Après les splendeurs de la construction romaine, les compétences techniques et les connaissances relatives au béton ne se transmettent que localement et en sous-main, jusqu’à ce qu’au cours du XVIIIe siècle, dans plusieurs régions d’Europe, de nombreux chercheurs et constructeurs s’intéressent à l’étude de la chaux, des mortiers et des ciments. Les recherches sur les roches se multiplient afin de découvrir des matières premières facilement disponibles dans la nature pour produire des mortiers qui soient non seulement résistants, durs et compacts, mais aussi capables de durcir sous l’eau. Ces travaux sont stimulés tant par l’étude de l’archéologie et par la découverte de diverses oeuvres d’ingénierie hydraulique réalisées par les Romains, dont la résistance prend des connotations mythiques dans la littérature technique de l’époque, que par un besoin croissant de matériaux utiles à la construction de grandes oeuvres pour le développement du commerce (ports, ponts, canaux navigables et écluses) ou pour la défense militaire. À cette combinaison d’intérêts théoriques et pratiques s’ajoute la passion pour les explorations géographiques et les études naturalistes soutenues par les outils de la chimie moderne qui, depuis le siècle précédent, prend progressivement la place de l’alchimie, à la fois fascinante et insuffisamment vérifiable. Ainsi, des concepts au caractère presque magique, comme celui de phlogistique, sont abandonnés, tandis qu’à la moitié du XVIIIe siècle, le médecin et chimiste écossais Joseph Black découvre le cycle de transformation de la pierre à chaux en chaux, puis à nouveau en pierre à chaux. La découverte de l’origine de la capacité de certaines chaux à durcir dans l’eau, également appelée propriété hydraulique, est due aux recherches de nombreux chimistes et est attribuée, entre la fin du XVIIIe siècle et le début du XIXe siècle, à la présence de minéraux argileux dans certaines pierres calcaires, ouvrant ainsi la voie vers l’invention du ciment moderne, devenu célèbre sous le nom commercial de Portland.

Since 1989, and every 5 years, a group of database system researchers gather to reflect on the state of our field, to discuss the key directions the community is pursuing, and to speculate about the opportunities that lie ahead. The last meeting took place in Cambridge, Massachusetts, USA  in October 2023.

Recent advancements in large-scale additive manufacturing have extended its application in the building industry, delivering notable gains in productivity, efficiency, environmental sustainability, and safety compared with traditional construction methods. Aerial additive manufacturing (aerial AM), which uses aerial robots for unbounded construction tasks, offers distinct advantages, such as scalability at height, enhanced access to remote or challenging locations, and rapid on-demand repair capabilities. Despite several small-scale demonstrations, deploying aerial robots in construction still presents critical challenges and unresolved scientific questions. This Review provides a comprehensive analysis of current aerial AM research, highlights key opportunities and challenges at large scales, and introduces an autonomy framework aimed at clarifying the overarching challenges inherent in the technology.

Cet entretien vidéo réunit Dimitri Démétriadès, Patrick Chiché et Dimitri Papadaniel autour des enjeux portés par leurs projets notamment dans le domaine de l’architecture solaire et de l’expérimentation constructive.

Présenté dans le cadre de l'exposition: "Sun Shines on Architecture", Archizoom EPFL, Lausanne (21.03.2025 - 21.06.2025)

Previous research has demonstrated the existence of gender and sexuality differences in attitudes toward gay people (which in this paper includes both lesbian women and gay men unless specified). However, these studies did not account for people with diverse genders and sexual orientations ascribing different meanings to their gender identification and its potential role in attitudes towards gay people. This study aimed to analyze the relationship between gender identification and attitudes toward gay people among individuals of different genders and sexual orientations. Based on data obtained from 851 Russian respondents, the study reports the exploration of the direct link between two components of gender identification and four components of attitudes toward gay men and lesbians. Results indicated that stronger gender identification, in general, was related to more negative attitudes toward both gay men and lesbians. At the same time, compared to women and bisexual respondents, this link was stronger among men and straight participants respectively. A possible explanation via traditional gender ideologies is discussed.

Distributed systems, which enable the efficient processing of large-scale data and complex tasks across multiple interconnected processes, offer significant advantages over single-machine systems. These include enhanced scalability, improved fault tolerance, and the effective utilization of geographically distributed resources. A fundamental challenge in such systems lies in achieving coordination among unsynchronized processes that often operate over unreliable networks and must tolerate various types of failures. Achieving consensus -- agreement on a shared state or decision across processes -- is central to overcoming this challenge but remains a highly non-trivial problem. Consensus mechanisms underpin critical (distributed) services such as distributed key generation (DKG), secure multi-party computation (MPC), blockchain technologies, and state machine replication (SMR), emphasizing their indispensable role in modern computing.

