Sharif Digital Repository

All current highest efficiency perovskite solar cells (PSCs) use highly toxic, halogenated solvents, such as chlorobenzene (CB) or toluene (TLN), in an antisolvent step or as solvent for the hole transporter material (HTM). A more environmentally friendly antisolvent is highly desirable for decreasing chronic health risk. Here, the efficacy of anisole (ANS), as a greener antisolvent for highest efficiency PSCs, is investigated. The fabrication inside and outside of the glovebox showing high power conversion efficiencies of 19.9% and 15.5%, respectively. Importantly, a fully nonhalogenated solvent system is demonstrated where ANS is used as both the antisolvent and the solvent for the HTM.... 

Transmission health is an important factor in safety and maintenance costs in industries, so construction of test rigs for testing high-powered gearboxes under different operating conditions of helicopters is required. The studied test rig, which is developed at Sharif University of Technology branch of ACECR (Academic Centre of Education, Culture and Research) is mainly used for testing high-powered gearboxes through a mechanically closed-loop procedure. For providing a variety of speeds and torques in test rigs, torque applying system is required. According to generation of higher forces, reduced size of equipment and accurate positioning, electro hydraulic actuators (EHAs) are used for... 

Ultrasonic waves have been extensively used in many industrial applications including clean devices, pipes and vessels. A clear extension of this usage is the removal of wellbore contaminants by exposing it to high-power ultrasonic waves. In this paper, a mathematical model for ultrasonic propagation through the porous medium around the wellbore is presented. The equations of wave propagation are written in a cylindrical coordinate according to Biot theory and the induced stress in the rock are calculated at each point using finite difference approach Comparison of imposed local stresses with adhesion forces between scales and rock, the properties of ultrasonic transducer, such as frequency... 

Cascaded H-bridge converter has been utilized recently in different high-power applications due to its modular and simple structure. In order to have a balanced operation after a fault occurrence in this converter, it is necessary to detect the switch fault and its location. In this paper, a fast power-switch fault detection method is presented to identify a fault and its location. Only one voltage measurement per phase is required by this method, and the fault detection is faster compared to the existing methods. Moreover, it is suitable for implementation on an FPGA device due to the use of simple math, relational, and state machine blocks. The proposed method is verified by computer... 

We hereby demonstrate symmetric and asymmetric supercapacitors (SSCs and ASCs) based on core/shell-like Ni-Co oxide@cotton//Fe2O3-carbon nanotubes@cotton that are capable of storing a remarkable amount of energy, while retaining a high power density and long cycle life. Hierarchical, porous structures of Ni-Co-O nano-rod (NR) decorated Pd-activated cotton fibers (CFs) were fabricated using an eco-benign hydrothermal method and directly used as the cathode of the supercapacitors. Fe2O3-single-wall carbon nanotube (SWCNT) decorated CFs were employed as anodes of the fabricated ASCs. The assembled Ni-Co-O@cotton//Fe2O3-SWCNTs@cotton based ASCs possessed the benefits of a relatively high energy... 

A systematic method to design high power and high efficiency mm-wave fundamental oscillators is presented. By using a linear time variant method, we first obtain the optimum conditions and show that these conditions can be significantly different for high power and high efficiency fundamental oscillation. Next, we propose a modified multistage ring oscillator with interstage passive networks to exploit the full capacity of the transistors in terms of output power or efficiency. Analytical expressions are also derived to determine the value of passive elements used in the oscillator. To verify the validity of the method, a 77-GHz two-stage (differential) VCO is designed in a 65-nm CMOS... 

In this paper, a new interleaved DC–DC converter based on a coupled and a single input inductor is proposed. The suggested high step-up converter utilizes various inductive and capacitive methods to transfer magnetic energy more efficiently. The output voltage is regulated with the switches' duty cycle and the coupled inductor (CI) turns ratio, which provide a wide output voltage range. Interleaving improves the converter reliability, employs both the first and third areas of CI's B-H plane, cancels DC component of the CI, and reduces the input current ripple of the proposed converter with twice switching frequency. Utilization of two output ports for voltage stress and ripple reduction in... 

In this study, a reliable 10 W high-power amplifier (HPA) is presented along with its design procedure. Implemented on a 0.25-μm InGaAs/AlGaAs/GaAs pseudomorphic high electron mobility transistor (pHEMT) process, the designed HPA achieves power added efficiency (PAE) of more than 33% across the 7.8-12.8 GHz band. The proposed two-stage PA provides 15 dB large signal gain with an average small-signal gain of 18 dB. Peak results are achieved at 12.2 GHz with 40.8 dBm output power and 44% PAE. The reliability of the designed HPA is studied in detail along with a thorough discussion of related concerns  

Direct drive motors have the excellent ability for precision position control due to their direct connection to load and elimination of the gearbox and pulley backlash. Among the direct drive motors, permanent NdFeB magnet synchronous motors (PMSMs) are the best choice for control systems due to their high efficiency, high power density, good dynamic behaviour, and excellent controllability. This study deals with the design, analysis, and fabrication of a direct drive PMSM for precision position control. To reach this aim, the designed motor should have very low cogging torque and torque ripple to avoid the motor deviation at the target point. To achieve these purposes, at first, a suitable... 

A high-power short-pulse generator based on the dual action of two coupled diodes, a high-voltage step recovery diode and a high-current diode, is presented. This is made possible using a gas discharge tube. Both analysis and SPICE simulation show about 20-dB peak power increment. This gives a high output power level of 5.7 MW with 1-ns pulsewidth and 450-kHz repetition rate obtained from an input average power of 7.1 kW. An efficiency of about 73% is obtained with more than 30 dB increase in the average power delivered to a 50-Ω load