826 resultados para Difference Equations


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The local fractional Poisson equations in two independent variables that appear in mathematical physics involving the local fractional derivatives are investigated in this paper. The approximate solutions with the nondifferentiable functions are obtained by using the local fractional variational iteration method.

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The local fractional Poisson equations in two independent variables that appear in mathematical physics involving the local fractional derivatives are investigated in this paper. The approximate solutions with the nondifferentiable functions are obtained by using the local fractional variational iteration method.

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While fractional calculus (FC) is as old as integer calculus, its application has been mainly restricted to mathematics. However, many real systems are better described using FC equations than with integer models. FC is a suitable tool for describing systems characterised by their fractal nature, long-term memory and chaotic behaviour. It is a promising methodology for failure analysis and modelling, since the behaviour of a failing system depends on factors that increase the model’s complexity. This paper explores the proficiency of FC in modelling complex behaviour by tuning only a few parameters. This work proposes a novel two-step strategy for diagnosis, first modelling common failure conditions and, second, by comparing these models with real machine signals and using the difference to feed a computational classifier. Our proposal is validated using an electrical motor coupled with a mechanical gear reducer.

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This paper characterizes four ‘fractal vegetables’: (i) cauliflower (brassica oleracea var. Botrytis); (ii) broccoli (brassica oleracea var. italica); (iii) round cabbage (brassica oleracea var. capitata) and (iv) Brussels sprout (brassica oleracea var. gemmifera), by means of electrical impedance spectroscopy and fractional calculus tools. Experimental data is approximated using fractional-order models and the corresponding parameters are determined with a genetic algorithm. The Havriliak-Negami five-parameter model fits well into the data, demonstrating that classical formulae can constitute simple and reliable models to characterize biological structures.

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OBJECTIVE: In the last decade, some attention has been given to spirituality and faith and their role in cancer patients' coping. Few data are available about spirituality among cancer patients in Southern European countries, which have a big tradition of spirituality, namely, the Catholic religion. As part of a more general investigation (Southern European Psycho-Oncology Study--SEPOS), the aim of this study was to examine the effect of spirituality in molding psychosocial implications in Southern European cancer patients. METHOD: A convenience sample of 323 outpatients with a diagnosis of cancer between 6 to 18 months, a good performance status (Karnofsky Performance Status > 80), and no cognitive deficits or central nervous system (CNS) involvement by disease were approached in university and affiliated cancer centers in Italy, Spain, Portugal, and Switzerland (Italian speaking area). Each patient was evaluated for spirituality (Visual Analog Scale 0-10), psychological morbidity (Hospital Anxiety and Depression Scale--HADS), coping strategies (Mini-Mental Adjustment to Cancer--Mini-MAC) and concerns about illness (Cancer Worries Inventory--CWI). RESULTS. The majority of patients (79.3%) referred to being supported by their spirituality/faith throughout their illness. Significant differences were found between the spirituality and non-spirituality groups (p ≤ 0.01) in terms of education, coping styles, and psychological morbidity. Spirituality was significantly correlated with fighting spirit (r = -0.27), fatalism (r = 0.50), and avoidance (r = 0.23) coping styles and negatively correlated with education (r = -0.25), depression (r = -0.22) and HAD total (r = -0.17). SIGNIFICANCE OF RESULTS: Spirituality is frequent among Southern European cancer patients with lower education and seems to play some protective role towards psychological morbidity, specifically depression. Further studies should examine this trend in Southern European cancer patients.

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Bipedal gaits have been classified on the basis of the group symmetry of the minimal network of identical differential equations (alias cells) required to model them. Primary bipedal gaits (e.g., walk, run) are characterized by dihedral symmetry, whereas secondary bipedal gaits (e.g., gallop-walk, gallop- run) are characterized by a lower, cyclic symmetry. This fact has been used in tests of human odometry (e.g., Turvey et al. in P Roy Soc Lond B Biol 276:4309–4314, 2009, J Exp Psychol Hum Percept Perform 38:1014–1025, 2012). Results suggest that when distance is measured and reported by gaits from the same symmetry class, primary and secondary gaits are comparable. Switching symmetry classes at report compresses (primary to secondary) or inflates (secondary to primary) measured distance, with the compression and inflation equal in magnitude. The present research (a) extends these findings from overground locomotion to treadmill locomotion and (b) assesses a dynamics of sequentially coupled measure and report phases, with relative velocity as an order parameter, or equilibrium state, and difference in symmetry class as an imperfection parameter, or detuning, of those dynamics. The results suggest that the symmetries and dynamics of distance measurement by the human odometer are the same whether the odometer is in motion relative to a stationary ground or stationary relative to a moving ground.

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Every month we see to be published dozens of scientific papers about etiology and physiopathology of CP, imaging, treatment, survival, quality of life of patients and of mothers (just a few) and so on. Papers dealing with the feelings and the problems of siblings of children and adults with CP in the most important scientific journals are extremely rare. However in internet we can find the sites of the most important Cerebral Palsy Societies, like the British, the Australian and the American ones already devoting a special attention to the issue of siblings; we also can see several interesting blogs of parents sharing their experiences not only with the handicapped child but also with the siblings, even counseling some books written for children giving practical advices how to deal and live with a handicapped sibling. What was a surprise to me were the several sites of adults having a disabled sibling, frequently with CP, in a new situation: without parents to care them.

