Unique structure of fibrous ZSM-5 catalyst expedited prolonged hydrogen atom restoration for selective production of propylene from methanol

A unique mesostructured fibrous silica@ZSM-5 (HSi@ZSM-5) catalyst was synthesized via microemulsion ZSM-5 zeolite seed assisted synthesis method and successfully applied in enhanced propylene formation in methanol to olefin (MTO) process. Characterization of the catalysts were carried out by FESEM, TEM, XRD, TGA, N₂ adsorption-desorption, NH₃ and KBr probed FTIR. Catalytic performance of as-synthesized catalyst was examined using a micro-pulse reactor and compared with the commercial HZSM-5. The reaction mechanism was elucidated by in-situ methanol FTIR spectroscopy. It was found that HSi@ZSM-5 produced higher propylene selectivity (56%) and was stable for long time on stream (80 h), nearly three-fold higher than that of commercial HZSM-5. In addition, HSi@ZSM-5 displayed higher rate of methanol dehydration, surface methoxy species generation and olefin methylation, indicating that alkene catalytic cycle is the dominant reaction mechanism. The higher selectivity towards propylene was correlated to the existence of moderate acidity which impeded the formation of paraffins and polymethylbenzene intermediates. These observations are further supported by KBr probed FTIR findings which revealed negligible paraffinic carbon species on HSi@ZSM-5. Thus, the unique fibrous silica@ZSM-5 retarded coke deposition due to suppression of undesired side reactions thereby signifying intensified propylene formation, which is highly desirable in commercial MTO processes.     

Enhancement in Physical Properties of Silver-Doped Fe–Ni Invar Nano-alloy Using Chemical Reduction Method

Journal of Superconductivity and Novel Magnetism - Silver-substituted Fe–Ni nano invar alloy is a new and innovative field of research due to their interesting invar, magnetic and electrical...     

Synthesis and Antifungal Activity of Some Organotin(IV) Carboxylates

Six diorganotin(IV) carboxylates prepared by reacting diorganotin(IV) dichlorides with the respective silver carboxylate have been tested for antifungal activity against Aspergillus. niger, Aspergilluus flavus and Pencillium. citrinum in Sabourand dextrose broth. The compounds generally exhibit greater fungitoxicity than the diorganotin(IV) dichlorides and the carboxylic acids from which they were synthesized. In keeping with the generally accepted notion that the organotin moiety plays an important role in deciding the antifungal activity of an organotin compound, the diphenyltin(IV) compounds were more active than their di-n-butyltin(IV) analogues. However, the order of increasing fungitoxicity of the compounds parallels that of the uncomplexed carboxylic acids. The implications of the results are discussed.     

Competency‐based IT personnel selection using a hybrid SWARA and ARAS‐G methodology

In the knowledge economy, human capital is a key factor in any organization to achieve a sustainable competitive advantage. Thus, selection of competent personnel is the most important function of human resource managers. However, because of a wide range of criteria and organizational factors that affect the process, personnel selection is often regarded as a complex problem that can be answered through multicriteria decision‐making (MCDM) procedures. Despite the great importance of determining a comprehensive set of criteria, it has not gained enough attention in the literature. This study presents a competency framework with five criteria for choosing the best information technology (IT) expert from five alternatives. The stepwise weight assessment ratio analysis (SWARA) and grey additive ratio assessment (ARAS‐G) methods are also used to derive the criteria weights and provide the final alternative, respectively. The results reveal that subject competency is the major criteria in IT personnel selection.     

A comprehensive survey of AI-enabled phishing attacks detection techniques

In recent times, a phishing attack has become one of the most prominent attacks faced by internet users, governments, and service-providing organizations. In a phishing attack, the attacker(s) collects the client’s sensitive data (i.e., user account login details, credit/debit card numbers, etc.) by using spoofed emails or fake websites. Phishing websites are common entry points of online social engineering attacks, including numerous frauds on the websites. In such types of attacks, the attacker(s) create website pages by copying the behavior of legitimate websites and sends URL(s) to the targeted victims through spam messages, texts, or social networking. To provide a thorough understanding of phishing attack(s), this paper provides a literature review of Artificial Intelligence (AI) techniques: Machine Learning, Deep Learning, Hybrid Learning, and Scenario-based techniques for phishing attack detection. This paper also presents the comparison of different studies detecting the phishing attack for each AI technique and examines the qualities and shortcomings of these methodologies. Furthermore, this paper provides a comprehensive set of current challenges of phishing attacks and future research direction in this domain.

