A climatology of infrasound detections at Kerguelen Island

2020 ◽  
Author(s):  
Olivier F.C. den Ouden ◽  
Jelle D. Assink ◽  
Pieter S.M. Smets ◽  
Läslo G. Evers
Keyword(s):  
Low Frequency ◽  
Noise Model ◽  
High Noise ◽  
Kerguelen Island ◽  
Power Spectral ◽  
The World ◽  
Processing Techniques ◽  
Test Ban

<p>The International Monitoring System (IMS) is in place for the verification of the Comprehensive Nuclear-Test-Ban Treaty (CTBT). Part of the IMS are 60 infrasound arrays, of which 51 currently provide real-time infrasound recordings from around the world. Those arrays play a central role in the characterization of the global infrasonic wavefield and localization of infrasound sources.</p><p>Power Spectral Density (PSD) estimates give insight into the noise levels per station and array. The IMS global low and high noise model curves have been determined in a study by Brown et al. [2014] using a distribution of computed PSDs. All the IMS infrasound arrays, except IS23, have been included in the determination of the atmospheric ambient noise curves. IS23 is located at Kerguelen Island and exist of 15 elements that have been divided into five 100 meter aperture triplets arrays. The array is located at one of the noisiest locations in the world, due to the high wind conditions that exist year-round. The resulting high noise floor appears to hamper infrasound detection at this island array.</p><p>In this work, the effects of meteorological, oceanographic, and topographical conditions on the infrasound recordings at IS23 are studied. Five years of infrasound data is analyzed, as recorded by IS23, by using various processing techniques. Contributions within different frequency bands are evaluated. The infrasound detections are explained in terms of the stratospheric winds and ocean wave activity. Understanding and characterization of the low-frequency recordings of IS23 are of importance for successfully including this array for verification of the CTBT.</p>

Limitations of the Power Spectral Density as an Indicator of Test Severity

2011 ◽  
Vol 54 (2) ◽  
pp. 116-128 ◽  
Author(s):  
Mark Paulus
Keyword(s):  
Experimental Data ◽  
Spectral Density ◽  
Frequency Shift ◽  
Natural Frequency ◽  
Power Spectral Density ◽  
Low Frequency ◽  
Poor Correlation ◽  
Frequency Change ◽  
Power Spectral

This paper presents a set of experimental data comparing repetitive shock (RS) vibration, single-axis electrodynamic (ED) vibration, and multi-axis ED vibration. It was found that multi-axis testing is more severe than single-axis testing at the same level. In addition, weaknesses were found in the RS system at low frequency. Smoothing of the data or poor line resolution was also shown to change the overall severity of a test. A poor correlation was shown between the power spectral density (PSD) and the rate of natural frequency change (RFC) over a wide frequency shift. The change in natural frequency caused the initial PSD to be an ineffective indicator of test severity. Quantification of the severity of the test profile can be accomplished through characterization of the RFC.

scholarly journals The Use of SEM and Other Complimentary Techniques for the Determination of Properties of Cementitious Materials

1992 ◽  
Vol 00 (8) ◽  
pp. 4-4 ◽  
Author(s):  
Eric A. Draper ◽  
Jan Skalny
Keyword(s):  
Building Materials ◽  
State Of The Art ◽  
Raw Materials ◽  
Cementitious Materials ◽  
Modern State ◽  
Microscopic Evaluation ◽  
The World ◽  
Cost Effect

The need for continued rehabilitation of our concrete infrastructure has lead to the adaptation of modern “state-of-the-art” analytical methods for the characterization of concrete and other cementitious materials. Some of these techniques have not, until relatively recently, been commonly associated with the evaluation of concrete but are very useful both as tools for quality assurance and in the determination of the extent of existing damage. The technique of interest here is the coordinated electron-optical microscopic evaluation of concrete.Concrete is the most widely used building material in the world. Contrary to popular belief, concrete is not inert but chemically very complex and dynamic. While it is true that, pound for pound, concrete and its raw materials (cement, aggregate and water} are the most inexpensive building materials available for construction, it is also true that it responds to its environment in numerous and sometimes very subtle ways. These responses may sometimes result in a loss of durability and tremendous amounts of time and money being expended while searching for the cause(s) of the problem and providing a cost-effect solution A quick survey of any large metropolitan area and the on-going construction repairs to highways and bridge decks there will quickly confirm this.

