55 research outputs found
First-principles data for solid-solution strengthening of magnesium: From geometry and chemistry to properties
Solid-solution strengthening results from solutes impeding the glide of
dislocations. Existing theories of strength rely on solute-dislocation
interactions, but do not consider dislocation core structures, which need an
accurate treatment of chemical bonding. Here, we focus on strengthening of Mg,
the lightest of all structural metals and a promising replacement for heavier
steel and aluminum alloys. Elasticity theory, which is commonly used to predict
the requisite solute-dislocation interaction energetics, is replaced with
quantum-mechanical first-principles calculations to construct a predictive
mesoscale model for solute strengthening of Mg. Results for 29 different
solutes are displayed in a "strengthening design map" as a function of solute
misfits that quantify volumetric strain and slip effects. Our strengthening
model is validated with available experimental data for several solutes,
including Al and Zn, the two most common solutes in Mg. These new results
highlight the ability of quantum-mechanical first-principles calculations to
predict complex material properties such as strength.Comment: 9 pages, 7 figures, 2 table
Development of a nuclear test strategy for Test Program Element II
As part of Phase O in Test Program Element II of the Office of Fusion Energy's First Wall/Blanket/Shield Engineering Test Program, a test strategy has been developed to address the blanket/shield's (B/S's) thermal-hydraulic and thermomechanical data needs, which were identified in an earlier task through the use of nuclear and supporting nonnuclear testing. In Phase I, which extends through 1984, this strategy emphasizes the development of pre-design information and the nonnuclear supporting tests. After Phase I, nuclear testing will be emphasized, and B/S design-verification testing will become more important. The proposed program will investigate a solid-breeder-blanket concept via nuclear testing. This program can begin in Phase I with nonnuclear support tests, and can progress to integrated nuclear testing soon after the completion of Phase I. The program's approximate cost and schedule are presented. In addition, other possible areas of study for Phase I, and strategies for the use of nuclear and nonnuclear facilities after Phase I are outlined
Dangerous human-made interference with climate: A GISS modelE study
This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.We investigate the issue of "dangerous human-made interference with climate" using simulations with GISS modelE driven by measured or estimated forcings for 1880-2003 and extended to 2100 for IPCC greenhouse gas scenarios as well as the 'alternative' scenario of Hansen and Sato. Identification of 'dangerous' effects is partly subjective, but we find evidence that added global warming of more than 1 degree C above the level in 2000 has effects that may be highly disruptive. The alternative scenario, with peak added forcing ~1.5 W/m2 in 2100, keeps further global warming under 1 degree C if climate sensitivity is \~3 degrees C or less for doubled CO2. We discuss three specific sub-global topics: Arctic climate change, tropical storm intensification, and ice sheet stability. Growth of non-CO2 forcings has slowed in recent years, but CO2 emissions are now surging well above the alternative scenario. Prompt actions to slow CO2 emissions and decrease non-CO2 forcings are needed to achieve the low forcing of the alternative scenario
Climate simulations for 1880-2003 with GISS modelE
We carry out climate simulations for 1880-2003 with GISS modelE driven by ten
measured or estimated climate forcings. An ensemble of climate model runs is
carried out for each forcing acting individually and for all forcing mechanisms
acting together. We compare side-by-side simulated climate change for each
forcing, all forcings, observations, unforced variability among model ensemble
members, and, if available, observed variability. Discrepancies between
observations and simulations with all forcings are due to model deficiencies,
inaccurate or incomplete forcings, and imperfect observations. Although there
are notable discrepancies between model and observations, the fidelity is
sufficient to encourage use of the model for simulations of future climate
change. By using a fixed well-documented model and accurately defining the
1880-2003 forcings, we aim to provide a benchmark against which the effect of
improvements in the model, climate forcings, and observations can be tested.
