Ant collectives and their fluctuations

Treballs Finals de Grau de Física, Facultat de Física, Universitat de Barcelona, Curs: 2021, Tutors: Alberto Fernández-Nieves, Ramon PlanetWe know a lot about the behaviour of matter on equilibrium. In particular, we know fluctuations follow the central limit theorem. In contrast, only recently have we began to really understand how out of equilibrium active matter behaves. Here, we use fire ants and explore the relationship between ant number fluctuations and system size. We do this for two distinct ant states: a collective active state and a preferentially non-active state. We find that while fluctuations in the predominantly non-active state are similar to fluctuations in equilibrium systems, in the collective active there are giant number fluctuation

3D Reconstruction with Uncalibrated Cameras Using the Six-Line Conic Variety

We present new algorithms for the recovery of the Euclidean structure from a projective calibration of a set of cameras with square pixels but otherwise arbitrarily varying intrinsic and extrinsic parameters. Our results, based on a novel geometric approach, include a closed-form solution for the case of three cameras and two known vanishing points and an efficient one-dimensional search algorithm for the case of four cameras and one known vanishing point. In addition, an algorithm for a reliable automatic detection of vanishing points on the images is presented. These techniques fit in a 3D reconstruction scheme oriented to urban scenes reconstruction. The satisfactory performance of the techniques is demonstrated with tests on synthetic and real data

Problemas de estimación en transmisión digital: Demostraciones por métodos elementales

En el diseño de receptores de sistemas de transmisión digital es necesario resolver ciertos problemas de estimación de variables aleatorias o procesos aleatorios a partir de observaciones de los mismos afectadas por distorsión y ruido. En este breve documento abordamos estos problemas de estimación mediante métodos matemáticos absolutamente elementales. La observación básica es que si sabemos encontrar el mínimo de una función cuadrática real de variable compleja, podemos resolver estos problemas de forma sencilla y rigurosa. En particular evitamos el uso del principio de ortogonalidad, que requeriría que el lector estuviera familiarizado con el manejo de un espacio de variables aleatorias como conjunto con producto interno

Directional Geodesic Active Contours

We present a non-conformal metric that generalizes the geodesic active contours approach for image segmentation. The new metric is obtained by adding to the Euclidean metric an additional term that penalizes the misalignment of the curve with the image gradient and multiplying the resulting metric by a conformal factor that depends on the edge intensity. In this way, a closer fitting to the edge direction results. The provided experimental results address the computation of the geodesics of the new metric by applying a gradient descent to externally provided curves. The good performance of the proposed techniques is demonstrated in comparison with other active contours methods

Research overview of cooling in office buildings

This chapter serves as a general introduction to the topics explored throughout the dissertation, presenting a panorama of the available knowledge on façade related cooling strategies in office buildings. This was carried out by categorising and discussing reported research experiences from the past 25 years in order to identify knowledge gaps and define current paths and trends for further exploration. Peer reviewed journal articles were selected as the source for the study, given the reliability of the information published under peer-review processes. Several queries were carried out throughout online journal article databases, considering published papers from 1990 onwards. The resulting article database was then explored through descriptive analysis and in-depth review of some articles to expand on specific topics in order to thoroughly visualise scientific interest and tendencies within the field of study for the last 25 years. Results show the high current relevance of cooling research, having experienced an increase of publications under different climate contexts and varied topics ranging from passive to solar cooling, which is seen as a research field on its own. Also, in terms of research methods, software simulations seem to be the primary tool for cooling research, which makes sense for performance driven developments. On the other hand, the main knowledge gaps identified are the need for specific research regarding possibilities for application and architectural integration of cooling systems; the lack of articles addressing some specific cooling strategies, such as the use of evaporative and ground cooling; and the need for more information about the operation of cooling systems, especially taking users’ perception and their behaviour into account

Conclusion

This dissertation aimed to explore the possibilities and constraints for the façade integration of solar cooling systems, in order to support the design of climate responsive architectural products for office buildings as an alternative to conventional AC systems. This final chapter summarises and discusses the main outcomes of the dissertation. Firstly, responses to the research questions are showcased, starting with the subquestions and their particular findings, leading to a comprehensive answer to the main research question driving the research project. Then, general conclusions are drafted, outlining the scientific contribution and limitations of the study to finalise with recommendations for further developments in the field

COOLFACADE: Architectural Integration of Solar Cooling Technologies in the Building Envelope

