Adaptation of model parameters of VLF radio signals phase variations on the Novosibirsk-Yakutsk propagation path

2014 ◽  
Author(s):  
Alexey A. Korsakov ◽  
Vladimir I. Kozlov ◽  
Viktor A. Mullayarov ◽  
Rustam R. Karimov
Keyword(s):  
Propagation Path ◽  
Model Parameters ◽  
Radio Signals ◽  
Phase Variations

scholarly journals Diurnal and seasonal amplitude and phase variations of the radio signals of RSDN-20 transmitters and the intensity of radio noise (11.9 kHz) registered in Yakutsk during 2009-2017

2021 ◽  
pp. 122-136
Author(s):  
А.А. Корсаков ◽  
В.И. Козлов ◽  
Е.А. Павлов
Keyword(s):  
Seasonal Variations ◽  
Phase Delay ◽  
Propagation Path ◽  
Radio Noise ◽  
Night Time ◽  
Radio System ◽  
Radio Signals ◽  
Delay Increase ◽  
Phase Variations ◽  
Seasonal And Interannual Variations

В работе проводится анализ суточных, сезонных и межгодовых вариаций интенсивности радиошума, а также амплитуды и фазы сигналов радиотехнической системы дальней навигации РСДН-20 по данным регистрации на частоте 11.904 кГц в г. Якутске в периоды нарастания, максимума и спада в 24-м цикле солнечной активности (2009-2017 годы). Наиболее ярко выражены сезонные дневные вариации амплитуды. Зарегистрировано увеличение фазовой задержки радиосигнала от дня к ночи, что характерно для увеличения эффективной высоты волновода Земля – ионосфера. Наблюдаемое уменьшение фазовой задержки в ночное зимнее время на радиотрассе малой протяженности Хабаровск-Якутск возможно объясняется интерференцией мод высших порядков. Наблюдается асимметрия дневных сезонных вариаций амплитуды ОНЧ радиосигналов (11.904 кГц). Амплитуда сигнала в период осеннего равноденствия ближе к летнему солнцестоянию, а амплитуда весеннего равноденствия — к зимнему солнцестоянию. В дневные часы сезонные вариации амплитуды и фазы относительно стабильны год от года. В периоды нарастания, максимума и спада в 24-м цикле солнечной активности отмечены большие изменения амплитуды ОНЧ-сигнала, зарегистрированные зимой, по сравнению с летом. На фоне повышения солнечной активности в зимний период ночью регистрируется повышение фазовой задержки на радиотрассе меньшей протяженности Хабаровск-Якутск (1400 км) на 23 ± 6°. The daily, seasonal and interannual variations of the radio noise intensity, the amplitude and phase of signals from the long-range navigation radio system RSDN-20 are analyzed based on the registration at a frequency of 11.904 kHz in Yakutsk during increase, maximum and decrease periods in the 24th solar cycle activity (2009-2017). The most pronounced seasonal daytime amplitude variations. The signal phase delay increase from day to night was recorded, which is characteristic of an increase in the effective height of the Earthionosphere waveguide. The observed phase delay decrease in the winter night time on the short radio propagation path Khabarovsk-Yakutsk can be explained by the interference of higher-order modes. There is an asymmetry of the daytime seasonal variations of the amplitude of VLF radio signals (11.904 kHz). During daytime, seasonal variations in amplitude and phase are relatively stable from year to year. Against the background of an increase in solar activity in winter, at night, the phase delay increase is recorded by 23 ± 6°on a shorter radio path Khabarovsk-Yakutsk (1400 km).

CFD Analysis of Swirling Flows in Premixers

2014 ◽  
Author(s):  
Vladislav A. Nazukin ◽  
Valery G. Avgustinovich
Keyword(s):  
Flow Pattern ◽  
Turbulence Model ◽  
Swirling Flow ◽  
Pressure Fluctuations ◽  
Flow Analysis ◽  
Propagation Path ◽  
Model Parameters ◽  
Detached Eddy Simulation ◽  
Mixing Processes ◽  
Eddy Structures

