scholarly journals A preliminary survey of the broadband seismic wavefield at Puu Oo, the active vent of Kilauea volcano, Hawaii

1996 ◽  
Vol 39 (2) ◽  
Author(s):  
D. Seidl ◽  
M. Hellweg ◽  
P. Okubo ◽  
H. Rademacher
Keyword(s):  
Frequency Band ◽  
Power Spectra ◽  
Volcanic Tremor ◽  
Digital Data ◽  
Periodic Pattern ◽  
Data Logger ◽  
Remarkable Feature ◽  
Wide Range ◽  
Active Vent ◽  
Seismic Wavefield

The seismic wavefield near an active volcanic vent consists of superimposed signals in a wide range of frequency bands from sources inside and outside the volcano. To characterize the broadband wavefield near Puu Oo, we deployed a profile of three three-component broadband sensors in a 200 m long line about 1.5 km WSW of the active vent. During this period, Puu Oo maintained a constant, but very low level of activity. The digital data logger recorded the wavefield continuously in the frequency band between 0.01 and 40 Hz between June 25 and July 9, 1994. At the same time, local wind conditions along with air temperature and pressure were monitored by a portable digital weather station. On the basis of characteristic elements, such as waveform, spatial coherence between stations, particle motion and power spectra, the wavefield can be divided into three bands. The dominant signals in the frequency band between 0.01 and 0.1 Hz are not coherent among the stations. Their ground velocities correlate with the wind speed. The signals in the 0.1 to 0.5 Hz band are coherent across the profile and most probably represent a superposition of volcanic tremor and microseisms from the Pacific Ocean. Much of the energy above 0.5 Hz can be attributed to activity at the vent. Power spectra from recordings of the transverse components show complex peaks between 0.5 and 3 Hz which vary in amplitude due to site effects and distance. On the other hand, power spectra calculated from the radial components show a clearly periodic pattern of peaks at 1 Hz intervals for some time segments. A further remarkable feature of the power spectra is that they are highly stationary.

scholarly journals Statistical analysis of Stromboli VLP tremor in the band [0.1–0.5] Hz: some consequences for vibrating structures

2006 ◽  
Vol 13 (4) ◽  
pp. 393-400 ◽  
Author(s):  
E. De Lauro ◽  
S. De Martino ◽  
M. Falanga ◽  
M. Palo
Keyword(s):  
Frequency Band ◽  
High Frequency ◽  
Noise Source ◽  
Volcanic Tremor ◽  
Large Data ◽  
Musical Instruments ◽  
Data Set ◽  
Long Period ◽  
Vibrating Structures ◽  
Analyze Time Series

Abstract. We analyze time series of Strombolian volcanic tremor, focusing our attention on the frequency band [0.1–0.5] Hz (very long period (VLP) tremor). Although this frequency band is largely affected by noise, we evidence two significant components by using Independent Component Analysis with the frequencies, respectively, of ~0.2 and ~0.4 Hz. We show that these components display wavefield features similar to those of the high frequency Strombolian signals (>0.5 Hz). In fact, they are radially polarised and located within the crater area. This characterization is lost when an enhancement of energy appears. In this case, the presence of microseismic noise becomes relevant. Investigating the entire large data set available, we determine how microseismic noise influences the signals. We ascribe the microseismic noise source to Scirocco wind. Moreover, our analysis allows one to evidence that the Strombolian conduit vibrates like the asymmetric cavity associated with musical instruments generating self-sustained tones.

A comparison of select trigger algorithms for automated global seismic phase and event detection

1998 ◽  
Vol 88 (1) ◽  
pp. 95-106 ◽  
Author(s):  
Mitchell Withers ◽  
Richard Aster ◽  
Christopher Young ◽  
Judy Beiriger ◽  
Mark Harris ◽  
...  
Keyword(s):  
Real Time ◽  
Data Streams ◽  
Event Detection ◽  
Spectral Characteristics ◽  
Digital Data ◽  
Robust Detection ◽  
Location System ◽  
Global Correlation ◽  
Seismic Coda ◽  
Wide Range

