Production of low ester (LM) pectin by de-esterification of high ester (HM) apple pectin

, Article Scientia Iranica ; Volume 12, Issue 3 , 2005 , Pages 306-310 ; 10263098 (ISSN) Alemzadeh, I ; Saifkordi, A. A ; Kahforooshan, D ; Nahid, P ; Sharif University of Technology

Sharif University of Technology 2005

Abstract

In this paper, LM pectin production from commercial apple pectin by using acid, alkali and ammonia methods in the presence of ethanol was studied. Also, the effect of different parameters such as, temperature, time, acid, alkali and ammonia treatment in LM pectin production were evaluated. In all the experiments, low temperature showed a better influence from a recovery, purity and low de-polymerization viewpoint. Optimum conditions in the acid method reached at pH = 2, t = 17 hrs and T = 30°C, in the alkaline method reached at pH = 11, t = 3 hrs and T = 5°C and in the ammonia method reached at 2 N ammonia and T = 5°C, were determined. © Sharif University of Technology

Alkaline protease production by immobilized cells using B. licheniformis

, Article Scientia Iranica ; Volume 20, Issue 3 , 2013 , Pages 607-610 ; 10263098 (ISSN) Maghsoodi, V ; Kazemi, A ; Nahid, P ; Yaghmaei, S ; Sabzevari, M. A ; Sharif University of Technology

2013

Abstract

In recent years there has been potential increase in the use of alkaline protease as industrial catalysts. Many major industrial and commercial applications, such as food and textile industries, and medical diagnoses, are highly dependent on the protease enzyme. In the cell immobilization technique, the free movement of microorganisms is restricted in the process, and a continuous system of fermentation can be used. In the present work, this technique has been used for alkaline protease production using different carriers, such as chitosan, corn cob and corn tassel. Enzyme activity before immobilization (72 h) was 78.3 U/ml. Corn cob, with 65% immobilization capacity and the highest enzyme...

Treatment of bakers yeast wastewater with a Biopack system

, Article Process Biochemistry ; Volume 37, Issue 5 , 2001 , Pages 447-451 ; 13595113 (ISSN) Nahid, P ; Vossoughi, M ; Alemzadeh, I ; Sharif University of Technology

2001

Abstract

The purpose of this study was to investigate the use of a horizontal packed bed bioreactor, named Biopack, to treat high strength wastewater, such as bakers yeast wastewater. The Biopack system (RBCP) is a modified rotating biological contactor and the system was applied for secondary treatment. The RBCP system produced high treatment efficiencies, COD removal was 94.9% when COD was 472 mg/l and surface organic loading = 0.187 kg COD/m2 per day and surface hydraulic loading = 6 l/m2 per day. Variations of surface hydraulic loading from 6 to 11.9 l/m2 per day produced a decrease in COD removal efficiency from 94.9 to 58.6%. Other factors, such as shock load, retention time and rotational...

Preparation and Characterization of Inhibitor Loaded Nanodiamond for Anticorrosion Coating

, M.Sc. Thesis Sharif University of Technology Rahmani, Pooria (Author) ; Shojaei, Akbar (Supervisor) ; Pirhadi, Nahid (Co-Supervisor)

Abstract

In recent years, nanodiamond (ND) has been used as reinforcement in polymeric nanocomposites in order to improve mechanical properties, thermal conductivity, etc. The surface of nanodiamond has several functional groups which make it appropriate adsorbent. In this study, nanodiamond was modified with dodecylamine corrosion inhibitor and was utilized (1wt %) in epoxy based nanocomposite. Fourier transform infrared spectroscopy (FTIR) analysis was used to confirm the surface modification of Nanodiamond. In order to estimate the loading amount of corrosion inhibitor, thermogravimetric analysis was investigated. FE-SEM analysis demonstrated nanoparticle dispersibility in epoxy matrix. Regarding...

Synthesis and Characterization of Anticorrosive Hybrid Epoxy Coating based on Polyaniline/Nanodiamond Nanostructures

, M.Sc. Thesis Sharif University of Technology Mohammadkhani, Rahman (Author) ; Shojaei, Akbar (Supervisor) ; Pirhady, Nahid (Co-Advisor)

Abstract

One of the ways that corrosion control is presented is the use of coatings that have good properties such as high adhesion, impact resistance, ultraviolet radiation, and so on. They also have other unique properties like anti-corrosion property. To achieve coatings with these advanced properties, they use special properties of nanocomposites. Nanocomposites can add or improve one or more properties to coating properties.In the present study, we tried to first synthesize NanoDiamond/Polyaniline hybrid nanoparticles in different percentages and then use this hybrid in epoxy ester coating. To characterize this hybrid, various analyzes such as FE-SEM, TEM, FT-IR, UV-Visible, TGA and XRD were...

