Análisis del crowdfunding y sus distintas modalidades en España

Este trabajo ofrece un análisis detallado del crowdfunding en España desde 2011 a 2016. Es el primer trabajo, hasta la fecha, donde se ofrece un análisis cuantitativo y cualitativo pormenorizado para cada uno de los cuatro tipos de crowdfunding que existen: crowdfunding de donación, crowdfunding de recompensa, crowdlending y equity crowdfunding. Para cada uno de los tipos se muestran aspectos comunes: las tarifas, la recaudación anual, la distribución de los proyectos según actividades a las que financian y la importancia que tiene cada CC.AA. dentro de los distintos tipos, en términos de recaudación por territorio y en la realización de proyectos por territorios. Adicionalmente, se añaden aspectos particulares inherentes a cada una de las modalidades. Además, se realiza una descripción y un análisis crítico del marco normativo vigente para cada uno de ellos. Los datos han sido obtenidos en su mayoría a través de la consulta directa en las plataformas, junto a la información obtenida de otras fuentes documentales, destacando: SABI, CNMV, la Comisión Europea y la consultora especializada Universo Crowdfunding. Se llega a la conclusión, de que el crowdfunding ha experimentado un importante crecimiento en su conjunto (cantidad total recaudada, número de mecenas y número de campañas realizadas), si bien el crecimiento es dispar entre los distintos tipos. El crowdfunding en nuestro país se encuentra principalmente en dos ámbitos territoriales: Cataluña y la Comunidad de Madrid. Además, se está produciendo un proceso de consolidación de las principales plataformas en el mercado, puesto que, las menos competitivas comienzan a desaparecer. Sin embargo, es necesario la reforma legal y su cumplimiento como elemento básico para la confiabilidad en esta nueva vía de financiación de proyectos empresariales y socialesUniversidad de Sevilla. Máster Universitario en Consultoría Económica y Análisis Aplicad

Analytical ray transfer matrix for the crystalline lens

We present the formulation of a paraxial ray transfer or ABCD matrix for onion-type GRIN lenses. In GRIN lenses, each iso-indicial surface (IIS) can be considered a refracting optical surface. If each IIS is a shell or layer, the ABCD matrix of a GRIN lens is computed by multiplying a typically high number of translation and refraction matrices corresponding to the K layers inside the lens. Using a differential approximation for the layer thickness, this matrix product becomes a sum. The elements A, B, C, and D of the approximated GRIN ray transfer matrix can be calculated by integrating the elements of a single-layer matrix. This ABCD matrix differs from a homogeneous lens matrix in only one integration term in element C, corresponding to the GRIN contribution to the lens power. Thus the total GRIN lens power is the sum of the homogeneous lens power and the GRIN contribution, which offers a compact and simple expression for the ABDC matrix. We then apply this formulation to the crystalline lens and implement both numerical and analytical integration procedures to obtain the GRIN lens power. The analytical approximation provides an accurate solution in terms of Gaussian hypergeometric functions. Last, we compare our numerical and analytical procedures with published ABCD matrix methods in the literature, and analyze the effect of the iso-indicial surface’s conic constant (Q) and inner curvature gradient (G) on the lens power for different lens models

Intracapsular accommodation mechanism in terms of lens curvature gradient

The intracapsular accommodation mechanism (IAM) may be understood as an increase in the lens equivalent refractive index as the eye accommodates. Our goal was to evaluate the existence of an IAM by analysing observed changes in the inner curvature gradient of the lens. To this end, we fitted a gradient index and curvature lens model to published experimental data on external and nucleus geometry changes during accommodation. For each case analysed, we computed the refractive power and equivalent index for each accommodative state using a ray transfer matrix. All data sets showed an increase in the effective refractive index, indicating a positive IAM, which was stronger for older lenses. These results suggest a strong dependence of the lens equivalent refractive index on the inner curvature gradient

Orthogonal basis for the optical transfer function

We propose systems of orthogonal functions qn to represent optical transfer functions (OTF) characterized by including the diffraction-limited OTF as the first basis function q0 = OTFperfect. To this end, we apply a powerful and rigorous theoretical framework based on applying the appropriate change of variables to well-known orthogonal systems. Here we depart from Legendre polynomials for the particular case of rotationally symmetric OTF and from spherical harmonics for the general case. Numerical experiments with different examples show that the number of terms necessary to obtain an accurate linear expansion of the OTF mainly depends on the image quality. In the rotationally symmetric case we obtained a reasonable accuracy with approximately 10 basis functions, but in general, for cases of poor image quality, the number of basis functions may increase and hence affect the efficiency of the method. Other potential applications, such as new image quality metrics are also discussed.Ministerio de Economía y Competitividad (MINECO) (MTM2014-52859-P, FIS2014-58303-P).Peer Reviewe

Online signature verification systems on a low-cost FPGA

This paper describes three different approaches for the implementation of an online signature verification system on a low-cost FPGA. The system is based on an algorithm, which operates on real numbers using the double-precision floating-point IEEE 754 format. The doubleprecision computations are replaced by simpler formats, without affecting the biometrics performance, in order to permit efficient implementations on low-cost FPGA families. The first approach is an embedded system based on MicroBlaze, a 32-bit soft-core microprocessor designed for Xilinx FPGAs, which can be configured by including a single-precision floating-point unit (FPU). The second implementation attaches a hardware accelerator to the embedded system to reduce the execution time on floating-point vectors. The last approach is a custom computing system, which is built from a large set of arithmetic circuits that replace the floating-point data with a more efficient representation based on fixed-point format. The latter system provides a very high runtime acceleration factor at the expense of using a large number of FPGA resources, a complex development cycle and no flexibility since it cannot be adapted to other biometric algorithms. By contrast, the first system provides just the opposite features, while the second approach is a mixed solution between both of them. The experimental results show that both the hardware accelerator and the custom computing system reduce the execution time by a factor ×7.6 and ×201 but increase the logic FPGA resources by a factor ×2.3 and ×5.2, respectively, in comparison with the MicroBlaze embedded system.This research was funded by Spanish MCIN/AEI/10.13039/501100011033, grant number PID2019-107274RB-I00.Peer ReviewedPostprint (published version

