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    Aluminothermic Reduction of Neodymium Oxide (Nd2O3) for Synthesis of Nanostructured Nd-Fe-B Alloys

    , M.Sc. Thesis Sharif University of Technology Hosseini Kouhkamari, Mahsa (Author) ; Halali, Mohammad (Supervisor)
    Nd-Fe-B alloys as permanent magnets are used in the components of the computer, sensors, medical equipments and etc. Two main methods which used for making these alloys, are calciothermic reduction process and fused salt electrolysis technique. In this study, a new affordable process for producing Fe-Nd alloys have been suggested.In this research, aluminothermic reduction and co-reduction processes were used to make a Pb-Nd alloy from neodymium oxide (Nd2O3) and Lead Oxide (PbO). Then by using liquid-liquid extraction at high temperature, Fe-Nd alloy was produced. Experiments were performed at temperature of about 1600°C and in the air atmosphere. Different weight ratios were also tried. The... 

    Improved photovoltaic performance of nanostructured solar cells by neodymium-doped TiO2 photoelectrode

    , Article Materials Letters ; Volume 159 , November , 2015 , Pages 273-275 ; 0167577X (ISSN) Shogh, S ; Mohammadpour, R ; Zad, A. I ; Taghavinia, N ; Sharif University of Technology
    Elsevier  2015
    Well-crystallized TiO2 and neodymium (Nd)-doped TiO2 nanoparticles with various doping levels were synthesized by hydrothermal method and utilized as the photoanode of nanostructured solar cells. The results indicated that Nd-doping was caused the absorption spectra shift to higher wavelength while the morphology and surface area were unchanged. As a result, by employing 0.4 mol% Nd in the TiO2 photoelectrode, the overall conversion efficiency of the cell reached 9.08% which is 26% higher than pure one. Based on the photo-electrochemical characterizations, the improvement is a consequence of electrons injection increment from dye to TiO2 conduction... 

    Design and test of an astigmatism compensated dynamical stable ring resonator for a subjoule class Nd:YAG laser without external elements

    , Article Optical Engineering ; Volume 58, Issue 2 , 2019 ; 00913286 (ISSN) Razzaghi, D ; Rezanejad, M ; Shayganmanesh, M ; Gohari, N ; Sharif University of Technology
    SPIE  2019
    An astigmatism compensated isosceles triangular ring resonator is designed and tested for a subjoule class Nd:YAG laser, considering the thermal lensing effects. The ABCD approach is used and the laser rod is considered as a lens like media whose optical power is induced by dissipated heat in the rod. The beam spot size, divergence angle, and some other parameters were studied for both sagittal and tangential planes and a minimal astigmatic configuration is designed applying dynamic stability condition. It is shown practically that the designed resonator emits a circular TEM00 Gaussian beam (using an aperture). Comparative studies were also done considering a linear resonator especially for... 

    A study on the corrosion behavior of the (Nd, MM)2(Fe, Co, Ni)14B-type sintered magnets

    , Article Journal of Alloys and Compounds ; Volume 419, Issue 1-2 , 2006 , Pages 337-341 ; 09258388 (ISSN) Madaah Hosseini, H. R ; Dadoo, A ; Dolati, A ; Kianvash, A ; Sharif University of Technology
    The binary powder blending technique (BPBT) was employed in production of anisotropic (Nd, MM)2(Fe, Co, Ni)14B-type sintered magnets (MM: denotes a Misch-metal). The composition of the master alloy was close to the stoichiometric Nd2Fe14B compound, while the sintering aid (SA) had a composition of MM38.1Co46.4Ni15.4. The magnets were made by blending different ratios of the master alloy and the sintering aid. The corrosion behavior of these magnets was compared with that of the Nd17Fe75B8 base alloy by potentiodynamic polarization measurements in H2SO4 solution. By decreasing the amount of Nd-rich grain boundary phases and substitution of some Fe atoms by Co and Ni, an improvement in the... 

    The effect of target annealing temperature on optical and structural properties and composition of CdS thin films prepared by pulsed laser

    , Article Optical Materials ; Volume 27, Issue 10 , 2005 , Pages 1583-1586 ; 09253467 (ISSN) Mahdavi, S. M ; Iraji Zad, A ; Tilaki, R. M ; Sharif University of Technology
    Elsevier  2005
    We studied the effect of target annealing temperature on optical and structural properties and composition of CdS thin films prepared by pulsed Nd:YAG laser. Deposited samples from annealed targets at 300 °C showed a mixed cubic and hexagonal structure, a band gap of about 2.56 eV and Cd/S ratio equal 1. This ratio increased to 2.40 and its band gap decreased to 2.46 eV when the sample was annealed at 500 °C for 1 h in air. However, films prepared from annealed targets at 500 °C became dark due to existence of polymorphous phase of CdO. Films changed to transparent yellow color with a hexagonal CdS structure and some peaks related to CdO after annealing above 250 °C in air. Its band gap... 

