An innovative dynamics and control algorithm is developed for a dual-nanosatellite formation flying mission. The principal function of this algorithm is to use regular GPS state measurements to determine the controlled satellite's tracking error from a set of reference trajectories in the local-vertical/local-horizontal reference frame. A linear state-feedback control law--designed using a linear quadratic regulator method--calculates the optimal thrusts necessary to correct this error and communicates the thrust directions to the attitude control system and the thrust durations to the propulsion system. The control system is developed to minimize the conflicting metrics of tracking error and ΔV requirements. To reconfigure the formation, an optimization algorithm is designed using the analytical solution to the state-space equation and the Hill-Clohessy-Wiltshire state transition matrix to solve for dual-thrust reconfiguration maneuvers. The resulting trajectories require low ΔV, use finite-time thrusts and are accurate in a fully nonlinear orbital environment. This algorithm will be used to control the CanX-4&5 formation flying demonstration mission. In addition, an iterative method which numerically generates quasi periodic trajectories for a satellite formation is presented. This novel technique utilizes a shooting approach to the Newton method to close the relative deputy trajectory over a specific number of orbits, then fits the actual perturbed motion of the deputy with a Fourier series to enforce periodicity. This process is applied to two well-known satellite formations: a projected circular orbit and a J2-invariant formation. Compared to conventional formations, these resulting quasi-periodic trajectories require a dramatically lower control effort to maintain and could therefore be used to extend ΔV-limited formation flying missions. Finally, an analytical study of the stability of the formation flying algorithm is conducted. To facilitate the proof, the control algorithm is converted into a discrete-time linear time-varying system. Stability of the system is determined via discrete Floquet theory. This analysis is applied to the CanX-4&5 control laws for tracking along-track orbits, projected circular orbits, and quasi J2-invariant formations.

The work performed here studies particle dynamics in local two-dimensional simulations of self-gravitating accretion discs with a simple cooling law. It is well known that the structure which arises in the gaseous component of the disc due to a gravitational instability can have a significant effect on the evolution of dust particles. Previous results using global simulations indicate that spiral density waves are highly efficient at collecting dust particles, creating significant local over-densities which may be able to undergo gravitational collapse. This thesis expand on these findings, using a range of cooling times to mimic the conditions at a large range of radii within the disc. The PENCIL Code is used to solve the 2D local shearing sheet equations for gas on a fixed grid together with the equations of motion for solids coupled to the gas solely through aerodynamic drag force. The work contained here shows that spiral density waves can create significant enhancements in the surface density of solids, equivalent to 1-10cm sized particles in a disc following the profiles of Clarke (2009) around a solar mass star, causing it to reach concentrations several orders of magnitude larger than the particles mean surface density. These findings suggest that the density waves that arise due to gravitational instabilities in the early stages of star formation provide excellent sites for the formation of large, planetesimal-sized objects. These results are expanded on, with subsequent results introducing the effects of the particles self-gravity showing these concentrations of particles can gravitationally collapse, forming bound structures in the solid component of the disc.

The syntheses of many cycloalkene and cycloalkeneone annelated DHPs have been achieved. A late ring formation approach was used to synthesize the dicycloalkeneone annelated DHP 63 (Scheme 4) and the unsymmetrical dicycloalkeneone annelated DHPs 70a and 70b (Scheme 5). To synthesize the other ring annelated DHPs, a more versatile early ring approach was employed. Through an asymmetrical coupling followed by a series of standard transformations, the cyclopentene-, cyclohexene-, cyclopentenone- and cyclohexenone-annelated DHPs 64 , 118 , 130 , 131 were synthesized (Schemes 13 and 15). Similarily, the dicycloalkene and dicycloalkenone annelated DHPs such as 41 , 42, 123, 124 and 136 were obtained by a symmetrical coupling followed by a series of standard transformations (Schemes 12, 14 and 16). Other than the cycloalkene or cycloalkenone annelated DHPs, the acyclic tetra-substituted DHPs 142 and 143 (Scheme 17) were also synthesized as model compounds. As well, the asymmetrical DHPs 148 and 149 (Scheme 18), having a benzene and a cyclopentenone annelation or with a benzene and a cyclopentenone annelation, were also synthesized to test the annelation effect with a combination of a benzene and a five-membered ring. In the cycloalkene and cycloalkenone annelated DHP series, it was demonstrated that the [pi]-bond fixation effect could be indirectly probed by the internal methyl proton chemical shifts. These are based on the ring current of DHP and the magnitude of bond fixation depends on the annelating ring size, the coplanarity of the carbonyl group with the [pi]-system of DHP (for the cycloalkenone annelated DHPs) and the relative arrangement of the annelated rings (cisoid versus transoid for the diannelated compounds). Thus, when the ring size varied from four to seven in the cycloalkene- and dicycloalkenene annelated DHP series, the cyclohexene ring has the strongest bond fixation effect. When the ring size varied from five to seven in the cycloalkenone- and the dicycloalkenone-annelated DHP series, the cyclopentenone annelated DHPs have the strongest bond fixation effect. In the mono-cycloalkenone annelated DHP series (ring size =5 to 7), the Kekulé structures of the cycloalkenone annelated DHPs were determined by the vicinal coupling constant (3Jhh) to adopt an endocyclic structure (the double bond appears at the ring junction between the DHP and the annelating ring). For the diannelated DHP derivatives, the cisoid arrangement of ring annelation always has a stronger bond fixation effect compared to that of a transoid arrangement in almost all cases. In this thesis work, the use of DHP as a sensitive NMR probe was successfully demonstrated in that its internal methyl proton chemical shift responds to a change of ring current caused by different ring annelations. It is so sensitive, that even the very small perturbation on ring annelation (by cycloalkanes) can be sensed. DHP is a better NMR probe molecule than benzene because the chemical shifts of the internal methyl protons of DHP are less seriously affected by any effects such as geometrical distortion, rehybridization, steric compression, hyperconjugation and through space effects as probed by the ¹H and ¹³C-NMR spectroscopies in benzocycloalkenes. The ring annelation effect probed by DHP is closer to a pure [pi]-effect due to a change in ring current which is different from benzene, which is a mixture of both α- and [pi]-effects... / Graduate

