Infoscience
(66.951 recursos)
Repository of the publications, research reports, PhD Theses, Ms Theses, semester works, lectures, etc., of the Facultés, Laboratories and Researchers at the EPFL.
Mostrando recursos 1 - 20 de 418
1.
Choix de variantes d'infrastructures routières: méthodes multicritères - Tille, Micaël
This study provides a tool by means of which a road planner, usually a civil engineer, can achieve a durable infrastructure of high quality, acceptable to all parties concerned. The various elements which facilitate the work of planning are united into a modernized methodology for the elaboration of road projects, called a methodology of concert. After analysing the sort of problems encountered in the planning of road infrastructure (Chapter 1), the author classifies the main causes of these into a hierarchy. This brings to light many factors which may stem from the structure of the project, the environment or from...
3.
Modèle d'évolution de l'état des ponts-routes en béton - Roelfstra, Guido
The management of existing road infrastructures is a multidisciplinary activity that involves structural engineering, material science, management, economics and ecology. The objective is to achieve maximum availability of road links at minimum societal costs. Recently, tools (Bridge Management Systems, BMSs) have been developed to help decision makers to determine the optimal management strategies within available resources. The condition development model is a key element of the BMSs. Currently this model is using empirical approach making use of data collected during inspections and is formulated with Markov chains. The assessment units are structural elements and these are classified into condition classes...
4.
Il caso della Cogne di Aosta: siderurgia, territorio, architettura - Moretto, Luca
Within the "industrial architecture", the thesis is – in a general sense – the story of a travel in the space (from the Liguria sea – but not only – to the Valle dlAosta mountains), and in the time (the XXth century). The structure of the narration previews three main levels of reading: historical-philological, restoring and clearing up, as much clear as possible, on the horizon of the Italian steel iron industry, the vicissitudes in the time of the iron and steel plant "Cogne" of Aosta; geographical/urban, bringing to light the impact of the plant on the city of Aosta...
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The use of Boolean concepts in general classification contexts - Moreira, Luis Miguel
Data classification, in the present context, concerns the use of computers in order to create systems that learn how to automatically decide to which of a predefined set of classes a given object belongs. Boolean concepts have long been present in data classification, and still are today, at various levels. We consider a kind of Boolean elements, called patterns, which consist of specific conjunctions of Boolean facts. Assuming the existence of two classes of objects, the positive and the negative, patterns can be expressed as conditionals of the type "If A and B and not C, then positive", where A,...
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Modeling diversity by strange attractors with application to temporal pattern recognition - De Feo, Oscar
This thesis belongs to the general discipline of establishing black-box models from real-word data, more precisely, from measured time-series. This is an old subject and a large amount of papers and books has been written about it. The main difficulty is to express the diversity of data that has essentially the same origin without creating confusion with data that has a different origin. Normally, the diversity of time-series is modeled by a stochastic process, such as filtered white noise. Often, it is reasonable to assume that the time series is generated by a deterministic dynamical system rather than a stochastic...
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An experimental investigation of a lean burn natural gas prechamber spark ignition engine for cogeneration - Röthlisberger, Roger
The operation of a cogeneration internal combustion engine with unscavenged prechamber ignition was investigated. The objective was to evaluate the potential to reduce the exhaust gas emissions, particularly the CO emissions, below the Swiss limits (NOx and CO emissions: 250 and 650 mg/m3N, 5% O2 , respectively), without exhaust gas after treatment. The investigation was carried out on a small size gas engine (6 cylinders, 122 mm bore, 142 mm stroke) and required the development of cooled prechambers and the modification of the engine cylinder heads. The approach was essentially experimental, but included a numerical simulation based on the CFD-code...
8.
