Potential distribution for a harmonic current point source in horizontally stratified multilayer medium

Pre-industrial emission levels can serve as a basis to set emission requirements in current conditions to approximate natural circulation of resources and protect the environment. In Denmark, the year 1900 has been set as a reference for water regulation purposes. Reliable measurements from this time are not available. To define reference conditions, we estimate point source emissions of nutrients from Danish towns in 1900 based on historic documentation and current quantitative data. The flow of nutrients emitted by humans and animals and in industrial wastewater is quantified based on the assessment of typical discharge routes in a set of model towns. We find that point source emissions were significant, with 4261 t nitrogen and 764 t phosphorous emitted from towns in 1900. The main source were human excrements (61%), followed by excrements of animals held in towns (32%) and industry (6%). Further, 59% of nutrients were discharged directly to water, 22% were used as fertilizer on agricultural soil and 19% were emitted to soil via landfills and spills. Current point source emissions of nutrients to water (6600 t N/year and 900 t P/year) are significantly higher, revealing a need for radical reductions if historic emission levels should not be exceeded in the future.

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Influence of Power Supply Current in Electrical Landfill Leakage Detection Method

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.29-32.2686 ◽

2010 ◽

Vol 29-32 ◽

pp. 2686-2691

Author(s):

Shao Peng Guan ◽

Yu Ling Wang ◽

Chang Xin Nai ◽

Jing Cai Liu

Keyword(s):

Point Source ◽

Power Supply ◽

Electrical Current ◽

Source Model ◽

Electrical Method ◽

Current Point ◽

Supply Current ◽

Geomembrane Liners ◽

Set Up ◽

A Current

The electrical method is effective on detecting and locating leaks in geomembrane liners for landfills. If a leak exists in the liner, an anomaly in the measured potential is generated in the immediate vicinity of the leak through which electrical current is flowing. But the power supply current above the liner can affect the potential distribution. A current point source model for power supply current was set up in this paper. The potential equation induced by the point source was derived. The analysis of potential expression shows that: 1) the potential generated by the power supply current is proportional to the current size and the medium resistivity; 2) as the medium thickness increases, the potential reduces; 3) to reduce the influence of power supply current, the power supply electrode should be away from the detection area as far as possible.

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The effects of surface absorbed monolayer microdiffraction patterns

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100105461 ◽

1988 ◽

Vol 46 ◽

pp. 680-681

Author(s):

M. Pan ◽

J.M. Cowley

Keyword(s):

Surface Potential ◽

Electron Probe ◽

Potential Distribution ◽

Crystal Surface ◽

Normal Direction ◽

Surface Image ◽

Extended Surface ◽

Gas Molecules ◽

Surface Nature ◽

Electron Microdiffraction

Electron microdiffraction patterns, obtained when a small electron probe with diameter of 10-15 Å is directed to run parallel to and outside a flat crystal surface, are sensitive to the surface nature of the crystals. Dynamical diffraction calculations have shown that most of the experimental observations for a flat (100) face of a MgO crystal, such as the streaking of the central spot in the surface normal direction and (100)-type forbidden reflections etc., could be explained satisfactorily by assuming a modified image potential field outside the crystal surface. However the origin of this extended surface potential remains uncertain. A theoretical analysis by Howie et al suggests that the surface image potential should have a form different from above-mentioned image potential and also be smaller by several orders of magnitude. Nevertheless the surface potential distribution may in practice be modified in various ways, such as by the adsorption of a monolayer of gas molecules.

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XRMF applications of a monolithic, polycapillary, focusing x-ray optic

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100163666 ◽

1996 ◽

Vol 54 ◽

pp. 240-241

Author(s):

D. A. Carpenter ◽

Ning Gao ◽

G. J. Havrilla

Keyword(s):

Trace Elements ◽

Point Source ◽

Focal Spot ◽

Fluorescence Analysis ◽

X Rays ◽

Focal Distance ◽

Spot Diameter ◽

X Ray ◽

Focal Spot Diameter

A monolithic, polycapillary, x-ray optic was adapted to a laboratory-based x-ray microprobe to evaluate the potential of the optic for x-ray micro fluorescence analysis. The polycapillary was capable of collecting x-rays over a 6 degree angle from a point source and focusing them to a spot approximately 40 µm diameter. The high intensities expected from this capillary should be useful for determining and mapping minor to trace elements in materials. Fig. 1 shows a sketch of the capillary with important dimensions.The microprobe had previously been used with straight and with tapered monocapillaries. Alignment of the monocapillaries with the focal spot was accomplished by electromagnetically scanning the focal spot over the beveled anode. With the polycapillary it was also necessary to manually adjust the distance between the focal spot and the polycapillary.The focal distance and focal spot diameter of the polycapillary were determined from a series of edge scans.

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