scholarly journals Sublimation-driven morphogenesis of Zen stones on ice surfaces

2021 ◽  
Vol 118 (40) ◽  
pp. e2109107118
Author(s):  
Nicolas Taberlet ◽  
Nicolas Plihon
Keyword(s):  
Thermal Conduction ◽  
Far Infrared ◽  
Black Body ◽  
Ablation Rate ◽  
Physical Explanation ◽  
Sublimation Rate ◽  
Local Ablation ◽  
Ice Surface ◽  
Slow Surface ◽  
Rule Out

In this article, the formation of Zen stones on frozen lakes and the shape of the resulting pedestal are elucidated. Zen stones are natural structures in which a stone, initially resting on an ice surface, ends up balanced atop a narrow ice pedestal. We provide a physical explanation for their formation, sometimes believed to be caused by the melting of the ice. Instead, we show that slow surface sublimation is indeed the physical mechanism responsible for the differential ablation. Far from the stone, the sublimation rate is governed by the diffuse sunlight, while in its vicinity, the shade it creates inhibits the sublimation process. We reproduced the phenomenon in laboratory-scale experiments conducted in a lyophilizer and studied the dynamics of the morphogenesis. In this apparatus, which imposes controlled constant sublimation rate, a variety of model stones consisting of metal disks was used, which allows us to rule out the possible influence of the thermal conduction in the morphogenesis process. Instead, we show that the stone only acts as an umbrella whose shade hinders the sublimation, hence protecting the ice underneath, which leads to the formation of the pedestal. Numerical simulations, in which the local ablation rate of the surface depends solely on the visible portion of the sky, allow us to study the influence of the shape of the stone on the formation of the ice foot. Finally, we show that the far-infrared black-body irradiance of the stone itself leads to the formation of a depression surrounding the pedestal.

STUDYING THE SUBLIMATION OF CARBON DIOXIDE

2021 ◽  
Vol 17 (37) ◽  
pp. 1-12
Author(s):  
Evgeniy N. NEVEROV ◽  
Igor A. KOROTKIY ◽  
Elena V. KOROTKAYA ◽  
Aleksandr N. RASSHCHEPKIN
Keyword(s):  
Carbon Dioxide ◽  
Storage Temperature ◽  
Thermal Conditions ◽  
Ambient Air ◽  
Sublimation Rate ◽  
Temperature Relation ◽  
Dry Ice ◽  
Weight Losses ◽  
Ice Surface ◽  
The Difference

Background: The utilization of dry ice in cooling and storage units requires adjusting the intensity of sublimation due to the requirements of prudently using CO2 to maintain preset thermal conditions. Aim: When designing a carbon dioxide cycle, it is essential to consider the influence of thermal gradients on the adsorption and desorption of carbon dioxide. Methods: tests were conducted to study the production and sublimation of carbon dioxide. The testes were aimed to define the temperature relation of the dry ice sublimation period, the density of pressed СО2, and the humidity of the environment and concentration. Results and Discussion: According to the obtained test data, there was a linear relationship between the sublimation intensity and the ambient air temperature in the specified conditions. The effect of moisture condensation on the sublimation rate appeared weaker than expected, for the amount of moisture on the surface of the specimens was insignificant. The heat exchange was intensified by the fall of hoarfrost and the related surface expansion. However, much moisture froze out without reaching the dry ice surface, and the formed layer of ice formed a heat insulation surface, and the sublimation under that layer was less intensive. The direct influence of sublimation came from the pressure at which a specific specimen was formed; however, 75 kN pressure was optimal. Conclusion: Despite higher weight losses during the storage, the difference in spent energy is more critical than 90 kN. The factor no less important was the carbon dioxide storage temperature. The maximal sublimation time of a 55 g cylinder formed at 75 kN and stored at – 80°С was 135 hours, much higher than at similar parameters but at -60°С. That said, the amount of energy spent on operating a low-temperature chamber was almost identical.

