Advances in atomic oxygen simulation

Atomic oxygen (AO) present in the atmosphere at orbital altitudes of 200 to 700 km has been shown to degrade various exposed materials on Shuttle flights. The relative velocity of the AO with the spacecraft, together with the AO density, combine to yield an environment consisting of a 5 eV beam energy with a flux of 10(exp 14) to 10(exp 15) oxygen atoms/sq cm/s. An AO ion beam apparatus that produces flux levels and energy similar to that encountered by spacecraft in low Earth orbit (LEO) has been in existence since 1987. Test data was obtained from the interaction of the AO ion beam with materials used in space applications (carbon, silver, kapton) and with several special coatings of interest deposited on various surfaces. The ultimate design goal of the AO beam simulation device is to produce neutral AO at sufficient flux levels to replicate on-orbit conditions. A newly acquired mass spectrometer with energy discrimination has allowed 5 eV neutral oxygen atoms to be separated and detected from the background of thermal oxygen atoms of approx 0.2 eV. Neutralization of the AO ion beam at 5 eV was shown at the Martin Marietta AO facility

Recent advances in the simulation of particle-laden flows

A substantial number of algorithms exists for the simulation of moving particles suspended in fluids. However, finding the best method to address a particular physical problem is often highly non-trivial and depends on the properties of the particles and the involved fluid(s) together. In this report we provide a short overview on a number of existing simulation methods and provide two state of the art examples in more detail. In both cases, the particles are described using a Discrete Element Method (DEM). The DEM solver is usually coupled to a fluid-solver, which can be classified as grid-based or mesh-free (one example for each is given). Fluid solvers feature different resolutions relative to the particle size and separation. First, a multicomponent lattice Boltzmann algorithm (mesh-based and with rather fine resolution) is presented to study the behavior of particle stabilized fluid interfaces and second, a Smoothed Particle Hydrodynamics implementation (mesh-free, meso-scale resolution, similar to the particle size) is introduced to highlight a new player in the field, which is expected to be particularly suited for flows including free surfaces.Comment: 16 pages, 4 figure

Simulation-assisted control in building energy management systems

Technological advances in real-time data collection, data transfer and ever-increasing computational power are bringing simulation-assisted control and on-line fault detection and diagnosis (FDD) closer to reality than was imagined when building energy management systems (BEMSs) were introduced in the 1970s. This paper describes the development and testing of a prototype simulation-assisted controller, in which a detailed simulation program is embedded in real-time control decision making. Results from an experiment in a full-scale environmental test facility demonstrate the feasibility of predictive control using a physically-based thermal simulation program

Advances in Molecular Simulation

Molecular simulations are commonly used in physics, chemistry, biology, material science, engineering, and even medicine. This book provides a wide range of molecular simulation methods and their applications in various fields. It reflects the power of molecular simulation as an effective research tool. We hope that the presented results can provide an impetus for further fruitful studies

Simulation in Statistics

Simulation has become a standard tool in statistics because it may be the only tool available for analysing some classes of probabilistic models. We review in this paper simulation tools that have been specifically derived to address statistical challenges and, in particular, recent advances in the areas of adaptive Markov chain Monte Carlo (MCMC) algorithms, and approximate Bayesian calculation (ABC) algorithms.Comment: Draft of an advanced tutorial paper for the Proceedings of the 2011 Winter Simulation Conferenc

Status of NASA/Army rotorcraft research and development piloted flight simulation

The status of the major NASA/Army capabilities in piloted rotorcraft flight simulation is reviewed. The requirements for research and development piloted simulation are addressed as well as the capabilities and technologies that are currently available or are being developed by NASA and the Army at Ames. The application of revolutionary advances (in visual scene, electronic cockpits, motion, and modelling of interactive mission environments and/or vehicle systems) to the NASA/Army facilities are also addressed. Particular attention is devoted to the major advances made in integrating these individual capabilities into fully integrated simulation environment that were or are being applied to new rotorcraft mission requirements. The specific simulators discussed are the Vertical Motion Simulator and the Crew Station Research and Development Facility

Building on the DEPLOY Legacy: Code Generation and Simulation

The RODIN, and DEPLOY projects laid solid foundations for further theoretical, and practical (methodological and tooling) advances with Event-B. Our current interest is the co-simulation of cyber-physical systems using Event-B. Using this approach we aim to simulate various features of the environment separately, in order to exercise deployable code. This paper has two contributions, the first is the extension of the code generation work of DEPLOY, where we add the ability to generate code from Event-B state-machine diagrams. The second describes how we may use code, generated from state-machines, to simulate the environment, and simulate concurrently executing state-machines, in a single task. We show how we can instrument the code to guide the simulation, by controlling the relative rate that non-deterministic transitions are traversed in the simulation.Comment: In Proceedings of DS-Event-B 2012: Workshop on the experience of and advances in developing dependable systems in Event-B, in conjunction with ICFEM 2012 - Kyoto, Japan, November 13, 201