scholarly journals Fraunhofer Diffraction Description In The Approximation Of The Light Field Theory

2020 ◽  
pp. 25-30
Author(s):  
Vladimir P. Budak ◽  
Dmitry S. Efremenko ◽  
Pavel A. Smirnov
Keyword(s):  
Fresnel Zone ◽  
Radiation Power ◽  
Incident Radiation ◽  
Spatial Density ◽  
Fraunhofer Diffraction ◽  
Computationally Efficient ◽  
Near Zone ◽  
Diffraction Phenomenon ◽  
Before And After ◽  
Wavelength Scale

The wavelength is that natural scale that determines the applicability domains of the ray approximation and the wave approximation of light. If the change of the radiation power spatial density is significant at the wavelength scale, then we deal with the light diffraction phenomenon, which is a subject to the wave optics. Consider the diffraction phenomenon at the diaphragm. It is possible to distinguish the near zone with significant wave inhomogeneities (i.e. the Fresnel zone) and the far Fraunhofer diffraction zone, in which the wave becomes close to homogeneous (the so-called quasi-homogeneous) and the ray approximation is possible. The problem is that there is no explicit relationship between the radiance of the rays before and after diaphragm. Method for determining the boundary conditions for the radiance in the Fraunhofer zone through the radiance of the incident radiation is proposed in the paper. This approach for computing the radiance field in the Fraunhofer zone can be generalized to other problems of optics, thereby providing the possibility of using computationally efficient ray-approximation-based methods to determine the light fields.

scholarly journals Observation evidences of atmospheric Gravity Waves induced by seismic activity from analysis of subionospheric LF signal spectra

2007 ◽  
Vol 7 (5) ◽  
pp. 625-628 ◽  
Author(s):  
A. Rozhnoi ◽  
M. Solovieva ◽  
O. Molchanov ◽  
P.-F. Biagi ◽  
M. Hayakawa
Keyword(s):  
Gravity Waves ◽  
Fresnel Zone ◽  
Signal Amplitude ◽  
Magnetic Storms ◽  
Frequency Range ◽  
Atmospheric Gravity Waves ◽  
Period Range ◽  
Before And After ◽  
Atmospheric Gravity ◽  
Large Earthquakes

Abstract. We analyze variations of the LF subionospheric signal amplitude and phase from JJY transmitter in Japan (F=40 kHz) received in Petropavlovsk-Kamchatsky station during seismically quiet and active periods including also periods of magnetic storms. After 20 s averaging, the frequency range of the analysis is 0.28–15 mHz that corresponds to the period range from 1 to 60 min. Changes in spectra of the LF signal perturbations are found several days before and after three large earthquakes, which happened in November 2004 (M=7.1), August 2005 (M=7.2) and November 2006 (M=8.2) inside the Fresnel zone of the Japan-Kamchatka wavepath. Comparing the perturbed and background spectra we have found the evident increase in spectral range 10–25 min that is in the compliance with theoretical estimations on lithosphere-ionosphere coupling by the Atmospheric Gravity Waves (T>6 min). Similar changes are not found for the periods of magnetic storms.

scholarly journals Боковой перенос энергии при возбуждении плазмонов терагерцовой волной в периодической пространственно несимметричной графеновой структуре

2019 ◽  
Vol 53 (9) ◽  
pp. 1189
Author(s):  
Д.В. Фатеев ◽  
К.В. Машинский ◽  
И.М. Моисеенко ◽  
В.В. Попов
Keyword(s):  
Incident Wave ◽  
Radiation Power ◽  
Power Conversion ◽  
Incident Radiation ◽  
Terahertz Wave ◽  
Wave Power ◽  
Excitation Condition ◽  
Maximum Conversion

AbstractThe power conversion of a terahertz wave normally incident on a periodic graphene structure to propagating-plasmon power is theoretically studied. The conditions of the maximum conversion of the incident radiation power to the propagating-plasmon power and excitation condition of unidirectional traveling plasmon are determined. It is found that up to 15% of the incident wave power can be converted to propagating-plasmon power.

