Capacitive sensors are frequently applied to curved target surfaces for precision displacement measurements. In most cases, these sensors have not been recalibrated to take the curvature of the target into consideration. This recalibration becomes more critical as the target surface becomes smaller in comparison to the sensor. Calibration data are presented for a variety of capacitance probe sizes with widely varying geometries. One target surface particularly difficult to characterize is the inner surface of small holes, less than one millimeter in diameter. Although contact probes can successfully measure the inner surface of a hole, these probes are often fragile and require additional sensors to determine when contact occurs. Probes may adhere to the wall of the hole, and only a small number of data points are collected. Direct capacitance measurement of small holes requires a completely new capacitance probe geometry and method of operation. A curved, elongated surface minimizes the gap between the sensor surface and the inner surface of the hole. Reduction in the size of the sensing area is weighed against electronics limitations. The performance of a particular probe geometry is studied using computer simulations to determine the optimal probe design. Multiple, overlapping passes are deconvolved to reveal finer features on the surface of the hole. A prototype sub-millimeter capacitance probe is machined from tungsten carbide, with four additional material layers added using ebeam deposition. Several techniques are studied to remove these layers and create a sensing area along one side of the probe. Both mechanical processes and photolithography are employed.

This dissertation develops surface integral equations using constraint-based Helmholtz decompositions for electromagnetic modeling. This new approach is applied to the electric field integral equation (EFIE), and it incorporates a Helmholtz decomposition (HD) of the current. For this reason, the new formulation is referred to as the EFIE-hd. The HD of the current is accomplished herein via appropriate surface integral constraints, and leads to a stable linear system. This strategy provides accurate solutions for the electric and magnetic fields at both high and low frequencies, it allows for the use of a locally corrected Nyström (LCN) discretization method for the resulting formulation, it is compatible with the local global solution framework, and it can be used with non-conformal meshes. To address large-scale and complex electromagnetic problems, an overlapped localizing local-global (OL-LOGOS) factorization is used to factorize the system matrix obtained from an LCN discretization of the augmented EFIE (AEFIE). The OL-LOGOS algorithm provides good asymptotic performance and error control when used with the AEFIE. This application is used to demonstrate the importance of using a well-conditioned formulation to obtain efficient performance from the factorization algorithm.

<p>This thesis explores the use of nonlinear crystals from theKTiOPO₄(KTP) family with the aim to extend the possibleapplications for laser sources and to gain more knowledge aboutthe material’s benefits and limits. The work focussed onoptical parametric oscillators (OPOs) and optical parametricamplifiers (OPAs), which employ second order nonlinearprocesses. Both devices transfer energy from a laser beam at aparticular wavelength to a different wavelength, which istuneable. In OPOs two new beams at different wavelengths aregenerated, whereas in OPAs an existing weak beam is amplified.The essential part of these devices, which enables theoccurrence of the energy conversion, is a nonlinear crystal. Inthis work the ferroelectric crystals KTP and RbTiOPO₄(RTP) have been utilized.</p><p>By modifying the material’s structure,quasi-phasematching can be obtained, which is a crucialrequirement for achieving efficient energy conversion betweenthe incident and the generated waves. The fabrication ofquasi-phasematched crystals is dependent on the controlledreversion of the material’s spontaneous polarisation,which is accomplished by periodic electric field poling.</p><p>Nanosecond pulses of more than 200 kW were generated in the“eye-safe”region by employing a double pass OPA.Small signal gains exceeding 75 dB were obtained for anessentially diffraction limited beamwithout spectralbroadening of the seed. By subsequent signal coupling intofibres substantial broadening was accomplished. A systematicmeasurement series of several RTP crystals allowed us toaccurately determine the wavelength and temperature dispersionof the refractive index, which are two essential requirementsfor further employment of this material. The OPOs based on RTPwere widely tuneable by controlling the temperature. It wasalso concluded that RTP behaves similar to KTP in parametricdevices, thus being a material, which can sustain high powers,possesses large nonlinear coefficients and can operate in abroad wavelength region.Efficient Raman oscillation concurrent with parametricoscillation was observed and analysed in several KTP samples.This gave further insight into the processes taking placeinside the material when performing as a frequency converter,if the generated idler lies in the absorption band.This thesis also covers the investigation of afemtosecond optical parametric chirped pulse amplifier.Temporally stretched seed pulses were amplified to 85 µJ,resulting in a gain above 60 dB, and subsequent recompressionresulted in 270 fs pulses.</p><p><b>Keywords:</b>nonlinear optics, KTiOPO₄, optical parametric oscillator, optical parametricamplifier, RbTiOPO₄, quasi-phasematching, electric field poling,stimulated Raman scattering.</p>

