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Microstructure and mechanical properties of dissimilar nickel-based superalloys resistance spot welds
, Article Materials Science and Engineering A ; Volume 773 , 2020 ; Pouranvari, M ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
This paper addresses the factors affecting the mechanical properties of dissimilar resistance spot welds between Nimonic 263 and Hastelloy X nickel-based superalloys. The fusion zone (FZ) of the dissimilar weld displayed higher hardness values compared to the base metals which can be attributed to (i) the formation of Mo-rich carbide in the interdendritic zone due to positive segregation behavior of Mo and C during non-equilibrium solidification of the weld, (ii) the enhanced solid solution strengthening due to mixing of the base metals, and (iii) the formation of ultra-fine dendritic structure in the FZ due to ultra-fast cooling rate of the resistance spot welding. Formation of...
Resistance spot welding of Nimonic 263 nickel-based superalloy: microstructure and mechanical properties
, Article Science and Technology of Welding and Joining ; Volume 25, Issue 1 , 2020 , Pages 28-36 ; Pouranvari, M ; Sharif University of Technology
Taylor and Francis Ltd
2020
Abstract
This paper addresses the metallurgical and mechanical response of Nimonic 263 nickel-based superalloy to resistance spot welding. Solidification structure of the fusion zone is described in terms of dendrite arm spacing, segregation behaviour and secondary carbide formation in the inter-dendritic area. The heat affected zone is featured by negligible grain growth and constitutional liquation of primary (Ti, Mo)C carbide present in the initial microstructure of the base metal. Mechanical behaviour of the welds was characterised by interfacial to pullout failure mode transition, peak load and energy absorption of the joints during the tensile-shear loading. The fusion zone size and the...
Application of ANFIS-PSO as a novel method to estimate effect of inhibitors on asphaltene precipitation
, Article Petroleum Science and Technology ; Volume 36, Issue 8 , 2018 , Pages 597-603 ; 10916466 (ISSN) ; Suleymani, M ; Bemani, A ; Sharif University of Technology
Taylor and Francis Inc
2018
Abstract
Asphaltene precipitation in petroleum industries is known as major problems. To solve problems there are approaches for inhibition of asphaltene precipitation, Asphaltene inhibitors are known effective and economical approach for inhibition and prevention of asphaltene precipitation. In the present study Adaptive neuro-fuzzy inference system (ANFIS) was coupled with Particle swarm optimization (PSO) to create a novel approach to predict effect of inhibitors on asphaltene precipitation as function of crude oil properties and concentration and structure of asphaltene inhibitors.in order to training and testing the algorithm, a total number of 75 experimental data was gathered from the...
A dual-band feed network for series-fed antenna arrays using extended composite right/left-handed transmission lines
, Article IEEE Transactions on Antennas and Propagation ; Volume 65, Issue 1 , 2017 , Pages 178-189 ; 0018926X (ISSN) ; Nikmehr, S ; Fozi, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2017
Abstract
In this paper, extended composite right/left-handed (E-CRLH) structures are studied to design multiband microwave devices. As an example, a three-way series power divider (SPD) is designed. The overall effects of the E-CRLH structures, as the feeding networks of the antenna arrays, on the antenna arrays main-beam variations are investigated. We also design and implement two antenna arrays with N=3 elements and the same interelement distances each fed by a distinct three-way SPD. The radiation patterns of the antennas are examined. Simulation and measurement results demonstrate that the desired main-beam squinting of the antenna array could be obtained by engineering the parameters of the...
An Evaluation of an Iranian Secondary School EFL Textbook: A Teachers’ and Learners’ Attitude Study
, M.Sc. Thesis Sharif University of Technology ; Jahangard, Ali (Supervisor)
Abstract
Textbooks play major roles in education and incorporation of textbooks into the courses can better the outcome of the learning (McGrath, 2006; Sheldon, 1988). Considering the role of textbooks, it seems crucial to examine and evaluate textbooks to select the best material for the educational courses (Tomlinson, 2001). This study focused on the evaluation of the EFL textbook, Prospect 1, which is currently taught at secondary schools of Iran. The researcher intended to evaluate the textbook from the perspectives of both teachers and learners based on the evaluation model proposed by Litz (2005). The participants of the study were 173 learners and 102 teachers who filled out the questionnaires...
