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    Wyświetlanie 1-23 z 23
    Tytuł:
    Effectiveness of Monte Carlo Simulations of the S&P 500 Index before and after the Outbreak of the SARS-COV-2 Pandemic*
    Efektywność symulacji Monte Carlo indeksu S&P 500 przed ogłoszeniem i po ogłoszeniu pandemii SARS-COV-2
    Autorzy:
    Nawrocki, Piotr
    Powiązania:
    https://bibliotekanauki.pl/articles/16472961.pdf
    Data publikacji:
    2023
    Wydawca:
    Wydawnictwo Uniwersytetu Ekonomicznego we Wrocławiu
    Tematy:
    Monte Carlo (MC) method
    Black-Scholes (B-S) model
    index simulation
    COVID-19 pandemic
    metoda Monte Carlo
    model Blacka-Scholesa
    symulacja indeksu
    pandemia COVID-19
    Opis:
    Risk analysis is an integral part of studying the behavior of financial markets. Crises and emergencies challenge analysts trying to predict the value of stock indices by questioning their assumptions. One such event was the coronavirus pandemic, which undoubtedly affected our economy. The purpose of this study was to examine the impact of the COVID-19 pandemic on the US market and to assess the change in effectiveness of the Monte Carlo method due to the pandemic. The study was realized with 12 MC simulations of daily S&P 500 index prices using historical data from 11.03.2015 to 11.03.2021. The negative impact of the pandemic on the accuracy of MC simulations was observed, lowering the confidence of the results. Changes in sensitivity depending on the chosen time period were also detected. The results may prompt consideration of modifying MC simulations during instability and provide information indicating the use of shorter time series to improve simulation efficiency during crises.
    Analiza ryzyka jest integralną częścią badania zachowania rynków finansowych. Sytuacje kryzysowe stanowią wyzwanie dla analityków próbujących przewidzieć wartość indeksów giełdowych, kwestionując ich założenia. Jednym z takich wydarzeń była pandemia koronawirusa, która niewątpliwie wpłynęła na naszą gospodarkę. Celem niniejszego badania było zbadanie wpływu pandemii COVID-19 na rynek USA oraz ocena zmiany efektywności metody Monte Carlo na skutek pandemii. Badanie zostało zrealizowane za pomocą 12 symulacji MC dziennych cen indeksu S&P 500 przy użyciu danych historycznych między 11.03.2015 a 11.03.2021. Zaobserwowano negatywny wpływ pandemii na efektywność symulacji, obniżający wiarygodność wyników. Wykryto również zmiany czułości w zależności od wybranego okresu. Wyniki mogą skłonić do rozważenia modyfikacji symulacji MC podczas braku stabilności i dostarczyć informacji skłaniających do skorzystania z krótszych szeregów czasowych w celu poprawy efektywności symulacji podczas kryzysów.
    Źródło:
    Financial Sciences. Nauki o Finansach; 2023, 28, 1; 1-16
    2080-5993
    2449-9811
    Pojawia się w:
    Financial Sciences. Nauki o Finansach
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Singular Vectors in Acoustic Simulation Tests of St. Paul the Apostle Church in Bochnia
    Autorzy:
    Kosała, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/177255.pdf
    Data publikacji:
    2012
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    acoustic quality
    index method
    churches
    singular value decomposition (SVD)
    acoustics adaptation
    Opis:
    A new approach to acoustic quality assessment of churches during simulation tests is proposed in the article. The numerical global index, based on four partial indices: reverberation, speech intelligibility, music sound index and a proposed new one – sound strength index, assesses the acoustic parameters of the model of the tested church in a complex manner. The global single number index was obtained from 17 simulations of acoustic adaptation options of the investigated church’s interior. The equation of the approximate global index has been obtained by means of singular vectors, obtained from Singular Value Decomposition (SVD) of the Index Observation Matrix of Simulation Variants (IOMSV). The weights of four partial indices and a universal equation of the global index have been calculated using the SVD technique to solve the problem of correlated acoustical parameters. The global index may be a helpful tool during simulation tests of acoustic quality assessment of churches. The proposed final equation of the global index does not require knowledge of the SVD technique and the values of acoustic parameters preferred for churches. Therefore the methodology proposed is easily applicable.
