Wyniki wyszukiwania - BazTech

1

Accounting for the random character of nucleation in the modelling of phase transformations in steels

Poloczek Łukasz, Kuziak Roman, Foryś Jakub, Szeliga Danuta, Pietrzyk Maciej

Computer Methods in Materials Science

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2023

|

Vol. 23, No. 2

17--28

EN

In our earlier work, a stochastic model of multi-stage deformation at elevated temperatures was developed. The model was applied to calculate histograms of dislocation density and grain size at the onset of phase transformation. The histograms were used as input data for the simulation of phase transitions using the traditional deterministic model. Following this approach, microstructural inhomogeneity was predicted for different cooling conditions. The results obtained, showing the effect of dislocation density and inhomogeneity of austenite grain size on the microstructural inhomogeneity of the final product, can be considered reliable as they are based on material models determined in previous publications and validated experimentally. The aim of the present work was to extend the model by taking into account the stochastic nature of nucleation during phase transitions. The analysis of existing stochastic models of nucleation was performed, and a model for ferritic transformation in steels was proposed. Simulations for constant cooling rates as well as for industrial cooling processes of steel rods were performed. In the latter case, uncertainties in defining the boundary conditions and segregation of elements were also considered. The reduction of the computing costs is an important advantage of the model, which is much faster when compared to full field models with explicit microstructure representation.

2

Stochastic model to estimate the waiting time for container vessel turnaround times

Elentably A., Fisher K., Holger S., Alghanmi A., Alhrbi S.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2022

|

Vol. 16 No. 3

515--519

EN

By developing possible solutions for Saudi ports to limit the increase in damage to the marine ecosystem, the random system for estimating the waiting time of ships in Saudi ports has been developed as a model to guide the application of the multiple benefits to the beneficiaries such as ship owners, shipping companies and port authorities so that it is applied to create multiple economic and environmental savings. An imperative optimization model for solving container slot allocation problems for time-sensitive commodities under the dynamics of port congestion pricing. The proposed new pricing mechanism has proven to be effective when compared to a generic slot allocation model that does not take into account shipping time limits and port congestion, with results showing that the proposed pricing scheme can significantly improve ship companies' revenues and improve customer satiation. In terms of reducing carbon emissions from the ship's stay for a longer period at the docks.

3

Thermal-mechanical finite element simulation of flat bar rolling coupled with a stochastic model of microstructure evolution

Szeliga Danuta, Czyżewska Natalia, Kusiak Jan, Kuziak Roman, Morkisz Paweł, Oprocha Piotr, Pietrzyk Maciej, Piwowarczyk Michał, Poloczek Łukasz, Przybyłowicz Paweł, Rauch Łukasz, Wolańska Natalia

Computer Methods in Materials Science

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2022

|

Vol. 22, No. 3

137--148

EN

It is generally recognized that the kinetics of phase transformations during the cooling of steel products depends to a large extent on the state of the austenite after rolling. Austenite deformation (when recrystallization is not complete) and grain size have a strong influence on the nucleation and growth of low-temperature phases. Thus, the general objective of the present work was the formulation of a numerical model which simulates thermal, mechanical and microstructural phenomena during multipass hot rolling of flat bars. The simulation of flat bar rolling accounting for the evolution of a heterogeneous microstructure was the objective of the work. A conventional finite-element program was used to calculate the distribution of strains, stresses, and temperatures in the flat bar during rolling and during interpass times. The FE program was coupled with the stochastic model describing austenite microstructure evolution. In this model, the random character of the recrystallization was accounted for. Simulations supplied information about the distributions of the dislocation density and the grain size at various locations through the thickness of the bars.

