Sharif Digital Repository

Due to growth of the number of passengers in subway transportation systemsthe capacity of the metro stations are on the rise.The generated heat loads in subway line shall be increased by thegrowth of the its capacity. As a result, current subway ventilation systems cannot provide comfort conditions for passengers. Nowadays, modern ventilation systems are designedto improve ventilation performance and to create suitable thermal conditions. Among of these, the under platform andover track exhaust systems and use of platform screen doors can be Cited. The aim of this study is three-dimensional simulation of air flow in modern ventilation systems of subway stations. Numerical simulations are in... 

Ionization chamber is used in radiotherapy for to get precise information from amount activity of radionuclide. Ionization chamber filled with Argon is used to measure the activity of brachytherapy radionuclide. This device measures the activity according to the produced current by the incident radiation. In order to obtain the precise activity of the radionuclide, it is necessary to the precise amount of the device calibration factor which relates the amount of the produced current to the activity. Because of little access to standard radionuclide and for appointing the activity of unknown samples, ionization chamber calibration is done indirectly and with the help of the simulation of the... 

In the industry, there are nonlinear processes that can not be controlled with classical methods. Also, there are many processes that are more than one controlled variable that with classical methods, the design of a multiple input - multiple output controler is very difficult for them as well as the constraints on the inputs and outputs of the process exist, using classical controllers will be far more difficult. A model-based predictive control method for controlling nonlinear processes is useful in addition to having very high efficiency, extended to multi-mode interference together with constraints on the control variables and other controlled Problem with dynamic properties such as... 

Incline in the population and civilization, development of agriculture, and expansion of industries, in addition to limitations on surface and groundwater resources necessitate the existence of correct and efficient planning of management and utilization of water resources. Prediction of behavioral models of changes in water resources systems, influenced by utilizing strategies, absolutely helps stakeholders for conservative development of these resources. System dynamics is an object oriented method that is based on system's feedback. Not only it gives real description of complex systems, but also it provides the ability to influence effectively in development of the model for the user. The... 

It is common to inject gas in naturally fractured reservoirs to maintain the reservoir pressure. Recovery will be the result of the complex interplay of several mechanisms such as viscous flow, extraction by molecular diffusion, gravity drainage, oil swelling and capillary force. Generally the main mechanism is gravity drainage However in many cases like low permeability of matrix, small matrix block size and high capillary pressure; gravity drainage may be very low or ineffective. Low permeability results inefficient viscous displacement too. Therefore in these cases the main mechanism is diffusion. The parameters influences the diffusion are: The nature of the injected gas, the composition... 

Necessity of a public transport network, environmental protection and a highly land cost in urban areas have increased the desire for underground transportation systems. On the other hand, ventilation system design should be done precisely specially for longer tunnels, large undergrounds spaces and crowded places. Rate of energy reduction for vent systems operation is dependent on their proper implementation. Tunnel design efficiently is influenced by ventilation system. The tunnel mid shaft is complementary part of the underground railway systems that is required for exchange air between the tunnel and the railway station with ambient fresh air. An important application of the tunnel mid... 

Nowadays, computer simulations have an important role in the investigation of the thermal performance of the systems. In this thesis, a software program was developed for simulation of cooling system of an ER24PC Locomotive diesel engine. For this purpose, the C + + programming language is applied. One of the most important components in the cooling system is the radiator. In order to model the radiator, a relationship must be used to determine the heat transfer coefficient for coolant side and air side of the radiator. This relationship can be based on experimental, analytical, or numerical solutions. Offset strip fins are used in radiator of ER24PC locomotives. With application of... 

One of the main applications of revenue management is in healthcare industry. By combining these two concepts, subjects such as patient allocation and scheduling and no-show rates were developed in the literature. Up until now, allocation and scheduling were considered separately in the literature. Also, no-show rates were predicted using regression models and data mining tools and these predictions were rarely used in scheduling systems. In this thesis, we combined allocation based on patients’ insurance type with scheduling based on patients’ no-show rates. Also, patients’ no-show rates were predicted and these rates were used in the proposed scheduling model. Firstly, the integrated... 

Power Amplifiers are key components in new modern communication systems such as space and airborne applications, point to point networks and phase array modules. There are miscellaneous challenges in designing power amplifiers based on application and type of the system; high power, gain, bandwidth, linearity, efficiency, reliability, cost and size. Compromising among existence trade-offs is the state of the art for designing PAs. Meanwhile, technology improvements pay the way toward developing appropriate process in the realm of cost, cut-off frequency, voltage breakdown, thermal and reliance features. Throughout this thesis, challenges in designing high power amplifiers in the pHEMT GaAs... 

Polyethylene terephthalate (PET) is known as the most important polyester in the world. This polymer is the raw material for synthetic fibers, films and plastic objects and widely used in textiles and food industry. In this project transesterification and polycondensation reactors of a semi-batch process with dimethyl terephthalate/ethylene glycol feedare simulated. First simulations areperformed for reactors in the laboratory scale.Then the reactors are scaled up to industrial scale in order to produce 100 tons per year of PET product. The optimal temperature trajectory for the fisrt reactor is obtained based on a performance index. This performance index includes the reaction time and... 

