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    Simply decoded efficient full-rate space-time block codes over correlated Rician fading channels

    , Article IET Communications ; Volume 8, Issue 10 , 3 July 2014 , Pages 1684-1695 Kuhestani, A ; Pilaram, H ; Mohammadi, A ; Sharif University of Technology
    A novel technique is presented to design efficient full-rate space-time block codes (STBCs) over correlated Rician fading channels. The authors first derive a formula for the achievable information rate of a linear dispersion coded multi-input single-output system as a function of correlation at the transmitter in a Rician fading channel. In addition, the authors obtain the bit-error-rate (BER) equations for this system, when multiple phase shift keying and multiple quadrature amplitude modulation schemes are used at the transmitter. Therefore with regard to derived formulae and using a genetic algorithm, a method is presented to construct STBCs over correlated Rician fading channels. The... 

    Dynamics of nanodroplets on wettability gradient surfaces

    , Article Journal of Physics Condensed Matter ; Volume 23, Issue 8 , February , 2011 ; 09538984 (ISSN) Moosavi, A ; Mohammadi, A ; Sharif University of Technology
    A lubrication model is used to study the dynamics of nanoscale droplets on wettability gradient surfaces. The effects of the gradient size, size of the nanodroplets and the slip on the dynamics have been studied. Our results indicate that the position of the center of mass of the droplets can be well described in terms of a third-order polynomial function of the time of the motion for all the cases considered. By increasing the size of the droplets the dynamics increases. It is also shown that the slip can considerably enhance the dynamics. The results have been compared with the results obtained using theoretical models and molecular dynamics simulations  

    Environmentally responsive surface-modified silica nanoparticles for enhanced oil recovery

    , Article Journal of Nanoparticle Research ; Volume 18, Issue 9 , 2016 ; 13880764 (ISSN) Behzadi, A ; Mohammadi, A ; Sharif University of Technology
    Springer Netherlands 
    Environmentally responsive surface-modified nanoparticles are colloidal nanoparticles coated with, at least, two physicochemically distinct surface groups. Recent advances in the synthesis and production of nanoparticles have enabled the production of environmentally responsive surface-modified nanoparticles with both hydrophilic and hydrophobic surface groups. These nanoparticles act like colloidal surfactants. In this paper, environmentally responsive surface-modified silica nanoparticles are synthesized and used for enhancement of oil recovery. For this purpose, silica nanoparticles are coated with polyethylene glycol chains as hydrophilic agent and propyl chains as hydrophobic agent at... 

    Wettability alteration properties of fluorinated silica nanoparticles in liquid-loaded pores: An atomistic simulation

    , Article Applied Surface Science ; Volume 371 , 2016 , Pages 349-359 ; 01694332 (ISSN) Sepehrinia, K ; Mohammadi, A ; Sharif University of Technology
    Elsevier  2016
    Control over the wettability of reservoir rocks is of crucial importance for enhancing oil and gas recovery. In order to develop chemicals for controlling the wettability of reservoir rocks, we present a study of functionalized silica nanoparticles as candidates for wettability alteration and improved gas recovery applications. In this paper, properties of fluorinated silica nanoparticles were investigated in water or decane-loaded pores of mineral silica using molecular dynamics simulation. Trifluoromethyl groups as water and oil repellents were placed on the nanoparticles. Simulating a pore in the presence of trapped water or decane molecules leads to liquid bridging for both of the... 

    A low cost, efficient method for chip fabrication in cell analysis

    , Article 2016 23rd Iranian Conference on Biomedical Engineering and 2016 1st International Iranian Conference on Biomedical Engineering, ICBME 2016, 23 November 2016 through 25 November 2016 ; 2017 , Pages 93-96 ; 9781509034529 (ISBN) Rahmani, A ; Mohammadi, A ; Kalhor, H ; Sharif University of Technology
    in recent decades, DEP due to its high efficiency has been exploited widely in separation and manipulation of bioparticles. In the present work a simple, low-cost, and efficient procedure for fabrication of microfluidic chips applied in medicine and biochemistry has been presented. In this method, electrodes are not in direct contact with biological samples which results in elimination of conventional systems' cons. Efficacy of the designed system has been evaluated by injecting samples containing yeast and Ecoli cells into the system and analyzing their trajectory. Experimental results demonstrate that precise adjustment of voltage and frequency can lead to the desired separation in this... 

