Zur Elektrodynamik turbulent bewegter leitender Medien

1968 ◽  
Vol 23 (11) ◽  
pp. 1851-1860 ◽  
Author(s):  
K.-H. Rädler
Keyword(s):  
General Result ◽  
Homogeneous Turbulence ◽  
Mean Square ◽  
Intensity Gradient ◽  
Electrically Conducting ◽  
Mean Fields ◽  
The Mean ◽  
Special Case ◽  
Foregoing Paper

In a foregoing paper the foundations for an electrodynamics of mean fields in turbulently moving electrically conducting media were developed. With the method demonstrated there a special case is treated. The turbulence is supposed to deviate from a homogeneous isotropic one showing reflexion symmetry, only due to a gradient of intensity, i. e. of the mean square velocity. The calculations are carried out for small intensities. As a result, expressions for the modified conductivity introduced for homogeneous turbulence in the foregoing paper are given and discussed. The effect of the intensity gradient is illustrated by a simple example. Furthermore, a possibility is shown for describing the general result in terms of modified conductivity and permeability.

scholarly journals On the decay of inhomogeneous turbulence

1997 ◽  
Vol 342 ◽  
pp. 335-354 ◽  
Author(s):  
J. R. CHASNOV
Keyword(s):  
Scaling Laws ◽  
Initial Conditions ◽  
Homogeneous Turbulence ◽  
Mean Square ◽  
Asymptotic Decay ◽  
Inhomogeneous Turbulence ◽  
Spectral Coefficients ◽  
The Mean ◽  
Decaying Turbulence ◽  
High Reynolds

The decay of high-Reynolds-number inhomogeneous turbulence in an unbounded domain is considered. The turbulence may be initially localized in one to three spatial directions and the fluid is assumed to be at rest at infinity in those directions. Previous arguments used to determine the decay laws of homogeneous turbulence are extended to the decay of inhomogeneous turbulence by integrating the turbulence statistics over the inhomogeneous directions. Dimensional arguments based on the invariance or near-invariance of low-wavenumber spectral coefficients associated with the integrated mean-square velocity are used to determine asymptotic decay laws for inhomogeneous turbulence. These decay laws depend on the number of inhomogeneous directions of the flow field and reduce to the well-known decay laws of homogeneous turbulence when this number is zero. Different decay laws are determined depending on the spectral behaviour at low wavenumbers. Asymptotic similarity states of the spectrum during the decay and of the distribution of the mean-square velocity along the inhomogeneous directions are also determined. An analytical result for the decay of the mean-square velocity at the centre of the initial disturbance is found, and the decay proceeds more rapidly with increasing number of inhomogeneous directions due to the transport of energy along those directions.Large-eddy simulations of decaying turbulence homogeneous in a plane and localized in a single direction are performed to test the theoretical scaling laws. The numerically determined asymptotic decay laws of the integrated mean-square velocity agree well with the theoretical predictions. A self-similar decay of the spectra and mean-square velocity distributions is also observed. The simulation results suggest that when the low-wavenumber spectral coefficient is an exact invariant, a unique similarity state depending only on the initial value of this invariant and independent of all other aspects of the initial conditions is attained asymptotically.

Zur Elektrodynamik turbulent bewegter leitender Medien

1968 ◽  
Vol 23 (11) ◽  
pp. 1841-1851 ◽  
Author(s):  
K.-H. Rädler
Keyword(s):  
Isotropic Turbulence ◽  
Additional Term ◽  
Magnetic Flux Density ◽  
Dynamo Action ◽  
Ohm’S Law ◽  
Electrically Conducting ◽  
Mean Fields ◽  
The Mean ◽  
Ohm's Law ◽  
General Method

This paper deals with the behaviour of electromagnetic fields in electrically conducting media carrying out turbulent motions. The basis is formed by Maxwell’s and the corresponding constitutive equations inclusive Ohm’s law, all with the neglections usual in magnetohydrodynamics. Attention is directed to certain mean fields defined by statistical averaging.From the equations mentioned above, except Ohm’s law, one gets equations of the same kind for the mean fields. In Ohm’s law, however, the transition to the mean fields leads to an additional term , the averaged vector product of the fluctuations in the velocity of the medium and the magnetic flux density. The investigation of this term makes up the centre in the elaboration of an electrodynamics of mean fields.As a very simple example a homogeneous isotropic turbulence showing reflexion symmetry is considered. In this case makes allowance for the introduction of a modified electrical conductivity. If the reflexion symmetry is violated, describes an effect allowing a dynamo action.Furthermore, a general method for calculation of for arbitrary turbulent motions is developed, and a survey is given of the results which can be expected for some special kinds of turbulence.

scholarly journals Prediction Error of the Chain Ladder Reserving Method applied to Correlated Run-off Triangles

2007 ◽  
Vol 2 (1) ◽  
pp. 25-50 ◽  
Author(s):  
M. Merz ◽  
M. V. Wüthrich
Keyword(s):  
Time Series ◽  
Mean Square Error ◽  
Prediction Error ◽  
Time Series Model ◽  
Mean Square ◽  
Run Off ◽  
Chain Ladder Method ◽  
The Mean ◽  
Chain Ladder ◽  
Special Case

ABSTRACTIn Buchwalder et al. (2006) we revisited Mack's (1993) and Murphy's (1994) estimates for the mean square error of prediction (MSEP) of the chain ladder claims reserving method. This was done using a time series model for the chain ladder method. In this paper we extend the time series model to determine an estimate for the MSEP of a portfolio of N correlated run-off triangles. This estimate differs in the special case N = 2 from the estimate given by Braun (2004). We discuss the differences between the estimates.

