Extreme-Value-Based Statistical Bounding of Low, Mid, and High Frequency Responses of a Forced Plate With Random Boundary Conditions

2012 ◽  
Vol 134 (2) ◽  
Author(s):  
A. Seçgin ◽  
J. F. Dunne ◽  
L. Zoghaib
Keyword(s):  
Monte Carlo ◽  
Energy Density ◽  
Boundary Conditions ◽  
Total Energy ◽  
High Frequency ◽  
Extreme Value ◽  
Frequency Range ◽  
Random Boundary ◽  
Total Energy Density ◽  
Dsc Method

The problem of statistically bounding the response of an engineering structure with random boundary conditions is addressed across the entire frequency range: from the low, through the mid, to the high frequency region. Extreme-value-based bounding of both the FRF and the energy density response is examined for a rectangular linear plate with harmonic point forcing. The proposed extreme-value (EV) approach, previously tested only in the low frequency region for uncoupled and acoustically-coupled uncertain structures, is examined here in the mid and high frequency regions in addition to testing at low frequencies. EV-based bounding uses an asymptotic threshold exceedance model of Type-I, to extrapolate the m-observational return period to an arbitrarily-large batch of structures. It does this by repeatedly calibrating the threshold model at discrete frequencies using a small sample of response data generated by Monte Carlo simulation or measurement. Here the discrete singular convolution (DSC) method – a transfrequency computation approach for deterministic vibration - is used to generate Monte Carlo samples. The accuracy of the DSC method is first verified (i) in terms of the spatial distribution of total energy density and (ii) across the frequency range, by comparison with a mode superposition method and Statistical Energy Analysis (SEA). EV-based bound extrapolations of the receptance FRF and total energy density are then compared with: (i) directly-estimated bounds using a full set of Monte Carlo simulations and (ii) with total mean energy levels obtained with SEA. This paper shows that for a rectangular plate structure with random boundary conditions, EV-based statistical bounding of both the FRF and total energy density response is generally applicable across the entire frequency range.

Abinitio Micromagnetic Calculations in Steel with Ferromagnetic Behavior

2015 ◽  
Vol 644 ◽  
pp. 282-285
Author(s):  
Christina Stefani
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Energy Density ◽  
Boundary Conditions ◽  
Total Energy ◽  
Magnetic Materials ◽  
Computing Methods ◽  
Ferromagnetic Behavior ◽  
Total Energy Density ◽  
Mathematical Formula

The numerical magnetization modeling in magnetic materials is achieved by computing methods which determine the specific characteristics of each material by region and boundary conditions. Finite element method is presented, in comparison with other methods. Furthermore, there is presented the mathematical formula used, based on the minimization of the total energy density of configuration of magnetization.

scholarly journals Latitudinal and seasonal variability of gravity-wave energy in the South-West Indian Ocean

2007 ◽  
Vol 25 (12) ◽  
pp. 2479-2485 ◽  
Author(s):  
F. Chane-Ming ◽  
D. Faduilhe ◽  
J. Leveau
Keyword(s):  
Energy Density ◽  
Indian Ocean ◽  
Total Energy ◽  
Seasonal Variability ◽  
La Réunion ◽  
Raman Lidar ◽  
Total Energy Density ◽  
South West Indian Ocean ◽  
South West ◽  
West Indian Ocean

Abstract. Vertical temperature profiles obtained by radiosonde and Raman lidar measurements are used to investigate a climatology of total energy density of gravity waves (GW) in the Upper Troposphere (UT) and the Lower Stratosphere (LS) from 1992 to 2004 above Mahé (4° S, 55° E), Tromelin (15° S, 54° E) and La Réunion (21° S, 55° E) located in the tropical South-West Indian Ocean. The commonly used spectral index value (p≈5/3) of the intrinsic frequency spectrum is used for calculating estimated total energy density in the UT and LS. Estimated total energy density provides good estimation of total energy density in the LS but underestimates total energy density by one half in the UT above Mahé and Tromelin probably due to the activity of near-inertial frequency waves. Estimated total energy density reveals a strong seasonal variability as a function of latitude and convection as an evident active source of GW activity in the LS in austral summer. Above La Réunion, a semi-annual GW activity is observed in the LS with the signature of the subtropical barrier in the UT. Moreover, radiosondes and Raman lidar provide consistent GW surveys in the UT/LS at heights<23 km above La Réunion.

