Sharif Digital Repository

In contacts, the presence of both variable loading and low-amplitude movements causes a kind of fatigue in these components called FRETTING FATIGUE. fretting fatigue has reduced the life of parts. Due to the high cost of replacing some parts in case of failure, it is necessary to take effective measures to delay this exhaustion. One of the effective solutions that can be applied is the use of coating and surface treatments in the contact areas. In this research, first, the fretting fatigue maps of Ti-6Al-4V alloy have been calculated and drawn according to the recommendations of the ASTM standard by using finite element methods. In the next step, by using experimental experiments, the damage... 

The most crucial physical component in human-robot interaction is the head of the robot, which may have the potential to interact via representing facial expressions. There are several different types of robotic heads. This thesis presents the design process and realization of a retro-projected social robotic head, “Taban”. Taban is a cost-effective portable robot with a lifelike robotic face which can produce different facial expressions, different 3D face animation avatars (ranging from different ages, races, and gender) with the help of rear-projector in its head to projects animations onto a translucent 3D printout mask. It has a neck system with two degrees of freedom, a camera in the... 

Study of "Strategic Renewal" by means of "Organizational Learning's processes" was the main intention of this research. At first, we reviewed strategic renewal and organizational learning literature to have better knowledge of relationships between them. 4i Model considered as a base for our research. Tehran Information Technology Organization (TITO) was selected as a case study environment because of many strategic changes, it had in recent years. We designed a qualitative research method for studying 4i model and relationships between strategic renewal and organizational learning, based on research method used previously for testing 4i model. Accordingly, some considerable outcomes... 

As far as reliable supply and cost-effective methods of power delivery to end-users are concerned, new advancements in smart grids and, in particular, smart pricing are of high significance to grid operators. In the recent decade, there has been a considerable raise in penetration of renewable energy resources and also the number of hybrid electric vehicles which can act as a huge mobile storage in the network. Hence, finding a practical and cost-effective method of management of all these new resources and avoiding potential problems associated with them seems to be of high importance. In this study, first, the response of demand to pricing signals has been modeledAfterwards, the response... 

Land subsidence is a gradual settling or sudden sinking of the land surface from changes that take place underground. There are different causes of land subsidence; most notably, groundwater overdraft and severe weather conditions. Subsidence of the land surface due to ground water overdraft is caused by an increase in the intergranular pressure in unconsolidated aquifers, which results in a loss of buoyancy of solid particles in the zone dewatered by the falling water table and accordingly compaction of the aquifer. In this study, an experimental approach was developed to examine applicability of Microbially induced carbonate precipitation (MICP) for land subsidence control under... 

Microbially-induced calcium carbonate precipitation is a low-cost, environmentally friendly, novel ground improvement technique that has received much attention in recent years. Most studies on biological soil stabilization have investigated the mechanical and hydraulic behavior of soils in dry and saturated conditions. However, the behavior of soils stabilized by this method in the unsaturated state should be of immense concern through the extent of unsaturated soils in nature. Therefore, this study aims to investigate the effects of microbially-induced calcium carbonate precipitation on the soil-water retention curve and changes of small strain shear modulus of unsaturated cemented and... 

In this study an internal combustion rotary (Wankel) engine and its specifications is analyzed and the proper lubrication system is described. The acceleration acting on apex seals, and engine speed fluctuations together with the leading and trailing cells gas pressure forces are analyzed in the present work using the second Newton law. The research shows that cell gas pressure effects are important and inclusion of these effects will provide results which are more compatible with the reality and lead to a much more accurate analysis of the system. Theoretical calculations reveal that gas cell pressure forces represent about 78% of the overall calculated force and ignoring these pressure... 

We study intraday patterns of trading volume, size, return, and volatility using the Tehran Stock Exchange high frequency data from 2008 to 2015. Intraday test results indicate that trade size and volume follow a J-shape behavior, whereas return and return volatility exhibit an L-shape pattern. To examine the behavior of informed traders as predicted by Barclay and Warner’s (1993), we examine midsize volume and find that it has a higher price impact compared to other trade sizes, which is consistent with the predictions of Barclay and Warner’s (1993) stealth-trading hypothesis. However, our findings do not support the intraday stealth trading pattern, as insiders prefer to trade in low and... 

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’...