Evaluation of spatially clustered ordnance when using compliance sampling surveys after clean-up at military training sites     

John E. Hathaway  Richard O. Gilbert  John E. Wilson  Brent A. Pulsipher 《Stochastic Environmental Research and Risk Assessment (SERRA)》2009,23(2):253-261

After site clean-up teams have removed all of what they believe to be UXO within a specific impact area, statistical compliance sampling is a possible method for verifying with a specified probability that this area has been cleaned to specifications. Schilling [J Qual Technol 10(2):47–51, 1978, Acceptance sampling in quality control. Marcel Dekker, Inc., New York, 1982] developed a compliance sampling methodology based on the hypergeometric distribution. Bowen and Bennett (1987) also use compliance sampling where they provide an approximation for estimating the number of samples (n) required to state with desired probability that the entire population of sample units (N, where n < N) are in compliance with cleanup goals. This article describes two methods (anomaly and transect) for applying the Schilling [J Qual Technol 10(2):47–51, 1978, Acceptance sampling in quality control. Marcel Dekker, Inc., New York, 1982] compliance sampling method to military training sites. After describing these methods, a simulation study is presented which demonstrates the performance of transect compliance sampling calculations based on varied degrees of clustered UXO within a specific impact area and different types of sampling routines.  相似文献   

Data reporting norms for 40Ar/39Ar geochronology     

Paul R. Renne  Alan L. Deino  Willis E. Hames  Matthew T. Heizler  Sidney R. Hemming  Kip V. Hodges  Anthony A.P. Koppers  Darren F. Mark  Leah E. Morgan  David Phillips  Brad S. Singer  Brent D. Turrin  Igor M. Villa  Mike Villeneuve  Jan R. Wijbrans 《Quaternary Geochronology》2009,4(5):346-352

Data reported in ⁴⁰Ar/³⁹Ar geochronology studies are commonly insufficient to allow computation of ages. This deficiency renders it difficult to compare ages based on different standards or constants, and often hinders critical evaluation of the results. Herein are presented an enumeration of the data that should be reported in all ⁴⁰Ar/³⁹Ar studies, including a discussion in support of these requirements. The minimum required data are identified and distinguished from parameters that are useful but may be derived from them by calculation. Finally, recommendations are made for metadata needed to document age calculations (e.g., from age spectrum or isochron analyses).  相似文献   

The policy relevance of global environmental change research     

Brent Yarnal 《Global and Planetary Change》1996,11(4):167-175

Many scientists are striving to identify and promote the policy implications of their global change research. Much basic research on global environmental change cannot advance policy directly, but new projects can determine the relevance of their research to decision makers and build policy-relevant products into the work. Similarly, many ongoing projects can alter or add to the present science design to make the research policy relevant. Thus, this paper shows scientists working on global change how to make their research policy relevant. It demonstrates how research on physical global change relates to human dimensions studies and integrated assessments. It also presents an example of how policy relevance can be fit retroactively into a global change project (in this case, SRBEX—the Susquehanna River Basin Experiment) and how that addition can enhance the project's status and science. The paper concludes that policy relevance is desirable from social and scientific perspectives.  相似文献   

The Taylor Creek Rhyolite of New Mexico: a rapidly emplaced field of lava domes and flows   总被引：1，自引：0，他引：1  

Wendell A Duffield  G Brent Dalrymple 《Bulletin of Volcanology》1990,52(6):475-487

The Tertiary Taylor Creek Rhyolite of southwest New Mexico comprises at least 20 lava domes and flows. Each of the lavas was erupted from its own vent, and the vents are distributed throughout a 20 km by 50 km area. The volume of the rhyolite and genetically associated pyroclastic deposits is at least 100 km³ (denserock equivalent). The rhyolite contains 15%–35% quartz, sanidine, plagioclase, ±biotite, ±hornblende phenocrysts. Quartz and sanidine account for about 98% of the phenocrysts and are present in roughly equal amounts. With rare exceptions, the groundmass consists of intergrowths of fine-grained silica and alkali feldspar. Whole-rock major-element composition varies little, and the rhyolite is metaluminous to weakly peraluminous; mean SiO₂ content is about 77.5±0.3%. Similarly, major-element compositions of the two feldsparphenocryst species also are nearly constant. However, whole-rock concentrations of some trace-elements vary as much as several hundred percent. Initial radiometric age determinations, all K–Ar and fission track, suggest that the rhyolite lava field grew during a period of at least 2 m.y. Subsequent ⁴⁰Ar/³⁹Ar ages indicate that the period of growth was no more than 100 000 years. The time-space-composition relations thus suggest that the Taylor Creek Rhyolite was erupted from a single magma reservoir whose average width was at least 30 km, comparable in size to several penecontemporaneous nearby calderas. However, this rhyolite apparently is not related to a caldera structure. Possibly, the Taylor Creek Phyolite magma body never became sufficiently volatile rich to produce a large-volume pyroclastic eruption and associated caldera collapse, but instead leaked repeatedly to feed many relatively small domes and flows.The new ⁴⁰Ar/³⁹Ar ages do not resolve preexisting unknown relative-age relations among the domes and flows of the lava field. Nonetheless, the indicated geologically brief period during which Taylor Creek Rhyolite magma was erupted imposes useful constraints for future evaluation of possible models for petrogenesis and the origin of trace-element characteristics of the system.  相似文献   

