Sharif Digital Repository

The molecular dynamic (MD) method was first reported by Alder and Wainwright in the late 1950s to study the interaction of hard spheres. Molecular dynamic (MD) simulation is a technique for computing equilibrium and forwarding properties for classical many-body systems. This is a reasonable and often excellent approximation for a wide range of systems and properties. Although molecular dynamics method provide the kind of detail necessary to resolve molecular structure and localized interaction, this fidelity comes with a price. Namely, both the size and time scales of the model are limited by numerical and computational boundaries.The multi scale approach taken by the computational materials... 

The fast-growing development of engineering and medical sciences leads to the diagnosis and treatment of diseases with higher accuracy and in the early stages of the disease. Medical imaging systems are considered as a crucial and effective tool in this field that based on the principle of technology used, are able to image various tissues with high quality. In recent years, photoacoustic imaging has attracted the attention of many researchers and engineers, because it able to image different tissues with good resolution and penetration depth non-invasively and without the use of ionizing radiation. The photoacoustic system response is a low-pass filter that passes only low-frequency... 

Nowadays, various policies are adopted by transportation managers and planners. These policies aim to improve system performance, reduce user costs, control and reduce air pollution, reduce noise pollution, and ultimately reduce congestion. A set of these policies in the form of transportation demand management is presented in the literature. A common way to find the effect of a policy on user behavior is to use questionnaires. Other causal inference models have been proposed in disciplines such as statistics, political science, marketing science, epidemiology, and psychology. The purpose of these models is to find the causal effect of an intervention (treatment) on a system. These studies... 

In this thesis the hourly concentration of different gaseous air pollutants in Tehran is modeled using Land Use Regression (LUR) and Artificial Neural Network, separately. Both models are provided with the same set of input data; the first step is to find these data. Since traffic affects air pollution, information about traffic conditions is one of the main inputs in air pollution modeling. Therefore, to obtain traffic information, in this thesis, first a novel method is developed to extract and analyze Google Maps traffic data. In this method, image processing is used along with the Geographic Information System (GIS) to count the number of pixels of different traffic colors for each road... 

Radio waves can penetrate through walls and various scattering environments, allowing us to communicate with mobile phones within buildings or use wireless waves to transfer data from one room to another despite physical obstacles. Radio signals, especially at lower frequencies, are highly effective in traversing such environments. However, the ability to penetrate walls does not imply the ability to "see through" them. In this thesis, we focus on examining the development and improvement of imaging techniques in the presence of walls. The aim is to present the concept of imaging through walls in a comprehensible manner for researchers and enthusiasts, facilitating the development and... 

One of the most important factors that make breast cancer such a dangerous and deadly disease is its hidden. One of the most important methods of revealing this disease is imaging. There are different types of imaging to reveal cancerous tissues (tumors), such as ultrasound, mammography, X-ray, etc. Ultrasound imaging is a cheap, convenient and accessible imaging. The aim of this project is to provide a breast cancer detection system that uses the images taken with this method according to the characteristics of ultrasonic imaging. Regarding cancer diagnosis, doctors identify the tumor with the help of their personal experience, which is based on the characteristics of the tumor image. In... 

Power system operators are facing with imperative challenges to integrate high penetration of renewable power plants. The main challenge is required investment cost for accommodating the grid with uncertainties of renewable resources. In addition, intermittency and fluctuations of renewable resources are another challenges of system operators. Therefore, choosing a proper control procedure to respond the grid disturbances is a crucial task. However, the strategic behaviours of generation companies lead to a competition between them which affects the control performance. In this thesis, an integrated mechanism is proposed that consider both dynamic and strategic behaviours of generation... 

Recently, the researchers try to identify the application of nanofluids for wettability alteration. Changing the wettability of reservoirs, which gas injects to them, to gas wet can lead to enhanced oil recovery. Although several studies have been conducted to introduce proper nanofluids for altering the wettability of reservoirs to gas wet, there is not enough study to investigate the application of nanocomposites for wettability alteration of carbonate reservoirs. In this study, 20 nanoparticles with different compositional structures were synthesized, and then various nanofluids were prepared for the experimental survey. Also, the potential of these nanofluids for wettability alteration... 

