Special Issue on Incorporating Fuzzy Sets in Geographic Information Systems     

Vincent B Robinson  Frederick E Petry  & Maria A Cobb 《Transactions in GIS》2003,7(1):1-1

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Investigation of a cyclic laterally loaded model pile group     

Robb Eric S. Moss  Joseph A. Caliendo  Loren R. Anderson 《Soil Dynamics and Earthquake Engineering》1998,17(7-8):519-523

In certain regions of the world, designing deep foundations to withstand seismic loading is a reality. Seismic loading of structures and foundations reaches its most critical state as a cyclic lateral force. The response of soils and foundations to repetitive lateral forces is highly complex, relegating most design methods to be based upon overly conservative rules-of-thumb. The primary objective of this research was to analyze the mechanics of seismic loading on pile groups in clay soils. To achieve this a model testing facility was constructed to house a fully instrumented 1×5 model pile group that was subjected to cyclic lateral loading. An empirically based method for pile group design is suggested based upon the results generated from model pile group testing.  相似文献   

New fumarolic activity on Mt. Baker: observations during April through July, 1975     

J.C. Eichelberger  G. Heiken  R. Widdicombe  D. Wright  C.J. Keady  D.D. Cobb 《Journal of Volcanology and Geothermal Research》1976,1(1):35-53

On 10 March, 1975, large amounts of steam were first sighted coming from the Sherman Crater of Mt. Baker, long the site of mild fumarole activity. To document and evaluate the new activity, we conducted a series of aerial and ground-based observations and experiments including the collection of samples within the crater, installation of 35-mm automatic sequence cameras at Park and Anderson Buttes, and overflights with a mapping camera and infrared scanner. Significant changes characterizing the new activity are: development of a new, energetic fumarole in an area of earlier mild activity; growth of crevasses within and concentric to the crater walls; collapse of a central 70 m diameter plug of ice to form a warm lake; and ejection of tephra rich in analcite and sulfides from the new fumarole. Although the tephra contains minor amounts of unaltered glass, it does not differ in this or other respects from material collected from the west crater wall, where fumaroles have long been active. This suggests that the glass is older tephra derived from the fumarole vent walls.Weather and lighting conditions were such that the Park Butte sequence camera provided acceptable images of the crater area on 27% of the frames for the period 1825 Pacific Daylight Time June 5 to 1825 PDT August 2. Of these, 8% show a significant plume (>300 m above the vent). Large plumes occur during favorable weather conditions of low wind and high relative humidity, and all appear white.While there are abundant manifestations of increased heat emission from Sherman Crater, there is as yet no sign of a fundamental change in the style of activity, or that the rise of fresh magma is the cause.  相似文献   

Seston Removal by Natural and Constructed Intertidal Eastern Oyster (<Emphasis Type="Italic">Crassostrea virginica</Emphasis>) Reefs: A Comparison with Previous Laboratory Studies,and the Value of in situ Methods     

Raymond E. Grizzle  Jennifer K. Greene  Loren D. Coen 《Estuaries and Coasts》2008,31(6):1208-1220

