Wyniki wyszukiwania - BazTech

1

Selected polynomial identification techniques to evaluate maritime transport trends around Covid-19

Borucka Anna, Kozłowski Edward

Zeszyty Naukowe. Transport / Politechnika Śląska

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2023

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z. 120

51--68

EN

The Covid-19 pandemic has drastically affected the transport sector, because of the restrictions introduced to limit the spread of the threat. They concerned primarily passenger traffic, but trade in goods also faced completely new challenges, related to increased consumption and the dynamic development of e-commerce on the one hand and restrictions related to the pandemic and sealing borders on the other. One of the most susceptible to fluctuations in international trade is the maritime economy, which has been analysed in this article. It was checked how the global threat affected sea traffic in terms of gross weight of goods handled in main ports. The aim of the study was to characterize the impact of the pandemic on sea transport depending on the type of ship and to evaluate the current state of sea transport in the context of the level shaped by forecasts based on observations from before the coronavirus pandemic. The authors' assumption was to check whether the rail transport market has already reached the level it could reach in the absence of the virus threat. The use of a polynomial function was proposed for the study. Time series containing observations up to the outbreak of the pandemic and forecasts based on them, as well as time series containing additional observations from the pandemic period were analysed. The study results obtained allowed to conclude how the global crisis caused by the Covid-19 pandemic affected the cargo traffic in the sea transport, expressed by the mass of goods transshipped in major ports, depending on the individual types of ships.

2

Uncertainty of the conversion function caused by systematic effects in measurements of input and output quantities

Dorozhovets Mykhaylo

Metrology and Measurement Systems

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2023

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Vol. 30, nr 3

581--600

EN

The paper presents an evaluation with the Type A and B methods for standard uncertainties of coefficients of a polynomial function of order 𝑘 determined by 𝑛 points obtained by measurement of input and output quantities. A method for deriving a posteriori distributions of function coefficients based on the transformation of estimator distributions without assuming any a priori distributions is presented. It was emphasized that since the correct values of the standard uncertainty of type A depend on the √(n-k-3) and not on the √(n-k-1), therefore, with a small number of measurement points, the use of the classical approach leads to a significant underestimation of uncertainty. The relationships for direct evaluation with the type B method of uncertainties caused by uncorrected systematic additive (offset error) and multiplicative (gain error) effects in the measurements of both input and output quantities are derived. These standard uncertainties are determined on the basis of the manufacturers’ declared values of the maximum permissible errors of the measuring instruments used. A Monte Carlo experiment was carried out to verify the uncertainties of the coefficients and quadratic function, the results of which fully confirmed the results obtained analytically.

3

Elastic buckling analysis of uniaxially compressed CCCC stiffened isotropic plates

Ibeabuchi V. T., Ibearugbulem O. M., Ezeah C., Ugwu O. O.

International Journal of Applied Mechanics and Engineering

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2020

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Vol. 25, no. 4

84--95

EN

This paper reports a research study that investigated buckling of stiffened rectangular isotropic plates elastically restrained along all the edges (CCCC) under uniaxial in-plane load, using the work principle approach. The stiffeners were assumed to be rigidly connected to the plate. Analyses for critical buckling of stiffened plates were carried out by varying parameters, such as the number of stiffeners, stiffness properties and aspect ratios. The study involved a theoretical derivation of a peculiar shape function by applying the boundary conditions of the plate on Taylor Maclaurin’s displacement function and substituted on buckling equation derived to obtain buckling solutions. The present solutions were validated using a trigonometric function in the energy method from previous works. Coefficients, K, were compared for various numbers of stiffeners and the maximum percentage difference obtained within the range of aspect ratios of 1.0 to 2.0 is shown in Figs 2 - 7. A number of numerical examples were presented to demonstrate the accuracy and convergence of the current solutions.

4

On some stability properties of polynomial functions

Budzik D.

Scientific Issues of Jan Długosz University in Częstochowa. Mathematics

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2011

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Vol. 16

11--14

EN

In this paper we present conditions under which a function F with a control function f, in the following sense [wzór], can by uniformly approximated by a polynomial function of degree at most n.

5

Application of Trefftz method for temperature rise analysis on human skin exposed to radiation

Kita E., Hirayama Y.

Computer Assisted Mechanics and Engineering Sciences

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2008

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Vol. 15, No. 1

45-52

EN

This paper describes the application of the Trefftz method to the temperature rise in human skin exposed to radiation from a cellular phone. A governing equation is given as the Poisson equation. An inhomogeneous term of the equation is approximated with a polynomial function in Cartesian coordinates. The use of the approximated term transforms the original boundary-value problem to that governed with a homogeneous differential equation. The transformed problem can be solved by the traditional Trefftz formulation. Firstly, the present method is applied to a simple numerical example in order to confirm the formulation. The temperature rise in a skin exposed to radiation is considered as a second example.

6

Porównanie wielomianu i funkcji Fouriera opisujących roczny przebieg temperatury i wilgotności powietrza w Ursynowie SGGW

Rozbicki T., Rozbicka K.

Przegląd Naukowy Inżynieria i Kształtowanie Środowiska

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2004

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Vol. 13, No. 2

85--93

EN

The aim of the paper is to compare two methods of estimation main meteorological elements annual course - polynomial function and Fourier function. Long-term mean monthly data of Ursynów Warsaw Agricultural University meteorological station was used in the analysis: air temperature, maximum and minimum air temperature, amplitude of the temperature, vapor pressure, saturation deficit and relative humidity. Very high values of squared correlation coefficients calculated for two compared methods indicate that both polynomial form of equation and Fouier function may estimate annual course of air temperature and humidity very good. It is noticed that the coefficients for polynomial equations are slightly better than for Fourier functions, particularly for humidity elements.

7

Discrete time sliding mode control - an advanced reaching law approach

Bartoszewicz A.

Systems Science

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2002

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Vol. 28, nr 4

35-42

EN

In this paper, an advanced discrete-time reaching law is proposed and applied to the design of a sliding mode controller. The controller reduces the influence of a sinusoidal disturbance and parameter uncertainty on the system dynamics to an arbitrarily small level. Furthermore, the controller guarantees existence of the ideal sliding mode in the discrete-time system provided that the total influence of disturbance and parameter uncertainty on the system dynamics is represented by a polynomial function of time. The sliding mode is reached in a finite time. The strategy proposed in this paper can be applied to linear time-varying systems subject to disturbance and modelling uncertainty