Far-infrared spectrally selective LiTaO3 and AlN pyroelectric detectors using resonant subwavelength metal surface structures

MRS Advances ◽  
2020 ◽  
Vol 5 (39) ◽  
pp. 2005-2012
Author(s):  
Christopher Arose ◽  
Anthony C. Terracciano ◽  
Robert E. Peale ◽  
Francisco Javier Gonzalez ◽  
Zachary Loparo ◽  
...  
Keyword(s):  
Far Infrared ◽  
Black Body ◽  
Selective Absorption ◽  
Backward Wave Oscillator ◽  
Similar Work ◽  
Sensing Applications ◽  
Spectrally Selective ◽  
Wave Oscillator ◽  
Infrared Spectral ◽  
Pyroelectric Detectors

AbstractPlasmonic near-perfect absorbers, comprising metal films with a periodic array of subwavelength openings, were deposited on the surface of pyroelectric materials to create wavelength-selective far-infrared detectors. The detectors fabricated and investigated were based on one of two pyroelectric materials: (i) z-cut monocrystalline lithium tantalate (LiTaO3) wafers or, (ii) reactively sputtered aluminum nitride (AlN), with absorbers fabricated by contact photolithography. Spectrally selective absorption resonances were demonstrated by Fourier-transform spectroscopy. Spectrally-selective photoresponse was demonstrated with a tunable THz backward wave oscillator. Responsivity was estimated using a black body source to be ∼ 1 mV/W for AlN samples and ∼ 100 mV/W for LiTaO3 samples. Most similar work has focused on detectors for mid-wave and long-wave infrared spectral regions. Our focus on THz wavelengths beyond 20 μm is motivated by specific security and contraband sensing applications.

scholarly journals Far-infrared Excesses in Classical Be Stars

2000 ◽  
Vol 175 ◽  
pp. 484-487 ◽  
Author(s):  
A.S. Miroshnichenko ◽  
K.S. Bjorkman
Keyword(s):  
High Resolution ◽  
Far Infrared ◽  
Infrared Emission ◽  
Circumstellar Dust ◽  
Spectral Energy ◽  
Be Stars ◽  
Spectral Energy Distributions ◽  
Energy Distributions ◽  
Rule Out

AbstractA sample of Be stars with large far-infrared excesses detected by IRAS is selected and their high-resolution IRAS images are examined. The far-infrared emission from most of them is marginally extended and is associated with the optical sources. Modeling of the stars’ spectral energy distributions allows us to rule out the infrared cirrus nature of the excesses. We suggest that the excesses are more likely due to circumstellar dust, possibly formed early in the evolution of the star.

About unidentified features in the Voyager far infrared spectra of Jupiter and Saturn

1983 ◽  
Vol 61 (10) ◽  
pp. 1455-1461 ◽  
Author(s):  
D. Gautier ◽  
A. Marten ◽  
J. P. Baluteau ◽  
G. Bachet
Keyword(s):  
Complex Shape ◽  
Thermal Structure ◽  
Far Infrared ◽  
High Spectral Resolution ◽  
Physical Conditions ◽  
Main Components ◽  
Measurement Artifacts ◽  
Far Infrared Spectra ◽  
Rule Out ◽  
The Continuum

Two faint spectral features are visible in Jupiter's spectra recorded during the infrared interferometer experiment aboard the two spacecraft of the Voyager mission. These features are located at the frequencies of the S(0) and S(1) pressure induced rotation lines of the free H2 molecule, and are superimposed over the absorption spectrum induced by collisions between H2–H2 and H2–He molecules, which are the main components of the atmospheres of the giant planets. We demonstrate conclusively that these features are real and not measurement artifacts. The feature located at the S(0) frequency, which also exists in the Voyager spectra of Saturn, exhibits a complex shape, characterized by a lack of absorption in the continuum at 354.4 cm−1 and a local excess of absorption over the continuum at 350.5 cm−1. The feature corresponding to the S(1) frequency seems to be due mainly to an absorption dip in the continuum at 587.1 cm−1. Physical conditions prevailing at the atmospheric levels of formation of the features rule out the possibility that they can be attributed to H2 quadrupolar lines or to a dip in absorption resulting from intercollisional effects in the H2–He component of the pressure induced absorption. We speculate that they could be due to an intercollisional effect in the H2–H2 component, but the lack of laboratory measurements precludes any firm interpretation.Laboratory studies of the S lines in the collision induced spectrum of H2, made at high spectral resolution and low temperatures, are absolutely necessary in order to be able to complete the interpretation of the observed phenomena and to derive from them information on the atmospheric thermal structure or composition of Jupiter and Saturn.

