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Tytuł:
Pomiary i analiza zmian cisnienia w poduszce powietrznej
Measurements and analysis of pressure changes in airbag
Autorzy:
Tokarska, M.
Leśnikowski, J.
Powiązania:
https://bibliotekanauki.pl/articles/152420.pdf
Data publikacji:
2002
Wydawca:
Stowarzyszenie Inżynierów i Techników Mechaników Polskich
Tematy:
pomiary zmian ciśnienia
analiza zmian ciśnienia
poduszka powietrzna
analysis of pressure changes
airbeg
measurements of pressure changes
Opis:
W artykule przedstwiono komputerowy system pomiarowy do pomiaru zmian ciśnienia w wystrzeliwanej samochodowej poduszce powietrznej. Oceniono przebieg czasowy ciśnienia w poduszce, będący klasycznym przykładem dynamicznego przepływu gazu przez materiał włókienniczy.
In the paper computherized measuring system for measuring pressure changes in airbags is presented. Time domain function of pressure in airbag is estimated. This function i s classical example of dynamic flow of gas through textiles.
Źródło:
Pomiary Automatyka Kontrola; 2002, R. 48, nr 3, 3; 17-19
0032-4140
Pojawia się w:
Pomiary Automatyka Kontrola
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:
MIĘDZYDOBOWE ZMIANY BODŹCOWOŚCI CIŚNIENIA ATMOSFERYCZNEGO W POZNANIU W LATACH 1988–2017
Autorzy:
Nawrocka, Marta
Szyga–Pluta, Katarzyna
Powiązania:
https://bibliotekanauki.pl/articles/943778.pdf
Data publikacji:
2018
Wydawca:
Poznańskie Towarzystwo Przyjaciół Nauk
Tematy:
interdiurnal air pressure changes
the stimuli of the atmospheric pressure
Grosswetterlagen (GWL)
biometeorology
Poznań
Opis:
The aim of the paper was to investigate the stimuli of the atmospheric pressure and the dependence of large pressure changes on atmospheric circulation in Poznań. The values of the average daily atmospheric pressure from the Poznań-Ławica meteorological station in years 1988-2017 were used. The frequency of days with atmospheric pressure greater than 1015 hPa and lower than 985 hPa as well as the number of days with interdiurnal change of the atmospheric pressure were calculated in specified ranges: 0.0-4.0 hPa, 4.1-8.0 hPa, 8.1-16.0 hPa and >16.1 hPa. Next, the conditional probability of the interdiurnal changes of the air pressure and the Grosswetterlagen (GWL) types of atmospheric circulation was determined. In Poznań in 1988–2017, the most stimulus air pressure changes occurred between November and February and the least stimulus – from May to August. Strong and very strong stimulus of atmospheric pressure is most often found in cyclonic circulation types with masses of air flowing from north-western directions.
Źródło:
Badania Fizjograficzne Seria A - Geografia Fizyczna; 2018, 9(69); 135-149
2081-6014
Pojawia się w:
Badania Fizjograficzne Seria A - Geografia Fizyczna
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:
Monitorowanie i kontrola zmian ciśnienia atmosferycznego kopalni dla potrzeb bezpieczeństwa
Monitoring and control of changes in atmospheric pressure of a mine aimed at needs for safety
Autorzy:
Tomczyk, A.
Rutecki, K.
Powiązania:
https://bibliotekanauki.pl/articles/186595.pdf
Data publikacji:
2009
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Technik Innowacyjnych EMAG
Tematy:
ciśnienie atmosferyczne kopalni
kontrola zmian ciśnienia atmosferycznego
monitorowanie zmian ciśnienia atmosferycznego
atmosphere pressure of a mine
control of changes in atmospheric pressure
monitoring of changes in atmospheric pressure
Opis:
Zmiana ciśnienia barometrycznego ma znaczący wpływ na migrację gazów zrobowych (tzw. oddychanie zrobów), stąd od wielu lat prowadzi się rejestrację zmian ciśnienia z sygnalizacją zniżki [2,5]. Dynamika zmian ciśnienia jest procesem wolnozmiennym, jednak każdego dnia obserwuje się krótkookresowe skoki ciśnienia. W artykule przedstawiono wybrane metody analizy trendu zmian dla szeregu czasowego jakim jest zarejestrowany przebieg zmian ciśnienia, które następnie poddano weryfikacji skuteczności działania na przykładzie rzeczywistych danych pomiarowych.
