Acousto-optic modulation of optical reflection properties in fiber Bragg gratings and the application in fiber lasers

This thesis aims to investigate the interaction of acoustic waves and fiber Bragg gratings (FBGs) in standard and suspended-core fibers (SCFs), to evaluate the influence of the fiber, grating and modulator design on the increase of the modulation efficiency, bandwidth and frequency. Initially, the frequency response and the resonant acoustic modes of a low frequency acousto-optic modulator (f < 1.2 MHz) are numerically investigated by using the finite element method. Later, the interaction of longitudinal acoustic waves and FBGs in SCFs is also numerically investigated. The fiber geometric parameters are varied and the strain and grating properties are simulated by means of the finite element method and the transfer matrix method. The study indicates that the air holes composing the SCF cause a significant reduction of the amount of silica in the fiber cross section increasing acousto-optic interaction in the core. Experimental modulation of the reflectivity of FBGs inscribed in two distinct SCFs indicates evidences of this increased interaction. Besides, a method to acoustically induce a dynamic phase-shift in a chirped FBG employing an optimized design of modulator is shown. Afterwards, a combination of this modulator and a FBG inscribed in a three air holes SCF is applied to mode-lock an ytterbium doped fiber laser. To improve the modulator design for future applications, two other distinct devices are investigated to increase the acousto-optic interaction, bandwidth and frequency (f > 10 MHz). A high reflectivity modulation has been achieved for a modulator based on a tapered fiber. Moreover, an increased modulated bandwidth (320 pm) has been obtained for a modulator based on interaction of a radial long period grating (RLPG) and a FBG inscribed in a standard fiber. In summary, the results show a considerable reduction of the grating/fiber length and the modulator size, indicating possibilities for compact and faster acousto-optic fiber devices. Additionally, the increased interaction efficiency, modulated bandwidth and frequency can be useful to shorten the pulse width of future all-fiber mode-locked fiber lasers, as well, to other photonic devices which require the control of the light in optical fibers by electrically tunable acoustic waves.

Ultrasonic wave reflection measurements on self-compacting pastes and concretes

The objective of this study was to extend the use of combined longitudinal (P-wave) and shear (S-wave) ultrasonic wave reflection (UWR) to monitor the setting and stiffening of self-compacting pastes and concretes. An additional objective was to interpret the UWR responses of various modified cement pastes. A polymeric buffer with acoustic impedance close to that of cement paste, high impact polystyrene, was chosen to obtain sensitive results from the early hydration period. Criteria for initial and final set developed by our group in a prior study were used to compute setting times by UWR. UWR results were compared with standard penetration measurements. Stiffening behavior and setting times for normal cement pastes, pastes modified with mineral and chemical admixtures, self-compacting pastes, and concretes were explored using penetration resistance, S-wave and P-wave reflection. All three methods showed that set times of pastes varied linearly with w/c, that superplasticizer and fly ash delayed the set times of pastes, and that differences in w/cm, sp/cm, and fa/cm could be detected. Final set times determined from UWR correlated well with those from penetration resistance. Initial set times from S-wave reflection did not correlate very well with those from penetration resistance. Final set times from P-wave and S-wave reflection were roughly the same. Pastes with different chemical admixtures were tested, and the effects of these admixtures on stiffening were determined using UWR. Self-compacting concretes were studied using UWR, and their response and setting times were largely similar to that of corresponding self-compacting pastes. The P-wave reflection response was explored in detail, and the phenomenon of partial debonding and the factors affecting it were explained. Partial debonding is probably caused by autogenous shrinkage at final set, and was controlled and limited by water. The extent of partial debonding was higher with the transducers placed on the side as opposed to the bottom, and the S-wave transducer seemed to promote debonding in the P-wave reflection, whereas the P-wave transducer seemed to reduce debonding in the S-wave reflection. Simultaneous formwork pressure testing and UWR were performed; however, no clear correlation was seen between the two properties.

