The evolution of the laws of software evolution. A discussion based on a systematic literature review

After more than 40 years of life, software evolution should be considered as a mature field. However, despite such a long history, many research questions still remain open, and controversial studies about the validity of the laws of software evolution are common. During the first part of these 40 years the laws themselves evolved to adapt to changes in both the research and the software industry environments. This process of adaption to new paradigms, standards, and practices stopped about 15 years ago, when the laws were revised for the last time. However, most controversial studies have been raised during this latter period. Based on a systematic and comprehensive literature review, in this paper we describe how and when the laws, and the software evolution field, evolved. We also address the current state of affairs about the validity of the laws, how they are perceived by the research community, and the developments and challenges that are likely to occur in the coming years.

Simulation of Temperatures and Stresses during Construction of a RCC Dam

Se describen las variaciones de temperaturas y de tensiones durante la construcción de presas de hormigón compactado. The curing of concrete is an exothermic process. The heat of hydration generated induces temperature increases in the concrete, which will disappear in the long term by heat conduction in the concrete mass and thermal exchanges with the environment. The problem is of particularly interest for large concrete masses, as is the case of dams, because the time involved in the heat diffusion process grows with the square of the dimensions and a hotter dam interior implies the possibility of cracking the exposed surfaces of the dam. The Cuira dam, currently being built in Venezuela using roller compacted concrete, is a 134 m high, arch-gravity dam. In support of the design, different strategies were analysed, including various combinations of cooling of the water and the aggregate in order to achieve acceptable results. The calculations were conducted with Abaqus, taking into account all the necessary mechanical and thermal characteristics, as well as the relevant non-linearities. The analyses led to the conclusion that no cooling was required, even taking into account the stress state imposed by an early and rapid filling of the reservoir.

Calibración de Modelos Constitutivos de Hormigón

En este artículo se describen diversos modelos constitutivos del comportamiento dilatante del hormigón. Se describe una metodología para caracterizar el comportamiento mecánico del hormigón. En particular se calibra el modelo de plasticidad y daño para hormigón de Abaqus/Standard y Abaqus/Explicit a partir de ensayos uniaxiales y tria xiales en probetas cilíndricas. El modelo se enriquece con una subrutina de usuario para capturar mejor la ductilidad del material sometido a moderadas presiones de confinamiento. Además se define una variable de estado para controlar la eliminación de elementos. Finalmente se muestran algunos ejemplos de aplicación de impactos de proyectiles deformables y rígidos sobre muros de hormigón armado, incluyendo técnicas especiales como la conversión de elementos sólidos a partículas (SPH).

Concrete Swelling in a Double Curvature Dam

Se describe el problema del hinchamiento del hormigón en las presas de doble curvatura. Several chemical reactions are able to produce swelling of concrete for decades after its initial curing, a problem that affects a considerable number of concrete dams around the world. The object of the work reported is to simulate the underlying mechanisms with sufficient accuracy to reproduce the past history and to predict the future evolution reliably. Having studied the available formulations, that considered to be more promising was adopted and introduced via user routines in a commercial finite element code. It is a non isotropic swelling model,compatible with the cracking and other non-linearities displayed by the concrete. The paper concentrates on the work conducted for a double-curvature arch dam. The model parameters were determined on the basis of some parts of the dam’s monitored histories, reliability was then verified using other parts and, finally, predictions were made about the future evolution of the dam and its safety margin.

Fluid-Structure Interaction in Civil Engineering Structures

The problems being addressed involve the dynamic interaction of solids (structure and foundation) with a liquid (water). Various numerical procedures are reviewed and employed to solve the problem of establishing the expected response of a structure subjected to seismic excitations while duly accounting for those interactions. The methodology is applied to the analysis of dams, lock gates, and large storage tanks, incorporating in some cases a comparison with the results produced by means of simplified analytical procedures.

