Search results for "variance"
showing 10 items of 2030 documents
Temporal-range estimation of multiple objects: evidence for an early bottleneck.
2011
When making parallel time-to-contact (TTC) estimates of two approaching objects, the two respective TTC estimates interfere with one another in an asymmetric fashion. The TTC of the later-arriving object is systematically overestimated, while the estimated TTC for the first-arriving object is as accurate as in a condition presenting only a single object. This asymmetric interference points to a processing bottleneck that could be due to early (e.g., during the estimation of the TTC from the optic flow) or late (e.g., during the timing of the response or the motor execution) constraints in the TTC estimation process. We used a Sperling-like prediction-motion task to differentiate between the…
Frequency Stability Measurement of Cryogenic Sapphire Oscillators with a Multichannel Tracking DDS and the Two-Sample Covariance
2018
This article shows the first measurement of three 100 MHz signals exhibiting fluctuations from 2E-16 to parts in 1E-15 for integration time tau between 1 s and 1 day. Such stable signals are provided by three Cryogenic Sapphire Oscillators (CSOs) operating at about 10 GHz, also delivering the 100 MHz output via a dedicated synthesizer. The measurement is made possible by a 6-channel Tracking DDS (TDDS) and the two-sample covariance tool, used to estimate the Allan variance. The use of two TDDS channels per CSO enables high rejection of the instrument background noise. The covariance outperforms the Three-Cornered Hat (TCH) method in that the background converges to zero "out of the box," wi…
Comparaison de différents plans de sondage et construction de bandes de confiance pour l'estimation de la moyenne de données fonctionnelles : une ill…
2012
Accepté pour publication dans Survey Methodology/Techniques d'Enquêtes.; Lorsque les variables étudiées sont fonctionnelles et que les capacités de stockage sont limitées ou que les coûts de transmission sont élevés, les sondages, qui permettent de sélectionner une partie des observations de la population, sont des alternatives intéressantes aux techniques de compression du signal. Notre étude est motivée, dans ce contexte fonctionnel, par l'estimation de la courbe de charge électrique moyenne sur une période d'une semaine. Nous comparons différentes stratégies d'estimation permettant de prendre en compte une information auxiliaire telle que la consommation totale de la période précédente. …
Bienestar Subjetivo de los Adolescentes: Un Estudio Comparativo entre Argentina y Brasil
2012
ResumenEl objetivo del presente estudio es conocer y comparar los niveles de bienestar subjetivo de adolescentes argentinos y brasileños. La muestra está compuesta por 640 adolescentes de ambos sexos con edades entre los 12 y 16 años, siendo el 46.3% argentinos y el 53.7% brasileños. Se han utilizado tres escalas: el Personal Wellbeing Index (PWI), la Satisfaction with Life Scale (SWLS) y la Brief Multidimensional Students’ Life Satisfaction Scale (BMSLSS). El PWI y la BMSLSS mostraron puntuaciones más altas en los adolescentes argentinos (MPWI=82.42y MBMSLSS=41.19) que en los brasileños (MPWI=80.88y MBMSLSS=40.09), y mientras que la SWLS mostró resultados semejantes (MSWLS-Arg=31.50y MSWLS…
A more efficient second order blind identification method for separation of uncorrelated stationary time series
2016
The classical second order source separation methods use approximate joint diagonalization of autocovariance matrices with several lags to estimate the unmixing matrix. Based on recent asymptotic results, we propose a novel unmixing matrix estimator which selects the best lag set from a finite set of candidate sets specified by the user. The theory is illustrated by a simulation study. peerReviewed
Bone marrow-derived progenitors are greatly reduced in patients with severe COPD and low-BMI.
2009
Chronic obstructive pulmonary disease (COPD) patients have reduced circulating hemopoietic progenitors. We hypothesized that severity of COPD parallels the decrease in progenitors and that the reduction in body mass index (BMI) could be associated with more severe bone marrow dysfunction. We studied 39 patients with moderate to very severe COPD (18 with low-BMI and 21 with normal-BMI) and 12 controls. Disease severity was associated to a greater reduction in circulating progenitors. Proangiogenetic and inflammatory markers correlated with disease severity parameters. Compared to normal-BMI patients, low-BMI patients showed: greater reduction in circulating progenitors; higher VEGF-A, VEGF-C…
Factor Structure and Measurement Invariance of the Spanish Burnout Inventory Among Professionals Across 17 Countries and Regions
2022
AbstractStudies on the prevalence of burnout in professionals in service organizations who work in direct contact with the clients or users of the organization have concluded that burnout is a serious health disorder that has increased due to the COVID-19 pandemic. A significant advantage of the Spanish Burnout Inventory (SBI) over other instruments is that it provides a broader conceptualization of burnout by including feelings of guilt as a dimension of burnout to explain its development. However, the measurement invariance of the SBI across countries has not been investigated. The purpose of this study was to test the measurement invariance of the SBI among professionals across 17 countr…
High frequency rTMS over the left parietal lobule increases non-word reading accuracy
2012
Increasing evidence in the literature supports the usefulness of Transcranial Magnetic Stimulation (TMS) in studying reading processes. Two brain regions are primarily involved in phonological decoding: the left superior temporal gyrus (STG), which is associated with the auditory representation of spoken words, and the left inferior parietal lobe (IPL), which operates in phonological computation. This study aimed to clarify the specific contribution of IPL and STG to reading aloud and to evaluate the possibility of modulating healthy participants' task performance using high frequency repetitive TMS (hf-rTMS). The main finding is that hf-rTMS over the left IPL improves non-word reading accu…
Short-time non-work-related computing and creative performance
2014
It has been argued that non-work-related computing (NWRC) takes time away from work and, hence, decreases work productivity. On the other hand, it has also been claimed that short-time non-work-related computing (STNWRC) (a maximum of 15 minutes), has a positive impact on work productivity, including relief from boredom, higher creativity, and the underlying recovery mechanisms. To examine the impact of STNWRC on creative performance, we draw on Fredrickson's broaden-and-build theory, the concept of recovery with mental well-being and low cognitive effort. A 2 × 2 factorial experiment with 40 subjects was conducted. The results indicate that STNWRC has a positive effect on creative performa…
Comportamiento de las correlaciones producto-momento y tetracórica-policórica en escalas ordinales: un estudio de simulación
2017
El análisis estadístico multivariante de escalas de respuesta tipo Likert, dado su empleo generalizado, resulta un tema controvertido en la comunidad científica, principalmente desde la especificación del problema de la medida. Este trabajo tiene como objeto estudiar cómo afectan diversas condiciones de estas escalas ordinales al cálculo de los coeficientes de correlación producto-momento y tetracórico-policórico. Para ello, se aplica un estudio de simulación en el que se generaron 90 bases de datos con 10 ítems cada una, controlando las siguientes variables: número de categorías de respuesta, distribución simétrica o asimétrica de los datos, tamaño de la muestra y nivel de relación entre l…