Ultrasonic Guided Wave Sensor Network Optimization for Monitoring Rivet Line

Guided waves using piezo-electric wafer active sensors (PWAS) is one of the useful techniques of damage detection. Sensor network optimization with minimal network hardware footprint and maximal area of coverage remains a challenging problem. PWAS sensors are placed at discrete locations in order to inspect damages in plates and the idea has the potential to be extended to assembled structures. Various actuator-sensor configurations are possible within the network in order to identify and locate damages. In this paper we present a correlation based approach to monitor cracks emanating from rivet line using a simulated guided wave signal whose sensor is operating in pulse echo mode. Discussions regarding the identification of phase change due to reflections from the crack are also discussed in this paper.

Ultrasonic Guided Wave Based Damage Detection Using Low-dimensional Data from Laser Doppler Scan

In the current state of the art, it remains an open problem to detect damage with partial ultrasonic scan data and with measurements at coarser spatial scale when the location of damage is not known. In the present paper, a recent development of finite element based model reduction scheme in frequency domain that employs master degrees of freedom covering the surface scan region of interests is reported in context of non-contact ultrasonic guided wave based inspection. The surface scan region of interest is grouped into master and slave degrees of freedom. A finite element wise damage factor is derived which represents damage state over distributed areas or sharp condition of inter-element boundaries (for crack). Laser Doppler Vibrometer (LDV) scan data obtained from plate type structure with inaccessible surface line crack are considered along with the developed reduced order damage model to analyze the extent of scan data dimensional reduction. The proposed technique has useful application in problems where non-contact monitoring of complex structural parts are extremely important and at the same time LDV scan has to be done on accessible surfaces only.

Prior image based temporally constrained reconstruction algorithm for magnetic resonance guided high intensity focused ultrasound

Purpose: A prior image based temporally constrained reconstruction ( PITCR) algorithm was developed for obtaining accurate temperature maps having better volume coverage, and spatial, and temporal resolution than other algorithms for highly undersampled data in magnetic resonance (MR) thermometry. Methods: The proposed PITCR approach is an algorithm that gives weight to the prior image and performs accurate reconstruction in a dynamic imaging environment. The PITCR method is compared with the temporally constrained reconstruction (TCR) algorithm using pork muscle data. Results: The PITCR method provides superior performance compared to the TCR approach with highly undersampled data. The proposed approach is computationally expensive compared to the TCR approach, but this could be overcome by the advantage of reconstructing with fewer measurements. In the case of reconstruction of temperature maps from 16% of fully sampled data, the PITCR approach was 1.57x slower compared to the TCR approach, while the root mean square error using PITCR is 0.784 compared to 2.815 with the TCR scheme. Conclusions: The PITCR approach is able to perform more accurate reconstructions of temperature maps compared to the TCR approach with highly undersampled data in MR guided high intensity focused ultrasound. (C) 2015 American Association of Physicists in Medicine.

A quality-guided displacement tracking algorithm for ultrasonic elasticity imaging.

Displacement estimation is a key step in the evaluation of tissue elasticity by quasistatic strain imaging. An efficient approach may incorporate a tracking strategy whereby each estimate is initially obtained from its neighbours' displacements and then refined through a localized search. This increases the accuracy and reduces the computational expense compared with exhaustive search. However, simple tracking strategies fail when the target displacement map exhibits complex structure. For example, there may be discontinuities and regions of indeterminate displacement caused by decorrelation between the pre- and post-deformation radio frequency (RF) echo signals. This paper introduces a novel displacement tracking algorithm, with a search strategy guided by a data quality indicator. Comparisons with existing methods show that the proposed algorithm is more robust when the displacement distribution is challenging.

Effect of Surface Condition of Electrode on the Surface Melting of Material by Laser-Guided Micro-Arc Discharge

This paper studies the surface melting in the atmosphere by YAG laser-guided micro-arc discharge. In three kinds of surface conditions (free, oiled, and polyethylene covered), we try to control the diameter and the power density of discharge pit. It is found that the power density of 3 x 10(6) W/cm(2) of discharge pit on the oiled surface is moderate to form the melted layer thicker than that of the others, adapting to strengthen the surface of material, and the power density of 1.07 x 10(7) W/cm(2) of discharge pit on the polyethylene-covered surface is highest to form the deepest discharge pit among them, adapting to remove the material.

