Sharif Digital Repository

Blazed gratings have so far been made tunable by mechanically changing the grating geometry, such as its periodicity. In this work, a low-profile planar blazed metasurface grating is demonstrated which is electronically tunable, with no moving or mechanically changing parts. The reflective metasurface is comprised of planar patch resonators with a cutting slot loaded with a surface mount varactor in each unit cell. Coupling of the incident wave to the resonant surface provides a high efficiency back reflection or blazing. We show that by changing the DC bias, we are able to control the blazing frequency and the reflection angle of the operation. This tuning has been confirmed by simulations... 

Hydrogen bonds are the dominant motif for organizing the three-dimensional structures of biomolecules such as carbohydrates, nucleic acids, and proteins, and serve as templates for proton transfer reactions. Computations, gas-phase acidity measurements, and pKa determinations in dimethyl sulfoxide on a series of polyols indicate that multiple hydrogen bonds to a single charged center lead to greatly enhanced acidities. A new class of Brønsted acids, consequently, is proposed. © 2009 American Chemical Society  

B3LYP/aug-cc-pVDZ computations were carried out on polyamines with up to seven amino groups. The gas-phase proton affinities of these compounds are 219.6 (1-BuNH2), 238.6 (H2NCH2CH2CH 2CH2NH2), 252.8 [(H2NCH 2CH2CH2)2CHNH2], 261.3 [(H2NCH2CH2CH2) 3CNH 2 (1)], and 288.5 kcal mol-1 [(H2NCH 2CH2CH(NH2)CH2CH2) 3CNH2]. These results indicate that the tetraamine is near the top of the basicity scale and the heptaamine is more basic than any neutral organic compound which has been measured to date. A gas-phase equilibrium acidity determination between 1 and DBU also was carried out, and PA(1) = 256.2 ± 2.1 kcal mol-1 was obtained. This demonstrates that multiple intramolecular hydrogen bonds can... 

In this study, a ternary ZnO@spinel cobalt ferrite@carbon nanotube magnetic photocatalyst (ZSCF@CNT) was successfully synthesized and used to activate peroxymonosulfate (PMS) for Cefixime (CFX) antibiotic degradation under UVC irradiation. The morphology, optical, structural, and physicochemical properties of ZSCF@CNT were characterized and analyzed by XPS, XRD, FESEM-EDX, TEM, BET, VSM, UV–vis DRS and PL analysis. The results indicated that the ternary ZSCF@CNT photocatalyst exhibited superior catalytic activity on CFX elimination than that of individual components and binary composite catalysts, in which CFX with was rapidly removed under UVC irradiation and PMS. The effect of operational... 

Application of construction and demolition (C&D) wastes were considered as sustainable development goals (SDGs) for maintaining raw materials. Also, lightweight concretes such as aerated autoclaved concrete (AAC) were used for partitioning spaces in the building industry. Moreover, the waste products of the mentioned materials were increased due to the rise of old construction demolitions. This study contributes a calcinated aerated autoclaved concrete (CAAC) which is efficient, powerful, highly rapid, non-expensive and novel adsorbent for the removal of cationic dyes including malachite green (MG), methyl violet (MV) and methylene blue (MB) form water samples. The impacts of different... 

Application of construction and demolition (C&D) wastes were considered as sustainable development goals (SDGs) for maintaining raw materials. Also, lightweight concretes such as aerated autoclaved concrete (AAC) were used for partitioning spaces in the building industry. Moreover, the waste products of the mentioned materials were increased due to the rise of old construction demolitions. This study contributes a calcinated aerated autoclaved concrete (CAAC) which is efficient, powerful, highly rapid, non-expensive and novel adsorbent for the removal of cationic dyes including malachite green (MG), methyl violet (MV) and methylene blue (MB) form water samples. The impacts of different... 

A ternary hetero-junction was prepared by anchoring ZnO@CoFe2O4 (ZCF) on activated carbon (AC) and employed as a UV-assisted peroxymonosulfate (PMS) activator to boost the degradation of diazinon (DZN) pesticide. The structure, morphology, and optical properties of the ZCFAC hetero-junction were characterized through a series of techniques. The highest degradation efficiency of DZN (100% in 90 min) was achieved by the PMS-mediated ZCFAC/UV system, superior to other single or binary catalytic systems due to the strong synergistic effect between ZCFAC, PMS, and UV. The operating reaction conditions, synergistic effects, and the possible pathways of DZN degradation were investigated and... 

Orthogonal Matching Pursuit is an iterative greedy algorithm used to find a sparse approximation for high-dimensional signals. The algorithm is most popularly used in Compressive Sensing, which allows for the reconstruction of sparse signals at rates lower than the Shannon-Nyquist frequency, which has traditionally been used in a number of applications such as MRI and computer vision and is increasingly finding its way into Big Data and data center analytics. OMP traditionally suffers from being computationally intensive and time-consuming, this is particularly a problem in the area of Big Data where the demand for computational resources continues to grow. In this paper, the data-level... 

For the 4th IUPAP International Conference of Women in Physics, we report on activities in science and engineering in Iran, and conditions for women in physics, in the three years since the 3rd IUPAP International Conference of Women in Physics was held in 2008. Iran has made prominent advancements and astonishing progress in laser technology, biotechnology, nanotechnology, genetics, computer software and hardware, and robotics. Iranian scientists have been very productive in several experimental fields, such as pharmaceutical, organic, and polymer chemistry. Conditions for women in physics have improved greatly in recent years. A project to improve the environment for learning physics, and... 

