Short term evolution of coronal hole boundaries     

Jerome T. Nolte  Allen S. Krieger  Craig V. Solodyna 《Solar physics》1978,57(1):129-139

In an examination of the evolution of coronal hole boundaries on a time scale of 1 day, we find that 38% of all the boundaries of coronal holes observed near central meridan passage during the Skylab period shifted in location by >1° heliocentric in 1 day. Of these boundary changes, 70% were on a scale 3 times the average supergranulation cell size. However, large-scale shifts in the boundary locations also occurred, which involved changes in the X-ray emission from these areas of the Sun. X-ray emitting structures on the borders of isolated and evolving holes were less clearly defined than those on the boundaries of well-established, elongated holes. There were generally more changes in the boundaries of the most rapidly evolving holes, but no simple relationship between the amount of change and the rate of hole growth or decay.Skylab Solar Workshop post-doctoral appointee 1975–1976. The Skylab Solar Workshops are sponsored by NASA and NSF and managed by the High Altitude Observatory, National Center for Atmosoheric Research.  相似文献   

Analysis of the distribution of inorganic constituents in a landfill leachate-contaminated aquifer: Astrolabe Park,Sydney, Australia     

L.?B.?JorstadEmail author  J.?Jankowski  R.?I.?Acworth 《Environmental Geology》2004,46(2):263-272

An investigation was conducted at Astrolabe Park landfill, a decommissioned municipal landfill in Sydney, Australia, to assess the physical and chemical processes affecting the distribution of inorganic constituents in the leachate plume. The plume is migrating from the landfill towards a groundwater-fed pond into which leachate-impacted groundwater discharges. Borehole geophysical logging and depth-discrete groundwater sampling were used to delineate the distribution of the leachate plume along two groundwater flow paths between the landfill and the shore of the pond. Borehole geophysical logs indicate a strong correlation between bulk and fluid electrical conductivity (EC) values, and help to identify small-scale heterogeneities that comprise a major constraint on contaminant transport within the aquifer. Variations in the distribution of several indicator parameters (EC, HCO₃^–, pH, Eh, NH₄⁺/NO₃^–, S^2–/SO₄^2–) are used to assess the dominant processes affecting contaminant distribution along the flow path, including mixing of fresh and contaminated groundwater, oxidation/reduction reactions and ion exchange.  相似文献   

Experiments with scale models of oil collectors for subsea well blowouts — Part II     

Jerome H. Milgram  Christopher J. Von Alt  James J. Burgess 《Applied Ocean Research》1983,5(3):120-128

A previous paper of the same title indicated the feasibility of the collection of oil by an open bottom collector above a blowout with a marine riser above the collector; the whole collection system being driven by gas lift from the blowout gas. That paper was based on small-scale laboratory experiments and it identified the salient dimensionless parameters governing those experiments. This paper describes laboratory experiments on a refinement of the collection system and also describes the results of intermediate scale experiments. The length scale of these experiments was about four times greater than laboratory scale and about one-fourth of full scale. Generally, the intermediate scale results are consistent with the laboratory predictions. Furthermore, two scale-dependent parameters have been identified. The effects of these have been included in an analysis of the results.  相似文献   

Experiments with scale models of oil collectors for subsea well blowouts     

James J. Burgess  Jerome H. Milgram 《Applied Ocean Research》1983,5(1):2-12

Laboratory experiments on conically shaped oil collectors beneath a marine riser are described. The collection concept involves oil, water and gas entering the collector and being driven into a separating sytem by gas-lift. A parametric study involving various collector shapes, heights above the wellhead, and gas, oil and water flow rates was carried out. The important dimensionless variables were identified and quantified with the conclusion that effective collection is possible if the collector height is sufficiently small and the ratio of water pumped to gas flow is sufficiently large. Increased collector heights can be accommodated at the expense of requiring increased water flows by use of larger diameter risers. The amount of gas required for most efficient oil collection is found to be much less than is expected to come from most blowouts when a single collector and riser system is used. This difficulty can be greatly diminished by the use of a specially designed gas-separating collector which passes most of the gas to the surface through a riser separate from the one which carries the liquids.  相似文献   

