449 research outputs found
Analytische Modellierung des Zeitverhaltens und der Verlustleistung von CMOS-Gattern
In modernen CMOS-Technologien werden die Verzögerungszeit, die Ausgangsflankensteilheit und der Querstrom eines Gatters sowohl durch die Lastkapazität als auch durch die Steilheit des Eingangssignals beeinflusst. Die heute verwendeten Technologiebibliotheken beinhalten Tabellenmodelle mit 25 oder mehr Stützpunkten dieser Abhängigkeiten, woraus durch Interpolation die benötigten Zwischenwerte berechnet werden. Bisherige Versuche, analytische Modelle abzuleiten beruhten darauf, den Querstrom zu vernachlässigen oder Transistorströme als stückweise linear anzunähern. Der hier gezeigte Ansatz beruht auf einer näherungsweisen Lösung der Differentialgleichung, die aus den beiden Transistorströmen und einer Lastkapazität besteht und damit das Schaltverhalten eines Inverters beschreibt. Mit wenigen Technologieparametern können daraus für einen beliebig dimensionierten Inverter die für eine Timing- und Verlustleistungsanalyse notwendigen Größen berechnet werden. Das Modell erreicht bei einem Vergleich zu Referenzwerten aus SPICE Simulationen eine Genauigkeit von typischerweise 5%.</p><p style="line-height: 20px;">In modern CMOS-technologies the gate delay, output transition time and the short-circuit current depend on the capacitive load as well as on the input transition time. Today’s technology libraries use table models with 25 or more samples for these dependencies. Intermediate values have to be calculated through interpolation. Attempts to derive analytical models are based on neglecting the short-circuit current or approximating it by piecewise linear functions. The approach shown in this paper provides an approximate solution for the differential equation describing the dynamic behavor of an inverter circuit. It includes the influence of both transistor currents and a single load capacitance. The required values for timing and power analysis can be calculated with a small set of technology parameters for an arbitrary designed inverter. Compared to reference values extracted from SPICE simulations, the model achieves a typical precision of 5%
High contrast optical imaging of companions: the case of the brown dwarf binary HD-130948BC
High contrast imaging at optical wavelengths is limited by the modest
correction of conventional near-IR optimized AO systems.We take advantage of
new fast and low-readout-noise detectors to explore the potential of fast
imaging coupled to post-processing techniques to detect faint companions to
stars at small separations. We have focused on I-band direct imaging of the
previously detected brown dwarf binary HD130948BC,attempting to spatially
resolve the L2+L2 benchmark system. We used the Lucky-Imaging instrument
FastCam at the 2.5-m Nordic Telescope to obtain quasi diffraction-limited
images of HD130948 with ~0.1" resolution.In order to improve the detectability
of the faint binary in the vicinity of a bright (I=5.19 \pm 0.03) solar-type
star,we implemented a post-processing technique based on wavelet transform
filtering of the image which allows us to strongly enhance the presence of
point-like sources in regions where the primary halo dominates. We detect for
the first time the BD binary HD130948BC in the optical band I with a SNR~9 at
2.561"\pm 0.007" (46.5 AU) from HD130948A and confirm in two independent
dataset that the object is real,as opposed to time-varying residual speckles.We
do not resolve the binary, which can be explained by astrometric results
posterior to our observations that predict a separation below the NOT
resolution.We reach at this distance a contrast of dI = 11.30 \pm 0.11, and
estimate a combined magnitude for this binary to I = 16.49 \pm 0.11 and a I-J
colour 3.29 \pm 0.13. At 1", we reach a detectability 10.5 mag fainter than the
primary after image post-processing. We obtain on-sky validation of a technique
based on speckle imaging and wavelet-transform processing,which improves the
high contrast capabilities of speckle imaging.The I-J colour measured for the
BD companion is slightly bluer, but still consistent with what typically found
for L2 dwarfs(~3.4-3.6).Comment: accepted in A\&
Differential functional benefits of ultra highfield MR systems within the language network
Several investigations have shown limitations of fMRI reliability with the current standard field strengths. Improvement is expected from ultra highfield systems but studies on possible benefits for cognitive networks are lacking. Here we provide an initial investigation on a prominent and clinically highly-relevant cognitive function: language processing in individual brains. 26 patients evaluated for presurgical language localization were investigated with a standardized overt language fMRI paradigm on both 3T and 7T MR scanners. During data acquisition and analysis we made particular efforts to minimize effects not related to static magnetic field strength differences. Six measures relevant for functional activation showed a large dissociation between essential language network nodes: although in Wernicke's area 5/6 measures indicated a benefit of ultra highfield, in Broca's area no comparison was significant. The most important reason for this discrepancy was identified as being an increase in susceptibility-related artifacts in inferior frontal brain areas at ultra high field. We conclude that functional UHF benefits are evident, however these depend crucially on the brain region investigated and the ability to control local artifacts
A direct and differential imaging search for sub-stellar companions to epsilon Indi A
We have carried out a direct and differential imaging search for sub-stellar
companions to eps Indi A using the adaptive optics system NACO at the ESO VLT.
