Tese de mestrado integrado. Engenharia Electrotécnica e de Computadores. Universidade do Porto. Faculdade de Engenharia. 2011

As Si MOS approaches its maximum limits in speed and bandwidth, new devices are desired to meet the needs of high speed communications and signal processing. A device that exhibits superior performance to Si MOS, BJT, and GaAs technology is the HEMT (high electron mobility transistor). The HEMT offers superior transconductance, mobility, speed, and noise performance compared to Si MOS, BJT, and standard GaAs technology. The high performance is a result of improved channel mobility due to a heterojunction. At the heterointerface, the majority carriers are confined to a very thin sheet forming what has been termed a 2DEG (two dimensional electron gas). The purpose of this thesis is to demonstrate the suitability of Honeywell's delta-doped self-aligned complimentary HIGFET process for the realization of high speed analog circuits. An operational amplifier and switched-capacitor circuit are presented. The operational amplifier has been fabricated at Honeywell and preliminary tests have been performed on the op-amp which are also presented. / Graduation date: 1998

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2006. / Includes bibliographical references. Also available in electronic version.

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This study proposes a new, easily applied method to quantify uncertainty in production forecasts for a volumetric gas reservoir based on a material balance model (p/z vs. Gp). The new method uses only observed data and mismatches between regression values and observed values to identify the most probable value of gas reserves. The method also provides the range of probability of values of reserves from the minimum to the maximum likely value. The method is applicable even when only limited information is available from a field. Previous methods suggested in the literature require more information than our new method. Quantifying uncertainty in reserves estimation is becoming increasingly important in the petroleum industry. Many current investment opportunities in reservoir development require large investments, many in harsh exploration environments, with intensive technology requirements and possibly marginal investment indicators. Our method of quantifying uncertainty uses a priori information, which could come from different sources, typically from geological data, used to build a static or prior reservoir model. Additionally, we propose a method to determine the uncertainty in our reserves estimate at any stage in the life of the reservoir for which pressure-production data are available. We applied our method to San Juan reservoir at Santa Rosa Field, Venezuela. This field was ideal for this study because it is a volumetric reservoir for which the material balance method, the p/z vs. Gp plot, appears to be appropriate.

<p><strong>Syfte och frågeställningar</strong></p><p>Syftet med studien har varit att jämföra lärares och rektorers syn på friluftsdagar avseende mål, innehåll och organisation. Resultatet har tolkats med utgångspunkt i en läroplansteoretisk modell. De mer preciserade frågeställningarna var:</p><ul><li>Vad vill skolan uppnå med friluftsdagarna?</li><li>Hur ramar skolan in begreppet friluftsdag genom förekomsten av olika inslag?</li><li>Hur ofta vill lärarna att olika inslag ska förekomma på friluftsdagarna samt vilka skolämnen är och bör finnas representerade?</li><li>Hur ser organisationen ut kring friluftsdagarna på skolan enligt lärare och rektorer samt hur bör den se ut enligt lärarna?</li><li>Vilken kompetens anser lärare och rektorer vara viktig för planeringen av friluftsdagarna?</li></ul><p><strong> Metod</strong></p><p>En enkätstudie med kvalitativa inslag genomfördes på 121 ämneslärare i svenska och idrott och hälsa samt 67 rektorer från högstadieskolor i Stockholms län. Enkäter skickades ut via e-post till respondenterna som valts ut genom ett obundet slumpmässigt urval från en förteckning på Skolverkets hemsida. Studien fick, efter tre påminnelser, en svarsfrekvens på 44,1 procent (n=83).</p><p><strong>Resultat och diskussion</strong></p><p>Resultatet visar att ”naturvistelse/friluftsliv” var det som lärare och rektorer tyckte var viktigast att uppnå på friluftsdagar och detta realiseras också genom inslag av natur- och utomhusvistelse. Lärare och rektorer ramar in begreppet friluftsdag olika. De har olika uppfattning om förekomsten av inslaget ”friluftsliv” och det gäller också inslaget ”fysisk aktivitet”. Rektorerna ansåg att dessa inslag förkommer i större utsträckning än lärarna. I jämförelsen mellan lärares uppfattning om vad som förekommer och hur det bör se ut på skolan visades en signifikant skillnad på inslagen ”tävlingsmoment”, ”ämnesintegrering”, ”naturvistelse”, ”fysisk aktivitet” samt ”miljö och hållbar utveckling”. Tävlingsmoment förekommer för ofta och kan tänkas ta plats från de andra inslagen som lärarna önskade mer av på friluftsdagarna. Ämnet som var och bör vara mest representerande på friluftsdagarna var ämnet idrott och hälsa. Idrottsläraren anses vara den som har kompetensen att planera och organisera friluftsdagar och är också den som oftast planerar och organiserar friluftsdagarna. Lärarna i studien tycker dock att planeringen borde fördelas på fler lärare.</p><p><strong>Slutsats</strong></p><p>Det tycks finnas en kontinuitet i övergången mellan intentionerna på transformeringsarenan och realiseringsarenan när det kommer till frisk luft, natur och friluftsliv på friluftsdagarna. Däremot delar lärare respektive rektorer, på de olika arenorna, inte uppfattningen om hur ofta friluftsliv och fysisk aktivitet förekommer på friluftsdagarna.</p> / <p><strong>Aim and questions</strong></p><p>The aim of this study has been to compare teachers’ and headmasters’ view on field-days’ goal, content and organisation. The results were interpreted on the basis of a “curriculum theoretical model”. The questions are:</p><ul><li>What do schools strive to attain with field days?</li><li>How do schools define the conception of field day by the existence of different features?</li><li>How often do teachers want different features to occur at field days and what school subjects are, and should be represented according to teachers?</li><li>How does the organization around the field days look like according to teachers and headmasters, and how should it look like according to teachers?</li><li>Which qualifications are important when planning field days according to teachers and headmasters?</li></ul><p><strong>Method</strong></p><p>The study was carried out on 121 teachers of Swedish and teachers of PE and 67 headmasters from secondary schools in Stockholm country. A questionnaire was sent by e-mail to the respondents who were chosen by an independent random selection with the help of a list at the web page of the National Agency for education. The percentage of answers, after three reminders, were 44.1% (n = 83).</p><p><strong>Results and discussion</strong></p><p>Results shows that ”being in nature/outdoor life” was what the schools considered to be most important to attain at field-days and this is also what becomes realized by features as being in nature and being outdoor. Teachers and headmasters do frame the term of field-days in different ways. They have different opinions about the existence of the feature ”outdoor life” and this also applies to the feature ”physical education”. Headmasters think that those features exist more often than the teachers. When comparing teachers opinion about how it looks like in school and how it should look like there was a significant difference within the features ”elements of competition”, ”integrating school subjects”, ”being in nature”, ”physical activity” and ”environment and sustainable development”. Elements of competition do exist often on field days and are supposed to take place from other features that the teachers wanted more of. The school subject which was and should be most represented at the field days was the subject physical education. The PE-teacher is the one who is regarded to have the competence and who does most of the planning and organizing around the field days Nevertheless teachers think that the planning should be spread more among teachers.</p><p><strong>Conclusion</strong></p><p>There seems to be continuity in the transition between the intentions at the transforming arena and implementation at the field when it comes to fresh air, nature and outdoor life at the field days. However, the teachers respectively headmasters, on the different arenas, does not always share the same opinion about how often outdoor life and physical activity do exist on the field days.</p>

