El Sayed H. El Ashry  Samir A. Senior 《Corrosion Science》2011,(3):1025-1034

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Mostafa Safdari Shadloo  Amir Zainali  Samir H. Sadek  Mehmet Yildiz 《Computer Methods in Applied Mechanics and Engineering》2011,200(9-12):1008-1020

In this article, we present numerical solutions for flow over an airfoil and a square obstacle using Incompressible Smoothed Particle Hydrodynamics (ISPH) method with an improved solid boundary treatment approach, referred to as the Multiple Boundary Tangents (MBT) method. It was shown that the MBT boundary treatment technique is very effective for tackling boundaries of complex shapes. Also, we have proposed the usage of the repulsive component of the Lennard-Jones Potential (LJP) in the advection equation to repair particle fractures occurring in the SPH method due to the tendency of SPH particles to follow the stream line trajectory. This approach is named as the artificial particle displacement method. Numerical results suggest that the improved ISPH method which is consisting of the MBT method, artificial particle displacement and the corrective SPH discretization scheme enables one to obtain very stable and robust SPH simulations. The square obstacle and NACA airfoil geometry with the angle of attacks between 0° and 15° were simulated in a laminar flow field with relatively high Reynolds numbers. We illustrated that the improved ISPH method is able to capture the complex physics of bluff-body flows naturally such as the flow separation, wake formation at the trailing edge, and the vortex shedding. The SPH results are validated with a mesh-dependent Finite Element Method (FEM) and excellent agreements among the results were observed.  相似文献   

    

Manel Nourine  Moulai Karim Boulkadid  Sabri Touidjine  Elamine Louafi  Hamdane Akbi  Hamoud Abdelali  Moulay Yahia Zakaria  Samir Belkhiri 《Propellants, Explosives, Pyrotechnics》2024,49(5):e202300274

In this investigation, we successfully synthesized a hybrid material, N-rGO@Fe₂O₃, via a one-step hydrothermal process, comprising nitrogen-doped reduced graphene oxide and α-Fe₂O₃. Thorough characterization using diverse analytical methods validated its structure. Employing this hybrid composite as a catalyst, we studied its efficacy in the catalytic thermal decomposition of ammonium nitrate (AN). The N-rGO@Fe₂O₃/AN composite was prepared using a recurrent spray coating method with 3 % mass of the hybrid material. Thermo-gravimetric (TG) and differential scanning calorimetric (DSC) analyses were employed to investigate the catalytic effect. Computational assessment of Arrhenius parameters was conducted through isoconversional kinetic approaches. Results from the kinetic analysis allowed the determination of the critical ignition temperature. Furthermore, calorific values for pure AN and N-rGO@Fe₂O₃/AN were measured using an oxygen calorimetric bombe, revealing a 41 % reduction in activation energy barrier and a lowering of the critical ignition temperature from 292 °C to 283 °C upon incorporation of the hybrid material. Notably, the surface modification of AN with N-rGO@Fe₂O₃ resulted in an increase of 1440 J/g in the observed calorific values. These findings highlight the potential of N-rGO@Fe₂O₃ as an effective catalyst, offering promising implications for applications in enhancing ammonium nitrate thermal decomposition.  相似文献   

    

Mohamed Hasanin  Amal H. Abdel Kader  Essam S. Abd El-Sayed  Samir Kamel 《Starch - St?rke》2023,75(5-6):2200132

The possibility of manufacturing edible packaging materials with tailored properties and low cost has attracted much interest. This work presents a new material for edible packaging made from flaxseed gum (FSG) and chitosan (Ch) loaded with zinc oxide nanoparticles (ZnO-NPs). ZnO-NPs are synthesized in situ during the preparation of the edible film. The Ch/FSG/ZnO-NPs films are prepared by casting Ch in different ratios of FSG (12.5%, 25%, 37.5%, and 50%). The resulting films are evaluated for their physicochemical, mechanical, and barrier properties to determine their suitability for coating or packaging food or bioproducts. By studying the antimicrobial activities of the ZnO-NPs loaded films, we can see that ZnO-NP's concentration highly affects these activities. In addition, the FSG improves mechanical properties. Films developed by incorporating ZnO-NPs are proposed to be appropriate for low-moisture food and pharmaceutical products, which can reduce environmental problems associated with synthetic packaging. Consequently, Ch/FSG composite films have the potential to replace conventional packaging.  相似文献   

    

Salsabeel N. El Gendy  Amira K. Elmotayam  Reham Samir  Marwa I. Ezzat  Aly M. El Sayed 《Journal of the American Oil Chemists' Society》2023,100(8):591-614