    Halogen-lithium exchange reaction using an integrated glass microfluidic device: an optimized synthetic approach

    , Article Organic Process Research and Development ; Volume 21, Issue 3 , 2017 , Pages 292-303 ; 10836160 (ISSN) Zeibi Shirejini, S ; Mohammadi, A ; Sharif University of Technology
    American Chemical Society  2017
    A telescoped approach was developed for the efficient synthesis of methoxybenzene through the generation of an unstable intermediate reagent, based on the Br-Li exchange reaction of p-bromoanisole and n-BuLi, followed by its reaction with water. In the first stage, p-methoxyphenyllithium was synthesized and consumed immediately in the second stage. For this purpose, an integrated glass microfluidic device was fabricated using laser ablation followed by the thermal fusion bonding method. The impact of various parameters, including solvent, reaction time, molar ratio, concentration of reagents, and flow rates were investigated to achieve the highest yield of the desired product, leading to an... 

    Transient forced convection with viscous dissipation to power-law fluids in thermal entrance region of circular ducts with constant wall heat flux

    , Article Energy Conversion and Management ; Volume 50, Issue 4 , 2009 , Pages 1062-1068 ; 01968904 (ISSN) MolaeiDehkordi, A ; Mohammadi, A. A ; Sharif University of Technology
    A numerical investigation was conducted on the transient behavior of a hydrodynamically, fully developed, laminar flow of power-law fluids in the thermally developing entrance region of circular ducts taking into account the effect of viscous dissipation but neglecting the effect of axial conduction. In this regard, the unsteady state thermal energy equation was solved by using a finite difference method, whereas the steady state thermal energy equation without wall heat flux was solved analytically as the initial condition of the former. The effects of the power-law index and wall heat flux on the local Nusselt number and thermal entrance length were investigated. Moreover, the local... 

    Extended haessler heuristic algorithm for cutting stock problem: a case study in film industry

    , Article Australian Journal of Basic and Applied Sciences ; Volume 3, Issue 4 , 2009 , Pages 3944-3953 ; 19918178 (ISSN) Pazand, K ; Mohammadi, A ; Sharif University of Technology
    The cutting stock problem is an important problem in the field of combinational optimization. In classic versions of this problem, the aim is to find a solution for cutting some equal-width mother rolls into smaller parts with given width so that the amount of trim-loss become as small as possible. There are plenty of works which addressed the classic cutting stock problem. However in real world applications there are usually some constraints which make the problem different form classical version and make it harder to solve. In this paper we investigate a special cutting stock problem in film industry and show that it can not be solved by using previous methods. We propose a new hybrid... 

    Fluid-structure interaction simulation of blood flow and cerebral aneurysm: effect of partly blocked vessel

    , Article Journal of Vascular Research ; Volume 56, Issue 6 , 2019 , Pages 296-307 ; 10181172 (ISSN) Saeedi, M ; Shamloo, A ; Mohammadi, A ; Sharif University of Technology
    S. Karger AG  2019
    In this study, using fluid-structure interaction (FSI), 3-dimensional blood flow in an aneurysm in the circle of Willis-which is located in the middle cerebral artery (MCA)-has been simulated. The purpose of this study is to evaluate the effect of a partly blocked vessel on an aneurysm. To achieve this purpose, two cases have been investigated using the FSI method: in the first case, an ideal geometry of aneurysm in the MCA has been simulated; in the second case, modeling is performed for an ideal geometry of the aneurysm in the MCA with a partly blocked vessel. All boundary conditions, properties and modeling methods were considered the same for both cases. The only difference between the... 

    Continuous synthesis of plate-like silica microparticles using microfluidics

    , Article Journal of Flow Chemistry ; Volume 9, Issue 3 , 2019 , Pages 161-174 ; 2062249X (ISSN) Tamtaji, M ; Mohammadi, A ; Sharif University of Technology
    Springer International Publishing  2019
    The synthesis of plate-like silica particles, which are of importance for a variety of applications, are mainly based on the widely adopted method of the sol-gel reaction of silicon alkoxides in traditional batch-wise instrumentation. In this study, continuous-flow synthesis of amorphous plate-like silica particles is reported through combining droplet-based microfluidics and the sol-gel reaction of tetraethyl orthosilicate. The reaction was conducted at the surface of oil droplets, comprising tetraethyl orthosilicate (TEOS), suspended in acidic (HCl) water, resulting in silica particles on the surface of the droplets, leaving the device with outlet flow. The synthesized particles had... 

    The stability and surface activity of environmentally responsive surface-modified silica nanoparticles: the importance of hydrophobicity

    , Article Journal of Dispersion Science and Technology ; Volume 41, Issue 9 , 2020 , Pages 1299-1310 Ghaleh, V.R ; Mohammadi, A ; Sharif University of Technology
    Taylor and Francis Inc  2020
    In this study, the effect of hydrophobicity of environmentally responsive surface-modified silica nanoparticles on the stability and surface activity of the nanoparticles is examined. To this end, n-propyl, n-hexyl, or n-octyl chains and methoxy poly(ethylene glycol) chains at various quantities were coated covalently on the surface of silica nanoparticles to regulate the hydrophobicity of the responsive nanoparticles. Various experimental tools such as stability analysis, interfacial-tension and contact-angle measurements, and emulsion formation were performed to investigate the effect of hydrophobicity. It became evident that the presence of the hydrophobic agents influences considerably... 

