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Weight, Braden Michael. "Inspection of Excited State Properties in Defected Carbon Nanotubes from Multiple Exciton Generation to Defect-Defect Interactions". Thesis, North Dakota State University, 2020. https://hdl.handle.net/10365/31784.
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Covalent SP3-hybridization defects in single-walled carbon nanotubes (CNTs) have been prevalent in recent experimental and theoretical studies for their interesting photophysical properties. These systems are able to act as excellent sources of single, infrared photons, even at room temperature, making them marketable for applications to sensing, telecommunications, and quantum information. This work was motivated by recent experimental studies on controllable defect placement and concentration as well as investigating carrier multiplication (CM) using DFT-based many-body perturbation theory (MBPT) methods to describe excitonic relaxation processes. We find that pristine CNTs do not yield appreciable MEG at the minimum threshold of twice the optical gap 2Eg, but covalent functionalization allows for improved MEG at the threshold. Finally, we see that defect-defect interactions within CNT systems can be modeled simply as HJ-aggregates in an effective Hamiltonian model, which is shown to be valid for certain, highly-redshifted defect configurations at low defect-defect separation lengths.
2
Liu, Chen. "VLSI circuit defect diagnosis : open defects and run-time speed". Diss., University of Iowa, 2008. http://ir.uiowa.edu/etd/8.
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Hassan, Syed Karimuddin and Syed Muhammad. "Defect Detection in SRS using Requirement Defect Taxonomy". Thesis, Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-5253.
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Context: Defects occurred in the SRS may cause problems in project due to implementation of poor requirements which require extra time, effort, resources and budget to complete it. Reading techniques i.e., checklist based reading (CBR) helps to guide reviewers in identifying defects in software requirement specification (SRS) during individual requirement inspections. Checklists contain potential defects/problems to look for, but often lack clear definitions with examples of the problem, and also their abstractions are different. Therefore, there is a need for identifying existing defects and classifiers and to create a consolidated version of taxonomy. Objectives: We developed taxonomy for requirement defects that are in requirement specifications and compared it with the checklist based approach. The main objective was to investigate and compare the effectiveness and efficiency of inspection techniques (checklist and taxonomy) with M.Sc. software engineering students and industry practitioners by performing a both controlled student and industry experiment. Methods: Literature review, controlled student experiment and controlled industry experiment were the research methods utilized to fulfill the objectives of this study. INSPEC and Google scholar database was used to find the articles from the literature. Controlled student experiment was conducted with the M.Sc. software engineering students and controlled industry experiment was performed with the industry practitioners to evaluate the effectiveness and efficiency of the two treatments that are checklist and taxonomy. Results: An extensive literature review helped us to identify several types of defects with their definitions and examples. In this study, we studied various defect classifiers, checklists, requirement defects and inspection techniques and then built taxonomy for requirement defects. We evaluated whether the taxonomy performed better with respect to checklist using controlled experiments with students and practitioners. Moreover, the results of student experiment (p= 0.90 for effectiveness and p=0.10 for efficiency) and practitioner experiment (p=1.0 for effectiveness and p=0.70 for efficiency) did not show significant values with respect to effectiveness and efficiency. But because of less number of practitioners it is not possible to apply a statistical test since we also have used standard formulas to calculate effectiveness and efficiency. 2 out of the 3 reviewers using taxonomy found more defect types compared to 3 reviewers using checklist. 10-15% more defects have been found by reviewers using taxonomy. 2 out of the 3 reviewers using taxonomy are more productive (measuring in hours) compared to reviewers of checklist. Although the results are quite better than the student experiment but it is hard to claim that reviewers using taxonomy are more effective and efficient than the reviewers using checklist because of less subjects in number. The results of the post experiment questionnaire revealed that the taxonomy is easy to use and easy to understand but hard to remember while inspecting SRS than the checklist technique. Conclusions: Previously researchers created taxonomies for their own purpose or on industry demand. These taxonomies lack clear and understandable definitions. To overcome this problem, we built taxonomy with requirement defects which consists of definitions and examples. No claims are made based on student experiment because of insignificant values with respect to effectiveness and efficiency. Although the controlled industry experiment results showed that taxonomy performed slightly better than the checklist in efficiency i.e., in defect detection rate and effectiveness i.e., number of defect found. From this we can conclude that taxonomy helps guiding the reviewers to indentify defects from SRS but not quite much so it is recommended to perform a further study with practitioners in a large scale for effective results.skarimuddin@yahoo.com, hassanshah357@gmail.com
4
Steinegger, Thomas. "Defect Engineering". Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2009. http://nbn-resolving.de/urn:nbn:de:swb:105-8973489.
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Die Kenntnisse über die zur Passivierung führenden Wechselwirkungen des Verunreinigungselements Cu mit EL2 und EL6 wurden dahingehend erweitert, dass ein Gültigkeitsbereich für die Messungen zur Bestimmung der konzentrationsproportionalen Messgröße der Defekte festgelegt wurde. Der Defekt EL6 ist das die 0.8 eV-PL-Emission bedingende und die Ladungsträgerlebensdauer determinierende Rekombinationszentrum. Die Lebensdauer wird durch mindestens ein weiteres Zentrum beeinflusst. Die atomare Struktur des EL6 wurde mit AsGa VAs und die des weiteren Zentrums mit Asi bestimmt. Mittels Wärmebehandlung kann die Ladungsträgerlebensdauer gezielt beeinflusst werden. Bei der Bildung und Annihilation sowie der Verteilung der Defekte EL2, EL6, VGa und der As-Ausscheidungen besteht eine wechselseitige Korrelation. Sowohl strukturelle Defekte als auch die Inkorporation von Dotierelementen, deren Atomradien deutlich kleiner sind als Ga und As, stellen beeinflussende Faktoren dar. Das Defekt-Transformations-Modell erklärt die Bildung wachstumsfähiger Keime einer As-Ausscheidung durch EL2 bzw. EL6 mit den sich in der ersten Koordingationssphäre befindenden As-Atomen. Das Gitterrelaxations-Modell ermöglicht die Interpretation der katalytischen Wirkung des Dotierelements C. Die Umsetzung dieser Ergebnisse bedeutet die Anwendung des Defect Engineerings im SI-LEC-GaAs.
