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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.
61

Network Traffic Regulator for Diagnostic Messages in Modular Product / Reglering av nätverkstrafik för diagnoskommunikation i en modulär produkt

Thakrar, Nikhil January 2017 (has links)
The aim of this thesis project is to explore a network traffic regulator using bandwidth management techniques that regulates data traffic with the objective to use the network bandwidth to its maximum capacity while ensuring that the network is not overloaded. The bandwidth in the existing network architecture is shared between two co-existing, distinct data flows for on-board communication and diagnostic communication in an in-vehicle network. The diagnostic communication must not interfere with the more critical on-board communication and it should comply with the remaining bandwidth. In the existing solution, fixed delays are imposed on the data traffic which result in a waste of network capacity. The approach presented in this thesis uses two regulation algorithms for different types of diagnostic services. One regulation algorithm is activated for diagnostic services that require data segmentation and multiple data frames to accommodate the transferred data. This algorithm makes use of the Flow Control parameter Separation Time specified in ISO 15765-1:2011 "Road vehicles -- Diagnostic communication over Controller Area Network (DoCAN)". The other algorithm regulates diagnostic services that generate bursts of single frames where data segmentation is not required and it does so using traffic shaping techniques. The results in this thesis show that the network traffic indeed can be regulated for different diagnostic services by using the two mentioned regulation algorithms. The results also show that data is not lost due to high network utilisation and that the bandwidth is used to its maximum capacity without having to impose fixed delays on the network system. The regulator is adaptive in the sense that it can be used for different vehicle configurations with compatible network systems to ensure quality of service and a robust network system. / I detta examensarbete är målet att utforska en metod för att reglera  nätverkstrafik genom att använda tekniker inom bandbreddshantering  med syfte att utnyttja bandbredden till dess maximala kapacitet utan att överbelasta nätverket. Bandbredden i den nuvarande nätverksarkitekturen delas mellan två dataflöden för onboard kommunikation och diagnostisk kommunikation. Den diagnostiska kommunikationen får inte på någotvis störa onboard kommunkationen och får anpassa sig till den bandbredd som kvarstår. I det existerande systemet införs fixa fördröjningar i nätverkstrafiken vilket medför ett onödigt slöseri på nätverkskapaciteten och som också medför att de diagnostiska tjänsterna tar längre tid att utföra.  Tillvägagångssättet som presenteras i detta arbete använder två regleringsalgoritmer för olika typer av diagnostiska tjänster. En algoritm används för tjänster som kräver datasegmentering och flera dataramar för att skicka data. Den här algoritmen använder parametern Separation Time som är specificerad i ISO standarden 15765-1:2011 "Road vehicles -- Diagnostic communication over Controller Area Network (DoCAN)". Diagnostiska tjänster som istället genererar en skur av enstaka dataramar regleras med en traffic shaping algoritm som heter Token Bucket. Resultaten i detta arbete visar att det går att reglera nätverkstrafiken för olika typer av diagnostiska tjänster genom att använda de två utvecklade algoritmerna. Resultaten visar också att data inte går förlorat vid höga nätverkslaster och att bandbredden används maximalt utan att behöva införa fixa fördröjningar i nätverkssystemet. Regleraren är adaptiv i bemärkelsen att den kan användas för alla tänkbara fordonskonfigurationer med kompatibelt nätverkssystem för att försäkra quality of service och robusthet.
62

Utveckling av plogklaff till Ålös snöröjningsredskap / Development of add-on plow for Ålös snow clearing implement

