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haghi--mahdi
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Construction of Membrane Bioreactor for Glucose Separation from Enzymatic Hydrolysis of Corn Fiber
, M.Sc. Thesis Sharif University of Technology ; Soltanieh, Mohammad (Supervisor)
Abstract
Production of cellulosic ethanol from lignocellulosic biomass represents a alternative to the petroleum fuel due to its renewable nature and sustainable availability. The major strategy used for cellulosic ethanol production includes three main steps of biomass pretreatment, enzymatic hydrolysis and ethanol fermentation. The enzymatic hydrolysis contributes significantly to the cost of cellulosic ethanol and from the process economics perspective, the improvement in the enzymatic hydrolysis step is a prerequisite. The fiber is composed of cell wall fractions and residual starch which can be hydrolyzed to reducing sugar.A method of hydrolysis of polysaccharides in corn fiber, feed...
Developing a Model for Design of Small Hydro Power Systems and It’s Validation with Empirical Results
, M.Sc. Thesis Sharif University of Technology ; Saboohi, Yadollah (Supervisor)
Abstract
Hydro power is a clean energy resource which has numerous advantages over other renewable energy systems including competitiveness with fossil fuel systems, high reliability, considerable potential, and availability of technology. These advantages have drawn attention to hydropower systems. Small Hydro Power (SHP) systems can be used for supplying the demand of rural and remote areas where electricity network rarely exists. SHP may also provide an investment opportunity. Comprehensive analysis of design features and operation of SHP and management of risks involved requires development and application of reliable analytical tools. The present research aims at developing a model for optimal...
An isolated three-phase soft-switched buck rectifier
, Article 2010 IEEE International Conference on Power and Energy, PECon2010, Kuala Lumpur, 29 November 2010 through 1 December 2010 ; 2010 , Pages 813-818 ; 9781424489466 (ISBN) ; Zolghadri, M.R ; Haghi, R ; Sharif University of Technology
2010
Abstract
In this paper a novel soft switching isolated buck rectifier is proposed. Various switching state sequences of a three-phase three-switch buck-type unity power factor rectifier are reviewed and the value of switching power loss in each state transition is investigated. The switching power loss of the converter is decreased by using zero current switching (ZCS) method. The operation modes of the converter are explained and analyzed. By using an auxiliary circuit with a simple method of energy recovery, the current is diverted away from the main power switches before they are turned off; so, switching losses in the converter are reduced. In this topology, the power transformer has only the...
Spherical collapse in modified newtonian dynamics
, Article Astrophysical Journal ; Volume 694, Issue 2 , 2009 , Pages 1220-1227 ; 0004637X (ISSN) ; Rahvar, S ; Haghi, H ; Sharif University of Technology
2009
Abstract
Modeling the structure formation in the universe, we extend the spherical-collapse model in the context of modified Newtonian dynamics (MOND) starting with the linear Newtonian structure formation followed by the MONDian evolution. In MOND, the formation of structures speeds up without a need for dark matter. Starting with the top-hat overdense distribution of the matter, the structures virialize with a power-law profile of the distribution of matter. We show that the virialization process takes place gradually from the center of the structure to the outer layers. In this scenario, the smaller structures enter the MONDian regime earlier and evolve faster, hence they are older than larger...
Developing a model for optimal sizing of a small hydropower/PV hybrid system for electrification
, Article 2017 5th IEEE International Conference on Smart Energy Grid Engineering, SEGE 2017, 14 August 2017 through 17 August 2017 ; 2017 , Pages 170-176 ; 9781538617755 (ISBN) ; Farshidian, B ; Saboohi, Y ; Sharif University of Technology
2017
Abstract
The present study investigates the possibility of using a small hydropower/PV hybrid power system for low-cost electricity production which can satisfy the energy load requirements of a typical rural-urban area. In this context, the optimal dimensions to improve the technical and economical performances of the hybrid system are determined according to the load energy requirements and the solar and hydro resources data using linear programming. The application of the model is demonstrated using a case study of a rural-urban area in Mazandaran province, Iran. Two scenarios were considered for optimizing the system components. In the first scenario, a stand-alone hybrid small hydropower/PV...