    Źródło:
    Archives of Acoustics; 2012, 37, 1; 23-30
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Konstytucyjna zasada proporcjonalności wyborów a wielkość okręgu i metoda podziału mandatów. Symulacja zmiany parametrów na przykładzie wyników głosowania w wyborach do Sejmu RP
    The Constitutional Principle of Proportionality in the Choice of the Size of the Constituency and the Method of Distributing Seats. Simulation of Changes in Parameters in the Elections to the Polish Sejm
    Autorzy:
    Peszyński, Wojciech
    Tomczak, Łukasz
    Powiązania:
    https://bibliotekanauki.pl/articles/2047745.pdf
    Data publikacji:
    2022-04-30
    Wydawca:
    Wydawnictwo Adam Marszałek
    Tematy:
    system wyborczy
    formuła wyborcza
    proporcjonalność wyborów
    okręgi wyborcze
    indeks proporcjonalności
    wybory do Sejmu RP
    metoda D’Hondta
    metoda Sainte Lague
    electoral formula
    electoral systems
    proportionality of the election
    constituencies
    proportionality index
    elections to the Polish parliament
    D’Hondt method
    Sainte Lague method
    Opis:
    The aim of this article is to, on the basis of the case study of Polish elections to the Sejm, answer the question of which factor has a greater impact on the increase in the proportionality of the electoral system - the minimization of the number of constituencies or the change in the method. In order to do it, the Authors specified the results of six elections to the Sejm in the years 2005-2019 and the value of the proportionality index in two simulation versions. In the first one, the number of constituencies was limited from 41 to 16. In the second, the method of determining the result was changed from D’Hondt into modified Sainte Lague. The results were relatively surprising.
    Celem artykułu jest, na podstawie analizy przypadku polskich wyborów do Sejmu, udzielenie odpowiedzi na pytanie, który z czynników bardziej wpływa na wzrost proporcjonalności systemu wyborczego - zmniejszenie liczby okręgów czy zmiana metody podziału mandatów? Aby odpowiedzieć na to pytanie Autorzy ustalili wyniki wyborów do Sejmu z lat 2005, 2007, 2011, 2015, 2019 oraz wartości indeksu proporcjonalności w dwóch wersjach symulacji. Wyniki symulacji porównywano również do rzeczywistych wyników wyborów. W pierwszym wariancie, zmniejszono liczbę okręgów wyborczych z 41 na 16. W drugim, zmieniono metodę ustalania wyników wyborów z d’Hondta na zmodyfikowaną Sainte Lague (1.4). Wyniki przeprowadzonego badania okazały się dość zaskakujące.
    Źródło:
    Przegląd Prawa Konstytucyjnego; 2022, 2(66); 163-176
    2082-1212
    Pojawia się w:
    Przegląd Prawa Konstytucyjnego
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Cимуляция
    Autorzy:
    Сенкевич, Василий
    Powiązania:
    https://bibliotekanauki.pl/articles/1826494.pdf
    Data publikacji:
    2019-09-16
    Wydawca:
    Uniwersytet Przyrodniczo-Humanistyczny w Siedlcach
    Tematy:
    simulation
    reality
    sign
    symbol
    index
    Opis:
    The adverse effects of simulation on the phenomenal reality of a principal cultural institution - the language are viewed here. Bid to identify and put into shape everything captures anything and everything that has no nature and is understood as things existent. Speculative substitutions of a live "here is"-reality for its significant and indicative alternative lead to the validation of a reality that is not involved in existence.
    Źródło:
    Conversatoria Litteraria; 2016, 10; 447-476
    1897-1423
    Pojawia się w:
    Conversatoria Litteraria
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Control system with the specific performance index for an evaporator
    Autorzy:
    Świtalski, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/206591.pdf
    Data publikacji:
    1999
    Wydawca:
    Polska Akademia Nauk. Instytut Badań Systemowych PAN
    Tematy:
    system sterowania
    concentration control
    evaporator control system
    performance index
    simulation
    Opis:
    In some cases the classical performance indexes are not adequate for the performance evaluation of the concentration control systems. Therefore, the specific performance index is proposed in this paper. This index depends on the product of the product flow rate and some function of the deviation of the product concentration from the set point. In order to minimize this performance index the special control system is proposed. This special control system used to the forced circulation evaporator is studied using simulation techniques. The simulation results show that the system described in this paper produces the performance index less than classical control system.
    Źródło:
    Control and Cybernetics; 1999, 28, 2; 315-329
    0324-8569
    Pojawia się w:
    Control and Cybernetics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Sweet Corn Yield Simulation Using Normalized Difference Vegetation Index and Leaf Area Index
    Autorzy:
    Lykhovyd, Pavlo
    Powiązania:
    https://bibliotekanauki.pl/articles/124254.pdf
    Data publikacji:
    2020
    Wydawca:
    Polskie Towarzystwo Inżynierii Ekologicznej
    Tematy:
    direct measurement
    mathematical model
    regression analysis
    remote sensing
    sweet corn
    yield prediction
    Opis:
    The authors determined the accuracy and reliability of yielding models by using the values of two differently obtained indices – the leaf area index (LAI) obtained through direct surface measurements, and the normalized difference vegetation index (NDVI) obtained through spatial remote sensing of crops. The study based on the drip-irrigated sweet corn yielded the data obtained in the field experiment held in the semi-arid climate on darkchestnut soil in the South of Ukraine. The suitability of the LAI and NDVI for the simulation of sweet corn yields was estimated by the regression analysis of the yielding data by correlation (R) and determination (R2) coefficients. Additionally, mathematical models for the crop yields estimation based on the regression analysis were developed. It was determined that LAI is a more suitable index for the crop yield prediction: the R2 value was 0.92 and 0.94 against 0.85 for the NDVI-based models.I It was determined that it is better to use the LAI values obtained at the stage of flowering, when R2 averaged to 0.94, and the NDVI-based models does not depend on the crop stage (the R2 was 0.85 both for the flowering and ripening stages of the plant development). The combined NDVI-LAI model showed that there is no necessity in the complication of the LAI-based model through introduction of the remotely sensed index because of insignificant improvement in the performance (R2 was 0.94 and 0.92).
