Measurement of glass transition in native wheat flour by dynamic mechanical thermal analysis (DMTA)

This work describes a method to study glass transition on native starch powders, based on dynamical mechanical thermal analysis using compression tests, and was applied to wheat flour (13.5% water content). This method will allow the determination of Tg in native (unprocessed) starchy materials, with minimal disturbance of the natural structures. The influence of the test conditions (heating rate, frequency and strain) on the glass transition measurements was determined using factorial designs. The values of Tg determined as the maxima of the energy dissipation (peaks in E ) of native flour and of freezedried pre-gelatinized flour were not statistically different (around 64 C). The heating rate did not affect the measurements in the range tested (0.25 to 1 C min 1). An interactive effect of the strain amplitude and the frequency was detected. The significance of this interaction can be caused by differences in mechanical energy dissipation, which would indicate that not only temperature but also the total energy input may affect this transition. Slight effects of phase separation between gluten and starch were found on native flour

Exchange market pressure and the credibility of Macau's currency Board

In this study, we assess the credibility of the currency board arrangement (CBA) of the Macau Special Administrative Region by studying the relationship between exchange market pressure (EMP) and the anchors of a rule-based CBA, namely, interest rate arbitrage, exchange rate arbitrage and economic discipline. A pure CBA signals its credibility by allowing the first two anchors to function automatically and by pursuing sound fiscal policies. The analysis’ results suggest that Macau’s CBA has been characterised by a state of low volatility since late 1992, with the brief exception of the East Asian financial crisis period. The paper’s main finding is that fiscal fundamentals seem to have a more pronounced role in reducing EMP’s variability during periods of low volatility whilst interest rate arbitrage is more important in periods of high volatility. We conclude that Macau’s CBA is credible at present as reflected in the low frequency of observed EMP, in the narrowing of Macau’s interest rate differential vis-à-vis U.S. interest rates and in Macau’s substantial fiscal reserves.

Um novo método de dimensionamento de reforços de pavimentos flexíveis considerando a reflexão de fendas

No presente trabalho é proposto um método de dimensionamento de reforços de pavimentos flexíveis, considerando como critérios de ruína o aparecimento de fendas à superfície da camada de desgaste, resultantes da reflexão do fendilhamento existente nas camadas betuminosas do pavimento existente, bem como o fendilhamento por fadiga. O método proposto baseia-se no dimensionamento estrutural corrente, acrescido duma verificação do critério de reflexão de fendas, tendo como base resultados laboratoriais de avaliação da reflexão de fendas em misturas betuminosas, realizados em deslocamento controlado e associados ao conceito de actividade das fendas após reforço

The improvement of pavement performance using asphalt rubber hot mixes

The need of a better pavement performance has led researchers to develop new road materials, mainly for the asphalt layers, where the modification of the asphalt is the main example. This modification usually forces the use of polymers and fibers and, more recently, the use of crumb rubber from ground tires, where the modified asphalt is known as asphalt rubber. This asphalt rubber used in asphalt mixtures produces a superior performance if compared to the asphalt mixtures with conventional asphalt. The crumb rubber modification of the asphalts also presents a higher resistance to climatic effects, compared to the other binders. Based on these assumptions, this paper presents the results of the evaluation of mechanical properties, related to the pavement performance, of asphalt rubber mixtures when compared to conventional mixtures. Two types of aggregate were used (pebble and diorites) and two binders utilized (asphalt rubber and conventional asphalt). The aging effect due to the asphalt mixture production and compaction was taken into account. The materials performance was evaluated through stiffness, fatigue and permanent deformation tests. Reflective cracking performance was also predicted using a mechanistic-empirical method

Reabilitação de pavimentos utilizando misturas betuminosas com betumes modificados

Na reabilitação estrutural do pavimento do lanço CRIL-Loures da A8, a Auto-Estradas do Atlântico utilizou duas soluções distintas de reforço recorrendo a misturas betuminosas com betumes modificados. No sentido Norte-Sul foi utilizada uma mistura betuminosa com betume modificado com borracha reciclada de pneus usados (BMB) e no sentido Sul-Norte foi utilizada uma mistura betuminosa com um betume modificado com polímeros (SBS). O betume com polímeros foi utilizado num betão betuminoso aplicado com 5 cm de espessura e o betume modificado com borracha foi utilizado numa mistura betuminosa aberta aplicada com uma espessura de 2 cm. Após quatro anos em serviço foi realizado um estudo para determinar as características mecânicas das misturas betuminosas aplicadas de modo a avaliar a sua qualidade e obter indicações relativamente ao seu desempenho futuro. Para a realização deste trabalho foram retiradas lajes dos trechos experimentais que permitiram a avaliação laboratorial do módulo de deformabilidade, da resistência à fadiga e da resistência à deformação permanente. Este trabalho permitiu concluir que, em termos de comportamento mecânico, a mistura BMB, com apenas 2 cm de espessura apresenta uma resistência à fadiga e à deformação permanente superior à mistura SBS aplicada com 5 cm de espessura

O tipo de modelação dos pneus dos veículos pesados na avaliação do desempenho dos pavimentos

