Sharif Digital Repository

The aim of this study is to survey the ability of vortex tube cascade for separating heavy components of a gas mixture. For this purpose, three vortex tubes based on previous experiences have been manufactured. Also, a helical double pipe heat exchanger has been designed and constructed. Because of the vortex tube’s ability in developing thermal separation, the effect of thermophysical parameters like feed’s temperature, inlet and outlet pressure of air on the thermal separation performance were evaluated. The recommended correlations for estimating outlet temperature of hot and cold flows, have been validated against experimental data. Moreover, various arrangements of vortex tubes to... 

Phase behavior calculations and compositional simulation for the hydrocarbon systems containing many components, are time consuming and impractical. Therefore the number of the components those describe the fluid description must be kept to a minimum using grouping techniques. In this research, it is tried to apply a new set of grouping techniques in compositional simulation of oil and gas reservoir. In these methods, the components are automatically placed in the pseudo-components, and their critical and thermo-physical properties are calculated simultaneously or after grouping process according to different mixing rules. These set of techniques areworking based on the distances between... 

In the present work a comprehensive mathematical model has been developed for CFD simulation of transport phenomena in the hollow fiber membrane contactors. The system which has been studied was a gas sweetening including methane, carbon dioxide, and hydrogen sulfide in the gas phase and MEA aqueous solution as the solvent. Effects of temperature distribution on the contactor efficiency predicted taking into account the heat of solution, the heat of reaction, and the viscous dissipation. Major focus of the present study was on dynamic behavior of the contactor considering the entrance regions of momentum, energy, and mass transfers. CFD methods have been developed to solve the nonlinear... 

The one pot, three component 1,3-dipolar cycloaddition reaction of azomethine ylides with a series of new dipolarophiles (E)-3 -benzylidene- indolin-2 -ones in methanol under the reflux condition yields ,3′-dispiropyrrolidine oxindole library. The product is produced with high regioselectivity. Catalyst free, excellent yield , easy workup process, short reaction time, and convenient operation are the characteristics of this procedure. NMR and X-ray are used to determine the structure and stereochemistry of cycloadduct products.
 

Using membrane contactors for acid gas removal, combines the advantages of membrane based separation processes and traditional ones. In this project we aim to study the use of a membrane absorption system for sweetening gas streams containing mixed acid gases with composition similar to raw natural gas. H2S and CO2 exist in the gas stream simultaneously which can be removed by mixture of alkanolamine solvents, including MDEA, DEA and MEA, are used for treating. A lab-scale membrane absorption setup with feed capacity of 2 lit/min, was designed, constructed and commissioned. Several hollow fiber modules equipped with PSf and PVDF membranes were fabricated. Our results revealed that reaching... 

Undoubtedly, machine learning and its practical applications have become essential topics in research and industry. Among these, representation learning holds special importance. The goal in this field is to find low-dimensional and meaningful representations of high-dimensional data that encapsulate essential information. Most existing methods focus only on the statistical correlations in data, which do not necessarily indicate real relationships between variables and can affect learning performance. This becomes even more problematic when the distribution of test data differs from the training data, as it makes the learned representations less generalizable. To tackle this problem, causal... 

As more renewables step in, the ongoing change will be drastic for the electrical grid. The energy sector must find new ways to balance energy production and consumption. Electric vehicle (EV) batteries are by far the most cost-efficient form of energy storage since they require no additional investments in hardware. A bidirectional EV charger is a new technology that enables energy to be pushed back to the power grid and auxiliary loads from the battery. The electrical requirements of the EV charger are examined in detail to find an appropriate power electronics converter to meet all the requirements. The CLLC resonant converter is a promising candidate for high efficient, bidirectional... 

The quantity and quality of information extracted from the brain, in addition to data collection methods, is also related to the statistical tools used. As extracting maximum information in both temporal and spatial dimension require electrophysiological approaches on the physical side, the statistical methods should be optimized to that end, on the theoretical side. The time histogram method is the most basic tool for capturing a time-dependent rate of neuronal spikes. Generally, in the neurophysiological literature, the bin size that critically determines the goodness of the fit of the time histogram to the underlying spike rate has been subjectively selected by individual researchers.... 

The prevalence of epilepsy in the world and the need for surgery to treat patients have made it essential to locate the site of epilepsy before surgery. One method is to apply source localization algorithms to the EEG signals of epileptic patients in the ictal and interictal periods. However, because these signals are contaminated with various noises, they are challenging to interpret and require noise cancellation. Therefore, various methods have been proposed to eliminate the noise. Among these methods, a new method recently used to remove noise from the epileptic signal is Morphological Component Analysis (MCA). This method uses the basic concepts of sparse representation of signals to... 

Objective: Joint analysis of multi-subject brain imaging datasets has wide applications in biomedical engineering.In these datasets, some sources belong to all subjects (joint), a subset of subjects (partially-joint), or a single subject (individual). In this thesis, this source model is referred to as joint/partiallyjoint/individual multiple datasets unidimensional (JpJI-MDU), and accordingly, a source extraction method is developed.Method: We present a deflation-based algorithm utilizing higher order cumulants to analyze the JpJI-MDU source model. The algorithm maximizes a cost function which leads to an eigenvalue problem solved with thin-SVD (singular value decomposition) factorization.... 

