DATAWorks Sessions Archive

Spectrograms (i.e., squared magnitude of short-time Fourier transform) are commonly used as features to classify audio signals in the same way that social media companies (e.g., Google, Facebook, Yahoo) use images to classify or automatically tag people in photos. However, a serious problem arises when using spectrograms to classify acoustic signals, in that the user must choose the input parameters (hyperparameters), and such choices can have a drastic effect on the accuracy of the resulting classifier. Further, considering all possible combinations of the hyperparameters is a computationally intractable problem. In this study, we simplify the problem making it computationally tractable, explore the utility of response surface methods for sampling the hyperparameter space, and find that response surface methods are a computationally efficient means of identifying the hyperparameter combinations that are likely to give the best classification results.

One of the major pillars of experimental design is sequential learning. The experimental design should not be viewed as a “one-shot” effort, but rather as a series of experiments where each stage builds upon information learned from the previous study. It is within this realm of sequential learning that experimentation soundly supports the application of the scientific method. This presentation illustrates the value of sequential experimentation and also the connection between the scientific method and experimentation through a discussion of a multi-stage project supported by NASA’s Engineering Safety Center (NESC) where the objective was to assess the safety of composite overwrapped pressure vessels (COPVs). The analytical team was tasked with devising a test plan to model stress rupture failure risk in carbon fiber strands that encase the COPVs with the goal of understanding the reliability of the strands at use conditions for the expected mission life. This presentation highlights the recommended experimental design for the strand tests and then discusses the benefits that resulted from the suggested sequential testing protocol.

Frangible Joints are linear pyrotechnic devices used to separate launch vehicle and spacecraft stages and fairings. Advantages of these systems include low mass, low dynamic shock, and low debris. However the primary disadvantage for human space flight applications is the design’s use of a single explosive cord to effect function, rendering the device zero fault tolerant. Commercial company proposals to utilize frangible joints in human space flight applications spurred a NASA Engineering and Safety Center (NESC) assessment of the reliability of frangible joints. Empirical test and LS-DYNA based finite element analysis was used to understand and assess the design and function, and a deterministic system Design of Experiments (dsDOE) study was conducted to assess the sensitivity of function to frangible joint design variables and predict the device’s design reliability. The collaboration between statistical engineering experts and LS-DYNA analysis experts enabled a comprehensive understanding of these devices.

Uncertainty appears in many aspects of systems design including stochastic design parameters, simulation inputs, and forcing functions. Uncertainty Quantification (UQ) has emerged as the science of quantitative characterization and reduction of uncertainties in both simulation and test results. UQ is a multidisciplinary field with a broad base of methods including sensitivity analysis, statistical calibration, uncertainty propagation, and inverse analysis. Because of their ability to bring greater degrees of confidence to decisions, uncertainty quantification methods are playing a greater role in test, evaluation, and modeling and simulation in defense and aerospace. The value of UQ comes with better understanding of risk from assessing the uncertainty in test and modeling and simulation results. The presentation will provide an overview of UQ and then discuss the use of some advanced statistical methods, including DOEs and emulation for multiple simulation solvers and statistical calibration, for efficiently quantifying uncertainties. These statistical methods effectively link test, evaluation and modeling and simulation by coordinating the valuation of uncertainties, simplifying verification and validation activities.

Since its publication, Statistical Methods for Reliability Data by W. Q. Meeker and L. A. Escobar has been recognized as a foundational resource in analyzing failure time to and survival data. Along with the text, the authors provided an S-Plus software package, called SPLIDA, to help readers utilize the methods presented in the text. Today, R is the most popular statistical computing language in the world, largely supplanting S-Plus. The SMRD package is the result of a multi-year effort to completely rebuild SPLIDA, to take advantage of the improved graphics and workflow capabilities available in R. This presentation introduces the SMRD package, outlines the improvements and shows how the package works seamlessly with the rmarkdown and shiny packages to dramatically speed up your workflow. The presentation concludes with a discussion on what improvements still need to be made prior to publishing the package on the CRAN.

Jones and Nachtsheim (2011) introduced a class of three-level screening designs called definitive screening designs (DSDs). The structure of these designs results in the statistical independence of main effects and two-factor interactions; the absence of complete confounding among two-factor interactions; and the ability to estimate all quadratic effects. Because quadratic effects can be estimated, DSDs can allow for the screening and optimization of a system to be performed in one step, but only when the number of terms found to be active during the screening phase of analysis is less than about half the number or runs required by the DSD (Errore, et al., 2016). Otherwise, estimation of second-order models requires augmentation of the DSD. In this paper we explore the construction of series of augmented designs, moving from the starting DSD to designs capable of estimating the full second-order model. We use power calculations, model-robustness criteria, and model-discrimination criteria to determine the number of runs by which to augment in order to identify the active second-order effects with high probability.

