Number of found documents: 626
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Subspace Methods in Linear DS - CDMA Detection
Šimša, Jan
2011 - English
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 Keywords: spread spectrum; multiuser detectors; subspace methods Available at various institutes of the ASCR
Subspace Methods in Linear DS - CDMA Detection

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 ...

Šimša, Jan
Ústav fotoniky a elektroniky, 2011

Study of layers of metal nanoparticles on semiconductor wafers for hydrogen detection
Muller, M.; Žďánský, Karel; Zavadil, Jiří; Piksová, K.
2011 - English
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. Keywords: semiconductor devices; nanostructures; sensors Available at various institutes of the ASCR
Study of layers of metal nanoparticles on semiconductor wafers for hydrogen detection

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 ...

Muller, M.; Žďánský, Karel; Zavadil, Jiří; Piksová, K.
Ústav fotoniky a elektroniky, 2011

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
2011 - English
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 Keywords: porous semiconductors; heterotransitions; electrochemical etching of metals Available at various institutes of the ASCR
Applications of porous III-V semiconductors in heteroepitaxial growth and in preparation of nanocomposite structures

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 ...

Nohavica, Dušan; Grym, Jan; Gladkov, Petar; Hulicius, Eduard; Pangrác, Jiří
Ústav fotoniky a elektroniky, 2011

Time and frequency transfer in all-optical network
Smotlacha, V.; Kuna, Alexander
2011 - English
This paper describes usage of all-optical network for time metrology application - Time and frequency transfer between two geographically distant sites. Although several approaches exist, there is no production implementation yet. Our method is based on newly developed adapters utilizing channels in a DWDM (Dense Wavelength-Division Multiplexing) network. We present results of tests performed in real production all-optical network including the time transfer between atomic clocks in Prague and Vienna over more than 500 km long optical path Keywords: Time transfer; Frequency transfer; All-optical network Available on request at various institutes of the ASCR
Time and frequency transfer in all-optical network

This paper describes usage of all-optical network for time metrology application - Time and frequency transfer between two geographically distant sites. Although several approaches exist, there is no ...

Smotlacha, V.; Kuna, Alexander
Ústav fotoniky a elektroniky, 2011

Analysis of spectral changes in speech affected by orthodontic appliances
Přibil, Jiří; Přibilová, Anna
2010 - English
This paper is focused at investigation of influence of the upper removable plate and the lower fixed orthodontic brackets and their combination on spectral properties of produced speech. Spectral changes were analyzed and evaluated by spectrograms and mean Welch’s periodograms. From obtained results follows that the removable orthodontic appliance mainly affects spectrograms of speech, and these changes are most significant in voiced parts of spectrograms – corresponding to vowels, voiced consonants etc. Keywords: Signal processing; Speech analysis Available at various institutes of the ASCR
Analysis of spectral changes in speech affected by orthodontic appliances

This paper is focused at investigation of influence of the upper removable plate and the lower fixed orthodontic brackets and their combination on spectral properties of produced speech. Spectral ...

Přibil, Jiří; Přibilová, Anna
Ústav fotoniky a elektroniky, 2010

Přenos přesného času pomocí družicových systémů
Pánek, Petr
2010 - Czech
Článek se zabývá využitím družicových navigačních systémů pro přenos přesného času. Popisuje jevy, které tento přenos času ovlivňují a uvádí příklady výsledků měření. The paper deals with the use of the satellite navigation systems for a precise time transfer. Effects affecting the time transfer are described and examples of measurement results are presented. Keywords: time measurement; satellite navigation Available at various institutes of the ASCR
Přenos přesného času pomocí družicových systémů

Článek se zabývá využitím družicových navigačních systémů pro přenos přesného času. Popisuje jevy, které tento přenos času ovlivňují a uvádí příklady výsledků měření....

Pánek, Petr
Ústav fotoniky a elektroniky, 2010

GLOTTAL SIGNAL MODIFICATION FOR EMOTIONAL SPEECH SYNTHESIS
Vondra, Martin; Vích, Robert
2010 - English
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 Keywords: analysis of speech; speech synthesis Available at various institutes of the ASCR
GLOTTAL SIGNAL MODIFICATION FOR EMOTIONAL SPEECH SYNTHESIS

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 ...

Vondra, Martin; Vích, Robert
Ústav fotoniky a elektroniky, 2010

PD NANOLAYERS FOR HYDROGEN SENSORS
Yatskiv, Roman; Žďánský, Karel; Grym, Jan; Piksová, K.
2010 - English
We presented study nanoparticle layers created by electrophoretic deposition. A possibility of using Pd nanolayers for the formation of Schottky barriers with a large Schottky barrier height (SBH) value on n-type tin doped InP is proposed together with its potential application in high-sensitive hydrogen sensors. Keywords: Nanoparticles; Schottky barriers; Hydrogen sensor Available at various institutes of the ASCR
PD NANOLAYERS FOR HYDROGEN SENSORS

We presented study nanoparticle layers created by electrophoretic deposition. A possibility of using Pd nanolayers for the formation of Schottky barriers with a large Schottky barrier height (SBH) ...

Yatskiv, Roman; Žďánský, Karel; Grym, Jan; Piksová, K.
Ústav fotoniky a elektroniky, 2010

Notes to multistage Wiener filter in DS-CDMA detector
Šimša, Jan
2010 - English
The contribution follows report oriented towards design of Wiener filter in DS-CDMA detector of signals as a multistage structure. Such approach avoids evaluation of the inverse of a known autocorrelation matrix of a sampled response of the chip matched filter to a wide-sense stationary input signal. The contribution gives more detailed description of detector signal processing and its consequences. Keywords: CDMA; multiuser detector; interference Available at various institutes of the ASCR
Notes to multistage Wiener filter in DS-CDMA detector

The contribution follows report oriented towards design of Wiener filter in DS-CDMA detector of signals as a multistage structure. Such approach avoids evaluation of the inverse of a known ...

Šimša, Jan
Ústav fotoniky a elektroniky, 2010

IMPROVING UNIT CONCATENATIONS IN EXPERIMENTAL SPEECH SYNTHESIS BASED UPON COMPLEX CEPSTRUM IN THE CONCATENATION-BASED TTS SYSTEM EPOS
Staněk, Jan
2010 - English
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. Keywords: analysis of speech; speech synthesis Available at various institutes of the ASCR
IMPROVING UNIT CONCATENATIONS IN EXPERIMENTAL SPEECH SYNTHESIS BASED UPON COMPLEX CEPSTRUM IN THE CONCATENATION-BASED TTS SYSTEM EPOS

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 ...

Staněk, Jan
Ústav fotoniky a elektroniky, 2010

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