Search NASA⌕ Search

SEARCH · Search NASA

Results for “surface reconstructions”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,495 records · Page 83
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

On the frequency bifurcations of the MHD startup modes in NSTX

The observed bifurcations of the low frequency (<50 kHz) and low toroidal periodicity (n < 5) magnetohydrodynamic (MHD) activity often present in the initial part of the National Spherical Tokamak Experiment (NSTX) discharges can be explained by the evolution of the radial profile of the safety factor (q=rB φ /RB θ ) crossing multiple rational surfaces in the core. Important performance limiting instability mechanisms in the NSTX spherical tokamak are often linked to low frequency and low-n MHD activity. They are quite common in long-pulse NSTX plasmas. They can be present at the beginning of the plasma current flat-top, at the end of the discharge or during the whole duration, and they have been observed to deleteriously impact performance over a wide range of q 95 . An interesting feature observed in some NSTX discharges is the presence of a bifurcation in the frequency of the low n modes, as low as n = 1, that have frequencies comparable to the plasma core rotation divided by n. Equilibrium reconstructions constrained by magnetic diagnostics data and motional stark effect pitch angle radial profiles suggest that the observed bifurcations are linked to a fast evolving minimum value of q. Finally, 3D non-linear resistive MHD simulations show that these modes are ideal and exist as non-resonant before the correspondent rational surface enters the plasma.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2017

Enhancement of spin-lattice coupling in nanoengineered oxide films and heterostructures by laser MBE

The objective of the proposed research is to investigate nanoengineered oxide films and multilayer structures that are predicted to show desirable properties. The main focus of the project is an atomic layer-by-layer laser MBE (ALL-Laser MBE ) technique that is superior to the conventional laser MBE in broadening the conditions for the synthesis of high quality nanoscale oxides and new designer materials. In ALL-Laser MBE, separate oxide targets are used instead of one compound target in the conventional laser MBE. The targets are switched back and forth in front of a UV laser beam as they are alternately ablated. The oxide film is thus constructed one atomic layer at a time. The growth of each atomic layer is monitored and controlled by the reflection high energy electron diffraction (RHEED). The intensity of the diffraction spots increases or decreases depending on the chemistry of each atomic layer as well as the surface roughness. This allows us to determine whether the chemical ratio of the different elements in the films meets the desired value and whether each atomic layer is complete. ALL-Laser MBE is versatile: it works for non-polar film on non-polar substrate, polar film on polar substrate, and polar film on non-polar substrate. (In a polar material, each atomic layer is charged whereas in a non-polar material the atomic layers are charge neutral.) It allows one to push the thermodynamic boundary further in stabilizing new phases than reactive MBE and PLD, two of the most successful techniques for oxide thin films. For example, La 5 Ni 4 O 13 , the Ruddlesden-Popper phase with n = 4, has never been reported in the literature because it needs atomic layer-by-layer growth at high oxygen pressures, not possible with other growth techniques. ALL-Laser MBE makes it possible. We have studied the interfacial 2-dimensional electron gas in the LaAlO 3 /SrTiO 3 system, whose mechanism has been a subject of controversy. According to the most prevailing electronic reconstruction mechanism, a positive diverging electric potential is built up in the polar LaAlO 3 film when it is grown on a TiO 2 -terminated SrTiO 3 substrate, which is non-polar. This leads to the transfer of half of an electron from the LaAlO 3 film surface to SrTiO 3 when the LaAlO 3 layer is thicker than 4 unit cells, creating a 2D electron gas at the interface with a sheet carrier density of 3.3×10 14 /cm 2 for sufficiently thick LaAlO 3 . A serious inconsistency with this mechanism is that the carrier densities reported experimentally are invariably lower than the expected value. The most likely reason is that the SrTiO 3 substrate is oxygen difficient due to the low oxygen pressures (< 10 mTorr) during growth, and post-growth annealing in oxygen is often used to remove the oxygen vacancies. People cannot grow the LaAlO 3 film in higher oxygen pressures - it results in insulating samples or 3D island growth. Because we grow the LaAlO 3 film one atomic layer at a time, we were able to grow conducting LaAlO 3 /SrTiO 3 interfaces at a high oxygen pressure with ALL-Laser MBE, as high as 37 mTorr. The high oxygen pressure helps to prevent the possible oxygen reduction in SrTiO 3 , ensure that the LaAlO 3 films are sufficiently oxygenated. Measurements of x-ray linear dichroism (XLD) and x-ray magnetic circular dichroism (XMCD) both show that the spectra of our films are similar to those of well oxygenated samples. In the LaAlO 3 /SrTiO 3 interfaces grown by ALL-Laser MBE at 37 mTorr oxygen pressure, a quantitative agreement between our experimental result and the theoretical prediction was observed, which provides a strong support to the electronic reconstruction mechanism. The key differences between our result and the previous reports are the high oxygen pressure during the film growth and the high film crystallinity. The high oxygen pressure suppresses the likelihood of oxygen vacancies in SrTiO 3 . Well oxygenated samples produced during film growth can avoid possible defects when sufficient oxygen is provided only after the growth by annealing. Using ALL-Laser MBE, we also synthesized high-quality singlec-rystalline CaMnO 3 films. The systematic increase of the oxygen vacancy content in CaMnO 3 as a function of applied in-plane strain is observed and confirmed experimentally using high-resolution soft x-ray XAS and hard x-ray photoemission spectroscopy (HAXPES). The relevant defect states in the densities of states are identified and the vacancy content in the films quantified using the combination of first-principles theory and core-hole multiplet calculations with holistic fitting. The strain-induced oxygen-vacancy formation and ordering are a promising avenue for designing and controlling new functionalities in complex transition-metal oxides.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Deglaciation of coastal south-western Spitsbergen dated with in situ cosmogenic 10 Be and 14 C measurements

