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Wyświetlanie 1-12 z 12
Tytuł:
Time-independent stochastic design sensitivity analysis of structural systems with second-order accuracy
Autorzy:
Weber, H.
Powiązania:
https://bibliotekanauki.pl/articles/281017.pdf
Data publikacji:
2016
Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Tematy:
design sensitivity
statics
random parameter
finite element
Opis:
In the paper, the static sensitivity of complex structures with respect to random design parameters is presented. Using the adjoint system method, based on the mean-point second-order perturbation method, the first two probabilistic moments of time-independent sensitivity are formulated with means and cross-covariances of random design parameters as the input data. It enables one to obtain the second-order accuracy of the solution. The presented formulations are illustrated by a number of numerical examples. The influence of finite element mesh density for the obtained results is discussed using the analysis of the spatial bar dome.
Źródło:
Journal of Theoretical and Applied Mechanics; 2016, 54, 3; 783-794
1429-2955
Pojawia się w:
Journal of Theoretical and Applied Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of uncertainty in aerodynamic performance on the dynamic response of a two stage gear system
Autorzy:
Tounsi, M.
Beyaoui, M.
Abboudi, K.
Feki, N.
Walha, L.
Haddar, M.
Powiązania:
https://bibliotekanauki.pl/articles/281135.pdf
Data publikacji:
2016
Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Tematy:
gearbox
uncertainty
power coefficient
random parameter
polynomial chaos
Opis:
In this paper, the nonlinear dynamic response in a wind turbine system is considered and the quantification of uncertainty effects on the variability of this nonlinear response is investigated. Under dynamic conditions, a lumped model with 12 degrees of freedom is proposed taking into account the uncertainty associated to the power coefficient of the input aerodynamic torque. The dynamic response of the two-stage spur gear system is obtained using ODE45 solver of Matlab. The Polynomial Chaos (PC) method is used to introduce the uncertainties on the proposed model. A comparison between the two dynamic responses given by the proposed lumped dynamic model takes into account the uncertainty. It is performed on the existed model without uncertainty. Thus, the efficiency and robustness of the proposed new methodology is evaluated.
Źródło:
Journal of Theoretical and Applied Mechanics; 2016, 54, 2; 601-612
1429-2955
Pojawia się w:
Journal of Theoretical and Applied Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Heavy vehicle crashes in Addis Ababa: Relationship between contributing factors and severity of outcomes
Autorzy:
Tulu, Getu Segni
Lisinge, Robert Tama
Wedajo, Bikila Teklu
Powiązania:
https://bibliotekanauki.pl/articles/2176020.pdf
Data publikacji:
2022
Wydawca:
Fundacja Centrum Badań Socjologicznych
Tematy:
heavy vehicle
crashes
road safety
random parameter logit regression
risk
Ethiopia
Addis Ababa
Opis:
Random parameter logit regression is used to analyze police-reported data on 8,253 heavy vehicle-related crashes in Addis Ababa between July 2014 and June 2017. The analysis shows that fatal crashes are more likely to occur during the day and on weekdays, particularly when the circulation of trucks is high. It also shows the disproportionately high involvement of young drivers in heavy vehicle crashes in the city. However, the likelihood of crashes resulting in fatalities and serious injuries increases slightly compared to those resulting only in property damage as the age of drivers increases. Low levels of drivers' education, the fact that drivers are often not the owners of vehicles, ownership of vehicles by companies and government organizations, and inappropriate road medians' inappropriate design are also significant contributors to fatal crashes. Curbing deaths and injuries from heavy vehicle crashes in Addis Ababa requires strict enforcement of traffic rules and regulations, particularly speed limits; reforms in driver's training and certification; improved safety culture of vehicle owners and design of road infrastructure. Ethiopia's national road safety strategy launched in July 2022 addresses these issues. Hence the government is taking steps in the right direction.
Źródło:
Journal of Sustainable Development of Transport and Logistics; 2022, 7, 2; 25--40
2520-2979
Pojawia się w:
Journal of Sustainable Development of Transport and Logistics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Badania korelacji między podstawowymi estymatorami parametru położenia dla serii obserwacji nieskorelowanych
Investigations of correlation between the main location parameter estimators of random uncorrelated observations
Autorzy:
Dorozhovets, M.
Powiązania:
https://bibliotekanauki.pl/articles/158119.pdf
Data publikacji:
2012
Wydawca:
Stowarzyszenie Inżynierów i Techników Mechaników Polskich
Tematy:
korelacja
wartość średnia
mediana
środek rozstępu
correlation
mean
median
midrange
Opis:
W pracy przedstawiono wyniki badań korelacji pomiędzy wartością średnią, medianą oraz środkiem rozstępu nieskorelowanych wyników obserwacji o wybranych rozkładach prawdopodobieństwa: Laplace'a, normalnym, trójkątnym, trapezowym, jednostajnym oraz arksinusoidalnym. Stwierdzono, że istnieje silna korelacja pomiędzy wartością średnią a medianą, mediana i środek rozstępu są najmniej skorelowane, a korelacja pomiędzy średnią i środkiem rozstępu przyjmuje wartości pośrednie. Przy wzroście liczby obserwacji korelacja pomiędzy wartością średnią a medianą stabilizuje się, natomiast korelacja pomiędzy środkiem rozstępu i wartością średnią oraz medianą monotoniczne zmniejsza się.
