Automatic phase pickers: Their present use and future prospects

1982 ◽  
Vol 72 (6B) ◽  
pp. S225-S242
Author(s):  
Rex Allen
Keyword(s):  
Characteristic Function ◽  
Threshold Value ◽  
Seismic Signal ◽  
Automatic Phase ◽  
False Report ◽  
Power Limits ◽  
Single Trace ◽  
Automatic Phase Picking ◽  
Measures Of Performance

abstract Automatic phase-picking algorithms are designed to detect a seismic signal on a single trace and to time the arrival of the signal precisely. Because of the requirement for precise timing, a phase-picking algorithm is inherently less sensitive than one designed only to detect the presence of a signal, but still can approach the performance of a skilled analyst. A typical algorithm filters the input data and then generates a function characterizing the seismic time series. This function may be as simple as the absolute value of the series, or it may be quite complex. Event detection is accomplished by comparing the function or its short-term average (STA) with a threshold value (THR), which is commonly some multiple of a long-term average (LTA) of a characteristic function. If the STA exceeds THR, a trigger is declared. If the event passes simple criteria, it is reported. Sensitivity, expected timing error, false-trigger rate, and false-report rate are interrelated measures of performance controlled by choice of the characteristic function and several operating parameters. At present, computational power limits most systems to one-pass, time-domain algorithms. Rapidly advancing semi-conductor technology, however, will make possible much more powerful multi-pass approaches incorporating frequency-domain detection and pseudo-offline timing.

Automatic Phase‐Picking Method for Detecting Earthquakes Based on the Signal‐to‐Noise‐Ratio Concept

2019 ◽  
Vol 91 (1) ◽  
pp. 334-342
Author(s):  
Jihua Fu ◽  
Xu Wang ◽  
Zhitao Li ◽  
Hao Meng ◽  
Jianjun Wang ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
Ratio Method ◽  
Mean Deviation ◽  
Signal To Noise ◽  
Short Term ◽  
Low Snr ◽  
Automatic Phase ◽  
Noise Ratio ◽  
Automatic Phase Picking

Abstract The automatic phase‐picking detection of earthquakes is a challenge under the background of big data and strong noise circumstances. The short‐term average/long‐term average (STA/LTA) ratio is widely used to detect earthquake due to its simplicity and robustness. However, STA/LTA‐based methods may not perform well with noisy data. Based on the signal‐to‐noise‐ratio (SNR) concept, a short‐term power/long‐term power (STP/LTP) ratio method is proposed. The characteristic function and the detection thresholds of the STP/LTP method are given physical meanings. Through a sample analysis, the STP/LTP detection results of both the P and S phases are better than the results of the STA/LTA by means of mean deviation, standard deviations, distributions of detection results, error rate, and missed rate on different SNR levels. In general, the STP/LTP method inherits the simple characteristics of the STA/LTA method, and it is suitable for phase picking of low‐SNR seismic data.

scholarly journals Long-term analysis of clear-sky new particle formation events and non-events in Hyytiälä

2016 ◽  
Author(s):  
Lubna Dada ◽  
Pauli Paasonen ◽  
Tuomo Nieminen ◽  
Stephany Buenrostro Mazon ◽  
Jenni Kontkanen ◽  
...  
Keyword(s):  
Formation Rate ◽  
Threshold Value ◽  
Particle Formation ◽  
New Particle Formation ◽  
Organic Vapors ◽  
Clear Sky ◽  
Sky Conditions ◽  
Oxidized Products ◽  
Condensation Sink

Abstract. New particle formation (NPF) events have been observed all around the world and are known to be a major source of atmospheric aerosol particles. Here we combine 20 years of observations in a boreal forest at the SMEAR II station (Station for Measuring Ecosystem-Atmosphere Relations) in Hyytiälä, Finland, by utilizing previously accumulated knowledge, and by focusing on clear-sky (non-cloudy) conditions. We first investigated the effect of cloudiness on NPF and then compared the NPF event and non-event days during clear-sky conditions. In this comparison we considered, for example, the effects of calculated particle formation rates, condensation sink, trace gas concentrations and various meteorological quantities. The formation rate of 1.5 nm particles was calculated by using proxies for gaseous sulfuric acid and oxidized products of low volatile organic compounds. As expected, our results indicate an increase in the frequency of NPF events under clear-sky conditions. Also, focusing on clearsky conditions enabled us to find a clear separation of many variables related to NPF. For instance, oxidized organic vapors showed higher concentration during the clear-sky NPF event days, whereas the condensation sink (CS) and some trace gases had higher concentrations during the non-event days. The calculated formation rate of 3 nm particles showed a notable difference between the NPF event and non-event days during clear-sky conditions, especially in winter and spring. For spring time, we are able to find a threshold value for the combined values of ambient temperature and CS, above which practically no clear-sky NPF event could be observed. Finally, we present a probability distribution for the frequency of NPF events at a specific CS and temperature.

