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Caractérisation des paramètres de l'habitat du castor qui favorisent l'utilisation des ponceaux comme site de construction du barrageTremblay, Geneviève 04 1900 (has links) (PDF)
L'utilisation des routes comme assise pour la construction de barrages par le castor est fréquente dans l'ensemble de son aire de répartition et s'avère être un problème récurrent dans la gestion des réseaux routiers en milieux forestiers. Au Québec, c'est en Abitibi qu'on trouve la plus grande densité de castors, ce qui engendre un nombre élevé de conflits. L'objectif principal de ce projet vise à déterminer les variables associées à l'habitat du castor permettant de prédire le risque d'utilisation des ponceaux comme sites de construction de barrages, ce qui permettrait d'améliorer le tracé des nouvelles routes forestières ou de mieux cibler les sites nécessitant des mesures préventives d'atténuation. Les hypothèses de travail réfèrent à la géomorphologie et à l'hydrologie des sites, à l'abondance de ressources alimentaires, à la hauteur du remblai et à la présence d'autres barrages de castors à proximité d'un échantillon de 128 ponceaux localisés au sein de la ceinture d'argile, en Abitibi. Les données associées à chaque hypothèse ont été mesurées directement ou extraites à partir d'un modèle d'élévation, de cartes écoforestières et d'images LANDSAT. La présence ou l'absence d'un barrage a également été validée sur le terrain. Parmi les 12 variables caractérisées, la comparaison des hypothèses par sélection de modèles (critère d'information d'Akaike) et l'inférence multi-modèles a permis de dégager que la surface du bassin de drainage, le nombre de kilomètres de ruisseaux environnants et la hauteur du remblai avaient un effet négatif sur la probabilité d'utilisation des ponceaux par le castor, alors que le rapport entre le débit et le diamètre du ponceau avait un effet positif. Les prédictions réalisées à partir de nos modèles indiquent que presque tous les ponceaux ont une probabilité de plus de 50% d'être utilisés par le castor dans notre aire d'étude, ce qui permet de croire que vraisemblablement tous les tracés de routes présenteront des problèmes avec les barrages créés par ce rongeur. Nous concluons donc qu'au sein de la ceinture d'argile, il serait plus adéquat de tenir compte de la présence probable de barrages au moment même de la construction des routes en prévoyant l'installation de mesures d'atténuation appropriées telles que des pré-barrages, plutôt que de lutter contre la présence de cette espèce suite à la construction des ponceaux.
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A Modified AODV with Ack-Path Traffic Rerouting for TCP Performance Improvement in Ad Hoc Wireless NetworksLin, Chun-Hsien 27 August 2004 (has links)
In this thesis, a modified routing protocol, MAODV (Modified Ad Hoc On-Demand Distance Vector), is proposed for wireless Ad Hoc networks. MAODV uses ACK paths for rerouting data traffic whenever there is a route failure. We create new flags in the routing information of AODV to timely notify TCP layer the network status. After a route failure, the source node monitors ACK packets from the destination node. Every ACK packet when it is received from the destination node, its carried information is used to update the routing tables. Thus, without any interruption, TCP can take the reverse route of the ACK forwarding paths to continue to transmit the rest of data packets. In our proposed scheme, without decreasing the size of TCP congestion window (CWND), a lost packet can be immediately retransmitted as soon as the first duplicate ACK is received. We use NS-2 to simulate the proposed MAODV. From our simulation results, we have shown that when the position of route failures is near the source node, it may take more time to find new data paths. Hence, MAODV has the advantages by taking the reverse ACK paths to transmit data packets before new routing paths are found. Finally, we have demonstrated that MAODV performs better than TCP-BuS (BUffering capability and Sequence information) and the original TCP, when there are many hops between the source node and the destination node. On the other hand, when the position of route failures is near the destination node, the advantages of MAODV become not so significant because there exists some local repair mechanisms to be applied.
