1,721,001 research outputs found
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Creating and teaching Introduction to Linux as a Master's student
Get PDFIn this report, I discuss my experience creating and teaching a course called Introduction to Linux. The course provides students with enough knowledge to feel comfortable with a command line in the Linux operating system. Introduction to Linux is geared toward underclassmen in the ECE department at The University of Texas at Austin, though it is open to anyone interested in becoming familiar with Linux. I describe the motivation for creating the course, the methodology I employed when teaching the class, and steps that can be taken to improve the course in future semesters.Electrical and Computer Engineerin
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Perfusion and heat transfer in the canine prostate
No full texttextA variety of thermally-based treatments for prostate-related diseases has motivated
efforts to analyze heat transfer in the prostate. In order to develop an accurate heat
transfer model of living tissue, the complex interaction of perfusion and heat
transfer must be addressed. An initial step to quantifying the effect is to measure
the normal perfusion level and response to thermal stimuli. Using the conventional
microspheres method, the spatial and temporal heterogeneity in perfusion within
canine prostates were quantified as well as the perfusion response to hyperthermic
conditions. Besides the direct measurement of perfusion with microspheres,
thermal diffusion methods infer perfusion by assuming the Pennes tissue heat
transfer model. Simultaneous measurements of perfusion by both methods in the
normothermic and hyperthermic canine prostates revealed disagreements. This was
hypothesized to arise from the inability of the Pennes model to account for discrete
thermally significant blood vessels. To test this, a heat transfer model of the
thermal measurement technique in canine prostate tissue was developed. The
perfusion heat transfer was modeled with discrete blood vessels based upon vascular
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parameters collected in canine prostates. This model was then analyzed numerically
using finite element methods. Similar differences were shown by the numerical
experiments. Comparison of the two different perfusion measurement methods
provided insights into the utility of each method. Furthermore, the new perfusion
heat transfer model can be used to replace the commonly adopted Pennes model.
Overall, this dissertation provided insights into the areas of prostate perfusion,
perfusion measurement methods, and heat transfer in perfused prostate tissue.Biomedical Engineerin
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High performance wireless bio-impedance measurement system
Get PDFtextElectrical and Computer EngineeringA high performance, wireless bio-impedance measurement system has been designed for the purpose of monitoring essential electrical properties of the heart during cardiac ablation. The system is broken into three parts: a spring-loaded device to house a tetrapolar surface probe and sensors, a wireless bio-impedance measurement system, and a desktop base station for graphical data display and acquisition. The system is specifically designed for a tetrapolar-electrode configuration where the two outer electrodes served as a current source operating at 20 kHz with an amplitude of 100 µArms and the two inner electrodes served as voltage sensing electrodes. In addition, the system also has a dedicated channel for current sense. The system is designed to be modular and reconfigurable for different measurement needs. Epochs of both discrete voltage and current samples generated by the voltage-controlled current source are processed using a digital signal processing algorithms to generate admittance measurements. In addition to the admittance’s magnitude and phase, pressure, electrocardiogram (EKG), and temperature (two channels) data are also acquired. The measurements are then wirelessly transmitted from the bio-impedance measurement system to a base station where data are processed and viewed graphically. The final system updates the admittance, pressure, EKG, and two temperature channels at 320 Hz, consumes less than 3 W, and has percent of measurement errors of 7 % and 2 % for capacitive and resistive measurements in the range of 100 pF to 10000 pF and 300 Ω to 1600 Ω, respectively. Instrument design, calibration, verification, and modeling are at the heart of this thesis. In the future, the instrument will be deployed for various bio-impedance measurements that require a high degree of linearity, precision, and a wide input range.Electrical and Computer Engineerin
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Application specific DAC and ADC for a bio-impedance measurement circuit
Get PDFA transistor level implementation of a 3 bit digital harmonic canceling (DHC) digital to analog converter (DAC), and a 10 bit successive approximation register (SAR) analog to digital converter (ADC) is designed. The circuits are intended to be a part of a bio-impedance measurement system in which a current is injected into the myocardium tissue and blood pool for the purpose of determining the heart’s stroke volume. The DHC DAC injects a 100 μA[subscript rms] current at a 20 kHz fundamental frequency using appropriately weighted current mirrors from a 160 kHz square-wave reference clock. A [function subscript s] = 160 kS/s ADC is designed with synchronous SAR logic, bottom-plate sampling, and a charge-redistribution capacitive DAC.Electrical and Computer Engineerin
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Low-power techniques for high-performance pipelined analog to digital converter
