Search results for "Correlation"

Development of a γ-γ-perturbed angular correlation one-detector method (1-PAC) for investigation of physico-chemical properties of matter

2002

Abstract A new method of the perturbed angular γ – γ -correlation (PAC) measurements was developed using one HPGe detector only (1-PAC). For quantifying the perturbation factor, the ratio R γ 1 + γ 2 of the summing peak composed of two cascade γ -rays (the perturbation-affected parameter) to the summing peak composed of one γ -ray and one X-ray (the perturbation non-affected parameter) was used. This method was demonstrated for the radionuclides 111 In and 111m Cd, identifying the chemical status of the radionuclides in aqueous solutions.

CORRELATIONS AMONG FORWARD RETURNS IN THE NORDIC ELECTRICITY MARKET

2009

I analyze empirical correlations of electricity forward returns from the perspective of a random field model that specifies the correlations in terms of the temporal separation between forward maturities. It turns out that temporal separation cannot fully account for the empirical forward return correlations. Specifically, the relation between correlations and temporal separation does not seem to be invariant across segments of the electricity forward market or trading periods.

Growth, percolation, and correlations in disordered fiber networks

1997

This paper studies growth, percolation, and correlations in disordered fiber networks. We start by introducing a 2D continuum deposition model with effective fiber-fiber interactions represented by a parameter $p$ which controls the degree of clustering. For $p=1$, the deposited network is uniformly random, while for $p=0$ only a single connected cluster can grow. For $p=0$, we first derive the growth law for the average size of the cluster as well as a formula for its mass density profile. For $p>0$, we carry out extensive simulations on fibers, and also needles and disks to study the dependence of the percolation threshold on $p$. We also derive a mean-field theory for the threshold ne…

Reorientational dynamics in simple supercooled liquids

1998

Abstract The geometry of the reorientational dynamics in the van der Waals liquid, toluene, and the hydrogen bond network, glycerol, are compared. Both systems have contributions from small angle fluctuations. In glycerol the fraction of these small angle fluctuations is much larger than in toluene, due to the stronger anisotropic interactions in the former substance. The average reorientational angle in both systems is similar and on the order of 10 ∘ . In addition we analyze the stretching of the rotational correlation functions of rank one and two. In both cases we find that the second rank correlation function has a more pronounced stretching than the corresponding first rank correlatio…

A Lotka-type model for oscillations in surface reactions

1997

In this paper we introduce a reaction model on a lattice which leads to oscillations. The model consists of two monomolecular and one bimolecular reaction step and is related to the Lotka model. Despite the simple evolution rules, the model shows a complex behaviour (i.e. the appearance of oscillations). This offers us the opportunity to test different types of stochastic approximations and compare them with the results of a Monte Carlo simulation. The simulation is performed on a large lattice (L = 1024) in order to take long-range correlations into account. Comparing the results of this simulation with the stochastic approaches shows that only advanced numerical approximations are able to…

Indirect evaluation of pit and fissure sealants: a 3D-based method validation

2019

Background The aim of the present study was to compare indirect methods to assess the clinical performance of pit and fissure sealants and validate the use of 3D scanners. Material and Methods Sample consisted of 58 plaster models of upper and lower first permanent molars, sealed with resin sealants, as well as photographs obtained during the 18-month follow-up. Pre-established criteria were applied to categorize the sealant presence/absence and marginal integrity. Two calibrated examiners performed the evaluations, independently, using Scanning Electron Microscopy (SEM; gold-standard), Photography, 3D (CEREC In Lab) and Stereomicroscope analysis. Results The intra-examiner Spearman correla…

CHILDREN’S DEPRESSION RATING SCALE-REVISED (CDRS-R) – DEVELOPMENT OF THE LATVIAN VERSION AND PSYCHOMETRIC PROPERTIES IN A CLINICAL AND NON-CLINICAL S…

2019

Depression is one of the most widespread mental disorders worldwide. Adolescence is a vulnerable period for developing depression. It is associated with a number of challenges in biological, psychological and social areas. Valid and reliable measurement instruments are required for assessment of symptoms of depression in clinical samples of adolescents in Latvia. Children's Depression Rating Scale Revised (CDRS-R, Posnanski & Mokros, 1996) is a semi-structured, clinician-rated interview for assessment of depression in children and adolescents. While the CDRS-R is the most widely used rating scale for research and clinicians’ practical use worldwide, there's no validated version in Latvi…

Why the Universe is not a fractal

1990

L'etude du survey des redshifts CfA montre que la distribution des galaxies dans l'Univers obeit a une loi d'echelle sur des echelles de longueur inferieures a environ 5 h −1 Mpc. Cependant, l'Univers n'est pas bien represente par une fractale homogene sur ces echelles. La dependance de la longueur de correlation avec la profondeur des echantillons et la luminosite est etudiee. Une methode basee sur l'arbre maximal est presentee pour determiner la dimension de Hausdorff d'une distribution de points. Cette technique est ensuite appliquee au catalogue CfA

Wavelet correlation filter for wide-angle seismic data

2002

A new filtering technique for single-fold wide-angle reflection/refraction seismic data is presented. The technique is based on the wavelet decomposition of a set of adjacent traces followed by coherence analysis. The filtering procedure consists of three steps. In the first, a wavelet decomposition of traces into different detail levels is performed. In the second, the coherence attributes for each level are evaluated by calculating cross-correlation functions of detail portions contained in a space–time moving window. Finally, the filtered traces are obtained as a weighted reconstruction of the trace details. Each weight is obtained from the coherence-attributes distribution estimated in …

Metodi automatici di analisi e caratterizzazione di esami radiologici del massiccio facciale.

L'obiettivo di questo lavoro è lo sviluppo di algoritmi e procedure di analisi di referti radiografici digitali di tipo CBCT delle strutture della mandibola e dell’apparato dentario. In particolare, mediante un’opportuna campagna di sperimentazione, in collaborazione con i reparti di radiologia ed odontoiatria del Policlinico di Palermo, è stata realizzata un procedura in grado di: • eliminare i problemi di sovrapponibilità dei referti tridimensionali effettuati in tempi successivi; • identificare lo spazio parodontale su indagini CBCT per la valutazione dei possibili difetti nello stesso e prevedere l’insorgenza di parodontiti. • individuare gli elementi di maggiore interesse medico caratt…