Current Search: Weeks, Arthur (x)
View All Items
(1 - 20 of 20)
- Title
- Color image enhancement using both chromatic and luminance components.
- Creator
-
Hague, George Eric, Weeks, Arthur R., Engineering
- Abstract / Description
-
University of Central Florida College of Engineering Thesis; A vast amount of work has been published regarding grayscale processing of digital images. Although some of this work has been adapted for color images, many of the resulting algorithms neglect the correlation that exists between the individual RGB color components. Consequently, they introduce color artifacts. Attempts have been made to decouple the RGB components through color space transformations that isolate the luminance from...
Show moreUniversity of Central Florida College of Engineering Thesis; A vast amount of work has been published regarding grayscale processing of digital images. Although some of this work has been adapted for color images, many of the resulting algorithms neglect the correlation that exists between the individual RGB color components. Consequently, they introduce color artifacts. Attempts have been made to decouple the RGB components through color space transformations that isolate the luminance from the chromatic information. Color image enhancement is then considered a two step process, where the luminance and the chromatic components are processed independently. However, the RGB color space only has a finite number of available colors, which limits the attainable chromatic values for any given luminance level. This recoupling of the chromatic and luminance components constrains the independent processing of these two components. This thesis investigates this coupling and how it effects a number of color image processing algorithms. Specifically, new algorithms for color histogram equalization, automatic white balance and color filtering are presented using the C-Y (color difference) color model. Coupling the chromatic components to the luminance produces improved white balanced results and enhances the ability of histogram equalization to increase saturation contrast. Furthermore, several adaptive filters are implemented using the C-Y color space. Because this color model closely matches the human concept of color, the noise is filtered from color components that closely match the perceptually significant quantities. This improves the results for these adaptive filters, but also requires special attention when filtering the hue component. Improper filtering of the hue component can often lead to color artifacts.
Show less - Date Issued
- 1994
- Identifier
- CFR0011934, ucf:53115
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFR0011934
- Title
- AN AUTHENTIC ECG SIMULATOR.
- Creator
-
Michalek, Paul, Weeks, Arthur, University of Central Florida
- Abstract / Description
-
An ECG (electrocardiogram) simulator is an electronic tool that plays an essential role in the testing, design, and development of ECG monitors and other ECG equipment. Principally an ECG simulator provides ECG monitors with an electrical signal that emulates the human heart's electrical signal so that the monitor can be tested for reliability and important diagnostic capabilities. However, the current portable commercially available ECG simulators are lacking in their ability to fully...
Show moreAn ECG (electrocardiogram) simulator is an electronic tool that plays an essential role in the testing, design, and development of ECG monitors and other ECG equipment. Principally an ECG simulator provides ECG monitors with an electrical signal that emulates the human heart's electrical signal so that the monitor can be tested for reliability and important diagnostic capabilities. However, the current portable commercially available ECG simulators are lacking in their ability to fully test ECG monitors. Specifically, the portable simulators presently on the market do not produce authentic ECG signals but rather they endeavor to create the ECG signals mathematically. They even attempt to mathematically create arrhythmias (irregular heartbeats of which there are many different types). Arrhythmia detection is an important capability for any modern ECG monitor because arrhythmias are often the critical link to the diagnosis of heart conditions or cardiovascular disease. The focus of this thesis is the design and implementation of a portable ECG simulator. The important innovation of this prototype simulator is that it will not create its ECG signals mathematically, but rather it will store ECG data files on a memory module and use this data to produce an authentic ECG signal. The data files will consist of different types of ECG signals including different types of arrhythmias. The data files are obtained via the internet and require formatting and storing onto a memory chip. These files are then processed by a digital to analog converter and output on a four lead network to produce an authentic ECG signal. The system is built around the ultra-low power Texas Instruments MSP430 microcontroller.
Show less - Date Issued
- 2006
- Identifier
- CFE0001214, ucf:46951
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001214
- Title
- THE REMOVAL OF MOTION ARTIFACTS FROM NON-INVASIVE BLOOD PRESSURE MEASUREMENTS.
- Creator
-
Thakkar, Paresh, Weeks, Arthur, University of Central Florida
- Abstract / Description
-
Modern Automatic Blood Pressure Measurement Techniques are based on measuring the cuff pressure and on sensing the pulsatile amplitude variations. These measurements are very sensitive to motion of the patient or the surroundings where the patient is. The slightest unexpected movements could offset the readings of the automatic Blood Pressure meter by a large amount or render the readings totally meaningless. Every effort must be taken to avoid subjecting the body of the patient or the...
Show moreModern Automatic Blood Pressure Measurement Techniques are based on measuring the cuff pressure and on sensing the pulsatile amplitude variations. These measurements are very sensitive to motion of the patient or the surroundings where the patient is. The slightest unexpected movements could offset the readings of the automatic Blood Pressure meter by a large amount or render the readings totally meaningless. Every effort must be taken to avoid subjecting the body of the patient or the patient's surroundings to motion for obtaining a reliable reading. But there are situations in which we need Blood Pressure Measurements with the patient or his surroundings in motion; for instance in an ambulance while a patient is being transported to a hospital. In this thesis, we present a technique to reduce the effect of motion artifact from Blood Pressure measurements. We digitize the blood pressure waveform and use Digital Signal Processing Techniques to process the corrupted waveform. We use the differences in frequency spectra of the Blood Pressure signal and motion artifact noise to remove the motion artifact noise. The motion artifact noise spectrum is not very well defined, since it may consist of many different frequency components depending on the kind of motion. The Blood Pressure signal is more or less a periodic signal. That translates to periodicity in the frequency domain. Hence, we designed a digital filter that could take advantage of the periodic nature of the Blood Pressure Signal waveform. The filter is shaped like a comb with periodic peaks around the signal frequency components. Further processing of the filtered signal: baseline restoration and level shifting help us to further reduce the noise corruption.
