Problem of Hydroelectric Resources Management: Numerical Approach

In this work we analyze an optimal control problem for a system of two hydroelectric power stations in cascade with reversible turbines. The objective is to optimize the profit of power production while respecting the system’s restrictions. Some of these restrictions translate into state constraints and the cost function is nonconvex. This increases the complexity of the optimal control problem. The problem is solved numerically and two different approaches are adopted. These approaches focus on global optimization techniques (Chen-Burer algorithm) and on a projection estimation refinement method (PERmethod). PERmethod is used as a technique to reduce the dimension of the problem. Results and execution time of the two procedures are compared.

Evaluation of water use, yield and water productivity of a high-density orchard (cv. Cobrançosa) subjected to different irrigation regimes – An account of four years

The impact of different irrigation scheduling regimes on the water use, yield and water productivity from a high-density olive grove cv. Cobrançosa in southern Portugal was assessed during the irrigation seasons of 2011, 2012, 2013 and 2014. The experiments were conducted in a commercial olive orchard at the Herdade Álamo de Cima, near Évora (38o 29' 49.44'' N, 7o 45' 8.83'' W; alt. 75 m) in southern Alentejo, Portugal. The orchard was established with 10-year old Cobrançosa trees in grids of 8.0 x 4.2 m (300 trees ha-1) in the E-W direction, and experiments conducted on a shallow sandy loam Regosoil Haplic soil. From mid-May to the end of September the orchard was irrigated and three plots were subjected to one of two irrigation treatments: a control treatment A, irrigated to replace 100% ETc, a moderate deficit irrigation treatment B irrigated to 70% of ETc, and a more severe deficit irrigation treatment C that provided for approximately 50% of ETc. Daily tree transpiration rates were obtained by continuously monitoring of sap flow in representative trees per treatment. Among the irrigated treatments, water use efficiency (WUE, ratio of water used to irrigation- water applied) of treatment C was the highest, with a value of 0.89, being treatment B slightly lower, with a WUE of 0.76. Olive harvest for 2012 was an exceptional “on year”. Bearing yields showed contrasting differences within years where an “on year” was followed by an “off year”. In 2011 and 2012 treatment B yields were 41 and 50% higher than treatment C, respectively. In 2013 treatment B yield was 45% higher than yield of the fully irrigated treatment A, and treatment C showed practically the same yield than treatment A. In the “on year” of 2014 treatment B averaged 48% higher yield than treatment C. Treatment B farm irrigation water productivity (WPI-Farm, ratio of yield to water applied) was the highest among all treatments. Treatment A showed the lowest conversion efficiency of all treatments, indicating treatment B as the adequate deficit irrigation treatment for our Cobrançosa orchard

Assessment of environment, land management, and spatial variables on recent changes in montado land cover in southern Portugal

Montado decline has been reported since the end of the nineteenth century in southern Portugal and increased markedly during the 1980s. Consensual reports in the literature suggest that this decline is due to a number of factors, such as environmental constraints, forest diseases, inappropriate management, and socioeconomic issues. An assessment on the pattern of montado distribution was conducted to reveal how the extent of land management, environmental variables, and spatial factors contributed to montado area loss in southern Portugal from 1990 to 2006. A total of 14 independent variables, presumably related to montado loss, were grouped into three sets: environmental variables, land management variables, and spatial variables. From 1990 to 2006, approximately 90,054 ha disappeared in the montado area, with an estimated annual regression rate of 0.14 % year-1. Variation partitioning showed that the land management model accounted for the highest percentage of explained variance (51.8 %), followed by spatial factors (44.6 %) and environmental factors (35.5 %). These results indicate that most variance in the large-scale distribution of recent montado loss is due to land management, either alone or in combination with environmental and spatial factors. The full GAM model showed that different livestock grazing is one of the most important variables affecting montado loss. This suggests that optimum carrying capacity should decrease to 0.18–0.60 LU ha-1 for livestock grazing in montado under current ecological conditions in southern Portugal.