Get PDFLow-power and small size analog to digital converters (ADCs) are the strategic building blocks in state of the art mobile wireless communication systems. Various techniques have been developed to reduce both power consumption and die area of the ADC. Among these, the opamp-sharing technique shows the most promise. In opamp-sharing, power and die area are saved by sharing one opamp between two successive pipeline stages. However, this technique suffers from the well-known memory effect drawback due to the absence of the reset phase that discharges the opamp's input parasitics. In this dissertation, this drawback is solved by introducing a discharge phase before the opamp is used for the pipeline stages without compromising speed and resolution of the ADC. Further power and area reduction is achieved by using a capacitor-sharing technique. This technique reduces the effective load capacitance of the opamp by reusing the charge on the feedback capacitor for the MDAC operation of the following stage, resulting in faster settling without increasing opamp power. The proposed low input-capacitance variable-gm opamp also helps to reduce the memory effect and improves the settling behavior of the stage output by increasing the bandwidth of the opamp while input parasitics of the opamp are kept small. The prototype designs of a 10-bit 50MSample/s pipelined ADC and a 14-bit 100MSample/s pipelined ADC implemented in 0.18¹m CMOS technology demonstrate the effectiveness of the proposed techniques. The first ADC achieves 56.2dB SNDR and 72.7dB SFDR for a Nyquist input at full sampling rate while consuming 12 mW from a 1.8-V supply. The FOM, defined as, [power/2[superscript ENOB].Fs], is 0.46 pJ/step with Fin = 24.5MHz at 50MS/s. The second ADC achieves 72.4dB SNR and 88.5dB SFDR at 100MS/s with a 46MHz input and consumes 230mW from a 3V supply. The FOM of the second ADC is 0.69 pJ/step with Fin = 46MHz at 100MS/s.Electrical and Computer Engineerin
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High-performance [delta sigma] analog-to-digital conversion
No full texttextThis dissertation is about a new [delta sigma] analog-to-digital converter that offers enhanced quantization noise suppression at low oversampling ratios. This feature makes the converter attractive in applications where speed and resolution are simultaneously demanded. The converter exploits double-sampling for speed, and takes advantage of a new loop-filter to pin down passband quantization noise. A proto-type is fabricated in 0.18-[mu]m CMOS and tested. Results show that at 200-MS/s, the converter achieves an effective number of bits (ENOB) of 12.2-b in a 12.5-MHz signal band while consuming 89-mW from a 1.8-V supply. Using a common performance metric that takes into account of ENOB and signal bandwidth, the prototype outperforms all previously-reported IEEE switched-capacitor [delta sigma] modulators.Electrical and Computer Engineerin
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Implantable intracardiac bioimpedance system
Get PDFtextAn implantable intracardiac bioimpedance system has been designed to measure the real and imaginary parts of impedance in a dynamic cardiac setting. The system is broken into two parts: an implantable wireless device and a desktop base station. This measurement is performed using both tetrapolar and tripolar electrode configurations where a 20 kHz current field is applied to the intracardiac blood pool and myocardium. Epochs of discrete voltage samples from the resulting electric field are analyzed using a digital signal processing algorithm to generate impedance measurements. Measurements are then wirelessly transmitted from the implantable device to a base station where advanced signal processing algorithms are applied and the data is plotted in real-time. The final system measures 485 impedance samples/sec, consumes 50 mA when active, and has a percent of measurement error less than 1% for the intracardiac bioimpedance range. The device has been extensively tested to ensure the quality of measurements required for future human use. Instrument design, calibration, verification, experimentation, and modeling are the primary topics of this thesis. Moving forward, the system will be used in studies where dynamic bioimpedance signals measured in the right and left ventricles of the heart will be used to derive stroke volume.Electrical and Computer Engineerin
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Medical instrumentation and finite element analysis for the assessment of vulnerable plaque
Get PDFtextElectrical and Computer Engineerin
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In vivo measurements of the heat convection coefficient on the endocardial surface
Get PDFtextThis work describes the fundamentals, calibration procedure and in vivo results
of an instrument for the measurement of the heat convection coefficient between
the endocardium and the circulating blood flow. The heat transfer parameters
will assist calculating the proper dose for radio-frequency ablation. The probe is
a thermistor mounted in a Swan-Ganz catheter, and it is driven by a constant
temperature anemometer circuit. A 1-D thermal model of the sensor behavior in
a convective medium, the calibration procedure, and the apparatus are explained
in detail. A performance analysis of the instrument in the range tested showed
that the average absolute error of full scale was 7.4 %, and its time-constant was
0.05 s. This instrument was used to measure the heat transfer on the right atrial and
ventricular endocardial surfaces of two pigs in vivo. The average heat convection
coefficients found were between 510 and 4800 Wm−2K−1
. It was found that the
average heat convection coefficient varied significantly both spatially and temporally
on the endocardium.Electrical and Computer Engineerin
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Design and development of a modular robot for research use
Get PDFtextThis report summarizes the work performed for the design and development of the Proteus research robot. The Proteus design is motivated by the need for a modular, flexible, and usable autonomous robotic platform. To accomplish these goals, a modular hardware architecture coupled with low-power, high-computation processing is presented. The robot is subdivided into three layers: mobility, computation, and application. The interface between layers is characterized by well defined APIs and may be individually replaced to achieve different functionality. An efficient low-level event scheduler is described along with higher-level software algorithms for motion control and navigation. Experiments of Proteus robots are provided including field tests and collaboration with outside research institutions.Electrical and Computer Engineerin
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