Mise au point d'une méthode de détermination de la température moyenne de la mésosphère à partir de la mesure de la vitesse de phase des ondes longues sur un trajet grande distance

1993 ◽  
Vol 71 (3-4) ◽  
pp. 106-114
Author(s):  
M. Ayachi
Keyword(s):  
Nitric Oxide ◽  
Experimental Data ◽  
Mean Value ◽  
Scale Height ◽  
Height Distribution ◽  
Long Distance ◽  
Phase Measurements ◽  
Mesospheric Temperature ◽  
D Region ◽  
Solar Angle

The.mechanism of the Lyman α ionization of nitric oxide, which is mainly responsible for the formation of the D region, the lowest part of the ionosphere, is first briefly reviewed. From equations of the photochemical equilibrium, a model of the height distribution of the electron density is proposed as a function of the solar angle Θ and the scale height H, which is a function of the mesospheric temperature T. A method named Geoscanner based upon a set of curves that illustrate the theoretical relations between the phase of a continuous VLF radio wave for a long-distance transmission and the different parameters of the daytime atmosphere is described. This method is applied to analyse experimental data obtained by phase measurements for the 10.2 kHz transmission Trelew (Argentina) – Caen (France), nearly 12 000 km distant. It provides a mean value of the mesospheric temperature that is a characteristic of the studied path and day. The significance of such an integrated temperature, ranging between 190 and 200 K, is discussed.

Nonlinear Wave Crest Distribution on a Vertical Breakwater

2018 ◽  
Author(s):  
Valentina Laface ◽  
Giovanni Malara ◽  
Felice Arena ◽  
Ioannis A. Kougioumtzoglou ◽  
Alessandra Romolo
Keyword(s):  
Experimental Data ◽  
Free Surface ◽  
Vertical Wall ◽  
Surface Elevation ◽  
Wave Crest ◽  
Height Distribution ◽  
Free Surface Elevation ◽  
Pressure Transducers ◽  
Pressure Time ◽  
Time Histories

The paper addresses the problem of deriving the nonlinear, up to the second order, crest wave height probability distribution in front of a vertical wall under the assumption of finite spectral bandwidth, finite water depth and long-crested waves. The distribution is derived by relying on the Quasi-Deterministic representation of the free surface elevation in front of the vertical wall. The theoretical results are compared against experimental data obtained by utilizing a compressive sensing algorithm for reconstructing the free surface elevation in front of the wall. The reconstruction is pursued by starting from recorded wave pressure time histories obtained by utilizing a row of pressure transducers located at various levels. The comparison shows that there is an excellent agreement between the proposed distribution and the experimental data and confirm the deviation of the crest height distribution from the Rayleigh one.

scholarly journals Stress Fracture Influences Bone Resorption marker (u-NTX) in Female Long Distance Runners

2017 ◽  
Vol 38 (14) ◽  
pp. 1070-1075 ◽  
Author(s):  
Shimpei Fujita ◽  
Keishoku Sakuraba ◽  
Atsushi Kubota ◽  
Kenta Wakamatsu ◽  
Natsue Koikawa
Keyword(s):  
Bone Resorption ◽  
Stress Fracture ◽  
Premenopausal Women ◽  
Mean Value ◽  
Bone Resorption Marker ◽  
Distance Runners ◽  
Survey Period ◽  
Long Distance ◽  
Bone Resorption Markers ◽  
The Mean

AbstractIn this study, we aim to clarify the influence based on bone resorption markers at onset of stress fracture. Also, we will clarify the state of the bone resorption markers of female long distance runners who have a history of stress fracture and also ones who routinely practices running long distances. Participants comprised 19 female long distance athletes. The survey period was 2011–2014, and we measured u-NTX as a bone resorption marker at least twice a year, taking the mean±SD of the periodic measured values without stress fracture as the mean value. Measurements were collected sample when stress fractures developed. 132 u-NTX measurements were taken from 19 participants. As a result, the average was 41.03±12.31 nmolBCE/mmolCRE (Q1: 33.15, Q2: 40.55, Q3: 47.95). In six of the 19 participants, u-NTX could be measured following a stress fracture. The mean value of u-NTX for those participants was 40.16±9.10 nmolBCE/mmolCRE, increasing to 64.08±16.07 nmolBCE/mmol CRE with the stress fracture (p<0.01). The findings showed that, in adult female long distance runners, u-NTX values when there was no stress fracture were within the standard value for mean premenopausal women, but increased when the athletes suffered from a stress fracture.

