Assessing Doppler velocities of Rankin Inlet F-region echoes

Doppler velocities observed by the Rankin Inlet （RKN） PolarDARN radar are assessed with a focus on data in the beams oriented roughly along the magnetic meridian. Hourly scatter plots for every month are built. They are shown to vary widely, with median values showing very clear magnetic local time variation with maximum magnitude during pre-noon and pre-midnight hours. The histograms contain a significant amount of very small velocity data that dominates at farther ranges and during the daytime. Near noon data show generally antisunward flows but at large ranges/magnetic latitudes and very close to noon, sunward flows occur for periods of positive IMF Bz. The reverse flows are stronger during spring equinox. The velocity magnitude was found to depend linearly on the IMF Be and interplanetary electric field. Velocities are often found to be smaller than those expected from the statistical convection model of Ruohoniemi and Greenwald -1996.

Mapping sea surface velocities in the Changjiang coastal zone with advanced synthetic aperture radar

Range Doppler velocities derived from the Envisat advanced synthetic aperture radar（ASAR） wide swath images are analyzed and assessed against the numerically simulated surface current fields derived from the finite volume coastal ocean model（FVCOM） for the Changjiang Estuary. Comparisons with the FVCOM simulations show that the European Space Agency（ESA） Envisat ASAR based Doppler shift anomaly retrievals have the capability to capture quantitative information of the surface currents in the Changjiang Estuary. The uncertainty analysis of the ASAR range Doppler velocity estimates are discussed with regard to the azimuthal and range bias corrections, radar incidence angles, inaccuracy in the wind field corrections and the presence of rain cells.The corrected range Doppler velocities for the Changjiang Estuary area are highly valuable as they exhibit quantitative expressions related to the multiscale upper layer dynamics and surface current variability around the East China Sea, including the Changjiang Estuary.

Preliminarily study of Saturn’s upper atmosphere density by observing Cassini plunging via China’s deep space station

When the Cassini spacecraft finally plunged into the Saturnian atmosphere on 2017 September15,China’s deep space telescope pointed to Saturn to observe Cassini and study the Saturnian upper neutral atmosphere.In this first Chinese Saturnian radio science experiment,X band Doppler velocity radio science data between the deep space telescope and the Cassini spacecraft were obtained.After removing Saturnian and solar gravity effects,Earth rotation effect,the remaining Saturnian atmosphere drag information was retrieved in the Cassini final plunge progress.Saturn’s upper neutral atmosphere mass density profile is approximately estimated based on atmosphere mass density derived principally by real orbit measurement data.Saturn’s upper neutral atmosphere mass density from 76000 km to 1400 km is estimated from the orbit measurement data,the mass density results are about from 1.4×10^-15 kg cm^-3 to 2.5×10^-14 kg cm^-3.

Portal hemodynamics in cirrhotics with portal hypertension using color Doppler velocity profile

Objective To investigate portal hemodynamics and its correlation with e sophageal variceal bleeding (EVB) in cirrhotics with portal hypertension by usin g a newlydeveloped technique, color Doppler velocity profile (CDVP) Methods Hemodynamics of portal trunk (PT), right anterior branch (RAB) and splenic vein (SV) were evaluated in 48 cirrhotics with portal hypertension a nd 35 normal volunteers by CDVP The parameters included maximum crosssection a l velocity (CSVmax), flow volume, congestion index (CI), profile parameter N a nd pattern of flow curve Stepwise logistic regression model was employed to de termine EVBrelating factors in cirrhotics Results CSVmax in PT and RAB was significantly lower in cirrhotic gro up than that of normal group, being 1491308?cm/s, 944270?cm/s vs 3 052 675?cm/s, 1282269?cm/s, respectively ( P <001 for both) Fl ow volume of PT and SV was significantly higher in cirrhotic group compared with that of normal group, being 25161048?mlmin1kg1, 15 8 3918?mlmin1kg1 vs 2043557?mlmin1kg 1, 581 204?mlmin1kg1, respectively ( P <001 for bo th) C I of PT,RAB and SV was significantly higher in cirrhotic group than in normal gr oup, being 014200654, 010500496, 0088400431 vs 003260014 2, 0075 700342, 0048300230, respectively ( P <001 for all) In d ynami c variation of flow volume over time, RAB and SV in cirrhotic group increasingly presented flat pattern and periodically changed pattern, respectively ( P <001 for both) Between cirrhotic subgroups without and with EVB histor y, there were significant differences in flow volume, CI and N value of SV, splenic size, degree of esophageal varices (EV) and portal hypertensive gastropathy (PH G), and stepwise logistic regression revealed that N value of SV, splenic size, degree of EV and PHG were four independent factors in relation to EVB EVB sco r es calculated from the regression equation had a close correlation with EVB I n patients with EVB score>0, 889% of them had EVB, and in those with EVB<0, 76 9% of them had no history of EVB Conclusion In cirrhotics with portal hypertension, portal venous system has the features of elevated vascular resistance and hyperdynamics, and the lat ter mainly results from increased blood flow in SV EVB score may become a val uable parameter in predicting occurrence of EVB

Noise reduction in LOS wind velocity of Doppler lidar using discrete wavelet analysis

The line of sight (LOS) wind velocity can be determined from the incoherent Doppler lidar backscattering signals. Noise and interference in the measurement greatly degrade the inversion accuracy. In this paper, we apply the discrete wavelet denoising method by using biorthogonal wavelets and adopt a distance-dependent thresholds algorithm to improve the accuracy of wind velocity measurement by incoherent Doppler lidar. The noisy simulation data are processed and compared with the true LOS wind velocity. The results are compared by the evaluation of both the standard deviation and correlation coefficient. The results suggest that wavelet denoising with distance-dependent thresholds can considerably reduce the noise and interfering turbulence for wind lidar measurement.

