scholarly journals Application of Subspace-Based Detection Algorithm to Infrasound Signals in Volcanic Areas

2021 ◽  
Vol 8 ◽  
Author(s):  
Mariangela Sciotto ◽  
Placido Montalto
Keyword(s):  
Cross Correlation ◽  
Confusion Matrix ◽  
Detection Threshold ◽  
Detection Algorithm ◽  
Volcano Monitoring ◽  
Signal Subspace ◽  
Long Time ◽  
Time Average ◽  
Short Time ◽  
Correlation Detector

Infrasonic signals investigation plays a fundamental role for both volcano monitoring purpose and the study of the explosion dynamics. Proper and reliable detection of weak signals is a critical issue in active volcano monitoring. In particular, in volcanic acoustics, it has direct consequences in pinpointing the real number of generated events (amplitude transients), especially when they exhibit low amplitude, are close in time to each other, and/or multiple sources exist. To accomplish this task, several algorithms have been proposed in literature; in particular, to overcome limitations of classical approaches such as short-time average/long-time average and cross-correlation detector, in this paper a subspace-based detection technique has been implemented. Results obtained by applying subspace detector on real infrasound data highlight that this method allows sensitive detection of lower energy events. This method is based on a projection of a sliding window of signal buffer onto a signal subspace that spans a collection of reference signals, representing similar waveforms from a particular infrasound source. A critical point is related to subspace design. Here, an empirical procedure has been applied to build the signal subspace from a set of reference waveforms (templates). In addition, in order to determine detectors parameters, such as subspace dimension and detection threshold, even in presence of overlapped noise such as infrasonic tremor, a statistical analysis of noise has been carried out. Finally, the subspace detector reliability and performance, have been assessed by performing a comparison among subspace approach, cross-correlation detector and short-time average/long-time average detector. The obtained confusion matrix and extrapolated performance indices have demonstrated the potentiality, the advantages and drawbacks of the subspace method in tracking volcanic activity producing infrasound events. This method revealed to be a good compromise in detecting low-energy and very close in time events recorded during Strombolian activity.

scholarly journals Comparison of sound velocity estimation and classification methods for ultrasonic testing of cheese

2016 ◽  
Vol 12 (1) ◽  
pp. 51-62
Author(s):  
I. Kertész ◽  
J. Felföldi
Keyword(s):  
Wavelet Decomposition ◽  
Information Criterion ◽  
Velocity Estimation ◽  
Classification Methods ◽  
New Approach ◽  
Linear Discriminant ◽  
Ultrasonic Measurements ◽  
Long Time ◽  
Time Average ◽  
Short Time

Testing of two methods novel to ultrasonic measurements was carried out on cheese samples to estimate the Time-of-Flight (TOF) parameter. The Short Time Average/Long Time Average (STA/LTA) method and the Autoregressive Akaike Information Criterion Picker (AR-AIC picker) method are used mainly in seismology for earthquake event detection. The STA/LTA method proved to be ineffective with such noise level that is present during ultrasonic measurements, but the AIC picker algorithm yielded reliable results. A new approach for classification was tested on two types of samples, those were matching in composition, but different in treatment and texture. The method used is based on the results of wavelet decomposition, and after retrieving sufficient spectral data, a linear discriminant analysis (DA) resulted in 100% correct classification, which was compared to the DA classification results based on other methods.

STRUCTURE AND DYNAMICAL PROPERTIES OF AuN, N = 12–14 CLUSTERS: MOLECULAR DYNAMICS SIMULATION

2005 ◽  
Vol 16 (01) ◽  
pp. 99-116 ◽  
Author(s):  
ERDEM K. YILDIRIM ◽  
MURAT ATİŞ ◽  
ZİYA B. GÜVENÇ
Keyword(s):  
Molecular Dynamics ◽  
Thermal Quenching ◽  
Melting Behavior ◽  
Dynamics Simulation ◽  
Embedded Atom Method ◽  
Coordination Numbers ◽  
Embedded Atom ◽  
Long Time ◽  
Time Average ◽  
Short Time

