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    Development of fcc-Al nanoparticles during crystallization of amorphous Al–Ni alloys containing mischmetal: Microstructure and hardness evaluation [electronic resource]

    , Article Materials Science and Engineering A ; Volume 604, 16 May 2014, Pages 92-97 Mansouri, M. (Mehdi) ; Simchi, A ; Varahram, N ; Park, E. S ; Sharif University of Technology
    Abstract
    In the present work, fcc-Al nanoparticle development in Al90−xNi10MMx (MM: Ce mischmetal; x=2, 4) amorphous alloys was studied via non-isothermal differential scanning calorimetry, X-ray diffraction, transmission electron microscopy, and nanoindentation test. Results showed that the crystallization of Al88Ni10MM2 alloy occurred by the precipitation of fcc-Al nanoparticles followed by the crystallization of Al11MM3 and Al3Ni phases. Transmission electron microscopy revealed that the aluminum precipitates had an average size of ~12 nm with a round morphology. Increasing the mischmetal content to 4 at% (Al86Ni10MM4 alloy) caused a three-stage crystallization process with a change in the size... 

    On the development of direct metal laser sintering for rapid tooling

    , Article Journal of Materials Processing Technology ; Volume 141, Issue 3 , 2003 , Pages 319-328 ; 09240136 (ISSN) Simchi, A ; Petzoldt, F ; Pohl, H ; Sharif University of Technology
    2003
    Abstract
    An iron based powder blend has been developed for rapid tooling using a direct laser sintering process. The powder consists of a mixture of different elements including Fe, C, Cu, Mo and Ni. High sintering activities were obtained by tailoring the powder characteristics and optimizing the chemical constituents. The manufacturing of complex-shaped parts is possible at rates of 6.75 cm3/h according to CAD data. The residual porosity is less than 5 vol.%. The bending strength is around 900 MPa and the artifact hardness is 490 HV30. To further improve the service life of tools, the processed parts are sintered again in a vacuum furnace at 1260 °C for 30 min. This enables to manufacture precision... 

    Molecular dynamics simulation of melting, solidification and remelting processes of aluminum [electronic resource]

    , Article Iranian Journal of Science and Technology ( IJST): Transactions of Mechanical Engineering ; 2012, Vol.36, No. M1, P.13-23 Solhjoo, S ; Simchi, A. (Abdolreza) ; Aashuri, H ; Sharif University of Technology
    Abstract
    A molecular dynamics simulation study has been performed to investigate the solidification and remelting of aluminum using Sutton - Chen many body potential. Different numbers of atoms from 108 to 2048 atoms were considered to find an adequate size for the system. Three different cooling and heating rates, i.e. 1 0 12 K/s, 10 13 K/s and 10 14 K/s, were used. The structure of the system was examined using radial distribution function. The melting and crystallization temperatures of aluminum were evaluated by calculating the variation of heat capacity during the phase t ransformation. Additionally, Wendt – Abraham parameters were calculated to determine the glass transition temperature. It is... 

    Quick deployment of open-source hardware and software for a dual-channel biosignal recorder

    , Article 2013 IEEE International Conference on Smart Instrumentation, Measurement and Applications, ICSIMA 2013 ; 2013 ; 9781479908431 (ISBN) Zahedi, E ; Sharif University of Technology
    2013
    Abstract
    Access to a prototype during R&D can play a crucial role in early identification of the weaknesses in the design. Under circumstances that a particular commercial subsystem with the exact required specific features is unavailable, the realization of such a prototype can be delayed. In this paper, an example of rapid prototyping for a dual-channel biosignal data acquisition system based on the open-source concept is described. The selected biosignal is the finger photoplethysmogram. Except for Matlab, all other software components are open-source. The hardware design of the optical sensor utilized to record the signals is also open-source, making the system extremely affordable with the... 

    Application of a new rapid transit network design model to bus rapid transit network design: Case study Isfahan metropolitan area

    , Article Transport ; Volume 30, Issue 1 , Oct , 2013 , pages 93-102 ; 16484142 (ISSN) Kermanshahi, S ; Shafahi, Y ; Bagherian, M ; Sharif University of Technology
    2013
    Abstract
    The problem of Rapid Transit Network Design (RTND) is studied in this paper. Due to the noticeable contribution of rapid transit lines in public transportation network of large urban areas, this problem is interesting to the transportation specialists. On the other hand, the success stories of Bus Rapid Transit (BRT) systems in different countries have motivated us to study BRT network planning. BRT systems can be developed with less investment costs and construction time in comparison with rail-based systems. Therefore, planning Bus Rapid Transit lines, either to develop a new rapid transit network or extend a current one can be an interesting research topic. This problem, like other... 