Abstract Digital algorithms for robust detection of phase arrivals in the presence of stationary and nonstationary noise have a long history in seismology and have been exploited primarily to reduce the amount of data recorded by data logging systems to manageable levels. In the present era of inexpensive digital storage, however, such algorithms are increasingly being used to flag signal segments in continuously recorded digital data streams for subsequent processing by automatic and/or expert interpretation systems. In the course of our development of an automated, near-real-time, waveform correlation event-detection and location system (WCEDS), we have surveyed the abilities of such algorithms to enhance seismic phase arrivals in teleseismic data streams. Specifically, we have considered envelopes generated by energy transient (STA/LTA), Z-statistic, frequency transient, and polarization algorithms. The WCEDS system requires a set of input data streams that have a smooth, low-amplitude response to background noise and seismic coda and that contain peaks at times corresponding to phase arrivals. The algorithm used to generate these input streams from raw seismograms must perform well under a wide range of source, path, receiver, and noise scenarios. Present computational capabilities allow the application of considerably more robust algorithms than have been historically used in real time. However, highly complex calculations can still be computationally prohibitive for current workstations when the number of data streams become large. While no algorithm was clearly optimal under all source, receiver, path, and noise conditions tested, an STA/LTA algorithm incorporating adaptive window lengths controlled by nonstationary seismogram spectral characteristics was found to provide an output that best met the requirements of a global correlation-based event-detection and location system.

scholarly journals Multiscaling and joint multiscaling description of the atmospheric wind speed and the aggregate power output from a wind farm

2014 ◽  
Vol 21 (2) ◽  
pp. 379-392 ◽  
Author(s):  
R. Calif ◽  
F. G. Schmitt
Keyword(s):  
Wind Speed ◽  
Power Output ◽  
Wind Farm ◽  
Power Spectra ◽  
Physical Space ◽  
Scaling Properties ◽  
Developed Turbulence ◽  
Output Fluctuations ◽  
Wide Range ◽  
Generalized Correlation

Abstract. We consider here wind speed time series and the aggregate output wind power from a wind farm. We study their scaling statistics in the framework of fully developed turbulence and Kolmogorov's theory. We estimate their Fourier power spectra and consider their scaling properties in the physical space. We show that the atmospheric wind speed and the aggregate power output from a wind farm are intermittent and multifractal over a wide range of scales. The coupling between simultaneous data of the wind speed and aggregate power output is investigated through a joint multifractal description using the generalized correlation functions (GCFs). This multiscaling test is compatible with a linear relation between the wind speed and the aggregate power output fluctuations for timescales T ⩾ 103 s ≃ 15 min.

scholarly journals Does temperature affect the accuracy of vented pressure transducer in fine-scale water level measurement?

2015 ◽  
Vol 4 (1) ◽  
pp. 65-73 ◽  
Author(s):  
Z. Liu ◽  
C. W. Higgins
Keyword(s):  
Water Level ◽  
Pressure Transducer ◽  
Performance Test ◽  
Thermal Fluctuations ◽  
Field Conditions ◽  
Digital Data ◽  
Water Level Fluctuations ◽  
Fine Scale ◽  
Data Logger ◽  
Pressure Transducers

Abstract. Submersible pressure transducers have been utilized for collecting water level data since the early 1960s. Together with a digital data logger, it is a convenient way to record water level fluctuations for long-term monitoring. Despite the wide use of pressure transducers for water level monitoring, little has been reported regarding their accuracy and performance under field conditions. The effects of temperature fluctuations on the output of vented pressure transducers were considered in this study. The pressure transducers were tested under both laboratory and field conditions. The results of this study indicate that temperature fluctuation has a strong effect on the transducer output. Rapid changes in temperature introduce noise and fluctuations in the water level readings under a constant hydraulic head while the absolute temperature is also related to sensor errors. The former is attributed to venting and the latter is attributed to temperature compensation effects in the strain gauges. Individual pressure transducers responded differently to the thermal fluctuations in the same testing environment. In the field of surface hydrology, especially when monitoring fine-scale water level fluctuations, ignoring or failing to compensate for the temperature effect can introduce considerable error into pressure transducer readings. It is recommended that a performance test for the pressure transducer is conducted before field deployment.

Six-degree-of-freedom ground-motion measurement

1994 ◽  
Vol 84 (5) ◽  
pp. 1665-1669
Author(s):  
Robert L. Nigbor
Keyword(s):  
Ground Motion ◽  
Strong Ground Motion ◽  
Rotational Velocity ◽  
Free Field ◽  
Degree Of Freedom ◽  
Digital Data ◽  
Vertical Acceleration ◽  
Data Logger ◽  
Six Degree Of Freedom ◽  
Strong Ground

Abstract True six-degree-of-freedom (6DOF) measurement of free-field strong ground motion has been accomplished using a prototype 6DOF accelerograph system. This system consists of a traditional triaxial translational accelerometer, three new rotational velocity sensors, and a digital data logger. Rotational and translational ground motions at a single free-field location were measured successfully during the recent NPE event, a very large (1 kton) chemical explosion. Peak vertical acceleration at the near-field measurement site exceeded 1g for this event; the peak measured rotational velocity was 2.2°/sec. Earthquake strong-ground-motion measurements are currently in progress.

