51 research outputs found
Single scattering by realistic, inhomogeneous mineral dust particles with stereogrammetric shapes
Light scattering by single, inhomogeneous mineral dust particles was
simulated based on shapes and compositions derived directly from measurements
of real dust particles instead of using a mathematical shape model. We
demonstrate the use of the stereogrammetric shape retrieval method in the context
of single-scattering modelling of mineral dust for four different dust types
â all of them inhomogeneous â ranging from compact, equidimensional shapes
to very elongated and aggregate shapes. The three-dimensional particle shapes
were derived from stereo pairs of scanning-electron microscope images, and
inhomogeneous composition was determined by mineralogical interpretation of
localized elemental information based on energy-dispersive spectroscopy.
Scattering computations were performed for particles of equal-volume
diameters, from 0.08 ÎŒm up to 2.8 ÎŒm at 550 nm wavelength, using the
discrete-dipole approximation. Particle-to-particle variation in scattering
by mineral dust was found to be quite considerable and was not well
reproduced by simplified shapes of homogeneous spheres, spheroids, or
Gaussian random spheres. Effective-medium approximation results revealed that
particle inhomogeneity should be accounted for even for small amounts of
absorbing media (here up to 2% of the volume), especially when considering
scattering by inhomogeneous particles at size parameters 3<<i>x</i><8. When
integrated over a log-normal size distribution, the linear depolarization
ratio and single-scattering albedo were also found to be sensitive to
inhomogeneity. The methodology applied is work-intensive and the
light-scattering method used quite limited in terms of size parameter
coverage. It would therefore be desirable to find a sufficiently accurate but
simpler approach with fewer limitations for single-scattering modelling of
dust. For validation of such a method, the approach presented here could be
used for producing reference data when applied to a suitable set of target
particles
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Ground-based off-line aerosol measurements at Praia, Cape Verde, during the Saharan Mineral Dust Experiment: Microphysical properties and mineralogy
A large field experiment of the Saharan Mineral Dust Experiment (SAMUM) was performed in Praia, Cape Verde, in
January and February 2008. This work reports on the aerosol mass concentrations, size distributions and mineralogical
composition of the aerosol arriving at Praia. Three dust periods were recorded during the measurements, divided by
transitional periods and embedded in maritime-influenced situations. The total suspended particle mass/PM10/PM2.5
were 250/180/74ÎŒg/m3 on average for the first dust period (17â21 January) and 250/230/83ÎŒg/m3 for the second (24â26
January). The third period (28 January to 2 February) was the most intensive with 410/340/130 ÎŒg/m3. Four modes were
identified in the size distribution. The first mode (50â70 nm) and partly the second (700â1100 nm) can be regarded as
of marine origin, but some dust contributes to the latter. The third mode (2â4 ÎŒm) is dominated by advected dust, while
the intermittently occurring fourth mode (15â70 ÎŒm) may have a local contribution. The dust consisted of kaolinite
(dust/maritime period: 35%wt./25%wt.),K-feldspar (20%wt./25%wt.), illite (14%wt./10%wt.), quartz (11%wt./8%wt.),
smectites (6%wt./4%wt.), plagioclase (6%wt./1%wt.), gypsum (4%wt./7%wt.), halite (2%wt./17%wt.) and calcite
(2%wt./3%wt.)
Architecture landscape
The network architecture evolution journey will carry on in the years ahead, driving a large scale adoption of 5th Generation (5G) and 5G-Advanced use cases with significantly decreased deployment and operational costs, and enabling new and innovative use-case-driven solutions towards 6th Generation (6G) with higher economic and societal values. The goal of this chapter, thus, is to present the envisioned societal impact, use cases and the End-to-End (E2E) 6G architecture. The E2E 6G architecture includes summarization of the various technical enablers as well as the system and functional views of the architecture
Metamorphism and microstructures along a highâtemperature metamorphic field gradient: the northâeastern boundary of the KrĂĄlovskĂœ hvozd unit (Bohemian Massif, Czech Republic)
Exhumation, strain localization, and emplacement of granitoids along the western part of the Central Bohemian shear zone (Bohemian Massif)
Geothermal drilling in an Alpine karst aquifer and its impact on downstream springsâA case study from Finkenberg, Tyrol, Austria
A borehole heat exchanger array was installed in an Alpine karst aquifer for the first time in Europe. It is composed of nine 400 m deep boreholes in the dolomitic marble of the Hochstegen Formation. New approaches were developed for this unprecedented application and potential risks were checked throughout the sinking of the initial exploratory wellbore. As Finkenberg is located in a tourist area, drilling operations had to be executed within only a few weeks. Several springs downstream from the drilling site are sources of drinking water and tap water supply. Given that the degree and distribution of the Hochstegen Formation karstification was unknown, a spring monitoring program was mandatory in order to obtain drilling permission from public authorities. A practicable and affordable spring monitoring program including several physical and chemical parameters was developed and implemented to document the potential impact of the drilling activities on the spring water. A temporary and locally limited impact of the drilling works on groundwater quality was detected by turbidity measurements. This paper reports the implementation of geothermal drilling in a karst aquifer with a focus on karstification as well as planning, implementation and the results of the spring monitoring program. Such a program can be recommended for comparable projects or questions, adapting the characteristic parameters to be collected and the measurement intervals in consultation with the relevant authorities. It might also increase the chances of gaining approval for geothermal projects in karst and could enhance public acceptance.
Key words: Pneumatic down hole hammer drilling, Borehole heat exchanger, Groundwater monitoring, Turbidity, Hochstegen Formation
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