Hydrogen Distributions and Model Lineshapes of ESR Signals of Dangling Bonds in a-Si:H

2001 ◽  
Vol 664 ◽  
Author(s):  
P. A. Fedders
Keyword(s):  
Experimental Data ◽  
Experimental Evidence ◽  
Esr Spectra ◽  
Dangling Bonds ◽  
Model Calculations ◽  
Induced Defects

ABSTRACTFor many years it has been assumed widely that hydrogen is involved in some way in the formation of light induced defects. However recently some doubt has been cast on this because of experimental evidence that there is little H near light induced dangling bonds. In this paper we present a number of model calculations comparing ESR spectra of dangling bonds with and without correlations with H positions. The above models include different distributions of H and correlations or anti correlations of nearby H. In all cases the spectra are compared to those with no correlations or clustering. Our results coupled with published experimental data strongly suggest that dangling bonds are not correlated positively with the presence of nearby H and, in fact, it appears that light induced dangling bonds are negatively correlated with nearby H.

A Method for Estimating Mass Transfer Coefficients in a Packed Column Using Reactive Absorption Data

2005 ◽  
Vol 70 (3) ◽  
pp. 383-402
Author(s):  
Valery A. Danilov ◽  
Il Moon
Keyword(s):  
Experimental Data ◽  
Mass Transfer ◽  
Optimization Technique ◽  
Packed Column ◽  
Effective Area ◽  
Transfer Coefficients ◽  
Mass Transfer Coefficients ◽  
Model Calculations ◽  
Unit Model ◽  
Reactive Absorption

This paper is devoted to the development of a new method for estimating mass transfer coefficients and effective area in packed columns in the case of reactive absorption. The method is based on a plug-flow model of reactive absorption of carbon dioxide with sodium hydroxide solution. The parameter estimation problem is solved using an optimization technique. Some mass transfer parameters are found to be correlated. Global sensitivity analysis by Sobol's technique showed that the unit model with the defined objective function is sensitive to the estimated parameter. Case studies of reactive absorption with different packings illustrate application of the proposed method for estimating mass transfer coefficients and effective area from column operation data. The model calculations are compared with experimental data obtained by other authors. The concentration profiles calculated by the unit model with the estimated parameters are shown to match well with experimental profiles from literature. A good agreement between estimated values and experimental data from literature confirms the applicability of this method.

Convective Losses From Cavity Solar Receivers—Comparisons Between Analytical Predictions and Experimental Results

1983 ◽  
Vol 105 (1) ◽  
pp. 29-33 ◽  
Author(s):  
A. M. Clausing
Keyword(s):  
Experimental Data ◽  
Experimental Evidence ◽  
Analytical Model ◽  
Excellent Agreement ◽  
Experimental Results ◽  
Simple Analytical Model ◽  
Refined Model ◽  
Wall Area

Cavity solar receivers are generally believed to have higher thermal efficiencies than external receivers due to reduced losses. A simple analytical model was presented by the author which indicated that the ability to heat the air inside the cavity often controls the convective loss from cavity receivers. Thus, if the receiver contains a large amount of inactive hot wall area, it can experience a large convective loss. Excellent experimental data from a variety of cavity configurations and orientations have recently become available. These data provided a means of testing and refining the analytical model. In this manuscript, a brief description of the refined model is presented. Emphasis is placed on using available experimental evidence to substantiate the hypothesized mechanisms and assumptions. Detailed comparisons are given between analytical predictions and experimental results. Excellent agreement is obtained, and the important mechanisms are more clearly delineated.

Evolution of hindlimb posture in nonmammalian therapsids: biomechanical tests of paleontological hypotheses

Paleobiology ◽  
2001 ◽  
Vol 27 (1) ◽  
pp. 14-38 ◽  
Author(s):  
Richard W. Blob
Keyword(s):  
Experimental Data ◽  
Biomechanical Model ◽  
Axial Rotation ◽  
Morphological Data ◽  
Upright Posture ◽  
Cross Sectional ◽  
Model Calculations ◽  
Limb Bones ◽  
Plausible Model ◽  
Bending Stresses