Electromagnetic traveltime tomography: Application for reservoir characterization in the Lost Hills oil field, California

Geophysics ◽  
2005 ◽  
Vol 70 (3) ◽  
pp. G51-G58 ◽  
Author(s):  
Tae Jong Lee ◽  
Toshihiro Uchida
Keyword(s):  
Reservoir Characterization ◽  
Fresnel Zone ◽  
Region Of Interest ◽  
Oil Field ◽  
Data Sets ◽  
Traveltime Tomography ◽  
Conductivity Structure ◽  
Before And After ◽  
Conductivity Image ◽  
Induction Logs

Electromagnetic (EM) traveltime tomography has been applied for reservoir characterization at the Lost Hills oil field, California. Four data sets at frequencies of 24, 90, 370, and 1000 Hz were obtained along a pair of monitoring boreholes located 80.5 m apart. Traveltime information was first extracted from these EM data sets using a wavefield transform with a ray series approximation. The conductivity contrast of each layer is no greater than two in the region of interest, so the first arrivals can be estimated within 5% error by the approximate scheme. A nonlinear traveltime tomography algorithm adopting a Fresnel zone concept was then applied to obtain the conductivity model between the boreholes. The resultant conductivity image represents the conductivity structure between the boreholes. This image is consistent with the results of both a finite-difference inversion and the induction log obtained prior to waterflooding. Comparing the two conductivity images with the induction logs, we observe major differences in the fracture-dominant resistive reservoir layer, which may have been caused by changes in reservoir condition before and after waterflooding.

Recommendations for Jet Fire Model Selection When Performing Consequence Assessments of Onshore Natural Gas Pipelines and Facilities

2020 ◽  
Author(s):  
Shawn Smith ◽  
Alex M. Fraser ◽  
Mari Shironishi
Keyword(s):  
Natural Gas ◽  
Incident Radiation ◽  
Empirical Models ◽  
Multiple Point ◽  
Computationally Efficient ◽  
Fire Model ◽  
Natural Gas Pipelines ◽  
Fire Modelling ◽  
Lift Off ◽  
Semi Empirical

Abstract The thermal radiation from a jet fire is the dominant hazard resulting from accidental natural gas releases from onshore pipelines or facilities. To assess the consequences to both individuals and equipment, we require models to estimate the incident radiation from the jet fire to the surroundings. Simpler models with shorter implementation and run times are more viable for use in a full probabilistic risk assessment, in which the number of scenarios assessed could number in the millions. However, the level of accuracy within these models must be considered to ensure a reasonably conservative estimate is produced. A review and comparison of semi-empirical models from literature was performed and used to develop a decision tree to recommend the most computationally efficient jet fire modelling approaches based on the release scenario, while maintaining reasonable conservatism. Options for both vertical and non-vertical releases are presented, as well as corrections for lift-off, wind, and buoyancy. Additionally, an efficient algorithm from the area of computer graphics was adapted and applied to a weighted multiple point source jet fire model to account for the reduction in incident radiation to a receptor due to topography or structures partially obstructing the view of the jet fire.

Study of focusing parameters of wavelength-scale binary phase Fresnel zone plate

2021 ◽  
Author(s):  
Yuri E Geints ◽  
Ekaterina K. Panina ◽  
Igor V Minin ◽  
Oleg V Minin
Keyword(s):  
Fresnel Zone ◽  
Zone Plate ◽  
Fresnel Zone Plate ◽  
Binary Phase ◽  
Wavelength Scale

INVESTIGATION OF NONLINEAR INTERACTION OF ELECTROMAGNETIC RADIATION WITH SPACE CHARGE IN VACUUM ELECTRONIC DEVICES

2012 ◽  
Vol 15 ◽  
pp. 105-112
Author(s):  
A.H. MAKARYAN ◽  
H.S. HAROYAN ◽  
V.A. SAHAKYAN ◽  
V.R. TADEVOSYAN
Keyword(s):  
Electromagnetic Radiation ◽  
Space Charge ◽  
Nonlinear Interaction ◽  
Radiation Power ◽  
Incident Radiation ◽  
Polarization Current ◽  
Vacuum Electronic Devices ◽  
Power Direction ◽  
Current Characteristics ◽  
Detection Characteristics

