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Wyświetlanie 1-15 z 29
Tytuł:
Analog-based duobinary-4-PAM for electrical bandwidth limited optical fiber links
Autorzy:
Suhr, L.F.
Madsen, P.
Monroy, I. T.
Olmos, J. J. V.
Powiązania:
https://bibliotekanauki.pl/articles/173933.pdf
Data publikacji:
2016
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
optical communications
advanced modulation formats
multilevel modulation
Opis:
This paper presents a demonstration of a seven level duobinary-4-PAM signal operating at 10.16 Gbit/s. The polybinary generation is achieved by a simple electrical Bessel filter of 5th order, with a frequency cut-off of 1.8 GHz. We assess the impact of the filter placement, either at the transmitter or the receiver, and find the impact is minimal in terms of bit error rate performance in transmissions of up to 40 km of single mode fiber.
Źródło:
Optica Applicata; 2016, 46, 1; 71-78
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Modified Topology and Modulation Technique for Z-Source Neutral-Point Clamped Inverter
Autorzy:
Akbari, Ehsan
Zishan, Farhad
Powiązania:
https://bibliotekanauki.pl/articles/2175930.pdf
Data publikacji:
2022
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
modulation
optimization
multilevel inverter
MZS-NPC
Opis:
The impedance network makes it possible to increase and decrease the voltage, which is not available in normal inverters (voltage and current sources).This paper presents a modified topology and modulation technique for a three-phase Modified Z-Source Neutral-Point Clamped (MZS-NPC) inverter. A modulation scheme for the proposed topology is designed based on maximum gain control method to achieve the maximum voltage gain by simple implementation and balancing the neutral point voltage of the dc link. In order to supply the desired voltage to the critical load in an islanded micro-grid, a closed-loop ac voltage controller is realized in fuel cell or photovoltaic applications based on the proposed inverter. The ability to reinforce and validity of topology operations and modulation techniques has been demonstrated by simulation. It should be noted that the simulations are implemented in MATLAB / Simulink software.
Źródło:
Power Electronics and Drives; 2022, 7, 42; 210--226
2451-0262
2543-4292
Pojawia się w:
Power Electronics and Drives
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Optical gradient force of cosh-Gaussian with sine-azimuthal and half-space phase modulation
Autorzy:
Fu, R.
Gao, X.
Shen, H.
Xin, Q
Lu, X.
Guo, L.
Powiązania:
https://bibliotekanauki.pl/articles/173789.pdf
Data publikacji:
2013
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
optical gradient force
cosh-Gaussian beams
wavefront modulation
Opis:
The optical gradient force distributions in focal plane of cosh-Gaussian beams with sine-azimuthal variation wavefront and half space phase modulation were investigated. Results show that optical gradient force distributions can be affected considerably by the phase retardation of half-space phase modulation, of a phase parameter that indicates the phase change frequency on an increasing azimuthal angle, and beam parameters in cosh terms of the incident beams. Many gradient force patterns occur, including cross-shape, multiple optical trap arrays, multiple-trap wheel, and many kinds of gradient force lines and curves. Symmetry of the whole gradient force pattern can also be altered remarkably. Above results may find wide applications in optical trapping systems.
Źródło:
Optica Applicata; 2013, 43, 4; 719-730
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Focus shaping of the radially polarized Bessel–Gauss beam with a sine-azimuthal variation wavefront
Autorzy:
Gao, X
Zhang, D.
Mei, T.
Fu, R.
Zhuang, S.
Powiązania:
https://bibliotekanauki.pl/articles/174283.pdf
Data publikacji:
2013
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
Bessel-Gauss beam
wavefront modulation
vector diffraction theory
Opis:
Focusing properties of the radially polarized Bessel–Gauss beam with a sine-azimuthal variation wavefront was investigated by the vector diffraction theory. The wavefront distribution is the sine function of the azimuthal angle with one phase parameter that indicates the phase change frequency. Results show that the focal pattern can be altered by the phase parameter, and many novel focal patterns may occur, such as multiple dark-foci focal pattern, crescent shape, and wheel shape. For case of a higher phase beam, the whole focal pattern turns on a symmetric wheel shape with multiple reduplicate intensity elements. When the phase parameter is an odd number, the number of reduplicate elements equals the phase parameter, while when the phase parameter is an even number, the number of reduplicate elements is two times the phase parameter. In addition, the effect of the phase parameter on the focal pattern is more considerable than that of the beam parameter under low numerical aperture. Under higher numerical aperture, the effect of the beam parameter on the focal pattern gets stronger.
