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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

THE DEVELOPMENT OF A LOW DENSITY RADIOCHROMIC GEL DOSIMETER

Al Rashed, Hailah January 2019 (has links)
This research aims to develop a tissue-mimicking material and produce a 3D gelatin that has density of approximately a human lung, which is in the ranges of (0.25 – 0.35) g/cm3. Tissue equivalent models are important in order to study the radiation dose planned for patients. To achieve the desired density of a human tissue, different types of gelatin were whisked for 300 seconds using a typical hand mixer. The mechanical properties of the gelatin mixtures, standard and foamed, were evaluated by applying different forces. The mechanical properties for the gels were measured using an indentation technique, which showed that the gels act as elastic materials. The mechanical properties of the foams were also evaluated. Mixtures that contained 300 bloom gelatin, glycerol, and sorbitol, were whisked for 60, 180, 300 seconds to achieve different densities evaluated by CT imaging. The density of the180 - and 300 - seconds gelatin foams were found to be 0.33 ± 0.16 and 0.33  0.052 g/cm3, respectively, which is similar to the human lung density. Finally, FXO gel sheets and the FXO foam sheets were irradiated and the radiosensitivity quantified by measuring transmission using a spectrometer. The change in the attenuation coefficient was linear with dose. / Thesis / Master of Science (MSc)
2

Quality Assurance Techniques in OpenUP (Open Unified Process)

Sardar, Raham, Fazal, Usman January 2011 (has links)
Agile methods change the software processes. Agile processes such as Scrum, ExtremeProgramming (XP), Open Unified Process (OpenUP) etc. have techniques that improve softwarequality. No doubt that the purpose of these techniques is to inject quality assurance into theproject under development. This thesis presents quality assurance techniques in Open UnifiedProcess (OpenUP) along with comparative study to extreme programming (XP) for agilesoftware development. OpenUP is an agile and unified process that contains the minimal set ofpractices that help teams to be more effective in developing software. It assists to achieve qualityby an iterative and incremental approach with artifacts, checklists, guidelines, disciplines androles. On the other side XP emphasizes on values such as communication, feedback, respect,and courage. In addition, XP prescribes a collection of techniques, which aim to improvesoftware quality. Both these processes have the same purpose, to develop software that meets the stakeholder’sneeds and expectations, however they uses different approaches to achieve their goals. Thisthesis compares both processes in four different points of view, by comparing their qualitytechniques, focus in time, and cost of usage and social perspective. We have proposed an extrarole of the quality coordinator (QC) in OpenUP/XP. QC can support and coordinate project inall quality assurance activities. The objective of an extra role is to use the knowledge of QC toachieve highest possible product quality in software development process.Keywords: Agile Development, Quality assurance (QA), Open unified process (OpenUP),extreme programming (XP), Quality coordinator (QC)
3