    Źródło:
    Journal of Ecological Engineering; 2020, 21, 3; 228-236
    2299-8993
    Pojawia się w:
    Journal of Ecological Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A Global Index of Acoustic Assessment of Machines—Results of Experimental and Simulation Tests
    Autorzy:
    Pleban, D.
    Powiązania:
    https://bibliotekanauki.pl/articles/90747.pdf
    Data publikacji:
    2011
    Wydawca:
    Centralny Instytut Ochrony Pracy
    Tematy:
    acoustic assessment
    machinery
    noise
    Opis:
    A global index of machines was developed to assess noise emitted by machines and to predict noise levels at workstations. The global index is a function of several partial indices: sound power index, index of distance between the workstation and the machine, radiation directivity index, impulse and impact noise index and noise spectrum index. Tests were carried out to determine values of the global index for engine-generator; the inversion method for determining sound power level was used. It required modelling each tested generator with one omnidirectional substitute source. The partial indices and the global index were simulated, too. The results of the tests confirmed the correctness of the simulations.
    Źródło:
    International Journal of Occupational Safety and Ergonomics; 2011, 17, 3; 277-286
    1080-3548
    Pojawia się w:
    International Journal of Occupational Safety and Ergonomics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Unmanned ship simulation with real-time dynamic risk index
    Autorzy:
    Brake, M. C. ter
    Iperen, E. (W. H.) van
    Looije, D.
    Koldenhof, Y.
    Powiązania:
    https://bibliotekanauki.pl/articles/135142.pdf
    Data publikacji:
    2015
    Wydawca:
    Akademia Morska w Szczecinie. Wydawnictwo AMSz
    Tematy:
    autonomous ship
    ship domain
    simulation
    dynamic risk
    real-time
    risk
    Opis:
    Currently there is growing interest in unmanned shipping. In the case of unmanned ‘autonomous’ shipping, navigation is automated by on-board decision-making systems. Important motives for unmanned ships include the shortage of skilled mariners, the facilitation of slow steaming strategies, efficiency improvements in confined shipping areas, and increased safety. The aim of the present research is to simulate an unmanned ship through an Automatic Identification System (AIS) based traffic situation. In order to do this, the Maritime Research Institute Netherlands (MARIN) will use the existing simulation technology Dolphin, implement a new tool to read AIS data, simulate a large amount of ships, and develop an auto-captain. The real-time dynamic risk index developed by MARIN will be integrated in Dolphin, to monitor nautical safety of all ships with focus on the unmanned ship. The simulated unmanned ship will navigate according to the International Regulations for Preventing Collisions at Sea (COLREGS). In more complex situations, the auto-captain may use a dedicated decision support tool to find a more efficient solution to pass safely. This approach will be analysed using the real-time dynamic risk index, which will be updated based on latest insights. This paper will discuss the latest development and plans in the unmanned ship simulation project.
    Źródło:
    Zeszyty Naukowe Akademii Morskiej w Szczecinie; 2015, 43 (115); 48-54
    1733-8670
    2392-0378
    Pojawia się w:
    Zeszyty Naukowe Akademii Morskiej w Szczecinie
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Computer simulation of vibration surveillance of discretely idealised mechanical systems. Part I: Optimal control at the energy performance index for open non-stationary systems
    Autorzy:
    Kaliński, K. J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1955706.pdf
    Data publikacji:
    2004
    Wydawca:
    Politechnika Gdańska
    Tematy:
    dynamics
    control
    simulation
    railway weighing systems
    Opis:
    The paper discusses means of mechanical vibration surveillance using elements of control theory, dynamic optimisation, modern methods of computer simulation and measurement techniques. A mixed method of rigid and flexible finite elements is applied to discrete modelling of non-stationary controlled systems. A method of vibration surveillance in the time domain is elaborated, which utilises optimal control at the energy performance index with respect to the trajectory of given motion. An example is given of surveillance of transient vibration of a railway freight wagon weighing device.
