Dissertations / Theses: 'Defects'

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Bagués, Salguero Núria. "Atomic and electronic structure of self-organized defects in epitaxial films of functional perovskite-type oxides." Doctoral thesis, Universitat Autònoma de Barcelona, 2017. http://hdl.handle.net/10803/405668.

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Les capes fines epitaxials d’òxids funcionals tipus perovskita (ABO3) presenten mecanismes d’acoblament d’intercara i de relaxació del desajust governats per un joc complex de graus de llibertat químics, electrònics i estructurals. Aquests mecanismes poden acomodar defectes, tals com dislocacions de desajust i parets de macla, que presenten una gran tendència a l’auto-organització amb escales característiques de desenes de nanòmetres. L’estructura de la xarxa en el nucli d’aquests defectes és diferent de la major part del material, i per tant pot ser considerat com una nano-fase amb propietats físiques probablement diferents, portant a la formació de nano-estructures funcionals. La correlació entre l’estructura del defecte i la funcionalitat, juntament amb la capacitat d’aquests defectes per auto-organitzar-se, ofereix una oportunitat única per l’elaboració bottom-up de nano-dispositius d’òxids funcionals complexes. Aquesta Tesi es centra en la caracterització de la microestructura, l’intercara i els defectes auto-organitzats de capes epitaxials i nanoestructures funcionals de materials d’òxids mitjançant l’ús de Microscòpia Electrònica de Transmissió. Es presta especial atenció a l’estructura atòmica i electrònica de les intercares i defectes generats, tals com dislocacions, parets de macla i segregacions de fases, així com als camps de deformació i la seva relació amb les homogeneïtats químiques. En aquesta direcció, dos sistemes diferents compostos per manganites de Lantà són considerats: nanocompost de LaMnO3:MnOx crescut sobre substrats de (001)SrTiO3 i de (001)LaAlO3; i capes de La0.7Sr0.3MnO3 amb defectes auto-organitzats crescudes sobre substrats de (001)SrTiO3 i de (001)LaAlO3. Els materials estudiats en aquest treball poden ser considerats com capes nanoestructurades resultants de l’autoorganització de defectes que relaxen el desajust: nanoinclusions de MnOx (defectes de volum) en el LaMnO3; parets de macla entre dominis de macla (defectes planars) en La0.7Sr0.3MnO3/SrTiO3 i dislocacions de desajust (defectes lineals) en La0.7Sr0.3MnO3 /LaAlO3. En el nanocompost de LaMnO3:MnOx, s’analitza la formació regular de nanoinclusions d’òxid de manganès verticalment alienades dins d’una capa de LaMnO3 a través d’una caracterització microestructural. Aquestes anàlisis inclouen la determinació de la microestructura del LaMnO3 respecte el substrat conjuntament amb la identificació de la fase de l’òxid de manganès i d’una fase secundària, una capa rica en La a prop de l’intercara LaMnO3-SrTiO3. En el cas del La0.7Sr0.3MnO3/SrTiO3, es realitza una anàlisi detallada de les parets de macla i de les implicacions d’aquestes en les propietats funcionals. Els canvis locals en les propietats físiques i estructurals de les parets de macla permeten veure una capa amb macles com a una estructura auto-organitzada consistint en nano-lamines verticals de La0.7Sr0.3MnO3 fortament comprimides dins d’una matriu tensionada de La0.7Sr0.3MnO3. En el cas de les capes ultrafines de La0.7Sr0.3MnO3/LaAlO3, s’analitza el mecanisme de relaxament d’aquestes capes, les quals alleugen la tensió de desajust a través de la formació de dislocacions per sobre d’un gruix de crític de capa de 2.5nm. Es realitza un estudi detallat dels canvis estructurals, químics i electrònics associats amb les dislocacions, posant especial atenció a la influència dels camps de deformació en la composició química a la nanoescala. En aquesta direcció, s’observa una reorganització química a la regió del nucli de la dislocació, la qual té lloc per acomodar la deformació. També s’explora la dependència de l’organització de les dislocacions amb el gruix de les capes. Finalment, són analitzades les implicacions del camp de deformació de les dislocacions en la topografia i el transport elèctric a la superfície de les capes, demostrant que la naturalesa multi-escala de les dislocacions és de gran potencial per la creació de nanoestructures funcionals organitzades espontàniament en la superfície de capes fines d’òxids complexes. Els principals resultats i conclusions obtinguts en aquesta Tesis obren una nova perspectiva per al desenvolupament d’estructures funcionals auto-organitzades basades en defectes que relaxen tensions.
The epitaxial thin films of functional perovskite-type oxides (ABO3) present interfacial coupling and misfit relaxation mechanisms governed by a complex interplay of chemical, electronic and structural degrees of freedom. The relaxation mechanisms of strained films may accommodate defects, such as misfit dislocations or twin walls, which exhibit a strong tendency towards self-organization with characteristic length scales of tens of nanometres. The core lattice structure of these defects is different from the bulk of the material and thus may be considered as a nano-phase with likely different physical properties, leading to the formation of functional nanostructures. The correlation between defect structure and functionality, together with the capacity of these defects to self-organize, offers a unique opportunity for the bottom-up elaboration of functional complex oxides nanodevices. This thesis focuses on the characterization of the microstructure, interface and self-organized defects of epitaxial films and functional nanostructures of oxide materials by using advanced transmission electron microscopy. Special emphasis is put on the atomic and chemical structure of the interfaces and generated defects, such as dislocations, twin walls and phase segregations, as well as on the strain fields and their correlation with chemical heterogeneities. In this regard, two different systems composed of lanthanum manganites are considered: LaMnO3:MnOx nanocomposite grown on (001)SrTiO3 and on (001)LaAlO3 substrates; and La0.7Sr0.3MnO3 films with self-organized defects grown on (001)SrTiO3 and on (001)LaAlO3. The materials studied in this work may be regarded as nanostructured films resulting from the self-organization of misfit relieving defects as follows: nanoinclusions of a MnOx phase (volume defects) in LaMnO3; twin walls between twin domains (planar defects) in La0.7Sr0.3MnO3 on SrTiO3; and misfit dislocations (line defects) in La0.7Sr0.3MnO3 on LaAlO3. In the LaMnO3:MnOx nanocomposite, the formation of regular vertically aligned nanoinclusions of a manganese oxide (MnOx) embedded in an LaMnO3 film is analysed via microstructural characterization. This analysis includes the determination of the LaMnO3 matrix microstructure with respect to the substrate together with the identification of the manganese oxide phase and a secondary phase: a La-rich layer close to LaMnO3-substrate interface. In the case of La0.7Sr0.3MnO3 on (001)SrTiO3 substrates, a detailed analysis of twin walls and their implications on the functional properties is performed. Local changes in the physical and structural properties of the TWs lead to the view of a twinned film as a self-organized nanostructure consisting of vertical nano-sheets of strongly compressed La0.7Sr0.3MnO3 embedded in a matrix of tensile strained La0.7Sr0.3MnO3. In the case of La0.7Sr0.3MnO3 ultrathin films grown on (001)LaAlO3, the relaxation mechanism of this films is analysed. These films relieve the misfit strain by the formation of misfit dislocations above a critical film thickness of 2.5 nm. A detailed study of structural, chemical and electronic changes associated with the dislocation is also performed paying particular attention to the influence of strain fields on chemical composition at the nanoscale. A chemical reorganization occurs to accommodate the strain at the dislocations core region. The dependence of the degree of order of the dislocation pattern on film thickness is also explored. Finally, the implications of the dislocation strain field on surface topography and electrical transport are analysed, demonstrating that the multiscale nature of dislocations holds great promise for the creation of spontaneous surface ordered functional nanostructures in complex oxide thin films.The results and main conclusions obtained in this work open new perspectives for the development of functional self-organized nanostructures based on strain relieving defects.