scholarly journals Monitoring long-term changes of glacial seismic activity with continuous seismological observations: a case study from Spitsbergen

2016 ◽  
Author(s):  
W. Gajek ◽  
J. Trojanowski ◽  
M. Malinowski
Keyword(s):  
Seismic Activity ◽  
Seismic Station ◽  
Flow Analysis ◽  
Seismic Signal ◽  
Signal Frequency ◽  
Steady Increase ◽  
Fuzzy Logic Algorithm ◽  
Temperature And Precipitation ◽  
Seismological Data

Abstract. Changes in the global temperature balance have proved to have a major impact on the cryosphere and therefore retreating glaciers are the symbol of the warming climate. Long-term measurements of geophysical parameters provide the insight into the dynamics of those processes over many years. Here we explore the possibility of using data recorded by permanent seismological stations to monitor glacial seismic activity. Our study focuses on year-to-year changes in seismicity of the Hansbreen glacier (southern Spitsbergen). We have processed 7-year-long continuous seismological data recorded by a broadband station located in the fjord of Hornsund, obtaining seismicity distribution between 2008 and 2014. To distinguish between glacier- and non-glacier-origin events with the data from only one seismic station in the area, we developed a new fuzzy logic algorithm based on the seismic signal frequency and the energy flow analysis. Our research has revealed that the number of detected glacier-origin events over the last two years has doubled. We also observed that the annual events distribution correlates well with the temperature and precipitation data. In order to further support our observations, we have analysed 5-year-long seismological data recorded by a broadband station located in Ny-Ålesund (western Spitsbergen). Distribution of glacier-origin tremors detected in the vicinity of the Kronebreen glacier shows a steady increase from year to year, however not as significant as for the Hornsund dataset.

scholarly journals A novel neural prosthesis providing long-term electrocorticography recording and cortical stimulation for epilepsy and brain-computer interface

2019 ◽  
Vol 130 (4) ◽  
pp. 1166-1179 ◽  
Author(s):  
Pantaleo Romanelli ◽  
Marco Piangerelli ◽  
David Ratel ◽  
Christophe Gaude ◽  
Thomas Costecalde ◽  
...  
Keyword(s):  
Nonhuman Primate ◽  
Large Scale ◽  
Brain Activity ◽  
Threshold Value ◽  
Time Span ◽  
Cortical Stimulation ◽  
Neural Prosthesis ◽  
Lower Limbs ◽  
Custom Made

OBJECTIVEWireless technology is a novel tool for the transmission of cortical signals. Wireless electrocorticography (ECoG) aims to improve the safety and diagnostic gain of procedures requiring invasive localization of seizure foci and also to provide long-term recording of brain activity for brain-computer interfaces (BCIs). However, no wireless devices aimed at these clinical applications are currently available. The authors present the application of a fully implantable and externally rechargeable neural prosthesis providing wireless ECoG recording and direct cortical stimulation (DCS). Prolonged wireless ECoG monitoring was tested in nonhuman primates by using a custom-made device (the ECoG implantable wireless 16-electrode [ECOGIW-16E] device) containing a 16-contact subdural grid. This is a preliminary step toward large-scale, long-term wireless ECoG recording in humans.METHODSThe authors implanted the ECOGIW-16E device over the left sensorimotor cortex of a nonhuman primate (Macaca fascicularis), recording ECoG signals over a time span of 6 months. Daily electrode impedances were measured, aiming to maintain the impedance values below a threshold of 100 KΩ. Brain mapping was obtained through wireless cortical stimulation at fixed intervals (1, 3, and 6 months). After 6 months, the device was removed. The authors analyzed cortical tissues by using conventional histological and immunohistological investigation to assess whether there was evidence of damage after the long-term implantation of the grid.RESULTSThe implant was well tolerated; no neurological or behavioral consequences were reported in the monkey, which resumed his normal activities within a few hours of the procedure. The signal quality of wireless ECoG remained excellent over the 6-month observation period. Impedance values remained well below the threshold value; the average impedance per contact remains approximately 40 KΩ. Wireless cortical stimulation induced movements of the upper and lower limbs, and elicited fine movements of the digits as well. After the monkey was euthanized, the grid was found to be encapsulated by a newly formed dural sheet. The grid removal was performed easily, and no direct adhesions of the grid to the cortex were found. Conventional histological studies showed no cortical damage in the brain region covered by the grid, except for a single microscopic spot of cortical necrosis (not visible to the naked eye) in a region that had undergone repeated procedures of electrical stimulation. Immunohistological studies of the cortex underlying the grid showed a mild inflammatory process.CONCLUSIONSThis preliminary experience in a nonhuman primate shows that a wireless neuroprosthesis, with related long-term ECoG recording (up to 6 months) and multiple DCSs, was tolerated without sequelae. The authors predict that epilepsy surgery could realize great benefit from this novel prosthesis, providing an extended time span for ECoG recording.

