Proportion in school mathematics textbooks: A comparative study

This paper analyses how proportion is introduced and developed in selected mathematics textbooks for middle school students of Portugal, Spain, Brazil, and USA. The analysis focuses on the nature of the approach and on the cognitive demand, structure, and context of the tasks. The results show that the textbooks tend to present tasks at an intermediate level of cognitive demand and with a closed structure. Nonmathematical contexts predominate in three of the four textbooks. However, there are marked differences in the way textbooks approach the conceptual and procedural aspects of proportion. The way the students are addressed also varies, ranging from a questioning/problem solving style, to an explaining/practicing style, each of these styles supporting a rather different kind of activity.Este artigo analisa como proporção é introduzida e desenvolvida nos livros didáticos matemática para alunos do ensino médio (Ensino Fundamental II) em Portugal, Espanha, Brasil e EUA. A análise incide sobre a natureza da abordagem e na demanda cognitiva, estrutura e contexto das tarefas. Os resultados mostram que os livros didáticos tendem a apresentar as tarefas em um nível intermediário de demanda cognitiva e com uma estrutura fechada. Contextos não-matemáticos predominam em três dos quatro livros didáticos analisados. No entanto, há diferenças marcantes no modo como os livros abordam os aspectos conceituais e procedimentais de proporção. A forma didática de tratar o assunto também varia, indo de um estilo de questionamento / resolução de problemas, a um modo explicativo/prático; cada um deles ampara-se em um tipo diferente de atividade

Beliefs, values and attitudes of Portuguese population and their relationship with human and social capital

Studying economic values and beliefs and their relationship with attitudes and behavior has been common in most social sciences throughout the world, at least since the 1960s. However, Portugal remained very much outside this research program and, contrary to the majority of European countries or the United States, it still lacks a coherent an integrative research on economic values, beliefs and behaviors. On the other hand, the existing data (European and World Value Surveys, Eurobarometer or the Portuguese Statistics Institute) only offers a partial view of the individual’s relationship with the economic system, namely consumer confidence or general ideas of trust. The studies already developed on this subject are normally restricted to the association of economic values and beliefs with socio-demographic characteristics, failing to include both the analysis of behaviors and the impact all these variables may have on economic performance indicators. The current study is intended as a first step towards a deeper comprehension of these phenomena.

Monetary Policy Effects: Evidence from the Portuguese Flow of Funds

This paper uses a VAR approach to study the transmission of monetary policy shocks in Portugal, focusing in particular on the financial decisions of households, corporations (financial/non-financial), the government and the rest of the world. We confirm that, in many ways, households and firms react in a similar way as found in other countries, with evidence that the monetary policy shock has a contractionary effect on economic activity and increases the financing needs of households and non-financial corporations. We also find evidence that the financial sector plays an important role, supplying the necessary funds to these sectors. We do not find much evidence of a significant systematic behaviour of the government or the rest of the world.

How the U.S. capital markets volatility interacts with economic growth

Empirical finance suggests that capital markets volatility has a negative relationship with economic growth, in the United States. However, the main focus has been on the equity market volatility dynamics and less on other equally important asset classes, given their significant role in the structure of capital markets. In this thesis, I examine the leading and lagging dynamics between money markets, government debt, corporate debt and equities volatilities, in the U.S., and a real GDP growth proxy, between January, 1963 and March, 2009. I also introduce the concept of aggregate capital markets portfolio volatility, which follows the assumptions of a mean-variance portfolio calculation, and test its interaction with growth. Moreover, it is analysed the degree of explaining power of volatilities to the GDP proxy in specific time periods and also in NBER recessions, slowdowns and expansions periods. The empirical results posit that asset classes and capital markets portfolio volatilities are essentially counter-cyclical of growth, on a contemporaneous basis. However, this interaction changes significantly across decades. Finally, in recessions and slowdown periods rising volatility leads the economic cycle, but in expansions its downtrend lags the cycle.Os estudos empíricos financeiros sugerem que a volatilidade dos mercados de capitais evidencia uma relação negativa com o crescimento económico, nos Estados Unidos. No entanto, o maior foco tem sido sobre a dinâmica da volatilidade do mercado de acções e menos noutras classes de activos, igualmente importantes, dada a sua relevância na estrutura do mercado de capitais. Nesta tese, examino as dinâmicas entre as volatilidades dos mercados monetários, das obrigações do tesouro, das obrigações de risco de crédito e das acções, nos E.U.A., e uma variável próxima do produto interno bruto real, entre Janeiro de 1963 e Março de 2009. Também introduzo o conceito de volatilidade de carteira agregada de mercados de capitais, que obedece aos pressupostos de cálculo de rendibilidade e risco de uma carteira de activos financeiros, e testo a respectiva interacção com o crescimento. Adicionalmente, é analisado o grau de poder explicativo de volatilidades para a variável próxima de crescimento, em periodos de tempo específicos e também em recessões decretadas pelo instituto NBER, em conjunturas de abrandamento e de expansão. Os resultados empíricos sugerem que as volatilidades das classes de activos e da carteira de mercados de capitais são essencialmente contra-cíclicas do crescimento, numa base contemporânea. No entanto, a intensidade desta relação varida de forma substancial entre as várias décadas. Finalmente, em periodos de recessão ou de abrandamento, uma tendência de subida da volatilidade lidera a evolução do cíclo económico, mas em periodos de expansão a respectiva tendência de descida segue o crescimento económico

Using the Asymmetric Trimmed Mean as a Core Inflation Indicator

This paper discusses the use of the trimmed mean as a core inflation indicator when the price changes distribution is fat tailed and asymmetric and computes several asymmetric trimmed means that meet all the conditions suggested in Marques et al. (2000). It turns out that the 10 per cent trimmed mean centred on the 51.5th percentile is the one with the lowest volatility and so, its use, as a core inflation indicator, is recommended.

“And [they] built a crooked h[arbour]” – the Schrems ruling and what it means for the future of data transfers between the EU and US

Safe Harbour (Henceforth, SH) has been the main enabler of EU-US personal data transfers since Decision 2000/520/EC came into force. Initially, Safe Harbour was seen as an innovative solution to a difficult problem. However, the problems the agreement was created to solve were never remedied. Thus, it did not come as a surprise that the Court of Justice of the European Union (hereinafter, CJEU), in Case C-362/14 (the Schrems ruling), deemed the agreement invalid. In the story “And he built a crooked house”, the infamous ‘crooked house’, designed by Robert A. Heinlein’s character Quintus Teal, mirrors SH’s flawed design. It also exemplifies the fact that great innovations can fail if not thought through carefully. Although the Schrems ruling’s scope does not go beyond Decision 2000/520/EC, it will force European Data Protection Agencies to look deeper into alternative data transfer mechanisms and possibly, consider transfers to jurisdictions other than the US. Furthermore, this decision highlights the fact that if any progress on this front is going to be made going forward regarding personal data transfers, any solution(s) would have to be made at a global level. This paper will provide an overview of the implications of the CJEU ruling on data transfers between the EU and the US going forward

Alignment of velocity fields for video surveillance

Velocity fields play an important role in surveillance since they describe typical motion behaviors of video objects (e.g., pedestrians) in the scene. This paper presents an algorithm for the alignment of velocity fields acquired by different cameras, at different time intervals, from different viewpoints. Velocity fields are aligned using a warping function which maps corresponding points and vectors in both fields. The warping parameters are estimated by minimizing a non-linear least squares energy. Experimental tests show that the proposed model is able to compensate significant misalignments, including translation, rotation and scaling