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Synthesis, crystal structures and Hirshfeld surface analyses of two new Salen type nickel/sodium heteronuclear complexes
, Article Journal of Molecular Structure ; Volume 1110 , 2016 , Pages 119-127 ; 00222860 (ISSN) ; Behzad, M ; Tarahhomi, A ; Maroney, M ; Rudbari, H. A ; Bruno, G ; Ghanbari, B ; Sharif University of Technology
Elsevier
Abstract
Two new heteronuclear Nickel(II)/Sodium(I) complexes of a side-off compartmental Schiff base ligand were synthesized and characterized by spectroscopic methods. Crystal structures of both of the complexes were also obtained. The Schiff base ligand was synthesized from the condensation of meso-1,2-diphenyl-1,2-ethylenediamine with 2-hydroxy-3-methoxybenzaldehyde. In both of the complexes the Ni(II) ion is coordinated to the inner N2O2 coordination sphere with square-planar geometry and the Na(I) ion is coordinated to the outer O2O2′ coordination sphere. In Complex (1) with general formula [Ni(L)Na(CH3OH)(ClO4)] the sodium ion is seven coordinated while in (2) with general formula...
Dynamic Analysis, Design, and Impelmentation of a Planar Piezo-actuated Stick-slip Microrobot
, M.Sc. Thesis Sharif University of Technology ; Vossoughi, Gholamreza (Supervisor) ; Moradi, Hamed (Supervisor)
Abstract
Due to small size, flexibility, and low cost of manufacturing, micorobots are potentially suitable for implementation in a broad range of applications. Control and inspection, medical utilities, manufacturing and micromanipulation of small-sized devices with nano-metric precisions, and precise measurements are some of the most important applications of microrobots. Mobile microrobots are one of the significant divisions of microrobots that are capable of movement with small steps and possess a motion range of at least several times the robot’s body length. In this project, Modulated Friction Inertial Drive (MFID) is utilized as a mechanism for creating a mobile microrobot. The micorobot is...
Continuum modelling of a circular planar array of coupled microwave oscillators
, Article European Microwave Week 2009, EuMW 2009: Science, Progress and Quality at Radiofrequencies, Conference Proceedings - 39th European Microwave Conference, EuMC 2009, 28 September 2009 through 2 October 2009, Rome ; 2009 , Pages 1349-1352 ; 9782874870118 (ISBN) ; Banai, A ; Sharif University of Technology
Abstract
in this paper the phase distribution in an array of coupled oscillators arranged on a circular surface is discussed. Coupling is considered to be weak and each oscillator is coupled to its four nearest neighbours. In a continuum limit where the number of oscillators goes to infinity a theoretical formulation in polar coordinates is proposed to describe the dynamic behaviour of phases of the array elements. A Green's function for phase distribution of the array is proposed in terms of its normalized eigenfunctions. Beam steering can be done via detuning the edge oscillators. © 2009 EuMA
Design and Analysis of Vibration-Based, Friction-Drive Micro-Mechanisms for Planar, Nano-Scale Locomotion
, M.Sc. Thesis Sharif University of Technology ; Vossoughi, Gholamreza (Supervisor)
Abstract
Design and modeling of a micromechanism for generating planar, nano-scaled locomotion is the subject of this thesis. First, we introduced the concepts and fundamental definitions used throughout the thesis. Then, based on the classification of the locomotion principles employed in microrobots, the related literature about design and fabrication of different microrobots is investigated. Inertial slip generation and contact force variation, as the preferred group, is utilized for further analysis. Since friction force is the main propelling source in the microrobot’s locomotion principle, different models proposed for this phenomenon are investigated and the Coulomb friction model is selected...
Analysis of Artificial Dielectric Waveguides for Millimeter Wave Applications
, Ph.D. Dissertation Sharif University of Technology ; Rejaei, Behzad (Supervisor)
Abstract
Millimeter wave technology may prove to be one of the key technologies of the 21st century, covering a broad range of applications including high-speed telecommunication, wireless sensing, and ultra-fast digital computing. The ultimate (commercial) success of these technologies depends on the ability to integrate mm-wave circuitry on a chip, bringing about significant size and cost reduction. Traditionally, mm-wave systems have made extensive use of waveguides based on hollow- or dielectric-filled metallic cavities for the transfer and processing of signals. Cavity waveguides exhibit very low loss, but are not well-suited to high volume manufacturing or on-chip integration due to their...
