Surface tension and microgravity

The behaviour of confined liquids on board an orbiting spacecraft is mainly driven by surface tension phenomena, which cause an apparently anomalous response of the liquid when compared with the behaviour that can be observed on an Earth laboratory provided that the amount of liquid is high enough. The reason is that in an orbiting spacecraft the different inertial forces acting on the bulk of the liquid are almost zero, causing thus capillary forces to be the dominant ones. Of course, since gravity forces are proportional to the liquid volume, whereas surface tension forces are proportional to the liquid surface, there are situations on Earth where capillarity can be the dominant effect, as it happens when very small volume liquid samples are considered. However, work with small size samples may require the use of sophisticated optical devices. Leaving aside the neutral buoyancy technique, a way of handling large liquid interfaces is by using drop towers, where the sample falls subjected to the action of Earth's gravity. This approach is suitable when the characteristic time of the problem under consideration is much smaller than the drop time. In this work the transformation of an out-of-use chimney into a drop tower is presented. Because of the miniaturization, hardiness and low cost of current electronic devices, a drop tower can be used as an inexpensive tool for undergraduate students to experimentally analyse a large variety of surface tension driven phenomena.

On the loading-rate dependence of the Al 7017-T73 fracture-initiation toughness

While static fracture toughness is a widely studied and standardised parameter, its dynamic counterpart has not been exhaustively examined. Therefore, in this research a series of quasi-static and different loading-rate dynamic tests were carried out to determine the evolution of fracture toughness with the velocity of the application of the load on aluminium 7017-T73 alloy. Three-point bending tests of pre-fatigued standard specimens (ASTM E399) at four loading-rates were carried out. The experiments were conducted by employing the subsequent apparatus ordered from lowest to highest load application velocity: a servo-hydraulic universal testing machine, a free-drop tower, a modified Split Hopkinson Pressure Bar and an explosive load testing device. In order to perform the dynamic fracture toughness tests, it was necessary to design and develop some experimental devices. The fracture-initiation toughness of the aluminium 7017-T73 alloy did not exhibit a significant variation for the studied cases. As a conclusion, the research showed that fracture-initiation toughness remained constant regardless of the velocity at which the load was applied.

An experimental analysis od the stability and the dynamics of asixymmetric liquid bridges between unequal disks

In this paper experimental results related to both stability an the dynamic of a asiximmetric liquid bridge between unequal disk are presented. Experiments have been performed by using a drop tower facility and the response of the liquid bridge to a sudden change of the acceleration level acting on it has bee obtained.

The Ciborium or Lantern Tower of Valencia Cathedral: Geometry, Construction and Stability

Early 18th century treatise writer Tomas Vicente Tosca1 includes in his Tratado de la montea y cortes de Canteria [On Masonry Design and Stone Cutting], what is an important documentary source about the lantern of Valencia Cathedral. Tosca writes about this lantern as an example of vaulting over cross arches without the need of buttresses. A geometrical description is followed by an explanation of the structural behavior which manifests his deep understanding of the mechanics of masonry structures. He tries to demonstrate the absence of buttresses supporting his thesis on the appropriate distribution of loads which will reduce the "empujos" [horizontal thrusts] to the point of not requiring more than the thickness of the walls to stand (Tosca [1727] 1992, 227-230). The present article2 assesses T osca' s appreciation studying how loads and the thrusts they generate are transmitted through the different masonry elements that constitute this ciborium. In order to do so, we first present a geometrical analysis and make considerations regarding its materials and construction methods to, subsequently, analyze its stability adopting an equilibrium approach within the theoretical framework of the lower bound limit analysis.

The Ciborium or Lantern Tower of Valencia Cathedral: Geometry, Construction and Stability

Early 18th century treatise writer Tomas Vicente Tosca1 includes in his Tratado de la montea y cortes de Canteria [On Masonry Design and Stone Cutting], what is an important documentary source about the lantern of Valencia Cathedral. Tosca writes about this lantern as an example of vaulting over cross arches without the need of buttresses. A geometrical description is followed by an explanation of the structural behavior which manifests his deep understanding of the mechanics of masonry structures. He tries to demonstrate the absence of buttresses supporting his thesis on the appropriate distribution of loads which will reduce the "empujos" [horizontal thrusts] to the point of not requiring more than the thickness of the walls to stand (Tosca [1727] 1992, 227-230). The present article2 assesses T osca' s appreciation studying how loads and the thrusts they generate are transmitted through the different masonry elements that constitute this ciborium. In order to do so, we first present a geometrical analysis and make considerations regarding its materials and construction methods to, subsequently, analyze its stability adopting an equilibrium approach within the theoretical framework of the lower bound limit analysis.

Control rod drop surveillance using two friction coefficients

In the case of large burnup, a control rod (CR) guide tube in the pressurized water reactor of a commercial nuclear power plant might bend. As a consequence, a CR drop experiment may indicate an event of a CR partially inserted and whether the CR should be deemed inoperable. Early prevention of such an event can be achieved by measuring two friction coefficients: the hydraulic coefficient and the sliding coefficient. The hydraulic coefficient hardly changes, so that the curvature of the guide tube can only be detected thanks to a variation of the sliding coefficient. A simple model for the CR drop is established and validated with CR drop experiments. If tmx denotes the instant of CR maximum velocity, a linear relationship between (tmx)_2 and the sliding coefficient is found.

