Sharif Digital Repository

Considering that the agricultural sector is the largest consumer of water in the basin of Lake Urmia, it seems necessary to provide comprehensive methods of water resources management and formulate appropriate policies to increase water productivity in this sector. For this reason, in this research, we examine the effects of creating a water market in the basin of Lake Urmia. For this purpose, models of agricultural economics and positive mathematical programming techniques at the regional level have been used for modeling to analyze the various effects of water market creation. According to the model, the farmer chooses his cultivation pattern according to the price of the crop and the... 

Centrifugal compressors have wide applications in the turbochargers, aircraft propulsion and petrochemical industry. Therefore it is important to design high efficiency centrifugal compressor. Knowledge of compressor performance at different conditions, energy losses and the contribution of each component of compressor in efficiency losses have of great importance.
In this research, different loss models of the centrifugal compressor were reviewed and investigated. Then 1D codes were developed based on the loss models, and performance characteristics of S2B Schweitzer and GT4082 Garret compressors at different conditions were achieved. In order to evaluate the modeling results,... 

Electrochemical capacitors are type of electrical energy storage devices that research on them has grown due to the development of hybrid vehicles. It is proved that lectrodes configuration has vital role in electrochemical capacitors performance. In this thesis, transition metal hydroxides, oxides and sulfides along with carbonaceous materials have benn used as active materials in supercapacitors. In first section, graphite has been poroused by applying anodic potential of 2V in acidic electrolyte which results in exfoliation of graphite planes due to gas diffusion to the interlayer of graphite sheets. The prepared porous graphite was used as precursor for electrodeposition of nickel... 

Design of a spiking neural network suitable for electronic hardware implementation has been a hot research topic for a long time, in recent years implementation of spiking neural network in real time and biological scale has become important for scientists. This is due to the proximity of these networks to human brain, and the efforts led to the creation of numerous biological models and hardware which has been proposed in this context. This research includes two main parts, the first part is effort to implement a greater number of neurons per device and the second part proposes a communication system among devices to achieve biological scale. This work investigates novel neural elements and... 

Performing research and development in the field of modern vessel types which serve several functions is considerably necessary because of their importance and rapid development. HARTH vessel is considered one of the important ships which has been recently attracted much attention from the world. In this respect, a full investigation of its performance could make a big contribution to its optimum design and appropriate exploitation.“HARTH” ship is the abbreviation for “High Aspect Ratio Twin Hull” is included in the catamaran vessel category with a high aspect ratio with respect to their underwater cross-section’s ratio of length to width.A host of crucial issues should be considered for... 

Currently, the relatively long time of the turbine life passes and their parts and equipment damage are different, that loss optimum performance and thus reducing their efficiency and may lead to faults and other unexpected stops in their production cycle. Process used to estimate the remaining life of the various components of this turbine is an important tool for improving the efficiency of these units to perform preventive maintenance. In the present thesis, the types of damages in different parts of gas turbines and various methods for detection of critical points, particularly finite element method, high cycle fatigue, modal analysis, methods to estimate the lifetime of a gas turbine... 

Conventional two-dimensional photos are images of a three-dimensional scene. In fact, since the recording medium record only the intensity of the incoming light, information about the phase of the light couldn't be recorded and this results in making 2D photos from a real 3D scene.
In this research a mechanism for getting three-dimensional images in endoscopy and laparoscopy by Digital Holography has been designed based on the criteria standards in this field.
 

Controlling four legged robots is a complex challenge. The previous works in this field can be divided into two main categories, Analytic method and intelligence method. The analytic method is based on extracting the motion equations of the robot, but in most cases these equations are so complicated, and their implementation is difficult. Another method is intelligence method, which is based on learning algorithms. Despite the improvements in walking robots field, still their walking quality is far from human and animal walking. Researchers believe that this advantage is the result of the learning ability in animals and human. Therefore in this paper the human learning ability is used to... 

The purpose of drilling is to create a safe path to access underground hydrocarbon resources. Therefore, during drilling operations, barriers should be considered to ensure the safety of the well. When drilling a well, if for some reason, brine, gas or oil enter the well, the pressure of the mud column decreases, which will continue to collapse the stability and integrity of the well. In this case, the external fluid may reach the wellhead and blowout. For this reason, blowout preventers should be installed at the wellhead to secure the well with high confidence by closing the valves and preparing for the continuation of the drilling process. Well blowout may lead to loss of personnel lives,... 