Show less - Date Issued
- 2004
- Identifier
- CFE0000324, ucf:46289
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000324
- Title
- RR INTERVAL ESTIMATION FROM AN ECG USING A LINEAR DISCRETE KALMAN FILTER.
- Creator
-
Janapala, Arun, WEEKS, ARTHUR, University of Central Florida
- Abstract / Description
-
An electrocardiogram (ECG) is used to monitor the activity of the heart. The human heart beats seventy times on an average per minute. The rate at which a human heart beats can exhibit a periodic variation. This is known as heart rate variability (HRV). Heart rate variability is an important measurement that can predict the survival after a heart attack. Studies have shown that reduced HRV predicts sudden death in patients with Myocardial Infarction (MI). The time interval between each beat...
Show moreAn electrocardiogram (ECG) is used to monitor the activity of the heart. The human heart beats seventy times on an average per minute. The rate at which a human heart beats can exhibit a periodic variation. This is known as heart rate variability (HRV). Heart rate variability is an important measurement that can predict the survival after a heart attack. Studies have shown that reduced HRV predicts sudden death in patients with Myocardial Infarction (MI). The time interval between each beat is called an RR interval, where the heart rate is given by the reciprocal of the RR interval expressed in beats per minute. For a deeper insight into the dynamics underlying the beat to beat RR variations and for understanding the overall variance in HRV, an accurate method of estimating the RR interval must be obtained. Before an HRV computation can be obtained the quality of the RR interval data obtained must be good and reliable. Most QRS detection algorithms can easily miss a QRS pulse producing unreliable RR interval values. Therefore it is necessary to estimate the RR interval in the presence of missing QRS beats. The approach in this thesis is to apply KALMAN estimation algorithm to the RR interval data calculated from the ECG. The goal is to improve the RR interval values obtained from missed beats of ECG data.
Show less - Date Issued
- 2005
- Identifier
- CFE0000340, ucf:46279
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000340
- Title
- AUTONOMOUS REPAIR OF OPTICAL CHARACTER RECOGNITION DATA THROUGH SIMPLE VOTING AND MULTI-DIMENSIONAL INDEXING TECHNIQUES.
- Creator
-
Sprague, Christopher, Weeks, Arthur, University of Central Florida
- Abstract / Description
-
The three major optical character recognition (OCR) engines (ExperVision, Scansoft OCR, and Abby OCR) in use today are all capable of recognizing text at near perfect percentages. The remaining errors however have proven very difficult to identify within a single engine. Recent research has shown that a comparison between the errors of the three engines proved to have very little correlation, and thus, when used in conjunction, may be useful to increase accuracy of the final result. This...
Show moreThe three major optical character recognition (OCR) engines (ExperVision, Scansoft OCR, and Abby OCR) in use today are all capable of recognizing text at near perfect percentages. The remaining errors however have proven very difficult to identify within a single engine. Recent research has shown that a comparison between the errors of the three engines proved to have very little correlation, and thus, when used in conjunction, may be useful to increase accuracy of the final result. This document discusses the implementation and results of a simple voting system designed to prove the hypothesis and show a statistical improvement in overall accuracy. Additional aspects of implementing an improved OCR scheme such as dealing with multiple engine data output alignment and recognizing application specific solutions are also addressed in this research. Although voting systems are currently in use by many major OCR engine developers, this research focuses on the addition of a collaborative system which is able to utilize the various positive aspects of multiple engines while also addressing the immediate need for practical industry applications such as litigation and forms processing. Doculex TM, a major developer and leader in the document imaging industry, has provided the funding for this research.
Show less - Date Issued
- 2005
- Identifier
- CFE0000380, ucf:46337
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000380
- Title
- DETECTION OF THE R-WAVE IN ECG SIGNALS.
- Creator
-
Valluri, Sasanka, Weeks, Arthur, University of Central Florida
- Abstract / Description
-
This thesis aims at providing a new approach for detecting R-waves in the ECG signal and generating the corresponding R-wave impulses with the delay between the original R-waves and the R-wave impulses being lesser than 100 ms. The algorithm was implemented in Matlab and tested with good results against 90 different ECG recordings from the MIT-BIH database. The Discrete Wavelet Transform (DWT) forms the heart of the algorithm providing a multi-resolution analysis of the ECG signal. The...
Show moreThis thesis aims at providing a new approach for detecting R-waves in the ECG signal and generating the corresponding R-wave impulses with the delay between the original R-waves and the R-wave impulses being lesser than 100 ms. The algorithm was implemented in Matlab and tested with good results against 90 different ECG recordings from the MIT-BIH database. The Discrete Wavelet Transform (DWT) forms the heart of the algorithm providing a multi-resolution analysis of the ECG signal. The wavelet transform decomposes the ECG signal into frequency scales where the ECG characteristic waveforms are indicated by zero crossings. The adaptive threshold algorithms discussed in this thesis search for valid zero crossings which characterize the R-waves and also remove the Preventricular Contractions (PVC's). The adaptive threshold algorithms allow the decision thresholds to adjust for signal quality changes and eliminate the need for manual adjustments when changing from patient to patient. The delay between the R-waves in the original ECG signal and the R-wave impulses obtained from the algorithm was found to be less than 100 ms.
Show less - Date Issued
- 2005
- Identifier
- CFE0000498, ucf:46369
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000498
- Title
- DEVELOPMENT OF A MOTOR SPEED CONTROL SYSTEM USING MATLAB AND SIMULINK, IMPLEMENTED WITH A DIGITAL SIGNAL PROCESSOR.
