Search results for "VOLUME"

2016

Abstract. Particle concentration measurements with underwing probes on aircraft are impacted by air compression upstream of the instrument body as a function of flight velocity. In particular, for fast-flying aircraft the necessity arises to account for compression of the air sample volume. Hence, a correction procedure is needed to invert measured particle number concentrations to ambient conditions that is commonly applicable to different instruments to gain comparable results. In the compression region where the detection of particles occurs (i.e. under factual measurement conditions), pressure and temperature of the air sample are increased compared to ambient (undisturbed) conditions i…

Nano-hygroscopicity tandem differential mobility analyzer (nano-HTDMA) for investigating hygroscopic properties of sub-10 nm aerosol nanoparticles

2020

Interactions between water and nanoparticles are relevant for atmospheric multiphase processes, physical chemistry, and materials science. Current knowledge of the hygroscopic and related physicochemical properties of nanoparticles, however, is restricted by the limitations of the available measurement techniques. Here, we present the design and performance of a nano-hygroscopicity tandem differential mobility analyzer (nano-HTDMA) apparatus that enables high accuracy and precision in hygroscopic growth measurements of aerosol nanoparticles with diameters less than 10 nm. Detailed methods of calibration and validation are provided. Besides maintaining accurate and stable sheath and a…

Aerosol columnar properties retrieved from CIMEL radiometers during VELETA 2002

2008

During the 2002 summer, the VELETA 2002 field campaign has been carried out at the Sierra Nevada Massif, close to Granada in South-Eastern Spain. During the campaign, CIMEL CE-318 robotic radiometer has been one of the key instruments in the characterization of the atmospheric aerosol columnar properties. This kind of radiometers have been operated at Motril, a coastal location at sea level, Pitres (1200 m a.s.l.), located in the South slope of Sierra Nevada Massif, Las Sabinas (2200m a.s.l.), located on the north slope of the mountain range, and Armilla (680m a.s.l.), located in the valley. The principal feature of the locations is that they provide a strong altitudinal gradient. This work…

Obtaining the three-dimensional structure of tree orchards from remote 2D terrestrial LIDAR scanning

2009

In recent years, LIDAR (light detection and ranging) sensors have been widely used to measure environmental parameters such as the structural characteristics of trees, crops and forests. Knowledge of the structural characteristics of plants has a high scientific value due to their influence in many biophysical processes including, photosynthesis, growth, CO2-sequestration and evapotranspiration, playing a key role in the exchange of matter and energy between plants and the atmosphere, and affecting terrestrial, above-ground, carbon storage. In this work, we report the use of a 2D LIDAR scanner in agriculture to obtain three-dimensional (3D) structural characteristics of plants. LIDAR allows…

Sorption-Caused Attenuation and Delay of Water Vapor Signals in Eddy-Covariance Sampling Tubes and Filters

2014

AbstractAdsorption and desorption (together called sorption) processes in sampling tubes and filters of eddy-covariance stations cause attenuation and delay of water vapor signals, leading to an underestimation of water vapor fluxes by tens of percent. The aim of this work was (i) to quantify the effects on sorption in filters and tubes of humidity, flow rate, and dirtiness and (ii) to test a recently introduced sorption model that facilitates correction of fluxes. Laboratory measurements on the transport of water vapor pulses through tubes and filters were carried out, and eddy-covariance field measurements were also used.In the laboratory measurements, the effects of sorption processes we…

Hygroscopic properties and water-soluble volume fraction of atmospheric particles in the diameter range from 50 nm to 3.8 μm during LACE 98

2002

[1] Hygroscopic properties of atmospheric aerosol particles in the Aitken, large, and giant particle range were studied during the Lindenberg Aerosol Characterization Experiment (LACE 98) in a rural area 80 km southeast of Berlin. The hygroscopic behavior of Aitken particles were determined in situ in four size classes (50, 100, 150, 250 nm) with a Hygroscopic Tandem Differential Mobility Analyzer for relative humidities (RH) of 60% and 90%. Measurements at 60% RH served as reference data used by other LACE 98 investigators for mass closure and radiative transfer calculations. In most cases, at 90% RH, the atmospheric particles could be classified into two groups (“more” and “less” hygrosco…

CO2flux measurements in volcanic areas using the dynamic concentration method: Influence of soil permeability

2006

[1] In order to evaluate the influence of soil permeability on soil CO2 flux measurements performed with the dynamic concentration method, several tests were carried out using soils characterized by different permeability values and flow rates. A special device was assembled in the laboratory to create a one-dimensional gas flow through a soil of known permeability. Using the advective-diffusion theory, a physical model to predict soil concentration gradients was also developed. The calculated values of CO2 concentrations at different depths were compared with those measured during the tests and a good agreement was found. Four soils with different gas permeability (3.6 × 10−2 to 1.23 × 102…

Une méthode rapide et simple pour l'estimation de la position de la courbe de dissociation de l'oxyhémoglobine

1989

The methods currently available for assessing the oxyhaemoglobin dissociation curve parameters are expensive, lengthy, require a large volume of blood, and the results obtained are modified by anaesthetic gases. The equipment required for the method described includes: a microtonometre, microcuvettes, 3 gas bottles containing different oxygen, carbon dioxide and nitrogen mixtures (4.5%, 5.6%, 89.9%; 3.5%, 5.6%, 90.9%; 2.5%, 5.6%, 91.9% respectively), a microxymetre, and a micropHmetre. The samples in the microcuvettes are incubated at 37 degrees C in a gas flow of 45 ml.min-1 from the bottles. SO2 is then read using the microxymetre. P50, i.e. PO2 at 50% saturation, is calculated, as well a…

Surface tension and density of binary mixtures of monoalcohols, water and acetonitrile: equation of correlation of the surface tension

2009

Measurements of the surface tension (σ) and density (ρ) of binary mixtures of monoalcohols, water and acetonitrile at 298.15 K and at atmospheric pressure, as a function of mole fraction (x) have been made. The experimental values of the deviation of surface tension and the excess of molar volume (Δσ, V E) have been correlated by the Redlich–Kister equation. An empirical correlation equation is presented for the study of the surface tension of these mixtures, and comparisons are made of the experimental values of surface tension versus those obtained with the correlation equation and with other models of correlation. Finally, with the purpose of corroborating the validity of the correlation…

Density, Viscosity, and Sound Speed of Bis(trifluoromethylsulfonyl)imide-Based Ionic Liquids + 1-Propanol Mixtures

2015

The density, viscosity, and speed of sound of three mixtures formed by 1-propanol and an ionic liquid were measured in a temperature range of 278.15–338.15 K. All measurements were made at atmospheric pressure and covered the entire range of miscible compositions. The three ionic liquids have the same anion but differ in the cation: 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [emim][NTf2], 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [bmim][NTf2], and 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [hmim][NTf2]. The experimental data allowed calculate the molar volume and isentropic compressibility of the mixture and their respective exces…