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Estima y detección de series temporales mediante múltiples sensoresRamírez García, David 15 July 2011 (has links)
El problema de detección de series temporales multivariadas surge en aplicaciones tan dispares como radar, sonar, ingeniería biomédica o comunicaciones. Aunque, sin lugar a dudas, dos de las aplicaciones más importantes en la actualidad son el sensado espectral multiantena para radio cognitiva (CR) y las redes de sensores. En el primer caso, el objetivo consiste en detectar bandas del espectro vacías, para permitir la transmisión oportunista de usuarios secundarios. En el segundo, a partir de las señales adquiridas por un conjunto de sensores, se quiere determinar qué modelo ha generado dichas observaciones.
Los problemas de detección multicanal se pueden resolver de diferentes maneras en función de la información a priori disponible. En concreto, en esta Tesis se consideran los detectores basados en la estructura espacial, que es una característica especialmente interesante dado que permite desarrollar tests que necesitan muy poca información a priori sobre las señales. / The multiple-channel signal detection problem appears in many applications, such as radar and sonar, bioengineering, or communications. Nevertheless, two of the most important applications nowadays are multiantenna spectrum sensing and sensor networks. In the first case, we must detect frequency sub-bands which are not occupied, to allow the opportunistic transmission of secondary users. In the second case, the goal consists in determining, from a set of observations, the model which better explains the data.
Multiple-channel detection problems may be solved following different approaches depending on the available information. Concretely, in this Thesis, spatial-structure based detectors are considered, providing tests that use no or very limited a priori information about the signal to be detected.
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Molecularly imprinted polymer sensor systems for environmental estrogenic endocrine disrupting chemicalsNtshongontshi, Nomaphelo January 2018 (has links)
Philosophiae Doctor - PhD (Chemistry) / There is growing concern on endocrine disrupting compounds (EDCs). The presence of drugs
in water supplies was first realized in Germany in the early 1990s when environmental
scientists discovered clofibric acid. Clofibric acid has the ability to lower cholesterol in ground
water below a water treatment plant. Endocrine disrupting compounds can be defined as those
chemicals with the ability to alter daily functioning of the endocrine system in living organisms.
There are numerous molecules that are regarded or referred to as EDCs such as but not limited
to organochlorinated pesticides, industrial chemicals, plastics and plasticizers, fuels, estrogens
and many other chemicals that are found in the environment or are in widespread use. 17?-
estradiol is the principal estrogen found in mammals during reproductive years. Estriol is
produced in large quantities during pregnancy. 17?-estradiol is the strongest, estriol the
weakest. Estriol is water soluble, estrone and estradiol are not. Although estrogen is produced
in women they are also at risk of over exposure to estrogen. Pesticides are extensively used
today in agricultural settings to prevent and control pests. Various pesticides, including banned
organochlorines (OCs) and modern non-persistent pesticides, have shown the ability to disrupt
thyroid activity, disturbing the homeostasis of the thyroid system. Because these EDCs have
adverse effects on health of both human and wildlife, it is imperative to develop viable costeffective
analytical methods for the detection of these EDCs in complicated samples and at
very low concentrations. Very high selectivity towards particular compounds is a very
important property for the suitability of a detection method. This is because these compounds
mostly coexist in complex matrices which makes the detection of a specific compound very
challenging. It is paramount to develop highly sensitive and selective methods for the detection
of these estrogens and phosphoric acid-based pesticides at trace levels. / 2021-08-31
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