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Tran, Qui Can Cuong. "Empirical evaluation of defect identification indicators and defect prediction models". Thesis, Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-2553.
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Context. Quality assurance plays a vital role in the software engineering development process. It can be considered as one of the activities, to observe the execution of software project to validate if it behaves as expected or not. Quality assurance activities contribute to the success of software project by reducing the risks of software’s quality. Accurate planning, launching and controlling quality assurance activities on time can help to improve the performance of software projects. However, quality assurance activities also consume time and cost. One of the reasons is that they may not focus on the potential defect-prone area. In some of the latest and more accurate findings, researchers suggested that quality assurance activities should focus on the scope that may have the potential of defect; and defect predictors should be used to support them in order to save time and cost. Many available models recommend that the project’s history information be used as defect indicator to predict the number of defects in the software project. Objectives. In this thesis, new models are defined to predict the number of defects in the classes of single software systems. In addition, the new models are built based on the combination of product metrics as defect predictors. Methods. In the systematic review a number of article sources are used, including IEEE Xplore, ACM Digital Library, and Springer Link, in order to find the existing models related to the topic. In this context, open source projects are used as training sets to extract information about occurred defects and the system evolution. The training data is then used for the definition of the prediction models. Afterwards, the defined models are applied on other systems that provide test data, so information that was not used for the training of the models; to validate the accuracy and correctness of the models Results. Two models are built. One model is built to predict the number of defects of one class. One model is built to predict whether one class contains bug or no bug.. Conclusions. The proposed models are the combination of product metrics as defect predictors that can be used either to predict the number of defects of one class or to predict if one class contains bugs or no bugs. This combination of product metrics as defect predictors can improve the accuracy of defect prediction and quality assurance activities; by giving hints on potential defect prone classes before defect search activities will be performed. Therefore, it can improve the software development and quality assurance in terms of time and cost
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Hansen, Mark David. "Zero defect data". Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/13812.
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Rogers, Stuart Craig. "Defect Detection Microscopy". BYU ScholarsArchive, 2010. https://scholarsarchive.byu.edu/etd/2256.
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The automotive industry's search for stronger lighter materials has been hampered in its desire to make greater use of Magnesium alloys by their poor formability below 150°C. One current challenge is to identify the complex structure and deformation mechanisms at work and determine which of these are primary contributors to the nucleation of defects. Orientation Imaging Microscopy has been the most accessible tool for microstructural analysis over the past 15 years. However, using OIM to analyze defect nucleation sites requires prior knowledge of where the defects will occur because once the defects nucleate the majority of microstructural information is destroyed. This thesis seeks to contribute to the early detection of nucleation sites via three mechanisms: 1. Detection of cracks that have already nucleated, 2. Detection of surface topography changes that may indicate imminent nucleation and 3. Beam control strategies for efficiently finding areas of interest in a scan. Successive in-situ OIM scans of a consistent sample region while strain is increased, while using the three techniques developed in this thesis, will be employed in future work to provide a powerful defect analysis tool. By analyzing retrieved EBSD patterns we are able to locate defect / crack sites via shadowing on the EBSD patterns. Furthermore, topographical features (and potentially regions of surface roughening) can be detected via changes in intensity metrics and image quality. Topographical gradients are currently only detectable in line with the beam incidence. It is therefore suggested that the tensile specimens to be examined are orientated such that the resulting shear bands occur preferentially to this direction. The ability to refine the scan around these areas of interest has been demonstrated via an off-line adaptive scan routine that is implemented via the custom scan tool. A first attempt at a defect detection framework has been outlined and coded into MATLAB. These tools offer a first step to accessing the information about defect nucleation that researchers are currently seeking.
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Chroneos, Alexander. "Defect processes in germanium". Thesis, Imperial College London, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.443837.
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Huang, H.-C. "Defect-free shell elements". Thesis, Swansea University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378091.
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Hendren, Stuart. "Extra special defect groups". Thesis, University of Birmingham, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.403603.
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Ye, Xin. "Automated Software Defect Localization". Ohio University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1462374079.
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Zucca, Matthew. "Defect At Manitoulin Permaculture". Thesis, Université d'Ottawa / University of Ottawa, 2019. http://hdl.handle.net/10393/39827.
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The purpose of this research was to describe technopolitics on a permaculture farm. The literature on technology and technopolitics is beginning to take shape around a series of unanswered questions regarding the role and potential of objects in social life. Using an actor-network theory framework and relying on Callon's (1984) sociology of translation and its principles, I identified the concept of defect and tracked how it was mobilized at Manitoulin Permaculture through participant observation across two summers. The concept of defect incorporated both sociopolitical as well as technological factors. The makers at Manitoulin Permaculture made sense of their choice to defect to a new life at Manitoulin Permaculture. In addition, their technologies, both new and old, became defective, animating their community in new and unforeseen ways.
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Kirrander, Adam. "Quantum defect theory of molecules". Thesis, University of Oxford, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.422660.
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Ngan, Yuk-tung Henry, i 顏旭東. "Patterned Jacquard fabric defect detection". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2004. http://hub.hku.hk/bib/B30070880.
