Search results for " Cooling"
showing 10 items of 278 documents
Aerosol influence on radiative cooling
2011
Aerosol particles have a complex index of refraction and therefore contribute to atmospheric emission and radiative cooling rates. In this paper calculations of the longwave flux divergence within the atmosphere at different heights are presented including water vapour and aerosol particles as emitters and absorbers. The spectral region covered is 5 to 100 microns divided into 23 spectral intervals. The relevant properties of the aerosol particles, the single scattering albedo and the extinction coefficient, were first calculated by Mie-theory and later by an approximation formula with a complex index of refraction given by Volz. The particle growth with relative humidity is also incorporat…
Are urban water bodies really cooling?
2020
Abstract Small urban water bodies, like ponds or canals, are often assumed to cool their surroundings during hot periods, when water bodies remain cooler than air during daytime. However, during the night they may be warmer. Sufficient fetch is required for thermal effects to reach a height of 1–2 m, relevant for humans. In the ‘Really cooling water bodies in cities’ (REALCOOL) project thermal effects of typical Dutch urban water bodies were explored, using ENVI-met 4.1.3. This model version enables users to specify intensity of turbulent mixing and light absorption of the water, offering improved water temperature simulations. Local thermal effects near individual water bodies were assesse…
Modeling impacts of super cool roofs on air temperature at pedestrian level in mesoscale and microscale climate models
2021
Abstract Passive daytime radiative cooling is gaining increasing relevance as recent studies report that newly developed materials with very high reflectivity and emissivity could be able to effectively reduce urban heat stress, when applied as roofing material (super cool roofs). A recent microscale sensitivity study with ENVI-met modeled the impact of super cool roofs with maximum air temperature reductions of around 0.85 K at pedestrian level for an idealized model area. To verify these findings in real urban structures featuring complex building morphologies and varying meteorological conditions, we conducted climate simulations for two contrasting cities: New York City, NY, and Phoenix…
Space-borne Bose–Einstein condensation for precision interferometry
2018
Space offers virtually unlimited free-fall in gravity. Bose-Einstein condensation (BEC) enables ineffable low kinetic energies corresponding to pico- or even femtokelvins. The combination of both features makes atom interferometers with unprecedented sensitivity for inertial forces possible and opens a new era for quantum gas experiments. On January 23, 2017, we created Bose-Einstein condensates in space on the sounding rocket mission MAIUS-1 and conducted 110 experiments central to matter-wave interferometry. In particular, we have explored laser cooling and trapping in the presence of large accelerations as experienced during launch, and have studied the evolution, manipulation and interf…
Anisotropic light-shift and magic-polarization of the intercombination line of Dysprosium atoms in a far-detuned dipole trap
2018
We characterize the anisotropic differential ac-Stark shift for the Dy $626$ nm intercombination transition, induced in a far-detuned $1070$ nm optical dipole trap, and observe the existence of a "magic polarization" for which the polarizabilities of the ground and excited states are equal. From our measurements we extract both the scalar and tensorial components of the dynamic dipole polarizability for the excited state, $\alpha_E^\text{s} = 188 (12)\,\alpha_\text{0}$ and $\alpha_E^\text{t} = 34 (12)\,\alpha_\text{0}$, respectively, where $\alpha_\text{0}$ is the atomic unit for the electric polarizability. We also provide a theoretical model allowing us to predict the excited state polari…
Effect of Plastic hot deformation on the hardness and continuous cooling transformations of 22MnB5 micro-alloyed boron steel
2009
The strains, transformation temperatures, microstructure, and microhardness of a microalloyed boron and aluminum precoated steel, which has been isothermally deformed under uniaxial tensile tests, have been investigated at temperatures between 873 and 1223 K, using a fixed strain rate value of 0.08 s−1. The effect of each factor, such as temperature and strain value, has been later valued considering the shift generated on the continuous cooling transformation (CCT) diagram. The experimental results consist of the starting temperatures that occur for each transformation, the microhardness values, and the obtained microstructure at the end of each thermomechanical treatment. All the thermome…
Vegetation growth parameters and leaf temperature: Experimental results from a six plots green roofs' system
2016
Abstract The paper provides a contribution for populating database of three physical parameters needed to model energy performance of buildings with green roofs: “coverage ratio” ( σ f ), leaf area index (LAI) and leaf temperature ( T f ). On purpose, six plant species were investigated experimentally: Phyla nordiflora, Aptenia lancifolia , Mesembryanthenum barbatus , Gazania nivea, Gazania uniflora , and Sedum . Proper ranges of the cited parameters have been found for each species. The here indicated ranges of σ f values refer to different growth levels of the species in the same lapse of time, that is four months. Single measured LAI values are also reported for the same plants. As for t…
Bulk carbonate isotope stratigraphy from CRP-3 core (Victoria Land Basin, Antarctica): evidence for Eocene–Oligocene palaeoclimatic evolution
2005
Bulk carbonate isotope compositions and carbonate petrography from upper Eocene and lower Oligocene siliciclastic sediments of the CRP-3 sediment core (Victoria Land Basin, Antarctica) have been investigated with the aim of contributing to reconstruction of the Antarctic Cenozoic palaeoclimate. Most of the carbonate is calcite cement occurring as patches, nodules and horizons and consisting of equant and/or drusy sparry calcite, pervasive blocky calcite and rare poikilotopic calcite spar. 18O-depleted values (from −17 to −8 δ‰) of the CRP-3 carbonates suggest that the precipitating fluids were a mixing between marine and meteoric waters from melting glaciers. The δ18O record exhibits a numb…
Temperature concepts for small, isolated systems: 1/t decay and radiative cooling
2003
We report on progress in our investigations of cluster cooling. The analysis of measurements is based on introduction of the microcanonical temperature and a statistical description of the decay of an ensemble with a broad distribution in temperature. The resulting time dependence of the decay rate is a power law close to t �1 , replaced by nearly exponential decay after a characteristic time for quenching by radiative cooling. We focus on results obtained for fullerenes, both anions and cations and recently also neutral C60.
2016
This commentary describes important findings of the article published by Sheroziya and Timofeev in The Journal of Neuroscience in 2015. The authors use moderate cortical temperature change, local cooling or heating of somatosensory cortex, to modulate excitable states of the brain. These changes, under physiological conditions, result from neuromodulation, as well as other network effects. They report that cooling disrupts thalamocortical slow oscillations and induces an activated cortical state, while mild heating has the opposite effect and increases slow-wave rhythmicity. We evaluate these findings regarding their utility for inducing and investigating cortical state fluctuations, compar…