Institution
Penn State DuBois
About: Penn State DuBois is a based out in . It is known for research contribution in the topics: Ice stream & Dipole antenna. The organization has 27 authors who have published 108 publications receiving 2390 citations. The organization is also known as: Penn State.
Topics: Ice stream, Dipole antenna, Fractal antenna, Antenna (radio), Fractal
Papers published on a yearly basis
Papers
More filters
••
TL;DR: Some important properties of fractal arrays are introduced, including the frequency-independent multi-band characteristics, schemes for realizing low-sidelobe designs, systematic approaches to thinning, and the ability to develop rapid beam-forming algorithms by exploiting the recursive nature of fractals.
Abstract: A fractal is a recursively generated object having a fractional dimension. Many objects, including antennas, can be designed using the recursive nature of a fractal. In this article, we provide a comprehensive overview of recent developments in the field of fractal antenna engineering, with particular emphasis placed on the theory and design of fractal arrays. We introduce some important properties of fractal arrays, including the frequency-independent multi-band characteristics, schemes for realizing low-sidelobe designs, systematic approaches to thinning, and the ability to develop rapid beam-forming algorithms by exploiting the recursive nature of fractals. These arrays have fractional dimensions that are found from the generating subarray used to recursively create the fractal array. Our research is in its infancy, but the results so far are intriguing, and may have future practical applications.
441 citations
••
Goddard Space Flight Center1, University of Tokyo2, University of Alaska Fairbanks3, University of Maine4, University of Montana5, Hokkaido University6, University of Texas at Austin7, University of Colorado Boulder8, University of Potsdam9, Los Alamos National Laboratory10, Potsdam Institute for Climate Impact Research11, University of California, Irvine12, Penn State DuBois13, Pennsylvania State University14, Curtin University15, Japan Agency for Marine-Earth Science and Technology16, California Institute of Technology17, University of Maryland, College Park18
TL;DR: In this article, the authors used ten models to study the sensitivity of the Greenland and Antarctica ice sheets to prescribed changes of surface mass balance, sub-ice-shelf melting and basal sliding, and found that Greenland is more sensitive than Antarctica to likely atmospheric changes in temperature and precipitation.
Abstract: Ten ice-sheet models are used to study sensitivity of the Greenland and Antarctic ice sheets to prescribed changes of surface mass balance, sub-ice-shelf melting and basal sliding. Results exhibit a large range in projected contributions to sea-level change. In most cases, the ice volume above flotation lost is linearly dependent on the strength of the forcing. Combinations of forcings can be closely approximated by linearly summing the contributions from single forcing experiments, suggesting that nonlinear feedbacks are modest. Our models indicate that Greenland is more sensitive than Antarctica to likely atmospheric changes in temperature and precipitation, while Antarctica is more sensitive to increased ice-shelf basal melting. An experiment approximating the Intergovernmental Panel on Climate Change's RCP8.5 scenario produces additional first-century contributions to sea level of 22.3 and 8.1 cm from Greenland and Antarctica, respectively, with a range among models of 62 and 14 cm, respectively. By 200 years, projections increase to 53.2 and 26.7 cm, respectively, with ranges of 79 and 43 cm. Linear interpolation of the sensitivity results closely approximates these projections, revealing the relative contributions of the individual forcings on the combined volume change and suggesting that total ice-sheet response to complicated forcings over 200 years can be linearized.
225 citations
••
Goddard Space Flight Center1, University of Tokyo2, University of Alaska Fairbanks3, University of Maine4, Florida State University College of Arts and Sciences5, Hokkaido University6, University of Texas at Austin7, Cooperative Institute for Research in Environmental Sciences8, California Institute of Technology9, Potsdam Institute for Climate Impact Research10, Los Alamos National Laboratory11, University of California, Irvine12, Penn State DuBois13, Pennsylvania State University14, Curtin University15, Japan Agency for Marine-Earth Science and Technology16, University of Maryland, College Park17
TL;DR: In this article, the authors applied SeaRISE simulations to six three-dimensional thermomechanical models to assess Antarctic ice sheet sensitivity over a 500 year timescale and to inform future modeling and field studies.
