Sharif Digital Repository

“Entrepreneurship ecosystem” is defined as the elements – individuals, organizations or institutions – apart from the individual entrepreneur that are conducive to, or inhibitive of, the choice of a person to become an entrepreneur, or the probabilities of his or her success following launch. Entrepreneurial businesses operate locally or regionally and are therefore subject to local or regional contextual influence. Moreover particularly in larger countries there can exist significant variation in industry structure and economic base across regions, emphasizing the importance of regional focus. Adopting appropriate policies at the regional level need to have a deep and accurate... 

Today, the pace of information generation, fast processing and instant decision-making is increasing. In this regard, one of the main needs in the field of data management and processing is stream data processing. Today's world needs new methods to deal with and analyze these data. Two of the most challenging aspects of data streams are (i) concept drift, i.e. evolution of data stream over time, which requires the ability to make timely decisions against the high speed of receiving new data; (ii) limited memory storage and the impracticality of using memory due to the large amount of data. Clustering is one of the common methods for processing data streams, without having basic knowledge... 

In this study, we explore the dynamics of the stock market using an agent-based simulation platform. Our approach involves creating a multi-strategy market where each agent considers both fundamental and technical factors when determining their strategy. The agents vary in their approach to these factors and the time interval they use for technical analysis. Our findings indicate that investing heavily in reducing the value–price gap was a successful strategy, even in markets where there were no trading forces to reduce this gap. Furthermore, our results remain consistent across various modifications to the simulation’s structure  

Although existing literature on organizational culture and its change process contains meaningful and rich theories but our studies show that there is no perfect and detailed framework on linking organizational culture change and corporate entrepreneurship culture. In addition to that, Gamification –defined as taking the game design elements into non-game contexts– is a fruitful and academically rich research area. Fortunately an idea proposed recently to explain a method for enhancements in organizational culture in general, and in corporate entrepreneurship culture in particularby Yavari and Jafarian based on using game mechanisms. In their paper "A Gamification-Based Method for Corporate... 

Anaerobic digestion is a useful process that is very important, addition to producing methane as energy source, it can be used for treatment of solid waste and sewage sludge. This process due to the presene of chemical and biological reactions and abundant chemical species, is very complicated and sensitive, so it is very unstable against any kind of change. as for the large importance of the process, we need control and optimization. In order to improving the performance of the process and increasing biogas and methane production, we should control and optimize the process. ADM1 is principal and the most accurate model for this process, a variety of reduced order models used to design... 

Obtaining polymers with desired properties is very important from industrial point of view. Weight average molecular weight and polydispersity are two important polymer properties. It is also important to obtain a high monomer conversion. In this thesis production of polyvinyl acetate is considered. Under special conditions, the vinyl acetate reactor dynamics become oscillatory which makes the reactor control difficult. For obtaining polymer with desired properties, an objective function which includes weight average molecular weight, polydispersity and monomer conversion has been defined. Then by minimizing this objective function the optimal temperature trajectory is obtained. In this... 

Modeling and Control of Ethylene Oxide Reactor In this thesis, steady and dynamic modeling of an ethylene oxide fixed bed reactor has been studied and one dimensional pseudo homogeneous model was used for simulating the reactor. Kinetic parameters were obtained by minimizing an object function and using the genetic algorithm. A good agreement is observed between simulation and experimental results. In steady state condition, the influence of some parameters such as shell temperature, feed rate were investigated on the performance of the reactor. The heat of reaction is used to produce steam. A dynamic model for steam drum was also considered and used for control purpose. A PI controller was... 

Most of Final properties of polymers such as morphological characteristics are related to molecular weight distribution (MWD) and particle size distribution (PSD). It is possible to obtain the desired properties by controlling of these indices. In this work, modeling, simulation, and control of final properties of styrene have been considered. First, kinetic of reaction has been investigated which is a free radical type. Molecular weight distribution has been calculated by using moment method. Next, population balance equation (PBE) has been used to model PSD. For this system, mass, energy, and moment conservation equations are a set of stiff ordinary differential equations (ODEs). PBE is a... 

Time delay systems may arise in practice for a variety of reasons, such as autonomous systems (without feedback control), and the delay is the result of an intrinsic property of the system. Sometimes the delay results from feedback control action, instead from the system itself; that is, due to the nature of the system, the feedback is delayed. Another type of delays of similar effects may be incurred due to delayed measurements. In both delayed control and delayed measurement, the delay is usually considered undesirable, which has the tendency to deteriorate the system performance or even destabilize the system.

In this thesis, three types of adaptive controller are proposed for... 

