Arts et Metiers Institute of Technology

Abstract Maritime piracy represents a significant international challenge, impacting both economic stability and political dynamics. Researchers from diverse disciplines have been drawn to this multifaceted issue, each aiming to understand and address different aspects of piracy’s impact and implications. This study offers a comprehensive overview of maritime piracy research based on bibliographic analysis. Its objective is threefold. First, to delineate the key domains of inquiry within maritime piracy research. These domains encompass a wide range of topics, including the socio-economic drivers of piracy, the legal frameworks governing maritime security, and computer science to analyse piracy acts. Second, to identify major contributions in the field, recognising seminal works, influential authors and significant findings related to maritime piracy. Lastly, to discern emerging research trends within maritime piracy, and to identify novel areas of inquiry, innovative methodologies and promising avenues for future exploration. Furthermore, the most popular datasets from these studies that include relevant information are presented in this work.

The effects of compressibility on the flow past circular cylinders are not yet well understood, particularly with regard to their influence on flow dynamics, such as transition waves and the vortex shedding regime. A recent experiment by Nagata et al. [J. Fluid Mech., 2020] investigating a range of Reynolds numbers between 1000 and 5000 and Mach numbers between 0.1 and 0.5 revealed unusual behaviour at the highest Mach and Reynolds numbers. The studied flow regime is particularly sensitive due to the transition waves in the shear layers before they roll up to form von Kármán alternate vortices. The authors attributed the abrupt change in regime to possible oblique instabilities in the shear layers due to compressibility. The present paper aims to reproduce their experimental setup numerically in order to explain the observed flow dynamics and understand how compressibility can alter cylinder flow in the shear-layer transition regime.

Abstract The integration of Variable-Angle Tow (VAT) composites with shell geometries offers significant potential for enhancing structural performance in aerospace engineering. This is attributed to the high stiffness-to-weight ratio of these structures and the expanded design space made possible by curvilinear fibers applied to doubly curved geometrical domains. However, the numerical analysis of such structures is often challenging due to the complexity of the governing equations and the increased computational cost associated with the higher number of unknowns. Carrera’s Unified Formulation (CUF) provides an effective approach to address these challenges, reducing computational cost while maintaining accuracy in predicting the three-dimensional (3D) stress fields characteristic of VAT composites. This study extends the application of CUF to VAT shell structures with variable curvature radii. Fibers curvature is modeled using a linear variation law. The governing equations for free vibration analysis are derived through the Principle of Virtual Displacements (PVD) within a hierarchical shell finite element framework. A two-layer ellipsoidal VAT shell is analyzed, with thickness considered as a study parameter. Validation against Abaqus 3D models demonstrates the accuracy and efficiency of the method, with strong agreement observed in fundamental frequencies and modal shapes. These findings highlight CUF as a robust and computationally efficient tool for analyzing complex VAT shells, paving the way for its implementation in practical applications.

Bioactive glass (BG)/polylactic acid (PLA) nanocomposites have gained significant attention for bone repair applications due to their mechanical and biological properties. In this study, sol-gel-derived bioactive glass nanoparticles (nBG) with a mean diameter of 53.38 nm were surface-modified with (3-Aminopropyl) triethoxysilane (APTES) to ensure uniform dispersion within the PLA matrix. Composite materials containing 0, 2, 8, and 16 wt% of surface-modified bioactive glass nanoparticles (m-nBG) were synthesized using a solvent-evaporation method. The composites’ mechanical properties (tensile and flexural), degradation rate, hydrophilicity, and cellular responses were evaluated. The addition of 2 wt% m-nBG significantly improved the mechanical performance, achieving a tensile strength of 37.14 MPa and a flexural strength of 72.2 MPa. However, increasing the filler content beyond this threshold resulted in agglomeration, leading to a reduction in mechanical strength, though the tensile modulus continued to rise with higher nanoparticle loading. Biodegradation tests showed that m-nBG fillers accelerated the degradation process, with higher filler concentrations further promoting matrix degradation and increasing water absorption. The 2 wt% m-nBG nanocomposite exhibited optimal cell viability, proliferation, and attachment, highlighting its potential for bone tissue engineering applications. These findings suggest that a balanced nanoparticle content enhances both mechanical integrity and biological activity in PLA-based composites.

