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Publication Metadata only A 35--μm pitch IR thermo-mechanical MEMS sensor with AC-coupled optical readout(IEEE-Inst Electrical Electronics Engineers Inc, 2015) Ferhanoğlu, Onur; Torun, Hamdi; N/A; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Adiyan, Ulaş; Çivitçi, Fehmi; Ürey, Hakan; PhD Student; Researcher; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Sciences; College of Engineering; N/A; 194282; 8579A thermo-mechanical MEMS detector with 35-mu m pixel pitch is designed, fabricated, and characterized. This fabricated design has one of the smallest pixel sizes among the IR thermo-mechanical MEMS sensors in the literature. The working principle of the MEMS detector is based on the bimaterial effect that creates a deflection when exposed to IR radiation in the 812-mu m waveband. The nanometer level out of plane mechanical motion is observed in response to IR heating of the pixel, which is detected by a diffraction grating-based optical readout. Performance of MEMS sensor arrays with optical readout have been limited by a large DC bias that accompanies a small AC signal. We developed a novel optical setup to reduce the DC term and the related noise using an AC-coupled detection scheme. Detailed noise characterization of the pixel and the readout system is reported in this paper. The noise equivalent temperature difference of our detector is measured as 216 mK using f/0.86 lens with the AC-coupled optical readout. Finally, we obtained a thermal image using a single MEMS pixel combined with a scanning configuration. Despite the reduced pixel size, the measured noise levels are comparable to the state-of-the-art thermo-mechanical IR sensors.Publication Metadata only A communication theoretical analysis of synaptic multiple-access channel in hippocampal-cortical neurons(IEEE-Inst Electrical Electronics Engineers Inc, 2013) N/A; N/A; Department of Electrical and Electronics Engineering; Malak, Derya; Akan, Özgür Barış; PhD Student; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 6647Communication between neurons occurs via transmission of neural spike trains through junctional structures, either electrical or chemical synapses, providing connections among nerve terminals. Since neural communication is achieved at synapses, the process of neurotransmission is called synaptic communication. Learning and memory processes are based on the changes in strength and connectivity of neural networks which usually contain multiple synaptic connections. In this paper, we investigate multiple-access neuro-spike communication channel, in which the neural signal, i.e., the action potential, is transmitted through multiple synaptic paths directed to a common postsynaptic neuron terminal. Synaptic transmission is initiated with random vesicle release process from presynaptic neurons to synaptic paths. Each synaptic channel is characterized by its impulse response and the number of available postsynaptic receptors. Here, we model the multiple-access synaptic communication channel, and investigate the information rate per spike at the postsynaptic neuron, and how postsynaptic rate is enhanced compared to single terminal synaptic communication channel. Furthermore, we analyze the synaptic transmission performance by incorporating the role of correlation among presynaptic terminals, and point out the postsynaptic rate improvement.Publication Metadata only A cross-layer approach for minimum delay content adaptive video streaming over variable bitrate channels(European Association for Signal Processing, 2005) N/A; N/A; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Özçelebi, Tanır; Tekalp, Ahmet Murat; Civanlar, Mehmet Reha; Sunay, Mehmet Oğuz; PhD Student; Faculty Member; Faculty Member; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; College of Engineering; N/A; 26207; 16372; N/AA novel cross-layer scheduling and stream switching algorithm for content and channel adaptive video streaming over 1xEV-DO (CDMA-HDR), where stream switching is done according to the receiver buffer level is presented. The instantaneous transmission rate to each user is determined by a multi-objective optimized scheduler, maximizing network throughput and individual receiver buffer levels simultaneously, while the instantaneous coding rate for each user is determined according to buffer status feedback. The transmitter always switches to the most suitable pre-optimized bitstream with minimum delay and visual distortion calculated for various channel capacity values and under constant bitrate assumption. The main target of the proposed framework is to guarantee continuous playout of the transmitted content at all user devices while providing maximum system throughput, minimum overall distortion and minimum pre-roll delay. Experimental results show that decoder buffer overflows and underflows that cause pauses in the playout are prevented as opposed to the case without stream switching.Publication Open Access A deep learning approach for data driven vocal tract area function estimation(Institute of Electrical and Electronics Engineers (IEEE), 2018) Department of Computer Engineering; Department of Electrical and Electronics Engineering; Erzin, Engin; Asadiabadi, Sasan; Faculty Member; Department of Computer Engineering; Department of Electrical and Electronics Engineering; College of Sciences; Graduate School of Sciences and Engineering; 34503; N/AIn this paper we present a data driven vocal tract area function (VTAF) estimation using Deep Neural Networks (DNN). We approach the VTAF estimation problem based on sequence to sequence learning neural networks, where regression over a sliding window is used to learn arbitrary non-linear one-to-many mapping from the input feature sequence to the target articulatory sequence. We propose two schemes for efficient estimation of the VTAF; (1) a direct estimation of the area function values and (2) an indirect estimation via predicting the vocal tract boundaries. We consider acoustic speech and phone sequence as two possible input modalities for the DNN estimators. Experimental evaluations are performed over a large data comprising acoustic and phonetic features with parallel articulatory information from the USC-TIMIT database. Our results show that the proposed direct and indirect schemes perform the VTAF estimation with mean absolute error (MAE) rates lower than 1.65 mm, where the direct estimation scheme is observed to perform better than the indirect scheme.Publication Open