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1.
Bounouri Yassine Berkani Madjid Zamouche Abdelmalek Dańczak Anna Chojnacka Ida Rycerz Leszek 《Journal of Thermal Analysis and Calorimetry》2018,134(3):1589-1597
Thixoforming involves heating different types of alloys to the semisolid state at high heating rates and forming in die-casting machines or conventional presses. At temperatures higher than the solidus and lower than the liquidus, the mush metal behaves like a high-viscosity thixotropic material. Therefore, determining the thermodynamic behavior of the solid-to-liquid transition is paramount to control thixoforming processes. This article describes a simple, novel experimental setup based on differential thermal analysis (DTA) for analyzing the phase transitions in an alloy heated using high heating rates typical of industrial applications. A365 alloy was chosen to demonstrate the effectiveness of the method as the phase transformations for this alloy in semisolid materials (SSM) processing are well understood. Samples were heated to 750 °C using constant linear heating rates of 5, 10, 15, 20, 25, 50, 75, 100 and 125 °C min in a Norax 25 kW 8 kHz induction furnace with an Omron E5CK temperature controller. AISI 316 austenitic stainless steel was used as the inert reference. Comparison of the results of DTA using the proposed method and the results of simulation with Thermo-Calc® indicates that the proposed in situ DTA device and its method is suitable for analyzing phase transitions when high heating rates are used. 相似文献
2.
Farid Halet Ahmed Réda Yeddou Abdelmalek Chergui Salima Chergui Boubekeur Nadjemi Aïssa Ould-Dris 《Journal of Dispersion Science and Technology》2013,34(12):1736-1741
Cyanide is considered one of the most dangerous compounds for the environment. They are discharged by various industries: chemical and metallurgical processes (extraction of gold and silver) and food industries. Adsorption is among the most used processes for elimination of cyanides particularly for the low concentrations. In this work, the cyanide removal is carried out by adsorption onto activated carbons prepared from olive stones and coffee ground. So we can promote this by-product as an inexpensive adsorbent. The prepared activated carbons are characterized by scanning electron micrograph and by determination of the physicochemical properties and specific surface area. All the adsorption experiments were performed in batch mode on synthetic water cyanide (KCN) at pH 10.8–11.0 to avoid volatilization of very toxic HCN. To describe the adsorption kinetics, the kinetic models of pseudo-first-order, pseudo-second-order, and intra-particle diffusion were applied. The experimental equilibrium data for adsorption of free cyanide were analyzed by the Langmuir, Freundlich, and Temkin isotherm models. 相似文献
3.
4.
Using numerically simulated results, we show that an efficient laser-to-optical fibre coupling is possible by incorporating a uniform spot size converter (SSC) based on diluted waveguides with low contrast index waveguide. We propose photonic devices and circuits composed of a laser coupled through a SSC to a one and more microdisks, which are coupled to an optical fibre. Using the finite-difference time-domain (FDTD) method, we simulate the propagation characteristics of light in the fundamental elements as the pulse propagates down the whole structure. Also by the use of the FDTD method, we model and predict the geometrical parameters used for the design of the different types of the proposed devices. It is shown that the coupling efficiency is less than 10% without the diluted waveguide, but the SSC couplers have over 73% power transmission. The gap width between the microdisks, coupling between the laser and the sequence of microdisks is investigated. We report the microdisk effect on the coupling efficiency between the laser-SSC structure and the optical fibre. 相似文献
5.
Abdelmalek Abdesselam 《Annales Henri Poincare》2011,12(7):1321-1347
We provide an explicit combinatorial expansion for the ground state energy of the massless spin-Boson model as a power series
in the coupling parameter. Our method uses the technique of cluster expansion in constructive quantum field theory and takes
as a starting point the functional integral representation and its reduction to an Ising model on the real line with long
range interactions. We prove the analyticity of our expansion and provide an explicit lower bound on the radius of convergence.
We do not need multiscale nor renormalization group analysis. A connection to the loop-erased random walk is indicated. 相似文献
6.
Abdelmalek Zahra Khan Sami Ullah Waqas Hassan Riaz Arshad Khan Israr Ali Tlili Iskander 《Journal of Thermal Analysis and Calorimetry》2021,144(1):205-217
Journal of Thermal Analysis and Calorimetry - The significant bioconvection phenomenon with the utilization of nanoparticles encountered fundamental industrial and technological applications in... 相似文献
7.
Nabih N. Abdelmalek 《BIT Numerical Mathematics》1977,17(3):249-261
A numerically stable simplex algorithm for calculating the restricted Chebyshev solution of overdetermined systems of linear equations is described. In this algorithm minimum computer storage is required and no conditions are imposed on the coefficient matrix or on the right hand side of the system of equations. Also a new way of implementing a triangular decomposition method to the basis matrix is used. The ordinary Chebyshev solution, the one-sided Chebyshev solutions and the Chebyshev approximation by non-negative functions are obtained as special cases in this algorithm. Numerical results are given. 相似文献
8.
In this paper we are interested in a strong bilevel programming problem (S). For such a problem, we establish necessary and sufficient global optimality conditions. Our investigation is based on the use of a regularization of problem (S) and some well-known global optimization tools. These optimality conditions are new in the literature and are expressed in terms of \(\max \)–\(\min \) conditions with linked constraints. 相似文献
9.
Physisorption and chemisorption of hydrogen on solid-state materials are two fundamentally different interactions, both of which display advantages and drawbacks for hydrogen storage. It has been hypothesised that their combination by merging two classes of materials showing different sorption behaviour towards hydrogen in the same composite may synergistically combine their desirable properties. As representatives of such composites, palladium nanoparticles, nanoclusters, and single atoms have been encapsulated in a metal-organic framework matrix, embedded, or immobilised in its pores, respectively. In this minireview, we review advances on the understanding and potential applications of the combination of Pd with metal-organic framework matrices through the analysis of the nanocomposite materials’ interaction with hydrogen and sorption properties. 相似文献
10.
Lachtar Zohra Khorief Nacereddine Abdelmalek Djerourou Abdelhafid 《Structural chemistry》2020,31(1):253-261
Structural Chemistry - The enantioselectivity of the oxazaborolidine-catalysed asymmetric reduction reaction of ketimine generated from acetophenone has been investigated by transition state theory... 相似文献