Search results for "Frequency analysis"
showing 10 items of 113 documents
Catecholamine Response Curves of Male Hypertensives Identified by Lehmacher's Two Sample Configural Frequency Analysis
1997
A new application of LEHMACHER'S (1980) marginal homogeneity sign tests is given by analysis of bivariate response curves (or response surfaces) in two unpaired samples of hypertensive versus normotensive patients. Rationale and computations are illustrated by empirical data from sympathomedullary stress research.
Test Procedures in Configural Frequency Analysis (CFA) Controlling the Local and Multiple Level
1987
The test statistics used until now in the CFA have been developed under the assumption of the overall hypothesis of total independence. Therefore, the multiple test procedures based on these statistics are really only different tests of the overall hypothesis. If one likes to test a special cell hypothesis, one should only assume that this hypothesis is true and not the whole overall hypothesis. Such cell tests can then be used as elements of a multiple test procedure. In this paper it is shown that the usual test procedures can be very anticonservative (except of the two-dimensional, and, for some procedures, the three-dimensional case), and corrected test procedures are developed. Further…
Sequentially Rejective Test Procedures for Detecting Outlying Cells in One- and Two-Sample Multinomial Experiments
1985
For multiple testing of multinomial models in the case of one or two samples we propose using test procedures based on the principle described by MARCUS, PERITZ and GABRIEL (1976). These methods are based in each step of the sequentially rejective strategy on tests which exhaust the full α level (i.e. which are not conservative). The tests can be performed in a finite or asymptotic version.
Time, frequency and information domain analysis of short-term heart rate variability before and after focal and generalized seizures in epileptic chi…
2019
OBJECTIVE In this work we explore the potential of combining standard time and frequency domain indexes with novel information measures, to characterize pre- and post-ictal heart rate variability (HRV) in epileptic children, with the aim of differentiating focal and generalized epilepsy regarding the autonomic control mechanisms. APPROACH We analyze short-term HRV in 37 children suffering from generalized or focal epilepsy, monitored 10 s, 300 s, 600 s and 1800 s both before and after seizure episodes. Nine indexes are computed in time (mean, standard deviation of normal-to-normal intervals, root mean square of the successive differences (RMSSD)), frequency (low-to-high frequency power rati…
Effect of fatigue on the intra-cycle acceleration in front crawl swimming: a time-frequency analysis.
2007
The present study analyzes the changes in acceleration produced by swimmers before and after fatiguing effort. The subjects (n=15) performed a 25-m crawl series at maximum speed without fatigue, and a second series with fatigue. The data were registered with a synchronized system that consisted of a position transducer (1 kHz) and a video photogrametry (50 Hz). The acceleration (m s−2) was obtained by the derivative analysis of the variation of the position with time. The amplitude in the time domain was calculated with the root mean square (RMS); while the peak power (PP), the peak power frequency (PPF) and the spectrum area (SA) were calculated in the frequency domain with Fourier analysi…
Boundedness and compactness of operators related to time-frequency analysis
2018
En esta tesis, estudiamos diferentes aspectos de los operadores relacionados con el análisis tiempo-frecuencia. Cada operador lineal y continuo de la clase de Schwartz en su dual, el espacio de distribuciones temperadas, se puede escribir como un operador integral con núcleo K, o también como un operador integral de Fourier (de hecho, pseudodiferencial). Las diferentes condiciones en el núcleo o el símbolo y la fase (en el caso de los operadores integrales de Fourier) permiten extender el operador a varios espacios de funciones y distribuciones. A continuación detallamos los contenidos de la memoria. En el primer capítulo presentamos la notación, las definiciones de algunos espacios, de suc…
Multilinear Fourier multipliers related to time–frequency localization
2013
We consider multilinear multipliers associated in a natural way with localization operators. Boundedness and compactness results are obtained. In particular, we get a geometric condition on a subset A⊂R2d which guarantees that, for a fixed synthesis window ψ∈L2(Rd), the family of localization operators Lφ,ψA obtained when the analysis window φ varies on the unit ball of L2(Rd) is a relatively compact set of compact operators.
Ar dabas aizsardzību saistīto terminu lietojums uzņēmumu mājas lapu tekstos
2021
Uzņēmumi savās mājas lapās var izmantot ar dabas aizsardzību (DA) saistītus terminus, lai sabiedrība tos uztvertu noteiktā veidā. Šī bakalaura darba mērķis ir analizēt DA terminu lietojumu desmit izvēlētu uzņēmumu mājas lapu tekstos, kas ņemti no piecām dažādām nozarēm. Galvenās pētījuma metodes ir literatūras apskats, absolūtā biežuma analīze un diskursa analīze. Dati parāda, ka automašīnu ražotāji savās mājaslapās izmanto visvairāk DA terminu, savukārt apģērbu firmas izmanto vismazāk DA terminu. Lielākā daļa atrasto DA terminu ir lietvārdi. Tiek secināts, ka uzņēmumus, kas savās mājaslapās lielākoties izmanto DA terminus no „vides risinājumu” kategorijas, var uztvert kā dabai draudzīgākus…
Rotational coherence imaging and control for CN molecules through time-frequency resolved coherent anti-Stokes Raman scattering
2011
Numerical wave packet simulations are performed for studying coherent anti-Stokes Raman scattering (CARS) for CN radicals. Electronic coherence is created by femtosecond laser pulses between the X²Σ and B²Σ states. Due to the large energy separation of vibrational states, the wave packets are superpositions of rotational states only. This allows for a specially detailed inspection of the second- and third-order coherences by a two-dimensional imaging approach. We present the time-frequency domain images to illustrate the intra- and intermolecular interferences, and discuss the procedure to rationally control and experimentally detect the interferograms in solid Xe environment. peerReviewed
Time-Frequency behaviour of the a-wave of the human electroretinogram
2007
The electroretinogram is the record of the electrical response of the retina to a light stimulus. The two main components are the a-wave and the b-wave, the former is related to the early photoreceptoral activity. Aim of this paper is to acquire useful information about the time-frequency features of the human a-wave, by means of the wavelet analysis. This represents a proper approach in dealing with nonstationary signals. We have used the Mexican Hat as mother wavelet. The analysis, carried out for four representative values of the luminance, comprehends the frequency dependence of the variance and the skeleton. The results indicate a predominance of low frequency components, their time di…