Comportamiento de torres de enfriamiento de tiro natural, tipo híbrido

El presente trabajo contiene las bases de cálculo para determinar el comportamiento de torres de enfriamiento híbridas de tiro natural. En el tipo de torre de enfriamiento tratado aquí, el agua es primero enfriada en una parte seca y luego en una parte húmeda. El aire fluye en paralelo por las partes seca y húmeda. A partir de las ecuaciones básicas se obtiene un sistema de ecuaciones, por medio del cual es posible determinar el comportamiento de ese tipo de torres de enfriamiento bajo distintas condiciones ambientales. Como ejemplo de aplicación se estudió una torre de enfriamiento que debe disparar 435 MW de energía térmica, lo cual corresponde a la disipación de una planta de fuerza de 300 MW de energfa eléctrica. La temperatura de salida del agua de enfriamiento se ve afectada por dos factores de efectos contrarios: La parte húmeda es en parte descargada por la parte seca, lo cual afecta positivamente el enfriamiento del agua. La parte seca disminuye el tiraje de la torre de enfriamiento y con ello también el flujo de aire que fluye a través de La parte húmeda. Debido a esto el enfriamiento es afectado negativamente. Cuál de ambos factores influye más fuertemente, depende de las condiciones ambientales

The public funding of innovation in agri-food businesses

Public administrations have in recent years developed programs of public funding for innovation to boost the competitiveness of business. The study of how companies have used these funding sources generates knowledge to improve the design of support for private innovation and to provide advice for innovative companies. This paper investigates these issues in the agri-food sector which is of particular interest as it is comprised mainly of small and medium enterprises with a wide regional presence and interaction with their local environment. A survey on technological innovation was used to estimate panel logit models with random effects, taking as dependent variables three types of funding: regional, state and European Union. The results generally show a positive relationship between innovation efforts and access to public funding, but also significant differences between types of funding and between sectors. Food companies that obtain public funding tend to have a more innovative profile than Agriculture ones. Both types of firm present higher probabilities than others companies when it comes to gaining access to regional funding, though the opposite often occurs in the case of state funding. Firm size is not significant for regional funding and no overlap was detected between regional and state funding. The financial crisis has adversely affected regional and national aid, which experienced a significant decrease in the period from 2008 to 2013

Influence of the Second Flexural Mode on the Response of High-Speed Bridges

This paper deals with the assessment of the contribution of the second flexural mode to the dynamic behaviour of simply supported railway bridges. Alluding to the works of other authors, it is suggested in some references that the dynamic behaviour of simply supported bridges could be adequately represented taking into account only the contribution of the fundamental flexural mode. On the other hand, the European Rail Research Institute (ERRI) proposes that the second mode should also be included whenever the associated natural frequency is lower than 30 Hz]. This investigation endeavours to clarify the question as much as possible by establishing whether the maximum response of the bridge, in terms of displacements, accelerations and bending moments, can be computed accurately not taking account of the contribution of the second mode. To this end, a dimensionless formulation of the equations of motion of a simply supported beam traversed by a series of equally spaced moving loads is presented. This formulation brings to light the fundamental parameters governing the behaviour of the beam: damping ratio, dimensionless speed $\alpha$=VT/L, and L/d ratio (L stands for the span of the beam, V for the speed of the train, T represents the fundamental period of the bridge and d symbolises the distance between consecutive loads). Assuming a damping ratio equal to 1%, which is a usual value for prestressed high-speed bridges, a parametric analysis is conducted over realistic ranges of values of $\alpha$ and L/d. The results can be extended to any simply supported bridge subjected to a train of equally spaced loads in virtue of the so-called Similarity Formulae. The validity of these formulae can be derived from the dimensionless formulation mentioned above. In the parametric analysis the maximum response of the bridge is obtained for one thousand values of speed that cover the range from the fourth resonance of the first mode to the first resonance of the second mode. The response at twenty-one different locations along the span of the beam is compared in order to decide if the maximum can be accurately computed with the sole contribution of the fundamental mode

Influence of the Second Bending Mode on the Response of High-Speed Bridges at Resonance