Synthesis and Characterization of a Copper Catalyst for Low Temperature Water –Gas Shift Reaction

, M.Sc. Thesis Sharif University of Technology Rafiee Renani, Mansoureh (Author) ; Khorasheh, Farhad (Supervisor) ; Khandan, Nahid (Co-Advisor)

Abstract

Water Gas Shift (WGS) reaction is an old reaction in which syngas is used for producing Hydrogen. At the present time, the major application of this reaction is in fuel cells, since the necessary Hydrogen for these cells is provided by this reaction.
The present study investigate the influence of different preparation methods on properties of Cu-ZnO/Al2O3 catalyst for water gas shift (WGS) reaction, which is now known as the Commercial catalyst for low temperature WGS, and its influence on performance of Cu-ZnO/Al2O3 catalyst to derive an optimal Cu-ZnO/Al2O3 catalyst for water gas shift (WGS) reaction. Cu-ZnO/Al2O3 catalysts was synthesized by CP, DP, DP-Ultra, IWI , CP-Urea, and...

Investigation of Effective Parameters on Membrane Fouling in Membrane Bioreactors

, M.Sc. Thesis Sharif University of Technology Khorasanizadeh, Mohaddeseh (Author) ; Kariminia, Hamid Reza (Supervisor) ; Nahid, Parvin (Co-Advisor)

Abstract

Critical flux is an important parameter in membrane bioreactors, which studying it can give a better understanding of treatment by these bioreactors and make utilizing them easier. In this study, the effect of some sludge properties like it’s concentration, sludge volum index, concentration of protein and carbohydrate in EPS and SMP and the effect of some operating conditions like aeration flow rate and rest mode on critical flux in a submerged membrane bioreactor are investigated. In addition to comparison of TMP-t figures drived from flux step experiment, the hystersis figures are also compared. Finally, two long term experiments at two sub critical fluxes are done in order to study the...

Production of glucoamylase by aspergillus niger under solid state fermentation

, Article International Journal of Engineering, Transactions B: Applications ; Volume 25, Issue 1 , 2012 , Pages 1-7 ; 1728-144X (ISSN) Nahid, P ; Vossoughi, M ; Roostaazad, R ; Ahmadi, M ; Zarrabi, A ; Hosseini, S. M ; Sharif University of Technology

2012

Abstract

In this study, Glucoamylase production by Aspergillus niger was investigated under solid state fermentation using low cost by-products of agricultural processes as substrate. Highest enzyme production was observed when a combination of wheat bran (WB) and corn flour (CF) was used as compared to WB+ rice bran, WB+ rice flour and WB alone. Several compositions of corn flours were experimented. The best combination of WB in addition of 10% corn flour resulted maximum enzyme activities. Study of the fermentations in flasks revealed 373.3 IU/gds and 41.4 g/l for the enzyme activity and protein concentration respectively under conditions of 30± 1°C, pH 4.7 and time 96 h. Optimum conditions...

Kinetics Study and Determining an Optimum Reactor Condition for Dimethyl-ether Synthesis by Dehydration of Methanol over Nano-Crystalline γ-Al2O3

, M.Sc. Thesis Sharif University of Technology Alamolhoda, Sarah (Author) ; Kazemeini , Mohammad (Supervisor) ; Khorashe, Farhad (Supervisor) ; Khandan, Nahid (Supervisor)

Abstract

Dimethyl Ether (DME) is a pure and economic fuel which can be used as a suitable alternative for diesel fuels. Two processes are traditionally used for DME synthesis: producing methanol from synthesis gas and then dehydrating it to DME (direct process), and converting methanol into DME in a catalytic dehydration reactor over a solid-acid catalyst (indirect process), in which the indirect process seems to have economical advantage. In this research, the γ-Al2O3 catalyst was synthesized through precipitation process and then characterized by powder X-ray diffraction (XRD) and porosimetry analysis. Afterwards this catalyst was utilized in methanol dehydration reaction in a slurry reactor. Next,...

Investigation of the Governing Liquid-Liquid Interactions at the Oil-Brine Interface in Low-Salinity Waterflooding using Molecular Dynamics Simulations

, M.Sc. Thesis Sharif University of Technology Seif, Arya (Author) ; Mahani, Hassan (Supervisor) ; Ayatollahi, Shahaboddin (Supervisor) ; Pourkhiabani, Nahid (Co-Supervisor) ; Koleini, Mohammad Mehdi (Co-Supervisor)

Abstract

The characteristics of the brine-crude oil interface in hydrocarbon reservoirs are very important, especially during water-based enhanced oil recovery (EOR) operations such as low-salinity waterflooding. At the interface of the two aforementioned fluids, the interaction mechanisms between the molecules of these two non-miscible fluids would affect capillary forces hence the efficiency of the EOR method. However, based on the published literature, there are still many open questions and uncertainties about the interaction of oil and brine molecules at the interface and their roles in the interfacial tension (IFT) changes for different oil and brine compositions. In this regard, molecular...