Źródło:
Optica Applicata; 2013, 43, 3; 567-582
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Study of all-optical logic XOR gate based on linear optical amplifier cross-gain modulation
Autorzy:
Li, X
Jin, J
Li, H
Zhang, Q
Powiązania:
https://bibliotekanauki.pl/articles/174514.pdf
Data publikacji:
2015
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
linear optical amplifier
cross-gain modulation
XOR gate
Opis:
All-optical logic is the key to future high speed and large capacity optical transmission, the realization of optical packet switching and optical computing, and it has a very profound influence on the development of future optical communication. A linear optical amplifier as a new type of semiconductor optical amplifier, which has a good gain characteristic, has better signal performance than a traditional semiconductor optical amplifier in the wavelength conversion. This article presents a numerical simulation model of all-optical logic XOR gate and its logic operation based on cross-gain modulation of linear optical amplifier, and has also completed some of the basic logic operations, including AND, OR, NOT operations.
Źródło:
Optica Applicata; 2015, 45, 4; 447-457
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Modulation index optimization for wavelength modulation spectroscopy
Autorzy:
Mohammadi, M. J.
Khorsandi, A.
Ghavami, S. S.
Powiązania:
https://bibliotekanauki.pl/articles/949416.pdf
Data publikacji:
2016
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
wavelength modulation spectroscopy
NIR laser spectroscopy
molecular spectroscopy
Opis:
In this work, the second-harmonic component of wavelength modulation spectroscopy is simulated for R(22) CO2 absorption line to investigate the effect of gas temperature and pressure on the modulation index. We found that the optimum value of modulation index, that is 2.2, is not affected by temperature but gas pressure will change the optimized modulation index. Specifically, when the gas pressure decreased to lower pressures of less than 100 mbar, the modulation index is also decreased and tended exponentially to about two. Accordingly, the optimum value of modulation index is recalculated for a range of CO2 gas pressures to establish a nearly zero pressure deviation in the spectroscopy of very low pressure samples.
Źródło:
Optica Applicata; 2016, 46, 4; 639-650
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of viscosity on the far-field diffraction pattern of spatial self-phase modulation
Autorzy:
Nibu, A. G.
Silpa, S. S.
Ardra, S. N.
Anisha, M. M.
Ambika, D.
Powiązania:
https://bibliotekanauki.pl/articles/174699.pdf
Data publikacji:
2017
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
self-phase modulation
nonlinear refractive index
chlorophyll
engine oil
Opis:
Effect of viscosity of a liquid on the far-field diffraction pattern due to spatial self-phase modulation is investigated. Chlorophyll extract in acetone at different concentrations is used as the low viscous nonlinear samples and commercial engine oils, synthetic and natural. It is also used as high viscous media. In the case of chlorophyll solution, the self-induced diffraction ring pattern in the far-field is a series of circular rings at the beginning; but later it is transformed to half circular symmetry. But for the high viscous engine oils we have observed circular fringes and there is no time dependent structural variation in the pattern. The coefficient of the intensity dependent nonlinear refractive index for all the liquid samples is evaluated.
Źródło:
Optica Applicata; 2017, 47, 4; 591-599
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Optical self-phase modulation using a new photonic crystal coupled-cavity waveguide
Autorzy:
Bahadori-Haghighi, S
Ghayour, R
Powiązania:
https://bibliotekanauki.pl/articles/173977.pdf
Data publikacji:
2014
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
photonic crystal
slow light
coupled-cavity waveguide
self-phase modulation
Opis:
In this paper, self-phase modulation of an optical pulse using a new photonic crystal coupled-cavity waveguide is simulated and analyzed. The structure of the new coupled-cavity waveguide is introduced and its advantage over the previous type of coupled-cavity waveguide is discussed. In order to obtain a high group index over a large bandwidth and benefit from the slow light phenomenon, the group index and group velocity dispersion parameter curves of the guided mode are calculated. Finally, the transient simulation of the structure is performed using a finite-difference time-domain method. The calculated required length of the coupled-cavity waveguide for a maximum phase shift of π is about 31 μm. Spectral broadening of the optical pulse as a result of self-phase modulation is also presented and discussed.
Źródło:
Optica Applicata; 2014, 44, 1; 29-38
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of glistening and calcium deposits in artificial intraocular lenses on retinal image quality – numerical model
Autorzy:
Geniusz, M.
Zajac, M.
