scholarly journals Scattering Attenuation of the Martian Interior through Coda-Wave Analysis

2021 ◽  
Author(s):  
Foivos Karakostas ◽  
Nicholas Schmerr ◽  
Ross Maguire ◽  
Quancheng Huang ◽  
Doyeon Kim ◽  
...  
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Scattered Wave ◽  
Coda Wave ◽  
Very High Frequency ◽  
Scattering Layer ◽  
Scattering Attenuation ◽  
Trade Offs ◽  
Scattering Strength ◽  
Diffusive Layer

ABSTRACT We investigate the scattering attenuation characteristics of the Martian crust and uppermost mantle to understand the structure of the Martian interior. We examine the energy decay of the spectral envelopes for 21 high-quality Martian seismic events from sols 128 to 500 of InSight operations. We use the model of Dainty, Toksöz, et al. (1974) to approximate the behavior of energy envelopes resulting from scattered wave propagation through a single diffusive layer over an elastic half-space. Using a grid search, we mapped the layer parameters that fit the observed InSight data envelopes. The single diffusive layer model provided better fits to the observed energy envelopes for high-frequency (HF) and very-high-frequency (VF) than for the low-frequency and broadband events. This result is consistent with the suggested source depths (Giardini et al., 2020) for these families of events and their expected interaction with a shallow scattering layer. The shapes of the observed data envelopes do not show a consistent pattern with event distance, suggesting that the diffusivity and scattering layer thickness is nonuniform in the vicinity of InSight at Mars. Given the consistency in the envelope shapes between HF and VF events across epicentral distances and the trade-offs between the parameters that control scattering, the dimensions of the scattering layer remain unconstrained but require that scattering strength decreases with depth and that the rate of decay in scattering strength is the fastest near the surface. This is generally consistent with the processes that would form scattering structures in planetary lithospheres.

scholarly journals Peranan Lingkungan Sosial terhadap Pembentukan Karakter Peduli Lingkungan Mahasiswa Pendidikan Geografi di Universitas Samudra Langsa

2018 ◽  
Vol 10 (2) ◽  
pp. 235
Author(s):  
Fitria Mustika ◽  
Tengku Muhammad Sahudra
Keyword(s):  
Family Environment ◽  
High Frequency ◽  
Low Frequency ◽  
Measurement Scale ◽  
Education Student ◽  
Achievement Level ◽  
Very High Frequency ◽  
Environmental Care ◽  
The Family

This study aims to determine the role of the family, community, and tertiary environment towards the formation of caring character in the geography education student environment. The output of this study was a four-indexed indexed education journal and a UNIMED google scolar. Samples from the study population were 20 respondents with 30 items about questionnaires. The time of the study starts from May 2018 to October 2018. The measurement scale in this study is the scale of the briquette. Data collection by means of library studies, interviews, questionnaires, and documentation. This research was conducted by distributing questionnaire questionnaires and interviews. Based on the results of questionnaire data processing, the family environment has a very high frequency in the formation of character of the student's environmental care with an achievement level of a total score of 91%. Furthermore, the role of the campus environment also has a high frequency in the formation of the character of the student's environmental care with a total score of 89%. Whereas the family environment has a low frequency in the formation of character of student environmental care with a total score of 57%. It can be concluded that the family environment has the most role in forming the character of the student's environmental care.

Investigating Thunderstorm HF/VHF Radio Bursts with Weak Lower Frequency Radiation

2020 ◽  
Author(s):  
Ningyu Liu ◽  
Joseph Dwyer
Keyword(s):  
High Frequency ◽  
Large Scale ◽  
Strong Field ◽  
Large Fraction ◽  
Low Frequency ◽  
Very High Frequency ◽  
Lightning Initiation ◽  
Study Support ◽  
Volcanic Lightning ◽  
Frequency Radiation

