Search results for "source"
showing 10 items of 6139 documents
The relationship between visible light emission and species fraction of the hydrogen ion beams extracted from 2.45 GHz microwave discharge.
2015
The relationship between Balmer-α and Fulcher-band emissions with extracted H + , H + 2 , and H + 3 ions is demonstrated for a 2.45 GHz microwave discharge. Ion mass spectra and optical measurements of Balmer-α and Fulcher-band emissions have been obtained with a Wien Filter having an optical viewport on the plasma chamber axis. The beam of approximately 1 mA is analyzed for different plasma conditions simultaneously with the measurement of light emissions both with temporal resolution. The use of visible light emissions as a valuable diagnostic tool for monitoring the species fraction of the extracted beams is proposed. peerReviewed
Photoelectron emission experiments with ECR-driven multi-dipolar negative ion plasma source
2017
Photoelectron emission measurements have been performed using a 2.45 GHz ECR-driven multi-dipolar plasma source in a low pressure hydrogen discharge. Photoelectron currents induced by light emitted from ECR zone and H− production region are measured from Al, Cu, Mo, Ta, and stainless steel (SAE 304) surfaces as a function of microwave power and neutral hydrogen pressure. The total photoelectron current from the plasma chamber wall is estimated to reach values up to 1 A for 900 W of injected microwave power. It is concluded that the volumetric photon emission rate in wavelength range relevant for photoelectron emission is a few times higher in arc discharge. peerReviewed
VUV emission spectroscopy combined with H- density measurements in the ion source Prometheus I
2016
“Prometheus I” is a volume H− negative ion source, driven by a network of dipolar electron cyclotron resonance (ECR; 2.45 GHz) modules. The vacuum-ultraviolet (VUV) emission spectrum of low-temperature hydrogen plasmas may be related to molecular and atomic processes involved directly or indirectly in the production of negative ions. In this work, VUV spectroscopy has been performed in the above source, Prometheus I, both in the ECR zones and the bulk (far from ECR zones and surfaces) plasma. The acquired VUV spectra are correlated with the negative ion densities, as measured by means of laser photodetachment, and the possible mechanisms of negative ion production are considered. The well-e…
Facile and efficient chemical functionalization of aliphatic polyesters by cross metathesis
2016
International audience; An effective preparation of new tailor-made macromolecular materials via a combination of two (atom-efficient) catalytic transformations is reported. First, new aliphatic polyesters with alternated composition have been prepared using a salen aluminum catalyst system. Next, the pendant vinyl moieties in those copolymers have been selectively transformed into various functional groups by metathesis in the presence of homogeneous Grubbs catalysts. The latter metathesis reaction has been optimized in terms of catalytic activity and selectivity, to define the conditions for an effective and safe procedure that does not affect the macromolecular architecture. All polymer …
Measures of performance for the portfolio management
2012
Development of bidirectional dc-dc converters for hybrid power sources - Final Report
2018
A Bidirectional Isolated Full-Bridge Converter was designed, prototyped and tested. The device is intended to interface a Bank of Supercapacitors with a battery-powered bus, in order to boost the capability of supplying large power peaks. The converter was based on the Isolated Dual Active Bridge configuration. When driven by an external control voltage, it is capable of generating in both directions a train of current pulses, with 2kW peak power, for any battery voltage in the range 24-32V and for any supercapacitor voltage in the range 35-70V. Worst-case battery current was 70A. Pulse duration was 100ms with 50% duty cycle and 1 ms rise time.
Harmonic sources detection in power systems via nonactive power measurements according to IEEE Std. 1459-2010: theoretical approach and experimental …
2010
In this paper an enhanced decision-making strategy is presented for the detection of harmonic sources in power systems able to detect also which is the prevailing nature of the disturbance (nonlinearity or unbalance). It makes use of some simple indices, which are evaluated by means of the measurements of some nonactive power quantities, proposed by the authors and derived from the approach of the IEEE Std. 1459-2010. The decision-making rules for the proposed strategy are presented and discussed by means of simulation and experimental tests. The results obtained are presented, showing the effectiveness of the proposed strategy for the detection of the dominant harmonic source upstream or d…
Ziņu diskurss un ziņu rakstu mašīntulkošana
2019
Pēdējā desmitgadē mašīntulkošana ir ievērojami attīstījusies un tiek plaši izmantota tulkošanas nozarē, lai izpildītu pieaugošo pieprasījumu pēc ātrākiem tulkojumiem un samazinātu izmaksas. Lai maksimāli palielinātu mašīntulkošanas efektivitāti un iegūtu augstas kvalitātes tulkojumu, mašīntulkošanas darbplūsmā parasti tiek iekļauti divi papildus procesi: rediģēšana pirms un pēc mašīntulkošanas. Pētījuma mērķis ir izpētīt gan latviešu, gan angļu ziņu diskursu, kā arī salīdzināt divu mašīntulkošanas rīku – Google Translate un Tilde Translator – efektivitāti, tulkojot ziņu rakstus no angļu valodas latviešu valodā. Darbā tiek pielietotas teorētiskas un praktiskas pētniecības metodes. Teorētiskā…
Connectivity Analysis in EEG Data: A Tutorial Review of the State of the Art and Emerging Trends
2023
Understanding how different areas of the human brain communicate with each other is a crucial issue in neuroscience. The concepts of structural, functional and effective connectivity have been widely exploited to describe the human connectome, consisting of brain networks, their structural connections and functional interactions. Despite high-spatial-resolution imaging techniques such as functional magnetic resonance imaging (fMRI) being widely used to map this complex network of multiple interactions, electroencephalographic (EEG) recordings claim high temporal resolution and are thus perfectly suitable to describe either spatially distributed and temporally dynamic patterns of neural acti…