The product of this thesis aims to enable the study of the biochemical and physical dynamics of the lower limbs at high levels of muscle tension and fast contraction speeds. This is accomplished in part by a magnetic resonance (MR) compatible ergometer designed to apply a load as a torque of up to 420 Nm acting against knee extension at speeds as high as 4.7 rad/s. The system can also be adapted to apply the load as a force of up to 1200 N acting against full leg extension. The ergometer is designed to enable the use of magnetic resonance spectroscopy and imaging in a three Tesla Siemens Skyra MRI system. Due to the electromagnetic limitations of having the device operate inside the magnet, the design is split into two components. One designed to fit inside the 70 cm bore of the scanner. This component is electromagnetically passive; made out of materials exhibiting minimal magnetic interference, and having no electrically powered parts. The other component is electromagnetically active; it contains all of the powered elements and actuates the passive part from another room. A tensioned cable transmits power through a waveguide; a pipe through the wall of the MRI room with an RF shield. The device was tested applying a sagittal plane moment on the knee joint during isometric, isokinetic, isotonic, and constant power contractions.

In dieser Arbeit wird die digital-holographisch-interferometrische Zwei-Wellenlängen-Formerfassung sehr schnell bewegter Objekte behandelt und dafür unter Nutzung einer Ultrakurzpuls-Laserquelle mit der digitalen Einzelimpuls-Mehr-Wellenlängen-Holographie ein neuartigen Ansatz der digital-holographischen Aufnahme und Auswertung entwickelt. Mit der Entwicklung spezieller Methoden zur Formung der spektralen Signatur einer Ultrakurzpuls-Laserquelle hoher Leistungsdichte wurde zum ersten Mal die Voraussetzung für eine Zwei-Wellenlängen-Formerfassung hochdynamischer Objekte geschaffen. Die intrinsisch kurze Belichtungszeit unter einer Pikosekunde macht das Verfahren absolut stabil gegenüber Umwelteinflüssen. Für die simultane Aufnahme werden die spektral verschiedenen Hologramme mit einem eigens entwickelten Prinzip der Polarisationskodierung räumlich getrennt und zum ersten Mal mit zwei synchron laufenden Kameras gespeichert. Mit den in der digital-holographischen Einzelimpuls-Mehr-Wellenlängen-Interferometrie zusammengefassten numerischen Routinen zur Rekonstruktion und Phasenauswertung wird eine Zwei-Wellenlängen-Formerfassung mit mehreren Kameras möglich. In Anwendung des neuartigen Verfahrens an verschiedenen dynamischen Mikrosystemen konnte eine Genauigkeit von einem Zwanzigstel der erzeugten synthetischen Wellenlänge, bei der Auswertung der spektralen Differenzphase an Objekten in Reflexion erreicht werden. In einer digital-holographischen Hochgeschwindigkeitsformerfassung in Transmission wurden erstmals Bildfolgefrequenz von mehr als 0,4 kHz erreicht und der interferometrische Eindeutigkeitsbereich auf mehr als das 60-fache der optischen Wellenlänge ausgedehnt. Es wurden die Voraussetzungen für eine digitale Vier-Wellenlängen-Holographie geschaffen. Zukünftig wird eine Formerfassung mit einer Genauigkeit von 10nm über einen eindeutigen interferometrischen Bereich einiger 10 μm und die Untersuchungen von Prozessen auf einer Pikosekunden-Zeitskala möglich sein. / This work deals with the digital holographic interferometric two-wavelength contouring of very fast moving objects and develops with the digital single pulse multiwavelength holography a novel approach of digital holographic recording and analysis, using an ultrashort pulse laser source. The development of several methods to shape the spektral signature of an high power ultrashort pulse laser source provides the precondition for a two-wavelength contouring of highly dynamic objects for the first time. The intrinsically short exposure time shorter than a picosecond makes the system stable regarding external impacts. For the simultaneous recording the spektral different holograms are spatially separated in novel interferometric setups by the especially developed principle of polarization encoding and stored with two synchronized cameras for the first time. The digital holographic single pulse multi-wavelength interferometry combines the numeric routines of reconstruction and phase evaluation that make a two-wavelength contouring possible using more than one camera. The novel approach is successfully demonstrated on several dynamic microsystems. Evaluating the spectral phase difference for objects in reflection an accuracy of 2 μm, which corresponds to the twentieth of the realized synthetic wavelength, could be achieved. In a digital holographic high speed contouring in transmission a frame rate higher than 0,4 kHz was achieved for the first time and the interferometric range of unambiguity was extended larger than sixty times the optical wavelength. Furthermore, the developed digital holographic single pulse multi-wavelength interferometry is not limited to the evaluation of two wavelength. The principles of the method allow to perform digital four-wavelength holography. Future a contouring with an accuracy of 10nm over the unambiguous interferometric range of several 10 μm and the investigation of processes on a picosecond time scale will be possible.

