In this paper we describe the OpenGeoSys (OGS) project, which is a scientific open-source initiative for numerical simulation of thermo-hydro-mechanical-chemical processes in porous media. The basic ...concept is to provide a flexible numerical framework (using primarily the Finite Element Method (FEM)) for solving multifield problems in porous and fractured media for applications in geoscience and hydrology. To this purpose OGS is based on an object-oriented FEM concept including a broad spectrum of interfaces for pre- and postprocessing. The OGS idea has been in development since the mid-eighties. We provide a short historical note about the continuous process of concept and software development having evolved through Fortran, C, and C++ implementations. The idea behind OGS is to provide an open platform to the community, outfitted with professional software-engineering tools such as platform-independent compiling and automated benchmarking. A comprehensive benchmarking book has been prepared for publication. Benchmarking has been proven to be a valuable tool for cooperation between different developer teams, for example, for code comparison and validation purposes (DEVOVALEX and CO
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BENCH projects). On one hand, object-orientation (OO) provides a suitable framework for distributed code development; however, the parallelization of OO codes still lacks efficiency. High-performance-computing efficiency of OO codes is subject to future research.
► A micromechanical based creep and damage model was developed for 9Cr–1Mo steel. ► High temperature behavior of 9Cr–1Mo was modeled based on dislocations glide and climb. ► The generation and ...annihilation of single and dipole dislocations was modeled. ► Creep tests were performed at several stress and temperature levels. ► Numerical results were compared to the experimental results for 9Cr–1Mo steel.
A micromechanical model is developed for the evaluation of creep deformation and rupture times of modified 9Cr–1Mo steel specimens. Creep deformation in metals is generally induced by the dislocation generation, motion, and annihilation. To evaluate the creep behavior of the modified 9Cr–1Mo steel the Orowan’s equation was employed, which is valid for both glide and climb-controlled dislocation movement. The evolution of the dislocation density was modeled by considering the generation and annihilation of single and dipole dislocations. In addition to dislocation motion as a basis for creep deformation, there are several other factors which determine the creep resistance of this steel. Among these, the most significant are precipitate coarsening, solid solutions depletion, and void/crack nucleation and growth. The evolution of these mechanisms during creep deformation was accounted for by introducing specific continuum damage terms. Creep tests were also performed at several stress and temperature levels. The comparison of the numerical model results with the experimental data showed satisfactory agreement.
•An overview of the FRS Ion Catcher experiment at GSI is given.•The FRS Ion Catcher consists of the FRS, a cryogenic stopping cell, an RF quadrupole-based beam transport and diagnostics unit and a ...multiple-reflection time-of-flight mass spectrometer.•Off-line tests of the stopping cell with 219Rn ions.•First on-line operation of a stopping cell for exotic nuclei at cryogenic temperatures.•First mass measurements of heavy projectile fragments using a multiple-reflection time-of-flight mass spectrometer.
At the FRS Ion Catcher at GSI, projectile and fission fragments are produced at relativistic energies, separated in-flight, range-focused, slowed down and thermalized in a cryogenic stopping cell. A multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS) is used to perform direct mass measurements and to provide an isobarically clean beam for further experiments, such as mass-selected decay spectroscopy. A versatile RF quadrupole transport and diagnostics unit guides the ions from the stopping cell to the MR-TOF-MS, provides differential pumping, ion identification and includes reference ion sources. The FRS Ion Catcher serves as a test facility for the Low-Energy Branch of the Super-FRS at the Facility for Antiproton and Ion Research (FAIR), where the cryogenic stopping cell and the MR-TOF-MS will be key devices for the research with stopped projectile and fission fragments that will be performed with the experiments MATS and LaSpec. Off-line tests of the stopping cell yield a combined ion survival and extraction efficiency for 219Rn ions of about 30% and an extraction time of about 25ms. The stopping cell and the MR-TOF-MS were commissioned on-line as part of the FRS Ion Catcher. For the first time, a stopping cell for exotic nuclei was operated on-line at cryogenic temperatures. Using a gas density almost two times higher than ever reached before for a stopping cell with RF ion repelling structures, various 238U projectile fragments were thermalized and extracted with very high efficiency. Direct mass measurements of projectile fragments were performed with the MR-TOF-MS, among them the nuclide 213Rn with a half-life of 19.5ms only.
