Damp trend Grey Model forecasting method for airline industry

This paper presents a modification of the Grey Model (GM) to forecast routes passenger demand growth in the air transportation industry. Forecast methods like Holt-Winters, autoregressive models, exponential smoothing, neural network, fuzzy logic, GM model calculate very high airlines routes pax growth. For this reason, a modification has been done to the GM model to damp trend calculations as time grows. The simulation results show that the modified GM model reduces the model exponential estimations grow. It allows the GM model to forecast reasonable routes passenger demand for long lead-times forecasts. It makes this model an option to calculate airlines routes pax flow when few data points are available.The United States domestic air transport market data are used to compare the performance of the GM model with the proposed model.     

A simulation analysis of the detectability of understory burns in miombo woodlands

The miombo woodlands of southern Africa are one of the most extensively burned biomes in the tropics. The detectability of understory burns in these woodlands was assessed with a sensitivity analysis approach, based on a hybrid geometrical-optical radiative transfer model. Model input data were obtained from a variety of sources, including field biometry and spectroradiometry, and satellite data. The effects of variable tree percent cover, leaf area index, stand density, burn scar age, illumination and observation geometry, and spectral region, were taken into account. Detectability of understory burns was defined as the spectral separability of burned and unburned understory, measured with the Jeffries-Matusita distance, for all possible combinations of the green, red, and near-infrared channels of the Moderate Resolution Imaging Spectrometer (MODIS) sensor. Single channels, or pairwise combinations of channels perform poorly at detecting understory burns, but a large improvement in detectability is obtained for the combination of the three spectral domains. The detectability of understory burns is largely insensitive to the effects of stand structure and illumination/observation geometry, and depends primarily on burn scar age. Our results agree with those of previous satellite-based studies of burns scar detectability in African savanna woodlands.     

User Modelling for News Web Sites with Word Sense Based Techniques

SiteIF is a personal agent for a bilingual news web site that learns user’s interests from the requested pages. In this paper we propose to use a word sense based document representation as a starting point to build a model of the user’s interests. Documents passed over are processed and relevant senses (disambiguated over WordNet) are extracted and then combined to form a semantic network. A filtering procedure dynamically predicts new documents on the basis of the semantic network. There are two main advantages of a sense-based approach: first, the model predictions, being based on senses rather than words, are more accurate; second, the model is language independent, allowing navigation in multilingual sites. We report the results of a comparative experiment that has been carried out to give a quantitative estimation of these improvements.     

Element-by-Element Post-Processing of Discontinuous Galerkin Methods for Timoshenko Beams

In this paper, we consider discontinuous Galerkin approximations to the solution of Timoshenko beam problems and show how to post-process them in an element-by-element fashion to obtain a far better approximation. Indeed, we show numerically that, if polynomials of degree p≥1 are used, the post-processed approximation converges with order 2p+1 in the L ^∞-norm throughout the domain. This has to be contrasted with the fact that before post-processing, the approximation converges with order p+1 only. Moreover, we show that this superconvergence property does not deteriorate as the the thickness of the beam becomes extremely small.Supported in part by NSF Grant DMS-0411254 and by the University of Minnesota Supercomputing Institute.     

Developing uranium dicarbide-graphite porous materials for the SPES project

Uranium carbide dispersed in graphite was produced under vacuum by means of carbothermic reduction of different uranium oxides (UO₂, U₃O₈ and UO₃), using graphite as the source of carbon. The thermal process was monitored by mass spectrometry and the gas evolution confirmed the reduction of the U₃O₈ and UO₃ oxides to UO₂ before the carbothermic reaction, that started to occur at T > 1000 °C. XRD analysis confirmed the formation of α-UC₂ and of a minor amount of UC. The morphology of the produced uranium carbide was not affected by the oxides employed as the source of uranium.     

The Computation of a Locally Conservative Stress for the Continuous Galerkin Method for Compressible Linearly Elastic Materials

We show how to postprocess the approximate displacement given by the continuous Galerkin method for compressible linearly elastic materials to obtain an optimally convergent approximate stress that renders the method locally conservative. The postprocessing is extremely efficient as it requires the inversion of a symmetric, positive definite matrix whose condition number is independent of the mesh size. Although the new stress is not symmetric, its asymmetry can be controlled by a small term which is of the same order as that of the error of the approximate stress itself. The continuous Galerkin method is thus competitive with mixed methods providing stresses with similar convergence properties. The first author was supported in part by the National Science Foundation (Grant DMS-0411254) and by the University of Minnesota Supercomputing Institute.     

Preparation, processing and characterization of biodegradable wood flour/starch-cellulose acetate compounds

A novel biodegradable material was prepared by compounding, in different proportions, pine wood flour (WF) and a commercial starch-cellulose acetate blend on a configurable co-rotating twin screw extruder. After pelletizing, the compounds were injection moulded and the mechanical and rheological properties of the mouldings determined. As the content of wood flour increases up to 50% (wt/wt), the tensile strength and the modulus improve significantly, whereas the toughness drops gradually. The effect of the wood flour content on the shear viscosity is complex, being impossible to establish a linear relationship between the two. The shear viscosity decreases with shear rate, but for a level of 40% and 50% of WF there is evidence of a quasi-Newtonian behaviour, irrespective of the test temperature. Compounds with 50% WF present the highest tensile strength and modulus but are difficult to process. However, the processability can be improved by using glycerol as plasticizer, without paying a too severe penalty in mechanical properties. In fact, by adding 15% glycerol (wt/wt), compounds with 50% WF can be successfully injection moulded into specimens with good mechanical properties.     

The effect of a solid additive on rolling fatigue life

Behaviour of a series of lubricant oils and the effect of a non stoichiometric inorganic compound, as solid extreme pressure additive, on rolling fatigue life are studied using the rolling four-ball accelerated service simulation test proposed by Barwell and Scott. The results show, in all tested cases, the remarkable efficacy of this type of additive. The Total Acidity Number (tan) was found to increase with performance time for the case of the base lubricant, while for the oils with additives, it remained at its constant low value. This led to a proposal of a possible mechanism of the additive performance in the rolling process.