Analyses of limb joint morphology in nonmammalian therapsid “mammal-like reptiles” have suggested that among many lineages, individual animals were capable of shifting between sprawling and upright hindlimb postures, much like modern crocodilians. The ability to use multiple limb postures thus might have been ancestral to the generally more upright posture that evolved during the transition from “mammal-like reptiles” to mammals. Here I derive a biomechanical model to test this hypothesis through calculations of expected posture-related changes in femoral stress for therapsid taxa using different limb postures. The model incorporates morphological data from fossil specimens and experimental data from force platform experiments on iguanas and alligators.Experimental data suggest that the evolutionary transition from sprawling to nonsprawling posture was accompanied by a change in the predominant loading regime of the limb bones, from torsion to bending. Changes in the cross-sectional morphology of the hindlimb bones between sphenacodontid “pelycosaurs” and gorgonopsid therapsids are consistent with the hypothesis that bending loads increased in importance early in therapsid evolution; thus, bending stresses are an appropriate model for the maximal loads experienced by the limb bones of theriodont therapsids. Results from the model used to estimate stresses in these taxa do not refute the use of both sprawling and more upright stance among basal theriodont therapsids. Thus, the hypothesis that the use of multiple postures was ancestral to the more upright posture typical of most mammals is biomechanically plausible. Model calculations also indicate that the axial rotation of the femur typical in sprawling locomotion can reduce peak bending stresses. Therefore, as experimental data from alligators and iguanas suggest, the evolution of nonsprawling limb posture and kinematics in therapsids might have been accompanied by increased limb bone bending stress.

N-N-N∗ model calculations for experimental η-mesic 3He searches

2019 ◽  
Vol 28 (08) ◽  
pp. 1950066 ◽  
Author(s):  
N. G. Kelkar ◽  
H. Kamada ◽  
M. Skurzok
Keyword(s):  
Experimental Data ◽  
Data Analysis ◽  
Momentum Distribution ◽  
Selection Criteria ◽  
Data Selection ◽  
Model Calculations ◽  
Faddeev Equations ◽  
Essential Ingredient ◽  
Momentum Distributions ◽  
Three Body

The possibility for the existence of the exotic [Formula: see text] states is explored with the objective of calculating the [Formula: see text] momentum distribution inside such nuclei. Even though the latter is an essential ingredient for the analysis of the experimental data on the [Formula: see text], [Formula: see text] and [Formula: see text] reactions aimed at finding an [Formula: see text]-mesic 3He, the data analysis is usually performed by approximating the [Formula: see text] momentum distribution by that of a nucleon. Here, we present calculations performed by solving the three-body Faddeev equations to obtain the momentum distribution of the [Formula: see text] inside possible ([Formula: see text])[Formula: see text], ([Formula: see text])[Formula: see text] and ([Formula: see text])[Formula: see text]-[Formula: see text] states. The [Formula: see text] momentum distributions are found to be much narrower than those of the nucleons and influence the data selection criteria.

scholarly journals Methyl-Eliminierung aus dem metastabilen Homoadamantan-Radikalkation / Methyl Loss from Metastable Homoadamantane Cation Radical

1980 ◽  
Vol 35 (2) ◽  
pp. 207-211 ◽  
Author(s):  
Helmut Schwarz ◽  
Chrysostomos Wesdemiotis ◽  
Thomas Weiske ◽  
Helmut Schwarz ◽  
Chrysostomos Wesdemiotis ◽  
...  
Keyword(s):  
Experimental Evidence ◽  
Cation Radical ◽  
Model Calculations ◽  
Direct Ionization ◽  
Cation Radicals

Abstract It is demonstrated that methyl loss from ionized homoadamantane (1) yields exclusively the 1-adamantyl cation (4); there is no experimental evidence for the formation of the secondary adamantyl cation (5). From both model calculations and the investigation of [4-13C]-homoadamantane (1a) and 1(13C-methyl)adamantane (2a) it is concluded, that 24% of the metastable homoadamantane cation radicals dissociate after one isomerization (1→2); the remaining 76% are able to undergo at least a second (degenerate) isomerization cycle (2→1→2) prior to methyl loss. 78% of metastable 1-methyl-adamantane cation radical, obtained upon direct ionization of the corresponding neutral hydrocarbon, dissociate directly, whereas the loss of methyl from the remaining 22% is preceded by an isomerization 2 →1 →2.

