Sharif Digital Repository

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... 

A novel broadband and tunable terahertz (THz) source based on the modulation instability phenomenon (MI) is proposed. By introducing higher-order dispersion terms in nonlinear Schrodinger equation (NLSE) the MI gain is spread toward larger frequencies which in turn shifts the input optical frequency to the THz range. In this method, the need for any further pump signal is eliminated while the input power is reasonable, less than 1W, due to using EDFA fiber. By changing the input signal power, the generated THz signal frequency could be tuned. The proposed structure is numerically simulated in the designed values of dispersion orders  

The number of operating vehicles has increased in recent years and as a result global pollutants have widely spread. Therefore, the regulations on the vehicle exhaust emissions have become much stricter. For an automobile to pass the emission tests successfully an accurate calibration of the ECU tables is needed, especially the tables which have direct impact on the amount of pollutant emissions. To achieve the optimum performance of the catalyst existing in the exhaust system of the engine, the fuel/air ratio must have nearly stoichiometric value. The present research studies the ECU strategies for implementing this objective by appropriate management and control of catalyst and oxygen... 

This project is dedicated to design and implementation of a 77 GHz Power Amplifier for FMCW automotive radar application. Design of this type of Power amplifier faces several main challenges. The first challenge is due to the limits of technology used for implementing the power amplifier design (CMOS 65nm), for example the low breakdown voltage of transistors forces us to use low supply voltage. The other challenges are high frequency effects and complexity of design in mm-wave frequency. however, there are phenomena which dont have any important effect on output results in low frequency, but we should consider those when designing Power Amplifier in mm-wave frequencies.In order to... 

The dynamic nature of today’s manufacturing industry, which is caused by the intense global competition and constant technological advancements, requires systems that are easily adaptable with new functions and technologies. In fact, a highly responsive manufacturing system is needed in which, introducing new products, adjusting system capacity with demand fluctuations and integrating new technologies with the existing ones are quickly possible.Reconfigurable Manufacturing systems (RMS) are a relatively new paradigm in industry that enable rapid adjustments of production capacity to changes in product mix and volume through their main characteristics including modularity, scalability and... 

In-fiber and all-optical wavelength-selective signal processing are key aspects of fiber Bragg grating (FBG)-based devices in optical communication systems. FBGs with sharp filtering properties have already been used in fiber optic communication networks as dispersion compensators, optical add–drop multiplexers, fiber lasers, and optical label switching modules. We have developed an in-fiber wavelength-selective optical intensity modulator to superimpose low rate overhead data on the transit high-speed payload signals. The tunable fiber Bragg grating (FBG), as the heart of a wavelength-selective modulator (WSM), is designed and properly biased to implement the desired modulation... 

In Modular Multilevel converter, it is necessary to attain different objectives simultaneously. One of the most effective control methods which can cope with this kind of systems is the Model Predictive Control (MPC). This method predicts the values of control objectives based on different feasible states and determines the optimal one using cost functions. The number of feasible states can increase when the number of switches increases in the converter. This makes the MPC unable to be applied in the MMCs with hundereds of submodules (SMs) in each arm because of its heavy computational burden. In this thesis, a modified model predictive control is proposed to reduce the computational burden.... 

This thesis investigates various modulation recognition systems both in analogue and digital forms. We are looking for a recognition technique considering practical implementation issues. To recognize the modulation, the career frequency is supposed to be known and a bandpass signal is received. Besides, we investigate some digital Automatic Modulation Recognition (AMR) methods. The techniques based on the features of the signal have less computational complexity compared to Maximum Likelihood (ML) techniques; hence they are more desirable for practical implementation. In this project, analog modulations are implemented using C++ software. For the convenience of users, here, two graphical... 

Nowadays almost all the research laboratories use femtosecond lasers, and Ti: sapphire laser is the most popular among them. Therefore, in this thesis, a Ti: sapphire pulsed laser with z-fold cavity with output of 50 fs and repetition rate of 100MHz has designed and simulated. Therefore, in the first chapter, introduction to the theory of ultrashort pulses and situation to create these pulses are presented. In addition, as regards to produce of short pulses, it is necessary to set laser in cw mode, in the second chapter we have investigated laser in cw mode. So, in this chapter, rate equations of gain medium, the stability zone of the laser, manner of removing astigmatism in the cavity,... 

