Tunis University

About: Tunis University is a education organization based out in Tunis, Tunisia. It is known for research contribution in the topics: Population & Thin film. The organization has 11745 authors who have published 15400 publications receiving 154900 citations. The organization is also known as: University of Tunis & UT.

Selective catalytic reduction of NO with NH3 over Cr-ZSM-5 catalysts: General characterization and catalysts screening

Abstract: Cr exchanged ZSM-5 catalysts (Cr/Al = 1) prepared by solid-state ion exchange were tested in SCR of NO with ammonia. Since CrCl3 precursor sublimates during the solid-state reaction, chromate species were stabilized in the exchange sites of H+-ZSM-5 (Si/Al = 15) and Cr2O3 formation is, therefore, limited. However, using Cr nitrate and NH4+-ZSM-5 (Si/Al = 26) zeolite, massive particles of α-Cr2O3 occupied the catalyst surface. At the contrary, well-dispersed particles of Cr2O3 were detected with H+-ZSM-5 and Cr nitrate precursor. Starting from Cr acetate precursor, agglomerates of amorphous oxide were detected with H+-ZSM-5 like support. In the temperature range 50–300 °C, Cr chloride and Cr nitrate precursors and H+-ZSM-5 led to highly active catalysts, while Cr nitrate and NH4+-ZSM-5 led to a poorly active catalyst. However, catalysts issued from Cr acetate are promising in SCR but inefficient agglomerates of oxide (amorphous or crystalline chromia) could be avoided with NH4+-ZSM-5 like support.

Structures, relative stability and binding energies of neutral water clusters, (H2O)2–30

Abstract: We have revised the structures of neutral water clusters, (H2O)n=2–30, with the affordable M06-2X functional, presenting up to 25 isomers for each cluster size. Besides, relative energies, relative free energies and binding energies of all the investigated clusters are also provided. Temperature dependent isomer distributions of the clusters are also presented. As a result, significant new local minima structures are located on the PESs of water clusters. When available our global minima structures are in agreement with the CCSD(T)/CBS reports. We noted that the cage isomer with a central solvated water molecule starts to be the global minimum structure from n = 17. In addition, we found that from n = 19, the cage isomers are the global minimum structure or they are among the most stable structures, on the PESs of water clusters. From the water 26-mer till 30-mer (excluding the 29-mer), the most stable structures are cage isomers with two central solvated water molecules. Moreover, these cage isomers dominate the population of clusters for temperatures ranging from 20 to 400 K. As far as the energetic study is concerned, binding energies of neutral water clusters are computed using M06-2X, APFD, MN15 and ωB97XD functionals associated with the aug-cc-pVTZ (aVTZ) basis set for n = 2–30. As a result, the MN15/aVTZ binding energies are reported to be in good agreement with the CCSD(T)/CBS benchmark results for n = 2–10. The mean absolute deviation (MAD) for n = 2–10 is calculated to be 1.0 kcal mol−1.

Preference-Based Many-Objective Evolutionary Testing Generates Harder Test Cases for Autonomous Agents

Abstract: Despite the high number of existing works in software testing within the SBSE community, there are very few ones that address the problematic of agent testing. The most prominent work in this direction is by Nguyen et al. [13], which formulates this problem as a bi-objective optimization problem to search for hard test cases from a robustness viewpoint. In this paper, we extend this work by: 1 proposing a new seven-objective formulation of this problem and 2 solving it by means of a preference-based many-objective evolutionary method. The obtained results show that our approach generates harder test cases than Nguyen et al. method ones. Moreover, Nguyen et al. method becomes a special case of our method since the user can incorporate his/her preferences within the search process by emphasizing some testing aspects over others.