A change in barometric pressure has a significant impact on migration of goaf gases (so called goaf breathing). Hence for many years there have been recording the changes in pressure allowing for drops in pressure [2, 5]. Dynamics of changes in pressure is a low-variable process; however every day one may observe short-period pressure jumps. Selected methods of analysis of trends in changes in time series in form of a recorded course of changes in pressure have been presented in the paper. Next the methods have been verified regarding their effectiveness exemplified by real measuring data.
Źródło:
Mechanizacja i Automatyzacja Górnictwa; 2009, R. 47, nr 7, 7; 99-107
0208-7448
Pojawia się w:
Mechanizacja i Automatyzacja Górnictwa
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:
O "arktycznych" i "atlantyckich" mechanizmach sterujących zmiennością temperatury powietrza na obszarze Europy i północo-zachodniej Azji
On "Arctic" and "Atlantic" mechanisms controlling the changeability in air temperature in the region of Europe and NW Asia
Autorzy:
Marsz, A. A.
Styszyńska, A.
Powiązania:
https://bibliotekanauki.pl/articles/260919.pdf
Data publikacji:
2006
Wydawca:
Stowarzyszenie Klimatologów Polskich
Tematy:
zmiany temperatury powietrza
zmiany temperatury wody powierzchniowej
NAO
Oscylacja Eurazjatycka
AO
Arktyka Atlantycka
NW Azja
Europa
Atlantyk Północny
NW Asia
Europe
changes in pressure
changes in air temperature
Opis:
Praca omawia wpływ zmian ciśnienia atmosferycznego w Arktyce Atlantyckiej (dalej AA) na kształtowanie zmienności temperatury powietrza na obszarze Europy (na N od 40°N) i NW Azji (do 120°E). Wpływ zmian ciśnienia w AA na temperaturę powietrza zaznacza się we wszystkich, z wyjątkiem czerwca, miesiącach roku, tworząc charakterystyczny cykl z maksimum siły oddziaływania zimą. Zimowe (01-03) zmiany ciśnienia w AA objaśniają od kilkunastu do ponad 60% zmienności temperatury rocznej (z maksimum na obszarze wokół-bałtyckim; 1951-2000). W pracy analizuje się współdziałanie zmian ciśnienia w Arktyce Atlantyckiej ze zmianami ciśnienia w Wyżu Syberyjskim w kształtowaniu zmienności temperatury powietrza na obszarze Europy i NW Azji. Dyskutuje się również kwestie związków zmian ciśnienia w AA z NAO, AO oraz frekwencją makrotypów cyrkulacji środkowotroposferycznej wg klasyfikacji Wangengejma-Girsa. Wyniki analiz wykazują, że o zimowych zmianach ciśnienia w AA decyduje wcześniejszy rozkład zasobów ciepła w wodach Atlantyku Północnego.
The research on relations between climatic elements of Europe and the Arctic has indicated that there are significant correlations between changes in atmospheric pressure in the Atlantic part of the Arctic and air temperature in northern Europe and NW Asia. The strongest correlations are observed between changes in pressure over relatively small area of the Atlantic part of the Arctic (72.5 - 80.0°N, 10.0 - 25.0°E), in addition, the point over which changes in pressure explain most of changes in air temperature is located 75.0°N, 015.0°E. Pressure at this point is further referred as P[75,15] with an index denoting a month (e.g. P[75,15]03 denotes mean pressure in March and P[75,15]01-03 defines mean pressure at this point from the period January till March). Over the Atlantic part of the Arctic within the pressure area there is no marked climatic centre which could be regarded as the centre of atmospheric activity. The research made use of monthly series of SLP values (reanalysis: set NOAA.NCEP-NCAR. CDAS-1.MONTHLY.Intrinsic.MSL.pressure) and the values of monthly air temperature from 211 stations (Fig. 1). The observational period common for both elements covers 50 years, i.e. the period from January 1951 to December 2000. The character of correlations between P[75,15] and air temperature in the following months, from June to May, and their spatial distribution have been presented by isocorrelates maps (Fig. 2). Changes in the strength of correlations between P[75,15] and the temperature over Europe and NW Asia form a clear annual cycle interrupted in June. In June the correlations between P[75,15] and air temperature became very weak and not significant over the most of the area and not continuous in space. During the months after June these correlations got stronger and stronger reaching their maximum during cold season (from November to April). This maximum is located in the region adjacent to the Baltic Sea, where annual and winter (01-03) changes in P[75,15] explain from more than 60% to 50% of annual temperature variances (Fig. 3) The strongest correlation between P[75,15] and air temperature in Siberia is located N of Baikal, where winter (01-03) changes in P[75,15] explain 43-45% of annual temperature variances. At the end of the cold season a visible delay of the decrease in the strength of correlation is observed in the region of Siberia in relation to the European region (in Europe after March, in Siberia after April). Variability in winter and annual values of pressure at 75°N, 015°E also indicates relatively strong correlations with the changeability in temperature of the warmest month in the year in the west and central region of Europe. The annual variability in P[75,15] explains from 40% to 30% changeability of maximum temperature in the region extending from the Atlantic coast of France to central Germany. This belt extends farther east towards the Baltic Sea. The latter correlation has not been explained in this work. The