A 3D DEM-LBM approach for the assessment of the quick condition for sands

We present a 3D numerical model to assess the quick condition (the onset of the boiling phenomenon) in a saturated polydisperse granular material. We use the Discrete Element Method (DEM) to study the evolution of the vertical intergranular stress in a granular sample subjected to an increasing hydraulic gradient. The hydrodynamic forces on the grains of the sample are computed using the Lattice Boltzmann Method (LBM). The principal assumption used is that grains remain at rest until the boiling onset. We show that the obtained critical hydraulic gradient is close to that defined in classical soil mechanics. To cite this article: M. Mansouri et al., C. R. Mecanique 337 (2009).     

Crystal structure and fast ionic conduction of TIZrF5

TlZrF₅ crystallizes in the monoclinic system with unit cell dimensions a = 8.112(1) Å, b = 7.927(3) Å, c = 7.929(1) Å, β = 123.99(1)° and space group P2₁/c (n^o 14); Z = 4. The structure was solved by conventional Patterson and Fourier methods and refined by full-matrix least-squares techniques to a conventional R of 0.057 (R_ω = 0.063). The structure consists of sheets of (ZrF₅)^? that may be described as edge-shared and corner-shared bicapped trigonal prisms (ZrF₈). The sheets run parallel to the y0z plan and are bonded together by the Tl ions which are surrounded by 12 F^? ions. The ionic conductivity of TlZrF₅ and TlHfF₅ has been investigated by complex impedance measurements and the relationships between structure and fast-ionic conduction are discussed.     

Minimizing energy consumption and makespan in a two-machine flowshop scheduling problem

Energy consumption has become a key concern for manufacturing sector because of negative environmental impact of operations. We develop constructive heuristics and multi-objective genetic algorithms (MOGA) for a two-machine sequence-dependent permutation flowshop problem to address the trade-off between energy consumption as a measure of sustainability and makespan as a measure of service level. We leverage the variable speed of operations to develop energy-efficient schedules that minimize total energy consumption and makespan. As minimization of energy consumption and minimization of makespan are conflicting objectives, the solutions to this problem constitute a Pareto frontier. We compare the performance of constructive heuristics and MOGAs with CPLEX and random search in a wide range of problem instances. The results show that MOGAs hybridized with constructive heuristics outperform regular MOGA and heuristics alone in terms of quality and cardinality of Pareto frontier. We provide production planners with new and scalable solution techniques that will enable them to make informed decisions considering energy consumption together with service objectives in shop floor scheduling.     

Study of the ionic conductivity of some fluorides of monovalent and tetravalent elements

Recently some interest has attached to ionic conductivity in the fluorides of metals with large cation radius because of the high fluorine mobility in these materials.A.c. conductivity measurements using the complex impedance method were carried out on sintered samples and showed that some binary fluorides of monovalent elements (M^I = K, Rb, Tl) and tetravalent elements (M^IV = Zr,Hf, Th, U) exhibit an appreciable ionic conductivity at moderate temperature : σ at 200°C (Ω^?1 cm^?1) Tl₃ZrF₇ 3.5 × 10^?3 Tl₂ZrF₆ 1.1 × 10^?2 Tl ZrF₅ 5 × 10^?4A single crystal study of Tl₃ZrF₇ shows that this compound crystallizes in the cubic system with space group Fm3m and cell parameter a = 9.34 Å. Therefore its crystal structure may be related to that of (NH₄)₃ZrF₇ [1 to 3] which is characterized by the presence of (ZrF₇)^3? ions with a pentagonal bipyramid as probable configuration. There are two crystallographically independent fluorine ions in position (96 j) of the space group Fm3m with a percentage of occupancy of 20.8 and 8.3 respectively. Thus Tl₃ZrF₇ is an example of fluoride where a three dimensional ionic conductivity occurs due to an incomplete occupation of a special symmetry position and where temperature increase might create rotation of (ZrF₇)^3? polyhedra giving rise to an important anionic disorder.In order to determine the origin of the ionic conductivity in TlZrF₅ we have undertaken the determination of the crystal structure of this fluoride from X-ray intensity measurements made with the aid of an automatic four circle diffractometer.TlZrF₅ cristallizes in the monoclinic system with unit-cell dimensions a = 8.112(1)Å, b = 7.927(3)Å, c = 7.929(1)Å, β = 123.99(1)° and space group P2 /c (No 14), Z = 4.In this structure, the Zr⁴⁺ ion is surrounded by eight F^? ions, the coordination polyhedron being a bicapped trigonal prism. This crystal structure consists of sheets (ZrF₅)^? that may be described as edge-shared and corner-shared bicapped trigonal prisms (ZrF₈). The sheets run parallel to the yOz plane and are bonded together by the Tl⁺ ions which are surrounded by twelve F^?ions. This arrangement produces relatively open tunnels in the b direction delimited by the cations. Of the five independent fluorine atoms, two of them, namely F(1) and F(4) are different from the other from the point of view of bonding and are located in these tunnels. Thus they are probably primarily responsible for the high conductivity of this material [4].With regard to Tl₂ZrF₆, it is the best as far as ionic conductivity is concerned. However its crystal structure is still unknown and its determination is actually under investigation in our laboratory.All this materials are good electronic insulators and their transport properties due to the high fluorine ion mobilities allow us to think that some of them hold considerable promise for use as solid electrolytes.     

