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    Wyświetlanie 1-19 z 19
    Tytuł:
    Analysis of short-terms height changes of the Hans Glacier using quasi-continuous GPS observations
    Autorzy:
    Walo, J.
    Adamek, A.
    Puczko, D.
    Powiązania:
    https://bibliotekanauki.pl/articles/225003.pdf
    Data publikacji:
    2007
    Wydawca:
    Politechnika Warszawska. Wydział Geodezji i Kartografii
    Tematy:
    GPS
    satelita GPS
    system pozycjonowania obiektów
    lodowiec Hans
    wysokośc lodowca
    pomiary geodezyjne
    GPS satellite
    Global Positioning System
    Hans Glacier
    glacier height
    engineering surveying
    Opis:
    The analysis of the measurement results exemplifies very valuable information about the glacier behavior which glaciologists need to understand phenomena occurring on the glacier in different seasons. Beside the experiences collected during this experiment it will be the background to design similar investigations from survey technology and methodology point of view. Basing on these results and experiment analysis we can draw some conclusions: - In the period of the experiment the glacier surface felt down as much as 2 meters. This is the natural tendency and consequences of flowing down the glacier to the fiord and his ablation. - In the figures we could notice wavy nature of the phenomenon of the glacier surface which probably is connected with topography of the fiord bottom, ocean tides affected on the glacier front and some processes connected with the ablation water delivery to the glacier bed. This problem requires a detailed study based on environmental data. - The results of determined heights were periodically disrupted by atmospheric conditions (snowing, wind). - The GPS data used to follow the vertical velocity of the glacier surface let us to monitor the glacier with height accuracy. Also the automation of the survey and post-processing is possible. - There are some disadvantages of using this monitoring technology in surveys: one point of observations, influence of atmospheric conditions on the results of surveys, periodically hard access to equipment and not good enough way of installation of the satellite antenna on the glacier (ablation pole).
    Źródło:
    Reports on Geodesy; 2007, z. 1/82; 367-373
    0867-3179
    Pojawia się w:
    Reports on Geodesy
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Estimation of height changes of GNSS stations from the solutions of short vectors and PSI measurements
    Autorzy:
    Krynski, J.
    Zak, L.
    Ziolkowski, D.
    Cisak, J.
    Lagiewska, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/145302.pdf
    Data publikacji:
    2017
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    height changes
    GNSS
    Persistent Scatterer Interferometry
    radar satelitarny
    deformacja powierzchni
    Opis:
    Time series of weekly and daily solutions for coordinates of permanent GNSS stations may indicate local deformations in Earth’s crust or local seasonal changes in the atmosphere and hydrosphere. The errors of the determined changes are relatively large, frequently at the level of the signal. Satellite radar interferometry and especially Persistent Scatterer Interferometry (PSI) is a method of a very high accuracy. Its weakness is a relative nature of measurements as well as accumulation of errors which may occur in the case of PSI processing of large areas. It is thus beneficial to confront the results of PSI measurements with those from other techniques, such as GNSS and precise levelling. PSI and GNSS results were jointly processed recreating the history of surface deformation of the area of Warsaw metropolitan with the use of radar images from Envisat and Cosmo-SkyMed satellites. GNSS data from Borowa Gora and Jozefoslaw observatories as well as from WAT1 and CBKA permanent GNSS stations were used to validate the obtained results. Observations from 2000–2015 were processed with the Bernese v.5.0 software. Relative height changes between the GNSS stations were determined from GNSS data and relative height changes between the persistent scatterers located on the objects with GNSS stations were determined from the interferometric results. The consistency of results of the two methods was 3 to 4 times better than the theoretical accuracy of each. The joint use of both methods allows to extract a very small height change below the level of measurement error.
    Źródło:
    Geodesy and Cartography; 2017, 66, 1; 73-88
    2080-6736
    2300-2581
    Pojawia się w:
    Geodesy and Cartography
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    On the estimation of physical height changes using GRACE satellite mission data – A case study of Central Europe
    Autorzy:
    Godah, W.
    Szelachowska, M.
