Experimental and Simulation Study of Barite Settlement Phenomenon under Static and Dynamic Condition

, M.Sc. Thesis Sharif University of Technology Movahhedi, Hamed (Author) ; Shad, Saeed (Supervisor) ; Hosseini Mokhtari, Zahra (Co-Advisor)

Abstract

In petroleum related drilling, Barite particles settling and Barite sag as major problems in drilling wells can potentially impose significant operational issues. In this study, a computational fluid dynamics (CFD) and experimental investigation of Barite settlement in annular space were conducted in both static and dynamic conditions. The Euler-Euler approach was used to model the multiphase flow of solid Barite particles and drilling fluid. In this approach, the momentum lost between phases has been taken into account by means of particle-particle and particle-fluid exchange coefficients. The governing equations were numerically solved using finite volume method by CFD software package...

Mesoporous silica nanoparticles (MCM-41) coated PEGylated chitosan as a pH-Responsive nanocarrier for triggered release of erythromycin [electronic resource]

, Article International Journal of Polymeric Materials and Polymeric Biomaterials ; 2014, Volume 63, Issue 13, Pages 692-697 Pourjavadi, A. (Ali) ; Mazaheri Tehrani, Zahra ; Sharif University of Technology

Abstract

A pH-responsive drug delivery system based on core shell structure of mesoporous silica nanoparticle (MSN) and chitosan-PEG copolymer was prepared and characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), scanning electron microscope (SEM), and high-resolution transmission microscope (HR-TEM) techniques. In order to improve compatibility MSN and drug, mesoporous nanosilica was modified by 3-aminopropyl triethoxysilane. The release of erythromycin (a macrolide antibiotic) as a model drug was investigated in two pHs, 7.4 and 5.5

Performance evaluation of thyristor-based static transfer switch with respect to cross current

, Article IEEE/PES Transmission and Distribution Conference and Exhibition 2002 : Asia Pacific, Yokahama, 6 October 2002 through 10 October 2002 ; Volume 2, Issue ASIA PACIFIC , 2002 , Pages 1326-1331 Mokhtari, H ; Sharif University of Technology

2002

Abstract

Providing clean, continuous and reliable power to many industrial customers has become a necessity. Where possible, sensitive customers are supplied by two medium-voltage utility feeders one of which is used as back up. Thyristor-based Static Transfer Switches (STSs) are able to provide the loads with a fast transfer to the back up feeder when the main one fails. In addition to being fast, the transfer must be performed with no source paralleling which creates a cross current flowing between the main feeder and the back up one. Due to practical limitations, however, in some cases, cross current cannot be avoided. This paper investigates the performance of thyristor-based STSs with respect to...

Theoretical and Computational Investigation of Quantum Plasmonic Properties of Nanocluster Dimers

, M.Sc. Thesis Sharif University of Technology Mahmoudi, Erfan (Author) ; Jamshidi, Zahra (Supervisor)

Abstract

In today's era, metal nanoparticles play an important role in technologies emerging from different sciences, such as chemistry, physics, optics, material science, due to their unique characteristics. In the development of nanooptics science, it can be said that metal nanoparticles play an important role. The ability of conductive electrons collective oscillation causes surface charge density fluctuations in nanoparticles, this phenomenon is known as surface plasmons. Surface plasmons are surprisingly coupled with light and cause the significant increase in the intensity of optical fields induced in nanoparticles. Therefore, with the presence of localized surface plasmons or plasmon...

Theoretical Investigation of Ab-initio MD Approach to Increase the Efficiency and Accuracy of VCD Spectrum Calculation

, M.Sc. Thesis Sharif University of Technology Hadi, Hossein (Author) ; Jamshidi, Zahra (Supervisor)

Abstract

Understanding of the Molecules is the main purpose of the chemistry. Ab-initio molecular dynamics (AIMD) as a branch of the computational chemistry, tries to give us a deep comprehension of the molecule, and its chemical, physical and optical activities. This comprehension, relies on the accuracy of quantum mechanics, in addition to the speed of the classical mechanics. The mixing of the quantum mechanics and the classical mechanics could simulate activities of the atoms in the time-domain, provided the mixing is done with precaution. This, in turn, helps us to forecast the response of a molecule in different situations, and also translating the macroscopic phenomena in a nanoscopic...