Optimización del diseño geométrico de glorietas mediante algoritmos genéticos

El funcionamiento de las glorietas es sensible a las características geométricas de los elementos que componen el diseño. Generalmente el diseño geométrico es llevado a cabo mediante procedimientos manuales e iterativos, lo que genera un elevado consumo de tiempo del proyectista. Durante el proceso, los ingenieros tratan de encontrar una solución satisfactoria al problema, tanto en planta como en alzado, aplicando unos criterios derivados de normativas y de la propia experiencia del proyectista. Esta tarea es compleja y laboriosa debido al elevado número de variables, y puede ser simplificada mediante la elaboración de unos algoritmos adecuados. En este artículo se presenta el planteamiendo de una metodología que servirá de base para el desarrollo de un modelo de optimización que proporcione la geometría de la glorieta en planta en base a dos objetivos: la consistencia de las velocidades de circulación y la eficiencia operativa. La eficiencia operativa se caracteriza mediante la demora media de los vehículos y su estudio determina el número de carriles necesarios en las entradas y en la calzada anular. La optimización de la consistencia de las velocidades tiene como objetivo reducir los conflictos y la accidentalidad, además de contribuir a la mejora de la eficiencia de la circulación, ya que permite simplificar la tarea de incorporación de los vehículos en el flujo de la calzada anular. Para su cálculo es necesario determinar previamente las trayectorias de los vehículos y los perfiles de velocidades de las trayectorias más rápidas. Una buena consistencia debe minimizar la variación de velocidad entre los elementos geométricos consecutivos y la velocidad relativa entre corrientes de tráfico en conflicto. Para resolver el problema de optimización se plantea un procedimiento heurístico basado en algoritmos genéticos. El modelo requiere de unos procedimientos para la generación de forma aleatoria de la geometría de la glorieta y para el cálculo de las trayectorias de los vehículos y de las funciones objetivo a partir de la geometría, junto al diseño de unos operadores genéticos que tengan en consideración las interacciones que se presentan entre los elementos que definen la geometría de la glorieta.

Método bayesiano de estimación del potencial de reducción de costes de la accidentalidad en los tramos de una red de carreteras

La directiva europea sobre gestión de la seguridad de las infraestructuras viarias establece el requerimiento de implantar un procedimiento de clasificación de los tramos de la red en función del ahorro potencial en costes derivados de los accidentes en las carreteras que forman parte de la Red Transeuropea. El potencial de mejora de la seguridad debe reflejar la reducción en coste de accidentalidad que podría alcanzarse a través de medidas de mejora de la infraestructura y puede estimarse como la diferencia entre el coste por km de la accidentalidad del tramo durante el período considerado y el coste esperado para carreteras del mismo tipo que dispongan de las condiciones de seguridad alcanzables mediante actuaciones preventivas de mejora de las infraestructuras. En la ponencia se describe un procedimiento para mejorar la precisión de la estimación del potencial de reducción de la accidentalidad en los tramos de una red de carreteras a partir de la calibración de modelos lineales generalizados de estimación de la frecuencia de accidentes y de su combinación con la información registrada de accidentalidad aplicando un procedimiento bayesiano empírico.

FRe building technological products

Nowadays "Flood Resilient (FRe) Building Technological Products" is an undefined concept, and concerned FRe solutions cannot be even easily identified. There is an interest in offering an identification and classification of the referred products, since it will be useful for stakeholders and populations at flood risk for adopting the most adequate protections when facing floods. There are many barriers for the implementation of "FRe building technological products", and particularly their standardization is still a major challenge. To put into contact such solutions with final customers, it appears necessary to protocolize them all. The classification effort achieved in this document shall be considered as a necessary preliminary step in order to open the road to the market to FRe building technological solutions.

Looking for a more comprehensive approach

The necessity/convenience for improving accuracy in determining the flood frequency is widely accepted further than among hydrologists, and is increasingly deepened in relationship with the statement of different thresholds related to the respective management systems. And both Scientific and Management Communities fully accept the necessity of living with determined levels of flood risk. Most of the approaches for “Advancing Methods” improving concentrate on the statistical ways, even since Climate in fact is not a Stationary process. The question is here reflected since the SMARTeST research and final highlights, policy and recommendations. The paper looks at a better agreement between Hydrology and the whole Climate as the result of the Global Thermal Machine and takes mainly into account a historical approach, trying to show the necessity of a wider collection and analysis of climate data for statistical approaches.

