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Wyświetlanie 1-15 z 18
Tytuł:
Influence of atmospheric turbulence on bomb release
Wpływ turbulencji atmosferycznych na zrzut bomby
Autorzy:
Kowaleczko, G.
Żyluk, A.
Powiązania:
https://bibliotekanauki.pl/articles/280204.pdf
Data publikacji:
2009
Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Tematy:
atmospheric turbulence
bombing
Opis:
A model of the bomb release dynamics is presented in the paper, and how it is influenced by a wind field. The applied way of describing this field is discussed with account taken of its stochastic nature. Exemplary results of a numerical simulation of bombing are submitted and concluded.
W pracy przedstawiono model dynamiki zrzutu bomby. Pokazano wpływ pola wiatru na szybowanie bomby. Strukturę wiatru opisano, uwzględniając jego stochastyczny charakter. Pokazano wyniki symulacji numerycznej zrzutu oraz poddano je analizie.
Źródło:
Journal of Theoretical and Applied Mechanics; 2009, 47, 1; 69-90
1429-2955
Pojawia się w:
Journal of Theoretical and Applied Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Sensitivity of a bomb to wind turbulence
Wrażliwość bomby na turbulencje wiatru
Autorzy:
Żyluk, A.
Powiązania:
https://bibliotekanauki.pl/articles/279357.pdf
Data publikacji:
2009
Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Tematy:
bomb release
atmospheric turbulence
Opis:
This paper presents results of numerical investigations into the bomb release in a turbulent wind field. Short descriptions of mathematical models of both the bomb dynamics and the stochastic wind are shown. The effect of parameters of the turbulent wind field on a random distribution of points of the impact is investigated.
W pracy przedstawiono wyniki numerycznej symulacji wpływu turbulencji wiatru na zrzut bomby. Praca zawiera opis matematyczny dynamiki lotu bomby oraz stochastycznego pola wiatru. Badano zależność pomiędzy parametrami turbulencji i punktem upadku bomby.
Źródło:
Journal of Theoretical and Applied Mechanics; 2009, 47, 4; 815-828
1429-2955
Pojawia się w:
Journal of Theoretical and Applied Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Optimal threshold detection for Málaga turbulent optical links
Autorzy:
Jurado-Navas, A.
Garrido-Balsells, J. M.
Castillo-Vázquez, M.
Puerta-Notario, A.
Monroy, I. T.
Olmos, J. J. V.
Powiązania:
https://bibliotekanauki.pl/articles/173418.pdf
Data publikacji:
2016
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
atmospheric propagation
atmospheric turbulence
Malaga distribution
scintillation
Opis:
A new and generalized statistical model, called Málaga distribution (M distribution), has been derived recently to characterize the irradiance fluctuations of an unbounded optical wave front propagating through a turbulent medium under all irradiance fluctuation conditions. As great advantages associated to that model, we can indicate that it is written in a simple tractable closed-form expression and that it is able to unify most of the proposed statistical models for free-space optical communications derived until now in the scientific literature. Based on that Málaga model, we have analyzed in this paper the role of the detection threshold in a free-space optical system employing an on-off keying modulation technique and involved in different scenarios, and taking into account the extinction ratio associated to the employed laser. First we have derived some analytical expressions for the lower-bound performance of the free-space optical system with the light intensity fading induced by turbulence obtained when the additive white Gaussian noise is not present in the system. Then, we have analyzed the optimal threshold in the system and how it changes when atmospheric conditions vary. Finally, a closed form expression for the bit error rate of that system is derived.
Źródło:
Optica Applicata; 2016, 46, 4; 577-595
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Dynamic evolution and classification of coherent vortices in atmospheric turbulence
Autorzy:
Zeng, J.
Li, J
Powiązania:
https://bibliotekanauki.pl/articles/174463.pdf
Data publikacji:
2015
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
vortex beam
coherent vortices
atmospheric turbulence
Opis:
Based on the extended Huygens–Fresnel principle, the analytical expressions for the cross-spectral density function of partially coherent sine-Gaussian vortex beams and partially coherent sine-Gaussian non-vortex beams propagating through free space and atmospheric turbulence are derived, and used to study the dynamic evolution behavior of coherent vortices in free space and atmospheric turbulence. According to the creation, the coherent vortices are grouped into three classes: the first is their inherent coherent vortices of the vortex beam, the second is created by the vortex beam itself during transmission process in free space, and the third is created by the atmospheric turbulence inducing the vortex beam.
