Wyniki wyszukiwania - BazTech

1

On the theory of order statistics of the flexible Lomax distribution

Jamal Farrukh, Ijaz Muhammad, Mustafa Ghulam, Khan Sadaf, Shafiq Shakaiba

Operations Research and Decisions

|

2024

|

Vol. 34, No. 2

33--45

EN

This paper studies the flexible Lomax distribution’s order statistics with graphical and numerical findings. Along with the quantitative measurements, some plots are furnished, including those for the skewness and kurtosis measures. We will dwell on the numerous results that relate to statistics of moments of order. We consider the single and product moment of order statistics from the new distribution. Further, we establish some recurrence relation for single moments of order statistics. We have sought to apply the derived relations to empirically evaluate the moments of smallest (largest) order statistics to establish well-known moments and related measures. For order statistics of a flexible Lomax distribution, exact analytical expressions of entropy, residual entropy, and past latent entropy are determined.

2

Reliability analysis of subway sliding plug doors based on improved FMECA and Weibull distribution

Wang Weibo, Liu Wenxiu, Fang Yu, Zheng Yongkang, Lin Chuan, Jiang Yonghua, Liu Dong

Eksploatacja i Niezawodność

|

2024

|

Vol. 26, no. 2

art. no. 178275

EN

Using traditional failure mode effects and criticality analysis (FMECA) to analyze the hazard of subway sliding plug door system, there are problems such as easy-to-take repetitive values, irrational allocation of expert's weights, and failure to consider the weights of evaluation factors. To address the above problems, this paper proposes an improved FMECA by using linear interpolation to increase the differentiation of the same fault probability occurrence among various fault modes. Apply the dependent uncertain ordered weighted averaging (DUOWA) algorithm to assign weights to different experts dynamically. The analytic hierarchy process (AHP) is used to endow weights to diverse evaluation factors to make them more suitable for engineering needs. We collected 1,836 days of metro train operation records from the Shanghai subway manufacturing plant and studied 17 common faults. Next, use a reliability-centered maintenance (RCM) strategy to determine maintenance periods for different fault modes. Finally, through the Weibull distribution fitting test, the fault rate function of the door is obtained, and the remaining useful life (RUL) of the door is predicted. The consistency between the vulnerable parts obtained by our proposed method and the statistics of the maintenance records of the subway sliding plug door verifies the effectiveness and reliability of our improved FMECA.

3

Study of the flow field and permeability characteristics in the goaf using the OpenPNM package

Gao Ke, Li Qiwen, Shi Lianzeng, Yang Aobo, Qi Zhipeng

Archives of Mining Sciences

|

2024

|

Vol. 69, no. 1

51--66

EN

The roof-caving step scale goaf behind the working face is sensitive to the region’s spontaneous combustion and gas concentration distribution, including many rock block cracks and holes. A severe deviation from the dynamics of fluids in porous media by representative element volume (REV), leading to the results of Computational Fluid Dynamics (CFD) simulation, has a significant error. A heterogeneous two-dimensional pore network model was established to simulate the goaf flow accurately. The network was first created using the simple cubic lattice in the OpenPNM package, and the spatial distribution of the “O-ring” bulking factor was mapped to the network. The bulking factor and Weibull distribution were combined to produce the size distribution of the pore and throat in the network. The constructed pore network model was performed with single-phase flow simulations. The study determined the pore structure parameters of the pore network through the goaf’s risked falling characteristics and described the flow field’s distribution characteristics in the goaf. The permeability coefficient increases as pore diameter, throat diameter, pore volume and throat volume increase and increases as throat length decreases. The correlation between throat volume and permeability coefficient is the highest, which indicates that the whole throat is the main control factor governing the air transport capacity in the goaf. These results may provide some guidelines for controlling thermodynamic disasters in the goaf.

