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1

Analysis of time series for accuracy estimation of GPS kinematic methods

100%
Barta L.
Acta Scientiarum Polonorum. Geodesia et Descriptio Terrarum
|
2005
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tom 04
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nr 2
2

Deterministic brain oscillations in the magnetoencephalogram

100%
Kowalik Z. J., Witte O. W.
Acta Neurobiologiae Experimentalis
|
2000
|
tom 60
|
nr 2
Determinism is a special property of some systems and is defined by its state-space behavior in which the trajectories in time never intersect. Whether or not determinism exists in brain activities is a question that may be resolved by analysis of the dynamical properties of the electroencephalogram (EEG) or magnetoencephalogram (MEG). We will show that even though there are strong nonstationarities in most brain behaviors, small epochs of deterministic dynamics can still be observed. We will also show that the local Lyapunov exponents are measures that can demonstrate smooth transitions into these deterministic states.
3
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Prediction of airborne Alnus pollen concentration by using ARIMA models

100%
Rodriguez-Rajo F. J., Valencia-Barrera R. M., Vega-Maray A. M., Suarez F. J., Fernandez-Gonzales D., Jato V.
Annals of Agricultural and Environmental Medicine
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2006
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tom 13
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nr 1
To take preventative measures to protect allergic people from the severity of the pollen season, one of aerobiology’s objectives is to develop statistical models enabling the short- and long-term prediction of atmospheric pollen concentrations. During recent years some attempts have been made to apply Time Series analysis, frequently used in biomedical studies and atmospheric contamination to pollen series. The aim of this study is to understand the behaviour of atmospheric alder pollen concentrations in northwest Spain in order to develop predictive models of pollen concentrations by using Time Series analysis. The prediction line proposed for Oviedo and Ponferrada are similar (Arima 2,0,1) while in Vigo a more accurate model founded by Arima (3,0,1) and in León (1,0,1) was used. The results suggest that Ponferrada and Oviedo are the cities in northwest Spain where Alnus pollen allergic individuals should to take preventive measures to protect themselves from the severity of the pollen season. Alnus pollen values higher than 30 grains/m3, a quantity considered sufficient to trigger severe allergy symptoms of other trees of the Betulaceae family, could be reached during 25 days in some years. The predicted lines conformed with the observed values overall in the case of León and Ponferrada. Time Series regression models are especially suitable in allergology for evaluating short-term effects of time-varying pollen appearance in the atmosphere.
4

Changes in species composition of an abandoned limestone grassland in relation to climatic conditions

84%
Dzwonko Z., Loster S.
Polish Journal of Ecology
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2011
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tom 59
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nr 4
After abandonment many species-rich limestone grasslands have been overgrown by tall grasses and forbs, and often by shrubs and trees. As a result, communities with many regionally rare and endangered species are vanishing. We examined to what extend changes in the cover of sociological species groups and plant functional types in an unmanaged grassland depend on fluctuations in climatic conditions. Vegetation data from permanent plots in an abandoned grassland in southern Poland collected over 12 years were used. Relations between weather variables, time, and the cover of species groups were analysed using multiple linear regression and canonical correspondence analysis (CCA). The climatic data included mean temperatures and precipitation sums for each month from January to December (for the current year from January to July), and for 2, 3 and 4 consecutive months, with time lags of 0, 1, 2 and 3 years. It was found that both inter-annual fluctuation of climatic conditions and successional processes considerably influenced species composition of the study grassland. The fluctuations in precipitation and temperature explained from 0.8% to 27.1% of the variation in the cover of various sociological groups. The greatest effect on the cover dynamics of all species and majority of sociological groups had precipitation in spring and early summer in the current year. Most of species groups were affected also by temperature in spring and/or summer in the previous years, but its effect as lower than precipitation. The obtained results suggest that climatic conditions have also a significant impact on the rate of changes in abandoned limestone grasslands. Higher precipitation in spring and summer favour growth and spread of tall meadow grasses and forbs, accelerating changes from less compact communities dominated by smaller xerothermic species to more compact vegetation with a closed structure. In consequence the role of xerothermic calcareous species decreases and many of them may locally extinct within decades.
5