    Źródło:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2004, 8, 1; 79-87
    1428-6394
    Pojawia się w:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Options Pricing by Monte Carlo Simulation, Binomial Tree and BMS Model: a comparative study of Nifty50 options index
    Autorzy:
    Bendob, Ali
    Bentouir, Naima
    Powiązania:
    https://bibliotekanauki.pl/articles/2041933.pdf
    Data publikacji:
    2019-04-03
    Wydawca:
    Uniwersytet Warszawski. Wydawnictwo Naukowe Wydziału Zarządzania
    Tematy:
    options pricing
    option markets
    Black-Scholes model
    Binomial model
    Monte-Carlo Simulation model
    Greek letters
    Opis:
    Investment behaviour, techniques and choices have evolved in the options markets since the launch of options trading in 1973. Today, we are entering the field of Big Data and the explosion of information, which has become the main feature of science, impacts investors' decisions and their trading position, particularly in the financial markets. Our paper aims to testing the effectiveness of the most popular options pricing models , which are the Monte Carlo simulation method, the Binomial model, and the benchmark model; the Black-Scholes model, when we ignore/take on account the Moneyness categories and different time to maturities; five months, one year, and two years, in addition to comparing these models, we will then test the effect of each model on the prediction of the current options prices, using the regression analysis, and the Nifty50 option index during the period of 25/07/2014 to 30/06/2016. The result shows that all models are overpriced in all Moneyness categories with a high level of volatility in In-the money category, other finding concludes that the Monte Carlo Simulation method is outperforming when the volatility is lower, while the Black-Sholes model and the Binomial model are outperforming in the entire sample with ignoring the Moneyness.
    Źródło:
    Journal of Banking and Financial Economics; 2019, 1(11); 79-95
    2353-6845
    Pojawia się w:
    Journal of Banking and Financial Economics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Maternal Nutritional Status and Lactational Amenorrhea in India: A Simulation Analysis
    Autorzy:
    Dwivedi, Laxmi K.
    Powiązania:
    https://bibliotekanauki.pl/articles/465748.pdf
    Data publikacji:
    2013
    Wydawca:
    Główny Urząd Statystyczny
    Tematy:
    simulative approach
    maternal nutritional status
    body mass index
    postpartum amenorrhea
    India
    Opis:
    Apart from breast-feeding, socio-economic and biological factors, maternal health also influences the length or distribution of waiting time to conception. The main objective of this paper is to examine the linkages between maternal nutritional status (measured by body mass index-BMI) and postpartum amenorrhea among currently breast-feeding women in India and its region. Further, the probability to remain amenorrheic through simulative approach has been estimated to get better understanding of the impact of maternal nutritional status on postpartum amenorrhea. Using National Family Health Survey-2 data, women who were not pregnant, who were breast-feeding and who were not using any hormonal contraceptives at the time of the survey were included in the analysis. Missing cases for body mass index and child nutritional status were imputed by fitting the linear regression equation. There was no significant difference existing between mean BMI of each region of India before and after imputation of missing cases. The interaction term between maternal nutritional status and duration of breast-feeding (child’s age) was significantly associated with the likelihood of having resumed menstruation after controlling for breast-feeding practices, child nutritional status and socio-economic and demographic covariates. The effect of maternal nutritional status on lactational amenorrhea was not found to be significant when women were breast-feeding since last 12 months except in the northern region of India. However, after 12 months of breast-feeding, the probability of undernourished women to remain amenorrheic was likely to be greater and this trend was highly consistent across all the six regions included in the analysis.
    Źródło:
    Statistics in Transition new series; 2013, 14, 1; 107-128
    1234-7655
    Pojawia się w:
    Statistics in Transition new series
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Calculation Models for Acoustic Analysis of St. Elizabeth of Hungary Church in Jaworzno Szczakowa
    Autorzy:
    Kosała, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/177877.pdf
    Data publikacji:
    2016
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    acoustic quality
    index method
    church acoustics
    Singular Value Decomposition
    SVD
    acoustic simulation tests
    Opis:
    In parallel with research conducted using conventional methods, a uniform index method for assessing the acoustic quality of Roman Catholic churches has been developed. The latest version of the index method has been created using the index observation matrix of 12 churches which have been rated by means of the single number global index. Assessments of the acoustic quality of any Roman Catholic church, using two calculation models: the Global Acoustic Properties Index (GAP) and the Global Index (GI), are shown in the article. The verification was performed on the example of one church, showing the way of calculating global indices to assess the acoustic quality of a new facility. The next stages in the development of the index method for assessing the acoustic quality of churches were taking into account the audience, using simulation tests and determining the spatial distribution of the single number GAP index in an examined church. An attempt to use the GAP and GI calculation models to assess the acoustic properties of some churches is also shown in the article.
    Źródło:
    Archives of Acoustics; 2016, 41, 3; 485-498
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Traffic simulation in a telecommunication system based on queuing systems with different input flows
    Autorzy:
    Bobalo, Y.
    Politanskyi, R.