    Krynski, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/145591.pdf
    Data publikacji:
    2017
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    satelita GRACE
    pole grawitacji
    przemieszczenia pionowe
    GRACE
    height anomaly variations
    vertical displacements
    physical height changes
    Opis:
    The dedicated gravity satellite missions, in particular the GRACE (Gravity Recovery and Climate Experiment) mission launched in 2002, provide unique data for studying temporal variations of mass distribution in the Earth’s system, and thereby, the geometry and the gravity fi eld changes of the Earth. The main objective of this contribution is to estimate physical height (e.g. the orthometric/normal height) changes over Central Europe using GRACE satellite mission data as well as to analyse them and model over the selected study area. Physical height changes were estimated from temporal variations of height anomalies and vertical displacements of the Earth surface being determined over the investigated area. The release 5 (RL05) GRACE-based global geopotential models as well as load Love numbers from the Preliminary Reference Earth Model (PREM) were used as input data. Analysis of the estimated physical height changes and their modelling were performed using two methods: the seasonal decomposition method and the PCA/ EOF (Principal Component Analysis/Empirical Orthogonal Function) method and the differences obtained were discussed. The main fi ndings reveal that physical height changes over the selected study area reach up to 22.8 mm. The obtained physical height changes can be modelled with an accuracy of 1.4 mm using the seasonal decomposition method.
    Źródło:
    Geodesy and Cartography; 2017, 66, 2; 211-226
    2080-6736
    2300-2581
    Pojawia się w:
    Geodesy and Cartography
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    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:
    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:
    Zmiany wysokości ciała w okresie 13 lat w grupie dorosłych mieszkańców Krakowa
    Changes in body height within 13 years in the group of adult residents in Cracow
    Autorzy:
    Gorynski, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/872816.pdf
    Data publikacji:
    1986
    Wydawca:
    Narodowy Instytut Zdrowia Publicznego. Państwowy Zakład Higieny
    Źródło:
    Roczniki Państwowego Zakładu Higieny; 1986, 37, 3
    0035-7715
    Pojawia się w:
    Roczniki Państwowego Zakładu Higieny
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Zmiany przyrostu wysokości sosny zwyczajnej pod wpływem emisji związków azotowych
    Izmenenija prirosta vysoty sosny obyknovennojj pod vlijaniem ehmissi azotnykh soedinenijj
    Changes of height growth in the Scots pine under the impact of the emission of nitrogen compounds
    Autorzy:
    Madejski, A.
    Rucinski, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/814439.pdf
    Data publikacji:
    1976
    Wydawca:
    Polskie Towarzystwo Leśne
    Źródło:
    Sylwan; 1976, 120, 07
    0039-7660
    Pojawia się w:
    Sylwan
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Selected models for the description of the kinematics of changes of height differences between points in a geodesic network under the influence of mining
    Wybrane modele opisu kinematyki sieci geodezyjnej wysokościowej pod wpływem eksploatacji górniczej
    Autorzy:
    Mrówczyńska, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/396085.pdf
    Data publikacji:
    2012
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    teren eksploatacji górniczej
    deformacja powierzchni
    Legnicko-Głogowski Okręg Miedziowy
    sieci geodezyjne
    model przemieszczeń pionowych
    sieci neuronowe
    deformation of surface
    Legnica-Głogów Copper Mining Area
    reference system
    model of vertical displacements
    neural networks
    Opis:
    The article attempts to describe the progress of deformation of the surface of the Legnica-Głogów Copper Mining Area in the years 1967-2008. The state of deformation has been described with kinematical models of the displacement of points representing the area under research. It has been analysed whether there are possibilities of using a counter-propagation algorithm for estimating displacements of selected points for which an assumption has been made that during the research they were damaged or destroyed. The numerical procedures of the estimation of parameters of displacement models were carried out by means of traditional optimisation methods and neural networks.
    W treści artykułu podjęto próbę opisu przebiegu deformacji powierzchni terenu obszaru Legnicko – Głogowskiego Okręgu Miedziowego w latach 1967 – 2008. Stan deformacji został opisany modelami kinematycznymi przemieszczeń punktów reprezentujących badany obszar. Przeprowadzono rozważania dotyczące możliwości wykorzystania algorytmu kontrpropagacji do oszacowania przemieszczeń wybranych punktów, dla których przyjęto założenie, że w trakcie prowadzonych badań punkty zostały uszkodzone bądź zniszczone. Procedury numeryczne estymacji parametrów modeli przemieszczeń realizowano za pomocą tradycyjnych metod optymalizacji i sieci neuronowych.
