Browsing by Issue Date, starting with "2009-04"
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- Coefficient shifts in geographical ecology: an empirical evaluation of spatial and non-spatial regressionPublication . Bini, L. Mauricio; Diniz-Filho, J. Alexandre F.; Rangel, Thiago F. L. V. B.; Akre, Thomas S. B.; Albaladejo, Rafael G.; Albuquerque, Fabio S.; Aparicio, Abelardo; Araújo, Miguel B.; Baselga, Andrés; Beck, Jan; Bellocq, M. Isabel; Böhning-Gaese, Katrin; Borges, Paulo A. V.; Castro-Parga, Isabel; Chey, Vun Khen; Chown, Steven L.; Marco, Paulo de Jr; Dobkin, David S.; Ferrer-Castán, Dolores; Field, Richard; Filloy, Julieta; Fleishman, Erica; Gómez, Jose F.; Hortal, Joaquín; Iverson, John B.; Kerr, Jeremy T.; Kissling, W. Daniel; Kitching, Ian J.; León-Cortés, Jorge L.; Lobo, Jorge M.; Montoya, Daniel; Morales-Castilla, Ignacio; Moreno, Juan C.; Oberdorff, Thierry; Olalla-Tárraga, Miguel Á.; Pausas, Juli G.; Qian, Hong; Rahbek, Carsten; Rodríguez, Miguel Á.; Rueda, Marta; Ruggiero, Adriana; Sackmann, Paula; Sanders, Nathan J.; Terribile, Levi Carina; Vetaas, Ole R.; Hawkins, Bradford A.A major focus of geographical ecology and macro ecology is to understand the causes of spatially structured ecological patterns. However, achieving this understanding can be complicated when using multiple regressions, because the relative importance of explanatory variables, as measured by regression coefficients, can shift depending on whether spatially explicit or non-spatial modelling is used. However, the extent to which coefficients may shift and why shifts occur are unclear. Here, we analyze the relationship between environmental predictors and the geographical distribution of species richness, body size, range size and abundance in 97 multi-factorial data sets. Our goal was to compare standardized partial regression coefficients of non-spatial ordinary least squares regressions (i.e. models fitted using ordinary least squares without taking autocorrelation into account; “OLS models” hereafter) and eight spatial methods to evaluate the frequency of coefficient shifts and identify characteristics of data that might predict when shifts are likely. We generated three metrics of coefficient shifts and eight characteristics of the data sets as predictors of shifts. Typical of ecological data, spatial autocorrelation in the residuals of OLS models was found in most data sets. The spatial models varied in the extent to which they minimized residual spatial autocorrelation. Patterns of coefficient shifts also varied among methods and datasets, although the magnitudes of shifts tended to be small in all cases. We were unable to identify strong predictors of shifts, including the levels of autocorrelation in either explanatory variables or model residuals. Thus, changes in coefficients between spatial and non-spatial methods depend on the method used and are largely idiosyncratic, making it difficult to predict when or why shifts occur. We conclude that the ecological importance of regression coefficients cannot be evaluated with confidence irrespective of whether spatially explicit modelling is used or not. Researchers may have little choice but to be more explicit about the uncertainty of models and more cautious in their interpretation.
- Human pressure on a protected area : a monitoring program for the Islet of Vila Franca do Campo.Publication . Álvaro, Nuno V.; Neto, Ana I.; Alves, Maria F. L.
- Description of Intertidal Algal-based Biotopes of Pico Island, Azores, Portugal.Publication . Pinto, Fátima V.; Wallenstein, Francisco; Álvaro, Nuno V.; Neto, Ana I.
