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The Effect of Shock and Vibration Loads on Disconnection and Fluctuations of Electrical Current in Connectors
, M.Sc. Thesis Sharif University of Technology ; Behzad, Mehdi (Supervisor)
Abstract
Electrical connectors that used in high speed systems interrupt the connection at the effect of Inertia. Also connectors should be able to work in high vibration conditions without any problems. Vibration of the connector pins can reduce the contact area or even remove it at very short time intervals, which lead to increase connector resistance or disconnection of instantaneous current. These current fluctuations will result in unpredictable performance disturbanceof the electrical system in very sensitive systems and therefore it should be avoided. In this Project, impacts of shock and vibration loads on the connectors is modeled by using FEM and with consideration of this model, connection...
Graphene oxide sheets involved in vertically aligned zinc oxide nanowires for visible light photoinactivation of bacteria
, Article Journal of Alloys and Compounds ; Vol. 612 , 2014 , pp. 380-385 ; ISSN: 09258388 ; Rahighi, R ; Akhavan, O ; Moshfegh, A ; Sharif University of Technology
Abstract
Vertically aligned ZnO nanowires (NWs) hybridized with reduced graphene oxide sheets (rGO) were applied in efficient visible light photoinactivation of bacteria. To incorporate graphene oxide (GO) sheets within the NWs two different methods of drop-casting and electrophoretic deposition (EPD) were utilized. The EPD method yielded effective penetration of the positively charged GO sheets into the NWs to form a spider net-like structure, whereas the drop-casting method resulted in only a surface coverage of the GO sheets on top of the NWs. The electrical connection between the EPD-incorporated sheets and the NWs was checked by monitoring the electron transfer from UV-assisted photoexcited ZnO...
Large scale inkjet-printing of carbon nanotubes electrodes for antioxidant assays in blood bags
, Article Journal of Electroanalytical Chemistry ; Vol. 717-718 , 2014 , Pages 61-68 ; ISSN: 15726657 ; Cortes Salazar, F ; Prudent, M ; Delobel, J ; Rastgar, S ; Lion, N ; Tissot J. D ; Tacchini, P ; Girault, H. H ; Sharif University of Technology
Abstract
Herein, we present the large scale fabrication of carbon nanotubes (CNT) electrodes supported on flexible polymeric sheets by subsequent multilayer inkjet printing of a silver layer for electrical connection, CNT layers as active electrode material and an insulation layer to define a stand-alone CNT active electrode area with high accuracy. Optical and electrochemical characterization using several redox mediators demonstrates the reproducibility of the electrode surfaces and their functionality even with a single inkjet printed CNT layer. These electrodes are targeted to the clinical sector for the determination of the antioxidant power (AOP) of biologically relevant fluids by...
An exact Analytical solution to exponentially tapered piezoelectric energy harvester
, Article Shock and Vibration ; Volume 2015 , 2015 ; 10709622 (ISSN) ; Rahimi, G. H ; Hosseini Kordkheili, S. A ; Sharif University of Technology
Hindawi Publishing Corporation
2015
Abstract
It has been proven that tapering the piezoelectric beam through its length optimizes the power extracted from vibration based energy harvesting. This phenomenon has been investigated by some researchers using semianalytical, finite element and experimental methods. In this paper, an exact analytical solution is presented to calculate the power generated from vibration of exponentially tapered unimorph and bimorph with series and parallel connections. The mass normalized mode shapes of the exponentially tapered piezoelectric beam with tip mass are implemented to transfer the proposed electromechanical coupled equations into modal coordinates. The steady states harmonic solution results are...
Initial tests on a rolling element bearing with built-in vibration sensor for condition monitoring
, Article 17th International Congress on Sound and Vibration 2010, ICSV 2010, 18 July 2010 through 22 July 2010, Cairo ; Volume 2 , 2010 , Pages 1315-1322 ; 9781617822551 (ISBN) ; Beheshtkar, N ; Bastami, A. R ; Hale, J. M ; Sharif University of Technology
2010
Abstract
This paper presents a novel modification to a conventional rolling element bearing that allows it to monitor its own condition, and describes some preliminary tests on a prototype. The self monitoring feature is a thick-film vibration sensor deposited in a shallow groove around the outer race of the bearing. This has the virtue of being very close to the source of the impacts that are characteristic of a damaged bearing, as well as being robust and low cost. The form of the sensor is such that the loading surfaces of the outer race are only slightly modified and the bearing can be fitted into any conventional bearing housing with only minor modification to make electrical connection to the...
