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41.
42.
Bi-Qing For Elizabeth M. Green Gilles Fontaine Scott Shaw 《Astrophysics and Space Science》2010,328(1-2):87-90
In this paper, we report a rare reflection effect eclipsing sdB+dM binary, 2M?1533+3759. It is the seventh eclipsing sdB+dM binary that has been discovered to date. This system has an orbital period of 0.16177042 day and a velocity semi-amplitude of 71.1 km?s?1. Using a grid of zero-metallicity NLTE model atmospheres, we derived T eff=29250 K, log?g=5.58 and [He/H]=?2.37 from spectra taken near the reflection effection minimum. Lightcurve modeling resulted in a system mass ratio of 0.301 and an orbital inclination angle of 86.6°. The derived primary mass for 2M?1533+3759, 0.376±0.055 M ⊙, is significantly lower than the canonical mass (0.48 M ⊙) found for most previously investigated sdB stars. This implies an initial progenitor mass >1.8 M ⊙, at least a main sequence A star and perhaps even one massive enough to undergo non-degenerate helium ignition. 相似文献
43.
Water introduced to surface drainages, such as agricultural and roadway runoff, mine drainage, or coalbed natural gas (CBNG)-produced water, potentially can be of environmental concern. In order to mitigate potential environmental effects, it may be important to be able to trace water discharged to the surface as it infiltrates and interacts with near-surface aquifers. We have chosen to study water withdrawn during CBNG production for isotope tracing in the hyporheic zone because it poses a variety of economic, environmental, and policy issues in the Rocky Mountain states. Ground water quality must be protected as CBNG water is added to semiarid ecosystems. Strontium (Sr) isotopes are effective fingerprints of the aquifer from which water originates. In this study, CBNG water was found to have a higher (87)Sr/(86)Sr ratio than the local alluvial aquifer water. This measurable difference allows the strontium isotope ratio and concentration to be used as tracers of CBNG water following its discharge to the surface. The dissolution and mobilization of salts from soil are an important contributor to ground water quality degradation. In the Powder River basin of Wyoming, the soils are calcium carbonate-buffered systems. The chemical similarity of strontium to calcium allows it to substitute into calcium minerals and enabled us to use strontium isotopes to identify calcium salts mobilized from the soil. Strontium isotopes are an effective monitor of the source of ions and the volume and direction of introduced water flow in the hyporheic zone. 相似文献
44.
Interviewing landed elites in post-war Guatemala 总被引:1,自引:0,他引:1
Elizabeth Oglesby 《Geoforum》2010,41(1):23-25
This essay explores the methodological challenges of conducting ethnographic research among economic and managerial elites in Guatemala’s landed sector during the country’s post-war transition. Guatemala’s 34-year civil war ended with peace accords in 1996. From the mid 1990s through 2001, I conducted interviews with leading representatives of the private sector in Guatemala, including the owners and top managers of the country’s sugar plantations. The Guatemalan sugar elite describes itself as the new face of the private sector in Central America, implementing “corporate social responsibility” programs linked to the World Bank and other international agencies. Questions of access and interview dynamics are often discussed in relation to qualitative research on “elites.” Yet, I found the interview process to be less complicated than I anticipated. Of greater concern were the problems of research dissemination and praxis. The experience discussed here raises questions about whether research on particular elite groups can be sustained over long periods of time. 相似文献
45.
Antti Pulkkinen Michael Hesse Shahid Habib Luke Van der Zel Ben Damsky Fritz Policelli David Fugate William Jacobs Elizabeth Creamer 《Natural Hazards》2010,53(2):333-345
In this paper, central elements of the Solar Shield project, launched to design and establish an experimental system capable
of forecasting the space weather effects on high-voltage power transmission system, are described. It will be shown how Sun–Earth
system data and models hosted at the Community Coordinated Modeling Center (CCMC) are used to generate two-level magnetohydrodynamics-based
forecasts providing 1–2 day and 30–60 min lead-times. The Electric Power Research Institute (EPRI) represents the end-user,
the power transmission industry, in the project. EPRI integrates the forecast products to an online display tool providing
information about space weather conditions to the member power utilities. EPRI also evaluates the economic impacts of severe
storms on power transmission systems. The economic analysis will quantify the economic value of the generated forecasting
system. The first version of the two-level forecasting system is currently running in real-time at CCMC. An initial analysis
of the system’s capabilities has been completed, and further analysis is being carried out to optimize the performance of
the system. Although the initial results are encouraging, definite conclusions about system’s performance can be given only
after more extensive analysis, and implementation of an automatic evaluation process using forecasted and observed geomagnetically
induced currents from different nodes of the North American power transmission system. The final output of the Solar Shield
will be a recommendation for an optimal forecasting system that may be transitioned into space weather operations. 相似文献
46.
