scholarly journals Threat object classification with a close range polarimetric imaging system by means of H-α decomposition

2014 ◽  
Vol 6 (3-4) ◽  
pp. 415-421 ◽  
Author(s):  
Julian Adametz ◽  
Lorenz-Peter Schmidt
Keyword(s):  
Imaging System ◽  
Object Classification ◽  
Calibration Procedure ◽  
Radar Data ◽  
Weighted Averaging ◽  
Polarimetric Synthetic Aperture Radar ◽  
Security Applications ◽  
Measurement Results ◽  
Close Range ◽  
Thick Layers

In this paper, an approach to differentiate between various dielectric threat objects in security applications is investigated. The scattering information in form of the Sinclair matrix of relevant scenarios is gained from a fully polarimetric, synthetic aperture radar. Both monostatic and multistatic array configurations are examined. A possible polarimetric calibration procedure is presented. The radar data are processed with the H-α decomposition algorithm. The H-α scattering characteristics of threat objects are analyzed in terms of a weighted averaging. It is shown that an object classification is possible even for threat objects conceiled under thick layers of clothing. Measurement results are presented to illustrate the topic.

The Multiple-Vortex Structure of the El Reno, Oklahoma, Tornado on 31 May 2013

2018 ◽  
Vol 146 (8) ◽  
pp. 2483-2502 ◽  
Author(s):  
Howard B. Bluestein ◽  
Kyle J. Thiem ◽  
Jeffrey C. Snyder ◽  
Jana B. Houser
Keyword(s):  
Doppler Radar ◽  
Radar Data ◽  
Rapid Scan ◽  
X Band ◽  
Close Range ◽  
Formation And Evolution ◽  
Using Data ◽  
Secondary Vortices ◽  
The Right ◽  
Gust Front

Abstract This study documents the formation and evolution of secondary vortices associated within a large, violent tornado in Oklahoma based on data from a close-range, mobile, polarimetric, rapid-scan, X-band Doppler radar. Secondary vortices were tracked relative to the parent circulation using data collected every 2 s. It was found that most long-lived vortices (those that could be tracked for ≥15 s) formed within the radius of maximum wind (RMW), mainly in the left-rear quadrant (with respect to parent tornado motion), passing around the center of the parent tornado and dissipating closer to the center in the right-forward and left-forward quadrants. Some secondary vortices persisted for at least 1 min. When a Burgers–Rott vortex is fit to the Doppler radar data, and the vortex is assumed to be axisymmetric, the secondary vortices propagated slowly against the mean azimuthal flow; if the vortex is not assumed to be axisymmetric as a result of a strong rear-flank gust front on one side of it, then the secondary vortices moved along approximately with the wind.

scholarly journals Experimental study of the dynamic behaviour of High Performance Concrete (HPC) under tensile loading

2018 ◽  
Vol 183 ◽  
pp. 02043 ◽  
Author(s):  
Bratislav Lukić ◽  
Dominique Saletti ◽  
Pascal Forquin
Keyword(s):  
High Speed ◽  
High Performance ◽  
High Performance Concrete ◽  
Imaging System ◽  
Spall Strength ◽  
High Speed Imaging ◽  
Dynamic Tensile Strength ◽  
Full Field ◽  
Local Point ◽  
Measurement Results

This paper presents the measurement results of the dynamic tensile strength of a High Performance Concrete (HPC) obtained using full-field identification method. An ultra-high speed imaging system and the virtual fields method were used to obtain this information. Furthermore the measurement results were compared with the local point-wise measurement to validate the data pressing. The obtained spall strength was found to be consistently 20% lower than the one obtained when the Novikov formula is used.

scholarly journals Three-dimensional imaging of hold baggage for airport security

2014 ◽  
Vol XL-5 ◽  
pp. 331-336
Author(s):  
S. Kolokytha ◽  
R. Speller ◽  
S. Robson
Keyword(s):  
3D Imaging ◽  
Imaging System ◽  
Tomographic Reconstruction ◽  
Three Dimensional ◽  
Handling Time ◽  
Cost Effective ◽  
Airport Security ◽  
X Ray ◽  
Common System ◽  
Close Range

This study describes a cost-effective check-in baggage screening system, based on "on-belt tomosynthesis" (ObT) and close-range photogrammetry, that is designed to address the limitations of the most common system used, conventional projection radiography. The latter's limitations can lead to loss of information and an increase in baggage handling time, as baggage is manually searched or screened with more advanced systems. This project proposes a system that overcomes such limitations creating a cost-effective automated pseudo-3D imaging system, by combining x-ray and optical imaging to form digital tomograms. Tomographic reconstruction requires a knowledge of the change in geometry between multiple x-ray views of a common object. This is uniquely achieved using a close range photogrammetric system based on a small network of web-cameras. This paper presents the recent developments of the ObT system and describes recent findings of the photogrammetric system implementation. Based on these positive results, future work on the advancement of the ObT system as a cost-effective pseudo-3D imaging of hold baggage for airport security is proposed.

