Sharif Digital Repository

Interactive vibrations and buckling of double current-carrying strips (DCCS) are investigated in this study. Considering the rotational and transverse deformation of the strip, four coupled equations of motion are obtained using Hamilton’s principle. Using the Galerkin method, mass and stiffness matrices are extracted and the stability of the system is determined by solving the eigenvalue problem. Effects of pretension and elevated temperature on the stability of DCCS are studied for three types of materials and various arrangements. Finally, the effect of horizontal or vertical distance between strips on the critical current value is investigated. According to the results, the effects of... 

Estimating precipitation at high spatial-temporal resolution is vital in manifold hydrological, meteorological and water management applications, especially over areas with un-gauged networks and regions where water resources are on the wane. This study aims to evaluate five downscaling methods to determine the accuracy and efficiency of which on generating high-resolution precipitation data at annual and monthly scales. To establish precipitation-Land surface characteristics relationship, environmental factors, including Normalized Difference Vegetation Index (NDVI), Land Surface Temperature (LST) and Digital Elevation Model (DEM), were considered as proxies in the spatial downscaling... 

LiNi0.8Co0.1Mn0.1O2 (NCM811) has been considered as a promising cathode for Li-ion batteries (LIBs) due to its high electrochemical capacity and low cost; however, poor cycling stability is one of the main restricting factors in industrial applications of the NCM811 cathode material. Notably, the capacity fading and low structural stability of NCM811 are intensified at elevated temperatures. ZrO2- and composite rGO-ZrO2-coated NCM811 were fabricated by a facile wet chemical method and evaluated at 25 and 55 °C to overcome these impediments. The ZrO2 coating provides superior cycling and thermal stability and perfectly protects the cathode active material from deleterious side reactions, and... 

In this article, the self-compacting lightweight concretes (SCLC) with different fibers were prepared and exposed to elevated temperatures, and their mechanical properties were investigated. Three types of fibers were steel fibers (SF), polypropylene fibers (PPF), and metal springs with a volume fraction of 0.4%. One hundred and fifty cylindrical specimens were prepared, and the compression, tensile and flexural tests were carried out on them after exposure to high temperatures ranging from 25 to 700°C. The findings indicate that incorporation of steel fibers and springs enhanced the compressive strength of concrete by 20% compared to the control specimen. Meanwhile, the polypropylene fibers... 

This study examines the use of timber as a filler material for steel and pultruded GFRP tube elements and the performance of these sections is compared to solid timber columns, hollow steel and hollow pultruded GFRP tube element after exposure to elevated temperature. In total, 102 specimens were fabricated and exposure to elevated temperature ranging from 20 to 700 °C was evaluated. It was found out that filled tubes using timber could improve the compressive strength and stiffness of tubular section specimens up to 73 and 212 percent, respectively. Timber filled steel tube (TFST) and hollow steel tube specimens had a better performance at elevated temperature in comparison to other... 

Alkali-activated slag (AAS) binder has been recognized as a suitable material for construction applications owing to its low carbon footprint and good mechanical and durability performance. As a promising alternative to the conventional Portland cement binder, it is important to maximize the performance of AAS composites under normal and harsh environmental conditions such as exposure to fire. The use of fibers in a brittle matrix is a well-known approach to enhance the mechanical strength and cracking behavior under thermal loading. In this study, polypropylene fiber (PPF), glass fiber (GF), and basalt fiber (BF) are used at volume fractions of 0.5%, 1%, and 1.5% in AAS mortar mixes. First,... 

Usage of concrete-filled pultruded glass fiber-reinforced polymer (GFRP) tubes (CFPGT) as columns can increase the service life of structures. However, marine structures such as oil platforms are always prone to fire because of the low resistance to the elevated temperatures. The purpose of this investigation is to evaluate the effects of concrete core strength (30 and 60 MPa), and exposure temperature (25, 100, 200, 300, and 400 °C) and time (60 and 120 min) on the compressive and bond behavior of CFPGTs. The properties of unexposed and exposed concrete core, pultruded GFRP hollow tubes, and CFPGTs were determined via compressive and disk-split tests. Also, the push-out test was used to... 

