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    Wyświetlanie 1-13 z 13
    Tytuł:
    An assessment of the transient effect on helicopter main rotor stability and power demand
    Autorzy:
    Raczyński, Radosław
    Siadkowska, Ksenia
    Ścisłowski, Karol
    Wendeker, Mirosław
    Powiązania:
    https://bibliotekanauki.pl/articles/2202519.pdf
    Data publikacji:
    2022
    Wydawca:
    Polskie Towarzystwo Naukowe Silników Spalinowych
    Tematy:
    propulsion
    rotor
    power demand
    helicopter
    transient effect
    napęd
    wirnik
    zapotrzebowanie na moc
    śmigłowiec
    efekt przejściowy
    Opis:
    The researched object is a helicopter main rotor with blades of variable geometric twist characteristics. Variable torsion refers to systems of actuators made of shape memory alloys. The presented numerical analyses allow for evaluating both the dynamics of the rotor in transient states, i.e. in the zone between the static phase and the full activation phase and the impact of the change on the pulsation of the amplitude of the necessary power generated by the rotor corresponding the flight state, and thus covering the demand by the disposable power generated by the engine. This study follows a methodology of numerical analyses based on Multi Body Dynamics and the Finite Element Method and uses fluid mechanics elements and algorithms to analyze lift generation, compiled in a single computational environment referring to the same period of time.
    Źródło:
    Combustion Engines; 2022, 61, 4; 23--28
    2300-9896
    2658-1442
    Pojawia się w:
    Combustion Engines
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Hall effect on MHD transient flow past an impulsively started infinite horizontal porous plate in a rotating system
    Autorzy:
    Prabhakar Reddy, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/266176.pdf
    Data publikacji:
    2018
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    magnetohydrodynamika
    płyta pozioma
    metoda Galerkina
    Hall current
    MHD
    transient
    rotation
    horizontal plate
    Galerkin FEM
    Opis:
    In this paper, the effect of Hall current on an unsteady MHD transient three dimensional flow of an electrically conducting viscous incompressible fluid past an impulsively started infinite horizontal porous plate relative to a rotating system has been studied. It is assumed that the entire system rotates with a constant angular velocity about the normal to the plate and a uniform magnetic field is applied along the normal to the plate and directed into the fluid region. The magnetic Reynolds number is assumed to be so small that the induced magnetic field can be neglected. The expressions for the primary and secondary fields and shearing stress at the plate due to primary and secondary velocity fields are obtained in a non-dimensional form. The non-dimensional governing equations of the flow are solved by using the Galerkin FEM. The effects of the physical parameters, such as the Hartmann number (M), rotation parameter (Ω), porosity parameter (K) and Hall parameter (m) on primary and secondary velocities and shearing stresses τx and τy due to primary and secondary velocities are discussed through graphs and tables, and results are physically interpreted.
    Źródło:
    International Journal of Applied Mechanics and Engineering; 2018, 23, 2; 471-483
    1734-4492
    2353-9003
    Pojawia się w:
    International Journal of Applied Mechanics and Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effect of Deep-Level Defects on Transient Photoconductivity of Semi-Insulating 4H-SiC
    Autorzy:
    Suproniuk, M.
    Kamiński, P.
    Kozłowski, R.
    Pawłowski, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/1364028.pdf
    Data publikacji:
    2014-04
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    72.40.+w
    71.55.-i
    72.20.-i
    Opis:
    A model enabling the equilibrium conductivity and transient photoconductivity of semi-insulating 4H-SiC to be simulated has been demonstrated. Using this model, the simulations of both equilibrium conductivity and transient photoconductivity have been carried out. Both the simulation and experimental results have shown that the evolution of photoconductivity in time after switching on the band-to-band generation of electron-hole pairs is strongly affected by the properties of deep level defects. The results of transient photocurrent measurements confirm the simulations results indicating that the $Z_{1/2}$ center is a very effective recombination center in semi-insulating 4H-SiC having detrimental effect on the transient photoconductivity.
