Sharif Digital Repository

Demand for high performance components has caused a propensity towards high strength alloys, especially 7000 series, having extended applications in aerospace, automotive and medical industries. Due to high strength, heat treatability, and optimum weight, these alloys have been implemented in various conditions, specifically AA7075, being directly used in airframes. Through the years, numerous attempts have been made to improve the corrosion and formability properties of these alloys, resulting in the development of various tempering methods such as retrogression and re-ageing. Despite achiving optimal properties, it has been of less interest through literature to assess the formability of... 

In nuclear power plants, the fission reaction takes place inside the fuel rods, and the heat generated inside the fuel rods is transferred through the clad wall to the cooling fluid, which is single-phase, subcooled and in the turbulence zone. In the hot channel of the reactor core, where the axial and radial heat flux reaches its maximum state, the fluid leaves the single-phase state and some steam is formed in the area close to the clad wall.Therefore, in some cases, in the hot channel, the steam near the clad wall may reach a point that reduces the heat transfer coefficient, rapidly increases the wall temperature and thus destroys or melts the sheath surface. If this happens, it means... 

According to the growing population and the need to make optimal use of available resources, the discussion of planning and scheduling in healthcare will be useful. One of the most expensive and lucrative sections in a hospital, which always spends a large percentage of renewable and non-renewable resources, is the Operating rooms (ORs). These ORs are the most important part of the hospital in terms of health and financial issues. In these scheduling problems, in order to be able to model the real situation, we needed to consider the recovery section integrated with the ORs. Also, the duration of surgery and stay in the recovery rooms are considered stochastic. In this study, we solve the... 

Nowadays, with progresses made in manufacturing technologies, it is possible to produce micro-scale products such as micro-electromechanical systems. Micro-motors are one type of these systems that can be used in such applications as power supply of electronic devices. To achieve a better performance, these systems must rotate at high rotational speeds (about one million revolutions per minute). At such a high rotational speed, vibrational analysis is highly crucial. The results of recent studies indicate the inability of classical theories of continuum mechanics to analyze the behavior of these micro systems. Therefore, in this research, the rotor of micro-motors are modeled using the... 

Aluminum alloys have became one of the most important metals in industries because of its good corrosion resistance and good machinability and high strength to weight ratio. But its properties are still in need to be improved for essentials affairs.in previous researches the effect of various factors before, between and after the multidirectional forging process has been investigated. But there is a gap between the effect of the isothermal final annealing and the effects of heating time between these studies. In this research the main focus is on microstructure improvement using severe plastic deformation and final annealing. First specimen deforms by 4pass of multi directional forging then... 

In this study, based on Households Income and Expenditure Survey (HIES) data, we examined the socio-economic characteristics and transition of Iranian urban households in each of the three different income groups from 1997 to 2020. Moreover, factors affecting entry to poverty or persistence in poverty in Iranian urban households are discussed.The results of this study show that, contrary to popular belief, there is no evidence of accumulation of entrepreneurs and business owners in the urban middle class. Rather, middle-income households have higher-skilled jobs and pay more for social security than low-income ones, as well as pay more attention to investing in human capitals (education and... 

The aim of this study is to investigate the feasibility of in-situ stabilization of collapsible soil using grouting. Collapsible soils are a type of problematic soils that are found mostly in arid and semi-arid regions. Loess is stable in its natural unsaturated state, but when it is inundated under a sufficient stress, it will suffer a severe volume reduction due to reduction in matric suction and dissolution of its cementious bonds in water. So, finding a method for in situe remmediation of such a soil is very important especially for the built environments. The collapsible soil used in this study is a loessial soil sampled from the northeast of Golestan province, Iran. The undisturbed... 

Shear modulus and damping ratio are the most important parameters for evaluating the performance of geotechnical systems under seismic and dynamic loads. According to the definition, secant shear modulus is the slope of the hysteresis shear stress-shear strain loop and damping ratio indicates the dissipation of wave energy during propagation in the soil. These parameters depend on stress state, shear strain and void ratio of the soil. Shear strain amplitude has an important effect on the behavior of shear modulus and damping ratio and it is necessary to study the behavior of these parameters in the range of small to large strains. In addition to dynamic loading, climate change and wet and... 

The use of stepped weirs dates back at least 3500 years. In this research, the hydrodynamics of gabion stepped weirs have been investigated as a three-dimensional simulation of two-phase flow air-water using Flow3D software and the method of computational fluid dynamics (CFD) analysis. In order to solve the Reynolds-Averaged Navier-Stokes (RANS) equations, the RNG turbulence model (k-ε) was used and the free surface elevation of fluid was determined by the volume of fluid (VOF) method. The experimental results of Wutrish and Chanson (2014) over gabion stepped weirs are used to validate the numerical model simulations. Gabion stepped weirs with steps of 3, 7.5, and 10 cm in height, as well as... 

Lateral spreading is the downstream movement of mild slopes or free fronts occurring due to soil liquefaction during a dynamic loading such as an earthquake. The magnitude of this movement can be from a few centimeters to tens of meters depending on parameters such as slope length, soil type, cyclic loading intensity, etc. Large displacements caused by this phenomenon can cause severe damage to some structures and infrastructures located in the direction of their movement. Numerous articles and reports of damage caused by the lateral spreading of soil have been presented during several earthquakes. Understanding this phenomenon and observing and testing its effective parameters can help... 

