Roberge-Weiss endpoint at the physical point ofNf=2+1QCD

The term “stochastic hydrology” implies a statistical approach to hydrologic problems as opposed to classic hydrology which can be considered deterministic in its approach. During the International Hydrology Symposium, held 6-8 September 1967 at Fort Collins, a number of hydrology papers were presented consisting to a large extent of studies on long records of hydrological elements such as river run-off, these being treated as time series in the statistical sense. This approach is, no doubt, of importance for future work especially in relation to prediction problems, and there seems to be no fundamental difficulty for introducing the stochastic concepts into various hydrologic models. There is, however, some developmental work required – not to speak of educational in respect to hydrologists – before the full benefit of the technique is obtained. The present paper is to some extent an exercise in the statistical study of hydrological time series – far from complete – and to some extent an effort to interpret certain features of such time series from a physical point of view. The material used is 30 years of groundwater level observations in an esker south of Uppsala, the observations being discussed recently by Hallgren & Sands-borg (1968).

Download Full-text

Neutron electric dipole moment using lattice QCD simulations at the physical point

Physical Review D ◽

10.1103/physrevd.103.054501 ◽

2021 ◽

Vol 103 (5) ◽

Author(s):

C. Alexandrou ◽

A. Athenodorou ◽

K. Hadjiyiannakou ◽

A. Todaro

Keyword(s):

Dipole Moment ◽

Lattice Qcd ◽

Electric Dipole Moment ◽

Electric Dipole ◽

Neutron Electric Dipole Moment ◽

Physical Point

Download Full-text

New Developments in Aerosol Characterization from the Physical Point of View

Particle & Particle Systems Characterization ◽

10.1002/ppsc.19910080108 ◽

1991 ◽

Vol 8 (1-4) ◽

pp. 35-39

Author(s):

Andreas Schmidt-Ott

Keyword(s):

Point Of View ◽

Physical Point ◽

New Developments ◽

Aerosol Characterization

Download Full-text

Percolation and tortuosity in heart-like cells

Scientific Reports ◽

10.1038/s41598-021-90892-2 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

R. Rabinovitch ◽

Y. Biton ◽

D. Braunstein ◽

I. Aviram ◽

R. Thieberger ◽

...

Keyword(s):

Action Potential ◽

Forest Fire ◽

Sinus Node ◽

Heart Tissue ◽

Point Of View ◽

Physical Point ◽

Electrical Currents ◽

Single Wave ◽

Heart Arrhythmia ◽

The One

AbstractIn the last several years, quite a few papers on the joint question of transport, tortuosity and percolation have appeared in the literature, dealing with passage of miscellaneous liquids or electrical currents in different media. However, these methods have not been applied to the passage of action potential in heart fibrosis (HF), which is crucial for problems of heart arrhythmia, especially of atrial tachycardia and fibrillation. In this work we address the HF problem from these aspects. A cellular automaton model is used to analyze percolation and transport of a distributed-fibrosis inflicted heart-like tissue. Although based on a rather simple mathematical model, it leads to several important outcomes: (1) It is shown that, for a single wave front (as the one emanated by the heart's sinus node), the percolation of heart-like matrices is exactly similar to the forest fire case. (2) It is shown that, on the average, the shape of the transport (a question not dealt with in relation to forest fire, and deals with the delay of action potential when passing a fibrotic tissue) behaves like a Gaussian. (3) Moreover, it is shown that close to the percolation threshold the parameters of this Gaussian behave in a critical way. From the physical point of view, these three results are an important contribution to the general percolation investigation. The relevance of our results to cardiological issues, specifically to the question of reentry initiation, are discussed and it is shown that: (A) Without an ectopic source and under a mere sinus node operation, no arrhythmia is generated, and (B) A sufficiently high refractory period could prevent some reentry mechanisms, even in partially fibrotic heart tissue.

Download Full-text

Experimental travelling waves identification in mechanical structures

Mathematics and Mechanics of Solids ◽

10.1177/1081286517732825 ◽

2017 ◽

Vol 24 (1) ◽

pp. 152-167

Author(s):

Izhak Bucher ◽

Ran Gabai ◽

Harel Plat ◽

Amit Dolev ◽

Eyal Setter

Keyword(s):