It has been shown in previous studies that at 110 km altitude, the electron temperature can be quite large in the presence of strong electric fields. This thesis explores the possibility of deviations from the normal trends in the high latitude E-region electron heating in reaction to strong electric fields. The study is based on data from the EISCAT Incoherent Scatter Radar during the International Polar Year. Out of a large number of possibilities (the radar operated essentially on a continuous basis for a year) only seven events proved to have sufficiently strong electric fields and large enough plasma densities to be characterized as ‘good heating events’. The electron temperature enhancements in these events, at 110 km, were several hundred K above from the background temperature and correlated well with ion temperature at 150 km altitude. The results for these good events agreed very well with past studies, aside from the smaller starting temperatures which were likely connected to the quiet solar conditions at the time. This stated, a different type of E region electron heating event was identified. In that case the E region electron densities were small (night-time conditions free of electron precipitation) and the electron temperatures reached a maximum near 150 km altitude. In those events the electron temperature enhancements extended down to the lower altitudes, introducing small, but detectable, electron temperature enhancements all the way down to 105 km altitude. .

This paper presents the early-stage simulation results of linear dark field control (LDFC) as a new approach to maintaining a stable dark hole within a stellar post-coronagraphic PSF. In practice, conventional speckle nulling is used to create a dark hole in the PSF, and LDFC is then employed to maintain the dark field by using information from the bright speckle field. The concept exploits the linear response of the bright speckle intensity to wavefront variations in the pupil, and therefore has many advantages over conventional speckle nulling as a method for stabilizing the dark hole. In theory, LDFC is faster, more sensitive, and more robust than using conventional speckle nulling techniques, like electric field conjugation, to maintain the dark hole. In this paper, LDFC theory, linear bright speckle characterization, and first results in simulation are presented as an initial step toward the deployment of LDFC on the UA Wavefront Control testbed in the coming year.

This study examines the potential of Schwann cells (SCs) to be manipulated by electric fields (EFs) in order to improve recovery from spinal cord injury (SCI). It had long been believed that the central nervous system (CNS) is incapable of regeneration, but recent studies have proven otherwise. SC transplants are known to be useful in promoting axon regeneration after SCI, but is not sufficient for functional recovery. EFs are known to exist in vivo, and have been known to drastically affect the morphology and behavior of cells in various tissues. It was the hypothesis of this study that the conditioning and observed alignment of SCs was a reproducible phenomenon that could promote the growth of axons. It was found that SCs could be aligned at various field strengths and preliminary data suggest that aligned SCs increased the length and directionality of axons extending from DRG explants.

Anisotropic thermoelectric effects can be measured in certain materials. Anisotropy can also be simulated using a repeated, layered structure of two materials cut at an angle. Various aspect ratios and angles of inclination are investigated in device geometry in order to maximize the thermopower. Eddy currents have been shown to occur in thermoelectric devices, and evidence of these currents are revealed in finite element analysis of the artificially synthesized anisotropic Peltier effect.

Em processos de crescimento de cristais pelo método de Czochralski, é observado que um campo elétrico aplicado ao cristal durante o processo de crescimento modifica a quantidade de dopante incorporada ao cristal. É desenvolvido um modelo, baseado na teoria de Burton, Prim e Slichter, levando-se em consideração as duas classes de material envolvidas, os óxidos e os semicondutores, e os efeitos produzidos pelo campo elétrico, eletromigração, subresfriamento constitucional, Efeito Peltier e efeito Seebeck. Resultados experimentais obtidos em crescimentos de LiNbO3:Cr2O3 e Si:Al são usados para aplicações do modelo / In crystal growth processes through the Czochralski method, it is observed that an electrical field applied to the crystal during the growth process modifies the quatity of the dopant incorporated to the crystal. A model is developed based on Burton, Prim and Slichter´s theory, taking into consideration two classes of materials, the oxides and the semiconductors, and the effects produced by the electrical field, electromigration, constitutional supercooling, Peltier Effect, Seebeck Effect. Experimental results obtained from the growth of the LiNbO3:Cr2O3 e Si:Al singlecrystals are used to the model application

