Search for: characterization
0.007 seconds
Total 375 records

    Synthesis, chemical and thermal characterization of poly(cis-2-butenylene oxalate) [electronic resource]

    , Article International Journal of Polymeric Materials and Polymeric Biomaterials ; Volume 46, Issue 3-4, 2000 Pourdjavadi, A. (Ali) ; Zohuriaan-Mehr, M. J ; Rezai, N ; Sharif University of Technology
    A non-terminated, low molecular weight, highly crystalline, linear aliphatic polyester was successfully synthesized via ester-interchange polycondensation of cis-2-butene-1,4-diol and diethyl oxalate by using of lead (II) oxide as the catalyst. No decarboxylation occurred during the optimized polymerization. Structural and Chemical identification was performed by elemental analysis, FTIR, 'H-NMR, and Mass spectroscopy. Some macrocyle species were detected in the product, according to GPC. Fragmentation patterns were suggested for the main m/e's of the mass spectrum. Thermal characterization was performed by DSC and TGA. It was found that the overall thermal stability of the polyester is... 

    Controlling the geometry of silver nanostructures for biological applications

    , Article Physics Procedia, Ancona ; Volume 40 , 2013 , Pages 76-83 ; 18753884 (ISSN) Ashkarran, A. A ; Estakhri, S ; Nezhad, M. R. H ; Eshghi, S ; Sharif University of Technology
    Noble metals nanostructures, particularly silver, have attracted much attention in the fields of electronics, chemistry, physics, biology and medicine due to their unique properties which are strongly dependent on the size and shape of metal nanomaterials. This study discusses on silver nanostructures with different geometries including wire, cube, sphere and triangle prepared using solution-phase method and applied for antibacterial activities. X-ray diffraction (XRD), Ultra Violet Visible (UV-Vis) spectroscopy, Dynamic Light Scattering (DLS) and electron microscopy studies of different types of silver nanostructures revealed distinct optical and structural properties of an individual... 

    Dynamic Gossip

    , Article Bulletin of the Iranian Mathematical Society ; Volume 45, Issue 3 , 2019 , Pages 701-728 ; 10186301 (ISSN) van Ditmarsch, H ; van Eijck, J ; Pardo, P ; Ramezanian, R ; Schwarzentruber, F ; Sharif University of Technology
    Springer International Publishing  2019
    A gossip protocol is a procedure for spreading secrets among a group of agents, using a connection graph. The goal is for all agents to get to know all secrets, in which case we call the execution of the protocol successful. We consider distributed and dynamic gossip protocols. In distributed gossip, the agents themselves instead of a global scheduler determine whom to call. In dynamic gossip, not only secrets are exchanged but also telephone numbers (agent identities). This results in increased graph connectivity. We define six such distributed dynamic gossip protocols, and we characterize them in terms of the topology of the graphs on which they are successful, wherein we distinguish... 

    A remark on the bourgain-brezis-mironescu characterization of constant functions

    , Article Houston Journal of Mathematics ; Volume 46, Issue 1 , 2020 , Pages 113-115 Ranjbar Motlagh, A ; Sharif University of Technology
    University of Houston  2020
    The purpose of this paper is to describe a simple proof for a result originally presented by H. Brezis in [B], with roots in J. Bourgain, H. Brezis and P. Mironescu [BBM]. © 2020 University of Houston  

    Improving CNT distribution and mechanical properties of MWCNT reinforced alumina matrix

    , Article Materials Science and Engineering A ; Vol. 617 , 2014 , pp. 110-114 ; ISSN: 09215093 Ghobadi, H ; Nemati, A ; Ebadzadeh, T ; Sadeghian, Z ; Barzegar-Bafrooei, H ; Sharif University of Technology
    In this work, an attempt was made to improve the distribution of CNTs in CNT/alumina nanocomposites. The composite powders containing 1 and 3vol% of CNTs were produced and calcined at 500°C for 2h. Surface coating with boehmite nanoparticles was used to improve CNT distribution in alumina matrix. Calcined powders were shaped into compacted samples by cold isostatic pressing at 180MPa and sintered at 1600°C for 2h in flowing gas atmosphere (95%Ar+5%H2). Phase analysis of the calcined composite powders showed complete transformation of boehmite into gamma-alumina. The maximum flexural strength was 465±31MPa corresponding to addition of 1vol% CNTs. Evaluating the fracture toughness via DCM... 

