Solitons in Ideal Optical Fibers - A Numerical Development

This work developed a numerical procedure for a system of partial differential equations (PDEs) describing the propagation of solitons in ideal optical fibers. The validation of the procedure was implemented from the numerical comparison between the known analytical solutions of the PDEs system and those obtained by using the numerical procedure developed. It was discovered that the procedure, based on the finite difference method and relaxation Gauss-Seidel method, was adequate in describing the propagation of soliton waves in ideals optical fibers.Comment: Article accepted for publication in Semina: Ci\^encias Exatas e Tecnol\'ogica

Severity of specific language impairment predicts delayed development in number skills

The extent to which mathematical development is dependent upon language is controversial. This longitudinal study investigates the role of language ability in children's development of number skills. Participants were 229 children with specific language impairment (SLI) who were assessed initially at age 7 and again 1 year later. All participants completed measures of psycholinguistic development (expressive and receptive), performance IQ, and the Basic Number Skills subtest of the British Ability Scales. Number skills data for this sample were compared with normative population data. Consistent with predictions that language impairment would impact on numerical development, average standard scores were more than 1 SD below the population mean at both ages. Although the children showed improvements in raw scores at the second wave of the study, the discrepancy between their scores and the population data nonetheless increased over time. Regression analyses showed that, after controlling for the effect of PIQ, language skills explained an additional 19 and 17% of the variance in number skills for ages 7 and 8, respectively. Furthermore, logistic regression analyses revealed that less improvement in the child's language ability over the course of the year was associated with a greater odds of a drop in performance in basic number skills from 7 to 8 years. The results are discussed in relation to the interaction of linguistic and cognitive factors in numerical development and the implications for mathematical education

Ab initio calculations of response properties including electron-hole interaction

We discuss the current status of a computational approach which allows to evaluate the dielectric matrix, and hence electronic excitations like optical properties, including local field and excitonic effects. We introduce a recent numerical development which greatly reduces the use of memory in such type of calculations, and hence eliminates one of the bottlenecks for the application to complex systems. We present recent applications of the method, focusing our interest on insulating oxides.Comment: 11 pages, 5 figures, 1999 MRS Proceedin

Dispositional factors affecting children's early numerical development

Children show large individual differences in numerical skills, even before they begin formal education. These early differences have significant and long-lasting effects, with numerical knowledge before school predicting mathematical achievement throughout the primary and secondary school years. Currently, little is known about the dispositional factors influencing children's numerical development. Why do some children engage with and succeed in mathematics from an early age, whilst others avoid mathematics and struggle to acquire even basic symbolic number skills? This thesis examines the role of two dispositional factors: First, spontaneous focusing on numerosity (SFON), a recently developed construct which refers to an individual's tendency to focus on the numerical aspects of their environment; and second, mathematics anxiety (MA), a phenomenon long recognised by educators and researchers but one which is relatively unexplored in young children. These factors are found to have independent effects on children's numerical skills, thus the empirical work is presented in two separate parts. The SFON studies start by addressing methodological issues. It is shown that the current measures used to assess children's SFON vary in their psychometric properties and subsequently a new and reliable picture-based task is introduced. Next, the studies turn to theoretical questions, investigating the causes, consequences and mechanisms of SFON. The findings give rise to three main conclusions. First, children's SFON shows little influence from parental SFON and home numeracy factors. Second, high SFON children show a symbolic number advantage. Third, the relationship between SFON and arithmetic can be explained, in part, by individual differences in children's ability to map between nonsymbolic and symbolic representations of number. The MA studies focus primarily on gender issues. The results reveal no significant differences between boys' and girls' overall levels of MA; however, there are gender differences in the correlates of MA. Specifically, boys' (but not girls') MA is related to parents' MA. Moreover, the relationship between MA and mathematical outcomes is stronger for boys than it is for girls. Possible causal explanations for these gender differences are explored in two ways: First, by examining the reliability of the scales used to assess MA in boys and girls. Second, by investigating the relationship between girls' (and boys') mathematics anxiety and their societal math-gender stereotypes. The findings from both sets of studies draw a link between children's emerging dispositions towards mathematics and their early numerical skills. Future research needs to examine how these dispositional factors interact with other (cognitive and non-cognitive) predictors of mathematics achievement