analysis of correlations of changes in pressure at 75°N, 15°E with NAO indicates to the occurrence of statistically significant correlations during months of cold season in the year (October - March, May and June; Tab. 2). Similar analysis of correlations of changes in P[75,15] with AO index (Arctic Oscillation) shows strong and highly statistically significant correlations in all months of the year with maximum falling in January and February. Annual changes in P[75,15], i.e. in pressure at one point explain 73% annual changeability in AO index (r = 0.86) and the winter changeability in (December - March) P[75,15] explains 78% of winter changeability in AO index (r = 0.88) which is the first vector EOF of pressure field (1000 hPa) covering the area from 20°N to the North Pole (90°N), that is the most area of the Northern Hemisphere. This analysis shows that the changes in pressure at the point 75°N, 15°E result in intensification of cyclogenesis over west and central part of the North Atlantic and the consequent long waves (waves of W type following Wangengejm-Girs classification) cause that anticyclones formed over the Atlantic will direct towards Fram Strait through the region of Iceland. The above process has nothing or almost nothing to do with the form of changeability in polar strato-spheric eddy, as assumed by Tomphson and Wallace (1998, 2000, Thompson, Wallace, Hegerl 2000) to be essential for the Arctic Oscillation functioning. Occurrence of correlations between P[75,15] and air temperature over vast areas from 10°W to 130°E suggests that also changes in pressure in the Siberian High are engaged in this process. Theanalysis shows that in a yearly process, changes in pressure in the Atlantic part of the Arctic and in the Siberian High occur in opposite phases (see Tab.1). Barometric gradient between the Atlantic part of the Arctic and the Siberian High becomes extremely strong during the cold season of the year contributing to "pumping" air from eastern Europe to the far end of the Siberia. During the summer season the gradient becomes very weak as the about-turn takes place. The cooperation of changes in pressure in the Atlantic part of the Arctic and pressure in region located farther Baikal -- Mongolia results in very strong oscillation which partly can be identified with Euro-Asian Oscillation (Monahan et al. 2000). During winter season interannual changes in pressure in the Siberian High are relatively small and explain 10.4% variances of barometric gradient between P[75,15] and point 45°N, 110°E (the region of the centre of the Siberian High), whereas the interannual changes in P[75,15] explain 77.5% of variances in this gradient. This means that in the cold season of the year the intensity of air transfer from the west towards Asian land depends on variability in pressure in the Atlantic part of the Arctic. Because in the months of the cold season of the year NAO is the strongest and significantly correlated with changes in P[75,15] therefore, a two-element, with the same phase "conveyor belt" is formed, which during positive phases of NAO transfers the air from over the Atlantic to Europe (NAO) and then towards and into the Siberia (Euro-Asian Oscillation). P[75,15] during cold season months of the year (01-03) indicates statistically significant negative trend (-0.153 hPa/year; p < 0.006) which enables to state that the observed, over the years 1951-2000, increase in air temperature in the Siberia can be, in great extent, attributed to the activity of the above described circulation mechanism. The analysis of reasons for interannual changes in P[75,15] has indicated that there are strong and significant correlations between variability in P[75,15] and the earlier variability in the thermal conditions of the Atlantic Ocean. A very important role in this relation plays thermal condition of three sea areas, i.e. waters of the subtropical region of central part of the North Atlantic (characterized by SST anomalies in grid 34°N, 40°W from August and September), waters of the middle latitudes zone of the central part of the North Atlantic (characterized by SST anomalies from August and September in grid 54°N, 30°W) and waters of the North Atlantic Current from the approach to the Farero-Shetland Passage (characterized by SST anomalies from January and April in grid 60°N, 10°W). Thermal state of these three sea water areas (see formulas [1] and [2]) explains 58% changeability in P[75,15] which will be observed in the following winter (DJFM). The cause of the described correlation is attributed to the fact that the earlier thermal state of the above mentioned sea areas controls the occurrence of long waves, of W and E Wangengejm-Girs type during the following winter. Further, these waves influence the occurrence of low cyclones over the Atlantic part of the Arctic during winter resulting in adequate changes in mean monthly pressure. As a result, it can be stated that the interannual variability in air temperature over vast areas of Europe and over NW Asia is influenced by the processes observed over the North Atlantic and the Atlantic part of the Arctic. The research covers years 1971-2003 (ano-malies in SST taken from 1970-2002) due to the fact that the data have been not only accessible and reliable but also homogeneous with respect to climatological data of SST (CACSST data set (Reynolds and Roberts 1987, Reynolds 1988) and SST OI v.1. (Reynolds et al. 2002).
