Ocean effects on time delay estimation requiring adaptation     

Carter  G.C. Robinson  E.R. 《Oceanic Engineering, IEEE Journal of》1993,18(4):367-378

In active sonar and in passive sonar localization, time delay is a fundamental parameter whose extraction is vital to the sonar function. The underlying time delay parameter (or parameter vector) contains information about the acoustic source (or reflector) as seen through the ocean at a receiver. The ocean effects require sonar adaptation. A tutorial review of ocean effects in time delay estimation is provided, with references to benchmark work. It covers coherence, time-delay estimation, localization, time-varying time delay estimation, the complexity of the ocean environment, and depth estimation using mode matching  相似文献   

An analysis of history matching errors     

Z. Tavassoli  Jonathan N. Carter  Peter R. King 《Computational Geosciences》2005,9(2-3):99-123

We use a simple 2D model of a layered reservoir with three unknown parameters: the throw of a fault, and high and low permeabilities. Then consider three different cases where in each case two parameters are kept fixed and the third one is varied within a specific range. Using a weighted sum of squares of the difference in production for the objective function, we plot it against the varying parameter for each case. It mainly shows a complex function with multiple minima. We see that geological ‘symmetry’ and also vertical spreading are some sources of non-monotonicity in the production and transmissibility curves. These result in a multi-modal objective function and consequently non-unique history matches. The behaviour of the system in the forecast period is also studied, which shows that a good history matched model could give a bad forecast.  相似文献   

Prototyping a global soft X‐ray imaging instrument for heliophysics,planetary science,and astrophysics science     

M.R. Collier  F.S. Porter  D.G. Sibeck  J.A. Carter  M.P. Chiao  Dj. Chornay  T. Cravens  M. Galeazzi  J.W. Keller  D. Koutroumpa  K. Kuntz  A.M. Read  I.P. Robertson  S. Sembay  S. Snowden  N. Thomas 《Astronomische Nachrichten》2012,333(4):378-382

We describe current progress in the development of a prototype wide field‐of‐view soft X‐ray imager that employs Lobster‐eye optics and targets heliophysics, planetary, and astrophysics science. The prototype will provide proof‐of‐concept for a future flight instrument capable of imaging the entire dayside magnetosheath from outside the magnetosphere. Such an instrument was proposed for the ESA AXIOM mission (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Orbital identification of clays and carbonates in Gusev crater     

John Carter  Francois Poulet 《Icarus》2012,219(1):250-253

Gusev crater was selected as the landing site of one of the two NASA Mars Exploration Rovers because water once could have ponded within the crater and partly filled it with sediments as suggested by the presence of a feeder channel and the fluvial-lacustrine morphology of the in-filling. However, the paucity of mineralogical evidence for fluvial-lacustrine activity revealed by the Spirit rover has remained a puzzle for years. Using orbital, near-infrared imaging spectroscopy, we report the detection of phyllosilicates and carbonates within and around the landing site of Spirit on the floor of Gusev crater. Placed in their geomorphological context, these minerals shed new light on the aqueous history of this crater, and offer a framework for the Spirit in situ measurements.  相似文献   

AXIOM: advanced X-ray imaging of the magnetosphere   总被引：1，自引：0，他引：1  

Graziella Branduardi-Raymont  Steve F. Sembay  Jonathan P. Eastwood  David G. Sibeck  Tony A. Abbey  Patrick Brown  Jenny A. Carter  Chris M. Carr  Colin Forsyth  Dhiren Kataria  Steve Kemble  Steve E. Milan  Chris J. Owen  Lisa Peacocke  Andy M. Read  Andrew J. Coates  Michael R. Collier  Stan W. H. Cowley  Andrew N. Fazakerley  George W. Fraser  Geraint H. Jones  Rosine Lallement  Mark Lester  F. Scott Porter  Tim K. Yeoman 《Experimental Astronomy》2012,33(2-3):403-443

Planetary plasma and magnetic field environments can be studied in two complementary ways—by in situ measurements, or by remote sensing. While the former provide precise information about plasma behaviour, instabilities and dynamics on local scales, the latter offers the global view necessary to understand the overall interaction of the magnetospheric plasma with the solar wind. Some parts of the Earth’s magnetosphere have been remotely sensed, but the majority remains unexplored by this type of measurements. Here we propose a novel and more elegant approach employing remote X-ray imaging techniques, which are now possible thanks to the relatively recent discovery of solar wind charge exchange X-ray emissions in the vicinity of the Earth’s magnetosphere. In this article we describe how an appropriately designed and located X-ray telescope, supported by simultaneous in situ measurements of the solar wind, can be used to image the dayside magnetosphere, magnetosheath and bow shock, with a temporal and spatial resolution sufficient to address several key outstanding questions concerning how the solar wind interacts with the Earth’s magnetosphere on a global level. Global images of the dayside magnetospheric boundaries require vantage points well outside the magnetosphere. Our studies have led us to propose ‘AXIOM: Advanced X-ray Imaging of the Magnetosphere’, a concept mission using a Vega launcher with a LISA Pathfinder-type Propulsion Module to place the spacecraft in a Lissajous orbit around the Earth–Moon L1 point. The model payload consists of an X-ray Wide Field Imager, capable of both imaging and spectroscopy, and an in situ plasma and magnetic field measurement package. This package comprises a Proton-Alpha Sensor, designed to measure the bulk properties of the solar wind, an Ion Composition Analyser, to characterise the minor ion populations in the solar wind that cause charge exchange emission, and a Magnetometer, designed to measure the strength and direction of the solar wind magnetic field. We also show simulations that demonstrate how the proposed X-ray telescope design is capable of imaging the predicted emission from the dayside magnetosphere with the sensitivity and cadence required to achieve the science goals of the mission.  相似文献   