Solid hydrogen coated graphite particles may be expelled from regions of star -formation into the general interstellar medium. The solid para- hydrogen mantles, which contain a small proportion of orthomolecules are stable against evaporation in the general interstellar radiation field. They are also stable against physical and chemical sputtering in HI regions. Extinction efficiencies are calculated for solid hydrogen particles and for graphite particles with solid hydrogen mantles. Graphite core -solid hydrogen grains are capable of producing excellent agreement with the interstellar extinction observations from 2u - 1100 A. The graphite core radius may be in the range ro = 0.04 - 0.06u and the solid hydrogen mantle radius in the range r = 0.15 - 0.25u. The albedo and phase function of these particles are consistent with the requirements imposed by the diffuse galactic light. Solid hydrogen is strongly anisotropic in its crystal structure and optical properties. Approximate models yield good agreement with the observed trends of the wavelength dependence of interstellar polarisation.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

This thesis investigates the morphology of early-type galaxies in two rich clusters using 2D surface photometry. In particular, the amount of light in the 'disk' component is focussed upon, as the presence of a disk is the main morphological criterion in distinguishing between the traditional 'elliptical' and 'S0' classes. Extensive and photometric E-band CCD observations of continuous areas of the Coma and Abell 1367 clusters were obtained at the 2.5 m Isaac Newton telescope, La Palma during March 1994. A subset of this large data-set has been used in this study, comprising a magnitude-limited (to R = 15.6) sample of 153 galaxies in the two clusters. Surface photometry measurements, including surface brightness profiles and isophotal shapes, have been made for the sample. Atmospheric seeing is a major problem when measuring light profiles at the distance of Coma from ground-based telescopes. Typical seeing at La Palma (FWHM~1.2") is a significant fraction of the effective radius of many Coma/Abell 1367 galaxies (r(_e)~3" for small ellipticals). An iterative algorithm was developed to deconvolve the effects of seeing from surface brightness profiles. The result of the algorithm is to extend the range of useful surface photometry inwards to within 2 times the FWHM. In order to parametrise the surface brightness profiles and discriminate between different profile-types, further software was developed to fit one- and two-component model profiles to the seeing-corrected data. The following parameters were measured and tabulated for each of the 153 galaxies: total magnitude M(_t); half-light parameters r (_1/2) and (μ)(_1/2); SB at half-light radius μ(r(_1/2)); photometric diameter D(_19.23) (equivalent to D(_n)); ellipticity at R = 21.5 isophote ϵ(_21.5); averaged isophote high-order terms (C(_3)), (S(_3)), (C(_4)) and (S(_4)); effective radii and surface brightnesses of 5 single power-law r(^1)(_n) models, r"e and (^)"^ (n = 1,2,3,4,5); best-fitting power-law index n; bulge effective radii and surface brightnesses from the two-component fit and (/^)\; disk effective parameters r'^e and {nY^] and disk-to-bulge luminosity ratio DjB. The measured parameters have been used to investigate various aspects of early-type galaxy morphology. The conclusions are outlined below. Firstly, a two-component r? plus exponential model is a better fit to most galaxies than a single component law fit. Secondly, the traditional division of early-type galaxies into 'elliptical' and 'SO' classes is severely biased by the viewing angle. In fact, it appears that early-type galaxies comprise a population of objects with smoothly varying bulge-to-disk ratio - although a few ellipticals (less than 13%) do not appear to have a exponential component. Finally, there is a general correlation (with much scatter) between the size and the profile shapes of early-type galaxies. The interpretation is that smaller galaxies are more disk-dominated than larger galaxies, which can be linked to the merging process in rich clusters.

