• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 9
  • 1
  • Tagged with
  • 14
  • 14
  • 8
  • 5
  • 4
  • 3
  • 3
  • 3
  • 3
  • 3
  • 2
  • 2
  • 2
  • 2
  • 2
  • 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.
11

Evolving Information Technology: A Case Study of the Effects of Constant Change on Information Technology Instructional Design Architecture

Helps, C. Richard G. 02 December 2010 (has links) (PDF)
A major challenge for Information Technology (IT) programs is that the rapid pace of evolution of computing technology leads to frequent redesign of IT courses. The problem is exacerbated by several factors. Firstly, the changing technology is the subject matter of the discipline and is also frequently used to support instruction; secondly, this discipline has only been formalized as a four-year university program within recent years and there is a lack of established textbooks and curriculum models; finally, updating courses is seldom rewarded in a higher education system that favors research and teaching for promotion and tenure. Thus, continuously updating their courses place a significant burden on the faculty. A case study approach was used to describe and explain the change processes in updating IT courses. Several faculty members at two institutions were interviewed and course changes were identified and analyzed. The analysis revealed a set of recurrent themes in change processes. An instructional design architecture approach also revealed a set of design domains representing the structure of the change processes. The design domains were analyzed in terms of the design decisions they represented, and also in terms of structures, functions and activities, which are related to Structures-Behaviors-Functions (SBF) analysis. The design domains model helped to explain both negative and positive outcomes that were observed in the data. When design efforts impact multiple domains the design is likely to be more difficult. Understanding the design domain architecture will assist future designers in this discipline.
12

MODELING AND SIMULATION OF CUTTING MECHANICS IN CFRP MACHINING AND ITS MACHINING SOUND ANALYSIS

Kyeongeun Song (13169763) 28 July 2022 (has links)
<p>Carbon fiber bending during Carbon Fiber Reinforced Plastic (CFRP) milling is an important factor on the quality of the machined surface. When the milling tool rotates, the fiber first contacts the rake face instead of the tool edge at a certain cutting angle, then the fiber is bent instead of being cut by the tool. It causes the matrix and the fiber to fall out, and the fiber is broken from deep inside the machined surface. The broken fibers are pulled out as the tool rotates, which is known as pull-out fibers. The machining defect is the main cause of deteriorating the quality of the machined surface. To reduce such machining defects, it is important to predict the carbon fiber bending during CFRP milling. However, it is difficult to determine a point where fiber bending occurs because the fiber cutting angle changes every moment as the tool rotates. Therefore, in this study, CFRP milling simulation was performed to numerically analyze the machining parameters such as fiber cutting angle, fiber length, and the magnitude of fiber bending according to the different milling conditions. In addition, the deformation of the matrix existing between carbon fibers is predicted based on the fiber bending information obtained through simulation, and matrix shear strain energy model is developed. Also, the relationship between the matrix shear strain energy and machining quality is analyzed. Through verification experiments under various machining conditions, it is confirmed that the quality of the machined surface deteriorated as the matrix shear strain energy increased. Moreover, this study analyzed the fiber cutting mechanism considering bent fibers during CFRP milling and proposed a method to identify the type of machining mechanism through machining sound analysis. Through experiments, it was verified that fiber bending or defects can be identified through machining sound analysis in the high-frequency range between 7,500 Hz and 14,800 Hz. From the analysis, the effect of different chip thickness in up-milling and down-milling on fiber bending was investigated by analyzing simulation and sound signal. From machining experiments, the effect of this difference on cutting force and machining quality was verified. Lastly, we developed a minimum chip thickness and fiber fracture model in CFRP milling and analyzed the effect of fractured fibers on the machining sound. Carbon fibers located below the minimum chip thickness do not contact the tool edge and are compressed by the bottom face of the tool, and these fibers are excessively bent and broken. As these broken fibers are discharged while scratching the flank face of the tool, a loud machining sound is generated. Moreover, through the verification experiment, it was confirmed that the number of broken fibers is proportional to the loudness of the sound, and calculated number of broken fibers for one second using the fiber fracture model coincides with the high-frequency machining sound range of 7,500 Hz to 14,800 Hz.</p>
13

