Search results for "ratio [mass spectrum]"
showing 10 items of 70 documents
Testing Equality of Multiple Power Spectral Density Matrices
2018
This paper studies the existence of optimal invariant detectors for determining whether P multivariate processes have the same power spectral density. This problem finds application in multiple fields, including physical layer security and cognitive radio. For Gaussian observations, we prove that the optimal invariant detector, i.e., the uniformly most powerful invariant test, does not exist. Additionally, we consider the challenging case of close hypotheses, where we study the existence of the locally most powerful invariant test (LMPIT). The LMPIT is obtained in the closed form only for univariate signals. In the multivariate case, it is shown that the LMPIT does not exist. However, the c…
Locally optimal invariant detector for testing equality of two power spectral densities
2018
This work addresses the problem of determining whether two multivariate random time series have the same power spectral density (PSD), which has applications, for instance, in physical-layer security and cognitive radio. Remarkably, existing detectors for this problem do not usually provide any kind of optimality. Thus, we study here the existence under the Gaussian assumption of optimal invariant detectors for this problem, proving that the uniformly most powerful invariant test (UMPIT) does not exist. Thus, focusing on close hypotheses, we show that the locally most powerful invariant test (LMPIT) only exists for univariate time series. In the multivariate case, we prove that the LMPIT do…
THE INTERPRETAZION OF DIAGNOSTIC TEST: A PRIMER OF ALLERGIST. PRICIPLES OF EVIDENCE BASED MEDICINE TO OBTAIN A PRECISE DIAGNOSIS
2008
El viaje desde los cuestionarios Likert a los cuestionarios de elección forzosa: evidencia de la invarianza de los parámetros de los ítems
2019
Multidimensional forced-choice questionnaires are widely regarded in the personnel selection literature for their ability to control response biases. Recently developed IRT models usually rely on the assumption that item parameters remain invariant when they are paired in forced-choice blocks, without giving it much consideration. This study aims to test this assumption empirically on the MUPP-2PL model, comparing the parameter estimates of the forced-choice format to their graded-scale equivalent on a Big Five personality instrument. The assumption was found to hold reasonably well, especially for the discrimination parameters. In the cases in which it was violated, we briefly discuss the …
Dilepton photoproduction on a deuteron target
2019
We investigate the sensitivity of the cross section for lepton pair production off a deuteron target, $\gamma d \to l^+ l^- d$, to the deuteron charge radius. We show that for small momentum transfers the Bethe-Heitler process dominates, and that it is sensitive to the charge radius such that a cross section ratio measurement of about $0.1 \%$ relative accuracy could give a deuteron charge radius more accurate that the current electron scattering value and sufficiently accurate to distinguish between the electronic and muonic atomic values.
Distribution of Heavy Metals in Marine Sediments of Palermo Gulf (Sicily, Italy)
2008
Concentrations of Cr, Cu, Hg, Pb and Zn have been measured, by atomic absorption spectrophotometry, in the fine fraction (<63 μm) of surface sediments collected in 30 sites in the Palermo Gulf (Sicily, Italy) in order to assess the levels and the spatial distribution of these elements. Enrichment factors calculated with respect to clean areas have been considered to discriminate between levels due to background or to pollution contributions. The sampling stations, which form a grid inside these areas, are characterized by geographic proximity and by the presence of pollution sources. Ratio matching technique along with hierarchical clustering, minimum spanning tree and principal component a…
Rutas cognitivas de futuros maestros ante una situación comparativa de razones desiguales
2019
En esta investigación se analizan las rutas cognitivas que subyacen a las resoluciones de un grupo de futuros maestros ante una tarea de comparación de razones desiguales en el contexto de las ofertas comerciales. La revisión de la literatura y el análisis en profundidad de las componentes críticas de la tarea nos han permitido definir las dimensiones de análisis de las resoluciones. A partir de ellas hemos realizado un análisis cualitativo de corte interpretativo del cual se desprende que los participantes poseen un escaso desarrollo del pensamiento relativo. Un número importante de ellos presenta dificultades con la comparación de las cantidades relativas desiguales cuando estas se les pr…
Bot or not? a case study on bot recognition from web session logs
2018
This work reports on a study of web usage logs to verify whether it is possible to achieve good recognition rates in the task of distinguishing between human users and automated bots using computational intelligence techniques. Two problem statements are given, offline (for completed sessions) and on-line (for sequences of individual HTTP requests). The former is solved with several standard computational intelligence tools. For the second, a learning version of Wald’s sequential probability ratio test is used.
Accademia alla rovescia: lezioni di diritto per dirottare il verso del sapere
2022
In questo scritto parlerò di alcuni esperimenti educativi che ho condotto secondo la metodologia didattica che ho chiamato "accademia alla rovescia". Questo metodo si ispira all'educazione clinico-legale, ma ne mette in discussione alcuni presupposti, traendo spunto dalle teorie critiche del diritto e dall'approccio pedagogico di Paulo Freire, Danilo Dolci e dei Maestri di Strada. L'educazione clinico-legale si basa sull'apprendimento attraverso il fare e sull'esposizione dei discenti al diritto vivente in contesti autentici. Questi programmi, tuttavia, presuppongono che l'accademia detenga un primato, se non un monopolio epistemico. Il "metodo dell'accademia alla rovescia" parte da una "mi…
Computerized Interpretation of H P L C Chromatogramms by Means of Absorbance Ratio Method and Derivative Spectroscopy
1985
As in other chromatographic processes it is the aim of high pressure liquid chromatography (HPLC) to identify the components of a mixture, whereby there may be some information on the class of substances in question. The analytical procedure can shortly be desribed as follows. The mixture is injected in a mobile phase (solvent) and passes a column where the separation takes place. The separated components leave the column at different retention times. A following detection device generates a signal as a function of concentration (chromatographic peak). Usually the components are identified by relating retention times of external standards to the times of occurence of chromatographic peaks. …