Sharif Digital Repository

Industrial air pollution from point and nonpoint sources of steel complexes has drawn increasingly more public attention in the past decades. Previous research efforts have been more concentrated on point sources of particulate emissions from these complexes. However, wind-induced particulate emissions from iron ore storage piles not only result in ambient air pollution but also increase economic adverse effects to the industry by loss of process raw materials. Experiments were conducted to assess the impact of wind speed and humidity on particulate emission rates from iron ore storage piles. A wind-generating system and specific iron ore, experimental piles (L:W:H of 30:11.5:5 cm) were... 

The lead is a heavy metal with hazardous impacts on environment and human life. Lead-free perovskite solar cells have attracted much attention in recent years, due to eco-friendly characteristics. Meanwhile, Pb-containing cells showed the highest efficiencies among the various types of cells. Hence, designing novel Pb-free solar cells with comparable or better performance than the Pb-containing ones is highly required. In this work, a lead-free methyl-ammonium-germanium-iodide (MAGeI3)-based perovskite solar cell with ITO/TiO2/MAGeI3/Spiro-OMeTAD/Ag multilayer nanostructure has been proposed and its main characteristics including open-circuit voltage (VOC) and power conversion efficiency (η)... 

In this study, the effect of protection methods regarding the corrosion decrement of steel in concrete was simulated by artificial neural networks (ANNs) and fuzzy logic (FL) approaches. Hot dip galvanizing as a protective coating, Ferrogard 901 corrosion inhibitor, a pozzolanic component, such as fly ash (FA) and micro-silica (MS), and eventually rebar AISI-304 were employed in concrete. Reinforced concrete samples were held under impressed voltage of 30 V in 3.5 % NaCl electrolyte for 350 hours toward a stainless-steel auxiliary electrode. Corrosion currents have been modelled using feed forward back propagation ANNs and FL methods. The results demonstrate good consistency between... 

In recent years, Wireless Ad-hoc networks have been considered as one of the most important technologies. The application domains of Wireless Ad-hoc Networks gain more and more importance in many areas. One of them is controlling and management the packet traffic. In this paper our goal is controlling the performance of every sections of pipeline of the factory by checking network periodically. Along the factory the traffic is modeled with a Poisson process. We present, with obtaining traffic packets at time (t) for each node in Wireless Ad-hoc Network, we can completely train a Neural Network and successfully predict the traffic at time (t+1) for each node. By this way we can recognize the... 

The number of humidity outputs on the cap of a cylindrical capacitance sensor is optimized by designing three different probes with direct and indirect windows. The time interval is measured within which 30- 70 % humidity can influence the dielectric constant and conductivity of the capacitance when exposed to a range of relative humidity. It is then compared with a simple set-up including a simplified equivalent circuit. The direct probes had four and double outputs on the window of the cylindrical capacitive sensor while the indirect probe had a thin plastic layer only. We observed that the dielectric constant and its conductivity depend closely to the humidity outgoing pathway and also to... 

In this paper, an approach for optimal determining reserve capacity in the electricity market is presented. This paper describes a method for setting the optimum value of reserve capacity based on the cost of its provision and the benefit derived from its availability. Reduction of customer outage cost is interpreted as the benefit of reserve capacity. In the proposed method, reserve is procured up to the point where the marginal cost of procuring reserve is equal to the marginal value of this reserve capacity. The proposed method can be formulated as a mixed-integer linear program (MILP) and solved with large-scale commercial solvers. The proposed method is applied to the IEEE reliability... 

Highly selective epoxidation (> 95%) of unfunctionalized alkenes was performed by tetrabutylammonium periodate in the presence of six different phenyl substituted manganese(III) meso-tetraphenylporphyrins [Mn(Por)] and imidazole in CH2Cl2. Electron-withdrawing and bulky substituents on the phenyl groups lowered the catalytic activities of the corresponding Mn(Por). Less bulky alkenes with electron -rich double bonds showed greater reactivity in the epoxidation. Co-catalytic activities of four different classes of axial nitrogen donors are compared in the presence of various Mn(Por). In general no direct correlation was found between co-catalytic activities and the pKa values of the nitrogen... 

We discuss a fine-tuning of rather generic 3-dimensional higher-curvature gravity actions that leads to gauge symmetry enhancement at the linearized level via partial masslessness. Requiring this gauge symmetry to be present also nonlinearly reduces such actions to conformal Chern-Simons gravity. We perform a canonical analysis of this theory and construct the gauge generators and associated charges. We provide and classify admissible boundary conditions. The boundary conditions on the conformal equivalence class of the metric render one chirality of the partially massless Weyl gravitons normalizable and the remaining one non-normalizable. There are three choices-trivial, fixed, or free-for... 

We show that conformal Chern-Simons gravity in three dimensions has various holographic descriptions. They depend on the boundary conditions on the conformal equivalence class and the Weyl factor, even when the former is restricted to asymptotic anti-de Sitter behavior. For constant or fixed Weyl factor our results agree with a suitable scaling limit of topologically massive gravity results. For varying Weyl factor we find an enhancement of the asymptotic symmetry group, the details of which depend on certain choices. We focus on a particular example where an affine u^(1) algebra related to holomorphic Weyl rescalings shifts one of the central charges by 1. The Weyl factor then behaves as a... 