    Controlling the microscale separation of immiscible liquids using geometry: A computational fluid dynamics study

    , Article Chemical Engineering Science ; Volume 220 , 2020 Kamrani, S ; Mohammadi, A ; Sharif University of Technology
    Elsevier Ltd  2020
    In this study, we numerically determined the performance of a microscale separator comprising a lateral and a main channel to separate a two-phase flow. It was aimed to conduct continuous phase through the lateral channel and dispersed phase through the main channel. The continuous and dispersed phases were modeled as incompressible Newtonian fluids with the corresponding interface tracked by the phase-field model. The dynamics, including pressure fluctuations in the separator, were further examined. It was mechanistically demonstrated how the geometry of the separator modulates the phase separation. Further examined were the influences of various geometrical parameters on the performance of... 

    Sediment yield in the Daryacheh-Namak drainage basin, Iran, and its relation to land-use changes

    , Article IAHS-AISH Publication, 11 July 2007 through 13 July 2007, Perugia ; Issue 314 , 2007 , Pages 306-311 ; 01447815 (ISSN) ; 9781901502145 (ISBN) Feiznia, S ; Mohammadi, A ; Zakikhani, S ; Sharif University of Technology
    Monthly and annual variations in sediment yield during a 24-year period were analysed for 10 sub-catchments in the Daryacheh-Namak drainage basin, Iran. Highest specific suspended sediment yields were recorded at Razin and the lowest at Solan, reflecting large land-use changes in the former, and the presence of relatively resistant formations in thelatter sub-catchment. Highest sediment yields were observed in the months of April, March, May and November, and the lowest in September and August. At almost all stations, the highest sediment yield occurs in the spring, reflecting higher rainfall in that season. Copyright © 2007 IAHS Press  

    On-line trace enrichment of phenolic compounds from water using a pyrrole-based polymer as the solid-phase extraction sorbent coupled with high-performance liquid chromatography

    , Article Analytica Chimica Acta ; Volume 513, Issue 2 , 2004 , Pages 445-449 ; 00032670 (ISSN) Bagheri, H ; Mohammadi, A ; Salemi, A ; Sharif University of Technology
    A pyrrole-based conductive polymer was prepared and applied as new sorbent for on-line solid-phase extraction (SPE) of phenol and chlorophenols from water samples. Polypyrrole (PPy) was synthesized by chemical oxidation of the monomer in non-aqueous solution. The efficiency of this polymer for extraction of phenol and chlorophenols was evaluated using 35 mg of PPy as the sorbent in an on-line SPE system coupled to reversed-phase liquid chromatography with UV detection. The mobile phase were mixture of phosphate buffer-acetonitrile and compounds were eluted by the mobile phase using a six-port switching valve. High volumes of water, up to 160 ml, could be preconcentrated without the loss of... 

    Pyrrole-based conductive polymer as the solid-phase extraction medium for the preconcentration of environmental pollutants in water samples followed by gas chromatography with flame ionization and mass spectrometry detection

    , Article Journal of Chromatography A ; Volume 1015, Issue 1-2 , 2003 , Pages 23-30 ; 00219673 (ISSN) Bagheri, H ; Mohammadi, A ; Sharif University of Technology
    Elsevier  2003
    A pyrrole-based polymer was synthesized and applied as a new sorbent for solid-phase extraction (SPE) of some environmental pollutants from water samples. Polypyrrole (PPy) was synthesized by chemical oxidation of the monomer in nonaqueous solution. SPE of selected phenols, pesticides, and polyaromatic hydrocarbons (PAHs) from aqueous samples were performed using 200mg PPy. The determination was subsequently carried out by gas chromatography-flame ionization detection (GC-FID) and gas chromatography-mass spectrometry (GC-MS). The polymer showed much higher recoveries for aromatic compounds than aliphatics. Preconcentration of sample volumes up 1l led to acceptable recoveries for aromatic and... 

