Methods for Evaluation of Possibilities of Operation of a Laser Communication Line Based on the Use of Aerosol Formations for Bypassing Obstacles Along the Propagation Path

2008 ◽  
Vol 67 (12) ◽  
pp. 1051-1060
Author(s):  
A. Yu. Koziratskii ◽  
D. V. Prokhorov
Keyword(s):  
Propagation Path ◽  
Laser Communication ◽  
Communication Line

SIGNAL NOISE IMMUNITY IN ALAMOUTI SYSTEMS TAKING INTO ACCOUNT PARAMETERS OF MULTIPATH COMMUNICATION CHANNELS

2020 ◽  
Author(s):  
М.А. БЫХОВСКИЙ
Keyword(s):  
Wave Propagation ◽  
Radio Wave ◽  
Noise Immunity ◽  
Multipath Propagation ◽  
Communication Channels ◽  
Spatial Diversity ◽  
Propagation Path ◽  
Communication Line ◽  
Radio Waves ◽  
Physical Features

Представлен метод анализа системы Аламоути - простейшей системы MISO, в которой для устранения интерференции лучей, приходящих в место приема, на передающем конце линии связи применяются только две передающие антенны с определенным пространственным разнесением. Метод основан на рассмотрении физических особенностей распространения радиоволн и позволяет учесть конкретные характеристики многолучевых трасс распространения между передающей и приемной станциями. Система Аламоути позволяет уменьшить флуктуации уровня сигнала, поступающего на вход демодулятора, полностью или частично устраняя интерференцию приходящих на вход приемника лучей. Получены формулы, которые позволяют оценить необходимую для обеспечения требуемой надежности приема сигналов энергетику линии связи, влияние расположения передающих антенн по отношению к трассе распространения радиоволн (вдоль или поперек трассы), а также величину необходимого пространственного разнесения передающих антенн, при котором может быть обеспечена максимально возможная помехоустойчивость приема сигналов. The paper offers the method of analysis of the Alamouti system, the simplest MISO system in which at the transmitting end of the communication line only two transmitting antennas with a certain spatial diversity are used to eliminate the interference of the rays arriving at the receiving site. The method is based on the study of the physical features of radio wave propagation and allows taking into account the specific characteristics of multipath propagation paths between the transmitting and receiving stations. The Alamouti system allows the reduction of fluctuations in the level of the signal entering the input of the demodulator, completely or partially eliminating the interference of the rays coming to the input of the receiver. The paper offers formulas that allow us to estimate the energy of the communication line, necessary to ensure the required reliability of signal reception, the influence of the location of the transmitting antennas relative to the propagation path of the radio waves (along or across the track), as well as the amount of necessary spatial diversity of the transmitting antennas at which the maximum possible noise immunity of signal reception can be ensured.

Probability of error in an atmospheric laser communication line

1976 ◽  
Vol 6 (7) ◽  
pp. 759-763
Author(s):  
T P Symera ◽  
P A Uusmaa ◽  
Kh V Khinrikus ◽  
Yu É Mal'sub
Keyword(s):  
Laser Communication ◽  
Communication Line ◽  
Probability Of Error

An Alternative Technique to Evaluate Crack Propagation Path in Hyperelastic Materials

2012 ◽  
Vol 40 (1) ◽  
pp. 42-58 ◽  
Author(s):  
R. R. M. Ozelo ◽  
P. Sollero ◽  
A. L. A. Costa
Keyword(s):  
Constitutive Model ◽  
Crack Propagation ◽  
Experimental Tests ◽  
Growth Direction ◽  
Propagation Path ◽  
J Integral ◽  
Alternative Technique ◽  
Crack Propagation Path ◽  
Hyperelastic Materials ◽  
Material Constitutive Model

Abstract REFERENCE: R. R. M. Ozelo, P. Sollero, and A. L. A. Costa, “An Alternative Technique to Evaluate Crack Propagation Path in Hyperelastic Materials,” Tire Science and Technology, TSTCA, Vol. 40, No. 1, January–March 2012, pp. 42–58. ABSTRACT: The analysis of crack propagation in tires aims to provide safety and reliable life prediction. Tire materials are usually nonlinear and present a hyperelastic behavior. Therefore, the use of nonlinear fracture mechanics theory and a hyperelastic material constitutive model are necessary. The material constitutive model used in this work is the Mooney–Rivlin. There are many techniques available to evaluate the crack propagation path in linear elastic materials and estimate the growth direction. However, most of these techniques are not applicable to hyperelastic materials. This paper presents an alternative technique for modeling crack propagation in hyperelastic materials, based in the J-Integral, to evaluate the crack path. The J-Integral is an energy-based parameter and is applicable to nonlinear materials. The technique was applied using abaqus software and compared to experimental tests.

scholarly journals Fatigue Crack Growth Analysis with Extended Finite Element for 3D Linear Elastic Material

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 397
Author(s):  
Yahya Ali Fageehi
Keyword(s):  
Finite Element ◽  
Fatigue Crack ◽  
Fatigue Life ◽  
Crack Propagation ◽  
Crack Growth ◽  
Mixed Mode ◽  
Propagation Path ◽  
Loading Conditions ◽  
Extended Finite Element ◽  
Linear Elastic

This paper presents computational modeling of a crack growth path under mixed-mode loadings in linear elastic materials and investigates the influence of a hole on both fatigue crack propagation and fatigue life when subjected to constant amplitude loading conditions. Though the crack propagation is inevitable, the simulation specified the crack propagation path such that the critical structure domain was not exceeded. ANSYS Mechanical APDL 19.2 was introduced with the aid of a new feature in ANSYS: Smart Crack growth technology. It predicts the propagation direction and subsequent fatigue life for structural components using the extended finite element method (XFEM). The Paris law model was used to evaluate the mixed-mode fatigue life for both a modified four-point bending beam and a cracked plate with three holes under the linear elastic fracture mechanics (LEFM) assumption. Precise estimates of the stress intensity factors (SIFs), the trajectory of crack growth, and the fatigue life by an incremental crack propagation analysis were recorded. The findings of this analysis are confirmed in published works in terms of crack propagation trajectories under mixed-mode loading conditions.

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