Very-small-aperture 3D infrasonic array for volcanic jet observation at Stromboli Volcano

2021 ◽  
Author(s):  
Kazuya Yamakawa ◽  
Mie Ichihara ◽  
Giorgio Lacanna ◽  
Claudia Sánchez ◽  
Maurizio Ripepe
Keyword(s):  
Elevation Angle ◽  
Three Dimensional ◽  
Synthetic Data ◽  
Stromboli Volcano ◽  
Music Algorithm ◽  
Small Aperture ◽  
Planar Array ◽  
Back Azimuth ◽  
Frequency Functions ◽  
Volcanic Jet

Summary This study tested a very-small-aperture three-dimensional (VSA-3D) infrasonic array. A 3D array is ideal for resolving the back elevation angle (BEL), which has become important in the analysis of volcanic jet noise or geologic flows on steep mountain slopes. Although a VSA infrasonic array, with an aperture as small as a few tens of meters, has recently been shown to have a sufficient resolution of the back azimuth (BAZ) of incident signals, its BEL resolution is considered to be poor. We performed a four-element 3D array experiment with a 20-m aperture and 2-m height at the summit of Stromboli Volcano. We analyzed the direction of arrival (DOA) with the MUSIC algorithm as a function of frequency and conducted a cluster analysis for the estimated DOA–frequency functions of eruption signals. As a result, individual infrasonic signals were successfully related to eruptive vents. We also calculated the standard deviation (STD) of the DOAs in each cluster. Of the observed BAZ-STDs and BEL-STDs, 80 per cent were <2.0° and <4.6°, respectively. A comparison among the array geometries showed that the installation of a sensor above the ground, even at only 2 m, improved the BEL resolution, indicating that the VSA-3D array provides more detailed information about the wavefield than a planar array. The observed signals had higher BELs (−20° to 0°) than the vent direction (−30° to −25°) at 3–6 Hz, although signals above 20 Hz arrived from the vent direction. Our array verified that such DOA deviations were significant by the STD analysis and some tests with synthetic data. We infer that the DOA deviations do not indicate the source location and are caused by topographical diffraction.

scholarly journals A flexible framework for sequential estimation of model parameters in computational hemodynamics

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Christopher J. Arthurs ◽  
Nan Xiao ◽  
Philippe Moireau ◽  
Tobias Schaeffter ◽  
C. Alberto Figueroa
Keyword(s):  
Unscented Kalman Filter ◽  
Three Dimensional ◽  
Synthetic Data ◽  
Sequential Estimation ◽  
Wall Material ◽  
Patient Specific ◽  
Model Parameters ◽  
Computational Framework ◽  
Lumped Parameter ◽  
Estimation Of Model Parameters

AbstractA major challenge in constructing three dimensional patient specific hemodynamic models is the calibration of model parameters to match patient data on flow, pressure, wall motion, etc. acquired in the clinic. Current workflows are manual and time-consuming. This work presents a flexible computational framework for model parameter estimation in cardiovascular flows that relies on the following fundamental contributions. (i) A Reduced-Order Unscented Kalman Filter (ROUKF) model for data assimilation for wall material and simple lumped parameter network (LPN) boundary condition model parameters. (ii) A constrained least squares augmentation (ROUKF-CLS) for more complex LPNs. (iii) A “Netlist” implementation, supporting easy filtering of parameters in such complex LPNs. The ROUKF algorithm is demonstrated using non-invasive patient-specific data on anatomy, flow and pressure from a healthy volunteer. The ROUKF-CLS algorithm is demonstrated using synthetic data on a coronary LPN. The methods described in this paper have been implemented as part of the CRIMSON hemodynamics software package.

