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A Counting Formula for the Kervaire Semi-Characteristic
, M.Sc. Thesis Sharif University of Technology ; Esfahani Zadeh, Mustafa (Supervisor)
Abstract
Similar to the classical Poincare-Hopf index formula for the Euler characteristic, Zhang gave a counting formula for the Kervaire semi-characteristic of a 4q+1 manifold. We first study Witten deformation techniques in the proof of the Poincare-Hopf formula. Then we will represent Zhang’s formula which uses similar analysis. Both these formulas establish a connection between topological and geometrical data on a manifold. Both proofs will be analytical. Index theory will play the ’bridge’ between the topology and analysis. We begin with an analytic interpretation of the topologically defined quantities as indices of differential operators. We deform the operators with respect to appropriate...
Load Shedding in Microgrids to preserve System Stability In The Islanded Operation Mode
, M.Sc. Thesis Sharif University of Technology ; Parniani, Mustafa (Supervisor)
Abstract
In the near future, it is expected that the microgrids become widespreed due to issues such as reliability, increased penetration of renewable energy sources and distributed generation, environmental concerns and shortage of fossil fuels. Different control methods have been suggested to regulate the frequency and voltage of the system so that these quantities remain in their permissible range upon islanding and in the islanded operation mode. However, in emergency conditions, such as shortage of generated power compared to the load of microgrid, frequency or voltage reduction occures due to imbalance. In this situation, it is invitable to shed extra load to maintain the stability and...
The Correlation between Science & Abrahamic Religions (Emphasizing on Evolutionary Biology & Islam)
, Ph.D. Dissertation Sharif University of Technology ; Tagavi, Mustafa (Supervisor) ; Miandari, Hassan (Supervisor)
Abstract
While the science–religion debate on human creation has been widely explored in the Muslim world، Iranian Muslim opinions have been missed in the mainstream literature. To see whether they follow the lead of the majority of Muslim thinkers or not، here is an overview of the Qur’anic Perspective of Iranian Muslim Scholars. After reviewing the previously categorized approaches of Muslims encountering evolution mentioned in the literature، this thesis will survey the Qur’anic verses related to the biological creation of man with the “scientific-lexical” method of all possible states. Afterward، the views of the most-cited Iranian scholars، such as Saḥābī، Ṭabāṭabā’ī، Muṭahharī، and Jawādī، will...
A synergistic program between engineering and business schools towards medical technology commercialization
, Article IEEE TENSYMP 2014 - 2014 IEEE Region 10 Symposium ; 14- 16 April , 2014 , pp. 456-461 ; ISBN: 9781479920280 ; Gan, K. B ; Chellappan, K ; Ali, M. A. M ; Mustafa, M. M ; Sharif University of Technology
2014
Abstract
Governments in developing countries have invested in institutions of higher learning in order to develop homegrown, high technology products. Among these, the National University of Malaysia (Universiti Kebangsaan Malaysia), recognized as a Research University, is actively involved in projects related to medical technology through its various faculties. The net result of these activities is impressing from the point of view of patents and publications, but unfortunately not yet in terms of commercialization. This paper starts by presenting the main obstacles towards the objective of bringing a laboratory prototype to the market in the context of Malaysia. Then, a framework is presented...
Semi-IPN carrageenan-based nanocomposite hydrogels: Synthesis and swelling behavior
, Article Journal of Applied Polymer Science ; Volume 118, Issue 5 , 2010 , Pages 2989-2997 ; 00218995 (ISSN) ; Marandi, G. B ; Pourjavadi, A ; Kiani, G ; Sharif University of Technology
2010
Abstract
Inclusion of nano-clays into hydrogels is an efficient approach to produce nanocomposite hydrogels. The introduction of nano-clay into hydrogels causes an increase in water absorbency. In the present work, Nanocomposite hydro-gels based on kappa-carrageenan were synthesized using sodium montmorillonite as nano-clay. Acrylamide and meth-ylenebisacrylamide were used as monomer and crosslinker, respectively. The structure of nanocomposite hydrogels was investigated by XRD and SEM techniques. Swelling behavior of nanocomposite hydrogels was studied by varying clay and carrageenan contents as well as methylenebisacrylamide concentration. An optimum swelling capacity was achieved at 12% of sodium...