The process for testing military systems which are largely software intensive involves techniques and procedures often different from those for hardware-based systems. Much of the testing can be performed in laboratories at many of the acquisition stages, up to operational testing. Testing software systems is not different from testing hardware-based systems in that testing earlier and more intensively benefits the acquisition program in the long run. Automated testing of software systems enables more frequent and more extensive testing, allowing for earlier discovery of errors and faults in the code. Automated testing is beneficial for unit, integrated, functional and performance testing, but there are costs associated with automation tool license fees, specialized manpower, and the time to prepare and maintain the automation scripts. This presentation discusses some of the features unique to automated software testing and offers a framework organizations can implement to make the business case for, to organize for, and to execute and benefit from automating the right aspects of their testing needs. Automation has many benefits in saving time and money, but is most valuable in freeing test resources to perform higher value tasks.

This presentation will provide a brief overview of sensitivity testing, and emphasize applications to several products and system of importance to the Defense as well as private industry, including Insensitive Energetics, Ballistic testing of protective armor, testing of munition fuzes and Microelectromechanical Systems (MEMS) components, and safety testing of high-pressure test ammunition, and packaging for high-value materials.

Rigorous characterization of system capabilities is essential for defensible decisions in test and evaluation (T&E). Analysis of designed experiments is not usually associated “big” data analytics as there are typically a modest number of runs, factors, and responses. The Mars Rover program has recently conducted several disciplined DOEs on prototype coring drill performance with approximately 10 factors along with scores of responses and hundreds of recorded covariates. The goal is to characterize the ‘atthis-time’ capability to confirm what the scientists and engineers already know about the system, answer specific performance and quality questions across multiple environments, and inform future tests to optimize performance. A ‘rigorous’ characterization required that not just one analytical path should be taken, but a combination of interactive data visualization, classic DOE analysis screening methods, and newer methods from predictive analytics such as decision trees. With hundreds of response surface models across many test series and qualitative factors, these methods used had to efficiently find the signals hidden in the noise. Participants will be guided through an end-to-end analysis workflow with actual data from many tests (often Definitive Screening Designs) of the Rover prototype coring drill. We will show data assembly, data cleaning (e.g. missing values and outliers), data exploration with interactive graphical designs, variable screening, response partitioning, data tabulation, model building with stepwise and other methods, and model diagnostics. Software packages such as R and JMP will be used.

NASA has instituted requirements for establishing Agency-level safety thresholds and goals that define “long-term targeted and maximum tolerable levels of risk to the crew as guidance to developers in evaluating ‘how safe is safe enough’ for a given type of mission.” With the adoption of this policy for human space flight and with ongoing Agency efforts to increase formality in the development and review of the basis for risk acceptance, the decision-support demands placed on risk models are becoming more stringent at NASA. While these models play vital roles in informing risk acceptance decisions, they are vulnerable to incompleteness of risk identification, as well as to incomplete understanding of probabilities of occurrence, potentially leaving a substantial portion of the actual risk unaccounted for, especially for new systems. This presentation argues that management of uncertainty about the “actual” safety performance of a system must take into account the contribution of unknown and/or underappreciated (UU) risk. Correspondingly, responsible risk-acceptance decision-making requires the decision-maker to think beyond the model and address factors (e.g., organizational and management factors) that live outside traditional engineering risk models. This presentation advocates the use of a safety-case approach to risk acceptance decision-making.

Rigorous characterization of system capabilities is essential for defensible decisions in test and evaluation (T&E). Analysis of designed experiments is not usually associated “big” data analytics as there are typically a modest number of runs, factors, and responses. The Mars Rover program has recently conducted several disciplined DOEs on prototype coring drill performance with approximately 10 factors along with scores of responses and hundreds of recorded covariates. The goal is to characterize the ‘atthis-time’ capability to confirm what the scientists and engineers already know about the system, answer specific performance and quality questions across multiple environments, and inform future tests to optimize performance. A ‘rigorous’ characterization required that not just one analytical path should be taken, but a combination of interactive data visualization, classic DOE analysis screening methods, and newer methods from predictive analytics such as decision trees. With hundreds of response surface models across many test series and qualitative factors, these methods used had to efficiently find the signals hidden in the noise. Participants will be guided through an end-to-end analysis workflow with actual data from many tests (often Definitive Screening Designs) of the Rover prototype coring drill. We will show data assembly, data cleaning (e.g. missing values and outliers), data exploration with interactive graphical designs, variable screening, response partitioning, data tabulation, model building with stepwise and other methods, and model diagnostics. Software packages such as R and JMP will be used.

