Energy harvesting from transverse galloping

Some elastic bluff bodies under the action of a fluid flow can experience transverse galloping and lose stability if the flow velocity exceeds a critical value. For flow velocities higher than this critical value, there is an energy transfer from the flow to the body and the body develops an oscillatory motion. Usually, it is considered as an undesirable effect for civil or marine structures but here we will show that if the vibration is substantial, it can be used to extract useful energy from the surrounding flow. This paper explores analytically the potential use of transverse galloping in order to obtain energy. To this end, transverse galloping is described by a one-degree-of-freedom model where fluid forces obey the quasi-steady hypothesis. The influence of cross-section geometry and mechanical properties in the energy conversion factor is investigated

Chaotic Vibrations in a Buckled Beam Induced by a Galloping Phenomenon

Chaos theory has spectacularly evolved since the pioneering work by E. Lorenz on chaotic motion in a simple, deterministic system. Since then, the chaotic behavior of many other deterministic, low-dimensional systems in a large variety of fields has been developed. In the particular field of aeroelasticity of aircraft structures several reports of chaos have been documented. However, we are unaware of any report of chaotic systems of civil (non-aeronautical) use induced by an aeroelastic phenomenon. In this paper a well defined civil, aeroelastic system, susceptible to exhibit chaotic behavior is presented. The system consists of a buckled beam from which a second beam is suspended. This last beam (hereafter, galloping beam) has a square cross- section and can undergo transverse galloping. The system is subjected to an uniform wind flow and, as it will be shown in the paper, for wind velocities larger than a threshold value, the galloping beam begins to oscillate and induces, for a determined set of parameter values, a chaotic motion in the buckled bea

UNA METODOLOGÍA PARA LA UTILIZACIÓN ÓPTIMA DE LOS INCENTIVOS POR ADQUISICIÓN DE VIVIENDA HABITUAL EN EL IRPF

I In this paper we develop a methodology to find out how to optimize the use of the three incentives to owner-occupied housing in the income tax : tax credit for the saving invested in a bank account, assigned to the future adquisition of the home, for cash payment or borrowing. The criterion we use is the maximization of the net profit gained by the buyer, that is estimated as the difference between the profit gained through the tax credit and the financial cost generated, if is the case, from the anticipation or the postponement of the investement, related to the moment of the purchase. With this methodology we find out a negative relation beween the maximum profit allowed by the law and the income of the buyer of the home, wich shows the progressivity of the incentives policy for owner-occupied housing trough the income tax. Classification-JEL : H24, H31.Income tax, owner-occupied housing, tax credit.

The educational improvement trough the Professional Practice of the EOE Counselor

Los procesos que tienen lugar dentro de los centros educativos son bastante complejos; en muchas ocasiones el profesorado no se siente preparado para asumir tales retos. Es ahí donde entra en juego la labor del equipo de zona. Los orientadores de EOE pueden ser un gran apoyo para que el profesorado afronte los obstáculos educativos. Y no solo eso, pueden también capacitar y formar al colectivo docente a asumir nuevos desafíos escolares y a provocar la reflexión ante su práctica diaria. Podría decirse que el orientador es un promotor del liderazgo pedagógico, a poco que incide en la mejora de los aprendizajes; y un generador del liderazgo distribuido, otorgando poder a todos y cada uno de los docentes del centro como generadores de iniciativas. En el presente trabajo se muestran los resultados de un ejemplo concreto de un orientador de zona en el trabajo con cuatro centros de Educación Infantil y Primaria. Se han recogido las percepciones de los equipos directivos y del inspector de zona, en base a la labor generadora del orientador, y cómo esta ha repercutido en prácticas concretas de centroThe processes that takes places within the educational establishments are quite complex. In many cases, teachers do not feel prepared to assume such challenges. And that is where the EOE comes in. EOE counselors can be a great support for teachers to face educational obstacles. They can also train and empower teachers to take on new educational challenges and to make them reflect on their daily practice. The counselor is a promoter of pedagogical leadership so that have un impact on the improvement of learning, and he generates distributed leadership, giving power to each and every one of the teachers of the establishment as generators of initiatives. The perceptions of the management teams and the area inspector have been collected based on the work of the counselor and how it has impacted on concrete establishment practices. In the present work, the results of a concrete example of a zone counselor in the work with four centers of Infantile and Primary Education are show

Biometric presentation attack detection: beyond the visible spectrum

The increased need for unattended authentication in multiple scenarios has motivated a wide deployment of biometric systems in the last few years. This has in turn led to the disclosure of security concerns specifically related to biometric systems. Among them, presentation attacks (PAs, i.e., attempts to log into the system with a fake biometric characteristic or presentation attack instrument) pose a severe threat to the security of the system: any person could eventually fabricate or order a gummy finger or face mask to impersonate someone else. In this context, we present a novel fingerprint presentation attack detection (PAD) scheme based on i) a new capture device able to acquire images within the short wave infrared (SWIR) spectrum, and i i) an in-depth analysis of several state-of-theart techniques based on both handcrafted and deep learning features. The approach is evaluated on a database comprising over 4700 samples, stemming from 562 different subjects and 35 different presentation attack instrument (PAI) species. The results show the soundness of the proposed approach with a detection equal error rate (D-EER) as low as 1.35% even in a realistic scenario where five different PAI species are considered only for testing purposes (i.e., unknown attacks

Whipping Instabilities in Electrified Liquid Jets

A liquid jet may develop different types of instabilities, like the so-called Rayleigh-Plateau instability, which breaks the jet into droplets. However, another type of instabilities may appear when we electrify a liquid jet and induce some charge at his surface. Among them, the most common is the so-called Whipping Instability, which is characterized by violent and fast lashes of the jet. In the submitted fluid dynamic video(see http://hdl.handle.net/1813/11422), we will show an unstable charged glycerine jet in a dielectric liquid bath, which permits an enhanced visualization of the instability. For this reason, it is probably the first time that these phenomena are visualized with enough clarity to analyze features as the effect of the feeding liquid flow rate through the jet or as the surprising spontaneous stabilization at some critical distance to the ground electrode.Comment: 3 pages, no figures, links to videos, Submission to the 26th Gallery of Fluid Motion (2009

Homomorphic Encryption for Speaker Recognition: Protection of Biometric Templates and Vendor Model Parameters

Data privacy is crucial when dealing with biometric data. Accounting for the latest European data privacy regulation and payment service directive, biometric template protection is essential for any commercial application. Ensuring unlinkability across biometric service operators, irreversibility of leaked encrypted templates, and renewability of e.g., voice models following the i-vector paradigm, biometric voice-based systems are prepared for the latest EU data privacy legislation. Employing Paillier cryptosystems, Euclidean and cosine comparators are known to ensure data privacy demands, without loss of discrimination nor calibration performance. Bridging gaps from template protection to speaker recognition, two architectures are proposed for the two-covariance comparator, serving as a generative model in this study. The first architecture preserves privacy of biometric data capture subjects. In the second architecture, model parameters of the comparator are encrypted as well, such that biometric service providers can supply the same comparison modules employing different key pairs to multiple biometric service operators. An experimental proof-of-concept and complexity analysis is carried out on the data from the 2013-2014 NIST i-vector machine learning challenge