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AODV-ABR:Adaptive Backup Route in Ad-hoc NetworksHsiao, Sheng-Yu 06 September 2004 (has links)
An ad-hoc network operates without a central entity or infrastructure, and is composed of highly mobile hosts. In ad-hoc network, routing protocols are with host mobility and bandwidth constraints. There have been many recent proposals of routing protocols for ad-hoc networks. A recent trend in ad hoc network routing is the reactive on-demand philosophy where routes are established only when required. AODV(Ad-hoc On-demand Distance Vector routing) evaluates routes only on an as-needed basis and routes are maintained only as long as they are necessary. Because the network topology changes frequently in ad-hoc networks, some on-demand protocols with multi-paths or backup routes have been proposed. Sung-Ju Lee and Mario Gerla proposed an AODV-BR scheme to improve existing on-demand routing protocols by creating a mesh and providing multiple alternate routes . The algorithm establishes the mesh and multi-path using the RREP (Route Reply) of AODV, which does not transmit any extra control message. In this paper, we propose two schemes : AODV-ABR(Adaptive Backup Route) and AODV-ABL (Adaptive Backup Route and Local repair) to increase the adaptation of routing protocol to topology changes by modifying AODV-BR. In AODV-ABR, the alternative route can be creating by overhearing not only RREP packets but also data packets. AODV-ABL combines the benefits of AODV-ABR and Local Repair. Finally, we evaluate the performance improvement by simulation.
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A Pre-Setup-Path for Fast Handoff in Mobile IPLin, Bo-hao 07 September 2004 (has links)
With recent growth in mobile components and advances in wireless communication technology, mobile computing is an increasingly important area of research. Enabling mobility in IP networks becomes more and more significant. Mobile IP is the only current means for offering seamless roaming to mobile computers in the Internet. It has recently progressed along the ladder to standardization within the Internet Engineering Task Force (IETF). However, Mobile IP suffers from so-called triangular-routing problem and packet loss due to handoff. In this paper, we propose a new architecture to solve these two problems noted above. We assume that network routers such as Home Agent¡BForeign Agent¡BGeneral Router can equip our Pre-Accessing Engine (Mobile IP Engine) to access IP packets before IP routing Engine. With our Mobile IP table established in Mobile IP Engine, we can set up a transmission path for each correspondent node (CN) to transmit data to mobile node (MN). Therefore, we not only solve triangular-routing problem by direct transmission path, but also decrease handoff latency from path updating function. Furthermore, we use retransmission and flush schemes to avoid packet loss and out-of-order problems. Finally, we use simulation to prove our architecture is useful.
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Adaptive Route Selection Scheme of Multiple Paths for Mobile Ad Hoc NetworkKe, Chu-wei 29 July 2008 (has links)
Mobile ad hoc network is an architecture which do not exist any infrastructure or centralized administration. There are many routing protocols have been proposed so far, such as AODV, DSR and CGSR. These protocols were classified as reactive in which routes are established only when required. Due to the movement of mobile nodes, network topology changes frequently, and the routing path could be broken easily. This phenomenon will cause higher routing overhead and delivery latency.
In conventional routing protocols, the source-destination pair only establishes a single path for data transmission. These routing scheme, however, suffer from the drawback of node movement. When route broken, the source node must reconstruct another new path.
This paper presents an adaptive routing protocol named Adaptive Route Selection Scheme of Multiple Paths for Mobile Ad Hoc Network (ARSMA). The aim of the work is to improve the delivery ratio. In the route request phase, source nodes will discovery two routes to the destination node, one for primary path, and the other for the backup path. During the discovery procedure, each node will estimate the link expire time through the movement speed and direction of the precursor node. When a link breakage is about to occur, source node will try to switch the transmission to the backup route.The simulation result shows that ARSMA is able to achieve a remarkable improvement in delivery ratio and end-to-end dealy.
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Optimal Route Selection Schemes for QoS-constraint Traffic in WiMAX Mesh NetworksLee, Yi-Chin 04 September 2008 (has links)
WiMAX (Worldwide Interoperability for Microwave Access) provides wide
transmission range and broadband network services. However, in IEEE 802.16
standard, there is no specific definition for SS (Subscriber Station) to select an
optimal route in a mesh-based WiMAX network. In this thesis, we propose an
Optimal Route Selection Scheme (ORSS) for SS to select a route to its BS (Base
Station). ORSS basically considers three influential factors, the bandwidth SS to be
assigned, the number of interference nodes around SS, and the hop counts to BS. We
also investigate QoS (Quality of Service) issue in a mesh-based WiMAX network; an
SS transferring the rtPS traffic type will share bandwidth with the neighboring SS of
the same level that transmit the same traffic type. To ensure the selected route that can
meet the bandwidth requirements of rtPS and the delay constraints, we estimate the
average transmission delay from SS to BS. For the purpose of evaluation, we establish
a mathematical model to analyze the proposed ORSS and discuss the impact of
varying network parameters on the successful rate of route selection. Through the
Matlab simulation, we validate our mathematical model. The simulation results
demonstrate that our ORSS, in comparison to a previous work, is more effective in
ensuring the delay constraints when selecting a route to transfer rtPS traffic.
