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Wyświetlanie 1-15 z 375
Tytuł:
On the structure of characteristic surfaces related with partial differential equations of first and higher orders. Pt. 1
Autorzy:
Prykarpatska, N.K.
Pytel-Kudela, M.
Powiązania:
https://bibliotekanauki.pl/articles/255195.pdf
Data publikacji:
2005
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
characteristic surface
vector fields
tangency
Monge cone
tensor fields
Opis:
The geometric structure of characteristic surfaces related with partial differential equations of first and higer orders is studied making use the vector field technique on hypersurfaces. It is shown, that corresponding characteristics are defined uniquely up to some smooth tensor fields, thereby supplying additional information about the suitable set of their solutions. In particular, it may be very useful for studying asymptotic properties of solutions to our partial differential equations under some boundary conditions.
Źródło:
Opuscula Mathematica; 2005, 25, 2; 299-306
1232-9274
2300-6919
Pojawia się w:
Opuscula Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Surface Impedance Boundary Conditions applied to solving nonlinear electrodynamic systems
Autorzy:
Pawłowski, S.
Plewako, J.
Powiązania:
https://bibliotekanauki.pl/articles/141489.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
nonlinear electrodynamics
Surface Impedance Boundary Conditions
harmonic fields
quasi-stationary fields
skin effect
Opis:
The paper presents a method for solving electromagnetic field problems by applying impedance boundary conditions for systems including conducting bodies of nonlinear magnetic properties in an excited harmonic field. Three types of impedance boundary conditions were derived. A procedure for computing surface impedance based on the transfer matrix is proposed. This procedure has been tested by comparing computational results to calculations where time function distortions were considered, and to the experimental data.
Źródło:
Archives of Electrical Engineering; 2017, 66, 2; 433-446
1427-4221
2300-2506
Pojawia się w:
Archives of Electrical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Wybrane zagadnienia analizy pola elektromagnetycznego miasta Lublin i uzdrowiska Nałęczów
Analysis of electromagnetic fields of provincial capital Lublin and Spa Naleczow
Autorzy:
Mazurek, P. A.
Wac-Włodarczyk, A.
Przytuła, K.
Wójtowicz, P. A.
Staszek, J.
Ścirka, T.
Masłowski, G.
Powiązania:
https://bibliotekanauki.pl/articles/400472.pdf
Data publikacji:
2012
Wydawca:
Polskie Towarzystwo Inżynierii Ekologicznej
Tematy:
emisja elektromagnetyczna
natężenie pola elektrycznego i magnetycznego
electromagnetic emission
electric fields
magnetic fields
Opis:
Na przekroju kilkudziesięciu ostatnich lat obserwowany jest duży wzrost liczby urządzeń wytwarzających pola elektromagnetyczne, który przekłada się na coraz większe zainteresowanie społeczeństwa zakresem oddziaływania tych urządzeń na środowisko. Obok tradycyjnych źródeł pól elektromagnetycznych jakimi są przesyłowe linie elektroenergetyczne, trakcje kolejowe czy tradycyjne nadajniki radiowo - telewizyjne, masowo pojawiają się nadajniki telefonii komórkowej i inne urządzenia radiokomunikacyjne. Pracownicy i studenci Wydziału Elektrotechniki i Informatyki Politechniki Lubelskiej przeprowadzili badania terenowe w dwóch miastach, w zakresie pomiaru natężeń pól elektrycznych i magnetycznych niskich częstotliwości oraz natężenia pola elektromagnetycznego w wysokich częstotliwościach. W artykule przedstawiono wyniki pomiarów oraz ich odniesienie do dopuszczalnych limitów.
The number of devices that produce electromagnetic fields is growing for decades. This translates into a growing public interest in range of influence of these devices on the environment. In addition to traditional sources of electromagnetic fields such as transmission power lines, rail traction or traditional radio- television transmitters, mass are built mobile transmitters and other radio communications equipment. Staff and students of the Lublin University of Technology measurements conducted in two cities - Lublin and Naleczow. The tests involved measuring intensities of electric and magnetic fields at low and high frequencies. The article presents the results of measurements and their reference to limits.
Źródło:
Inżynieria Ekologiczna; 2012, 30; 194-205
2081-139X
2392-0629
Pojawia się w:
Inżynieria Ekologiczna
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Illustration of the elliptical field in the screened flat 3-phase high current busduct
Autorzy:
Kusiak, D.
Piątek, Z.
Szczegielniak, T.