- Creator
-
Klee, Andrew, Weeks, Arthur, University of Central Florida
- Abstract / Description
-
This thesis describes an improved methodology for embedded software development. MATLAB and Simulink allow engineers to simplify algorithm development and avoid duplication of effort in deploying these algorithms to the end hardware. Special new hardware targeting capabilities of MATLAB and Simulink are described in detail. A motor control system design served to demonstrate the efficacy of this new method. Initial data was collected to help model the motor in Simulink. This allowed for the...
Show moreThis thesis describes an improved methodology for embedded software development. MATLAB and Simulink allow engineers to simplify algorithm development and avoid duplication of effort in deploying these algorithms to the end hardware. Special new hardware targeting capabilities of MATLAB and Simulink are described in detail. A motor control system design served to demonstrate the efficacy of this new method. Initial data was collected to help model the motor in Simulink. This allowed for the design of the open and closed loop control systems. The designed system was very effective, with good response and no steady state error. The entire design process and deployment to a digital signal processor took significantly less time and effort than other typical methods. The results of the control system design as well as the details of these development improvements are described.
Show less - Date Issued
- 2005
- Identifier
- CFE0000477, ucf:46367
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000477
- Title
- REDUCING EDDY CURRENTS IN HIGH MAGNETIC FIELD ENVIRONMENTS.
- Creator
-
Case, Russell, Weeks, Arthur, University of Central Florida
- Abstract / Description
-
When an electrical conducting volume is placed into the bore of an MRI undergoing an image scan, time varying magnetic gradients induce eddy currents in this conducting material. These eddy currents in turn produce a mechanical torque on this volume. It is the goal of this thesis to produce a computer simulation of eddy currents produced by placing conducting materials inside an MRI bore. The first part of the thesis establishes the physics and principles behind an MRI system along with...
Show moreWhen an electrical conducting volume is placed into the bore of an MRI undergoing an image scan, time varying magnetic gradients induce eddy currents in this conducting material. These eddy currents in turn produce a mechanical torque on this volume. It is the goal of this thesis to produce a computer simulation of eddy currents produced by placing conducting materials inside an MRI bore. The first part of the thesis establishes the physics and principles behind an MRI system along with several applications. Next, this thesis presents an analysis of eddy current effects produced on a conductor placed into an MRI bore. The design and construction of simulated MRI magnetic fields is then presented along with a study of simulated eddy currents in various test conducting volumes of selected materials. Finally, techniques are discussed for reducing eddy currents in these conducting volumes and materials, along with simulation results showing the reduction in the applied eddy current. The findings of this thesis are summarized in the conclusions and recommendations are made for modification and future applications of these techniques and simulations.
Show less - Date Issued
- 2008
- Identifier
- CFE0002015, ucf:47611
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002015
- Title
- SIGNAL PROCESSING OF AN ECG SIGNALIN THE PRESENCE OF A STRONG STATIC MAGNETIC FIELD.
- Creator
-
Gupta, Aditya, Weeks, Arthur, University of Central Florida
- Abstract / Description
-
This dissertation addresses the problem of elevation of the T wave of an electrocardiogram (ECG) signal in the magnetic resonance imaging (MRI). In the MRI, due to the strong static magnetic field the interaction of the blood flow with this strong magnetic field induces a voltage in the body. This voltage appears as a superimposition at the locus of the T wave of the ECG signal. This looses important information required by the doctors to interpret the ST segment of the ECG and detect...
Show moreThis dissertation addresses the problem of elevation of the T wave of an electrocardiogram (ECG) signal in the magnetic resonance imaging (MRI). In the MRI, due to the strong static magnetic field the interaction of the blood flow with this strong magnetic field induces a voltage in the body. This voltage appears as a superimposition at the locus of the T wave of the ECG signal. This looses important information required by the doctors to interpret the ST segment of the ECG and detect diseases such as myocardial infarction. This dissertation aims at finding a solution to the problem of elevation of the T wave of an ECG signal in the MRI. The first step is to simulate the entire situation and obtain the magnetic field dependent T wave elevation. This is achieved by building a model of the aorta and simulating the blood flow in it. This model is then subjected to a static magnetic field and the surface potential on the thorax is measured to observe the T wave elevation. The various parameters on which the T wave elevation is dependent are then analyzed. Different approaches are used to reduce this T wave elevation problem. The direct approach aims at computing the magnitude of T wave elevation using magneto-hydro-dynamic equations. The indirect approach uses digital signal processing tools like the least mean square adaptive filter to remove the T wave elevation and obtain artifact free ECG signal in the MRI. Excellent results are obtained from the simulation model. The model perfectly simulates the ECG signal in the MRI at all the 12 leads of the ECG. These results are compared with ECG signals measured in the MRI. A simulation package is developed in MATLAB based on the simulation model. This package is a graphical user interface allowing the user to change the strength of magnetic field, the radius of the aorta and the orientation of the aorta with respect to the heart and observe the ECG signals with the elevation at the 12 leads of the ECG. Also the artifacts introduced due to the magnetic field can be removed by the least mean square adaptive filter. The filter adapts the ECG signal in the MRI to the ECG signal of the patient outside the MRI. Before the adaptation, the heart rate of the ECG outside the MRI is matched to the ECG in the MRI by interpolation or decimation. The adaptive filter works excellently to remove the T wave artifacts. When the cardiac output of the patient changes, the simulation model is used along with the adaptive filter to obtain the artifact free ECG signal.
Show less - Date Issued
- 2007
- Identifier
- CFE0001857, ucf:47389
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001857
- Title
- TEXT-IMAGE RESTORATION AND TEXT ALIGNMENT FOR MULTI-ENGINE OPTICAL CHARACTER RECOGNITION SYSTEMS.
