Effect of hole drilling at the overlap on the strength of single-lap joints

Bonded unions are gaining importance in many fields of manufacturing owing to a significant number of advantages to the traditional fastening, riveting, bolting and welding techniques. Between the available bonding configurations, the single-lap joint is the most commonly used and studied by the scientific community due to its simplicity, although it endures significant bending due to the non-collinear load path, which negatively affects its load bearing capabilities. The use of material or geometric changes in single-lap joints is widely documented in the literature to reduce this handicap, acting by reduction of peel and shear peak stresses at the damage initiation sites in structures or alterations of the failure mechanism emerging from local modifications. In this work, the effect of hole drilling at the overlap on the strength of single-lap joints was analyzed experimentally with two main purposes: (1) to check whether or not the anchorage effect of the adhesive within the holes is more preponderant than the stress concentrations near the holes, arising from the sharp edges, and modification of the joints straining behaviour (strength improvement or reduction, respectively) and (2) picturing a real scenario on which the components to be bonded are modified by some external factor (e.g. retrofitting of decaying/old-fashioned fastened unions). Tests were made with two adhesives (a brittle and a ductile one) varying the adherend thickness and the number, layout and diameter of the holes. Experimental testing showed that the joints strength never increases from the un-modified condition, showing a varying degree of weakening, depending on the selected adhesive and hole drilling configuration.

Role of abrasive material on micro-abrasion wear tests

Micro-abrasion wear tests with ball-cratering configuration are widely used. Sources of variability are already studied by different authors and conditions for testing are parameterized by BS EN 1071-6: 2007 standard which refers silicon carbide as abrasive. However, the use of other abrasives is possible and allowed. In this work, ball-cratering wear tests were performed using four different abrasive particles of three dissimilar materials: diamond, alumina and silicon carbide. Tests were carried out under the same conditions on a steel plate provided with TiB2 hard coating. For each abrasive, five different test durations were used allowing understanding the initial wear phenomena. Composition and shape of abrasive particles were investigated by SEM and EDS. Scar areas were observed by optical and electronic microscopy in order to understand the wear effects caused by each of them. Scar geometry and grooves were analyzed and compared. Wear coefficient was calculated for each situation. It was observed that diamond particles produce well-defined and circular wear scars. Different silicon carbide particles presented dissimilar results as consequence of distinct particle shape and size distribution.

On the ranks of certain monoids of transformations that preserve a uniform partition

The rank of a semigroup, an important and relevant concept in Semigroup Theory, is the cardinality of a least-size generating set. Semigroups of transformations that preserve or reverse the order or the orientation as well as semigroups of transformations preserving an equivalence relation have been widely studied over the past decades by many authors. The purpose of this article is to compute the ranks of the monoid

Consumo de benzodiazepinas por idosos institucionalizados: inapropriação, qualidade de sono e contributo para a segurança na medicação

