Resonance frequency detuning (RFD) is a piezoelectric-based vibration reduction approach that applies to systems experiencing transient excitation through the system*s resonance—for example, turbomachinery experiencing changes in rotation speed, such as on spool-up and spool-down. This technique relies on the inclusion of piezoelectric material and manipulation of its electrical boundary conditions, which control the stiffness of the piezoelectric material. Resonance frequency detuning exploits this effect by intelligently switching between the open-circuit (high stiffness) and short-circuit (low stiffness) conditions as the excitation approaches resonance, subsequently shifting the natural frequency to avoid this resonance crossing and limit the response. The peak response dynamics are then determined by the system*s sweep rate, modal damping ratio, electromechanical coupling coefficient, and, most importantly, the trigger (represented here in terms of excitation frequency) that initiates the stiffness state switch. This thesis identifies the optimal frequency-based switch trigger over a range of sweep rates, damping ratios, and electromechanical coupling coefficients. With perfect knowledge of the system, the optimal frequency-based switch trigger decreases approximately linearly with the square of the coupling coefficient. Furthermore, phase of vibration at the time of the switch has a very small effect; switching on peak strain energy is marginally optimal. In practice, perfect knowledge is unrealistic and an alternate switch trigger based on an easily measurable parameter is necessary. As such, this thesis also investigates potential methods using the open-circuit piezoelectric voltage response envelope and its derivatives. The optimal switch triggers collapse to a near linear trend when measured against the response envelope derivatives and, subsequently, an empirical control law is extracted. This control law agrees well with and produces a comparable response to that of the optimal control determined using perfect and complete knowledge of the system.

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No. of bitstreams: 1 roscamp_m_me_jabo.pdf: 9443012 bytes, checksum: 69bacbdda807a3e9fee0f785465385c3 (MD5) Previous issue date: 2017-10-09 / A cirurgia piezoelétrica ou piezocirurgia é utilizada há várias décadas, porém em medicina veterinária são escassos os artigos publicados utilizando esta modalidade em cirurgias descompressivas da coluna vertebral de cães e gatos. Assim, aventou-se com esse trabalho investigar a aplicabilidade da mesma na realização da espondilectomia parcial ventral cervical (EPVC), comparando-a com a técnica convencional que utiliza brocas esféricas de alta rotação para o desgaste ósseo, utilizando o coelho (Oryctolagus cuniculus) como modelo experimental de cães e gatos. Para tanto foi utilizado o aparelho médico Mastersonic®, que possui duas peças de mão, uma piezoelétrica com ponteira ultrassônica tipo cinzel delicado (T1) e na outra, motor de alta rotação com brocas esférica de 2 mm (técnica convencional) (T2). A EPVC foi realizada entre a terceira e quarta vértebras cervicais e cada técnica foi realizada em 15 animais, devidamente anestesiados, os quais foram avaliados quanto à duração de cada etapa da cirurgia, variações de temperatura durante a execução da EPVC, visibilidade do campo cirúrgico, complicações trans e pós-operatórias e monitoração anestésica. Aos 14, 28 e 56 dias de pós-operatório (PO), cinco animais de cada tratamento foram submetidos à eutanásia e realizado estudo histopatológico do local da cirurgia, avaliando à resposta inflamatória, à cicatrização óssea e as lesões medulares. Os resultados mostraram que T1 demandou mais tempo para a execução da curetagem e maior perda de temperatura no foco cirúrgico durante a cirurgia. O tempo de acesso cirúrgico reduziu progressivamente em torno de 50% até o oitavo procedimento de cada tratamento (T1 e T2), e após isso se manteve com a mesma duração nos dois tratamentos. O tempo de uso do aparelho foi mais homogêneo em T1 e diminuiu progressivamente em T2, mas ao avaliar o tempo total da técnica de EPVC, não houve diferença entre os tratamentos. O T1 proporcionou melhor visibilidade do campo cirúrgico, com apenas um caso de sangramento ósseo, contra seis casos em T2. Observaram-se quatro casos de hemorragia de seio venoso vertebral durante a curetagem no T1 e dois casos no T2. Também ocorreram três casos de déficits proprioceptivos transitórios, com duração de até 72 horas no T1. A temperatura corporal e a taxa de uso do isoflurano decaíram com o tempo nos dois tratamentos, assim como a frequência cardíaca em T1. No estudo histopatológico observou-se resposta inflamatória mais ativa em T1 aos 14 dias de PO, porém aos 28 e 56 dias de PO foi semelhante entre os tratamentos, assim como a cicatrização óssea. Ainda houve mais lesões medulares com a piezocirurgia (T1), principalmente aos 14 e 28 dias de PO, com presença de malácia, esferócitos e células “Gitter”. Enquanto que na técnica convencional (T2), notou-se discreta degeneração Walleriana, apenas aos 14 dias de PO. Conclui-se que a piezocirurgia é aplicável na realização da EPVC com excelente visibilidade do campo operatório, facilidade de manuseio e rápida curva de aprendizagem, no entanto, demandou maior tempo para execução da espondilectomia e provocou mais complicações cirúrgicas e de lesões medulares, quando comparada à técnica convencional. / Piezoelectric surgery or piezosurgery has been used for several decades, but in veterinary medicine, articles published using this modality in decompressive surgery of the