In Chapter 1, we give an introduction to the topic of open string field theory. The concepts presented include gauge invariance, tachyon condensation, as well as the star product. In Chapter 2, we give a brief review of vacuum string field theory (VSFT), an approach to open string field theory around the stable vacuum of the tachyon. We discuss the sliver state explaining its role as projector in the space of half-string basis. We review the construction of D-brane solutions in vacuum string field theory. We show that in the sliver basis the star product correspond to a matrix product. Using the material introduced in the previous chapters, in Chapter 3 we establish a translation dictionary between open and closed strings, starting from open string field theory. Under this correspondence, we show that (off--shell) level--matched closed string states are represented by star algebra projectors in open string field theory. As an outcome of our identification, we show that boundary states, which in closed string theory represent D-branes, correspond to the identity string field in the open string side. We then turn to noncommutative field theories. In Chapter 4, we introduce the framework in which we will work. The tools introduced are solitons, projectors, and partial isometries. The ideas of Chapter 4 are applied to specific examples in Chapter 5, where we present new solutions of noncommutative gauge theories in which coincident vortices expand into circular shells. As the theories are noncommutative, the naive definition of the locations of the vortices and shells is gauge-dependent, and so we define and calculate the profiles of these solutions using the gauge-invariant noncommutative Wilson lines introduced by Gross and Nekrasov. We find that charge 2 vortex solutions are characterized by two positions and a single nonnegative real number, which we demonstrate is the radius of the shell. We find that the radius is identically zero in all 2-dimensional solutions. If one considers solutions that depend on an additional commutative direction, then there are time-dependent solutions in which the radius oscillates, resembling a braneworld description of a cyclic universe. There are also smooth BIon-like space-dependent solutions in which the shell expands to infinity, describing a vortex ending on a domain wall. In Chapter 6, we review the Fronsdal models for free high-spin fields that exhibit peculiar properties. We discuss the triplet structure of totally symmetric tensors of the free String Field Theory and their generalization to AdS background. In Chapter 7, in the context of massless higher spin gauge fields in constant curvature spaces discussed in chapter 6, we compute the surface charges which generalize the electric charge for spin one, the color charges in Yang-Mills theories and the energy-momentum and the angular momentum for asymptotically flat gravitational fields. We show that there is a one-to-one map from surface charges onto divergence free Killing tensors. These Killing tensors are computed by relating them to a cohomology group of the first quantized BRST model underlying the Fronsdal action.

Split and normal gate A1GaAs /GaAs MODFETs were fabricated along with the ohmic test structures and the Hall bar geometries. The DC characteristics of normal gate transistors were evaluated at room temperature and at 77K and the threshold voltages were extracted from the measurements and compared to the theoretical results. The performance of normal gate transistors was reasonable. The sheet carrier density and the mobility extracted from Hall measurements using the Hall bar geometry showed increase of carrier density with increasing gate voltage and an increase of mobility with increasing carrier density. The contact resistance obtained from the ohmic test structure was high and not uniform within the sample. / Graduation date: 1991