Sharif Digital Repository

Due to continuous improvements in manufacturing and the fact that modern technologies such as microprocessors, are becoming more efficient along the rapid growth of nonlinear control methods usage, the application of these two tools together has entered various fields of biomedical engineering, particularly neural prostheses. In this study, the methods of analysis and control of nonlinear systems were used to investigate and improve the behavior of the neural breathing system on the basis of Hodkgin-Huxley model as the original model of the neuron. Using the principles of differential geometry and robust control methods – based on combination of exact input-output linearization ideas,... 

In this study, single-phase and two-phase, incompressible flow in a non-deformable porous media was modeled and also simulated. The Reynolds numbers have been considered high enough to justify the use of the model including inertial terms. Afterwards, the mass conservative equations were discretized. Then, the numerical model has been developed for heterogeneous porous media. The heterogeneous porous media was comprised by several specified homogeneous regions, each having isotropic transport properties or permeability distribution with applying stochastic methods. The developed numerical model was used for predicting of saturation profile in water flooding process in one, two and... 

In this study, a tree-dimensional random pore-scale network model is used to simulate the membrane contactor porous medium. Drainage and imbibition phenomena is simulated to have a better knowledge of liquid and/gas intrusion trough the membrane porous structure. A genetic algorithm is used as an optimization tool. Several variables such as the number, radius and location of pores, the coordination number, as well as the radius and length of the throats are used herein as the optimization parameters. The difference between the binary SEM images and virtual sections on the generated network in conjunction with the permeability and mean pore size data were selected as the objective function.... 

Development of pore network models for real porous media requires a detailed understanding of physical processes occurring on the microscopic scale and a complete description of porous media morphology. In this study, the microstructure of porous media has been represented by three dimensional networks of interconnected pores and throats which are designed by an object oriented approach. Afterwards, the connectivity of the system has been optimized by an optimization algorithm. To validate the methodology, a network of a carbonate sample is constructed. In this model, the geometrical characteristics of the pores and throats, such as their shapes, effective radii and lengths, are selected... 

A modeling framework is proposed for complex chemical process networks. Concept such as passivity systems, thermodynamic function and graph theory are some important and applicable concept which seems to be useful for process network. The state is represented by energy, volume and mass inventories. The dynamic behavior of the process system is constrained so that all trajectories satisfy the first and second laws of thermodynamics. The concavity of the entropy function is used to define a storage function for passivity design. The proposed storage function is closely related to the Gibbs tangent plane condition. Stability analysis, pairing and controller design could be done by this new... 

Many processes in the real world are multiple-input multiple-output (MIMO) systems. There are often some interactions between the inputs and outputs. In the other words, every input affects on several outputs, and every output is affected by several inputs. In order to control of these systems, we usually desire to decouple the loops into multiple non-interacting SISO systems after proper pairing of manipulated and controlled variables. Loop interactions can destabilize a control system, so tuning controllers in an interacting MIMO system can be difficult. Decoupling problem has been discussed in the two domains: linear control and nonlinear control. However, both of them need an exact model... 

The accurate fault diagnosing system design helps the process safety and also helps increasing the products quality of the process. In this project, the fuzzy system and neural network have been used for fault detection and diagnosis of a yeast fermentation bioreactor. In one case, parameters of membership functions are selected in a conventional manner. In second case, the optimal values of these parameters have been obtained using the genetic algorithm. In another case, the neural network system is used for fault detection. These three cases are compared based on their performances in fault diagnosis of a yeast fermentation bioreactor for three different conditions. The results indicate... 

In this thesis, in the first step, design of an Agent Based framework was accomplished. Agent oriented programming is a kind of programming based on distributed processing by agents in a same location or not. UML was used to design the the agent based framework. To implement the designed framework, C++ programming language was used. Embarcadero C++ Builder IDE was chosen to implement the design. Then the designed framework was used to develop a sofware for data reconciliation. The branch for dynamic data reconciliation of this project was extended. To validate the ability of the sofware, a distillation column model with 7 states was selected. The result of gross error detection and data... 

Nowadays diabetes is considered as one of the common diseases among mankind. Different body organs utilize the glucose or the sugar existed in various kinds of food as an energy source in order to provide required energy for their activities. Insulin hormone which is created by the pancreas gland has a very significant role in easing the respective procedure. Therefore, when the body is not capable of producing enough insulin, then glucose aggregation in the blood leads to higher blood sugar and thus a disease called diabetes type1. Up to now, considerable research activities have been done regarding the diabetes type1modelling. One of the bolded drawbacks of such models is that the effect... 

Gravity drainage is the self-propulsion of oil downward in the reservoir rock. Under favorable natural and operational conditions, it has been found to effect recoveries comparable to water displacement. With modern technical knowledge, the operator can often make a choice between dissolved gas drive, water drive and gravity drainage as the principal recovery agent in a reservoir. So far, gravity drainage has received less consideration than the other two. Gravity drainage is one of the most important processes taking place in fractured reservoirs and it plays a major role in oil recovery from low permeability matrix blocks during gas injection process. Gravity drainage is responsible for... 