Statistical characteristics of riverflow variability in the Odra River basin, Southwestern Poland

84%
Sen A. K., Niedzielski T.
Polish Journal of Environmental Studies
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2010
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tom 19
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nr 2
387-396
We have analyzed the statistical characteristics of riverflow variability in the Odra River basin in southwestern Poland. In particular, we have examined the daily discharge time series recorded at 15 sites from November 1971 to October 2006. The skewness and kurtosis values of the time series are computed to determine if the empirical distribution of the data follows a normal distribution. The empirical distributions of all the time series are found to be non-Gaussian. The kurtosis values are interpreted in terms of intermittency, and together with skewness they are found to be significantly correlated with morphometric properties of the subbasins. In addition, several theoretical probability distributions are fitted to the riverflow data at each site. Among them, the 5-parameter Wakeby distribution is found to provide the best overall fit. Subsequently, the Wakeby distribution is used to calculate the return periods. Finally, the trend and stationarity around a trend of the various riverflow time series are assessed using the Cox-Stuart and Phillips-Perron (Dickey-Fuller) statistical tests. A decreasing trend is found in the daily discharge data at all sites, but there is no evidence of nonstationarity around the trend over the time span of the data record. A good understanding of the statistical characteristics of riverflow fluctuations in the Odra River basin is essential for water resources planning and management, including flood control and prediction in SW Poland.
6

Zastosowanie sztucznych sieci neuronowych do predykcji szeregow czasowych stanow wod i przeplywow w rzece

84%
Krzanowski S., Walega A.
Acta Scientiarum Polonorum. Formatio Circumiectus
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2007
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tom 06
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nr 4
59-73
7

Nonlinearity in human resting, eyes-closed EEG: an in-depth case study

84%
Pritchard W. S., Stam C. J.
Acta Neurobiologiae Experimentalis
|
2000
|
tom 60
|
nr 1
The question of nonlinearity in the human electroencephalogram (EEG) is important, since linear methods of EEG analysis are more well-developed and computationally faster than nonlinear methods. Furthermore, the presence or absence of nonlinearity has important theoretical implications for understanding the nature of the brain's oscillatory activity. Using a linear summary measure as a control, we report a failure to reject the null hypothesis of a (largely) stationary linear-Gaussian process for normal, resting, eyes-closed EEG from a single participant. We found significant evidence of nonlinearity at two occipital sites (01 and 02) where the 8-12.5 Hz alpha rhythm was prominent. However, this element of nonlinear structure appeared trivial, as (1) we found no evidence of time irreversibility at these loci, and (2) best-fitting linear models accounted on-average for over 94% of the variance in the data with nonlinear modeling doing no better. Half of the remaining variance could be accounted for by nonstationarity. While our findings technically apply only to the one individual tested, his EEG was typical of those seen under the conditions that we employed.
8

Odkrywanie liniowych trendow w wartosciach wzglednych kursow akcji z zastosowaniem metody wnioskowania opartej na bazie przypadkow

67%
Kluza A.
Acta Scientiarum Polonorum. Oeconomia
|
2003
|
tom 02
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nr 2
49-57
9

