117,491 research outputs found
Imigraçao e cultura
No full textRecensione del Volume Imigraçao e cultura a cura di L. Slomp Giron e R. Radunz, che raccoglie gli atti del Convegno storico internazionale svoltosi nel 2005 presso l'Università di Caxias do Sul per celebrare il 130° anniversario dell'inizio dell'emigrazione italiana nello stato di Rio Grande do Sul e della fondazione della città di Caxias do Su
Strain relaxation mechanism in a reverse compositionally graded SiGe heterostructure
No full textA concept of compositional reverse-grading (RG) in SiGe/Si heteroepitaxy has been proposed, in which the graded layer lattice mismatch starts at the highest value at the RG/Si interface and decreases to a final mismatch at the SiGe/RG interface. Using various characterization techniques, the authors show that this low-dislocation-density strain relaxation mechanism relies on the large nucleation rates of misfit dislocations at the abrupt RG/Si interface and the reduction of threading dislocations at the SiGe/RG interface by facilitating glide. The RG concept enables the growth of high-quality relaxed epitaxial layer on a thin buffer layer, suitable as a substrate for many microelectronic and optoelectronic applications
Scalable cover song identification based on melody indexing
No full textIn this work, we describe an efficient method for cover song identification focusing our target on pop and rock music genres. The procedure proposed is based on the fact that every pop/rock song has usually a main melody or a easily recognizing theme inside. Usually this theme or this melody, even if the cover song is really different from the original, is present in every version of the original song. This means that if we can identify the melody in each song we can identify also the original son
Structural characterization and surface lattice strain determination of ZnS/GaAs heterostructures grown by metalorganic vapour phase epitaxy
No full textWe report on the structural characterization of ZnS epilayers grown on (100)GaAs by metalorganic vapour-phase epitaxy (MOVPE). The crystalline quality at the ZnS epilayer surface and the defect depth distribution was studied by Rutherford Backscattering Spectrometry (RBS)-ion channeling measurements as a function of the epilayer thickness. Transmission electron microscopy (TEM) observations were performed on selected ZnS/GaAs heterostructures. Misfit dislocations (MD) were observed at the ZnS/GaAs interface. In addition, a high density of planar defects such as stacking faults (SF) and microtwins (MT) were identified into the epilayer up to 200-300 nm. The density of these defects decreases by increasing the epilayer thickness, but a quite high and constant density of microtwins still occurs in epilayers thicker than 400 nm. However, absorption measurements point out a high optical quality for all the measured ZnS epitaxial layers. Finally, surface lattice strain was determined in the ZnS/GaAs samples by ion channeling measurements. Our data indicate that the initial lattice misfit is already fully relaxed in epilayers as thick as 400 nm and only a small residual thermal strain is measured in thicker samples
Influence of different calibration methods on surface electromyography-informed musculoskeletal models with few input signals
No full textBackground: Although model personalization is critical when assessing individuals with morphological or neurological abnormalities, or even non-disabled subjects, its translation into routine clinical settings is hampered by the cumbersomeness of experimental data acquisition and lack of resources, which are linked to high costs and long processing pipelines. Quantifying the impact of neglecting subject-specific information in simulations that aim to estimate muscle forces with surface electromyography informed modeling approaches, can address their potential in relevant clinical questions. The present study investigates how different methods to fine-tune subject-specific neuromuscular parameters, reducing the number of electromyography input data, could affect the estimation of the unmeasured excitations and the musculotendon forces. Methods: Three-dimensional motion analysis was performed on 8 non-disabled adult subjects and 13 electromyographic signals captured. Four neuromusculoskeletal models were created for 8 participants: a reference model driven by a large set of sEMG signals; two models informed by four electromyographic signals but calibrated in different fashions; a model based on static optimization. Findings: The electromyography-informed models better predicted experimental excitations, including the unmeasured ones. The model based on static optimization obtained less reliable predictions of the experimental data. When comparing the different reduced models, no major differences were observed, suggesting that the less complex model may suffice for predicting muscle forces with a small set of input in clinical gait analysis tasks. Interpretation: Quantitative model performance evaluation in different conditions provides an objective indication of which method yields the most accurate prediction when a small set of electromyographic recordings is available
Selective ion-channeling study of misfit dislocation grids in semiconductor heterostructures: theory and experiments
No full textPlanar dechanneling by networks of misfit dislocations was measured in a series of InxGa1-xAs/GaAs samples (001) grown by molecular-beam epitaxy. At the beginning of the strain-relaxation process the dechanneling probability exhibits different values for nominally equivalent (110) planes. At larger strain relaxation, the dechanneling probability saturates at a value around 1/2 as the beam-energy increases. In order to explain these results a new model for planar dechanneling by dislocations is proposed. This model is based on the harmonic approximation of the continuum potential but anharmonicity effects are taken into account. The perturbation to the harmonic oscillations caused by the lattice plane curvature around a dislocation is written in terms of a distortion function that depends only on the geometrical configuration of the channeling direction and of the dislocation line. This function is explicitly calculated for geometrical configurations relevant to the present samples allowing us then to solve the equation of motion. The results show that the dechanneling a probability saturates at a level sensibly lower than 100% due to the quasiplanar distribution of dislocations. Without any adjustable parameter, the comparison between computed and measured dechanneling probabilities supplies dislocation density values in excellent agreement with those measured by transmission electron microscopy and in good agreement with results deduced from previous strain-relaxation data
Strain induced effects on the transport properties of metamorphic InAlAs/InGaAs quantum wells
No full textThe relationship between structural and low-temperature transport properties is explored for InxAl1-xAs/InxGa1-xAs metamorphic quantum wells with x > 0.7 grown on GaAs by molecular beam epitaxy. Different step-graded buffer layers are used to gradually adapt the in-plane lattice parameter from the GaAs towards the InGaAs value. We show that using buffer layers with a suitable maximum In content the residual compressive strain in the quantum well region can be strongly reduced. Samples with virtually no residual strain in the quantum well region show a low-temperature electron mobility up to 29 m(2)/V s while for samples with higher residual compressive strain the low-temperature mobility is reduced. Furthermore, for samples with buffers inducing a tensile strain in the quantum well region, deep grooves are observed on the surface, and in correspondence we notice a strong deterioration of the low-temperature transport properties. (c) 2005 Elsevier B.V. All rights reserved
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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