4

Stochastic model describing evolution of microstructural parameters during hot rolling of steel plates and strips

Szeliga Danuta, Czyżewska Natalia, Klimczak Konrad, Kusiak Jan, Kuziak Roman, Morkisz Paweł, Oprocha Piotr, Pietrzyk Maciej, Poloczek Łukasz, Przybyłowicz Paweł

Archives of Civil and Mechanical Engineering

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2022

|

Vol. 22, no. 3

art. no. e139

EN

Enhancing strength-ductility synergy of materials has been for decades an objective of research on structural metallic materials. It has been shown by many researchers that significant improvement of this synergy can be obtained by tailoring heterogeneous multiphase microstructures. Since large gradients of properties in these microstructures cause a decrease of the local fracture resistance, the objective of research is to obtain smoother gradients of properties by control of the manufacturing process. Advanced material models are needed to design such microstructures with smooth gradients. These models should supply information about distributions of various microstructural features, instead of their average values. Models based on stochastic internal variables meet this requirement. Our objective was to account for the random character of the recrystallization and to transfer this randomness into equations describing the evolution of dislocations and grain size during hot deformation and during interpass times. The idea of this stochastic model is described in the paper. Experiments composed of uniaxial compression tests were performed to supply data for the identification and verification of the model in the hot deformation and static recrystallization parts. Histograms of the grain size were measured after hot deformation and at different times after the end of deformation. Identification and validation of the model were performed. The validated model, which predicts evolution of heterogeneous multiphase microstructure, is the main output of our work. The model was implemented in the finite element program for hot rolling of plates and sheets and simulations of these processes were performed. The model’s capability to compare and evaluate various rolling strategies are demonstrated in the paper.

5

Comparison of statistical versus stochastic models for Work Index determination in quartz-marble mixtures

Perez Sebastián, Vargas Juan, Mellado Miguel, Quevedo Caro Ricardo, Jarufe Juan, Hurtado Cruz Juan Pablo, Muñoz Lagos Angélica Patricia, Jara Muñoz Pamela Paz

Mining Science

|

2021

|

Vol. 28

127--140

EN

The required work for ore trituration is represented by the Bond Work Index value and is determined by the grindability test for ball mills. This article examines the grinding behavior of ore blends with different mechanical properties in standard ball mills. The goal of this research was to compare statistic and stochastic models of the Work Index value for mixtures of quartz and marble at different proportions of each material. Quartz and marble bearing rocks were selected for this study due to the high difference between the Work Index value of each material, making the variability of the results more evident. Work Index values obtained for each mixture are shown, from which a deterministic model was proposed defined by data regression. The novelty of this research lies in the non-linear model, which was the best fit for the Work Index value of the quartz-marble blends. Our methodology allows us to build more accurate models and can be used for quartz-marble blends and other materials.

6

Cognitive technologies in the management and formation of directions of the priority development of industrial enterprises

Kwilinski Aleksy, Kuzior Aleksandra

Management Systems in Production Engineering

|

2020

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nr 2 (28)

133--138

EN

The possibilities of using cognitive technologies in the organization of systematic industrial enterprise management are described in the article. Strategic links are defined in the development of a system of stochastic models of enterprise management based on artificial intelligence. The possibility of introduction of the Perceptron model in the industrial enterprise management with the purpose of identification of "bottlenecks" in the functionality of business activity and improvement of procedures of decision-making in the framework of creation of the program of development and technical re-equipment of the enterprise is proven. The authors offered an organizational and economic mechanism of operation of an industrial enterprise, which includes new means of implementation of managerial actions through the use of a matrix of assessment of the level of implementation of cognitive technologies. The method of determining priority directions for the implementation of cognitive technologies at an enterprise was developed based on the results of the assessment of the depth of penetration of cognitive technologies and the result obtained from their implementation, which additionally takes into account the resource ratio of the implemented technologies defined as the ratio of estimates of the actual level of competencies to what is needed to work with new cognitive technologies, which allows to obtain the planned economic and organizational effect.

