Transverse Spectral Velocity Estimation
Jensen, Jørgen Arendt
2014-01-01
array probe is used along with two different estimators based on the correlation of the received signal. They can estimate the velocity spectrum as a function of time as for ordinary spectrograms, but they also work at a beam-to-flow angle of 90°. The approach is validated using simulations of pulsatile...... flow using the Womersly–Evans flow model. The relative bias of the mean estimated frequency is 13.6% and the mean relative standard deviation is 14.3% at 90°, where a traditional estimator yields zero velocity. Measurements have been conducted with an experimental scanner and a convex array transducer....... A pump generated artificial femoral and carotid artery flow in the phantom. The estimated spectra degrade when the angle is different from 90°, but are usable down to 60° to 70°. Below this angle the traditional spectrum is best and should be used. The conventional approach can automatically be...
Spectral Velocity Estimation in the Transverse Direction
Jensen, Jørgen Arendt
A method for estimating the velocity spectrum for a fully transverse flow at a beam-to-flow angle of 90is described. The approach is based on the transverse oscillation (TO) method, where an oscillation across the ultrasound beam is made during receive processing. A fourth-order estimator based on...... the correlation of the received signal is derived. A Fourier transform of the correlation signal yields the velocity spectrum. Performing the estimation for short data segments gives the velocity spectrum as a function of time as for ordinary spectrograms, and it also works for a beam-to-flow angle of...... for creating the lateral oscillation. Pulsatile flow in a femoral artery placed 40 mm from the transducer is simulated for one cardiac cycle using the Womersly-Evan’s flow model. The bias of the mean estimated frequency is 13.6% compared to the true velocity and the mean relative std is 14.3%. This...
Maximum Possible Transverse Velocity in Special Relativity.
Medhekar, Sarang
1991-01-01
Using a physical picture, an expression for the maximum possible transverse velocity and orientation required for that by a linear emitter in special theory of relativity has been derived. A differential calculus method is also used to derive the expression. (Author/KR)
Xu, Zongbo; Xia, Jianghai; Luo, Yinhe; Cheng, Feng; Pan, Yudi
2016-04-01
People have calculated Rayleigh-wave phase velocities from vertical component of ambient seismic noise for several years. Recently, researchers started to extract Love waves from transverse component recordings of ambient noise, where "transverse" is defined as the direction perpendicular to a great-circle path or a line in small scale through observation sensors. Most researches assumed Rayleigh waves could be negligible, but Rayleigh waves can exist in the transverse component when Rayleigh waves propagate in other directions besides radial direction. In study of data acquired in western Junggar Basin near Karamay city, China, after processing the transverse component recordings of ambient noise, we obtain two energy trends, which are distinguished with Rayleigh-wave and Love-wave phase velocities, in the frequency-velocity domain using multichannel analysis of surface waves (MASW). Rayleigh waves could be also extracted from the transverse component data. Because Rayleigh-wave and Love-wave phase velocities are close in high frequencies (>0.1 Hz), two kinds of surface waves might be merged in the frequency-velocity domain. Rayleigh-wave phase velocities may be misidentified as Love-wave phase velocities. To get accurate surface-wave phase velocities from the transverse component data using seismic interferometry in investigating the shallow geology, our results suggest using MASW to calculate real Love-wave phase velocities.
Transverse, Propagating Velocity Perturbations in Solar Coronal Loops
De Moortel, I; Wright, A N; Hood, A W
2015-01-01
This short review paper gives an overview of recently observed transverse, propagating velocity perturbations in coronal loops. These ubiquitous perturbations are observed to undergo strong damping as they propagate. Using 3D numerical simulations of footpoint-driven transverse waves propagating in a coronal plasma with a cylindrical density structure, in combination with analytical modelling, it is demonstrated that the observed velocity perturbations can be understood in terms of coupling of different wave modes in the inhomogeneous boundaries of the loops. Mode coupling in the inhomogeneous boundary layers of the loops leads to the coupling of the transversal (kink) mode to the azimuthal (Alfven) mode, observed as the decay of the transverse kink oscillations. Both the numerical and analytical results show the spatial profile of the damped wave has a Gaussian shape to begin with, before switching to exponential decay at large heights. In addition, recent analysis of CoMP (Coronal Multi-channel Polarimeter)...
Longitudinal and transverse velocity fields in parsec-scale jets
Mertens, Florent
2015-01-01
Radio-loud AGN typically manifest powerful relativistic jets extending up to millions of light years and often showing superluminal motions organised in a complex kinematic pattern. A number of physical models are still competing to explain the jet structure and kinematics revealed by radio images using the VLBI technique. Robust measurements of longitudinal and transverse velocity field in the jets would provide crucial information for these models. This is a difficult task, particularly for transversely resolved jets in objects like 3C 273 and M87. To address this task, we have developed a new technique for identifying significant structural patterns (SSP) of smooth, transversely resolved flows and obtaining a velocity field from cross-correlation of these regions in multi-epoch observations. Detection of individual SSP is performed using the wavelet decomposition and multiscale segmentation of the observed structure. The cross-correlation algorithm combines structural information on different scales of the...
Transverse Oscillation Vector Velocity Estimation using a Phased Array Transducer
Marcher, Jønne; Pihl, Michael Johannes; Seerup, Gert;
2012-01-01
The Transverse Oscillation method has shown its commercial feasibility, providing the user with 2D velocity information. Todays implementation on commercial ultrasound platforms only support linear array transducers and are limited in depth. Extending the implementation to a phased array transduc...... leaves room for optimization. Despite the bias, the method has shown to work and produce reliable results, and 2D velocity estimates are provided within the entire color-box down to a depth of more than 100 mm making vector velocity imaging possible in the entire heart....
Measuring 3D Velocity Vectors using the Transverse Oscillation Method
Pihl, Michael Johannes; Jensen, Jørgen Arendt
Experimentally obtained estimates of threedimensional (3D) velocity vectors using the 3D Transverse Oscillation (TO) method are presented. The method employs a 2D transducer and synthesizes two double-oscillating fields in receive to obtain the axial, transverse, and elevation velocity components....... Velocity measurements are conducted in an experimental flow-rig with steady flow in two different directions (mainly in x or y direction). Velocity estimates are obtained along the z axis. All three velocity components (vx, vy, vz) are measured with relative biases and standard deviations (normalized to...... expected value) below 5% and 12%, respectively. For an expected velocity magnitude of 25.2 cm/s, the method estimates 24.4±3.1 cm/s and 25.1±1.9 cm/s for the two directions. Under similar conditions, Field II simulations yield 25.1±1.5 cm/s and 25.4±1.6 cm/s. The experimental results validate the results...
Experimental investigation of transverse velocity estimation using cross-correlation
Bjerngaard, Rasmus; Jensen, Jørgen Arendt
2001-01-01
.23 m/s. The volume flow was determined by a Danfoss MAG 1100 flow meter. The velocity profiles were measured for different beam-to-flow angles of 90, 65, and 45 degrees. A Harming apodized beam focused at the vessel was transmitted using 64 elements and the received signals on all elements were sampled......A technique for estimating the full flow velocity vector has previously been presented by our group. Unlike conventional estimators, that only detect the axial component of the flow, this new method is capable of estimating the transverse velocity component. The method uses focusing along the flow...... direction to produce signals that are influenced by the shift of the scatterer's position. The signals are then cross-correllated to find the shift in position and thereby the velocity. The performance of the method is investigated using both a flow phantom and in-vivo measurements. A flow phantom capable...
Phased-array vector velocity estimation using transverse oscillations
Pihl, Michael Johannes; Marcher, Jønne; Jensen, Jørgen Arendt
2012-01-01
of the TO method using a phased-array transducer for vector velocity estimation is evaluated through simulation and flow-rig measurements are acquired using an experimental scanner. The vast number of calculations needed to perform flow simulations makes the optimization of the TO fields a cumbersome process......A method for estimating the 2-D vector velocity of blood using a phased-array transducer is presented. The approach is based on the transverse oscillation (TO) method. The purposes of this work are to expand the TO method to a phased-array geometry and to broaden the potential clinical....... Therefore, three performance metrics are proposed. They are calculated based on the complex TO spectrum of the combined TO fields. It is hypothesized that the performance metrics are related to the performance of the velocity estimates. The simulations show that the squared correlation values range from 0...
Velocity Estimation of the Main Portal Vein with Transverse Oscillation
Brandt, Andreas Hjelm; Hansen, Kristoffer Lindskov; Nielsen, Michael Bachmann;
2015-01-01
This study evaluates if Transverse Oscillation (TO) can provide reliable and accurate peak velocity estimates of blood flow the main portal vein. TO was evaluated against the recommended and most widely used technique for portal flow estimation, Spectral Doppler Ultrasound (SDU). The main portal...... vein delivers blood from the bowls to the liver, and patients with certain liver diseases have decreased flow in the portal vein. Errors in velocity estimation with SDU are well described, when the beam-to-flow angle is >70 degrees. TO estimates the flow angle independently and is not limited by the...... measurements were performed with a commercial ultrasound scanner (BK 3000, BK Ultrasound, Herlev Denmark) and a convex probe (BK ultrasound 6C2, Herlev, Denmark). Ten healthy volunteers were scanned, and recordings of the portal flow during 3-5 heartbeats were conducted with an intercostal and subcostal view...
Using Phased Array for Transverse Oscillation Vector Velocity Imaging
Pihl, Michael Johannes; Haugaard, Per; Jensen, Jørgen Arendt
be expanded to phased arrays enabling vector velocity imaging of the heart. Therefore, the performance of the TO estimator has to be evaluated for depths up to 10-15 cm. Methods The TO method is based on creating a double oscillating field. Flow phantoms were simulated with a transverse (90º) parabolic flow...... profile (peak = 1 m/s) and a vessel radius of 5 mm, and ‘scanned’ orthogonal to the flow with a 3.5 MHz phased array transducer. The performance of the lateral velocity estimates were evaluated by calculating the relative mean bias, Br, and relative mean standard deviation, σr, inside the vessel of N=20...
Seeding of ambient electrons in critical velocity ionization
Despite repeated demonstration of high ionization efficiencies in critical ionization velocity (CIV) experiments in the laboratory, much lower efficiencies have been reported in space CIV experiments. A survey of the CIV experiments in space reveals that higher ambient electron density appears to favor ionization. The authors discuss some theoretical reasons on the density correlation. Since the natural ambient electron density in the ionosphere is limited, the authors propose an experiment in which electrons are seeded artifically to form a high electron density region through which a neutral beam is injected with a velocity above its critical ionization velocity
Robust seismic velocity change estimation using ambient noise recordings
Daskalakis, E; Garnier, J; Melis, N S; Papanicolaou, G; Tsogka, C
2016-01-01
We consider the problem of seismic velocity change estimation using ambient noise recordings. Motivated by [23] we study how the velocity change estimation is affected by seasonal fluctuations in the noise sources. More precisely, we consider a numerical model and introduce spatio-temporal seasonal fluctuations in the noise sources. We show that indeed, as pointed out in [23], the stretching method is affected by these fluctuations and produces misleading apparent velocity variations which reduce dramatically the signal to noise ratio of the method. We also show that these apparent velocity variations can be eliminated by an adequate normalization of the cross-correlation functions. Theoretically we expect our approach to work as long as the seasonal fluctuations in the noise sources are uniform, an assumption which holds for closely located seismic stations. We illustrate with numerical simulations and real measurements that the proposed normalization significantly improves the accuracy of the velocity chang...
Shear velocity of the Rotokawa geothermal field using ambient noise
Civilini, F.; Savage, M. K.; Townend, J.
2014-12-01
Ambient noise correlation is an increasingly popular seismological technique that uses the ambient seismic noise recorded at two stations to construct an empirical Green's function. Applications of this technique include determining shear velocity structure and attenuation. An advantage of ambient noise is that it does not rely on external sources of seismic energy such as local or teleseismic earthquakes. This method has been used in the geothermal industry to determine the depths at which magmatic processes occur, to distinguish between production and non-production areas, and to observe seismic velocity perturbations associated with fluid extraction. We will present a velocity model for the Rotokawa geothermal field near Taupo, New Zealand, produced from ambient noise cross correlations. Production at Rotokawa is based on the "Rotokawa A" combined cycle power station established in 1997 and the "Nga Awa Purua" triple flash power plant established in 2010. Rotokawa Joint Venture, a partnership between Mighty River Power and Tauhara North No. 2 Trust currently operates 174 MW of generation at Rotokawa. An array of short period seismometers was installed in 2008 and occupies an area of roughly 5 square kilometers around the site. Although both cultural and natural noise sources are recorded at the stations, the instrument separation distance provides a unique challenge for analyzing cross correlations produced by both signal types. The inter-station spacing is on the order of a few kilometers, so waves from cultural sources generally are not coherent from one station to the other, while the wavelength produced by natural noise is greater than the station separation. Velocity models produced from these two source types will be compared to known geological models of the site. Depending on the amount of data needed to adequately construct cross-correlations, a time-dependent model of velocity will be established and compared with geothermal production processes.
Robust seismic velocity change estimation using ambient noise recordings
Daskalakis, E.; Evangelidis, C. P.; Garnier, J.; Melis, N. S.; Papanicolaou, G.; Tsogka, C.
2016-06-01
We consider the problem of seismic velocity change estimation using ambient noise recordings. Motivated by Zhan et al., we study how the velocity change estimation is affected by seasonal fluctuations in the noise sources. More precisely, we consider a numerical model and introduce spatio-temporal seasonal fluctuations in the noise sources. We show that indeed, as pointed out by Zhan et al., the stretching method is affected by these fluctuations and produces misleading apparent velocity variations which reduce dramatically the signal to noise ratio of the method. We also show that these apparent velocity variations can be eliminated by an adequate normalization of the cross-correlation functions. Theoretically we expect our approach to work as long as the seasonal fluctuations in the noise sources are uniform, an assumption which holds for closely located seismic stations. We illustrate with numerical simulations in homogeneous and scattering media that the proposed normalization significantly improves the accuracy of the velocity change estimation. Similar behaviour is also observed with real data recorded in the Aegean volcanic arc. We study in particular the volcano of Santorini during the seismic unrest of 2011-2012 and observe a decrease in the velocity of seismic waves which is correlated with GPS measured elevation.
A multi-dimensional electron phase-space hole (electron hole) is considered to be unstable to the transverse instability. We perform two-dimensional (2D) particle-in-cell (PIC) simulations to study the evolutions of electron holes in weakly magnetized plasma (Ωe pe, where Ωe and ωpe are the electron gyrofrequency and plasma frequency, respectively), and the effects of perpendicular thermal velocities on the transverse instability are investigated. The transverse instability can cause decay of the electron holes. We find that with the increasing perpendicular thermal velocity tending to stabilize the transverse instability, the corresponding wave numbers decrease
Transverse Oscillations for Phased Array Vector Velocity Imaging
Pihl, Michael Johannes; Jensen, Jørgen Arendt
(correlation coefficient, R: -0.76), and therefore predict estimator performance. CV is correlated with the standard deviation (R=0.74). The results demonstrate the potential for using a phased array for vector velocity imaging at larger depths, and potentially for imaging the heart....... receive to obtain lateral spatial in-phase and quadrature components. The relative mean bias and standard deviation of the lateral velocity component are computed as performance measures. For the PEF, the coefficient of variance, CV, of the spectral frequencies, and the energy ratio, ER, of leakage into...
Data adaptive estimation of transversal blood flow velocities
Pirnia, E.; Jakobsson, A.; Gudmundson, E.; Jensen, Jørgen Arendt
The examination of blood flow inside the body may yield important information about vascular anomalies, such as possible indications of, for example, stenosis. Current Medical ultrasound systems suffer from only allowing for measuring the blood flow velocity along the direction of irradiation...
Using a 2-D simulation model, the spreading of a passive solute is investigated varying the transversal distribution assumed for the diffusion coefficient and the velocity. Using strongly different laws, the simulation results show a larger influence on the dispersion process by the velocity distribution, while the influence of the diffusion coefficient distribution is very small, so that it is important just to catch the average value for this coefficient. Different transversal distributions of velocity produce values of maximum concentration with a scatter in the 30-40% range
Improved Vector Velocity Estimation using Directional Transverse Oscillation
Jensen, Jørgen Arendt
2015-01-01
8820e transducer with a focal point at 105.6 mm (F#=5) for Vector Flow Imaging (VFI). A 6 mm radius tube in a circulating flow rig was scanned and the parabolic volume flow of 112.7 l/h (peak velocity 0.55 m/s) measured by a Danfoss Magnetic flow meter for reference. Velocity estimates for DTO are...... found for 32 emissions at a 90 degrees beam-to-flow angle at a vessel depth of 30 mm. The standard deviation (SD) drops from 9.14% for TO to 5.4%, when using DTO. The bias is -5.05% and the angle is found within +/- 3.93 degrees. At 70 mm a relative SD of 7% is obtained, the bias is -1.74%, and the...
Precision measurement of transverse velocity distribution of a strontium atomic beam
F. Gao; Liu, H.; P. Xu; Tian, X.; Y Wang; Ren, J; Haibin Wu; Hong Chang
2014-01-01
We measure the transverse velocity distribution in a thermal Sr atomic beam precisely by velocity-selective saturated fluorescence spectroscopy. The use of an ultrastable laser system and the narrow intercombination transition line of Sr atoms mean that the resolution of the measured velocity can reach 0.13 m/s, corresponding to 90$\\mu K$ in energy units. The experimental results are in very good agreement with the results of theoretical calculations. Based on the spectroscopic techniques use...
WU Ming-Yu; WU Hong; LU Quan-Ming; XUE Bing-Sen
2010-01-01
@@ A multi-dimensional electron phase-space hole(electron hole)is considered to be unstable to the transverse instability.We perform two-dimensional(219)particle-in-cell(PIC)simulations to study the evolutions of electron holes in weakly magnetized plasma(Ωe < ωpe,where Ωe and ωpe are the electron gyrofrequency and plasma frequency,respectively),and the effects of perpendicular thermal velocities on the transverse instability are investigated.
Magnetic domain-wall velocity enhancement induced by a transverse magnetic field
Yang, Jusang; Beach, Geoffrey S. D.; Knutson, Carl; Erskine, James L.
2016-01-01
Spin dynamics of field-driven domain walls (DWs) guided by permalloy nanowires are studied by high-speed magneto-optic polarimetry and numerical simulations. DW velocities and spin configurations are determined as functions of longitudinal drive field, transverse bias field, and nanowire width. Nanowires having cross-sectional dimensions large enough to support vortex wall structures exhibit regions of drive-field strength (at zero bias field) that have enhanced DW velocity resulting from coupled vortex structures that suppress oscillatory motion. Factor of 10 enhancements of the DW velocity are observed above the critical longitudinal drive-field (that marks the onset of oscillatory DW motion) when a transverse bias field is applied. Nanowires having smaller cross-sectional dimensions that support transverse wall structures also exhibit a region of higher mobility above the critical field, and similar transverse-field induced velocity enhancement but with a smaller enhancement factor. The bias-field enhancement of DW velocity is explained by numerical simulations of the spin distribution and dynamics within the propagating DW that reveal dynamic stabilization of coupled vortex structures and suppression of oscillatory motion in the nanowire conduit resulting in uniform DW motion at high speed. The enhanced velocity and drive field range are achieved at the expense of a less compact DW spin distribution.
Magnetic domain-wall velocity enhancement induced by a transverse magnetic field
Yang, Jusang; Beach, Geoffrey S. D.; Knutson, Carl; Erskine, James L.
2011-01-01
Spin dynamics of field-driven domain walls (DWs) guided by Permalloy nanowires are studied by high-speed magneto-optic polarimetry and numerical simulations. DW velocities and spin configurations are determined as functions of longitudinal drive field, transverse bias field, and nanowire width. Nanowires having cross-sectional dimensions large enough to support vortex wall structures exhibit regions of drive-field strength (at zero bias field) that have enhanced DW velocity resulting from cou...
Pedersen, Mads Møller; Pihl, Michael Johannes; Haugaard, Per; Hansen, Jens Munk; Hansen, Kristoffer Lindskov; Nielsen, Michael Bachmann; Jensen, Jørgen Arendt
2011-01-01
Spectral velocity estimation is considered the gold standard in medical ultrasound. Peak systole (PS), end diastole (ED), and resistive index (RI) are used clinically. Angle correction is performed using a flow angle set manually. With Transverse Oscillation (TO) velocity estimates the flow angle, peak systole (PSTO), end diastole (EDTO), and resistive index (RITO) are estimated. This study investigates if these clinical parameters are estimated equally good using spectral and TO data. The ri...
Yang, Ya-Ting; Yoshida, Yasuyuki; Hortobagyi, Tibor; Suzuki, Shuji
2013-01-01
We determined the angular range of motion and the relative timing of displacement in the thorax, lumbar spine, and pelvis in the transverse plane during treadmill walking at three velocities. Nine healthy young females walked on a treadmill for three minutes at 0.40, 0.93, and 1.47 m/s. The position
New Developments in Vector Velocity Imaging using the Transverse Oscillation Approach
Jensen, Jørgen Arendt; Pihl, Michael Johannes; Olesen, Jacob Bjerring; Møller Hansen, Peter; Lindskov Hansen, Kristoffer; Bachmann Nielsen, Michael
2013-01-01
Vector velocity imaging using the Transverse Oscillation (TO) approach has recently been FDA approved for linear array transducers on a commercial platform. It can now be used clinically for studying the complex flow at e.g. bifurcations, valves, and the heart in real time. Several clinical...... examples from venous flow to rotational flow in the heart will be shown. The technique is also being further developed and adapted for convex and phased array probes, for spectral velocity estimation, pressure estimation, and for three dimensional velocity tensor imaging. It is shown how the methods are...... optimized using Field II simulations along with several examples of their performance....
Jensen, Jørgen Arendt
2014-01-01
Vector velocity imaging can reveal both the magnitude and direction of the blood velocity. Several techniques have been suggested for estimating the velocity, and this paper compares the performance for directional beamforming and transverse oscillation (TO) vector flow imaging (VFI). Data have...... for TO estimation was 7.0% at a beam-to-flow angle of 75. This was 3.8% for directional beamforming and at 60 it was 2.2%. The general improvement, however, comes at an increase by a factor of roughly 11 in the number of calculations for the directional beamformation compared to the TO method....
Precision measurement of transverse velocity distribution of a Strontium atomic beam
Gao, F; Xu, P; Tian, X; Wang, Y; Ren, J; Wu, Haibin; Chang, Hong
2013-01-01
We measure precisely the transverse velocity distribution in a thermal Sr atomic beam with a velocity selective saturated fluorescence spectroscopy. By using the ultrastable laser system and narrow intercombination transition line of Sr atoms, the resolution of the velocity measured can be reached 0.13m/s, corresponding to 90$\\mu K$ in energy unit. The experimental results are agreement very well with a theoretical calculation. With the spectroscopic techniques, the absolute frequency of the intercombination transition of $^{88}$Sr is measured by an optical-frequency comb generator referenced to the SI second through an H maser, which is given by 434 829 121 318(10)kHz.
Pihl, Michael Johannes; Stuart, Matthias Bo; Tomov, Borislav Gueorguiev;
2014-01-01
, transverse, and elevation velocity components simultaneously. Data are acquired using a research ultrasound scanner. The velocity measurements are conducted with steady flow in sixteen different directions. For a specific flow direction with [α,β]= [45,15]°, the mean estimated velocity vector at the center...... of the vessel is (vx,vy,vz) = (33.8,34.5,15.2) ± (4.6,5.0,0.6)cm/s where the expected velocity is (34.2,34.2,13.0)cm/s. The velocity magnitude is 50.6 ± 5.2cm/s with a bias of 0.7cm/s.The flow angles α and β are estimated as 45.6 ± 4.9° and 17.6± 1.0°. Subsequently, the precision and accuracy are calculated...
New method of calculation of conditional and complete averages of transverse velocity in intermittent turbulent flows is proposed. Comparison between the results of experiments and calculations of transverse velocity and axial-symmetric jet, in the trail down steam the round cylinder and in the external area of wall boundary layer showed close fit. (author)
Leveque, Emmanuel
2014-01-01
Based on geometric considerations, longitudinal and transverse Lagrangian velocity increments are introduced as components along, and perpendicular to, the displacement of fluid particles during a time scale {\\tau}. It is argued that these two increments probe preferentially the stretching and spinning of material fluid elements, respectively. This property is confirmed (in the limit of vanishing {\\tau}) by examining the variances of these increments conditioned on the local topology of the flow. Interestingly, these longitudinal and transverse Lagrangian increments are found to share some qualitative features with their Eulerian counterparts. In particular, direct numerical simulations at turbulent Reynolds number up to 300 show that the distributions of the longitudinal increment are negatively skewed at all {\\tau}, which is a signature of time irreversibility of turbulence in the Lagrangian framework. Transverse increments are found more intermittent than longitudinal increments, as quantified by the compa...
High Frame Rate Vector Velocity Estimation using Plane Waves and Transverse Oscillation
Jensen, Jonas; Stuart, Matthias Bo; Jensen, Jørgen Arendt
2015-01-01
This paper presents a method for estimating 2-D vector velocities using plane waves and transverse oscillation. The approach uses emission of a low number of steered plane waves, which result in a high frame rate and continuous acquisition of data for the whole image. A transverse oscillating field...... in a flow rig phantom is scanned at beam-to-flow angles of 90, 75, and 60◦ . The relative bias is between -1.4 % and -5.8 % and the relative std. between 5 % and 8.2 % for the lateral velocity component at the measured beam-to-flow angles. The estimated flow angle is 73.4◦± 3.6◦ for the measurement...
