Biblioteca Digital

O tema "segurança de fundações" tem merecido especial atenção, tanto na lide acadêmica quanto na prática profissional, em virtude da necessidade de se buscar soluções cada vez mais otimizantes para a dicotomia custo versus segurança, soluções essas que diferem pela forma de tratamento das incertezas envolvidas no projeto e execução das fundações. As provas de carga sobre as fundações têm desempenhado papel central na redução dessas incertezas. Ultimamente, tem-se discutido muito, particularmente no âmbito da revisão da NBR 6122, o papel das provas de carga na redução das incertezas inerentes a qualquer obra de fundações. Se é ponto pacífico que as provas de carga devem reduzir as incertezas, já não há consenso quanto aos níveis dessa redução em função do tipo e da quantidade de provas de carga, nem tampouco como a variabilidade dos resultados das provas de carga efetuadas em dada obra influenciam no fator de segurança. Desta feita, o presente trabalho apresenta uma formulação consistente para combinação das previsões de capacidade de carga de estacas de deslocamento com as informações derivadas da realização de provas de carga estáticas conduzidas até a ruptura ou ensaios de carregamento dinâmico...

O objetivo desta dissertação é avaliar se as tecnologias de Web Semântica podem contribuir para o desenvolvimento do protocolo Internet Registry Information Service Protocol (IRIS). IRIS é um novo protocolo para o serviço de informação sobre registros da Internet. Ele ainda encontra-se em fase de desenvolvimento por um grupo de trabalho do Internet Engineering Task Force (IETF). O objetivo do grupo de trabalho é desenvolver e padronizar um novo protocolo para substituir o protocolo Whois. Whois é o protocolo padrão utilizado atualmente para serviços de informação sobre registros da Internet, por exemplo nomes de domínios, endereços Internet Protocol (IP), sistemas autônomos, dentre outros. A principal motivação para o desenvolvimento do novo protocolo foi a crescente preocupação com a segurança dos dados armazenados na base de dados Whois pois o protocolo Whois não provê nenhum mecanismo de segurança. Outro motivo foi a ausência de suporte a base de dados distribuída porque o protocolo Whois foi desenvolvido para uma base de dados centralizada e, consequentemente, não atende aos requisitos padrões para protocolos da Internet. Até agora, o grupo de trabalho abordou e solucionou dois dos principais problemas do protocolo Whois: (1) segurança e (2) suporte à base de dados distribuída. Entretanto...

Os circuladores tradicionais são amplamente utilizados em telecomunicações e defesa militar para o simultâneo envio e recepção de sinais por um único meio. Esses circuitos passivos, fabricados a partir de materiais ferromagnéticos, possuem a desvantagem do aumento de dimensões, peso e custos de fabricação com a diminuição da frequência de operação definida no projeto destes dispositivos, inviabilizando sua aplicação em frequências abaixo de 500 MHz. O circulador ativo surgiu como uma alternativa aos tradicionais, tendo aplicações em frequências desde o nível DC até a ordem de dezenas de gigahertz. As suas maiores aplicações ocorrem quando são necessários dispositivos compactos, de baixo custo e de baixa potência. Os primeiros circuitos propostos possuíam uma grande limitação em termos de frequência de operação e de potência entregue à carga. Entretanto, com os avanços tecnológicos na eletrônica, tais problemas podem ser amenizados atualmente. Neste trabalho é apresentado o desenvolvimento de um circuito circulador ativo para a utilização em instrumentação eletrônica, em particular para a operação em frequências na ordem das utilizadas em equipamentos de ultrassom Doppler de ondas contínuas...

