Theoretical Concepts and Experimental Data in Compton Densitometry

2015 ◽  
pp. 33-47
Author(s):  
B. Conrad
Keyword(s):  
Experimental Data ◽  
Theoretical Concepts

scholarly journals Velocity distribution in a turbulent flow

2021 ◽  
Vol 263 ◽  
pp. 04047
Author(s):  
Evgenii Ignatenko ◽  
Yuliya Bryanskaya
Keyword(s):  
Experimental Data ◽  
Turbulent Flow ◽  
Velocity Distribution ◽  
Fluid Motion ◽  
Experimental Studies ◽  
Measurement Data ◽  
Phenomenological Approach ◽  
Theoretical Background ◽  
Modern Technology ◽  
Theoretical Concepts

The article considers the issue of velocity distribution in a turbulent flow. The logarithmic velocity profile obtained on the basis of semiempirical theory of turbulence by L. Prandtl is given. A comparison of the calculations of the velocity distribution for various dependencies with the measurement data is performed. It is shown that the calculated dependencies show discrepancy with each other and experimental data. The study of the hydraulic characteristics of water flows is required to solve problems of water supply and water disposal, engineering problems of hydraulic construction, regulation of riverbed processes and environmental monitoring of water bodies. The characteristics of the turbulence of a uniform and uneven flow need to be clarified, that will be possible due to the study of the theoretical background of hydraulics and hydrodynamics. Despite the usage of modern computer technologies, the creation of an actual theory of turbulence is still not complete. The separation of the fluid motion into molar and basic motion led to a non-closed system of equations of turbulent motion, that slowed down further progress in the search for a solution for turbulent flow. The most widely used theory is the semi-empirical theory of turbulence by L. Prandtl, based on a phenomenological approach that links turbulence with the characteristics of the averaged flow. The use of modern technology has allowed us to obtain new experimental data that require analysis and generalization. The calculated dependences for the velocity distribution developed on the basis of various phenomenological models, including the well-known logarithmic profiles of L. Prandtl, are compared with the measurement data. The calculations of the velocity distribution for various dependencies are compared with the measurement data. A significant quantitative, and sometimes qualitative, discrepancy of the calculated dependences with each other and with the experimental data was revealed. The discrepancy between the results of calculating the velocity distribution for different dependencies requires an additional critical analysis of the accuracy and reliability of the experimental data of other authors and performing experimental studies under different conditions using a mutually agreed method. The low effectiveness of the considered statistical approaches leads to the need to develop new approaches that represent a combination of some theoretical concepts and experimental data.

scholarly journals A probabilistic approach to modeling collisions with thin barriers

2019 ◽  
Vol 221 ◽  
pp. 01039 ◽  
Author(s):  
Sergey Pashkov
Keyword(s):  
Experimental Data ◽  
Probabilistic Approach ◽  
Material Model ◽  
Strength Properties ◽  
Strength Characteristics ◽  
Additional Parameter ◽  
Computational Domain ◽  
Distribution Law ◽  
Theoretical Concepts ◽  
Probabilistic Character

In many fracture problems, fragmentation is essentially a probabilistic process, which is determined by the stochastic nature of the distribution of inhomogeneities of the internal structure of material. The probabilistic approach is described, which allows us to model structural heterogeneities of the material in a simple form, practically without any complication of the model and additional experiments. Using experimental data and numerical simulation results, it is shown that the introduction of only one additional parameter (dispersion of the strength properties distribution) into the material model makes it possible to give a probabilistic character to the crack formation process at any scale level, which corresponds to theoretical concepts and experimental data. Distribution of materials strength characteristics (according to the selected distribution law) in the cells of the computational domain is used for initial heterogeneities and materials structure defects modeling. It is shown that the number and size of the “petals” at the penetration of thin barriers depend of the speed of the projectile and the strength characteristics of the barrier.

scholarly journals Pleiotropic and Potentially Beneficial Effects of Reactive Oxygen Species on the Intracellular Signaling Pathways in Endothelial Cells

Antioxidants ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 904
Author(s):  
Nadezhda Barvitenko ◽  
Elisaveta Skverchinskaya ◽  
Alfons Lawen ◽  
Elena Matteucci ◽  
Carlota Saldanha ◽  
...  
Keyword(s):  
Experimental Data ◽  
Reactive Oxygen Species ◽  
Endothelial Cells ◽  
Signaling Pathways ◽  
Intracellular Signaling ◽  
Reactive Oxygen ◽  
Oxygen Species ◽  
Theoretical Concepts ◽  
Beneficial Effects ◽  
Gi Protein

