Sharif Digital Repository

Al–5·6Zn, Al–5·6Zn–2·5Mg and Al–5·6Zn–2·5Mg–1·6Cu (wt-%) powder blends were compacted at 350 MPa and sintered in nitrogen at different temperatures to study microstructural evolution during sintering. Densification, dimensional changes and mechanical properties of the Al alloys were investigated. Microstructural analyses were performed by scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and simultaneous thermal analysis (STA) in order to determine the temperature and chemical composition of the phases formed during sintering. It was shown that various liquids and intermetallic phases including Al0·71Zn0·29 at 438°C,... 

Straintronics of two-dimensional (2D) materials is a new research area in condensed matter physics for studying 2Dmaterials under strain. Anisotropic strained graphene does not seem to preserve the polarization of the incident light. This suggests intriguing possibilities for developing surface plasmon resonances (SPRs) in graphene-based optoelectronics. In this work, we investigate the SPR properties of a graphene-prism coupling structure under a relatively small anisotropic strain. We demonstrate that, for an incident linearly polarized light in the strained graphene-prism coupling structure, anisotropic SPRs would emerge along with specific strain directions. © 2023 Optica Publishing... 

Porphyrin-POM hybrid materials with excellent NLO properties are supposed to be a worthy entrant for forthcoming telecommunication, optical fibers, optical data storage and optical limiting devices, but due to adverse solubility problems, they are replaced by polymeric materials. Herein, we assessed third order NLO and second hyperpolarizability of porphyrin-polyimide compounds (NH-PI and Zn-PI) synthesized from the reaction of 4,4ʹ-hexafluoroisopropylidene-diphthalic anhydride (6FDA) with C44H32N6 (NH-DATPP) and C44H30N4Zn (Zn-DATPP) porphyrins under ambient conditions. The Z-scan measurement of these compounds revealed reverse saturation absorption as well as self-defocusing performance.... 

We prove the existence of relatively large Goos–Hänchen (GH) shifts for graphene in the presence of an applied strain in different crystallographic directions for p and s polarized beams. It is shown that GH shifts are smoothly increased by stretching the graphene’s lattice. Moreover, we investigate the GH effect for strained graphene as a function of Fermi energy, which can be controlled by external factors such as gate voltage. We show that applied strain along zigzag and armchair orientations gives different results for GH shifts, which could provide a proper tool for the detection of strain in graphene. © 2022 Optica Publishing Group  

In the present investigation, design of integrated numerical computing through Levenberg-Marquardt backpropagation neural network (LMBNN) is presented to examine the fluid mechanics problems governing the dynamics of expanding and contracting cylinder for Cross magneto-nanofluid flow (ECCCMNF) model in the presence of time dependent non-uniform magnetic force and permeability of the cylinder. The original system model ECCCMNF in terms of PDEs is converted to nonlinear ODEs by introducing the similarity transformations. Reference dataset of the designed LMBNN methodology is formulated with Adam numerical technique for scenarios of ECCCMNF by variation of thermophoresis temperature ratio... 

Rare earth oxides with a trivalent nature play a pivotal role in reinforcing the magneto-optical attributes of spinel ferrite nanoparticles by replacing Fe3+ ions. In this study, rare earth Gd oxide doped with CoFe2O4 NPs with a composition of Co1+xGdxFe2-2xO4 (x = 0, 0.05, 0.10, and 0.15) were synthesized using sol-gel auto-combustion. The outcome of Gd cations on the physical, magneto-optical and electrical characteristics of the cobalt ferrite NPs were reported. X-ray diffraction (XRD), and Fourier transform infrared (FTIR) investigations confirmed the single-phase cubic crystalline nature and metal ion stretching in the cobalt ferrite synthesized samples. Decreasing drift in the average... 

