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Effects of temperature and mixing modes on the performance of municipal solid waste anaerobic slurry digester 09 Engineering 0907 Environmental Engineering 09 Engineering 0904 Chemical Engineering
, Article Journal of Environmental Health Science and Engineering ; Volume 17, Issue 2 , 2020 , Pages 1077-1084 ; Shayegan, J ; Sharif University of Technology
Springer
2020
Abstract
Purpose: Anaerobic digestion is a promising technology for simultaneous treatment of biodegradable organic matter of municipal solid waste (MSW) and production of renewable energy. Mixing modes and temperature have influences on biogas production in anaerobic digesters treating MSW. Therefore, in this study, digester was operated at different modes of mixing and temperatures to obtain design criteria. Methods: The experiments were carried out in a semi-continuous digester. In the first part of the investigation, temperature was set at 25, 28, 31 and 34 °C. During this step, digester content was mixed in an intermittent mode by mechanical mixers. In the second part of the study, mixing...
Comparison of different trophic cultivations in microalgal membrane bioreactor containing N-riched wastewater for simultaneous nutrient removal and biomass production
, Article Process Biochemistry ; Volume 51, Issue 10 , 2016 , Pages 1568-1575 ; 13595113 (ISSN) ; Mehrnia, M. R ; Shayegan, J ; Sarrafzadeh, M. H ; Sharif University of Technology
Elsevier Ltd
2016
Abstract
In this study, a submerged membrane was installed in a bioreactor to treat N-riched wastewater and obtain high biomass productivity. Chlorella vulgaris was cultivated under mixotrophic, heterotrophic, and photoautotrophic conditions in different kinds of nitrogen sources (nitrate and ammonium) to compare the microalgae growth and nutrient removal in a membrane bioreactor. Further, the respirometric and photosynthetic activities of microalgae were investigated to evaluate the viability of microalgae in different conditions. The highest biomass productivity was obtained under mixotrophic cultivation in ammonium source (0.230 ± 0.009 gr/L d). Moreover, with this type of cultivation and nitrogen...
Improved advection algorithm of computational modeling of free surface flow using structured grids
, Article Computer Methods in Applied Mechanics and Engineering ; Volume 195, Issue 7-8 , 2006 , Pages 775-795 ; 00457825 (ISSN) ; Abdollahi, J ; Homayonifar, P ; Varahram, N ; Davami, P ; Sharif University of Technology
2006
Abstract
In the present study a finite difference method has been developed to model the transient fluid flow and heat transfer. A single fluid has been selected for modeling of mold filling and The SOLA-VOF 3D technique was modified to increase the accuracy of simulation of filling phenomena for shape castings. The model was then evaluated with the experimental methods. Refereeing to the experimental and simulation results a good consistency and the accuracy of the suggested model are confirmed. © 2005 Published by Elsevier B.V
Photobiochemical changes in Chlorella g120 culture during trophic conversion (metabolic pathway shift) from heterotrophic to phototrophic growth regime
, Article Journal of Applied Phycology ; Volume 32, Issue 5 , 2020 , Pages 2807-2818 ; Ranglová, K ; Malapascua, J. R ; Torzillo, G ; Shayegan, J ; Silva Benavides, A. M ; Masojídek, J ; Sharif University of Technology
Springer Science and Business Media B.V
2020
Abstract
Physiological and photobiochemical changes and growth in the heterotrophic strain Chlorella vulgaris g120 were studied during trophic conversion from heterotrophic to phototrophic growth regime. After the exposure of the Chlorella g120 culture to light, it revealed a significant activity of the electron transport (450–700 μmol e− m−2 s−1 as measured by chlorophyll fluorescence) and high PSII photochemical yield Fv/Fm between 0.7 and 0.8. Fast fluorescence induction kinetics showed that PSII electron acceptors in the plastoquinone pool remained partly oxidized, indicating no downregulation of PSII electron transport. The data further revealed that high photobiochemical activity is lost in...
