Search results for "SII"
showing 10 items of 3468 documents
Individual arc-discharge synthesized multiwalled carbon nanotubes probed with multiple measurement techniques
2020
Arc-discharge synthesized multiwalled carbon nanotubes (AD-MWNT), or related MWNTs, exhibit a good quality compared to the more common type of MWNT synthesized by catalytic chemical vapor deposition methods. Yet experimental measurements on these are rather few and typically have not correlated data from different measurement techniques. Here, the authors report Raman spectroscopy, scanning probe microscopy, conductivity measurements, and force microscopy on single AD-MWNTs. The results demonstrate the high quality of AD-MWNTs and are compatible with the view of them as the best approximation of MWNTs as an assembly of defect-free concentric individual single-walled carbon nanotubes. The au…
Failure Estimates for SiC Power MOSFETs in Space Electronics
2018
Silicon carbide (SiC) power metal-oxide-semiconductor field effect transistors (MOSFETs) are space-ready in terms of typical reliability measures. However, single event burnout (SEB) due to heavy-ion irradiation often occurs at voltages 50% or lower than specified breakdown. Failure rates in space are estimated for burnout of 1200 V devices based on the experimental data for burnout and the expected heavy-ion linear energy transfer (LET) spectrum in space. peerReviewed
Laser-induced time-resolved luminescence in analysis of rare earth elements in apatite and calcite
2021
Laser-induced time-resolved luminescence was used to study rare earth element (REE) containing natural apatite and calcite minerals. The luminescence from 400 nm to 700 nm in the minerals was analyzed with excitation ranges 210–340 nm and 405–535 nm. As an outcome, several useful excitation wavelengths to detect one or more REE from apatite and calcite are reported. The feasibility of selected excitations in e.g. avoiding the disturbance of intense Mn2+ luminescence band, results was demonstrated with a non-gated detector. peerReviewed
Spectroscopic method to study low charge state ion and cold electron population in ECRIS plasma
2018
The results of optical emission spectroscopy experiments probing the cold electron population of a 14 GHz Electron Cyclotron Resonance Ion Source (ECRIS) are reported. The study has been conducted with a high resolution spectrometer and data acquisition setup developed specifically for the diagnostics of weak emission line characteristic to ECRIS plasmas. The optical emission lines of low charge state ions and neutral atoms of neon have been measured and analyzed with the line-ratio method. The aforementioned electron population temperature of the cold electron population (Te < 100 eV) is determined for Maxwell-Boltzmann and Druyvesteyn energy distributions to demonstrate the applicability …
Microwave emission from ECR plasmas under conditions of two-frequency heating induced by kinetic instabilities
2018
Multiple frequency heating is one of the most effective techniques to improve the performances of ECR ion sources. It has been demonstrated that the appearance of the periodic ion beam current oscillations in ECRIS at high heating power and low magnetic field gradient is associated with kinetic plasma instabilities. Recently it was proven that one of the main features of multiple frequency heating is connected with stabilizing effect, namely the suppression of electron cyclotron instability in ECRIS plasmas. Due to this kind of stabilization it is possible to run the ion source in stable mode using higher total microwave power and thus to obtain better ion beam parameters. Unfortunately, ev…
Investigation into the gas mixing effect in ECRIS plasma using Kα and optical diagnostics
2018
Mixing a lighter gas species into the plasma of an ECRIS is known to enhance high charge state production of the heavier gas species. With this investigation, Kα diagnostics, optical emission spectroscopy and the measured charge state distribution of the extracted beam were combined to shed more light on the physics governing this phenomenon. Kα diagnostics data from two ion sources, the JYFL 14 GHz ECRIS and the GTS at iThemba LABS, are presented to gain confidence on the observed trends. The results seem to favor ion cooling as the most likely mechanism responsible for the favorable influence of the gas mixing.Mixing a lighter gas species into the plasma of an ECRIS is known to enhance hi…
Energy-Efficient Resource Optimization with Wireless Power Transfer for Secure NOMA Systems
2018
In this paper, we investigate resource allocation algorithm design for secure non-orthogonal multiple access (NOMA) systems empowered by wireless power transfer. With the consideration of an existing eavesdropper, the objective is to obtain secure and energy efficient transmission among multiple users by optimizing time, power and subchannel allocation. Moreover, we also take into consideration for the practical case that the statistics of the channel state information of the eavesdropper is not available. In order to address the optimization problem and its high computational complexity, we propose an iterative algorithm with guaranteed convergence to deliver a suboptimal solution for gene…
Temperature dependence of recombination radiation in semiconductor nanostructures with quantum dots containing impurity complexes
2021
Temperature dependence of the spectral intensity of recombination radiation in a quasi-zero-dimensional structure, containing impurity complexes “A++e” (a hole localized on a neutral acceptor, interacting with an electron localized in the ground state of a quantum dot), has been investigated in an external electric field in the presence of tunneling decay of a quasistationary A+-state. Probability of dissipative tunneling of a hole has been calculated in the one-instanton approximation, and the influence of tunneling decay and of an external electric field on the A+-state binding energy and on the spectra of recombination radiation, associated with the optical transition of an electron from…
Optimal transport maps on Alexandrov spaces revisited
2018
We give an alternative proof for the fact that in $n$-dimensional Alexandrov spaces with curvature bounded below there exists a unique optimal transport plan from any purely $(n-1)$-unrectifiable starting measure, and that this plan is induced by an optimal map.
Soita ja laula kuin Näppäri : näppäripedagogiikan toteutuminen lyhytkurssilla
2012
Näppäripedagogiikka on kaustislaisen Mauno Järvelän (s. 1949) kehittämä kansanmusiikinopetustyyli, jota toteutetaan Näppäreiksi kutsuttavissa ryhmissä. Mauno Järvelä on koulutukseltaan klassinen viulisti, joka esittää aktiivisesti myös kansanmusiikkia. Näppäreiden opetus alkoi 1980-luvun puolessa välissä Perhonjokilaakson kansalaisopiston suojissa. Kansalaisopistotoiminnan lisäksi näppäripedagogiikkaan nojautuvaa opetusta annetaan nykyisin erilaisilla näppärikursseilla eri puolella Suomea. Näppäreiden ohjelmisto on alusta lähtien nojautunut lähinnä kaustislaiseen perinnemusiikkiin. Tutkielma keskittyy näppäripedagogiikan kuvaamiseen laadullisten tutkimusmenetelmien, kuten havainnoinnin ja h…