    Źródło:
    Civil and Environmental Engineering Reports; 2012, 8; 5-17
    2080-5187
    2450-8594
    Pojawia się w:
    Civil and Environmental Engineering Reports
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A new problem of hydrodynamic lubrication with temperature and viscosity variations in gap height direction
    Autorzy:
    Wierzcholski, K.
    Miszczak, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/245652.pdf
    Data publikacji:
    2016
    Wydawca:
    Instytut Techniczny Wojsk Lotniczych
    Tematy:
    liquid viscosity changes in thin gap height direction
    temperature
    adhesion or capillary forces variations in thin gap height direction new analytical solutions
    Opis:
    Numerous Authors of scientific papers occurring in hydrodynamic theory of slide bearing lubrication, up to now almost always had neglected the oil dynamic viscosity variations caused by temperature, adhesion forces, capillary forces, or hydrogen ion concentration across the film thickness by virtue of the statement of the constant temperature as well constant adhesion as capillary forces in the thin bearing gap height direction. In addition, simultaneously by virtue of boundary layer simplifications for energy equation and by virtue of new measurements performed in micro and nano- level follows that oil temperature gradients and its values differences and adhesion or capillary gradients of forces in bearing gap height directions are not negligible small. The contemporary hydrodynamic theory of lubrication for non-isothermal lubricant flow is unfortunately based on the assumption of constant viscosity values across the film thickness, despite abovementioned self-evident contradiction between the fact of constant viscosity and simultaneously temperature variations in gap height direction. Such problem was up to now not sufficient critical examined and explained in practical and theoretical sense. After Authors, knowledge by virtue of above problem the most scientific papers in the domain of non-isothermal and lamellar hydrodynamic slide bearing or biobearing lubrication were up to now not sufficient correctly solved. It denotes that the main hydrodynamic lubrication solutions presenting for example hydrodynamic pressure by the modified Reynolds equation and temperature by the energy conservation equation are not sufficiently correctly obtained and next not correctly solved. Therefore are assumed simultaneously the temperature T and oil dynamic viscosity variations in length, width and bearing gap- height directions. From this assumption follows, that the energy equation must be solved simultaneously with the equations of motion i.e. consequently with pressure equation where viscosity depends on temperature and temperature depends on the coordinate in gap height direction.
    Źródło:
    Journal of KONES; 2016, 23, 2; 423-430
    1231-4005
    2354-0133
    Pojawia się w:
    Journal of KONES
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Dynamic site index model and trends in changes of site productivity for Alnus glutinosa (L.) Gaertn. in southern Poland
    Autorzy:
    Socha, Jarosław
    Ochał, Wojciech
    Powiązania:
    https://bibliotekanauki.pl/articles/956987.pdf
    Data publikacji:
    2017
    Wydawca:
    Polska Akademia Nauk. Instytut Dendrologii PAN
    Tematy:
    height growth model
    height-age relationship
    forest site
    evaluating site productivity
    alder
    Opis:
    Black alder is naturally widespread across all of Europe and has an increasing importance for forest ecosystems. Thanks to the considerable tolerance to adverse climatic and edaphic environmental conditions black alder is important both in open landscapes and can also be involved in the rehabilitation of disturbed soils. Assessment of site productivity is essential for providing a frame of reference for silvicultural diagnosis and prescription in order to ensure the sustainability of existing and newly established ecosystems. The most accepted method of evaluating site productivity is the site index (SI). The aim of the presented research was to develop the SI model for black alder in southern Poland. The developed SI model was used as a tool in order to test the research hypothesis assuming the increase in site productivity for black alder in southern Poland. The research material for development of SI model were stem analysis data from 180 research plots. Both, the local model parameter, which was estimated individually for every tree, and the other parameters estimated globally for the whole data set were estimated simultaneously. Changes in site productivity were analyzed on research plots and a set of 12,974 stands from the forest inventory database. Site indices calculated using the developed model are negatively correlated with age/ positively correlated with establishment year of the stands. This confirms the existence of the phenomenon of increasing site productivity for black alder. During the last century site productivity measured with site index increased on average 5 m. Therefore, black alder that belongs to the fast-growing tree species should be considered of the increasing importance for forest management.