A racionalização do uso de medicamentos constitui-se como um fator contribuinte para a melhoria da segurança do doente, particularmente no que respeita à segurança na medicação, tendo-se tornado prioritária para as organizações e instituições de saúde. A avaliação do uso de medicamentos inapropriados no idoso constitui-se como uma medida que concorre para evitar, prevenir ou corrigir eventos adversos associados ao seu uso. As benzodiazepinas são uma das classes de medicamentos mais prescritas em idosos. No entanto, e apesar de sua utilidade clínica, algumas benzodiazepinas são consideradas inapropriadas nesta faixa etária por potenciarem o efeito sedativo e aumentar a incidência de quedas e fraturas. A longo prazo, na promoção da qualidade do sono, a sua efetividade é discutível já que a toma de uma benzodiazepina para a resolução de um problema como o sono, muitas vezes pontual, passa a ser um problema crónico de exigência de toma contínua, sem que a qualidade deste seja restabelecida, pondo em risco a segurança do doente. Este estudo tem como objetivo caracterizar o consumo de benzodiazepinas por idosos institucionalizados, numa instituição de longa permanência do concelho de Sesimbra, sua inapropriação e a relação com a qualidade de sono. Foi desenvolvido um estudo descritivo e transversal, assente no paradigma qualitativo, com a recolha de dados a decorrer em três momentos: registo de informação em grelha própria da caracterização sociodemográfica e da caracterização do consumo de benzodiazepinas; aplicação do índice de Katz para determinar a funcionalidade dos participantes; aplicação do questionário adaptado do Pittsburgh Sleep Quality Index para avaliação da qualidade do sono. A inapropriação foi avaliada pela aplicação dos critérios de Beers. Após aplicação dos critérios de inclusão (idade superior a 65 anos e capacidade funcional) aos 97 utentes da instituição, a amostra foi constituída por 51 utentes. Foi recolhido consentimento informado de todos os participantes. Os resultados obtidos mostram que 46% das benzodiazepinas consumidas são de duração intermédia de ação, observando-se ainda um valor considerável de consumo de benzodiazepinas de longa duração de ação (36%). Estes valores correspondem a um grau elevado de inapropriação, potenciando os riscos para a segurança do doente nesta faixa etária. O lorazepam 2,5mg é a benzodiazepina mais utilizada como hipnótico. Mas, apesar do consumo deste grupo de medicamentos 81,6% dos idosos que consumem benzodiazepinas não apresentam boa qualidade de sono (PSQI>5), enquanto 77% dos idosos que não consomem benzodiazepinas apresentam boa qualidade de sono (PSQI≤5). Nos idosos que consomem benzodiazepinas, a média de tempo despendido na cama até adormecer foi de cerca de 55 minutos, valor superior ao grupo que não consome benzodiazepinas, onde a média é de 27 minutos. Neste grupo de idosos, o consumo de benzodiazepinas não só é inapropriado como não contribuiu para uma melhoria na qualidade de sono nem para a segurança do doente, como são os consumidores de benzodiazepinas que apresentam uma pior qualidade de sono, nas suas várias dimensões.

The effects of clinical support surfaces on pressure as a risk factor in the development of pressure ulcers, from a radiographical perspective: a narrative literature review

Purpose: Pressure ulcers are a high cost, high volume issue for health and medical care providers, having a detrimental effect on patients and relatives. Pressure ulcer prevention is widely covered in the literature, but little has been published regarding the risk to patients in the radiographical setting. This review of the current literature is to identify findings relevant to radiographical context. Methods: Literature searching was performed using Science Direct and Medline databases. The search was limited to articles published in the last ten years to remain current and excluded studies containing participants less than 17 years of age. In total 14 studies were acquired; three were excluded as they were not relevant. The remaining 11 studies were compared and reviewed. Discussion: Eight of the studies used ‘healthy’ participants and three used symptomatic participants. Nine studies explored interface pressure with a range of pressure mat technologies, two studies measured shear (MRI finite element modelling, and a non-invasive instrument), and one looked at blood flow and haemoglobin oxygenation. A range of surfaces were considered from trauma, nursing and surgical backgrounds for their ability to reduce pressure including standard mattresses, high specification mattresses, rigid and soft layer spine boards, various overlays (gel, air filled, foam). Conclusion: The current literature is not appropriate for the radiographic patient and cannot be extrapolated to a radiologic context. Sufficient evidence is presented in this review to support the need for further work specific to radiography in order to minimise the development of PU in at risk patients.

A system verification strategy based on the BST infrastructure

A good verification strategy should bring near the simulation and real functioning environments. In this paper we describe a system-level co-verification strategy that uses a common flow for functional simulation, timing simulation and functional debug. This last step requires using a BST infrastructure, now widely available on commercial devices, specially on FPGAs with medium/large pin-counts.

Demux devices based on A-SiC:H

In this paper we present results about the functioning of a multilayered a-SiC:H heterostructure as a device for wavelength-division demultiplexing of optical signals. The device is composed of two stacked p-i-n photodiodes, both optimized for the selective collection of photogenerated carriers. Band gap engineering was used to adjust the photogeneration and recombination rates profiles of the intrinsic absorber regions of each photodiode to short and long wavelength absorption and carrier collection in the visible spectrum. The photocurrent signal using different input optical channels was analyzed at reverse and forward bias and under steady state illumination. This photocurrent is used as an input for a demux algorithm based on the voltage controlled sensitivity of the device. The device functioning is explained with results obtained by numerical simulation of the device, which permit an insight to the internal electric configuration of the double heterojunction.These results address the explanation of the device functioning in the frequency domain to a wavelength tunable photocapacitance due to the accumulation of space charge localized at the internal junction. The existence of a direct relation between the experimentally observed capacitive effects of the double diode and the quality of the semiconductor materials used to form the internal junction is highlighted.