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Wang, Yutian. "Defect-induced ferromagnetism in SiC". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-164623.
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Defect-induced ferromagnetism is attracting intensive research interest. It not only challenges the traditional opinions about ferromagnetism, but also has some potential applications in spin-electronics. SiC is a new candidate for the investigation of defect-induced ferromagnetism after graphitic materials and oxides due to its high material purity and crystalline quality.
In this thesis, we made a comprehensive investigation on the structural and magnetic properties of ion implanted and neutron irradiated SiC sample. In combination with X-ray absorption spectroscopy and first-principles calculations, we try to understand the mechanism in a microscopic picture.
For neon or xenon ion implanted SiC, we identify a multi-magnetic-phase nature. The magnetization of SiC can be decomposed into paramagnetic, superparamagnetic and ferromagnetic contributions. The ferromagnetic contribution persists well above room temperature and exhibits a pronounced magnetic anisotropy. We qualitatively explain the magnetic properties as a result of the intrinsic clustering tendency of defects. By combining X-ray magnetic circular dichroism and first-principles calculations, we clarify that p electrons of the nearest-neighbor carbon atoms around divacancies are mainly responsible for the long-range ferromagnetic coupling. Thus, we provide a direct correlation between the collective magnetic phenomena and the specific electrons/orbitals.
With the aim to verify if the defect-induced magnetization can be increased by orders of magnitude, i.e., if a sample containing defects through its bulk volume can persist ferromagnetic coupling, we applied neutron irradiation to introduce defects into SiC. Besides a weak ferromagnetic contribution, we observe a strong paramagnetism, scaling up with the neutron fluence. The ferromagnetic contribution induced by neutron irradiation only occurs in a narrow fluence window or after annealing. It seems non-realistic to make the bulk specimens ferromagnetic by introducing defects. Instead, we speculate that defect-induced ferromagnetism rather locally appears in particular regions, like surface/interface/grain boundaries. A comparable investigation on neutron irradiated graphite supports the same conclusion.
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Sokol, Alexey Abramovich. "Defect structures in zeolite crystals". Thesis, University College London (University of London), 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326272.
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Vuong, Amanda. "Nanocarbon : defect architectures and properties". Thesis, University of Surrey, 2017. http://epubs.surrey.ac.uk/845194/.
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The allotropes of carbon make its solid phases amongst the most diverse of any element. It can occur naturally as graphite and diamond, which have very different properties that make them suitable for a wide range of technological and commercial purposes. Recent developments in synthetic carbon include Highly Oriented Pyrolytic Graphite (HOPG) and nano-carbons, such as fullerenes, nanotubes and graphene. The main industrial application of bulk graphite is as an electrode material in steel production, but in purified nuclear graphite form, it is also used as a moderator in Advanced Gas-cooled Reactors across the United Kingdom. Both graphene and graphite are damaged over time when subjected to bombardment by electrons, neutrons or ions, and these have a wide range of effects on their physical and electrical properties, depending on the radiation flux and temperature. This research focuses on intrinsic defects in graphene and dimensional change in nuclear graphite. The method used here is computational chemistry, which complements physical experiments. Techniques used comprise of density functional theory (DFT) and molecular dynamics (MD), which are discussed in chapter 2 and chapter 3, respectively. The succeeding chapters describe the results of simulations performed to model defects in graphene and graphite. Chapter 4 presents the results of ab initio DFT calculations performed to investigate vacancy complexes that are formed in AA stacked bilayer graphene. In AB stacking, carbon atoms surrounding the lattice vacancies can form interlayer structures with sp2 bonding that are lower in energy compared to in-plane reconstructions. From the investigation of AA stacking, sp2 interlayer bonding of adjacent multivacancy defects in registry creates a type of stable sp2 bonded wormhole between the layers. Also, a new class of mezzanine structure characterised by sp3 interlayer bonding, resembling a prismatic vacancy loop has also been identified. The mezzanine, which is a V6 hexavacancy variant, where six sp3 carbon atoms sit midway between two carbon layers and bond to both, is substantially more stable than any other vacancy aggregate in AA stacked layers. Chapter 5 presents the results of ab initio DFT calculations performed to investigate the wormhole and mezzanine defect that were identified in chapter 4 and the ramp defect discovered by Trevethan et al. DFT calculations were performed on these defects in twisted bilayer graphene. From the investigation of vacancy complexes in twisted bilayer graphene, it is found that vacancy complexes are unstable in the twisted region and are more favourable in formation energy when the stacking arrangement is close to AA or AB stacking. It has also been discovered that the ramp defect is more stable in the twisted bilayer graphene compared to the mezzanine defect. Chapter 6 presents the results of ab initio DFT calculations performed to investigate a form of extending defect, prismatic edge dislocation. Suarez-Martinez et al.’s research suggest the armchair core is disconnected from any other layer, whilst the zigzag core is connected. In the investigation here, the curvature of the mezzanine defect allows it to swing between the armchair, zigzag and Klein in the AA stacking. For the AB stacking configuration, the armchair and zigzag core are connected from any other layer. Chapter 7 present results of MD simulations using the adaptive intermolecular reactive empirical bond order (AIREBO) potential to investigate the dimensional change of graphite due to the formation of vacancies present in a single crystal. It has been identified that there is an expansion along the c-axis, whilst a contraction along the a- and b- axes due to the coalescence of vacancy forming in-plane and between the layers. The results here are in good agreement with experimental studies of low temperature irradiation. The final chapter gives conclusions to this work.
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Phull, Harpinder Singh. "Investigation into Turbocharger crazing defect". Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/5447/.
