502 research outputs found
The Visual Programming Environment ROBI for Educational Robotics
No full textThis paper presents the outcomes of a research project focused on the training of Computational Thinking, resorting to a block-based visual programming language created to program an Arduino Uno based robot. To support the design and implementation of the visual programming environment Robi, we start discussing the relevance of Educational Robotics to motivate and engage children in programming activities. Students usually face great difficulties to learn computer programming and it is nowadays accepted that young people shall be trained in Computational Thinking to acquire the skills necessary to easily solve problems within and beyond the realm of Computer Science and Engineering. The resolution of obstacles imposed by the costs and reduced availability of typical Educational Robotics kits, in combination with the benefits of existing block-based programming languages, like simplicity and intuitiveness, motivated the project here reported and analyzed. We aim at showing that Robi, a visual block-based programming language and robot programming environment, provides an easy, accessible and intuitive platform to learn how to solve problems programming a computer and support the training of Computational Thinking
Programmers' Affinity to Languages
No full textStudents face several challenges when learning computer programming languages, a central topic to acquire programming skills. While those challenges that present a predominantly technical nature have been intensely studied by researchers along the years, the ones that are concerned with qualitative, and personal aspects have not. Affinity to a programming language is one of the many personal factors that may contribute to surpass these qualitative aspects that describe the difficulties that students face. From this point-of-view, this paper presents a proposal for treating and studying programmers' affinity to programming languages as an important factor for learning computer programming. It also reports a preliminary questionnaire conducted on a master’s degree class at Universidade do Minho that showed that affinity may have a broader relation to learning computer programming than anticipated. Finally, a set of relevant questions are stated to compose a future inquiry aimed at deepening the knowledge on the affinity between programmers and languages, paving the way for following research
Representing Roomates' Preferences with Symmetric Utilities
No full textIn the context of the stable roommates problem, it is shown that acyclicity of preferences is equivalent to the existence of symmetric utility functions, i.e. the utility of agent i when matched with j is the same as j 's utility when matched with i .
Monetary Policy Surprises and the Brazilian Term Structure of Interest Rates
No full textThis paper examines the information content of COPOM decisions to change or to leave unchanged monetary policy by estimating the responses of the term structure to changes in the target for interest rates on COPOM meeting days. Within an event-study approach the evidence suggests that market participants anticipate, at least partially, monetary policy actions. Furthermore, it is found that the introduction of the floating exchange and inflation-targeting regime has had a dampening effect on interest rate surprises along the term structure.
Optimal Monetary Rules: The Case of Brazil
No full textWithin a dynamic programming approach we derive an optimal rule for the central bank to attain it's inflation targeting goals. The short-run nominal interest rate is used as an instrument to achieve monetary objectives. The model is tested for the Brazilian economy and compared with results found for other countries. Evidence for the estimated feedback interest rule for the Central Bank suggests that the cost of reducing inflation in an open economy is lower than that of a closed economy.
Judicial Risk and Credit Market Performance: Micro Evidence from Brazil Payroll Loans
No full textA large body of literature has stressed the institution-development nexus as critical in explaining differences in countries' economic performance. The empirical evidence, however, has been mainly at the aggregate level, associating macro performance with measures of quality of institutions. This paper, by relating a judicial decision on the legality of payroll debit loans in Brazil to bank-level decision variables, provides micro evidence on how creditor legal protection affects market performance. Payroll loans are personal loans with principal and interests payments directly deducted from the borrowers' payroll check, which, in practice, makes a collateral out of future income. In June 2004, a high-level federal court upheld a regional court ruling that had declared payroll deduction illegal. Using personal loans without payroll deduction as a control group, we assess whether the ruling had an impact on market performance. Evidence indicates that it had an adverse impact on risk perception, interest rates, and amount lent.