Abstract: Atmospheric, oceanic, and subglacial forcing scenarios from the Sea-level Response to Ice Sheet Evolution (SeaRISE) project are applied to six three-dimensional thermomechanical ice-sheet models to assess Antarctic ice sheet sensitivity over a 500 year timescale and to inform future modeling and field studies. Results indicate (i) growth with warming, except within low-latitude basins (where inland thickening is outpaced by marginal thinning); (ii) mass loss with enhanced sliding (with basins dominated by high driving stresses affected more than basins with low-surface-slope streaming ice); and (iii) mass loss with enhanced ice shelf melting (with changes in West Antarctica dominating the signal due to its marine setting and extensive ice shelves; cf. minimal impact in the Terre Adelie, George V, Oates, and Victoria Land region of East Antarctica). Ice loss due to dynamic changes associated with enhanced sliding and/or sub-shelf melting exceeds the gain due to increased precipitation. Furthermore, differences in results between and within basins as well as the controlling impact of sub-shelf melting on ice dynamics highlight the need for improved understanding of basal conditions, grounding-zone processes, ocean-ice interactions, and the numerical representation of all three.
127 citations
••
TL;DR: Comparison across a diverse set of ice shelves demonstrates that iceberg calving increases with the along-flow spreading rate of a shelf, which suggests that frictional buttressing loss, which increases spreading, also leads to shelf retreat, a process known to accelerate ice-sheet flow and contribute to sea-level rise.
Abstract: A major problem for ice-sheet models is that no physically based law for the calving process has been established. Comparison across a diverse set of ice shelves demonstrates that iceberg calving increases with the along-flow spreading rate of a shelf. This relation suggests that frictional buttressing loss, which increases spreading, also leads to shelf retreat, a process known to accelerate ice-sheet flow and contribute to sea-level rise.
104 citations
••
TL;DR: For the Thwaites Glacier, West Antarctica, the threshold may already have been exceeded, although rapid change may be delayed by centuries, and the reduced state will likely involve loss of most of the West Antarctic Ice Sheet, causing >3 m of sea-level rise as mentioned in this paper.
Abstract: Ocean-ice interactions have exerted primary control on the Antarctic Ice Sheet and parts of the Greenland Ice Sheet, and will continue to do so in the near future, especially through melting of ice shelves and calving cliffs. Retreat in response to increasing marine melting typically exhibits threshold behavior, with little change for forcing below the threshold but a rapid, possibly delayed shift to a reduced state once the threshold is exceeded. For Thwaites Glacier, West Antarctica, the threshold may already have been exceeded, although rapid change may be delayed by centuries, and the reduced state will likely involve loss of most of the West Antarctic Ice Sheet, causing >3 m of sea-level rise. Because of shortcomings in physical understanding and available data, uncertainty persists about this threshold and the subsequent rate of change. Although sea-level histories and physical understanding allow the possibility that ice-sheet response could be quite fast, no strong constraints are yet available on...
95 citations
Authors
Showing all 27 results
Name | H-index | Papers | Citations |
---|---|---|---|
John A. Johnson | 28 | 81 | 7137 |
Ramakrishnan Rajagopalan | 24 | 103 | 1793 |
Arshad Khan | 21 | 59 | 1038 |
Pingjuan L. Werner | 17 | 123 | 1674 |
Larry F. Forthun | 16 | 35 | 1088 |
B. R. Parizek | 9 | 15 | 739 |
Richard Brazier | 9 | 18 | 363 |
N. M. Abreu | 9 | 40 | 517 |
Robert E. Loeb | 9 | 32 | 251 |
Daudi R. Waryoba | 8 | 25 | 205 |
Evelyn F. Wamboye | 5 | 11 | 110 |
Maureen Casile | 4 | 10 | 220 |
A.S.B. Madiligama | 3 | 5 | 21 |
Douglas W. McLaughlin | 3 | 5 | 28 |
Raj Mittra | 2 | 3 | 19 |