7

Improving the stochastic model for VRS network-based GNSS surveying

Jongrujinan Thanate, Satirapod Chalermchon

Artificial Satellites : Journal of Planetary Geodesy

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2019

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Vol. 54, No. 1

17--30

EN

The VRS network-based technique has become the main precise GNSS surveying method especially for medium-range baselines (approximately 20-70 km). The key concept of this approach is to use the observables of multiple reference stations to generate the network correction in the form of a virtual reference station for mitigating distance-dependent errors including atmospheric effects and orbital uncertainty at the user’s location. Numerous GNSS data processing strategies have been adopted in the functional model in order to improve both the positioning accuracy and the success of ambiguity resolution. However, it is impossible to completely model the aforementioned errors. As a result, the unmodelled residuals still remain in the virtual reference station observables when the least squares estimation is employed. An alternative approach to deal with these residuals is to construct a more realistic stochastic model whereby the variance-covariance matrix is assumed to be homoscedastic. This research aims to investigate a suitable stochastic model used for the VRS technique. The rigorous statistical method, MINQUE has been applied to estimate the variance-covariance matrix of the double-difference observables for a virtual reference station to rover baseline determination. The findings of the comparison to the equal-weight model and the satellite elevation-based model indicated that the MINQUE procedure could enhance the positioning accuracy. In addition, the reliability of ambiguity resolution is also improved.

8

A stochastic model for estimation of repair rate for system operating under performance based logistics

Kontrec N., Panić S., Petrović M., Milošević H.

Eksploatacja i Niezawodność

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2018

|

Vol. 20, no. 1

68--72

EN

Performance Based Logistics (PBL) concept has an aim to improve the system availability and it has been extensively researched in the recent years. These researches showed that inventory level does not impact system availability as much as component reliability and repair time in repairable system operating under PBL contract. Based on that, in this paper, we propose a new stochastic model for determination of annual repair rate for critical aircraft components in such system in order to achieve desired availability. The result obtained could be used for planning of base stock level and capacity of repair facilities.

PL

Koncepcja Logistyki Opartej na Wydajności (Performance Based Logistics, PBL), której celem jest poprawa gotowości systemów, została w ostatnich latach szeroko zbadana. Badania te wykazały, że w przypadku systemów działających w warunkach PBL, poziom zapasów nie wpływa na gotowość systemu w tak dużym stopniu jak niezawodność elementów składowych oraz czasy napraw. Opierając się na tej obserwacji, w niniejszym artykule proponujemy nowy model stochastyczny do określania rocznej intensywności napraw krytycznych elementów samolotu tworzących system tego typu. Model ten pozwala na osiągnięcie pożądanej gotowości. Uzyskany model może być wykorzystany do planowania bazowego poziomu zapasów oraz przepustowości zakładów remontowych.

9

Rainfall models in small catchments in the context of hydrologic and hydraulic assessment of watercourses

Gruss Łukasz, Wiatkowski Mirosław

Ecological Chemistry and Engineering. A

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2018

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Vol. 25, nr 1

19--27

EN

This paper presents a proposed application of methods for determining heavy rainfall in small ungauged agricultural catchments in lowland areas. Moreover, we discuss the methodology for a comprehensive hydrological and hydraulic analysis of the functioning of a small lowland watercourse. In order to properly (correctly) use the methods for determining heavy rainfall, a comprehensive workflow had to be created for the dimensioning of structures designed to evacuate rainfall water (i.e. drainage, irrigation and sewer systems), that could be used by designers and would account for the small water retention solutions. In the paper we propose methods for determining heavy rainfall that allow the management of rainfall water in small ungauged agricultural catchments in lowland areas. The calculations of the rainfall intensity with assumed duration times are proposed using three precipitation models: the Bogdanowicz and Stachy formula, the Lambor formula and the Woloszyn formula. The models of Lambor and Woloszyn are advantageous because they are local. On the other hand, the Bogdanowicz and Stachy formula is the recommended model for the dimensioning of structures intended to evacuate rainfall water; this formula makes use of the intensity of design storm in rural areas (p = 10 %). As an example of calculations, we present the initial rainfall intensity results and the values of runoff for a rainfall with the exceedance probability p = 10 % and the duration time 15, 30, 60 and 120 minutes, for the micro-catchment of the watercourse R-4 located in the Dobrzen Wielki commune, south-west of Poland. In the calculations each of the three formulae was used, but the highest values were obtained for the Bogdanowicz and Stachy formula. An analysis of the runoff values for each duration time reveals that the longer the duration time of rainfall, the lower the rainfall intensity. The runoff of precipitation water from the catchment was determined using the European standard EN 752:2008. Moreover, in order to properly select and dimension the retention reservoir for precipitation water the authors used the ATV-A117 guidelines and a study about this standard. The proposed methodology for the determination of heavy rainfall in small ungauged agricultural catchments in lowland areas for the purpose of rainfall water management could be of interest in practical water management applications.