scholarly journals Normalization in dynamic speckle analysis for non-destructive monitoring of speed of processes

2021 ◽  
Vol 2091 (1) ◽  
pp. 012002
Author(s):  
Elena Stoykova ◽  
Dimana Nazarova ◽  
Lian Nedelchev ◽  
Mikhail Levchenko ◽  
Nataliya Berberova-Buhova ◽  
...  
Keyword(s):  
Experimental Data ◽  
Mean Value ◽  
High Contrast ◽  
Object Surface ◽  
Laser Illumination ◽  
Dynamic Speckle ◽  
The Mean ◽  
Spatially Varying ◽  
Non Destructive

Abstract The paper is dedicated to analysis of normalized intensity-based pointwise algorithms for processing dynamic speckle images with spatially varying speckle statistics in non-destructive visualization of regions of faster or slower changes across an object. Both existing and newly proposed algorithms are analyzed. Extraction of speed of changes is done by acquiring correlated in time speckle images formed on the object surface under laser illumination. The studied algorithms have been applied to simulated low and high contrast speckle data. Their performance has been compared to processing of binary patterns as another approach for dealing with varying speckle statistics in the acquired images. The efficiency of the algorithms have been checked on the experimental data, including data in a compressed format. We have proven that the algorithms with normalization at successive instants by a sum of two intensities or a single intensity outperform as a whole the algorithms which apply the time-averaged estimates of the mean value and the variance of speckle intensity.

scholarly journals Contamination Level, Distribution Characteristics, and Ecotoxicity of Tetrabromobisphenol A in Water and Sediment from Weihe River Basin, China

2020 ◽  
Vol 17 (11) ◽  
pp. 3750
Author(s):  
Xueli Wang ◽  
Chenyang Li ◽  
Xiaoyu Yuan ◽  
Shengke Yang
Keyword(s):  
River Basin ◽  
Water Samples ◽  
Mean Value ◽  
Tetrabromobisphenol A ◽  
Pollution Level ◽  
Long Distance ◽  
Water And Sediment ◽  
Local Point ◽  
Weihe River ◽  
Weihe River Basin

Tetrabromobisphenol A (TBBPA) is a brominated flame retardant, which is widely present in the various environmental and biological media. The knowledge on the contamination of TBBPA in Weihe River Basin is still limited. In order to know the pollution level and distribution of tetrabromobisphenol A (TBBPA) in the Weihe River Basin, a total of 34 sediment samples and 36 water samples were collected from the main stream and tributaries of the WeiHe River Basin, and the concentration of TBBPA in the samples was analyzed by high-performance liquid chromatography–electrospray ionization–mass spectrometry (HPLC-ESI-MS). The detection frequency of TBBPA in sediments and water samples was 61.8% and 27.8%, respectively; the TBBPA concentrations in sediments and water samples were in the range of not detected (N.D.)–3.889 ng/g (mean value of 0.283 ng/g) and N.D—12.279 ng/L (mean value of 0.937 ng/L), respectively. Compared with other areas in China, the residues of TBBPA in the Weihe River Basin were at a relatively low level. The spatial distributions of TBBPA in surface sediments and water indicated that the local point-input was their major source. This is related to the proximity of some sampling sites to industrial areas and domestic sewage discharge areas. The insignificant correlation between TBBPA and total organic carbon (TOC) indicated that TBBPA in sediments is not only influenced by TOC but also affected by atmosphere and land input, wet deposition, and long-distance transmission. The potential risks posed by TBBPA in water and sediment were characterized using the risk quotient (RQ) method. The calculated RQ for TBBPA was less than 0.01, showing that the ecological risk due to TBBPA was quite low for aquatic organisms.

Study on the height distribution of atmospheric nonlinear refractive index with a theoretical calculation model

2018 ◽  
Vol 27 (04) ◽  
pp. 1850044
Author(s):  
QingWei Zeng ◽  
Lei Liu ◽  
TaiChang Gao ◽  
Ming Chen ◽  
Qi Wang ◽  
...  
Keyword(s):  
Refractive Index ◽  
Nonlinear Refractive Index ◽  
Laser Pulses ◽  
Femtosecond Laser Pulses ◽  
Ultrashort Laser Pulses ◽  
Lower Atmosphere ◽  
Nonlinear Propagation ◽  
Accurate Estimation ◽  
Height Distribution ◽  
Long Distance

The crucial role of nonlinear propagation effects in the self-guiding of femtosecond laser pulses required accurate representation of nonlinearities to describe them. In this paper, an improved theoretical model has been proposed to study the height distribution of the atmospheric nonlinear refractive index. The results show that the revised model obviously improves accurate estimation of nonlinear index at the long wavelength band. Based on the model, we also found the atmospheric nonlinear refractive index differs much from the lower atmosphere to the upper atmosphere. Our results are essential for engineering applications based on the long-distance ultrashort laser pulses’ transmission in diverse atmosphere.

