Coaxial coil towed EMI sensor array for UXO detection and characterization     

Haoping Huang  Bill SanFilipo  Alex Oren  I.J. Won 《Journal of Applied Geophysics》2007,61(3-4):217-226

A new broadband electromagnetic induction (EMI) array sensor, GEM-5, for detecting and characterizing Unexploded Ordnance (UXO) has been developed in order to provide high production rates for EMI surveys. The sensor consists of a single rectangular loop transmitter around a linear array of seven pairs of coaxial receiver coils, with each coil in a pair located at the same vertical distance above and below the loop transmitter. The coil pairs are wired in an inverted series so that the signal consists of the difference between the voltage induced in the upper and lower coils. This particular configuration provides a high degree of primary field cancellation, dense spatial sampling rate due to simultaneous and continuous operation of all sensors, suppression of motion-induced and environmental noise, and strong source fields at typical UXO burial depths providing deep detection range. Our prototype tests indicate that the array yields a lower static and motion-induced noise over the critical low frequencies than that of existing sensors, and in particular, the signal-to-noise ratio at 90 Hz is 32 dB higher. Environmental noise can be largely removed from the difference measurements. The field test results from UXO test sites show that the prototype sensor has smoother background and appears to detect more seeded targets than the GEM-3 concentric sensor, however some of that gain can be attributed to higher power transmitter electronics.  相似文献   

A Seasonal Statistical Evaluation of COAMPS® over the Arabian Gulf Region     

Rebecca E. Eager  Sethu Raman  Teddy R. Holt  Douglas Westphal  Jeffrey Reid  Jason Nachamkin  Ming Liu  Abdulla Al Mandoos 《Pure and Applied Geophysics》2007,164(8-9):1747-1764

A statistical evaluation of the Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS^®) was performed over the Arabian Gulf region for the period, 1 August to 5 October, 2004. Verification skill scores of bias and root-mean-square error were estimated for surface variables and for vertical profiles to investigate any diurnal variations. The model predictions of boundary-layer heights are compared with the observations at Abu Dhabi, United Arab Emirates. The Middle East presents challenges to numerical weather prediction due to complex land-ocean-land mesoscale processes. An independent data set of surface measurements from 50 stations in the UAE was available from the Department of Water Resources Studies, Abu Dhabi for model verification. The results indicate a diurnal variation in the model errors. The errors are small considering the magnitudes of the observed variables. Errors in the coastal region can be attributed to the differences in the timing of the onset of sea and land breeze circulations in the simulations as compared to the observations. Errors are relatively smaller in the offshore locations.  相似文献   

In-flight Performance of the Advanced Camera for Surveys CCDs     

Mark Clampin  Marco Sirianni  George F. Hartig  Holland C. Ford  Garth D. Illingworth  Bill Burmester  William Koldewynd  Andre R. Martel  Adam Riess  Ronald J. Schrein  Pamela C. Sullivan 《Experimental Astronomy》2002,14(2):107-115

The Advanced Camera for Surveys (ACS), installed in the Hubble Space telescope in March 2002, will significantly extend HST's deep, survey imaging capabilities. ACS has met, or exceeded, all of its key performance specifications. In this paper we briefly review the in-flight performance of the instrument's CCD detectors and preview early ACS science observations. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Spectrophotometry of Jupiter     

Willem Wamsteker  Theodore D. Fay  Bill J. Duncan 《Icarus》1976,29(2):315-319

Spectrophotometric maps of Jupiter were made between 24 and 27(UT) November 1974 on the McMath Solar Telescope at Kitt Peak National Observatory. We report a comparison between observed scaled reflectivities of the Jovian North Tropical Zone and the North Equatorial Belt at System II longitudes between 195 and 205 degrees. The belt/zone reflectivity ratios between 430 and 740nm are related to the optical transmission curves of the organic and/or sulfur polymers synthesized by Khare and Sagan in a simulated Jovian atmosphere.  相似文献   

Microwave links: The future for urban rainfall measurement?     