We report the Svalbard–Barents ice sheet was predominantly a marine-based ice sheet and reconstructing the timing and rate of its decay during the last deglaciation informs predictions of future decay of marine-based ice sheets (e.g. West Antarctica). Records of ice-sheet change are routinely built with cosmogenic surface exposure ages, but in some regions, this method is complicated by the presence of isotopic inheritance yielding artificially old and erroneous exposure ages for the most recent deglaciation. We present 46 10 Be ages from south-western Spitsbergen that, when paired with in situ 14 C measurements (n = 5), constrain the timing of coastal deglaciation following the last glacial maximum. 10Be and in situ 14 C measurements from bedrock along a ~400-m elevation transect reveal inheritance-skewed 10Be ages, whereas in situ 14 C measurements constrain 400 m of ice-sheet thinning and coastal deglaciation at 17.4 ± 1.5 ka. Our in situ 14 C-dated transect, combined with three additional 10 Be-dated coastal sites, show that the south-western margin of the Svalbard–Barents ice sheet retreated out of the Norwegian Sea between ~18 and 16 ka. In situ 14 C measurements provide key chronological information on ice-sheet response to the last termination in cases where measurements of long-lived nuclides are compromised by isotopic inheritance.

58 GEOSCIENCES↗
DOE OSTI2024

Glacial to periglacial transition at the end of the last ice age in the subtropical semiarid Andes

Atmospheric warming and circulation reorganization at the end of the last ice age represent the most important climate change of the last 100,000 years and provide an opportunity to uncover how the southern subtropics cryosphere responded to strong changes in the global climate system. Extensive mapping and chronologic records on cryogenic landforms to better understand the association and interactions between glaciers and viscous creep of ice-rich permafrost landforms (rock glaciers) are widely missing in the region. In this paper, we reconstruct the geomorphic imprint of the Last Glacial Maximum (LGM) and the Termination I in the high Andes of the Río Limarí Basin (30–31°S) in the subtropical semiarid Andes of Chile. 74 new 10 Be surface exposure dating ages constrain the timing of glaciation, deglaciation, and glacial to periglacial transition. Glacial advances occurred first by 41.2 ± 0.6 – 35.0 ± 0.5 ka during Marine Isotope Stage 3, but probably earlier also; then, a second advance occurred during the global LGM between 24.2 ± 0.4 and 18.6 ± 0.2 ka. Deglaciation by 17.6 ± 0.2 ka left extensive hummocky moraines on the main valleys. Characteristic patterns of furrows and ridges typical of rock glaciers and solifluction superimposed on the LGM hummocky moraine indicate ice-rich permafrost in glacial deposits likely between 15.5 ± 0.3 and 13.6 ± 0.3 ka. We propose that moraines deposited by LGM debris-covered glaciers served as a niche for strong seasonal frost and permafrost creep, which substantially modified the original landforms. Finally, our results contribute to a better understanding of major transformations in an ice-rich high mountain area of the southern hemisphere where the interplay of temperature and precipitation changes drove glacial to periglacial transitions.

