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    Wyświetlanie 1-9 z 9
    Tytuł:
    3D hydrodynamic pressure in gap height direction for cylindrical bearing viscoelastic lubrication
    Autorzy:
    Wierzcholski, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/246411.pdf
    Data publikacji:
    2013
    Wydawca:
    Instytut Techniczny Wojsk Lotniczych
    Tematy:
    pressure changes in gap height direction
    HDD micro-bearings
    viscoelastic lubrication
    Źródło:
    Journal of KONES; 2013, 20, 1; 367-374
    1231-4005
    2354-0133
    Pojawia się w:
    Journal of KONES
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Recurrent nets for tribology solutions
    Autorzy:
    Wierzcholski, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/244153.pdf
    Data publikacji:
    2013
    Wydawca:
    Instytut Techniczny Wojsk Lotniczych
    Tematy:
    pressure changes in gap height direction
    HDD micro-bearings
    viscoelastic lubrication
    Opis:
    The contemporary problems of numerical calculations ocurring in powertrain tribology and transport problems demand the more and more exactness for obtained results.Moreover in performed calculations very important is the convergence, stability and reliability of the gained numerical values. The main scientific topic of the presented paper concerns the method of the determination of the optimum net for numerical calculations of partial difference and recurrence equations. The abovementioned optimum difference and recurrence method is referring to the stability of obtained particular and general numerical solutions and assures the convergence process of obtained calculation values. The Unit Net Region (UNR) was assumed at first for Laplace Operator. The optimum of the nod geometry localization was examined at first for UNR. The optimization index is defined and derived for UNR to determine the most useful net among the various geometries of the nods localization during the difference methods performances of partial recurrence numerical calculations. In the next considerations had been proved the corollary, where taking into account the optimum UNR, we can create optimum nets for other numerous partial difference and recurrence equations in discrete spaces. For example the numerous calculation results of presented optimum net for recurrent calculations are applied for numerical solutions of a Reynolds partial recurrence equation with variable coefficients in curvilinear orthogonal coordinates for curvilinear boundary conditions, and for other numerical problems occurring in applied and hydrodynamics.
    Źródło:
    Journal of KONES; 2013, 20, 2; 401-408
    1231-4005
    2354-0133
    Pojawia się w:
    Journal of KONES
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Researching and modeling of the dynamic viscosity of the ferro-oils with the different concentrations of magnetic particles in the aspect of pressure changes
    Badania i modelowanie lepkości dynamicznej ferro-olejów o różnym stężeniu cząstek magnetycznych w aspekcie zmian ciśnienia
    Autorzy:
    Frycz, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/190936.pdf
    Data publikacji:
    2017
    Wydawca:
    Stowarzyszenie Inżynierów i Techników Mechaników Polskich
    Tematy:
    ferro-oil
    magnetic particles concentration
    pressure changes
    models of viscosity
    ferro-olej
    stężenie cząstek magnetycznych
    zmiany ciśnienia
    modele lepkości
    Opis:
    In this article, the results of the experimental research of determining the dynamic viscosity of the ferro-oils with different concentration of the magnetic particles in terms of pressure change are presented. The research was conducted on the Thermo Scientific Haake Mars III rheometer in the configuration with a pressure chamber. The applied configuration allowed the author to conduct research on the change of viscosity for the selected pressure values p in range from 0 to 100 bars. The research was conducted for three selected temperature values, including t = 30°C, 60°C, and 90°C, as well as selected shear rates of 200 and 600s-1. The chosen concentration values of the magnetic particles were nCS = 1%, 2%, 4%, 6%, and 8%. The viscous characteristics gathered as a result of the research have been analysed with the aim of identifying the nature of the correlations and to create mathematical-physical models of changes in the dynamic viscosity of the ferrooils due to the change in pressure in terms of concentrations of the magnetic particles. Analysis, identification, and adaptation of the characteristics were conducted using the StatSoft STATISTICA ver. 9 software. Selected mathematical adaptations of the acquired results were submitted through the enhanced analysis. In addition, parameters of the course of functions were designated and their qualitative assessments were made.