Analysis and modeling of green wood milling: Chip production by slabber

During the primary transformation of wood, logs are faced with slabber heads. Chips produced are raw materials for pulp paper and particleboard industries. Efficiency of these industries is partly due to particle size distribution. Command of this distribution is no easy matter because of great dependence on cutting conditions and variability in material. This study aimed a better understanding and predictionof chip fragmentation. It starts with a detailed description of cutting kinematic and interaction between knife and log. This leads to the numerical development of a generic slabber head. Chip fragmentation phenomena were studied through experiments in dynamic conditions. These experiments were carried out thanks to a pendulum (Vc = 400 m/min). It was instrumented with piezoelectric force sensors and high speed camera. Obtained results agreed very well with previous quasi-static experiments

Computer aided design and analysis of gear tooth geometry

A simulation method for gear hobbing and shaping of straight and spiral bevel gears is presented. The method is based upon an enveloping theory for gear tooth profile generation. The procedure is applicable in the computer aided design of standard and nonstandard tooth forms. An inverse procedure for finding a conjugate gear tooth profile is presented for arbitrary cutter geometry. The kinematic relations for the tooth surfaces of straight and spiral bevel gears are proposed. The tooth surface equations for these gears are formulated in a manner suitable for their automated numerical development and solution

Drag enhancement and drag reduction in viscoelastic flow

Creeping flow of polymeric fluid without inertia exhibits elastic instabilities and elastic turbulence accompanied by drag enhancement due to elastic stress produced by flow-stretched polymers. However, in inertia-dominated flow at high \mbox{Re} and low fluid elasticity $El$, a reduction in turbulent frictional drag is caused by an intricate competition between inertial and elastic stresses. Here, we explore the effect of inertia on the stability of viscoelastic flow in a broad range of control parameters $El$ and (\mbox{Re}, \mbox{Wi}). We present the stability diagram of observed flow regimes in \mbox{Wi}-\mbox{Re} coordinates and find that instabilities' onsets show unexpectedly non-monotonic dependence on $El$. Further, three distinct regions in the diagram are identified based on $El$. Strikingly, for high elasticity fluids we discover a complete relaminarization of flow at Reynolds number of the order of unity, different from a well-known turbulent drag reduction. These counterintuitive effects may be explained by a finite polymer extensibility and a suppression of vorticity at high \mbox{Wi}. Our results call for further theoretical and numerical development to uncover the role of inertial effect on elastic turbulence in a viscoelastic flow.Comment: 8 pages, 6 figure

