Search results for "wave"
showing 10 items of 6009 documents
Discrete exterior calculus for photonic crystal waveguides
2022
The discrete exterior calculus (DEC) is very promising, though not yet widely used, discretization method for photonic crystal (PC) waveguides. It can be seen as a generalization of the finite difference time domain (FDTD) method. The DEC enables efficient time evolution by construction and fits well for nonhomogeneous computational domains and obstacles of curved surfaces. These properties are typically present in applications of PC waveguides that are constructed as periodic structures of inhomogeneities in a computational domain. We present a two-dimensional DEC discretization for PC waveguides and demonstrate it with a selection of numerical experiments typical in the application area. …
Automated detection and localization system of myocardial infarction in single-beat ECG using Dual-Q TQWT and wavelet packet tensor decomposition
2020
Background and objective. It is challenging to conduct real-time identification of myocardial infarction (MI) due to artifact corruption and high dimensionality of multi-lead electrocardiogram (ECG). In the present study, we proposed an automated single-beat MI detection and localization system using dual-Q tunable Q-factor wavelet transformation (Dual-Q TQWT) denoising algorithm. Methods. After denoising and segmentation of ECG, a fourth-order wavelet tensor (leads × subbands × samples × beats) was constructed based on thediscretewavelet packet transform (DWPT), to represent the features considering the information of inter-beat, intra-beat, inter-frequency, and inter-lead. To reduce the t…
Quantitative Rotor Broken Bar Evaluation in Double Squirrel Cage Induction Machines under Dynamic Operating Conditions
2013
Advanced monitoring techniques leading to fault diagnosis and prediction of induction machine faults, operating under non-stationary conditions have gained strength because of its considerable influence on the operational continuation of many industrial processes. In case of rotor broken bars, fault detection based on sideband components issued from currents, flux, instantaneous control or power signals under different load conditions, may fail due to the presence of inter-bar currents that reduce the degree of rotor asymmetry, especially for double squirrel cage induction motors. But the produced core vibrations in the axial direction, can be investigated to overcome the limitation of the …
Dynamics of Strongly Coupled Modes between Surface Plasmon Polaritons and Photoactive Molecules: The Effect of the Stokes Shift
2017
We have investigated the dynamics of strongly coupled modes of surface plasmon polaritons (SPPs) and fluorescent molecules by analyzing their scattered emission polarization. While the scattered emission of SPPs is purely transverse magnetic (TM) polarized, the strong coupling with molecules induces transverse electric (TE) polarized emission via the partial molecular nature of the formed SPP–molecule polariton mode. We observe that the TM/TE ratio of the polariton emission follows the contribution of the molecular excited states in this hybrid mode. By using several types of molecules, we observe that, in addition to the coupling strength, which determines the contribution of the molecular…
On the intrinsic population of the lowest triplet state of uracil
2007
Abstract From CASPT2//CASSCF quantum-chemical computations it is determined that the lowest triplet state of uracil can be efficiently populated from the initially activated singlet manifold through respective singlet–triplet crossings of the singlet state with the low-lying 3nπ∗ state at 4.6 eV and with the lowest 3ππ∗ state at 4.2 eV located along the minimum energy path of the low-lying 1ππ∗ state. Large spin–orbit coupling elements predict, in particular for the former case, efficient intersystem crossing processes. The wavelength dependence measured for the triplet quantum yield can be explained by the location of the singlet–triplet crossing regions.
Active photonic crystals based on surface acoustic waves
2003
An active photonic crystal (PC) based on the modulation of a one-dimensional cavity resonator by electrically-generated surface acoustic waves is described. The high nonthermal population of surface modes combined with the enhanced Brillouin scattering in the cavity increases the intensity of the scattered light to values comparable to the excitation intensity. This process is employed to switch and modulate light beams in PCs.
Theoretical study of Fe doping and oxidation–reduction influence on the photorefractive effect in BaTiO_3
1993
We numerically solve charge-transport and Poisson equations for photorefractive BaTiO3 single crystals with a band model, using four impurity levels, Fe2+–Fe3+, Fe3+–Fe4+, VO••–VO•, and VO•-VOx. Densities and photoinduced spatial distributions of each population are computed as a function of annealing O partial pressure. Space-charge field and beam-coupling gain are also computed as a function of annealing O partial pressure, temperature, Fe concentration, grating wave vector, and light intensity. We discuss the intervening mechanism of impurity centers and the correlations between experimental conditions of crystal growth, oxidation–reduction treatments, and measurement parameters.
Population analysis of pair densities. A study on cyclic systems
2000
Abstract Pair population analysis seems a reliable method for evaluating atomic valency states and bond orders from the MO wavefunction of molecular systems. A test on some cyclic organic systems was performed. The results confirm the capability of the method to provide a correct description of the molecules in terms of simple VB approach.
Hippocampal Sharp Waves: A Physiological Correlate of LTP?
1988
The irregularly occurring large amplitude hippocampal sharp waves (SPWs) are correlated with synchronous population bursts of CA1-CA3 and subicular pyramidal cells, dentate granule cells and interneurons in all hippocampal fields. We suggest that the SPW-associated neuronal burst is the best candidate for a physiological basis of long-term potentiation (LTP).
SU-8 viļņvadu izveide ar tiešā ieraksta lāzera litogrāfijas tehniku un to optisko īpašību raksturošana
2016
Kopš 20.gs. beigām lieli pūliņi ieguldīti telekomunikāciju attīstībā, arvien tiek meklēti jauni materiāli, lai aizvietotu elektroniskās komponentes integrētajās shēmās, jo tās ir ierobežojošais faktors informācijas pārvades ātrumam. Viens no risinājumiem būtu veidot shēmas, kas satur tikai optiskās komponentes. Optisko komponenšu pamatā ir viļņvadi, kuriem jābūt ar noteiktām optiskām īpašībām. Viena no perspektīvākajām materiālu klasēm pielietojumiem fotoniskās integrālās shēmās ir organiskie materiāli. Darbā aprakstīta tīru un funkcionalizētu organisku SU 8 viļņvadu izgatavošana ar tiešā ieraksta lāzera litogrāfijas tehniku. Ir aprakstīti viļņvadu izgatavošanas soļi un metodes ierobežojumi…