10Be surface exposure dating↗
DOE OSTI2015

Dynamic Collimator Angle Adjustments During Volumetric Modulated Arc Therapy to Account for Prostate Rotations

Purpose: Rotations of the prostate gland induce considerable geometric uncertainties in prostate cancer radiation therapy. Collimator and gantry angle adjustments can correct these rotations in intensity modulated radiation therapy. Modern volumetric modulated arc therapy (VMAT) treatments, however, include a wide range of beam orientations that differ in modulation, and corrections require dynamic collimator rotations. The aim of this study was to implement a rotation correction strategy for VMAT dose delivery and validate it for left-right prostate rotations. Methods and Materials: Clinical VMAT treatment plans of 5 prostate cancer patients were used. Simulated left-right prostate rotations between +15° and −15° were corrected by collimator rotations. We compared corrected and uncorrected plans by dose volume histograms, minimum dose (D{sub min}) to the prostate, bladder surface receiving ≥78 Gy (S78) and rectum equivalent uniform dose (EUD; n=0.13). Each corrected plan was delivered to a phantom, and its deliverability was evaluated by γ-evaluation between planned and delivered dose, which was reconstructed from portal images acquired during delivery. Results: On average, clinical target volume minimum dose (D{sub min}) decreased up to 10% without corrections. Negative left-right rotations were corrected almost perfectly, whereas D{sub min} remained within 4% for positive rotations. Bladder S78 and rectum EUD of the corrected plans matched those of the original plans. The average pass rate for the corrected plans delivered to the phantom was 98.9% at 3% per 3 mm gamma criteria. The measured dose in the planning target volume approximated the original dose, rotated around the simulated left-right angle, well. Conclusions: It is feasible to dynamically adjust the collimator angle during VMAT treatment delivery to correct for prostate rotations. This technique can safely correct for left-right prostate rotations up to 15°.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2020

Anthropogenic Impacts on Atmospheric Carbonyl Sulfide Since the 19th Century Inferred From Polar Firn Air and Ice Core Measurements

Carbonyl sulfide (COS) was measured in firn air collected during seven different field campaigns carried out at four different sites in Greenland and Antarctica between 2001 and 2015. A Bayesian probabilistic statistical model is used to conduct multisite inversions and to reconstruct separate atmospheric histories for Greenland and Antarctica. The firn air inversions cover most of the 20th century over Greenland and extend back to the 19th century over Antarctica. The derived atmospheric histories are consistent with independent surface air time series data from the corresponding sites and the Antarctic ice core COS records during periods of overlap. Atmospheric COS levels began to increase over preindustrial levels starting in the 19th century, and the increase continued for much of the 20th century. Atmospheric COS peaked at higher than present-day levels around 1975 CE over Greenland and around 1987 CE over Antarctica. An atmosphere/surface ocean box model is used to investigate the possible causes of observed variability. The results suggest that changes in the magnitude and location of anthropogenic sources have had a strong influence on the observed atmospheric COS variability.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2015

Interfacial Coupling and Electronic Structure of Two-Dimensional Silicon Grown on the Ag(111) Surface at High Temperature

Freestanding silicene, a monolayer of Si arranged in a honeycomb structure, has been predicted to give rise to massless Dirac fermions, akin to graphene. However, Si structures grown on a supporting substrate can show properties that strongly deviate from the freestanding case. Here, combining scanning tunneling microscopy/spectroscopy and differential conductance mapping, we show that the electrical properties of the (√3 x √3) phase of few-layer Si grown on Ag(111) strongly depend on film thickness, where the electron phase coherence length decreases and the free-electron-like surface state gradually diminishes when approaching the interface. These features are presumably attributable to the inelastic inter-band electron-electron scattering originating from the overlap between the surface state, interface state and the bulk state of the substrate. We further demonstrate that the intrinsic electronic structure of the as grown (√3 x √3) phase is identical to that of the (√3 x √3) R30° reconstructed Ag on Si(111), both of which exhibit the parabolic energy-momentum dispersion relation with comparable electron effective masses. Lastly, these findings highlight the essential role of interfacial coupling on the properties of two-dimensional Si structures grown on supporting substrates, which should be thoroughly scrutinized in pursuit of silicene.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Electron-doping-induced destabilization of the dimerized insulating state in monolayer IrTe 2

