iLogDemons: A Demons-Based Registration Algorithm for Tracking Incompressible Elastic Biological Tissues

Tracking soft tissues in medical images using non-linear image registration algorithms requires methods that are fast and provide spatial transformations consistent with the biological characteristics of the tissues. LogDemons algorithm is a fast non-linear registration method that computes diffeomorphic transformations parameterised by stationary velocity fields. Although computationally efficient, its use for tissue tracking has been limited because of its ad-hoc Gaussian regularisation, which hampers the implementation of more biologically motivated regularisations. In this work, we improve the logDemons by integrating elasticity and incompressibility for soft-tissue tracking. To that end, a mathematical justification of demons Gaussian regularisation is proposed. Building on this result, we replace the Gaussian smoothing by an efficient elastic-like regulariser based on isotropic differential quadratic forms of vector fields. The registration energy functional is finally minimised under the divergence-free constraint to get incompressible deformations. As the elastic regulariser and the constraint are linear, the method remains computationally tractable and easy to implement. Tests on synthetic incompressible deformations showed that our approach outperforms the original logDemons in terms of elastic incompressible deformation recovery without reducing the image matching accuracy. As an application, we applied the proposed algorithm to estimate 3D myocardium strain on clinical cine MRI of two adult patients. Results showed that incompressibility constraint improves the cardiac motion recovery when compared to the ground truth provided by 3D tagged MRI.     

Towards the creation of a CNL adapted to requirements writing by combining writing recommendations and spontaneous regularities: example in a space project

The Quality Department of the French National Space Agency (CNES, Centre National d’Études Spatiales) wishes to design a writing guide based on the real and regular writing of requirements. As a first step in this project, the present article proposes a linguistic analysis of requirements written in French by CNES engineers. One of our goals is to determine to what extent they conform to several rules laid down in two existing Controlled Natural Languages (CNLs), namely the Simplified Technical English developed by the AeroSpace and Defense Industries Association of Europe and the Guide for Writing Requirements proposed by the International Council on Systems Engineering. Indeed, although CNES engineers are not obliged to follow any controlled language in their writing of requirements, we believe that language regularities are likely to emerge from this task, mainly due to the writers’ experience. We are seeking to identify these regularities in order to use them as a basis for a new CNL for the writing of requirements. The issue is approached using natural language processing tools to identify sentences that do not comply with the rules or contain specific linguistic phenomena. We further review these sentences to understand why the recommendations cannot (or should not) always be applied when specifying large-scale projects.     

Numerical calculation of the base inertial parameters of robots

This article presents a new approach to the problem of determining the minimum set of inertial parameters of robots. The calculation is based on numerical QR and SVD factorizations and on the scaling procedure of matrices. It proceeds in three steps:

• eliminate standard inertial parameters which have no effect on the dynamic model,
• determine the number of base parameters,

and

• determine a set of base parameters by regrouping some standard parameters to some others in linear relations.

Different models, linear in the inertial parameters are used: a complete dynamic model, a simplified dynamic model, and an energy model. The method is general, it can be applied to open loop, or graph-structured robots. The algorithms are easy to implement. An application for the PUMA 560 robot is given.     

Electrocatalyse de la réduction de l'oxygène sur oxyde mixte: Cu1+x Mn2−x O4 en milieu alcalin. Etude par électrode disque-anneau

Résumé La réduction cathodique de l'oxygène sur des électrodes de manganites de cuivre et liant de Téflon est étudiée par la technique de l'électrode disque-anneau en milieu alcalin. L'interprétation des résultats suggère que la réduction de O₂ en OH^– procède à la fois par la voie directe et, simultanément, par une voie indirecte, parallèle, qui est constituée de deux étapes en série, avec formation de l'intermédaire HO ₂ ^– . La réduction directe en OH^– (constante de vitessek ₁) et la première étape de la réduction indirecte, formant HO ₂ ^– (constante de vitessek ₂) ne dépendent pas de la même manière du potentiel. En outre les ions HO ₂ ^– peroxyde se décomposent probablement catalytiquement chimiquement sur les manganites de cuivre.

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Oxygen reduction on copper manganite Teflon-bonded electrodes in alkaline solution was studied using a rotating ring-disc technique. The interpretation of these data suggests that the cathodic oxygen reduction proceeds through multistep reactions involving a peroxide intermediate. The direct reduction to OH^– (k ₁) and the first reduction step to HO ₂ ^– (k ₂) were found to have different dependences on the potential. Furthermore a catalytic chemical reaction of decomposition of the peroxide intermediate possibly occurs on the manganese copper oxides.