In this work, the formability of a hybrid material of Interstitial-Free 240 (IF240) steel and AZ31 magnesium alloy as IF240/AZ31/IF240 tri-layered sheets was investigated. For this purpose, the bonding feasibility of the high-formability IF240 steel and low-formability AZ31 sheets was first assessed. Then, the hot formability behavior of the manufactured laminated composite was evaluated. The rolling of the preheated samples established the layer bonding. The bonding strength was determined using the shear punch test. The texture and its effects on the forming behavior were studied using the x-ray Goniometry method. Nakazima dome tests were employed at ambient and elevated temperatures to... 

In this work, the formability of a hybrid material of Interstitial-Free 240 (IF240) steel and AZ31 magnesium alloy as IF240/AZ31/IF240 tri-layered sheets was investigated. For this purpose, the bonding feasibility of the high-formability IF240 steel and low-formability AZ31 sheets was first assessed. Then, the hot formability behavior of the manufactured laminated composite was evaluated. The rolling of the preheated samples established the layer bonding. The bonding strength was determined using the shear punch test. The texture and its effects on the forming behavior were studied using the x-ray Goniometry method. Nakazima dome tests were employed at ambient and elevated temperatures to... 

Copper slag (CS) is an industrial by-product, which is commonly disposed in engineered landfills. Prior studies have successfully incorporated CS as an aggregate phase in cementitious materials. However, the alkali-activated material (AAM) incorporating CS has been scarcely studied. Specifically, the elevated temperature behavior of AAM with CS has not been investigated previously. The present paper aims to study the effects of elevated temperature treatment on the mass loss and residual strength of alkali-activated slag mortars incorporating 0–100% (by volume) of CS with an incremental step of 20% instead of natural sand. The mass loss, compressive and flexural strengths, and microstructure... 

The authors regret that there was an error in the XRD pattern for pumice shown in Fig. 8. The authors have re-analyzed the pumice to address the concerns over the reliability of the pattern due to the presence of noises, and the updated XRD pattern has been shown in Fig. 8 here for more accuracy of the presented information. It is noteworthy that this change does not affect any of the conclusions. The authors would like to apologise for any inconvenience caused. © 2021 Elsevier Ltd  

SiBNC nanofibers were synthesized through the polymeric route by a one-pot synthesis approach. DMTA (dichloroboryl methyl trichlorosilyl amine) polymer was selected as pre-ceramic for SiBNC, which was shaped into nanofibers by electrospinning. Then, the nanofibers were cured in an inert atmosphere in order to obtain the final ceramic. By changing the curing atmosphere, the compound of final ceramic has been manipulated. In addition, the ceramic yield of DMTA as a preceramic was increased in the nitrogen atmosphere. The effects of applied voltage, solution concentration, and feeding rate on the morphology of final electrospun ceramic nanofibers were also investigated. Final ceramic remains... 

This study investigates the tensile properties of various GFRP laminates after exposure to elevated temperatures. Fiber configuration, exposure temperature and laminate thickness were considered as the test variables. A total number of 180 specimens were tested in tension to obtain the mechanical properties of GFRP laminates. Alongside the mechanical tests, SEM analyses were conducted on selected samples before testing to investigate the resin, fiber, and their interface damages. Regardless of the sample type, it was generally observed that the reduction rate in the tensile strength increased with an increase in the exposure time and a decrease in the laminates’ thickness. The results of... 

