Inférence robuste à la présence des valeurs aberrantes dans les enquêtes

Cette thèse comporte trois articles dont un est publié et deux en préparation. Le sujet central de la thèse porte sur le traitement des valeurs aberrantes représentatives dans deux aspects importants des enquêtes que sont : l’estimation des petits domaines et l’imputation en présence de non-réponse partielle. En ce qui concerne les petits domaines, les estimateurs robustes dans le cadre des modèles au niveau des unités ont été étudiés. Sinha & Rao (2009) proposent une version robuste du meilleur prédicteur linéaire sans biais empirique pour la moyenne des petits domaines. Leur estimateur robuste est de type «plugin», et à la lumière des travaux de Chambers (1986), cet estimateur peut être biaisé dans certaines situations. Chambers et al. (2014) proposent un estimateur corrigé du biais. En outre, un estimateur de l’erreur quadratique moyenne a été associé à ces estimateurs ponctuels. Sinha & Rao (2009) proposent une procédure bootstrap paramétrique pour estimer l’erreur quadratique moyenne. Des méthodes analytiques sont proposées dans Chambers et al. (2014). Cependant, leur validité théorique n’a pas été établie et leurs performances empiriques ne sont pas pleinement satisfaisantes. Ici, nous examinons deux nouvelles approches pour obtenir une version robuste du meilleur prédicteur linéaire sans biais empirique : la première est fondée sur les travaux de Chambers (1986), et la deuxième est basée sur le concept de biais conditionnel comme mesure de l’influence d’une unité de la population. Ces deux classes d’estimateurs robustes des petits domaines incluent également un terme de correction pour le biais. Cependant, ils utilisent tous les deux l’information disponible dans tous les domaines contrairement à celui de Chambers et al. (2014) qui utilise uniquement l’information disponible dans le domaine d’intérêt. Dans certaines situations, un biais non négligeable est possible pour l’estimateur de Sinha & Rao (2009), alors que les estimateurs proposés exhibent un faible biais pour un choix approprié de la fonction d’influence et de la constante de robustesse. Les simulations Monte Carlo sont effectuées, et les comparaisons sont faites entre les estimateurs proposés et ceux de Sinha & Rao (2009) et de Chambers et al. (2014). Les résultats montrent que les estimateurs de Sinha & Rao (2009) et de Chambers et al. (2014) peuvent avoir un biais important, alors que les estimateurs proposés ont une meilleure performance en termes de biais et d’erreur quadratique moyenne. En outre, nous proposons une nouvelle procédure bootstrap pour l’estimation de l’erreur quadratique moyenne des estimateurs robustes des petits domaines. Contrairement aux procédures existantes, nous montrons formellement la validité asymptotique de la méthode bootstrap proposée. Par ailleurs, la méthode proposée est semi-paramétrique, c’est-à-dire, elle n’est pas assujettie à une hypothèse sur les distributions des erreurs ou des effets aléatoires. Ainsi, elle est particulièrement attrayante et plus largement applicable. Nous examinons les performances de notre procédure bootstrap avec les simulations Monte Carlo. Les résultats montrent que notre procédure performe bien et surtout performe mieux que tous les compétiteurs étudiés. Une application de la méthode proposée est illustrée en analysant les données réelles contenant des valeurs aberrantes de Battese, Harter & Fuller (1988). S’agissant de l’imputation en présence de non-réponse partielle, certaines formes d’imputation simple ont été étudiées. L’imputation par la régression déterministe entre les classes, qui inclut l’imputation par le ratio et l’imputation par la moyenne sont souvent utilisées dans les enquêtes. Ces méthodes d’imputation peuvent conduire à des estimateurs imputés biaisés si le modèle d’imputation ou le modèle de non-réponse n’est pas correctement spécifié. Des estimateurs doublement robustes ont été développés dans les années récentes. Ces estimateurs sont sans biais si l’un au moins des modèles d’imputation ou de non-réponse est bien spécifié. Cependant, en présence des valeurs aberrantes, les estimateurs imputés doublement robustes peuvent être très instables. En utilisant le concept de biais conditionnel, nous proposons une version robuste aux valeurs aberrantes de l’estimateur doublement robuste. Les résultats des études par simulations montrent que l’estimateur proposé performe bien pour un choix approprié de la constante de robustesse.