Um dos testes mais eficientes para verificar a segurança de uma estrutura concluída é uma prova de carga. Quando existem dúvidas quanto à estabilidade de uma estrutura, devido a fatores, dentre outros, como qualidade dos materiais de construção, utilização ou manutenção inadequada ou até mesmo uma nova utilização da edificação, diferente daquela inicialmente prevista no projeto, uma prova de carga é recomendada. Este trabalho visa apresentar os critérios mais importantes que devem ser considerados em uma prova de carga. Avalia procedimentos das normas brasileira (NBR 9607-1986), americana (ACI 318-2002), australiana (AS 3600-2001) e recomendações espanhola (EHE-1998) e européia (Rilem TBS-2 ?1984). Destaca aspectos como a obrigatoriedade de uma prova de carga, intensidade do carregamento a ser aplicado, análise dos resultados e critérios de aceitação estipulados pelas referidas normas e recomendações; One of the most efficient tests to verify the safety of a structure concluded is a load test. When doubts exist about the stability of a structure, due to factors, among other, as quality of the construction materials, use or inadequate maintenance or even a new use of the construction, different from that initially foreseen in the project...

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências da Saúde, Programa de Pós-Graduação em Odontologia, Florianópolis, 2013.; ; Abstract : The aim of this in vitro study was to evaluate the flexural strength of the resin bisacrílica Systemp.c&bII (S) - Ivoclar / Vivadent AG , and methyl methacrylate resin Duralay (D) - Reliance on two types of flexural tests , in order to suggest a test pattern most appropriate to assess this mechanical property . The materials were subjected to two tests of flexural strength, one uniaxial (RFU) and another three-point biaxial (RFB) with ball load in three levels of support (B3B), after 24 hours and 30 days of the making of the body proof (CP) stored in distilled water at 37 ° C. For each type of testing were made of each material 40 CPs, 20 of these tested 24 hours after preparation and the other 20 after 30 days of storage. CPs and flexural tests were performed according to ISO 4049 and ISO 6872. The tests were conducted on an Instron 4444 machine (Chicago, IL - USA) with a crosshead speed of 0.5 mm/min until fracture. The load values obtained were related to the effective area of the test and converted into MPa. The results were tested using the Anderson- Darling normality...

The well-documented viral safety of albumin arises from several factors operating in concert, including virus removal during preparation, immune neutralization, serendipitous inactivation, virus sterilization through pasteurization. Safety with respect to HBV transmission was achieved even prior to the development of sensitive screening tests for HBsAg, as can be predicted given the initial virus load and the influence of factors affecting removal and inactivation. Coagulation factor concentrates, as traditionally prepared, are known to have transmitted the viral agents of hepatitis and AIDS with high frequency. Application of virucidal procedures to these concentrates, in some cases, appears to have eliminated virus transmission, raising the question as to whether absolute safety has now been achieved. Clinical proof of absolute safety is made difficult by the small number of eligible patients who can be monitored, lengthy and expensive monitoring procedures, and opportunity for transmission of virus by product-independent routes. Based on viral load analysis, modern coagulation factor concentrates are predicted to have the same probability of freedom from HIV, HBV, and HCV transmission as that exhibited by albumin.

With their excellent biocompatibility and relatively high mechanical strength, polylactides are attractive candidates for application in load-bearing, resorbable implants. Pre-clinical studies provided a proof of principle for polylactide cages as temporary constructs to facilitate spinal fusion, and several cages already made it to the market. However, also failures have been reported: clinical studies reported considerable amounts of subsidence with lumbar spinal fusion cages, and in an in vivo goat study, polylactide spinal cages failed after only three months of implantation, although mechanical testing had predicted sufficient strength for at least eight months. The failures appear to be related to the long-term performance of polylactides under static loading conditions, a phenomenon which is common to all glassy polymers and finds its origin in stress-activated molecular mobility leading to plastic flow. This paper reviews the mechanical properties and deformation kinetics of amorphous polylactides. Compression tests were performed with various strain rates, and static stress experiments were done to determine time-to failure. Pure PLLA appeared to have a higher yield strength than its co-polymers with d-lactide, but the kinetic behaviour of the polymers was the same: an excellent short-term strength at higher loading rates...