Using molecular dynamics and thermal quenching methods on the basis of Voter–Chen version of the embedded-atom method, we have studied the melting behavior of Au N (N = 12, 13, 14) clusters. This behavior is described in terms of overall and atom resolved root-mean-square bond-length fluctuations, specific-heat, short- and long-time average coordination numbers of each atom and short-time average temperatures of the clusters. The isomer sampling probabilities are obtained from the thermal quenching of the molten clusters, and their energy-spectrum widths are investigated. Phase change of a cluster takes place with the collective and simultaneous motion of all the atoms.

scholarly journals An improved method for hydrofracture-induced microseismic event detection and phase picking

Geophysics ◽  
2010 ◽  
Vol 75 (6) ◽  
pp. A47-A52 ◽  
Author(s):  
Fuxian Song ◽  
H. Sadi Kuleli ◽  
M. Nafi Toksöz ◽  
Erkan Ay ◽  
Haijiang Zhang
Keyword(s):  
Matched Filter ◽  
S Phase ◽  
Data Set ◽  
Small Magnitude ◽  
Long Time ◽  
Time Average ◽  
Short Time ◽  
Master Event ◽  
Microseismic Event ◽  
Downhole Monitoring

The ability to detect small microearthquakes and identify their P- and S-phase arrivals is a key issue in hydrofracture downhole monitoring because of the low signal-to-noise ratios (S/N). An array-based waveform correlation approach (matched filter) is applied to improve the detectability of small magnitude events with mechanisms and locations similar to a nearby master event. After detecting the weak events, a transformed spectrogram method is used to identify the phase arrivals. The technique has been tested on a downhole monitoring data set of the microseismic events induced by hydraulic fracturing. It is shown that, for this case, one event with a S/N around [Formula: see text], which is barely detectable using an array-stacked short-time average/long-time average (STA/LTA) detector under a reasonable false alarm rate, is readily detected on the array-stacked correlation traces. The transformed spectrogram analysis of the detected events improves P- and S-phase picking.

Small Floating Target Detection Algorithm Based on Time-Frequency Similarity

2014 ◽  
Vol 1030-1032 ◽  
pp. 1805-1809
Author(s):  
Jin Jiang ◽  
Ming Li ◽  
Yan Shen ◽  
Chong Yi Li
Keyword(s):  
Target Detection ◽  
Average Power ◽  
Detection Algorithm ◽  
Observation Time ◽  
Similarity Analysis ◽  
Mean Square ◽  
Time Frequency ◽  
Radar Echo ◽  
Time Average ◽  
Short Time

The features of radar echo of small floating target within sea clutter exists not only in target bins, but also exist in extend range bins. These lead to certain characteristic are similar between targets and extend bins. Short-time average power and mean-square Doppler bandwidth are extracted as two of these features and their similarities are been proved existing between target bin and extend bins by IPIX data. Although clutter bins may also have this similarity, it could be distinguished when observation time is enhanced. According to this characteristic, a detection algorithm is proposed based on time-frequency similarity analysis, the method works well when the average signal clutter ratio is about 5dB and the observation time is 300ms.

scholarly journals Representation of Multiple Acoustic Sources in a Virtual Image of the Field of Audition from Binaural Synthetic Aperture Processing as the Head is Turned

Robotics ◽  
2018 ◽  
Vol 8 (1) ◽  
pp. 1
Author(s):  
Duncan Tamsett
Keyword(s):  
Cross Correlation ◽  
World View ◽  
Synthetic Aperture ◽  
Time Base ◽  
Virtual Image ◽  
Acoustic Image ◽  
Long Time ◽  
Ongoing Development ◽  
Acoustic Sources ◽  
Short Time

