Página 1 dos resultados de 321 itens digitais encontrados em 0.003 segundos

Structural integrity assessment of dissimilar girth welds in lined and clad offshore pipelines installed by the reeling method

Souza, Rodolfo Ferronatto de; Ruggieri, Claudio
Fonte: SOBENA; Rio de Janeiro Publicador: SOBENA; Rio de Janeiro
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
27.45%
The increasing demand for energy has motivated the oil and natural gas exploration in very hostile environments, including very deep water operation and the transport of corrosive fluids. Technological advances favor the use of high strength steel pipelines either clad or mechanically lined with a corrosion resistant alloy (CRA), such as Alloy 625, for the transport of corrosive hydrocarbons. Moreover, these pipelines are subjected to severe installation conditions and a case of interest is the pipe reeling process which allows pipe welding and inspection to be conducted at onshore facilities. While cost effective, fracture assessments and specification of critical flaw sizes for the girth welds of lined/clad pipes become more complex due to the dissimilar nature of these materials and the high levels of plastic strain imposed during installation. In particular, effective analyses of crack driving forces in undermatched or partially mismatched pipe girth welds remain essential to determine more accurate acceptable flaw sizes for the piping system based upon conventional ECA procedures. This work focuses on development of a procedure to determine the elastic-plastic crack driving forces for pipe girth welds with circumferential surface cracks subjected to bending load for a wide range of geometries and weld mismatch levels based upon the EPRI methodology and its applicability to ECA analysis of undermatched clad pipe girth welds.; FAPESP through grants 304132/2009-8 and 476581/2009-5

Soldagem por FSW de ligas de alumínio Alcalad AA2024-T3 e AA7075-T6; Friction stir welding of AA2024-T3 and AA7075-T6 clad aluminum alloys

Fioravanti, Artur Suárez
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
27.27%
A soldagem das ligas de alumínio AA2024-T3 e AA7075-T6 sempre foi um obstáculo para indústria devido à alta suscetibilidade a trincas durante o processo de soldagem ao arco elétrico. Estas ligas são largamente utilizadas na indústria aeronáutica devido a sua alta resistência mecânica e baixo peso específico do alumínio, sendo que o método de união mais utilizado é a rebitagem. Com o advento da soldagem por FSW, surge uma nova oportunidade de união destas ligas sendo que os estudos apresentados até o momento demonstram excelentes propriedades mecânicas da junta. “Friction Stir Welding” – FSW é uma técnica de soldagem desenvolvida em 1991 pelo “The Welding Institute” (TWI) na Inglaterra. Esta solda tem a vantagem de ocorrer no estado sólido, que preserva as propriedades mecânicas das ligas, ao contrário dos métodos de soldagem convencionais que envolvem fusão e produzem, em grande parte, microestruturas com baixas propriedades mecânicas. No processo FSW uma ferramenta de alta resistência mecânica com um determinado perfil é rotacionada de forma a gerar atrito nas peças a serem soldadas. Este atrito gera calor suficiente para aumentar a ductilidade e misturar o material na junta, consolidando o mesmo...

