DATAWorks Sessions Archive

In reliability, methods used to estimate failure probability are often limited by the costs associated with model evaluations. Many of these methods, such as multi-fidelity importance sampling (MFIS), rely upon a cheap, surrogate model like a Gaussian process (GP) to quickly generate predictions. The quality of the GP fit, at least in the vicinity of the failure region(s), is instrumental in propping up such estimation strategies. We introduce an entropy-based GP adaptive design that, when paired with MFIS, provides more accurate failure probability estimates and with higher confidence. We show that our greedy data acquisition scheme better identifies multiple failure regions compared to existing contour-finding schemes. We then extend the method to batch selection. Illustrative examples are provided on benchmark data as well as an application to the impact damage simulator of a NASA spacesuit design.

As advanced technologies and capabilities are enabling machines to engage in tasks that only humans have done previously, new challenges have emerged for the rigorous testing and evaluation (T&E) of human-machine teaming (HMT) concepts. We differentiate the distinction between a HMT and a human using a tool, and new challenges are enumerated: Agents’ mental models are opaque, machine-to-human communications need to be evaluated, and self-tasking and autonomy need to be evaluated. We argue that a focus on mission outcomes cannot fully characterize team performance due to the increased problem space evaluated and that the T&E community needs to develop and refine new metrics for agents of teams and teammate interactions. Our IDA HMT framework outlines major categories for HMT evaluation, emphasizing team metrics and parallelizing agent metrics across humans and machines. Major categories are tied to the literature and proposed as a starting point for additional T&E metric specification for robust evaluation.

Human-system interaction is a critical yet often neglected aspect of the system development process. It is mostly commonly incorporated into system performance assessments late in the design process leaving little opportunity for any substantive changes to be made to ensure satisfactory system performance achieved. As a result, workarounds and compromises become a patchwork of “corrections” that end up in the final fielded system. But what if mission outcomes, the work context, and performance expectations can be articulated earlier in the process, thereby influencing the development process throughout? This presentation will discuss how a formative method from the field of cognitive systems engineering, cognitive work analysis, can be leveraged to derive design requirements compatible with traditional systems engineering processes. This method establishes not only requirements from which system designs can be constructed, but also how system performance expectations can be more acutely defined a priori to guide the validation and verification process. Cognitive work analysis methods will be described to highlight how ‘cognitive work’ and ‘information relationship’ requirements can be derived and will be showcased in a case-study application of building a decision support system for future human spaceflight operations. Specifically, a description of the testing campaign employed to verify and validate the fielded system will be provided. In summary, this presentation will cover how system requirements can be established early in the design phase, guide the development of design solutions, and subsequently be used to assess the operational performance of the solutions within the context of the work domain it is intended to support.

Physics-based simulation of nondestructive evaluation (NDE) inspection can help to advance the inspectability and reliability of mechanical systems. However, NDE simulations applicable to non-idealized mechanical components often require large compute domains and long run times. This has prompted development of custom NDE simulation software tailored to high performance computing (HPC) hardware. Verification and validation (V&V) is an integral part of developing this software to ensure implementations are robust and applicable to inspection problems, producing tools and simulations suitable for computational NDE research. This presentation addresses factors common to V&V of several elastodynamic simulation codes applicable to ultrasonic NDE. Examples are drawn from in-house simulation software at NASA Langley Research Center, ranging from ensuring reliability in a 1D heterogeneous media wave equation solver to the V&V needs of 3D cluster-parallel elastodynamic software. Factors specific to a research environment are addressed, where individual simulation results can be as relevant as the software product itself. Distinct facets of V&V are discussed including testing to establish software reliability, employing systematic approaches for consistency with fundamental conservation laws, establishing the numerical stability of algorithms, and demonstrating concurrence with empirical data. This talk also addresses V&V practices for small groups of researchers. This includes establishing resources (e.g. time and personnel) for V&V during project planning to mitigate and control the risk of setbacks. Similarly, we identify ways for individual researchers to use V&V during simulation software development itself to both speed up the development process and reduce incurred technical debt.

The spread of COVID-19 across the United States provides an interesting case study in the modeling of spatio-temporal data. In this breakout session we will provide an overview of commonly used spatio-temporal models and demonstrate how Bayesian Inference can be performed using both exact and approximate inferential techniques. Using COVID data, we will demonstrate visualization techniques in R and introduce “off-the-shelf” spatio-temporal models. We will introduce participants to the Integrated Nested LaPlace approximation (INLA) methodology and show how results from this technique compare to using Markov Chain Monte Carlo (MCMC) techniques. Finally, we will demonstrate the short-falls in using “off-the-shelf” models and show how epidemiological motivated partial differential equations can be used to generate spatio-temporal models and discuss inferential issues when we move away from common models.

With the rise of machine learning and artificial intelligence, there has been a huge surge in data-driven approaches to solve computational science and engineering problems. In the context of uncertainty propagation, machine learning is often employed for the construction of efficient surrogate models (i.e., response surfaces) to replace expensive, physics-based simulations. However, relying solely on surrogate models without any recourse to the original high-fidelity simulation will produce biased estimators and can yield unreliable or non-physical results. This talk discusses multi-model Monte Carlo methods that combine predictions from both fast, low-fidelity models with reliable, high-fidelity simulations to enable efficient and accurate uncertainty propagation. For instance, the low-fidelity models could arise from coarsened discretizations in space/time (e.g., Multilevel Monte Carlo – MLMC) or from general data-driven or reduced order models (e.g., Multifidelity Monte Carlo – MFMC; Approximate Control Variates – ACV). Given a fixed computational budget and a collection of models of varying cost/accuracy, the goal of these methods is to optimally allocate and combine samples across the models. The talk will also present a NASA-developed open-source Python library that acts as a general multi-model uncertainty propagation capability. The effectiveness of the discussed methods and Python library is demonstrated on a trajectory simulation application. Here, orders of magnitude computational speedup and accuracy are obtained for predicting the landing location of an umbrella heat shield under significant uncertainties in initial state, atmospheric conditions, etc.