Simmondsia chinensis (Link) C.K. Schneider (Jojoba) is a valuable shrub that can bear harsh conditions and is cultivated in many countries globally. Its prominence originates from the unique oil that constitutes more than 50% of the seeds. The great economic value of jojoba oil is highlighted in many fields, especially the cosmetic industry. The remaining meal, which is rich in proteins, constitutes a good source for cattle feeding. However, the presence of antinutritional principles in the meal limited its use and encouraged the researchers to find different ways for its detoxification. The detoxification ways of jojoba meal included physical, biological, and chemical treatments. The phytochemical composition of the oil was deeply studied, but for the remaining plant, only few studies have reported its chemical composition. Jojoba oil composed of wax esters (97%), fatty acids, fatty alcohols, sterols, and small percentage of vitamin E. Jojoba possesses a long traditional history. It has been used in folklore for treatment of cold, dysuria, and obesity. Many recent studies reported its medicinal and pharmacological properties like antioxidant, anti-inflammatory, antimicrobial, anticancer, anti-acne, anti-psoriasis, wound healing, and hepatoprotective activities. Many of these biological activities have been attributed to the presence of several phytochemicals such as simmondsin and phenolic compounds. In this review, the authors will highlight the previous phytochemical studies, medicinal applications of jojoba oil and different plant parts, and the various ways of meal detoxification.  相似文献   

    

Thibaut Duhail  Samir Messaoudi  Guillaume Dagousset  Jérôme Marrot  Christiane André-Barrès  Emmanuel Magnier  Elsa Anselmi 《Advanced Synthesis u0026amp; Catalysis》2023,365(14):2392-2399

We describe the preparation of S-perfluoroalkyl benzodithiazole trioxides as radical perfluoroalkylating reagents. Their syntheses were performed on a multi-gram scale by an oxidative cyclization connecting the nitrogen of a sulfoximine and a sulfur atom previously introduced in the ortho position of this group. The structures and properties of these new molecules were carefully examined by X-Ray diffraction, DFT calculations and cyclic voltammetry. These data clearly highlight the enhanced reactivity of these cyclic sulfoximines compared to their open analogues. This was confirmed by photoredox catalysis experiments that revealed interesting reactivity, most especially for the introduction of di- and monofluoroalkyl chains.  相似文献   

    

Samir Mowafy  Yanhong Liu 《Journal of the science of food and agriculture》2024,104(5):2679-2691

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Elizaveta Semenova  Yidan Xu  Adam Howes  Theo Rashid  Samir Bhatt  Swapnil Mishra  Seth Flaxman 《Journal of the Royal Society Interface》2022,19(191)

Gaussian processes (GPs), implemented through multivariate Gaussian distributions for a finite collection of data, are the most popular approach in small-area spatial statistical modelling. In this context, they are used to encode correlation structures over space and can generalize well in interpolation tasks. Despite their flexibility, off-the-shelf GPs present serious computational challenges which limit their scalability and practical usefulness in applied settings. Here, we propose a novel, deep generative modelling approach to tackle this challenge, termed PriorVAE: for a particular spatial setting, we approximate a class of GP priors through prior sampling and subsequent fitting of a variational autoencoder (VAE). Given a trained VAE, the resultant decoder allows spatial inference to become incredibly efficient due to the low dimensional, independently distributed latent Gaussian space representation of the VAE. Once trained, inference using the VAE decoder replaces the GP within a Bayesian sampling framework. This approach provides tractable and easy-to-implement means of approximately encoding spatial priors and facilitates efficient statistical inference. We demonstrate the utility of our VAE two-stage approach on Bayesian, small-area estimation tasks.  相似文献   

    

Shuo Dou  Li Tao  Ruilun Wang  Samir El Hankari  Ru Chen  Shuangyin Wang 《Advanced materials (Deerfield Beach, Fla.)》2018,30(21)

Renewable energy technology has been considered as a “MUST” option to lower the use of fossil fuels for industry and daily life. Designing critical and sophisticated materials is of great importance in order to realize high‐performance energy technology. Typically, efficient synthesis and soft surface modification of nanomaterials are important for energy technology. Therefore, there are increasing demands on the rational design of efficient electrocatalysts or electrode materials, which are the key for scalable and practical electrochemical energy devices. Nevertheless, the development of versatile and cheap strategies is one of the main challenges to achieve the aforementioned goals. Accordingly, plasma technology has recently appeared as an extremely promising alternative for the synthesis and surface modification of nanomaterials for electrochemical devices. Here, the recent progress on the development of nonthermal plasma technology is highlighted for the synthesis and surface modification of advanced electrode materials for renewable energy technology including electrocatalysts for fuel cells, water splitting, metal–air batteries, and electrode materials for batteries and supercapacitors, etc.  相似文献   

    

Béatrice Quiclet-Sire  Samir Z. Zard 《Israel journal of chemistry》2017,57(3-4):202-217

The present brief account relates synthetic endeavours revolving around a novel chemistry of xanthates (dithiocarbonates) being developed in our group. The degenerative reversible transfer of xanthates has a unique ability to store reactive radicals in a dormant form, and thereby to enhance their lifetime in a concentrated medium, while at the same time, regulating their absolute and relative concentrations. It allows intermolecular radical additions even to unactivated alkenes, and can promote otherwise sluggish radical processes, such as 5-endo, 6-exo, 6-endo, 7-endo, and 8-endo cyclisations, as well as ring closures on (hetero)aromatic structures. This chemistry has proved remarkably versatile and powerful, both for solving synthetic problems and for the industrial production of block copolymers through the RAFT/MADIX technology.  相似文献