The hourly concentrations of particulate matter in Tehran are modelled in this study. High levels of particles are one of the main air pollution challenges in this metropolis, especially in the colder seasons. A probabilistic neural network is used for modelling. The model uses Bayes' theorem which has a very high ability to tackle the complexities and uncertainties. Traffic, meteorology, land use, baseline concentration (at 5 am), vegetation, along with other data including the location of each station, time of recording each concentration data, area and population of the municipal district of each station are considered. This research introduced a cheap and accurate method for collecting... 

Thesedays, personnel surveillance at security checkpoints, such as airports, is becoming increasingly important. Improvements in various fields of imaging techniques provided an attractive opportunity for automatic personnel servaillance at high security checkpoints. Millimeter-wave imaging systems are capable of penetrating through clothes and thin layers to form an image of a person with very high resolution and without no health hazard at moderate power levels. Therefore millimeter-wave imaging is becoming an important method for surveillance purposes. Typically, there are two common methods for microwave imaging, including synthetic aperture imaging and phased-array imaging. Synthetic... 

Permanent Magnet Synchronous Motors (PMSMs) are more conventional and widely employed in Electric Vehicles (EVs) applications. The rotor position performed an essential role through PMSMs drive; therefore, any deviation in the detected position will be evaded in coordinate transformations, originating from external or inherence sources. Subsequently, the discussed faults will be conducted to three-phase currents and output torque through erroneous transformations. Resolver’s estimated rotor position due to fault occurrence will be defined as aggregating ideal and non-ideal components. Moreover, based on inherence periodic in resolvers’ principle, non-ideal components could be written by the... 

Today, due to the increasing activity of terrorist groups, monitoring people in important and busy places such as airports and train stations is very important. One of the technologies that has been developed for this purpose in recent years is 3D imaging technology using millimeter wave. These systems use millimeter waves to image people and identify objects hidden under clothing, which do not have the limitations of conventional imaging techniques such as x-rays and metal detectors. One of the advantages of using these systems is the ability to automatically detect objects in millimeter wave images using deep neural networks such as Segmented, Faster R-CNN and Mask R-CNN, which using these... 

The main purpose of this research was functionalizing graphene, in order to achieve higher hydrophobicity, and producing nanocomposite of functionalized graphene and titanium dioxide by hydrothermal method, and sequently invastigation on photocatalytic properties of the powders and corrosion properties of EPD coated samples. Graphene oxide was synthesized by improved Hummers method and reduced and sequently was functionalized through the chemical process with hydrazine and octadecylamine respectively. Then the nanocomposite of functionalized graphene-titania was synthesized by use of titanium isopropoxide precursor and its photocatalytic properties were measured. The analysis of the... 

Nowadays active Millimeter Wave Imaging Systems are used in verity of medical and security applications. This widespread application re- sults from the intrinsic characteristic of electromagnetic waves in this rang of frequency that can penetrate through interior body structures and clothing with- out bringing harmful ionizing efects to the body. Millimeterwave systems can be very high resolution due to the relatively short wavelength. The current state-of-the-art in active millimeter-wave imaging systems use a set of transmit/receive antennae. The transmitter antennae illuminated the intended person with millimeter waves while the back scattered signal is recorded by the receiver antennae.... 

Nowadays millimeter wave imaging technology has found various applications in industry, medical and security systems. From one side the capability of penetration of this frequency spectrum into non-metal objects, and being harmless to humankind on the other side, has made this spectrum an appropriate alternative instead of dangerous spectrums such as X-ray. Recently, development of millimeter wave electronic circuits and antenna arrays has made the optimal design and implementation of millimeter wave imaging systems feasible. Among actions which have been taken in industry, medical and security systems until now, we can refer to efforts for detection of defects in production line,... 

Ultrafast signal processing in time-domain with high resolution and reconfigura-bility is a challenging task. This paper, for the first time, introduces a time-varying metasurface consisting of graphene microribbon array for implementing time-lens in the terahertz domain. Given that the surface conductivity of graphene is proportional to the Fermi energy level in the THz regime, it is possible to change the phase property of the incident electromagnetic pulse by changing the Fermi level while the Fermi level itself is a function of voltage. Upon this fact, a quadratic temporal phase modulator, namely time-lens has been realized. This phase modulation is applied to the impinging signal in the...