Measurements of the surface flow above round bubble plumes     

Jerome H. Milgram  James J. Burgess 《Applied Ocean Research》1984,6(1):40-44

When a bubble plume exists beneath a free surface, such as after a subsea gas well blowout, a generally horizontal flow occurs in the vicinity of the surface and this flow is influenced by the fact that the surface is free. Two very different theories for such surface flows have been developed in the past and the bases of these theories are reviewed here. The results of measurements of surface flows above plumes of relatively large scale are given. These are compared with both of the existing theories. One theory is found to be accurate at small radii from the plume centre and the other theory is found to be accurate at large radii. The needed boundary condition for the theory that is accurate at large radii is supplied by the results of the theory that is accurate at small radii.  相似文献   

Geo‐questionnaire: A Method and Tool for Public Preference Elicitation in Land Use Planning          下载免费PDF全文

Piotr Jankowski  Michał Czepkiewicz  Marek Młodkowski  Zbigniew Zwoliński 《Transactions in GIS》2016,20(6):903-924

Geo‐questionnaire involves an integration of sketchable maps with questions, aimed at eliciting public preferences and attitudes about land allocation and services. Respondents can link their answers with corresponding locations on a map by marking points or sketching polygon features. Geo‐questionnaires have been used to learn about perceptions and preferences of city residents for specific types of land use, place‐based services, and development projects. This article reports on results of an empirical study, in which an online geo‐questionnaire was designed and implemented to elicit preferences of residents in guiding an urban development plan. Preferences collected in the form of polygon sketches were processed using GIS operations and mapped for visual interpretation. The article focuses on aggregation and analysis of respondent preferences including the analysis of positional and attribute uncertainty. Results of the study show that geo‐questionnaire is a scalable method for eliciting public preferences with a potential for meaningfully informing land use planning.  相似文献   

Soil evolution and subalpine ecosystem changes in the French Alps inferred from geochemical analysis of lacustrine sediments   总被引：1，自引：0，他引：1  

Brice Mourier  Jerome Poulenard  Christopher Carcaillet  David Williamson 《Journal of Paleolimnology》2010,44(2):571-587

This study aimed to reconstruct the history of soil development, ecosystem changes and associated erosional processes in a small mountain lacustrine basin at the decennial to millennial scale. Geochemical proxies of soil evolution were analysed in the Holocene lacustrine sediments and peats from Thyl Lake, Maurienne Valley, French Alps. Podzolization and chemical weathering processes were assessed using secondary Al- and Fe-bearing phases together with major and Rare Earth Elements (REE). The resulting proxy records, spanning ca. 4,400 years between 8.6 and 4.2 cal ka BP, indicate that progressive pedogenesis occurred after deglaciation in a relatively stable subalpine ecosystem. As shown by the associated increase in Al- and Fe-bearing phases and some REE fractions, the establishment of a mixed cembra pine ecosystem from ca. 7.2–6.5 ka BP was associated with enhanced podzolisation processes in the catchment. The progressive soil development was followed by a rapid transformation of the local environment and plant cover (the open waters of the lake were replaced by a confined peat environment) together with changes in forest fire regimes from ca. 6.8 ka BP. Depleted REE patterns, associated with low contents of secondary Al and Fe, suggest a decrease in chemical weathering and podzolization in the catchment at that time, possibly associated with local intensification of weathering and drainage processes in a relatively acidic peat environment. The higher variability of cembra pine and the increased abundance of sedge and other herbaceous plant remains in the lake sediment indicate semi-open vegetation environments from 5.7 cal ka BP onwards. Whereas fire events and plant cover appear to be significantly related, the soil processes seem primarily linked to vegetation composition, and secondarily to changes in fire regime.  相似文献   

Review: Carbonate aquifers and future perspectives of karst hydrogeology in India   总被引：2，自引：0，他引：2  

Farooq Ahmad Dar  Jerome Perrin  Shakeel Ahmed  Allu China Narayana 《Hydrogeology Journal》2014,22(7):1493-1506

