Sharif Digital Repository

Fischer-Tropsch (FT) is a process which is studied recently by many companies and researchers. Due to limited sources of petroleum, conversion of Synthesis gas to liquid hydrocarbons as gasoil, gasoline has been considered a lot from 1980. In this thesis new design for FT process is presented (based on Fe-Cu-K catalyst) to produce gasoline, gasoil and wax, this design is simulated by HYSYS 3.1 software. Lumping strategy of reactions involved in FT mechanism is used to reduce simulation time. Not being FT reactions in HYSYS, reaction extensions are used (via customization capability) to include complex lumped reaction rates. Afterward, PI controller is implemented to control concentration... 

Strongly correlated electron systems are an interesting topic among condensed matter systems. The electrons in such systems are strongly correlated to each other in a way that the behavior of the systems cannot be described by single particle theories. One of the most famous of these systems are heavy fermionic materials which are called so due to heavy quasi particles mass.
This kind of materials have been investigated via different methods. The most im-portant model that can describe characteristics of these materials is Kondo lattice model. When we are only interested in magnetic properties of them, the model can be reduced to Kondo-necklace model which only involves with spin degrees... 

Semi-automated Continuous Speech system deals with collecting corpus speech. It has very different problems in various natural languages because of different types of speech, and collecting speech corpus containing continuous word is very time-and- cost consuming. To overcome this problem, human-based computing techniques are proposed to collect speech corpus. In this thesis, we describe influencing factors in collecting steps of continuous speech and provide a description of human-based techniques to solve problems specially collecting of continuous speech. To collect speech corpus using human-based techniques, a game has been used so that speech corpus of web users are collected during the... 

In this thesis, we consider the Kondo-necklace model to investigate the quantum phase transition between the Kondo-singlet and antiferromagnetic phases. There is no exact solution for this model. We would like to study the quantum critical behaviour of this model on one, two and three dimensional spaces in addition to ladder geometry. In this respect, we looked for a proper method which can give us some information for our model on any spaces mentioned above. Therefore, we implemented the perturbation continuous unitary transformation (PCUT) for the Kondo-necklace model. By using this method, we can not only calculate the ground state energy for 1, 2, 3 dimension and n-leg ladder... 

In this research performance of microbial fuel cells (MFCs) in continuous flow mode was studied. Different anodic chambers were tested and it was found that granular activated carbons (GACs) produced the highest power density (1228 mW/m3) in comparison with multiple anodes (731 mW/m3), single anode (294 mW/m3) and polymeric packings (40 mW/m3). It was also shown that in a plug-anodic chamber (PAC) the power output is reduced by reducing agitation of anodic volume. Adding more GACs to anodic chamber results in power increase, however by increasing occupied volume from 80% to 100% the power increase was negligible in result of cathodic reactions limitations. Feed flowrate was increased from... 

In this thesis, possibility and advanteges of dynamic descent route assignment during busy traffics and implementing changes within navigation infrastructure is examined. Facilitating Continuous Descent Approaches (CDA) as optimum descent paths is the main goal of this research. One advantage of this project with respect to previous works in this field is dynamic CDA routing between cruise altitude and Terminal Radar Approach Control (TRACON) entry to meet the demand of traffic during peak hours.The other superiority is proposition of LASER technology as an alternative/backup NAVAID system in order to facilitate the latter.Terminal area of Hartsfield-Jackson international airport with real... 

A cooperative aerial system to defense a Ground Station (GS), against an Incoming aerial Targets (IT) is presented. GS is surrounded by given terrains and a group of homogenous Unmanned Aerial Vehicles (UAVs) are employed using a novel online guidance algorithm in a decentralized manner. The proposed algorithm includes loiter, midcourse and terminal phases. During loiter; UAVs follow an optimal circular path. IT is supposed to approach GS along an optimal low altitude trajectory with respect to the terrains. UAVs are informed the initial position and velocity of IT and they are unaware of IT trajectory. Each UAV decides on whether to engage with IT or not, and shares its decision with other... 

Regarding decreasing resources of fossil fuels and their increasing costs in addition to their environmental pollutions, today, producing bio fuels from wastes such as lignocellulosic materials is of great interest. A fundamental stage in conversion of lignocellulosic materials into bio fuels, such as bio ethanol, is the enzymatic hydrolysis of these materials to produce reducing sugars. Researches have shown high costs of this stage. Optimization of enzymatic hydrolysisconditions is a major step in economization of this process.In this work corn hull is used to produce glucose. Corn hull is a kind of lignocellulosic material that due to high carbohydrate content is used as substrate. Our... 

Modeling and performance evaluation of the real time distributed systems is a significant problem. Stochastic activity network is one of the high level models used for this purpose. This network is an extension of generalized stochastic Petri net which is more powerful and flexible than other Petri net extensions. Checking the satisfiability of properties such as performance, dependability and user's expected properties is considerable in these models. Thus, using the approaches and generating modeling and model checking tools with the mentioned purpose is attractive. A model checker automatically checks the correctness of the system behaviors as properties against the model by getting the... 

