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Investigation of mechanical properties, antibacterial features, and water vapor permeability of polyvinyl alcohol thin films reinforced by glutaraldehyde and multiwalled carbon nanotube
, Article Polymer Composites ; Vol. 35,Issue. 9 , 2014 , pp. 1736-1743 ; ISSN: 1548-0569 ; Kavoosi, G ; Mohammad Ali Dadfar, S ; Sharif University of Technology
2014
Abstract
Polyvinyl alcohol (PVA) thin films were reinforced by glutaraldehyde and multiwalled carbon nanotubes (MWCNTs) and then mechanical, water solubility, water swelling, water uptake, water vapor permeability, and antibacterial properties of the films were examined. Cross-linking by glutaraldehyde or incorporation of MWCNT caused a significant increase in tensile strength, decrease in elongation at break, and increase in Young's modulus of the PVA films, while MWCNTs were more effective rather than that of glutaraldehyde. Cross-linking by glutaraldehyde or incorporation of MWCNT caused a significant decrease in water solubility, water swelling and water uptake, with a similar manner....
Antioxidant, antifungal, water binding, and mechanical properties of poly(vinyl alcohol) film incorporated with essential oil as a potential wound dressing material
, Article Journal of Applied Polymer Science ; Vol. 131, issue. 20 , 2014 ; Nateghpoor, B ; Dadfar, S. M. M ; Dadfar, S. M. A ; Sharif University of Technology
2014
Abstract
In this study, the properties of poly (vinyl alcohol)(PVA) films incorporated with Zataria multiflora essential oil (ZMO) as a potential antioxidant/antibacterial material was investigated. PVA films were prepared from PVA solutions (2% w/v) containing different concentrations of ZMO. Water solubility, moisture absorption, water swelling, and water vapor permeability for pure PVA films were 57 ± 1.1, 99 ± 3.2%, 337 ± 8%, and 0.453 ± 0.015 g mm/m2 h, respectively. Incorporation of ZMO into PVA films caused a significant decrease in water swelling and moisture absorption and increase in solubility and water vapor permeability. Tensile strength, elastic modulus, and elongation at break for pure...
Studies on the oxygen barrier and mechanical properties of low density polyethylene/organoclay nanocomposite films in the presence of ethylene vinyl acetate copolymer as a new type of compatibilizer
, Article Materials and Design ; Volume 32, Issue 4 , 2011 , Pages 1806-1813 ; 02641275 (ISSN) ; Alemzadeh, I ; Reza Dadfar, S. M ; Vosoughi, M ; Sharif University of Technology
2011
Abstract
Nanocomposite films based on low density polyethylene (LDPE), containing of 2, 3, and 4. wt.% organoclay (OC) and ethylene vinyl acetate (EVA) copolymer as a new compatibilizer were prepared and characterized using rheological tests, X-ray diffraction, differential scanning calorimetry, oxygen permeation measurements, and tensile tests. There was no exfoliation or intercalation of the clay layers in the absence of EVA, while an obvious increase in d-spacing was observed when the samples were prepared with EVA present. This issue was reflected in the properties of nanocomposites. The oxygen barrier properties of the LDPE/EVA/OC film were significantly better than those of the LDPE/OC film....
Investigation of oxygen barrier properties of organoclay/HDPE/EVA nanocomposite films prepared using a two-step solution method
, Article Polymer Composites ; Volume 30, Issue 6 , 2009 , Pages 812-819 ; 02728397 (ISSN) ; Ramezani Saadat Abadi, A ; Dadfar, M. A ; Sharif University of Technology
2009
Abstract
In this article, oxygen barrier properties of nanocomposite films composed of organoclay (OC), high-density polyethylene (HDPE), and ethylene vinyl acetate (EVA) copolymer have been investigated. The nanocomposite films whose EVA forms a dominant fraction were prepared using the solution method. The dispersion of the OC in the HDPE/EVA blend was improved through taking two-step procedure in the preparation of nanocomposite. First, the OC and EVA were dissolved in chloroform. Then, the resulting product, after evaporating most of the solvent, along with HDPE was dissolved in xylene. The obtained nanocomposite films underwent a number of tests in order to examine their barrier properties...
