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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.
1

Modely diskrétní binární volby / Discrete binary choice models

Lejnarová, Šárka January 2007 (has links)
Ve své diplomové práci se zabývám modely diskrétní binární volby. Zkoumám je nejprve z teoretického hlediska, jaká je jejich podstata, jaká jsou jejich specifika a problémy. Postupně rozebírám jednotlivé modely diskrétní binární volby a to lineární pravděpodobnostní model, logitový model a probitový model. Zabývám se jejich odhadem, testováním významnosti jednotlivých koeficientů a shodou modelů s daty. V praktické části se zaměřuji na problematiku životního prostředí a třídění odpadu. Aplikuji jednotlivé modely na získaná data a snažím se vysvětlit, na čem závisí volba jedince mezi ?třídím odpad? a nebo ?netřídím odpad?. Na základě analýzy poté doporučuji, na koho a jakým způsobem zacílit osvětu.
2

MicroCuckoo Hash Engine for High-Speed IP Lookup

Tata, Nikhitha 23 June 2017 (has links)
The internet data traffic is tripling every two years due to the exponential growth in the number of routers. Routers implement the packet classification methodology by determining the flow of the packet, based on various rule checking mechanisms that are performed on the packet headers. However, the memory components like TCAMs used by these various rules are very expensive and power hungry. Henceforth, the current IP Lookup algorithms implemented in hardware are even though able to achieve multi-gigabit speeds, yet suffer with great memory overhead. To overcome this limitation, we propose a packet classification methodology that comprises of MicroCuckoo-hash technique, to route packets. This approach alleviates the memory requirements significantly, by completely eliminating the need for TCAM cells. Cuckoo hash is used to achieve very high speed, hardware accelerated table lookups and also are economical compared to TCAMs. The proposed IP Lookup algorithm is implemented as a simulation-based hardware/software model. This model is developed, tested and synthesized using Vivado HLS tool. / Master of Science
3

Social klass och förtroende för public service : En kvantitativ studie om lågt förtroende för nyhetsrapporteringen i Sveriges Radio och Sveriges Television.

Rosenberg, Edith January 2024 (has links)
Tillgången till opartisk information är av stor vikt för demokratiska samhällen. Där fyller public service-kanalernas nyhetsrapportering en viktig roll. Grupper med lågt förtroende för public service nyhetsrapportering riskerar att missgynnas genom högre utsatthet för desinformation, vilket har negativa effekter på samhälleligt engagemang och demokratiskt deltagande. Denna studie syftar till att utreda effekten av klass på sannolikheten att ha lågt förtroende för public service nyhetsrapportering. Social klass definieras utifrån Bourdieus teori om kulturellt och ekonomiskt kapital vilka mäts i form av utbildningsnivå och hushållsinkomst. Förtroende knyts an till Bourdieus begrepp habitus och till Putnams teori om socialt kapital. Studien använder sig av surveydata från 1 154 personer bosatta i Sverige och den primära analysmetoden är linjär sannolikhetmodell (LPM). I analysen kontrolleras effekten av kön, ålder, mellanmänsklig tillit och partisympati på sambandet. H1 var att sannolikheten att ha ett lågt förtroende för public service nyhetsrapportering minskar med stigande utbildningsnivå. Denna hypotes bekräftas. H2 var att sannolikheten att ha ett lågt förtroende för public service nyhetsrapportering minskar med stigande hushållsinkomst. Resultaten indikerar att hypotesen kan bekräftas men uppvisar ingen signifikans. H3 var att kontrollvariablerna har en förklarande effekt på sambandet mellan social klass och lågt förtroende för public service nyhetsrapportering. Denna hypotes bekräftas när social klass mäts genom kulturellt kapital, men inte ekonomiskt kapital. Över lag har den svenska befolkningen högt förtroende för nyhetsrapporteringen i public service. Social klass har mycket liten förklaringsförmåga på sannolikheten att ha lågt förtroende. I stället tycks egenskaper som manlig könsidentitet, sympati med Sverigedemokraterna samt låg mellanmänsklig tillit vara riskfaktorer för lågt förtroende. Studien belyser ett nödvändigt område för vidare forskning för att på sikt säkerställa lika tillgång till opartisk information bland hela Sveriges befolkning.
4

Sensitivity of the IceCube detector for ultra-high energy electron-neutrino events

