Transient Three-Dimensional Side Load Analysis of Out-of-Round Film Cooled Nozzles

The objective of this study is to investigate the effect of nozzle out-of-roundness on the transient startup side loads. The out-of-roundness could be the result of asymmetric loads induced by hardware attached to the nozzle, asymmetric internal stresses induced by previous tests and/or deformation, such as creep, from previous tests. The rocket engine studied encompasses a regeneratively cooled thrust chamber and a film cooled nozzle extension with film coolant distributed from a turbine exhaust manifold. The computational methodology is based on an unstructured-grid, pressure-based computational fluid dynamics formulation, and a transient inlet history based on an engine system simulation. Transient startup computations were performed with the out-of-roundness achieved by four degrees of ovalization of the nozzle: one perfectly round, one slightly out-of-round, one more out-of-round, and one significantly out-of-round. The computed side load physics caused by the nozzle out-of-roundness and its effect on nozzle side load are reported and discussed

Aquilegia, Vol. 13 No. 1, January-February 1989: Newsletter of the Colorado Native Plant Society

https://epublications.regis.edu/aquilegia/1044/thumbnail.jp

The academic task performance scale:psychometric properties, and measurement invariance across ages, genders and nations

Academic task performance (TP) refers to the proficiency with which students perform in academic tasks through making the right choices and completing core tasks central to their academic studies, on time and to specification. We adapted Koopmans et al.’s task performance scale (TPS) for use within tertiary education and investigated its psychometric properties, internal consistency and measurement invariance across age, gender and national groups in university students (n = 3,265). The results showed that a hierarchical ESEM model with one higher-order task performance factor consisting of time management and task efficiency fitted the data best. The TPS exhibited full measurement invariance across gender and age groups, implying that the latent mean scores can be used to determine differences. However, invariance could only partially be established for national cohorts, implying that cross-national comparisons may not be possible. These findings offer preliminary support for the TPS as a valid instrument for gauging students’ academic task performance.</p

The study demands and resources scale:psychometric properties, longitudinal invariance, and criterion validity

The Study Demands and Resources Scale (SDRS) has shown promise as a valid and reliable measure for measuring students’ specific study demands and -resources. However, there is no evidence as to its psychometric properties outside of the original context in which it was developed. This study aimed to assess the psychometric properties of the SDRS in a cross-national student population through examining its longitudinal factorial validity, internal consistency, and temporal invariance as well as criterion validity through its association with study engagement and task performance over time. Results showed that a Bifactor Exploratory Structural Equation Model (ESEM) with one general factor (overall study characteristics) and five specific factors (workload, growth opportunities, lecturer support, peer support, information availability) fitted the data, showed strong measurement invariance over time, and was reliable at different time points. The study further established criterion validity for the overall study characteristics factor through its concurrent and predictive associations with study engagement and task performance. However, the specific factors’ concurrent and predictive capacity could only partially be established when controlling for the general study characteristics factor. These findings suggest that study characteristics should be measured as a dynamic interaction between study demands and resources, rather than a hierarchical model.</p