• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 344
  • 88
  • 60
  • 60
  • 28
  • 27
  • 21
  • 13
  • 12
  • 9
  • 4
  • 3
  • 3
  • 2
  • 2
  • Tagged with
  • 828
  • 123
  • 77
  • 72
  • 63
  • 55
  • 54
  • 54
  • 51
  • 51
  • 50
  • 47
  • 47
  • 47
  • 46
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
231

Interaction of oxygen and nitrogen impurities with dislocations in silicon single-crystals

Giannattasio, Armando January 2004 (has links)
An experimental technique based on the immobilisation of dislocations by segregation of impurity atoms to the dislocation core (dislocation locking) has been developed and used to investigate the critical conditions for slip occurrence in Czochralski-grown and nitrogen-doped floating-zone-grown silicon crystals. The accumulation of nitrogen and oxygen impurities along a dislocation and the resulting dislocation locking effect has been investigated in silicon samples subjected to different annealing conditions. In particular, the stress needed to unlock the dislocations after their decoration by impurities has been measured as a function of annealing duration and temperature. The approach used in this study has allowed the determination of new diffusivity data for oxygen and nitrogen in silicon in the technologically important range of temperatures 350-850°C. No other data covering such wide temperature range are available in the literature. In addition to transport properties, the binding energy of an impurity atom to a dislocation in silicon has been deduced from the experimental data in the case of oxygen and nitrogen impurities. A discussion in terms of the impurity species responsible for transport (monomers or dimers) and dislocation locking is also presented. The role of oxide precipitates in the generation of glide dislocation loops and the parameters affecting the occurrence of slip have been investigated in silicon samples containing precipitates of different sizes and different morphologies. The fundamental parameters deduced in this work have been used to develop a numerical model to investigate the effect of different heat treatments on the mechanical properties of silicon wafers containing a controlled distribution of impurities. This model has then been used to simulate real wafer processing conditions during device fabrication to show how they may be modified to increase dislocation locking. It is hoped that these results will have relevance to how wafers are processed in order to minimise or eliminate dislocation multiplication and consequent warpage.
232

Molecular Rydberg dynamics

Batchelor, Colin January 2003 (has links)
A simple theory relating the dynamics of electrons to the long-range properties of the molecular ionic core is developed for asymmetric top molecules in general and water in particular. It is combined with the molecular version of multichannel quantum defect theory developed by Fano and Jungen and applied to the resonance-enhanced multiphoton ionization spectra of Child and Glab (M. S. Child and W. G. Glab, J. Chem. Phys., 2001, 112, 3754-3765), the mass-analysed threshold ionization spectra of Dickinson et al. (H. Dickinson, S. R. Mackenzie and T. P. Softley, Phys. Chem. Chem. Phys., 2000, 2, 4669-4675) and the as-yet unpublished work of Glab on the photoelectron branching ratios of the nd and nf Rydberg lines of the water molecule. The effect of resonances between electronic and rotational motion in Rydberg molecules is investigated using multichannel quantum defect theory with special reference to the time-resolved wave packet experiments of Smith et al. (R. A. L. Smith, J. R. R. Verlet, E. D. Boleat, V. G. Stavros and H. H. Fielding, Faraday Discuss., 2000, 115, 63-70).
233

Upplevelser hos föräldrar till barn med medfödda hjärtfel : En litteraturstudie / Experiences of parents to children with congenital heart defects : A literature study