DNS of velocity and thermal fields in turbulent channel flow with transverse-rib roughness
A detailed knowledge of both velocity and thermal fields in wall turbulence disturbed by a row of ribs on the wall is important for clarifying the chief factors of fluid and thermal dynamics related to the control of heat transfer. In this study, in order to elucidate the effects of roughness on the statistical quantities in the velocity and thermal fields, direct numerical simulations (DNS) of heat transfer in turbulent channel flows with transverse-rib roughness have been performed by varying their spacing, width and height, in which the turbulent heat transfer with k-type and d-type roughness walls are simulated. It is found that since turbulent mixing is promoted by arranging ribs, the distributions of mean velocity and temperature become markedly asymmetric. Systematic variations of secondary flow patterns between ribs are clearly identified. The best heat transfer performance is found to be obtained with the k-type roughness
Precision measurement of transverse velocity distribution of a strontium atomic beam
F. Gao
2014-02-01
Full Text Available We measure the transverse velocity distribution in a thermal Sr atomic beam precisely by velocity-selective saturated fluorescence spectroscopy. The use of an ultrastable laser system and the narrow intercombination transition line of Sr atoms mean that the resolution of the measured velocity can reach 0.13 m/s, corresponding to 90 μK in energy units. The experimental results are in very good agreement with the results of theoretical calculations. Based on the spectroscopic techniques used here, the absolute frequency of the intercombination transition of 88Sr is measured using an optical-frequency comb generator referenced to the SI second through an H maser, and is given as 434 829 121 318(10 kHz.
Precision measurement of transverse velocity distribution of a strontium atomic beam
Gao, F.; Liu, H.; Tian, X. [CAS Key Laboratory of Time and Frequency Primary Standards, National Time Service Center, Xi' an 710600 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Xu, P.; Wang, Y.; Ren, J. [CAS Key Laboratory of Time and Frequency Primary Standards, National Time Service Center, Xi' an 710600 (China); Wu, Haibin, E-mail: hbwu@phy.ecnu.edu.cn [State Key Laboratory of Precision Spectroscopy, Department of Physics, East China Normal University, Shanghai 200062 (China); Chang, Hong, E-mail: changhong@ntsc.ac.cn [CAS Key Laboratory of Time and Frequency Primary Standards, National Time Service Center, Xi' an 710600 (China); State Key Laboratory of Precision Spectroscopy, Department of Physics, East China Normal University, Shanghai 200062 (China)
2014-02-15
We measure the transverse velocity distribution in a thermal Sr atomic beam precisely by velocity-selective saturated fluorescence spectroscopy. The use of an ultrastable laser system and the narrow intercombination transition line of Sr atoms mean that the resolution of the measured velocity can reach 0.13 m/s, corresponding to 90 μK in energy units. The experimental results are in very good agreement with the results of theoretical calculations. Based on the spectroscopic techniques used here, the absolute frequency of the intercombination transition of {sup 88}Sr is measured using an optical-frequency comb generator referenced to the SI second through an H maser, and is given as 434 829 121 318(10) kHz.
Convex Array Vector Velocity Imaging Using Transverse Oscillation and Its Optimization
Jensen, Jørgen Arendt; Brandt, Andreas Hjelm; Bachmann Nielsen, Michael
2015-01-01
A method for obtaining vector flow images using the transverse oscillation (TO) approach on a convex array is presented. The paper presents optimization schemes for TO fields and evaluates their performance using simulations and measurements with an experimental scanner. A 3-MHz 192-element convex...... array probe (pitch 0.33 mm) is used in both simulations and measurements. A parabolic velocity profile is simulated at a beam-to-flow angle of 90°. The optimization routine changes the lateral oscillation period λx as a function of depth to yield the best possible estimates based on the energy ratio...
The Transverse velocity of the Andromeda system, derived from the M31 satellite population
Salomon, J -B; Famaey, B; Martin, N F; Lewis, G F
2015-01-01
We present a dynamical measurement of the tangential motion of the Andromeda system, the ensemble consisting of the Andromeda Galaxy (M31) and its satellites. The system is modelled as a structure with cosmologically-motivated velocity dispersion and density profiles, and we show that our method works well when tested using the most massive substructures in high-resolution {\\Lambda} Cold Dark Matter ({\\Lambda}CDM) simulations. Applied to the sample of 40 currently-known galaxies of this system, we find a value for the transverse velocity of 164.4 +/- 61.8 km/s (v_{East} = -111.5 +/- 70.2 km/s and v{North} = 99.4 +/- 60.0 km/s), significantly higher than previous estimates of the proper motion of M31 itself. This result has significant implications on estimates of the mass of the Local Group, as well as on its past and future history.
Hayashida, T.; Yoshimi, M.; Horikawa, H.
2014-12-01
We have applied seismic interferometry to three-component ambient noise data recorded around the Ise bay area, central Japan, to validate published three-dimensional S-wave velocity models. For the bay area, detailed seismic velocity structure models have been constructed based on P-wave reflection surveys. There is no direct information on the S-wave velocities beneath the bay and the parameters are assigned by reference to those in a land area. We used one-year continuous data from 20 permanent stations of the NIED Hi-net (High-sensitivity seismograph network) to obtain stacked cross-correlation functions (CCFs) of ambient noise between station pairs that cross the bay. The CCFs were calculated, using one-hour data in the radial-radial (R-R), transverse-transverse (T-T) and vertical-vertical (Z-Z) directions for time lags of ±500s. Horizontal distances between the stations range form 15 km to 103 km. Although the Hi-net stations deploy seismometers with the natural period of 1 s, we found that the yearly stacked CCFs for selected 101 Hi-net station pairs are comparable with those derived from neighboring broadband seismic stations in the frequency range between 0.1 and 0.5 Hz, by deconvolving the instrument response. The CCFs shows clear Rayleigh waves from all directions in the R-R and Z-Z components, and clear Love waves in the T-T component with reasonable signal-to-noise ratios. The derived group velocities and waveforms of the wave trains are variable in the higher frequency range (> 0.2 Hz), indicating deep sedimentary basin beneath the bay. We compared obtained group velocities with theoretical ones to find systematic differences between the expected structure model from the CCFs and the published models in the northwest part of the bay, while the agreements are generally good for many other station pairs. This result indicates that the seismic interferometry technique provides valuable information for validation and improvement of a velocity structure
We propose a parameter-free method to determine the temperature of a thermalized state in relativistic nuclear interactions, using the experimental μq/T and μs/T values, obtained from strange particle ratios. The hadron gas formalism and strangeness neutrality are employed to relate the quark-chemical potential μq and μs to the temperature and thus determine its value at chemical freeze-out. This temperature, together with the inverse slope parameter from mT distributions, enable the determination of the transverse flow velocity of the fireball matter, thus disentangling the thermal and flow effects. We study several nucleus-nucleus interactions from AGS and SPS and obtain the temperature, transverse flow velocity, and quark-chemical potentials. Extrapolating the systematics we predict the values of these quantities for ongoing and future experiments at AGS, SPS, and RHIC. We discuss the possibility of reaching the conditions for quark deconfinement and QGP formation and give distinct and identifiable signature. copyright 1996 The American Physical Society
Pihl, Michael Johannes; Jensen, Jørgen Arendt
2014-01-01
A method for 3-D velocity vector estimation us - ing transverse oscillations is presented. The method employs a 2-D transducer and decouples the velocity estimation into three orthogonal components, which are estimated simultane - ously and from the same data. The validity of the method is invest......A method for 3-D velocity vector estimation us - ing transverse oscillations is presented. The method employs a 2-D transducer and decouples the velocity estimation into three orthogonal components, which are estimated simultane - ously and from the same data. The validity of the method...... - tions cover the positive octant of the unit sphere. In terms of accuracy, the median bias is −2%. The precision of v x and v y depends on the flow angle β and ranges from 5% to 31% rela - tive to the peak velocity magnitude of 1 m/s. For comparison, the range is 0.4 to 2% for v z . The parameter study...
Alkhalifah, T.
2010-06-13
A transversely isotropic model in which the tilt is constrained to be normal to the dip (DTI model) allows for simplifications in the imaging and velocity model building efforts as compared to a general TTI model. Though this model, in some cases, can not be represented physically like in the case of conflicting dips, it handles all dips with the assumption of symmetry axis normal to the dip. It provides a process in which areas that meet this feature is handled properly. We use efficient downward continuation algorithms that utilizes the reflection features of such a model. For lateral inhomogeneity, phase shift migration can be easily extended to approximately handle lateral inhomogeneity, because unlike the general TTI case the DTI model reduces to VTI for zero dip. We also equip these continuation algorithms with tools that expose inaccuracies in the velocity. We test this model on synthetic data of general TTI nature and show its resilience even couping with complex models like the recently released anisotropic BP model.
:,; Barbeau, P S; Beck, D; Belov, V; Breidenbach, M; Brunner, T; Burenkov, A; Cao, G F; Cen, W R; Chambers, C; Cleveland, B; Coon, M; Craycraft, A; Daniels, T; Danilov, M; Daugherty, S J; Daughhetee, J; Davis, J; Delaquis, S; Der Mesrobian-Kabakian, A; DeVoe, R; Didberidze, T; Dilling, J; Dolgolenko, A; Dolinski, M J; Dunford, M; Fairbank, W; Farine, J; Feyzbakhsh, S; Fierlinger, P; Fudenberg, D; Gornea, R; Graham, K; Gratta, G; Hall, C; Hughes, M; Jewell, M J; Johnson, A; Johnson, T N; Johnston, S; Karelin, A; Kaufman, L J; Killick, R; Koffas, T; Kravitz, S; Krucken, R; Kuchenkov, A; Kumar, K S; Lan, Y; Leonard, D S; Licciardi, C; Lin, Y H; MacLellan, R; Marino, M G; Mong, B; Moore, D; Njoya, O; Nelson, R; Odian, A; Ostrovskiy, I; Piepke, A; Pocar, A; Prescott, C Y; Retiere, F; Rowson, P C; Russell, J J; Schubert, A; Sinclair, D; Smith, E; Stekhanov, V; Tarka, M; Tolba, T; Tsang, R; Twelker, K; Vuilleumier, J -L; Waite, A; Walton, J; Walton, T; Weber, M; Wen, L J; Wichoski, U; Wood, J; Yang, L; Yen, Y -R; Zeldovich, O Ya; Zettlemoyer, J
2016-01-01
The EXO-200 Collaboration is searching for neutrinoless double beta decay using a liquid xenon (LXe) time projection chamber. This measurement relies on modeling the transport of charge deposits produced by interactions in the LXe to allow discrimination between signal and background events. Here we present measurements of the transverse diffusion constant and drift velocity of electrons at drift fields between 20~V/cm and 615~V/cm using EXO-200 data. At the operating field of 380~V/cm EXO-200 measures a drift velocity of 1.705$_{-0.010}^{+0.014}$~mm/$\\mu$s and a transverse diffusion coefficient of 55$\\pm$4~cm$^2$/s.
Roque Leal Salcedo
2008-01-01
Full Text Available El derecho internacional ambiental es un conocimiento de carácter transversal, que entre otras consideraciones refleja las preocupaciones de la sociedad por la implementación de un modelo de desarrollo sustentable para el respeto a las reglas del medio natural que garantizan la integridad y renovación de los sistemas naturales. El presente artículo enfoca esta visión a través del análisis de material documental revisado, entre ellos tratados internacionales que permiten distinguir el desarrollo del derecho internacional ambiental y el papel de Organización de las Naciones Unidas (ONU, en el propósito común del derecho individual y colectivo de disfrutar de una vida, un ambiente seguro, sano y ecológicamente equilibrado. En función a estas disertaciones las consideraciones finales exponen parte de la visión que ha estructurado la ONU y que representan un aporte considerable en el fomento de la conciencia mundial sobre la necesidad de establecer vínculos entre las naciones para el continuo desarrollo de esta rama del derecho.
Spatial coherences of the sound pressure and the particle velocity in underwater ambient noise
YAN Jin; LUO Xianzhi; HOU Chaohuan
2007-01-01
The spatial coherences were investigated between the sound pressure and the three orthogonal components of the particle velocity in underwater ambient noise. Based on the ray theory, integral expression was derived for the spatial coherence matrix of the sound pressure and the particle velocity in a stratified ocean with dipole noise sources homogenously distributed on the surface. The integrand includes a multiplying factor of the vertical directivity of the noise intensity, and the layered ocean environment affects the spatial coherences via this directivity factor. For a shallow water environment and a semi-infinite homogenous medium, the coherence calculation results were given. It was showed that the sound speed profile and the sea bottom could not be neglected in determining the spatial coherences of the ambient noise vector field.
SPATIAL VARIABILTY OF AMBIENT TEMPERATURE, RELATIVE HUMIDITY AND AIR VELOCITY IN A COLD STORE
SERAP AKDEMIR; SELCUK ARIN
2006-01-01
Spatial distribution the ambient temperature, relative humidity and air velocity were determined for different storage temperatures such as 0 oC, 1 oC, 2 oC and 3 oC in an experimental cold store. Mapping software were used to show the variability. Spatial distribution of the temperature and the relative humidity was not uniform in the cold store. Reason of bad spatial distributions was bad spatial distribution of air velocity distributed by evaporator. A temperature and/or a relative humi...
On measuring surface wave phase velocity from station-station cross-correlation of ambient signal
Boschi, Lapo; Weemstra, Cornelis; Verbeke, Julie; Ekström, Göran; Zunino, Andrea; Giardini, Domenico
2013-01-01
International audience We apply two different algorithms to measure surface wave phase velocity, as a function of frequency, from seismic ambient noise recorded at pairs of stations from a large European network. The two methods are based on consistent theoretical formulations, but differ in the implementation: one method involves the time-domain cross-correlation of signal recorded at different stations; the other is based on frequency-domain cross-correlation, and requires finding the ze...
High resolution Rayleigh wave group velocity tomography in North-China from ambient seismic noise
This study presents the results of the Rayleigh wave group velocity tomography in North-China performed using ambient seismic noise observed at 190 broadband and 10 very broadband stations of the North-China Seismic Array. All available vertical component time-series for the 14 months span between January, 2007 and February, 2008 are cross-correlated to obtain empirical Rayleigh wave Green functions that are subsequently processed, with the multiple filter method, to isolate the group velocity dispersion curves of the fundamental mode of Rayleigh wave. Tomographic maps, with a grid spacing of 0.25 deg. x 0.25 deg., are computed at the periods of 4.5s, 12s, 20s, 28s. The maps at short periods reveal an evident lateral heterogeneity in the crust of North-China, quite well in agreement with known geological and tectonic features. The North China Basin is imaged as a broad low velocity area, while the Taihangshan and Yanshan uplifts and Ordos block are imaged as high velocity zones, and the Quaternary intermountain basins show up as small low-velocity anomalies. The group velocity contours at 4.5s, 12s and 20s are consistent with the Bouguer gravity anomalies measured in the area of the Taihangshan fault, that cuts through the lower crust at least. Most of the historical strong earthquakes (M≥6.0) are located where the tomographic maps show zones with moderate velocity gradient. (author)
Crustal velocity structure of Central and Eastern Turkey from ambient noise tomography
Warren, Linda M.; Beck, Susan L.; Biryol, C. Berk; Zandt, George; Özacar, A. Arda; Yang, Yingjie
2013-09-01
In eastern Turkey, the ongoing convergence of the Arabian and African plates with Eurasia has resulted in the westward extrusion of the Anatolian Plate. To better understand the current state and the tectonic history of this region, we image crust and uppermost mantle structure with ambient noise tomography. Our study area extends from longitudes of 32° to 44°E. We use continuous data from two temporary seismic deployments, our 2006-2008 North Anatolian Fault Passive Seismic Experiment and the 1999-2001 Eastern Turkey Seismic Experiment, as well as from additional seismographs in the region. We compute daily cross-correlations of noise records between all station pairs and stack them over the entire time period for which they are available, as well as in seasonal subsets, to obtain interstation empirical Green's functions. After selecting interstation cross-correlations with high signal-to-noise ratios and measuring interstation phase velocities, we compute phase velocity maps at periods ranging from 8 to 40 s. At all periods, the phase velocity maps are similar for winter and summer subsets of the data, indicating that seasonal variations in noise sources do not bias our results. Across the study area, we invert the phase velocity estimates for shear velocity as a function of depth. The shear velocity model, which extends to 50 km depth, highlights tectonic features apparent at the surface: the Eastern Anatolian Plateau is a prominent low-velocity anomaly whereas the Kirşehir Massif has relatively fast velocities. There is a large velocity jump across the Inner Tauride Suture/Central Anataolian Fault Zone throughout the crust whereas the North Anatolian Fault does not have a consistent signature. In addition, in the southeastern part of our study area, we image a high velocity region below 20 km depth which may be the northern tip of the underthrusting Arabian Plate.
Mediavilla, E; Munoz, J A; Battaner, E
2016-01-01
We propose to use the flux variability of lensed quasar images induced by gravitational microlensing to measure the transverse peculiar velocity of lens galaxies over a wide range of redshift. Microlensing variability is caused by the motions of the observer, the lens galaxy (including the motion of the stars within the galaxy), and the source; hence, its frequency is directly related to the galaxy's transverse peculiar velocity. The idea is to count time-event rates (e.g., peak or caustic crossing rates) in the observed microlensing light curves of lensed quasars that can be compared with model predictions for different values of the transverse peculiar velocity. To compensate for the large time-scale of microlensing variability we propose to count and model the number of events in an ensemble of gravitational lenses. We develop the methodology to achieve this goal and apply it to an ensemble of 17 lensed quasar systems. In spite of the shortcomings of the available data, we have obtained tentative estimates...
McKee, K. F.; Waite, G. P.; Richardson, J. P.
2012-12-01
We used the Green's functions from auto-correlations and cross-correlations of seismic ambient noise to monitor temporal velocity changes in the subsurface at Villarrica Volcano in the Southern Andes of Chile. Campaigns were conducted from March to October 2010 and February to April 2011 with 8 broadband and 6 short-period stations, respectively. We prepared the data by removing the instrument response, normalizing with a root-mean-square method, whitening the spectra, and filtering from 1 to 10 Hz. This frequency band was chosen based on the relatively high background noise level in that range. Hour-long auto- and cross-correlations were computed and the Green's functions stacked by day and total time. To track the temporal velocity changes we stretched a 24 hour moving window of correlation functions from 90% to 110% of the original and cross correlated them with the total stack. The average increase in velocity gleaned from the auto-correlations during the 2010 array was 0.13%, as seen in the figure. Cross-correlations from station V01, near the summit, to the other stations show comparable increases in velocity. We attribute this change to the closing of cracks in the subsurface due either to seasonal snow loading or regional tectonics. In addition to the common increase in velocity across the stations, there are excursions in velocity on the same order lasting several days. Amplitude decreases as the station's distance from the vent increases suggesting these excursions may be attributed to changes within the volcanic edifice. Two occurrences are highlighted in the figure in which it is seen that the amplitudes at stations V06 and V07, the stations farthest from the vent, are smaller. Similar short temporal excursions were seen in the auto-correlations from 2011, however, there was little to no increase in the overall velocity.ercent change in velocity at Villarrica Volcano, Chile from March to October 2010 (stations offset by 0.2%)
Analytical solution of transverse shear strain vibration of a tube caused by internal gaseous detonation near the second critical speed (shear group velocity) is not reported in the literature. It is performed based on a steady state model and first order shear deformation theories (model I and II) in this paper, and the results are verified through comparison with the finite element results reported in the literature. There are no known experimental ways of directly measuring dynamic transverse shear strain and only theoretical results and numerical data are available. The finite element method is very time consuming compared with the analytical solution. It is shown in this paper that the resonance phenomenon of the transverse shear strain vibration near the second critical speed can be predicted by steady state model and first order shear deformation theories. The first order shear deformation theory (model II) has a good agreement with finite element results in prediction of dynamic amplification factors and critical speeds.
Borges, J. F.; Silva, H. G.; Torres, R. J. G.; Caldeira, B.; Bezzeghoud, M.; Furtado, J. A.; Carvalho, J.
2016-07-01
During its history, several significant earthquakes have shaken the Lower Tagus Valley (Portugal). These earthquakes were destructive; some strong earthquakes were produced by large ruptures in offshore structures located southwest of the Portuguese coastline, and other moderate earthquakes were produced by local faults. In recent years, several studies have successfully obtained strong-ground motion syntheses for the Lower Tagus Valley using the finite difference method. To confirm the velocity model of this sedimentary basin obtained from geophysical and geological data, we analysed the ambient seismic noise measurements by applying the horizontal to vertical spectral ratio (HVSR) method. This study reveals the dependence of the frequency and amplitude of the low-frequency (HVSR) peaks (0.2-2 Hz) on the sediment thickness. We have obtained the depth of the Cenozoic basement along a profile transversal to the basin by the inversion of these ratios, imposing constraints from seismic reflection, boreholes, seismic sounding and gravimetric and magnetic potentials. This technique enables us to improve the existing three-dimensional model of the Lower Tagus Valley structure. The improved model will be decisive for the improvement of strong motion predictions in the earthquake hazard analysis of this highly populated basin. The methodology discussed can be applied to any other sedimentary basin.
Ueli, Meier; Brenguier, Florent; M. Shapiro, N.
2010-01-01
International audience We analyze 3 years of continuous seismic records from broadband stations of the Caltech Regional Seismic Network (CI) in vicinity of the Los Angeles basin. Using correlations of ambient seismic noise, relative velocity variations in the order of 0.1 % can be measured between all inter-station pairs. It is the first time that such an extensive study between 861 inter-station pairs over such a large area has been carried out. We perform these measurements using the 'st...
SPATIAL VARIABILTY OF AMBIENT TEMPERATURE, RELATIVE HUMIDITY AND AIR VELOCITY IN A COLD STORE
SERAP AKDEMIR
2006-10-01
Full Text Available Spatial distribution the ambient temperature, relative humidity and air velocity were determined for different storage temperatures such as 0 oC, 1 oC, 2 oC and 3 oC in an experimental cold store. Mapping software were used to show the variability. Spatial distribution of the temperature and the relative humidity was not uniform in the cold store. Reason of bad spatial distributions was bad spatial distribution of air velocity distributed by evaporator. A temperature and/or a relative humidity sensor are used in cooling systems to measure temperature and relative humidity. The umber of sensors are not enough to determine variability of temperature and relative humidity. There should be additional sensors located different places to give idea for cold storage.
MSNoise: a Python Package for Monitoring Seismic Velocity Changes using Ambient Seismic Noise
Lecocq, Thomas; Caudron, Corentin; Brenguier, Florent
2014-05-01
We present MSNoise, a complete software suite to compute relative seismic velocity changes under a seismic network, using ambient seismic noise. The whole is written in Python, from the monitoring of data archives, to the production of high quality figures. All steps have been optimized to only compute the necessary steps and to use 'job'-based processing. All steps can be changed by matching the in/outs. MSNoise exposes an API for communication with the data archive and the database. We present a validation of the software on a dataset acquired during the UnderVolc project on the Piton de la Fournaise Volcano, La Réunion Island, France, for which precursory relative changes of seismic velocity are visible for three eruptions betwee 2009 and 2011. MSNoise is available on http://www.msnoise.org
Investigating Near Surface S-Wave Velocity Properties Using Ambient Noise in Southwestern Taiwan
Chun-Hsiang Kuo
2015-01-01
Full Text Available Ambient noise is typically used to estimate seismic site effects and velocity profiles instead of earthquake recordings, especially in areas with limited seismic data. The dominant Horizontal to Vertical Spectral Ratio (HVSR frequency of ambient noise is correlated to Vs30, which is the average S-wave velocity in the top 30 m. Vs30 is a widely used parameter for defining seismic amplification in earthquake engineering. HVSR can detect the vertical discontinuity of velocities, that is, the interfaces between hard bedrock and soft sediments. In southwestern Taiwan most strong motion stations are located in the plains and show a dominant frequency lower than 3 Hz. Several stations near the coast have low dominant frequencies of less than 1 Hz. The dominant frequencies are higher than 4 Hz at piedmont stations. The stations in the mountains with dominant frequencies over 8 Hz are typically located on very hard sites. This study analyzed the HVSR characteristics under different seismic site conditions considering the Vs30 from previous study (Kuo et al. 2012. The result implies that HVSRs are a better tool than Vs30 to classify the sites where bedrock is deeper than 30 m. Furthermore, we found a linear correlation between Vs30 and dominant HVSR frequency which could be used as a proxy of Vs30. The Vs30 map in this area was derived using the Engineering Geological Database for Taiwan Strong Motion Instrumentation Program (EGDT. The comparable distribution pattern between the dominant frequency and Vs30 demonstrate that HVSR can recognize S-wave velocity properties at the shallow subsurface.
Hasan Alfaisal
2011-01-01
Full Text Available Abstract The electrogravitational instability of a dielectric oscillating streaming fluid cylinder surrounded by tenuous medium of negligible motion pervaded by transverse varying electric field has been investigated for all the perturbation modes. The model is governed by Mathieu second-order integro-differential equation. Some limiting cases are recovering from the present general one. The self-gravitating force is destabilizing only in the axisymmetric perturbation for long wavelengths, while, the axial electric field interior, the fluid has strong destabilizing effect for all short and long wavelengths. The transverse field is strongly stabilizing. In the case of non-axisymmetric perturbation, the self-gravitating force is stabilizing for short and long waves, while the electric field has stabilizing effect on short waves.
Hasan Alfaisal
2011-01-01
Abstract The electrogravitational instability of a dielectric oscillating streaming fluid cylinder surrounded by tenuous medium of negligible motion pervaded by transverse varying electric field has been investigated for all the perturbation modes. The model is governed by Mathieu second-order integro-differential equation. Some limiting cases are recovering from the present general one. The self-gravitating force is destabilizing only in the axisymmetric perturbation for long wavelengths, wh...
