951 resultados para Intersonic Crack Extension


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The aim of this study was to use photoelastic models to analyze the distribution of stress caused by the incidence of loads on a mandibular distal extension removable partial denture, both on the abutment teeth and on differently shaped residual ridges: distal ascending, descending-ascending, horizontal and distal descending. The best type of retainer and location of the rest on the last abutment tooth were determined for the different types of ridge. Four models were made from photoelastic resin (PL-1 for the teeth and PL-2 for the alveolar ridge), one for each kind of ridge. For each model, 4 removable partial dentures (RPD) were made (16 RPD altogether): T-bar retainer and distal rest, T-bar retainer and mesial rest, circumferential retainer and distal rest, and circumferential retainer and mesial rest. The models were placed on a circular polariscope and a 100 N axial load (point load) was applied to premolars and molars of the RPD. The formation of photoelastic bands was photographed for qualitative analysis. Results showed that the horizontal ridge had better distribution of stress, while the distal descending ridge had greater concentration of stress. The circumferential retainer had greater areas of stress for all types of ridges except the horizontal ridge, where there was no influence related to retainer type. The distribution of stress was similar among the different types of ridges when the rest was mesial or distal to the last abutment tooth, except for the distal descending ridge, where there was greater concentration of stress when the rest was located distally to the last abutment tooth. Thus, it may be concluded that (1) the situation was least favorable for the distal descending ridge and most favorable for the horizontal ridge, (2) the T-bar retainer had more favorable stress distribution, except when the ridge was horizontal, in which case there was no influence in relation to the type of retainer, (3) the location of the rest showed similar behavior in all except the distal descending ridge.

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We present the first record of Odontophrynus carvalhoi for the state of Alagoas, Brazil, and a distribution map for this species. This new record represents the nearest location to the Brazilian coast known for this species. © 2010 Check List and Authors.

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The geographic distribution of Leptodactylus furnarius Sazima and Bokermann, 1978 comprises Argentina, Brazil (southern, southeastern, and west-central regions), Paraguay, and Uruguay. Herein, we report for the first time the occurrence of L. furnarius in northeastern and north regions of Brazil, at the states of Bahia and Tocantins, respectively. © 2010 Check List and Authors.

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Herein I present a new geographical record of Ischnocnema verrucosa Reinhardt and Lütken, 1862 for northeastern Brazil and briefly discuss the new record with a previous record of similar characteristics. © 2010 Check List and Authors.

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Hypsiboas raniceps is a large treefrog typically found in the Cerrado and Caatinga biomes. Here we provide information about new records of this species in the Atlantic Forest and raise some hypotheses that could explain the late record of this species in this biome. © 2010 Check List and Authors.

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The present study reports new records of the Dipsadid snake Rhachidelus brazili Boulenger, 1908, from Mato Grosso and Mato Grosso do Sul states, Brazil. Our data extend the known geographical distribution ca. 713 km to the northwest and constitute the first record in the Upper Paraguay sub-basin. © 2011 Check List and Authors.

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Erythroxylaceae have tropical and subtropical distribution with four genera and about 250 species. Erythroxylum is the biggest genus of the family with approximately 100 species cited for Brazil. Erythroxylum subsessile (Mart.) O.E. Schulz is a species cited just for Rio de Janeiro state and now first recorded for the state of Espírito Santo, increasing its area of distribution. © 2012 Check List and Authors.

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The use of crack cocaine has given rise to an intense discussion in society. Research has contributed to the characterization of users and the negative consequences of its use. However, few studies have conducted in-depth study of the social and cultural contexts in which crack cocaine is used. Thus, this study seeks to discuss the ritual of crack cocaine use and its social and health consequences for the user. It is a qualitative study developed in the Psychosocial Care Centers for Alcohol and Drugs (Portuguese acronym: Caps-ad). The individuals were selected in two groups of keyinformants: crack cocaine users undergoing treatment and health professionals. Data was obtained by means of semi-structured interviews. The results revealed that the use of crack cocaine is not dissociated with the current organizational structure of society. There is a link between the use of this substance and the social organization for its use. By using crack cocaine, the individuals try to be part of a consumer market, actively participating in what society perceives as new. The forms and locations of use are directly related to users' health, making it necessary for healthcare services to detect, approach and make health interventions in these locations of use.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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This paper aims to contribute to the three-dimensional generalization of numerical prediction of crack propagation through the formulation of finite elements with embedded discontinuities. The analysis of crack propagation in two-dimensional problems yields lines of discontinuity that can be tracked in a relatively simple way through the sequential construction of straight line segments oriented according to the direction of failure within each finite element in the solid. In three-dimensional analysis, the construction of the discontinuity path is more complex because it requires the creation of plane surfaces within each element, which must be continuous between the elements. In the method proposed by Chaves (2003) the crack is determined by solving a problem analogous to the heat conduction problem, established from local failure orientations, based on the stress state of the mechanical problem. To minimize the computational effort, in this paper a new strategy is proposed whereby the analysis for tracking the discontinuity path is restricted to the domain formed by some elements near the crack surface that develops along the loading process. The proposed methodology is validated by performing three-dimensional analyses of basic problems of experimental fractures and comparing their results with those reported in the literature.

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Delamination or crack propagation between plies is a critical issue for structural composites. In viewing this issue and the large application of woven fabrics in structural applications, especially the ones that requires high drapeability to be preformed in a RTM mold cavity such as the asymmetric ones, e.g HS series, this research aimed in dynamically testing the carbon fiber 5HS/RTM6 epoxy composites under opening mode using DCB set up in order to investigate the crack growth rate behavior in an irregular surface produced by the fabric waviness. The evaluation of the energy involved in each crack increment was based on the Irwin-Kies equation using compliance beam theory. The tests were conducted at constant stress ratio of R=0.1 with displacement control, frequency of 10 Hz, in accordance to ASTM E647-00 for measurement of crack growth rate. The results showed large scatter when compared to unidirectional carbon fiber composites due to damage accumulation at the fill tows.