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Uncertainty reduction in robust optimization
No full textInternational audienceUncertainty reduction has recently been introduced in the robust optimization literature as a relevant special case of decision-dependent uncertainty. Herein, we identify two relevant situations in which the problem is polynomially solvable. We further provide insights into possible MILP reformulations and the strength of their continuous relaxations
Ontology-Based Query Answering over Datalog-Expressible Rule Sets is Undecidable
No full textInternational audienceOntology-based query answering is a problem that takes as input an ontology R (in our context, a set of existential rules), a set F of facts, and a Boolean conjunctive query (CQ) q, and asks whether q follows from (R, F) under standard first-order semantics. This problem is undecidable in general, and a widely investigated approach to tackle it in some cases is query rewriting: given a "rule query" (R, q), we compute a Boolean query q' such that, for any fact set F, it holds that q follows from (R, F) if and only if q' follows from F. Insofar, previous work has mostly focused on output queries q' expressed as union of Boolean conjunctive queries (UCQs), and an effective algorithm that computes such a query q' whenever it exists has been proposed in the literature. However, UCQ-rewritability is not a very general notion and many real-world interesting rule queries do no admit UCQ-rewritings. This raises the question whether such a generic algorithm can be designed for a more expressive target language, such as datalog. We solve this question by the negative, by studying the difference between datalog-expressibility and datalog-rewritability. More precisely, we show that query answering under datalog-expressible rule queries is undecidable
Epid Data Explorer: A Visualization Tool for Exploring and Comparing Spatio-Temporal Epidemiological Data
No full textInternational audienceThe analysis of large sets of spatio-temporal data is a fundamental challenge in epidemiological research. As the quantity and the complexity of such kind of data increases, automatic analysis approaches, such as statistics, data mining, machine learning, etc., can be used to extract useful information. While these approaches have proven effective, they require a priori knowledge of the information being sought, and some interesting insights into the data may be missed. To bridge this gap, information visualization offers a set of techniques for not only presenting known information, but also exploring data without having a hypothesis formulated beforehand. In this paper, we introduce Epid Data Explorer (EDE), a visualization tool that enables exploration of spatio-temporal epidemiological data. EDE allows easy comparisons of indicators and trends across different geographical areas and times. It facilitates this exploration through ready-to-use pre-loaded datasets as well as user-chosen datasets. The tool also provides a secure architecture for easily importing new datasets while ensuring confidentiality. In two use cases using data associated with the COVID-19 epidemic, we demonstrate the substantial impact of implemented lockdown measures on mobility and how EDE allows assessing correlations between the spread of COVID-19 and weather conditions
Butterfly probes: estimating the derivative of the magnetic field
No full textInternational audienceThe main way to increase the spatial selectivity hasbeen to make coils with smaller and smaller diameters. Thisis especially true for secure applications (side-channel attacks).In this paper, we investigate an alternative way with secureapplications in mind. It consists in designing probes that measurethe derivative of the magnetic flux instead of the flux itself.The paper presents the motivation, the concept and preliminaryresults obtained with a first prototype
Unified protocol to evaluate intraoral scanner resolution, trueness and precision: the RTP-protocol
No full textInternational audienceOver the past decade, studies published on the evaluation of intraoral scanners (IOSs) have mainly considered two parameters, precision and trueness, to determine accuracy. The third parameter, resolution, not much studied, seems essential for an application in dentistry. Objective: The objective of this preliminary study is to create an original method – a Resolution-Trueness- Precision (RTP) protocol to evaluate these three main parameters – resolution trueness and precision – at the same time. Material and Method: A ceramic tip with particular and calibrated dimensions is determined as the reference object and its mesh recorded with a scanning microtomograph, and compared with the one extracted to the IOS. It is the particular geometric shape of the object that will make it possible to simultaneously assess: resolution, trueness and precision. Results: The results have shown a mean resolution of 79.2 μm, a mean for trueness of 17.5 and a mean for precision of 12.3 μm. These values are close to previous results published for this camera. So, the RTP protocol is the first including the three parameters at the same time. Simple, fast and precise, its application can be useful for comparisons between IOSs within research laboratories or test organizations. Finally, this study could be a first step to create a reference kit for practitioners allowing them to control the quality of their IOS over time
Hardware accelerator for FIPS 202 hash functions in post-quantum ready SoCs
No full textInternational audienceIn today’s digital landscape, cryptography plays a vital role in ensuring communication security through encryption and authentication algorithms. While traditional cryptographic methods rely on hard mathematical problems for security, the rise of quantum computing threatens their effectiveness. Post-Quantum Cryptography (PQC) algorithms, like CRYSTALSKyber, aim to withstand quantum attacks. Recently standardized, CRYSTALS-Kyber is a lattice-based algorithm designed to resist quantum attacks. However, its implementation faces computational challenges, particularly with Keccak-based functions, which are crucial for security and upon which the FIPS 202 standard is based. Our paper addresses this technological challenge by designing a FIPS 202 hardware accelerator to enhance CRYSTALS-Kyber efficiency and security. We chose to implement the entire FIPS 202 standard in hardware in order to widen the applicability of the accelerator to all possible algorithms that rely on such hash functions, taking care to provide realistic assumptions on system-level integration inside a System-on-Chip (SoC). We provide results in terms of area, frequency, and clock cycles for both ASIC and FPGA targets. An area reduction of up to 22.3% is achieved with respect to state-ofthe-art solutions. In addition, we integrated the accelerator inside a 32-bit RISC-V based security-oriented SoC, where we show a strong performance gain on CRYSTALS-Kyber execution. The design presented in this paper performs better in all Kyber1024 primitives, with an improvement up to 3.21× in Kyber-KeyGen
Can we harmonize the monitoring of plants and pollinators?