Studying of Micro-structure and Mechanical Properties of Resistant Spot Welds of Nickel Base Super Alloys
, M.Sc. Thesis Sharif University of Technology ; Pouranvari, Majid (Supervisor)
Abstract
Resistance spot welding is one of the fabrication processes of gas turbines. Due to few published works about using RSW for joining participation hardened nickel base super alloys like Nimonic C263 and solid solution hardened ones like Hastelloy X, this work tries to investigate the microstructure and mechanical properties of RSW joints of these super alloys. In phase one, effect of welding current on structural properties of welds, hardness profile from the center of the weld to the edge of it, failure mod and failure energy were investigated. In phase two, effect of standard heat treatment of Nimonic C263 and the initial microstructure of the base metal on the micro-structure and...
Design of dual- and quad-band E-CRLH-TLs with arbitrary phase characteristics
, Article Progress In Electromagnetics Research M ; Vol. 35, issue , 2014 , p. 141-149 ; Nikmehr, S ; Ghurt-Tappeh, M.V ; Bemani, M ; Sharif University of Technology
2014
Abstract
In this paper, extended composite right/left-handed (E-CRLH) transmission line (TL) metamaterial structures, with two left-handed (backward) and two right-handed (forward) pass bands, are investigated. Also, design procedures in order to design dual- and quad-band E-CRLH-TLs are presented in detail and the parameters of these structures are extracted by clean formulas, while satisfying arbitrary phase shifts at the operating frequencies. Finally, the dispersion and characteristic impedances of these transmission lines are derived and plotted. The results of this paper can be applied to any type of TL-based dual- and quad-band microwave component
Plasma core at the center of a sonoluminescing bubble
, Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 87, Issue 1 , 2013 ; 15393755 (ISSN) ; Sadighi Bonabi, R ; Sharif University of Technology
2013
Abstract
Considering high temperature and pressure during single bubble sonoluminescence collapse, a hot plasma core is generated at the center of the bubble. In this paper a statistical mechanics approach is used to calculate the core pressure and temperature. A hydrochemical model alongside a plasma core is used to study the bubble dynamics in two host liquids of water and sulfuric acid 85 wt % containing Ar atoms. Calculation shows that the extreme pressure and temperature in the plasma core are mainly due to the interaction of the ionized Ar atoms and electrons, which is one step forward to sonofusion. The thermal bremsstrahlung mechanism of radiation is used to analyze the emitted optical energy...
Application of ANFIS-GA algorithm for forecasting oil flocculated asphaltene weight percentage in different operation conditions
, Article Petroleum Science and Technology ; Volume 36, Issue 12 , 2018 , Pages 862-868 ; 10916466 (ISSN) ; Soltani Soulgani, B ; Bemani, A ; Sharif University of Technology
Taylor and Francis Inc
2018
Abstract
Asphaltene which cover range of 1% to over 10% of oil by weight, is well-known as most problematic part of oil that can deposit during production in reservoir, well tubing, and surface production lines, and consequently impose a serious restriction on production which in turn increases total cost of entire operation. Through decades an extensive research has been performed in order to identify asphaltene molecular structure, its behavior at different condition, and its separation mechanism from oil. One of most critical parameter associated with asphaltene precipitation modeling is flocculated asphaltene weight percentage in oil at given operation condition. In this study, to eliminate cost...
Application of MLP-ANN strategy to predict higher heating value of biomass in terms of proximate analysis
, Article Energy Sources, Part A: Recovery, Utilization and Environmental Effects ; Volume 39, Issue 22 , 2017 , Pages 2105-2111 ; 15567036 (ISSN) ; Zanbouri, H ; Bemani, A ; Hamule, T ; Sharif University of Technology
2017
Abstract
One of the important parameters in development of bioenergy industry and economical investigation of fuels is higher heating value (HHV) of biomass in the present study; multi-layer perceptron (MLP) artificial neural network was applied to predict HHV of biomass in terms of volatile matters (VMs), fixed carbon (FC), and ash content (ASH). The purposed algorithm was trained and tested by utilizing 350 experimental data points which extracted from literature. Based on results, the MLP-ANN has great ability to estimate HHV for biomass. This method can be developed as a user-friendly software for prediction of HHV of the fuel in terms of proximate analysis. The predicting software can be wide...