Investigation of Plasmonic Excitation in Carbonic Nanostructures Within Near-IR

, M.Sc. Thesis Sharif University of Technology Madadi, Mahkam (Author) ; Jamshidi, Zahra (Supervisor)

Abstract

To date, the plasmonic properties of many metallic and semi-conducting materials have been investigated and used in various industries. One of the plasmonic material categories that have always been considered is polycyclic aromatic hydrocarbon or PAH, whose plasmonic resonance energy depends on the charge state of the molecule. In this regard, it is easy to change the plasmonic resonance energy via changing the induced charge, which is a unique feature of the mentioned materials. In addition, plasmonic structures with excitations in the infrared region are able to enhance the vibration intensity of absorbed molecules by increasing the electric field around themselves. Therefore, they have...

Using Nonlinear Effects of Light for Optical Signal Processing

, M.Sc. Thesis Sharif University of Technology Shatery, Farshid (Author) ; Kavehvash, Zahra (Supervisor)

Abstract

Ultrafast signal processing in time-domain with high resolution and reconfigura-bility is a challenging task. This paper, for the first time, introduces a time-varying metasurface consisting of graphene microribbon array for implementing time-lens in the terahertz domain. Given that the surface conductivity of graphene is proportional to the Fermi energy level in the THz regime, it is possible to change the phase property of the incident electromagnetic pulse by changing the Fermi level while the Fermi level itself is a function of voltage. Upon this fact, a quadratic temporal phase modulator, namely time-lens has been realized. This phase modulation is applied to the impinging signal in the...

Using Simulation-Optimization Approach for Fire Station Location and Vehicle Assignment Problem: a Case Study in Tehran, Iran

, M.Sc. Thesis Sharif University of Technology Pirmohammadi, Ali (Author) ; Amini, Zahra (Supervisor)

Abstract

In this research, the problem of locating fire stations and allocating equipment has been studied and a simulation-optimization approach has been presented to solve the problem. The mathematical models of this research were developed based on the idea of the randomness of the covered demand and the maximum expected coverage model. In these models, the issue of non-availability of equipment to cover accidents, the random nature of accidents, various fire incidents and the equipment needed to cover them are considered. Two mathematical models with deterministic and non-deterministic approach with different scenarios for demand are proposed. The non-deterministic model is developed with the aim...

Introducing An Integrated Framework For Solving The Fleet Planning Problem Using A Simulation-Optimization Approach

, M.Sc. Thesis Sharif University of Technology Sahebi, Armin (Author) ; Amini, Zahra (Supervisor)

Abstract

One of the main concerns of industrial companies’ managers is providing an efficient logistics system. To achieve an efficient logistics system, the fleet planning problem is studied by many researchers in recent years. This problem consists of multiple sub-problems at three levels: operational, tactical, and strategic. These sub-problems are closely related to each other and need to be studied and addressed in an integrated manner. In this research, an attempt is made to provide an integrated framework to solve the vehicle routing problem (operational), outsourcing problem (tactical), and fleet composition problem (strategic). These problems have various uncertainties, including customer...

Analytical Modelling and Optimization of Disk Type, Slot Less Resolver

, M.Sc. Thesis Sharif University of Technology Moheyseni, Atefeh (Author) ; Nasiri Gheidari, Zahra (Supervisor)

Abstract

Resolvers, due to their robust structure, are widely used in automation systems. Among the types of resolvers, the accuracy of the Wound Rotor (WR) resolver in the occurrence of common mechanical errors is higher than other types of resolvers. therefore, in this thesis, an AFWRR is studied to improve the performance. Increasing the number of poles in WR resolvers is a good solution for increasing the accuracy of these electromagnetic position sensors. However, high-speed WR resolvers due to employing fractional slot windings suffer from rich sub-harmonics in the induced voltages. A common solution for suppressing the undesirable sub-harmonics is using multi-layer winding with appropriate...