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Pourmatin, Hossein. "Computational Multiscale Methods for Defects: 1. Line Defects in Liquid Crystals; 2. Electron Scattering in Defected Crystals." Research Showcase @ CMU, 2014. http://repository.cmu.edu/dissertations/458.

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In the first part of this thesis, we demonstrate theory and computations for finite-energy line defect solutions in an improvement of Ericksen-Leslie liquid crystal theory. Planar director fields are considered in two and three space dimensions, and we demonstrate straight as well as loop disclination solutions. The possibility of static balance of forces in the presence of a disclination and in the absence of ow and body forces is discussed. The work exploits an implicit conceptual connection between the Weingarten-Volterra characterization of possible jumps in certain potential fields and the Stokes-Helmholtz resolution of vector fields. The theoretical basis of our work is compared and contrasted with the theory of Volterra disclinations in elasticity. Physical reasoning precluding a gauge-invariant structure for the model is also presented. In part II of the thesis, the time-harmonic Schrodinger equation with periodic potential is considered. We derive the asymptotic form of the scattering wave function in the periodic space and investigate the possibility of its application as a DtN non-reflecting boundary condition. Moreover, we study the perfectly matched layer method for this problem and show that it is a reliable method, which converges rapidly to the exact solution, as the thickness of the absorbing layer increases. Moreover, we use the tight-binding method to numerically solve the Schrodinger equation for Graphene sheets, symmetry-adapted Carbon nanotubes and DNA molecules to demonstrate their electronic behavior in the presence of local defects. The results for Y-junction Carbon nanotubes depict very interesting properties and confirms the predictions for their application as new transistors.

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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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Горобченко, Неля Георгіївна, Неля Георгиевна Горобченко, Nelia Heorhiivna Horobchenko, and O. Byeda. "Birth defects." Thesis, Вид-во СумДУ, 2007. http://essuir.sumdu.edu.ua/handle/123456789/17636.

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Nowadays the cases of birth defects have increased. It is connected with the environment contamination and genetic factors. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/17636

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Gidby, Marcus. "Defects in ceria." Thesis, Linköping University, Department of Physics, Chemistry and Biology, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-17576.

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The solid oxide fuel cell (SOFC) technology has been under research since thelate 1950s, and most of the research has been on designs utilizing yttria stabilized zirconia (YSZ) as the electrolyte of choice. However, the SOFC technology has the major drawback of requiring high operation temperatures (up to 1000 degrees Celcius), so research of alternative materials have come into interest that would possibly require a lower working temperature without any significant loss of conductivity.One such material of interest for the electrolyte is compounds of ceriumdioxide (ceria). Ceria is well known for its ability to release oxygen by formingoxygen vacancies under oxygen-poor conditions, which increases its oxygen ionconductivity, and works at a lower temperature than the YSZ compounds whenproperly doped. Conversely, ceria is also able to absorb oxygen under oxygen-rich conditions, and those two abilities make it a very good material to use in catalytic converters for reduction of carbon monoxide and nitrogen oxide emission. The ability for the oxygen ions to easily relocate inbetween the different lattice sites is likely the key property of oxygen ion transportation in ceria. Also, in oxygen-rich conditions, the absorbed oxygen atom is assumed to join the structure at either the roomy octrahedral sites, or the vacant tetrahedral sites. Following that, the oxygen atom may relocate to other vacant locations, given it can overcome a possible potential barrier.

This thesis studies how those interstitial oxygen vacancies (defects) affect theenergy profile of ceria-based supercells by first principles calculations. The system is modeled within the density functional theory (DFT) with aid of (extended) local density approximation (LDA+U) using the software VASP. Furthermore, it is studied how those vacancies affect neighbouring oxygen atoms, and wether or not it is energetically benificial for the neighbouring atoms to readjust their positions closer or further away from the vacancy. The purpose of this thesis is to analyze wether or not it is theoretically possible that interstitial oxygen vacancies may cause neighbouring oxygen atoms to naturally relocate to the octahedral site in ceria, and how this affects the overall energy profile of the material.

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Abraham, Edward R. C. "Charged topological defects." Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259536.

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Jesurum, Caroline Esther 1969. "Coloring with defects." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/37006.

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Tang, Xun. "Diagnosis Of VLSI circuit defects: defects in scan chain and circuit logic." Diss., University of Iowa, 2010. https://ir.uiowa.edu/etd/894.

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Given a logic circuit that fails a test, diagnosis is the process of narrowing down the possible locations of the defects. Diagnosis to locate defects in VLSI circuits has become very important during the yield ramp up process, especially for 90 nm and below technologies where physical failure analysis machines become less successful due to reduced defect visibility by the smaller feature size and larger leakage currents. Successful defect isolation relies heavily on the guidance from fault diagnosis and will depend even more for the future technologies. To assist a designer or a failure analysis engineer, the diagnosis tool tries to identify the possible locations of the failure effectively and quickly. While many defects reside in the logic part of a chip, defects in scan chains have become more and more common recently as typically 30%-50% logic gates impact the operation of scan chains in a scan design. Logic diagnosis and scan chain diagnosis are the two main fields of diagnosis research. The quality of diagnosis directly impacts the time-to-market and the total product cost. Volume diagnosis with statistical learning is important to discover systematic defects. An accurate diagnosis tool is required to diagnose large numbers of failing devices to aid statistical yield learning. In this work, we propose techniques to improve diagnosis accuracy and resolution, techniques to improve run-time performance. We consider the problem of determining the location of defects in scan chains and logic. We investigate a method to improve the diagnosability of production compressed test patterns for multiple scan chain failures. Then a method to generate special diagnostic patterns for scan chain failures was proposed. The method tries to generate a complete test pattern set to pinpoint the exact faulty scan cell when flush tests tell which scan chain is faulty. Next we studied the problem of diagnosis of multiple faults in the logic of circuits. First we propose a method to diagnose multiple practical physical defects using simple logic fault models. At last we propose a method based on fault-tuple equivalence trees to further improve diagnosis quality.