Logic cells as basic structures to add/drop WDM information signals

Nowadays, in order to take advantage of fiber optic bandwidth, any optical communications system tends to be WDM. The way to extract a channel, characterized by a wavelength, from the optical fiber is to filter the specific wavelength. This gives the systems a low degree of freedom due to the fact of the static character of most of the employed devices. In this paper we will present a different way to extract channels from an optical fiber with WDM transmission. The employed method is based on an Optically Programmable Logic Cells (OPLC) previously published by us, for other applications as a chaotic generator or as basic element for optical computing. In this paper we will describe the configuration of the OPLC to be employed as a dropping device. It acts as a filter because it will extract the data carried by a concrete wavelength. It does depend, internally, on the wavelength. We will show how the intensity of the signal is able to select the chosen information from the line. It will be also demonstrated that a new idea of redundant information it is the way of selecting the concrete wavelength. As a matter of fact this idea is apparently the only way to use the OPLC as a dropping device. Moreover, based on these concepts, a similar way to route signals to different routes is reported. The basis is the use of photonic switching configurations, namely Batcher or Bayan structures, where the unit switching cells are the above indicated OPLCs.

A landscape architectural design approach:the restoration of the Angel Tower and the Cloister of the Cathedral of Cuenca.

Este artículo trata de analizar la reciente evolución de los conceptos sobre intervención en el Patrimonio Cultural. Para ello utiliza como modelo el proyecto metodológico aplicado sobre las dos últimas actuaciones efectuadas en la Catedral de Cuenca. La Carta de Atenas, 1931, que estableció las bases de la modernidad sobre las dos trayectorias de espacio y tiempo, concuerdan hoy después de casi un siglo, recuperando su punto de encuentro. El artículo básicamente valora el potencial que los proyectos contemporáneos de intervención en el patrimonio pueden ofrecer cuando estudias su trayectoria en el paisaje. En orden a certificar sus transformaciones desde la actualidad, el singular monumento de la Catedral de Cuenca, utilizado como modelo, nos aporta a través de sus materiales y morfología la memoria secular que nos informa de sus técnicas constructivas y valores sociales. Este modelo abre un diálogo entre teoría y práctica reflejado a través de los trabajos de restauración aplicados. Después de treinta años de experiencia restauradora llevada a cabo por los autores, las dos últimas intervenciones que son minuciosamente expuestas, revelan algunas nuevas estrategias de aplicación en el proyecto de intervención.

Alminar Tower, Dubai (2013)

ALGHURAIR ALMINAR. A white tower in Dubai = ALGHURAIR ALMINAR. Una torre blanca en Dubai

Telefónica Tower

A tower is proposed in the highest part of the city of Madrid, in La Moraleja, so high, so very high that one might just see the sea on a clear day. = Se propone una torre en lo más alto de Madrid, en la Moraleja, tan alta tan alta que desde ella podría verse el mar en los días claros.

The influence of gravity on the solidifcation of a drop

In this paper the influence of gravity on the solidification of a drop formed at the end of a rod is analyzed. Although similar studies (but ignoring gravity effects) already exist, a theoretical analysis including gravity effects allows one to improve the experimental procedure to measure on Earth relevant properties of crystals (mainly the receding contact angle <£,) which are of importance in shaped crystal growth processes. One of the main results here obtained are the shapes of the sohdified drops, which are strongly dependent on the value of <#>,. Therefore, fitting theoretical shapes to experimental ones is a wav to perform accurate measurements of <^.

Tower of Martín González or castle of La Raya (Soria): territory, history, defense and construction / La torre de Martín González o castillo de La Raya (Soria): territorio, historia, defensa y construcción

Abstract The Tower of Martín González, also known as castle of La Raya, is placed in the actual border between the Spanish provinces of Soria and Zaragoza and in the historical limit between the Crowns of Castile and Aragon: this is the reason for its name. The castle dominates the hedge of the plain-moors that surround the Valley of Nágima River. It is a castle with courtyard and a high tower in the western flank. The paper analyzes the castle in four main levels. All references about the castle are studied to draw a historical narration and to relate with the territory and other fortifications, both Castilian and Aragonese. Despite its advanced state of ruin, it preserves many rests that allow making an analysis of its defensive elements and constructive aspects. Resumen La torre de Martín González, también conocida como el castillo de La Raya, se sitúa en el límite actual entre las provincias de Soria y Zaragoza y en el límite histórico entre las coronas de Castilla y Aragón. Domina el extremo de los páramos que circundan el río Nágima. Es un castillo de tipo torrejón con patio de armas y una torre del homenaje adosada a su flanco occidental. El análisis contempla cuatro niveles fundamentales para el entendimiento de la arquitectura fortificada. La comunicación revisa la documentación existente sobre los elementos históricos que se ponen en relación, mediante el análisis territorial, con el sistema fortificado de frontera. A pesar de su avanzado estado de ruina, conserva restos que permiten realizar una lectura interpretativa de sus elementos defensivos y de sus aspectos constructivos.