The ability to tune the electronic phases of two-dimensional (2D) materials through external perturbations provides a powerful route to engineer functional nanoscale systems. In particular, the ground state of monolayer (ML) 1T-IrTe 2 is highly sensitive to the interplay between local chemical bonding and global electronic topology, leading to a unique 2 × 1 dimerized insulating phase. Here, we present an angle-resolved photoemission study on the evolution of the electronic structure in ML IrTe 2 induced by in situ Rb adsorption. We find that Rb adsorption suppresses the 2 × 1 dimerized phase in ML IrTe 2 , inducing a clear insulator-to-metal transition. This transition is characterized by a reconstruction of the band topology toward a bilayer-like metallic configuration. Combined with first-principles calculations, our results demonstrate that the collapse of the insulating state originates from Ir valence change and suppression of Fermi surface nesting-driven instabilities. Our findings establish ML IrTe 2 as a model system for investigating instability-driven phase control in 2D materials and highlight its potential for tunable electronic applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Paleodust Insights into Dust Impacts on Climate

Abstract Mineral dust acts both as a tracer and a forcing agent of climate change. Past dust variability, imprinted in paleodust records from natural archives, offers the unique opportunity to reconstruct the global dust cycle within a range of possibilities that plausibly encompass future variations in response to climate change and land-cover and land-use changes. Dust itself has direct and indirect feedbacks on the climate system, through impacts on the atmosphere radiative budget and the carbon cycle. Starting from well-constrained reconstructions of the present and past dust cycle, we focus on quantifying dust direct impacts on the atmospheric radiation. We discuss the intrinsic effects of dust onto climate, and how changes in the global dust budget and surface conditions modulate the effective impacts on surface temperatures and precipitation. Most notably, the presence of dust tends to enhance the West African monsoon and warm the Arctic. We also highlight how different choices in terms of dust optical properties and size distributions may yield opposite results, and what are the observational constraints we can use to make an informed choice of model parameters. Finally, we discuss how dust variability might have influenced ongoing climate transitions in the past. In particular we found that a reduction in dust load, along with a reduced cryosphere cover, acted to offset Arctic warming during the deglaciation, potentially playing a role in shaping the Northern Hemisphere deglacial dynamics.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2016

THE MUSCLES TREASURY SURVEY. II. INTRINSIC LY α AND EXTREME ULTRAVIOLET SPECTRA OF K AND M DWARFS WITH EXOPLANETS

The ultraviolet (UV) spectral energy distributions (SEDs) of low-mass (K- and M-type) stars play a critical role in the heating and chemistry of exoplanet atmospheres, but are not observationally well-constrained. Direct observations of the intrinsic flux of the Ly α line (the dominant source of UV photons from low-mass stars) are challenging, as interstellar H i absorbs the entire line core for even the closest stars. To address the existing gap in empirical constraints on the UV flux of K and M dwarfs, the MUSCLES Hubble Space Telescope Treasury Survey has obtained UV observations of 11 nearby M and K dwarfs hosting exoplanets. This paper presents the Ly α and extreme-UV spectral reconstructions for the MUSCLES targets. Most targets are optically inactive, but all exhibit significant UV activity. We use a Markov Chain Monte Carlo technique to correct the observed Ly α profiles for interstellar absorption, and we employ empirical relations to compute the extreme-UV SED from the intrinsic Ly α flux in ∼100 Å bins from 100–1170 Å. The reconstructed Ly α profiles have 300 km s{sup −1} broad cores, while >1% of the total intrinsic Ly α flux is measured in extended wings between 300 and 1200 km s{sup −1}. The Ly α surface flux positively correlates with the Mg ii surface flux and negatively correlates with the stellar rotation period. Stars with larger Ly α surface flux also tend to have larger surface flux in ions formed at higher temperatures, but these correlations remain statistically insignificant in our sample of 11 stars. We also present H i column density measurements for 10 new sightlines through the local interstellar medium.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