At present, the key element of lean low NOx combustors is a premixer where swirlers are often used for intensification of mixing processes and further formation of required flow pattern in combustor liner. Swirling flow leads to significant effect of some parts of hardware on stream features and mixing quality, emergence of flashback and flame blowout, formation of complex eddy structures causing flow perturbations. Therefore, at design phase, it is necessary to pay great attention to aerodynamics of premixers. The most effective method of swirling flow analysis in real combustor design is computational fluid dynamics (CFD). The present work is dedicated to study the effect of some computational model parameters, such as a turbulence model, grid size on calculation results as well as the analysis of the flow pattern in real swirler. Comparison between the analysis and experimental data showed that use of Detached Eddy Simulation (DES) allows to defining flow structure more accurately rather than use of RANS (URANS) with SST turbulence model also the size of computational grid elements influences stability of vortex structures. Analysis of swirling flow in production combustor swirler showed presence of large number of different eddy structures that can be conditionally divided into three types relative to its location of origin and a propagation path. Further, features of each eddy type were subsequently defined. Comparison of calculated and experimental pressure fluctuations spectrums verified correctness of computations. It was also noted that for the studied construction there is not even qualitative agreement between the steady and the time-averaged results of unsteady computations.

scholarly journals Modeling of Amplitude Characteristic in Radio Channels of Code Division Multiple Access Systems

2020 ◽  
Vol 6 (2) ◽  
pp. 30-38
Author(s):  
V. Gurevich ◽  
S. Egorov
Keyword(s):  
Amplitude Characteristic ◽  
Model Parameters ◽  
Radio Access ◽  
Electronic Model ◽  
Nonlinear Amplifier ◽  
Destabilizing Factors ◽  
Radio Signals ◽  
Transmission Quality ◽  
Analytical Relations ◽  
Code Division Multiple

In CDMA radio access systems, amplitude distortions in a nonlinear amplifier (NA) of a group signal lead to bit errors at the outputs of subscriber channels. To assess the permissible distortion limits and their influence on the transmission quality of subscriber signals, an electronic model of the amplitude characteristic (AC) and analytical relations are needed that relate the probability of an error when registering the output signal of the communication channel with the nonlinearity of the AC NA and other destabilizing factors. The article compares alternative mathematical models of AC NA. In contrast to traditional methods of analysis, usually limited to the choice of models with fixed parameters, a method for variably determining the parameters of AC is considered. The results are: a comparison of known methods for approximating the AC of broadband nonlinear power amplifiers of radio signals is given, an algorithm for selecting model parameters for CDMA systems with QAM using the Rapp model is proposed.

scholarly journals A study of the behavior of the terminator time shifts using multiple VLF propagation paths during the Pakistan earthquake (<i>M</i> = 7.2) of 18 January 2011

2013 ◽  
Vol 13 (6) ◽  
pp. 1501-1506 ◽  
Author(s):  
S. Ray ◽  
S. K. Chakrabarti
Keyword(s):  
Low Frequency ◽  
Space Physics ◽  
The Other ◽  
Propagation Path ◽  
Very Low Frequency ◽  
Radio Signals ◽  
Propagation Paths ◽  
Vlf Propagation ◽  
Indian Centre

Abstract. On 18 January 2011, at 20:23 UTC, an earthquake of magnitude 7.2 occurred in southwestern Pakistan (latitude 28°44' N, longitude 63°56' E) at a depth of 68 km. We present the results of the analysis of very low frequency (VLF) radio signals, received at three stations located in India. We analyze the VLF signals around this earthquake day and look for possible precursory effects of this earthquake. For our analysis, we use four different VLF propagation paths. These propagation paths are DHO–IERC (Sitapur), VTX–Pune, VTX–ICSP (Indian Centre for Space Physics, Kolkata) and NWC–IERC. We observed significant shifts of the "sunrise terminator time" (SRT) for DHO–IERC and VTX–Pune paths. For DHO–IERC path, the SRT of the VLF signals shifted towards nighttime three days before the earthquake day, and in the case of VTX–Pune path it shifted towards nighttime just one day before the earthquake day. For VTX–Kolkata path, the shift of SRT is four days before the earthquake day, but here the shift is not so strong, somewhere between 2σ and 3σ lines. For the other two paths, namely, DHO–IERC and VTX–Pune, the terminator time shifts crossed the 3σ line. We found no significant shifts of SRT for NWC–IERC propagation path. Higher deviation in the VTX–Pune path as compared to VTX–ICSP path could be due to the proximity of the former to the epicenter. Similarly, DHO–IERC path is over the epicenter while NWC–IERC path is totally away from the epicenter. This could be the reason why the effect in DHO–IERC path is stronger than that in NWC–IERC path.