    Effect of Pr doping on transport properties of Nd(Ba2-xPr x)Cu3O7+8

    , Article Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers ; Volume 44, Issue 11 , 2005 , Pages 7934-7942 ; 00214922 (ISSN) Maleki, P ; Akhavan, M ; Sharif University of Technology
    Solid-state-reacted polycrystalline Nd(Ba2-xPr x)Cu3O7+8 materials have been prepared and investigated using X-ray diffraction and resistivity measurements. Our results show that Nd(Ba2-xPrx)Cu3O7+8 is a superconductor when x < 0.3. The Tc depression in superconductivity of Pr at Ba sites is due to both hole filling/localization and depairing effects. The normal state conductivity undergoes a dimensional crossover from two-dimensional to three-dimensional in the frame of the variable range hopping regime. The localization length of carriers shows that Pr doping localizes carriers in the normal state and causes the Tc depression. The magnetoresistance of the samples has been investigated... 

    Analysis of Heat Transfer in Laser Assisted Machining of Slip Cast Fused Silica Ceramics

    , Article 7th CIRP Conference on High Performance Cutting, HPC 2016, 31 May 2016 through 2 June 2016 ; Volume 46 , 2016 , Pages 571-574 ; 22128271 (ISSN) Roostaei, H ; Movahhedy, M. R ; Ihlefeldt S ; Wertheim R ; Hochmuth C ; Putz M ; Sharif University of Technology
    Elsevier  2016
    Machining of ceramics often involves many challenges due to their high hardness, brittleness, and low thermal properties. Laser assisted machining (LAM) is a promising technology for improving the machinability of hard-to-cut materials. In this work, laser assisted machining of slip cast fused silica (SCFS) ceramics is investigated by presenting a numerical thermal analysis of laser effects on material behaviour. A transient three-dimensional heat transfer analysis for laser assisted turning of SCFS is performed using finite element method. Temperature distributions in SCFS cylindrical specimens are obtained. Experimental results are provided to validate the numerical results  

    Investigation of optimum condition in oxygen gas-assisted laser cutting

    , Article Optics and Laser Technology ; Volume 41, Issue 4 , 2009 , Pages 454-460 ; 00303992 (ISSN) Golnabi, H ; Bahar, M ; Sharif University of Technology
    Laser cutting characteristics including power level and cutting gas pressure are investigated in order to obtain an optimum kerf width. The kerf width is investigated for a laser power range of 50-170 W and a gas pressure of 1-6 bar for steel and mild steel materials. Variation of sample thickness, material type, gas pressure and laser power on the average cut width and slot quality are investigated. Optimum conditions for the steel and mild steel materials with a thickness range of 1-2 mm are obtained. The optimum condition for the steel cutting results in a minimum average kerf width of 0.2 mm at a laser power of 67 W, cutting rate of 7.1 mm/s and an oxygen pressure of 4 bar. A similar... 

    Study and Fabrication of Dye Sensitized Solar Cells Based on Nitrogen and Neodymium Doped Titanium Dioxide Photoelectrodes

    , Ph.D. Dissertation Sharif University of Technology Shogh, Shiva (Author) ; Iraji Zad, Azam (Supervisor) ; Mohammadpour, Raheleh (Co-Advisor) ; Taghavinia, Nima (Co-Advisor)
    In this thesis, we focus on studying and fabrication of doped titanium dioxide electrodes and their application in nanostructured dye sensitized solar cells (DSSCs). For this purpose, non-metallic nitrogen (N) and metallic neodymium (Nd) elements were selected. N-doped titanium dioxide nanoparticles were synthesized via solvothermal method and their structural and optoelectrical properties were investigated in comparison to undoped titanium dioxide synthesized by the same method. Based on the obtained results, doping of titanium dioxide by nitrogen resulted in shifting the Fermi level up-ward, increase in charge carriers density, shift of optical absorbance to higher wavelength, and decrease... 

    Leaching, Solvent Extraction and Separation of Cerium, Lanthanum, Neodymium Rare Earth Elements from Apatite Concentrate of Chadormalu Mine

    , Ph.D. Dissertation Sharif University of Technology Ferdowsi, Ali (Author) ; Youzbashizadeh, Hossein (Supervisor)
    Waste of iron ore concentrate production plant of Chadormalu contains apatite mineral. The content of rare earths elements (REEs) in apatite concentrate of Chadormalu is about one percent. However, considering apatite deposite and production rate, extraction of REEs from apatite is one of valuable source for production of REEs. Lanthanum, cerium and neodymium which have most application amonge other REEs and have the highest frequency in the apatite. Due to their similar physical and chemical properties, it is difficult to separate individual rare earths from each other and the separation process are too complicated. In this study, in order to extract REEs from apatite, it was leached by... 