Improved Full-Newton Step <Emphasis Type="Italic">O</Emphasis>(<Emphasis Type="Italic">nL</Emphasis>) Infeasible Interior-Point Method for Linear Optimization

We present several improvements of the full-Newton step infeasible interior-point method for linear optimization introduced by Roos (SIAM J. Optim. 16(4):1110–1136, 2006). Each main step of the method consists of a feasibility step and several centering steps. We use a more natural feasibility step, which targets the μ ⁺-center of the next pair of perturbed problems. As for the centering steps, we apply a sharper quadratic convergence result, which leads to a slightly wider neighborhood for the feasibility steps. Moreover, the analysis is much simplified and the iteration bound is slightly better.     

Comparison of electron beam and gamma ray irradiations effects on ruminal crude protein and amino acid degradation kinetics,and in vitro digestibility of cottonseed meal

This study was conducted to compare effects of electron beam (EB) and gamma ray (GR) treatments at doses of 25, 50 and 75 kGy on ruminal degradation kinetics of crude protein (CP), amino acid (AA), and in vitro digestibility of cottonseed meal (CSM). Ionizing radiations of EB and GR had significant effects (P<0.05) on CP and AA ruminal degradability characteristics of CSM. Effective ruminal degradability (ERD) of CP was lower in EB and GR irradiated CSM (P<0.05) than in unirradiated CSM. GR and EB treatments had the same effects on ERD decreasing of CP (P>0.05). Irradiation processing caused decrement in AA degradation after 16 h of ruminal incubation (P<0.05). EB irradiation was more effective than GR irradiation in lessening the ruminal degradability of AA (P<0.05). EB and GR treatments at a dose of 75 kGy increased in vitro digestibility of CSM numerically. This study showed that EB could cause CP and AA bypass rumen as well as GR. Therefore, ionizing irradiation processing can be used as an efficient method in improving nutritional value of CSM.     

A Novel 1:1 Co-Crystal of Bis(1,10-Phenanthroline)(1,10-Phenanthroline-5,6-Dione)Nickel(II) Hexafluorophosphate and Tris(1,10-Phenanthroline)Nickel(II) Hexafluorophosphate Complexes, [Ni(phen)2(phen-dione)] [Ni(phen)3] (PF6)4

Abstract  

The purpose of this study was to investigate whether co-crystals form by simply mixing pure solutions of [Ni(phen)₃](PF₆)₂ and [Ni(phen)₂(phen-dione)](PF₆)₂ where phen is 1,10-phenanthroline and phen-dione is 1,10-phenanthroline-5,6-dione. The 1:1 cocrystal, [Ni(phen)₂(phen-dione)][Ni(phen)₃](PF₆)₄·CH₃CN has been characterized by elemental analysis, IR, paramagnetic NMR, and UV–vis spectroscopies, cyclic voltammetry, and single crystal X-ray structure analysis. The title complex crystallized in triclinic crystal system (z = 2) with space group of Pī, a = 13.201(2) ?, b = 14.782(3) ?, c = 22.294(4) ?, α = 81.575(15)^o, β = 88.756(15)^o, γ = 88.032(15)^o and V = 4300.1(14) ?³. A careful inspection of the packing pattern in the lattice reveals that non-covalent interactions of three different types, viz. C–H···F, C=O···H−C and C−H···π interactions, are active in the lattice. The coordination around the Ni(II) centers is a distorted octahedral, with bite angles of 78.3−79.8^o for the chelating phen and phen-dione ligands. Cyclic voltammetry of this co-crystal shows that the Ni(III/II) couple is quasi-reversible. The effective magnetic moment (μ_eff) of the co-crystal was measured to be 2.87 BM per Ni(II) ion by Evans method. The magnitude of μ_eff is consistent with magnetic moment for octahedral Ni(II) complexes.     

Polynomial interior-point algorithm for P * {(\kappa)} horizontal linear complementarity problems

In this paper an interior-point algorithm for P _*(κ) horizontal linear complementarity problems is proposed that uses new search directions. The theoretical complexity of the new algorithm is calculated. It is investigated that the proposed algorithm has quadratically convergent with polynomial iteration complexity $O((1+\kappa)\sqrt{n}\log\frac{n}{\varepsilon})$ , coincide with the best known iteration bound for P _*(κ) horizontal linear complementarity problems.