    Klymash, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/411201.pdf
    Data publikacji:
    2015
    Wydawca:
    Polska Akademia Nauk. Oddział w Lublinie PAN
    Tematy:
    herst index
    self-similar flow
    queuing system
    Poisson flow
    Opis:
    The simulation method of queuing system for traffic simulation in telecommunication system is studied. Different types of input flow are considered: uniform distributed, Poisson distributed and self-similar flow with different Herst indexes.
    Źródło:
    ECONTECHMOD : An International Quarterly Journal on Economics of Technology and Modelling Processes; 2015, 4, 1; 11-15
    2084-5715
    Pojawia się w:
    ECONTECHMOD : An International Quarterly Journal on Economics of Technology and Modelling Processes
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Modeling and simulation of novel stepped DC coupled quasi Z-Multilevel Inverter for single phase systems
    Autorzy:
    Meenakshi, T.
    Suthanthira Vanitha, N.
    Powiązania:
    https://bibliotekanauki.pl/articles/140968.pdf
    Data publikacji:
    2016
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    multilevel inverter
    shoot through
    quasi Z-Source
    modulation index
    Opis:
    This paper presents the modeling and simulation of a novel topology of quasi Z-Multilevel Inverter with stepped DC input. The proposed inverter incorporates a simple switching technique with reduced component count and is aimed at producing boosted multilevel output AC voltage. The inverter consists of two stages and the buck /boost operation is obtained by varying the shoot through period of the pulses obtained by maximum constant boost control with third harmonic injection. With all the advantages of the quasi Z-network, the proposed inverter eliminates the fly back diodes and capacitors present in a conventional Z-Multilevel Inverter. Further the stress on the devices is less which leads to reduction in component value and hence the cost. The novel stepped DC coupled Single Phase quasi Z-Multilevel Inverter is modeled and simulated in the MATLAB – SIMULINK environment and its performance is analyzed for varying input and switching conditions. The voltage and current waveforms across each stage of the inverter is analyzed and the results are presented for different levels of input.
    Źródło:
    Archives of Electrical Engineering; 2016, 65, 3; 437-448
    1427-4221
    2300-2506
    Pojawia się w:
    Archives of Electrical Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Modelowanie i symulacja drgań układu nośnego manipulatora dla potrzeb sterowania modalnego przy energetycznym wskaźniku jakości
    Modelling and simulation of the structural model vibration of manipulators carrying system for a use of modal control at energy performance index
    Autorzy:
    Kaliński, K.
    Jasiński, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/329020.pdf
    Data publikacji:
    2005
    Wydawca:
    Polska Akademia Nauk. Polskie Towarzystwo Diagnostyki Technicznej PAN
    Tematy:
    roboty
    modelowanie
    sterowanie
    symulacja
    robots
    modelling
    control
    simulation
    Opis:
    W pracy rozważa się drgania modelowanego dyskretnie niestacjonarnego układu nośnego manipulatora IRb-6 metodą sztywnych elementów skończonych. Do nadzorowania drgań wykorzystano algorytm sterowania modalnego przy energetycznym wskaźniku jakości. Uwzględnia on zmianę w czasie, względem trajektorii ruchu zadanego, energii potencjalnej, kinetycznej oraz energii sygnału sterującego. Przedstawiono zmodyfikowany model dyskretny, uwzględniający podatność połączenia przegubowego między ramionami robota. Model obliczeniowy został zweryfikowany za pomocą eksperymentalnej analizy modalnej.
    Here is considered vibration of modified discrete model of non-stationary carrying system of manipulator IRb-6. For a use of vibration surveillance, an algorithm of modal control at energy performance index has been applied. It comprises changes with time, along trajectory of given motion, of potential, kinetic and control energies. Modification of the discrete model allows us to include flexibility of a joint between robot arms. The model is well-verified by experiments.
    Źródło:
    Diagnostyka; 2005, 33; 71-76
    1641-6414
    2449-5220
    Pojawia się w:
    Diagnostyka
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Simulation study on the Influence of EEDI requirements to shiphandling in heavy weather
    Autorzy:
    Nishizaki, C.
    Okazaki, T.
    Yabuki, H.
    Yoshimura, Y.
    Powiązania:
    https://bibliotekanauki.pl/articles/116458.pdf
    Data publikacji:
    2019
    Wydawca:
    Uniwersytet Morski w Gdyni. Wydział Nawigacyjny
    Tematy:
    ship handling
    Energy Efficiency Design Index (EEDI)
    CO2
    heavy weather
    main engine
    Energy Efficiency Operational Index (EEOI)
    Maritime Environmental Protection Committee (MEPC)
    Pure Car Carrier (PCC)
    Opis:
    In order to reduce the CO2 emission from ships, International Maritime Organization executes the restriction of Energy Efficiency Design Index (EEDI) which limits amount of CO2 when freight of one ton is carried at one mile. Although the realization of higher efficiency of main engine without reduction of engine output is the best solution, it might be impossible. To comply with the EEDI requirements, it is assumed that the ship’s engine power becomes smaller than the existing ship by means of improving the ship propulsive efficiency. However, shiphandling in rough seas is expected to become difficult when the engine power is reduced. In this paper it is shown that the influence of the degraded main engine exerts on the safety of shiphandling in heavy weather based on the simulation study. In these experiments, both the simulation model that decreased engine power corresponding to EEDI requirement and that with the conventional engine power were tested, and masters in active service maneuvered the test ships in the rough seas.