Partial root zone drying irrigation improves water use efficiency but compromise the yield and quality of cotton crop
, Article Communications in Soil Science and Plant Analysis ; Volume 52, Issue 13 , 2021 , Pages 1558-1573 ; 00103624 (ISSN) ; Raza, M. A. S ; Rashid, M .A ; Toleikiene, M ; Ayaz, M ; Mustafa, F ; Ahmed, M. Z ; Hyder, S ; Rahman, M. H. U ; Ahmad, S ; Aslam, M. U ; Haider, I ; Sharif University of Technology
Bellwether Publishing, Ltd
2021
Abstract
Water shortage is the main limitation for agricultural production in many parts of the world. Drought or unavailability of water may seriously limit plant growth as well as yield. A pot experiment was carried out to evaluate the effects of various irrigation strategies, i.e., Full (FI), deficit (DI) and partial root-zone drying (PRD) on physiological, biochemical and yield-related attributes of cotton crop. Irrigation treatments started 60 days after planting and lasted for 60 days. For FI and DI, 100% and 50% of evapotranspiration (ET) was replaced by irrigating the entire pot surface every 4–5 days. For PRD, root system was split into two equal halves and during each irrigation event, only...
Comparison between isothermal and non-isothermal fatigue behavior in a cast aluminum-silicon-magnesium alloy
, Article Strength of Materials ; Volume 47, Issue 6 , November , 2015 , Pages 840-848 ; 00392316 (ISSN) ; Winter, G ; Farrahi, G. H ; Sharif University of Technology
Springer New York LLC
2015
Abstract
In the present study, the out-of-phase thermomechanical fatigue (OP-TMF) behavior of a cast aluminum-silicon-magnesium alloy, the A356.0 alloy which has been widely used in diesel engine cylinder heads, is compared to room-temperature and high-temperature low cycle fatigue (RT-, HT-LCF) behaviors. For this purpose, strain/temperature-controlled isothermal and non-isothermal fatigue tests were performed based on realistic loading conditions in cylinder heads. Fatigue tests results showed that the plastic strain increased during cycles under constant mechanical strain amplitude, while the specimen failed. Under LCF loadings, the cyclic hardening occurred at low temperatures for the A356.0...
Machine learning in energy economics and finance: A review
, Article Energy Economics ; Volume 81 , 2019 , Pages 709-727 ; 01409883 (ISSN) ; Creamer, G. G ; Rafizadeh, N ; Sharif University of Technology
Elsevier B.V
2019
Abstract
Machine learning (ML) is generating new opportunities for innovative research in energy economics and finance. We critically review the burgeoning literature dedicated to Energy Economics/Finance applications of ML. Our review identifies applications in areas such as predicting energy prices (e.g. crude oil, natural gas, and power), demand forecasting, risk management, trading strategies, data processing, and analyzing macro/energy trends. We critically review the content (methods and findings) of more than 130 articles published between 2005 and 2018. Our analysis suggests that Support Vector Machine (SVM), Artificial Neural Network (ANN), and Genetic Algorithms (GAs) are among the most...
Fault-tolerant earliest-deadline-first scheduling algorithm
, Article 21st International Parallel and Distributed Processing Symposium, IPDPS 2007, Long Beach, CA, 26 March 2007 through 30 March 2007 ; 2007 ; 1424409101 (ISBN); 9781424409105 (ISBN) ; Miremadi, S. G ; Deconinck, G ; Sharif University of Technology
2007
Abstract
The general approach to fault tolerance in uniprocessor systems is to maintain enough time redundancy in the schedule so that any task instance can be re-executed in presence of faults during the execution. In this paper a scheme is presented to add enough and efficient time redundancy to the Earliest-Deadline-First (EDF) scheduling policy for periodic real-time tasks. This scheme can be used to tolerate transient faults during the execution of tasks. We describe a recovery scheme which can be used to re-execute tasks in the event of transient faults and discuss conditions that must be met by any such recovery scheme. For performance evaluation of this idea a tool is developed. © 2007 IEEE
Addressing NoC reliability through an efficient fibonacci-based crosstalk avoidance codec design
, Article Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), 18 November 2015 through 20 November 2015 ; Volume 9530 , 2015 , Pages 756-770 ; 03029743 (ISSN); 9783319271361 (ISBN) ; Miremadi, S. G ; Wang, G ; Perez, G. M ; Zomaya, A ; Li, K ; Sharif University of Technology
Springer Verlag
2015
Abstract
The reliable transfer in Network on Chips (NoCs) can be threatened by crosstalk fault occurring in wires. Crossstalk fault is due to inter-wire coupling capacitance that based on the patterns of transitions appearing on the wires, significantly limits the reliability of NoCs. Among these transitions, 101 and 010 bit patterns impose the worst crosstalk effects to wires. This work intends to increase the reliability of NoCs against crosstalk faults by applying an improved Fibonacci-based numeral system, called Doubled-Penultimate Fibonacci (DP-Fibo). In the DP-Fibo coding algorithm, code words without ‘101’ and ‘010’ bit patterns are produced to reduce crosstalk faults. Experimental results...
