A program to evaluate a control system based on feedback of aerodynamic pressure differentials, part 1

The use of pressure differentials in a flight control system was evaluated. The pressure profile around the test surface was determined using two techniques: (1) windtunnel data (actual); and (2) NASA/Langley Single Element Airfoil Computer Program (theoretical). The system designed to evaluate the concept of using pressure differentials is composed of a sensor drive and power amplifiers, actuator, position potentiometer, and a control surface. The characteristics (both desired and actual) of the system and each individual component were analyzed. The desired characteristics of the system as a whole are given. The flight control system developed, the testing procedures and data reduction methods used, and theoretical frequency response analysis are described

Misbehavior, Suspensions, and Security Measures in High School: Racial/Ethnic and Gender Differences

This study used merged data from three national surveys to address questions about security measures in American high schools, suspension rates, and student misbehavior. First, the study identified the characteristics of schools that implemented the most extreme security measures and those with the highest levels of discipline. Second, the study used data on individual students to examine misbehavior and race and gender disparities in suspensions not attributable to misbehavior. The main findings were: (1) In-school suspensions serve a ‘gateway’ function with regard to out-of-school suspensions. They may provide a time and place to address behavior problems before they escalate or disproportionate out-of-school suspensions before they occur; (2) Out-of-school suspensions were more frequent among schools in higher-crime neighborhoods. Thus students suspended may be relegated to an environment not conducive to positive educational or social outcomes; (3) African-American students and Hispanic/Latino students were suspended at higher rates than were non-Hispanic whites, differences in most cases not attributable to different levels of misbehavior; (4) Overall, males were more likely to be suspended than were females, an effect above and beyond that explained by differences in behavior. There was little or no difference in the suspension rates of black males and females, however; (5) High degrees of school security were associated with increased suspension rates and increased black – white disparities in total suspensions. At the same time, most black students were enrolled in schools with high degrees of security; (6) Black males were suspended at higher and higher rates as school size increased. All of these have implications for school policy and practice. These are discussed in the paper together with limitations of the investigation

On the spin of gravitational bosons

We unearth spacetime structure of massive vector bosons, gravitinos, and gravitons. While the curvatures associated with these particles carry a definite spin, the underlying potentials cannot be, and should not be, interpreted as single spin objects. For instance, we predict that a spin measurement in the rest frame of a massive gravitino will yield the result 3/2 with probability one half, and 1/2 with probability one half. The simplest scenario leaves the Riemannian curvature unaltered; thus avoiding conflicts with classical tests of the theory of general relativity. However, the quantum structure acquires additional contributions to the propagators, and it gives rise to additional phases.Comment: Honorable mention, 2002 Gravity Research Foundation Essay

Detecting an association between γ\gamma Ray and Gravitational Wave Bursts

If $\gamma$-ray bursts (GRBs) are accompanied by gravitational wave bursts (GWBs) the correlated output of two gravitational wave detectors evaluated in the moments just prior to a GRB will differ from that evaluated at times not associated with a GRB. We can test for this difference independently of any model of the GWB signal waveform. If we invoke a model for the GRB source population and GWB radiation spectral density we can find a confidence interval or upper limit on the root-mean-square GWB signal amplitude in the detector waveband. To illustrate we adopt a simple, physically motivated model and estimate that initial LIGO detector observations coincident with 1000 GRBs could lead us to exclude, with 95% confidence, associated GWBs with $h_{RMS} be Gaussian or that any inter-detector correlated noise be measured or measurable; it does not require advanced or a priori knowledge of the source waveform; and the limits obtained on the wave-strength improve with the number of observed GRBs

Psychosocial Correlates of Physical Activity in Children and Adolescents in a Rural Community Setting