No description available.

When darkmatter haloes are accreted by massive host clusters, strong gravitational tidal forces begin stripping mass from the accreted subhaloes. This stripping eventually removes all mass beyond a subhalo's tidal radius, with unbound mass remaining in the vicinity of the satellite for at most a dynamical time t(dyn). The N-body subhalo study of Chamberlain et al. verified this picture and pointed out a useful observational consequence: correlations between subhaloes beyond the tidal radius are sensitive to the infall time, t(infall), of the subhalo on to its host. We perform this correlation using similar to 160 000 red satellite galaxies in Sloan Digital Sky Survey redMaPPer clusters and find evidence that subhalo correlations do persist well beyond the tidal radius, suggesting that many of the observed satellites fell into their current host less than a dynamical time ago, t(infall) < t(dyn). Combined with estimated dynamical times t(dyn) similar to 3-5 Gyr and SED fitting results for the time at which satellites stopped forming stars, t(quench) similar to 6 Gyr, we infer that for a significant fraction of the satellites, star formation quenched before those satellites entered their current hosts. The result holds for red satellites over a large range of cluster-centric distances 0.1-0.6 Mpc h(-1). We discuss the implications of this result formodels of galaxy formation.

Thesis advisor: Ana Martinez-Aleman / Roman Catholic Seminaries are post-secondary schools where men study in preparation for ordination for priesthood. In recent visitations by bishops to American seminaries faculty and students at all the seminaries were interviewed regarding the effectiveness of the curriculum. Noticeably absent from the consultations were the priests who had recently graduated from the seminary. This study, influenced by Dr. Dean Hoge's study: The First Five Years of the Priesthood interviewed twenty men who were ordained to the priesthood for the Archdiocese of Boston in the years 2001-2006. Using Pope John Paul II's seminal work of Pastores Dabo Vobis the qualitative study focused on the four areas of formation: human, intellectual, pastoral, and spiritual. The interviews were recorded, transcribed, and coded using axial coding and open coding as well as cross case analysis and triangulation. Among the findings are loneliness of the recently ordained, the need for clearer boundaries in relationships with faculty members and women in the parish, more realistic training, the need for more support from the archdiocese, and better screening of pastoral sites prior to and after ordination. The findings suggest from the perceptions of the recently ordained men that there is significant room for improvement in all areas of formation. / Thesis (PhD) — Boston College, 2008. / Submitted to: Boston College. Lynch School of Education. / Discipline: Higher Education and Educational Administration.

L'accession a l'éducation d'un nombre toujours plus grand d'individus a conduit a considérer la performance des systèmes de formation comme un véritable facteur de développement économique. C'est dans ce contexte que s'inscrivent nos travaux de thèse qui ont visé au développement de méthodes et outils pour l'aide à la conception de la partie opérationnelle d'un système de formation et notamment tout le système de transformation permettant l'accroissements de compétences chez les apprenants. Après avoir présenté un bilan des systèmes de formation en définissant leur périmètre puis leur fonctionnement et résultats, nous précisons alors les facteurs qui nous ont conduits a nous préoccuper des processus opérationnels des systèmes de formation. Dans un deuxième chapitre, nous précisons la démarche que nous avons choisi d'adopter et déclinons ainsi l'ensemble de notre méthode, associée a des outils spécifiques, qui vise à l'aide a la conception et la mise en oeuvre des formations. Nous nous éloignons de la logique de l'offre pour migrer vers une logique de la demande. Nous proposons une identification contraintes subies par un système de formation (ressources à capacité finie, cohérence pédagogique, indisponibilité de ressources, compétences et aptitudes des ressources, etc.) - - Dans une troisième partie, nous illustrons notre propos en appliquant les méthodes et outils développes a un cas pratique. Enfin, nous concluons sur l'apport scientifique constitué par ces travaux et ouvrons la voie vers de nombreuses perspectives, le domaine de l'ingénierie de la formation étant encore à ses balbutiements / The accession with the education of a number increasingly larger indivlduals resulted in regarding the performance of the systems of formation as a true factor of economic development. It is in ths context that our work of thesis is registered which aimed to the development of methods and tools for the assistance with the design of the operational part of an education system and in particular al the transformation s y s t v leading to the increase of students competences. After having presented an assessment of the education systems by defining their perimeter, their operation and results, we specify the factors whch led us to worry us about operational processes of the education systems. In a second chapter, we specifi the steps whch we chose to adopt and we decline the whole of our method, associated to specific tools, which aims to the assistance to the design and the setting of formations. We move away from the logic of supply to migrate towards logic of demand. We propose an identification of constraints in education systems (resources with limited capaciîy, teachmg coherence, unavailability of resources, competences and aptitudes of the resources, etc.) In a third part, we illustrate our concept by applying methods and tools developed with a practical case. Lastly, we conclude on the scientific contribution made up by t h work and open the way towards rnany prospects, the field of the engineering of the formation being still to its beginnings