Efficiency Improvement of a PWM Rectifier Using Soft Switching and Redesign of the Modified Converter
, M.Sc. Thesis Sharif University of Technology ; Zolghadri, Mohammad Reza (Supervisor)
Abstract
In this project, the Line-Modulated Fixed Off-Time method is used as the current control strategy for a Power Factor Corrector (PFC) pre-regulator. A zero voltage switching PWM (ZVS-PWM) auxiliary circuit is configured to perform ZVS in the switches. To reduce conduction losses, the rectifier circuit and the PFC are combined to create bridgeless PFC and a new zero-voltage-switching is introduced for reduse switching loss. Soft commutation of the main switch with zero voltage is achieved without additional current stress. When main switch is turned off ,the voltage across the switch rises very slowly. when the current of the switch decays to zero the voltage across the switch is very low.A...
Stochastic Programming Approach for Resource Assignment and Patient Scheduling
, M.Sc. Thesis Sharif University of Technology ; Modarres Yazdi, Mohammad (Supervisor)
Abstract
In this study, we examine all decisions related to operating room planning and scheduling problem by considering uncertainty in surgery durations. To achieve this purpose, first, a mixed integer linear program is developed to determine the master surgical schedule. Then, two different approaches are investigated to model the weekly planning and scheduling of elective patients problem considering uncertain surgery durations. In the first approach, a unified model is proposed and an effective and efficient method, based on the recently introduced anarchic society optimization algorithm, is developed to solve the problem. In the second approach, first an advance scheduling problem is formulated...
Novel unbreakable solid-phase microextraction fibers on stainless steel wire and application for the determination of oxadiargyl in environmental and agricultural samples in combination with gas chromatography-mass spectrometry
, Article Talanta ; Vol. 128, issue , 2014 , Pages 231-236 ; ISSN: 00399140 ; Baghernejad, M ; Bagheri, H ; Sharif University of Technology
2014
Abstract
Sol-gel based solid-phase microextraction fibers supported by a stainless steel wire were fabricated and employed for GC-MS determination of oxadiargyl in real samples. The fibers were based on four compounds with different polarity: polar and non-polar (end-capped) poly(dimethylsiloxane) (PDMS), polyethylene glycol (PEG), and poly(ethylene-propyleneglycol)-monobutyl ether (UCON). For this purpose, the surface of the stainless steel was initially modified by (3-mercaptopropyl) trimethoxysilane. The results of the modification procedure were evaluated by cyclic voltammetry and energy dispersive X-ray (EDX) spectroscopy. After the modification, four different sol-gel based SPME fibers with...
Preparation, characterization, and applications of a novel solid-phase microextraction fiber by sol-gel technology on the surface of stainless steel wire for determination of poly cyclic aromatic hydrocarbons in aquatic environmental samples
, Article Analytica Chimica Acta ; Vol. 813 , 2014 , pp. 48-55 ; ISSN: 00032670 ; Hosseininasab, V ; Bagheri, H ; Sharif University of Technology
2014
Abstract
A novel solid-phase microextraction(SPME) fiber was prepared using sol-gel technology with ethoxylated nonylphenol as a fiber coating material. The fiber was employed to develop a headspace SPME-GC-MS method suitable for quantification of 13 polycyclic aromatic hydrocarbons (PAHs) in water samples. Surface characteristics of the fibers were inspected by energy dispersive X-ray (EDX) spectroscopy as well as by scanning electron microscopy (SEM). The SEM measurements showed the presence of highly porous nano-sized particles in the coating. Important parameters affecting the extraction efficiency such as extraction temperature and time, desorption conditions as well as ionic strength have been...
In situ solid-phase microextraction and post on-fiber derivatization combined with gas chromatography-mass spectrometry for determination of phenol in occupational air
, Article Analytica Chimica Acta ; Volume 742 , 2012 , Pages 17-21 ; 00032670 (ISSN) ; Baghernejad, M ; Bagheri, H ; Sharif University of Technology
Elsevier
2012
Abstract
A method based on solid-phase microextraction (SPME) followed by on-fiber derivatization and gas chromatography-mass spectrometry detection (GC-MS) for determination of phenol in air was developed. Three different types of SPME fibers, polar and non-polar poly(dimethylsiloxane) (PDMS) and polyethylene glycol (PEG) were synthesized using sol-gel technology and their feasibility to the sampling of phenol were investigated. Different derivatization reagents for post on-fiber derivatization of phenol were studied. Important parameters influencing the extraction and derivatization process such as type of fiber coating, type and volume of derivatizing reagent, derivatization time and temperature,...