    Drug nano-particles formation by supercritical rapid expansion method; operational condition effects investigation

    , Article Iranian Journal of Chemistry and Chemical Engineering ; Volume 30, Issue 1 , 2011 , Pages 7-15 ; 10219986 (ISSN) Zabihi, F ; Akbarnejad, M. M ; Vaziri Yazdi, A ; Arjomand, M ; Safekordi, A. A ; Sharif University of Technology
    2011
    Abstract
    Dissolution pressure and nozzle temperature effects on particle size and distribution were investigated for RESS (Rapid Expansion of Supercritical Solution) process. Supercritical CO2 was used as solvent and Ibuprofen was applied as the model component in all runs. The resulting Ibuprofen nano-particles (about 50 nm in optimized runs) were analyzed by SEM and laser diffraction particle size analyzer systems. Results show that in low supercritical pressure ranges, depending on the solvent and solid component properties (Lower than 105 bar for Ibuprofen-CO2 system), nozzle temperature should be as low as possible (80-90 °C for Ibuprofen-CO2 system). In the other hand in high supercritical... 

    Rapid annealing of severely deformed low carbon steel in subcritical temperature range

    , Article Metals and Materials International ; Volume 23, Issue 5 , 2017 , Pages 984-993 ; 15989623 (ISSN) Ghiabakloo, H ; Kazeminezhad, M ; Sharif University of Technology
    Abstract
    A low-carbon steel sheet containing 0.05 C, 0.203 Mn, and 0.0229 Si (all in wt%) was rapidly annealed in a temperature range of 300 °C to 600 °C after severe plastic deformation by using constrained groove pressing (CGP) technique. Microstructure evolution was investigated by scanning electron and optical microscopes. Mechanical properties were evaluated by hardness measurements and shear punch test. The results showed a thermal stability up to 400 °C where recrystallization did not occur in the specimens even after 7200 s. This thermal stability is in agreement with previously reported results of conventional annealing of the same steel after CGP. However, annealing at 500 °C and 600 °C led... 

    Grain-Refining ability of ultra-rapid annealing for low-carbon steel: Severe plastic deformation

    , Article Materiali in Tehnologije ; Volume 51, Issue 1 , 2017 , Pages 173-177 ; 15802949 (ISSN) Mostafaei, M. A ; Kazeminezhad, M ; Sharif University of Technology
    Institute of Metals Technology  2017
    Abstract
    To study the grain-refinement ability of ultra-rapid annealing (URA), heating rates from 0.3 °C/s up to 1200 °C/s with conventional annealing and URA in the intercritical temperature range were performed on severely deformed low-carbon steel. The results show that recrystallization in conventional annealing is completed below the critical temperature of Ac1 without grain refinement. URA up to 730 °C at a heating rate of 200 °C/s causes grain refinement due to full interaction between the recrystallization and phase transformation. URAs up to 730 °C with heating rates of 600 °C/s and 1000 °C/s lead to partial grain refinement and no grain refinement, respectively. During annealing with a... 

    Feasibility analysis of the use of rigid polyurethane foam in modular sandwich panels for rapid assembly structures

    , Article International Journal of GEOMATE ; Volume 15, Issue 51 , 2018 , Pages 113-120 ; 21862982 (ISSN) Samali, B ; Nemati, S ; Sharafi, P ; Yaghmaei, F ; Farrokhi, A ; Sharif University of Technology
    GEOMATE International Society  2018
    Abstract
    Mobile and rapidly assembled structures play an important role in building temporary and semi-permanent accommodations and shelters in post-disaster management. One of the most efficient construction systems that can be used in rapidly assembled buildings is lightweight panelized systems. Use of rapidly assembled panelized systems is becoming very popular for cutting the construction time and transportation costs that make them suitable options for rapid assembly construction. In addition, when acoustic and thermal insulation of buildings is important, foam filled composite sandwich panels are an effective solution. Soft, semi-rigid and rigid Polyurethane (PU) foams, which are first... 

    Synthesis of "(aminomethyl)phosphonic acid-functionalized graphene oxide", and comparison of its adsorption properties for thorium(IV) ion, with plain graphene oxide

    , Article Radiochimica Acta ; 2021 ; 00338230 (ISSN) Doram, A ; Outokesh, M ; Ahmadi, S.J ; Zahakifar, F ; Sharif University of Technology
    De Gruyter Open Ltd  2021
    Abstract
    The current study presents a simple and scalable method for the synthesis of (aminomethyl)phosphonic acid-functionalized graphene oxide (AMPA-GO) adsorbent. The chemical structure of the new material was disclosed by different instrumental analyses (e.g. FTIR, Raman, XPS, AFM, TEM, XRD, CHN, and UV), and two pertinent mechanisms namely nucleophilic substitution and condensation were suggested for its formation. Adsorption experiments revealed that both AMPA-GO and plain GO have a high affinity toward Th(IV) ions, but the AMPA-GO is superior in terms of adsorption capacity, rate of adsorption, selectivity, pH effect, etc. Indeed, the AMPA-GO can uptake Th(IV) nearly instantaneously, and... 

