Sharif Digital Repository

Computer-assisted language learning (CALL) has been the focus of investigation in the field of foreign language learning for many years. This study aimed to investigate the impact of learning through blogging on the students’ essay writing skill and attitude in the Iranian context. As an extension of the research conducted earlier by Lin (2015) 32 Sharif University of Technology students were selected as the participants of the study. To this end, the students were divided into two groups of experimental group and control group. Then, they were instructed in two different ways by using different teaching methodologies. The bloggers, experimental group students, did not receive any direct... 

Surgical simulators present a safe, practical, and ethical method for surgical training. In order to enhance realism and provide the user with an immersive training experience, simulators should have the capability to provide haptic feedback to the user. Accurate modeling of the interaction between surgical instruments and organs has been recognized as a key requirement in the development surgical simulators. Researchers have attempted to model tool-tissue interactions in a wide variety of ways, which can be broadly classified as (1) continuum mechanics-based,(2) discrete elements-based methods.
This thesis presents an improved model of static Long Elements Method (LEM), a new method... 

Due to population growth, the demand for water supply has increased. This need has drawn attention to the use of consumed and treatable water resources. Organic pollutants are a key source of water pollution. On the other hand, petrochemical oil pollution and frequent oil accidents during oil production or maritime transport have become one of the environmental problems.There are different methods for water and oil separation and water purification that in the present project, selective separation can be achieved by using hydrophobic materials and surface roughness and creating surfaces with two properties: superhydrophobic and ultra-oil friendly. This method is also very effective, cheap... 

Today with growth of wireless communications and progress of small and cheap sensors which have capability of communication and calculation, wireless sensor networks are important and useful topic. But due to energy restrictions, efficient use of resources and increasing network lifetime, have been considered as key factors in network design. In this regard, using efficient multicast routing in energy consumption, for an efficient data transmission to specific number of nodes instead of all nodes code updates, information requests, task assignments and etc., is necessary.On the other hand these networks use unlicensed spectrum and suffer from collision due to congestion caused by other... 

In this project a high spectral purity C-band (4.25-5GHz) frequency synthesizer has been analyzed and designed and implemented in CMOS 0.18μm technology. This synthesizer has been embedded in TX path of a transceiver module as a frequency translator for digital phased array system applications. The system includes Phase Locked Loops (PLLs) and Direct Digital Frequency Synthesizer (DDFS). Due to desired Low spur level (90 dBc) in C-band, system level design, frequency plan, choosing proper PLL topology and etc. have been considered in details. One of the important challenges in system design is the signal spectrum purity. In other words, the system should produce minimum phase noise. Output... 

In this paper we empirically explore the bank lending channel and firm borrowing channel in Iran. Using the Embezzlement Scandal of 2011 as an instrumental variable for change in banks’ lending behavior, we identify the effect of credit constraints on borrowers’ performance. We use the firm-bank level data of short term loans from 2007- 2014 to maintain the goal. Results show that the banks’ lending behavior changes as a result of embezzlement shock and the borrowers’ performance get affected respectively. We show that the troubled banks reduce their lending by about 2.35 percent as compared to non-troubled ones. The results suggest that 10 percent decrease in loan supply, reduces the firms’... 

Learning is an essential mechanism for the survival of living things. There are different types of learning, and value learning is among the most important types. A child learns that water resolves the thirst need by repeatedly experiencing this situation. Eventually, the value of water, which has been valueless before that, increases gradually in his mind. How this concept is encoded in the brain? previous works reveal the role of different neurons and regions that are relevant to value learning. However, population analysis and dynamic modeling are less considered. Moreover, the links between different brain regions are unknown.Finding the relationship between two relevant regions of the... 

With the introduction of SDN and OpenFlow as novel approaches for better network management and virtualization, it is now easier to perform QoS measurement anywhere, anytime, and anyplace through the use of self-directed, self-tuning mechanisms that continuously monitor and measure network performance and react swiftly to problems. Using programmable interfaces to OpenFlow controllers, software-defined measurement solutions provide consistent traffic measurement of flow parameters, such as bandwidth, packet loss, and latency to support the diversity requirements of next generation network applications and services. The flexibility of software-defined measurement gives the network operator... 

Till today types of demand response program have been identified as one of the most effective and usefull programs in order to the energy efficient consumption and followed by, improving the network's reliability. Also some of these plans have reduced the risk of the retailers and as much as possible prevent the likely loss of these companies at the high energy tariffs times. The required for doing some of these types of plans is investing on various parts like infrastructure mutual relationships between retailers and customer and also smart meters which will require valuation. Till now so many various ways have been done for valuation on types of demand response program plans. This thesis... 

Ultrasound hyperthermia is a commonly used noninvasive approach to destroy cancer tumors. High Intensity Focused Ultrasound (HIFU) is a technique based on hyperthermia. It creates short and local elevations of temperature at a focus site within the tissue of interest. The main goal of HIFU is to maintain the temperature between 50 and 100 °C for a few seconds (typically less than 10 s), in order to cause tissue necrosis. In order to predict the effects of hyperthermia, accurate and effective modeling is needed. This study considers a 3D simulation of the hyperthermia based on HIFU method in the liver tissue. Temperature distribution and lesion volume changes, with a temperature of above... 

Using magnetic torquers as the sole actuator for attitude control of small satellite despite its benefits has a drawback that is lack of controllability. Mechanical torques can be created only perpendicular to the instantaneous magnetic field vector, thus at each time instant the satellite can be controlled only around two axes out of its three perpendicular axes.
Fortunately because of the satellite motion, the direction of uncontrollable axis changes by time, therefore the sufficient attitude control can be achieved along time. Almost all of the present magnetic attitude control methods need more than one orbital period to control and cause the attitude to converge to the desired... 

Structural defects such as cracks may be produced in structures and machineries under fatigue load operating conditions. The presence of crack can lead to catastrophic failures in certain conditions. The occurrence of cracks affects the dynamic and vibration behavior of the structure considerably. These vibrations can be used for identifying the cracks and appropriate actions can be taken to prevent more damage to the system. Therefore, in this thesis vibration analysis of a Timoshenko beam with a vertical and horizontal crack has been considered. A continuous model for vibration analysis of a beam with an open edge crack including the effects of shear deformation and rotary inertia has been... 

Understanding many issues related to environmental geotechnics and soil sciences such as: instability and collapse of soil slopes, sinkholes, leakage from landfills and isolation of nuclear landfills, and optimization Agricultural processing depends on our knowledge of the behavior of unsaturated soils and their volume changes. To better understand the behavior of unsaturated soils, it is important to study the soil-water retention curve (SWRC) and the factors affecting it. These include factors such as porosity, grain size distribution, soil minerals, pore size distribution, and pore water chemistry, which affect soil-water retention curves and volume changes. Since the simultaneous effect...