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- Blind Prediction of a Full-Scale RC Bridge Column Tested Under Dynamic ConditionsPublication . Bianchi, Federica; Sousa, Romain; Pinho, RuiThe definition of appropriate modelling approaches combined with a consistent software framework is a topic of major importance in the present days for structural engineering in general and, particularly, for earthquake engineering. The accuracy of the results obtained in the recent “Concrete Column Blind Prediction Contest 2010” for a full-scale reinforced concrete bridge column tested on the NEES Large High-Performance Outdoor Shake Table, seems to indicate that current modelling strategies are on the right track. The 1.2 m diameter cantilevered column spans 7.2 m from the footing. A massive 230 tonne reinforced concrete block supported by the column generates the inertial forces to mobilize the column capacity. Seismic performance was investigated under 6 ground motions, starting with lowintensity shaking and bringing the column progressively to near-collapse conditions. Based on the obtained results from the pre-contest simulation, as well with the post-contest analysis, it was possible to extract some important conclusions regarding the application of several strategies, namely the use of different type elements, element discretization, constitutive laws for materials.
- Modelling Issues on Seismic Assessment of Irregular RC StructuresPublication . Sousa, Romain; Bianchi, Federica; Pinho, Rui; Nascimbene, Roberto; Kazantzidou, DanaiMany existing RC structures worldwide were designed for gravity loads only, with inadequate lateral load resistance, lateral stiffness and poor detailing of the reinforcement. Moreover, the concept of regularity both in plan and elevation that characterise a good conceptual design was, in most cases, not taken into account. The introduction in Europe of the regulations for seismic assessment of existing structures imposed stricter performance requirements for building structures. In order to take into account the poor seismic behaviour of such buildings, recent seismic codes – namely EC8 and NTC08 (Italian code), introduce a number of prescriptions regarding issues such as analysis type, load distribution, accidental eccentricity, etc. At the same time, these codes give room for engineering judgment to be used with reference to the definition of structural and nonstructural elements such as slabs or infill walls, and obviously leave it up to the analyst decisions regarding Finite Elements typology, meshing, mass modelling, etc. The main goal of this work is thus to provide an extensive and wide evaluation on the influence of each of the abovementioned parameter on the seismic assessment of structures. For this purpose, nonlinear static procedures, as well as nonlinear dynamic analysis are performed on a real building that has also been experimentally tested in the past. The results will hopefully provide indications on the relative importance of each modelling parameter or decision.
- Liderança e autonomia. Da teoria progressista à prática retrógradaPublication . Silva, José ManuelA comunicação aborda a emergência do novo modelo de autonomia, administração e gestão das escolas e agrupamentos dos ensinos básico e secundário, estabelecido pelo Decreto-Lei n.º 75/2008 e aprofunda a reflexão sobre as questões da liderança, autonomia e poder nas escolas, os seus reflexos nas relações com parceiros da comunidade local e as contradições decorrentes de permanecer intocado o modelo centralizado de gestão macro dos estabelecimentos de ensino estatais.
- Dynamic jitter accumulation in clock repeaters considering power and ground noise correlationsPublication . Figueiredo, Mónica; Aguiar, Rui L.This paper discusses the mechanism behind dynamic jitter accumulation in clock repeaters, considering the impact of power supply noise correlations. We show that differential and common mode noise have a different impact on jitter accumulation, depending on correlations between cascaded repeater stages. We also propose a simple accumulation model that can be used to replace time-consuming transient noise simulations. Besides providing an useful insight regarding the impact of noise correlations on jitter accumulation, the model's accuracy is shown to be within 10% of SPICE results.
