scholarly journals Holographic integral geometry with time dependence

2020 ◽  
Vol 2020 (12) ◽  
Author(s):  
Bartłomiej Czech ◽  
Yaithd D. Olivas ◽  
Zi-zhi Wang
Keyword(s):  
Time Dependence ◽  
Global Symmetries ◽  
Integral Geometry ◽  
Time Dependent ◽  
Rotation Symmetry ◽  
Kinematic Space

Abstract We write down Crofton formulas — expressions that compute lengths of space- like curves in asymptotically AdS3 geometries as integrals over kinematic space — which apply when the curve and/or the background spacetime is time-dependent. Relative to their static predecessor, the time-dependent Crofton formulas display several new features, whose origin is the local null rotation symmetry of the bulk geometry. In pure AdS3 where null rotations are global symmetries, the Crofton formulas simplify and become integrals over the null planes, which intersect the bulk curve.

scholarly journals Renormalization Group Approach to Pandemics as a Time-Dependent SIR Model

2021 ◽  
Vol 8 ◽  
Author(s):  
Michele Della Morte ◽  
Francesco Sannino
Keyword(s):  
Renormalization Group ◽  
Time Dependence ◽  
Recovery Rate ◽  
Sir Model ◽  
Time Dependent ◽  
Cumulative Number ◽  
Group Approach ◽  
Renormalization Group Approach

We generalise the epidemic Renormalization Group framework while connecting it to a SIR model with time-dependent coefficients. We then confront the model with COVID-19 in Denmark, Germany, Italy and France and show that the approach works rather well in reproducing the data. We also show that a better understanding of the time dependence of the recovery rate would require extending the model to take into account the number of deaths whenever these are over 15% of the cumulative number of infected cases.

scholarly journals The Diffraction of Transient Electro-Magnetic Waves by a Wedge

1958 ◽  
Vol 11 (2) ◽  
pp. 95-103 ◽  
Author(s):  
A. C. Butcher ◽  
J. S. Lowndes
Keyword(s):  
Wave Equation ◽  
Time Dependence ◽  
Half Plane ◽  
Line Source ◽  
Time Dependent ◽  
Dimensional Case ◽  
Two Dimensional ◽  
Electro Magnetic ◽  
Infinite Wedge ◽  
Magnetic Waves

Much of the work on the theory of diffraction by an infinite wedge has been for cases of harmonic time-dependence. Oberhettinger (1) obtained an expression for the Green's function of the wave equation in the two dimensional case of a line source of oscillating current parallel to the edge of a wedge with perfectly conducting walls. Solutions of the time-dependent wave equation have been obtained by Keller and Blank (2), Kay (3) and more recently by Turner (4) who considered the diffraction of a cylindrical pulse by a half plane.

scholarly journals DARBOUX CLASS OF COSMOLOGICAL FLUIDS WITH TIME-DEPENDENT ADIABATIC INDICES

2000 ◽  
Vol 15 (15) ◽  
pp. 979-990 ◽  
Author(s):  
H. C. ROSU
Keyword(s):  
Mathematical Method ◽  
Cosmological Constant ◽  
Time Dependence ◽  
Adiabatic Index ◽  
Time Dependent ◽  
Accelerating Universe ◽  
Constant Parameter ◽  
Darboux Transformations ◽  
Scale Factors ◽  
Experimental Findings

A one-parameter family of time-dependent adiabatic indices is introduced for any given type of cosmological fluid of constant adiabatic index by a mathematical method belonging to the class of Darboux transformations. The procedure works for zero cosmological constant at the price of introducing a new constant parameter related to the time dependence of the adiabatic index. These fluids can be the real cosmological fluids that are encountered at cosmological scales and they could be used as a simple and efficient explanation for the recent experimental findings regarding the present day accelerating universe. In addition, new types of cosmological scale factors, corresponding to these fluids, are presented.

scholarly journals Time dependence of recruitment and derecruitment in the lung: a theoretical model

2002 ◽  
Vol 93 (2) ◽  
pp. 705-713 ◽  
Author(s):  
Jason H. T. Bates ◽  
Charles G. Irvin
Keyword(s):  
Mechanical Ventilation ◽  
Theoretical Model ◽  
Lung Injury ◽  
Time Dependence ◽  
Computer Model ◽  
Lung Volume ◽  
Critical Pressure ◽  
Time Dependent ◽  
Lung Elastance ◽  
Parallel Arrangement

Recruitment and derecruitment (R/D) of air spaces within the lung is greatly enhanced in lung injury and is thought to be responsible for exacerbating injury during mechanical ventilation. There is evidence to suggest that R/D is a time-dependent phenomenon. We have developed a computer model of the lung consisting of a parallel arrangement of airways and alveolar units. Each airway has a critical pressure (Pcrit) above which it tends to open and below which it tends to close but at a rate determined by how far pressure is from Pcrit. With an appropriate distribution of Pcrit and R/D velocity characteristics, the model able to produce realistic first and second pressure-volume curves of a lung inflated from an initially degassed state. The model also predicts that lung elastance will increase transiently after a deep inflation to a degree that increases as lung volume decreases and as the lung becomes injured. We conclude that our model captures the time-dependent mechanical behavior of the lung due to gradual R/D of lung units.

scholarly journals Depth- and time-dependent vertical strain rates at Siple Dome, Antarctica

2004 ◽  
Vol 50 (171) ◽  
pp. 511-521 ◽  
Author(s):  
Daniel H. Elsberg ◽  
William D. Harrison ◽  
Mark A. Zumberge ◽  
John L. Morack ◽  
Erin C. Pettit ◽  
...  
Keyword(s):  
Strain Rate ◽  
Time Dependence ◽  
Strain Gauge ◽  
Water Pressure ◽  
Time Dependent ◽  
Strain Rates ◽  
Ice Streams ◽  
Vertical Strain ◽  
Siple Dome ◽  
A Site

