scholarly journals A k-mean characteristic function for optimizing short- and long-term-average-ratio-based detection of microseismic events

Geophysics ◽  
2019 ◽  
Vol 84 (4) ◽  
pp. KS143-KS153
Author(s):  
Jubran Akram ◽  
Daniel Peter ◽  
David Eaton
Keyword(s):  
Event Detection ◽  
Field Data ◽  
Roc Analysis ◽  
Detection Threshold ◽  
Noisy Data ◽  
Data Sets ◽  
Average Ratio ◽  
Short And Long Term ◽  
Microseismic Events

Event detection is an essential component of microseismic data analysis. This process is typically carried out using a short- and long-term-average-ratio (STA/LTA) method, which is simple and computationally efficient but often yields inconsistent results for noisy data sets. We have aimed to optimize the performance of the STA/LTA method by testing different input forms of 3C waveform data and different characteristic functions (CFs), including a proposed [Formula: see text]-mean CF. These tests are evaluated using receiver operating characteristic (ROC) analysis and are compared based on synthetic and field data examples. Our analysis indicates that the STA/LTA method using a [Formula: see text]-mean CF improves the detection sensitivity and yields more robust event detection on noisy data sets than some previous approaches. In addition, microseismic events are detected efficiently on field data examples using the same detection threshold obtained from the ROC analysis on synthetic data examples. We recommend the use of the Youden index based on ROC analysis using a training subset, extracted from the continuous data, to further improve the detection threshold for field microseismic data.

Estimating microseismic detectability of the surface-monitoring network using downhole-monitoring array

2018 ◽  
Vol 6 (3) ◽  
pp. SH107-SH115
Author(s):  
Paweł Wandycz ◽  
Eryk Święch ◽  
Leo Eisner ◽  
Andrzej Pasternacki ◽  
Denis Anikiev ◽  
...  
Keyword(s):  
Detection Threshold ◽  
Low Frequency ◽  
Monitoring Network ◽  
Microseismic Monitoring ◽  
Data Sets ◽  
Surface Monitoring ◽  
Microseismic Events ◽  
Downhole Array ◽  
Two Stages ◽  
Downhole Monitoring

We have analyzed microseismic monitoring data sets obtained from the surface and downhole-monitoring arrays recorded during the first experiment of hydraulic fracturing in Poland. Using the downhole-monitoring network, we were able to record and locate 844 microseismic events, including 10 perforation shots from six stages of the stimulation. We detected 2 perforation shots and no microseismic events using the surface array, which was operational only during the first two stages of the stimulation. To explain the poor detectability of the surface array, we analyzed the spectral content of the events from the downhole-monitoring array. We found that the detectability of the perforation shots on the surface array was consistent with the low-frequency part of the signal on the downhole recordings. Our observation is in agreement with the fact that microseismic events with low-frequency signal weaker than the two detected perforation shots were not detected by the surface-monitoring array. Using the low-frequency part of the spectra of the events recorded by the downhole array, we predicted the surface-array detection threshold. We found that some events from the later stages could have been detected if only the surface array had been operational during that time.

scholarly journals A survey for Doppler-shift oscillations in K giants

1988 ◽  
Vol 123 ◽  
pp. 277-280
Author(s):  
Peter H. Smith ◽  
Robert S. McMillan ◽  
William J. Merline
Keyword(s):  
Doppler Shift ◽  
Power Spectra ◽  
Fold Increase ◽  
Time Base ◽  
Data Sets ◽  
Short Term ◽  
Ccd Detector ◽  
Short And Long Term ◽  
K Giants

A survey of K giants is being conducted to search for both short- and long-term oscillations. Our radial velocity spectrometer has a short-term precision on bright stars of 4 m/s after an exposure of 3 minutes on the CCD detector. Extensive sets of observations have been reduced for Arcturus, Pollux, and Aldebaran. Power spectra show no apparent oscillations within these data sets for frequencies between 0.15 and 2.0 mHz. However, the nightly averages over a 4 month time base show a three-fold increase in variance for Arcturus when compared to Pollux. A periodogram reveals a period of 1.844 0.005 days (or its alias of 2.174 days).

Covariance in parasite burdens: the effect of predisposition to infection

Parasitology ◽  
1990 ◽  
Vol 100 (1) ◽  
pp. 153-159 ◽  
Author(s):  
H. I. McCallum
Keyword(s):  
Probability Theory ◽  
Helminth Infection ◽  
Published Data ◽  
Data Sets ◽  
Susceptibility To Infection ◽  
Short And Long Term ◽  
Over Dispersion

SummaryRecently the phenomenon of predisposition to helminth infection has been reported in a number of studies: those individuals which are heavily infected before treatment with an anthelmintic tend also to acquire heavy parasite burdens following a period of reinfection. This correlation between parasite burdens in initial and reinfections is generated by differences between hosts in their exposure to infective stages and in their susceptibility to infection. Inter-host differences in these factors also generate the aggregated or over-dispersed parasite distributions that are usually observed. This paper uses probability theory to predict the correlation between initial and reinfection parasite burdens assuming that those inter-host differences which generate over-dispersion remain constant for a given individual between initial and reinfection periods. The predicted correlation is considerably greater than is observed in most published data sets. Over-dispersion is thus generated by variability between hosts which has components that remain constant between initial and reinfection and also components which vary between infection periods. The model is modified to account for those two sources of variability, and the result applied to published data to determine the contributions made by short and long-term factors to the observed distributions.