The American National Standards Institute (ANSI) maintains a set of test standards that provide methods to characterize and determine the acceptability of radiation detection systems for use in Homeland security. With a focus on the environmental, electromagnetic, and mechanical functionality tests, we describe the test formulation and discuss challenges faced in administering the standard to include the assurance of comparable evaluations across multiple test facilities and the handling of systems that provide a non-standard, unit-less response. We present proposed solutions to these difficulties that are currently being considered in updated versions of the ANSI standards. We briefly describe a decision analytic approach that could allow for the removal of minimum performance requirements from the standards and enable the end user to determine system suitability based on operation-specific requirements.

A question about whether how post-processing affects the flammability of a given metal an oxygen enriched environment could be answered with the sensitivity of a standard test that is typically used to measure differences in flammability between different metals. The principal investigator was familiar with design of experiments (DOE) and wanted to optimize the value of the information to be gained. This talk will focus on the interchange between the engineer and a statistician. Their negotiations will illustrate the process of clarifying the problem, planning the test including choosing factors and responses, running the experiment and analyzing and reporting on the data. It will focus on the choices made to help squeeze extra knowledge from each test run and leverage statistics to result in increased engineering insight.

This paper presents the results of two hypervelocity impact failure probabilistic risk assessments for critical wire bundles exposed aboard the Joint Polar Satellite System (JPSS-1) to an increased orbital debris environment at its 824 km, 98.8 deg inclination orbit. The first “generic” approach predicted the number of wires broken by orbital debris ejecta emerging from normal impact with multi-layer insulation (MLI) covering 36-, 18-, and 6-strand wire bundles at a 5 cm standoff using the Smooth Particle Hydrodynamic (SPH) code. This approach also included a mathematical approach for computing the probability that redundant wires were impacted then severed within the bundle. Based in part on the high computed risk of a critical wire bundle failure from the generic approach, an enhanced orbital debris protection design was examined, consisting of betacloth-reinforced MLI suspended at a 5 cm standoff over a seven layer betacloth and Kevlar blanket, draped over the exposed wire bundles. A second SPH-based risk assessment was conducted that also included the beneficial effects from the high (75 degree) obliquity of orbital debris impact and shadowing by other spacecraft components, and resulted in a considerably reduced likelihood of critical wire bundle failure compared to the original baseline design.

For the past 7 years, USAF DT&E has been exploring ways to adapt the principles of experimental design to rapidly evolving developmental test articles and test facilities – often with great success. This paper discusses three case studies that span the range of USAF DT&E activities from EW to Ground Test to Flight Test and shows the truly revolutionary impact Fisher’s DOE can have on development. The Advanced Strategic and Tactical Expendable (ASTE) testing began in 1990 to develop, enhance, and test new IR flares, flare patterns, and dispense tactics. More than 60 aircraft & flare types have been tested. The typical output is a “Pancake Plot” of 200+ “cases” of flare, aspect angle, range, elevation, and flare effectiveness using a stop-light chart (red-yellow-green) approach. In usual testing – ~3000 flare engagements costing $1M to participate. The response, troublingly enough, is binary – 15-30 binomial response trials measuring P(Decoy). Binary responses are information-poor. Legacy testing does not assess present statistical power in reporting P(decoy) results. Analysts investigated replacing P(Decoy) w/ continuous metrics – e.g. time to decoy. This research is ongoing. We found we could spread the replicates out to examine 3x to 5x more test conditions without affecting power materially. Analysis with the Generalized Linear Model (GLZ) replaced legacy “cases” analysis with 75% improvement to confidence intervals with same data. We are seeking to build a Monte-Carlo simulation to estimate how many runs are required in a logistics regression model to achieve adequate power. We hope to reduce customer expenditures for flare information by as much as 50%. Co-authors J. Higdon, B, Knight. AEDC completed a major upgrade with new nozzle hardware to vary Mach. The Arnold Transonic Wind Tunnel 4T spans the range of flows from subsonic to approximately M9. The new wind tunnel was to be computer controlled. A number of key instrumentation improvements were made at the same time. The desire was to calibrate the resulting modified tunnel. The last calibration of 4T was 25 years ago in 1990. The calibration ranged across the full range of Mach and pressure capabilities, spanning a four-D space: pressure, Mach, wall angle, and wall porosity. Both the traditional OFAT effort – vary one factor at a time – and a parallel DOE effort were run to compare design, execution, modeling, and prediction capabilities against cost and time to run. The robust embedded face-centered CCD DOE design (J. Simpson and D. Landman ’05) employed 75 vs. 176 OFAT runs. The RSM design achieved 57% run savings. Due to an admirable discipline in randomization during the DOE trials, the smaller design required longer to run. As a result of using the DOE approach, engineers found it easier predict offcondition tunnel operating characteristics using RSM models, optimize facility flow quality for any given test condition. In addition, the RSM regression models support future “spot check” calibration in future by comparing predictions to measured values. If the measurement falls within the prediction interval, the existing calibration still appropriate. AEDC is using split-plot style designs a for current wind tunnel probe calibration. Co-author: Dr Dough Garrard.