29,794 research outputs found
AlGaN/GaN HEMT micro-sensor technology for gas sensing applications
No full text Wide bandgap gallium nitride material has highly favorable electronic properties for next generation power and high frequency electronic devices. A less widely studied application is highly miniaturized chemical and gas sensors capable of operating in harsh environment conditions. In this work we present our recent developments on design, fabrication and testing of AlGaN/GaN high electron mobility transistor (HEMT) based sensors for detection of various gases. First, the method of as-fabricated device baseline value stabilization is demonstrated. Secondly, the impact of sensor design is discussed with the emphasis on gate electrode geometry optimizations to enhance sensing performance. Then we present the sensing characteristics of Pt-HEMTs towards H 2 S and compare them to H 2 and NO 2 . Finally we demonstrate recent results of NO 2 detection with Ti/Au based HEMT sensors, which are superior to those using Pt based devices. Accepted author manuscriptElectronic Components, Technology and Material
Viagem ao céu, authored by Monteiro Lobato: Author Philologys Notes
No full textEsta dissertação tem como objetivo investigar as etapas de gênese e estabelecimento da obra Viagem ao céu, de Monteiro Lobato, com a finalidade de identificar, descrever e analisar as alterações atribuídas ao autor ao longo dos anos. O corpus é constituído por 10 testemunhos, publicados entre 1932 e 1948. Partindo dos princípios norteadores da Crítica Genética e da Filologia do Autor, realizam-se, portanto, a recensão de testemunhos e o exame das variantes textuais encontradas. Realiza-se, também, a descrição dos testemunhos de acordo com as determinações da Bibliografia Material. Ao examinar as lições variantes de cada testemunho do texto, foi possível identificar alguns padrões, relacionados à sua classificação e à sua frequência. Identificam-se casos de variação por adição, alteração de ordem, omissão e substituição, além de mudanças na paragrafação e reelaboração textualThe main objective of this dissertation is to investigate the settlement and genesis steps of the literary work named Viagem ao Céu, authored by Monteiro Lobato, to identify, to describe and to analyze the variations conducted on the text during years by the author. The corpus is composed of eight testimonials, published between 1932 and 1948. Considering the guiding fundaments of the Textual Bibliography and the Genetics, this dissertation shows the resumption from the testimonies and the examination of the variants found in the text. The description of the testimonies was also made according to Material Bibliography rules. During the variant lessons survey from each testimony of the text, it was possible to identify some patterns related to its classification and frequency. It was also possible to recognize variations cases by addition, change of order, omissions, and substitutions, besides paragraph and chapter changes and textual rewritin
Simulating multiple diffraction in imaging systems using a path integration method
No full textWe present a method for simulating multiple diffraction in imaging systems based on the Huygens–Fresnel principle. The method accounts for the effects of both aberrations and diffraction and is entirely performed using Monte Carlo ray tracing.We compare the results of this method to those of reference simulations for field propagation through optical systems and for the calculation of point spread functions. The method can accurately model a wide variety of optical systems beyond the exit pupil approximation.Accepted Author ManuscriptImPhys/Optic
Challenges in simulating advanced control methods for AO
No full textThis paper discusses various practical problems arising in the design and simulation of predictive control methods for adaptive optics. Although there has been increased attention towards optimal prediction and control methods for AO systems, they are often tested in simplified simulation environments. The use of advanced AO simulators however, is a valuable alternative to the use of real data or laboratory experiments, as they provide both a flexible environment which is ideal for testing a new algorithm and are more accessible to non-experts. Topics that are often not explicitly discussed, such as the identification of a turbulence dynamics model from data, the use of matrix structures in AO systems to decrease the computational complexity and the implementation of Kalman filters to optimally deal with realistic noise conditions are examined. All topics discussed are illustrated by an accompanying Matlab code, which is based on the existing Matlab AO toolbox OOMAO.Team Raf Van de Pla
Characterization and closed-loop performance of a liquid mirror adaptive optical system