The objective of ultrarelativistic heavy ions collisions is to produce an energy density and a temperature in the region of overlap between two colliding ions, that is high enough so that the quarks, initially confined in hadrons, can move freely. The study of this phase transition between quark-gluon plasma and hadron plasma provides information about the Universe evolution. The present cosmological theories consider that, in the early Universe such state of deconfined quarks and gluons existed, a few microseconds after Big Bang. At RHIC (Relativistic Heavy Ions Collider) - BNL (Brookhaven National Laboratory), the BRAHMS (Broad RAnge Hadron Magnetic Spectrometers) measured hadron spectra from Au-Au collisions at 200 AGeV. >From charged pions, kaons, protons and antiprotons transverse mass spectra we determine the effective temperatures and particles yields.The mass dependence of the effective temperatures provides evidence of collective transverse flow of the nuclear matter formed in these collisions. We deduce the velocity of the collective transverse expansion of hadrons produced in these collisions until they freeze-out at a temperature Tfo. We study the flow velocity and the freeze-out temperature dependence of centrality of the collisions for charged pions, kaons, protons and antiprotons. (authors)
In this experiment we studied the possibility of producing a pulsed beam for greater instantaneous beam flux, cooling the beam transversely to increase the effective beam flux and finally optical pumping to produce spin polarized atomic beam. We successfully and reliably produced a pulsed beam, and observed definite transverse cooling of the beam. We developed rather elaborate control program and interface hardware to produce the pulsed beam, and transversely cool, optically pump, and detect the atoms. We have produced the low-velocity intense source(LVIS) beam and operated it in a pulsed mode. Using an electronically controlled shutter we could load a Magneto Optical Trap(MOT) for 1 sec and launched a pulse of rubidium atoms. We performed the transverse cooling experiment using the pulses. In order to detect how the cooling is working, we used a slit to narrow down the probe beam. The probe beam had a width of 1 mm and we scanned it using a micrometer-controlled translational stage. (Cho, G.S.). 7 refs., 2 figs
Efficient focusing scheme for transverse velocity estimation using cross-correlation
Jensen, Jørgen Arendt
2001-01-01
The blood velocity can be estimated by cross-correlation of received RE signals, but only the velocity component along the beam direction is found. A previous paper showed that the complete velocity vector can be estimated, if received signals are focused along lines parallel to the direction of...... the flow. Here a weakly focused transmit field was used along with a simple delay-sum beamformer. A modified method for performing the focusing by employing a special calculation of the delays is introduced, so that a focused emission can be used. The velocity estimation was studied through extensive...
On measuring surface wave phase velocity from station–station cross-correlation of ambient signal
Boschi, Lapo; Weemstra, Cornelis; Verbeke, Julie;
2012-01-01
We apply two different algorithms to measure surface wave phase velocity, as a function of frequency, from seismic ambient noise recorded at pairs of stations from a large European network. The two methods are based on consistent theoretical formulations, but differ in the implementation: one...... method involves the time-domain cross-correlation of signal recorded at different stations; the other is based on frequency-domain cross-correlation, and requires finding the zero-crossings of the real part of the cross-correlation spectrum. Furthermore, the time-domain method, as implemented here and in...... the literature, practically involves the important approximation that interstation distance be large compared to seismic wavelength. In both cases, cross-correlations are ensemble-averaged over a relatively long period of time (1 yr). We verify that the two algorithms give consistent results, and...
Eje transversal ambiental en el Instituto Tecnológico de Costa Rica
Miriam Brenes
2008-05-01
Full Text Available Este artículo es el resumen de una las actividades realizadas en el proyecto “Introducción de la Dimensión Ambiental (IDA en el currículo del Instituto Tecnológico de Costa Rica (ITCR, elproyecto se desarrolló con recursos de la Vicerrectoría de Docencia en el año 2005-2006. Los resultados obtenidos que se presentan son de una encuesta aplicada a todos los docentes de la institución en el Campus Central de Cartago y el Centro Académico en San José en el año 2005. En total fueron 281 docentes universitarios.
Highly transverse velocity distribution of convoy electrons emitted by highly charged ions
Seliger, M.; Tőkési, K.; Reinhold, C. O.; Burgdörfer, J.
2003-05-01
We present a theoretical study of convoy electron emission resulting from highly charged ion (HCI) transport through carbon foils. Employing a classical transport theory we analyze the angular and energy distribution formed by multiple scattering of electrons in the solid. We find that the convoy electron distribution becomes highly transverse at intermediate foil thicknesses representing an oblate spheroidal distribution due to the stepwise excitation of the HCI. The calculated convoy electron spectra are found to be in good agreement with recent measurements.
Suzuki, Y.
2016-05-01
This article demonstrates the practical applicability of a method of modelling shape memory alloys (SMAs) as actuators. For this study, a pair of SMA wires was installed in an antagonistic manner to form an actuator, and a linear differential equation that describes the behaviour of the actuator’s generated force relative to its input voltage was derived for the limited range below the austenite onset temperature. In this range, hysteresis need not be considered, and the proposed SMA actuator can therefore be practically applied in linear control systems, which is significant because large deformations accompanied by hysteresis do not necessarily occur in most vibration control cases. When specific values of the parameters used in the differential equation were identified experimentally, it became clear that one of the parameters was dependent on ambient airflow velocity. The values of this dependent parameter were obtained using an additional SMA wire as a sensor. In these experiments, while the airflow distribution around the SMA wires was varied by changing the rotational speed of the fans in the wind tunnels, an input voltage was conveyed to the SMA actuator circuit, and the generated force was measured. In this way, the parameter dependent on airflow velocity was estimated in real time, and it was validated that the calculated force was consistent with the measured one.
Optimization of Transverse Oscillating Fields for Vector Velocity Estimation with Convex Arrays
Jensen, Jørgen Arendt
2013-01-01
A method for making Vector Flow Images using the transverse oscillation (TO) approach on a convex array is presented. The paper presents optimization schemes for TO fields for convex probes and evaluates their performance using Field II simulations and measurements using the SARUS experimental...... flow) at a depth of 40 mm. Measurements have been made using the SARUS experimental ultrasound scanner and a BK Medical 8820e convex array transducer. Sixty-four elements was used in transmit and 2 x 32 elements in receive for creating a color flow map image of a flow rig phantom with a laminar...
Kolínský, Petr; Zigone, Dimitri; Fuchs, Florian; Bianchi, Irene; Qorbani, Ehsan; Apoloner, Maria-Theresia; Bokelmann, Götz; AlpArray-EASI Working Group
2016-04-01
The Eastern Alpine Seismic Investigation (EASI) was a complementary experiment to the AlpArray project. EASI was composed of 55 broadband seismic stations deployed in a winding swath of 540 km length along longitude 13.350 E from the Czech-German border to the Adriatic Sea. Average north-south inter-station distance was 10 km, the distance of each station to either side of the central line was 6 km. Such a dense linear network allows for surface wave dispersion measurements by both deterministic and ambient noise sources along the same paths. During the experiment (July 2014 - August 2015), three earthquakes ML = 2.6, 2.9 and 4.2 occurred in Austria and Northern Italy only several kilometers off the swath. We measure Rayleigh and Love wave group velocities between the source and a single station for the recorded earthquakes, as well as phase velocities between selected pairs of stations using the standard two-station method. We also calculate cross-correlations of ambient noise between selected pairs of stations and we determine the corresponding group velocity dispersion curves. We propose a comparison of phase velocities between two stations measured from earthquakes with group velocities obtained from cross-correlations for the same station pairs. We also compare group velocities measured at single station using earthquakes, which occurred along the swath, with group velocities measured from cross-correlations. That way we analyze velocities of both deterministic and ambient noise reconstructed surface waves propagating along the same path. We invert the resulting dispersion curves for 1D shear wave velocity profiles with depth and we compile a quasi-2D velocity model along the EASI swath.
Real-Time GPU Implementation of Transverse Oscillation Vector Velocity Flow Imaging
Bradway, David; Pihl, Michael Johannes; Krebs, Andreas;
2014-01-01
Rapid estimation of blood velocity and visualization of complex flow patterns are important for clinical use of diagnostic ultrasound. This paper presents real-time processing for two-dimensional (2-D) vector flow imaging which utilizes an off-the-shelf graphics processing unit (GPU). In this work......, Open Computing Language (OpenCL) is used to estimate 2-D vector velocity flow in vivo in the carotid artery. Data are streamed live from a BK Medical 2202 Pro Focus UltraView Scanner to a workstation running a research interface software platform. Processing data from a 50 millisecond frame of a duplex...... vector flow acquisition takes 2.3 milliseconds seconds on an Advanced Micro Devices Radeon HD 7850 GPU card. The detected velocities are accurate to within the precision limit of the output format of the display routine. Because this tool was developed as a module external to the scanner’s built...
Blood flow velocity in the Popliteal Vein using Transverse Oscillation Ultrasound
Bechsgaard, Thor; Lindskov Hansen, Kristoffer; Brandt, Andreas Hjelm; Holbek, Simon; Lönn, Lars; Strandberg, Charlotte; Bækgaard, Niels; Bachmann Nielsen, Michael; Jensen, Jørgen Arendt
2016-01-01
the veins of the lower limbs. Four volunteers were recruited for the study. A standardized flow was provoked with a cuff compression-decompression system placed around the lower leg. The average peak velocity in the popliteal vein of the four volunteers was 151.5 cm/s for SDUS and 105.9 cm/s for TOUS...
Jensen, Jørgen Arendt; Pihl, Michael Johannes; Udesen, Jesper;
2010-01-01
a double oscillating field. A special estimator is then used for finding both the axial and lateral velocity component, so that both magnitude and phase can be calculated. The method for generating double oscillating ultrasound fields and the special estimator are described and its performance revealed...
Liu, G.; England, S.L.; Frey, H.U.; Immel, T.J.; Lin, C.S.; Pacheco, E.E.; Häusler, K.; Doornbos, E.N.
2013-01-01
This is the first study to compare plasma depletion drifts with the ambient plasma drifts and neutral winds in the post sunset equatorial ionosphere using global-scale satellite observations. The local time and latitude variations of the drift velocities of O+ plasma depletions at 350–400 km altitud
Compact High-Velocity Atmospheric Pressure Dielectric Barrier Plasma Jet in Ambient Air
In this paper, a non-thermal atmospheric pressure plasma jet at high streaming velocity operating with ambient air is highlighted. In the present technological approach, the employment of air poses a significant challenge. The high oxygen concentration in air results in a reduced concentration of reactive species in combination with a short species lifetime. The plasma jet assembly presented here contains a special dielectric barrier with a high secondary emission coefficient. In this way, the electron density and in turn the density of reactive species is increased. In addition, the plasma jet assembly is equipped with a short electrode. This leads to a higher voltage across the discharge gap and in turn to an increased density of reactive plasma species. The plasma jet is formed within and emitted by a small conical nozzle. A high-speed gas flow with gas velocity of 340 m/s was achieved at the end of the nozzle. In the jet the concentration of toxic and unwanted neutral plasma species like O3 or NOx is significantly reduced because of the shorter residence time within the plasma. The range of short-lived active plasma species is in turn considerably enhanced. The jet efficiency and action range measured through the oxidation of a test surface were determined by measuring the increase of surface tension of a polypropylene substrate via contact angle measurements after plasma treatment. Numerical modeling of the plasma plume indicates that oxygen atoms are in fact the main active species in the plasma plume. (low temperature plasma)
Pedersen, Mads Møller; Pihl, Michael Johannes; Haugaard, Per;
2011-01-01
angles and std were calculated { 52±18 ; 55±23 ; 60±16 }°. Spectral angles { 52 ; 56 ; 52 }° were obtained from the B-mode images. Obtained values are: PSTO { 76±15 ; 89±28 ; 77±7 } cm/s, spectral PS { 77 ; 110 ; 76 } cm/s, EDTO { 10±3 ; 14±8 ; 15±3 } cm/s, spectral ED { 18 ; 13 ; 20 } cm/s, RITO { 0.......87±0.05 ; 0.79±0.21 ; 0.79±0.06 }, and spectral RI { 0.77 ; 0.88 ; 0.73 }. Vector angles are within ±two std of the spectral angle. TO velocity estimates are within ±three std of the spectral estimates. RITO are within ±two std of the spectral estimates. Preliminary data indicates that the TO and spectral...... velocity estimates are equally good. With TO there is no manual angle setting and no flow angle limitation. TO velocity estimation can also automatically handle situations where the angle varies over the cardiac cycle. More detailed temporal and spatial vector estimates with diagnostic potential...
The transverse velocity and excitation structure of the HH 110 jet
Riera, A.; López, R.; Raga, A. C.; Estalella, R.; Anglada, G.
2003-03-01
We present long-slit spectroscopic observations of the HH 110 jet obtained with the 4.2 m William Herschel Telescope. We have obtained for the first time, spectra for slit positions along and across the jet axis (at the position of knots B, C, I, J and P) to search for the observational signatures of entrainment and turbulence by studying the kinematics and the excitation structure. We find that the HH 110 flow accelerates from a velocity of 35 km s-1 in knot A up to 110 km s-1 in knot P. We find some systematic trends for the variation of the emission line ratios along the jet. No clear trends for the variation of the radial velocity are seen across the width of the jet beam. The cross sections of the jet show complex radial velocity and line emission structures which differ quite strongly from each other. Based on observations made with the 4.2 m William Herschel Telescope operated on La Palma by the Issac Newton Group of Telescopes at the Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.
Wei, Hua-Rong; Lacey, Roy A
2015-01-01
Experimental results of the transverse momentum spectra of final-state light flavour particles produced in gold-gold (Au-Au), copper-copper (Cu-Cu), lead-lead (Pb-Pb), proton-lead (p-Pb), and proton-proton (p-p) collisions at various energies, measured by the PHENIX, STAR, ALICE, and CMS Collaborations, are described by the Tsallis-standard (Tsallis form of Fermi-Dirac or Bose-Einstein) distribution, Tsallis distribution, and two- or three-component standard distribution, in the framework of a multisource thermal model. The effective temperatures and real temperatures (kinetic freeze-out temperatures) of interacting system at the stage of kinetic freeze-out, and the radial flow velocities of final-state particles are successively extracted from the transverse momentum spectra by the three distributions which can be in fact regarded as three types of "thermometers" and "speedometers". The dependences of effective temperatures on particle mass and centrality, and the dependences of kinetic freeze-out temperatur...
Xu, Zhen J; Song, Xiaodong
2009-08-25
Detecting temporal changes of the medium associated with major earthquakes has implications for understanding earthquake genesis. Here we report temporal changes of surface wave velocity over a large area associated with 3 major Sumatra earthquakes in 2004, 2005, and 2007. We use ambient noise correlation to retrieve empirical Green's function (EGF) of surface waves between stations. Because the process is completely repeatable, the technique is powerful in detecting possible temporal change of medium. We find that 1 excellent station pair (PSI in Indonesia and CHTO in Thailand) shows significant time shifts (up to 1.44 s) after the 2004 and 2005 events in the Rayleigh waves at 10-20 s but not in the Love waves, suggesting that the Rayleigh time shifts are not from clock error. The time shifts are frequency dependent with the largest shifts at the period band of 11-16 s. We also observe an unusual excursion approximately 1 month before the 2004 event. We obtain a total of 17 pairs for June, 2007 to June, 2008, which allow us to examine the temporal and spatial variation of the time shifts. We observed strong anomalies (up to 0.68 s) near the epicenter after the 2007 event, but not in the region further away from the source or before the event or 3 months after the event. The observations are interpreted as stress changes and subsequent relaxation in upper-mid crust in the immediate vicinity of the rupture and the broad area near the fault zone. PMID:19667205
We use a kinetic treatment to study the linear transverse dispersion relation for a magnetized isotropic relativistic electron-positron plasma with finite relativistic temperature. The explicit linear dispersion relation for electromagnetic waves propagating along a constant background magnetic field is presented, including an analytical continuation to the whole complex frequency plane for the case of Maxwell-Jüttner velocity distribution functions. This dispersion relation is studied numerically for various temperatures. For left-handed solutions, the system presents two branches, the electromagnetic ordinary mode and the Alfvén mode. In the low frequency regime, the Alfvén branch has two dispersive zones, the normal zone (where ∂ω/∂k > 0) and an anomalous zone (where ∂ω/∂k < 0). We find that in the anomalous zone of the Alfvén branch, the electromagnetic waves are damped, and there is a maximum wave number for which the Alfvén branch is suppressed. We also study the dependence of the Alfvén velocity and effective plasma frequency with the temperature. We complemented the analytical and numerical approaches with relativistic full particle simulations, which consistently agree with the analytical results
López, Rodrigo A. [Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Concepción, Concepción (Chile); Moya, Pablo S. [NASA Goddard Space Flight Center, Heliophysics Science Division, Geospace Physics Laboratory, Mail Code 673, Greenbelt, Maryland 20771 (United States); Department of Physics, Catholic University of America, Washington DC, DC 20064 (United States); Muñoz, Víctor [Departamento de Física, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago (Chile); Viñas, Adolfo F. [NASA Goddard Space Flight Center, Heliophysics Science Division, Geospace Physics Laboratory, Mail Code 673, Greenbelt, Maryland 20771 (United States); Valdivia, J. Alejandro [Departamento de Física, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago (Chile); Centro para el Desarrollo de la Nanociencia y la Nanotecnología, CEDENNA, Santiago (Chile)
2014-09-15
We use a kinetic treatment to study the linear transverse dispersion relation for a magnetized isotropic relativistic electron-positron plasma with finite relativistic temperature. The explicit linear dispersion relation for electromagnetic waves propagating along a constant background magnetic field is presented, including an analytical continuation to the whole complex frequency plane for the case of Maxwell-Jüttner velocity distribution functions. This dispersion relation is studied numerically for various temperatures. For left-handed solutions, the system presents two branches, the electromagnetic ordinary mode and the Alfvén mode. In the low frequency regime, the Alfvén branch has two dispersive zones, the normal zone (where ∂ω/∂k > 0) and an anomalous zone (where ∂ω/∂k < 0). We find that in the anomalous zone of the Alfvén branch, the electromagnetic waves are damped, and there is a maximum wave number for which the Alfvén branch is suppressed. We also study the dependence of the Alfvén velocity and effective plasma frequency with the temperature. We complemented the analytical and numerical approaches with relativistic full particle simulations, which consistently agree with the analytical results.
Trofimov, Vyacheslav A.; Lysak, T. M.
2016-05-01
We demonstrate a new possibility of a soliton velocity control at its propagation in a nonlinear layered structure (1D photonic crystal) which is placed in a nonlinear ambient medium. Nonlinear response of the ambient medium, as well as the PhC layers, is cubic. At the initial time moment, a soliton is spread over a few layers of PhC. Then, soliton propagates across the layered structure because of the initial wave-vector direction presence for the laser beam. The soliton reaches the PhC faces and reflects from them or passes through the face. As a nonlinear medium surrounds the PhC, the laser beam obtains additional impulse after interaction with this medium and accelerates (or slows down or stops near the PhC face). Nonlinear response of the ambient medium can be additionally created by another laser beam which shines near the PhC faces.
Jin Xing; Li Jun; Lin Shu; Zhou Zhengrong; Kang Lanchi; Ou Yiping
2008-01-01
This paper uses the 8 broad-band stations' microseism data recorded by the Seismic Monitoring Network of Fujian Province to calculate the vertical correlation coefficient between two stationsat intervals of 5 minutes. According to the time intervals technique we obtain the different coefficients and then add the correlative coefficients. Depending on this, we extract the group velocity of Rayleigh waves from the cross correlation of the ambient seismic noise between two seismic stations and figure out the group velocity' spatial distribution. The results show that the signal noise ratio (SNR) increases proportionally to the superposition times, but the results from different days are similar to one another. Synchronously, the arrival-time is also stable and there is no obvious change when coming across typhoons. It is found the velocity of the surface wave is 2.9～3. 1km/s in Fujian Province, which is close to the observationally attained value.
Droplet velocity in horizontal two-phase air/water free jet flow in stagnant ambient
Surma, R.; Friedel, L. [Wissenschaftlicher Arbeitsbereich Stroemungsmechanik, TU Hamburg-Harburg, Eissendorferstr. 38, D-21073 Hamburg (Germany)
2004-08-01
For the case of an isothermal free jet flow the velocity and the size of the drops were measured with a Phase-Doppler-Anemometer. The axial velocity decay downstream from the nozzle outlet and the radial drop velocity profile are reproducible within reasonable limits, if a so-called homogeneous flow mixture density in the nozzle outlet is introduced. In case of low mass flow qualities an adjustment of the entrainment coefficient and a virtual jet origin as well as a reduced exponent for the Gaussian function type radial velocity profile is required. (Abstract Copyright [2004], Wiley Periodicals, Inc.)
Yousif Alaeldeen Altag
2016-01-01
Full Text Available In the present work, experimental investigation on laminar combustion of iso-butane-air mixtures was conducted in constant volume explosion vessel. The experiments were conducted at wide range of equivalence ratios ranging between Ф = 0.6 and 1.4 and atmospheric pressure of 0.1 MPa and ambient temperature of 303K. Using spherically expanding flame method, flame parameters including stretched, unstretched flame propagation speeds, laminar burning velocities and Markstein length were calculated. For laminar burning velocities the method of error bars of 95% confidence level was applied. In addition, values of Markstein lengths were measured in wide range of equivalence ratios to study the influence of stretch rate on flame instability and burning velocity. It was found that the stretched flame speed and laminar burning velocities increased with equivalence ratios and the peak value was obtained at equivalence ratio of Ф = 1.1. The Markstein length decreased with the increases in equivalence ratios, which indicates that the diffusion thermal flame instability increased at high equivalence ratios in richer mixture side. However, the total deviations in the laminar burning velocities have discrepancies of 1.2-2.9% for all investigated mixtures.
Farrugia, D.; Paolucci, E.; D'Amico, S.; Galea, P. M.
2014-12-01
The use of microtremors to obtain shear wave velocity (Vs) profiles of the subsurface is becoming a widespread approach due to its various advantages. Noise measurements were carried out at four sites on Malta (Central Mediterranean). Array techniques were first tested in an area where a ≈45 m layer of soft Blue Clay (BC) overlies the harder limestone. Three array configurations (two arrays of 17 geophones in an L-shape and circle respectively and one 42 geophone array in an L-shape) were tested and processed using the f-k and two SPAC techniques: Modified and Extended SPAC. No significant difference was observed in the dispersion curve from the two short arrays despite having different shapes. However, a significant variation was observed between the dispersion curve from the long and short arrays in the low frequency part. A joint inversion, using two direct search methods, of the dispersion and the H/V curve was then used to obtain the Vs profile for the site, with most of the profiles being in agreement both in terms of velocity and depth. A study was also conducted at three other sites on Malta where hard Upper Coralline Limestone (UCL) overlies the soft BC creating a velocity inversion in the soil profile. The shape of the effective dispersion curves obtained using ESAC show both an inverse dispersive trend and normal dispersion. This shape is tentatively explained in terms of the presence of higher mode Rayleigh waves. A Genetic Algorithm approach was then used to jointly invert the H/V and Rayleigh wave dispersion curve. It was observed that the BC velocity was higher when overlain by a large thickness of UCL. This could be linked to the effective pressure caused by the hard UCL, making the BC more compact, and having a higher velocity. The theoretical implications of a prominent low-velocity layer on site amplification and the interpretation of ambient noise data are investigated and discussed.
Palomeras, I.; Villasenor, A.; Thurner, S.; Levander, A.; Gallart, J.; Harnafi, M.
2014-12-01
The westernmost Mediterranean comprises the Iberian Peninsula and Morocco, separated by the Alboran Sea and the Algerian Basin. From north to south this region consists of the Pyrenees, resulting from Iberia-Eurasia collision; the Iberian Massif, which has been undeformed since the end of the Paleozoic; the Central System and Iberian Chain, regions with intracontinental Oligocene-Miocene deformation; the Gibraltar Arc (Betics, Rif and Alboran terranes), resulting from post-Oligocene subduction roll-back; and the Atlas Mountains. We analyzed data from recent broad-band array deployments and permanent stations in the area (IberArray and Siberia arrays, the PICASSO array, the University of Munster array, and the Spanish, Portuguese and Moroccan National Networks) to characterize its lithospheric structure. The combined array of 350 stations has an average interstation spacing of ~60 km. We calculated the Rayleigh waves phase velocities from ambient noise (periods 4 to 40 s) and teleseismic events (periods 20 to 167 s). We inverted the phase velocities to obtain a shear velocity model for the lithosphere to ~200 km depth. Our results correlate well with the surface expression of the main structural units with higher crustal velocity for the Iberian Massif than for the Alpine Iberia and Atlas Mountains. The Gibraltar Arc has lower crustal shear velocities than the regional average at all crustal depths. It also shows an arc shaped anomaly with high upper mantle velocities (>4.6 km/s) at shallow depths (Atlas, the northeastern end of the Betic Mountains and the Late Cenozoic volcanic fields in Iberia and Morocco, indicative of high temperatures at relatively shallow depths, and suggesting that the lithosphere has been removed beneath these areas.
Kohler, M. D.; Bowden, D. C.; Tsai, V. C.; Weeraratne, D. S.
2015-12-01
The Pacific-North America plate boundary in Southern California extends far west of the coastline, and a 12-month ocean bottom seismometer (OBS) array spanned the western side of the plate boundary to image lithospheric seismic velocities. Velocities are modeled through stacked cross correlations of ambient noise data. Twelve months of continuous data were used from 22 OBS stations and ~30 coastal and island Southern California Seismic Network stations. Particular attention has been paid to improving signal-to-noise ratios in the noise correlations with OBS stations by removing the effects of instrument tilt and infragravity waves. Different applications of preprocessing techniques allow us to distinguish the fundamental and first higher order Rayleigh modes, especially in deep water OBS pairs where the water layer dominates crustal sensitivity of the fundamental mode. Standard time domain and frequency domain methods are used to examine surface wave dispersion curves for group and phase velocities between 5 and 50 second periods, and these are inverted for 3D velocity structure. The results define the transition in three dimensions from continental lithospheric structure in the near-shore region to oceanic structure west of the continental borderland. While the most prominent features of the model relate to thinning of the crust west of the Patton Escarpment, other notable anomalies are present north-to-south throughout the continental borderland and along the coast from the Los Angeles Basin to the Peninsular Ranges. The velocity model will help describe the region's tectonic history, as well as provide new constraints for determination of earthquake relocations and rupture styles.
The saturated alluvium located south of Yucca Mountain, Nevada is expected to serve as the final barrier to radionuclide transport from the proposed high-level nuclear waste repository at Yucca Mountain. The alluvium will act as a barrier if radionuclides breach the engineered barriers in the repository, move through the unsaturated zone beneath the repository to the water table, and then migrate through saturated volcanic tuffs to the alluvium. Three single-well injection-withdrawal tracer tests were conducted between December 2000 and April 2001 in the saturated alluviuni at NC-EWDP-19D1, a Nye County-Early Warning Drilling Program well located about 18 km south of Yucca Mountain. The tests had the objectives of (1) distinguishing between a single- and a dual-porosity conceptual radionuclide transport model for the alluvium, and (2) obtaining estimates of ambient groundwater velocity in the alluvium.
Ku, C. S.; You, S. H.; Kuo, Y. T.; Huang, B. S.; Wu, Y. M.; Chen, Y. G.; Taylor, F. W.