Evaluation of nutrient removal and biomass production through mixotrophic, heterotrophic, and photoautotrophic cultivation of chlorella in nitrate and ammonium wastewater
, Article International Journal of Environmental Research ; Volume 12, Issue 2 , 2018 , Pages 167-178 ; 17356865 (ISSN) ; Mehrnia, M. R ; Shayegan, J ; Sarrafzadeh, M. H ; Amini, E ; Sharif University of Technology
Springer International Publishing
2018
Abstract
In this study, the effect of mixotrophic, heterotrophic, photoautotrophic (CO2 of air source), and photoautotrophic (bicarbonate source) cultivation of Chlorella vulgaris was investigated on microalgae growth rate and nutrient removal under different kinds of nitrogen sources. The highest N–NH3 +, N–NO3 −, P–PO4 3− (in ammonium source), and P–PO4 3− (in nitrate source) removal efficiency (87.28 ± 0.89, 70.00 ± 1.20, 87.00 ± 3.10, and 78.10 ± 1.95%, respectively) was reached in the mixotrophic culture. In all cultivations, when nitrate was used as the nitrogen source, specific growth rate, biomass productivity, and specific oxygen production rate (SOPR) were higher than the one with ammonium...
Point to point Control of a Brachiation Robot Based on Neural Network
, M.Sc. Thesis Sharif University of Technology ; Vossoughi, Gholamreza (Supervisor)
Abstract
• Brachiation robot is a kind of under-actuated robots. A brachiating robot is a type of a mobile arm that is capable of moving from branch to branch similar to a long-armed ape. The purpose of this thesis is control of a two link Brachiation robot. The purpose of this thesis is control of a two link Brachiation robot using neural network and geometry control. For this purpose a genetic algorithm based training Neural Network is used to produce a suitable path for the second link of the robot and then using input-output linearization method, the second link is controlled to follow the path. The simulations shows that the Nero Controller designed in this thesis is suitable. The controller can...
Traffic Source Particle Pollution Distribution Using Micro-scale Simulation
, M.Sc. Thesis Sharif University of Technology ; Hosseini, Vahid (Supervisor)
Abstract
Today air pollution has become one of the major urban management concerns. Air pollution could have dangerous effects on human health in short time or long time in many situations. Numerical modelling is one of the most applicable among different ways for predicting pollutant concentration like field measurement, physical model in wind tunnel, and simulation. Modelling of pollutant dispersion is a way for estimating concentration and aggregation of the pollutant near the surface and with different distances from pollution source. In different dispersion models, one of simplest is the Gaussian model. In this approach it is supposed that emission plume obeys from Gaussian distribution and is...
Modeling catalyst deactivation in dehydrogenation of ethylbenzene to styrene
, Article 11AIChE - 2011 AIChE Spring Meeting and 7th Global Congress on Process Safety, Conference Proceedings ; 2011 , Pages - ; 9780816910670 (ISBN) ; Baghalha, M ; Sharif University of Technology
American Institute of Chemical Engineers
2011
Abstract
The long-term deactivation of a commercial K-promoted Fe2O3 catalyst used in the dehydrogenation of ethylbenzene to styrene monomer was investigated using 30 mo of operating data of three industrial SM radial fixed bed adiabatic reactors. The Langmuir-Hinshelwood, Hougen-Watson model was used for reaction kinetics modeling. The kinetics of coking from ethylbenzene and styrene and the short-term deactivation function due to the quick coke formation were considered in the model. The kinetics of long-term deactivation of the catalyst for ethylbenzene dehydrogenation to styrene at 550°-630°C were determined. Unknown parameters of the long-term activity function, related to the slow loss of...
Modeling catalyst deactivation in dehydrogenation of ethylbenzene to styrene
, Article AIChE Annual Meeting, Conference Proceedings, 13 March 2011 through 17 March 2011 ; March , 2011 ; 9780816910670 (ISBN) ; Baghalha, M ; Sharif University of Technology
2011
Abstract
Long-term deactivation of a commercial K-promoted Fe 2O 3 catalyst used in the dehydrogenation of ethylbenzene to styrene monomer was studied using 30 months of operating data of three industrial SM radial fixed bed adiabatic reactors. The Langmuir-Hinshelwood, Hougen-Watson model (LHHW) was used for reaction kinetics modeling. The kinetics of coking from ethylbenzene and styrene and the short-term deactivation function due to the quick coke formation were also considered in the model. The kinetics of long-term deactivation of the catalyst for ethylbenzene dehydrogenation to styrene between 550 and 630 °C were determined by allowing the effects of temperature and time on the catalyst...
