• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 361
  • 121
  • 70
  • 55
  • 39
  • 22
  • 11
  • 10
  • 10
  • 9
  • 9
  • 9
  • 9
  • 9
  • 9
  • Tagged with
  • 916
  • 155
  • 151
  • 112
  • 110
  • 84
  • 75
  • 67
  • 57
  • 52
  • 51
  • 48
  • 46
  • 46
  • 46
  • 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.
691

Numerical behaviour of buried flexible pipes in geogrid-reinforced soil under cyclic loading

Elshesheny, Ahmed, Mohamed, Mostafa H.A., Nagy, N.M., Sheehan, Therese 23 March 2021 (has links)
Yes / Three-dimensional finite element models were executed and validated to investigate the performance of buried flexible high-density Polyethylene (HDPE) pipes, in unreinforced and multi-geogrid-reinforced sand beds, while varying pipe burial depth, number of geogrid-layers, and magnitude of applied cyclic loading. Geogrid-layers were simulated considering their geometrical thickness and apertures, where an elasto-plastic constitutive model represented its behaviour. Soil-geogrid load transfer mechanisms due to interlocked soil in-between the apertures of the geogrid-layer were modelled. In unreinforced and reinforced cases, pipe burial depth increase contributed to decreasing deformations of the footing and pipe, and the crown pressure until reaching an optimum value of pipe burial depth. On the contrary, the geogrid-layers strain increased with increasing pipe burial depth. A flexible slab was formed due to the inclusion of two-geogrid-layers, leading to an increase in the strain in the lower geogrid-layer, despite its lower deformation. Inclusion of more than two geogrid-layers formed a heavily reinforced system of higher stiffness, and consequently, strain distribution in the geogrid-layers varied, where the upper layer experienced the maximum strain. In heavily reinforced systems, increasing the amplitude of cyclic loading resulted in a strain redistribution process in the reinforced zone, where the second layer experienced the maximum strain.
692

Utmaningar med hyressättning efter renovering : En analys av lagstiftningen kring hyreshöjningar vid renoveringar inom miljonprogrammet / The challenges of the rent setting system during renovation : Analysis of Legislation on Rent Increases During Renovations Within the Million Programme

Mikho, Maria January 2024 (has links)
Bostadshusen från miljonprogrammet är i behov av genomgripande renoveringar. Samtidigt riskerar detta att medföra omfattande hyreshöjningar för hyresgästerna som utgör en socioekonomiskt utsatt grupp i samhället. De hyreshöjningar som hyresgästerna står inför, och som har stöd i rådande lagstiftning, kan resultera i en renovräkning som innebär att ett flertal hyresgäster behöver lämna sina hem.  Syftet med detta arbete är att erhålla en djupare förståelse för hur hyressättningssystemet i samband med renovering fungerar för att undersöka dels rimligheten i de hyreshöjningar som sker, dels om rådande lagstiftning skyddar hyresgästen i samband med detta. Främst fokus har riktats mot hyreslägenheterna som tillhör miljonprogrammet. Tre centrala frågeställningar har väglett arbetet: Vilka lagar och regler styr hyreshöjningar vid renoveringar av lägenheter inom miljonprogrammet? Hur bedöms rimligheten i en hyreshöjning efter renoveringar ur ett juridiskt perspektiv? Skyddar dagens lagstiftning hyresgäster från markanta hyreshöjningar? För att besvara samtliga frågeställningar har en rättsdogmatisk ansats tillämpats, där utgångspunkten har tagits i lagstiftning, rättspraxis, lagförarbeten, viss rättshistoria och doktrin. Vidare har tillhörande litteratur samt rättsfall studerats för att undersöka hur hyressättningssystemet kring renoveringar ter sig i praktiken.  Arbetet konstaterar att hyreshöjningar följt av renoveringar kan få betydande konsekvenser för hyresgästerna, speciellt i områden som tillhör miljonprogrammet, som präglas av socioekonomisk utsatthet. Rådande regelsystem möjliggör betydande hyreshöjningar där hyresgäster har ett begränsat inflytande trots de skyddsregler som idag finns för att tillgodose ett skydd för dem. Dagens lagstiftning står därmed inför stora utmaningar, inte minst när det gäller att tillgodose behovet av en rimlig bostadsstandard samtidigt som hyresgästens ekonomiska situation ska beaktas. / The residential buildings from the Million program are in need of extensive renovation. This can lead to substantial rent increases for the tenants, who represent a socio-economically vulnerable group in society. The rent increases, which are supported by current legislation, may result in renovation eviction, where several tenants are forced to leave their homes due to rent increase. The aim of this study is to gain a deeper understanding of how the rent setting system during renovation works, in order to examine both the reasonableness of the rent increases and whether current legislation protects the tenant in such cases. The focus has been on rental apartments from the Million program. Three central questions have guided this work: What laws and regulations govern rent increases when renovating apartments from the Million program? How is the reasonableness of a rent increase after renovations assessed from a legal perspective? Does current legislation protect tenants from significant rent increases? To answer the questions presented, different methods, including a legal-dogmatic approach, have been applied, where the current legislation, case law, selective legislative history and doctrine have been studied. Other literature on the subject have also been studied, in order to obtain an insight of the rent setting system during renovation, both from a theoretical and practical perspective.  This work finds that rent increases followed by renovation can have significant consequences for tenants, especially in areas belonging to the Million program with high socio-economic vulnerability. The current legislation allows for extensive rent increases where tenants have limited influence despite the current influence that is supported by law to provide protection for them. Today's legislation thus faces major challenges, not least when it comes to meeting the need for a reasonable standard of housing while taking into account the tenant's financial situation.
693

