Chaotic Planar Piecewise Smooth Vector Fields With Non Trivial Minimal Sets

In this paper some aspects on chaotic behavior and minimality in planar piecewise smooth vector fields theory are treated. The occurrence of non-deterministic chaos is observed and the concept of orientable minimality is introduced. It is also investigated some relations between minimality and orientable minimality and observed the existence of new kinds of non-trivial minimal sets in chaotic systems. The approach is geometrical and involve the ordinary techniques of non-smooth systems.Comment: arXiv admin note: text overlap with arXiv:1307.682

Asset-liability management in pension funds

Mestrado em Mathematical FinanceOs fundos de pensão têm uma participação representativa nos mercados financeiros, seja considerando o capital investido ou o perfil de escolha de ativos. Nos planos de pensão de benefício definido, o foco é assegurar cobrir os passivos com os ativos existentes. A gestão de ativos e passivos (em inglês ALM) é o conjunto de métodos e ferramentas projetadas com a finalidade de orientar como os fundos devem investir seus ativos a fim de que, em determinada data, seja possível pagar seus passivos. Este conceito é amplamente utilizado em empresas seguradoras e fundos de pensão. O portfolio de investimentos é construído de acordo com análises de mercado, definição dos riscos em que o fundo deseja se expor e os objetivos de retorno. O propósito deste projeto é, aplicando a teoria de investimentos orientados a passivos, recuperar o nível de financiamento de um fundo de pensões, a fim de cumprir com as metas do esquema e se expondo ao menor risco possível. Este projeto terá como informação base a estimativa dos passivos, da taxa de juros e da inflação. A partir deles, contruiremos o portfolio de investimentos, projetaremos o fluxo de caixa e monitoraremos o risco de não cumprimento dos objetivos. Para validar a consistência do modelo, iremos comparar contra uma estratégia mais arriscada. As conclusões, após contextualização (prática e teórica), demonstram que é possível recuperar o nível de financiamento, de acordo com prazos estabelecidos e com um nível moderado de risco.Pension funds have a very representative role in the financial markets, considering investments made and the asset allocations profile. In defined benefit pension schemes, the major focus is to secure the participants future payments with the accumulated contributions. Or, in other words, to cover the liabilities with the assets. Asset Liability Management (ALM) is a collection of methodologies and tools structured to guide the assets investments in order to protect the liabilities. This concept has been used largely in insurance companies and pension funds. It analyzes market expectations, scheme risks and objectives, in order to create the best asset investment option. The purpose of this project is, using a Liability Driven Investment (LDI) technique, recover the Funding Ratio of a pension fund, achieve the scheme goals and minimize the risk. Project liabilities, interest rate and inflation are the bases of this work. Build the asset portfolio, project the fund cashflow and track the risk are the principal steps to achieve the goal. To check the results adherence, the output will be compared with a bold recovery strategy. To conclude, after setting the context (theoretical and practical perspectives), the work will show how to recover a Funding Ratio using a developed model and keeping the risk inside pension plan limits.info:eu-repo/semantics/publishedVersio

The computational role of short-term plasticity and the balance of excitation and inhibition in neural microcircuits: experimental and theoretical analysis

The computations performed by the brain ultimately rely on the functional connectivity between neurons embedded in complex networks. It is well known that the neuronal connections, the synapses, are plastic, i.e. the contribution of each presynaptic neuron to the firing of a postsynaptic neuron can be independently adjusted. The modulation of effective synaptic strength can occur on time scales that range from tens or hundreds of milliseconds, to tens of minutes or hours, to days, and may involve pre- and/or post-synaptic modifications. The collection of these mechanisms is generally believed to underlie learning and memory and, hence, it is fundamental to understand their consequences in the behavior of neurons.(...

Field-effect transistors based on Zinc oxide nanoparticles

This work reports the development of field-effect transistors (FETs), whose channel is based on zinc oxide (ZnO) nanoparticles (NPs). Using screen-printing as the primary deposition technique, different inks were developed, where the semiconducting ink is based on a ZnO NPs dispersion in ethyl cellulose (EC). These inks were used to print electrolyte-gated transistors (EGTs) in a staggered-top gate structure on glass substrates, using a lithium-based polymeric electrolyte. In another approach, FETs with a staggered-bottom gate structure on paper were developed using a sol-gel method to functionalize the paper’s surface with ZnO NPs, using zinc acetate dihydrate (ZnC4H6O4·2H2O) and sodium hydroxide (NaOH) as precursors. In this case, the paper itself was used as dielectric. The various layers of the two devices were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier Transform Infrared spectroscopy (FTIR), thermogravimetric and differential scanning calorimetric analyses (TG-DSC). Electrochemical impedance spectroscopy (EIS) was used in order to evaluate the electric double-layer (EDL) formation, in the case of the EGTs. The ZnO NPs EGTs present electrical modulation for annealing temperatures equal or superior to 300 ºC and in terms of electrical properties they showed On/Off ratios in the order of 103, saturation mobilities (μSat) of 1.49x10-1 cm2(Vs)-1 and transconductance (gm) of 10-5 S. On the other hand, the ZnO NPs FETs on paper exhibited On/Off ratios in the order of 102, μSat of 4.83x10- 3 cm2(Vs)-1and gm around 10-8 S