    Źródło:
    TransNav : International Journal on Marine Navigation and Safety of Sea Transportation; 2019, 13, 4; 855-860
    2083-6473
    2083-6481
    Pojawia się w:
    TransNav : International Journal on Marine Navigation and Safety of Sea Transportation
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Reliability-Based Assessment of Galloping Instability of Thin-Walled Steel Beams
    Autorzy:
    Nguyen, Huu Anh Tuan
    Powiązania:
    https://bibliotekanauki.pl/articles/27314733.pdf
    Data publikacji:
    2022
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    instability
    wind speed
    Monte Carlo simulation
    reliability index
    safety factor
    niestabilność
    prędkość wiatru
    Monte Carlo
    wskaźnik niezawodności
    współczynnik bezpieczeństwa
    Opis:
    Galloping instability relating to cross-wind vibrations can be found in flexible and lightly damped structures. In the present paper, the reliability of a thin-walled steel beam in maintaining its galloping stability was examined using a probabilistic approach. The analysis considered random variation in the cross-sectional geometrical properties of the beam, the material elastic modulus, the structural damping and the wind speed. A large number of Monte Carlo simulations were performed with normal and Gumbel distributions applied to the random variables to determine the probability distribution function of the safety margin. The limit state is considered violated when the wind speed exceeds the onset wind velocity of galloping, resulting in the aerodynamic damping being greater than the structural damping. It was shown by a conventional codified safety factor method that the beam was robust enough for galloping stability. By contrast, the probability-based assessment revealed that the beam failed to achieve the target reliability index in case the coefficient of variation of wind speed was greater than 5%. The analysis results suggested that the code-satisfied slenderness of the beam should be reduced by a factor of 1.5-1.7 under the action of wind speed with a coefficient of variation in the range 30-40%.
    Źródło:
    Civil and Environmental Engineering Reports; 2022, 32, 2; 23--35
    2080-5187
    2450-8594
    Pojawia się w:
    Civil and Environmental Engineering Reports
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A toy model of prebiotic peptide evolution: the possible role of relative amino acid abundances
    Autorzy:
    Polanco, Carlos
    Buhse, Thomas
    Samaniego, José
    Castañón González, Jorge
    Powiązania:
    https://bibliotekanauki.pl/articles/1039570.pdf
    Data publikacji:
    2013
    Wydawca:
    Polskie Towarzystwo Biochemiczne
    Tematy:
    polarity index method.
    computer simulation
    prebiotic polymerization
    toy model
    peptides
    amino acids
    Opis:
    This paper presents a mathematical-computational toy model based on the assumed dynamic principles of prebiotic peptide evolution. Starting from a pool of amino acid monomers, the model describes in a generalized manner the generation of peptides and their sequential information. The model integrates the intrinsic and dynamic key elements of the initiation of biopolymerization, such as the relative amino acid abundances and polarities, as well as the oligomer reversibility, i.e. fragmentation and recombination, and peptide self-replication. Our modeling results suggest that the relative amino acid abundances, as indicated by Miller-Urey type electric discharge experiments, played a principal role in the early sequential information of peptide profiles. Moreover, the computed profiles display an astonishing similarity to peptide profiles observed in so-called biological common ancestors found in the following three microorganisms; E. coli, M. jannaschii, and S. cereviasiae. The prebiotic peptide fingerprint was obtained by the so-called polarity index method that was earlier reported as a tool for the identification of cationic amphipathic antibacterial short peptides.
    Źródło:
    Acta Biochimica Polonica; 2013, 60, 2; 175-182
    0001-527X
    Pojawia się w:
    Acta Biochimica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Specification of estimation of a passenger car ride smoothness under various exploitation conditions
    Autorzy:
    Vaičiūnas, Gediminas
    Steišūnas, Stasys
    Bureika, Gintautas
    Powiązania:
    https://bibliotekanauki.pl/articles/2038040.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Polskie Naukowo-Techniczne Towarzystwo Eksploatacyjne PAN
    Tematy:
    railway transport
    passenger car
    running gear
    independently rotating wheels
    Sperling's comfort index
    divergences
    numerical simulation
    software package UM
    Opis:
    The stability and smoothness of rolling stock running could be defined accurately by universal Sperling's comfort index. The divergences of variation of Sperling's comfort index of a passenger car under specific operating conditions of running gear are examining in this paper. Numerical simulations of a passenger car running with independently rotating wheels under various conditions have been performing. Gained results showed that divergences of the Sperling's comfort index variation are particularly significant due to running gear component oscillations in the horizontal plane (lateral direction). A field experiment of a passenger car with a solid (traditional) wheelset with a flat running surface proved this hypothesis. The obtained results of this experiment confirmed this assumption. Therefore, the study of the regularities of lateral oscillations of a passenger car is the logical direction of further research.
