scholarly journals Evolutionary Algorithm Geometry Optimization of Optical Antennas

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
Ramón Díaz de León-Zapata ◽  
Gabriel González ◽  
Efrén Flores-García ◽  
Ángel Gabriel Rodríguez ◽  
Francisco Javier González
Keyword(s):  
Electromagnetic Waves ◽  
Geometry Optimization ◽  
Antenna Design ◽  
Optical Antennas ◽  
Optical Antenna ◽  
Printed Antennas ◽  
Printed Circuit ◽  
Wide Range ◽  
Printed Circuit Antennas ◽  
Rf Antenna

Printed circuit antennas have been used for the detection of electromagnetic radiation at a wide range of frequencies that go from radio frequencies (RF) up to optical frequencies. The design of printed antennas at optical frequencies has been done by using design rules derived from the radio frequency domain which do not take into account the dispersion of material parameters at optical frequencies. This can make traditional RF antenna design not suitable for optical antenna design. This work presents the results of using a genetic algorithm (GA) for obtaining an optimized geometry (unconventional geometries) that may be used as optical regime antennas to capture electromagnetic waves. The radiation patterns and optical properties of the GA generated geometries were compared with the conventional dipole geometry. The characterizations were conducted via finite element method (FEM) computational simulations.

scholarly journals Catalyst Ammonia Storage Measurements Using Radio Frequency Sensing1

2018 ◽  
Vol 140 (11) ◽  
Author(s):  
Jonathan Aguilar ◽  
Leslie Bromberg ◽  
Alexander Sappok ◽  
Paul Ragaller ◽  
Jean Atehortua ◽  
...  
Keyword(s):  
Radio Frequency ◽  
Electromagnetic Waves ◽  
Catalytic Reduction ◽  
Cavity Resonator ◽  
Wide Range ◽  
Ammonia Storage ◽  
Catalyst Temperature ◽  
Rf Antenna ◽  
Scr System ◽  
Rf Signal

Motivated by increasingly strict nitrogen oxides (NOx) limits, engine manufacturers have adopted selective catalytic reduction (SCR) technology to reduce engine-out NOx. In the SCR process, NOx react with ammonia (NH3) to form nitrogen and water vapor. The reaction is influenced by several variables, including stored ammonia on the catalyst, exhaust gas composition, and catalyst temperature. Currently, measurements from NOx and/or NH3 sensors upstream and downstream of the SCR are used with predictive models to estimate ammonia storage levels on the catalyst and control urea dosing. This study investigated a radio frequency (RF)-based method to directly monitor the ammonia storage state of the SCR. This approach utilizes the catalyst as a cavity resonator, in which an RF antenna excites electromagnetic waves within the cavity to monitor changes in the catalyst state. Ammonia storage causes changes in the dielectric properties of the catalyst, which directly impacts the RF signal. Changes in the RF signal relative to stored ammonia (NH3) were evaluated over a wide range of frequencies, temperatures, and exhaust conditions. The RF response to NH3 storage, desorption, and oxidation on the SCR was well correlated with changes in the catalyst state. Calibrated RF measurements demonstrate the ability to monitor the adsorption state of the SCR to within 10% of the sensor full scale. The results indicate direct measurement of SCR ammonia storage levels, and resulting catalyst feedback control, via RF sensing to have significant potential for optimizing the SCR system to improve NOx conversion and decrease urea consumption.

Microwaves: Application in Electron Microscopy

1990 ◽  
Vol 48 (3) ◽  
pp. 140-141
Author(s):  
Anthony S-Y Leong ◽  
David W Gove
Keyword(s):  
Electron Microscopy ◽  
Light Microscopy ◽  
Chemical Reactions ◽  
Electromagnetic Waves ◽  
Tissue Fixation ◽  
Primary Method ◽  
Dipolar Molecules ◽  
Wide Range ◽  
Time Required ◽  
Cryostat Sections

Microwaves (MW) are electromagnetic waves which are commonly generated at a frequency of 2.45 GHz. When dipolar molecules such as water, the polar side chains of proteins and other molecules with an uneven distribution of electrical charge are exposed to such non-ionizing radiation, they oscillate through 180° at a rate of 2,450 million cycles/s. This rapid kinetic movement results in accelerated chemical reactions and produces instantaneous heat. MWs have recently been applied to a wide range of procedures for light microscopy. MWs generated by domestic ovens have been used as a primary method of tissue fixation, it has been applied to the various stages of tissue processing as well as to a wide variety of staining procedures. This use of MWs has not only resulted in drastic reductions in the time required for tissue fixation, processing and staining, but have also produced better cytologic images in cryostat sections, and more importantly, have resulted in better preservation of cellular antigens.

Suitable Conditions for Effective Inter Chip Communication based on Surface Wave Phenomenon

2021 ◽  
Vol 14 ◽  
Author(s):  
Mahaveer Penna ◽  
Shiva Shankar ◽  
Keshava Murthy ◽  
Jijesh J J
Keyword(s):  
Surface Wave ◽  
Integrated Circuits ◽  
Electromagnetic Waves ◽  
Printed Circuit Boards ◽  
Analytical Models ◽  
Circuit Boards ◽  
High Frequencies ◽  
Printed Circuit ◽  
High Data ◽  
Low Dispersion