- Creator
-
Kozlovski, Nikolai, Weeks, Arthur, University of Central Florida
- Abstract / Description
-
Previous research showed that combining three different optical character recognition (OCR) engines (ExperVision® OCR, Scansoft OCR, and Abbyy® OCR) results using voting algorithms will get higher accuracy rate than each of the engines individually. While a voting algorithm has been realized, several aspects to automate and improve the accuracy rate needed further research. This thesis will focus on morphological image preprocessing and morphological text restoration that goes to OCR...
Show morePrevious research showed that combining three different optical character recognition (OCR) engines (ExperVision® OCR, Scansoft OCR, and Abbyy® OCR) results using voting algorithms will get higher accuracy rate than each of the engines individually. While a voting algorithm has been realized, several aspects to automate and improve the accuracy rate needed further research. This thesis will focus on morphological image preprocessing and morphological text restoration that goes to OCR engines. This method is similar to the one used in restoration partial finger prints. Series of morphological dilating and eroding filters of various mask shapes and sizes were applied to text of different font sizes and types with various noises added. These images were then processed by the OCR engines, and based on these results successful combinations of text, noise, and filters were chosen. The thesis will also deal with the problem of text alignment. Each OCR engine has its own way of dealing with noise and corrupted characters; as a result, the output texts of OCR engines have different lengths and number of words. This in turn, makes it impossible to use spaces a delimiter as a method to separate the words for processing by the voting part of the system. Text aligning determines, using various techniques, what is an extra word, what is supposed to be two or more words instead of one, which words are missing in one document compared to the other, etc. Alignment algorithm is made up of a series of shifts in the two texts to determine which parts are similar and which are not. Since errors made by OCR engines are due to visual misrecognition, in addition to simple character comparison (equal or not), a technique was developed that allows comparison of characters based on how they look.
Show less - Date Issued
- 2006
- Identifier
- CFE0001060, ucf:46799
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001060
- Title
- PASSIVE WIRELESS SAW SENSORS WITH NEW AND NOVEL REFLECTOR STRUCTURES: DESIGN AND APPLICATIONS.
- Creator
-
Kozlovski, Nikolai, Weeks, Arthur, University of Central Florida
- Abstract / Description
-
Surface acoustic wave (SAW) devices are a solution for today's ever growing need for passive wireless sensors. Orthogonal frequency coding (OFC) together with time division multiplexing (TDM) provides a large number of codes and coding algorithms producing devices that have excellent collision properties. Novel SAW noise-like refector (NLR) structures with pulse position modulation (PPM) are shown to exhibit good auto- and cross-correlation, and anti-collision properties. Multi-track, multi...
Show moreSurface acoustic wave (SAW) devices are a solution for today's ever growing need for passive wireless sensors. Orthogonal frequency coding (OFC) together with time division multiplexing (TDM) provides a large number of codes and coding algorithms producing devices that have excellent collision properties. Novel SAW noise-like refector (NLR) structures with pulse position modulation (PPM) are shown to exhibit good auto- and cross-correlation, and anti-collision properties. Multi-track, multi-transducer approaches yield devices with adjustable input impedances and enhanced collision properties for OFC TDM SAW sensor devices. Each track-transducer is designed for optimum performance for loss, coding, and chip reflectivity. Experimental results and theoretical predictions confirm a constant Q for SAW transducers for a given operational bandwidth, independent of device and transducer embodiment. Results on these new NLR SAW structures and devices along with a new novel 915 MHz transceiver based on a software radio approach was designed, built, and analyzed. Passive wireless SAW temperature sensors were interrogated and demodulated in a spread spectrum correlator system using a new adaptive filter. The first-ever SAW OFC four-sensor operation was demonstrated at a distance of 1 meter and a single sensor was shown to operate up to 3 meters. Comments on future work and directions are also presented.
Show less - Date Issued
- 2011
- Identifier
- CFE0003636, ucf:48851
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003636
- Title
- A Contextual Approach to Real Time, Interactive Narrative Generation.
- Creator
-
Hollister, James, Richie, Samuel, Weeks, Arthur, Wanielista, Martin, University of Central Florida
- Abstract / Description
-
Oral story telling has become a lost art of family histories because social media and technology have taken over the personal interactions that once passed on the important stories and facts from generation to generation. This dissertation presents and evaluates a method of generating a narrative with input from the listener without actually forcing him or her to become an actual character in the narrative. This system is called CAMPFIRE Story Telling System (STS) and employs a contextual...
Show moreOral story telling has become a lost art of family histories because social media and technology have taken over the personal interactions that once passed on the important stories and facts from generation to generation. This dissertation presents and evaluates a method of generating a narrative with input from the listener without actually forcing him or her to become an actual character in the narrative. This system is called CAMPFIRE Story Telling System (STS) and employs a contextual approach to story generation. This system uses the Cooperating Context Method (CCM) to generate and tell dynamic stories in real time and can be modified by the listener. CCM was created to overcome the weaknesses found in other contextual approaches during story generation while still meeting the design criteria of 1) being able to plan out a story; 2) being able to create a narrative that is entertaining to the listener; and 3) being able to modify the story that could incorporate the listener's request in the story. The CCM process begins by creating a list of tasks by analyzing the current situation. A list of contexts is narrowed down through a series of algorithms into two lists: high priority and low priority lists. These lists are analyzed and a set of context best suited to handle the tasks are selected. The CAMPFIRE STS was rigorously assessed for its functionality, novelty, and user acceptance as well as the time needed to modify the knowledge base. These evaluations showed that the CAMPFIRE STS has the ability to create novel stories using the same knowledge base. A group of 38 test subjects used and evaluated CAMPFIRE STS with respect to its use for children, story entertainment, story creativity and the system's ease of use answering a extensive survey of 54 questions. The survey showed that CAMPFIRE STS can create stories appropriate for bedtime stories with some minor modifications and that the generated stories are novel and entertaining stories, and that it was an easy system to use.