     

Development of a high resolution and high dispersion Thomson parabola

Here, we report on the development of a novel high resolution and high dispersion Thomson parabola for simultaneously resolving protons and low-Z ions of more than 100 MeV/nucleon necessary to explore novel laser ion acceleration schemes. High electric and magnetic fields enable energy resolutions of ΔE∕E < 5% at 100 MeV/nucleon and impede premature merging of different ion species at low energies on the detector plane. First results from laser driven ion acceleration experiments performed at the Trident Laser Facility demonstrate high resolution and superior species and charge state separation of this novel Thomson parabola for ion energies of more than 30 MeV/nucleon.     

Parametric study of riveted joints

As one of the most reliable fasteners, solid riveted joints are widely utilized in many industrial areas. In the present work, the authors recalled some results on the riveting process and the strength of one kind of riveted joints obtained by simulation and experimental investigations in a previous paper. The numerical results were in very good agreement with the experimental results, allowing us to validate our simulation approach and its use for further studies. We selected several engineering parameters for the riveted joint: initial assembly, friction coefficient, rivet’s geometry and sheets’ geometry, in order to carry out a parametric study and determine their relative importance. These were conducted in FEA software. The results showed the impact on riveting process and the strength of the riveted joint by varying each parameter which was interesting for the industry.     

Computing all subtree repeats in ordered trees

We consider the problem of computing all subtree repeats in a given labeled ordered tree. We first transform the tree to a string representing its postfix notation, and then present an algorithm based on the bottom-up technique to solve it. The proposed algorithm consists of two phases: the preprocessing phase and the phase where all subtree repeats are computed. The linear time and space complexity of the proposed algorithm are important parts of its quality.     

WO3 nano-ribbons: their phase transformation from tungstite (WO3·H2O) to tungsten oxide (WO3)

Tungsten oxide (WO₃) nano-ribbons (NRs) were obtained by annealing tungstite (WO₃·H₂O) NRs. The latter was synthesized below room temperature using a simple, environmentally benign, and low cost aging treatment of precursors made by adding hydrochloric acid to diluted sodium tungstate solutions (Na₂WO₄·2H₂O). WO₃ generates significant interests and is being used in a growing variety of applications. It is therefore important to identify suitable methods of production and better understand its properties. The phase transformation was observed to be initiated between 200 and 300 ^°C, and the crystallographic structure of the NRs changed from orthorhombic WO₃·H₂O to monoclinic WO₃. It was rigorously studied by annealing a series of samples ex situ in ambient air up to 800 ^°C and characterizing them afterward. A temperature-dependent Raman spectroscopy study was performed on tungstite NRs between minus 180 and 700 ^°C. Also, in situ heating experiments in the transmission electron microscope allowed for the direct observation of the phase transformation. Powder X-ray diffraction, electron diffraction, electron energy-loss spectroscopy, and X-ray photoelectron spectroscopy were employed to characterize precisely this transformation.     

Optimization of the spark plasma sintering processing parameters affecting the properties of polyimide

The present study deals with the optimization of polyimide (PI) mechanical properties, obtained by Spark Plasma Sintering (SPS), by using a method combining Design of Experiments (DOE) with physical, structural, and mechanical characterizations. The effects of SPS parameters such as temperature, pressure, dwell time, and cooling rate on the density, mechanical properties, and structure of PI were investigated. The experimental results revealed that the mechanical properties of the material were optimized by raising the sintering temperature up to 350°C. The optimized SPS processing parameters were a temperature of 350°C, a pressure of 40 MPa, and a dwell time of 5 min. Under these conditions, a relative density of 99.6% was reached within only a few minutes. The corresponding mechanical properties consisted of Young's modulus of 3.43 GPa, a Shore D hardness of 87.3, and a compressive strength of 738 MPa for a maximum compressive strain of 61.8%. Moreover, when working at 320°C and at 100 MPa, an increase in the dwell time was necessary to enhance the properties. Contrary to the other parameters, the cooling rate appeared to be a non‐significant parameter. Finally, correlations between the PI structure and the mechanical properties were made to demonstrate the densification mechanisms. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41542.