Źródło:
Problemy Klimatologii Polarnej; 2006, 16; 47-89
1234-0715
Pojawia się w:
Problemy Klimatologii Polarnej
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:
Bodźcowe oddziaływanie ciśnienia atmosferycznego w rejonie Polskiej Stacji Polarnej w Hornsundzie w latach 1991-2000
Biometeorological stimuli due to air pressure over the Polish Polar Station in Hornsund area, 1991-2000
Autorzy:
Owczarek, M.
Powiązania:
https://bibliotekanauki.pl/articles/260854.pdf
Data publikacji:
2005
Wydawca:
Stowarzyszenie Klimatologów Polskich
Tematy:
Hornsund
ciśnienie atmosferyczne
zmiany międzydobowe
bodźcowość
stimuli due
atmospheric pressure
day to day changes
Opis:
W pracy rozpatrzono ciśnienie atmosferyczne jako dynamiczny bodziec biometeorologiczny. Zana-lizowano roczny przebieg ciśnienia atmosferycznego i występowanie ciśnienia o wartościach wyższych od 1015 hPa lub niższych od 985 hPa. Określono zakres zmienności oraz częstość występowania bodźców dynamicznych o różnym natężeniu, związanych z międzydobowymi zmianami ciśnienia atmosferycznego w odniesieniu do skali odczucia według Bokšy i Boguckiego. Występowanie bodźcowego oddziaływania ciśnienia atmosferycznego przebadano także w odniesieniu do sytuacji synoptycznej według klasyfikacji Niedźwiedzia.
Biometeorological stimuli according to high or low values of air pressure and air pressure changes from one to the next day are the subject of this paper. Maximum value of air pressure was 1042.8 hPa and minimum one was 948.2 hPa during analyzed period. Monthly possibility of occurrence of air pressure values >1015 hPa varied from over 17% to over 60% and in case of values <985 hPa - varied from 0.8% to 18% occurrence. 'Great' stimuli according to day to day changes of air pressure (8 to 16 hPa/day) was the most frequent in January (37%), November and December. 'Very great' stimuli (over 16 hPa/day) were the most frequent in January (11%), December and March. July and August cover the most convenient period. Moderate dependence of dynamic stimuli due to day to day changes of air pressure on type of circulation (acc. to Niedźwiedź 2004) was pointed. Cyclonic situations are the most important for occurrence of 'great' and 'very great' stimuli (unadvective one and N+NE, E+SE types).
Źródło:
Problemy Klimatologii Polarnej; 2005, 15; 143-153
1234-0715
Pojawia się w:
Problemy Klimatologii Polarnej
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Koncepcja kształtowania rozkładu potencjału aerodynamicznego w podziemnych kopalniach węgla kamiennego dla przeciwdziałania zagrożeniom pożarowym i gazowym związanym ze zmianami ciśnienia atmosferycznego
Concept of aerodynamic potential´s distribution structuring in underground hard coal mines to counteract the fire and gas threats associated with changes of atmospheric pressure
Autorzy:
Markefka, P.
Przystolik, A.
Stefanowicz, T.