4

Numerical investigation of production-related characteristics regarding their influence on the fatigue strength of additively manufactured components

Zeißig Michaela, Jablonski Frank

Acta Mechanica et Automatica

|

2023

|

Vol. 17, no. 2

288--291

EN

In order to further enhance the application of additive manufacturing (AM) processes, such as the laser powder bed fusion (L-PBF) process, reliable material data are required. However, the resulting specimen properties are significantly influenced by the process parameters and may also vary depending on the material used. Therefore, the prediction of the final properties is difficult. In the following, the effect of residual stresses on the fatigue strength of 316L steel, a commonly used steel in AM, is investigated using a Weibull distribution. The underlying residual stress distributions as a result of the building process are approximated for two building directions using finite element (FE) models. These imply significantly different distributions of tensile and compressive residual stresses within the component. Apart from the residual stresses, the impact of the mean stress sensitivity is discussed as this also influences the predicted fatigue strength values.

5

Estimation of Weibull distribution parameters based on sequences of minimal repairs

Malinowski Jacek

Safety and Reliability of Systems and Processes

|

2022

|

Summer Safety and Reliability Seminar 2022

163--172

EN

A new method of estimating the scale and shape parameters of the Weibull distribution is presented. According to this method, a Weibull distributed time-to-failure (TTF) of a test item is measured m times. It undergoes a minimal repair after each of the first m-1 failures, and is put out of use after the m-th failure. This procedure is repeated n times. Based on m TTFs of one test item, which are neither independent nor identically distributed (IID), the maximum likelihood estimators (MLE) of the scale and shape parameters, called n m-sample estimators, are obtained. The accuracy of the m-sample estimators is low, however, it can be improved by using the mean values of their n IID realizations as more precise estimators. The latter are called n·m-sample estimators, have the same biases as the respective m-sample ones, but their variances are n times smaller. Interestingly enough, the n·m-sample estimators of the scale and shape parameters, as well as their biases, are given by relatively simple explicit formulas. This is somewhat unexpected in view of the fact that the standard MLE of the shape parameter, based on IID TTFs of non-repairable test items, is obtained from an equation that cannot be solved analytically.

6

Prediction model of the pandemic spreading based on weibull distribution

Guľáš Ľuboš, Talian Matej, Szabo Stanislav, Semrádová Beáta

Management Systems in Production Engineering

|

2022

|

nr 2 (30)

179--186

EN

Pandemics have the potential to cause immense disruption of our everyday activities and has impact on the communities and societies mainly through the restrictions applied to the business activities, services, manufacturing, but also education, transportation etc. Therefore, it is important to create suitable prediction models to establish convenient methods for the planning of the operations and processes to cope with the difficulty. In this paper, the prediction model for the spread of the viral disease in term of the estimated maximal weekly confirmed cases and weekly deaths using the Weibull distribution as a theoretical model for statistical data processing is presented. The theoretical prediction model was applied and confirmed on the data available for the whole world and compared to the situation in Europe and Slovakia for the pandemic waves and can be used for the more precise prediction of the pandemic situation and to enhance planning of the activities and processes regarding to the restrictions applied during the worsening pandemic situation.

7

A study of health management of LWD tool based on data-driven and model-driven

Li Hui, He Zi Hua, Zhang Yu ting, Feng Jin, Jian Zun Yi, Jiang Yi Bo

Acta Geophysica

|

2022

|

Vol. 70, no 2

669--676

EN

Electromagnetic wave logging-while-drilling (LWD) tool plays an important role in unconventional oil and gas exploitation and deep-sea oil and gas resource exploration process. The reliability such as reliable life and durability of the tool can control drilling efficiency and production cost in extreme environmental conditions. In this paper, main faults of the electromagnetic wave LWD tool have been analyzed when it working to the drilling site. Failure time of antenna coils, circuit boards, and power supply have been recorded. Therefore, failure mode and failure mechanism can be analyzed of the tool. Secondly, a fault analysis model of electromagnetic wave LWD tool based on Weibull distribution model has been built up, and by using this fault analysis model the reliable life and the remaining useful life of antenna system can be calculated. The last, the goodness-of-ft test can be operated to Weibull distribution model by using Kolmogorov–Smirnov test. Study results show that the reliability and the law of fault occurrence of electromagnetic wave LWD tool can be directly reflected. And it has practical significance to reliability evaluation of the instrument system and joint optimization of safe operation and maintenance of the tool.