Energy Flux ◽

Power Flow ◽

Reactive Power ◽

Mechanical Energy ◽

Travelling Waves ◽

Electrical Power ◽

Normal Modes ◽

Standing Waves ◽

Amplitude Curve ◽

Physical Point

Vibrations are often represented as a sum of standing waves in space, i.e. normal modes of vibration. While this can be mathematically accurate, the representation as travelling waves can be compact and more appropriate from a physical point of view, in particular when the energy flux along the structure is meaningful. The quantification of travelling waves assists in computing the energy being transferred and propagated along a structure. It can provide local as well as global information about the structure through which the mechanical energy flows. Presented in this paper is a new method to quantify the fraction of mechanical power being transmitted in a vibration cycle at a specific direction in space using measured data. It is shown that the method can detect local defects causing slight non-uniformity of the energy flux. Equivalence is being made with the electrical power factor and electromagnetic standing waves ratio, commonly employed in such cases. Other methods to perform experiment based wave identification in one-dimension are compared with the power flow based identification. Including a signal processing approach that fits an ellipse to the complex amplitude curve and Hilbert transform for obtaining the local phase and amplitude. A new representation of the active and reactive power flow is developed and its relationship to standing waves ratio is demonstrated analytically and experimentally.

Download Full-text

Focal transformation, an imaging concept for signal restoration and noise removal

Geophysics ◽

10.1190/1.2356996 ◽

2006 ◽

Vol 71 (6) ◽

pp. A55-A59 ◽

Cited By ~ 36

Author(s):

A. J. Berkhout ◽

D. J. Verschuur

Keyword(s):

Input Data ◽

Noise Removal ◽

Point Of View ◽

Data Interpolation ◽

Signal Restoration ◽

Physical Point ◽

Seismic Processing ◽

Promising Tool ◽

Focal Area ◽

Forward Operator

Interpolation of data beyond aliasing limits and removal of noise that occurs within the seismic bandwidth are still important problems in seismic processing. The focal transform is introduced as a promising tool in data interpolation and noise removal, allowing the incorporation of macroinformation about the involved wavefields. From a physical point of view, the principal action of the forward focal operator is removing the spatial phase of the signal content from the input data, and the inverse focal operator restores what the forward operator has removed. The strength of the method is that in the transformed domain, the focused signals at the focal area can be separated from the dispersed noise away from the focal area. Applications of particular interest in preprocessing are interpolation of missing offsets and reconstruction of signal beyond aliasing. The latter can be seen as the removal of aliasing noise.

Download Full-text

Nucleon electromagnetic form factors using lattice simulations at the physical point

Physical Review D ◽

10.1103/physrevd.96.034503 ◽

2017 ◽

Vol 96 (3) ◽

Cited By ~ 23

Author(s):

C. Alexandrou ◽

M. Constantinou ◽

K. Hadjiyiannakou ◽

K. Jansen ◽

Ch. Kallidonis ◽

...

Keyword(s):

Form Factors ◽

Electromagnetic Form Factors ◽

Physical Point

Download Full-text

Comparison of Different Approaches to Predict the Performance of Pumps As Turbines (PATs)

Energies ◽

10.3390/en11041016 ◽

2018 ◽

Vol 11 (4) ◽

pp. 1016 ◽

Cited By ~ 4

Author(s):

Mauro Venturini ◽

Stefano Alvisi ◽

Silvio Simani ◽

Lucrezia Manservigi

Keyword(s):

Simulation Model ◽

Ad Hoc ◽

Polynomial Regression ◽

Point Of View ◽

Box Model ◽

Physical Point ◽

Evolutionary Polynomial Regression ◽

Box Models ◽

Performance Curves ◽

Physics Based Simulation

This paper deals with the comparison of different methods which can be used for the prediction of the performance curves of pumps as turbines (PATs). The considered approaches are four, i.e., one physics-based simulation model (“white box” model), two “gray box” models, which integrate theory on turbomachines with specific data correlations, and one “black box” model. More in detail, the modeling approaches are: (1) a physics-based simulation model developed by the same authors, which includes the equations for estimating head, power, and efficiency and uses loss coefficients and specific parameters; (2) a model developed by Derakhshan and Nourbakhsh, which first predicts the best efficiency point of a PAT and then reconstructs their complete characteristic curves by means of two ad hoc equations; (3) the prediction model developed by Singh and Nestmann, which predicts the complete turbine characteristics based on pump shape and size; (4) an Evolutionary Polynomial Regression model, which represents a data-driven hybrid scheme which can be used for identifying the explicit mathematical relationship between PAT and pump curves. All approaches are applied to literature data, relying on both pump and PAT performance curves of head, power, and efficiency over the entire range of operation. The experimental data were provided by Derakhshan and Nourbakhsh for four different turbomachines, working in both pump and PAT mode with specific speed values in the range 1.53–5.82. This paper provides a quantitative assessment of the predictions made by means of the considered approaches and also analyzes consistency from a physical point of view. Advantages and drawbacks of each method are also analyzed and discussed.

Download Full-text