Micropore filters are used during extracorporeal circulation to prevent gaseous and solid particles from entering the patient’s systemic circulation. Although these devices improve patient safety, limitations in current designs have prompted the development of a new concept in micropore filtration. A prototype of the new design was made using 40-μm filter screens and compared against four commercially available filters for performance in pressure loss and gross air handling. Pre- and postfilter bubble counts for 5- and 10-mL bolus injections in an ex vivo test circuit were recorded using a Doppler ultrasound bubble counter. Statistical analysis of results for bubble volume reduction between test filters was performed with one-way repeated-measures analysis of variance using Bonferroni post hoc tests. Changes in filter performance with changes in microbubble load were also assessed with dependent t tests using the 5- and 10-mL bolus injections as the paired sample for each filter. Significance was set at p < .05. All filters in the test group were comparable in pressure loss performance, showing a range of 26–33 mmHg at a flow rate of 6 L/min. In gross air-handling studies, the prototype showed improved bubble volume reduction...

Charcoal made from bagasse, the fibrous remains of sugarcane production, has the potential to serve as an alternate cooking fuel in Haiti, where the reliance on wood has led to severe deforestation. Current production methods for charcoal briquettes range from laborious hand- forming to expensive industrial machinery. Thus, there is a need for an intermediate technology. This thesis describes the development of an affordable, locally manufacturable, briquette-making device that produces higher quality charcoal than hand-formed briquettes. The device is intended for small-scale briquette production in rural villages to supply charcoal to local markets. Since little is known about the materials properties and characteristics of bagasse charcoal, several production possibilities have been considered and evaluated. The most important finding during this process was that impact loading is more effective than steady compression because the required forces are not easily achievable by simple mechanisms. The final concept is a pile driver press, which uses a hammer to strike a metal piston and drive it into a tall channel to compact a column of charcoal. Several briquettes can be formed at once by using thin spacers to separate sections of charcoal within the channel.; (cont.) A single channel prototype has been constructed as a proof-of-concept model. Cylindrical briquettes formed using this prototype had an average density of 0.29 g/cm3...

Conectores de fixação por carga explosiva é um inovador método de fixação podendo ser utilizado em aços pré-pintados sem danificar o revestimento da superfície. São componentes que possuem rosca feita em aço de alta resistência, utilizados para fixar suportes e equipamentos em estruturas metálicas. O sistema de fixação se dá pelo processo de difusão e fricção. Este sistema de fixação tem aumentado crescentemente a sua utilização na Indústria Offshore devido a sua grande produtividade, não necessitando retrabalho em superfícies pré-pintadas. Atualmente não existe uma legislação específica para fabricação destes pinos, sendo necessário então a sua comprovação via ensaios práticos simulando a sua aplicação e os seus limites de carga. Sendo assim, foram feitos ensaios de metalografia, ensaios de tração axial e cisalhamento e comparados aos limites estabelecidos pelo fabricante. A motivação deste trabalho é investigar esta técnica, efetuando um estudo de caso simulando uma aplicação na indústria offshore, definindo suas características e esforços aplicados e indicando como se dá o processo de ancoragem dos conectores com a superfície base.; Attachable connectors for explosive charge is an innovative method of attachment can be used in pre - painted steel without damaging the surface coating. Are components having thread made of high strength steel used for securing brackets metal structures and equipment. The fastening system is given by the diffusion and friction process. This fastening system has increasingly increased their use in Offshore Industry due to its high productivity...

Unreinforced masonry (URM) partition walls of William Weir House in Wellington were subjected to out-of-plane forces to investigate the as-built wall characteristic behaviour. The lateral load resisting system of the 1932 reinforced concrete building was scheduled to undergo seismic strengthening, and due to the absence of reliable wall out-of-plane assessment data, consulting engineers adopted an experimental proof-testing approach. A team of student researchers from the University of Auckland tested four URM partition walls by subjecting the walls to out-of-plane uniform pressure applied by means of a system of airbags. The testing included two mid-storey and two top-storey URM partitions, which had developed prior minor structural cracks. The full-scale in-situ testing confirmed that the precracked partitions had sufficient strength to resist the current New Zealand seismic demand, and the experimental programme resulted in substantial financial benefits for the client as none of the walls were identified as demolition or strengthening candidates. In addition to the as-built out-of-plane tests, two tests were conducted on partition walls retrofitted using near surface- mounted (NSM) fibre-reinforced polymer (FRP) strips. The results of the as-built and the retrofitted wall testing are reported...