2015-12-01
A MW 8.1 earthquake occurred on 1 April 2007 in the western Solomon Islands. Following this event, a damaging tsunami was induced and hit the Island Gizo where the capital city of Western Province of Solomon Islands located. Several buildings of this city were destroyed and several peoples lost their lives during this earthquake. However, during this earthquake, no near source seismic instrument has been installed in this region. The seismic evaluations for the aftershock sequence, the possible earthquake early warning and tsunami warning were unavailable. For the purpose of knowing more detailed information about seismic activity in this region, we have installed 9 seismic stations (with Trillium 120PA broadband seismometer and Q330S 24bit digitizer) around the rupture zone of the 2007 earthquake since September of 2009. Within a decade, it has been demonstrated both theoretically and experimentally that the Green's function or impulse response between two seismic stations can be retrieved from the cross-correlation of ambient noise. In this study, 6 stations' observations which are more complete during 2011/10 ~ 2012/12 period, were selected for the purpose of the cross-correlation analysis of ambient seismic noise. The group velocities at period 2-20 seconds of 15 station-pairs were extracted by using multiple filter technique (MFT) method. The analyzed results of this study presented significant results of group velocities with higher frequency contents than other studies (20-60 seconds in usually cases) and opened new opportunities to study the shallow crustal structure of the western Solomon Islands.
Wei, Hua-Rong; Lacey, Roy A
2016-01-01
The transverse momentum spectra of final-state light flavor particles produced in proton-proton (p-p), copper-copper (Cu-Cu), gold-gold (Au-Au), lead-lead (Pb-Pb), and proton-lead (p-Pb) collisions for different centralities at relativistic heavy ion collider (RHIC) and large hadron collider (LHC) energies are studied in the framework of a multisource thermal model. The experimental data measured by the STAR, CMS, and ALICE Collaborations are consistent with the results calculated by the multi-component Erlang distribution and Tsallis Statistics. The effective temperature and real temperature (kinetic freeze-out temperature) of interacting system at the stage of kinetic freeze-out, the mean transverse (or radial) flow velocity and mean flow velocity of particles, and the relationships between them are extracted. The dependences of effective temperature and mean (transverse) momentum on rest mass, moving mass, centrality, and center-of-mass energy, and the dependences of kinetic freeze-out temperature and mean...
横向双极电除尘器的速度分布特征%Characteristics of the Velocity Distribution in Bipolar Transverse Plate ESP
向晓东; 聂衍韬; 丁娣
2015-01-01
为了提高现有电除尘器的除尘效果，提出一种横向双极电除尘器。用计算流体动力学（CFD ）软件的模拟结果表明，当横向双极电除尘器入口风速为1 m／s时，在距横向双极电除尘器极板迎风面40 mm范围内，平均速度小于0．7m／s，在距极板背风面40mm范围内，平均速度小于0．3m／s。不同的异极距的流速模拟对比发现，异极距在150～250 mm之间时，横向双极电除尘器极板附近的平均流速较小，远远小于普通电除尘器极板附近的风速，这将非常有利于横向双极电除尘器获得更高的除尘效率。理论、模拟与实验的结果证明，极板附近的速度分布规律呈凹形。%In order to improve the particle collection efficiency of the electrostatic precipitator (ESP) ,a bipolar transverse-plate ESP is proposed .The results obtained by the CFD software show that ,when the inlet velocity of the bipolar trans-verse plate ESP is 1 m/s ,the average velocities of windward side and leeward side are less than 0 .7 m/s and 0 .3 m/s re-spectively in the range of 40 mm from the collection electrode plate .It is also found that the average velocities are lower when the electrode distance changes between 150~250 mm .The velocity near the collection electrode plate of the bipolar transverse plate ESP is far lower than that of the ordinary ESP .Therefore ,the bipolar charged transverse-plate ESP can get higher efficiency for fine particulate collection .The theories ,simulations and experiments indicate that the velocity distribu-tion near the plates shows concave .
Nam, Sang Boo
2009-01-01
The transverse and longitudinal Doppler effects of the sunbeam spectra are shown to result in the earth parameters such as the earth-self rotation and revolution velocities, the earth orbit semi-major axis, the earth orbital angular momentum, the earth axial tilt, the earth orbit eccentricity, the local latitude and the mass of the sun. The sunbeam global positioning scheme is realized, including the earth orbital position. PACS numbers: 91.10.Fc, 95.10.Km, 91.10.Da, 91.10.Jf.
Yao, H.; Hilst, R.D. van der; Hoop, M.V. de
2006-01-01
Empirical Green’s functions (EGFs) between pairs of seismographs can be estimated from the time derivative of the long-time cross-correlation of ambient seismic noise. These EGFs reveal velocity dispersion at relatively short periods, which can be used to resolve structures in the crust and uppermos
Maksimov, L.A.; Sibiriakov, B.P.; Tatarnikov, M.A.
1981-01-01
Data are given from calculations on the velocities of P- and S waves in a two-dimensional micro-inhomogenious medium whose center is filled with a gas. These calculation results demonstrate the anisotropy of this medium relative to the structure of the porous space. These calculations are in accord with measurement data in two-dimensional models.
Gerea, C.V.
2001-06-01
Complementary to the recording of compressional (P-) waves, the observation of P-S converted waves has recently been receiving specific attention. This is mainly due to their tremendous potential as a tool for fracture and lithology characterization, imaging sediments in gas saturated rocks, and imaging shallow sediments with higher resolution than conventional P-P data. In a conventional marine seismic survey, we cannot record P-to-S converted-wave energy since the fluids cannot support shear-wave strain. Thus, to capture the converted-wave energy, we need to record it at the water-bottom casing an ocean-bottom cable (OBC). The S-waves recorded at the seabed are mainly converted from P to S (i.e., PS-waves or C-waves) at the subsurface reflectors. The most accurate way to image seismic data is pre-stack depth migration. In this thesis, I develop a numerically efficient 2.5-D true-amplitude elastic Kirchhoff pre-stack migration algorithm designed to handle OBC data gathered along a single line. All the kinematic and dynamic elastic Green's functions required in the computation of true-amplitude weight term of Kirchhoff summation, are based on the non-hyperbolic explicit approximations of P- and SV-wave travel-times in layered transversely isotropic (VTI) media. Hence, this elastic imaging algorithm is very well-suited for migration-based velocity analysis techniques, for which fast, robust and iterative pre-stack migration is desired. In this thesis, I approach also the topic of anisotropic velocity model building for elastic pre-stack time-imaging. and propose an original methodology for joint PP-PS migration-based velocity analysis (MVA) in layered VTI anisotropic media. Tests on elastic synthetic and real OBC seismic data ascertain the validity of the pre-stack migration algorithm and velocity analysis methodology. (author)
Wang, Kai; Luo, Yinhe; Yang, Yingjie
2016-05-01
We collect two months of ambient noise data recorded by 35 broad-band seismic stations in a 9 × 11 km area (1-3 km station interval) near Karamay, China, and do cross-correlation of noise data between all station pairs. Array beamforming analysis of the ambient noise data shows that ambient noise sources are unevenly distributed and the most energetic ambient noise mainly comes from azimuths of 40°-70°. As a consequence of the strong directional noise sources, surface wave components of the cross-correlations at 1-5 Hz show clearly azimuthal dependence, and direct dispersion measurements from cross-correlations are strongly biased by the dominant noise energy. This bias renders that the dispersion measurements from cross-correlations do not accurately reflect the interstation velocities of surface waves propagating directly from one station to the other, that is, the cross-correlation functions do not retrieve empirical Green's functions accurately. To correct the bias caused by unevenly distributed noise sources, we adopt an iterative inversion procedure. The iterative inversion procedure, based on plane-wave modeling, includes three steps: (1) surface wave tomography, (2) estimation of ambient noise energy and biases and (3) phase velocities correction. First, we use synthesized data to test the efficiency and stability of the iterative procedure for both homogeneous and heterogeneous media. The testing results show that: (1) the amplitudes of phase velocity bias caused by directional noise sources are significant, reaching ˜2 and ˜10 per cent for homogeneous and heterogeneous media, respectively; (2) phase velocity bias can be corrected by the iterative inversion procedure and the convergence of inversion depends on the starting phase velocity map and the complexity of the media. By applying the iterative approach to the real data in Karamay, we further show that phase velocity maps converge after 10 iterations and the phase velocity maps obtained using
Mordret, Aurélien; Rivet, Diane; Landès, Matthieu; Shapiro, Nikolaï M.
2015-01-01
We cross correlate 4 years of seismic noise from the seismic network of Piton de la Fournaise Volcano (La Réunion Island) to measure the group velocity dispersion curves of Rayleigh and Love waves. We average measurements from vertical and radial components to obtain 577 Rayleigh wave dispersion curves. The transverse components provided 395 Love wave dispersion curves. We regionalize the group velocities measurements into 2-D velocity maps between 0.4 and 8 s. Finally, we locally inverted these maps for a pseudo 3-D anisotropic shear-velocity model down to 3 km below the sea level using a Neighborhood Algorithm. The 3-D isotropic shear-wave model shows three distinct high-velocity anomalies surrounded by a low-velocity ring. The anomaly located below the present "Plaine des Sables" could be related to an old intrusive body at the location of the former volcanic center before it migrated toward its present location. The second high-velocity body located below the summit of the volcano likely corresponds to the actual preferential dyke intrusion zone as highlighted by the seismicity. The third high-velocity anomaly located below the "Grandes Pentes" and the "Grand Brûlé" areas and is an imprint of the solidified magma chamber of the dismantled "Les Alizés" Volcano. Radial anisotropy shows two main anomalies: positive anisotropy above sea level highlighting the recent edifice of Piton de la Fournaise with an accumulation of horizontal lava flows and the second one below the sea level with a negative anisotropy corresponding to the ancient edifice of Piton de la Fournaise dominated by intrusions of vertical dykes.
Vassallo, Maurizio; Festa, Gaetano; Bobbio, Antonella; Serra, Marcello
2016-06-01
We extracted the Green's functions from cross correlation of ambient noise recorded at broadband stations located across the Apennine belt, Southern Italy. Continuous records at 26 seismic stations acquired for 3 years were analyzed. We found the emergence of surface waves in the whole range of the investigated distances (10-140 km) with energy confined in the frequency band 0.04-0.09 Hz. This phase reproduces Rayleigh waves generated by earthquakes in the same frequency range. Arrival time of Rayleigh waves was picked at all the couples of stations to obtain the average group velocity along the path connecting the two stations. The picks were inverted in separated frequency bands to get group velocity maps then used to obtain an S wave velocity model. Penetration depth of the model ranges between 12 and 25 km, depending on the velocity values and on the depth of the interfaces, here associated to strong velocity gradients. We found a low-velocity anomaly in the region bounded by the two main faults that generated the 1980, M 6.9 Irpinia earthquake. A second anomaly was retrieved in the southeast part of the region and can be ascribed to a reminiscence of the Adria slab under the Apennine Chain.
Navarro, M.; Vidal, F.; García-Jerez, A.; Alguacil, G.; Ruíz-Sibaja, A.; Aguirre, J.; Cárdenas, R.
2013-05-01
The shallow geological structure of Tapachula town has been estimated applying an association of the spatial autocorrelation (SPAC) method and the horizontal-to-vertical spectral ratio (HVSR, Nakamura 1989) method for ambient noise. Regular pentagonal arrays with radii up to 24 m have been employed for velocity computation. The measurements were carried out at six open spaces. Vertical components of ground motion, excited by ambient noise, were recorded at the surface. Five high-sensitivity sensors surrounding a sixth central sensor with same characteristics were used. All the records were analysed by using an implementation of the SPAC method (Aki, 1957). The phase-velocity of the Rg-wave was computed for each frequency from the correlation coefficient. The frequencies of the obtained curves ranged from 2.7 to 16.5 Hz and the phase velocity values varied between 226 and 594 m s-1. Nakamura's method was applied to determine the ground predominant period in the center of such arrays. The predominant period values vary in the 0.2-0.8 s range. Inversions of the S-wave velocity profiles corresponding to the six array sites have been achieved by using dispersion curves derived from SPAC and HVSR shapes. In order to classify the top shallow structure of Tapachula town, following the characterization of site adopted in several seismic codes (e.g. NEHRP 1994, Eurocode-8), the average shear-wave velocity of the upper 30 m (VS30) has been calculated. The results show differences between central part of the town and the peripheral zones close to both rivers rounding the city.
LongJohn, T.; Kelly, C.; Seats, K.; Lawrence, J.
2013-12-01
Hydrothermal system studies are important for geothermal energy exploration and geysers are also believed to be functional analogues of volcanoes. However, the mechanism of eruption and the characteristics of the plumbing system of most geysers are poorly understood given their subsurface location and sparse global distribution. An accurate acoustic velocity model could yield important insight into subsurface density and thermal variations in a geyser system. Passive seismic data was collected at El Jefe geyser in El Tatio Geyser Field, northern Chile during October of 2012. An array of 6 broadband seismometers and 51 high frequency geophones were deployed for ~1 week in a grid array with station spacing of 2-10 meters (geophones) and 3-50 meters (broadbands) centered around El Jefe Geyser. Using ambient seismic noise generated by the geyser system, I constructed a preliminary subsurface velocity model for El Jefe Geyser. As a result of the close station spacing, the seismic signals sampled shallow depths corresponding to high frequency waves. Coherent seismic records from different seismic station pairs were cross correlated to produce noise correlation functions (NCF). Adaptive covariance filtering and stacking techniques were utilized to amplify the signal of the NCFs and one-dimensional velocities between station pairs at varying depths were determined. Next, a tomographic inversion was done to interpolate between the one-dimensional velocities and produce a three-dimensional velocity model for the entire geyser area. From the velocity model, we can identify regions of low and high acoustic velocity that potentially represent water reservoirs and bedrock respectively.
Růžek, Bohuslav; Plomerová, Jaroslava; Babuška, Vladislav
2012-01-01
Roč. 56, č. 1 (2012), s. 107-140. ISSN 0039-3169 R&D Projects: GA ČR GA205/07/1088; GA AV ČR IAA300120709; GA MŠk LM2010008 Institutional research plan: CEZ:AV0Z30120515 Keywords : receiver function * seismic noise * joint inversion * Bohemian Massif * velocity structure Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 0.975, year: 2012
Ugalde, Arantza; Gaite, Beatriz; Villaseñor, Antonio
2016-04-01
During September 2013, the injection of the base gas in a depleted oil reservoir used as an underground natural gas storage (CASTOR) caused a sudden seismic activity increase in the eastern coast of Spain. As a result, a compact cluster of more than 550 earthquakes with magnitudes mbLg > 0.7 were located in the shallow offshore area of the Gulf of Valencia during two months. The strongest event, having a magnitude of Mw=4.2, was followed by two Mw=4.1 events the day after and took place once the gas injection activities had finished. Using the seismic data recorded by permanent stations at more than 25 km from the injection well, we applied coda wave interferometry to monitor changes in seismic velocity structure between similar earthquakes. Then we solved for a continuous function of velocity changes with time by combining observations from all the closely located earthquake sources. The rate of repeating events allowed measurements of relative velocity variations for about 30 days on a daily scale. To extend the analysis in time, we also processed the continuous data using the autocorrelation of band-pass filtered ambient seismic noise. A 10-day average was required to achieve a sufficient signal-to-noise ratio in the 0.2-0.5 Hz and 0.5-1 Hz frequency bands. We quantified the time lags between two traces in the frequency and time domains by means of the Moving Window Cross Spectral Analysis and a Dynamic Time Warping technique, respectively. Injection of fluids in geologic formations causes variations in seismic velocities associated to changes in fluid saturation, increase in pore pressure or opening or enlargement of cracks due to the injection process. Time delays associated with stress changes caused by moderate to large earthquakes have also been established. In this work, we found no velocity changes during the gas injection period nor on the occasion of the Mw 4.2 earthquake. The sensitivity of the method is dependent on the seismic network geometry and
Witek, M.; Kang, T. S.; van der Lee, S.
2015-12-01
We have collected three-component data from 122 Korean accelerometer stations for the month of December in 2014. We apply similar techniques described by Zha et al. (2013) to retrieve accurate station orientation angles, in order to rotate the horizontal component data into the radial and transverse frame of reference, and for subsequent measurement of Love wave group velocity dispersion. We simultaneously normalize all three components of a daily noise record via the frequency-time normalization (FTN) method. Each component is divided by the average signal envelope in an effort to retain relative amplitude information between all three components. Station orientations are found by a grid search for the orientation azimuth which maximizes the coherency between the radial-vertical cross-correlation and the Hilbert transformed vertical-vertical cross-correlation. After measuring orientation angles, we cross-correlate and rotate the data. Typically, the group velocity dispersion curves are measured using the frequency time analysis technique (FTAN), effectively producing spectrograms with significant uncertainty in the time-frequency plane. The spectrogram approach retains only the amplitude information of the short-time Fourier transform (STFT). However, Kodera et al (1976) show that by taking into account the phase information, the concepts of instantaneous frequency and group-time delay can be used to compute the first moment of the signal power in the frequency and time domains. During energy reassignment, the signal power calculated using the STFT at a point (t0,f0t_0, f_0) is reassigned to the location of the first moment (t^g,f^ihat{t}_g,hat{f}_i), where t^ghat{t}_g is the group-time delay and f^ihat{f}_i is the instantaneous frequency. We apply the method of energy reassignment to produce precise Rayleigh and Love wave group velocity measurements in the frequency range 0.1 - 1.0 Hz. Tests on synthetic data show more accurate retrieval of group velocities at
Pilz, M.; Parolai, S.; Picozzi, M.; Wang, R.; Leyton, F.; Campos, J. A.; Zschau, J.
2009-12-01
Generally, the most intense shaking during an earthquake occurs near the rupture fault and decreases with distance away from the fault. However, in a single earthquake the shaking at one site can easily be several times stronger than at another site, even when their distance from the rupture fault is the same. Such site effects are mainly caused by the softness of the soil near the surface and by the thickness of the sediments above hard rock. Seismic site characterization therefore requires usually substantial investment both in time and money for geophysical data acquisition. On the other hand, the necessity of estimating seismic risk for large urban areas like Santiago de Chile wants for at least a first order classification of soil and building vulnerability and therefore needs the definition of proxies. Recently, Wald and Allen (2007) suggested that the slope of topography might serve as a suitable parameter for the estimation of site effects irrespective of the spatial resolution used. Measurements of seismic noise at 146 sites have been carried out in the northern part of Santiago de Chile to determine the fundamental resonance frequency of the sites. The spatial variation in the thickness of the sedimentary cover, known from previous gravimetric investigations, varies significantly over short scale and is roughly retrieved from the peak in the horizontal-to-vertical (H/V) ratios of ambient noise. We inverted the H/V spectra individually for receiving local S-wave velocity profiles. For the inversion procedure, we also used additional geological and geophysical information. The resulting 3D model was derived for a 26 km X 12 km area by interpolation between the single S-wave velocity profiles with a kriging technique and shows good agreement with the few existing velocity profiles but also allows to image the entire area as well as deeper parts of the basin in more detail. Significant variations in the S-wave velocity-depth gradient are found. The wealth of
Lepore, Simone; Gomez, Martin; Draganov, Deyan
2015-04-01
The main force driving the tectonics in South America is the subduction of the Nazca Plate below the South American plate. The subduction process generated numerous volcanoes in both Chile and Argentina, of which the majority is concentrated along the Chilean Argentine border. The recent explosive eruptions of some volcanoescaused concern of the population in both countries. At the beginning of 2012, a large temporary array was installed in the Malargüe region, Mendoza, Argentina, with the purpose of imaging the subsurface and monitoring the tectonic activity. The array was deployed until the end of 2012 to record continuously ambient noise and the local, regional, and global seismicity. It consisted of 38 seismic stations divided in two sub arrays, namely the PV array of six stations located on the east flank of the Peteroa volcano, and the T array of thirty two stations spread out on a plateau just north east of the town of Malargüe. Here,the focus will be on the PV array, which has a patch-like shape. Due to the intra-station distances, we chose to use for surface-wave retrieval the bands 0.8 Hz ÷ 4.0 Hz, 10 Hz ÷ 25 Hz. At the investigated area, most of the year there is little anthropogenic noise, which normally dominates frequencies above 1 Hz, meaning that the selected frequency bands can be used for surface-wave retrieval from noise. Using beamforming, we showed that for these bands, the noise is illuminating the stations from the west. This means that a correct surface-wave arrivals can be retrieved for station pairs oriented in that direction. Because of this, we used for retrieval only such station pairs. We cross-correlated the recordings on the vertical components and retrieved Rayleigh waves. By manual picking, we estimated for both bands velocity dispersion curves from the retrieved surface-wave arrivals. The curves were then inverted to obtain the velocity structure under the stations. The obtained S wave velocity depth profiles for the 10 Hz
Investigation of Transverse Oscillation Method
Udesen, Jesper; Jensen, Jørgen Arendt
2006-01-01
Conventional ultrasound scanners can only display the axial component of the blood velocity vector, which is a significant limitation when vessels nearly parallel to the skin surface are scanned. The transverse oscillation method (TO) overcomes this limitation by introducing a transverse oscillat...
Marcio Ricardo Salla
2008-12-01
Full Text Available The size of the cross section of an ozonization column influences its hydrodynamic characteristics, which, on its turn, has effects on phenomena that depend on the relative movement between gas bubbles and liquid. To observe the influence of the cross sectional area on gas concentration and bubbles velocity, two columns were used. The first column had a square cross section with side of 0.19m and the second had a circular cross section with diameter of 0.10 m. The ascendant velocities of the bubbles and their concentration were measured in both columns and compared. The transversal spread of the plumes of bubbles was also quantified. The results show that the increase of the cross section of the column, in the proportion studied here, does not result in a similar increase of the cross section of the ascending plume of bubbles. Furthermore, the results of average velocities and concentrations obtained for the smallest cross section resulted independent of the liquid level in the column, while the results for the largest cross section showed to be dependent of this level. The ratio between the cross sectional areas of the larger and the smaller plumes of bubbles decreases for higher distances to the bottom of the columns.La sección transversal de una columna de ozonización posee influencia directa sobre las características hidrodinámicas de esa columna, lo que se refleja en los fenómenos que dependen de la transferencia de masa en la interfase gas-líquido. En este estudio se utilizaron dos columnas con secciones transversales diferentes cuanto a la forma y al tamaño. La primera con sección transversal cuadrada de 0,19m y la segunda con sección transversal circular de 0,10 m de diámetro. Se midieron las velocidades ascensionales de las burbujas y su concentración. Los resultados obtenidos muestran que el aumento de la sección transversal en la proporción aquí estudiada no conlleva un aumento semejante de la sección transversal de la
张兴敢; 柏业超
2009-01-01
The one-order phase of the echo changes if there is relative radial moving between the object and the radar, i.e., the Doppler effect. The Doppler effect is widely used in radar signal processing. The transverse motion of the object cannot change the one-order phase of the echo, but the high-order phase. The high-order Doppler effect of the transverse moving target is presented and a new algorithm for obtaining the transverse velocity is given. The scalar velocity of a target moving steadily in any direction can be calculated with one-order and two-order items of the echo phase. The calculating method and simulating results are given.As the transverse speed is 900 km/h, the speed calculation error is less than 0.06% if SNR of echo signal is higher than 0 dB.%目标与雷达存在相对径向运动时回波相位一次项发生变化,产生多普勒效应.多普勒效应广泛用于雷达信号处理.目标横向运动分量不会导致回波相位一次项变化,但会导致回波相位高次项的变化,据此本文提出横向运动物体的高阶多普勒效应及其横向速度的计算方法.高阶多普勒效应与常规多普勒效应配合可以计算任意向平稳运动物体的标量速度.文中给出了计算方法和仿真结果.当目标横向运动速度为900 km/h,且回波信号信噪比大于0 dB时,计算误差小于0.06 %.
... to overcome, circumvent, or compensate for permanent disabilities. Rehabilitation as yet cannot reverse the physical damage resulting from transverse myelitis or other forms of spinal cord injury. But it can help people, even those with ...
... functioning while hoping for either complete or partial spontaneous recovery of the nervous system. If an individual ... Throughout the U.S. and Worldwide NINDS Clinical Trials Organizations Column1 Column2 Transverse Myelitis Association 1787 Sutter Parkway ...
Budi-Santoso, Agus; Lesage, Philippe
2016-04-01
We present a study of the seismic velocity variations that occurred in the structure before the large 2010 eruption of Merapi volcano. For the first time to our knowledge, the technique of Coda Wave Interferometry is applied to both families of similar events (multiplets) and to correlation functions of seismic noise. About half of the seismic events recorded at the summit stations belong to one of the ten multiplets identified, including 120 similar events that occurred in the last 20 hours preceding the eruption onset. Daily noise cross-correlation functions (NCF) were calculated for the six pairs of short-period stations available. Using the stretching method, we estimate time series of apparent velocity variation (AVV) for each multiplet and each pair of stations. No significant velocity change is detected until September 2010. From 10 October to the beginning of the eruption on 26 October, a complex pattern of AVV is observed with amplitude of up to ±1.5%. Velocity decrease is first observed from families of deep events and then from shallow earthquakes. In the same period, AVV with different signs and chronologies are estimated from NCF calculated for various station pairs. The location in the horizontal plane of the velocity perturbations related with the AVV obtained from NCF is estimated by using an approach based on the radiative transfer approximation. Although their spatial resolution is limited, the resulting maps display velocity decrease in the upper part of the edifice in the period 12-25 October. After the eruption onset, the pattern of velocity perturbations is significantly modified with respect to the previous one. We interpret these velocity variations in the framework of a scenario of magmatic intrusion that integrates most observations. The perturbation of the stress field associated with the magma migration can induce both decrease and increase of the seismic velocity of rocks. Thus the detected apparent velocity variations can be
Budi-Santoso, Agus; Lesage, Philippe
2016-07-01
We present a study of the seismic velocity variations that occurred in the structure before the large 2010 eruption of Merapi volcano. For the first time to our knowledge, the technique of coda wave interferometry is applied to both families of similar events (multiplets) and to correlation functions of seismic noise. About half of the seismic events recorded at the summit stations belong to one of the ten multiplets identified, including 120 similar events that occurred in the last 20 hr preceding the eruption onset. Daily noise cross-correlation functions (NCF) were calculated for the six pairs of short-period stations available. Using the stretching method, we estimate time-series of apparent velocity variation (AVV) for each multiplet and each pair of stations. No significant velocity change is detected until September 2010. From 10 October to the beginning of the eruption on 26 October, a complex pattern of AVV is observed with amplitude of up to ±1.5 per cent. Velocity decrease is first observed from families of deep events and then from shallow earthquakes. In the same period, AVV with different signs and chronologies are estimated from NCF calculated for various station pairs. The location in the horizontal plane of the velocity perturbations related with the AVV obtained from NCF is estimated by using an approach based on the radiative transfer approximation. Although their spatial resolution is limited, the resulting maps display velocity decrease in the upper part of the edifice in the period 12-25 October. After the eruption onset, the pattern of velocity perturbations is significantly modified with respect to the previous one. We interpret these velocity variations in the framework of a scenario of magmatic intrusion that integrates most observations. The perturbation of the stress field associated with the magma migration can induce both decrease and increase of the seismic velocity of rocks. Thus the detected AVVs can be considered as precursors of
Transverse myelitis is a known complication of radiation treatment for carcinoma of the heat and neck. In a five year period, 1970 to 1975, 120 patients with head and neck cancer received radiation as part of their treatment in this hospital. A review of the records of these patients showed only two cases of myelitis, an incidence of about 2%. This paper reviews the clinical syndrome; treatment and preventive measures are discussed and a survey of the literature is presented
Black, M.J.; Motaghedi, B.; Robitaille, Y.
