The rolling ball problem on the plane revisited

By a sequence of rollings without slipping or twisting along segments of a straight line of the plane, a spherical ball of unit radius has to be transferred from an initial state to an arbitrary final state taking into account the orientation of the ball. We provide a new proof that with at most 3 moves, we can go from a given initial state to an arbitrary final state. The first proof of this result is due to Hammersley ( 1983). His proof is more algebraic than ours which is more geometric. We also showed that generically no one of the three moves, in any elimination of the spin discrepancy, may have length equal to an integral multiple of 2 pi.

Using Universal Line Model (ULM) for Representing Electromagnetic Transients in Three-Phase Transmission Lines

The second-order differential equations that describe the polyphase transmission line are difficult to solve due to the mutual coupling among them and the fact that the parameters are distributed along their length. A method for the analysis of polyphase systems is the technique that decouples their phases. Thus, a system that has n phases coupled can be represented by n decoupled single-phase systems which are mathematically identical to the original system. Once obtained the n-phase circuit, it's possible to calculate the voltages and currents at any point on the line using computational methods. The Universal Line Model (ULM) transforms the differential equations in the time domain to algebraic equations in the frequency domain, solve them and obtain the solution in the frequency domain using the inverse Laplace transform. This work will analyze the method of modal decomposition in a three-phase transmission line for the evaluation of voltages and currents of the line during the energizing process.

Phonological working memory and reading in students with dyslexia

Purpose: To investigate parameters related to fluency, reading comprehension and phonological processing (operational and short-term memory) and identify potential correlation between the variables in Dyslexia and in the absence of reading difficulties.Method: One hundred and fifteen students from the third to eighth grade of elementary school were grouped into a Control Group (CG) and Group with Dyslexia (GDys). Reading of words, pseudowords and text (decoding); listening and reading comprehension; phonological short-term and working memory (repetition of pseudowords and Digit Span) were evaluated.Results: The comparison of the groups showed significant differences in decoding, phonological short-term memory (repetition of pseudowords) and answers to text-connecting questions (TC) on reading comprehension, with the worst performances identified for GDys. In this group there were negative correlations between pseudowords repetition and TC answers and total score, both on listening comprehension. No correlations were found between operational and short-term memory (Digit Span) and parameters of fluency and reading comprehension in dyslexia. For the sample without complaint, there were positive correlations between some parameters of reading fluency and repetition of pseudowords and also between answering literal questions in listening comprehension and repetition of digits on the direct and reverse order. There was no correlation with the parameters of reading comprehension.Conclusion: GDys and CG showed similar performance in listening comprehension and in understanding of explicit information and gap-filling inference on reading comprehension. Students of GDys showed worst performance in reading decoding, phonological short-term memory (pseudowords) and on inferences that depends on textual cohesion understanding in reading. There were negative correlations between pseudowords repetition and TC answers and total score, both in listening comprehension.

Transmission network expansion planning for the Colombian electrical system: Connecting the Ituango hydroelectric power plant

The hydroelectric power plant Hidroltuango represents a major expansion for the Colombian electrical system (with a total capacity of 2400 MW). This paper analyzes the possible interconnections and investments involved in connecting Hidroltuango, in order to strengthen the Colombian national transmission system. A Mixed Binary Linear Programming (MBLP) model was used to solve the Multistage Transmission Network Expansion Planning (MTEP) problem of the Colombian electrical system, taking the N-1 safety criterion into account. The N-1 safety criterion indicates that the transmission system must be expanded so that the system will continue to operate properly if an outage in a system element (within a pre-defined set of contingencies) occurs. The use of a MBLP model guaranteed the convergence with existing classical optimization methods and the optimal solution for the MTEP using commercial solvers. Multiple scenarios for generation and demand were used to consider uncertainties within these parameters. The model was implemented using the algebraic modeling language AMPL and solved using the commercial solver CPLEX. The proposed model was then applied to the Colombian electrical system using the planning horizon of 2018-2025. (C) 2014 Elsevier B.V. All rights reserved.

Técnica para dedução do modelo algébrico PTT, aplicações e análises numéricas em escoamentos bidimensionais

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Compreensão de leitura: princípios avaliativos e interventivos no contexto educacional

Reading is a complex process that involves cognitive and linguistic skills, such as decoding and comprehension. When the skill to understand texts is not performed there is a commitment throughout the learning process interfering with the development of the student as a whole. Ensuring that the student carries out reading efficiently is one of the main challenges of schools. Considering these aspects, this study, through reflection of previous studies, presents the processes involved in reading comprehension, as well as problems that can interfere with these processes, assessment and intervention strategies with the students so that possible difficulties in the educational context can be minimized.

