1,101 research outputs found
Predicting attrition for women at West Point : is it a function of adopting the male dominant culture?
This study examined 40 selected items from the Student Information Form that had been identified as representing cultural differences between men and women at the United States Military Academy. A principal components analysis of the data collected from 3005 male and 314 female cadets yielded 7 factors for men and 6 factors for women suitable for interpretation. As hypothesized, men and women were found to have similar cultual values, attitudes and experiences based on their similar factor structures. Next, item responses from 58 women attriters were compared to responses from the nonattriters. Using all the factors identified for the women, a discriminant function analysis to predict attrition resulted in the correct classification of 70% of the women. This exploratory approach is unique in that it is an attempt to predict and understand attrition of women from West Point through comparison to a norm of success based on women. Recommendations are made to focus future research on experiences and attitudes towards sexual harrassment at West Point along with measures of cultural ideation to better understand the dynamics which effect attrition
Tomography applied to Lamb wave contact scanning nondestructive evaluation
The aging world-wide aviation fleet requires methods for accurately predicting the presence of structural flaws that compromise airworthiness in aircraft structures. Nondestructive Evaluation (NDE) provides the means to assess these structures quickly, quantitatively, and noninvasively. Ultrasonic guided waves, Lamb waves, are useful for evaluating the plate and shell structures common in aerospace applications. The amplitude and time-of-flight of Lamb waves depend on the material properties and thickness of a medium, and so they can be used to detect any areas of differing thickness or material properties which indicate flaws. By scanning sending and receiving transducers over an aircraft, large sections can be evaluated after a single pass. However, while this technique enables the detection of areas of structural deterioration, it does not allow for the quantification of the extent of that deterioration. Tomographic reconstruction with Lamb waves allows for the accurate reconstruction of the variation of quantities of interest, such as thickness, throughout the investigated region, and it presents the data as a quantitative map. The location, shape, and extent of any flaw region can then be easily extracted from this Tomographic image. Two Lamb wave tomography techniques using Parallel Projection tomography (PPT) and Cross Borehole tomography (CBT), are shown to accurately reconstruct flaws of interest to the aircraft industry. A comparison of the quality of reconstruction and practicality is then made between these two methods, and their limitations are discussed and shown experimentally. Higher order plate theory is used to derive analytical solutions for the scattering of the lowest order symmetric Lamb wave from a circular inclusion, and these solutions are used to explain the scattering effects seen in the Tomographic reconstructions. Finally, the means by which this scattering theory can be used to develop Lamb wave Tomographic algorithms that are more generally applicable in-the-field, is presented
Spinors in Weyl Geometry
We consider the wave equation for spinors in -dimensional Weyl
geometry. By appropriately coupling the Weyl vector as well as
the spin connection to the spinor field, conformal
invariance can be maintained. The one loop effective action generated by the
coupling of the spinor field to an external gravitational field is computed in
two dimensions. It is found to be identical to the effective action for the
case of a scalar field propagating in two dimensions.Comment: 13 pages, REVTEX, no figure
Wall-bounded turbulent flows at high Reynolds numbers: Recent advances and key issues
Wall-bounded turbulent flows at high Reynolds numbers have become an increasingly active area of
research in recent years. Many challenges remain in theory, scaling, physical understanding,
experimental techniques, and numerical simulations. In this paper we distill the salient advances of
recent origin, particularly those that challenge textbook orthodoxy. Some of the outstanding
questions, such as the extent of the logarithmic overlap layer, the universality or otherwise of the
principal model parameters such as the von Kármán “constant,” the parametrization of roughness
effects, and the scaling of mean flow and Reynolds stresses, are highlighted. Research avenues that
may provide answers to these questions, notably the improvement of measuring techniques and the
construction of new facilities, are identified. We also highlight aspects where differences of opinion
persist, with the expectation that this discussion might mark the beginning of their resolution
Supersymmetry on AdS3 and AdS4
We consider a supersymmetric extension of the algebra associated with three
and four dimensional Anti de Sitter space. A representation of the
supersymmetry operators in superspace is given. Supersymmetry invariant models
are constructed for the superspace associated with AdS3.Comment: 14 pages, no figures. Final published version. Now includes a
discussion of the relation of our approach to previous work on supersymmetry
in AdS space
Peculiarities of the Canonical Analysis of the First Order Form of the Einstein-Hilbert Action in Two Dimensions in Terms of the Metric Tensor or the Metric Density
The peculiarities of doing a canonical analysis of the first order
formulation of the Einstein-Hilbert action in terms of either the metric tensor
or the metric density along with the affine connection are discussed. It is shown that the
difference between using as opposed to
appears only in two spacetime dimensions. Despite there being a different
number of constraints in these two approaches, both formulations result in
there being a local Poisson brackets algebra of constraints with field
independent structure constants, closed off shell generators of gauge
transformations and off shell invariance of the action. The formulation in
terms of the metric tensor is analyzed in detail and compared with earlier
results obtained using the metric density. The gauge transformations, obtained
from the full set of first class constraints, are different from a
diffeomorphism transformation in both cases.Comment: 13 page
Ulnar collateral ligament injuries of the thumb: phalangeal translation during valgus stress in human cadavera