The conceptual design of a next-generation cryogenic stopping cell (CSC) for the Low-Energy Branch (LEB) of the Super-FRS has been developed. It builds on advanced techniques implemented in the ...prototype version of the CSC, which has recently been commissioned as part of the FRS Ion Catcher with 238U projectile and fission fragments produced at 1000MeV/u. These techniques include cryogenic operation to ensure a high purity of the stopping gas and high-density operation enabled using an RF carpet with a small electrode structure size. The next generation CSC implements several novel concepts (e.g. perpendicular extraction) which lead to enhanced performance compared to the prototype CSC: (i) extremely short extraction times, (ii) higher rate capability, (iii) increased areal density without deteriorating extraction times, efficiencies or rate capability, (iv) minimized RF power, (v) precise range measurement of the ions and (vii) improved cleanliness of the CSC.
Thermal use of the shallow subsurface for heat generation, cooling, and thermal energy storage is increasingly gaining importance in reconsideration of future energy supplies. Shallow geothermal ...energy use is often promoted as being of little or no costs during operation, while simultaneously being environmentally friendly. Hence, the number of installed systems has rapidly risen over the last few decades, especially among newly built houses. While the carbon dioxide reduction potential of this method remains undoubted, concerns about sustainability and potential negative effects on the soil and groundwater due to an intensified use have been raised—even as far back as 25 years ago. Nevertheless, consistent regulation and management schemes for the intensified thermal use of the shallow subsurface are still missing—mainly due to a lack of system understanding and process knowledge. In the meantime, large geothermal applications, for example, residential neighborhoods that are entirely dependent up on shallow geothermal energy use or low enthalpy aquifer heat storage, have been developed throughout Europe. Potential negative effects on the soil and groundwater due to an intensive thermal use of the shallow subsurface as well as the extent of potential system interaction still remain unknown.
Dairy farms producing 98% of the US milk supply participate in the Farmers Assuring Responsible Management (FARM) Animal Care Program. Producers who sell milk to cooperatives or processors ...participating in FARM must follow program standards. The objectives of this study were to assess producer perceptions about the knowledge, experience, and value of FARM and to determine whether perceptions differ based on demographics. A concurrent triangulation design was implemented through collecting quantitative and qualitative data using a 30-question survey instrument. Quantitative questions aimed to address project objectives, and qualitative data were provided through 1 open-ended survey question that asked participants what they thought the main goal of the FARM program was. Participants offered additional feedback through providing text in comment boxes, writing on the back of the survey, or writing a separate letter and returning it with their survey. Quantitative data were analyzed using principal components analysis and modeling, and qualitative data were analyzed through thematic analysis. Dairy producers from cooperatives or processors that participate in the FARM program were recruited via electronic and postal mail. A total of 487 respondents from 40 states completed the survey. Of the survey participants, 414 (85.0%) answered the open-ended question and 190 (39.0%) provided additional qualitative feedback. Thematic analysis revealed 5 main themes: distrust of program, producers on the defense, anger, efficiency, and nostalgia. Of respondents, 73.6% reported being knowledgeable about the FARM Animal Care Program. Greater level of formal education and larger herd size were associated with greater producer knowledge. More dairy producer input in the revisions of FARM was identified as a need by 83.3% of respondents. Although 89.3% of respondents reported positive experiences with evaluations and relationships with evaluators, 45.6% did not think that the program had value overall. Respondent age was positively associated with perceived value of FARM. Respondent age was also significant in determining the reasons why FARM was considered to be important. Results indicate that to increase buy-in and positive perceptions from producers, future versions of FARM should solicit producer input during the development of program standards, target specific producer demographics for program promotion, and address perceived communication deficits and program inequalities. Findings from this study can be used to inform future versions of the program.
