Technological change, accident prevention and civil liability

The improvement of accident prevention technology in many fields of social life has spurred new challenges to the doctrinal tools of fault and strict based civil liability in the law of torts. Amid these challenges lies the identification of the proper scope of the respective criteria of liability in a changing factual environment, their suitability as doctrinal tools, as well as their actual application to concrete cases given the amount of information which would be needed to render adequate judgments. Precedents and old laws should be assessed with caution, taking into account the tacit cost-benefit analysis embedded in them, for they may or may not serve the interests of welfare maximization in an environment with constantly renewed accident prevention technology

A Benchmarking of the Undergraduate Economics Major in Europe and the United States

We compare the undergraduate Economics majors and their underlying structure in the top-ranked Economics departments of Europe and the USA, identifying the fundamental courses included in an Economics major in top-ranked universities. We further distinguish between those courses that are required and those that are usually offered as electives, finding striking differences between Europe and the USA, especially regarding the nature of the main electives offered. The insights from this comparative study may be useful for the ongoing restructuring of undergraduate Economics majors in European countries caused by the Bologna Process.

Petri nets based components within globally asynchronous locally synchronous systems

Dissertação apresentada na Faculdade de Ciências e Tecnologias da Universidade Nova de Lisboa para a obtenção do grau de Mestre em Engenharia Electrotécnica e ComputadoresThe main goal is to develop a solution for the interconnection of components constituent of a GALS - Globally Asynchronous, Locally Synchronous – system. The components are implemented in parallel obtained as a result of the partition of a model expressed a Petri net (PN), performed using the PNs editor SNOOPY-IOPT in conjunction with the Split tool and the tools to automatically generate the VHDL code from the representations of the PNML models resulting from the partition (these tools were developed under the project FORDESIGN and are available at http://www.uninova.pt/FORDESIGN). Typical solutions will be analyzed to ensure proper communication between components of the GALS system, as well as characterized and developed an appropriate solution for the interconnection of the components associated with the PN sub-models. The final goal (not attained with this thesis) would be to acquire a tool that allows generation of code for the interconnection solution from the associated components, considering a specific application. The solution proposed for componentes interconnection was coded in VHDL and the implementation platforms used for testing include the Xilinx FPGA Spartan-3 and Virtex-II

Predicting rheological parameters of natural viscoplastic fluids through artificial neural networks

Debris flows are geological phenomena that can represent serious threats to life and property. They are fast mass movements of water-sediment mixtures, saturated with sediments that scale from smaller than 2 µm to up to 2 cm. Debris flow has heavy bulk densities and can travel at speeds up to 30 kph. They have high erosive capacity and can carry large items such as rocks (up to 1 m), trees, and cars. To assess the occurrence susceptibility and hazard risk of these phenomena, the evaluation of constitutive laws for the debris flow materials is required. Phenomenological models that describe these materials' behavior by fixed rheometric parameters, such as yield stress and consistency, had been attested as an effective alternative. Thus, the evaluation of these material rheological parameters plays a key role in this rheology framework. The objective of this study is to develop a predictive model using artificial neural networks to identify the mixture's rheological properties (yield stress, consistency, and flow index), based on the mixture solid concentration and the sediment grainsize distribution. 178 data points obtained from previous studies were used to build the model. Three single-hidden layer neural networks were built to predict each rheological property. The models showed that the prediction of these rheological properties based on mixture composition is feasible but needs further efforts to improve the model’s accuracy and precision.As corridas de detritos são fenômenos geológicos com grande potencial de causar prejuízos e danos a vida humana. Esses fenômenos são rápidos escoamentos de um fluido composto por uma mistura de água saturada com sedimentos, de alta densidade e que pode alcançar velocidades de mais de 30km/h. As corridas de detritos têm alto poder erosivo e são capazes de arrastar grandes objetos como árvores e carros. Para avaliar as áreas sujeitas a esses fenômenos e estimar seus impactos, é necessário conhecer as equações constitutivas que governam os fluidos desses fenômenos. Uma eficiente alternativa é o uso de modelos que descrevem o comportamento desses fluidos com base em parâmetros reométricos fixos, como a tensão limite de escoamento e a consistência, o que torna crítica a mensuração destes parâmetros reológicos. O objetivo deste trabalho é desenvolver um modelo utilizando o método de redes neurais para prever propriedades reológicas desses fluidos com base na sua composição sedimentar. 178 observações coletadas de estudos já publicados foram empregadas na construção e validação do modelo. Três redes neurais, uma para cada propriedade reológica, foram construídas. Os resultados mostraram que é possível usar dessa tecnologia para prever as propriedades reológicas com base na composição sedimentar. Mais estudos, porém, são necessários para melhorar a precisão e acurácia desses modelos

