Proposed benchmark problem for machine-learning in phase field
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Dingreville, Remi Philippe Michel↗
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Steady-state solution to the conduction problem of a spherical balloon radiometer, phases 1 and 2
A satellite system proposed for observing the earth's radiation balance employing spherical balloon radiometers is investigated. In the steady-state condition of radiative equilibrium, the magnitudes of absorbed external irradiances are sensed by internal radiometers mounted on the skin of each balloon. The temperatures of the radiometers are monitored as a measure of the balloons' internal irradiances (equal to absorbed external irradiances) and telemetered to earth. The effect of the magnitude of irradiant sources, balloon thickness, and thermal conductivity on the conduction of heat is assessed mathematically in order to determine its impact on measurement accuracy. Results indicate that observations are acceptable during daytime and nighttime modes of operation.
House, F. B.↗
QAOA: State Preparation, Phase Separators and Mixers for constrained problems
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Baertschi, Andreas↗
An implementation of the phase-field model based on coupled thermomechanical finite element solvers for large-strain twinning, explicit dynamic fracture and the classical Stefan problem
The implementation of a phase-field model in finite elements usually requires significant expertise and involves the development of a user element with additional degrees of freedom. An alternative implementation of the phase-field model within a thermo-mechanical finite element simulation package was presented in (Cho et al 2012 Int. J. Solids Struct. 49 1973–1992), where the phase-field variable is treated as the temperature degree of freedom. However, this approach has only been used for small strain phase-field modelling of martensitic transformations and quasistatic phase-field modelling of fracture. Here, we present a phase-field finite element implementation via the temperature degree of freedom for several additional cases from the literature: (i) the large-strain phase-field description of deformation twinning presented in (Clayton and Knap 2011 Physica D 240 841–858), (ii) phase-field description of brittle fracture with inertial effects based on the theory from (Molnár and Gravouil 2017, Finite Elem. Anal. Des. 130 27–38) and (Miehe et al 2010 Int. J. Numer. Methods Eng. 83 1273–1311) and (iii) the classical Stefan problem of solidification presented in (Mackenzie and Robertson 2002 J. Comput. Phys. 181 526–544). The last problem involves the temperature and phase-field variables as unknowns.
36 MATERIALS SCIENCE↗
Clarification process: Resolution of decision-problem conditions
A model of a general process which occurs in both decisionmaking and problem-solving tasks is presented. It is called the clarification model and is highly dependent on information flow. The model addresses the possible constraints of individual indifferences and experience in achieving success in resolving decision-problem conditions. As indicated, the application of the clarification process model is only necessary for certain classes of the basic decision-problem condition. With less complex decision problem conditions, certain phases of the model may be omitted. The model may be applied across a wide range of decision problem conditions. The model consists of two major components: (1) the five-phase prescriptive sequence (based on previous approaches to both concepts) and (2) the information manipulation function (which draws upon current ideas in the areas of information processing, computer programming, memory, and thinking). The two components are linked together to provide a structure that assists in understanding the process of resolving problems and making decisions.
Dieterly, D. L.↗
Profiles of fatigue damage in graphite/epoxy composites from ultrasonic transmission power spectra
Early fatigue damage in non-unidirectional multi-ply graphite/epoxy composites is manifested by a distribution of cracks and disbonds through the bulk of the material. Such damage is subtle and is difficult to detect with conventional ultrasonic technology. Consequently, a new ultrasonic measurement technique called phase-insensitive tone-burst spectroscopy has been developed. The new technique eliminates problems associated with phase cancellation and pulse shape artifacts inherent to conventional broadband ultrasonic spectral measurement systems and produces clean spectral information irrespective of specimen inhomogeneity or irregularities in surface geometry. Application of the new technique to measurements of graphite/epoxy composites has yielded frequency-domain profiles that show distinct differences in ultrasonic attenuation, attenuation slope, and velocity for each specimen experiencing a different level of fatigue damage.
Cantrell, J. H., Jr.↗
Mixed Integer Programming and Heuristic Scheduling for Space Communication Networks
In this paper, we propose to solve the constrained optimization problem in two phases. The first phase uses heuristic methods such as the ant colony method, particle swarming optimization, and genetic algorithm to seek a near optimal solution among a list of feasible initial populations. The final optimal solution can be found by using the solution of the first phase as the initial condition to the SQP algorithm. We demonstrate the above problem formulation and optimization schemes with a large-scale network that includes the DSN ground stations and a number of spacecraft of deep space missions.
