Sharif Digital Repository

Low carbon steel is widely used in the automotive industry by improving ductility and minimizing hardness to achieve greater strain. Applying severe plastic deformation to metals and alloys increases strength and decreases ductility. In the process of severe plastic deformation, the pressure is limited in the grooved form. Low carbon steel, after two passes of severe plastic deformation, experiences a rapid drop in strength in addition to ductility, which may indicate the presence of microcracks. Therefore, in this research, annealing between passes during the pressure process in the form of limited grooves has been used so that without a serious decrease in strength, some ductility... 

Microfluidic technology is a field of science that deals with the design, implementation, optimization, and testing of fluid systems in small dimensions. This technology has made significant progress in various fields in the last decade, especially in medical engineering. As an interdisciplinary scientific field, this growing technology has many applications in medicine, pharmaceuticals, chemistry, and electronic industries. One of the primary applications of microfluidic devices is the development of "lab-on-a-chip" systems as point-of-care diagnostic tools, such as rapid diagnosis during surgery. A microfluidic system includes various functional modules: sample preparation and fluid... 

In this research, a Reusable Flexible Launch Vehicle (RFLV) design problem is presented by Multi-Disciplinary Design Optimization (MDO) approach in primary design phase. Trajectory, structure, aerodynamic, aeroelasticity and thermal protection system are considered as involved disciplines in design problem. The study purpose will be to obtain an optimal trajectory which meets all the control and structure limitation while the estimating body skin and thermal protection thicknesses base on structural evaluating in re-entry trajectory is in process. The flexible launch vehicle body is considered as a free-free Bernoulli-Euler beam and D’alembert’s principle addresses inertia force in static... 

Bridges play a vital role in road-related transport industries. Significant changes to contemporary bridge design specifications have also been mainly related to strength issues. The transitions from allowable stress design to load factor design, and more recently to load and resistance factor design (LRFD), reflect this line of thinking. It is important to note that in the early 1970s, bridge engineers developed criteria for steel bridge details to protect against fatigue and fracture failure. These were indeed service life design provisions. By industry growth and extensive need for goods transportation, there is a need for the construction of new bridges and renewal of older bridges plus... 

In recent years, various research has been done on the severe deformation of low carbon steel sheets. One of the methods used is the pressing in the grooved die, only two passes of the pressing process in the grooved mold have been successful when applied to these sheets, but on the other hand, these two passes also lessen the sheet's ductility while increasing its strength. Due to the fact that the sheet surface produced by the pressing in the grooved die is not entirely smooth, the attempt in this project was to improve the ductility to some extent using warm rolling in addition to the smoothness of the surface using higher temperature while improving the strength or maintain it. To... 

The Emergency Department is one of the most important departments in a hospital, which is continuously active and plays a crucial role in saving patients' lives. For this reason, using research methods in operations and optimization can greatly help improve the performance of the Emergency Department. In this thesis, the emergency scheduling problem is examined with the objective function of minimizing the total weighted sum of job completion times, considering the random nature of service times. Since the objective function of the problem is to minimize the total job completion time, the job completion time is obtained as the sum of several random variables. Considering the additivity... 

The goal of this research is to study the effect of local microcracking due to step by step pressure loading on the durability properties of geopolymer concrete. To better understand the behavior of GGBS-based GPC under different pressure stress levels, some experiments such as water permeability and water absorption conducted on the samples at each state of damage. Also, non-destructive tests such as ultrasonic waveform and pulse velocity (UPV) was used to quantify the extent of damage at each step. GGBFS and a blend of sodium silicate solution and 10 molar sodium hydroxide solution with SSSH⁄ ratio of 2 were used for production of GPC samples. GPC, OGPC and OPC samples with water to binder... 

There are several case history records of liquefaction in gravelly layers with more broadly-graded particles than uniform sands which have been typically examined. Liquified deposits, in many cases, were subjected to initial static shear stress associated with the sloping ground condition or the adjacent shallow foundations prior to liquefaction. There are several graphs and recommendations for practitioners to consider the effects of the initial static shear stress on liquefaction resistance in design processes, developed based on the results of experiments on uniform clean sands. However, data for the effect of the initial static shear stress on the liquefaction strength of gravelly soils... 

Corneal keratoconus is one of the common eye diseases that usually occurs in the teenage years or the beginning of the third decade of life. In this disease, the cornea thins and loses its original shape and becomes conical. To treat this disease, ophthalmologists use different methods such as using glasses, contact lenses (hard and soft), corneal transplantation, and also corneal cross-linking, each of these methods has limitations, on the other hand, considering that The disease progresses and its severity increases, Ophthalmologists use corneal rings to treat this disease in more advanced stages, implanting a suitable ring in the patient's cornea both increases the strength of the... 

Shear modulus and damping ratio are the most important parameters for evaluating and designing the performance of geotechnical systems under dynamic loads. According to the definition, the secant shear modulus is the slope of the hysteresis shear stress-shear strain loop. Also, the damping ratio indicates the dissipation of wave energy during propagation in the soil. This research presents an experimental laboratory study on the effect of non-plastic fines content and hydraulic hysteresis on the Gmax of unsaturated sand-silt mixtures. A significant part of the previous research has been done to determine Shear modulus and damping ratio parameters. It has been done in completely saturated or... 