Dynamic roughness model for large-eddy simulation of turbulent flow over multiscale, fractal-like rough surfaces

2011 ◽  
Vol 679 ◽  
pp. 288-314 ◽  
Author(s):  
W. ANDERSON ◽  
C. MENEVEAU
Keyword(s):  
Large Eddy Simulation ◽  
Turbulent Flow ◽  
Power Law ◽  
Rough Surfaces ◽  
Scale Height ◽  
Small Scale ◽  
Height Distribution ◽  
Subgrid Scale ◽  
Eddy Simulation ◽  
Large Eddy

Many flows especially in geophysics involve turbulent boundary layers forming over rough surfaces with multiscale height distribution. Such surfaces pose special challenges for large-eddy simulation (LES) when the filter scale is such that only part of the roughness elements of the surface can be resolved. Here we consider LES of flows over rough surfaces with power-law height spectra Eh(k) ~ kβs (−3 ≤ βs < −1), as often encountered in natural terrains. The surface is decomposed into resolved and subgrid-scale height contributions. The effects of the unresolved small-scale height fluctuations are modelled using a local equilibrium wall model (log-law or Monin–Obukhov similarity), but the required hydrodynamic roughness length must be specified. It is expressed as the product of the subgrid-scale root-mean-square of the height distribution and an unknown dimensionless quantity, α, the roughness parameter. Instead of specifying this parameter in an ad hoc empirical fashion, a dynamic methodology is proposed based on test-filtering the surface forces and requiring that the total drag force be independent of filter scale or resolution. This dynamic surface roughness (DSR) model is inspired by the Germano identity traditionally used to determine model parameters for closing subgrid-scale stresses in the bulk of a turbulent flow. A series of LES of fully developed flow over rough surfaces are performed, with surfaces built using random-phase Fourier modes with prescribed power-law spectra. Results show that the DSR model yields well-defined, rapidly converging, values of α. Effects of spatial resolution and spectral slopes are investigated. The accuracy of the DSR model is tested by showing that predicted mean velocity profiles are approximately independent of resolution for the dynamically computed values of α, whereas resolution-dependent results are obtained when using other, incorrect, α values. Also, strong dependence of α on βs is found, where α ranges from α ~ 0.1 for βs = −1.2 to α ~ 10−5 for βs = −3.

Are voltage-dependent ion channels involved in the endothelial cell control of vasomotor tone?

2007 ◽  
Vol 293 (3) ◽  
pp. H1371-H1383 ◽  
Author(s):  
Xavier F. Figueroa ◽  
Chien-Chang Chen ◽  
Kevin P. Campbell ◽  
David N. Damon ◽  
Kathleen H. Day ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Electrical Stimulation ◽  
Endothelial Cell ◽  
Nitric Oxide Synthase ◽  
Endothelial Nitric Oxide Synthase ◽  
Long Distance ◽  
Voltage Dependent ◽  
Oxide Synthase ◽  
Endothelial Nitric Oxide ◽  
Vessel Axis