10 th semester pre-service teacher beliefs and cognitive dissonances : a narrative reflection on efl practice at la Salle University

Tesis (Licenciado en Lenguas Castellana, Inglés y Francés).--Universidad de La Salle. Facultad de Ciencias de La Educación. Licenciatura en Lengua Castellana, Inglés y Francés, 2014

The interaction factor as a challenge for foreign language learning in the technology based education: a pedagogical reflection

The author carries out a pedagogical reflection on how the technology driven distance learning repeatedly neglects the scientific achievements of Second Language Acquisition and Language Pedagogy. Seeing communicative competence as a major goal of a language classroom, she presents the main challenges that the communicative approach poses to distance learning. To this end, a general distance learning theory by Moore is adapted to the needs of language education, through a distinction between three aspects of learner interaction – with the teacher, with other learners and with content. In this three-dimensional paradigm the learner is seen as the main actor of the process, the teacher as a facilitator, the text as a main source of communicative data and the learner autonomy as the fundament of the process.

Intergranular Corrosion and Stress Corrosion Cracking of Extruded AA6005A

A research program focused on understanding the intergranular corrosion (IGC) and stress corrosion cracking (SCC) behavior of AA6005A aluminum extrusions is presented in this dissertation. The relationship between IGC and SCC susceptibility and the mechanisms of SCC in AA6005A extrusions were studied by examining two primary hypotheses. IGC susceptibility of the elongated grain structure in AA6005A exposed to low pH saltwater was found to depend primarily on the morphology of Cu-containing precipitates adjacent to the grain boundaries in the elongated grain structure. IGC susceptibility was observed when a continuous (or semi-continuous) film of Cu-containing phase was present along the grain boundaries. When this film coarsened to form discrete Cu-rich precipitates, no IGC was observed. The morphology of the Cu-rich phase depended on post-extrusion heat treatment. The rate of IGC penetration in the elongated grain structure of AA6005A-T4 and AA6005A-T6 extrusions was found to be anisotropic with IGC propagating most rapidly along the extrusion direction, and least rapidly along the through thickness direction. A simple 3-dimensional geometric model of the elongated grain structure was accurately described the observed IGC anisotropy, therefore it was concluded that the anisotropic IGC susceptibility in the elongated grain structure was primarily due to geometric elongation of the grains. The velocity of IGC penetration along all directions in AA6005A-T6 decreased with exposure time. Characterization of the local environment within simulated corrosion paths revealed that a pH gradient existed between the tip of the IGC path and the external environment. Knowledge of the local environment within an IGC path allowed development of a simple model based on Fick's first law that considered diffusion of Al3+ away from the tip of the IGC path. The predicted IGC velocity agreed well with the observed IGC velocity, therefore it was determined that diffusion of Al3+ was the primary factor in determining the velocity of IGC penetration. The velocity of crack growth in compact tensile (CT) specimens of AA6005A-T6 extrusion exposed to 3.5% NaCl at pH = 1.5 was nearly constant over a range of applied stress intensities, exposure times, and crack lengths. The crack growth behavior of CT specimens of AA6005A-T6 extrusion exposed to a solution of 3.5% NaCl at pH = 2.0 exhibited similar behavior, but the crack velocity was ~10.5X smaller than that those exposed to a solution at pH =1.5. Analysis of the local stress state and polarization behavior at the crack tip predicted that increasing the pH of the bulk solution from 1.5 to 2.0 would decrease the corrosion current density at the crack tip by approximately 11.8X. This predicted decrease in corrosion current density was in reasonable agreement with the observed decrease in SCC velocity associated with increasing the solution pH from 1.5 to 2.0. The agreement between the predicted and observed SCC velocities suggested that the electrochemical reactions controlling SCC in AA6005A-T6 extrusions are ultimately controlled by the pH gradient that exists between the crack tip and external environment.

