Finite-element analysis of errors on stress and strain measurements in dynamic tensile testing of low-ductile materials

Tensile dynamic tests are essential experiments to develop and validate constitutive equations. In this paper, we studied the errors on stress and strain measurement in dynamic tensile tests by using finite-element analysis. Two strain and one stress measures were discussed. Mainly, we considered the influence of the material and multiple geometrical and testing parameters. We were limited to the case of elastic behaviour of the material. We observed that the errors on the strain measures are essentially influenced by the geometrical parameters. On the other hand, the error on the stress measure are highly correlated to stress field homogeneity.     

AMPN: a semantic resource for Arabic morphological patterns

In this paper, we present a pilot Arabic morphological Pattern Net study based on a lexical semantic resource. During this study, a limited number of Arabic Morphological Patterns have been selected in order to analyze the structure and the behavior of the verbs in the Arabic PropBank, which is a semantically annotated corpus of newswire text from the Annahar Journal. Our goal is twofold: (a) to study whether there is a direct relationship between morphological patterns and verbal semantic roles; and, (b) to verify that this direct relationship is a pervasive component of Arabic verb morphology. The approach to building our morphological Patterns database is based on linguistic generalization of the semantic roles of the verbal predicates. The results obtained show promising outcome for a future, more comprehensive study.     

From SIR to SEAIRD: A novel data-driven modeling approach based on the Grey-box System Theory to predict the dynamics of COVID-19

Applied Intelligence - Common compartmental modeling for COVID-19 is based on a priori knowledge and numerous assumptions. Additionally, they do not systematically incorporate asymptomatic cases....     

Chemical composition, angiotensin I-converting enzyme inhibitory, antioxidant and antimicrobial activities of essential oil of Tunisian Thymus algeriensis Boiss. et Reut. (Lamiaceae)

The present study describes chemical composition, angiotensin I-converting enzyme (ACE) inhibitory, antioxidant and antimicrobial activities of the essential oil of wild growing Thymus algeriensis Boiss. et Reut. (Lamiaceae), a traditional medicinal plant which is mainly endemic in Tunisia and Algeria. The essential oil from the fresh leaves and flowers of T. algeriensis were extracted by hydrodistillation and analysed by GC and GC/MS. Fifty-seven compounds were identified accounting for 97.71% of the total oil, where oxygenated monoterpenes constituted the main chemical class (44.85%). The oil was dominated by camphor (7.82%), 4-terpineol (7.36%), α-pinene (6.75%), 1,8-cineole (5.54%) and cis-sabinene hydrate (5.29%). The T. algeriensis essential oil was found to possess an interesting inhibitory activity towards ACE with an IC50 value of 150 μg/ml. The obtained results also showed that this oil can act as radical scavengers (IC₅₀ = 0.8 mg/ml) and displayed a lipid peroxidation inhibitory activity (IC₅₀ = 0.5 mg/ml) as evaluated by 2,2-diphenyl-1-picrylhydrazyl and β-carotene bleaching methods, respectively. Furthermore, the oil was tested for antimicrobial activity against six bacterial strains and two fungal strains. The inhibition zones and minimal inhibitory concentration values of microbial strains were in the range of 13.5-64 mm and 1-6 μl/ml, respectively. The oil exhibited remarkable inhibitory activity against fungal and Gram-positive bacteria strains.     

Synthesis,Crystal Structure,Vibrational and Magnetic Properties of a New Organic–inorganic Hybrid Material: 2-Amonium-methyl-1-Ethylpyrrolidinium Tetrachlorocuprate (II)

Synthesis, crystal structure, vibrational study and magnetic properties of the compound (C₇H₁₈N₂) CuCl₄ are reported. The latter crystallizes in the monoclinic system (space group P2 ₁, Z = 4) with the following unit cell dimensions: a = 7.569(5) Å b = 14.174(5) Å, c = 13.193(2) Å and β = 105.53(3)^°. Besides, its structure was solved using 5754 independent reflections down to R = 0.0475. The atomic arrangement can be described by alternating organic and inorganic layers stacked in the [\(\bar {1}\)01] direction, made up of tetrahedral of tetrachlorocuprate CuCl\(_{4}^{2-}\) sandwiched between two organic layers. In crystal structure, the inorganic layer, built up by independent monomeric [CuCl₄]^2?, is connected to the organic ones through hydrogen bonding in order to build a three-dimensional network. The magnetic behavior of (C₇H₁₈N₂) CuCl₄ samples was investigated as a function of temperature and applied field. At hightemperature paramagnetic behavior, and at low temperature, evidence for weak ferromagnetism, reinforced by a hysteresis loop at 2 K is observed. The magnetic behavior of (C₇H₁₈N₂) CuCl₄ is attributed to Cu (II) due to the presence of an active Jahn–Teller effect in the d ⁹ electronic system, which give rise to short-range weak ferromagnetism.     

