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Modeling the coupled effects of surface layer and size effect on the static and dynamic instability of narrow nano-bridge structure
, Article Journal of the Brazilian Society of Mechanical Sciences and Engineering ; Volume 39, Issue 5 , 2017 , Pages 1735-1744 ; 16785878 (ISSN) ; Koochi, A ; Kanani, A ; Navazi, H. M ; Abadyan, M ; Sharif University of Technology
Springer Verlag
2017
Abstract
For modeling the electromechanical behavior of nano-bridge structures with slender narrow-width beam elements, not only the simultaneous effects of surface layer and size dependency should be taken into account but also corrected force models should be considered. In this paper, the instability of a narrow-width nano-bridge is studied based on strain gradient theory and Gurtin–Murdoch surface elasticity. The mid-plane stretching is incorporated in the governing equation as well as corrected force distribution. Using Rayleigh–Ritz method, a parametric analysis is conducted to examine the impacts of surface layer, size dependence, dispersion forces and structural damping on static and dynamic...
Modeling the size dependent pull-in instability of cantilever nano-switch immersed in ionic liquid electrolytes using strain gradient theory
, Article Scientia Iranica ; Volume 23, Issue 3 , 2016 , Pages 976-989 ; 10263098 (ISSN) ; Koochi, A ; Farahani, M ; Rouhi, E ; Abadyan, M ; Sharif University of Technology
Sharif University of Technology
2016
Abstract
It is well recognized that size-effect often plays a significant role in the mechanical performance of nano-structures. Herein, strain gradient continuum elasticity is employed to investigate the size dependent pull-in instability of the cantilever nanoactuators immersed in ionic liquid electrolyte. The presence of dispersion forces, i.e. Casimir and van der Waals field, is considered in the theoretical model as well as the double-layer electrochemical attraction. To solve the non-linear constitutive equation of the system, two approaches, i.e. the Rayleigh Ritz Method (RRM) and the numerical solution method, are employed. Impact of the size dependency and dispersion forces on the...
Development and application of model for planning and development of technology in Oil & Gas Upstream
, M.Sc. Thesis Sharif University of Technology ; Saboohi, Yadollah (Supervisor)
Abstract
Products on Research and Development (R&D) are followed by Technology development. Projects on R&D are cost intensive and considerable of financial resources should be allocated. Optimal allocation of resources could be managed through cost effective strategy. Hence, a “Model for planning and development of technology” has been developed in the present work, which lends itself to the analysis of the industrial application of planning of technological development based on minimizing costs of both development and application of a technology. Mixed Integer Programming optimization model has been developed which enables studying the structure of R&D activities. This model is based on the concept...
Economic Analysis of Energy Supply Security based on Energy Security Indices
, Ph.D. Dissertation Sharif University of Technology ; Maleki, Abbas (Supervisor)
Abstract
As a problem, generally, energy security components do not interfere with the calculation of the optimal energy supply situation. In this paper, we are looking to find a solution to make a framework of the impact of energy security on energy supply in order to obtain comprehensive analysis of the economic optimal point. Method is based on the competition of energy costs to meet demand during the study period. Threats that have been addressed in the energy security are seen as risky and stochastic parameters in the model. The nature of these parameters is of uncertainty type, therefore, based on the probable scenarios of the stochastic model, the perspective of the energy supply system is...
The size-dependent electromechanical instability of double-sided and paddle-type actuators in centrifugal and Casimir force fields
, Article Scientia Iranica ; Volume 24, Issue 3 , 2017 , Pages 1077-1090 ; 10263098 (ISSN) ; Farahani, M ; Kanani, A ; Rach, R ; Keivani, M ; Abadyan, M ; Sharif University of Technology
Sharif University of Technology
2017
Abstract
The present research is devoted to theoretical study of the pull-in performance of double-sided and paddle-type NEMS actuators fabricated from cylindrical nanowire operating in the Casimir regime and in the presence of the centrifugal force. D'Alembert's principle was used to transform the angular velocity into an equivalent static, centrifugal force. Using the couple stress theory, the constitutive equations of the actuators were derived. The equivalent boundary condition technique was applied to obtain the governing equation of the paddle-type actuator. Three distinct approaches, the Duan-Adomian Method (DAM), Finite Difference Method (FDM), and Lumped Parameter Model (LPM), were applied...