A fracture model for pearlitic steel bars using a cohesive model

The fracture of ductile materials, such as metals, is usually explained with the theory of nucleation, growth and coalescence of microvoids. Based on this theory, many numerical models have been developed, with a special mention to Gurson-type models. These models simulate mathematically the physical growth of microvoids, leading to a progressive development of the internal damage that takes place during a tensile test. In these models, the damage starts to develop in very early stages of the test. Tests carried out by the authors suggest that, in the case of some eutectoid steels such as those used for manufacturing prestressing steel wires, the internal damage that takes place as a result of the growth of microvoids is only noticeable in very late stages of the tensile test. In the authors’ opinion, using a cohesive model as a failure criterion may be interesting in this case; a cohesive model only requires two parameters to be defined, with the fracture energy being one of them, which can be obtained experimentally. In addition to this, given that it is known that the stress triaxiality has a strong influence on the fracture of ductile materials, a cohesive model whose parameters are affected by the value of the stress triaxiality can be considered. This work presents a fracture model for steel specimens in a tensile test, based on a cohesive behaviour and taking into account the effect of stress triaxiality, which is different at each point of the fracture plane.

Simulación del proceso de rotura por tracción de alambres de acero perlítico con un modelo de fisura cohesiva

La fractura de metales dúctiles como el acero suele explicarse a partir de la hipótesis de nucleación, crecimiento y coalescencia de microhuecos. A partir de esta teoría, se han desarrollado diversos modelos numéricos, entre los que el modelo de Gurson y sus variantes son los más extendidos. Dichos modelos reproducen matemáticamente el fenómeno físico de crecimiento de huecos resultando en un desarrollo progresivo del daño en el interior del material durante un ensayo de tracción. En estos modelos, el daño comienza a desarrollarse en fases muy tempranas del ensayo, incluso anteriores a la carga máxima. Ensayos realizados por los autores parecen indicar, sin embargo, que en el caso de barras de acero eutéctico empleado en la fabricación de alambres de pretensado, el daño originado en el interior del material como consecuencia del crecimiento de microhuecos sólo es apreciable en un estado muy avanzado del ensayo, momentos antes de producirse la rotura. Además, desde hace décadas se conoce que la triaxialidad de tensiones tiene una fuerte influencia sobre la rotura de los materiales. En este trabajo se presenta un modelo de rotura para elementos de acero sometidos a tracción, basado en un comportamiento cohesivo del material y que contempla el valor de la triaxialidad de tensiones, diferente en cada punto de la sección crítica de rotura. The fracture of ductile materials, such as steel, is usually explained with the theory of nucleation, growth and coalescence of microvoids. Based on this theory, many numerical models have been developed, with a special mention to Gurson-type models. These models simulate mathematically the physical growth of microvoids, leading to a progressive development of the internal damage that takes place during a tensile test. In these models, the damage starts to develop in very early stages of the test. Tests carried out by the authors seem to point out that, in the case of eutectoid steel bars used for manufacturing prestressing steel wires, the internal damage that takes place as a result of the growth of microvoids is only noticeable in a very advanced state of the test. In addition to this, it is known that the stress triaxiality has a strong influence over the fracture of ductile materials. This work presents a fracture model for steel specimens in a tensile test, based on a cohesive behaviour and taking into account the effect of stress triaxiality, which is different in every point of the fracture plane.