Powiązania:
https://bibliotekanauki.pl/articles/166127.pdf
Data publikacji:
2014
Wydawca:
Stowarzyszenie Inżynierów i Techników Górnictwa
Tematy:
wentylacja główna
zmiany ciśnienia atmosferycznego
przeciwdziałanie zagrożeniom pożarowym i gazowym od zrobów
main ventilation
changes of atmospheric pressure
counteracting the fire and gas threats from the cavities
Opis:
W polskich kopalniach węgla kamiennego obserwuje się wzrost zagrożeń pożarowych i gazowych od zrobów wywoływanych zmianami ciśnienia atmosferycznego, czyli zagrożeń związanych ze zjawiskiem tzw. oddychania zrobów. Jest to w głównej mierze konsekwencja lokalizacji robót górniczych przygotowawczych i eksploatacyjnych, prowadzonych z konieczności coraz częściej w sąsiedztwie dużych przestrzeni zrobowych. Stosowane dotychczas sposoby i środki dla przeciwdziałania niepożądanym skutkom zagrożeniowym tego zjawiska, nie są w pełni wystarczające i racjonalne. Wymusza to poszukiwanie i stosowanie bardziej efektywnych rozwiązań prewencyjnych w tym zakresie. W artykule przedstawiono wiele dodatkowych, praktycznych możliwości eliminowania lub łagodzenia wpływu zmian ciśnienia atmosferycznego na przestrzenie zrobowe, poprzez dokonywanie odpowiednich zmian w rozkładzie potencjału aerodynamicznego wokół danej przestrzeni. Takie racjonalne działania – koncepcja kształtowania rozkładu potencjału aerodynamicznego dla przeciwdziałania zagrożeniom pożarowym i gazowym związanym z „oddychaniem zrobów” – zostały zrealizowane z pozytywnym skutkiem w kilku kopalniach KHW S.A. Wobec nasilania się zagrożeń aerologicznych związanych ze zmianami ciśnienia atmosferycznego, celowe wydaje się dążenie do szerszego stosowania tej koncepcji w polskich kopalniach węgla kamiennego.
In the Polish hard coal mines one observes an increase of fire and gas hazards from post-mining cavities triggered by changes of atmospheric pressure. i.e. threats associated with phenomenon of so called cavities´ respiration. To a large extent it is a consequence of location of mining preparation works and extraction works, in principal by necessity, more often, in the vicinity of large cavity spaces. The methods and means of counteracting undesirable dangerous effects of that phenomenon applied so far are not fully sufficient and rational. That impels seeking and applying more efficient preventive solutions in that respect. This paper presents a number of additional practical possibilities of either eliminating or mitigating the atmospheric pressure alterations´ influence on cavity spaces by implementing appropriate modifications in aerodynamic potential distribution around the space given. Such rational actions - the concept of aerodynamic potential distribution´s structuring to counteract the fire and gas threats associated with “cavities respiration” – have been successfully executed in several coal mines of KHW S.A. Having considered the intensification of aerologic dangers associated with changes of atmospheric pressure, the efforts to apply this concept in Polish hard coal mines seem reasonable.
Źródło:
Przegląd Górniczy; 2014, 70, 7; 112-124
0033-216X
Pojawia się w:
Przegląd Górniczy
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:
Wieloletnie zmiany ciśnień piezometrycznych wód podziemnych w wyżynnym subregionie środkowej Wisły
Long-term changes in groundwater piezometric pressures in the upland subregion of the middle Vistula River
Autorzy:
Prażak, Jan
Powiązania:
https://bibliotekanauki.pl/articles/20223317.pdf
Data publikacji:
2023
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
wody gruntowe
ciśnienie piezometryczne
zmiany długoterminowe
wyżyna środkowej Wisły
groundwaters
piezometric pressure
long-term changes
upland of the middle Vistula
Opis:
This report provides insight into long-term changes in the position of groundwater table in the upland subregion of the middle Vistula River based on the research conducted in seven 1st order hydrogeological stations of the national groundwater monitoring network. These changes reveal a clear temporal relationship/trend noted in the vertical profile of aquifers even in conditions of their significant mutual isolation. They have been described as an effect of the phenomenon, but without establishing its measurable causes. The report indicates that the dynamic of groundwater pressure needs further studies and discussion of hydrogeologists dealing with this topic.
Źródło:
Przegląd Geologiczny; 2023, 71, 2; 82-91
0033-2151
Pojawia się w:
Przegląd Geologiczny
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
Wyświetlanie 1-15 z 17

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