567 resultados para FBG interrogation


Relevância:

10.00% 10.00%

Publicador:

Resumo:

Este trabalho tem por objetivo levantar e analisar algumas concepções sobre a avaliação escolar em Matemática e sobre a Avaliação em Matemática do Sistema de Avaliação de Rendimento Escolar do Estado de São Paulo (SARESP), procurando desvendar a realidade que é encontrada nas escolas paulistas referente à avaliação dessa disciplina. O intuito é verificar os pontos de vista dos alunos, professores, gestores escolares, família e especialistas para articular uma organização escolar que desenvolva um processo permanente de construção do conhecimento. Para verificar quais as concepções referentes às avaliações já citadas foram adotadas entrevistas, questionários e desenhos realizados pelos alunos, mostrando o que pensam sobre as avaliações previamente aplicadas. As entrevistas somente foram aplicadas aos discentes, pois seus depoimentos são fundamentais para a pesquisa. Para a concretização destas entrevistas foi solicitado aos alunos à produção de desenhos que representassem o que são as avaliações já mencionadas anteriormente. Levantamos uma grande quantidade de informações a partir desses depoimentos e desenhos sobre as avaliações pesquisadas, a opinião que possuem sobre a escola, seus professores de Matemática, de como são ministradas as aulas e também sobre a forma de avaliar dos professores. Os questionários foram dirigidos ao corpo docente de Matemática, diretor, vice-diretor, professor coordenador, supervisor de ensino, família e especialistas em Educação, Psicologia da Educação e Matemática para verificar também sua concepção sobre avaliação escolar em Matemática e sobre a prova de Matemática do SARESP, que fazem parte fundamental de todo o processo de avaliação, pois, direta ou indiretamente, estão ligados a ela e são responsáveis pelos seus resultados. Na análise dos dados obtidos foram destacados, nos depoimentos dos questionários e das entrevistas, as,unidades significativas referentes aos processos de avaliações pesquisadas, para com isso analisarmos e verificarmos quais são as opiniões e fatos que podem ajudar ou atrapalhar todo o processo de Avaliação em Matemática, tanto o escolar quanto o de grande escala como o SARESP. Também foram analisados o que os alunos representaram na produção dos desenhos. As imagens adquiridas demonstraram muitas informações sobre o que os discentes pensam sobre a Avaliação em Matemática ao desenhar monstros, corações, números e até mesmo pontos de exclamação e de interrogação. Este estudo foi desenvolvido em uma escola pública da rede Estadual de ensino do Estado de São Paulo. Essa pesquisa investiga o que realmente está acontecendo em todo o processo de Avaliação em Matemática, possibilitando identificar no que cada sujeito envolvido neste processo pode contribuir ou atrapalhar para sua concretização, evidenciando assim áreas críticas efavoráveis sobre a tão temida e polêmica Avaliação em Matemática.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Social cognitive neuroscience is an emerging branch of cognitive neuroscience that bridges together social psychology and neuroscience. At its core is an understanding of the relationship between the brain and social interaction. The social cognitive neuroscientist places empirical endeavor within a three–stage framework, and questions falling under the SCN rubric undergo interrogation at each of these three levels. Firstly, we seek to understand a neuroscience of social interactions at the social level. Here we need to understand the motivational and other social factors that drive our behavior and experience in the real world. It goes without saying that any study of the cognitive neuroscience of socially interactive behavior must first be informed by social psychological theory to maintain ecological validity. Second, the social cognitive neuroscientist must be an adroit cognitive psychologist and be able to examine interactive behavior from the cognitive level. It is here that information–processing models and theories are applied to the understanding of our social behavior. Finally, studies at the neural level seek to inform us about the cortical structures, as well as the way they interact with other, in the mediation of the previous cognitive level. This volume brings together contributions from leading thinkers in both the social cognitive neurosciences and business to provide a comprehensive introduction and overview of a social cognitive neuroscience of the business brain. NOTE: Annals volumes are available for sale as individual books or as a journal. For information on institutional journal subscriptions, please visit www.blackwellpublishing.com/nyas. ACADEMY MEMBERS: Please contact the New York Academy of Sciences directly to place your order (www.nyas.org). Members of the New York Academy of Science receive full–text access to the Annals online and discounts on print volumes. Please visit http://www.nyas.org/MemberCenter/Join.aspx for more information about becoming a member

Relevância:

10.00% 10.00%

Publicador:

Resumo:

This thesis presents detailed investigation of UV inscribed fibre grating based devices and novel developments in the applications of such devices in optical sensing and fibre laser systems. The major contribution of this PhD programme includes the systematic study on fabrication, spectral characteristics and applications of different types of UV written in-fibre gratings such as Type I and IA Fibre Bragg Gratings (FBGs), Chirped Fibre Bragg Gratings (CFBGs) and Tilted Fibre Gratings (TFGs) with small, large and 45º tilted structures inscribed in normal silica fibre. Three fabrication techniques including holographic, phase-mask and blank beam exposure scanning, which were employed to fabricate a range of gratings in standard single mode fibre, are fully discussed. The thesis reports the creation of smart structures with self-sensing capability by embedding FBG-array sensors in Al matrix composite. In another part of this study, we have demonstrated the particular significant improvements made in sensitising standard FBGs to the chemical surrounding medium by inducing microstructure to the grating by femtosecond (fs) patterning assisted chemical etching technique. Also, a major work is presented for the investigation on the structures, inscription methods and spectral Polarisation Dependent Loss (PDL) and thermal characteristics of different angle TFGs. Finally, a very novel application in realising stable single polarisation and multiwavelength switchable Erbium Doped Fibre Lasers (EDFLs) using intracavity polarisation selective filters based on TFG devices with tilted structures at small, large and exact 45° angles forms another important contribution of this thesis.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

This thesis presents a numerical and experimental investigation on applications of ultralong Raman fibre lasers in optical communications, supercontinuum generation and soliton transmission. The research work is divided in four main sections. The first involves the numerical investigation of URFL intra-cavity power and the relative intensity noise transfer evolution along the transmission span. The performance of the URFL is compared with amplification systems of similar complexity. In the case of intracavity power evolution, URFL is compared with a first order Raman amplification system. For the RIN transfer investigation, URFL is compared with a bi-directional dual wavelength pumping system. The RIN transfer function is investigated for several cavity design parameters such as span length, pump distribution and FBG reflectivity. The following section deals with experimental results of URFL cavities. The enhancement of the available spectral bandwidth in the C-band and its spectral flatness are investigated for single and multi-FBGs cavity system. Further work regarding extended URFL cavity in combination with Rayleigh scattering as random distributed feedback produced a laser cavity with dual wavelength outputs independent to each other. The last two sections relate to URFL application in supercontinuum (SC) generation and soliton transmission. URFL becomes an enhancement structure for SC generation. This thesis shows successful experimental results of SC generation using conventional single mode optical fibre and pumped with a continuous wave source. The last section is dedicated to soliton transmission and the study of soliton propagation dynamics. The experimental results of exact soliton transmission over multiple soliton periods using conventional single mode fibre are shown in this thesis. The effect of the input signal, pump distribution, span length and FBGs reflectivity on the soliton propagation dynamics is investigated experimentally and numerically.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Synaptic plasticity is the dynamic regulation of the strength of synaptic communication between nerve cells. It is central to neuronal development as well as experience-dependent remodeling of the adult nervous system as occurs during memory formation. Aberrant forms of synaptic plasticity also accompany a variety of neurological and psychiatric diseases, and unraveling the biological basis of synaptic plasticity has been a major goal in neurobiology research. The biochemical and structural mechanisms underlying different forms of synaptic plasticity are complex, involving multiple signaling cascades, reconfigurations of structural proteins and the trafficking of synaptic proteins. As such, proteomics should be a valuable tool in dissecting the molecular events underlying normal and disease-related forms of plasticity. In fact, progress in this area has been disappointingly slow. We discuss the particular challenges associated with proteomic interrogation of synaptic plasticity processes and outline ways in which we believe proteomics may advance the field over the next few years. We pay particular attention to technical advances being made in small sample proteomics and the advent of proteomic imaging in studying brain plasticity.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

We present a new method for the interrogation of large arrays of Bragg grating sensors. Eight gratings operating between the wavelengths of 1533 and 1555 nm have been demultiplexed. An unbalanced Mach—Zehnder interferometer illuminated by a single low-coherence source provides a high-phase-resolution output for each sensor, the outputs of which are sequentially selected in wavelength by a tunable Fabry-Perot interferometer. The minimum detectable strain measured was 90 ne-vHz at 7 Hz for a wavelength of 1535 nm.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