Ozone and water vapor measurements by Raman lidar in the planetary boundary layer - Lazzarotto, Benoît
The temporal and spatial retrieve of ozone (O3) concentration and water vapor (H2O) mixing ratio in the troposphere is of essential interest. Contrary to the stratospheric case, the tropospheric ozone can have a harmful impact, with its toxic effect, on humans and vegetation, accelerating the degradation of the minerals and participating in the green-house problem. Concerning the water vapor, knowledge of its highly variable concentration is essential to both the chemistry of the troposphere (O(1D) + H2O —> 2 OH) where it participates, among others, in the generation of the hydroxyl radical (OH) and to the meteorology. Water vapor is...
9.
Extrinsic contributions to the piezoelectric response of lead-based ferroelectrics - Robert, Gilles
The present study aims at a better understanding of the high piezoelectric properties encountered in lead-based ferroelectrics by focusing on the extrinsic contributions to the response. The main characteristics of these materials are the highly nonlinear character of the electro-mechanical response and the presence of a morphotropic phase boundary (MPB) where properties are reaching a maximum. Thus, our approach was first to develop a new description for the piezoelectric hysteresis and nonlinearities and second to investigate MPB effects on the extrinsic contributions to the piezoelectric response. For these purposes, lead titanate (PT), lead zirconate titanate (PZT), and lead nickel niobate-lead...
10.
A virtual model for simulation and design of architectures in MPEG-4 audio and multimedia context - Zoia, Giorgio
Research in multimedia for consumer electronics is dominated by the problem of incredibly short times-to-market, that means fast complexity estimations and fast design of new architectures. On one side more and more sophisticated and flexible applications are rapidly developed, on the other side the exponential growth in IC computational power seems to be hardly capable to keep pace with requirements for real-time applications, since their complexity is exponentially growing as well. The processor's performance, often slowed down by bottlenecks in memories and buses, is further reduced by the time wasted in communication among the several application layers. From this problem...
11.
Sampling innovations - Marziliano, Pina
Sampling theory has prospered extensively in the last century. The elegant mathematics and the vast number of applications are the reasons for its popularity. The applications involved in this thesis are in signal processing and communications and call out to mathematical notions in Fourier theory, spectral analysis, basic linear algebra, spline and wavelet theory. This thesis is divided in two parts. Chapters 2 and 3 consider uniform sampling of non-bandlimited signals and Chapters 4, 5, and 6 treat different irregular sampling problems. In the first part we address the problem of sampling signals that are not bandlimited but are characterized...
12.
Inverse kinematics techniques of the interactive posture control of articulated figures - Baerlocher, Paolo
The context of this thesis is the interactive manipulation of complex articulated figures by means of geometric constraints (here called tasks), for the purpose of posture control and design. The goal is to determine a posture satisfying a set of prescribed tasks, usually expressed in the Cartesian space. This approach is known as Inverse Kinematics, and a number of analytic and numerical resolution methods have been developed for the control of robot manipulators. These methods have been applied to the computer animation of articulated figures, and to the control of human models for computer-aided ergonomic evaluations of products or workplaces....
13.
Développement de réacteurs microstructurés pour la conversion du propane en produits valorisés - Wolfrath, Olivier
Industry requires continuously new chemical processes to convert raw materials to valuable products limiting the formation of by-products. Since a few years, an increasing interest has been given to the intensification of chemical processes. This represents a new approach in chemical reaction engineering and calls for a new type of chemical reactors: the microstructured reactors. They are characterized by miniature structures whose components have a sub-millimeter size. The flow channels, for example, have a diameter from ten to several hundred microns. The distinctive feature of these structures is a very large surface/volume ratio, namely between 10'000 and 50'000 m2/m3. In...
14.
Organically modified silicates as stationary phases for capillary electrochromatography - Constantin, Stéphane
Capillary electrochromatography (CEC) is a microfluidic separation technique where the liquid flow is powered by an electric field instead of a pressure gradient. This mode of propulsion, reducing the dispersion of the analytes and leading to the absence of pressure drops, contributes to an increasing interest for CEC compared to pressure driven liquid chromatography. Efficient stationary phases need to be developed to promote a widespread use of CEC. Toward this goal, the present work describes the synthesis and the use of organically modified silicates (ormosils) as stationary phases for capillary electrochromatography. Ormosils, made by the sol-gel technique, consist of a...