This work developed a process to provide physical, electrical, and environmental protection to the electrical lead system of an optical switch device. A literature review was conducted to find materials and processes suitable to the stress-sensitive, high voltage characteristics of many optical switch devices. An automatic dispensing dam and fill process, and three candidate materials (two epoxy and one silicone) were selected for investigation. Experimental and analytical techniques were used to evaluate the materials. Methods applied included interferometric die warpage measurements, electrochemical migration resistance tests (ECMT), thermal cycling, and finite element analysis. The silicone dam and fill system was selected based upon the results of die warpage and electrochemical migration resistance tests. A modified, selective dam and fill process was developed and preliminary reliability testing was performed. The paper provides detailed instructions for successful encapsulation of the optical switch's lead system.

Orientador: Samuel da Silva / Resumo: Os métodos envolvendo simetria têm grande importância para o estudo das equações diferenciais decorrentes de áreas como a matemática, física, engenharia entre muitas outras. A existência de simetrias em equações diferenciais pode gerar transformações em variáveis dependentes e independentes que podem facilitar a integração. Em especial, Sophus Lie desenvolveu no século XIX uma forma de extração de simetrias que podem ser usadas efetivamente para revelar as integrais primeiras, ou seja, as constantes de movimento, que muitas vezes podem estar escondidas. Estes invariantes podem em algumas situações ser identificados pelo teorema de Noether ou a partir de manipulações das próprias equações com transformações de Lie. Assim, nesta tese foi proposto utilizar as simetrias de Lie para aplicação em problemas da dinâmica de sistemas mecânicos. As simetrias de Lie são aplicadas em dois problemas clássicos, primeiro em um pêndulo oscilando em um aro rotativo e em seguida em um pião simétrico com movimento de precessão estacionária com um ponto fixo. No primeiro problema foi realizada uma redução de ordem para solução por quadraturas da equação de movimento. Já no segundo foram mostradas as relações entre os invariantes e as leis de conservação extraídas das simetrias de Lie. Uma outra análise foi realizada através da teoria de referencial móvel, mostrando a possibilidade de outras aplicações das simetrias de Lie. Uma das aplicações desta teoria, também é a redução de ordem das equações ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The methods involving symmetry are of great importance for the study of the di erential equations arising from areas such as mathematics, physics, engineering among many others. The existence of symmetries in di erential equations can generate transformations in dependent and independent variables that may be easier to integrate. In particular, Sophus Lie developed in the nineteenth century a form of extraction of symmetries that can be used e ectively to reveal the rst integrals, that is, the motion constants, which can often be hidden. These invariants can in some situations be identi ed by the Noether theorem or from manipulations of the equations themselves with Lie transformations. Thus, in this thesis it was proposed to use the Lie symmetries for application in problems of the dynamics of mechanical systems. The Lie symmetries are applied in two classic problems, rst in a bead on a rotating wire hoop and then in a symmetric top with stationary precession with a xed point. In the rst problem, a reduction of order of the equation of motion was performed by quadratures. In the second one, the relations between the invariants and the conservation laws extracted from the Lie symmetries were shown. Another analysis was performed through the theory of moving frames, showing the possibility of other applications of Lie symmetries. One of the applications of this theory is also the order reduction of the resulting di erential equations. Thus, moving frames were calculated for th... (Complete abstract click electronic access below) / Doutor

The objective of this whole study was to evaluate a LiDAR sensor for high-resolution remote sensing in agriculture. A linear motion system was developed to precisely control the dynamics of LiDAR sensor in effort to remove uncertainty in the LiDAR position/velocity while under motion. A user control interface was developed to operate the system under different velocity profiles and log LiDAR data synchronous to the motion of the system. The LiDAR was then validated using multiple test targets with five different velocity profiles to determine the effect of sensor velocity and height above a target on measurement error. The results indicated that the velocity of the LiDAR was a significant factor affecting the error and standard deviation of the LiDAR measurements, although only by a small margin. Then the concept of modeling the alfalfa using the linear motion system was introduced. Two plots of alfalfa were scanned and processed to extract height and volume and was compared with photogrammetric and field measurements. Insufficient alfalfa plots were scanned which prevented any statistical analysis from being used to compare the different methods. However, the comparison between LiDAR and photogrammetric data showed some promising results which may be further replicated in the future.