This thesis focuses on modeling, simulation and control of bulk polymerization of styrene in an autorefrigerated reactor where the generated heat is removed by heat of vaporization of the monomer. By means of two mathematical models for the kinetics of reaction, static and dynamic simulations were performed. For this purpose the equilibrium points were calculated using the steady state analysis, and then the reactor temperature was controlled at the unstable point using PI and adaptive generalized predictive controller (AGPC). In order to implement the GPC scheme a process model is required to provide the process output estimate over the prediction horizon. For this purpose an auto... 

In this thesis, simulation and control of intracranial pressure and temperature has been studied. Common methods for control of intracranial pressure and temperature are hypothermia treatment and drug therapy. Hypothermia is a clinical treatment for cooling the patient body with cold water-circulating blanket to decompress intracranial pressure by decreasing body temperature. In order to simulate the patient body, two mathematical models for single-input single-output and multi-input multi-output systems that are proposed in the literature are chosen. The thermodynamic- hemodynamic model was simulated as single-input single-output system and the thermodynamic- hemodynamic- pharmacokinetic... 

In this study design of controller for a nonlinear system in the presence of state observer was investigated. First, nonlinear observers including non-adaptive and adaptive versions and their design procedures were studied. Then nonlinear adaptive controllers, based on sliding mode, feedback linearization and back-stepping techniques were implemented in the presence of observer dynamics. Two versions of adaptive law were proposed for unknown parameters identification in feedback linearization and sliding mode techniques. A new adaptive law was proposed to relax the restrictive condition that is used in adaptive observer design. The closed loop stability of back stepping technique was studied... 

This project presents algorithms for intelligent control of the viral load in a HIV-1 infection model. The first part of thesis was dedicated to the study of the three states model adopted to describe the HIV-1 infection. A sensitivity analysis of the model parameters was described and computer simulations were provided to show the influence of the parameters explicitly. Then, an internal model control based on neural networks was implemented on the introduced infection model with including the RTIs and PIs drugs efficacies as control input. A stable adaptive neuro-control approach was presented for affine in the control nonlinear dynamical systems, whose nonlinearities were assumed to be... 

Biotechnology is one of the fields that has had great advances in the past decades, and therefore controlling biological processes (bioreactors) is considered as an important issue. The purpose of current thesis is designing an adaptive controller for a bioreactor by considering input constrain and proving the stability of closed loop. A standard bioreactor has been chosen for this purpose. First a non-adaptive controller has been designed. Then an adaptive controller is designed and implemented on a bioreactor in the presence of input constraint, because in practice the system parameters are unknown. Finally by applying disturbance to the system, it has been shown that the proposed control... 

Immediate control of pandemic influenza to avoid casualties and financial losses is an important issue. In this thesis, two types of controllers including optimal controller and adaptive generalized predictive controller based on linear input-output model, with vaccine, treatment and quarantine being controlling variables, have been used to control influenza. Each controlling methods were investigated for different states including single-input single-output and multi-input single-output. Single-input single-output and multi-input single-output models are identified as online and offline using least squares method. Since it is difficult to exactly identify the model parameters, especially at... 

The Smith Predictor does not work for unstable plants; therefore a lot of modifications have been proposed in order to solve this problem. In this project, advantages and disadvantages of most of these methods are studied in a general framework and based on Diophantine equation and using pole-placement technique. a discrete control scheme for unstable processes has been proposed. This structure can be used for non-minimum phase and stochastic processes. Robust stability of the suggested control structure has been shown. Performance of the proposed method is compared with previous works through computer simulations and its superiority for robust stability, load rejection; set-point tracking... 

The goal of this project is finding an appropriate method for controlling four different bioreactors with unknown dynamics. At first, an introduction to bioreactor dynamic hase been presented, then their nonlinear behavior has been discussed. In the following, four output control systems using adaptive neural network have been designed separately for four different dynamics. The applied control method has been adapted from a method of references with some changes. Performances of designed controllers in set point tracking, load rejection and model mismatch have been evaluated using simulation. In these studies, input saturation has been considered in simulations but it is not existed in... 

In this thesis, a chaotic chemical process has been studied and a control method has been proposed. To do this, a reactor in which two autocatalytic reactions take place in parallel has been modeled. The catalyst decay has been considered as a separate reaction. The reactor dynamic is chaotic for a set of parameter values. In this thesis, dynamic behavior of this chaotic reactor has been analyzed. The main objective is to control the product concentration and a state feedback controller based on the process linearized model has been proposed. The suggested controller possesses integral action on desired concentration to eliminate control offset. Since concentration measurement is difficult... 

Selection of the most appropriate control configuration for two point control strategy in a distillation column is a challenging problem. In the present work, three control configurations namely , and , have been employed to control a high purity distillation column separating the binary mixture of Benzene-Toluene. A simple linear model for the process has been derived via a system identification technique. The uncertainty and performance weights have been defined and have been utilized to design a robust controller based on the μ-synthesis approach. The genetic algorithm is employed and the peak value of μ is minimized in order to obtain appropriate PI controller parameters for each...