Powiązania:
https://bibliotekanauki.pl/articles/97732.pdf
Data publikacji:
2012
Wydawca:
Politechnika Poznańska. Wydawnictwo Politechniki Poznańskiej
Tematy:
high-current busduct
magnetic fields
Opis:
The paper demonstrates the elliptical magnetic field in the flat 3-phase high current screened busduct in the context of the both the external and internal proximity effect. The modules and the amplitudes of the complex components of the magnetic field strength in the high-current busducts of this type are the functions of the two variables: r and Ѳ of the cylindrical coordinate system which subsequently provokes to the conclusion that the harmonic magnetic field in shielded high-current busducts is a rotating elliptical field. For the characterisation of complex vector values for this field, it is suggested that the length of the longer semi axis of an ellipse as showed at the end of the vector within one period should be used. The article presents the elliptic magnetic field in the screen, and the internal and external area of the screen of the flat 3-phase high current busduct.
Źródło:
Computer Applications in Electrical Engineering; 2012, 10; 80-97
1508-4248
Pojawia się w:
Computer Applications in Electrical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Levels of electromagnetic fields from rail vehicles in the context of formal requirements
Autorzy:
Miszkiewicz, Andrzej
Tchórzewski, Krzysztof
Powiązania:
https://bibliotekanauki.pl/articles/215391.pdf
Data publikacji:
2020
Wydawca:
Instytut Kolejnictwa
Tematy:
electromagnetic fields
civil protection
measurements
Opis:
The article discusses the issue of electromagnetic field levels emitted from rail vehicles with regard to civil protection. The article presents the lack of legal solutions, limits and research methods in the railway industry in Poland. It also depicts the initial results of measurements from rail vehicles. Based on the findings, taking into consideration the measurement results and suppression of electromagnetic waves in free space, electromagnetic fields may reach substantial levels which can affect people’s health and life. The authors of the article conclude that the problem should not be ignored and requires further research, bearing in mind the progressing saturation of all rail vehicles with devices and electronic systems which will serve as sources of electromagnetic fields.
Źródło:
Problemy Kolejnictwa; 2020, 187; 109-116
0552-2145
2544-9451
Pojawia się w:
Problemy Kolejnictwa
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electromagnetic fields exposure assessment among workers at broadcast centers in Poland
Autorzy:
Politański, Piotr
Aniołczyk, Halina
Gadzicka, Elżbieta
Bortkiewicz, Alicja
Zmyślony, Marek
Powiązania:
https://bibliotekanauki.pl/articles/2162494.pdf
Data publikacji:
2018-10-30
Wydawca:
Instytut Medycyny Pracy im. prof. dra Jerzego Nofera w Łodzi
Tematy:
occupational exposure
television
electromagnetic fields
exposure assessment
radio
work safety in electromagnetic fields
Opis:
Background In the studies investigating the potential health effects of occupational exposure to electromagnetic fields (EMF), the key problem is the assessment of workers’ exposure. Electromagnetic fields exposure assessment requires determining maximum EMF levels, for the acute effect, and the dose absorbed, for the cumulative effect. A study was undertaken to determine EMF exposure in workers at broadcasting centers (BCs) in Poland. It was the first part of a comprehensive project on health effects of occupational exposure to EMF. Material and Methods The study was conducted in 4 selected BCs. Spot measurements of electric field strength (E), and the results of E measurements that were made in the past for occupational hygiene assessments, were used for determining workers’ exposure to electric field. The parameters considered were the maximum E value ($\text{E}_\text{max}$), the weighted average E value ($\text{E}_\text{avg}$) and the E lifetime dose ($\text{E}_\text{lifetime dose}$). Results In the group of workers examined, the E values did not exceed 16.7 V/m for Emax (the occupational exposure limit (OEL) for work shift in Poland is 20 V/m), 2.9 V/m for $\text{E}_\text{avg}$ and 1 500 000 (V/m)²×h for $\text{E}_\text{lifetime dose}$. Conclusions In view of the lack of dosimetry data, a retrospective assessment of BC workers’ exposure to very high frequency and ultra-high frequency EMF was conducted, which made it possible to estimate EMF lifetime dose for the workers. Since the EMF exposure levels at BCs did not exceed the admissible values, they can be considered safe to the workers’ health, according to the approach used for developing OELs for EMF exposure. Med Pr 2018;69(5):477–482
Źródło:
Medycyna Pracy; 2018, 69, 5; 477-482
0465-5893
2353-1339
Pojawia się w:
Medycyna Pracy
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The use of computer simulations to assess the effectiveness of the revitalization of mature oil fields using the selected reservoir as an example
Autorzy:
Podsobiński, D.