Experimental Analysis of Immiscible Displacements of Heavy Oil in Heterogeneous Porous Media under Ultrasonic Effect
, M.Sc. Thesis Sharif University of Technology ; Ghotbi, Siroos (Supervisor) ; Ghazanfari, Mohammad Hossein (Supervisor)
Abstract
In the recent years, there has been an increasing attention toward usage of ultrasonic for enhanced oil recovery practices. But, thorough knowledge of active mechanisms and spreading and characterization of developed fingers during this practice is not available. From the other hand, due to limited amount of light oil fields, more attentions towards recovery from heavy oils is the need of the hour. Documents show that the big issues during the enhanced oil recovery from heavy crudes are high density of reservoir oil as well as poor development of fingers during injection due to high mobility ratios. In this study, results of ultrasound effect on the heavy oil recovery and its effect on the...
Sensitivity Analysis on Individual Judgments in Analytic Hierarchy Process and Analytic Network Process
, M.Sc. Thesis Sharif University of Technology ; Kianfar, Farhad (Supervisor)
Abstract
Nowadays, the world is full of multi criteria decision problems and all the people should make decisions in different situations. Sometimes, the result of a decision problem is so important as a wrong decision may result in a loss that cannot be compensated. Therefore a decision making tool seems as a must. On the other hand, in this era of rapid social and technological change leading to increasing life complexity, sensitivity analysis is an important issue in all decision making processes. Analytic Hierarchy Process and Analytic Network Process, as two common tools for multi criteria decision making, are widely used throughout the past decade in different fields. Designing the model and...
Evaluation of Vermifilter Efficiency in Petroleum Wastewater Treatment (BTEX)
, M.Sc. Thesis Sharif University of Technology ; Torkian, Ayub (Supervisor) ; Mirzai, Mohammad (Supervisor)
Abstract
The aim of this thesis was to find the optimum retention time for treatment of synthetic petroleum wastewater by a wastewater treatment system made with a bucket, mineral material and earthworms residing in a vermibed. In order to make the desired flow happen, height difference was utilized. The polluting substance used for making wastewater was BTEX. As the wastewater was synthetic, the concentration was also a variable. The ultimate soluble concentration was 3200 mg/l and more concentrations were not tested. Parameters such as number of worms, worm’s growth rate and their distribution pattern, humidity amount and distribution and worm’s acclimatization time during organic loading shock...
Implementation of Productivity Management Cycle and Case Study in Radiator-e-Iran company
, M.Sc. Thesis Sharif University of Technology ; Eshraghniaye Jahromi, Abdolhamid (Supervisor)
Abstract
Productivity is the effective usage of input or resources for production or output. Input (including Energy, raw materials, capital and work force), which is being used for output (including final products or services performed by an organization). Productivity, increases gross domestic product and competitiveness, and improves level of living. Firms and related management levels play the main role in improving productivity. Using productivity cycle management brings the productivity to improve as a permanent process, specifies the rout for productivity and prepares the ground. The most important step in productivity cycle (PDCA) is the measurement of productivity. In this research several...
Analysis of Factors Affecting IPO Initial Returns of the Tehran Stock Exchange
, M.Sc. Thesis Sharif University of Technology ; Talebian, Masoud (Supervisor) ; Ebrahimnejad, Ali (Supervisor)
Abstract
In the present study, the factors that affect the IPO underpricing in the Tehran Stock Exchange are investigated. We define the variables of IPO percentage, age and size of companies, dummy variable for rounded IPO prices, market return in a month before the initial public offering, average return of IPOs that had been done during one month before the IPO of each ticker and the dummy variable for industrial group in which the company is located. We had to calculate the initial return of 246 companies that were offered in the years 1380 to 1395. In this study, due to the existence of a daily stock price volatility constraint, a new algorithm was introduced to calculate the dependent...
