Center for MathematicaL studies and their Applications

IntroductionThe recognized credibility crisis in scientific research has led to an increasing focus on reproducibility studies, particularly in computer science. Existing studies predominantly examine specific technological aspects of reproducibility but neglect the critical interplay between authors and publishers in enabling reproducible computational scientific research.MethodsA systematic review was conducted following the PRISMA Literature Review methodology, complemented by a Journals Survey. This approach enabled a comprehensive analysis of reproducibility policies and software/data management practices in scientific computing journals.ResultsThe survey revealed significant variability in reproducibility policies and practices across computer science journals. Many gaps and challenges were identified, including inconsistencies in policy enforcement, lack of standardized tools, and insufficient recognition of software as a research artifact. The analysis highlighted the potential of Reproducibility as a Service (RaaS) as an innovative solution to address these challenges.DiscussionThis study underscores the need for improved standardization and implementation of reproducibility policies. Strategies to enhance reproducibility include fostering collaboration among authors, publishers, and technology providers, as well as recognizing software as a critical research output. The findings aim to guide stakeholders in bridging the current gaps and advancing the reproducibility of computational scientific articles.

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The scattering by objects with singular geometries is a particularly delicate problem, and the Sommerfeld-Maliuzhinets representation of field, when it isassociated to Maliuzhinets inversion [3]-[4] and single face representation [7]-[8] methods, is a powerful tool to investigate the acoustic and electromagnetic wavesdiffraction by a complex wedge-shaped region, in particular based on remarkableproperties of spectral functions in this representation. In first step of this chapter, wereview some general expressions and properties in scalar case for these problems :general properties in complex plane, spectral representation of Green function, single face representation of spectral function and consequences, are analysed for scatterers with imperfectly reflecting surfaces that can extend to infinity. In a second step, we consider the general solution for a wedge with face impedances of arbitrary signs (passive or active case), then the solution for the diffraction of a skew incident plane wave by a passive anisotropic impedance wedge of any angle in vectorial case [9] (2D 1/2 electromagnetism problems), and detail efficient expansions of special functions used for them and their properties. In a third step, an explicitely causal representation of field in time domain is developed within a large domain of validity, including the case of a dispersive wedge with multimode boundary conditions.

7-Tesla MRI of the hippocampus enhances the visualization of its internal substructures. Among these substructures, the cornu Ammonis and subiculum form a contiguous folded ribbon of gray matter. Here, we propose a method to analyze local thickness measurements of this ribbon. We introduce an original approach based upon the estimation of a diffeomorphic vector field that traverses the ribbon. The method is designed to handle specificities of the hippocampus and corresponding 7-Tesla acquisitions: highly convoluted surface, non-closed ribbon, incompletely defined inner/outer boundaries, anisotropic acquisitions. We furthermore propose to conduct group comparisons using a population template built from the central surfaces of individual subjects. We first assessed the robustness of our approach to anisotropy, as well as to inter-rater variability, on a post-mortem scan and on in vivo acquisitions respectively. We then conducted a group study on a dataset of in vivo MRI from temporal lobe epilepsy (TLE) patients and healthy controls. The method detected local thinning patterns in patients, predominantly ipsilaterally to the seizure focus, which is consistent with medical knowledge. This new technique allows measuring the thickness of the hippocampus from 7-Tesla MRI. It shows good robustness with respect to anisotropy and inter-rater variability and has the potential to detect local atrophy in patients. As 7-Tesla MRI is increasingly available, this new method may become a useful tool to study local alterations of the hippocampus in brain disorders. It is made freely available to the community (code: https://github.com/aramis-lab/hiplay7-thickness, postmortem segmentation: https://doi.org/10.5281/zenodo.3533264).

The possibility to apply phase-space methods to many-body interacting systems might provide accurate descriptions of correlations with a reduced numerical cost. For instance, the so--called stochastic mean-field phase-space approach, where the complex dynamics of interacting fermions is replaced by a statistical average of mean-field like trajectories is able to grasp some correlations beyond the mean-field. We explore the possibility to use alternative equations of motion in the phase-space approach. Guided by the BBGKY hierarchy, equations of motion that already incorporate part of the correlations beyond mean-field are employed along each trajectory. The method is called Hybrid Phase-Space (HPS) because it mixes phase-space techniques and the time-dependent reduced density matrix approach. The novel approach is applied to the one-dimensional Fermi-Hubbard model. We show that the predictive power is improved compared to the original stochastic mean-field method. In particular, in the weak-coupling regime, the results of the HPS theory can hardly be distinguished from the exact solution even for long time.

The generation of up-to-date accurate 3D models from multi-view satellite images has recently become a hot research topic. A well-known challenge of this problem is to put all cameras into a common frame of reference, since depending on the satellite geopositioning equipment the camera parameters may contain errors of up to tens of meters on the ground. In this context, bundle adjustment based techniques, relying on the identification of a set of tie-points and the correction of the camera models to make them coincident, have become a generally accepted practice. However, new approaches capable of producing state-of-the-art results without the use of prior bundle adjustment have also been proposed. This work aims to compare both strategies and assess the practical impact of using bundle adjustment for 3D reconstruction from multi-view satellite images.

Interpolation is a vital piece of many image processing pipelines. In this document we present how to optimize the implementation of image B-spline interpolation for GPU architectures. The implementation is based on the one proposed by Briand and Monasse in 2018 and works for orders up to 11. The two main optimizations consist in: (1) transposing the B-spline coefficients before the prefiltering of the rows and (2) dividing columns into subregions in order to use more threads. We assess the impact of the floating point precision and of using high B-spline orders.

These last years, earth observation imagery has significantly improved. Public satellites such as WorldView-3 can now produce images with a Ground Sample Distance of 31cm, reaching a resolution equivalent to aerial images. Perhaps more importantly, the revisit frequency has also been greatly enhanced: providers such as Planet can now acquire images of a given ground location on a daily basis. These major improvements are fueled by an increasing demand for frequent objects detection. An application generating a particular interest is vehicle detection. Indeed, vehicle detection can give to public and private actors valuable data such as traffic monitoring and parking occupancy rate estimations. Several datasets, such as DOTA or VehSat, already exist, allowing researchers to train machine learning algorithms to detect vehicles. However, these datasets focus on relatively high definition and expensive aerial and satellite images. In this paper, we will present a method for detecting vehicles on medium resolution satellite images, with a GSD comprised between 1 and 5 meters. This approach can notably be used on Planet images, allowing to monitor traffic of an area on a daily basis.

My mother died thirty years ago from a stroke. Her life had been sad. Her marriage was a failure. My father never wished to live with us, even when I was a baby. I was born in 1939 and my sister, Daniele, in 1938. My father sold the pharmacy he was running at 17 boulevard du Temple, Paris, and he enrolled in the Army in 1944. He was assigned to the Hospital Pharmacy Department at Rabat, Morocco. My mother stayed a full year with us in Paris. She finally decided to take us to Rabat against the wish of my father. In Rabat, the three of us were living in a single room of a low-cost hotel. My father was working, living, and sleeping at the hospital. We were used to his absence.

The goal of these lecture notes is to present in a unified way various models for the dynamics of aligning self-propelled rigid bodies at different scales and the links between them. The models and methods are inspired from [12,13], but, in addition, we introduce a new model and apply on it the same methods. While the new model has its own interest, our aim is also to emphasize the methods by demonstrating their adaptability and by presenting them in a unified and simplified way. Furthermore, from the various microscopic models we derive the same macroscopic model, which is a good indicator of its universality.