Search results for "Soida"

A novel approach to current transformer characterization in the presence of harmonic distortion

2009

The current transformer (CT) performance under distorted waveform conditions is usually characterized by means of the frequency-response test. In this paper, a new way to characterize CTs, closer to real operation conditions, is proposed. The harmonic phase-angle and ratio errors are measured using a nonsinusoidal current composed of fundamental and one harmonic with adjustable phase shift. The new method was tested by determining the performance of two metering class CTs commonly used by the Italian power company. The errors measured using the proposed approach are larger than the ones obtained with the frequency response. This result suggests that the frequency-response approach for the e…

Applications of sinusoidal phase modulation in temporal optics to highlight some properties of the Fourier transform

2019

International audience; Fourier analysis plays a major role in the analysis and understanding of many phenomena in physics and contemporary engineering. However, students, who have often discovered this notion through numerical tools, do not necessarily understand all the richness that can be derived from joint analysis in the temporal and spectral domains, particularly in the field of optics. As part of the second year of the Master's degree in Physics Lasers and Materials at the University of Burgundy, we have set up a set of experiments to highlight these concepts and to show, on a non-trivial example of periodic phase modulation, the precautions to be taken in the interpretation of the …

Improvement of Hall Effect Current Transducer Metrological Performances in the Presence of Harmonic Distortion

2010

The performance of Hall effect current transducers (HECTs), under distorted waveform conditions, is usually characterized by means of a frequency response test. In this paper, it was investigated if frequency response is able to correctly evaluate the ratio and the phase errors under distorted conditions. Two HECTs, with the accuracy class level of 1% and 0.5%, respectively, were experimentally characterized under two conditions: 1) sinusoidal excitation with frequencies ranging from 50 to 750 Hz, which is the well-known frequency response test, and 2) nonsinusoidal excitation using fundamental frequency and one harmonic with adjusted amplitude and phase shift. It was found that ratio and p…

Large Eddy Simulations of Rough Turbulent Channel Flows Bounded by Irregular Roughness: Advances Toward a Universal Roughness Correlation

2020

The downward shift of the mean velocity profile in the logarithmic region, known as roughness function, $$\Delta U^+$$ , is the major macroscopic effect of roughness in wall bounded flows. This speed decrease, which is strictly linked to the friction Reynolds number and the geometrical properties which define the roughness pattern such as roughness height, density, shape parameters, has been deeply investigated in the past decades. Among the geometrical parameters, the effective slope (ES) seems to be suitable to estimate the roughness function at fixed friction Reynolds number, Re $$_{\tau }$$ . In the present work, the effects of several geometrical parameters on the roughness function, i…

Sinusoidal endothelial cells from guinea pig liver synthesize and secrete cellular fibronectin in vitro.

1987

Endothelial liver cells were obtained from guinea pig by enzymatic digestion and centrifugal elutriation. Cells were cultured on gelatin and fibronectin pretreated culture vessels. Endothelial cells were characterized by phase-contrast microscopy, electron microscopy and the presence of Factor VIII-related antigen. Fibronectin secretion was determined in cell-free supernatants by a sensitive and specific ELISA and localized on fixed cultured cells by immunofluorescence. [35S]Methionine endogeneously labeled fibronectin was immunoprecipitated from supernatants and cellular lysates and displayed on sodium dodecyl sulfate polyacrylamide slab gel electrophoresis. After attachment to the culture…

Large eddy simulations on the effect of the irregular roughness shape on turbulent channel flows

2019

Abstract Large Eddy Simulations (LES) are carried out to investigate on the mean flow in turbulent channel flows over irregular rough surfaces. Here the attention is focused to selectively investigate on the effect induced by crests or cavities of the roughness. The irregular shape is generated through the super-imposition of sinusoidal functions having random amplitude and four different wave-lengths. The irregular roughness profile is reproduced along the spanwise direction in order to obtain a 2D rough shape. The analysis of the mean velocity profiles shows that roughness crests induce higher effect in the outer-region whereas roughness cavities cause the highest effects in the inner-reg…

Baltu filoloģija, 9

2000

Baltu filoloģija, 1: zinātniski informatīvi ziņojumi

1991

Improvement of matrix solutions of generalized nonlinear wave equation

2005

Four classes of nonlinear wave equations are joined in one generalized nonlinear wave equation. A theorem is proved that the whole series of matrix functions satisfy the generalized wave equation. A justification of rotational properties of matrix solutions is given and a mathematical model of the ring vortex around the acute edge is proposed using of matrix solutions.

On the methodologies for the calibration of static electricity meters in the presence of harmonic distortion

2010

This paper is focused on the problems related to the calibration of static electricity meters with nonsinusoidal test waveforms. This is an up-to-date issue since the harmonic distortion levels are ever increasing, especially in low-voltage power systems, and in such conditions the performances of the modern static electricity meters can be negatively affected, depending on the implemented measurement algorithm. Thus it is important to test the meters with nonsinusoidal waveforms. The paper analyzes the problems related to both the choice of the test signals to be used for calibration and the implemented metric, with a particular focus on the reactive energy meters. The analysis is supporte…