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1

Statistics of tropospheric amplitude scintillation over selected locations in tropical Nigeria

Ashidi Ayodeji Gabriel, Ojo Joseph Sunday, Kareem Afan Idowu, Ojo Olusola Samuel, Emmanuel Israel

Acta Geophysica

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2021

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Vol. 69, no. 3

947--957

EN

Tropospheric scintillation depends signifcantly on any location’s prevailing weather condition, and its variation must be statistically analyzed to ensure accurate fade margin determination. This study examines the distribution of Ku-band amplitude scintillation across selected locations in tropical Nigeria. Eight years of daily averaged data of surface temperature and relative humidity were employed for computing scintillation intensity (σ) and amplitude (χ) using international telecommunications union recommended model across eighteen (18) stations, that are subdivided into four (4) regions and spread over tropical Nigeria. The data, spanning January 2010 to December 2017, were obtained from the archive of the European center for medium-range weather forecasts (ECMWF) with a resolution of 0.125° by 0.125°. Three (3) years of in-situ data of concurrently measured satellite radio beacons and primary radio-climatic parameters at Akure (7° 17′ N, 5° 18′ E, 358 m), South-west Nigeria, were employed for comparison and validation. Statistical analyses involving time series, probability density, and cumulative distribution functions were performed on the scintillation dataset annually. Results indicate that the magnitude of tropospheric amplitude scintillation varies across diferent locations; nevertheless, it exhibits a similar distribution pattern characterized by the generalized extreme value (GEV) probability density function (pdf). The study has shown the need to incorporate the scintillation component into the fade mitigation architecture of telecommunication systems in tropical Nigeria while considering its regional variability. Also, experimental validation of the observations raised in this study should be encouraged at all the locations for better prediction accuracy.

2

A logical device for processing nautical data

Filipowicz W.

Zeszyty Naukowe Akademii Morskiej w Szczecinie

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2017

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nr 52 (124)

65--73

EN

Nautical measurements are randomly and systematically corrupted. There is a rich scope of knowledge regarding the randomness shown by results of observations. The distribution of stochastic distortions remains an estimate and is imprecise with respect to their parameters. Uncertainties can also occur through the subjective assessment of each piece of available data. The ability to model and process all of the aforementioned items through traditional approaches is rather limited. Moreover, the results of observations, the final outcome of a quality evaluation, can be estimated prior to measurements being taken. This a posteriori analysis is impaired and it is outside the scope of traditional, inaccurate data handling methods. To propose new solutions, one should start with an alternative approach towards modelling doubtfulness. The following article focusses on belief assignments that may benefit from the inclusion of uncertainty. It starts with a basic interval uncertainty model. Then, assignments engaging fuzzy locations around nautical indications are discussed. This fragment includes transformation from density functions to probability distributions of random errors. Diagrams of the obtained conversions are included. The presentation concludes with a short description of a computer application that implements the presented ideas.

3

Research on the influence of operational factors on the number of failures of diesel locomotives’ engines

Gelumbickas G., Vaciunas G.

Transport Problems

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2014

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T. 9, z. 1

5--12

EN

Having replaced the diesel locomotives operated in Lithuanian railways by new ones, part of old diesel locomotives (21 units) were renovated. They were equipped with new diesel engines made in Kolomna (Russia). These diesel locomotives are used as reserve locomotives or for carrying small scope freight on local routes. After a few years from their renovation diesel engines as well as the locomotives started to fail. Failures happened to be repeated. The article analyses these locomotives’ failure patterns such as number distribution of engine failures according to locomotive mileage, distribution of engine failures according to diesel locomotive turnover, distribution of engine failure number according to consumed fuel. It suggested to regard the density of engine failure probability according to consumed fuel as one of the indicators of engine reliability.