Stopa, J.
Wojnarowski, P.
Powiązania:
https://bibliotekanauki.pl/articles/298613.pdf
Data publikacji:
2017
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
revitalization
mature fields
reservoir simulations
Opis:
The decrease in new oil field discoveries over the years makes it necessary to return to the abandoned partially depleted oil fields. Due to remaining significant amount of geological resources, mature oil field can be important in the overall balance. The production rate can be increased using various recovery methods. This paper presents a method of revitalizing mature oil fields used in Poland and wide world as well as screening criteria were presented. This article indicate the role of computer simulation as a tool in planning process of revitalization works in case of mature oil fields exploration and management. A recovery methods would be proposed, using computer simulation for the selected reservoir in south – eastern Poland as an example. The effectiveness of the recovery method would be determined through forecast of future production. An preliminary economic analysis would be performed to determine the feasibility of the seletected method taking into account the initial investment costs and different oil prices.
Źródło:
AGH Drilling, Oil, Gas; 2017, 34, 1; 67-80
2299-4157
2300-7052
Pojawia się w:
AGH Drilling, Oil, Gas
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Distribution system for generating slowly varying magnetic fields
Autorzy:
Zaguła, G.
Puchalski, C.
Czernicka, M.
Bajcar, M.
Saletnik, B.
Powiązania:
https://bibliotekanauki.pl/articles/411311.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Oddział w Lublinie PAN
Tematy:
magnetic fields
magnetic stimulation
coils
Opis:
The presented system describes a concept for generating slowly varying signals to stimulate biological objects with magnetic field. The system enables independent control of up to 10 induction coil and it generates changeable signal inducing magnetic fields in the range from 0.1 to 150μT and the frequencies from 0.1 to 100 Hz. The proposed system was applied to investigate the influence of magnetic fields with the aforementioned parameters on physical and chemical properties in selected types of fruits.
Źródło:
ECONTECHMOD : An International Quarterly Journal on Economics of Technology and Modelling Processes; 2016, 5, 4; 73-78
2084-5715
Pojawia się w:
ECONTECHMOD : An International Quarterly Journal on Economics of Technology and Modelling Processes
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Application of laser sheet technique for analysis of 3D particle velocity fields
Autorzy:
Mirek, P.
Powiązania:
https://bibliotekanauki.pl/articles/280557.pdf
Data publikacji:
2001
Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Tematy:
PIV
specklegram
velocity fields
particle trajectory
Opis:
The author has applied the laser sheet technique to acquire velocity fields and mass flows at the outlet of nozzle system, used for introducing limestone particles into a power boiler for a desulfurization process. This brings an effect in the form of multiexposure pictures, called specklegrams, which record single particle trajectories or their agglomerates in selected areas of the flow. On the basis of this the parameters of velocity field can be estimated. The author proposes a new approach to quantitative analysis of the specklegrams. It enables one to combine correlation processing with scanline particle tracking.
Zastosowanie techniki noża świetlnego w analizie trójwymiarowych pól prędkości ziaren. Autor zastosował technikę noża świetlnego do rejestracji pól prędkości i przepływów masowych przy wylocie dyszy służącej do wprowadzania sorbentu wapniowego do kotła energetycznego w procesie odsiarczania spalin. Efektem są wieloekspozycyjne obrazy zwane speklogramami, rejestrujące pojedyńcze tory cząstek lub ich aglomeratów w wybranych strefach przepływu. Na tej podstawie oszacować można parametry pola prędkości. Analiza jakościowa speklogramów może zostać przeprowadzona za pomocą zaproponowanego przez autra algorytmu, będącego połączeniem tradycyjnychmetod korelacyjnych oraz techniki obrotowej linii skanującej.
Źródło:
Journal of Theoretical and Applied Mechanics; 2001, 39, 1; 33-49
1429-2955
Pojawia się w:
Journal of Theoretical and Applied Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Laboratory measurement of wettability for Ciężkowice sandstone
Autorzy:
Czarnota, R.
Janiga, D.
Stopa, J.
Wojnarowski, P.