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Wong, Hai Ming. "Developmental defects of enamel." Click to view the E-thesis via HKUTO, 2005. http://sunzi.lib.hku.hk/hkuto/record/B36269815.

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Sharp, Joanne. "Electron tomography of defects." Thesis, University of Cambridge, 2010. https://www.repository.cam.ac.uk/handle/1810/228638.

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Tomography of crystal defects in the electron microscope was first attempted in 2005 by the author and colleagues. This thesis further develops the technique, using a variety of samples and methods. Use of a more optimised, commercial tomographic reconstruction program on the original GaN weak beam dark-field (WBDF) tilt series gave a finer reconstruction with lower background, line width 10-20 nm. Four WBDF tilt series were obtained of a microcrack surrounded by dislocations in a sample of indented silicon, tilt axes parallel to g = 220, 220, 400 and 040. Moiré fringes in the defect impaired alignment and reconstruction. The effect on reconstruction of moiré fringe motion with tilt was simulated, resulting in an array of rods, not a flat plane. Dislocations in a TiAl alloy were reconstructed from WBDF images with no thickness contours, giving an exceptionally clear reconstruction. The effect of misalignment of the tilt axis with systematic row g(ng) was assessed by simulating tilt series with diffraction condition variation across the tilt range of Δn = 0, 1 and 2. Misalignment changed the inclination of the reconstructed dislocation with the foil surfaces, and elongated the reconstruction in the foil normal direction; this may explain elongation additional to the missing wedge effect in experiments. Tomography from annular dark-field (ADF) STEM dislocation images was also attempted. A tilt series was obtained from the GaN sample; the reconstructed dislocations had a core of bright intensity of comparable width to WBDF reconstructions, with a surrounding region of low intensity to 60 nm width. An ADF STEM reconstruction was obtained from the Si sample at the same microcrack as for WBDF; here automatic specimen drift correction in tomography acquisition software succeeded, a significant improvement. The microcrack surfaces in Si reconstructed as faint planes and dislocations were recovered as less fragmented lines than from the WBDF reconstruction. ADF STEM tomography was also carried out on the TiAl sample, using a detector inner angle (βin) that included the first order Bragg spots (in other series βin had been 4-6θ B). Extinctions occurred which were dependent on tilt; this produced only weak lines in the reconstruction. Bragg scattering in the ADF STEM image was estimated by summing simulated dark-field dislocation images from all Bragg beams at a zone axis; a double line was produced. It was hypothised that choosing the inner detector angle to omit these first Bragg peaks may preclude most dynamical image features. Additional thermal diffuse scattering (TDS) intensity due to dilatation around an edge dislocation was estimated and found to be insignificant. The Huang scattering cross section was estimated and found to be 9Å, ten times thinner than experimental ADF STEM dislocation images. The remaining intensity may be from changes to TDS from Bloch wave transitions at the dislocation; assessing this as a function of tilt is for further work. On simple assessment, only three possible axial channeling orientations were found over the tilt range for GaN; if this is typical, dechanneling contrast probably does not apply to defect tomography.

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Wong, Hai Ming, and 王海明. "Developmental defects of enamel." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B36269815.

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Durose, Ken. "Structural defects in CdTe." Thesis, Durham University, 1986. http://etheses.dur.ac.uk/7020/.

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This thesis is primarily concerned with the characterisation of the native defects present in CdTe crystals grown from the vapour phase using two different methods. The principal characterisation techniques used were TEM, SEM and etching/optical microscopy. Crystal defects in bulk CdTe are of great importance since this material is in demand as a substrate for the epitaxial growth of Cd(_x)Hg(_1-x)Te for use in large area infra-red imaging devices. Large single crystals grown using the 'Durham' technique invariably contain first order twin boundaries lying on {111} planes and these are of the 'ortho'-type. Twin boundaries on other planes were characterised using the coincidence site lattice models of twin boundaries in sphalerite which were developed during this work. First order lateral twin boundaries lying on {511}-{111}, {112}-{112}, {001}-{221} and {110}-{114} and second order twin boundaries lying on {111}-{115} {114}-{114} and {22l}-{22l} are discussed. Twinning in CdTe is thought to be due to post-growth stress rather than to a growth phenomenon. The dislocations which are present in crystals grown by the 'Durham’ method are predominantly concentrated into well-formed arrays which are sometimes associated with other crystal defects. These arrays were shown by EBIC studies to be electrically active and the average sub-grain dimension was found to be ~ 150 µm. It is thought that the arrays form as a result of dislocation polygonisation during the latter stages of growth. Precipitates, which were identified as being comprised of Te, are found in the bulk of the crystals although they are more often seen on twin boundaries. The relationship between boundary type and the density of precipitates is discussed. Sub-grain boundaries and precipitates were also examined in a small number of CdTe crystals which had been grown by a modified 'Piper-Polich' technique. The differences between the defects in this material and those in CdTe crystals grown by the 'Durham' method are fully explained in terms of the differences in the crystal growth conditions employed in the two techniques. Networks of dislocations in Cd(_0.95) Zn(_0.0 5) Te crystals grown by the 'Durham' technique were also investigated. A mechanochemical polishing machine which was developed during the course of this work and which is capable of producing high quality chemically polished surfaces is described. Also the use of chemical etchants to determine the crystallographic polarity of {111} oriented surfaces is clarified. Important features of this work include; the development of coincidence site lattice models of first order lateral and second order twin boundaries in the sphalerite structure and the thorough characterisation of these boundaries in as-grown CdTe crystals, and the comparison of the sub-grain boundaries and precipitates present in material grown from the vapour phase by two different techniques.

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Flack, Keith W. "Defects in lithium oxide." Thesis, University of Kent, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238119.

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Bindoff, L. A. "Defects of mitochondrial oxidations." Thesis, University of Newcastle Upon Tyne, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241373.

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Goodband, Michael James. "Perturbations about topological defects." Thesis, University of Sussex, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336276.

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Gregory, Ruth Ann Watson. "Topological defects in cosmology." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292897.