Źródło:
Optica Applicata; 2015, 45, 3; 299-308
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Characterization of sub-channel based Málaga atmospheric optical links with real β parameter
Autorzy:
López-González, F. J.
Jurado-Navas, A.
Garrido-Balsells, J. M.
Castillo-Vázquez, M.
Puerta-Notario, A.
Powiązania:
https://bibliotekanauki.pl/articles/174807.pdf
Data publikacji:
2017
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
Malaga distribution
generalized-K distribution
atmospheric optical communications
atmospheric propagation
atmospheric turbulence
scintillation
Opis:
A generalization of the Málaga atmospheric optical communications links treated as a finite number of generalized-K distributed sub-channels is analyzed in terms of outage probability and outage rate when its β parameter belongs to the set of real numbers. To the best of the author’s knowledge, this is the first time that β ∈ ℜ is considered. The new analytical expressions derived in this paper lead to a new physical and more realistic interpretation of atmospheric optical links, especially in terms of performance.
Źródło:
Optica Applicata; 2017, 47, 4; 545-556
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Performance Analysis of WDM-FSO Link under Turbulence Channel
Autorzy:
Mazin, Ali A. Ali
Powiązania:
https://bibliotekanauki.pl/articles/1192036.pdf
Data publikacji:
2016
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
free space optics
BER
Atmospheric Turbulence
NRZ format
RZ technique
Opis:
In this paper, the performance analysis of FSO communication link in various atmospheric turbulence has been analysis for different bit rate using NRZ and RZ technique. The effect of turbulence on the link performance has been investigated by varying bit rate, turbulence strength and modulation format. FSO performance carried out for BER, Q. factor, received power under maximum link. Simulation results show that RZ format is best for strong turbulence. Where NRZ technique is used for low and medium turbulence.
Źródło:
World Scientific News; 2016, 50; 160-173
2392-2192
Pojawia się w:
World Scientific News
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Study on self-repairing and non-diffraction of Airy beams in slant atmospheric turbulence
Autorzy:
Li, Y.-Q.
Wang, L.-G.
Powiązania:
https://bibliotekanauki.pl/articles/174867.pdf
Data publikacji:
2018
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
atmospheric turbulence
Airy beam
self-repairing
non-diffraction
numerical simulation
Opis:
The Airy beams propagation in atmospheric turbulence along a slant path was simulated numerically, based on the split-step Fourier method. Also, the self-repairing and non-diffraction characteristics of Airy beams were investigated and compared with beams propagation on a horizontal path. The effects of parameters including zenith angle, propagation distance, radii of Gaussian aperture and turbulence intensity on the two characteristics of beams were revealed. Additionally, the two characteristics of the Airy beam were compared with those of a Bessel–Gauss beam. The results showed that the two beams obscured by Gaussian apertures can be repaired after propagating some distance along a slant path. However, the non-diffraction characteristic of an Airy beam was stronger than that of a Bessel–Gauss beam and the amplitude attenuation rate of the Bessel–Gauss beam was greater than that of the Airy beam in the process of self-repairing. Results obtained can provide a theoretical basis for an outdoor experiment as well as theoretical guidance for various practical applications including laser communications, laser warning systems, and remote sensing.
