1,721,121 research outputs found
Noncontact heart rate measurement via period detection methods of periodic signals
Full text linkConventional heart rate measurement techniques, including manual measurement by placing two fingers on the wrist or side of the neck, electrocardiogram (ECG) or pulse oximetry devices require direct physical contact to the subject and this has the potential to cause inconveniences in cases when the subject has skin irritations or severe burns, contagious disease or intensive care conditions. Hence, there is a need for noncontact heart rate measurement. Previous research on noncontact heart rate measurement utilizes either a complex hardware setup, such as laser illuminators or high-speed cameras, or expensive computational methods, such as independent component analysis. The aim of this work is to apply different signal processing methods utilized in pitch detection problems of periodic signals, namely zero-crossings, autocorrelation, maximum likelihood and Fourier-based methods, to the signal obtained from the average pixel values of the frames of a video recording of the subject’s face obtained using a standard webcam in order to find simple yet effective methods and compare them to previous works, under the same stability assumptions of the subject and illumination of the environment. For this purpose, first, the noncontact heart rate measurement problem is posed as a sinusoidal parameter estimation problem in order to analyze it from a sinusoidal parameter estimation problem point of view. Then, nonparametric methods that are used in period detection of periodic signal problems is presented and their performances are compared with each other as well as previous research. Algorithms are tested on both synthetically generated data and data obtained from input video files. Findings indicate that under stability conditions, inexpensive pitch detection techniques perform almost as well or better compared to computationally expensive methods. Finally, a different approach is taken from the oscillator devices perspective, and an oscillator circuit is used in a similar fashion to an injection locking problem in order to find the period of the input signal from the output of the oscillator circuit. In cases where the circuit parameters such as resistor and capacitor values are tuned accordingly based on the input signal, it is possible to extract heart rate information from the falling edge occurrences of output oscillator voltage with high accuracy.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2018-12-01The student, Gizem Tabak, accepted the attached license on 2016-12-07 at 13:25.The student, Gizem Tabak, submitted this Thesis for approval on 2016-12-07 at 13:33.This Thesis was approved for publication on 2016-12-07 at 16:04.DSpace SAF Submission Ingestion Package generated from Vireo submission #10472 on 2017-02-28 at 14:43:22Made available in DSpace on 2017-03-01T17:02:07Z (GMT). No. of bitstreams: 2
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Previous issue date: 2016-12-07Embargo set by: Seth Robbins for item 98737
Lift date: 2019-03-01T17:02:22Z
Reason: Author requested closed access (OA after 2yrs) in Vireo ETD systemEmbargo set by: Seth Robbins for item 98737
Lift date: 2019-03-01T17:03:32Z
Reason: Author requested closed access (OA after 2yrs) in Vireo ETD systemEmbargo set by: Seth Robbins for item 98737
Lift date: 2019-03-01T17:05:02Z
Reason: Author requested closed access (OA after 2yrs) in Vireo ETD systemEmbargo set by: Seth Robbins for item 98737
Lift date: 2019-03-01T17:06:55Z
Reason: Author requested closed access (OA after 2yrs) in Vireo ETD systemLimited Restriction Lifted for Item 98737 on 2019-03-02T10:15:14Z
An MLSE receiver for electronic dispersion compensation of OC-192 fiber links
No full textA maximum-likelihood sequence estimation (MLSE) receiver is fabricated to combat dispersionlintersymbol interference (chromatic and polarization mode), noise (optical and electrical), and nonlinearities (e.g., fiber, receiver photodiode, or laser) in OC-192 metro and long-haul links. The MLSE receiver includes a variable gain amplifier with 40-dB gain range and 7.5-GHz 3-dB bandwidth, a 12.5-Gb/s 4-bit analog-to-digital converter, a dispersion-tolerant phase-locked loop, a 1:8 demultiplexer, and a digital 'equalizer implementing the MLSE algorithm. The MLSE receiver achieves more than 50% reach extension at signal-to-noise levels of interest as compared to conventional clock data recovery systems
Minimum-delay HF communications
Full text linkHF radio communications offer latency advantages over fiber-optics and are more economical than satellite links in long-distance communication applications. As a result, there is renewed interest in the field of HF from the high-frequency trading industry, as a means of transmitting financial data. Ideally, decisions should be made on received symbols as soon as they arrive, without waiting for other samples to accumulate. A significant problem is that the ionospheric HF channel is a dynamic medium that is considered one of the most challenging communication channels. In this thesis, we investigate alternative techniques towards reliable communication with minimum delay. We study HF channel models and communication link design tools, which indicate that our minimum-delay problem is feasible but difficult to solve. Extant HF modems are observed to add prohibitive amounts of latency to ensure robustness, motivating us to design receivers that provide good performance given a delay constraint. We adapt a coupled MAP-RLS receiver studied in literature to the HF channel to yield minimal decision-making delay. We introduce a multitrellis adaptive Viterbi algorithm (MAVA) that solves the problem of equalization for sparse and time-varying ISI channels, producing a robust MLSE receiver with several milliseconds of decision-making delay. Finally, we cascade this MLSE receiver with MAP detection to obtain high-fidelity low-delay performance, finding a practical solution to minimum-delay HF communications.Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2017-08-10 without embargo termsThe student, Toros Arikan, accepted the attached license on 2017-04-27 at 13:14.The student, Toros Arikan, submitted this Thesis for approval on 2017-04-27 at 15:32.This Thesis was approved for publication on 2017-04-27 at 17:44.DSpace SAF Submission Ingestion Package generated from Vireo submission #11116 on 2017-08-10 at 13:46:56Made available in DSpace on 2017-08-10T19:16:20Z (GMT). No. of bitstreams: 27