Coal is a very prominent energy source in the world, but it is environmentally unattractive due to its high sulfur and ash content as well as its alleged contribution towards climate change, but it is affordable, abundant, and has high energy content. Thus, utilizing coal in a cleaner and more efficient way has become necessary. One promising clean coal technology involves fully gasifying coal into synthesis gas, cleaning it, and feeding it into a high-efficiency combined cycle, such as an Integrated Gasification Combined Cycle (IGCC). Inspired by the recent success of warn gas cleanup (WGCU), mild and partial gasification are proposed as less energy intensive options. This Integrated Mild/Partial Gasification Combined Cycle (IMPGC) could significantly save energy and improve efficiency. The objective of this study is to investigate the capabilities of IMPGC as both a new plant and a retrofit option for traditional coal power plants with and without carbon capture. I MPGC relies on the principles of mild and partial gasification and the recently available WGGU technology with the following benefits: a.) completely negate the need for syngas cooling; b.) significantly reduce the energy needed to fully thermally crack the volatiles and completely gasify the char as in the IGCC system; c.) preserve the high chemical energy hydro-carbon bonds within the feedstock to allow more efficient combustion in the gas turbine; d.) reduce the size of gasifier and piping to reduce the costs; and e.) enable retrofitting of an old coal power plant by preserving the existing equipment. The software used (Thermoflex®) was first validated with established cases from the U.S. Department of Energy. For new plants, the results show that IMPGC’s efficiency is 8 percentage points (20%) higher than IGCC, 8 points higher than a modern subcritical Rankine cycle, and 3-4 points higher than an ultra-supercritical (USC) cycle. When retrofitting older plants, a minimum improvement of over 4 points is predicted. When carbon capture is involved, IMPGC’s efficiency becomes 10 points better than a subcritical plant and 8 points better than a USC plant. Emissions wise, IMPGC is better than IGCC and much better than Rankine cycle plants.

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Varactors form an important part of many communication circuits. They are utilized in oscillators, tunable matching networks, tunable filters and phase-shifters. This thesis deals with the design, analysis, characterization and applications of a novel MEMS varactor. Lower actuation voltage and higher dynamic range are the two important issues widely addressed in the study of MEMS varactors. The pull-in instability, due to which only 33% of the gap between plates could be covered smoothly, greatly reduces useful dynamic range of MEMS varactors. We propose a torsional MEMS varactor that exploits “displacement amplification” whereby pull-in is overcome and wide dynamic range is achieved. The torsion beam in the device undergoes torsion as well as bending. Behavior of the device has been analyzed through torque and force balance. Based on the torque balance and the force balance expressions, theoretical limits of torsion angle and bending for stable operation have been derived. Torsional MEMS varactors and its variants are fabricated through a commercial fabrication process (polyMUMPS) and extensive characterization has been carried out. Capacitance-voltage characteristics show a maximum dynamic range of 1:16 with parasitic capacitance subtracted out from the capacitance values. A bidirectional torsional varactor, in which the top AC plate moves not only towards bottom plate but also away from bottom plate, is also tested. The bottom AC plate is isolated from low resistivity substrate with a thin nitride layer. This gives rise to large parasitic capacitances at higher frequencies. So to avoid this, a varactor with both AC plates suspended in air is designed and fabricated. A dynamic range of 1:8 including parasitic capacitances has been achieved. Self-actuation is studied on fabricated structures and a torsional varactor that overcomes self-actuation has been proposed. Hysteresis behavior of the torsional varactor is analyzed for different AC signals across the varactor plates. Effects of residual stress on C-V characteristics are studied and advantages and disadvantages of residual stress on device performance are discussed. The torsional varactors have been cycled between Cmax and Cmin for 36 hours continuously without any failure. High-frequency characteristics of torsional varactors are analyzed through measurements on one-port and two port configurations. Measurements are done on polyMUMPS devices to study the capacitance variation with voltage, quality factor (Q) and capacitance variation with frequency. Effects of substrate are de-embedded from the device and characteristics of device are studied. An analog phase shifter based on torsional varactor proposed and analyzed through HFSS simulations. Very high tuning range can be achieved with a LC-VCO based on torsional varactors. A LC VCO with the torsional varactor as a capacitor in LC tank is designed. The torsional varactor and IC are fabricated separately and are integrated through wire bonding. Bond-wires are used as inductors.