Produtividade da palma forrageira cultivada em diferentes densidades de plantio

Silva,Laerte Marques da; Fagundes,Jailson Lara; Viegas,Pedro Alberto Almeida; Muniz,Evandro Neves; Rangel,José Henrique de Albuquerque; Moreira,Andréia Luciane; Backes,Alfredo Acosta
Fonte: Universidade Federal de Santa Maria Publicador: Universidade Federal de Santa Maria
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/11/2014 PT
Relevância na Pesquisa
27.45%
Entre as práticas e técnicas empregadas para obtenção de maior produtividade de massa seca, a escolha do arranjamento de plantas é, entre as decisões de manejo das plantas cultivadas, uma das mais importantes, associada à escolha da cultivar e do sistema de cultivo. Em função do exposto, objetivou-se com este trabalho avaliar a produtividade de forragem de palma forrageira cultivada em diferentes densidades de plantio. O experimento foi instalado no Campo Experimental do CPATC - Embrapa, em Frei Paulo - SE. O delineamento experimental utilizado foi em blocos casualizados, com parcelas subdivididas e quatro repetições. As parcelas foram representadas por genótipos de palma forrageira (Miúda, Redonda e Gigante) e as subparcelas pelas seguintes densidades de plantio (10.000, 20.000, 40.000 e 80.000 plantas ha-1). Os genótipos de palma forrageira apresentam comportamento diferente quanto ao número de cladódios na 1a inserção e no número de cladódios por planta. O aumento da densidade de plantio reduz o comprimento e a largura do cladódio. Existe comportamento diferencial dos genótipos quanto à capacidade produtiva em diferentes densidades. A palma forrageira Miúda apresenta melhor potencial produtivo no cultivo adensado. Já a palma Redonda e Gigante tem maior teor de umidade na massa verde da forragem...

Double-clad fiber with a tapered end for confocal endomicroscopy

Lemire-Renaud, Simon; Strupler, Mathias; Benboujja, Fouzi; Godbout, Nicolas; Boudoux, Caroline
Fonte: Optical Society of America Publicador: Optical Society of America
Tipo: Artigo de Revista Científica
Publicado em 03/10/2011 EN
Relevância na Pesquisa
27.27%
We present a double-clad fiber coupler (DCFC) for use in confocal endomicroscopy to reduce speckle contrast, increase signal collection while preserving optical sectioning. The DCFC is made by incorporating a double-clad tapered fiber (DCTF) to a fused-tapered DCFC for achromatic transmission (from 1265 nm to 1325 nm) of > 95% illumination light trough the single mode (SM) core and collection of > 40% diffuse light through inner cladding modes. Its potential for confocal endomicroscopy is demonstrated in a spectrally-encoded imaging setup which shows a 3 times reduction in speckle contrast as well as 5.5 × increase in signal collection compared to imaging with a SM fiber.

Improved Synthesis of Carbon Clad Silica Stationary Phases

Ahmad, Imad A. Haidar; Carr, Peter W.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
27.45%
Previously we described a novel method for clading elemental carbon onto the surface of catalytically activated silica by a chemical vapor deposition (CVD) method using hexane as the carbon source and its use as a substitute for carbon clad zirconia.1,2 In that method, we showed that very close to exactly one uniform monolayer of Al (III) was deposited on the silica by a process analogous to precipitation from homogeneous solution in order to preclude pore blockage. The purpose of the Al(III) monolayer layer is to activate the surface for subsequent CVD of carbon. In this work, we present an improved procedure for preparing the carbon clad silica (denoted CCSi) phases along with a new column packing process. The new method yields CCSi phases having better efficiency, peak symmetry and higher retentivity compared to carbon clad zirconia.

Laser tissue coagulation and concurrent optical coherence tomography through a double-clad fiber coupler

Beaudette, Kathy; Baac, Hyoung Won; Madore, Wendy-Julie; Villiger, Martin; Godbout, Nicolas; Bouma, Brett E.; Boudoux, Caroline
Fonte: Optical Society of America Publicador: Optical Society of America
Tipo: Artigo de Revista Científica
Publicado em 16/03/2015 EN
Relevância na Pesquisa
27.27%
Double-clad fiber (DCF) is herein used in conjunction with a double-clad fiber coupler (DCFC) to enable simultaneous and co-registered optical coherence tomography (OCT) and laser tissue coagulation. The DCF allows a single channel fiber-optic probe to be shared: i.e. the core propagating the OCT signal while the inner cladding delivers the coagulation laser light. We herein present a novel DCFC designed and built to combine both signals within a DCF (>90% of single-mode transmission; >65% multimode coupling). Potential OCT imaging degradation mechanisms are also investigated and solutions to mitigate them are presented. The combined DCFC-based system was used to induce coagulation of an ex vivo swine esophagus allowing a real-time assessment of thermal dynamic processes. We therefore demonstrate a DCFC-based system combining OCT imaging with laser coagulation through a single fiber, thus enabling both modalities to be performed simultaneously and in a co-registered manner. Such a system enables endoscopic image-guided laser marking of superficial epithelial tissues or laser thermal therapy of epithelial lesions in pathologies such as Barrett’s esophagus.