Iran’s oil development scenarios by 2025 [electronic resource]
, Article Energy Policy ; Volume 56, May 2013, Pages 612-622 ; Sharif University of TechnologyIntelligent semi-active vibration control of eleven degrees of freedom suspension system using magnetorheological dampers
, Article Journal of Mechanical Science and Technology ; Volume 26, Issue 2 , 2012 , Pages 323-334 ; 1738494X (ISSN) ; Sarrafan, A ; Khayyat, A. A. A ; Zabihollah, A ; Sharif University of Technology
2012
Abstract
A novel intelligent semi-active control system for an eleven degrees of freedom passenger car's suspension system using magnetorheological (MR) damper with neuro-fuzzy (NF) control strategy to enhance desired suspension performance is proposed. In comparison with earlier studies, an improvement in problem modeling is made. The proposed method consists of two parts: a fuzzy control strategy to establish an efficient controller to improve ride comfort and road handling (RCH) and an inverse mapping model to estimate the force needed for a semi-active damper. The fuzzy logic rules are extracted based on Sugeno inference engine. The inverse mapping model is based on an artificial neural network...
Performance and exhaust emission characteristics of a spark ignition engine operated with gasoline and CNG blend
, Article Proceedings of the Spring Technical Conference of the ASME Internal Combustion Engine Division ; 2012 , Pages 179-187 ; 15296598 (ISSN) ; 9780791844663 (ISBN) ; Hamidi, A. A ; Mozafari, A. A ; Sharif University of Technology
2012
Abstract
Using CNG as an additive for gasoline is a proper choice due to higher octane number of CNG enriched gasoline with respect to that of gasoline. As a result, it is possible to use gasoline with lower octane number in the engine. This would also mean the increase of compression ratio in SI engines resulting in higher performance and lower gasoline consumption. Over the years, the use of simulation codes to model the thermodynamic cycle of an internal combustion engine have developed tools for more efficient engine designs and fuel combustion. In this study, a thermodynamic cycle simulation of a conventional four-stroke spark-ignition engine has been developed. The model is used to study the...
A comparative study of the performance of a SI engine fuelled by natural gas as alternative fuel by thermodynamic simulation
, Article 2009 ASME Internal Combustion Engine Division Fall Technical Conference, ICEF 2009, Lucerne, 27 September 2009 through 30 September 2009 ; 2009 , Pages 49-57 ; 9780791843635 (ISBN) ; Hamidi, A. A ; Mozafari, A. A ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2009
Abstract
With the declining energy resources and increase of pollutant emissions, a great deal of efforts has been focused on the development of alternatives for fossil fuels. One of the promising alternative fuels to gasoline in the internal combustion engine is natural gas [1-5]. The application of natural gas in current internal combustion engines is realistic due to its many benefits. The higher thermal efficiency due to the higher octane value and lower exhaust emissions including CO2 as a result of the lower carbon to hydrogen ratio of the fuel are the two important feature of using CNG as an alternative fuel. It is well known that computer simulation codes are valuable economically as a cost...
Analytical and experimental analyses of nonlinear vibrations in a rotary inverted pendulum
, Article Nonlinear Dynamics ; Volume 107, Issue 3 , 2022 , Pages 1887-1902 ; 0924090X (ISSN) ; Pasharavesh, A ; Khayyat, A. A. A ; Sharif University of Technology
Springer Science and Business Media B.V
2022
Abstract
Gaining insight into possible vibratory responses of dynamical systems around their stable equilibria is an essential step, which must be taken before their design and application. The results of such a study can significantly help prevent instability in closed-loop stabilized systems by avoiding the excitation of the system in the neighborhood of its resonance. This paper investigates nonlinear oscillations of a rotary inverted pendulum (RIP) with a full-state feedback controller. Lagrange’s equations are employed to derive an accurate 2-DoF mathematical model, whose parameter values are extracted by both the measurement and 3D modeling of the real system components. Although the governing...
A suction-controlled ring device to measure the coefficient of lateral soil pressure in unsaturated soils
, Article Geotechnical Testing Journal ; Volume 44, Issue 1 , 2020 ; Garakani, A. A ; Golshani, A ; Mirzaii, A ; Sharif University of Technology
ASTM International
2020
Abstract
A suction-controlled ring device has been developed to continuously measure the coefficient of lateral soil pressure in deformable unsaturated soil samples from the at-rest to the active condition under application of increasing vertical pressure and controlled matric suction. The device incorporates a thin aluminum specimen ring equipped with horizontal strain gages for recording the lateral soil strains. In addition, a sensor recording water volume changes is utilized to continuously monitor the degree of saturation of the soil sample during tests. The matric suction within the soil texture is controlled using the axis translation technique. In order to verify the performance of the ring...