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A programme of research was undertaken to identify the mechanisms of formation of voids and defects in aluminium alloy C354 and C355 castings. The following aspects of the material processing were studied as independent and linked effects: casting technique and associated variables, hot isostatic pressing cycle parameters, and heat treatment cycle. Microstructure related driving forces for defect formation were quantified using differential scanning calorimetry and quantitative metallography and surface effects investigated using x-ray photoelectron spectroscopy. It was shown that by controlling key variables within casting, the component can become less sensitive to subsequent defect evolution from further thermal processing. Optimised parameters were defined and the mechanism of defect formation elucidated. A Non Destructive Testing (NDT) method for the detection of defects within C354 components was developed.
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Monmeyran, Corentin. "Point defect engineering in germanium". Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/108207.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2016.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 121-127).
In 1947, the first transistor was made of germanium, but soon silicon became the core material of computer chips because of its processability. However, as the typical dimensions of transistors are getting closer to the atomic size, the traditional approach of scaling down transistors to improve performance is reaching its limits, and other elements need to be used in conjunction with silicon. Germanium is one of the key materials to empower silicon based devices because it possesses electronic and optoelectronic properties complementary to those of silicon, among them higher carrier mobilities and a direct band gap (G-valley) at 1.55 [mu]m (the telecom C-band, therefore adding new capabilities to silicon integrated microphotonics). Furthermore, good quality Ge layers can be grown epitaxially on a Si substrate, allowing a monolithic integration of devices. However, compared to silicon, little is known about the point defects in germanium. The goal of the present doctoral work is to remedy this gap. To this end, we have used radiation (gamma rays, alpha particles, and neutrons) to controllably introduce point defects in crystalline germanium, which were then characterized by Deep-Level Transient Spectroscopy (DLTS), a technique that allows the determination of the activation energy, capture cross-section, and concentration of the said defects. By studying their electronic properties, annealing kinetics, and introduction rates, we were able to separate vacancy-containing from interstitial-containing defects and gain insight on their physical nature and formation process. We especially identified a di-interstitial defect and a tri-interstitial defect. In addition, we proved that in the case of alpha particles and neutron irradiation, the fact that defects are generated in a collision cascade influences their carrier capture rates and annealing behaviors. We have also characterized the impact of radiation on commercial germanium-on-silicon photodetectors, and showed that point defects associate with dislocations in epitaxial Ge-on-Si layers. Finally, we have investigated the passivation of midgap states by implanting germanium with fluorine, and showed how the interaction between the halogen element, the amorphous/crystalline interface during the solid phase epitaxy, and the implantation damage is key in obtaining a high performance material
by Corentin Monmeyran.
Ph. D.
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Ginder, John Matthew. "Electronic defect states in polyaniline". The Ohio State University, 1988. http://rave.ohiolink.edu/etdc/view?acc_num=osu1343059710.
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Flynn, Kevin Joseph. "Defect analysis using resonant ultrasound spectroscopy". [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-2348.
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Ng, Nga-yi Ada. "Defect detection in semiconductor die images". Click to view the E-thesis via HKUTO, 2005. http://sunzi.lib.hku.hk/hkuto/record/B32040799.
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Portnoy, William. "Distributable defect localization using Markov models /". Thesis, Connect to this title online; UW restricted, 2005. http://hdl.handle.net/1773/6883.
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Linden, Matthew D. "The haemostatic defect of cardiopulmonary bypass". University of Western Australia. School of Surgery and Pathology, 2003. http://theses.library.uwa.edu.au/adt-WU2006.0009.
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[Truncated abstract] Cardiac surgery involving cardiopulmonary bypass is a complex procedure that results in significant changes to blood coagulation, fibrinolytic biochemistry, platelet number and function, and the vasculature. These are due to pharmacological agents which are administered, haemodilution and contact of the blood with artificial surfaces. Consequently there are significant risks of thrombosis and haemorrhage associated with this procedure. The research presented in this thesis utilises in vitro, in vivo, and a novel ex vivo model to investigate the nature of the haemostatic defect induced by cardiopulmonary bypass. The components studied include the drugs heparin, protamine sulphate, and aprotinin, different types of bypass circuitry (including heparin bonded circuits) and procedures such as acute normovolaemic haemodilution. Patient variables, such as Factor V Leiden, are also studied. Each of these components is assessed for the effects on a number of laboratory measures of haemostasis including activated partial thromboplastin time, prothrombin time, activated protein C ratio, antithrombin concentration, heparin concentration, thrombin-antithrombin complex formation, prothrombin fragment 1+2 formation, markers of platelet surface activation and secretion, activated clotting time, haemoglobin concentration and coagulation factor assays.
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Thetford, Roger. "Theory of defect interactions in metals". Thesis, University of Oxford, 1989. http://ora.ox.ac.uk/objects/uuid:f6a8f36e-4d17-4834-a4b5-5ce2de9aab11.
