Ograniczanie wyników
Czasopisma help
Autorzy help
Lata help
Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 617

Liczba wyników na stronie
first rewind previous Strona / 31 next fast forward last
Wyniki wyszukiwania
Wyszukiwano:
w słowach kluczowych:  magnetic field
help Sortuj według:

help Ogranicz wyniki do:
first rewind previous Strona / 31 next fast forward last
EN
The linear theory of viscoelasticity remains an important field of research like most solids and polymer materials when exposed to a vicious dynamic loading effect. This article introduces a new model for describing the behavior of thermoviscoelastic microbeams considering the effects of temperature change and the longitudinal magnetic field. The governing equations in this model are derived based on the Euler–Bernoulli beam theory, Kelvin–Voigt model of viscosity, the generalized thermoelasticity, and the classical Maxwell equations. The two ends of the microbeam are clamped and subjected to the influence of a laser pulse with a temporal intensity profile. The analytical solutions to the physical fields are evaluated using the Laplace transform and its inversion transforms are performed numerically. The thermo-viscoelastic responses of the microbeam are calculated numerically and investigated graphically. The effect of different parameters such as viscosity, laser intensity, and the magnitude of the magnetic field are studied in detail.
2
Content available remote The influence of Helmholtz and Golay coil homogenity on rectangular plate bending
EN
The subject of the paper is a rectangular plate. The structure of the plate issymmetrical. The plate is made of a cellular structure of a core and two external faces. There isferrofluid in each cell of the porous core. The core is made of polyethylene foam and two facesare polyurethane sheets. It is assumed that cells in the core are regular and dense and the facesare thin, therefore, a plate filled in with ferrofluid can be treated as homogeneous. The plateis placed in the magnetic field. The magnetic field is generated by two systems of coils – theHelmholtz coil (HC ) and the Golay coil (GC). The former generates an almost fixed magneticfield in the considered volume (where the plate is placed), and the latter generates a gradientmagnetic field. The changing size of each subsystem of magnetic field coils, the distribution andstrength of the magnetic field change as well. The magnetic field induces loads in the plate,both perpendicular and in plane. The plate bending function is approximated by the bicubicspline function presented by normalized B-spline functions. The influence of changes in thehomogeneity volume and the magnetic field strength (by changing the coil size) on the platebending is analyzed in the paper. The results of the analysis are presented in tables and figures.
PL
Przedmiotem rozważań pracy jest jedno z rozwiązań konstrukcyjnych magnetycznych separatorów wysokogradientowych jakim jest separator matrycowy. W polu magnetycznym generowanym przez nadprzewodzące uzwojenie o konstrukcji osiowo - symetrycznej (solenoid) znajduje się matryca (kanister wypełniony elementami gradientotwórczymi w postaci wiórek lub waty ferromagnetycznej), w której zachodzi proces ekstrakcji cząstek z zawiesiny przepływającej przez separator. Wysokogradientowy separator matrycowy (HGMS) pracuje cyklicznie: po okresie napełnienia matrycy produktem magnetycznym (efektywny czas pracy separatora), następuje okres czyszczenia matrycy, tzn. przywracanie jej zdolności akumulacyjnych (czas martwy). Proces technologiczny jest efektywny, jeśli czas napełniania matrycy jest długi, zaś czas martwy - krótki. Wydłużenie czasu efektywnego możliwe jest m. in. poprzez stosowanie pól magnetycznych o dużych wartościach indukcji magnetycznej.
EN
The subject of deliberation in this paper is one of the constructional solutions of high gradient magnetic separators, which is a matrix separator. In the magnetic field generated by the superconducting winding of the axial-symmetric construction (solenoid), there is a matrix (a canister filled with gradient forming elements in the form of chips or ferromagnetic steel wool), in which the process of extracting particles from the slurry flowing through the separator takes place. The high gradient matrix separator (HGMS) works cyclically: filling the matrix with a magnetic product (effective operation time), is followed by period of matrix cleaning, i.e. restoring its storage capacity (still time). The technological process is effective if the time of filling the matrix is long and still time is short. Prolonging the effective time is possible, through e.g. application of magnetic fields with high values of magnetic induction.