- The effects of drought and timing of precipitation on the inter-annual variation in ecosystem-atmosphere exchange in a Mediterranean grasslandPublication . Jongen, Marjan; Pereira, João Santos; Igreja Aires, Luis Miguel; Pio, Casimiro AdriãoWe studied the seasonal and inter-annual variation in carbon, water and energy fluxes over a Mediterranean grassland ecosystem in Portugal, dominated by annual species, using the eddy-covariance technique. The study period, from 2004 to 2008, was characterised by high intra- and inter-annual precipitation variation: the hydrological years 2004–2005 and 2007–2008 had precipitation below average (‘dry’ years) whereas the other two hydrological years had precipitation above average (‘wet’ years). The variation in energy partitioning into sensible heat (H) and latent heat (λE) fluxes was associated with changes in soil water content, coinciding with plant emergence and senescence. The ecosystem was λE-dominated in those periods with soil water content above 15%, and became H-dominated when soil water content fell below 15%. Annually integrated net ecosystem carbon exchange (NEE) was highly sensitive to drought, varying from a carbon sink in ‘wet’ years (e.g., 2005–2006, −190 g C m−2 y−1), to a carbon source in ‘dry’ years (e.g., 2004–2005, +49 g C m−2 y−1). There was a negative correlation between annually integrated NEE and annual precipitation (r2 = 0.78). However, timing of precipitation influenced NEE, with individual rain events in the dry season resulting in large pulses of ecosystem respiration (Reco). Low precipitation at the peak of the growing season, as in the spring of 2007, decreased carbon sequestration. The best descriptor for inter-annual variation in NEE was leaf area duration (LAD), which explained 96% of the variance. Average radiation-use efficiency (RUE) was 1.59 g MJ−1 and inherent water-use efficiency (IWUE) was 24.6 g C hPa kg−1 H2O. RUE and IWUE had similar trends in inter-annual variation, reflecting differences in productivity and timing of precipitation. Our study showed that carbon and energy fluxes in this Mediterranean environment depended strongly upon water availability. Research highlights ► Carbon and energy fluxes in a Mediterranean grassland depend on water availability. ► Annually integrated NEE correlates with total precipitation. ► The best descriptor for inter-annual variation in NEE is leaf area duration (LAD). ► Radiation- and water-use efficiencies are sensitive to timing of precipitation.
- Suitability of the TBA method for assessing lipid oxidation in a meat system with added phenolic-rich materialsPublication . Maneta Ganhão, Rui Manuel; Estévez, Mario; Morcuende, DavidNumerous protocols and modifications of the thiobarbituric acid (TBA) test are available in the literature. The present paper compares the effectiveness of different TBA tests in minimizing the interferences caused by the addition of phenolic-rich materials (wild fruits) as antioxidants in cooked burger patties. The aqueous acid extraction procedure (EM) and a modified distilation TBA method (DM) were tested with different conditions of incubation - boiling (B) vs. room temperature (RT) - for monitoring lipid oxidation in cooked burger patties during refrigerated storage. DM-B and DM-RT were more suitable than EM procedures for assessing TBA-reactive substances (TBA-RS) in meat samples containing compounds such as anthocyanins, with similar spectral properties than that of the TBA-malondialdehyde (MDA) adduct. Additionally, interferences caused by browning development during incubation were avoided by DM procedures or by performing RT incubations. Correlations between TBA-RS numbers and hexanal contents in cooked pork burger patties were calculated in order to corroborate the suitability of the tested TBA procedures. The DM-RT procedure showed the highest correlation with hexanal content (R2 = 0.90; p < 0.001). © 2010 Elsevier Ltd. All rights reserved.
- How happiness mediates the organizational virtuousness and affective commitment relationshipPublication . Rego, Arménio; Ribeiro, Neuza; Cunha, Miguel Pina e; Jesuino, Jorge Correia; Ribeiro, NeuzaRecent moral and financial collapse of high profile organizations around the world led the business community, the popular and business press, and researchers to rediscover the worthiness of organizations' virtues. Aiming to contribute to this momentum, this empirical study investigates how perceptions of organizational virtuousness (OV) predict affective well-being (AWB) and affective commitment (AC). Two hundred five individuals participate. The findings show that perceptions of OV predict AC both directly and through the mediating role of AWB. The study suggests that fostering organizational virtuousness (e.g., through honesty, interpersonal respect, and compassion; combining high standards of performance with a culture of forgiveness and learning from mistakes) improves employees' AWB and promotes a more committed workforce. Considering these findings and mirroring the growing contributions of the positive psychology, positive organizational behavior, and positive organizational scholarship movements, the study suggests that a "positive-people-management" perspective should be considered, both by practitioners and scholars.