A novel zero-voltage-transition bridgeless PFC with reduced conduction losses
, Article 2011 2nd Power Electronics, Drive Systems and Technologies Conference, PEDSTC 2011, 16 February 2011 through 17 February 2011 ; February , 2011 , Pages 587-592 ; 9781612844213 (ISBN) ; Zolghadri, M. R ; Beiranvand, R ; Sharif University of Technology
2011
Abstract
In this paper, a new zero-voltage-switching high power-factor (PF) rectifier with Line-Modulated Fixed-Off-Time current control is introduced, that off time is a function of the instantaneous line voltage. The auxiliary circuit provides soft switching for all semiconductor devices, without any extra current and voltage stress on the main switches. The proposed converter is bridgeless, and all semiconductor devices are soft switched. In addition, there is no extra stress on the switches. Thus, the conduction and switching losses are reduced and maximum efficiency is achieved. A 250W, with an input ac voltage of 90265 Vrms and an output voltage 400 Vdc, 100 kHz is designed and simulated to...
Novel zero-voltage-switching bridgeless PFC converter
, Article Journal of Power Electronics ; Volume 13, Issue 1 , 2013 , Pages 40-50 ; 15982092 (ISSN) ; Zolghadri, M. R ; Beiranvand, R ; Sharif University of Technology
2013
Abstract
In this paper, a new zero-voltage-switching, high power-factor, bridgeless rectifier is introduced. In this topology, an auxiliary circuit provides soft switching for all of the power semiconductor devices. Thus the switching losses are reduced and the highest efficiency can be achieved. The proposed converter has been analyzed and a design procedure has been introduced. The control circuit for the converter has also been developed. Based on the given approach, a 250 W, 400 Vdc prototype converters has been designed at 100 kHz for universal input voltage (90-264 Vrms) applications. A maximum efficiency of 94.6% and a power factor correction over 0.99 has been achieved. The simulation and...
Immersed solvent microextraction of aryloxyphenoxypropionate herbicides from aquatic media
, Article International Journal of Environmental Analytical Chemistry ; Volume 93, Issue 4 , Feb , 2013 , Pages 450-460 ; 03067319 (ISSN) ; Es'haghi, A ; Es-haghi, A ; Sharif University of Technology
2013
Abstract
An immersed solvent microextraction (SME) method was successfully developed for the trace enrichment of aryloxyphenoxypropionate herbicides from aquatic media. A microdrop of toluene was used as the extraction solvent. Some important extraction parameters such as type of solvent, solvent dropsize, stirring rate, ionic strength and extraction time were investigated and optimized. The microdrop volume of 1.5 μL, a sampling time of 25 min, and use of toluene were major parameters for achieving high enrichment factors. The linearity was studied by preconcentration of 4 mL of the water samples spiked with a standard solution of aryloxyphenoxypropionates at the concentration range of 0.15 to 30 ng...
Magellanic Stream: A possible tool for studying dark halo model
, Article New Astronomy ; Volume 14, Issue 8 , 2009 , Pages 692-699 ; 13841076 (ISSN) ; Hasani Zonoozi, A ; Rahvar, S ; Sharif University of Technology
2009
Abstract
We model the dynamics of Magellanic Stream with the ram-pressure scenario in the logarithmic and power-law galactic halo models and construct numerically the past orbital history of Magellanic Clouds and Magellanic Stream. The parameters of models include the asymptotic rotation velocity of spiral arms, halo flattening, core radius and rising or falling parameter of rotation curve. We obtain the best-fit parameters of galactic models through the maximum likelihood analysis, comparing the high resolution radial velocity data of HI in Magellanic Stream with that of theoretical models. The initial condition of the Magellanic Clouds is taken from the six different values reported in the...
Imprinted silica nanofiber formation via sol-gel-electrospinning for selective micro solid phase extraction
, Article New Journal of Chemistry ; Volume 42, Issue 16 , 2018 , Pages 13864-13872 ; 11440546 (ISSN) ; Bagheri, H ; Es Haghi, A ; Sharif University of Technology
Royal Society of Chemistry
2018
Abstract
Sol composition and ripening conditions are two important parameters in silica fiber production through the conventional sol-gel process. In the current study, silica nanofibers were successfully obtained via the electrospinning technique, and sol-gel formation occurred during this process. Based on previous reports, with the aim of increasing the selectivity, we used the molecular imprinted methodology to produce a selective medium via sol-gel electrospinning. In this process, sol-gel was formed during electrospinning and then, the backbone polymer was removed by heating. To obtain a thin layer of silica nanofibers, the influencing parameters such as backbone polymer types, imprinting time...
