- About
-
The Global ETD Search service is a free service for researchers
to find electronic theses and dissertations. This service is
provided by the
Networked Digital Library of Theses and Dissertations.
Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
Search results
Showing 701 to 710 of 712 (0.025 seconds)| 701 |
Axiomatic approach to cellular algebrasAhmadi, Amir 01 1900 (has links)
Les algèbres cellulaires furent introduite par J.J. Graham et G.I. Lehrer en 1996. Elles forment
une famille d’algèbres associatives de dimension finie définies en termes de « données
cellulaires » satisfaisant certains axiomes. Ces données cellulaires, lorsqu’elles sont identifiées
pour une certaine algèbre, permettent une construction explicite de tous ses modules
simples, à isomorphisme près, et de leurs couvertures projectives. Dans ce mémoire, nous
définissons ces algèbres cellulaires en introduisant progressivement chacun des éléments constitutifs
d’une façon axiomatique.
Deux autres familles d’algèbres associatives sont discutées, à savoir les algèbres quasihéréditaires
et celles dont les modules forment une catégorie de plus haut poids. Ces familles
furent introduites durant la même période de temps, au tournant des années quatre-vingtdix.
La relation entre ces deux familles ainsi que celle entre elles et les algèbres cellulaires
sont prouvées. / Cellular algebras were introduced by J.J. Graham and G.I. Lehrer in 1996. They are a class of
finite-dimensional associative algebras defined in terms of a “cellular datum” satisfying some
axioms. This cellular datum, when made explicit for a given associative algebra, allows for
the explicit construction of all its simple modules, up to isomorphism, and of their projective
covers. In this work, we define these cellular algebras by introducing each building block of
the cellular datum in a fairly axiomatic fashion.
Two other families of associative algebras are discussed, namely the quasi-hereditary
algebras and those whose modules form a highest weight category. These families were
introduced at about the same period. The relationships between these two, and between
them and the cellular ones, are made explicit.
|
| 702 |
Formwork-free, continuous production of variable frame elements for modular shell structuresIvaniuk, Egor, Mechtcherine, Viktor 10 November 2022 (has links)
Conventional construction of concrete shells involves a costly and time-consuming erection of custom formwork. An alternative approach that avoids this is an on-site assembly of shells from prefabricated
modules. This article presents a new, highly automated method for the production of such modules. The proposed method combines the technology of full-width 3D concrete printing using strain-hardening cement-based composite and the technology of robotic textile mesh production from mineral-impregnated carbon yarns.
|
| 703 |
AI based prediction of road users' intents and reactionsGurudath, Akshay January 2022 (has links)
Different road users follow different behaviors and intentions in the trajectories that they traverse. Predicting the intent of these road users at intersections would not only help increase the comfort of drive in autonomous vehicles, but also help detect potential accidents. In this thesis, the research objective is to build models that predicts future positions of road users (pedestrians,cyclists and autonomous shuttles) by capturing behaviors endemic to different road users. Firstly, a constant velocity state space model is used as a benchmark for intent prediction, with a fresh approach to estimate parameters from the data through the EM algorithm. Then, a neural network based LSTM sequence modeling architecture is used to better capture the dynamics of road user movement and their dependence on the spatial area. Inspired by the recent success of transformers and attention in text mining, we then propose a mechanism to capture the road users' social behavior amongst their neighbors. To achieve this, past trajectories of different road users are forward propagated through the LSTM network to obtain representative feature vectors for each road users' behaviour. These feature vectors are then passed through an attention-layer to obtain representations that incorporate information from other road users' feature vectors, which are in-turn used to predict future positions for every road user in the frame. It is seen that the attention based LSTM model slightly outperforms the plain LSTM models, while both substantially outperform the constant velocity model. A comparative qualitative analysis is performed to assess the behaviors that are captured/missed by the different models. The thesis concludes with a dissection of the behaviors captured by the attention module.