No full textA deformable mirror based on the principle of total internal reflection of light from an electrostatically deformed liquid–air interface was realized and used to perform closed-loop adaptive optical (AO) correction on a collimated laser beam aberrated by a rotating phase disk. Equations describing the resonant and oscillatory behavior of the liquid system were obtained and applied to the system under consideration. Characterization of the mirror included open- and closed-loop frequency responses, determination of rise times, the damping times of the liquid, and the influence of liquid surface motion in the absence of external optical aberrations. The performance of the AO system was determined for static and dynamic aberrations for various sets of system parameters. The predictions of the general expressions were compared to the results of the experimental realization and were found to be in good agreement.MicroelectronicsElectrical Engineering, Mathematics and Computer Scienc
Counseling in the Manitou, Colorado, junior and senior high school
No full textMay 26, 1932.Includes bibliographical references (pages 67-71).In this study the writer deals chiefly with vocational and educational guidance, with the understanding that health, character and social guidance are included in a lesser degree. The author interprets the aim of the counseling program in educational guidance to be the study of the interests, abilities and aptitudes of the child and the adjustment of the curricular and extra-curricular activities to meet the needs of the individual pupil. This program should also stimulate interests and develop and increase abilities. In short, it is the advisement by a counselor of the curricular subjects in which the student should matriculate as the result of research on the part of the counselor and student. It is very closely allied with health, vocational, social and character guidance, the other factors with which this thesis deals. The author feels that educational guidance should follow the choosing of a vocation and should include information upon courses of study to be pursued which will train the student in his occupational choice
Joint optimization of phase diversity and adaptive optics: Demonstration of potential
No full textWe study different possibilities to use adaptive optics (AO) and phase diversity (PD) together in a jointly optimized system. The potential of the joint system is demonstrated through numerical simulations. We find that the most significant benefits are obtained from the improved deconvolution of AO-corrected wavefronts and the additional wavefront sensor (WFS) information that reduces the computational demands of PD algorithms. When applied together, it is seen that the image error can be reduced by 20% compared to traditional PD, working with one focused and one defocused camera image, and the computational load is reduced by a factor of 20 compared to a more reliable PD algorithm requiring more camera images. In addition, we find that the system performance can be optimized by adjusting the magnitude of the applied diversity wavefronts.Delft Center for Systems and ControlMechanical, Maritime and Materials Engineerin
Introdução ao pensamento de Bakhtin
No full textReview of the text “Introduction to the thought of Baktin” (2006), by the author José Luiz de Fiorin.Review of the text “Introduction to the thought of Baktin” (2006), by the author José Luiz de Fiorin.Resenha do texto "Introdução ao pensamento de Baktin" (2006), do autor José Luiz de Fiorin
As limitaçoes ao direito de autor referentes ao software
No full textO presente artigo traz uma breve exposição acerca das formas existentes de proteção exclusiva ao software no direito brasileiro, em especial na legislação autoral, enfatizando as influências da legislação internacional, quando oportuno; e destacando as limitações ao direito exclusivo do autor como forma de assegurar, de certa maneira, o acesso ao conhecimento e à informação.The present article gives a brief statement about existing forms of software exclusive to the Brazilian law, in particular copyright law protection, emphasizing the influences of, international law where appropriate; and highlighting the limitations on the exclusive right of the author in order to ensure, in a way, access to knowledge and information
Rapid Surface Large-Change Monitoring by Repeat-Pass GEO SAR Multibaseline Interferometry
No full textFast observations of rapid surface large-changes are demanded in disaster evaluations and scientific studies. Digital elevation model (DEM) differencing before and after the events is an effective way to retrieve the changes. Owing to a short repeat cycle, geosynchronous synthetic aperture radar (GEO SAR) systems can quickly obtain repeat-pass data and generate postevent DEMs by interferometry. However, interferometric baselines under its quick revisit cases are short, resulting in generating low-accuracy postevent DEMs. Moreover, surface large-changes can bring height ambiguity problems under the single-baseline interferometric processing. In this letter, we address the problem through a multibaseline (MB) processing. Since GEO SAR MB data can derive from the repeat-pass interferometric data of different subapertures and revisits, a subaperture-decomposition-based temporal and spatial MB method is proposed. The simulation results verify the effectiveness of the proposed method, where the quickly generated postevent DEM can help to realize the rapid large-elevation change observations. Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Mathematical Geodesy and Positionin
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