NUMERICAL DEVELOPMENT AND OPTIMIZATION OF THERMAL STORAGE SYSTEMS BY PHASE CHANGE

The building sector accounts for a large portion of energy consumption and carbon dioxide emissions in Europe reducing buildings energy footprint can bring significant decreases in energy consumption. In this specific case, reducing the energetic footprint in residential buildings is a step in the right direction. One way of achieving this is using renewable en- ergies, however these have unreliable production windows, often with a mismatch between production and demand. Using the technical solutions presented here, this mismatch is bridged storing energy whenever it is available to use it when need, even when not available, thermally storing the energy. It was studied the behaviour of Phase Change Materials (PMCs) in heat exchanging and thermal energy storage applications using Computational Fluid Dynamic (CFD) tools. The work presented here successfully developed several tech- nical solutions of heat exchangers for different thermal storage systems components and applications using PCMs, specifically the heat exchangers that would allow for the maxi- mum benefit to use from the PCMs properties in order to heat, cool and provide domestic hot water (DHW) by means of a geothermal heat pump coupled with PCM enhanced bore- holes . The heat exchangers developed are to be employed in the domestic storage tanks applications and in the geothermal boreholes, thus storing renewable energy from solar and geothermal sources for domestic use. Additionally, developing heat exchangers that allow either macro or microscopic encapsulation usage of PCM to help maintain the underground soil average temperature in order to benefit from geothermal heat pump efficiency. It was concluded from these applications that a good methodology was achieved that allows for thermal storage system based on PCMs to be used in residential dwellings either already existing and retrofitted or designed specifically for new residences and successfully decrease their overall energy consumption and carbon footprint.O sector dos edifícios corresponde a uma grande porção do consumo energético e emissões de dióxido de carbono na Europa. Ajudar a reduzir a pegada energética dos edifícios pode trazer reduções significativas no consumo de energia. Neste caso, reduzir a pegada ener- gética de edifícios residenciais é um passo na direção certa. Uma maneira de atingir este objetivo é utilizando energias renováveis. Contudo estas tendem a ter intervalos de produ- ção pouco fiáveis, em que as fases de produção e de consumo têm um desfasamento entre si. Com as soluções técnicas apresentadas este desfasamento é minorado, armazenando termicamente a energia quando disponível para que possa ser utilizada quando necessária. Foi estudado o comportamento de Materiais de Mudança de Fase (PCM em inglês) para aplicações de permuta de calor e armazenamento térmico de energia utilizando ferramen- tas de simulação de Dinâmica de Fluidos Computacional (CFD em inglês).O trabalho apresentado desenvolveu várias soluções técnicas de permutadores de calor para diferentes componentes de sistemas de armazenamento térmico recorrendo a PCMs, especificamente permutadores que permitem tirar o beneficio máximo da propriedades térmicas endémicas do PCM para aquecer, arrefecer e fornecer águas quentes sanitárias (AQS) através de uma bomba de calor geotérmica combinada com furos geotérmicos otimizados com PCMs . Os permutadores de calor foram desenvolvidos para serem instalados em tanques de armazena- mento e em furos geotérmicos, armazenando energia renovável solar e geotérmica para uso doméstico. Adicionalmente, procurou desenvolver-se os permutadores de calor dos furos geotérmicos de modo a permitir a utilização do encapsulamento macro ou microscópico dos PCMs procurando alcançar a manutenção da temperatura média do subsolo, de modo a beneficiar a eficiência da bomba de calor geotérmica. Pode ser concluído destas aplicações que uma boa metodologia foi desenvolvida que permite a utilização de um sistema de ar- mazenamento térmico com base em PCMs que possa ser utilizado em edifícios residenciais, novos, ou já existentes através de uma remodelação técnica das instalações e reduzir o consumo energético dos mesmos bem como a pegada de carbono

The role of mass media in church development in the twenty first century

The life of man has been influenced greatly by modern Mass Media in the 21st century. Such Media include the radio, television, newspaper, magazines, billboards, internet, cable networks, mobile phones, pamphlets, handbills among others. They have greatly enhanced the instant or rapid transfer of information, opinion and ideas. These have influenced man positively and negatively in all aspects of life, ranging from physical, educational, moral, economic to spiritual and religious. Hence this write up has been conceived to explore and highlight the role of the mass media in church development in the 215 century. The mass media is very influential in human life. This is because it enhances rapid communication of news, information, ideas and opinions which affect and influence human life positively and negatively. This two edged influence is also applicable in the religious life of man. The mass media has been used to communicate and influence the growth and development of religious organizations, such as churches. On the other hand, the media in some cases, has contributed to some problems in the church through its abuse and misuse, such as the communication of false doctrines, propaganda and inciting of members to rebel against church authorities. This paper attempts to highlight both the positive and negative roles of the mass media in church development, in addition to suggesting ways of improvemen

LATEST TRENDS OF UNEMPLOYMENT TALLY AND NUMERICAL DEVELOPMENT IN THE BALTIC COUNTRIES

Publication describes two main types of unemployment official tally - statistical evaluation and official registration of the unemployed. Brief description is provided with regard to the employment facilitation authorities in Latvia, Lithuania and Estonia, as well as the unemployment tally and support legislation in all three countries. The statistically estimated unemployment trends between countries are compared from 1998 to 2012 and quarterly trends from 2007 to 2012, as well as the trends of recorded unemployment changes from 2004 to 2012. Statistically evaluated and registered unemployment is compared. Hypotheses for the potential causes of differences are raised