DEVELOPMENT OF A TRANSPARENT AND DEFORMABLE TWO DIMENSIONAL RADIOCHROMIC GEL DOSIMETER

Ataei, Pouria 04 1900 (has links)
<p>Radiotherapy is used in many clinics to deliver a sufficient and uniform dose to the cancerous tumours while the dose to normal tissues is minimized. However, there is a possibility of missing the target volume due to patient set up/motion errors, or any fluctuation in treatment delivery. Therefore, accurate dose verification tools are essential to evaluate the delivered dose distribution of the designed treatment plan under realistic treatment conditions.</p> <p>Current research is focused on developing 3D dose verification tools to record the complex dose distributions for quality assurance purposes and the evaluation of new treatment techniques. New and novel materials and read-out techniques suitable for use in hospitals are desirable. The objective of this research is to fabricate a transparent radiochromic gel dosimeter that may be used as quality assurance tool. Also, the fabricated gel must be analyzed using a simple optical read-out technique.</p> <p>Gel dosimeters are gels that undergo some chemical changes upon irradiation as a function of absorbed dose. The absorbed dose may be recorded in three dimensions depending on the type of gel dosimeter. Radiochromic gels are dosimeters that change colour upon irradiation. A radiosensitive dye, leucomalachite green (LMG) is dissolved in a matrix material to record the dose distribution in 3D. LMG changes its colour upon irradiation, and has an absorbance band of 629nm.</p> <p>In this research two different matrix materials were investigated: poly (vinyl alcohol) and gelatin. PVA was studied as the primary agent due to its adjustable mechanical strength and high transparency. PVA has also been studied to have a low diffusion rate when it was used as the matrix material in Fricke gel dosimeters [41]. Even though PVA had all the desired characteristics, fabricating a PVA based radiochromic dosimeter was not successful. Consequently, gelatin was used as the matrix material to fabricate a gelatin-based radiochromic dosimeter.</p> <p>Using gelatin, highly transparent radiosensitive gels were successfully fabricated. The absorbencies of the irradiated gels were measured as a function of absorbed dose, using a 1D set up. After, the gels were formed into 5mm thick films and used as two-dimensional dose verification tools. The relationship between absorbance and absorbed dose for 1D measurement was obtained to be 0.00241± 0.00004 , and 0.0022 ± 0.00007 for 2D gels scaled to a thickness of 1 cm.</p> <p>In all of the experiments the absorbance-dose relationships were similar in slopes, but there was an offset between different batches. The offset was 20% between the different experiments. Moreover, there was less than 5% error associated with the physical set up; the major source of error was due to the production and handling of the mixture, possibly due to the effects of inconsistent heating and UV light exposure.</p> <p>The 2D gels were used to verify the dose distribution for the purpose of quality assurance. Six different complicated beams were delivered to the gels and their dose distributions were compared to their respective Pinnacle Calculated Planar (PCP) dose maps. The difference was found to be about 35% at worst; however, this error may be reduced by utilizing more sophisticated data processing methods. Nevertheless, the images were quite similar above 20Gy. Furthermore, the dose distributions recorded by the gels are qualitatively and quantitatively similar to the (PCP) dose map. Although the fabricated gel dosimeters show some promise as future tools for quality assurance purposes, they must go through many more stages of research to be used clinically.</p> / Master of Science (MSc)
4

Quality Assuring of Stator Winding Production : Using electrical tests to quality assure the process steps of a series stator winding production

Sayed Hamad, Tarek January 2021 (has links)
The demands for sustainable transportation have made battery electric vehicles an increasingly popular subject in the world of both businesses and engineering. This thesis has been made in collaboration with Scania, which is currently investigating the possibility of manufacturing stators and rotors in-house in a series production line. For Scania, the topic of quality assurance is of great importance as Scania wants to ensure their trucks and buses fulfil the quality requirements of both customers and society. The goal of the thesis is to provide Scania with a set of guidelines for what quality assurance steps to perform in a series stator winding production, and where in the production they should be placed. The investigated stator winding type is a continuous hairpin winding, and the investigated quality assurance steps are solely electrical tests used to ensure the safety, functionality, and quality of the stator windings. A process-failure modes and effects analysis were conducted to identify the risks associated with each production step. The results indicates where the quality assurance steps should be taken. Further analysis, based on the provided background of electrical tests, also provides an answer to what electrical tests to perform as quality assurance steps. The result of the thesis is a concept, presented in a flow chart diagram, which indicates what electrical tests to perform and where the tests should be performed in the stator winding production chain. / De krav som sätts på hållbar transport har gjort batteridrivna elektriska fordon ett alltmer populärt ämne i världens företag och ingenjörskonst. Denna avhandling har gjort i samarbete med Scania, som i nuläget utreder möjligheterna för att tillverka statorer och rotorer in- house i en serie produktionslinje. För Scania är ämnet kvalitetssäkring (QA) ett viktigt ämne, för att Scania vill säkerställa att deras lastbilar och bussar lever upp till de kvalitetskrav som både kunder och samhället ger. Avhandlingens mål är därför att förse Scania med en uppsättning av riktlinjer för vilka QA steg som ska utföras i en serie statorlindningsproduktion, och var i produktionen de ska placeras. Den statorlindningstypen i fokus är en kontinuerlig hårnålslindning, och att de kvalitetssäkringar som undersöks är enbart elektriska test som säkrar säkerhet, funktionalitet samt kvalitén av statorlindningarna. En P-FMEA har utförts som en risk och felläges analys i syfte att identifiera de risker som är associerat med varje produktionssteg. Resultatet pekar på var QA steg ska utföras någonstans. Fortsatt analys, baserat på den givna bakgrunden av elektriska test, ger även ett svar på vilka elektriska test som ska utföras som QA steg. Avhandlingens resultat är ett koncept, presenterat i ett flödesdiagram, som visar vilka elektriska test som ska utföras samt var dessa tests ska utföras i statorlindningsproduktionen.

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