On: “The critical reflection theorem” by J. T. Fokkema and A. Ziolkowski (GEOPHYSICS, 52, 965–972, July 1987).

Geophysics ◽  
1988 ◽  
Vol 53 (11) ◽  
pp. 1490-1491
Author(s):  
Andrew Walden ◽  
Roy White
Keyword(s):  
Critical Reflection ◽  
The Earth ◽  
Reflection Theorem

In this paper, Fokkema and Ziolkowski consider precritical and postcritical incidence and resulting implications for the reflection response of the earth. The ideas are interesting and thought provoking, but their inferences with regard to the whiteness assumption in standard deconvolution are misleading. We will endeavor to show why.

scholarly journals The critical reflection theorem

Geophysics ◽  
1987 ◽  
Vol 52 (7) ◽  
pp. 965-972 ◽  
Author(s):  
Jacob T. Fokkema ◽  
Anton Ziolkowski
Keyword(s):  
Plane Wave ◽  
Half Space ◽  
Critical Reflection ◽  
Lower Layer ◽  
Plane Waves ◽  
Source Spectrum ◽  
Demarcation Criterion ◽  
The Earth ◽  
Reflection Theorem ◽  
Uppermost Layer

In predictive deconvolution of seismic data, it is assumed that the response of the earth is white. Any nonwhite components are presumed to be caused by the source wavelet or by unwanted multiples. We show that this whiteness assumption is invalid at precritical incidence. We consider plane waves incident on a layered acoustic half‐space. At exactly critical incidence at any interface in the half‐space, the lower layer acts similar to a rigid plate. The response of the half‐space is then all‐pass, or white. This result we call the critical reflection theorem. The response is also white if the waves are postcritically incident on the lower half‐space. In normal data processing these postcritical components are removed by muting. Thus the whiteness assumption is normally applied to exactly that part of the data where it is invalid. The demarcation between precritical and postcritical incidence can be exploited for the purposes of deconvolution, provided the data can be decomposed into plane waves. To develop this application, we consider the response of a point source in the uppermost layer of the layered half‐space, with a free surface above. The response is simply a superposition of the plane‐wave responses already studied, with complications introduced by the source and receiver ghosts and by multiples in the upper layer. At postcritical incidence the earth response is white for all plane‐wave components; the source spectrum may be estimated from the postcritical plane‐wave components after removing the effects of ghosts and multiples in the upper layer. If the source signature is already known, the demarcation criterion can be used to separate intrinsic absorption effects from attenuation effects caused by scattering.

scholarly journals De strijd der twee zielen in het werk van Walter Schubart

Literator ◽  
2012 ◽  
Vol 33 (2) ◽  
Author(s):  
Hans Ester
Keyword(s):  
Twentieth Century ◽  
Cultural History ◽  
Critical Reflection ◽  
Western Culture ◽  
The Other ◽  
Cultural Critique ◽  
The Earth ◽  
The People ◽  
The One ◽  
Europe Today

The struggle between two souls in the work of Walter Schubart.This essay explores the relevance of the work of Walter Schubart (1897-±1941), a virtually unknown cultural philosopher from Lithuania, for today. The writer focuses on the importance of Schubart’s programme of spiritual rebirth and on his intriguing vision for the people of Europe today. To counterbalance the metaphysical egotism of Europe, Schubart finds in Russia, and in Dostoyevsky in particular, a living consciousness of a relation to the whole that could heal Europe. The twentieth century is for Schubart a battlefield between, on the one hand, the promethean period of deserting God focusing on the earth, and on the other hand, the johannean period of the Messianic era that acts out of a desire for charity and healing. Despite criticism of Schubart’s somewhat simplistic views of cultural history, the author emphasises the surprising topical manner in which Schubart’s cultural critique confronts modern Western culture with a critical reflection of itself.

scholarly journals The critical reflection theorem

1985 ◽  
Author(s):  
J. T. Fokkema ◽  
A. Ziolkowski
Keyword(s):  
Critical Reflection ◽  
Reflection Theorem

scholarly journals El horizonte del sol poniente. Una reflexión histórico-crítica sobre el Camino de Santiago / The Horizon of the Setting Sun. A historical-Critical Reflection on the St. James' Way

2016 ◽  
Vol 23 ◽  
pp. 113
Author(s):  
Fernando DOMÍNGUEZ REBOIRAS
Keyword(s):  
At Risk ◽  
Critical Reflection ◽  
Ordinary Life ◽  
Camino De Santiago ◽  
The Earth ◽  
The World ◽  
End Of The World ◽  
Miraculous Healing

One of the most remarkable features of the St. James’ Way in its heyday (12th to 15th centuries) was, no doubt, the consideration of St. James’ grave as the border of the Christian boundaries and cosmos. Compostela was the shrine at the end of the world; it marked the Western limit of the Christendom, i.e., Rome’s domains towards the setting sun. This constituted its strategic privilege and was the main source of its meaning: A way towards the end but with the willingness to start afresh. The Jacobean pilgrim did not look for any miraculous healing, but he longed for a renewed comeback to his ordinary life after he had put his life at risk and made that unique effort of experiencing the boundaries of the earth and the last skyline.