Rare earth oxides with a trivalent nature play a pivotal role in reinforcing the magneto-optical attributes of spinel ferrite nanoparticles by replacing Fe3+ ions. In this study, rare earth Gd oxide doped with CoFe2O4 NPs with a composition of Co1+xGdxFe2-2xO4 (x = 0, 0.05, 0.10, and 0.15) were synthesized using sol-gel auto-combustion. The outcome of Gd cations on the physical, magneto-optical and electrical characteristics of the cobalt ferrite NPs were reported. X-ray diffraction (XRD), and Fourier transform infrared (FTIR) investigations confirmed the single-phase cubic crystalline nature and metal ion stretching in the cobalt ferrite synthesized samples. Decreasing drift in the average... 

The controlled and stable crystal structure, reduction in Curie temperature and semiconducting nature of oxide materials are the key factors for magnetoelectrical applications. Therefore, Co0.6Mn0.4GdxFe2-xO4 where x = 0, 0.033, 0.066 and 0.10 were synthesized to analyse the structural, morphological, magnetic, and electrical properties using a sol-gel autocombustion approach. The X-ray diffraction pattern reveals that the cubic crystallite size decreases with increasing smaller content of Gd3+ oxides without any secondary phase. Field emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM) study explain the complete morphology,... 

Curcumin incorporated polyurethanes (CPU) are gaining much attention as a biomaterial. However, challenges are still remained due to hydrophobicity and low mechanical strength of CPU. Herein, we synthesized the CPU/ZnO nanocomposites with good mechanical and improved hydrophilic properties via in-situ polymerization. A series of curcumin incorporated polyurethane with different concentrations of ZnO nanoparticles (ZnCPU) are synthesized by using the curcumin, polyethylene glycol (PEG) as the soft segment, hexamethylene diisocyanate (HDI) as the hard segment, and 1,4-butanediol (BDO) as the chain extender. The addition of ZnO nanoparticles (NPs) facilitated the soft domain of PU which is... 

Silver nanoparticles (Ag. NPs) have shown a biological activity range, synthesized under different environment-friendly approaches. Ag. NPs were synthesized using aqueous crude extract (ACE) isolated from Plantago lanceolata. The ACE and Ag. NPs were characterized and assessed their biological and antioxidant activities. The existence of nanoparticles (NPs) was confirmed by color shift, atomic force microscopy (AFM), and UV–Vis’s spectroscopy. The FT-IR analysis indicated the association of biomolecules (phenolic acid and flavonoids) to reduce silver (Ag+) ions. The SEM study demonstrated a sphere-shaped and mean size in the range of 30 ± 4 nm. The EDX spectrum revealed that the Ag. NPs were... 

Network function virtualization (NFV) and software-defined networking (SDN) are two promising technologies to enable 5G and 6G services and achieve cost reduction, network scalability, and deployment flexibility. However, migration to full SDN/NFV networks in order to serve these services is a time-consuming process and costly for mobile operators. This paper focuses on energy efficiency during the transition of mobile core networks (MCN) to full SDN/NFV networks and explores how energy efficiency can be addressed during such migration. We propose a general system model containing a combination of legacy nodes and links, in addition to newly introduced NFV and SDN nodes. We refer to this... 

In this work, a corresponding-states correlation is presented for prediction of crude oil density in an undersaturated state. The correlation is the extension of corresponding-states liquid densities correlation. The modified corresponding states liquid densities method for predicting saturated liquid densities was coupled with the Tait equation to predict undersaturated densities. Correlations are proposed for the temperature-dependence of Tait equation parameters. Applying proper mixing and combining rules, we calculated the density of 26 crude-oil samples, mainly from Iranian reservoirs. The mixtures included a variety of compositions including N2, H 2S, CO2, and hydrocarbons. The AAD%... 

A localized magnetic field is a vector field that alters in space because of magnetic materials or electric currents. Some examples of localized magnetic fields are indoor localization, magnetic anomaly detection, magnetoencephalography, and quantum physics. Magnetic fields can be used to estimate the orientation and position of a device inside a building by measuring the changes in the magnetic field caused by ferromagnetic substances. On the other hand, a Tri-hybrid nanofluid can transfer heat better than a normal hybrid nanofluid by mixing three different nanoparticles with synergistic effects. It can have more varied physical and thermal properties by choosing different combinations of... 

