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A reflexão e a prática docente: considerações a partir de uma pesquisa-ação.; The reflection and the teachers practices: considerations on a research-action.

Acker, Maria Teresa Vianna Van
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 26/05/2008 Português
Relevância na Pesquisa
36.51%
Esta tese tem em vista compreender de que modo a reflexão sobre as vivências dos professores na escola e na sala de aula geram conhecimento da prática em benefício do maior comprometimento profissional e, por conseguinte, com efeitos sobre autorização que reconhecem ter. Por se tratar de um tema que implica em considerar os processos de reflexão sobre a prática vivenciada pelos professores, ele exige metodologias de pesquisa que levem à colaboração eles. Escolhemos como abordagem metodológica a pesquisa-ação existencial pelo seu caráter de estímulo à reflexão. Como toda pesquisa-ação, essa investigação também se desenvolveu em diferentes etapas. Na primeira etapa, delineamos de que modos os professores produziam conhecimentos a partir de suas vivências práticas. Para isso nos utilizamos observações seguidas por entrevistas, as quais denominamos de entrevistas de explicação, inspiradas nas entrevistas de explicitação, descritas por Pierre Vermersch. Nessa etapa, identificamos que os professores valem-se de dois tipos de reflexão quando analisam e explicam suas práticas: uma reflexão que justifica o que fazem a partir de um costume, por um lado; por outro lado, uma reflexão que explica o percurso que traçaram até elaborarem um modo original de ensinar. Percebemos também que todos os professores...

Determinação de metais na bacia do rio Piracicaba usando as técnicas de Difusão em Filmes Finos por Gradiente de Concentração (DGT) e Fluorescência de Raios X Dispersiva em Energia (EDXRF) e por Reflexão Total (TXRF); Determination of metals in Piracicaba river basin using Diffusive Gradients in Thin Films, and Energy Dispersive X-ray Fluorescence (EDXRF) and Total Reflection (TXRF) techniques

Almeida, Eduardo de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 06/09/2011 Português
Relevância na Pesquisa
36.48%
O desenvolvimento e aplicação de métodos analíticos na avaliação das concentrações de metais nas frações dissolvida e lábil na bacia do rio Piracicaba são de relevante importância para o estudo do comportamento químico-ambiental desses metais e para seu monitoramento, devido ao impacto das atividades antropogênicas nessa bacia. A técnica de difusão em filmes finos por gradiente de concentração (DGT, do inglês diffusive gradients in thin-films), é uma promissora ferramenta analítica de amostragem, pois permite pré-concentração, análise temporal, remoção de interferentes, avaliação lábil e amostragem in situ. A quantificação dos metais pelas técnicas de fluorescência de raios X dispersiva em energia por reflexão total (TXRF, total reflection X-ray fluorescence analysis) para amostras líquidas e da fluorescência de raios X dispersiva em energia (EDXRF, energy dispersive X-ray fluorescence) para amostras sólidas, mostram-se interessantes devido ao caráter multielementar, simultâneo e não destrutivo da análise. Neste trabalho avaliou-se a DGT para a determinação de Cr, Mn, Co, Ni, Cu, Zn e Pb em águas naturais, utilizando-se como agente ligante a membrana de celulose P 81 e como meio difusivo...

O jovem Hegel leitor de Kant: crítica, reflexão e especulação; The joung Hegel reader of Kant: critique, reflection and speculation

Rehfeld, Daniel
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 01/10/2012 Português
Relevância na Pesquisa
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Este trabalho tem como objetivo abordar a leitura que o jovem Hegel faz da filosofia kantiana, tendo como foco o desenvolvimento da noção de especulação a partir da relação estabelecida com a reflexão, característica fundamental daquela filosofia. Através do reconhecimento da presença de idéias especulativas nessa filosofia, Hegel orienta sua interpretação pela crítica ao caráter formal das filosofias da reflexão e ao princípio da subjetividade no qual elas se enraízam. Sua leitura é conduzida pela tentativa de restituir a idéia da razão, como unidade primordial e absoluta do sujeito e objeto, que na filosofia crítica somente pôde ser vislumbrada enquanto tarefa, mas cuja realização se encontra ali de antemão impedida. Pretende-se, ao longo do trabalho, acompanhar como Hegel chega a constatar a ambigüidade inscrita na reflexão filosófica kantiana e de que maneira ele a submete a uma reinterpretação especulativa que destaca, de sua interpretação finita (crítica), uma reflexão especulativa como instrumento positivo do conhecer absoluto. Através do reconhecimento destas duas formas distintas de interpretar o sentido da reflexão e de sua atividade, voltamo-nos ao modo com que Hegel desenvolve a distinção kantiana entre Razão e Entendimento...