Depth-of-field after orthokeratology: a theoretical study

Trabajo presentado al 8th European Meeting on Visual and Physiological Optics, celebrado en Antwerp (Bélgica) del 22 al 24 de agosto de 2016.We evaluated the possible effect of orthokeratology on accommodative response. Using optical modelling we computed the negative half of the depth-of-field (DoFi) for the range of target vengeances from –1.00 D to –3.00 D, of two eye models designed to mimic the levels of primary and secondary spherical aberration found in 24 patients before and after undergoing orthokeratology (ortho-k). Five trained observers were subjected to a resolution task to identify the negative threshold of the depth-of-field of these model eyes by viewing a set of computed images representative of the model eyes trough focus retinal image quality for five target vengeances (TV), from –1.00 to – 3.00 D. The differences in the DoFi estimated by the five observers were maximum for a –3.00 D TV (0.21 D), with the post ortho-k model presenting a higher DoFi compared to the pre ortho-k model. Differences were consistent for all five observers and all TV’s. In conclusion, the increase in spherical aberration after ortho-k seems to contribute to a small increase in the DoFi. Although small, the benefits might be sufficient to improve retinal image quality in eyes with high accommodative lag.Peer reviewe

Orthogonal basis for the optical transfer function

We propose systems of orthogonal functions qn to represent optical transfer functions (OTF) characterized by including the diffraction-limited OTF as the first basis function q0 OTF perfect. To this end, we apply a powerful and rigorous theoretical framework based on applying the appropriate change of variables to well-known orthogonal systems. Here we depart from Legendre polynomials for the particular case of rotationally symmetric OTF and from spherical harmonics for the general case. Numerical experiments with different examples show that the number of terms necessary to obtain an accurate linear expansion of the OTF mainly depends on the image quality. In the rotationally symmetric case we obtained a reasonable accuracy with approximately 10 basis functions, but in general, for cases of poor image quality, the number of basis functions may increase and hence affect the efficiency of the method. Other potential applications, such as new image quality metrics are also discussed.This research was supported by the Spanish Ministry of Economía y Competitividad and the European Union MTM2014-52859 and FIS2014-58303

Morphology, topography, and optics of the orthokeratology cornea

The goal of this work was to objectively characterize the external morphology, topography, and optics of the cornea after orthokeratology (ortho-k). A number of 24 patients between the ages of 17 and 30 years (median ¼ 24 years) were fitted with Corneal Refractive Therapy® contact lenses to correct myopia between −2.00 and −5.00 diopters (D) (median ¼ −3.41 D). A classification algorithm was applied to conduct an automatic segmentation based on the mean local curvature. As a result, three zones (optical zone, transition zone, and peripheral zone) were delimited. Topographical analysis was provided through global and zonal fit to a general ellipsoid. Ray trace on partially customized eye models provided wave aberrations and retinal image quality. Monozone topographic description of the ortho-k cornea loses accuracy when compared with zonal description. Primary (C0 4) and secondary (C0 6) spherical aberration (SA) coefficients for a 5-mm pupil increased 3.68 and 19 times, respectively, after the treatments. The OZ area showed a strong correlation with C0 4 (r ¼ −0.49, p < 0.05) and a very strong correlation with C0 6 (r ¼ 0.78, p < 0.01). The OZ, as well as the TZ, areas did not correlate with baseline refraction. The increase in the eye’s positive SA after ortho-k is the major factor responsible for the decreased retinal optical quality of the unaccommodated eyeThis work was funded in part by European Fund for Regional Development (FEDER) through the COMPETE Program and by the Portuguese Foundation for Science and Technology (FCT). FCT provided financial support in the framework of projects PTDC/SAU-BEB/098391/2008, PTDC/SAU-BEB/ 098392/2008 and the Strategic Project PEST-C/FIS/UI607/ 2011. The authors have no proprietary interest in the methods and devices described in this manuscript

Acceleration of Complex Algorithms on a Fast Reconfigurable Embedded System on Spartan-3

Complex algorithms usually require several computation stages. Many embedded microprocessors have not enough computational performance to resolve these algorithms in a reasonable time, so dedicated coprocessors accelerate them although the main drawback is the area devoted to them. A reconfigurable coprocessor can drastically reduce the area, since it accommodates a set of coprocessors whose execution is multiplexed on time, although the reconfiguration speed reduces the overall system performance. Although self-reconfigurable systems are possible on Spartan-3 FPGAs, it requires a hard design task due to the lack of software and hardware support available on higher-cost families. This paper describes the architecture of a fast self-reconfigurable embedded system mapped on Spartan-3, used as computation platform to solve a complex algorithm, such as the image-processing carried out in a fingerprint biometric algorithm. In order to reduce the reconfiguration time, the system uses our custom-made memory and reconfiguration controllers. Moreover, the dynamic coprocessor can access directly to external memory through our memory controller to improve processing time.Peer ReviewedPostprint (published version