The Studies of ScB2 (0001) Surfaces from the First-Principles

2014 ◽  
Vol 989-994 ◽  
pp. 688-693
Author(s):  
Hui Zhao ◽  
Qian Han
Keyword(s):  
Energy Density ◽  
Total Energy ◽  
Electronic Properties ◽  
First Principles ◽  
Density Functional Calculations ◽  
Density Functional ◽  
Surface Structures ◽  
Charge Accumulation ◽  
Total Energy Density ◽  
Energy Density Functional

We conduct first-principles total-energy density functional calculations to study the ScB2 (0001) surfaces. The optimized surface structures and electronic properties are obtained. The results show that Sc-terminated surface is thermodynamically more favorable in most of range. The relaxations indicate that it is mainly localized within top three layers and it is less relaxation for Sc-terminated surface. The surface induced features in DOS disappear slowly for the B-terminated surface but vanish rapidly for the Sc-terminated surface. For the Sc-terminated surface, it shows strong metallic property. Simultaneously, both termination surfaces are found charge accumulation relative to the idea surface. Sc-B bonds are strengthened result in the outermost interface spacing are all contracted.

scholarly journals THE EXISTENCE OF AN OLD QUASAR AT z=3.91 AND ITS IMPLICATIONS FOR Λ(t) DEFLATIONARY COSMOLOGIES

2004 ◽  
Vol 13 (07) ◽  
pp. 1321-1325 ◽  
Author(s):  
JOÃO VITAL CUNHA ◽  
ROSE CLÍVIA SANTOS
Keyword(s):  
Dark Matter ◽  
Energy Density ◽  
Total Energy ◽  
Lower Limit ◽  
Cold Dark Matter ◽  
High Redshift ◽  
Observational Constraints ◽  
Total Energy Density ◽  
Lower Limits

We investigate some observational constraints on decaying vacuum cosmologies based on the recently discovered old high redshift quasar APM 08279+5255. This object is located at z=3.91 and has an estimated age of 2–3 Gyr. The class of Λ(t) cosmologies is characterized by a positive β parameter smaller than unity which quantifies the ratio between the vacuum and the total energy density. Assuming the lower limit age (2 Gyr) and that the cold dark matter contributes with Ω M =0.2 we show that β is constrained to be ≥0.07 while for an age of 3 Gyr and Ω M =0.4 the β parameter must be greater than 0.32. Our analysis includes closed, flat and hyperbolic scenarios, and it strongly suggests that there is no age crisis for this kind of Λ(t) cosmologies. Lower limits to the redshift quasar formation are also briefly discussed to the flat case. For Ω M =0.4 we found that the redshift formation is constrained by zf≥8.0.

scholarly journals Climatology of gravity wave activity during the West African Monsoon

2008 ◽  
Vol 26 (12) ◽  
pp. 4081-4089 ◽  
Author(s):  
P. Kafando ◽  
F. Chane-Ming ◽  
M. Petitdidier
Keyword(s):  
Energy Density ◽  
Total Energy ◽  
Gravity Wave ◽  
West African Monsoon ◽  
Wave Activity ◽  
West African ◽  
The West ◽  
Total Energy Density ◽  
Monsoon Period ◽  
African Monsoon

Abstract. Gravity wave activity is analysed in the lower stratosphere using 6 year radiosonde data (2001–2006) above two meteorological stations in the West African tropical region such as Niamey (13.47° N; 2.16° E) and Ouagadougou (12.35° N; 1.51° W). Monthly total energy density of gravity waves is computed with temperature and horizontal wind perturbations to highlight the West African Monsoon period from June to September. Comparison with monthly total energy density calculated with temperature only supports that observed small-scale temperature and wind perturbations are mostly associated with gravity waves in the lower stratosphere especially for large values during the wet season. Above the two sites, monthly evolution of gravity wave total energy density reveals a maximum intensity of gravity wave activity in July during the West African Monsoon period. Indicators of convective activity such as mean Outgoing Longwave Radiation (OLR) and Tropical Rainfall Measuring Mission (TRMM) rain rates reveal to be adequate monsoon proxies to be compared to gravity wave energy intensity during the West African Monsoon.

scholarly journals Role of substorm-associated impulsive electric fields in the ring current development during storms

