This work investigates the ion transport mechanisms in binary and ternary electrolyte systems based on polymers and ionic liquids for Na-ion batteries. Molecular dynamics (MD) simulations were ...performed on poly(ethylene oxide) (PEO) and ionic liquids (IL) based electrolytes, bis(trifluoromethanesulfonyl)imide (TFSI)/N-methyl-N-propylpyrrolidinium (Pyr13) and bis(fluorosulfonyl)imide (FSI)/Pyr13, varying the composition at 0, 5, 10 and 20 wt% over a range of temperatures from 313 to 400 K. The simulations could satisfactorily reproduce the experimental densities and trends in diffusivities and conductivity data. It was observed that there exists a stronger interaction between sodium ions and the FSI anions as compared to the TFSI counterparts, correlated to a difference in interaction energy between the ionic species. This controls how well the different ILs act as plasticizers for the Na-PEO system, with TFSI actually displaying lower conductivity for low IL loadings while the conductivity increases continuously for the FSI counterparts. Moreover, the simulations show that the sodium ions interact more strongly with the polymer at lower temperatures, leading to a lower polymer free volume which explains the trends in ionic transport. Thereby, these MD simulations unveil an interplay between the coordination chemistry and the dynamic properties in these ternary polymer-ionic liquid-salt electrolytes, and how the coordination strength controls the conductive properties.
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•Numerical study on the seismic behavior of masonry towers.•Non-linear dynamic and pushover analyses on detailed 3D FEM models.•Critical insight into the results obtained and comparison on active ...failure mechanisms found.•Sophisticated masonry model with distinct damage parameters in tension and compression.
The behavior of eight historical masonry towers, located in the North-East region of Italy, is analyzed under horizontal loads by means of detailed 3D FE models. The geometry of the towers is deduced from both existing available documentation and in-situ surveys. The towers, albeit unique for geometric and architectural features, show some affinities that justify a comparative analysis, as for instance the location and the similar masonry material. Their structural behavior under horizontal loads is therefore influenced by geometrical issues, such as slenderness, walls thickness, openings, presence of internal vaults and irregularities.
Non-linear dynamic analyses are performed on detailed 3D FE models of the towers using a real accelerogram with different peak ground accelerations. A damage plasticity material model, exhibiting softening in both tension and compression, is used for masonry. Non-linear dynamic simulations show the high vulnerability of ancient masonry towers under horizontal loads. Numerical results are then compared with a non-linear static procedure based on pushover analyses in terms of displacement demand and tensile damage distribution. It is found that the results obtained with the non-linear static procedure are in a good agreement with those obtained through more time-consuming non-linear dynamic simulations, with a slight less conservative trend.
The acoustic assessment of phonation after total laryngectomy is challenged by signal aperiodicity which makes frequency-based acoustic measures less reliable. This is important for patients who use ...esophageal voice since voice samples mostly include type III (highly aperiodic) and 4 (chaotic) signals. As such, using non-linear measures, which are better suited for aperiodic phonation, may be useful to investigate the relationship between acoustic signal characteristics and perception of esophageal voice quality.
This study aimed to investigate whether nonlinear dynamic acoustic methods, nonlinear energy difference Ratio (NEDR) and spectrum convergence ratio (SCR), were correlated with perceptual measures in subjects who used esophageal phonation.
Thirty-one subjects who had undergone total laryngectomy and use esophageal voice as a rehabilitation method were included in this study. Expert and non-expert raters listened to the esophageal voice samples from the subjects and rated vowels and connected speech samples on a scale from 1 to 7 on dysphonia severity and intelligibility. In addition, non-linear acoustic analysis was performed to calculate NEDR and SCR. Analysis from the raters was compared to the non-linear acoustic analysis to find the correlation between the variables.
There were no significant correlations between any of the non-linear acoustic measures NEDR and SCR and the perceptual ratings at the significance level of 0.05. Correlations were calculated for each acoustic measure among the expert raters and among the non-expert raters in both connected speech samples and sustained vowel fragments.
In conclusion, the nonlinear dynamic acoustic analyses of spectrum convergence ratio and nonlinear energy difference ratio do not have a significant correlation with perceptual measures of esophageal voice.
Summary
Multistorey buildings often have a valuable inventory consisting of objects that their possible damage during an earthquake will cause unacceptable losses. The paper presents a novel, fully ...performance‐based seismic reliability and risk assessment framework for freestanding structural components and contents that can be modelled as rocking rigid blocks. The seismic response of building contents depends on several parameters such as the geometry of the object, the dynamic characteristics of the building and the storey that the object is located. The demand at the storey level is first obtained, and then the response of the contents is calculated using the storey acceleration response history. The demand of the structure is obtained with the aid of a modified version of the Incremental Dynamic Analysis method and subsequently the fragility curves of the rocking building contents are derived for every storey of interest. Different options for fragility assessment are discussed, and the underlying details of the problem are investigated. A simplified approach, where the fragility of the freestanding components and the structure are derived separately, is also presented. The method combines existing fragility curves and thus is suitable for quickly assessing the reliability of a building's inventory, offering sufficient risk estimates.
•Machine learning approaches are presented as optimization formulations.•Supervised and unsupervised learning approaches are surveyed.•Emerging applications in machine learning and deep learning are ...presented.•The strengths and the shortcomings of the optimization models are discussed.•Potential research directions and open problems are highlighted.
This paper surveys the machine learning literature and presents in an optimization framework several commonly used machine learning approaches. Particularly, mathematical optimization models are presented for regression, classification, clustering, deep learning, and adversarial learning, as well as new emerging applications in machine teaching, empirical model learning, and Bayesian network structure learning. Such models can benefit from the advancement of numerical optimization techniques which have already played a distinctive role in several machine learning settings. The strengths and the shortcomings of these models are discussed and potential research directions and open problems are highlighted.
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