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Previous issue date: 2017-04-2
Design of energy-efficient ultrasonic communication systems on steel pipes
Full text linkUltrasonic communication provides an alternative to radio-frequency (RF) by transmitting guided ultrasonic signals along installed or buried metallic pipes. Buried pipe corrosion monitoring and intermittent infrastructure data collection are potential application areas, for which reliable wireless links are unavailable, due to strong RF attenuation in soil, or through shielded building infrastructure. When designing a network of such links, energy efficiency, defined as the average energy per transmitted bit, can be far more important than Shannon capacity, for such battery-powered, relatively inaccessible links. This work focuses on the low-rate, total life-time energy-limited regime to maximize battery life, while maintaining reliable information transfer at a nominal average rate. The strong frequency selectivity of the through-pipe ultrasonic channel poses several challenges for low-power systems, including strong intersymbol interference (ISI). Previous works have suggested a variety of ad hoc design schemes to implement low-power communication systems satisfying minimum data rate requirements under highly frequency selective and lossy conditions, but failed to propose a systematic methodology to optimize design parameters for energy efficiency. In this work, we apply the concept of energy efficiency maximization to ultrasonic communication over steel pipe channels. A cross-layer approach accounting for both transmit power and signal processing power is suggested, where frequency division multiplexing is explored to counter frequency selectivity. Finally, bits-per-Joule capacity of this channel, based on experimentally measured channel responses, are determined numerically, and an example of an optimized multi-tone frequency shift keying (MFSK) scheme is suggested.Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2017-08-10 without embargo termsThe student, Sijung Yang, accepted the attached license on 2017-04-26 at 02:09.The student, Sijung Yang, submitted this Thesis for approval on 2017-04-26 at 17:13.This Thesis was approved for publication on 2017-04-27 at 09:39.DSpace SAF Submission Ingestion Package generated from Vireo submission #11080 on 2017-08-10 at 13:46:35Made available in DSpace on 2017-08-10T19:16:13Z (GMT). No. of bitstreams: 2
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Previous issue date: 2017-04-2
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
On low-pass reconstruction and stochastic modeling of PWM signals
Full text linkMathematical modeling of pulse width modulation (PWM) is given. For a band-limited, finite energy input signal, a PWM generation mechanism is investigated in linear and non-linear blocks separately. Following the common practice, a comparator block with a periodic reference signal is offered as a PWM generator and different sampling methodologies are discussed. For natural sampling, where the input signal is compared to the reference signal directly, lossless sampling conditions are derived. For a sawtooth reference signal, the convergence characteristics between lossless natural sampling and uniform sampling, where a zero-order hold (ZOH) block precedes the comparator, are analyzed. For a given input model, the convergence characteristics are tested with simulations and signal to absolute deviation energy for the difference between natural and uniform sampling is observed for different oversampling levels.
Motivated by the separation of linear and non-linear blocks in PWM generation, a similar method for the analysis at the reconstruction end is pursued. In this pursuit, continuous-time low-pass filtering, preceded by oversampling, is analyzed as a linear suboptimal reconstruction mechanism from a PWM signal. Observing the mapping between input samples and pulse widths, an infinite energy, input-independent, structural component of a PWM signal is revealed. Manipulating the linear nature of the low-pass filtering, and equivalent model is proposed to analyze the finite energy, input-dependent component of the PWM signal separately. Frequency domain analysis for fixed-edge and double-edge PWM orientations and their corresponding input-dependent components are given. Using the frequency domain representations, performance bounds for low-pass reconstruction of a band-limited, finite energy input signal are derived and fundamental trade-offs between generator complexity and distortion attenuation capacity are revealed.
Stochastic modeling of PWM processes for independent identically distributed (i.i.d.) pulse widths is discussed. For a fixed starting model of a PWM process, the violation of wide sense stationarity (WSS) is observed. By introducing a randomized starting point, independent of the pulse widths and uniformly distributed over a symbol interval, a WSS PWM process is constructed and its stochastic characteristics are analyzed. For i.i.d. uniform pulse widths, second moments are simulated revealing a smoothing effect in the double-edge PWM construction, consistent to the frequency domain analysis.Submission published under a 24 month embargo labeled 'U of I only', the embargo will last until 2017-08-01The student, Noyan Sevuktekin, accepted the attached license on 2015-07-06 at 11:30.The student, Noyan Sevuktekin, submitted this Thesis for approval on 2015-07-06 at 11:47.This Thesis was approved for publication on 2015-07-06 at 13:27.DSpace SAF Submission Ingestion Package generated from Vireo submission #8350 on 2015-09-29 at 14:59:10Made available in DSpace on 2015-09-29T20:49:44Z (GMT). No. of bitstreams: 2
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Previous issue date: 2015-07-06Embargo set by: Seth Robbins for item 89442
Lift date: 2017-09-29T20:50:34Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemU of I Only Restriction Lifted for Item 89442 on 2017-09-30T09:15:27Z
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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