    The effect of ultraviolet lasers on conversion of methane into higher hydrocarbons

    , Article Laser and Particle Beams ; Volume 31, Issue 3 , 2013 , Pages 481-486 ; 02630346 (ISSN) Navid, H. A ; Irani, E ; Sadighi Bonabi, R ; Sharif University of Technology
    Conversion of CH4 molecule into higher hydrocarbons using two different wavelengths of 248 nm KrF laser and 355 nm of third harmonic of Nd:YAG laser is studied experimentally and theoretically. The stable products are analyzed and the effect of pressure on conversion of methane is measured. The detected reaction products are C2H2, C2H4, and C2H6. The conversion efficiency of 33.5% for 355 nm in comparison to 2.2% conversion for 248 nm for C2H2 is achieved. The potential of laser parameters as an important variable in controlling of final products is investigated  

    Narrow linewidth, tunable dye laser by multiple-prism beam expander

    , Article Optical and Quantum Electronics ; Volume 49, Issue 9 , 2017 ; 03068919 (ISSN) Pasandideh, K ; Rahbari, M ; Bonabi, R. S ; Sharif University of Technology
    12 mJ, 10-Hz green pulses from frequency doubled Nd:YAG laser was used for pumping Rhodamine 6G in a dye laser based on multiple-prism beam expander. In order to increase the stability of the output pulse, a unique dye cell with variable dimensions of active medium was designed and constructed. By using multiple-prism dispersion theory, conditions for zero-dispersion in two and four-prism beam expander configuration was calculated. In the case of two-prism configuration, tuning range of dye laser was 565–595 nm and the linewidth of pulse at 580 nm was about 1.8 nm and it is in good agreement with the calculated amount of 1.6 nm. Furthermore, using four-prism configuration tuning range of... 

    Controlling the properties of TiO2 nanoparticles generated by nanosecond laser ablation in liquid solution

    , Article Laser Physics ; Volume 28, Issue 8 , 2018 ; 1054660X (ISSN) Pashazadeh, M ; Irani, E ; Golzan, M. M ; Sadighi Bonabi, R ; Sharif University of Technology
    Institute of Physics Publishing  2018
    Laser ablation of titanium target in distilled water for synthesis of colloidal nanoparticles is studied both experimentally and theoretically. The effects of laser parameters such as wavelength, pulse energy, fluence and shot numbers on the ablation rate and size properties of colloidal nanoparticles are investigated. The experimental approach addresses the interesting issue for finding the optimal main experimental parameters of laser ablation. The theoretical thermal model of nanosecond pulsed laser ablation is developed to visualize the evolution of temperature distributions and ablation depth. The simulation result of ablation depth has been compared with the experimental result... 

    Improving the relativistic self-focusing of intense laser beam in plasma using density transition

    , Article Physics of Plasmas ; Volume 16, Issue 8 , 2009 ; 1070664X (ISSN) Sadighi Bonabi, R ; Habibi, M ; Yazdani, E ; Sharif University of Technology
    The propagation of a Gaussian beam in underdense plasma with upward increasing density ramp is analyzed. In this work are shown that the spot size oscillations of laser beam increases and its amplitude shrinks with proper plasma density ramp. This causes the laser beam to become more focused and penetrations deep into the plasma by reduction of diffraction effect. The related focusing parameters are optimized to get the best possible focusing at the relativistic threshold intensity of Nd-glass laser and the effect of the laser intensity in the self-focusing parameters is also investigated. The analytical calculations are presented and showed more reliable results in comparison to the... 

    Tunable wide-band graphene plasmonic nano-color-sorter: Application in scanning near-field optical microscopy

    , Article Journal of the Optical Society of America B: Optical Physics ; Volume 36, Issue 2 , 2019 , Pages 435-442 ; 07403224 (ISSN) Heydarian, H ; Yazdanfar, P ; Shahmansouri, A ; Rashidian, B ; Sharif University of Technology
    OSA - The Optical Society  2019
    Tunability of the Fermi level of graphene is exploited to implement a plasmonic nano-color-sorter for scanning near-field optical microscope (SNOM) applications capable of handling large tip sample couplings. Nano-color-sorting has been used in SNOM through creating multiple spatially separated hot spots for different incident wavelengths. We show that in the presence of high-refractive-index samples an unwanted redshift in the spectral response of the dual-color probe occurs. This limitation can be compensated for using graphene and adjusting its chemical potential to obtain a blueshift in probe spectral response. The Method of Moments analysis technique is employed to engineer the probe... 