Gum tragacanth gels as a new supporting matrix for immobilization of whole-cell
, Article Iranian Journal of Chemistry and Chemical Engineering ; Volume 24, Issue 4 , 2005 , Pages 1-7 ; 10219986 (ISSN) ; Vaziri, A ; Seifkordi, A. A ; Kheirolomoom, A ; Sharif University of Technology
2005
Abstract
We introduce a new smooth, non-toxic, biocompatible method for cross-linking of gum tragacanth (GT), a polysaccharide of natural origin, in order to serve as a new supporting matrix for immobilization systems. The modified gum is used as a matrix for the catalysis of the conversion of benzyl penicillin to 6-aminopenicillanic acid (6-APA) by means of Escherichia coli ATCC11105 with penicillin G acylase (PGA) activity. The results show that GT beads can not only serve as a proper matrix for immobilization, but show enhanced hydrolysis rate and stability compared to other immobilization systems used for this reaction. This signifies the potential of GT as a biocompatible matrix for...
True Class-E Design For Inductive Coupling Wireless Power Transfer Applications
, Article 30th International Conference on Electrical Engineering, ICEE 2022, 17 May 2022 through 19 May 2022 ; 2022 , Pages 864-868 ; 9781665480871 (ISBN) ; Safarian, A ; Fotowat Ahmady, A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2022
Abstract
The Class-E power amplifier has been widely studied and formulated in the literature. Although the majority of reported inductive coupling wireless power transfer (WPT) systems use a class-E power amplifier for driving the primary coil, still there is a lack of a comprehensive study on class-E circuit dedicated to WPT, providing a set of closed form design equations for proper class-E operation. This paper presents the required design equations needed to design a 'true' class-E circuit for WPT applications. Equations for the series-tuned secondary coil WPT system are presented, as well as two different design procedures for the parallel-tuned secondary coil. The derived equations have been...
Crashworthiness determination of side doors and B pillar of a vehicle subjected to pole side impact
, Article Applied Mechanics and Materials ; Vol. 663, issue , 2014 , p. 552-556 ; Faieza, A. A ; Sahari, B. B ; Nuraini, A. A ; Halali, M ; Sharif University of Technology
2014
Abstract
Pole Side Impact Tes is one out of three crash tests described by Euro NCAP standard for star rating of a vehicle and is required for assessing the Adult Occupant Protection. In this paper the goal is to determine the crashworthiness of side doors and B pillar in a Pole Side Impact Test based on Euro New Car Assessment Program (Euro-NCAP) using computer and simulation method. In this matter, a vehicle model has been prepared and meshed using Hypermesh and CATIA. The velocity of 29 km/h has been assigned to the vehicle which was on top of a cart while the pole has been assigned as a rigid static object based on Euro NCAP requirements specifically. Results show that different amounts of energy...
Investigation of Thickness Influences On Energy Absorption For Side Doors And B Pillar In Euro NCAP Pole Side Impact Test
, Article Applied Mechanics and Materials ; Vol. 663, issue , Oct , 2014 , p. 585-589 ; Faieza, A. A ; Sahari, B. B ; Nuraini, A. A ; Halali, M ; Sharif University of Technology
2014
Abstract
To assess a car under the Euro New Car Assessment Program (Euro-NCAP), Adult Occupant Protection is one out of three parameters which need to be calculated with a weight factor of 50% while the other parameters, Child Occupant Protection and Pedestrian Occupant Protection, have a weight factor of 20%. The Pole Side Impact Test, beside two other tests, Side and Front Impact, is also required to calculate the Adult Occupant Protection. It shows how important the Pole Side Impact Test is and what an effective role it has in the car rating assessment. In this paper, the objective is to evaluate the effect of thickness on the energy absorbed by the side doors and the B pillar and its...