Sharif Digital Repository

In the general case of minimum color-spanning tree which is one of the color-spanning set problems, given a weighted graph with n vertices of k different colors, the goal is to find a subtree of minimum weight such that vertices of this subtree include all the colors in the graph. In the planar case, the input is a complete graph with n colored vertices on the plane and the weight of each edge is the Euclidean distance between its corresponding vertices. In this thesis we consider the problem of minimum color-spanning tree. To this end, first we present various color-spanning set problems and some other related problems like Steiner tree and we study the previous work on these problems. Then... 

In this thesis we study the possibility of unidirectional transmission of light using reciprocal and nonreciprocal elements. Unidirectional transmission will allow us to separate the coupling of light into and out of resonators and design unidirectional waveguides. We start by studying the effects of one-sided modulations of dielectric constant of reciprocal structures. One-sided modulation will satisfy the phase matching condition for the coupling of two waves only in one direction. Using coupled mode theory, we study one sided modulation in layered media. Next, we find the exact solution to such strucures using transfer matrix method and analyze one-sided modulation in waveguide... 

This research aims to introduce a nanocatalyst based on open-cell nickel foam (NiFm) with 40 pore per inch(ppi) to save energy during methane steam reforming (MSR), an endothermic reaction, by increasing catalyst thermal properties with improved progressive compression strength. The nanocatalyst is synthesized with a chemical stepwise synthesis approach, thermal-chemical pretreatment, pulsed electrocodeposition of Ni-Al2O3 (γ) nanoparticles, and calcination. Herein, a polyurethane (PU) nonconductive substrate is transformed to nickel foam by using replication sponge method. The purchased PU became conductive by nickel electroless bath using sodium hypophosphite with 5-15 (µm) thickness... 

Temperature and the resulting thermal behavior of electric power generation and distribution equipment and industrial electrical systems and processes are the most critical factors in the reliability of any operation or facility. Temperature is by far the most measured quantity in any industrial environment. For these reasons, monitoring the thermal operating condition of electrical and electromechanical equipment is considered to be a key factor to increasing operational reliability. Infrared thermography (IR/T) as a condition monitoring technique is used to remotely gather thermal information for monitoring the condition of virtually all of the electrical components on an entire system and... 

Seismic isolation is well known as an effective and applicable technique to protect structures from destructive ground motions. Considerable functional and economical advantages of this technique have led to application of isolation systems at upper levels. In this study, seismic responses of a 6-story structure with a constant fundamental period, which is seismically isolated at the base and mid-height by non-linear isolation systems with variable nominal periods, are investigated. Analytical results indicate that stories below mid-height isolator show large changes in seismic responses caused by changes in isolator nominal period in comparison with upper stories. Although the fundamental... 

Anomalous top quark interactions with gluon (tug , tcg) allow the production of single top quarks at the LHC. Two main sources of backgrounds which we took into account are W +1j and standard model single top production. In order to do it, we examine the reconstructed angular distribution of the charged lepton in the rest frame of W boson from the top quark. It is defined in terms of the angle θ_l , between the charged lepton momentum in the rest frame of the W boson and the momentum of the W boson in the rest frame of the top quark. Using this angular distribution of the charged lepton from the W boson in the top decay، we show that with the data of 10fb^(-1) of integrated luminosity and... 

Optimum conditions for the proton acceleration using radiation pressure acceleration in light sail regime is investigated using particle-in-cell simulations. Simulations results show that for a laser pulse with a dimensionless laser amplitude of a0 = 31 using circularly polarized laser pulse with sin2 shape at perpendicularly incidence are the best. Effect of two pulses with different duration and different amplitudes (a0 = 25; a′ 0 = 13) is also investigated in the condition of equal total energy of them to the single pulse and amplitudes of both of them are less than the single efficient laser pulse amplitude. Best delay time between two pulses was found by changing the delay time in... 

Hadron therapy is one of the cancer treatment methods using the targeted dose distributhion. In hadron therapy, the prompt gamma is produced from excited nucleas of target in the following of non-elastic nuclear interactions between the target and the incident proton within few nano-seconds and with energy less than 10 MeV. The excited energy level depends on incident particle energy and the target materials. Since the Spatial distribution of prompt gamma rays depends on incident particles energy, it can be useful for determinding the incident particle range. Also, the prompt gamma energy spectrum of each element is an individual feature, thereby targets with different composition of... 

One of the main problems in proton computed tomography is the reduction of the spatial resolution of the image due to multiple Coulomb scattering of protons while passing through the material. Estimating the most likely path of protons inside the material can be beneficial to solve this problem. In this regard, artificial neural networks, as one of the innovative solutions in the field of machine learning, have helped to improve the accuracy of estimating the most likely path of protons. In this study, an artificial neural network with an adaptive moment estimation optimization algorithm was designed to estimate the most likely path of protons. The network was trained using data obtained...