East Antarctic Ice Sheet variability in the central Transantarctic Mountains since the mid Miocene

The response of the East Antarctic Ice Sheet to warmer-than-present climate conditions has direct implications for projections of future sea level, ocean circulation, and global radiative forcing. Nonetheless, it remains uncertain whether the ice sheet is likely to undergo net loss due to amplified melting coupled with dynamic instabilities or whether such losses will be balanced, or even offset, by enhanced accumulation under a higher-precipitation regime. The glacial depositional record from the central Transantarctic Mountains (TAM) provides a robust geologic means to reconstruct the past behaviour of the East Antarctic Ice Sheet, including during periods thought to have been warmer than today, such as the mid-Pliocene Warm Period (~3.3–3.0 Ma). This study describes a new surface-exposure-dated moraine record from Otway Massif in the central TAM spanning the last ~9 Myr and synthesises these data in the context of previously published moraine chronologies constrained with cosmogenic nuclides. The resulting record, although fragmentary, represents the majority of direct and unambiguous terrestrial evidence for the existence and size of the East Antarctic Ice Sheet during the last 14 Myr, and it thus provides new insight into the long-term relationship between the ice sheet and global climate. At face value, the existing TAM moraine record does not exhibit a clear signature of the mid-Pliocene Warm Period, thus precluding a definitive verdict on the East Antarctic Ice Sheet's response to this event. In contrast, an apparent hiatus in moraine deposition both at Otway Massif and the neighbouring Roberts Massif suggests that the ice sheet surface in the central TAM was potentially lower than present during the late Miocene and earliest Pliocene.

58 GEOSCIENCES↗
NASA NTRS1983

Electron temperature measurements using a 12-channel array probe

The most common technique for determining the mean kinetic energy of electrons in low-temperature plasmas utilizes the so-called Langmuir probe. The present investigation is concerned with the study of the electron temperature in a pulsed high-beta plasma as a function of time by means of a miniature array of 12 planar Langmuir probes. By using a probe with many individually collecting surfaces, each biased at a different fixed voltage, an approximation to the true probe characteristic is obtained when monitoring the collected currents for each independent subprobe. The employed method, by using many points, provides enough information to reconstruct the entire I-V curve. Attention is given to the principle of operation of the new probe, calibration, accuracy, time resolution, and applications of the new method. By employing two probes it is possible to perform correlation measurements to study heat flow and temperature fluctuations.

Wild, N.↗
NASA NTRS2002

Geometric, Kinematic and Radiometric Aspects of Image-Based Measurements

This paper discusses theoretical foundations of quantitative image-based measurements for extracting and reconstructing geometric, kinematic and dynamic properties of observed objects. New results are obtained by using a combination of methods in perspective geometry, differential geometry. radiometry, kinematics and dynamics. Specific topics include perspective projection transformation. perspective developable conical surface, perspective projection under surface constraint, perspective invariants, the point correspondence problem. motion fields of curves and surfaces. and motion equations of image intensity. The methods given in this paper arc useful for determining morphology and motion fields of deformable bodies such as elastic bodies. viscoelastic mediums and fluids.

Liu, Tianshu↗
NASA NTRS2014

Mars Entry Atmospheric Data System Modeling, Calibration, and Error Analysis

The Mars Science Laboratory (MSL) Entry, Descent, and Landing Instrumentation (MEDLI)/Mars Entry Atmospheric Data System (MEADS) project installed seven pressure ports through the MSL Phenolic Impregnated Carbon Ablator (PICA) heatshield to measure heatshield surface pressures during entry. These measured surface pressures are used to generate estimates of atmospheric quantities based on modeled surface pressure distributions. In particular, the quantities to be estimated from the MEADS pressure measurements include the dynamic pressure, angle of attack, and angle of sideslip. This report describes the calibration of the pressure transducers utilized to reconstruct the atmospheric data and associated uncertainty models, pressure modeling and uncertainty analysis, and system performance results. The results indicate that the MEADS pressure measurement system hardware meets the project requirements.