Modelling and Analysis of Some Time Series

The thesis deals with some of the non-linear Gaussian and non-Gaussian time models and mainly concentrated in studying the properties and application of a first order autoregressive process with Cauchy marginal distribution. In this thesis some of the non-linear Gaussian and non-Gaussian time series models and mainly concentrated in studying the properties and application of a order autoregressive process with Cauchy marginal distribution. Time series relating to prices, consumptions, money in circulation, bank deposits and bank clearing, sales and profit in a departmental store, national income and foreign exchange reserves, prices and dividend of shares in a stock exchange etc. are examples of economic and business time series. The thesis discuses the application of a threshold autoregressive(TAR) model, try to fit this model to a time series data. Another important non-linear model is the ARCH model, and the third model is the TARCH model. The main objective here is to identify an appropriate model to a given set of data. The data considered are the daily coconut oil prices for a period of three years. Since it is a price data the consecutive prices may not be independent and hence a time series based model is more appropriate. In this study the properties like ergodicity, mixing property and time reversibility and also various estimation procedures used to estimate the unknown parameters of the process.

Atomic parity nonconservation, neutron radii, and effective field theories of nuclei

Accurately calibrated effective field theories are used to compute atomic parity nonconserving (APNC) observables. Although accurately calibrated, these effective field theories predict a large spread in the neutron skin of heavy nuclei. Whereas the neutron skin is strongly correlated to numerous physical observables, in this contribution we focus on its impact on new physics through APNC observables. The addition of an isoscalar-isovector coupling constant to the effective Lagrangian generates a wide range of values for the neutron skin of heavy nuclei without compromising the success of the model in reproducing well-constrained nuclear observables. Earlier studies have suggested that the use of isotopic ratios of APNC observables may eliminate their sensitivity to atomic structure. This leaves nuclear structure uncertainties as the main impediment for identifying physics beyond the standard model. We establish that uncertainties in the neutron skin of heavy nuclei are at present too large to measure isotopic ratios to better than the 0.1% accuracy required to test the standard model. However, we argue that such uncertainties will be significantly reduced by the upcoming measurement of the neutron radius in 208^Pb at the Jefferson Laboratory.

Los grupos paramilitares en Colombia: el incierto tránsito de la guerra a la paz

Esta investigación aborda las condiciones bajo las que se llevó a cabo en Colombia, en el primer gobierno del presidente Álvaro Uribe Vélez (2002-2006), la negociación entre el Estado y los grupos paramilitares. Se establecen las características de ese proceso de paz, su correspondencia con modelos tradicionales de negociación y sus alcances sobre el proceso de Desmovilización, Desarme y Reinserción (DDR) de las organizaciones paramilitares.

