3D discrete element modeling of concrete: study of the rolling resistance effects on the macroscopic constitutive behavior

The Discrete Element Method (DEM) is appropriate for modeling granular materials [14] but also cohesive materials as concrete when submitted to a severe loading such an impact leading to fractures or fragmentation in the continuum [1, 5, 6, 8]. Contrarily to granular materials, the macroscopic constitutive behavior of a cohesive material is not directly linked to contact interactions between the rigid Discrete Elements (DE) and interaction laws are then defined between DE surrounding each DE. Spherical DE are used because the contact detection is easy to implement and the computation time is reduced in comparison with the use of 3D DE with a more complex shape. The element size is variable and the assembly is disordered to prevent preferential cleavage planes. The purpose of this paper is to highlight the influence of DE rotations on the macroscopic non-linear quasi-static behavior of concrete. Classically, the interactions between DE are modeled by spring-like interactions based on displacements and rotation velocities of DE are only controlled by tangential forces perpendicular to the line linking the two sphere centroids. The disadvantage of this modeling with only spring-like interactions based on displacements is that excessive rolling occurs under shear, therefore the macroscopic behavior of concrete is too brittle. To overcome this problem a non linear Moment Transfer Law (MTL) is introduced to add a rolling resistance to elements. This solution has no influence on the calculation cost and allows a more accurate macroscopic representation of concrete behavior. The identification process of material parameters is given and simulations of tests performed on concrete samples are shown

Entanglement of Two Impurities through Electron Scattering

We study how two magnetic impurities embedded in a solid can be entangled by an injected electron scattering between them and by subsequent measurement of the electron's state. We start by investigating an ideal case where only the electronic spin interacts successively through the same unitary operation with the spins of the two impurities. In this case, high (but not maximal) entanglement can be generated with a significant success probability. We then consider a more realistic description which includes both the forward and back scattering amplitudes. In this scenario, we obtain the entanglement between the impurities as a function of the interaction strength of the electron-impurity coupling. We find that our scheme allows us to entangle the impurities maximally with a significant probability

Lead Removal from Agricultural Soil of Kurdistan Region by Fe3O4 Nanoparticles

Lead toxicity became a major concern worldwide and it is one of the most harmful pollutants in soil and groundwater. Hence, to remove lead from the soil, a high efficient technology with improved materials and system is required. This paper is a study shows removing of lead ions from soil samples, which have been taken from different sites in the Kurdistan Region, and investigated the adsorption of lead ions on high efficient adsorbent Fe3O4 nanoparticles. The magnetite nanoparticles of 27nm were synthesized by using a co-precipitation method and characterized by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDX). The adsorption experiments occurred at pH 8.0 under room temperature (25 °C) and the adsorption capacity was 22.8 mg/g which is 4 times higher than that of coarse particles. The correlation is measured between pH and absorbance, pH and concentration, electrical conductivity and concentration of lead ions in agricultural soil. These relationships indicate that the correlation coefficient values of (r = - 0.68, – 0.70 and + 0.83) are statistically significant at (ɑ= 0.05). The limit of detection (LOD) and limit of quantification (LOQ) were found to be 0.73 mg/L and 2.44 mg/L, respectively

Optimal State Discrimination Using Particle Statistics

We present an application of particle statistics to the problem of optimal ambiguous discrimination of quantum states. The states to be discriminated are encoded in the internal degrees of freedom of identical particles, and we use the bunching and antibunching of the external degrees of freedom to discriminate between various internal states. We show that we can achieve the optimal single-shot discrimination probability using only the effects of particle statistics. We discuss interesting applications of our method to detecting entanglement and purifying mixed states. Our scheme can easily be implemented with the current technology