Nonlinear vibrations of an inclined beam subjected to a moving load
, Article Journal of Physics: Conference Series, 8 September 2009 through 10 September 2009, Cambridge ; Volume 181, Issue 1 , 2009 ; 17426588 (ISSN) ; Kargarnovin, M ; Younesian, D ; Sharif University of Technology
Abstract
In this paper, the nonlinear dynamic responses of an inclined pinned-pinned Euler-Bernoulli beam with a constant cross section and finite length subjected to a concentrated vertical force traveling with constant velocity is investigated by using the mode summation method. Frequency analysis of the PDE's governing equations of motion for steady-state response is studied by applying multiple scales method. The nonlinear dynamic deflections of the beam are obtained by solving two coupled nonlinear PDE's governing equations of planar motion for both longitudinal and transverse oscillations of the beam. The dynamic magnification factor and normalized time histories of mid-point of the beam are...
A Survey on Min-cut On Planar Graphs
, M.Sc. Thesis Sharif University of Technology ; Foroughmand Arabi, Mohammad Hadi (Supervisor)
Abstract
In minimum cut problem we aim at finding a set of edges with minimum overall cost possible, such that removing them would separate two specific vertices, source and sink. This problem has been studied thoroughly, however the available algorithms were not proven to be time-wise optimal. Nowadays, planar graphs have attracted more attention because of their applications in cities and countries map. Moreover,their characteristics and properties, make some problems easier to solve in planar case. In this thesis, we will have a survey on algorithms for minimum cut on planar graphs. Our motivation to choose these algorithms is the balance between how easily they could be implemented and how fast...
Integrated monolayer planar flux transformer and resonator tank circuit for high-$t-{c}$ rf-squid magnetometer
, Article IEEE Transactions on Applied Superconductivity ; Volume 27, Issue 4 , 2017 ; 10518223 (ISSN) ; Jabbari, T ; Qaderi, F ; Fardmanesh, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2017
Abstract
The authors propose a new design for monolayer superconducting planar flux transformer integrated with a coplanar resonator serving as a gigahertz range tank circuit for high-Tc rf-SQUID magnetometers. Based on the proposed design, which is optimized using the finite element method, the transformer-resonator configuration is made of 200-nm-thick monolayer YBCO film on a crystalline LaAlO3 substrate. In this optimized design, the SQUID magnetometer is coupled through flip-chip configuration with the configuration providing high coupling coefficient between the devices. The design permits coupling of the rf signals to the SQUID efficiently, whereas the transformer is designed to couple the dc...
Spatial integration by a dielectric slab and its planar graphene-based counterpart
, Article Optics Letters ; Volume 42, Issue 10 , 2017 , Pages 1954-1957 ; 01469592 (ISSN) ; Khavasi, A ; Sharif University of Technology
Abstract
In this contribution a new approach to perform spatial integration is presented using a dielectric slab. Our approach is indeed based on the fact that the transmission coefficient of a simple dielectric slab at its mode excitation angle matches the Fourier-Green's function of first-order integration. Inspired by the mentioned dielectric-based integrator, we further demonstrate its graphene-based counterpart. The latter is not only reconfigurable but also highly miniaturized in contrast to the previously reported designs [Opt. Commun. 338, 457 (2015)]. Such integrators have the potential to be used in ultrafast analog computation and signal processing. © 2017 Optical Society of America
Interactions near the triple-phase boundaries metal/glass/air in planar solid oxide fuel cells
, Article International Journal of Hydrogen Energy ; Volume 42, Issue 8 , 2017 , Pages 5306-5314 ; 03603199 (ISSN) ; Kokabi, A. H ; Nemati, A ; Zinatlou Ajabshir, S ; Sharif University of Technology
Abstract
The possible interactions near the triple-phase boundaries (TPB) metal/glass/air, and their effects on joint strength are investigated. Two types of samples (joined couples and glass coated coupons) are prepared with the coupon of AISI 430 (nickel plated and uncoated) and a slurry of compliant silicate sealing glass (SCN-1). The joined and coated samples are heated at 850 °C for 1000 h in air. The joined couples are cooled using two different schedules and then tested in uniaxial tension. For investigating the metal-oxides precipitation procedure in glass near the TPB, glass coated coupons are either cooled at the rate of 5 °C min−1 or water-quenched from aging temperature. The mechanical...
