Frequency-domain and stochastic model for an articulated wave power device

To have the first look into device performance, analytical and numerical tools must be used. Assuming that the wave power system hydrodynamics has a linear behaviour, diffraction and radiation coefficients can be computed. If the power take-off equipment may be, for the first approach, regarded as holding a linear behaviour then overall (i.e. hydrodynamic plus mechanical) device performance can be studied for regular waves. In this study a frequency-domain model describes the articulated system behaviour for regular waves. For this paper a stochastic model is found for an articulated wave power device, and probability density functions are defined for the relevant parameters that characterize the wave power system behaviour. For these parameters and for different sea states the probability density functions are found. The articulated system is characterized by these probability density functions. Also, average values for capture width are obtained for these sea state conditions

Modelling, control and Pontryagin Maximum Principle for a two-body wave energy device

Frequency domain analysis is applied to a wave energy device composed by two coaxial axisymmetric bodies. For each frequency optimal damping coefficient values which maximize absorbed power are obtained. Several displacement amplitude restriction scenarios are considered. A stochastic model to describe the device’s behaviour in irregular waves is developed. Optimal mechanical damping and spring coefficients are computed. Considering different sea state conditions, probability density functions are defined for relevant parameters and time averaged absorbed power values are obtained.A time domain model is also developed for the device. A non-linear power take-off mechanism configuration, consisting in a hydraulic circuit with low-pressure and high-pressure gas accumulators, is devised. Time averaged absorbed power is maximized in terms of characteristic mechanism parameter. A sub-optimal method of phase control by latching is applied to the device in order to improve its performance. Analytical development of Pontryagin Maximum Principle is used to establish an algorithm for device’s control

Stochastics, Time Domain Models and Pontryagin Maximum Priciple for a Two Body Wave Power Device

In this study a stochastic model to describe the behaviour of an articulated system is developed.Optimal mechanical damping and spring coefficients are computed. Probability density functions are defined for the relevant parameters that characterize the device behaviour. For these parameters and for different sea state conditions the probability density functions are found and the articulated system is characterized in terms of these functions. Average values for useful power and capture width are also obtained for these sea state conditions. Time domain models allow the computation of time series for the variables that chracterize the wave power system behaviour. In this study a time domain model is also developed for the articulated wave power device. Results are obtained for regular and irregular waves. Pontryagin Maximum Principle is presented as an algorithm for the control of the device

Frequency and Stochastic Domain Models for Two Geometries of the IPS Wave Power Buoy

Frequency-domain analysis is applied to a geometry of the original IPS buoy device concept. The analysis is particularly useful in the early development stages to establish the response of power take-off mechanism characteristic parameters to different frequencies of the wave spectrum. Optimal mechanical damping and spring coefficients are computed for some parameters restrictions. Absorbed power, capture width and other variables, such as relative displacement,are computed for regular waves and these optimal mechanical coefficients. A stochastic model is developed in order to evaluate the IPS buoy behaviour for irregular waves’ conditions. This allows defining probability density functions for parameters that characterize the device’s behaviour. Assuming that the overall system behaviour is linear and that the surface elevation for irregular waves may be regarded as a stochastic process with a Gaussian probability density function, the variables that define the system behaviour, such as bodies’ displacements and velocities, will also hold a Gaussian probability density function. The average power extraction is computed for different sea state conditions.Aiming to enhance the device’s hydrodynamic performance, a new non-axisymmetric IPS geometry is conceived. Using the stochastic modelling approach, the device’s behaviour is studied for several wave directions and compared to the axisymmetric configuration’s behaviour

Avaliação de coliformes e vírus entéricos na água e no mexilhão (Mytella guyanensis) em área de manguezal da Baía de Vitória (ES)