|
| 704 |
The use of technology for improving throughput rates in an ODL context by lecturers in the School of ComputingMukasa-Lwanga, Theopista Nazziwa 03 1900 (has links)
The improvement of throughput rates is a crucial factor at higher education institutions; hence, university departments focus on improving pass rates per module. This study investigated how lecturers in the School of Computing (SoC) at the University of South Africa, use technology for improving throughput rates in an Open Distance Learning (ODL) context. The study sought answers to the main research question on how lecturers in the SoC use technology for improving throughput rates in an ODL institution. A mixed research methods approach was used, where quantitative data was extracted from the university systems and integrated with the qualitative data collected from interviews. Thirteen lecturers for the thirty modules under investigation were interviewed. A thematic analysis was used on the qualitative data, and quantitative data was analysed using rankings and correlation coefficients, leading to the interpretation that the use of myUnisa technology assisted to improve throughput on the modules. / Mathematics Education / M. Sc. (Computing Education)
|
| 705 |
How Often do Experts Make Mistakes?Palix, Nicolas, Lawall, Julia L., Thomas, Gaël, Muller, Gilles January 2010 (has links)
Large open-source software projects involve developers with a wide variety of backgrounds and expertise. Such software projects furthermore include many internal APIs that developers must understand and use properly. According to the intended purpose of these APIs, they are more or less frequently used, and used by developers with more or less expertise. In this paper, we study the impact of usage patterns and developer expertise on the rate of defects occurring in the use of internal APIs. For this preliminary study, we focus on memory management APIs in the Linux kernel, as the use of these has been shown to be highly error prone in previous work. We study defect rates and developer expertise, to consider e.g., whether widely used APIs are more defect prone because they are used by less experienced developers, or whether defects in widely used APIs are more likely to be fixed.
|
| 706 |
Malleability, obliviousness and aspects for broadcast service attachmentHarrison, William January 2010 (has links)
An important characteristic of Service-Oriented Architectures is that clients do not depend on the service implementation's internal assignment of methods to objects. It is perhaps the most important technical characteristic that differentiates them from more common object-oriented solutions. This characteristic makes clients and services malleable, allowing them to be rearranged at run-time as circumstances change. That improvement in malleability is impaired by requiring clients to direct service requests to particular services. Ideally, the clients are totally oblivious to the service structure, as they are to aspect structure in aspect-oriented software. Removing knowledge of a method implementation's location, whether in object or service, requires re-defining the boundary line between programming language and middleware, making clearer specification of dependence on protocols, and bringing the transaction-like concept of failure scopes into language semantics as well. This paper explores consequences and advantages of a transition from object-request brokering to service-request brokering, including the potential to improve our ability to write more parallel software.
|
| 707 |
Inovační aspekty elektronickeho výběru mýtného v ČR / Innovation Aspects of the Electronic Toll System in the Czech RepublicŠindelářová, Jana January 2008 (has links)
This thesis deals with the innovation of information system (IS) as a decision problem. The main objective of this thesis is the construction and the application of a method to select an optimal innovation variant of IS in an organisation of any scale. The designed method is based on the conception of the innovation of IS in the methodology "Multidimensional Management and Development of Information System (MMDIS)". The proposed selection method (Method of Innovation Modules based on MMDIS - MIM) is intended to serve mainly for decision-making on a strategic level. The IS structure is mapped in accordance with the MMDIS methodology. Innovation aspects are derived from two approaches: innovation aspects based on the MMDIS principles ("module of principles" - e.g. integration, flexibility, standardisation, measurability) and innovation aspects based on the IS dimensions defined in MMDIS methodology ("module of dimensions" - e.g. software, hardware, processes and functions, finances). The proposal method enforces a systematic approach to evaluation of the innovation variants, ensuring that the innovation aspects (the principles and the dimensions) are aligned with key requirements. As an example, this method is applied to an existing electronic toll system operated in the Czech Republic. Basic innovation variants of the electronic toll system are described - the microwave, the satellite and the hybrid toll system. Case studies from the Czech Republic, Austria and Germany are used for support the proposed innovation variants, as well as evaluation of variants. The principles and the dimensions form a framework for description and evaluation of the telematics, of the electronic toll and of the innovation variants of the electronic toll. The variants are compared within the framework of refined principles and dimensions, the optimal variant is proposed. The used evaluation parameters are a result of an analysis of published studies and specific toll system technical designs. The Method of Innovation Modules was constructed on the basis of MMDIS methodology and demonstrated by application in an example scenario (electronic toll). The key result of the proposed method is the comprehensive structured map of available system innovation opportunities.