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The static relaxation program DEVIL has been updated to use N-body Finnis-Sinclair potentials. Initial calculations of self-interstitial and monovacancy formation energies confirm that the modified program is working correctly. An extra repulsive pair potential (constructed to leave the original fitting unaltered) overcomes some deficiencies in the published Finnis-Sinclair potentials. The modified potentials are used to calculate interstitial energies and relaxations in the b.c.c. transition metals vanadium, niobium, tantalum, molybdenum and tungsten. Further adaptation enables DEVIL to model dislocations running parallel to any lattice vector. Periodic boundary conditions are applied in the direction of the dislocation line, giving an infinite straight dislocation. The energies per unit length of two different dislocations are compared with experiment. A study of migration of point defects in the perfect lattice provides information on the mobility of interstitials and vacancies. The possible reorientation of split dumbbell interstitials in a migration step comes under scrutiny. The total energy needed to form and migrate an interstitial is compared with that required for a vacancy. The interaction between point defects and dislocations is studied in detail. Binding energies for both sclf-intcrstitials and monovacancies at edge dislocations are calculated for the five metals mentioned above. Formation energies of the point defects in the neighbourhood of the edge dislocation are calculated for niobium, and the extent of the regions from which the defects are spontaneously absorbed are found. For split dumbbell interstilials, the size and shape of the absorption region depends on the orientation of the dumbbell. Migration of both interstitials and vacancies into the absorption zone is studied; the presence of the dislocation has a particularly dramatic effect on vacancy migration. The results on absorption zones are related to the dislocation sink strengths vital in radiation damage theory.
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Ng, Nga-yi Ada, i 伍雅怡. "Defect detection in semiconductor die images". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B32040799.
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Wong, Boon Kwei. "Automatic surface defect recognition and classification". Thesis, University of Sunderland, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283762.
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Hawtin, Benjamin Charles. "Defect criticality of carbon fibre composites". Thesis, University of Bath, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425875.
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Zhang, Wei Dong. "Defect generation and characterization in MOSFETs". Thesis, Liverpool John Moores University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275794.
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Rowell, D. K. "Point defect calculations in ionic crystals". Thesis, University of Reading, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370129.
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Wilson, Raymond A. "Towards a zero defect welding system". Thesis, University of Liverpool, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321249.
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Howard, Neil John. "Defect-tolerant Field-Programmable Gate Arrays". Thesis, University of York, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359290.
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Xie, Xianghua. "Defect detection in random colour textures". Thesis, University of Bristol, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425096.
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Tailor, Mitul. "Automatic surface defect quantification in 3D". Thesis, Loughborough University, 2013. https://dspace.lboro.ac.uk/2134/14429.
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Three-dimensional (3D) non-contact optical methods for surface inspection are of significant interest to many industrial sectors. Many aspects of manufacturing processes have become fully automated resulting in high production volumes. However, this is not necessarily the case for surface defect inspection. Existing human visual analysis of surface defects is qualitative and subject to varying interpretation. Automated 3D non-contact analysis should provide a robust and systematic quantitative approach. However, different 3D optical measurement technologies use different physical principles, interact with surfaces and defects in diverse ways, leading to variation in measurement data. Instrument s native software processing of the data may be non-traceable in nature, leading to significant uncertainty about data quantisation. Sub-millimetric level surface defect artefacts have been created using Rockwell and Vickers hardness testing equipment on various substrates. Four different non-contact surface measurement instruments (Alicona InfiniteFocus G4, Zygo NewView 5000, GFM MikroCAD Lite and Heliotis H3) have been utilized to measure different defect artefacts. The four different 3D optical instruments are evaluated by calibrated step-height created using slipgauges and reference defect artefacts. The experimental results are compared to select the most suitable instrument capable of measuring surface defects in robust manner. This research has identified a need for an automatic tool to quantify surface defect and thus a mathematical solution has been implemented for automatic defect detection and quantification (depth, area and volume) in 3D. A simulated defect softgauge with a known geometry has been developed in order to verify the implemented algorithm and provide mathematical traceability. The implemented algorithm has been identified as a traceable, highly repeatable, and high speed solution to quantify surface defect in 3D. Various industrial components with suspicious features and solder joints on PCB are measured and quantified in order to demonstrate applicability.
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Lai, Liang Simon. "Defect correction methods for computational aeroacoustics". Thesis, University of Greenwich, 2013. http://gala.gre.ac.uk/11452/.
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The idea of Defect Correction Method (DCM) has been around for a long time. It can be used in a number of different ways and can be applied to solve various linear and non-linear problems. Most defect correction related methods were used in conjunction with discretisation methods and two-level multigrid methods. This thesis examines how various iterative methods, both for linear and nonlinear problems, may be built into a unified framework through the use of defect correction. The framework is extended to the area of Computational Aeroacoustics (CAA) where sound waves generated by the pressure fluctuations are typically several orders of magnitude smaller than the pressure variations in the main flow field that accounts for flow acceleration. A decomposition of variables is used to break down the components of a typical flow variable into (1) the mean flow, (2) flow perturbations or aerodynamic sources of sound, and (3) the acoustic perturbation. The framework as discussed in this thesis would incorporate such variable decomposition. The basic principle of DCM can be applied to recover the propagating acoustic perturbation through a coupling technique. This provides an excellent concept in the re-use of existing commercial CFD software based on the framework and in the retrieval of acoustic pressure. Numerical examples demonstrating the defect correction framework for a typical car sun-roof problem was examined with promising numerical results. To this end the complete process of coupling Reynolds average Navier-Stokes and the Helmholtz equation is also presented using the DCM framework. The DCM framework is also extended to handle higher order numerical methods for the numerical solutions of partial differential equations leading to an easy re-use of existing software approximating derivatives with a lower order discretisation. Numerical experiments were performed to demonstrate the capability of the DCM framework. It is also used to a simplified 2-D problems aiming at the understanding of Large Eddy Simulation (LES) and filtering techniques. To this end the framework of DCM leads to an efficient and robust software implementation for many CFD and aeroacoustic computation in a simple nutshell.
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Song, Keng Yew. "Surface defect detection on textured background". Thesis, University of Surrey, 1993. http://epubs.surrey.ac.uk/844113/.