O Congresso Nacional e a política externa brasileira : posicionamento dos senadores frente às negociações para a formação da ALCA (1994-2005)

Analisa o posicionamento dos integrantes do Congresso Nacional frente às negociações para a formação da Área de Livre Comércio das Américas (ALCA), a concentrar sua atenção sobre o Senado Federal, com eventuais incursões pela Câmara dos Deputados. O período por nós delimitado compreende, respectivamente, o lançamento da proposta pela integração continental, ocorrida na I Cúpula das Américas, nos EUA, em 1994, até o ano de 2005, em que se evidenciou a paralisação do processo negociador. Dois fatores estimularam-nos a realizar esta tarefa. Primeiro, colocar à prova a tese, disseminada pelo senso comum, de que o Parlamento não demonstra interesse por questões ou assuntos internacionais. Segundo, fornecer uma contribuição à escassa bibliografia disponível a respeito da relação entre os congressistas e a produção da política externa brasileira de integração regional, em particular. Apesar de não ignorarmos o papel predominante do Poder Executivo na formulação e condução da política externa nacional, e nem a comprovada carência de mecanismos participativos e decisórios formais à disposição do Parlamento para atuar nas diferentes facetas deste plano, procuramos aferir em que medida a atividade parlamentar se restringe ou não, na prática, ao seu exercício constitucional de aprovar ou rejeitar matérias sobre política exterior, conforme nos aponta o senso comum. O caráter polêmico das negociações e dos debates ocorridos no Brasil a respeito da conformação da ALCA, ao longo de mais de uma década, levou-nos a questionar qual teria sido o posicionamento dos congressistas com relação ao assunto, ou seja, se teriam manifestado interesse em se envolver mais intensamente com a questão, ou se reservado a debatê-la somente na ocasião em que fosse submetida, na forma de um acordo, à sua apreciação. A elaboração do presente trabalho orientou-se pela pretensão em alcançar respostas para duas perguntas formuladas por nós: a ausência de mecanismos formais de participação parlamentar nas negociações sobre a ALCA teria refletido um suposto desinteresse dos senadores pela questão? Em que medida esta referida ausência não teria impelido o Parlamento a buscar influenciar o processo por outros meios, ou até mesmo fomentado demandas pela ampliação de seu papel constitucional no tratamento de questões externas? Para tentar responder a tais perguntas, servimo-nos especialmente dos apanhamentos taquigráficos dos pronunciamentos realizados pelos senadores; de proposições elaboradas pelos congressistas e de atas e notas tquigráficas de audiências públicas promovidas por Comissões do Congresso Nacional.

Guided pollards in the Basque Country (Spain) during the Early Modern Ages

Publicado en: "End of Tradition?.Part 1 : History of Commons and Commons Management (Cultural Severance and Commons Past)", edited by Ian D. Rotherham, Mauro Agnoletti and Christine Handley

Redescription of Hypoptopoma inexspectata (Holmberg, 1883), with notes on its anatomy (Siluriformes: Loricariidae).

Hypoptopoma inexspectata is diagnosed and redescribed based on the examination of additional material and comparison with its congeners. This poorly known hypoptopomine species is distributed in the Paraguay and Paraná river draínages. Hypoptopoma inexspectata is diagnosable based on the autapomorphy biserial arrangement of anterior snout rostral margin odontodes, laterally extended to limit between second and third infraorbital plates, with dorsally directed dorsad series separated from ventrally directed ventrad series by a narrow odontode-free area, which at the level of first and second infraorbital plates is reduced to a dividing line of the series. The species can be further distinguished by the combination (1) low number of canal-bearing lateral plates (20-22, typically 21), (2) presence of a shield of prepectoral dermal plates, (3) arrangement of abdominal plates in one paired series of 3-5 plates, (4) shorter least interorbital distance 4856% head lengh, (5) larger horizontal eye diameter 17-20% head lengh, and (6) least orbit-nare distance 812% head lengh. Intraspecific variation skull dermal bones, neuracranium and suspensorium bones, dermal plates, adipose fin is reported. (PDF has 20 pages.)

Voyage dans le district des Diamans et sur le littoral du Brésil : suivi de notes sur quelques plantes caracteristiques et d'un precis de l'histoire des revolutions de l'empire bresilien, depuis le commencement du regne de Jean vi jusqu'a l'abdication de D. Pedro

As Voyages... são estudos completos, abrangendo todos os aspectos das regiões percorridas; servem de subsídio ao estudo das condições de vida no Brasil no século passado. "Fonte primordial de informações sobre os prédios coloniais do Rio de Janeiro, Minas Gerais, São Paulo, Santa Catarina e Goiás. Poucas obras no gênero atingem o valor de Saint-Hilarire. São clássicas e indispensáveis para o estudo do sul do Brasil, antes da Independência" segundo Borba de Moraes

Notes on some specimens of a species of onychophore (Oroperipatus corradoi) new to the fauna of Panama

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Lowestoft College - Riding the waves of change: How mobile learning has guided learners through rough seas

Over the past six years Lowestoft College has embraced the revolution in mobile learning by welcoming Web 2.0, social media, cloud computing and Bring Your Own Device (BYOD). This open attitude to new technologies has led to a marked improvement in student achievement rates, has increased staff and student satisfaction and has resulted in a variety of cost savings for senior management during the current economic downturn.