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Search Results: 1 - 10 of 810 matches for " Ebrahim Forati "
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Soft-boundary graphene nanoribbon formed by a graphene sheet above a perturbed ground plane: conductivity profile and SPP modal current distribution
Ebrahim Forati,George W. Hanson
Physics , 2013, DOI: 10.1088/2040-8978/15/11/114006
Abstract: An infinite sheet of graphene lying above a perturbed ground plane is studied. The perturbation is a two dimensional ridge, and a bias voltage is applied between the graphene and the ground plane, resulting in a graphene nanoribbonlike structure with a soft-boundary (SB) The spatial distribution of the graphene conductivity forming the soft-boundary is studied as a function of the ridge parameters and the bias voltage. The current distribution of the fundamental TM surface plasmon polariton (SPP) is considered. The effect of the ridge parameters and shape of the soft boundary on the current distributions are investigated, and the conditions are studied under which the mode remains confined to the vicinity of the ridge region.
Surface plasmon polaritons on soft-boundary graphene nanoribbons and their application as voltage controlled plasmonic switches and frequency demultiplexers
Ebrahim Forati,George W. Hanson
Physics , 2013, DOI: 10.1063/1.4822044
Abstract: A graphene sheet gated with a ridged ground plane, creating a soft-boundary (SB) graphene nanoribbon, is considered. By adjusting the ridge parameters and bias voltage a channel can be created on the graphene which can guide TM surface plasmon polaritons (SPP). Two types of modes are found; fundemental and higher-order modes with no apparent cutoff frequency and with energy distributed over the created channel, and edge modes with energy concen-trated at the soft-boundary edge. Dispersion curves, electric near-field patterns, and current distributions of these modes are determined. Since the location where energy is concentrated in the edge modes can be easily controlled electronically by the bias voltage and frequency, the edge-mode phenomena is used to propose a novel voltage controlled plasmonic switch and a plasmonic frequency demultiplexer.
On the difference between breakdown and quench voltages of argon plasma and its relation to $4p-4s$ atomic state transitions
Ebrahim Forati,Shiva Piltan,Dan Sievenpiper
Physics , 2014, DOI: 10.1063/1.4907414
Abstract: Using a relaxation oscillator circuit, breakdown ($V_{\mathrm{BD}}$) and quench ($V_{\mathrm{Q}}$) voltages of a DC discharge microplasma between two needle probes are measured. High resolution modified Paschen curves are obtained for argon microplasmas including a quench voltage curve representing the voltage at which the plasma turns off. It is shown that, for a point to point microgap (e.g. the microgap between two needle probes) which describes many realistic microdevices, neither Paschen's law applies nor field emission is noticeable. Although normally $V_{\mathrm{BD}}>V_{\mathrm{Q}}$, it is observed that depending on environmental parameters of argon, such as pressure and the driving circuitry, plasma can exist in a different state with equal $V_{\mathrm{BD}}$ and $V_{\mathrm{Q}}$. Using emission line spectroscopy, it is shown that $V_{\mathrm{BD}}$ and $V_{\mathrm{Q}}$ are equal if the atomic excitation by the electric field dipole moment dominantly leads to one of the argon's metastable states ($4P_{5}$ in our study).
Graphene as a tunable THz reservoir for shaping the Mollow triplet of an artificial atom via plasmonic effects
Ebrahim Forati,George W. Hanson,Stephen Hughes
Physics , 2014, DOI: 10.1103/PhysRevB.90.085414
Abstract: Using a realistic quantum master equation we show that the resonance fluorescence spectra of a two-level artificial atom (quantum dot) can be tuned by adjusting its photonic local density of states via biasing of one or more graphene monolayers. The structured photon reservoir is included using a photon Green function theory which fully accounts for the loss and dispersion. The field-driven Mollow triplet spectrum can be actively controlled by the graphene bias in the THz frequency regime. We also consider the effect of a dielectric support environment, and multiple graphene layers, on the emitted fluorescence. Finally, thermal bath effects are considered and shown to be important for low THz frequencies.
Optical plasma microelectronic devices
Ebrahim Forati,Shiva Piltan,Thyler Dill,Dan Sievenpiper
Physics , 2015,