scholarly journals Low Frequency Cutoffs in the Spectra of Radioquiet Quasars

1987 ◽  
Vol 121 ◽  
pp. 135-139
Author(s):  
R. Antonucci ◽  
R. Barvainis
Keyword(s):  
High Frequency ◽  
Near Infrared ◽  
Dust Emission ◽  
Low Frequency ◽  
Far Infrared ◽  
Low Energy Electrons ◽  
Order Of Magnitude ◽  
Infrared Continuum ◽  
Lower Cutoff ◽  
Rule Out

Radio-quiet and normal radio-loud quasars have very similar spectral properties in the ultraviolet, optical and near infrared regions, but their radio powers differ by several orders of magnitude. Somewhere between the near infrared and the radio their spectra must diverge dramatically.The IRAS survey detected 17 radio quiet quasars and luminous Seyfert 1's with −29. 5 ≤ Mv ≤ −21.6 (for Ho = 75). By coadding the survey data and using pointed observations, we have detections of most of these objects in all four IRAS passbands. The spectra are all rising with wavelength all the way to 100μ. We are measuring fluxes in the centimeter, millimeter, and, together with R Cutri, the near infrared and optical regions for each of these objects. Our goal is to constrain the location, shape, and spectral context of the low frequency cutoffs. Here we present the IRAS, millimeter and centimeter data. Measurements at the other wavelengths are still in progress.Although the spectra are rising steeply between 60μ and 100μ, we find that all of our objects are undetectable at 1.3 mm with the NRAO 12-m telescope. Our limits are typically an order of magnitude below the 100μ fluxes. (Ennis et al (1982) and Robson et al (1985) have already shown that the 1 mm fluxes of some radio quiet quasars must be below the extrapolation of the near infrared continuum.) Our objects are all extremely weak or undetected with the VLA at 2 cm and 1.3 cm, at levels typically three orders of magnitude below the 100μ fluxes. The sharpness of the required cutoffs allows us to rule out the hypothesis that the infrared is synchrotron radiation with the cutoff due to an absence of low energy electrons. The high frequency of the cutoffs makes free-free absorption implausible, but not impossible. It is possible that synchrotron self-absorption is suppressing the radio. There is circumstantial evidence that the far infrared is thermal dust emission. This would require a lower cutoff in the distribution of dust temperatures, which we think we can explain.

scholarly journals Local and Global Optical, Far-Infrared (FIR) and X-ray Properties of the FIR Quiescent Sc Galaxy NGC 247

1995 ◽  
Vol 164 ◽  
pp. 429-429
Author(s):  
Glen Mackie ◽  
G. Fabbiano ◽  
D.-W. Kim ◽  
Y. Ikebe
Keyword(s):  
Far Infrared ◽  
Late Type ◽  
X Ray ◽  
Luminous Galaxies ◽  
Non Linear ◽  
First Results ◽  
Linear Behaviour ◽  
Abstract Submission ◽  
X Ray Binaries ◽  
Rule Out

We present an Optical, FIR and X-ray study of the low LFIR Sc galaxy, NGC 247. Global correlations (ie. B or X vs. Radio or FIR) in late-type spirals suggest that some luminosities do not scale linearly. We describe first results of a program to study emission in late-type spirals on local (kpc) scales to investigate this non-linear behaviour. Our data includes B, I, Hα+[Nii] CCD, IRAS 60, 100μm (Rice 1993), and ROSAT PSPC, (0.1-2.4keV) images. Since abstract submission we have added H I (Carignan and Puche 1990) and 1.49 GHz continuum (Condon 1987). The Hα+[Nii] is generally coextensive with the IRAS emission and H I. The brightest Hα+[Nii] region (log LHα~38.6 ergs s−1) in a region of low FIR flux, may possess a locally warm 60/100μm ratio suggesting a similarity with more luminous galaxies that have warm 60/100μm ratios globally. 1.49 GHz sources are not cospatial with bright X-ray sources, nor with Hα+[Nii]. Three extended 1.49 GHz sources are cospatial with very faint, soft X-ray emission, suggesting a SNR origin. We cannot rule out a direct 1.49 GHz/X-ray or 1.49 GHz/ H ii origin due to relativistic e− propagation. ROSAT PSPC results suggest 4 4σ (0.1-2.4 keV) X-ray sources are intrinsic. Their LX range of 1036–37 ergs s−1 is consistent with X-ray binaries, whilst the total LX = 3.0×1037 ergs s−1 is underluminous by ~3, compared to previous regression fits. A faint soft, LX ~ 1×1036 ergs s−1 nuclear X-ray feature may be a SNR outflow, and similar to plumes/outflows seen in starbursts, but 104 less luminous.