2005 ◽  
Vol 23 (2) ◽  
pp. 579-591 ◽  
Author(s):  
N. Yu. Ganushkina ◽  
T. I. Pulkkinen ◽  
T. Fritz
Keyword(s):  
Energy Density ◽  
Electric Field ◽  
Total Energy ◽  
Large Scale ◽  
Ring Current ◽  
High Energy ◽  
Time Dependent ◽  
Small Scale ◽  
Total Energy Density ◽  
Current Energy

Abstract. Particles with different energies produce varying contributions to the total ring current energy density as the storm progresses. Ring current energy densities and total ring current energies were obtained using particle data from the Polar CAMMICE/MICS instrument during several storms observed during the years 1996-1998. Four different energy ranges for particles are considered: total (1-200keV), low (1-20keV), medium (20-80keV) and high (80-200keV). Evolution of contributions from particles with different energy ranges to the total energy density of the ring current during all storm phases is followed. To model this evolution we trace protons with arbitrary pitch angles numerically in the drift approximation. Tracing is performed in the large-scale and small-scale stationary and time-dependent magnetic and electric field models. Small-scale time-dependent electric field is given by a Gaussian electric field pulse with an azimuthal field component propagating inward with a velocity dependent on radial distance. We model particle inward motion and energization by a series of electric field pulses representing substorm activations during storm events. We demonstrate that such fluctuating fields in the form of localized electromagnetic pulses can effectively energize the plasma sheet particles to higher energies (>80keV) and transport them inward to closed drift shells. The contribution from these high energy particles dominates the total ring current energy during storm recovery phase. We analyse the model contributions from particles with different energy ranges to the total energy density of the ring current during all storm phases. By comparing these results with observations we show that the formation of the ring current is a combination of large-scale convection and pulsed inward shift and consequent energization of the ring current particles.

Shape Optimization Under Vibroacoustic Criteria in the Mid-High Frequency Range

2014 ◽  
Vol 22 (02) ◽  
pp. 1450003 ◽  
Author(s):  
Renata Troian ◽  
Sebastien Besset ◽  
Frederic Gillot
Keyword(s):  
Energy Density ◽  
Shape Optimization ◽  
Energy Method ◽  
High Frequency ◽  
Optimization Method ◽  
Optimization Process ◽  
Cavity Surface ◽  
High Frequency Range ◽  
Frequency Range ◽  
Acoustic Cavity

This paper deals with shape optimization issues under vibroacoustic criteria. The aim of the conducted research is to minimize the energy density in the cavity by changing its geometry parameters. The energy density is obtained through an energy method called simplified energy method (MES). The optimization method is based on a transformation function mapping 3D cavity surface on a 2D domain. The optimization process directly relies on this function and thus avoids remeshing of the geometry. The proposed method allows to describe the geometry through Bezier, Bspline and NURBS parametrization. To illustrate the method, we process a shape optimization on a simple acoustic cavity.

scholarly journals About the Origin of the Dark Energy and the Zero Mass/Energy Universe

2021 ◽  
pp. 1-7
Author(s):  
Guenter Frohberg
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Total Energy ◽  
Average Energy ◽  
Friedmann Equation ◽  
Relativity Theory ◽  
Total Energy Density ◽  
Gravitational Fields ◽  
Expansion Of The Universe ◽  
The Universe

Based on the Gravito-Electro-Magnetic (GEM) equations as another form (for low fields) of Einstein's Equations of General Relativity Theory (GRT) an equation is derived for the total energy density in the universe, including the gravitational fields, the contribution thereof is always negative and so it seems to represents the Dark Energy (DE).  When calculating the total energy of the universe from this equation, the result is near to zero because of negative contributions from gravitational fields, depending a little on the available parameters of the universe as e.g. it's baryonic mass. Thus the assumption is given a high amount of probability, that the total energy (mass) in the universe is really zero and very likely is always zero. This  would mean, that the universe developed from empty space-time or from nothing (may be by quantum fluctuations). Looking on the development it could be  that the average energy density is zero for each sufficient large part of the universe at any time, except for very local deviations (e.g. galaxies, black holes etc.). As a consequence the expansion of the universe is probably not retarded by gravity (thus the Friedmann equation and others do not apply). The expansion of the universe can be considered as driven by the pressure of a gas-like medium with positive masses as by intergalactic gas, dust, stars and galaxies. Conclusions are drawn as to the interpretation of the formation of voids in the universe, flat space etc.

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