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Now showing items 1 - 16 of 60437

  • Transition metal complexes of polyhydroxamic acid grafted on chitosan

    Hosseini, S. H.   Mousavi, S. M.   Hosseini Ashtiani, N.  

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  • Cathodic arc deposition of NiCrAlY coating: oxidation behaviour and thermodynamic

    Khakzadian, J.   Hosseini, S. H.   Zangeneh Madar, K.  

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  • A New Transformer-less Five-level Grid-Tied Inverter for Photovoltaic Applications

    Vosoughi, N.   Hosseini, S. H.   Sabahi, M.  

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  • Investigating the transition time reduction in evaporation of NiCrAlY using EB–PVD

    Hosseini, S. H.   Rastegari, S.   Mirdamadi, S.  

    Thermal barrier coatings have been widely considered owing to increasing efficiency of gas turbine engines. These coatings are often available in ceramic, thermally grown oxide and metallic bond layers. The function of metallic bond layer in these coatings is adhesion improvement and substrate protection. This layer can also be applied for electron beam–physical vapour deposition (EB–PVD). Yet, EB–PVD method cannot control evaporation process to be able to induce a deposit with uniform chemical composition along the coating thickness. The present study investigates composition variation during evaporation process of Ni–20Cr–11Al–0·3Y alloy using computational models and experimental results along with transition time prediction by computational model. To this end, EB–PVD by an electron gun with power of 3 kW in 4–6×10 −5 mbar vacuums was used. The results indicated that applying an initial molten pool with a composition similar to that of equilibrium pool (Ni–2Cr–15Al–0·5Y) decreases transition time by 70%.
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  • Zero-voltage switching bi-directional power electronic transformer

    Sabahi, M.   Hosseini, S. H.   Sharifian, M. B.   Goharrizi, A. Y.   Gharehpetian, G. B.  

    In this study, a bi-directional power flow zero-voltage switching (ZVS) power electronic transformer (PET) with phase shift modulation controller (PSM) is proposed. The PET contains input full-bridge active rectifier (FBAR), full-bridge DC-link inverter (FBDCI), high-frequency isolating transformer (HFIT), cycloconverter and output filter. FBDCI switches operate under ZVS condition. In addition, ZVS commutation of both cycloconverter bi-directional switches and FBAR switches are achieved. Dynamic voltage regulation is obtained without utilising energy storage elements. Therefore good efficiency can be achieved as a result of ZVS operation together with the absence of energy storage elements. The values of output filter are calculated to provide soft switching operation and voltage regulation. Based on the simulation and experimental results, the steady-state operation principles of the PET are described. Experimental results from a laboratory prototype with specification of 110 V/50 Hz input to 24 V/50 Hz output are presented to verify feasibility of the proposed PET.
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  • Applicability of a modified backward extrusion process on commercially pure aluminum

    Hosseini, S. H.   Abrinia, K.   Faraji, G.  

    In this study, a modified novel backward extrusion process implementing severe plastic deformation is presented for processing of ultrafine-grained materials. Deformation zone geometry was modified by elimination of mandrel's fillet for enhancing plastic strain and adding particular slope. Finite element analysis has been revealed higher strain value and more strain uniformity in this process. The process was applied to commercially pure aluminum, and microstructure and microhardness measurements were investigated. Surveying of microstructure in extruded specimen showed significant grain refinement resulted from the higher plastic strain of about 3.5 after only single pass new process. Uniform equivalent plastic strain through the thickness and length of the sample was achieved. Higher hydrostatic compression stress resulted from new die geometry limits the formation of any defects. Microhardness evolution in extruded part showed more than 52% improvement. (C) 2014 Elsevier Ltd. All rights reserved.
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  • Adaptive neuro-fuzzy inference system based automatic generation control

    Hosseini, S. H.   Etemadi, A. H.  

    Fixed gain controllers for automatic generation control are designed at nominal operating conditions and fail to provide best control performance over a wide range of operating conditions. So, to keep system performance near its optimum, it is desirable to track the operating conditions and use updated parameters to compute control gains. A control scheme based on artificial neuro-fuzzy inference system (ANFIS), which is trained by the results of off-line studies obtained using particle swarm optimization, is proposed in this paper to optimize and update control gains in real-time according to load variations. Also, frequency relaxation is implemented using ANFIS. The efficiency of the proposed method is demonstrated via simulations. Compliance of the proposed method with NERC control performance standard is verified. (c) 2007 Elsevier B.V. All rights reserved.
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  • Religion and Media, Religious Media, or Media Religion: Theoretical Studies

    Hosseini, S. H.  

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  • Distributed resources and DC distribution system combination for high power quality

    Noroozian, R.   Abedi, M.   Gharehpetian, G. B.   Hosseini, S. H.  

    This paper presents a DC distribution system supplied by an external AC system as well as local distributed resources (DRs) including distributed generations (DGs) and battery storage bank in order to demonstrate an overall solution to power quality issue. The power flow control in DC distribution system has been achieved by network and storage converters. A suitable control strategy for these converters has been proposed. They have DC voltage droop regulator and novel instantaneous power regulation scheme. Also a new control system has been proposed for DG converters. In this paper, several case studies have been studied based on proposed methods. The simulation results, based on PSCAD/EMTDC software, show that DC distribution systems including DR units can provide the high power quality. (C) 2010 Elsevier Ltd. All rights reserved.
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  • Minimum Spouting Velocity of Draft Tube Conical Spouted Beds Using Neural Network Approach

    Hosseini, S. H.   Valizadeh, M.   Olazar, M.   Altzibar, H.  