Åkerström, Justina, Blomstedt, Marie January 2015 (has links)
Bakgrund: Varje år föds 1 % av alla barn i Sverige med medfött hjärtfel. Barnet med denna diagnos och dess föräldrar är i stort behov av omvårdnad. Viktiga komponenter i denna omvårdnad är stöd och uppmuntran, information på rätt nivå för mottagaren och att frågor blir besvarade. Föräldrar till barn med medfött hjärtfel lider i större mån än andra föräldrar av någon form av psykosocial stress eller ångest relaterat till barnets diagnos. Syfte: Syftet var att beskriva föräldrars upplevelser av att ha barn med medfödda hjärtfel. Metod: En litteraturstudie baserad på kvalitativa vetenskapliga artiklar. Artiklarna hittades via sökningar i CINAHL Complete, MEDLINE, Academic Search Elite och CINAHL with Full Text där tio artiklar inkluderades efter kvalitetsgranskning. Resultat: I studiens analys av artiklarna framkom fyra teman som präglade föräldrarnas upplevelser under barnens uppväxt. Dessa var; känslan av otillräcklighet och osäkerhet, en ny komplex situation, stress samt stöd och tillit. Slutsats: När ett barn får diagnosen medfött hjärtfel står hela familjen inför en ny situation som innebär stora omställningar i vardagen. Stress var en konstant börda och föräldrarna upplevde att de kände sig otillräckliga och osäkra i föräldrarollen. Behovet av stöd och tillit, från både vårdpersonal, släkt och vänner, var stort för att orka med situationen. Klinisk betydelse: Resultatet i denna litteraturstudie kan bidra med kunskap om föräldrars upplevelser av att ha ett barn med medfött hjärtfel. Studien kan medvetandegöra behoven hos denna grupp föräldrar, vilket kan vara till hjälp för utformning av riktlinjer inom denna ram för omvårdnad. / Background: Each year, 1% of all children born in Sweden are diagnosed at birth with congenital heart defects. The child with this diagnosis and its parents are in great need of care. Key components of this care are support and encouragement, information given at the right level for the receiver, and making sure that questions are answered. Parents of children with congenital heart disease suffer to a greater extent than other parents from some form of psychosocial stress or anxiety related to their child's diagnosis. Aim: The aim of this study was to describe parents' experiences of having children with congenital heart defects. Method: A literature study based on qualitative scientific articles. The articles were found through the databases CINAHL Complete, MEDLINE, Academic Search Elite and CINAHL with Full Text and ten articles were included after quality control. Findings: The study's analysis of the articles revealed four themes that characterized the parents' experiences as the children grew. These were; feeling of inadequacy and insecurity, new complex situation, stress, and also support and trust. Conclusion: In the new situation in which a child where diagnosed with congenital heart defect, the whole family underwent major changes in everyday life. Stress was a constant burden and parents experienced inadequacy and insecurity in the parental role. The need for support and trust from both health care workers, friends and, family was great when dealing with the situation. Relevance to clinical practice: The results of this study will hopefully contribute knowledge about parents' experiences of having a child with congenital heart defects. The study may sensitize the needs of this group of parents, which can be helpful for the development of guidelines within this framework of nursing care.
234

Effect of Hyperbaric Oxygen on Non-Grafted and Grafted Calvarial Critical-sized Defects

Jan, Ahmed M. A. 12 February 2010 (has links)
Objectives: The purpose of this study was to evaluate whether the effects of hyperbaric oxygen (HBO) therapy could alter the critical size defect (CSD) diameter and to evaluate the effect of HBO on the repair of CSD in the presence and absence of a non-vascularized autogenous bone graft (ABG). Study Design: Twenty rabbits were divided in two groups of ten animals each. CSD were created in the parietal bones bilaterally. Defects were critical-sized, 15 mm on one side and supracritical-sized, 18 mm on the contralateral side. Group 1 received a 90-min HBO treatment sessions at 2.4 absolute atmospheric pressure (ATA) for 90 minutes per day for 20 days. Group 2 served as a normobaric roomair control (NBO). Additional ten animals were divided into 2 groups of 5 animals each. Bilateral CSD were created. ABG were allocated to one side of each calvarium. Group 1 received HBO treatments. Group 2 served as NBO. After sacrifice, data were collected including qualitative assessment, radiographic analysis, Micro CT bone analysis and histomorphometric analysis. ANOVA and paired sample t test were used for statistical analysis. Results: Both radiographic analysis and histomorphometric analysis demonstrated more new bone in the HBO CSD (p<.001). Micro CT analysis indicated a higher bone mineral content (BMC) in ABG CSD (p<.05). Histologically, complete bridging of the defect was observed in ABG defects. Histomorphometric analysis showed that HBO treatment increased new bone and marrow and reduced fibrous tissue in the defects (p<.01 for all). Conclusion: Bone regeneration was significantly greater in the HBO animals regardless of the defect size. HBO may have changed the accepted diameter of CSD to more than 18 mm. HBO enhances bony healing in non-grafted CSD.
235

Optimizing Test Pattern Generation Using Top-Off ATPG Methodology for Stuck–AT, Transition and Small Delay Defect Faults

Gill, Arjun 03 October 2013 (has links)
The ever increasing complexity and size of digital circuits complemented by Deep Sub Micron (DSM) technology trends today pose challenges to the efficient Design For Test (DFT) methodologies. Innovation is required not only in designing the digital circuits, but also in automatic test pattern generation (ATPG) to ensure that the pattern set screens all the targeted faults while still complying with the Automatic Test Equipment (ATE) memory constraints. DSM technology trends push the requirements of ATPG to not only include the conventional static defects but also to include test patterns for dynamic defects. The current industry practices consider test pattern generation for transition faults to screen dynamic defects. It has been observed that just screening for transition faults alone is not sufficient in light of the continuing DSM technology trends. Shrinking technology nodes have pushed DFT engineers to include Small Delay Defect (SDD) test patterns in the production flow. The current industry standard ATPG tools are evolving and SDD ATPG is not the most economical option in terms of both test generation CPU time and pattern volume. New techniques must be explored in order to ensure that a quality test pattern set can be generated which includes patterns for stuck-at, transition and SDD faults, all the while ensuring that the pattern volume remains economical. This thesis explores the use of a “Top-Off” ATPG methodology to generate an optimal test pattern set which can effectively screen the required fault models while containing the pattern volume within a reasonable limit.
236