Effects of truck traffic on top-down fatigue cracking performance of flexible pavements using a new mechanics-based analysis framework

The mechanics-based analysis framework predicts top-down fatigue cracking initiation time in asphalt concrete pavements by utilising fracture mechanics and mixture morphology-based property. To reduce the level of complexity involved, traffic data were characterised and incorporated into the framework using the equivalent single axle load (ESAL) approach. There is a concern that this kind of simplistic traffic characterisation might result in erroneous performance predictions and pavement structural designs. This paper integrates axle load spectra and other traffic characterisation parameters into the mechanics-based analysis framework and studies the impact these traffic characterisation parameters have on predicted fatigue cracking performance. The traffic characterisation inputs studied are traffic growth rate, axle load spectra, lateral wheel wander and volume adjustment factors. For this purpose, a traffic integration approach which incorporates Monte Carlo simulation and representative traffic characterisation inputs was developed. The significance of these traffic characterisation parameters was established by evaluating a number of field pavement sections. It is evident from the results that all the traffic characterisation parameters except truck wheel wander have been observed to have significant influence on predicted top-down fatigue cracking performance.

Loop openness: a video reflection on the open work of art

The objective of this article is to reflect on the video art work in its loop production to perceive the possibility of it being received as an open work. In order to contextualize this reflection the text is anchored in the concept of image-crystal from Gilles Deleuze. For the purpose of empirically explore theoretical concepts such as video art, open work and image-crystal it was produced a practical project of video art that intends to reflect on the notion of time in a context of a loop exhibition. Therefore this project aims to motivate the reflection on the loop as a mechanism to contour the ephemeral character of video art and, at the same time, it seeks to emphasize questions about the element of multiplicity and plurality in art. It is a scientific and artistic project in which the practical component supports the dialectic between theory and practice, action and reflection. In this sense, based on the video entitled "The Walk" this article demonstrates how the theoretical concepts were used to support the artistic creation. Finally the conclusions sustain that the work of video art, when presented in loop, is a creative and expository strategy which encourages multiple interpretations that vary according to the narrative, the context in which it takes place and the attitude and the background of the spectator.

Systems 1 and 2 thinking processes and cognitive reflection testing in medical students

Background: Diagnostic decision-making is made through a combination of Systems 1 (intuition or pattern-recognition) and Systems 2 (analytic) thinking. The purpose of this study was to use the Cognitive Reflection Test (CRT) to evaluate and compare the level of Systems 1 and 2 thinking among medical students in pre-clinical and clinical programs. Methods: The CRT is a three-question test designed to measure the ability of respondents to activate metacognitive processes and switch to System 2 (analytic) thinking where System 1 (intuitive) thinking would lead them astray. Each CRT question has a correct analytical (System 2) answer and an incorrect intuitive (System 1) answer. A group of medical students in Years 2 & 3 (pre-clinical) and Years 4 (in clinical practice) of a 5-year medical degree were studied. Results: Ten percent (13/128) of students had the intuitive answers to the three questions (suggesting they generally relied on System 1 thinking) while almost half (44%) answered all three correctly (indicating full analytical, System 2 thinking). Only 3-13% had incorrect answers (i.e. that were neither the analytical nor the intuitive responses). Non-native English speaking students (n = 11) had a lower mean number of correct answers compared to native English speakers (n = 117: 1.0 s 2.12 respectfully: p < 0.01). As students progressed through questions 1 to 3, the percentage of correct System 2 answers increased and the percentage of intuitive answers decreased in both the pre-clinical and clinical students. Conclusions: Up to half of the medical students demonstrated full or partial reliance on System 1 (intuitive) thinking in response to these analytical questions. While their CRT performance has no claims to make as to their future expertise as clinicians, the test may be used in helping students to understand the importance of awareness and regulation of their thinking processes in clinical practice.

Reflection Framework

Suggested framework for reflection

Reflection Framework - feedback

Expanding the framework for reflection

Reflection examples

Expanding the framework for reflection

Monomanias - auto-narrativas e auto-ficções: estudo sobre as manias do eu como sintoma civilizacional e seu reflexo nas artes plásticas : Monomanias - auto narratives and auto-fictions: study on the manias of the self as a civilizational symptom and their reflection in contemporay art

