Accurate strain measurements in highly strained Ge microbridges

Ge under high strain is predicted to become a direct bandgap semiconductor. Very large deformations can be introduced using microbridge devices. However, at the microscale, strain values are commonly deduced from Raman spectroscopy using empirical linear models only established up to 1.2% for uniaxial stress. In this work, we calibrate the Raman-strain relation at higher strain using synchrotron based microdiffraction. The Ge microbridges show unprecedented high tensile strain up to 4.9 % corresponding to an unexpected 9.9 cm-1 Raman shift. We demonstrate experimentally and theoretically that the Raman strain relation is not linear and we provide a more accurate expression.Comment: 10 pages, 4 figure

From least action in electrodynamics to magnetomechanical energy -- a review

The equations of motion for electromechanical systems are traced back to the fundamental Lagrangian of particles and electromagnetic fields, via the Darwin Lagrangian. When dissipative forces can be neglected the systems are conservative and one can study them in a Hamiltonian formalism. The central concepts of generalized capacitance and inductance coefficients are introduced and explained. The problem of gauge independence of self-inductance is considered. Our main interest is in magnetomechanics, i.e. the study of systems where there is exchange between mechanical and magnetic energy. This throws light on the concept of magnetic energy, which according to the literature has confusing and peculiar properties. We apply the theory to a few simple examples: the extension of a circular current loop, the force between parallel wires, interacting circular current loops, and the rail gun. These show that the Hamiltonian, phase space, form of magnetic energy has the usual property that an equilibrium configuration corresponds to an energy minimum.Comment: 29 pages, 9 figures, 65 reference

A review of composite product data interoperability and product life-cycle management challenges in the composites industry

A review of composite product data interoperability and product life-cycle management challenges is presented, which addresses “Product Life-cycle Management”, developments in materials. The urgent need for this is illustrated by the life-cycle management issues faced in modern military aircraft, where in-service failure of composite parts is a problem, not just in terms of engineering understanding, but also in terms of the process for managing and maintaining the fleet. A demonstration of the use of ISO 10303-235 for a range of through-life composite product data is reported. The standardization of the digital representation of data can help businesses to automate data processing. With the development of new materials, the requirements for data information models for materials properties are evolving, and standardization drives transparency, improves the efficiency of data analysis, and enhances data accuracy. Current developments in Information Technology, such as big data analytics methodologies, have the potential to be highly transformative

Retours CGDD-IRSTEA sur la méthodologie appliquée à la réalisation des ACB du PAPI Gave de Pau Bigourdan

Cet avis porte sur la méthodologie de la mise en oeuvre de l'analyse coût-bénéfice du PAPI Gave de Pau Bigourdan

Modeling magnetic saturation and saliency effects via Euler-Lagrange models with complex currents for three-phase permanent magnet machines

International audiencePermanent magnet machines with both magnetic saturation and saliency effects can be directly described via Euler-Lagrangian formulation with complex currents. The Lagrangian is the sum of a mechanical kinetic energy and a magnetic Lagrangian. This second term is expressed in terms of rotor angle, complex stator and rotor magnetizing currents. Via simple modification of magnetic Lagrangian we derive a non-trivial dynamical model describing permanent-magnet machines with both saturation and saliency. We propose an experimental validation of such models on a customized torque machine of 1.2 kW. This first validation relies on injections of high frequency oscillations on the stator voltage. According to the proposed saturation model, the resulting amplitudes of the current-ripples is an increasing function of the current offset. Such dependance is effectively observed experimentally and confirmed by simulations

Graphene monolayer produced on Pt reusable substrates for transparent conductive electrodes applications

International audienc

Constrained Optimization of Energy Management for a Mild-Hybrid Vehicle

International audienceHybrid-electric vehicles appear to be oneof the most promising technologies for reducing fuel consumptionand pollutant emissions. The presented work focuses on a powertrain architecture for mild hybrid vehicles. The completemild-hybrid vehicle is modelled in AMESim environment and the fuelconsumption for given driving cycles is estimated. The controlstrategies for the energy management between the two power sourcesare optimized with respect to fuel consumption with a classicaldynamic programming (DP) method. We propose an other method basedon Pontryagin Minimum Principle which furnishes results very closeto the DP results for a significantly reduced calculation time.These optimization results furnish the optimal control laws fromwhich could be derived the control laws to be implemented on thevehicle. To illustrate the potential of optimization for componentdesign, mild hybrid vehicles with varying battery and electricmotor sizes, with different types of engine (gasoline / naturalgas), are evaluated in terms of consumption gain with thepresented methodology

Hybrid piezoelectric motor based on electroactive lubrication principle

A novel conception of hybrid piezoelectric motor is presented in this paper. Proposed conception required synchronized work of quasi-static and resonant piezoelectric actuators that results in a rotary movement. The motor's working principle is explained and the main characteristics are described. Studied topology is compared to the existing piezoelectric motors with regards to its field of applications. The assembling process of the motor is briefly explained with emphasis put on the frequency and impedance tuning of the piezoelectric actuators. Next, the power supply system is described. Finally, conclusions are presented concerning the features of the hybrid piezoelectric motor and possible solutions of the faced problems