Sellgren, Marc January 2017 (has links)
Detta examensarbete har utförts åt Ålö, som är en tillverkare av frontlastare och redskap till dessa. Ett av deras redskap, vars syfte är snöröjning, är utrustat med hydrauliskt justerbara sidoklaffar som kan fällas bakåt och nyttjas som plogblad. De fyller dock inte denna uppgift tillfredsställande då snö tenderar falla tillbaka bakom dem. Det bildas även en triangulär spalt mellan klaffarna och underlaget vid plogning, detta lämnar kvar en sträng av snö, utöver det som faller ner bakom klaffarna. Målet i detta projekt var att utveckla en plogklaff som löser tidigare nämnda problem genom att ersätta den högra sidoklaffen till skopan. Utvecklingen har initierats med en studie av rapporter, existerande plogar, kontakt med brukare och fastställande av de begränsningar som råder. Detta har sedan utgjort grunden för en rad koncept, av vilka de mest lovande sammanfogades till en prototyp. Kraftberäkningar utifrån det lastfall som uppstår vid plogning har sedan använts för att bl.a. dimensionera skruvförband och skapa randvillkoren för en finita element-analys. Finita element-analysen har sedan nyttjats för att göra en uppskattning av antalet cykler med momentan maximal belastning plogklaffen klarar innan utmattningsbrott sker. Kraftberäkningarna visade att hydraulcylinderns tryckbegränsare öppnar redan innan maximal belastning uppnås. Finita element-analys och kraftberäkningar till skruvförband förutsätter likväl att maximal belastning kan erhållas momentant i syfte att ge konservativa resultat. Under denna förutsättning skiljer belastningen i skruvförbanden endast ca 7-10 % mellan finita element-analys och handberäkningar. Samtliga beräkningar är inom spannen för skruvförbandens hållfasthet. Utmattningsberäkningarna visade att antalet cykler plogklaffen klarar vid maximal belastning uppgår till ca 346 000. Detta avser områden av intresse och inkluderar således ej delar vilka redan utvärderats i originalklaffen. Svetsförband, som i regel är dimensionerande i situationer som dessa, har ej sett någon utmattningsmässig utvärdering utan kommer istället behandlas vid tester av prototypen. Prototypen uppfyller de utsatta målen och tillverkningsunderlag i form av 3D-CAD modeller och 2D-ritningar (inklusive svetsritningar) har levererats. En fysisk prototyp är även beställd och kommer tillverkas av Vännäs Verkstads AB, planerat leveransdatum är 2017-06-08. Den kommer utvärderas under vintern 2017/2018. / This thesis work has been carried out for Ålö, a manufacturer of front loaders and implements for these. One of their implements, whose purpose is snow clearing, is equipped with hydraulically adjustable flaps that can be folded backwards and used as plows. However, they do not fill this task satisfactorily as snow tends to fall down behind them. A triangular gap between the flaps and the ground is also formed during plowing. This leaves a string of snow behind, aside from the snowmass already falling down behind the flaps. The goal for this project was to develop a plow that solves the aforementioned problems by replacing the right side flap on the bucket. The development was initiated with a study of reports, existing plows, contact with users and determining existing constraints. This has since provided the basis for a series of concepts, of which the most promising ones were joined to a prototype. Force calculations based on the load scenario that occurs during plowing have been used to find appropriate fasteners and create boundary conditions for a finite element analysis. The finite element analysis has then been used to estimate the number of cycles with maximum load the plow can be subjected to before it succumbs to fatigue failure. Force calculations showed that the pressure limiter for the hydraulic cylinder opens even before maximum load is reached. Despite this, finite element analysis and force calculations for fasteners were still based on the condition that maximum load is achieved momentarily to produce convervative results. Under this condition, the load on fasteners differs only ca 7-10 % between finite element analysis and calculations made by hand. All calculations are within the span for the fasteners proof strength. Fatigue calculations showed that the number of cycles the plow can handle with maximum load amounts to approximately 346 000. This refers to areas of interest and thus does not include parts already evaluated in the original flap. Welds, which usually dictate minimum strength in situations like these, have not seen any fatigue evaluations, but will instead be addressed while testing the prototype. The prototype meets the set goals and production documentation in the form of 3D-CAD models and 2D drawings (including weldment drawings) have been delivered. A physical prototype is also ordered and will be manufactured by Vännäs Verkstads AB, scheduled delivery date is 2017-06-08. It will be evaluated during the winter of 2017/2018.
63