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Tapio, O. (Ossi). "Topological defects in cosmology." Master's thesis, University of Oulu, 2013. http://urn.fi/URN:NBN:fi:oulu-201302121030.

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In this dissertation I use one dimensional numerical simulations of classical scalar field theories to study density of topological defects. I devise and compare three methods of counting defects and run multiple simulations with varying parameters. Thesis begins with general description of evolution of the Universe and how topological defects might have influenced it. This is followed by general mathematical description of Kibble-Zurek Mechanism (the mechanism that causes topological defects to form). In the first chapter I go through of all textbook theory regarding one dimensional field and defects needed to understand the model I am simulating, the model itself being a 1+1 dimensional scalar field theory with O(N) symmetry. In the second chapter I derive three methods for finding defects in the simulation data. In the third chapter I describe the simulations themselves and go through the immediate results. In the fourth chapter I discuss the results of the simulations and suggest future simulations in order to study this subject further. In the Appendix are exact results of simulations, more detailed derivation of certain equations and the simulation code written in pseudo-code.

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Almossawi, Ali. "Investigating the architectural drivers of defects in open-source software systems : an empirical study of defects and reopened defects in GNOME." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/76566.

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Thesis (S.M. in Engineering and Management)--Massachusetts Institute of Technology, Engineering Systems Division, System Design and Management Program, 2012.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 64-67).
In major software systems that are developed by competent software engineers, the existence of defects in production is unlikely to be an acceptable situation. And yet, we find that in several such systems, defects remain a reality. Furthermore, the number of changes that are fixed only to then be reopened is noticeable. The implications of having defects in a system can be frustrating for all stakeholders, and when they require constant rework, they can lead to the problematic code-test-code-test mode of development. For management, such conditions can result in slipped schedules and an increase in development costs and for upper management and users, they can result in losing confidence in the product. This study looks at the drivers of defects in the mature open-source project GNOME and explores the relationship between the various drivers of these defects and software quality. Using defect-activity and source-code data for 32 systems over a period of eight years, the work presents a multiple regression model capable of explaining 16.2% of defects and a logistic regression model capable of explaining between 13.6% and 18.1% of reopened defects. The study also shows that although defects in general and reopened defects appear to move together, defects in general correlate with a measure of complexity that captures how components connect to each other whereas reopened defects correlate with a measure that captures the inner complexities of components, thereby suggesting that different types of defects are correlated with different forms of complexity.
by Ali Almossawi.
S.M.in Engineering and Management

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Paudyal, Anju. "Genetic, cellular and molecular defects in mouse mutants with severe neural tube defects." Thesis, Open University, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.530492.

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Neural tube defects are one of the most common birth defects. This thesis includes genetic, molecular and cellular analysis of three mouse mutants with neural tube defects. chuzhoi was identified from an ENU G3 screen and exhibits craniorachischisis through failure to initiate neural tube closure. In this thesis, I show that chuzhoi carries a point mutation affecting a splice-site in the Ptk7 gene, leading to addition of three extra amino acids in the protein. Through phenotypic analysis I show that chuzhoi has a wider midline and a smaller length to width ratio, suggesting a defect in convergent extension. Previous work has shown that the Planar Cell Polarity (PCP) signalling pathway is required for the initiation of neural tube closure. Through genetic crosses between chuzhoi and mutants of PCP signalling, I show that Ptk7 can influence the PCP pathway without being a direct component of the pathway. Carrying a mutation in Scribble, Circletail is another mutant displaying craniorachischisis. Scribble in Drosophila is required for the establishment of apical-basal polarity and to control the rate of cell proliferation. I show that mouse Scribble is not required for the establishment of apical-basal polarity nor to control proliferation, during neural tube closure. Previous work in zebrafish has shown that the axis elongation of an embryo requires PCP-dependent orientation of cell division. Here, I show that the orientation of cell division is random in mice during the shaping of the neural plate prior to the initiation of the neural tube closure. Mouse mutants of Tulp3 exhibit spina bifida and exencephaly. The molecular role of Tulp3 is largely unknown; however, domains present in the Tulp3 protein suggest that it may act as a transcription factor and/or be involved in protein-protein interactions. I provide evidence to suggest that Tulp3 is not likely to function as a transcription factor but may participate in many protein-protein interactions to deliver its role during mouse embryogenesis.

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Benjamin, Anne Laura. "Scanning Tunneling Microscopy Studies of Defects in Semiconductors: Inter-Defect and Host Interactions of Zn, Er, Mn, V, and Co Single-Atom Defects in GaAs(110)." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu15254254578788.

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Gatti, Fabio Garcia. "Uma contribuição para caracterização de níveis de energia de impurezas em AlxGa1-xAs tipo n." Universidade de São Paulo, 2000. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-05052010-153410/.

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Neste trabalho apresentamos medidas de fotocondutividade, decaimento da fotocondutividade persistente, resistência em função da temperatura em amostras de AlxGa1-xAs de gap direto e indireto, dopadas com Si. Comparamos as teorias de Brooks-Herring e Takimoto, ambas referentes ao espalhamento por impurezas ionizadas, e sua aplicabilidade para nosso material. Interpretamos a presença de um estado de energia intermediário nos cálculos da energia de ativação baseado nos resultados de concentração de elétrons livres em função da temperatura .como devido ao defeito D-. Nos resultados de decaimento da fotocondutividade persistente no intervalo de 80 - 100K, contamos com a contribuição do espalhamento por dipolos e propomos o par d+ - VAS- como os responsáveis pela formação destes dipolos e conseqüente melhoria do ajuste da simulação numérica.
In this work, we show results of photoconductivity, decay of persistent photoconductivity, resistance x temperature in Si doped direct and indirect bandgap AlxGa1-xAs. We compare Brooks-Herring and Takimoto theories, both in reference to ionized impurity scattering applied to our material. We interpret the intermediate state in our calculation of activation energy as a D- defect. In the numerical simulation of decay of persistent photoconductivity in the range 80-100 K, we propose the dipole pair d+ - VAS- responsible for the fitting improvement, when the dipole scattering is taken into account.

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Imel, Clint J. "Analysis of defects associated with leaks on skid steer loaders." Thesis, Kansas State University, 2008. http://hdl.handle.net/2097/4602.