Zdravotně technické instalace v nemocnici / Sanitation installation in the hospital

Peřinová, Jitka January 2022 (has links)
The task of this diploma thesis is to prepare the design of sanitary and gas pipeline installations in the assigned hospital building. The building has one underground and four above-ground floors. On the underground floor there are technical premises including a boiler room, hygienic facilities of staff and rooms for storage and cleaning. On the first floor there are ambulances of various kinds. Patient rooms are located over the second and third floors. Each room has its own built-in bathroom. There are also doctor's examination rooms and daily room of staff. On the fourth floor there is an ICU. In the theoretical part I deal with the legionella bacterium. I explain what causes this bacterium, what are the conditions for its reproduction, where it occurs and what measures will prevent its multiplication in water pipes. In the next part, I compare two possible variants of the solution of the design of water pipe routes with the subsequent selection of a more suitable option. The calculation part contains all the calculations used to design sewerage, water supply and gas pipeline, including their connection to utilities.
694

Etude d'une structure de multiprocesseur virtuel : application à un réseau d'opérateurs adapté au traitement du signal

Mitrani Abenchuchan, Enrique 29 January 1975 (has links) (PDF)
.
695

Near real-time detection and approximate location of pipe bursts and other events in water distribution systems

Romano, Michele January 2012 (has links)
The research work presented in this thesis describes the development and testing of a new data analysis methodology for the automated near real-time detection and approximate location of pipe bursts and other events which induce similar abnormal pressure/flow variations (e.g., unauthorised consumptions, equipment failures, etc.) in Water Distribution Systems (WDSs). This methodology makes synergistic use of several self-learning Artificial Intelligence (AI) and statistical/geostatistical techniques for the analysis of the stream of data (i.e., signals) collected and communicated on-line by the hydraulic sensors deployed in a WDS. These techniques include: (i) wavelets for the de-noising of the recorded pressure/flow signals, (ii) Artificial Neural Networks (ANNs) for the short-term forecasting of future pressure/flow signal values, (iii) Evolutionary Algorithms (EAs) for the selection of optimal ANN input structure and parameters sets, (iv) Statistical Process Control (SPC) techniques for the short and long term analysis of the burst/other event-induced pressure/flow variations, (v) Bayesian Inference Systems (BISs) for inferring the probability of a burst/other event occurrence and raising the detection alarms, and (vi) geostatistical techniques for determining the approximate location of a detected burst/other event. The results of applying the new methodology to the pressure/flow data from several District Metered Areas (DMAs) in the United Kingdom (UK) with real-life bursts/other events and simulated (i.e., engineered) burst events are also reported in this thesis. The results obtained illustrate that the developed methodology allowed detecting the aforementioned events in a fast and reliable manner and also successfully determining their approximate location within a DMA. The results obtained additionally show the potential of the methodology presented here to yield substantial improvements to the state-of-the-art in near real-time WDS incident management by enabling the water companies to save water, energy, money, achieve higher levels of operational efficiency and improve their customer service. The new data analysis methodology developed and tested as part of the research work presented in this thesis has been patented (International Application Number: PCT/GB2010/000961).
696