The thesis ‘COOLFACADE – Architectural integration of solar cooling strategies in the building envelope’ aims to shed light on the possibilities and constraints for architectural integration of solar cooling systems in façades, in order to support the design of climate responsive architectural products for office buildings as self-sufficient alternatives to conventional air-conditioning systems. Increasing cooling needs in the built environment present an important and complex challenge for the design of sustainable buildings and cities. Even though the first course of action should always aim to reduce energy consumption through saving measures and passive design, this is often not enough to avoid mechanical equipment altogether, particularly in the case of office buildings in warm climate contexts. Solar cooling technologies have been increasingly explored, as an environmentally friendly alternative to harmful refrigerants used within vapour compression systems; while also being driven by solar, thus, renewable energy. The principles behind some of these technologies have been researched for over a century, reaching mature solutions and components, and being recognised as promising alternatives to common air-conditioning units. Nonetheless, building application remains mostly limited to demonstration projects and pilot experiences. Recently, façade integrated concepts have been explored, as a way to promote widespread application throughout the development of multifunctional building components. However, while these are regarded as relevant and promising standalone concepts, further research is still needed to assess the integration potential of diverse solar cooling technologies, and identify barriers to overcome, in order to promote the widespread application of solar cooling components in the built environment. The aim of this research project is to explore the possibilities and constraints for architectural integration of solar cooling strategies in façades, in order to support the design of climate responsive architectural products for office buildings, without compromising the thermal comfort of users. The underlying hypothesis then is that self-sufficient solar cooling integrated facades may be a promising alternative to conventional centralised air-conditioning systems widely used in office buildings in warm climates. Most research efforts on solar cooling currently deal with the optimisation of the systems in terms of their performance, testing new materials and simplifying their operation to increase reported efficiencies. However, there is a lack of knowledge on the requirements and current limits for widespread façade application. In order to achieve the research goal and comprehensively assess the façade integration potential of solar technologies and discuss current barriers, different aspects must be acknowledged. These distinct aspects are addressed through several research questions, which in turn define the different chapters of the dissertation. Introduction and conclusions aside, the research body is structured on three sequential parts, with 2-3 chapters each. The first part deals with the state-of-the-art in the field and the theoretical framework, laying the groundwork for the following sections. The second part explores different aspects required as input for façade integration; while the third part comprises the evaluation of solar cooling technologies in terms of current possibilities and constraints for the development of integrated façades, based on the inputs identified in the second part. Furthermore, all chapters were published or submitted for publication as scientific articles in peer review academic journals. The first part considers two chapters that lay the foundations for the research project, The first chapter after the introduction expands the background of the dissertation by identifying knowledge gaps and research trends while contributing to the generation of a reference database of research experiences, throughout a systematic literature review of cooling research in office buildings during the last 25 years. On the other hand, the following chapter delves specifically in the main themes addressed within the dissertation, proposing a framework for the understanding of solar cooling integrated façades. This considers the theoretical discussion of the concept of architectural façade integration; and the identification of the main working principles and technical components from most common solar cooling technologies, based on a state-of-the-art review. The second part explores different required inputs for façade integration. Design and construction requirements for façade integration are explored; while the response from façade design parameters to various climate conditions is assessed in parallel. The exploration of design and construction requirements is conducted through the identification of the main perceived problems for the façade integration of building services and solar technologies, by means of a survey addressed to façade professionals. On the other hand, a separate chapter explores the relation between climate conditions and cooling requirements in office buildings, evaluating the potential impact of several passive cooling strategies in various warm climates, as a first step before considering further technologies. This was conducted through the statistical analysis of reported research experiences, and dynamic energy simulations of a base scenario using specialised software. The third part of the dissertation consists of two chapters that incorporate previous outcomes for the evaluation of selected solar cooling technologies in terms of current possibilities and constraints for the development of integrated façades. The first of these chapters showcases a qualitative evaluation of the façade integration potential of several solar cooling technologies, based on a comprehensive review of key aspects of each technology and their prospects to overcome the identified barriers for façade integration. This is complemented by a feasibility assessment of integrated concepts in several climates, throughout numerical calculations based on climate data and building scenarios simulated with specialised software; showcased in the following and final chapter. The driving force of the research project is the intention to test the limits of solar cooling integration in façades, showcasing current possibilities while identifying technical constrains and barriers to overcome for the widespread application of integrated façade concepts. Although interesting prospects were identified in this dissertation, important technical constraints need to be solved to conceive a façade component fail-tested for application in buildings. Furthermore, several barriers related to the façade design and development process would need to be tackled in order to introduce architectural products such as these into the building market. The identification and discussion of these barriers, along with the definition of technology driven development paths and recommendations for the generation of distinct architectural products, are regarded as the main outcomes of this dissertation, serving as a compass to guide further explorations in the topic, under an overall environmentally conscious design approach

The wage gap between immigrant and native workers in Spain: an analysis using matched employer-employee data

The fact that Spain has witnessed a sharp increase in the number of immigrants over the past decade has generated considerable interest, particularly as regards wages earned by immigrants in host industries. We analyze whether controlling for both observable and unobservable characteristics of employers —in addition to individual variables and the economic context— makes any difference as regards the debate regarding the existence of wage differences between immigrant and native workers in Spain. As we show, doing this considerably reduces (or even eliminates) the inequalities found in previous research, thereby questioning the results attained by previous studies on this issue.Immigration, salaries, assimilation.

Tourist Influence on Nightlife Noise

Although environmental noise from entertainment and leisure activities is causing a growing number of complaints from EU population, this noise issue is not covered by the current EU initiatives on environmental noise management. This noise problem is difficult to tackle strategically and technically – no specific standards have yet been established for measurements, methods and indicators, and the practical remedies are still limited. This paper reviews nightlife noise and more specifically how the presence of tourists influences the variation of the noise. Several case studies were conducted in some Spanish locations by the seasonal tourist incursion, mainly in the summer months. Variations in the nightlife noise in recreational zones during the weekends and “working days” are compared. This research also discusses data from different years and seasonal periods and reinforced with data obtained through surveys specifically designed for foreign tourists. These surveys reveal practical information about how tourists perceive noise, and their behaviour and reactions to it. Those data could be useful for Environmental Noise Authorities to develop noise action plans, as recreational noise is a source not considered when noise mapping by means of using simulation techniques