scholarly journals RAVAN: CubeSat Demonstration for Multi-Point Earth Radiation Budget Measurements

2019 ◽  
Vol 11 (7) ◽  
pp. 796 ◽  
Author(s):  
William Swartz ◽  
Steven Lorentz ◽  
Stergios Papadakis ◽  
Philip Huang ◽  
Allan Smith ◽  
...  
Keyword(s):  
Spatial Information ◽  
Spectral Response ◽  
Far Infrared ◽  
Black Body ◽  
Total Solar Irradiance ◽  
Radiation Budget ◽  
Outgoing Radiation ◽  
Black Bodies ◽  
Vertically Aligned ◽  
Synchronous Orbit

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) 3U CubeSat mission is a pathfinder to demonstrate technologies for the measurement of Earth’s radiation budget, the quantification of which is critical for predicting the future course of climate change. A specific motivation is the need for lower-cost technology alternatives that could be used for multi-point constellation measurements of Earth outgoing radiation. RAVAN launched 11 November 2016, into a nearly 600-km, Sun-synchronous orbit, and collected data for over 20 months. RAVAN successfully demonstrates two key technologies. The first is the use of vertically aligned carbon nanotubes (VACNTs) as absorbers in broadband radiometers for measuring Earth’s outgoing radiation and the total solar irradiance. VACNT forests are arguably the blackest material known and have an extremely flat spectral response over a wide wavelength range, from the ultraviolet to the far infrared. As radiometer absorbers, they have greater sensitivity for a given time constant and are more compact than traditional cavity absorbers. The second technology demonstrated is a pair of gallium phase-change black body cells that are used as a stable reference to monitor the degradation of RAVAN’s radiometer sensors on orbit. Four radiometers (two VACNT, two cavity), the pair of gallium black bodies, and associated electronics are accommodated in the payload of an agile 3U CubeSat bus that allows for routine solar and deep-space attitude maneuvers, which are essential for calibrating the Earth irradiance measurements. The radiometers show excellent long-term stability over the course of the mission and a high correlation between the VACNT and cavity radiometer technologies. Short-term variability—at greater than the tenths-of-a-Watt/m2 needed for climate accuracy—is a challenge that remains, consistent with insufficient thermal knowledge and control on a 3U CubeSat. There are also VACNT–cavity biases of 3% and 6% in the Total and SW channels, respectively, which would have to be overcome in a future mission. Although one of the black bodies failed after four months, the other provided a repeatable standard for the duration of the project. We present representative measurements from the mission and demonstrate how the radiometer time series can be used to reconstruct outgoing radiation spatial information. Improvements to the technology and approach that would lead to better performance and greater accuracy in future missions are discussed.

scholarly journals Source Characteristics of 20 MeV Tabletop Synchrotron Radiation Source

2009 ◽  
Vol 2 (1) ◽  
pp. 9-16
Author(s):  
M. M. Haque ◽  
A. Moon ◽  
N. Miura
Keyword(s):  
Synchrotron Radiation ◽  
Light Source ◽  
Storage Ring ◽  
Far Infrared ◽  
Black Body ◽  
Far Infrared Spectroscopy ◽  
Source Characteristics ◽  
Electron Orbit ◽  
Ft Ir ◽  
Ir Emission