Molecular Dynamics Simulation of Hydrogen Diffusion into Brine: Implications for Underground Hydrogen Storage

, M.Sc. Thesis Sharif University of Technology Kalati, Saba (Author) ; Ayatollahi, Shahaboddin (Supervisor) ; Mahani, Hassan (Supervisor) ; Pourkhiabani, Nahid (Co-Supervisor) ; Esmaeilbeig, Mohammad Amin (Co-Supervisor)

Abstract

The high consumption of worldwide fossil energy and its detrimental effects on the environment and climate have prompted a transition toward renewable energy sources. The availability of renewable energy sources depends on weather and seasonal changes; therefore, an imbalance between supply and demand would be unavoidable. Hydrogen storage as an energy carrier, can fulfill this energy mismatch. Storing hydrogen in underground formations, such as aquifers, has been the subject of extensive research recently. In these storage reservoirs, hydrogen contacts the resident brine which will be lost through the dissolution-diffusion mechanism. Therefore, successful design of these storages requires...

Molecular Dynamics Simulation of Fluid-Fluid and Solid-Fluid Interactions in Underground Hydrogen Storage

, M.Sc. Thesis Sharif University of Technology Haghighatnejad, Yasaman (Author) ; Mahani, Hassan (Supervisor) ; Ayatollahi, Shahaboddin (Supervisor) ; Pourkhiabani, Nahid (Co-Supervisor) ; Esmaeilbeig, Mohammad Amin (Co-Supervisor)

Abstract

Hydrogen is recognized as a clean energy carrier, playing a crucial role in energy transition. Subsurface formations, such as aquifers with large storage capacities, present economically viable options for hydrogen storage. However, optimizing the storage and recovery of hydrogen depends significantly on the wetting behavior of surfaces under various conditions. Determination of the wetting properties under different conditions is challenging due to experimental limitations, safety concerns, and the time required for tests, all of which can impact the efficiency of the process. For this reason, limited data are available in the published literature on the wettability of...

Investigation of Ionic Diffusion and Mixing Phenomena in Polymer-Enhanced Low-Salinity Waterflooding Using Molecular Dynamics Simulation

, M.Sc. Thesis Sharif University of Technology Abdolmaleki, Amir Hossein (Author) ; Ayatollahi, Shahaboddin (Supervisor) ; Mahani, Hassan (Supervisor) ; Esmaeilbeig, Mohammad Amin (Co-Supervisor) ; Pourkhiabani, Nahid (Co-Supervisor)

Abstract

Various studies have confirmed that water salinity and its composition significantly affect the efficiency of the waterflooding process. Field-scale operation of low-salinity water injection has been proven to be a cost-effective enhanced oil recovery (EOR) method which is also compatible with the environmental regulations. Although this method has satisfactory results, it faces some challenges, such as in-situ mixing of the injection low-salinity water with the saline water in the host reservoir. The salinity of the injected water increases, as it contacts the high-salinity reservoir brine in the pores. This phenomenon significantly impairs the efficiency of this technique, and increases...

Secrecy capacity scaling in large cooperative wireless networks

, Article IEEE Transactions on Information Theory ; Volume 63, Issue 3 , 2017 , Pages 1923-1939 ; 00189448 (ISSN) Mirmohseni, M ; Papadimitratos, P. P ; Sharif University of Technology

Institute of Electrical and Electronics Engineers Inc 2017

Abstract

We investigate large wireless networks subject to security constraints. In contrast to point-to-point, interferencelimited communications considered in prior works, we propose active cooperative relaying-based schemes. We consider a network with nl legitimate nodes, ne eavesdroppers, and path loss exponent α ≥ 2. As long as n2e (log(ne))γ = o(nl ), for some positive γ , we show that one can obtain unbounded secure aggregate rate. This means zero-cost secure communication, given fixed total power constraint for the entire network. We achieve this result through: 1) the source using Wyner randomized encoder and a serial (multi-stage) block Markov scheme, to cooperate with the relays and 2) the...

Fast estimation of connectivity in fractured reservoirs using percolation theory

, Article SPE Journal ; Volume 12, Issue 2 , 2007 , Pages 167-178 ; 1086055X (ISSN) Masihi, M ; King, P. R ; Nuratza, P ; Sharif University of Technology

Society of Petroleum Engineers (SPE) 2007

Abstract

Investigating the impact of geological uncertainty (i.e., spatial distribution of fractures) on reservoir performance may aid management decisions. The conventional approach to address this is to build a number of possible reservoir models, upscale them, and then run flow simulations. The problem with this approach is that it is computationally very expensive. In this study, we use another approach based on the permeability contrasts that control the flow, called percolation approach. This assumes that the permeability disorder of a rock can be simplified to either permeable or impermeable. The advantage is that by using some universal laws from percolation theory, the effect of the complex...