Polar codes were introduced by Arikan in 2009. These codes are the first family of codes that with low encoding complexity and successive cancellation decoder, can achieve the channel capacity. Polar codes, at first were implemented for channel coding, but in 2010 performance of these codes in binary and q-ary alphabet source was studied. It is shown that these codes can perform efficiently in channel coding and source coding. On the other hand, one of the most important continuous sources are Gaussian sources. Due to the importance of Gaussian sources and good performance of polar codes, we try to evaluate the performance of these codes in Gaussian sources. Note that, these codes have... 

The fascinating subject of heavy fermion physics in rare-earth and actinide systems has been a challenge for theoretical and experimental investigations for decades. Kondo Necklace model is one of the promising models in the study of strongly-correlated heavy fermion compounds, which is studied in this project.One of the methods to diagonalize a Hamiltonian properly, regardless of system size, is the continuous unitary transformation. In this approach, the Hamiltonian is considered as a function of a flow parameter. The Hamiltonian is transformed to a simpler form (diagonal or band-block diagonal) under a flow equation which is based on applying infinite numbers of infinitesimal unitary... 

In this work, inertial guidance and control of an axisymmetric flying vehicle with a spinning part is performed based on dynamic modeling and seven degree of freedom simulation. Flying vehicle is composed of front and aft bodies and these bodies are connected to each other via a hydrodynamic bearing. Front body is roll isolated from the aft body and includes all necessary guidance and control equipments such as sensors, canard set and so on. The control fins, located on the nose, is used to control the roll angle of the nose and to execute the lateral acceleration commands. Also, the aft body is freely rolling and includes the stabilizing fins. In this project, the translational and... 

Continuous approximation of pressure and flux fields is one of main goals of simulating flow in porous media. To compute the pressure field in heterogeneous and anisotropic media using minimum memory and time, it is necessary to use a conservative flux-continuous scheme. Nowadays, one of the most efficient approaches to minimize the solving time of large-scale problems is parallel computing. In this research, a parallel algorithm for flux-continuous multi-point flux approximation (MPFA) scheme with full pressure support (FPS) is designed and implemented on unstructured triangular grids by cell-centered approach. In this work, 2D single phase flows are investigated. The results are presented... 

Gravity drainage is known as one of the major mechanisms of oil recovery in naturally fractured reservoirs which petroleum engineers conducted research in this realm. Block to block interaction such as capillary continuity and reinfiltration mainly control the efficiency of this mechanism. In this study, first of all, free fall and forced gravity drainage experiments have been conducted in a single block apparatus and effect of some parameters like, density viscosity relation, matrix permeability, vertical fracture aperture, presence of viscose force and type of injected gas were investigated, in the second step, three stack block apparatus were designed and constructed. This apparatus were... 

Continuous casting is one of the ingot production methods in which the product has uniform chemical structure, low defects and high production rates. These days, carbon steel and nonferrous alloys are mainly produced by this special method. The design of continuous casting process includes a lot of difficulties due to its technological complexity. One of the most important aspects of this process is the heat transfer during solidification. In the present study, a new mathematical model and its corresponding numerical solution method have been introduced to establish the condition of directional solidification along the major ingot’s axis. The controlling parameters used in the model are... 

This research is trying to investigate the control algorithms of unknown control direction systems. Since Nussbaum function is the most common method which in used for these systems this research focus on this algorithm to overcome control the effect of unknown control direction. This research study the performance of different control algorithms in controlling such systems followed by analysis of two control modes of continuous and discrete using Nussbam Function. Additionally, in continuous mode, the performance of two methods of backstepping and liding mode has been compared on the given system in variety of situation. Results demonstrate that backstepping method shows better performance... 

Increasing use of new data technologies have made data collection possible in large scales. Practicallity of the data relies upon the extraction of meaningful knowledge.Data mining is a solution to this problem. One of the new areas in data mining is consideration of the concern of privacy alongside the usefulness of the mining results.Main goal of privacy preserving data mining is to develop data mining models which only extract the useful knowledge. In recent years, many researches have been done in this area. Since the literature and notation of these published works vary, a survey would help to better understand these concepts. This thesis tries to explain, analyse,unify and categorize... 

Sigma-delta modulators have largely been implemented as discrete-time (DT) circuits because of their low sensitivity to circuit nonidealities, and their frequency scaling specification, however a continuous-time (CT) design offers significant advantage in the design of high accuracy, high speed analog to digital converters (ADC). A CT design allows for relaxed amplifier(s) bandwidth and power requirements, which enables the realization of high accuracy modulators with bandwidths of several megahertz at low power consumption. Furthermore CT modulators provide inherent anti-aliasing filtering which becomes especially important at low oversampling ratios. This thesis reports the design of a... 

Hydrocracking is one of the most versatile petroleum refining process for production of valuable products including gasoline, gas oil, and kerosene. Various kinetic models have been proposed for hydrocracking process. A commonly used approach is to consider the mixture in terms of selected lums, which can be specified in terms of structural characteristics, such as boiling point. From this approach the reaction mixture can be considered in two types of discrete lumping and continuous lumping. In this thesis, a 5 parameter continuous kinetic lumping model was studied for modeling of the Isomax reactor of Tabriz refinery whose feedstock is a low quality gasoil from vaccum distillatin column....