Powiązania:
https://bibliotekanauki.pl/articles/298866.pdf
Data publikacji:
2016
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
Ciężkowice sandstone
rock wettability
oil fields
Opis:
The type of reservoir rock wettability is one of the most important factors affecting flow of formation fluids in rock pores. It impacts on the characteristics of capillary pressure curves and residual oil saturation, what result in final recovery factor. There are generally, four differ states of wettability for hydrocarbon fields. These are: water wet, oil wet, mixed and fractional. For determination of wettability both quantitative and qualitative methods are implemented. In presented work, the results of wettability laboratory measurement for Ciężkowice sandstone by Amott–Harvey has been shown. Obtained outcomes underline the influence of wettability phenomena on the recovery factor for Carpathian hydrocarbon fields, where Ciężkowice sandstone is the oil bearing formation. The proper understanding of the wettability of reservoir is essential for determining the most efficient way of oil production.
Źródło:
AGH Drilling, Oil, Gas; 2016, 33, 1; 167-172
2299-4157
2300-7052
Pojawia się w:
AGH Drilling, Oil, Gas
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Enhanced Oil Recovery methods on offshore fields in the light of world literature
Autorzy:
Bednarz, P.
Stopa, J.
Powiązania:
https://bibliotekanauki.pl/articles/299090.pdf
Data publikacji:
2014
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
EOR
enhanced oil recovery
offshore fields
Opis:
Enhanced Oil Recovery methods (EOR) are known since long time, but in recent years they have been used primarily in the U.S. mostly for research purposes. The increased interest in their use was in the 70's of the twentieth century, and associated with the increase in oil prices. Currently for several years there has been a return to the these methods, including offshore fields. Experience in the application of EOR methods in Poland is small, currently no exploitation is carried out using them. The purpose of this article is to present the current trends and latest technologies in enhanced oil recovery methods in terms of the applicability by the Polish oil companies. Statistical data of current and planned EOR methods in the world with special emphasis on offshore reservoirs is presented. Current trends in technological development of EOR methods are given, both which are still in the phase of laboratory tests and the first tests on fields such as: carbon dioxide flooding, water alternating gas injection, Iow salinity water injection, carbonated water injection, conventional technologies of polymer gels and thermally activated polymers.
Źródło:
AGH Drilling, Oil, Gas; 2014, 31, 2; 215-229
2299-4157
2300-7052
Pojawia się w:
AGH Drilling, Oil, Gas
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Multitone nonlinear coding
Autorzy:
Nowicki, A.
Wójcik, J.
Secomski, W.
Powiązania:
https://bibliotekanauki.pl/articles/331604.pdf
Data publikacji:
2008
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
MNC method
virtual fields
acoustic source
Opis:
A new method that utilizes nonlinear properties of tissue (or another media) to improve ultrasound image resolution is presented. In our novel method the acoustic source is activated with two tones burst (2.2 and 4.4 MHz) with specially designed polarization of the individual tone burst. This new approach is called multi tone nonlinear coding MNC because the choice of polarization of the both tones (and their amplitudes) allowing optimization of the receiving properties depends on the nonlinear properties of tissue. The calculations were done for two tones bursts propagating in the tissue-like lossy medium with absorption of 7 Np/mźMHz. The concept of the Virtual Fields was introduced to explain abilities and properties of pulse inversion and MNC method and to compare both. Comparison of the spatial field distribution obtained using MNC and conventional harmonic imaging approach, in which the first harmonic is used to reconstruct the image are presented.
Źródło:
Hydroacoustics; 2008, 11; 289-298
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A variation of zero-divisor graphs
Autorzy:
Gupta, Raibatak
Sen, M.
Ghosh, Shamik
Powiązania:
https://bibliotekanauki.pl/articles/729141.pdf
Data publikacji:
2015
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
rings
zero-divisor graphs
finite fields
Opis:
In this paper, we define a new graph for a ring with unity by extending the definition of the usual 'zero-divisor graph'. For a ring R with unity, Γ₁(R) is defined to be the simple undirected graph having all non-zero elements of R as its vertices and two distinct vertices x,y are adjacent if and only if either xy=0 or yx=0 or x+y is a unit. We consider the conditions of connectedness and show that for a finite commutative ring R with unity, Γ₁(R) is connected if and only if R is not isomorphic to ℤ₃ or $ℤ₂^k$ (for any k ∈ ℕ-{1}\). Then we characterize the rings R for which Γ₁(R) realizes some well-known classes of graphs, viz., complete graphs, star graphs, paths (i.e., $P_n$), or cycles (i.e., $C_n$). We then look at different graph-theoretical properties of the graph Γ₁(F), where F is a finite field. We also find all possible Γ₁(R) graphs with at most 6 vertices.
Źródło:
Discussiones Mathematicae - General Algebra and Applications; 2015, 35, 2; 159-176
1509-9415
Pojawia się w:
Discussiones Mathematicae - General Algebra and Applications
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 375

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