PL

Po zastąpieniu lokomotyw spalinowych pracujących w kolejach litewskich przez nowe cześć ze starych lokomotyw spalinowych (21 jednostek) zostało odnowionych. Wyposażono je w nowe silniki spalinowe wyprodukowane w Kołomnie (Rosja). Te lokomotywy spalinowe są używane jako lokomotywy rezerwowe lub do przewozu małego zakresu towarowego po trasach lokalnych. Po kilku latach od ich renowacji silniki spalinowe oraz lokomotywy zaczęły się psuć. Awarie zaczęły się powtarzać. Artykuł przedstawia awarie tych lokomotyw, rozkład liczby awarii silnika zgodnie z przebiegiem lokomotywy, dystrybucję awarii silnika według przebiegu lokomotywy spalinowej, rozkład liczby awarii silnika zgodnie ze zużytym paliwem. Sugeruje się wzięcie pod uwagę gęstości prawdopodobieństwa awarii silnika, zgodnie ze zużytym paliwem, jako jednego ze wskaźników niezawodności silnika.

4

A Robust Digital Watermarking Based on Local Complex Angular Radial Transform

Niu P.-P., Wang X.-Y., Yang H.-Y., Wang P., Wang A.-L.

Fundamenta Informaticae

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2014

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Vol. 135, nr 3

243--268

EN

Geometric distortions that cause displacement between embedding and detection are usually difficult for watermark to survive. It is a challenging work to design a robust image watermarking scheme against geometric distortions, especially for local geometric distortions. Based on probability density and complex angular radial transform theory, a new image watermarking algorithm robust to geometric distortions is proposed in this paper. We firstly extract the steady image feature points by using new image feature point detector, which is based on the probability density. Then we build the affine invariant local feature regions based on probability density auto-correlation matrix. And finally, we present a new image watermarking algorithm robust to geometric distortions, in which the digital watermark is embedded into the local complex angular radial transform (CART) coefficients. Experiments results show that the proposed image watermarking is not only invisible and robust against common image processing operations, but also robust against the geometric distortions.

5

Podstawy stochastycznego opisu hydrodynamicznej teorii smarowania

Wierzcholski K., Miszczak A.

Tribologia

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2012

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nr 5

207--213

PL

Głównym powodem generowania zmian losowych w czasie eksploatacji poprzecznych łożysk ślizgowych, nie wyłączając biołożysk a w szczególności mikrołożysk, jest stochastycznie zmieniająca się chropowatość w skali mikro i nano dwóch współpracujących powierzchni, a także probabilistycznie zmienne impulsy zewnętrzne wywołane drganiami lub mikrodrganiami układu łożyskowego oraz zewnętrznej jego obudowy. Oba wymienione czynniki powodują stochastyczną zmianę wysokości szczeliny łożyskowej w takim zakresie, że ma to wpływ na rozkłady prędkości czynnika smarującego, rozkłady ciśnienia hydrodynamicznego, wartości sił nośnych, wartości momentów tarcia, współczynniki tarcia oraz na końcowym etapie na zużycie. Celem badań w niniejszej pracy jest przedstawienie podstawowych zasad dotyczących wykorzystania metod stochastycznych przy rozwiązywaniu problemów hydrodynamicznej teorii smarowania poprzecznych łożysk ślizgowych z uwzględnieniem odchylenia standardowego.

EN

The aim of this paper is the presentation of basic principles referring to the application of stochastic methods during the solution of hydrodynamic lubrication problems for slide journal bearings, taking into account the standard deviation and expectancy values of gap height between two cooperating surfaces. A description of real gap height changes in microand bio-bearings depend on the variations of cooperating surfaces. Random changes of the surface are described by the probability density functions based on a comparison between results of the J. Cwanek and K. Wierzcholski’s experiments and the investigations of D. Dowson and Mow. Such experiments are performed for micro-bearing surface samples as well cartilage surface samples obtained from human bio-joints. The random influence of the surface roughness on the change of the flow and operational parameters is indicated by many experiments. The presented methods based on values of probability density function obtained in experimental way enable one to formulate basic hydrodynamic dependencies for lubrication theory in random description.

