Sharif Digital Repository

Nowadays, radiation therapy is one of the most common methods for the cancer treatment. Intensity Modulated Radiation Therapy(IMRT) is a novel technique of radiation therapy that aims to delivere sufficient dose to cancerous tissues while sparing healthy organs. There are various uncertainties in radiation therapy problems, including uncertainty about device setup, device errors, interfraction and intrafraction motions. One of the most important uncertainties is the movement of the tumor during the treatment process(intrafraction motion), as this displacement may cause the cancer tissue to not receive sufficient dose and also to damage the healthy tissue due to a violation of their dose... 

Breast cancer has been one of the main causes of women's deaths in recent years. Today, various methods are used to treat this disease, among which intensity-modulated radiation therapy is one of the most common methods. The goal of radiation therapy is to destroy cancer cells while protecting the surrounding healthy tissues. In left breast cancer, due to the proximity of the heart and breast tissue, we are at risk of delivering an excessive dose to the heart and increasing cardiac complications after the treatment. In addition, due to the irregular and unpredictable breathing movements of the patient during the treatment and the resulting uncertainty, we face more challenges. In order to... 

In this Mater thesis, we o?er a general Prime Ideal Principle for proving that certain ideals in a commutative ring are prime. This leads to a direct and uniformtreatment of a number of standard results on prime ideals in commutative algebra,due to Krull, Cohen, Kaplansky, Herstein, Isaacs, McAdam, D.D. Anderson, andothers. More signi?cantly, the simple nature of this Prime Ideal Principle enablesus to generate a large number of hitherto unknown results of the “maximal impliesprime” variety. The key notions used in our uniform approach to such prime idealproblems are those of Oka families and Ako families of ideals in a commutative ring.In chapter 2, we amplify this study by developing... 

Estimating the nonlinear behavior of sturctures, always have been one of the main concerns of civil engineers. One of the most recent methods for estimating behavior of structures is MIDA technique. It is a procedure that in some levels, substituted for IDA. Although this method presents the approximate results, high accuracy, fastness and inexpensive procedure made this manner to an efficient method. Indeed, this method has been presented to be exerted instead of exact IDA method which is too complicated and prolix. Up to now, no one has used this method for structures incorporating soil-structure interaction. In theMIDA manner, there is no dynamic analysis of ... 

Determining nonlinear dynamic behavior of structures is always one of the main goals of structure and earthquake engineers. The Modal Incremental Dynamic Analysis (MIDA) is one of the newest methods for analyzing the seismic behavior of structures. Indeed, this method has superseded the exact IDA method which is too complicated and prolix. Although, this method represents approximate results, high accuracy, fastness and low cost procedure made it an efficient and useful technique. Many researchers have used this method and investigated the accuracy of that and achieved proper results. Up to now no one has applied this method on structures which are equipped with dampers. In the procedure of... 

Performance based design becomes an effective method for estimating seismic demands of buildings. Incremental dynamic analysis (IDA) based on a nonlinear response time history analysis (NL-RHA) is considered to be the most accurate method in seismic demand calculations. However, modal incremental dynamic analysis (MIDA), based on the equivalent single degree-of-freedom (SDF) oscillator, is also often used in studying structural engineering performances. The MIDA procedure for estimating seismic demands is extended to unsymmetric-plan buildings. In the MIDA procedure, the seismic demand due to individual terms in the modal expansion of the effective earthquake forces is determined by... 

In this thesis, we study some connections between the graph-theoretic and algebraic properties of co-maximal graph of algebraic structures. We follow two purposes. First, what properties of algebraic structures can be found from co-maximal graph of algebraic structures. Second, what geometric or graph theoretical properties of co-maximal graph of algebraic structures can be found from specefic algebraic structures. Let G be a group and I(G)∗be the set of all non-trivial sub-groups of G. The co-maximal graph of subgroups of G, denoted byΓ(G), is a graph with the vertex set I(G)∗and two distinct vertices H and K are adjacent if and only if HK=G. We char-acterize all groups whose co-maximal... 

Let K be a field and S=K[x0,…,xn-1] be the polynomial ring in n variables over the field K. Let G be a finite undirected graph without loops or multiple edges with the vertex set V(G)={0,…,n-1} and the edge set E(G). One can associate a squarefree quadratic monomial ideal I(G)=of S to the graph G. The ideal I (G) is called the edge ideal of G in S. It is an algebraic object whose invariants can be related to the properties of G and vice versa. The graph G is called Cohen–Macaulay over K (Gorenstein over K) if the ring S/I (G) is Cohen–Macaulay (Gorenstein). Let n ≥ 2 be an integer. The Grimaldi graph represented by G(n) is obtained by letting all the elements of... 

converters, the different configurations for matrix converters are proposed. In this thesis, a one-phase to three-phase matrix converter is used to control in three-phase induction motor. Different control methods are proposed to control the induction motor. The novel control methods include close loop speed and converter output current controls of induction motor are proposed based on SPWM. The structure of indirect matrix converter for the mentioned application also investigated. Moreover, three usual method of control of induction motor: DTC (Direct Torque Control), FOC (Field Oriented Control) and Space Vector Modulation are applied to the single to three- phase matrix converter. Each of... 

Reduction of power converters’ cost is one of the most important efforts to improve machines control systems. In this way, some new topologies for power electronic converters have been proposed. Among various topologies, four switch three phase inverter (FSTPI) thanks to the simple circuit, low cost, minimized conduction and switching losses and high reliability has attracted much attention recently. In this thesis, direct torque control (DTC) method is utilized to control of four switch inverter fed induction motor. In this way, in order to decrease flux and torque ripple and achieving constant switching frequency, a new Discrete Space Vector Modulation (DSVM) method have been proposed in... 

