735 research outputs found

    A process very similar to multifractional Brownian motion

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    In Ayache and Taqqu (2005), the multifractional Brownian (mBm) motion is obtained by replacing the constant parameter HH of the fractional Brownian motion (fBm) by a smooth enough functional parameter H(.)H(.) depending on the time tt. Here, we consider the process ZZ obtained by replacing in the wavelet expansion of the fBm the index HH by a function H(.)H(.) depending on the dyadic point k/2jk/2^j. This process was introduced in Benassi et al (2000) to model fBm with piece-wise constant Hurst index and continuous paths. In this work, we investigate the case where the functional parameter satisfies an uniform H\"older condition of order \beta>\sup_{t\in \rit} H(t) and ones shows that, in this case, the process ZZ is very similar to the mBm in the following senses: i) the difference between ZZ and a mBm satisfies an uniform H\"older condition of order d>suptRH(t)d>\sup_{t\in \R} H(t); ii) as a by product, one deduces that at each point tRt\in \R the pointwise H\"older exponent of ZZ is H(t)H(t) and that ZZ is tangent to a fBm with Hurst parameter H(t)H(t).Comment: 18 page

    Validation of a multi-scale simulation strategy based on the Pointwise Strain Superposition Method

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    This paper details the experimental validation of a multi-scale simulation strategy that we developed for predicting the stresses and distortions induced by Powder Bed Fusion processes. The strategy comprises a meso-scale model, a macro-scale model, and a scaling method named Pointwise Strain Superposition. The first model evaluates the temperature, stress, and strain fields produced by a single scan line. The scaling method transfers the meso-scale results to the macro-scale model, which is then able to simulate the entire manufacturing process with a reasonable computational cost. The simulation strategy was validated by comparing its results with the stresses and distortions measured on several specimens made of selective laser melted Inconel 718. Stresses were measured through the blind hole drilling method on a cylindrical specimen printed with two different scanning strategies, while distortions were measured on a hollow cylinder and on a cantilever-shaped specimen after removing its supports. In both cases, the simulation showed first- or higher-order accuracy despite the significant uncertainties regarding the input parameters and material properties. This robustness, coupled with its computational efficiency, leads us to believe that our simulation strategy could enhance the process optimization and provide a better understanding of the underlying physical phenomena along with their effects on the manufactured parts

    Microwave Devices for Wearable Sensors and IoT

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    The Internet of Things (IoT) paradigm is currently highly demanded in multiple scenarios and in particular plays an important role in solving medical-related challenges. RF and microwave technologies, coupled with wireless energy transfer, are interesting candidates because of their inherent contactless spectrometric capabilities and for the wireless transmission of sensing data. This article reviews some recent achievements in the field of wearable sensors, highlighting the benefits that these solutions introduce in operative contexts, such as indoor localization and microwave sensing. Wireless power transfer is an essential requirement to be fulfilled to allow these sensors to be not only wearable but also compact and lightweight while avoiding bulky batteries. Flexible materials and 3D printing polymers, as well as daily garments, are widely exploited within the presented solutions, allowing comfort and wearability without renouncing the robustness and reliability of the built-in wearable sensor

    Modificações ambientais causadas pela implantação de Sistemas Agroflorestais em Áreas de Preservação Permanente: marco zero.

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    Sistemas agroflorestais (SAF) são alternativa para recuperação de Áreas de Preservação Permanente, mantendo-se a área produtiva do ponto de vista ecológico e agrícola. Está sendo feito um estudo, sob princípios da pesquisa-ação participativa, para acompanhamento e avaliação da evolução de SAF sucessionais na APA da Serra da Esperança e caracterização do efeito dos mesmos sobre o ecossistema, bem como sua inserção nos sistemas de produção locais. O objetivo deste trabalho é caracterizar as parcelas anteriormente à implantação dos SAF. Em cada parcela de estudo, em três propriedades de agricultores familiares de Inácio Martins/PR, Brasil, fez-se análises química e física do solo e levantamento florístico. Os solos apresentam baixa fertilidade natural e elevada acidez. O conteúdo de matéria orgânica é elevado e a estrutura apresenta excelentes condições. As parcelas experimentais tem semelhanças quanto à vegetação, entretanto há diferenças em função das práticas agrícolas associadas.Edição dos resumos do 7º Congresso Brasileiro de Agroecologia, 2013, Porto Alegre

