104 research outputs found
Ability of the e-TellTale sensor to detect flow features over wind turbine blades: flow separation/reattachment dynamics
Monitoring the flow features over wind turbine blades is a challenging task
that has become more and more crucial. This paper is devoted to demonstrate the
ability of the e-TellTale sensor to detect the flow separation/reattachment
dynamics over wind turbine blades. This sensor is made of a strip with a strain
gauge sensor at its base. The velocity field was acquired using TR- PIV
measurements over an oscillating thick blade section equipped with an
e-TellTale sensor. PIV images were post-processed to detect movements of the
strip, which was compared to movements of flow. Results show good agreement
between the measured velocity field and movements of the strip regarding the
separation/reattachment dynamics
Determining the Spectral Signature of Spatial Coherent Structures
We applied to an open flow a proper orthogonal decomposition (pod) technique,
on 2D snapshots of the instantaneous velocity field, to reveal the spatial
coherent structures responsible of the self-sustained oscillations observed in
the spectral distribution of time series. We applied the technique to 2D planes
out of 3D direct numerical simulations on an open cavity flow. The process can
easily be implemented on usual personal computers, and might bring deep
insights on the relation between spatial events and temporal signature in (both
numerical or experimental) open flows.Comment: 4 page
On wall pressure fluctuations and their coupling with vortex dynamicsin a separate dâreattache d turbulent flow over a blunt flat plate
This study deals with the numerical predictions through Large-Eddy Simulation ( LES ) of the separatedâreattached turbulent flow over a blunt flat plate for analyzing main coherent structure features and theirrelation to the unsteady pressure field. A compressible approach that inherently includes acoustic prop- agation is here followed to describe the relationship between pressure fluctuations and vortex dynam- ics around the separation bubble. The objective of the present work is then to contribute to a betterunderstanding of the coupling between the vortex dynamics and the wall pressure fluctuations. The fil- tered compressible NavierâStokes equations are then solved with a numerical method that follows a LaxâWendroffapproach to recover a high accuracy in both time and space. For validations, the present numer- ical results are compared to experimental measurements, coming from both the Pprime laboratory (Sicotel al., 2012) and the literature (Cherry et al., 1984; Kiya and Sasaki, 1985; Tafti and Vanka,1991; Sicotet al., 2012). Our numerical results very well predict mean and fluctuating pressure and velocity fields.Flapping, shedding as well as KelvinâHelmholtz characteristic frequencies educed by present simulationsare in very good agreement with the experimental values generally admitted. These characteristic modesare also visible on unsteady pressure signatures even far away from the separation. Spectral, POD andEPOD (extended POD) analyses are then applied to these numerical data to enhance the salient featuresof the pressure and velocity fields, especially the unsteady wall pressure in connection with either thevortex shedding or the low frequency shear-layer flapping. A contribution to the understanding of thecoupling between wall pressure fluctuations and eddy vortices is finally proposed
PHOTONS/AERONET sunphotometer network overview. Description â Activities - Results
Fourteenth International Symposium on Atmospheric and Ocean Optics/Atmospheric Physics celebrado del 24 al 30 de junio de 2007 en Buryatia, Russia
An algorithm to retrieve ice water content profiles in cirrus clouds from the synergy of ground-based lidar and thermal infrared radiometer measurements
The algorithm presented in this paper was developed to retrieve ice water
content (IWC) profiles in cirrus clouds. It is based on optimal estimation
theory and combines ground-based visible lidar and thermal infrared (TIR)
radiometer measurements in a common retrieval framework in order to retrieve
profiles of IWC together with a correction factor for the backscatter
intensity of cirrus cloud particles. As a first step, we introduce a method
to retrieve extinction and IWC profiles in cirrus clouds from the lidar
measurements alone and demonstrate the shortcomings of this approach due to
the backscatter-to-extinction ambiguity. As a second step, we show that TIR
radiances constrain the backscattering of the ice crystals at the visible