The goals of this research are to develop and validate the use of distributed fibre optic sensors for use in strain monitoring of buried culverts, and to use full-scale experiments to evaluate the performance of both deteriorated steel and reinforced concrete culverts rehabilitated with grouted slipliners subjected to surface loading. Bench scale experiments were conducted to evaluate the use of fibre optic sensors against conventional strain sensors. Then, fibre optic sensors were attached to a full-scale culvert that was tested in a buried state as a proof of concept. Finally, fibre optic sensors were used in two large scale buried pipe tests to explore the performance of rehabilitated flexible and rigid culverts. A deteriorated steel culvert was tested in a buried state under surface loading, then rehabilitated with a grouted high density polyethylene (HDPE) slipliner while still in a buried state and tested under surface loading at 0.9 m and 0.6 m burial depths. The rehabilitated steel pipe was tested under service loading, and up to 1250 kN of applied load. The results suggested that the grouted annulus stiffened the overall structure, and increased the capacity of the system to over 3 times the fully factored design load. A deteriorated reinforced concrete culvert was tested and rehabilitated in a similar fashion. The grout in the annulus penetrated the cracks at the crown...

Dissertação de mestrado em Engenharia Informática; Esta dissertação surge no contexto das análises de dados gerados pelo LHC (Large Hadron Collider), do esperado crescimento do volume de dados produzidos depois da atualização de 2013-2014 e do atual paradigma pseudo-paralelo destas aplicações no LIP-Minho (Laboratório de Instrumentação e física experimental de Partículas, delegação Minho). O trabalho surgiu como um estudo da utilização do PROOF (Parallel ROOT Facilities) como plataforma para habilitar a extração automática de paralelismo nas aplicações de análises de dados do LIP-Minho. Na consideração que as análises em estudo têm uma estrutura semelhante que é susceptível de ser paralelizada, partimos de um caso de estudo para a familiarização e experimentação do ambiente PROOF. Face às dificuldades de adaptação da aplicação para utilização do sistema PROOF, desenvolvemos e testamos uma nova estrutura de classes, chamada event, que pode eliminar uma série de problemas na fase de desenvolvimento. Esta proposta é suportada por um gerador de código esqueleto de aplicações deste tipo, o makeEvent. Os testes efetuados comprovam a possibilidade de usar a estrutura event como alternativa à API TSelector...

Properties of typical MEMS materials have been widely investigated. Mechanical properties of MEMS structures depend not only on the bulk material properties, but also structural factors. A measurement system has been made to measure force/deflection on microstructures to examine some of the structural properties. This is a stylus setup integrated with a load cell and a linear actuator. First, the requirements for the measurement system were established. Then the system was built up and characterized. We have successfully made measurements on a typical micromechanical structure, a cantilever accelerometer design. The stylus placement accuracy, the spring constant along the proof mass, analysis of the force/deflection curve shape and destructive tests on the cantilever have been investigated in our experiment and will be presented in this paper.; Comment: Submitted on behalf of EDA Publishing Association (http://irevues.inist.fr/handle/2042/16838)

We describe a program logic for weak memory (also known as relaxed memory). The logic is based on Hoare logic within a thread, and rely/guarantee between threads. It is presented via examples, giving proofs of many weak-memory litmus tests. It extends to coherence but not yet to synchronised assignment (compare-and-swap, load-logical/store-conditional). It deals with conditionals and loops but not yet arrays or heap. The logic uses a version of Hoare logic within threads, and a version of rely/guarantee between threads, with five stability rules to handle various kinds of parallelism (external, internal, propagation-free and two kinds of in-flight parallelism). There are $\mathbb{B}$ and $\mathbb{U}$ modalities to regulate propagation, and temporal modalities $\mathsf{since}$, $\mathbb{S}\mathsf{ofar}$ and $\mathbb{O}\mathsf{uat}$ to deal with global coherence (SC per location). The logic is presented by example. Proofs and unproofs of about thirty weak-memory examples, including many litmus tests in various guises, are dealt with in detail. There is a proof of a version of the token ring.; Comment: This paper reports the joint work of its authors. But the words in the paper were written by Richard Bornat. Any opprobrium, bug reports...