Detection and source parameterization of small-energy fireball events in Western Alps with ground-based infrasonic arrays

2021 ◽  
Author(s):  
Giacomo Belli ◽  
Emanuele Pace ◽  
Emanuele Marchetti
Keyword(s):  
Western Alps ◽  
Apparent Velocity ◽  
Array Analysis ◽  
Small Energy ◽  
Small Aperture ◽  
Energy Estimation ◽  
Trajectory Reconstruction ◽  
Tnt Equivalent ◽  
Back Azimuth ◽  
Aperture Arrays

Summary We present infrasound signals generated by four fireball events occurred in Western Alps between 2016 and 2019 and that were recorded by small aperture arrays at source-to receiver distances < 300 km. Signals consist in a series of short-lived infrasonic arrivals that are closely spaced in time. Each arrival is identified as a cluster of detections with constant wave parameters (back-azimuth and apparent velocity), that change however from cluster to cluster. These arrivals are likely generated by multiple infrasonic sources (fragmentations or hypersonic flow) along the entry trajectory. We developed a method, based on 2D ray-tracing and on the independent optically determined time of the event, to locate the source position of the multiple arrivals from a single infrasonic array data and to reconstruct the 3D trajectory of a meteoroid in the Earth's atmosphere. The trajectories derived from infrasound array analysis are in excellent agreement with trajectories reconstructed from eyewitnesses reports for the four fireballs. Results suggest that the trajectory reconstruction is possible for meteoroid entries located up to ∼300 km from the array, with an accuracy that depends on the source-to-receiver distance and on the signal-to-noise level. We also estimate the energy of the four fireballs using three different empirical laws, based both on period and amplitude of recorded infrasonic signals, and discuss their applicability for the energy estimation of small energy fireball events ($\le 1{\rm{kt\,\,TNT\,\,equivalent}}$).

Large‐scale three‐dimensional seismic models and their interpretive significance

Geophysics ◽  
1990 ◽  
Vol 55 (9) ◽  
pp. 1166-1182 ◽  
Author(s):  
Irshad R. Mufti
Keyword(s):  
Finite Difference ◽  
Wave Field ◽  
Large Scale ◽  
Three Dimensional ◽  
Synthetic Data ◽  
Real Data ◽  
The Real ◽  
Need To Evaluate ◽  
Zero Offset ◽  
Seismic Models

Finite‐difference seismic models are commonly set up in 2-D space. Such models must be excited by a line source which leads to different amplitudes than those in the real data commonly generated from a point source. Moreover, there is no provision for any out‐of‐plane events. These problems can be eliminated by using 3-D finite‐difference models. The fundamental strategy in designing efficient 3-D models is to minimize computational work without sacrificing accuracy. This was accomplished by using a (4,2) differencing operator which ensures the accuracy of much larger operators but requires many fewer numerical operations as well as significantly reduced manipulation of data in the computer memory. Such a choice also simplifies the problem of evaluating the wave field near the subsurface boundaries of the model where large operators cannot be used. We also exploited the fact that, unlike the real data, the synthetic data are free from ambient noise; consequently, one can retain sufficient resolution in the results by optimizing the frequency content of the source signal. Further computational efficiency was achieved by using the concept of the exploding reflector which yields zero‐offset seismic sections without the need to evaluate the wave field for individual shot locations. These considerations opened up the possibility of carrying out a complete synthetic 3-D survey on a supercomputer to investigate the seismic response of a large‐scale structure located in Oklahoma. The analysis of results done on a geophysical workstation provides new insight regarding the role of interference and diffraction in the interpretation of seismic data.