Diseño y aplicación de una metodología prospectiva para la determinación de los condicionantes futuros del crecimiento de los grandes buques portacontenedores

Durante las últimas décadas se observa una tendencia sostenida al crecimiento en las dimensiones de los grandes buques portacontenedores, que produce, que las infraestructuras portuarias y otras destinadas al tráfico de contenedores deban adaptarse para poder brindar los servicios correspondientes y mantenerse competitivas con otras para no perder el mercado. Esta situación implica importantes inversiones y modificaciones en los sistemas de transporte de contenedores por el gran volumen de carga que se debe mover en un corto periodo de tiempo, lo que genera la necesidad de tomar previsiones relacionadas con la probable evolución a futuro de las dimensiones que alcanzarán los grandes buques portacontenedores. En relación a los aspectos citados surge la inquietud de determinar los condicionantes futuros del crecimiento de los grandes buques portacontenedores, con una visión totalizadora de todos los factores que incidirán en los próximos años, ya sea como un freno o un impulso a la tendencia que se verifica en el pasado y en el presente. En consideración a que el tema a tratar y resolver se encuentra en el futuro, con un horizonte de predicción de veinte años, se diseña y se aplica una metodología prospectiva, que permite alcanzar conclusiones con mayor grado de objetividad sobre probables escenarios futuros. La metodología prospectiva diseñada, conjuga distintas herramientas metodológicas, cualitativas, semi-cuantitativas y cuantitativas que se validan entre sí. Sobre la base del pasado y el presente, las herramientas cuantitativas permiten encontrar relaciones entre variables y hacer proyecciones, sin embargo, estas metodologías pierden validez más allá de los tres a cuatro años, por los vertiginosos y dinámicos cambios que se producen actualmente, en las áreas política, social y económica. Las metodologías semi-cuantitativas y cualitativas, empleadas en forma conjunta e integradas, permiten el análisis de circunstancias del pasado y del presente, obteniendo resultados cuantitativos que se pueden proyectar hacia un futuro cercano, los que integrados en estudios cualitativos proporcionan resultados a largo plazo, facilitando considerar variables cualitativas como la creciente preocupación por la preservación del medio ambiente y la piratería. La presente tesis, tiene como objetivo principal “identificar los condicionantes futuros del crecimiento de los grandes buques portacontenedores y determinar sus escenarios”. Para lo cual, la misma se estructura en fases consecutivas y que se retroalimentan continuamente. Las tres primeras fases son un enfoque sobre el pasado y el presente, que establece el problema a resolver. Se estudian los antecedentes y el estado del conocimiento en relación a los factores y circunstancias que motivaron y facilitaron la tendencia al crecimiento de los grandes buques. También se estudia el estado del conocimiento de las metodologías para predecir el futuro y se diseña de una metodología prospectiva. La cuarta fase, denominada Resultados, se desarrolla en distintas etapas, fundamentadas en las fases anteriores, con el fin de resolver el problema dando respuestas a las preguntas que se formularon para alcanzar el objetivo fijado. En el proceso de esta fase, con el objeto de predecir probables futuros, se aplica la metodología prospectiva diseñada, que contempla el análisis del pasado y el presente, que determina los factores cuya influencia provocó el crecimiento en dimensiones de los grandes buques hasta la actualidad, y que constituye la base para emplear los métodos prospectivos que permiten determinar qué factores condicionarán en el futuro la evolución de los grandes buques. El probable escenario futuro formado por los factores determinados por el criterio experto, es validado mediante un modelo cuantitativo dinámico, que además de obtener el probable escenario futuro basado en las tendencias de comportamiento hasta el presente de los factores determinantes considerados, permite estudiar distintos probables escenarios futuros en función de considerar un cambio en la tendencia futura de los factores determinantes. El análisis del pasado indica que la tendencia al crecimiento de los grandes buques portacontenedores hasta el presente, se ha motivado por un crecimiento económico mundial que se tradujo en un aumento del comercio internacional, particularmente entre los países de Asia, con Europa y Estados Unidos. Esta tendencia se ha visto favorecida por el factor globalización y la acelerada evolución tecnológica que ha permitido superar los obstáculos que se presentaron. Es de destacar que aún en periodos de crisis económicas, con pronósticos de contracciones en el comercio, en los últimos años continuó la tendencia al crecimiento en dimensiones, en busca de una economía de escala para el transporte marítimo de contenedores, en las rutas transoceánicas. La investigación de la evolución de los grandes buques portacontenedores en el futuro, se efectúa mediante el empleo de una metodología prospectiva en la que el criterio experto se valida con un método cuantitativo dinámico, y además se fundamenta en una solida base pre-prospectiva. La metodología diseñada permite evaluar con un alto grado de objetividad cuales serán los condicionantes que incidirán en el crecimiento en tamaño de los grandes buques portacontenedores en el escenario con mayor probabilidad de acontecer en los próximos veinte años (2032), y también en otros escenarios que podrían presentarse en el caso de que los factores modifiquen su tendencia o bien se produzcan hechos aleatorios. El resultado se sintetiza en que la tendencia al crecimiento de los grandes buques portacontenedores en los próximos 20 años se verá condicionada por factores en relación a los conceptos de oferta (los que facilitan u obstaculizan la tendencia), demanda (los que motivan o impulsan la tendencia) y factores externos (los que desestabilizan el equilibrio entre oferta y demanda). La tendencia al crecimiento de los grandes buques portacontenedores se verá obstaculizada / limitada principalmente por factores relacionados a las infraestructuras, resultando los pasos y/o canales vinculados a las rutas marítimas, los limitantes futuros al crecimiento en dimensiones de los grandes buques portacontenedores; y la interacción buque / infraestructura (grúas) un factor que