    Źródło:
    Dendrobiology; 2017, 77; 45-57
    1641-1307
    Pojawia się w:
    Dendrobiology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effects of Construction Changes in the Teeth of a Gear Transmission on Acoustic Properties
    Autorzy:
    Wieczorek, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/90168.pdf
    Data publikacji:
    2012
    Wydawca:
    Centralny Instytut Ochrony Pracy
    Tematy:
    gear
    tooth height
    gear contact ratio
    sound pressure level
    Opis:
    This paper presents results of experimental research on the acoustic properties of gear wheels with high-profile teeth with differentiated tooth height. Those results showed that gear transmissions with high-profile teeth have the best acoustic properties, with the value of the transverse contact ratio εα ≈ 2.0. They also showed that a reduction in tooth height, and thereby in contact ratio, increased the sound pressure level.
    Źródło:
    International Journal of Occupational Safety and Ergonomics; 2012, 18, 4; 499-507
    1080-3548
    Pojawia się w:
    International Journal of Occupational Safety and Ergonomics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Wave Climate in the Gulf of Gdańsk vs. Open Baltic Sea near Lubiatowo, Poland
    Autorzy:
    Różyński, G.
    Powiązania:
    https://bibliotekanauki.pl/articles/241345.pdf
    Data publikacji:
    2010
    Wydawca:
    Polska Akademia Nauk. Instytut Budownictwa Wodnego PAN
    Tematy:
    Baltic Sea
    climate changes
    global processes
    North Atlantic Oscillation
    significant wave height
    singular spectrum analysis
    Opis:
    The paper analyses long-term variability in the wave climate near Lubiatowo, ca. 15 km east of Łeba harbor, and in the Gulf of Gdańsk, near the Vistula river mouth. The wave climate was reconstructed for the 1958-2001 period by the German Institute for Coastal Research (GKSS). Using basic statistical tools - empirical mean values of significant wave height, estimation of the number of threshold crossings above a prescribed value of that height and conditional empirical probability density functions of wave approach directions - a comparison of wave height at the two locations was executed. A substantial reduction in wave height inside the Gulf (sheltering effect) was measured. Further, the increased storminess over the winter season was estimated for the open sea location. Finally, the analysis of wave approach direction in the open sea location revealed substantial growth in extreme waves from the western sector. Given the geographic configuration of the Gulf and the combined rise in storminess and evolution in extreme wave direction, it can be inferred that the sheltering effect of the Gulf can vary depending on locations within the Gulf. Identification of sheltering patterns in the Gulf emerges as obvious follow-up research. This study could also prove useful in analyses aiming at integrated management of coastal zones in the Gulf, mainly in the implementation of Coastal Protection Law (Apr. 2003), which postulates maintenance of the 2001 shoreline configuration along the entire Polish coast.
    Źródło:
    Archives of Hydro-Engineering and Environmental Mechanics; 2010, 57, 2; 167-176
    1231-3726
    Pojawia się w:
    Archives of Hydro-Engineering and Environmental Mechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Decadal variations in wave heights off Cape Kelba, Saaremaa Island, and their relationships with changes in wind climate
    Autorzy:
    Suursaar, U.
    Kullas, T.
    Powiązania:
    https://bibliotekanauki.pl/articles/47497.pdf
    Data publikacji:
    2009
    Wydawca:
    Polska Akademia Nauk. Instytut Oceanologii PAN
    Tematy:
    wave height
    decadal variation
    climate change
    wave parameter
    relationship
    Cape Kelba
    storm
    wind
    Saaremaa Island
    wave measurement
    Opis:
    Based on wind data from the Vilsandi meteorological station and a 5-month calibration measurement with a bottom-mounted Recording Doppler Current Profiler (RDCP), a semi-empirical hindcast of wave parameters near the quickly developing accumulative Kelba Spit is presented for the period 1966–2006. The significant wave heights with a gross mean value of 0.56 m exhibited some quasiperiodic cycles, with the last high stage in 1980–95 and a decreasing overall trend of −0.001 m per year. At the same time, both the frequency and intensity of high wave events showed rising trends, and the mean wave heights during winter (December to February) increased as well. As the study area has the longest fetches in westerly directions, the discussed tendencies in wave conditions are sensitive to regional changes in the wind climate and can be related to a decrease in the local average wind speed on the one hand, but an intensification of westerly winds, storm events and the wintertime NAO index on the other. The roughest wave storms on record were associated with prominent W-storms on 2 November 1969 and 9 January 2005; a few other extreme wind events (e.g. in 1967, 1999, 2001), however, did not yield equally prominent waves.