    W artykule zaprezentowane zostały wyniki eksperymentalnych badań wyznaczania lepkości dynamicznej ferro-olejów o różnym stężeniu cząstek magnetycznych w aspekcie zmian ciśnienia. Badania zostały przeprowadzone na reometrze Thermo Scientific Haake Mars III w konfiguracji z tzw. komorą ciśnieniową. Zastosowana konfiguracja pozwalała na prowadzenie badań zmian lepkości dla wybranych wartości ciśnienia p z zakresu od 0 do 100 bar. Badania przeprowadzono dla trzech wybranych wartości temperatur dla t = 30°C, 60°C oraz 90°C i wybranych prędkości ścinania: 200 oraz 600 s-1. Przyjęte wartości stężenia cząstek magnetycznych wynosiły nCS = 1%, 2%, 4%, 6% i 8%. Uzyskane w wyniku badań charakterystyki lepkościowe poddane zostały analizie zmierzającej do identyfikacji charakteru zależności i wykreowanie matematyczno-fizycznych modeli zmian lepkości dynamicznej ferro-olejów od zmian ciśnienia w aspekcie stężenia cząstek magnetycznych. Analizy, identyfikacji i dopasowania charakterystyk dokonano przy wykorzystaniu oprogramowania StatSoft STATISTICA wer. 9. Pogłębionej analizie poddano wyselekcjonowane dopasowania matematyczne uzyskanych wyników doświadczalnych. Wyznaczono ponadto parametry przebiegu funkcji i dokonano ich oceny jakościowej.
    Źródło:
    Tribologia; 2017, 272, 2; 39-48
    0208-7774
    Pojawia się w:
    Tribologia
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The effect of 200 MPa pressure on specific surface area of clay
    Autorzy:
    Koszela-Marek, E.
    Powiązania:
    https://bibliotekanauki.pl/articles/178875.pdf
    Data publikacji:
    2014
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    clay
    high pressure
    specific surface area
    microstructural changes
    Opis:
    The paper presents the results of laboratory studies of the 200 MPa pressure effect on specific surface area of clay. The original high-pressure investigation stand was used for the pressure tests. Determination of the specific surface area was performed by the methylene blue adsorption method. The results of the specific surface area test were compared for non-pressurized clays and for clays pressured in a high-pressure chamber. It was found that the specific surface area of pressurized soil clearly increased. This shows that some microstructural changes take place in the soil skeleton of clays.
    Źródło:
    Studia Geotechnica et Mechanica; 2014, 36, 4; 3-6
    0137-6365
    2083-831X
    Pojawia się w:
    Studia Geotechnica et Mechanica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Natural and anthropogenic changes in the environment during the Holocene at the Kraków region (Southern Poland) from study of mollusc assemblages
    Autorzy:
    Alexandrowicz, Witold Paweł
    Powiązania:
    https://bibliotekanauki.pl/articles/2058731.pdf
    Data publikacji:
    2021
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    mollusc assemblages
    environmental changes
    anthropogenic pressure
    Holocene
    Southern Poland
    Opis:
    Malacological analysis was used to reconstruct Holocene environmental changes from profiles of calcareous tufa and fluvial deposits exposed in the Kobylanka stream valley, several kilometres west of Kraków in southern Poland. The abundant and diversified mollusc fauna was characterized by clear variability within the vertical succession where five types of molluscan assemblages were distinguished. The pattern of sedimentary and molluscan facies allowed characterization of two main intervals of environmental change during Holocene. In the lower interval, until the end of the Middle Holocene, human activity was not detected and environmental processes were controlled by natural factors. In the upper interval, corresponding to the Late Holocene, human impact can be seen, in the form of rapid deforestation and agricultural development. Anthropogenic impact has been particularly evident during the last millennium. The mollusc assemblages studied allowed accurate reconstruction of natural and anthropogenic factors affecting the natural environment.
    Źródło:
    Geological Quarterly; 2021, 65, 1; 9
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The influence of oil’s exploitation time on load carrying capacity in a slider bearing
    Autorzy:
    Sikora, G.