Oil reservoirs, have integrated identity; that is they consist of different parameters such as wettablity, initial water saturation, capillary and gravity forces, etc. which are related to each other and affect ultimate recovery simultaneously. In fractured reservoirs, other parameters such as fractures and complex geological structures are also considered  among  important  parameters  which  affect  ultimate  recovery.  Due  to  large  amount  of reserves,  fractured  reservoirs  are  subject  to  different  studies  and  simulations.  In  this  research, different  parameters  which  affect  ultimate  recovery  in  fractured  reservoirs,  are  studied  and simulated. Different  studies ... 

The hydrocarbon reservoirs with temperature between critical temperature and cricondentherm are called gas condensate reservoirs. The hydrocarbon fluids of gas condensate reservoirs have retrograde behavior, i.e. when the pressure falls below the dewpoint, condensate liquid appears. This phenomenon usually occurs around the production wells, because pressure is typically the lowest in the near-well region.This so-called condensate blockage leads to reduced gas production because the condensate causes a decrease in gas relative permeability.
This phenomenon is difficult to capture in the standard compositional simulators, because well blocks are typically too large. The condensate... 

In this thesis non-ideal behavior of fluids and its effects on hydrodynamic and mass transfer in multiphase flow is studied. A numerical framework has been proposed to model the interacting effects of mixture non-ideality and mass transfer on hydrodynamics of a multiphase system using CFD methods. Using the numerical framework mass and momentum transfer in a system was simulated. The system consists of a cylindrical vessel filled with vapor and liquid hydrocarbons which selected as the benchmark. The liquid hydrocarbon is chosen to be pure Octane and the hydrocarbon in the gas phase is assumed to be Propane. Due to operating condition (T=323 K, P =445 kpa) the behavior of fluid is non-ideal... 

Since steady state behavior of a plant is affected by the change of various inputs to the plant, the transient behavior of the chemical plants are also very important in their general performance. On the other hand, catalytic hydrotreating is one of the most important processes in crude oil refining process in many aspects such as economical, technical and environmental. Thus, the goal of this project was dynamic simulation and control of catalytic hydrotreating unit (UNIFINER Unit) of Tehran Refinery with using the HYSYS software. To fulfill this target, data that were necessary for simulation were gathered from Unifiner unit of Tehran refinery at first. Then, steady state simulation of the... 

In most chemical processes, at the first stage, the feed are being treated in physical steps such as preheating. Afterward it enters reaction system to undergo chemical treatment. In the final stage, product of reaction system is physically processed to prepare them to exit the boundary of the process. There are various ways to process materials chemically. This process can be continuous, batch and even semi-batch, via a single reactor or a network of the reactors. And also it can be performed under various range of operating condition. Moreover in some cases, intermediate cooling and heating is necessary. The question is that which configuration and operating condition is the best. The goal... 

Finding the optimal heat integrated distillation column sequence is an utmost important optimization problem in process engineering. The frequently used approach in this area is to obtain a suitable sequencing candidate and then accomplish the heat integration based on the application of Pinch technology to finalize the design. This approach reduces the problem complexity at the expense of not necessarily reaching the best possible result. This work follows a genetic super structure approach to systematic and rigorous synthesis of optimal multi-component distillation sequences (including simple and thermally coupled complex columns) and simultaneously heat exchanger networks by using a... 

This work describes the use of a two-dimensional numerical simulator for Steam Assisted Gravity Drainage (SAGD) using the model proposed by Coats et al with some improvements. Despite the Coats model this developed model accounts for capillary and gravity effects in the energy equation with a variable thermal conductivity of the formation. First, a sensitivity analysis is performed for SAGD process. Then, the simulator is used to describe the pre-heating process preceding SAGD. We studied two methods of preheating process and found that there exists an optimum method of preheating for any reservoir. We concluded that longer preheating period does not necessarily yield a faster recovery  

Asphaltene, the heaviest and most polarizable fraction of crude oil, has a potential to precipitate, deposit and plug pipelines, causing considerable production costs. The main objective of this study is to contribute to the thermodynamic and transport modeling of asphaltene in order to predict its precipitation, segregation and deposition. Potential calculation of some thermophysical properties of asphaltene is also explored. Predicting the flow assurance issues caused by asphaltene requires the ability to model the phase behavior of asphaltene as a function of pressure, temperature and composition. It has been previously demonstrated that the Perturbed Chain form of Statistical Association... 

In this project a framework for Model Based Fault Diagnosis (MBFD) in a Gas Transmission Network (GTN) was developed. A black-box linear state-space model was used to capture dynamic behavior of an industrial benchmark for GTN. A full fledge commercial network simulator were used to obtain the required data for process identification. In order to check the robustness of the model zero mean white noise was imposed on various output obtained by the commercial simulator. Kalman filter was used to estimate the states of the GTN. These estimated states along with the measured output (all obtained from the commercial simulator) are almost similar to their corresponding estimated signal. This shows... 

Mathematical models are used for describing physical systems to make it possible to study and investigate the behavior of these systems and compare their performance and improve them. For this reason, a mathematical model for cardiovascular system and respiratory system is used to study how these two systems interact. The cardiovascular system model and the respiratory system model comprise four and two compartments, respectively. In fact, the combined model contains the left and right ventricles, body tissue, lung, systemic blood circulation, and pulmonary compartments. Heart rate and alveolar ventilation are assumed to be the quantities through them the central nervous system controls the...