    Preparation of a naltrexone HCL potentiometric sensor and its application to pharmaceutical analysis and drug determination in biological fluids

    , Article Journal of Food and Drug Analysis ; Volume 19, Issue 4 , 2011 , Pages 445-451+539 ; 10219498 (ISSN) Ghorbani Bidkorbeh, F ; Shahrokhian, S ; Mohammadi, A ; Dinarvand, R ; Sharif University of Technology
    A novel ion selective electrode is fabricated for naltrexone HCl and used in pharmaceutical analysis and drug determination in biological fluids without complicated pretreatments and extractions, using direct potentiometry. The naltrexone complex with sodium tetraphenyl borate (NaTPB) is obtained by in situ soaking PVC membrane electrode in an 1 × 10 -3 M naltrexone solution. The sensor exhibited fast, reproducible and linear sub-Nernstian response over concentration range of 1 × 10 -5 - 1 × 10 -3 M with a detection limit of 5 × 10 -6 M. The membrane sensor was successfully applied to the determination of naltrexone in capsules as well as for its determination in urine and plasma samples  

    Simultaneous voltammetric determination of tramadol and acetaminophen using carbon nanoparticles modified glassy carbon electrode

    , Article Electrochimica Acta ; Volume 55, Issue 8 , 2010 , Pages 2752-2759 ; 00134686 (ISSN) Ghorbani Bidkorbeh, F ; Shahrokhian, S ; Mohammadi, A ; Dinarvand, R ; Sharif University of Technology
    A sensitive and selective electrochemical sensor was fabricated via the drop-casting of carbon nanoparticles (CNPs) suspension onto a glassy carbon electrode (GCE). The application of this sensor was investigated in simultaneous determination of acetaminophen (ACE) and tramadol (TRA) drugs in pharmaceutical dosage form and ACE determination in human plasma. In order to study the electrochemical behaviors of the drugs, cyclic and differential pulse voltammetric studies of ACE and TRA were carried out at the surfaces of the modified GCE (MGCE) and the bare GCE. The dependence of peak currents and potentials on pH, concentration and the potential scan rate were investigated for these compounds... 

    Electrochemical determination of naltrexone on the surface of glassy carbon electrode modified with Nafion-doped carbon nanoparticles: Application to determinations in pharmaceutical and clinical preparations

    , Article Journal of Electroanalytical Chemistry ; Volume 638, Issue 2 , 2010 , Pages 212-217 ; 15726657 (ISSN) Ghorbani Bidkorbeh, F ; Shahrokhian, S ; Mohammadi, A ; Dinarvand, R ; Sharif University of Technology
    A new sensitive and selective electrochemical sensor was developed for determination of naltrexone (NAL) in pharmaceutical dosage form and human plasma. Naltrexone is an opioid antagonist which is commonly used for the treatment of narcotic addiction and alcohol dependence. A voltammetric study of naltrexone has been carried out at the surface of glassy carbon electrode (GCE) modified with Nafion-doped carbon nanoparticles (CNPs). The electrochemical oxidation of naltrexone was investigated by cyclic and differential pulse voltammetric techniques. The dependence of peak currents and potentials on pH, concentration and the potential scan rate was investigated. The electrode characterization... 

    Behaviour of an innovative universal structural connection under monotonic and cyclic shear loading

    , Article Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE, 31 May 2009 through 5 June 2009, Honolulu, HI ; Volume 2 , 2009 , Pages 765-775 ; 9780791843420 (ISBN) Khonsari, S ; England, G. L ; Mohammadi, A. R ; Sharif University of Technology
    A new structural connection with special unique features was developed. While under bending it showed very high rotational capacity, in shear, unlike other existing connections, it also demonstrated a large shear deformation capacity. The ductile response of this connection stems from its innovative geometry as well as the ductility of the elements embedded in it. Since the previous shear tests on the specimens of this connection were carried out under 'unrestricted' conditions, the tests reported here were all under 'restricted' conditions. These shear tests consisted of 'monotonie' as well as 'cyclic' tests on mild steel specimens. Due to the restrictions imposed on the specimens during... 

    Realization of constant envelope OFDM using quantization and CPM technique

    , Article AEU - International Journal of Electronics and Communications ; Volume 80 , 2017 , Pages 172-178 ; 14348411 (ISSN) Rezaie, S ; Mohammadi, A ; Afrashteh, N ; Sanjaroonpouri, V ; Sharif University of Technology
    Orthogonal frequency division multiplexing (OFDM) is used in many wireless communication. The important drawback of this modulation is its high peak-to-average power ratio (PAPR). In this paper, a new modulation scheme of constant-envelope OFDM (CE-OFDM) is proposed. This scheme uses a combination of OFDM, quantizer and continuous phase modulation (CPM) to achieves 0 dB PAPR. The statistical signatures of signals, based on system parameters such as the length of discrete Fourier transform (DFT) and the number of quantization levels are presented. There are two sources of noise in proposed CE-OFDM scheme: quantization noise and channel noise. The theoretical analysis of these noises is...