    Direct laser sintering of iron-graphite powder mixture

    , Article Materials Science and Engineering A ; Volume 383, Issue 2 , 2004 , Pages 191-200 ; 09215093 (ISSN) Simchi, A ; Pohl, H ; Sharif University of Technology
    2004
    Abstract
    In the present work, the role of graphite addition on the laser sintering of iron powder was studied. Powder mixtures containing iron and 0.4, 0.8, 1.2, and 1.6 wt.% graphite were prepared by blending elemental powders. These powders were sintered layer-by-layer under nitrogen atmosphere using a continuous wave CO2 laser beam. A laser power of 70-225 W, scan rate of 50-600 mm s-1, scan line spacing of 0.1-0.3 mm, and layer thickness of 0.1 mm was used. It was found that the processing parameters play a key role on the densification of the iron-graphite powder mixtures. The addition of graphite enhances the densification of the iron powder and improves the surface quality of the laser... 

    Rapid design space exploration of DSP applications using programmable SOC devices - A case study

    , Article 15th Annual IEEE International ASIC/SOC Conference, ASIC/SOC 2002, 25 September 2002 through 28 September 2002 ; Volume 2002-January , 2002 , Pages 273-277 ; 10630988 (ISSN); 0780374940 (ISBN) Hashempour, M ; Sharifì, S ; Gudarzi, M ; Hessabi, S ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2002
    Abstract
    In this paper, we present results of our experiments in implementation of a widely used DSP primitive on a programmable SoC (System-on-a-Chip) Device. The DSP primitive is a 16-bit digital FIR filter which we implemented on Triscend E5 CSoC® family. Experimental results show that by properly breaking the DSP task into hardware and software parts, one can achieve higher throughput compared to DSP processor implementations, while having more flexibility and less time-to-design compared to full-hardware realizations. Programmable SoC device facilitates rapid design-space exploration, which we employed to optimize our mixed hardware-software architecture. We compared our filter throughput to... 

    ALR detector for coherent radar detection of rapid fluctuating signals

    , Article IEICE Transactions on Communications ; Volume E83-B, Issue 11 , 2000 , Pages 2519-2525 ; 09168516 (ISSN) Modarres Hashemi, M ; Sharif University of Technology
    Institute of Electronics, Information and Communication, Engineers, IEICE  2000
    Abstract
    In this paper, we consider the coherent radar detection of rapid fluctuating signals in the Gaussian noise. This problem has been previously solved by employing the GLR technique, but we use the ALR to improve the detection performance. So, after deriving an approximate ALR detector, we compare the new detector with the GLR and ' Square-law detectors and we show its superiority  

    Synthesis of "(aminomethyl)phosphonic acid-functionalized graphene oxide", and comparison of its adsorption properties for thorium(IV) ion, with plain graphene oxide

    , Article Radiochimica Acta ; Volume 110, Issue 1 , 2022 , Pages 37-49 ; 00338230 (ISSN) Doram, A ; Outokesh, M ; Ahmadi, S. J ; Zahakifar, F ; Sharif University of Technology
    De Gruyter Open Ltd  2022
    Abstract
    The current study presents a simple and scalable method for the synthesis of (aminomethyl)phosphonic acid-functionalized graphene oxide (AMPA-GO) adsorbent. The chemical structure of the new material was disclosed by different instrumental analyses (e.g. FTIR, Raman, XPS, AFM, TEM, XRD, CHN, and UV), and two pertinent mechanisms namely nucleophilic substitution and condensation were suggested for its formation. Adsorption experiments revealed that both AMPA-GO and plain GO have a high affinity toward Th(IV) ions, but the AMPA-GO is superior in terms of adsorption capacity, rate of adsorption, selectivity, pH effect, etc. Indeed, the AMPA-GO can uptake Th(IV) nearly instantaneously, and... 

    Solving the Bus Rapid Transit Network Design Problem with Ant System Algorithm (in Realistic Urban Network)

    , M.Sc. Thesis Sharif University of Technology Kishani, Najme (Author) ; Poorzahedy, Hossein (Supervisor)
    Abstract
    Network design problem (NDP) is an important problem in transportation planning, in which transit network design is one the most important problems. Public transportation means, however, can not meet urban mobility needs in the developing countries satisfactorily. Bus services are usually unsuitable, insufficient, and unreliable. Bus Rapid Transit (BRT) system, is an emerging public transport alternative designed to provide appropriate, low cost, and effective services, and improve mobility in both developed and developing countries. To design public transportation systems, existing constraints such as resources and budget have to be considered to serve estimated demand properly. Bus Rapid... 

