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Fabrication of Nanoscale Josephson Junctions and Superconducting Quantum Interference DevicesKitapli, Feyruz January 2011 (has links)
Fabrication of nanoscale Josephson junctions and Superconducting Quantum Interference Devices (SQUID) is very promising but challenging topic in the superconducting electronics and device technology. In order to achieve best sensitivity of SQUIDs and to reproduce them easily with a straightforward method, new fabrication techniques for realization of nanoSQUIDs needs to be investigated.
This study concentrates on investigation of new fabrication methodology for manufacturing nanoSQUIDs with High Temperature Bi-Crystal Grain Boundary Josephson Junctions fabricated onto SrTiO3 bi-crystal substrates using YBa2Cu3O7-δ (YBCO) thin-films.
In this process nanoscale patterning of YBCO was realized by using electron beam patterning and physical dry etching of YBCO thin films on STO substrates. YBCO thin films were deposited using RF magnetron sputtering technique in the mixture of Ar and O2 gases and followed by annealing at high temperatures in O2 atmosphere. Structural characterization of YBCO thin films was done by Scanning Electron Microscope (SEM) and Energy Dispersive X-ray Spectroscopy (EDX). Superconducting properties of thin films was characterized by AC magnetic susceptibility measurements. Nanoscale structures on YBCO thin films were fabricated by one E-Beam Lithography (EBL) step followed by Reactive Ion Etching (RIE) and physical dry etching. First SiO2 thin film were deposited on YBCO by RF magnetron sputtering and it was patterned by EBL using Polystyrene (PS) as resist material and RIE. Then SiO2 was used as an etch mask for physical dry etching of YBCO and nanoscale structures on YBCO were formed.
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Usage of Business Intelligence : Testing the Technology Acceptance Model on a BI SystemPettersson, Dennis, Arvidsson, Pär January 2012 (has links)
Business Intelligence (BI) has become an essential part of the modern enterprise, and what used to be thought of as a luxury is now a matter of survival. Recent economic developments have forced companies to rethink their IT investment strategy. BI investments are now targeting the majority of people in the organisation instead of a select few. Thus, it is important to understand why users of a BI system choose to accept and use the system. Previous research has established the Technology Acceptance Model (TAM) as one of the most powerful and parsimonious models explaining user acceptance and usage behaviour of information technologies. This quantitative study replicates the original TAM study with the purpose to increase the understanding of BI usage, and investigates the behaviour of the users of the BI system QlikView in the case company GE Healthcare. The results showed a lower explanatory power for the model when compared to previous research. This indicates that how useful a user perceives a BI system to be does not affect the amount of usage to the same extent as predicted by TAM. Possible causes for this are discussed, with an emphasis on the influence of what tasks a user is confronted with and the measurement of system use.
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Business Intelligence : Vilka av de utlovade fördelarna motsvaras av högskolor och universitets förväntningar?Larsson, Anna, Renemark, Alma January 2012 (has links)
Det första systemet som skapades för att integrera alla affärstransaktioner var ERP-systemet som skapades 1960. Detta system samlar verksamhetens data i olika databaser och för att kunna hantera och analysera denna data har utvecklare skapat ett BI-system. Detta system extraherar data och omvandlar den till användbar information som kan bidra till en underlättad och förbättrad styrning. Författarna av viss litteratur påstår att information är viktig för alla verksamheter då det är avgörande för ett beslutsfattande. Med hjälp av ett BI-system kan verksamheten få denna efterfrågade information samt att chefer med hjälp av systemet kan fatta taktiska och strategiska beslut. Syftet med denna studie var att beskriva högskolor och universitets förväntningar på ett BI-system och jämföra dessa med de fördelar som viss litteratur utlovar. Vi genomförde studien på två lärosäten, Högskolan i Halmstad och Göteborgs universitet, för att se vilka förväntningar de har på ett BI-system samt om det liknar eller skiljer sig med det som viss litteratur utlovar. Denna studie har genomförts utifrån en kvalitativ metod där vi har undersökt de utvalda lärosätenas förväntningar på ett BI-system. Vi har gjort det genom att utföra besöksintervjuer samt en mail- och telefonintervju med de ansvariga och användarna av lärosätenas BI-system. Resultatet som vi kommit fram till i denna studie är att många av de utlovade fördelarna som kan utläsas i viss litteratur stämmer överens med respondenternas förväntningar. Dessa förväntningar är bland annat att via ett BI-system förbättra verksamhetens styrning, underlätta kontrollen på strategiuppfyllelse samt få ökad tillgång till viktig information. Förväntningarna kan även utläsas i viss litteratur men vi kan även utläsa skillnader som till exempel är åsikter angående utbildning i systemet, mätning av systemets effektivitet samt problematik med systemet.