A re-examination of pseudoleucite from Spotted Fawn Creek, west-central Yukon

1969 ◽  
Vol 6 (1) ◽  
pp. 55-62 ◽  
Author(s):  
Dirk J. Tempelman-Kluit
Keyword(s):  
Experimental Data ◽  
Experimental Evidence ◽  
Water Pressure ◽  
Fluid Phase ◽  
Yukon Territory ◽  
Chemical Data ◽  
Partial Removal ◽  
West Central

New petrographic and chemical data for pseudoleucite from Spotted Fawn Creek and two new nearby localities in central Yukon Territory are presented and discussed in the light of recent experimental evidence on the origin of pseudoleucite. The petrologic, chemical, and experimental data suggest that natural pseudoleucite results from subsolidus breakdown of leucite under water pressure and that the space provided by this breakdown results in influx of the fluid phase that accomplishes partial removal of potash, enrichment in soda, and addition of water.

scholarly journals Radiation induced currents in mineral-insulated cables and in pick-up coils: model calculations and experimental verification in the BR1 reactor

2018 ◽  
Vol 170 ◽  
pp. 02008
Author(s):  
Ludo Vermeeren ◽  
Willem Leysen ◽  
Benoit Brichard
Keyword(s):  
Experimental Data ◽  
Careful Analysis ◽  
Mitigation Strategies ◽  
Nuclear Radiation ◽  
Model Calculations ◽  
Irradiation Test ◽  
Lower Amplitude ◽  
Model Predictions ◽  
Radiation Induced ◽  
Induced Currents

Mineral-insulated (MI) cables and Low-Temperature Co-fired Ceramic (LTCC) magnetic pick-up coils are intended to be installed in various position in ITER. The severe ITER nuclear radiation field is expected to lead to induced currents that could perturb diagnostic measurements. In order to assess this problem and to find mitigation strategies models were developed for the calculation of neutron-and gamma-induced currents in MI cables and in LTCC coils. The models are based on calculations with the MCNPX code, combined with a dedicated model for the drift of electrons stopped in the insulator. The gamma induced currents can be easily calculated with a single coupled photon-electron MCNPX calculation. The prompt neutron induced currents requires only a single coupled neutron-photon-electron MCNPX run. The various delayed neutron contributions require a careful analysis of all possibly relevant neutron-induced reaction paths and a combination of different types of MCNPX calculations. The models were applied for a specific twin-core copper MI cable, for one quad-core copper cable and for silver conductor LTCC coils (one with silver ground plates in order to reduce the currents and one without such silver ground plates). Calculations were performed for irradiation conditions (neutron and gamma spectra and fluxes) in relevant positions in ITER and in the Y3 irradiation channel of the BR1 reactor at SCK•CEN, in which an irradiation test of these four test devices was carried out afterwards. We will present the basic elements of the models and show the results of all relevant partial currents (gamma and neutron induced, prompt and various delayed currents) in BR1-Y3 conditions. Experimental data will be shown and analysed in terms of the respective contributions. The tests were performed at reactor powers of 350 kW and 1 MW, leading to thermal neutron fluxes of 1E11 n/cm2s and 3E11 n/cm2s, respectively. The corresponding total radiation induced currents are ranging from 1 to 7 nA only, putting a challenge on the acquisition system and on the data analysis. The detailed experimental results will be compared with the corresponding values predicted by the model. The overall agreement between the experimental data and the model predictions is fairly good, with very consistent data for the main delayed current components, while the lower amplitude delayed currents and some of the prompt contributions show some minor discrepancies.

Evolution of Oxygen Associated Defects in Cz Silicon during Thermal Annealing Treatments: Comparison between Experiment and Simulation

2011 ◽  
Vol 178-179 ◽  
pp. 188-191
Author(s):  
Julien Nicolai ◽  
Nelly Burle ◽  
Bernard Pichaud
Keyword(s):  
Experimental Data ◽  
Nucleation And Growth ◽  
Growth Stages ◽  
Interstitial Oxygen ◽  
High Temperature Annealing ◽  
Annealing Effects ◽  
Annealing Cycle ◽  
Oxygen Precipitates ◽  
Induced Defects ◽  
Evolution Of Oxygen

High temperature annealing effects on Oxygen-induced defects formation has been studied by IR-LST, FTIR and TEM techniques. The results show that most defects are amorphous oxygen precipitates and/or dislocations. Ham’s theory has been modified in order to take into account the variations of interstitial oxygen concentration during the formation of precipitates. Comparison between experimental data and simulation shows that the specificity of annealing cycle is to combine both nucleation and growth stages. The morphology and stoechiometry of SiOx precipitates are also studied.

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