Funnel Vision

Grainger, David 01 January 2008 (has links)
This paper will talk about the videos and sculptural installation in my thesis exhibition. Shooting videos outside of the studio developed into a project overarching any individual video or its particular signs. Thus, this paper will focus on the video project with examples that follow a timeline of development, rather than the actual 6 videos on display in the exhibit. The two-part sculpture "Deer in the Headlights" is created in the context of these videos, and coexists with them in a specific architectural space. This space, as well as the clichéd meaning of the deer's gaze, have a relation to the title of the show.
697

Transition laminaire-turbulent en conduite cylindrique pour un fluide non Newtonien

López Carranza, Santiago Nicolás 19 October 2012 (has links)
L'objectif de cette thèse est de fournir une analyse de la transition vers la turbulence d'un fluide rhéofluidifiant (fluide de Carreau) dans une conduite cylindrique. Pour cela, un code pseudo-spectral de type Petrov-Galerkin a été développé. Une analyse linéaire de stabilité de l'écoulement laminaire est effectuée, montrant que cet écoulement est linéairement stable. Ensuite, des perturbations sous la forme des rouleaux longitudinaux contra-rotatifs sont utilisées comme condition initiale. Les termes non linéaires d'inertie et visqueux créent un écoulement secondaire avec des points d'inflexion, linéairement instable vis-à-vis de perturbations 3D. Une analyse linéaire de stabilité de ce nouvel écoulement de base bidimensionnelle est réalisée. La forme des vecteurs propres critiques est analysé. Enfin, une analyse non linéaire de stabilité de rouleaux vis-à-vis des perturbations tridimensionnelles de faible amplitude est effectuée, obtenant un retard pour la transition vers la turbulence des fluides rhéofluidifiants par rapport au cas Newtonien et une tendance à l'asymétrie du profil de vitesse axiale / The main objective of this thesis is to provide a description of the transition to turbulence of a shear thinning fluid in pipe flow. A linear stability analysis of the base flow is done. Results show that the flow is linearly stable and the optimal perturbation is given by a pair of counter rotating vortex. This kind of perturbation is used as an initial condition of a computational code which integrates the governing equations. Inertial and viscous non linear terms generate a secondary base flow with inflection points, which is linearly unstable to 3D perturbations. A secondary instability analysis is done, regarding the shape of unstable eigenvectors. Depending the rheological parameters and the size of the primary perturbation, the unstable mode might be near the wall or the center of the pipe. Finally, a non linear stability analysis of the streaks to 3D perturbations of weak amplitude, obtaining a delay in the transition to turbulence due to shear thinning
698

Spiral Welded Pipe Piles For Structures In Southeastern Louisiana

Richard, Leeland 17 December 2010 (has links)
In an effort to obtain 100-year level hurricane protection for southeastern Louisiana, the U.S. Army Corps of Engineers (USACE) has implemented design guidelines that both levees and structures shall be designed to. Historically, USACE has used concrete piles or steel H-piles as the foundations for these structures. Because of the magnitude of obtaining 100-year level hurricane protection, limited resources, and a condensed timeline, spiral welded pipe piles can be manufactured as an alternative to either the concrete piles or steel H-piles. This research will provide the necessary background for understanding pile foundations, will compare the behaviors of spiral welded pipe piles to that of other piles with respect to geotechnical concerns through a series of pile load tests, and will offer a current cost analysis. This background, testing, and cost analysis will show that spiral welded pipe piles are a viable alternative for USACE structures from a geotechnical and economic perspective.
699