Production and Investigation of Properties of a Nanocomposite for Food Packaging
, M.Sc. Thesis Sharif University of Technology ; Alemzadeh, Iran (Supervisor) ; Vossoughi, Manuchehr (Supervisor)
Abstract
Nanocomposite films based on low density polyethylene (LDPE), containing of 2, 3, and 4 wt% organoclay (OC) and ethylene vinyl acetate (EVA) copolymer as a new compatibilizer were prepared and characterized using X-ray diffraction, tensile tests, and oxygen permeation measurements. There was no exfoliation or intercalation of the clay layers in the absence of EVA, while an obvious increase in d-spacing was observed when the samples were prepared with EVA present. This issue was reflected in the properties of nanocomposites. The oxygen barrier properties of the OC/EVA/LDPE film were significantly better than those of the OC/LDPE film. The average aspect ratio of clay platelets in...
Waveform Design for Joint Radar-Communication Systems
, Ph.D. Dissertation Sharif University of Technology ; Nayebi, Mohammad Mahdi (Supervisor) ; Naghsh, Mohammad Mahdi (Co-Supervisor) ; Karbasi, Mohammad (Co-Supervisor)
Abstract
The integration of radar and communication functionalities into a unified Joint Radar-Communication (JRC) system offers enhanced spectral efficiency and reduced hardware complexity. Recognized as a key enabler for next-generation wireless networks, JRC systems require a careful balance between radar and communication demands, where waveform design plays a pivotal role in achieving this equilibrium. Although waveform design has been extensively studied separately in radar and communication domains, the requirements of modern networks necessitate a unified approach that simultaneously addresses the needs of both systems. This thesis advances waveform design methodologies for JRC systems,...
Radar Target Parameter Estimation Using Frequency and Space Diversity
, Ph.D. Dissertation Sharif University of Technology ; Nayebi, Mohammad Mahdi (Supervisor)
Abstract
In this dissertation, the application of frequency and space diversities in radar target parameter estimation are investigated. On this basis, multi-frequency signal is used to improve the range resolution, array structure is used to increase the angle estimation accuracy and the merger of the multi-frequency signal and array structure are used to increase the maximum number of targets that can be uniquely identified.Considering the desirable properties of multi-frequency signals such as high bandwidth efficiency, high range resolution achievement without chip length decrease and …, there has been increased interest in the vast area of research on the design of such signals that has...
Using the Echo of Rotating Parts to Recognize a Radar Target
, M.Sc. Thesis Sharif University of Technology ; Nayebi, Mohammad Mahdi (Supervisor)
Abstract
Target recognition techniques based on micro Doppler phenomenon are popular because they are applicable even on low resolution radars, in contrast to other techniques such as High Resolution Range Profile (HRRP) which need high resolution in range or angle. Usually, main purpose of such techniques is generating robust features against target initial state, velocity, aspect angle, etc. rather than features which exactly identify a target. Main approaches in the literature are based on time-frequency transforms (TFT) such as spectrogram in order to generate features to classify targets, but in this thesis, we propose a totally different method using Recurrence Plot for generating features...
Numerical Analysis of Mechanized Tunneling Effects in Different Conditions on Internal Forces and Settlement of Superstructures
, M.Sc. Thesis Sharif University of Technology ; Ahmadi, Mohammad Mahdi (Supervisor)
Abstract
In this research with Finite Element Methods in ABAQUS, numerical modeling has done in three-dimensions, which can be used to determine the effect of different factors on the surface settlement. Also, various factors such as geotechnical conditions, tunnel diameter,tunnel depth, the impact of the thickness of the segments and the amount of eccentricity of the structure relative to the longitudinal axis of the tunnel considered in this study. Face Pressure Supports, and Grout Injection Pressures are taken into account, too.Tunnel drilling causes a change in the displacement area and creates a changing zone around the tunnel. In this regard, not only adjacent buildings will be affected by...