    Źródło:
    Eksploatacja i Niezawodność; 2021, 23, 4; 719-725
    1507-2711
    Pojawia się w:
    Eksploatacja i Niezawodność
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The Choice of Initial Conditions and of Solution in the Problem of Efficiency Increase of Pipes Calibration on a Mandrel
    Autorzy:
    Salikhyanov, D.
    Bogatov, A.
    Dyja, H.
    Powiązania:
    https://bibliotekanauki.pl/articles/352003.pdf
    Data publikacji:
    2018
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    hot-rolled pipe
    pipe calibration on a mandrel
    pipe precision index
    extrafocal deformation
    finite element simulation
    FEM
    Opis:
    This research work is devoted to the theoretical study of the pipe calibration on a mandrel. The aim of the study is to improve the precision of the calibrated pipes. As the paper shows, it is advisable to apply different methods of research depending on the purpose of the study of metal forming processes: mathematical, computer or physical simulation. Analytical review of existing mathematical models of the pipes calibration on a mandrel showed that the set of assumptions adopted in the mathematical modeling does not allow assessing the precision of the pipes during calibration. Therefore, finite-element method simulation package was used for this research. Research method and pipes precision index were developed on the basis of the computer simulation using Deform-3D package. The investigations have allowed us to get the dependence of the pipe precision on technological factors and to identify the root cause of reduced efficiency calibration – extrafocal deformation.
    Źródło:
    Archives of Metallurgy and Materials; 2018, 63, 2; 739-742
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Numeryczne próby morskie uwzględniające właściwości morskie statku
    Numerical Sea Tests Simulation of Seakeeping Properties
    Autorzy:
    Cepowski, T.
    Powiązania:
    https://bibliotekanauki.pl/articles/360187.pdf
    Data publikacji:
    2004
    Wydawca:
    Akademia Morska w Szczecinie. Wydawnictwo AMSz
    Tematy:
    właściwości morskie
    efektywność operacyjna
    kołysania boczne
    kryteria stateczności
    kryteria operacyjno-ograniczające
    wskaźnik efektywności operacyjnej
    EXPLO-SHIP 2004
    seakeeping properties
    seakeeping operability
    roll
    stability criteria
    seakeeping criteria
    seakeeping performance index
    Opis:
    Przedstawiono metodę oceny stateczności statku, umożliwiającą uwzględnienie zachowania się statku na fali. Istotą metody jest ocena zachowania się statku poddanego tzw. numerycznym próbom morskim. W artykule podano przykład metody uwzględniającej właściwości morskie statku i na tej podstawie opracowano wskazówki do zastosowania tych właściwości w kryterium stateczności poprzecznej.
    The paper presents a method for the stability assessment taking into account ship behavior in waves. The m the method aims at examining ship seakeeping ability by the numerical sea test simulation in real-life operation scenarios. The article presents an application of the method for seakeeping analysis which served as a basis for stability criterion formulation.
    Źródło:
    Zeszyty Naukowe Akademii Morskiej w Szczecinie; 2004, 2 (74); 67-77
    1733-8670
    2392-0378
    Pojawia się w:
    Zeszyty Naukowe Akademii Morskiej w Szczecinie
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Study of the derailment safety index Y/Q of the low-floor tram bogies with different types of guidance of independently rotating wheels
    Autorzy:
    Opala, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/223583.pdf
    Data publikacji:
    2016
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    derailment safety
    safety
    simulation
    independently rotating wheels
    low-floor tram
    wykolejenie
    bezpieczeństwo
    symulacja
    niezależnie obracające się koła
    tramwaj niskopodłogowy
    Opis:
    Modern tram designs use different conceptions of how to implement the low-floor functionality. The key construction part is the bogie running gear which has to accommodate the lower part of the tram body. To adjust the low-floor level, many low-floor tram bogies have different types of guidance of independently rotating wheels with no central axle between the two wheels. Lack of self-steering mechanism in the form of central axle coupling or an external guiding device creates several inherent problems, such as insufficient guiding and excessive wear. Another important context is the safety against derailment when the vehicle negotiates a curved track. In this study the dynamic behaviour of non-powered bogies with different types of guidance of independently rotating wheels are presented using computer simulation models. The simulation results of the Y/Q index are compared for the two track configurations (curved and tangent sections) and four different kinds of bogie running gear.
