3,381 research outputs found
Phase substitution of spare converter for a failed one of parallel phase staggered converters
Failure detection and substitution of a spare module is provided in a system having a plurality of phase staggered modules connected in parallel to deliver regulated voltage from an unregulated source. Phase control signals applied to the active converter modules are applied to the spare module through NOR gates associated with and disabled by the power output of respective modules such that failure of any one enables its phase control signal to be applied to the spare module, thus controlling the spare module to operate in the phase position of the failed module. A NAND gate detects when any one active module fails and enables a gate in the spare module, thus activating the spare module
Directed percolation in aerodynamics: resolving laminar separation bubble on airfoils
In nature, phase transitions prevail amongst inherently different systems,
while frequently showing a universal behavior at their critical point. As a
fundamental phenomenon of fluid mechanics, recent studies suggested
laminar-turbulent transition belonging to the universality class of directed
percolation. Beyond, no indication was yet found that directed percolation is
encountered in technical relevant fluid mechanics. Here, we present first
evidence that the onset of a laminar separation bubble on an airfoil can be
well characterized employing the directed percolation model on high fidelity
particle image velocimetry data. In an extensive analysis, we show that the
obtained critical exponents are robust against parameter fluctuations, namely
threshold of turbulence intensity that distinguishes between ambient flow and
laminar separation bubble. Our findings indicate a comprehensive significance
of percolation models in fluid mechanics beyond fundamental flow phenomena, in
particular, it enables the precise determination of the transition point of the
laminar separation bubble. This opens a broad variety of new fields of
application, ranging from experimental airfoil aerodynamics to computational
fluid dynamics.Comment: 8 pages, 11 figure
Pulse shape discrimination performance of Inverted Coaxial Ge detectors
We report on the characterization of two inverted coaxial Ge detectors in the
context of being employed in future Ge neutrinoless double beta
() decay experiments. It is an advantage that such detectors
can be produced with bigger Ge mass as compared to the planar Broad Energy Ge
detectors (BEGe) that are currently used in the GERDA decay
experiment. This will result in lower background for the search of
decay due to a reduction of cables, electronics and holders.
The measured resolution near the Ge Q-value at 2039 keV is 2.5 keV and
their pulse-shape characteristics are similar to BEGe-detectors. It is
concluded that this type of Ge-detector is suitable for usage in Ge
decay experiments
Modelling the role of electron attachment rates on column density ratios for CnH-/CnH (n=4; 6; 8) in dense molecular clouds
(abridged) The fairly recent detection of a variety of anions in the
Interstellar Molecular Clouds have underlined the importance of realistically
modeling the processes governing their abundance. To this aim, our earlier
calculations for the radiative electron attachment (REA) rates for C4H-, C6H-,
and C8H- are employed to generate the corresponding column density ratios of
anion/neutral (A/N) relative abundances. The latter are then compared with
those obtained from observational measurements. The calculations involved the
time-dependent solutions of a large network of chemical processes over an
extended time interval and included a series of runs in which the values of REA
rates were repeatedly scaled. Macroscopic parameters for the clouds' modeling
were also varied to cover a broad range of physical environments. It was found
that, within the range and quality of the processes included in the present
network,and selected from state-of-the-art astrophysical databases, the REA
values required to match the observed A/N ratios needed to be reduced by orders
of magnitude for C4H- case, while the same rates for C6H- and C8H- only needed
to be scaled by much smaller factors. The results suggest that the generally
proposed formation of interstellar anions by REA mechanism is overestimated by
current models for the C4H- case, for which is likely to be an inefficient path
to formation. This path is thus providing a rather marginal contribution to the
observed abundances of C4H-, the latter being more likely to originate from
other chemical processes in the network, as we discuss in some detail in the
present work.Possible physical reasons for the much smaller differences against
observations found instead for the values of the (A/N) ratios in two other,
longer members of the series are put forward and analyzed within the
evolutionary modeling discussed in the present work.Comment: Journal of Physics B, accepte
- …