Intergrain connectivity in YBa2Cu3O7-δ superconductor added with Dy2O3 nanoparticles: AC susceptibility investigation

Algarni R.,Slimani Y.,Hannachi E.,Almessiere M.A.,Alqahtani B.H.,Akhtar Sultan,Ben Azzouz F. 한국물리학회 2021 Current Applied Physics Vol.27 No.-

YBa2Cu3O7-δ (or YBCO) superconductors added with various concentrations of dysprosium oxide nanoparticles (NP-Dy2O3) were prepared using the solid-state process. The additive NP-Dy2O3 has a size of about 10 nm and presents a para/ferromagnetic transition at about 300 K. The characterization of samples was probed via XRD, TEM, SEM, DC magnetization, and AC susceptibility measurements. Some models were employed to compute superconducting parameters like intragranular critical current density under a magnetic field (Jcm(H)), the density of intragranular pinning force for Abrikosov vortex (εg(0)), intergranular critical current density (Jc,inter), intergranular electrical character, superconductor grain volume fraction (fs). The correlation between these parameters and microstructure was discussed. The inclusion of NP-Dy2O3 does not alter the structural properties and the spatial growth of YBa2Cu3O7-δ. NP-Dy2O3 addition led to significant enhancements of Jcm(H) and εg(0). The decrement in Jc,inter was attributed to the change of grain boundary characteristics that transformed from SNS to SINS junction due to NP-Dy2O3 addition.

The Security and Privacy Issues of Fog Computing

Sultan Algarni,Khalid Almarhabi,Ahmed M. Alghamdi,Asem Alradadi International Journal of Computer ScienceNetwork S 2023 International journal of computer science and netw Vol.23 No.4

Fog computing diversifies cloud computing by using edge devices to provide computing, data storage, communication, management, and control services. As it has a decentralised infrastructure that is capable of amalgamating with cloud computing as well as providing real-time data analysis, it is an emerging method of using multidisciplinary domains for a variety of applications; such as the IoT, Big Data, and smart cities. This present study provides an overview of the security and privacy concerns of fog computing. It also examines its fundamentals and architecture as well as the current trends, challenges, and potential methods of overcoming issues in fog computing.

Numerical Modeling of Ferrofluid Convective Behavior Within an Enclosure Under the Influence of a Magnetic Field

Mohammed Algarni 한국자기학회 2024 Journal of Magnetics Vol.29 No.1

With the goal of improving the performance of cooling systems of magnetic sensors, the effects of adding nanoparticles and employing ferrohydrodynamics (FHD) are studied with numerical simulations. To produce ferrohydrodynamics, a wire near the hot surface is used to produce a varying Kelvin force. To better describe the magnetic force, a ferrofluid consisting of iron oxide and water is used. In the velocity and temperature equations, new terms are added to represent ferrohydrodynamics and buoyancy. To apply such complex physics, the control volume finite element method (CVFEM) is applied, and the equations are written in vorticity form to help remove pressure terms. This modeling approach is validated against previously published work and the results show good agreement. An improvement of 11.65 % in the convection rate is achieved by adding nanoparticles. Considering a higher buoyancy force results in a 118.92 % increase in the Nusselt number Nu. As MnF increases up to 2 × 10³, Nu increases by about 81.88 % at the lowest Rayleigh number Ra. The influence of ferrohydrodynamics on Nu declines as the gravity force increases. The hot surface becomes cooler by about 10 % and 37.5 % when MnF and Ra are increased.

An Efficient Technique for Non-Uniformity Correction of Infrared Video Sequences with Histogram Matching

Abbass Mohammed Y.,Sadic Nevein,Ashiba Huda I.,Hassan Emad S.,El-Dolil Sami,Soliman Naglaa F.,Algarni Abeer D.,Alabdulkreem Eatedal A.,Algarni Fatimah,El-Banby Ghada M.,Abdel-Rahman Mohamed R.,Aldosar 대한전기학회 2022 Journal of Electrical Engineering & Technology Vol.17 No.5

Infrared (IR) image sequences are acquired with certain types of cameras. These cameras give the sequence of images according to the heat distribution. With time, some deterioration of the quality of the sequence occurs due the thermal noise eff ect generated in the camera. This thermal noise eff ect leads to some sort of non-uniformity in the obtained image sequence. Hence, it is necessary to perform some sort of non-uniformity correction in the video sequence according to the fi rst frame. This type of non-uniformity correction is scene-based. This paper introduces a scene-based non-uniformity correction technique that depends mainly on histogram matching. The noise eff ect on each frame in the sequence leads to some drift in the histogram of that frame. Hence, the proposed technique depends on the histogram matching concept to correct the histogram of each frame in the sequence based on the histogram of the fi rst frame that is free from the thermal noise eff ect. Diff erent image quality metrics including entropy, contrast, edge intensity, average gradient, and correlation with the fi rst frame are adopted to assess the quality of the obtained frames after adjustment. It is required in the frames to be corrected to reduce entropy, edge intensity and average gradient as these metrics are increased with the presence of thermal noise eff ect on all pixels represented as much details and unnecessary information. In addition, the contrast of the video sequences should be increased to determine objects in a better way. The correlation of the corrected frames with the fi rst one should be increased to reduce the noise eff ect. Simulation results reveal enhanced quality of the obtained video sequences after processing with the proposed technique.

