scholarly journals Generalized Conditions for Hydraulic Criticality of Oceanic Overflows

2005 ◽  
Vol 35 (10) ◽  
pp. 1782-1800 ◽  
Author(s):  
Larry Pratt ◽  
Karl Helfrich
Keyword(s):  
Critical Condition ◽  
Degrees Of Freedom ◽  
Single Layer ◽  
Direct Calculation ◽  
Dissipative Systems ◽  
Hydraulic Analysis ◽  
Wave Speeds ◽  
Long Wave ◽  
Functional Formulation ◽  
Arbitrary Potential

Abstract Two methods for assessing the hydraulic criticality of an observed or modeled overflow are discussed. The methods are valid for single-layer deep flows with arbitrary potential vorticity and cross section. The first method is based on a purely steady view in which the flow at a given section is divided up into a group of “streamtubes.” A hydraulic analysis requires an extension of Gill’s functional formulation to systems with many degrees of freedom. The general form of the critical condition and associated compatibility condition for such a system are derived and applied to the streamtube model. As an aside, it is shown by example that Gill’s original critical condition can fail to capture all possible critical states, but that this problem is fixed when the multivariable approach is used. It is also shown how Gill’s method can be applied to certain dispersive or dissipative systems. The second method of assessing criticality involves direct calculation of linear, long-wave speeds using a time-dependent version of the streamtube model. This approach turns out to be better suited to the analysis of geophysical datasets. The significance of the local Froude number F is discussed. It is argued that F must take on the value unity at some point across a critical section.

Random Vibrations of Constructions and their Damping

2009 ◽  
Vol 147-149 ◽  
pp. 345-349
Author(s):  
Danielius Gužas ◽  
A. Čiučelis
Keyword(s):  
Statistical Theory ◽  
Closed Form ◽  
Statistical Characteristic ◽  
Degrees Of Freedom ◽  
Viscous Friction ◽  
Spectral Approach ◽  
Mechanical Vibrations ◽  
Vibratory System ◽  
Long Wave ◽  
Wave Size

In the article, the equation of the equivalent movement of the oscillator with viscous friction is provided. The statistical specifications and the spectral approach for the density of intensity of the established vibrations are provided. Non-stationary vibrations in the closed form are investigated. The statistical characteristic for intensity of vibrations is obtained. The work presents a method of investigation of vibration processes of random mechanical vibrations in the equipment and apparatus. The vibratory system of a sufficiently small (as compared to vibrations of a long wave) size is described; the models with the limited number of degrees of freedom are applied. The statistical theory for discussing of vibrations at constructional damping is applied.

scholarly journals The Doubling of the Degrees of Freedom in Quantum Dissipative Systems, and the Semantic Information Notion and Measure in Biosemiotics

Proceedings ◽  
2020 ◽  
Vol 47 (1) ◽  
pp. 60
Author(s):  
Gianfranco Basti ◽  
Antonio Capolupo ◽  
GiuseppeVitiello
Keyword(s):  
Degrees Of Freedom ◽  
Semantic Information ◽  
Quantum Dissipative Systems ◽  
Dissipative Systems ◽  
Recent History ◽  
History Of

In the recent history of the effort for defining a suitable. [...]

Torque-Fiber-Winding (TFW)-Procedure: Manufacturing of Textile-Based Unidirectional Prepreg for Raw Material and Material Development of Carbon Fibre Reinforced Thermoplastics

2017 ◽  
Vol 742 ◽  
pp. 498-505
Author(s):  
Angelika Kolonko ◽  
Frank Helbig ◽  
Jürgen Tröltzsch ◽  
Daisy Nestler ◽  
Lothar Kroll
Keyword(s):  
Carbon Fibre ◽  
Degrees Of Freedom ◽  
Single Layer ◽  
Nonwoven Fabric ◽  
Fibre Volume ◽  
Raw Material ◽  
Laboratory Staff ◽  
Material Development ◽  
Fiber Winding ◽  
Reinforced Thermoplastics

