A number of methods have been proposed that utilize the time domain transformations of the frequency dependent impedance functions to perform time-history analysis of structures accounting for soil-structure interaction (SSI). Though these methods have been available in literature for a number of years, this study is the first to rigorously examine the limitations and advantages of these methods in comparison to one another. These methods contain certain stability issues that required investigating which lead to the formation of an analysis procedure that assesses a transform method’s stability. The general applicability of these methods was demonstrated by utilizing them to model increasingly sophisticated reference problems. Additionally the suitability of these methods to being incorporated into hybrid simulations of nonlinear inelastic structures considering soil-structure interaction was confirmed. The modelling of a nonlinear structure considering soil-structure interaction is an improvement over the most common modelling strategies that model solely linear-elastic behaviour.

Electrolyte additives are generally used in commercial Li-ion cells to improve capacity retention and calendar life. Although it is apparent that electrolyte additives play an important role, the details of how they work are poorly understood. In order to be able to distinguish the effect of an additive on the positive or negative electrodes, an experimental method has been developed based on electrochemical impedance spectroscopy of symmetric cells constructed from electrodes of disassembled full cells similar to the method described by previous workers. This technique proved to be useful and showed that the effects of additives on both electrodes depend strongly on their concentration. It also showed that in some cases, when two additives are introduced in the same cell, both additives contribute to the formation of the surface layer of both electrodes. In other cases, each additive controls the formation of the surface layer of only one electrode.

No description available.

No description available.

A number of methods have been proposed that utilize the time domain transformations of the frequency dependent impedance functions to perform time-history analysis of structures accounting for soil-structure interaction (SSI). Though these methods have been available in literature for a number of years, this study is the first to rigorously examine the limitations and advantages of these methods in comparison to one another. These methods contain certain stability issues that required investigating which lead to the formation of an analysis procedure that assesses a transform method’s stability. The general applicability of these methods was demonstrated by utilizing them to model increasingly sophisticated reference problems. Additionally the suitability of these methods to being incorporated into hybrid simulations of nonlinear inelastic structures considering soil-structure interaction was confirmed. The modelling of a nonlinear structure considering soil-structure interaction is an improvement over the most common modelling strategies that model solely linear-elastic behaviour.

The motor control of anthropomorphic robotic systems is a challenging computational task mainly because of the high levels of redundancies such systems exhibit. Optimality principles provide a general strategy to resolve such redundancies in a task driven fashion. In particular closed loop optimisation, i.e., optimal feedback control (OFC), has served as a successful motor control model as it unifies important concepts such as costs, noise, sensory feedback and internal models into a coherent mathematical framework. Realising OFC on realistic anthropomorphic systems however is non-trivial: Firstly, such systems have typically large dimensionality and nonlinear dynamics, in which case the optimisation problem becomes computationally intractable. Approximative methods, like the iterative linear quadratic gaussian (ILQG), have been proposed to avoid this, however the transfer of solutions from idealised simulations to real hardware systems has proved to be challenging. Secondly, OFC relies on an accurate description of the system dynamics, which for many realistic control systems may be unknown, difficult to estimate, or subject to frequent systematic changes. Thirdly, many (especially biologically inspired) systems suffer from significant state or control dependent sources of noise, which are difficult to model in a generally valid fashion. This thesis addresses these issues with the aim to realise efficient OFC for anthropomorphic manipulators. First we investigate the implementation of OFC laws on anthropomorphic hardware. Using ILQG we optimally control a high-dimensional anthropomorphic manipulator without having to specify an explicit inverse kinematics, inverse dynamics or feedback control law. We achieve this by introducing a novel cost function that accounts for the physical constraints of the robot and a dynamics formulation that resolves discontinuities in the dynamics. The experimental hardware results reveal the benefits of OFC over traditional (open loop) optimal controllers in terms of energy efficiency and compliance, properties that are crucial for the control of modern anthropomorphic manipulators. We then propose a new framework of OFC with learned dynamics (OFC-LD) that, unlike classic approaches, does not rely on analytic dynamics functions but rather updates the internal dynamics model continuously from sensorimotor plant feedback. We demonstrate how this approach can compensate for unknown dynamics and for complex dynamic perturbations in an online fashion. A specific advantage of a learned dynamics model is that it contains the stochastic information (i.e., noise) from the plant data, which corresponds to the uncertainty in the system. Consequently one can exploit this information within OFC-LD in order to produce control laws that minimise the uncertainty in the system. In the domain of antagonistically actuated systems this approach leads to improved motor performance, which is achieved by co-contracting antagonistic actuators in order to reduce the negative effects of the noise. Most importantly the shape and source of the noise is unknown a priory and is solely learned from plant data. The model is successfully tested on an antagonistic series elastic actuator (SEA) that we have built for this purpose. The proposed OFC-LD model is not only applicable to robotic systems but also proves to be very useful in the modelling of biological motor control phenomena and we show how our model can be used to predict a wide range of human impedance control patterns during both, stationary and adaptation tasks.

