Node-recording method for stiffness matrix wavefront reduction in structural analysis

Method provides approach to automatic node relabeling that is consistent with requirements of wavefront concept. Specific applications are in analysis of aircraft, building structures, radar and surveillance structures, bridges, etc., or any other structure that is studied with aid of large and complex analytical model. Minimum growth sequencing is effective, rapid, and capable of producing economies

Improved procedures for mass matrix-reductions in eigenvalue solutions

Analytical models of three structures were used to test mass matrix-reduction schemes. Accuracy of four mode shapes and frequencies was tracked through successive mass matrix-reductions with diminishing numbers of indicator degrees of freedom. Results were consistently disappointing. Two new procedures were developed in attempt to improve accuracy

Reanalysis, compatibility and correlation in analysis of modified antenna structures

A simple computational procedure is synthesized to process changes in the microwave-antenna pathlength-error measure when there are changes in the antenna structure model. The procedure employs structural modification reanalysis methods combined with new extensions of correlation analysis to provide the revised rms pathlength error. Mainframe finite-element-method processing of the structure model is required only for the initial unmodified structure, and elementary postprocessor computations develop and deal with the effects of the changes. Several illustrative computational examples are included. The procedure adapts readily to processing spectra of changes for parameter studies or sensitivity analyses

The diocotron instability in a cylindrical geometry

Diocotron, slipping stream, instability of low density electron beams in electric and magnetic field

The effect of coherent radiation on the stability of a crossed-field electron beam Research report no. 213

Coherent radiation effect on crossed field electron beam stabilit

How Are HOPE VI Families Faring? Income and Employment

While the primary goal of the HOPE VI program is to improve the living environment of public housing residents, it also aims to help residents move toward self-sufficiency by helping them find new or better jobs (see page 6). The program's Community Support Services (CSS) component can help identify what residents need, such as job training or placement, to make them more likely to find employment. Relocation itself might help residents find employment if they move to less poor neighborhoods with more job opportunities and better job information networks. Residents who move back to new mixed-income developments on the HOPE VI sites could experience similar improved job networks. However, whether these expectations of increased employment and self-sufficiency are realistic for HOPE VI residents is unclear. For both employed and nonemployed residents, the gap between household income and the income needed for housing and other costs of living is wide. The HOPE VI Panel Study is tracking the well-being of residents from five HOPE VI sites (see page 7). These respondents, mostly African American women, were extremely poor at baseline.[1] The vast majority reported household incomes below the poverty level, and over a third (35 percent) reported annual incomes of less than $5,000. Less than half (45 percent) of respondents were employed, and those who were working earned low wages (Popkin et al. 2002). This brief discusses income and employment findings for working-age adults under 62 years old two years after relocation started at the five HOPE VI Panel Study sites.[2] It examines various barriers to employment for respondents, and considers both expectations for future employment and the services and support systems that might best mitigate those barriers. Future research will examine how residents' employment experiences are affected as relocation is completed and some residents return to the revitalized developments. Notes from this section 1. Among respondents under 62 years old, 82 percent were non-Hispanic African American women and 9 percent were Hispanic women. 2. A future brief in the "A Roof Over Their Heads" series will examine income and employment findings for adults over 62 years old

DSS-14 subreflector actuator dynamics during the Landers earthquake

The 28 Jun. 1992 Landers earthquake ground motion records at the Echo site (DSS-12 antenna) were adjusted to provide a better match with spectra from the measured Mars site (DSS-14 antenna) instrument tower response. A finite-element model of the antenna structural system was analyzed for response to this ground motion. Dynamic forces and displacements were computed in the locality of components that had failed during the earthquake. Calculated forces in the range of 30,000 to 35,000 lb on failed Y-axis actuator U-joints were consistent with laboratory load tests. The load capacity of these joints was found to be below the range of 34,000 to 42,000 lb. Dynamic amplification factors of from 6 to 16 were computed for the quadripod apex accelerations with respect to the ground accelerations. The largest factor--25--was found at the outboard end of the X-actuator