Powiązania:
https://bibliotekanauki.pl/articles/173584.pdf
Data publikacji:
2017
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
intraocular lens (IOL)
glistenings
modulation transfer function
MTF
calcium deposits
Opis:
In modern ophthalmology the natural eye lens is sometimes replaced with an artificial implant – intraocular lens which remains in the eye for a long time. This can lead to the formation of numerous microdefects occurring on the intraocular lens surface or inside its volume. The most common include calcium deposits or microvacuoles referred to as glistenings. The presence of those defects causes deterioration of retinal image thus lowering the quality of vision. The purpose of this research is to develop a numerical model of human eye with intraocular lens burden with defects useful to predict the impact of calcium deposits and glistenings on the retinal image quality. The calculations made in accordance with this model suggest that the quality of retinal image deteriorates when the density of defects increases, but the degree of image deterioration does not depend on the location of the defects and transmittance of individual particles. The main deterioration effect is observed for low spatial frequencies (< 12 cycles/deg) both in case of calcium deposits and glistenings while for the spatial frequency of 30 cycles/deg the changes in modulation transfer function are insignificant. The presence of microvacuoles in the intraocular lens influences the worsening of modulation transfer function parameters only for the diameter of microvacuoles greater than 10 μm.
Źródło:
Optica Applicata; 2017, 47, 3; 341-350
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A method of reducing switch count in three-level NPC inverter – analysis in steady states
Autorzy:
Beniak, R.
Rogowski, K.
Powiązania:
https://bibliotekanauki.pl/articles/1193464.pdf
Data publikacji:
2017
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
reduction of switch count
three-level NPC inverter
space vector modulation
Opis:
The proof of a concept for a new method of modulation has been presented which reduce switch count in a three-level neutral point clamped (3L-NPC) inverter. The method is an implementation of space vector modulation (SVM) by means of a prediction algorithm and sequences of transistors, which are not common in use. Those sequences make active use of clamping diodes of the inverter. The prediction algorithm analyzes possible sequences of transistors’ states and choose those which offers smaller switch count. Measurements of steady states were taken on prototype 3L-NPC.
Źródło:
Power Electronics and Drives; 2017, 2, 37/2; 117-126
2451-0262
2543-4292
Pojawia się w:
Power Electronics and Drives
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
THREE PHASE WARSAW BOOST RECTIFIER FOR HIGH POWER VARIABLE SPEED POWER GENERATION
Trójfazowy „Warsaw Rectifier” w układzie wytwarzania energii dużej mocy o regulowanej prędkości generatora
Autorzy:
Bałkowiec, T.
Powiązania:
https://bibliotekanauki.pl/articles/1817906.pdf
Data publikacji:
2015
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
Warsaw rectifier
delta-switch rectifier
high power
PWM modulation
Vienna rectifier
Opis:
Artykuł przedstawia topologię prostownika „Warsaw Rectifier”, jego zasadę działania oraz wyniki symulacyjne, w których prostownik zasilany był ze źródła napięcia o zmiennej amplitudzie i częstotliwości, np. generatora z magnesami trwałymi. Wyniki symulacyjne potwierdzają poprawność opracowanego układu sterowania, opartego na modulacji szerokości impulsów o stałej częstotliwości łączeń. Przedstawione wyniki w tabeli 3 również potwierdzają, że topologia umożliwia pobór sinusoidalnego prądu oraz stabilizację napięcia wyjściowego prostownika w układach o dużej mocy, w których częstotliwość łączeń jest ograniczona. Układ prostownika umożliwia zapewnia małe pulsacje mocy, które w generatorze przekładają się na małe pulsacji momentu. Topologia Warsaw Rectifier jest podobna do topologii Vienna Rectifier, natomiast różni się sposobem połączeń. Co więcej, rozważany prostownik Warsaw Rectifier wytwarza dwupoziomowe napięcie wyjściowe, podczas gdy prostownik Vienna wytwarza stałe, trójpoziomowe napięcie.
