[pt] Neste trabalho descreve-se o projeto e desenvolvimento de um controlador inteligente de unidades de disco flexível para microcomputadores. O controlador inteligente é baseado no microprocessador 8085 e no controlador de disco 8271 da INTEL. Sua finalidade é livrar o computador hospedeiro das tarefas referentes ao controle de unidades de disco flexível, introduzindo capacidade de processamento paralelo no sistema. Este projeto faz parte do projeto MULTIPUC de estudos de redes de microcomputadores, em execução no Laboratório de Engenharia e Sistema de Computação (LESC) da PUC/RJ. / [en] This work describes the Project and realisation of a floppy-disk intelligent controller. The intelligent controller is besed on the INTEL 8085 microprocessor and on the INTEL 8271 disk controller. Its main purpose is to free the host computer of all the floppy-disk controlling tasks, which results in a additional parallel processing capacity of the system. This work is part of a microcomputer network project called MULTIPUC, which is being built at the Laboratório de Engenharia e Sistemas de Computação (LESC).

We discuss a parallel library of efficient algorithms for the solution of linear-quadratic optimal control problems involving largescale systems with state-space dimension up to $O(10^4)$. We survey the numerical algorithms underlying the implementation of the chosen optimal control methods. The approaches considered here are based on invariant and deflating subspace techniques, and avoid the explicit solution of the associated algebraic Riccati equations in case of possible ill-conditioning. Still, our algorithms can also optionally compute the Riccati solution. The major computational task of finding spectral projectors onto the required invariant or deflating subspaces is implemented using iterative schemes for the sign and disk functions. Experimental results report the numerical accuracy and the parallel performance of our approach on a cluster of Intel Itanium-2 processors.

La régulation du moment cinétique est l'une des questions les plus importantes dans la formation d'étoiles. Du nuage moléculaire à l'étoile finale, le système perd la grande majorité de son moment cinétique et plusieurs processus sont avancés pour l'expliquer. Nous nous concentrons sur la magneto-hydrodynamique (MHD) non-idéale, qui permet de décrire le couplage entre un champ magnétique et un fluide. Son efficacité pour réguler le moment cinétique dans des conditions réalistes a été montrée à plusieurs reprises. Dans un premier temps, nous développons un code qui calcule l'équilibre chimique d'éléments présents dans les premières étapes de la formation d'étoile. Ainsi, nous pouvons retrouver la valeur des coefficients définissant l'intensité de chaque processus de la MHD non-idéale. Nous nous intéressons ensuite à l'un d'entre eux, l'effet Hall, encore peu étudié dans ce contexte. Nous l'implémentons dans le code eulérien RAMSES, et l'utilisons pour quantifier son influence pendant un effondrement gravitationnel. Comme prévu par la théorie, l'effet Hall influence grandement la taille du disque protoplanétaire, dans lequel se forment les planètes, et crée des enveloppes de gas tournant en sens inverse du reste du système / The angular momentum regulation is a hot topic in star formation. From the molecular cloud to th final star, the system loses most of its angular momentum, and several processes are proposed to explain this phenomenon. We focus on non-ideal magnetohydrodynamics (MHD), which describes the coupling between a fluid and its magnetic field. Its efficiency to regulate the angular momentum in realistic conditions has been shown in several studies. First, we develop a code that computes the chemical equilibrium of elements present in the early stages of star formation. We can therefore obtain the values of coefficients defining the strength of the phyical processes associated with non-ideal MHD. We then take interest in one of them, the Hall effect, still poorly studied in this context. We implement it in the eulerian code RAMSES, and use it to quantify its influence during a gravitational collapse. As predicted by theory, the Hall effect greatly influences the size of the protoplanetary disk, in which planets form, and creates envelopes of gas rotating backward compared to the rest of the system

