Constant Flux States in Anisotropic Turbulence

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
Robert Rubinstein ◽  
Ye Zhou
Keyword(s):  
Present Theory ◽  
Scaling Analysis ◽  
Anisotropic Turbulence ◽  
Comprehensive Theory ◽  
Small Scales ◽  
Characteristic Features ◽  
Kolmogorov Theory ◽  
Angular Energy ◽  
Elementary Closure ◽  
Closure Theory

An elementary closure theory is used to compute the scaling of anisotropic contributions to the correlation function in homogeneous turbulence. These contributions prove to decay with wavenumber more rapidly than the energy spectrum; this property is sometimes called the “recovery of isotropy” at small scales and is a key hypothesis of the Kolmogorov theory. Although comparisons with a more comprehensive theory suggest that the present theory is too crude, its elementary character makes the scaling analysis straightforward. The analysis reveals some characteristic features of anisotropic turbulence, including “angular” energy transfer in wavevector space.

scholarly journals A Comprehensive Theory of Yielding and Failure for Isotropic Materials

2007 ◽  
Vol 129 (2) ◽  
pp. 173-181 ◽  
Author(s):  
Richard M. Christensen
Keyword(s):  
Stress State ◽  
Brittle Failure ◽  
Three Dimensional ◽  
Present Theory ◽  
Full Density ◽  
Isotropic Materials ◽  
Comprehensive Theory ◽  
General Material ◽  
Ductile Behavior ◽  
Limiting Case

A theory of yielding and failure for homogeneous and isotropic materials is given. The theory is calibrated by two independent, measurable properties and from those it predicts possible failure for any given state of stress. It also differentiates between ductile yielding and brittle failure. The explicit ductile-brittle criterion depends not only upon the material specification through the two properties, but also and equally importantly depends upon the type of imposed stress state. The Mises criterion is a special (limiting) case of the present theory. A close examination of this case shows that the Mises material idealization does not necessarily imply ductile behavior under all conditions, only under most conditions. When the first invariant of the yield/failure stress state is sufficiently large relative to the distortional part, brittle failure will be expected to occur. For general material types, it is shown that it is possible to have a state of spreading plastic flow, but as the elastic-plastic boundary advances, the conditions for yielding on it can change over to conditions for brittle failure because of the evolving stress state. The general theory is of a three-dimensional form and it applies to full density materials for which the yield/failure strength in uniaxial tension is less than or at most equal to the magnitude of that in uniaxial compression.

scholarly journals On Discontinuties in Thermoelastic Plane Waves without Energy Dissipation Due to a Thermo-Mechanical Shock

2013 ◽  
Vol 18 (2) ◽  
pp. 503-519
Author(s):  
N. Sarkar ◽  
A. Lahiri
Keyword(s):  
Energy Dissipation ◽  
Plane Waves ◽  
Generalized Thermoelasticity ◽  
Present Theory ◽  
Mechanical Shock ◽  
Field Equations ◽  
Characteristic Features ◽  
Thermoelastic Solid ◽  
Matrix Differential ◽  
Without Energy Dissipation

The present paper deals with the thermoelastic plane waves due to a thermo-mechanical shock in the form of pulse at the boundary of a homogeneous, isotropic thermoelastic half-space. The field equations of the Green- Naugdhi theory without energy dissipation for an thermoelastic solid in the generalized thermoelasticity theory are written in the form of a vector-matrix differential equation using Laplace transform techniques and then solved by an eigenvalue approach. Exact expressions for the considered field variables are obtained and presented graphically for copper-like material. The characteristic features of the present theory are analyzed by comparing these solutions with their counterparts in other generalized thcrmoelasticity theories.

scholarly journals Multiscaling analysis of high resolution space-time lidar-rainfall

2009 ◽  
Vol 16 (5) ◽  
pp. 579-586 ◽  
Author(s):  
P. V. Mandapaka ◽  
P. Lewandowski ◽  
W. E. Eichinger ◽  
W. F. Krajewski
Keyword(s):  
High Resolution ◽  
Time Lag ◽  
Space Time ◽  
Time Transformation ◽  
Dynamic Scaling ◽  
Scaling Analysis ◽  
Scaling Exponent ◽  
Temporal Data ◽  
Spatial Averaging ◽  
Small Scales

Abstract. In this study, we report results from scaling analysis of 2.5 m spatial and 1 s temporal resolution lidar-rainfall data. The high resolution spatial and temporal data from the same observing system allows us to investigate the variability of rainfall at very small scales ranging from few meters to ~1 km in space and few seconds to ~30 min in time. The results suggest multiscaling behaviour in the lidar-rainfall with the scaling regime extending down to the resolution of the data. The results also indicate the existence of a space-time transformation of the form t~Lz at very small scales, where t is the time lag, L is the spatial averaging scale and z is the dynamic scaling exponent.