    Miszczak, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/244279.pdf
    Data publikacji:
    2015
    Wydawca:
    Instytut Techniczny Wojsk Lotniczych
    Tematy:
    oil ageing
    numerical calculations
    Reynolds equation
    pressure distribution
    load carrying capacities
    viscosity changes in time
    Opis:
    In this paper, authors are presenting conclusions of the numerical calculations of pressure distribution and capacity in a slider bearing with taking changes of oil viscosity in exploitation time into account. Changes of the engine oil’s viscosity, which depend on the exploitation time, were determined on Haake Mars III rheometer and the conclusions were published in Solid State Phenomena and Logistyka in 2015. Numerical calculations were performed by solving of Reynolds equation, using finite difference method and own calculation procedures in Mathcad 15. Reynolds equation was developed by solving the continuity equation and the momentum conservation equation from the fundamentals. For the considerations, the laminar and stationary lubricating of the slider bearing of finite length and full angle of wrap were taken. Assumption of the stationary flow concerns lack of changes in flow parameters in short period of considered phenomena, f. ex. in one hour. Smooth and non-porous bushing were assumed. The aim of this paper was preliminary estimation of influence of viscosity changes in the exploitation time on the load carrying capacities of the cross slider bearing. Wherefore, the viscosity changes dependence on the pressure, temperature and also shear rate, were not taken into account. The basic equations were developed to the non-dimensional form and estimated according to the thin layer theory. In the calculations, the Reynolds boundary conditions concerning pressure distribution were taken into account. Preliminary calculations were performed for different models of viscosity changes in time and circumstances, where the viscosity increases and decreases in exploitation time.
    Źródło:
    Journal of KONES; 2015, 22, 3; 207-212
    1231-4005
    2354-0133
    Pojawia się w:
    Journal of KONES
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Operating parameters of slide micro – bearings with consideration of oil temperature changes and micro - grooves on sleeve surface
    Autorzy:
    Miszczak, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/247490.pdf
    Data publikacji:
    2012
    Wydawca:
    Instytut Techniczny Wojsk Lotniczych
    Tematy:
    HDD micro-bearings
    micro-grooved surfaces
    oil viscosity changes in gap height
    hydrodynamic pressure
    friction forces
    load carrying capacity
    Opis:
    In this paper author presents results of numerical calculations of hydrodynamic pressure distribution in bearing gap, load-carrying capacity, friction force and friction coefficient of slide micro-bearing considering the influence of lubricating oil temperature changes and also taking into account the influence of micro-grooves, which occur on sleeve internal surface. The micro-grooves on that surface are in longitudinal direction. The equation, which describes a bearing gap with micro-grooves on sleeve surface, was adopted from prof. K Wierzcholski's investigations. In very thin gap height of cylindrical micro-bearings, large gradients of temperature can be observed. This causes significant changes of oil dynamic viscosity in the gap height direction. According to this, oil flow velocity, friction forces, and a hydrodynamic pressure during the micro-bearing operation are changing. Up to now the influence of temperature on oil viscosity changes and due to this, on hydrodynamic pressure and on load carrying capacity in cylindrical micro-bearing gap in numerical way were not considered yet. The numerical calculations were performed with the use of Mathcad 14. The finite differences method and own computational procedures were implemented. The calculations were begun by solving the Reynolds' equation, assuming, that the dynamic viscosity is constant. After calculating the hydrodynamic pressure distribution, the temperature distribution in lubricating oil was determined. The obtained function of temperature was used to describe the viscosity changes with temperature. Next step involved determining the hydrodynamic pressure distribution taking into account the viscosity dependence on temperature, and then new distribution of temperature and again new values of viscosity were calculated. Calculations were repeated until assumed convergence and accuracy were reached. The friction force depends on pressure gradient and rotational motion of bearing journal. Part of friction force, which resulting from the pressure gradient, is determined for the area, where the oil film occurs, i.e. from omega p to omega k. Part of friction force, which is related to journal motion, is determined for full wrap angle, i.e. from 0 to 2 pi. The results were presented in the form of graphs, for eccentricity ratio gamma from 0.1 to 0.9, for dimensionless length of the bearing L1=1/4. In numerical calculations were used the theoretical considerations and solutions presented in papers of K. Wierzcholski and A. Miszczak.
    Źródło:
    Journal of KONES; 2012, 19, 2; 329-336
    1231-4005
    2354-0133
    Pojawia się w:
    Journal of KONES
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A Mathematical Model of Membrane Gas Separation with Energy Transfer by Molecules of Gas Flowing in a Channel to Molecules Penetrating this Channel from the Adjacent Channel
    Autorzy:
    Szwast, M.
    Szwast, Z.