     

Sinc-Galerkin method for solving nonlinear weakly singular two point boundary value problems

A study of Sinc-Galerkin method based on double exponential transformation for solving a class of nonlinear weakly singular two point boundary value problems with non-homogeneous boundary conditions is given. The properties of the Sinc-Galerkin approach are utilized to reduce the computation of nonlinear problem to nonlinear system of equations with unknown coefficients. This method tested on several test examples. We compare our numerical results with several numerical results of existing methods. The demonstrated results confirm that proposed method is considerably efficient, accurate nature and rapidly converge.     

Rheological characterization of polypropylene/poly(ethylene-<Emphasis Type="Italic">co</Emphasis>-propylene) in-reactor blends synthesized under different polymerization conditions

In-reactor blends of polypropylene/poly(ethylene-co-propylene) with complex microstructure, synthesized through different polymerization procedures; two-step (one homopolymerization and one copolymerization under high ethylene concentration) and three-step (with an additional copolymerization step under low ethylene concentration), were characterized by rheological measurements. The effects of a change in the polymerization process on the types and amounts of block copolymers in the blends were evaluated using small amplitude oscillation rheometry in the linear viscoelastic region. The Palierne model in its complete form was employed to model the rheological behavior of the blends. For this analysis the reactor products were separated into xylene cold insoluble (XCI) and xylene cold soluble fractions. Besides, another two copolymer fractions at 80 and 100 °C, which are crystallizable copolymer fractions and contain block copolymers rich in polyethylene and polypropylene, respectively, were separated from XCI fraction by xylene using temperature gradient elution fractionation method. Considering all copolymer fractions as dispersed and the remained fraction (mostly polypropylene) as matrix phase, it was shown that the rheological properties of the blends could not be predicted by Palierne model. It was found that only by considering part of block copolymer fractions having long polypropylene sequences along with polypropylene homopolymer as one phase, the rheological properties of the blends could be predicted by Palierne model. By rheological modeling, it was confirmed that the amounts of copolymers with long polypropylene sequences which are miscible with the matrix are higher in the case of three-step blends and also the elasticity of three-step polymerized blends is higher than two-step polymerized blends.     

Reconciliation between experimental and Monte Carlo-based simulation of the pore size distribution in mesoporous silicon

It is demonstrated for the first time that mesoporous PS structures obtained by the electrochemical etching of p(+)(100) oriented silicon wafers might assume the peculiarity of invariance of the first peak positions in their pore size distribution curves, albeit for current densities far from the electropolishing region and at constant electrolyte composition. A new Monte Carlo-based simulation model is presented that predicts reasonably the pore size distribution of the PS layers and the observed invariance of peak position with respect to changes in current density. The main highlight of the new model is the introduction of a 'light avalanche breakdown' process in a mathematical fashion. The model is also able to predict an absolute value of 4.23?? for the smallest pore created experimentally. It is discussed that the latter value has an exact physical meaning: it corresponds with great accuracy to the width of a void created on the surface due to the exclusion of one Si atom.     

Confinement-Induced Phonon Softening and Hardening in Sb2Te3 Thin Films

Scaling effects in Sesqui-chalcogenides are of major interest to understand and optimize their performance in heavily scaled applications, including topological insulators and phase-change devices. A combined experimental and theoretical study is presented for molecular beam epitaxy-grown films of antimony-telluride  (Sb₂Te₃). Structural,vibrational, optical, and bonding properties upon varying confinement are studied for thicknesses ranging from 1.3 to 56 nm. In ultrathin films, the low-frequency coherent phonons of A_1g¹ symmetry are softened compared to the bulk (64.5 cm⁻¹ at 1.3 nm compared to 68 cm⁻¹ at 55.8 nm). A concomitant increase of the high-frequency A_1g² Raman mode is seen. X-ray diffraction analyses unravel an accompanying out of plane stretch by 5%, mainly stemming from an increase in the Te-Te gap. This conclusion is supported by density functional theory slab models, which reveal a significant dependency of chemical bonding on film thickness. Changes in atomic arrangement, vibrational frequencies, and bonding extend over a thickness range much larger than observed for other material classes. The finding of these unexpectedly pronounced thickness-dependent effects in quasi-2D material Sb₂Te₃ allows tuning of the film properties with thickness. The results are discussed in the context of a novel bond-type, characterized by a competition between electron localization and delocalization.