|
| 708 |
AspectKE*: Security aspects with program analysis for distributed systemsFan, Yang, Masuhara, Hidehiko, Aotani, Tomoyuki, Nielson, Flemming, Nielson, Hanne Riis January 2010 (has links)
Enforcing security policies to distributed systems is difficult, in particular, when a system contains untrusted components. We designed AspectKE*, a distributed AOP language based on a tuple space, to tackle this issue. In AspectKE*, aspects can enforce access control policies that depend on future behavior of running processes. One of the key language features is the predicates and functions that extract results of static program analysis, which are useful for defining security aspects that have to know about future behavior of a program. AspectKE* also provides a novel variable binding mechanism for pointcuts, so that pointcuts can uniformly specify join points based on both static and dynamic information about the program. Our implementation strategy performs fundamental static analysis at load-time, so as to retain runtime overheads minimal. We implemented a compiler for AspectKE*, and demonstrate usefulness of AspectKE* through a security aspect for a distributed chat system.
|
| 709 |
Settling-Time Improvements in Positioning Machines Subject to Nonlinear Friction Using Adaptive Impulse ControlHakala, Tim 31 January 2006 (has links) (PDF)
A new method of adaptive impulse control is developed to precisely and quickly control the position of machine components subject to friction. Friction dominates the forces affecting fine positioning dynamics. Friction can depend on payload, velocity, step size, path, initial position, temperature, and other variables. Control problems such as steady-state error and limit cycles often arise when applying conventional control techniques to the position control problem. Studies in the last few decades have shown that impulsive control can produce repeatable displacements as small as ten nanometers without limit cycles or steady-state error in machines subject to dry sliding friction. These displacements are achieved through the application of short duration, high intensity pulses. The relationship between pulse duration and displacement is seldom a simple function. The most dependable practical methods for control are self-tuning; they learn from online experience by adapting an internal control parameter until precise position control is achieved. To date, the best known adaptive pulse control methods adapt a single control parameter. While effective, the single parameter methods suffer from sub-optimal settling times and poor parameter convergence. To improve performance while maintaining the capacity for ultimate precision, a new control method referred to as Adaptive Impulse Control (AIC) has been developed. To better fit the nonlinear relationship between pulses and displacements, AIC adaptively tunes a set of parameters. Each parameter affects a different range of displacements. Online updates depend on the residual control error following each pulse, an estimate of pulse sensitivity, and a learning gain. After an update is calculated, it is distributed among the parameters that were used to calculate the most recent pulse. As the stored relationship converges to the actual relationship of the machine, pulses become more accurate and fewer pulses are needed to reach each desired destination. When fewer pulses are needed, settling time improves and efficiency increases. AIC is experimentally compared to conventional PID control and other adaptive pulse control methods on a rotary system with a position measurement resolution of 16000 encoder counts per revolution of the load wheel. The friction in the test system is nonlinear and irregular with a position dependent break-away torque that varies by a factor of more than 1.8 to 1. AIC is shown to improve settling times by as much as a factor of two when compared to other adaptive pulse control methods while maintaining precise control tolerances.