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)... 

Core/shell structure of ZnO nanowires coated with a monolayer of TiO 2 is investigated using Density Functional Theory (DFT). The electronic states of the semiconductor is calculated and compared before and after coating of the TiO2 monolayer on a ZnO [101 0] surface. The effect of TiO2 coating induce surface states changes and shifts the conduction and valence band edges to higher energies. Our results, in qualitative agreement with the experimental work of Matt Law et al. (J. Phys. Chem. B, 110, 22652), show an increase in open circuit voltage and a decrease in short circuit current in ZnO/TiO2 core shell dye sensitized solar cells. Regarding the semiconductor density of states (DOS), TiO2... 

Due to the important role of commitment and trust in the relationship marketing, the factors which can directly result in a committed relationship along with the factors which can influence the commitment through influencing trust, according to the model of commitment and trust by (Morgan & Hunt, 1994) have been introduced and their level of importance has been investigated here. The article uses fuzzy cognitive maps (FCMs) in the proposed model to find the most important paths leading to relationship commitment. The FCM analyzes the responses of a group of 30 people including general practitioners in dentistry, managers of dental departments in some of the public clinics and hospitals who... 

Conventionally, a film of TiO2 particles of 300 nm size is employed in Dye-sensitized solar cells (DSCs) as the back reflector film to enhance the light harvesting. Perfect reflectance of silver in visible and near infrared motivates to investigate its potential as the material for the light back reflector film in DSCs. In this study, light back reflector films consisting of 300 nm-sized silver particles, as well as vacuum evaporated silver flat film, were fabricated and compared to 300 nm-sized rutile-type TiO2 particulate reflector film to study their optical aspects. Conventional TiO2 rutile-type particulate film demonstrates slightly lower performance... 

Monolithic dye-sensitized solar cells are conventionally fabricated using carbon composite layer as the counter electrode. In the current research, the brittle carbon composite layer is replaced with a metal foil, aiming to decrease the device series resistance and using less catalyst material in counter electrode. This metallic structure has also an advantage of mechanical strength and decreases the fabrication complexity. The counter electrode is prepared by electrodepositing Cr film followed by electrodepositing Pt nanoparticles on a metal foil. As the porous spacer layer, different composite layers of SiO2, TiO2, and Al2O3 are investigated and the best results are obtained for TiO2... 

Microbial fuel cells (MFCs) have been a potential green energy source for a long time but one of the problems is that either the technology must be used on a large scale or special equipment have been necessary to keep the fuel cells running such as syringe pumps. Paper-based microbial fuel cells do not need to have a syringe pump to run and can run entirely by themselves when placed in contact with the fluids that are necessary for it to run. Paper-based microbial fuel cells are also more compact than traditional MFCs since the device doesn't need any external equipment to run. The goal of this paper is to develop a microbial fuel cell that does not require a syringe pump to function. This... 

This paper proposes a novel decentralized control approach for islanded direct-current (DC) microgrids (MGs) based on model predictive control (MPC) to regulate the distributed generation unit (DGU) output voltages, i.e. the voltages of the point of common coupling (PCC). A local controller is designed for each DGU, in the presence of uncertainties, disturbances, and unmodeled dynamics. First, a discrete-time state-space model of an MG is derived. Afterward, an MPC algorithm is designed to perform the PCC voltage control. The proposed MPC scheme ensures that the PCC voltages remain within an acceptable range. Several simulation studies have been conducted to illustrate the effectiveness of... 

Sophisticated surgeons are widely indicating the use of surgical robots in order to reject human error, increase precision, and speed. Among well-known robotic mechanisms, parallel robots are broadly more investigated regarding their special characters as higher acceleration, speed, and accuracy, and less weight. Specific surgical procedures confine, and restrict their workspace, while controlling and validating the robots are complicated regarding to their complex dynamic. To this end, in this paper, a 6-DOF robot, with rotary manipulators, is designed and controlled. Addressing nonlinearity of parallel robots, an innovative methodology is formulated to robustly penalize the error of... 

Sophisticated surgeons are widely indicating the use of surgical robots in order to reject human error, increase precision, and speed. Among well-known robotic mechanisms, parallel robots are broadly more investigated regarding their special characters as higher acceleration, speed, and accuracy, and less weight. Specific surgical procedures confine and restrict their workspace, while controlling and validating the robots are complicated based on their complex dynamic. To this end, in this paper, a 6-DOF robot, with linear manipulators, is designed and controlled. Addressing the inherent nonlinearity of the robot mechanism, an adaptive PID manipulator is employed and validated with nonlinear... 

Although so many advances have been proposed in the field of artificial intelligence and superconductivity, there are few reports on their combination. On the other hand, because of the nonlinear and multivariable characteristics of the superconductive elements and capabilities of neural networks in this field, it seems useful to apply the neural networks to model and control the superconductive phenomena or devices. In this paper, a new constructive neural network (CNN) trained by two different optimization algorithms; back-propagation and genetic algorithm, is proposed which models the behavior of the superconductive fault current limiters (SFCLs). Simulation results show that the proposed...