tenderá a obstaculizar esta tendencia de los grandes portacontenedores. El desarrollo económico mundial que estimula el comercio internacional y los factores precio del petróleo y condicionantes medioambientales impulsarán la tendencia al crecimiento de los grandes buques portacontenedores. Recent years have seen a sustained tendency towards the growth in the dimensions of large container ships. This has meant that port and other infrastructure used for container traffic has had to be adapted in order to provide the required services and to maintain a competitive position, so as not to lose market share. This situation implies the need for major investments in modifications to the container transport system, on account of the large volume of traffic to be handled in a short period of time. This in turn has generated a need to make provision for the probable future evolution of the ultimate dimensions that will be reached by large container ships. Such considerations give rise to the question of what are the future determinants for the growth of large container ships, requiring an overall vision of all the factors that will apply in future years, whether as a brake on or an incentive to the growth tendency which has been seen in the past and present In view of the fact that the theme to be dealt with and resolved relates to the future, with a forecasting horizon of some 20 years, a foresight methodology has been designed and applied so as to enable conclusions about probable future scenarios to be reached with a greater degree of objectivity. The designed methodology contains different methodological tools, both qualitative, semi-quantitative and quantitative, which are internally consistent. On the basis of past and present observations, the quantitative elements enable relationships to be established and forecasts to be made. Nevertheless such an approach loses validity more than three or four years into the future, on account of the very rapid and dynamic changes which may be seen at present in political, social and economic spheres. The semi-quantitative and qualitative methodologies are used coherently together and allow the analysis of past and present conditions, thus obtaining quantitative results which for short-term projections, which when integrated with the qualitative studies provide results for the long-term, facilitating the consideration of qualitative variables such as the increasing importance of environmental protection and the impact of piracy. The principal objective of the present thesis is "to identify the future conditions affecting the growth of large container ships and to determine possible scenarios". The thesis is structured in consecutive and related phases. The first three phases focus on the past and present in order to determine the problem to be resolved. The background is studied in order to establish the state of knowledge about the factors and circumstances which have motivated and facilitated the growth tendency for large container ships and the methodologies that have been used. In this way a specific foresight methodology is designed. The fourth phase, Results, is developed in distinct stages based on the previous phases, so as to resolve the problem posed and responding to the questions that arise. In this way the determined objective is reached. The fourth phase sees the application of the methodology that has been designed in order to predict posible futures. This includes analysis of the past and present factors which have caused the growth in the dimensions of large container ships up to the present. These provide the basis on which to apply the foresight methods which enable the future factors which will condition the development of such large container ships. The probable future scenarios are made up of the factors identified by expert judgement (using the Delphi technique) and validated by means of a dynamic quantitative model. This model both identifies the probable future scenarios based on past and present factors and enables the different future scenarios to be analysed as a function of future changes in the conditioning factors. Analysis of the past shows that the growth tendency up to the present for large container ships has been motivated by the growth of the world economy and the consequent increased international trade, especially between the countries of Asia with Europe and the United States. This tendency has been favoured by the trend towards globalization and by the rapid technical evolution in ship design, which has allowed the obstacles encountered to be overcome. It should be noted that even in periods of economic crisis, with an expectation for reduced trade, as experienced in recent years, the tendency towards increased ship dimensions has continued in search of economies of scale for the maritime transport of containers on transoceanic routes. The present investigation of the future evolution of large container ships has been done using a foresight methodology in which the expert judgement is validated by a dynamic quantitative methodology, founded on a firm pre-foresight analysis. The methodology that has been designed permits the evaluation, with a high degree of objectivity, of the future factors that will affect the growth of large container ships for the most probable scenario expected in the next 20 years (up to 2032). The evaluation applies also to other scenarios which may arise, in the event that their component factors are modified or indeed in the light of random events. In summary, the conclusión is that the tendency for growth in large container ships in the future 20 years will be determined by: factors related to supply, which slow or halt the tendency; factors related to demand, which encourage the tendency and finally, external factors which interrupt the equilibrium between supply and demand. The tendency for increasing growth in large container ships will be limited or even halted by factors related to infrastructure, including the natural and man-made straits and canals used by maritime transport. In addition the infrastructure required to serve such vessels both in port (including cranes and other equipment) and related transport, will tend to slow the growth tendency. The factors which will continue to encourage the tendency towards the growth of large container ships include world economic development, which stimulates international trade, and an increasing emphasis on environmental aspects.

