Vibration Responses of Simple Curved Panels to High-intensity Random and Discrete Frequency Noise

Vibration effects of simple curved panels to high intensity random and discrete frequency nois

Response-to-noise studies of some aircraft and spacecraft structures

Fatigue and response to noise of aircraft and spacecraft viscoelastic panels, shell structure, and payload

The Necessity for Rodent Extermination in American Seaports

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Long-run Impacts of School Desegregation & School Quality on Adult Attainments

This paper investigates the long-run impacts of court-ordered school desegregation on an array of adult socioeconomic and health outcomes. The study analyzes the life trajectories of children born between 1945 and 1970, and followed through 2011, using the Panel Study of Income Dynamics (PSID). The PSID data are linked with multiple data sources that describe the neighborhood attributes, school quality resources, and coincident policies that prevailed at the time these children were growing up. I exploit quasirandom variation in the timing of initial court orders, which generated differences in the timing and scope of the implementation of desegregation plans during the 1960s, 70s, and 80s. Event study analyses as well as 2SLS and sibling-difference estimates indicate that school desegregation and the accompanied increases in school quality resulted in significant improvements in adult attainments for blacks. I find that, for blacks, school desegregation significantly increased both educational and occupational attainments, college quality and adult earnings, reduced the probability of incarceration, and improved adult health status; desegregation had no effects on whites across each of these outcomes. The results suggest that the mechanisms through which school desegregation led to beneficial adult attainment outcomes for blacks include improvement in access to school resources reflected in reductions in class size and increases in per-pupil spending.

Simple Power-Law Characterization of Transient Ground-Borne Vibrations

Practical characterization of transient ground-borne vibrations in civil and geotechnical engineering problems is often a difficult and frustrating task. Some modem engineering seismographs now routinely permit the collection of histogram-type data where the peak vibration for a pre-set time interval can be measured and stored for significant time periods. Such data is amenable to analysis utilizing concepts of fractal geometry and self-ordered criticality. Resulting data trends tend to follow power-law relationships that plot as essentially straight lines in log-log space. This application is similar to the Gutenberg-Richter relationship for earthquakes where the relationship between magnitude and frequency is fractal. However, the largest vibrations appear to follow another power-law trend appropriate to characterizing extreme events. Four cases of monitoring apparently random transient ground-borne vibrations are examined using this power-law approach: traffic induced vibrations near the curb of an urban arterial street, an unidentified vibration interfering with a precision machining operation, vibrations induced by vacationing children using the front door of a residence, and vibrations induced by water transport in a pipeline. All cases could be characterized by this approach

Targeted Derepression of the Human Immunodeficiency Virus Type 1 Long Terminal Repeat by Pyrrole-Imidazole Polyamides

The host factor LSF represses the human immunodeficiency virus type 1 long terminal repeat (LTR) by mediating recruitment of histone deacetylase. We show that pyrrole-imidazole polyamides targeted to the LTR can specifically block LSF binding both in vitro and within cells via direct access to chromatin, resulting in increased LTR expression

Uniaxial pressure dependence of magnetic order in MnSi

We report comprehensive small angle neutron scattering (SANS) measurements complemented by ac susceptibility data of the helical order, conical phase and skyrmion lattice phase (SLP) in MnSi under uniaxial pressures. For all crystallographic orientations uniaxial pressure favours the phase for which a spatial modulation of the magnetization is closest to the pressure axis. Uniaxial pressures as low as 1kbar applied perpendicular to the magnetic field axis enhance the skyrmion lattice phase substantially, whereas the skyrmion lattice phase is suppressed for pressure parallel to the field. Taken together we present quantitative microscopic information how strain couples to magnetic order in the chiral magnet MnSi.Comment: 23 pages, includes supplemen

Regulation of Consumer Credit in Virginia: A Suggestion for Legislative Improvement

The American economic system is the most successful yet developed, and consumer credit has played a vital role in that economy. Consumer credit has experienced tremendous growth, and has adjusted to the demands of changing life-styles, economic needs, and geographic distinctions, as well as to the different types of consumer goods which have become available with a minimal amount of government intervention. What government intervention there has been has involved restraint and restriction. There now exists the need to improve the consumer credit industry to enable the citizens of Virginia to continue to be able to obtain both the necessities and amenities of life

Large Payload Transportation and Test Considerations

Ironically, the limiting factor to a national heavy lift strategy may not be the rocket technology needed to throw a heavy payload, but rather the terrestrial infrastructure - roads, bridges, airframes, and buildings - necessary to transport, acceptance test, and process large spacecraft. Failure to carefully consider how large spacecraft are designed, and where they are manufactured, tested, or launched, could result in unforeseen cost to modify/develop infrastructure, or incur additional risk due to increased handling or elimination of key verifications. During test and verification planning for the Altair project, a number of transportation and test issues related to the large payload diameter were identified. Although the entire Constellation Program - including Altair - was canceled in the 2011 NASA budget, issues identified by the Altair project serve as important lessons learned for future payloads that may be developed to support national "heavy lift" strategies. A feasibility study performed by the Constellation Ground Operations (CxGO) project found that neither the Altair Ascent nor Descent Stage would fit inside available transportation aircraft. Ground transportation of a payload this large over extended distances is generally not permitted by most states, so overland transportation alone would not have been an option. Limited ground transportation to the nearest waterway may be permitted, but water transportation could take as long as 66 days per production unit, depending on point of origin and acceptance test facility; transportation from the western United States would require transit through the Panama Canal to access the Kennedy Space Center launch site. Large payloads also pose acceptance test and ground processing challenges. Although propulsion, mechanical vibration, and reverberant acoustic test facilities at NASA s Plum Brook Station have been designed to accommodate large spacecraft, special handling and test work-arounds may be necessary, which could increase cost, schedule, and technical risk. Once at the launch site, there are no facilities currently capable of accommodating the combination of large payload size and hazardous processing (which includes hypergolic fuels, pyrotechnic devices, and high pressure gasses)