The results of studies of the correlation between the main location parameter estimators (mean, median and midrange) of uncorrelated random observations are presented. Analytical calculations of the correlation coefficients are based on preliminary determination of the location parameter joint distributions. The joint distributions of the median and midrange are described by simplest formula (7), based on the distribution of order statistics (6). But analytical calculations of the joint distribution of other pairs of position parameters are very difficult and can only be realized by numerical procedures. Formulas (11) - (15) for determining the asymptotical values of all correlation coefficients for a large numbers of observations are presented. The main studies of the correlation coefficients for the number observation from n = 2 to n = 100 are realised by the Monte Carlo method. The results of simulation investigations are shown in Fig. 1. The median and mean are most correlated, and the asymptotical value of the correlation coefficient is equal to the inverse value of a form factor of the sample probability density function (PDF). The value of the correlation coefficient between the median and midrange does not practically depend on the type of PDF and decreases approximately proportionally to the square root of the number of observations (13, Fig. 1). The value of the correlation coefficient between the mean and midrange also decreases monotonically with an increase in the number of observations, but the rate of decrease depends on the amplitude factor of a sample (15, Fig. 1).
Źródło:
Pomiary Automatyka Kontrola; 2012, R. 58, nr 8, 8; 697-700
0032-4140
Pojawia się w:
Pomiary Automatyka Kontrola
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On a strongly consistent estimator of the squared L_2-norm of a function
Autorzy:
Różański, Roman
Powiązania:
https://bibliotekanauki.pl/articles/1340253.pdf
Data publikacji:
1995
Wydawca:
Polska Akademia Nauk. Instytut Matematyczny PAN
Tematy:
strong consistency
stochastic integral with respect to a p-parameter martingale
Poisson random field
Wiener random field
asymptotic unbiasedness
kernel estimator
Opis:
A kernel estimator of the squared $L_2$-norm of the intensity function of a Poisson random field is defined. It is proved that the estimator is asymptotically unbiased and strongly consistent. The problem of estimating the squared $L_2$-norm of a function disturbed by a Wiener random field is also considered.
Źródło:
Applicationes Mathematicae; 1995-1996, 23, 3; 279-284
1233-7234
Pojawia się w:
Applicationes Mathematicae
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Representation formulae for (C₀) m-parameter operator semigroups
Autorzy:
Zhou, Mi
Anastassiou, George
Powiązania:
https://bibliotekanauki.pl/articles/1311136.pdf
Data publikacji:
1996
Wydawca:
Polska Akademia Nauk. Instytut Matematyczny PAN
Tematy:
multi-parameter operator semigroups
representation formulae
multivariate approximation
sum of random vectors
Banach space
multiplier enlargement method
rate of convergence
second modulus of continuity
inequalities
Opis:
Some general representation formulae for (C₀) m-parameter operator semigroups with rates of convergence are obtained by the probabilistic approach and multiplier enlargement method. These cover all known representation formulae for (C₀) one- and m-parameter operator semigroups as special cases. When we consider special semigroups we recover well-known convergence theorems for multivariate approximation operators.
Źródło:
Annales Polonici Mathematici; 1996, 63, 3; 247-272
0066-2216
Pojawia się w:
Annales Polonici Mathematici
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Stress-weighted spatial averaging of random fields in geotechnical risk assessment
Autorzy:
Brząkała, Włodzimierz
Powiązania:
https://bibliotekanauki.pl/articles/2041287.pdf
Data publikacji:
2021
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
spatial variability
effective soil parameter
variance reduction
Vanmarcke averaging
safety factor
Opis:
Effects of spatial fluctuations of soil parameters are considered in a new context – considering variability of soil parameters in conjunction with non-uniform stress fields, which can locally amplify (or suppress) subsoil inhomogeneities. In this way, several design situations for the Coulomb frictional material with random tan(φ(x)) reveal a reduction of variance, which is less significant than for the standard volume averaging. When looking for an 'effective' random variable [tan(φ)]a – that is, a random variable, which is equivalent to the random field tan(φ(x)) – the Vanmarcke averaging by simple volume integrals is insufficient; it systematically overestimates effects of variance reduction, thus causing potentially unsafe situations. The new proposed approach is coherent, formally defined and more realistic.
Źródło:
Studia Geotechnica et Mechanica; 2021, 43, 4; 465-478
0137-6365
2083-831X
Pojawia się w:
Studia Geotechnica et Mechanica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Note on estimating bed shear stress caused by breaking random waves
Autorzy:
Myrhaug, D.
Ong, M.C.