In the microcirculation, longitudinal conduction of vasomotor responses provides an essential means of coordinating flow distribution among vessels in a complex network. Spread of current along the vessel axis can display a regenerative component, which leads to propagation of vasomotor signals over many millimeters; the ionic basis for the regenerative response is unknown. We examined the responses to 10 s of focal electrical stimulation (30 Hz, 2 ms, 30 V) of mouse cremaster arterioles to test the hypothesis that voltage-dependent Na+ (Nav) and Ca2+ channels might be activated in long-distance signaling in microvessels. Electrical stimulation evoked a vasoconstriction at the site of stimulation and a spreading, nondecremental conducted dilation. Endothelial damage (air bubble) blocked conduction of the vasodilation, indicating an involvement of the endothelium. The Nav channel blocker bupivacaine also blocked conduction, and TTX attenuated it. The Nav channel activator veratridine induced an endothelium-dependent dilation. The Nav channel isoforms Nav1.2, Nav1.6, and Nav1.9 were detected in the endothelial cells of cremaster arterioles by immunocytochemistry. These findings are consistent with the involvement of Nav channels in the conducted response. BAPTA buffering of endothelial cell Ca2+ delayed and reduced the conducted dilation, which was almost eliminated by Ni2+, amiloride, or deletion of α1H T-type Ca2+ (Cav3.2) channels. Blockade of endothelial nitric oxide synthase or Ca2+-activated K+ channels also inhibited the conducted vasodilation. Our findings indicate that an electrically induced signal can propagate along the vessel axis via the endothelium and can induce sequential activation of Nav and Cav3.2 channels. The resultant Ca2+ influx activates endothelial nitric oxide synthase and Ca2+-activated K+ channels, triggering vasodilation.

Can nitric oxide induce migraine in normal individuals?

Cephalalgia ◽  
2015 ◽  
Vol 35 (12) ◽  
pp. 1125-1129 ◽  
Author(s):  
Jes Olesen ◽  
Messoud Ashina
Keyword(s):  
Nitric Oxide ◽  
Experimental Data ◽  
Migraine Attack ◽  
Environmental Influences ◽  
Strong Stimulus ◽  
Human Data ◽  
Human Models ◽  
Normal Individuals ◽  
Data Point

Introduction For many years, scientists have debated the possibility that an individual “migraine threshold” determines the likelihood with which individuals may express migraine attacks. Discussion Recent discoveries provided evidence for both genetic and environmental influences on individual migraine expression. The question is whether any person may express a migraine attack given a sufficiently strong stimulus or provocation. Here, we reviewed and discussed the ability of nitric oxide to induce migraine-like attacks in normal individuals. Conclusion Experimental data show that normal individuals may develop a migraine-like attack and that the human data point to different ways of further developing existing animal and human models.

Modelling of Nitric Oxide Formation During Liquid Fuel Combustion

2016 ◽  
Vol 246 ◽  
pp. 279-283
Author(s):  
Stanisław Gil ◽  
Wojciech Bialik
Keyword(s):  
Nitric Oxide ◽  
Experimental Data ◽  
Carbon Monoxide ◽  
Liquid Fuel ◽  
Combustion Process ◽  
Fuel Combustion ◽  
Nitric Oxides ◽  
Oxide Formation ◽  
Nitric Oxide Formation ◽  
The Impact

A liquid fuel combustion process, being a source of many environmentally hazardous pollutants (e.g. nitric oxides, carbon monoxide, polycyclic aromatic hydrocarbons, soot and sulphur oxides), is a subject of extensive research aimed at reduction of their emissions. A high temperature of the combustion air tends to increase the content of NOX in exhaust gases. Based on the experimental data and literature as well as using the CFD tools, a model of light fuel oil combustion has been developed with an emphasis on nitric oxide formation. The model adequately reflects the impact of geometry changes in the flow of combustion substrates on concentrations of carbon monoxide and nitric oxides in the chamber. The quantitative results obtained are comparable to the experimental data.

Plastic Energy Required for Fatigue Failure of Specimens Containing Cracks

1975 ◽  
Vol 97 (2) ◽  
pp. 172-178 ◽  
Author(s):  
Thang Bui-Quoc ◽  
Andre Biron
Keyword(s):  
Experimental Data ◽  
Crack Propagation ◽  
Hysteresis Loops ◽  
Mean Value ◽  
Repeated Loading ◽  
Plastic Energy ◽  
Propagation Law ◽  
The Mean ◽  
Damage Rule ◽  
Propagation Stage

A study is conducted to determine the plastic energy absorbed by a material subjected to cyclic loading during the crack propagation stage. The analysis is based on Liu’s elastoplastic solution for calculating the plastic energy around the crack tip combined with a modified crack propagation law. The plastic energy per cycle Δw is found to be dependent upon the fatigue crack length and therefore varies with the number of applied cycles. The mean value of this energy corresponds to the plastic energy obtained by measuring the area within the stress-strain hysteresis loops of the material under repeated loading. If fatigue damage is based on plastic energy, the trend of variation of Δw with the applied cycles in the present analysis shows that the application of the linear damage rule (such as Miner’s law) should be more successful in the low-cycle region than in the high-cycle region. This is consistent with experimental data.

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