The nonlinear interaction of electromagnetic radiation in microwave, terahertz, and optical regions with non-uniformly distributed space charge in the interelectrode space of vacuum devices is investigated. The detection of electromagnetic radiation in the vacuum electronic tubes (diode and triode) with parallel plate electrodes is experimentally demonstrated. The dependence of the detected signal on the incident radiation power, direction of wave polarization, current characteristics and frequency of modulating signal has been investigated. The equation of motion of an electron in the field of electromagnetic wave in the presence of space charge was obtained, according to which, the detection is due to nonlinearity associated with the non-uniform distribution of electrons along the electrostatic field direction. The measured detection characteristics are in reasonable agreement with theoretical estimates.

scholarly journals Neutral and Ionic Particle Emission Produced by Laser Irradiation of a GaAs Surface

1984 ◽  
Vol 5 (1) ◽  
pp. 1-10 ◽  
Author(s):  
G. R. Möhlmann
Keyword(s):  
Radiation Power ◽  
Incident Radiation ◽  
Particle Emission ◽  
Gaas Surface ◽  
Experimental Result ◽  
Atomic Ions ◽  
Neutral Particles ◽  
Incident Laser Radiation ◽  
Thermal Mechanism ◽  
Set Up

The emission of gas phase particles from a GaAs surface, due to irradiation at 1064 nm by an unfocussed Q-switched Nd:YAG laser beam, has been studied. Mass spectra have been recorded with the aid of a quadrupole mass spectrometer, and the ion-neutral ratio of the emitted particles has been measured with an electrical diode set up. The applied incident laser radiation power density was varied in the range 1.2–9.6 × 107 Watts/cm2 and was delivered as 10 ns (fwhm) long pulses. It appeared that mainly Ga atoms and As2 molecules were emitted, together with minor amounts (<1%) of Ga2 and GaAs molecules. Besides the emission of neutral particles, the formation of Ga+ atomic ions was observed. By measuring the ratio of Ga+ ions and Ga neutral atoms it could be shown that the (ionic) particle emission is governed by a thermal mechanism for 1064 nm incident radiation. This latter experimental result differs from that obtained if a ruby laser (694 nm) is used as the radiation source.

scholarly journals Investigation of the effect of HIP processing on the physical and mechanical characteristics of parts obtained by the SLM method

2021 ◽  
Vol 2077 (1) ◽  
pp. 012024
Author(s):  
A S Raznoschikov ◽  
A A Voznesenskaya ◽  
D A Kochuev ◽  
M N Gerke ◽  
R V Chkalov
Keyword(s):  
Selective Laser Melting ◽  
Powder Material ◽  
Mechanical Characteristics ◽  
Radiation Power ◽  
Hot Isostatic Pressing ◽  
Laser Melting ◽  
Isostatic Pressing ◽  
Before And After ◽  
Aisi 321 ◽  
Physical And Mechanical Characteristics

Abstract In this paper presents the results of studying the powder material AISI 321. Selective laser melting (SLM) of the samples was carried out in modes with a change in the radiation power. The subsequent processing of the samples by the method of hot isostatic pressing (HIP) was carried out. The roughness of the surfaces and the microhardness of the samples before and after the HIP were studied.

scholarly journals Высокоэффективное преобразование лазерного излучения высокой плотности

2019 ◽  
Vol 45 (2) ◽  
pp. 26
Author(s):  
А.Н. Паньчак ◽  
П.В. Покровский ◽  
Д.А. Малевский ◽  
В.Р. Ларионов ◽  
М.З. Шварц
Keyword(s):  
Laser Radiation ◽  
Power Density ◽  
Open Circuit Voltage ◽  
Radiation Power ◽  
Incident Radiation ◽  
Open Circuit ◽  
Incident Laser ◽  
Voltage Level ◽  
Incident Laser Radiation ◽  
Radiation Conversion

AbstractAlGaAs/GaAs-based semiconductor photovoltaic converters (PVCs) of laser radiation, capable of operating at an illuminance up to 9 kW/cm^2 with retained isothermal state have been studied. This state was confirmed by the logarithmic shape of dependences of the open-circuit voltage on the power density of incident laser radiation. At maximum illuminance, the open-circuit voltage level was close to 1.33 V. It is shown that the proposed PVCs can provide laser radiation conversion at an 840-nm wavelength with efficiency above 51% at an incident radiation power density of 2.5 kW/cm^2.

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