    Źródło:
    Acta Physica Polonica A; 2014, 125, 4; 1042-1048
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Transient approach for iron loss separation of non-grain-oriented electrical steels considering the impact of cut edge effect
    Autorzy:
    Mülder, Christoph
    Elfgen, Silas
    Hameyer, Kay
    Powiązania:
    https://bibliotekanauki.pl/articles/140851.pdf
    Data publikacji:
    2019
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    cut edge effect
    hysteresis losses
    iron losses
    transient loss model
    Opis:
    The purpose of this paper is to focus on the loss separation of non-grain-oriented electrical steels used for speed-variable rotating electrical machines. The impact of laser-cutting, used in prototype manufacturing and of flux density harmonics, occurring locally in the lamination, on the loss distribution is studied in detail. Iron losses occurring under operation can physically be separated in different loss components. In this paper, a frequency-based loss model with parameters identified for single-sheet tester specimens, cut in strips of different widths, is therefore used. Moreover, a time-domain approach considers loss distributions occurring from higher harmonics. Hysteresis losses having high sensitivity to cut edge effects are calculated by the well-known Jiles-Atherton model adapting the frequency-based loss parameters. The model is validated by free-curve measurements at a single-sheet tester. It has been shown that the studied elliptical hysteresis model becomes inaccurate particularly for specimens with small strip widths with similar dimensions as teeth of electrical machine laminations. The incorrect mapping of losses occurring from minor hysteresis loops due to higher harmonics is concluded. The results showconsequently that both, the impact of a cut edge effect and local distributions of flux density harmonics need to be considered in terms of accurate iron loss prediction of electrical machine design.
    Źródło:
    Archives of Electrical Engineering; 2019, 68, 2; 237-244
    1427-4221
    2300-2506
    Pojawia się w:
    Archives of Electrical Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effect of lambda-cyhalothrin on memory and movement in mice after transient incomplete cerebral Ischemia
    Autorzy:
    Nieradko- Iwanicka, B.
    Borzecki, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/51205.pdf
    Data publikacji:
    2011
    Wydawca:
    Instytut Medycyny Wsi
    Źródło:
    Annals of Agricultural and Environmental Medicine; 2011, 18, 1
    1232-1966
    Pojawia się w:
    Annals of Agricultural and Environmental Medicine
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The transition effect in rail tracks – assessment of transient energy for low frequency vibrations
    Autorzy:
    Sołkowski, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/231030.pdf
    Data publikacji:
    2014
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    strefa przejściowa
    efekt przejścia
    modelowanie
    tor kolejowy
    podtorze
    właściwości
    analiza stanów przejściowych
    metoda energii
    drgania niskiej częstotliwości
    transition zone
    transition effect
    modelling
    railtrack
    track foundation
    characteristics
    transient analysis
    energy approach
    low frequency vibration
    Opis:
    The transition effect between different track-foundation systems is examined from the point of view of energy that is produced during the passage of load. Analytical solution is given. A model of beam on elastic foundation with damping is used as the base model. It is developed into a model composed of two parts that represent the track-subgrade system with an abrupt change in mechanical parameters: bending stiffness, foundation stiffness, damping, and mass. Several calculations are carried out including examples of comparative calculations with the Finite Difference Model and the Finite Element Model. Transient rail deflections and energy are determined, which may serve to estimate the rate of track-subgrade deterioration.
    Źródło:
    Archives of Civil Engineering; 2014, 60, 1; 123-143
    1230-2945
    Pojawia się w:
    Archives of Civil Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The Effect of Power Ultrasound on Microstructure Evolution During the Transient Liquid Stage of Ultrasonic-Promoted TLP Bonding SiCp/Al MMCs
    Autorzy:
    Zhou, Changzhuang
    Ma, Lin
    Zhu, Chao
    Cui, Qinghe
    Liang, Jindi
    Song, Yujian
    Powiązania:
    https://bibliotekanauki.pl/articles/2174569.pdf
    Data publikacji:
    2022
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    transient liquid phase bonding
    silicon carbide reinforced aluminum matrix composites
    ultrasonics
    zinc interlayer
    Opis:
    Ultrasound-promoted transient liquid phase bonding (U-TLP) is a high quality, high efficiency, and low-cost method for fast bonding of difficult-wetting materials in the atmospheric environment. In this paper, U-TLP was used to bond SiC particles reinforced aluminium-based metal matrix composite which particle volume fraction was 70%. The pure zinc foil was used as the intermediate layer. The effects of ultrasonic on microstructure evolution and mechanical properties of joints during the transient liquefaction stage were investigated. The mechanism of ultrasonic effects in the transient liquefaction stage of U-TLP was also inducted. The results showed that high volume fraction SiCp/Al MMCs were bonded well at low temperature in the air environment. Ultrasonic vibration can remove the oxide film on the surface of aluminum matrix composites, enhance the wettability of SiC particles with weld metal, promote atomic diffusion and homogenization of SiC particles, and improve the welding quality and efficiency. Reasonable increase of ultrasonic vibration time could effectively improve the joint strength.
    Źródło:
    Archives of Metallurgy and Materials; 2022, 67, 4; 1283--1291
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The Effect of Seat Design on Vibration Comfort
    Autorzy:
    Wijaya, A. R.
    Jönsson, P.
    Johansson, O.
