Search results for "thermal [correlation function]"

Zirconium and hafnium fractionation and distribution of Rare Earth Elements in neutral–alkaline waters: Case study of Lake Van hydrothermal system, T…

2021

International audience; We investigated the distribution of Zr, Hf, and rare earth elements (REE) as the sum of lanthanides plus Y in the hydrothermal system in the Lake Van area of south-eastern Turkey. This system is characterised by water with variable pH in alkaline conditions resulting from hydrothermal CO2 upraise and neoformation of calcite minerals in near equilibrium with the interacting waters. Zr, Hf, and REE determinations were carried out for aqueous phases and suspended solids in lake water and surrounding thermal springs. We found that dissolved Hf is partitioned relative to Zr during calcite formation and that such fractionation is a function of the Ca2+ activity in warm wat…

The geological CO2degassing history of a long-lived caldera

2015

The majority of the ~100 Holocene calderas on Earth host vigorously active hydrothermal systems, the heat and volatile budgets of which are sustained by degassing of deeply stored magma. Calderas may thus contribute a nontrivial, although poorly quantified, fraction of the global budget of magmatic volatiles such as CO2. Here we use original isotopic a d petrological results from Campi Flegrei volcano, Italy, to propose that hydrothermal calcites are natural mineral archives for the magmatic CO2 that reacted with reservoir rocks during the geological history of a caldera. We show that Campi Flegrei calcites, identified in core samples extracted from 3-km-deep geothermal wells, formed at iso…

Paper consolidation with Halloysite nanotubes. TGA, DMA and contact angle investigations

2013

Driven Brownian particle as a paradigm for a nonequilibrium heat bath: Effective temperature and cyclic work extraction

2017

We apply the concept of a frequency-dependent effective temperature based on the fluctuation-dissipation ratio to a driven Brownian particle in a nonequilibrium steady state. Using this system as a thermostat for a weakly coupled harmonic oscillator, the oscillator thermalizes according to a canonical distribution at the respective effective temperature across the entire frequency spectrum. By turning the oscillator from a passive "thermometer" into a heat engine, we realize the cyclic extraction of work from a single thermal reservoir, which is feasible only due to its nonequilibrium nature.

Evidence of low land surface thermal infrared emissivity in the presence of dry vegetation

2007

International audience; Land surface emissivity in the thermal infrared usually increases when the vegetation amount increases, reaching values that are larger than 0.98. During an experiment in Morocco over dry barley crops, it was found that emissivity may be significantly lower than 0.98 at full cover and that in some situations, it might decrease with increasing amount of vegetation, which was unexpected. Older data acquired in Barrax, Spain, over senescent barley also exhibited emissivity values lower than 0.98. The decrease of emissivity was also observed by means of Simulations done with our land surface emissivity model developed earlier. The main reason for such behavior might be f…

Influence of row orientation on the canopy temperature of Sicilian vineyards

2021

Row orientation can have significant effects on grape quality as it directly affects the exposure of the fruits with indirect consequences on wine quality. In this study, a Flir i7 thermal camera was used to measure the temperature of both canopy sides of a ‘Sauvignon blanc’ vineyard trained to vertical shoot position and with north-south (NS) and east-west (EW) row orientations. Photosynthetically active radiation (PAR) measurements using a 0.8-m sensor bar were taken along with the thermal imaging camera measurements. Considering both row orientations, south and east canopy sides were those that intercepted the greatest radiant energy during the day, 57.7 and 47.5%, respectively. The EW r…

An integrated approach for high spatial resolution mapping of water and carbon fluxes using multi-sensor satellite data

2012

In the last years, modeling of surface processes - such as water, energy and carbon budgets, as well as vegetation growth- seems to be focused on integrated approaches that combine aspects of hydrology, biology and meteorology into unified analyses. In this context, remotely sensed data often have a core role due to the cross-cutting impact of this novel source of spatially distributed information on all these research areas. However, several applications - such as drought monitoring, yield forecasting and crop management - require spatially detailed products at sub-field scales, which can be obtained only with support of adequately fine resolution remote sensing data (< 100 m). In particul…

Comparison of Canopy Emissivity Parametric Models With TES Emissivity Measurements

2018

Canopy temperature is a key factor in many studies, such as evapotranspiration and heat fluxes estimation. To retrieve it accurately, it is needed a precise characterization of the emissivity in the thermal infrared spectral range. Several parametric models are proposed to retrieved effective emissivity at different observation angles, from the previous knowledge of the vegetation and soil emissivities. The present work compares some of these models with emissivity measurements obtained with Temperature-Emissivity Separation (TES) method. For that, FR97, Mod3 and Rmod3 parametric models have been compared with radiometric measurements. Emissivity measurements were done for 7 different obser…

Influence of Component Temperature Derivation from Dual Angle Thermal Infrared Observations on TSEB Flux Estimates Over an Irrigated Vineyard

2015

A two-source model for deriving surface energy fluxes and their soil and canopy components was evaluated using multi-angle airborne observations. In the original formulation (TSEB1), a single temperature observation, Priestley–Taylor parameterization and the vegetation fraction are used to derive the component fluxes. When temperature observations are made from different angles, soil and canopy temperatures can be extracted directly. Two dual angle model versions are compared versus TSEB1: one incorporating the Priestley–Taylor parameterization (TSEB2I) and one using the component temperatures directly (TSEB2D), for which data from airborne campaigns over an agricultural area in Spain are u…

Effects of temperature and pressure on microcantilever resonance response.

2003

Abstract The variation in resonance response of microcantilevers was investigated as a function of pressure (10 −2 –10 6  Pa) and temperature (290–390 K) in atmospheres of helium (He) and dry nitrogen (N 2 ). Our results for a silicon cantilever under vacuum show that the frequency varies in direct proportion to the temperature. The linear response is explained by the decrease in Young's modulus with increasing the temperature. However, when the cantilever is bimaterial, the response is nonlinear due to differential thermal expansion. Resonance response as a function of pressure shows three different regions, which correspond to molecular flow regime, transition regime, and viscous regime. …