Lightning characteristics of derecho producing mesoscale convective systems     

Mace L. Bentley  John R. Franks  Katelyn R. Suranovic  Brent Barbachem  Declan Cannon  Stonie R. Cooper 《Meteorology and Atmospheric Physics》2016,128(3):303-314

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Tracking hydrological responses of a thermokarst lake in the Old Crow Flats (Yukon Territory,Canada) to recent climate variability using aerial photographs and paleolimnological methods     

Lauren A. MacDonald  Kevin W. Turner  Ann M. Balasubramaniam  Brent B. Wolfe  Roland I. Hall  Jon N. Sweetman 《水文研究》2012,26(1):117-129

Recent studies using remote sensing analysis of lake‐rich thermokarst landscapes have documented evidence of declining lake surface area in response to recent warming. However, images alone cannot identify whether these declines are due to increasing frequency of lake drainage events associated with accelerated thermokarst activity or to increasing evaporation in response to longer ice‐free season duration. Here, we explore the potential of combining aerial photograph time series with paleolimnological analyses to track changes in hydrological conditions of a thermokarst lake in the Old Crow Flats (OCF), Canada, and to identify their causes. Images show that the water level in lake OCF 48 declined markedly sometime between 1972 and 2001. In a sediment core from OCF 48, complacent stratigraphic profiles of several physical, geochemical, and biological parameters from ～1874–1967 indicate hydro‐limnological conditions were relatively stable. From ～1967–1989, declines in organic matter content, organic carbon isotope values, and pigment concentrations are interpreted to reflect an increase in supply of minerogenic sediment, and subsequent decline in aquatic productivity, caused by increased thermo‐erosion of shoreline soils. Lake expansion was likely caused by increased summer rainfall, as recorded by increased cellulose‐inferred lake‐water oxygen isotope compositions. Stratigraphic trends defining the lake expansion phase terminated at ～1989, which likely marks the year when the lake drained. Above‐average precipitation during the previous year probably raised the lake level and promoted further thermo‐erosion of the shoreline soils that caused the lake to drain. These are meteorological conditions that have led to other recent lake‐drainage events in the OCF. Thus, the decline in lake level, evident in the aerial photograph from 2001, is unlikely to have been caused by evaporation, but rather is a remnant of a drainage event that took place more than a decade earlier. After drainage, the lake began to refill, and most paleolimnological parameters approach levels that are similar to those during the stable phase. These findings indicate that combined use of aerial images and paleolimnological methods offers much promise for identifying the hydrological consequences of recent climatic variations on thermokarst lakes. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

A lagoonal interlude with occasional hypersalinity in the deposition of the Early–Middle Miocene Brasso Formation of Trinidad     

Brent Wilson 《Journal of South American Earth Sciences》2010,29(2):254-261

An outcrop of the Early–Middle Miocene age Brasso Formation along the Guaico-Tamana Road of Trinidad was logged and sampled for 20 m at 1 m intervals. The log revealed two sand- and silt-rich successions separated by a claystone-rich interval with thinner sands. One horizon yielded gypsum that is concluded to indicate that conditions occasionally became hypersaline. With the exception of one laminated siltstone interval ～1 m thick, all the beds lacked primary sedimentary structures, but many contained much mollusc debris. The lack of primary structures is thought to reflect bioturbation. Pyrite was common throughout much of the section, but replaced by hematite in two intervals. The pyrite is indicative of anoxic conditions in the sediment below the bioturbated layer, while the hematite shows that conditions occasionally became strongly oxic. The development of low-diversity benthonic foraminiferal communities dominated by porcellaneous-walled Quinqueloculina seminulangulata supports a model of occasional hypersalinity. These conditions are concluded to have developed in a leaky lagoon situated between the carbonate bioherms of the Tamana Formation of Central Trinidad and the mountainous allochthon of the Northern Range. Occasional high numbers of planktonic foraminifera are suggested to result from onshore winds blowing surface seawater into the lagoon. The lagoonal interlude came at the end of a tectonically-induced transgressive–regressive cycle. The influence of tectonics on the deposition of the Brasso Formation complicates at least for the Early–Middle Miocene any attempt to tie the sequence stratigraphy of Trinidad to a global sea-level model. It remains to be seen how much this is true for the remainder of the Neogene succession.  相似文献   