An occupational exposure to hand-arm vibration can cause a complex of neurological, vascular and musculo-skeletal disturbances, known as the 'vibration syndrome'. However, the underlying pathophysiological mechanisms are not at all clear. Early signs of an incipient vibration syndrome are often intermittent disturbances in the cutaneous sensibility of the fingers, i.e. numbness and/or tactile paresthesias. At later stages, a vasoconstrictive phenomenon appears, usually as episodes of finger blanching. When using a vibratory tool, all mechanical energy entering the body has to be transmitted through, or absorbed by, the glabrous skin in contact with the handle. Therefore, the aims of this study was to investigate: (i) mechanical responses of the skin to vibrations, (ii) the response properties of cutaneous mechanoreceptors to vibrations, and (iii) influences of vibration exposure on touch perception. It was found by measuring the mechanical point impedance (0.02-10 kHz) that the skin is easy to make vibrate within the range of 80 to 200 Hz. Within or close to this range are the dominant frequencies of many vibratory tools. Thus, strong mechanical loads, such as compressive and/or tensile strain, can appear in the skin which, in turn, may induce temporary or permanent injuries. Recordings of impulses in single mechanoreceptive afferents, while the skin as exposed to vibrations, were obtained using needle electrodes inserted into the median nerve. The 4 types of mechanoreceptive afferents (FA I, FA II, SA I, and SA II) in the glabrous skin exhibited different response characteristics to vibrations. The FA I units were most easily excited at vibratory frequencies between ca 8 and 64 Hz and the FA II units between ca 64 and 400 Hz. The SA units were most sensitive at lower frequencies. At high stimulus amplitudes, such as may occur while using vibratory tools, a considerable overlap existed between the frequency ranges at which the units were exited. Evidence was also provided, that mechanical skin stimuli produced by edges of a vibrating object, compared to flat surfaces, more vigorously excited the FA I and particularly the SA I units. Thus, a marked edge enhancement, essential for tactile gnosis and precision manipulation, seems to exist already within the peripheral nervous system. Acure impairment of tactile sensibility caused by vibrations, proved to be due to a reduced sensitivity of the mechanoreceptive afferents. A loss of manual dexterity a*vi an increased risk for accidents may therefore appear, both during and after a vibration exposure. Percussive tools, high speed drills and ultrasonic devices are known to generate mechanical energy at frequencies above 1 kHz, i.e. frequencies usually not felt. At these frequencies, it is known that most of the energy, entering the body, is absorbed by the skin. Therefore, it was investigated whether a long-term exposure to high-frequency vibration may have a detrimental effect on the cutaneous sensitivity. One group of dentists and one of therapists, professionally exposed to high-frequency vibrations, were studied with regard to vibrotactile thresholds in their hands. The study showed that deleterious effects on tactile sensibility, at local exposure to high frequency vibration, can not be excluded. / <p>Diss. (sammanfattning) Umeå : Umeå universitet, 1985, härtill 6 uppsatser</p> / digitalisering@umu

The purpose of this study was to examine the effects of hydration status on the prediction of body composition using BIA, NIR, and DEXA. Twenty healthy males and females ages 18 to 28 were recruited for this study. The subjects were dehydrated in the climate control chamber and engaged in physical exercise, until they lost approximately 1%, 2%, and 3% of their pre-exercise body weight. Percent body fat (%BF), body weight, and urinalysis measures were taken initially on day 1, on day 4 at euhydration, following 1%, 2%, and 3% dehydration, and upon rehydration during day 5. The results indicated that there were significant decreases for %BFBIA and %BFNIR between euhydration and 1%, 2%, and 3% dehydration. %BFDExA did not significantly change.There were also significant differences in the response to dehydration between each technique. Proper hydration should be ensured before %BF is estimated with BIA and NIR. / School of Physical Education

A systematic study of formic acid electrooxidation on polycrystalline palladium is presented. The study begins with a discussion on the oxide growth process on platinum and palladium. CO electrooxidation under controlled mass transport is studied in order to elucidate the manner in which Pd interacts with CO, a proposed poisoning species in formic acid oxidation. The mechanism of formic acid oxidation is studied using various potentiodynamic techniques, including dynamic electrochemical impedance spectroscopy, which provides impedance measurements during a voltammogram. Through kinetic analysis, a model for the oxidation was developed. The impedance measurements support both the dc measurements as well as the results of the oxidation model. It was determined that CO formation was slow on Pd within the time scale of the experiments. The chief cause of surface deactivate was then determined to be the Pd surface interaction with the (bi)sulfate adsorption in the double layer region. / Graduate

This thesis presents design, modeling, and fabrication of an RF MEMS adjustable impedance matching network. The device employs the basic triple stub matching technique for impedance matching. It has three adjustable length stubs which are implemented using capacitively loaded coplanar waveguides. The capacitive loading of the stubs are realized using the MEMS switches which are evenly distributed over the stubs. There are 40 MEMS bridges on each stub whichare separated with &amp / #955 / /40 spacing making a total of 120 MEMS switches in the structure. The variability of the stub length is accomplished by closing the MEMS switch nearest to the required stub length, and making a virtual short circuit to ground. The device is theoretically capable of doing matching to every point on the Smith chart. The device is built on coplanar waveguide transmission lines. It has a center operating frequency of 10GHz, but because of its adjustability property it is expected to work in 1-40GHz range. It has dimensions of 8950 &times / 5720&micro / m2. This work is the continuation of the first national work on fabrication of RF MEMS devices. The device in this work is fabricated using the surface micromachining technology in the microelectronic facilities of Middle East Technical University.