Background: The communication between two Integrated Circuits (IC) of the Printed Circuit Boards (PCB) currently happening through copper traces which allow electric charge to flow. Several limitations being encountered with the copper traces during high data rate communication because of the resistivity factors, which eventually leads to the damage of traces and the system. Methods: The solution for this issue comes with the design of surface wave communication-based waveguide/channel between the IC’s. Surface wave communication over a specified communication fabric/channel performs the propagation of electromagnetic waves effectively even at high frequencies compared to the copper traces using conductor-dielectric combination. This paper deals in revealing suitable conditions through profound analytical models for achieving effective surface wave communication between the pins of integrated circuits. Results: The analysis includes defining the possible wave propagation terms, suitable channel design aspects for PCB application and corresponding analysis for effective communication at frequencies from 50GHz to 500GHz of millimeter range. This study provides the roadmap to explore a deterministic channel/fabric for pin to pin communication between the IC’s as an alternate for the copper traces. Conclusion: In this process, the proposed channel achieves low dispersion compared to the copper traces at millimeter frequency range.

scholarly journals Controlling Resonator Nonlinearities and Modes through Geometry Optimization

Micromachines ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1381
Author(s):  
Amal Z. Hajjaj ◽  
Nizar Jaber
Keyword(s):  
Axial Stress ◽  
Geometry Optimization ◽  
Beam Equation ◽  
Design Parameters ◽  
Dynamical Response ◽  
Successful Implementation ◽  
Shape Effect ◽  
Mems Resonators ◽  
Wide Range ◽  
The Galerkin Method

Controlling the nonlinearities of MEMS resonators is critical for their successful implementation in a wide range of sensing, signal conditioning, and filtering applications. Here, we utilize a passive technique based on geometry optimization to control the nonlinearities and the dynamical response of MEMS resonators. Also, we explored active technique i.e., tuning the axial stress of the resonator. To achieve this, we propose a new hybrid shape combining a straight and initially curved microbeam. The Galerkin method is employed to solve the beam equation and study the effect of the different design parameters on the ratios of the frequencies and the nonlinearities of the structure. We show by adequately selecting the parameters of the structure; we can realize systems with strong quadratic or cubic effective nonlinearities. Also, we investigate the resonator shape effect on symmetry breaking and study different linear coupling phenomena: crossing, veering, and mode hybridization. We demonstrate the possibility of tuning the frequencies of the different modes of vibrations to achieve commensurate ratios necessary for activating internal resonance. The proposed method is simple in principle, easy to fabricate, and offers a wide range of controllability on the sensor nonlinearities and response.

scholarly journals Alexander Lamb Cullen OBE. 30 April 1920—27 December 2013

2018 ◽  
Vol 64 ◽  
pp. 131-148
Author(s):  
J. Brian Davies
Keyword(s):  
Electromagnetic Waves ◽  
Electrical Engineering ◽  
Measurement Techniques ◽  
Science And Engineering ◽  
Engineering Research ◽  
British Science ◽  
Wide Range ◽  
The Media ◽  
Great Sense ◽  
The Times

Alex Cullen combined the sharpest of scientific minds with a gentle personality and a great sense of humour. He was Professor and Head of the Department of Electrical Engineering at Sheffield from 1955 to 1967, and then Head of the Department of Electrical Engineering at University College London (UCL) until 1980. He continued his research there as a Science and Engineering Research Council Senior Fellow until 1985, and for some years as Research Fellow of UCL. His research concerned electromagnetic waves over a wide range of microwave devices and measurement techniques, the latter at a fundamental level. These contributions were of a highly innovative and ‘ground-breaking’ nature. He was appointed OBE in 1960, and elected Fellow of the Royal Society in 1977. He was an accomplished jazz musician, playing drums and clarinet. He was a signatory of a letter to The Times in January 1986, calling on Prime Minister Margaret Thatcher to ‘Save British Science’. This led to the foundation of the Save British Science pressure group, now the Campaign for Science and Engineering (CaSE), which has built up an enviable reputation with politicians and the media in representing the concerns of scientists and engineers. When (now Sir) Eric Ash left UCL in 1985 to become Rector of Imperial College, he remarked that Alex was ‘the last gentleman in the business’.

AN IMAGE EXTRACTION APPROACH TO MODELING PRINTED CIRCUIT ANTENNAS

1986 ◽  
Vol 6 (2) ◽  
pp. 161-170 ◽  
Author(s):  
C. L. Chi ◽  
N. G. Alexopoulos
Keyword(s):  
Printed Circuit ◽  
Printed Circuit Antennas

Technical Analysis and Overview of the Application of Artificial Dielectric Materials in the Form of Photonic Crystal Cavity with Resonance in Dirac Leaky-Wave Antennas

2019 ◽  
Vol 960 ◽  
pp. 231-237 ◽  
Author(s):  
Ritu Walia ◽  
Kamal Nain Chopra
Keyword(s):  
Photonic Crystal ◽  
Dielectric Material ◽  
Dielectric Materials ◽  
Optical Antennas ◽  
Optical Antenna ◽  
Layer By Layer ◽  
Leaky Wave ◽  
Incident Intensity ◽  
Photonic Crystal Cavity ◽  
Artificial Dielectric

Application of Artificial Dielectric Materials in the form of Photonic crystal cavity with resonance in Dirac leaky-wave Antennas. The system investigated is a Photonic crystal cavity for the radiation properties of an antenna formed by a combination of a monopole radiation source and a cavity by a dielectric layer-by-layer 3D photonic crystal. The Photonic crystal cavity under study is working at resonance, since a high directivity, and a high power enhancement are obtainable at the resonant frequency of the cavity.In addition, an approach based on (i) Hughen's wavelets and (ii) the components of the incident Intensity after transmission through the system, is suggested for optimizing the performance of the optical antennas. Also, it has been discussed that the Optical antenna fabricated by Dielectric material - Photonic crystal is a better alternative to a conventional focusing lens, in Nanoscopy, in order to concentrate the laser radiation to dimensions smaller than the diffraction limit.

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