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Previous Predictions (previous + prediction)
Selected AbstractsA new recursive neural network algorithm to forecast electricity price for PJM day-ahead marketINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 6 2010Paras Mandal Abstract This paper evaluates the usefulness of publicly available electricity market information in predicting the hourly prices in the PJM day-ahead electricity market using recursive neural network (RNN) technique, which is based on similar days (SD) approach. RNN is a multi-step approach based on one output node, which uses the previous prediction as input for the subsequent forecasts. Comparison of forecasting performance of the proposed RNN model is done with respect to SD method and other literatures. To evaluate the accuracy of the proposed RNN approach in forecasting short-term electricity prices, different criteria are used. Mean absolute percentage error, mean absolute error and forecast mean square error (FMSE) of reasonably small values were obtained for the PJM data, which has correlation coefficient of determination (R2) of 0.7758 between load and electricity price. Error variance, one of the important performance criteria, is also calculated in order to measure robustness of the proposed RNN model. The numerical results obtained through the simulation to forecast next 24 and 72,h electricity prices show that the forecasts generated by the proposed RNN model are significantly accurate and efficient, which confirm that the proposed algorithm performs well for short-term price forecasting. Copyright © 2009 John Wiley & Sons, Ltd. [source] The effect of plasticity on incipient mixed-mode fatigue crack growthFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 7 2003P. DAHLIN ABSTRACT Several criteria for the prediction of incipient crack path direction of non-proportional mixed-mode fatigue cracks, immediately after a change of load from steady mode I conditions are investigated. The analysis is based on two-dimensional plane strain FE-simulations in which the actual elasto-plastic stress distribution is used for the MTS, MTSR and MEPSR criteria. The purpose of the analysis is to compare the numerical results with experimental results as well as with previous predictions based on solely elastic stress analyses, taken from the literature. It is shown that the influence from elasto-plastic deformation on crack branching direction is of utmost importance. It is found that the incipient crack growth of metals falls into two categories: high strength metals follow the MTSp criterion whereas more ductile metals follow the MTSRp criterion. The subscript p indicates that the elasto-plastic evaluation of the respective criterion should be used. [source] Egg-yolk androgen and carotenoid deposition as a function of maternal social environment in barn swallows Hirundo rusticaJOURNAL OF AVIAN BIOLOGY, Issue 4 2010Rebecca J. Safran Evidence is mounting that female animals use egg-yolk compounds (e.g. steroids, antioxidants) to adaptively engineer the quality of their offspring as a function of several maternal and environmental factors. Though adjustments to yolk allocation have been well-characterized as a function of parental phenotypes, we know very little about how an individual's social environment influences yolk composition. Here, we consider how two types of yolk compounds, androgens and carotenoids, relate to the maternal social environment during the egg-laying period, controlling statistically for known correlations between various aspects of parental quality and egg yolk compounds. Barn swallows Hirundo rustica erythrogaster breed in groups of highly variable size and spacing, allowing us to test whether or not the social environment is correlated with these maternal effects. We found no relationship between carotenoid levels in eggs as a function of colony size, colony density, or nearest-neighbor distance. However, eggs from females in larger groups had lower concentrations and total amounts of yolk androgens than those from females in smaller, less dense social settings. Our results counter previous predictions and literature, showing that females breeding in large groups deposit more androgen in eggs, mechanistically, because they compete more with conspecifics and have higher circulating androgen levels themselves and, functionally, because it could be advantageous for their offspring to show high androgen-mediated competitive abilities early in life. Instead, because group size in this species is governed largely by site fidelity and the availability of old nests for re-use, and because reproductive output does not differ as a function of group size, it may be that competition is greater for limited nests in small groups, thus elevating androgen levels. Further, yolk androgens were previously shown to be affected by male quality, and the greater concentrations and amounts of yolk androgens in smaller sites may reflect differential allocation to darker males found at these sites. [source] Plastic changes in seed dispersal along ecological succession: theoretical predictions from an evolutionary modelJOURNAL OF ECOLOGY, Issue 2 2005OPHÉLIE RONCE Summary 1We use a deterministic model to explore theoretically the ecological and evolutionary relevance of plastic changes in seed dispersal along ecological succession. Our model describes the effect of changing disturbance regime, age structure, density and interspecific competition as the habitat matures, enabling us to seek the evolutionarily stable reaction norm for seed dispersal rate as a function of time elapsed since population foundation. 2Our model predicts that, in the context of ecological succession, selection should generally favour plastic strategies allowing plants to increase their dispersal rate with population age, contrary to previous predictions of models that have assumed genetically fixed dispersal strategies. 3More complex patterns can evolve showing periods with high production of dispersing seeds separated by periods of intense local recruitment. These patterns are due to the interaction of individual senescence with change in ecological conditions within sites. 4Evolution of plastic dispersal strategies affects the patterns of density variation with time since foundation and accelerates successional replacement. An interesting parallel can be drawn between the evolution of age-specific dispersal rates in successional systems and the evolution of senescence in age-structured populations. 5Seed dispersal plasticity could be a potential mechanism for habitat selection in plants and have implications for range expansion in invasive species because recently founded populations at the advancing front may show different patterns to those in the established range. [source] | ||||||||||