5,610 research outputs found
Analysis domain model for shared virtual environments
The field of shared virtual environments, which also
encompasses online games and social 3D environments, has a
system landscape consisting of multiple solutions that share great functional overlap. However, there is little system interoperability between the different solutions. A shared virtual environment has an associated problem domain that is highly complex raising difficult challenges to the development process, starting with the architectural design of the underlying system. This paper has two main contributions. The first contribution is a broad domain analysis of shared virtual environments, which enables developers to have a better understanding of the whole rather than the part(s). The second contribution is a reference domain model for discussing and describing solutions - the Analysis Domain Model
Um novo mĂ©todo de dimensionamento de reforços de pavimentos flexĂveis considerando a reflexĂŁo de fendas
No presente trabalho Ă© proposto um mĂ©todo de dimensionamento de reforços de pavimentos flexĂveis, considerando como critĂ©rios de ruĂna o aparecimento de fendas Ă superfĂcie da camada de desgaste, resultantes da reflexĂŁo 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
Matching slowly rotating spacetimes split by dynamic thin shells
We investigate within the Darmois-Israel thin shell formalism the match of
neutral and asymptotically flat, slowly rotating spacetimes (up to the second
order in the rotation parameter) when their boundaries are dynamic. It has
several important applications in general relativistic systems, such as black
holes and neutron stars, which we exemplify. We mostly focus on stability
aspects of slowly rotating thin shells in equilibrium and surface degrees of
freedom on the hypersurfaces splitting the matched slowly rotating spacetimes,
e.g., surface energy density and surface tension. We show that the stability
upon perturbations in the spherically symmetric case automatically implies
stability in the slow rotation case. In addition, we show that when matching
slowly rotating Kerr spacetimes through thin shells in equilibrium, surface
degrees of freedom can decrease compared to their Schwarzschild counterparts,
meaning that energy conditions could be weakened. Frame-dragging aspects of the
match of slowly rotating spacetimes are also briefly discussed.Comment: 10 pages, 4 figures. Accepted for publication in Universe (Feature
Papers 2023-Gravitation
Muscle-specific function of the centronuclear myopathy and Charcot-Marie-Tooth neuropathy-associated dynamin 2 is required for proper lipid metabolism, mitochondria, muscle fibers, neuromuscular junctions and peripheral nerves
The ubiquitously expressed large GTPase Dynamin 2 (DNM2) plays a critical role in the regulation of intracellular membrane trafficking through its crucial function in membrane fission, particularly in endocytosis. Autosomal-dominant mutations in DNM2 cause tissue-specific human disorders. Different sets of DNM2 mutations are linked to dominant intermediate Charcot-Marie-Tooth neuropathy type B, a motor and sensory neuropathy affecting primarily peripheral nerves, or autosomal-dominant centronuclear myopathy (CNM) presenting with primary damage in skeletal muscles. To understand the underlying disease mechanisms, it is imperative to determine to which degree the primary affected cell types require DNM2. Thus, we used cell type-specific gene ablation to examine the consequences of DNM2 loss in skeletal muscle cells, the major relevant cell type involved in CNM. We found that DNM2 function in skeletal muscle is required for proper mouse development. Skeletal muscle-specific loss of DNM2 causes a reduction in muscle mass and in the numbers of muscle fibers, altered muscle fiber size distributions, irregular neuromuscular junctions (NMJs) and isolated degenerating intramuscular peripheral nerve fibers. Intriguingly, a lack of muscle-expressed DNM2 triggers an increase of lipid droplets (LDs) and mitochondrial defects. We conclude that loss of DNM2 function in skeletal muscles initiates a chain of harmful parallel and serial events, involving dysregulation of LDs and mitochondrial defects within altered muscle fibers, defective NMJs and peripheral nerve degeneration. These findings provide the essential basis for further studies on DNM2 function and malfunction in skeletal muscles in health and disease, potentially including metabolic diseases such as diabete
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 polĂmeros (SBS).
O betume com polĂmeros foi utilizado num betĂŁo 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
caracterĂsticas 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 Ă mistura SBS aplicada com 5 cm de espessura
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
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