- libboincexec: A Generic Virtualization Approach for the BOINC MiddlewarePublication . Ferreira, Diogo; Araujo, Filipe; Domingues, PatricioBOINC is a client-server desktop grid middleware that has grown to power very large computational projects. BOINC clients request computing jobs to a central server and run them alongside other regular applications. Unfortunately, this kind of execution causes two kinds of problems. Firstly, developers must port their application to every single operating system target, which usually means maintaining several different versions of the same application. Secondly, any application running natively on desktop grid hardware is a potential security threat to the volunteer client. During the course of this research we sought an efficient and generic method for alternative execution of jobs in BOINC clients. Our approach is strongly guided by the principles of non-intrusiveness and contains two main components. The first is a library, libboincexec, which is able to control several virtual machines monitors. The second is a modified BOINC wrapper that provides the glue between libboincexec and the middleware. Through the use of this solution we are able to effectively use virtual machines to perform computation on desktop grids. This computation is inherently safe because virtual machines provide sand boxing. Additionally, by targeting the same virtual operating system, the problem of maintaining different versions of an application does not exist, thereby solving the heterogeneity problem of desktop grid nodes.
- Relationship Between Tethered Forces and the Four Swimming Techniques PerformancePublication . Morouço, Pedro; Keskinen, Kari L.; Vilas-Boas, João Paulo; Fernandes, Ricardo JorgeThe purpose of the current study was to identify the relationships between competitive performance and tether forces according to distance swam, in the four strokes, and to analyze if relative values of force production are better determinants of swimming performance than absolute values. The subjects (n = 32) performed a 30 s tethered swimming all-out effort. The competitive swimming velocities were obtained in the distances 50, 100 and 200 m using official chronometric values of competitions within 25 days after testing protocol. Mean force and velocity (50 m event) show significant correlations for front crawl (r = .92, p < .01), backstroke (r = .81, p < .05), breaststroke (r = .94, p < .01) and butterfly (r = .92, p < .01). The data suggests that absolute values of force production are more associated to competitive performance than relative values (normalized to body mass). Tethered swimming test seems to be a reliable protocol to evaluate the swimmer stroking force production and a helpful estimator of competitive performance in short distance competitive events.
- Biodiesel Density: Experimental Measurements and Prediction ModelsPublication . Pratas, Maria Jorge; Freitas, Samuel V. D.; Oliveira, Mariana B.; Monteiro, Silvia; Lima, Álvaro S.; Coutinho, João A. P.Density is an important biodiesel parameter, with impact on fuel quality. Predicting density is of high relevance for a correct formulation of an adequate blend of raw materials that optimize the cost of biodiesel fuel production while allowing the produced fuel to meet the required quality standards. The aim of this work is to present new density data for different biodiesels and use the reported data to evaluate the predictive capability of models previously proposed to predict biodiesel or fatty acid methyl ester densities. Densities were measured here for 10 biodiesel samples, for which detailed composition is reported, at atmospheric pressure and temperatures from 278.15 to 373.15 K. Density dependence with temperature correlations was proposed for the biodiesels, and isobaric expansivities are presented. The new experimental data presented here were used along with other literature data to evaluate predictive density models, such as those based on Kay’s mixing rules and the GCVOL group contribution method. It is shown that Kay’s mixing rules and a revised form of the GCVOL model are able to predict biodiesel densities with average deviations of only 0.3%. A comparison between biodiesel densities produced from similar vegetable oils, by different authors, highlights the importance of knowing the detailed composition of the samples. An extension of GCVOL for high pressures is also proposed here. It is shown that it can predict the densities of biodiesel fuels with average deviations less than 0.4%.