Alternatives for NASTRAN maintenance, modification and dissemination

Various alternatives to direct NASA support of the program are considered ranging from no support at one end of the spectrum to subsidizing a non profit user's group at the other. Of all the alternatives that are developed, the user group appears to be most viable. NASA's past and future roles in the development of computerized technology are also considered. The need for an institute for computational analysis is identified and NASA's possible involvement is described. The goals of the proposed institute and research funds to support an activity that has the potential of a much larger impact on the technical community are identified

Design of helicopter rotors to noise constraints

Results of the initial phase of a research project to study the design constraints on helicopter noise are presented. These include the calculation of nonimpulsive rotor harmonic and broadband hover noise spectra, over a wide range of rotor design variables and the sensitivity of perceived noise level (PNL) to changes in rotor design parameters. The prediction methodology used correlated well with measured whirl tower data. Application of the predictions to variations in rotor design showed tip speed and thrust as having the most effect on changing PNL

Random trees between two walls: Exact partition function

We derive the exact partition function for a discrete model of random trees embedded in a one-dimensional space. These trees have vertices labeled by integers representing their position in the target space, with the SOS constraint that adjacent vertices have labels differing by +1 or -1. A non-trivial partition function is obtained whenever the target space is bounded by walls. We concentrate on the two cases where the target space is (i) the half-line bounded by a wall at the origin or (ii) a segment bounded by two walls at a finite distance. The general solution has a soliton-like structure involving elliptic functions. We derive the corresponding continuum scaling limit which takes the remarkable form of the Weierstrass p-function with constrained periods. These results are used to analyze the probability for an evolving population spreading in one dimension to attain the boundary of a given domain with the geometry of the target (i) or (ii). They also translate, via suitable bijections, into generating functions for bounded planar graphs.Comment: 25 pages, 7 figures, tex, harvmac, epsf; accepted version; main modifications in Sect. 5-6 and conclusio

Supersonic flutter of a thermally stressed flat panel with uniform edge loads

Supersonic flutter of thermally stressed flat panel with uniform edge load

The effect of brain breaks on student outcomes of school-aged children in k-12 classrooms: a meta-analysis

BACKGROUND: Integrated physical activity in the classroom has been shown to affect K-12 students’ development positively. Students of all abilities benefit from multimodality learning. PURPOSE: This study investigates the relationship between classroom brain breaks and school-aged students\u27 classroom behaviors. METHODS: The Meta-analysis search process consisted of 3 Phases: (1) Screen the titles, (2) Screen the abstracts, and (3) Retrieve the Full Text. Literature searches were conducted in eight electronic academic journal databases: SPORTDiscus, PsycINFO, PsycARTICLES, Cochrane Database, Web of Science/Web of Knowledge, ProQuest, Child Development and Adolescent Studies, and ERIC. Students (N) are enrolled in schools serving students from kindergarten through twelfth grade. RESULTS: The overall effect that brain breaks provided across all outcomes was small (k = 56, g = 0.36, 95% CI = 0.22, 0.50, P \u3c 0.001) with large prediction intervals for each of the category outcomes that suggest a large degree of variability. CONCLUSIONS: Future research should consider the methods used to implement brain breaks by following specified guidelines that produce positive results for the intended outcomes being studied

Estimation of covariance components between one continuous and one binary trait

International audienc

Data-driven PDE discovery with evolutionary approach

The data-driven models allow one to define the model structure in cases when a priori information is not sufficient to build other types of models. The possible way to obtain physical interpretation is the data-driven differential equation discovery techniques. The existing methods of PDE (partial derivative equations) discovery are bound with the sparse regression. However, sparse regression is restricting the resulting model form, since the terms for PDE are defined before regression. The evolutionary approach described in the article has a symbolic regression as the background instead and thus has fewer restrictions on the PDE form. The evolutionary method of PDE discovery (EPDE) is described and tested on several canonical PDEs. The question of robustness is examined on a noised data example

A SPATIAL MODEL OF REGIONAL VARIATIONS IN EMPLOYMENT GROWTH IN APPALACHIA

In this study, a spatial equilibrium model of employment growth is developed and empirically estimated by Generalized Spatial Two-Stage Least Squares (GS2SLS) estimator using cross-sectional data from Appalachian counties for 1990-2000. Besides the existence of spatial spillover effects, the results suggest that agglomerative effects that arise from the demand and the supply side contribute to employment growth in the study area during the study period. The policy implications of the findings are: (1) Regional cooperation of counties and communities is advisable and may in fact be necessary to design effective policies to encourage employment growth; and (2) Policy makers at the county level may need to design policies that can attract people with high endowments of human capital and higher income into their respective counties.APPALACHIA, EMPLOYMENT GROWTH, SPATIAL MODEL