Effect of magnetic field on the screening due to hot electrons in the presence of shallow attractive traps

2009 ◽  
Vol 87 (11) ◽  
pp. 1203-1211 ◽  
Author(s):  
S. Midday ◽  
D. P. Bhattacharya
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Present Theory ◽  
Hot Electrons ◽  
Relaxation Processes ◽  
Screening Length ◽  
Perturbation Potential ◽  
Characteristic Features ◽  
Energy And Momentum ◽  
The Magnetic Field

The electrostatic screening of the perturbation potential due to lattice imperfections has been investigated here in the presence of crossed electric and non-quantizing magnetic fields, under conditions where the lifetime of the carriers of the non-equilibrium ensemble in a semiconductor is controlled by shallow attractive traps. The screening characteristics are obtained in the general case of any mechanism of energy and momentum scattering of the hot carriers in the strong and weak magnetic field limits. For some definite scattering mechanisms, however, the characteristics are calculated in the presence of any finite value of the magnetic field. The results show interesting characteristic features that are quite different from what one can obtain for an ensemble of carriers that is in thermodynamic equilibrium with the lattice atoms. It has been observed that, depending upon the prevalent conditions with respect to the dominant momentum and energy relaxation processes and the strength of the applied electric field, the presence of the magnetic field sometimes brings in significant changes in both the qualitative and the quantitative aspects of the field dependence of the screening length. Apart from that, the screening length now shows a rather complex and altogether different dependence upon the lattice temperature. The numerical results featuring the interesting characteristics under different prevalent conditions are presented for Ge. It has been explained in what novel way the present problem describes the dependence of the screening length due to an ensemble of hot electrons on the external electric and magnetic fields. The limitations of the present theory, as well as its possible applicability for the characterization of semiconductors under high field conditions at low lattice temperatures, are discussed.

Ultrastructural modification of cellular interactions in cancer tumor

1978 ◽  
Vol 36 (2) ◽  
pp. 318-319
Author(s):  
N. P. Dmitrieva
Keyword(s):  
Cancer Cells ◽  
Human Thyroid ◽  
Adjacent Cell ◽  
Main Role ◽  
Cellular Interactions ◽  
Electron Microscopic ◽  
Cancer Tumor ◽  
Normal Human ◽  
Characteristic Features

One of the most characteristic features of cancer cells is their ability to metastasia. It is suggested that the modifications of the structure and properties of cancer cells surfaces play the main role in this process. The present work was aimed at finding out what ultrastructural features apear in tumor in vivo which removal of individual cancer cells from the cell population can provide. For this purpose the cellular interactions in the normal human thyroid and cancer tumor of this gland electron microscopic were studied. The tissues were fixed in osmium tetroxide and were embedded in Araldite-Epon.In normal human thyroid the most common type of intercellular contacts was represented by simple junction formed by the parallelalignment of adjacent cell membranees leaving in between an intermembranes space 15-20 nm filled with electronlucid material (Fig. 1a). Sometimes in the basal part of cells dilatations of the intercellular space 40-50 nm wide were found (Fig. 1a). Here the cell surfaces may form single short microvilli.

Development of 200kV ultrahigh-resolution analytical electron microscope

1989 ◽  
Vol 47 ◽  
pp. 108-109
Author(s):  
T. Kaneyama ◽  
M. Naruse ◽  
Y. Ishida ◽  
M. Kersker
Keyword(s):  
Electron Microscope ◽  
Optical Constants ◽  
Materials Science ◽  
Objective Lens ◽  
The Finite Element Method ◽  
Ultrahigh Resolution ◽  
Analytical Electron ◽  
Analytical Electron Microscope ◽  
Characteristic Features ◽  
Better Than

In the field of materials science, the importance of the ultrahigh resolution analytical electron microscope (UHRAEM) is increasing. A new UHRAEM which provides a resolution of better than 0.2 nm and allows analysis of a few nm areas has been developed. [Fig. 1 shows the external view] The followings are some characteristic features of the UHRAEM.Objective lens (OL)Two types of OL polepieces (URP for ±10' specimen tilt and ARP for ±30' tilt) have been developed. The optical constants shown in the table on the next page are figures calculated by the finite element method. However, Cs was experimentally confirmed by two methods (namely, Beam Tilt method and Krivanek method) as 0.45 ∼ 0.50 mm for URP and as 0.9 ∼ 1.0 mm for ARP, respectively. Fig. 2 shows an optical diffractogram obtained from a micrograph of amorphous carbon with URP under the Scherzer defocus condition. It demonstrates a resolution of 0.19 nm and a Cs smaller than 0.5 mm.

Toward a Comprehensive Theory of Group Therapy

1982 ◽  
Vol 27 (7) ◽  
pp. 565-566
Author(s):  
Stephen I. Abramowitz
Keyword(s):  
Group Therapy ◽  
Comprehensive Theory
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