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Utepedagogik, drama och bild : språkutvecklande arbetsmetoderYousif, Lina January 2010 (has links)
The purpose of this essay is to examine how out-pedagogy, drama and art can be used as means of promoting language development of bi-and multi-language learners, and to show what benefits these three methods offer to children of year three of an elementary school in Stockholm City. This is a small survey of work-style and the results are based on observations and interviews with five teachers which included three class teachers, one resource teacher and one other language teacher and it was carried out two full days of observations in both classroom and outdoor environment. In this work, I note how out-pedagogy, drama and art can help bi- and multilingual children develop language. My study shows, in accordance with the respondents interviewed, as well as research in general that out-pedagogy, drama and art is language development practices. They argue that out-pedagogy and the aesthetic elements promote language development of bi- and multilingual children in different ways and complements the traditional approach. Through my observation and interview with the teachers, I came to know that they were implementing integrated teaching (though they do not realise, they follow it). Gibbons in his book "Stärk språket stärk lärandet" emphasizes the importance of working on an integrated approach and in particular the meeting the demands of multilingual children. (Gibbons, 2009). There is no doubt that these three methods are language-development practices in the meeting with more language bars. But some of the interviewees expressed negative opinion about drama and art. However I could not find any research indicating negative opinion about out-pedagogy. My results shows that out-pedagogy and its aesthetic elements integrated language and linked several of the child's senses, emotions and thinking in a natural and enjoyable way and promoted language development of bi- and multilingual children.
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Bi-directional Current-fed Medium Frequency Transformer Isolated AC-DC ConverterEssakiappan, Somasundaram 2010 May 1900 (has links)
The use of high power converters has increased tremendously. Increased demand for
transportation, housing and industrial needs means that more number of power
converters interact with the utility power grid. These converters are non-linear and they
draw harmonic currents, significantly affecting power quality. To reduce harmonics,
filters, power factor correction circuits and capacitor banks are required. And the
development of hybrid technologies and renewable energy power stations trigger a
demand for power converters with bi-directional capabilities. The objective of this thesis
is to develop a high power quality, bi-directional AC-DC power converter that is a
solution to the aforementioned problems.
This thesis studies an existing topology for a high power AC-DC power conversion with
transformer isolation. The topology consists of an uncontrolled rectifier followed by a
DC-DC converter to produce a set voltage output. A design example of the topology is
simulated using the PSIM software package (version 6). Critical performance
characteristics such as power factor and total harmonic distortion are analyzed.
Following that study a new topology is proposed, which is an improvement over the
older design, with reduced power conversion stages. The new topology has a fully
controlled current source Pulse Width Modulation (PWM) rectifier at the front end to
replace the uncontrolled rectifier and DC-DC combination. This topology has multiquadrant
operational capabilities and the controller employs Selective Harmonic
Elimination techniques to produce the programmed PWM switching functions for the
rectifier. A design example of the converter and the digital controller are simulated in
PSIM environment. The converter input current THD (Total Harmonic Distortion) and
input power factor are within IEEE 519 and DoE standards. The converter is simulated
in both first and fourth quadrant operations.
A side-by-side comparison of the two topologies is done with respect to design and
performance features such as power factor, THD, filter size, etc. The new topology
converter provides performance superior to that of the older topology. Finally the thesis
explores possible applications for the converter in power supplies, renewable energy and
hybrid technologies.
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Production of the Alpha-Particle Emitting Radionuclide Astatine-211 at the Texas A&M Cyclotron InstituteBhakta, Viharkumar Satish 2011 August 1900 (has links)
The need of a stable production of At-211 is necessary to continue research in alpha-particle targeted radionuclide therapy. Our objectives were to establish the production of Astatine-211 at Texas A&M Cyclotron Institute, optimize the production methods to reduce the generation of contaminants and maximize At-211 production, and assess the radiological safety aspects of At-211 production. The production of the alpha-particle emitting radionuclide At-211 was performed at the Texas A&M Cyclotron Institute using the K500 superconducting cyclotron following the production reaction Bi-209(α, 2n)At-211 using a thick bismuth target of 500 μm. We carried out two irradiation experiments where the initial energy of the alpha-particle beam, 80 MeV, was degraded using multiple copper and aluminum foils to 27.8 and 25.3 MeV, respectively. The end of beam time was 4 hours for both experiments.
The resulting At-211 yields were 36.0 and 12.4 MBq/μA-h, respectively. Several impurities were produced using the 27.8 MeV, which included At-210 and Po-210. However, when the 25.3 MeV beam was used, the impurities At-210 and Po-210 were resolved and other contaminants were minimized to less than 0.8% of At-211 yield. The production yields were in accordance to previous published results.