ERICA: prevalence of asthma in Brazilian adolescents

ABSTRACT OBJECTIVE To describe the prevalence of asthma and physician-diagnosed asthma in Brazilian adolescents. METHODS Cross-sectional, national, school-based study with adolescents from 12 to 17 years old, participants in the Study of Cardiovascular Risks in Adolescents (ERICA). The study stratified the sample by region and grouped according to schools and classes with representativeness to the set of cities with more than 100,000 inhabitants of the Country, macro-regions, capitals, and Federal District. A questionnaire collected data through a self-filled in method. We calculated the prevalences and their confidence intervals of 95% (95%CI) according to sex, age group, type of school and skin color. RESULTS Between 2013 and 2014, 74,589 adolescents were evaluated, 55.3% of the female sex. The total prevalence of active asthma was of 13.1% (95%CI 12.1-13.9), being higher in girls (14.8%; 95%CI 13.7-16.0) when compared to boys (11.2%; 95%CI 10.3-12.2) in all geographical strata examined. It was also higher between students of private schools (15.9%; 95%CI 14.2-17.7) when compared to public ones (12.4%; 95%CI 11.4-13.4). It was higher in the Southeast region (14.5%; 95%CI 12.9-16.1), and in the city of Sao Paulo (16.7%; 95%CI 14.7-18.7). The lowest prevalence was observed in North region (9.7%; 95%CI 9.7-10.5), and in Teresina (6.3%; 95%CI 4.9-7.7). The prevalence of physician-diagnosed asthma was of 8.7% (95%CI 8.2-9.1); higher in the North region (13.5%; 95%CI 12.7-14.2), and in Porto Alegre (19.8%; 95%CI 17.5-22.3). It was lower in the Midwest (6.9%; 95%CI 6.0-7.8), and in Cuiaba (4.8%; 95%CI 3.8-5.9). We found no significant difference in the expression of this rate between the sexes, as well as in other variables evaluated by the study. CONCLUSIONS The prevalence of asthma in Brazilian adolescents is high. Rates of active asthma and physician-diagnosed asthma vary widely in different regions and capitals evaluated by the ERICA. These results may assist in the preparation of preventive programs and policies on health and a better understanding of the factors associated with asthma in this age group.

Light-activated amplification in SiC Tandem devices: A capacitive active filter model

Characteristics of tunable wavelength pi'n/pin filters based on a-SiC:H multilayered stacked cells are studied both experimentally and theoretically. Results show that the device combines the demultiplexing operation with the simultaneous photodetection and self amplification of the signal. An algorithm to decode the multiplex signal is established. A capacitive active band-pass filter model is presented and supported by an electrical simulation of the state variable filter circuit. Experimental and simulated results show that the device acts as a state variable filter. It combines the properties of active high-pass and low-pass filter sections into a capacitive active band-pass filter using a changing capacitance to control the power delivered to the load.

Optical nonlinearity in Tandem SI-C photodetectors

The behavior of tandem pin heterojunctions based on a-SiC: H alloys is investigated under different optical and electrical bias conditions. The devices are optimized to act as optically selective wavelength filters. Depending on the device configuration (optical gaps, thickness, sequence of cells in the stack structure) and on the applied voltage (positive or negative) and optical bias (wavelength, intensity, frequency) it is possible to combine the wavelength discrimination function with the self amplification of the signal. This wavelength nonlinearity allows the amplification or the rejection of a weak signal-impulse. The device works as an active tunable optical filter for wavelength selection and can be used as an add/drop multiplexer (ADM) which enables data to enter and leave an optical network bit stream without having to demultiplex the stream. Results show that, even under weak transient input signals, the background wavelength controls the output signal. This nonlinearity, due to the transient asymmetrical light penetration of the input channels across the device together with the modification on the electrical field profile due to the optical bias, allows tuning an input channel without demultiplexing the stream. This high optical nonlinearity makes the optimized devices attractive for the amplification of all optical signals. Transfer characteristics effects due to changes in steady state light, control d.c. voltage and applied light pulses are presented. Based on the experimental results and device configuration an optoelectronic model is developed. The transfer characteristics effects due to changes in steady state light, dc control voltage or applied light pulses are simulated and compared with the experimental data. A good agreement was achieved.