Voigt, Bernhard 21 November 2008 (has links)
Zur Zeit wird das IceCube Neutrino-Teleskop am Südpol im Eis der Antarktis installiert, die Hälfte des Detektors ist bereits im Betrieb. Bei Fertigstellung im Jahr 2011 wird mehr als 1 km^3 Eis mit Photovervielfachern instrumentiert sein. IceCube bietet damit eine einzigartige Möglichkeit, die Quellen der kosmischen Strahlung mit Hilfe hochenergetischer Neutrinos zu finden. Im Rahmen dieser Arbeit wurde die Sensitivität des kompletten Icecube Detektors für den Nachweis eines diffusen Flusses von Elektronneutrinos bestimmt. Ziel war es, die Eigenschaften des Detektors für Energien oberhalb von einem PeV zu bestimmen. Besonderes Augenmerk wurde dabei auf die Simulation von elektromagnetischen Kaskaden gelegt, die in Neutrino-Nukleon-Wechselwirkungen auftreten. Da existierende Parametrisierungen die Unterdrückung der Wechselwirkungsquerschnitte durch den LPM-Effekt nicht beinhalten, wurde eine Simulation des Energieverlustes von elektromagnetischen Kaskaden für Energien oberhalb von 1 PeV entwickelt, die entsprechend modifizierte Wirkungsquerschnitte verwendet. Die Analyse, die in dieser Arbeit vorgestellt wird, nutzt die komplette Information des durch einen Photovervielfacher aufgezeichneten Ladungsverlaufes aus, die mit der Datennahme des IceCube Detektors zur Verfügung steht. Es werden neue Methoden entwickelt, um zwischen atmosphärischen Myonen-Hintergrund- und Signalereignissen von Kaskaden aus Neutrino-Nukleon-Wechselwirkungen zu unterscheiden. Die erreichbare Sensitivität innerhalb einer Laufzeit von einem Jahr ist 1.5*10^-8 E^-2 GeV/(cm^2 sr s) in einem Energiebereich von 16 TeV bis 13 PeV für den Nachweis von Elektronneutrinos eines diffusen Flusses. Eine Verbesserung von mindestens einer Größenordnung wird erwartet, wenn alle Neutrinofamilien in die Analyse einbezogen werden. Damit sollte eine Sensitivität erreicht werden, die auf dem gleichen Niveau einer diffusen Myonenanalyse liegt. / IceCube is a neutrino telescope currently under construction in the glacial ice at South Pole. At the moment half of the detector is installed, when completed it will instrument 1 km^3 of ice providing a unique experimental setup to detect high energy neutrinos from astrophysical sources. In this work the sensitivity of the complete IceCube detector for a diffuse electron-neutrino flux is analyzed, with a focus on energies above 1 PeV. Emphasis is put on the correct simulation of the energy deposit of electromagnetic cascades from charged-current electron-neutrino interactions. Since existing parameterizations lack the description of suppression effects at high energies, a simulation of the energy deposit of electromagnetic cascades with energies above 1 PeV is developed, including cross sections which account for the LPM suppression of bremsstrahlung and pair creation. An attempt is made to reconstruct the direction of these elongated showers. The analysis presented here makes use of the full charge waveform recorded with the data acquisition system of the IceCube detector. It introduces new methods to discriminate efficiently between the background of atmospheric muons, including muon bundles, and cascade signal events from electron-neutrino interactions. Within one year of operation of the complete detector a sensitivity of 1.5*10^-8 E^-2 GeV/(cm^2 sr s) is reached, which is valid for a diffuse electron-neutrino flux in the energy range from 16 TeV to 13 PeV. Including all neutrino flavors in this analysis, an improvement of at least one order of magnitude is expected, reaching the anticipated performance of a diffuse muon analysis.
5

Robust Generator System Using PM Assisted Synchronous Reluctance Generator with Current-fed Drive