Estimation of the higher heating value of biomass using proximate analysis
, Article Energy Sources, Part A: Recovery, Utilization and Environmental Effects ; Volume 39, Issue 20 , 2017 , Pages 2025-2030 ; 15567036 (ISSN) ; Zanbouri, H ; Bemani, A ; Hamule, T ; Sharif University of Technology
2017
Abstract
The higher heating value (HHV) parameter of biomass is well known for its wide application in bioenergy industry and the economical study of energy resources. In the present study, the least squares support vector machine (LSSVM) strategy is used as a novel approach to estimate HHV of biomass as a function of volatile matters (VM), fixed carbon (FC), and ash content (ASH). A total number of 350 experimental data points have been extracted from previous works to train and test the proposed algorithm. In order to judge the proposed model, the statistical parameters such as R2, RMSE, and AARD are calculated as 0.92936, 4.2731%. Based on the calculated parameters, it can be concluded that the...
Application of novel ANFIS-PSO approach to predict asphaltene precipitation
, Article Petroleum Science and Technology ; Volume 36, Issue 2 , 2018 , Pages 154-159 ; 10916466 (ISSN) ; Taherpour, A ; Bemani, A ; Hamule, T ; Sharif University of Technology
Taylor and Francis Inc
2018
Abstract
Asphaltene precipitation is known as one of the challenging problems in petroleum industries which have significant effects on production such as formation damage and wellbore plugging. To solve this problem, calculation of precipitated asphaltene becomes highlighted so in the present study a novel approach is proposed based on ANFIS algorithm to estimate precipitated asphaltene in terms of dilution ration, carbon number of precipitants and temperature. The particle swarm optimization (PSO) method is applied to optimize ANFIS algorithm parameters. The proposed model was evaluated based on statistical parameters and the calculated R2, AARD and RMSE for the total data are 0.90309, 9.4908 and...
The Effect of Ambient Parameters on Argon Single Bubble Sonoluminescence in Sulfuric Acid
, M.Sc. Thesis Sharif University of Technology ; Sadighi Bonabi, Rasoul (Supervisor)
Abstract
In this research, using a hydrochemical model alongside three dominant instabilities of shape, Bjerknes and diffusion, the effect of ambient parameters on the single bubble sonoluminescence (SBSL) in Sulfuric Acid (SA) is studied. The phase diagrams of the bubble in the (R0 − Pa) space are presented, and the parametric dependence of the light intensity is discussed. In a part of this research a hot plasma core is considered at the center of the bubble. The study of ambient temperature shows that in contrast to water, the calculated thermalbremsstrahlung mechanism of light emission at the fixed degassing condition of high SA concentrations shows that with increasing the temperature of aqueous...
Channel Estimation in mmWave MIMO Systems
, M.Sc. Thesis Sharif University of Technology ; Nasiri Kenari, Masoumeh (Supervisor)
Abstract
Millimeter-wave (mmWave) communication systems exhibit large bandwidth and severe channel attenuations. To maintain the received signal-to-noise ratio on an acceptable level, mmWave systems use large antenna arrays and directional beamforming at both transmitter and receiver. The existence of many antenna elements, however, challenges traditional approaches for pilot transmission and channel estimation wherein the number of pilots linearly scales up with the total number of transmit antennas. For instance, for the uplink channel estimation with a constant coherence interval, adding more antennas to the users comes at the expense of a linear penalty on the number of users, which can...
