The Experts below are selected from a list of 186 Experts worldwide ranked by ideXlab platform
Frederick C Meinzer - One of the best experts on this subject based on the ideXlab platform.
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regulation of transpiration in field grown sugarcane evaluation of the stomatal response to humidity with the bowen ratio technique
Agricultural and Forest Meteorology, 1991Co-Authors: David A Grantz, Frederick C MeinzerAbstract:Abstract Parallel time courses of net radiation, canopy conductance and evapotranspiration in a sugarcane canopy demonstrate the interaction of environmental and physiological factors in regulating water loss. The Bowen ratio-energy balance technique was used to evaluate the stomatal response to humidity in the absence of potential artifacts associated with Porometer and leaf chamber measurements. Canopy conductance ( g c ) responded to leaf-air vapor pressure difference ( V ), supporting the validity of available physiological data showing clear stomatal responses to V in Porometers and leaf chambers. Several factors were found to obscure the stomatal response to V under field conditions. The stomatal closing stimulus, V , and the opening stimulus, photon flux density ( I ), were positively correlated. This caused offsetting stomatal responses to V and I , which reduced the net stomatal response when V changed with radiation-driven changes in leaf temperature. Normalization of g c by I revealed the expected hyperbolic decline of g c with increasing V . Low boundary layer conductance attenuated V imposed at the leaf surface relative to V measured with reference to humidity in the bulk atmosphere. This reduced the stimulus for stomatal response to V , below that indicated by agrometeorological measurements. Use of air saturation deficit ( D ) rather than V to express evaporative demand overestimates V , minimizing apparent stomatal sensitivity to evaporative demand, when leaves are cooler than the air. These factors may result in small stomatal responses to V that escape detection by indirect measures of stomatal movement, such as those based on the temperature of exposed leaves.
D. Varentsov - One of the best experts on this subject based on the ideXlab platform.
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Fast six-channel pyrometer for warm-dense-matter experiments with intense heavy-ion beams
Lawrence Berkeley National Laboratory, 2008Co-Authors: Pavel Ni, M.i. Kulish, V. Mintsev, D.n. Nikolaev, V.ya. Ternovoi, S. Udrea, N.a. Tahir, Dieter Hoffmann, D. VarentsovAbstract:This paper describes a fast multi-channel radiation pyrometer that was developed for warmdense-matter experiments with intense heavy ion beams at Gesellschaft fur Schwerionenforschung mbH (GSI). The pyrometer is capable of measuring of brightness temperatures from 2000 K to 50000 K, at 6 wavelengths in visible and near-infrared parts of spectrum, with 5 nanosecond temporal resolution and several micrometers spatial resolution. The pyrometer's spectral discrimination technique is based on interference filters, which act as filters and mirrors to allow for simultaneous spectral discrimination of the same ray at multiple wavelengths.
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Temperature measurement of warm-dense-matter generated by intense heavy-ion beams
Laser and Particle Beams, 2008Co-Authors: P.a. Ni, M.i. Kulish, V. Mintsev, D.n. Nikolaev, V.ya. Ternovoi, D.h.h. Hoffmann, S. Udrea, N.a. Tahir, D. VarentsovAbstract:AbstractThis paper describes a fast multi-channel radiation pyrometer that was developed for warm dense-matter experiments with intense heavy ion beams at the Gesellschaft für Schwerionenforschung mbH (GSI). The pyrometer is capable of measuring brightness temperatures from 2000 K to 50,000 K, at six wavelengths in the visible and near-infrared parts of the spectrum, with 5 ns temporal resolution, and several micrometers spatial resolution. The pyrometer's spectral discrimination technique is based on interference filters, which also act as mirrors to allow for simultaneous spectral discrimination of the same ray at multiple wavelengths.
David A Grantz - One of the best experts on this subject based on the ideXlab platform.
