Coulomb forces acting between close flying charged spacecraft provide near zero propellant relative motion control, albeit with added nonlinear coupling and limited controllability. This novel concept has numerous potential applications, but also many technical challenges. In this dissertation, two- and three-craft Coulomb formations near GEO are investigated, using a rotating Hill frame dynamical model, that includes Debye shielding and differential gravity. Aspects of dynamical systems theory and optimization are applied, for insights regarding stability, and how inherent nonlinear complexities may be beneficially exploited to maintain and maneuver these electrostatic formations. Periodic relative orbits of two spacecraft, enabled by open-loop charge functions, are derived for the first time. These represent a desired extension to more substantially studied, constant charge, static Coulomb formations. An integral of motion is derived for the Hill frame model, and then applied in eliminating otherwise plausible periodic solutions. Stability of orbit families are evaluated using Floquet theory, and asymptotic stability is shown unattainable analytically. Weak stability boundary dynamics arise upon adding Coulomb forces to the relative motion problem, and therefore invariant manifolds are considered, in part, to more efficiently realize formation shape changes. A methodology to formulate and solve two-craft static Coulomb formation reconfigurations, as parameter optimization problems with minimum inertial thrust, is demonstrated. Manifolds are sought to achieve discontinuous transfers, which are then differentially corrected using charge variations and impulsive thrusting. Two nonlinear programming algorithms, gradient and stochastic, are employed as solvers and their performances are compared. Necessary and sufficient existence criteria are derived for three-craft collinear Coulomb formations, and a stability analysis is performed for the resulting discrete equilibrium cases. Each specified configuration is enabled by non-unique charge values, and so a method to compute minimum power solutions is outlined. Certain equilibrium cases are proven maintainable using only charge control, and feedback stabilized simulations demonstrate this. Practical scenarios for extending the optimal reconfiguration method are also discussed. Lastly, particular Hill frame model trajectories are integrated in an inertial frame with primary perturbations and interpolated Debye length variations. This validates qualitative stability properties, reveals particular periodic solutions to exhibit nonlinear boundedness, and illustrates higher-fidelity solution accuracies. / text

This examines the interplay of structure and local electrostatic fields in protein-protein and protein-solvent interactions. The partial charges of the protein amino acids and the polarization of the surrounding solvent create a complex system of electrostatic fields at protein-protein and protein-solvent interfaces. An approach incorporating vibrational Stark effect (VSE) spectroscopy, dissociation constant measurements, and molecular dynamics (MD) simulations was used to investigate the electrostatic interactions in these interfaces. Proteins p21Ras (Ras) and Rap1A (Rap) have nearly identical amino acid sequences and structures along the effector-binding region but bind with different affinities to Ral guanine nucleotide dissociation stimulator (RalGDS). A charge reversion mutation at position 31 alters the binding affinity of Ras and Rap with RalGDS from 0.1 [mu]M and 1 [mu]M, to 1 [mu]M and 0.5 [mu]M, respectively. A spectral probe was placed at various locations along the binding interface on the surface of RalGDS as it was docked with Ras and Rap single (position 30 or 31) and double mutants (both positions). By comparing the probes' absorption energies with the respective wild-type (WT) analogs, VSE spectroscopy was able to measure molecular-level electrostatic events across the protein-protein interface. MD simulations provided a basis for deconvoluting the structural and electrostatic changes observed by the probes. The mutation at position 31 was found to be responsible for both structural and electrostatic changes compared to the WT analogs. Furthermore, previous identification of positions N27 and N29 on RalGDS as "hot spots" that help discriminate between structurally similar GTPases was supported. The RalGDS probe-containing variants and three model compounds were placed in aqueous solvents with varying dielectric constants to measure changes in absorption energy. We investigated the ability of the Onsager solvent model to describe the solvent induced changes in absorption energy, while MD simulations were employed to determine the location and solvation of the probes at the protein-solvent interface. The solvent accessible-surface area, a measure of hydration, was determined to correlate well with the change in magnitude of the probe's absorption energy and the displaced solvent by the probe. / text

