Theoretical study of the structural stability, electronic and magnetic properties of XVSb (X == Fe, Ni, and Co) half-Heusler compounds

The structural, electronic and magnetic properties of half-Heusler compounds XVSb (X $=$ Fe, Co and Ni) are investigated by using the density functional theory with generalized gradient approximation (GGA), and Tran-Blaha modified Becke-Johnson (TB-mBJ) exchange potential approximation. It is found that the half-metallic gaps are generally reasonably widened by mBJ as compared to the GGA approximation. The magnetic proprieties of XVSb (X $=$ Fe, Co and Ni) are well defined within mBJ with an exact integer value of magnetic moment. The band gaps given by TB-mBJ are in good agreement with the available theoretical data. The FeVSb exhibits a semiconductor nature. The CoVSb and NiVSb present half-metallic behaviour with total magnetic moment of $1\mu_\text{B}$ and $2\mu_\text{B}$ in good agreement with Slater-Pauling rule. These alloys seem to be a potential candidate of spintronic devices.Comment: 9 pages, 5 figure

Vibration Signal Analysis for the Lifetime-Prediction and Failure Detection of Future Turbofan Components

Planetary gearbox and hydrodynamic journal bearings (HJB) are going to be integrated in future turbofan engines. This paper presents the results of applied methods to detect failures of these components. At first, failure detection requirements are derived by using system engineering techniques. In consideration of the identified failures theoretical assumptions are discussed and subsequently verified. Vibration and acoustic emission (AE) sensors seem promising to detect failures in an early stage. To prove the theoretical considerations experiments are carried out on test benches. Tooth flank damage of a planet gear in a planetary gearbox design is investigated. High demands are placed on the signal processing due to design-related amplitude modulation effects. Vibrations are measured using acceleration and AE sensors, which are mounted on the ring gear. The investigated failure type leads to excitation of non-stationary AE signals. It is proposed that the AE signals have a cyclostationary characteristic. Using cyclostationary-based processing techniques the signal’s hidden periodicities can be revealed. A separated analysis of each planet and evaluation of the envelope spectrum finally allows the detection of this failure type. Instead of roller bearings, HJB can be integrated in planet gears. The most essential damaging mechanism for HJB is wear as a result of mixed or boundary friction. These friction states are caused by conditions like Start/Stop Cycles, insufficient oil supply, overload or oil contamination. The accumulated intensity and duration of friction can be a measure of the remaining useful lifetime (RUL). To estimate the RUL friction has to be differentiated regarding the intensity. AE technology is a promising method to detect friction in HJB. Therefore, AE signals of the mentioned conditions are acquired. Due to rotating planet gears there is no possibility to place AE sensors directly on the surface of HJB. Finally suitable features for both components are extracted from the processed signals. Their separation efficiency with respect to the failure types is evaluated

Contact mechanics and friction for transversely isotropic viscoelastic materials

Transversely isotropic materials are an unique group of materials whose properties are the same along two of the principal axes of a Cartesian coordinate system. Various natural and artificial materials behave effectively as transversely isotropic elastic solids. Several materials can be classified as transversely isotropic materials including crystals, rocks, piezoelectrics, some biological tissues such as muscles, skin, cartilage tissue or brainstem and fibrous composites. In this study, the theory of contact mechanics developed by Persson is extended in such a way that it can model the contact and friction of a transversely isotropic viscoelastic solid in contact with a rigid rough surface. Numerical results show that anisotropy should be taken into account when dealing with transversely isotropic materials. The hysteresis friction between a transversely isotropic viscoelastic rubber, reinforced unidirectionally by fibers and two rough counter surfaces are measured by a pin-on-disk setup. The experimental results validate the theory

Neuro-Immuno-Endocrine Interactions in Early Life Stress and Heroin Withdrawal Timeline

Both heroin abuse and early life stress (ELS) affect the immune system and the hypothalamic-pituitary-adrenal (HPA) axis. Additionally, accelerated aging due to mild inflammation has been indicated in these conditions. The present study aims to compare plasma levels of apoptosis markers, inflammatory markers, and stress hormones during early heroin abstinence period. Thirty-one individuals with heroin/opioid use disorder who had heroin-ELS and 26 of their siblings who were not abusing substances (ELS), and 32 individuals with heroin/opioid use disorder without a history of ELS (heroin-no ELS) were included in the study. The levels of interleukin-6, C-reactive protein, erythrocyte sedimentation rate, albumin, alanine transaminase, aspartate transaminase, and white blood cell count were assessed as the inflammatory and biochemistry markers. Also, apoptosis markers including tumor necrosis factor (TNF)-related weak inducer of apoptosis, TNF-related apoptosis-inducing ligand, soluble tumor necrosis factor receptor type I as apoptosis markers were detected by enzyme-linked immunosorbent assay. ELS was simultaneously evaluated using the Childhood Trauma Questionnaire, Minnesota Multiphasic Personality Inventory, and beck depression inventory scales. Besides, heroin craving was assessed by Daily Drinking/Drug Questionnaire score in individuals with heroin use disorder. This is the first study to evaluate the inflammatory, stress, and apoptosis markers during heroin abstinence, supporting the association between ELS and peripheral pro-inflammatory markers' levels and HPA axis. © 2019 S. Karger AG, Basel