A reflexão como método de conhecimento psicológico em Agostinho e Husserl; Reflection as a method of psychological knowledge in Augustine and Husserl

Peres, Sávio Passafaro
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 28/02/2011 Português
Relevância na Pesquisa
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O objetivo desta tese consiste em avaliar, sob um prisma fenomenológico, as concepções presentes na obra de Santo Agostinho referentes ao uso da reflexão como instrumento do conhecimento de si. Para isso, analisamos as obras As confissões (397d.C.) A trindade (416 d.C.) e fragmentos de outras obras em que ele aborda o tema da reflexão. Consideramos dois diferentes níveis em que as ideias se encontram presentes nas obras: nas descrições de estados subjetivos narrados em primeira pessoa por Agostinho nas Confissões e nas exposições feitas por Agostinho em outras de suas obras. Investigamos alguns temas que se mostraram de grande importância para se compreender o papel da reflexão em Agostinho. Em primeiro lugar, o espírito humano entendido como uma realidade íntima, um ser reflexivo e imaterial. Em segundo lugar, analisamos o papel do método reflexivo em suas investigações acerca da memória, da percepção e das inter-relações entre o corpo e a mente. Em terceiro lugar procuramos observar como Agostinho compreende a vida do espírito em suas inter-relações com o mundo e com Deus. Na segunda parte da tese, os temas foram retomados e abordados sob um prisma fenomenológico. Para isso procuramos expor e avaliar, no que tange aos temas abordados por Agostinho...

Aprendizagem transformadora : a reflexão crítica na formação gerencial; Transformative learning: a critical reflection in managerial education

Closs, Lisiane Quadrado; Antonello, Cláudia Simone
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Artigo de Revista Científica Formato: application/pdf
Português
Relevância na Pesquisa
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Dadas as crescentes demandas por aprendizagens exigidas de gestores no atual contexto e a importância de seu papel para as organizações e a sociedade, sugere-se a necessidade de ampliar perspectivas para a educação gerencial. Esta vem recebendo críticas de correntes que destacam tanto a importância da reflexão como da reflexão crítica para a aprendizagem. Apresenta-se um levantamento de estudos brasileiros realizados sobre aprendizagem gerencial que corrobora a importância de ambas nos seus processos de aprendizagem, embora a reflexão crítica ainda seja pouco evidenciada no meio gerencial ou na educação de gestores. Propõe-se que a teoria da aprendizagem transformadora possa contribuir para a aprendizagem gerencial, suscitando reflexões críticas que favoreçam o pensamento autônomo e a liberação de pressupostos condicionados sobre o mundo, sobre os outros e sobre si, cruciais para o mundo do trabalho, para a cidadania e para a tomada de decisões morais.; Due to the growing learning requests demanded of managers in the actual context and the importance of their role for organizations and society, the need for broadening management education perspectives is suggested. Business education have been criticized either by scholars that point out the reflection importance as by those that emphasize the critical reflection role for management learning. The article presents Brazilian studies developed in the management learning field which corroborate the reflection and the critical reflection importance in learning processes...

P3L-3 Viscosity measurement of Newtonian liquids using the complex reflection coefficient

Franco, Ediguer E.; Adamowski, Julio C.; Higuti, Ricardo T.; Buiochi, Flávio
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Conferência ou Objeto de Conferência Formato: 2257-2260
Português
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This work presents the implementation of the ultrasonic shear reflectance method for viscosity measurement of Newtonian liquids using wave mode conversion from longitudinal to shear waves and vice-versa. The method is based on measuring the complex reflection coefficient (magnitude and phase) at a solid-liquid interface. Viscosity measurements were made in the range from 1 to 3.5MHz at 22.5°C for automotive oil (SAE40) and at 15°C for olive oil. Moreover, measurements of the olive oil were also conducted in the range from 15 to 30°C at 3.5MHz. The experimental results agree with those provided by a rotational viscometer. © 2006 IEEE.

