Sharif Digital Repository

An acinus is defined as the complex of airways supplied by one first order respiratory or transitional bronchiole. In this part, the replenishment of oxygen at the alveolar surface occurs by a combination of convective air flow with diffusion of oxygen in the air. So for studying gas exchange in the lung, modeling gas species transport and exchange in an acinus is important. Due to lacking direct measurements of the distribution of oxygen (or carbon dioxide) concentration in the acinus, several mathematical models have been developed and studied by numerical simulations. But in none of them the influence of breathing pattern and the role of blood flow in restricting the gas exchange rate have... 

The existing statistical studies implies that in Iran like most of developing countries, the great percent of houses are traditional. Statistics of the most disastrous current quakes also show damages caused by masonry structures in developing countries. The main problem of brick and masonry structures especially the unreinforced one is their weak performance against quake. Different methods are use to analyse the seismic performance of this structures. The modern endurance time method is a kind of time history analysis using standard increasing accelerograms which examines different parameters of structure behavior during excitation actions. In this project we analyse these structures using... 

Compressors are one of the most important components of gas turbines and turbomachinery processes. Thus some precise and quick tools are needed for design and analysis purposes. Despite of vast development of Computational Fluid Dynamics (CFD) tools, Through-Flow Streamline Curvature Methods (SCM) has retained their position. 2D and quasi-3D forms of SCM in combination with CFD results nowadays make more than 80% of turbomachinery design process of axial and radial compressors and turbines. In this thesis, the basics of developing a tool for axial-flow compressor analysis are introduced. As will be seen, this analysis tool can be used for design purposes too. The method that is chosen for... 

Natural disasters, such as earthquakes and hurricanes, can strike without warning, resulting in a range of destruction from structural damage to loss of life. For this reason, research on structural control, which provides a new basis for design of structural systems against winds, earthquakes, waves, and traffic loadings, become of interest in civil engineering. This thesis focuses on using fluid dampers as a passive energy dissipation device. Viscous Fluid Dampers (VFD) are the most commonly used passive energy dissipation devices that are manufactured in various forms. However, the orifice type of Viscous Fluid Damper (VFD) is considered for structural applications. In this thesis, the... 

Effect of utilizing Central Beam Column (CBC) structure on shallow, large span underground spaces excavation is studied. The CBC method focuses on increasing the overall rigidity of tunnel supporting system prior to full face excavation, in which central drift excavation is limited to the dimensions of the central beam and column to reduce disturbances. Constructing the central beam and column structure, the excavation is completed with NATM excavation method in a symmetric manner about centerline. In CBC method on each side of the centerline there is an arch structure composed of the initial lining resting on roof beam on top and bottom beam at the invert. The roof and bottom beams take the... 

Since, seepage- related problems account for more than forty percents of earth dams’ failure, seepage analysis is one of the most important stages in designing of embankment dams. The most usual method of making a seepage analysis is doing a two dimensional one in the maximum cross- section and generalizing its results to the third dimension. As a natural consequence of this kind of seepage analysis, the effect of valley shape and material properties’ changes along the third dimension are ignored and so, in narrow valleys where the cross-section changes along longitude profile or in the specific cases of nonhomogeneity, using this kind of analysis can make false results. Besides, because of... 

For penalty detection and interpretation of sport match scenes (such as soccer), it is sometimes necessary to watch the scene from an arbitrary viewpoint captured by a virtual camera. In this research, we focus on 3D reconstruction of soccer players using videos that are captured from relatively far distance to the soccer field. In capturing videos from sport scenes, such as soccer scenes, an important issue is the problem of capturing videos from a wide environment to cover almost all parts of the field. Using many cameras with overlapped views might be an answer to this problem but it is impractical due to its cost for capturing and transmitting the data. Furthrmore, because of capturing... 

One major problem in sport match analysis and interpretation is that there are restricted viewpoints of the game. 3D reconstruction allows us to have virtual replay from any viewpoint so that the events such as penalties can be detected easily. For achieving this purpose, we use many cameras with overlapped views that cover almost all parts of the field. After some preprocessing, 3D reconstruction and texture mapping, we can enhance the viewer experience by having arbitrary viewpoint of the match. In this research, we use two different visual hull methods for 3D reconstruction. In the first method, the visual hull of an object is computed efficiently and robustly from image contours. This... 

The aim of this project is decentralized control of a group of robots (swarm robots); such that the aggregation maneuver, leader following, Identification and imaging the target, will be performed so good as to make a three-dimensional model of the target from these images. Swarm robots consist of a number of similar and limited features robots which interaction in a group of robots, will lead to special features for the group. Any agent of group decides what to do only with its local information from the environment. Swarm robots are more applicable for the jobs in which a distributed perception from the environments needed, for example space exploration and military operations.In this... 

Pipe freezing has become well established in industry as a method of short-termisolation in order to carry out maintenance or repairs. It is often necessary to repair system components without plant shutdown or drainage of system having many piping structures which may have hazardous or expensive fluid. Therefore, a series of tests has been arranged to investigate the ice plug formation in two standard pipes with different diameter size. The freeze zone on the pipe has been created by means of an aluminum jacket which liquid nitrogen flows in it. In the tests the freezing time, amount of liquid nitrogen usage andthe pressure tolerance of ice plug have been determined. Moreover, the numerical... 