Études thermiques du stockeur d'énergie électrique automobile

Tran, Thanh-Ha 13 March 2014 (has links)
Le but de la thèse est de développer d’une part, une méthode permettant de quantifier la chaleur générée par la cellule de manière précise. D’autre part, il s’agit d’évaluer la performance thermique d’un panel de solutions de refroidissement pour les batteries destinées à des applications HEV/PHEV/EV. La première partie de ce rapport présente une méthode d’estimation de la chaleur globale de la cellule, permettant de prendre en compte la chaleur ohmique et la chaleur entropique. Ce modèle d’estimation de perte est couplé à un modèle thermique 2D afin d’estimer la température de la cellule. La température obtenue par simulation pour une cellule LiNi0.8Co0.15Al0.05O2/graphite 22 Ah correspond très bien aux mesures expérimentales. Dans la deuxième partie du rapport, la performance thermique de plusieurs solutions de refroidissement (refroidissement à air, refroidissement par matériau à changement de phase (MCP) et refroidissement par caloduc) pour la batterie a été évaluée expérimentalement sous plusieurs puissances de perte et plusieurs conditions de ventilation. Le refroidissement par caloduc s’est révélé d’être une solution efficace, même sous des conditions de ventilation critiques. Quant à la solution de refroidissement par MCP, le prototype qui a été expérimenté a une faible performance thermique. Cela est principalement dû à la faible conductivité thermique de la formulation MCP utilisée. Toutefois, l’utilisation d’autres formulations alternatives de MCP est envisageable. Les résultats de simulation montrent que ces formulations permettraient une amélioration significative de la performance thermique du système de refroidissement par MCP. / Lithium-ion batteries, characterized by their high energy and power density, are highly recommended as power sources for electrified vehicles (HEV/PHEV/EV). However, lithium-ion batteries are very sensitive to their environment and are prone to thermal runaway at high temperature. The goals of this thesis are to develop an accurate lithium-ion cell heat loss calculation method and to investigate the thermal performance of several cooling solutions for HEV/PHEV/EV batteries. The first part presents a global heat calculation procedure for lithium-ion cell which takes into account both the polarization heat and the entropic heat. This heat generation model was coupled with a cell two-dimensional thermal model in order to predict the cell’s temperature. Temperature estimations obtained by simulation for a 22 Ah LiNi0.8Co0.15Al0.05O2/graphite cell showed a very good agreement with experimental results. In the second part, thermal performances of several cooling solutions for HEV/PHEV/EV batteries (air, phase change material (PCM) and heat pipe) were evaluated experimentally under several heat rates and cooling conditions. Heat pipe cooling was found to be a promising cooling solution which works efficiently even under low rate ventilation cooling condition. The experimented PCM cooling system had very poor thermal performance, mainly due to the low thermal conductivity of the used PCM formulation. However, simulations showed that significant improvement could be achieved by using another alternative PCM formulation.
700

Étude numérique et expérimentale du refroidissement des convertisseurs auxiliaires de puissance dans les trains par convection naturelle, film liquide et caloduc / Numerical and experimental study of cooling of the auxiliary converters in trains by natural convection, liquid film and heat pipe

Zouitene, Saâd 06 June 2014 (has links)
Cette thèse porte sur l’étude et l’optimisation du refroidissement des convertisseurs électriques de puissance (CVS) utilisés dans les trains. Ces composants de grandes dimensions sont lourds, bruyants, et représentent un gouffre énergétique à cause de leur système de refroidissement composé de ventilateur. Nous analysons d’autres types de refroidissements économiques et efficaces. Nous étudions numériquement sous Comsol Multiphysics le refroidissement des CVS par convection naturelle en utilisant l’effet cheminée et par film liquide en exploitant le changement de phase pour évacuer le maximum de chaleur. Les résultats numériques sont validés avec les résultats issus de la littérature et ceux obtenus expérimentalement grâce à un dispositif réalisé pour cette étude. Les résultats obtenus ont permis de constater que la convection naturelle n’est pas suffisante pour évacuer la chaleur et que le refroidissement par film liquide représente une solution très efficace. Nous avons aussi étudié expérimentalement l’efficacité du refroidissement par caloducs. L’influence de la répartition de la chaleur a aussi été analysée pour optimiser l’emplacement des composants électroniques dans le CVS. Une comparaison générale de tous les résultats a permis de proposer le système le plus optimiser en fonction des paramètres choisis. / This thesis is about a study and optimization of the cooling electric power converters (CVS) used in trains. These components are heavy, noisy, and are not energetically efficient. We analyze other types of economic and efficient cooling. We used Comsol Multiphysics to study numerically CVS cooling by natural convection using the chimney effect and liquid film by exploiting the phase change to evacuate heat. The numerical results are validated with the results from literature and those obtained experimentally. The results have shown that natural convection is not sufficient to evacuate the heat and the cooling by liquid film represents an interesting solution. We also studied experimentally the effect of the heat pipe cooling. The influence of the heat distribution was also analyzed to optimize the location of the electronic components in the CVS. A general comparison of all results was proposed to optimize the cooling system.

Page generated in 0.0478 seconds