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Mechanical and metallurgical properties of wide-gap aluminothermic rail welds

, Article Iranian Journal of Materials Science and Engineering ; Volume 8, Issue 4 , 2011 , Pages 27-33 ; 17350808 (ISSN) Mohassel, A ; Kokabi, A.H ; Davami, P ; Sharif University of Technology

2011

Abstract

The wide-gap aluminothermic rail welds with root opening of 50-70 mm were produced using plain carbon steel rail and non-alloy aluminothermic charge. Mechanical properties and micro-structure of the weld metal and HAZ as well as the impact energy and the fracture toughness of the welds were investigated. The yield and tensile strength of wide-gap welds were about 98% and 95% of the base metal, respectively. Both minimum and maximum hardnesses of the joint were seen in HAZ which were related to the grain coarsening and normalizing, respectively. The mean value of wide-gap weld fracture toughness is more than narrow-gap weld. Moreover, trans-granular cleavage indicated the brittle fracture...

Sidelobe level optimization using modified genetic algorithm

, Article IEEE Antennas and Propagation Society, AP-S International Symposium (Digest) ; Volume 1 , 2002 , Pages 742-745 ; 15223965 (ISSN) Varahram, A. A ; Rashed Mohassel, J ; Sharif University of Technology

2002

Abstract

The sidelobe level (SLL) of a linear array is optimized using modified continuous genetic algorithms (GAs) in this work. The amplitude and phase of the current as well as the separation of the antennas are all taken as variables to be controlled. The results of the design using modified GA versions are compared with other methods. Two design problems were studied several continuous modified GA version and the results are presented as several plots. As a final example, the design specifications for an array with 200 elements is given. The effectiveness and advantages of the modified GA version is outlined

Radiation properties enhancement of a GSM/WLAN microstrip antenna using a dual band circularly symmetric EBG substrate

, Article IEEE Transactions on Antennas and Propagation ; Volume 60, Issue 11 , 2012 , Pages 5491-5494 ; 0018926X (ISSN) Salarrahimi, M ; Rashed Mohassel, J ; Edalatipour, M ; Sharif University of Technology

2012

Abstract

This communication presents a dual band circular patch antenna with improved radiation properties at GSM and WLAN frequency bands, i.e., 1.8 and 2.4 GHz. The improvement has been achieved using a dual band circularly symmetric EBG (CS-EBG) structure. The structure has been simulated, fabricated and measured demonstrating notable enhancement in antenna radiation patterns at both frequency bands. Results show 5 dB and 7 dB improvement in front to back ratio at design frequencies of 1.8 GHz and 2.4 GHz respectively. In addition, measurement results demonstrate 0.8 dB increase in antenna gain and significant reduction in cross polarization level at both frequency bands

Miniaturized patch antenna using a circular spiral-based metamaterial

, Article Microwave and Optical Technology Letters ; Volume 59, Issue 9 , 2017 , Pages 2276-2279 ; 08952477 (ISSN) Kavousi, H ; Rashed Mohassel, J ; Edalatipour, M ; Sharif University of Technology

2017

Abstract

A miniaturized patch antenna is proposed and its radiation properties are experimentally investigated. A new metamaterial configuration based on circular spiral inclusion is used as the patch antenna substrate. The proposed antenna has not only a lighter profile but also a higher gain in comparison with its previously reported counterparts. It is shown that by using this new configuration a miniaturization factor of 3.1 can be realized. © 2017 Wiley Periodicals, Inc

Low complexity resource allocation in the relay channels with energy harvesting transmitters

, Article Ad Hoc Networks ; Volume 77 , 2018 , Pages 108-118 ; 15708705 (ISSN) Mohassel Feghhi, M ; Abbasfar, A ; Mirmohseni, M ; Sharif University of Technology

Elsevier B.V 2018

Abstract

Energy Harvesting (EH) is a novel technique to prolong the lifetime of the wireless Ad-hoc and sensor networks with replenishable nodes. In this sense, it has emerged as a promising technique for Green Communications. On the other hand, cooperative communication with the help of relay nodes improves the performance of wireless communication networks. In this paper, we investigate the cooperation in EH nodes. We consider the optimal power and rate allocation in the full-duplex Gaussian relay channel in which source and relay can harvest energy from their environments. In our model, the energy arrivals at the source and the relay are general stochastic processes with known EH times and amounts...