    Powiązania:
    https://bibliotekanauki.pl/articles/89698.pdf
    Data publikacji:
    2003
    Wydawca:
    Centralny Instytut Ochrony Pracy
    Tematy:
    seat design
    transient vibration
    vibration discomfort
    warunki pracy
    drgania
    kierowcy i maszyniści
    Opis:
    A field study was done to evaluate different seat designs in the aspect of minimizing vibration transmission and reducing the level of discomfort experienced by drivers subjected to transient vibration. Two seat designs (sliding or fixed in the horizontal direction) were compared in an experimental based on variation of sitting posture, speed, and type of obstacle. The comparison was done by assessing discomfort and perceived motion and by vibration measurement. Ten professional drivers were used as participants. Maximum Transient Vibration Value and Vibration Dose Value were used in the evaluation. The results showed that a sliding seat is superior in attenuating vibration containing transient vibration in the horizontal direction. It was also perceived as giving less overall and low back discomfort compared to a fixed seat.
    Źródło:
    International Journal of Occupational Safety and Ergonomics; 2003, 9, 2; 193-210
    1080-3548
    Pojawia się w:
    International Journal of Occupational Safety and Ergonomics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effect of doping on time-of-flight transient currents in twin crystalline layers: a Monte-Carlo study
    Autorzy:
    Rybicki, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1941715.pdf
    Data publikacji:
    2000
    Wydawca:
    Politechnika Gdańska
    Tematy:
    hopping transport
    time-of-flight experiment
    Monte Carlo methods
    Opis:
    In the paper we present the results of the Monte Carlo simulations of time-of-flight transient currents in hopping systems containing various, concentrations of transport-active centres placed in an inert matrix, and doped with various concentrations of additional transport-active centres, characterised by a different ionisation potential than the host transport centres. Such hopping centre distribution can be found in molecularly doped organic crystals. The carriers are allowed to jump between localised states of two kinds: the host transport sites of concentration c/sub 0/, and the additional doping sites of concentration c/sub d/. We deal only with the dependence of the carrier mobility on doping level, and on the difference of ionisation potentials between the host and dopant centres, at fixed external field and temperature. The results of simulations performed for various dopings, and various hopping sites distributions in energy, are discussed. The carrier jump statistics is discussed in detail.
    Źródło:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2000, 4, 1; 33-48
    1428-6394
    Pojawia się w:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Temperature changes in the vicinity of thermally loaded structure embedded in the soil: effect of sand content and saturation degree
    Autorzy:
    Różański, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/178365.pdf
    Data publikacji:
    2017
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    transient heat flow
    temperature
    quartz
    organic matter
    degree of saturation
    Opis:
    Due to the rapid development of geothermal technologies, the problem of efficient and proper evaluation of soil thermal conductivity becomes extremely important. Factors mostly affecting the soil conductivity are the conductivity of solid phase and the degree of saturation. The former one is mainly affected by the mineral composition, in particular, by the content of quartz whose conductivity is the highest one among all the minerals forming soil skeleton. Organic matter, because of its relatively low conductivity, influences the solid conductivity as well. The problem addressed in the paper is the influence of mentioned factors on temperature changes in the vicinity of thermally loaded structure embedded in the soil medium. Numerical simulations are carried out for different values of soil thermal conductivity resulting from various quartz contents and degrees of saturation. In addition, a weak coupled – heat and water transport – problem is considered.
    Źródło:
    Studia Geotechnica et Mechanica; 2017, 39, 2; 61-71
    0137-6365
    2083-831X
    Pojawia się w:
    Studia Geotechnica et Mechanica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The grooved lip effect on reciprocating hydraulic rod seal performances in transient condition: elastohydrodynamic lubrication
    Autorzy:
    Bahi, Y.
    El Gadari, M.
    Rahmoune, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/264834.pdf
    Data publikacji:
    2020
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    chropowatość
    siła tarcia
    wyciek
    hydraulic rod seal
    surface textured
    roughness
    friction force
    leakage
    Opis:
    It is commonly known that the sealing performance of dynamic seals is significantly influenced by the surface finish. To reduce friction effect and leakage ratio, new generations of grooved lip or shaft have emerged, but only two computational models were performed up to now with a textured elastomeric lip: spiral groove in the axial direction or micro-cavities according to the circumferential direction. However, if the numerical results have confirmed the slight effect of the grooved lip on the rotary lip seal performances, it seems relevant to investigate the influence of such grooves on the reciprocating hydraulic rod seal behavior. Thus, the scope of this work is to perform a parametric study of the grooved lip throughout a one-dimensional elastohydrodynamic model by taking into account the elasticity of the lip and the shaft roughness. After confirming the validity of the current model, numerical simulations have been performed and compared with experiments. The effect of lip grooves on the hydraulic rod seal behavior in outstroke and instroke shaft motion has been underlined. Thereby, it is shown that the leakage and the average film thickness are sensible to both the depth and the density of the lip groove. Additionally, a slight effect of the pattern shape is observed on the friction force.
