1,318 research outputs found

    Estimation of Standardized Effort in the Heterogeneous Gulf of Mexico Shrimp Fleet

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    In this paper we estimate nominal and standardized shrimping effort in the Gulf of Mexico for the years 1965 through 1993. We accomplish this by first developing a standardization method (model) and then an expansion method (model). The expansion model estimates nominal days fished for noninterview landings data. The standardization model converts nominal days fished to standard days fished. We then characterize the historical trends of the penaeid shrimp fishery byvessel configuration, relative fishing power, and nominal and standardized effort. Wherever possible, we provide comparison with previous estimates by the National Marine Fisheries Service, NOAA

    Thirteen Months of Sunshine

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    Thirteen Months of Sunshine

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    Traumatic and Healing Memory in Leslie Marmon Silko\u27s Ceremony and Toni Morrison\u27s Song of Solomon

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    A comparative analysis of Leslie Marmon Silko’s Ceremony and Toni Morrison’s Song of Solomon, with a focus on individual as well as collective memory work in historically marginalized indigenous and African-American communities, respectively. This represents a critical study of how the novels invoke progressive and redemptive models of remembering, as well as foreground the role of spiritual guides in the transformative process from trauma towards healing

    Traumatic and Healing Memory in Leslie Marmon Silko\u27s Ceremony and Toni Morrison\u27s Song of Solomon

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    A comparative analysis of Leslie Marmon Silko’s Ceremony and Toni Morrison’s Song of Solomon, with a focus on individual as well as collective memory work in historically marginalized indigenous and African-American communities, respectively. This represents a critical study of how the novels invoke progressive and redemptive models of remembering, as well as foreground the role of spiritual guides in the transformative process from trauma towards healing

    An Assessment of Ares I-X Aeroacoustic Measurements with Comparisons to Pre-Flight Wind Tunnel Test Results

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    During the recent successful launch of the Ares I-X Flight Test Vehicle, aeroacoustic data was gathered at fifty-seven locations along the vehicle as part of the Developmental Flight Instrumentation. Several of the Ares I-X aeroacoustic measurements were placed to duplicate measurement locations prescribed in pre-flight, sub-scale wind tunnel tests. For these duplicated measurement locations, comparisons have been made between aeroacoustic data gathered during the ascent phase of the Ares I-X flight test and wind tunnel test data. These comparisons have been made at closely matching flight conditions (Mach number and vehicle attitude) in order to preserve a one-to-one relationship between the flight and wind tunnel data. These comparisons and the current wind tunnel to flight scaling methodology are presented and discussed. The implications of using wind tunnel test data scaled under the current methodology to predict conceptual launch vehicle aeroacoustic environments are also discussed

    Space Launch System Scale Model Acoustic Test Ignition Overpressure Testing

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    The overpressure phenomenon is a transient fluid dynamic event occurring during rocket propulsion system ignition. This phenomenon results from fluid compression of the accelerating plume gas, subsequent rarefaction, and subsequent propagation from the exhaust trench and duct holes. The high-amplitude unsteady fluid-dynamic perturbations can adversely affect the vehicle and surrounding structure. Commonly known as ignition overpressure (IOP), this is an important design-to environment for the Space Launch System (SLS) that NASA is currently developing. Subscale testing is useful in validating and verifying the IOP environment. This was one of the objectives of the Scale Model Acoustic Test (SMAT), conducted at Marshall Space Flight Center (MSFC). The test data quantifies the effectiveness of the SLS IOP suppression system and improves the analytical models used to predict the SLS IOP environments. The reduction and analysis of the data gathered during the SMAT IOP test series requires identification and characterization of multiple dynamic events and scaling of the event waveforms to provide the most accurate comparisons to determine the effectiveness of the IOP suppression systems. The identification and characterization of the overpressure events, the waveform scaling, the computation of the IOP suppression system knockdown factors, and preliminary comparisons to the analytical models are discussed

    Reducing the Effect of Transducer Mount Induced Noise on Aeroacoustic Wind Tunnel Testing Data with a New Transducer Mount Design

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    Flight vehicle aeroacoustic environments induced during transonic and supersonic flight are usually predicted by subscale wind tunnel testing utilizing high frequency miniature pressure transducers. In order to minimize noise induced by the measurement itself, transducer flush mounting with the model surface is very important. The National Aeronautics and Space Administration (NASA) has accomplished flushness in recent testing campaigns via use of a transducer holder that can be machined and sanded. A single hole in the holder allows the flow medium to interact with the transducer diaphragm. Noise is induced by the resulting cavity however, and is a challenge to remove in post-processing. A new holder design has been developed that minimizes the effects of this transducer mount induced noise (XMIN) by reducing the resonance amplitude or increasing its resonance frequency beyond the range of interest. This paper describes a test conducted at the NASA/George C. Marshall Space Flight Center Trisonic Wind Tunnel intended to verify the effectiveness of this design. The results from this test show that this new transducer holder design does significantly reduce the influence of XMIN on measured fluctuating pressure levels without degrading a transducer's ability to accurately measure the noise external to the model

    Dental Anatomy Carving Computer-Assisted Instruction Program: An Assessment of Student Performance and Perceptions

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    The purpose of this study was to compare the performance of students exposed to two different instructional modalities for dental anatomy wax carving: CAI (computer-assisted instruction) using DVD technology, or traditional laboratory instruction. Students’ self-assessment scores were also compared to faculty scores, and students’ perceptions of their teaching modality were analyzed. Seventy-three first-year dental students (response rate 81 percent) participated in this randomized single blind trial, in which faculty graders were blinded to student group assignment. There were no statistical differences, as determined by the Wilcoxon non-parametric test and a t-test, between the faculty grades on the wax carving from the two teaching methods the students experienced. The student self-assessments revealed higher mean grades (3.0 for the DVD-only group and 3.1 for the traditional group) than the faculty actual mean grades (2.2 for both the DVD-only group and the traditional group) by almost one grade level on a 4.0 grade scale. Similar percentages of students in the traditional group had either favorable or unfavorable perceptions of their learning experience, while more students in the DVD-only group reported favorable perceptions. Students from both groups said they wanted more faculty feedback in the course. Based on these objective and subjective data, merging CAI and traditional laboratory teaching may best enhance student learning needs
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