Os veículos pesados são os principais responsáveis pela degradação dos pavimentos rodoviários provocando principalmente fendilhamento por fadiga e deformações permanentes. Os pavimentos rodoviários são dimensionados para suportar o tráfego de projecto, o qual é composto por diferentes tipos de veículos com diferentes tipos de eixos e rodas, sendo a carga total do veículo função de vários factores. Alguns destes veículos pesados causam maiores degradações nos pavimentos devido ao tipo de suspensão, tipo de pneu, localização dos eixos ou pressão de enchimento dos pneus. No entanto, em termos de dimensionamento, esta diversidade de veículos é considerada de modo semelhante pela atribuição de uma área onde é aplicada a carga dos veículos, verificando-se que a configuração desta área não representa correctamente o contacto dos pneus com o pavimento. Deste modo, este trabalho pretende estudar a acção dos veículos pesados na avaliação do comportamento do pavimento considerando a carga dos veículos pesados modelada de forma mais aproximada da real, nomeadamente, considerando os sulcos dos pneus e a variação não uniforme da pressão de contacto pneu-pavimento. Assim, neste trabalho é modelado um pavimento representativo da rede rodoviária no qual são aplicadas diferentes configurações de carga sendo obtido o estado de tensão/deformação instalado no pavimento. A modelação numérica do pavimento foi realizada utilizando um modelo elástico linear de elementos finitos em três dimensões desenvolvido para analisar a influência de um veículo pesado possuindo uma configuração de pneus duplos com 245mm de largura. Neste estudo foram consideradas duas configurações de distribuição de pressões de contacto, em que foram considerados as seguintes pressões totais: 700, 800, 900, 1200 e 1500 kPa. Com base nos resultados obtidos é possível observar as diferenças significativas no estado de tensão/deformação do pavimento, principalmente à superfície a qual poderá ser responsável pelo fendilhamento com origem à superfície.Road pavements have been designed to support the design traffic which is composed by different type of vehicles with different axle configurations, load magnitudes, wheel types and tire inflation pressures. Traffic loads are the major source of pavement damage by causing fatigue, which leads to cracking and permanent deformation. Heavy vehicles do not cause equal damage because the differences in wheel loads, number and location of axles, types of suspensions and tires. Furthermore, the damage is specific to the pavement properties, operating conditions and environmental factors. This research proposes a model for predicting the mechanical behaviour of flexible pavement subjected to heavy load vehicle with dual-tire configuration using a numerical simulation. An elastic finite element model in three dimensions (3D) was developed to analyze the influence of a heavy vehicle with dual-tire configuration featuring 245 mm wide on each tire. This research studied three configurations of contact pressure considering the following pressures: 700, 800, 900, 1200 and 1500 kPa. The results show that it is possible to observe significant differences in the state of stress/strain on the pavement, especially on the surface which is responsible for cracking originating at the surface. The simulation model present here will be useful for future pavement design and material selection

Transversely projective foliations on surfaces: existence of normal forms and prescription of the monodromy

We introduce a notion of normal form for transversely projective structures of singular foliations on complex manifolds. Our first main result says that this normal form exists and is unique when ambient space is two-dimensional. From this result one obtains a natural way to produce invariants for transversely projective foliations on surfaces. Our second main result says that on projective surfaces one can construct singular transversely projective foliations with prescribed monodromy

Genetic diversity of two Portuguese populations of the pullet carpet shell Venerupis senegalensis, based on RAPD markers: contribution to a sustainable restocking program

The pullet carpet shell Venerupis senegalensis (=V. pullastra) is a commercially important species in Portugal, Spain, France, and Italy. In Portugal, this species was once abundant in the Ria Formosa (southern Portugal

Recycling of porous bituminous mixtures

Once flexible pavements reach minimal bearing capacity, their structural rehabilitation is normally undertaken us ing bituminous mixture overlay. The number of layers and the thickness depend of the existing quality of the pavement and of the required quality determined by the rehabilitation program for a next life period. The rehabilitation of a pavement with a porous bituminous mixture wearing course is usually undertaken without any treatment to increase its bearing capacity. The bearing capacity of this type of mixture can be increased by the use of a grout to fill its voids, increasing its resistance. The new material is produced by spreading a grout over the pavement surface, with the help of rubber scrapers, penetrating the voids of the mixture until it reaches the bottom of the layer. The properties of this material are dependent on void connectivity, in order to allow the grout to flow through them. An adequate viscosity of the grout is essential so as to fill the voids completely. The objective of this paper is to analyse the recycling of porous bituminous mixtures, studying the grout and evaluating new mixture properties in terms of stiffness, fatigue life and permanent deformation

A model for pavement temperature prediction

A finite element model has been developed to calculate the temperature of a pavement located in the Northeast of Portugal. The goal of the case study presented in this paper is the validation of this model. Input data to the model are the hourly values for solar radiation and temperature, and mean daily values of wind speed obtained from a meteorological station. The thermal response of a multilayered pavement structure is modeled using a transient thermal analysis for four months time-period (December 2003 - April 2004) and the analysis was initiated with the full depth constant initial temperature obtained from field measurements. During these four months, pavement temperature was measured at a new pavement section, located at IP4 main road, near Bragança, in the north of Portugal. At that location, seven thermocouples were installed in the AC layers, at seven different depths. These pavement data was used to validate this simulation model, by comparing model calculated data with measured pavement temperatures. As conclusion, the 3-D finite-element analysis proved to be an interesting tool to simulate the transient behavior of asphalt concrete pavements. The suggested simulation model can predict the pavement temperature at different levels of bituminous layers with a good accuracy.Instituto de Estradas de Portugal, Direcção de Bragança