Seismic Rehabilitation of Irregular Steel Structures Using Friction Dampers
, M.Sc. Thesis Sharif University of Technology ; Moghaddam, Hassan (Supervisor)
Abstract
The purpose of this study was to find the optimal position and slip force of friction dampers, for improving the seismic performance of regular and irregular steel structures and comparison of dampers final pattern of these buildings.In this regard, one to six floor regular and irregular buildings were designed. These buildings were modeled three-dimensionally in the OpenSees Software, and were subjected to horizontal components of seven far field accelerogram in order to investigate the need for their rehabilitation. The results of the time history analysis of these buildings showed that inter-story drifts exceeds the acceptance criteria which has been assumed 2.5% according to the Life...
Probabilistic tolerance analysis of compliant assemblies
, Article 2007 World Congress, Detroit, MI, 16 April 2007 through 19 April 2007 ; 2007 ; 01487191 (ISSN) ; Movahhedy, M. R ; Sharif University of Technology
SAE International
2007
Abstract
Tolerance analysis is essential for estimation of final error of key product characteristic (KPC) in a mechanical assembly caused by errors in production and assembly of individual parts. Many mechanical assemblies, especially in automotive and aerospace industries, include sheet metal parts with a small ratio of thickness to width or length. Such parts are substantially flexible and thus, are prone to large errors due to elastic deformations during assembly production. Phenomena such as deformation due to fixture force, spring back, welding distortion and so on are common to such parts. Unlike tolerance analysis of rigid parts, here, the elastic deformation of the parts plays a significant...
Fabrication and Characterization of Nickel-Cobalt Catalyst by One-pot Combustion Synthesis Method for Synthesis Gas Production in Dry Reforming Methane Process
, M.Sc. Thesis Sharif University of Technology ; Sadrnezhad, Khatiboleslam (Supervisor)
Abstract
Dry reforming methane is a process during which two greenhouse gases, CH4 and CO2, using Ni-based catalysts, are altered into valuable H2 and CO gases, which are very useful from an economic and environmental point of view. The main problem with Ni-based catalysts is the formation of carbon in the dry methane reforming, which leads to rapid deactivation of the catalyst. In this research, a 10Ni-5Co/Al2O3 bimetallic catalyst was prepared by one-pot microwave-assisted combustion synthesis with a stoichiometric amount of fuel (urea) and without the use of additives. The catalyst was then calcined for 12 h at 550oC. The structure, chemical composition, particle distribution, and morphology of...
Analysis of Stock Return Volatility Using GARCH Models and Panel Data in Tehran Stock Exchange
, M.Sc. Thesis Sharif University of Technology ; Keshavarz Haddad, Gholamreza (Supervisor)
Abstract
Due to its extensive applications in financial analysis, stock market volatility modeling is a considerably important issue for stock market practitioners and academics. Using GARCH models to formulate the conditional variance heteroskedasticity with respect to the advantages of panel data technique such as higher degrees of freedom, more flexibility in the control of the omitted or unobserved variables effects, lead to a significant increase in the accuracy of estimations. In this thesis, in order to examine the similarities and differences between the conditional variance structure of stocks in the inter and intra industries, we have used a general to specific methodology of nested tests...
Synchronization of Two Chemical Reactors
, M.Sc. Thesis Sharif University of Technology ; Shahrokhi, Mohammad (Supervisor)
Abstract
Chaotic behavior takes place in different physical systems such as chemical reactors. In this thesis, dynamical behavior of chemical reactors in which polymerization or series reactions take place has been considered. It has been shown that these reactors have chaotic dynamics under special condition. Two reactors of the second type (with series reactions) for cases of known and unknown parameters have been synchronized by a control method and stability of the proposed scheme has been established by the Lyapunov stability theorem. Simulation results show the effectiveness of proposed method. Since concentration measurement is difficult and expensive, an observer has been used for...
Sliding Contact Problem of a Round Wedge with a FGM Coated Substrate with Finite Element Method
, M.Sc. Thesis Sharif University of Technology ; Adib Nazari, Saeid (Supervisor)
Abstract
Most of the current application and potential FGM included in the areas related to contact mechanic .These issues essentially are related to the transfer of force between two objects, that in general is with friction, so in this study the contact under the loading of horizontal and vertical with its different aspect such as the effect of contact region, the effect of round and also the effect of getting harden and soften of FGM.