The observations were carried out in September 2004 with NACO/SDI as well as
with NACO's S27 camera in the H and Ks filters. The SDI data cover an area of
\~2.8" around eps Indi A. No detection was achieved in the inner neighbourhood
down to 53 Mj (5 sigma confidence level) at a separation > 0.4" (1.45 AU) and
down to 21 Mj for separations > 1.3" (4.7 AU). To cover a wider field of view,
observations with the S27 camera and a coronagraphic mask were obtained. We
detected a faint source at a separation of (7.3 +/- 0.1)" and a position angle
of (302.9 +/- 0.8) degree. The photometry for the candidate companion yields
m(H)=(16.45 +/- 0.04)mag and m(Ks) = (15.41 +/- 0.06)mag, respectively. Those
magnitudes and the resulting color (H-Ks) = (1.04 +/- 0.07)mag fit best to a
spectral type of L5 - L9.5 if it is bound. Observations done with HST/NICMOS by
M. Endl have shown the source to be a background object.Comment: 6 pages, 5 figures, accepted by A&
Automated processing of oceanic bubble images for measuring bubble size distributions underneath breaking waves
Accurate in situ measurements of oceanic bubble size distributions beneath breaking waves are needed for a better understanding of air–sea gas transfer and aerosol production processes. To achieve this goal, a novel high-resolution optical instrument for imaging oceanic bubbles was designed and built in 2013 for the High Wind Gas Exchange Study (HiWinGS) campaign in the North Atlantic Ocean. The instrument is able to operate autonomously and can continuously capture high-resolution images at 15 frames per second over an 8-h deployment. The large number of images means that it is essential to use an automated processing algorithm to process these images. This paper describes an automated algorithm for processing oceanic images based on a robust feature extraction technique. The main advantages of this robust algorithm are it is significantly less sensitive to the noise and insusceptible to the background changes in illumination, can extract circular bubbles as small as one pixel (approximately 20 μm) in radius accurately, has low computing time (approximately 5 seconds per image), and is simple to implement. The algorithm was successfully used to analyze a large number of images (850 000 images) from deployment in the North Atlantic Ocean as part of the HiWinGS campaign in 2013
Concepts of health and well-being in managers: An organizational study
Global changes and new managerial challenges require new concepts of health and well-being in organizational contexts. In the South African context, health and well-being of managers have gained relevance in organizations and in management sciences. International organizations, in particular, attempt to address the increasing demand for health care and the delivery of health services to their managers. Careful and appropriate health management requires research to evaluate context-specific health concepts and strategies. The purpose and aim of this article is to assess managerial concepts on health and well-being that could be used by the organization to contribute to managerial well-being by implementing health promotion according to managerial needs. At the same time, this article contributes to salutogenetic health research that is very rare with regard to the South African organizational management research
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