Show less - Date Issued
- 2016
- Identifier
- CFE0006687, ucf:51923
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006687
- Title
- SAW Correlator Temperature Compensation Using a Pulse Width Modulated Temperature Controller.
- Creator
-
Betancourt, Daniel, Weeks, Arthur, Malocha, Donald, Richie, Samuel, Gong, Xun, University of Central Florida
- Abstract / Description
-
A Surface Acoustic Wave (SAW) correlator built on a Lithium Niobate substrate is temperature compensated in order to maintain a constant center frequency. Frequency shifts as a result of temperature variations limit device performance. An Arduino(&)#174;-based PWM temperature controller is developed to read the device temperature from a resistance temperature detector located on the SAW wafer and to regulate its temperature to a specified setpoint by providing current to a heater which is co...
Show moreA Surface Acoustic Wave (SAW) correlator built on a Lithium Niobate substrate is temperature compensated in order to maintain a constant center frequency. Frequency shifts as a result of temperature variations limit device performance. An Arduino(&)#174;-based PWM temperature controller is developed to read the device temperature from a resistance temperature detector located on the SAW wafer and to regulate its temperature to a specified setpoint by providing current to a heater which is co-located with the temperature sensor on the SAW correlator substrate. The final temperature controller achieves frequency shifts of 0.013 MHz from room temperature with a worst-case PPM experienced over 30(&)deg;C of temperature variation of 0.48 PPM/(&)deg;C. Linear and non-linear plant models are developed successfully to predict the device's temperature based on any input setpoint. Although there are alternatives to limit temperature drift at different temperatures, this thesis presents a simple method that works on a standard Lithium Niobate substrate.
Show less - Date Issued
- 2019
- Identifier
- CFE0007787, ucf:52331
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007787
- Title
- Programmable Low Loss Orthogonal Frequency Coded Surface Acoustic Wave Correlator Filters.
- Creator
-
Smith, Marshall, Malocha, Donald, Weeks, Arthur, Sundaram, Kalpathy, Richie, Samuel, Youngquist, Robert, University of Central Florida
- Abstract / Description
-
Simultaneous Transmit and Receive (STAR) communication is being developed as a means of improving spectral efficiency in wireless communication systems. If the obstacle of self-interference can be sufficiently overcome, it is possible to double the spectral efficiency of an equivalent time or frequency division duplexed system. Spread spectrum techniques can reduce self-interference by using orthogonal or pseudo-orthogonal codes to encode the transmit signal and decode the receive signal...
Show moreSimultaneous Transmit and Receive (STAR) communication is being developed as a means of improving spectral efficiency in wireless communication systems. If the obstacle of self-interference can be sufficiently overcome, it is possible to double the spectral efficiency of an equivalent time or frequency division duplexed system. Spread spectrum techniques can reduce self-interference by using orthogonal or pseudo-orthogonal codes to encode the transmit signal and decode the receive signal.Hardware correlator filters are developed for use with STAR radio systems using orthogonal frequency coded (OFC) surface acoustic wave (SAW) devices. OFC is a type of spread spectrum communication that can be implemented using SAW transducers to create a correlator filter, also known as a matched filter. OFC allows code division multiple access and processing gain, similar to other spread spectrum techniques, but is more well-suited to low loss inline SAW design due to the use of multiple orthogonal carriers.The development of low loss fixed code OFC SAW correlator filters is documented, including design criteria and multiple approaches that progressively reduce insertion loss. Using the results from progressive designs and experiments, a pair of correlator filters with matched codes are presented with approximately 6 dB insertion loss at 950 MHz.A second development focusing on OFC SAW correlator filters with programmable codes using RF switches is also described. The programmable correlators use a fixed OFC code with programmable binary phase shift keying (BPSK), and demonstrate positive results. The programmable correlators presented require less than 1 mW of DC power.
Show less - Date Issued
- 2018
- Identifier
- CFE0007768, ucf:52372
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007768
- Title
- Variance in Fade-Time of a Gamma-Gamma Distributed Irradiance Signal.
- Creator
-
Leclerc, Troy, Phillips, Ronald, Weeks, Arthur, Richardson, Martin, Marinescu, Dan, Andrews, Larry, University of Central Florida
- Abstract / Description
-
Free-space optical communications are predominantly hindered by optical turbulence, an effect caused by temperature and pressure variations within the atmosphere. The result is an optical wave interfering with itself due to multipath propagation via tiny refractive-index fluctuations across the wave-front. Optical communication systems are affected when the channel conditions induce fading in the irradiance signal that is received at the detector. The nature of optical interference imparted...
Show moreFree-space optical communications are predominantly hindered by optical turbulence, an effect caused by temperature and pressure variations within the atmosphere. The result is an optical wave interfering with itself due to multipath propagation via tiny refractive-index fluctuations across the wave-front. Optical communication systems are affected when the channel conditions induce fading in the irradiance signal that is received at the detector. The nature of optical interference imparted by the atmosphere is a random process and therefore the received irradiance signal is often characterized by an appropriate probability density function (PDF). Data collected during past free-space optical experiments in the atmosphere support the gamma-gamma distribution as a practical PDF model for received irradiance fluctuations, although the irradiance fluctuations do occasionally tend towards a lognormal distribution.Utilization of the gamma-gamma irradiance PDF allows for calculation of statistical moments of the irradiance threshold level-crossing distribution. Presented analysis focuses on the results of the gamma-gamma irradiance PDF. Previously, expressions were developed for the expected number of gamma-gamma distributed irradiance threshold level-crossings. Expressions for the mean square number of gamma-gamma distributed irradiance threshold level-crossings are derived and presented. The derived expressions lead to the mean and variance of signal fade time. Outcomes of the derived expressions are presented in relation to free-space optical communication system performance.Comparisons are made between the theoretical analysis and experimental data taken at the Innovative Science and Technology Facility (ISTEF) located at the Kennedy Space Center in Cape Canaveral, Florida. The strength of the atmospheric turbulence is often characterized by three measurable parameters: the refractive index structure constant Cn2, the inner scale l0, and the outer scale L0. The optical path (L~1km) was instrumented such that direct comparisons could be drawn between the measured atmospheric turbulence parameters and the parameters of the gamma-gamma irradiance model. Variance of fade time data were found to agree well for smaller apertures where effects of aperture averaging are not present and in cases where scintillation is weak to moderate. It is suggested that a more appropriate PDF, with a heavier focus on aperture averaging, may be applied in future studies of these fade statistics.