The present research examines the effects of UV radiation, moisture and elevated temperature on the mechanical properties of GFRP pultruded profiles. Flexural, compressive and tensile properties of different GFRP sections were studied after they were exposed for 1000, 1500, 2000 and 3000 h to UV radiation and water vapour condensation cycles. Mechanical tests, including three-point bending, compression and tension tests, SEM analyses, and statistical studies were conducted to gather comprehensive results. The results showed that the mechanical properties of various GFRP sections generally decreased with the duration of conditioning: however, the rate of the decrease that was only slight up... 

Interactive vibrations and buckling of double current-carrying strips (DCCS) are investigated in this study. Considering the rotational and transverse deformation of the strip, four coupled equations of motion are obtained using Hamilton’s principle. Using the Galerkin method, mass and stiffness matrices are extracted and the stability of the system is determined by solving the eigenvalue problem. Effects of pretension and elevated temperature on the stability of DCCS are studied for three types of materials and various arrangements. Finally, the effect of horizontal or vertical distance between strips on the critical current value is investigated. According to the results, the effects of... 

The compressive performance of glass fiber reinforced polymer (GFRP) profiles subjected to elevated temperature was investigated through a large number of (3 0 0) tests. The effects of profile cross-sectional area, slenderness, and temperature on the behavior of the GFRP profiles at temperatures ranging from 25 to 400 °C were determined. It was observed that the compressive strength of the GFRP profiles has been decreased by half as the temperature exceeded 90 °C, i.e., close to the glass transition temperature of the matrix. The temperature and ratio of cross-sectional area to external perimeter were determined as two major parameters affecting section capacity. © 2020 Elsevier Ltd  

Surface passivation of organic-inorganic halide perovskites (OIHPs) is a crucial step to annihilate the surface defects and to control the deteriorated ion migration phenomenon. Here, we study the role of lead sulfate (PbSO4) as an effective passivator in OIHP single crystals (SCs). Using impedance spectroscopy, we evaluate the ion migration and electrical properties of lead sulfate-passivated methylammonium lead tri-bromide (MAPbBr3) SCs. We found that the low-frequency impedance response that is assigned to the ionic motion in the MAPbBr3 SC is strongly affected by the inorganic PbSO4 surface treatment. The activation energy corresponding to the ion migration of MAPbBr3 SC is increased... 

An intense decrease in cycling performance and safety is a challenge for elevated temperature application of LiNi0.5Co0.2Mn0.3O2 (NCM) cathode material. In this paper, effect of two types of nano-coatings on improvement of elevated temperature performance of NCM cathode material has been investigated. One of the coatings contains SiO2 nanoparticles and the other one contains composite of reduced graphene oxide and SiO2 nanoparticles (rGO-SiO2). The coatings were fabricated by a facile wet chemical method. The SiO2 coated cathode material showed an excellent elevated temperature cycling stability, however, a decrease in discharge capacity and rate capability of this sample was observed. On... 

Ammonium polyphosphate (APP) is one of the most widely used halogen-free flame retardant, added in various resins to improve the fire properties, such as flame and smoke spread ratings and LOI, of fiber-reinforced polymer (FRP) composites. This paper experimentally investigates the effects of using APP, as a fire-retardant filler, on mechanical properties (i.e. ultimate tensile, flexural, and bond strength) of glass fiber-reinforced polymer (GFRP) and carbon fiber-reinforced polymer (CFRP) composites. Based on two fiber types (i.e. carbon and glass) and three different APP mass fractions in resin (i.e. 0, 20, and 40% of total weight of matrix), six sets of specimens were prepared for each... 

As radar signals propagate above the ocean surface to determine the trajectory of a target, the signals that are reflected directly from the target arrive at the receiver along with indirect signals reflected from the ocean surface. These unwanted signals must be properly filtered; otherwise, their interference may mislead the signal receiver and significantly degrade the tracking performance of the radar. To this end, we propose a low-elevation target tracking mechanism considering the specular and diffuse reflection effects of multipath propagation over the ocean surface simultaneously. The proposed mechanism consists of a state-space model and a particle filtering algorithm and promises...