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The Ponseti method is reportedly effective for treating clubfoot in children up to 9 years of age. However, whether age at the beginning of treatment influences the rate of successful correction and the rate of relapse is unknown. We therefore retrospectively reviewed 68 consecutive children with 102 idiopathic clubfeet treated by the Ponseti technique in four Portuguese hospitals. We followed patients a minimum of 30 months (mean, 41.4 months; range, 30–61 months). The patients were divided into two groups according to their age at the beginning of treatment; Group I was younger than 6 months and Group II was older than 6 months. All feet(100%) were initially corrected and no feet required extensive surgery regardless of age at the beginning of treatment. There were no differences between Groups I and II in the number of casts, tenotomies, success in terms of rate of initial correction, rate of recurrence, and rate of tibialis anterior transference. The rate of the Ponseti method in avoiding extensive surgery was 100% in Groups I and II; relapses occurred in 8% of the feet in younger and older children. Level of Evidence: Level II, prognostic study. See the Guidelines for Authors for a complete description of levels of evidence.

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A Work Project, presented as part of the requirements for the Award of a Masters Degree in Management from the NOVA – School of Business and Economics

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In this paper, we investigate whether being part of the euro area influences the conditional probability of going through a sudden stop or a bonanza of capital flows. Our sample period is from 1995 until 2014. We identify these two phenomena and we evaluate which push and pull factors help predict the conditional probability of experiencing one of them. We find that most countries had significant capital inflows until 2008 and that there were more sudden stops during the recent financial crisis than in any other moment in our sample. The factors that better help forecast the conditional probability of a sudden stop are global uncertainty (represented by the push factor “Volatility Index”), and the domestic economic activity (pull factors “GDP growth” and “consumer confidence”). An indicator of country risk (pull factor “change in credit rating”) is the most significant one for predicting bonanzas. Ultimately, we find no evidence that being part of the euro area influences the conditional probability of going through a sudden stop or a bonanza.

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The difference between the statutory and effective tax rate for listed groups is a complex variable influenced by a variety of factors. This paper aims to analyze whether this difference exists for listed groups in the German market and tests which factors have an impact on it. Thus the sample consists of 130 corporations listed in the three major German stock indices. The findings suggest that the companies that pay less than the statutory rate clearly outweigh the ones that pay more, and that the income earned from associated companies has a significant impact on this difference.

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Breastfeeding is the natural and safe way of feeding small infants, providing nutritional, immunological, psychological and economic recognized and unquestionable advantages. These qualities are especially important in premature infants, because of their vulnerability. Despite highly desirable, there is, in general, little success in breastfeeding preterm infants, especially in special care neonatal units. There are evidences that a high supportive hospital environment, with an interdisciplinary team, makes possible to these infants to be breastfed. In this article, the authors present an up-to-date review about the components of human milk and its unique characteristics, as well as describes aspects that make the breast milk particularly suitable for feeding the premature newborn.

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This paper aims at developing a collision prediction model for three-leg junctions located in national roads (NR) in Northern Portugal. The focus is to identify factors that contribute for collision type crashes in those locations, mainly factors related to road geometric consistency, since literature is scarce on those, and to research the impact of three modeling methods: generalized estimating equations, random-effects negative binomial models and random-parameters negative binomial models, on the factors of those models. The database used included data published between 2008 and 2010 of 177 three-leg junctions. It was split in three groups of contributing factors which were tested sequentially for each of the adopted models: at first only traffic, then, traffic and the geometric characteristics of the junctions within their area of influence; and, lastly, factors which show the difference between the geometric characteristics of the segments boarding the junctionsâ area of influence and the segment included in that area were added. The choice of the best modeling technique was supported by the result of a cross validation made to ascertain the best model for the three sets of researched contributing factors. The models fitted with random-parameters negative binomial models had the best performance in the process. In the best models obtained for every modeling technique, the characteristics of the road environment, including proxy measures for the geometric consistency, along with traffic volume, contribute significantly to the number of collisions. Both the variables concerning junctions and the various national highway segments in their area of influence, as well as variations from those characteristics concerning roadway segments which border the already mentioned area of influence have proven their relevance and, therefore, there is a rightful need to incorporate the effect of geometric consistency in the three-leg junctions safety studies.

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The present study reviews the scientific literature that describes the criteria equations for defining the mismatch between students and school furniture. This mismatch may negatively affect students' performance and comfort. Seventeen studies met the criteria of this review and twenty-one equations to test six furniture dimensions were identified. There was substantial mismatch between the relative heights of chairs and tables. Some systematic errors have been found during the application of the different equations, such as the assumption that students are sitting on chairs with a proper seat height. Only one study considered the cumulative fit. Finally, some equations are based on contradictory criteria and need to develop and evaluate new equations for these cases. Relevance to industry: Ultimately, the present work is a contribution toward improving the evaluation of school furniture and could be used to design ergonomic-oriented classroom furniture.

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Forest regrowth occupies an extensive and increasing area in the Amazon basin, but accurate assessment of the impact of regrowth on carbon and nutrient cycles has been hampered by a paucity of available allometric equations. We develop pooled and species-specific equations for total aboveground biomass for a study site in the eastern Amazon that had been abandoned for 15 years. Field work was conducted using randomized branch sampling, a rapid technique that has seen little use in tropical forests. High consistency of sample paths in randomized branch sampling, as measured by the standard error of individual paths (14%), suggests the method may provide substantial efficiencies when compared to traditional procedures. The best fitting equations in this study used the traditional form Y=a×DBHb, where Y is biomass, DBH is diameter at breast height, and a and b are both species-specific parameters. Species-specific equations of the form Y=a(BA×H), where Y is biomass, BA is tree basal area, H is tree height, and a is a species-specific parameter, fit almost as well. Comparison with previously published equations indicated errors from -33% to +29% would have occurred using off-site relationships. We also present equations for stemwood, twigs, and foliage as biomass components.