scholarly journals Assessment of traffic-induced vibrations of Ozanam Building of Adamson University

2018 ◽  
Vol 169 ◽  
pp. 01042
Author(s):  
Earl Shadd D. Araña, ◽  
Leira Liz A. Bisain ◽  
Rae Cecil N. Acedera ◽  
John Elmer C. Guillermo ◽  
Albert A. Griño
Keyword(s):  
Particle Velocity ◽  
Structural Damage ◽  
Structural Integrity ◽  
Preventive Measures ◽  
Threshold Value ◽  
Structural Members ◽  
Heavy Vehicles ◽  
Maximum Peak ◽  
Main Factors

Vibration is one of the main factors for fatigue in structures which can cause damages such as cracks and in critical cases could result to collapse. Long term contact to vibrations can induce the cracks to be transmitted through the structural members of the building that can compromise the structural integrity of the structure. The Ozanam Building of Adamson University is situated near the Romualdez Street, which is considered as one of the main routes of cargo trucks and other heavy vehicles from the Manila North Harbor Port. It was observed that cracks were visible on the façade of the building. For that reason, the structural integrity of Ozanam Building was evaluated against the traffic-induced vibrations using vibration meter. It was found out that the maximum peak particle velocity present in Ozanam Building is 8.60 mm/s which means that the building is safe and below the threshold value for risk in structural damage. Thus, vibration due to traffic has no significant effect that can cause structural damage to the building. In addition, preventive measures were discussed in this paper to reduce the traffic-induced vibrations to an acceptable level.

Usefulness of plateletcrit in the prediction of major adverse cardiac and cerebrovascular events in patients with carotid artery stenosis

Vascular ◽  
2019 ◽  
Vol 27 (5) ◽  
pp. 479-486 ◽  
Author(s):  
Serkan Aslan ◽  
Ali Rıza Demir ◽  
Yusuf Demir ◽  
Ömer Taşbulak ◽  
Mehmet Altunova ◽  
...  
Keyword(s):  
Carotid Artery ◽  
Carotid Stenosis ◽  
Complete Information ◽  
Threshold Value ◽  
Multivariate Regression Analysis ◽  
Adverse Outcomes ◽  
Operating Characteristics ◽  
Cerebrovascular Events ◽  
Long Term Mortality

Objectives Platelets play an important role in the pathogenesis of atherosclerosis and the physiopathology of cardiovascular events. Plateletcrit provides complete information on total platelet mass. The relationship between plateletcrit values and long-term outcomes in patients with carotid stenosis is not known. The purpose of the present study is to evaluate the reliability of plateletcrit for predicting major adverse cardiac and cerebrovascular events (MACCE) in patients with carotid stenosis. Methods A total of 230 patients with more than 50% stenosis of the carotid artery were retrospectively included in this study. All cases were divided into two groups according to the calculated threshold value of plateletcrit with receiver operating characteristics curve and baseline parameters and clinical outcomes were compared. Univariate and multivariate analyses were used to evaluate the association between the plateletcrit and MACCE. Results The cut-off value for plateletcrit was found to be 0.233 for predicting MACCE, with 56.2% sensitivity and 68.0% specificity. High plateletcrit levels were demonstrated to be statistically higher in patients with MACCE (0.247 in the MACCE (+) group vs. 0.213 in the MACCE (–) group, p < 0.001). In the Kaplan–Meier survival analysis, the long-term mortality rate was higher in the high plateletcrit group ( p = 0.006). Multivariate regression analysis showed that plateletcrit was independently associated with MACCE (OR: 2.196, CI: 1.200–4.018; p = 0.011). Conclusions Our data suggest that plateletcrit has an independently predictive value for long-term mortality and MACCE, and it can be used as a marker to predict the long-term adverse outcomes in patients with carotid stenosis.

Tracking earthquake sequences in real time: application of Seismicity-Scanning based on Navigated Automatic Phase-picking (S-SNAP) to the 2019 Ridgecrest, California sequence

2020 ◽  
Vol 223 (3) ◽  
pp. 1511-1524
Author(s):  
Fengzhou Tan ◽  
Honn Kao ◽  
Edwin Nissen ◽  
Ryan Visser
Keyword(s):  
Real Time ◽  
Fault Zone ◽  
Southern California ◽  
Main Shock ◽  
Waveform Data ◽  
Major Earthquake ◽  
Automatic Phase ◽  
Seismicity Monitoring ◽  
Earthquake Sequences ◽  
Automatic Phase Picking

