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Wyszukujesz frazę "correlation" wg kryterium: Temat


Tytuł:
Digital volume correlation in an environment with intensive salt-and-pepper noise and strong monotonic nonlinear distortion of light intensity
Autorzy:
Tu, P.
Bai, Y.
Xu, W.
Dong, B.
Ye, S.
Yang, Q.
Zhou, Y.
Powiązania:
https://bibliotekanauki.pl/articles/173712.pdf
Data publikacji:
2017
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
digital volume correlation
correlation function
salt-and-pepper noise
nonlinear effects
Opis:
Digital volume correlation is an image-based technique for internal 3D displacement and strain fields measurement or analysis widely used in the field of experimental mechanics. A widely used correlation function (criterion) of digital volume correlation is Pearson correlation function, which suffers from the problem of the acquired data being contaminated by salt-and-pepper noise and monotonic nonlinear distortion of the light intensity. In this work, a 3D correlation function called the Spearman correlation function is used to deal with those interferences. A numerical experiment shows that the performance of Spearman correlation function using integer-pixel registration in an environment with 10% salt-and-pepper noise is better than that of Spearman and Pearson correlation functions using sub-pixel registration in an environment with 1% salt-and-pepper noise. As the light intensity distortion is significant, the error of Pearson correlation function is considerable; meanwhile, the error of Spearman correlation function is small. In conclusion, Spearman correlation function is, in particular, practical and useful in digital volume correlation.
Źródło:
Optica Applicata; 2017, 47, 2; 209-223
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Advances in antithetic time series analysis: separating fact from artifact
Autorzy:
Ridley, D.
Powiązania:
https://bibliotekanauki.pl/articles/406377.pdf
Data publikacji:
2016
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
combining
antithetic
time series
bias correction
serial correlation
Opis:
The problem of biased time series mathematical model parameter estimates is well known to be insurmountable. When used to predict future values by extrapolation, even a de minimis bias will eventually grow into a large bias, with misleading results. This paper elucidates how combining antithetic time series solves this baffling problem of bias in the fitted and forecast values by dynamic bias cancellation. Instead of growing to infinity, the average error can converge to a constant.
Źródło:
Operations Research and Decisions; 2016, 26, 3; 57-68
2081-8858
2391-6060
Pojawia się w:
Operations Research and Decisions
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Contagion between selected European indexes during the Covid-19 pandemic
Autorzy:
Gurgul, Henryk
Syrek, Robert
Powiązania:
https://bibliotekanauki.pl/articles/2204099.pdf
Data publikacji:
2023
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
European indexes
pandemic Covid-19
dynamic conditional correlation
contagion
Opis:
The main aim of this study is to examine dynamic dependence and proof of contagion during the Covid-2019 pandemic. The empirical data are daily prices from six European indexes. The FTSE, DAX and CAC indexes represent the largest and most developed stock markets in Europe, while the Austrian ATX index represents small developed markets. The WIG and BUX indexes represent emerging European markets. This empirical study, based on the Dynamic Conditional Correlation model, which is applied to different pairs of indexes, aims to convince the reader of the increase in the correlation between the time of the pandemic (after 30 December 2019) and the period before the beginning of the pandemic. For all pairs, the mean value of the conditional correlations in the pre-Covid period was statistically below the values in the Covid period. The results indicate contagion in Europe after the outbreak of the Covid-2019 pandemic.
Źródło:
Operations Research and Decisions; 2023, 33, 1; 47--59
2081-8858
2391-6060
Pojawia się w:
Operations Research and Decisions
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Particle shape effect on macroscopic behaviour of underground structures: numerical and experimental study
Autorzy:
Szarf, K.
Combe, G.
Villard, P.
Powiązania:
https://bibliotekanauki.pl/articles/178734.pdf
Data publikacji:
2014
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
discrete element method
particle shape
underground pipe
digital image correlation
Opis:
The mechanical performance of underground flexible structures such as buried pipes or culverts made of plastics depend not only on the properties of the structure, but also on the material surrounding it. Flexible drains can deflect by 30% with the joints staying tight, or even invert. Large deformations of the structure are difficult to model in the framework of Finite Element Method, but straightforward in Discrete Element Methods. Moreover, Discrete Element approach is able to provide information about the grain–grain and grain–structure interactions at the microscale. This paper presents numerical and experimental investigations of flexible buried pipe behaviour with focus placed on load transfer above the buried structure. Numerical modeling was able to reproduce the experimental results. Load repartition was observed, being affected by a number of factors such as particle shape, pipe friction and pipe stiffness.