lidar wavelength by constraining the ice water path (IWP) and hence the IWC,
which is linked to the optical properties of the ice crystals via a realistic
bulk ice microphysical model. The scattering phase function obtained from the
microphysical model is flat around the backscatter direction (i.e., there is
no backscatter peak). We show that using this flat backscattering phase
function to define the backscatter-to-extinction ratio of the ice crystals in
the retrievals with the lidar-only algorithm results in an overestimation of
the IWC, which is inconsistent with the TIR radiometer measurements. Hence, a
synergy algorithm was developed that combines the attenuated backscatter
profiles measured by the lidar and the measurements of TIR radiances in a
common optimal estimation framework to retrieve the IWC profile together with
a correction factor for the phase function of the bulk ice crystals in the
backscattering direction. We show that this approach yields consistent lidar
and TIR results. The resulting lidar ratios for cirrus clouds are found to be
consistent with previous independent studies.</p
Crustal constraint through complete model space screening for diverse geophysical datasets facilitated by emulation
Deep crustal constraint is often carried out using deterministic inverse methods, sometimes using seismic refraction, gravity and electromagnetic datasets in a complementary or âjointâ scheme. With increasingly powerful parallel computer systems it is now possible to apply joint inversion schemes to derive an optimum model from diverse input data. These methods are highly effective where the uncertainty in the system is small. However, given the complex nature of these schemes it is often difficult to discern the uniqueness of the output model given the noise in the data, and the application of necessary regularization and weighting in the inversion process means that the extent of user prejudice pertaining to the final result may be unclear. We can rigorously address the subject of uncertainty using standard statistical tools but these methods also become less feasible if the prior model space is large or the forward simulations are computationally expensive. We present a simple Monte Carlo scheme to screen model space in a fully joint fashion, in which we replace the forward simulation with a fast and uncertainty-calibrated mathematical function, or emulator. This emulator is used as a proxy to run the very large number of models necessary to fully explore the plausible model space. We develop the method using a simple synthetic dataset then demonstrate its use on a joint data set comprising first-arrival seismic refraction, MT and scalar gravity data over a diapiric salt body. This study demonstrates both the value of a forward Monte Carlo approach (as distinct from a search-based or conventional inverse approach) in incorporating all kinds of uncertainty in the modelling process, exploring the entire model space, and shows the potential value of applying emulator technology throughout geophysics. Though the target here is relatively shallow, the methodology can be readily extended to address the whole crust
Long-range-transported Canadian smoke plumes in the lower stratosphere over northern France
Long-range-transported Canadian smoke layers in the stratosphere over
northern France were detected by three lidar systems in August 2017. The
peaked optical depth of the stratospheric smoke layer
exceeds 0.20 at 532 nm, which is
comparable with the simultaneous tropospheric aerosol optical depth. The
measurements of satellite sensors revealed that the observed stratospheric
smoke plumes were transported from Canadian wildfires after being lofted by
strong pyro-cumulonimbus. Case studies at two observation sites, Lille (lat
50.612, long 3.142, 60 m a.s.l.) and Palaiseau (lat 48.712, long 2.215,
156 m a.s.l.), are presented in detail. Smoke particle depolarization
ratios are measured at three wavelengths: over 0.20 at 355 nm, 0.18â0.19 at
532 nm, and 0.04â0.05 at 1064 nm. The high depolarization ratios and their
spectral dependence are possibly caused by the irregular-shaped aged smoke
particles and/or the mixing with dust particles. Similar results are found by
several European lidar stations and an explanation that can fully resolve
this question has not yet been found. Aerosol inversion based on lidar
2α+3ÎČ data derived a smoke effective radius of about
0.33 ”m for both cases. The retrieved single-scattering albedo is
in the range of 0.8 to 0.9, indicating that the smoke plumes are absorbing.
