Sharif Digital Repository

Aluminum sulfate is widely used in water treatment as a polyelectrolyte. Its dissolution and recrystallization into nanoparticles directly affects the working conditions. This study concerns determination of the metastable zone and induction time in nucleation of aluminum sulfate nanoparticles in aqueous media and in presence of acetone as anti-solvent. Later the effect of SDS on the metastable zone and induction time are also studied.. The study also shows if the presence of anti-solvents and surface active agents can vary this phenomenon. The study also adds to our understanding of the media in creation and stabilization of nanoparticles. This project has a special focus on the changes... 

This study presents an integrated two-dimensional numerical framework for simulating rainfall-induced landslides from instability initiation to post-failure flow. The discrete element method (DEM) is used to establish a rheological model that relates the apparent viscosity of a granular sand to shear rate, normal stress, and water saturation. A theoretical model is developed to determine water distribution and water-induced forces between particles for different saturations. The resulting forces are embedded in a 3D shear cell as a numerical rheometer and a wet sand is sheared between two walls. A power law rheological model is obtained as a function of inertia number and saturation. It was... 

In a solar central system plant about 40% of energy losses occurs in the heliostat field. Furtheremore, half of the investment costs for construction of the plant is related to the heliostat field. Therefore, an optimal design of the heliostat field is necessary for reduction of levelized cost of energy in solar tower power plants. In this study, in order to optimally design the heliostat field, first energy performance of the helistat field in one year is simulated. Solar power and sun’s position at each moment of the day is determined by mathematical relations. Then, loss factors in the field are modelled and heliostat field layout is designed by an algorithm. Finally, by using PSO... 

Today, due to the scarcity of fossil energy resources, security of energy supply, and increasing environmental concerns, we need to develop new technologies to promote energy-saving and reduce greenhouse gas emissions. One of the suitable options for this purpose is to use the simultaneous production of electric power, cooling, and heating. Meanwhile, trigeneration systems that provide part of their energy needs from the sun, due to the free solar energy source and low environmental impact, can be an ideal technology for clean and safe scattered production. The present study has suggested a trigeneration system of cooling, heating, and power generation based on the organic Rankin cycle and... 

Today, due to increasing electricity consumption and demand, the use of conventional systems such as thermal, hydro and nuclear power plants is not enough to convert energy. Over the past century, scientists have sought to discover new technologies for exploiting different forms of energy and converting them into high-efficiency electrical energy. One of these ways is to use the phenomenon of magnetohydrodynamics (magnetic fluid dynamics) to convert thermal energy directly into electrical energy. Magnetohydrodynamics is a theoretical field that studies the dynamics of fluids with electrical conductivity. Induction magneto-hydrodynamic generators use ionized hot plasma (a quasi-neutral gas of... 

The power generation system of this type of power plants operates on the air flowing through the power plant’s chimney and colliding with the turbine blades within the chimney. When the solar collector warms the nearby air and thus expands the air by absorbing the sunlight, a difference is created in the density. Then, this difference in the density creates the phenomenon of buoyancy, making the air pass to the top of the chimney through the collector.This study simulated and optimized a solar chimney power plant. The simulation and optimization were performed based on the information of Manzanares Solar Chimney Power Plant in Spain (located in 150 km from the south of Madrid). It was... 

The issue under discussion in this paper is to optimize the fuel consumption of the Toyota Prius hybrid car. In order to solve this problem, the ADVISOR design model used by NREL in the Matlab / Simulink environment has been used. Various parts of this model are described. The optimization performed on this issue is based on the emotional controller. This controller works by simulating learning in animals based on encouraging and punishing them. With the introduction of the controller, the model and its inclusion in the fuel consumption control and its implementation have achieved good results. In the initial state and the controller in the model, the fuel consumption was 4.9 liters per 100... 

In this thesis, an attempt has been made to provide a smart and innovative system to optimize fuel consumption in cars by using the combination of engineering sciences, aerospace, and machine learning. Considering the current challenges of societies, the economic importance of saving fuel, as well as recent developments in the fields of machine learning and reinforcement learning, this research tries to improve the performance of cars in order to minimize the air resistance force of car bodies. In this regard, deep neural networks have been used to learn the dynamics of aerodynamic forces and reinforcement learning algorithms, especially DDPG (Deep Deterministic Policy Gradient), have been... 

In the preceding years, hydroxyapatite (HA)-based coatings and scaffolds have been known as the best biomaterials for dental and orthopedics applications. Biocompatible and bioactive hydroxyapatite-based Coatings on metallic implants is one of the best methods for reaching both suitable mechanical properties and appropriate bioactivity, leading to better osseointegration and osteoblast proliferation. The ultimate goal of this project is characterization as well as mechanical and electrochemical behavior investigation of Hydroxyapatite- Chitosan nanocomposite coating by electrophoretic deposition (EPD) method on Plasma Electrolyte Oxidation (PEO) treated titanium substrates and Magnesium (Mg)... 