On the energy harvesting via doubly curved piezoelectric panels
, Article Journal of Intelligent Material Systems and Structures ; Volume 27, Issue 19 , 2016 , Pages 2692-2706 ; 1045389X (ISSN) ; Rahnama, F ; Sharif University of Technology
SAGE Publications Ltd
Abstract
This article presents an analytical solution for power output from a doubly curved piezoelectric energy harvester. The energy harvester is made of an elastic core layer coupled with one or two surface-bonded piezoelectric layers. Five mechanical equations of motion together with Gauss's equation are derived on the basis of first-order shell theory and solved simultaneously for simply supported mechanical boundary conditions. The influence of structural damping is taken into account using Rayleigh damping. The electromechanical frequency response functions that relate the power output and circuit load resistance are identified from the exact solutions. Finally, the performance of the system...
A tunable reflection/transmission coefficient circuit using a 45° hybrid coupler with two orthogonal variables
, Article IEEE Transactions on Microwave Theory and Techniques ; Volume 67, Issue 4 , 2019 , Pages 1402-1411 ; 00189480 (ISSN) ; Meng, X ; Fotowat Ahmady, A ; Yue, C. P ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
This paper presents a tunable reflection/transmission coefficient (TRTC) circuit based on a 45° hybrid coupler that is potentially useful for leakage cancelation purposes. The analysis of the proposed TRTC circuit shows that the circuit can cover any reflection/transmission coefficient of less than 0.5 on the Smith chart by adjusting only two variable resistors. Meanwhile, the real and imaginary parts of the reflection/transmission coefficient can be tuned independently, facilitating the use of this circuit in feedback systems. To implement the 45° hybrid coupler used in the proposed TRTC circuit, a new wideband planar topology for arbitrary phase and amplitude hybrid coupler is introduced....
Shielding factor enhancement method for Bi-stage active shield in SQUID-based magnetocardiography system
, Article 29th Iranian Conference on Electrical Engineering, ICEE 2021, 18 May 2021 through 20 May 2021 ; 2021 , Pages 129-133 ; 9781665433655 (ISBN) ; Esmaeili, F ; Shanehsazzadeh, F ; Fardmanesh, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2021
Abstract
We proposed a simple method to enhance shielding factor of our previously proposed bi-stage active shield system employed in a SQUID-based magnetocardiography system. The additional proposed design is optimized for canceling the power-line magnetic interference field to provide a calmer magnetic environment for the bi-stage active shield. A 50 Hz cancellation coil is placed around the bi-stage shielding system which includes inner and outer coils designed for compensating low-frequency (0-0.1Hz) and high-frequency (0.1-100Hz) environmental magnetic noise, respectively. In this configuration, a SQUID magnetometer is located at the center of these coils. Considering that the power-line...
Shielding factor enhancement method for bi-stage active shield in SQUID-based magnetocardiography system
, Article 29th Iranian Conference on Electrical Engineering, ICEE 2021, 18 May 2021 through 20 May 2021 ; 2021 , Pages 129-133 ; 9781665433655 (ISBN) ; Esmaeili, F ; Shanehsazzadeh, F ; Fardmanesh, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2021
Abstract
We proposed a simple method to enhance shielding factor of our previously proposed bi-stage active shield system employed in a SQUID-based magnetocardiography system. The additional proposed design is optimized for canceling the power-line magnetic interference field to provide a calmer magnetic environment for the bi-stage active shield. A 50 Hz cancellation coil is placed around the bi-stage shielding system which includes inner and outer coils designed for compensating low-frequency (0-0.1Hz) and high-frequency (0.1-100Hz) environmental magnetic noise, respectively. In this configuration, a SQUID magnetometer is located at the center of these coils. Considering that the power-line...