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This thesis addresses the problem of defect detection on complex textural surfaces. In general, whether the texture to be inspected is regular or random, in image terms it is characterized by local variations in pixel grey level values. These normal variations render the problem of texture defect detection extremely difficult as defects are often manifested by grey level changes and their detection requires more than mere pixel comparisons. In the thesis, classical techniques on texture representation are studied and various existing texture defect detection algorithms are reviewed. Three novel algorithms have been developed to tackle the problem of defect detection on random or regular textures. The first two are devoted to the problem of crack detection and the third algorithm is devoted to the problem of detecting regional defects. For texture crack detection, a cojoint spatial and spatial frequency representation, that is, wigner distribution is proposed to model the inspected texture surface. A detailed analysis of the wigner distribution, its properties and the effect of windowing on its crack detection performance are carried out. Two postprocessing methods, ie, probabilistic relaxation labelling and linear filtering are incorporated into the crack detection algorithm to refine the results. The potential of the Wigner model has also been explored by modifying the crack detection algorithm so as to detect other types of defects. For real world applications, an efficient crack detection algorithm based on a new distribution is proposed. The algorithm is shown to produce comparable results but in much shorter time. For regional defect detection, a hybrid chromato-structural approach to colour texture representation is proposed where combined colour texture information is extracted from various chromatic classes associated with the inspected surface. In the approach, a unified defect detection framework which combines a new colour clustering scheme, morphological smoothing and blob analysis are used to capture the relevant combined colour texture information. With this framework, good defect detection results are obtained and presented in this thesis.
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Foster, Moira. "Defect Detection in Selective Laser Melting". DigitalCommons@CalPoly, 2018. https://digitalcommons.calpoly.edu/theses/1874.
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Additively manufactured parts produced using selective laser melting (SLM) are prone to defects created during the build process due to part shrinkage while cooling. Currently defects are found only after the part is removed from the printer. To determine whether cracks can be detected before a print is completed, this project developed print parameters to print a test coupon with inherent defects – warpage and cracking. Data recorded during the build was then characterized to determine when the defects occurred.
The test coupon was printed using two sets of print parameters developed to control the severity of warpage and cracking. The builds were monitored using an accelerometer recording at 12500 samples per second, an iphone recording audio at 48000 samples a second, and a camera taking a photo every build layer. Data was analyzed using image comparison, signal amplitude, Fourier Transform, and Wavelet Decomposition.
The developed print parameters reduced warpage in the part by better distributing heat throughout the build envelope. Reducing warpage enabled the lower portion of the part to be printed intact, preserving it to experience cracking later in the build. From physical evidence on the part as well as time stamps from the machine script, several high energy impulse events in the accelerometer data were determined to be when cracking occurred in the build. This project’s preliminary investigation of accelerometers to detect defects in selective laser melting will be used in future work to create machine learning algorithms that would control the machine in real time and address defects as they arise.
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Long, Stephen M. "Structure of defect states in polyaniline". The Ohio State University, 1995. http://rave.ohiolink.edu/etdc/view?acc_num=osu1343061764.
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Xiao, Xinhua. "Automated Defect Recognition in Digital Radiography". University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1439309683.
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Lotharukpong, Chalothorn. "Defect characterisation in multi-crystalline silicon". Thesis, University of Oxford, 2015. http://ora.ox.ac.uk/objects/uuid:a803fada-2296-41c3-9d96-864c186957a2.
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Electron beam induced current (EBIC) and atom probe tomography (APT) were used in this study to determine electrical activities and impurity compositions at extended defects in multicrystalline silicon (mc-Si) samples. The results provide, for the first time, information regarding the chemical species present at defects whose electrical activity has previously been measured. A new APT specimen fabrication process was developed with the ability to select a specific defect for APT analysis. Development of the APT specimen fabrication process proceeded by first selecting and optimising the preferential etching for nano-scale defect delineation. Three etchants were evaluated, namely Secco, Sirtl and Dash, from which the Secco etch was selected. Three parameters were optimised to produce etch pits with geometries that meet the requirements imposed by APT specimen fabrication methods. The optimum parameters were 0.05M potassium dichromate concentration, 20°C etch temperature, and 30sec etch time. In the second stage, marking techniques were developed in order for the defects to be located throughout the APT specimen fabrication process. However, it became apparent that the conventional APT specimen fabrication method could not be used to fabricate APT specimens containing selected defects in a mc-Si sample. This led to the development of a novel APT specimen fabrication approach which allowed APT specimens to be fabricated, reproducibly, containing grain boundaries and isolated dislocations. In order to evaluate accurately iron contamination in mc-Si, four atom probe parameters were optimised to maximise detection sensitivity: the evaporation rate, the laser beam energy, the pulse repetition rate and the specimen temperature. The optimisation process can be divided in to two parts. In the first part, a matrix of pre-sharpened single-crystal silicon specimens was subjected to a variety of experimental parameters. The optimised parameters were determined to be 0.3% evaporation rate, 0.5nJ beam energy, 160kHz repetition rate and 55K specimen temperature. The second part was to determine the iron detection efficiency –the percentage of detected Fe ions that can be correctly identified as Fe– and sensitivity using these parameters to analyse a specially prepared iron calibration specimen. The values were determined to be a detection efficiency of about 35% and sensitivity of 54ppm or 2.70x1018 atom/cm3. The APT specimen fabrication process and the optimised APT analysis parameters were used to analyse four extended defects in mc-Si samples subjected to three different processing conditions, namely gold-contaminated, as-grown and phosphorus diffusion gettering (PDG). The important aspects of the analysis are listed below: • Gold was not detected at the grain boundary and its associated dislocations in the gold-contaminated specimen. The binding enthalpy of gold to such defects is thus less than 0.63eV. • Iron was not detected in any specimen. • Copper was observed at the grain boundary in the as-grown specimen in the form of individual atoms as well as clusters with diameters ranging between 4nm and 9nm. The electrical activity of the grain boundary was about 58%. • Nickel and carbon were detected at the grain boundary in the post-PDG specimen with the former having platelet structures with diameters and thicknesses ranging between 4nm-7nm and 2nm-4nm, respectively. The recombination strength of the defect was about 22%. • Two nickel clusters were found at the isolated dislocation in the post-PDG specimen. The clusters were spherical with an average diameter of 10nm. The distance between the two clusters was 35nm. The recombination strength of the defect was about 4%.