We report a distinctive polarization mode coupling behaviour of tilted fibre Bragg gratings (TFBGs) with a tilted angle exceeding 45°. The ex-45° TFBGs exhibit pronounced polarization mode splitting resulted from the birefringence induced by the grating structure asymmetry. We have fabricated TFBGs with a tilted structure at 81° and studied their properties under transverse load applied to their equivalent fast and slow axes. The results show that the light coupling to the orthogonally polarized modes of the 81°-TFBGs changes only when the load is applied to their slow axis, giving a prominent directional loading response. For the view of real applications, we further investigated the possibility of interrogating such a TFBG-based load sensor using low-cost and compact-size single wavelength source and power detector. The experimental results clearly show that the 81°-TFBGs plus the proposed power-measurement interrogation scheme may be developed to an optical fibre vector sensor system capable of not just measuring the magnitude but also recognizing the direction of the applied transverse load. Using such an 81°-TFBG based load sensor, a load change as small as 1.6 × 10-2 g may be detected by employing a standard photodiode detector.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Smart structure sensors based on embedded fibre Bragg grating (FBG) arrays in aluminium alloy matrix by ultrasonic consolidation (UC) technique have been proposed and demonstrated successfully. The temperature, loading and bending responses of the embedded FBG arrays have been systematically characterized. The embedded FBGs exhibit an average temperature sensitivity of ~36 pm °C-1, which is three times higher than that of normal FBGs, a bending sensitivity of 0.73 nm/m-1 and a loading responsivity of ~0.1 nm kg-1 within the dynamic range from 0 kg to 3 kg. These initial experimental results clearly demonstrate that the UC produced metal matrix structures can be embedded with FBG sensor arrays to become smart structures with capabilities to monitor the structure operation and health conditions in applications.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Single- and multi-core passive and active germanate and tellurite glass fibers represent a new class of fiber host for in-fiber photonics devices and applications in mid-IR wavelength range, which are in increasing demand. Fiber Bragg grating (FBG) structures have been proven as one of the most functional in-fiber devices and have been mass-produced in silicate fibers by UV-inscription for almost countless laser and sensor applications. However, because of the strong UV absorption in germanate and tellurite fibers, FBG structures cannot be produced by UVinscription. In recent years femtosecond (fs) lasers have been developed for laser machining and microstructuring in a variety of glass fibers and planar substrates. A number of papers have been reported on fabrication of FBGs and long-period gratings in optical fibers and also on the photosensitivity mechanism using 800nm fs lasers. In this paper, we demonstrate for the first time the fabrication of FBG structures created in passive and active single- and three-core germanate and tellurite glass fibers by using 800nm fs-inscription and phase mask technique. With a fs peak power intensity in the order of 1011W/cm2, the FBG spectra with 2nd and 3rd order resonances at 1540nm and 1033nm in a single-core germanate glass fiber and 2nd order resonances between ~1694nm and ~1677nm with strengths up to 14dB in all three cores of three-core passive and active tellurite fibers were observed. Thermal and strain properties of the FBGs made in these mid-IR glass fibers were characterized, showing an average temperature responsivity of ~20pm/°C and a strain sensitivity of 1.219±0.003pm/µe.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Two in-fiber Bragg grating (FBG) temperature sensor systems for medical applications are demonstrated: (1) an FBG flow-directed thermodilution catheter based on interferometric detection of wavelength shift that is used for cardiac monitoring; and (2) an FBG sensor system with a tunable Fabry-Perot filter for in vivo temperature profiling in nuclear magnetic resonance (NMR) machines. Preliminary results show that the FBG sensor is in good agreement with electrical sensors that are widely used in practice. A field test shows that the FBG sensor system is suitable for in situ temperature profiling in NMR machines for medical applications.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

A low cost interrogation scheme is demonstrated for a refractometer based on an in-line fiber long period grating (LPG) Mach–Zehnder interferometer. Using this interrogation scheme the minimum detectable change in refractive index of ?n ~ 1.8×10-6 is obtained, which is the highest resolution achieved using a fiber LPG device, and is comparable to precision techniques used in the industry including high performance liquid chromatography and ultraviolet spectroscopy.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

A novel quasidistributed in-fiber Bragg grating (FBG) temperature sensor system has been developed for temperature proving in vivo in the human body for medical applications, e.g., hyperthermia treatment. This paper provides the operating principle of FBG temperature sensors and then the design of the sensor head. High-resolution detection of the wavelength-shifts induced by temperature changes are achieved using drift-compensated interferometric detection while the return signals from the FBG sensor array are demultiplexed with a simple monochromator which offers crosstalk-free wavelength-division-multiplexing (WDM). A “strain-free” probe is designed by enclosing the FBG sensor array in a protection sleeve. A four FBG sensor system is demonstrated and the experimental results are in good agreement with those obtained by traditional electrical thermocouple sensors. A resolution of 0.1°C and an accuracy of ±0.2°C over a temperature range of 30-60°C have been achieved, which meet established medical requirements.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The use of high birefringence fibre forming a differential path interferometer as an interrogation unit for heterodyne fibre optic sensing applications is described.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Reported are observations and measurements of the inscription of fibre Bragg gratings in two different types of microstructured polymer optical fibre: few-moded and endlessly single mode. Contrary to FBG inscription in silica microstructured fibre, where high energy laser pulses are a prerequisite, we have successfully used a low power CW laser source operating at 325nm to produce 1-cm long gratings with a reflection peak at 1570 nm. Peak reflectivities of more than 10% have been observed.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

We have designed and fabricated a new type of fibre Bragg grating (FBG) with a V-shaped dispersion profile for multi-channel dispersion compensation in communication links.