Various coupling configurations on the performance of two-dimensional coupled oscillator arrays
, Article IET Microwaves, Antennas and Propagation ; Volume 11, Issue 3 , 2017 , Pages 426-432 ; 17518725 (ISSN) ; Banai, A ; Sharif University of Technology
Institution of Engineering and Technology
2017
Abstract
Coupled oscillator arrays (COAs) can be used to control the phase distribution across the aperture of an array antenna in such a manner as to affect steering of the beam without the use of phase shifters. Given the various possible planar configurations of COAs, a systematic design approach is necessary. In this study, the authors present a comprehensive comparison of various configurations of planar COAs based on their sensitivity to random errors in their free running frequencies. The parameters considered are (a) the beam pointing error of the array, (b) the locking probability, (c) the side lobe level, and (d) the beam width of the radiation pattern. These results can serve as a design...
Robustness enhancement of optical flow sensors accuracy to surface texture variations using point tracking algorithm
, Article 5th RSI International Conference on Robotics and Mechatronics, IcRoM 2017, 25 October 2017 through 27 October 2017 ; 2018 , Pages 406-410 ; 9781538657034 (ISBN) ; Vossoughi, G ; Sharif University of Technology
Abstract
Novel architecture of high precision localization using optical flow sensor (OFS) combined with Iterative Point Tracking Algorithm (IPTA) is proposed. This work focuses on attenuation of OFS' sensitivity dependency on texture of surface over which sensor is moving. The aim for the design of experimental setup is to verify how much a robustness of OFS's sensitivity on various surfaces improves. In this regard, four different surfaces' texture including iron, paper, textile and granite stone is opted. Experimental results indicate that sensor's resolution via IPTA on surfaces of iron, paper, textile and granite stone respectively equal to 382, 460, 528 and 448 CPI. Optimal value of the...
Excitation and propagation of surface polaritonic rogue waves and breathers
, Article Physical Review A ; Volume 98, Issue 1 , 2018 ; 24699926 (ISSN) ; Sadighi Bonabi, R ; Sanders, B. C ; Sharif University of Technology
American Physical Society
2018
Abstract
Excitation and propagation of the surface polaritonic rogue waves and breathers are investigated by proposing a coupler free optical waveguide that consists of a transparent layer, middle negative index metamaterial layer, and bottom layer of the cold four level atomic medium. In this planar optical waveguide, a giant controllable Kerr nonlinearity is achieved by sufficient field concentration and a proper set of intensities and detunings of the driven laser fields. As a result, various kinds of temporal surface polaritonic solitons, rogue waves, and breathers can be propagated in the narrow window for electromagnetically induced transparency. We find that the giant intensity and extreme...
Design and Implementation of a High-Efficient High-Power-Density Telecom Battery Charger using Planar Matrix Transformers
, M.Sc. Thesis Sharif University of Technology ; Tahami, Farzad (Supervisor)
Abstract
In creating a telecom battery charger there are three challenging factors which are high power density, high efficiency and modularity. A telecome battery charger consist of a rectifier with power factor correction capability and a DC-DC converter. The power stage of DC-DC converter with high output current and low output voltage has a vital role in the battery charger. The isolation transformer and magnetic component of LLC resonant tank are two huge and heavy parts of the DC-DC converter. With the emergence of GaN and SiC switches pushing frequency to to megahertz is possible which resulted in decreasing the volume of passive divices. But with increasing the frequency, designing of the...
Blue and red wavelength resolved impedance response of efficient perovskite solar cells
, Article Sustainable Energy and Fuels ; Volume 2, Issue 11 , 2018 , Pages 2407-2411 ; 23984902 (ISSN) ; Tavakoli, M. M ; Turren Cruz, S. H ; Pandey, K ; Saliba, M ; Yadav, P ; Sharif University of Technology
Royal Society of Chemistry
2018
Abstract
The identification of recombination centers in perovskite solar cells is highly challenging. Here, we demonstrate the red and blue excitation wavelength resolved impedance response in state-of-the-art perovskite solar cells (PSCs) providing insights into charge recombination and ion accumulation. To get insight into the interfacial electronic characteristics, we fabricated PSCs with a planar architecture containing state-of-the-art triple-cation perovskite materials as absorber layers. The capacitance-frequency response under various blue and red illumination conditions were used to investigate interfacial charge accumulations and found that under high energy photons irradiation maximum...