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  • Characterisation of aluminium nanopowder produced by evaporation-condensation method

    Hosseini, S. H.   Sheibani, S.   Valefi, Z.  

    In the present paper, aluminium nanoparticles were produced using evaporation of metal at high temperatures, 1500 degrees C, and subsequent cooling in cold argon gas. The samples were characterised in terms of composition, morphology, structure, particle size and surface area using complementary techniques such as X-ray diffraction, scanning electron microscopy, electron dispersive spectroscopy and the Brunauer-Emmett-Teller method. It was found that the nanoparticles were covered by a crystalline oxide layer. In addition, the Brunauer-Emmett-Teller results showed that the produced nanoparticles reached an average diameter of 85 nm under modified condition. Thermal analysis showed that the reactivity was affected by average particle diameter, size distribution and crystallinity of passivating oxide layer. The produced aluminium nanoparticles were compared with the micrometre sized and commercially available aluminium explosive (Alex) nanopowder. Results showed that the reactivity of broad size distribution Alex nanopowder is analogous to the narrow size distribution produced nanopowder even though the average particle size is larger for the Alex nanopowder.
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  • Smithsonite flotation using potassium amyl xanthate and hexylmercaptan

    Hosseini, S. H.   Forssberg, E.  

    The influence of potassium amyl xanthate (KAX) and hexylmercaptan (HM) adsorption on smithsonite surface at various concentrations were investigated through using zeta potential, contact angle, microflotation and diffuse reflectance FTIR studies at different pH. The zeta potential measurements of KAX showed that the adsorption of ionic charge (more negative charge after KAX treatment) takes place on the surface of pure crystalline smithsonite. The charges vary between -38 and -45 mV at pH 10middot5. Flotation results using potassium amyl xanthate reveal that the maximum recovery of 81middot3% and the maximum contact angle of 98middot7deg occurs at pH 10middot5 at KAX concentration of 2middot96 times 10 -3M in sodium sulphide (2middot6 times 10 -2M) and copper sulphate (9middot4 times 10 -3M) solution. The highest recovery and contact angle for flotation by means of HM occurs at pH 9 at values of 78middot6% and 92middot3deg respectively with HM concentration 1middot1 times 10 -2M. The FTIR spectra studies of smithsonite conditioned by KAX confirmed the adsorption of KAX and the presence of CS 2 on smithsonite surface. The FTIR spectra in HM studies showed the adsorption of RS - on the oxidised zinc surface and the S-H bond in the mercaptan is destroyed on adsorption. The comparison between the results using anionic collectors showed that the presence of different amounts of reagents on smithsonite surface in two cases confer different degree of hydrophobicity on the smithsonite surface.
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  • Modeling and control of C-UPFC for power system transient studies

    Ajami, A.   Hosseini, S. H.   Khanmohammadi, S.   Gharehpetian, G. B.  

    This paper presents the transient model of a new FACTS device, the center node unified power flow controller (CUPFC), installed at the midpoint of a transmission line. The C-UPFC consists of three voltage source inverters (VSI) with common DC link. One of the converters. is connected in parallel at the midpoint of line and the other two converters are connected in series. The simulation results indicate that the C-UPFC is capable of independently controlling the active and reactive power flows at the both ends of line and the magnitude of AC voltage at line mid point. It is shown that by adding a supplementary control system to the shunt inverter control system, it is possible to balance line current too. (c) 2005 Elsevier B.V. All rights reserved.
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  • Adsorption studies of smithsonite flotation using dodecylamine and oleic acid

    Hosseini, S. H.   Forssberg, E.  

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  • Determination of optimum generation level in DTEP using a GA-based quadratic programming

    Haddadian, H.   Hosseini, S. H.   Shayeghi, H.   Shayanfar, H. A.  

    In this paper, a new approach by accomplishing dynamic transmission expansion planning (DTEP) problem, the optimum generation level of generators is determined for annual load peak using a genetic algorithm (GA) based quadratic programming (QP) method. This study is carried out in order to achieve a better prospect from the generation network and consequently the suitable planning for its future expansion. Another important aspect of this paper is taking the advantage of line outage distribution factors (LODFs) or sensitivity analysis for the evaluation of network reliability instead of the direct current load flow (DCLF), that the computations and performance of DTEP problem considerably speeds up in comparison with previous researches. Also, the applied coding for problem solution using GA is more flexible and is significantly improved the performance of the proposed method. The proposed method is successively applied to a realistic system of the 18-buses Azerbaijan regional electric network, which is located in the northwest of Iran, and the results are extensively analyzed. The results evaluation reveals that the generators with high capacity operated in full capacity almost the whole of the planning period, because the generation cost coefficients is decreased as the generator capacity increased and vice versa. (C) 2010 Elsevier Ltd. All rights reserved.
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  • Applicability of friction-assisted tube straining method to produce high-strength copper tubes

    Hosseini, S. H.   Sedighi, M.  

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