Abordagem multimetodológica do impacto da mentoria e relações de ajuda no processo informal de employee branding: o efeito de marca de empregado

O processo de employee branding tem demonstrado promover e reforçar o contrato psicológico entre os colaboradores e a organização, pelo incremento e potenciação do sentimento de comprometimento e lealdade do colaborador de acordo com Miles e Mangold. Esta investigação foca-se no estudo do impacto da mentoria e relações de ajuda no processo de employee branding, numa visão integrada da gestão de recursos humanos e do comportamento organizacional, com base nas relações de troca do marketing do relacionamento numa perspetiva da gestão por competências e foco nas Pessoas. Com a introdução da nova variável (mentoria e relações de ajuda) esta investigação, ao enriquecer e incrementar o processo de employee branding de Miles e Mangold proposto em 2004 e 2005, apresenta a construção de um instrumento de diagnóstico do inovador processo de Efeito de Marca de Empregado. A investigação decorreu em 30 organizações, com um total de 725 questionários, que permitiu a validação e fiabilidade do instrumento, bem como demonstra através de métodos estatísticos a influência das ações de mentoria e relações de ajuda e da atuação das relações interpessoais que promovem o processo employee branding. Se o processo de employee branding já incrementava os resultados organizacionais, com esta investigação, pode-se afirmar que o processo de Efeito de Marca de Empregado não só incrementa como também impulsiona a imagem de marca da organização pela atuação dinâmica e catalisadora das relações interpessoais dos seus colaboradores, dentro e fora da organização, com a introdução e promoção de ações mentoria e relações de ajuda entre chefias e chefiados; ABSTRACT: The employee branding process has shown as to promote and strengthen the psychological contract between employees and the organization, by increasing and maximizing the sense of employees’ commitment and loyalty, according with Miles and Mangold. This research focuses on the impact of mentoring and helping relationships in the employee branding process, in an integrated view of human resources management and organizational behavior, based on the exchange ratio of the relationship marketing in a perspective of management by competencies and people focused approach. With the introduction of the new variable (mentoring and helping relationships), this research enriches and enhances the Miles and Mangold employee branding process proposed in 2004 and 2005 and presents the construction of an diagnostic instrument for the innovative process of Employee Brand Effect. This research took place in 30 organizations with a total of 725 questionnaires, which allowed the validation and reliability of the instrument and the evidence through statistical methods of the influence of mentoring and helping relationships actions and of the interaction of interpersonal relationships promoting the employee branding process. If the employee branding process was already boosting organizational results with this research, it can be stated that the Employee Brand Effect process not only increases, but also boosts the organization’s brand image by the actuation of the dynamics of employees’ interpersonal relationships, inside and outside the organization, with the introduction and promotion of mentoring and helping relationships actions between leaders and followers.

Water Delivery Quality and Automatic Control Modes in Irrigation Canals. A Case Study.

Regarding canal management modernization, water savings and water delivery quality, the study presents two automatic canal control approaches of the PI (Proportional and Integral) type: the distant and the local downstream control modes. The two PI controllers are defined, tuned and tested using an hydraulic unsteady flow simulation model, particularly suitable for canal control studies. The PI control parameters are tuned using optimization tools. The simulations are done for a Portuguese prototype canal and the PI controllers are analyzed and compared considering a demand-oriented-canal operation. The paper presents and analyzes the two control modes answers for five different offtake types – gate controlled weir, gate controlled orifice, weir with or without adjustable height and automatic flow adjustable offtake. The simulation results are compared using water volumes performance indicators (considering the demanded, supplied and the effectives water volumes) and a time indicator, defined taking into account the time during which the demand discharges are effective discharges. Regarding water savings, the simulation results for the five offtake types prove that the local downstream control gives the best results (no water operational losses) and that the distant downstream control presents worse results in connection with the automatic flow adjustable offtakes. Considering the water volumes and time performance indicators, the best results are obtained for the automatic flow adjustable offtakes and the worse for the gate controlled orifices, followed by the weir with adjustable height.