Uncertainty Evaluation of Computational Model Used to Support the Integrated Powerhead Demonstration Project

NASA and the U.S. Air Force are working on a joint project to develop a new hydrogen-fueled, full-flow, staged combustion rocket engine. The initial testing and modeling work for the Integrated Powerhead Demonstrator (IPD) project is being performed by NASA Marshall and Stennis Space Centers. A key factor in the testing of this engine is the ability to predict and measure the transient fluid flow during engine start and shutdown phases of operation. A model built by NASA Marshall in the ROCket Engine Transient Simulation (ROCETS) program is used to predict transient engine fluid flows. The model is initially calibrated to data from previous tests on the Stennis E1 test stand. The model is then used to predict the next run. Data from this run can then be used to recalibrate the model providing a tool to guide the test program in incremental steps to reduce the risk to the prototype engine. In this paper, they define this type of model as a calibrated model. This paper proposes a method to estimate the uncertainty of a model calibrated to a set of experimental test data. The method is similar to that used in the calibration of experiment instrumentation. For the IPD example used in this paper, the model uncertainty is determined for both LOX and LH flow rates using previous data. The successful use of this model is then demonstrated to predict another similar test run within the uncertainty bounds. The paper summarizes the uncertainty methodology when a model is continually recalibrated with new test data. The methodology is general and can be applied to other calibrated models

Noun Phrase Elaboration in Children’s Spoken Stories.

Purpose: One feature of literate language, noun phrase elaboration, was examined in the oral fictional narratives of school-aged children. Method: Two narratives were elicited from 5-, 8- and 11-year-old children, 1 in response to a picture sequence and 1 in response to a single picture. Noun phrases were categorized into 4 types. Results: Simple designating noun phrases were produced by all children at age 5, simple descriptive noun phrases by all children at age 8, and noun phrases with postmodification by all children at age 11. All noun phrase types were produced by more children in object than in subject position and in the single picture than in the picture sequence context. Conclusion: There are important developmental changes in noun phrase elaboration in the elementary school years as children learn to manage narrative contexts. Even within picture tasks, variations in visual depiction can affect the use of elaborated noun phrases (ENPs), with more descriptive language more likely to occur in narratives based on a single picture fantasy context than on a realistic picture sequence context. Performance expectations for types of ENPs within these contexts are provided. These findings will be useful to school clinicians in evaluating and working on narrative language within the elementary school period