scholarly journals Inert gas effects in the photosynthesis of hydrogen bromide

1934 ◽  
Vol 146 (859) ◽  
pp. 828-848 ◽  
Keyword(s):  
Hydrogen Bromide ◽  
Diffusion Theory ◽  
Triple Collision ◽  
Mass Action ◽  
Inert Gas ◽  
Atom Concentration ◽  
Simple Diffusion ◽  
Photochemical Formation ◽  
Empirical Correction ◽  
Semi Empirical

Recent studies of many chemical gas reactions which involve the production and behaviour of atoms, have shown that the effect of the surface of the reaction vessel on the atom concentration can seldom be regarded as a small disturbing factor to be allowed for by a semi-empirical correction, but must be adequately considered in relation to the other processes determining the velocity of reaction. In this connection, therefore, alteration in the pressure of any one reactant must involve an effect depending on the diffusion coefficient of the atom concerned, with regard to the expected from the mass action principles of the chemical kinetics. Examples of this simple diffusion effect are well known. The results to be expected on these lines are sometimes complicated by the existence of other factors consequent on increase in pressure in the reacting system. In the photosynthesis of hydrogen bromide, where bromine atoms are involved, it has been shown that increase in total pressure, by the introduction of an otherwise inert gas, produces a relative decrease in reaction velocity, where the application of the simple diffusion theory as above would lead one to expect an increase in velocity by prevention of the removal of bromine atoms by the walls. This decrease has been attributed to the stabilization of the bromine “quasi-molecule” by the added gas molecule, the removal of bromine atoms being thus facilitated by what is virtually a triple collision. Similar considerations apply to the photochemical formation of posgene.

Optical Limiting with Lithium Niobate

1999 ◽  
Vol 597 ◽  
Author(s):  
Gary Cook ◽  
David C. Jones ◽  
Craig J. Finnan ◽  
Lesley L. Taylor ◽  
Tony W. Vere ◽  
...  
Keyword(s):  
Lithium Niobate ◽  
Diffusion Theory ◽  
Photovoltaic Effect ◽  
Optical Gain ◽  
Optical Limiting ◽  
Dark Conductivity ◽  
Simple Diffusion ◽  
Beam Coupling ◽  
Coupling Equations ◽  
Focusing Lens

AbstractIron doped lithium niobate (Fe:LiNbO3) in a simple focal plane geometry has demonstrated efficient optical limiting through two-beam coupling. The performance is largely independent of the total Fe concentration and the oxidation state of the Fe ions, providing the linear optical transmission of uncoated crystals is between 30% and 60%. Fe has been found to be the best dopant for LiNbO3, giving the widest spectral coverage and the greatest optical limiting. Optical limiting in Fe:LiNbO3 has been shown to be very much greater than predicted by simple diffusion theory. The reason for this is a higher optical gain than expected. It is suggested that this may be due to an enhancement of the space-charge field arising from the photovoltaic effect. The standard two-beam coupling equations have been modified to include the effects of the dark conductivity. This has produced a theoretical intensity dependence on the ΔOD which closely follows the behaviour observed in the laboratory. A further modification to the theory has also shown that the focusing lens f-number greatly affects the optical limiting characteristics of Fe:LiNbO3. A lens f-number of approximately 20 gives the best results.

The application of diffusion theory to inert-gas motion in ion-bombarded solids

1966 ◽  
Vol 20 (2) ◽  
pp. 171-183 ◽  
Author(s):  
Roger Kelly ◽  
Hansjoachim Matzke
Keyword(s):  
Diffusion Theory ◽  
Inert Gas

scholarly journals BIDIRECTIONAL REFLECTANCE DISTRIBUTION FUNCTION (BRDF) OF MIXED PIXELS

2021 ◽  
Vol XLIII-B3-2021 ◽  
pp. 195-200
Author(s):  
F. Kizel ◽  
Y. Vidro
Keyword(s):  
Mutual Influence ◽  
Laboratory Data ◽  
Spectral Unmixing ◽  
Spectral Signature ◽  
Empirical Correction ◽  
Reflected Light ◽  
Wide Range ◽  
Mixed Pixels ◽  
Semi Empirical ◽  
Spectral Mixture

Abstract. Hyperspectral imaging is crucial for a variety of land-cover mapping and analyzing tasks. The available large number of reflected light measurements along a wide range of wavelengths allows for distinguishing between different materials under various conditions. Though, several effects bear an undesired variability within hyperspectral images and increase the complexity of interpreting such data. Two of the most significant effects in this regard are the BRDF and the spectral mixture. Due to the first, the acquisitions geometrical and viewing conditions influences the measured spectral signature of a surface to a large extent. On the other hand, because of the typical low spatial resolution of remotely sensed images, each pixel can contain more than one material. Despite much research addressing either the BRDF effect and ways to correct it or the spectral unmixing, too few works considered these two effects' mutual influence. In this work, we study the BRDF of mixed pixels and present preliminary insights of testing a strategy to correct its undesired impact on the data by incorporating the EMs fractions within an unmixing-based semi-empirical correction model. Experimental results using real laboratory data acquired under controlled conditions clearly show the significant improvement of the corrected reflectance results through the proposed model.

