Formulation of gradient multiaxial fatigue criteria

International audienceA formulation of gradient fatigue criteria is proposed in the context of multiaxial high-cycle fatigue (HCF) of metallic materials. The notable dependence of fatigue limit on some common factors not taken into account in classical fatigue criteria, is analyzed and modeled. Three interconnected factors, the size, stress gradient and loading effects, are here investigated. A new class of fatigue criteria extended from classical ones with stress gradient terms introduced not only in the normal stress but also in the shear stress components, is formulated. Such a formulation allows to capture gradient effects and related “size” effects, as well as to cover a wide range of loading mode, then can model both phenomena “Smaller is Stronger” and “Higher Gradient is Stronger”. Gradient versions of some classical fatigue criteria such as Crossland and Dang Van are provided as illustrations

Dark exciton energy splitting in monolayer WSe2: insights from time-dependent density-functional theory

We present here a formalism based on time-dependent density-functional theory (TDDFT) to describe characteristics of both intra- and inter-valley excitons in semiconductors, the latter of which had remained a challenge. Through the usage of an appropriate exchange-correlation kernel (nanoquanta), we trace the energy difference between the intra- and inter-valley dark excitons in monolayer (1L) WSe2 to the domination of the exchange part in the exchange-correlation energies of these states. Furthermore, our calculated transition contribution maps establish the momentum resolved weights of the electron-hole excitations in both bright and dark excitons thereby providing a comprehensive understanding of excitonic properties of 1L WSe2. We find that the states consist of hybridized excitations around the corresponding valleys which leads to brightening of the dark excitons, i.e., significantly decreasing their lifetime which is reflected in the PL spectrum. Using many-body perturbation theory, we calculate the phonon contribution to the energy bandgap and the linewidths of the excited electrons, holes and (bright) exciton to find that as the temperature increases the bandgap significantly decreases, while the linewidths increase. Our work paves for describing the ultrafast charge dynamics of transition metal dichalcogenide within an ab initio framework

Inexact reduced gradient methods in smooth nonconvex optimization

This paper proposes and develops new line search methods with inexact gradient information for finding stationary points of nonconvex continuously differentiable functions on finite-dimensional spaces. Some abstract convergence results for a broad class of line search methods are reviewed and extended. A general scheme for inexact reduced gradient (IRG) methods with different stepsize selections are proposed to construct sequences of iterates with stationary accumulation points. Convergence results with convergence rates for the developed IRG methods are established under the Kurdyka-Lojasiewicz property. The conducted numerical experiments confirm the efficiency of the proposed algorithms

High Efficiency Water Splitting using Ultrasound Coupled to a BaTiO 3 Nanofluid

To date, a number of studies have reported the use of vibrations coupled to ferroelectric materials for water splitting. However, producing a stable particle suspension for high efficiency and long-term stability remains a challenge. Here, the first report of the production of a nanofluidic BaTiO3 suspension containing a mixture of cubic and tetragonal phases that splits water under ultrasound is provided. The BaTiO3 particle size reduces from approximately 400 nm to approximately 150 nm during the application of ultrasound and the fine-scale nature of the particulates leads to the formation of a stable nanofluid consisting of BaTiO3 particles suspended as a nanofluid. Long-term testing demonstrates repeatable H2 evolution over 4 days with a continuous 24 h period of stable catalysis. A maximum rate of H2 evolution is found to be 270 mmol h–1 g–1 for a loading of 5 mg l–1 of BaTiO3 in 10% MeOH/H2O. This work indicates the potential of harnessing vibrations for water splitting in functional materials and is the first demonstration of exploiting a ferroelectric nanofluid for stable water splitting, which leads to the highest efficiency of piezoelectrically driven water splitting reported to date

Electromyography (EMG) based Classification of Neuromuscular Disorders using Multi-Layer Perceptron

Electromyography (EMG) signals are the measure of activity in the muscles. The aim of this study is to identify the neuromuscular disease based on EMG signals by means of classification. The neuromuscular diseases that have been identified are myopathy and neuropathy. The classification was carried out using Artificial Neural Network (ANN). There are five feature extraction techniques that were used to extract the signals such as Autoregressive (AR), Root Mean Square (RMS), Zero Crossing (ZC), Waveform length (WL) and Mean Absolute Value (MAV). A comparative analysis of these different techniques were carried out based on the results. The Multilayer Perceptron (MLP) was used for carrying out the classification

Influence of Ba[Mg2Al2N4]Eu2+ phosphor particle size on optical properties of the 6000K CPW-LEDs

In this paper, we consider the red phosphor Ba[Mg2Al2N4]Eu2+ as the novel recommendation for improving the optical properties of the 6000K conformal packaging WLEDs (CPW-LEDs). For this purpose, we investigate the influence of the Ba[Mg2Al2N4]Eu2+ particle size on the optical properties in terms of CCT, CQS, CRI, and LO using the Light Tools and Mat Lab software. From the research results, it can be observed that the optical properties of the 6000K CPW-LEDs are significantly influenced by the size of the Ba[Mg2Al2N4]Eu2+ particle. The CRI and CQS increase from 65 to 67 and 64 to 68 while the size of the Ba[Mg2Al2N4]Eu2+ particle varies from 1 μm to 10 μm, respectively. This research can provide a novel recommendation for LEDs industry at this time