Engineering topics

Sloan, David

Publications and source records attributed to Sloan, David.

5 records

DOE OSTI2016

Relative likelihood for life as a function of cosmic time

Is life most likely to emerge at the present cosmic time near a star like the Sun? We address this question by calculating the relative formation probability per unit time of habitable Earth-like planets within a fixed comoving volume of the Universe, dP ( t )/ dt , starting from the first stars and continuing to the distant cosmic future. We conservatively restrict our attention to the context of ''life as we know it'' and the standard cosmological model, ΛCDM . We find that unless habitability around low mass stars is suppressed, life is most likely to exist near ∼ 0.1 M {sub ⊙} stars ten trillion years from now. Spectroscopic searches for biosignatures in the atmospheres of transiting Earth-mass planets around low mass stars will determine whether present-day life is indeed premature or typical from a cosmic perspective.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2016

Current observations with a decaying cosmological constant allow for chaotic cyclic cosmology

We use the phase plane analysis technique of Madsen and Ellis [1] to consider a universe with a true cosmological constant as well as a cosmological 'constant' that is decaying. Time symmetric dynamics for the inflationary era allows eternally bouncing models to occur. Allowing for scalar field dynamic evolution, we find that if dark energy decays in the future, chaotic cyclic universes exist provided the spatial curvature is positive. This is particularly interesting in light of current observations which do not yet rule out either closed universes or possible evolution of the cosmological constant. We present only a proof of principle, with no definite claim on the physical mechanism required for the present dark energy to decay.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2013

Process/Engineering Co-Simulation of Oxy-Combustion and Chemical Looping Combustion

Over the past several years, the DOE has sponsored various funded programs, collectively referred to as Advanced Process Engineering Co-Simulator (APECS) programs, which have targeted the development of a steady-state simulator for advanced power plants. The simulator allows the DOE and its contractors to systematically evaluate various power plant concepts, either for preliminary conceptual design or detailed final design.

20 FOSSIL-FUELED POWER PLANTS↗

DOE OSTI2011

Hamiltonian formulation of the Belinskii-Khalatnikov-Lifshitz conjecture

The Belinskii, Khalatnikov, and Lifshitz conjecture [V. A. Belinskii, I. M. Khalatnikov, and E. M. Lifshitz, Adv. Phys. 19, 525 (1970)] posits that on approach to a spacelike singularity in general relativity the dynamics are well approximated by ''ignoring spatial derivatives in favor of time derivatives.'' In A. Ashtekar, A. Henderson, and D. Sloan, Classical Quantum Gravity 26, 052 001 (2009), we examined this idea from within a Hamiltonian framework and provided a new formulation of the conjecture in terms of variables well suited to loop quantum gravity. We now present the details of the analytical part of that investigation. While our motivation came from quantum considerations, thanks to some of its new features, our formulation should be useful also for future analytical and numerical investigations within general relativity.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2010

Software Framework for Advanced Power Plant Simulations

This report summarizes the work accomplished during the Phase II development effort of the Advanced Process Engineering Co-Simulator (APECS). The objective of the project is to develop the tools to efficiently combine high-fidelity computational fluid dynamics (CFD) models with process modeling software. During the course of the project, a robust integration controller was developed that can be used in any CAPE-OPEN compliant process modeling environment. The controller mediates the exchange of information between the process modeling software and the CFD software. Several approaches to reducing the time disparity between CFD simulations and process modeling have been investigated and implemented. These include enabling the CFD models to be run on a remote cluster and enabling multiple CFD models to be run simultaneously. Furthermore, computationally fast reduced-order models (ROMs) have been developed that can be 'trained' using the results from CFD simulations and then used directly within flowsheets. Unit operation models (both CFD and ROMs) can be uploaded to a model database and shared between multiple users.

99 GENERAL AND MISCELLANEOUS↗