Baek, Jeihoon 2009 December 1900 (has links)
The growth of embedded generation and portable electrical installations has led to an increased demand for low cost, flexible and reliable generator systems for military and commercial applications. An interior permanent magnet (IPM) machine has high power density due to its reluctance torque and magnetic torque components so it can produce a large constant power-speed range. However, an IPM machine needs demagnetizing current at high-speed during the flux-weakening region and thus develops an inverter shutdown problem in an uncontrolled generator mode operation. In order to overcome the disadvantages of the IPM machine, the permanent magnet assisted synchronous reluctance generator (PMa-SynRG) can be a good solution for low cost, high efficiency reliable generator systems. A PMa-SynRG can produce a high efficiency drive by utilizing the proper amount of magnet and reluctance torque. This work proposes a PMa-SynRG with two flux barriers and permanent magnets embedded in the second layer of the rotor. A neodymium magnet (NdFeB) was used as permanent magnets in the rotor to prevent demagnetization. Finding the minimum amount of magnet is one of the goals of the optimization process. The objectives of this work are to build an optimal design for the 3kW generator and an advanced power electronics converter for the PMa-SynRG drive system. In order to find the optimized 3kW machine, a Lumped Parameter Model (LPM) was used to achieve fast computation, and Differential Evolution Strategy (DES) was used to embed the LPM in an efficient numerical optimization routine to identify optimum designs. Finite Element Analysis (FEA) was used for test performance of optimum designs. On the basis of differences between LPM and FEA, model predictions were used to fine tune the LPM model. For new optimum design converges, numerical optimizations and iterations were performed to produce LPM and FEA predictions. For the drive system, the thyristor based, current-fed drive is much simpler and has lower power losses compared to the pulse width modulation (PWM) drive. Eliminating the requirement for self-controlled switches is a distinct advantage for lower cost. Another feature of the developed current-fed drive is its inherent capability to provide generating action by making the PMa-SynRG operates as a generator, rectifying the phase voltages by means of the three-phase rectifier and feeding the power into the load. These features make the current-fed drive a good candidate for driving any type of synchronous generators including the proposed PMa-SynRG.
6

Screening procedure to identify power system events of the Texas Synchrophasor Network

Sant, Aprajita 09 July 2012 (has links)
This work presents a method for screening synchrophasor data to search for power system events of interest. The method employs prony algorithm to perform modal analysis and estimate mode amplitude, frequency, and damping ratio on the data obtained from the Texas Synchrophasor Network. The procedure uses seven different Linear Prediction Model (LPM) orders, plus a 10 second window width that slides in steps of 1 second, to minimize the possibility of overlooking events of interest. Further, the algorithm is extended to include user defined modal characteristics thresholds, window length and step size to capture specific power system events. / text
7

Algoritmy pro vyhledání nejdelšího shodného prefixu / Longest Prefix Match Algorithms

Kováčik, Michal January 2012 (has links)
This thesis focuses on algorithms for longest prefix match (LPM), which is the key operation in packet classification and routing in TCP/IP networks. A space for analysis of commonly used algorithms with emphasis on their speed and memory efficiency is dedicated along with necessary theory. Focus is then oriented on IPv6 networks, their typical prefix sets and comparison of suitable algorithms. Afterwards, the optimization for selected algorithm is suggested and implemented in programming language Python.
8

Vyhledání nejdelšího shodného prefixu / Longest Prefix Match Algorithms

Weigner, Martin January 2011 (has links)
The speed of computer network is increasing. One of the basic tasks which has to be solved by the network devices is longest prefix match. Many algorithms are able to solve this task but it's necessary to solve it very fast because of increasing transfer speed and the routing standard IPv6. This standard has longer addresses and it's necessary to search prefixes in much bigger sets. The thesis describes present algorithms that solve the problem. These are confronted with new algorithm HashTreeBitmap which is also described in the work. On the tests is documented that this algorithm is able to cope with high demands which are placed on it.
9

Electrohydraulic Power Steering Simulation : Dynamic, thermal and hydraulic modelling

