Sharif Digital Repository

According to the increasing amount of data exchanged among data centers, the need for speeding up and bandwidth and reduced power consumption has been increased. The information show that about 77% of the data is moved into the data centers. On the other hand, 10% of data center’s power consumption is used to data transmission. Improving the interconnection network of data centers can play an important role in reducing power consumption and speeding up. In recent years, optical interconnects have gained attention as a promising solution. Nevertheless, offering an all-optical and efficient architecture is an important issue. In this study, we intend to provide a multi-stage, all-optical... 

Today with the deployment of cloud computing and web applications; We need to have powerful datacenters with provisioning high bandwidth. Current data centers with electronic network interconnects, using excessive power to provisioning requisite bandwidth. Nevertheless, interconnecting networks in data centers isn’t in maximum efficiency and many components of them aren't used efficiently. So it is necessary to use an optical network with dynamic provisioning variable bandwidth and energy management. In this approach, our proposed architecture is designing topology with adopting dynamically for energy management in optical interconnect networks in data centers. To achieve this we can study... 

The importance of vocabulary, the building blocks of every language, in having a good command of a second language is evident. However, the best way to improve the lexical knowledge of the students is an issue that is open to discussions. This study aimed at investigating three different methods for teaching new vocabularies to Iranian students who were striving to take command of English as a second language in order to determine the advantages of one method over the other in terms of immediate and delayed retention. In this endeavor, we set 105 intermediate adult learners of English into three groups and instructed each group with a specific method, teaching them a number of new words... 

The goal of this project is finding an appropriate method for controlling four different bioreactors with unknown dynamics. At first, an introduction to bioreactor dynamic hase been presented, then their nonlinear behavior has been discussed. In the following, four output control systems using adaptive neural network have been designed separately for four different dynamics. The applied control method has been adapted from a method of references with some changes. Performances of designed controllers in set point tracking, load rejection and model mismatch have been evaluated using simulation. In these studies, input saturation has been considered in simulations but it is not existed in... 

The occurrence of natural disasters and damages caused by them has greatly impacted humans' lives, which reveals need for us to prepare for confrontation with various disasters. For this purpose, in this research, we are seeking to develop a programming model to reduce damages caused by various disasters. This thesis includes 3 main sections. In first section, some major impacts of disasters are reviewed and studied during the past 118 years and some major lessons are summarized based on statistical data analysis. In second section, a 3-demontional probability density function has been developed to categorize different types of disasters. Furthermore, a scaling system is presented to... 

Increasing dynamics of mobile users intensifies the Doppler effect and degrades the performance of the communication system. Considering Fourier kernel-based modulation, in this research, we focus on dealing with the Doppler effect and compensating non-ideal communication channel response suffered from the Doppler-delay spread. In the first step, we study Zak transform and present a new transform for 2-D representation of time signals. This mapping is a well-known transformation that can be considered as a generalized discrete-time Fourier transform in the field of signal processing and can be used to represent a signal in the delay-Doppler domain. After providing a new 2-D transform, we... 

In this correspondence, a non-linear method of convergence accelerating and improving for iteration based algorithms is introduced. After convergence analysis, some enough conditions are proposed to guarantee convergence of the algorithm.For the sake of low complexity implementation of the proposed algorithm, some simple stabilizing methods are suggested. Simulation results show desirable performance of the proposed method and its capability to stabilize the iteration based algorithms. In the literature of missing samples recovery, the proposed method is applied to an Iterative Method (IM) as a general signal reconstruction method,then it is extended to the image recovery problem where... 

Lobe blowers are positive displacement machines (PDM) that are widely used in various industries. The efficiency of lobe blowers depends on the clearance between fixed and moving parts. If the clearance between the parts increases, backflow occurs, which means that the flow returns from the high-pressure zone of the outlet to the low-pressure zone of the inlet, and this makes the blower not have the initial efficiency and work with a lower capacity than its design. This research is carried out with the aim of checking the feasibility of backflow detection using two condition monitoring methods, including ultrasonic and thermography techniques. The sample of this research includes seven... 

The prediction of Remaining Useful Life (RUL) has become a critical tool in enhancing the availability of rotating machinery. By knowing the remaining time before a bearing failure occurs during operation, significant reductions in unplanned production downtimes and associated costs can be achieved. In this study, by analyzing the time signals of vibration and ultrasonic data related to the bearing of a 4.1 MW electromotor from installation to replacement, and by investigating the behavior trends and correlation between extracted features, RMS has been ultimately identified as the health indicator in both vibration and ultrasonic techniques for monitoring the bearing’s condition. First,... 

Rotating machinery is a critical component in many industries, and its failure can lead to process interruptions and significant economic losses. Rolling bearings, as key elements of these machines, account for approximately 45–55% of failures. Therefore, timely detection of bearing faults plays a crucial role in reducing maintenance costs and improving safety. However, achieving timely fault detection is challenging due to weak signals and the presence of noise, which necessitates the use of advanced algorithms with strong diagnostic capabilities. Despite the considerable success of deep learning models in pattern recognition, their application to fault diagnosis of rotating machinery faces... 

One of the main components of any solar power plant is the heat storage. Implementing heat storage reduc-es the cost of power generation by increasing the capacity factor of the system. This Thesis aims to analyze the operation of heat storages by modeling latent heat
storage. In this regard, an efficient method named "Method of Characteristics" is utilized. Models developed based on this method are possible to be used for comparison, sensitivity analysis, and optimization due to their low computation time. Sensitivity analysis was carried out based on various parameters such as void fraction, fiUer material size. Results show that using latent heat storage, storage c-apacity is... 

This thesis presents a new method for scheduling wind generation companies to participate in day-ahead market. The assumed market structure of this thesis, considers day-ahead energy market and balancing market, simultaneously. The stochastic model of this, implements a robust function to face the uncertainties of these markets. The risk of participation in these market are controlled with Information Gap Decision Theory (IGDT). Finally the allowable percent of each uncertain parameters are introduced to met an specific level of profit for the company  

Pyrotechnic devices are widely used by the aerospace and defense industries and consist of a broad family ofsophisticated devices using self-contained energy sourcessuch as explosives and/or pyrotechnic compositions.Pyrotechnic shock, or pyroshock, is the transient oscillatoryresponse of a structure to loading (high frequency, highmagnitude stress waves) induced by the detonation ofpyrotechnic devices incorporated into or attached to thestructure.Pyroshock Test is one of importantenvironmental tests in satellite design process. Pyroshock is one of loads that exerted on spacecraft and it's subsystems during launch process. Pyroshock can cause failure in some subsystems like sensitive...