Źródło:
Optica Applicata; 2018, 48, 3; 435-447
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Research on the propagation of laser beams array with coherent and incoherent combination in dynamic atmosphere turbulence
Autorzy:
Deng, Wantao
Wang, Chengcheng
Gan, Chunquan
Xue, Liangping
Xia, Huijun
Wang, Peng
Yang, Huan
Powiązania:
https://bibliotekanauki.pl/articles/2086761.pdf
Data publikacji:
2022
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
laser propagation
dynamic atmospheric turbulence
coherent combination
incoherent combination
beam quality
Opis:
High-power laser systems mostly use coherent or incoherent combined beams to achieve higher laser output power to satisfy the application. However, the far-field beam quality of laser will be reduced when propagating over atmosphere. Based on the propagation model of laser beams array, we use atmospheric coherence length, laser duration and average wind velocity to construct dynamic atmospheric turbulence which is characterized as a phase screen sequence. Meanwhile, considered as the indexes to evaluate beam quality, peak intensity and intensity in bucket are comparatively analysed in coherent and incoherent combined beams in far-field. The results indicate that in weaker turbulence circumstances, coherent combined beam has an advantage compared with the incoherent combined beams when laser duration is short, and coherent combination is more suitable for pulsed laser. With laser duration is increasing, the beam quality of incoherent and coherent combined beams both decrease and tend to be close. In stronger turbulence circumstances, the corresponding laser duration will be shorter when the beam quality of coherent combined beams is extraordinary close to that of incoherent combined beams. The researches can provide important data for high-power laser system to select the optimal beam combination mode to improve its performance.
Źródło:
Optica Applicata; 2022, 52, 2; 243--257
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Dynamic evolution of mixed circular edge-screw dislocations
Autorzy:
Gao, P.
Li, J.
Cheng, K.
Duan, M.
Powiązania:
https://bibliotekanauki.pl/articles/173359.pdf
Data publikacji:
2017
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
mixed circular edge-screw dislocations
optical vortex
circular edge dislocations
atmospheric turbulence
Opis:
Based on the extended Huygens–Fresnel principle, the analytical expressions for the cross-spectral density function of mixed circular edge-screw dislocations beams propagating through atmospheric turbulence have been derived, and used to study the dynamic evolution of mixed circular edge-screw dislocations in free space and atmospheric turbulence. It is shown that the radius of circular edge dislocations increases with increasing propagation distance, and both the positions of the optical vortex and the center of circular edge dislocations are located at the point (0, 0) when mixed circular edge-screw dislocations propagate in free space. When mixed circular edge-screw dislocations propagate in the atmospheric turbulence, the position of optical vortices varies with increasing propagation distance, the circular edge dislocation evolves into a pair of optical vortices with the opposite topological charge ±1, and the pair of optical vortices will annihilate as soon as the propagation distance becomes large enough.
Źródło:
Optica Applicata; 2017, 47, 3; 471-481
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Variable antennas positions solution to reduce pointing errors due to wind speed and temperature coupled effects during free space optical link using matrix Rician pointing error model
Autorzy:
Teuma Mbezi, Michel
Eke, Samuel
Som, Idelette Hermine Judith
Mouangue, Ruben Martin
Powiązania:
https://bibliotekanauki.pl/articles/27310098.pdf
Data publikacji:
2023
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
atmospheric turbulence
pointing error
free space optical transmission
Rician pointing error model
Opis:
Pointing errors (PE) during free space optical (FSO) transmission can be caused by laser beam wander due to thermal and wind dynamic instability. The aim of this work is to study the coupled effects of temperature and wind speed on PE using matrix Rician pointing error (MRPE) model; then show how variable antennas height can reduce PE due to wind speed and temperature coupled effects. To achieve this purposes, average PE expression was established using MRPE model. Then considering a Gaussian beam wave and Monin–Obukhov similarity functions for the structure parameters of temperature, explicit relationship was established between average PE, temperature and wind speed. It comes out of this study that under dynamic turbulence, one can appropriately modify temperature to reduce PE due to dynamic instability and reciprocally. Depending on turbulence large cells or frozen turbulence eddies distribution, PE can be reduced by appropriately modified antennas height or the distance between transmitter and receiver. That is why this work suggests to install variable or dynamic antennas (rather than fixed ones) which could intelligently modify its positions according to laser beam wander created by atmospheric turbulence.
