Sharif Digital Repository

Commercially pure aluminum sheets, AA 1050, are processed by accumulative roll bonding (ARB) up to eight cycles to achieve ultrafine-grained (UFG) aluminum as primary material for mechanical testing. Optical microscopy and electron backscattering diffraction analysis are used for microstructural analysis of the processed sheets. Strain rate sensitivity (m-value) of the specimens is measured over a wide range of strain rates by stress relaxation test under plane strain compression. It is shown that the flow stress activation volume is reduced by decrease of the grain size. This reduction which follows a linear relation for UFG specimens, is thought to enhance the required effective (or... 

Good knowledge of fracture parameters and cracking behavior of self-compacting concrete (SCC) from early ages until the SCC becomes mature plays an important role in design of SCC structure and also in evaluation of durability and consequently prevention of damage. In this paper, variation of fracture parameters and corresponding ductility behavior of SCC at different ages (e.g. 3days, 7days, 28days and 90days) for SCC mixes with w/c ratios of 0.45 and 0.65 have been experimentally studied. To do so, three-point bending tests were carried out on 120 notched beams. Then, size effect method (SEM) and work of fracture method (WFM) were applied to interpret the results. The results of analyses... 

Al-15wt.% Mg2Si composites were prepared by in situ casting and characterized in wear tests. Previous to the extrusion of specimens at 470°C - varying extrusion ratio (7.4, 14.1 and 25), the as-cast composites were homogenized at 500°C for 5h, followed by slow furnace cooling. The microstructure, hardness and sliding wear behavior were characterized for both, the as-cast and hot extruded composites. Results show that increasing the extrusion ratio causes a significant improvement in hardness and wear resistance. This is ascribed to the observed decrease in average size and better distribution of Mg2Si particles, in tandem with a remarkable decrease in porosity percentages, which goes from... 

A novel technique is presented to design efficient full-rate space-time block codes (STBCs) over correlated Rician fading channels. The authors first derive a formula for the achievable information rate of a linear dispersion coded multi-input single-output system as a function of correlation at the transmitter in a Rician fading channel. In addition, the authors obtain the bit-error-rate (BER) equations for this system, when multiple phase shift keying and multiple quadrature amplitude modulation schemes are used at the transmitter. Therefore with regard to derived formulae and using a genetic algorithm, a method is presented to construct STBCs over correlated Rician fading channels. The... 

Permeability reduction in porous media as a result of frail and tenuous fine particles migration would decrease the productivity index in the subterranean reservoirs. During reservoir stimulation by injecting fluids into the reservoir, as the salinity condition of the formation brine changes, fine particles initiate the triggering process. In this study, MgO-based nanofluid as a fines fixation agent was stably prepared based on the particle size distribution and characterized through transmission electron microscopy analysis. Afterward, several core flooding tests were performed using Berea sandstone cores to study the effect of nanofluid injection on fines fixation in the water shock... 

Prostate cancer (PCa) is one of the two solid malignancies in which a higher T cell infiltration in the tumor microenvironment (TME) corresponds with a worse prognosis for the tumor. The inability of T cells to eliminate tumor cells despite an increase in their number reinforces the possibility of impaired antigen presentation. In this study, we investigated the TME at single-cell resolution to understand the molecular function and communication of dendritic cells (DCs) (as professional antigen-presenting cells). According to our data, tumor cells stimulate the migration of immature DCs to the tumor site by inducing inflammatory chemokines. Many signaling pathways such as TNF-α/NF-κB,... 

With the increasing rate of population in big cities around the world, the tendency to build new buildings in the suburb of main cities or to build large apartments in the main cities has been highlighted. In this regard, building residential complexes has seen a dramatic increase in these areas as it makes it possible to build a large number of residential units within a reasonable space. Although these complexes have brought numerous benefits, they are some challenges regarding their construction processes. One main concern associated with these complexes is how to optimally install energy components such as transformers, combined heat and power (CHP) units, boilers etc., in the shared... 

With the application of chemical enhanced oil recovery methods, water separation is a major issue in a production facility. Oil/water separation is suppressed with a stable emulsion. The present study evaluated the impact of different emulsifiers in enhanced oil recovery. The effectiveness of each additive such as an alkali, surfactant, or polymer on the stability of the emulsion was anticipated using laser scattering to measure the emulsion’s stability. An artificial neural network was applied to predict the effectiveness of the additives on stabilization/destabilization and to assess how alkali/surfactants, surfactant/polymers, and polymer/surfactants affect the separation profiles.... 

The authors regret the following mistakes: 1) In section 2, 3rd paragraph, the sentence:“Fe3O4/MWCNT-COOH/Extract has a much higher roughness than Fe3O4/MWCNT-COOH, which is unacceptable in agreement with similar results in the literature and electron microscopy observations [88–90].” must be replaced by “Fe3O4/MWCNT-COOH/Extract has a much higher roughness than Fe3O4/MWCNT-COOH, which is in agreement with similar results in the literature and electron microscopy observations [88–90].” 2) In section 3.8, the sentence:“The release of DOX from prepared nanocomposites were investigated under typical conditions: At 37 °C and different pH values of 7.4, 5.5, and 4.5 were tested in the phosphate... 

The optical implementation of mathematical spatial operators is a critical step toward achieving practical high-speed, low-energy analog optical processors. In recent years, it has been shown that using fractional derivatives in many engineering and science applications leads to more accurate results. In the case of optical spatial mathematical operators, the derivatives of the first and second orders have been investigated. But no research has been performed on fractional derivatives. On the other hand, in previous studies, each structure is dedicated to a single integer order derivative. This paper proposes a tunable structure made of graphene arrays on silica to implement fractional... 