When a crack is subjected to a compression field, it will close and its edges will get into contact with each other. Depending on the direction and magnitude of the loads and also the coefficient of friction, ‘stick’ or ‘slip’ situationsbetween the edges will occur. This type of crack is known as ‘frictional crack.’ In this project, first these cracks are studied analytically and the order of singularity is derived using asymptotic analysis and also the analytical fields are determined for both ‘isotropic’ and ‘orthotropic’ materials. Then, numerical simulations are carried out using extended finite element method which is considered as the most powerful means for analyzing the problems... 

Today, microreactors come into focus due to their exclusive characteristics including high surface-to-volume, lower consumption of reagents and fast mixing. In this study, optimization of the Br-Li exchange reaction as a consecutive reaction using glass microreactor is investigated. To construct glass microreactor, laser ablation and thermal bonding method are utilized. In order to find the best yield and selectivity of the reaction, various parameters, such as solvent, equivalent ration of the two reagents, concentration of the reagents, residence time and flow rates of the reagents are examined. In addition, atomic force microscopy (AFM) analysis was used to determine the surface... 

MPD technique manages drilling pressure to keep bottom hole Pressure balanced in the well. The objective to this studs, is to approximate the well pressure to formation pressure to prevent entry of fluid into the well. MPD is a new method drilling in which, driller controls the annulus pressure in order prevent drilling problems. the circulating fluids system employed by MPD technology is more akin to that of a pressure vessel. In this thesis, using in laboratory-made machine, reacts with sudden changes in pressure at the bottom hole in the shortest possible time. Basically, this system is a system where well bore pressure management is obtained by adjusting the pressures along the well bore... 

Parkinson's disease is a neurodegenerative disorder that affects motor functions. Performing mobility exercises help patients slowing down the progression of the illness and improving symptoms of the disease. Assessment and evaluation of activities of mobility exercises are critical for any treatment program particularly in tele-rehabilitation system. The purpose of the current study is to design an affordable and accurate wearable device with inertial measurement units (IMUs) for mobility activity recognition in Parkinson’s patients. The optimum number and arrangement (i.e. configuration) were found to minimize the cost while maintaining a fair accuracy. The activity recognition was... 

In the last decades, noticeable experimental and analytical investigations have been carried out on cast-in-place Reinforced Concrete column to Steel beam (RCS) connections, however rarely have been conducted on the precast RCS. In this reaserch, test results of five half-scale interior precast RCS connections with variable joint configurations are presented. The steel beams were connected to the precast column, using face bearing plates, embedded in the connection zone. The flanges of beams were strengthened with respect to scaled section, in order to increase the load transfer to the joint. All samples were loaded under reversed displacement controlled condition. The failure mode, joint... 

The surge phenomenon, as the most important aerodynamic instability, has caused a severe drop in efficiency and performance in centrifugal compressors, and its prevention and control is considered one of the main concerns of industrialists. The purpose of this study is to design and develop a surge control system in order to improve the stability and safety of the system under the effect of surge. In this research, after simulating the existing control system and working line in Borzouyeh Petrochemical Industry, by designing and adding the piston surge active control system to the above centrifugal compressor and using the combined control system, the flow rate of the bypass path has been... 

In this thesis, the behavior of proposed moment resisting precast beam-column concrete connection under cyclic and monotonic loads is investigated. In this study, the finite element models of precast and monolithic middle and corner connections are created. The results of finite element analysis under cyclic loading is verified with existing experimental results based on failure mode, ductility, energy dissipation capacity and flexural strength. Based on the results of nonlinear finite element analysis, the analytical behavior of samples is in good agreement with experimental results and finite element analysis of proposed precast connection can be replaced with supplementary tests. Then the... 

The Southern Caspian Basin, which includes northern Iran, western Turkmenistan, and eastern Azerbaijan, is known as the Land of Fire due to its abundant gas springs. This region possesses unique geological features, including active mud volcanoes that are associated with the release of methane gas. These characteristics indicate a high potential for oil and gas exploration in the area. The Gorgan Plain, located in Golestan Province and bordered by the Alborz and Koupeh-Dagh mountain ranges and the southern Caspian Sea, witnesses several active and dormant mud volcanoes, which serve as indicators of energy resource presence in the region. The drilling problems faced in wells A and B in the... 

Voting has been considered as one of the principal of democracy which by this, people can announce their convictions and ideas officially. E-voting is a method of online voting based on cryptographic mechanisms. E-voting schemes by keeping voters' privacy safe and providing security requirement same as verifiability, fairness, coercion resistance, receipt freeness, undeniability, and eligibility has been noticed in recent years. Security of many presenting schemes is based on existence of trusted third party that plays an important role in process of getting and counting votes. Also, some of security problems which are in this scheme, originated from centralization and generic trust of third...