Principal model deficiencies include unrealistically weak tropical El Nino-like
variability and a poor distribution of sea ice, with too much sea ice in the
Northern Hemisphere and too little in the Southern Hemisphere. The greatest
uncertainties in the forcings are the temporal and spatial variations of
anthropogenic aerosols and their indirect effects on clouds.Comment: 44 pages; 19 figures; Final text accepted by Climate Dynamic
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Dangerous human-made interference with climate: a GISS modelE study
We investigate the issue of "dangerous human-made interference with climate" using simulations with GISS modelE driven by measured or estimated forcings for 1880â2003 and extended to 2100 for IPCC greenhouse gas scenarios as well as the "alternative" scenario of Hansen and Sato (2004). Identification of "dangerous" effects is partly subjective, but we find evidence that added global warming of more than 1°C above the level in 2000 has effects that may be highly disruptive. The alternative scenario, with peak added forcing ~1.5 W/m2 in 2100, keeps further global warming under 1°C if climate sensitivity is ~3°C or less for doubled CO2. The alternative scenario keeps mean regional seasonal warming within 2Ï (standard deviations) of 20th century variability, but other scenarios yield regional changes of 5â10Ï, i.e. mean conditions outside the range of local experience. We conclude that a CO2 level exceeding about 450 ppm is "dangerous", but reduction of non-CO2 forcings can provide modest relief on the CO2 constraint. We discuss three specific sub-global topics: Arctic climate change, tropical storm intensification, and ice sheet stability. We suggest that Arctic climate change has been driven as much by pollutants (O3, its precursor CH4, and soot) as by CO2, offering hope that dual efforts to reduce pollutants and slow CO2 growth could minimize Arctic change. Simulated recent ocean warming in the region of Atlantic hurricane formation is comparable to observations, suggesting that greenhouse gases (GHGs) may have contributed to a trend toward greater hurricane intensities. Increasing GHGs cause significant warming in our model in submarine regions of ice shelves and shallow methane hydrates, raising concern about the potential for accelerating sea level rise and future positive feedback from methane release. Growth of non-CO2 forcings has slowed in recent years, but CO2 emissions are now surging well above the alternative scenario. Prompt actions to slow CO2 emissions and decrease non-CO2 forcings are required to achieve the low forcing of the alternative scenario
The Legal Landscape of Wave Energy Pilot Projects on the Oregon Coast
26 pagesThis Note focuses on wave energy development off the Oregon Coast. Specifically, it focuses on the permitting and licensing requirements related to the development of experimental facilities, pilot projects, and phased developments set against the backdrop of Oregonâs commitment to develop wave energy based on a precautionary approach
Die deutschen Provincial Reconstruction Teams: Ein neues Instrument zum Nation-Building
Die erstmals Anfang 2003 von den USA in Afghanistan eingesetzten "Provincial Reconstruction Teams" (PRTs) sind ein neues Instrument der Internationalen Gemeinschaft zur UnterstĂŒtzung des Peace-, Nation- und State-Building in Post-Konflikt-Gesellschaften. Eine deutsche Variante ist seit Ende 2003 in Kunduz und Feyzabad im Einsatz. Die Wiedererrichtung und Stabilisierung von Gesellschaften und Staaten nach der Beendigung gewaltsamer Konflikte ist zu einer prioritĂ€ren Aufgabe der deutschen AuĂen-, Sicherheits- und Entwicklungspolitik und zu einer zentralen Strategie globaler Sicherheitskooperation geworden. Deutschland und seine Partner sehen sich beim Nation-Building vor allem zwei Problemen gegenĂŒber: der Knappheit an personellen, finanziellen und politisch-legitimatorischen Ressourcen und dem Mangel an Konzepten und Instrumenten, die zivile und militĂ€rische Aufgaben so effizient wie möglich bewĂ€ltigen helfen. PRTs sollen dazu beitragen, die nur begrenzt zur VerfĂŒgung stehenden Soldaten, Diplomaten, zivilen Experten und finanziellen Mittel möglichst optimal zur Stabilisierung und zum Wiederaufbau des gescheiterten Staates einzusetzen. Die Studie untersucht Struktur, Aufgaben und Arbeitsweise der deutschen PRTs, setzt sich mit den Hauptkritikpunkten an Konzept und Praxis auseinander und bietet einen Ausblick auf die LeistungsfĂ€higkeit der PRT-Strategie und ihre Ăbertragbarkeit auf kĂŒnftige Nation-Building-Operationen und Hilfsaktionen zur BewĂ€ltigung groĂer Naturkatastrophen. PRTs eröffnen der AuĂen- und Sicherheitspolitik mit ihrer einzigartigen Integration ziviler und militĂ€rischer Handlungsformen neue Möglichkeiten. Sie werden dann ihre Synergien voll entfalten können, wenn die zivilen und militĂ€rischen Akteure bereits in der politischen Einsatzplanung und in der schulenden Einsatzvorbereitung zusammenwirken. Die Einsatzergebnisse der PRTs sollten in einer zentralen Nation-Building-Datenbank erfasst und durch Praktiker wie Wissenschaftler gemeinsam aufbereitet werden. (SWP-Studie / SWP
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