Endothelial cells (ECs) are exposed to molecular dioxygen and its derivative reactive oxygen species (ROS). ROS are now well established as important signaling messengers. Excessive production of ROS, however, results in oxidative stress, a significant contributor to the development of numerous diseases. Here, we analyze the experimental data and theoretical concepts concerning positive pro-survival effects of ROS on signaling pathways in endothelial cells (ECs). Our analysis of the available experimental data suggests possible positive roles of ROS in induction of pro-survival pathways, downstream of the Gi-protein-coupled receptors, which mimics insulin signaling and prevention or improvement of the endothelial dysfunction. It is, however, doubtful, whether ROS can contribute to the stabilization of the endothelial barrier.

Zero-Pressure-Gradient Turbulent Boundary Layer

1997 ◽  
Vol 50 (12) ◽  
pp. 689-729 ◽  
Author(s):  
William K. George ◽  
Luciano Castillo
Keyword(s):  
Experimental Data ◽  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Pressure Gradient ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Governing Equations ◽  
Dynamical Equations ◽  
Navier Stokes Equations ◽  
Theoretical Concepts

Of the many aspects of the long-studied field of turbulence, the zero-pressure-gradient boundary layer is probably the most investigated, and perhaps also the most reviewed. Turbulence is a fluid-dynamical phenomenon for which the dynamical equations are generally believed to be the Navier-Stokes equations, at least for a single-phase, Newtonian fluid. Despite this fact, these governing equations have been used in only the most cursory manner in the development of theories for the boundary layer, or in the validation of experimental data-bases. This article uses the Reynolds-averaged Navier-Stokes equations as the primary tool for evaluating theories and experiments for the zero-pressure-gradient turbulent boundary layer. Both classical and new theoretical ideas are reviewed, and most are found wanting. The experimental data as well is shown to have been contaminated by too much effort to confirm the classical theory and too little regard for the governing equations. Theoretical concepts and experiments are identified, however, which are consistent-both with each other and with the governing equations. This article has 77 references.

scholarly journals Mutual Cooperation and Tolerance to Defection in the Context of Socialization: The Theoretical Model and Experimental Evidence

2021 ◽  
Author(s):  
T. S. Kozitsina ◽  
I. V. Kozitsin ◽  
I. S. Menshikov
Keyword(s):  
Experimental Data ◽  
Nash Equilibrium ◽  
Theoretical Model ◽  
Experimental Evidence ◽  
Quantal Response ◽  
Mutual Cooperation ◽  
Theoretical Concepts ◽  
Before And After ◽  
Low Levels ◽  
Markov Strategies

Abstract The study of the nature of human cooperation still contains gaps needing investigation. Previous findings reveal that socialization effectively promotes cooperation in the well-known Prisoner’s dilemma (PD) game. However, theoretical concepts fail to describe high levels of cooperation (probability higher than 50%) that were observed empirically. In this paper, we derive a symmetrical quantal response equilibrium (QRE) in PD in Markov strategies and test it against experimental data. Our results indicate that for low levels of rationality, QRE manages to describe high cooperation. In contrast, for high rationality QRE converges to the Nash equilibrium and describes low-cooperation behavior of participants. In the area of middle rationality, QRE matches the curve that represents the set of Nash equilibrium in Markov strategies. Further, we find that QRE serves as a dividing line between behavior before and after socialization, according to the experimental data. Finally, we successfully highlight the theoretically-predicted intersection of the set of Nash equilibrium for PD in Markov strategies and the QRE curve.

scholarly journals Other Race Effect: Theoretical Concepts, Research Tools, Experimental Data

2021 ◽  
Vol 14 (4) ◽  
pp. 142-163
Author(s):  
K.I. Ananyeva
Keyword(s):  
Experimental Data ◽  
Literature Review ◽  
The Other ◽  
Racial Groups ◽  
Theoretical Concepts ◽  
Race Effect ◽  
The Rich ◽  
Research Tools

The results of a literature review on the effect of other races are presented. The studies are presented that demonstrate the rich phenomenology of the features of perception, recognition and memorization of the faces of one’s own and other racial groups. The main models explaining the occurrence of the effect of the other race are given.