Study of the foundations, bearing soil and stability of the minaret-tower of Cordobas Mosque

This research in Cordoba's mosque tower main objective was to analyze and characterize the foundations and the underlying soil, calculating the stability of the monument as well as the settlement and deformations performed, using traditional calculation methods and also by finite elements, and to determine differences between both, as well as the stability factor of the Minaret Tower. The works done to study the soil, were drill bores and dynamic penetration tests, classification of samples by size, Atterberg limits, physical and chemical analysis, showing the typical geotechnical composition of the Guadalquivir valley: an alluvial material composed by sand, gravels and silt clays. To study the foundations, inclined bore samples were extracted with 10-65º, showing calcarenite stone ashlars and lime concrete alternating with stone and brick masonry.

De la isla de Menorca a las costas sur y este de Inglaterra: análisis del prototipo de torre Martello = From the island of Minorca to the south and east coasts of England: analysis of the prototype of the Martello tower

Esta tesis doctoral desarrolla una investigación original sobre las torres defensivas de Menorca y las torres Martello de las costas sur y este de Inglaterra. Con respecto a las torres menorquinas, se distinguen las de Alcaufar y Punta Prima, construidas por ingenieros militares españoles, en 1786; de las levantadas por el ejército británico durante su último periodo de dominación de la isla, entre 1798 y 1802. Estos ingenieros reales británicos construyen las torres Martello en las costas inglesas, entre 1805 y 1812; y otras, semejantes a ellas, en el resto de su Imperio, hasta mediados del siglo XIX. La falta de estudios que relacionen las torres defensivas de Menorca y las Martello inglesas dentro del marco disciplinario de la construcción, ha constituido la justificación de esta investigación. La hipótesis de trabajo plantea un objetivo principal: el estudio y análisis comparativo entre ellas, que se desarrolla en varios niveles de análisis: morfológico, físico-constructivo, de visibilidades; pero también territorial, histórico y poliorcético. Esta tesis cuestiona, en consecuencia, la idea tradicionalmente aceptada de que las torres Martello tomaran la torre de Mortella, en Córcega, o cualquiera de las denominadas torres "preMartello", como referencia para crear su prototipo. La metodología empleada combina los trabajos de gabinete con una intensa labor de campo, en la que se documentaron cincuenta y siete torres, catorce en Menorca y cuarenta y tres en Inglaterra. Se han redactado sus correspondientes fichas de datos, que incluyen aspectos generales - morfológicos y constructivos -, así como documentación fotográfica. Se han elaborado los levantamientos morfológicos de siete de estas torres, aquellas que por sus particularidades constructivas, o bien representan un determinado tipo de torre, o bien se distinguen del resto. Del mismo modo, se han desarrollado los levantamientos físico-constructivos y la caracterización de materiales de las cuatro torres más relevantes para este estudio: las menorquinas Alcaufar y Punta Prima, y las torres 24 y C, que ejemplifican, respectivamente, las levantadas en las costas sur y este de Inglaterra. El sistemático método de trabajo llevado a cabo ha favorecido la investigación y ha ayudado a obtener conclusiones que verifican la hipótesis planteada en la tesis y cumplen los objetivos establecidos al comienzo de la misma. ABSTRACT This doctoral thesis develops an original research on the defensive towers of Minorca, and the Martello towers on the south and east coasts of England. Regarding the Minorcan towers, Alcaufar and Punta Prima, built by the Spanish military engineers in 1786, must be distinguished from those erected by the British Army during its last period of domination of the island between 1798 and 1802. These Royal Engineers build the Martello towers on the English coasts between 1805 and 1812; and others, similar to them, in the rest of their Empire until the middle of the 19th century. The lack of studies linking these Minorcan and English towers, within the disciplinary framework of construction, has been the justification for this research. The hypothesis poses a main goal: the study and comparative analysis of them, which takes place at several levels of analysis: morphological, constructive, of visibilities; but also territorial, historical and poliorcetic. Consequently, this thesis questions the traditionally accepted notion that the Martello towers took the Corsican Mortella Tower, or any of the so-called “preMartello” towers as a reference to create their prototype. The methodology combines the cabinet works with significant fieldwork, in which fifty seven towers were documented, fourteen in Minorca and forty three in England. The corresponding data sheets were drafted including general aspects - morphological and constructive-, and photographic documentation. Morphological survey plans were developed for seven of these towers due to their construction peculiarities, which either denote a specific type of tower or makes it stand out from the rest. Likewise, constructive survey plans and material characterisation sheets of the four more relevant towers in this study were developed: the Minorcan Alcaufar and Punta Prima, and towers 24 and C, both respectively exemplifying those built on the south and east coasts of England. The systematic method of work encouraged the research and helped to draw conclusions that both confirm the hypothesis raised in the thesis and meet the objectives established at the beginning of it.