1980-05-01
Transverse myelitis is a known complication of radiation treatment for carcinoma of the heat and neck. In a five year period, 1970 to 1975, 120 patients with head and neck cancer received radiation as part of their treatment in this hospital. A review of the records of these patients showed only two cases of myelitis, an incidence of about 2%. This paper reviews the clinical syndrome; treatment and preventive measures are discussed and a survey of the literature is presented.
Balme, M. R.; Pathare, A.; Metzger, S. M.; Towner, M.C.; Lewis, S R; Spiga, A.; Fenton, L.; Renno, N. O.; Elliott, H. M.; Saca, F. A.; Michaels, T.; Russell, P; Verdasca, J.
2012-01-01
Dust devils – convective vortices made visible by the dust and debris they entrain – are common in arid environments and have been observed on Earth and Mars. Martian dust devils have been identified both in images taken at the surface and in remote sensing observations from orbiting spacecraft. Observations from landing craft and orbiting instruments have allowed the dust devil translational forward motion (ground velocity) to be calculated, but it is unclear how these velocities relate to t...
2000-01-01
Using a pulsed ultrasound field, the two-dimensional velocity vector can be determined with the invention. The method uses a transversally modulated ultrasound field for probing the moving medium under investigation. A modified autocorrelation approach is used in the velocity estimation. The new...... estimator automatically compensates for the axial velocity, when determining the transverse velocity by using fourth order moments rather than second order moments. The estimation is optimized by using a lag different from one in the estimation process, and noise artifacts are reduced by using averaging of...... RF samples. Further, compensation for the axial velocity can be introduced, and the velocity estimation is done at a fixed depth in tissue to reduce spatial velocity dispersion....
Experimental investigation of transverse flow estimation using transverse oscillation
Udesen, Jesper; Jensen, Jørgen Arendt
2003-01-01
. The flow is generated with the Compuflow 1000 programmable flow pump giving a parabolic velocity profile of the blood mimicking fluid in the flow phantom. The profiles are estimated for 310 trials each containing of 32 data vectors. The relative mean bias over entire blood vessel is found to be 10......Conventional ultrasound scanners can only display the blood velocity component parallel to the ultrasound beam. Introducing a laterally oscillating field gives signals from which the transverse velocity component can be estimated using 2:1 parallel receive beamformers. To yield the performance of...... the approach, this paper presents simulated and experimental results, obtained at a blood velocity angle transverse to the ultrasound beam. The Field II program is used to simulate a setup with a 128 element linear array transducer. At a depth 27 mm a virtual blood vessel of radius 2.4 mm is situated...
Li, Xianguo
Linear temporal instability analysis of a moving thin viscous liquid sheet of uniform thickness in an inviscid gas medium shows that surface tension always opposes, while surrounding gas and relative velocity between the sheet and gas favour the onset and development of instability. For gas Weber number smaller than the density ratio of gas to liquid, liquid viscosity enhances instability; If gas Weber number is slightly larger, aerodynamic and viscosity -induced instabilities interact with each other, displaying complicated effects of viscosity via Ohnesorge number; For much larger values of gas Weber numbers, aerodynamic instability dominates, liquid viscosity reduces disturbance growth rate and increases the dominant wavelength. Droplet probability distribution function (PDF) in sprays is formulated through information theory without resorting to the details of atomization processes. The derived analytical droplet size PDF is Nukiyama-Tanasawa type if conservation of mass is considered alone. If conservation of mass, momentum and energy is all taken into account, the joint droplet size and velocity PDF depends on Weber number, and compares favourably with measurements. Droplet velocity PDF is truncated Gaussian for any specific droplet size. Mean velocity approaches a constant value and velocity variance decreases as droplet size increases. Mean droplet diameters calculated agree well with observations. The computation indicates that atomization efficiency is very low, usually less than 1%. Droplet size, velocity and temperature PDF in sprays under combusting environment has also been derived. Effects of combustion on PDF occur mainly through the heat transferred into liquid sheet prior to its breakup. Experimental studies identify three modes of spray behaviours due to its interaction with various annular air flows, and show that bluff-body type of combustor has ability and easement to control aerodynamically spray angle, shape and droplet trajectories. It is
Ruzek, Bohuslav
2010-05-01
Joint inversion of P-waveforms from distant earthquakes recorded by 41 broadband seismic stations located on the territory of Bohemian Massif and Rayleigh/Love group velocities gained by using cross-correlation technique applied to seismic noise recorded by the same set of broadband stations has been performed. Together with joint inversion also individual inversions using single data sets have been carried out. All computations were arranged inside isotropic, locally 1D layered models. Remarkable result is indication of horizons just above MOHO in the lower crust below some stations where low-velocity S-wave channel is needed in order to ensure correct modeling of measured events. This indication follows both from individual and joint inversions. P-waveform inversion is based on using a set of 271 well-recorded teleseismic events from epicentral distances 3000-10000 km. The inversion was originally based on the popular 'receiver function' methodology, but due to the instability of needed deconvolution it was modified. We search for optimum layered velocity model, which correctly projects radial to vertical components (and vice versa, deconvolution is no more needed). Regarding second source of data, both Rayleigh and Love surface waves were extracted from seismic noise by using cross-correlation. Long time series covering the period 2001-2009 were processed. Such measurements provide group velocities between arbitrary pairs of stations. Local group velocity dispersion curves were computed by using 2D tomography-like approach for periods 4-20 s. The subject of inversion (both individual and joint) were just group velocity dispersion curves. Inversion required exhaustive computations. We used HPC cluster nemo.ig.cas.cz and ANNI inversion software, capable to run in parallel regime.
Transverse correlation: An efficient transverse flow estimator - initial results
Holfort, Iben Kraglund; Henze, Lasse; Kortbek, Jacob; Jensen, Jørgen Arendt
vascular hemodynamics, the flow angle cannot easily be found as the angle is temporally and spatially variant. Additionally the precision of traditional methods is severely lowered for high flow angles, and they breakdown for a purely transverse flow. To overcome these problems we propose a new method for...... estimating the transverse velocity component. The method measures the transverse velocity component by estimating the transit time of the blood between two parallel lines beamformed in receive. The method has been investigated using simulations performed with Field II. Using 15 emissions per estimate, a...... at 45 degrees. The method performs stable down to a signal-to-noise ratio of 0 dB, where a standard deviation of 5.5% and a bias of 1.2% is achieved....
Álvaro Fernández González
2012-11-01
Full Text Available El objetivo de este proyecto es brindar, a docentes, herramientas teóricas y prácticas relevantes, con actividades curriculares o extracurriculares de gestión ambiental en primaria, secundaria o educación diversificada, a fin de que puedan desarrollar y evaluar propuestas sistemáticas de innovación didáctica en este campo. Se procura crear las condiciones para que centros educativos públicos del sur de Costa Rica incorporen un componente que estimule el desarrollo de destrezas y habilidades para la participación ciudadana en la gestión ambiental a escala local (cantonal o distrital. El proyecto inició con la Dirección Regional de Educación de Pérez Zeledón y, en el 2012, el proyecto se extendió a la Dirección Regional de Educación Grande de Térraba (la cual abarca los cantones de Buenos Aires de Puntarenas y Osa por solicitud expresa de esta dirección regional. Se aplicó un enfoque de extensión docente y educación continua para fortalecer el currículo de centros educativos con innovaciones didácticas en el tema transversal de cultura ambiental para el desarrollo sostenible. La estrategia fundamental del proyecto se ha centrado en el desarrollo de un curso modular de “Innovación educativa de la gestión integrada de la salud y el ambiente” (IE- GISA, en cuyo marco los docentes participantes diseñan y ejecutan, en sus centros educativos, acciones curriculares y extracurriculares en este campo, apoyados por especialistas de la zona. Los docentes participantes son convocados por las autoridades competentes del Ministerio de Educación Pública, de manera que están autorizados para dedicar tiempo laboral al desarrollo del curso. Además, reciben acreditación para el Servicio Civil por parte de las unidades académicas ejecutoras. Este trabajo se acompaña con un eje paralelo de proyección comunitaria centrado en la incorporación de los padres de familia a los proyectos institucionales; estas actividades y las redes
Höfle, W
2012-01-01
Plans for the operation of the transverse damper in 2012 at bunch spacings of 50 ns and 25 ns and at increased collision energy will be reviewed. The increased energy and the experience that will be gained at 25 ns are very important to define any upgrades that may be necessary for the high luminosity operation at 7 TeV after LS1. This means that the available parameter space must be probed in 2012 which in particular includes a higher feedback gain in the ramp and with colliding beams. Limits for the feedback gain for the current system will be outlined. The potential benefits of running with higher feedback gain for a better emittance preservation will be stressed and weighed against the operational difficulties and the potential impact of noise in the damper system. A plan for re-commissiong at 50 ns and 25 ns for operation at 4 TeV will be outlined.
Spica, Zack; Perton, Mathieu; Calò, Marco; Legrand, Denis; Córdoba Montiel, Francisco; Iglesias, Arturo
2016-07-01
This work presents an innovative strategy to enhance the resolution of surface wave tomography obtained from ambient noise cross-correlation (C1) by bridging asynchronous seismic networks through the correlation of coda of correlations (C3). Rayleigh wave group dispersion curves show consistent results between synchronous and asynchronous stations. Rayleigh wave group travel times are inverted to construct velocity-period maps with unprecedented resolution for a region covering Mexico and the southern United States. The resulting period maps are then used to regionalize dispersion curves in order to obtain local 1-D shear velocity models (VS) of the crust and uppermost mantle in every cell of a grid of 0.4°. The 1-D structures are obtained by iteratively adding layers until reaching a given misfit, and a global tomography model is considered as an input for depths below 150 km. Finally, a high-resolution 3-D VS model is obtained from these inversions. The major structures observed in the 3-D model are in agreement with the tectonic-geodynamic features and with previous regional and local studies. It also offers new insights to understand the present and past tectonic evolution of the region.
Spica, Zack; Perton, Mathieu; Calò, Marco; Legrand, Denis; Córdoba-Montiel, Francisco; Iglesias, Arturo
2016-09-01
This work presents an innovative strategy to enhance the resolution of surface wave tomography obtained from ambient noise cross-correlation (C1) by bridging asynchronous seismic networks through the correlation of coda of correlations (C3). Rayleigh wave group dispersion curves show consistent results between synchronous and asynchronous stations. Rayleigh wave group traveltimes are inverted to construct velocity-period maps with unprecedented resolution for a region covering Mexico and the southern United States. The resulting period maps are then used to regionalize dispersion curves in order to obtain local 1-D shear velocity models (VS) of the crust and uppermost mantle in every cell of a grid of 0.4°. The 1-D structures are obtained by iteratively adding layers until reaching a given misfit, and a global tomography model is considered as an input for depths below 150 km. Finally, a high-resolution 3-D VS model is obtained from these inversions. The major structures observed in the 3-D model are in agreement with the tectonic-geodynamic features and with previous regional and local studies. It also offers new insights to understand the present and past tectonic evolution of the region.
Al Rabadi, S.; Friedel, L. [Fluid Mechanics Institute, Technical University of Hamburg-Harburg (Germany); Al Salaymeh, A. [Mechanical Engineering Department, University of Jordan (Jordan)
2007-01-15
Measurements using two-dimensional Phase Doppler Anemometry as well as high speed cinematography in free jets at several nozzle exit pressures and mass flow rates, show that the Sauter mean droplet diameter decreases with increasing air and liquid-phase mass flow ratio due to the increase of the air stream impact on the liquid phase. This leads to substantial liquid fragmentation, respectively primary droplet breakup, and hence, satellite droplet formation with small sizes. This trend is also significant in the case of a liquid viscosity higher than that of water. The increased liquid viscosity stabilizes the droplet formation and breakup by reducing the rate of surface perturbations and consequently droplet distortions, ultimately also leading, in total, to the formation of smaller droplets. The droplet velocity decreases with the nozzle downstream distance, basically due to the continual air entrainment and due to the collisions between the droplets. The droplet collisions may induce further liquid fragmentation and, hence, formation of a number of relatively smaller droplets respectively secondary breakup, or may induce agglomeration to comparatively larger liquid fragments that may rain out of the free jet. (Abstract Copyright [2007], Wiley Periodicals, Inc.)
Introduction to vector velocity imaging
Jensen, Jørgen Arendt; Udesen, Jesper; Hansen, Kristoffer Lindskov;
virtually impossible to compensate for the factor and obtain correct velocity estimates for either CFM or spectral velocity estimation. This talk will describe methods for finding the correct velocity by estimating both the axial and lateral component of the velocity vector. The transverse oscillation...... method introduces an ultrasound field that oscillation not only along the ultrasound beam both also transverse to it to estimate both the lateral and axial velocity for the full velocity vector. The correct velocity magnitude can be found from this as well as the instantaneous angle. This can be obtained...... over the full region of interest and a real time image at a frame rate of 20 Hz can be displayed. Real time videos have been obtained from both our research systems and from commercial BK Medical scanners. The vector velocity images reveal the full complexity of the human blood flow. It is easy to see...
Vector blood velocity estimation in medical ultrasound
Jensen, Jørgen Arendt; Gran, Fredrik; Udesen, Jesper;
2006-01-01
Two methods for making vector velocity estimation in medical ultrasound are presented. All of the techniques can find both the axial and transverse velocity in the image and can be used for displaying both the correct velocity magnitude and direction. The first method uses a transverse oscillation....... Using a correlation search can also yield the direction, and the full velocity vector is thereby found. An examples from a flow rig is shown....
Ambient Space and Ambient Sensation
Schmidt, Ulrik
The ambient is the aesthetic production of the sensation of being surrounded. As a concept, 'ambient' is mostly used in relation to the music genre 'ambient music' and Brian Eno's idea of environmental background music. However, the production of ambient sensations must be regarded as a central...... aspect of the aesthetization of modern culture in general, from architecture, transport and urbanized lifeforms to film, sound art, installation art and digital environments. This presentation will discuss the key aspects of ambient aesthetization, including issues such as objectlessness...
Schmidt, Ulrik
Om begrebet "det ambiente", der beskriver, hvad der sker, når vi fornemmer baggrundsmusikkens diskrete beats, betragter udsigten gennem panoramavinduet eller tager 3D-brillerne på og læner os tilbage i biografsædet. Bogen analyserer, hvorfan ambiente oplevelser skabes, og hvilke konsekvenser det...
Börner, Dirk; Specht, Marcus
2014-01-01
This software sketches comprise two custom-built ambient sensors, i.e. a noise and a movement sensor. Both sensors measure an ambient value and process the values to a color gradient (green > yellow > red). The sensors were built using the Processing 1.5.1 development environment. Available under the GNU LGPL licence version 3 or higher.
Börner, Dirk; Specht, Marcus
2014-01-01
This software sketches comprise two custom-built ambient sensors, i.e. a noise and a movement sensor. Both sensors measure an ambient value and process the values to a color gradient (green > yellow > red). The sensors were built using the Processing 1.5.1 development environment. Available under th
Transverse Injection Experiment
The motion of a plasma stream injected transverse to a magnetic field has been discussed by several authors. In early experiments with the injection of a fast (50 to 70 cm/μsec) dense (1014 ion/cm3) plasma transverse to a magnetic field, a self polarization electric field was observed and the stream crossed the magnetic field with an E x B drift. The magnetic field was only slightly disturbed by the stream (| ΔB/B | <0.1) while the drift across magnetic fields up to 5 kG was at approximately the velocity of the injected stream. The height of the stream in the direction of V x B is compressed as it drifts into high magnetic field regions. At the same time, electron density measurements using interferometry techniques with the He-Ne laser show that the transverse field up to 7 kG causes no appreciable spreading of the stream to take place in the direction of B. Of interest is the action of the stream as it crosses a region where magnetic field lines reverse direction about a field null line. As the stream proceeds across the separatrix between the two field line directions, the electric field must change direction if the stream drift is to continue. The stream halts in the region of the separatrix while large currents are measured along magnetic field lines connecting the front of the stream with the following portions. Insulators placed to interrupt the current allow the stream to proceed into the reversed field region. By making use of the inductance associated with the depolarization current when magnetic field lines are tied at some distance to the side of the stream, a separation of fast and slow stream components can be made. The cutoff of the slow stream component is observed with the He-Ne laser interferometry techniques. Electric field measurements at several points along the stream show some of the more complicated features of the plasma flow. (author)
The first part of this report addresses the dosimetry of γ emitting radio-elements which are present in vegetal samples. The dose measurements were performed by spectrometry and results were processed by using a least square method. The second part reports works performed in the Grenoble transverse valley by using the same techniques. Radioactivity fluctuations of various radio-elements (40K, 54Mn, 95Zr + 95Nb, 103Ru + 106Rh, 137Cs, 137Ba, 140Ba + 140La, 144Ce + 144Pr) in various vegetal species, in water and in sediments have been monitored in seven points of the Isere river banks, upstream and downstream the city of Grenoble, from March 1966 to August 1968. Fluctuations observed for each radio-element are explained by comparison with physiologic, hydrologic and atmospheric climate conditions. The principles of a systematic control of a site for the detection of possible radioactive pollutions are then defined
Transverse Myelitis Association
... first large-scale North-American study of pediatric transverse myelitis LEARN MORE We are seeking over 100 patients ... TMA QUALITY OF LIFE FAMILY CAMP 2016 THE TRANSVERSE MYELITIS ASSOCIATION ADVOCATING FOR THOSE WITH ACUTE DISSEMINATED ENCEPHALOMYELITIS, ...
Transversity: theory and phenomenology
D'Alesio, Umberto
2013-01-01
The distribution of transversely polarized quarks inside a transversely polarized nucleon, known as transversity, encodes a basic piece of information on the nucleon structure, sharing the same status with the more familiar unpolarized and helicity distributions. I will review its properties and discuss different ways to access it, with highlights and limitations. Recent phenomenological extractions and perspectives are also presented.
Schmidt, Ulrik
Det ambiente er iscenesættelsen af en karakteristisk sanseoplevelse, der er kendetegnet ved fornemmelsen af at være omgivet. I dag bliver begrebet om det ambiente mest anvendt i forbindelse med musikgenren ’ambient musik’. Det ambiente er dog ikke essentielt knyttet til det musikalske, men må...... forstås som et betydeligt bredere fænomen i den moderne æstetiske kultur, der spiller en væsentlig rolle i oplevelsen af moderne transportformer, arkitektur, film, lydkunst, installationskunst og digitale multimedieiscenesættelser. En forståelse af det ambiente er derfor centralt for forståelsen af en...... moderne æstetiseret oplevelseskultur i almindelighed. Da det ambiente ikke hidtil har været gjort til genstand for en mere indgående teoretisk behandling, er der dog stor usikkerhed omkring, hvad fænomenet overhovedet indebærer. Hovedformålet med Det ambiente – Sansning, medialisering, omgivelse er derfor...
Karam, Maria; Hare, Jonathon; Lewis, Paul; schraefel, m.c.
2006-01-01
We present Ambient Gestures, a novel gesture-based system designed to support ubiquitous ‘in the environment’ interactions with everyday computing technology. Hand gestures and audio feedback allow users to control computer applications without reliance on a graphical user interface, and without having to switch from the context of a non-computer task to the context of the computer. The Ambient Gestures system is composed of a vision recognition software application, a set of gestures to be p...
Transversity and Meson Photoproduction
Goldstein, G R; Goldstein, Gary R.; Gamberg, Leonard
2002-01-01
Both meson photoproduction and semi-inclusive deep inelastic scattering can potentially probe transversity in the nucleon. We explore how that potential can be realized dynamically. The role of rescattering in both exclusive and inclusive meson production as a source for transverse polarization asymmetry is examined. We use a dynamical model to calculate the asymmetry and relate that to the transversity distribution of the nucleon.
Jaffe, R. L.
1997-01-01
I review the ways that have been proposed to measure the quark transversity distribution in the nucleon. I then explain a proposal, developed by Xuemin Jin, Jian Tang and myself, to measure transversity through the final state interaction between two mesons ($\\pi\\pi$, $K \\bar K$, or $\\pi K$) produced in the current fragmentation region in deep inelastic scattering on a transversely polarized nucleon.
Sanders, David; Gegov, Alexander
2006-01-01
This paper considers some history and the state of the art of Ambient Intelligence and from that seeks to identify new topics and future work. Ubiquitous computing, communications, human-centric computer interaction, embedded systems, context awareness, adaptive systems and distributed device networks are considered.
Weber, W; Aarts, E
2005-01-01
Addresses ambient intelligence used to support human contacts and accompany an individual''s path through the complicated modern world, from applications that are imminent, since they use essentially existing technologies, to ambitious ideas whose realization is still far away, due to major unsolved technical challenges.
Makin, Alexis David James
2011-01-01
This Thesis, entitled ‘Velocity Memory’ is submitted to the University of Manchester by Alexis David James Makin (30/09/2010) for the degree of Doctor of Philosophy. It is known that primates are sensitive to the velocity of moving objects. We can also remember velocity information after moving objects disappear. This cognitive faculty has been investigated before, however, the literature on velocity memory to date has been fragmented. For example, velocity memory has been disparately descri...
Transverse gravity versus observations
Theories of gravity invariant under those diffeomorphisms generated by transverse vectors, ∂μξμ = 0 are considered. Such theories are dubbed transverse, and differ from General Relativity in that the determinant of the metric, g, is a transverse scalar. We comment on diverse ways in which these models can be constrained using a variety of observations. Generically, an additional scalar degree of freedom mediates the interaction, so the usual constraints on scalar-tensor theories have to be imposed. If the purely gravitational part is Einstein-Hilbert but the matter action is transverse, the models predict that the three a priori different concepts of mass (gravitational active and gravitational passive as well as inertial) are not equivalent anymore. These transverse deviations from General Relativity are therefore tightly constrained, actually correlated with existing bounds on violations of the equivalence principle, local violations of Newton's third law and/or violation of Local Position Invariance
Chatter in a transverse grinding process
Yan, Yao; Xu, Jian; Wiercigroch, Marian
2014-02-01
In transverse grinding, the wheel moves along the workpiece, which induces unique grinding dynamics. To understand these dynamic phenomena, specifically the grinding chatter, a new dynamical model of the process is proposed, in which the wheel position is assumed to be quasi-static since the transverse wheel velocity is small. From the stability and bifurcation analyses of the chatter vibration, it appears that the dynamics of the process is governed by the quasi-static interactions. Moreover, the obtained results also show that the wheel and workpiece chatters are quite different, having continuous and intermittent characters respectively.
Algorithms for estimating blood velocities using ultrasound
Jensen, Jørgen Arendt
2000-01-01
Ultrasound has been used intensively for the last 15 years for studying the hemodynamics of the human body. Systems for determining both the velocity distribution at one point of interest (spectral systems) and for displaying a map of velocity in real time have been constructed. A number of schemes...... parallel to the skin surface. Angling the transducer will often disturb the flow, and new techniques for finding transverse velocities are needed. The various approaches for determining transverse velocities will be explained. This includes techniques using two-dimensional correlation (speckle tracking...
Transversely Compressed Bonded Joints
Hansen, Christian Skodborg; Schmidt, Jacob Wittrup; Stang, Henrik
2012-01-01
The load capacity of bonded joints can be increased if transverse pressure is applied at the interface. The transverse pressure is assumed to introduce a Coulomb-friction contribution to the cohesive law for the interface. Response and load capacity for a bonded single-lap joint was derived using...... non-linear fracture mechanics. The results indicated a good correlation between theory and tests. Furthermore, the model is suggested as theoretical base for determining load capacity of bonded anchorages with transverse pressure, in externally reinforced concrete structures....
Nikola Vlacic
2010-01-01
In this project, we investigated if it is feasible for a single staged rocket with constant thrust to attain escape velocity. We derived an equation for the velocity and position of a single staged rocket that launches vertically. From this equation, we determined if an ideal model of a rocket is able to reach escape velocity.
Transversity measurements at HERMES
Diefenthaler, Markus
2005-01-01
Azimuthal single-spin asymmetries (SSA) in semi-inclusive electroproduction of charged pions in deep-inelastic scattering (DIS) of positrons on a transversely polarised hydrogen target are presented. Azimuthal moments for both the Collins and the Sivers mechanism are extracted. In addition the subleading-twist contribution due to the transverse spin component from SSA on a longitudinally polarised hydrogen target is evaluated.
Basten, Twan; de Groot, Harmke
2007-01-01
""This book is truly an eye-opener as it is the first book that relates the dream scenarios of Ambient Intelligence quantitatively to the technical challenges and requirements of the huge distributed and interoperable embedded systems needed to implement AmI systems in the real world. This book is strongly recommended to a wide spectrum of engineers interested to embark in this rapidly emerging and fascinating technology."" (From the foreword by Hugo De Man, Professor K.U. Leuven and Senior Research Fellow IMEC)
Analytic solution for relativistic transverse flow at the softest point
Biro, T S
2000-01-01
We obtain an extension of Bjorken's 1+1 dimensional scaling relativistic flow solution to relativistic transverse velocities with cylindrical symmetry in 1+3 dimensions at constant, homogeneous pressure (vanishing sound velocity). This can be the situation during a first order phase transition converting quark matter into hadron matter in relativistic heavy ion collisions.