The search for cathode materials with fast oxygen reduction reaction (ORR) catalytic activities and high ionic conductivity is the key obstacle to SOFCs commercialization and its operation at low temperatures. In order to search for a cathode with enhanced catalytic functionality, herein we report a single-phase CoFe2O4 (CFO) and CoGd0.2Fe1.80O4 (CGFO), which can be employed as an active cathode to improve electrocatalytic ORR functionalities at low temperature. It is found that CGFO having enriched oxygen vacancies exhibits the least polarization resistance (RP) of 0.42 Ωcm2 compared to the pure CFO which shows polarization resistance of 0.56 Ω cm2 under H2/air conditions. Furthermore,... 

Counter-based broadcasting improves the performance of flooding by preventing the network from being swamped by a large number of rebroadcast messages. In such approach, the rebroadcast decision is made based on counting duplicated packets in order to restrict the number of extra retransmissions. In this article, using a rigorous theoretic analysis, an upper bound on the performance of counter-based broadcasting for saturated networks is derived. Our model assumes a CSMA-based static multi-hop ad-hoc network. The derived analytical model can be used to predict the behavior of counter-based broadcasting schemes. It especially provides the required insight on the impact of different network... 

Lattice defects in rare earth (RE) doped single-phase semiconductor materials play a key role in structural modifications and physicochemical characteristics, resulting to enhance the ionic conductivity. In this work, we synthesized lanthanum doped samarium oxide with different mole ratios and applied it as a ceramics membrane fuel cell device to enable high peak power density (PPD) at low operational temperatures (520–400 °C). The samples are capable of triple charge H+/O2−/e− conduction and enhance the catalytic function of the cell in terms of HOR and ORR kinetics by producing lattice defects. The fabricated Sm1.5La1.5Fe5O12 (2-SLFO) fuel cell device exhibits a high OCV of 1.13 V with a... 

Flooding and its variants are the simplest and most widely used broadcasting methods. Therefore, analysis of its performance in an ad-hoc environment using realistic assumptions is an important research topic. In this article, deploying a rigorous theoretic analysis, an upper bound on the performance of probabilistic flooding running over CSMA as a real and suitable MAC layer protocol for broadcasting scenarios is derived in a static multi-hop ad-hoc network in saturated condition. This model reveals the relation between network parameters and the performance of flooding and thus, helps the designer to have a better understanding of the effect of different design parameters. Using this... 

In this work, the effects of the surface-modified nanodiamond particles (NDs) on the barrier, rheological, mechanical and thermal properties of ethylene vinyl acetate (EVA) composites for the packaging applications were investigated. Fourier transform infrared spectroscopy, as well as thermal gravimetric analysis were employed to study the grafting of vinyltriethoxy silane (VTS) on the surface of NDs. Afterwards, EVA samples containing 0, 0.1, 0.5, 1, 1.5 and 2 wt% of surface-modified NDs were prepared by a two-stage process including the solution and injection processes. In order to evaluate the physicochemical, rheological, mechanical and thermal properties of the EVA/NDs samples, field... 

Many applications in wireless networks impose locally distributed traffic on the network. We consider the effect of traffic localization on throughput of large wireless networks in the scaling sense. We show that by careful exploitation of traffic localization, one can enhance the throughput of various schemes in wireless networks. Also, the important case of Small World traffic distribution in wireless networks is addressed. In this type of traffic, in addition to the local traffic, a non-negligible amount of global traffic should be handled by the network. It is shown that a non-negligible amount of network-wide traffic can be tolerated by network without any performance degradation in the... 

In this paper, we derive the rate of route discovery process for finding a randomly chosen destination in large wireless networks. The well-known protocol for route discovery is flooding in which each node simply rebroadcasts the route request packet once. Rate of route discovery process is defined as the inverse of time between transmitting two successive route request packets which shows how fast a node can request a route to its destination. Discovery time is another parameter of interest. For a single node discovering routes to its destination, at most the rate of Eθ (1/3√n) is feasible when n identical nodes are optimally placed in network area and the discovery time is of order...