scholarly journals Comparative analysis of the accuracy requirements of the equipment for determining the mean integral refractive index of air using different realizations of the gradient method

2021 ◽  
pp. 20-24
Author(s):  
Pavel Neyezhmakov ◽  
Alexander Prokopov ◽  
Tatiana Panasenko ◽  
Andrii Shloma
Keyword(s):  
Refractive Index ◽  
Gradient Method ◽  
Electromagnetic Waves ◽  
Meteorological Parameters ◽  
Distance Measurement ◽  
Integral Group ◽  
Long Distance ◽  
Uncertainty Of Measurements ◽  
Group Refractive Index ◽  
The Mean

The speed of propagation of electromagnetic waves in the Earth’s atmosphere differs from the speed of their propagation in a vacuum, which is one of the main factors that have a significant impact on the accuracy of long distance measurement. This influence is taken into account in long distance measurement with the correction for the mean integral group refractive index of air, which depends on such meteorological parameters as temperature, atmospheric pressure and relative air humidity. The purpose of this work is to compare the accuracy requirements for equipment designed to measure temperature, pressure, and relative humidity required to determine the above correction by the gradient method using the Euler-Maclaurin quadrature formula (hereafter, the Euler-Maclaurin method) and the formula based on Hermite interpolation polynomials (hereafter, the Hermite method). The requirements for the uncertainty of measurements carried out with the sensors of meteorological parameters, allowing to find the mean integral group refractive index of air, providing length measurements of the baselines of up to 5 km with an expanded uncertainty of not more than 1 mm, are established. Keywords: atmosphere; mean integral group refractive index of air; laser long distance measurement

scholarly journals Analysis of the temperature component of the combined standard uncertainty of the refractive index according to the test data of the control system for meteorological parameters developed for the Lyptsi geodetic polygon

2021 ◽  
pp. 34-38
Author(s):  
Pavel Neyezhmakov ◽  
Alexander Prokopov ◽  
Tatiana Panasenko ◽  
Andrii Shloma
Keyword(s):  
Refractive Index ◽  
Electromagnetic Waves ◽  
Large Scale ◽  
Meteorological Parameters ◽  
Accurate Determination ◽  
Practical Implementation ◽  
Main Task ◽  
Accuracy Of Measurements ◽  
Length Measurements ◽  
The Mean

The National Scientific Centre “Institute of Metrology” is actively involved in the implementation of a number of international projects under the EMPIR programme. One of such joint projects is the EMPIR 18SIB01 GeoMetre research project “Large-scale dimensional measurements for geodesy”. The overall goal of the project is to ensure traceability of length measurements – from the measurement standard of the unit of length to long distances typical for geodetic measurements. As a result of the project, it is necessary to provide length measurements of at least 5 km with an expanded uncertainty of no more than 1 mm. The main task of the NSC “Institute of Metrology” within this project is the development, research and practical implementation of methods and means of accounting for the influence of the earth’s atmosphere on the results of measurements of long distances in geodesy, carried out using electromagnetic waves in the optical range. When performing the section Task 1.4 of the project, new methods of highly accurate determination of the mean integral refractive index of air, used as a correction taking into account the influence of the atmosphere on the measurement results, are justified. Requirements for the accuracy of measurements of meteorological parameters at discrete points of the baseline are formulated, which are necessary to determine the mean integral refractive index. That is, the requirements for the metrological characteristics of temperature, pressure and humidity sensors are determined. The article discusses the results of the development, manufacture and testing of the sensors for temperature measurement. It is shown that the created sensors meet the requirements of the GeoMetre project.

scholarly journals SURVEY OF SELECTED PROCEDURES FOR THE INDIRECT DETERMINATION OF THE GROUP REFRACTIVE INDEX OF AIR

2018 ◽  
Vol 58 (1) ◽  
pp. 9
Author(s):  
Filip Dvořáček
Keyword(s):  
Refractive Index ◽  
High Accuracy ◽  
Distance Measurement ◽  
Refractive Indices ◽  
Laser Tracker ◽  
Atmospheric Parameters ◽  
Indirect Determination ◽  
Group Refractive Index ◽  
Laser Interferometers

The main aim of the research was to evaluate numeric procedures of the indirect determination of the group refractive index of air and to choose the suitable ones for requirements of ordinary and high accuracy distance measurement in geodesy and length metrology. For this purpose, 10 existing computation methods were derived from various authors’ original publications and all were analysed for wide intervals of wavelengths and atmospheric parameters. The determination of the phase and the group refractive indices are essential parts in the evaluation of the first velocity corrections of laser interferometers and electronic distance meters. The validity of modern procedures was tested with respect to updated CIPM-2007 equations of the density of air. The refraction model of Leica AT401 laser tracker was analysed.