BACKGROUND: The clinical diagnosis of thumb ulnar collateral ligament disruption has been based on joint angulation during valgus stress testing. This report describes a definitive method of distinguishing between complete and partial ulnar collateral ligament injuries by quantifying translation of the proximal phalanx on the metacarpal head during valgus stress testing. METHODS: Sixty-two cadaveric thumbs underwent standardized valgus stress testing under fluoroscopy with the ulnar collateral ligament intact, following an isolated release of the proper ulnar collateral ligament, and following a combined release of both the proper and the accessory ulnar collateral ligament (complete ulnar collateral ligament release). Following complete ulnar collateral ligament release, the final thirty-seven thumbs were also analyzed after the application of a valgus force sufficient to cause 45° of valgus angulation at the metacarpophalangeal joint to model more severe soft-tissue injury. Two independent reviewers measured coronal plane joint angulation (in degrees), ulnar joint line gap formation (in millimeters), and radial translation of the proximal phalanx on the metacarpal head (in millimeters) on digital fluoroscopic images that had been randomized. RESULTS: Coronal angulation across the stressed metacarpophalangeal joint progressively increased through the stages of the testing protocol: ulnar collateral ligament intact (average [and standard deviation], 20° ± 8.1°), release of the proper ulnar collateral ligament (average, 23° ± 8.3°), and complete ulnar collateral ligament release (average, 30° ± 8.9°) (p < 0.01 for each comparison). Similarly, gap formation increased from the measurement in the intact state (5.1 ± 1.3 mm), to that following proper ulnar collateral ligament release (5.7 ± 1.5 mm), to that following complete ulnar collateral ligament release (7.2 ± 1.5 mm) (p < 0.01 for each comparison). Radial translation of the proximal phalanx on the metacarpal head did not increase after isolated release of the proper ulnar collateral ligament (1.6 ± 0.8 mm vs. 1.5 ± 0.9 mm in the intact state). There was a significant increase in translation following release of the complete ulnar collateral ligament complex (3.0 ± 0.9 mm; p < 0.01) and an additional increase after forcible angulation of the joint to 45° (4.1 ± 0.9 mm; p < 0.01). Translation 2 mm greater than that in the stressed control was 100% specific for complete disruption of the ulnar collateral ligament complex. CONCLUSIONS: While transection of the proper ulnar collateral ligament leads to an increase in metacarpophalangeal joint angulation and gapping on stress fluoroscopic evaluation, only release of both the accessory and the proper ulnar collateral ligament significantly increases translation of the proximal phalanx on the metacarpal head. CLINICAL RELEVANCE: A finding of phalangeal translation on a stress fluoroscopic image distinguishes partial from complete tears of the thumb ulnar collateral ligament
Lamb Wave Tomography for Corrosion Mapping
As the world-wide civil aviation fleet continues to age, methods for accurately predicting the presence of structural flaws-such as hidden corrosion-that compromise airworthiness become increasingly necessary. Ultrasonic guided waves, Lamb waves, allow large sections of aircraft structures to be rapidly inspected. However, extracting quantitative information from Lamb wave data has always involved highly trained personnel with a detailed knowledge of mechanical-waveguide physics. Our work focuses on using a variety of different tomographic reconstruction techniques to graphically represent the Lamb wave data in images that can be easily interpreted by technicians. Because the velocity of Lamb waves depends on thickness, we can convert the travel times of the fundamental Lamb modes into a thickness map of the inspection region. In this paper we show results for the identification of single or multiple back-surface corrosion areas in typical aluminum aircraft skin structures
Enhancing Environmental Health Literacy about the Asthma- Air Pollution Connection at Childcare Centers in Asthma Prevalent Philadelphia Neighborhoods
Objective: To determine environmental health literacy of childcare providers about outdoor air quality alert resources, the connection between air pollution and asthma and determine if childcare providers would use the resource to benefit children in their care. Methods: We designed a free outreach program about asthma prevalence, dangers of poor air quality, and air quality alert resources for staff at childcare centers in Philadelphia, Pennsylvania during summer and fall of 2015-2017. Pre-surveys were administered to evaluate baseline understanding. Post-surveys were administered at 4 weeks and returned within 4-12 weeks. Summary statistics were calculated, and pre/post knowledge compared using a paired t-test. Results: 258 staffers at 45 childcare centers attended the presentations. 214 completed both pre/post surveys. 74% reported never/rarely using air quality alerts before the program. Post-survey, 40% reported signing up for alerts. Post-survey there was an 8% mean increase in knowledge score (95% CI: 6.3-9.5%, Conclusions: This easily administered program using freely available information was useful to childcare providers and increased their environmental health literacy to benefit children in their care.
Keywords: Environmental Health Literacy; Air Pollution; Asthma; Community Engagement; Public Health
Objective: To determine environmental health literacy of childcare providers about outdoor air quality alert resources, the connection between air pollution and asthma and determine if childcare providers would use the resource to benefit children in their care. Methods: We designed a free outreach program about asthma prevalence, dangers of poor air quality, and air quality alert resources for staff at childcare centers in Philadelphia, Pennsylvania during summer and fall of 2015-2017. Pre-surveys were administered to evaluate baseline understanding. Post-surveys were administered at 4 weeks and returned within 4-12 weeks. Summary statistics were calculated, and pre/post knowledge compared using a paired t-test. Results: 258 staffers at 45 childcare centers attended the presentations. 214 completed both pre/post surveys. 74% reported never/rarely using air quality alerts before the program. Post-survey, 40% reported signing up for alerts. Post-survey there was an 8% mean increase in knowledge score (95% CI: 6.3-9.5%, pConclusions: This easily administered program using freely available information was useful to childcare providers and increased their environmental health literacy to benefit children in their care
Performance Asymmetry in the Star Excursion Balance Test
Please refer to the pdf version of the abstract located adjacent to the title
- …