spine of dogs and cats are scarce. The aim of this study was to investigate the applicability of this technique to the performance of cervical ventral partial spondylectomy (CVPS), comparing it with the conventional technique using high-rotation spherical drills for bone wear using rabbit (Oryctolagus cuniculus) as an experimental model of dogs and cats.. For this was used Mastersonic® medical device that has two hand pieces, one piezoelectric type with ultrasonic delicate chisel tip (T1) and the other, high speed engine with spherical drills 2 mm (conventional technique) (T2). The CVPS was held between the third and fourth cervical vertebrae and each technique was performed on 15 animals, under anesthesia, which were evaluated for the duration of each stage of surgery, temperature variations during the execution of CVPS, the surgical field visibility, trans and postoperative complications and anesthetic monitoring. At 14, 28 and 56 postoperative days (PO), five animals per treatment were euthanized, and histological studies were carried to the surgical site by assessing the inflammatory response, and bone healing spinal injuries. The results showed that T1 required more time for curettage execution and highest loss of temperature at the surgical focus during surgery. Surgical access time progressively reduced by 50% until the eighth procedure of each treatment (T1 and T2), and after that it remained the same duration in both treatments. The time of use of the device was more homogeneous in T1 and progressively decreased in T2, but when evaluating the total time of the CVPS technique, there was no difference between treatments. The T1 provided better visibility of the surgical field, with only one case of bone bleeding, against six cases in T2. Four cases of vertebral venous sinus hemorrhage were seen during curettage in T1 and two cases in T2. There were also three cases of transient proprioceptive deficits, lasting up to 72 hours in T1. Body temperature and the rate of use of isoflurane declined over time in both treatments, as did heart rate in T1. Histopathological study there was more active inflammatory response in T1 at 14 days postoperatively, but after 28 and 56 days postoperatively was similar among treatments, as well as to bone healing. There were still more spinal cord injuries with the piezosurgery (T1), especially at 14 and 28 days of PO, with presence of malacia, spherocytes and Gitter cells. While the conventional technique (T2), it was noted discrete Wallerian degeneration, only at 14 days postoperatively. It is concluded that the piezosurgery is applicable in the performance of the CVPS with excellent visibility of the operative field, ease of handling and rapid learning curve, however, demanded more time for the execution of the spondylectomy and caused more surgical complications and spinal cord injuries, when compared to the conventional technique.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第22112号 / 理博第4539号 / 新制||理||1652(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 前野 悦輝, 教授 松田 祐司, 教授 石田 憲二 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

abstract: In engineering, buckling is mechanical instability of walls or columns under compression and usually is a problem that engineers try to prevent. In everyday life buckles (wrinkles) on different substrates are ubiquitous -- from human skin to a rotten apple they are a commonly observed phenomenon. It seems that buckles with macroscopic wavelengths are not technologically useful; over the past decade or so, however, thanks to the widespread availability of soft polymers and silicone materials micro-buckles with wavelengths in submicron to micron scale have received increasing attention because it is useful for generating well-ordered periodic microstructures spontaneously without conventional lithographic techniques. This thesis investigates the buckling behavior of thin stiff films on soft polymeric substrates and explores a variety of applications, ranging from optical gratings, optical masks, energy harvest to energy storage. A laser scanning technique is proposed to detect micro-strain induced by thermomechanical loads and a periodic buckling microstructure is employed as a diffraction grating with broad wavelength tunability, which is spontaneously generated from a metallic thin film on polymer substrates. A mechanical strategy is also presented for quantitatively buckling nanoribbons of piezoelectric material on polymer substrates involving the combined use of lithographically patterning surface adhesion sites and transfer printing technique. The precisely engineered buckling configurations provide a route to energy harvesters with extremely high levels of stretchability. This stiff-thin-film/polymer hybrid structure is further employed into electrochemical field to circumvent the electrochemically-driven stress issue in silicon-anode-based lithium ion batteries. It shows that the initial flat silicon-nanoribbon-anode on a polymer substrate tends to buckle to mitigate the lithiation-induced stress so as to avoid the pulverization of silicon anode. Spontaneously generated submicron buckles of film/polymer are also used as an optical mask to produce submicron periodic patterns with large filling ratio in contrast to generating only ~100 nm edge submicron patterns in conventional near-field soft contact photolithography. This thesis aims to deepen understanding of buckling behavior of thin films on compliant substrates and, in turn, to harness the fundamental properties of such instability for diverse applications. / Dissertation/Thesis / Ph.D. Mechanical Engineering 2014