Show less - Date Issued
- 2012
- Identifier
- CFE0004397, ucf:53153
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004397
- Title
- Passive, Wireless SAW OFC Strain Sensor and Software Defined Radio Interrogator.
- Creator
-
Humphries, James, Malocha, Donald, Richie, Samuel, Weeks, Arthur, Sundaram, Kalpathy, Saha, Haripada, University of Central Florida
- Abstract / Description
-
Surface acoustic wave (SAW) devices have exhibited unique capabilities to meet the demands for many applications due to the inherent properties of SAW devices and piezoelectric materials. In particular, SAW devices have been adapted as sensors that can be configured to operate both passively and wirelessly. SAW sensors can be operated in harsh environmental extremes where typical sensor technologies are not able to operate. Because the sensors are passive, a radio transceiver is required to...
Show moreSurface acoustic wave (SAW) devices have exhibited unique capabilities to meet the demands for many applications due to the inherent properties of SAW devices and piezoelectric materials. In particular, SAW devices have been adapted as sensors that can be configured to operate both passively and wirelessly. SAW sensors can be operated in harsh environmental extremes where typical sensor technologies are not able to operate. Because the sensors are passive, a radio transceiver is required to interrogate the sensor and receive the reflected response that has been modulated by the SAW device. This dissertation presents the design of a passive, wireless SAW OFC strain sensor and software defined radio (SDR) interrogator.A SAW strain sensor has been designed and tested using orthogonal frequency coding (OFC) on YZ-LiNbO3. OFC for SAW devices has been previously developed at UCF and provides both frequency and time diversity in the RFID code as well as providing processing gain to improve the sensor SNR. Strain effects in SAW devices are discussed and two sensor embodiments are developed. The first embodiment is a cantilever structure and provides insight on how strain effects the SAW device. The second embodiment bonds the SAW die directly to a test structure to measure the strain on the structure. A commercial wired foil strain gage provides a performance comparison and shows that the wireless SAW sensor performs comparably. A commercial-off-the-shelf SDR platform has been employed as the SAW sensor interrogator. The Universal Software Radio Peripheral (USRP) is available in many embodiments and is capable of operation of to 6GHz and up to 160MHz of bandwidth. In particular, the USRP B200 is utilized as the RF transceiver platform. Custom FPGA modifications are discussed to fully utilize the USRP B200 bandwidth (56MHz) and synchronize the transmit and receive chains. External hardware has also been introduced to the B200 to improve RF performance, all of which are incorporated into a custom enclosure. Post-processing of the SAW sensor response is accomplished in Python using a matched filter correlator routine to extract sensor information. The system is demonstrated by interrogating wireless OFC SAW temperature and strain sensors at 915MHz.
Show less - Date Issued
- 2016
- Identifier
- CFE0006329, ucf:51560
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006329
- Title
- Multi-transit echo suppression for passive wireless surface acoustic wave sensors using 3rd harmonic unidirectional transducers and Walsh-Hadamard-like reflectors.
- Creator
-
Rodriguez Cordoves, Luis, Malocha, Donald, Weeks, Arthur, Abdolvand, Reza, Moharam, Jim, Youngquist, Robert, University of Central Florida
- Abstract / Description
-
A passive wireless surface acoustic wave sensor of a delay-line type is composed of an antenna, a transducer that converts the EM signal into a surface acoustic wave, and a set of acoustic reflectors that reflect the incoming signal back out through the antenna. A cavity forms between the transducer and the reflectors, trapping energy and causing multiple unwanted echoes. The work in this dissertation aims to reduce the unwanted echoes so that only the main transit signal is left(-)the signal...
Show moreA passive wireless surface acoustic wave sensor of a delay-line type is composed of an antenna, a transducer that converts the EM signal into a surface acoustic wave, and a set of acoustic reflectors that reflect the incoming signal back out through the antenna. A cavity forms between the transducer and the reflectors, trapping energy and causing multiple unwanted echoes. The work in this dissertation aims to reduce the unwanted echoes so that only the main transit signal is left(-)the signal of interest with sensor information.The contributions of this dissertation include reflective delay-line device response in the form of an infinite impulse response (IIR) filter. This may be used in the future to subtract out unwanted echoes via post-processing. However, this dissertation will use a physical approach to echo suppression by using a unidirectional transducer. Thus a unidirectional transducer is used and also optimized for 3rd harmonic operation. Both the directionality and the coupling of the 3rd harmonic optimized SPUDT are improved over a standard electrode width controlled (EWC) SPUDT. New type of reflectors for the reflective delay-line device are also presented. These use BPSK type coding, similar to that of the Walsh-Hadamard codes. Two types are presented, variable reflectivity and variable chip-lengths. The COM model is used to simulate devices and compare the predicted echo suppression level to that of fabricated devices. Finally, a device is mounted on a tunable antenna and the echo is suppressed on a wireless operating device.
