Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

Thesis (M.S.)--University of Michigan, 1978.

Thesis (M.S.)--University of Michigan, 1979.

Thesis (M.S.)--California Polytechnic State University, 2010. / Title from PDF title page; viewed on May 3, 2010. Major professor: Robert S. Crockett, Ph.D. "Presented to the faculty of California Polytechnic State University, San Luis Obispo." "In partial fulfillment of the requirements for the degree [of] Master of Science in Engineering, with a Specialization in Biomedical Engineering." "March 2010." Includes bibliographical references (p. 39-41).

Thesis (M.S.)--University of Michigan, 1978.

Thesis (M.S.)--University of Michigan, 1979.

This work addresses issues in energy harvesting that have plagued the potential use of harvesting through the piezoelectric effect at the MEMS scale. Effective energy harvesting devices typically consist of a cantilever beam substrate coated with a thin layer of piezoceramic material and fixed with a tip mass tuned to resonant at the dominant frequency of the ambient vibration. The fundamental natural frequency of a beam increases as its length decreases, so that at the MEMS scale the resonance condition occurs orders of magnitude higher than ambient vibration frequencies rendering the harvester ineffective. Here we study two new geometries for MEMS scale cantilever harvesters. The zigzag and spiral geometries have low fundamental frequencies which can be tuned to the ambient vibrations. The second issue in energy harvesting is the frequency sensitivity of the linear vibration harvesters. A nonlinear hybrid energy harvester is presented that has a wide frequency bandwidth and large power output. Finally, linear and nonlinear energy harvesting devices are designed for powering the cardiovascular pacemakers using the vibrations in the chest area induced by the heartbeats. The mechanical and electromechanical vibrations of the zigzag structure are analytically modeled, verified with Rayleigh's method, and validated with experiments. An analytical model of coupled bending torsional vibrations of spiral structure is presented. A novel approximation method is developed for analyzing the electromechanical vibrations of energy harvesting devices. The unified approximation method is effective for linear, nonlinear mono-stable, and nonlinear bi-stable energy harvesting. It can also be utilized for piezoelectric, electromagnetic or hybrid energy harvesters. The approximation method accurately approximates the effect of energy harvesting on vibrations of energy harvester with changes in damping ratio and excitation frequency. Experimental investigations are performed to verify the analytical model of the nonlinear hybrid energy harvester. A detailed experimental parametric study of the nonlinear hybrid design is also performed. Linear and nonlinear energy harvesting devices have been designed that can generate sufficient amounts of power from the heartbeat induced vibrations. The nonlinear devices are effective over a wide range of heart rate. / Ph. D.

published_or_final_version / Medicine / Doctoral / Doctor of Philosophy

Orientador: Marcos Augusto de Moraes e Silva / Coorientador: Juliana Bassalobre Carvalho Borges / Banca: Rubens Ramos de Andrade / Banca: Reinaldo Ayer de Oliveira / Banca: Alfredo José Rodrigues / Banca: Cláudio José Rubira / Resumo: Desde os primeiros relatos (1957 e 1959) até os tempos atuais, não há dúvida de que os marca-passos cardíacos modificaram a história natural das doenças do ritmo cardíaco. No entanto, o fato de prolongarem a sobrevida dos pacientes que se beneficiaram dessa tecnologia não tem, ainda nos dias de hoje, uma avaliação da sua influência na qualidade de vida (QV) que responda a todas as questões pertinentes. O objetivo do presente estudo foi avaliar a percepção da QV em pacientes portadores de marca-passo (MP) cardíaco definitivo e a sua relação com gênero, classe funcional (CF), idade, índice de massa corporal (IMC), modo de estimulação e tempo de implante. Foram estudados 107 pacientes, de ambos os gêneros (50,5% masculino e 49,5% feminino), com tempo de implante de MP entre um e doze meses (média de 6,36 ± 2,99 meses), estáveis clinicamente e com idade acima de 18 anos (média de 69,3 ± 12,6 anos). Os voluntários foram avaliados utilizando-se protocolo com dados pessoais, sinais vitais, antecedentes pessoais e perguntas referentes ao MP cardíaco. Foram aplicados também testes específicos como: IMC, CF (Goldman) e questionários de QV (SF-36 e AQUAREL). Foi realizada análise estatística pelos testes t, Kruskal-Wallis e correlação de Spearman, com nível de significância de 5%. O estudo foi aprovado pelo Comitê de Ética em Pesquisa Envolvendo Seres Humanos, da Faculdade de Medicina de Marília. Encontraram-se 70% dos pacientes com CF I e 63,4% acima do peso (média IMC 27,2 ± 7,86). A maioria das indicações para implante foi por bloqueios atrioventriculares (57,9%) e doença do nó sinusal (28%), sendo os marca-passos bicamerais utilizados em 86,9%. As principais comorbidades encontradas foram: doença de Chagas, hipertensão arterial sistêmica e diabetes mellitus. No questionário SF-36, o menor escore ocorreu... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Since the first reports (1957, 1959) until nowadays, there is no doubt that cardiac pacemakers changed the natural history of the cardiac rhythm diseases. However, the fact that prolonging survival of patients who have benefited from this technology has not yet today, an assessment of its impact on quality of life (QoL) to answer all relevant questions. The aim of this trial was to evaluate the perception of QoL in patients using definitive cardiac pacemaker, and its relation with gender, functional class (FC), age, Body Mass Index (BMI), pacing mode, and time of implant. One hundred and seven patients were evaluated (50,5% male and 49.5% female), with implant time of the pacemaker between one and 12 months (mean 6.36 ±2.99 months), clinically stables, and aged ≥18 years (mean 69.3 ±12.6 years). Subjects were evaluated using a protocol that included: personal data, vital signs, personal history, and questions regarding the cardiac pacemaker. It also included specific tests, such as: BMI, functional class (FC; Goldman) and QoL questionnaires (SF-36 and AQUAREL). Statistical analysis with t test, Kruskal-Wallis and Spearman correlation, 5% significance level, were conducted. The trial was approved by the Committee of Ethics in Research Involving Humans, Marília's Medical School. The investigators found 70.0% of the patients with functional class I (FC I) and 63.4% (overall) overweight (mean BMI 27.2 ±7.86). Most of the implant indications were atrioventricular block (57.9%) and sinus node disease (28%). Bicameral pacemaker was used in 86.9% of the patients. Primary co-morbidities were: Chagas Disease, systemic hypertension and Diabetes Mellitus. The lowest score at SF-36 questionnaire was at the domain Physical Aspects, with 58.4, and the highest at Social Aspects, with 89.1. The lowest score at Aquarel questionnaire was found at the domain... (Complete abstract click electronic access below) / Doutor