    Źródło:
    Oceanologia; 2009, 51, 1; 39-61
    0078-3234
    Pojawia się w:
    Oceanologia
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Operating parameters of a slide bearing with parabolic-shaped slide surfaces with consideration of the stochastic changes in the lubrication gap height
    Autorzy:
    Miszczak, Andrzej
    Wierzcholski, Krzysztof
    Powiązania:
    https://bibliotekanauki.pl/articles/244155.pdf
    Data publikacji:
    2019
    Wydawca:
    Instytut Techniczny Wojsk Lotniczych
    Tematy:
    hydrodynamic lubrication
    analytical stochastic principles
    solutions
    apparent viscosity
    numerical calculation
    load carrying capacity
    friction force
    Opis:
    In this article, the authors present the equations of the hydrodynamic theory for a slide bearing with parabolicshaped slide surfaces. The lubricating oil is characterized by non-Newtonian properties, i.e. an oil for which, apart from the classic oil viscosity dependence on pressure and temperature, also an effect of the shear rate is taken into account. The first order constitutive equation was adopted for considerations, where the apparent viscosity was described by the Cross equation. The analytical solution uses stochastic equations of the momentum conservation law, the stream continuity and the energy conservation law. The solution takes into account the expected values of the hydrodynamic pressure EX[p(ϕ,ζ)], of the temperature EX[T(ϕ,y,ζ)], of the velocity value of lubricating oil EX[vi(ϕ,y,ζ)], of the viscosity of lubricating oil EX[ηT(ϕ,y,ζ)] and of the lubrication gap height EX[εT(ϕ,ζ)]. It was assumed, that the oil is incompressible and the changes in its density and thermal conductivity were omitted. A flow of lubricating oil was laminar and non-isothermal. The research concerned the parabolic slide bearing of finite length, with a smooth sleeve surface, with a full wrap angle. The aim of this work is to derive the stochastic equations, that allow to determine the temperature distribution, hydrodynamic pressure distribution, velocity vector components, load carrying capacity, friction force and friction coefficient, in the parabolic sliding bearing, lubricated with nonNewton (Cross) oil, including the stochastic changes in the lubrication gap height. The paper presents the results of analytical and numerical calculation of flow and operating parameters in parabolic sliding bearings, taking into account the stochastic height of the lubrication gap. Numerical calculations were performed using the method of successive approximations and finite differences, with own calculation procedures and the Mathcad 15 software.
    Źródło:
    Journal of KONES; 2019, 26, 4; 171-178
    1231-4005
    2354-0133
    Pojawia się w:
    Journal of KONES
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Ocena zmian obrazu białek surowicy krwi dzieci wiejskich z niedoborami wzrostowo-wagowymi
    Assessment of changes in serum protein pattern in rural children with weight and height deficits
    Autorzy:
    Bilczuk, L.
    Szponar, L.