There is the need to determine the process capability of available and novel carbon fibre (CF) roving with minimal material and reproducible procedures in the field of research and development of continuous fibre reinforced composites and structural components, as well as to identify the power delivery in thermoplastic laminate constructions. The innovative TFW procedure with the appropriate system technology allows the production of piece size variable unidirectional (UD) prepreg in a continuous sequential process of spiral winding. A flexible surface design, resulting in the partial fixation of a single highly spread CF roving on fine nonwoven fabric. By defined accumulating of composite components, the fibre volume content (FVC) is adjustable and correspond to the level of spreading and to the grammage of nonwoven fabric. Minimum single layer thickness promote compound homogeneity and thereby allow the generation of greatest possible degrees of freedom in load-oriented structural design of CF-reinforced thermoplastic lightweight products in the laboratory staff.

Wigner Distribution Function for Open Quantum Systems

1997 ◽  
Vol 11 (09n10) ◽  
pp. 391-397 ◽  
Author(s):  
S. Baskoutas
Keyword(s):  
Distribution Function ◽  
Degrees Of Freedom ◽  
Wigner Distribution ◽  
Open Quantum Systems ◽  
Equations Of Motion ◽  
Analytical Form ◽  
Dissipative Systems ◽  
Wigner Distribution Function ◽  
Dissipative Tunneling ◽  
Lie Algebraic Structure

Using the modified biorthonormal Heisenberg equations of motion for non-Hermitian (NH) Hamilton operators, in order to imply a consistent Lie-algebraic structure and also the equivalence between the Heisenberg and Schrödinger pictures, we have obtained the analytical form of the Wigner distribution function which is unavoidable complex. Its imaginary part accounts for the influence of additional degrees of freedom, which are always present in the phenomenological representation of dissipative systems through (NH) Hamiltonians. Applications of the above formalism can be found, for instance, in dissipative macroscopic quantum tunneling (MQT) effect for Josephson junctions, and in the dissipative tunneling of trapped atoms in optical crystals.

scholarly journals Salvesen’s Method for Added Resistance Revisited

2021 ◽  
Vol 143 (5) ◽  
Author(s):  
Mostafa Amini-Afshar
Keyword(s):  
Direct Calculation ◽  
Wave Resistance ◽  
The Body ◽  
Ship Motions ◽  
Exact Equation ◽  
Added Resistance ◽  
Scattering Problems ◽  
Correct Treatment ◽  
Long Wave ◽  
Strip Theory

Abstract Almost 4 years after the appearance of Salvesen–Tuck–Faltinsen (STF) strip theory (Salvesen et al., 1970, “Ship Motions and Sea Loads,” Annual Meeting of the Society of Naval Architecture and Marine Engineers (SNAME), New York, Nov. 12–13), Salvesen in 1974 published his popular method for calculation of added resistance (Salvesen, 1974, “Second-Order Steady State Forces and Moments on Surface Ships in Oblique Regular Waves,” Vol. 22; Salvesen, 1978, “Added Resistance of Ships in Waves,” J. Hydronautics, 12(1), pp. 24–34). His method is based on an exact near-field formulation; however, he applied the long-wave and the weak-scatterer assumptions to present his approximate method using the integrated quantities (hydrodynamic and geometrical coefficients). Considering the available computational powers in the 1970s, both of these assumptions were absolutely justifiable. The intention of this paper is to disseminate the results of a recent study at the Technical University of Denmark, whereby the Salvesen’s formulation has been revisited and the added resistance is computed from the original exact equation without invoking the weak-scatterer or the long-wave assumptions. This is performed using the solutions of the radiation and the scattering problems, obtained by a low-order boundary element method and the two-dimensional free-surface Green function inside our in-house STF theory implementation (Bingham and Amini-Afshar, 2020, DTU_Strip Theory Solver). The weak-scatterer assumption is then removed through a direct calculation of the x-derivatives of the velocity potentials and the normal vectors along the body. Knowing the velocity potentials over each panel, the long-wave assumption is also avoided by a piece-wise analytical integration of sectional Kochin Function (Kochin, 1936, “On the Wave Resistance and Lift of Bodies Submerged in Fluid,” Transactions of the Conference on the Theory of Wave Resistance, Moscow.). The presented results for five ship geometries testify that the correct treatment of the original equation is achieved only after both of the above-mentioned assumptions are removed. Implemented in this manner, Salvesen’s method proves to be relatively more accurate and robust than has been generally perceived during all these years.

