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101.
Ibtissem Boumnijel Hedi Ben Amor Hassen Chekir Nejib Hajji 《International journal of environmental analytical chemistry》2019,99(10):936-948
The aim of this study was to develop and validate a simple, new and efficient method for the analysis of hydrogen sulphide (H2S) released from the effluents of phosphoric acid production units. H2S sampling was performed by absorption of the industrial gas into a cadmium acetate absorbing solution. The formed cadmium sulphide (CdS), as a result of a chemical reaction, was analysed by turbidimetry. A methodical validation study of the proposed method was performed according to the requirements of ISO 17025 standards. The proposed method was demonstrated to be precise, linear and accurate over a concentration range of 6.91–92.16 mg/l. Detection and quantification limits were equal to 5.09 mg/l and 6.91 mg/l, respectively. Sample analysis had to be performed within 48 h of the sampling step. The turbidimetry method was applied successfully to the industrial gaseous effluents and can be considered as an economical alternative to the iodometric method. 相似文献
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Hanen Jrad Hanen Mallek Mondher Wali Fakhreddine Dammak 《Comptes Rendus Mecanique》2018,346(12):1159-1178
For the analysis and design process of smart structures with integrated piezoelectric patches, the finite element method provides an effective simulation approach. In this paper, an attempt on modeling and simulation of the behavior of hybrid active structures is carried out using developed Kirchhoff-type-four-node shell element.The finite element results are compared with reference solutions taking into account the electromechanical responses of smart structures with various geometries, and the results show very high agreement. The main aspect of the application of the proposed element is to predict the behavior of FGM shells containing piezoelectric layers. A set of numerical analyses is performed in order to highlight the applicability and effectiveness of the present finite element model, notably for smart FGM structures. A comprehensive parametric study is conducted to show the influence of material composition, the placement and the thickness of the piezoelectric layers on the deformation of the laminated structure. 相似文献
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Regularized formulation of the variational brittle fracture with unilateral contact: Numerical experiments 总被引:3,自引:0,他引:3
This paper presents a modified regularized formulation of the Ambrosio-Tortorelli type to introduce the crack non-interpenetration condition in the variational approach to fracture mechanics proposed by Francfort and Marigo [1998. Revisiting brittle fracture as an energy minimization problem. J. Mech. Phys. Solids 46 (8), 1319-1342]. We focus on the linear elastic case where the contact condition appears as a local unilateral constraint on the displacement jump at the crack surfaces. The regularized model is obtained by splitting the strain energy in a spherical and a deviatoric parts and accounting for the sign of the local volume change. The numerical implementation is based on a standard finite element discretization and on the adaptation of an alternate minimization algorithm used in previous works. The new regularization avoids crack interpenetration and predicts asymmetric results in traction and in compression. Even though we do not exhibit any gamma-convergence proof toward the desired limit behavior, we illustrate through several numerical case studies the pertinence of the new model in comparison to other approaches. 相似文献
104.
In this Perspective we discuss the ability of transition metal complexes to activate and cleave the Si–H and B–H bonds of hydrosilanes and hydroboranes (tri- and tetra-coordinated) in an electrophilic manner, avoiding the need for the metal centre to undergo two-electron processes (oxidative addition/reductive elimination). A formal polarization of E–H bonds (E = Si, B) upon their coordination to the metal centre to form σ-EH complexes (with coordination modes η1 or η2) favors this type of bond activation that can lead to reactivities involving the formation of transient silylium and borenium/boronium cations similar to those proposed in silylation and borylation processes catalysed by boron and aluminium Lewis acids. We compare the reactivity of transition metal complexes and boron/aluminium Lewis acids through a series of catalytic reactions in which pieces of evidence suggest mechanisms involving electrophilic reaction pathways.In this Perspective we compare the ability of transition metals and p-block Lewis acids to activate electrophilically hydrosilanes and hydroboranes. The mechanistic similarities and dissimilarities in different catalytic transformations are analyzed. 相似文献
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Pablo Ríos Dr. Josefina Díez Dr. Joaquín López‐Serrano Dr. Amor Rodríguez Dr. Salvador Conejero 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(47):16791-16795
The low‐electron‐count cationic platinum complex [Pt(ItBu’)(ItBu)][BArF], 1 , interacts with primary and secondary silanes to form the corresponding σ‐SiH complexes. According to DFT calculations, the most stable coordination mode is the uncommon η1‐SiH. The reaction of 1 with Et2SiH2 leads to the X‐ray structurally characterized 14‐electron PtII species [Pt(SiEt2H)(ItBu)2][BArF], 2 , which is stabilized by an agostic interaction. Complexes 1 , 2 , and the hydride [Pt(H)(ItBu)2][BArF], 3 , catalyze the hydrosilation of CO2, leading to the exclusive formation of the corresponding silyl formates at room temperature. 相似文献
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