Design and Implementation of Proton Precession Magnetometer
, M.Sc. Thesis Sharif University of Technology ; Fardmanesh, Mahdi (Supervisor)
Abstract
Proton precession magnetometers are one of the most sensitive scalar magnetic sensors. Their function is based on Zeeman effect and also nuclear magnetic resonance phenomena. In this project we have designed and implemented needed coils, swithching and signal detection circuits. Because of extremely high sensitivity of this sensor to induced noises and also gradient of earth’s magnetic fileld, detection of precession signal needs design of low noise electronic circuits with special EMC considerations. The implemented system in this project contains different blocks, such as switching circuit and its related control unit, amplifier, filter and frequency meter. Using this system, the obtained...
Positivity Bounds on Effective Field Theories: Galileon Theories as a Case Study
, M.Sc. Thesis Sharif University of Technology ; Torabian, Mahdi (Supervisor)
Abstract
Effective field theory is a practical method for model building and explaining experimental/observational data. These theories are constructed based on knowing low energy degrees of freedom and symmetries (accidental or fundamental). By construction, these theories are applicable up to a cut-off scale and their predictions beyond that are not reliable. For applications to higher energies a UV completion is needed through which modifications are applied or new heavy degrees of freedom are introduced. In order to complete a theory in a Wilsonian approach, scattering amplitudes must satisfy some constraints. These constraints are derived from basic assumptions like Lorentz invariance,...
Numerical Study of Pile Behavior under Seismic Loading
, M.Sc. Thesis Sharif University of Technology ; Ahmadi, Mohammad Mahdi (Supervisor)
Abstract
Numerous structures which are involved in seismic soil-pile-structure interaction have been destroyed. Considering complexities which exist in soil-pile interaction problems and lack of precise methods without imperfect bases, it is necessary to use numerical methods for analyzing soil-pile interaction problems. In this research, three-dimensional modeling and studying the effect of changing soil and pile parameters on the behavior of pile under earthquake loading is performed using finite difference software, FLAC3D. The soil in this model has a softening behavior. Real earthquake spectrum has been applied into the model as the acceleration time history at the bedrock level. The results of...
Effect of different configurations on 3-D analysis of flow through stay vanes And guide vanes of a francis turbine
, Article Scientia Iranica ; Volume 17, Issue 6 B , NOVEMBER-DECEMBER , 2010 , Pages 419-432 ; 10263098 (ISSN) ; Firoozabadi, B ; Ahmadi, G ; Sharif University of Technology
2010
Abstract
Stay and guide vanes (distributor) are essential parts of a turbine. They are used to control the flow rate and to appropriately transfer the flow momentum to the runner. In this work, flow through the distributor is analyzed. For various Boundary Conditions (BC) and different configurations, threedimensional flows in the distributor of a Francis turbine are evaluated and compared with each other. The numerical simulations were carried out using Fluent software and the results were validated with a GAMM Francis turbine, where the geometry and detailed best efficiency measurements were publically available. In these simulations, the flow was assumed to be steady and the effect of turbulence...
Identifying and Ranking Factors Affecting High Rise Concrete Construction Productivity (Study Current Situation and Strategies to Improve productivity)
,
M.Sc. Thesis
Sharif University of Technology
;
Mortaheb, Mohammad Mahdi
(Supervisor)
Abstract
The current global economy challenges and the importance of maintaining a sustainable development strategy has increasingly bolded the importance of construction productivity measures. This research describes the results of a running research that is to find the most critical factors affecting the productivity of high rise concrete building projects in developing countries. To achieve that, we have conducted Delphi method in two phases. In the first phase we had a brainstorming program with construction experts from owner organizations, construction contractors and designing engineers to identify factors that have influenced productivity in recent concrete building construction projects.50...