With the continuous growth of non-linear power electronic components and the increasing penetration of the distributed generation (DG), the potential for degradation in the power quality of the existing grid exists. There are concerns that the total harmonic distortion (THD) could reach unacceptable levels of 5% or higher. Moreover, there is additional potential of the presence of amplified harmonic components in the power network grid when the harmonic frequencies align with the resonant frequencies that are being injected by power electronic components of the DG. The above conditions could increase the electrical stresses on the insulation system of the power system components, and in particular, cable terminations are a concern. Standard cable terminations are designed to operate under power frequency in the power system network and their service life is considered accordingly. The research work aims to provide an understanding of the performance of the stress grading (SG) system of a commercial cable termination when the voltage waveform is distorted due to the presence of harmonics and when the high frequency and high dV/dt voltage waveforms are present from a typical power electronic drive. An aging experiment was performed for over a 600 hour time period using the pulse width modulated (PWM) high-voltage generator to quantify the impact of high frequency stress on SG system of cable termination. Furthermore, the cable termination was tested under power frequency, distorted voltage waveforms composed of fundamental and low order harmonics using an experiment setup that generate distorted voltage waveforms. Diagnostic techniques such as surface potential distribution measurements and surface temperature monitoring are used to analyze the termination performance. The surface tangential field is calculated based on the gradient of the termination surface potential as measured with an electrostatic voltmeter. The study shows that distorted voltage waveforms with high frequency and high dV/dt components, increase the electric field, resistive heating, and surface temperature rise in the terminations that use the field-dependent SG materials. The rise of electric field by as high as 27.1% and surface temperature rise of as high as 17C demonstrates the severity on the cable terminations. Such electric field enhancements for a period of time have a potential to initiate partial discharge that could lead to degradation of the termination. Moreover, surface temperature rise of 17 deg C could reduce the allowable ampacity of the cable conductor, reduce the short circuit levels, and reduce the feeder loading limits. The field-dependent electrical conductivity (σ(E,T)), permittivity (ε), and the temperature dependencies of (σ(E,T) and ε) have strong impact to degrade the electrical and thermal properties of the termination due to stress from the non-sinusoidal distorted voltage waveform. In order to minimize the surface temperature rise from the hotspot and electrical stress enhancement that eventually lead to insulation degradation and failure, the following recommendations are made for a suitable SG design for a termination to handle the severe voltage stress: Apply the capacitively graded termination in the grid where the distortion levels are low. Under the increased total harmonic distortion levels and HF components, resistively grading with higher degree of nonlinearity (achieved through the use of ZnO filler) is beneficial. The utilities could take preventive maintenance on medium voltage power cable accessories to prevent the termination failure before it actually occurs. Researchers could focus to resolve and minimize the rising power quality issues when the distribution generations are operated, improve the power electronic converters, and provide cost-effective harmonic filter solutions for harmonic mitigation.

Osteoarthritis is a degenerative joint disease characterized by progressive erosion of the articular cartilage. Epidemiological studies have established a relationship between osteoarthritis and menopause suggesting that estrogen may be important in the development of cartilage regeneration therapies. The overall goal of this research project was to advance the field of cartilage tissue regeneration by investigating the role of 17 ß -estradiol (E2), an active estrogen metabolite, on the chondrocyte phenotype. The central hypothesis was that E2 plays an important and sex-specific role in regulating chondrogenesis. Specific Aim-1 focused on establishing and characterizing a primary human articular chondrocyte (HAC) cell source, and then examining the response of the cells in culture to E2. It was demonstrated that the response of HACs to E2 treatment was sex-specific despite both male and females cells expressing estrogen receptors. Female HACs showed changes in proliferation, matrix production, and differentiation while male cells did not. In addition, the female response was regulated through a rapid membrane signaling pathway mediated by protein kinase C. Specific Aim-2 involved establishing an ovariectomized animal model to investigate the effects of E2 on orthopaedic tissue implants. Human demineralized bone matrix (DBM) was implanted intramuscularly into female nude mice and rats. Ovariectomy was shown to reduce the ability of DBM to induce the formation of cartilage and bone tissue. Moreover, the inductive properties of DBM were reestablished with subcutaneous E2 supplementation. Specific Aim-3 entailed developing and characterizing a microencapsulation method for in vitro culture and in vivo delivery of chondrocytes to study the effects of E2 on chondrogenesis. Rat growth plate chondrocytes and HACs were microencapsulated in alginate using an extrusion method in conjunction with high electrostatic potential. Chondrocytes maintained their phenotype in alginate suspension but were unable to form cartilage tissue when implanted into our animal model. Further optimization of the system is required before the role of E2 on chondrogenesis of tissue engineered constructs can be determined. In summary, our results suggest that the successful production of tissue engineered therapies will likely depend on understanding and manipulating the actions of sex hormones in both the in vitro and in vivo environment.

