Sharif Digital Repository

Alumina nanofluids are one of the most useful nanofluids. In order to evaluate the colloidal behavior of nanoparticles in alumina/water nanofluid, the influence of effective factors such as pH, ionic strength and surfactants, was studied. Zeta potential, particle size and turbidity change of each nanofluid was investigated. According to the results for 0.05, 0.1 and 0.2 mass% nanofluid, point of zero charge was obtained at pH values of 9.5, 10.2 and 10.5, respectively. The highest nanofluid stability occurred at pH 4 and its lowest was at pH 10. The anionic surfactant had a greater effect on the stability in compared with cationic and nonionic surfactants. By increasing in ionic strength,... 

Alumina nanofluids are one of the most useful nanofluids, especially for increasing the thermal conductivity. Due to importance of porous media in the improvement of heat transfer, this study investigates the transport and retention of gamma alumina/water nanofluid in the water-saturated porous media. For this purpose, alumina nanofluids were introduced to the porous media consisting of water-saturated glass beads possessing various pH values (4, 7 and 10) and different ionic strengths (0.001 M of KCl, CaCl2, AlCl3, K2SO4, CaSO4, Al2(SO4)3, K2CO3 and CaCO3). Then the break through curve of each experiment was drawn and modeled by combining classical filtration theory with... 

Alumina nanofluids are one of the most useful nanofluids. In order to evaluate the colloidal behavior of nanoparticles in alumina/water nanofluid, the influence of effective factors such as pH, ionic strength and surfactants, was studied. Zeta potential, particle size and turbidity change of each nanofluid was investigated. According to the results for 0.05, 0.1 and 0.2 mass% nanofluid, point of zero charge was obtained at pH values of 9.5, 10.2 and 10.5, respectively. The highest nanofluid stability occurred at pH 4 and its lowest was at pH 10. The anionic surfactant had a greater effect on the stability in compared with cationic and nonionic surfactants. By increasing in ionic strength,... 

This paper studied the durability, microstructure, and fire behavior of lightweight mortars based on cement, metakaolin (MK), ultrafine ground granulated blast furnace slag (UGGBFS), ceramic waste powder (CWP), and clay brick waste powder (CBWP). Two sets of mixes were prepared with two types of lightweight aggregate including lightweight expanded clay aggregate (LECA) and pumice aggregate. Regarding the durability assessment, the electrical resistivity and water absorption of the mortars were measured. The UGGBFS-based alkali-activated mortar with pumice aggregate exhibited the highest electrical resistivity and lowest water absorption, while CBWP-based geopolymer mortar with LECA showed... 

This study investigated the effects of combined utilization of wollastonite particles and recycled waste ceramic aggregate (RWCA) on high strength concrete (HSC) properties. Two groups of mixtures were manufactured: 1) concrete mixtures in which cement was partially replaced with wollastonite at values ranging from 10% to 50%, and 2) mixtures in which wollastonite was used at the aforementioned dosages and 50% of natural coarse aggregate was replaced with RWCA. In addition, 10% of cement weight micro-silica was added to all mixtures. The concrete behavior in terms of strength, durability, resistance against acidic environment, and performance under elevated temperatures ranging from 20 °C to... 

The authors regret that there was a minor error in the chemical composition of cement and micro-silica presented in Table 2 of the previously print version of the article. The authors have re-analyzed the materials for more accuracy of the presented information. Please refer to the corrected table as presented here. 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  

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  

The authors regret that there was a minor error in the chemical composition of cement and micro-silica presented in Table 2 of the previously print version of the article. The authors have re-analyzed the materials for more accuracy of the presented information. Please refer to the corrected table as presented here. 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  

The authors regret that there was an error in the caption of Fig. 15. The corrected caption for Fig. 15 as presented here. It is noteworthy that this change does not affect any of the conclusions. Fig. 15. SEM micrograph of geopolymer mortar with clay brick waste: (a) with LECA and magnification of 60×, (b) with pumice aggregates and magnification of 2000×, (c) with pumice aggregates and magnification of 500×, (d) with pumice aggregates and magnification of 1000×. The authors would like to apologize for any inconvenience caused. © 2022 Elsevier Ltd  