This paper deals with the assessment of the contribution of the second bending mode to the dynamic behavior of simply supported railway bridges. Traditionally the contributions of modes higher than the fundamental have been considered of little importance for the computation of the magnitudes of interest to structural engineers (vertical deflections, bending moments, etc.). Starting from the dimensionless equations of motion of a simply supported beam subjected to moving loads, the key parameters governing the dynamic behavior are identified. Then, a parametric study over realistic ranges of values of those parameters is conducted, and the influence of the second mode examined in detail. The main purpose is to decide whether the second mode should be taken into account for the determination of the maximum displacement and acceleration in high-speed bridges. In addition, the reasons that cause the contribution of the second bending mode to be relevant in some situations are highlighted, particularly with regard to the computation of the maximum acceleration

Methodology for Zero-moment Point Experimental Modeling in the Frequency Domain

Frequency domain methodology is applied to obtain a nominal model for the Zero-Moment Point (ZMP) stability index of a biped robot in an attempt to establish a relationship between the robot trunk trajectories and the stability margin of the contact surface of the foot (or feet) touching the supporting soil. To this end the biped robot trunk is excited with a variable frequency sinusoidal signal around several operating points. These input oscillations generate other output oscillations that can be analyzed with the help of the ZMP measurement system. The proposed ZMP modeling approach not only considers classical rigid body model uncertainties but also non-modelled robot mechanical structure vibration modes. The non-linear ZMP model is obtained following three consecutive stages: Equivalent inverted pendulum dynamics, where saturation and acceleration upper bounds are taken into account, non-modelled inverted pendulum dynamics, including non-linear effects, and low-pass dynamics defining the system cut-off frequency. The effectiveness of this method is demonstrated in practice with the SILO2 biped robot prototype, and a simple control strategy is implemented in order to validate experimentally the usefulness of the models developed.Frequency domain methodology is applied to obtain a nominal model for the Zero-Moment Point (ZMP) stability index of a biped robot in an attempt to establish a relationship between the robot trunk trajectories and the stability margin of the contact surface of the foot (or feet) touching the supporting soil. To this end the biped robot trunk is excited with a variable frequency sinusoidal signal around several operating points. These input oscillations generate other output oscillations that can be analyzed with the help of the ZMP measurement system. The proposed ZMP modeling approach not only considers classical rigid body model uncertainties but also non-modelled robot mechanical structure vibration modes. The non-linear ZMP model is obtained following three consecutive stages: Equivalent inverted pendulum dynamics, where saturation and acceleration upper bounds are taken into account, non-modelled inverted pendulum dynamics, including non-linear effects, and low-pass dynamics defining the system cut-off frequency. The effectiveness of this method is demonstrated in practice with the SILO2 biped robot prototype, and a simple control strategy is implemented in order to validate experimentally the usefulness of the models developed

Determination of 15N stable isotope natural abundances for assessing the use of saline reclaimed water in grapefruit

We reported the results of an isotopic study aimed at evaluating the medium to long-term effects of different water qualities and deficit irrigation strategies on the ecophysiology of grapefruit in a 7-year-old plantation in SE Spain. For a better understanding of the interaction between nitrogen and salts from reclaimed water, RW, an experiment using natural abundance (δ) of 15N was conducted. This study showed that in grapefruit crop irrigated with RW leaf δ15N value increased. We concluded that: (i) causal links exist between leaf δ15N isotope and salt stress: positive correlation between values of this isotope and leaf salt content was showed; (ii) excess of nitrates provided by the reclaimed irrigation water were lost in the ecosystem through leaching, denitrification, etc., enriching the medium with δ15N and increasing δ15N values in plants. Therefore, the results of this study highlight the key role that salt content from RW can play in N uptake by plants and, hence, isotopic discrimination of leaf N. Consequently, it has been demonstrated the usefulness of isotopic discrimination measure to predict crop sustainability in the medium to long term when using water sources of different quality combined with deficit irrigation strategies

The theoretical and practical construction of a new modern habitat: some patios and a street (1946-1954)

