It is assumed that the observation mixture is obtained through an unknown memoryless linear mapping of independent and bounded magnitude sources. We further assume an initial adaptive prewhitening of the original observation vector which transforms it into a white vector with the same dimension as the original source vector. Our approach is centered around the basic geometric fact that, under a certain boundedness assumption, the unitary mapping which transforms the whitening output vector into an,independent vector has the minimum value of maximum (real component) magnitude output over the ensemble of all output components. Therefore, the related criterion is the minimization of the infinity norm of the real component of the unitary separator's output over all possible output combinations. For the minimization of the corresponding nondifferentiable cost function, we propose the use of subgradient optimization methods to obtain a low complexity iterative adaptive solution. The resulting algorithm is fairly intuitive and simple, and provides a low complexity solution especially to a class of multiuser digital communications problems. We provide examples at the end of this paper to illustrate the performance of our algorithm.