Triangulation de Delaunay et arbres multidimensionnels

Lemaire, Christophe 19 December 1997 (has links) (PDF)
Les travaux effectués lors de cette thèse concernent principalement la triangulation de Delaunay. On montre que la complexité en moyenne - en termes de sites inachevés - du processus de fusion multidimensionnelle dans l'hypothèse de distribution quasi-uniforme dans un hypercube est linéaire en moyenne. Ce résultat général est appliqué au cas du plan et permet d'analyser de nouveaux algorithmes de triangulation de Delaunay plus performants que ceux connus à ce jour. Le principe sous-jacent est de diviser le domaine selon des arbres bidimensionnels (quadtree, 2d-tree, bucket-tree. . . ) puis de fusionner les cellules obtenues selon deux directions. On étudie actuellement la prise en compte de contraintes directement pendant la phase de triangulation avec des algorithmes de ce type. De nouveaux algorithmes pratiques de localisation dans une triangulation sont proposés, basés sur la randomisation à partir d'un arbre binaire de recherche dynamique de type AVL, dont l'un est plus rapide que l'algorithme optimal de Kirkpatrick, au moins jusqu'à 12 millions de sites K Nous travaillons actuellement sur l'analyse rigoureuse de leur complexité en moyenne. Ce nouvel algorithme est utilisé pour construire " en-ligne " une triangulation de Delaunay qui est parmi les plus performantes des méthodes " en-ligne " connues à ce jour.
64

Beitrag zur Analyse des Grabwiderstandes am Schaufelradbagger

Kreßner, Martin 02 March 2020 (has links)
Mit dem Anspruch, den Informationsgehalt heute standardmäßig erhobener Prozess- und Betriebsdaten mit beliebiger zeitlicher Auflösung für die Zwecke der Grabwiderstandsanalyse zu erschließen, wurde auf Grundlage der konventionellen Methode der indirekten Grabwiderstandsermittlung ein umfassendes mathematisches Modell der Gesamtheit aller Teilprozesse bei der schneidenden Gewinnung am Graborgan des vorschublosen Schaufelrad-baggers erarbeitet und bisher unberücksichtigte zeitabhängige Einflussgrößen integriert. Das Ziel der Anwendung der hochauflösenden indirekten Grabwiderstandsanalyse (HIG) auf verschiedene theoretische und praktische Aufgabenstellungen war die Prüfung der Ergebnisplausibilität sowie die umfassende Diskussion der Potentiale und Grenzen der Methode. Für die Schneidwerkzeugentwicklung ist die Anwendung der HIG die einzige Möglichkeit, ohne zusätzliche Kosten, Umbaumaßnahmen oder Betriebsstillstände den Einfluss von Werkzeugparametern unter betrieblichen Bedingungen zu analysieren. Für die theoretische Weiter¬entwicklung des Fachgebietes ermöglicht die Prozessmodellierung auf Basis beliebiger Zeitinkremente die umfassende Analyse konventioneller und spanunabhängiger Grabwiderstandskenngrößen.
65

Characteristics of the Specific Fuel Consumption for Jet Engines

Bensel, Artur January 2018 (has links) (PDF)
Purpose of this project is a) the evaluation of the Thrust Specific Fuel Consumption (TSFC) of jet engines in cruise as a function of flight altitude, speed and thrust and b) the determination of the optimum cruise speed for maximum range of jet airplanes based on TSFC characteristics from a). Related to a) a literature review shows different models for the influence of altitude and speed on TSFC. A simple model describing the influence of thrust on TSFC seems not to exist in the literature. Here, openly available data was collected and evaluated. TSFC versus thrust is described by the so-called bucket curve with lowest TSFC at the bucket point at a certain thrust setting. A new simple equation was devised approximating the influence of thrust on TSFC. It was found that the influence of thrust as well as of altitude on TSFC is small and can be neglected in cruise conditions in many cases. However, TSFC is roughly a linear function of speed. This follows already from first principles. Related to b) it was found that the academically taught optimum flight speed (1.316 times minimum drag speed) for maximum range of jet airplanes is inaccurate, because the derivation is based on the unrealistic assumption of TSFC being constant with speed. Taking account of the influence of speed on TSFC and on drag, the optimum flight speed is only about 1.05 to 1.11 the minimum drag speed depending on aircraft weight. The amount of actual engine data was extremely limited in this project and the results will, therefore, only be as accurate as the input data. Results may only have a limited universal validity, because only four jet engine types were analyzed. One of the project's original value is the new simple polynomial function to estimate variations in TSFC from variations in thrust while maintaining constant speed and altitude.
66