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regulation of transpiration in field grown sugarcane evaluation of the stomatal response to humidity with the bowen ratio technique
Agricultural and Forest Meteorology, 1991Co-Authors: David A Grantz, Frederick C MeinzerAbstract:Abstract Parallel time courses of net radiation, canopy conductance and evapotranspiration in a sugarcane canopy demonstrate the interaction of environmental and physiological factors in regulating water loss. The Bowen ratio-energy balance technique was used to evaluate the stomatal response to humidity in the absence of potential artifacts associated with Porometer and leaf chamber measurements. Canopy conductance ( g c ) responded to leaf-air vapor pressure difference ( V ), supporting the validity of available physiological data showing clear stomatal responses to V in Porometers and leaf chambers. Several factors were found to obscure the stomatal response to V under field conditions. The stomatal closing stimulus, V , and the opening stimulus, photon flux density ( I ), were positively correlated. This caused offsetting stomatal responses to V and I , which reduced the net stomatal response when V changed with radiation-driven changes in leaf temperature. Normalization of g c by I revealed the expected hyperbolic decline of g c with increasing V . Low boundary layer conductance attenuated V imposed at the leaf surface relative to V measured with reference to humidity in the bulk atmosphere. This reduced the stimulus for stomatal response to V , below that indicated by agrometeorological measurements. Use of air saturation deficit ( D ) rather than V to express evaporative demand overestimates V , minimizing apparent stomatal sensitivity to evaporative demand, when leaves are cooler than the air. These factors may result in small stomatal responses to V that escape detection by indirect measures of stomatal movement, such as those based on the temperature of exposed leaves.
Desmet Bernard - One of the best experts on this subject based on the ideXlab platform.
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Measurements of brake disc surface temperature and emissivity by two-color pyrometry
Applied Thermal Engineering, 2009Co-Authors: Thevenet Jean, Siroux Monica, Desmet BernardAbstract:A fiber optic two-color pyrometer was developed for brake disc surface temperature and emissivity measurements. The two-color pyrometer consists of a fluoride glass optical fiber, two HgCdTe detectors equipped with bandwidth filters and a data conditioning and acquisition device. The two-color pyrometer measures the brake disc temperature in the 200-800°C range with a time resolution of 8 μs. The calibration formula for the signals obtained using a blackbody of known temperature is used to compute the true temperature. The uncertainty estimation for temperature and emissivity was obtained from the calibration results. Tests were carried out on known temperature target and a good correlation was found between results obtained with our two-color pyrometer and those obtained with a commercial two-color pyrometer. Hold braking and deceleration braking tests performed on a braking test bench enabled us to reach the brake disc surface temperature and emissivity during braking. Experimental results show a significant variation of emissivity during braking. Direct measurement of emissivity was carried out on the brake disc after braking and shows the emissivity dependence with the surface quality.
Wang Xiang - One of the best experts on this subject based on the ideXlab platform.
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Dynamic linear response range for instantaneous radiation pyrometer
Journal of Applied Optics, 2011Co-Authors: Wang XiangAbstract:The dynamic linearity is an important technical parameter for instantaneous radiation pyrometer,which has great impact on measurement accuracy.In order to study the factors which influence the dynamic linearity of radiation pyrometer,a test technique is proposed for measuring pulse dynamic linearity,which is based on pulse LED and high linearity photodetector.An instantaneous radiation pyrometer,based on photomultiplier tubes(PMT),is tested and measured under various conditions.The measurement results show that the factors such as PMT type,voltage divider and operation voltage have impact on the dynamic current linearity of pyrometer.
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A fast pyrometer with wide dynamic linearity for shock temperature measurements
Explosion and Shock Waves, 2009Co-Authors: Wang XiangAbstract:By adopting linear-focused photomultiplier tubes(PMT),an eight-channel radiation pyrometer was developed for shock temperature measurements.The dynamic linearity in each channel of the pyrometer,using the developed voltage divider circuit,exceeds 8 mA at the work voltage of-800 V.The saturated light intensity is better than the level of 100 μW and the response time is less than 3 ns.The relative uncertainties of spectral radiances,which are measured by the pyrometer,are about 3%.The pyrometer was successfully used to measure the radiance history and shock temperature within 50 kK.