6.1 Proyectos de investigación científica
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PublicaciónTotal attenuation compensation for backscatter coefficient estimation using full angular spatial compounding(Elsevier B.V., 2021)The backscatter coefficient (BSC) quantifies the frequency-dependent reflectivity of tissues. Accurate estimation of the BSC is only possible with the knowledge of the attenuation coefficient slope (ACS) of the tissues under examination. In this study, the use of attenuation maps constructed using full angular spatial compounding (FASC) is proposed for attenuation compensation when imaging integrated BSCs. Experimental validation of the proposed approach was obtained using two cylindrical physical phantoms with off-centered inclusions having different ACS and BSC values than the background, and in a phantom containing an ex vivo chicken breast sample embedded in an agar matrix. With the phantom data, three different ACS maps were employed for attenuation compensation: (1) a ground truth ACS map constructed using insertion loss techniques, (2) the estimated ACS map using FASC attenuation imaging, and (3) a uniform ACS map with a value of 0.5 dBcm\protect \relax \special {t4ht=?}1MHz\protect \relax \special {t4ht=?}1, which is commonly used to represent attenuation in soft tissues. Comparable results were obtained when using the ground truth and FASC-estimated ACS maps in term of inclusion detectability and estimation accuracy, with averaged fractional error below 2.8 dB in both phantoms. Conversely, the use of the homogeneous ACS map resulted in higher levels of fractional error (>10 dB), which demonstrates the importance of an accurate attenuation compensation. The results with the ex vivo tissue sample were consistent with the observations using the physical phantoms, with the FASC-derived ACS map providing comparable BSC images to those formed using the ground truth ACS map and more accurate than those BSC images formed using a uniform ACS. These results suggest that BSCs can be reliably estimated using FASC when a self-consistent attenuation compensation stemming from prior estimation of an accurate ACS map is used. © 2021 Elsevier B.V.
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PublicaciónAn Evaluation of Physiological Public Datasets for Emotion Recognition Systems(Springer Science and Business Media Deutschland GmbH, 2021)[Background] The performance of emotion recognition systems depends heavily on datasets used in their training, validation, or testing stages. [Aims] This research aims to evaluate the extent to which public available physiological datasets created for emotion recognition systems meet a set of reference requirements. [Method] Firstly, we analyze the applicability of some reference requirements proposed for stress datasets and adjust the corresponding evaluation criteria. Secondly, nine public physiological datasets were identified from a previous survey. [Results] None of the evaluated datasets satisfy all the reference requirements in order to be considered as a reference dataset for being used in the construction of reliable emotion recognition systems. [Conclusion] Although the evaluated datasets do not support the whole reference requirements, they provide a baseline for further development. Also, a greater effort is needed to establish specific reference requirements that can appropriately guide the creation of physiological datasets for emotion recognition systems. © 2021, Springer Nature Switzerland AG.
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PublicaciónResistencia a la roya amarilla (Hemileia vastatrix Berk & Broome) en el café (Coffea spp) a través de estudios moleculares(Universidad Nacional Agraria la Molina, 2019)Las técnicas moleculares vienen siendo muy utilizadas en programas de mejoramiento genético del café para la identificación de fuentes de resistencia a la roya amarilla, sin embargo, debe ser considerado el estudio de la estructura y evolución de las poblaciones del hongo, con la finalidad de determinar el tipo de estrategia de mejoramiento genético que debe utilizarse para la generación de nuevas variedades de cafetos resistentes a esta enfermedad.
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PublicaciónProjection of upwelling-favorable winds in the Peruvian upwelling system under the RCP8.5 scenario using a high-resolution regional model(Springer Science and Business Media Deutschland GmbH, 2021)The Peruvian upwelling system (PUS) is the most productive Eastern Boundary Upwelling System (EBUS) of the world ocean. Contrarily to higher latitude EBUSs, there is no consensus yet on the response of upwelling-favorable winds to regional climate change in this region. Global climate models are not able to reproduce the nearshore surface winds, and only a few downscaling studies have been performed by using relatively coarse-grid atmospheric models forced by idealized climate change scenarios. In the present study, the impact of climate change on the PUS upwelling-favorable winds was assessed using a high resolution regional atmospheric model to dynamically downscale the multi-model mean projection of an ensemble of 31 CMIP5 global models under the RCP8.5 worst-case climate scenario. We performed a 10-year retrospective simulation (1994–2003) forced by NCEP2 reanalysis data and a 10-year climate change simulation forced by a climate change forcing (i.e. differences between monthly-mean climatologies for 2080–2100 and 1989–2009) from CMIP5 ensemble added to NCEP2 data. We found that changes in the mean upwelling-favorable winds are weak (less than 0.2 m s?1). Seasonally, summer winds weakly decrease (by 0–5%) whereas winter winds weakly increase (by 0–10%), thus slightly reinforcing the seasonal cycle. A momentum balance shows that the wind changes are mainly driven by the alongshore pressure gradient, except in a local area north of the Paracas peninsula, downstream the main upwelling center, where wind increase in winter is driven by the shoreward advection of offshore momentum. Sensitivity experiments show that the north–south sea surface temperature gradient plays an important role in the wind response along the north and central coasts, superimposed onto the South Pacific Anticyclone large-scale forcing. A reduction (increase) of the gradient induces a wind weakening (strengthening) up to 15% (25%) off the northern coast during summer. This local mechanism is not well represented in global climate models projections, which underlines the strong need for dynamical downscaling of coastal wind in order to study the impact of climate change on the Peruvian upwelling ecosystem. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH, DE part of Springer Nature.
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PublicaciónInfluence of tara gum and xanthan gum on rheological and textural properties of starch-based gluten-free dough and bread(Springer, 2019)The aim of this research was to determine the influence of tara gum and xanthan gum on rheological and textural properties of gluten-free doughs and breads made from corn starch and potato starch. Four formulations were developed: corn starch with xanthan gum (CS-XG), corn starch with tara gum (CS-TG), potato starch with xanthan gum (PS-XG) and potato starch with tara gum (PS-TG) (XG and TG—0.5% of flour). Rheological and textural properties of doughs were evaluated, as well as specific volume, alveolar structure and texture profile of breads. The results showed that the addition of tara gum increased pasting properties of the potato starch formulation, however, in the corn starch formulations, it was not significantly different from xanthan gum addition. All formulations showed more elastic than viscous behavior (G′>G″) and these viscoelastic properties had an influence on the kinetics of dough growth during the leavening process. The formulation PS-XG presented high specific volume, low crumb hardness, and good crumb structure, while the PS-TG showed inferior properties. In contrast, in the corn starch formulations, CS-XG and CS-TG presented very similar physical characteristics. The application of tara gum in gluten-free breads is reported for the first time and depending on the starch used it showed desirable properties for obtaining good quality products.
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