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Master of Agribusiness
Department of Agricultural Economics
Ted C. Schroeder
The CNH Wichita Product Center has had a chronic leak problem with the Skid Steer Loaders. The objective of this project was to analyze the manufacturing plant leak data and make improvements to correct the issue. The objective is twofold: 1) to make process or design improvements on current products produced in the plant and 2) to make recommendations for future designs to prevent such leak issues from reoccurring. The manufacturing data had to be transformed into usable form and then it was analyzed mostly by utilizing Pareto Charts. The highest six problem leak points were chosen from the manufacturing data. Process changes were implemented on these particular leak joints and the results were analyzed using two proportions hypothesis tests. The process changes reduced the leak rate by an average percent reduction of 86 percent. The process changes implemented will also be applied to other similar joints, and results documented in the future. The future design recommendations made from the analyzed data included the increased use of o-ring face seal connections at certain locations and where possible, reducing the number of joints per machine.

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Forsblom, Mattias. "Atomistic simulation of lattice defects." Doctoral thesis, KTH, Physics, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-253.

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Mechanical properties of solids are governed by crystal imperfections. Computational materials science is largely concerned with the modelling of such defects, e.g. their formation, migration, and interaction energies. Atomistic simulations of systems containing lattice defects are inherently difficult because of the generally complicated geometrical structure of the defects, the need for large simulation cells, etc.

In this thesis, the role of lattice defects in the mechanism behind homogeneous melting is demonstrated. Also, a generic calculational scheme for studying atomic vibrations close to extended defects (applied to a dislocation) has been considered. Furthermore, heat capacities in the solid and liquid phases of aluminium have been calculated, as well as various thermophysical defect properties.

The work was carried out using classical atomistic simulations, mainly molecular dynamics, of aluminium and copper. The interatomic forces were modelled with effective interactions of the embedded-atom type.

The main results of this thesis are the following:

• The thermal fluctuation initiating melting is an aggregate typically with 6-7 interstitials and 3-4 vacancies.

• In the initial stage of melting, no signs of a shear modulus melting mechanism, or the presence of line-like defects (dislocations), can be seen.

• The typical time interval from when melting initiates to the time at which the liquid phase is fully developed is of the order of 1000τ, where the period τ corresponds to the maximum vibrational frequency in the solid.

• The solid-liquid boundary advances at a pace comparable to that of thermal transport by vibrating atoms in the crystal at high temperatures.

• The seemingly small anharmonic effect in the heat capacity of aluminium is caused by a partial cancellation of the low-order term linear in the temperature and anharmonic terms of higher order in the temperature.

• The core region of an edge dislocation in face-centred cubic aluminium has compressed and expanded regions. The excess volume associated with the dislocation core is small, about 6 percent of the atomic volume, as a result of a partial cancellation between the volume changes of the compressed and expanded regions.

• The compressed and expanded regions of the edge dislocation core give negative and positive contributions, respectively, to the excess vibrational entropy. The overall effect is a positive vibrational excess entropy of the dislocation core which is about 2kB per atomic repeat length along the dislocation core.

• The atomic vibrations near the dislocation core are modelled by considering an atomic cluster with about 500-1000 atoms containing the core of dislocation, embedded in a large discrete, but relaxed, lattice of about 23 000 atoms. An atomic region that is four atomic layers thick and about 18 atomic diameters long in the direction parallel to the Burgers vector, accounts for most of the excess entropy.

• The constant-pressure heat capacity of aluminium shows a minimum as a function of temperature in the liquid phase.

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Vranch, Richard Leslie. "Defects in irradiated MOS structures." Thesis, University of Cambridge, 1985. https://www.repository.cam.ac.uk/handle/1810/252810.

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The MOS device is the basic switching element in modern integrated circuits, and its reliability is vital to the successful operation of electronic equipment. Exposure to ionising radiation seriously affects MOS devices because of charge trapping and the formation of defects at the silicon-silicon dioxide interface. After an introductory chapter on MOS devices and radiation effects, experiments are described which give information about the nature of the interface defects and how they interact with each other. A particular device current Irec is measured whose magnitude depends on the recombination of charge carriers at the defects. The device is so minute, and the interface so thin, that the paramagnetic defects are too few in number to be detected and identified by conventional electron spin resonance methods. However, the static and microwave magnetic fields corresponding to spin resonance affect the recombination of carriers on the defects, and this causes a detectable change in Irec. This phenomenon is called Spin-Dependent Recombination (SOR), and a survey of SOR studies in semiconductors is given in Chapter 2 . The experimental results confirm a model which suggests that SOR occurs between adjacent trapped pairs. The results of the experiments are compared with ESR data on similar (but much larger) MOS structures. Spin-Dependent Generation of carriers is also investigated. The recombination is also found to be strongly dependent on a static magnetic field of zero to 5 milliTesla, even with no microwaves. Results of experiments on these "non-resonant" spin-dependent effects are presented with a model, relating them to the resonance experiments, which involves the recombination of singlet and triplet electron-hole pairs in a magnetic field. Electrical charge injection can affect MOS devices in similar ways to ionising radiation, and this is discussed in Chapter 6. Experimental results are presented which show that there are spin-dependent effects associated with defects produced by electrical charge injection. There are two Appendices, on slow radiation-induced instabilities in MOS structures, and on the size of the recombination current Irec�

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Forsblom, Mattias. "Atomistic simulations of lattice defects." Doctoral thesis, Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-253.

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26

Gratz, Kenneth R. "Biomechanics of articular cartilage defects." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2007. http://wwwlib.umi.com/cr/ucsd/fullcit?p3284116.

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Thesis (Ph. D.)--University of California, San Diego, 2007.
Title from first page of PDF file (viewed January 9, 2008). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references.

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27

Ferguson, Kyle Akira. "Meiotic defects in infertile men." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/1228.

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While the introduction of intracytoplasmic sperm injection (ICSI) has revolutionized the treatment of male infertility, concerns have been raised regarding the risk of chromosomal abnormalities in pregnancies derived from ICSI. Studies on sperm from infertile men have suggested that this population may produce higher rates of aneuploid sperm. Thus, we hypothesized that defects in early meiotic events may contribute to both male infertility and the production of aneuploid sperm. We used immunofluorescent techniques to observe the synapsis and recombination of chromosomes during meiosis, and fluorescent in-situ hybridization (FISH) to assess sperm aneuploidy. We analyzed testicular tissue from thirty-one men (10 fertile and 21 infertile men). We observed that ~36% (5/14) of men with impaired spermatogenesis displayed reduced genome-wide recombination. When all men were pooled, we observed an inverse correlation between the frequency of sex chromosome recombination and XY disomy in the sperm. We combined immunofluorescent and FISH techniques to study recombination patterns on chromosomes 13, 18 and 21 in fifteen men (5 fertile and 10 infertile men). Four of the infertile men displayed altered recombination distributions on at least one of the chromosome arms studied. Finally, we examined early meiotic events in two biopsies from an azoospermic t(8;13) carrier. While global recombination rates were not altered, recombination frequencies were reduced specifically on the rearranged chromosomes. Asynapsed quadrivalents were observed in 90% and 87% of pachytene nuclei from the first and second biopsies, respectively, and were frequently associated with the sex chromosomes. BRCA1 and γH2AX, two proteins implicated in meiotic sex chromosome inactivation, localized along asynapsed regions regardless of whether or not they were associated with the sex chromosomes, suggesting that regions of autosomal chromosomes that fail to synapse undergo transcriptional silencing in humans. In summary, we observed that a subset of infertile men display alterations in the number and position of meiotic crossovers, which may contribute to both infertility and an increased risk of sperm aneuploidy. The fidelity of synapsis is also a critical factor in determining the outcome of gametogenesis in humans, as the transcriptional inactivation of asynapsed regions may silence meiotic genes, leading to meiotic arrest and infertility.

