1,421 research outputs found

    Space shuttle high pressure auxiliary propulsion subsystem definition study Summary report

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    Space shuttle high pressure hydrogen oxygen auxiliary propulsion subsystem conceptual and design study summar

    Timescales for the development of methanogenesis and free gas layers in recently-deposited sediments of Arkona Basin (Baltic Sea)

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    Arkona Basin (southwestern Baltic Sea) is a seasonally-hypoxic basin characterized by the presence of free methane gas in its youngest organic-rich muddy stratum. Through the use of reactive transport models, this study tracks the development of the methane geochemistry in Arkona Basin as this muddy sediment became deposited during the last 8 kyr. Four cores are modeled each pertaining to a unique geochemical scenario according to their respective contemporary geochemical profiles. Ultimately the thickness of the muddy sediment and the flux of particulate organic carbon are crucial in determining the advent of both methanogenesis and free methane gas, the timescales over which methanogenesis takes over as a dominant reaction pathway for organic matter degradation, and the timescales required for free methane gas to form

    Condition-Based Maintenance Implementation and Potential in USMC Ground Transport

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    NPS NRP Technical ReportCondition-Based Maintenance (CBM) has been successfully implemented in private-sector operations to reduce maintenance costs and asset downtime. USMC is currently transitioning to a CBM+ approach to maintenance, addressing its unique organizational and operating environment. This project identifies private-sector best practices and lessons learned most applicable to USMC as well as important hurdles for USMC adoption. It identifies maintenance and readiness metrics changes that may be relevant in future USMC and joint sustainment operations, taking into account both CBM and maintenance in an expeditionary environment.HQMC Installations and Logistics (I&L)This research is supported by funding from the Naval Postgraduate School, Naval Research Program (PE 0605853N/2098). https://nps.edu/nrpChief of Naval Operations (CNO)Approved for public release. Distribution is unlimited.

    Condition-Based Maintenance Implementation and Potential in USMC Ground Transport

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    NPS NRP Project PosterCondition-Based Maintenance (CBM) has been successfully implemented in private-sector operations to reduce maintenance costs and asset downtime. USMC is currently transitioning to a CBM+ approach to maintenance, addressing its unique organizational and operating environment. This project identifies private-sector best practices and lessons learned most applicable to USMC as well as important hurdles for USMC adoption. It identifies maintenance and readiness metrics changes that may be relevant in future USMC and joint sustainment operations, taking into account both CBM and maintenance in an expeditionary environment.HQMC Installations and Logistics (I&L)This research is supported by funding from the Naval Postgraduate School, Naval Research Program (PE 0605853N/2098). https://nps.edu/nrpChief of Naval Operations (CNO)Approved for public release. Distribution is unlimited.

    Condition-Based Maintenance Implementation and Potential in USMC Ground Transport

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    NPS NRP Executive SummaryCondition-Based Maintenance (CBM) has been successfully implemented in private-sector operations to reduce maintenance costs and asset downtime. USMC is currently transitioning to a CBM+ approach to maintenance, addressing its unique organizational and operating environment. This project identifies private-sector best practices and lessons learned most applicable to USMC as well as important hurdles for USMC adoption. It identifies maintenance and readiness metrics changes that may be relevant in future USMC and joint sustainment operations, taking into account both CBM and maintenance in an expeditionary environment.HQMC Installations and Logistics (I&L)This research is supported by funding from the Naval Postgraduate School, Naval Research Program (PE 0605853N/2098). https://nps.edu/nrpChief of Naval Operations (CNO)Approved for public release. Distribution is unlimited.

    Continental shelves as a variable but increasing global sink for atmospheric carbon dioxide

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    It has been speculated that the partial pressure of carbon dioxide (pCO2) in shelf waters may lag the rise in atmospheric CO2. Here, we show that this is the case across many shelf regions, implying a tendency for enhanced shelf uptake of atmospheric CO2. This result is based on analysis of long-term trends in the air–sea pCO2 gradient (ΔpCO2) using a global surface ocean pCO2 database spanning a period of up to 35 years. Using wintertime data only, we find that ΔpCO2 increased in 653 of the 825 0.5° cells for which a trend could be calculated, with 325 of these cells showing a significant increase in excess of +0.5 Όatm yr−1 (p 2 during the last century

    In situ generation of coronal Alfvén waves by jets

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    Within the framework of 3D resistive magnetohydrodynamic, we simulate the formation of a plasma jet with the morphology, upward velocity up to 130 km s−1, and time-scale formation between 60 and 90 s after beginning of simulation, similar to those expected for type II spicules. Initial results of this simulation were published in paper by, e.g. GonzĂĄlez-AvilĂ©s et al. (2018), and present paper is devoted to the analysis of transverse displacements and rotational-type motion of the jet. Our results suggest that 3D magnetic reconnection may be responsible for the formation of the jet in paper by GonzĂĄlez-AvilĂ©s et al. (2018). In this paper, by calculating times series of the velocity components vx and vy in different points near to the jet for various heights we find transverse oscillations in agreement with spicule observations. We also obtain a time-distance plot of the temperature in a cross-cut at the plane x = 0.1 Mm and find significant transverse displacements of the jet. By analysing temperature isosurfaces of 104 K with the distribution of vx, we find that if the line-of-sight (LOS) is approximately perpendicular to the jet axis then there is both motion towards and away from the observer across the width of the jet. This red–blue shift pattern of the jet is caused by rotational motion, initially clockwise and anti-clockwise afterwards, which could be interpreted as torsional motion and may generate torsional AlfvĂ©n waves in the corona region. From a nearly vertical perspective of the jet the LOS velocity component shows a central blue-shift region surrounded by red-shifted plasma
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