1,638 research outputs found

    Alternatives to the Gypsy Moth Eradication Program in Michigan

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    Responding to questions of what the gypsy moth, Porthetria dispar, would do in Michigan forests, a computer simulation model was constructed. The model consisted of three subunits: a submodel of gypsy moth population dynamics, a submodel of forest growth and a submodel of tree defoliation and mortality. Several different policies were simulated for an 80 year period. The eradication policy now employed in Michigan failed due to survival of small portions of the population. Allowing the gypsy moth to become established in Michigan forests and then responding by spraying when defoliation is visible provided a policy with the least economic and environmental cost

    A comparison of profits from pullets and yearling hens with and without artificial lights

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    Design and Evaluation of Dual-Expander Aerospike Nozzle Upper Stage Engine

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    The goal of the Dual-Expander Aerospike Nozzle, a modification to traditional engine architectures, is to find those missions and designs for which it has a competitive advantage over traditional upper stage engines such as the RL10. Previous work focused on developing an initial design to demonstrate the feasibility of the Dual-Expander Aerospike Nozzle. This research expanded the original cycle model in preparation for optimizing the engine\u27s specific impulse and thrust-to-weight ratio. The changes to the model allowed automated parametric and optimization studies. Preliminary parametric studies varying oxidizer-to-fuel ratio, total mass flow, and chamber length showed significant improvements. Drawing on modeling lessons from previous research, this research developed a new engine simulation capable of achieving a specific impulse comparable to the RL10. Parametric studies using the new model verified the Dual-Expander Aerospike Nozzle architecture conforms to rocket engine theory while exceeding the RL10\u27s performance. Finally, this research concluded by optimizing the Dual-Expander Aerospike Nozzle engine for three US government missions: the Next Generation Engine program, the X-37 mission, and the Space Launch System. The optimized Next Generation Engine design delivers 35,000 lbf of vacuum thrust at 469.4 seconds of vacuum specific impulse with a thrust-to-weight ratio of 127.2 in an engine that is one quarter the size of a comparable RL10. For the X-37 mission, the optimized design operates at 6,600 lbf of vacuum thrust and has a vacuum specific impulse of 457.2 seconds with a thrust-to-weight ratio of 107.5. The Space Launch System design produces a vacuum thrust of 100,000 lbf with a vacuum specific impulse of 465.9 seconds and a thrust-to-weight ratio of 110.2. When configured in a cluster of three engines, the Dual-Expander Aerospike Nozzle matches the J2-X vacuum thrust with a 4% increase in specific impulse

    Design and Evaluation of Dual-Expander Aerospike Nozzle Upper Stage Engine

    Get PDF
    The goal of the Dual-Expander Aerospike Nozzle, a modification to traditional engine architectures, is to find those missions and designs for which it has a competitive advantage over traditional upper stage engines such as the RL10. Previous work focused on developing an initial design to demonstrate the feasibility of the Dual-Expander Aerospike Nozzle. This research expanded the original cycle model in preparation for optimizing the engine\u27s specific impulse and thrust-to-weight ratio. The changes to the model allowed automated parametric and optimization studies. Preliminary parametric studies varying oxidizer-to-fuel ratio, total mass flow, and chamber length showed significant improvements. Drawing on modeling lessons from previous research, this research developed a new engine simulation capable of achieving a specific impulse comparable to the RL10. Parametric studies using the new model verified the Dual-Expander Aerospike Nozzle architecture conforms to rocket engine theory while exceeding the RL10\u27s performance. Finally, this research concluded by optimizing the Dual-Expander Aerospike Nozzle engine for three US government missions: the Next Generation Engine program, the X-37 mission, and the Space Launch System. The optimized Next Generation Engine design delivers 35,000 lbf of vacuum thrust at 469.4 seconds of vacuum specific impulse with a thrust-to-weight ratio of 127.2 in an engine that is one quarter the size of a comparable RL10. For the X-37 mission, the optimized design operates at 6,600 lbf of vacuum thrust and has a vacuum specific impulse of 457.2 seconds with a thrust-to-weight ratio of 107.5. The Space Launch System design produces a vacuum thrust of 100,000 lbf with a vacuum specific impulse of 465.9 seconds and a thrust-to-weight ratio of 110.2. When configured in a cluster of three engines, the Dual-Expander Aerospike Nozzle matches the J2-X vacuum thrust with a 4% increase in specific impulse

    Precision Electroweak Constraints on Hidden Local Symmetries

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    In this talk we discuss the phenomenology of models with replicated electroweak gauge symmetries, based on a framework with the gauge structure [SU(2) or U(1)] x U(1) x SU(2) x SU(2).Comment: 7 pages, talk given at SCGT0

    Aeroelastic Optimization of Sounding Rocket Fins

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    This research effort develops a multidisciplinary design tool to optimize sounding rocket fin geometries that minimize the mass of the fins while maintaining aerodynamic performance. This research grew out of a design problem experienced by the US Air Force Academy\u27s Falcon LAUNCH program. The Falcon LAUNCH program is a senior design capstone project during which Air Force Academy cadets design, build and fly a sounding rocket over the course of an academic year. In the Spring of 2007, the Falcon LAUNCH V vehicle experienced a catastrophic failure when three of its four fins sheared off due to flutter. When the following year\u27s team developed the fins for Falcon LAUNCH VI, the design requirement that the fins not experience flutter led to substantially more massive fins. The Falcon LAUNCH team needs a design tool that can balance the competing needs for minimal mass sounding rocket components and aerodynamic performance. The tool developed during this research is designed to find an optimal solution for the fin geometry based on the competing needs of minimizing the fins\u27 mass and ensuring the fins will not experience flutter. The design tool then provides for verification of the design throughout the designed flight profile

    Power Posing: P-Curving the Evidence

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    In a well-known article, Carney, Cuddy, and Yap (2010) documented the benefits of “power posing”. In their study, participants (N=42) who were randomly assigned to briefly adopt expansive, powerful postures sought more risk, had higher testosterone levels, and had lower cortisol levels than those assigned to adopt contractive, powerless postures. In their response to a failed replication by Ranehill et al. (2015), Carney, Cuddy, and Yap (2015) reviewed 33 successful studies investigating the effects of expansive vs. contractive posing, focusing on differences between these studies and the failed replication, to identify possible moderators that future studies could explore. But before spending valuable resources on that, it is useful to establish whether the literature that Carney et al. (2015) cited actually suggests that power posing is effective. In this paper we rely on p-curve analysis to answer the following question: Does the literature reviewed by Carney et al. (2015) suggest the existence of an effect once we account for selective reporting? We conclude not. The distribution of p-values from those 33 studies is indistinguishable from what is expected if (1) the average effect size were zero, and (2) selective reporting (of studies and/or analyses) were solely responsible for the significant effects that are published. Although more highly powered future research may find replicable evidence for the purported benefits of power posing (or unexpected detriments), the existing evidence is too weak to justify a search for moderators or to advocate for people to engage in power posing to better their lives
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