scholarly journals Estimation of Wind Tunnel Corrections Using Potential Models

2019 ◽  
Vol 11 (1) ◽  
pp. 53-60 ◽  
Author(s):  
Ionut BUNESCU ◽  
Sterian DANAILA ◽  
Mihai-Victor PRICOP ◽  
Adrian DINA
Keyword(s):  
Wind Tunnel ◽  
Experimental Model ◽  
Solid Wall ◽  
Actual Problem ◽  
Potential Models ◽  
Empirical Correction ◽  
Semi Empirical ◽  
Solid Walls ◽  
Potential Flow Model ◽  
Mathematical And Numerical Modeling

The evaluation of the tunnel correction remains an actual problem, especially for the effect of tunnel walls. Even if the experimental campaign meets the basic similitude criteria (Mach, Reynolds etc.), the wall effect on the measured data is always present. Consequently, the flow correction due the limited by walls must be evaluated. Solid wall corrections refer to the aerodynamic interference between the experimental model and the walls of the wind tunnel. This interaction affects the measured forces and implicitly the angle of attack. Usually, these effects are introduced through semi-empirical correction factors which change the global measured forces. The present paper refers to the mathematical and numerical modeling of aerodynamic interferences between the experimental model and the solid walls based on the potential flow model. The main goal is to asses a method allowing an estimate of the corrections for each configuration with a minimum computational resource.

Diffusion of Colloids and Other Waste Species in Brine–Saturated Backfill Materials

1983 ◽  
Vol 26 ◽  
Author(s):  
E. J. Nowak
Keyword(s):  
Colloidal Gold ◽  
Diffusion Theory ◽  
Distribution Coefficients ◽  
Low Density ◽  
Sorption Data ◽  
Simple Diffusion ◽  
Diffusion Cells ◽  
Backfill Materials ◽  
Cylindrical Diffusion ◽  
Waste Repositories

ABSTRACTThe diffusion of plutonium (IV) and pertechnetate and the migration of colloidal gold in brine-saturated bentonite was measured. High ionic strength brine characterizes potentially intruding groundwater for radioactive waste repositories in salt. Plastic diffusion cells containing cylindrical diffusion columns were used for low density bentonite. Metal diffusion cells constructed entirely from Hastelloy C-276 were used for the diffusion of pertechnetate in highly compacted bentonite. Apparent distribution coefficients calculated from plutonium diffusion in two columns of low density bentonite are 2 m3/kg and 3 m3/kg. These values are in good agreement with the value of 3m3/kg that was calculated from previous batch sorption data. Pertechnetate anions migrated out of a brine-saturated high density bentonite diffusion column at rates that are too large to be rationalized with a simple diffusion theory. Additional measurements that take into account possible channeling of pertechnetate are required. Colloidal gold was excluded from low density brine-saturated bentonite, but colloidal gold may have channeled between the bentonite and the wall of the diffusion cell. These results support the effectiveness of brine-saturated bentonite as an engineered barrier to plutonium. The results also highlight the need for additional measurements of pertechnetate and gold transport in bentonite. Needs for transport measurements that take into account site-specific materials interactions are also described.

Semi-empirical correction algorithm for AC-9 measurements in a coccolithophore bloom

2003 ◽  
Vol 42 (21) ◽  
pp. 4369 ◽  
Author(s):  
David McKee ◽  
Alex Cunningham ◽  
Susanne Craig
Keyword(s):  
Correction Algorithm ◽  
Empirical Correction ◽  
Semi Empirical

The oxidation of iso butene catalyzed by hydrogen bromide

1962 ◽  
Vol 268 (1334) ◽  
pp. 405-423 ◽  
Keyword(s):  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Double Bond ◽  
Small Proportion ◽  
Main Chain ◽  
Hydrogen Bromide ◽  
Inert Gas ◽  
Static System ◽  
Peroxy Radicals ◽  
Methyl Group

The oxidation of iso butene catalyzed by hydrogen bromide in a static system between 100 and 200 °C has been investigated. In a boric oxide coated vessel below about 170 °C the pressure decreased continually during the reaction, the rate accelerating rapidly to a maximum and then falling gradually and the main products being BrCH 2 .C(CH 3 ) 2 .OOH and a diperoxide. The reaction ceased after only a small proportion of the olefin was oxidized owing to the HBr being used up. At 145 °C ρ max. ∝ [C 4 H 8 ] 0.35 [O 2 ] 0.5 [HBr] 1.76 . Added inert gas or packing the vessel had little effect on the rate, but the reaction was accelerated by added bromine, t .-butyl hydroperoxide and di- t .-butylperoxide and retarded by added alcohols. At 195 °C the pressure decreased to a minimum and then rose, most of the iso butene being now oxidized and other products, CH 2 =C(CH 3 )CH 2 OOH, methacrolein, acetone, carbon monoxide, carbon dioxide and water being formed in appreciable yields. It is suggested that autocatalysis is due to the reaction of a small proportion of the hydroperoxides produced with HBr to give radicals, and that the main chain carriers are bromine atoms and peroxy radicals, the former either adding to the double bond of the olefin or at the higher temperatures abstracting hydrogen from a methyl group and the latter abstracting hydrogen from HBr to give the hydroperoxides, adding to the double bond of iso butene to give eventually diperoxides or at the higher temperatures decomposing.

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