Modeling Interactive Behaviors While Learning With Digitized Objects in Virtual Reality Environments

2020 ◽  
pp. 215-234
Author(s):  
Eric Poitras ◽  
Kirsten R. Butcher ◽  
Matthew P. Orr
Keyword(s):  
Learning Environments ◽  
Time Series Data ◽  
Three Dimensional ◽  
Synthetic Data ◽  
Virtual Learning ◽  
Virtual Learning Environments ◽  
Series Data ◽  
Student Behaviors ◽  
Virtual Models ◽  
Interaction Behaviors

This chapter outlines a framework for automated detection of student behaviors in the context of virtual learning environments. The components of the framework establish several parameters for data acquisition, preprocessing, and processing as a means to classify different types of behaviors. The authors illustrate these steps in training and evaluating a detector that differentiates between students' observations and functional behaviors while students interact with three-dimensional (3D) virtual models of dinosaur fossils. Synthetic data were generated in controlled conditions to obtain time series data from different channels (i.e., orientation from the virtual model and remote controllers) and modalities (i.e., orientation in the form of Euler angles and quaternions). Results suggest that accurate detection of interaction behaviors with 3D virtual models requires smaller moving windows to segment the log trace data as well as features that characterize orientation of virtual models in the form of quaternions. They discuss the implications for personalized instruction in virtual learning environments.

scholarly journals Stereological Estimation of Orientation Distribution of Generalized Cylinders from a Unique 2D Slice

2013 ◽  
Vol 19 (6) ◽  
pp. 1678-1687 ◽  
Author(s):  
Jean-Pierre Da Costa ◽  
Stefan Oprean ◽  
Pierre Baylou ◽  
Christian Germain
Keyword(s):  
Cross Sections ◽  
Composite Structures ◽  
Large Scale ◽  
Fibrous Composite ◽  
Three Dimensional ◽  
Synthetic Data ◽  
Inequality Constraints ◽  
Orientation Distribution ◽  
Industrial Applications ◽  
Cost Constraints

AbstractThough three-dimensional (3D) imaging gives deep insight into the inner structure of complex materials, the stereological analysis of 2D snapshots of material sections is still necessary for large-scale industrial applications for reasons related to time and cost constraints. In this paper, we propose an original framework to estimate the orientation distribution of generalized cylindrical structures from a single 2D section. Contrary to existing approaches, knowledge of the cylinder cross-section shape is not necessary. The only requirement is to know the area distribution of the cross-sections. The approach relies on minimization of a least squares criterion under linear equality and inequality constraints that can be solved with standard optimization solvers. It is evaluated on synthetic data, including simulated images, and is applied to experimental microscopy images of fibrous composite structures. The results show the relevance and capabilities of the approach though some limitations have been identified regarding sensitivity to deviations from the assumed model.

scholarly journals A statistical analysis for pattern recognition of small cloud particles sampled with a PMS-2DC probe

1997 ◽  
Vol 15 (6) ◽  
pp. 840-846 ◽  
Author(s):  
A. Fouilloux ◽  
J. Iaquinta ◽  
C. Duroure ◽  
F. Albers
Keyword(s):  
Pattern Recognition ◽  
Statistical Analysis ◽  
Three Dimensional ◽  
Synthetic Data ◽  
Spherical Particles ◽  
Data Sets ◽  
Ice Water Content ◽  
Dimensional Shape ◽  
Exact Shape ◽  
Ice Water

Abstract. Although small particles (size between 25 µm and 200 µm) are frequently observed within ice and water clouds, they are not generally used properly for the calculation of structural, optical and microphysical quantities. Actually neither the exact shape nor the phase (ice or water) of these particles is well defined since the existing pattern recognition algorithms are only efficient for larger particle sizes. The present study describes a statistical analysis concerning small hexagonal columns and spherical particles sampled with a PMS-2DC probe, and the corresponding images are classified according to the occurrence probability of various pixels arrangements. This approach was first applied to synthetic data generated with a numerical model, including the effects of diffraction at a short distance, and then validated against actual data sets obtained from in-cloud flights during the pre-ICE'89 campaign. Our method allows us to differentiate small hexagonal columns from spherical particles, thus making possible the characterization of the three dimensional shape (and consequently evaluation of the volume) of the particles, and finally to compute e.g., the liquid or the ice water content.

Sign in / Sign up

Export Citation Format

Share Document