AbstractAs part of a project to investigate the flow of ice at low effective stress, two independent strain-gauge systems were used to measure vertical strain rate as a function of depth and time at Siple Dome, Antarctica. The measurements were made from January 1998 until January 2002 at the ice divide and a site 7km to the northeast on the flank. The strain-rate profiles place constraints on the rheology of ice at low stress, show the expected differences between divide and flank flow (with some structure due to firn compaction and probably ice stratigraphy), and suggest that the flow of the ice sheet has not changed much in the last 8.6 kyr. The strain rates show an unexpected time dependence on scales ranging from several months to hours, including discrete summer events at the divide. Time dependence in strain rate, water pressure, seismicity, velocity and possibly basal motion has been seen previously on the Siple Coast ice streams, but it is especially surprising on Siple Dome because the bed is cold.

Reliability Analysis and Numerical Simulation on Time-Dependence of RC Free Beams

2011 ◽  
Vol 105-107 ◽  
pp. 823-826
Author(s):  
Wen Hui Tan ◽  
Yong Gang Pei ◽  
Da Li
Keyword(s):  
Time Dependence ◽  
Working Life ◽  
Reliability Theory ◽  
Time Dependent ◽  
Qualitative And Quantitative Analysis ◽  
Qualitative And Quantitative ◽  
Dependence Problem ◽  
Load Effects ◽  
Influent Factors ◽  
Free Beam

Load effects and resistance are supposed to constant in traditional reliability theory. In fact, load effects and resistances change with time because some influent factors of structures change in long working life. Thus, only structures are safe at every moment in working life are structures safe. A synthetical method of qualitative and quantitative analysis is proposed in this paper to study the time-dependence problem of a RC free beam. Firstly, the time-dependence character of a free beam is simulated by ANSYS program. Then, a time-dependent reliability model of the free beam is established, and a program is edited to get values of resistance and index of reliability in different years, thus, the time-dependent reliability of the RC free beam is assessed. The results showed that the value of the resistance decreased 20 percent and the reliability index cut half down after 50 years, so time-dependence should be considered to achieve correct results when the reliability of in-service structures is estimated and new structures are designed.

scholarly journals Dynamic Time Dependent Hexagonal Magnetoconvection

1985 ◽  
Vol 38 (6) ◽  
pp. 885 ◽  
Author(s):  
JM Lopez ◽  
JO Murphy
Keyword(s):  
Magnetic Field ◽  
Rayleigh Number ◽  
Time Dependence ◽  
Single Mode ◽  
Time Dependent ◽  
Oscillatory Solutions ◽  
Field Amplification ◽  
Nonzero Mean ◽  
Dynamic Time ◽  
Parameter Ranges

The time dependence of the single mode hexagonal magnetoconvective system has been investigated numerically at high Rayleigh number. It is established that, in certain parameter ranges, the system has oscillatory solutions which not only have a periodic nature, but also develop into chaotic and intermittent solutions. Further, the system generates nonzero mean kinetic and magnetic helicity together with substantial magnetic field amplification. These features are shown to be maintained in time without any externally imposed rotation of the system.

Understanding the Excited State Photophysics of Pyrrolopyrrole-Dione Isomers and Derivatives Using Time-Dependence Density Functional Theory

2017 ◽  
Vol 05 (03) ◽  
pp. 1750009
Author(s):  
Teck Lip Dexter Tam ◽  
Ting Ting Lin ◽  
Steven Lukman
Keyword(s):  
Density Functional Theory ◽  
Photodynamic Therapy ◽  
Excited State ◽  
Time Dependence ◽  
Density Functional ◽  
Photophysical Properties ◽  
Cost Effective ◽  
Time Dependent ◽  
Functional Theory ◽  
Dependent Density

The ability to understand and predict excited state photophysics is vital for the development of photo- and electroluminescence materials, as well as light harvesting materials and photodynamic therapy. Herein, we demonstrate that single determinant time-dependent density functional theory can be computationally cost-effective and has the ability to explain both experimental singlet and triplet dynamics of pyrrolo[3,4-[Formula: see text]]pyrrole-1,4-dione and pyrrolo[3,2-b]pyrrole-2,5-dione isomers with intriguing photophysical properties. We also used the methodology to predict the photophysical properties of pyrrolo[3,4-c]pyrrole-1,3-dione and a hypothetical hybrid pyrrolo[3,4-b]pyrrole-2,4-dione isomers.

Critical issues In The Mechanical Reliability of Lightguide Fibers

1998 ◽  
Vol 531 ◽  
Author(s):  
C. R. Kurkjian
Keyword(s):  
Time Dependence ◽  
Safety Factor ◽  
Strength Degradation ◽  
Time Dependent ◽  
Mechanical Reliability ◽  
Strength Limit ◽  
Dependent Behavior ◽  
Critical Issues

AbstractIn order to guarantee a minimum initial strength, lightguide fibers are proof-tested. However, the strength of these fibers is known to depend on time (due to fatigue and aging) and this time-dependence must be taken into account in the calculation of fiber lifetimes. While hermetic coatings can be applied to eliminate strength degradation with time, they are rarely used. It is thus necessary to understand the time-dependent behavior well enough to ensure a desired lifetime (without an excessive and costly safety factor), or alternatively, it is necessary to validate a fundamental strength limit. This paper discusses the progress that has been made on issues related to such fiber lifetime predictions. In particular, it is pointed out that the possible variations in flaw character and coating chemistry make simple generalizations difficult and require that fundamental understandings be developed.

Sign in / Sign up

Export Citation Format

Share Document