As shown by Wenzel et al. (J. Fluid Mech., vol. 930, 2022, A1), the Eckert number $Ec$ defined using the difference between recovery temperature $\bar{T}_r$ and wall temperature $\bar{T}_w$ can be understood as a meaningful quantity to compare heat-transfer effects inside compressible turbulent boundary layers (for a calorically perfect gas), no matter whether these are caused by different Mach-number or wall-temperature conditions. While the named study deduced this comparative behaviour of $Ec$ from an integral perspective in a strict sense, Cogo et al. (J. Fluid Mech., vol. 974, 2023, A10) performed a systematic parameter study based on the previous findings to look at wall-normal profiles. They have shown that the diabatic parameter $\varTheta$ , being equivalent to $Ec$ , is capable of categorizing heat-transfer effects for cases at different Mach numbers, even to some extent for some of the wall-normal profiles. Building on this progress, the present paper provides a comprehensive classification of both existing and newly computed super- and hypersonic direct numerical simulation data at various wall temperature conditions into heated cases, adiabatic cases or weakly/moderately/strongly/quasi-incompressibly cooled cases. Hereby, the classification is largely based on the wall-normal position of the temperature peak occurring in cooled boundary-layer cases, which is one of the determining factors for the topological characteristics of diabatic boundary-layer profiles. Integrating high-enthalpy data into the analysis allowed us to confirm the reliability of the proposed classification also in more complex scenarios, where the calorically perfect gas assumption no longer applies and additional heat-transfer mechanisms come into play. While the Eckert number is shown to well characterize heat-transfer effects on most important temperature-related quantities for a wide range of Mach numbers and $\bar {T}_w/\bar {T}_r$ conditions, also the local Reynolds number $Re_{\tau }$ is shown to notably affect the strength of heat-transfer effects. Since both $Ec$ and $Re_{\tau }$ can be determined in advance – or estimated to a reasonable extent – a key advantage of the classification scheme is to allow for an effective a priori estimation of the extent to which heat-transfer effects are to be expected for a given compressible turbulent boundary-layer configuration.

Abstract Microneedles are an emerging class of transdermal drug delivery systems for biomedical applications. These devices allow minimally invasive and painless drug delivery, making them an attractive alternative to hypodermic injections. This paper focuses on the study of polymer‐based solid microneedles fabrication process using the fused deposition modeling (FDM) method. Biodegradable and biocompatible polymers are selected as printing materials. For this study, the thermoplastic polylactic acid (PLA), currently used for FDM microneedle preparation was selected. To overcome the potential brittleness of PLA during transdermal application, two other materials are also studied: polycaprolactone (PCL) and a PLA/PCL blend. The effect of 3D printing parameters on the dimensional accuracy of the microneedles is studied to determine the optimum printing conditions for each filament. In addition, the dimensions and/or geometry of the microneedles are modified to print its with minimal dimensions. Then, a post‐fabrication chemical etching treatment is used to improve both, size and shape of the printed solid microneedles.

We report here the first equation of state measurements of Fe$_2$O$_3$ obtained with laser-driven shock compression. The data are in excellent agreement with previous dynamic and static compression measurements at low pressure, and extend the known Hugoniot up to 700 GPa. We observe a large volume drop of $\sim$10% at 86 GPa, which could be associated, according to static compression observations, with the iron spin transition. Our measurements also suggest a change of the Hugoniot curve between 150 and 250 GPa. Above 250 GPa and within our error bars, we do not observe significant modifications up to the maximum pressure of 700 GPa reached in our experiment.

X-ray free electron laser (XFEL) sources coupled to high-power laser systems offer an avenue to study the structural dynamics of materials at extreme pressures and temperatures. The recent commissioning of the DiPOLE 100-X laser on the high energy density (HED) instrument at the European XFEL represents the state-of-the-art in combining x-ray diffraction with laser compression, allowing for compressed materials to be probed in unprecedented detail. Here, we report quantitative structural measurements of molten Sn compressed to 85(5) GPa and ∼3500 K. The capabilities of the HED instrument enable liquid density measurements with an uncertainty of ∼1% at conditions which are extremely challenging to reach via static compression methods. We discuss best practices for conducting liquid diffraction dynamic compression experiments and the necessary intensity corrections which allow for accurate quantitative analysis. We also provide a polyimide ablation pressure vs input laser energy for the DiPOLE 100-X drive laser which will serve future users of the HED instrument.

International audience