Handling qualities of large flexible control-configured aircraft

The effects on handling qualities of low frequency symmetric elastic mode interaction with the rigid body dynamics of a large flexible aircraft was analyzed by use of a mathematical pilot modeling computer simulation. An extension of the optimal control model for a human pilot was made so that the mode interaction effects on the pilot's control task could be assessed. Pilot ratings were determined for a longitudinal tracking task with parametric variations in the undamped natural frequencies of the two lowest frequency symmetric elastic modes made to induce varying amounts of mode interaction. Relating numerical performance index values associated with the frequency variations used in several dynamic cases, to a numerical Cooper-Harper pilot rating has proved successful in discriminating when the mathematical pilot can or cannot separate rigid from elastic response in the tracking task

Characteristics of Private Schools in the United States: Results From the 2011-12 Private School Universe Survey

In 1988, the National Center for Education Statistics (NCES) developed a private school data collection that improved on the sporadic collection of private school data dating back to 1890 bydeveloping an alternative to commercially available private school sampling frames. Since 1989, the U.S. Bureau of the Census has conducted the biennial Private School Universe Survey (PSS) for NCES. The PSS is designed to generate biennial data on the total number of private schools, students, and teachers, and to build a universe of private schools to serve as a sampling frame of private schools for NCES sample surveys. For more information about the methodology and design of the PSS, please see the Technical Notes in appendix B of this report. The target population for the PSS is all schools in the 50 states and the District of Columbia that are not supported primarily by public funds, provide classroom instruction for one or more of grades kindergarten through 12 (or comparable ungraded levels), and have one or more teachers. Organizations or institutions that provide support for home schooling, but do not provide classroom instruction, are not included. The 2011 -- 12 PSS data were collected between September 2011 and May 2012. All data are for the 2011 -- 12 school year except the high school graduate data, which are for the 2010 -- 11 school year.Because the purpose of this report is to introduce new NCES survey data through the presentation of tables containing descriptive information, only selected findings are listed below. These findings are purely descriptive in nature and are not meant to imply causality. These findings have been chosen to demonstrate the range of information available from the 2011 -- 12 PSS rather than to discuss all of the observed differences, emphasize any particular issue, or make comparisons over time.The tables in this report contain counts and percentages demonstrating bivariate relationships. All of the results have been weighted to reflect the sample design and to account for nonresponse and other adjustments. Comparisons drawn in the selected findings have been tested for statistical significance at the .05 level using Student's t statistics to ensure that the differences are larger than those that might be expected due to sampling variation. No adjustments were made for multiple comparisons. Many of the variables examined are related to one another, and complex interactions and relationships have not been explored. Statistical Analysis Software (SAS 9.2) and SUDAAN (10.0) were used to compute the statistics for this report

A unique formulation of elastic airplane longitudinal equations of motion

Control-configured vehicle technology has increased the demand for detailed analysis of dynamic stability and control, handling and ride qualities, and control system dynamics at early stages of preliminary design. An approximate, but reasonably accurate, set of equations of motion are needed for these early analyses. Such a formulation is developed for the longitudinal dynamics of elastic airplanes. It makes use of only rigid-body aerodynamic stability derivatives in formulating the forces and moments due to elastic motion. Verification of accuracy using data for the B-1 airplane shows very good agreement. Frequencies and damping ratios of the coupled modes corresponding to complex roots of the characteristic equations agree closely with four symmetric elastic modes included

Effects of dynamic aeroelasticity on handling qualities and pilot rating

Pilot performance parameters, such as pilot ratings, tracking errors, and pilot comments were determined for a longitudinal pitch tracking task using a large, flexible bomber with parametric variations in the undamped natural frequencies of the two lowest frequency symmetric elastic modes. This pitch tracking task was programmed on a fixed base simulator with an electronic attitude-director display of pitch command, pitch angle, and pitch error. Low frequency structural flexibility significantly affects the handling qualities and pilot ratings in the task evaluated

Does offshoring reduce industry employment?

This paper looks at the implications of offshoring for industry employment whilst explicitly accounting for the scale and technology effects of offshoring. The effects of offshoring on employment are analysed using industry-level data for 17 high income OECD countries. Our findings indicate that offshoring has no effect or a slight positive effect on sectoral employment. Offshoring within the same industry (“intra-industry offshoring”) reduces the labour-intensity of production, but does not affect overall industry employment. Inter-industry offshoring does not affect labour-intensity, but may have a positive effect on overall industry employment. These findings suggest that the productivity gains from offshoring are sufficiently large that the jobs created by higher sales completely offset the jobs lost by relocating certain production stages to foreign production sites.international outsourcing, labour demand

Causality and information transfer in simultaneously slow- and fast-light media

We demonstrate the simultaneous propagation of slow- and fast-light optical pulses in a four-wave mixing scheme using warm potassium vapor. We show that when the system is tuned such that the input probe pulses exhibit slow-light group velocities and the generated pulses propagate with negative group velocities, the information velocity in the medium is nonetheless constrained to propagate at, or less than, c. These results demonstrate that the transfer and copying of information on optical pulses to those with negative group velocities obeys information causality, in a manner that is reminiscent of a classical version of the no-cloning theorem. Additionally, these results support the fundamental concept that points of non-analyticity on optical pulses correspond to carriers of new information.Comment: 11 pages, 6 figure

The Roles of Possibility and Mechanism in Narrative Explanation

There is a fairly longstanding distinction between what are called the ideographic as opposed to nomothetic sciences. The nomothetic sciences, such as physics, offer up explanations in terms of the laws and regular operations of nature. The ideographic sciences, such as natural history (or, more controversially, evolutionary biology), cast explanations in terms of narratives. This paper offers an account of what is involved in offering an explanatory narrative in the historical (ideographic) sciences. I argue that narrative explanations involve two chief components: a possibility space and an explanatory causal mechanism. The possibility space is an ineluctable consequence of the fact that the presently available evidence underdetermines the true historical sequence from an epistemic perspective. But the introduction of an adequate causal mechanism gives us a reason to favor one causal history over another; that is, causal mechanisms enhance our epistemic position in the face of widespread underdetermination. This work stands in contrast to some recent work that has argued against the use of mechanisms in some narrative contexts. I argue instead that an adequate causal mechanism is always involved in narrative explanation, or else we do not have an explanation at all