Multi-period Value-at-Risk Forecasting
, M.Sc. Thesis Sharif University of Technology ; Barakchian, Mahdi (Supervisor)
Abstract
Multi-period Value-at-Risk (VaR) forecasting is important for risk management. Financial institutions especially commercial banks according to Basel Committee regulations for capital adequacy in “Internal Approach”, should forecast their VaR for multi-period horizons (longer than one day). The most conventional approach for forecasting multi-period VaR is scaling one-day forecasted VaR that is called “square root of time rule”; therefore most works in this area have been focused on forecasting one-day VaR. In this study, we review performance of a wide range of different methods in forecasting multi-period VaR. The results of our study show that historical simulation performs weakly in...
Beamforming Through Array Thinning
, M.Sc. Thesis Sharif University of Technology ; Nayebi, Mohammad Mahdi (Supervisor)
Abstract
Modern communication and space systems such as satellite communication devices, radars, SAR and radio astronomy interferometers are realized with large antenna arrays since this kind of radiating systems are able to generate radiation patterns with high directivity and resolution. In such a framework, conventional arrays with uniform inter-element spacing could be not satisfactory in terms of costs and dimensions. An interesting alternative is to reduce the array elements obtaining the so called ‘ thinned arrays’. Large thinned arrays have been exploited because of their advantages in terms of weight,consumption, hardware complexity, and cost over the...
Effects of Soil-Pile-Structure Interaction on the Seismic Response of a Bridges
, M.Sc. Thesis Sharif University of Technology ; Ahmadi, Mohammad Mahdi (Supervisor)
Abstract
A large number of structures subjected to the seismic loading have been damaged or have experienced failure in different parts such as the pile structure or even in the entire structure due to unanticipated effects of the soil-pile-structure interaction.The complexity of problems regarding the soil-pile-structure interaction is an influencing factor in prediction of the behavior of structure during the earthquakes. In this study, the effect of the interaction on the dynamic response of bridges was investigated using the finite element software ABAQUS. The primary purpose of this study, as previously described, is to study the effects of the soil-structure interaction on a bridge located on a...
Fully Homomorphic Encryption Implementation
, M.Sc. Thesis Sharif University of Technology ; Shabany, Mahdi (Supervisor)
Abstract
After being introduced in 2009, the first fully homomorphic encryption (FHE) scheme has created significant excitement in academia and industry. Despite rapid advances in the last 6 years, FHE schemes are still not ready for deployment due to an efficiency bottleneck. Here we introduce a hardware/software codesign, in fact a hardware accelerator optimized for a class of reconfigurable logic to bring homomorphic encryption schemes one step closer to deployment in real-life applications. The accelerator we present is connected via a fast PCIe interface to a CPU platform to provide homomorphic evaluation services to any application that needs to support blinde computations. Specifically we...
Application of Adaptive Neural Network Systems in Controller Design of Nonlinear Processes
, M.Sc. Thesis Sharif University of Technology ; Shahrokhi, Mohammad (Supervisor)
Abstract
In this project design of adaptive neural network controller for uncertain nonlinear systems in the presence of different restrictions has been investigated. After providing introduction and motivation, two general forms of nonlinear systems including strict- feedback and pure- feedback have been introduced. In order to solve the problem caused by each restriction, a solution has been proposed. For the strict- feedback nonlinear systems several restrictions are considered such as, unknown dynamic model, unmeasured state, input saturation, unknown control directions, time delays in states and input. Stability analysis based on the Lyapunov theorem has been established. In addition, two kinds...
A Numerical Study of Train-induced Vibration and the Screening Effectiveness of Shredded-tire-Infilled Trenches
, M.Sc. Thesis Sharif University of Technology ; Ahmadi, Mohammad Mahdi (Supervisor)
Abstract
Train-induced vibrations can disturb the residential areas close to the rail as well as making ground-borne noises that can create problems for sensitive apparatus and devices. To reduce these problems, there need to be an evaluation of the amplitude of the ground-borne vibrations. The goal in this study is creating a suitable finite difference model in order to predict the intensity of train induced vibrations propagating inside or on the surface of the soil using FLAC (Fast Lagrangian Analysis of Continua) software as well as assessing the effectiveness of recycled shredded tires in reducing the surface vibrations by using these material as the filler for vibration isolation trenches. The...