Źródło:
Studia Geotechnica et Mechanica; 2014, 36, 3; 67-74
0137-6365
2083-831X
Pojawia się w:
Studia Geotechnica et Mechanica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Investigation into spatial stochastization of an optical field scattered by nematic
Autorzy:
Maksimyak, P.
Gavrylyak, M
Powiązania:
https://bibliotekanauki.pl/articles/174140.pdf
Data publikacji:
2014
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
liquid crystal
Williams’s domains
Lyapunov’s maximal index
correlation exponent
Opis:
This paper presents the investigation results of spatial chaotization of an optical field scattered by liquid crystals during phase transition liquid–liquid crystal under an electric field. Two stochastic parameters of the field, namely, Lyapunov’s maximal index and correlation exponent were chosen for this study. It has been established that maximum variances of phase inhomogeneities of the nematic liquid crystal correspond to maximum fluctuations of an order parameter under the temperature of phase transition liquid–liquid crystal. It has been found that the analysis of the radiation field scattered during the phase transition process in the liquid–liquid crystal allows to accurately determine the phase transition temperature and voltage of forming Williams’s domains.
Źródło:
Optica Applicata; 2014, 44, 4; 555-566
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Non-uniform illumination correction based on the retinex theory in digital image correlation measurement method
Autorzy:
Gu, G.
She, B.
Xu, G.
Xu, X.
Powiązania:
https://bibliotekanauki.pl/articles/173506.pdf
Data publikacji:
2017
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
digital image correlation (DIC)
non-uniform illumination correction
retinex theory
deformation measurement
Opis:
Digital image correlation is a well-known optical measurement method for full-field deformation and strain measurements. The quality of speckle images used in digital image correlation calculation can directly affect the measurement accuracy of digital image correlation. In most practical measurement circumstances, a uniform illumination environment is usually required to illuminate the detected object in order to capture speckle images upon different deformed states with uniform background intensity. However, the tested object becomes so large that the adopted light source cannot cover all the interested area with uniform illumination, and the speckle images acquired by CCD camera may have non-uniform background intensity distributions. In this paper, the influence of non-uniform illumination is first analyzed in detail by means of a comparison of experimental results of digital image correlation using speckle patterns with both uniform and non-uniform intensity distributions. Then, a new correctional method based on the combination of the basic retinex theory and the illumination formulae of a point light source is proposed. Finally, a real experiment with non-uniform illumination is implemented to verify the effectiveness of this method.
Źródło:
Optica Applicata; 2017, 47, 2; 199-208
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Contagion effects on capital and forex markets around GFC and COVID-19 crises : a comparative study
Autorzy:
Brania, Krzysztof
Gurgul, Henryk
Powiązania:
https://bibliotekanauki.pl/articles/2099837.pdf
Data publikacji:
2021
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
contagion
correlation
exchange rate
return
volatility
GFC in 2007–2009
COVID-19
Opis:
The spread of crises across the financial and capital markets of different countries has been studied. The standard method of contagion detection is based on the evolution of the correlation matrix for the example of exchange rates or returns, usually after removing univariate dynamics with the GARCH model. It is a common observation that crises that have occurred in one financial market are usually transmitted to other financial markets/countries simultaneously and that they are visible in different financial variables such as returns and volatility which determine probability distribution. The changes in distributions can be detected through changes in the descriptive statistics of, e.g., returns characterised by expected value, variance, skewness, kurtosis, and other statistics. They determine the shape of the distribution function of returns. These descriptive statistics display dynamics over time. Moreover, they can interreact within the given financial or capital market and among markets. We use the FX currency cluster represented by some of the major currencies and currencies of the Višegrad group. In analysing capital markets in terms of equity indexes, we chose developed markets, such as DAX 30, AEX 25, CAC 40, EURSTOXX 50, FTSE 100, ASX 200, SPX 500, NASDAQ 100, and RUSSEL 2000. We aim to check the changes in descriptive statistics, matrices of correlation concerning exchange rates, returns and volatility based on the data listed above, surrounding two crises: the global financial crisis (GFC) in 2007–2009 and Covid 2019.