An important ecological role ascribed to oysters is the transfer of materials from the water column to the benthos as they feed on suspended particles (seston). This ecosystem service has been often touted as a major reason for many oyster restoration efforts, but empirical characterization and quantification of seston removal rates in the field have been lacking. Changes in chlorophyll a (chl a) concentrations in the water column were measured in May 2005 and June 2006 in South Carolina using in situ fluorometry and laboratory analysis of pumped water samples taken upstream and downstream as water flowed over natural and constructed intertidal oyster reefs. Both methods gave similar results overall, but with wide variability within individual reef datasets. In situ fluorometer data logged at 10 to 30-s intervals for up to 1.3 h over eight different reefs (three natural and five constructed) showed total removal (or uptake) expressed as % removal of chl a ranging from −9.8% to 27.9%, with a mean of 12.9%. Our data indicate that restored shellfish reefs should provide water-quality improvements soon after construction, and the overall impact is probably determined by the size and density of the resident filter feeder populations relative to water flow characteristics over the reef. The measured population-level chl a removal was converted to mean individual clearance rates to allow comparison with previous laboratory studies. Although direct comparisons could not be made due to the small size of oysters on the study reefs (mean shell height, 36.1 mm), our calculated rates (mean, 1.21 L h⁻¹) were similar to published laboratory measured rates for oysters of this size. However, the wide variability in measured removal by the oyster reefs suggests that individual oyster feeding rates in nature may be much more variable than in the laboratory. The proliferation of ecosystem-level models that simulate the impacts of bivalves on water quality based only on laboratory-feeding measurements underscores the importance of further research aimed at determining ecologically realistic feeding rates for oysters in the field. Because in situ methods provide many replicate measurements quickly, they represent a potentially powerful tool for quantifying the effects of oyster reefs, including all suspension-feeding taxa present, on water quality.  相似文献   

Getting it right for the North Atlantic right whale (Eubalaenaglacialis): A last opportunity for effective marine spatial planning?     

Loren M. Petruny  Andrew J. Wright  Courtney E. Smith 《Marine pollution bulletin》2014

The North Atlantic right whale (Eubalaena glacialis) faces increasing pressure from commercial shipping traffic and proposed marine renewable energy developments. Drawing upon the successful Stellwagen Bank National Marine Sanctuary model, we propose a multi-stakeholder marine spatial planning process that considers both appropriate positioning of offshore wind farms and redefining commercial shipping lanes relative to whale migration routes: placement of wind turbines within certain right whale habitats may prove beneficial for the species. To that end, it may be advisable to initially relocate the shipping lanes for the benefit of the whales prior to selecting wind energy areas. The optimal end-state is the commercial viability of renewable energy, as well as a safe shipping infrastructure, with minimal risk of collision and exposure to shipping noise for the whales. This opportunity to manage impacts on right whales could serve as a model for other problematic interactions between marine life and commercial activities.  相似文献   

Proposed GSSP for the base of Cambrian Stage 9, coinciding with the first appearance of Agnostotes orientalis, at Duibian, Zhejiang, China     

Loren E. BABCOCK  Gabriella BAGNOLI 《中国科学D辑(英文版)》2009,(4)

Exposed in natural outcrops near the Duibian Village, Jiangshan County, Zhejiang Province, China, the Duibian B section is proposed as the boundary stratotype for the base of an unnamed stage termed provisionally Cambrian Stage 9. The proposed position of the GSSP is 108.12 m above the base of the Huayansi Formation, at a horizon coinciding with the first appearance of the cosmopolitan agnostoid trilobite Agnostotes orientalis. This horizon coincides also with the first appearance of the cosmopoli-tan polym...  相似文献   

How the Distribution of Anthropogenic Nitrogen Has Changed in Narragansett Bay (RI,USA) Following Major Reductions in Nutrient Loads     

Autumn Oczkowski  Courtney Schmidt  Emily Santos  Kenneth Miller  Alana Hanson  Donald Cobb  Jason Krumholz  Adam Pimenta  Leanna Heffner  Sandra Robinson  Joaquín Chaves  Rick McKinney 《Estuaries and Coasts》2018,41(8):2260-2276