8

Comparison of methods applied to measuring the lightning impulse breakdown voltage of insulating pressboard impregnated with mineral oil and natural ester

Klarecki Artur, Rózga Paweł, Stuchała Filip

Metrology and Measurement Systems

|

2021

|

Vol. 28, nr 4

693--709

EN

The aim of this paper is to compare three different methods of analysis of results of lightning impulse breakdown voltage measurements of solid materials such as insulating pressboard. These three methods are the series method, the step method and the up-and-down method which are applied to withstand voltage estimation commonly in high voltage engineering. To obtain the data needed for the analysis a series of experimental studies was carried out. It included studies of mineral oil and natural ester impregnating 1 mm of thick cellulose-based pressboard. In order to show the distribution of breakdown voltage the Weibull distribution was additionally applied in data analysis. The results were also assessed from the viewpoint of dielectric liquid used for impregnation. The studies carried out showed that series and step methods give comparable results opposite to the up-and-down method. The latest overstates the results for mineral oil impregnated pressboard and understates for natural ester impregnated pressboard when juxtaposing them with the rest of the methods applied. In addition, there is lack of possibility to assess the withstand voltage for the up-and-down method directly from the vector of random variable. It is possible only as a result of a specially developed equation which always arouses doubt. From the methods applied it seems that the step method can be a great substitution for the series method as intuitive, fast in application and limiting the number of samples in solid insulation material testing.

9

A method for estimating the probability distribution of the lifetime for new technical equipment based on expert judgement

Andrzejczak Karol, Bukowski Lech

Eksploatacja i Niezawodność

|

2021

|

Vol. 23, no. 4

757--769

EN

Managing the exploitation of technical equipment under conditions of uncertainty requires the use of probabilistic prediction models in the form of probability distributions of the lifetime of these objects. The parameters of these distributions are estimated with the use of statistical methods based on historical data about actual realizations of the lifetime of examined objects. However, when completely new solutions are introduced into service, such data are not available and the only possible method for the initial assessment of the expected lifetime of technical objects is expert methods. The aim of the study is to present a method for estimating the probability distribution of the lifetime for new technical facilities based on expert assessments of three parameters characterizing the expected lifetime of these objects. The method is based on a subjective Bayesian approach to the problem of randomness and integrated with models of classical probability theory. Due to its wide application in the field of maintenance of machinery and technical equipment, a Weibull model is proposed, and its possible practical applications are shown. A new method of expert elicitation of probabilities for any continuous random variable is developed. A general procedure for the application of this method is proposed and the individual steps of its implementation are discussed, as well as the mathematical models necessary for the estimation of the parameters of the probability distribution are presented. A practical example of the application of the developed method on specific numerical values is also presented.

10

Application of Python libraries for variance, normal distribution and Weibull distribution analysis in diagnosing and operating production systems

Chmielowiec Andrzej, Klich Leszek

Diagnostyka

|

2021

|

Vol. 22, No. 4

89--105

EN

The use of statistical methods in the diagnosis of production processes dates back to the beginning of the 20th century. Widespread computerization of processes made enterprises face the challenge of processing large sets of measurement data. The growing number of sensors on production lines requires the use of faster and more effective methods of both process diagnostics and finding connections between individual systems. This article is devoted to the use of Python libraries to effectively solve some problems related to the analysis of large data sets. The article is based on the experience related to data analysis in a large company in the automotive industry, whose annual production reaches 10 million units. The methods described in this publication were the basis for the initial analysis of production data in the plant, and the obtained results fed the production database and the created automatic anomaly detection system based on artificial intelligence algorithms.

