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Canalization of surface plasmon polaritons (SPPs) on a layer of suspended graphene is investigated. In the canalization regime (Phys. Rev. B. vol. 71, pp. 193105, 2005), spatial harmonics propagate with the same phase velocity. One application of canalization is in sub-wavelength imaging to overcome the diffraction limit. It is shown that a graphene sheet with anisotropic conductivity can provide...
Increasing the absorption efficiency is one of the key tasks towards maximizing the overall solar cell efficiency which is a product of absorption efficiency, carrier generation efficiency, and carrier extraction efficiency. It has been shown that nano-pillar array photovoltaic (PV) solar cells exhibit increased electromagnetic absorption in comparison to conventional flat solar cells. Furthermore,...
To accurately predict how the distribution of extreme events may change in the future we need to understand the mechanisms that influence such events in our current climate. This includes understanding how modes of natural climate variability, such as the El Nino Southern Oscillation (ENSO), the North Atlantic Oscillation (NAO) and the Pacific Decadal Oscillation (PDO) impact the weather extremes...
Antenna design for small satellites such as CubeSats constitute a challenge for designers especially at UHF frequencies. The small size of the CubeSat (10 cm × 10 cm × 10 cm) imposes several constraints on the antenna design. Extreme packaging ratios and advanced deployment mechanisms have to be employed to cater for UHF antennas on a CubeSat platform.
As Cube Satellites have become a very important low cost tool for space explorations, integrating antennas with their solar panels is gaining increased importance. Such integration resolves two main issues for a Cube Satellite (CubeSat): (1) saving surface real estate, and (2) reduce the deployment that is needed for the traditional wire antennas. By examining the solar panel assembly, it is straightforward...
To predict the impact of ionospheric scintillations on communications, navigation, and space radar systems it can be useful to simulate the RF conditions under which these systems must operate. Several beacon satellites currently in orbit broadcast radio signals that can be monitored by receivers on the ground to specify scintillations at one or more frequencies. In this paper, we present an inverse...
The Weather Research and Forecasting (WRF) model was applied to dynamically downscale global analyses from the Climate Forecast System Reanalysis over a 200km×200km domain centered on Toulon, France; on the East coast of the occidental Mediterranean, for the month of February and June over 10 years. To insure accuracy, observational data from the NCAR ADP historical database were used in combination...
We describe further results in the development of an approach to imaging through dilute obscuring particulate media, in which energy absorption in the scatterers is small and the attenuation is caused primarily by scattering.
Humvees are typically furnished with a wide range of antenna systems commonly mounted on the roof or bumper of the vehicle. While antennas mounted in these locations may have good performance, they both (roof and bumper) have limited room for additional antennas with new or expanded functionalities. Additionally, the roof- and bumper-based antenna systems may contribute to a large visual profile and...
Microwave and millimeter wave propagation over rough sea surfaces is dominated by the effects of coherent multipath interference between direct and surface reflected paths. In addition, the omnipresent near surface atmospheric refractivity ducting creates additional multipath phenomena. The prediction of the propagated electromagnetic fields is complicated by a number of effects including: 1) non-flat...
Trident Warrior 2013 was conducted off the coast of Norfolk, VA from July 12–18, 2013. Passive RF measurements were made between 80–700 Hz using a vertically polarized monopole and a horizontally polarized bicone antennas that are mounted on the R/V Knorr. The RF measurements are composed of three phases: 1. Estimation of unknown source parameters from ship measurements next to the shore as a function...
A transmission line transformer (TLT) is a device that transforms a circuit impedance and is implemented with interconnected transmission lines. While traditional TLTs, operating at UHF and low microwave frequencies, are constructed from pairs of coaxial lines wound around ferrite cores, various compact implementations at higher frequency without magnetic materials have been demonstrated with multilayer...
High power RF sources are used in many applications including Satellite communications, Radar, Electronic Counter-Measures (ECM). Most of them consist of Klystrons, Magnetrons or Gyrotrons which are narrow band, bulky structures. Very few TWTs compatible with very high power (above 100KW) in S-band have been reported in literature. A challenge in designing small, high power TWTs relates to over-heating...
We present several results that use transistors within the context of metamaterials. Transistors are a fundamental device in the construction of several RF systems and applications. The basic device physics of the transistor allow for the convenient construction of variable resistors, oscillators, switches, and amplifiers. Embedding transistors within the confines of a split ring resonator (SRR),...
As the wireless communication devices shrink in size, transmission bandwidth becomes a challenging factor for antenna designers. For example, biomedical implants are among the most critical devices that are required to have a minimized size while transmitting high data-rate information. Particularly, devices that interact with the nervous system such as cochlear and visual prostheses must be able...
The concept of “polarizing lens” is presented and its generalization to design novel lenses is examined. After exploring the general theoretical formulations, optimal designs to realize polarizing lenses at infrared frequencies are presented. An efficient phase-amplitude synthesis method is also employed in the design of polarizing lenses. The proposed method provides the phase and amplitude distribution...
The Earth's lower thermosphere region between 90–140 Km is subjected to episodic energy and momentum forcing from the solar wind in the form of Joule heating and particle precipitation. This is believed to be the largest driver of global thermospheric temperature variability. In addition, this region is also subjected to the periodic and episodic energy and momentum forcing through tides, planetary...
One of the most promising satellite observation strategies still to be developed is the capability to conduct simultaneous multipoint observations of the Earth system from space. These types of observations are required to understand the “big picture” of coupling between disparate regions: solar-wind, magnetosphere, ionosphere, thermosphere, mesosphere, atmosphere, land, ocean on a planetary scale...
Small satellites are increasingly attractive platforms for performing high-quality Earth science radiometric observations. Traditional scientific satellites and instruments are extremely expensive, one-of-a-kind designs with long design cycles. In order to maintain long-term uninterrupted science data collection, re-designing new large satellites and instruments for each application every few decades...
The Distributed Collaborative Adaptive Sensing (DCAS) paradigm introduced by the National Science Foundation Engineering Research Center (NSF-ERC) for Collaborative Adaptive Sensing of the Atmosphere (CASA) has shown great advantages to observe and track low-level atmospheric conditions during the 5 years operation (2007–2011) in Southwestern Oklahoma. To demonstrate the DCAS concept and mitigate...
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