On the Characterization of Dynamic Properties of Random Processes by Spectral Parameters

2000 ◽  
Vol 67 (3) ◽  
pp. 519-526 ◽  
Author(s):  
G. Petrucci ◽  
M. Di Paola ◽  
B. Zuccarello
Keyword(s):  
Dynamic Properties ◽  
Time Derivative ◽  
Wide Band ◽  
Random Processes ◽  
Spectral Parameters ◽  
Unambiguous Determination ◽  
Power Spectral ◽  
Bandwidth Parameter

This paper deals with the general problem of directly relating the distribution of ranges of wide band random processes to the power spectral density (PSD) by means of closed-form expressions. Various attempts to relate the statistical distribution of ranges to the PSD by means of the irregularity factor or similar parameters have been done by several authors but, unfortunately, they have not been fully successful. In the present study, introducing the so-called analytic processes, the reasons for which these parameters are insufficient to an unambiguous determination of the range distribution and the fact that parameters regarding the time-derivative processes are needed have been explained. Furthermore, numerical simulations have shown that the range distributions depend on the irregularity factor and bandwidth parameter of both the process and its derivative. These observations are the basis for the determination of accurate relationships between range distributions and PSDs. [S0021-8936(00)02903-2]

scholarly journals Open Database Searching Enables the Identification and Comparison of Bacterial Glycoproteomes without Defining Glycan Compositions Prior to Searching

2020 ◽  
Vol 19 (9) ◽  
pp. 1561-1574 ◽  
Author(s):  
Ameera Raudah Ahmad Izaham ◽  
Nichollas E. Scott
Keyword(s):  
Bacterial Species ◽  
Low Frequency ◽  
Burkholderia Cenocepacia ◽  
Database Searching ◽  
Modified Peptides ◽  
Fetus Subsp ◽  
Indispensable Tool ◽  
Bacterial Proteomes

Mass spectrometry has become an indispensable tool for the characterization of glycosylation across biological systems. Our ability to generate rich fragmentation of glycopeptides has dramatically improved over the last decade yet our informatic approaches still lag behind. Although glycoproteomic informatics approaches using glycan databases have attracted considerable attention, database independent approaches have not. This has significantly limited high throughput studies of unusual or atypical glycosylation events such as those observed in bacteria. As such, computational approaches to examine bacterial glycosylation and identify chemically diverse glycans are desperately needed. Here we describe the use of wide-tolerance (up to 2000 Da) open searching as a means to rapidly examine bacterial glycoproteomes. We benchmarked this approach using N-linked glycopeptides of Campylobacter fetus subsp. fetus as well as O-linked glycopeptides of Acinetobacter baumannii and Burkholderia cenocepacia revealing glycopeptides modified with a range of glycans can be readily identified without defining the glycan masses before database searching. Using this approach, we demonstrate how wide tolerance searching can be used to compare glycan use across bacterial species by examining the glycoproteomes of eight Burkholderia species (B. pseudomallei; B. multivorans; B. dolosa; B. humptydooensis; B. ubonensis, B. anthina; B. diffusa; B. pseudomultivorans). Finally, we demonstrate how open searching enables the identification of low frequency glycoforms based on shared modified peptides sequences. Combined, these results show that open searching is a robust computational approach for the determination of glycan diversity within bacterial proteomes.

scholarly journals Resolved Hyperfine at L-band for High-Spin CoEDTA, A Model for Co Sites in Proteins

2019 ◽  
Vol 20 (10) ◽  
pp. 2385
Author(s):  
William E. Antholine
Keyword(s):  
Accurate Determination ◽  
Cobalt Complex ◽  
Low Frequency ◽  
Paramagnetic Resonance ◽  
X Band ◽  
Epr Parameters ◽  
L Band ◽  
Band Spectra

Low-frequency electron paramagnetic resonance (EPR) spectra were obtained for the Co complex of ethylene diamine tetraacetic acid (CoEDTA). It was found that the cobalt hyperfine at geff-mid is better resolved at a low frequency, L-band (1.37 GHz), and not resolved at X-band (9.631 GHz), which is the conventional frequency used for most spectra for metal complexes. Resolved cobalt hyperfine lines lead to additional EPR parameters like A-mid for cobalt and a more-accurate determination of g-mid. Resolved hyperfine lines in the L-band, but not the S-band, spectra were obtained at a concentration of 1 mM. Knowing these additional EPR parameters provides a means to better determine the electron density in the ground state orbital for each cobalt complex, as well as to determine differences upon a change of ligation. If zinc sites can be replaced by cobalt, the cobalt spectra for these sites will enhance the characterization of the zinc sites.