In this project, a convolutional neural network is trained to classify Persian handwritten digits and different neural network models are compared for this problem. To train and evaluate this network, the "HODA" data set has been used, which includes 80,000 images of Persian handwritten digits, including 60,000 images of training data and 20,000 images of test data. In the modeling section, we have used a comparison of recent top architectures of convolutional neural networks to identify Persian and English handwritten numbers. In this experiment, the Tensorflow library in the Python programming language was used. Parameter values and network hyper parameters are obtained from the values... 

In the area of material studies, the atom structure models are the basis of all simulations and methods. With improvements in computers power, these models have become more consistent with experimental results. New theoretical methods combined with supercomputers assist to an understanding with detail and accuracy of material behavior at the atomic scale that leads to develop of the Computational Materials Science. Recently, developments in fields such as quantum mechanics, statistical physics, solid-state physics, quantum chemistry, computer science and graphics, allowed for faster computing which leads a powerful tool for material calculations and designs. New computer applications allow... 

One of the most common applications of multi-unit auctions is the energy markets, including the electricity markets. In this study, using the simulation of a uniform price wholesale electricity market, the effects of the price ceiling on the behavior of power plants and market clearing prices have been investigated. The results show that the implication of price ceilings causes power plants to reduce the slope of their bidding function near the ceiling price, and as a result, the market-clearing price decreases compared to the previous state in the absence of the price ceiling. It was also observed that the higher the probability of reaching the price ceiling (higher total demand), the more... 

So far, a lot of research has been done on the hot behavior of different alloys; These studies have generally been performed using tensile, compression and torsion tests and isothermal conditions, which have greatly contributed to the understanding of the mechanisms of deformation at high temperatures. Due to the fact that in real deformation processes, it is less common for the material to experience isothermal conditions during deformation, so in this project, the aim is to investigate the behavior of 2024 aluminum-alloy in non-isothermal hot compression test. In this regard, non-isothermal hot pressure test was performed from 300℃ to 600℃ و temperature range and at different deformation... 

Inverse reinforcement learning (IRL) is one of the machine learning frameworks based on learning from humans; That is, instead of producing a decision process maximizing a predefined reward function, seeks to find the reward function based on the observed behavior of an agent. The biggest motivation of IRL is that, usually, determining a reward function for a problem is very difficult. We consider IRL in Markov decision processes; that is, the problem of extracting a reward function with the assumption of knowing the optimal behavior. IRL could be useful for apprenticeship learning to obtain skilled behavior, and for optimizing a reward function by a natural system. We first, determine a set... 

Digital analysis of reservoir rocks prepares a powerful tool in the field of porous media studies and provides appropriate information of single / multiphase flows by performing numerical simulations on porous media images. In order to access the necessary tools to benefit from digital rock analysis and characterization, we need accessing the porous media images, the geometric distribution and the spatial distribution of pores and grains through imaging or reconstruction methods. Porous media reconstruction methods are known as an alternative to imaging techniques. In addition, reconstruction methods have the ability to fix problems and imperfections associated with imaging, such as... 

During the production of crude oil from reservoirs, the production of quantities of formation water along with this oil, causes the crude oil does not have the necessary indicators for transportation, refining and ultimately export. The presence of water and salt along with crude oil causes corrosion of refinery and transmission equipment and makes oil unfavorable in terms of economic efficiency (both for domestic use and for export). water and salt produce stable emulsion with oil that can be stable for a long time and can not be easily separated from crude oil. Therefore, separation of water and salt from crude oil is one of the most important issues in the oil industry. Breaking this... 

Severe plastic deformation (SPD) is an ideal approach to fabricate light-weight alloys, such as aluminum alloys, with ultrafine-grained (UFG) structure up to nano-scale. Thus, it is known as a process that boosts the strength of materials. This method is also adopted to enhance the specific strength of materials, which is essential in the transportation and aerospace industries. Because of limitations like load capacity, and as a result, low-size productions, it is not possible to use them in industries. A practical solution is to join the productions and fabricate them on bigger scales. Welding of SPDed materials by employing solid-state welding techniques is appropriate for joining UFG... 

Earth and rockfill dams are enormous three-dimensional structures constructed from earth and rockfill materials. They are mainly built for water supply, agricultural land irrigation, electricity generation, and flood control. Earthquake is one of the most significant natural hazards affecting the stability of these dams. Nowadays, with the development of computers and software, the seismic behavior of most dams are assessed by dynamic analysis. In a considerable part of technical literature, dynamic analysis of earth and rockfill dams have been performed by applying only the horizontal component of the earthquakes, and the effects of vertical component of the earthquakes have often been... 

Karun 4 arch concrete dam with a height of 230 meters is designed and built in one of the most complex natural places. Therefore, monitoring the behavior and evaluating the safety and stability of this dam, both with regard to the height and nature of the dam itself and with regard to its national and international dimensions, is of special importance and sensitivity. This sensitivity is doubled due to some problems and issues encountered in the body of the Karun 4 dam, which of course are considered probable and possible phenomena in arch concrete dams. The Karun 4 Dam construction site is located in the southwest of Iran on the Karun River, immediately upstream of the Karun 3 Dam reservoir...