A atitude dos alunos face à inclusão dos seus pares com deficiência

RESUMO: A escola actual encontra-se perante o desafio de responder com afectividade às necessidades educativas especiais de uma população cada vez mais heterogénea, onde se adopte um modelo de atendimento adequado a cada um. Neste contexto, consideramos os alunos, os professores e os encarregados de educação elementos chave de todo o processo, sobre os quais recaem responsabilidades acrescidas na concretização da filosofia inclusiva. O presente estudo tem como objectivo averiguar a atitude dos alunos face à inclusão dos seus pares com deficiência, determinando o modo como estes percepcionam as atitudes dos professores e dos pais face à inclusão de alunos com NEE de carácter permanente, vantagens e desvantagens da inclusão de alunos com NEE de carácter permanente e a cooperação entre alunos com e sem deficiência, tendo em conta a tipologia da deficiência (motora e mental). No caso do nosso estudo, contámos com a participação de 520 alunos (N= 270 género feminino e N=250 do género masculino), uma amostra distribuída pelo 2ºciclo, 3º ciclo e secundário dos distritos de Setúbal e Lisboa. A recolha de dados concretizou-se pela aplicação do AID – EF, questionário da autoria de Ramos Leitão, 2011.Esta metodologia de recolha e tratamento de informação permitiu-nos concluir que, na opinião dos alunos ditos normais a atitude dos professores face à inclusão de alunos com NEE de carácter permanente (dimensão d1), não varia em função da tipologia da deficiência (deficiência motora e mental). Da mesma forma, não foram encontradas diferenças significativas entre os dois grupos (deficiência motora e mental), na opinião dos alunos ditos normais, no que respeita às vantagens da inclusão dos alunos com NEE de carácter permanente (dimensão d2). Na opinião dos alunos ditos normais os resultados demonstraram que a cooperação entre alunos com e sem deficiência (dimensão d3), varia em função da tipologia da deficiência (deficiência motora e mental), apontando esses resultados para uma maior cooperação entre os alunos ditos normais e os seus pares com deficiência mental. Não foram igualmente encontradas diferenças significativas no que respeita às desvantagens da inclusão dos alunos com NEE de carácter permanente (dimensão 4), quando temos em consideração a tipologia da deficiência (deficiência motora e mental). Da mesma forma, na opinião dos alunos normais ditos normais a atitude dos pais face à inclusão de alunos com NEE de carácter permanente (dimensão d5) não variam em função da tipologia da deficiência (deficiência motora e mental).ABSTRACT: Currently the school is faced with the challenge of responding affectionately to the special educational needs of an increasingly heterogeneous population, where a standard model is adopted for each individual. In this context, we consider the students, teachers and guardians, key elements in the whole process, over which fall increased responsibilities in the implementation of the inclusive philosophy. The present study aims to determine the attitude of students towards the inclusion of peers with disabilities, determining how they perceive the attitudes of teachers and parents towards the inclusion of pupils with permanent special education needs, advantages and disadvantages of including students with permanent special education needs and the cooperation between students with and without disabilities, taking into account the type of disability (mental and motor). In the case of our study, we had the participation of 520 students (N = 270 N = female and 250 male), a sample distributed to the 2nd cycle, 3rd cycle and Secondary schools in the districts of Setúbal and Lisbon. The data collected was enabled by the application of the IDA - EF, questionnaire by Ramos Leitão, 2011. This methodology of collecting and processing information allowed us to conclude that, in the opinion of the so-called normal students the teachers´ attitude towards the inclusion of pupils with permanent special education needs (dimension d1) does not vary according to the type of disability (motor and mental). Likewise, no significant differences were found between the two groups (mental and motor), in the opinion of the so-called normal students, with regard to the benefits of the inclusion of pupils with permanent special education needs (dimension d2). In the opinion of the so-called normal students, the results demonstrated that the cooperation between students with and without disabilities (dimension d3), vary depending on the type of disability (mental and motor), these results pointing to a greater cooperation between the so-called normal students and their peers with mental disabilities. There were also no significant differences with respect to the disadvantages of inclusion of pupils with permanent special education needs (dimension d4), when we take into account the type of disability (mental and motor). Similarly, in the opinion of the so-called normal students, the parents´ attitude towards the inclusion of pupils with permanent special education needs (dimension d5) does not vary according to the type of disability (mental and motor).

Ateliê caderneta de cromos : estudo sobre a relação de uma prática artística visual não formal e inclusão

Esta investigação teve como objeto de estudo o Ateliê Caderneta de Cromos, do projeto Geração Cool, fruto de uma parceria entre várias instituições do concelho de Almada. Trata--se de um projeto de desenvolvimento social comunitário, multicultural, associado a uma escola. Através de um estudo de caso, pretendeu analisar-se, criticamente, um modelo não formal de práticas ligadas às artes visuais, vocacionado para jovens em risco e mostrar como as aprendizagens desenvolvidas num ateliê de artes visuais contribuem para o processo de inclusão desses jovens. Desenvolveu-se um quadro teórico abrangente, no sentido de sustentar as perguntas iniciais, referenciando questões consideradas pertinentes tais como: visões contemporâneas das realidades multiculturais das periferias urbanas; perspetivas pós-modernistas de ensino artístico, defensoras de uma construção cognitiva; ação dos projetos artísticos de desenvolvimento social e ainda, a importância ética e social dos currículos artísticos atuais. Tendo como referência a hipótese de antagonismo e/ou complementaridade entre o ato pedagógico não formal e o institucional, o estudo procurou estabelecer uma relação entre essa prática e a inclusão, ao identificar e desmontar um roteiro estratégico de aprendizagens. O ato pedagógico no Ateliê mostrou potenciar uma aprendizagem construtiva nas respostas produzidas, sendo também significativa pelo caráter experiencial vivido e cognitiva no sentido em que determina a construção de um significado, assumido como a própria assunção identitária.

