994 resultados para NONPARAMETRIC PROBLEMS


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We propose a nonparametric method for estimating derivative financial asset pricing formulae using learning networks. To demonstrate feasibility, we first simulate Black-Scholes option prices and show that learning networks can recover the Black-Scholes formula from a two-year training set of daily options prices, and that the resulting network formula can be used successfully to both price and delta-hedge options out-of-sample. For comparison, we estimate models using four popular methods: ordinary least squares, radial basis functions, multilayer perceptrons, and projection pursuit. To illustrate practical relevance, we also apply our approach to S&P 500 futures options data from 1987 to 1991.

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One of the tantalising remaining problems in compositional data analysis lies in how to deal with data sets in which there are components which are essential zeros. By an essential zero we mean a component which is truly zero, not something recorded as zero simply because the experimental design or the measuring instrument has not been sufficiently sensitive to detect a trace of the part. Such essential zeros occur in many compositional situations, such as household budget patterns, time budgets, palaeontological zonation studies, ecological abundance studies. Devices such as nonzero replacement and amalgamation are almost invariably ad hoc and unsuccessful in such situations. From consideration of such examples it seems sensible to build up a model in two stages, the first determining where the zeros will occur and the second how the unit available is distributed among the non-zero parts. In this paper we suggest two such models, an independent binomial conditional logistic normal model and a hierarchical dependent binomial conditional logistic normal model. The compositional data in such modelling consist of an incidence matrix and a conditional compositional matrix. Interesting statistical problems arise, such as the question of estimability of parameters, the nature of the computational process for the estimation of both the incidence and compositional parameters caused by the complexity of the subcompositional structure, the formation of meaningful hypotheses, and the devising of suitable testing methodology within a lattice of such essential zero-compositional hypotheses. The methodology is illustrated by application to both simulated and real compositional data

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Presentation in CODAWORK'03, session 4: Applications to archeometry

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We study four measures of problem instance behavior that might account for the observed differences in interior-point method (IPM) iterations when these methods are used to solve semidefinite programming (SDP) problem instances: (i) an aggregate geometry measure related to the primal and dual feasible regions (aspect ratios) and norms of the optimal solutions, (ii) the (Renegar-) condition measure C(d) of the data instance, (iii) a measure of the near-absence of strict complementarity of the optimal solution, and (iv) the level of degeneracy of the optimal solution. We compute these measures for the SDPLIB suite problem instances and measure the correlation between these measures and IPM iteration counts (solved using the software SDPT3) when the measures have finite values. Our conclusions are roughly as follows: the aggregate geometry measure is highly correlated with IPM iterations (CORR = 0.896), and is a very good predictor of IPM iterations, particularly for problem instances with solutions of small norm and aspect ratio. The condition measure C(d) is also correlated with IPM iterations, but less so than the aggregate geometry measure (CORR = 0.630). The near-absence of strict complementarity is weakly correlated with IPM iterations (CORR = 0.423). The level of degeneracy of the optimal solution is essentially uncorrelated with IPM iterations.

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A major obstacle to processing images of the ocean floor comes from the absorption and scattering effects of the light in the aquatic environment. Due to the absorption of the natural light, underwater vehicles often require artificial light sources attached to them to provide the adequate illumination. Unfortunately, these flashlights tend to illuminate the scene in a nonuniform fashion, and, as the vehicle moves, induce shadows in the scene. For this reason, the first step towards application of standard computer vision techniques to underwater imaging requires dealing first with these lighting problems. This paper analyses and compares existing methodologies to deal with low-contrast, nonuniform illumination in underwater image sequences. The reviewed techniques include: (i) study of the illumination-reflectance model, (ii) local histogram equalization, (iii) homomorphic filtering, and, (iv) subtraction of the illumination field. Several experiments on real data have been conducted to compare the different approaches

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A list of considerations on the problems with large groups. This material was sent to Debra Morris in 2007, by David Jaques, an educationist with many years' experience of working with groups.

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Seminar given as part of social networking course, to give a brief overview of some applied examples game theory used in social network simulation

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A clinical psychotherapy needs to turn its gaze to the current demands, and update its practice in empirical studies. The objective of this research is to ascertain the sociodemographic and clinical characteristics of children treated in psychotherapy by learning problems. We conducted a retrospective documentary study with records of 2106 children treated between 1979 and 2007 in two outpatient psychological care of the city of Porto Alegre, southern Brazil. The results showed that demand for Learning Problems is the fourth largest cause of psychotherapeutic care. There was no statistically significant difference regarding gender. Children with learning problems come to psychotherapy more frequently in the early stages of elementary school, around 7 years old. Increased demand for psychotherapy of children with learning problems takes place in May. Perhaps, learning difficulties can be understood simultaneously as a symptom global, in which other aspects, besides the uniqueness of the subject are involved. We conclude that individual and social aspects involved in Learning Problems may be useful in the clinical management of these children by professionals who are dedicated to meeting this particular clientele. One must be aware of ongoing partnership which should be placed between psychologist and pedagogue. Both professionals, education and health, account for components of the child to know

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The physical, psychological and sexual violence among the couples of adolescents and young adults that are not married neither cohabiting (well-known generally as “dating violence”), has been object of a vast number of investigations in the last two decades that show a high prevalence inside the adolescent and juvenile population. The objective of this work was to carry out an analysis of the literature in connection with the prevalence, risk factors and difficulties associated with this partner violence type. This analysis allowed to elaborate an outline of the factors that could favor the acts of violence, including the previous experiences of victimization inside and outside the family, the acceptance of the violence toward the couple, and the relationship with pairs that have exercised this form of violence.

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Este estudio explora el estado actual y el potencial competitivo de las exportaciones agrícolas colombianas a los mercados de Estados Unidos y la Unión Eurpea. Los mercados de estos paises industrializados se constituyen en los más importantes para Colombia, pero al mismo tiempo tienen varias restricciones en el sector agrícola. Este estudio mostrará que la competitividad no es solamente una función de los impedimentos locales o internacionales tales como la pobreza institucional, la baja capacidad tecnológica, la disponibilidad de capital, capital humano y mano de obra, sino también de impedimentos externos como el acceso a los mercados. Por lo tanto, éste es un importante objetivo del presente estudio con el objeto de proyectar posibles escenarios para el comercio colombiano, a fin de investigar la eliminación de estas restricciones. En la parte empírica se enfatizará en los impactos de las restricciones externas en el sentido de un estudio econométrico, sin embargo, la influencia de las restricciones internas será discutida como tal.

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In this work we analyze the reforms carried out by the Mexican state in the nineties of the 20th century, in the items concerning the policies of housing and urban land, based on an exhaustive review of the main actions, programs and changes in the legal and institutional frame that applies for each of these fields. The nineties represent a "breaking point" in the way the State considers the satisfaction of the right to the housing and attends the offer of urbanized land for a tidy and sustainable urban development. In this period of time, the approach of direct intervention in developing and financing housing and creation of land reserves has changed into another one, ruled by the logic of the market. The balance to the first decade of the 21st century is ambiguous, as neither the housing policy has solved the housing shortage for low-income population, nor the land policy has eliminated the illegal urban growth.

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The purpose of this expository arti le is to present a self- ontained overview of some results on the hara terization of the optimal value fun tion of a sto hasti target problem as (dis ontinuous) vis osity solution of a ertain dynami programming PDE and its appli ation to the problem of hedging ontingent laims in the presen e of portfolio onstraints and large investors