A robust two-degree-of-freedom control strategy for an islanded microgrid
, Article IEEE Transactions on Power Delivery ; Volume 28, Issue 3 , 2013 , Pages 1339-1347 ; 08858977 (ISSN) ; Karimi, H ; Sharif University of Technology
2013
Abstract
This paper presents a new robust control strategy for an islanded microgrid in the presence of load unmodeled dynamics. The microgrid consists of parallel connection of several electronically interfaced distributed generation units and a local load. The load is parametrically uncertain and topologically unknown and, thus, is the source of unmodeled dynamics. The objective is to design a robust controller to regulate the load voltage in the presence of unmodeled dynamics. To achieve the objective, the problem is first characterized by a two-degree-of-freedom (2DOF) feedback-feedforward controller. The 2DOF control design problem is then transformed to a nonconvex optimization problem....
Analysis of impedance stabilization of natural and metallic DNA molecules
, Article 2012 19th Iranian Conference of Biomedical Engineering, ICBME 2012 ; 2012 , Pages 139-142 ; 9781467331302 (ISBN) ; Khakestar, A. S ; Hejazi, M. S ; Fardmanesh, M ; Sharif University of Technology
2012
Abstract
In this work, we used λ-DNA to produce metallic DNA samples and we investigated the stabilization time of their impedances. This is in order to show that the DNA molecules can possibly be utilized as a frame for assembling the nanocircuits and as an electronic element as well, in nanoelectric devices. It has been shown that metallic DNA has lower stabilization time than natural DNA. As expected, it is shown that making the bundled DNA oriented, impacts their impedance stabilization. In order to find the characteristic impedance of the DNA molecules under direct current, we designed and made patterned electrodes to make electrical connections between the DNAs and the used current source. The...
Power management strategy for a multi-hybrid fuel cell/energy storage power generation systems
, Article 2012 3rd Power Electronics and Drive Systems Technology, PEDSTC 2012, 15 February 2012 through 16 February 2012 ; February , 2012 , Pages 354-359 ; 9781467301114 (ISBN) ; Hamzeh, M ; Mokhtari, H ; Sharif University of Technology
2012
Abstract
This paper depicts a new configuration for modular hybrid power conversion systems, namely, multi-hybrid generation system (MHGS), and parallel connection at the output, such that the converter of each unit shares the load current equally. This is a significant step towards realizing a modular power conversion system architecture, where smaller units can be connected in any series/parallel grouping to realize any required unit specifications. The supercapacitor (SC) as a complementary source is used to compensate for the slow transient response of the fuel cell (FC) as a main power source. It assists the FC to meet the grid power demand in order to achieve a better performance and dynamic...
μ-Synthesis control for an islanded microgrid with structured uncertainties
, Article IECON Proceedings (Industrial Electronics Conference), 7 November 2011 through 10 November 2011 ; November , 2011 , Pages 3064-3069 ; 9781612849720 (ISBN) ; Karimi, H ; Sharif University of Technology
2011
Abstract
This paper presents a robust control scheme for an islanded microgrid in the presence of structured uncertainties. The microgrid consists of parallel connection of two Distributed Generation (DG) units and a passive load. The DG units are connected to the passive load by using the power electronics converters. The microgrid model is structurally uncertain due to the large perturbations in the load parameters. To deal with the uncertainties, a Linear Fractional Representation (LFR) of the parametrically uncertain system is obtained. To achieve robust performance, the μ-synthesis approach is applied to the derived LFR model to design a μ controller. The resultant controller is structurally...
Energy harvesting via shallow cylindrical and spherical piezoelectric panels using higher order shear deformation theory
, Article Composite Structures ; Volume 147 , 2016 , Pages 155-167 ; 02638223 (ISSN) ; Rahnama, F ; Askari Farsangi, M. A ; Sharif University of Technology
Elsevier Ltd
Abstract
In this article an analytical solution is presented for power output from a piezoelectric shallow shell energy harvester using higher order shear deformation theory (HSDT). The energy harvester is made of an elastic substrate layer coupled with one or two surface bonded piezoelectric layers. Mechanical equations of motion with Gauss's equation are derived on the basis of HSDT and solved simultaneously for simply-supported mechanical boundary conditions. The electromechanical frequency response functions that relate the power output and circuit load resistance are identified from the exact solutions. Using Rayleigh damping the influence of structural damping is taken into account. Also...