Experimental study of the complex reflection coefficient of shear waves from the solid-liquid interface

Franco, Ediguer E.; Adamowski, Julio C.; Higuti, Ricardo T.; Buiochi, Flávio
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Conferência ou Objeto de Conferência Formato: 803-809
Português
Relevância na Pesquisa
36.54%
The determination of the reflection coefficient of shear waves reflected from a solid-liquid interface is an important method in order to study the viscoelastic properties of liquids at high frequency. The reflection coefficient is a complex number. While the magnitude measurement is relatively easy and precise, the phase measurement is very difficult due to its strong temperature dependence. For that reason, most authors choose a simplified method in order to obtain the viscoelastic properties of liquids from the measured coefficient. In this simplified method, inconsistent viscosity results are obtained because pure viscous behavior is assumed and the phase is not measured. This work deals with an effort to improve the experimental technique required to measure both the magnitude and phase of the reflection coefficient and it intends to report realistic values for oils in a wide range of viscosity (0.092 - 6.7 Pa.s). Moreover, a device calibration process is investigated in order to monitor the dynamic viscosity of the liquid.

Study of reflection and transmission of plane waves at thermoelastic-diffusive solid/liquid interface

Sharma,J.N.; Kaur,R.
Fonte: Associação Brasileira de Ciências Mecânicas Publicador: Associação Brasileira de Ciências Mecânicas
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2014 Português
Relevância na Pesquisa
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The paper concentrates on the study of reflection and transmission characteristics of waves at the interface of a thermoelastic-diffusive solid half-space underlying an inviscid liquid. The analytic expressions for amplitude ratios, reflection and transmission coefficients, in terms of incident angles and material parameters have been obtained for quasi-longitudinal (qP) and quasi-transverse (qSV) wave incidence. The normal and grazing incidence cases have also been derived and discussed. The total reflection phenomenon has also been discussed. The energy law has been shown to be obeyed by the incidence, reflected and transmitted waves by deriving energy equation and its simulation. The numerical computations of reflection and transmission coefficients have been carried out for copper material half-space in contact with water at the interface by using MATLAB software. The computer simulated results have been presented graphically in order to bring out clear comparison of various situations.

Using Color to Separate Reflection Components

Shafer, Steven A.
Fonte: University of Rochester. Computer Science Department. Publicador: University of Rochester. Computer Science Department.
Tipo: Relatório
Português
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This paper presents an algorithm for analyzing a standard color image to determine intrinsic images of the amount of interface ("specular") and body ("diffuse") reflection at each pixel. The interface reflection represents the highlights from the original image, and the body reflection represents the original image with highlights removed. Such intrinsic images are of interest because the geometric properties of each type of reflection are simpler than the geometric properties of intensity in a black-and-white image.

Resonant over-reflection of waves by jets.

Lapin, Vladimir Nikolaevich
Fonte: University of Limerick Publicador: University of Limerick
Tipo: Doctoral thesis; all_ul_research; ul_published_reviewed; ul_theses_dissertations; none
Português
Relevância na Pesquisa
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peer-reviewed; The present thesis studies the problem of scattering of large-scale waves by surface currents in the ocean. It has been known for more than a century that corresponding linear equations governing propagation of small amplitude waves across the shear flow contain critical layer singularities (Rayleigh [74]). And more than 40 years ago it was established that propagating waves can effectively interact with the mean flow at such points. As the result, the waves can be partly absorbed (Booker & Bretherton [8]) or over-reflected (i.e. amplified) (Jones [40]). A special case of this phenomenon, when amplification is infinitely strong, is traditionally referred to as resonant over-reflection. Physically the latter corresponds to spontaneous emission of waves by the current. Resonant over-reflection was poorly studied in the past with only a few cases reported in the literature. The aim of this study is to fill this gap and clarify the nature of the phenomenon. We examine scattering of inertia-gravity gravity waves by zonal currents within the reduced gravity rotating shallow water model and Rossby-wave scattering by “two-jet” currents on the quasi-geostrophic β-plane. In both cases reflection and transmission coefficients were calculated numerically for the case when mean flow velocity profiles are approximated by Bickley jets. Resonant over-reflection was found to occur within these two models. We proposed a plausible physical interpretation of the phenomenon as a “resonance” of a wave trapped between two containing potential barriers. It is further demonstrated that...