Architecting Safe Automated Driving with Legacy Platforms

Mohan, Naveen January 2018 (has links)
Modern vehicles have electrical architectures whose complexity grows year after year due to feature growth corresponding to customer expectations. The latest of the expectations, automation of the dynamic driving task however, is poised to bring about some of the largest changes seen so far. In one fell swoop, not only does required functionality for automated driving drastically increase the system complexity, it also removes the fall-back of the human driver who is usually relied upon to handle unanticipated failures after the fact. The need to architect thus requires a greater rigour than ever before, to maintain the level of safety that has been associated with the automotive industry. The work that is part of this thesis has been conducted, in close collaboration with our industrial partner Scania CV AB, within the Vinnova FFI funded project ARCHER. This thesis aims to provide a methodology for architecting during the concept phase of development, using industrial practices and principles including those from safety standards such as ISO 26262. The main contributions of the thesis are in two areas. The first area i.e. Part A contributes, (i) an analysis of the challenges of architecting automated driving, and serves as a motivation for the approach taken in the rest of this thesis, i.e. Part B where the contributions include, (ii) a definition of a viewpoint for functional safety according to the definitions of ISO 42010, (iii) a method to systematically extract information from legacy components and (iv) a process to use legacy information and architect in the presence of uncertainty to provide a work product, the Preliminary Architectural Assumptions (PAA), as required by ISO 26262. The contributions of Part B together comprise a methodology to architect the PAA.   A significant challenge in working with the industry is finding the right fit between idealized principles and practical utility. The methodology in Part B has been judged fit for purpose by different parts of the organization at Scania and multiple case studies have been conducted to assess its usefulness in collaboration with senior architects. The methodology was found to be conducive in both, generating the PAA of a quality that was deemed suitable to the organization and, to find inadequacies in the architecture that had not been found earlier using the previous non-systematic methods. The benefits have led to a commissioning of a prototype tool to support the methodology that has begun to be used in projects related to automation at Scania. The methodology will be refined as the projects progress towards completion using the experiences gained. A further impact of the work is seen in two patent filings that have originated from work on the case studies in Part B. Emanating from needs discovered during the application of the methods, these filed patents (with no prior publications) outline the future directions of research into reference architectures augmented with safety policies, that are safe in the presence of detectable faults and failures. To aid verification of these ideas, work has begun on identifying critical scenarios and their elements in automated driving, and a flexible simulation platform is being designed and developed at KTH to test the chosen critical scenarios. / Efterfrågan på nya funktioner leder till en ständigt ökande komplexitet i moderna fordon, speciellt i de inbyggda datorsystemen. Införande av autonoma fordon utgör inte bara det mest aktuella exemplet på detta, utan medför också en av de största förändringar som fordonsbranschen sett. Föraren, som ”back-up” för att hantera oväntade situationer och fel, finns inte längre där vid höggradig automation, och motsvarande funktioner måste realiseras i de inbyggda system vilket ger en drastisk komplexitetsökning. Detta ställer systemarkitekter för stora utmaningar för att se till att nuvarande nivå av funktionssäkerhet bibehålls. Detta forskningsarbete har utförts i nära samarbete med Scania CV AB i det Vinnova (FFI)-finansierade projektet ARCHER. Denna licentiatavhandling har som mål att ta fram en metodik för konceptutveckling av arkitekturer, förankrat i industriell praxis och principer, omfattande bl.a. de som beskrivs i funktionssäkerhetsstandards som ISO 26262. Avhandlingen presenterar resultat inom två områden. Det första området, del A, redovisar, (i) en analys av utmaningar inom arkitekturutveckling för autonoma fordon, vilket också ger en motivering för resterande del av avhandlingen. Det andra området, del B, redovisar, (ii) en definition av en ”perspektivmodell” (en s.k. ”viewpoint” enligt ISO 42010) för funktionssäkerhet, (iii) en metod för att systematiskt utvinna information från existerande komponenter, och (iv) en process som tar fram en arbetsprodukt för ISO 26262 – Preliminära Arkitektur-Antaganden (PAA). Denna process använder sig av information från existerande komponenter – resultat (iii) och förenklar hantering av avsaknad/osäker information under arkitekturarbetet. Resultaten från del B utgör tillsammans en metodik för att ta fram en PAA. En utmaning i forskning är att finna en balans mellan idealisering och praktisk tillämpbarhet. Metodiken i del B har utvärderats i flertalet industriella fallstudier på Scania i samverkan med seniora arkitekter från industrin, och har av dessa bedömts som relevant och praktiskt tillämpningsbar. Erfarenheterna visar att metodiken stödjer framtagandet av PAA’s av   lämplig kvalitet och ger ett systematiskt sätt att hantera osäkerhet under arkitekturutvecklingen. Specifikt så gjorde metoden det möjligt att identifiera komponent-felmoder där arkitekturen inte var tillräcklig för åstadkomma önskad riskreducering, begränsningar som inte hade upptäckts med tidigare metoder. Ett prototypverktyg för att stödja metodiken har utvecklats och börjat användas på Scania i projekt relaterade till autonoma fordon. Metodiken kommer sannolikt att kunna förfinas ytterligare när dessa projekt går mot sitt slut och mer erfarenheter finns tillgängliga. Arbetet i del B har vidare lett till två patentansökningar avseende koncept som framkommit genom fallstudierna. Dessa koncept relaterar till referensarkitekturer som utökats med policies för personsäkerhet (Eng. ”safety”) för att hantera detekterbara felfall, och pekar ut en riktning för framtida forskning. För att stödja verifiering av dessa koncept har arbete inletts för att identifiera kritiska scenarios för autonom körning. En flexibel simuleringsplattform håller också på att designas för att kunna testa kritiska scenarios. / Vinnova-FFI funded Project ARCHER
14

ALGORITHM TO DEVELOP A MODEL PROVIDING SECURITY AND SUSTAINABILITY FOR THE U.S. INFRASTRUCTURE BY PROVIDING INCREMENTAL ELECTRICAL RESTORATION AFTER BLACKOUT

Casey Allen Shull (7039955) 15 August 2019 (has links)
<p>Is North America vulnerable to widespread electrical blackout from natural or man-made disasters? Yes. Are electric utilities and critical infrastructure (CI) operators prepared to maintain CI operations such as, hospitals, sewage lift stations, food, water, police stations etc., after electrical blackout to maintain National security and sustainability? No. Why? Requirements to prioritize electrical restoration to CI do not exist as a requirement or regulation for electrical distribution operators. Thus, the CI operators cannot maintain services to the public without electricity that provides power for the critical services to function. The problem is that electric utilities are not required to develop or deploy a prioritized systematic plan or procedure to decrease the duration of electrical outage, commonly referred to as blackout. The consequence of local blackout to CI can be multi-billion-dollar financial losses and loss of life for a single outage event attributed to the duration of blackout. This study utilized the review of authoritative literature to answer the question: “Can a plan be developed to decrease the duration of electrical outage to critical infrastructure”. The literature revealed that electric utilities are not required to prioritize electrical restoration efforts and do not have plans available to deploy minimizing the duration of blackout to CI. Thus, this study developed a plan and subsequent model using Model Based System Engineering (MBSE) to decrease the duration of blackout by providing incremental electrical service to CI.</p>

Page generated in 0.0486 seconds