Communication Network Scheduling↗
Optimal dynamic remapping of parallel computations
A large class of computations are characterized by a sequence of phases, with phase changes occurring unpredictably. The decision problem was considered regarding the remapping of workload to processors in a parallel computation when the utility of remapping and the future behavior of the workload is uncertain, and phases exhibit stable execution requirements during a given phase, but requirements may change radically between phases. For these problems a workload assignment generated for one phase may hinder performance during the next phase. This problem is treated formally for a probabilistic model of computation with at most two phases. The fundamental problem of balancing the expected remapping performance gain against the delay cost was addressed. Stochastic dynamic programming is used to show that the remapping decision policy minimizing the expected running time of the computation has an extremely simple structure. Because the gain may not be predictable, the performance of a heuristic policy that does not require estimnation of the gain is examined. The heuristic method's feasibility is demonstrated by its use on an adaptive fluid dynamics code on a multiprocessor. The results suggest that except in extreme cases, the remapping decision problem is essentially that of dynamically determining whether gain can be achieved by remapping after a phase change. The results also suggest that this heuristic is applicable to computations with more than two phases.
Nicol, David M.↗
MEUMAPPS (C++ Version)
Many materials, metal alloys in particular, have features on the on micrometer or nanometer scale that have a large impact on the properties of the material. These features are known as the microstructure of the material. Understanding why and how the microstructure forms in a material is of fundamental scientific interest as well as of significant technological interest. The capability to predict microstructure evolution in a material allows the intentional design of microstructures and hence the intentional design of material properties. The phase-field method is one of the leading methods for predicting microstructure evolution. One of the most significant problems for phase-field models is their computational expense. Even limited phase-field simulations can easily require thousands of CPU core-hours to complete, which significantly limits their use. This code provides both a general framework for creating scalable, GPU-accelerated phase-field model applications as well as several applications themselves. The code is capable of using hundreds of GPUs efficiently, which greatly reduces the time required to perform simulations. The code is written with an emphasis on performance portability, that is the ability for the code to run efficiently on a number of different computing architectures without modification of the source code. The performance portability of this code is primarily enabled through the use of two libraries, Kokkos (performance portable data structures and execution patterns) and heFFTe (performance portable distributed 3D fast Fourier transforms). The code consists of a core library, applications, and tests. The core library includes shared functionality between applications. This includes interfaces with fast Fourier transform (FFT) libraries such as heFFTe, data structures based on Kokkos, file input and output capabilities, and a solver for infinitesimal strain mechanical equilibrium problems. Five applications are included in the code. The flagship application is the MEUMAPPS-SS application, which implements the Kim-Kim-Suzuki phase-field model for precipitation for an arbitrary number of phases and components in a metal alloy. Five simpler applications are also included that solve the Eshelby inclusion problem, Allen-Cahn equation, the coupled Allen-Cahn and diffusion equations, and the Cahn-Hilliard equation. The code includes two applications to solve the Cahn-Hilliard equation, one with constant-step-size first-order time integration and the second with adaptive high-order time integration.
DeWitt, Stephen [Oak Ridge National Lab. (ORNL), O↗
Numerical integration of nearly-Hamiltonian systems
The reported investigation is concerned with the solution of systems of differential equations which are derived from a Hamiltonian function in the extended phase space. The problem selected involves a one-dimensional perturbed harmonic oscillator. The van der Pol equation considered has an exact asymptotic value for its amplitude. Comparisons are made between a numerical solution and a known analytical solution. In addition to the van der Pol problem, known solutions regarding the restricted problem of three bodies are used as examples for perturbed Keplerian motion. The extended phase space Hamiltonian discussed by Stiefel and Scheifele (1971) is considered. A description is presented of two canonical formulations of the perturbed harmonic oscillator.
Bond, V. R.↗
Pathfinder operations
In 1981, the Inter-Agency Consultative Group (composed of European, Soviet, Japanese and American space agency representatives) conceived the idea of using the two Soviet Vega spacecraft as pathfinders for Giotto since they would arrive at Halley's Comet approximately one week before Giotto. The Vega trajectory data and the Halley camera angle data were combined to improve the comet orbit accuracy. This was used to improve the Giotto fly-by targeting. The DSN performed delta DOR (VLBI) and one-way Doppler measurements of the Vega spacecraft for orbit determination. Although the early part-up phase had many problems, the results during the critical November 30, 1985 to March 4, 1986 operational phase had an overall 95 percent success rate, with 59 successes out of 62 two-station passes.
Wilcher, J.↗
Cross-Talk in QPSK Communication Systems
This report investigates the effects of cross-talk on the Bit Error Rate (BER) performance of QPSK communication systems. There are four different sources that can cause cross-talk in QPSK systems, namely, a band-limited channel, asymmetry in filters, phase imbalance between the channels, and imperfect carrier tracking. This report emphasizes the last two problems (where either phase imbalance in the local VCOs or imperfect carrier tracking exists).
Bit Error Rate Cross Talk Bandlimitted Channel Asy↗
Staging Two-Phase Turbines
Staging method solves problem of friction loss and low efficiency of two phase (liquid/gas) flow in turbines by using high blade-tip speeds in first stage for progressively lower tip speeds in succeeding stages.