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Wells, George Henry. "Growth and defect formation in graphene". Thesis, Durham University, 2016. http://etheses.dur.ac.uk/11616/.
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In this work, few-layer graphene (FLG) was grown from SiC(0001) with temperature, growth time and cooling rate as variables. Samples were characterised by Scanning Tunnelling Microscopy (STM), Low Energy Electron Diraction (LEED), Auger Electron Spectroscopy (AES) and Raman Spectroscopy (RS) to determine graphene quality. The information obtained from these techniques was then used to determine optimal conditions for growing graphene from SiC(0001). Contamination on graphene lms is also discussed and a facile method for the removal of large scale metal contaminant layers from the surface is described. To study adhesion of FLG to a substrate, a continuum energy model was developed to obtain the adhesion energy via the measurement of pleat defects by STM. This model was applied to graphene grown from SiC(0001) and its adhesion energy was found to be signicantly larger than the those measured for graphene on other substrates. Variation of pleat defects on graphene grown from SiC(0001) with dierent growth parameters was also studied by STM. The factors that aect the dimensions and concentration of pleats were determined and discussed in relation to the quality of the lm. Further investigation was conducted on the stability of pleat defects under STM imaging, with the presence of contamination and defects found to have a signicant eect in reducing the dragging of pleats by the probe tip. A comparative study of the dynamics of extrinsic defects on FLG and graphite is also presented in this work. Samples were bombarded with 0.2 keV Ar+ ions, heated to dierent temperatures and studied with STM. The concentration, mobility, agglomeration and alignment of defects was examined and mechanisms suggested for the behaviour observed. The Local Density of States (LDOS) at defect sites of both graphite and FLG were studied by Scanning Tunnelling Spectroscopy (STS) to determine if signicant dierences in electronic structure due to defects were observed between the two systems. Preliminary experiments to optimise the growth of graphene on Cu substrates by \hot-wall" and \cold-wall" methods have been performed, to determine whether cold-wall growth presents a viable alternative to hot-wall for the production of high quality graphene. Graphene was grown by both methods using dierent growth periods to determine the optimal growth time for each method. The use of evaporated Cu on SiO2 as growth substrates is also discussed. Samples produced by both methods were studied by Scanning Electron Microscopy (SEM) to determine their quality. Electron Back-Scatter Diraction (EBSD) measurements were also performed on samples produced by both methods to determine the extent to which Cu grain orientation aects the growth of graphene.
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Fox, Matthew William. "Thermography approaches for building defect detection". Thesis, University of Plymouth, 2016. http://hdl.handle.net/10026.1/4304.
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Thermography is one technology, which can be used to detect thermally significant defects in buildings and is traditionally performed using a walk-through methodology. Yet because of limitations such as transient climatic changes, there is a key performance gap between image capture and interpretation. There are however new methodologies currently available, which actively address some of these limitations. By better understanding alternative methodologies, the performance gap can be reduced. This thesis contrasts three thermography methodologies (Walk-through, time-lapse and pass-by) to learn how they deal with limitations and address specific building defects and thermal performance issues. For each approach, practical methodologies were developed and used on laboratory experiments (hot plate) and real dwelling case studies. For the real building studies, 133 dwellings located in Devon and Cornwall (South West England) were studied; this sample represents a broad spectrum of construction types and building ages. Experiments testing these three methodologies found individual strengths and weaknesses for each approach. Whilst traditional thermography can detect multiple defects, characterisation is not always easy to achieve due to the effects of transient changes, which are largely ignored under this methodology. Time-lapse thermography allows the observation of transient changes from which more accurate assessment of defect behaviour can be gained. This is due to improved differentiation between environmental conditions (such as cloud cover and clear sky reflections), actual material thermal behaviour and construction defects. However time-lapse thermography is slow, complex and normally only observes one view. Walk-past thermography is a much faster methodology, inspecting up to 50 dwellings per survey session. Yet this methodology misses many potential defects due to low spatial resolutions, single (external only) elevation inspection and ignoring transient climate and material changes. The implications of these results for building surveying practice clearly indicate that for an improved defect characterisation of difficult to interpret defects such as moisture ingress, thermographers should make use of time-lapse thermography. A review of methodology practicalities illustrates how the need for improved characterisation can be balanced against time and resources when deciding upon the most suitable approach. In order to help building managers and thermographers to decide on the most suitable thermography approach, two strategies have been developed. The first combines different thermography methodologies into a phased inspection program, where spatial and temporal resolution increase with each subsequent thermography inspection. The second provides a decision-making framework to help select the most appropriate thermography methodology for a given scenario or defect.
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Pathak, Ajay Kumar. "Automated defect detection in textured materials". Thesis, Hong Kong : University of Hong Kong, 2001. http://sunzi.lib.hku.hk/hkuto/record.jsp?B23295168.
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"Defects and Defect Clusters in Compound Semiconductors". Doctoral diss., 2020. http://hdl.handle.net/2286/R.I.57438.