Static strings in Randall-Sundrum scenarios and the quark anti-quark potential

We calculate the energy of a static string in an AdS slice between two D3-branes with orbifold condition. The energy for configurations with endpoints on a brane grows linearly for large separation between these points. The derivative of the energy has a discontinuity at some critical separation. Choosing a particular position for one of the branes we find configurations with smooth energy. In the limit where the other brane goes to infinity the energy has a Coulombian behaviour for short separations and can be identified with the Cornell potential for a quark anti-quark pair. This identification leads to effective values for the AdS radius, the string tension and the position of the infrared brane. These results suggest an approximate duality between static strings in an AdS slice and a heavy quark anti-quark configuration in a confining gauge theory.Comment: More clarifications added, typos corrected. Results unchange

Optimization model for banking asset liability management

This study introduces an optimization model to assist Asset and Liability Management (ALM) departments in mitigating interest rate risk (IRR) within fixed-income portfolios. The model incorporates real-world constraints, including the cost of administering interest rate derivatives and liquidity constraints, aiming to formulate effective hedge strategies across diverse scenarios. In particular, liquidity constraints gain significance, as market limitations can hinder the execution of derivatives hedging strategies, a concern particularly relevant in emerging markets with lower trading volumes. The study provides a comprehensive backtesting of the model under various portfolio lengths, nominal values, and shapes, revealing key insights. The analysis underscores the critical role of $duration and$convexity constraints in determining hedge strategy effectiveness. Liquidity constraints emerge as a pivotal factor influencing the allocation of future contracts and strategy feasibility. The study contributes a nuanced understanding of interest rate risk management, offering practitioners a valuable decision-making framework considering real-world constraints.Este estudo apresenta um modelo de otimização projetado para auxiliar os departamentos de Gestão de Ativos e Passivos (ALM) na mitigação do risco de taxa de juros (IRR) em carteiras de renda fixa. O modelo incorpora restrições práticas, incluindo o custo de administracao de derivativos de taxa de juros e restricoes de liquidez, com o objetivo de formular estrategias eficazes de protecao em diversos cenarios. Em particular, as restricoes de liquidez ganham importancia, uma vez que limitações de mercado podem dificultar a execucao de estrategias de protecao com derivativos, uma preocupacao especialmente relevante em mercados emergentes com volumes de negociacao mais baixos. O custo de negociação, nesse contexto, engloba as despesas associadas a negociacao e monitoramento de multiplos instrumentos derivativos. Notavelmente, nossa abordagem minimiza o numero de contratos futuros necessarios para a protecao contra o risco de taxa de juros. O estudo oferece uma análise abrangente do modelo em diversos comprimentos de carteira, valores nominais e formatos, revelando insights importantes. A analise destaca o papel das restrições de $duration e$convexity na determinação da eficácia da estrategia de proteção. Restrições de liquidez surgem como um fator fundamental que influencia a alocação de contratos futuros e a viabilidade da estratégia. O estudo contribui para uma compreensão detalhada da gestão de risco de taxa de juros, oferecendo aos profissionais um valioso framework de tomada de decisão considerando restrições práticas como liquidez e custo de administração das estratégias

Many-body effects on the ρxx\rho_{xx} ringlike structures in two-subband wells

The longitudinal resistivity $\rho_{xx}$ of two-dimensional electron gases formed in wells with two subbands displays ringlike structures when plotted in a density--magnetic-field diagram, due to the crossings of spin-split Landau levels (LLs) from distinct subbands. Using spin density functional theory and linear response, we investigate the shape and spin polarization of these structures as a function of temperature and magnetic-field tilt angle. We find that (i) some of the rings "break" at sufficiently low temperatures due to a quantum Hall ferromagnetic phase transition, thus exhibiting a high degree of spin polarization ($\sim 50$%) within, consistent with the NMR data of Zhang \textit{et al.} [Phys. Rev. Lett. {\bf 98}, 246802 (2007)], and (ii) for increasing tilting angles the interplay between the anticrossings due to inter-LL couplings and the exchange-correlation (XC) effects leads to a collapse of the rings at some critical angle $\theta_c$, in agreement with the data of Guo \textit{et al.} [Phys. Rev. B {\bf 78}, 233305 (2008)].Comment: 4 pages, 3 figure