An introduction to titanium minerals is provided along with a brief history of high tension roll (HTR) separation and its applications. Current HTR theory is critically reviewed and deficiencies in previous modelling work are identified. These problems are recognised as the likely reason why past models required empirical manipulation to reproduce observed separation behaviour. An updated theory of charge decay in a particle bed is developed for HTR applications. Particle bed interactions and their effects on electrostatic forces and discharge rates are examined, leading to a reviewed analysis of force balance. The theoretical contributions are incorporated into a new HTR model which takes a mechanistic approach to describing machine operation, as opposed to previous empirical-based work in the area. A simplified electrostatic field model is also developed. Atmospheric effects on separation behaviour are ignored in the modelling. Experimental separations are used to validate new model performance, where comparisons are specifically designed to test the theoretical developments on charge decay and force balance in a particle bed. The new model is also compared to the Dance (1992) HTR model, embedded in JKSimSand, the most recent HTR model with an empirical basis. An error analysis shows the new model performs as well as, or better, than JKSimSand in most respects. The fact that this is achieved with a mechanistic approach validates the new developments in particle bed charge decay and force theory, and sets the foundation for mechanistic HTR simulation.

This thesis presents the research done towards the development of the final mirror suspension stage for the high power test facility at AIGO, Western Australia. One of the goals of the facility is to test advanced suspension methods that may be useful in future gravitational wave detectors. An in depth study of current mirror suspension techniques is presented and areas of possible improvement are highlighted. The extension of an existing suspension modelling toolkit written in Mathematica is also presented, where added functions allow one to include the violin modes of a suspension into their analysis. Through this tool, new suspension geometries boasting a lower number of violin modes with lower Q factors where developed. The orthogonal ribbon suspension and the thin tube suspension boast a lower number of lower Q violin modes compared to typical ribbon suspensions. For the latter, a reduction in the number of violin modes below 5kHz down to 5 and peak thermal noise amplitude by approximately 30dB is predicted. Presented also is the affect that such suspension geometries have on pendulum mode dilution factor and overall suspension thermal noise. It is seen that the violin mode improvement comes at a cost of a small increase in thermal noise above approximately 50Hz. A theoretical analysis of the AIGO cavity locking control scheme is also given. Issues of sensor noise and dynamic range are considered to produce a possible hierarchical locking method that would be compatible with advanced detectors. The resulting actuator force range requirements for AIGO at each actuation location on the vibration isolation system are given. Requirements of local controls before achieving cavity lock are also discussed. Finally, the suspension of a dummy sapphire mirror using removable modular niobium ribbons is presented. The design and performance of an electrostatic actuator and sensor for suspended mirror control is given. Initial experimental results of positioning and control of the final stage suspension through a digital interface is also included.

Thèse (D.Sc.)--Université du Québec à Chicoutimi, 1978. / Document électronique également accessible en format PDF. CaQCU

Στην παρούσα εργασία σχεδιάστηκε και εφαρμόστηκε ένας νέος αλγόριθμος χειρισμού των ηλεκτροστατικών αλληλεπιδράσεων. Οι αλληλεπιδράσεις ηλεκτροστατικής φύσεως αποτελούν αντικείμενο εκτενούς μελέτης στον ερευνητικό κλάδο των μοριακών προσομοιώσεων. Ιδιαίτερα σε βιολογικά μοριακά συστήματα, τα οποία αποτελούνται από υδατικά διαλύματα πολυηλεκτρολυτών, οι ηλεκτροστατικές αλληλεπιδράσεις κυριαρχούν. Η ευρέως διαδεδομένη μέθοδος άθροισης κατά Ewald η οποία χαρακτηρίζεται για την ακρίβεια της, είναι ιδιαίτερα απαιτητική σε υπολογιστικό χρόνο δεδομένου ότι κλιμακώνεται ως Ν2, όπου Ν ο συνολικός αριθμός φορτίων του συστήματος. Στην παρούσα εργασία περιγράφεται η προσεγγιστική μέθοδος σφαιρικής αποκοπής για την περίπτωση πολυηλεκτρολυτών. Έως σήμερα, η μέθοδος της σφαιρικής αποκοπής έχει εφαρμοστεί σε μοριακά συστήματα ιοντικών κρυστάλλων. Σύμφωνα με τη μέθοδο αυτή, εισάγοντας μια σφαιρική αποκοπή στον υπολογισμό του ηλεκτροστατικού δυναμικού και παράλληλα επιτυγχάνοντας ηλεκτροουδετερότητα του υπό εξέταση σφαιρικού συστήματος, πραγματοποιείται μείωση του υπολογιστικού χρόνου σε δίχως σημαντικές απώλειες σε ακρίβεια. Στην παρούσα εργασία σχεδιάστηκε ο αλγόριθμος της σφαιρικής αποκοπής για δύο κατηγορίες μορίων: τους πολυηλεκτρολύτες χωρίς ενδομοριακές αλληλεπιδράσεις όπως είναι το μόριο του νερού και τους πολυηλεκτρολύτες με ενδομοριακές αλληλεπιδράσεις όπως είναι τα μόρια CiEj των αλκυλικών αιθέρων πολυ-(οξυ-αιθυλενίου). Επιπρόσθετα, επεκτείναμε τη μέθοδο άθροισης κατά Ewald για την εφαρμογή της σε πολυηλεκτρολύτες, χωρίς και με ενδομοριακές αλληλεπιδράσεις προκειμένου να προχωρήσουμε σε σύγκριση της ακριβής μεθόδου Ewald με τα αποτελέσματα του νέου αλγορίθμου της σφαιρικής αποκοπής. Συγκρίνοντας τα αριθμητικά αποτελέσματα των δύο μεθόδων για τα δύο διαφορετικά είδη πολυηλεκτρολυτών ( H2Ο και CiEj ) από ατομιστικές προσομοιώσεις μοριακής δυναμικής οδηγηθήκαμε σε πλήρη συμφωνία των δύο μεθόδων γεγονός που επιβεβαιώνει την εγκυρότητας της νέας μεθόδου. Επίσης, μέσω των αποτελεσμάτων των προσομοιώσεων μοριακής δυναμικής μελετήθηκαν οι θερμοδυναμικές, δομικές και δυναμικές ιδιότητες των δύο συστημάτων. Η παρούσα εργασία είναι δομημένη ως εξής: Στο πρώτο κεφάλαιο γίνεται μια εισαγωγή στο θεωρητικό υπόβαθρο προσομοιώσεων μοριακής δυναμικής. Στο δεύτερο κεφάλαιο περιγράφονται οι μέθοδοι χειρισμού των ηλεκτροστατικών αλληλεπιδράσεων που συναντούμε έως σήμερα στη βιβλιογραφία. Στη συνέχεια, στο κεφάλαιο 3 περιγράφεται ο αλγόριθμος της σφαιρικής αποκοπής. Στο τέταρτο κεφάλαιο παρουσιάζονται τα αποτελέσματα από τις προσομοιώσεις μοριακής δυναμικής με τις μεθόδους σφαιρικής αποκοπής και άθροισης κατά Ewald. / -