PMA Supplier Selection Using the Mahalanobis Taguchi System

2010 ◽  
pp. 1230-1237 ◽  
Author(s):  
T.T. Wong
Keyword(s):  
Data Mining ◽  
Financial Stability ◽  
Measurement Model ◽  
Data Sets ◽  
Mining System ◽  
Supplier Performance ◽  
Economic Climate ◽  
Short And Long Term ◽  
The Right

Most hi-tech industries owe at least some of their success to being in the right place at the right time. This is especially true for the aircraft parts manufacturer approval (PMA) industry. A PMA is both a design approval and a production approval. It is issued for the production of modification or replacement parts for aircraft, which includes materials, parts, processes, and appliances. In the current economic climate, airlines throughout the world are looking for partners with financial stability. The reason is simple, they want partners that will continue to support them with extra savings opportunities in the short and long-term future. As more and more PMA companies are advertising through the Internet, a supplier performance measurement model applying to each of these networked organizations will facilitate the airline selection of long-term PMA partners. In this chapter, the Mahalanobis Taguchi System (MTS) approach, a multivariate data based selection system, will be used to identify the promising PMA suppliers. Suppliers who are known to be promising are called promising groups and their performance data sets are used to create a reference metric for the promising PMA supplier population. In view of the synergetic performance of neural network and data mining technologies, it is expected that this MTS-based PMA partner selection method, implementing through a neural data mining system (NDMS) will provide a practical solution in the identification of the promising PMA suppliers.

scholarly journals Methodology of Lithuanian climate atlas mapping

2015 ◽  
Vol 64 (1) ◽  
pp. 101-112
Author(s):  
Donatas Valiukas ◽  
Audronė Galvonaitė ◽  
Algimantas Česnulevičius
Keyword(s):  
Visual Information ◽  
Qualitative Data ◽  
Data Sets ◽  
Climate Conditions ◽  
Large Sets ◽  
Long Term Changes ◽  
Short And Long Term ◽  
Time Periods ◽  
Meteorological Observations

Abstract Climate atlases summarize large sets of quantitative and qualitative data and are results of complex analytical cartographic work. These special geographical publications summarize long term meteorological observations, provide maps and figures which characterise different climate elements. Visual information is supplemented with explanatory texts. A lot of information on short and long term changes of climate elements were provided in published Lithuanian atlases (Atlas of Lithuanian SDR, 1981; Climate Atlas of Lithuania, 2013), as well as in prepared but unpublished Lithuanian Atlas (1989) and in upcoming new national atlas publications (National Atlas of Lithuania. 1st part, 2014). Climate atlases has to be constantly updated to be relevant and to describe current climate conditions. Comprehensive indicators of Lithuanian climate are provided in different cartographic publications. Different time periods, various data sets and diverse cartographic data analysis tools and visualisation methods were used in these different publications.

Short- and Long-Term Results of Total vs Subtotal Thyroid- ectomies in the Surgical Treatment of Graves' Disease

Swiss Surgery ◽  
2001 ◽  
Vol 7 (1) ◽  
pp. 20-24 ◽  
Author(s):  
Robert ◽  
Mariéthoz ◽  
Pache ◽  
Bertin ◽  
Caulfield ◽  
...  
Keyword(s):  
Recurrent Laryngeal Nerve ◽  
Nerve Palsy ◽  
Recurrent Laryngeal Nerve Palsy ◽  
Laryngeal Nerve ◽  
Long Term Results ◽  
Graves Disease ◽  
Laryngeal Nerve Palsy ◽  
Short And Long Term

Objective: Approximately one out of five patients with Graves' disease (GD) undergoes a thyroidectomy after a mean period of 18 months of medical treatment. This retrospective and non-randomized study from a teaching hospital compares short- and long-term results of total (TT) and subtotal thyroidectomies (ST) for this disease. Methods: From 1987 to 1997, 94 patients were operated for GD. Thirty-three patients underwent a TT (mostly since 1993) and 61 a ST (keeping 4 to 8 grams of thyroid tissue - mean 6 g). All patients had received propylthiouracil and/or neo-mercazole and were in a euthyroid state at the time of surgery; they also took potassium iodide (lugol) for ten days before surgery. Results: There were no deaths. Transient hypocalcemia (< 3 months) occurred in 32 patients (15 TT and 17 ST) and persistent hypocalcemia in 8 having had TT. Two patients developed transient recurrent laryngeal nerve palsy after ST (< 3 months). After a median follow-up period of seven years (1-15) with five patients lost to follow-up, 41 patients having had a ST are in a hypothyroid state (73%), thirteen are euthyroid (23%), and two suffered recurrent hyperthyroidism, requiring completion of thyroidectomy. All 33 patients having had TT - with follow-ups averaging two years (0.5-8) - are receiving thyroxin substitution. Conclusions: There were no instances of persistent recurrent laryngeal nerve palsy in either group, but persistent hypoparathyroidism occurred more frequently after TT. Long after ST, hypothyroidism developed in nearly three of four cases, whereas euthyroidy was maintained in only one-fourth; recurrent hyperthyroidy was rare.

Short- and long-term memory tasks predict working memory performance, and vice versa.

2019 ◽  
Vol 73 (2) ◽  
pp. 79-93 ◽  
Author(s):  
Ian Neath ◽  
Jean Saint-Aubin ◽  
Tamra J. Bireta ◽  
Andrew J. Gabel ◽  
Chelsea G. Hudson ◽  
...  
Keyword(s):  
Working Memory ◽  
Memory Performance ◽  
Long Term Memory ◽  
Term Memory ◽  
Short And Long Term

Short- and Long-Term Consequences of Directed Forgetting

2012 ◽  
Author(s):  
Sara B. Festini ◽  
Patricia A. Reuter-Lorenz
Keyword(s):  
Directed Forgetting ◽  
Short And Long Term ◽  
Long Term Consequences
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