A power divider/combiner realized by ridge gap waveguide technology for millimeter wave applications
, Article 4th International Conference on Millimeter-Wave and Terahertz Technologies, MMWaTT 2016, 20 December 2016 through 22 December 2016 ; 2017 , Pages 5-8 ; 21570965 (ISSN); 9781509054145 (ISBN) ; Banai, A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2017
Abstract
A half power divider using ridge gap waveguide technology is realized in millimeter wave frequencies. By machining a piece of metal the divider was fabricated. There is no need to an electrical connection between the divider constitutive parts. The fabricated divider is self-packaged. Cylindrical pins are used in the divider structure for ease of fabrication. Low loss power division and good isolation between ports is measured. Also the measured impedance matching of the divider ports is acceptable. Good agreement between the simulation and measurement is achieved. © 2016 IEEE
Enhancement of antibacterial properties of Ag nanorods by electric field
, Article Science and Technology of Advanced Materials ; Volume 10, Issue 1 , 2009 ; 14686996 (ISSN) ; Ghaderi, E ; Sharif University of Technology
2009
Abstract
The effect of an electric field on the antibacterial activity of columnar aligned silver nanorods was investigated. Silver nanorods with a polygonal cross section, a width of 20-60 nm and a length of 260-550 nm, were grown on a titanium interlayer by applying an electric field perpendicular to the surface of a Ag/Ti/Si(100) thin film during its heat treatment at 700 °C in an Ar+H2 environment. The optical absorption spectrum of the silver nanorods exhibited two peaks at wavelengths of 350 and 395 nm corresponding to the main surface plasmon resonance bands of the one-dimensional silver nanostructures. It was found that the silver nanorods with an fcc structure were bounded mainly by {100}...
Active power management of multihybrid fuel cell/supercapacitor power conversion system in a medium voltage microgrid
, Article IEEE Transactions on Smart Grid ; Volume 3, Issue 4 , 2012 , Pages 1903-1910 ; 19493053 (ISSN) ; Hamzeh, M ; Mokhtari, H ; Karimi, H ; Sharif University of Technology
2012
Abstract
This paper proposes a hierarchical active power management strategy for a medium voltage (MV) islanded microgrid including a multihybrid power conversion system (MHPCS). To guarantee excellent power management, a modular power conversion system is realized by parallel connection of small MHPCS units. The hybrid system includes fuel cells (FC) as main and supercapacitors (SC) as complementary power sources. The SC energy storage compensates the slow transient response of the FC stack and supports the FC to meet the grid power demand. The proposed control strategy of the MHPCS comprises three control loops; dc-link voltage controller, power management controller, and load current sharing...
Phase synchronizing in Hindmarsh-Rose neural networks with delayed chemical coupling
, Article Neurocomputing ; Volume 74, Issue 10 , 2011 , Pages 1551-1556 ; 09252312 (ISSN) ; Sharif Unversity of Technology
2011
Abstract
Although diffusive electrical connections in neuronal networks are instantaneous, excitatory/inhibitory couplings via chemical synapses encompass a transmission time-delay. In this paper neural networks with instantaneous electrical couplings and time-delayed excitatory/inhibitory chemical connections are considered and scaling of the spike phase synchronization with the unified time-delay in the network is investigated. The findings revealed that in both excitatory and inhibitory chemical connections, the phase synchronization could be enhanced by introducing time-delay. The role of the variability of the neuronal external current in the phase synchronization is also investigated. As...
Decentralized control of parallel connection of two distributed generation units
, Article 35th Annual Conference of the IEEE Industrial Electronics Society, IECON 2009, Porto, 3 November 2009 through 5 November 2009 ; 2009 , Pages 358-362 ; Karimi, H ; Iravani, R ; Sharif University of Technology
Abstract
This paper presents a decentralized control strategy for the autonomous (islanded) operation of parallel connection of two distributed generation (DG) units. The DG units are electronically interfaced to the host grid at the same point of common coupling (PCC), where the local load is also supplied. In the grid-connected mode, the voltage-sourced converter (VSC) of each DG unit controls the exchange of real and reactive power components with the host grid, based on the conventional dq-current control strategy. In the islanded mode, one of the DG units provides voltage and frequency control for the island, and the other DG unit continues to operate with the pre-islanding dq-current control...