Show less - Date Issued
- 2017
- Identifier
- CFE0006912, ucf:51697
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006912
- Title
- Ultra-wideband Spread Spectrum Communications using Software Defined Radio and Surface Acoustic Wave Correlators.
- Creator
-
Gallagher, Daniel, Malocha, Donald, Delfyett, Peter, Richie, Samuel, Weeks, Arthur, Youngquist, Robert, University of Central Florida
- Abstract / Description
-
Ultra-wideband (UWB) communication technology offers inherent advantages such as the ability to coexist with previously allocated Federal Communications Commission (FCC) frequencies, simple transceiver architecture, and high performance in noisy environments. Spread spectrum techniques offer additional improvements beyond the conventional pulse-based UWB communications. This dissertation implements a multiple-access UWB communication system using a surface acoustic wave (SAW) correlator...
Show moreUltra-wideband (UWB) communication technology offers inherent advantages such as the ability to coexist with previously allocated Federal Communications Commission (FCC) frequencies, simple transceiver architecture, and high performance in noisy environments. Spread spectrum techniques offer additional improvements beyond the conventional pulse-based UWB communications. This dissertation implements a multiple-access UWB communication system using a surface acoustic wave (SAW) correlator receiver with orthogonal frequency coding and software defined radio (SDR) base station transmitter.Orthogonal frequency coding (OFC) and pseudorandom noise (PN) coding provide a means for spreading of the UWB data. The use of orthogonal frequency coding (OFC) increases the correlator processing gain (PG) beyond that of code division multiple access (CDMA); providing added code diversity, improved pulse ambiguity, and superior performance in noisy environments. Use of SAW correlators reduces the complexity and power requirements of the receiver architecture by eliminating many of the components needed and reducing the signal processing and timing requirements necessary for digital matched filtering of the complex spreading signal.The OFC receiver correlator code sequence is hard-coded in the device due to the physical SAW implementation. The use of modern SDR forms a dynamic base station architecture which is able to programmatically generate a digitally modulated transmit signal. An embedded Xilinx Zynq (TM) system on chip (SoC) technology was used to implement the SDR system; taking advantage of recent advances in digital-to-analog converter (DAC) sampling rates. SDR waveform samples are generated in baseband in-phase and quadrature (I (&) Q) pairs and upconverted to a 491.52 MHz operational frequency.The development of the OFC SAW correlator ultimately used in the receiver is presented along with a variety of advanced SAW correlator device embodiments. Each SAW correlator device was fabricated on lithium niobate (LiNbO3) with fractional bandwidths in excess of 20%. The SAW correlator device presented for use in system was implemented with a center frequency of 491.52 MHz; matching SDR transmit frequency. Parasitic electromagnetic feedthrough becomes problematic in the packaged SAW correlator after packaging and fixturing due to the wide bandwidths and high operational frequency. The techniques for reduction of parasitic feedthrough are discussedwith before and after results showing approximately 10:1 improvement.Correlation and demodulation results are presented using the SAW correlator receiver under operation in an UWB communication system. Bipolar phase shift keying (BPSK) techniques demonstrate OFC modulation and demodulation for a test binary bit sequence. Matched OFC code reception is compared to a mismatched, or cross-correlated, sequence after correlation and demodulation. Finally, the signal-to-noise power ratio (SNR) performance results for the SAW correlator under corruption of a wideband noise source are presented.
Show less - Date Issued
- 2015
- Identifier
- CFE0005794, ucf:50054
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005794
- Title
- Design, Fabrication, and Interrogation of Integrated Wireless SAW Temperature Sensors.
- Creator
-
Gallagher, Mark, Malocha, Donald, Richie, Samuel, Weeks, Arthur, Youngquist, Robert, Delfyett, Peter, University of Central Florida
- Abstract / Description
-
Wireless surface acoustic wave (SAW) sensors offer unique advantages over other sensor technologies because of their inherent ability to operate in harsh environments and completely passive operation, providing a reliable, maintenance-free life cycle. For certain SAW sensor applications the challenge is building a wirelessly interrogatable device with the same lifetime as the SAW substrate. The design of these application intensive sensors is complicated by the degradation of device bond...
Show moreWireless surface acoustic wave (SAW) sensors offer unique advantages over other sensor technologies because of their inherent ability to operate in harsh environments and completely passive operation, providing a reliable, maintenance-free life cycle. For certain SAW sensor applications the challenge is building a wirelessly interrogatable device with the same lifetime as the SAW substrate. The design of these application intensive sensors is complicated by the degradation of device bond wires, die adhesive, and antenna substrate. In an effort to maximize the benefits of the platform, this dissertation demonstrates wafer-level integrated SAW sensors that directly connect the thin film SAW to a thick film on-wafer antenna. Fully integrated device embodiments are presented that operate over a wide range of temperatures using different fabrication techniques, substrates, and coding principles.
Show less - Date Issued
- 2015
- Identifier
- CFE0005795, ucf:50047
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005795
- Title
- Automatic Detection of Brain Functional Disorder Using Imaging Data.
- Creator
-
Dey, Soumyabrata, Shah, Mubarak, Jha, Sumit, Hu, Haiyan, Weeks, Arthur, Rao, Ravishankar, University of Central Florida
- Abstract / Description
-
Recently, Attention Deficit Hyperactive Disorder (ADHD) is getting a lot of attention mainly for two reasons. First, it is one of the most commonly found childhood behavioral disorders. Around 5-10% of the children all over the world are diagnosed with ADHD. Second, the root cause of the problem is still unknown and therefore no biological measure exists to diagnose ADHD. Instead, doctors need to diagnose it based on the clinical symptoms, such as inattention, impulsivity and hyperactivity,...