An?lise clad?stica e descri??o de um grupo novo de esp?cies de Edessa (Heteroptera, Pentatomidae, Edessinae)

SILVA, Val?ria Juliete da
Fonte: Universidade Federal do Pará Publicador: Universidade Federal do Pará
Tipo: Dissertação de Mestrado
POR
Relevância na Pesquisa
27.45%
A subordem Heteroptera, ? o maior t?xon dentre os hemimet?bolos, composta por sete infraordens, 23 superfam?lias e 80 fam?lias. Dentre estas, Pentatomidae ? a quarta fam?lia mais numerosa e diversa entre os heter?pteros, possuindo 4.100 esp?cies distribu?das em 760 g?neros e em sete subfam?lias. Edessinae possui atualmente cerca de 290 esp?cies distribu?das em seis g?neros: Edessa, Brachystethus, Peromatus, Olbia, Pantochlora e Doesburgedessa. De todos estes g?neros, Edessa ? o que possui o maior n?mero de esp?cies e o que concentra quase a totalidade dos problemas taxon?micos e nomenclaturas da subfam?lia. Devido ao seu tamanho, a revis?o est? sendo feita em partes, a partir do estudo de grupos de esp?cies unidos por poss?veis sinapomorfias. Assim o objetivo geral do trabalho ? propor e descrever um novo grupo de esp?cies com base em uma an?lise clad?stica. Para o estudo foram examinados 114 exemplares pertencentes a institui??es nacionais e internacionais e a cole??es particulares. As descri??es seguem um modelo tradicional tamb?m usado para Edessinae. S?o apresentadas medidas e fotografias das esp?cies, desenhos do processo metasternal e genit?lia de ambos os sexos, chave dicot?mica e mapa de distribui??o. Para a analise clad?stica...

Planejamento estrat??gico governamental em contexto democr??tico: li????es da Am??rica Latina

Cardoso J??nior, Jos?? Celso (Organizador); Garcia, Ronaldo Coutinho (Organizador)
Fonte: Escola Nacional de Administra????o P??blica (ENAP); Centro Latino Americano de Administra????o para o Desenvolvimento (CLAD) Publicador: Escola Nacional de Administra????o P??blica (ENAP); Centro Latino Americano de Administra????o para o Desenvolvimento (CLAD)
Tipo: Peri??dico/Revista/Caderno
IDIOMA::ESPANHOL:ESPA??OL:ES; IDIOMA::PORTUGU??S:PORTUGU??S:PT
Relevância na Pesquisa
37.27%
Livro sobre Planejamento Estrat??gico, decorrente de curso do mesmo nome, realizado na ENAP em 2013, em parceria com o Centro Latino Americano de Administra????o para o Desenvolvimento (CLAD); N??mero de p??ginas: 138 p.; Planejamento Estrat??gico; Sum??rio: Apresenta????o ??? Paulo Carvalho Pref??cio ??? Gregorio Montero Introdu????o ??? Governo e planejamento em democracias progressivas: desafios para a Am??rica Latina - Ronaldo Coutinho Garcia e Jos?? Celso Cardoso Jr Cap??tulo 1 ??? Planejamento governamental e gest??o p??blica no Brasil: balan??o da experi??ncia federal e desafios no s??c. XXI ??? Jos?? Celso Cardoso Jr Cap??tulo 2 ??? Planificaci??n estrat??gica gubernamental en un entorno democr??tico, lecciones de Am??rica Latina: el caso de Argentina ??? Mart??n Astarita, Javier Cach??s e Mariano Montes Cap??tulo 3 ??? Planificaci??n estrat??gica gubernamental en un entorno democr??tico, lecciones de Am??rica Latina: la ley de v??ctimas ??? pol??tica que contribuye a la paz y el desarrollo en Colombia ??? Andr??s Alejandro Camelo Giaraldo Cap??tulo 4 ??? Planificaci??n estrat??gica gubernamental en un entorno democr??tico, lecciones de Am??rica Latina: el caso de Costa Rica ??? Yanory Castillo Garc??a e Irene Rom??n Fuentes Cap??tulo 5 ??? Planificaci??n estrat??gica gubernamental en un entorno democr??tico...