PL
Celem pracy było zbadanie wpływu stymulacji sadzeniaków (Solanum tuberosum L.) w zmiennym polu magnetycznym na wybrane parametry wegetacji roślin ziemniaka bardzo wczesnej odmiany Red Sonia (typ ogólnoużytkowy). Sadzeniaki ziemniaka stymulowano w zmiennym polu magnetycznym z wykorzystaniem cewki powietrznej bez rdzenia magnetycznego (solenoidu). Stosowano pole magnetyczne o indukcji w zakresie 20-80 mT oraz czas ekspozycji 1-30 s. Zakresem badań objęto wschody roślin oraz liczbę i długość łodyg roślin ziemniaka. Uzyskane wyniki poddano analizie statystycznej. Wyniki badań wskazują, że pole magnetyczne zastosowane w odniesieniu do sadzeniaków modyfikuje liczbę pędów rośliny ziemniaka. Nie wykazano statycznie istotnego wpływu pola magnetycznego na tempo wschodów roślin oraz długość łodyg.
EN
The aim of the study was to investigate the effect of stimulation of seed potatoes (Solanum tuberosum L.) in a variable magnetic field on selected vegetation parameters of potato plants of the very early Red Sonia variety (general use type). Potato seed was stimulated in a variable magnetic field using an air coil without a magnetic core (solenoid). A magnetic field with an induction in the range of 20-80 mT and an exposure time of 1-30 s were used. The scope of research included plant emergence and the number and length of potato plant stems. The obtained results were subjected to statistical analysis. The research results indicate that the magnetic field applied to seed potatoes modifies the number of shoots of the potato plant. There was no statistically significant effect of the magnetic field on the rate of plant emergence and stem length.
5
EN
The article presents an analysis of the effectiveness of the Wireless Power Transfer (WPT) periodic system consisting of transmitting and receiving coils. In the analysis taken into account various variants of the system geometry (radius of the coil, number of turns, distance between the transmitting-receiving coils). The influence of variable system geometry and frequency on system efficiency was analysed. The Finite Element Method (FEM) with the using periodic boundary conditions for the analysis was used. Based on the results obtained, it was checked at which system parameters wireless power transfer of the system is possible.
PL
W artykule przedstawiono analizę efektywności układu periodycznego WPT (Wireless Power Transfer) złożonego z cewek nadawczych i odbiorczych. W analizie uwzględniono różne warianty geometrii układu (promień cewki, liczba zwojów, odległość między cewkami). Analizowano wpływ zmiennej geometrii układu oraz częstotliwości na sprawność układu. Do analizy wykorzystano metodę elementów skończonych (FEM) z zastosowaniem periodycznych warunków brzegowych. Na podstawie uzyskanych wyników sprawdzono, przy jakich parametrach układu możliwy jest bezprzewodowy transfer energii
EN
The article presents a method and results for numerical and analytical analysis of Wireless Power Transfer (WPT) system consisting of transmitting and receiving plane coils. In the analysis took into account different variants of the WPT system geometry (number of turns, distance between the transmitting-receiving coils). The influence of variable system geometry and the frequency on system efficiency was analysed. The Finite Element Method (FEM) with the using antiperiodicity boundary conditions for the analysis was used. The results obtained by numerical and analytical method indicate at which system parameters wireless energy transfer is possible.
PL
W artykule przedstawiono metody i wyniki analizy numerycznej oraz analitycznej układu Wireless Power Transfer (WPT) złożonego z cewek płaskich (nadawczych i odbiorczych). W analizie uwzględniono różne warianty geometrii układu WPT (liczba zwojów, odległość między cewkami). Analizowano wpływ geometrii układu oraz częstotliwości na sprawność układu. Do analizy wykorzystano metodę elementów skończonych (FEM) z zastosowaniem aperiodycznych warunków brzegowych. Otrzymane wyniki wskazują, przy jakich parametrach układu możliwy jest bezprzewodowy transfer energii.
7
Content available remote Magnes Bittera wykonany z wolframu i chłodzony ciekłym helem
PL
Opisano projekt magnesu Bittera wykonanego z płyt wolframowych i chłodzonego ciekłym helem o temperaturze 4,2 K. Obliczono indukcję pola magnetycznego wytwarzanego przez ten magnes, jego moc zasilania i parametry układu chłodzenia. Moc ta jest ok. 104 razy mniejsza, niż moc zasilania powszechnie używanych magnesów Bittera wykonanych z miedzi i chłodzone wodą. Wykazano wykonalność tego magnesu przy użyciu dostępnych obecnie możliwości technicznych.
EN
The project of the Bitter magnet made of tungsten plates and coiled by liquid helium in temperature of 4 K is described. The magnetic flux density produced by this magnet, power supply and coiling system parameters are calculated. This power is about 104 times smaller than power of commonly used Bitter’s magnets made of cooper and coiled by water. Feasibility of this magnet by using of the present accessible technical aids is demonstrated.