Źródło:
Optica Applicata; 2023, 53, 3; 393--406
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of Atmospheric Turbulence on the Striking Accuracy of Guided Bombs
Wpływ parametrów atmosfery na dokładność trafienia bomby w cel
Autorzy:
Grajewski, Krzysztof
Kowaleczko, Grzegorz
Pietraszek, Mariusz
Powiązania:
https://bibliotekanauki.pl/articles/403464.pdf
Data publikacji:
2020
Wydawca:
Wojskowa Akademia Techniczna im. Jarosława Dąbrowskiego
Tematy:
guided bomb
numerical simulation
atmospheric turbulence
bomba korygowana
symulacja numeryczna
turbulencja atmosfery
Opis:
This paper presents the test results of a simulation of an air-to-surface guided bomb drop in a turbulent atmosphere. The guided bomb was developed from a practice bomb built and upgraded by the Air Force Institute of Technology. The paper presents the test results of a numerical simulation of an air-to-surface guided bomb drop ran in a proprietary software environment. The numerical simulation inputs included aerodynamic characteristics calculated with PRODAS software and verified by wind tunnel tests. The stochastic components of atmospheric turbulence were simulated with a stochastic process model proposed by Shinozuki. Examples of the guided bomb drop simulation results are given in the paper. The effect of atmospheric turbulence parameters, i.e. standard deviation, σ and turbulence scale, Lw on the striking accuracy and ground impact scatter, are also shown.
W artykule przedstawiono wyniki przeprowadzonych symulacji zrzutu bomby w turbulentnej atmosferze. Bomba ta powstała na bazie bomby ćwiczebnej zbudowanej i zmodernizowanej w Instytucie Technicznym Wojsk Lotniczych. W artykule przedstawiono wyniki numerycznej symulacji z wykorzystaniem autorskiego oprogramowania. W obliczeniach użyto charakterystyki aerodynamiczne wyliczone programem PRODAS, które weryfikowano badaniami w tunelu aerodynamicznym. Do opisu składowej turbulencji wykorzystano model procesów stochastycznych zaproponowany przez Shinozukiego. Przedstawiono przykładowe wyniki symulacji zrzutu bomby. Pokazano wpływ parametrów turbulencji atmosfery - odchylenia standardowego i skali turbulencji σ, Lw, na celność i rozrzut.
Źródło:
Problemy Mechatroniki : uzbrojenie, lotnictwo, inżynieria bezpieczeństwa; 2020, 11, 1 (39); 31-48
2081-5891
Pojawia się w:
Problemy Mechatroniki : uzbrojenie, lotnictwo, inżynieria bezpieczeństwa
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An approach to investigating the feasibility of free-space optical communication technology deployment under scintillation effects
Autorzy:
Mahmood, Aras S.
Powiązania:
https://bibliotekanauki.pl/articles/27315698.pdf
Data publikacji:
2023
Wydawca:
Polska Akademia Nauk. Stowarzyszenie Elektryków Polskich
Tematy:
free-space optical communication
atmospheric turbulence
scintillation attenuation
refractive index structure parameter (Cn²)
Opis:
Local weather conditions have an impact on the availability of free-space optical (FSO) communication. The variation in meteorological parameters, such as temperature, humidity, and wind speed, leads to variations of the refractive index along the transmission path. These refractive index inhomogeneities produced by atmospheric turbulence induce optical turbulence which is responsible for random fluctuations in the intensity of the laser beam that carries the signal (irradiance) called scintillations that can significantly degrade the performance of FSO systems. This paper aims to investigate the feasibility of deploying FSO communication technology under scintillation effects in any urban region and atmospheric environment. To achieve that, firstly by utilizing the Hufnagel-Vally day with the Sadot and Kopeika models together, the scintillation strength for a specified region, Sulaimani City in north-eastern Iraq as an example, has been estimated through the calculation of the refractive index structure parameter (Cn²) over a period of 10 years and it was found to be at the strong turbulence level. Secondly, from the same estimated parameter, the scintillation attenuation of the signal carrying the laser beam intensity can be calculated to investigate the feasibility of FSO communication using Optysistem-7 software. The optimal link distance for northeastern Iraq (Sulaimani City) has been found to be within the limit of about 5.5 km. Analysing the max. Q-factor, bit-error rate and signal to noise ratio for an average of 120 months between 2013-2022 assessed the best and worst seasons for FSO.