The absorption can cause perturbations to the temperature vertical profile,
as observed by ground-based radiosonde, and it is also related to the ascent
of the smoke plumes when exposed in sunlight. A direct radiative
forcing (DRF) calculation is performed using the obtained optical and
microphysical properties. The calculation revealed that the smoke plumes in
the stratosphere can significantly reduce the radiation arriving at the
surface, and the heating rate of the plumes is about 3.5 K dayâ1. The
study provides a valuable characterization for aged smoke in the
stratosphere, but efforts are still needed in reducing and quantifying the
errors in the retrieved microphysical properties as well as radiative forcing
estimates.</p
Interiorized Feminism and Gendered Nostalgia of The âDaughter Generationâ in Ning Ying's Perpetual Motion
This is the author's accepted manuscript. The original publication is available at http://dx.doi.org/10.1386/jcc.5.3.253_1Ning Yingâs 2006 film Wuqiong dong/Perpetual Motion can be regarded as her first attempt to explore the genre of âwomenâs filmâ. Deviating from her previous neo-realist style, this film seeks to cultivate an alternative cinematic practice through developing a heavy-handed negative aesthetics. Ning Ying interiorizes the filmic exploration of female subjectivity in an enclosed time and space, which is constantly haunted by a spectral aesthetics characterized by audio-visual allusions to loss, grave, ruins and ghosts. However, the filmâs radical content and alternative aesthetics are, ironically, packaged in prevailing consumer aesthetics and commodity fetishism on and off the silver screen. All these competing drives and accounts render the film a contested narrative constantly oscillating between avant-garde feminism and domestic melodrama, and between a register of disintegrating sisterhood and a celebrity scandal of adultery. This article examines the discursive and aesthetic innovations, contradictions and limits of Ning Yingâs cinematic feminism
Enhancing mobile aerosol monitoring with CE376 dual-wavelength depolarization lidar
We present the capabilities of a compact dual-wavelength depolarization lidar to assess the spatiotemporal variations in aerosol properties aboard moving vectors. Our approach involves coupling the lightweight Cimel CE376 lidar, which provides measurements at 532 and 808ânm and depolarization at 532ânm, with a photometer to monitor aerosol properties. The assessments, both algorithmic and instrumental, were conducted at ATOLL (ATmospheric Observatory of LiLle) platform operated by the Laboratoire d'Optique AtmosphĂ©rique (LOA), in Lille, France. An early version of the CE376 lidar co-located with the CE318-T photometer and with a multi-wavelength Raman lidar were considered for comparisons and validation. We developed a modified Klett inversion method for simultaneous two-wavelength elastic lidar and photometer measurements. Using this setup, we characterized aerosols during two distinct events of Saharan dust and dust smoke aerosols transported over Lille in spring 2021 and summer 2022. For validation purposes, comparisons against the Raman lidar were performed, demonstrating good agreement in aerosol properties with relative differences of up to 12â% in the depolarization measurements. Moreover, a first dataset of CE376 lidar and photometer performing on-road measurements was obtained during the FIREX-AQ (Fire Influence on Regional to Global Environments and Air Quality) field campaign deployed in summer 2019 over the northwestern USA. By lidar and photometer mapping in 3D, we investigated the transport of released smoke from active fire spots at William Flats (northeast WA, USA). Despite extreme environmental conditions, our study enabled the investigation of aerosol optical properties near the fire source, distinguishing the influence of diffuse, convective, and residual smoke. Backscatter, extinction profiles, and column-integrated lidar ratios at 532 and 808ânm were derived for a quality-assured dataset. Additionally, the extinction Ă
ngström exponent (EAE), color ratio (CR), attenuated color ratio (ACR), and particle linear depolarization ratio (PLDR) were derived. In this study, we discuss the capabilities (and limitations) of the CE376 lidar in bridging observational gaps in aerosol monitoring, providing valuable insights for future research in this field.</p
Parental and infant characteristics and childhood leukemia in Minnesota
<p>Abstract</p> <p>Background</p> <p>Leukemia is the most common childhood cancer. With the exception of Down syndrome, prenatal radiation exposure, and higher birth weight, particularly for acute lymphoid leukemia (ALL), few risk factors have been firmly established. Translocations present in neonatal blood spots and the young age peak of diagnosis suggest that early-life factors are involved in childhood leukemia etiology.</p> <p>Methods</p> <p>We investigated the association between birth characteristics and childhood leukemia through linkage of the Minnesota birth and cancer registries using a case-cohort study design. Cases included 560 children with ALL and 87 with acute myeloid leukemia (AML) diagnoses from 28 days to 14 years. The comparison group was comprised of 8,750 individuals selected through random sampling of the birth cohort from 1976â2004. Cox proportional hazards regression specific for case-cohort studies was used to compute hazard ratios (HR) and 95% confidence intervals (CIs).</p> <p>Results</p> <p>Male sex (HR = 1.41, 95% CI 1.16â1.70), white race (HR = 2.32, 95% CI 1.13â4.76), and maternal birth interval â„ 3 years (HR = 1.31, 95% CI 1.01â1.70) increased ALL risk, while maternal age increased AML risk (HR = 1.21/5 year age increase, 95% CI 1.0â1.47). Higher birth weights (>3798 grams) (HRALL = 1.46, 1.08â1.98; HRAML = 1.97, 95% CI 1.07â3.65), and one minute Apgar scores †7 (HRALL = 1.30, 95% CI 1.05â1.61; HRAML = 1.62, 95% CI 1.01â2.60) increased risk for both types of leukemia. Sex was not a significant modifier of the association between ALL and other covariates, with the exception of maternal education.</p> <p>Conclusion</p> <p>We confirmed known risk factors for ALL: male sex, high birth weight, and white race. We have also provided data that supports an increased risk for AML following higher birth weights, and demonstrated an association with low Apgar scores.</p
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