    Signed graphs cospectral with the path

    , Article Linear Algebra and Its Applications ; Volume 553 , 2018 , Pages 104-116 ; 00243795 (ISSN) Akbari, S ; Haemers, W. H ; Maimani, H. R ; Parsaei Majd, L ; Sharif University of Technology
    Elsevier Inc  2018
    A signed graph Γ is said to be determined by its spectrum if every signed graph with the same spectrum as Γ is switching isomorphic with Γ. Here it is proved that the path Pn, interpreted as a signed graph, is determined by its spectrum if and only if n≡0,1, or 2 (mod 4), unless n∈{8,13,14,17,29}, or n=3. © 2018 Elsevier Inc  

    Comparison of liquefaction evaluation based on SPT and geophysical tests (case study: Mahabad dam, Iran)

    , Article 5th International Conference on Geotechnical and Geophysical Site Characterisation, 5 September 2016 through 9 September 2016 ; Volume 1 , 2016 , Pages 657-661 ; 9780994626110 (ISBN) Shahrabi, M. M ; Jafarzadeh, F ; Akbari Garakani, A ; Eskandari, N ; Banikheir, M ; Jahromi, H. F ; Sharif University of Technology
    Australian Geomechanics Society 
    Standard Penetration Test (SPT) is the most commonly used insitu test for soil characterization, including the liquefaction resistance. Many studies have sought to correlate SPT number to cyclic resistance ratio (CRR) as a frequently-used approach for assessment of liquefaction potential. However, it has been shown that SPT has major deficiencies (e.g., inaccuracy in coarse sands and clays) which have given rise to development and utilization of new characterization methods such as geophysical tests (e.g., down-hole and cross-hole). In this paper, a comparison is made between the results of SPT and geophysical tests in three boreholes through the body and foundation of Mahabad Dam (located... 

    On hypercontractivity and a data processing inequality

    , Article IEEE International Symposium on Information Theory - Proceedings ; 29 June through 4 July , 2014 , pp. 3022-3026 Anantharam, V ; Gohari, A ; Kamath, S ; Nair, C ; Sharif University of Technology
    In this paper we provide the correct tight constant to a data-processing inequality claimed by Erkip and Cover. The correct constant turns out to be a particular hypercontractivity parameter of (X,Y), rather than their squared maximal correlation. We also provide alternate geometric characterizations for both maximal correlation as well as the hypercontractivity parameter that characterizes the data-processing inequality  

    Measurement of Critical Current Density in Bulk Superconductors Based on Small Point Contact Characterization

    , Article Journal of Superconductivity and Novel Magnetism ; 2013 , Pages 1-4 ; 15571939 (ISSN) Hosseini, N ; Zabetian, A ; Kananian, S ; Fardmanesh, M ; Sharif University of Technology
    A new approach to measure the critical current density of bulk superconductors is presented in this paper. In the proposed technique, the characterization uses a pulsed current which passes through a small point contact at the middle of the bulk and distributes uniformly, while the other contact is a copper ring around the bulk. By increasing the pulsed current above a threshold current, a normal zone appears and develops into a semi-oblate spheroid forming around the contact point. By analyzing its size and shape, and electromagnetic fundamentals, the voltage-current relationship in the normal zone is obtainable. In addition, experimental works have been performed and the results are in... 

    On the Formation of TiO2 Nanoparticles Via Submerged Arc Discharge Technique: Synthesis, Characterization and Photocatalytic Properties

    , Article Journal of Cluster Science ; Volume 21, Issue 4 , 2010 , Pages 753-766 ; 10407278 (ISSN) Ashkarran, A. A ; Kavianipour, M ; Aghigh, S. M ; Ahmadi Afshar, S. A ; Saviz, S ; Iraji Zad, A ; Sharif University of Technology
    We report a simple and inexpensive synthesis route of TiO2 nanoparticles using electrical arc discharge between titanium electrodes in oxygen bubbled deionized (DI) water followed by heat treatment. The resulting nanoparticles were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), dynamic light scattering (DLS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). XRD patterns demonstrate formation of TiO2 phase in oxygen bubbled water after heat treatment and dominance of rutile to anatase phase. The size and morphology of TiO2 nanoparticles were studied using different arc currents as a crucial parameter in properties of final... 