scholarly journals Intertwined density waves in a metallic nickelate

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Junjie Zhang ◽  
D. Phelan ◽  
A. S. Botana ◽  
Yu-Sheng Chen ◽  
Hong Zheng ◽  
...  
Keyword(s):  
Fermi Surface ◽  
Metal Oxides ◽  
Transition Metal Oxides ◽  
Degrees Of Freedom ◽  
Density Wave ◽  
Single Layer ◽  
Late Transition Metal ◽  
Density Waves ◽  
Paramagnetic Metal ◽  
Late Transition

AbstractNickelates are a rich class of materials, ranging from insulating magnets to superconductors. But for stoichiometric materials, insulating behavior is the norm, as for most late transition metal oxides. Notable exceptions are the 3D perovskite LaNiO3, an unconventional paramagnetic metal, and the layered Ruddlesden-Popper phases R4Ni3O10, (R = La, Pr, Nd). The latter are particularly intriguing because they exhibit an unusual metal-to-metal transition. Here, we demonstrate that this transition results from an incommensurate density wave with both charge and magnetic character that lies closer in its behavior to the metallic density wave seen in chromium metal than the insulating stripes typically found in single-layer nickelates like La2-xSrxNiO4. We identify these intertwined density waves as being Fermi surface-driven, revealing a novel ordering mechanism in this nickelate that reflects a coupling among charge, spin, and lattice degrees of freedom that differs not only from the single-layer materials, but from the 3D perovskites as well.

scholarly journals Flow and Hydraulics near the Sill of Hood Canal, a Strongly Sheared, Continuously Stratified Fjord

2010 ◽  
Vol 40 (5) ◽  
pp. 1087-1105 ◽  
Author(s):  
M. C. Gregg ◽  
L. J. Pratt
Keyword(s):  
Washington State ◽  
Hydraulic Control ◽  
Cross Sectional ◽  
Wave Speeds ◽  
Hood Canal ◽  
Tidal Cycles ◽  
Long Wave ◽  
Lee Waves ◽  
Lee Wave ◽  
Large Amplitude Wave

Abstract Hood Canal, a long fjord in Washington State, has strong tides but limited deep-water renewal landward of a complex constriction. Tide-resolving hydrographic and velocity observations at the constriction, with a depth-cycling towed body, varied markedly during three consecutive years, partly because of stratification variations. To determine whether hydraulic control is generally important and to interpret observations of lee waves, blocking, and other features, hydraulic criticality is estimated over full tidal cycles for channel wide internal wave modes 1, 2, and 3, at five cross-channel sections, using mode speeds from the extended Taylor–Goldstein equation. These modes were strongly supercritical during most of ebb and flood on the gentle seaward sill face and for part of flood at the base of the steep landward side. Examining local criticality along the thalweg found repeated changes between mode 1 being critical and supercritical approaching the sill crest during flood, unsurprising given local minima and maxima in the cross-sectional area, with the sill crest near a maximum. Density crossing the sill sometimes resembled an overflow with an internal hydraulic control at the sill, followed by a hydraulic jump or lee wave. Long-wave speeds, however, suggest cross waves, particularly along the shallower gentler side, where flow downstream of a large-amplitude wave was uniformly supercritical. Supercritical approaching the sill, peak ebb was critical to mode 1 and supercritical to modes 2 and 3 at the base while forming a sluggish dome of dense water over the sill. Full interpretation exceeds observations and existing theory.