Recent advances in blood flow vector velocity imaging
Jensen, Jørgen Arendt; Nikolov, Svetoslav; Udesen, Jesper;
2011-01-01
A number of methods for ultrasound vector velocity imaging are presented in the paper. The transverse oscillation (TO) method can estimate the velocity transverse to the ultrasound beam by introducing a lateral oscillation in the received ultrasound field. The approach has been thoroughly investi...
Transverse excitations in liquid metals
Hosokawa, S.; Munejiri, S.; Inui, M.; Kajihara, Y.; Pilgrim, W.-C.; Baron, A. Q. R.; Shimojo, F.; Hoshino, K.
2013-02-01
The transverse acoustic excitation modes were detected by inelastic x-ray scattering in liquid Ga, Cu and Fe in the Q range around 10 nm-1 using a third-generation synchrotron radiation facility, SPring-8, although these liquid metals are mostly described by a simple hard-sphere liquid. Ab initio molecular dynamics simulations clearly support this finding for liquid Ga. From the detailed analyses for the S(Q,ω) spectra with good statistic qualities, the lifetime of less than 1 ps and the propagating length of less than 1 nm can be estimated for the transverse acoustic phonon modes, which correspond to the lifetime and size of cages formed instantaneously in these liquid metals. The microscopic Poisson's ratio estimated from the dynamic velocities of sound is 0.42 for liquid Ga and about -0.2 for liquid transition metals, indicating a rubber-like soft and extremely hard elastic properties of the cage clusters, respectively. The origin of these microscopic elastic properties is discussed in detail.
Transverse spin and transverse momentum in scattering of plane waves
Saha, Sudipta; Ray, Subir K; Banerjee, Ayan; Gupta, Subhasish Dutta; Ghosh, Nirmalya
2016-01-01
We study the near field to the far field evolution of spin angular momentum (SAM) density and the Poynting vector of the scattered waves from spherical scatterers. The results show that at the near field, the SAM density and the Poynting vector are dominated by their transverse components. While the former (transverse SAM) is independent of the helicity of the incident circular polarization state, the latter (transverse Poynting vector) depends upon the polarization state. It is further demonstrated that the magnitudes and the spatial extent of the transverse SAM and the transverse momentum components can be controllably enhanced by exploiting the interference of the transverse electric and transverse magnetic scattering modes.
Demonstration of a Vector Velocity Technique
Hansen, Peter Møller; Pedersen, Mads M.; Hansen, Kristoffer L.;
2011-01-01
With conventional Doppler ultrasound it is not possible to estimate direction and velocity of blood flow, when the angle of insonation exceeds 60–70°. Transverse oscillation is an angle independent vector velocity technique which is now implemented on a conventional ultrasound scanner. In this...
Performance of a vector velocity estimator
Munk, Peter; Jensen, Jørgen Arendt
1998-01-01
tracking can be found in the literature, but no method with a satisfactory performance has been found that can be used in a commercial implementation. A method for estimation of the velocity vector is presented. Here an oscillation transverse to the ultrasound beam is generated, so that a transverse motion...... autocorrelation approach that yields both the axial and the lateral velocity, and thus the velocity vector. The method has the advantage that a standard array transducer and a modified digital beamformer, like those used in modern ultrasound scanners, is sufficient to obtain the information needed. The signal...
Nondiffracting transversally polarized beam.
Yuan, G H; Wei, S B; Yuan, X-C
2011-09-01
Generation of a nondiffracting transversally polarized beam by means of transmitting an azimuthally polarized beam through a multibelt spiral phase hologram and then highly focusing by a high-NA lens is presented. A relatively long depth of focus (∼4.84λ) of the electric field with only radial and azimuthal components is achieved. The polarization of the wavefront near the focal plane is analyzed in detail by calculating the Stokes polarization parameters. It is found that the polarization is spatially varying and entirely transversally polarized, and the polarization singularity disappears at the beam center, which makes the central bright channel possible. PMID:21886250
Turbine airfoil with ambient cooling system
Campbell, Jr, Christian X.; Marra, John J.; Marsh, Jan H.
2016-06-07
A turbine airfoil usable in a turbine engine and having at least one ambient air cooling system is disclosed. At least a portion of the cooling system may include one or more cooling channels configured to receive ambient air at about atmospheric pressure. The ambient air cooling system may have a tip static pressure to ambient pressure ratio of at least 0.5, and in at least one embodiment, may include a tip static pressure to ambient pressure ratio of between about 0.5 and about 3.0. The cooling system may also be configured such that an under root slot chamber in the root is large to minimize supply air velocity. One or more cooling channels of the ambient air cooling system may terminate at an outlet at the tip such that the outlet is aligned with inner surfaces forming the at least one cooling channel in the airfoil to facilitate high mass flow.
Starting with the space-time action of the transversally extended string, we derive its world-sheet action, which is that of a gravitational and gauge theory with matter fields on the world-sheet, with additional effects of the second fundamental quantity. (author)
Transverse myelitis spectrum disorders
Pandit Lekha
2009-01-01
Full Text Available Acute transverse myelitis (ATM is an inflammatory demyelinating disorder that affects the spinal cord focally resulting in motor sensory and autonomic dysfunction. Establishing the diagnosis of ATM is not as difficult as determining the possible etiology. There is a difference in the perception of ATM seen in the West as compared to developing countries. In the West multiple sclerosis (MS is the most common inflammatory disorder of the central nervous system. An attack of ATM may be the beginning of MS. However, this may not be the case in developing countries where MS is uncommon. Most often transverse myelitis is monophasic and at best represents a site-restricted form of acute disseminated encephalomyelitis (ADEM. Traditionally the combination of optic neuritis and ATM, occurring as a monophasic illness would have been called as neuromyelitis optica (NMO. Changing concepts in the definition of NMO and the discovery of a biomarker, neuromyelitis optica immunoglobulin (NMO_IgG, has changed the way relapsing autoimmune disorders are being perceived currently. A variety of idiopathic inflammatory disorders such as Japanese form of optic spinal MS, recurrent myelitis, and recurrent optic neuritis have been brought under the umbrella of neuromyelitis spectrum disorders because of the association with NMO-IgG. Complete transverse myelitis accompanied by longitudinally extensive transverse myelitis which is seronegative for this biomarker has also been reported from several countries including Japan, Australia, and India. Thus, ATM is a heterogeneous disorder with a varied clinical spectrum, etiology, and outcome.
Three dimensional (3d) transverse oscillation vector velocity ultrasound imaging
2013-01-01
An ultrasound imaging system (300) includes a transducer array (302) with a two- dimensional array of transducer elements configured to transmit an ultrasound signal and receive echoes, transmit circuitry (304) configured to control the transducer array to transmit the ultrasound signal so as to...... the same received set of two dimensional echoes form part of the imaging system...
Transverse testicular ectopia.
Yıldız, Abdullah; Yiğiter, Murat; Oral, Akgün; Bakan, Vedat
2014-02-01
Described herein are six cases of transverse testicular ectopia. All patients who underwent orchidopexy at the one pediatric surgical unit between October 2001 and January 2008 were evaluated. The medical records of all patients diagnosed with transverse testicular ectopia were evaluated retrospectively. Five patients (84%) were admitted with a symptomatic right inguinal hernia and empty scrotum on the left side. Only one child (16%) had left-sided hernia and right non-palpable testis (age ranged from 1 month to 3 years). Four patients (66%) were diagnosed in the operating theatre and the last two (33%) on inguinal ultrasound preoperatively. Magnetic resonance imaging was also performed in the last patient. Herniorrhaphy with fixation of the ectopic gonad to the opposite hemiscrotum through a transseptal incision was performed in all patients. Postoperative complications were not observed. PMID:24548194
Transverse polarization in ; production
Saurabh D Rindani
2007-11-01
With the use of transverse polarization (TP), a CP-odd and T-odd observable can be constructed when the final-state particles are self-conjugate. In the case of production, this observable can be used to probe a certain effective four-point + - CP-violating coupling, not accessible without TP. Effective CP-violating coupling does not contribute to this observable. A similar observable in production can be used to probe + - four-point couplings.
The distribution of h1(x) of quark transverse polarization can be measured by Deep Inelastic Scattering using Collins effect as quark polarimeter. We propose to calibrate this polarimeter in e+e- → 2 jets. We give an explanation of single spin asymmetries in inclusive meson production based on the Collins effect. We propose a proportionality between the electric dipole moment of the nucleon on its tensor charge. (authors)
Transverse myelitis spectrum disorders
Pandit Lekha
2009-01-01
Acute transverse myelitis (ATM) is an inflammatory demyelinating disorder that affects the spinal cord focally resulting in motor sensory and autonomic dysfunction. Establishing the diagnosis of ATM is not as difficult as determining the possible etiology. There is a difference in the perception of ATM seen in the West as compared to developing countries. In the West multiple sclerosis (MS) is the most common inflammatory disorder of the central nervous system. An attack of ATM may be the beg...
Transverse Spin Physics: Recent Developments
Yuan, Feng
2009-01-01
Transverse-spin physics has been very active and rapidly developing in the last few years. In this talk, I will briefly summarize recent theoretical developments, focusing on the associated QCD dynamics in transverse spin physics.
Transverse tomography and radiotherapy
This study was intended to delineate the indications for radiotherapy treatment-planning with the help of computerized axial tomography (C.T.) and transverse analog tomography (T.A.T.). Radiotherapy localisation procedures with the conventional method (simulator), with the CT-scanner and with the transverse analog tomograph (T.A.T., Simtomix, Oldelft) were compared. As criterium for evaluation differences in reconstruction drawing based on these methods were used. A certain method was judged ''superior'' to another if the delineation of the target volume was more accurate, if a better impression was gained of the site of (for irradiation) organs at risk, or if the localisation could only be performed with that method. The selected group of patients consisted of 120 patients for whom a reconstruction drawing in the transverse plane was made according to the treatment philosophy. In this group CT-assisted localisation was judged on 68 occasions superior to the conventional method. In a number of cases it was found that a ''standard'' change in a standard target volume, on the base of augmented anatomical knowledge, made the conventional method sufficient. The use of CT-scanner for treatment planning was estimated. For ca. 270/1000 new patients a CT-scan is helpful (diagnostic scan), for 140 of them the scan is necessary (planning scan). The quality of the anatomical information obtained with the T.A.T. does not yet fall within acceptable limits, but progress has been made. (Auth.)
Characteristics of transverse waves in chromospheric mottles
Kuridze, D.; Mathioudakis, M.; Jess, D. B.; Keenan, F. P. [Astrophysics Research Center, School of Mathematics and Physics, Queen' s University, Belfast BT7 1NN (United Kingdom); Verth, G.; Erdélyi, R. [Solar Physics and Space Plasma Research Center (SP2RC), University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH (United Kingdom); Morton, R. J. [Mathematics and Information Science, Northumbria University, Camden Street, Newcastle Upon Tyne NE1 8ST (United Kingdom); Christian, D. J., E-mail: dkuridze01@qub.ac.uk [Department of Physics and Astronomy, California State University, Northridge, CA 91330 (United States)
2013-12-10
Using data obtained by the high temporal and spatial resolution Rapid Oscillations in the Solar Atmosphere instrument on the Dunn Solar Telescope, we investigate at an unprecedented level of detail transverse oscillations in chromospheric fine structures near the solar disk center. The oscillations are interpreted in terms of propagating and standing magnetohydrodynamic kink waves. Wave characteristics including the maximum transverse velocity amplitude and the phase speed are measured as a function of distance along the structure's length. Solar magnetoseismology is applied to these measured parameters to obtain diagnostic information on key plasma parameters (e.g., magnetic field, density, temperature, flow speed) of these localized waveguides. The magnetic field strength of the mottle along the ∼2 Mm length is found to decrease by a factor of 12, while the local plasma density scale height is ∼280 ± 80 km.
Neutron Transversity at Jefferson Lab
Jian-Ping Chen; Xiaodong Jiang; Jen-chieh Peng; Lingyan Zhu
2005-09-07
Nucleon transversity and single transverse spin asymmetries have been the recent focus of large efforts by both theorists and experimentalists. On-going and planned experiments from HERMES, COMPASS and RHIC are mostly on the proton or the deuteron. Presented here is a planned measurement of the neutron transversity and single target spin asymmetries at Jefferson Lab in Hall A using a transversely polarized {sup 3}He target. Also presented are the results and plans of other neutron transverse spin experiments at Jefferson Lab. Finally, the factorization for semi-inclusive DIS studies at Jefferson Lab is discussed.
On the Transverse Invariant for Bindings of Open Books
Vela-Vick, David Shea
2011-01-01
Let $T \\subset (Y,\\xi)$ be a transverse knot which is the binding of some open book, $(T,\\pi )$, for the ambient contact manifold $(Y,\\xi)$. In this paper, we show that the transverse invariant $\\hat{\\mathscr{T}(T) \\in \\widehat{HFK}(−Y,K)$, defined in P. Lisca, P. Ozsváth, A. I. Stipsicz & Z. Szabó, "Heegaard Floer invariants of Legendrian knots in contact three-manifolds," J. Eur. Math. Soc. (JEMS) 11 (2009), no. 6, 1307–1363, MR 2557137, Zbl pre05641376, is nonvanishing for such...
Geotail observations of FTE velocities
G. I. Korotova
2009-01-01
Full Text Available We discuss the plasma velocity signatures expected in association with flux transfer events (FTEs. Events moving faster than or opposite the ambient media should generate bipolar inward/outward (outward/inward flow perturbations normal to the nominal magnetopause in the magnetosphere (magnetosheath. Flow perturbations directly upstream and downstream from the events should be in the direction of event motion. Flows on the flanks should be in the direction opposite the motion of events moving at subsonic and subAlfvénic speeds relative to the ambient plasma. Events moving with the ambient flow should generate no flow perturbations in the ambient plasma. Alfvén waves propagating parallel (antiparallel to the axial magnetic field of FTEs may generate anticorrelated (correlated magnetic field and flow perturbations within the core region of FTEs. We present case studies illustrating many of these signatures. In the examples considered, Alfvén waves propagate along event axes away from the inferred reconnection site. A statistical study of FTEs observed by Geotail over a 3.5-year period reveals that FTEs within the magnetosphere invariably move faster than the ambient flow, while those in the magnetosheath move both faster and slower than the ambient flow.
Modestino, Giuseppina
2016-01-01
The trajectory and the orbital velocity are determined for an object moving in a gravitational system, in terms of fundamental and independent variables. In particular, considering a path on equipotential line, the elliptical orbit is naturally traced, verifying evidently the keplerian laws. The case of the planets of the solar system is presented.
Seismic Tomography Around the Eastern Edge of the Alps From Ambient-Noise-Based Rayleigh Waves
Zigone, Dimitri; Fuchs, Florian; Kolinsky, Petr; Gröschl, Gidera; Apoloner, Maria-Theresia; Qorbani, Ehsan; Schippkus, Sven; Löberich, Eric; Bokelmann, Götz; AlpArray Working Group
2016-04-01
Inspecting ambient noise Green's functions is an excellent tool for monitoring the quality of seismic data, and for swiftly detecting changes in the configuration of a seismological station. Those Green's functions readily provide stable information about structural variations near the Earth's surface. We apply the technique to a network consisting of about 40 broadband stations in the area of the Easternmost Alps, in particular those operated by the University of Vienna (AlpArrayAustria) and the Vienna University of Technology. Those data are used to estimate Green's functions between station pairs; the Green's function consist mainly of surface waves, and we use them to investigate crustal structure near the Eastern edge of the Alps. To obtain better signal-to-noise ratios in the noise correlation functions, we adopt a procedure using short time windows (2 hr). Energy tests are performed on the data to remove effects of transient sources and instrumental problems. The resulting 9-component correlation tensor is used to make travel time measurements on the vertical, radial and transverse components. Those measurements can be used to evaluate dispersion using frequency-time analysis for periods between 5-30 seconds. After rejecting paths without sufficient signal-to-noise ratio, we invert the velocity measurements using the Barmin et al. (2001) approach on a 10 km grid size. The obtained group velocity maps reveal complex structures with clear velocity contrasts between sedimentary basins and crystalline rocks. The Bohemian Massif and the Northern Calcareous Alps are associated with fast-velocity bodies. By contrast, the Vienna Basin presents clear low-velocity zones with group velocities down to 2 km/s at period of 7 s. The group velocities are then inverted to 3D images of shear wave speeds using the linear inversion method of Herrmann (2013). The results highlight the complex crustal structure and complement earthquake tomography studies in the region. Updated
Huang Jian-Xin; Song Min-Feng; Li Zhang; Liu Peng; Chen Rou-Xi; He Ji-Huan; Wang Shu-Qiang
2015-01-01
Transverse vibration of an axially moving slender fiber of viscoelastic fluid is studied. The governing equations are derived under the assumptions of onedimensional steady and incompressible flow and linear Euler-Bernoulli bar. Effect of the moving velocity of the liquid fiber on natural frequencies is discussed, and the critical velocities of moving fibers are derived, below which transverse vibration is exponentially damped.
Particle-in-cell simulations of the critical ionization velocity effect in finite size clouds
Moghaddam-Taaheri, E.; Lu, G.; Goertz, C. K.; Nishikawa, K. - I.
1994-01-01
The critical ionization velocity (CIV) mechanism in a finite size cloud is studied with a series of electrostatic particle-in-cell simulations. It is observed that an initial seed ionization, produced by non-CIV mechanisms, generates a cross-field ion beam which excites a modified beam-plasma instability (MBPI) with frequency in the range of the lower hybrid frequency. The excited waves accelerate electrons along the magnetic field up to the ion drift energy that exceeds the ionization energy of the neutral atoms. The heated electrons in turn enhance the ion beam by electron-neutral impact ionization, which establishes a positive feedback loop in maintaining the CIV process. It is also found that the efficiency of the CIV mechanism depends on the finite size of the gas cloud in the following ways: (1) Along the ambient magnetic field the finite size of the cloud, L (sub parallel), restricts the growth of the fastest growing mode, with a wavelength lambda (sub m parallel), of the MBPI. The parallel electron heating at wave saturation scales approximately as (L (sub parallel)/lambda (sub m parallel)) (exp 1/2); (2) Momentum coupling between the cloud and the ambient plasma via the Alfven waves occurs as a result of the finite size of the cloud in the direction perpendicular to both the ambient magnetic field and the neutral drift. This reduces exponentially with time the relative drift between the ambient plasma and the neutrals. The timescale is inversely proportional to the Alfven velocity. (3) The transvers e charge separation field across the cloud was found to result in the modulation of the beam velocity which reduces the parallel heating of electrons and increases the transverse acceleration of electrons. (4) Some energetic electrons are lost from the cloud along the magnetic field at a rate characterized by the acoustic velocity, instead of the electron thermal velocity. The loss of energetic electrons from the cloud seems to be larger in the direction of
A STATISTICAL STUDY OF TRANSVERSE OSCILLATIONS IN A QUIESCENT PROMINENCE
Hillier, A. [Kwasan and Hida Observatories, Kyoto University, Kyoto 607-8471 (Japan); Morton, R. J. [Mathematics and Information Science, Northumbria University, Pandon Building, Camden Street, Newcastle upon Tyne NE1 8ST (United Kingdom); Erdélyi, R., E-mail: andrew@kwasan.kyoto-u.ac.jp [Solar Physics and Space Plasma Research Centre (SP2RC), University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH (United Kingdom)
2013-12-20
The launch of the Hinode satellite has allowed for seeing-free observations at high-resolution and high-cadence making it well suited to study the dynamics of quiescent prominences. In recent years it has become clear that quiescent prominences support small-amplitude transverse oscillations, however, sample sizes are usually too small for general conclusions to be drawn. We remedy this by providing a statistical study of transverse oscillations in vertical prominence threads. Over a 4 hr period of observations it was possible to measure the properties of 3436 waves, finding periods from 50 to 6000 s with typical velocity amplitudes ranging between 0.2 and 23 km s{sup –1}. The large number of observed waves allows the determination of the frequency dependence of the wave properties and derivation of the velocity power spectrum for the transverse waves. For frequencies less than 7 mHz, the frequency dependence of the velocity power is consistent with the velocity power spectra generated from observations of the horizontal motions of magnetic elements in the photosphere, suggesting that the prominence transverse waves are driven by photospheric motions. However, at higher frequencies the two distributions significantly diverge, with relatively more power found at higher frequencies in the prominence oscillations. These results highlight that waves over a large frequency range are ubiquitous in prominences, and that a significant amount of the wave energy is found at higher frequency.
Transverse Wobbling in $^{135}$Pr
Matta, J T; Li, W; Frauendorf, S; Ayangeakaa, A D; Patel, D; Schlax, K W; Palit, R; Saha, S; Sethi, J; Trivedi, T; Ghugre, S S; Raut, R; Sinha, A K; Janssens, R V F; Zhu, S; Carpenter, M P; Lauritsen, T; Seweryniak, D; Chiara, C J; Kondev, F G; Hartley, D J; Petrache, C M; Mukhopadhyay, S; Lakshmi, D Vijaya; Raju, M Kumar; Rao, P V Madhusudhana; Tandel, S K; Ray, S; Dönau, F
2015-01-01
A pair of transverse wobbling bands has been observed in the nucleus $^{135}$Pr. The wobbling is characterized by $\\Delta I$ =1, E2 transitions between the bands, and a decrease in the wobbling energy confirms its transverse nature. Additionally, a transition from transverse wobbling to a three-quasiparticle band comprised of strong magnetic dipole transitions is observed. These observations conform well to results from calculations with the Tilted Axis Cranking (TAC) model and the Quasiparticle Triaxial Rotor (QTR) Model.
Transverse wobbling in ^{135}pr.
Matta, J T; Garg, U; Li, W; Frauendorf, S; Ayangeakaa, A D; Patel, D; Schlax, K W; Palit, R; Saha, S; Sethi, J; Trivedi, T; Ghugre, S S; Raut, R; Sinha, A K; Janssens, R V F; Zhu, S; Carpenter, M P; Lauritsen, T; Seweryniak, D; Chiara, C J; Kondev, F G; Hartley, D J; Petrache, C M; Mukhopadhyay, S; Lakshmi, D Vijaya; Raju, M Kumar; Madhusudhana Rao, P V; Tandel, S K; Ray, S; Dönau, F
2015-02-27
A pair of transverse wobbling bands is observed in the nucleus ^{135}Pr. The wobbling is characterized by ΔI=1, E2 transitions between the bands, and a decrease in the wobbling energy confirms its transverse nature. Additionally, a transition from transverse wobbling to a three-quasiparticle band comprised of strong magnetic dipole transitions is observed. These observations conform well to results from calculations with the tilted axis cranking model and the quasiparticle rotor model. PMID:25768759
A new estimator for vector velocity estimation [medical ultrasonics
Jensen, Jørgen Arendt
2001-01-01
A new estimator for determining the two-dimensional velocity vector using a pulsed ultrasound field is derived. The estimator uses a transversely modulated ultrasound field for probing the moving medium under investigation. A modified autocorrelation approach is used in the velocity estimation. The...... new estimator automatically compensates for the axial velocity when determining the transverse velocity. The estimation is optimized by using a lag different from one in the estimation process, and noise artifacts are reduced by averaging RF samples. Further, compensation for the axial velocity can be...... introduced, and the velocity estimation is done at a fixed depth in tissue to reduce the influence of a spatial velocity spread. Examples for different velocity vectors and field conditions are shown using both simple and more complex field simulations. A relative accuracy of 10.1% is obtained for the...
Pediatric transverse myelitis.
Absoud, Michael; Greenberg, Benjamin M; Lim, Ming; Lotze, Tim; Thomas, Terrence; Deiva, Kumaran
2016-08-30
Pediatric acute transverse myelitis (ATM) is an immune-mediated CNS disorder and contributes to 20% of children experiencing a first acquired demyelinating syndrome (ADS). ATM must be differentiated from other presentations of myelopathy and may be the first presentation of relapsing ADS such as neuromyelitis optica (NMO) or multiple sclerosis (MS). The tenets of the diagnostic criteria for ATM established by the Transverse Myelitis Consortium Working Group can generally be applied in children; however, a clear sensory level may not be evident in some. MRI lesions are often centrally located with high T2 signal intensity involving gray and neighboring white matter. Longitudinally extensive ATM occurs in the majority. Asymptomatic lesions on brain MRI are seen in more than one-third and predict MS or NMO. The role of antibodies such as myelin oligodendrocyte glycoprotein in monophasic and relapsing ATM and their significance in therapeutic approaches remain unclear. ATM is a potentially devastating condition with variable outcome and presents significant cumulative demands on health and social care resources. Children generally have a better outcome than adults, with one-half making a complete recovery by 2 years. There is need for standardization of clinical assessment and investigation protocols to enable international collaborative studies to delineate prognostic factors for disability and relapse. There are no robust controlled trials in children or adults to inform optimal treatment of ATM, with one study currently open to recruitment. This review provides an overview of current knowledge of clinical features, investigative workup, pathogenesis, and management of ATM and suggests future directions. PMID:27572861
Microstructural characterization of carbon steels using ultrasonic velocity measurements
Vera Lúcia de Araújo Freitas; Antonio Almeida Silva; Edgard de Macedo Silva; de Albuquerque, Victor Hugo C.; João Manuel Ribeiro da Silva Tavares
2009-01-01
Non-destructive techniques are suitable alternatives for analysis and microstructural characterization of steels#8217; phases. Based on this, this work aims to analyze the behavior of longitudinal and transverse ultrasonic velocities in three different types of AISI steels: 1006, 1080 and quenched 1045. These materials were selected due to their distinct microstructures: ferrite, pearlite and martensite, respectively. By measuring sound velocities for both longitudinal and transversal waves, ...