15.
Remote data acquisition of embedded systems using Internet technologies: a role-based generic system specification - Nieva, Txomin
Data Acquisition Systems (DAS) are the basis for building monitoring tools that enable the supervision of local and remote systems. DASs are complex systems. It is difficult for developers to compare proprietary generic DAS products and/or standards, and the design of a specific DAS is costly. In this thesis we propose an implementation independent specification, based on conceptual and role-based use case modeling, of a generic architecture for DASs. This generic DAS specification gives DAS developers an abstraction of DASs; it enables them to compare existing DAS products and standards; and it provides the DAS developers that aim to develop...
16.
MHD stability limits in the TCV tokamak - Reimerdes, Holger
Magnetohydrodynamic (MHD) instabilities can limit the performance and degrade the confinement of tokamak plasmas. The Tokamak à Configuration Variable (TCV), unique for its capability to produce a variety of poloidal plasma shapes, has been used to analyse various instabilities and compare their behaviour with theoretical predictions. These instabilities are perturbations of the magnetic field which usually extend to the plasma edge where they can be detected with magnetic pick-up coils as magnetic fluctuations. A spatially dense set of magnetic probes, installed inside the TCV vacuum vessel, allows for a fast observation of these fluctuations. The structure and temporal evolution of...
17.
Atmospheric heterogeneous reactions of chlorine and bromine containing molecules: a laboratory study - Aguzzi, Arnaud
This thesis deals with a laboratory study of heterogeneous reactions involving bromine and chlorine containing reservoir species on alkali salt substrates which are relevant to the marine boundary layer, and on ice substrates which are relevant to the lower stratosphere. The aim is to obtain reliable data on uptake coefficients γ and reaction mechanisms for the sake of extrapolation of results obtained in the laboratory to atmospheric conditions. The experiments have been performed in a Teflon coated Knudsen flow reactor equipped with a quadrupole mass spectrometer. The reactions of BrONO2 with solid alkali halides have been studied at ambient temperature....
18.
Shear strength of rock joints based on quantified surface description - Grasselli, Giovanni
One of the primary objectives of this work is to better understand the frictional behavior of joints under shear loads, including the creation of damage zones. Discontinuities have an important influence on the deformational behavior of rock systems. The choice of a general criterion to determine the shear strength of rough rock joints is a general problem that has been investigated for many years. Numerous shear models have been proposed in the last decades to relate shear-strength to measurable joint parameters, but their limitations have to be recognized. The problem is how to measure and then to express the roughness...
19.
Acoustic goniometry: a spatio-temporal approach - Van Lancker, Eric
This work was motivated by the increasing need for acoustic localization systems. The various localization systems that were implemented during this PhD include localization of snow avalanches, artillery and supersonic aircraft in the infrasound domain, the localization of helicopters, civilian aircraft, speakers and auditorium reflections in the audio domain and the localization of chirps in the underwater ultrasound domain. The "goniometer" is defined as an instrument that measures angles. An "acoustic goniometer" is therefore a system that measures the direction of arrival (DOA) of sounds, and thus estimates the source direction. A goniometer is made up of an antenna, composed...
20.
Typology of recent groundwaters from different aquifer environments based on geogenic tracer elements - Kilchmann, Sybille
A key problem in environmental science and in engineering geology is the often incomplete understanding of the origin of dissolved components in groundwater. The dissolved contents of trace elements in groundwater are of special importance for groundwater quality control. The AQUITYP project aims to establish a detailed typology of recent groundwaters based on their geogenic trace element compositions, and to derive a so-called "geo-reference" for groundwaters from five principal aquifer lithologies in the Alpine belt. This geo-reference provides a database for investigations related to groundwater contamination, groundwater resources management and engineering geology. Groundwaters from crystalline, carbonate, and evaporite rocks, as...
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