12. Encountering the Anthropocene

2021 ◽  
pp. 251-260
Author(s):  
John S. Dryzek
Keyword(s):  
Critical Reflection ◽  
Earth System ◽  
The Earth ◽  
Environmental Discourses ◽  
Democratic Engagement ◽  
Important Quality

This chapter examines environmental discourses in light of recognition of humanity’s entry into the Anthropocene, an emerging geological epoch that dramatizes what is at stake in the politics of the Earth. The Anthropocene is the successor to the unusually benign and stable Holocene of the previous 12,000 years, during which human civilization evolved. The human institutions, practices, ideas, and discourses that still dominate the politics of the Earth all took shape under perceived Holocene conditions. The most important quality demanded of the configuration of environmental discourses is now a capacity to generate critical reflection on the trajectory of human societies in the context of an unstable Earth system. This will require meaningful deliberative and democratic engagement across discourses.

The motion of a lunar orbiter

1966 ◽  
Vol 25 ◽  
pp. 373
Author(s):  
Y. Kozai
Keyword(s):  
Degrees Of Freedom ◽  
Dimensional Space ◽  
Artificial Satellite ◽  
Equations Of Motion ◽  
Triaxial Ellipsoid ◽  
The Moon ◽  
Secular Motion ◽  
The Earth ◽  
Close Satellite ◽  
The Mean

The motion of an artificial satellite around the Moon is much more complicated than that around the Earth, since the shape of the Moon is a triaxial ellipsoid and the effect of the Earth on the motion is very important even for a very close satellite.The differential equations of motion of the satellite are written in canonical form of three degrees of freedom with time depending Hamiltonian. By eliminating short-periodic terms depending on the mean longitude of the satellite and by assuming that the Earth is moving on the lunar equator, however, the equations are reduced to those of two degrees of freedom with an energy integral.Since the mean motion of the Earth around the Moon is more rapid than the secular motion of the argument of pericentre of the satellite by a factor of one order, the terms depending on the longitude of the Earth can be eliminated, and the degree of freedom is reduced to one.Then the motion can be discussed by drawing equi-energy curves in two-dimensional space. According to these figures satellites with high inclination have large possibilities of falling down to the lunar surface even if the initial eccentricities are very small.The principal properties of the motion are not changed even if plausible values ofJ3andJ4of the Moon are included.This paper has been published in Publ. astr. Soc.Japan15, 301, 1963.

Formation of Lunar Craters and Bright Rays as a Result of Meteorite Impacts

1962 ◽  
Vol 14 ◽  
pp. 415-418
Author(s):  
K. P. Stanyukovich ◽  
V. A. Bronshten
Keyword(s):  
Explosive Charge ◽  
The Moon ◽  
Meteorite Impacts ◽  
The Earth ◽  
Lunar Craters ◽  
The Impact

The phenomena accompanying the impact of large meteorites on the surface of the Moon or of the Earth can be examined on the basis of the theory of explosive phenomena if we assume that, instead of an exploding meteorite moving inside the rock, we have an explosive charge (equivalent in energy), situated at a certain distance under the surface.

The Origin of the Moon

1962 ◽  
Vol 14 ◽  
pp. 149-155 ◽  
Author(s):  
E. L. Ruskol
Keyword(s):  
Chemical Composition ◽  
Solar System ◽  
The Moon ◽  
The Earth ◽  
The Difference ◽  
Origin Of The Moon

The difference between average densities of the Moon and Earth was interpreted in the preceding report by Professor H. Urey as indicating a difference in their chemical composition. Therefore, Urey assumes the Moon's formation to have taken place far away from the Earth, under conditions differing substantially from the conditions of Earth's formation. In such a case, the Earth should have captured the Moon. As is admitted by Professor Urey himself, such a capture is a very improbable event. In addition, an assumption that the “lunar” dimensions were representative of protoplanetary bodies in the entire solar system encounters great difficulties.

The Origin of the Moon and its Relationship to the Origin of the Solar System

1962 ◽  
Vol 14 ◽  
pp. 133-148 ◽  
Author(s):  
Harold C. Urey
Keyword(s):  
Solar System ◽  
The Moon ◽  
The Past ◽  
The Earth ◽  
Short Period ◽  
Origin Of The Moon

During the last 10 years, the writer has presented evidence indicating that the Moon was captured by the Earth and that the large collisions with its surface occurred within a surprisingly short period of time. These observations have been a continuous preoccupation during the past years and some explanation that seemed physically possible and reasonably probable has been sought.

Probable Structure and Nature of the Formations on the Reverse Side of the Moon According to Photometric Measurements of Lunar Photographs

1962 ◽  
Vol 14 ◽  
pp. 39-44
Author(s):  
A. V. Markov
Keyword(s):  
The Moon ◽  
Probable Structure ◽  
The Earth ◽  
Interplanetary Station ◽  
Photometric Measurements ◽  
Automatic Interplanetary Station

Notwithstanding the fact that a number of defects and distortions, introduced in transmission of the images of the latter to the Earth, mar the negatives of the reverse side of the Moon, indirectly obtained on 7 October 1959 by the automatic interplanetary station (AIS), it was possible to use the photometric measurements of the secondary (terrestrial) positives of the reverse side of the Moon in the experiment of the first comparison of the characteristics of the surfaces of the visible and invisible hemispheres of the Moon.

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