PL

Wykorzystywanie metod statystycznych w diagnostyce procesów produkcyjnych sięga swoimi korzeniami początków XX wieku. Powszechna informatyzacja procesów postawiła przedsiębiorstwa przed wyzwaniem przetwarzania dużych zbiorów danych pomiarowych. Rosnąca liczba czujników na liniach produkcyjnych wymaga stosowania szybszych i skuteczniejszych metod zarówno diagnostyki procesu, jak i znajdowania powiązań pomiędzy poszczególnymi systemami. Niniejszy artykuł został poświęcony wykorzystaniu bibliotek języka Python do efektywnego rozwiązywania niektórych problemów związanych z analizą dużych zbiorów danych pomiarowych. Artykuł powstał na bazie doświadczeń związanych z analizą danych w dużym przedsiębiorstwie branży motoryzacyjnej, którego roczna produkcja sięga 10 milionów sztuk. Opisane w niniejszej publikacji metody stanowiły podstawę wstępnej analizy danych produkcyjnych we wspomnianym zakładzie, a uzyskane wyniki zasiliły bazę danych produkcyjnych oraz tworzony system automatycznego wykrywania anomalii oparty na algorytmach sztucznej inteligencji.

11

Statistical damage constitutive model based on the Hoek-Brown criterion

Chen Yifan, Lin Hang, Wang Yixian, Xie Shijie, Zhao Yanlin, Yong Weixun

Archives of Civil and Mechanical Engineering

|

2021

|

Vol. 21, no. 3

556--564

EN

The constitutive models of rock are essentially the general depictions of the mechanical responses of rock mass under complex geological environments. Statistical distribution-based constitutive models are of great efficacy in reflecting the rock failure process and the stress–strain relation from the perspective of damage, while most of which were achieved by adopting Drucker–Prager criterion or Mohr–Coulomb criterion to characterize microelement failure. In this study, underpinned by Hoek–Brown strength criterion and damage theory, a new statistical damage constitutive model, which is simple in terms of model expression and capable of reflecting the strain softening characteristics of rock in post-peak stage, was established. First, the rock in the failure process was divided into infinite microelements including elastic part satisfying Hooke’s law and damaged part retaining residual strength. Based on strain equivalence hypothesis, the relation between rock microelement strength and damage variable was derived. By assuming the statistical law of microelement strength obeying Weibull distribution and the microelement failure conforming to Hoek–Brown criterion, the new statistical damage constitutive model based on Hoek–Brown criterion was, therefore, gained. The mathematical expressions of the corresponding model parameters were subsequently deduced in accordance with the geometric characteristics of the deviatoric stress–strain curve. Last, the existing conventional triaxial compression test data of representative rock samples under different confining stresses were employed to compare with the theoretical curves by proposed model, the consistency between which was quantified by utilizing the correlation factor evaluation method. The result indicated that the proposed model could well describe the entire stress–strain relationship of rock failure process and manifest the characteristics of rock residual strength. It is of great significance to the researches on rock damage and softening issues and rock reinforcement treatments.

12

Analiza wydajności energetycznej dwuwirnikowej turbiny wiatrowej o pionowej osi obrotu

Bugała Artur, Bednarek Karol

Przegląd Elektrotechniczny

|

2020

|

R. 96, nr 1

206--209

PL

W pracy włączono sie w powszechnie prowadzone rozważania dotyczące ekologicznych aspektów wytwarzania energii elektrycznej. Bardziej szczegółowo zajęto sie wydajnością energetyczną turbin wiatrowych, przy czym skupiono się głównie na turbinach wiatrowych małej mocy o pionowej osi obrotu. Analizy przeprowadzono dla lokalizacji systemu w mieście Poznań. W końcowej części porównano własności użytkowe turbin o pionowej osi obrotu (VAWT) z powszechnie stosowanymi turbinami o poziomej osi obrotu (HAWT).

