Stochastic Sequences with a Regenerative Structure that May Depend Both on the Future and on the Past

Many regenerative arguments in stochastic processes use random times which are akin to stopping times, but which are determined by the future as well as the past behaviour of the process of interest. Such arguments based on ‘conditioning on the future’ are usually developed in an ad-hoc way in the context of the application under consideration, thereby obscuring the underlying structure. In this paper we give a simple, unified, and more general treatment of such conditioning theory. We further give a number of novel applications to various particle system models, in particular to various flavours of contact processes and to infinite-bin models. We give a number of new results for existing and new models. We further make connections with the theory of Harris ergodicity.

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Stochastic Sequences with a Regenerative Structure that May Depend Both on the Future and on the Past

Advances in Applied Probability ◽

10.1239/aap/1386857859 ◽

2013 ◽

Vol 45 (4) ◽

pp. 1083-1110 ◽

Cited By ~ 1

Author(s):

Sergey Foss ◽

Stan Zachary

Keyword(s):

Ad Hoc ◽

Particle System ◽

Stopping Times ◽

Underlying Structure ◽

Contact Processes ◽

The Past ◽

Conditioning Theory ◽

The Future ◽

Novel Applications ◽

Random Times

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Time Direction of Information Propagation and Cosmology

Australian Journal of Physics ◽

10.1071/ph720207 ◽

1972 ◽

Vol 25 (2) ◽

pp. 207 ◽

Cited By ~ 2

Author(s):

DT Pegg

Keyword(s):

Steady State ◽

Ad Hoc ◽

Big Bang ◽

Information Propagation ◽

The Past ◽

The Future ◽

Consistent Solution ◽

Electrodynamic Theory ◽

The Universe ◽

State Universe

In conventional electrodynamic theory, the advanced potential solution of Maxwell's equations is discarded on the ad hoc basis that information can be received from the past only and not from the future. This difficulty is overcome by the Wheeler?Feynman absorber theory, but unfortunately the existence of a completely retarded solution in this theory requires a steady-state universe. In the present paper conventional electrodynamics is used to obtain a condition which, if satisfied, allows information to be received from the past only, and ensures that the retarded potential is the only consistent solution. The condition is that a function Ua of the future structure of the universe is infinite, while the corresponding function Ur of the past structure is finite. Of the currently acceptable cosmological models, only the steady-state, the open big-bang, and the Eddington-Lema�tre models satisfy this condition. In these models there is no need for an ad hoc reason for the preclusion of advanced potentials.

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The Future of Analytical Paleobiology

Short Courses in Paleontology ◽

10.1017/s2475263000002208 ◽

1991 ◽

Vol 4 ◽

pp. 207-216 ◽

Cited By ~ 20

Author(s):

David M. Raup

Keyword(s):

Ad Hoc ◽

Full Range ◽

The Past ◽

The Future ◽

The Way

In the past few decades, we have come a long way in making paleobiology more rigorous. We have accumulated an impressive array of quantitative techniques – statistical and otherwise – and these are in use with the full range of paleobiological problems. Also striking is the way the added rigor of our science has spilled over into non-quantitative judgments and interpretations. No longer is the Just-So Story allowed to stand unchallenged. Rather, we respond to these bald assertions and ad hoc theories with: “Can you prove it?” or “Can this be tested?”

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ASME Post Construction Standards: 25 Years of Progress

10.1115/pvp2021-62836 ◽

2021 ◽

Author(s):

Clay D. Rodery

Keyword(s):

Ad Hoc ◽

Task Group ◽

Maintenance And Repair ◽

The Past ◽

The Future ◽

History Of ◽

Inspection And Maintenance ◽

Engineering Practices

Abstract The ASME Post Construction Standards Committee was formed in 1995 in response to an identified need for recognized and generally accepted engineering practices for the inspection and maintenance of pressure equipment after it has been placed in service. In 2020, the Committee marked its 25th year since its inception. This paper provides an overview of the history of that journey. It begins with a review of how post construction activities were addressed in the past, and how requirements for inspection, maintenance and repair of pressure equipment were addressed up until the early 1990s. It then chronicles the ASME activities from the formation of an ad-hoc task group through the formation of the committee, the identification of areas where standards were needed, and the publication of post construction standards within its scope. The paper also provides an overview of the post construction standards the committee has published, as well as other related documents and workshop activities. The paper concludes with a look into the future, including strengths, weaknesses, opportunities, and threats. It is hoped that this paper offers unique insights into the history of post construction standards for pressure equipment and provides a case for continued involvement by interested volunteers to further develop and advance the mission of the committee.

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