    Źródło:
    International Journal of Applied Mechanics and Engineering; 2020, 25, 2; 11-21
    1734-4492
    2353-9003
    Pojawia się w:
    International Journal of Applied Mechanics and Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Control of operability of Peltier modules in cooling systems based on the analysis of transient operating modes
    Autorzy:
    Kuzichkin, Oleg Rudolfovich
    Konstantinov, Igor Sergeevich
    Vasilyev, Gleb Sergeevich
    Surzhik, Dmitry Igorevich
    Powiązania:
    https://bibliotekanauki.pl/articles/1845461.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    thermoelectric system
    agriculture
    complex
    transients
    peltier effect
    identification algorithms
    Opis:
    The paper is devoted to the control of operability of Peltier modules based on the analysis of transient modes of their operation. Advantages of using low-power thermoelectric modules for the development of thermoelectric plants with adaptive control systems for the needs of the agricultural complex, which significantly reduce their cost characteristics, are shown. The problem of using the stationary mode of their operation, associated with the low efficiency of the modules, as well as the dynamic mode, associated with the presence of transient processes, is indicated. It is noted that overcoming this problem requires solution of the task of automation of reliability providing the well-known approaches to its solution are shown, for which the key advantages and disadvantages are given. An approach is proposed to complex control of the operability and quality of thermoelectric modules during their expluatation in three components of the physical process of thermoelectric conversion (Peltier thermoelectric effect, electrical and thermal transfer phenomena) by analyzing transients in the system based on identification algorithms. To justify it, the necessary equations and mathematical relations are given. Aprobating of the proposed approach was carried out experimentally by determining the time constants for operable and defective commercially available modules and showed its significant advantages over the standard verification procedure.
    Źródło:
    Archives of Thermodynamics; 2021, 42, 2; 31-42
    1231-0956
    2083-6023
    Pojawia się w:
    Archives of Thermodynamics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Numerical and finite element contact temperature analysis of friction material’s type effect on a thermal transient behavior of a single-disc dry clutch
    Analiza numeryczna i elementów skończonych temperatury styku jako efektu rodzaju materiału trącego i jej wpływ na zachowanie termiczne suchych sprzęgieł jednotarczowych
    Autorzy:
    Faidh-Allah, M. H.
    Powiązania:
    https://bibliotekanauki.pl/articles/190080.pdf
    Data publikacji:
    2017
    Wydawca:
    Stowarzyszenie Inżynierów i Techników Mechaników Polskich
    Tematy:
    dry friction clutch
    thermoelastic problem
    Friction materials
    suche sprzęgło tarciowe
    termosprężystość
    materiały tarciowe
    Opis:
    The sliding period is considered a critical period in the lifetime of friction clutches, because most failures occur during this period. High temperatures due to sliding velocity will appear on the contacting surfaces of the friction clutch system (e.g., in single -disc clutch are pressure plate, clutch discs and flywheel). The finite element technique has been developed to investigate the effect of the type of friction material (material properties) on the transient thermoelastic behaviour of a single-disc dry clutch. Two types of friction materials are used in this work: organic and sintered friction materials. Axisymmetric models are developed to simulate a friction clutch system (single disc with two effective sides). The results represent the comparisons between organic and sintered friction discs, behaviours during slipping periods in clutches.
    Stan poślizgu tarciowego ze względu na występowanie największej ilości uszkodzeń jest krytycznym stanem pracy sprzęgieł tarciowych. Wysoka temperatura pracy występująca na powierzchniach trących elementów sprzęgieł spowodowana jest poślizgiem (np. w sprzęgłach jednotarczowych na klockach, tarczach i kole zamachowym). Metoda elementów skończonych została wykorzystana do zbadania wpływu rodzaju materiału (właściwości materiału) na zagadnienie termosprężystości w suchych sprzęgłach tarciowych. W pracy wykorzystano dwa rodzaje materiałów tarciowych: organiczny i spiekany. Opracowano osiowosymetryczne modele symulujące sprzęgło tarciowe (pojedyncza tarcza z dwoma okładzinami). Wynikiem pracy jest porównanie cyklów poślizgu pomiędzy dyskami wykonanymi z materiału organicznego oraz spiekanego.
    Źródło:
    Tribologia; 2017, 271, 1; 35-43
    0208-7774
    Pojawia się w:
    Tribologia
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-13 z 13

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