EN

The study joins the commonly conducted considerations regarding ecological aspects of electricity generation. The energy efficiency of wind turbines was analyzed in details, with a focus on low power wind turbines with a vertical axis of rotation. The analyzes were carried out for the system located in the city of Poznań. Finally, the performance characteristics of vertical rotation axis wind turbines (VAWT) were compared with commonly used horizontal axis wind turbines (HAWT).

13

Verification of the Methods for Calculating the Probable Maximum Flow in the Widawa River in the Aspect of Water Management in the Michalice Reservoir

Gruss Łukasz, Wiatkowski Mirosław, Buta Bogna, Tomczyk Paweł

Rocznik Ochrona Środowiska

|

2019

|

Tom 21, cz. 1

566-585

EN

Flows with a given probability of exceedance are important from the point of view of water management, especially in water reservoirs. By determining these flows, it is possible to design a reservoir adapted to local conditions that will operate in line with the assumed function. Various methods exist in the world for determining the probable maximum flows; these methods are based on various assumptions. The aim of the article is to verify and assess the applicability of the Flood Frequency Analysis (FFA) and the IMGW method for use in catchments of controlled rivers where a retention reservoir was built during the hydrological observation period. This is important in updating the water management instructions and in designing new retention reservoirs. The authors undertook to investigate whether a series of maximum flows prepared for the IMGW method allows one to recognize the regime change, caused by the construction of the retention reservoir, in the water gauge Zbytowa profile on the Widawa River, using the Mann-Kendall test. The following distributions were used in the study: Pearson type III, log-normal and Weibull. The Mann-Kendall test showed homogeneity of three observational series: 1971-2000, 2001-2017 and 1971-2017 prepared for the FFA method despite the fact that in 2001 the Michalice retention reservoir was commissioned on the Widawa river and the water management in the basin changed this watercourse. However, the observational series prepared for the IMGW method were homogenous only prior to the construction of the reservoir (1971-2000). The observational series prepared in this way enabled the Mann-Kandall test to exclude the homogeneous series caused by the regime change as a result of the construction and operation of the Michalice retention reservoir. Only after the construction of the retention reservoir the observational series from the winter half-year were homogeneous. This is due to the fact that the flows in the winter half-year are definitely lower than those in the summer half-year. The best-fitting distribution for the empirical distribution for the Widawa (the Zbytowa profile) in the analyzed series is a log-normal distribution that can be used to calculate the probable maximum flows needed to update the reservoir's water management instructions. The Wilcoxon test showed no difference between the calculation methods analyzed and used to estimate the probable maximum flows in the Zbytowa profile on the Widawa river. Therefore, as a method for calculating the probable maximum flows for the Widawa river (the Zbytowa profile) in the aspect of managing the Michalice reservoir or some other river with controlled catchment and parameters similar to those of the Widawa (in the Zbytowa profile), one can recommend either of the two analyzed methods: both FFA and IMGW.