    Powiązania:
    https://bibliotekanauki.pl/articles/872440.pdf
    Data publikacji:
    1973
    Wydawca:
    Narodowy Instytut Zdrowia Publicznego. Państwowy Zakład Higieny
    Tematy:
    ocena
    surowica krwi
    dzieci
    czlowiek
    wies
    niedobory fizjologiczne
    wzrost
    masa ciala
    Źródło:
    Roczniki Państwowego Zakładu Higieny; 1973, 24, 1
    0035-7715
    Pojawia się w:
    Roczniki Państwowego Zakładu Higieny
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The problems of hydrodynamic non-isothermal lubrication
    Problemy hydrodynamicznego nieizotermicznego smarowania
    Autorzy:
    Wierzcholski, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/190086.pdf
    Data publikacji:
    2016
    Wydawca:
    Stowarzyszenie Inżynierów i Techników Mechaników Polskich
    Tematy:
    liquid viscosity
    changes in thin gap height direction
    temperature
    adhesion
    or phospholipids
    analytical model
    micro-bearings
    joints applications
    initial results
    lepkość cieczy
    zmiany po grubości cienkiej warstwy
    temperatura
    adhezja
    fosfolipidy
    model analityczny
    mikrołożyska
    stawy
    wstępne rezultaty
    Opis:
    The classical hydrodynamic theory of slide bearing lubrication has been constituted on the assumption of constant pressure and viscosity perpendicular to the thin oil layer thickness. These fundamental assumptions are in contradiction to contemporary achievements connected with new devices such as micro-bearing, nano-bearing, magnetic bearings, artificial joints in humanoid robots, micro-motors. Therefore, new methods of measurements and calculations using AFM and a new mathematical computer programs are needed. Energy conservation equations after boundary layer simplifications confirm the fact that temperature gradient variations across the film thickness have the same order of magnitude as the variations in longitudinal or circumferential directions. The fact that temperature gradient variations cross the bearing gap height can be significantly large are evident, despite the temperature differences across the film thickness that are negligibly small. This statement cannot be compliant with the assumption of a constant viscosity value in the gap height direction. It has been proven that hydrodynamic pressure is not constant across the film thickness for non-Newtonian oils with Rivlin Erickson constitutive equations. For pseudo-plastic non-Newtonian oils, the apparent dynamic viscosity significantly decreases with shear rate increases. However, for pseudo-plastic oils, the shear rate increments during the oil flow are strictly connected with the average flow velocity increments. Therefore, the apparent dynamic viscosity depends strongly on the oil velocity gradients. It is evident that flow velocity gradients across the film thickness have intensive variations, particularly in regions where gap height attains the least value. In these places, the dynamic viscosity attains the largest variations in gap height directions. If gap height in micro-bearing is smaller than one micrometre, than the largest oil dynamic viscosity increments caused by the velocity variations across the film thickness are located near the superficial layer of the movable journal surfaces in the case of the hydrodynamic lubrication by rotation, but in the neighbourhood where each of two come near lubricated surfaces during the squeezing. Hence, in these places, dynamic viscosity increases across the film thickness and attains the local maximum values. A gap height smaller than one micrometre has the largest oil dynamic viscosity increments caused by the adhesion force variations across the film thickness located near the motionless sleeve surfaces. In a similar manner, the influences on the viscosity variations caused by the luster points of concentrations of nano particles as oil inhibitors or oil additives smaller than 5 nm occurring in micro-bearing gaps and the cluster concentration regions of collagen fibres occurring in human joint gap are observed. This paper describes and comments on the above-mentioned problem of oil viscosity changes in the gap height direction, and it presents the apparent dynamic viscosity functions for Newtonian and non-Newtonian oils as well indicates the largest viscosity variations in bearing gap height direction and gives examples of initial calculation results.
    W niniejszej pracy wykazano, że lepkość dynamiczna nie-newtonowskiego nieizotermicznego czynnika smarującego zmienia się po kierunku wysokości szczeliny łożyskowej oraz że zmiany te mają istotny wpływ na parametry pracy poprzecznego łożyska ślizgowego łącznie z siłami tarcia, współczynnikami tarcia oraz zużyciem materiału. Zmiany lepkości nieizotermicznej nienewtonowskiej cieczy smarującej po grubości warstwy czynnika smarującego uzasadnia się poprzez: · wpływ zmian gradientów temperatury po grubości warstwy smarującej, · wpływ zmian wartości składowych prędkości nienewtonowskiego, nieizotermicznego oleju po kierunku wysokości szczeliny, · wpływ lokalizacji w cieczy smarującej obszarów skupienia (clustering regions) nanometrowych cząsteczek i ich liczebności. Dla wyjaśnienia mechanizmu opisanych wpływów podano komentarze. 1. Zmiany wartości temperatury pomiędzy powierzchnią czopa i panewki są małe i ich wartość osiąga zaledwie od 3 K do 7 K. Dlatego nie mają one wpływu na zmiany lepkości po grubości warstwy, chociaż z równania zachowania energii wynika zmienność wartości temperatury po kierunku wysokości szczeliny łożyska. Jednak zmiany gradientów temperatury po kierunku wysokości szczeliny mogą być znaczące i one wpływają na zmiany lepkości w kierunku wysokości szczeliny. 2. Zmiany wartości składowych prędkości nienewtonowskiego, nieizotermicznego oleju po kierunku wysokości szczeliny są znacząco malejące (rosnące), powodują spadek (wzrost) prędkości deformacji w cieczach nienewtonowskich, a stąd na mocy praw mechaniki cieczy odpowiednio znacząco wzrasta (maleje) lepkość. 3. Obszary skupienia dotyczą: inhibitorów, dodatków polimerowych, zanieczyszczeń solami ołowiu, molekuł magnetycznych o ok. 2–5 nm wielkości cząsteczek w obszarze szczeliny smarnej łożysk mechanicznych oraz chondrocytów, włókien kolagenowych, miceli, liposomów, fosfolipidów o wielkości 5 nm w obszarze cieczy synowialnej wypełniającej szczelinę stawu. Obszary skupienia lokalizują się na ogół w pobliżu współpracujących powierzchni i tam wywołują znaczne wzrosty lepkości pozornej cieczy smarującej. 4. Siły adhezji w szczelinach łożysk o wysokości poniżej mikrometra osiągają największe wartości w pobliżu współpracujących powierzchni, powodując w tych obszarach największe wzrosty lepkości oleju po kierunku wysokości szczeliny.