PL

W niniejszej pracy przedstawiono propozycje zastosowania metod wyznaczania opadów nawalnych w małych niekontrolowanych zlewniach użytkowanych rolniczo, na terenach nizinnych. Ponadto w pracy przedstawiono metodykę wykonania kompleksowej analizy hydrologiczno-hydraulicznej funkcjonowania małego cieku nizinnego. Dla właściwego (poprawnego) stosowania metod wyznaczania opadów nawalnych konieczne było stworzenie kompleksowego schematu postępowania dla wymiarowania urządzeń odprowadzaj ących wody opadowe, tj. systemów melioracyjnych i kanalizacyjnych, który może być stosowany przez projektantów uwzględniając zastosowanie rozwiązania małej retencji wodnej. W pracy zaproponowano metody wyznaczania opadów nawalnych umożliwiających zagospodarowanie wód opadowych w małych niekontrolowanych zlewniach nizinnych na terenach rolniczych. Zaproponowano obliczenia natężenia deszczy przy założonych czasach ich trwania przy zastosowaniu 3 modeli opadów: wg Bogdanowicza i Stachego, Lambora oraz Wołoszyna. Zaletą stosowania modeli Lambora i Wołoszyna jest fakt, że są modelami lokalnymi. Natomiast zalecanym modelem w wymiarowaniu urządzeń odprowadzających wody opadowe, który wykorzystuje natężenie deszczu miarodajnego na terenach wiejskich (p = 10 %) jest model Bogdanowicza i Stachego. Jako przykład obliczeń przedstawiono wstępne wyniki natężenia deszczu i wartości odpływów dla deszczu o prawdopodobieństwie przewyższenia p = 10% i czasie trwania 15, 30, 60,120 minut dla mikrozlewni cieku R-4 zlokalizowanej w południowo – zachodniej Polsce w Gminie Dobrzeń Wielki. W obliczeniach zastosowano wszystkie wymienione modele, jednak najwyższe wartości uzyskano modelem Bogdanowicza i Stachego. Analiza wartości odpływów wskazuje, że im czas trwania deszczu jest dłuższy, tym mniejsze jest jego natężenie. Ustalono wartości odpływu wód opadowych ze zlewni przy zastosowaniu normy europejskiej EN 752:2008. Ponadto dla właściwego doboru i wymiarowania zbiornika do retencji wód opadowych autorzy zastosowali wytyczne normy ATV-A117 oraz opracowania poświęcone tej normie Zaproponowana w niniejszej pracy metodologia wyznaczania opadów nawalnych w małych niekontrolowanych zlewniach użytkowanych rolniczo, na terenach nizinnych, na potrzeby zagospodarowania wód opadowych, stanowi interesującą propozycję do wykorzystania w praktyce gospodarki wodnej.

10

Modelowanie struktury przepływu strumieni pojazdów na przykładzie ładunków z i do terminalu BCT

Stasiak N., Smolarek L.

Prace Naukowe Politechniki Warszawskiej. Transport

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2017

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z. 117

343--350

PL

W artykule przedstawiono model struktury przepływu strumieni pojazdów opracowany w oparciu o dane przepływu ładunków z i do terminalu BCT Gdynia. W pracy zastosowano model stochastyczny który może być wykorzystany do modelu symulacyjnego zaimplementowanego w programie PTV Vissim. Artykuł jest analizą ruchu samochodów ciężarowych wjeżdżających i wyjeżdżających z portu BCT w Gdyni w latach 2008-2016.

11

Application of Markov chains to a navigator visual attention model

Muczyński B., Gucma M., Bilewski M.

