Can dissonance engineering improve risk analysis of human–machine systems?

The paper discusses dissonance engineering and its application to risk analysis of human–machine systems. Dissonance engineering relates to sciences and technologies relevant to dissonances, defined as conflicts between knowledge. The richness of the concept of dissonance is illustrated by a taxonomy that covers a variety of cognitive and organisational dissonances based on different conflict modes and baselines of their analysis. Knowledge control is discussed and related to strategies for accepting or rejecting dissonances. This acceptability process can be justified by a risk analysis of dissonances which takes into account their positive and negative impacts and several assessment criteria. A risk analysis method is presented and discussed along with practical examples of application. The paper then provides key points to motivate the development of risk analysis methods dedicated to dissonances in order to identify the balance between the positive and negative impacts and to improve the design and use of future human–machine system by reinforcing knowledge

Polymorphism and magnetic properties of Li2MSiO4 (M 5 Fe, Mn) cathode materials

Transition metal-based lithium orthosilicates (Li2MSiO4,M=Fe, Ni, Co, Mn) are gaining a wide interest as cathode materials for lithium-ion batteries. These materials present a very complex polymorphism that could affect their physical properties. In this work, we synthesized the Li2FeSiO4 and Li2MnSiO4 compounds by a sol-gel method at different temperatures. The samples were investigated by XRPD, TEM, 7Li MAS NMR, and magnetization measurements, in order to characterize the relationships between crystal structure and magnetic properties. High-quality 7Li MAS NMR spectra were used to determine the silicate structure, which can otherwise be hard to study due to possible mixtures of different polymorphs. The magnetization study revealed that the Neel temperature does not depend on the polymorph structure for both iron and manganese lithium orthosilicates

NMR-Based Structural Modeling of Graphite Oxide Using Multidimensional 13C Solid-State NMR and ab Initio Chemical Shift Calculations

Chemically modified graphenes and other graphite-based materials have attracted growing interest for their unique potential as lightweight electronic and structural nanomaterials. It is an important challenge to construct structural models of noncrystalline graphite-based materials on the basis of NMR or other spectroscopic data. To address this challenge, a solid-state NMR (SSNMR)-based structural modeling approach is presented on graphite oxide (GO), which is a prominent precursor and interesting benchmark system of modified graphene. An experimental 2D C-13 double-quantum/single-quantum correlation SSNMR spectrum of C-13-labeled GO was compared with spectra simulated for different structural models using ab initio geometry optimization and chemical shift calculations. The results show that the spectral features of the GO sample are best reproduced by a geometry-optimized structural model that is based on the Lerf-Klinowski model (Lerf, A. et al. Phys. Chem. B 1998, 102, 4477); this model is composed of interconnected sp(2), 1,2-epoxide, and COH carbons. This study also convincingly excludes the possibility of other previously proposed models, including the highly oxidized structures involving 1,3-epoxide carbons (Szabo, I. et al. Chem. Mater. 2006, 18, 2740). C-13 chemical shift anisotropy (CSA) patterns measured by a 2D C-13 CSA/isotropic shift correlation SSNMR were well reproduced by the chemical shift tensor obtained by the ab initio calculation for the former model. The approach presented here is likely to be applicable to other chemically modified graphenes and graphite-based systems

Applying physical acoustics to near-seafloor object echo-structure estimation

In HF sonars (50kHz-500kHz), the assumption of a perfect rigid body for targets of interest is often admitted and the ratio "wave-length/object-length" leads to use physical acoustics theory to describe target-wave interactions. This has been done extensively for the determination of target strengths, especially for targets isolated in the water volume. However, it is experimentally well-known that echoes of near-seafloor objects are different in amplitude and shape from echoes of the same objects in free water. Despite the presence of such boundaries (seasurface or seafloor), physical acoustics theory can still be used in this case as a first approximation. In this paper, we propose a general method to rapidly evaluate strengths and structures of echoes from simple objects located near the seafloor and we present the validation of this target echo model by means of a specific experiment : a small scale experiment (1/5 scale) made around 200 kHz in a large water test tank and using the sea surface as reflecting interface. The results obtained during this experiment well square with the envisaged target-wave interaction mechanism

Recherche de codes optimaux en courantométrie Döppler sous-marine large bande

Ce travail concerne l'amélioration en performances des courantomètres acoustiques sous-marins utilisant l'effet Dôppler sur les échos diffus issus des particules en suspension. Les méthodes à large bande aujourd'hui émergentes sont replacées dans un contexte théorique général. Au moyen d'une interprétation de l'origine des limitations en performances, on montre que les méthodes large bande sont en continuité avec les méthodes à bande étroite actuellement encore les plus répandues et l'on construit progressivement des codes de modulation à bande large aux performances améliorées

A Multitechnique Approach to Spin-Flips for Cp2Cr(II) Chemistry in Confined State

Paramagnetic solid-state NMR, extended X-ray absorption fine structure (EXAFS), and Raman spectroscopies, along with detailed quantum mechanical calculations performed with different density functional theory (DFT) functionals, are successfully applied to investigate the magnetic, structural, and vibrational properties of molecularly isolated chromocene (Cp2Cr, where Cp = C5H5) and of its Cp2Cr(CO) adduct. Paramagnetic solid-state NMR unequivocally demonstrates that a spin flip occurs by coming from the paramagnetic Cp2Cr (triplet state) to the diamagnetic Cp2Cr(CO) adduct (singlet state), thus clarifying the theoretical dilemma of the disagreement among different functionals in predicting the most stable spin state. EXAFS and Raman spectroscopies are able to experimentally discriminate between singlet and triplet states, because a different spin state corresponds to a different geometry of the molecule, and therefore to different vibrational features. The here reported multitechnique approach could have great relevance in establishing the occurrence of spin flip in the chemical reactivity of transition metal complexes in both homo- and heterogeneous catalysis

A Multitechnique Approach to Spin-Flips for Cp2Cr(II) Chemistry in Confined State

Paramagnetic solid-state NMR, extended X-ray absorption fine structure (EXAFS), and Raman spectroscopies, along with detailed quantum mechanical calculations performed with different density functional theory (DFT) functionals, are successfully applied to investigate the magnetic, structural, and vibrational properties of molecularly isolated chromocene (Cp2Cr, where Cp = C5H5) and of its Cp2Cr(CO) adduct. Paramagnetic solid-state NMR unequivocally demonstrates that a spin flip occurs by coming from the paramagnetic Cp2Cr (triplet state) to the diamagnetic Cp2Cr(CO) adduct (singlet state), thus clarifying the theoretical dilemma of the disagreement among different functionals in predicting the most stable spin state. EXAFS and Raman spectroscopies are able to experimentally discriminate between singlet and triplet states, because a different spill state corresponds to a different geometry of the molecule, and therefore to different vibrational features. The here reported multitechnique approach could have great relevance in establishing the occurrence of spill flip in the chemical reactivity of transition metal complexes in both homo- and heterogeneous catalysis