Research on Morphology of N80 Casing Drilling Steel Fatigue Crack Growth with Low-Frequency Noise

2011 ◽  
Vol 239-242 ◽  
pp. 2795-2798
Author(s):  
Dang Hui Wang ◽  
Tian Han Xu ◽  
Ting Zhen Yao
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Low Frequency ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Power Spectral ◽  
Microstructure Morphology ◽  
Casing Drilling

Microstructure and low-frequency noise test were measured for N80 steel casing drilling, through SEM analyzed their morphology. Results showed that: (1) power spectral density of 1/f noise increases two orders of magnitude after fatigue crack growth. (2) 1/f noise parameters of γ and B are significantly increased, indicating that the process of fatigue produced more cracks, defects, and combination centers, which were proved by microstructure morphology. From the mechanism of fatigue crack growth of N80, defects and cracks resulting from fatigue are the numbers of kind of fluctuations. In essence, low-frequency noise is a type of fluctuations, which can serve as a viable tool to study the defects and the characterization of defects.

scholarly journals The Use of SEM and Other Complimentary Techniques for the Determination of Properties of Cementitious Materials

1992 ◽  
Vol 00 (8) ◽  
pp. 11-14
Author(s):  
Eric A. Draper ◽  
Jan Skalny
Keyword(s):  
Building Materials ◽  
State Of The Art ◽  
Raw Materials ◽  
Cementitious Materials ◽  
Modern State ◽  
Microscopic Evaluation ◽  
The World ◽  
Cost Effect

The need for continued rehabilitation of our concrete infrastructure has lead to the adaptation of modern “state-of-the-art” analytical methods for the characterization of concrete and other cementitious materials. Some of these techniques have not, until relatively recently, been commonly associated with the evaluation of concrete but are very useful both as tools for quality assurance and in the determination of the extent of existing damage. The technique of interest here is the coordinated electron-optical microscopic evaluation of concrete.Concrete is the most widely used building material in the world. Contrary to popular belief, concrete is not inert but chemically very complex and dynamic. While it is true that, pound far pound, concrete and its raw materials (cement, aggregate and water) are the most inexpensive building materials available for construction, it is also true that it responds to its environment in numerous and sometimes very subtle ways. These responses may sometimes result in a loss of durability and tremendous amounts of time and money being expended while searching far the cause(s) of the problem and providing a cost-effect solution. A quick survey of any large metropolitan area and the on-going construction repairs to highways and bridge decks there will quickly confirm this.

scholarly journals New reproduction number and acceleration parameter introduced and applied to COVID-19

2021 ◽  
Author(s):  
Eckhard Rebhan
Keyword(s):  
Exponential Growth ◽  
Reproduction Number ◽  
Analytical Form ◽  
Precise Determination ◽  
Acceleration Parameter ◽  
Infection Dynamics ◽  
The World

Abstract To characterize the progression of a pandemic, a well interpretable reproduction number is introduced which is easily applicable to many different situations due to its handy analytical form. On the basis of its derivation it can be understood as a cross between a volatile instantaneous reproduction number and the more robust effective reproduction number commonly used. Starting from it, a further quantity, termed acceleration parameter, is introduced, which facilitates a more differentiated characterization of the infection dynamics. In particular, it enables the precise determination of when the limit to exponential growth is reached and exceeded. A variety of possible developments is examined, including linear and exponential growth of the infection numbers as well as sub- and super-exponential growth. It turned out useful to incorporate the incidence as a further epidemiological indicator. It is used for calculating the trace that the progression of the pandemic leaves behind on a plain spanned by itself and the acceleration parameter. This plane can be divided into a dangerous area, where the pandemic becomes uncontrollable, and a safer area that must be the target of mitigation efforts. At present, many countries and the world as a whole are mired in the dangerous area.

Noise Modeling and Characterization of Piezoresistive Transducers

2006 ◽  
Author(s):  
Toshikazu Nishida ◽  
Robert Dieme ◽  
Mark Sheplak ◽  
Gijs Bosman
Keyword(s):  
Dynamic Range ◽  
Measurement Techniques ◽  
Low Frequency ◽  
Noise Model ◽  
Noise Modeling ◽  
Mems Microphone ◽  
Output Noise ◽  
Noise Measurements ◽  
Transducer Output

This paper presents detailed results on noise modeling and experimental characterization applicable to piezoresistive MEMS transducers using a piezoresistive MEMS microphone as an example. To accurately model the lower limit of the dynamic range of piezoresistive MEMS transducers, a detailed noise equivalent circuit, piezoresistor noise model, and experimental noise measurements are needed. From the sensitivity and the total root-mean-square output noise, the minimum detectable signal (MDS) may be computed. Key experimental results include comparison of the DC bridge and AC bridge noise measurement techniques and use of the AC measurement technique when the piezoresistive transducer output noise is less than the low frequency DC setup noise.

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