Elizabeth Hooper Lee Chapman Andrew Quinn 《Theoretical and Applied Climatology》2014,117(1-2):303-316
Although the fundamental traffic diagram provides the characteristics of a typical road traffic speed–flow relationship, little consideration has been given to the impact of adverse weather conditions on the relationship and the subsequent impact on local speed–flow. For the first time, this study uses precipitation radar along with a state-of-the art traffic information system to ascertain the relationship between speed–flow and precipitation on a UK transport corridor at the local (junction to junction) scale. It is evident that precipitation causes a significant reduction in speed and maximum flow on many links of the corridor as well as a downward reduction in the overall speed-flow relationship. With increased instances of heavy precipitation predicted in the UK as a result of climate change, these findings highlight the subsequent impact on journey travel times and associated economic costs. 相似文献
47.
Elizabeth Dologlou 《International Journal of Earth Sciences》2014,103(4):977-980
Here, we propose an alternative physical model, based on the concept of criticality, for the explanation of the observed magnetic signals prior to the M6.0 Parkfield and the M5.4 Alum Rock earthquakes. Motivated by an analogous experience from major earthquakes in Greece, where both magnetic field variations and seismic electric signals were also recorded few weeks before the main shock, we suggest that in all these cases, similar dynamic processes characterized by critical behaviour should govern the corresponding pre-focal areas when the relevant precursory signals emerged. 相似文献
48.
Elizabeth Dologlou 《International Journal of Earth Sciences》2014,103(2):397-400
An anomalous behaviour of the scaling exponent derived from the detrended fluctuation analysis (DFA) of the time series of low frequency variations of the horizontal and vertical magnetic field components has been recently reported as being observed 2 months prior to the Mw 6.3 earthquake on 6 April 2009, close to L’Aquila city, Italy. Here, we suggest a possible physical explanation of this effect based on the experience from similar measurements in Greece. In particular, for example, we compare these observations associated with Aquila earthquake with the ones of the Mw 6.6 earthquake on 13 May 1995 at Kozani-Grevena, Greece where both magnetic field variations and seismic electric signals (SES) were recorded. Almost 1 month before the latter earthquake, anomalous variations in both electric and magnetic field were detected, the time series of that were analysed by means of DFA and led to an exponent close to unity. Similarly, the calculated DFA exponent for the Aquila earthquake time series of the anomalous magnetic field variations 2 months before the main shock was also found close to unity. These results could imply that in the case of Aquila, according to the Maxwell’s laws, one should expect to observe simultaneously with the magnetic signal an associated SES activity, provided that an appropriate station to monitoring the earth’s electric field variations in the same area was available. Hence, it seems that similar underlying non-linear dynamic processes in mechanical and as well as electromagnetic sense, with features of criticality, dominated in both pre-focal areas. 相似文献
49.
Mapping collective human activity in an urban environment based on mobile phone data 总被引:1,自引:0,他引:1
Identifying and characterizing variations of human activity – specifically changes in intensity and similarity – in urban environments provide insights into the social component of those eminently complex systems. Using large volumes of user-generated mobile phone data, we derive mobile communication profiles that we use as a proxy for the collective human activity. In this article, geocomputational methods and geovisual analytics such as self-organizing maps (SOM) are used to explore the variations of these profiles, and its implications for collective human activity. We evaluate the merits of SOM as a cross-dimensional clustering technique and derived temporal trajectories of variations within the mobile communication profiles. The trajectories’ characteristics such as length are discussed, suggesting spatial variations in intensity and similarity in collective human activity. Trajectories are linked back to the geographic space to map the spatial and temporal variation of trajectory characteristics. Different trajectory lengths suggest that mobile phone activity is correlated with the spatial configuration of the city, and so at different times of the day. Our approach contributes to the understanding of the space-time social dynamics within urban environments. 相似文献