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Johnson, Megan

Publications and source records attributed to Johnson, Megan.

At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS2017

CARA Status and Upcoming Enhancements

CAS 8.4.3 was deployed to operations on 13 June 2017. Discrepancies Between 3D Pc Estimates and advanced Monte Carlo Equinoctial-Sampling Pc Estimates discovered and discussed at 23 May 2017 Useras (Registered Trademark) Forum. The patch created the Reporting Pc, which is the greater value between the calculated 2D and 3D Pc values This changed the Pc reported in the CDMs to the Reporting Pc This changed the Pc reported on the Summary Report to the Reporting Pc This changed the Pc reported on Maneuver Screening Analysis (MSA) Report to the Reporting Pc. Both the 2D and 3D Pc added to the Summary Report details section The patch also updated the 3D Pc algorithm to eliminate velocity covariance from the Pc calculation This will bring 2D and 3D Pc into close alignment for vast majority of events, particularly for the events in which the 2D/3D discrepancy was found.

conjunction assessmen↗
DOE OSTI2017

The H i Chronicles of LITTLE THINGS BCDs. III. Gas Clouds in and around Mrk 178, VII Zw 403, and NGC 3738

In most blue compact dwarf (BCD) galaxies, it remains unclear what triggers their bursts of star formation. We study the H i of three relatively isolated BCDs, Mrk 178, VII Zw 403, and NGC 3738, in detail to look for signatures of star formation triggers, such as gas cloud consumption, dwarf–dwarf mergers, and interactions with companions. High angular and velocity resolution atomic hydrogen (H i) data from the Very Large Array (VLA) dwarf galaxy H i survey, Local Irregulars That Trace Luminosity Extremes, The H i Nearby Galaxy Survey (LITTLE THINGS), allow us to study the detailed kinematics and morphologies of the BCDs in H i. We also present high-sensitivity H i maps from the NRAO Green Bank Telescope (GBT) of each BCD to search their surrounding regions for extended tenuous emission or companions. The GBT data do not show any distinct galaxies obviously interacting with the BCDs. The VLA data indicate several possible star formation triggers in these BCDs. Mrk 178 likely has a gas cloud impacting the southeast end of its disk or it is experiencing ram pressure stripping. VII Zw 403 has a large gas cloud in its foreground or background that shows evidence of accreting onto the disk. NGC 3738 has several possible explanations for its stellar morphology and H i morphology and kinematics: an advanced merger, strong stellar feedback, or ram pressure stripping. Although apparently isolated, the H i data of all three BCDs indicate that they may be interacting with their environments, which could be triggering their bursts of star formation.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

National Hydropower Plant Dataset, Version 1 (Update FY18Q2)

The National Hydropower Plant Dataset, Version 1, Update FY18Q2, includes geospatial point-level locations and key characteristics of existing hydropower plants in the United States that are currently online. These data are a subset extracted from NHAAP’s Existing Hydropower Assets (EHA) dataset, which is a cornerstone of NHAAP’s EHA effort that has supported multiple U.S. hydropower R&D research initiatives related to market acceleration, environmental impact reduction, technology-to-market activities, and climate change impact assessment.

13 HYDRO ENERGY↗
DOE OSTI2016

Hydropower Vision A New Chapter for America's 1st Renewable Electricity Source

The U.S. Department of Energy’s (DOE’s) Wind and Water Power Technologies Office has led a first-of-its- kind comprehensive analysis to evaluate future pathways for low-carbon, renewable hydropower (hydropower generation and pumped storage) in the United States, focused on continued technical evolution, increased energy market value, and environmental sustainability. Undertaken through a broad-based collaborative effort, the Hydropower Vision initiative had four principal objectives: characterize the current state of hydropower in the United States, including trends, opportunities, and challenges; identify ways for hydropower to maintain and expand its contributions to the electricity and water management needs of the nation from the present through 2030 and 2050; examine critical environmental and social factors to assess how existing hydropower operations and potential new projects can minimize adverse effects, reduce carbon emissions from electricity generation, and contribute to stewardship of waterways and watersheds; and develop a roadmap identifying stakeholder actions that could support responsible ongoing operations and potential expansion of hydropower facilities. The Hydropower Vision analysis finds that U.S. hydropower could grow from 101 gigawatts (GW) of capacity to nearly 150 GW by 2050. Growth under this modeled scenario would result from a combination of 13 GW of new hydropower generation capacity (upgrades to existing plants, adding power at existing dams and canals, and limited development of new stream-reaches), and 36 GW of new pumped storage capacity. If this level of growth is achieved, benefits such as a savings of $209 billion from avoided greenhouse gas (GHG) emissions could be realized, of which $185 billion would be attributable to operation of the existing hydropower fleet. Transformative technical innovations able to meet the co-objectives of environmental sustainability and low-carbon energy will be critical to enabling additional hydropower growth beyond these levels. The Hydropower Vision report specifically does not evaluate or recommend new policy actions but instead analyzes the feasibility and certain benefits and costs of various credible scenarios, all of which could inform policy decisions at the federal, state, tribal, and local levels.

13 HYDRO ENERGY↗