Zeszyty Naukowe Akademii Morskiej w Szczecinie

|

2016

|

nr 46 (118)

95--100

EN

This paper presents initial results from a series of eye-tracking experiments on a Full Mission Bridge simulator. The aim of this research was to develop a stochastic model of a navigator’s attention distribution during their navigational watch. Such model could be used as a tool for workload and usability studies for navigators and navigational equipment interfaces. A structure of the model is discussed together with the evaluation of Markov chains as a main modelling tool. Initial results are presented and discussed. It is suggested that 1st order Markov chains are not fully applicable for this problem. A combination of the 1st and higher-order Markov chains will be applied in the next stage of research.

12

Choosing the optimal strategy for information security in a business organization

Chojnacki A., Pieniążek G.

Computer Science and Mathematical Modelling

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2016

|

No. 3

13--21

EN

The paper describes the method of choosing the optimal strategy to implement security measures in a business organization. Strategies are categorized depending on time horizons, the history of threats and implemented security measures. Next, the method of choosing the optimal strategy for a business organization in a given context is outlined. Then this method is used to select the optimal strategy in a particular business context. The method is based on a deterministic time-based information security model, which was extended to a random model. With this simulation method, an organization can choose a strategy to implement security measures that best suits its needs. It is important for organizations to conduct an analysis of costs and threats in order to select appropriate safeguards.

PL

W artykule opisano strategie wdrażania zabezpieczeń w organizacji biznesowej. Strategie są sklasyfikowane w grupy według zależności od historii występowania zagrożeń oraz zależności od historii wdrażanych zabezpieczeń. Następnie przedstawiona jest metoda wyboru optymalnej strategii dla organizacji biznesowej, przy ustalonym kontekście. W kolejnym kroku wprowadzona metoda jest użyta do wyboru optymalnej strategii w przykładowym przypadku biznesowym. Metoda bazuje na deterministycznym, czasowym modelu bezpieczeństwa informacyjnego, który został rozszerzony do modelu losowego. Dzięki metodzie symulacyjnej organizacja może wybrać najlepszą, dla siebie, strategię wdrażania zabezpieczeń. Jest to istotne we współczesnych organizacjach, aby przeprowadzić analizę kosztów i ryzyka, w celu doboru odpowiednich zabezpieczeń.

13

Stohastic Model to Determine the Elements of the Production Cycle Time: Case of Serbian Textile Industry

Stanisavljev S., Ćoćkalo D., Klarin M., Spasojević B. V., Đorđević D.

Fibres & Textiles in Eastern Europe

|

2015

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Vol. 23, no. 5 (113)

23--29

EN

The paper presents an original method of determining the elements of the production cycle time by using the modified work sampling method applied to a textile factory. It is shown that the movement of the elements of time can be viewed as a process and in the mathematical sense can establish control limits of error of ± 3 SD. The mean time of the production cycle of the groups created by the number of pieces in the series – tpcu moving the hyperbolic function, which has the asymptote c, a function of the form tpcu = c + b/log n, where all groups of the production cycle in the mathematical sense do not act like strata but are function tpcu related to technology and deterministic factors of the production series.

PL

Artykuł przedstawia oryginalną metodę określania elementów trwania cyklu produkcyjnego przy zastosowaniu zmodyfikowanej metody podziału pracy w odniesieniu do przedsiębiorstwa produkującego tekstylia. Pokazano, że przemieszczanie elementów czasu cyklu produkcyjnego można rozpatrywać jako proces, w którym matematycznie ustawia się błąd ± 3s. Średni czas cyklu produkcyjnego poszczególnych grup określa się przez liczbę elementów uszeregowanych w serię. Poszczególne zależności systemu można opisać matematycznie.

14

Model liniowy i stochastyczny osiowosymetrycznego kontaktu skrętnego z uwzględnieniem sił tarcia i powierzchniowej chropowatości

Brzoza A.

Logistyka

|

2014

|

nr 3

756--765

PL

W artykule przedstawiono kontakt skrętny z uwzględnieniem sił tarcia i powierzchniowej chropowatości stosując model liniowy i stochastyczny. Oba podejścia podają ogólne rozwiązanie osiowosymetrycznego kontaktu skrętnego biorąc pod uwagę częściowe poślizgi i sprowadzają się do równań całkowych, które rozwiązywane są numerycznie. Podejścia różnią się od klasycznego rozwiązania, w którym używana jest teoria Hertza. Rezultaty są zgodne z wynikami dotyczącymi klasycznych zagadnień kontaktu skrętnego.