The ice giant planets, Uranus and Neptune, are fundamentally different from the gas giant and terrestrial planets. Though ice giants represent the most common size of exoplanet and possess ...characteristics that challenge our understanding of the way our solar system formed and evolved, they remain the only class of planetary object without a dedicated spacecraft mission. The inclusion of a Uranus orbiter as the third highest priority Flagship mission in the NASA Planetary Science Decadal Survey “Vision and Voyages for Planetary Science in the Decade 2013–2022” indicates a high level of support for exploration of the ice giants by the planetary science community. However, given the substantial costs associated with a flagship mission, it is critical to explore lower cost options if we intend to visit Uranus within an ideal launch window of 2029–2034 when a Jupiter gravity assist becomes available. In this paper, we describe the Quest to Uranus to Explore Solar System Theories (QUEST), a New Frontiers class Uranus orbiter mission concept study performed at the 30th Annual NASA/JPL Planetary Science Summer Seminar. The proposed QUEST platform is a spin-stabilized spacecraft designed to undergo highly elliptical, polar orbits around Uranus during a notional one-year primary science mission. The proposed major science goals of the mission are (1) to use Uranus as a natural laboratory to better understand the dynamos that drive magnetospheres in the solar system and beyond and (2) to identify the energy transport mechanisms in Uranus' magnetic, atmospheric, and interior environments in contrast with the other giant planets. With substantial mass, power, and cost margins, this mission concept demonstrates a compelling, feasible option for a New Frontiers Uranus orbiter mission.
•QUEST is a Uranus orbiter mission concept based extensively on the Juno mission.•The mission would address the top two objectives for a Uranus flagship mission in the NASA Decadal Survey.•The mission would investigate Uranus' unique magnetic field, atmosphere and interior environments.
211Po ions in the ground and isomeric states were produced via 238U projectile fragmentation at 1000 MeV/u. The 211Po ions were spatially separated in flight from the primary beam and other reaction ...products by the fragment separator FRS. The ions were energy-bunched, slowed-down and thermalized in a gas-filled cryogenic stopping cell (CSC). They were then extracted from the CSC and injected into a high-resolution multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS). The excitation energy of the isomer and, for the first time, the isomeric-to-ground state ratio were determined from the measured mass spectrum. In the subsequent experimental step, the isomers were spatially separated from the ions in the ground state by an ion deflector and finally collected with a silicon detector for decay spectroscopy. This pioneering experimental result opens up unique perspectives for isomer-resolved studies. With this versatile experimental method new isomers with half-lives longer than a few milliseconds can be discovered and their decay properties can be measured with highest sensitivity and selectivity. These experiments can be extended to studies with isomeric beams in nuclear reactions.
Grade 91 steel is considered a potential structural material for advanced nuclear reactors. The creep deformation behavior of Grade 91 steel was studied in the temperature range of 600–700°C and at ...stresses of 35–350MPa. The data were analyzed in terms of Monkman-Grant relation and Larson–Miller parameter. Creep damage tolerance factor and stress exponent were used to identify the cause of creep damage. The fracture surface morphology of the ruptured specimens was studied by scanning electron microscopy to elucidate the failure mechanisms. Fracture mechanism map for Grade 91 steel was developed based on the available material parameters and experimental observations.
Travel times and flow paths of groundwater from its recharge area to drinking-water production wells will govern how the quality of pumped groundwater responds to contaminations. Here, we studied the ...180 km² Ammer catchment in southwestern Germany, which is extensively used for groundwater production from a carbonate aquifer. Using a 3-D steady-state groundwater model, four alternative representations of discharge and recharge were systematically explored to understand their impact on groundwater travel times and flow paths. More specifically, two recharge maps obtained from different German hydrologic atlases and two plausible alternative discharge scenarios were tested: (1) groundwater flow across the entire streambed of the Ammer River and its main tributaries and (2) groundwater discharge via a few major springs feeding the Ammer River. For each of these scenarios, the groundwater model was first calibrated against water levels, and subsequently travel times and flow paths were calculated for production wells using particle tracking methods. These computed travel times and flow paths were indirectly evaluated using additional data from the wells including measured concentrations of major ions and environmental tracers indicating groundwater age. Different recharge scenarios resulted in a comparable fit to observed water levels, and similar estimates of hydraulic conductivities, flow paths and travel times of groundwater to production wells. Travel times calculated for all scenarios had a plausible order of magnitude which were comparable to apparent groundwater ages modelled using environmental tracers. Scenario with groundwater discharge across the entire streambed of the Ammer River and its tributaries resulted in a better fit to water levels than scenario with discharge at a few springs only. In spite of the poorer fit to water levels, flow paths of groundwater from the latter scenario were more plausible, and these were supported by the observed major ion chemistry at the production wells. We concluded that data commonly used in groundwater modelling such as water levels and apparent groundwater ages may be insufficient to reliably delineate capture zones of wells. Hydrogeochemical information relating only indirectly to groundwater flow such as the major ion chemistry of water sampled at the wells can substantially improve our understanding of the source areas of recharge for production wells.
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