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  • 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.
51

HMX detektering i transparent plastslang

Niyongabo, Hervé January 2012 (has links)
Orica Miningsservices är ett företag som tillverkar sprängämnen till civil förbrukning. I deras produktutbud finns ett sätt att initiera en sprängning utan att använda elektriska sprängkapslar.  De använder en plastslang som är belagd med ett tunt sprängämnesskikt runt kanten på insidan, och sprängämnen kallas HMX. De finns idag ett analogt detekteringssystem som är baserat på optisk detektering. En lasergivare skickar ljuset igenom plastslangen och den detekteras med en fotocell. För ett säkert mätresultat används två lasergivare med respektive fotodetektorer, de mäter horisontellt respektive vertikalt. Deras resultatvärden summeras i en OP-förstärkare. Vid fel laddmängden ska en gränsvärdesvakt dra igång ett relä. Dessutom skickas utsignalen till en PLC för att visa värden på en operatörspanel. Projektet handlar om att förbättra detekteringssystemet med mikrokontroller. Den skulle A/D-omvandlas utsignalen från förstärkare och dra igång ett relä vid fel laddmängden. Dessutom ska mängdvärden visas hela tiden på en LCD-display. För att kommunicera med PLC, D/A-omvandlas den digitala utsignalen inne i mikrokontrollen och skickar in en analog signal. Som mikrokontroller används Xmega A1 Xplained. I projektet framställdes en prototyp som provkördes med tillfredställande resultat. Rapporten beskriver teori bakom detekteringsmaterial och detekteringssystem. Dessutom tar den upp projektarbetsgång, mätresultaten och de vidareförbättringar som kan göras.
52

Backbone Ad Hoc Networks using Two-Tier Routing

Liao, Chun-kai 11 January 2005 (has links)
In this paper, a mobile network is combined with backbone structure to form a hierarchical ad hoc network. Usually, a mobile ad hoc network is assumed to be homogeneous such that each mobile node uses the same radio capability. However, a homogenous ad hoc network suffers from poor scalability. In this thesis we establish a physical (not logical) hierarchical network to solve this problem in which backbone nodes are employed to transmit for long distance using larger radio power at high tier and cluster structure is used to efficiently utilize resources in a wide and dynamic network. We propose a cluster head determination scheme based on the degree variations of nodes. The nodes with minimum degree variation in the neighborhood are considered more stable and will be selected as the cluster heads. The cluster heads form the backbone nodes and other nodes are the cluster members. The information of cluster members and the nodes in neighboring clusters are recorded in a table of cluster head. According to the information, we have the knowledge of whether the destination node is close to the source node and can determine how to route the transmission. Routing is divided into low tier and high tier routing to relieve the workload of backbone network. The simulation results demonstrate that the proposed hierarchical routing in two tiers (HRTT) improves some problems occurred in the flat network.
53

A Modified EDCF to support QoS in IEEE 802.11 Wireless LANs

Chen, Ming-Yin 23 August 2005 (has links)
This paper describes an adaptive service differentiation scheme for QoS enhancement in IEEE 802.11 wireless ad-hoc networks. Our approach is called Dynamic Age-Dependent Backoff (DADB) which is derived from the ADB scheme and aims to improve the ADB scheme when the traffic load is high. Improvement of our scheme are provisioned by adjusting the size of the persistent factor of high traffic categories taking into account both age time of frame and network conditions. We evaluate the performance of DADB through simulations and compare it with the ADB scheme proposed in the 802.11e. Results show that our scheme DADB is similar to ADB scheme which can improve the delay and jitter in wireless network. Especially at high traffic load conditions, DADB outperforms the basic ADB: our scheme improve the throughput of high priority traffic category and decrease collision rate when traffic load is heavy.
54

Truthful resource management in wireless ad hoc networks

Cai, Jianfeng 01 November 2005 (has links)
In wireless mobile ad hoc networks (MANETs), cooperation cannot be an im- plicit assumption anymore. Each profit-oriented network node has the intention to be selfish due to limited resource possession. In this dissertation, we investigate the truthful resource management that induces network nodes to reveal true information and stimulate cooperation. We propose the Transmission Power Recursive Auction Mechanism routing pro- tocol (TEAM) and the Truthful Topology Control mechanism (TRUECON) to cope with the selfish intention and achieve resource effciency in a non-cooperative envi- ronment. We prove both are strategy-proof and have some theoretic bounds on the performance. Compared with the existing routing protocols and topology control al- gorithms, TEAM and TRUECON are more effcient when dealing with the selfishness in MANETs. We conduct a study on anonymity enhancement in MANETs by reducing trans- mission power of network nodes. A routing protocol - Whisper is presented. Simu- lation results show that it has desirable properties in terms of anonymity and power effciency.
55