Landslides, like earthquakes, floods, and volcanoes, are important natural disasters that occur frequently in the mountainous and high regions of our country, especially in the Alborz and Zagros regions, which induce considerable damages. Various factors such as topography, lithology, weather conditions, hydrology, tectonics, earthquakes, and various human activities are effective factors in the instability of natural and man-made slopes. Not one factor can cause instability in slops, however, a combination of the named factors may cause landslides. Therefore, knowing the factors affecting the occurrence of landslides and identifying different areas in terms of sensitivity to their... 

Additive manufacturing enables fabricating lattice structures with tailored mechanical responses based on lattice materials. Full exploitation of such a possibility requires reliable and efficient mechanical analysis tools to be explored by topology optimization algorithms for designing the interior architecture of the structures to meet the desired mechanical behavior. However, detailed mechanical analysis of lattice-based structures using the conventional finite element approach is prohibitively expensive due to lattices’ complex and fine features that demand adopting very fine space discretization. As an alternative, equivalent models based on the homogenization principle have widely been... 

We examined the Phase-Type distribution to calculate project activity duration and solve the resource constraint project scheduling problem with non-deterministic activity duration through meta-heuristic techniques. The activity usually doesn't have a fixed duration. The problem is caused by numerous factors that exist when carrying out a project, such as a lack of resources, late delivery of resources, and mistakes made by people. The literature review revealed that the scheduling problem had been thoroughly researched. The more accurate and realistic the activity duration estimates, the better the project planning and cost control. For this purpose, in this research, the duration of the... 

Many researches have been done on the severe plastic deformation of 2024 aluminum alloy, but there is limited information on the effect of severe plastic deformation for this alloy in the over-aged condition. In this study, the effect of severe plastic deformation and annealing heat treatment on the microstructure and strength of the over-aged AA2024 has been investigated. 1, 3, 5 and 7 two-dimensional multi-directional forging passes carried out to the over-aged samples at room temperature as one of the methods of severe plastic deformation process. After applying strain, samples were subjected to annealing heat treatment at 200, 300 and 400 °C for 30 minutes and then quenched in water. For... 

Many of oil reservoirs in Iran that are fractured, do not have high Recovery Factor (RF), therefor Enhanced Oil Recovery (EOR) methods are exerted in them. In fractured reservoirs, due to high capillary pressure in matrix and low amount of it in fracture, the wetting phase tends to imbibe to the matrix from the fracture. Altering the wettability of reservoir rock from Oil-Wet (OW) to Water-Wet (WW) enables the injected water to imbibe to matrix and sweep its oil. Also reducing oil/water IFT turns oil to small droplets, helps them to pass narrow pores and be produced. In one of the new EOR methods called chemical EOR, chemical additives are injected to the reservoirs along with water to... 

Determining the time of breakthrough of injected water is important when assessing waterflood in an oil reservoir. Breakthrough time distribution for a passive tracer (for example water) in percolation porous media (near the percolation threshold) gives insights into the dynamic behavior of flow in geometrically complex systems. However, the application of such distribution to realistic two-phase displacements can be done based on scaling of all parameters. Here, we propose two new approaches for scaling of breakthrough time (characteristic times) in two-dimensional flow through percolation porous media. The first is based on the flow geometry, and the second uses the flow parameters of a... 

Nowadays, due to advancements in technology and processing power, earthquake engineering is moving toward more realistic modeling of actual problems in different fronts. In the case of considering seismic waves for design and analysis of concrete dams, numerous challenges exists due to complex nature of the problem which have absorbed abundant attention from a number of researchers around the world. In recent studies about earthquake input mechanisms, accounting for true nature of the foundation and applied earthquake have been hot topics. Therefore, in this thesis, thorough investigation on these effective factors in dynamic analysis of concrete dams is performed.In the first part of this... 

Sensors are one of the most vital instruments in Nuclear Power Plants (NPP), and operators and safety systems monitor various parts of the NPP and control transients by analyzing the values reported by the sensors. Failure to detect malfunctions or anomalies in them would lead to catastrophic consequences. A new approach based on thermo-hydraulic simulation by RELAP5 code and Feed-Forward Neural Networks (FFNN) is given to detect faulty sensors and estimate their correct value which are two main objectives of the current study. This approach consists of two main parts; The first part, Fault Detection Hyper Block (FDHB), responsible for detecting faulty sensors, and the second part,... 

The widespread use of nuclear energy leads to obtain detailed information, such as neutron flux distribution (power) which is very effective in designing and evaluating the reactor safety. The neutron flux (power) reconstruction method uses the homogeneous flux distribution and the heterogeneous form function in a fuel assembly to calculate the heterogeneous power in the fuel rods. Therefore, this method has been widely developed in the last two decades. This study investigates to calculate two-dimensional and two-group neutron flux (power) in the fuel rod for both quadrilateral and hexagonal geometry related to core results by using nodal method. To achieve a more complete program and join... 

Cardiovascular diseases are one of the leading causes of death in the world. Identifying the mechanical behavior of arteries and their growth and remodeling under applied loadings can help to better understand the progression of the disease and provide more effective clinical interventions. Therefore, many researchers in recent decades have turned their attention to modeling the process of stress-mediated growth and remodeling in soft tissues. Among the most important models proposed to study this process are the constrained mixture model proposed by Humphrey et al. and the volumetric growth model proposed by Hoger et al.. The constrained mixture model is based on the continuous turnover of...