Sharif Digital Repository

the gravitational wave (GW) which is a prediction of General Relativity has entered a new era after being detected by Ligo observatory in 2015. new discoveries are still being made. the discovery of GW is a new opportunity for studying gravity, astrophysical sources of GWs like binary black-holes or binry neutron stars as well as testing cosmology models.on the other hand, it should be mentioned that the astronomy of gravitational waves is in its dawn stage. in future having numerous precise detectors and by accumulation of data, speaking about exact phenomena and statistical analysis will become meaningful. as in the case of cosmic microwave background physics, in which researchers started... 

Increase of concentration of CO2 and other greenhouse gases will have significant effect on global climate. Climate change affects precipitation and hydrology, which in turn influences recharge to groundwater. Recharge to groundwater is an important source, which has the main role in groundwater resources availability. To trace these changes to recharges and its consequent effect on groundwater state, a combined modeling of climate change and groundwater is necessary. In This study impact of climate change on groundwater recharge in two different climatic plains of Karkheh river basin in Khuzestan, Iran, has been investigated using a physically-based methodology that can be used for... 

To produce polyurea, a secondary or higher amine must be combined with a diisocyanate. For this purpose, we first combined diethylenetriamine, and hexamethylene diisocyanate, which did not have good mechanical properties due to the aliphatic nature of the molecules. Then, instead of hexamethylene diisocyanate, we used MDI, which was mixed using a mechanical mixer but became a paste that was not suitable for coating applications. To reduce the viscosity of MDI, propylene carbonate was added to improve mixing, but the gel time also increased. Because the solvent was non-polar and the amine was polar, it was decided to add the solvent, amine, and polyvinyl alcohol as surfactants to allow faster... 

Lightweight aluminum and magnesium alloy sheets do not generally possess as much strength as steel sheets and their strength need to be increased by a suitable process such as Accumulative Roll Bonding (ARB). One of the most important limitations of ARB is the low ductility and formability of the sheets produced by this process. In the present research conducted on the 5083 aluminum and AZ31 magnesium alloy sheets efforts have beem made to overcome this limitation by heating up the sheets whether during metal forming process as hot deformation or as distinct controlled annealing process subsequent to the deformation, in order to develop the application domain of the sheets. Results... 

This study investigates the relationship between U.S. presidential elections (1976–2024) and the energy market, with a focus on the impact of fluctuations in oil supply and gasoline prices on voter behavior and its implications for Iran’s energy policymaking. Employing a data-driven approach, the study utilizes random forest models to assess the importance of various variables in predicting election outcomes, point-biserial correlation analysis to examine the relationships between economic and energy indicators, and game theory modeling to develop optimal energy policy strategies for Iran in response to U.S. actions. Historical data on energy markets, election results, and relevant policies... 

Isopropanol purifying denotes dehydration of it to utilize in industries become important these days. Conventional process like distillation could not produce this product in high purity. Using membrane-based process, pervaporation, to dehydrate Isopropanol and other organic compound has been noticed in the last years. Among all type of membranes to dehydrate alcohols, poly (vinyl alcohol) is more effective due to its high hydrophilic characteristic. But it swallows in aqueous solutions and decrease its selectivity. To enhance structural and separation properties Chitosan, TiO2 and glurataldehyde added to polymeric membranes. Nine membranes have been made in this study that can be grouped in... 

Phospholipid membranes and vesicles play important roles in the cellular functioning, otein signaling and material transport inside cells. Protein-embedded vesiclesare also used for targeted drug delivery. In this thesis, we use molecular dynamicsmethods and study (i) the formation of vesicles from flat lipid bilayers (ii) the mechanicalproperties of vesicles under compressive forces (iii) the shape variations ofvesicles with and without transmembrane proteins (iv) protein clustering.We grow our vesicles from lipid bilayers, which may contain proteins with differentconcentrations. We start with a random initial distribution of proteins that allowsus to monitor the clustering and... 

The use of superhydrophobic surfaces is one the most promising methods for reducing the friction and increasing the flow rate in fluid transfer systems. Since in such systems the surface structure plays a key role, in the first part of this study, the performance of the hierarchical nanostructures is explored. These nanostructures are inspired by the superhydrophobic surface of the lotus leaf. The flow is considered between two walls with hierarchical nanostructures and simulate the system via the molecular dynamics (MD) method. The size of the nanostructures and the distance between them have been studied to find whether a design with maximum flow rate exists. The nanostructures have two... 

