Sharif Digital Repository

Performance of a multi tube pulse detonation engine has been investigated experimentally. A pulse detonation engine uses detonation phenomena and simply consists of a large narrow tube which has closed head, and has feeding system and ignition system. In this tube, detonation is produced periodically to generate thrust. In multi-tube mode, several tubes are arranged in parallel which detonate sequentially. Our PDE consists of 2 tubes with 70 cm length and 25 mm inner diameter which have several places performed for high speed pressure sensors installation. The premixed hydrogen-oxygen mixture are controlled by solenoid valve and injected on head-end and ignited by conventional spark plug.... 

This thesis is about one of the newest attractive theories in mathematics and theoretical physics; Topological Quantum Field Theory (TQFT) has some basic algebraic requirements called tensor categories, after introducing them and describing axioms of the theory which has suggested by Atiyah in 1988, we will see that the category of 2d-TQFT is equivalent to the category of commutative frobenius algebras over an arbitrary field .In the last part we focus on some topological aspects of theory in dimension 3 and some invariants of 3d manifolds , we will see these invariants are the main tool for construction a 3d-TQFT  

Reinforced concrete is one of the most important structural materials used in the construction industry worldwide. Nevertheless, certain physical and chemical factors in the service environment can contribute to its deterioration and failure. One of the most significant factors is the reinforcing steel bar (rebar) corrosion. In order to minimize the rebars corrosion, different kinds of coatings were investigated and evaluated by scientists. In this investigation comparative studies were performed on two different kinds of coated rebars (zinc-rich epoxy and polyamide epoxy coated rebars) and uncoated rebar. In order to evaluate these reinforced concretes, the adhesion, durability, thickness... 

In this thesis, a model is presented to detect and monitor the rotor bar's condition of large motors. This proposed model uses two diagnostic methods MCSA and ZCT, to extract the fault components. The input of the proposed model is only the motor current at two levels of 80% and 100% of the nominal motor load, which by using the two methods MCSA and ZCT and making changes in how to use them can be the disadvantages of other methods such as incorrect detection of rotor bars in Large motors with variable load, the harmonical stator voltage (or the presence of the drives) and asymmetric conditions. The extracted components are classified using two learnable algorithms, the k-NN algorithm and... 

Concerns have increased about global warming caused by CO2 emissions in the atmosphere. At the moment, carbon capture and storage is the best available solution. Among the current technologies for CCS, amine-based chemical absorption appears to be the most common method. Amines show several inherent drawbacks such as high vapor pressure, high energy consumption in regeneration, corrosivity and degradability. So, researchers have developed new solvents with the foresight of being superior to amines. Ionic liquids (ILs) are among the most suitable alternatives. The most prominent feature of ILs is their tunable thermophysical properties. In this work, physical absorption by ILs is chosen as... 

Production logging consists of running measurement instruments called logging tools into an oil or gas well to measure various parameters such as temperature, flow velocity, pressure, density, etc. The primary purpose for production logging is to allow enhancing production profits and decreasing costs. Nowadays the common way for fluid density measurement as a part of these tools depends on radioactive source. Special considerations must be taken upon the use of this principle due to its radioactive character. This thesis is focused on a non-radioactive method of determining density. The subject of this thesis is to consider methods for measuring density based on principle of acoustic... 

The problem of joint design of transmit code and receive filter is considered in many application scenarios of multiple input multiple output (MIMO) radar systems. The performance of the joint design problem is evaluated with the signal-to-interference ratio (SINR) metric in the presence of noise. In such problems, the optimization problem is to maximize SINR on the receiver side with the constraints that are applied on the transmitted waveform. Our proposed method, RTR, is a manifold-based geometric method that performs better than the SDP method in terms of algorithm execution speed and calculation complexity. For simulation, we took sampled and real TIR with Target Aspect Angle (TAA) in a... 

Sonic and ultrasonic measurements are used for checking status of wells. Well logging is used to estimate well specifications like borehole diameter, casing thickness, cement bond quality and cement sheath thickness. In this thesis, some reported works in field of sonic/ultrasonic measurement of oil wells are reviewed and results of software implementation of ultrasonic measurement with pitch-catch arrangement, pulse-echo arrangement and phased array arrangement are presented. ultrasonic measurement with pitch-catch arrangement uses one transducer for transmitting ultrasonic waves and two transducers (in different distances) for receiving ultrasonic waves. Ultrasonic measurement with... 

In this study, different metal oxides were impregnated on the surface of ZSM-5 employed as photocatalysis for degradation of methylene blue dye used in the presence of ultraviolet light. The final products were characterized by powder X-ray diffraction (XRD) and fourier transform infrared (FT-IR) method. According to the proposed mechanism for the photocatalytic degradation of methylene blue based on these results, it was found that the reaction followed from the first-order mechanism. The results indicated that rate constant for pure ZSM-5 was 9.3〖 ₓ10〗^(-3) (min-1). Furthermore the impregnated ZSM-5 having 12% zinc oxide demonstrated the highest photocatalytic activity with rate constant... 

In the oil industry, a better understanding of the well condition leads to improve the management and increase the oil production. Production logging tools is a set of tools for measuring different parameters such as density, diameter and flow in oil and gas wells. These tools are considered among high-tech tools in the oil industry. The reason is that they should work in harsh conditions, i.e. high temperature about 170 ° C and pressure around 15000 psi, and at the same time give an accurate measurement of the quantity. Current production-logging tools measure the fluid velocity and the diameter of an oil well by individual mechanical tools, and the density by a radioactive densitometer. ... 

Disturbance is one of the inseparable components of the mechanical systems which cannot be avoided. In these systems a number of inner and outer sources exist which are the cause of disturbance. Abrupt changes in torque, uncertainty in parameters, mechanical impulses and external forces on robot’s parts all can be mentioned as examples which introduce disturbance that affects the output of mechanical and robotic systems. Therefore, disturbance rejection is considered indispensable in robotic control systems. There are number of problems which are associated with disturbance rejection. In several methods, mostly optimization based methods, system fails to completely reject the disturbance and... 

Most of the time there are three different materials in oil wells; Oil, water and gas. Measuring volume percentage and flow of the individual materials (phases) is an important issue, due to their critical role in extraction process control. Measuring tool should be able to measure flow and percentage of each phase in a case that they are separated (in deviated wells due to gravity). In addition, the measurement should be carried on in a high temperature and high pressure environment and in presence of corrosive substances. Most of previous researches on Multi-Phase Flow Meter (or MPFM) led to mechanical methods to measure flow and they usually use electrical impedance or permittivity for... 

This study aimed to investigate the efficiency of machine learning algorithms in capturing the dynamics of water particles' age distribution and in estimating the time series of median travel time (MTT) in river basins. The mechanism of solute transport in a catchment does not follow the hydrograph shape of the catchment and depends on the spatial and temporal distribution of solute resident time. The equations governing the age dynamics of water particles discharged from a catchment have been presented analytically in recent research. These equations showed that the transfer of solutes depends on various factors, including climatic conditions, basin topography, and basin vegetation. Also,... 

In the past few decades there has been rapid advance in the use of digital cameras in different fields of art and science. Photo editing softwares have provided extensive facilities for their users and graphic softwares have astonished people with artificial yet fabulous images. Under these circumstances, recognition and distinction of authentic images from digitally-manipulated ones have become a critically important but notoriously daunting task. Users of the internet and computers need to recognize authentic images from the manipulated ones, or distinguish a composite photo from an original one. Digital image forensicsa was born as a response to these demands and has so far provided...