Motion planning and control synthesis are challenging problems for underactuated mechanical systems due to the presence of passive (non-actuated) degrees of freedom. For those systems that are additionally not feedback linearizable and with unstable internal dynamics there are no generic methods for planning trajectories and their feedback stabilization. For fully actuated mechanical systems, on the other hand, there are standard tools that provide a tractable solution. Still, the problem of generating efficient and optimal trajectories is nontrivial due to actuator limitations and motion-dependent velocity and acceleration constraints that are typically present. It is especially challenging for manipulators with kinematic redundancy. A generic approach for solving the above-mentioned problems is described in this work. We explicitly use the geometry of the state space of the mechanical system so that a synchronization of the generalized coordinates can be found in terms of geometric relations along the target motion with respect to a path coordinate. Hence, the time evolution of the state variables that corresponds to the target motion is determined by the system dynamics constrained to these geometrical relations, known as virtual holonomic constraints. Following such a reduction for underactuated mechanical systems, we arrive at integrable second-order dynamics associated with the passive degrees of freedom. Solutions of this reduced dynamics, together with the geometric relations, can be interpreted as a motion generator for the full system. For fully actuated mechanical systems the virtually constrained dynamics provides a tractable way of shaping admissible trajectories. Once a feasible target motion is found and the corresponding virtual holonomic constraints are known, we can describe dynamics transversal to the orbit in the state space and analytically compute a transverse linearization. This results in a linear time-varying control system that allows us to use linear control theory for achieving orbital stabilization of the nonlinear mechanical system as well as to conduct system analysis in the vicinity of the motion. The approach is applicable to continuous-time and impulsive mechanical systems irrespective of the degree of underactuation. The main contributions of this thesis are analysis of human movement regarding a nominal behavior for repetitive tasks, gait synthesis and stabilization for dynamic walking robots, and description of a numerical procedure for generating and stabilizing efficient trajectories for kinematically redundant manipulators.

Accelerometer sensors fabricated with micromachining technologies started to take place of yesterday&rsquo / s bulky sensors in many application areas. The application areas include a wide range from consumer electronics and health systems to military and aerospace applications. Therefore, the performance requirements extend form 1 &mu / g&rsquo / s to 100 thousand g&rsquo / s. However, high performance strategic grade MEMS accelerometer sensors still do not exist in the literature. Smart designs utilizing the MEMS technology is necessary in order to acquire high performance specifications. This thesis reports a high performance accelerometer with a new process by making the use of bulk micromachining technology. The new process includes the utilization of Silicon-on-Insulator (SOI) wafer and its buried oxide (BOX) layer. The BOX layer helps to realize interdigitated finger structures, which commonly find place in surface micromachined CMOS-MEMS capacitive accelerometers. The multi-metal layered CMOS-MEMS devices inherently incorporate interdigitated finger structures. Interdigitated finger structures are highly sensitive to acceleration in comparison with comb-finger structures, which generally find usage in bulk-micromachined devices, due to absence of anti-gap. The designed sensors based on this fabrication process is sought to form a fully-differential signal interfaced sensor with incorporation of the advantages of high sensitive interdigitated finger electrodes and high aspect ratio SOI wafer&rsquo / s bulk single crystal silicon device. Under the light of the envisaged process, sensor designs were made, and verified using a computing environment, MATLAB, and a finite element analysis simulator, CoventorWARE. The verified two designs were fabricated, and all the tests, except the centrifuge test, were made at METU-MEMS Research Center. Among the fabricated sensors, the one designed for the high performance achieves a capacitance sensitivity of 178 fF with a rest capacitance of 8.1 pF by employing interdigitated finger electrodes, while its comb-finger implementation can only achieve a capacitance sensitivity of 75 fF with a rest capacitance of 10 pF.