Students in rural schools have limited access to advanced mathematics courses

This Carsey brief reveals that students in rural areas and small towns have less access to higher-level mathematics courses than students in urban settings, which results in serious educational consequences, including lower scores on assessment tests and fewer qualified students entering science, technology, engineering, and mathematics (STEM) job pipelines

Theoretical study of refraction effects on noise produced by turbulent jets

The transmission of acoustic disturbances from the interior of a jet into the ambient air is studied. The jet is assumed infinitely long with mean velocity profile independent of streamwise location. The noise generator is a sequence of transient sources drifting with the local fluid and confined to a short length of the jet. In Part 1, supersonic jets are considered. Numerical results for mean-square pressure versus angle in the far-field show unexpected peaks which are very sharp. Analysis of simplified models indicates that these are complex quasi-resonant effects which appear to the stationary observer in a high frequency range. The peaks are real for the idealized model, but would be smoothed by mathematical integration over source position, velocity, and frequency. Subsonic jets were considered in part 2, and a preliminary study of the near-field was attempted. Mean-square radial displacements (or mean radial energy flow or space-time correlations of radial pressure gradient) are first found for very simple cases. The most difficult case studied is a sequence of transient sources at the center of a uniform-velocity circular cylindrical jet. Here a numerical triple integration is required and seems feasible although only preliminary results for mean square radial displacement are now available. These preliminary results show disturbances decreasing with increasing radial distance, and with increasing distance upstream and downstream from the source. A trend towards greater downstream disturbances appears even in the near field

Effect of Gimbal friction modeling technique on control stability and performance for Centaur upper-stage

The powered-phase autopilot for the Centaur upper stage rocket uses an autopilot forward loop gain scheduler that decreases the proportional gain as propellant mass is depleted. Nonlinear time response simulation studies revealed that Centaur vehicles with low-gain autopilots would have large attitude error limit cycles. These limit cycles were due to the assumed presence of Coulomb friction in the engine gimbals. This situation could be corrected through the use of an harmonic dither, programmed into the on-board digital computer and added to the engine command signal. This would introduce impending motion to the engines, allowing control of the engines even under small commands. Control authority was found to be restored when dither was used. A concern arose that the Centaur could be unacceptably excited at resonances near the dither frequency, if the dither amplitude was to be chosen on the basis of friction level present, a test was conducted to measure this level. Dither characteristics were to be based on the test results. The test results showed that the gimbal friction characteristic was actually hysteretic rather than the assumed Coulomb friction. The simulation results showed that, using this new model of gimbal friction, dither would no longer be necessary

Reading levels of rural and urban third graders lag behind their suburban peers

This brief examines the complex interplay of family, school, and place factors in the reading achievement levels of third grade students. Third grade reading achievement is critical to later academic and occupational success. Using data from the Early Childhood Longitudinal Study, the authors report that suburban children realize greater gains in reading achievement from kindergarten to Grade 3 than their rural or urban counterparts. Rural students who were struggling readers at the beginning of kindergarten have lower average reading achievement in third grade than both urban and suburban students when children of the same socioeconomic status are compared. The differences in third grade reading achievement between rural and nonrural children who were low achievers in kindergarten most likely reflect different educational opportunities and school resources available to these children. The authors suggest that improved professional development opportunities for rural teachers may help narrow the differences in the third grade reading achievement of rural, urban, and suburban students who were struggling readers in kindergarten

Acoustic emission frequency discrimination

In acoustic emission nondestructive testing, broadband frequency noise is distinguished from narrow banded acoustic emission signals, since the latter are valid events indicative of structural flaws in the material being examined. This is accomplished by separating out those signals which contain frequency components both within and beyond (either above or below) the range of valid acoustic emission events. Application to acoustic emission monitoring during nondestructive bond verification and proof loading of undensified tiles on the Space Shuttle Orbiter is considered

Quasi-Bell inequalities from symmetrized products of noncommuting qubit observables

Noncommuting observables cannot be simultaneously measured, however, under local hidden variable models, they must simultaneously hold premeasurement values, implying the existence of a joint probability distribution. We study the joint distributions of noncommuting observables on qubits, with possible criteria of positivity and the Fr\'echet bounds limiting the joint probabilities, concluding that the latter may be negative. We use symmetrization, justified heuristically and then more carefully via the Moyal characteristic function, to find the quantum operator corresponding to the product of noncommuting observables. This is then used to construct Quasi-Bell inequalities, Bell inequalities containing products of noncommuting observables, on two qubits. These inequalities place limits on local hidden variable models that define joint probabilities for noncommuting observables. We find Quasi-Bell inequalities have a quantum to classical violation as high as $\frac{3}{2}$, higher than conventional Bell inequalities. The result demonstrates the theoretical importance of noncommutativity in the nonlocality of quantum mechanics, and provides an insightful generalization of Bell inequalities.Comment: 17 page

Starting Salary Differences Between Women and Men: Organization-Level Findings and an Analysis of Current Policy Options

This study examined the starting salaries paid by over 250 employers to 2,800 university graduates. Of the overall female-male salary difference of $4,396, the majority, or$3,175 (72%), occurred between employers; $1,221 (28$1,221 (28%) of the female-male pay difference. Although adjustment for qualifications such as degree level, grade point average, and college major reduced the pay difference between women and men, our findings indicate that, on average, the same employer pays graduating women 3.5% to 5.8% less than graduating men with similar qualifications