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An accurate hysteresis model is fundamental to well capture the non-linearity phenomena occurring in structural and non-structural elements in building structures, that are usually made of reinforced concrete or steel materials. In this sense, this paper aims to numerically estimate through simplified non-linear analyses, the cyclic response of a reinforced concrete frame using different hysteretic models present in the literature. A commercial Finite Element Method package is used to carry out most of the simulations using polygonal hysteretic models and a fiber model, and additionally, a MATLAB script is developed to use a smooth hysteresis model. The experimental data is based on the experiments carried out in the Laboratório Nacional de Engenharia Civil, Portugal. The numerical outcomes are further compared with the experimental result to evaluate the accuracy of the simplified analysis based on the lumped plasticity or plastic hinge method for the reinforced concrete bare frame. Results show that the tetralinear Takeda's model fits closely the experimental hysteresis loops. The fiber model can well capture the hysteresis behavior, though it requires knowledge and expertise on parameter calibration. Sivaselvan and Reinhorn's smooth hysteresis model was able to satisfactorily reproduce the actual non-linear cyclic behavior of the RC frame structure in a global way. [ABSTRACT FROM AUTHOR]

Testing the validity of hypotheses of the natural rate of unemployment and hysteresis in unemployment rates is important in determining the employment policies to be applied. Generally, unit root tests are used to determine the existence of these hypotheses. The hysteresis hypothesis is represented by the unit root process. If the unit root is rejected, it is concluded that the unemployment series is stationary and the natural rate of unemployment hypothesis is valid. The aim of this study is to test the validity of the natural rate of unemployment or hysteresis hypotheses in the total unemployment, female unemployment, youth unemployment, and young female unemployment rates in 28 European Union countries. For this reason, Fourier panel KSS unit root test was applied to the unemployment series of total, young, female, and young female in the period 2003Q2-2019Q1. According to the findings, in with fixed and with trend model, total unemployment rate series in all countries except Hungary and Portugal have mean reverting process. In this case, while the hysteresis hypothesis in total unemployment rate is valid for the two countries mentioned, the natural rate of unemployment hypothesis is valid in other countries. Also, the findings show that the hypothesis of natural rate of unemployment is valid for female unemployment in 22 other countries except the UK, Spain, Hungary, Germany, Slovenia and Portugal. Besides, it shows that the hypothesis of natural rate of unemployment is valid in all countries for youth unemployment and in 27 other countries except England for youth female unemployment. [ABSTRACT FROM AUTHOR]

The temporal variability of particulate (POC) and dissolved (DOC) organic carbon concentrations was analyzed in the Enxoé temporary river, southern Portugal, between September, 2010 and August, 2013. The overall aim was to study the variability of those elements during storm events, and determine their origin and the main transfer mechanisms to the river. Twenty-one flood events were observed. An empirical model was used to describe changes in solute concentrations, and the magnitude and rotational patterns of the hysteretic loops during flood events. POC and DOC concentrations varied between 0.49-88.93 and 0.25-25.75 mg L, respectively. POC and DOC annual yields varied between 0.06-2.15 and 0.03-1.47 t km, respectively. Flood events had greater effect in POC than in DOC variability. POC had mostly a terrestrial origin, with exports being related to soil erosion and runoff. POC revealed a flushing behavior during the entire monitored period, and clockwise or anticlockwise trajectory loops whenever the predominant origin of the exports was in river bed deposits or arable lands, respectively. DOC had also a terrestrial origin, but it revealed a contrasting dilution behavior and, in general, anticlockwise hysteresis loops. DOC showed a delay in the arrival of solutes to the river, consistent with mass flow through subsurface flow. DOC exports were thus associated with soil weathering and crop mineralization. This work highlights the main processes involved in POC and DOC loads in a temporary river during flood events, with a precise quantification of those elements. [ABSTRACT FROM AUTHOR]