EN

The paper is concerned with the linear and stochastic modelling of a torsional contact, taking into account friction forces and boundary roughness. Both approaches provide a general solution to the problem of axially symmetric torsion contact, taking into consideration partial slip. The partial slip problem was reduced to integral equations, which were solved numerically. The approaches differ from the classical solution, in which the Hertz theory is used. The results are in agreement with the results provided by the classical solutions to torsional contact problems.

15

Model of operational changes in the combustion chamber tightness of a diesel engine

Koszałka G.

Eksploatacja i Niezawodność

|

2014

|

Vol. 16, no. 1

133--139

PL

W artykule przedstawiono wyniki badań szczelności komory spalania silnika o zapłonie samoczynnym w czasie długotrwałej eksploatacji. Badania przeprowadzono na 5 egzemplarzach sześciocylindrowego silnika wykorzystywanego do napędu samochodów ciężarowych. Zmiany szczelności w zakresie przebiegów 0–500 tys. km określono na podstawie wyników pomiarów: spadku ciśnienia z wykorzystaniem próbnika szczelności komory spalania, maksymalnego ciśnienie sprężania w cylindrach oraz natężenia przedmuchów spalin do skrzyni korbowej w różnych warunkach pracy silnika. Wyniki badań poddano analizie statystycznej. Opracowano stochastyczne modele zmian szczelności komory spalania silnika w funkcji przebiegu samochodu. Model opisuje przebieg wartości średniej wybranego parametru diagnostycznego w czasie oraz granic obszaru prawdopodobnych zmian tego parametru. Wyniki badań wykazały, że zarówno prędkość jak i charakter zmian w funkcji czasu eksploatacji były różne dla różnych parametrów. Najmniejszą dynamiką zmian wyróżniało się maksymalne ciśnienie sprężania (spadek o mniej niż 20% w zakresie przebiegów samochodu: 0–500 tys. km), średnią dynamiką – wskaźnik szczelności, a największą – natężenie przedmuchów spalin (3-krotny wzrost przy 2200 obr/min), przy czym dla dwóch pierwszych parametrów szybkość zmian zwiększała się wraz z przebiegiem samochodu, natomiast w przypadku przedmuchów spalin zmiany miały charakter liniowy. Wyznaczono również pola rozproszeń (zmian odchyleń standardowych) dla badanych parametrów diagnostycznych.

EN

The paper presents the results of tightness testing of an internal combustion engine combustion chamber during long-term operation. The tests were conducted on 5 six-cylinder diesel engines used in motor trucks. Changes in tightness for the distance range 0–500,000 km were determined based on the measurement results of the following: pressure drop measured using a cylinder leakdown tester, maximum compression pressure in the cylinders, and the blow-by flow rate at different engine operating conditions. The obtained test results were analyzed statistically. Stochastic models of changes in engine combustion chamber tightness versus distance traveled were developed. Each model describes the time history of the mean value of a selected diagnostic parameter and the limits of probable changes in this parameter. The test results have shown that both the rate and character of changes as a function of engine operation time differed depending on a parameter. The maximum compression pressure was characterized by the lowest dynamics of changes (a decrease by less than 20% for the distance range 0–500,000 km), the cylinder leakage was characterized by a moderate change dynamics, while the blow-by flow rate exhibited the highest dynamics of changes (a threefold increase at 2200 rpm). It should also be mentioned that in the case of the first two parameters, the rate of changes increased with the distance traveled, whereas in the case of the blow-by the observed changes were linear. Also, dispersion fields (i.e. changes in standard deviations) were calculated for the tested diagnostic parameters.

16

Critical case stochastic phylogenetic tree model via the Laplace transform

Bartoszek K., Krzemiński M.