PL

Przepływy o zadanym prawdopodobieństwie przewyższenia są istotne z punktu widzenia gospodarowania wodami na zbiornikach wodnych. Dzięki wyznaczeniu tych przepływów możliwe jest zaprojektowanie zbiornika dostosowanego do lokalnych warunków, który będzie funkcjonował zgodnie z założoną funkcją. Na świecie obowiązują różne metody wyznaczania przepływów maksymalnych prawdopodobnych, które bazują na odmiennych założeniach. Celem artykułu jest weryfikacja i ocena możliwości zastosowania metody Flood Frequency Analysis (FFA) i metody IMGW do zastosowania w zlewniach rzek kontrolowanych, na których w okresie obserwacji hydrologicznej wybudowano zbiornik retencyjny. Ma to znaczenie w aktualizacji instrukcji gospodarowania wodą oraz w projektowaniu nowych zbiorników retencyjnych. Autorzy podjęli się zbadania czy serie przepływów maksymalnych przygotowane dla metody IMGW pozwalają na rozpoznanie zmiany reżimu, w rzece Widawie w przekroju Zbytowa, przy pomocy testu Manna-Kendalla, spowodowanej wybudowaniem zbiornika retencyjnego. W pracy wykorzystano następujące rozkłady: Pearsona typ III, logarytmiczno-normalnego oraz rozkład Weibulla. Test Manna-Kendalla wykazał jednorodności trzech serii obserwacyjnych: 1971-2000, 2001-2017 i 1971-2017 przygotowanych dla metody FFA pomimo, że na rzece Widawie w 2001 roku został oddany do eksploatacji zbiornik retencyjny Michalice i zmieniło się gospodarowanie wodą w zlewni tego cieku. Natomiast serie obserwacyjne sporządzone dla metody IMGW były jednorodne jedynie przed budową zbiornika (okres 1971-2000). Tak przygotowana seria obserwacyjna umożliwiła testowi Manna-Kandalla wykluczyć serie jednorodne spowodowane zmianą reżimu na skutek wybudowania i pracy zbiornika retencyjnego Michalice. Jedynie po budowie zbiornika retencyjnego serie obserwacyjne z półrocza zimowego były jednorodne. Jest to spowodowane tym, że przepływy w półroczu zimowym są zdecydowanie niższe niż przepływy w półroczu letnim. Najbardziej dopasowanym rozkładem zmiennej Qmax dla rzeki Widawy (profil Zbytowa) w analizowanych seriach jest rozkład logarytmiczno-normalny, który może zostać wykorzystany do obliczeń przepływów maksymalnych prawdopodobnych potrzebnych do aktualizacji instrukcji gospodarki wodnej zbiornika. Test Wilcoxona wykazał, brak różnic pomiędzy analizowanymi metodami obliczeniowymi użytymi do obliczeń maksymalnych przepływów o określonym prawdopodobieństwie przewyższenia rzeki Widawy (profil Zbytowa), dlatego też jako metodę do obliczania przepływów maksymalnych prawdopodobnych w zlewni rzeki Widawy w profilu Zbytowa w aspekcie gospodarowania wodami zbiornika retencyjnego Michalice lub innej rzeki o zlewni kontrolowanej o podobnych parametrach zlewni co zlewnia rzeki Widawa (profil Zbytowa), można wskazać obie analizowane metody: FFA i IMGW.

14

Fatigue life prediction of glass reinforced composite materials using Weibull distribution

Djeghader Djamel, Redjel Bachir

Composites Theory and Practice

|

2019

|

R. 19, nr 3

100-106

EN

Cyclic bending fatigue tests were conducted on randomly oriented short multidirectional glass fiber-reinforced polyester matrices. Standard test specimens were manufactured in rectangles with a volume fraction of 40% glass fibers. The experimental fatigue life results were fitted using S-N curves, which are based on power function equations. S-N curves, which are characterized by important and significant scatter over the lifetime, were correlated using the two-parameter Weibull distribution function to determine the probability of failure and to plot the S-N curves at different reliability levels. These curves are of considerable design value in practical applications of composite materials and predict the sample response at the time of service depending on the degree of reliability.

15

Ocena wytrzymałości granul nawozów mineralnych przy wykorzystaniu rozkładu Weibulla

Przystupa W., Rusek P., Nowak J.

Przemysł Chemiczny

|

2018

|

T. 97, nr 12

2124--2127

PL

Przedstawiono wyniki badań wytrzymałości na ściskanie granul superfosfatu, polifoski oraz Salmagu. Do analizy otrzymanych danych zastosowano dwuparametrowy rozkład Weibulla. Parametry rozkładu wyznaczono metodą graficzną. Sporządzono empiryczne dystrybuanty siły niszczącej pojedyncze granule, na podstawie których można określić prawdopodobieństwo ich zniszczenia.