 The low energy storage ring MIRRORCLE-20, operating at electron energy Eel = 20 MeV can produce a powerful infrared (IR) synchrotron radiation with wavelengths over mid-IR and far-IR regions. To clarify the applicability of this light source, its far-IR output as well as spectrum was measured. The IR emission is forced by a circular optics, named photon storage ring (PhSR), placed around the electron orbit, and is collected by a magic mirror associated with two plane mirrors in the storage ring. It is proven that the FIR intensity is boosted by the PhSR. The SR spectrum of MIRRORCLE-20 in the far-IR region is much broader and more intense than that of a typical black body light source, and therefore can be used for far infrared spectroscopy (FIRS).  Keywords: Storage ring; FIR source; 20 MeV MIRRORCLE; FIRS; FT/IR.  © 2010 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved. DOI: 10.3329/jsr.v2i1.2637                J. Sci. Res. 2 (1), 9-16 (2010) 

scholarly journals Temporal Variability of Surface Reflectance Supersedes Spatial Resolution in Defining Greenland’s Bare-Ice Albedo

2021 ◽  
Vol 14 (1) ◽  
pp. 62
Author(s):  
Tristram D. L. Irvine-Fynn ◽  
Pete Bunting ◽  
Joseph M. Cook ◽  
Alun Hubbard ◽  
Nicholas E. Barrand ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
Temporal Dynamics ◽  
Model Performance ◽  
Greenland Ice Sheet ◽  
Surface Reflectance ◽  
Primary Control ◽  
Local Ablation ◽  
Ice Surface ◽  
Moderate Resolution ◽  
Reflectance Data

Ice surface albedo is a primary modulator of melt and runoff, yet our understanding of how reflectance varies over time across the Greenland Ice Sheet remains poor. This is due to a disconnect between point or transect scale albedo sampling and the coarser spatial, spectral and/or temporal resolutions of available satellite products. Here, we present time-series of bare-ice surface reflectance data that span a range of length scales, from the 500 m for Moderate Resolution Imaging Spectrometer’s MOD10A1 product, to 10 m for Sentinel-2 imagery, 0.1 m spot measurements from ground-based field spectrometry, and 2.5 cm from uncrewed aerial drone imagery. Our results reveal broad similarities in seasonal patterns in bare-ice reflectance, but further analysis identifies short-term dynamics in reflectance distribution that are unique to each dataset. Using these distributions, we demonstrate that areal mean reflectance is the primary control on local ablation rates, and that the spatial distribution of specific ice types and impurities is secondary. Given the rapid changes in mean reflectance observed in the datasets presented, we propose that albedo parameterizations can be improved by (i) quantitative assessment of the representativeness of time-averaged reflectance data products, and, (ii) using temporally-resolved functions to describe the variability in impurity distribution at daily time-scales. We conclude that the regional melt model performance may not be optimally improved by increased spatial resolution and the incorporation of sub-pixel heterogeneity, but instead, should focus on the temporal dynamics of bare-ice albedo.

Ice in Coulthard Cave, Alberta

1974 ◽  
Vol 11 (4) ◽  
pp. 510-518 ◽  
Author(s):  
P. Marshall ◽  
M. C. Brown
Keyword(s):  
Sea Level ◽  
Water Surface ◽  
Warm Period ◽  
Sublimation Rate ◽  
Mean Sea Level ◽  
Ice Surface ◽  
Pleistocene Period ◽  
Normal Trajectory ◽  
Ice Surfaces

Coulthard Cave is located in the Crowsnest Pass area of southwestern Alberta, at an elevation of 2650 m above mean sea level. The entrance of the cave faces north, and alt but one of the passages in the cave end in massive ice blockages. Oriented ice samples were removed and studied by crystallographic techniques in a cold laboratory which revealed a layering (not evident to the eye) similar to that formed by the freezing of a horizontal water surface, i.e. a 'pond.' Although present-day temperatures in the cave never exceed 0 °C, large scallop-like depressions in the ice suggest slow erosion by sublimation. An experiment indicated a sublimation rate of 3 mm/yr. Sublimation of the ice permits entrapped sediment to reach the ice surface. Continual downward lowering of the ice surface facilitates the movement by normal trajectory of sediment toward the scallop edges where it forms interstitial ridges. These ridges form on both vertical and overhanging ice surfaces. It is concluded that the ice probably did not form during the Pleistocene Period but rather after the late Hypsithermal warm period.

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