- Decision support for enhanced productivity with R software: an Azorean farms case study.Publication . Mendes, Armando B.; Noncheva, Veska; Silva, EmilianaAzores is a Portuguese insular territory where the main economic activity is dairy and meat farming. Dairy policy depends on Common Agricultural Policy of the European Union and is limited by quotas. On top of that the transformation sector had implemented a program for penalising the worst quality agricultural raw materials. The current historical context is particularly complex as some major changes are likely to occur. This is the case for the increase prices of some food products in international markets and, locally, the end of milk quota system. The multiplying effect of agriculture in both a small economy and the Azorean society, makes of major interest this kind of work not only to protect the income of farmers, but also to keep the society in equilibrium on employment matters and reduce immigration cycles. In this context, decision makers need information and knowledge for deciding the best policies in promoting quality and best practices. So, in this project we apply benchmarketing methodologies to estimate the efficiency of the agricultural system in Azores. We also propose to identify the inefficiency units and delineate action plans for correcting production or organizational identified problems. The data analysis will be possible using non parametric methods like data envelopment analysis – DEA. We develop a new data-driven methodology, called PAR (Productivity Analysis with R), which combines DEA with a statistical technique need for analysing a reduced number of farms. All Terceira (the second biggest island) farms are analyze according to their efficiency measurements to define groups of “good” practices and groups of “less good” practices. This makes the system appropriate to support public policies in agriculture sector in Azores. The decision makers we intend to support are of two different levels: farmers or services responsible for agriculture improvement and political decision makers. These two types of decision makers need information that is very specific and concrete in the first case and much more aggregated and general in the second case. The data analysis methods we are using can support the needs of both decision makers’ types, but the software interface must be specific designed. PAR project is designed to provide a bridge from mathematical models to productivity study using R statistical software. Several DEA models are described in literature. Some of them are implemented as functions in statistical software R which are being used for PAR system. Some works in restricted data sets were already done for the dairy sector in Azores using different approaches, by the authors. We use this data and results to validate and correct the software system we are developing. R statistical software is not very user friendly. Much programing is needed to make the output of the PAR computer program self explanatory and easily understandable.
- The poverty effect of remittance flows : evidence from GeorgiaPublication . Uzagalieva, Ainura; Menezes, António Gomes deThe main purpose of this study is to analyze the poverty effects of emigration and inward remittance flows through direct and indirect channels within the context of a standard computable general equilibrium (CGE) model. For that purpose, we use a novel approach in modeling a social accounting matrix (SAM) based CGE model by combining a novel and original data set, containing rich, highly-disaggregated household budget suveys with detailed macro-level data for Georgia. A distinctive contribution of this study is the attention paid to regional differences in terms of market access and transaction costs, in addition to households’ factor endowments and consumption patterns. The main questions of interest are if and to what extent remittance flows contribute to the production and consumption pattern of the poor. Two aspects of poverty reduction are emphasized: (1) the impact of remittances on the aggregate and sectoral economic growth; and (2) the impact of remittances on poor households, their production and consumption patterns across regions. The study concludes that while having a strong macroeconomic growth effect at the aggregate level, emigration and inward remittance flows do not affect all sectors and residents symmetrically. Moreover, they have a rather limited impact in terms of poverty and income inequality.
- Método para estabelecimento de medidas de segurança contra incêndio, ordenadas em função da razão eficácia/custoPublication . Vasconcelos, João Carlos Gaspar; Ventura, João Miguel PiresComo é do conhecimento geral, em Portugal existe uma grande quantidade de edifícios construídos ao abrigo de legislação pouco exigente em matéria de segurança contra incêndio. Esses edifícios apresentam condicionantes sob ponto de vista estrutural e funcional que dificultam, e até mesmo impedem, a implementação das medidas de segurança contra incêndio previstas no quadro legal vigente. Este trabalho utiliza o método de decisão hierárquica, apoiado pelo método de Delphi e por uma folha de cálculo designada de Cost-Effectiveness.xls, metodologia desenvolvida no âmbito do projecto europeu FiRE-TECH (Fire Risk Evaluation To European Cultural Heritage), para proceder a uma aplicação num edifício de habitação de grande altura, construído há cerca de três décadas. O objectivo consiste em concluir-se acerca da possibilidade de utilização da metodologia em estruturas de tipo diferentes das do património cultural.