Sharif Digital Repository

The process of implementing a damage detection strategy for aerospace, civil and mechanical engineering infrastructure is referred to as Structural Health Monitoring (SHM). Many portions of our technical infrastructure are approaching or exceeding their initial design life. As a result of economic issues, these civil, mechanical and aerospace structures are being used in spite of aging and the associated damage accumulation. Therefore, the ability to monitor the health of these structures is becoming increasingly important. In many cases, damage causes a structure that initially behaves in a predominantly linear manner to exhibit nonlinear response when subject to its operating environment.... 

The primary purpose of the present thesis is to understand the dynamic behavior of partially premixed flames of counterflow burners. In this project, work has been done on the previously designed and built counterflow burner. By setting up partially premixed flames in this burner, acoustic excitation of these flames has been done, and finally data acquisition by taking video of the flame and then using image processing to extract the dynamic response of these flames. The flames that we have examined in this project are all in a laminar regime and the fuel used in these flames is also natural gas. The frequencies that we have examined in these flames are 25 and 40 Hz, and these tests were... 

In the present work, the local Chemiluminescence method has been implemented on a laminar premixed propane-air flame. The goal of this work is to achieve a system capable of measuring the intensity of Chemiluminescent radiations of CH* and OH* radicals locally and with high spatial and temporal accuracy. For this purpose, a setup has been designed and developed. In order to achieve high spatial accuracy for local measurements, a Cassegrain lens has been designed and built, which has the ability to collect light from a cylindrical control volume with a cross-sectional diameter of 58 μm and a depth of 3.4 mm. An optical system for dividing and filtering light based on wavelength has also been... 

In this study, growth of MWCNTs in form of thin film and powder for hydrogen storage was investigated. Different analytical techniques including SEM, TEM, STA, XRD, XPS, BET, BJH and Raman spectroscopy were applied to characterize the samples. The results showed that substrate, catalyst thickness and type of catalyst are influenced in yield of the growth, structure and quality of MWCNTs. The study has also indicated that MWCNTs grown on Fe-Pd bimetallic catalyst with 25-75 proportion had the highest growth yield. Moreover, decreasing of the growth temperature from 970 to 920 oC produced single-walled carbon nanotubes (SWCNTs) with high quality (IG/ID = 15.8) and low growth yield.... 

Polycarbonate (PC) is known as one of the engineering plastics with remarkable mechanical properties, but the application of this polymer is limited due to its high notch sensitivity. Blending polycarbonate with other polymers such as acrylonitrile butadiene styrene (ABS) is a method to resolve this disadvantage. PC/ABS blends are commonly used in automotive industry, electrical and electronic devices. As PC and ABS are not completely miscible, a variety of compatibilizers are used to achieve a suitable microstructure and high engineering properties. Considering crucial applications of PC/ABS blends, different flame retardants are also used to reduce the flammability. These flame retardants... 

Today, base lead piezoelectrics are the center of attention due to their very good electrical properties, and low cost of production. Among these ceramics are PZT which is a combination of Pb(ZrxTi1-x)O3 and PCN which is a combination of Pb(CoxNb1-x)O3. PZT is a normal piezoelectric whose dielectric properties would be improved if relaxor is added. PCN is ferroelectric with perovskite structure and curie temperature -27℃ which is known as a relaxor with high constant dielectric properties. In this research, adding PCN to PZT was done by sol-gel seeding method. Calcination at a temperature of 900℃ was causing the creation of single-phase perovskite powder. After that, conventional sintering... 

The aim of this study is to investigate the effect of Copper oxide on the microstructure, properties, and grain growth kinetic in Tin oxide- Based varistors. Copper oxide was mixed in Tin oxide with different concentration, including 0, 0.1, 0.25, 0.5, and 1 mol% and the samples were sintered at 1250, 1300, and 1350 oC. Then, phase and microstructural characterization was investigated and consequently, electrical properties were evaluated. According to results, Copper Oxide with forming the liquid phase through the sintering process, accelerated grain growth. It was found that, by increasing concentration of CuO, mean grain size was increased from 2.6 µm in 1250 oC and 5 hours to 17.1 µm... 

Recently, Polypropylene has been extensively used in a variety of applications in the polymer industry, but its quite low stiffness and toughness limit this polyolefin’s application in the engineering functions; thus, the market of polymer blend and composite manufacturing has grown noticeably in the last few years. In the current project, short Flax fibers are used in order to reinforce the PP matrix. Firstly, Flax fibers were washed with the gentle and harsh condition during the alkalization process, then the optimized alkalization condition was determined through comparison of results from X-ray Diffraction (XRD ), Attenuated Total Reflectance FTIR (ATR-FTIR) and microscopic surface... 

In this study, experimental results of Ahvaz produced water treatment obtained in ultrafiltration process using a polymeric membrane formed from Polyacrylonitrile (PAN) with 0.2 µm poreshave been reported. In this process the effects of different factors including transmembrane pressure (TMP), cross flow velocity (CFV) and feed temperature on permeate flux, membrane fouling resistance and TOC rejection was investigated. The results show that optimum conditionswere found in the range of TMP: 1.5-3 bar, CFV: 1-1.5 m/s and operating temperature 40°C.Results show that under optimum conditions the final permeate flux for produced water of Asmari outlet of Skimmer unit was 30 L/m2.h, and the... 

In this research, the surface of multi-walled carbon nanotubes (CNTs), as template, were coated by Lead zirconate titanate (PZT) with composition of Pb(Zr0.52Ti0.48)O3 via sol-gel process. The final product is called PZT-CNT hybrid material. For functionalizing of CNTs, benzyl alcohol was used. Simultaneous thermal analysis (STA) proved that the as-derived amorphous material crystallized at 520 ˚C. Scanning Electron Microscope (SEM) images verified the deposition of a uniform coating of PZT on the surface of CNTs and proved that the functionalizing treatment was done successfully. X-ray diffraction (XRD) showed that the crystal structure of the hybrid was tetragonal perovskite.... 

Nowadays, the development of different polymer blend nanocomposites is of great importance for achieving electrical and antistatic properties for various applications such as auto parts and the packaging industry. Immiscible polymer blends with conductive nanoparticles such as carbon nanotube, graphene, etc. can reach the conductivity threshold with low amounts of nanoparticles and produce desired electrical properties. In the present study, we have attempted to develop a polystyrene(PS)/ethylene-octene copolymer(EOC)/carbon nanotube(CNT) blend nanocomposite with suitable electrical conductivity. The compounding was performed by melt mixing at two weight percent of 80/20 and 50/50 (PS/EOC)...