Elever med diagnosen AD/HD i ämnet Idrott och hälsa : En kvalitativ studie av idrottslärares erfarenheter och strategier för elever med AD/HD / AD/HD-students in physical education : A qualitative study of PE teacher’s experiences and strategies with AD/HD

Öggesjö, Victor, Nilsson, Sandra January 2013 (has links)
Bakgrunden till arbetet bygger på våra tidigare erfarenheter från den verksamhetsförlagda utbildningen där vi upplever svårigheter med att undervisa elever utifrån deras behov och förutsättningar. Syftet med arbetet är att undersöka vilka erfarenheter lärare har av att undervisa elever med diagnosen AD/HD. Vi har även tagit del av idrottslärares strategier i förhållande till dessa elever. För att uppnå vårt syfte har vi valt att genomföra en kvalitativ undersökning som är baserad på semistrukturerade intervjuer av lärare i ämnet Idrott och hälsa. Resultatet visar att lärarna använder olika strategier för elever med AD/HD. Vidare upplever lärarna att det krävs mer utbildning om diagnosen på universiteten.
56

"I can actually do stuff" : Ein kvalitativ studie om opplevinga av å vere i ei ressursgruppe og deltakarane sitt syn på seg sjølv og forventningar til meistring.

Knutsen, Lone Ellingvåg January 2011 (has links)
Fokuset for denne masteroppgåva har vore å undersøke kva opplevingar deltakarane i ei ressursgruppe for studentar med AD/HD og liknande utfordringar har. Studien vil spesielt belyse korleis tre informantar frå denne gruppa opplever det å vere studentar og deltakarar i gruppa, og kva opplevingar dei har i forhold til meistring av studiane og synet på seg sjølv. Teoretisk utgangspunkt har vore kva ressursgruppa er, og korleis dette tilbodet står i forhold til definisjonar av mellom anna rådgjevingsgrupper, støttegrupper og sjølvhjelpsgrupper, og forsking gjort på slike grupper. Vidare vart det nytta ulike teoriar og tradisjonar som forklarar omgrepet sjølvoppfatning. For å gjere greie for prosessen deltakarane har vore igjennom kom ein slik innom teoriar om myndiggjering, bevisstgjering og det å vere agent i eige liv. For å svare på problemstillinga vart kvalitativ metode med inspirasjon frå fenomenologisk tilnærming nytta. Analysen vart gjennomført ved å kategorisere dei tema som kom fram i intervjua. Ved å bruke setningar, ord og uttrykk frå det informantane fortalde forma det seg tre hovudkategoriar; meistring, solidaritet og synet på seg sjølv. Desse gav også ramma for ei forståing og ein kunnskap om dei erfaringane og opplevingane informantane har gjort seg. Hovudfunna til studien ligg i forhold til opplevinga av å vere i ressursgruppa og det meir positive synet informantane no har på seg sjølv og si forventning til meistring av studiekvardagen.
57

Secure and efficient wireless ad hoc networking

Khabbazian, Majid 11 1900 (has links)
Wireless ad hoc networks have been emerged to support applications, in which it is required/desired to have wireless ommunications among a variety of devices without relying on any infrastructure or central managements. In ad hoc networks, wireless devices, simply called nodes, have limited transmission range. Therefore, each node can directly communicate with only those within its transmission range and requires other nodes to act as routers in order to communicate with out-of-range estinations. One of the fundamental operations in ad hoc networks is broadcasting, where a node sends a message to all other nodes in the network. This can be achieved through flooding, in which every node transmits the first copy of the received message. However, flooding can impose a large number of redundant transmissions, which can result in significant waste of constrained resources such as bandwidth and battery power. One of the contributions of this work is to propose efficient broadcast algorithms which can significantly reduce the number of redundant transmissions. We also consider some of the security issues of ad hoc networks. In particular, we carefully analyze the effect of the wormhole attack, which is one of the most severe threats against ad hoc networks. We also propose a countermeasure, which is an improvement over the existing timing-based solutions against the wormhole attack. Finally, in the last chapter, we propose novel point compression techniques which can be used in Elliptic Curve Cryptography (ECC). ECC can provide the same level of security as other public key cryptosystems (such as RSA) with substantially smaller key sizes. Smaller keys can result in smaller system parameters, bandwidth savings, faster implementations and lower power consumption. These advantages make ECC interesting for ad hoc networks with restricted devices.
58

A MAC Protocol for Multihop RP-CDMA Ad Hoc Wireless Networks

Mortimer, Richard T Unknown Date
No description available.
59

Stabile Kommunikation in dynamischen Ad-hoc-Netzen

Gerharz, Michael January 2006 (has links)
Zugl.: Bonn, Univ., Diss., 2006
60

Evaluierung von partitionierungsbewußten MANET Protokollen mit ns-2

Dietrich, Rüdiger Oliver. January 2005 (has links)
Stuttgart, Univ., Studienarbeit, 2005.

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