Prediction by Genetic Algorithm and measurement by center hole drilling of residual stresses of MAG weldment
, Article Advanced Materials Research, 2 November 2008 through 5 November 2008 ; Volume 83-86 , 2010 , Pages 738-745 ; 10226680 (ISSN) ; 0878492976 (ISBN); 9780878492978 (ISBN) ; Majzoobi, G. H ; Fadaee, A ; Sharif University of Technology
2010
Abstract
In the present work, specimens were cut out from St-37 plates with 19 mm thickness. The thickness of plates was reduced to 12.5 mm by milling and grinding operations. Then a standard V-shaped fillet was made on one edge of the plates. Two plates were butt-welded by standard metal arc gas (MAG) welding process. Residual stresses induced by welding were measured on 20 specimens by centre hole drilling. Load controlled axial fatigue tests were carried out to determine the fatigue life of specimens. Crack growth rates were obtained from experiment. Fractography of specimens was performed. Genetic Algorithm (GA) was employed for prediction of residual stress value in weldments using the crack...
Solutions for the Double Sine-Gordon equation by Exp-function, Tanh, and extended Tanh methods
, Article Numerical Methods for Partial Differential Equations ; Volume 26, Issue 2 , 2010 , Pages 384-398 ; 0749159X (ISSN) ; Davodi, A. G ; Davodi, A. G ; Sharif University of Technology
2010
Abstract
In this work, we implement some analytical techniques such as the Exp-function, Tanh, and extended Tanh methods for solving nonlinear partial differential equation, which contains sine terms, its name Double Sine-Gordon equation. These methods obtain exact solutions of different types of differential equations in engineering mathematics
Probabilistic analysis of welding residual stress on fatigue crack growth
, Article Arabian Journal for Science and Engineering ; Volume 34, Issue 1 C , 2009 , Pages 195-205 ; 13198025 (ISSN) ; Farrahi, G. H ; Fadaee, A ; Sharif University of Technology
2009
Abstract
The qualitative effects of residual stress parameters on fatigue crack growth are investigated using Monte Carlo probabilistic analysis technique. These parameters include the maximum residual stress,σ0, half-width of the tensile residual stress region, b, and the redistribution of residual stress parameter, β. A normal distribution is assumed for all parameters considered in the investigation and fatigue life is determined using Forman equation. The results indicate that: (i) fatigue life decreases nonlinearly if the mean of random maximum residual stress and the half-width of tensile residual stress region increases; (ii) fatigue life increases nonlinearly if the rate of residual stress...
Influence of residual stress on fatigue life of st-37 butt-mag weldment
, Article 12th International Conference on Metal Forming, METAL FORMING 2008, Krakow, 21 September 2008 through 24 September 2008 ; Volume 79, Issue 2 , 2008 , Pages 280-287 ; 16113683 (ISSN) ; Majzoobi, G. H ; Fadaee, A ; Sharif University of Technology
Wiley-VCH Verlag
2008
Abstract
In this paper residual stresses induced by butt metal arc gas welding (MAGW), in accordance with ASTM E837, are determined by hole drilling. The results are analyzed by probabilistic methods. Also, the effect of fatigue life on relaxation of welding residual stress is investigated. The specimens are tested to measure fatigue life and crack growth rates in accordance with ASTM E466 for force controlled amplitude axial fatigue testing. © 2008 Verlag Stahleisen GmbH, Düsseldorf
Effect of contact geometry on fretting fatigue life of aluminium alloy 2024-T3
, Article Indian Journal of Engineering and Materials Sciences ; Volume 12, Issue 4 , 2005 , Pages 331-336 ; 09714588 (ISSN) ; Majzoobi, G. H ; Chinekesh, H ; Sharif University of Technology
2005
Abstract
The effect of contact geometry on fretting fatigue life was investigated by experiments and numerical simulation. The experiments were conducted for flat and cylindrical pads under the same contact normal force. The post-test examinations including crack growth measurements and fractography were carried out using optical and scanning electron microscopy (SEM). Numerical simulations of pad-specimen assembly with and without crack were performed using a finite element (FE) analysis. The experimental study revealed that the rate of crack growth was higher at the early stages of fretting fatigue for cylindrical pads. This stage corresponds to a higher KII for cylindrical contact model. After...