Parameters Design of Pull-off Deceptive Jamming to Terminal Guidance Radar

A deceptive pull-off jamming method to terminal guidance radar is put forward in this paper.The design rules about the important jamming parameters are discussed in detail,including the number of the decoy targets in range dimension,the velocity of the range gate pull-off,and the number of the decoy targets in velocity dimension and the velocity of the Doppler frequency pull-off.Also,the steps to design these parameters are brought out.The rules and design procedure discussed in this paper have important meaning for the choice of the reasonable jamming parameters in the practical applications,which can help to obtain good jamming effect.

Doppler effect in high-speed rail seismic wavefield and its application

We demonstrate by theoretical analysis that periodically distributed viaduct piers of high-speed rail result in the Doppler effect in the seismic wavefield of high-speed rail at specific frequencies and analyze the Doppler effect’s influence on the wavefield’s spectrum feature.We further verify our theoretical prediction by using observational data of the high-speed rail seismic wavefield in Rongcheng,Hebei Province,China.We find that the wavefield component with a noticeable Doppler effect vibrates in the propagation direction and only has a unique apparent wave speed,indicating that P-wave is dominant.Furthermore,we propose a speed measurement method based on the Doppler effect and measure the wave speed of the medium along the rail.Measurement results are highly stable and consistent.

VERTICAL VELOCITY DISTRIBUTION IN STEADY NON-UNIFORM AND UNSTEADY OPEN-CHANNEL FLOW

Based on the continuity equation, the distribution of vertical velocity in equilibrium steady non-uniform and unsteady open-channel flows were deduced theoretically. Then a recently developed Acoustic Doppler Velocity Profiler (ADVP) at the Swiss Federal Institute of Technology was used to measure instantaneously the flow profiles. From these measurements, the vertical velocity and the other flow parameters were obtained. Additional data measured using an Acoustic Doppler Velocimeter (ADV) at the Nanyang Technological University were also presented. The agreement between the theoretical distribution of vertical velocity and the measured data is reasonably good.

Analysis of the Microphysical Properties of a Stratiform Rain Event Using an L-Band Profiler Radar

This paper investigates spatial and temporal distributions of the microphysical properties of precipitating stratiform clouds based on Doppler spectra of rain particles observed by an L-band profiler radar.The retrieval of raindrop size distributions（RSDs） is accomplished through eliminating vertical air motion and isolating the terminal fall velocity of raindrops in the observed Doppler velocity spectrum.The microphysical properties of raindrops in a broad stratiform region with weak convective cells are studied using data collected from a 1320-MHz wind profiler radar in Huayin,Shaanxi Province on 14 May 2009.RSDs and gamma function parameters are retrieved at altitudes between 700 and 3000 m above the surface,below a melting layer.It is found that the altitude of the maximum number of raindrops was closely related to the surface rain rate.The maximum number of large drops was observed at lower altitudes earlier in the precipitation event but at higher altitudes in later periods,suggesting decreases in the numbers of large and medium size raindrops.These decreases may have been caused by the breakup of larger drops and evaporation of smaller drops as they fell.The number of medium size drops decreased with increasing altitude.The relationship between reflectivity and liquid water content during this precipitation event was Z = 1.69×10~4M^（1.5）,and the relationship between reflectivity and rain intensity was Z = 256I^（1.4）.

Solids behavior in dilute zone of a CFB riser under turbulent conditions

The behavior of the solid phase in the upper zone of a circulating fluidized bed riser was studied using a phase Doppler anemometer. Glass particles of mean diameter 107μm and superficial gas velocities UE covering the turbulent and the beginning of the fast fluidization regime were investigated. Three static bed heights were tested. Ascending and descending particles were found co-existing under all oper ating conditions tested, and at all measurement locations. Superficial gas velocity proved/happened to have a larger effect on descending particles at the wall and on ascending particles in the central region. Transversal particle velocities in both directions （toward the center and toward the wall） behaved rela- tively equivalently, with only slight difference observed at the wall. However, observation of the number of particles moving in either transversal direction showed a change in bed structure when increasing Ug. Furthermore, a balance was constantly observed between the core zone and the annulus zone where the mutual mass transfer between these two zones occurred continuously. Transition from a slow to a fast particle motion was accompanied by a transition to high levels of velocity fluctuations, and was found corresponding to the appearance of significant solid particle flow rate.