In temporary (or intermittent) rivers the first storm event after a dry period is responsible for transferring large amounts of sediment and nutrients into water reservoirs, thereby justifying close monitoring. The objective of this study was to analyse the contribution of storm events to sediment and nutrient transport in the Enxoé temporary river (southern Portugal) using detailed monitoring collected during three hydrological years (September, 2010 to August, 2013), and identify possible sediment and nutrient source areas based on the interpretation of hysteresis in the concentration–discharge relationship. The Enxoé River was monitored for suspended sediment concentration (SSC), total phosphorus (TP), particulate phosphorus (PP), soluble reactive phosphorus (SRP), and nitrate (NO 3 − ). An empirical model was used to describe changes in solute concentrations, and the magnitude and rotational patterns of the hysteretic loops. Twenty-one storm events were registered. SSC, TP, PP, SRP, and NO 3 − concentrations varied between 1.6 and 3790.1, 0.05–11.4, 0–7.6, 0–0.67, and 0–27.84 mg l − 1 , respectively. The highest SSC, TP, and PP concentrations were registered during the first storm event after an extended drought period. Annual sediment yields (13–480 kg ha − 1 y − 1 ) and nitrate (4.4–45.5 kg ha − 1 y − 1 ) were relatively low, while phosphorus losses (0.04–0.96 kg ha − 1 y − 1 ) reached relatively high values during humid years. Sediment and phosphorus transport was influenced by the stream transport capacity and particle availability, whereas nitrate loads were influenced by rainfall, soil hydraulic characteristics, and land management. This work highlights the main processes involved in sediment and nutrients loads in a temporary river during storm events, with a quantification of the relevant elements. [ABSTRACT FROM AUTHOR]

The heritage value of the mixed wood-masonry 18th century Pombalino buildings of downtown Lisbon is recognized both nationally and internationally. These buildings have a three-dimensional timber structure composed of wooden floors, stairs and walls intended to provide better seismic resistance and are enclosed by masonry walls. These interior wooden walls are called 'frontal' walls and their behaviour under cyclic loading has scarcely been studied. This report describes an experimental programme to determine the hysteretic behaviour of these 'frontal' walls, using static cyclic shear testing with imposed displacements. Two tests were conducted on two identical real-size walls. A new hysteretic model for the cyclic behaviour of these 'frontal' walls in Pombalino buildings is presented and calibrated based on the experimental results. The hysteresis model was developed based on a minimum number of path following rules that can reproduce the response of the wall tested under general monotonic or cyclic loading. The model is constructed using a series of exponential functions and linear functions. The nine parameters in this model capture the nonlinear hysteretic response of the wall. The hysteretic behaviour of such walls subjected to cyclic loading exhibit high nonlinear force-displacement responses and high ductility. [ABSTRACT FROM AUTHOR]

Abstract: The Mondego estuary (Portugal) suffered major changes in environmental quality due to eutrophication, however, in the late 1990s a restoration project was implemented in order to return the system to its original condition. The main goal of this paper is to evaluate the ecosystem response to the restoration measures applied at three different levels: water quality, primary producers and primary consumers. In post-restoration period a clear decline was observed in dissolved inorganic nitrogen which was reflected in the gradual recovery of Zostera noltii and a concomitant decline in green macroalgae. Macrobenthic assemblages responded variably to the recovery process. In the seagrass bed and intermediate area, there was a large increase in total biomass, but in the eutrophic area species diversity increased. Despite improvement in the ecological status of the system, full recovery has not been achieved yet, possible due to hysteresis in the dynamics of this system. [Copyright &y& Elsevier]

The European Space Agency Climate Change Initiative Soil Moisture (ESA CCI SM) product provides soil moisture estimates from radar satellite data with a daily temporal resolution. Despite validation exercises with ground data that have been performed since the product's launch, SM has not yet been consistently related to soil water storage, which is a key step for its application for prediction purposes. This study aimed to analyse the relationship between soil water storage (S), which was obtained from soil water balance computations with ground meteorological data, and soil moisture, which was obtained from radar data, as affected by soil water storage capacity (Smax). As a case study, a 14-year monthly series of soil water storage, produced via soil water balance computations using ground meteorological data from northeast Portugal and Smax from 25 mm to 150 mm, were matched with the corresponding monthly averaged SM product. Linear (I) and logistic (II) regression models relating S with SM were compared. Model performance (r2 in the 0.8–0.9 range) varied non-monotonically with Smax, with it being the highest at an Smax of 50 mm. The logistic model (II) performed better than the linear model (I) in the lower range of Smax. Improvements in model performance obtained with segregation of the data series in two subsets, representing soil water recharge and depletion phases throughout the year, outlined the hysteresis in the relationship between S and SM. [ABSTRACT FROM AUTHOR]