8
Content available remote Laboratory stands for generating an alternating magnetic field
EN
The research paper reviews two laboratory stands, based on a Helmholtz coil, for generating an alternating magnetic field. The first stand enables generating an alternating magnetic field of any shape and frequency up to 26 Hz. The task of the second one is to generate an attenuated harmonic signal, with a fundamental frequency of 7.7 kHz. The article also presents a time waveform of the generated magnetic field.
PL
pracy przedstawiono dwa stanowiska laboratoryjne do generowania zmiennego pola magnetycznego, oparte na cewce Helmholtza. Stanowisko pierwsze umożliwia generowanie zmiennego pola magnetycznego o dowolnym kształcie i częstotliwości do 26 Hz. Zadaniem drugiego stanowiska jest wytwarzanie sygnału harmonicznego tłumionego o częstotliwości podstawowej 7,7 kHz. W artykule przedstawiono postać czasową generowanego pola magnetycznego.
EN
The static magnetic field MF (0.44 T) effects on the adsorption of three surfactants: cationic bromide (DTAB) and hexadecyltrimethylammonium bromide (CTAB), and anionic sodium dodecylsulfate (SDS) from their 10-3 M solutions were studied on bare and low-temperature air plasma treated glass plates. The surface properties of the adsorbed surfactants layers were determined via the water advancing and receding contact angles measurements and then calculation of the apparent surface free energy. An optical profilometer was used to determine the structure and topography of the adsorbed layers. The DTAB and SDS concentrations were below their critical micelle concentration and that of CTAB very close to its cmc. The results showed that in the case of DTAB solution (much below its cmc) a small decrease in the contact angle appeared while in CTAB (close to its cmc) an increase in the contact angle value was observed if adsorbed in the MF presence. Quite good reproducibility of the contact angle values was obtained. This was not the case for the SDS solution where the contact angle values were scattered. The reason was that the anionic surfactant did not adsorb homogeneously on the negatively charged glass surface. The contact angles and the calculated values of the work of water spreading clearly show that MF influences the structure of the surfactant adsorbed layer which was also supported by the optical profilometry images.
EN
A numerical investigation of two dimensional steady magnetohydrodynamics heat and mass transfer by laminar free convection from a radiative horizontal circular cylinder in a non-Darcy porous medium is presented by taking into account the Soret/Dufour effects. The boundary layer conservation equations, which are parabolic in nature, are normalized into non-similar form and then solved numerically with the well-tested, efficient, implicit, stable Keller–Box finite-difference scheme. We use simple central difference derivatives and averages at the mid points of net rectangles to get finite difference equations with a second order truncation error. We have conducted a grid sensitivity and time calculation of the solution execution. Numerical results are obtained for the velocity, temperature and concentration distributions, as well as the local skin friction, Nusselt number and Sherwood number for several values of the parameters. The dependency of the thermophysical properties has been discussed on the parameters and shown graphically. The Darcy number accelerates the flow due to a corresponding rise in permeability of the regime and concomitant decrease in Darcian impedance. A comparative study between the previously published and present results in a limiting sense is found in an excellent agreement.
EN
This paper is focused on the study of two dimensional steady magnetohydrodynamics heat and mass transfer by laminar free convection from a radiative horizontal circular cylinder in a non-Darcy porous medium by taking into account of the Soret/Dufour effects. The boundary layer equations, which are parabolic in nature, are normalized into non-similar form and then solved numerically with the well-tested, efficient, implicit, stable Keller–Box finite-difference scheme. Numerical results are obtained for the velocity, temperature and concentration distributions, as well as the local skin friction, Nusselt number and Sherwood number for several values of the parameters, namely the buoyancy ratio parameter, Prandtl number, Forchheimer number, magnetohydrodynamic body force parameter, Soret and Dufour numbers. The dependency of the thermophysical properties has been discussed on the parameters and shown graphically. Increasing the Forchheimer inertial drag parameter reduces velocity but elevates temperature and concentration. Increasing the Soret number and simultaneously reducing the Dufour number greatly boosts the local heat transfer rate at the cylinder surface. A comparative study of the previously published and present results in a limiting sense is made and an excellent agreement is found between the results.
EN
The influence of thermal emission and unvarying magnetic field of convective heat and mass transfer of a rotating nano-liquid in an upright conduit constrained by a stretching and motionless wall is studied. The temperature, concentration profile, primary and secondary velocities have been computed through similarity transformation and fourth-order Runge-Kutta shooting technique. The objective of this article is to measure the impact of emission constraint, Brownian movement constraint and Eckert number, thermophoresis constraint, Prandtl number, space, and temperature-dependent heat source constraint on velocity. The results are presented in tables and graphs. Further, various constraint impacts on the skin friction coefficient, heat and mass transfer rates are also explored. This work is pertinent to biotechnological and engineering uses, like mass and heat transfer enhancement of microfluids and design of bioconjugates.