In this thesis, we study the f-vectors and h-vectors of simplicial complexes and we state and prove a theorem of Kruskal and Katona that characterizes the f-vectors of simplicial complexes. We then define the Stanley-Reisner ring A associated to a simplicial complex, and state certain connections between f and h-vectors of this simplicial complex with Hilbert function of A, and show that if A is a Cohen-Macaulay ring then the h-vector of the simplicial complex in an O-sequence. conversely any O-sequence, equivalently, the f-vector of any multicomplex is the h-vector of a simplicial complex. Finally it is shown that if a simplicial complex arises from a triangulation of the sphere and A is... 

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... 

The increasing demand for high speed communications has made the optical fiber a favorite choice for different networks ranging from Local Area Networks (LANs) to Wide Area Networks (WANs). In this research we focus on the analysis and design of improved optical communication techniques with a focus on LAN applications.Noting the advantages of Optical Code Division Multiple Access (OCDMA), we have selected this method as the base of data transmission. Different modulation schemes can be implemented in an OCDMA system. Among these, Pulse Position Modulation (PPM) schemes can improve the system performance. We have evaluated Overlapping PPM (OPPM) in an OCDMA system employing Generalized... 

The dynamic nature of today’s manufacturing industry, which is caused by the intense global competition and constant technological advancements, requires systems that are easily adaptable with new functions and technologies. In fact, a highly responsive manufacturing system is needed in which, introducing new products, adjusting system capacity with demand fluctuations and integrating new technologies with the existing ones are quickly possible. Reconfigurable Manufacturing systems (RMS) are a relatively new paradigm in industry that enable rapid adjustments of production capacity to changes in product mix and volume through their main characteristics including modularity, scalability and... 

Nowadays integrated circuits are extremely vulnerable to hardware trojans (HT). Hardware trojans can be injected into the ICs in design or fabricate phase, and damage system’s functionality or security. In this thesis, we first describe hardware trojan definition, classification and types of HTs, negative effects, detection ways and analysis of them. Then we propose a new solution in order to solve the negative points of previous methods  

In this project a high spectral purity C-band (4.25-5GHz) frequency synthesizer has been analyzed and designed and implemented in CMOS 0.18μm technology. This synthesizer has been embedded in TX path of a transceiver module as a frequency translator for digital phased array system applications. The system includes Phase Locked Loops (PLLs) and Direct Digital Frequency Synthesizer (DDFS). Due to desired Low spur level (90 dBc) in C-band, system level design, frequency plan, choosing proper PLL topology and etc. have been considered in details. One of the important challenges in system design is the signal spectrum purity. In other words, the system should produce minimum phase noise. Output... 

In this project, the Line-Modulated Fixed Off-Time method is used as the current control strategy for a Power Factor Corrector (PFC) pre-regulator. A zero voltage switching PWM (ZVS-PWM) auxiliary circuit is configured to perform ZVS in the switches. To reduce conduction losses, the rectifier circuit and the PFC are combined to create bridgeless PFC and a new zero-voltage-switching is introduced for reduse switching loss. Soft commutation of the main switch with zero voltage is achieved without additional current stress. When main switch is turned off ,the voltage across the switch rises very slowly. when the current of the switch decays to zero the voltage across the switch is very low.A... 

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... 

Modulation Recognition of communication signals has been an important theme in the field of wireless communication. Modulation Recognition has various applications for both military and civil purposes. Recently there has been considerable attention to Digital Modulation Recognition, due to the vast application of this kind of Modulation Recognition tasks. In this thesis, we proposed a Digital Modulation Recognition Algorithm, which is able to identify various types of digital modulations in low SNRs. These include BASK, BFSK, BPSK, 4-ASK, 4-FSK, 4-PSK, 8-FSK, 8-PSK, MQAM (M=16, 32, 64). The proposed method uses a general pattern recognition scheme, consisting of a feature extraction phase... 

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 ... 

In the present work, numerical simulation of cross-flow microfiltration of non-alcoholic beer in a tubular membrane has been studied. Finite element analysis was used as a powerful tool for simulation. The feed stream, which flows mainly tangentially to the porous membrane surface, is modeled by the Navier-Stokes equations. Porous wall conditions are described by the Darcy equation that relates the pressure gradient within a flow stream to the flow rate through the permeable wall. A pilot-scale cross-flow membrane filter was developed to verify the model results. Ceramic tubular membranes were used in this study. The cross-flow velocity of the feed solution was controlled at the laminar...