Access A fast, accurate, and separable method for fitting a Gaussian function(Institute of Electrical and Electronics Engineers (IEEE), 2019) Al-Nahhal Ibrahim; Dobre Octavia A.; Moloney Cecilia; Ikki Salama; Department of Electrical and Electronics Engineering; Başar, Ertuğrul; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 149116Publication Open Access A generalization of multiple-mode OFDM with index modulation(Institute of Electrical and Electronics Engineers (IEEE), 2018) Wen, Miaowen; Li, Qiang; Zhang, Wensong; Department of Electrical and Electronics Engineering; Başar, Ertuğrul; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 149116In this paper, we propose the scheme of generalized multiple-mode orthogonal frequency division multiplexing with index modulation (GMM-OFDM-IM), which allows a different subcarrier to utilize a signal constellation of a different size while conveying the same number of IM hits. Considering phase shift keying (PSK) constellations, we present design guidelines for GMM-OFDM-IM to achieve the optimal error performance in the asymptotically high signal-to-noise ratio region. A computationally efficient and near-optimal detector based on the idea of sequential decoding is also tailored to GMM-OFDM-IM to avoid the detection of an illegimate constellation permutation. Monte Carlo simulations are conducted to examine GNIM-OFDM-IM, whose inherent properties and advantages are revealed by the simulation results.Publication Open Access A lightning discharge producing a beam of relativistic electrons into space(American Geophysical Union (AGU), 2010) Cohen, M. B.; Said, R. K.; Briggs, M. S.; Fishman, G. J.; Connaughton, V.; Cummer, S. A.; Department of Electrical and Electronics Engineering; İnan, Umran Savaş; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; 177880Strong electric fields associated with lightning generate brief (similar to 1 ms) but intense Terrestrial Gamma-ray Flashes (TGFs), detected by spacecrafts. A few events are thought to be the signature of a relativistic electron beam escaping the atmosphere, which is distinguishable from a TGF since the lightning discharge is along the geomagnetic field line from the spacecraft, rather than below. We refer to this event herein as a 'Terrestrial Energetic-electron Flash' (TEF), and present the first TEF with associated discharge. The TEF was detected by the Gamma-ray Burst Monitor aboard the Fermi satellite, and is correlated with a lightning discharge detected by three Stanford University AWESOME ELF/VLF receivers, a Duke University ULF receiver, and by the GLD360 lightning geolocation network. The discharge, nearly simultaneous with the generated electrons, was of intense peak current and of positive polarity, and with a modest total charge transfer, similar to TGF-associated discharges.Publication Open Access A low-SWaP, low-Cost transceiver for physically secure UAV communication with visible light(Springer, 2020) Department of Electrical and Electronics Engineering; Ergen, Sinem Çöleri; Soner, Burak; Faculty Member; Department of Electrical and Electronics Engineering; College of Engineering; Graduate School of Sciences and Engineering; 7211; N/AUnmanned aerial vehicles (UAV) are expected to utilize optical wireless technologies alongside radio frequency technologies for reliable, secure and high bandwidth communications. While terrestrial and atmospheric laser-based solutions in the past have achieved physically secure communication with very complex beam tracking/pointing mechanisms with large and costly telescopes, such systems are neither suitable nor necessary for medium-range (<100 m) commercial UAV communications. With the proliferation of low-cost solid-state lighting equipment and visible band photodetectors, visible light communications (VLC) offer a low-size-weight-and-power (SWaP) and low-cost solution. This paper presents a novel low-SWaP and low-cost transceiver for physically secure VLC in medium-range commercial UAV applications. Full implementation details for a proof-of-concept prototype built completely with off-the-shelf components are also reported.Publication Metadata only A mechanical transduction-based molecular communication receiver for ınternet of nano things (IoNT)(Assoc Computing Machinery, 2021) N/A; Department of Electrical and Electronics Engineering; Aktaş, Dilara; Akan, Özgür Barış; PhD Student; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 6647Molecular conununication (MC) is one of the most promising technology to enable nanonetworks. Despite many aspects of MC have been investigated broadly, the physical design of the MC receiver has gained little interest. High-performance MC receivers based on bioFETs are proposed and extensively analyzed. However, they have some challenges such as limited detection with charged molecules, Debye screening, and the need for reference electrodes. To overcome these shortcomings, we propose a mechanical-based transducing scheme. In particular, we focus on a Flexure field-effect transistor (FET)-based MC receiver architecture, which provides exponentially high sensitivity by utilizing a nonlinear electromechanical coupling. In addition, the detection of neutral molecules with much simpler instrumentation is possible. In this paper, we analyze its fundamental performance metrics; sensitivity, noise power, signal-to-noise ratio, and the symbol error probability, from an MC theoretical perspective.Publication Open Access A MEMS based visible-NIR Fourier transform microspectrometer - art. no. 61860C(Society of Photo-optical Instrumentation Engineers (SPIE), 2006) Wolter, A.; Department of Electrical and Electronics Engineering; Ataman, Çağlar; Ürey, Hakan; Işıkman, Serhan Ömer; PhD Student; Faculty Member; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 8579; N/ADesign, fabrication and characterization of a novel out-of-plane vertical comb-drive actuator based Fourier transform microspectrometer (FTS) is presented. The spectrometer utilizes resonant mode vertical comb actuators as a variable-depth diffraction grating and a single photodetector to monitor the 0th order of the diffraction pattern. The spectrum of the source illuminating the gratings is computed by Fourier transforming the 0th order intensity as a function of the optical path difference. The vertical comb actuators have a travel range of 100 mu m under atmospheric pressure with 28V excitation, which yields a theoretical spectral resolution of 0.5nm in the visible and better than 5nm in the telecom wavelengths.