O conceito de que estimulação elétrica promove o reparo de fraturas tem uma longa história, datada de 1812. O mecanismo pelo qual estimulação elétrica promove a osteogênese ainda é assunto de especulação científica, entretanto esse método não farmacológico, utilizado no presente trabalho, já mostrou efeitos positivos na promoção e estímulo da osteogênese. O presente trabalho objetivou analisar a influência da aplicação de campo elétrico pulsado nas características histológicas e propriedades mecânicas do tecido ósseo em osteotomias experimentais realizadas em tíbias de ratos. Foram utilizados 52 ratos com fraturas cirúrgicas unilaterais do terço médio da tíbia, sem lesão dos músculos e do periósteo. Os animais foram divididos em dois grupos: grupo controle, que não recebeu estimulação e grupo tratado com campo elétrico. Esses foram divididos em dois subgrupos: animais sacrificados no 19º pós-operatório e animais sacrificados no 27º pós-operatório. O membro fraturado foi tratado com campo elétrico pulsado com freqüência fundamental de 1,5 MHz e 200 \'mü\'s de largura de pulso, em sessões diárias de 20 minutos. Realizou-se radiografia desse membro no dia da cirurgia e do sacrifício. Após o tratamento sacrificaram-se os ratos e extraíram-se suas tíbias para a obtenção de material para a análise morfométrica e ensaio mecânico de flexão. Os ensaios biomecânicos revelaram que houve diferença significativa entre as médias dos grupos tratado 18 e 12 dias somente para a tensão, sendo esta maior para o grupo tratado 18 dias, para as demais propriedades mecânicas analisadas não houve diferença significativa. A análise morfométrica determinou que a relação entre os grupos controle 18 dias com tratado 18 dias bem como entre os grupos tratado 12 dias e tratado 18 dias das médias das áreas de osso formado apresentaram diferenças estatisticamente significantes. Esses resultados sugerem que existe um incremento na síntese de matriz orgânica no grupo tratado, não acompanhado linearmente pela síntese mineral. A diferença estatisticamente significativa nas tensões de ruptura, por outro lado, sugere que o aumento no grau de mineralização encontra-se em curso. / The concept that electrical stimulation promotes the repair of fractures has a long history, dated of 1812. The mechanism for which electrical stimulation promotes osteogenesis is still subject of scientific speculation, however that method non-pharmacological, used in the present work has already showed positive effects in the promotion and incentive of osteogenesis. The present work objectified to analyze the influence of the application of electric field pulsed in the histological characteristic and mechanical properties of the bone tissue in experimental osteotomy accomplished in tibias of rats. 52 rats were used with unilateral surgical fractures of the medium third of the tibia, without lesion of the muscles and of the periosteum. The animals were divided in two groups: group control, that didn\'t receive stimulation and treated group with electric field. These were divided in two subgroups: animals sacrificed in the 19th after operation and animals sacrificed in the 27th after operation. The fracture member was treated with electric field pulsed with fundamental frequency of 1,5 MHz and 200 \'mü\'s of pulse width, in daily sessions of 20 minutes. The x-ray of that member took place in the day of the surgery and of the sacrifice. After the treatment the rats were sacrificed and their tibias were extracted for the material obtaining for analysis morfometric and mechanical rehearsal of flexion. The mechanical rehearsals revealed that there was only significant difference among the averages of the treated groups 18 and 12 days for the tension, the treated group 18 days had a larger tension, for the other analyzed mechanical properties there was not significant difference. The averages of the moment of inertia and area went significantly larger for the treated group 18 days compared with the respective averages of the control group controls. The treated group 12 days presented averages significantly larger when compared to the properties: moment of inertia, neutral line and area with the control group 12 days. These results suggest that an increment exists in the synthesis of organic matrix in the treated group, not accompanied lineally by the mineral synthesis. The difference significant statistic in the rupture tensions, on the other hand, suggests that the increase in the mineralization degree meets in course.

Acredita-se que sinais elétricos endógenos afetem remodelamento, metabolismo, reparo e crescimento ósseos. Existe uma ampla literatura que trata do efeito de sinais elétricos externos sobre as respostas de síntese, mitogênese e proliferação em osteoblastos e células ósseas in vitro. Acredita-se que as respostas fisiológicas ao estimulo elétrico sejam devidas a mecanismos celulares que envolvem variações na concentração citosólica de cálcio. No presente estudo esse efeito celular foi observado através da estimulação direta, por campo elétrico de intensidade fisiologicamente significativa de 10mV/cm e frequência 1,5 MHz, de células ósseas em cultura primária obtidas a partir da calota calvária de ratos da raça Sprague-Dawley. Os mecanismos de transdução do campo elétrico são investigados pela mensuração em tempo real do efeito do campo elétrico na concentração citosólica de Ca2+ utilizando-se técnica de fluorescência de Fura-2, em um sistema que permite a medida em células individuais. As estimulações elétricas resultaram em variações significativas na concentração de cálcio citosólico. Mais especificamente, observou-se um aumento na amplitude e na duração das oscilações de cálcio iônico, com tempos de latência variáveis para as células estudadas. / Endogenous electrical signals have been thought to affect bone remodeling, metabolism, healing and growth. Much literature exists concerning the effect of external electrical signals on synthetic, mitogenic, and proliferative responses of osteoblasts or osteoblast-like cells in vitro. Physiological responses to electrical stimulation are thought to be due to cellular mechanisms involving cytosolic calcium concentration changes. In this study this cellular effect was observed by directly stimulating primary culture bone cells from Sprague-Dawley rat calvaria at physiological significant field strength of 10 mV/cm and frequency 1,5 MHz. Electric field transduction mechanisms are investigated by measuring the real-time electric field effect on cytosolic Ca+2 concentrations using Fura-2 fluorescence technology in a system capable of measurement on a cell-by-cell basis. The electrical stimulations resulted in significant changes in cytosolic calcium concentration. More specifically, an increase was noted in calcium oscillation amplitude and duration, and a variable response latency period for the cells studied.