Study on the strengthening mechanisms of Cu/CNT nano-composites

Long, Xiang,Bai, Yuanli,Algarni, Mohammed,Choi, Youngsik,Chen, Quanfang Elsevier 2015 Materials science & engineering. properties, micro Vol.645 No.-

<P><B>Abstract</B></P> <P>Recent experimental studies by Chen et al. showed that copper (Cu) matrix reinforced by a small amount of carbon nanotubes (CNT, about 4% volume fraction) will increase material strength by about 300% while sacrificing some material ductility. The strengthening mechanisms of Cu/CNT nano-composites were firstly studied numerically using 2D axial symmetric unit cell finite element (FE) models in Ls-Dyna, which consist of both copper matrix and CNTs. The simulation results were verified by existing experimental data. A round of parametric studies was performed to investigate the effects of several modeling parameters in the FE simulations. These parameters include the volume fraction of CNTs, aspect ratio of CNTs, size of hardening zone, and the “equivalent” hardened plastic strain in the hardened zone. Two main strengthening mechanisms are found that affect CNTs reinforcement prediction. The first one is the load-bearing effect resulting from boundary condition imposed in the models. The CNTs significantly affect the plastic flow of copper around CNTs during plastic deformation, which is one important reinforcement mechanism because of high aspect ratio ( H / D ) of CNTs. The second strengthening mechanism is found to be the hardened zone of Cu matrix around CNTs, which is introduced by manufacturing processes and/or the Orowan effect. The Orowan effect plays a key role in reinforcement especially in the nano-scale, which results in a very small inter-particle spacing. The Orowan effect was also studied using analytical methods. Both analytical solution and unit cell FE modeling well correlated with the experimental results for various Cu/CNT composites with different CNT outside diameters.</P>

Characteristics of Sustainable Concrete with Partial Substitutions of Glass Waste as a Binder Material

Jawad Ahmad,Rebeca Martinez-Garcia,Salem Algarni,Jesús de-Prado-Gil,Talal Alqahtani,Kashif Irshad 한국콘크리트학회 2022 International Journal of Concrete Structures and M Vol.16 No.3

Manufacturing waste has been quickly increasing over time as a result of the fast-rising population as well as the consumption of foods that are thrown away dishonestly, resulting in environmental contamination. As a result, it has been suggested that industrial waste disposal may be considerably reduced if it could be integrated into cement concrete manufacturing. The aim of this study is to analyze the properties of concrete employing waste glass (WG) as a binding material in proportions of 5%, 10%, 15%, 20%, 25%, and 30% by weight of cement. The fresh property was assessed using a slump cone test, while mechanical performance was assessed using flexural, compressive, splitting tensile, and pull-out strength after 7, 28, and 56 days. Furthermore, microstructure analysis was studied by scan electronic microscopic (SEM), Fourier-transform infrared spectroscopy (FTIR) and thermo-gravimetric analysis (TGA) test. The results reveal that the addition of discarded glass reduces the workability of concrete. Furthermore, mechanical performance was increased up to a 20% substitution of waste glass and then gradually declined. Waste glass can be employed as a micro filler or pozzolanic material without affecting the mechanical performance of concrete, according to microstructure research.

Dynamic analysis of nanosize FG rectangular plates based on simple nonlocal quasi 3D HSDT

Boutaleb, Sabrina,Benrahou, Kouider Halim,Bakora, Ahmed,Algarni, Ali,Bousahla, Abdelmoumen Anis,Tounsi, Abdelouahed,Tounsi, Abdeldjebbar,Mahmoud, S.R. Techno-Press 2019 Advances in nano research Vol.7 No.3

In the present work the dynamic analysis of the functionally graded rectangular nanoplates is studied. The theory of nonlocal elasticity based on the quasi 3D high shear deformation theory (quasi 3D HSDT) has been employed to determine the natural frequencies of the nanosize FG plate. In HSDT a cubic function is employed in terms of thickness coordinate to introduce the influence of transverse shear deformation and stretching thickness. The theory of nonlocal elasticity is utilized to examine the impact of the small scale on the natural frequency of the FG rectangular nanoplate. The equations of motion are deduced by implementing Hamilton's principle. To demonstrate the accuracy of the proposed method, the calculated results in specific cases are compared and examined with available results in the literature and a good agreement is observed. Finally, the influence of the various parameters such as the nonlocal coefficient, the material indexes, the aspect ratio, and the thickness to length ratio on the dynamic properties of the FG nanoplates is illustrated and discussed in detail.