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abstract: Extended crystal defects often play a critical role in determining semiconductor device performance. This dissertation describes the application of transmission electron microscopy (TEM) and aberration-corrected scanning TEM (AC-STEM) to study defect clusters and the atomic-scale structure of defects in compound semiconductors.
An extensive effort was made to identify specific locations of crystal defects in epitaxial CdTe that might contribute to degraded light-conversion efficiency. Electroluminescence (EL) mapping and the creation of surface etch pits through chemical treatment were combined in attempts to identify specific structural defects for subsequent TEM examination. Observations of these specimens revealed only surface etch pits, without any visible indication of extended defects near their base. While chemical etch pits could be helpful for precisely locating extended defects that intersect with the treated surface, this study concluded that surface roughness surrounding etch pits would likely mitigate against their usefulness.
Defect locations in GaAs solar-cell devices were identified using combinations of EL, photoluminescence, and Raman scattering, and then studied more closely using TEM. Observations showed that device degradation was invariably associated with a cluster of extended defects, rather than a single defect, as previously assumed. AC-STEM observations revealed that individual defects within each cluster consisted primarily of intrinsic stacking faults terminated by 30° and 90° partial dislocations, although other defect structures were also identified. Lomer dislocations were identified near locations where two lines of strain contrast intersected in a large cluster, and a comparatively shallow cluster, largely constrained to the GaAs emitter layer, contained 60° perfect dislocations associated with localized strain contrast.
In another study, misfit dislocations at II-VI/III-V heterovalent interfaces were investigated and characterized using AC-STEM. Misfit strain at ZnTe/GaAs interfaces, which have relatively high lattice mismatch (7.38%), was relieved primarily through Lomer dislocations, while ZnTe/InP interfaces, with only 3.85% lattice mismatch, were relaxed by a mixture of 60° perfect dislocations, 30° partial dislocations, and Lomer dislocations. These results were consistent with the previous findings that misfit strain was relaxed primarily through 60° perfect dislocations that had either dissociated into partial dislocations or interacted to form Lomer dislocations as the amount of misfit strain increased.Dissertation/Thesis
Doctoral Dissertation Physics 2020
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Han-Chia, Cheng. "Layout-Based Defect-Driven Diagnosis for Intra-Cell Bridging Defects". 2006. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0016-1303200709465952.
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Cheng, Han-Chia, i 鄭漢嘉. "Layout-Based Defect-Driven Diagnosis for Intra-Cell Bridging Defects". Thesis, 2006. http://ndltd.ncl.edu.tw/handle/83096677301786868453.
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碩士國立清華大學
電機工程學系
95
In this thesis we provide a link between gate-level diagnosis and defect-based diagnosis to pinpoint the exact physical locations of the defects. Physical defects are converted into equivalent sub-circuits at logic domain based on a butterfly structure. Diagnostic test pattern generation is formulated as a stuck-at fault detection problem that can be piggybacked on SAT solver. Experimental results indicate that we can reduce 86% possible defect locations and pinpoint the actual locations of the defects for ISCAS85 benchmark circuits. Once the cell defect library is constructed, the proposed method can be applied to any cell-based design without additional stress.
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Fu, Hsu-Cheng, i 傅旭正. "Integrated Circuit Yield Model with Defect Source and Defect Clustering". Thesis, 1999. http://ndltd.ncl.edu.tw/handle/99281842382907924574.
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碩士國立交通大學
工業工程與管理系
87
For the integrated circuits (IC) manufacturer, the yield of each wafer is a key index to evaluate the profit. Therefore, yield management has been developed to promote the yield quickly and effectively. One of the most important tool in the yield management is the yield model. The conventional yield models considered only the correlation between the defect counts and the yield, consequently, the models can not predict the yield accurately. The prediction becomes worse when the wafer size increases and the defect clustering phenomenon becomes more apparent. Although the modified yield models have better prediction than that of the conventional yield model, the modified yield model are too complicated for engineers to use in practice. This study considers the effects of defect sources, defect counts and defect clustering on wafer and builds a forecasting yield model by using the neural networks. The proposed yield model not only can promote the prediction power efficiently, but also is very easy to implement. The proposed yield model is illustrated by a real case provided by an IC manufacturer in Taiwan to verify the effectiveness of the proposed yield model. Comparisons are also made among the conventional yield models, modified yield models and the proposed yield model.
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Jiang, Tian. "Personalized Defect Prediction". Thesis, 2013. http://hdl.handle.net/10012/7786.
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Academia and industry expend much effort to predict software defects. Researchers proposed many defect prediction algorithms and metrics. While previous defect prediction techniques often take the author of the code into consideration, none of these techniques build a separate prediction model for each developer. Different developers have different coding styles, commit frequencies, and experience levels, which would result in different defect patterns. When the defects of different developers are combined, such differences are obscured, hurting the prediction performance.
This thesis proposes two techniques to improve defect prediction performance: personalized defect prediction and confidence-based hybrid defect prediction. Personalized defect prediction builds a separate prediction model for each developer to predict software defects. Confidence-based hybrid defect prediction combines different models by picking the prediction from the model with the highest confidence. As a proof of concept, we apply the two techniques to classify defects at the file change level. We implement the state-of-the-art change classification as the baseline and compare with the personalized defect prediction approach. Confidence-based defect prediction combines these two models. We evaluate on six large and popular software projects written in C and Java—the Linux kernel, PostgreSQL, Xorg, Eclipse, Lucene and Jackrabbit.
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Costa, João Rui Machado. "Software Defect Classification". Master's thesis, 2016. https://hdl.handle.net/10216/96898.
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Costa, João Rui Machado. "Software Defect Classification". Dissertação, 2016. https://hdl.handle.net/10216/96898.
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