    Powiązania:
    https://bibliotekanauki.pl/articles/185043.pdf
    Data publikacji:
    2015
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    membrane
    membrane module
    reciprocal transfer of energy between gas molecules
    changes of the pressure of gas along the length of flow channel
    membrana
    wzajemne przekazywanie energii między cząsteczkami gazu
    zmiany ciśnienia gazu na długości kanału przepływowego
    Opis:
    The paper presents the mathematical modelling of selected isothermal separation processes of gaseous mixtures, taking place in plants using membranes, in particular nonporous polymer membranes. The modelling concerns membrane modules consisting of two channels – the feeding and the permeate channels. Different shapes of the channels cross-section were taken into account. Consideration was given to co-current and counter-current flows, for feeding and permeate streams, respectively, flowing together with the inert gas receiving permeate. In the proposed mathematical model it was considered that pressure of gas changes along the length of flow channels was the result of both – the drop of pressure connected with flow resistance, and energy transfer by molecules of gas flowing in a given channel to molecules which penetrate this channel from the adjacent channel. The literature on membrane technology takes into account only the drop of pressure connected with flow resistance. Consideration given to energy transfer by molecules of gas flowing in a given channel to molecules which penetrate this channel from the adjacent channel constitute the essential novelty in the current study. The paper also presents results of calculationsobtained by means of a computer program which used equations of the derived model. Physicochemical data concerning separation of the CO2/CH4 mixture with He as the sweep gas and data concerning properties of the membrane made of PDMS were assumed for calculations.
    Źródło:
    Chemical and Process Engineering; 2015, 36, 2; 151-169
    0208-6425
    2300-1925
    Pojawia się w:
    Chemical and Process Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Exclusion of lands from agricultural production and urban pressure – case study
    Wyłączenia gruntów z produkcji rolnej a zjawisko presji urbanistycznej – case study
    Autorzy:
    Prus, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/100464.pdf
    Data publikacji:
    2016
    Wydawca:
    Uniwersytet Rolniczy im. Hugona Kołłątaja w Krakowie
    Tematy:
    historical changes in land use
    local changes in land use
    urban pressure
    original use
    target use
    objects’ classification
    spatial taxonomy
    historyczne zmiany użytkowania gruntów
    lokalne zmiany użytkowania gruntów
    presja urbanistyczna
    użytkowanie pierwotne
    użytkowanie docelowe
    klasyfikacja obiektów
    taksonomia przestrzenna
    Opis:
    Though agricultural lands are subject to legal protection limiting their use for non-agricultural purposes, recent research shows that investment areas are becoming larger at the cost of agricultural production areas. The analysis of cases in which lands have been excluded from agricultural production within Ropczyce-Sędziszów district (powiat), covering the period of 15 years, confirms that the change of area of particular lands is taking place. The biggest change affected grasslands and arable lands. The lands excluded from agricultural production are transformed into single-family housing, recreational and communication areas. Moreover the research allowed to show similarities in communes (gminy) with respect to lands excluded from agricultural production. The communes were singled out that were homogeneous as regards exclusion carried out in years 1999–2014. The choice of a research unit – Ropczyce-Sędziszów district – is determined by accessibility of data regarding exclusions and the fact the district is regarded as a unit with an average outlook for socioeconomic development. Simple statistical methods, quantitative analyses and a method of spatial taxonomy were used in the research.
    Pomimo, że grunty rolne podlegają prawnej ochronie polegającej na ograniczaniu przeznaczania na cele nierolnicze, badania wskazują na rosnącą powierzchnię terenów inwestycyjnych kosztem rolniczej przestrzeni produkcyjnej. Analiza przypadków wyłączeń gruntów z produkcji na terenie powiatu ropczycko-sędziszowskiego, obejmująca okres 15 lat, potwierdza zmiany w powierzchniach poszczególnych użytków gruntowych. Największym zmianom podlega powierzchnia użytków zielonych oraz gruntów ornych. Grunty wyłączone z produkcji zamieniane są na obszary zabudowy mieszkaniowej jednorodzinnej, rekreacyjnej oraz tereny komunikacyjne. Ponadto badania pozwoliły na określenie podobieństwa gmin w zakresie gruntów wyłączanych z produkcji rolnej. Wydzielono gminy jednorodne pod względem przeprowadzonych w latach 1999-2014 wyłączeń. Wybór jednostki badawczej (powiatu ropczycko-sędziszowskiego) uwarunkowany był możliwością pozyskania danych dotyczących wyłączeń oraz faktem, że powiat ten jest zaliczany do jednostek o przeciętnych warunkach rozwoju społeczno-gospodarczego. W badaniach wykorzystane zostały proste metody statystyczne, analizy ilościowe oraz metoda taksonomii przestrzennej.
    Źródło:
    Geomatics, Landmanagement and Landscape; 2016, 4; 169-182
    2300-1496
    Pojawia się w:
    Geomatics, Landmanagement and Landscape
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-9 z 9

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