    Design, analysis, and fabrication of a direct drive permanent NdFeB magnet synchronous motor for precision position control

    , Article IET Electric Power Applications ; Volume 14, Issue 8 , 2020 , Pages 1438-1445 Hariri, A. M ; Damaki Aliabad, A. A ; Ghafarzadeh, M ; Shamlou, S ; Sharif University of Technology
    Institution of Engineering and Technology  2020
    Direct drive motors have the excellent ability for precision position control due to their direct connection to load and elimination of the gearbox and pulley backlash. Among the direct drive motors, permanent NdFeB magnet synchronous motors (PMSMs) are the best choice for control systems due to their high efficiency, high power density, good dynamic behaviour, and excellent controllability. This study deals with the design, analysis, and fabrication of a direct drive PMSM for precision position control. To reach this aim, the designed motor should have very low cogging torque and torque ripple to avoid the motor deviation at the target point. To achieve these purposes, at first, a suitable... 

    Visiting a polygon on the optimal way to a query point

    , Article 2nd International Frontiers in Algorithmics Workshop, FAW 2008, Changsha, 19 June 2008 through 21 June 2008 ; Volume 5059 LNCS , 2008 , Pages 245-251 ; 03029743 (ISSN); 3540693106 (ISBN); 9783540693109 (ISBN) Khosravi, R ; Ghodsi, M ; Sharif University of Technology
    We study a constrained version of the shortest path problem in polygonal domains, in which the path must visit a given target polygon. We provide an efficient algorithm for this problem based on the wavefront propagation method and also present a method to construct a subdivision of the domain to efficiently answer queries to retrieve the constrained shortest paths from a single-source to the query point. © 2008 Springer-Verlag Berlin Heidelberg  

    Design of a hybrid inertial and magnetophoretic microfluidic device for ctcs separation from blood

    , Article Micromachines ; Volume 12, Issue 8 , 2021 ; 2072666X (ISSN) Nasiri, R ; Shamloo, A ; Akbari, J ; Sharif University of Technology
    MDPI AG  2021
    Circulating tumor cells (CTCs) isolation from a blood sample plays an important role in cancer diagnosis and treatment. Microfluidics offers a great potential for cancer cell separation from the blood. Among the microfluidic-based methods for CTC separation, the inertial method as a passive method and magnetic method as an active method are two efficient well-established methods. Here, we investigated the combination of these two methods to separate CTCs from a blood sample in a single chip. Firstly, numerical simulations were performed to analyze the fluid flow within the proposed channel, and the particle trajectories within the inertial cell separation unit were investigated to... 

    Synthesis and characterisation of nanostructured neodymium titanium oxides by sol-gel process: Controlling the phase composition, crystal structure and grain size

    , Article Materials Chemistry and Physics ; Volume 122, Issue 2-3 , 2010 , Pages 512-523 ; 02540584 (ISSN) Mohammadi, M. R ; Fray, D. J ; Sharif University of Technology
    Nanocrystalline neodymium titanium oxide thin films and powders with different phase compositions with mesoporous structure were produced by a straightforward particulate sol-gel route. The sols were prepared in various Nd:Ti molar ratios and they showed a narrow particle size distribution in the range 20-26 nm. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) revealed that the powders contained mixtures of Nd4Ti9O24, Nd2Ti4O11, Nd3Ti4O12 for titanium dominant powders (Nd:Ti ≤ 45:60), mixtures of Nd2TiO5 and Nd2O3 for neodymium dominant powders (Nd:Ti ≥ 75:25) and pure Nd3Ti4O12 phase for equal molar ratio of Nd:Ti, depending on the annealing temperature and Nd:Ti... 

    Polycarbonate surface cell's adhesion examination after Nd:YAG laser irradiation

    , Article Materials Science and Engineering C ; Volume 29, Issue 4 , 2009 , Pages 1491-1497 ; 09284931 (ISSN) Ramezani Saadat Abadi, A ; Mousavi, A ; Seyedjafari, E ; Poursalehi, R ; Sareh, S ; Silakhori, K ; Poorfatollah, A. A ; Shamkhali, A. N ; Sharif University of Technology
    Nd:YAG laser treatment was used in order to increase surface cell adhesion aspects of polycarbonate (PC) films prepared via melt process. The treatment was carried out under different wavelengths and beam diameters. ATR-FTIR and UV spectra obtained from different samples before and after laser treatment in air showed that laser irradiation has induced some chemical and physical changes in surface properties. The irradiated films were also characterized using scanning electron microscopy (SEM) and contact angle measurements. Effect of pulse numbers on the surface properties was also investigated. Cell culture test was used to evaluate cell adhesion property on the PC films before and after...