The representation of multiple acoustic sources in a virtual image of the field of audition based on binaural synthetic-aperture computation (SAC) is described through use of simulated inter-aural time delay (ITD) data. Directions to the acoustic sources may be extracted from the image. ITDs for multiple acoustic sources at an effective instant in time are implied for example by multiple peaks in the coefficients of a short-time base (≈2.25 ms for an antennae separation of 0.15 m) cross correlation function (CCF) of acoustic signals received at the antennae. The CCF coefficients for such peaks at the time delays measured for a given orientation of the head are then distended over lambda circles in a short-time base instantaneous acoustic image of the field of audition. Numerous successive short-time base images of the field of audition generated as the head is turned are integrated into a mid-time base (up to say 0.5 s) acoustic image of the field of audition. This integration as the head turns constitutes a SAC. The intersections of many lambda circles at points in the SAC acoustic image generate maxima in the integrated CCF coefficient values recorded in the image. The positions of the maxima represent the directions to acoustic sources. The locations of acoustic sources so derived provide input for a process managing the long-time base (>10s of seconds) acoustic image of the field of audition representing the robot’s persistent acoustic environmental world view. The virtual images could optionally be displayed on monitors external to the robot to assist system debugging and inspire ongoing development.

Short-Time Tests for Long-Time Endurance

1923 ◽  
Vol 128 (4) ◽  
pp. 264-264
Author(s):  
J. W. Harsch
Keyword(s):  
Long Time ◽  
Short Time

Effect of Vial shaking on Loading Time of Epirubicin into Drug-Eluting Bead

2015 ◽  
Vol 5 (3) ◽  
Author(s):  
Kenji Ikeda ◽  
Yusuke Kawamura ◽  
Masahiro Kobayashi ◽  
Taito Fukushima ◽  
Yushi Sorin ◽  
...  
Keyword(s):  
Antitumor Agent ◽  
Loading Rates ◽  
Vortex Mixer ◽  
Long Time ◽  
Group A ◽  
Drug Eluting ◽  
Large Hepatocellular Carcinoma ◽  
Group B ◽  
Time Required ◽  
Short Time

Background: Although DC Bead has been useful in treatment of multiple and large hepatocellular carcinoma, loading time of doxorubicin into the DC Bead takes a long time of 30-120 minutes. Epirubicin is also used as an antitumor agent together with DC Bead, but its loading efficiency was not sufficiently elucidated. Methods: To shorten loading time of epirubicin into DC Bead (100-300µm, 300-500µm, 500-700µm), we examined the following three methods after mixing the drug: (a) let stand in room temperature, (b) agitated for 30 seconds with Vortex mixer, and (c) sonicated for 30 seconds with ultrasonic cleaner. After loading of epirubicin by each method, supernatant concentration for epirubicin was assayed at 5, 10, 30, 60, and 120 minutes. Results: Epirubicin loading rates for small bead (100-300µm) at 5 minutes were 82.9 % in group a, 93.8% in group b, and 79.9 % in group c. Similarly, medium bead (300-500µm), 40.1% in group a, 65.7% in group b and 45.5% in group c, respectively. In large-sized bead (500-700µm), loaded rates of epirubicin were 38.8% in group a, 59.0% in group b and 48.0% in group c. Agitation of mixture of epirubicin and DC Bead with Vortex mixer significantly shortened the loading time, but sonication did not affect the time required. Microscopic examination did not lead to any morphological change of microspheres in all the methods. Conclusions: Short time of agitation with Vortex mixer reduced the necessary time for loading of epirubicin in every standard of DC Bead.