The nature of the Moho in Australia from reflection profiling: a review

Kennett, B. L. N.; Saygin, E.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
36.51%
The transition between the crust and mantle across the Australian continent shows considerable variations in both depth and sharpness. Recent extensive seismic reflection profiling provides a comprehensive data set to investigate the nature of the Moho in a wide range of geological environments. In reflection seismology the crust is normally characterized by distinct reflectivity whose base is taken as the location of the reflection Moho. This attribution to the base of the crust ties well to refraction and receiver function studies that make a more direct estimate of the depth to the base of the crust. The character of the reflection Moho varies widely across the Precambrian areas of Australia with no consistent link to the surface geology or the estimated age of the crust. In a number of places a double Moho is preserved with underthrusting, suggesting that the reflection Moho is a very ancient feature (at least 1400 Ma in the Capricorn Orogen). Elsewhere, the current Moho reflects multiple generations of crustal reworking.

DOES SCAFFOLDED BLOGGING PROMOTE PRESERVICE TEACHER REFLECTION? EXAMINING THE RELATIONSHIPS BETWEEN LEARNING TOOL AND SCAFFOLDING IN A BLENDED LEARNING ENVIRONMENT

Tan, Ashley
Fonte: [Bloomington, Ind.] : Indiana University Publicador: [Bloomington, Ind.] : Indiana University
Tipo: Doctoral Dissertation
Português
Relevância na Pesquisa
36.58%
Thesis (PhD) - Indiana University, School of Education, 2006; This study examined the effect of two variables, type of online tool and type of hard scaffolding, on the levels of reflection by preservice teachers. The online tools were a discussion forum and personal weblogs (blogs). The scaffolding types were minimal and enhanced. The participants were forty-eight preservice teachers and their instructor from a course on integrating technology into K-12 environments. The preservice teachers reflected online after watching an online video case study and after planning a lesson that integrated technology. Multiple sources of data were collected and analyzed in order to triangulate findings: the reflective online discourse, two questionnaires, interviews with preservice teachers and the instructor, and observations of classroom and online behavior. Levels of reflection were measured by using a reflection rubric by Hawkes and Romiszowski (2001) and a reflection scale by Crotty and Allyn (2001). The results revealed that enhanced scaffolding had a statistically significant effect on promoting higher levels of reflection over minimal scaffolding. This was because the guiding questions in the enhanced scaffold provided structure and focus as well as an expert practitioner's perspective on technology integration. The type of online tool did not have a statistically significant effect on promoting higher levels of reflection. Results suggest that this was due to the different personal preferences of the preservice teachers and their perceived affordances of the online tools. This study suggests that the nature of scaffolding has a more critical role in promoting reflection than the technical affordances of the online tool. In addition...

A qualitative analysis of reflection in undergraduate and graduate programs

Power, Denise Rosemary.
Fonte: Brock University Publicador: Brock University
Tipo: Electronic Thesis or Dissertation
Português
Relevância na Pesquisa
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The purpose ofthis study was to explore various types ofreflection and to explore reflection on action, reflection as a practice, and reflection as a process. In doing this, the intent was to discover the perceived benefits of reflection in the classroom and to provide guidelines for future use at the undergraduate and graduate level. The qualitative components in this study included the data collection strategy of semistructured interviews with 2 undergraduate students, 2 graduate students, 1 undergraduate studies professor, and 1 graduate studies professor. The data analysis strategies included a within-case analysis and a cross-case analysis. Through the interviews participants discussed their experiences with the use ofreflection in the classroom. Through the completion ofthis analysis the researcher expected to discover the benefits ofreflection at this level of education, as well as provide suggestions for future use. Both undergraduate and graduate students and professors were found to benefit from the use of reflection in the classroom. The use ofreflection in the undergraduate and graduate classroom was found to improve student/teacher and student/peer relationships, foster critical thinking, allow for connections between learned theory and life experience...