Band Structure and Optical Spectra of Bulk, Tri-Layer, Bi-Layer and Monolayer CdS System: A Comparative Study

A. Gueddim,N. Bouarissa,H. Algarni,M. Ajmal Khan 한국전기전자재료학회 2022 Transactions on Electrical and Electronic Material Vol.23 No.4

A computational study based on the density functional theory calculations is carried out for the band structure and optical spectra of bulk, tri-layer, bi-layer and monolayer CdS system in the hexagonal-wurtzite structure. The aim of this contribution is to see how the electronic and optical properties of CdS change when moving from the bulk form to the monolayer one through tri-layer and bi-layer Cds systems. Our results show that the monolayer form still has a direct (Г-Г) band gap, but with an increased magnitude with respect to that of bulk CdS. The optical properties of the tri-layer, bi-layer and monolayer form are found to be diff erent from those of the bulk form. An anisotropic character has been shown by the optical spectra for light polarized parallel and perpendicular to the x axis of the crystal. Our fi ndings indicate that novel electronic and optical properties may be obtained when passing from bulk to tri-layer, bi-layer and monolayer CdS system.

A UML-based Approach towards Test Case Generation and Optimization

Shahid Saleem,Saif U. R. Malik,Bilal Mehboob,Roobaea Alroobaea,Sultan Algarni,Abdullah M. Baqasah,Naveed Ahmad,Muhammad Hasnain 한국인터넷정보학회 2024 KSII Transactions on Internet and Information Syst Vol.18 No.3

Software testing is an important phase as it ensures the software quality. The software testing process comprises of three steps: generation, execution, and evaluation of test cases. Literature claims the usage of single and multiple 'Unified Modeling Language' (UML) diagrams to generate test cases. Using multiple UML diagrams increases test case coverage. However, the existing approaches show limitations in test case generation from UML diagrams. Therefore, in this research study, we propose an approach to generate the test cases using UML State Chart Diagram (SCD), Activity Diagram (AD), and Sequence Diagram (SD). The proposed approach transforms UML diagrams into intermediate forms: SCD Graph, AD Graph, and SD Graph respectively. Furthermore, by integrating these three graphs, a System Testing Graph (STG) is formed. Finally, test cases are identified from STG by using a traversal algorithm such as Depth First Search (DFS) that is an optimization method. The results show that the proposed approach is better compared to existing approaches in terms of coverage and performance. Moreover, the generated test cases have the ability to detect faults at the unit level, integration, and system level testing.

Salp swarm algorithm with iterative mapping and local escaping for multi-level threshold image segmentation: a skin cancer dermoscopic case study

Hao Shuhui,Huang Changcheng,Heidari Ali Asghar,Chen Huiling,Li Lingzhi,Algarni Abeer D.,Elmannai Hela,Xu Suling 한국CDE학회 2023 Journal of computational design and engineering Vol.10 No.2

If found and treated early, fast-growing skin cancers can dramatically prolong patients’ lives. Dermoscopy is a convenient and reliable tool during the fore-period detection stage of skin cancer, so the efficient processing of digital images of dermoscopy is particularly critical to improving the level of a skin cancer diagnosis. Notably, image segmentation is a part of image preprocessing and essential technical support in the process of image processing. In addition, multi-threshold image segmentation (MIS) technology is extensively used due to its straightforward and effective features. Many academics have coupled different meta-heuristic algorithms with MIS to raise image segmentation quality. Nonetheless, these meta-heuristic algorithms frequently enter local optima. Therefore, this paper suggests an improved salp swarm algorithm (ILSSA) method that combines iterative mapping and local escaping operator to address this drawback. Besides, this paper also proposes the ILSSA-based MIS approach, which is triumphantly utilized to segment dermoscopic images of skin cancer. This method uses two-dimensional (2D) Kapur’s entropy as the objective function and employs non-local means 2D histogram to represent the image information. Furthermore, an array of benchmark function test experiments demonstrated that ILSSA could alleviate the local optimal problem more effectively than other compared algorithms. Afterward, the skin cancer dermoscopy image segmentation experiment displayed that the proposed ILSSA-based MIS method obtained superior segmentation results than other MIS peers and was more adaptable at different thresholds.