|
| 710 |
Contribution à l'intégration d'une liaison avionique sans fil. L'ingénierie système appliquée à une problématique industrielleBerrebi, Johanna 21 February 2013 (has links) (PDF)
Dans un avion, un hélicoptère ou un lanceur actuel, des milliers de capteurs, pour la plupart non critiques sont utilisés pour la mesure de divers paramètres (températures, pressions, positions...) Les résultats sont ensuite acheminés par des fils vers les calculateurs de bord qui les traitent. Ceci implique la mise en place de centaines de kilomètres de câbles (500 km pour un avion de ligne) dont le volume est considérable. Il en résulte une grande complexité de conception et de fabrication, des problèmes de fiabilité, notamment au niveau des connexions, et une masse importante. Par ailleurs l'instrumentation de certaines zones est impossible car leur câblage est difficilement envisageable par manque d'espace. En outre, s'il est souvent intéressant d'installer de nouveaux capteurs pour faire évoluer un aéronef ancien, l'installation des câbles nécessaires implique un démantèlement partiel, problématique et coûteux, de l'appareil. Pour résoudre ces problèmes, une idée innovante a émergé chez les industriels de l'aéronautique : commencer à remplacer les réseaux filaires reliant les capteurs d'un aéronef et leur centre de décision par des réseaux sans fil. Les technologies de communication sans fil sont aujourd'hui largement utilisées dans les marchés de l'électronique de grande consommation. Elles commencent également à être déployées pour des applications industrielles comme l'automobile ou le relevé à distance de compteurs domestiques. Cependant, remplacer des câbles par des ondes représente un défi technologique considérable comme la propagation en milieu confiné, la sécurité, la sureté de fonctionnement, la fiabilité ou la compatibilité électromagnétique. Cette thèse est motivée d'une part par l'avancée non négligeable dans le milieu aérospatial que pourrait être l'établissement d'un réseau sans fil à bord d'aéronefs dans la résolution de problématique classiques comme l'allégement et l'instrumentation. Il en résulterait donc : * Une meilleure connaissance de l'environnement et de la santé de l'aéronef * Un gain sur le poids. * Un gain en flexibilité. * Un gain en malléabilité et en évolutivité. * Un gain sur la complexité. * Un gain sur la fiabilité D'autre part, étant donnée la complexité de la conception de ce réseau de capteur sans fil, il a été nécessaire d'appliquer une méthodologie évolutive et adaptée mais inspirée de l'ingénierie système. Il est envisageable, vu le nombre de sous-systèmes à considérer, que cette méthodologie soit réutilisable pour d'autre cas pratiques. Une étude aussi complète que possible a été réalisée autour de l'existant déjà établi sur le sujet. En effet, on peut en lisant ce mémoire de thèse avoir une idée assez précise de ce qui a été fait. Une liste a été dressée de toutes les technologies sans fil en indiquant leur état de maturité, leurs avantages et leurs inconvénients afin de préciser les choix possibles et les raisons de ces choix. Des projets de capteurs sans fil ont été réalisés, des technologies sans fil performantes et personnalisables ont été développées et arrivent à maturité dans des secteurs variés tels que la domotique, la santé, l'automobile ou même l'aéronautique. Cependant aucun capteur sans fil n'a été véritablement installé en milieu aérospatial car de nombreux verrous technologiques n'ont pas été levés. Fort des expériences passées, et de la maturité qu'ont prise certaines technologies, des conclusions ont été tirées des projets antérieurs afin de tendre vers des solutions plus viables. Une fois identifiés, les verrous technologiques ont été isolés. Une personnalisation de notre solution a été à envisager afin de remédier tant que faire se peut à ces points bloquants avec les moyens mis à disposition. La méthodologie appliquée nous a permis d'identifier un maximum de contraintes, besoins et exigences pour mieux focaliser les efforts d'innovation sur les plus importantes et choisir ainsi les technologies les plus indiquées.
|
Page generated in 0.042 seconds