163 research outputs found
Aquifers survey in the context of source rocks exploitation: from baseline acquisition to long term monitoring.
International audienc
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
The rolling problem: overview and challenges
In the present paper we give a historical account -ranging from classical to
modern results- of the problem of rolling two Riemannian manifolds one on the
other, with the restrictions that they cannot instantaneously slip or spin one
with respect to the other. On the way we show how this problem has profited
from the development of intrinsic Riemannian geometry, from geometric control
theory and sub-Riemannian geometry. We also mention how other areas -such as
robotics and interpolation theory- have employed the rolling model.Comment: 20 page
Normal forms and internal regularization of nonlinear differential-algebraic control systems
In this article, we propose two normal forms for nonlinear differential-algebraic control systems (DACSs) under external feedback equivalence, using a notion called maximal controlled invariant submanifold. The two normal forms simplify the system structures and facilitate understanding the various roles of variables for nonlinear DACSs. Moreover, we study when a given nonlinear DACS is internally regularizable, that is, when there exists a state feedback transforming the DACS into a differential-algebraic equation (DAE) with internal regularity, the latter notion is closely related to the existence and uniqueness of solutions of DAEs. We also revise a commonly used method in DAE solution theory, called the geometric reduction method. We apply this method to DACSs and formulate it as an algorithm, which is used to construct maximal controlled invariant submanifolds and to find internal regularization feedbacks. Two examples of mechanical systems are used to illustrate the proposed normal forms and to show how to internally regularize DACSs
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
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
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