Wykrywanie sygnałów skokowych w szeregach czasowych zmian współrzędnych GPS

67%
Kontny B.
Acta Scientiarum Polonorum. Geodesia et Descriptio Terrarum
|
2011
|
tom 10
|
nr 3
W pracy zaprezentowano zmodyfikowaną metodę różnicową wykrywania zmian skokowych w dyskretnych sygnałach pomiarowych (np. szeregach czasowych zmian współrzędnych punktów GPS) w obecności zakłóceń sygnału przypadkowym szumem pomiarowym (white noise) oraz obserwacji odstających (outliers). Metoda polega na zastąpieniu średniej ruchomej w klasycznym algorytmie metody różnicowej poprzez medianę, przez co w znacznym stopniu ogranicza się wpływ obserwacji odstających. Metodę przetestowano na symulowanych sygnałach pomiarowych. Jak wykazały obliczenia testowe, metoda jest skuteczna nawet dla stosunkowo wąskiego okna po stronie obserwacji następujących po testowanej i-tej epoce pomiarowej. Pozwala to na stosunkowo szybkie alarmowanie o zaistnieniu zmiany skokowej o amplitudzie nawet na granicy szumu po- miarowego (3 sigma). Metoda może znaleźć zastosowanie w automatycznych systemach kontrolno-pomiarowych do monitorowania przemieszczeń obiektów inżynierskich wykorzystujących satelitarny system GPS, w szczególności do monitorowania deformacji obiektów hydrotechnicznych, przemysłowych i górniczych.
10

Jakość prognoz budowanych w oparciu o szeregi czasowe cen produktów rolnych

67%
Gedek S.
Zeszyty Problemowe Postępów Nauk Rolniczych
|
2009
|
tom 542
|
nr 2
Trafność prognoz cen produktów rolnych sporządzanych w oparciu o szeregi czasowe cen produktów rolnych oceniana była przy pomocy średniego bezwzględnego błędu procentowego (MAPE). Analiza MAPE wykazała większą dokładność prognoz krótkookresowych sporządzanych przy pomocy wyrównania wykładniczego. Z kolei lepsza była jakość prognoz długookresowych sporządzanych na zasadzie ekstrapolacji struktury szeregu czasowego. Generalnie jednak trafność prognoz mierzona MAPE była w dużym stopniu zależna od momentu sporządzania prognozy.
11

Long-term monitoring data reveal pH dynamics, trends and variability in the Western Gulf of Finland

67%
Brutemark A., Engstrom-Ost J., Vehmaa A.
Oceanological and Hydrobiological Studies
|
2011
|
tom 40
|
nr 3
12
Artykuł dostępny w postaci pełnego tekstu - kliknij by otworzyć plik
Content available

Comparative analysis of methods for hourly electricity demand forecasting in the absence of data - a case study

67%
Zawadzki J.
Economic and Regional Studies
|
2023
|
tom 16
|
nr 1
13
Artykuł dostępny w postaci pełnego tekstu - kliknij by otworzyć plik
Content available

Changes in plant species composition in abandoned and restored limestone grasslands - the effects of tree and shrub cutting

67%
Dzwonko Z., Loster S.
Acta Societatis Botanicorum Poloniae
|
2008
|
tom 77
|
nr 1
Abandoned semi-natural limestone grasslands are often overgrown by shrubs and trees. Little is know if and to what extant xerothermic limestone grasslands can be restored by tree cutting. This was tested in a 12-year experiment after the clearing of a 35-year-old secondary pine wood developed on unmanaged grassland in the close proximity of not overgrown old grassland. After 12 years, there were no significant differences in the number of field layer species on the plots in the old and restored grasslands. But over this period the number of meadow species increased in all sites, while the number of xerothermic calcareous species increased significantly only in the old grassland plots. The developing shrub layer negatively influenced the number of nitrophilous and ruderal species in grasslands restored in the former close and open woods, and the number of all species, including the number of non-tufted perennials and perennials with vegetative spread, in the former open wood. The number of meadow species increased in years with higher precipitation in late spring and early summer. The obtained results suggest that in overgrowing grasslands shrubs and trees should be cut every few years, before their covers increase to about 30%. However, this treatment alone will not stop the changes to communities with dominance of tall and vegetatively spreading grasses and forbs. Cutting trees and shrubs in sites where most grassland species have already vanished, without additional managements supporting their dispersal, seedling recruitment and development, is not sufficient to restore limestone grasslands rich in xerothermic species.
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