Using remote lab networks to provide support to public secondary school education level

The advantages of networking are widely known in many areas (from business to personal ones). One particular area where networks have also proved their benefits is education. Taking the secondary school education level into account, some successful cases can be found in literature. In this paper we describe a particular remote lab network supporting physical experiments accessible to students of institutions geographically separated. The network architecture and application examples of using some of the available remote experiments are illustrated in detail.

Tuning and application of integer and fractional order PID controllers

Fractional calculus (FC) is widely used in most areas of science and engineering, being recognized its ability to yield a superior modeling and control in many dynamical systems. In this perspective, this article illustrates two applications of FC in the area of control systems. Firstly, is presented a methodology of tuning PID controllers that gives closed-loop systems robust to gain variations. After, a fractional-order PID controller is proposed for the control of an hexapod robot with three dof legs. In both cases, it is demonstrated the system's superior performance by using the FC concepts.

Pose Estimation using a C-Arm Fluoroscope

Os métodos clínicos que são realizados com recurso a tecnologias de imagiologia têm registado um aumento de popularidade nas últimas duas décadas. Os procedimentos tradicionais usados em cirurgia têm sido substituídos por métodos minimamente invasivos de forma a conseguir diminuir os custos associados e aperfeiçoar factores relacionados com a produtividade. Procedimentos clínicos modernos como a broncoscopia e a cardiologia são caracterizados por se focarem na minimização de acções invasivas, com os arcos em ‘C’ a adoptarem um papel relevante nesta área. Apesar de o arco em ‘C’ ser uma tecnologia amplamente utilizada no auxílio da navegação em intervenções minimamente invasivas, este falha na qualidade da informação fornecida ao cirurgião. A informação obtida em duas dimensões não é suficiente para proporcionar uma compreensão total da localização tridimensional da região de interesse, revelando-se como uma tarefa essencial o estabelecimento de um método que permita a aquisição de informação tridimensional. O primeiro passo para alcançar este objectivo foi dado ao definir um método que permite a estimativa da posição e orientação de um objecto em relação ao arco em ‘C’. De forma a realizar os testes com o arco em ‘C’, a geometria deste teve que ser inicialmente definida e a calibração do sistema feita. O trabalho desenvolvido e apresentado nesta tese foca-se num método que provou ser suficientemente sustentável e eficiente para se estabelecer como um ponto de partida no caminho para alcançar o objectivo principal: o desenvolvimento de uma técnica que permita o aperfeiçoamento da qualidade da informação adquirida com o arco em ‘C’ durante uma intervenção clínica.

SmART: an application reconfiguration framework

Dissertação apresentada na Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para a obtenção do Grau de Mestre em Engenharia Informática.

On chaos, transient chaos and ghosts in single populations models with allee effects

Density-dependent effects, both positive or negative, can have an important impact on the population dynamics of species by modifying their population per-capita growth rates. An important type of such density-dependent factors is given by the so-called Allee effects, widely studied in theoretical and field population biology. In this study, we analyze two discrete single population models with overcompensating density-dependence and Allee effects due to predator saturation and mating limitation using symbolic dynamics theory. We focus on the scenarios of persistence and bistability, in which the species dynamics can be chaotic. For the chaotic regimes, we compute the topological entropy as well as the Lyapunov exponent under ecological key parameters and different initial conditions. We also provide co-dimension two bifurcation diagrams for both systems computing the periods of the orbits, also characterizing the period-ordering routes toward the boundary crisis responsible for species extinction via transient chaos. Our results show that the topological entropy increases as we approach to the parametric regions involving transient chaos, being maximum when the full shift R(L)(infinity) occurs, and the system enters into the essential extinction regime. Finally, we characterize analytically, using a complex variable approach, and numerically the inverse square-root scaling law arising in the vicinity of a saddle-node bifurcation responsible for the extinction scenario in the two studied models. The results are discussed in the context of species fragility under differential Allee effects. (C) 2011 Elsevier Ltd. All rights reserved.