EN

Granules of 3 fertilizer types (superphosphate, NPKS and NCaMg) were divided into 7 size fractions (1–6 mm) by using a sieve analyzer and then the force destroying the granules of each fraction of fertilizers tested was detd. by using a head with a variable pressure. Two-parameter Weibull distribution was used to analyze the results to det. the probability of destruction of each granule fraction as a function of the force acting on it.

16

Markov reliability model for heat meters

Pałasz P., Żurek J., Przysowa R.

Journal of KONBiN

|

2018

|

No. 45

83--96

EN

The reliability of thermal energy meters is analysed using the Markov model which describes the operation of these meters in a large number of apartments and offices by a media accounting company. The data has been extracted from a relational database storing information on the operation, installation and exchange of these measures from the last 10 years. The built Markov model turned out to be ergodic, which allowed determining its limiting distribution. In addition, the probability distributions for the cumulated consumption were determined in the work - separately for all meters and meters' failures.

PL

Tematem publikacji jest analiza niezawodności mierników energii cieplnej z użyciem modelu Markowa. Omawiany model został zbudowany w oparciu o badanie procesu użycia tychże mierników w firmie zajmującej się rozliczaniem mediów. Dane zostały wyekstrahowane z relacyjnej bazy danych przechowującej informacje o eksploatacji, instalacji i wymianie tych mierników z ostatnich 10 lat. Zbudowany model Markowa okazał się być ergodyczny, co pozwoliło na wyznaczenie jego rozkładu granicznego. Oprócz tego w pracy wyznaczono rozkłady prawdopodobieństwa dla przebiegu mierników ciepła – osobno dla wszystkich mierników i osobno dla mierników uległych awarii.

17

Critical Condition of Sewage Network

Raganowicz A.

Geomatics and Environmental Engineering

|

2018

|

Vol. 12, no. 1

91--108

PL

W artykule przedstawiono metodykę modelowania statystyczno-stochastycznego krytycznego stanu technicznego sieci kanalizacyjnej. Stan krytyczny badanego obiektu zdfiniowano jako przejście przewodów kanalizacyjnych od stanu konserwycji do stanu rehabilitacji technicznej. Badania modelowe obejmują kolektory betonowe DN 600/1100, DN 800/1200, DN 900/1350 mm, przewody kamionkowe DN 200–400 mm i przyłącza kamionkowe DN 100-200 mm. Modelowanie statystyczne oparto na rozkładzie Weibulla, a estymację jego parametrów na metodzie momentów. Natomiast modelowanie stochastyczne przeprowadzono na podstawie kombinacji rozkładu Weibulla z metodą Monte-Carlo. Ustalenie krytcznego stanu pozwala na szczegółową ocenę techniczną badanej sieci kanalizacyjnej.

EN

The paper presents the methodology formulated for determining the critical technical state of operating sewer pipes that is based on statistical-stochastic modeling. It describes the theoretical boundary between the area comprised of pipes that do not show any damage or require only maintenance measures and the area comprised of pipes that require renovation. The study includes concrete collectors with dimensions of DN 600/1100, 800/1200, and 900/1350 mm, stoneware pipes of with diameters ranging from DN 200 mm to 400 mm, and stoneware connections (DN 100–200 mm). The statistical modeling phase was carried out using Weibull distribution, and its parameters were evaluated by the method of moments. In contrast, the stochastic studies were based on a combination of the method of moments and Monte-Carlo mathematical simulations. On the basis of the proposed forecasting, it was possible to carry out a qualitative and quantitative analysis of the technical condition of the exploited sewage systems. Quantitative analysis helped us to determine the necessary range of renovation, which is an important operation component of every linear sewage network.

18

Comparison of Design Wave Heights Determined on the Basis of Long- and Short-term Measurement Data

Szmytkiewicz M., Szmytkiewicz P., Marcinkowski T.