    Źródło:
    Archives of Transport; 2016, 38, 2; 39-47
    0866-9546
    2300-8830
    Pojawia się w:
    Archives of Transport
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Określenie możliwości zastosowania symulacji komputerowej do przewidywania kierunku przebiegu reakcji podczas zatłaczania wód złożowych
    The possibility of application of computer simulation to predict the direction of the reaction during injection of reservoir waters
    Autorzy:
    Jakubowicz, Piotr
    Steliga, Teresa
    Kluk, Dorota
    Wojtowicz, Katarzyna
    Powiązania:
    https://bibliotekanauki.pl/articles/2145720.pdf
    Data publikacji:
    2021
    Wydawca:
    Instytut Nafty i Gazu - Państwowy Instytut Badawczy
    Tematy:
    wody złożowe
    zatłaczanie wód
    indeks rozpuszczalności
    PHREEQC
    reservoir waters
    water injection
    solubility index
    Opis:
    Obecnie praktycznie całość wód wydobytych w procesie eksploatacji węglowodorów zostaje zagospodarowana poprzez zatłoczenie do wyeksploatowanych złóż. Zmiany parametrów fizyczno-chemicznych (pH, potencjału redox, temperatury itp.) wody podczas wydobycia oraz kontakt wody zatłaczanej z obecną w złożu wodą rodzimą i skałą złożową mogą skutkować wytrącaniem cząstek osadów i zawiesin. Powoduje to kolmatację strefy przyodwiertowej i ograniczenie ilości wody możliwej do zatłoczenia odwiertem chłonnym. Z uwagi na wysoki stopień skomplikowania układu woda zatłaczana–woda złożowa–skała zbiornikowa oraz szeroki wachlarz oddziaływań pomiędzy poszczególnymi składnikami dysponowanie danymi analitycznymi nie zawsze pozwala na prawidłową interpretację przebiegu procesów i określenie ich wpływu na przepuszczalność strefy przyodwiertowej. Wykorzystując wyniki analiz fizyczno-chemicznych składu próbek wód separatorowych o zróżnicowanych właściwościach – dwie próbki o niskiej mineralizacji S1K (575 mg/dm3 ) i S4K (551 mg/dm3 ), próbka o wysokiej mineralizacji S2K (306 428 mg/dm3 ) i próbka o średniej mineralizacji S3K (79 858 mg/dm3 ) – przeprowadzono obliczenia z wykorzystaniem programu PHREEQC dla trzech baz danych: phreeqc.dat, wateq4f.dat oraz pitzer.dat. Stwierdzono, że w przypadku wód o niskiej mineralizacji wyniki uzyskane na podstawie każdej z baz danych są zbliżone dla minerałów występujących we wszystkich bazach. Natomiast w przypadku roztworów o wysokiej mineralizacji pojawiają się wyraźne różnice w otrzymanych rezultatach. Obliczone indeksy rozpuszczalności pozwoliły na określenie kierunku przebiegu reakcji wytrącania/rozpuszczania poszczególnych minerałów w złożu i wskazanie zagrożeń – głównie ze względu na powstające osady związków żelaza – dla pracy odwiertu zatłaczającego. Przeprowadzono także badania laboratoryjne mieszania wód, podczas których zaobserwowano powstawanie osadów tlenków żelaza, mogących uszkadzać strefę przyodwiertową, co potwierdziło dane uzyskane podczas symulacji komputerowych.
    Currently, practically the entire volume of water extracted in the process of hydrocarbon exploitation is utilized by injection into deposits. Changes in the physico-chemical parameters (pH, red-ox potential, temperature, etc.) of the water during extraction and the contact of the injected water with the native water and deposit rock may result in the precipitation of sediment particles and suspensions. It causes clogging of the near-wellbore zone and limits the amount of water that can be injected with the injection well. Due to the high complexity of the system: the injected water–reservoir rock, and a wide range of interactions between individual components, the analytical data does not always allow for the correct interpretation of the course of the processes and determination of their impact on the permeability of the near-well zone. Using the results of physico-chemical analyses of the composition of separator water samples with different properties – two samples with low mineralization S1K (575 mg/dm3 ) and S4K (551 mg/dm3 ), a sample with high S2K (306 428 mg/dm3 ) and medium mineralization S3K (79 858 mg/dm3 ) – calculations were performed using the PHREEQC program for the three databases: phreeqc.dat, wateq4f.dat and pitzer.dat. It was found that in the case of low mineralization waters, the results obtained in each of the databases are similar for the minerals present in all the databases. However, in the case of solutions with high mineralization, there are significant differences in the obtained results. The calculated solubility indices allowed to determine the direction of the precipitation/dissolution reaction of individual minerals in the deposit and to indicate the risks, mainly with the formation of iron compounds deposits, for the operation of the injection well. Laboratory tests of water mixing were also carried out. The formation of iron oxide deposits that could damage the near-well zone was observed, which confirmed the results obtained during computer simulations.
    Źródło:
    Nafta-Gaz; 2021, 77, 4; 244-254
    0867-8871
    Pojawia się w:
    Nafta-Gaz
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
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