Źródło:
Operations Research and Decisions; 2021, 31, 2; 59--92
2081-8858
2391-6060
Pojawia się w:
Operations Research and Decisions
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Implications of market frictions: serial correlations in indexes on the emerging stock markets in Central and Eastern Europe
Autorzy:
Olbrys, J.
Majewska, E.
Powiązania:
https://bibliotekanauki.pl/articles/406526.pdf
Data publikacji:
2014
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
CEE stock markets
market frictions
nonsynchronous trading
index serial correlation
market efficiency
Opis:
Implications of market frictions in the context of serial correlations in indexes on the Central and Eastern European (CEE) stock markets have been analysed. Market frictions, such as non-trading effects, bid/ask spreads, other transaction costs, etc., may be detected by direct measurement, or by indirect identification. Direct measurement of frictions is difficult as intraday trading data are unavailable in the case of most of the emerging CEE stock markets. Indirect identification may be conducted by detecting some empirical phenomena. One of them is evidence of serial correlations in indexes, the so-called the Fisher effect. We explore the problem of serial correlations in indexes on the eight CEE stock markets using data samples from each CEE market separately, as well as a “common trading window” approach, which is widely applied in the case of databases with multivariate time series. The evidence is that nonsynchronous trading effect II between markets may substantially disrupt the analysis of index returns on a domestic market. Using a synchronized database, one may erroneously conclude that the Fisher effect does not exist, although it is present.
Źródło:
Operations Research and Decisions; 2014, 24, 1; 51-70
2081-8858
2391-6060
Pojawia się w:
Operations Research and Decisions
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ground reaction force analysed with correlation coefficient matrix in group of stroke patients
Autorzy:
Szczerbik, E.
Krawczyk, M.
Syczewska, M.
Powiązania:
https://bibliotekanauki.pl/articles/307491.pdf
Data publikacji:
2014
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
ground reaction force
correlation coefficient
stroke
siła reakcji podłoża
współczynnik korelacji
udar mózgu
Opis:
Stroke is the third cause of death in contemporary society and causes many disorders. Clinical scales, ground reaction force (GRF) and objective gait analysis are used for assessment of patient’s rehabilitation progress during treatment. The goal of this paper is to assess whether signal correlation coefficient matrix applied to GRF can be used for evaluation of post-stroke patients status. Group of patients underwent clinical assessment and instrumented gait analysis simultaneously three times. The difference between components of patient’s GRF (vertical, fore/aft, med/lat) and normal ones (reference GRF of healthy subjects) was calculated as correlation coefficient. Patients were divided into two groups (“worse and better”) based on the clinical functional scales tests done at the beginning of rehabilitation process. The results obtained by these two groups were compared using statistical analysis. Increase of median value of correlation coefficient is observed in all components of GRF, but only in non-paretic leg. Analysis of GRF signal can be helpful in assessment of post-stroke patients during rehabilitation. Improvement in stroke patients was observed in non-paretic leg of the “worse” group. GRF analysis should not be the only tool for objective validation of patient’s improvement, but could be used as additional source of information.
Źródło:
Acta of Bioengineering and Biomechanics; 2014, 16, 2; 3-9
1509-409X
2450-6303
Pojawia się w:
Acta of Bioengineering and Biomechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Range resolution improvement of range-gated vision system in backscattering hazy environments
Autorzy:
Park, S.-K.
Choi, I.-Y.
Baik, S.-H.
Jeong, K.-M.
Powiązania:
https://bibliotekanauki.pl/articles/174523.pdf
Data publikacji:
2017
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
range-gated vision system
range image
windowed center-of-mass
cross-correlation
Gaussian window
Opis:
A range-gated vision system simultaneously provides two-dimensional and range images because its light intensity contains the reflectance as well as depth information. The range-resolution of the system is usually inversely proportional to the induced backscattering noise. In this paper, a range imaging technique is proposed to precisely measure range information from highly backscattering foggy environments. A windowed center-of-mass position extracted from the peak area of a cross-correlation signal of two signals, a Gaussian window signal in reduced size and a range-gated signal according to distance, is adopted as the range depth. The proposed measuring technique provides more robust and more precise range information than conventional measuring techniques for hazy targets by virtue of the reduction of backscattering bias noise usually induced by airborne particles. The experimental results and the signal processing procedures to acquire precise range information from hazy targets are described in this paper.
