Sharif Digital Repository

Considering the wide range of applications of porous media for heat transfer enhancement in various components of industrial machineries, including solar collectors, air dryers, compact heat exchangers, electronic microchips, investigation of heat transfer characteristics in porous media has been a major concern for many researchers. On the other hand, precise understanding of the physics of porous media-flow interaction has been an open research topic for a long time. The present research however, has aimed at developing a computational method to simulate the interaction between fluid flow and porous media to investigate heat transfer from prously covered surfaces. Pore scale modeling of... 

Train timetabling is one of the most important problems in the railway scheduling field. It concerns with determining the trians’ arrival and departure times to/from each station so that some constraints are satisfied and some objectives are met. The objective in this thesis is to minimize the summation of dwell times of all trains. The timetables which are offered in this thesis are periodic. It means that each event repeats after a period time. The events are arrivals and departures of trains to/ from stations. In this timetable, the praying constraint is considered as wellso that after Azan time, the train has to dwell in the first station which has enough place for praying. So an integer... 

Schiff bases are used as prevalent ligands in coordination chemistry and are prepared easily. Their application as mild inhibitory agents for prevention of various steel’s corrosion in acidic solution has been proved. When their structure is altered, multi-purpose application for them is found. This property has led to a motive for research and study. In this study, electronic properties of a group of Schiff bases are investigated. The goal of this study is using quantum mechanics (QM) as a tool for specifying electronic properties of some of these bases. With respect to QM calculation which is done by density functional theory (DFT), their properties as inhibitory agents are studied. First,... 

Rail track deterioration models are integral components of rail infrastructure maintenance management systems. In particular, track geometry defects are one of the leading causes of train accidents, and control, management, and modification of the track geometric conditions are among the most important tasks of railway maintenance management systems. Track geometry data such as profile, alignment, gauge, cross-level, and twist constantly change over time. Therefore, these features have the characteristics of time series data.In this study, a large database from outputs of EM120, a track recording machine, was provided for the years 2009 to 2020 and for all 19 railway zones of Iranian... 

The process of human populations growth, limited resources of fossil fuels and its environmental consequences have driven the international community to Renewable Energy. Microbial fuel cell (MFC) has ability of simultaneous wastewater treatment and electricity generation (Energy). This technology can be considered as one of the proposed solutions to reduce costs of wastewater treatment and power generation. Separators are one of the major components of the MFC that have direct impact on cell performance. On the other hand, high costs of the conventional types have caused to limiting development of the MFC in the last decade.
In this study, inexpensive and available glass wool membrane... 

In the framework of surface elasticity theory, the scattering of in-plane elastic waves by a multicoated nanofiber embedded in an elastic matrix is studied. Atoms near an interface experience a local environment different from it within the bulk. Going from macro to nano dimensions, surface to volume ratio increases significantly. Thus, on this scale it is important to consider the surface/interface properties as well as the bulk properties. In this dissertation, the surface/interface is modeled by a very thin layer in which the traction and displacement are discontinuous. Effects of surface/interface parameters on the dynamic stress concentration factor (DSCF) and scattering cross section... 

Nitrate can be used as an oxidant in a cathode chamber of microbial fuel cell. Nitrate is known to be a pollutant of water particularly underground water and is considered a carcinogen of water. Nitrate was used in the cathode chamber of a microbial fuel cell as an oxidant that lead to simultaneous generation of electricity, removal of organic matter in anode, and removal of nitrate in the cathode. Using nitrate generated a voltage of 151 mV with an external resistance of 1000Ω. The maximum power density achieved was 1.375 mW/m2 with an external resistance of 800Ω. Seven days after the cell became operational and without the presence of a catalyst, the amount of COD had decreased by 25... 

Society is becoming increasingly dependent on computer systems, raising a somewhat neglected but vital question: Are these systems as safe as we think they are? To address this concern, many approaches have emerged alongside the testing process to enhance the reliability of our systems. One of the most successful approaches involves viewing computer systems as mathematical objects and making assertions about their intended behavior. Formal verification is the act of attempting to establish the truth of these statements and ensure the safe behavior of the system. Model Checking is a mainstream formal verification technique that has proven its usability in verifying complex software and...