Optimization of array factor in linear arrays using modified genetic algorithm

, Article International Journal of Engineering, Transactions B: Applications ; Volume 17, Issue 4 , 2004 , Pages 369-379 ; 1728-144X (ISSN) Varahram, A ; Rashed Mohassel, J ; Mafinezhad, K ; Sharif University of Technology

Materials and Energy Research Center 2004

Abstract

The array factor (sidelobe level, SLL) of a linear array is optimized using modified continuous genetic algorithms in this work. The amplitudes and phases of the currents as well as the separation of the antennas are all taken as variables to be controlled. The results of the design using modified GA versions are compared with other methods. Two design problems were studied using several continuous modified GA versions and the results are presented as several plots. As a final example, the design specifications for an array with 200 elements are given. The effectiveness and advantages of the proposed modified GA versions are outlined

Heat Transfer Modelling and Mechanical Properties Of Wide-Gap Thermite Rail Welds

, Ph.D. Dissertation Sharif University of Technology Mohassel, Abbas (Author) ; Kokabi, Amir Hossain (Supervisor) ; Davami, Parviz (Supervisor)

Abstract

Wide-gap aluminothermic rail welds with root opening of 60 mm were produced using plain carbon steel rail and non-alloy aluminothermic charge. Such process can repair defective rails, each with only one wide-gap weld instead of using a relatively long plug rail and two standard welds which reduces number of welds in railways and cause saving in money. Required equipments including metallic and sand molds, crucible and self-tapping thimble were designed. Mechanical properties and micro-structure of rail welds and corresponding heat affected zones as well as impact energies and fracture toughnesses of welds were investigated. Wide-gap aluminothermic rail welds exhibited 98% and 95% of yield...

High Saline Water Treatment by the Process of Membrane Distillation Combined with Solar Energy

, M.Sc. Thesis Sharif University of Technology Shokrollahi, Milad (Author) ; Rajabi, Abbas (Supervisor) ; Musavi, Abbas (Supervisor)

Abstract

In this study, membrane distillation process was used for treatment of high salinity waters. The focus of this study is to simulate and build a setup of membrane distillation process. Since the membrane distillation process is based on the driving force of the temperature difference, the required temperature is provided by both the use of heaters and the use of solar energy. To increase the feed temperature by solar energy, a black polymer coating on the main membrane is used. The main membrane used in this process is PVDF polymer and the polymer coated on the surface is the PAN polymer. After simulating and constructing the laboratory setup, the influence of a variety of parameters on the...

Microwave engineering in Iran's academia [around the globe]

, Article IEEE Microwave Magazine ; Volume 19, Issue 3 , May , 2018 , Pages 124-128 ; 15273342 (ISSN) Abdipour, A ; Banai, A ; Farzaneh, F ; Kamarei, M ; Moradi, G ; Rashed Mohassel, J ; Shahabadi, M ; Sharif University of Technology

Institute of Electrical and Electronics Engineers Inc 2018

Abstract

, M.Sc. Thesis Sharif University of Technology (Author) ; Akbarzadeh, Abbas (Supervisor)

Abstract

FGM sheets with component or grain size gradient in their thickness direction provide mechanical and physical gradient properties through ND direction. FGMs are fabricated by various methods including centrifugal casting, powder metallurgy, PVD and CVD,all of which suffer from some shortcomings such as porosity of the products, low rate and high cost of production and restrictions on mass production. In this study, 2 and 4 layered Al matrix FGM sheets containing SiC and Al2O3 powders were fabricated by laminating method of Accumulative Roll Bonding(ARB). Two approaches of stacking were chosen as accumulative coupled roll bonding (ACRB) and (ASRB) for initial roll bonding and subsequent...

