Sharif Digital Repository

Currently, one of the most important problems in the field of drilling is the issue of drilling fluid loss in different formations. The problem of mud loss has been evident since the beginning of oil and gas well drilling operations, so that oil companies spend millions of dollars annually to solve the problem of mud loss. Problems such as pipe jamming, loss of rig production time, well blowout, loss of a large volume of drilling mud and damage to reservoir formations due to loss of drilling fluid are caused. Regarding the drilling variables, many factors cause the decrease or increase of the loss, the most important of which are the weight on the drill bit, drilling speed, the rate of... 

In this thesis, the orbit determination of Low Earth Orbits (LEO) using the integrated magnetometer and horizon sensor data has been investigated. Orbit determination is an essential part of a space mission. Not only the modeling, guidance, navigation and control errors may results in error in injecting the satellite into its nominal orbit, the environmental disturbances deviate the satellite from its predicted orbit and from an operational perspective most satellites need continuous orbit determination. Traditionally, ground based orbit determination is used which are non-autonomous and expensive and just can be used for specific times which the satellite can be observed from the ground... 

The aquatic canopy areas such as wetlands play an important role in ecology of these area. The exchange flow between open water and vegetated area occurs due to sunlight and surface cooling. Wind also causes surface evaporation and create a cold layer at the surface of water. The creation of exchange flow and its magnitude depends on parameters like solid volume fraction and thermal gradient. In this thesis, the goal is to determine the effects of floating vegetation on the hydrodynamic characteristics of exchange flowas a result of surface cooling experimentally. In this research, the PIV method was used to measure velocity profiles. In the experiments, solid volume fraction, depth of... 

Clustering algorithms are developed to provide general attitudes on database, recognizing latent structures and their more effective accessibility. Recently, broad studies are conducted on clustering since it is recognized as an important tool to explore and analyze data. Clustering is a fundamental learning operation without monitoring in data exploration which divides data into groups of objects so that objects in one group have the most similarity to each other and lowest similarity to objects in other groups. Some clustering algorithms such fuzzy clustering model (FCM) are widely used in clustering problem solution although this technique addresses local optimized searches. Additionally,... 

Flameless combustion is among the newest combustion technologies that is used for reducing the pollutants in recent couple of decades. Within this combustion regime, diminution of super hot points throughout the combustion chamber along with decline in production of pollutant gases occur simultaneously. This kind of combustion often is created by applying two processes; first by preheating the fuel and/or oxydizer flows at the inlet to tempratures over the self-ignition level; and second with diluting the whole amount of fuel and oxidizer in the chamber. These two happen by using hot exhaust gas of the same chamber (via feedback) or of the previous section (in multi-section chambers).... 

By an increase in demands for multimedia services of mobile, wireless networks shall provide Quality of Service (QoS) requirements for users moving in cells. Multimedia services such as voice, data and image own different features and every QoS are different from the other due to delay and demand for bandwidth.
This thesis presents a new model of call admission control which consists of a few key elements for protecting the network in different conditions of workload in a manner that calls blocking /dropping are kept under desired level. This model consists of two traffic classes of voice and data in order to give apriority to handoff call over new call, the parameters in this model are... 

The growing number of disasters in recent years has become a significant threat to hospital buildings' resilience and preparedness. Besides, the stochastic nature of these disasters and the complexity of the hospital building systems exacerbate the difficulty of making appropriate decisions during and after disasters. To address the issue, this research proposes a novel model that utilizes the capabilities of Bayesian Networks (BNs) and Building Information Modeling (BIM). This model helps decision-makers in hospitals and medical centers measure various effects of disasters on utility systems and analyze the consequences of their decisions. The capabilities of the proposed model are tested... 

Nowadays, all of the devices that measure blood pressure commercially at home are using wrist or arm cuffs preventing the systolic or diastolic blood pressure from being measured continuously. Various parameters such as blood flow with some degree of correlation with blood pressure that can be measured noninvasively have been suggested. However, these parameters do not produce accurate estimates for blood pressure. Pulse Transit Time (PTT) which is defined as the interval between the R peak of ECG signal and the next PPG signal valley has shown to have over 90% correlation with systolic blood pressure in past studies. In this thesis, the relationship between the value of the systolic blood...