Por uma carta latino-ibero-americana de compet??ncias comuns para dirigentes p??blicos: a proposta de Portugal; Por una carta latino-ibero-americana de competencias comunes para los directivos p??blicos: la propuesta de Portugal; For a Latin-Ibero-American chart of common competencies for public leaders: the proposal from Portugal

Figueiredo, Jo??o; Tavares, Lu??s Valadares
Fonte: Escola Nacional de Administra????o P??blica (ENAP); Revista do Servi??o P??blico (RSP) Publicador: Escola Nacional de Administra????o P??blica (ENAP); Revista do Servi??o P??blico (RSP)
Tipo: Artigo de Revista Científica
IDIOMA::PORTUGU??S:PORTUGU??S:PT
Relevância na Pesquisa
27.45%
Nesta comunica????o, discutem-se as compet??ncias exigidas aos dirigentes pelos novos desafios de gest??o p??blica e prop??em-se as bases do que poder?? vir a constituir uma carta latino-iberoamericana sobre as compet??ncias que devem ser desenvolvidas e garantidas no grupo dirigente da Administra????o P??blica dos Estados representados no CLAD. Esta reflex??o baseia-se nos processos de diagn??stico e de forma????o que t??m vindo a ser promovidos pelo Instituto Nacional de Administra ????o no ??mbito da reforma da Administra????o P??blica em curso em Portugal.; En esta comunicaci??n, se discuten las competencias exigidas a los directivos por los nuevos retos de gesti??n p??blica y se proponen las bases de lo que podr?? constituir una carta latino-iberoamericano sobre las competencias que deben ser desarrolladas y garantizadas en el grupo directivo de la Administraci??n P??blica de los Estados representados en el CLAD. Esta reflexi??n se basa en los procesos de diagnostico y de formaci??n que han sido promovidos por el Instituto Nacional de Administraci??n en el ??mbito de la reforma de la Administraci??n P??blica en curso en Portugal.; This communication discusses the competencies required of public leaders regarding the new challenges of public management and proposes the basis of what may constitute a Latin-Ibero- American charter of competencies that must be developed and assured within the group of Public Administration leaders of the States represented in CLAD. This reflection is based on the diagnosis and capacity-building processes that have been taking place in the National Institute of Administration in the context of the ongoing Public Administration reform in Portugal.; Revista do Servi??o P??blico - RSP...

High absorption and low splice loss properties of hexagonal double-clad fiber

Li, Y.; Jackson, S.; Fleming, S.
Fonte: IEEE-Inst Electrical Electronics Engineers Inc Publicador: IEEE-Inst Electrical Electronics Engineers Inc
Tipo: Artigo de Revista Científica
Publicado em //2004 EN
Relevância na Pesquisa
37.27%
An accurate experimental comparison of the pump absorption and the lasing features between Nd/sup 3+/-doped fiber lasers using hexagonal-shaped and D-shaped fiber is reported. The measured slope efficiencies with respect to the absorbed pump power of 805 nm are nearly identical at /spl sim/65.3% for both fibers. Taking advantage of the near symmetrical shape of the hexagonal fiber, the lowest reported splice loss of 0.05 dB is achieved between the double-clad fiber and standard 125-/spl mu/m fiber with the use of the fiber etching techniques. The pump absorption can be improved by bending the hexagonal fibers into a kidney shape.; Yahua Li, Stuart D. Jackson, and Simon Fleming; Copyright © 2004 IEEE

Two micron Tm doped ZBLAN double clad fibre laser.