As áreas costeiras promovem benefícios diversos à população, porém, são largamente afetadas pelo influxo de esgoto sanitário sem tratamento, acarretando em prejuízo para a saúde da população. A contaminação por patógenos emergentes, tais como os vírus entéricos, é um agravante. Estes patógenos, podem ser encontrados em diversos ambientes, sobreviver por longos períodos, e causar diversas doenças. O sistema estuarino da Baía de Vitória, local de estudo deste trabalho, é um exemplo de área costeira afetada. Por isso, buscou-se avaliar a qualidade microbiológica da água e de mexilhões (sururu do mangue - Mytella guyanensis) em área de manguezal do sistema estuarino da Baía de Vitória, analisando 3 locais de coleta de água desse estuário ao longo de 14 meses de monitoramento (fevereiro/2008 a março/2009). Foram avaliados parâmetros físico-químicos (pH, turbidez, condutividade elétrica e Sólidos Dissolvidos Totais SDT), bacteriológicos (Coliformes Totais (CT) e E. coli) e virológicos (adenovírus, rotavírus e norovírus GII). Os vírus entéricos foram detectados por meio da técnica de PCR. Os resultados das análises físico-químicas revelaram maiores valores de turbidez e menores de condutividade e SDT nos meses mais chuvosos, especialmente no ponto mais próximo ao rio. Os resultados das análises bacteriológicas revelaram elevada contaminação do sururu, com densidades de até 106 NMP/25g de CT. Nas amostras de água, foram observadas densidades de até 105 NMP/100mL de CT, no ponto de coleta mais próximo ao cais do bairro. Valores mais elevados foram obtidos após eventos chuvosos. Quanto aos resultados das análises virológicas, adenovírus (AdV) foram detectados em 76,7% das amostras de água e de rotavírus (RV) em 88,1%. Nas amostras de sururu, AdV e RV foram detectados em 100% das amostras, evidenciando sua capacidade de concentrar partículas do meio circundante. O norovírus foi detectado em 4,8% das amostras de água e não foi detectado no sururu. A elevada contaminação fecal observada em pontos do estuário e do sururu indicam que esta área está sob impacto antropogênico. Assim, esta pesquisa torna-se um importante auxílio à decisões de implantação de medidas de proteção a este ambiente e na prevenção de surtos relacionados ao consumo de moluscos bivalves contaminados

Portuguese average cost of capital

The oldest Portuguese share index still being calculated is the BVL/PSI-General, one which started the daily series on 5/Jan/1988 with a base value of 1000 points. Everyday a single value is computed based on the closing prices of all the shares included in the sample. Also, all corporate events affecting the price of any share beyond market sentiment are taken into account through proper adjustments, either in the numerator or the denominator of the formula. However, for dates before January 1988, there is nothing comparable to this index since the two different series known either never disclosed the methodology adopted to calculate the index or followed solutions not compatible with the above index. The present paper explains the solutions adopted to replicate as closely as possible the methodology of the BVL-General index to the main market of the Lisbon Exchange for the period 1978 – 1987. This is the first estimate of the historical Equity Risk Premium in Portugal above short-term risk-free rate from the re-opening of the market following the Carnation Revolution (and the accompanying nationalizations), to the present. In showing a value of the same order of magnitude found in other countries, the paper invites further studies on the effects of political decisions such as privatizations and joining the European Union

Heterogeneous Impacts on Layoffs of Changes in Brazilian Unemployment Insurance Eligibility Rules

This paper is based on the first use of program administrative data from Brazil’s unemployment insurance (UI) program to assess the impact of changes in UI eligibility criteria on layoff probabilities. We exploit exogenous program changes introduced by executive and legislative changes in 2015 to estimate impacts while accounting for the number of prior UI benefit requests. We estimate that changes in UI eligibility criteria had heterogeneous impacts distinguished by the number of prior benefit requests. We show that the 2015 changes in UI eligibility rules reduced layoffs and find evidence that the changes reduced collusion between workers and employers for layoffs because it became harder to extract subsidies from the UI system. The layoff reductions were greatest before workers\u27 second benefit request

The Effect of Job Referrals on Labor Market Outcomes in Brazil

This paper is the first to use program administrative data from Brazil’s National Employment System (SINE) to assess the impact of SINE job interview referrals on labor market outcomes. Data for a five-year period (2012–2016) are used to evaluate the impact of SINE on employment probability, wage rates, time until reemployment, and job tenure. Difference-in-differences estimates suggest that a SINE job interview referral increases the probability of finding a job within three months of the referral and reduces the number of months to find reemployment, the average job tenure of the next job, and the reemployment wage. Subgroup analysis suggests that compared to more educated workers, SINE is more effective in helping less educated workers by increasing their probability of finding a job and reducing time until reemployment. Finally, the evidence suggests that the online labor exchange is less effective than in-person services provided at SINE offices