Desempenho de escolares com dislexia e transtorno do déficit de atenção e hiperatividade nos processos de leitura

This study aimed to characterize and to compare the performance of students with an interdisciplinary diagnosis of dyslexia and attention deficit hyperactivity disorder (ADHD) in students with good academic performance on the reading processes. Sixty students from both genders, from 2nd to 4th grades of municipal public schools in Marília - SP participated in this study, they were distributed as follows: GI, 20 students with interdisciplinary diagnosis of dyslexia; GII, 20 students with ADHD and GIII, 20 students with good academic performance, paired according to gender, age and grade level with GI and GII. The students were submitted to the application of the assessment of reading processes (PROLEC) composed by four processes: letters identification, lexical, syntactical and semantic. The results highlighted that the students of GIII showed superior performance comparing with GI and GII. There was difference between GI and GII only in low frequency word reading and non words reading of the lexical process. The inferior performance from GI and GII in the PROLEC tests can be justified by the difficulty on the coding and decoding abilities. In ADHD students this difficulty was due to impaired interaction between the visual, linguistic, attention and auditory processing and in the dyslexic students was due to failure at the phonological mediation process, which depends on the knowledge of rules of grapheme - phoneme conversion to the acquisition of word reading. These changes affect the reading achievement and the comprehension of the read text.

Caracterização do desempenho de crianças com dislexia do desenvolvimento em tarefas de escrita

INTRODUCTION: developmental dyslexia is characterized by impairment in reading and writing of simple words often involving deficits in phonological decoding and spelling. It affects individuals without sensory disabilities, free of significant emotional commitment and adequate educational opportunities. OBJECTIVE: to characterize the performance in activities related to writing observed in children with developmental dyslexia. METHOD: a total of six children (boys and girls) from 3rd to 7th grade from public schools in a city in the state of Sao Paulo, eight to thirteen years of age, participated in this study. Data were collected in CEES - Centro de Estudos de Educação e Saúde of UNESP - in Marília -SP in writing tasks. The results were analyzed descriptively by the score in percentage of correct answers. RESULTS: children with developmental dyslexia presented alterations in relation to the activities: writing of isolated words and writing of dictated words were below expectations for the education level, presenting phonological and orthographic changes. CONCLUSION: it is important that children with school problems make a more specific evaluation concerning these tasks.

Catalogação, formas de representação e construções mentais

The cataloging process, is responsible for building systems consisting of sets of interconnected elements and combined forms of representation, creating tools to facilitate the flow of information in various informational environments. It presents structures that offer favorable conditions for access to formal codes of symbolic representation and to the channels of information transfer, performing with competence the decoding and encoding of codes and rules used to represent knowledge and to describe information, documents and resources. The objective of this paper is to present the challenge of transforming operational data into consistent information, the role of the forms of representation and the mental constructions for defining the memory markers of users of catalogs. It shows as results the memory markers indicated by three categories of users for the description of a book like resource and points to the need of collaborative and cooperative work in cataloging and to the need of catalog modelling focused on the user.

Logic TK: algebric notions from Tarski's consequence operator

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Para além da leitura linear: uma contribuição ao processo de compreensão

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Grupos wallpaper e sua relação com cohomologia de grupos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Darboux invariants for planar polynomial differential systems having an invariant conic

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Pure Spinors in AdS and Lie Algebra Cohomology

We show that the BRST cohomology of the massless sector of the Type IIB superstring on AdS(5) x S (5) can be described as the relative cohomology of an infinite-dimensional Lie superalgebra. We explain how the vertex operators of ghost number 1, which correspond to conserved currents, are described in this language. We also give some algebraic description of the ghost number 2 vertices, which appears to be new. We use this algebraic description to clarify the structure of the zero mode sector of the ghost number two states in flat space, and initiate the study of the vertices of the higher ghost number.

Quasi-exactly-solvable confining solutions for spin-1 and spin-0 bosons in (1+1)-dimensions with a scalar linear potential

We point out a misleading treatment in the recent literature regarding confining solutions for a scalar potential in the context of the Duffin-Kemmer-Petiau theory. We further present the proper bound-state solutions in terms of the generalized Laguerre polynomials and show that the eigenvalues and eigenfunctions depend on the solutions of algebraic equations involving the potential parameter and the quantum number. (C) 2014 Elsevier Inc. All rights reserved.