Abstract: The semiconductor channel in conventional microelectronic devices was successfully replaced with an optically triggered gas plasma channel. The combination of DC and laser-induced gas ionizations controls the conductivity of the channel, enabling us to realize different electronic devices such as transistors, switches, modulators, etc. A special micro-scale metasurface was used to enhance the laser-gas interaction, as well as combining it with DC ionization properly. Optical plasma devices benefit form the advantages of plasma/vacuum electronic devices while preserving most of the integrablity of semiconductor based devices.
A planar hyperlens based on a modulated graphene monolayer
Ebrahim Forati,George W. Hanson,Alexander B. Yakovlev,Andrea Alu
Physics , 2013, DOI: 10.1103/PhysRevB.89.081410
Abstract: The canalization of terahertz surface plasmon polaritons using a modulated graphene monolayer is investigated for subwavelength imaging. An anisotropic surface conductivity formed by a set of parallel nanoribbons with alternating positive and negative imaginary conductivities is used to realize the canalization regime required for hyperlensing. The ribbons are narrow compared to the wavelength, and are created electronically by gating a graphene layer over a corrugated ground plane. Good quality canalization of surface plasmon polaritons is shown in the terahertz even in the presence of realistic loss in graphene, with relevant implications for subwavelength imaging applications.
Magneto-optical metamaterial
Mehdi Sadatgol,Mahfuzur Rahman,Ebrahim Forati,Miguel Levy,Durdu O. Guney
Physics , 2015,
Abstract: We propose a new class of metamaterials called magneto-optical metamaterials that offer enhanced angle of rotation in polarization compared to bulk magneto-optical materials. In the proposed approach, the permittivity tensor of a magneto-optical material is tailored by embedded wire meshes behaving as artificial plasma. We have shown that the angle of rotation in the magneto-optical metamaterial can be enhanced up to 9 times compared to bulk magneto-optical material alone while the polarization extinction ratio remains below -20dB and insertion loss is less than 1.5dB.
Effect of Hot Accumulative Roll Bonding Process on the Mechanical Properties of AA5083  [PDF]
Hassan Sheikh, Ebrahim Paimozd
Open Journal of Metal (OJMetal) , 2011, DOI: 10.4236/ojmetal.2011.11002
Abstract: In this work, accumulative roll bonding (ARB) process as a severe plastic deformation was applied on an AA5083 sheet up to 6 cycles at the temperature of 300℃ and at the strain rate of 50 s­‐1. The results of tensile tests show that the values of the yield stress and the ultimate tensile strength don't change considerably after 4 cycles. Also, transmission electron microscopy (TEM) micrograph confirmed that the microstructure has fine (sub) grains with the size of 200 nm - 400 nm.
A New Approach to Complex Bandpass Sigma Delta Modulator Design for GPS/Galileo Receiver  [PDF]
Nima Ahmadpoor, Ebrahim Farshidi
Circuits and Systems (CS) , 2012, DOI: 10.4236/cs.2012.31006
Abstract: In this paper, new complex band pass filter architecture for continuous time complex band pass sigma delta modulator is presented. In continuation of paper the modulator is designed for GPS and Galileo receiver. This modulator was simulated in standard 0.18 μm CMOS TSMC technology and has bandwidth of 2MHz and 4MHz for GPS and Galileo centered in 4.092 MHz. The dynamic range (DR) is 56.5/49 dB (GPS/Galileo) at sampling rate of 125 MHz. The modulator has power consumption of 4.1 mw with 3 V supply voltage.
Ochratoxin A in dried figs, raisings, apricots, dates on Iranian retail market  [PDF]
Ebrahim Rahimi, Amir Shakerian
Health (Health) , 2013, DOI: 10.4236/health.2013.512282
Abstract:

Ochratoxin A (OTA) is among the most important mycotoxins, and the International Agency for Research on Cancer (IARC) classifies it as possibly carcinogenic to humans (group 2B). A total of 121 samples of dried fruits from the central zone of Iran were analyzed for OTA by enzyme linked immunosorbent assay (ELISA) technique. The recovery percentages of OTA in spiked dried fruit samples at concentrations of 5, 10 and 20 ng/g were found to be 84.9%, 89.3% and 90.4% as mean, respectively. OTA was found in 20.7% of the analyzed samples by average concentration of 6.7 ± 3.9 ng/g. The incidence rates of OTA contamination in dried fig, raising, apricots, and date samples were 10.4%, 44.7%, 6.7% and 10.0%, respectively. The concentrations of OTA in 7.9% of contaminated dried raising samples and 2.1% of dried fig samples were higher than maximum tolerance limit accepted by European Union (10 ng/g). This value reflects that the analyzed samples have a minimal contribution to toxicological risk. To our best knowledge, the present study is the first report of the presence of OTA by ELISA in dried fruit samples in Iran.

 

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