Elliott, D. G.↗
ERISTAR: Earth Resources Information Storage, Transformation, Analysis, and Retrieval administrative report
The 1972 Systems Engineering program at Marshall Space Flight Center where 15 participants representing 15 U.S. universities, 1 NASA/MSFC employee, and another specially assigned faculty member, participated in an 11-week program is discussed. The Fellows became acquainted with the philosophy of systems engineering, and as a training exercise, used this approach to produce a conceptional design for an Earth Resources Information Storage, Transformation, Analysis, and Retrieval System. The program was conducted in three phases; approximately 3 weeks were devoted to seminars, tours, and other presentations to subject the participants to technical and other aspects of the information management problem. The second phase, 5 weeks in length, consisted of evaluating alternative solutions to problems, effecting initial trade-offs and performing preliminary design studies and analyses. The last 3 weeks were occupied with final trade-off sessions, final design analyses and preparation of a final report and oral presentation.
Vachon, R. I.↗
How well does voice interaction work in space?
The methods and results of an evaluation of the Voice Navigator software package are discussed. The first phase or ground phase of the study consisted of creating, or training, computer voice files of specific commands. This consisted of repeating each of six commands eight times. The files were then tested for recognition accuracy by the software aboard the microgravity aircraft. During the second phase, both voice training and testing were performed in microgravity. Inflight training was done due to problems encountered in phase one which were believed to be caused by ambient noise levels. Both quantitative and qualitative data were collected. Only one of the commands was found to offer consistently high recognition rates across subjects during the second phase.
Morris, Randy B.↗
Autonomous space processor for orbital debris
The development of an Autonomous Space Processor for Orbital Debris (ASPOD) was the goal. The nature of this craft, which will process, in situ, orbital debris using resources available in low Earth orbit (LEO) is explained. The serious problem of orbital debris is briefly described and the nature of the large debris population is outlined. The focus was on the development of a versatile robotic manipulator to augment an existing robotic arm, the incorporation of remote operation of the robotic arms, and the formulation of optimal (time and energy) trajectory planning algorithms for coordinated robotic arms. The mechanical design of the new arm is described in detail. The work envelope is explained showing the flexibility of the new design. Several telemetry communication systems are described which will enable the remote operation of the robotic arms. The trajectory planning algorithms are fully developed for both the time optimal and energy optimal problems. The time optimal problem is solved using phase plane techniques while the energy optimal problem is solved using dynamic programming.
Ramohalli, Kumar↗
Advanced design for orbital debris removal in support of solar system exploration
The development of an Autonomous Space Processor for Orbital Debris (ASPOD) is the ultimate goal. The craft will process, in situ, orbital debris using resources available in low Earth orbit (LEO). The serious problem of orbital debris is briefly described and the nature of the large debris population is outlined. This year, focus was on development of a versatile robotic manipulator to augment an existing robotic arm; incorporation of remote operation of robotic arms; and formulation of optimal (time and energy) trajectory planning algorithms for coordinating robotic arms. The mechanical design of the new arm is described in detail. The versatile work envelope is explained showing the flexibility of the new design. Several telemetry communication systems are described which will enable the remote operation of the robotic arms. The trajectory planning algorithms are fully developed for both the time-optimal and energy-optimal problem. The optimal problem is solved using phase plane techniques while the energy optimal problem is solved using dynamics programming.
Source record↗
Coronagraph Design Optimization for Segmented Aperture Telescopes
The goal of directly imaging Earth-like planets in the habitable zone of other stars has motivated the design of coronagraphs for use with large segmented aperture space telescopes. In order to achieve an optimal trade-o between planet light throughput and di racted starlight suppression, we consider coronagraphs comprised of a stage of phase control implemented with deformable mirrors (or other optical elements), pupil plane apodization masks (gray scale or complex valued), and focal plane masks (either amplitude only or complex-valued, including phase only such as the vector vortex coronagraph). The optimization of these optical elements, with the goal of achieving 10 or more orders of magnitude in the suppression of on-axis (starlight) di racted light, represents a challenging non-convex optimization problem with a nonlinear dependence on control degrees of freedom. We develop a new algorithmic approach to the design optimization problem, which we call the "Auxiliary Field Optimization" (AFO) algorithm. The central idea of the algorithm is to embed the original optimization problem, for either phase or amplitude (apodization) in various planes of the coronagraph, into a problem containing additional degrees of freedom, speci cally ctitious "auxiliary" electric elds which serve as targets to inform the variation of our phase or amplitude parameters leading to good feasible designs. We present the algorithm, discuss details of its numerical implementation, and prove convergence to local minima of the objective function (here taken to be the intensity of the on-axis source in a "dark hole" region in the science focal plane). Finally, we present results showing application of the algorithm to both unobscured o -axis and obscured on-axis segmented telescope aperture designs. The application of the AFO algorithm to the coronagraph design problem has produced solutions which are capable of directly imaging planets in the habitable zone, provided end-to-end telescope system stability requirements can be met. Ongoing work includes advances of the AFO algorithm reported here to design in additional robustness to a resolved star, and other phase or amplitude aberrations to be encountered in a real segmented aperture space telescope.
Redding, Dave↗