Robotics and autonomous systems (RAS) have great potential to propel the world to future growth. Electroadhesion is a promising and potentially revolutionising material handling technology for manufacturing automation applications. There is, however, a lack of an in-depth understanding of this electrostatic adhesion phenomenon based on a confident electroadhesive pad design, manufacture, and testing platform and procedure. This Ph.D. research endeavours to obtain a more comprehensive understanding of electroadhesion based on an extensive literature review, theoretical modelling, electrostatic simulation, and experimental validation based on a repeatable pad design, manufacture, and testing platform and procedure.

Ma thèse introduit cinq logiciels de trois différents domaines: le calcul parallèle et distribué, la biologie structurale computationnelle et la chémoinformatique. Le logiciel pour le calcul parallèle et distribué s'appelle PAR. PAR permet d'exécuter des expériences indépendantes de manière parallèle et distribuée. Les logiciels pour la biologie structurale computationnelle sont Durandal, EleKit et Fragger. Durandal exploite la propagation de contraintes géométriques afin d'accélérer l'algorithme de partitionnement exact pour des modèles de protéines. EleKit permet de mesurer la similarité électrostatique entre une petite molécule et la protéine qu'elle est conçue pour remplacer sur une interface protéine-protéine. Fragger est un cueilleur de fragments de protéines permettant de sélectionner des fragments dans la banque de protéines mondiale. Enfin, le logiciel de chémoinformatique est ACPC. ACPC permet l'encodage fin, d'une manière rotation-translation invariante, d'une molécule dans un ou une combinaison des trois espaces chimiques (électrostatique, stérique ou hydrophobe). ACPC est un outil de criblage virtuel qui supporte les requêtes consensus, l'annotation de la molécule requête et les processeurs multi-coeurs. / This thesis introduces five software useful in three different areas : parallel and distributed computing, computational structural biology and chemoinformatics. The software from the parallel and distributed area is PAR. PAR allows to execute independent experiments in a parallel and distributed way. The software for computational structural biology are Durandal, EleKit and Fragger. Durandal exploits the propagation of geometric constraints to accelerate the exact clustering algorithm for protein models. EleKit allows to measure the electrostatic similarity between a chemical molecule and the protein it is designed to replace at a protein-protein interface. Fragger is a fragment picker able to select protein fragments in the whole protein data-bank. Finally, the chemoinformatics software is ACPC. ACPC encodes in a rotation-translation invariant way a chemical molecule in any or a combination of three chemical spaces (electrostatic, steric or hydrophobic). ACPC is a ligand-based virtual screening tool supporting consensus queries, query molecule annotation and multi-core computers.