Robust Test Method of TSOP PEMs for Space Application

2019 ◽  
Author(s):  
Yasunobu Iwai ◽  
Koichi Shinozaki ◽  
Daiki Tanaka
Keyword(s):  
Evaluation Method ◽  
Low Cost ◽  
Reliability Evaluation ◽  
Test Method ◽  
Thermal Shock Test ◽  
Space Application ◽  
Space Applications ◽  
Limit Test ◽  
Long Time ◽  
Short Time

Abstract Compared with space parts, consumer parts are highly functional, low cost, compact and lightweight. Therefore, their increased usage in space applications is expected. Prior testing and evaluation on space applicability are necessary because consumer parts do not have quality guarantees for space application [1]. However, in the conventional reliability evaluation method, the test takes a long time, and the problem is that the robustness of the target sample can’t be evaluated in a short time. In this report, we apply to the latest TSOP PEM (Thin Small Outline Package Plastic Encapsulated Microcircuit) an evaluation method that combines preconditioning and HALT (Highly Accelerated Limit Test), which is a test method that causes failures in a short time under very severe environmental conditions. We show that this method can evaluate the robustness of TSOP PEMs including solder connections in a short time. In addition, the validity of this evaluation method for TSOP PEM is shown by comparing with the evaluation results of thermal shock test and life test, which are conventional reliability evaluation methods.

The Spread of Pollutants from Harbour Sludge Depots

1984 ◽  
Vol 16 (3-4) ◽  
pp. 623-633
Author(s):  
M Loxham ◽  
F Weststrate
Keyword(s):  
Time Scales ◽  
Molecular Diffusion ◽  
Near Field ◽  
Parameter Analysis ◽  
Migration Patterns ◽  
Long Time ◽  
Dilution Effects ◽  
Short Time ◽  
Harbour Sludge

It is generally agreed that both the landfill option, or the civil techniques option for the final disposal of contaminated harbour sludge involves the isolation of the sludge from the environment. For short time scales, engineered barriers such as a bentonite screen, plastic sheets, pumping strategies etc. can be used. However for long time scales the effectiveness of such measures cannot be counted upon. It is thus necessary to be able to predict the long term environmenttal spread of contaminants from a mature landfill. A model is presented that considers diffusion and adsorption in the landfill site and convection and adsorption in the underlaying aquifer. From a parameter analysis starting form practical values it is shown that the adsorption behaviour and the molecular diffusion coefficient of the sludge, are the key parameters involved in the near field. The dilution effects of the far field migration patterns are also illustrated.

Alteration of intrapancreatic serotonin, homocysteine, TNF-α, and NGF levels as predisposing factors for diabetes following exposure to 900-MHz waves

2021 ◽  
pp. 074823372110226
Author(s):  
Gholamali Jelodar ◽  
Mansour Azimzadeh ◽  
Fatemeh Radmard ◽  
Narges Darvishhoo
Keyword(s):  
Cell Damage ◽  
Pancreatic Beta Cell ◽  
Predisposing Factors ◽  
Male Rats ◽  
Control Group ◽  
Predisposing Factor ◽  
Time Exposure ◽  
Tnf Α ◽  
Long Time ◽  
Short Time

Exposure to mobile phone radiation causes deleterious health effects on biological systems. The objects of this study were to investigate the effect of 900-MHz radiofrequency waves (RFW) emitted from base transceiver station antenna on intrapancreatic homocysteine (Hcy), tumor necrosis factor-α (TNF-α), and nerve growth factor (NGF) as predisposing factors involved in pancreatic beta cell damage. Thirty male rats (Sprague-Dawley, 200 ± 10 g) were randomly divided into the control (without any exposure) and exposed groups: short time (2 h/day), long time (4 h/day), and exposed to 900-MHz RFW for 30 consecutive days. On the last days of the experiment, animals were killed and pancreas tissue was dissected out for evaluation of serotonin, Hcy, TNF-α, and NGF. There was a significant decrease in the serotonin and NGF levels in the pancreatic tissue of exposed groups compared to the control group ( p < 0.05). Also, the levels of serotonin and NGF in the long-time exposure were significantly lower than the short-time exposure ( p < 0.05). However, levels of Hcy and TNF-α were significantly increased in the pancreas of exposed groups compared to the control groups ( p < 0.05). Exposure to 900-MHz RFW decreased pancreatic NGF and serotonin levels and increased the proinflammatory markers (Hcy and TNF-α), which can be a predisposing factor for type 2 diabetes.

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