In this research, we simulate the corrosive behavior of steel reinforcements on 5 different mixtures to investigate the effect of two powerful protective methods, including pozzolanic additives and corrosion inhibitor on concrete, by artificial neural networks (ANNs). Related to this model, fly ash (FA), micro silica (MS), and slag were used as pozzolanic materials at an optimum 25%, 10%, and 25% of cement weight, respectively. Moreover, Ferrogard 901 as an inhibitor was also utilized. The producer recommends using12 kg/m3 to get the best possible results. The non-linear corrosion of concrete into a marine solution (3.5% NaCl) was simulated by the feed forward back propagation (FFBP)... 

In this research, we simulate the corrosive behavior of steel reinforcements on 5 different mixtures to investigate the effect of two powerful protective methods, including pozzolanic additives and corrosion inhibitor on concrete, by artificial neural networks (ANNs). Related to this model, fly ash (FA), micro silica (MS), and slag were used as pozzolanic materials at an optimum 25%, 10%, and 25% of cement weight, respectively. Moreover, Ferrogard 901 as an inhibitor was also utilized. The producer recommends using12 kg/m3 to get the best possible results. The non-linear corrosion of concrete into a marine solution (3.5% NaCl) was simulated by the feed forward back propagation (FFBP)... 

A three-step method for the deposition of CH3NH3PbI3 perovskite films with a high crystalline structure and large cuboid overlayer morphology is reported. The method includes PbI2 deposition, which is followed by dipping into a solution of C4H9NH3I (BAI) and (BA)2PbI4 perovskite formation. In the final step, the poorly thermodynamically stable (BA)2PbI4 phase converts into the more stable CH3NH3PbI3 perovskite by dipping into a solution of CH3NH3I. The final product is characterized by XRD, SEM, UV/Vis, and photoluminescence analysis methods. The experimental results indicate that the prepared perovskite has cuboids with high crystallinity and large sizes (up to 1 μm), as confirmed by XRD... 

Biphase TiO2 nanoparticles have been prepared by sol-gel method. Water/titanium molar ratio (r) has been used to control the hydrolysis and condensation of titanium isopropoxide in solution producing titanium oxide with two different polymorphs. The influence of crystallite size and morphology of prepared TiO2 on the phase transformation of the resultant materials has been investigated. Synthesized powders were characterized by X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Different trends can be observed in the phase transformation and particle growth of the prepared titanium oxide nanomaterial. It was concluded that, the rate of particle... 

This paper addresses the problem of finding the nearest neighbor (or one of the R-nearest neighbors) of a query object q in a database of n objects, when we can only use a comparison oracle. The comparison oracle, given two reference objects and a query object, returns the reference object most similar to the query object. The main problem we study is how to search the database for the nearest neighbor (NN) of a query, while minimizing the questions. The difficulty of this problem depends on properties of the underlying database. We show the importance of a characterization: combinatorial disorder D which defines approximate triangle inequalities on ranks. We present a lower bound of Ω(Dlog... 

A new algorithm named random particle optimization algorithm (RPOA) for local path planning problem of mobile robots in dynamic and unknown environments is proposed. The new algorithm inspired from bacterial foraging technique is based on particles which are randomly distributed around a robot. These particles search the optimal path toward the target position while avoiding the moving obstacles by getting help from the robot's sensors. The criterion of optimal path selection relies on the particles distance to target and Gaussian cost function assign to detected obstacles. Then, a high level decision making strategy will decide to select best mobile robot path among the proceeded particles,... 

A new approach for optimal reserve determination and cost allocation in the pool-based and disaggregated market model using a well-being framework is presented in this paper. In the proposed method, customers have the chance to specify the risk level which they are willing to accept. Firstly, the energy market is cleared, and afterwards the reserve market is cleared such that the required risk levels of different customers are satisfied. Then, according to the required risk levels and the provided reserve, the cost of reserve is allocated between the different customers with different reliability requirements. For fairly managing the shortage between different customers in the real time... 

The precipitation process considered here, involved the addition of orthophosphoric acid solution to a calcium hydroxide solution. Several parameters such as the effects of atmosphere controlling, pH, adding extra acid solution, the amount of stirring speed, and post-chemical treatment were studied. In order to study the thermal stability of synthesised powders, they were sintered for 2 h at 1200 °C and the as-precipitated and sintered powder samples were examined using SEM, XRD, FTIR and ICP methods. The results clearly revealed that the final precipitated powder is hydroxyapatite (HA) with good purity, stoichiometry and successful thermal stability. SEM high magnification micrographs... 

Using Renewable Energy (RE) is growing day by day. We need to locate RE in the best place to maximize energy production and supplier profit. As a result, we propose a novel method for RE location (REL). This model suggests a Data-Driven Robust Optimization (DDRO) for multi-objective REL by considering Risk (DDROMORELR). We consider risk by adding min function in energy and profit objectives (government and supplier objectives). A DDRO approach is added to the model to tackle uncertainty and be close to the real world. We utilize an improved Augmented ε-constraint (AUGEPS2) to solve objectives and produce a Pareto front. We compare problems with DDRO and without considering DDRO, and the... 

Corrosion of steel rebars in concrete can reduce the durability of concrete structures in coastal environments. The corrosion rate of these concrete structures can be reduced by using suitable concrete additives and coating on rebars. This paper investigates the corrosion resistance of steel rebars by the addition of pozzolanic materials including fly ash, silica fume, polypropylene fibers, and industrial 2-dimethylaminoethanol (FerroGard 901) inhibitors to the concrete mixture. Three different types of rebars including mild steel rebar st37, and two stainless steel reinforcements, AISI 304 and AISI 316, were used. Various types of primer and coating including alkyd based primer, hot-dip...