scholarly journals Lidar transmitter offers “non-diffracting” property through short distance in highly-dense random media

2018 ◽  
Vol 176 ◽  
pp. 08019
Author(s):  
Xiafukaiti Alifu ◽  
Peng Ziqi ◽  
Tatsuo Shiina
Keyword(s):  
High Resolution ◽  
Laboratory Experiment ◽  
Milk Fat ◽  
Short Distance ◽  
Random Media ◽  
Propagation Distance ◽  
Central Peak ◽  
Forward Scattering ◽  
Narrow View

Non-diffracting beam (NDB) is useful in lidar transmitter because of its high propagation efficiency and high resolution. We aimed to generate NDB in random media such as haze and cloud. The laboratory experiment was conducted with diluted processed milk (fat: 1.8%, 1.1μmφ). Narrow view angle detector of 5.5mrad was used to detect the forward scattering waveform. We obtained the central peak of NDB at the propagation distance of 5cm ~ 30cm in random media by adjusting the concentration of <10%.

scholarly journals On the sodium enhancement in spectra of slow meteors and the origin of Na-rich meteoroids

2020 ◽  
Author(s):  
Pavol Matlovič ◽  
Juraj Tóth ◽  
Leonard Kornoš ◽  
Stefan Loehle
Keyword(s):  
High Resolution ◽  
Wind Tunnel ◽  
Laboratory Experiment ◽  
High Enthalpy ◽  
Spectral Profiles

&lt;p&gt;Distinct Na-enhanced and Na-rich meteor spectra have been previously identified by different authors, but the explanation of their origin and interpretation of the corresponding meteoroid composition was lacking. To study this population, we utilized meteor spectra observations of the global AMOS network and high-resolution Echelle spectra of ablating meteorite samples obtained in a high-enthalpy plasma wind tunnel at the IRS facilities in Stuttgart. It was found that most Na-enhanced and Na-rich spectra can be explained by the effect of low meteor speed related to low ablation temperatures and generally do not reflect real meteoroid composition. Spectra obtained by the laboratory experiment simulating low meteor speeds show corresponding Na-rich spectral profiles irrespectively of the meteorite composition. For more clarity in the classification of Na-enhanced and Na-rich meteoroids, we propose new speed-dependent boundaries between the spectral classes. Based on this classification, we reveal real compositional Na enhancement in five cometary meteoroids including two Perseids, an

scholarly journals Fallspeed measurement and high-resolution multi-angle photography of hydrometeors in freefall

2012 ◽  
Vol 5 (4) ◽  
pp. 4827-4850 ◽  
Author(s):  
T. J. Garrett ◽  
C. Fallgatter ◽  
K. Shkurko ◽  
D. Howlett
Keyword(s):  
High Resolution ◽  
Aspect Ratio ◽  
High Altitude ◽  
Forward Scattering ◽  
Microwave Scattering ◽  
Continuous Measurements ◽  
New Instrument ◽  
Wasatch Front ◽  
Selection Of

Abstract. We describe here a new instrument for imaging hydrometeors in freefall. The Multi-Angle Snowflake Camera (MASC) captures high resolution photographs of hydrometeors from three angles while simultaneously measuring their fallspeed. Based on the stereoscopic photographs captured over the two months of continuous measurements obtained at a high altitude location within the Wasatch Front in Utah, we derive statistics for fallspeed, hydrometeor size, shape, orientation and aspect ratio. From a selection of the photographed hydrometeors, an illustration is provided for how the instrument might be used for making improved microwave scattering calculations. Complex, aggregated snowflake shapes appear to be more strongly forward scattering, at the expense of reduced back-scatter, than graupel particles of similar size.

scholarly journals Characteristic Length and Time Scales of the Highly Forward Scattering of Photons in Random Media

2019 ◽  
Vol 10 (1) ◽  
pp. 93 ◽  
Author(s):  
Hiroyuki Fujii ◽  
Moegi Ueno ◽  
Kazumichi Kobayashi ◽  
Masao Watanabe
Keyword(s):  
Radiative Transfer ◽  
Time Scales ◽  
Analytical Solutions ◽  
Random Media ◽  
Three Dimensional ◽  
Forward Scattering ◽  
Diffusion Equations ◽  
Transport Models ◽  
Photon Diffusion ◽  
Photon Transport

Background: Elucidation of the highly forward scattering of photons in random media such as biological tissue is crucial for further developments of optical imaging using photon transport models. We evaluated length and time scales of the photon scattering in three-dimensional media. Methods: We employed analytical solutions of the time-dependent radiative transfer, M-th order delta-Eddington, and photon diffusion equations (RTE, dEM, and PDE). We calculated the fluence rates at different source-detector distances and optical properties. Results: We found that the zeroth order dEM and PDE, which approximate the highly forward scattering to the isotropic scattering, are valid in longer length and time scales than approximately 10 / μ t ′ and 40 / μ t ′ v , respectively, where μ t ′ is the reduced transport coefficient and v the speed of light in a medium. The first and second order dEM, which approximate the highly forward-peaked phase function by the first two and three Legendre moments, are valid in the longer scales than approximately 4.0 / μ t ′ and 6.3 / μ t ′ v ; 2.8 / μ t ′ and 3.5 / μ t ′ v , respectively. The boundary conditions less influence the length scales, while they reduce the times scales from those for bulk at the longer length scale than approximately 4.0 / μ t ′ . Conclusion: Our findings are useful for constructions of accurate and efficient photon transport models. We evaluated length and time scales of the highly forward scattering of photons in various kinds of three-dimensional random media by analytical solutions of the radiative transfer, M-th order delta-Eddington, and photon diffusion equations.

