2,518 research outputs found
A parametric study of the value of hydrological information for irrigation and hydropower management of the Feather River
A case study analysis is presented of the relationships between improvements in the accuracy, frequency, and timeliness of information used in making hydrological forecasts and economic benefits in the areas of hydropower and irrigation. The area chosen for the case study is the Oroville Dam and Reservoir. Emphasis is placed on the use of timely and accurate mapping of the aerial extent of snow in the basin by earth resources survey systems such as LANDSAT. The subject of benefits resulting from improved runoff forecasts is treated in a generalized way without specifying the source of the improvements
Calcium-Rich Gap Transients: Tidal Detonations of White Dwarfs?
We hypothesize that at least some of the recently discovered class of
calcium-rich gap transients are tidal detonation events of white dwarfs (WDs)
by black holes (BHs) or possibly neutron stars. We show that the properties of
the calcium-rich gap transients agree well with the predictions of the tidal
detonation model. Under the predictions of this model, we use a follow-up X-ray
observation of one of these transients, SN 2012hn, to place weak upper limits
on the detonator mass of this system that include all intermediate-mass BHs
(IMBHs). As these transients are preferentially in the stellar haloes of
galaxies, we discuss the possibility that these transients are tidal
detonations of WDs caused by random flyby encounters with IMBHs in dwarf
galaxies or globular clusters. This possibility has been already suggested in
the literature but without connection to the calcium-rich gap transients. In
order for the random flyby cross-section to be high enough, these events would
have to be occurring inside these dense stellar associations. However, there is
a lack of evidence for IMBHs in these systems, and recent observations have
ruled out all but the very faintest dwarf galaxies and globular clusters for a
few of these transients. Another possibility is that these are tidal
detonations caused by three-body interactions, where a WD is perturbed toward
the detonator in isolated multiple star systems. We highlight a number of ways
this could occur, even in lower-mass systems with stellar-mass BHs or neutron
stars. Finally, we outline several new observational tests of this scenario,
which are feasible with current instrumentation.Comment: 10 pages, 1 figure, accepted for publication in MNRA
The economic value of remote sensing by satellite: An ERTS overview and the value of continuity of service. Volume 2: Source document
The economic value of an ERS system with a technical capability similar to ERTS, allowing for increased coverage obtained through the use of multiple active satellites in orbit is presented. A detailed breakdown of the benefits achievable from an ERS system is given and a methodology for their estimation is established. The ECON case studies in agriculture, water use, and land cover are described along with the current ERTS system. The cost for a projected ERS system is given
Separating baryons and dark matter in cluster cores: a full 2-D lensing and dynamic analysis of Abell 383 and MS2137-23
(abridged) We utilize existing imaging and spectroscopic data for the galaxy
clusters MS2137-23 and Abell 383 to present improved measures of the
distribution of dark and baryonic material in the clusters' central regions.
Our method, based on the combination of gravitational lensing and dynamical
data, is uniquely capable of separating the distribution of dark and baryonic
components at scales below 100 kpc. We find a variety of strong lensing models
fit the available data, including some with dark matter profiles as steep as
expected from recent simulations. However, when combined with stellar velocity
dispersion data for the brightest member, shallower inner slopes than predicted
by numerical simulations are preferred. For Abell 383, the preferred shallow
inner slopes are statistically a good fit only when the multiple image position
uncertainties associated with our lens model are assumed to be 0\farcs5, to
account for unknown substructure. No statistically satisfactory fit was
obtained matching both the multiple image lensing data and the velocity
dispersion profile of the brightest cluster galaxy in MS2137-23. This suggests
that the mass model we are using, which comprises a pseudo-elliptical
generalized NFW profile and a brightest cluster galaxy component may
inadequately represent the inner cluster regions. This may plausibly arise due
to halo triaxiality or by the gravitational interaction of baryons and dark
matter in cluster cores. However, the progress made via this detailed study
highlights the key role that complementary observations of lensed features and
stellar dynamics offer in understanding the interaction between dark and
baryonic matter on non-linear scales in the central regions of clusters.Comment: 18 pages, 9 figures; accepted for publication in the Astrophysical
Journa
IMPROVING UNRESTRICTED LINE OFFICER COMMUNITY CORPS LOGISTICS KNOWLEDGE: KEY CONCEPTS AND PROCESSES
Naval leadership has identified the lack of logistics experience as a critical force vulnerability in the Unrestricted Line (URL) community officer corps. They believe this gap will limit the Navy’s ability to sustain operations in contested and constrained environments. As the United States enters a new era of strategic competition with near-peer competitors, increasing the logistical knowledge and educational experiences of the URL community is of paramount importance. Peacetime naval operations have dominated the operational landscape for several decades with logistical support mirroring that static and predictable environment. Strategic competition will challenge the established logistic concepts and those concepts must also change. This project develops case studies to equip URL officers with the necessary mindset to approach and analyze complex logistic concerns. Each case study touches on specific logistics topics, incorporates broader logistical implications, and uses various investigative and analytic tools to help solve real-world problems. Equally important, this study will build a stronger foundation that will make the warfighter more combat effective and further enhance his or her grasp of operational and tactical environments.NPS Naval Research ProgramThis project was funded in part by the NPS Naval Research Program.Lieutenant Commander, United States NavyLieutenant Commander, United States NavyApproved for public release. Distribution is unlimited
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