The authors regret that there was an error in the labels of Fig. 5. The authors have re-analyzed the XRD patterns of micro-silica for more accuracy of the presented information. Please refer to the corrected figure as presented here. 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  

Copper slag (CS) is an industrial waste, which is generally disposed of in landfills, posing threats to the environment. Alternatively, it can be used as natural aggregate replacement in concrete/mortar, however, it results in a significant increase in material density, production and handling cost. The use of crumb rubber in combination with CS can overcome these problems, but there was no prior study on effect of such combination on the properties of alkali activated mortars (AAMs). The primary aim of this study is to address the problem stated above by replacing CS with 5, 10, 15% (by volume) crumb rubber in alkali-activated slag mortars. Furthermore, the effect of pre-treatment of crumb... 

The authors regret that there was an error in the SEM image presented in Fig. 4(c) of the previously print version of the article. Please refer to the corrected SEM image as presented here. 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  

The authors regret that there was an error in the SEM images presented in Fig. 4 of the article. The corrected SEM images as presented here. It is noteworthy that this change does not affect any of the conclusions. The authors would like to apologize for any inconvenience caused. © 2022 Elsevier Ltd  

This paper investigated the combined utilization of recycled waste ceramic aggregate (RWCA) and waste carpet fibers (WCFs) in high strength concrete (HSC). Concrete mixes containing different percentages of RWCA including 20%, 40%, 60% (by weight) as partial replacement of natural coarse aggregate (NCA) were prepared. To enhance the tensile and flexural strength of concrete, 1.0% (by volume) WCF was added to the mixes. The slump and density of the fresh concrete were evaluated, both of which demonstrated a decreasing trend with incorporation of RWCA and WCF. With regard to the hardened concrete, replacing 40% of NCA with RWCA led to the optimum mechanical properties and increased the... 

This study presents the results of an experimental evaluation of the performance of high strength concrete (HSC)with basic oxygen steel-making (BOS)slag and nano-silica respectively used as a partial replacement of sand and cement. The properties of fresh and hardened concrete specimens containing 25%, 50%, 75%, and 100% BOS as partial replacement of sand and 2% of cement replaced with nano-silica were evaluated. According to the results, concrete samples containing nano-silica with higher BOS percentages, demonstrated improvements in strength and durability properties, while workability was reduced. For example, at 50% BOS content, about 18% increase in compressive strength and 50%... 

Using multiple antennas at the transmit and receive sides of a passive radar brings both the benefits of MIMO radar and passive radar. However one of the obstacles arisen in such configuration is the receive antennas placement in proper positions so that the radar performance is improved. Here we just consider the case of positioning one receiver among multiple illuminators of opportunity. Indeed it is a start for the solution of optimizing the geometry of the multiple receivers in a passive radar  

SbCl3 supported on montmorillonite K-10 is an efficient catalyst for the ring opening of epoxides with aromatic amines under solvent-free conditions and microwave irradiation to give the corresponding b-amino alcohols in high yields with high regioselectivity  

One of the important obstacles in MIMO (Multiple Input Multiple Output) radars is the issue of designing proper transmit signals. Indeed, the capability of signal design is a significant advantage in MIMO radars, through which, the system can achieve much better performance. Many different aspects of this performance improvement have been considered yet, and the transmit signals have been designed to attain such goal, e.g., getting higher SNR or better detector's performance at the receiver. However, an important tool for evaluating the radar's performance is its ambiguity function. In this paper, we consider the problem of transmit signal design, in order to optimize the ambiguity function... 

Two gains play key roles in recently developed MIMO wireless communication systems: "spatial diversity" gain and "spatial multiplexing" gain. The diversity gain refers to the capability to decrease the error rate of the MIMO channel, while the multiplexing gain implicitly refers to the amount of increase in the capacity of the MIMO channel. It has been shown that there is a fundamental tradeoff between these two types of gains, meaning interplay between increasing reliability (via an increase in the diversity gain) and increasing data rate (via an increase in the multiplexing gain). On the other hand, recently, MIMO radars have attracted much attention for their superior ability to enhance...