Fundamental changes that has taken place in the restructured electricity industry require new methods to maintain the reliability of power system in the most possible economic way. Besides, power network maintenance processes has undeniable significance in promoting the desired level of reliability. Maintenance and repairs of electricity industry in generation units and power plants are more important than other parts of the power grid, because this part of the electric power infrastructure, compared to the other parts of the network, composes of more expensive equipments. Moreover, failures occurring in any of these parts cause a sharp decline in production leading to economic losses. Among... 

Thesedays, personnel surveillance at security checkpoints, such as airports, is becoming increasingly important. Improvements in various fields of imaging techniques provided an attractive opportunity for automatic personnel servaillance at high security checkpoints. Millimeter-wave imaging systems are capable of penetrating through clothes and thin layers to form an image of a person with very high resolution and without no health hazard at moderate power levels. Therefore millimeter-wave imaging is becoming an important method for surveillance purposes. Typically, there are two common methods for microwave imaging, including synthetic aperture imaging and phased-array imaging. Synthetic... 

In the past several decades, with the increasing evolution of electricity markets, maintenance philosophy has gradually changed, and maintenance process plays a crucial role on the profitability and effectiveness of companies. Therefore, this leads managers to use modern strategies that their performance has been proved in various industries and therefore, traditional strategies have lost their effectiveness. Reliability-Centered Maintenance (RCM) is one of the most successful strategies wherein the maintenance process of system components is linked to improvements in the system reliability and profit of companies. RCM has not been thoroughly furnished in generation system yet. This thesis... 

Transformer are one of the most important equipment in transmission and distribution network. Transformer unplanned outage have severe impacts on the continuity of power system operation and is also an irreparable economic harm to power network operators. To improve the reliability of transformers and to achieve an optimum operation cost, online condition monitoring is inevitbale. Information about the quality of the transformer insulation system is known as the best parameter to be monitored in transformer. Since partiale discharge (PD) signals are initiated long before the beginning of a severe damage, monitoring and its evaluation can be employed to warn the operator. Data mining on the... 

Autism spectrum disorders (ASD) have been defined as developmental disorders characterized by abnormalities in social interaction, communication skills, and behavioral flexibility. Over the past decades, studies using various genetic, neurobiological, cognitive and behavioral approaches have sought a single explanation for the heterogeneous manifestations of ASD, but no consensus on the etiology of ASD has emerged. Further studies aim to clarify the mechanism of disease.
Functional Magnetic Resonance Imaging (fMRI) is a new way of imaging which evaluates activity of brain by measuring magnetic difference caused by oscillation in blood oxygen level. fMRI has been widely used in recent... 

Separation of speech signals has many applications. For example, it is used human-machine communications. This problem can be divided into three categories: overdetermined, determined and underdetermined. If the number of mixtures is greater than the number of sources, the problem is called overdetermined; if it is equal to the number of sources, the problem is called determined and if it is less than the number of sources that problem is called underdetermined. This MS thesis studies the undertermined case. Moreover, speech signals are sparse in time-frequency domain, meaning that in each time-frequency point, usually only one source is active. So, for separatig the speech signals,the... 

Range Profile (RP) is known as one of the most important tools for radar target recognition. The main problem with range profile for radar target recognition is its sensitivity to aspect angle. To overcome this problem, range profiles are assumed to have the same statistical characteristics in small frames of aspect angles or context dependent models such as HMM may be used. All methods presented, seems to have some shortcomings to offer a model based on physical circumstances of target maneuver. For example in such models, consecutive samples of RPs in an aspect frame are assumed to be statistically independent with the same distribution (IID). Here we propose dynamic system (DS) for... 

Power generation stations, which are commonly called power plants, are treated as the core module of power systems and are in charge of producing power to be transmitted and distributed to the end consumers. As the beating heart of power industry, power plants need to be available and reliable all the time and so do their constituent components since the need for reliable electricity, nowadays, is ever increasingly highlighted. The reason lies in the rapid jump of population growth in one hand and the incredible amount of damages as a consequence to the power interruptions due to the power plant component outages, if happened, on the other one. So, power plants have to be kept within a... 

It is generally accepted that Electronic Warfare has three distinct components: (1) electronic support (ES), (2) electronic attack (EA), and (3) electronic protect (EP). ES is included those measures taken to collect information about an adversary by intercepting radiated emissions. EA refers to attempting to deny adversaries access to their information by radiating energy into their receivers. EP includes activities under taken to prevent an adversary from successfully conducting ES or EA on friendly forces.
The function of Electronic Support Measurement (ESM) System is considered as a part of the first component (i.e. ES). After receiving emitted signals from various radars by ESM... 

Ability to speak lucidly plays a key role in social relations. Consequently the role of larynx is quite important and timely diagnosis of laryngeal diseases has proved to be crucial. Since conventional diagnostic methods of the larynx are usually expensive or bothersome, the aim of this project is to analyze and classify diseases of the larynx with the aid of signal processing which tend to be faster and easier to implement and quite economical. This study utilizes the vowel sound /a/ and a well referenced database, namely MEEI (Massachusetts Eye and Ear Infirmary) which includes 53 normal and 213 abnormal voices in 7 classified diseases. In this work, using existing signal modeling and...