Robust Linear Regression Analysis - A Greedy Approach

The task of robust linear estimation in the presence of outliers is of particular importance in signal processing, statistics and machine learning. Although the problem has been stated a few decades ago and solved using classical (considered nowadays) methods, recently it has attracted more attention in the context of sparse modeling, where several notable contributions have been made. In the present manuscript, a new approach is considered in the framework of greedy algorithms. The noise is split into two components: a) the inlier bounded noise and b) the outliers, which are explicitly modeled by employing sparsity arguments. Based on this scheme, a novel efficient algorithm (Greedy Algorithm for Robust Denoising - GARD), is derived. GARD alternates between a least square optimization criterion and an Orthogonal Matching Pursuit (OMP) selection step that identifies the outliers. The case where only outliers are present has been studied separately, where bounds on the \textit{Restricted Isometry Property} guarantee that the recovery of the signal via GARD is exact. Moreover, theoretical results concerning convergence as well as the derivation of error bounds in the case of additional bounded noise are discussed. Finally, we provide extensive simulations, which demonstrate the comparative advantages of the new technique

Aspects of the chemistry of the Mannich reaction

The work described in the thesis is concerned with the development of new methodologies for the aminoalkylation of a wide range of aromatic substrates using non-aqueous conditions. The Mannich reagents derived from secondary amines, bis(N,N-dialkylamino)methanes laminalsl, and alkoxy(N,N-dialkylamino)methanes laminol ethersl, were used in "in situ" reactions activated by various Lewis acids. The objective was to devise new methods whereby a high concentration of hydrogen chloride did not accumulate in the reaction mixture. It was established that aminals activated by acetyl chloride or sulphur dioxide can be used for the aminoalkylation of n-excessive heterocycles. Good regioselective control was achieved for orthaaminoalkylation of phenols, especially 2,5-dimethylphenol, by both aminals and aminol ethers in the presence of sulphur dioxide. The use of chlorosilane derivatives in "in situ" reactions of aromatic heterocycles was investigated. Good yields of monosubstitution products were obtained using trichloromethyl-, dichlorodimethyl- and chlorotrimethyl-silane with aminol ethers in reactions with N-methylpyrrole. Aminals, however, activated by chlorotrimethylsilane afforded the 2,5-diaminoalkylated pyrroles. The catalytic effect of chlorotrimethylsilane in this system was established. The ipso addition-with-elimination reactions of aryltrialkylstannanes with aminals and aminol ethers in the presence of chlorosilane derivatives were examined. The Mannich reagents derived from primary amines bis(N-alkoxymethyl)-alkyl and -aralkyl amines lbis(aminol ethers)1 have been used in reactions with electron rich aromatic compounds. The aim was to activate an alkoxymethyl group and to protect the product by the same functional group. A versatile method for the preparation of secondary amine Mannich bases was developed. The possibility of carrying out tandem reactions with two different nucleophiles was investigated briefly. Bis(aminol ethers) derived from B -phenylethylamines, possessing a methoxy substituent at the 3-position of the ring, afforded a convenient method for the preparation of N-arylmethyltetrahydroisoquinoline derivative

An organizational systems perspective to business process modeling in small to medium enterprises (smes) : a case of food production

Taking an organizational systems perspective, this paper presents a review to business process modelling and examines the case of food manufacture in a Small to Medium Sized Enterprise (SME), which operates in Cyprus. As a result of the modelling and analysis carried out, areas of concern, issues and opportunities are identified and explored taking into consideration the current business environment of the SME, by focusing on the decision making processes of the production and scheduling activities. The knowledge gained from the modelling effort provides a deeper understanding of the operations and interrelationships between important processes such as “Make”, “Buy”, “Sell” and “Manage”. This proves to be useful for the effective re-design of a production/scheduling decision support system in the particular firm but it also represents the first step towards for the long term development of a generic framework for managerial decision making which takes into consideration the limitations and particularities of manufacturing SMEs.peer-reviewe

Primary students’ conceptions of the Earth: Re-examining a fundamental research hypothesis on mental models

Research on pupils’ conceptions of the earth has proposed certain mental models within the theoretical perspective known as coherent or theory-like knowledge. Alternatively, the fragmented knowledge hypothesis refutes the existence of such models and proposes a different perspective. Although the relevant discussion has not been converged in to a definite answer, recently, the debate between the two theories has been brought up into consideration by the advances in methodology and statistical analysis. In this paper pupils’ conceptions of the earth were analyzed by latent class analyses. Children’s ideas (N=184, grades 1st to 3rd), were investigated using a closed-ended questionnaire, which includes illustrations corresponding to certain mental models. The results showed that pupils’ conceptions of the earth are not characterized by consistency and thus they do not support the existence of coherent mental models. Implications for theory and practice are discussed

Primary students’ conceptions of the Earth: Re-examining a fundamental research hypothesis on mental models

Research on pupils’ conceptions of the earth has proposed certain mental models within the theoretical perspective known as coherent or theory-like knowledge. Alternatively, the fragmented knowledge hypothesis refutes the existence of such models and proposes a different perspective. Although the relevant discussion has not been converged in to a definite answer, recently, the debate between the two theories has been brought up into consideration by the advances in methodology and statistical analysis. In this paper pupils’ conceptions of the earth were analyzed by latent class analyses. Children’s ideas (N=184, grades 1st to 3rd), were investigated using a closed-ended questionnaire, which includes illustrations corresponding to certain mental models. The results showed that pupils’ conceptions of the earth are not characterized by consistency and thus they do not support the existence of coherent mental models. Implications for theory and practice are discussed

Primary students’ argumentation skills on evaporation: A teaching intervention

This paper reports the findings of a study exploring the possibilities of improving students’ argumentation skills concerning evaporation process and factors affecting evaporation by implementing two teaching schemes, with and without the use of particle theory. The participants (ages 10/11, n = 77) were students of four fifth-grade classes of two Greek regular public primary schools. The research data were collected through an open-ended written test (pre- and post-intervention) and a semi-structured interview (post-intervention). Results revealed that the improvement of students’ argumentation skills regarding the evaporation process and the factors affecting evaporation is feasible through an appropriate teaching intervention. This concerns mainly the components of claim and evidence, whereas the use of the particle theory seems to contribute further to this improvement, as well as to the improvement of the reasoning component. Implications for science education are also discussed