Show moreRecently, Attention Deficit Hyperactive Disorder (ADHD) is getting a lot of attention mainly for two reasons. First, it is one of the most commonly found childhood behavioral disorders. Around 5-10% of the children all over the world are diagnosed with ADHD. Second, the root cause of the problem is still unknown and therefore no biological measure exists to diagnose ADHD. Instead, doctors need to diagnose it based on the clinical symptoms, such as inattention, impulsivity and hyperactivity, which are all subjective.Functional Magnetic Resonance Imaging (fMRI) data has become a popular tool to understand the functioning of the brain such as identifying the brain regions responsible for different cognitive tasks or analyzing the statistical differences of the brain functioning between the diseased and control subjects. ADHD is also being studied using the fMRI data. In this dissertation we aim to solve the problem of automatic diagnosis of the ADHD subjects using their resting state fMRI (rs-fMRI) data.As a core step of our approach, we model the functions of a brain as a connectivity network, which is expected to capture the information about how synchronous different brain regions are in terms of their functional activities. The network is constructed by representing different brain regions as the nodes where any two nodes of the network are connected by an edge if the correlation of the activity patterns of the two nodes is higher than some threshold. The brain regions, represented as the nodes of the network, can be selected at different granularities e.g. single voxels or cluster of functionally homogeneous voxels. The topological differences of the constructed networks of the ADHD and control group of subjects are then exploited in the classification approach.We have developed a simple method employing the Bag-of-Words (BoW) framework for the classification of the ADHD subjects. We represent each node in the network by a 4-D feature vector: node degree and 3-D location. The 4-D vectors of all the network nodes of the training data are then grouped in a number of clusters using K-means; where each such cluster is termed as a word. Finally, each subject is represented by a histogram (bag) of such words. The Support Vector Machine (SVM) classifier is used for the detection of the ADHD subjects using their histogram representation. The method is able to achieve 64% classification accuracy.The above simple approach has several shortcomings. First, there is a loss of spatial information while constructing the histogram because it only counts the occurrences of words ignoring the spatial positions. Second, features from the whole brain are used for classification, but some of the brain regions may not contain any useful information and may only increase the feature dimensions and noise of the system. Third, in our study we used only one network feature, the degree of a node which measures the connectivity of the node, while other complex network features may be useful for solving the proposed problem.In order to address the above shortcomings, we hypothesize that only a subset of the nodes of the network possesses important information for the classification of the ADHD subjects. To identify the important nodes of the network we have developed a novel algorithm. The algorithm generates different random subset of nodes each time extracting the features from a subset to compute the feature vector and perform classification. The subsets are then ranked based on the classification accuracy and the occurrences of each node in the top ranked subsets are measured. Our algorithm selects the highly occurring nodes for the final classification. Furthermore, along with the node degree, we employ three more node features: network cycles, the varying distance degree and the edge weight sum. We concatenate the features of the selected nodes in a fixed order to preserve the relative spatial information. Experimental validation suggests that the use of the features from the nodes selected using our algorithm indeed help to improve the classification accuracy. Also, our finding is in concordance with the existing literature as the brain regions identified by our algorithms are independently found by many other studies on the ADHD. We achieved a classification accuracy of 69.59% using this approach. However, since this method represents each voxel as a node of the network which makes the number of nodes of the network several thousands. As a result, the network construction step becomes computationally very expensive. Another limitation of the approach is that the network features, which are computed for each node of the network, captures only the local structures while ignore the global structure of the network.Next, in order to capture the global structure of the networks, we use the Multi-Dimensional Scaling (MDS) technique to project all the subjects from an unknown network-space to a low dimensional space based on their inter-network distance measures. For the purpose of computing distance between two networks, we represent each node by a set of attributes such as the node degree, the average power, the physical location, the neighbor node degrees, and the average powers of the neighbor nodes. The nodes of the two networks are then mapped in such a way that for all pair of nodes, the sum of the attribute distances, which is the inter-network distance, is minimized. To reduce the network computation cost, we enforce that the maximum relevant information is preserved with minimum redundancy. To achieve this, the nodes of the network are constructed with clusters of highly active voxels while the activity levels of the voxels are measured based on the average power of their corresponding fMRI time-series. Our method shows promise as we achieve impressive classification accuracies (73.55%) on the ADHD-200 data set. Our results also reveal that the detection rates are higher when classification is performed separately on the male and female groups of subjects.So far, we have only used the fMRI data for solving the ADHD diagnosis problem. Finally, we investigated the answers of the following questions. Do the structural brain images contain useful information related to the ADHD diagnosis problem? Can the classification accuracy of the automatic diagnosis system be improved combining the information of the structural and functional brain data? Towards that end, we developed a new method to combine the information of structural and functional brain images in a late fusion framework. For structural data we input the gray matter (GM) brain images to a Convolutional Neural Network (CNN). The output of the CNN is a feature vector per subject which is used to train the SVM classifier. For the functional data we compute the average power of each voxel based on its fMRI time series. The average power of the fMRI time series of a voxel measures the activity level of the voxel. We found significant differences in the voxel power distribution patterns of the ADHD and control groups of subjects. The Local binary pattern (LBP) texture feature is used on the voxel power map to capture these differences. We achieved 74.23% accuracy using GM features, 77.30% using LBP features and 79.14% using combined information.In summary this dissertation demonstrated that the structural and functional brain imaging data are useful for the automatic detection of the ADHD subjects as we achieve impressive classification accuracies on the ADHD-200 data set. Our study also helps to identify the brain regions which are useful for ADHD subject classification. These findings can help in understanding the pathophysiology of the problem. Finally, we expect that our approaches will contribute towards the development of a biological measure for the diagnosis of the ADHD subjects.
Show less - Date Issued
- 2014
- Identifier
- CFE0005786, ucf:50060
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005786