Macro modeling of steel-concrete composite shear walls
, Article Structures ; Volume 23 , 2020 , Pages 383-406 ; Epackachi, S ; Taghi Kazemi, M ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
To date, many researchers have developed various types of macro models to simulate the general response of conventional steel plate and reinforced concrete shear walls. Although extensive numerical and experimental studies have been conducted to assess the seismic response of steel-plate concrete composite shear walls, a robust macro-model for simulation of the cyclic response of such systems has not been developed yet. Herein, a fiber-based model is proposed to simulate the nonlinear seismic response of SC walls using PERFORM-3D program. The details of the proposed model, including material properties, element type, and boundary condition, are presented. The proposed model is validated...
Cyclic performance of composite shear walls with boundary elements
, Article Structures ; Volume 27 , 2020 , Pages 102-117 ; Epackachi, S ; Taghi Kazemi, M ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
In the past three decades, several experiments were conducted to investigate the seismic behavior of composite plate shear walls (C-PSW) because of their advantages to conventional reinforced concrete (RC) and steel plate shear walls (SPSW). Numerical studies, however, are limited due to the complexities for the finite element modeling of the steel and concrete material behaviors and their composite action. Herein, the cyclic behavior of various C-PSW with and without boundary elements (BE) is investigated numerically. The effects of design parameters such as aspect ratio, axial load ratio, and the length of the BE on the response of C-PSW are investigated. The advanced finite element...
Super-porous semi-interpenetrating polymeric composite prepared in straw for micro solid phase extraction of antibiotics from honey, urine and wastewater
, Article Journal of Chromatography A ; Volume 1631 , 2020 ; Bagheri, H ; Es-haghi, A ; Sharif University of Technology
Elsevier B.V
2020
Abstract
A cryogel–based semi–interpenetrating polymer network (Cryo–SIPN) was prepared in which conductive polymers such as polyaniline (PANI) and polypyrrole (PPy) were formed within the super porous network of acrylic acid cryogel. For completion of cryo-polymerization, all the constituent solutions were severely mixed and placed into the plastic straws and kept at -20°C and then the synthesized cyrogels were cut into the 1-cm length and freeze dried after washing with water. The Cryo–SIPN polymeric composite was applied in micro solid phase extraction (µSPE) of some selected antibiotic residues from various samples. The µSPE method combined with a high performance liquid...
Planning of multi-hub energy system by considering competition issue
, Article International Journal of Sustainable Energy Planning and Management ; Volume 30 , 2021 , Pages 5-20 ; 22462929 (ISSN) ; Rajabi Ghahnavieh, A ; Haghi, E ; Sharif University of Technology
Aalborg University press
2021
Abstract
Energy hub concept has been emerged as a suitable tool to analyze multi-carrier energy systems. Deregulation and increasing competition in the energy industry have provided a suitable platform for developing the multi-agent energy systems. Planning of energy hubs considering the competition between the hubs has not been sufficiently addressed, yet. A model has been proposed in this study for planning of a multi-hub energy system considering the competition between the hubs. The hubs are interconnected via an electric transmission system. A linear model has been developed to determine the optimal planning/operation strategy for energy hubs in a multi-period planning horizon to meet the heat...
Turn-off chelation-enhanced fluorescence sensing of carbon dot-metallic deep eutectic solvent by imidazole-based small molecules
, Article Sensors and Actuators B: Chemical ; Volume 344 , 2021 ; 09254005 (ISSN) ; Bagheri, H ; Es-haghi, A ; Sharif University of Technology
Elsevier B.V
2021
Abstract
Low accuracy, requirement of expensive instruments, derivatization and multi-step sample preparation, inconsistencies during the fabrication process, time-consuming procedures and utilization of eco-unfriendly chemicals are some limitations of various developed methods for detection of 4-methylimidazol (4-MeI). Herein, a rapid and miniaturized fluorescent probe based on the ultrasound‒assisted formation of carbon dots (CDs) in a metallic deep eutectic solvent (MDES) was developed and conveniently implemented to detect 4-MeI in commercial dark soft drinks. In-situ synthesis of CDs-chelated metals in the presence of the target analyte facilitates a kinetically fluorescence emission with no...