G.J.G. Upton  A.R. Holt  R.J. Cummings  A.R. Rahimi  J.W.F. Goddard   《Atmospheric Research》2005,77(1-4):300

Microwave links are ideally suited to the urban environment, since there are many suitable vandal-free locations to which the receiver and transmitter can be attached. A signal sent along a link is received with reduced power as a consequence of scattering and absorption by intervening water droplets. Thus a measurement of the power loss can be transformed into a measure of total path rainfall. This paper discusses the requirements for the estimation process to be accurate. The paper presents results using a single frequency, together with the improved results from a dual-frequency link. Potential future applications of microwave links are presented.  相似文献   

Geography and the Emergence of Rural and Regional Australia     

Phil McManus  Bill Pritchard 《The Australian geographer》2000,31(3):383-391

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The weathering and element fluxes from active volcanoes to the oceans: a Montserrat case study     

Morgan T. Jones  Deborah J. Hembury  Martin R. Palmer  Bill Tonge  W. George Darling  Susan C. Loughlin 《Bulletin of Volcanology》2011,73(3):207-222

The eruptions of the Soufrière Hills volcano on Montserrat (Lesser Antilles) from 1995 to present have draped parts of the island in fresh volcaniclastic deposits. Volcanic islands such as Montserrat are an important component of global weathering fluxes, due to high relief and runoff and high chemical and physical weathering rates of fresh volcaniclastic material. We examine the impact of the recent volcanism on the geochemistry of pre-existing hydrological systems and demonstrate that the initial chemical weathering yield of fresh volcanic material is higher than that from older deposits within the Lesser Antilles arc. The silicate weathering may have consumed 1.3% of the early CO₂ emissions from the Soufrière Hills volcano. In contrast, extinct volcanic edifices such as the Centre Hills in central Montserrat are a net sink for atmospheric CO₂ due to continued elevated weathering rates relative to continental silicate rock weathering. The role of an arc volcano as a source or sink for atmospheric CO₂ is therefore critically dependent on the stage it occupies in its life cycle, changing from a net source to a net sink as the eruptive activity wanes. While the onset of the eruption has had a profound effect on the groundwater around the Soufrière Hills center, the geochemistry of springs in the Centre Hills 5 km to the north appear unaffected by the recent volcanism. This has implications for the potential risk, or lack thereof, of contamination of potable water supplies for the island’s inhabitants.  相似文献   

AGU新出版地球系统模拟杂志     

Bill Cook  左玉玲 《国际地震动态》2011,(2):7-7

美国地球物理联合会（AGU）很高兴地宣布,AGU不久将成为《地球系统模拟进展杂志》（Journal of Advances in Modeling Earth Systems,JAMES）新的出版机构。JAMES是一份同行评议、开放获取、全电子化的杂志,通过提供高质量的学术研究论文推动地球系统模拟科学的发展。  相似文献   

Letter     

Sidney J. Holt 《Marine pollution bulletin》1984,15(4):161-162

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Origin of the Lower Cambrian phosphatic bed at Vassbo, Sweden     

Bill Wallin 《地学学报》1989,1(3):274-279

An extensive phosphatic bed characterized by a black apatite-cemented sandstone is developed in the uppermost part of the Lower Cambrian formation over the entire Vassbo area, Sweden. The thickness of the layer is generally 0.1 m, increasing in places to 0.2 m. The lower boundary of the bed is transitional to a sandstone; the upper boundary displays a contact that is both sharp and irregular with a Middle Cambrian bituminous black shale.
The phosphatic bed was diagenetically formed by inorganic in situ precipitation of apatite in a sandstone at a depth of about 0.2 m below the sediment-water interface, where reducing conditions were developed, as a result of oxygen consumption during the degradation of organic matter. Sulphur isotope data from associated pyrite suggest that organic processes, such as bacterial sulphate reduction, were also involved in the formation of the phosphatic bed. The depositional environment of the bed was a marine shelf with a zero to very low sedimentation rate. The upper part of the apatite-cemented sandstone was partly reworked by bottom currents as demonstrated by a board containing numerous pebbles. Sedimentological as well as chemical data confirm a southern hemisphere position of the Baltic Shield in the early Cambrian in which an oceanic upwelling and high organic productivity was the probable source of the phosphorus along the palaeo-west-coast.  相似文献