Probability of missed detection as a criterion for receiver placement in MIMO PCL
, Article IEEE National Radar Conference - Proceedings, 7 May 2012 through 11 May 2012, Atlanta, GA ; 2012 , Pages 0924-0927 ; 10975659 (ISSN) ; 9781467306584 (ISBN) ; Chitgarha, M. M ; Radmard, M ; Nayebi, M. M ; Sharif University of Technology
IEEE
2012
Abstract
Using multiple antennas at the transmit and receive sides of a passive radar brings both the benefits of MIMO radar and passive radar. However one of the obstacles arisen in such configuration is the receive antennas placement in proper positions so that the radar performance is improved. Here we just consider the case of positioning one receiver among multiple illuminators of opportunity. Indeed it is a start for the solution of optimizing the geometry of the multiple receivers in a passive radar
An efficient method for the ring opening of epoxides with aromatic amines by Sb(III) chloride under microwave irradiation
, Article Journal of Chemical Research ; Issue 4 , 2008 , Pages 220-221 ; 03082342 (ISSN) ; Hashemi, M. M ; Mottaghi, M. M ; Foroughi, M. M ; Sharif University of Technology
2008
Abstract
SbCl3 supported on montmorillonite K-10 is an efficient catalyst for the ring opening of epoxides with aromatic amines under solvent-free conditions and microwave irradiation to give the corresponding b-amino alcohols in high yields with high regioselectivity
Resource allocation for uav-enabled integrated sensing and communication (isac) via multi-objective optimization
, Article ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings ; Volume 2023-June , 2023 ; 15206149 (ISSN); 978-172816327-7 (ISBN) ; Naghsh, M. M ; Karbasi, M ; Nayebi, M. M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2023
Abstract
In this paper, we consider an integrated sensing and communication (ISAC) system with wireless power transfer (WPT) where an unmanned aerial vehicle (UAV)-based radar serves a group of energy-limited communication users in addition to its sensing functionality. In this architecture, the radar senses the environment in phase 1 (namely sensing phase) and mean-while, the communications users (nodes) harvest and store the energy from the radar transmit signal. The stored energy is then used for information transmission from the nodes to UAV in phase 2, i.e., uplink phase. Performance of the radar system depends on the transmit signal as well as the receive filter; the energy of the transmit...
MIMO radar signal design to improve the MIMO ambiguity function via maximizing its peak
, Article Signal Processing ; Volume 118 , 2016 , Pages 139-152 ; 01651684 (ISSN) ; Radmard, M ; Nazari Majd, M ; Karbasi, S. M ; Nayebi, M. M ; Sharif University of Technology
Elsevier
2016
Abstract
One of the important obstacles in MIMO (Multiple Input Multiple Output) radars is the issue of designing proper transmit signals. Indeed, the capability of signal design is a significant advantage in MIMO radars, through which, the system can achieve much better performance. Many different aspects of this performance improvement have been considered yet, and the transmit signals have been designed to attain such goal, e.g., getting higher SNR or better detector's performance at the receiver. However, an important tool for evaluating the radar's performance is its ambiguity function. In this paper, we consider the problem of transmit signal design, in order to optimize the ambiguity function...
Detection-localization tradeoff in MIMO radars
, Article Radioengineering ; Volume 26, Issue 2 , 2017 , Pages 581-587 ; 12102512 (ISSN) ; Radmard, M ; Chitgarha, M. M ; Bastani, M. H ; Nayebi, M. M ; Sharif University of Technology
2017
Abstract
Two gains play key roles in recently developed MIMO wireless communication systems: "spatial diversity" gain and "spatial multiplexing" gain. The diversity gain refers to the capability to decrease the error rate of the MIMO channel, while the multiplexing gain implicitly refers to the amount of increase in the capacity of the MIMO channel. It has been shown that there is a fundamental tradeoff between these two types of gains, meaning interplay between increasing reliability (via an increase in the diversity gain) and increasing data rate (via an increase in the multiplexing gain). On the other hand, recently, MIMO radars have attracted much attention for their superior ability to enhance...
Antenna placement and power allocation optimization in MIMO detection
, Article IEEE Transactions on Aerospace and Electronic Systems ; Vol. 50, Issue 2 , April , 2014 , pp. 1468-1478 ; Chitgarha, M. M ; Majd, M. N ; Nayebi, M. M ; Sharif University of Technology
2014
Abstract
It is a well known fact that using multiple antennas at transmit and receive sides improves the detection performance. However, in such multiple-input multiple-output (MIMO) configuration, proper positioning of transmitters and receivers is a big challenge that can have significant influence on the performance of the overall system. In addition, determining the power of each transmitter under a total power constraint is a problem that should be solved in order to enhance the performance and coverage of such a system. In this paper, we design the Neyman-Pearson detector under the Rayleigh scatter model and use it to introduce a criterion for the antenna placement at both transmit and receive...