Models of Thermodynamic Properties of Prominences

1979 ◽  
Vol 44 ◽  
pp. 349-355
Author(s):  
R.W. Milkey
Keyword(s):  
Thermodynamic Properties ◽  
Mass Transport ◽  
Emission Spectrum ◽  
Thermodynamic Parameters ◽  
Working Group ◽  
Physical Processes ◽  
Theoretical Concepts ◽  
Group 3 ◽  
Observational Techniques

The focus of discussion in Working Group 3 was on the Thermodynamic Properties as determined spectroscopically, including the observational techniques and the theoretical modeling of physical processes responsible for the emission spectrum. Recent advances in observational techniques and theoretical concepts make this discussion particularly timely. It is wise to remember that the determination of thermodynamic parameters is not an end in itself and that these are interesting chiefly for what they can tell us about the energetics and mass transport in prominences.

Microdiffraction Patterns of Small Metallic Particles II; Theoretical Analysis

1982 ◽  
Vol 40 ◽  
pp. 668-669
Author(s):  
A. Gómez ◽  
P. Schabes-Retchkiman ◽  
M. José-Yacamán ◽  
T. Ocaña
Keyword(s):  
Experimental Data ◽  
Electron Diffraction ◽  
Theoretical Analysis ◽  
Size Range ◽  
Dynamical Theory ◽  
Metallic Particles ◽  
Splitting Effect

The splitting effect that is observed in microdiffraction pat-terns of small metallic particles in the size range 50-500 Å can be understood using the dynamical theory of electron diffraction for the case of a crystal containing a finite wedge. For the experimental data we refer to part I of this work in these proceedings.

Evidence for ordered Fe3Ni

1987 ◽  
Vol 45 ◽  
pp. 216-217
Author(s):  
K.B. Reuter ◽  
D.B. Williams ◽  
J.I. Goldstein
Keyword(s):  
Experimental Data ◽  
Martensitic Transformation ◽  
Electron Diffraction ◽  
Room Temperature ◽  
Direct Evidence ◽  
Transformation Product ◽  
Iron Meteorites ◽  
X Ray ◽  
Ni Content ◽  
Temperature Transformation

In the Fe-Ni system, although ordered FeNi and ordered Ni3Fe are experimentally well established, direct evidence for ordered Fe3Ni is unconvincing. Little experimental data for Fe3Ni exists because diffusion is sluggish at temperatures below 400°C and because alloys containing less than 29 wt% Ni undergo a martensitic transformation at room temperature. Fe-Ni phases in iron meteorites were examined in this study because iron meteorites have cooled at slow rates of about 10°C/106 years, allowing phase transformations below 400°C to occur. One low temperature transformation product, called clear taenite 2 (CT2), was of particular interest because it contains less than 30 wtZ Ni and is not martensitic. Because CT2 is only a few microns in size, the structure and Ni content were determined through electron diffraction and x-ray microanalysis. A Philips EM400T operated at 120 kV, equipped with a Tracor Northern 2000 multichannel analyzer, was used.

EELS white line intensities calculated for the 3d and 4d metals

1989 ◽  
Vol 47 ◽  
pp. 388-389
Author(s):  
C. C. Ahn ◽  
D. H. Pearson ◽  
P. Rez ◽  
B. Fultz
Keyword(s):  
Experimental Data ◽  
Line Intensity ◽  
Transition Probabilities ◽  
Initial Increase ◽  
White Line ◽  
Hartree Fock ◽  
Line Intensities ◽  
Integrated Intensity ◽  
X Ray Absorption ◽  
The Continuum

Previous experimental measurements of the total white line intensities from L2,3 energy loss spectra of 3d transition metals reported a linear dependence of the white line intensity on 3d occupancy. These results are inconsistent, however, with behavior inferred from relativistic one electron Dirac-Fock calculations, which show an initial increase followed by a decrease of total white line intensity across the 3d series. This inconsistency with experimental data is especially puzzling in light of work by Thole, et al., which successfully calculates x-ray absorption spectra of the lanthanide M4,5 white lines by employing a less rigorous Hartree-Fock calculation with relativistic corrections based on the work of Cowan. When restricted to transitions allowed by dipole selection rules, the calculated spectra of the lanthanide M4,5 white lines show a decreasing intensity as a function of Z that was consistent with the available experimental data.Here we report the results of Dirac-Fock calculations of the L2,3 white lines of the 3d and 4d elements, and compare the results to the experimental work of Pearson et al. In a previous study, similar calculations helped to account for the non-statistical behavior of L3/L2 ratios of the 3d metals. We assumed that all metals had a single 4s electron. Because these calculations provide absolute transition probabilities, to compare the calculated white line intensities to the experimental data, we normalized the calculated intensities to the intensity of the continuum above the L3 edges. The continuum intensity was obtained by Hartree-Slater calculations, and the normalization factor for the white line intensities was the integrated intensity in an energy window of fixed width and position above the L3 edge of each element.

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