    Study of mechanism and kinetic modeling of CO hydrogenation reaction over the impregnated Co-Ni/Al2O3 catalyst

    , Article Journal of the Chinese Chemical Society ; Volume 67, Issue 7 , 2020 , Pages 1152-1166 Arsalanfar, M ; Fatemi, M ; Mirzaei, N ; Abdouss, M ; Rezazadeh, E ; Sharif University of Technology
    Chinese Chemical Society Taiwan  2020
    An investigation of the kinetic and mechanism of CO hydrogenation reaction was performed on impregnated Co-Ni/Al2O3. Determination of kinetic parameters from the experiments was carried out in a micro fixed-bed reactor. Kinetic evaluations were performed under various operational conditions of T = 473–673 K, p = 1–14 bar, H2/CO = 1–3, and GHSV = 4,500 hr−1. Kinetic models and rate equations for CO consumption were obtained by using two main-type rate equations of Langmuir-Hinshelwood-Hougen-Watson (LHHW) and Eley-Rideal (ER). Estimation of various kinetic parameters was performed using a nonlinear regression method. According to the obtained experimental results and using statistical... 

    Quick, single-frequency dielectric characterization of blood samples of pediatric cancer patients by a cylindrical capacitor: Pilot study

    , Article Electronics (Switzerland) ; Volume 9, Issue 1 , 2020 Ghanbarzadeh Daghian, A ; Ahmadian, M. T ; Ghanbarzadeh Dagheyan, A ; Sharif University of Technology
    MDPI AG  2020
    In this paper, as an application in biometrics, the electrical capacitance of normal and cancerous blood samples is experimentally determined in order to test the null hypothesis that the electrical capacitance of the two samples differs. The samples taken from healthy donors and patients diagnosed with different types of hematologic cancer are examined by a cylindrical capacitor with blood as its dielectric. The capacitance of these samples is measured at room temperature and a single frequency of 120 Hz, well below the frequency where β-dispersion starts, using a simple LCR meter device. The measurements indicate that the capacitance of the blood increases under applied electric field for... 

    A new experimental and theoretical approach for viscosity Iranian heavy crude oils based on tuning friction theory and friction volume theory parameters

    , Article Inorganic Chemistry Communications ; Volume 139 , 2022 ; 13877003 (ISSN) Farajpour, E ; Jafari Behbahani, T ; Ghotbi, C ; Sharif University of Technology
    Elsevier B.V  2022
    In this research work, Friction Theory and Free Volume Theory are applied to live oil characterized based on SARA TEST for viscosity modeling and make a new model in combination with two equation of state (PR and PC-SAFT). Parameters for pseudo-components are obtained by tuning the viscosity at atmospheric pressure and temperatures of 10, 20, and 40 ℃. A new fitting approach is suggested where the number of fitting parameters is 17 and 12 for FT and FVT model, respectively. These parameters are tuned using the Genetic Algorithm and Particle Swarm Optimization and make eight new models. The results show that PC-SAFT provides viscosity predictions for all models with less deviation from... 

    Motion of deformable ring made of IPMC

    , Article Proceedings of SPIE - The International Society for Optical Engineering ; Volume 8409 , 2012 ; 0277786X (ISSN); 9780819490872 (ISBN) Firouzeh, A ; Alasty, A ; Ozmaeian, M ; National Institute of Standards and Technology; Asia Pacific Committee of Smart and Nano Materials; Nanyang Technol. Univ., Adv. Mater. Res. Cent.; The National Natural Science Foundation of China; Chinese Society of Composite Materials ; Sharif University of Technology
    In this paper application of Ionic Polymer Metal Composite (IPMC) as actuator in a deformable ring capable of locomotion is studied. Such a deformable ring moves as a result of gravitational force acting on its body when its shape changes. It can be used in exploration, search and rescue missions in future, where using conventional robots with rigid bodies and actuators is impossible. Large deformation induced by small stimulating voltage, low stiffness the sensing characteristics that in future work can be used in feedback control make IPMC a good choice for such an application. In this work first a model for IPMC is introduce that can be used in simulating deformation of IPMC in different... 

    Solid products characterization in a multi-step mineralization process

    , Article Chemical Engineering Journal ; Vol. 252 , 2014 , Pages 210-219 ; ISSN: 13858947 Hemmati, A ; Shayegan, J ; Sharratt, P ; Yeo, T. Y ; Bu, J
    In this paper, we describe a carbon dioxide mineralization process and its associated solid products. These solid products include amorphous silica, iron hydroxides and magnesium carbonates. These products were subjected to various characterization tests, and the results are published here. It was found that the iron hydroxides from this process can have different crystalline properties, and their formation depended very much on the pH of the reaction conditions. Different forms of magnesium carbonate were also obtained, and the type of carbonate precipitated was found to be dependent on the carbonation temperature. Hydromagnesite was obtained mainly at low temperatures, while dypingite was... 