About 3 % of India’s total land surface is occupied by carbonate rocks which are mostly karstified and constitute a significant source of groundwater. The groundwater drawn from these aquifers matches the water demand of ~35 million people living in 106 districts of the country and also the water needs of livestock, irrigation and industry. The studies on karst in India carried out so far have mostly addressed geology, hydrology and groundwater contamination. A literature survey suggests that there is a need for detailed research, applying new approaches and techniques for proper carbonate aquifer identification, characterization and management. Such specific approaches will improve modeling, exploitation and protection of karst groundwater. An overview of the research carried out on groundwater resources of karst formations in India is presented, which also throws light on the protection of karst aquifers from existing anthropogenic activities such as mining and groundwater over-exploitation.  相似文献   

A search for shocked quartz grains in the Allerød‐Younger Dryas boundary layer          下载免费PDF全文

Annelies Van Hoesel  Wim Z. Hoek  Gillian M. Pennock  Knut Kaiser  Oliver Plümper  Michal Jankowski  Maartje F. Hamers  Norbert Schlaak  Mathias Küster  Alexander V. Andronikov  Martyn R. Drury 《Meteoritics & planetary science》2015,50(3):483-498

The Younger Dryas impact hypothesis suggests that multiple airbursts or extraterrestrial impacts occurring at the end of the Allerød interstadial resulted in the Younger Dryas cold period. So far, no reproducible, diagnostic evidence has, however, been reported. Quartz grains containing planar deformation features (known as shocked quartz grains), are considered a reliable indicator for the occurrence of an extraterrestrial impact when found in a geological setting. Although alleged shocked quartz grains have been reported at a possible Allerød‐Younger Dryas boundary layer in Venezuela, the identification of shocked quartz in this layer is ambiguous. To test whether shocked quartz is indeed present in the proposed impact layer, we investigated the quartz fraction of multiple Allerød‐Younger Dryas boundary layers from Europe and North America, where proposed impact markers have been reported. Grains were analyzed using a combination of light and electron microscopy techniques. All samples contained a variable amount of quartz grains with (sub)planar microstructures, often tectonic deformation lamellae. A total of one quartz grain containing planar deformation features was found in our samples. This shocked quartz grain comes from the Usselo palaeosol at Geldrop Aalsterhut, the Netherlands. Scanning electron microscopy cathodoluminescence imaging and transmission electron microscopy imaging, however, show that the planar deformation features in this grain are healed and thus likely to be older than the Allerød‐Younger Dryas boundary. We suggest that this grain was possibly eroded from an older crater or distal ejecta layer and later redeposited in the European sandbelt. The single shocked quartz grain at this moment thus cannot be used to support the Younger Dryas impact hypothesis.  相似文献   

The effects of geological heterogeneities and piezometric fluctuations on groundwater flow and chemistry in a hard-rock aquifer, southern India   总被引：1，自引：0，他引：1  

Jerome Perrin  Shakeel Ahmed  Daniel Hunkeler 《Hydrogeology Journal》2011,19(6):1189-1201

Crystalline aquifers of semi-arid southern India represent a vital water resource for farming communities. A field study is described that characterizes the hydrodynamic functioning of intensively exploited crystalline aquifers at local scale based on detailed well monitoring during one hydrological year. The main results show large water-table fluctuations caused by monsoon recharge and pumping, high spatial variability in well discharges, and a decrease of well yields as the water table decreases. Groundwater chemistry is also spatially variable with the existence of aquifer compartments within which mixing occurs. The observed variability and compartmentalization is explained by geological heterogeneities which play a major role in controlling groundwater flow and connectivity in the aquifer. The position of the water table within the fracture network will determine the degree of connectivity between aquifer compartments and well discharge. The presented aquifer conceptual model suggests several consequences: (1) over-exploitation leads to a drop in well discharge, (2) intensive pumping may contribute to the hydraulic containment of contaminants, (3) groundwater quality is highly variable even at local scale, (4) geological discontinuities may be used to assist in the location of drinking-supply wells, (5) modeling should integrate threshold effects due to water-table fluctuations.  相似文献