Singularities in forward scattering through random media

1991 ◽  
Vol 1 (2) ◽  
pp. 195-206 ◽  
Author(s):  
P J Roberts ◽  
J B Pendry
Keyword(s):  
Random Media ◽  
Forward Scattering

High Resolution Numerical Simulation of Shock-to-Detonation Transition of Condensed-Phase Explosives

2013 ◽  
Vol 767 ◽  
pp. 40-45
Author(s):  
Wang Cheng ◽  
Xin Qiao Liu ◽  
Jian Guo Ning
Keyword(s):  
High Resolution ◽  
Condensed Phase ◽  
Pulse Width ◽  
Propagation Distance ◽  
Weno Scheme ◽  
Runge Kutta Method ◽  
Two Factors ◽  
Detonation Transition ◽  
Condensed Phase Explosives ◽  
Fifth Order

In this paper, shock-to-detonation transition for condensed phase explosives is numerically simulated by adopting high resolution numerical scheme. Fifth-order WENO scheme and third-order TVD Runge-Kutta method are employed to discretize Euler equations with chemical reaction source in space and time respectively, and parallel high resolution code is developed. Applying this code, the influence of incident pressure and pulse width on the run distance to detonation is investigated. The numerical results show that incident pressure and pulse width govern the initiation process. If appropriate values are taken for incident pressure and pulse width, the pressure will increase with the enlarging of the shock wave propagation distance, and finally the explosives reach steady detonation. The run distance to detonation is also influenced by those two factors, and it gets shorter with the increase of pulse width and incident pressure. When the incident pressure and the pulse width are small enough, the retonation phenomenon can be observed, and it becomes obvious along with the decreasing of incident pressure and pulse width.

scholarly journals A Numerical Analysis on Coral Larval Networks across Reef Areas on the Northwest Coast of Okinawa Main Island, Japan

2021 ◽  
Vol 945 (1) ◽  
pp. 012030
Author(s):  
Kimika Takeyasu ◽  
Yusuke Uchiyama ◽  
Xu Zhang ◽  
Kosei Matsushita ◽  
Satoshi Mitarai
Keyword(s):  
High Resolution ◽  
Ocean Circulation ◽  
Mixed Layer ◽  
Short Distance ◽  
Northwest Coast ◽  
Surface Mixed Layer ◽  
Lagrangian Particle ◽  
Coral Larvae ◽  
Main Island ◽  
Tracking Model

Abstract Coral bleaching has recently occurred extensively over the world’s oceans, primarily due to high water temperatures. Mesophotic corals that inhabit at depths of approximately 30–150 m are expected to survive during bleaching events and to reseed shallow water corals afterward. In particular, in Okinawa, Japan, mesophotic coral ecosystems (MCEs) have been reported to serve as a refuge to preserve genotypic diversities of bleaching-sensitive corals. Connectivity of larval populations between different habitats is a key element that determines the area to be conserved for desirable coral ecosystems. Coral larvae generally behave passively to the surrounding currents and are transported by the advective and dispersive effects of ambient ocean currents. Thus, numerical ocean circulation models enable us to quantify connectivity with detailed spatiotemporal network structures. Our aim in this study is to quantify the short-distance and vertical connectivity of coral larvae in reef areas on the northwest coast of Okinawa Main Island. For the reason that both short-distance and vertical larval transport are influenced by complex nearshore topography, a very high-resolution 3-D circulation model is required. Therefore, we developed a quadruple nested high-resolution synoptic ocean model at a lateral spatial resolution of 50 m, coupled with an offline 3-D Lagrangian particle-tracking model. After validation of the developed model, short-distance horizontal coral connectivity across reef areas on the northwest coast was successfully evaluated. Furthermore, a series of Lagrangian particle release experiments were conducted to identify the vertical coral migration and 3-D connectivity required for the preservation of MCEs. The model revealed that coral larvae released from the semi-enclosed areas tended to remain near the source area, whereas they were diffused and dispersed gradually with time. The mesophotic corals were dispersed vertically to the deeper zone below the mixed layer, while upward transport occurred to induce the mesophotic corals to emerge near the surface, under the influence of the surface mixed layer. The model results solidly indicated significant connectivity between MCEs and shallow coral ecosystems.

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