Search results for "VS."
showing 10 items of 1506 documents
Generalized PWM-VSI Control Algorithm Based on a Universal Duty-Cycle Expression: Theoretical Analysis, Simulation Results, and Experimental Validati…
2007
This paper presents a new approach in realizing various carrier-based pulsewidth-modulation techniques by a generalized control algorithm, which is referred to as the universal control algorithm and is obtained via unequal sharing of null states. The flexibility of such an approach allows one to easily and quickly control two-level inverters. Furthermore, this approach may be also extended with few changes to the control of multilevel inverters. The algorithm that is presented here for two-level voltage-source inverters (VSIs) also obtains efficient detection and management of both the linear and overmodulation ranges. In the overmodulation range, which is treated by using the alpha-beta co…
Closed-loop bandwidth impact on MVSA for rotor broken bar diagnosis in IRFOC double squirrel cage induction motor drives
2013
This paper investigates the detectability of rotor broken bars in indirect rotor flux oriented control (IRFOC) for variable speed double cage induction motor drives, using vibration signature analysis techniques. The Impact of the closed loop control system cannot be neglected when the detection of rotor asymmetries in the machine is based on the signature analysis of electrical or mechanical variables. Therefore, the investigation of rotor fault components for different bandwidths of closed-loop regulators is necessary to evaluate its relevance in the above listed variables. This paper investigates the impact of the control system on relevance of the fault components computed from axial an…
Vides apstākļu ietekme uz mikro- un makroelementu saturu pārtikas produktos Latvijā
2014
Bez vitāli svarīgo mikro- un makroelementu ieneses pārtikā no vides (augsnes, ūdens un gaisa) ir iespējams arī barības ķēdes, t. sk., pārtikas piesārņojums ar toksiskiem vai potenciāli toksiskiem elementiem, piemēram, As, Cd, Hg, Pb. Promocijas darba mērķa ietvaros tika veikta Latvijā iegūtu pārtikas produktu paraugu mikro- un makroelementu sastāva kvantitatīvā analīze, lai noskaidrotu vides apstākļu ietekmi uz elementu koncentrāciju un ieneses ceļiem pārtikā. Papildus, lai vērtētu elementu biopieejamību barības ķēdē, tika veikta eksperimentāla pārtikas kultūraugu audzēšana mākslīgi piesārņotā augsnē. Iegūtie dati liecina par vairāku dabiskas un antropogēnas izcelsmes vides apstākļu, piemēr…
Modality and Injunctive in Homeric Greek: The role of epistemic particles and adverbs in counterfactual constructions
2020
Structurally, unaugmented aorists and imperfects belong to the oldest layer of verbal forms attested in Greek, which continue the so-called Indo-European ‘injunctive’. The latter was inflectionally underspecified as regards verbal categories such as tense or mood (Hoffmann 1967; Kiparsky 1968). Thus, the question arises as to how the attitude of the speaker toward the content of his utterance was expressed. The aim of this paper is to investigate the role of epistemic particles and adverbs co-occurring with injunctives in the Iliad and the Odyssey, focusing in particular on past counterfactual constructions. Crosslinguistic studies have shown that such modal constructions reflect the univer…
Pressure Impact on the Stability and Distortion of the Crystal Structure of CeScO3
2017
[EN] The effects of high pressure on the crystal structure of orthorhombic (Pnma) perovskite-type cerium scandate were studied in situ under high pressure by means of synchrotron X-ray powder diffraction, using a diamond-anvil cell. We found that the perovskite-type crystal structure remains stable up to 40 GPa, the highest pressure reached in the experiments. The evolution of unit-cell parameters with pressure indicated an anisotropic compression. The room-temperature pressure¿volume equation of state (EOS) obtained from the experiments indicated the EOS parameters V0 = 262.5(3) Å3 , B0 = 165(7) GPa, and B0¿ = 6.3(5). From the evolution of microscopic structural parameters like bond distan…
Perovskite Solar Cells: Stable under Space Conditions
2020
Metal halide perovskite solar cells (PSCs) are of interest for high altitude and space applications due to their lightweight and versatile form factor. However, their resilience toward the particle spectrum encountered in space is still of concern. For space cells, the effect of these particles is condensed into an equivalent 1 MeV electron fluence. The effect of high doses of 1 MeV e-beam radiation up to an accumulated fluence to 10^16 e-cm-2 on methylammonium lead iodide perovskite thin films and solar cells is probed. By using substrate and encapsulation materials that are stable under the high energy e-beam radiation, its net effect on the perovskite film and solar cells can be studied.…
Kristne barnehager
2020
Artikkelen gir ny kunnskap om kristne barnehager som utgjør omkring 4,5 % av norske barnehager. Vi redegjør for lovgrunnlaget og undersøker blant annet ulike livssynsvedtekter og hvordan et utvalg ansatte forstår mandatet sitt, og bidrar til å gjøre verdigrunnlaget og fagområdet etikk, religion og filosofi (ERF) synlig i hverdagen og ved høytidene. En empirisk undersøkelse fra høsten 2019 og våren 2020 utgjør det viktigste empiriske materialet for artikkelen og omfattet 20 ansatte med pedagogisk ansvar i 19 barnehager i Oslo og på Agder. Ti av barnehagene var kristne. I denne artikkelen presenteres resultater fra den delen av undersøkelsen som var rettet inn mot de kristne barnehagene. Vi t…
Quantum mechanics-molecular dynamics approach to the interpretation of x-ray absorption spectra.
2009
The quantum mechanics-molecular dynamics approach to the simulation of configuration-averaged EXAFS spectra is proposed, and its application is discussed for the example of the Ti K-edge EXAFS spectrum in cubic perovskite SrTiO(3). Proper use of ab initio quantum mechanics allows a number of empirical parameters, used in the molecular dynamics simulation, to be reduced, whereas the molecular dynamics allows us to account for temperature effects. All together, the approach provides a way of accounting for static and dynamic disorder in EXAFS signals from the coordination shells above the first one, where many-atom (multiple-scattering) effects are often important.
Toward tailorable surfaces: a combined theoretical and experimental study of lanthanum niobate layered perovskites.
2014
A comprehensive theoretical investigation of the MLaNb2O7 (M = H, Li, Na, K, Rb, and Cs) series of ion-exchangeable layered perovskite is presented. These perovskites are in particular interesting in view of their potential applications as inorganic supports for the design of new hybrid inorganic-organic proton conductors. In particular, their structural and electronic properties have been investigated by periodic calculations in the framework of Density Functional Theory, using different exchange-correlation functionals. A general very good agreement with the available experimental (XRD, NPD, and EXAFS) data has been found. The structure of the protonated HLaNb2O7 form has also been furthe…
Extended X-Ray Absorption Fine Structure Spectroscopy of Perovskite-Type Compounds
2000
Application of the extended x-ray absorption fine structure (EXAFS) spectroscopy to a study of the local atomic structure in perovskitetype materials is discussed on the example of several compounds (m-WO3, NaxWO3, ReO3 and FeF3). The sensitivity of the EXAFS to the out-of-center and rotational distortions is discussed in details.