Powiązania:
https://bibliotekanauki.pl/articles/2078910.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Instytut Oceanologii PAN
Tematy:
shear stress
breaking wave
surf parameter
wave height
surf zone
Opis:
This note presents a method of how the bed shear stress caused by breaking random waves on slopes can be estimated. This is obtained by adopting the Sumer et al. (2013) bed shear stress formula due to spilling and plunging breaking waves on hydraulically smooth slopes combined with the Myrhaug and Fouques (2012) joint distribution of surf similarity parameter and wave height for individual random waves in deep water. The conditional mean value of the maxima of mean bed shear stress during wave runup given wave height in deep water is provided including an example for spilling and plunging breaking random waves corresponding to typical field conditions. Another example compares the present results with one case from Thornton and Guza (1983) estimating the wave energy dissipation caused by bed shear stress beneath breaking random waves
Źródło:
Oceanologia; 2021, 63, 3; 385-390
0078-3234
Pojawia się w:
Oceanologia
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Set-valued stochastic integrals and stochastic inclusions in a plane
Autorzy:
Sosulski, Władysław
Powiązania:
https://bibliotekanauki.pl/articles/729310.pdf
Data publikacji:
2001
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
stochastic inclusions in the plane
set-valued random field
two-parameter stochastic process
weak compactness
Opis:
We present the concepts of set-valued stochastic integrals in a plane and prove the existence of a solution to stochastic integral inclusions of the form
$z_{s,t} ∈ φ_{s,t} + ∫_{0}^{s} ∫_{0}^{t} F_{u,v}(z_{u,v})dudv + ∫_{0}^{s} ∫_{0}^{t}G_{u,v}(z_{u,v})dw_{u,v}$
Źródło:
Discussiones Mathematicae, Differential Inclusions, Control and Optimization; 2001, 21, 2; 249-259
1509-9407
Pojawia się w:
Discussiones Mathematicae, Differential Inclusions, Control and Optimization
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Method for prediction of cavitation erosion performance in hydro-turbines based on the two-parameter phenomenological model
Autorzy:
Gireń, B. G.
Noińska-Macińska, M.
Powiązania:
https://bibliotekanauki.pl/articles/1191846.pdf
Data publikacji:
2018
Wydawca:
Gdańska Szkoła Wyższa
Tematy:
cavitation erosion
materials performance
performance evaluation
random process modelling
wear
Opis:
Two-parameter phenomenological model for quantification of the cavitation damage process in its initial — incubation stage inspired by Förster energy migration theory is presented in the paper. The model built was supplemented with functional relationships between calculation parameters and strength parameters of the materials derived for chosen cavitation loading conditions. Experiments at the rotating disk set-up have been carried out in order to obtain necessary experimental data. The values of calculation parameters have been determined by adjusting the theoretical erosion curve to experimental one. Preliminary experimental verification of the model soundness consisted in comparing theoretical to experimental results obtained from both the ICET program and the experimental investigations of the cavitation erosion at Banki-Michel turbine blades. Reliability as well as the sources of inaccuracy and uncertainties were also discussed. The far-reaching aim of the work is to create the calculation tool for prediction of cavitation erosion performance in hydro-turbines during their operating cycle.
Źródło:
Eco-Energetics: technologies, environment, law and economy; 2018, 1; 21--32
2657-5922
2657-7674
Pojawia się w:
Eco-Energetics: technologies, environment, law and economy
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Opredelenie korreljacionnojj svjazi mezhdu otdel'nymi geometricheskimi parametrami zeren razlichnykh kul'tur
Determination of correlation relationship between individual geometrical parameters of grains of different cultures
Autorzy:
Kuzminskijj, R.
Sokolovskijj, O.
Sheremeta, R.
Powiązania:
https://bibliotekanauki.pl/articles/77786.pdf
Data publikacji:
2015
Wydawca:
Komisja Motoryzacji i Energetyki Rolnictwa
Tematy:
grain crop
wheat
rye
geometrical parameter
random variable
correlation analysis
Źródło:
Motrol. Motoryzacja i Energetyka Rolnictwa; 2015, 17, 4
1730-8658
Pojawia się w:
Motrol. Motoryzacja i Energetyka Rolnictwa
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Modeling of joint signal detection and parameter estimation on the background of non-Gaussian noise
Autorzy:
Palahin, V.
Filipov, V.
Leleko, S.
Ivchenko, O.
Palahina, O.
Powiązania:
https://bibliotekanauki.pl/articles/122532.pdf
Data publikacji:
2015
Wydawca:
Politechnika Częstochowska. Wydawnictwo Politechniki Częstochowskiej
Tematy:
non-Gaussian noise
moment and cumulant representation of random variables
truncated stochastic polynom
polynomial solving rules
Opis:
The paper presents the results and describes the process of modeling of a system of joint signal detection and parameter estimation on the background of a non-Gaussian noise based on moment and cumulant description of random variables, polynomials of Kunchenko and moment quality criterion type of Neyman-Pearson.
Źródło:
Journal of Applied Mathematics and Computational Mechanics; 2015, 14, 3; 87-94
2299-9965
Pojawia się w:
Journal of Applied Mathematics and Computational Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-12 z 12

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