Structural and Magnetic Properties of Pr0.6Sr0.4Mn1−x Fe x O3 (0≤x≤0.3) Manganites Oxide Prepared by the Ball Milling Method

We present the structural and magnetic properties of Pr_0.6Sr_0.4Mn_1?x Fe _x O₃ (x=0, 0.1, 0.2, and 0.3) compounds. Samples have been prepared by the ball milling method. Rietveld refinements of the X-ray powder diffraction data show that all our synthesized samples are single phase and crystallize in the orthorhombic symmetry with the Pnma space group. The unit cell volume increases with increasing the Fe content. The infrared spectrum shows two active bands, which can be ascribed to the internal stretching and bending modes. The magnetization measurements versus temperature showed that Fe doping leads to a weakening of the ferromagnetic ordering at low temperature, the Curie temperature T _C decreases from 300 K for x=0.0 to 88 K for x=0.2. The magnetization versus applied magnetic measurements at low temperature lead to conclude that the substitution of Mn³⁺ ions by Fe³⁺ ions triggers antiferromagnetic interactions between the Fe³⁺ and Mn⁴⁺ spins, and also the magnetization versus applied magnetic measurements at room temperature shows a small hysteresis loop and a low coercive field, which indicates that the samples are superparamagnetic.     

A photophysical technique for the measurement of local oxygen concentration near an electrode surface

Electrochemical processes involving gas production are of great technical importance but the mechanisms involved in the growth of electrogenerated bubbles and transport processes involving gas near an electrode still remain obscure. This paper describes an original technique, based on the inhibition of the fluorescence of an appropriate substance by dissolved oxygen, for the measurement of the local concentration of dissolved oxygen near an electrode. The possibilities offered by this technique and typical results are presented and discussed. This paper was presented at the International Workshop on Electrodiffusion Diagnostics of Flows held in Dourdan, France, May 1993.     

Effect of the interface states on the cell parameters of a thin film quasi-monocrystalline porous silicon as an active layer

Unlike crystalline silicon, quasi-monocrystalline porous silicon (QMPS) layers have a top surface with small voids in the body. What is more pertinent to the present study is the fact that, at a given wavelength of interest for solar cells, these layers are often reported, in the literature, to have a higher absorption coefficient than crystalline silicon. The present study builds on existing literature, suggesting an analytical model that simulates the performance of an elementary thin QMPS (as an active layer) solar cell. Accordingly, the effects that the interface states located at the void-silicon interface and that the porosity of this material have on the cell parameters are investigated. Furthermore, the effects of the optimum base doping, QMPS thickness, and porosity on the photovoltaic parameters were taken into consideration. The results show that the optimum base doping depends on the QMPS thickness and porosity. For an 8 μm thickness, the film QMPS layer gives a 35.4 mA/cm² for short-circuit current density, 15% for conversion efficiency, and 527 mV for open-circuit voltage when the value of the interface states is about 10¹² cm⁻² and the base doping is about 2×10¹⁸ cm⁻³ under AM 1.5 conditions.     

Effect of the front surface field on crystalline silicon solar cell efficiency

The present paper reports on a simulation study carried out to determine and optimize the effect of the high–low junction emitter (n⁺-n) on thin silicon solar cell performance. The optimum conditions for the thickness and doping level of the front surface layer with a Gaussian profile were optimized using analytical solutions for a one dimensional model that takes on the theory relevant for highly doped regions into account. The photovoltaic parameters of silicon solar cells with front surface field layer (n⁺-n-p structure) and those of the conventional one (n-p structure) are compared. The results indicate that the most important role played by the front surface field layer is to enhance the collection of light-generated free carriers, which improves the efficiency of the short wavelength quantum. This is achieved by a drastic reduction in the effective recombination at the emitter upper boundary, a property primarily responsible for the decrease in the emitter dark current density. The findings also indicate that the solar cell maximum efficiency increase by about 2.38% when the surface doping level of the n⁺-region and its thickness are equal to 2.10²⁰ cm^?3 and 0.07 μm, respectively.     

Magneto-Structural Studies of 2-(2-Ammoniumethyl)-1-méthyl Pyrrolidinium Tetrachlorocuprate (II)

The (C₇H₁₈N₂)CuCl₄ compound crystallized in the orthorhombic system with space group P 2₁2₁2₁ and the following unit cell are: a=7.353(3), b=11.608(5), c=16.666(8) Å, and Z=4; R=0.0327, wR=0.085. The crystal structure consists of infinite zigzag one-dimensional chains of 2-(2-ammoniumethyl)-1-méthyl pyrrolidinium dications and distorted [CuCl₄]^2? tetrahedral anions along the b axis. The cohesion of the atomic arrangement is ensured by hydrogen bonding (N–H?Cl). The temperature dependence of the magnetic susceptibility was measured in the temperature range of 2–100 K at different magnetic field intensities. The results indicate that the complex exhibit a weak antiferromagnetic coupling between the copper (II) centers. The ferromagnetic ordering is further confirmed by the magnetic field dependence of the magnetization between 2 and 30 K.