The standardization of contracts for construction

Contracts are put to a wide variety of uses. Those who draft construction contracts in the UK rarely consider all of the potential uses and therefore may produce documents that are less than ideal. The various uses are considered in their theoretical background before turning to the practical difficulties often encountered in trying to fulfil such diverse aims. The question of standardisation is examined within this context. Existing standard forms of contract in the UK are found to do little to overcome these difficulties, and this encourages either a significant level of amendment to the standards or experienced clients to draft their own forms. The solution is an approach to contract drafting which is designed to offer a compromise; better standard forms, based on the lessons learned from the drafting of non-standard forms and a pooling of experience, including that of lawyers, in the drafting process. Although this paper is based upon the experience of the UK, these conclusions are relevant for contract-drafting practice in general.

Design, implementation and characterisation of a contactless power transfer system for rotating applications

This paper describes the design, implementation and characterisation of a contactless power transfer system for rotating applications. The power transfer system is based upon a zero-voltage-switched, full-bridge, DC-DC converter, but utilises a non-standard transformer. This transformer allows power transfer between its primary and secondary windings while also allowing free rotation between these windings. The aim of this research is to develop a solution that could replace mechanical slip-rings in certain applications where a non-contacting system would be advantageous. Based upon the design method presented in this paper, a 2 kW prototype system is constructed. Results obtained from testing the 2 kW prototype are presented and discussed. This discussion considers how the performance of the transformer varies with rotation and also the overall efficiency of the system

Techniques for quantifying effects of dietary antioxidants on transcription factor translocation and nitric oxide production in cultured cells

Dietary antioxidants can affect cellular processes relevant to chronic inflammatory diseases such as atherosclerosis. We have used non- standard techniques to quantify effects of the antioxidant soy isoflavones genistein and daidzein on translocation of Nuclear Factor-KB (NF-KB) and nitric oxide (NO) production, which are important in these diseases. Translocation was quantified using confocal immunofluoresecence microscopy and ratiometric image analysis. NO was quantified by an electrochemical method after reduction of its oxidation products in cell culture supernatants. Activation of the RAW 264.7 murine monocyte/macrophage cell line increased the ratio of nuclear to cytoplasmic immunostaining for NF-kB. The increase was exacerbated by pre-treatment with genistein or daidzein. To show that decreases could also be detected, pre-treatment with the pine bark extract Pycnogenol (R) r was examined, and found to reduce translocation. NO production was also increased by activation, but was reduced by pre-treatment with genistein or daidzein. In the EA. hy926 human endothelial cell line, constitutive production was detectable and was increased by thrombin. The confocal and electrochemical methods gave data that agreed with results obtained using the established electromobility shift and Griess assays, but were more sensitive, more convenient, gave more detailed information and avoided the use of radioisotopes.

Style, experimentation and Jingju (Beijing Opera) as a decentered multiplicity

Jingju (Beijing Opera) is widely considered to be a fundamentally non-naturalistic practice that became known in the West after it caught the attention of western practitioners in 1935 following Mei Lanfang’s performance in Moscow. Given the implication that its importance is largely historical, some non-specialists have implied that Jingju has little relevance to contemporary modes of thinking, particularly the multiplicities of experience as outlined by philosophers such as Deleuze and Guattari. This article seeks to demonstrate the multiplicity of Jingju for a wider readership through both a historical analysis and a deconstruction of the form. It will show how, at the same time that Mei Lanfang was providing a ‘non-realistic’ model for western practitioners eager to displace the dominance of naturalism, realistic settings were becoming an integral part of Jingju performances in Shanghai. The article also engages with the various acting pai/styles that weave Jingju into a complex, multiple form. The article demonstrates how Deleuzian models actually facilitate a greater understanding of Jingju.

