Sharif Digital Repository

An event must be modeled in a way that either reflects a comprehensive perspective for the event or acts in an especial part of that event, roperly. The main aim of this thesis is to control. Therefore the models will be accepted whenever the suggested mathematical models can move towards controller final target, desirably.This thesis proposes a linear mathematical model, five nonlinear models and a simple model based upon Convolution, Fuzzy Regression and Neural Networks techniques for Acquired Immune Deficiency Syndrome (AIDS), respectively. The proposed models were achieved through studying 300 HIV+ Patients who were under Highly Active Antiretroviral Therapy (HAART) approach in Iranian... 

Hybrid engines are one of a variety of chemical propulsion systems that have been given special attention in recent years by various industries such as space and defense. The most important reasons for considering this type of system are its high safety, its affordable price compared with liquid fuel propulsion systems, the possibility of switching on and off and changing thrust. This system has a lot of disadvantages as well. This system cannot meet all the needs of different industries due to the low regression rate and, consequently, the limitation of the operating range, thrusts and special impulse. As a result, increasing the fuel regression rate in these engines can greatly expand... 

This research aims to investigate the cognitive factors affecting the managers involved in decision-making processes in business environments. It tries to examine the relationship between perfectionism, decision fatigue, and decision satisfaction, taking into account management decisions in complex situations as described in Cynefin framework. The data used for analysis has been obtained from 103 business managers in different work groups. Multiple regression analysis and mediation analysis have been implemented using the bootstrapping method. As a result, 4 out of 4 research hypotheses are supported. To sum up, it can be inferred that perfectionist managers, when they make decisions in the... 

Demand estimation has always been one of the most important components of marketing in all industries. Because the profitability of any organization depends on the demand for the product or service that the organization offers to the market. On the other hand, in order to optimize the performance of the organization and better planning, we need to have an estimate of demand in order to avoid wasting the available facilities by optimally allocating resources. Another issue that shows the importance of demand estimation is the dependence of optimal pricing on the amount of demand, which can be said to be the most important tool of the organization to manage its revenue. Optimal pricing can be... 

Today, the importance of scientific collaborations is due to the fact that researchers who jointly publish an article, research connections are formed between them, and as a result, professional learning is obtained. Each of these researchers brings a feature and advantage to the research team, such as mastering a particular topic and its subdivisions, team thinking, and division of labor between them. The importance of these collaborations is doubled when researchers collaborate with each other at the international level, because the networking of researchers through collaboration with colleagues from different countries, especially central and developed countries in science, in addition to... 

This research investigates the impact of Bitcoin and cryptocurrency news along with macroeconomic and financial indicators, on Bitcoin price fluctuations for two years (May 2016-2018). The reason for this examination is due to high variations of Bitcoin price in the late 2017 and beginning of 2018, while academic research focusing on Bitcoin price are mostly conducted before 2017. Findings show that the number of news with positive and negative contexts, and news related to cryptocurrency technology have a direct relationship with Bitcoin price change. The other result shows that among news concentrated on Bitcoin, the most effective is regarding adverse incidents, famous people concerns and... 

Are the returns of the mineral companies in Tehran Stock Exchange affected by the changes in the commodity price at the Iran Mercantile Exchange? By implementing a Multi-Factor Model we will calculate the firms’ value elasticity to the commodity price changes. We try to explain the estimated elasticities on the basis of the firm’s fundamental variables using a discounted cash flow valuation model. An unbalanced panel data estimation is employed for this purpose. Afterwards, we will suggest a novel model on the ground of the assumption that the commodity prices and firm values follow the Geometric Brownian Motion. The result of the model is that the elasticity can be explained by commodity... 

The present study was aimed at investigating the relationship between reading comprehension ability as probably the most vital language skill especially in academic contexts (Farrell, 2009) and critical thinking as one of the most debated issues among scholars in modern education (Ku, 2009; Rudd, 2006). To this end, 200 male and female university students studying English Translation and Literature were chosen as the participants who sat for two tests. The first was a reading section of a retired TOEFL test provided by educational testing service in which the participants' scores were regarded as their reading comprehension ability. The second was the California Critical Thinking Skills... 

Error concealment is one of the effective ways to alleviate the effect of packet loss in video communication over error-prone environments. In order to estimate lost macro-blocks, we have employed Bayesian estimation as an efficient and robust framework. Gaussian process regression has been used as the modeling approach through this framework. Considering luminance component as Gaussian process,a minimum mean squared error estimation of the lost macro-block is obtained. This estimator, as a function of the existing data, is only determined by the covariance matrix defined over them. Therefore,the main step in Gaussian process regression, is construction of the convenient covariance matrix... 

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... 