Reflexão absoluta como medium da crítica de arte : um estudo da crítica filosófica do jovem Walter Benjamin; Absolute reflection as medium of art criticism : a study on Walter Benjamin's early philosophical critique

Wagner de Avila Quevedo
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 25/02/2011 Português
Relevância na Pesquisa
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O presente estudo pretende apresentar a formação do conceito de crítica filosófica na obra do jovem Walter Benjamin a partir da teoria da reflexão dos primeiros românticos alemães (F. Schlegel e Novalis). Se para os românticos a teoria da reflexão é, na leitura de Benjamin, fundamento e pressuposto essencial da crítica de arte, o conceito de crítica benjaminiano se distingue do romântico por meio da problematização da clássica divisão entre forma e conteúdo na arte, para cuja discussão Benjamin traz à baila a estética tardia de Goethe. Contudo, a crítica de Benjamin se aproxima da romântica na medida em que aquela teoria da reflexão realiza, como crítica, uma profunda superação dos problemas clássicos da filosofia alemã, teoria que Benjamin interpreta como medium-de/da-reflexão capaz de elevar a crítica ao mesmo potencial revolucionário vislumbrado pelo romantismo enquanto ruptura estética e filosófica no século XVIII; The following study aims to focus on the concept of criticism in Walter Benjamin´s early writings by bringing up the articulation of Friedrich Schlegel´s and Novalis´ philosophical theory of reflection as ground for romantic art criticism. In this sense, the present study intends to show how Benjamin´s own criticism distinguishes itself from that of the romantic...

Unanticipated partial behavioral reflection: Adapting applications at runtime

Tanter, Éric Pierre; Denker, Marcus; Röthlisberger, David
Fonte: PERGAMON-ELSEVIER SCIENCE LTD Publicador: PERGAMON-ELSEVIER SCIENCE LTD
Tipo: Artículo de revista
Português
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Dynamic, unanticipated adaptation of running systems is of interest in a variety of situations, ranging from functional upgrades to on-the-fly debugging or monitoring of critical applications. In this paper we study a particular form of computational reflection, called unanticipated partial behavioral reflection (UPBR), which is particularly well suited for unanticipated adaptation of realworld systems. Our proposal combines the dynamicity of unanticipated reflection, i.e., reflection that does not require preparation of the code of any sort, and the selectivity and efficiency of partial behavioral reflection (PBR). First, we propose unanticipated partial behavioral reflection which enables the developer to precisely select the required reifications, to flexibly engineer the metalevel and to introduce the metabehavior dynamically. Second, we present a system supporting unanticipated partial behavioral reflection in Squeak Smalltalk, called GEPPETTO, and illustrate its use with a concrete example of a web application. Benchmarks validate the applicability of our proposal as an extension to the standard reflective abilities of Smalltalk.; We acknowledge the financial support of the Swiss National Science Foundation for the project “Analyzing...

Reflection impulsivity in binge drinking: behavioural and volumetric correlates

Banca, Paula; Lange, Iris; Worbe, Yulia; Howell, Nicholas A.; Irvine, Michael; Harrison, Neil A.; Moutoussis, Michael; Voon, Valerie
Fonte: Wiley on behalf of Society for the Study of Addiction Publicador: Wiley on behalf of Society for the Study of Addiction
Tipo: Article; published version
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This is the final published version. It first appeared from Wiley via http://dx.doi.org/10.1111/adb.12227; The degree to which an individual accumulates evidence prior to making a decision, also known as reflection impulsivity, can be affected in psychiatric disorders. Here, we study decisional impulsivity in binge drinkers, a group at elevated risk for developing alcohol use disorders, comparing two tasks assessing reflection impulsivity and a delay discounting task, hypothesizing impairments in both subtypes of impulsivity. We also assess volumetric correlates of reflection impulsivity focusing on regions previously implicated in functional magnetic resonance imaging studies. Sixty binge drinkers and healthy volunteers were tested using two different information-gathering paradigms: the beads task and the Information Sampling Task (IST). The beads task was analysed using a behavioural approach and a Bayesian model of decision making. Delay discounting was assessed using the Monetary Choice Questionnaire. Regression analyses of primary outcomes were conducted with voxel-based morphometry analyses. Binge drinkers sought less evidence prior to decision in the beads task compared with healthy volunteers in both the behavioural and computational modelling analysis. There were no group differences in the IST or delay discounting task. Greater impulsivity as indexed by lower evidence accumulation in the beads task was associated with smaller dorsolateral prefrontal cortex and inferior parietal volumes. In contrast...