Simulating the interannual variability of major dust storms on Mars using variable lifting thresholds

The redistribution of a finite amount of martian surface dust during global dust storms and in the intervening periods has been modelled in a dust lifting version of the UK Mars General Circulation Model. When using a constant, uniform threshold in the model’s wind stress lifting parameterisation and assuming an unlimited supply of surface dust, multiannual simulations displayed some variability in dust lifting activity from year to year, arising from internal variability manifested in surface wind stress, but dust storms were limited in size and formed within a relatively short seasonal window. Lifting thresholds were then allowed to vary at each model gridpoint, dependent on the rates of emission or deposition of dust. This enhanced interannual variability in dust storm magnitude and timing, such that model storms covered most of the observed ranges in size and initiation date within a single multiannual simulation. Peak storm magnitude in a given year was primarily determined by the availability of surface dust at a number of key sites in the southern hemisphere. The observed global dust storm (GDS) frequency of roughly one in every 3 years was approximately reproduced, but the model failed to generate these GDSs spontaneously in the southern hemisphere, where they have typically been observed to initiate. After several years of simulation, the surface threshold field—a proxy for net change in surface dust density—showed good qualitative agreement with the observed pattern of martian surface dust cover. The model produced a net northward cross-equatorial dust mass flux, which necessitated the addition of an artificial threshold decrease rate in order to allow the continued generation of dust storms over the course of a multiannual simulation. At standard model resolution, for the southward mass flux due to cross-equatorial flushing storms to offset the northward flux due to GDSs on a timescale of ∼3 years would require an increase in the former by a factor of 3–4. Results at higher model resolution and uncertainties in dust vertical profiles mean that quasi-periodic redistribution of dust on such a timescale nevertheless appears to be a plausible explanation for the observed GDS frequency.

Interpersonal interaction and economic theory: the case of public goods

Interpersonal interaction in public goods contexts is very different in character to its depiction in economic theory, despite the fact that the standard model is based on a small number of apparently plausible assumptions. Approaches to the problem are reviewed both from within and outside economics. It is argued that quick fixes such as a taste for giving do not provide a way forward. An improved understanding of why people contribute to such goods seems to require a different picture of the relationships between individuals than obtains in standard microeconomic theory, where they are usually depicted as asocial. No single economic model at present is consistent with all the relevant field and laboratory data. It is argued that there are defensible ideas from outside the discipline which ought to be explored, relying on different conceptions of rationality and/or more radically social agents. Three such suggestions are considered, one concerning the expressive/communicative aspect of behaviour, a second the possibility of a part-whole relationship between interacting agents and the third a version of conformism.

The evolution of the sun’s open magnetic flux: II. full solar cycle simulations

In this paper the origin and evolution of the Sun’s open magnetic flux is considered by conducting magnetic flux transport simulations over many solar cycles. The simulations include the effects of differential rotation, meridional flow and supergranular diffusion on the radial magnetic field at the surface of the Sun as new magnetic bipoles emerge and are transported poleward. In each cycle the emergence of roughly 2100 bipoles is considered. The net open flux produced by the surface distribution is calculated by constructing potential coronal fields with a source surface from the surface distribution at regular intervals. In the simulations the net open magnetic flux closely follows the total dipole component at the source surface and evolves independently from the surface flux. The behaviour of the open flux is highly dependent on meridional flow and many observed features are reproduced by the model. However, when meridional flow is present at observed values the maximum value of the open flux occurs at cycle minimum when the polar caps it helps produce are the strongest. This is inconsistent with observations by Lockwood, Stamper and Wild (1999) and Wang, Sheeley, and Lean (2000) who find the open flux peaking 1–2 years after cycle maximum. Only in unrealistic simulations where meridional flow is much smaller than diffusion does a maximum in open flux consistent with observations occur. It is therefore deduced that there is no realistic parameter range of the flux transport variables that can produce the correct magnitude variation in open flux under the present approximations. As a result the present standard model does not contain the correct physics to describe the evolution of the Sun’s open magnetic flux over an entire solar cycle. Future possible improvements in modeling are suggested.