Demonstratio Mathematica

|

2014

|

Vol. 47, nr 2

474--481

EN

Birth–and–death models are now a common mathematical tool to describe branching patterns observed in real–world phylogenetic trees. Liggett and Schinazi (2009) is one such example. The authors propose a simple birth–and–death model that is compatible with phylogenetic trees of both influenza and HIV, depending on the birth rate parameter. An interesting special case of this model is the critical case where the birth rate equals the death rate. This is a non–trivial situation and to study its asymptotic behaviour we employed the Laplace transform. With this, we correct the proof of Liggett and Schinazi (2009) in the critical case.

17

Fitting stochastic model into network traffic

Włodarski P.

Poznan University of Technology Academic Journals. Electrical Engineering

|

2013

|

No. 76

219--223

EN

This paper presents the results of fitting stochastic model into real network traffic. Accurate modeling of network traffic is the first step in optimizing resource allocation and Quality of Service requirements. Because measurements reveals presence of self-similarity and long-range dependence, unlike the models based on Poisson or Markov processes, fractional stochastic model seems to be a good approximation of network traffic, since it can capture both short-range and long-range dependence. A methods of generation as well as the model order selection and parameter estimation techniques will be presented and discussed.

18

Estimation of surrounding the spillage time

Mazurek J., Smolarek L.

Journal of Polish Safety and Reliability Association

|

2012

|

Vol. 3, No. 2

245--250

EN

This article presents the model of oil spill on the grid graph. We consider the three types of grid which parameters are corresponding to condition on the sea. The firefighter problem gives the algorithm to bound the oil spill. We compare the action starting time in model described by sum of N variables with the uniform probability distribution and the action starting time in real situation described by sum of two triangular random variables. For every type of grid we determine the Time Average of Going Around of the Spill.

19

Łańcuch Markowa jako model oddziaływań wyjątkowych

Pytlowany T.

Zeszyty Naukowe Politechniki Rzeszowskiej. Budownictwo i Inżynieria Środowiska

|

2011

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z. 58, nr 3/III

49-56

PL

W pracy przedstawiono krótki przegląd modeli probabilistycznych oddziaływań zmiennych, głównie klimatycznych oraz możliwości i konsekwencje wykorzystania modeli w postaci procesów stochastycznych Markowa. Jako podstawowy model przyjęto jednorodny łańcuch Markowa. Zawiera on kompletną informację dotyczącą częstości występowania poszczególnych stanów. Generując błądzenie losowe po stanach łańcucha obciążeń, można prognozować wartości okresu powrotu oddziaływań i oszacować wartości wystąpienia obciążeń ekstremalnych. Przedstawiony model wykorzystano do symulacji losowych stanów łańcucha Markowa opisującego obciążenie śniegiem gruntu. Szczególnie uwagę skupiono na obciążeniach, które odpowiadają obciążeniom charakterystycznym dla danej lokalizacji oraz tych, które przewyższają wartość obciążenia charakterystycznego. Uzyskane wyniki porównano ze standardowym modelem Gumbela, który jest powszechnie stosowany do estymacji parametrów rozkładów oddziaływań klimatycznych na konstrukcje budowlane.

EN

The paper presents issues related to loads of climate actions. An assessment of the possibilities and consequences of using the stochastic Markov chain model to predict return time T of climate actions was presented. Moreover, the author presents a model to estimate the limits of exceptional probability (extreme) of snow load S in subsequent cycles of discrete sampling which generates some random walk on the states of the stochastic chain load. Simulations of the chain states were shown in an example of four zones of snow load.

20

Solution of optimal control problem for the three-level HM-network. Part 1

Matalytski M., Kiturko O.

Prace Naukowe Instytutu Matematyki i Informatyki Politechniki Częstochowskiej

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2011

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Vol. 10, nr 1

163-174

EN

We studied the three-level exponential HM queueing network with one type of requests and incomes, which is a stochastic model for goods transport in a logistics transport system. We obtained a system of difference equations for the expected income of the central system with and without a reduction of future income to the current time in the case of a finite and infinite control horizon maximizing the expected income of the central system. These problems are proposed to be solved by the method of complete enumeration control strategies.