569 research outputs found
Hot-Film Anemometry in Air-Water Flow
The paper presents local measurements of void fraction and liquid velocity in a steady-state air- water bubbly flow at atmospheric pressure. Use is made of a constant temperature anemometer and of a conical hot-film probe.
The signal is processed with a multi-channel analyzer. Void fraction and liquid velocities are determined from the amplitude histogram of the signal.
The integrated void fraction over a diameter is compared with the average void fraction along the same diameter obtained with a γ-ray absorption method.
The liquid volumetric flow-rate is calculated from the void fraction and liquid velocity profiles and compared with the indication given by a turbine flowmeter
Recent Developments in Multichannel Raman Microprobing
This paper reviews the capabilities of multichannel Raman microprobing instruments with emphasis on some major innovative progress recently proposed which looks promising for the development of new fields of application. This new progress includes: confocal Raman microanalysis that provides better spatial resolution and background rejection, confocal Raman mapping that revitalizes the field of Raman imaging pioneered by us 20 years ago, the coupling of molecular Raman microanalysis to elemental electron microprobe, and finally, Raman spectroscopy with near-infrared excitation which permits avoiding the fluorescence limitation of visible Raman spectroscopy
Spectral Line-by-Line Pulse Shaping of an On-Chip Microresonator Frequency Comb
We report, for the first time to the best of our knowledge, spectral phase
characterization and line-by-line pulse shaping of an optical frequency comb
generated by nonlinear wave mixing in a microring resonator. Through
programmable pulse shaping the comb is compressed into a train of
near-transform-limited pulses of \approx 300 fs duration (intensity full width
half maximum) at 595 GHz repetition rate. An additional, simple example of
optical arbitrary waveform generation is presented. The ability to characterize
and then stably compress the frequency comb provides new data on the stability
of the spectral phase and suggests that random relative frequency shifts due to
uncorrelated variations of frequency dependent phase are at or below the 100
microHertz level.Comment: 18 pages, 4 figure
Prognostic value of the ratio between prothesis area and indexed annulus area measured by multiSlice-CT for transcatheter aortic valve implantation procedures
Background Postprocedural aortic regurgitations following transcatheter aortic valve implantation (TAVI) procedures remain an is- sue. Benefit of oversizing strategies to prevent them isn’t well established. We compared different level of oversizing in our cohort of con- secutive patients to address if severe oversizing compared to normal sizing had an impact on post-procedural outcomes. Methods From January 2010 to August 2013, consecutive patients were referred for TAVI with preoperative Multislice-CT (MSCT) and the procedures were achieved using Edwards Sapien® or Corevalve devices®. Retrospectively, according to pre-procedural MSCT and the valve size, pa- tients were classified into three groups: normal, moderate and severe oversizing; depending on the ratio between the prosthesis area and the annulus area indexed and measured on MSCT. Main endpoint was mid-term mortality and secondary endpoints were the Valve Academic Research Consortium (VARC-2) endpoints. Results Two hundred and sixty eight patients had a MSCT and underwent TAVI procedure, with mainly Corevalve®. While all-cause and cardiovascular mortality rates were similar in all groups, post-procedural new pacemaker (PM) implantation rate was significantly higher in the severe oversizing group (P = 0.03), while we observed more in-hospital congestive heart-failure (P = 0.02) in the normal sizing group. There was a trend toward more moderate to severe aortic regurgitation (AR) in the normal sizing group (P = 0.07). Conclusions Despite a higher rate of PM implantation, oversizing based on this ratio reduces aortic leak with lower rates of post-procedural complications and a similar mid-term survival
Correcting for static shift of magnetotelluric data with airborne electromagnetic measurements: a case study from Rathlin Basin, Northern Ireland
Galvanic distortions of
magnetotelluric (MT) data, such as the static-shift effect, are a known
problem that can lead to incorrect estimation of resistivities and erroneous
modelling of geometries with resulting misinterpretation of subsurface
electrical resistivity structure. A wide variety of approaches have been
proposed to account for these galvanic distortions, some depending on the
target area, with varying degrees of success. The natural laboratory for our
study is a hydraulically permeable volume of conductive sediment at depth,
the internal resistivity structure of which can be used to estimate reservoir
viability for geothermal purposes; however, static-shift correction is
required in order to ensure robust and precise modelling accuracy.We present here a possible method to employ frequency–domain electromagnetic
data in order to correct static-shift effects, illustrated by a case study
from Northern Ireland. In our survey area, airborne frequency domain electromagnetic (FDEM) data are regionally
available with high spatial density. The spatial distributions of the derived
static-shift corrections are analysed and applied to the uncorrected MT data
prior to inversion. Two comparative inversion models are derived, one with
and one without static-shift corrections, with instructive results. As
expected from the one-dimensional analogy of static-shift correction, at
shallow model depths, where the structure is controlled by a single local MT
site, the correction of static-shift effects leads to vertical scaling of
resistivity–thickness products in the model, with the corrected model showing
improved correlation to existing borehole wireline resistivity data. In turn,
as these vertical scalings are effectively independent of adjacent sites,
lateral resistivity distributions are also affected, with up to half a decade
of resistivity variation between the models estimated at depths down to
2000 m. Simple estimation of differences in bulk porosity, derived using
Archie's Law, between the two models reinforces our conclusion that the
suborder of magnitude resistivity contrasts induced by the correction of static
shifts correspond to similar contrasts in estimated porosities, and hence,
for purposes of reservoir investigation or similar cases requiring accurate
absolute resistivity estimates, galvanic distortion correction, especially
static-shift correction, is essential
Ultrafast imaging of the entire chest without ECG synchronisation or beta-blockade: to what extent can we analyse the coronary arteries?
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