Svensson, Oskar January 2019 (has links)
There are several benets of electrohydraulic power steering systems, as compared to hydraulicpower steering systems where the pump is driven directly by the engine of the vehicle. Someof these benets are increased eciency and improved steering performance. The purpose ofthis project is to create a simulation model of the electrohydraulic power steering system inSimulink, excluding the hydraulic circuit. The model should thus consist of the electric motor,the drive electronics, the control system, the hydraulic pump as well as the communication andinterface to the master simulation system in which the model will be used.As a start a mathematical model of the motor is derived. Then the motor controller includingtwo current controllers and a speed controller is developed. The switching signals for the threephase bridge that drives the motor are calculated using space vector modulation. The motordrives a hydraulic pump, which is modeled using data sheet eciency curves. Finally a thermalmodel of the drive is developed. To fulll real time requirements, a lumped parameter approachis chosen. The nal model is exported as a Functional Mock-up Unit, which is a black-boxencapsulation of the complete simulation model.The simulation model is compared to measurement data to conrm its validity. Thesecomparisons shows that the dynamic response of the motor and its controller are close to themeasured values and that the thermal model adequately corresponds to the thermal tests. Thehydraulic pump model varied from measurements more than the other sub-modules. It was,however, seen as acceptable. Overall the system response was satisfactory, but naturally a lotof future improvements and new features could be made to improve the model. / Det finns flera fördelar med elektrohydraulisk servostyrning, där hydraulpumpen drivs av en el-motor, jämfört med hydraulisk servostyrning, där pumpen drivs direkt av fordonets förbränningsmotor. Några av dessa fördelar är ökad effektivitet och förbättrad styrprestanda. Syftet med detta projekt är att skapa en Simulink-modell av ett elektrohydraulisk system för servostyrning, exklusive hydraulkretsen. Modellen ska alltså bestå av delmodeller för elmotorn, drivelektroniken, styrsystemet, hydraulpumpen samt kommunikation med den övergripande simuleringsplattformen.Inledningsvis beskrivs en matematisk modell av elmotorn och efter det utvecklas motorstyrningen, bestående av två strömregulatorer samt en hastighetsregulator. Spänningen från strömregulatorerna uppnås genom space vector-modulation, som beräknar de pulskvoter som krävs för att uppnå denna spänning. Elmotorn driver en pump. Denna pump modelleras med hjälp av data från pumpens datablad. Slutligen modelleras drivelektronikens termiska egenskaper med ett termiskt nätverk. Den slutliga modellen omsluts av en Functional Mock-up Unit somintegreras i den övergripande simuleringsplattformen.
10

CFD-informed Lumped Parameter Models Result In High-Fidelity Maneuvering Predictions of AUVs

Miller, Lakshmi Madhavan 11 July 2023 (has links)
Recent developments in autonomous underwater vehicles (AUV) have created the need for a low cost AUV that is comparable in class and payload capabilities to existing, commercially available, expensive and sub-optimal crafts. The Navy is active in research of autonomous, unmanned, highly efficient, high speed underwater craft. Small, low cost AUVs capable of swarm control are of special interest for military mine applications. No matter the nature of the application or class of craft, a common challenge is the accuracy of maneuvering predic- tions. Maneuvering predictions not only affect design, but also the real time understanding of mission capabilities and endurance. Thus the proliferation of AUVs in recent times for commercial and defense applications have led to the need of higher fidelity of physics based lumped parameter models. The sensor data, along with maneuvering model data can tie into a more accurate trajectory. Multiple such incremental advances in the literature for prediction of maneuvering shall lead to a more accuracy. This work hopes to bridge some important gaps that ensure the creation of such a non-linear LPM to predict the maneuver- ing characteristics of an AUV using non linear hydrodynamic derivatives obtained through static and dynamic CFD. This model shall be implemented for the craft designed for DIVE technologies, our industrial sponsor and an in-house craft, the 690. This model shall also be made generalized for most submerged craft with a torpedo or slender hull form, with cruciform or X configuration of fins. This dissertation looks to provide the framework to identify CFD informed high fidelity dynamic model for AUVs. The model thus created shall be spe- cialized to account for specific important effects such as flow interaction among appendages, effect of using steady and unsteady maneuvers as CFD information and kinematic charac- teristics of captive maneuvers. The specific, innovative contributions in this dissertation are listed below: 1. Definition of a new stability index to incorporate effects of gravity at low-moderate speeds 2. Novel method for identification of hydrodynamic derivatives 3. Systematic and comprehensive study on the parameters affecting VPMM / Doctor of Philosophy / The maneuvering model for an AUV is an indispensable tool that makes the autonomy part of AUVs possible and efficient. The maneuvering model that exists today is mostly linearized and of lower fidelity to increase efficiency. The use of a non linear, higher order hydrodynamic model facilitates better accuracy of maneuvering predictions, essential to mission completion of AUVs applied in research and defense sectors. This higher fidelity can be achieved through informing the model using CFD that is reasonably efficient in computation. This dissertation presents a non-linear, higher order hydrodynamic maneuvering model for the 690 and DIVE crafts, informed with steady and unsteady CFD.

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