    High-fidelity magnetic characterization and analytical model development for switched reluctance machines

    , Article IEEE Transactions on Magnetics ; Volume 49, Issue 4 , 2013 , Pages 1505-1515 ; 00189464 (ISSN) Nasirian, V ; Kaboli, S ; Davoudi, A ; Moayedi, S ; Sharif University of Technology
    This paper proposes a new experimental procedure for magnetic characterization of switched reluctance machines. In the existing methods, phase voltage and current data are captured and further processed to find the flux linkage. Conventionally, assuming zero initial flux value, the flux linkage can be found by integrating the corresponding voltage term. However, the initial flux value is usually unknown, e.g., it can be nonzero when the current is zero due to the residual flux effect, and, thus, imposes error in magnetic characterization. The proposed method addresses this issue by considering an additional equation in steady state. This method injects a low-frequency sinusoidal current to... 

    Investigation and Characterization of the Optical Response of High-Tc Josephson junction

    , M.Sc. Thesis Sharif University of Technology Sharif Azadeh, Mohammad Saeed (Author) ; Fardmanesh, Mehdi (Supervisor)
    Josephson junctions are the basic elements of superconducting technology. They play the same role of p-n junctions in semiconductor technology. Here, we investigated on the optical responses of the fabricated Josephson junctions in order to gain high sensitive optical sensors. The emission has both thermal and non-thermal effect on the current-voltage characteristics of the junctions. While the bolometric effect is the result of slight changes in the bias temperature of device, the non-thermal effect is due to depairing of Cooper pairs and generation of quasi-particles, which is dominant in temperatures far below TC especially in the case the superconducting layer is optically thin. In this... 

    Synthesis and Characterization of Grapheme Foams Fabricated by Chemical Vaporization Deposition

    , M.Sc. Thesis Sharif University of Technology Mahboubi, Sajad (Author) ; Akhavan, Omid (Supervisor) ; Azimirad, Rouhollah (Co-Advisor)
    The main purpose of this theses is to synthesize graphene by chemical vapor deposition (CVD) of a hydrocarbon gas such as methane on the nickel foam substrate and then to characterize this kind of graphene. Graphene is a single layer of carbon atoms, discovered in 2004, which has led mankind to new eras in all fields by its extraordinary features such as extra high electron mobility, high thermal conductivity, excellent mechanical strength, optical transparence and extra high specific surface. The advantage of this method compared to other methods is that the graphene generated has a better structural quality. Graphene foam firstly, because of the continuity of the foam structure, has better... 

    Synthesis and characterization of poly(methacrylates) containing spiroacetal and norbornene moieties in side chain [electronic resource]

    , Article Journal of Applied Polymer Science ; Volume 77, Issue 1, pages 30–38, 5 July 2000 Pourdjavadi, A. (Ali) ; Mirjalili, Bibi Fatemeh ; Sharif University of Technology
    A four-step synthetic strategy was applied to achieve novel methacrylic monomers. 5-Norbornene-2,2-dimethanol was prepared from a Diels–Alder reaction of cyclopentadiene and acrolein, followed by the treatment of the adduct with an HCHO/KOH/MeOH solution. The resulting 1,3-diol (1) was then acetalized with different aromatic aldehydes having OH groups on the ring to produce four spiroacetal derivatives. The reaction of methacryloyl chloride with the phenolic derivatives led to four new methacrylic monomers that were identified spectrochemically (mass, FTIR, 1H-NMR, and 13C-NMR spectroscopy). Free radical solution polymerization was used to prepare novel spiroacetal–norbornene containing... 

    Statistical characterization and the bit- error- rate analysis of lightwave systems with optical amplification using two-photon absorption receiver structures

    , Article IEEE/OSA Journal of Lightwave Technology ; 2006 Vol. 24, Issue 3, PP. 1302-1316 Jamshidi, K ; Salehi, J. A ; Sharif University Of Technology
    In this paper, the authors study the performance of a two-photon absorption (TPA) receiver in a typical communication system employing an optical amplifier. For the study, the authors develop a comprehensive performance analysis, taking into account noises due to an optical amplifier, shot noise, and thermal noise, using Gaussian approximation technique. In evaluating the performance of the system using this technique, the mean and the variance of the received signal will be derived. Comparing the results of receivers using the TPA process with that of a typical single-photon absorption (SPA) structure leads the authors to conclude that TPA receivers can be used when the speed of the...