scholarly journals Participatory governance over research in an academic research network: the case of Diabetes Action Canada

BMJ Open ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. e026828 ◽  
Author(s):  
Donald J Willison ◽  
Joslyn Trowbridge ◽  
Michelle Greiver ◽  
Karim Keshavjee ◽  
Doug Mumford ◽  
...  
Keyword(s):  
Clinical Care ◽  
Academic Research ◽  
Digital Data ◽  
Research Network ◽  
Data Governance ◽  
Data Repositories ◽  
Continuous Quality ◽  
Policies And Procedures ◽  
Wide Range ◽  
Governance Process

Digital data generated in the course of clinical care are increasingly being leveraged for a wide range of secondary purposes. Researchers need to develop governance policies that can assure the public that their information is being used responsibly. Our aim was to develop a generalisable model for governance of research emanating from health data repositories that will invoke the trust of the patients and the healthcare professionals whose data are being accessed for health research. We developed our governance principles and processes through literature review and iterative consultation with key actors in the research network including: a data governance working group, the lead investigators and patient advisors. We then recruited persons to participate in the governing and advisory bodies. Our governance process is informed by eight principles: (1) transparency; (2) accountability; (3) follow rule of law; (4) integrity; (5) participation and inclusiveness; (6) impartiality and independence; (7) effectiveness, efficiency and responsiveness and (8) reflexivity and continuous quality improvement. We describe the rationale for these principles, as well as their connections to the subsequent policies and procedures we developed. We then describe the function of the Research Governing Committee, the majority of whom are either persons living with diabetes or physicians whose data are being used, and the patient and data provider advisory groups with whom they consult and communicate. In conclusion, we have developed a values-based information governance framework and process for Diabetes Action Canada that adds value over-and-above existing scientific and ethics review processes by adding a strong patient perspective and contextual integrity. This model is adaptable to other secure data repositories.

scholarly journals Wild specimens of sand fly phlebotomine Lutzomyia evansi, vector of leishmaniasis, show high abundance of Methylobacterium and natural carriage of Wolbachia and Cardinium types in the midgut microbiome

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Rafael J. Vivero ◽  
Marcela Villegas-Plazas ◽  
Gloria E. Cadavid-Restrepo ◽  
Claudia Ximena Moreno Herrera ◽  
Sandra I. Uribe ◽  
...  
Keyword(s):  
16S Rrna ◽  
16S Rrna Gene ◽  
High Throughput Sequencing ◽  
Sand Fly ◽  
Human Populations ◽  
Rrna Gene ◽  
Remarkable Feature ◽  
Core Microbiome ◽  
Bacterial Phyla ◽  
Wide Range

AbstractPhlebotomine sand flies are remarkable vectors of several etiologic agents (virus, bacterial, trypanosomatid Leishmania), posing a heavy health burden for human populations mainly located at developing countries. Their intestinal microbiota is involved in a wide range of biological and physiological processes, and could exclude or facilitate such transmission of pathogens. In this study, we investigated the Eubacterial microbiome from digestive tracts of Lu. evansi adults structure using 16S rRNA gene sequence amplicon high throughput sequencing (Illumina MiSeq) obtained from digestive tracts of Lu. evansi adults. The samples were collected at two locations with high incidence of the disease in humans: peri-urban and forest ecosystems from the department of Sucre, Colombia. 289,068 quality-filtered reads of V4 region of 16S rRNA gene were obtained and clustered into 1,762 operational taxonomic units (OTUs) with 97% similarity. Regarding eubacterial diversity, 14 bacterial phyla and 2 new candidate phyla were found to be consistently associated with the gut microbiome content. Proteobacteria, Firmicutes, and Bacteroidetes were the most abundant phyla in all the samples and the core microbiome was particularly dominated by Methylobacterium genus. Methylobacterium species, are known to have mutualistic relationships with some plants and are involved in shaping the microbial community in the phyllosphere. As a remarkable feature, OTUs classified as Wolbachia spp. were found abundant on peri-urban ecosystem samples, in adult male (OTUs n = 776) and unfed female (OTUs n = 324). Furthermore, our results provide evidence of OTUs classified as Cardinium endosymbiont in relative abundance, notably higher with respect to Wolbachia. The variation in insect gut microbiota may be determined by the environment as also for the type of feeding. Our findings increase the richness of the microbiota associated with Lu. evansi. In this study, OTUs of Methylobacterium found in Lu. evansi was higher in engorged females, suggesting that there are interactions between microbes from plant sources, blood nutrients and the parasites they transmit during the blood intake.