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DAISY-formatets påverkan på läsning : En studie på barn i och utanför läs- och skrivsvårigheterAndersson, Niklas January 2007 (has links)
<p>I grundskolan skiljer det sig mycket från elev till elev när det gäller konsten att behärska läsning. Då läsning är något som tränas genom övning är det oftast de som tycker det är svårt som håller sig borta från läsandet. DAISY är ett format som erbjuder läsare att, samtidigt som de läser en text, få den uppläst. Genom att presentera text både visuellt och auditivt kan fokus tas bort från själva ordavkodningen, vilket är det som de flesta i läs- och skrivsvårigheter har problem med. I detta arbete undersöktes läshastighet, läsförståelse och läseffektivitet på 18 åttondeklassare, varav sju uppvisade olika grader av läs- och skrivsvårigheter. Resultaten mellan när de läste en text med DAISY och när de läste en text utan DAISY jämfördes. Resultatet visade att deltagarna läste långsammare med DAISY än utan. De i läs- och skrivsvårigheter hade dock både en större läsförståelse och läseffektivitet när de använde DAISY.</p>
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Histoire des marchands sogdiens /La Vaissière, Étienne de. January 2002 (has links)
Texte remanié de: Th. doct.--Hist.--Paris--EPHE, 1999. / Bibliogr. p. 337-379. Index.
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Le journal régional et l'"holocauste routier" l'exemple du Libre Poitou et Centre Presse (1955-2004) /Etsila, Judicaël Chauvaud, Frédéric January 2009 (has links) (PDF)
Reproduction de : Thèse doctorat : Histoire contemporaine : Poitiers : 2009. / Titre provenant de l'écran titre. Bibliogr. Réf. bibliogr.
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Constrained traffic equilibrium : impact of electric vehiclesJiang, Nan, Ph. D. 03 October 2012 (has links)
In many countries across the world, fossil fuels, especially petroleum, are the largest energy source for powering the socio-economic system and the transportation sector dominates the consumption of petroleum in these societies. As the petroleum price continuously climbs and the threat of global climate changes becomes more evident, the world is now facing critical challenges in reducing petroleum consumption and exploiting alternative energy sources. A massive adoption of plug-in electric vehicles (PEVs), especially battery electric vehicles (BEVs), offers a very promising approach to change the current energy consumption structure and diminish greenhouse gas emissions and other pollutants. Understanding how individual electric vehicle drivers behave subject to the technological restrictions and infrastructure availability and estimating the resulting aggregate supply-demand effects on urban transportation systems is not only critical to transportation infrastructure development, but also has determinant implications in environment and energy policy enactment.
Driving PEVs inevitably changes individual’s travel and activity behaviors and calls for fundamental changes to the existing transportation network and travel demand modeling paradigms to accommodate changing cost structures, technological restrictions, and supply infrastructures. A prominent phenomenon is that all PEV drivers face a distance constraint on their driving range, given the unsatisfactory battery-charging efficiency and scarce battery-charging infrastructures in a long period of the foreseeable future. Incorporating this distance constraint and the resulting behavioral changes into transportation network equilibrium and travel demand models (static and/or dynamic) raises a series of important research questions.
This dissertation focuses on analyzing the impact of a massive adoption of BEVs on urban transportation network flows. BEVs are entirely dependent on electricity and cannot go further once the battery is depleted. As a modeling requirement in its simplest form, a distance constraint should be imposed when analyzing and modeling individual behaviors and network congestions. With adding this simple constraint, this research work conceptualizes, formulates and solves mathematical programming models for a set of new BEV-based network routing and equilibrium problems. It is anticipated that the developed models and methods can be extensively used in a systematic way to analyze and evaluate a variety of system planning and policy scenarios in decision-making circumstances of BEV-related technology adoption and infrastructure development. / text
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