Voitech Stankevic

Prof. Voitech Stankevic

Department of Functional Materials and Electronics, Center for Physical Sciences and Technology, Lithuania
orcid

Research Focus & Metrics

Academic Career Length

32Years (1995-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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25 May 2022 in Foods
Verified
Journal Article
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Ahmed TahaAhmed Taha
Ahmed Taha
Federico CasanovaFederico Casanova
Federico Casanova
PSPovilas Simonis
Povilas Simonis
Voitech StankevicVoitech Stankevic
Voitech Stankevic
Mohamed A. E. GomaaMohamed A. E. Gomaa
Mohamed A. E. Gomaa
Arunas StirkeArunas Stirke
Arunas Stirke
Dairy and plant-based proteins are widely utilized in various food applications. Several techniques have been employed to improve the techno-functional properties of these proteins. Among them, pulsed electric field (PEF) technology has recently attracted considerable attention as a green technology to enhance the functional properties of food proteins. In this review, we briefly explain the fundamentals of PEF devices, their components, and pulse generation and discuss the impacts of PEF treatment on the structure of dairy and plant proteins. In addition, we cover the PEF-induced changes in the techno-functional properties of proteins (including solubility, gelling, emulsifying, and foaming properties). In this work, we also discuss the main challenges and the possible future trends of PEF applications in the food proteins industry. PEF treatments at high strengths could change the structure of proteins. The PEF treatment conditions markedly affect the treatment results with respect to proteins’ structure and techno-functional properties. Moreover, increasing the electric field strength could enhance the emulsifying properties of proteins and protein-polysaccharide complexes. However, more research and academia–industry collaboration are recommended to build highly effective PEF devices with controlled processing conditions.

12 June 2021 in Energies
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Journal Article
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JDJustas Dilys
Justas Dilys
Voitech StankevicVoitech Stankevic
Voitech Stankevic
KŁKrzysztof Łuksza
Krzysztof Łuksza
This paper addresses the implementation and optimization of an Extended Kalman Filter (EKF) for the Permanent Magnet Synchronous Motor (PMSM) sensorless control using an ARM Cortex-M3 microcontroller. A various optimization levels based on arithmetic calculation reduction was implemented in ARM Cortex-M3 microcontroller. The execution time of EKF estimator was reduced from 260.4 μs to 37.7 μs without loss of accuracy. To further reduce EKF execution time, the separation of a Kalman gain and covariance matrices calculation from prediction and measurement state update, a novel method was proposed, and the performance of it an EKF estimator with separation of a Kalman gain and covariance matrices calculation from prediction and measurement state update was analyzed. Simulation and experiments results validate that the proposed technique could provide the same accuracy with less computation time. A tendency of minimum Kalman gain and covariance matrices calculation frequency from rotor electrical frequency was analyzed and are presented in the paper.

4 August 2023 in Polymers
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Ahmed TahaAhmed Taha
Ahmed Taha
Federico CasanovaFederico Casanova
Federico Casanova
Martynas TalaikisMartynas Talaikis
Martynas Talaikis
Voitech StankevicVoitech Stankevic
Voitech Stankevic
Nerija ZurauskieneNerija Zurauskiene
Nerija Zurauskiene
Arunas StirkeArunas Stirke
Arunas Stirke
Pulsed electric field (PEF) as a green processing technology is drawing greater attention due to its eco-friendliness and potential to promote sustainable development goals. In this study, the effects of different electric field strengths (EFS, 0–30 kV/cm) on the structure and physicochemical features of casein micelles (CSMs) were investigated. It was found that the particle sizes of CSMs increased at low EFS (10 kV/cm) but decreased at high EFS (30 kV/cm). The absolute ζ-potential at 30 kV/cm increased from −26.6 (native CSMs) to −29.5 mV. Moreover, it was noticed that PEF treatment leads to changes in the surface hydrophobicity; it slightly increased at low EFS (10 kV/cm) but decreased at EFS > 10 kV/cm. PEF enhanced the protein solubility from 84.9 (native CSMs) to 87.1% (at 10 kV/cm). PEF at low EFS (10 kV/cm) intensified the emission fluorescence spectrum of CSMs, while higher EFS reduced the fluorescence intensity compared to native CSMs. Moreover, the analysis of the Amide Ι region showed that PEF-treated CSMs reduced the α-helix and increased the β-sheet content. Raman spectra confirmed that PEF treatment > 10 kV/cm buried tyrosine (Tyr) residues in a hydrophobic environment. It was also found that PEF treatment mainly induced changes in the disulfide linkages. In conclusion, PEF technology can be employed as an eco-friendly technology to change the structure and physiochemical properties of CSMs; this could improve their techno-functional properties.