    On the role of Eurasian autumn snow cover in dynamical seasonal predictions

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    Seasonal predictions leverage on predictable or persistent components of the Earth system that can modify the state of the atmosphere. The land surface provides predictability through various mechanisms, including snow cover, with particular reference to Autumn snow cover over the Eurasian continent. The snow cover alters the energy exchange between surface and atmosphere and induces a diabatic cooling that in turn can affect the atmosphere locally and remotely. Lagged relationships between snow cover in Eurasia and atmospheric modes of variability in the Northern Hemisphere have been documented but are deemed to be non-stationary and climate models typically do not reproduce observed relationships with consensus. The role of the snow in recent dynamical seasonal forecasts is therefore unclear. Here we assess the role of Autumn Eurasian snow cover in a set of five operational seasonal forecasts with large ensemble size and high resolution and with the help of targeted idealised simulations. Forecast systems reproduce realistically regional changes of the surface energy balance. Retrospective forecasts and idealised sensitivity experiments identify a coherent change of the circulation in the Northern Hemisphere. The main features of the atmospheric response are a wave-train downstream over the Pacific and North America and a signal in the Arctic. The latter does not emerge in reanalysis data but is compatible with a lagged but weak and fast feedback from the snow to the Arctic Oscillation

    Uncertainty in data integration systems: automatic generation of probabilistic relationships

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    This paper proposes a method for the automatic discovery of probabilistic relationships in the environment of data integration systems. Dynamic data integration systems extend the architecture of current data integration systems by modeling uncertainty at their core. Our method is based on probabilistic word sense disambiguation (PWSD), which allows to automatically lexically annotate (i.e. to perform annotation w.r.t. a thesaurus/lexical resource) the schemata of a given set of data sources to be integrated. From the annotated schemata and the relathionships defined in the thesaurus, we derived the probabilistic lexical relationships among schema elements. Lexical relationships are collected in the Probabilistic Common Thesaurus (PCT), as well as structural relationships

    Use of confocal microscopy imaging for in vitro assessment of adipose-derived mesenchymal stromal cells seeding on acellular dermal matrices: 3D reconstruction based on collagen autofluorescence

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    Background: Both mesenchymal stromal cells (MSCs) and acellular dermal matrices (ADMs) represent fascinating therapeutic tools in the wound healing scenario. Strategies aimed at combining these two treatment modalities are currently under investigation. Moreover, scarcity of quantitative, nondestructive techniques for quality assessment of engineered tissues poses great limitations in regenerative medicine and collagen autofluorescence-based imaging techniques are acquiring great importance in this setting. Objective: Our goals were to assess the in vitro interactions between ADSCs and ADMs and to analyze extracellular-matrix production. Methods: Adipose-derived MSCs (ADSC) were plated on 8-mm punch biopsies of a commercially available ADM (Integra\uae). Conventional histology with hematoxylin-eosin staining, environmental scanning electron microscopy, and confocal-laser scanning microscopy were used to obtain imaging of ADSC-seeded ADMs. Collagen production by ADSCs was quantified by mean fluorescence intensity (MFI), expressed in terms of positive pixels/field, obtained through ImageJ software processing of three-dimensional projections from confocal scanning images. Control conditions included: fibroblast-seeded ADM, ADSC- and fibroblast-induced scaffolds, and Integra\uae alone. Results: ADSCs were efficiently seeded on Integra\uae and were perfectly incorporated in the pores of the scaffold. Collagen production was revealed to be significantly higher when ADSCs were seeded on ADM rather than in all other control conditions. Collagen autofluorescence was efficiently used as a surrogate marker of ECM production. Conclusions: Combined therapies based on MSCs and collagenic ADMs are promising therapeutic options for chronic wounds. Not only ADSCs can be efficiently seeded on ADMs, but ADMs also seem to potentiate their regenerative properties, as highlightable from fluorescence confocal imaging

    Size quantization effects in thin film Casimir interaction

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    We investigate the role of size quantization in the vacuum force between metallic films of nanometric thickness. The force is calculated by the Lifshitz formula with the film dielectric tensor derived from the one-electron energies and wavefunctions under the assumption of a constant potential inside the film and a uniform distribution of the positive ion charge. The results show that quantization effects tend to reduce the force with respect to the continuum plasma model. The reduction is more significant at low electron densities and for film size of the order of few nanometers and persists for separation distances up to 10 nm. Comparison with previous work indicates that the softening of the boundary potential is important in determining the amount of the reduction. The calculations are extended to treat Drude intraband absorption. It is shown that the inclusion of relaxation time enhances the size quantization effects in the force calculations

    Functional Limit Theorems for Multiparameter Fractional Brownian Motion

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    We prove a general functional limit theorem for multiparameter fractional Brownian motion. The functional law of the iterated logarithm, functional L\'{e}vy's modulus of continuity and many other results are its particular cases. Applications to approximation theory are discussed.Comment: AMS-LaTeX, 23 page

    Cuban Tree Frogs in the Wild

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    This is where the abstract of this record would appear. This is only demonstration data
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