Despite their significance, existing consensus protocols face notable limitations. Many struggle to scale efficiently due to poor performance or over-reliance on cryptographic tools such as threshold signatures, which demand costly setup and computationally intensive algebraic operations. Furthermore, reliance on these ``heavyweight'' cryptographic primitives compromises their security in a post-quantum world. As distributed systems continue to grow in scale and importance, there is a pressing need for consensus solutions that are not only efficient but also resilient to emerging security threats and future technological advancements.

This thesis addresses these challenges by revisiting two fundamental problems in distributed computing -- \emph{graded consensus} and \emph{Byzantine agreement}. We present the first complexity-optimal protocols for these problems that either leverage only lightweight'' cryptographic primitives, such as hash functions, or entirely eliminate the reliance on cryptography. Our solutions span all major network models -- \emph{asynchrony}, \emph{partial synchrony}, and \emph{synchrony}. By introducing algorithms that match or exceed the best known solutions, all while relying on little'' cryptography, this thesis advances the state of the art in consensus protocols and lays the foundation for more efficient and future-proof distributed systems capable of meeting the evolving demands of modern computing.

Settlement Freidorf near Basel was the first global cooperative in Switzerland, in which a group of people organized parts of their lives - such as housing, consumption, and education - collectively instead of privately. It was commissioned by the Union of Swiss Consumer Associations (USC) and completed in 1924 as the first large project of Swiss architect Hannes Meyer (1889-1954).

This thesis aims at a deeper and comprehensive understanding of this work of architecture, as a case study depicting the possibilities and limitations of co-operative housing in general. As a prologue, two historical sources are presented. On the one hand, there is the influential novel The Goldmakers' Village (Das Goldmacherdorf) from 1817, by German writer Heinrich Zschokke, considered as the first co-op novel. This work of fiction is a founding document of the ideas and theories that led to Freidorf. On the other hand, there is the black-and-white film made by Fritz MattmÃŒller between 1920 and 1923, showing the construction of Freidorf. These images are silent witnesses of the material genesis of the Siedlung, but also of the way it was used and inhabited following completion.

The actual thesis consists of five parts. The first part is an overview of the literature on both Freidorf and its architect, to show how both have been historized and interpreted so far. The second part is a minute description of Meyer's biography leading up to 1919, in which he first visited the building site in Muttenz. The third part is a reconstruction of the social history and the theoretical arguments, mainly in Switzerland and in the German-speaking world, concerning the organization of consumers and the planning of co-operative housing. Starting in the late 18th century, theorizations were developed to "crush the vice of capitalism", as Swiss economist Johann Friedrich Schär expressed it, when writing about Freidorf in 1921. In the fourth part, the monographic approach of the second part is mixed with the history of ideas in the third part, by means of a reconstruction of the genesis of Siedlung Freidorf. Archival analysis of the more than hundred board meetings of the cooperative - the first was held on May 20th, 1919 - structures a chronology of the problems that arose and the decisions that were taken, both organizational and architectural, during the construction of Freidorf, up until the official inauguration on June 1st, 1924.

The fifth and final part is an examination of the immediate reception, interpretation, and representation of the project, by means of its presence at the Exposition Internationale de la Cooperation et des Oeuvres Sociales by the International Cooperative Alliance, in the summer of 1924 in Ghent. Here, Meyer installed the Theater Co-op: an auditorium, a series of paintings, a glazed showcase with consumer goods, as well as a puppet theater performing the dream of cooperation and its realization in Freidorf. Architecture became propaganda, but the event was also the occasion for Meyer to look back - critically - on what he had achieved.

In the epilogue of the thesis, a set of interpretations is given of the well-known image "Co-op Interieur", produced by Hannes Meyer in 1926, shortly after the completion of Freidorf. In an appendix, six of his seminal articles relating to Freidorf and written between 1919 and 1924, are translated into English, as well as two texts by Johann Friedrich Schär, and Bernhard Jaeggi and Karl

