HAL Portal UPHF (Université Polytechnique Hauts-de-France)
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Alternative and low-cost technique to transfer III-V DHBT transistors onto Si-HR using Cu-Cu bonding for sub-THz power amplification for 6G
No full textInternational audienceThis study introduces the preparation of a future transferred InP double heterojunction bipolar transistor (DHBT) on a high-resistivity silicon substrate. Our approach employs copper (Cu) as a thermal heat sink and chosen for its excellent thermal conductivity, which will make possible efficient heat dissipation in electronic devices. This ensures superior compatibility with industry standards and improves performance in high power applications and ultra-low-cost material bonding. The development includes the first instance of heatsink bonding using a Si-Fab copper layer, together with a method for removing InP substrate . This process involves also a mechanical thinning down to 10 µm, followed by etching with HCl. These advancements are expected to significantly improve power amplification performance at high frequency, paving the way for 6G-compatible CMOS integration
Stability Analysis of Variable Impedance Control for Rehabilitation Exoskeletons: quasi-LPV models and LMI conditions
No full textInternational audienceExoskeletons are set to play an important role in the future of rehabilitation processes, and safe interactions are therefore seen as a fundamental prerequisite. This article contributes by presenting a novel assistance modulation strategy to best meet the patients needs as well as a dedicated stability analysis to ensure operational safety. Using exact nonlinear model transformation, a polytopic quasi-LPV model of the closed-loop dynamics allows us to present stability conditions, written as LMI constraints. In addition, the impact of noise and model uncertainties is considered in a robustness analysis that paves the way for a secure rehabilitation process
Material characterization methods for investigating charge storage processes in 2D and layered materials-based batteries and supercapacitors
No full textInternational audienceTwo-dimensional (2D) materials offer distinct advantages for electrochemical energy storage (EES) compared to bulk materials, including a high surface-to-volume ratio, tunable interlayer spacing, and excellent in-plane conductivity, making them highly attractive for applications in batteries and supercapacitors. Gaining a fundamental understanding of the energy storage processes in 2D material-based EES devices is essential for optimizing their chemical composition, surface chemistry, morphology, and interlayer structure to enhance ion transport, promote redox reactions, suppress side reactions, and ultimately improve overall performance. This review provides a comprehensive overview of the characterization techniques employed to probe charge storage mechanisms in 2D and thin-layered material-based EES systems, covering optical spectroscopy, imaging techniques, X-ray and neutron-based methods, mechanical probing, and nuclear magnetic resonance spectroscopy. We specifically highlight the application of these techniques in elucidating ion transport dynamics, tracking redox processes, identifying degradation pathways, and detecting interphase formation. Furthermore, we discuss the limitations, challenges, and potential pitfalls associated with each method, as well as future directions for advancing characterization techniques to better understand and optimize 2D material-based electrodes
19 mW/μm² and 24.5 % PAE at 94 GHz for 0.30-μm Transferred InP/GaAsSb DHBT on Si-HR
No full textInternational audienceInP HBT technology is a suitable candidate for the future 6G networks that require very high bandwidth. It has already demonstrated high-frequency operation with fmax exceeding 1 THz [1]. However, this performance comes at the cost of aggressive scaling which increases thermal resistance (Rth) due to device narrowing and leads to self-heating limiting overall performance. Transferring InP DHBT to a high-thermal-conductivity substrate has shown a drastic reduction of Rth by 65 % on Si-HR [2] and 75 % on SiC [3] thanks to their superior heat dissipation properties however its effect on output power remains unexplored. We present continuous wave (CW) large-signal load-pull measurements at 94 GHz of a transferred InP/GaAsSb DHBT transistor fabricated on a high-resistivity silicon substrate (HR-Si). The characterized device features an emitter area of 0.29 × 4.9 μm² and was biased for both maximum output power and maximum power-added-efficiency (P.A.E). A peak output power of 14.25 dBm (18,84 mW/μm²) was achieved. This result demonstrates the impact of thermal dissipation in reducing self-heating and enabling higher output power
Nouveaux Grades Opérationnels et Tactiques pour l'Automatisation ferroviaire
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Telerehabilitation in gerontology: acceptability of patients after orthopaedic surgery