A new decoding scheme for errorless codes for overloaded CDMA with active user detection

, Article 2011 18th International Conference on Telecommunications, ICT 2011, Ayia Napa, 8 May 2011 through 11 May 2011 ; 2011 , Pages 201-205 ; 9781457700248 (ISBN) Mousavi, A ; Pad, P ; Delgosha, P ; Marvasti, F ; Sharif University of Technology

2011

Abstract

Recently, a new class of binary codes for overloaded CDMA systems are proposed that not only has the ability of errorless communication but also suitable for detecting active users. These codes are called COWDA. In [1], a Maximum Likelihood (ML) decoder is proposed for this class of codes. Although the proposed scheme for coding/decoding shows impressive performance, the decoder can be significantly improved. In this paper, by assuming practical conditions for the traffic in the system, we suggest and prove an algorithm that increases the performance of the decoder several orders of magnitude (the Bit-Error-Rate (BER) is divided by a factor of about 400 in some E b/N0's). The algorithm...

Estimation of the Effective Permeability of Heterogeneous Porous Media by Using Percolation Concepts

, Article Transport in Porous Media ; Volume 114, Issue 1 , 2016 , Pages 169-199 ; 01693913 (ISSN) Masihi, M ; Gago, P. A ; King, P. R ; Sharif University of Technology

Springer Netherlands 2016

Abstract

In this paper we present new methods to estimate the effective permeability (keff) of heterogeneous porous media with a wide distribution of permeabilities and various underlying structures, using percolation concepts. We first set a threshold permeability (kth) on the permeability density function and use standard algorithms from percolation theory to check whether the high permeable grid blocks (i.e., those with permeability higher than kth) with occupied fraction of “p” first forms a cluster connecting two opposite sides of the system in the direction of the flow (high permeability flow pathway). Then we estimate the effective permeability of the heterogeneous porous media in different...

Percolation-based effective permeability estimation in real heterogeneous porous media

, Article 15th European Conference on the Mathematics of Oil Recovery, 29 August 2016 through 1 September 2016 ; 2016 ; 9462821933 (ISBN); 9789462821934 (ISBN) Masihi, M ; Gago, P ; King, P ; DCSE; Schlumberger; Shell ; Sharif University of Technology

European Association of Geoscientists and Engineers 2016

Abstract

It has long been understood that flow behavior in heterogeneous porous media is largely controlled by the continuity of permeability contrasts. With this in mind, we are looking in new methods for a fast estimation of the effective permeability which concentrates on the properties of the percolating cluster. From percolation concepts we use a threshold permeability value (Kth) by which the gridblocks with the highest permeability values connect two opposite side of the system in the direction of the flow. Those methods can be applied to heterogeneous media of a range of permeabilities distribution and various underlying structures. We use power law relations and weighted power averages that...

Optimization of sputtering parameters for the deposition of low resistivity indium tin oxide thin films

, Article Acta Metallurgica Sinica (English Letters) ; Vol. 27, issue. 2 , Apr , 2014 , p. 324-330 Yasrebi, N ; Bagheri, B ; Yazdanfar, P ; Rashidian, B ; Sasanpour, P ; Sharif University of Technology

2014

Abstract

Indium tin oxide (ITO) thin films have been deposited using RF sputtering technique at different pressures, RF powers, and substrate temperatures. Variations in surface morphology, optical properties, and film resistances were measured and analyzed. It is shown that a very low value of sheet resistance (1.96 ω/sq.) can be achieved with suitable arrangement of the deposition experiments. First, at constant RF power, deposition at different pressure values is done, and the condition for achieving minimum sheet resistance (26.43 ω/sq.) is found. In the next step, different values of RF powers are tried, while keeping the pressure fixed on the previously found minimum point (1-2 Pa). Finally,...

Comparative assessment of gasification based coal power plants with various CO2 capture technologies producing electricity and hydrogen

, Article Energy and Fuels ; Volume 28, Issue 2 , 20 February , 2014 , Pages 1028-1040 ; ISSN: 08870624 Mukherjee, S ; Kumar, P ; Hosseini, A ; Yang, A ; Fennell, P ; Sharif University of Technology

2014

Abstract

Seven different types of gasification-based coal conversion processes for producing mainly electricity and in some cases hydrogen (H2), with and without carbon dioxide (CO2) capture, were compared on a consistent basis through simulation studies. The flowsheet for each process was developed in a chemical process simulation tool "Aspen Plus". The pressure swing adsorption (PSA), physical absorption (Selexol), and chemical looping combustion (CLC) technologies were separately analyzed for processes with CO2 capture. The performances of the above three capture technologies were compared with respect to energetic and exergetic efficiencies, and the level of CO2 emission. The effect of air...