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The effect of Cu powder during Friction stir welding on microstructure and mechanical properties of AA3003-H18
, Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Vol. 45, issue. 9 , 2014 , p. 3882-3891 ; Kazeminezhad, M ; Kokabi, A. H ; Sharif University of Technology
2014
Abstract
Friction stir welding (FSW) was used to join 3003-H18 non-heat-treatable aluminum alloy plates by adding copper powder. The copper powder was first added to the gap (0.1 and 0.2 mm) between two plates and then the FSW was performed. The specimens were joined at various rotational speeds of 800, 1000, and 1200 rpm at traveling speeds of 70 and 100 mm/min. The effects of rotational speed, second pass of FSW, and direction of second pass also were studied on copper particle distribution and formation of Al-Cu intermetallic compounds in the stir zone. The second pass of FSW was carried out in two ways; in line with the first pass direction (2F) and in the reverse direction of the first pass...
Effects of heat input in friction stir welding on microstructure and mechanical properties of AA3003-H18 plates
, Article Transactions of Nonferrous Metals Society of China (English Edition) ; Volume 25, Issue 7 , July , 2015 , Pages 2147-2155 ; 10036326 (ISSN) ; Kazeminezhad, M ; Kokabi, A. H ; Sharif University of Technology
Nonferrous Metals Society of China
2015
Abstract
The non-heat-treatable AA3003-H18 plates were joined by friction stir welding (FSW) to achieve a proper joint by optimizing the welding parameters. For this purpose, the effects of heat input on microstructure and mechanical properties of the welded samples were investigated by changing the ratios of rotational speed (800-1200 r/min) to travel speed (40-100 mm/min) (ω/v). It was revealed that the grain growth rate was strongly increased with the increase of the heat input by rotational speed at constant travel speed, while the grain growth rate was slightly increased with the increase of the heat input by travel speed at constant rotational speed. Subsequently, hardness reduction was...
Groups and Spread of News in Social Networks
, M.Sc. Thesis Sharif University of Technology ; Safari, Mohammad Ali (Supervisor)
Abstract
Groups are important elements in social networks. First of all, because in real life human beings are members of different groups from the begining of their life till their death and even more. Moreover, groups’ influence on people and on other groups are undeniable. Thus studying groups in the context of social networks is of a great importance. In this Thesis, we are trying to make an effort in proposing a model for group membership. We discuss two models here: in the first model we consider a set of groups and a set of people, each of which want to gain membership of a subset of the groups’ set in order to maximize their payoff. We neglect the relationships between people and their...
Friction Stir Welding of 3000 Series Aluminum Alloy by Adding Cu Powder
, M.Sc. Thesis Sharif University of Technology ; Kokabi, Amir Hossein (Supervisor) ; Kazeminezhad, Mohsen (Co-Advisor)
Abstract
An increase in strength of friction stir welded (FSW) AA3003-H18 sheets is important, due to the reduction of mechanical properties in weld area such as heat affected zone and stir zone during welding. In this research, at first FSW was used to join 3003-H18 non-heat-treatable aluminum plates without adding copper powder. The specimens were joined at various rotational speeds (800, 1000 and 1200 rpm) and traverse speeds (40, 70 and 100 mm/min). In these cases, the effects of welding parameters on microstructure and mechanical properties were investigated. The average grain size of stir zone was in the range of 21.7-7.8 μm and the microhardness of them was 28-37 Hv. Then FSW was used to join...
A reconfigurable fault-tolerant routing algorithm to optimize the network-on-chip performance and latency in presence of intermittent and permanent faults
, Article Proceedings - IEEE International Conference on Computer Design: VLSI in Computers and Processors ; 2011 , Pages 433-434 ; 10636404 (ISSN) ; 9781457719523 (ISBN) ; Modarressi, M ; Sarbazi Azad, H ; Sharif University of Technology
2011
Abstract
As the semiconductor industry advances to the deep sub-micron and nano technology points, the on-chip components are more prone to the defects during manufacturing and faults during system operation. Consequently, fault tolerant techniques are essential to improve the yield of modern complex chips. We propose a fault-tolerant routing algorithm that keeps the negative effect of faulty components on the NoC power and performance as low as possible. Targeting intermittent faults, we achieve fault tolerance by employing a simple and fast mechanism composed of two processes: NoC monitoring and route adaption. Experimental results show the effectiveness of the proposed technique, in that it offers...
Dynamic Modeling and Congestion Control in Computer Networks
, M.Sc. Thesis Sharif University of Technology ; Jahangir, Amir Hossein (Supervisor) ; Ebrahim, Behrouz (Co-Advisor)
Abstract
Active queue management (AQM) is a key factor in congestion control and should provide appropriate feedback for flow control in traffic sources to overcome the congestion problem. Beside providing congestion control, achieving predictable queuing delay, maximizing link utilization, simplicity and robustness are also the main objectives of an AQM controller. We propose in this thesis an improved queue dynamic model while incorporating the packet drop probability as well. The proposed model is evaluated using ns2 platform. By applying the improved model, a new compensated proportionalintegral- derivative (PID) AQM controller is developed for TCP network. The time-varying nature of the network...
Recovery of Uranium(VI) from UCF Waste by Selective Transportacross Aliquid Membrane
, M.Sc. Thesis Sharif University of Technology ; Samadfam, Mohammad (Supervisor) ; Fasihi, Javad (Supervisor)
Abstract
Due to environmental and economical impacts, recovery of the uranium from nuclear wastes is of continuing interest.This work reports the separation of uranyl ionusing transport technique through chloroform liquid membrane containing a mixture of DBDA15C4 and oleic acidas cooperative carrier.The pH of the feed phase (10-4 M of UO22+) was adjusted with nitric acid and acetic acid/NaOH for pHrange of 2-6.The receiving phase was hydrochloric acid 1M.The organic phase was chloroform which includesthe carrier DBDA15C4 (0.0001 M) and also the oleic acid (0.015M).The results showed that the transport increased with increasing pH and reached to maximumat pH of 5.Maximum cooperative effect of oleic...
Determination of Optimum Material and Thickness of Filter Based on Radiation Energy in Digital Industrial Radiography (CR) Using MCNP Monte Carlo Simulation Code
, M.Sc. Thesis Sharif University of Technology ; Vosoughi, Naser (Supervisor) ; Rokrok, Behrouz (Supervisor) ; Movafeghi, Amir (Co-Supervisor)
Abstract
In this study, the effect of external filter on the various parameters of image quality in digital industrial radiography by CR method for steel and aluminum piece has been investigated. The filter reduces the noise of scattered beams by absorbing the low-energy beams in the X-ray spectrum that are most likely to be scattered, but high filter thicknesses can attenuate the more energetic beams and have a negatively effect on the image quality. On the other hand, the absorption of those low-energy beams increases the average spectrum energy and thus reduce the contrast, so it is necessary to use the appropriate material and thickness of the filter. For this purpose, to examine the filter...