scholarly journals Statistical characterization of the 2.45 GHz propagation channel aboard trains

ACTA IMEKO ◽  
2015 ◽  
Vol 4 (1) ◽  
pp. 44 ◽  
Author(s):  
Annalisa Liccardo ◽  
Andrea Mariscotti ◽  
Attilio Marrese ◽  
Nicola Pasquino ◽  
Rosario Schiano Lo Moriello
Keyword(s):  
Free Space ◽  
Path Loss ◽  
Propagation Path ◽  
Delay Spread ◽  
Model Parameters ◽  
Propagation Channel ◽  
Experimental Distribution ◽  
Statistical Characterization ◽  
Best Fit

<p class="Abstract"><span lang="EN-US">The propagation channel aboard trains is investigated with reference to the propagation path loss within cars, the delay spread and the coherence bandwidth. Results show that the path loss exponent is slightly smaller than in free space, possibly due to reflections by metal walls, and that it does not depend significantly on the position of transmitter and receiver. The delay spread and coherence bandwidth depend on both the polarization and distance between transmitter and receiver while the effect of interaction is not statistically significant. The best fit for both delay spread’s and coherence bandwidth’s experimental distribution is also investigated. Results show that it does not always match models suggested in the literature and that the fit changes with the values of the input parameters. Finally, the functional law between coherence bandwidth and delay spread is determined. Results typically match expectations although the specific measurement configuration effects the model parameters.</span></p>

Instrumental and Ideological Union Commitment: Longitudinal Assessment of Construct Validity

2001 ◽  
Vol 17 (2) ◽  
pp. 98-111 ◽  
Author(s):  
Anders Sjöberg ◽  
Magnus Sverke
Keyword(s):  
Construct Validity ◽  
Temporal Stability ◽  
Strong Support ◽  
Internal Consistency Reliability ◽  
Measurement Model ◽  
Two Dimensions ◽  
Model Parameters ◽  
Longitudinal Assessment ◽  
Union Commitment ◽  
Union Participation

Summary: Previous research has identified instrumentality and ideology as important aspects of member attachment to labor unions. The present study evaluated the construct validity of a scale designed to reflect the two dimensions of instrumental and ideological union commitment using a sample of 1170 Swedish blue-collar union members. Longitudinal data were used to test seven propositions referring to the dimensionality, internal consistency reliability, and temporal stability of the scale as well as postulated group differences in union participation to which the scale should be sensitive. Support for the hypothesized factor structure of the scale and for adequate reliabilities of the dimensions was obtained and was also replicated 18 months later. Tests for equality of measurement model parameters and test-retest correlations indicated support for the temporal stability of the scale. In addition, the results were consistent with most of the predicted differences between groups characterized by different patterns of change/stability in union participation status. The study provides strong support for the construct validity of the scale and indicates that it can be used in future theory testing on instrumental and ideological union commitment.

Representation of bolted joints in a structure using finite element modelling and model updating

2020 ◽  
Vol 14 (3) ◽  
pp. 7141-7151 ◽  
Author(s):  
R. Omar ◽  
M. N. Abdul Rani ◽  
M. A. Yunus
Keyword(s):  
Finite Element ◽  
Dynamic Behaviour ◽  
Model Updating ◽  
Complex Structure ◽  
Bolted Joints ◽  
Model Parameters ◽  
Fe Model ◽  
Bolted Joint ◽  
Fe Modelling ◽  
Joint Structure

Efficient and accurate finite element (FE) modelling of bolted joints is essential for increasing confidence in the investigation of structural vibrations. However, modelling of bolted joints for the investigation is often found to be very challenging. This paper proposes an appropriate FE representation of bolted joints for the prediction of the dynamic behaviour of a bolted joint structure. Two different FE models of the bolted joint structure with two different FE element connectors, which are CBEAM and CBUSH, representing the bolted joints are developed. Modal updating is used to correlate the two FE models with the experimental model. The dynamic behaviour of the two FE models is compared with experimental modal analysis to evaluate and determine the most appropriate FE model of the bolted joint structure. The comparison reveals that the CBUSH element connectors based FE model has a greater capability in representing the bolted joints with 86 percent accuracy and greater efficiency in updating the model parameters. The proposed modelling technique will be useful in the modelling of a complex structure with a large number of bolted joints.

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