The purpose of this study was to evaluate the relationships between selected psychosocial factors and the physical activity behaviors of children (grade 4-8) and adolescents (grades 9-12) in a rural community setting. The Children’s Physical Activity Scale (CPAC)was used to measure the psychosocial factors of physical activity, The Physical Activity Questionnaire-Children (PAQ-C), and Physical Activity Questionnaire-Adolescents (PAQ-A) were used to measure the physical activity behaviors of the 167 participants. Results indicated that male and female physical activity behaviors were not significantly different. However, physical activity declined with age [F(8,147) = 5.44, p \u3c 0.05, ES = 0.23]. All psychosocial factors were significantly correlated with physical activity in youth with the single highest correlation for males being “liking of exercise” (r = .61) and the highest correlation for females was “liking of games and sports”(r = .44). Stepwise regression analyses identified three subscales (liking of games and sport, liking of exercise, and parental support) in a significant prediction model of physical activity in both genders. The results indicate that children\u27s physical activity is associated with a variety of psychosocial variables that represent import predisposing and reinforcing factors

On recurrence and ergodicity for geodesic flows on noncompact periodic polygonal surfaces

We study the recurrence and ergodicity for the billiard on noncompact polygonal surfaces with a free, cocompact action of $\Z$ or $\Z^2$. In the $\Z$-periodic case, we establish criteria for recurrence. In the more difficult $\Z^2$-periodic case, we establish some general results. For a particular family of $\Z^2$-periodic polygonal surfaces, known in the physics literature as the wind-tree model, assuming certain restrictions of geometric nature, we obtain the ergodic decomposition of directional billiard dynamics for a dense, countable set of directions. This is a consequence of our results on the ergodicity of \ZZ-valued cocycles over irrational rotations.Comment: 48 pages, 12 figure

Searching for Ground Truth: a stepping stone in automating genre classification

This paper examines genre classification of documents and its role in enabling the effective automated management of digital documents by digital libraries and other repositories. We have previously presented genre classification as a valuable step toward achieving automated extraction of descriptive metadata for digital material. Here, we present results from experiments using human labellers, conducted to assist in genre characterisation and the prediction of obstacles which need to be overcome by an automated system, and to contribute to the process of creating a solid testbed corpus for extending automated genre classification and testing metadata extraction tools across genres. We also describe the performance of two classifiers based on image and stylistic modeling features in labelling the data resulting from the agreement of three human labellers across fifteen genre classes.

The Origin of Black Hole Entropy in String Theory

I review some recent work in which the quantum states of string theory which are associated with certain black holes have been identified and counted. For large black holes, the number of states turns out to be precisely the exponential of the Bekenstein-Hawking entropy. This provides a statistical origin for black hole thermodynamics in the context of a potential quantum theory of gravity.Comment: 18 pages (To appear in the proceedings of the Pacific Conference on Gravitation and Cosmology, Seoul, Korea, February 1-6, 1996.

Improving the efficiency of the detection of gravitational wave signals from inspiraling compact binaries: Chebyshev interpolation

Inspiraling compact binaries are promising sources of gravitational waves for ground and space-based laser interferometric detectors. The time-dependent signature of these sources in the detectors is a well-characterized function of a relatively small number of parameters; thus, the favored analysis technique makes use of matched filtering and maximum likelihood methods. Current analysis methodology samples the matched filter output at parameter values chosen so that the correlation between successive samples is 97% for which the filtered output is closely correlated. Here we describe a straightforward and practical way of using interpolation to take advantage of the correlation between the matched filter output associated with nearby points in the parameter space to significantly reduce the number of matched filter evaluations without sacrificing the efficiency with which real signals are recognized. Because the computational cost of the analysis is driven almost exclusively by the matched filter evaluations, this translates directly into an increase in computational efficiency, which in turn, translates into an increase in the size of the parameter space that can be analyzed and, thus, the science that can be accomplished with the data. As a demonstration we compare the present "dense sampling" analysis methodology with our proposed "interpolation" methodology, restricted to one dimension of the multi-dimensional analysis problem. We find that the interpolated search reduces by 25% the number of filter evaluations required by the dense search with 97% correlation to achieve the same efficiency of detection for an expected false alarm probability. Generalized to higher dimensional space of a generic binary including spins suggests an order of magnitude increase in computational efficiency.Comment: 23 pages, 5 figures, submitted to Phys. Rev.