No full textMeeting report on the symposium ‘New solutions to monitor plants, pollinators and their interactions in a changing world’, held at Collège de France and Muséum national d'Histoire naturelle, Paris, France, 23–24 May 2024International audiencePollution, climate change, and shrinking habitats are driving major changes in flowering plant and pollinator populations. These include shifts in local abundance, population extirpations, range shifts, altered community composition, and reshuffled interactions. To date, evidence for these changes mostly reflect opportunistic efforts to collect occurrence data to document distributions. Coarse-scale perspectives on biodiversity change can be invaluable, especially when threats to rare habitats are widely distributed, but many changes occur slowly (decades) at such scales. Opportunistic occurrence data are therefore generally less useful for detecting short-term trends and monitoring the effectiveness of conservation policies. They are also typically biased for large-scale surveillance monitoring (Boyd et al., 2022) and rarely encompass both plants and pollinators, limiting our ability to estimate broad and fine-scale trends in populations and plant–pollinator interactions. Ecologists often prefer using plot-based methods for systematic surveys and monitoring, as these provide quantitative data on abundance and distributions. Resurveying such plots adds a time dimension, greatly enriching our understanding of how species abundances and distributions shift in response to drivers of global change. Monitoring and resurvey data remain scarce, leaving pictures of ecological conditions and change uncertain. Except for Switzerland and the UK, countries are slow to support systematic programs to monitor plants and pollinators.The 23–24 May Paris symposium on ‘New solutions to monitor plants, pollinators and their interactions in a changing world’ brought scientists together to assess the state of plant and pollinator monitoring schemes in Europe and to ponder how these might be improved, extended, and coordinated (https://www.college-de-france.fr/fr/agenda/colloque/nouvelles-approches-pour-le-suivi-des-plantes-des-pollinisateurs-et-de-leurs-interactions-dans-un). This group met to review existing schemes, compare the trends and indicators they produce, and outline future needs for research and policy. These needs include expanding the number of plots, species and habitats monitored, the different methods (e.g. by citizen scientists) and how frequently they are surveyed; how to identify and locate plants and insects quickly and reliably (including new technologies); how best to coordinate plant and pollinator sampling; and statistical tools to integrate heterogeneous data and infer causal relationships
Optimal Bending Stiffness Design of a Soft Micro-Robot for Cochlear Implantation
No full textInternational audienceIn this paper, a design method for a Soft Micro-Robot (SMR) used for medical intervention in the context of cochlear implant insertion is proposed. Optimal design of cochlear implants has been a highly active research area in recent years. Dozens of articles address the topic of optimal design using different actuation strategies, resulting overall in promising outcomes. From magnetic to fluid actuation and concentric tubes, current strategies are based on generating an optimal bending moment. However, this approach gives optimal results that cannot be manufactured. Considering the manufacturing constraints of micro-scale soft robots, an optimal design method based on varying the robot bending stiffness is studied here. The cochlear implant is actuated by a tendon and has an optimal bending stiffness to achieve a given objective. In the context of cochlear insertion, this objective is to minimize the root mean square error (RMSE) of the robot neutral axis in comparison to the cochlea helically shaped center-line. Simulation results are promising with an average distance error of 392μm and a standard-deviation of 33μm considering the robot material and manufacturing uncertainties
Kolmogorov complexity as a combinatorial tool
No full textInternational audienceKolmogorov complexity is often used as a convenient language for counting and/or probabilistic existence proofs. However, there are some applications where Kolmogorov complexity is used in a more subtle way. We provide one (somehow) surprising example where an existence of a winning strategy in a natural combinatorial game is proven (and no direct proof is known)