Sarker, Md. Samiul Islam
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2012
Relevância na Pesquisa
27.56%
Tm:ZBLAN fibre lasers have potential applications in many research areas, such as eye safe range detection, medical science and materials processing. In this thesis we investigate improving the laser performance of a thulium doped fluoride fibre (specifically ZBLAN) to generate laser output with wavelengths near 2 μm. Two approaches are demonstrated to investigate laser performance at 2 μm. One is 790 nm pumping in which the cross-relaxation mechanism is used for efficient operation by populating the upper laser level. Another is in-band pumping, where 1570 nm light is directly pumps the emitting laser level, reducing the quantum defect between the pump and lasing wavelengths, reducing the threshold and increasing the efficiency of the fibre laser. Tm:ZBLAN fibres fabricated in-house, we also characterized with the aim of processing towards the development of new classes of fibre laser. A Tm:ZBLAN double clad fibre laser operating at 1.96 μm is demonstrated with a 1.53 W maximum output power and slope efficiency of 45% with respect to the launch pump power. Thereafter, the laser performance is analysed using cavity mirrors of various reflectivities. A laser with an operating wavelength of 1.57 μm is demonstrated with 1 watt output power using an Er:Yb co-doped double clad fibre. The slope efficiency of this laser is measured to be 28.3% with respect to the diode pump power...

ENPOWER - Repair Welds and Residual Stresses in Clad Plates

BROWN Bruce; LAWRJANIEC Didier; OHMS CARSTEN; TRUMAN Chris; WIMPORY Robert
Fonte: ASME Publicador: ASME
Tipo: Contributions to Conferences Formato: CD-ROM
ENG
Relevância na Pesquisa
27.45%
One of the tasks of the European Commission sponsored project ENPOWER was to manufacture repair welds on clad plate specimens simulating the inner wall of a Reactor Pressure Vessel (RPV) and to establish their structural integrity. The paper summarizes the main results from the repair welds carried out on clad plates with an anticipated sub-clad defect including the results from various residual stress measurements and from numerical welding simulations as well as from some fracture mechanical calculations. The results are discussed with respect to support the repair weld optimization in particular by minimizing the residual stresses. Moreover, the application ranges and capabilities of numerical simulations for this kind of weld processes are discussed.; JRC.F.4-Nuclear design safety

Benchmark Analyses for Fracture Mechanics Methods for Assessing Sub-Clad Flaws - NESC-VI Final Report

LAUEROVA D.; TAYLOR Nigel; PISTORA V.; MINNEBO Philip; PAFFUMI Elena
Fonte: European Commission Publicador: European Commission
Tipo: EUR - Scientific and Technical Research Reports Formato: Printed
ENG
Relevância na Pesquisa
27.27%
The sixth project of the Network for Evaluating Structural Integrity (NESC-VI) deals with the fracture mechanics analysis of a set of 3 tests on beam specimens with simulated sub-surface flaws, which were performed by NRI Re¿ plc for the PHARE project ¿WWER Cladded Reactor Pressure Vessel Integrity Evaluation (with Respect to PTS Events)¿. The objectives were as follows: ¿ to assess the capability to predict whether the cracks propagating into the cladding arrest or cause full fracture, and ¿ to assess the capability to predict the location of first initiation: near-surface or deep crack tip. The project was launched in December 2006 and completed in March 2009. It brought together a group of 10 organisations from NESC to perform comparative analyses of selected tests, based on a comprehensive datapack prepared by NRI. The investigations focussed almost exclusively on assessing the capability to predict the location of first initiation. The main results are as follows: ¿ Comparison of analyses performed by individual partners showed that the FE simulations produced consistent predictions of the observed force vs. load-line displacement (or crack mouth opening displacement) behaviour. However the differences in predicted crack tip stress intensity...