Karlgaard, Christopher D.↗
DOE OSTI2017

Three-flavour neutrino oscillations with MINOS and CHIPS

MINOS was a long-baseline neutrino oscillation experiment comprising two functionally identical detectors that observed Fermilab's NuMI neutrino beam in its low energy tune, at distances of 1 km and 735 km. When NuMI switched to a higher-power medium energy tune in 2012, the MINOS detectors continued to operate as MINOS+. Since its commissioning in 2003, the MINOS Far Detector has also been able to detect atmospheric neutrinos. Atmospheric neutrino oscillations are sensitive to the mass splitting m2 32 and mixing angle 23, and are also subject to the Matter E ect as the neutrinos pass through the Earth, which a ects neutrinos and antineutrinos di erently in a way that depends upon the mass hierarchy. This thesis presents the rst atmospheric neutrino analysis using data from the MINOS+ era, and the rst dedicated MINOS atmospheric neutrino analysis to use a full three- avour mixing model. It includes 10.79 kiloton years of new data and encompasses almost an entire period of the 11-year solar cycle, from 2003 to 2014. The CHIPS experiment aims to reduce construction costs of large water Cherenkov detectors to $200-300k per kiloton by submerging detectors with a lightweight structure in bodies of water on the surface of the Earth. Such detectors could reach masses of 1 Mton and would assist with the search for CP violation in the neutrino sector by measuring the rate of e appearance in a beam. A detailed reconstruction framework for CHIPS has been developed, incorporating a novel method based on the timing of PMT hits. This framework has been used to study the performance of di erent designs for a 10 kiloton CHIPS R&D module, and to demonstrate that e events can be identi ed in a sparsely-instrumented detector with a 6% coverage of 3" PMTs.

Perch, Andrew John↗
DOE OSTI2026

Machine Learning for Multipactor Susceptibility Prediction in Planar RF Gaps

Multipactor discharge is a nonlinear electron avalanche that limits the performance of high-power radio-frequency (RF) and vacuum electronic devices. Predicting multipactor susceptibility traditionally relies on Monte Carlo or particle-in-cell (PIC) simulations, which become computationally expensive for large parametric studies. In this work, we present a supervised machine-learning (ML) framework for prediction of multipactor susceptibility in a two-surface planar geometry. The models are trained using high-fidelity PIC simulation generated susceptibility data and learn the relationship between operational parameters, geometry, and material-dependent secondary electron emission properties. The proposed approach enables rapid reconstruction of susceptibility charts while preserving the physical structure of multipactor growth regions.

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

Accounting for uncertainty sources in pyrometric measurements: Variables affecting Surface Temperature measurements using the LLNL Streak Spectrometers

Here we present a detailed analysis of the error sensitivities of the LLNL temperature analysis package used in analyzing streak spectrometer data. These sensitivities include noise, temperature, wavelength, emissivity, missing bands, and missing data points. The analysis package was tested for its ability to accurately reconstruct randomly generated noisy data and found to perform within specifications.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

On the effective spectral emissivity of clear skies and the radiative cooling potential of selectively designed materials

Thermophotonic devices are optically designed to be spectrally selective in order to reject heat to outer space through atmospheric windows of low thermal absorption. The determination of thermal equilibrium temperatures for thermophotonic devices requires the knowledge of the effective spectral emissivity of the sky. In this work, individual contributions of participating gases and aerosols to the spectral values of the sky emissivity are analyzed in the entire infrared spectrum as well as in seven distinct bands for which water vapor either dominates or is virtually transparent to infrared radiation. We also propose high-fidelity correlations for the effective sky emissivity as functions of the normalized ambient partial pressure of water vapor () for both broadband and for the seven spectral bands. Here, the correlations are derived using a combination of ground experimental data, high resolution spectral data for the main atmospheric constituents and spectral models to reconstruct the spectral distribution of infrared thermal radiation from the atmosphere to the ground. These results enable direct calculation of the equilibrium temperature and cooling efficiency of radiative cooling devices in terms of meteorological conditions observed at the surface level. For hot and dry conditions, the passive radiative coolers have a cooling potential of 150.8 W m–2 while for humid conditions, the coolers are mostly ineffective.

14 SOLAR ENERGY↗