The investigation of wire rope defect using contactless dynamic method / Plieninių lynų defektų tyrimas taikant bekontaktį dinaminį metodą

Šutinys, Ernestas 29 January 2014 (has links)
The dissertation investigates the diagnostics of wire rope by using forced characteristics. The main object of research is defects of prestressed ropes using a dynamic systems characteristic. The primary purpose of this dissertation is to research the characteristics of a prestressed rope with outside of broken wire and to create research methodology of broken wires and determine its location. The paper approaches a few major tasks such as by experiment detecting the dynamic characteristics of the wire rope and detection broken wire on the surface of the wire rope using dynamic characteristics. Task 1 is formulated as the literature review found that the wire rope defects detected by using of the dynamic characteristics received little attention. Task 2 relates to the first problem solution, as measured by vibrating amplitude of broken wire, it is important to assess the reliability of measuring instruments. The introduction reveals the investigated problem, importance of the thesis and the object of research and describes the purpose and tasks of the paper, research methodology, scientific novelty, the practical significance of results examined in the paper and defended statements. The introduction ends in presenting the author’s publications on the subject of the defended dissertation, offering the material of made presentations in conferences and defining the structure of the dissertation. Chapter 1 analysis used literature. It contains a wire rope defects and diagnostic... [to full text] / Disertacijoje nagrinėjama plieninių lynų defektų nustatymas taikant jėgines charakteristikas. Pagrindinis tyrimo objektas yra įtemptų plieninių lynų defektų nustatymas naudojant lyno, kaip dinaminės sistemos, savybes. Pagrindinis disertacijos tikslas – ištirti įtempto plieninio lyno su išoriniame sluoksnyje nutrūkusiomis vielomis savybes ir sukurti nutrūkusių vielų bei jų vietos nustatymo tyrimų metodiką. Darbe sprendžiami keli pagrindiniai uždaviniai: eksperimentiškai nustatytos plieninio lyno dinaminės charakteristikos ir naudojant jas aptinkamos įtempto plieninio lyno paviršiuje nutrūkusios vielos buvimo vieta. Pirmasis uždavinys suformuluotas, nes atlikus literatūros apžvalgą nustatyta, kad plieninių lynų defektams aptikti naudojant dinamines charakteristikas skirta mažai dėmesio. Antrasis siejasi su pirmojo uždavinio sprendimu, nes kai matuojamos virpančios nutrūkusios vielos amplitudės, labai svarbu įvertinti matavimo priemonių patikimumą. Disertaciją sudaro įvadas, trys skyriai, rezultatų apibendrinimas, naudotos literatūros ir autoriaus publikacijų disertacijos tema sąrašai. Įvadiniame skyriuje aptariama tiriamoji problema, darbo aktualumas, aprašomas tyrimų objektas, formuluojamas darbo tikslas bei uždaviniai, aprašoma tyrimų metodika, darbo mokslinis naujumas, darbo rezultatų praktinė reikšmė, ginamieji teiginiai. Įvado pabaigoje pristatomos disertacijos tema autoriaus paskelbtos publikacijos ir pranešimai konferencijose bei disertacijos struktūra. Pirmasis skyrius... [toliau žr. visą tekstą]
237

Application Of Statistical Process Control To Software Development Processes Via Control Charts

Sargut, Kamil Umut 01 January 2003 (has links) (PDF)
The application of Statistical Process Control (SPC) to software processes has been a challenging issue for software engineers and researchers. Although SPC is suggested for providing process control and achieving higher process maturity levels, there are very few resources that describe success stories, implementation details, and implemented guidelines for applying SPC to specific metrics. In this thesis the findings of a case study that is performed for investigating the applicability of SPC to software metrics in an emergent CMM Level 3 software organization are presented. As being one of the basic and most sophisticated tools of SPC, control charts are used for the analysis. The difficulties in application of Statistical Process Control to a CMM Level 3 organization are observed by using the existing data of defect density, rework percentage, productivity and review performance metrics and relevant suggestions are provided for dealing with them. Finally the analysis results are summarized and a guideline is prepared for software companies who want to utilize control charts by using their existing metric data.
238

Growth and Process-Induced Deep Levels in Wide Bandgap Semiconductor GaN and SiC / 結晶成長及びプロセスにより導入されるワイドバンドギャップ半導体GaN及びSiC中の深い準位