Źródło:
Optica Applicata; 2017, 47, 4; 533-543
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Evaluation of the reliability of a new non-invasive method for assessing the functionality and mobility of the spine
Autorzy:
Topalidou, A.
Tzagarakis, G.
Souvatzis, X.
Kontakis, G.
Katonis, P.
Powiązania:
https://bibliotekanauki.pl/articles/306560.pdf
Data publikacji:
2014
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
intraclass correlation coefficient
intra-rater reliabilit
mobility
range of motion
spinal mouse
mobilność
ruch
kręgosłup
Opis:
For the evaluation of the functionality and mobility of the spine, several methods have been developed. The purpose of this study was to estimate the test-retest reliability of the Spinal Mouse, a new, non-invasive, computer-assisted wireless telemetry device for the assessment of the curvatures, the mobility and the functionality of the spine. Materials and methods: the test-retest reliability was evaluated in 50 adults with back or low back pain. Twenty four parameters were studied in the sagittal and frontal plane. For the characterization of the precision, the intraclass correlation coefficient and the standard error of measurement were used. Results: in the sagittal plane, 22 of the 24 parameters showed high and good reliability, while only two fair and poor. In the frontal plane, 17 parameters showed high and good reliability, five fair and two poor. Discussion: the Spinal Mouse showed excellent test-retest reliability in the sagittal plane, while a slightly inferior performance in the frontal plane, for the evaluation of curvatures, deformation and mobility of the spine.
Źródło:
Acta of Bioengineering and Biomechanics; 2014, 16, 1; 117-124
1509-409X
2450-6303
Pojawia się w:
Acta of Bioengineering and Biomechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Digital Image Correlation Techniques for Strain Measurement in a Variety of Biomechanical Test Models
Autorzy:
Hensley, S.
Christensen, M.
Small, S.
Archer, D.
Lakes, E.
Rogge, R.
Powiązania:
https://bibliotekanauki.pl/articles/307418.pdf
Data publikacji:
2017
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
FEM
cyfrowa korelacja obrazów
wskaźnik naprężenia
DIC
finite element analysis
digital image correlation
strain gauges
Opis:
Purpose: Previous biomechanical studies have estimated the strains of bone and bone substitutes using strain gages. However, applying strain gages to biological samples can be difficult, and data collection is limited to a small area under the strain gage. The purpose of this study was to compare digital image correlation (DIC) strain measurements to those obtained from strain gages in order to assess the applicability of DIC technology to common biomechanical testing scenarios. Methods: Compression and bending tests were conducted on aluminum alloy, polyurethane foam, and laminated polyurethane foam specimens. Simplified single-legged stance loads were applied to composite and cadaveric femurs. Results Results: Showed no significant differences in principal strain values (or variances) between strain gage and DIC measurements on the aluminum alloy and laminated polyurethane foam specimens. There were significant differences between the principal strain measurements of the non-laminated polyurethane foam specimens, but the deviation from theoretical results was similar for both measurement techniques. DIC and strain gage data matched well in 83.3% of all measurements in composite femur models and in 58.3% of data points in cadaveric specimens. Increased variation in cadaveric data was expected, and is associated with the well-documented variability of strain gage analysis on hard tissues as a function of bone temperature, hydration, gage protection, and other factors specific to cadaveric biomechanical testing. Conclusions: DIC techniques provide similar results to those obtained from strain gages across standard and anatomical specimens while providing the advantages of reduced specimen preparation time and full-field data analysis.
Źródło:
Acta of Bioengineering and Biomechanics; 2017, 19, 3; 187-195
1509-409X
2450-6303
Pojawia się w:
Acta of Bioengineering and Biomechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Response of methane emissions to water levels in simulated constructed wetlands
Autorzy:
Li, Yanran
Xu, Qin
Ji, Shuping
Liu, Jian
Powiązania:
https://bibliotekanauki.pl/articles/2171840.pdf
Data publikacji:
2022
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
methane
Pearson correlation
wetland
temperature water
air temperature
metan
korelacja Pearsona
teren podmokły
temperatura wody
temperatura powietrza
Opis:
Wetland is an important natural source of methane (CH4) generated under the actions of methanogens in the anaerobic environment. A greenhouse experiment was conducted to quantify the response of methane emissions to water levels by simulating three water levels (10, 20, and 40 cm) in constructed wetlands and the methane was determined by the static chamber-gas chromatograph technique. Pearson correlation analysis showed that the emissions of CH4 were positively correlated with water temperature and air temperature while they were negatively correlated with air humidity. The water levels simulation experiment showed that the emission of CH4 was the highest when the water level was 20 cm and the CH4 concentrations of the water-air interface had different patterns at various water levels in the daytime. In conclusion, water level and temperature should be considered when accounting for greenhouse gas emissions in constructed wetlands as they both have important influences on CH4 emission.
