476 research outputs found
Cost of phosphate removal in municipal wastewater treatment plants
Construction and operating costs of advanced wastewater treatment for phosphate removal at municipal wastewater treatment plants have been investigated on orders from the Federal Environmental Bureau in Berlin. Particular attention has been paid to applicable kinds of precipitants for pre-, simultaneous and post-precipitation as well as to different phosphate influent and effluent concentrations. The article offers detailed comments on determination of technical data, investments, capital costs, operating costs and annual costs as well as potential cost reductions resulting from precipitation. Selected results of the cost investigation are shown in graphical form as specific investments, operating and annual costs depending on wastewater flow
Are the strengths of solar cycles determined by converging flows towards the activity belts?
It is proposed that the observed near-surface inflows towards the active
regions and sunspot zones provide a nonlinear feedback mechanism that limits
the amplitude of a Babcock-Leighton-type solar dynamo and determines the
variation of the cycle strength. This hypothesis is tested with surface flux
transport simulations including converging latitudinal flows that depend on the
surface distribution of magnetic flux. The inflows modulate the build-up of
polar fields (represented by the axial dipole) by reducing the tilt angles of
bipolar magnetic regions and by affecting the cross-equator transport of
leading-polarity magnetic flux. With flux input derived from the observed
record of sunspot groups, the simulations cover the period between 1874 and
1980 (corresponding to solar cycles 11 to 20). The inclusion of the inflows
leads to a strong correlation of the simulated axial dipole strength during
activity minimum with the observed amplitude of the subsequent cycle. This in
agreement with empirical correlations and in line with what is expected from a
Babcock-Leighton-type dynamo. The results provide evidence that the latitudinal
inflows are a key ingredient in determining the amplitude of solar cycles.Comment: accepted in A&
The cause of the weak solar cycle 24
The ongoing 11-year cycle of solar activity is considerably less vigorous
than the three cycles before. It was preceded by a very deep activity minimum
with a low polar magnetic flux, the source of the toroidal field responsible
for solar magnetic activity in the subsequent cycle. Simulation of the
evolution of the solar surface field shows that the weak polar fields and thus
the weakness of the present cycle 24 are mainly caused by a number of bigger
bipolar regions emerging at low latitudes with a `wrong' (i.e., opposite to the
majority for this cycle) orientation of their magnetic polarities in the
North-South direction, which impaired the growth of the polar field. These
regions had a particularly strong effect since they emerged within
latitude from the solar equator.Comment: 15 pages, 5 figures, accepted for publication in ApJ
Frequency comb vernier spectroscopy in the near infrared
We perform femtosecond frequency comb vernier spectroscopy in the near
infrared with a femtosecond Er doped fiber laser, a scanning high-finesse
cavity and an InGaAs camera. By utilizing the properties of a frequency comb
and a scanning high-finesse cavity such spectroscopy provides broad spectral
bandwidth, high spectral resolution, and high detection sensitivity on a short
time scale. We achieved an absorption sensitivity of ~8E-8 cm-1Hz-1/2
corresponding to a detection limit of ~70 ppbv for acetylene, with a resolution
of ~1.1 GHz in single images taken in 0.5 seconds and covering a frequency
range of ~5 THz. These measurements have broad applications for sensing other
greenhouse gases in this fingerprint near IR region with a simple apparatus.Comment: 14 pages, 5 figure
The solar magnetic field since 1700: I. Characteristics of sunspot group emergence and reconstruction of the butterfly diagram
We use the historic record of sunspot groups compiled by the Royal Greenwich
Observatory together with the sunspot number to derive the statistical
properties of sunspot group emergence in dependence of cycle phase and
strength. In particular we discuss the latitude, longitude, area and tilt angle
of sunspot groups as functions of the cycle strength and of time during the
solar cycle. Using these empirical characteristics the time-latitude diagram of
sunspot group emergence (butterfly diagram) is reconstructed from 1700 onward
on the basis of the Wolf and group sunspot numbers. This reconstruction will be
useful in studies of the long-term evolution of the Sun's magnetic field.Comment: A&A, accepte
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