Using ARB Process for Metal Matrix Foam and Composite Production

, M.Sc. Thesis Sharif University of Technology Khalkhali, Mohammad (Author) ; Akbarzadeh, Abbas (Supervisor)

Abstract

Metal matrix composites (MMC) and metal foams (MF) have been the topic of numerous researches during the last decades. The appropriate mechanical and physical properties of these materials make them useful in various industries. In this research, a unique approach is introduced for producing MMCs and MFs in which accumulative roll bonding (ARB) is employed in order to achieve a homogeneous distribution of ceramic particles in the metal matrix. Also, foamed structures can be made by subjecting Al/TiH2 composite to an appropriate annealing heat treatment where TiH2 particles decompose to hydrogen and titanium. In this work, the effect of number of ARB cycles on the size and distribution of...

Make Policy for Optimizing Iran Gas Export

, M.Sc. Thesis Sharif University of Technology Alvandi, Mehdi (Author) ; Maleki, Abbas (Supervisor)

Abstract

This project examines four alternatives such as pipelines, oil injection wells, LNG & GTL in the purpose of Iran gas utilization. In this Project four strategies using cost/benefit analysis are examined. For this purpose, at first the cost of inlet feed gas per Mmbtu are calculated. Then regarding various scenarios of average world gas prices for the following thirty years, the cost & benefit of any way will be counted. Then with the use of energy security, the project will make energy policy. For this purpose, Shannon indicator will be used as one of the most reliable indicators. Due to the of use this indicator, the popular project will be chosen accordingly as a certain amount of gas the...

Development of an Analytical Framework for Evaluation of Climate Change Mitigation Policies on Iran’s Energy Security

, M.Sc. Thesis Sharif University of Technology Eshraghi, Hadi (Author) ; Maleki, Abbas (Supervisor)

Abstract

Climate change and energy security are key drivers for future energy policy. While energy security has been a pillar of energy policy for about a century, concern about climate change is more recent and is bound to radically change the landscape of energy policy. Policy makers are now under increasing pressure to address these twin challenges: to develop cost-effective policies that will both ensure the security of our energy system and reduce greenhouse gas emissions.
Main Effort in this Project is to construct an integrated model of Iran’s energy system to serve as a policy analysis tool, by which policymakers are able to identify the future effects of a wide range of policies in...

Evaluation the Effect of Thermo-Mechanical Parameters on Microstructure and Texture of Electrical Steel for Improving Magnetic Permeability

, M.Sc. Thesis Sharif University of Technology Ahmadian, Peyman (Author) ; Akbarzadeh, Abbas (Supervisor)

Abstract

Dependence of some magnetic properties such as core loss and permeability on temper rolling was studied in this thesis. It is shown that with a proper temper rolling sharper textures are obtained in the electrical steel and the magnetic properties in the longitudinal and traverse directions are improved. By texture analysis, it is shown that because of temper rolling, shear strain on the surface of the sheet is the main factor for abnormal grain growth and shear texture formation on the surface. The result of formation of this texture is enhancement of the {100} intensity and reduction of the {111} intensity, leading to the improvement of the permeability. Temper rolling is always...

(Assessing the Role of Carbon Capture and Storage Technology on Iran’s Oncoming Energy System(Technology Deployment Policy Making

, M.Sc. Thesis Sharif University of Technology Banan, Zoya (Author) ; Maleki, Abbas (Supervisor)

Abstract

Based on International Energy Agency studies, achievement of 450 ppm CO2-equivalent emission target in global emission means that the CO2 emissions in 2050 must be reduced to %50 of 2005 level, and this implies that a portfolio of emission reduction policies and strategies need to be exploited through current century.
At the present time, Carbon Capture and Storage (CCS) Technology is a dominant strategy among all the long-term carbon abatement strategies in many countries. Nevertheless, its potential as a climate mitigating option will be proved, only if it is implemented in the countries which are developing at a great pace and taking advantage of fossil fuels in order to afford their...