The dominant frequency analysis of interfacial wave in wet-gas pipeline transportation based on NIR absorption

2021 ◽  
pp. 1-10
Author(s):  
Zhiyue Zhao ◽  
Ning Zhao ◽  
Lide Fang ◽  
Xiaoting Li
Keyword(s):  
Liquid Film ◽  
Predictive Accuracy ◽  
Film Surface ◽  
Dominant Frequency ◽  
Wave Frequency ◽  
Interfacial Wave ◽  
Long Distance ◽  
Wet Gas ◽  
The Mean ◽  
Predictive Correlation

During the long-distance transportation of wet-gas, the dominant frequency is of great significance for the study of pipeline fatigue and damage, and the safety production. Therefore, the theoretical and experimental researches for dominant frequency are carried out increasingly. However, most of the current prediction correlation of dominant frequency are mainly applicable to atmospheric pressure conditions (0.1 MPa), and the prediction accuracy is not accurate enough. The paper obtains the time series signal of liquid film thickness by near-infrared (NIR) sensor, and then calculates the wave frequency by the power spectrum density (PSD). The performance of typical predictive correlation is evaluated and analyzed by utilizing the experimental data at different flow and pressure conditions (0.1–0.8) MPa. The structure of Strouhal number and Lockhart-Martinelli (L-M) parameter are optimized reasonably, the mean velocity of the liquid film surface, the density increment of gas core, the gas core mass flow and average liquid film velocity are considered in the L-M parameter, a modified interfacial wave frequency correlation is proposed. The results indicate that the mean absolute error of the predictive correlation is 9.06% (current data) and 25.64% (literature data). The new correlation has a better predictive accuracy.

A near zero refractive index metalens to focus electromagnetic waves with phase compensation metasurface

2017 ◽  
Vol 69 ◽  
pp. 432-436 ◽  
Author(s):  
Akram Boubakri ◽  
Fethi Choubeni ◽  
Tan Hoa Vuong ◽  
Jacques David
Keyword(s):  
Refractive Index ◽  
Electromagnetic Waves ◽  
Phase Compensation

Simultaneous Measurements of Droplet Size, Temperature, and Velocity Using an Integrated Phase-Doppler/Rainbow Thermometer

2001 ◽  
Author(s):  
Matt O’ Donnell ◽  
Sumanta Acharya
Keyword(s):  
Refractive Index ◽  
Detailed Examination ◽  
Temperature Profiles ◽  
Droplet Temperature ◽  
Radial Temperature ◽  
Temperature Correlation ◽  
Simultaneous Measurements ◽  
Laser Diagnostic ◽  
The Mean ◽  
And Performance

Abstract This work summarizes efforts to determine the accuracy and performance characteristics of a new and novel laser diagnostic to measure instantaneous, in flight, droplet temperatures. The instrument uses the location of the rainbow peak to deduce the refractive index of the droplet, which in turn is related to the droplet temperature. Preliminary experiments were undertaken in order to understand the fundamental operating principles and limitations of the instrument. These experiments measured the temperature of an isothermal, single stream of monodisperse droplets. These measurements indicate that the mean refractive index can be measured with a standard deviation as low as 0.0001m. Once the operation of the refractometer was proved under isothermal conditions, the measurement of droplet temperatures in a swirl-stabilized combustor was performed. These measurements indicate that the strength of the rainbow signal is significantly hampered by the noise induced by the flame. Preliminary temperature measurements with the combustor equipped with 45° vanes showed relatively constant radial temperature profiles (∼55–60°C) at locations less than 2 inches from the nozzle exit. A detailed examination of the temperature correlation with velocity and diameter revealed that larger and faster moving droplets dominate the distributions. Thus, the smaller droplets that are suspected of having the highest temperatures are inadequately represented in the mean droplet temperature.

scholarly journals Whistler intensities above thunderstorms

2010 ◽  
Vol 28 (1) ◽  
pp. 37-46 ◽  
Author(s):  
J. Fiser ◽  
J. Chum ◽  
G. Diendorfer ◽  
M. Parrot ◽  
O. Santolik
Keyword(s):  
Background Noise ◽  
Electromagnetic Waves ◽  
Horizontal Distance ◽  
Average Amplitude ◽  
Oblique Propagation ◽  
Lightning Current ◽  
Processing Data ◽  
Demeter Satellite ◽  
Late Evening ◽  
The Mean

Abstract. We report a study of penetration of the VLF electromagnetic waves induced by lightning to the ionosphere. We compare the fractional hop whistlers recorded by the ICE experiment onboard the DEMETER satellite with lightning detected by the EUCLID detection network. To identify the fractional hop whistlers, we have developed software for automatic detection of the fractional-hop whistlers in the VLF spectrograms. This software provides the detection times of the fractional hop whistlers and the average amplitudes of these whistlers. Matching the lightning and whistler data, we find the pairs of causative lightning and corresponding whistler. Processing data from ~200 DEMETER passes over the European region we obtain a map of mean amplitudes of whistler electric field as a function of latitudinal and longitudinal difference between the location of the causative lightning and satellite magnetic footprint. We find that mean whistler amplitude monotonically decreases with horizontal distance up to ~1000 km from the lightning source. At larger distances, the mean whistler amplitude usually merges into the background noise and the whistlers become undetectable. The maximum of whistler intensities is shifted from the satellite magnetic footprint ~1° owing to the oblique propagation. The average amplitude of whistlers increases with the lightning current. At nighttime (late evening), the average amplitude of whistlers is about three times higher than during the daytime (late morning) for the same lightning current.

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