A new scenario framework for climate change research: the concept of shared socioeconomic pathways   总被引：4，自引：1，他引：3  

Brian C. O’Neill  Elmar Kriegler  Keywan Riahi  Kristie L. Ebi  Stephane Hallegatte  Timothy R. Carter  Ritu Mathur  Detlef P. van Vuuren 《Climatic change》2014,122(3):387-400

The new scenario framework for climate change research envisions combining pathways of future radiative forcing and their associated climate changes with alternative pathways of socioeconomic development in order to carry out research on climate change impacts, adaptation, and mitigation. Here we propose a conceptual framework for how to define and develop a set of Shared Socioeconomic Pathways (SSPs) for use within the scenario framework. We define SSPs as reference pathways describing plausible alternative trends in the evolution of society and ecosystems over a century timescale, in the absence of climate change or climate policies. We introduce the concept of a space of challenges to adaptation and to mitigation that should be spanned by the SSPs, and discuss how particular trends in social, economic, and environmental development could be combined to produce such outcomes. A comparison to the narratives from the scenarios developed in the Special Report on Emissions Scenarios (SRES) illustrates how a starting point for developing SSPs can be defined. We suggest initial development of a set of basic SSPs that could then be extended to meet more specific purposes, and envision a process of application of basic and extended SSPs that would be iterative and potentially lead to modification of the original SSPs themselves.  相似文献   

Inverse Modeling with PEST++ and GENIE     

David J. Dahlstrom  Jonathon T.V. Carter 《Ground water》2013,51(2):162-167

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A Plinian treatment of fallout from Hawaiian lava fountains     

Elisabeth A. Parfitt  Lionel Wilson 《Journal of Volcanology and Geothermal Research》1999,88(1-2)

A new model is presented which simulates the dispersal and deposition of material from a Hawaiian eruption column. The model treats the Hawaiian column as a coarse-grained Plinian column and uses a modified version of the Wilson and Walker [Wilson, L., Walker, G.P.L., 1987. Explosive volcanic eruptions: VI. Ejecta dispersal in Plinian eruptions: the control of eruption conditions and atmospheric properties. Geophys. J. R. Astron. Soc. 89, 657–679.] Plinian pyroclast dispersal model to simulate the fall out of material during a Hawaiian eruption. The model results are found to be in good agreement with independent estimates of various parameters made for the 1959 Kilauea Iki eruption of Kilauea volcano. The close agreement between the model results and these independent estimates shows that, dynamically, Hawaiian eruptions are indistinguishable from Plinian eruptions. The major differences in the styles and deposits of these two types of eruptions are accounted for by differences in the mass fluxes and gas contents of the erupting magmas and, most fundamentally, by differences in the grainsize distribution of the erupted clasts. Plume heights predicted by the model are greater than those found for previous models of Hawaiian eruptions. This is because previous models did not allow for the progressive fall out of particles from the plume and, more importantly, made no correction for the velocity disequilibrium between gas and clasts when the grainsize distribution is coarse.  相似文献   

A reply to Macphail's comments on “An evaluation of the contribution of soil micromorphology to the study of ancient arable agriculture”     

Stephen P. Carter  Donald A. Davidson 《Geoarchaeology》2000,15(5):499-502

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Landslide kinematics inferred from in situ measurements: the Cliets rock-slide (Savoie,French Alps)     

Desrues  Mathilde  Malet  Jean-Philippe  Brenguier  Ombeline  Carrier  Aurore  Mathy  Alexandre  Lorier  Lionel 《Landslides》2022,19(1):19-34

This paper presents an analysis of two large rock toppling/sliding events which occurred in January 2014 and February 2019 at the Cliets unstable slope (Savoie, French Alps). To understand the mechanism involved and its control by external forcings, a multi-technique analysis approach is used combining geological observations, meteorological data analysis, topographic measurements and simple physical modeling. The pre-failure stage of the events is more particularly analyzed. No direct relationships are found between triggering factors and surface motion though a kinematics analysis highlights the transition toppling-sliding. It showed that, at first order, this transition occurred 4 years before the first failure of 2014, while it happened 2 months before the second failure of 2019. From this date, the environment is considered like a block sliding on an inclined plane. By applying a frictional model (Helmstetter et al. in Journal of Geophysical Research: Solid Earth 109(B2), 2004), we illustrated that the two events belong to an unstable velocity-weakening sliding regime. The time to failure (Voight in Science 243(4888):200–203, 1989) is forecasted with the model, and the results are consistent with the observations. They confirm that the gravitational factor is predominant over the triggering factors for the two events.

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