Institute of Photonics and Electronics

Institute of Photonics and Electronics 627 records found  beginprevious21 - 30nextend  jump to record: Search took 0.00 seconds. 
Graphite/n-InP Schottky barrier with electrophoretically deposited Pt nanoparticles for hydrogen and nitrogen-monoxide detection
Žďánský, Karel ; Vaniš, Jan ; Černohorský, Ondřej ; Kacerovský, Pavel ; Fojtík, A.
N-type InP was deposited with Pt nanoparticles (NPs) by electrophoresis. The Pt NPs density was varied from a tenth of monolayer to several monolayers. Schottky contacts were made by colloidal graphite on the InP wafer site covered with Pt NPs. It was observed that H2 was detected by an increase of the current while NO was detected by its decrease. For explanation, we discuss mechanism which involves negative charging of adsorbed H atoms with electrons by increasing affinity level due to correlation efects
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Plný tet: UFE 0387602 - Download fulltextPDF
Speech Processing
Vích, Robert
Proceedings of the Workshop on Speech Processing is a periodic publication collecting the contributions presented at the Czech-German Workshop organized every year in September in Prague This proceedings volume includes 22 papers by 41 authors. Papers are devoted to phonetics and prosody, construction of dialogs, speech analysis, synthesis, and recognition and voice conversion.
GLOTTAL SIGNAL MODIFICATION FOR EMOTIONAL SPEECH SYNTHESIS
Vondra, Martin ; Vích, Robert
In the contribution speech decomposition into the source and vocal tract components is described. It is based on separation of the signal into the minimum- and maximum-phase speech components. Further the modification of the source speech component by changing the glottal model parameters is applied in order to achieve emotional speech by change of the neutral speech style
IMPROVING UNIT CONCATENATIONS IN EXPERIMENTAL SPEECH SYNTHESIS BASED UPON COMPLEX CEPSTRUM IN THE CONCATENATION-BASED TTS SYSTEM EPOS
Staněk, Jan
During testing phase of a new speech analysis and synthesis methods based upon complex cepstrum and implemented in a TTS system Epos, we have discovered disturbing speech artifacts on the borders of the concatenated units. To eliminate these artifacts, we have chosen to practically implement and test usage of smoothing algorithms in the cepstral domain and observe its impact on the resulting synthesized speech. The results of our tests are presented in this paper.
Applications of porous III-V semiconductors in heteroepitaxial growth and in preparation of nanocomposite structures
Nohavica, Dušan ; Grym, Jan ; Gladkov, Petar ; Hulicius, Eduard ; Pangrác, Jiří
We investigate the concept of epitaxial growth on porous substrates Both crystalographically oriented and current line oriented pore networks in InP and GaAs were created by electrochemical dissolution. Heat treatment of InP pores at 650 ºC and GaAs pores at 700-850ºC converted them into microcavities. The capability of improved structural quality homo- and hetero-epitaxially overgrown films is demonstrated on InAs and GaInAs layers with a different composition grown on porous GaAs substrates
Subspace Methods in Linear DS - CDMA Detection
Šimša, Jan
Application of signal subspace methods in linear mean square error (MSE) detectors of direct sequence CDMA signals. Focusing on the cross-spectral (CS) method, its origin and a relation to multistage Wiener filter (MWF) is shown. This filter results from splitting of correlation matrix
Graphite Schottky barriers on n-InP and n-GaN with deposited Pd, Pt or bimetallic Pd/Pt nanoparticles for H2 sensing
Žďánský, Karel ; Muller, M. ; Černohorský, Ondřej ; Yatskiv, Roman
High Schottky barriers have been achieved by applying colloidal graphite on n-type InP and on n-type GaN semiconductor crystal wafers. The barrier heights were shown to be close to Schottky-Mott limit ad thermionic emission theory. Porous properties of the graphite Schottky contacts were demonstrated by scanning electron microscopy.
Study of layers of metal nanoparticles on semiconductor wafers for hydrogen detection
Muller, M. ; Žďánský, Karel ; Zavadil, Jiří ; Piksová, K.
Colloid solutions of metal Pt, Pd and Pt/Pd alloy nanoparticles by reverse micelle technique in isooctane were prepared. Layers of the nanoparticles on InP and GaN substrates using electrophoretic deposition were prepared. Metal nanoparticles in the colloid and in deposits were characterized by SEM. Schottky diodes were fabricated by application of colloidal graphite on nanoparticle layer. An increase in current in hydrogen-nitrogen mixture was measured for hydrogen concentrations between 5 and 1000 ppm.
Study of layers of Pd on InP
Černohorský, Ondřej ; Žďánský, Karel ; Proška, J.
Pd nanoparticles were prepared in colloid solution stabilized by AOT. The layers were prepared by electrophoretic deposition through the mask of polystyrene spheres. SEM measurement showed that particles in colloid solution are separated and after deposition they form small aggregates on InP. The size of these aggregates depends on the time of deposition. I-V characteristics were measured and then Schottky barrier height and ideality factor were calculated. The morphology of layers was monitored by SEM.
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Plný tet: UFE 0374575 - Download fulltextPDF
Preparation and characterizatiobn of layers of Au, Pd and Rh nanoparticles deposited on n-InP substrates
Kostejn, M. ; Žďánský, Karel ; Piksová, K. ; Zavadil, Jiří
Colloids of Au, Pd and Rh nanoparticles (NPs) were prepared in reverse micelles and surface plasmon absorption bands were identified. Layers of metal NPs were deposited on InP substrates by electrophoretic deposition and imaged by SEM. Low-temperature photoluminescence spectrum of InP was found to be enhanced mainly by Au NPs. Sensitivity to hydrogen of Schottky barriers prepared by dropping colloidal graphite onto the surface of InP partly covered with Pd NPs was measured by current change in 100 ppm H2/N2.

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