Dual-Polarization Radar Data Analysis of the Impact of Ground-Based Glaciogenic Seeding on Winter Orographic Clouds. Part I: Mostly Stratiform Clouds

2015 ◽  
Vol 54 (9) ◽  
pp. 1944-1969 ◽  
Author(s):  
Xiaoqin Jing ◽  
Bart Geerts ◽  
Katja Friedrich ◽  
Binod Pokharel
Keyword(s):  
Radar Data ◽  
Control Area ◽  
Target Area ◽  
Dual Polarization ◽  
Stratiform Clouds ◽  
Orographic Clouds ◽  
Close Range ◽  
Glaciogenic Seeding ◽  
Differential Reflectivity ◽  
The Impact

AbstractThe impact of ground-based glaciogenic seeding on wintertime orographic, mostly stratiform clouds is analyzed by means of data from an X-band dual-polarization radar, the Doppler-on-Wheels (DOW) radar, positioned on a mountain pass. This study focuses on six intensive observation periods (IOPs) during the 2012 AgI Seeding Cloud Impact Investigation (ASCII) project in Wyoming. In all six storms, the bulk upstream Froude number below mountaintop exceeded 1 (suggesting unblocked flow), the clouds were relatively shallow (with bases below freezing), some liquid water was present, and orographic flow conditions were mostly steady. To examine the silver iodide (AgI) seeding effect, three study areas are defined (a control area, a target area upwind of the crest, and a lee target area), and comparisons are made between measurements from a treated period and those from an untreated period. Changes in reflectivity and differential reflectivity observed by the DOW at low levels during seeding are consistent with enhanced snow growth, by vapor diffusion and/or aggregation, for a case study and for the composite analysis of all six IOPs, especially at close range upwind of the mountain crest. These low-level changes may have been affected by natural changes aloft, however, as evident from differences in the evolution of the echo-top height in the control and target areas. Even though precipitation in the target region is strongly correlated with that in the control region, the authors cannot definitively attribute the change to seeding because there is a lack of knowledge about natural variability, nor can the outcome be generalized, because the sample size is small.

scholarly journals Mountain wave motions determined by the Esrange MST radar

1999 ◽  
Vol 17 (7) ◽  
pp. 957-970 ◽  
Author(s):  
A. Réchou ◽  
V. Barabash ◽  
P. Chilson ◽  
S. Kirkwood ◽  
T. Savitskaya ◽  
...  
Keyword(s):  
Imaging System ◽  
Weather Conditions ◽  
Radar Data ◽  
Visual Observation ◽  
Optical Measurements ◽  
Atmospheric Composition ◽  
Leeward Side ◽  
Mesoscale Meteorology ◽  
Mst Radar ◽  
Lee Waves

Abstract. A European campaign of ground-based radar, lidar and optical measurements was carried out during the winter of 1996/1997 (28 December-2 February) to study lee waves in the northern part of Scandinavia. The participants operated ozone lidars, backscatter lidars and MST radars at ALOMAR/Andoya and Esrange/Kiruna, and an ALIS imaging system in Kiruna. The Andoya site was generally windward of the Scandinavian mountains, the Kiruna site on the leeward side. The goal of the experiment was to examine the influence of lee waves on the formation of Polar Stratospheric Clouds (PSCs). This paper studies the radar data from MST-radar ESRAD located at Esrange [68.°N, 21.°E], i.e. in the lee of the mountains. We present three cases where strong lee waves were observed: in one case they propagated upwards to the lower stratosphere and in the other two cases they were trapped or absorbed in the troposphere. We examine the local waves and the direction and strength of the local wind using the radar, the synoptic meteorological situation using weather maps (European Meteorological Bulletin) and the synoptic stratospheric temperatures using ECMWF data. We observed that waves propagate up to the stratosphere during frontal passages. When anticyclonic ridges are present, the propagation to the stratosphere is very weak. This is due to trapping of the waves at or below the tropopause. We also show that the radar data alone can be used to characterise the different weather conditions for the three cases studied (through the variation of the height of the tropopause). The synoptic stratospheric temperatures in the three cases were similar, and were above the expected threshold for PSC formation. Lidar and visual observation of PSCs and nacreous clouds, respectively, showed that these were present only in the case when the lee waves propagated up to the lower stratosphere.Key words. Atmospheric composition and structure (aerosols and particles) · Electromagnetic (wave propa- gation) · Meteorology and atmospheric dynamics (mesoscale meteorology)

scholarly journals Calibration of Mangerud'S Boundaries

Radiocarbon ◽  
2010 ◽  
Vol 52 (4) ◽  
pp. 1639-1644 ◽  
Author(s):  
Adam Walanus ◽  
Dorota Nalepka
Keyword(s):  
Measurement Error ◽  
Calibration Procedure ◽  
Radiocarbon Age ◽  
Measurement Results ◽  
Standard Calibration ◽  
Typical Measurement ◽  
Natural Situation

The “calibration” of arbitrarily defined (in some sense, “conventional”) ages, given in conventional radiocarbon years BP, is now becoming necessary because the term “radiocarbon age” is used less often in archaeological and Quaternary practice. The standard calibration procedure is inappropriate here because Mangerud's boundaries are not measurement results. Thus, another approach to the problem is proposed in order to model the natural situation of many, uniformly distributed, dated samples, which should be similarly divided by the original and “calibrated” boundary. However, the result depends on the value of the typical measurement error and is not unequivocal.

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