DESIGN AND FABRICATION OF EDGE FILTER USING ABSORBED ZnS SINGLE LAYER PREPARED BY FLASH EVAPORATION TECHNIQUE

2010 ◽  
Vol 24 (28) ◽  
pp. 2821-2829 ◽  
Author(s):  
NADIR F. HABUBI ◽  
KHUDHEIR A. MISHJIL ◽  
HAYFA G. RASHID ◽  
H. L. MANSOUR
Keyword(s):  
Thin Film ◽  
Matrix Theory ◽  
Single Layer ◽  
Characteristic Matrix ◽  
Film Material ◽  
Flash Evaporation ◽  
Thin Film Material ◽  
Edge Filter ◽  
Long Wave ◽  
Evaporation Technique

Long-wave pass edge filter of high transmittance and wide bandpass have been designed and fabricated using on a single weakly absorbed ZnS thin film material of thickness of about 300 nm which was prepared by using the flash evaporation technique. The design was based on characteristic matrix theory, taking into account the effect of dispersion phenomena for all spectral wavelength.

Prototurbulent motions in dissipative model systems

1976 ◽  
Vol 80 (1) ◽  
pp. 153-163 ◽  
Author(s):  
A. Thyagaraja
Keyword(s):  
External Field ◽  
Degrees Of Freedom ◽  
Model Systems ◽  
Dissipative Systems ◽  
Qualitative Properties ◽  
Special Cases ◽  
Qualitative Nature ◽  
The Stability ◽  
Almost All ◽  
Dissipative Model

AbstractTwo different models of open, dissipative systems are considered. The stability and the asymptotic manifold of solutions are studied with respect to the variation of a model viscosity ν. Bifurcation theorems result from the analysis which shows the existence of a class of ‘prototurbulent’ motions. These are generalisations of the quasi-periodic asymptotic motions characteristic of Hopf's well-known mathematical model of turbulence. Given the statistics of the driving external field, it is shown how to calculate the correlation functions of the asymptotic motions (as t → ∞) for arbitrary values of the model viscosity. The systems treated are non-linear and except in special cases, cannot be solved in closed form. The relation to real systems is discussed. The effects of dimensionality on the qualitative nature of the motion is explored. It is found that for the models treated, perturbations of the external field do not affect the qualitative properties. Certain ‘mean’ quantities vary smoothly with the variation of the external field, but the details of the motion may be sensitive to the external perturbations. It is also found that even if the motion is strictly not quasiperiodic in the sense of Hopf and Landau, almost all asymptotic motions have a recurrent character under certain conditions. Some of the models also show the reverse of this behaviour, i.e. a non-dissipative, quasi-recurrent approach to ‘equilibrium’. This phenomenon can occur if the number of active degrees of freedom at a non-zero model viscosity is infinite.

General Beam Cross-Section Analysis Using a 3D Finite Element Slice

2014 ◽  
Author(s):  
Philippe Couturier ◽  
Steen Krenk
Keyword(s):  
Finite Element ◽  
Cross Section ◽  
Cross Sections ◽  
Degrees Of Freedom ◽  
Finite Thickness ◽  
Single Layer ◽  
Element Discretization ◽  
Cubic Polynomial ◽  
Hermitian Interpolation ◽  
Section Analysis

A formulation for analysis of general cross-section properties has been developed. This formulation is based on the stress-strain states in the classic six equilibrium modes of a beam by considering a finite thickness slice modelled by a single layer of 3D finite elements. The displacement variation in the lengthwise direction is in the form of a cubic polynomial, which is here represented by Hermitian interpolation, whereby the degrees of freedom are concentrated on the front and back faces of the slice. The theory is illustrated by application to a simple cross-section for which an analytical solution is available. The paper also shows an application to wind turbine blade cross-sections and discusses the effect of the finite element discretization on the cross-section properties such as stiffness parameters and the location of the elastic and shear centers.

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