No full textInternational audienceObjective: Aging healthily with minimal disability is essential. The orthopaedics surgery hip (THA) and knee (TKA) increase with age, making the development of innovative solutions crucial. Telerehabilitation is advancing, but the acceptability of digital tools remains underexplored, despite their role in promoting adherence to remote care. The acceptability and adoption of connected and/or embedded health, wellbeing, and autonomy devices by users are key challenges for their success and positive impact. Method: Semi-structured interviews were conducted with 20 THA (n=6), TKA (n=14) patients. These interviews were guided by an interview framework inspired by the Unified theory of acceptance and use of technology 2 (UTAUT2). The System Usability Scale (SUS) was used to assess users' perception of usability. Results: The interviews highlighted facilitators such as motivation for physical activity, personalized clinician follow-up (via gamification), complementarity with conventional therapy, and cost (urban travel). Barriers included injury risk and lack of professional interaction, key factors for usercentered design. SUS results were unaffected by gender, or age, with a mean score of 54.6 ± 19.6, indicating slightly acceptable usability. Conclusion: Creating a digital system that is tailored to patients' expectations and personalised could increase the adoption, relevance and usefulness of connected devices to improve tele-rehabilitation care
Entropic forces in rotaxane-based daisy chains: Toward tunable nanomechanical systems
No full textInternational audienceMechanically interlocked polymers and molecules exhibit unique topological, physical, and chemical properties, making them highly promising for applications in molecular machines, molecular switches, artificial muscles, nano-actuators, nano-sensors, and biomedical technologies. While significant progress has been made in their synthesis and practical implementation, theoretical studies remain underexplored. In this work, we examine the role of entropic forces in daisy chain structures incorporating rotaxanes, with the ultimate goal of characterizing entropic nano-springs for use in nanomechanics and nanotechnology. Potential applications include artificial cytoskeletons, synthetic cells, and nano-mechanical logic gates.</div
Abus d'autorité : (rares) précisions sur la nature des mesures destinées à faire échec à l'exécution de la loi
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Implementation of a program to strengthen oral hygiene in patient with cleft deformities: a prospective randomized controlled clinical trial
No full textInternational audienceBackground Cleft lip and/or palate is the most common congenital orofacial deformity, affecting 1/800 births. A thorough review of the literature has shown that children with cleft have poorer oral hygiene and dental health than other children, with higher levels of caries in both temporary and permanent teeth and poorer periodontal health. Cleft patients are treated by a multidisciplinary team that aims to provide comprehensive care from pre-or post-natal diagnosis to early adulthood and the end of growth. We aim to assess, through a single-center, prospective, randomized and controlled clinical trial conducted at the Nantes Cleft Centre, the impact of an enhanced dental program on oral hygiene and dental health in cleft patients.Methods Patients aged 3 to 15 years with unilateral or bilateral cleft lip and/or palate will be offered to participate in this study. After acceptance, patients will be randomly assigned to 2 groups: test group or control group. For the control group, there will be no change in the patient's care, and they will continue to see their surgeon on an annual basis.For the test group, a 30-45-min consultation will be added to the annual check-up. During this visit, patients and their parents will receive oral and written oral hygiene instructions to improve oral hygiene knowledge and brushing technique. If necessary, dental treatment will be provided at the same appointment or at a later date. In addition, patients will be contacted via telemedicine every 2 months to increase motivation, and an additional dental appointment will be scheduled at 6 months.Discussion This is a single-center study which, if conclusive, could lead to a paradigm shift in the dental care pathway for cleft patients.<p
Terahertz time-domain ellipsometry with spintronic emitters: Pauli coefficients as a superior alternative to Jones and Mueller matrices
No full textInternational audienceWe introduce terahertz complete time-domain spectroscopic ellipsometry (THz-cTDSE), extending traditional ellipsometry by determining full Jones and Mueller matrices for in-depth material characterization. This marks the first application of spintronic terahertz emitters in ellipsometry, achieving pure linear polarization for precise magnetization-based switching. Our complete phase-resolved ellipsometry transforms Jones matrices into an intuitive framework of diattenuations and retardations across all Stokes bases—Pauli exponential coefficients—previously unattainable with incomplete ellipsometry. A novel calibration technique ensures accurate Jones matrix reconstruction without requiring precise alignment of polarizing components, approaching the precision typical of visible-range ellipsometry. We demonstrate THz-cTDSE on quartz and Hg2Cl2 crystals, advancing the analysis of anisotropic materials