SUMMARY Recent improvements in seismic data processing techniques have enhanced our ability to detail the evolution of major earthquake sequences in space and time. One such advance is new scanning algorithms that allow large volumes of waveform data to be analysed automatically, removing human biases and inefficiencies that inhibit standardized monitoring. The Seismicity-Scanning based on Navigated Automatic Phase-picking (S-SNAP) workflow has previously been shown to be capable of producing high-quality earthquake catalogues for injection-induced seismicity monitoring. In this study, we modify the original S-SNAP workflow to enable it to delineate the spatiotemporal distribution of major earthquake sequences in real time. We apply it to the 2019 Ridgecrest, southern California earthquake sequence, which culminated in an Mw 6.4 foreshock on July 4 and an Mw 7.1 main shock on July 6 and generated tens of thousands of smaller earthquakes. Our catalogue—which spans the period 2019 June 1 to July 16—details the spatiotemporal evolution of the sequence, including early foreshocks on July 1 and accelerating foreshocks on July 4, a seismicity gap before the main shock around its epicentre, seismicity on discrete structures within a broad fault zone and triggered earthquakes outside the main fault zone. We estimate the accuracy and false detection rate of the S-SNAP catalogue based on the reviewed catalogue reported by Southern California Seismic Network (SCSN) and our own visual inspection. We demonstrate the advantages of S-SNAP over a generalized automatic earthquake monitoring software, Seiscomp3, and a customized real-time earthquake information system for southern California, TriNet. In comparison, the S-SNAP catalogue contains five times more events than the Seiscomp3 catalogue and 1.4–2.2 times as many events per hour as the TriNet catalogue at most times. In addition, S-SNAP is more likely to solve phase association ambiguities correctly and provide a catalogue with consistent quality through time. S-SNAP would be beneficial to both routine network operations and the earthquake review process.

Experimental Validation of Improved Exponential Companding Technique for SC-FDMA Systems Using WARP Hardware

2019 ◽  
Vol 29 (10) ◽  
pp. 2050154
Author(s):  
K. Shri Ramtej ◽  
S. Anuradha
Keyword(s):  
Power Level ◽  
Average Power ◽  
Original System ◽  
Threshold Value ◽  
Single Carrier ◽  
Power Spectral ◽  
Research Platform ◽  
Scatter Plots ◽  
Subcarrier Mapping

As single-carrier frequency division multiple access (SC-FDMA) is used in long-term evolution (LTE) uplink communications, high peak-to-average power ratio (PAPR) increases power consumption in mobile devices. It is severe when localized subcarrier mapping is used with higher-order modulations. Companding is an attractive technique that offers a tradeoff between PAPR and bit error rate (BER) performances. This paper proposes an exponential companding technique that uses two companding levels based on a threshold, to reduce PAPR in SC-FDMA systems. It does not increase the average power level of transmitted signal and maintains the BER level without significant degradation from the original system. The proposed scheme has three parameters that can be adjusted for a tradeoff between PAPR, BER, and power spectral density (PSD) performances. Hence it offers more flexibility than the conventional exponential companding scheme. We also present scatter plots to find the optimum threshold value and companding levels. Finally, we verify the proposed technique considering a real-time indoor channel by using a wireless open-access research platform (WARP).

scholarly journals Long-Term Monitoring of Atrazine Contamination in Soil by ELISA

2001 ◽  
Vol 84 (1) ◽  
pp. 150-155 ◽  
Author(s):  
Karl Kramer ◽  
Johann Lepschy ◽  
Bertold Hock
Keyword(s):  
Low Cost ◽  
Threshold Value ◽  
Soil Samples ◽  
Sample Throughput ◽  
Atrazine Contamination ◽  
Long Term Monitoring ◽  
Term Monitoring ◽  
Selection Of ◽  
Hplc Data

Abstract An enzyme-linked immunoassay (ELISA) was used for screening atrazine residues in soil. Samples were annually collected in Southern Germany between 1993 and 1998. An average of 419.5 samples was analyzed per year amounting to 2517 samples. The fraction of positive samples defined by atrazine concentrations &gt;100 μg/kg soil decreased successively from 8% (corresponding to 33 samples) in 1993 to 0.6% (corresponding to 2 samples) in 1998. All positive samples and a selection of negative samples were subsequently validated by HPLC. Comparison of ELISA and HPLC data yielded correlation coefficient values of r= 0.958–0.981 (n= 18–47), except for 1995 when only a correlation of r= 0.864 (n= 18) was obtained. Four samples were overestimated and another 4 were underestimated with respect to the atrazine threshold value of 100 μg/kg soil as revealed by HPLC validation. Thus, 99.68% of 2517 analyzed samples were correctly evaluated. The precision and reproducibility of the ELISA were adequate for a prescreening tool. The low cost per sample and the high sample throughput are not yet achievable by conventional analytical methods. The described combination of ELISA and HPLC has the potential to take advantage of both methods and to restrict determination errors to a minimum.

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