EN
A magnetic anomaly map of an underwater area indicates the places where the distortion of a magnetic field has occurred. Through the interpretation procedures, a hydrographer can easily indicate the places where the ferromagnetic objects are, then calculate the level of each distortion – by the value of total anomaly – and initially, based on their own knowledge, try to classify the sources of distortion. Objects that induce micro anomaly changes (>30 nT) – like industrial infrastructure, such as pipelines and cables; to unintendingly located targets with ferromagnetic characteristics: wrecks (vessels, planes, cars), military mines, UXO, lost anchors and chains. Interpretation of such a map with the attempt to identify the source of magnetic field distortion, requires a specific knowledge as well as experience. In this article the author presents the research results of dimensioning and location of potential ferromagnetic underwater objects based on a magnetic anomaly map. For further consideration an anchor of buoyage system is taken into account. Geolocation of ferromagnetic sources, contours extraction and dimensioning algorithms of ferromagnetic targets have been carried out in Matlab software. The map of magnetic anomaly enhanced with extracted information was developed in ArcGIS. The analysis was carried out for the purpose of the dissertation thesis and the results are used in further research.
PL
Mapa anomalii magnetycznych obszaru podwodnego wskazuje miejsca, w których występuje zniekształcenie ziemskiego pola magnetycznego. Za pomocą procedur interpretacyjnych hydrograf może łatwo wskazać miejsca, w których znajdują się obiekty ferromagnetyczne, a następnie obliczyć poziom każdego zniekształcenia – według wartości całkowitej anomalii – i na podstawie własnej wiedzy spróbować sklasyfikować źródła zniekształceń. Obiekty, które indukują zniekształcenie pola magnetycznego na obszarach wodnych, mogą być różne. Te wywołujące zmiany pola magnetycznego (anomalia >30 nT) to między innymi infrastruktura przemysłowa, np.: rurociągi i kable, a także nieumyślnie zlokalizowane cele o charakterystyce ferromagnetycznej: wraki (statków, samolotów, samochodów), miny wojskowe, niewybuchy, kotwice i łańcuchy statków. Interpretacja takiej mapy w celu zidentyfikowania źródła zniekształcenia pola magnetycznego wymaga specjalistycznej wiedzy i doświadczenia. Całkowita wartość anomalii magnetycznej określa wielkość poziomu ferromagnetyzmu obiektu, a wymiar powierzchni objętej anomalią umożliwia geolokalizację celu i ustalenie jego wymiarów. W artykule autorzy przedstawiają wyniki badań wymiarowania i lokalizacji potencjalnych ferromagnetycznych podwodnych obiektów na podstawie mapy anomalii magnetycznych. Przeanalizowano anomalię magnetyczną spowodowaną przez kotwicę oznakowania nawigacyjnego. Geolokalizacja źródeł ferromagnetycznych, ekstrakcja ich konturów i algorytmy wymiarowania celów ferromagnetycznych zostały przeprowadzone za pomocą oprogramowania Matlab. Porównano i podsumowano wyniki działania różnych filtrów stosowanych do przetwarzania obrazów. Mapa anomalii magnetycznej wzbogacona o wyodrębnione informacje została opracowana w ArcGIS. Analiza została przeprowadzona na potrzeby pracy doktorskiej, a jej wyniki wykorzystano w dalszych badaniach
EN
The paper presents the possibility of fabricating ceramic-metal composites by an innovative method of centrifugal slip casting in the magnetic field. It was examined whether the use of this method would allow obtaining a gradient concentration of metal particles in the ceramic matrix. In the applied technique, the horizontal rotation axis was used. The study investigated the effect of solid phase content on the properties and microstructure of the products. Water-based suspensions with 35, 40, 45 and 50 vol.% of solid-phase content were prepared with 10 vol.% additional of nickel powder. The viscosity of prepared slurries was considered. The gradient distribution of nickel particles in the zirconia matrix was observed on SEM. Vickers hardness of ZrO2-Ni composites has been measured. The research revealed that the physical properties depend on the volume fraction of solid content and increase as the volume of solid content increases.