Theoretical Study of Laser Beam Quality and Pulse Shaping by Volume Bragg Gratings

Kaim, Sergiy 01 January 2015 (has links)
The theory of stretching and compressing of short light pulses by the chirped volume Bragg gratings (CBG) is reviewed based on spectral decomposition of short pulses and on the wavelength-dependent coupled wave equations. The analytic theory of diffraction efficiency of a CBG with constant chirp and approximate theory of time delay dispersion are presented. Based on those, we performed comparison of the approximate analytic results with the exact numeric coupled-wave modeling. We also study theoretically various definitions of laser beam width in a given cross-section. Quality of the beam is characterized by the dimensionless beam propagation products (?x???_x)?? , which are different for each of the 21 definitions. We study six particular beams and introduce an axially-symmetric self-MFT (mathematical Fourier transform) function, which may be useful for the description of diffraction-quality beams. Furthermore, we discuss various saturation curves and their influence on the amplitudes of recorded gratings. Special attention is given to multiplexed volume Bragg gratings (VBG) aimed at recording of several gratings in the same volume. The best shape of a saturation curve for production of the strongest gratings is found to be the threshold-type curve. Both one-photon and two-photon absorption mechanism of recording are investigated. Finally, by means of the simulation software we investigate forced airflow cooling of a VBG heated by a laser beam. Two combinations of a setup are considered, and a number of temperature distributions and thermal deformations are obtained for different rates of airflows. Simulation results are compared to the experimental data, and show good mutual agreement.
67

IT’S IN THE DATA 2 : A study on how effective design of a digital product’s user onboarding experience can increase user retention

Fridell, Gustav January 2021 (has links)
User retention is a key factor for Software as a Service (SaaS) companies to ensure long-term growth and profitability. One area which can have a lasting impact on a digital product’s user retention is its user onboarding experience, that is, the methods and elements that guide new users to become familiar with the product and activate them to become fully registered users. Within the area of user onboarding, multiple authors discuss “best practice” design patterns which are stated to positively influence the user retention of new users. However, none of the sources reviewed showcase any statistically significant proof of this claim. Thus, the objective of this study was to: Design and implement a set of commonly applied design patterns within a digital product’s user onboarding experience and evaluate their effects on user retention Through A/B testing on the SaaS product GetAccept, the following two design patterns were evaluated: Reduce friction – reducing the number of barriers and steps for a new user when first using a digital product; and Monitor progress – monitoring and clearly showcasing the progress of a new user’s journey when first using a digital product. The retention metric used to evaluate the two design patterns was first week user retention, defined as the share of customers who after signing up, sign in again at least once within one week. This was tested by randomly assigning new users into different groups: groups that did receive changes related to the design patterns, and one group did not receive any changes. By then comparing the first week user retention data between the groups using Fisher’s exact test, the conclusion could be drawn that with statistical significance, both of the evaluated design patterns positively influenced user retention for GetAccept. Furthermore, due to the generalizable nature of GetAccept’s product and the aspects evaluated, this conclusion should also be applicable to other companies and digital products with similar characteristics, and the method used to evaluate the impact of implementing the design patterns should be applicable for evaluating other design patterns and/or changes in digital products. However, as the method used for data collection in the study could not ensure full validity of it, the study could and should be repeated with the same design patterns on another digital product and set of users in order to strengthen the reliability of the conclusions drawn.

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