The main goal of the current building design codes is to protect life safety, and generally, they do not directly address other societal, economic, etc., concerns regarding earthquakes. However, recent earthquakes around the world have shown that the effects of earthquakes' damages and losses can go beyond life-safety concerns. This observation has led many renowned scholars, organizations, and agencies to state the need to change the current design codes. In this regard, this thesis investigates the basis of setting the seismic design requirements and suggests a method in this respect. The study consists of two main parts. Part I (theory and design methodology) discusses some theoretical... 

Vehicle Kilometers of Travel (VKT) as one of the most important indicators of travel behavior, express the total kilometers traveled by all vehicles on city networks. Due to the expansion of urbanization and, consequently, the growth of cities, the need for awareness of citizen’s travel behavior and planning for it, is felt in more cities. Spatial transfer of a model which refers to transfer a model from on region (context) to another one, helps different regions to benefit from the results of modeling with a relatively low expense.The main purpose of the research was evaluating spatial transferability of models developed to estimate VKT in three metropolitan cities of Iran which are... 

Marine risers are tubular components, which are used to transfer fluids between seabed and floating platform. They may have a great share in cost of oil and gas production systems. One of the risers used in deep-water, is Steel Catenary Riser which is an economic alternative. However, amongst issues in designing this type of risers, high stress level in floating platform connection point and seabed touch- down zone is notable which is created due to platform movements, currents and wave loading and finally, leads to fatigue life reduction. Using buoyancy modules which are attached to risers is one of stress levels reduction solutions in hotspot points. In this study, considering the Caspian... 

Forecasting model of water consumption amounts could be used in order to manage water resources for future condition of city. In this thesis, a model for forecasting water demand for Tehran has been presented by evaluating regression models and intelligent models. In this study, uncertainties which are connected to climate and population changes are taken into account. The considered variables include minimum, maximum and medium temperature, precipitation and solar radiation. Considering objectives of this thesis and various forecasting methods and their advantages and regional conditions of Tehran, in addition to regression analysis, perceptron neural network, probabilistic neural network... 

The main purpose of this research is to investigate geotechnical parameters of surrounding rock mass of Taloun tunnels (Tehran-Shomal freeway, Iran), with application of back analysis technique and consideration of monitoring data, in order to analyzing stability of tunnel at particular monitoring station 10 (NPI10). First, the geo mechanical parameters were investigated by sensitivity analysis preceded back analysis due to determine significant geotechnical parameters of rock mass contributed to tunnel excavation with respect of displacement and stress level. Following this section sensitivity analysis of different parameters were conducted. In this section it has been found that, the most... 

Obtaining particulate matter (PM) concentration is very important in epidemiological studies. Measurement at the ground levels has been used as an accurate method to obtain PM levels. However, these measurements are more indicative of a small area around the stations than a whole region. Usually, limited space coverage and irregular distribution of air quality stations at the ground level is a restriction in the studies of air pollution and its effect on human health and environment. In this regard satellite measurements have been used for indirect estimation of PM concentration at ground levels. However, the correlation between satellite measurements and ground based data is affected by... 

Epidemiological studies have shown a positive association between particulate matters exposure and adverse health effects. However, the insufficient knowledge about the influences of components or characteristics of these particles on their health effects and toxicity leads into inefficient control practices for reducing particulates health effects. So, relationship between particles toxicity and their emission sources and components is a valuable criterion in particle emission control strategies. Moreover, as people spend most of their time in indoor environment, investigating the main sources and components of particulate toxicity in indoor environment and finding the influence of outdoor... 

Highway work zone is one of the important factors that create long queues and Delays, increase air population, fuel consumption, and road accident. Since in this zones, one and two or sometimes three lanes may be closed, more careful evaluation of the causes of queue formation seems necessary. The purpose of this research was to develop a method to estimate queue length at work zone in rural freeways, based on its traffic flow characteristics. In this study, traffic data from three work zone locations in Karaj-Qazvin freeway was collected. Results of different modeling show that platooning arrival of vehicles at work zone, increase in percentage of heavy vehicles, high variation of speed and... 

Due to water resources restriction and increase in water demand, optimum use of existing available resources is more essential. This needs accurate prediction of streamflow with lag time from one to several months. In recent decades identification of long term climate variables as predictors of hydrological process has made considerable evolution in climatic predictions and several studies have been made in this field. In this research streamflow volume of Dez Dam in dry season (April to August) has been predicted by using multiple regression models and considering seasonal rainfall data, climate indices and ocean-atmospheric variables including surface temperature of adjacent seas and... 

Fatigue is one of the most common failure modes that reduce the structural integrity of asphalt pavements. Dynamic tests are used as fatigue performance indicators for asphalt mixture. However, these tests are expensive and require special equipment and set up. At this research, the main goal is to develop a fuzzy model which is more efficient than the existing regression model for prediction of the fatigue life. A database from the available data from various research was compiled. For each model, a comparison between Fuzzy and regression output by actual outputs was done and it was seen that the fuzzy modeling can predict fatigue life very closely. Finally, the required software for this...