Sharif Digital Repository

Project Portfolio Selection as a part of Project Portfolio Management, is a very important issue for the organizations and is a key activity. In this thesis at the first with studding stock portfolios, it has been shown that because of mathematical features, Conditional Value at Risk is a coherent risk criteria and used efficiently in stock portfolio management. So in Project Portfolio Selection we use Conditional value at Risk as coherent risk criteria and based on that we will present a model that not only reach to the maximum utility but also but also reach to the minimum feasible Conditional Value at Risk. After that with the use of this model and with the use of mathematical features... 

Hydrogels are three-dimensional polymeric networks capable of absorbing significant amounts of water. Recently, hydrogels based on acrylic monomers have garnered significant attention from researchers for the fabrication of motion sensors that monitor body movements, owing to their inherent ionic conductivity, remarkable flexibility, and biocompatibility. However, one of the common limitations of these hydrogels for practical applications is their inadequate mechanical properties. In this study, hydrophobic physical crosslinks formed from micelles of hydrophobic monomers and coordination-based physical crosslinks induced by trivalent iron ions (Fe³⁺), along with tannic acid (TA)-modified... 

Geosteering is a process that is used in drilling oil and gas wells and its main goal is to reach hydrocarbon layers with high accuracy and optimal extraction from them. ROP is the distance drillied per unit of time, which has applications such as formation evaluation, boundary detection and maintaining the well path in geosteering. Gas ratio is another important parameter in this project which is strongly influenced by porosity, permeability and ROP. First, we give a brief introduction of various logs used in drilling like gamma-ray, density, neutron and sonic. Then in the literature review, we examine geosteering technologies such as automatic geosteering and machine learning. As we know,... 

Magnetic Resonance Imaging ,MRI, although as one of the most advanced medical imaging equipment is well known but compared to other medical imaging systems needs more time to imaging, so it has caused the patient dissatisfaction. According to the recently researches, filling the image data in a space of information that called ‘k-space’, in the process of image reconstruction, is the main reason of slow MRI. Image reconstruction methods for accelerating like half scan based on image reconstruction by using only a part of k-space is used in MRI systems today, but this method is associated with lower SNR image. Recent research on the theory of compressed sensing has been opened a new approach... 

Today, phased array antennas play important role in wireless communication systems. Utilizing optimum channel capacity, having better signal to noise ratio and, high data rate are the most important features of these systems.These systems are composed of several thousands of separated transceivers which provide possibility of directional electromagnetic radiation by changing the phase and the amplitude of the signal in each transceiver independently. So, the main components of such a system are amplifiers, phase shifters and, amplitude controllers. Also a high resolution phased array military radar system is another vital application of these systems at frequency band of 33-36 GHz.The... 

In the recent years, the role of combinatorics and graph theory have grown in the progress of computer sciences. For instance, the circulant graphs have applications in design of interconnection networks and the graphs with integer eigenvalues are applied in modelling quantum spin networks supporting the perfect state transfer. The circulant graphs with integer eigenvalues also found applications in molecular graph energy. In 2006, it was shown that an n-vertex circulant graph G has integer eigenvalues if G=Cay(Zn; T ) or G= Cay(Zn; T)∪Cay(Zn;U(Zn)), where T Z(Zn). The Cayley graph Cay(Zn;U(Zn)) is known as the unitary Cayley graph. Fuchs defined the unitary Cayely graph of a commutative... 

The main subject of this thesis is to improve conventional CFD algorithms applied in numerical simulation of inviscid unsteady flows around moving boundaries with large relative motions, on unstructured grids. All challenges in this regard are reviewed, and appropriate efficient schemes are introduced to address them. A new scheme is presented for valid grid generation during grid movement and is implemented for 2D and 3D problems. Customary three dimensional convergence acceleration techniques such as implicit time stepping and multigriding have been applied. For implicit solution of the flow equations a new algorithm is used. Via a special renumbering algorithm, the approximate... 

Nowadays, enterprise storage systems are widely used in data centers such as databases, servers, and bank institutes. Due to mechanical activity of disk drives, these systems are one of the most power consumptive components in data centers. Prefetching and RAID, which are employed to enhance performance, are widely used in data storage systems. These two methods, however, impose significant energy overhead to the system due to the increased disk activity. In this thesis, we first elaborate shortcomings of prefetching and RAID methods. Then, we propose a new energy efficient and RAID-compatible prefetching method (LPTAP), which aims at improving performance and energy consumption. To evaluate... 

In railway transportation network, there are spots that we have to intersect with highway network. These intersections break into two branches named grade crossing and unlevel crossing depend on their structure. Grade crossings from the view of protection are grouped into protected crossings and unprotected crossings. Protected crossings depend on their traffic control devices are categorized into active crossings and passive crossings.There are many factors that influence highway-railroad grade crossing design. Some of these factors can vary widely by drivers' behavior. These factors have been developed in models by AASHTO and its publications and shaped like we have them today. In order to...