Modeling Specular and Diffuse Reflection Sound Fields in Enclosures with an Energy-Intensity Boundary Element Method

Michalis, Krista
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Dissertação
Publicado em //2011 Português
Relevância na Pesquisa
36.48%

Steady-state sound fields in enclosures, with specular and diffuse reflection boundaries, are modeled with a first-principle energy-intensity boundary element method using uncorrelated broadband directional sources. The specular reflection field is represented by a limited set of spherical harmonics that are orthogonal on the half-space. The amplitudes of these harmonics are determined by a Lagrange multiplier method to satisfy the energy conservation integral constraint. The computational problem is solved using an iterative relaxation method starting from the 3-D diffuse reflection solution. At each iteration, directivity harmonics are estimated by post-processing and the influence matrix is refined accordingly. For internal sources, simple first reflection images improve accuracy with virtually no penalty on computation time. Monotonic convergence occurs in relatively few relaxation steps. Extrapolating to an infinite number of boundary elements and iterations gives very accurate results. The method is very computationally efficient. Results are compared to exact benchmark solutions obtained from a frequency-by-frequency modal analysis, and a broadband image method, demonstrating high accuracy. The method of absorption scaling is verified for complicated 3-D cases...

Inversion of seismic refraction and wide-angle reflection traveltimes for three-dimensional layered crustal structure

Rawlinson, Nicholas; Houseman, Gregory Austin; Collins, Chris
Fonte: Blackwell Publishing Ltd Publicador: Blackwell Publishing Ltd
Tipo: Artigo de Revista Científica
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We present a method for the determination of crustal structure by simultaneous inversion of seismic refraction and wide-angle reflection traveltimes for 3-D interface geometry and layer velocity. Crustal structure is represented by layers in which velocity varies linearly with depth, separated by smooth interfaces with a cubic B-spline parametrization. Lateral variations in structure are therefore represented by variations in interface depth only. The model parametrization we have chosen means that ray paths consist of piecewise circular are segments for which analytic expressions of trajectory and traveltime are calculated. The two-point problem of finding the first-arrival ray path and traveltime of a specified phase between a given source and receiver is solved using a shooting technique. A subspace inversion method is used to solve the inverse problem, which is formulated as a non-linear optimization problem in which we seek to minimize an objective function that consists of a data residual term and a regularization term. Before performing the inversion, each data pick must be assigned as a refraction or reflection from a particular layer or interface. Since our method represents structure in terms of interfaces, fewer parameters would generally be used in a reconstruction compared to an equivalent 3-D variable-velocity inversion. The method is well suited to wide-angle surveys that consist of many sources and relatively few receivers (or vice versa)...

Quenching of curve crossing probabilities by quantum reflection

Meister, Carlo; Friedrich, R W
Fonte: Pergamon-Elsevier Ltd Publicador: Pergamon-Elsevier Ltd
Tipo: Artigo de Revista Científica
Português
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When potential energy curves for the relative motion of two atoms in different electronic states cross, the probability for diabatic or adiabatic passage can be described by the Landau-Zener formula. For near-threshold energies, close to the asymptotic value of one of the curves, the corresponding velocity is very small at large separations. Then quantum reflection, which can prevent the atoms from coming close to the avoided crossing, becomes a dominating effect. The probabilities for transmission to smaller separations - in either electronic state - thus vanish towards threshold, a feature not contained in conventional Landau-Zener theory. We propose a correction which takes the effect of quantum reflection into account so that the correspondingly modified Landau-Zener formula remains accurate at low energies, all the way down to threshold.

Interferometric measurement of density in nonstationary shock wave reflection flow and comparison with CFD

Houwing, A Frank; Takayama, Kazuyoshi; Jiang, Zheng Yi; Sun, M; Yada, K; Mitobe, H
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
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We present density measurements from the application of interferometry and Fourier transform fringe analysis to the problem of nonstationary shock wave reflection over a semicircular cylinder and compare our experimental measurements to theoretical results from a CFD simulation of the same problem. The experimental results demonstrate our ability to resolve detailed structure in this complex shock wave reflection problem, allowing visualization of multiple shocks in the vicinity of the triple point, plus visualization of the shear layer and an associated vortical structure. Comparison between CFD and experiment show significant discrepancies with experiment producing a double Mach Reflection when CFD predicts a transitional Mach reflection.