Kanegae, Kazutaka 23 March 2022 (has links)
付記する学位プログラム名: 京都大学卓越大学院プログラム「先端光・電子デバイス創成学」 / 京都大学 / 新制・課程博士 / 博士(工学) / 甲第23909号 / 工博第4996号 / 新制||工||1780(附属図書館) / 京都大学大学院工学研究科電子工学専攻 / (主査)教授 木本 恒暢, 教授 川上 養一, 准教授 安藤 裕一郎 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM
239

Semiconducting properties of polycrystalline titanium dioxide

Burg, Tristan Kevin, Materials Science & Engineering, Faculty of Science, UNSW January 2008 (has links)
Titanium dioxide, TiO2, has potential applications as a photoelectrode for photoelectrochemical generation of hydrogen by splitting water using solar energy and as a photocatalyst for water purification. This study is part of the UNSW research program to process TiO2-based oxide semiconductors as high-performance photoelectrodes and photocatalysts. This study investigates the effect of defect disorder on semiconducting properties of polycrystalline TiO2. This study involved the processing of high-purity polycrystalline TiO2 and determination of its semiconducting properties through measurement of electrical conductivity and thermoelectric power at elevated temperatures (1073-1323K) in controlled oxygen activities [1x10-13 Pa < p(O2) < 75 kPa]. The study included two types of experiments: Determination of electrical properties under conditions of gas/solid equilibrium. The data obtained was used to derive defect disorder and related semiconducting properties Monitoring of electrical properties during equilibration. This data was used to determine the chemical diffusion coefficient. The data obtained under equilibrium conditions indicates that oxygen may be used as a dopant to impose controlled semiconducting properties. In reduced conditions TiO2 is an n-type semiconductor and under oxidizing conditions TiO2 is a p-type semiconductor. The n-type behaviour is associated with oxygen vacancies as the predominant defects and titanium interstitials as the minority defects. The p-type behaviour is closely related to titanium vacancies that are formed during prolonged oxidation. Charge transport at elevated temperature was shown to involve substantial contribution from ions. Analysis of electrical properties enabled determination of several defect-related quantities including the activation enthalpy for oxygen vacancy formation, and the activation energy of the electrical conductivity components related to electrons, holes and ions. The kinetic data obtained during gas/solid equilibration enabled determination of the chemical diffusion coefficient which exhibited a complex dependence on nonstoichiometry. In addition, prolonged oxidation showed that equilibration occurred in two kinetic regimes. One for highly mobile oxygen vacancies and titanium interstitials which quickly reached an ??operational equilibrium?? within hours and another slow kinetic regime for equilibration of titanium vacancies over many thousand hours. The determined chemical diffusion coefficient data may be used to select the processing conditions required to impose uniform concentration of defects within a TiO2.
240

How mitochondrial DNA mutations affect the growth of MCF-7 clones

Sin, Yuan Yan (Angie) January 2006 (has links)
Mitochondria are the main sites for adenosine triphosphate (ATP) generation within most cells. Structural and functional alterations of mitochondria due to genetic abnormalities of mitochondria can cause respiratory chain dysfunction. In this study, the important role of mitochondria in energy metabolism was determined by comparing the effect of mitochondrial DNA (mtDNA) mutations on growth patterns and oxidative phosphorylation (OXPHOS) enzyme activities of six isolated clones (B5, B12, D4, D9, E1 and E8); as well as the effect of ATP supplement to culture using the slowest growing clone. The isolated clones had shown distinct growth pattern and morphology. The difference in proliferation rates among the clones was ascertained by the doubling times (B5=26.4h. B12=43.2h. D4=25.7h. D9=33.6h. E1=26.9h and E8=28.8h). The clone's slow growth rate was likely the result of mitochondrial mutations in the 16S rRNA gene, ND1, ND4, ND6 and COX III. Five heteroplasmic mutations were found in clone B12 (G2480T, C2513G, A2520T, C9527T and C14263G), one heteroplasmic mutation in clone D9 (A4137G) and one homoplasmic mutation in clone D4 (C11496). The mutations in clone B12 appeared to be deleterious to the cell by disrupting mitochondrial OXPHOS activities and reducing energy output. Additionally, extracellular ATP supplement to OXPHOS deficient clone B12 facilitated cell growth and enhances the gene expression. Increased expression of mtDNA-encoded respiratory chain complexes observed in clone B12 compared to clone D4 may reflect mitochondrial genomic adaptation to perturbations in cellular energy requirements. The stimulation of mitochondrial biogenesis may be a cellular response in compensation for defects in OXPHOS associated with mtDNA mutations. My data support the hypothesis that the variability in functional manifestations of mtDNA is attributed to the nature of the mutation, number of mutation and the gene specifically affected. These results will help to further our understanding of the relationship between mitochondrial mutation and cellular function.

Page generated in 0.0298 seconds