Reliability and quality in the area of statistical thinking in Engineering

There is remarkable growing concern about the quality control at the time, which has led to the search for methods capable of addressing effectively the reliability analysis as part of the Statistic. Managers, researchers and Engineers must understand that 'statistical thinking' is not just a set of statistical tools. They should start considering 'statistical thinking' from a 'system', which means, developing systems that meet specific statistical tools and other methodologies for an activity. The aim of this article is to encourage them (engineers, researchers and managers) to develop a new way of thinking.

Las matemáticas del amor

Es indiscutible que las matemáticas resultan imprescindibles en la mayoría de las áreas científicas y son el fundamento de numerosos avances de la técnica. En este trabajo se pone de manifiesto como esta ciencia también puede explicar, ayudar y modelar problemas de tipo puramente social y humano. Concretamente veremos como puede aplicarse al estudio de las relaciones de pareja. Áreas como la estadística, la teoría de juegos, la geometría o las ecuaciones diferenciales entre otras, son válidas para ello.

Online games for the teaching of mathematics

In this article we present a didactic experience developed by the GIE (Group of Educational Innovation) “Pensamiento Matemático” of the Polytechnics University of Madrid (UPM), in order to bring secondary students and university students closer to Mathematics. It deals with the development of a virtual board game called Mate-trivial. The mechanics of the game is to win points by going around the board which consists of four types of squares identified by colours: “Statistics and Probability”, “Calculus and Analysis”, “Algebra and Geometry” and “Arithmetic and Number Theory ”. When landing on a square, a question of its category is set out: a correct answer wins 200 points, if wrong it loses 100 points, and not answering causes no effect on the points, but all the same, two minutes out of the 20 minutes that each game lasts are lost. For the game to be over it is necessary, before those 20 minutes run out, to reach the central square and succeed in the final task: four chained questions, one of each type, which must be all answered correctly. It is possible to choose between two levels to play: Level 1, for pre-university students and Level 2 for university students. A prototype of the game is available at the website “Aula de Pensamiento Matemático” developed by the GIE: http://innovacioneducativa.upm.es/pensamientomatematico/. This activity lies within a set of didactic actions which the GIE is developing in the framework of the project “Collaborative Strategies between University and Secondary School Education for the teaching and learning of Mathematics: An Application to solve problems while playing”, a transversal project financed by the UPM.