Sol-gel synthesis of Mn1.5Co1.5O4 spinel nano powders for coating applications
, Article Materials Research Bulletin ; Volume 102 , 2018 , Pages 180-185 ; 00255408 (ISSN) ; Dayaghi, A. M ; Askari, M ; Gannon, P. E ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
Mn1.5Co1.5O4 oxide spinels are widely used as protective coatings for stainless steel interconnects within planar solid oxide fuel cell stacks. Containing both cubic and tetragonal crystalline phases, these Mn/Co oxide spinels exhibit favorable thermal stability and electronic conductivity for the SOFC interconnect application. Slurry-based coating applications of Mn/Co oxides require precursor powders, which can benefit from being nano-structured. In this study, the sol-gel synthesis of nanocrystalline Mn1.5Co1.5O4 spinel is investigated. The decomposition of sol-gel precursors, as well as the crystalline phase structures and microstructures of the product Mn1.5Co1.5O4 are characterized by...
On uniquely k-list colorable planar graphs, graphs on surfaces, and regular graphs
, Article Graphs and Combinatorics ; Volume 34, Issue 3 , May , 2018 , Pages 383-394 ; 09110119 (ISSN) ; Hutchinson, J. P ; Ilchi, S. G ; Mahmoodian, E. S ; Matsumoto, N ; Shabani, M. A ; Sharif University of Technology
Springer Tokyo
2018
Abstract
A graph G is called uniquelyk-list colorable (UkLC) if there exists a list of colors on its vertices, say L= { Sv∣ v∈ V(G) } , each of size k, such that there is a unique proper list coloring of G from this list of colors. A graph G is said to have propertyM(k) if it is not uniquely k-list colorable. Mahmoodian and Mahdian (Ars Comb 51:295–305, 1999) characterized all graphs with property M(2). For k≥ 3 property M(k) has been studied only for multipartite graphs. Here we find bounds on M(k) for graphs embedded on surfaces, and obtain new results on planar graphs. We begin a general study of bounds on M(k) for regular graphs, as well as for graphs with varying list sizes. © 2018, Springer...
On the Computational Complexity of Graph Problems
, M.Sc. Thesis Sharif University of Technology ; Jafari, Amir (Supervisor)
Abstract
Computational complexity of graph problems is an important branch in the-oretical computer science. We introduce to some of ideas for computing the complexity of graph problems with some kind and beautiful examples. Next, we show hardness and inapproximability of some problems. Representation number of graphs has been introduce by Pavel Erdos by Number theory. We prove n1−ϵ inapproximability of that. Lucky number η has been studied by Grytczuk et.al . We show for planar and 3-colorable graphs, it is NP-Complete whether η = 2. Note that since a conjecture, for those graphs, 2 ≤ η ≤ 3. Also for each k ≥ 2, we show NP-completeness of η ≤ k for the graphs. Proper orientation number −→ is a...
High-precision impedance control method for flexible base moving manipulators
, Article Advanced Robotics ; Volume 23, Issue 1-2 , 2009 , Pages 65-87 ; 01691864 (ISSN) ; Vossoughi, G. R ; Sharif University of Technology
2009
Abstract
The general problem of impedance control is addressed for a robotic manipulator with a moving flexible base. Impedance control imposes a relation between force and displacement at the contact point with the environment. The concept of impedance control of flexible base moving manipulators (FBMMs) is rather new and is being considered. The dynamic of the manipulator is decomposed into slow and fast dynamics using the singular perturbation method. A new sliding mode impedance control (SMIC) method using an element on the end-effector is proposed for high-precision impedance control of FBMMs. The SMIC method as a robust impedance control law is derived for the slow dynamics. The asymptotic...
Defects Structure in Nematic Shell with Oblate Ellipsoidal Core
, M.Sc. Thesis Sharif University of Technology ; Ejtehadi, MohammadReza (Supervisor) ; Mozaffari, MohammadReza (Supervisor)
Abstract
Nematic liquid crystal shells (droplets) containing cores have attracted considerable attention in recent years. Defect structures that form in such systems do not emerge in the bulk.These shells which could be created using double emulsion techniques in the laboratory have provided applications in microscale optical structures.In the past just boundary conditions and bulk parameters were noticed but recently the geometry of the core is considered likewise.In this work oblate ellipsoid cores are examined numerically using finite-element method. The boundary conditions in studied systems are perpendicular in outer surface of droplet and planar in the vicinity of the core. First by minimizing...