Investigation of the temperature and density dependences of the effective pair potential parameters using variational theory
, Article International Journal of Thermophysics ; Volume 25, Issue 1 , 2004 , Pages 187-203 ; 0195928X (ISSN) ; Parsafar, G. A ; Mansoori, G. A ; Sharif University of Technology
Kluwer Academic/Plenum Publishers
2004
Abstract
A variational theory (VT), in which the potential energy of a real system is evaluated relative to the hard-sphere system, was used to investigate the medium's effects on the pair potential parameters. By adding the medium's effects to the isolated pair potential, the concept of an 'effective pair potential' (EPP) was introduced. The EPP parameters were compared with those of the average effective pair potential (AEPP) for Ar, which showed the importance of the medium effects and the long range interactions of the AEPP in dense fluids. The study showed that the depth parameter of the AEPP is much larger than that of the EPP
Thermo-mechanical behaviours of light alloys in comparison to high temperature isothermal behaviours
, Article Materials at High Temperatures ; Vol. 31, issue. 1 , 2014 , pp. 12-17 ; ISSN: 09603409 ; Farrahi, G. H ; Winter, G ; Eichlseder, W ; Sharif University of Technology
2014
Abstract
In this article, out-of-phase thermo-mechanical fatigue (TMF) behaviours of light alloys were investigated in comparison to their high temperature low cycle fatigue (LCF) behaviours. For this objective, strain based fatigue tests were performed on the A356 aluminium alloy and on the AZ91 magnesium alloy. Besides, TMF tests were carried out, where both strain and temperature changed. The fatigue lifetime comparison demonstrated that the TMF lifetime was less than that one under LCF loadings at elevated temperatures for both light alloys. The reason was due to severe conditions in TMF tests in comparison to LCF tests. The temperature varied in TMF test but it was constant under LCF loadings....
Fatigue lifetime of AZ91 magnesium alloy subjected to cyclic thermal and mechanical loadings
, Article Materials and Design ; Vol. 53, issue , 2014 , pp. 639-644 ; ISSN: 02613069 ; Farrahi, G. H ; Winter, G ; Eichlseder, W ; Sharif University of Technology
2014
Abstract
In the present paper, thermo-mechanical fatigue (TMF) and low cycle fatigue (LCF) or isothermal fatigue (IF) lifetimes of a cast magnesium alloy (the AZ91 alloy) were studied. In addition to a heat treatment process (T6), several rare elements were added to the alloy to improve the material strength in the first step. Then, the cyclic behavior of the AZ91 was investigated. For this objective, strain-controlled tension-compression fatigue tests were carried out. The temperature varied between 50 and 200. °C in the out-of-phase (OP) TMF tests. The constraint factor which was defined as the ratio of the mechanical strain to the thermal strain, was set to 75%, 100% and 125%. For LCF tests,...
Experimental fatigue lifetime of coated and uncoated aluminum alloy under isothermal and thermo-mechanical loadings
, Article Ceramics International ; Volume 39, Issue 8 , December , 2013 , Pages 9099-9107 ; 02728842 (ISSN) ; Farrahi, G. H ; Winter, G ; Eichlseder, W ; Sharif University of Technology
2013
Abstract
This paper presents the fatigue lifetime of an aluminum-silicon-magnesium alloy, widely used in diesel engine cylinder heads, both with and without a thermal barrier coating (TBC) system. The coating system in this study consists of two layers including a 150 μm thick metallic bond coat and a zirconium oxide top coat 350 μm thick. These coating layers were applied on the substrate of A356.0 alloy by air plasma thermal spraying. The isothermal fatigue tests were conducted in low cycle fatigue (LCF) regime at various temperatures. Out-of-phase thermo-mechanical fatigue (OP-TMF) tests were also performed at different maximum temperatures and constraint factors. Experimental results demonstrate...
A new energy-based isothermal and thermo-mechanical fatigue lifetime prediction model for aluminium-silicon-magnesium alloy
, Article Fatigue and Fracture of Engineering Materials and Structures ; Volume 36, Issue 12 , 2013 , Pages 1323-1335 ; 8756758X (ISSN) ; Azadi, M ; Winter, G ; Eichlseder, W ; Sharif University of Technology
2013
Abstract
In this paper, a new fatigue lifetime prediction model is presented for the aluminium-silicon-magnesium alloy, A356.0. This model is based on the plastic strain energy density per cycle including two correction factors in order to consider the effect of the mean stress and the maximum temperature. The thermal term considers creep and oxidation damages in A356.0 alloy. To calibrate the model, isothermal fatigue and out-of-phase thermo-mechanical fatigue (TMF) tests were conducted on the A356.0 alloy. Results showed an improvement in predicting fatigue lifetimes by the present model in comparison with classical theories and also the plastic strain energy density (without any correction...