Measurement of Residual Stress in as Received and Repaired Clad Components

OHMS CARSTEN; TRUMAN Chris; WIMPORY Robert; SMITH David J.; YOUTSOS Anastasius; GRIPENBERG Hans
Fonte: ASME Publicador: ASME
Tipo: Contributions to Conferences Formato: Printed
ENG
Relevância na Pesquisa
27.27%
The experimental assessment of residual stresses in clad components is particularly challenging because of the components size and because of sharp stress gradients. Components containing weld repairs are even more complicated to investigate. Three residual stress measurement methods are presented: neutron diffraction, deep hole drilling and the ring core method. Residual strains/stresses have been measured in a non-repaired clad component and components containing weld repairs. The measurement methods are described. An overview of the experimental results is given. The paper is concluded with a revue of the applicability of these measurement methods to claddings based on the results.; JRC.F.3-High Flux and Future Reactors

Reactor physics assessment of thick silicon carbide clad PWR fuels

Bloore, David A.
Fonte: Cambridge, Massachussetts, Massachussetts Institute of Technology Publicador: Cambridge, Massachussetts, Massachussetts Institute of Technology
Tipo: Tese de Doutorado
Relevância na Pesquisa
27.77%
CIVINS; High temparature tolerance, chemical stability and low neutron affinity make silicon carbide (SiC) a potential fuel cladding material that may improve the economics and safety of light water reactors (LWRs). "Thick" SiC cladding (0.089 cm.) is easier (and thus more economical) to manufacture than SiC of conventional Zircaloy (Zr) classing thickness (0.05 cm.) Five fuels and clad combinations are analyzed: Zr with solid UO2 pellets, reduced fuel fraction "thick" SiC (Thick SiC) with annular UO2 pellets, Thick Sic with solid UO2/BeO pellets, reduced coolant fraction annular fuel with "Thick" SiC (Thick SiC RCF), and Thick Sic with solid PuO2/ThO2 pellets. CASMO-4E and SIMULATE-3 have been utilized to model the above in a 193 assembly, 4-loop Westinghouse pressurized water reactor (PWR). A new program, CSpy, has been written to use CASMO/SIMULATE to conduct optimization searches of burnable poison layouts and core reload patterns. All fuel/clad combinations have been modeled using 84 assembly reloads, and Thick SiC clad annular UO2 has been modeled using both 84 and 64 assembly reloads. Dual Binary Swap (DBS) optimization via three Objective Functions (OFs) has been applied to each clad/fuel/reload # case to produce a single reload enrichment equilibrium core reload map. The OFs have the goals of minimal peaking...

Static Recovery of a Clad Aluminum Alloy After Cold Rolling

BAG, DEBARTHA
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
37.56%
This study examines the static recovery behaviour of a clad aluminum alloy manufactured by Novelis FusionTM technology after 72% cold rolling. The clad alloy system studied consisted of a core AA6XXX alloy clad on one side with AA3003. The Recovery at the inter-alloy region is compared with the recovery of core AA6XXX at the same depth from the rolling surface. Sample coupons from the inter-alloy region and core AA6XXX were heated isochronally and isothermally, at different temperatures and times, respectively, to probe the recovery kinetics of the X-ray peak broadening, X-ray macro-texture and micro-hardness from the cold rolled state. The recovery of the {220} and {311} X-ray line profiles were observed between the anneals. A pseudo-Voigt fit function was fit to the profile to obtain the defect related information. Recovery in the peak broadening began by 100°C and correlated to a decrease in the hardness. Sharpening of X-ray profiles during recovery is attributed to the microstructural evolution resulting from preferred release of the stored energy due to dislocation rearrangement and annihilation. Kinetic behaviour of the recovery is measured by observing the evolution of X-ray profiles and hardness during isothermal annealing at two different temperatures. Recovery behaviour in the inter-alloy region is measured to be relatively slower than the recovery of the core AA6XXX after same macroscopic pre-strain. Activation energy for recovery is calculated from the isothermal data to deduce a recovery mechanism. The activation energy calculated in core AA6XXX...

