Sharif Digital Repository

Ni-SiC nanocomposite coatings are considered as corrosion resistant coatings with better tribological properties. In order to get superior properties, the amount of added particles should be increased. But high concentration of particles has some drawbacks such as low adhesion to substrate, probability of cracking in coating due to heat expansion coefficient difference between substrate and coating and also embrittlement of coating and low elasticity. In this study, the possibility of producing Ni-SiC nanocomposite coatings with FGM structure was investigated. SiC particles concentration was 5 to 80 g/l and the current density was between 3 to 5 A/dm¬2. The pH of bath and temperature was... 

Regarding the numerous casualties and financial losses due to intense earthquakes, the ductility is considered of the main importance in addition to stability, stiffness, and strength criteria of the structure’s connections. In order to enhance the seismic behavior of the structures in such severe earthquakes, design codes for steel structures have suggested special types of connections. Among them, bolted end plate connection is considered a conventional type of connection used for creating ductile semi-rigid connection.In this study, in order to simulate the behavior of this joint, a 3-D finite element model is developed in Abaqus software, in which the inelastic behavior of the materials... 

In the present thesis, first of all we consider a particular class of fractional order plants which have uncertainty in their time constant.In order to make the closed loop system robust against variations of the aforementioned parameter, a robust fractional order controller will be designed and the corresponding tuning rule will be expressed. By using the proposed controller, phase margin of the system will be preserved on a desired value for any value of the uncertain parameter and also gain crossover frequency of the system, in the nominal case, will be adjustable.Also another class of fractional order system will be considered. For these systems, the problem is the same as the former... 

In this thesis a computational method for the design of optimum nozzle contour with consideration for chemical reactions has been presented. This method combines the method of characteristics, CFD and an optimization algorithm to develop a nozzle suitable for a specific operational condition. First using the method of characteristics an isentropic nozzle contour is achieved. then using the FLUENT solver, this initial contour is solved for flow containing finite-rate reactions and boundary layer effects and by iterating this process combined with an optimization algorithm, an optimum nozzle is found. Properties took into consideration in this method, in addition to chemical reaction between... 

The successive approximation digital to analog converters are appropriate selection for use in new technologies and low-powered applications. Despite the low power consumption of this kind of converters, there are some applications like medical which require very low power consumption. In order to reduce the power consumption of SAR ADC, capacitive digital to analog converters and comparators are great importance. In this Thesis, monotonic switching method has been used, the switching power of this method is lower than the conventional method by 81.2%. Since the common mode of the output of this type of switch is variable, the offset is sensitive and requires a technique to resolve this... 

This dissertation documents the study of Omni-max anchor, and the development of a computational procedure and its application to the analysis of OMNI-MAX anchor behavior under mooring loads. An OMNI-MAX anchor is an offshore anchor designed and developed in recent years, to overcome the uncertainty in the capacity of ordinary offshore anchors.In the process of this research to understand the capacity and mechanisms in which the anchor carries applied loads, the contribution of different parts of the anchor to the total capacity of the anchor is estimated using classical soil mechanics. Then, due to the failure of the used approach to model the dynamic behavior of the anchor and to better... 

In the first section, a novel No-Reference Video Quality Assessment (NR-VQA) method, based on Convolutional Neural Network (CNN) for High Efficiency Video Codec (HEVC) is presented. Deep Compressed-domain Video Quality (DCVQ) measures the video quality, with compressed domain features such as motion vector, bit allocation, partitioning and quantization parameter. For the training of the network, normalized PSNR is used due to the limitation of existing datasets. The evaluation of the proposed method shows that it has”96%” correlation to subjective quality assessment (MOS). The method can work simultaneously with the decoding process and measures the quality each frame in the different... 

In this thesis, we study recursion theory in the context of Bishop’s constructive mathematics.For this goal, at first, we redefine primitive recursive functions and then based on works of Fred Richman in [Church’s Thesis Without Tears, The Journal of Symbolic Logic, Vol. 48, No. 3 (Sep., 1983), pp. 797-803], give an interpretation of partial recursive functions. Finally we study some important theorems in recursion theory,for example, universal computation predicate, recursion theorem, s-m-n theorem and
Rice’s theorem  

How does retirement plane affect retirement decision? This paper uses the data of 24,000 retirees of oil industry of Iran between 1996 and 2016 to answer the question. We calculate Accrual, Option Value, and Peak Value to evaluate retirement behavior. These variables calculate the difference between utility of retirement in the current year and some time in the future. Theoretically we expect that higher values in these variables lower the probability of retirement. We use two types of probabilistic models, linear and non-linear. In the linear model we run a pooled OLS and in the non-linear model we use a Probit model to estimate the effect of the variables above on the retirement... 

