332 research outputs found
Inverse scattering approaches in through-wall imaging,” in Through-the-wall radar imaging
No full textTunable periodic microstrip structure on GaAs wafer
No full textA one dimensional tunable periodic structure in microstip technology on gallium arsenide (GaAs) substrate is numerically investigated. The unit cell contains a number of patches positioned between the ground plane and the microstrip line. The patches, representing reactive loads, can be selectively short-circuited by externally-controlled FET switches integrated in the hosting substrate. The possibility of controlling the position of the band-gap, and implicitly the value of the e®ective dielectric constant along the line, for different combinations of the switches is demonstrate
Microwave propagation through cultural vegetation canopies.
No full textThe need to understand the interaction of microwaves with vegetation canopies has markedly increased in recent years. This is due to advances made in remote sensing science, microwave technology, and signal processing circuits. One class of the earth's vegetation cover is man-made canopies, such as agricultural fields, orchards, and artificial forests. Contrary to natural vegetation terrain, location, spacing, and density of plants in a man-made vegetation canopy are deterministic quantities. As a result, the semi-deterministic nature of cultural vegetation canopies violate the random assumption of the radiative transfer theory and leads to experimented results that are in variance with model calculations. Hence, an alternative approach is needed to model the interaction of microwaves with such canopies. This thesis examines the propagation behavior through a canopy of corn plants. The corn canopy was selected as a representative of cultural vegetation canopies that are planted in parallel rows with an approximately fixed spacing between adjacent plants. Several experimental measurements were conducted to determine the transmission properties of a corn canopy in the 1-10 GHz range. The measurements which included horizontal propagation through the canopy as well as propagation at oblique incidence, were performed for defoliated canopies and for canopies with leaves. Through experimental observations and model development, the propagation behavior was found to be strongly dependent on the wavelength and the path length. At a wavelength in the neighborhood of 20 cm, for example, it was found that scattering by the stalks was coherent in nature for waves propagating horizontally through the canopy, which necessitated the development of a coherent-field model that uses Bragg scattering to account for the observed interference pattern in the transmitted beam. As the wavelength is made shorter, the semi-random spacing between plants becomes significant relative to the wavelength, thereby destroying the coherent properties of the propagating field, in which case propagating wave becomes partially incoherent in nature. Because of the short path lengths associated with oblique propagation through the canopy, Bragg scattering need not be considered and a much simpler formulation was found to provide good agreement with experimental observations.PhDApplied SciencesElectrical engineeringNuclear physics and radiationPure SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/128843/2/9208667.pd
Atlas pistachio (Pistacia atlantica) unripe fruit extract as a source of phytochemicals with anti-tyrosinase, antioxidant, and antibacterial properties
No full textThe current need for biologically active substances that are sustainable, allegedly beneficial to health, and may be employed as ingredients in cosmetic products has encouraged numerous researchers. Pistacia atlantica is known to contain compounds that possess strong biological effects beneficial to health. The objective of this study was the quantification of the polyphenols in unripe Atlas pistachio (AP) fruit extract and the evaluation of hydro-methanolic extract and anthocyanins for their antioxidant, anti-tyrosinase, and antimicrobial effects. The results revealed that the yield of the hydro-methanolic extract was 22.15%, characterized by 75.12 mg GAE/g DM for total phenolics and strong content of hydrolysable tannins (400.16 mg GAE/g DM). 1,1-dimethyl-allyl caffeate, hydroxytyrosol, ellagic acid, rutin, and kaempferol-3-O-glucoside were the most abundant components quantified by HPLC-DAD. The tyrosinase enzyme was significantly inhibited by AP extract (EC50 = 0.70 mg/mL). For the antioxidant properties, the hydrolyzed anthocyanin extract exhibited the best action against reducing power and β-carotene, compared to anthocyanins crude extract and fruits. This extract showed its stronger antibacterial activity. In conclusion, unripe AP fruit is a promising source of diverse phytochemicals that can be applied in medicinal, nutraceutical, and cosmetic applications as antioxidants and antimicrobials
Keynote talk: K.1 Sub-surface radar remote sensing for exploration and safe utilization of energy resources
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Novel microceramic structures for the design of monolithic millimeter-wave passive front-end components
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