Sharif Digital Repository

Fatigue crack growth can have harmful effects on the reliability rotary machine. While an early warning to crack, can be used to extend the life of these expensive machines and increase reliability.Structural Vibration Condition Monitoring as a primary fault detection method, achieved to a lot amazing result and for this reason studies vibration behavior of cracked rotational shaft is a big issue for engineers of dynamic machine.In this research, first check the fault detection methods based on structural vibration condition monitoring, mode shape methods were extracted. Then by modeling rotational shaft in computer and creation of crack on it, fault detection quality of these methods have... 

The utilization of wind power has been increasing in recent years which lead to enhance the the usage of wind power capacity in the range of MegaWatt. However, due to the limitation ofswitching devices capacity, which exists in power electronic converters, improving the capacity of wind power generation is not accessible. Thus, a feasible solution for this problem is paralleling power electronics converters, which increases both the capacity of power generation and the reliability of wind turbine systems. Nevertheless, paralleling converters may cause a circulating-current which brings current discrepancy, current waveform distortion, power losses, increase in THD of currents, and reduction... 

Cooperative coexistence of two kinds of users with different priorities in random access wireless networks has been studied in this thesis. Source burstiness, a phenomenon in data communication networks, allows using silence periods of primary users (PUs) to have a better spectrum utilization. In this respect, new users, known as secondary users (SUs), are considered to exploit the resources opportunistically. In usual spectrum sharing systems, SUs have to act in a way to be transparent for the PUs. Therefore, they are allowed to access the common spectrum band only when PUs are silent. However, seeking such opportunities needs sensing capability of secondary nodes.In this thesis, sensing... 

Predicting the trend of stock prices is always one of the concerns that stock market analysts and investors face with, which plays a critical role in maximizing the profit from investing in stocks. Past stock price charts, raw material prices, the value of the company's assets, the impact of global markets, the company's products, the organization's development plans, and the same other factors influencing the stock price. News reports are an important source of information for people. Recently, a lot of research has been done to examine the impact of news on stock price trends. This research has two research phases. In the first phase, a text mining method is presented which is using... 

Network coding, as a promising method for data exchange in wireless communication network, is investigated by many researchers. However, the random nature of packet generation and transmission as well as the collision among transmitted packets have not been fully addressed in network codingrelated literature. In this dissertation, we analyze the network coding-based wireless network from this point of view. In order to achieve this goal, we apply mathematical tools such as probability theory and queuing theory. In the first part of this dissertation, we address the interaction between MAC and network coding. In this respect, we consider a multihop tandem wireless network, where each node is... 

The low female labor force participation rate in the Iranian labor market relative to the global average and even to countries that do not differ significantly from the socio-economic characteristics of our country is one of the important questions of the Iranian labor market. In this study, we seek to answer the question of whether the economic participation rate of married women will increase if the gender gaps in wages, job findings and job losses among women and men are eliminated in the Iranian labor market. To answer this question using household expenditure and income data and labor force data, we show that between the two categories of occupations, in terms of the share of women's... 

In this dissertation we discuss various results presented in the literature on single user channels with causal or noncausal side information and multiuser channels with side information such as multiple access channel and broadcast channel. The Series Relay Networks (SRN) with delays, with and without channel state information (CSI) are investigated from an information theoretic point of view. For SRN with unlimited look ahead where the relays can use the whole received block to encode, upper and lower bounds on the capacity are derived which are tight for the degraded case. For SRN without-delay where the relays have access to the present received symbols in addition to the past symbols,... 

Sensitive ecosystem and scarcity of freshwater are the main characteristics of small islands. These islands have small catchments and usually lack tangible surface water resources. As a result these islands are dependent almost entirely on groundwater. Groundwater on small islands usually occurs in the form of a freshwater lens floating on the more dense saline water. The freshwater lens is highly sensitive to various stresses such as drought, pumping, sea tide, etc. Due to the importance of freshwater lens in islands, proper and optimal use of this vital resource should be studied. Kish island`s freshwater lens was three dimensionally simulated using the numerical model SUTRA. The aim was... 

Nowadays, with a constant increase in life expectancy, joints pain and deficiencies have become a major problem and the use of prosthesis is increasing. One of the most important joint in human body is the hip joint which bear a major share of forces in daily activities. Hip joint is a cup-sphere joint with 3 degrees of freedom (DOF). Therefore, design and manufacturing of such prosthesis is very important. The objective of this thesis is to develop the know how for manufacturing of a standard hip prosthesis by hot forging of Ti6Al4V alloy. First a review of kinematics of bones and joints and forces on hip joint is presented, then the proper process for manufacturing of the hip prosthesis... 

