ANNOUNCEMENT     

Derek W. G. Sears 《Meteoritics & planetary science》1991,26(3):264-264

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Shedding Light     

Derek Sears 《Meteoritics & planetary science》1994,29(3):297-297

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Holes at Lindal     

Derek Leviston 《Geology Today》2001,17(3):93-95

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Erratum to “The formation of asteroid satellites in large impacts: results from numerical simulations”: [Icarus 167 (2004) 382-396]     

Daniel D. Durda  William F. Bottke Jr.  Brian L. Enke  William J. Merline  Erik Asphaug  Derek C. Richardson  Zoë M. Leinhardt 《Icarus》2004,170(1):242

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Meteorites with your breakfast cereal     

Derek Sears 《Meteoritics & planetary science》2001,36(10):1291-1291

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INGRID: A near-infrared camera for the William Herschel Telescope     

Christopher Packham  Keith L. Thompson  Almudena Zurita  Johan H. Knapen  Ian Smail  Robert Greimel  Daniel F. M. Folha  Chris Benn  rew Humphrey  Rene Rutten  David Ciardi  Matthieu Bec  Richard Bingham  Simon Craig  Kevin Dee  Derek Ives  Paul Jolley  Peter Moore  Marti Pi i Puig  Simon Rees  Gordon Talbot  Sue Worswick 《Monthly notices of the Royal Astronomical Society》2003,345(2):395-405

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Instability of exogenous lava lobes during intense rainfall   总被引：1，自引：1，他引：0  

John?SimmonsEmail author  Derek?Elsworth  Barry?Voight 《Bulletin of Volcanology》2004,66(8):725-734

On many volcanoes, there is evidence of a relationship between dome collapse and periods of high precipitation. We propose a mechanism for this relationship and investigate the conditions that optimize failure by this process. Observations of elongate lobes that evolve through exogenous growth of lava domes reveal that they commonly develop tensile fractures perpendicular to the direction of motion. These cracks can increase in depth by localized cooling and volumetric contraction. During periods of high rainfall, water can fill these cracks, and the increase in fluid pressure on the base of the lobes and within the crack can trigger the collapse of the hot exogenous lava domes. Using limit-equilibrium analysis, it is possible to calculate the water and vapor forces acting on the rear and base of the potentially unstable part of the lobe. The model presented is rectangular in cross-section, with material properties representative of andesitic dome rocks. Vapor pressures at the base of cracks are sealed by the penetrating rainfall, which forms a saturated cap within the lobe. This leads to an increase in fluid pressurization both through the underlying gas pressure and the downslope component of the liquid water cap. Fluid pressurization increases as the penetration depth increases. This rainfall penetration depth is dependent on the thermal properties of the rocks, antecedent temperature, lobe geometry, and the intensity and duration of precipitation. Dominant parameters influencing the stability of the lobe are principally lobe thickness, duration and intensity of rainfall, and antecedent lobe temperature. Our modeling reveals that thicker lobes are intrinsically more unstable due to the amplification of downslope forces in comparison to cohesive strength. The increase in the duration and intensity of rainfall events also increases the potential for collapse, as it leads to deeper liquid penetration. Deeper penetration depths are also achieved through lower antecedent temperatures since less fluid is lost through vaporization. Thus, the potential for rain-triggered collapse increases with time from emplacement.Editorial responsibility: D. Dingwell  相似文献   

Earth Observation Scientific Workflows in a Distributed Computing Environment     

Terence L van Zyl  Anwar Vahed  Graeme McFerren  Derek Hohls 《Transactions in GIS》2012,16(2):233-248