Desde la creación de los CIAM, la arquitectura moderna se ha desarrollado en función de unas pautas teóricas y prácticas muy definidas. La definición inicial de una ciudad funcional donde la casa era considerada una “máquina de vivir” quedó modificada a partir de 1933 con la Carta de Atenas. Comenzaron a contar cuestiones vinculadas con el lugar que hasta entonces no habían sido consideradas. La Segunda Guerra Mundial supuso un fuerte paréntesis en la actividad crítica y de debate acerca de los nuevos planteamientos. La actividad en el exilio de muchos arquitectos europeos, con la figura de Sert como destacado ejemplo en Estados Unidos, propició nuevas líneas de trabajo. Las propuestas del arquitecto español de 1946 en la ciudad peruana de Chimbote mostraban una preocupación “más humana” que los ejemplos anteriores. El gran salto en estos planteamientos se produce en los primeros años 50 cuando los jóvenes colaboradores de Le Corbusier en la construcción de la Unidad de Habitación de Marsella se encomiendan, a través del conocido grupo ATBAT-Afrique, en la construcción de nuevos barrios periféricos en Casablanca. Las propuestas de casas patio desarrolladas allí por Ecochard y Candilis junto con las propuestas urbanas de los Smithson en Londres, fueron recogidas en el CIAM IX que propició la creación del TEAM 10. Ese fue el punto de inflexión y partida hacia un nuevo concepto del hábitat contemporáneo.Since the creation of the CIAM, modern architecture has been developed based on firmly defined theoretical and practical guidelines. The initial definition of a functional city where the house was considered a “machine for living” was modified as of 1933 with the Athens Charter. They began to have questions linked with the place, which until then had not been considered. World War II led to a strong interruption in the critical activity and debate about the new proposals. The activity of many European architects in exile, with the figure of the Spanish architect Sert as an outstanding example in the United States, favoured new lines of work. His 1946 proposals in the Peruvian city of Chimbote showed “a more human” concern than the previous examples. The great leap in these approaches took place in the early 50s when the young collaborators of Le Corbusier were entrusted with the construction of the Unité d’Habitation at Marseilles, and through the well-known ATBAT-Afrique group, in the construction of new suburbs in Casablanca. The proposals of patio houses developed there by Ecochard and Candilis, along with the urban proposals of the Smithsons in London, came together in the CIAM IX that brought about the creation of TEAM 10. This was the turning point and the start towards a new concept of the contemporary habitat

The dissolution of the limits. Topography of concrete at the EPFL Rolex Learning Centre of SANAA in Lausana.

[EN] The EPFL Rolex Learning Centre in Lausana, constructed by SANAA, is one of the most relevant buildings in the new concept of contemporary architectural space. The analytical and critical research that the present work develops comprises the design strategies and tools that define the building.[ES] El Centro de Aprendizaje Rolex de Lausana, obra de SANNA, constituye uno de los edificios más relevantes sobre la nueva concepción del espacio arquitectónico contemporáneo. Las estrategias y herramientas proyectuales que lo definen conforman la investigación analítica y crítica que desarrolla el presente artículo.García Martínez, P.; Sanz Alarcón, JP.; Centellas Soler, M. (2014). La disolución de los límites. Topografías de hormigón en el Centro de Aprendizaje Rolex de SANAA en Lausana. EN BLANCO. Revista de Arquitectura. 6(16):104-105. doi:10.4995/eb.2014.5816SWORD10410561

FOLDING ARCHITECTURE FOR AN ASTONISHING DECADE Emilio Pérez Piñero and the Architecture of the Sixties

[EN] The article reviews the work of Emilio Pérez Piñero, a designer of unfolding structures and geodesic domes, who leaped directly from isolated, impoverished Spain to the international forefront of technological development and died tragically a few years after. The paper describes the main aspects aspects of Piñero’s work and explains how his foldable, movable structures embody some key issues of the architecture of the nineteen-sixties, anticipating a number of roposals by Rayner Banham, Ron Herron or Peter Cook[ES] El artículo revisa la obra de Emilio Pérez Piñero, diseñador de estructuras plegables y cúpulas geodésicas, que saltó directamente desde una España empobrecida y aislada a la vanguardia internacional del desarrollo tecnológico, para morir de forma trágica a los pocos años de haber iniciado su carrera. El trabajo describe los aspectos fundamentales de su obra y expone cómo el carácter desmontable y transportable de sus estructuras resuelve algunos de los temas claves de la cultura arquitectónica europea y americana de los años sesenta, anticipándose a las propuestas teóricas de Rayner Banham, Ron Herron o Peter Cook.Calvo López, J.; Sanz Alarcón, JP. (2011). ARQUITECTURA PLEGABLE PARA UNA DÉCADA PRODIGIOSA La obra de Emilio Pérez Piñero y la arquitectura de los años sesenta. EGA. Revista de Expresión Gráfica Arquitectónica. 16(17):114-127. doi:10.4995/ega.2011.888SWORD114127161