The used method is a numerical method ¬(finite element method) that will resulted in contact equation discretisce by use of Penalty method. In this thesis is also presented the needed algorithms for solving the problem and the finite element code for solving the...
The used method is a numerical method ¬(finite element method) that will resulted in contact equation discretisce by use of Penalty method. In this thesis is also presented the needed algorithms for solving the problem and the finite element code for solving the...
Effect of Vertical Component of Earthquake on Cable-stayed Bridges
, M.Sc. Thesis Sharif University of Technology ; Maleki, Shervin (Supervisor)
Abstract
Cable stayed bridges have been used extensively in recent years for long span bridges up to 1000m. Although seismic behavior of these bridges has been researched in the last decade, however, the effect of vertical component of earthquake on cable-stayed bridges has not been studied before. In this thesis, the geometric nonlinear static analyses on dead loads followed by linear direct integration dynamic analyses have been used to study this effect. The results of analyses with three-component earthquakes are compared with two-component earthquakes. Fourteen models of cable-stayed bridges with different main span length, shape of pylons and the deck-pylon connection are employed. The errors...
Super-hydrophilic characteristic of thermochemically prepared CdS nanocrystals
, Article Physica E: Low-Dimensional Systems and Nanostructures ; Vol. 58 , April , 2014 , pp. 146-152 ; ISSN: 13869477 ; Taghavinia, N ; Babaei, A ; Sharif University of Technology
2014
Abstract
CdS nanocrystals were thermochemically (thermally activated) synthesized thorough the reaction between CdSO4 and Na2S 2O3 in an aqueous solution. Thioglycolic Acid (TGA) was used as the capping agent and catalyst of the reaction. The method was based on heat activated dissociation of Na2S2O3 and controllable release of S and free electrons in the solution. CdS NCs were formed by heating the sample solution at 96 C for 1 h. The results of optical spectroscopy and transmission electron microscopy demonstrated round shape NCs with sizes about 3.0 nm. The nanocrystals were also luminescent and represented a broad emission with a peak located at 515 nm and FWHM of 160 nm. Several samples were...
Distributed Compressed Sensing (DCS) and its Application in Wireless Sensor Network (WSN)
, M.Sc. Thesis Sharif University of Technology ; Babaei Zadeh, Masoud (Supervisor)
Abstract
Recent advances in Micro-Electro-Mechanical Systems (MEMS) technology, wireless communications,and digital electronics have enabled the development of low-cost, low-power,multifunctional sensor nodes that are small in size and communicate untethered in short distances.Wireless Sensor Network (WSN) including these sensors has been utilized in many applications, namely military and environmental applications. Due to unchangeable battery in most WSNs, Power consumption is an important challenge in such systems. A sensor node expends maximum energy in data communication. Control environmental parameter is among the most important applications of WSN. The actual physical environmental information...
Blind Speech Separation using Sparse Component Analysis
, M.Sc. Thesis Sharif University of Technology ; Babaei-Zadeh, Masoud (Supervisor)
Abstract
Separation of speech signals has many applications. For example, it is used human-machine communications. This problem can be divided into three categories: overdetermined, determined and underdetermined. If the number of mixtures is greater than the number of sources, the problem is called overdetermined; if it is equal to the number of sources, the problem is called determined and if it is less than the number of sources that problem is called underdetermined. This MS thesis studies the undertermined case. Moreover, speech signals are sparse in time-frequency domain, meaning that in each time-frequency point, usually only one source is active. So, for separatig the speech signals,the...
Molecular Dynamic Simulation of Metal and Ceramic Nanopowder Compaction Process and Investigation on Effective Factors
, M.Sc. Thesis Sharif University of Technology ; Khoei, Amir Reza (Supervisor)
Abstract
In present research forming process of nanopowders, which is a part of powder metallurgy was investigated by molecular dynamics method. Powder metallurgy is a relatively new method for production of industrial parts by pouring powder into die and compaction to desired density. One can reach parts with higher quality and strength by decreasing size of powder’s particles and entering the nano scale. Particle with smaller size have higher specific surface and due more intensity to react. Classic methods for investigation of this process don’t cover the atomic scale effects, so using newer procedures such as molecular dynamics is highly recommended. In present research, at first compaction of...