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Gill, Alasdair James. "Field theory and topological defects." Thesis, Imperial College London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244675.

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Cartmill, Ian. "Builders' liability for latent defects." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302694.

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Fisher, Andrew James. "Theoretical studies of point defects." Thesis, University of Oxford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.252958.

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Talbot-Ponsonby, Daniel. "Paramagnetic defects in CVD diamonds." Thesis, University of Oxford, 1997. http://ora.ox.ac.uk/objects/uuid:d934e6d5-a7d5-409f-9849-8f019a9707b3.

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Paramagnetic defects in free standing polycrystalline diamond films made by chemical vapour deposition (CVD) have been studied using electron paramagnetic resonance (EPR), electron-nuclear double resonance (ENDOR) and infrared absorption. EPR experiments at a range of frequencies (1-35 GHz) confirm the ¹H hyperfine parameters for the recently identified H1 defect (Zhou et al., Phys. Rev. B, 54:7881 (1996)). In the samples studied here, H1 is always accompanied by another defect at g=2.0028(1). Saturation recovery measurements are consistent with two defects centred on g=2.0028. The spin-lattice relaxation rate of H1 is a factor of 10-100 times more rapid than the single substitutional nitrogen centre (N⁰_S), which is known to be incorporated into the bulk diamond. ¹H matrix ENDOR measurements indicate that the H1 centre is in an environment with hydrogen atoms 2-10 A distant from the centre. The near neighbour hydrogen identified by the EPR was not detected in the ENDOR experiments. The concentration of H1 correlates with the total integrated C-H stretch absorption in the samples studied here. All the evidence is consistent with H1 being located at hydrogen decorated grain boundaries (or in intergranular material) rather than in the bulk diamond. The affect of annealing the films in vacuo up to 1900 K has been studied. On annealing at 1700 K it was found that some of the hydrogen on internal grain boundaries became mobile but was not lost from the sample, and the intensity of the EPR absorption at g=2.0028 decreased. Annealing at 1900 K severely degraded the optical properties of the samples, and a new defect with g=2.0035(2) was created. Infrared measurements show that hydrogen is lost from most CVD diamond samples when annealed to 1900 K for four hours. An EPR imaging (EPRI) probe was designed and built. This comprised a 3-loop, 2-gap loop-gap resonator and a pair of anti-Helmholtz coils providing a magnetic field gradient ∂B_z/∂z. Using this probe the distribution of N⁰_S was measured in the growth direction of four CVD diamonds to a resolution of 20 μm. The distribution of N⁰_S is shown to be different to the distribution of defects with g=2.0028. Two-dimensional images of the spin density of N⁰_S in single crystal type Ib diamonds made by the high temperature and pressure (HTP) method have been generated, demonstrating a resolution of 100 μm. A two-dimensional image of the spin density of g=2.0028 defects in a CVD sample is compared to a photograph of the same sample, showing the correlation between the distribution of the defects with the distribution of non-diamond material in the sample. The distribution of the [N-N]⁺ defect in a natural diamond has been examined using ∂B_z/∂B_ϰ field gradient coils.

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32

Bonjour, Filipe. "Extended defects in curved spacetimes." Thesis, Durham University, 1999. http://etheses.dur.ac.uk/4966/.

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This Thesis is concerned with three particular aspects of extended cosmic strings and domain walls in cosmology: their dynamics, gravitation and interaction with a black hole. In Chapter 3, we study the dynamics of an abelian-Higgs cosmic string. We find its equations of motion from an effective action and compare, for three test trajectories, the resulting motion with that observed in the Nambu-Gotō approximation. We also present a general argument showing that the corrected motion of any string is generically antirigid. We pursue the investigation of the dynamics of topological defects in Chapter 5, where we find (from integrability conditions rather than an effective action) the effective equations governing the motion of a gravitating curved domain wall. In Chapter 4 we investigate the spacetime of a gravitating domain wall in a theory with a general potential V(ɸ). We show that, depending on the gravitational coupling e of the scalar ɸ, all nontrivial solutions fall into two categories interpretable as describing respectively domain wall and false vacuum-de Sitter solutions. Wall solutions cannot exist beyond a value (^4)(_3)ɛmax, and vacuum-de Sitter solutions are unstable to decaying into wall solutions below ɛmax at ɛmax we observe a phase transition between the two types of solution. We finally specialize for the Goldstone and sine-Gordon potentials. In Chapter 6 we consider a Nielsen-Olesen vortex whose axis passes through the centre of an extremal Reissner-Nordstr0m black hole. We examine in particular the existence of piercing and expelled solutions (where the string respectively does and does not penetrate the black hole's horizon) and determine that while thin strings penetrate the horizon — and therefore can be genuinely called hair — thick strings are expelled; the two kinds of solution are separated by a phase transition.

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Wray, Andrew M. "Topological defects and black holes." Thesis, University of Newcastle Upon Tyne, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.332341.

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Hagon, J. P. "Localised defects in SiOsub(2)." Thesis, University of Newcastle Upon Tyne, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356816.

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Cobden, David Henry. "Individual defects in mesoscopic transistors." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386908.

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Chen, Charn-Ying. "The contrast of planar defects." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.338141.

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Swinburne, Thomas. "Stochastic dynamics of crystal defects." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/24878.