17 November 2009 in IEEE Transactions on Magnetics
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Journal Article
Closed access
OLOliver Liebfried
Oliver Liebfried
MLMarkus Loffler
Markus Loffler
MSMarkus Schneider
Markus Schneider
SBSaulius Balevicius
Saulius Balevicius
Voitech StankevicVoitech Stankevic
Voitech Stankevic
VPValentina Plausinaitiene
Valentina Plausinaitiene
We present local measurements of absolute values of pulsed magnetic fields in a typical electromagnetic launching system-a small coilgun. For this purpose, we designed magnetic field sensors based on thin polycrystalline La0.83Sr0.17MnO3 films exhibiting a colossal magnetoresistance (CMR) effect. We measured the magnetic field distribution inside the bore of a coilgun consisting of a multilayer coil and inserted a copper projectile in the shape of a hollow cylinder using an array of CMR-based sensors. In order to identify places with highly inhomogeneous magnetic field changes in direction and value, we simulated a pulsed magnetic field inside the coilgun. The measurements of magnetic induction compared well with simulations. CMR-based sensors are able to measure highly inhomogeneous magnetic fields in very small areas independently of the magnetic field direction with respect to the orientation of the sensor.

5 June 2022 in Materials
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GZGreta Zambzickaite
Greta Zambzickaite
Martynas TalaikisMartynas Talaikis
Martynas Talaikis
JDJorunas Dobilas
Jorunas Dobilas
Voitech StankevicVoitech Stankevic
Voitech Stankevic
ADAudrius Drabavicius
Audrius Drabavicius
Lina MikoliunaiteLina Mikoliunaite
Lina Mikoliunaite
The synthesis of magnetic particles triggers the interest of many scientists due to their relevant properties and wide range of applications in the catalysis, nanomedicine, biosensing and magnetic separation fields. A fast synthesis of iron oxide magnetic particles using an eco-friendly and facile microwave-assisted solvothermal method is presented in this study. Submicron Fe3O4 spheres were prepared using FeCl3 as an iron source, ethylene glycol as a solvent and reductor and sodium acetate as a precipitating and nucleating agent. The influence of the presence of polyethylene glycol as an additional reductor and heat absorbent was also evaluated. We reduce the synthesis time to 1 min by increasing the reaction temperature using the microwave-assisted solvothermal synthesis method under pressure or by adding PEG at lower temperatures. The obtained magnetite spheres are 200–300 nm in size and are composed of 10–30 nm sized crystallites. The synthesized particles were investigated using the XRD, TGA, pulsed-field magnetometry, Raman and FTIR methods. It was determined that adding PEG results in spheres with mixed magnetite and maghemite compositions, and the synthesis time increases the size of the crystallites. The presented results provide insights into the microwave-assisted solvothermal synthesis method and ensure a fast route to obtaining spherical magnetic particles composed of different sized nanocrystallites.

19 August 2022 in Nanomaterials
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Lina MikoliunaiteLina Mikoliunaite
Lina Mikoliunaite
Martynas TalaikisMartynas Talaikis
Martynas Talaikis
AMAleksandra Michalowska
Aleksandra Michalowska
JDJorunas Dobilas
Jorunas Dobilas
Voitech StankevicVoitech Stankevic
Voitech Stankevic
Gediminas NiauraGediminas Niaura
Gediminas Niaura
Bifunctional magneto-plasmonic nanoparticles that exhibit synergistically magnetic and plasmonic properties are advanced substrates for surface-enhanced Raman spectroscopy (SERS) because of their excellent controllability and improved detection potentiality. In this study, composite magneto-plasmonic nanoparticles (Fe3O4@AgNPs) were formed by mixing colloid solutions of 50 nm-sized magnetite nanoparticles with 13 nm-sized silver nanoparticles. After drying of the layer of composite Fe3O4@AgNPs under a strong magnetic field, they outperformed the conventional silver nanoparticles during SERS measurements in terms of signal intensity, spot-to-spot, and sample-to-sample reproducibility. The SERS enhancement factor of Fe3O4@AgNP-adsorbed 4-mercaptobenzoic acid (4-MBA) was estimated to be 3.1 × 107 for a 633 nm excitation. In addition, we show that simply by changing the initial volumes of the colloid solutions, it is possible to control the average density of the silver nanoparticles, which are attached to a single magnetite nanoparticle. UV-Vis and SERS data revealed a possibility to tune the plasmonic resonance frequency of Fe3O4@AgNPs. In this research, the plasmon resonance maximum varied from 470 to 800 nm, suggesting the possibility to choose the most suitable nanoparticle composition for the particular SERS experiment design. We emphasize the increased thermal stability of composite nanoparticles under 532 and 442 nm laser light irradiation compared to that of bare Fe3O4 nanoparticles. The Fe3O4@AgNPs were further characterized by XRD, TEM, and magnetization measurements.