Recently, due to the major need of the development of underground spaces in dense urban areas, excavating tunnels near to the earth surface is arising. Therefore, there is a possibility that the new tunnels drill and construct in the vicinity or along the available tunnels. Thus, the interaction mechanism of this tunnels on each other and on land subsidence should be taken into consideration. In this research using ABAQUS finite element analysis software the interactions of the cross road subway station of Bimeh-Mehrabad airport in the line 4 of the Tehran city subway lines which is excavated using multistage drilling method is investigated. This model includes Eastern, Western and a... 

Prediction of axial flow turbine’s performance with different operating conditions due to the high costs and lack of reliable empirical data is always under developing. In this type of turbine, fluid flow is three-dimensional, viscous and highly turbulent. Nowadays, although a relatively detailed picture of the flow field can be obtained by the computational and numerical tools, but using of appropriate loss models in one-dimensional modeling for the performance prediction as well as optimization of the turbine in initial design phases, is a common trend.
In the current study, aerodynamic losses in the axial flow turbine are investigated. Several loss models for the axial flow turbines... 

Deformation and Settlement of the ground surface and stability of large underground space is the main concern in the excavation under urban area. In order to control settlement and increase stability, it is necessary to use pre-Supporting system prior to excavation. Concrete Arc Pre-supporting System (CAPS) is one of the most useful pre-supporting methods which is used in exchange station of line 3 and 4 of Mashhad subway. Line 3 and 4 are parallel in Shohada square and the groundwater level is above the whole station structure. To analyze deformation of the ground due to excavation stages, the station was modeled in 2D and 3D by Abaqus. In this study, to estimate ground Deformation, we need... 

There are some problems in calculation of heavy and huge equations which are ill-posed and nonlinear. They need to be solved by the processors. The errors are important in our measurements because this precision is very important in calculation. The Block Method approach solving Forward Problem in Electrical Impedance Tomography (EIT) results produce an exact solution only if the measurements are done with enough accuracy. In this thesis, a 3D model of EIT with Block Method is implemented by means of Digital Signal Processor (DSP) to obtain exact results. In this work it has used a powerful processor called TMS320C6416DSK to reduce the measurement error in equations. It has used Code... 

In this study, the interaction of tunneling of line 2 of Mashhad metro and existing metro station (Shariati station) in line 1 has been investigated. To produce the stress and displacement which is caused by excavation of station, the process of station excavation has been modeled by method of cut and cover.This method is the common method for station construction at Shallow depth and is used in several cases in line 1 of Mashhad metro. The piled-raft system is used in foundation of central part of the station to reduce the settlements and the effects of interactions between the station and new tunnel. The new tunnel under the station is surrounded by two rows of lateral piles with distance... 

Axial-flow compressor is one of the most basic components of gas turbine engines. Consequently, it is essential to design this machine appropriately. Full three dimensional analyses of axial-flow compressors is time consuming due to the flow field complexity, so a method with minimum running time and producing an acceptable design is required. One dimensional design method is a low cost procedure with acceptable results for preliminary stages of design. It receives inlet flow conditions, such as total pressure ratio, mass flow and rotational speed and designs a compressor which satisfies the desired input data. Too many efforts have been accomplished to predict energy losses, design... 

In recent years, due to urban expansion and population growth, number of floors and excavations depth has increased. Stabilization of excavations is one of the most important issues in geotechnical engineering. Today, one of the most widely used methods that is used in deep excavations is brace soil by steels and pretension them. In this thesis tries to evaluate static behavior of flexible supporting structures with pretension anchors by using PLAXIS2D, FLAC3D and GEOSTUDIO softwares. The objective of this modeling is better understanding the static behavior of walls, comparing the two and three dimensional modeling and the effect of corners of excavation on deformation. The results shows... 

Sensibility of parameters that influence the Interaction between crossing tunnel at different level such as Soil charactristic, Construction procedure,Method of excavation,Rigidity of lining,Distance between tunnels and angle of intersection is studied. For comparison above parameters the surface settlement and bending moment during the excavation is measured .In order to simulate the Interaction between Crossing tunnels, use 3D finite element model with Abaqus program. The soil govern elasto-plastic mohr-coloumb constitutive equation.Parametric Analysis shows the great and different influence of each parameter that we can able to minimize this interaction with correct choose of this... 

In this thesis, we have derived the exact equations of motion for flexible beams. The derived equations are compared with similar equations reported in the literature, and they demonstrate significant power in prediction of the numerical results. The model for planar beams is verified by the performed experiments on carbon fiber rods. A new highly convergent, efficient technique which is quite fast is also developed for both approximating and controlling a system, entitled as fuzzy-Pade method. We then have studied effects of the wing flexibility on enhancing the lift and trust coefficients in the flapping flight. Aerodynamic force generation due to flapping is simulated for both the... 

Today, the global environmental restrictions as well as; energy problems have directed researchers toward developing ideas of producing a clean liquid fuel from coal or natural gas as a major research topic. In this regard, a special attention is paid to the dimethyl ether (DME) as a clean material containing 34.8% oxygen possessing enough positive potential to replace the diesel and LPG fuels. One of the most economic routes for producing the DME is known to be the direct conversion of the synthesis gases and carbon dioxide first to the methanol and then its dehydration to the DME. Moreover, the DME is not limited to a particular country or resource area since small reservoirs of natural...