6

Grafika rozkładu Weibulla

Rećko W. M.

Szkło i Ceramika

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2012

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R. 63, nr 2

40-44

PL

Przedstawiono metody graficzne prezentacji dystrybuanty i krzywej gęstości prawdopodobieństwa dla rozkładu Weibulla. Przedyskutowano diagramy Weibulla dla trzech tworzyw ceramicznych oraz dla siły łamiącej płytki podłogowe.

EN

The graphical methods for Weibull distribution (cumulative distribution function, probability density) are discussed. For three ceramics material, bending strenght and for floor tiles break force in term of WeibulI's diagram are discussed.

7

The research of the probabilistic characteristics of exhaust emissions from vehicle engines

Chłopek Z.

Silniki Spalinowe

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2011

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R. 50, nr 1

49-55

EN

The influence of the probability density of the average speed on the probability density of the specific road exhaust emissions has been analyzed in the paper. The characteristics of the exhaust emissions from internal combustion engines warmed up to normal operating temperature have been examined. The research has been carried out for characteristics of the exhaust emissions from internal combustion engines of passenger vehicles. The research has been carried out for two kinds of functions in the form courses of average speed: of constant and normal distribution. The Monte Carlo Method has been used in the research. The probability density of the specific road exhaust emissions has been estimated. The zero-dimensional characteristics: the median, the kurtosis and the skewness coefficient, have been examined. A significant regularity of the displacement of the probability density towards smaller values in relation to the average speed probability density has been ascertained.

PL

W artykule przeanalizowano wpływ gęstości prawdopodobieństwa prędkości średniej samochodu na gęstość prawdopodobieństwa emisji drogowych zanieczyszczeń. Rozpatrywano charakterystyki emisji zanieczyszczeń z silników nagrzanych do temperatury normalnej eksploatacji. Badania przeprowadzono dla charakterystyk emisji zanieczyszczeń z silników spalinowych samochodów osobowych. Wykonano je dla dwóch rodzajów wymuszeń w postaci procesów prędkości średniej samochodu o rozkładach: stałym i normalnym, stosując metodę Monte Carlo. Wyznaczono gęstości prawdopodobieństwa emisji drogowej zanieczyszczeń. Badano również charakterystyki punktowe rozpatrywanych zbiorów: medianę, kurtozę i współczynnik skośności. Stwierdzono wyraźną regularność przesuwania się gęstości prawdopodobieństwa emisji drogowej zanieczyszczeń w stronę mniejszych wartości w stosunku do gęstości prawdopodobieństwa prędkości średniej.

8

A method of estimating the risk of a catastrophic failure to engine's rotating members as related to fatigue - an outline

Tomaszek H., Żurek J., Jasztal M.

Journal of KONES

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2007

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Vol. 14, No. 2

505-511

EN

The paper has been intended to introduce a probabilistic method to estimate - from the standpoint of fatigue - the risk of a catastrophic failure to rotating (moving) members of an aircraft engine, i.e. to compressor blades. It has been assumed that there is a hidden defect in the material's structure, which initiates a small-size crack. Load-affected, the crack keeps growing. The crack propagation dynamics, when approached in a deterministic way, remains consistent with the Paris formula. The crack growth is effected by some random load characterised with the servicing load spectrum. While determining the load spectrum, all possible operational events are taken into account, excluding ones that could result in an immediate damage to the component. It has been assumed that random instances of load increase, which may result in an immediate damage, compose a separate set of events; hence, they have not been taken into account in this model. A partial differential equation of the Fokker-Planck type has been used to describe randomly approached dynamics of crack propagation. Having solved this equation enables a density function of the fatigue crack length to be found. This function, in turn, has been used to determine the risk of a catastrophic failure to a compressor blade. Furthermore, this function can also be used to find safe service life of the structure under consideration.