Search results for "atmospheric pressure"
showing 10 items of 105 documents
Dual-broadband rotational CARS modelling of nitrogen at pressures up to 9 MPa. II. Rotational Raman line widths
2002
International audience; Rotational coherent anti-Stokes Raman spectroscopy (CARS) is a well-established spectroscopic technique for thermometry at pre-combustion temperatures an atmospheric pressure. However, at pressures of several MPa, a previous investigation revealed large discrepancies between experimental data and the theoretical model. A re-evaluation has been made of these data (at room temperature and in the range 1.5-9 MPa) with two improvements to the spectral code. The first is the inclusion of an inter-branch interference effect, which is described in detail in Paper I. The second is the use of experimental S-1-branch Raman line widths measured at 295 K, with a temperature depe…
Characterization of a Superabsorbent Polymer.
2007
We studied an amorphous polymer superabsorbent, able to absorb until 1000 times its weight of water. It is consisted of macromolecular chains, dependent between them by chemical bonds. The swelling of the product in the presence of water gives rise to a polyelectrolytic gel. The chemical analysis of polymer by energy dispersive spectrometry and photoelectrons spectroscopy with a microsounder X showed that the product is homogeneous. It contains carbon, oxygen, and sodium. The measurements of specific surface of the product show that the polymer is nonporous and present a weak surface of about 2.1 m2/g. The thermal study of polymer showed that, under the effect of the temperature and with at…
Hybrid aerosol assisted atmospheric pressure Chemical Vapour Deposition: a facile route toward nano-composite thin films?
2009
A hybrid chemical vapour deposition strategy is presented as a facile route for the production of vanadium dioxide nano-composite thin films. The effect of the inclusion of gold nano-particles and the use of a surfactant molecule; tetraoctylammonium bromide (TOAB), is discussed. The films are fully characterised and it is shown that micro-structural changes lead to an enhancement of thermochromic properties, whilst gold nano-particles lead to a change in the films optical properties. Optical data is used in energy modelling studies to elucidate the films potential as an energy saving coating in architectural glazing.
Development of a sequential data correction method for isotope ratio analysis by resonance ionization mass spectrometry
2015
A sequential data correction method using several experimental parameters of pulsed resonance ionization mass spectrometry was developed to reduce mass discrimination effects for isotope ratio analysis as well as fluctuations in the ion count rate. This correction method was applied to isotope ratio determination of stable titanium isotopes using a two-step, single color ionization scheme. A significant improvement of the precision of the measured isotopic ratio of stable titanium isotopes was demonstrated after correction with a parameter set consisting of laser power, atmospheric pressure, and laser frequency.
On the Secondary Discharge of an Atmospheric-Pressure Pulsed DBD in He with Impurities
2008
The secondary discharge was induced at the end of a slow-falling voltage flank, when a semisine monopolar pulse voltage excites the dielectric-barrier discharge. Formation and properties of the secondary discharge with respect to different dielectric materials such as glass, ceramic, and polyethylene theraphtalate were studied. The tunable diode laser absorption spectrometry (at 777.194 nm) was used to analyze the time-space distribution of the density of the atomic oxygen in metastable state (35S2 rarr 35P3) in addition to both discharge voltage and discharge current versus time. The secondary discharge is always formed, and its amplitude, as well as the amplitude of the main discharge, de…
Characterization of pressure retarded osmosis lab-scale systems
2016
Power generation from salinity gradient is a viable alternative to produce energy from renewable sources. Pressure Retarded Osmosis (PRO) is one of the technologies proposed so far for the exploitation of such energy source. In the present preliminary work, two different geometry modules were tested under atmospheric pressure (i.e. forward osmosis or depressurized-PRO conditions). The first one is a conventional planar geometry cell. The second is a customized cylindrical membrane module, able to mechanically support the osmotic membrane along with the spacers. The latter, thanks to its design, allows membranes and spacers to be easily changed for testing purposes. A novel simplified proced…
Product Quantum Yields for the 350 nm Photodecomposition of Pyruvic Acid in Air
1992
Quantum yields for the products CH3CHO, CO2 and CH3COOH in the 350 nm photodecomposition of pyruvic acid are 0.48 ± 0.01, 1.27 ± 0.18 and 0.14, respectively, as measured in air at atmospheric pressure. In the presence of NO2 the quantum yield for CH3CHO was reduced to 0.30 ± 0.04 and peroxyacetyl nitrate was formed with a quantum yield of 0.15 ± 0.02. This is taken to indicate the formation of acetyl radicals in one of the primary processes.
Abnormal pressure dependence of the phase boundaries in TL/PEO/P(EO-b-DMS) ternary mixtures
2003
The cloud-point temperatures (T-cl's) of both binary poly(ethylene oxide) (PEO)-poly(ethylene oxide-b-dimethylsiloxane) [P(EO-b-DMS)] and ternary[toluene/PEO/P(EO-b-DMS)] systems were determined by light scattering measurements at atmospheric pressure. The phase separation behavior upon cooling in the ternary system has been investigated at atmospheric pressure and under high pressure and compared to the phase behavior in the binary system. The phase transition temperatures have been obtained for all of the samples. As a result, the pressure induces compatibility in the binary mixtures, but for the ternary system, pressure not only can induce mixing but also can induce phase separation.
A new approach to determination of the asymmetry parameter of Stark-broadened isolated spectral lines
2013
A new approach to evaluation of asymmetry parameters of Stark-broadened isolated spectral lines is presented. The procedure is discussed on the example of the N I line at λ = 9822.75 A. Line shape measurements were performed using a wall-stabilized arc, operated at atmospheric pressure. The radiation of the plasma, emitted from homogeneous plasma layers in end-on direction, was measured using a grating spectrometer equipped with a two-dimensional CCD detector. Griem-like profiles, convoluted with the corresponding Doppler and apparatus profiles, were fitted to experimental data. In this way the Stark broadening parameters (electron impact widths, shifts and asymmetry) have been determined. …
A fully manipulable damped driven harmonic oscillator using optical levitation
2020
We implement an experimental system based on optical levitation of a silicone oil droplet to demonstrate a damped driven harmonic oscillator. The apparatus allows us to control all the parameters present in the differential equation that theoretically describes such motion. The damping coefficient and driving force can be manipulated in situ by changing the pressure in the apparatus and by applying a variable electric field. We present two different experimental procedures. First, a transition from the overdamped to underdamped regimes is demonstrated by gradually lowering the air pressure. The characteristic resonance associated with an underdamped driven harmonic oscillator is observed by…