Over the past decade, nitrogen (N) loads to Narragansett Bay have decreased by more than 50%. These reductions were, in large part, the direct result of multiple wastewater treatment facility upgrades to tertiary treatment, a process which employs N removal. Here, we document ecosystem response to the N reductions and assess how the distribution of sewage N in Narragansett Bay has changed from before, during, and shortly after the upgrades. While others have observed clear responses when data were considered annually, our seasonal and regional comparisons of pre- and post-tertiary treatment dissolved inorganic nitrogen (DIN) concentrations and Secchi depth data, from bay-wide surveys conducted periodically from the early 1970s through 2016, resulted in only a few subtle differences. Thus, we sought to use stable isotope data to assess how sewage N is incorporated into the ecology of the Bay and how its distribution may have changed after the upgrades. The nitrogen (δ¹⁵N) and carbon (δ¹³C) stable isotope measurements of particulate matter served as a proxy for phytoplankton, while macroalgae served as short-term integrators of water column bio-available N, and hard clams (Mercenaria mercenaria) as integrators of water column production. In contrast to other estuarine stable isotope studies that have observed an increased influence of isotopically lower marine N when sewage N is reduced, the opposite has occurred in Narragansett Bay. The tertiary treatment upgrades have increased the effluent δ¹⁵N values by at least 2‰. The plants and animals throughout Narragansett Bay have similarly increased by 1–2‰, on average. In contrast, the δ¹³C values measured in particulate matter and hard clams have declined by about the same amount. The δ¹⁵N results indicated that, even after the N reductions, sewage N still plays an important role in supporting primary and secondary production throughout the bay. However, the δ¹³C suggests that overall net production in Narragansett Bay has decreased. In the 5 years after the major wastewater treatment facilities came on-line for nutrient removal, oligotrophication has begun but sewage remains the dominant source of N to Narragansett Bay.  相似文献   

Electromagnetic‐Induction Logging to Monitor Changing Chloride Concentrations     

Loren F. Metzger  John A. Izbicki 《Ground water》2013,51(1):108-121

Water from the San Joaquin Delta, having chloride concentrations up to 3590 mg/L, has intruded fresh water aquifers underlying Stockton, California. Changes in chloride concentrations at depth within these aquifers were evaluated using sequential electromagnetic (EM) induction logs collected during 2004 through 2007 at seven multiple‐well sites as deep as 268 m. Sequential EM logging is useful for identifying changes in groundwater quality through polyvinyl chloride‐cased wells in intervals not screened by wells. These unscreened intervals represent more than 90% of the aquifer at the sites studied. Sequential EM logging suggested degrading groundwater quality in numerous thin intervals, typically between 1 and 7 m in thickness, especially in the northern part of the study area. Some of these intervals were unscreened by wells, and would not have been identified by traditional groundwater sample collection. Sequential logging also identified intervals with improving water quality—possibly due to groundwater management practices that have limited pumping and promoted artificial recharge. EM resistivity was correlated with chloride concentrations in sampled wells and in water from core material. Natural gamma log data were used to account for the effect of aquifer lithology on EM resistivity. Results of this study show that a sequential EM logging is useful for identifying and monitoring the movement of high‐chloride water, having lower salinities and chloride concentrations than sea water, in aquifer intervals not screened by wells, and that increases in chloride in water from wells in the area are consistent with high‐chloride water originating from the San Joaquin Delta rather than from the underlying saline aquifer.  相似文献   

Geoarchaeology and geochronology of pluvial Lake Chapala,Baja California,Mexico     

Loren G. Davis 《Geoarchaeology》2003,18(2):205-223

Stratigraphic exposures in natural profiles, archaeological excavation units, backhoe trenches, and an uncased water well from the Laguna Seca Chapala basin in the Central Desert of Baja California (29°N, 115°W) record lake level and climate changes and provide a context for prehistoric occupation predating 9070 yr B.P. and extending through the Holocene. Lithofacies analysis points to the presence of a large (ca. 66 km²) lake prior to 9070 yr B.P., which desiccated by 7.45 ka yr B.P., promoting rapid dune growth. New dating and redefinition of stratigraphic units in the basin refutes earlier models of lacustrine history and prehistoric occupation including a proposed series of Pleistocene lake levels with associated cultural occupations. The geologic record from the Laguna Seca Chapala basin compares well with other paleoenvironmental records in southwestern North America, supporting interpretations of wet and cool conditions in Baja California during the late Pleistocene and early Holocene. © 2003 Wiley Periodicals, Inc.  相似文献