Because the voltage amplitude of a heart beat is small compared to the amplitude of exponential noise, pacemakers have difficulty registering the responding heart beat immediately after a pacing pulse. This thesis investigates use of digital filters, an inverse filter and a lowpass filter, to eliminate the effects of exponential noise following a pace pulse. The goal was to create a filter which makes recognition of a haversine wave less dependent on natural subsidence of exponential noise. Research included the design of heart system, pacemaker, pulse generation, and D sensor system simulations. The simulation model includes the following components: \ • Signal source, A MA TLAB generated combination of a haversine signal, exponential noise, and myopotential noise. The haversine signal is a test signal used to simulate the QRS complex which is normally recorded on an ECG trace as a representa tion of heart function. The amplitude is approximately 10 mV. Simulated myopotential noise represents a uniformly distributed random noise which is generated by skeletal muscle tissue. The myopotential noise has a frequency spectrum extending from 70 to 1000Hz. The amplitude varies from 2 to 5 mV. Simulated exponential noise represents the depolarization effects of a pacing pulse as seen at the active cardiac lead. The amplitude is about -1 volt, large in comparison with the haversine signal. • AID converter, A combination of sample & hold and quantizer functions translate the analog signal into a digital signal. Additionally, random noise is created during quantization. • Digital filters, An inverse filter removes the exponential noise, and a lowpass filter removes myopotential noise. • Threshold level detector, A function which detects the strength and amplitude of the output signal was created for robustness and as a data sampling device. The simulation program is written for operation in a DOS environment. The program generates a haversine signal, myopotential noise (random noise), and exponential noise. The signals are amplified and sent to an AID converter stage. The resultant digital signal is sent to a series of digital filters, where exponential noise is removed by an inverse digital filter, and myopotential noise is removed by the Chebyshev type I lowpass digital filter. The output signal is "detected" if its waveform exceeds the noise threshold level. To determine what kind of digital filter would remove exponential noise, the spectrum of exponential noise relative to a haversine signal was examined. The spectrum of the exponential noise is continuous because the pace pulse is considered a non-periodic signal (assuming the haversine signal occurs immediately after a pace pulse). The spectrum of the haversine is also continuous, existing at every value of frequency co. The spectrum of the haversine is overlapped by the spectrum of and amplitude of the exponential, which is several orders of magnitude larger. The exponential cannot be removed by conventional filters. Therefore, an inverse filter approach is used to remove exponential noise. The transfer function of the inverse filter of the model has only zeros. This type of filter is called FIR, all-zero, non recursive, or moving average. Tests were run using the model to investigate the behavior of the inverse filter. It was found that the haversine signal could be clearly detected within a 5% change in the time constant of the exponential noise. Between 5% and 15% of change in the time constant, the filtered exponential amplitude swamps the haversine signal. The sensitivity of the inverse filter was also studied: when using a fixed exponential time constant but changing the location of the transfer function, the effect of the exponential noise on the haversine is minimal when zeros are located between 0.75 and 0.85 of the unit circle. After the source signal passes the inverse filter, the signal consists only of the haversine signal, myopotential noise, and some random noise introduced during quantization. To remove these noises, a Chebyshev type I lowpass filter is used.