In this paper, a cost-effective and high-accuracy precoding technique based on ϵ-Fuzzy pareto active learning (FPAL) is proposed for millimeter wave (mmWave) massive MIMO communications. The proposed method achieves a low iteration convergence with low complexity. Two practical structures, namely fully-connected and partially-connected structures are considered for hybrid precoding. Furthermore, the effect of high and low-resolution quantization in the digital-to-analog converter, phase shifter, and imperfect channel state information are discussed. The performance results of the proposed technique and alternating minimization methods beside fully digital techniques are compared and... 

The common steering mechanisms approximately establish the Ackermann equation. The more the mechanism design parameters, the higher the accuracy can be achieved by using optimization. Also, some mechanisms have been developed to establish the Ackermann equation accurately. Most of these mechanisms contain non-circular gear or cam that have an infinite number of design parameters. In this paper, two novel mechanisms have been designed with a limited number of design parameters, but their geometric structure is such that the governing relationship is exactly the Ackermann equation. The proof of this claim has been given in detail and validated by GeoGebra software. Also, by using force... 

Let GS be a graph with loops obtained from a graph G of order n and loops at S⊆ V(G). In this paper, we establish a neccesary and sufficient condition on the bipartititeness of a connected graph G and the spectrum Spec (GS) and Spec (GV(G)S). We also prove that for every S⊆ V(G) , E(GS) ≥ E(G) when G is bipartite. Moreover, we provide an identification of the spectrum of complete graphs Kn and complete bipartite graphs Km,n with loops. We characterize any graphs with loops of order n whose eigenvalues are all positive or non-negative, and also any graphs with a few distinct eigenvalues. Finally, we provide some bounds related to GS. © 2023, The Author(s), under exclusive licence to Malaysian... 

Surface modification of ultrafiltration membranes has shown a significant potential to reduce fouling and increase flux and lifetime, which are the most important factors in membrane filtration. In this study, the surface-modified membranes were prepared by grafting hyperbranched polyethyleneimine (HBPEI) onto polyvinylidene fluoride (PVDF)-sulfonated polyethersulphone (SPES) blending membranes. Electrostatic interactions between HBPEI and SPES result in a well-attached positive-charged HBPEI grafting layer on the PVDF membrane surface. Surface-modified membranes were examined for the removal of cationic E-coat paint and their performance was measured in terms of total permeation flux, paint... 

Curved tunnels are more likely to have an accident and a fire source due to their physical characteristics. Using a 3D computational fluid dynamics tool with body-fitted grids, three different fire locations were investigated numerically in a series of curved tunnels with a turning radius of 50–1000 m and a heat release rate of 5–15 MW. Results showed that the critical velocity increased with increasing tunnel turning radius, and the straight tunnel had the highest critical velocity in all scenarios. For a tunnel with a 10 MW heat release rate, the critical velocity increased by 19 % from R = 50 to 1000 m. Furthermore, it was shown that the critical velocity was proportional to one-third... 

The oxygen-rich organic/inorganic (reduced graphene oxide (rGO)/ZnO2-Ag) nanoframeworks as suppliers of O2 nanobubbles (NBs) with dual pH-and-temperature-sensitive behavior were developed to suppress bacterial growth. It was demonstrated that not only the rate but also the final product of oxygen-rich ZnO2 decomposition (to an intermediate product of H2O2) rate was dramatically controlled by pH adjustment. Furthermore, in the presence of Ag nanoparticles, ̇OH radical generation switched to O2 NBs evolution by shifting the pH from acidic to basic/neutral conditions, demonstrating an adjustable nanozyme function-ability between catalase and peroxidase-like activity, respectively. Antibacterial... 

Perovskite solar cell (PSC) technology experiences a remarkably rapid growth toward commercialization with certified efficiency of over 25%, along with the outstanding breakthrough in the development of SnO2. Owing to the wide bandgap, high electron mobility, chemical stability, and low photocatalytic activity, SnO2 has been the rising star to serve as electron transporting layer (ETL). More importantly, the low-temperature fabrication process (<200 °C) enables SnO2 a promising candidate for the industry, making it compatible with the plastic substrates and large-scale production, which is crucial for the flexible and scalable devices fabrication. In this review, the processing methods... 

Land subsidence associated with using natural groundwater resources for serving the growing population needs has been receiving extensive research attention in the literature over the past few decades. The water content fluctuation in the of subsurface soil layers significantly impacts the land subsidence. The key objective of this study is to predict changes in water content profiles in soil layers over a long period of time using a deep learning-based approach. A convolution neural network algorithm that is commonly used in Artificial Intelligence (AI) applications is modified in the present study for processing in-situ measurement water content profiles. The approach used in the proposed... 

In this work, it is used three families of nonlinearities such as Kerr law, Power Law and Parabolic law over the High-order dispersive Nonlinear Schrödinger equation to inquire optical soliton solutions and diverse solutions by employing the Sardar Sub-equation method. Considering the constraint relation on some parameters of the NLSE, it is obtained bright and dark optical soliton solutions. However, under a certain condition on the method parameters, it is exposed singular soliton and trigonometric function solutions. More precisely, for ρ=[Formula presented], a new form of the complex solutions are obtained. The obtained results are depicted in 2D and 3D to show out the peakon soliton in... 

Titanium alloys have been used extensively as implants. However, they generally suffer from low biocompatibility as well as antibacterial activity. To date, several strategies have been proposed to address these issues. It is of practical interest to synergistically increase both cellular adhesion and antimicrobial activity in titanium-based implants. Here, Ti–6Al–4V alloys were surface-modified by Nd:YAG laser with different scanning speeds ranging from 1 to 5 mm s−1 and subsequently coated by drug-loaded polymer nanofibers for prolonged drug release. The laser-modified samples were both physically and metallurgically characterized through XRD, OM, AFM, FESEM, hardness, and wettability...