Źródło:
Prace Naukowe Instytutu Maszyn, Napędów i Pomiarów Elektrycznych Politechniki Wrocławskiej. Studia i Materiały; 2015, 71, 35; 3--15
1733-0718
Pojawia się w:
Prace Naukowe Instytutu Maszyn, Napędów i Pomiarów Elektrycznych Politechniki Wrocławskiej. Studia i Materiały
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Delayed differential detection for absorption spectroscopy recovery
Autorzy:
Cong, Menglong
Sun, Dandan
Powiązania:
https://bibliotekanauki.pl/articles/173211.pdf
Data publikacji:
2019
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
wavelength modulation spectroscopy
WMS
absorption
derivative spectrum
harmonic detection
laser diode
Opis:
An elaborately designed system has been devoted to the recovery of the line shape function of absorption spectrum. Laser power passing through trace gas has been divided into the real-time and delayed components, and their difference, i.e. the equivalent of the first-order derivative spectrum, is recorded and integrated to reconstruct the absorption line profile. Since the real-time and delayed signals are derived from the only gas cell and photodetector, the elimination of background is more effective, relative to the general used double beam detection that involves two gas cells and photodetectors. Compared with the 1st harmonic detection used in the wavelength modulation spectroscopy, here the generation of derivative spectrum is achieved without modulating the injection current of laser. Additionally, the expensive lock-in amplifier working for wavelength modulation spectroscopy is replaced by a homemade device, which is made of an all-pass filter and an instrumentation amplifier. Therefore, the complexity and cost are significantly reduced, and the stability is improved. For the purpose of validation, recovering of the absorption spectroscopy is carried out using a methane sample at its R(3) absorption line of the 2ν3 overtone, and the obtained data are found to be in a high agreement with theoretical deductions.
Źródło:
Optica Applicata; 2019, 49, 2; 303-315
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Research on a scheme of generating ultra-wideband doublet signal based on the cross-gain modulation in a semiconductor optical amplifier
Autorzy:
Zhang, K.
Shao, J.
Powiązania:
https://bibliotekanauki.pl/articles/173646.pdf
Data publikacji:
2018
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
ultra-wideband
UWB
semiconductor optical amplifier
SOA
cross-gain modulation
XGM
Opis:
We propose a novel scheme for generating ultra-wideband doublet signal based on the cross-gain modulation effect in a semiconductor optical amplifier. This scheme requires only a semiconductor optical amplifier and an optical source. By using OptiSystem software, we simulate and analyze the effect of the input signal light power and wavelength, the pulse width and injection current on the generated doublet pulse. In addition, the optimal range of parameters are also given in the simulation process.
Źródło:
Optica Applicata; 2018, 48, 1; 127-135
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A method of reducing switching losses in three-level NPC inverter
Autorzy:
Beniak, R.
Rogowski, K.
Powiązania:
https://bibliotekanauki.pl/articles/1193262.pdf
Data publikacji:
2016
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
reduction of switching losses
three-level NPC inverter
space vector modulation
Opis:
The aim of the paper is to present a concept of implementation of a space vector modulation (SVM) algorithm, which is used to create alternating current waveforms of changing amplitude and frequency in power inverters. The main goal of the method is to decrease the number of state changes in power transistors. It is realized by utilizing a prediction algorithm and sequences of transistors, which are not common in use. The method requires measurement of inverter output current flow. The prediction algorithm analyzes possible sequences of transistors’ states and choose those which offers smaller switch count. A decrease of about 20% was obtained for the cases tested. This paper presents simulation result for selected driving scenario. The described method decreases the number of state changes in power transistors and therefore it is a potentially good method to considerably decrease energy losses of multilevel inverter-powered drive.
Źródło:
Power Electronics and Drives; 2016, 1, 36/2; 55-63
2451-0262
2543-4292
Pojawia się w:
Power Electronics and Drives
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Control of the DTC-FSVM based induction motor drive in a wide speed range
Autorzy:
Nguyen Thac, K.
Orlowska-Kowalska, T.
Powiązania:
https://bibliotekanauki.pl/articles/1817721.pdf
Data publikacji:
2014
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
induction motor
direct torque control
Flux-Space-Vector Modulation
field weakening control
Opis:
In this paper the direct flux and torque control structure based on Flux-error Space Vector Modulation (DTC-FSVM) has been analyzed and compared to a classical DTC-SVM system. The control structures have been tested in a wide speed range including field weakening algorithm based on the voltage and current limits of the voltage inverter and the induction motor. The proposed control strategies are verified through simulation with a 3 kW induction motor drive.
Źródło:
Prace Naukowe Instytutu Maszyn, Napędów i Pomiarów Elektrycznych Politechniki Wrocławskiej. Studia i Materiały; 2014, 70, 34; 3--15
1733-0718
Pojawia się w:
Prace Naukowe Instytutu Maszyn, Napędów i Pomiarów Elektrycznych Politechniki Wrocławskiej. Studia i Materiały
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 29

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