Geospatially Enabled Scientific Workflows offer a promising toolset to help researchers in the earth observation domain with many aspects of the scientific process. One such aspect is that of access to distributed earth observation data and computing resources. Earth observation research often utilizes large datasets requiring extensive CPU and memory resources in their processing. These resource intensive processes can be chained; the sequence of processes (and their provenance) makes up a scientific workflow. Despite the exponential growth in capacity of desktop computers, their resources are often insufficient for the scientific workflow processing tasks at hand. By integrating distributed computing capabilities into a geospatially enabled scientific workflow environment, it is possible to provide researchers with a mechanism to overcome the limitations of the desktop computer. Most of the effort on extending scientific workflows with distributed computing capabilities has focused on the web services approach, as exemplified by the OGC's Web Processing Service and by GRID computing. The approach to leveraging distributed computing resources described in this article uses instead remote objects via RPyC and the dynamic properties of the Python programming language. The Vistrails environment has been extended to allow for geospatial processing through the EO4Vistrails package ( http://code.google.com/p/eo4vistrails/ ). In order to allow these geospatial processes to be seamlessly executed on distributed resources such as cloud computing nodes, the Vistrails environment has been extended with both multi‐tasking capabilities and distributed processing capabilities. The multi‐tasking capabilities are required in order to allow Vistrails to run side‐by‐side processes, a capability it does not currently have. The distributed processing capabilities are achieved through the use of remote objects and mobile code through RPyC.  相似文献   

The influence of negative emission technologies and technology policies on the optimal climate mitigation portfolio   总被引：1，自引：1，他引：0  

Derek M. Lemoine  Sabine Fuss  Jana Szolgayova  Michael Obersteiner  Daniel M. Kammen 《Climatic change》2012,113(2):141-162

Combining policies to remove carbon dioxide (CO₂) from the atmosphere with policies to reduce emissions could decrease CO₂ concentrations faster than possible via natural processes. We model the optimal selection of a dynamic portfolio of abatement, research and development (R&D), and negative emission policies under an exogenous CO₂ constraint and with stochastic technological change. We find that near-term abatement is not sensitive to the availability of R&D policies, but the anticipated availability of negative emission strategies can reduce the near-term abatement optimally undertaken to meet 2°C temperature limits. Further, planning to deploy negative emission technologies shifts optimal R&D funding from ??carbon-free?? technologies into ??emission intensity?? technologies. Making negative emission strategies available enables an 80% reduction in the cost of keeping year 2100 CO₂ concentrations near their current level. However, negative emission strategies are less important if the possibility of tipping points rules out using late-century net negative emissions to temporarily overshoot the CO₂ constraint earlier in the century.  相似文献   

Valuing the non-CO2 climate impacts of aviation     

Christian Azar  Daniel J. A. Johansson 《Climatic change》2012,111(3-4):559-579

The non-CO₂ climate impact of aviation (NO_x and contrails) is assessed and emissions weighting factors (EWFs) i.e., the factor by which aviation CO₂ emissions should be multiplied to get the CO₂-equivalent emissions for annual fleet average conditions are estimated. The EWFs are estimated using two economic metrics. One is based on the relative damage cost between non-CO₂ forcers and CO₂. The other is based on the cost-effective valuation between the non-CO₂ forcers and CO₂ given an upper ceiling on the global annual average surface temperature (set at 2?K above pre-industrial levels). We also estimate EWFs using three physical metrics, Global Warming Potential (GWP), Global Temperature change Potential (GTP) and Sustained GTP (SGTP) and compare our results with the economics based metrics. Given best estimates on the forcing contributions from CO₂, contrails and NO_x from aviation and by using a discount rate of 3%/year, the RDC based metric gives an EWF equal to 1.4 (slightly higher than EWFs based on GWP and SGTP using a 100?year time horizon). EWF using the cost-effective approach depends on the time that remains before stabilization occurs. It is roughly equal to unity until a few years before the temperature reaches its ceiling, and approximately 2 when stabilization has taken place. EWFs based on GTP resemble those based on CETO when the time left to when stabilization occurs is sufficiently large. Once stabilization has occurred CETO values resemble RDC based values. If aviation-induced cirrus clouds are included, uncertainties increase and the EWFs for GWP, SGTP and RDC based metrics end up in the range 1.3–2.9, while EWFs for GTP and CETO remain close to unity in the near term.  相似文献