Virtual Reality technologies and its related standards and tools, will play a remarkable role in our future digital life. Development of that topic will be definitely dependent on availability of a reliable, precise and low-cost video quality assessment method. In recent years, there was a significant amount of research works on 360 videos, notably among them are new video quality metrics. Unfortunately in terms of correlation to subjective scores, they are still far from ideal especially with respect to previous performances in regular video domain. In this research we focused on desiging a full-reference 360-video quality assessment method. First, we extracted 2D viewport videos from the... 

In economic literature, there are two major theories about population distribution; One perspective gives geography a central role, and the second one emphasizes path dependency. In this study, we investigate the Iran-Iraq war as an exogenous shock to the population of Iranian cities to answer the basic question of which theory best explains the population distribution. The Iran-Iraq war began in 1980, with Iraq invasion of Iran's western borders. Some border cities of Iran were captured at the beginning of the war and forced migration was inflicted on their population. non-captured cities near the western border were repeatedly targeted by artillery, airstrike and missile attacks, yet they... 

Investigation stability of chatter vibration is of great importance in machining processes. Finding frequency response function (FRF) at the tool tip is an effective method to predict stable machining regions. Commonly, the tool tip FRF is obtained using experimental modal analysis but this approach is often time consuming and requires expertise. In addition, changing tool or holder requires modal test which is a disadvantage, consequently modeling methods are of interest for researchers. Moreover, optimum design of machine tool is another benefit of modeling method. Also, in machining with flexible or micro tools in which experimental tests can not be performed, modeling methods would be... 

High-quality online services demand reliable and fast packet delivery at the network layer. However, clear evidence documents the existence of compromised routers in the ISP and enterprise networks, threatening network availability and reliability. A compromised router can stealthily drop, modify, inject, or delay packets in the forwarding path to launch Denial-of-Service, surveillance, man-in-the-middle attacks, etc. So researches tried to create intrusion detection methods to identify adversarial routers and switches. To this end, data-plane fault localization (FL) aims to identify faulty links and is an effective means of achieving high network availability. FL protocols use... 

Bubble collapse is a two-phase problem whose numerical simulation has many important applications in science and technology. In hydrodynamics systems (pumps, ship propellers, …), bubbles form due to cavitation. These bubbles grow and collapse These bubbles grow and collapse farther downstream and their energy destroys the surrounding walls. In medical sciences, the shear force caused by collapse of a bubble can be used to destroy adipose tissues in arteries. The small scales time in this phenomenon, as well as the compressibility of the flow in bubble collapse, are interesting challenges researchers face. The present thesis targets are two-dimensional numerical simulation of bubble collapse... 

Power harvesters are used to generate energy for electronic devices. These electrical energy generators consist of three main parts: energy source, power electronic converter and energy storage. In order to minimize some of the weaknesses of these devices, including low power density and low reliability, the hybrid power harvesting method can be utilized. In this thesis, we design and build a hybrid energy harvester considering the advantages of simultaneous usage of solar and thermal energies for a wearable sensor, focusing on "efficiency enhancement" and "availability improvement". In the designed device, both solar and thermal energy harvesting units operate independently. In the solar... 

With the advancement of technology, the volume of network traffic has also increased dramatically. The optical network, as the main part of the backbone communication system, plays a significant role in the transmission of network traffic. Due to the limited network resources, an efficient resource allocation in optical networks is required to increase network performance and reduce costs. To solve resource allocation optimization problems, an effective tool is needed to provide a suitable solution in a reasonable time. Resource allocation problems are usually developed on a graph, which is derived from network topology or other properties of the network. As a result, graph-based tools seem to... 

Uranium conversion process is one of the most important stages in nuclear fuel cycle. The Uranium Conversion Facilities (UFC) of Iran is located in Isfahan. In this plant, the Yellowcake (impure uranium oxide, U3O8) is converted to Uranium hexa-fluoride, UF6. During the process, considerable amounts of uranium-containing liquid waste are generated. This liquid waste was collected in evaporation pools inside the UCF Plant. In the course of time, a thick layer of precipitated salt form in bottom of the pools which are collected and stored in drums inside a building. This solid waste contains uranium at concentration levels much higher than that permitted for land disposal of the waste.... 

Weexaminetherelationshipbetweenfamilysizeandchildreneducationaloutcomes. Using a 2 percent sample of Iran Populaion Census 2011, we construct a sample of school age children. Estimation using unrestricted OLS with controls shows an inverse-U relationship between family size and educational outcomes; children educational performance improves significantly as their number increases form 1 to 2, but for families with 3 or more children, increasing the number of childern deteriorates educational outcomes  

The main goal of this research is to reduce aircraft design cycle period, by reducing the necessary number of design cycle iterations. The Design cycle period is one of the main characteristics of the design process and design cycle iterations play a major role in the design cycle period. To achieve the above mentioned goal, we present a mathematical model of iterations for the aircraft design process. This model describes the design coupled tasks as a discrete-linear time invariant dynamic system. This model also helps identify tasks which are the most important for generating iterations. This new method basically helps break information cycles that create iterations among important tasks....