Geology topics

W. Ji

Publications and source records attributed to W. Ji.

4 recordsLinked to original sources

USGS2011

Final report on the Seventh International Comparison of Absolute Gravimeters (ICAG 2005)

The Bureau International des Poids et Mesures (BIPM), Sevres, France, hosted the 7th International Comparison of Absolute Gravimeters (ICAG) and the associated Relative Gravity Campaign (RGC) from August to September 2005.;ICAG 2005 was prepared and performed as a metrological pilot study, which aimed:;(1) To determine the gravity comparison reference values;;(2) To determine the offsets of the absolute gravimeters; and;(3) As a pilot study to accumulate experience for the CIPM Key Comparisons.;This document presents a complete and extensive review of the technical protocol and data processing procedures. The 1st ICAG-RGC comparison was held at the BIPM in 1980-1981 and since then meetings have been organized every 4 years.;In this paper, we present an overview of how the meeting was organized, the conditions of BIPM gravimetric sites, technical specifications, data processing strategy and an analysis of the final results. This 7th ICAG final report supersedes all previously published reports.;Readings were obtained from participating instruments, 19 absolute gravimeters and 15 relative gravimeters. Precise levelling measurements were carried out and all measurements were performed on the BIPM micro-gravity network which was specifically designed for the comparison.

Metrologia↗

USGS2010

Migration of waterfowl in the east asian flyway and spatial relationship to HPAI H5N1 outbreaks

Poyang Lake is situated within the East Asian Flyway, a migratory corridor for waterfowl that also encompasses Guangdong Province, China, the epicenter of highly pathogenic avian influenza (HPAI) H5N1. The lake is the largest freshwater body in China and a significant congregation site for waterfowl; however, surrounding rice fields and poultry grazing have created an overlap with wild waterbirds, a situation conducive to avian influenza transmission. Reports of HPAI H5N1 in healthy wild ducks at Poyang Lake have raised concerns about the potential of resilient free-ranging birds to disseminate the virus. Yet the role wild ducks play in connecting regions of HPAI H5N1 outbreak in Asia is hindered by a lack of information about their migratory ecology. During 2007-08 we marked wild ducks at Poyang Lake with satellite transmitters to examine the location and timing of spring migration and identify any spatiotemporal relationship with HPAI H5N1 outbreaks. Species included the Eurasian wigeon ( Anas penelope ), northern pintail ( Anas acuta ), common teal ( Anas crecca ), falcated teal ( Anas falcata ), Baikal teal ( Anas formosa ), mallard ( Anas platyrhynchos ), garganey ( Anas querquedula ), and Chinese spotbill ( Anas poecilohyncha ). These wild ducks (excluding the resident mallard and Chinese spotbill ducks) followed the East Asian Flyway along the coast to breeding areas in northern China, eastern Mongolia, and eastern Russia. None migrated west toward Qinghai Lake (site of the largest wild bird epizootic), thus failing to demonstrate any migratory connection to the Central Asian Flyway. A newly developed Brownian bridge spatial analysis indicated that HPAI H5N1 outbreaks reported in the flyway were related to latitude and poultry density but not to the core migration corridor or to wetland habitats. Also, we found a temporal mismatch between timing of outbreaks and wild duck movements. These analyses depend on complete or representative reporting of outbreaks, but by documenting movements of wild waterfowl, we present ecological knowledge that better informs epidemiological investigations seeking to explain and predict the spread of avian influenza viruses. ?? 2010 American Association of Avian Pathologists.

Avian Diseases↗

USGS1997

Use of a spatial decision support system for analysis of habitat use by wintering northern pintails

A multi-functional spatial decision support system (SDSS) was,developed at the spatial analysis branch Of the National Wetlands Research Center, and the wildlife analysis module of the system was used to study habitat use by wintering pintail. We instrumented female pintails at Catahoula Lake, Louisiana, in October of 1992-94 and located the instrumented birds weekly through the following March. Using the SDSS developed in an ARC/INFO geographical information system (GIS) - environment. We were able to visualize movements of instrumented pintails over varied environmental conditions and landscape features to determine habitat use. Weather data were used to determine factors important in the timing of movements. The analyses indicated that female pintails dispersed from Catahoula Lake, Louisiana, in three general patterns, based upon wetland conditions. Timing of movements coincided with periods of precipitation or disturbance, primarily hunting. Pintails which arrived at Catahoula Lake in October and November remained in the agricultural areas of Louisiana and Arkansas, with very limited movements to the coastal marshes or westward into the agricultural areas of Texas. Northward movements into Arkansas occurred whenever there was substantial rainfall in the agricultural regions, and northward movements generally stopped at the frost-line. No differences in adult or juvenile female movement patterns were apparent.

Louisiana↗

USGS1992

A geographic information systems technique for monitoring contaminants in Galveston Bay, Texas

A geographic information system (GIS) was used to compile a series of databases containing details concerning metal contamination and pollution sources to study their impacts on the Galveston Bay (TX) ecosystem. Using these databases, a series of maps with various overlays was created with ARC/INFO software. These maps allowed patterns of spatial distribution of numerous variables to be easily visualized so that the impacts of urbanization and industrialization on the natural resources could be examined. Resource managers can use these capabilities in their comprehensive plans for managing individual activities within an overall regulatory framework. The visual displays and cartographic output of the system can be used to locate and identify ecologically sensitive areas and to study trends in these areas over time. These vector GIS techniques have the potential to be more integrated with aerial photography and other remotely sensed data for a more extensive overview of the environment and patterns of interaction

Texas↗