Improvement methodology of vehicle suspensions through model in virtual environment multibody
No full textEntre as etapas do desenvolvimento de automóveis pode-se apontar a definição das características de suas suspensões. A fase de definição da suspensão pode ser dividida dentro do seguinte cenário: a escolha de um determinado tipo de suspensão, os pontos (geometria) e quais os valores de rigidez/amortecimento para todo o sistema irá resultar em um comportamento dinâmico desejado para o veículo, bem como a viabilidade de produção. Além disso, o entendimento da interação entre os parâmetros de suspensão, é crucial para a otimização do desempenho. Este trabalho pretende propor um método para aperfeiçoar a fase de \"tuning\" da suspensão, com foco principal no conforto. O veículo considerado é um caminhão comercial, e entre os seus parâmetros considerados estão rigidezes de molas da cabine e suspensão, amortecimento da suspensão de cabine e curvas do amortecedor da suspensão primária. O modelo virtual do veículo foi desenvolvido em ambiente ADAMS, o qual, previamente à otimização, foi validado contra dados experimentais. Métricas foram especialmente desenvolvidas levando em consideração aspectos subjetivos de conforto veicular, para dessa forma eliminar a variabilidade entre as avaliações subjetivas e análises das simulações. Os resultados mostraram expressivas melhorias no conforto e através de dados experimentais essas melhorias foram confirmadas.Among the development phases of an automotive vehicle one can point out the definition of the characteristics of its suspensions. Suspension definition phase can be understood as the following scenario: given a suspension type, which hard points (geometric) and what values of stiffness/damping for the whole system will result in a desired dynamic behavior for the vehicle as well as production feasibility. Moreover, understanding the iteration among the suspension parameters, even considering just the tuning ones, is crucial for performance optimization. This work intends to propose a method for vehicle tuning characteristics optimization, having as a target the ride comfort. The vehicle considered here is a commercial truck, and among its parameters one considers cabin and suspension springs, cabin dampers and suspension damper curves. A vehicle model was developed in ADAMS environment and prior to the optimization the vehicle was validated against experimental data. Metrics were specially developed to take into account subjective aspects of ride, and, in this way, eliminating the gap between subjective evaluations and simulations analysis. Results showed improvements in ride comfort. The resulting setup was measured and the improvements were confirmed with experimental data
Out-Of-The_Money Monte Carlo Simulation Option Pricing: the join use of Importance Sampling and Descriptive Sampling
No full textAs in any Monte Carlo application, simulation option valuation produces imprecise estimates. In such an application, Descriptive Sampling (DS) has proven to be a powerful Variance Reduction Technique. However, this performance deteriorates as the probability of exercising an option decreases. In the case of out of the money options, the solution is to use Importance Sampling (IS). Following this track, the joint use of IS and DS is deserving of attention. Here, we evaluate and compare the benefits of using standard IS method with the joint use of IS and DS. We also investigate the influence of the problem dimensionality in the variance reduction achieved. Although the combination IS+DS showed gains over the standard IS implementation, the benefits in the case of out-of-the-money options were mainly due to the IS effect. On the other hand, the problem dimensionality did not affect the gains. Possible reasons for such results are discussed.
Interdependence and Contagion: an Analysis of Information Transmission in Latin America's Stock Markets
No full textThis paper brings evidences about the hypotheses of financial crisis contagion over Latin American stock markets in the 90's using a multivariate GARCH model. Beside the traditional volatility structure, we added a leverage term like GJR framework in order to avoid problems due to the use of conditional correlation as a measure of relationship between stock markets. The results show the existence of contagion only during the Asian (1997) and the Russian (1998) crises. The consequences of the Brazilian crisis (1999) can be identified as a result of interdependence among Latin American markets, while the crises of Mexico (1994) and Argentina (2001) show a specific mechanism of propagation. This result raises questions about the "contagion" and "interdependence" concepts' adequacy for the analysis of information transmission among stock markets.
Improvement methodology of vehicle suspensions through model in virtual environment multibody
No full textEntre as etapas do desenvolvimento de automóveis pode-se apontar a definição das características de suas suspensões. A fase de definição da suspensão pode ser dividida dentro do seguinte cenário: a escolha de um determinado tipo de suspensão, os pontos (geometria) e quais os valores de rigidez/amortecimento para todo o sistema irá resultar em um comportamento dinâmico desejado para o veículo, bem como a viabilidade de produção. Além disso, o entendimento da interação entre os parâmetros de suspensão, é crucial para a otimização do desempenho. Este trabalho pretende propor um método para aperfeiçoar a fase de \"tuning\" da suspensão, com foco principal no conforto. O veículo considerado é um caminhão comercial, e entre os seus parâmetros considerados estão rigidezes de molas da cabine e suspensão, amortecimento da suspensão de cabine e curvas do amortecedor da suspensão primária. O modelo virtual do veículo foi desenvolvido em ambiente ADAMS, o qual, previamente à otimização, foi validado contra dados experimentais. Métricas foram especialmente desenvolvidas levando em consideração aspectos subjetivos de conforto veicular, para dessa forma eliminar a variabilidade entre as avaliações subjetivas e análises das simulações. Os resultados mostraram expressivas melhorias no conforto e através de dados experimentais essas melhorias foram confirmadas.Among the development phases of an automotive vehicle one can point out the definition of the characteristics of its suspensions. Suspension definition phase can be understood as the following scenario: given a suspension type, which hard points (geometric) and what values of stiffness/damping for the whole system will result in a desired dynamic behavior for the vehicle as well as production feasibility. Moreover, understanding the iteration among the suspension parameters, even considering just the tuning ones, is crucial for performance optimization. This work intends to propose a method for vehicle tuning characteristics optimization, having as a target the ride comfort. The vehicle considered here is a commercial truck, and among its parameters one considers cabin and suspension springs, cabin dampers and suspension damper curves. A vehicle model was developed in ADAMS environment and prior to the optimization the vehicle was validated against experimental data. Metrics were specially developed to take into account subjective aspects of ride, and, in this way, eliminating the gap between subjective evaluations and simulations analysis. Results showed improvements in ride comfort. The resulting setup was measured and the improvements were confirmed with experimental data
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