Diffusion of Lipid and Protein Molecules in Cell Membranes

, Ph.D. Dissertation Sharif University of Technology Khoshnood, Atefeh (Author) ; Jalali, Abbas (Supervisor)

Abstract

Lipid membranes are fundamental constituents of cell membranes and are now used in lap-on-a-chip technology. Membranes in living cells contain a significant fraction of proteins, which undergo lateral random movements due to thermal fluctuations and shear forces imposed by the solvent fluid. Prominent natural and biotechnological systems where membranes are highly sheared include the plasma membrane of endothelial cells, and membranes used in biosensors for high throughput screening of drug candidates, and in water purification devices. In these systems membrane is in direct contact with the mainstream suspension flow, which is driven by pressure gradients. The efficiency and function of...

Hot Workability of a Free-cutting Steel with Severe Sulfur Segregation During Continuous Casting

, M.Sc. Thesis Sharif University of Technology Naghdy, Soroosh (Author) ; Akbarzadeh, Abbas (Supervisor)

Abstract

Splitting in ingot cast structures and transverse cracks in continuous cast structures are the main problems of hot rolling of low carbon resulfurized free-cutting (LCRF) steels. Presence of high volume fraction of manganese sulfide inclusions in cast structure increases the risk of alligatoring in hot rolling. Because of high sulfur content of these steels and probability of formation of low melting point phases, minimum level of manganese and maximum level of copper and tin is necessary. Morphology of manganese sulfide is another important factor in hot forming of these steels, which can be controlled by level of deoxidation in steel making. In fact, MnS2 is present in fully killed...

Deposition of Ceramic Nanoparticles on Aluminum Sheet by Air Gun Spraying for ARB Processing of Nanocomposite Sheets

, M.Sc. Thesis Sharif University of Technology Keramat, Ehsan (Author) ; Akbarzadeh, Abbas (Supervisor)

Abstract

Particle reinforced aluminum matrix composites have considerable attraction in automotive and aerospace industries due to their special properties as light weight, high ratio of strength/density, improved elastic modulus, low coefficient of thermal expansion and high wear and corrosion resistance. Among the production processes of metal matrix composites, accumulative roll bonding process has particular importance due to producing ultrafine grained composite sheets. However, uncontrolled and undesired agglomeration of particles is the main problem in producing these composites. In this research, the Al2O3 and SiC nanoparticles were electrostatically stabilized against agglomeration by...

Assessment of Caspian Gas Transit and its Effects on the Interests of the Iranian Desired

, M.Sc. Thesis Sharif University of Technology Khakpour, Hossein (Author) ; Maleki, Abbas (Supervisor)

Abstract

In this project a model for the analysis and assessment of gas transit in the Caspian Sea and its effects on the desired benefits of the approach of decision-making, has been developed.
The first comprehensive review of the supply and demand of gas in the world and the countries of the Caspian region and the cast has been affecting world energy developments.After a comprehensive analysis of the status of the gas transit routes from the Caspian region and provided. Then, using the Delphi method and elite views the main criteria related to gas transit and affecting the interests of the countries of the Caspian region to determine the detailed criteria for each main criterion was determined...

Risk Management for DG Owners

, M.Sc. Thesis Sharif University of Technology Karimi, Ahmad (Author) ; Rajabi, Abbas (Supervisor)

Abstract

Distributed generation (DG) and its utilization have some benefits and risks for its owner and power network. From owner perspective, benefits of DG include selling energy, reducing costs related to fuel, and other economic benefits. However, there are some risk factors for the owner including risk of supplying fuel, risk of selling generated power, and other risk factors related to establishment of the DG unit. Utilizing risk-reduction tools such as signing agreements for selling power, purchasing fuel, and related economic tools are necessary for risk management of the owners of DG units. The purpose of this thesis is to investigate the economic situation of the DG units and optimize the...