Źródło:
Environment Protection Engineering; 2022, 48, 3; 5--12
0324-8828
Pojawia się w:
Environment Protection Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Absolute and relative reliability of several measures of static postural stability calculated using a GYKO inertial sensor system
Autorzy:
Jaworski, Janusz
Ambroży, Tadeusz
Lech, Grzegorz
Spieszny, Michał
Bujas, Przemysław
Żak, Michał
Chwała, Wiesław
Powiązania:
https://bibliotekanauki.pl/articles/27324151.pdf
Data publikacji:
2020
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
balance
postural stability
accelerometer
test-retest reliability
intraclass correlation coefficient
balans
stabilność postawy
akcelerometr
niezawodność testu-retestu
współczynnik korelacji wewnątrzklasowej
Opis:
The aim of this study was to analyse absolute and relative reliability of a number of postural static stability measures obtained from a GYKO inertial sensor system in young adults. Methods: The study examined 29 healthy non-athlete young adults. A test was performed for 30 s while standing on one foot, without moving, with eyes open and arms relaxed along the sides of the body. The examinations were performed twice, with a one-week interval. Relative reliability was measured using the intraclass correlation coefficient (ICC) and the 95% confidence interval (95% CI), whereas the absolute reliability was evaluated based on the standard error of measurement (SEM) and the minimal detectable change (MDC). Results: The results of this study showed moderate to good relative reliability scores for all the postural stability measures, with ICC values ranging from 0.62 to 0.70. For most of the analysed variables, SEM% ranged from ca. 10 to 14%. Relatively high SEM% values were obtained only for two variables (Area, Convex Hull Area). Conclusions: The low costs of GYKO inertial sensor systems, the fast and easy installation, the mobility and high reliability of the measurement of postural stability show that it can be effective alternative to stabilographic platforms.
Źródło:
Acta of Bioengineering and Biomechanics; 2020, 22, 2; 93--99
1509-409X
2450-6303
Pojawia się w:
Acta of Bioengineering and Biomechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Digital image correlation of coated and uncoated Religa Heart_Ext ventricular assist device
Autorzy:
Kopernik, M.
Gawlikowski, M.
Milenin, A.
Altyntsev, I.
Kustosz, R.
Kąc, S.
Powiązania:
https://bibliotekanauki.pl/articles/307138.pdf
Data publikacji:
2015
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
komorowe wspomaganie pracy serca
VAD
korelacja obrazów
DIC
azotek tytanu
Tin
złoto
ventricular assist device
digital image correlation
titanium nitride
TiN
gold
Opis:
The digital image correlation is used to estimate influence of deposited heamocompatible coatings (gold and titanium nitride) on mechanical response of ventricular assist device Religa Heart_Ext made of Bionate II (thermoplastic polycarbonate urethane) under working conditions by comparison of the coated Religa Heart_Ext with uncoated Religa Heart_Ext. The DIC is applied for experimental investigation of the strains and displacements distribution on external surface of the blood chamber of ventricular assist device during loading. The experiment was conducted in a hydraulic system with water at operating temperatures of 25 and 37 °C, as well as under static pressures: 80, 120, 180, 220 and 280 mmHg, and static underpressures: –25, –45, –75 mmHg. The subsequent images were taken after stabilization of pressure on a set level. The applied research method shows that the nano-coating of 30 nm in thickness significantly affects deformation of the blood chamber of Religa Heart_Ext in macro scale. The proposed composition of coatings increases strain on external surface of the ventricular assist device.
Źródło:
Acta of Bioengineering and Biomechanics; 2015, 17, 4; 49-58
1509-409X
2450-6303
Pojawia się w:
Acta of Bioengineering and Biomechanics
Dostawca treści:
Biblioteka Nauki
Artykuł

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