La zone morte, région laminaire confinée au coeur des disques protoplanétaires dont la turbulence de l'écoulement à petite échelle explique l'accrétion de matière sur l'étoile en formation, semble être un lieu propice à la formation planétaire. En effet, au bord interne de la zone morte la différence d'accrétion entraîne le développement d'une sur-densité capable de piéger les grains de poussière qui dérivent vers l'étoile. L'écoulement à cet endroit est de plus potentiellement instable. Le cas échéant, il s'organise en structures tourbillonnaires appelées ''vortex'' qui collectent efficacement la poussière. La position du bord interne est toutefois très incertaine et dépend en particulier de la thermodynamique du modèle de disque considéré. Récemment, le déplacement du bord interne a été envisagé pour expliquer la variabilité de l'accrétion des étoiles jeunes. Cette thèse aborde le problème posé par l'influence de la thermodynamique sur la dynamique du bord interne de la zone morte. Des simulations MHD qui incluent le couplage entre les processus thermodynamiques avec la dynamique de l'écoulement ont tout d'abord permis de confirmer le comportement dynamique du bord interne ainsi que de réaliser la mesure inédite de sa vitesse typique de déplacement. La comparaison de ces résultats avec les prédictions données par un modèle de champ moyen a révélé le rôle du transport d'énergie par des ondes excitées au bord interne de la zone morte. Ces simulations présentent de plus un phénomène nouveau: les vortex formés à l'interface suivent un cycle de formation-migration-destruction. Cette découverte est susceptible de modifier notre vision du scénario de formation planétaire. En résumé, cette thèse met en évidence le fait que les processus thermodynamiques sont au coeur du fonctionnement de la région du bord interne de la zone morte dans les disques protoplanétaires. / The dead zone, a quiescent region enclosed in the turbulent flow of a protoplanetary disk, seems to be a promising site for planet formation. Indeed, the development of a density maximum at the dead zone inner edge, that has the property to trap the infalling dust, is a natural outcome of the accretion mismatch at this interface. Moreover, the flow here may be unstable and organize itself into vortical structures that efficiently collect dust grains. The inner edge location is however loosely constrained. In particular, it depends on the thermodynamical prescriptions of the disk model that is considered. It has been recently proposed that the inner edge is not static and that the variations of young stars accretion luminosity are the signature of this interface displacements. This thesis address the question of the impact of the gas thermodynamics onto its dynamics around the dead zone inner edge. MHD simulations including the complex interplay between thermodynamical processes and the dynamics confirmed the dynamical behaviour of the inner edge. A first measure of the interface velocity has been realised. This result has been compared to the predictions of a mean field model. It revealed the crucial role of the energy transport by density waves excited at the interface. These simulations also exhibit a new intriguing phenomenon: vortices forming at the interface follow a cycle of formation-migration-destruction. This vortex cycle may compromise the formation of planetesimals at the inner edge. This thesis claims that thermodynamical processes are at the heart of how the region around the dead zone inner edge in protoplanetary disks works.

Approved for public release; distribution is unlimited / This thesis describes the procedure used for the automatic measurement of particles from hologram taken in the combustion chamber of a rocket motor while firing. It describes the investigation done on two averaging techniques used to reduce speckle noise, capturing the image focused on a spinning mylar disk and software averaging of several image frames. The spinning disk technique proved superior for this application. The Kolmogorov-Smirnov two-sample test is applied to different particle samples in order to find an estimate of the number of particles required to obtain a stable distribution function. The number of particles is calculated and given. The last part of this study shows real particle distributions in the form of frequency histograms. / http://archive.org/details/automaticmeasure00carr / Major, Canadian Armed Forces

No description available.

In the case of cold accretion disk, coupling between charge neutral gas and magnetic field is too weak such that the magneto-rotational instability will be less effective or even stop working. In such a situation it is of prime interest to investigate the pure hydrodynamic turbulence and transport phenomenon. As the Reynolds number increases, the relative importance of the non-linear term in the hydrodynamic equation increases and in the case of accretion disk where molecular viscosity is too small the Reynolds number is large enough for the non-linear term to bring new effects. We investigate a scenario, the ‘weakly non-linear’ evolution of amplitude of linear mode when the flow is bounded by two parallel walls. The unperturbed flow is similar to plane Couette flow but with Coriolis force included in the hydrodynamic equation. Although there is no exponentially growing eigenmode, due to self-interaction the least stable eigenmode will grow in an intermediate phase. Later on this will lead to higher order non-linearity and plausible turbulence. Although the non-linear term in the hydrodynamic equation is energy conserving, within the weakly non-linear analysis it is possible to define a lower bound of the energy needed for flow to transform to turbulent phase. Such an unstable phase is possible only if the Reynolds number ≥ 103−4. In Chapter-2 we set up equation of amplitude for the hydrodynamic perturbation and study the effect of weak non-linear evolution of linear mode for general angular momentum distribution, where Keplerian disk is obtained as a special case. As we know that to explain observed hard X-rays the choice of Keplerian angular momentum profile is not adequate, we consider the sub-Keplerian regime of the disk. In Chapter-3 we assume that the cooling mechanism is dominated by bremsstrahlung process (without any strict knowledge of the magnetic field structure).We show that in a range of Shakura-Sunyaev viscosity 0.2 ≥ α ≥ 0.0005, flow behavior varies widely, particularly by means of the size of disk, efficiency of cooling and corresponding temperatures of ions and electrons. We also show that the disk around a rotating black hole is hotter compared to that around a Schwarzschild black hole, rendering a larger difference between ion and electron temperatures in the former case. We finally reproduce the observed luminosities(L) of two extreme cases—the under-fed AGNs and quasars and ultra-luminous X-ray sources at different combinations of mass accretion rate, ratio of specific heats, Shakura-Sunyaev viscosity parameter and Kerr parameter. In Chapter-4 we investigate the viscous two temperature accretion disk flows around rotating blackholes. We describe the global solution of accretion flows, unlike that in Chapter-3, with a sub-Keplerian angular momentum profile, by solving the underlying conservation equations including explicit cooling processes self-consistently. Bremsstrahlung, synchrotron and inverse comptonization of soft photons are considered as possible cooling mechanisms. We focus on the set of solutions for sub-Eddington, Eddington and super-Eddington mass accretion rates around Schwarzschild and Kerr black holes with a Kerr parameter 0.998. We analyse various phases of advection–general advective paradigm to radiatively inefficient paradigm. The solution may potentially explain the hard X-rays and γ-rays emitted from AGNs and X-ray binaries. We also compare the solutions for two different regimes of viscosity. We finally reproduce the observed luminosities of the under-fed AGNs and quasars, ultra-luminous X-ray sources at different combinations of input parameters such as mass accretion rate and ratio of specific heats.