    Źródło:
    Tribologia; 2016, 268, 4; 211-223
    0208-7774
    Pojawia się w:
    Tribologia
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Zmiana z wiekiem grubości, pola przekroju i wysokości robinii akacjowej z zachodniej Polski
    Age-related changes of diameter, basal area and height of black locust from western Poland
    Autorzy:
    Bronisz, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/880389.pdf
    Data publikacji:
    2018
    Wydawca:
    Szkoła Główna Gospodarstwa Wiejskiego w Warszawie. Leśny Zakład Doświadczalny. Centrum Edukacji Przyrodniczo-Leśnej w Rogowie
    Tematy:
    lesnictwo
    drzewostany robiniowe
    robinia akacjowa
    Robinia pseudoacacia
    piersnice drzew
    piersnicowe pole przekroju
    wysokosc drzew
    tablice zasobnosci drzewostanu
    Nadlesnictwo Slawa Slaska
    Nadlesnictwo Sulechow
    Nadlesnictwo Glogow
    Źródło:
    Studia i Materiały Centrum Edukacji Przyrodniczo-Leśnej; 2018, 20, 3[57]
    1509-1414
    Pojawia się w:
    Studia i Materiały Centrum Edukacji Przyrodniczo-Leśnej
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Próba oceny wpływu szerokości szlaków turystycznych na otaczające je środowisko lasu
    An attempt to assess the effect of tourist trail width on adjacent forest environment
    Autorzy:
    Skłodowski, J.
    Bartosz, S.
    Dul, L.
    Grzybek, D.
    Jankowski, S.
    Kajetanem, M.
    Kalisz, P.
    Korenkiewicz, U.
    Mazur, G.
    Myszek, J.
    Ostasiewicz, M.
    Primka, B.
    Puczyłowska, I.
    Radzikowski, M.
    Roeding, P.
    Serek, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/1009663.pdf
    Data publikacji:
    2009
    Wydawca:
    Polskie Towarzystwo Leśne
    Tematy:
    turystyka
    zwiezlosc gleb
    wskazniki ekologiczne
    oddzialywanie na srodowisko
    wysokosc
    runo lesne
    lasy
    erozja gleb
    lesnictwo
    szlaki turystyczne
    tourist trails
    environmental changes
    soil compaction
    erosion
    height of herbaceous vegetation
    plant life forms
    indicator figures
    Opis:
    The impact of narrow (up to 2 m), medium (up to 3.5 m) and wide (>3.5 m) tourist trails on the surrounding environment was investigated. On wide trails, the value of soil erosion and compaction indices was found to be the highest, while the herb height index was the lowest indicating the greatest impact of wide trails on the environment. The phytosociological relevés were used to determine ecological indicator figures. Wide trails were characterized by higher thermal and continentalism indices and lower pH and trophic indices. The proportion of therophytes and geophytes was higher, while of hemicryptophytes, phanerophytes and chamaephytes on wide trails were lower than on medium and narrow trails. All the analysed indices pointed to a stronger impact of wide trails on the environment in comparison with medium and narrow trails.
    Źródło:
    Sylwan; 2009, 153, 10; 699-709
    0039-7660
    Pojawia się w:
    Sylwan
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
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