A palavra monomania provém do grego monos que se traduz por "um" e mania que significa "mania". O emprego do termo em psiquiatria deve-se a Esquirol e mais tarde a Pierre Janet. Contudo, o uso da palavra não se circunscreve ao campo da psiquiatria, o conceito de monomania é também usado para definir as denominadas "manias do eu". Nos dias de hoje, a subjectividade, a particularidade de cada indivíduo apartou-se da noção de Homem como um todo objectivo. A massificação gerou a sociedade do narcisismo. A World Wide Web permitiu ao sujeito dar a conhecer ao mundo a sua individualidade. O sujeito é livre de se mostrar, de se fazer ouvir, de contar as suas histórias e principalmente a sua própria. À semelhança do nosso quotidiano, podemos encontrar na arte contemporânea propostas artísticas que se prendem com o conceito de monomania, como o exemplo das mitologias individuais, auto-narrativas e auto-ficções de Sophie Calle: "de vivre sa vie pour faire ceuvre et de faire ceuvre pour vivre sa vie." ABSTRACT: Etymologically, "monomania" originates from the Greek words "monos" and "mania". The former refers to the notion of "one" and the latter to "mania". The term's introduction in the field of psychiatry is attributed first to Esquirol and later Pierre Janet. Usage of the word isn’t, however, exclusive to psychiatric jargon: the concept of monomania is also used to define so called "manias of the self’. Today, the subjectivity and specificity of each individual have distanced themselves from the notion of Man as an objective whole. Massification has led to a society of narcissism. The World Wide Web has allowed the subject to make her individuality known to the world at large. The subject is free to exhibit herself, make herself heard, tell her stories, and especially her own. ln a way similar to daily life, we find agendas in contemporary art that approach the concept of monomania, such as the personal mythologies, self-narratives and selffictions of Sophie Calle: "de vivre sa vie pour faire oeuvre et de faire oeuvre pour vivre sa vie."

“The most artistic lesson I ever heard” - a contribution to the reflection on the comment made by William James regarding a lesson by Ernst Mach

On November the 2nd 1882, William James visited Ernst Mach in Prague, and attended one of his lectures. The conversation with Mach and the lecture were marking events for James. Based, namely, on James’s lectures for teachers and on Mach’s lectures for the general public, we propose a reflection on the defining traits that made that event "the most artistic lesson [James] ever heard". We shall remark on the imaginative joy contained in these texts, which appear to embody some of James' key ideas on Education. The experience of knowledge about the world contained in the texts, reveals that "to experiment" means "not coldly to observe a thing happening outside us, but to undergo, to feel within oneself, to live oneself this or that manner of being".

Online discussion forums: a tool to stimulate language teachers’ interaction and reflection

The decisions and approaches taken by the teachers in the classroom are guided by their beliefs of what it means to teach and learn which are built along their history as a student and teacher. However, only the experiences lived by the teachers do not guarantee their professional development (CELCE-MURCIA, 2001). The teacher’s engagement in a process of reflection on their beliefs and pedagogical practices, which leads to the construction and reconstruction of meaning about their actions and the classroom is essential to their development, in order to become an agent of reflection. Considering the importance of reflection in teacher education, in this article, we emphasize the potential of virtual discussion forums to foster the sharing and the reflection of beliefs and practices of postgraduate students (language teachers) about the language teaching and learning process through interactive situations. By means of guidance and online and offline reflection, the students were able to share experiences on teaching and learning, as well as discuss their beliefs and the beliefs of their colleagues. The results of this study point out that understanding and interpreting the teachers’ beliefs can be a path to the transformation of their teaching practice through reflective practice. They also emphasize that the use of virtual discussion forums as a pedagogical tool can contribute in this direction.

A new low temperature synthesis route of fraipontite (Zn,Al)3(Si,Al)2O5(OH)4

A low temperature synthesis method based on the decomposition of urea at 90°C in water has been developed to synthesise fraipontite. This material is characterised by a basal reflection 001 at 7.44 Å. The trioctahedral nature of the fraipontite is shown by the presence of a 06l band around 1.54 Å, while a minor band around 1.51 Å indicates some cation ordering between Zn and Al resulting in Al-rich areas with a more dioctahedral nature. TEM and IR indicate that no separate kaolinite phase is present. An increase in the Al content however, did result in the formation of some SiO2 in the form of quartz. Minor impurities of carbonate salts were observed during the synthesis caused by to the formation of CO32- during the decomposition of urea.