Crack initiation and propagation in the bladed disks of aero-engines caused by high-cycle fatigue under cyclic loads could result in the breakdown of the engines if not detected at an early stage. Although a number of fault detection methods have been reported in the literature, it still remains very challenging to develop a reliable online technique to accurately diagnose defects in bladed disks. One of the main challenges is to characterize signals contaminated by noises. These noises caused by very dynamic engine operation environment. This work presents a new technique for engine bladed disk crack detection, which utilizes advanced analysis of clearance and time-of-arrival signals acquired from blade tip sensors. This technique involves two stages of signal processing: 1) signal pre-processing for noise elimination from predetermined causes; and 2) signal post-processing for characterizing crack initiation and location. Experimental results from the spin rig test were used to validate technique predictions.

We present H band spectroscopic and H alpha photometric observations of HD 100546 obtained with the Gemini Planet Imager and the Magellan Visible AO camera. We detect H band emission at the location of the protoplanet HD 100546 b, but show that the choice of data processing parameters strongly affects the morphology of this source. It appears point-like in some aggressive reductions, but rejoins an extended disk structure in the majority of the others. Furthermore, we demonstrate that this emission appears stationary on a timescale of 4.6 years, inconsistent at the 2 sigma level with a Keplerian clockwise orbit at 59 au in the disk plane. The H band spectrum of the emission is inconsistent with any type of low effective temperature object or accreting protoplanetary disk. It strongly suggests a scattered-light origin, as this is consistent with the spectrum of the star and the spectra extracted at other locations in the disk. A nondetection at the 5 sigma level of HD 100546 b in differential H alpha imaging places an upper limit, assuming the protoplanet lies in a gap free of extinction, on the accretion luminosity of 1.7 x 10(-4) L-circle dot and M(M) over dot < 6.3 x 10(-7) M-Jup(2) yr(-1) for 1 R-Jup. These limits are comparable to the accretion luminosity and accretion rate of T-Tauri stars or LkCa 15 b. Taken together, these lines of evidence suggest that the H band source at the location of HD 100546 b is not emitted by a planetary photosphere or an accreting circumplanetary disk but is a disk feature enhanced by the point-spread function subtraction process. This non-detection is consistent with the non-detection in the K. band reported in an earlier study but does not exclude the possibility that HD 100546 b is deeply embedded.

We present the discovery of a brown dwarf companion to the debris disk host star HR 2562. This object, discovered with the Gemini Planet Imager (GPI), has a projected separation of 20.3 +/- 0.3 au (0".618 +/- 0".004) from the star. With the high astrometric precision afforded by GPI, we have confirmed, to more than 5 sigma, the common proper motion of HR 2562B with the star, with only a month-long time baseline between observations. Spectral data in the J-, H-, and K-bands show a morphological similarity to L/T transition objects. We assign a spectral type of L7 +/- 3 to HR 2562B. and derive a luminosity of log(L-bol/L-circle dot) = -4.62 +/- 0.12, corresponding to a mass of 30 +/- 15 M-Jup from evolutionary models at an estimated age of the system of 300-900 Myr. Although the uncertainty in the age of the host star is significant, the spectra and photometry exhibit several indications of youth for HR 2562B. The source has a position angle that is consistent with an orbit in the same plane as the debris disk recently resolved with Herschel. Additionally, it appears to be interior to the debris disk. Though the extent of the inner hole is currently too uncertain to place limits on the mass of HR 2562B, future observations of the disk with higher spatial resolution may be able to provide mass constraints. This is the first brown-dwarf-mass object found to reside in the inner hole of a debris disk, offering the opportunity to search for evidence of formation above the deuterium burning limit in a circumstellar disk.