Static Recovery Modeling of Dislocation Density in a Cold Rolled Clad Aluminum Alloy

Penlington, Alexander
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
37.45%
Clad alloys feature one or more different alloys bonded to the outside of a core alloy, with non-equilibrium, interalloy interfaces. There is limited understanding of the recovery and recrystallization behaviour of cold rolled clad aluminum alloys. In order to optimize the properties of such alloys, new heat treatment processes may be required that differ from what is used for the monolithic alloys. This study examines the recovery behaviour of a cold rolled Novelis FusionTM alloy containing an AA6XXX core with an AA3003 cladding on one side. The bond between alloys appears microscopically discrete and continuous, but has a 30 m wide chemical gradient. The as-deformed structure at the interalloy region consists of pancaked sub-grains with dislocations at the misorientation boundaries and a lower density organized within the more open interiors. X-ray line broadening was used to extract the dislocation density from the interalloy region and an equivalently deformed AA6XXX following static annealing using a modified Williamson-Hall analysis. This analysis assumed that Gaussian broadening contributions in a pseudo-Voigt function corresponded only to strain from dislocations. The kinetics of the dislocation density evolution to recrystallization were studied isothermally at 2 minute intervals...

Specific Aspects of Internal Corrosion of Nuclear Clad Made of Zircaloy

Minne, Jean-Baptiste; Desgranges, Lionel; Optasanu, Virgil; Largenton, Nathalie; Raceanu, Laura; Montesin, Tony
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 08/01/2013
Relevância na Pesquisa
27.72%
In PWR, the Zircaloy based clad is the first safety barrier of the fuel rod, it must prevent the dispersion of the radioactive elements, which are formed by fission inside the UO2 pellets filling the clad. We focus here on internal corrosion that occurs when the clad is in tight contact with the UO2 pellet. In this situation, with temperature of 400^{\circ}C on the internal surface of the clad, a layer of oxidised Zircaloy is formed with a thickness ranging from 5 to 15 $\mu$m. In this paper, we will underline the specific behaviour of this internal corrosion layer compared to wet corrosion of Zircaloy. Simulations will underline the differences of stress field and their influences on corresponding dissolved oxygen profiles. The reasons for these differences will be discussed as function of the mechanical state at inner surface of the clad which is highly compressed. Differences between mechanical conditions generated by an inner or outer corrosion of the clad are studied and their influences on the diffusion phenomena are highlighted.

Air-clad fibers: pump absorption assisted by chaotic wave dynamics?

Mortensen, Niels Asger
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 09/07/2007
Relevância na Pesquisa
27.65%
Wave chaos is a concept which has already proved its practical usefulness in design of double-clad fibers for cladding-pumped fiber lasers and fiber amplifiers. In general, classically chaotic geometries will favor strong pump absorption and we address the extent of chaotic wave dynamics in typical air-clad geometries. While air-clad structures supporting sup-wavelength convex air-glass interfaces (viewed from the high-index side) will promote chaotic dynamics we find guidance of regular whispering-gallery modes in air-clad structures resembling an overall cylindrical symmetry. Highly symmetric air-clad structures may thus suppress the pump-absorption efficiency eta below the ergodic scaling law eta proportional to Ac/Acl, where Ac and Acl are the areas of the rare-earth doped core and the cladding, respectively.; Comment: High-resolution figures and animations available in the freely available published version (click the DOI link)

Low Loss, Thin p-clad 980-nm InGaAs Semiconductor Laser Diodes with an Asymmetric Structure Design

Buda, Manuela; Hay, J; Tan, Hoe Hark; Wong-Leung, Yin-Yin (Jennifer); Jagadish, Chennupati
Fonte: Institute of Electrical and Electronics Engineers (IEEE Inc) Publicador: Institute of Electrical and Electronics Engineers (IEEE Inc)
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
37.27%
Thin p-clad InGaAs ridge waveguide quantum-well lasers having an asymmetric structure design were fabricated. The internal absorption coefficient is as low as 2.5 cm-1, due to the restricted field extension in the 0.3-μm-thick p-type top AlGaAs cladding