A Survey on Searchable Symmetric Encryption Schemes

, M.Sc. Thesis Sharif University of Technology Sajadieh, Zahra Sadat (Author) ; Khazaei, Shahram (Supervisor)

Abstract

Using “Searchable Encryption” enables us to encrypt the data, while preserving the possibility of running search queries. One of the most important applications of the mentioned is in Cloud Storage. As users do not trust the Cloud space, they are not inclined to store their data on the Could. The solution to this problem is of course, Cryptography. However, ordinary Cryptography methods, eliminate the data’s searchability. Hence, we need encryption schemes that code the data while retaining their searchability. So far, various schemes has been proposed that differ in their performance, security level, and usage. In this thesis, we aim to discuss and analyze these methods

Time Domain Optical Signal Processing Based on the Duality Between Dispersion and Diffraction

, M.Sc. Thesis Sharif University of Technology Eksiri, Fatemeh (Author) ; Kavehvash, Zahra (Supervisor)

Abstract

In the last decades, due to the growing demand of transferring information with high transmission rates, the complexity and development of telecommunication and optical systems is remarkable. Researchers around the world attempt to explore extraordinary potential of light to process information. In the mid-19th century, scientists discovered a mathematical symmetry between the spatial and temporal optics fields, which originated from the similarity of equations governing the paraxial diffraction of beams and the dispersion of narrow-band pulses known as space– time duality in scientific texts. This new approach provides more advanced and potent methods to temporal processing and...

Improving the Stability of an Urban Traffic Network with Limited Data by Using Percolation Theory and Dynamic Clustering

, M.Sc. Thesis Sharif University of Technology Hassanzadeh, Ehsan (Author) ; Amini, Zahra (Supervisor)

Abstract

One of the most vital aspects of understanding the traffic phenomenon is scrutinizing the traffic transition status, such as the transition from free flow to congestion. The Percolation Theory is a renowned theory focusing on analyzing various network types to detect the critical zones, which are the zones including links that are important to control to improve stability. By calculating the quality indices of network links, the Percolation Theory can simulate the traffic percolation propagation in the network and determine possible critical zones for further analysis. Most studies in this field assume access to data of several traffic parameters for the entire transportation network, such...

Temporal Depth Imaging Based on Dispersion

, M.Sc. Thesis Sharif University of Technology Behzadfar, Shiva (Author) ; Kavehvash, Zahra (Supervisor)

Abstract

In this thesis, the aim is designing an optical temporal imaging system. In recent years, due to many applications, including the receipt of high-rate data by slow receivers and compensation of dispersion in telecommunication systems, researchers have considered the topic of temporal imaging. This field of research is based on dispersion, electro-optical modulators or time lenses and space-time theory. By modeling dispersion properties as a depth dimension and taking ideas from three-dimensional spatial imaging systems we intended to increase the temporal resolution and depth of focus of the structure. We also present a novel technique for multiplexing and demultiplexing telecommunication...

Traffic Flow Imputation for Urban Roads with Graph Neural Networks

, M.Sc. Thesis Sharif University of Technology Sabzekar, Sina (Author) ; Amini, Zahra (Supervisor)

Abstract

Traffic data plays an essential role in Intelligent Transportation Systems (ITS) and offers numerous advantages, including efficient traffic control and system performance improvement. However, due to the scarcity of data collection systems, missing data in traffic datasets is inevitable. Therefore, traffic data imputation becomes an essential task. Graph Neural Network (GNN) is a type of neural network that operates on graph-structured data and has shown potential in handling traffic network related tasks such as traffic prediction and traffic data imputation. In this paper, we contribute to the body of knowledge with two aspects. First, we focus on traffic data imputation using solely...

