31,630 research outputs found
A direct helicopter EM sea ice thickness inversion, assessed with synthetic and field data
Accuracy and precision of helicopter electromagneticHEM sounding are the essential parameters for HEM seaicethickness profiling. For sea-ice thickness research, thequality of HEM ice thickness estimates must be better than10 cm to detect potential climatologic thickness changes.Weintroduce and assess a direct, 1D HEM data inversion algorithmfor estimating sea-ice thickness. For synthetic qualityassessment, an analytically determined HEM sea-ice thicknesssensitivity is used to derive precision and accuracy. Precisionis related directly to random, instrumental noise, althoughaccuracy is defined by systematic bias arising fromthe data processing algorithm. For the in-phase component ofthe HEM response, sensitivity increases with frequency andcoil spacing, but decreases with flying height. For small-scaleHEM instruments used in sea-ice thickness surveys, instrumentalnoise must not exceed 5 ppm to reach ice thicknessprecision of 10 cm at 15-m nominal flying height. Comparableprecision is yielded at 30-m height for conventional explorationHEM systems with bigger coil spacings. Accuracylosses caused by approximations made for the direct inversionare negligible for brackish water and remain better than10 cm for saline water. Synthetic precision and accuracy estimatesare verified with drill-hole validated field data fromEast Antarctica, where HEM-derived level-ice thicknessagrees with drilling results to within 4%, or 2 cm
Comparison of medium frequency pulsed radar interferometer and correlation analysis winds, part 2
In order to test whether the chosen Doppler peaks represent localized scatters in motion, as opposed to some sort of integrated composite, an attempt was made to determine the change in position of single scatterers over a series of sequential records. A four-antenna system was employed which had 1 degree of freedom in phase. Due to limitations N-S linear transmission and E-W linear reception were used. The Doppler frequency peak selection criteria were that at least two of the four power spectra should have a local peak, and that normalized phase discrepancy, should be less than 0.3. The lack of success in tracking individual scatters seems to suggest a short lifetime. If this is the case, then the present experiment is not able to resolve the difference found between the correlation analysis true velocity and the interferometer value. On the other hand, it appears that the interferometer may be of some use in tracking waves
The geography of strain: organizational resilience as a function of intergroup relations
Organizational resilience is an organization’s ability to absorb strain and preserve or
improve functioning, despite the presence of adversity. In existing scholarship there is
the implicit assumption that organizations experience and respond holistically to acute
forms of adversity. We challenge this assumption by theorizing about how adversity can
create differential strain, affecting parts of an organization rather than the whole. We
argue that relations among those parts fundamentally shape organizational resilience.
We develop a theoretical model that maps how the differentiated emergence of strain in
focal parts of an organization triggers the movements of adjoining parts to provide or
withhold resources necessary for the focal parts to adapt effectively. Drawing on core
principles of theories about intergroup relations, we theorize about three specific
pathways—integration, disavowal, and reclamation—by which responses of adjoining
parts to focal part strain shape organizational resilience. We further theorize about
influences on whether and when adjoining parts are likely to select different pathways.
The resulting theory reveals how the social processes among parts of organizations
influence member responses to adversity and, ultimately, organizational resilience. We
conclude by noting the implications for organizational resilience theory, research, and
practice.Accepted manuscrip
Constraining the Star Formation Histories of Spiral Bulges
Long-slit spectroscopic observations of line-strengths and kinematics made
along the minor axes of four spiral bulges are reported. Comparisons are made
between central line-strengths in spiral bulges and those in other
morphological types. The bulges are found to have central line-strengths
comparable with those of single stellar populations (SSPs) of approximately
solar abundance or above. Negative radial gradients are observed in
line-strengths, similar to those in elliptical galaxies. The bulge data are
consistent with correlations between Mg2, and central velocity dispersion
observed in elliptical galaxiess. In contrast to elliptical galaxies, central
line-strengths lie within the loci defining the range of and Mg2 achieved
by Worthey's (1994) solar abundance ratio, SSPs. The implication of solar
abundance ratios indicates differences in the star formation histories of
spiral bulges and elliptical galaxies. A ``single zone with in- fall'' model of
galactic chemical evolution, using Worthey's (1994) SSPs, is used to constrain
possible star formation histories in our sample. We show that , Mg2 and
Hbeta line-strengths observed in these bulges cannot be reproduced using
primordial collapse models of formation but can be reproduced by models with
extended in-fall of gas and star formation (2-17 Gyr) in the region modelled.
One galaxy (NGC 5689) shows a central population with luminosity weighted
average age of ~5 Gyr, supporting the idea of extended star formation.
Kinematic substructure, possibly associated with a central spike in
metallicity, is observed at the centre of the Sa galaxy NGC 3623.Comment: 14 pages. MNRAS latex file. Accepted for publication in MNRA
Retransmission of water resources data using the ERTS-1 data collection system
There are no author-identified significant results in this report
Science Leadership: Impact of the New Science Coordinators Academy
This article discusses the impact of the New Science Coordinators Academy (NSCA) on two cohorts of participants. The NSCA is one of four components of the Virginia Initiative for Science Teaching and Achievement (VISTA), a United States Department of Education (USED) science education reform grant. The NSCA is designed to support new school district science coordinators (with less than five years of experience) and to continue building the state science education infrastructure. Research in education leadership traditionally focuses on teacher leaders, principals, and district office personnel. Interestingly, research on district office personnel rarely distinguishes between the different roles of district personnel. This article seeks to inform the field by sharing the impact of an academy designed for new science coordinators on their learning, and to begin to understand their role and impact in their district. The five-day Academy engaged participants in a variety of experiences designed to facilitate the following: 1) build leadership skills; 2) build a common understanding and vision for hands-on science, inquiry, problem-based learning, and nature of science in the science classroom; 3) investigate data to improve student learning goals; 4) and, develop a science strategic plan. The data indicate that the NSCA was successful at meeting its goals to support the participants and to build a common language among these new coordinators. Initial data also support the variety of responsibilities of these participants and the positive impact of the Academy on their district work
Criteria for generalized macroscopic and mesoscopic quantum coherence
We consider macroscopic, mesoscopic and "S-scopic" quantum superpositions of
eigenstates of an observable, and develop some signatures for their existence.
We define the extent, or size of a superposition, with respect to an
observable \hat{x}, as being the range of outcomes of \hat{x} predicted by that
superposition. Such superpositions are referred to as generalized -scopic
superpositions to distinguish them from the extreme superpositions that
superpose only the two states that have a difference in their prediction
for the observable. We also consider generalized -scopic superpositions of
coherent states. We explore the constraints that are placed on the statistics
if we suppose a system to be described by mixtures of superpositions that are
restricted in size. In this way we arrive at experimental criteria that are
sufficient to deduce the existence of a generalized -scopic superposition.
The signatures developed are useful where one is able to demonstrate a degree
of squeezing. We also discuss how the signatures enable a new type of
Einstein-Podolsky-Rosen gedanken experiment.Comment: 15 pages, accepted for publication in Phys. Rev.
Exposition Parade March
https://digitalcommons.library.umaine.edu/mmb-ps/2335/thumbnail.jp
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