EN
The work discusses numerical and experimental researches, which are focused on developing a coherent model of magnetic interactions causing the levitation of the starting trolley of the unmanned aerial vehicle (UAV) catapult. The starting trolley is levitating over the catapult’s tracks, which generate the magnetic field. The levitation is made possible by the diamagnetic properties of high-temperature superconductors, placed in supports of the starting trolley. The introduction of the article briefly analyzes the catapult structure. Next, it explains the nature of associated with the Meissner and flux pinning effect magnetic interactions which causes the levitation phenomenon. The paper presents the results of numerical analysis of the magnetic field, generated by the catapult’s tracks arranged in two configurations: a “chessboard” and a “gutter” pattern. The numerical model was solved, using the finite element method. Parameterization of the numerical model was made based on the measurements of the magnetic field, generated by a single magnet.
EN
The paper is devoted to study the effect of gravity, magnetic field and laser pulse on the general model of the equations of generalized thermoelasticity for a homogeneous isotropic elastic half-space. The formulation is applied under four theories of generalized thermoelasticity: the coupled theory, Lord-Schulman theory, Green-Lindsay theory as well as Green-Naghdi theory. By employing normal mode analysis, the analytical expressions for the displacement components, temperature and the (mechanical and Maxwell’s) stresses distribution are obtained in the physical domain. These expressions are also calculated numerically and corresponding graphs are plotted to illustrate and compare the theoretical results. The effect of gravity, magnetic field and laser pulse are also studied and displayed graphically to show the physical meaning of the phenomena. A comparison has been made between the present results and the results obtained by the others. The results indicate that the effects of magnetic field, laser pulse and gravity field are very pronounced.
EN
The present study investigates the onset of penetrative convection induced by selective absorption of radiation in a magnetic nanofluid saturated porous medium. The influence of Brownian motion, thermophoresis, and magnetophoresis on magnetic nanofluid treatment is taken into consideration. The Darcy’s model is selected for the porous medium. We conduct a linear stability analysis to examine the onset of instability and evaluate the results for two different configurations, namely, when the layer is heated from below and when the layer is heated from above. The numerical investigations are carried out by applying the Chebyshev pseudospectral method. The effect of the porosity parameter E, parameter Y (represents the ratio of internal heating to boundary heating), Lewis number Le, concentration Rayleigh number Rn, Langevin parameter αL, width of nanofluid layer d, diffusivity ratio η, and modified diffusivity ratio NA is examined at the onset of convection. The results indicate that the convection commences easily with an increase in the value of Y, Le, and NA but opposite in the case with a decrease in the value of E, αL, η and d for both the two configurations. The parameter Rn advances the onset of convection when the layer is heated from below, while delays the onset of convection when the layer is heated from above.
PL
Na wstępie zostały podane trudności związane ze stabilizacją stanowiska tachimetru podczas pomiarów w geodezji inżynieryjnej. Opisano szczegółowo budowę i sposób użycia dwóch innowacyjnych stawideł do stabilizacji tej pozycji. W pierwszym z tych stawideł wykorzystano podciśnienie, a w drugim pole magnetyczne. Zaletami tych stawideł są skuteczność, prosta konstrukcja, niskie koszty i możliwość samodzielnego wykonania.
EN
In the introduction there are mentioned difficulties in stabilization of tachymeter position during measurements in the land surveying. The construction and applied method of two innovative devices for position stabilization are described in details. Subatmospheric pressure is used in the first device and the magnetic field is used in the other one. Efficiency, simple construction, low cost and possibilities of home-making are main advantages of those devices.
EN
Eddy-current separation can be an effective technique for sorting non-ferrous metals from nonmetallic wastes. In this paper, we simulate the magnetic characteristics of rotational eddy current separator rounded by drum of permanents magnets in two dimensions, used to sort a mixture of non ferrous particles of different nature. The induced current and magnetic force of ejection in different kind and size of non-ferrous particles are simulated and computed by using the finite element method with Comsol Multiphysics software. The aim of this work is to show the magnetic performance of separator and induced current density in particles, the influence of the conductivity of each of non-ferrous particles on the eddy current and the repulsion force.
PL
W artykule przedstawiono symulację pracy separatora magnetycznego z bębnem złożonym z magnesów i wykorzystującego prądy wirowe. Układ separatora i charakterystyki separowanych elementów modelowane są metodą elementu skończonego z wykorzystaniem oprogramowania Comsol Multiphysics.
PL
W artykule przedstawiono przykładowe metody komputerowe umożliwiające obliczenia pola magnetycznego przewodnika z prądem, oraz przykłady kształtowania pola magnetycznego.
EN
The article presents examples of computer methods that allow calculation of magnetic field of a conductor with current, and examples of magnetic field shaping.
first rewind previous Strona / 31 next fast forward last
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.