LBM Simulation of Flow Around an Oscillating Cylinder and a Stationary Cylinder in Side-by-Side Arrangement

2018 ◽  
Author(s):  
Yang Zhang ◽  
Li Sheng ◽  
Jinlong Duan ◽  
Ke Chen ◽  
Yunxiang You
Keyword(s):  
Lattice Boltzmann ◽  
Forced Oscillation ◽  
Power Spectra ◽  
Circular Cylinders ◽  
Wide Range ◽  
Pitch Ratio ◽  
Response State ◽  
Boltzmann Method ◽  
Different Characteristics ◽  
Flow Interference

Flow interference between two identical circular cylinders in side-by-side arrangement with one stationary and the other forced to oscillate in the transverse direction are studied. Direct numerical simulations are performed by Lattice Boltzmann Method (LBM) with a constant Reynolds number of 100. We consider four representative pitch ratios, T/D, ranging from 1.2 to 4, corresponding to four distinct flow patterns for two stationary side-by-side cylinders. The forced oscillation is fixed at a constant small amplitude of A/D = 0.1. A wide range of dimensionless oscillating frequency (fe/fs = [0.5, 2]) is examined. The results show that the response state of flow around two side-by-side cylinders when one cylinder is forced to vibrate is quite different from that of the corresponding stationary system. Four response states are identified according to the different characteristics on the power spectra and phase portrait of lift forces on cylinders. In addition, hydrodynamic forces on the cylinders are analyzed in terms of root-mean-square and time-averaged quantities. It is found that the pitch ratio, oscillating frequency and response state play different roles in determining the force quantities.

scholarly journals Artist: fast radiative transfer for large-scale simulations of the epoch of reionization

2019 ◽  
Vol 489 (4) ◽  
pp. 5594-5611 ◽  
Author(s):  
Margherita Molaro ◽  
Romeel Davé ◽  
Sultan Hassan ◽  
Mario G Santos ◽  
Kristian Finlator
Keyword(s):  
Radiative Transfer ◽  
Large Scale ◽  
Power Spectra ◽  
Physical Parameters ◽  
Speed Of Light ◽  
Photon Propagation ◽  
Wide Range ◽  
Gas Ionization ◽  
Excursion Set ◽  
Large Scale Simulations

ABSTRACT We introduce the ‘Asymmetric Radiative Transfer In Shells Technique’ (artist), a new method for photon propagation on large scales that explicitly conserves photons, propagates photons at the speed of light, approximately accounts for photon directionality, and closely reproduces results of more detailed radiative transfer (RT) methods. Crucially, it is computationally fast enough to evolve the large cosmological volumes required to predict the 21cm power spectrum on scales that will be probed by future experiments targeting the epoch of reionization (EoR). Most seminumerical models aimed at predicting the EoR 21cm signal on these scales use an excursion set formalism (ESF) to model the gas ionization, which achieves computational viability by making a number of approximations. While artist is still roughly two orders of magnitude slower than ESF, it does allow to model the EoR without the need for such approximations. This is particularly important when considering a wide range of reionization scenarios for which artist would help limit the assumptions made. By implementing our RT method within the seminumerical code simfast21, we show that Artist predicts a significantly different evolution for the EoR ionization field compared to the code’s native ESF. In particular, artist predicts up to a factor of two difference in the power spectra, depending on the physical parameters assumed. Its application to large-scale EoR simulations will therefore allow more physically motivated constraints to be obtained for key EoR parameters. In particular, it will remove the need for the artificial rescaling of the escape fraction.

scholarly journals Method for testing the calibration of acceleration and pressure gauges installed at the ocean bottom

2019 ◽  
Author(s):  
Mikhail Nosov ◽  
Viacheslav Karpov ◽  
Sergey Kolesov ◽  
Kirill Sementsov ◽  
Hiroyuki Matsumoto ◽  
...  
Keyword(s):  
Linear Relationship ◽  
Frequency Band ◽  
Power Spectra ◽  
Forced Oscillations ◽  
Ocean Bottom ◽  
Bottom Pressure ◽  
Ocean Bottom Pressure ◽  
Mean Pressure ◽  
Explicit Formulae ◽  
Gravity Acceleration

Abstract. A method is proposed for testing pressure gauges and z-accelerometers, installed in ocean-bottom observatories. The method is based on the linear relationship between variations of the ocean-bottom pressure and the z-acceleration, observed during seismic movements of the bottom within the frequency band of "forced oscillations". Calculation of the boundaries of this frequency band is based on the ocean depth at the observatory site making use of explicit formulae. In the case of correct calibration of the gauges calculation of the ratios of power spectra of bottom pressure variations and the z-accleration within the band of "forced oscillations" yields constant values equal to the square ratio of the total mean pressure and the gravity acceleration. The conditions for application of the proposed method are formulated.

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