A crowd sensing system identifying geotopics and community interests from user-generated content     

M. Tenney  G. Brent Hall  R. E. Sieber 《International journal of geographical information science》2019,33(8):1497-1519

This paper presents a crowd sensing system (CSS) that captures geospatial social media topics and allows the review of results. Using Web-resources derived from social media platforms, the CSS uses a spatially-situated social network graph to harvest user-generated content from selected organizations and members of the public. This allows ‘passively’ contributed social media-based opinions, along with different variables, such as time, location, social interaction, service usage, and human activities to be examined and used to identify trending views and influential citizens. The data model and CSS are used for demonstration purposes to identify geotopics and community interests relevant to municipal affairs in the City of Toronto, Canada.  相似文献   

40Ar/39Ar age of material returned from asteroid 25143 Itokawa          下载免费PDF全文

Jisun Park  Brent D. Turrin  Gregory F. Herzog  Fara N. Lindsay  Jeremy S. Delaney  Carl C. Swisher III  Masayuki Uesugi  Yuzuru Karouji  Toru Yada  Masanao Abe  Tatsuaki Okada  Yukihiro Ishibashi 《Meteoritics & planetary science》2015,50(12):2087-2098

The Hayabusa mission to asteroid 25143, Itokawa, brought back 2000 small particles, which most closely resemble material found in LL4‐6 chondrites. We report an ⁴⁰Ar/³⁹Ar age of 1.3 ± 0.3 Ga for a sample of Itokawa consisting of three grains with a total mass of ~2 μg. This age is lower than the >4.0 Ga ages measured for 75% of LL chondrites but close to one for Y‐790964 and its pairs. The flat ⁴⁰Ar/³⁹Ar release spectrum of the sample suggests complete degassing 1.3 Ga ago. Recent solar heating in Itokawa's current orbit does not appear likely to have reset that age. Solar or impact heating 1.3 Ga ago could have done so. If impact heating was responsible, then the 1.3 Ga age sets an upper bound on the time at which the Itokawa rubble pile was assembled and suggests that rubble pile creation was an ongoing process in the inner solar system for at least the first 3 billion years of solar system history.  相似文献   

The acid catalyzed nitration of methanol: formation of methyl nitrate via aerosol chemistry     

Laura T. Iraci  Brent G. Riffel  Carly B. Robinson  Rebecca R. Michelsen  Rachel M. Stephenson 《Journal of Atmospheric Chemistry》2007,58(3):253-266

The aqueous phase acid-catalyzed reaction of methanol (CH₃OH) with nitric acid (HNO₃) to yield methyl nitrate (CH₃ONO₂) under atmospheric conditions has been investigated using gas-phase infrared spectroscopy. Reactions were conducted in aqueous sulfuric acid solutions (50.5–63.6 wt.%) with [CH₃OH] = 0.00005–0.005 M and [HNO₃] = 0.02–0.21 M, at 278.2–328.6 K. Methyl nitrate production rates increased linearly with CH₃OH and HNO₃ concentrations and exponentially with sulfuric acid weight percent within the regime studied. Rates increased linearly with nitronium ion concentration, indicating that the reaction involves as the nitrating agent under these conditions. At 298 K, the rate of methyl nitrate production can be calculated from k _obs [CH₃OH][HNO₃], where k _obs  = 2.337 × 10⁻¹³(exp(0.3198*wt.% H₂SO₄)) when the solubility of CH₃ONO₂ in acidic solution is approximated by H* for pure water. The temperature dependence of the rate coefficient is related to solution composition, with activation energies of 59 and 49 kJ/mol at 51.1 and 63.6 wt.% H₂SO₄, respectively, when k is calculated from rate. The temperature dependence has also been parameterized for application to the atmosphere, but the small quantities of present in aerosol particles will result in methyl nitrate production rates too small to be of significance under most atmospheric conditions. An erratum to this article can be found at  相似文献