Nowadays, power electronics converters with pulse width modulation (PWM) are widely used in different power circuits. Operation of semi-conductive switches during on and off conditions causes switching dissipation and consequently decreases the efficiency of the PWMs. Recently, by increasing the required power for power electronics applications, quasi-resonant converters attract attentions. Quasi-resonant converters, by adding resonant circuits to the PWM converters causes the soft switching operation (switching with zero current or voltage) and decreases the energy loss. In conventional control methods of these converters, the nonlinear average circuit model is linearized around the... 

The reliability of power converters in various applications, including industrial, military, aerospace, and commercial applications, is of great importance. For this reason, the development of fault-tolerant power converters is crucial from the perspective of system availability and the prevention of adverse consequences. Tolerating various types of faults, maintaining full output capacity after a fault, and cost-effectiveness are the primary challenges for many existing solutions. In this thesis, a fault tolerance solution is presented for a five-level active-neutral-point-clamped converter. The proposed approach enhances fault-tolerant control for the older version of this converter by... 

Optical impairments, as a challenging obstacle in optical communication systems, have been under deep attention of optical engineers in recent years. These impairments can be divided into two categories of linear and nonlinear impairments. Dispersion is a significant linear impairment leads to broadening of the optical signal and interference between transmitted symbols during detection. Nonlinear impairments such as cross-phase modulation (XPM) and self-phase modulation (SPM) also distort the transmitted signal through the fiber, causing interference at the receiver and degrading the system's performance. An appropriate solution for compensating optical fiber impairments is to utilize... 

Cloud computing has a significant role in expanding applications of the Internet of Things (IoT). Currently, applications such as virtual reality and augmented reality require low latency, which is not achievable using traditional cloud computing in some scenarios. Edge computing is a new approach in IoT, which solves some of the limitations of the cloud computing by extending and developing its operations. Reducing response time and network traffic are some of the most important achievements of edge computing. Despite of its numerous advantages over cloud computing, edge computing faces serious challenges such as virtualization, implementation infrastructure, resource allocation and task... 

Environmental review, surveying land resources and the military mission requires high resolution imaging of large areas. in many cases, imaging should be performed during the night or in poor weather. Synthetic Aperture Radars (SAR)using long range propagation characteristics of radar signals and the complex information processing capability of modern digital electronics to provide high resolution image. The radar complements photographic and optical imaging capabilities because of them does not the time constraints, work and the weather. one of the most important methods for the extraction of synthetic aperture radar images by the method of imaging is the SPECAN algorithm. an important... 

Security of cryptographic devices lies amongst the most important issues in the field of hardware security. It is frequently seen that in the process of designing cryptographic systems insufficient attention is paid to the physical implementation details. This is happening while a lot of secret information is known to be leaked through side-channels such as power consumption, electromagnetic emission and execution time. Side-channel attacks are able to reveal secret keys by using these side-channel leakages. Additionally, side-channel attacks are one of the most powerful but low-cost attacks that put the security of cryptographic systems in vain. It can be claimed that the most dangerous... 

Let be a field and R= [x0, . . . , xn−1] be the polynomial ring in n variables over the field . Let G be a finite simple graph with the vertex set V(G) ={0, . . . , n − 1} and the edge set E(G). One can associate a square-free quadratic monomial ideal I(G) = (xixj | {i, j} ∈ E(G)) of R to the graph G. The ideal I(G) is called the edge ideal of G in R. The graph G is called Cohen–Macaulay (resp. Buchsbaum, Gorenstein) over if the ring R/I(G) is Cohen–Macaulay (resp. Buchsbaum, Gorenstein).Let n be a positive integer and let Sn be the set of all nonnegative integers less than n which are relatively prime to n. In this thesis, we investigate structural properties of Cayley graphs generated by... 

Analog-to-digital conversion and signal processing has been increasing due to its many advantages. So that mostly we prefer to convert signal from analog area to digital samples, then they are processed and finaly put the result signal at the system output. How ever because the restriction of the sampling rate, Prevent the spread of digital processing for the high-frequency signal (RF). In recent years, ADCs sampling rate rise up to several GHz (for example ADC with 4 GSPS and 12 bits for TI) that output of the these ADCs by powerful and fast FPGAs are processed but According to Shannon theorem band width of these ADCs is not desirable.the goal of this thesis uses of the compressed sensing... 

Light propagation through turbid media, such as biological tissues, experience scattering due to inhomogeneous distribution of refractive indices of their microscopic structure. Scattering and diffusion of light not only limit many optical imaging techniques, but are also big challenges for telecommunication, spectroscopy, and other optical techniques. Recently many new imaging methods are developed that work in strongly scattering media such as optical coherence tomography, diffusion tomography, and laser speckle velocimetry. In this thesis, we have studied how wavefront shaping techniques can tackle the problem of scattering. By spatially shaping the wavefront of the incident beam, using... 

In this thesis we study three versions of K−theory. The most well-known vesrsion is topological K−theory, a generalization of Grothendieck works on algebraic varieties to the topological setting by Atyiah and Hirzebruch. Since its birth it has been an indespensible tool in topology,differential geometry and index theory. In the early 1970s C∗−algebraic version of K−theory introduced through associating two abelian groups,K0(A)and K1(A)to a C∗−algebra like A. These functors proved to be a powerful machine, making it possible to calculate the K−theory of a great many C∗−algebras. At last,algebraic K−theory is dealig with linear algebra over a ring R by associating it, a sequence of abelian...