Understanding linear measure

This article provides strategies for enhancing tasks to offer students better opportunities to develop conceptual understanding of length measurement. Teachers are offered strategies that help move instruction beyond procedures

Degenerate Quantum Codes for Pauli Channels

A striking feature of quantum error correcting codes is that they can sometimes be used to correct more errors than they can uniquely identify. Such degenerate codes have long been known, but have remained poorly understood. We provide a heuristic for designing degenerate quantum codes for high noise rates, which is applied to generate codes that can be used to communicate over almost any Pauli channel at rates that are impossible for a nondegenerate code. The gap between nondegenerate and degenerate code performance is quite large, in contrast to the tiny magnitude of the only previous demonstration of this effect. We also identify a channel for which none of our codes outperform the best nondegenerate code and show that it is nevertheless quite unlike any channel for which nondegenerate codes are known to be optimal.Comment: Introduction changed to give more motivation and background. Figure 1 replace

Portland Junior College Newsance, 03/04/1955

Congratulations, Students of PJChttps://digitalcommons.usm.maine.edu/pjc_newsance/1028/thumbnail.jp

The question of ‘alternatives’ within food and drink markets and marketing: introduction to the special issue

The question of 'alternatives' within food and drink markets and marketing: introduction to the special issu

The Social and Ecological Correlates of Bankruptcy During the Farm Fiscal Crisis, 1970-1987

This article focuses upon the role of the fiscal crisis in the "agricultural transition." The thesis developed is that the fiscal crisis emerged in the late 1970's, and that it was followed by "rural immiseration" - a deteriorating social and economic condition for rural areas. Heffernan and Heffernan (1986) note that the individual suffering from farm stress continues to suffer stress after the loss of the farm. This is because the disengagement or "exit" from farming is far more complex than in prior years due to the structure of social and economic linkages to family, community, and government agencies. Communities suffer the misery of business closure. Families suffer from the effects of dislocation, a misery based upon the loss of friends, neighbors, and a valued way of life. Data to support this thesis are drawn from federal bankruptcy court records. The implications for the agrarian transition are discussed in the conclusion

Variable-camber systems integration and operational performance of the AFTI/F-111 mission adaptive wing

The advanced fighter technology integration, the AFTI/F-111 aircraft, is a preproduction F-111A testbed research airplane that was fitted with a smooth variable-camber mission adaptive wing. The camber was positioned and controlled by flexing the upper skins through rotary actuators and linkages driven by power drive units. The wing camber and control system are described. The measured servoactuator frequency responses are presented along with analytical predictions derived from the integrated characteristics of the control elements. A mission adaptive wing system chronology is used to illustrate and assess the reliability and dependability of the servoactuator system during 1524 hours of ground tests and 145 hours of flight testing

Ionization Equilibrium Timescales in Collisional Plasmas

Astrophysical shocks or bursts from a photoionizing source can disturb the typical collisional plasma found in galactic interstellar media or the intergalactic medium. The spectrum emitted by this plasma contains diagnostics that have been used to determine the time since the disturbing event, although this determination becomes uncertain as the elements in the plasma return to ionization equilibrium. A general solution for the equilibrium timescale for each element arises from the elegant eigenvector method of solution to the problem of a non-equilibrium plasma described by Masai (1984) and Hughes & Helfand (1985). In general the ionization evolution of an element Z in a constant electron temperature plasma is given by a coupled set of Z+1 first order differential equations. However, they can be recast as Z uncoupled first order differential equations using an eigenvector basis for the system. The solution is then Z separate exponential functions, with the time constants given by the eigenvalues of the rate matrix. The smallest of these eigenvalues gives the scale of slowest return to equilibrium independent of the initial conditions, while conversely the largest eigenvalue is the scale of the fastest change in the ion population. These results hold for an ionizing plasma, a recombining plasma, or even a plasma with random initial conditions, and will allow users of these diagnostics to determine directly if their best-fit result significantly limits the timescale since a disturbance or is so close to equilibrium as to include an arbitrarily-long time.Comment: 4 pages, 2 figures. Accepted for publication by the Astrophysical Journa

Simulation at Dryden Flight Research Facility from 1957 to 1982

The Dryden Flight Research Facility has been a leader in developing simulation as an integral part of flight test research. The history of that effort is reviewed, starting in 1957 and continuing to the present time. The contributions of the major program activities conducted at Dryden during this 25-year period to the development of a simulation philosophy and capability is explained