Sharif Digital Repository

In this thesis the resilience of a neural network is examined under structural perturbation.The network consists of Spiking neurons with specific dynamics or they are binary neurons and the network is non-spiking. Neural network is a multi-dimensional and multi-stable system therefore we can map their dynamical equations to effective one-dimensional equation with one parameter which shows the environmental conditions.The resilience of the system is evaluated with respect to changes in weights and edges of the network and the the resilience pattern of the system is obtained.Finally, the recovery and control methods are briefly discussed  

Electroosmosis is the predominant mechanism for flow generation in lab-on-a-chip devices. These microfluidic devices are microscale laboratories on a microchip that can perform clinical diagnoses. Since most biofluids encountered in these devices are considered to be non-Newtonian and the cross section of microchannels in these devices is close to a rectangular shape, In this study, the hydrodynamically and thermally fully developed combined electroosmotically and pressure driven flow of power-law fluids in rectangular microchannels is analyzed. The governing equations are first made dimensionless and then transformed into new ones based on the computational parameters which provide mesh... 

An implementation of Digital Section of a DVB-T receiver has been introduced in this research. Nowadays, low-power and area-efficient designs have proven their importance in IC design aspect, so many low-power and area efficient approaches have been considered in this implementation. This design has been segregated into independent blocks, and each of them has been designed respect to the design goals. After that, all these blocks linked together and a whole system design implemented in gate level, then downloaded into a FPGA (Field programmable Gate Array) to test the timing and functionality of implemented blocks. In this thesis, some innovations have been introduced. A new algorithm for... 

Online voltage stability assessment is essential for preventing the failure in power systems. Voltage instability in power systems usually occurs in consequence of contingency situations or continuous load increasing or both of them. A new method for online voltage stability assessment using the data acquired from phasor measurement units (PMUs) and offline trained decision trees is presented in this thesis. The index of voltage stability margin (VSM) is used for security assessment and considering WSCC criterion, different operation points are divided in two classes: safe and unsafe. In order to obtain the voltage stability margin and generate the database, a new method which has been named... 

First studies in internal combustion engines have focused on increasing engine power and efficiency, reducing engine volume and improving fuel quality. However, nowadays most studies are concentrated on decreasing exhaust emissions and usage of regenerative fuels while maintaining engine size, efficiency and power. Surveying fuel type in direct injection engines, requires investigation of microscopic and macroscopic spray characteristics including spray tip penetration, spray cone angle, spray area and sauter mean diameter, since these parameters determine air-fuel mixture quality. In this study, spray of ethanol as a regenerative fuel that reduces emissions such as NOx and CO is... 

Recent stringent HC and CO emission regulations are because of increasing consciousness of the perilous influences of exhaust emissions. The chief attempt to pass the standards is to decrease the emissions during cold-start, due to catalytic converters are not efficient until they arrive a light-off temperature. It has been discovered that 50% to 80% of the controlled HC and CO emissions are sent out from tailpipe of automotive during the cold-start. Therefore, in order to minimize the cold-start emissions and fast light-off of catalytic converters, it is important to understand the catalytic converter characteristics and techniques for rapid warm-up catalyst. This thesis describes a... 

Many of industrial processes include suspension in their middle section of production, final product or residue. Majority of these two-phase mixtures are unstable due to their large particle size (larger than one micrometer). Therefore, Study of particle distribution in suspensions for generation of stabilized suspension becomes significant. In this study a new mechanism in stabilization of microparticle suspension known as nanoparticle halo mechanism has been assessed. Experiments have been conducted in dilute suspension and two-way coupling range. The effect of the presence of silica nanoparticle on zirconia microparticle suspension has been investigated. The effect of zeta potential of... 

Investigation of flow field and vortex structures in swirl flows and their velocity components, have received widespread interest among the researchers in the field of fluid mechanics. Due to the importance of vortex structures and their applications in combustion chambers, a special type of combustion chamber which is called “bidirectional swirl combustor” has been investigated in this work. Accurate identification of vortex phenomenon and flow structure in vortex engine leads to better design and control of the engine in the field of stability, geometry, cooling and combustion efficiency. Eperimnetal methods in this area are difficult but very valuable and efficient. Numerical methods are... 

In this project, one-dimensional and two-dimensional numerical approaches are used to study the effect of applying electrohydrodynamics on the temperature and species mass fraction profiles along the micro-combustor. A premixed mixture of H2-Air with a multi-step chemistry (9 species and 19 reactions) is used and thermal conductivity of the mixture is considered as a function of species thermal conductivity and temperature by using a set of new relations. Both thermal and radical quenching mechanisms are important in the micro-scale combustion due to increasing of area-to-volume ratio and significant heat loss from the combustor walls. By inserting a number of electrodes into the... 