Źródło:
Opto-Electronics Review; 2023, 31, 3; art. no. e147037
1230-3402
Pojawia się w:
Opto-Electronics Review
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Spreading properties of a multi-Gaussian Schell-model vortex beam in slanted atmospheric turbulence
Autorzy:
Chang, Shuai
Song, Yansong
Dong, Yan
Dong, Keyan
Powiązania:
https://bibliotekanauki.pl/articles/174088.pdf
Data publikacji:
2020
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
average intensity
vortex beam
multi-Gaussian Schell-model source
atmospheric turbulence
slanted path
Opis:
The cross-spectral density function of a multi-Gaussian Schell-model vortex (MGSMV) beam propagating through slanted atmospheric turbulence was derived, and the influences of the MGSMV beam parameter and slanted atmospheric turbulence on the spreading properties of a MGSMV beam are studied. One can find that a MGSMV beam propagating in slanted atmospheric turbulence can evolve into the flat-topped beam, and a MGSMV beam with larger index N and topological charge M propagating in slanted atmospheric turbulence will lose the dark hollow center and evolve into the Gaussian beam more slowly than the MGSMV beam with smaller index N and topological charge M. It is also found that a MGSMV beam propagating in slanted atmospheric turbulence with larger strucutre parameter C will evolve into Gaussian beam faster, but the influences of zenith angle α on the spreading properties of MGSMV beam in the far field can be ignored.
Źródło:
Optica Applicata; 2020, 50, 1; 83-94
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Changes in the states of polarization of random electromagnetic beams in atmospheric turbulence
Autorzy:
Li, J.
Zhao, K.
Lai, Y.
Powiązania:
https://bibliotekanauki.pl/articles/174110.pdf
Data publikacji:
2017
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
non-Kolmogorov atmospheric turbulence
random electromagnetic beams
degree of polarization
orientation angle
degree of ellipticity
Opis:
Taking the random electromagnetic cosh-Gaussian beam as a typical example of random electromagnetic beams, the analytical expressions for the cross-spectral density matrix element of random electromagnetic cosh-Gaussian beams propagating through non-Kolmogorov atmospheric turbulence are derived, and used to study the changes in the states of polarization (degree of polarization, orientation angle and degree of ellipticity) of random electromagnetic cosh-Gaussian beams in non-Kolmogorov atmospheric turbulence. It is shown that the states of polarization of random electromagnetic cosh-Gaussian beams in non-Kolmogorov atmospheric turbulence are different from those in free space. The degree of polarization decreases, and the orientation angle and degree of ellipticity increase with increasing structure constant. The on-axis degree of polarization and the degree of ellipticity appear to have an oscillatory behavior and the orientation angle has a rapid transition for the larger cosh-part parameter of random electromagnetic cosh-Gaussian beams in atmospheric turbulence.
Źródło:
Optica Applicata; 2017, 47, 1; 51-62
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
FSO system performance analysis based on novel Gamma–Chi-square irradiance PDF model
Autorzy:
Todorović, Jelena
Spalević, Petar
Panić, Stefan
Milosavljević, Bojana
Gligorijević, Milan
Powiązania:
https://bibliotekanauki.pl/articles/2033970.pdf
Data publikacji:
2021
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
free space optics
FSO
Gamma-Chi-square distribution
atmospheric turbulence
pointing error
on-off keying
OOK
Opis:
In order to provide a novel analytically traceable free space optics (FSO) channel model for describing turbulence based irradiance fluctuations, following basic scintillation theory principles, we have derived closed-form expression for probability density function (PDF) of a new statistical Gamma–Chi-square model. Further, capitalizing on provided model, error performances of FSO system over on-off keying (OOK) transmission scheme both in the presence of atmospheric turbulence and misalignment fading (pointing error) is investigated. For both cases, the average bit error rate (ABER) at the receiving side of the system is determined in an analytically closed form. The results are graphically presented in order to analyze the impact of different levels of turbulence, as well as other relevant parameters, on the quality of the received signal in the OOK modulated FSO system.
Źródło:
Optica Applicata; 2021, 51, 3; 335-348
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
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