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The state of a deformed crystal is highly heterogeneous, with plasticity localised into linear and point defects such as dislocations, vacancies and interstitial clusters. The motion of these defects dictate a crystal's mechanical behaviour, but defect dynamics are complicated and correlated by external applied stresses, internal elastic interactions and the fundamentally stochastic influence of thermal vibrations. This thesis is concerned with establishing a rigorous, modern theory of the stochastic and dissipative forces on crystal defects, which remain poorly understood despite their importance in any temperature dependent micro-structural process such as the ductile to brittle transition and irradiation damage. From novel molecular dynamics simulations we parametrise an efficient, stochastic and discrete dislocation model that allows access to experimental time and length scales. Simulated trajectories of thermally activated dislocation motion are in excellent agreement with those measured experimentally. Despite these successes in coarse graining, we find existing theories unable to explain stochastic defect dynamics. To resolve this, we define crystal defects through projection operators, without any recourse to elasticity. By rigorous dimensional reduction we derive explicit analytical forms for the stochastic forces acting on crystal defects, allowing new quantitative insight into the role of thermal fluctuations in crystal plasticity.

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Carpio, Marcos Edgar. "The defects of the law." THĒMIS-Revista de Derecho, 2015. http://repositorio.pucp.edu.pe/index/handle/123456789/107748.

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All legislative acts shall have continuity in time. However, sometimes these acts contain defects that cause their unconstitutionality and the subsequent expulsion from the legal order. The important question that arises is: When can a legislative act be declared unconstitutional? Whichare the defects that cause the expulsion of a law from the legal system?In this article, the author seeks to address these questions through a presentation of the legal defects that cause the invalidity of an act. The author pays special attention to the discussed legislative power excess defect, contrasting foreign case law with jurisprudence from the Peruvian Constitutional Court to determine if it is enough for an act to have this defect to be declared unconstitutional.
Los actos legislativos deben tener continuidad enel tiempo. Sin embargo, muchas veces estos actos contienen vicios que ocasionan su inconstitucionalidad y consecuente expulsión del ordenamientojurídico. La gran pregunta que surge entonces es: ¿Cuándo un acto legislativo puede ser declaradoinconstitucional? ¿Cuáles son los vicios que causanla expulsión de una ley del sistema normativo?En el presente artículo, el autor busca responder estas interrogantes mediante la presentación de los vicios de la ley que ocasionan la invalidez de ésta. El autor presta especial atención al discutido vicio de exceso de poder legislativo, contrastando jurisprudencia extranjera con aquella del Tribunal Constitucional peruano para determinar si basta que una ley tenga este vicio para que pueda ser declarada inconstitucional.

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Kramer, Kaitrin. "Mantle Dentin Defects in Odontohypophosphatasia." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1583925166125378.

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40

Whateley, Philip N. "Defects in steel investment castings." Thesis, Aston University, 1991. http://publications.aston.ac.uk/11879/.

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A general investigation was performed, in an industrial environment, of the major types of defect specific to investment castings in steel. As a result of this work three types of metallurgical defect were selected for further study. In the first of these, defects in austenitic stainless steel castings were found to result from deoxidation by-products. As a result of metallographic investigation and the statistical analysis of experimental data, evidence was found to support the hypothesis that the other two classes of defects - in martensite stainless and low alloy steels -both resulted from internal or grain boundary oxidation of the chromium alloy constituent This was often found to be followed by reaction between the metal oxides and the ceramic mould material. On the basis of this study, proposals are made for a more fundamental investigation of the mechanisms involved and interim suggestions are given for methods of ameliorating the effect in an industrial situation.

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41

Wang, Dong Carleton University Dissertation Engineering Mechanical and Aerospace. "Correcting topological defects of tessellations." Ottawa, 1995.

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42

Wang, Dong 1968 Carleton University Dissertation Engineering Mechanical and Aerospace. "Correcting topological defects of tessellations." Ottawa, 1995.

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43

Hwang, Bing-Fang. "Water chlorination and birth defects." Available to US Hopkins community, 2002. http://wwwlib.umi.com/dissertations/dlnow/3068171.

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44

Benedetti, Cesare. "Defects in thermosensitive colloidal crystals." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amslaurea.unibo.it/4322/.

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Poly-N-Isopropylacrylamide (PNIPAM) colloidal particles form crystal phases that show a thermosensitive behaviour and can be used as atomic model systems. This polymer has both hydrophilic and hydrophobic character and has interesting stimuli-responsive properties in aqueous solution, of which the most important is the temperature response. Above a certain temperature, called Lower Critical Solution Temperature (LCST), the system undergoes a volume phase transition (VPT). Above the LCST, the water is expelled from the polymer network and the swollen state at low temperature transforms into a shrunken state at high temperature. The thermoresponsive behaviour of PNIPAM can be influenced by pH and ionic strength, as well as by the presence of copolymers, such as acrylic acid. In a system formed both by particles of PNIPAM and PNIPAM doped with acrylic acid, one can control the size ratio of the two components by changing the temperature of the mixture, while keeping particle interactions relatively the same. It is therefore possible to obtain thermoresponsive colloidal crystal in which temperature changes induce defects whose formation processes and dynamics can be analysed in an optical microscope at a convenient spatial and temporal scale. The goal of this thesis project was to find the conditions in which such a system could be formed, by using characterization techniques such as Static Light Scattering, Dynamic Light Scattering and Confocal Laser Scanning Microscopy. Two PNIPAM-AAc systems were available, and after characterization it was possible to select a suitable one, on the basis of its low polydispersity and the lack of a VPT, regardless of the external conditions (system JPN_7). The synthesis of a PNIPAM system was attempted, with particles of dimensions matching the JPN_7 system and, unlike JPN_7, displaying a VPT, and one suitable candidate for the mixed system was finally found (system CB_5). The best conditions to obtain thermoresponsive crystal were selected, and the formation and healing of defects were investigated with CLSM temperature scans. The obtained results show that the approach is the correct one and that the present report could represent a useful start for future developments in defect analysis and defect dynamics studies.

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Meineri, Marco. "Defects in Conformal Field Theories." Doctoral thesis, Scuola Normale Superiore, 2016. http://hdl.handle.net/11384/85893.

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46

Doolittle, William Alan. "Fundamental understanding, characterization, passivation and gettering of electrically active defects in silicon." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/15710.

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Bergugnat, Jean-Baptiste. "Strain and lattice rotation fields of deformed polycrystals." Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/17899.

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Couto, César Francisco de Moura. "Predicting software defects with causality tests = Predizendo defeitos de software com testes de causalidade." Universidade Federal de Minas Gerais, 2013. http://hdl.handle.net/1843/ESBF-9GMMLN.