    Conduct an Investigation on Nanostructure of Al-20Si-5Fe Alloy, Produced by Melt Spinning Process and Observation of Mechanical-Metallurgical Properties

    , M.Sc. Thesis Sharif University of Technology Azadi, Reza (Author) ; Davami, Parviz (Supervisor)
    Abstract
    In this study, Al-20Si-5Fe ribbons produced by melt-spinning method. Nanostructure and growth morphology of rapidly solidified products explored using optical microscope, scanning electron microscope and x-ray diffraction. Microstructural investigations depicted two distinctive zones of featureless (faceted morphology) and dendritic. In addition, no intermetallic phases could be observed in the rapidly solidified ribbons in comparison with coarsed and needle shaped intermetallic phases of as cast alloys which it demonstrates the extension of solid solubility of Si and Fe in the matrix and consequently intermetallics formation was hindered by higher cooling rates. Subsequently, ribbons... 

    Study of Melting and Rapid Solidification of TiAl alloy and Formation of its Diffusion Bonded Structure using Molecular Dynamics Simulation

    , M.Sc. Thesis Sharif University of Technology Yazdan Yar, Azade (Author) ; Aashuri, Hossin (Supervisor) ; Simchi, Abdolreza (Co-Advisor)
    Abstract
    The rapid pace of development of nanoscience and nanotechnology and their applications in various fields have made the study of materials in smaller scales more important than any time ever. Having an insight of materials’ microstructure and the mechanism of different phenomena in the atomic scale will be very beneficent in designing new and advanced materials or modifying the current manufacturing processes. Since molecular dynamics (MD) method has been well known as a mean of studying materials in atomic scale, it has been used in this study to investigate two different phenomena. The selection of the appropriate interatomic potential is of great importance in MD; Embedded Atom Method... 

    An improved methodology for design of custom-made hip prostheses to be fabricated using additive manufacturing technologies

    , Article Rapid Prototyping Journal ; Volume 18, Issue 5 , 2012 , Pages 389-400 ; 13552546 (ISSN) Rahmati, S ; Abbaszadeh, F ; Farahmand, F ; Sharif University of Technology
    Emerald  2012
    Abstract
    Purpose - The purpose of this paper is to present an improved methodology for design of custom-made hip prostheses, through integration of advanced image processing, computer aided design (CAD) and additive manufacturing (AM) technologies. Design/methodology/approach - The proposed methodology for design of custom-made hip prostheses is based on an independent design criterion for each of the intra-medullary and extra-medullary portions of the prosthesis. The intra-medullar part of the prosthesis is designed using a more accurate and detailed description of the 3D geometry of the femoral intra-medullary cavity, including the septum calcar ridge, so that an improved fill and fit performance... 

    Rapid start-up and improvement of granulation in SBR

    , Article Journal of Environmental Health Science and Engineering ; Volume 13, Issue 1 , 2015 ; 2052336X (ISSN) Jalali, S ; Shayegan, J ; Rezasoltani, S ; Sharif University of Technology
    BioMed Central Ltd  2015
    Abstract
    Abstract Background: The aim of this study is to accelerate and improve aerobic granulation within a Sequencing Batch Reactor (SBR) by cationic polymer addition. Methods: To identify whether the polymer additive is capable of enhancing granule formation, two SBRs (R1 and R2, each 0.15 m in diameter and 2 m in height) are used by feeding synthetic wastewater. The cationic polymer with concentration of 30 to 2 ppm is added to R2, while no cationic polymer is added to R1. Results: Results show that the cationic polymer addition causes faster granule formation and consequently shorter reactor start-up period. The polymer-amended reactor contains higher concentration of biomass with better... 

    Rapid manufacturing

    , Article Collaborative Engineering: Theory and Practice ; 2008 , Pages 127-152 ; 9780387473192 (ISBN) Asiabanpour, B ; Mokhtar, A. R ; Houshmand, M ; Sharif University of Technology
    Springer US  2008
    Abstract
    This chapter defines rapid manufacturing (RM) as a technique for manufacturing solid objects by the sequential delivery of energy and/or material to specified points in space. Current practice is to control the manufacturing process by using a computer-generated mathematical model. This chapter compares the large speed and cost advantages of RM to alternative polymer or metal manufacturing techniques such as powder metallurgy manufacturing or die casting. Moreover, the RM as an application of solid freeform fabrication for direct manufacturing of goods is addressed. Unlike methods such as computer numerical control (CNC) milling, these techniques allow the fabricated parts to be of high...