Ray-tracing method is extensively used for wave propagation analysis of indoor and outdoor environment for narrowband systems. The main goal of this research is to extend ray-tracing method for site-specific modeling of wideband electromagnetic propagation. In this thesis, Time-domain reflection and transmission coefficients have been computed for dielectric half-space and dielectric slab with frequency dependent permittivity. First, analytical form of Fresnel reflection coefficient for vertical and parallel polarizations in time-domain have been computed for dispersive half-spaces with lossy, extended Debye, two-pole Debye and multi-pole Debye models. By using these time-domain... 

In this research, diffraction limit is introduced as the major challenge in wave focusing. Common wave focusing techniques have been reviewed and classified into two categories: far-field and near-field techniques. Through examples that illustrate its major inherent and practical challenges, super-oscillation has been presented as a specific idea of focusing waves using remote sources. By introducing subwavelength inhomogeneities in the region of interest, we have demonstrated sub-diffraction wave focusing in a near-field approach. Using the multipole method, the effect of injecting sub-wavelength cylindrical particles on focusing electromagnetic waves has been studied. Since when there are... 

This dissertation focuses on addressing electromagnetic forward and inverse scattering problems using physics-based deep learning models. A key challenge in integrating physics with data-driven models lies in the implicit nature and nonlinearity of the forward scattering operator. To address this, a novel closed-form expression is proposed for piecewise homogeneous media. By formulating the scattered field as an implicit function of the permittivity values in each homogeneous region, the computational complexity of solving the forward problem for a fixed geometry is changed from O(N^3 ) to O(NΣM_k^2), where N is the total number of meshes, and M_k refers to the meshes in the kth region. This... 

This dissertation introduces a method for reducing errors in prior information related to the actual geometry of biological tissues in microwave imaging. These errors, often caused by boundary mismatches or inaccurate modeling of tissue heterogeneity, significantly impact the accuracy of retrieved tissue dielectric properties. To address this issue, we propose a shape optimization-based approach that aligns prior boundary data with actual tissue boundaries using measured microwave imaging data. Our method features an efficient technique for computing the sensitivity of scattered electric fields to node positions. By deforming the mesh structure without altering its topology, this approach... 

Energy and environment crisis in past decades raised concerns about fossil fuels use and has accelerated renewable energy application in terms of solar electric, solar thermal and wind turbines. Due to the fluctuating nature in renewable resources, renewable electric power generation has a stochastic nature that makes it difficult to use by the electricity consumers. Energy storage plays a key role to put more control on renewable power generation.Lead-acid battery is a storage technology that is widely used in photovoltaic systems. Battery investment and maintenance costs account for a big part of photovoltaic system costs. Charging and discharging profiles of the battery has a great impact... 

The design and development process of menu systems has always been a focus of researchers and engineers in the fields of software engineering and human-computer interaction. Considering the large and complex nature of the design space, it is nec- essary to provide automatic methods that aid designers during the design process. In this study, natural language processing is used to investigate the semantic relationship between menu system commands. Users expect related commands to be conveniently located next to each other, and a properly designed interface satisfies this need. As a result of this research, a fast-text-based model is developed that uses the data of past menu systems. In a... 

The potential future use of hydrogen as a transportation fuel must be evaluated from a supply chain perspective. However, the main challenge in motivating the hydrogen supply chain network is the lack of existing hydrogen infrastructure. Strategic decisions for planning sustainable infrastructure can be analyzed hierarchically in time-related stages (2025-2030-2035). Meanwhile, a time- and location-based design has been specifically applied to a few selected ports in southern Iran, with limited focus on a national or countrywide scale. This study proposes a mixed-integer linear programming (MILP) optimization model to logically design the hydrogen supply chain, considering primary energy... 

Electromagnetic wave scattering from rough surfaces has been the subject of intensive investigations over the past several decades for its applications in important remote sensing problems. The problem of scattering from random rough surfaces hasn't full analytical closed form solution. In millimeter-wave band some surfaces like asphalt, concrete, which has roughness in millimeter range, must be considered as rough surfaces. A major part of the literatures are specified to numerical and statistical approach. In this thesis the electromagnetic waves scattering from rough surfaces in millimeter-wave band is studied. The main goal of this thesis is to find the available ways for applying the...