Ramsey interaction with transverse decay
Xucheng Wang; Huadong Cheng; Liang Liu
2012-01-01
The Ramsey fringe contrast of a pulsed optically pumped cold atom clock is strongly affected by the transverse decay of the atomic sample.This letter calculates the Ramsey fringe with focus on transverse decay,and analyzes the Ramsey fringe contrast with different transverse decay rates.By fitting the experimental data,we obtain the transverse decay rate in a cold atom sample at an approximate value of 30.5 s-1,which is much smaller than that in a cell.
Cross-correlations of ambient noise recorded by accelerometers.
Rábade García, S. E.; Ramirez-Guzman, L.
2014-12-01
We investigate the ambient noise cross-correlations obtained by using properly corrected accelerometric recordings, and determine velocity structure in central Mexico based on a dispersion analysis. The data used comprise ten months of continuous recordings - from April 2013 to January 2014 - of ambient seismic noise at stations operated by the National Seismological Service of Mexico and the Engineering Strong Ground Motion Network of the National Autonomous University of Mexico (UNAM). The vertical component of ambient noise was base-line corrected, filtered, and properly integrated before extracting Green's functions (GF), which were compared successfully against GF obtained using recordings from broadband velocity sensors. In order to obtain dispersion curves, we estimated group and phase velocities applying the FTAN analysis technique and obtained s-wave velocity profiles at selected regions. We conclude and highlight that the use of widely deployed accelerographs to conduct regional studies using ambient noise tomography is feasible
An In-vivo investigation of transverse flow estimation
Udesen, Jesper; Jensen, Jørgen Arendt
2004-01-01
Conventional ultrasound scanners are restricted to display the blood velocity component in the ultrasound beam direction. By introducing a laterally oscillating field, signals are created from which the transverse velocity component can be estimated. This paper presents velocity and volume flow...... estimates obtained from flow phantom and in-vivo measurements at 90° relative to the ultrasound beam axis. The flow phantom experiment setup consists of a SMI140 flow phantom connected to a CompuFlow1000 programmable flow pump, which generates a flow similarly to that in the femoral artery. A B-K medical...
Transverse Spin Physics at HERMES
Elschenbroich, U.; G. Schnell; Seidl, R.; collaboration, for the HERMES
2004-01-01
Single-spin asymmetries in semi-inclusive pion production are measured by the HERMES experiment for the first time, with a transversely polarised hydrogen target. Two different sine-dependencies are extracted which can be related to the quark distributions transversity h_1(x) and the Sivers function f_1T^perp(x).
Transverse Spin Physics at HERMES
Hillenbrand, A.; collaboration, for the HERMES
2006-01-01
HERMES has measured azimuthal single-spin asymmetries of charged pions produced in deep-inelastic scattering of positrons on a transversely polarised hydrogen target. The presented azimuthal moments provide access to two yet unknown quark distribution functions, the transversity distribution function \\delta q and the Sivers function f_{1T}^{perp}.
An improved estimation and focusing scheme for vector velocity estimation
Jensen, Jørgen Arendt; Munk, Peter
The full blood velocity vector must be estimated in medical ultrasound to give a correct depiction of the blood flow. This can be done by introducing a transversely oscillating pulse-echo ultrasound field, which makes the received signal influenced by a transverse motion. Such an approach was...... suggested in [1]. Here the conventional autocorrelation approach was used for estimating the transverse velocity and a compensation for the axial motion was necessary in the estimation procedure. This paper introduces a new estimator for determining the two-dimensional velocity vector and a new dynamic...... beamforming method. A modified autocorrelation approach employing fourth order moments of the input data is used for velocity estimation. The new estimator calculates the axial and lateral velocity component independently of each other. The estimation is optimized for differences in axial and lateral...
An improved estimation and focusing scheme for vector velocity estimation
Jensen, Jørgen Arendt; Munk, Peter
1999-01-01
The full blood velocity vector must be estimated in medical ultrasound to give a correct depiction of the blood flow. This can be done by introducing a transversely oscillating pulse-echo ultrasound field, which makes the received signal influenced by a transverse motion. Such an approach...... was suggested in [1]. Here the conventional autocorrelation approach was used for estimating the transverse velocity and a compensation for the axial motion was necessary in the estimation procedure. This paper introduces a new estimator for determining the two-dimensional velocity vector and a new dynamic...... beamforming method. A modified autocorrelation approach employing fourth order moments of the input data is used for velocity estimation. The new estimator calculates the axial and lateral velocity component independently of each other. The estimation is optimized for differences in axial and lateral...
Antunes, Dalila; Bernardo, Fátima; Palma-Oliveira, José-Manuel
2011-01-01
Na aplicação da Psicologia à área do AMBIENTE importa em primeiro lugar definir o que se entende, neste contexto, por ambiente. O conceito é entendido como toda a envolvente que rodeia o ser humano. Referimo-nos pois ao espaço físico e aos estímulos que nele existem (som, ar, paisagem…), dirigindo-se a Psicologia do Ambiente ao estudo e intervenção sobre a forma como o ambiente influencia o indivíduo ou grupos, e sobre o modo como o comportamento dos indivíduos e grupos influenciam o ambiente...
Transverse Neutrino Polarization in $\
Sobkow, W
2000-01-01
In this paper a scenario admitting the participation of right-handed $S_{R}$ and left-handed $S_{L}$ scalar couplings in addition to the left-handed standard $(V, A)_{L}$ couplings in the muonic neutrino-electron elastic scattering is considered. Muon-neutrinos can come from pion-decay. We consider this process at the level of the four-fermion point (contact) interaction. Muon-neutrinos are assumed to be massive and to be Dirac fermions. We assume also that the incoming neutrinos are polarized. The formula for the laboratory differential cross section (in the limit of vanishing neutrino mass) in which the non-standard contributions coming from the interference between the left-handed vector $V_{L}$ and right-handed $S_{R}$ scalar couplings appear is given. These are the transverse components of the incoming neutrino polarization, both T-odd and T-even. The non-zero values of such observables would be the proof of the participation of the right-handed neutrinos in a pure leptonic process. As far as T-odd trans...
Schmidt, Ulrik
Atmosphere and Ambient Space This paper explores the relation between atmosphere and ambient space. Atmosphere and ambient space share many salient properties. They are both ontologically indeterminate, constantly varying and formally diffuse and they are both experienced as a subtle, non......-signifying property of a given space. But from a certain point of view, the two concepts also designate quite dissimilar experiences of space. To be ’ambient’ means to surround. Accordingly, ambient space is that space, which surrounds something or somebody. (Gibson 1987: 65) Since space is essentially...... of a surrounding character, all space can thus be described as having a fundamentally ambient character. So what precisely is an ambient space, then? As I will argue in my presentation, ambient space is a sensory effect of spatiality when a space is experienced as being particularly surrounding: a ‘space effect...
Relativistic Transverse Gravitational Redshift
Mayer, A. F.
2012-12-01
The parametrized post-Newtonian (PPN) formalism is a tool for quantitative analysis of the weak gravitational field based on the field equations of general relativity. This formalism and its ten parameters provide the practical theoretical foundation for the evaluation of empirical data produced by space-based missions designed to map and better understand the gravitational field (e.g., GRAIL, GRACE, GOCE). Accordingly, mission data is interpreted in the context of the canonical PPN formalism; unexpected, anomalous data are explained as similarly unexpected but apparently real physical phenomena, which may be characterized as ``gravitational anomalies," or by various sources contributing to the total error budget. Another possibility, which is typically not considered, is a small modeling error in canonical general relativity. The concept of the idealized point-mass spherical equipotential surface, which originates with Newton's law of gravity, is preserved in Einstein's synthesis of special relativity with accelerated reference frames in the form of the field equations. It was not previously realized that the fundamental principles of relativity invalidate this concept and with it the idea that the gravitational field is conservative (i.e., zero net work is done on any closed path). The ideal radial free fall of a material body from arbitrarily-large range to a point on such an equipotential surface (S) determines a unique escape-velocity vector of magnitude v collinear to the acceleration vector of magnitude g at this point. For two such points on S separated by angle dφ , the Equivalence Principle implies distinct reference frames experiencing inertial acceleration of identical magnitude g in different directions in space. The complete equivalence of these inertially-accelerated frames to their analogous frames at rest on S requires evaluation at instantaneous velocity v relative to a local inertial observer. Because these velocity vectors are not parallel, a
Relative Framing of Transverse knots
Chernov, Vladimir
2001-01-01
It is well-known that a knot in a contact manifold $(M,C)$ transverse to a trivialized contact structure possesses the natural framing given by the first of the trivialization vectors along the knot. If the Euler class $e_C\\in H^2(M)$ of $C$ is nonzero, then $C$ is nontrvivializable and the natural framing of transverse knots does not exist. We construct a new framing-type invariant of transverse knots called relative framing. It is defined for all tight $C$, all closed irreducible atoroidal ...
New technology - demonstration of a vector velocity technique
Møller Hansen, Peter; Pedersen, Mads M; Hansen, Kristoffer L;
2011-01-01
With conventional Doppler ultrasound it is not possible to estimate direction and velocity of blood flow, when the angle of insonation exceeds 60-70°. Transverse oscillation is an angle independent vector velocity technique which is now implemented on a conventional ultrasound scanner. In this pa...
Prognosis of Acute Transverse Myelitis
J Gordon Millichap; John J Millichap
2014-01-01
Investigators at Children's Hospital of Chongqing Medical University, China, reviewed children diagnosed with acute transverse myelitis (ATM) between 1995 and 2008 and selected 39 patients diagnosed according to the new Johns Hopkins Consortium criteria.
Precision Measuring of Velocities via the Relativistic Doppler Effect
Ozernoy, Leonid M.
1997-01-01
Just as the ordinary Doppler effect serves as a tool to measure radial velocities of celestial objects, so can the relativistic Doppler effect be implemented to measure a combination of radial and transverse velocities by using recent improvements in observing techniques. A key element that makes a further use of this combination feasible is the periodicity in changes of the orbital velocity direction for the source. Two cases are considered: (i) a binary star; and (ii) a solitary star with t...
Cantillon-Murphy, P., E-mail: padraig@mit.ed [Division of Gastroenterology, Brigham and Women' s Hospital, Boston, MA (United States); Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA (United States); Wald, L.L., E-mail: wald@nmr.mgh.harvard.ed [MGH-HST Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, MA (United States); Adalsteinsson, E., E-mail: elfar@mit.ed [Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA (United States); MGH-HST Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, MA (United States); Zahn, M., E-mail: zahn@mit.ed [Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA (United States)
2010-09-15
In the presence of alternating-sinusoidal or rotating magnetic fields, magnetic nanoparticles will act to realign their magnetic moment with the applied magnetic field. The realignment is characterized by the nanoparticle's time constant, {tau}. As the magnetic field frequency is increased, the nanoparticle's magnetic moment lags the applied magnetic field at a constant angle for a given frequency, {Omega}, in rad s{sup -1}. Associated with this misalignment is a power dissipation that increases the bulk magnetic fluid's temperature which has been utilized as a method of magnetic nanoparticle hyperthermia, particularly suited for cancer in low-perfusion tissue (e.g., breast) where temperature increases of between 4 and 7 {sup o}C above the ambient in vivo temperature cause tumor hyperthermia. This work examines the rise in the magnetic fluid's temperature in the MRI environment which is characterized by a large DC field, B{sub 0}. Theoretical analysis and simulation is used to predict the effect of both alternating-sinusoidal and rotating magnetic fields transverse to B{sub 0}. Results are presented for the expected temperature increase in small tumors ({approx}1cm radius) over an appropriate range of magnetic fluid concentrations (0.002-0.01 solid volume fraction) and nanoparticle radii (1-10 nm). The results indicate that significant heating can take place, even in low-field MRI systems where magnetic fluid saturation is not significant, with careful the goal of this work is to examine, by means of analysis and simulation, the concept of interactive fluid magnetization using the dynamic behavior of superparamagnetic iron oxide nanoparticle suspensions in the MRI environment. In addition to the usual magnetic fields associated with MRI, a rotating magnetic field is applied transverse to the main B{sub 0} field of the MRI. Additional or modified magnetic fields have been previously proposed for hyperthermia and targeted drug delivery within MRI
In the presence of alternating-sinusoidal or rotating magnetic fields, magnetic nanoparticles will act to realign their magnetic moment with the applied magnetic field. The realignment is characterized by the nanoparticle's time constant, τ. As the magnetic field frequency is increased, the nanoparticle's magnetic moment lags the applied magnetic field at a constant angle for a given frequency, Ω, in rad s-1. Associated with this misalignment is a power dissipation that increases the bulk magnetic fluid's temperature which has been utilized as a method of magnetic nanoparticle hyperthermia, particularly suited for cancer in low-perfusion tissue (e.g., breast) where temperature increases of between 4 and 7 oC above the ambient in vivo temperature cause tumor hyperthermia. This work examines the rise in the magnetic fluid's temperature in the MRI environment which is characterized by a large DC field, B0. Theoretical analysis and simulation is used to predict the effect of both alternating-sinusoidal and rotating magnetic fields transverse to B0. Results are presented for the expected temperature increase in small tumors (∼1cm radius) over an appropriate range of magnetic fluid concentrations (0.002-0.01 solid volume fraction) and nanoparticle radii (1-10 nm). The results indicate that significant heating can take place, even in low-field MRI systems where magnetic fluid saturation is not significant, with careful the goal of this work is to examine, by means of analysis and simulation, the concept of interactive fluid magnetization using the dynamic behavior of superparamagnetic iron oxide nanoparticle suspensions in the MRI environment. In addition to the usual magnetic fields associated with MRI, a rotating magnetic field is applied transverse to the main B0 field of the MRI. Additional or modified magnetic fields have been previously proposed for hyperthermia and targeted drug delivery within MRI. Analytical predictions and numerical simulations of the
Operational characteristics and power scaling of a transverse ﬂow transversely excited CW CO2 laser
Jai Khare; R Sreedhar; C P Paul; T Reghu; A K Nath
2003-01-01
Transverse ﬂow transversely excited (TFTE) CO2 lasers are easily scalable to multikilowatt level. The laser power can be scaled up by increasing the volumetric gas ﬂow and discharge volume. It was observed in a TFTE CW CO2 laser having single row of pins as an anode and tubular cathode that the laser power was not increasing when the discharge volume and the gas volumetric ﬂow were increased by increasing the electrode separation keeping the gas ﬂow velocity constant. The discharge voltage too remained almost constant with the change of electrode separation at the same gas ﬂow velocity. This necessitated revision of the scaling laws for designing this type of high power CO2 laser. Experimental results of laser performance for different electrode separations are discussed and the modiﬁcations in the scaling laws are presented.
Lu, Jie
2016-06-01
In this work, we report analytical results on transverse domain wall (TDW) statics and field-driven dynamics in quasi-one-dimensional biaxial nanowires under arbitrary uniform transverse magnetic fields (TMFs) based on the Landau-Lifshitz-Gilbert equation. Without axial driving fields, the static TDW should be symmetric about its center while twisted in its azimuthal angle distribution. By decoupling polar and azimuthal degrees of freedom, an approximate solution is provided which reproduces these features to a great extent. When an axial driving field is applied, the dynamical behavior of a TDW is viewed as the response of its static profile to external excitations. By means of the asymptotic expansion method, the TDW velocity in the traveling-wave mode is obtained, which provides the extent and boundary of the "velocity-enhancement" effect of TMFs on TDWs in biaxial nanowires. Finally, numerical simulations are performed and strongly support our analytics.
TRANSVERSE MIXING IN A TRAPEZOIDAL COMPOUND OPEN CHANNEL
ZENG Yu-hong; HUAI Wen-xin; GUYMER I
2008-01-01
Transverse mixing characteristics of solute in the open channel flow can provide useful information for river environmental management. The lateral mixing coefficient is a crucial parameter for reproducing the transverse mixing either by numerical simulation or by analytical prediction. Since the solute mixing can be greatly affected by the lateral variations in water depth, mixing coefficient should be determined in each sub-section (i.e., the main channel, side slope and flood plain) separately. In this article, the transverse mixing in a symmetric trapezoidal compound channel was studied based on laboratory measurement of longitudinal and transverse velocity components and lateral distribution of solute concentration. The lateral mixing coefficient was estimated by adopting different Schmidt numbers in different sub-sections divided according to the developing trend of the eddy viscosity, and finally a piecewise linear profile of mixing coefficient was adopted to analytically predict the transverse solute concentration. The comparison between the analytically predicted data and the measuring solute concentration proved that this is an effective way to estimate the lateral mixing in the open channel flow with lateral variations in water depth.
Ambient Noise Tomography of the British Isles
Nicolson, H. J.; Curtis, A.; Baptie, B.
2009-12-01
In recent years, surface wave tomography using empirical Green’s functions computed via the ambient noise interferometry method has become an established approach to lithospheric imaging problems. To date, ambient noise tomography has been successfully applied to seismometer arrays in the United States, Australia, Iceland, China, South Africa, Europe and the Tibetan Plateau. The basis of the ambient seismic interferometry method is that, by cross-correlating noise data between two seismic stations and stacking over a long enough time period, one can approximate the Green’s Function that would have been recorded at one of the stations if the other had actually been a source. Consequently, one of the main advantages of ambient noise interferometry is that traditional seismic sources such as earthquakes or ballistics are not required; therefore it is ideal for application to seismically quiescent areas such as the British Isles. The British Isles are an archipelago located adjacent to the Eurasian continental shelf in a typically intra-plate setting, formed by a complex amalgamation of several terranes. These range from Laurentian north of the Highland Boundary fault to Avalonian south of the Iapetus Suture and evidence of the regions turbulent geological past can be inferred from its lithospheric structure. Previous studies of the structure of the British Isles considered relatively few seismic stations and/or were limited to using offshore shots, quarry blasts or teleseismic earthquakes as seismic energy sources. We have applied the ambient noise tomography method to noise data recorded on approximately 100 broadband and short period seismometers, including many new stations, in the British Isles and mainland Europe. This dense coverage of the British Isles allows us to image the crust and upper mantle velocity structure with a horizontal resolution in the region of 100km across the North Sea and 30km in the mainland United Kingdom. Here we present the first
Spin Physics and Transverse Structure
Mulders, P J
2015-01-01
Spin is a welcome complication in the study of partonic structure that has led to new insights, even if theoretically and experimentally not all dust has settled, in particular on quark flavor dependence and gluon spin. At the same time it opened new questions on angular momentum and effects of transverse structure. In this talk the focus is on the role of the transverse momenta of partons. Like for collinear parton distribution functions (PDFs), we are also in the case of transverse momentum dependent (TMD) PDFs, talking about forward matrix elements. TMD PDFs (or in short TMDs) extend collinear PDFs with only spin-spin correlations to PDFs that include spin-momentum correlations, including also time-reversal-odd (T-odd) correlations, relevant for the description of single spin asymmetries. In this way TMDs open up new ways of studying the spin structure. Their operator structure within QCD, however, is more complex leading to various ways of breaking of universality.
Simulations of High-Velocity Clouds. I. Hydrodynamics and High-Velocity High Ions
Kwak, Kyujin; Henley, David B; Shelton, Robin L.
2011-01-01
We present hydrodynamic simulations of high-velocity clouds (HVCs) traveling through the hot, tenuous medium in the Galactic halo. A suite of models was created using the FLASH hydrodynamics code, sampling various cloud sizes, densities, and velocities. In all cases, the cloud-halo interaction ablates material from the clouds. The ablated material falls behind the clouds, where it mixes with the ambient medium to produce intermediate-temperature gas, some of which radiatively cools to less th...
La Transversal Cafetera por Caldas
Duque Escobar, Gonzalo
2014-01-01
Dada la necesidad de una transversal férrea para resolver las falencias estructurales del transporte de carga colombiano, con la construcción del nuevo Túnel Cumanday bimodal y doble cruzando la Cordillera Central por Caldas, la nueva Transversal Cafetera podría diseñarse con pendiente máxima del 6% y velocidad de 80 km/h, y convertirse en complemento al paso por la Línea, y en el soporte de un corredor logístico que integraría la región andina de Colombia, al detonar con el ferrocarril senda...
Cosmology in Weyl Transverse Gravity
Oda, Ichiro
2016-01-01
We study the Friedmann-Lemaitre-Robertson-Walker (FLRW) cosmology in the Weyl-transverse (WTDiff) gravity in a general space-time dimension. The WTDiff gravity is invariant under both the local Weyl (conformal) transformation and the volume preserving diffeormorphisms (transverse diffeomorphisms) and is believed to be equivalent to general relativity at least at the classical level (perhaps, even in the quantum regime). It is explicitly shown by solving the equations of motion that the FLRW metric is a classical solution in the WTDiff gravity only when the spatial metric is flat, that is, the Euclidean space, and the lapse function is a nontrivial function of the scale factor.
Acute transverse myelitis : MR characteristics.
Murthy J
1999-10-01
Full Text Available Magnetic resonance imaging findings in 13 patients with acute transverse myelitis are reviewed. In 12 cases centrally located high intensity signal extending over few spinal segments was noted. The lesion occupied more than two thirds of the cord′s cross-sectional area in 8 patients. Central dot sign was noted in 7 patients. Variable cord enlargement was seen in 5 patients. Contrast study in one patient showed peripheral enhancement. The MR characteristics that help in differentiating transverse myelitis from spinal form of multiple sclerosis are discussed.
Huang Jian-Xin
2015-01-01
Full Text Available Transverse vibration of an axially moving slender fiber of viscoelastic fluid is studied. The governing equations are derived under the assumptions of onedimensional steady and incompressible flow and linear Euler-Bernoulli bar. Effect of the moving velocity of the liquid fiber on natural frequencies is discussed, and the critical velocities of moving fibers are derived, below which transverse vibration is exponentially damped.
Dihadron Fragmentation Functions and Transversity
Radici, Marco; Bacchetta, Alessandro
2014-01-01
We present preliminary results for an updated extraction of the transversity parton distribution based on the analysis of pion-pair production in deep-inelastic scattering off transversely polarized targets in collinear factorization. Data for proton and deuteron targets by HERMES and COMPASS allow for a flavor separation of the valence components of transversity, while di-hadron fragmentation functions are taken from the semi-inclusive production of two pion pairs in back-to-back jets in $e^+ e^-$ annihilation. The latter data from Belle have been reanalyzed using the replica method and a more realistic estimate of the uncertainties on the chiral-odd interference fragmentation function has been obtained. After encoding this piece of information into the deep-inelastic scattering cross section, the transversity has been re-extracted by using the most recent and more precise COMPASS data for proton target. This picture represents the current most realistic estimate of the uncertainties on our knowledge of tran...
Transverse Energy Production at RHIC
Li, Qun; Pang, Yang; Xu, Nu
1999-01-01
We study the mechanism of transverse energy (E_T) production in Au+Au collisions at RHIC. The time evolution starting from the initial energy loss to the final E_T production is closely examined in transport models. The relationship between the experimentally measured E_T distribution and the maximum energy density achieved is discussed.
Longitudinal and Transverse Nuclear Shadowing
Barone, V.; M.; Genovese
1996-01-01
Nuclear shadowing arises from multiple scattering of the hadronic fluctuations of the virtual photon in a nucleus. We predict different longitudinal and transverse shadowing and an A-dependence of R which can be up to a 50% effect. The possibility of detecting nuclear effects on R at HERA is discussed.
Lorna Matarrita Román
2012-11-01
Full Text Available The purpose of this research was to analyze whether the use of technological resources may be feasible in the implementation of the environmental culture cross-cutting factor for sustainable development, which focuses on environmental issues related to the contents of the Science study program for the seventh year of the basic general education. The research design is qualitative with a dominant approach and uses some quantitative elements specifically in the design of instruments and some data analysis techniques. The type of study was developed with a multi-method approach; a trend that has been shaping a research style which integrates various methods in a single design. For this, we identified the didactic strategies and their relationship to both, technology and the environmental axis for sustainable development, used by six Science teachers of the 7th grade, in public institutions of the province of Heredia, Central Valley, Costa Rica, as well as the opinion of 20 students from that same grade. The main results include the opinions of the students, who showed a considerable interest in classes where technological resources are used. However, teachers do not show great interest or positive opinions on this matter; in addition, they are not well trained on the use of technological resources. It was also identified that the teaching personal who participated in the study do not develop this curricular axis.
Recibido 19 de junio de 2012 • Corregido 16 de setiembre de 2012 • Aceptado 07 de noviembre de 2012
El propósito de esta investigación fue analizar si, en la implementación del eje transversal cultural ambiental para el desarrollo sostenible, que enfatiza en problemáticas ambientales relacionadas con los contenidos del programa de Ciencias de séptimo año de la Educación Básica, puede ser factible la utilización de recursos tecnológicos. El diseño de la investigación fue cualitativo con enfoque dominante
Okamoto, Takenori J; De Pontieu, Bart; Uitenbroek, Han; Van Doorsselaere, Tom; Yokoyama, Takaaki
2015-01-01
Transverse magnetohydrodynamic (MHD) waves have been shown to be ubiquitous in the solar atmosphere and can in principle carry sufficient energy to generate and maintain the Sun's million-degree outer atmosphere or corona. However, direct evidence of the dissipation process of these waves and subsequent heating has not yet been directly observed. Here we report on high spatial, temporal, and spectral resolution observations of a solar prominence that show a compelling signature of so-called resonant absorption, a long hypothesized mechanism to efficiently convert and dissipate transverse wave energy into heat. Aside from coherence in the transverse direction, our observations show telltale phase differences around 180 degrees between transverse motions in the plane-of-sky and line-of-sight velocities of the oscillating fine structures or threads, and also suggest significant heating from chromospheric to higher temperatures. Comparison with advanced numerical simulations support a scenario in which transverse...
O direito ao meio ambiente sadio: a proteção pela Corte Interamericana de Direitos Humanos
Eneida Orbage de Britto Taquary
2013-01-01
O artigo tem por objetivo analisar a proteção do meio ambiente sadio no âmbito da Corte Interamericana de direitos Humanos. São analisadas as decisões da Corte que protege de forma transversal o direito ao meio ambiente, quando tutela a vida, a saúde e a integridade corporal.
P-wave signatures and parameterization of transversely isotropic media: An overview
Tsvankin, I.