Fluidized bed spray granulation is an important powder production process with several key advantages compared to other powder production processes, such as spray drying. Moreover, in fluidized bed granulators, whole process takes place in just one apparatus and there is no need to side processing. Most important characteristics and essential part of fluidized bed granulation is the wetting of primary particles by atomized liquid binder to coating the primary particles and producing granules. To date, a lot of research has focused on modeling and understanding of the separate particle growth mechanisms which have been integrated into the population balance models. Although, these concepts... 

In this thesis we propose a new metamodel based simulation optimization algorithm using sequential design of experiments. The main objective is to have a new method which can be used without deep knowledge of different kinds of metamodels, optimization techniques and design of experiments. The method uses three metamodels simulataneously and gradually adapts to the best metamodel. In each iteration, some points are chosen as candidates for future simulation. These points are ranked based on the quality of metamodel prediction and their placement among simulated points, the best point will be chosen for simulation. Comparing the proposed algorithm with some of the popular simulation... 

Because of the importance of gas-solid fluidized beds in chemical industrial plants, many experimental and modeling efforts have been conducted the prediction of their behaviors up to now. Gas bubbles have a pivotal role in the hydrodynamics of bubbling gas-solid fluidized beds; so, fundamental understanding of the bubbling behavior of fluidized beds is required to describe bubble-related phenomena such as solids mixing and segregation, reaction conversion, heat and mass transfer, erosion of heat-transfer tubes and particle entrainment. In this work, the effects of different parameters such as bed aspect ratio, bed width, superficial gas velocity, and particle size distribution on the... 

In the building, can be used variaty of Heating, Ventilating and Air conditioning systems. Among the items that affect to select the hvac system can be pointed to building thermal demand and system energy consumpsion. simulation of this systems is one of the ways that can compare hvac systems in the building. according to Iran needs for preparation of software for optimization of energy carriers consumption in building proportional with existing matrials and equipment in the country, in this research has been tried methodology and modeling of hvac systems in the way developed that producted software is capable simply and practical for engineers be operational in a residential unit. In realy... 

This research studies multi-objective master production schedule (MPS) and advanced order commitment (AOC) in two-stage supply chains. Simulation-based experimental analysis evaluates the impact of environmental and MPS design factors on schedule cost and instability. The results provide insight into multi-objective MPS design considerations through rolling schedule policies. The study reveals that the manufacturer's production smoothness utility coefficient and its interaction with other experimental factors considerably impact the system's performance. In addition, it introduces a simulation framework with embedded mixed integer programming models that could be used as a framework for... 

This project related to gas purification according to difference in the deposition point in the fludized bed.The reason for choosing fluidized bed is increasing erosion on wall of bed & increasing on heat transfer compared to other heat exchangers.Separation process, by cooling the wall causes the self- deposition gas phase shifts to solid phase. Solid formed on the wall, act as an insulating layer and greatly reduces the heat transfer therefore part of vessel not used. To solve this problem, the fluidized bed system is offered because the fluid particles can remove the insulating layer beside improving convection heat transfer coefficient. In this work we studied the quantative of erosion... 

One of the most important factors of reducing durability of concrete structures is corrosion of steel reinforcement in concrete. In this paper, corrosion behavior of reinforcing steel in concrete is investigated in two different methods of protection based on neural network. As regard the first method, pozzolanic additives with optimized percentage were added to Concrete mix design (the percentage of these additives are 25% Weight of cement of fly ash, Micro silica with 10 percent of weight of cement and 25% of Blast Furnace slag weight of cement). In the second approach of protection, 0/5 percent weight of cement of ferrogard 901 inhibitor is added to basic mix concrete design and the... 

Servo hydraulic pumps are being utilized in hydraulic circuits to prevent hydraulic oil reaching high temperatures in result of relief valve’s functions. In this study, we focus on modeling and sensitivity analysis of a pump of this kind. At first the importance of the current study and some of related studies has been discussed and some of the appropriate results has been represented. Then by employing CFD and Fluent code, the flow around servo valve of pump has been simulated, and operational curve of the valve has been calculated. This curve has been verified by results of the experimental set. At the next stage of the study, by modeling Dynamic parts of the pump in SIMULINK software and... 

Turbojet engine combustors play a key role to convert energy with very high rates. To reach this goal, the combustor must satisfy many conflicting requirements. Complexity of the flow field inside the combustormakes the 2D or 3D analysis very difficult. In this thesis, a quasi one-dimensional software is developed applying empirical and analytical 1D relations. Using data for a mini-turbojet engine, the range of some important design parameters is extracted and then a new combustor is designed using both velocity and pressure loss methods. Different disigns are investigated and are compared by employing an extended version of the simulation software. Due to the unacceptable performance... 

The present study aimed to investigate the effects of old and young oxide films on the mechanical properties and reliability of Cast Al A356.2 alloy. The results indicate that the presence of oxides within the microstructure of the alloy decreased the tensile properties of the alloy and increased their scattering. Beside this, the presence of the oxides decreased the reliability of the alloy. The results showed that the presence of double oxide films (especially old oxides) decreased the Weibull modulus of tensile properties and resulted in bi-Weibull distribution in tensile properties of the alloy. The results also indicate that using of a clean melt (with high quality), is vital for...