This research has been surveyed the impact of intermediate skilled and high skilled human labor force on the productivity of manufacturing sectors by the Nelson & Phelps and also Lucas approaches. first model is related to the level of productivity and the second model is related to the growth of it. We has been prepared the needed statistics from the raw figures of iran statistics center. regression analysis has been done on the basis of panel data model by the use of stata software. the results show that not good efficiency to optimize technology factor of Cobb-Douglas model although it shows higher marginal labor productivity of high skilled human labor force. we has proposed some... 

Today’s radio transmitters must be able to send information in several standards. One problem involved in these wide band electronic systems lies in its end part, ie power amplifier. To have a broad band width either switching must be made among several power amplifiers with narrow band width (tuned) or the transistor part of power amplifier must be the same and single and selection be made only among matching networks. In this thesis, a power amplifier with broad band width without requiring a matching network has been designed and laid out. Also considering the low breakdown voltage of the gate oxide of the today’s standard CMOS transistors, it is very difficult to get a high output power... 

Hybrid electric vehicles (HEV) are proving to be one of the most promising innovations in advanced transportation systems to reduce air pollution and fossil fuel consumption. EMS is one of the most vital aspects of the HEV powertrain system. This research aims to design an optimal EMS under the condition of meeting the goals of drivability control, fuel consumption reduction, and battery charge stability. The current EMS is based on the classical rule-based method derived from fuzzy logic, which guides to the suboptimal solution in episodic driving cycles. Previous experiences in implementing Reinforcement Learning (RL) suffer from late convergence, instability in tracking the driving... 

In recent decades, renewable energy resources (especially wind power as the fastest-growing energy source) have increasingly been employed for providing electrical energy all over the world given to the rising energy demands, reduction in non-renewable fossil fuels as well as severe restrictions applied to the utilization of these fuels because of their contribution in environmental pollution, generating greenhouse gas emissions, and consequently earth warming. The main factors in the development of wind energy systems to date are the easy access to this energy source in all seasons and its cost-effectiveness compared to other counterparts. One of the key components utilized for converting... 

Design and implementation of an efficient, 1 Watt, linear power amplifier (PA) with CMOS technology for UHF-RFID applications is presented in this thesis. Poor quality factor of inductors, high substrate noise and low breakdown voltage of CMOS, makes the implementation of Watt-level PAs challenging on this technology. Also the trade-off between linearity and efficiency, further hardens achieving an efficient high power linear PA. So the literature was reviewed first to come up with the appropriate structure of a linearized efficient PA. Afterwards, the structure was reformed and optimized for the application mentioned above with reasonable stability margins. Baseband relevant blocks were... 

We present a novel and simple method to calculate each Fourier series coefficient of ISFs in LC oscillators, analytically. This new approach explains the relationship between Fourier series coefficient of ISF and oscillator topology and parameters. This technique helps designers to obtain the great insight of how to decrease the output noise in oscillators. This method also can be used to derive the waveform of ISFs in time domain.Based on the features of our new technique and by presenting a general method to change the stationary noises to Cyclo-stationary ones, we suggest a step by step design guide which elucidates new ideas for designers to manipulate the oscillator parameters and... 

In this thesis, we intend to explore the application of active inductors in high-performance radio receivers. The proposed active inductor uses a feed-forward path to improve the noise performance. This is done without sacrificing the quality factor and the power consumption. The proposed active inductor is designed and implemented in a standard 0.18μm CMOS technology. The measurement results show an almost three fold improvement in the noise performance, comparing to the typical existing structures. The resonance frequency of the inductor can be tuned from 1.8 GHz to 5.5 GHz, while the quality factor can be adjusted up to 30. The total current consumption of the active inductor is 4.8... 

This thesis revises the conventional design of oscillators and presents new methods for shaping and improving the phase noise curve of the oscillators. These methods are based on the position of the zeros and poles of transfer functions in the S-plane and choosing their orders also. This thesis shows that the position of the zeroes and poles of the transfer functions can affect the phase noise performance of the oscillators. The basic idea is maximizing the slope of the phase of the transfer functions. It is proved that the maximizing the slope of the phase can expectedly reduce the phase noise of the oscillators. Increasing the order of the transfer functions with the proper selection of... 

One of the main components of any solar power plant is the heat storage. Implementing heat storage reduc-es the cost of power generation by increasing the capacity factor of the system. This Thesis aims to analyze the operation of heat storages by modeling latent heat
storage. In this regard, an efficient method named "Method of Characteristics" is utilized. Models developed based on this method are possible to be used for comparison, sensitivity analysis, and optimization due to their low computation time. Sensitivity analysis was carried out based on various parameters such as void fraction, fiUer material size. Results show that using latent heat storage, storage c-apacity is...