Modification of Biomedical Imaging Methods in Short Wavelength Infrared Window

, Ph.D. Dissertation Sharif University of Technology Hassan Abbasi (Author) ; Kavehvash, Zahra (Supervisor)

Abstract

In recent years, optical biomedical imaging techniques show great potential in noninvasive imaging. Although these methods have many advantages over other biomedical imaging methods (such as Computerized Tomography (CT), Magnetic Resonance Imaging (MRI) and etc.), these techniques confront with some problems such as optical scattering, light absorption and etc. For in vivo imaging, the short-wavelength infrared region (SWIR; 1,000–2,000 nm) provides several advantages over the visible and near-infrared regions: general lack of auto-fluorescence, low light absorption by blood and tissue, and reduced scattering. In this thesis we want to analyze the traditional IR imaging techniques and...

Upgrading the Ultrasound Imaging System Based on The Implementation of the Strain Imaging Mode

, M.Sc. Thesis Sharif University of Technology Fathi, Haniyeh (Author) ; Kavehvash, Zahra (Supervisor)

Abstract

Strain imaging is a non-invasive ultrasound modality for assessing cardiac function in echocardiography systems. In this thesis, we implemented a fully automated strain imaging system containing 5 steps: 1) echocardiographic view recognition, 2) cardiac cycle phase detection, i.e., the events of end-diastole (ED) and end-systole (ES), 3) segmentation of left ventricular (LV) myocardium, 4) motion estimation of this wall and 5) strain calculation. In this work, we propose a novel deep learning-based framework for phase detection of cardiac cycle by the use of echocardiographic images in multibeat videos. Further, by applying the augmentation technique, the model has been able to detect events...

The group delay ripple effects on the performance of phase-modulator based microwave-photonic filter

, Article 2011 18th International Conference on Telecommunications, ICT 2011, 8 May 2011 through 11 May 2011, Ayia Napa ; 2011 , Pages 162-166 ; 9781457700248 (ISBN) Mokhtari, A ; Akbari, M ; Sharif University of Technology

2011

Abstract

We have developed an analytic approach to investigate the effect of group delay ripple on the performance of phase-modulated microwave photonic filter. Two cases with and without ripple are analyzed to clarify the ripple's effects on the performance of microwave-photonic filter. Comparison of our proposed analytical approach with simulated OptiSystem® results shows a good agreement

Two building blocks of microwave photonics filters in the presence of group delay ripple: A comparative survey

, Article Optical and Quantum Electronics ; Volume 44, Issue 8-9 , 2012 , Pages 403-414 ; 03068919 (ISSN) Mokhtari, A ; Akbari, M ; Sharif University of Technology

Springer 2012

Abstract

We have developed an analytic approach to investigate the effect of group delay ripple of the dispersive devices on the performance of two major building blocks of microwave- photonic filters. Firstly, performance of PM-based block in the presence of an arbitrary group delay ripple (GDR) is analyzed and compared with the ripple-free case to reveal the destructive effects of added group delay ripple. In the next step, we repeat the proposed approach for the AM-based one; again, the performance is compared with the ripple-free case. Two distortion metrics are also introduced to quantify this distortion. Comparison of the performance of two building blocks in the presence of group delay ripple...

Performance of phase-modulated microwave photonics in the presence of group delay and reflection amplitude ripples of the dispersive device

, Article Conference Proceedings - 11th International Conference on Laser and Fiber-Optical Networks Modeling, LFNM 2011, 4 September 2011 through 8 September 2011, Kharkov ; 2011 ; 9781612848136 (ISBN) Mokhtari, A ; Akbari, M ; Sharif University of Technology

2011

Abstract

We develop an analytic approach to investigate the effect of reflection amplitude and group delay ripples of the dispersive device on the performance of phase-modulated microwave-photonic filters. Experimental results conform to our proposed analytical approach