Porous media are solid structures perforated by a matrix of pores, which may let a fluid flow across them. Geometrically, we can classify them as "thin" if their thickness is comparable with the size of their pores, and "bulk" otherwise. These structures can be found in various biological and man-made systems, such as cell membranes, sponges, insect feathers, flow control devices for aerodynamics and cooling applications and filtration devices. A common feature of these systems is the presence of a large difference in size between the pores and the full membrane. From the modeling point of view, two approaches are generally considered: direct solutions of the governing equations and average models. The first strategy guarantees high accuracy but may easily become computationally unaffordable, particularly when the pores are very small compared to the membrane. The second approach models the effect of the membrane using mathematical relations between the flow far from the membrane and the pore-scale behavior. These laws often rely on empirical coefficients, thus limiting their predictive capabilities. However, the computational cost associated with them is tiny compared to direct solutions, and they find use in many engineering simulation routines. Thanks to multi-scale techniques such as homogenization, we can derive such average models from first principles and find out that the coefficients appearing inside them stem from the solution of a set of solvability conditions valid at the pore level. Starting from the elementary case of Stokes flow across a thin membrane, developed by Zampogna & Gallaire (2020), we build further pieces of theory into this framework. Inspired by the microstructure heterogeneities found at the cellular level or in defective man-made membranes, in chapter 2, we introduce an efficient adjoint-based methodology to evaluate the effect of many geometric modifications of the microstructure at a glance. The effect of inertia at the pore level, which is relevant for applications in the flow-control domain, is introduced in chapter 3, where we also consider the presence of a solute advected by the fluid flow. These chapters use a simple but effective approximation, consisting of a unique value for the homogenized flow variables on the membrane. This approximation, however, is sub-optimal when we deal with ``contradictory'' membrane properties, found in the so-called "Janus membranes". A new, discontinuous flow description at the membrane level in the presence of solute transport is described in chapter 4. The model is subsequently used in chapter 5 to deal with diffusio-phoresis, i.e. when a difference in local solute concentration, interacting with the membrane wall, causes a fluid flow. However, in many systems such as reverse-osmosis filters and cell membranes, the pore dimensions are so small that a continuous flow description may not be accurate. In such cases, the proper simulation tool is constituted by molecular dynamics simulations. In chapter 6, we present some results of the coupling between conventional molecular dynamics simulations and homogenization. The objective of this chapter is to propose a hybrid strategy to exploit the convenient computational cost of homogenization with the accuracy of molecular dynamics simulation. In chapter 7, we summarize the main results and discuss future perspectives for our methodology.

This thesis addresses key challenges in developing adaptive lower-limb exoskeletons to enhance balance, mobility, and user autonomy during daily living activities. It presents a comprehensive exploration of three critical aspects: push recovery during standing, partial assistance during gait and stair navigation, and real-time locomotion transition detection.

A novel push recovery framework integrates a bio-inspired stepping strategy and online optimization of step parameters, enabling natural and effective responses to external perturbations. Experimental validation demonstrates the framework's capability to enhance stability and support synergistic human-exoskeleton interaction.

To support daily living activities such as walking and stairs navigation, 3D path and flow controllers were developed, extending 2D implementations by incorporating hip abduction/adduction control to improve mediolateral stability. These controllers maintain natural movement variability while offering targeted balance assistance. Experimental results reveal that the path controller enhances trajectory alignment with inter-joint coordination patterns, while the flow controller provides intuitive and user-preferred support.

For locomotion transition detection, a machine learning-trained threshold-based method was introduced, achieving high real-time classification accuracy across two distinct exoskeletons, eWalk and Autonomyo. Personalization techniques, including Bayesian optimization, tailored the system to individual gait patterns, enhancing robustness and adaptability.

The findings emphasize the importance of incorporating dynamic balance mechanisms, intuitive control frameworks, and user-specific adaptability to address the complex demands of daily living activities while maintaining user autonomy and comfort. Future research should aim to integrate all these aspects, balance recovery, partial assistance during daily living activities, and transition detection, into cohesive frameworks. These frameworks should explore dynamic and real-world environments while prioritizing user-centric design approaches. Involving end-users, physiotherapists, and clinicians in the development process can further enhance that exoskeleton systems align with practical needs and preferences, advancing their potential to improve mobility and quality of life for individuals with walking impairments.

Multi-Object Tracking (MOT) is a fundamental computer vision task that involves detecting objects of interest in video frames and associating detections of the same object across time to form trajectories. For association, appearance cues, extracted through person re-identification (ReID) models, play a crucial role by capturing distinctive visual features of the tracked targets. However, despite its importance for tracking, ReID has primarily been studied as an image retrieval problem, with state-of-the-art methods overlooking tracking-specific challenges. This thesis focuses on advancing person re-identification methods, with a particular emphasis on making them more robust and better suited for tracking applications. A key challenge in ReID and MOT is handling occlusions, where targets become partially hidden by objects or other people, leading to degraded re-identification accuracy and potential identity switches in tracking. Additionally, tracking methods often fail to effectively combine ReID with motion cues and scene context, relying instead on naive association strategies. To address these challenges, this thesis makes three key contributions: BPBreID, a part-based method for robust occluded re-identification; KPR, a keypoint promptable ReID model designed to address multi-person occlusions scenarios; and CAMELTrack, an online tracking-by-detection method that replaces traditional heuristic for detection association with a context-aware learnable module. At the time of writing, KPR and CAMELTrack achieve state-of-the-art performance on widely-used benchmarks for occluded person re-identification and multi-object tracking. Complementary to this thesis work, additional research contributions were made in sports analytics, including the development of specialized re-identification models for athletes and the introduction of novel datasets for player tracking, re-identification, and jersey number recognition. The thesis concludes with a critical analysis of the current state of tracking and re-identification technologies, offering my opinionated view about the future of these two rapidly evolving fields.