The Bordeaux Automatic Meridian Circle

1978 ◽  
Vol 48 ◽  
pp. 227-228
Author(s):  
Y. Requième
Keyword(s):  
Mean Square Error ◽  
Mean Square ◽  
Meridian Circle ◽  
The Mean ◽  
Full Automation

In spite of important delays in the initial planning, the full automation of the Bordeaux meridian circle is progressing well and will be ready for regular observations by the middle of the next year. It is expected that the mean square error for one observation will be about ±0.”10 in the two coordinates for declinations up to 87°.

The mean-square generalized delayed decision feedback sequence detector

2003 ◽  
Vol 14 (3) ◽  
pp. 265-268 ◽  
Author(s):  
Maurizio Magarini ◽  
Arnaldo Spalvieri ◽  
Guido Tartara
Keyword(s):  
Decision Feedback ◽  
Mean Square ◽  
The Mean

Limit tolerances for sums of measurement errors

2018 ◽  
Vol 934 (4) ◽  
pp. 59-62
Author(s):  
V.I. Salnikov
Keyword(s):  
Normal Distribution ◽  
Mean Square Error ◽  
Gaussian Distribution ◽  
Measurement Errors ◽  
Theory And Practice ◽  
Mean Square ◽  
The Mean ◽  
Limiting Values ◽  
Limiting Value

The question of calculating the limiting values of residuals in geodesic constructions is considered in the case when the limiting value for measurement errors is assumed equal to 3m, ie ∆рred = 3m, where m is the mean square error of the measurement. Larger errors are rejected. At present, the limiting value for the residual is calculated by the formula 3m√n, where n is the number of measurements. The article draws attention to two contradictions between theory and practice arising from the use of this formula. First, the formula is derived from the classical law of the normal Gaussian distribution, and it is applied to the truncated law of the normal distribution. And, secondly, as shown in [1], when ∆рred = 2m, the sums of errors naturally take the value equal to ?pred, after which the number of errors in the sum starts anew. This article establishes its validity for ∆рred = 3m. A table of comparative values of the tolerances valid and recommended for more stringent ones is given. The article gives a graph of applied and recommended tolerances for ∆рred = 3m.

scholarly journals Electrical stimulator with mechanomyography-based real-time monitoring, muscle fatigue detection, and safety shut-off: a pilot study

2020 ◽  
Vol 65 (4) ◽  
pp. 461-468
Author(s):  
Jannatul Naeem ◽  
Nur Azah Hamzaid ◽  
Amelia Wong Azman ◽  
Manfred Bijak
Keyword(s):  
Muscle Fatigue ◽  
Real Time ◽  
Isometric Force ◽  
Mean Square ◽  
Clear Indication ◽  
Initial Value ◽  
Cord Injury ◽  
The Mean ◽  
Electrical Stimulator ◽  
Fatigue Detection

AbstractFunctional electrical stimulation (FES) has been used to produce force-related activities on the paralyzed muscle among spinal cord injury (SCI) individuals. Early muscle fatigue is an issue in all FES applications. If not properly monitored, overstimulation can occur, which can lead to muscle damage. A real-time mechanomyography (MMG)-based FES system was implemented on the quadriceps muscles of three individuals with SCI to generate an isometric force on both legs. Three threshold drop levels of MMG-root mean square (MMG-RMS) feature (thr50, thr60, and thr70; representing 50%, 60%, and 70% drop from initial MMG-RMS values, respectively) were used to terminate the stimulation session. The mean stimulation time increased when the MMG-RMS drop threshold increased (thr50: 22.7 s, thr60: 25.7 s, and thr70: 27.3 s), indicating longer sessions when lower performance drop was allowed. Moreover, at thr70, the torque dropped below 50% from the initial value in 14 trials, more than at thr50 and thr60. This is a clear indication of muscle fatigue detection using the MMG-RMS value. The stimulation time at thr70 was significantly longer (p = 0.013) than that at thr50. The results demonstrated that a real-time MMG-based FES monitoring system has the potential to prevent the onset of critical muscle fatigue in individuals with SCI in prolonged FES sessions.

Die Molekülstruktur des N-Chlorsdiwefeloxiddifluoridimids ClNSOF2 / The Molecular Structure of ClNSOF2

1974 ◽  
Vol 29 (6) ◽  
pp. 901-904 ◽  
Author(s):  
O. Oberhammer ◽  
O. Glemser ◽  
H. Klüver
Keyword(s):  
Molecular Structure ◽  
Electron Diffraction ◽  
Geometric Parameters ◽  
Mean Square ◽  
The Mean

The molecular structure of ClNSOF2 was determined by electron diffraction of gases. The following geometric parameters were obtained:Cl-N=1.715(5), S=N=1.484(7), S=O=1.394(3), S-F=1.548(3) Å, ∢ ClNS=114.7 (8), ∢ FSF=92.6(.8), ∢ NSF=111.8(.9) ∢ NSO=117.4 (3.1) and ∢ OSF=108.6 (.8)°. The results for the mean square amplitudes of vibration are given in the paper and an attempt is made to explain differences in corresponding parameters of some related molecules.

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