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Defect prediction is a central area of research in software engineering that aims to identify the components of a software system that are more likely to present defects. Despite the large investment in research aiming to identify an effective way to predict defects in software systems, there is still no widely used solution to this problem. Current defect prediction approaches present at least two main problems in the current defect prediction approaches. First, most approaches do not consider the idea of causality between software metrics and defects. More specifically, the studies performed to evaluate defect prediction techniques do not investigate in-depth whether the discovered relationships indicate cause-effect relations or whether they are statistical coincidences. The second problem concerns the output of the current defect prediction models. Typically, most indicate the number or the existence of defects in a component in the future. Clearly, the availability of this information is important to foster software quality. However, predicting defects as soon as they are introduced in the code is more useful to maintainers than simply signaling the future occurrences of defects. To tackle these questions, in this thesis we propose a defect prediction approach centered on more robust evidences towards causality between source code metrics (as predictors) and the occurrence of defects. More specifically, we rely on a statistical hypothesis test proposed by Clive Granger to evaluate whether past variations in source code metrics values can be used to forecast changes in time series of defects. The Granger Causality Test was originally proposed to evaluate causality between time series of economic data. Our approach triggers alarms whenever changes made to the source code of a target system are likely to present defects. We evaluated our approach in several life stages of four Java-based systems. We reached an average precision greater than 50% in three out of the four systems we evaluated. Moreover, by comparing our approach with baselines that are not based on causality tests, it achieved a better precision.
Predição de defeitos é uma área de pesquisa em engenharia de software que objetiva identificar os componentes de um sistema de software que são mais prováveis de apresentar defeitos. Apesar do grande investimento em pesquisa objetivando identificar uma maneira efetiva para predizer defeitos em sistemas de software, ainda não existe uma solução amplamente utilizada para este problema. As atuais abordagens para predição de defeitos apresentam pelo menos dois problemas principais. Primeiro, a maioria das abordagens não considera a idéia de causalidade entre métricas de software e defeitos. Mais especificamente, os estudos realizados para avaliar as técnicas de predição de defeitos não investigam em profundidade se as relações descobertas indicam relações de causa e efeito ou se são coincidências estatísticas. O segundo problema diz respeito a saída dos atuais modelos de predição de defeitos. Tipicamente, a maioria dos modelos indica o número ou a existência de defeitos em um componente no futuro. Claramente, a disponibilidade desta informação é importante para promover a qualidade de software. Entretanto, predizer defeitos logo que eles são introduzidos no código é mais útil para mantenedores que simplesmente sinalizar futuras ocorrências de defeitos. Para resolver estas questões, nós propomos uma abordagem para predição de defeitos centrada em evidências mais robustas no sentido de causalidade entre métricas de código fonte (como preditor) e a ocorrência de defeitos. Mais especificamente, nós usamos um teste de hipótese estatístico proposto por Clive Granger (Teste de Causalidade de Granger) para avaliar se variações passadas nos valores de métricas de código fonte podem ser usados para predizer mudanças em séries temporais de defeitos. Nossa abordagem ativa alarmes quando mudanças realizadas no código fonte de um sistema alvo são prováveis de produzir defeitos. Nós avaliamos nossa abordagem em várias fases da vida de quatro sistemas implementados em Java. Nós alcançamos um precisão média maior do que 50% em três dos quatro sistemas avaliados. Além disso, ao comparar nossa abordagem com abordagens que não são baseadas em testes de causalidade, nossa abordagem alcançou uma precisão melhor.

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BORGES, Damares Santos Silva. "Defeitos em matéria condensada: de twistons a skyrmions." Universidade Federal de Campina Grande, 2018. http://dspace.sti.ufcg.edu.br:8080/jspui/handle/riufcg/1577.

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Submitted by Maria Medeiros (maria.dilva1@ufcg.edu.br) on 2018-08-29T13:41:49Z No. of bitstreams: 1 DAMARES SANTOS SILVA BORGES - DISSERTAÇÃO (PPGF) 2018.pdf: 14903609 bytes, checksum: 19118754fe275415f701d012e1d4515e (MD5)
Made available in DSpace on 2018-08-29T13:41:49Z (GMT). No. of bitstreams: 1 DAMARES SANTOS SILVA BORGES - DISSERTAÇÃO (PPGF) 2018.pdf: 14903609 bytes, checksum: 19118754fe275415f701d012e1d4515e (MD5) Previous issue date: 2018-07-26
Capes
Os defeitos topológicos são caracterizados como soluções estáveis de equações de movimento em uma ou mais dimensões espaciais e desempenham papel importante na ciência não-linear. Neste trabalho de dissertação, damos ênfase a defeitos em (1+1) e (2+1) dimensões espaço-temporais. No primeiro caso, abordamos configurações conhecidas como twistons (soluções topológicas tipo kink) presentes em cristais de polietileno. Nessa primeira abordagem, revisitamos trabalhos anteriores e, a partir do método de extensão, construímos novas famílias de potenciais que descrevem bem sistemas desse tipo. Apresentamos soluções topológicas analíticas e que não possuem problemas de degenerescência infinita. No segundo caso, estudamos estruturas conhecidas como skyrmions com base na sua descrição em materiais magnéticos, em que são denotados como configurações da magnetização em nanoescala e topologicamente estáveis.Recorremos novamente ao método de extensão e apresentamos um potencial, função de dois campos escalares acoplados, a partir do qual conseguimos modelar essas estruturas magnéticas. Além disso, o novo modelo de dois campos tem soluções analíticas conhecidas, permitindo análises interessantes como a determinação de uma quantidade topológica conservada, estudo das diferentes configurações da magnetização e cálculo do raio médio de matéria.
Topological defects are characterized as stable equation of motion solutions in one or more spatial dimensions and play an important role in nonlinear science. In this study, space-time (1 + 1) and (2 + 1) dimension defects are emphasized. In the first case, configurations known as twistons (kink-like topological solutions) present in polyethylene crystals are assessed. In this first approach, previous works were reviewed and new families of potentials that adequately describe these types of systems were constructed from the extension method, presenting analytical topological solutions that do not display infinite degeneracy problems. In the second case, structures known as skyrmions were studied based on their description in magnetic materials,where they are denoted as topologically stable nanoscale magnetization configurations. The extension method was applied and a potential from which such magnetic structures can be modelled, function of two coupled scalar fields was presented. In addition, the new two-field model possesses known analytical solutions, allowing for interesting analyses, such as the determination of a conserved topological quantity, the study of the different magnetization configurations and calculation of mean matter radius.

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Klíma, Jakub. "Automatické vyhodnocování termovizních snímků fotovoltaických panelů." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2016. http://www.nusl.cz/ntk/nusl-242855.

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This thesis deals with diagnostics of photovoltaic panels especially with infrared diagnostics. There are described defects which we can examine using thermovision and also this thesis explains the cause of their formation. Practical part deals with the design of the program that automatically detects defects on infrared images.

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Dissertations / Theses on the topic 'Defects'

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