Archives of Hydro-Engineering and Environmental Mechanics

|

2018

|

Vol. 65, nr 2

123--142

EN

The objective of this study is to determine differences between design wave heights determined on the basis of short- and long-term wave trains. Wave parameters measured over a period of 7.47 years in the vicinity of Coastal Research Station Lubiatowo were used as short-term wave data, while wave parameters determined through the so-called wave reconstruction for a period of 44 years for the same region and depth were used as long-term wave data. The results of the calculations lead to the conclusions the significant wave height distributions obtained for short and long-term wave data are similar.

19

Ocena niezawodności wytrzymałościowej drewna litego w warunkach działania czynnika termicznego

Pieniak Daniel, Pietrzyk Piotr, Walczak Agata

Zeszyty Naukowe / Wyższa Szkoła Oficerska Sił Powietrznych

|

2017

|

Nr 2

173--183

PL

W artykule przedstawiono analizę niezawodności wytrzymałościowej drewna litego w symulowanych warunkach termicznych pożaru. Uszkodzenie struktury drewna w warunkach pożaru najczęściej związane jest ze spadkiem wytrzymałości. Ponadto zmniejsza się nośność, w związku ze zmianą przekroju materiału. W przedmiotowych badaniach zakres temperatury i sposób obróbki termicznej zbliżony był do występującego w niezwęglonej części elementu konstrukcyjnego. Nie analizowano wpływu zwęglania. Analizę niezawodności przeprowadzono na podstawie wartości wytrzymałości uzyskanych w próbie zginania trójpunktowego drewna litego, w warunkach jednoczesnego działania czynnika termicznego. Niezawodność wytrzymałościowa rozumiana była jako prawdopodobieństwo nieosiągnięcia przez drewniany element konstrukcyjny wartości wytrzymałości przekraczających przyjęte dopuszczalne granice. W pracy oszacowano prawdopodobieństwo zniszczenia drewna litego w zależności od wartości naprężenia i temperatury. Na podstawie parametru rozkładu Weibulla, określono niepewność zachowania nośności.

EN

The paper presents an analysis of solid wood strength reliability in simulated fire conditions. The damage to the wood structure caused by fire heat is usually related to 183 decreasing strength. Additionally, carrying capacity is reduced due to the change of the cross–section of the material. In the research, the temperature ranges and the manner of thermal processing were similar to those found in the uncharred structural element. The influence of charring was not analysed. The reliability analysis was based on the strength values obtained in solid wood three-point bending tests carried out in a high temperature. The strength reliability was construed as the likelihood of the strength values not exceeding the adopted and admissible limits. In the paper, the likelihood of solid wood failure depending on stress values and temperature was estimated. Based on the Weibull distribution parameter, uncertainty of carrying capacity was determined.

20

Analiza wpływu prędkości wiatru na generację mocy na przykładzie farmy wiatrowej

Malska W., Mazur D.

Przegląd Elektrotechniczny

|

2017

|

R. 93, nr 4

54--57

PL

Elektrownie wiatrowe jako jedne ze źródeł energii odnawialnej rozwijają się dynamicznie, a ich specyficzny charakter pracy uzależniony jest parametrami i zmiennością wiatru. W artykule zaprezentowano analizę wpływu prędkości wiatru na generację mocy na przykładzie farmy wiatrowej. Rozwój energetyki opartej na odnawialnych źródłach energii sprawia, że analizy zmienności produkcji energii elektrycznej przez farmy wiatrowe mają znaczenie w aspekcie sprzedaży i wprowadzania energii elektrycznej do sieci przesyłowej.

EN

Wind power as one of the renewable energy sources are developing rapidly, and the specific nature of the work depends on the performance and volatility of the wind. The article presents an analysis of the impact of wind speed for power generation on the example of a wind farm. The development of energy based on renewable energy sources makes the analysis of the variability of the production of electric energy by wind farms are important in terms of sales and the introduction of electric energy to the grid.