Due to increasing of internal combustion engine applications in metropolitan, reduction of emission is one of the challenging issues for engine companies. Natural gas is a promising fuel for the strict legislation of emission in many countries. Vast variety of natural gas sources in Iran and also lower carbon to hydrogen content of natural gas motivates us to use this fuel for engine application. Using natural gas also helps to increase the variety of fuel basket in Iran. Present research has focused on mixture formation and injection characteristics of natural gas direct injection engine. Injection and mixture formation in direct injection engines is very important for good combustion and... 

Nowadays internal combustion engines play an important role in the power generation as well as transportation fields all over the world. By using the turbocharger in internal combustion engine, more power is obtained in compare with aspirated engine having the same size, which is limited for gasoline engines. In this research, by a three-zone computer simulation code and experimental tests, the power boost limitations of the gasoline turbocharged engine are investigated. The results of single cylinder aspirated gasoline engine tests are used for validation the natural aspirated part of the code. For validating the turbocharged engine simulation, the results of a four cylinders gasoline... 

Search for effective methods for treating cancer requires a deep understanding of the tumor microenvironment and its role in cancerous tumor growth and progression. Mathematical modeling methods, which have fewer limitations than experimental methods for examining the microcirculation of cancer in detail, are suggested to answer many questions about the behavior and dynamics of cancerous tumors. In the present study, a multi-scale mathematical model of the three-dimensional tumor microenvironment, including molecular, cellular, and tissue scales, is presented. In this model, important aspects of tumor microenvironmental dynamics including tumor growth, angiogenesis, cancer metabolism, and... 

In the recent decades, cleanrooms have found growing applications in broad range of industries such as pharmacy and microelectronics. Concerns about negative effects of the contaminant exposure on the human health and product quality motivate many researchers towards understanding of the airflow and contaminant distribution through these environments. With an improvement in computational capacity of the computers, computational fluid dynamics (CFD) technique has become a powerful tool to study the engineering problems including indoor air quality (IAQ). In this research, indoor airflow in a full-scale cleanroom is investigated numerically using Eulerian–Eulerian approachand the results are... 

Microbiologically Influenced Corrosion (MIC) of concrete sewer ptpes and wastewater collection systems has been reported in many places of the world. Recently, numerous copper compounds have been used for bacterial growth control in sewer pipes. In this thesis, bath parameterswere optimized in order to maximize copper osmosis to the porous concrete matrix.Concrete pipes were electrochemically coated inCopper Lactate bath in a constant current mode (1=0.6 A), while temperature was set to 25, 50, 75 and 95
°Cand pH to 9,10 and 11. Specimens were then characterized by scanning electron

microscopy, optical microscopy, XRD andAAS. Copper Osmosis was highest in pH=9 and... 

The purpose of this research is to provide a method for finding a “good” solution to the network design problem with less computational efforts, faster than the existing conventional methods of solving this problem. Network design problem is the problem of selecting a subset of projects from a set of alternative projects so that to optimize the objective function (e.g., the total travel time in the network) subject to the set of existing constraints (e.g., budget). Due to the combinatorial and non-convex nature of the problem, its solution could be very cumbersome and time-consuming. Various methods have been proposed to solve this problem efficiently, providing good solutions at high... 

Epilepsy is one of the diseases that affects the quality of life of epileptic patients. Epileptic patients lose control during epileptic seizures and are more likely to face problems. Designing and creating a seizure detection system can reduce casualties from epileptic attacks. In this study, we present an automatic method that reduces the artifact from the raw signals, and then classifies the seizure and non-seizure epochs. At all stages, it is assumed that no information is available about the patient and this detection is made only based on the information of other patients. The data from this study were recorded in Temple Hospital and the recording conditions were not controlled, so... 

A new experimental setup was fabricated; equipped with an adjustable chamber’s length, with air tangentially flowing through the wall of vortex engine. In a vortex combustion chamber, the tangential inlet fuel or oxidizer creates both inner and outer vortices which are rotating in the same angular direction. Indeed, inner vortex moves from head to the end of engine in the axial direction; however, outer vortex moves in the opposite direction. This setup was fabricated to see the effect of fuel nozzle characteristics on the wall temperature of the chamber. In a vortex engine, vortices affect spray droplets and force them to have a spiral path. Moreover, relative velocity of droplets and flow...