From the success of these initial experiments, additional steps were taken to produce At-211 in excess quantities for distillation purposes. In order to obtain viable quantities of At-211, the gross yield needed to be increased due to losses that are incurred during distillation and radioactive decay. The ability to produce high yields of this isotope required a redesign of the target and use of the K150 cyclotron using a higher beam intensity.
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Study of Fault Detection and Restoration Strategy by Artificial Neural NetworksWu, Yan-Ying 30 June 2005 (has links)
With the rapid growth of load demand, the distribution system is becoming more and more complicated, and the operational efficiency and service quality deteriorated. Power system protection is important for service reliability and quality assurance. Various faults may occur due to natural and artificial calamity. To reduce the outage duration and promptly restore power services, fault section estimate has to be done effectively with appeared fault alarms. The distribution system containing numerous protective facilities and switch equipment ranges over wide boundary. It becomes very complicated for dispatchers to obtain restoration plan for out-of-service areas. To cope with the problem, an effective tool is helpful for the restoration. This thesis proposes the use of Bi-directional associative memory networks (BAMN) to develop alarm processing. And use of Probabilistic Neural Network (PNN) to develop fault section detection, fault isolation, and restoration system. A distribution system is selected for computer simulation to demonstrate the effectiveness of the proposed system.
The thesis proposes to use Bi-directional Associative Memory Network¡]BAMN¡^ to pre-process the signal gained from SCADA Interface, and transmit correct signal to Probabilistic Neural Network (PNN) for restoration plan . Computer simulation shows a simplified model to shorten the processing time in this study.
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Influence Of Idealized Pushover Curves On Seismic ResponseKadas, Koray 01 September 2006 (has links) (PDF)
Contemporary approach performance based engineering generally relies on the approximate procedures that are based on the use of capacity curve derived from pushover analysis. The most important parameter in the displacement-based approach is the inelastic displacement demand computed under a given seismic effect and the most common procedures employed for this estimation / the Capacity Spectrum Method and the Displacement Coefficient Method are based on bi-linearization of the capacity curve. Although there are some recommendations for this approximation, there is a vital need for rational guidelines towards the selection of the most appropriate method among several alternatives.
A comprehensive research has been undertaken to evaluate the influence of several existing alternatives used for approximating the capacity curve on seismic demands. A number of frames were analyzed under a set of 100 ground motions employing OpenSees. In addition, the pushover curves obtained from nonlinear static analyses were approximated using several alternatives and the resulting curves were assigned as the force-deformation relationships of corresponding equivalent single-degree-of-freedom systems. These simplified systems were later analyzed to compute the approximate seismic response parameters.
Using the results of the complex and simplified analyses, the performance of each approximation method was evaluated in estimating the & / #8216 / exact& / #8217 / inelastic deformations of the multi-degree-of-freedom systems at various degrees of inelasticity. Dependency of the errors on ductility, strength reduction factor and period was also investigated. The interpretations made and the conclusions drawn in this study is believed to clarify the rationality and accuracy of selecting the appropriate idealization of the capacity curve.
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Production Of Coal Crusher Hammer Heads By Bi-metal CastingKirma, Turgut 01 September 2008 (has links) (PDF)
In this study, by considering different mechanical properties such as wear resistance and toughness of two different metal alloys in design and production stages, bi-metal casting technique was used for producing composite material which will be a solution for the cracking and wear problem in coal crushing hammer heads. The failure analysis of the classical hammer heads which are made from Hadfield steels (austenitic steel) showed that there are crack formations through austenitic grains and also the phase transformation from austenite to martensite is not completed until the material consumed its life.
Thermal analysis is the basic technique in this study to determine the solidification conditions. By using thermocouples with a suitable set-up, the cooling curves of the materials which were used in bi-metal casting had been taken and analysed. By using these cooling curve data with a written software program which is based on Newton Thermal Analysis, the solid fraction values by time and by temperate were obtained. According to these values, the interface was investigated by changing experimental conditions and solid fractions. At the last part of the study, a new approach was tried in white cast iron production.
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The Campaign Routing ProblemOzdemir, Emrah 01 September 2009 (has links) (PDF)
In this study, a new selective and time-window routing problem is defined for the first time in the literature, which is called the campaign routing problem (CRP). The two special cases of the CRP correspond to the two real-life problems, namely political campaign routing problem (PCRP) and the experiments on wheels routing problem (EWRP). The PCRP is based on two main decision levels. In the first level, a set of campaign regions is selected according to a given criteria subject to the special time-window constraints. In the second level, a pair of selected regions or a single region is assigned to a campaign day. In the EWRP, a single selected region (school) is assigned to a campaign day. These two problems are modeled using classical mathematical programming and bi-level programming methods, and a two-step heuristic approach is developed for the solution of the problems. Implementation of the solution methods is done using the test instances that are compiled from the real-life data. Computational results show that the solution methods developed generate good solutions in reasonable time.
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