Time-dependent origin-destination demand is a key input in dynamic traffic assignment in advanced traffic management systems, and the result of dynamic traffic assignment is dependent on the accuracy of this information. One method to achieve time dependent demand matrices is using a primary demand matrix and volume traffic counts in some links of network. In this thesis a bi-level model is used to correct the demand matrix and the extended gradient method is suggested to solve the problem. The extended gradient is an iterative method that in each iteration, corrects the demand matrix in a way that the estimated traffic flow be close to the observed traffic flow. Execution of this method in... 

Pricing problem in transportation networks focuses on determining tolls that cause travellers, motivated only by their travel costs, to choose routes that would collectively benefit all travellers and results in optimal utilization of transport network resources.This thesis addresses the toll pricing problem in which the objective is to minimize the number of required toll facilities in a transportation network. Minimum tollbooth problem (MINTB) has binary variables and is very difficult to solve. In this thesis a new heuristic approach has been presented for solving MINTB problem. The results show that, this approach is much faster than the existing algorithms and is able to solve real size... 

Groundwater is the primary source of freshwater in many coastal areas and small islands around the world. The most important hazard to groundwater quality in coastal aquifers is seawater intrusion (SWI) resulting from over pumping, prolonged drought conditions and sea level rise due to climate change impacts. Numerical models of SWI are an important tool in the management of coastal aquifers. However, numerical modeling of SWI is one of the most challenging problems in groundwater hydrology. One of the reasons for the challenging nature of SWI numerical modeling is the relatively large level of uncertainty associated with the estimation of the model input parameters. This study focused on... 

Due to the importance of hazardous materials (hazmat) transportation, this problem should be programmed and solved appropriately. Hazardous materials are substances that may endanger the health of humans, animals and the environment. One of the most important parameters in hazmat transportation problem is risk, since other routing researches don’t involve risk as an influencing parameter. In the scientific literature of the transport of hazardous materials, the risk is defined by the calculation of the probability and severity of damage to the endangered recipient through unwanted warnings from hazardous substances. In the model of this research, the accident rate is considered as the... 

In the present study, the effects of increasing the value of shale gas production, either due to increased production or price increases, have been studied on economic variables such as employment, wage, property value and the number of births. In this regard, the data for each of these variables was used at the county level in the United States of America between 2000 and 2011. In order to estimate the desired effects, counties are divided into two types of boom and non-boom counties. The findings indicate that increasing natural gas production will lead to more employment and wage growth in boom counties than non-boom counties. Also, during the period of increasing production, the value of... 

It is important to provide an appropriate and economically method with technical and engineering considerations to stabilize excavated underground spaces. The necessity of this, especially for the construction of underground metro stations located in the cities which faces many problems, is more evident. In this research, it has been tried to introduce an optimal method according to the type of area for the construction of the underground station. In order to obtain stress and strain condition in structural elements and surface deformations due to different stages of excavating, numerical modeling in FLAC3D has been used. By examining the parameters that affect the sustainability of this... 

In this study, we aim to learn representations from microscopic cell images that effectively capture the features of drugs affecting the cells, allowing us to identify effective drugs for treating a disease. We employ two parallel learning paths using predictive and generative models. Specifically, we have achieved a predictive model on the RxRx19a dataset that, unlike previous models, is interpretable, optimized, and robust to dras- tic changes in drug properties. Additionally, we have developed the first generative model on this dataset, which not only generates high-quality images but also discovers a meaningful latent space. This latent space divides the representation into relevant... 

Co-movement between inflation and nominal interest in response to an interest rate shock, dubbed neo-fisherianism, has been the subject of contentious debate since the advent of non-inflationary ZLB environment. We design an economic model rich with banking features to understand the economic responses to permanent and long-term interest rate shocks. We find that responses to a permanent positive interest rate shock depend on the monetary authorities’ speculation of the new long-term inflation rate, with the most probable outcome being a permanent increase in inflation. Responses to a long-term positive interest rate shock depict an increase and then decrease in inflation. We also discover... 

Influence of excavating the Tehran metro line 7 tunnel on surface settlement, stresses and deformations induced in Towhid tunnel is investigated using numerical modeling. Construction of Metro tunnel as the new one must be carried out without imposing any damage to the Towhid tunnel as the existing tunnel. Towhid tunnel is a set of twin tunnels along the Chamran highway in Tehran. The tunnels were constructed using sequential excavation method and lined with cast in place reinforced concrete; on the other side metro line 7 is being constructed using 2 EPB tunnel boring machines and lined with reinforced concrete segments. This research consists of the study of the effects of pillar width,...