Solving two-dimensional coupled Burgers equations via a stable hybridized discontinuous Galerkin method

The purpose of this paper is to design a fully discrete hybridized discon-tinuous Galerkin (HDG) method for solving a system of two-dimensional (2D) coupled Burgers equations over a specified spatial domain. The semi-discrete HDG method is designed for a nonlinear variational formulation on the spatial domain. By exploiting broken Sobolev approximation spaces in the HDG scheme, numerical fluxes are defined properly. It is shown that the proposed method is stable under specific mild conditions on the stabi-lization parameters to solve a well-posed (in the sense of energy method) 2D coupled Burgers equations, which is imposed by Dirichlet boundary conditions. The fully discrete HDG scheme is designed by exploiting the Crank–Nicolson method for time discretization. Also, the Newton–Raphson method that has the order of at least two is nominated for solving the obtained nonlinear system of coupled Burgers equations over the rect-angular domain. To reduce the complexity of the proposed method and the size of the linear system, we exploit the Schur complement idea. Numerical results declare that the best possible rates of convergence are achieved for approximate solutions of the 2D coupled Burgers equations and their first-order derivatives. Moreover, the proposed HDG method is examined for two other types of systems, that is, a system with high Reynolds numbers and a system with an unavailable exact solution. The acceptable results of examples show the flexibility of the proposed method in solving various problems

Passive Strategies for Building Retrofitting: Performances Analysis and Incentive Policies for the Iranian Scenario

A large amount of the Iranian energy demand is related to the building sector, mainly due to its obsolescence. In this paper, a second-skin system has been implemented as a retrofit action for an office building, evaluating the effect of a tensile material as second-skin in terms of primary energy saving, carbon dioxide equivalent emissions, and simple payback period. The analysis was carried out through numerical simulations across a whole year and for four Iranian cities (Tabriz, Teheran, Yazd, and Bandar Abbas) in four different climates (cold, temperate, hot-dry, and hot-wet), and with the building aligned at either north-south or east-west. Moreover, an economic analysis was carried out suggesting different incentive policies to promote building energy refurbishment. The simulation results highlighted a favorable orientation for buildings in Iran, suggesting a guideline for new constructions. Indeed, the best results were achieved for an east-west orientation of the building (up to a primary energy saving of 13.6% and reduction of carbon dioxide equivalent emissions of 45.5 MgCO2,eq, in Yazd), with a decrease of the annual specific total (cooling and thermal) energy demand of 37.9 kWh/m2 /year. The simple payback period values were also lower in the east-west orientation than the north-south one

Etude ethnobotanique de quelques lavandes marocaines spontanées

Le genre Lavandula est l'un des plus importants genres de la famille des Lamiacées et est riche en plantes à usage multiple, alimentaire, fourrager, aromatique, cosmétique et médicinal. Au Maroc, la bibliographie fait allusion à plusieurs espèces de ce genre, communément appelées lavandes, à écologie et phytogéographie diversifiées et dont d’une part la distinction taxinomique n’est pas des plus faciles et d’autre part l’éventualité d’un usage différent selon les localités et ou les espèces n’est pas investie. Aussi, l’objectif du présent travail est de rechercher les lavandes dans différentes régions du Maroc ; puis, par le biais d’investigations ethnobotaniques auprès d’herboristes et de vendeurs de plantes aromatiques et médicinales (PAM), inventorier leurs principaux usages traditionnels. Ainsi, durant l’année 2014, des prospections floristiques à la recherche de lavandes sauvages ont permis de repérer et localiser Lavandula stoechas L et L. atlantica Braun-Blanq , L. pedunculata Mill, L. multifida L, L. dentata L, L. maroccana Murb respectivement au plateau central « Oulmès, et Aguelmous » et au moyen atlas central « Ait Amro Ouali », la plaine de Sais « Ain Jerri », et en haut atlas occidental « bassin versant d’Ourika ». Les enquêtes ethnobotaniques menées auprès d’herboristes et vendeurs dans chaque site de récolte, via un questionnaire préétabli ont permis de dresser la liste des noms vernaculaires utilisés pour chaque espèce et ont révélé que les lavandes ont essentiellement des vertus thérapeutiques, que les feuilles et les fleurs sont les parties les plus utilisées surtout sous forme de décoction pour le traitement d’affections broncho-pulmonaires, gastrointestinales et uro-génitales.Mots clés : Lavandula, plantes aromatique et médicinales, enquête ethnobotanique, Maroc