Sharif Digital Repository

In recent years, UWB multiple access communication systems have received a great attention due to its many advantages. The most important advantages of a UWB system can be summarized as its high data rates, low power consumption, fading immunity and high precision routing. One of the important problems in a UWB system implementation is in its receiver part in which in order to use a coherent RAKE receiver, the channel coefficients have to be estimated. Since UWB channel is a dense multipath fading channel with a very high number of resolvable paths, the channel coefficient estimation based on using training sequence is very complicated. To resolve this problem, transmit reference (TR)... 

Endurance Time (ET) is a fairly comprehensive analytical method based on time history analysis applied for evaluating structural systems excited by dynamic loading of earthquake. In such evaluation assessment measure is based on endurance time of structure versus applied accelerogram function and parameters such as stiffness, lateral resistance, period of vibration and dynamic characteristics are not used directly. In this research nonlinear dynamic analysis of elevated steel tanks with laterally braced framed tower under the loading of earthquake records and ET accelerograms was studied and effectivity of ET method in analyzing such elevated tanks was verified. Due to complication of... 

One of the most common devices for terahertz (THz) wave generation and detection is a Terahertz photoconductive antenna. Impedance matching between the antenna and the photoconductive material is a primary factor to obtain high optical-THz conversion efficiency. Because of the time dependant conductivity of the photoconductive material, impedance mismatching is an obstacle for generating high power THz pulses. Moreover, the range of laser power (when using Ti:Sapphire) from the excitation source varies from a few tens of milliwatts to a few watts while the radiated THz power as compared to this laser pump power is very low (in the order of a few μW); this means a low power conversion... 

In this study, Euler-Bernoulli and Timoshenko beams with delayed boundary control are investigated. Deriving governing dynamic feedback control equations, exponential stability of these beams are obtained under more generalized conditions. For this purpose, time delay of system is omitted using tools in control engineering; then, an appropriate control approachis is found for this modified system.In the next step,closed loop system is extracted, which demonstrate that system is stable exponentially. This stability which is acquired for closed loop systems is also valid for primary system  

Daily price limits are boundaries that regulators impose to control daily volatility in stock market. This paper studies the impact of an imposing price limit in Tehran Stock Exchange. To this end we use all the data about companies which were accepted in stock exchange and fara-stock exchange in 1392.In this year the price limit imposed on companies in stock exchange and fara-stock exchange are 4 and 5 percent respectively. Therefore, to estimate the effect of price limit we use the propensity score matching method and inverse probability weighting.The results indicate no significant differences between returns and trade volume between 4% and 5% price limits, but a significant difference... 

Real-time (RT) communication support is a critical requirement for many complex embedded applications which are currently targeted to Network-on-chip (NoC) platforms. Average Delay and Average Bandwidth are historically the popular metrics used to evaluate the performance of an on-chip network. For RT communication, guaranteeing Minimum Delay and Maximum Bandwidth (performance bounds) which are known as the metrics for Quality-of-Service (QoS) have been at great importance during recent years. Networks-on-chip are classified to Best-Effort (BE) and Guaranteed-Service (GS) networks. Packets are processed without any precedence in BE networks, while there are special hardware and controlling... 

The goal of this research is to obtain optimal toll for saveh-salafchegan, Tehran-pardis and Ghazvin-karaj highways. To obtain optimal toll, Small and Yan value pricing model was extended and then parametrs of the model was estimated by using daily data of Maintenance and road transport Organization, then value of time parameter was structurally estimated and optimall toll was numerically obtained for the highways. Finally sensitivity analysis was performed for all parameters. Results show that optimall toll for saveh-salafchegan highway is unique and respectively, are in interval τ≤0.03 and τ≤3.72 . Magnitude of value of time of road users and difference between value of time of users... 

Iran has one of the lowest rates of female participation in the labor market among countries. In 2015, for every 100 men over 10 years old, only 21 women’s labor force participation was confirmed. This paper attemps to determine factors which cause low participation rate of women, particularly married ones. For this purpose, using structural estimation method, a dynamic discrete choice model was built, and estimated with means of simulated method of moments (SSM). The results indicated that the most important factor for low participation rate of married woman is children cost. Elimination of this cost would increase participation rate of married women about 30 percantage points  

This study investigates the price elasticity of gasoline smuggling demand in Iran. For this purpose, a panel data of monthly gasoline consumption has been used that contains data for 160 regions of distribution for Iran's Oil Production Company between 2005 and 2014. The results of estimating the monthly elasticity of gasoline smuggling demand in each region show a significant impact of the gasoline price differential between Iran and its neighboring countries, as well as the distance of each region with the neighboring countries on the demand. The results of this study show that whenever gasoline prices increase inside the country, the inclination to smuggling has been decreased due to a... 

This research is aimed at analyzing the effects of forming relationships between oil and gas companies and drilling rigs owned by drilling companies. For this purpose, panel data on 13240 contracts signed between 2000-2010 worldwide are used through employing a model with fixed effects and an instrumental variable for day-rate. Results show that repeated interaction between oil and gas companies and drilling rigs, does on one hand increase the number of contracted projects in future contracts, and on the other hand, improves their drilling performance. Moreover, it is seen that such effects are only captured by the first few interactions, and that they subside and vanish after the firms have... 

In this thesis, at first upstream transient error propagation and amplification phenomenon is introduced. Then, the previous methods to attenuate this phenomenon are presented. To overcome this drawback, a new method that is based on feed-forward and off-take disturbance estimation and lost data reconstruction in wireless communication is presented. In this thesis, an estimation of unknown off-take disturbance at the present time is approximated or in fact predicted using the last data. Also, in the presented method, the lost data is reconstructed using two different methods. At the end, the satisfactory performance of the proposed control method is illustrated by many computer simulations  

The paper aims to investigate the importance of firms’ financial constraints for pricing equity in Iran. We study the impact of financial constraints of non-financial firms on their stock returns using a sample of 241 manufacturing firms listed in Tehran Stock Exchange (TSE) for the period of 2007 to 2014. We use a similar index as in Kaplan and Zingales (1997), KZ, to measure financial constraint. We examine whether financial constraint influences stock returns and can improve the explanatory power of the Fama and French three-factor asset pricing model. Our findings indicate that financial constraints can be considered as an important factor affecting asset returns. Cross-sectional... 

The case for boosting the share of children benefiting from early childhood development (ECD) programs is strong, but expenditure has to be well-aimed. Not every program adopted under the name of ECD will provide the positive impacts that currently anchor ECD discussions among policy makers. In this report, we present results from an experimental evaluation of Cash Grant for Child Care program implemented in Sistan & Baluchestan province of Iran as a government subsidized ECD. The program provides monthly grants to ECD centers, as well as in-kind food quota per every child attending the center. At the end of school year, we did not find any significant differences in cognitive and...