1994-07-01
Progress in seismic inversion and processing in anisotropic media depends on our ability to relate different seismic signatures to the anisotropic parameters. While the conventional notation (stiffness coefficients) is suitable for forward modeling, it is inconvenient in developing analytic insight into the influence of anisotropy on wave propagation. The author gives a consistent description of P-wave signatures in transversely isotropic media with arbitrary strength of the anisotropy, using the notation suggested by Thomsen (1986). The influence of transverse isotropy on P-wave propagation is shown to be practically independent of the vertical S-wave velocity V{sub S0}, even in models with strong velocity variations. Therefore, the contribution of transverse isotropy to P-wave kinematic and dynamic signatures is controlled by just two anisotropic parameters, {epsilon} and {delta}, with the vertical velocity V{sub P0} being no more than a scaling coefficient in homogeneous models.
A New Method for Estimation of Velocity Vectors
Jensen, Jørgen Arendt; Munk, Peter
1998-01-01
The paper describes a new method for determining the velocity vector of a remotely sensed object using either sound or electromagnetic radiation. The movement of the object is determined from a field with spatial oscillations in both the axial direction of the transducer and in one or two...... signal influenced by transverse motion. Such a transverse modulation can be generated by using apodization on individual transducer array elements together with a special focusing scheme. A method for making such a field is presented along with a suitable two-dimensional velocity estimator. An...
VELOCITY INDICATOR FOR EXTRUSION PRESS
Digney, F.J. Jr.; Bevilacqua, F.
1959-04-01
An indicator is presented for measuring the lowspeed velocity of an object in one direction where the object returns in the opposite direction at a high speed. The indicator comprises a drum having its axis of rotation transverse to the linear movement of the object and a tape wound upon the drum with its free end extending therefrom and adapted to be connected to the object. A constant torque is applied to the drum in a direction to wind the tape on the drum. The speed of the tape in the unwinding direction is indicated on a tachometer which is coupled through a shaft and clutch means to the drum only when the tape is unwinding.
Piezoelectric energy harvesting from transverse galloping of bluff bodies
Abdelkefi, A.; Hajj, M. R.; Nayfeh, A. H.
2013-01-01
The concept of harvesting energy from transverse galloping oscillations of a bluff body with different cross-section geometries is investigated. The energy is harvested by attaching a piezoelectric transducer to the transverse degree of freedom of the body. The power levels that can be generated from these vibrations and the variations of these levels with the load resistance, cross-section geometry, and freestream velocity are determined. A representative model that accounts for the transverse displacement of the bluff body and harvested voltage is presented. The quasi-steady approximation is used to model the aerodynamic loads. A linear analysis is performed to determine the effects of the electrical load resistance and the cross-section geometry on the onset of galloping, which is due to a Hopf bifurcation. The normal form of this bifurcation is derived to determine the type (supercritical or subcritical) of the instability and to characterize the effects of the linear and nonlinear parameters on the level of harvested power near the bifurcation. The results show that the electrical load resistance and the cross-section geometry affect the onset speed of galloping. The results also show that the maximum levels of harvested power are accompanied with minimum transverse displacement amplitudes for all considered (square, D, and triangular) cross-section geometries, which points to the need for performing a coupled analysis of the system.
Introduction to Transverse Beam Dynamics
Holzer, B J
2014-01-01
In this chapter we give an introduction to the transverse dynamics of the particles in a synchrotron or storage ring. The emphasis is more on qualitative understanding rather than on mathematical correctness, and a number of simulations are used to demonstrate the physical behaviour of the particles. Starting from the basic principles of how to design the geometry of the ring, we review the transverse motion of the particles, motivate the equation of motion, and show the solutions for typical storage ring elements. Following the usual treatment in the literature, we present a second way to describe the particle beam, using the concept of the emittance of the particle ensemble and the beta function, which reflects the overall focusing properties of the ring. The adiabatic shrinking due to Liouville's theorem is discussed as well as dispersive effects in the most simple case.
Transversal Lines of the Debates
Yolanda Onghena
1998-12-01
Full Text Available The Transversal Lines of the Debates gathers for publication the presentations of the scholars invited to the seminar. In the papers, Yolanda Onghena observes that the evolution from the cultural to the inter-cultural travels along four axes: the relations between cultureand society; the processes of change within identity-based dynamics; the representations of the Other; and, interculturality. Throughout the presentations and subsequent debates, whenever the different participants referred to aspects of the cultural identity problematic--”angst”, “obsession”, “deficit”, manipulation”, and others, these same participants in the Transversal Lines of the Debates also showed that, in certain areas, an optimistic viewpoint is not out of the question.
Influence of speckle effect on doppler velocity measurement
Zheng, Zheng; Changming, Zhao; Haiyang, Zhang; Suhui, Yang; Dehua, Zhang; Xingyuan, Zheng; Hongzhi, Yang
2016-06-01
In a coherent Lidar system, velocity measurement of a target is achieved by measuring Doppler frequency shift between the echo and local oscillator (LO) signals. The measurement accuracy is proportional to the spectrum width of Doppler signal. Actually, the speckle effect caused by the scattering of laser from a target will broaden the Doppler signal's spectrum and bring uncertainty to the velocity measurement. In this paper, a theoretical model is proposed to predict the broadening of Doppler spectrum with respect to different target's surface and motion parameters. The velocity measurement uncertainty caused by the broadening of spectrum is analyzed. Based on the analysis, we design a coherent Lidar system to measure the velocity of the targets with different surface roughness and transverse velocities. The experimental results are in good agreement with theoretical analysis. It is found that the target's surface roughness and transverse velocity can significantly affect the spectrum width of Doppler signal. With the increase of surface roughness and transverse velocity, the measurement accuracy becomes worse. However, the influence of surface roughness becomes weaker when the spot size of laser beam on the target is smaller.
An investigation of ambient gameplay
Eyles, Mark
2012-01-01
Inspired by Brian Eno's ambient music, which is persistent and supports different levels of engagement, this research explores ambient gameplay in computer, video and pervasive games. Through the creation of original games containing ambient gameplay and looking for ambient gameplay in existing commercial games, this research focuses on gameplay that supports a range of depths of player engagement. This research is not concerned with ambient intelligent environments or other technologies that...
Transverse stability of Kawahara solitons
Karpman, V.I.
1993-01-01
The transverse stability of the planar solitons described by the fifth-order Korteweg-de Vries equation (Kawahara solitons) is studied. It is shown that the planar solitons are unstable with respect to bending if the coefficient at the fifth-derivative term is positive and stable if it is negative....... This is in agreement with the dynamics of the two-dimensional Kawahara solitons....
Acute transverse myelitis : MR characteristics.
Murthy J; Reddy J; Meena A; Kaul S
1999-01-01
Magnetic resonance imaging findings in 13 patients with acute transverse myelitis are reviewed. In 12 cases centrally located high intensity signal extending over few spinal segments was noted. The lesion occupied more than two thirds of the cord′s cross-sectional area in 8 patients. Central dot sign was noted in 7 patients. Variable cord enlargement was seen in 5 patients. Contrast study in one patient showed peripheral enhancement. The MR characteristics that help in differentiating ...
Transverse Myelitis: An unusual association
Kalkan, Gokhan; Karaoglu, Abdulbaki; Vurucu, Sebahattin; Unay, Bulent; Gok, Faysal; Akin, Ridvan; Arslan, Mehmet Tayyip
2012-01-01
Transverse myelitis (TM) is an acute inflammation of spinal cord characterized by demyelination. Infectious, inflammatory and autoimmune etiologies constitute the most common etiologies of TM. It is believed that pathlogical changes in infection related cases occur due to altered immune response rather than direct effect of the infection. Methicillin resistant Staphylococcus aureus (MRSA) a well known agent of hospital and sometimes community acquired pneumonia leads to increased morbidity an...
Transverse Aortic Constriction in Mice
deAlmeida, Angela C.; van Oort, Ralph J.; Wehrens, Xander H. T.
2010-01-01
Transverse aortic constriction (TAC) in the mouse is a commonly used experimental model for pressure overload-induced cardiac hypertrophy and heart failure.1 TAC initially leads to compensated hypertrophy of the heart, which often is associated with a temporary enhancement of cardiac contractility. Over time, however, the response to the chronic hemodynamic overload becomes maladaptive, resulting in cardiac dilatation and heart failure.2 The murine TAC model was first validated by Rockman et ...
Pore Velocity Estimation Uncertainties
Devary, J. L.; Doctor, P. G.
1982-08-01
Geostatistical data analysis techniques were used to stochastically model the spatial variability of groundwater pore velocity in a potential waste repository site. Kriging algorithms were applied to Hanford Reservation data to estimate hydraulic conductivities, hydraulic head gradients, and pore velocities. A first-order Taylor series expansion for pore velocity was used to statistically combine hydraulic conductivity, hydraulic head gradient, and effective porosity surfaces and uncertainties to characterize the pore velocity uncertainty. Use of these techniques permits the estimation of pore velocity uncertainties when pore velocity measurements do not exist. Large pore velocity estimation uncertainties were found to be located in the region where the hydraulic head gradient relative uncertainty was maximal.
Ambient oxygen promotes tumorigenesis.
Ho Joong Sung
Full Text Available Oxygen serves as an essential factor for oxidative stress, and it has been shown to be a mutagen in bacteria. While it is well established that ambient oxygen can also cause genomic instability in cultured mammalian cells, its effect on de novo tumorigenesis at the organismal level is unclear. Herein, by decreasing ambient oxygen exposure, we report a ∼50% increase in the median tumor-free survival time of p53-/- mice. In the thymus, reducing oxygen exposure decreased the levels of oxidative DNA damage and RAG recombinase, both of which are known to promote lymphomagenesis in p53-/- mice. Oxygen is further shown to be associated with genomic instability in two additional cancer models involving the APC tumor suppressor gene and chemical carcinogenesis. Together, these observations represent the first report directly testing the effect of ambient oxygen on de novo tumorigenesis and provide important physiologic evidence demonstrating its critical role in increasing genomic instability in vivo.
Zuluaga Sánchez, Gloria Patricia
1998-01-01
El debate sobre mujer y medio ambiente es bastante nuevo y, por lo tanto, aun no hay consenso sobre como abordarlo, ni análisis muy profundos sobre la interacción de estas dos problemáticas tan complejas y que además atraviesan las demás temáticas. Con ello no se quiere negar el importante aporte que se ha hecho en tal sentido, por parte de colectividades y de algunas personas. Selene Herculano y Jacqueline Pitanguy (1993), mencionan que el medio ambiente no es una categoría específica y que ...
Ambientes de aprendizaje computacionales
Señas, Perla
2001-01-01
En el marco de las aplicaciones de la tecnología computacional a la educación se destaca de manera especial el trabajo sobre Ambientes de Aprendizaje. En él convergen tópicos relevantes de las Ciencias de la Computación y de la Educación. Se puede definir un Ambiente de Aprendizaje Computacional como un entorno integrado por un conjunto no homogéneo de elementos capaces de crear o recrear situaciones a partir de las cuales el alumno puede construir conocimiento y realizar aprendizajes y meta-...
Transversity distribution functions in the valon model
Alizadeh Yazdi, Z.; Taghavi-Shahri, F.; Arash, F.; Zomorrodian, M. E.
2014-05-01
We use the valon model to calculate the transversity distribution functions inside the nucleon. Transversity distributions indicate the probability to find partons with spin aligned (antialigned) to the transversely polarized nucleon. The results are in good agreement with all available experimental data and also global fits.
Appraisal of transverse nasal groove: A study
Belagola D Sathyanarayana
2012-01-01
Full Text Available Background: Transverse nasal groove is a condition of cosmetic concern which awaits due recognition and has been widely described as a shallow groove that extends transversely over the dorsum of nose. However, we observed variations in the clinical presentations of this entity, hitherto undescribed in literature. Aims: We conducted a clinicoepidemiological study of transverse nasal lesions in patients attending our outpatient department. Methods: We conducted a prospective observational study. We screened all patients attending our out-patient department for presence of transverse nasal lesions, signs of any dermatosis and associated other skin conditions. Results: One hundred patients were recruited in the study. Females (80% predominated over males. Most patients were of 15-45 years age group (70%. Majority of the transverse nasal lesions were classical transverse nasal groove (39% and others included transverse nasal line (28%, strip (28%, ridge (4% and loop (1%. Seborrhoeic diathesis was the most common condition associated with transverse nasal lesion. Conclusions: Occurrence of transverse nasal line, strip, ridge and loop, in addition to classical transverse nasal groove implies that latter is actually a subset of transverse nasal lesions. Common association of this entity with seborrheic dermatitis, seborrhea and dandruff raises a possibility of whether transverse nasal lesion is a manifestation of seborrheic diathesis.
Analysis of ultrasonic wave propagation in transversely isotropic austenitic welds
Ultrasonic testing of austenitic welds is widely known to be difficult mainly due to the anisotropy and inhomogeneity of their elastic properties. This study investigates the physical phenomena of ultrasonic wave propagation and scattering in austenitic welds, modeled as homogeneous and transversely isotropic. The velocity and slowness surfaces are obtained for the transversely isotropic plane of austenitic welds, using the elasticity analysis. Also, the phenomena of wave generation, propagation and scattering in the same medium are simulated using the mass-spring lattice model. The numerical results show good qualitative agreement with the analytical results, and various waves in the numerical results are identified by comparing with the analytical results. Further development of this work will provide useful and practical results for the field ultrasonic testing of austenitic welds.
Plane wave propagation in transversely isotropic laser-excited solids
This paper concentrates on the study of body harmonic wave propagation in an anisotropic laser-excited solid in the context of the model based on coupled equations for the displacement and atomic defect concentration fields. The complex secular equations for transversely isotropic solids are derived and discussed. It is found, in general, four types of dispersive waves, namely a quasi-longitudinal (QL), two quasi-transverse (QT) and a quasi-defect wave (N-mode) can propagate in these types of crystals. The different characteristics of waves like phase velocity, attenuation coefficient are obtained and presented graphically. It is demonstrated that there is an appreciable variation in case of the QL mode as compared with QT and N-modes. Some particular cases have also been discussed
Rafael Núñez-Lagos Roglá
2011-01-01
Full Text Available Se explican los conceptos fundamentales relacionados con la radiactividad y se utilizan para describir la radiactividad ambiental. Se explican también los isótopos de largo periodo y las principales familias radioactivas junto con la radiación cósmica y los radionucleidos cosmogénicos.
Ambient mass spectrometry imaging
Janfelt, Christian; Nørgaard, Asger W
2012-01-01
Easy ambient sonic spray ionization (EASI) and desorption electrospray ionization (DESI) were used for imaging of a number of samples, including sections of rat brain and imprints of plant material on porous Teflon. A novel approach termed Displaced Dual-mode Imaging was utilized for the direct c...
Dynamic analysis of the mechanical systems vibrating transversally in transportation
A. Buchacz
2007-01-01
Full Text Available Purpose: Purpose of this paper is analysis and modelling of mechanical systems in transportation. Thecontemporary technical problems are lashed with high work demands such as high speeds of mechanisms, usinglower density materials, high precision of work, etc. The main objective of this thesis was the dynamical analysiswith taking into consideration the interaction between main motion and local vibrations during the model isloaded by transverse forces.Design/methodology/approach: Equations of motion were derived by classical methods, the Lagrangeequations with generalized coordinates and generalized velocities assumed as orthogonal projections ofindividual coordinates and velocities of the beam and manipulators to axes of the global inertial frame.Findings: Presented mathematical model of the transversally vibrating systems in planar transportation can beput to use to derivation of the dynamical flexibility of these systems, moreover those equations are the startingpoint to the analysis of complex systems. In particular we can use those equations to derivation of the substitutedynamical flexibility of multibody systems.Research limitations/implications: There were considered mechanical systems vibrating transversally in termsof plane motion. Next problem of dynamical analysis is the analysis of systems in non-planar transportation andsystems loaded by longitudinal forces.Practical implications: Results of this thesis can be put to use into all machines and mechanisms running intransportation such as wind power plants, high speed turbines, rotors, manipulators and in aerodynamics issues,etc. Some results ought to be modified and adopted to appropriate models.Originality/value: High requirements applying to parameters of work of machines and mechanisms are causedthe new research and new ways of modelling and analyzing those systems. One of these ways are presented inthis thesis. There was defined the transportation effect for models vibrating
Contribution to the study of transverse turbulent diffusion in streams
In this research our objective is to study the turbulent diffusion in a water flow, in particular the transverse diffusion. According to formulae reviewed in literature the diffusion coefficients (K) may be expressed as a function of several velocity parameters. A synthetic formula depending on a macro-scale length of turbulence Lx and a turbulent intensity √(u'2) is proposed: K = β.Lx.U-bar.(√(u'2/U-bar))2. In order to validate this expression we performed two in situ experiments (one in a wide river and the other in an irrigation canal) with a double set of measurements: turbulent velocities and concentrations of a diffusing tracer. The first set gives us usable data in our formula. The results, compared with values available in literature, give a good agreement. Moreover it appears that it is possible to roughly divide the data in two groups according to (1) the cross section shape and (2) the bed roughness. The second set allows us to evaluate a global turbulent mixing coefficient. The coefficients calculated by the two methods are in accordance so our formula is validated. Nevertheless some problems appear because of what is called secondary currents and coherent structures as those seen above bed cracks in the Garonne river. Those phenomenon may play a major part upon turbulent diffusion in real streams. Although they were made conspicuous by an analysis of transverse velocity component, it has not been yet possible to quantify their effects. (author)
Transversals in Non-Discrete Groups
Ramji Lal; R P Shukla
2005-11-01
The concept of `topological right transversal' is introduced to study right transversals in topological groups. Given any right quasigroup with a Tychonoff topology , it is proved that there exists a Hausdorff topological group in which can be embedded algebraically and topologically as a right transversal of a subgroup (not necessarily closeed). It is also proved that if a topological right transversal $(S, T_S, T^S, \\circ)$ is such that $T_S=T^S$ is a locally compact Hausdorff topology on , then can be embedded as a right transversal of a closed subgroup in a Hausdorff topological group which is universal in some sense.
Projectile transverse motion and stability in electromagnetic induction launchers
Shokair, I.R.
1993-12-31
The transverse motion of a projectile in an electromagnetic induction launcher is considered. The equations of motion for translation and rotation are derived assuming a rigid projectile and a flyway restoring force per unit length that is proportional to the local displacement. Linearized transverse forces and torques due to energized coils are derived for displaced or tilted armature elements based on a first order perturbation method. The resulting equations of motion for a rigid projectile composed of multiple elements in a multi-coil launcher are analyzed as a coupled oscillator system of equations and a simple linear stability condition is derived. The equations of motion are incorporated into the 2-D Slingshot circuit code and numerical solutions for the transverse motion are obtained. For a launcher with a 10 cm bore radius with a 40 cm long solid armature, we find that stability is achieved with a restoring force (per unit length) constant of k {approx} 1 {times} 10{sup 8} N/m{sup 2}. For k = 1.5 {times} 10{sup 8} N/m{sup 2} and sample coil misalignment modeled as a sine wave of 1 mm amplitude at wavelengths of one or two meters, the projectile displacement grows to a maximum of 4 mm. This growth is due to resonance between the natural frequency of the projectile transverse motion and the coil displacement wavelength. This resonance does not persist because of the changing axial velocity. Random coil displacement is also found to cause roughly the same projectile displacement. For the maximum displacement a rough estimate of the transverse pressure is 50 bars. Results for a wound armature with uniform current density throughout show very similar displacements.
Růžek, Bohuslav; Valentová, L.; Gallovič, F.
2016-01-01
Roč. 173, - (2016). ISSN 0033-4553 Institutional support: RVO:67985530 Keywords : ambient noise * geological units * Bohemian Massif * velocity model Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 1.618, year: 2014
Transverse momentum bounds and scaling in the hydrodynamical model
Chaichian, Masud; Suhonen, E
1974-01-01
It is shown that the equation of state of an ideal relativistic gas, as applied in the hydrodynamical model, leads not only to deviations from scaling in longitudinal rapidity distributions, but also to an average transverse momentum increasing asymptotically as a power of the incident energy. To prevent such an increase, one must use the equation of state of an interacting gas, in which the velocity of sound becomes asymptotically equal to that of light. This then also restores scaling (up to logarithmic terms) in longitudinal rapidity. (25 refs).
Delaminations in composite plates under transverse impact loads - Experimental results
Finn, Scott R.; He, Ye-Fei; Springer, George S.
1993-01-01
Tests were performed measuring the locations and geometries of delaminations in Fiberite T300/976 graphite/epoxy, Fiberite IM7/977-2 graphite-toughened epoxy, and ICI APC-2 graphite/PEEK plates subjected to transverse impact loads. The data provide specific information on the effects of impactor velocity, impactor mass, material, thickness of back ply group, difference in fiber orientation between adjacent ply groups, plate thickness, and impactor nose radius. The data were compared to the results of the Finn-Springer model. The model was found to describe the data with reasonable accuracy.
FAN Jing-yu; ZHANG Yan; WANG Dao-zeng
2009-01-01
The vortex formation and entrainment characteristics for a round transverse jet in shallow water were experimentally investigated by means of a combination of LIF flow visualization and PIV measurement. A scarf vortex wrapped around the main body of the jet is formed in the near-wall region due to the interaction between the resulting wall jet and sufficiently shallow crossflow, with some more or less unsteady flow properties and with spreading ranges as functions of both the velocity ratio and the water depth within the near field. The entrainment of the ambient crossflow fluid into the jet main body is closely associated with the time-evolving features of the shear layer between the jet and surrounding fluid as well as the induced vortical structures near the wall. In the case of slight impingement upon the wall, the interaction between the jet shear layer and the weak, unstable scarf vortex gives rise to an appreciable local entrainment enhancement, confined in the near-wall region in the vicinity of the stagnation point. While in the case of intense impingement upon the wall, the well-organized and stable scarf vortex gives rise to a greatly enhanced entrainment and a greatly increased lateral spreading rate nearly throughout the overall near field as compared to the conventional wall jet. In addition, the entrainment of the ambient crossflow fluid by the scarf vortex in this case occurs largely on the surface of the unique spiral roller structure by itself due to the presence of smaller and unorganized eddies, and accordingly the scarf vortex is likely to keep its spiral roller structure steadily to a relatively great downstream distance within the near field.
Ambient Air Quality Data Inventory
U.S. Environmental Protection Agency — The Office of Air and Radiation??s (OAR) Ambient Air Quality Data (Current) contains ambient air pollution data collected by EPA, other federal agencies, as well as...
Ambient Air Quality Data Inventory
U.S. Environmental Protection Agency — The Office of Air and Radiation's (OAR) Ambient Air Quality Data (Current) contains ambient air pollution data collected by EPA, other federal agencies, as well as...
NIF Ambient Vibration Measurements
LLNL has an ongoing research and development project that includes developing data acquisition systems with remote wireless communication for monitoring the vibrations of large civil engineering structures. In order to establish the capability of performing remote sensing over an extended period of time, the researchers needed to apply this technology to a real structure. The construction of the National Ignition Facility provided an opportunity to test the data acquisition system on a large structure to monitor whether the facility is remaining within the strict ambient vibration guidelines. This document will briefly discuss the NIF ambient vibration requirements and summarize the vibration measurements performed during the Spring and Summer of 1999. In addition, a brief description of the sensors and the data acquisition systems will be provided in Appendix B
Ground motion in the presence of complex topography: Earthquake and ambient noise sources
Hartzell, Stephen; Meremonte, Mark; Ramírez-Guzmán, Leonardo; McNamara, Daniel
2014-01-01
To study the influence of topography on ground motion, eight seismic recorders were deployed for a period of one year over Poverty Ridge on the east side of the San Francisco Bay Area, California. This location is desirable because of its proximity to local earthquake sources and the significant topographic relief of the array (439 m). Topographic amplification is evaluated as a function of frequency using a variety of methods, including reference‐site‐based spectral ratios and single‐station horizontal‐to‐vertical spectral ratios using both shear waves from earthquakes and ambient noise. Field observations are compared with the predicted ground motion from an accurate digital model of the topography and a 3D local velocity model. Amplification factors from the theoretical calculations are consistent with observations. The fundamental resonance of the ridge is prominently observed in the spectra of data and synthetics; however, higher‐frequency peaks are also seen primarily for sources in line with the major axis of the ridge, perhaps indicating higher resonant modes. Excitations of lateral ribs off of the main ridge are also seen at frequencies consistent with their dimensions. The favored directions of resonance are shown to be transverse to the major axes of the topographic features.
Resolution enhancement of slam using transverse wave
We studied the resolution enhancement of a novel scanning laser acoustic microscope (SLAM) using transverse waves. Mode conversion of the ultrasonic wave takes place at the liquid-solid interface and some energy of the insonifying longitudinal waves in the water will convert to transverse wave energy within the solid specimen. The resolution of SLAM depends on the size of detecting laser spot and the wavelength of the insonifying ultrasonic waves. Since the wavelength of the transverse wave is shorter than that of the longitudinal wave, we are able to achieve the high resolution by using transverse waves. In order to operate SLAM in the transverse wave mode, we made wedge for changing the incident angle. Our experimental results with model 2140 SLAM and an aluminum specimen showed higher contrast of the SLAM Image In the transverse wave mode than that in the longitudinal wave mode.
Salud ambiental: conceptos y actividades
Ordóñez Gonzalo A.
2000-01-01
La finalidad del trabajo es aportar información y propuestas conceptuales que faciliten la tarea de quienes tienen a su cargo la sistematización institucional de la salud ambiental. Se hace un análisis de la noción de "ambiente" para la cual se sugiere una definición, y se examina el lugar de la salud ambiental en el contexto de los problemas ambientales y sus vertientes "verde" y "azul". Se examinan denominaciones equivalentes de salud ambiental y se introducen los servicios de salud ambient...
Transverse Laplacians for Substitution Tilings
Julien, Antoine
2009-01-01
Pearson and Bellissard recently built a spectral triple - the data of Riemanian noncommutative geometry - for ultrametric Cantor sets. They derived a family of Laplace-Beltrami like operators on those sets. Motivated by the applications to specific examples, we revisit their work for the transversals of tiling spaces, which are particular self-similar Cantor sets. We use Bratteli diagrams to encode the self-similarity, and Cuntz-Krieger algebras to implement it. We show that the abscissa of convergence of the zeta-function of the spectral triple gives indications on the exponent of complexity of the tiling. We determine completely the spectrum of the Laplace-Beltrami operators, give an explicit method of calculation for their eigenvalues, compute their Weyl asymptotics, and a Seeley equivalent for their heat kernels.