<p>While the spectrum of lightning electromagnetic radiation is known to peak around 5-10 kHz in the very low frequency (VLF) range, intense high frequency/very high frequency (HF/VHF) radiation can be produced by various lightning related processes. In fact, thunderstorm narrow bipolar events (NBEs), which are capable of initiating lightning, are the most powerful HF/VHF sources in nature on Earth. But even for NBEs, the spectral intensity in HF/VHF is still many orders of magnitude weaker than that of lower frequencies (Liu et al., JGR, 124, https://doi.org/10.1029/2019JD030439, 2019). HF/VHF bursts with weak VLF signals, however, can also be produced by thunderstorms. These bursts may be related to the thunderstorm precursor events noted by Rison et al. (Nat. Commun., 7, 10721, 2016) and are also found to precede a large fraction of lightning initiation (Lyu et al., JGR, 124, 2994, 2019). They are also known as continual radio frequency (CRF) radiation associated with volcanic lightning (Behnke et. al., JGR, 123, 4157, 2018).</p><p> </p><p>In this talk, we report a theoretical and modeling study to investigate a physical mechanism for production of those HF/VHF bursts. The study is built on the theory developed recently concerning the radio emissions from an ensemble of streamers (Liu et al., 2019). We find an ensemble of streamer discharges that develop in random directions can produce HF/VHF radiation with intensity comparable to those all developing in a single direction, but the VLF intensity is many orders of magnitude weaker. The results of our study support the conclusions of Behnke et. al (2018) that CRF is produced in the absence of large-scale electric field, it results in insignificant charge transfer, and it is caused by streamers. In the context of the HF/VHF bursts preceding lightning initiation (Lyu et. al, 2019), our results imply that highly localized strong field regions exist in thunderstorms and streamers take place in those regions, which somehow precondition the medium for lightning initiation.</p>

scholarly journals Comparison of Low and High Frequency Partial Discharge Measurements on Stator Windings

2019 ◽  
pp. 134-138
Author(s):  
Greg C Stone ◽  
Howard Sedding
Keyword(s):  
High Frequency ◽  
Partial Discharge ◽  
Low Frequency ◽  
International Standards ◽  
Very High Frequency ◽  
Stator Windings ◽  
Advantages And Disadvantages ◽  
On Line ◽  
Winding Insulation

Partial discharge (PD) testing has been used for over 60 years primarily as a method to assess condition of the stator winding insulation in motors and generators rated 6 kV and above. More recently it has also been used by some machine manufacturers as a means of assuring the quality of the insulation on single winding elements (coils and bars). Although both on-line and off-line tests mainly use a high voltage capacitor to detect the PD, the PD measuring systems in use work either in the low frequency (LF) regime (less than about 1 MHz) or in the very high frequency (VHF) (30-300 MHz) range. By reference to several international standards, published work as well as some experiments described in this contribution, the advantages and disadvantages of the two approaches are compared. Based on this work, it is now clear that off-line PD tests should be done in the LF range. For on-line tests, either method may be used, but use of the VHF method has become more widespread with machine end users, since the owners themselves can perform and interpret the results with a relatively low risk of false indications.

scholarly journals Early Context-Conditioned Orthographic Knowledge in European Portuguese: The Spelling of the Schwa

2020 ◽  
Vol 5 ◽  
Author(s):  
Ana Paula Vale ◽  
Rafaela Perpétua
Keyword(s):  
High Frequency ◽  
First Graders ◽  
Low Frequency ◽  
Orthographic Knowledge ◽  
School Grade ◽  
Very High Frequency ◽  
Similar Frequency ◽  
Sound Learning ◽  
Letter Sound ◽  
Very High

This longitudinal study examined how the phonemic-orthographic context affects the spelling of the schwa (/ɨ/) by Portuguese beginning spellers at two time points in the first school grade. The schwa is phonetically unstable and phonologically ill-defined, has an unpredictable realization, is frequently deleted at the syllable's end, and is often spelt as <e>, a very high frequency grapheme with numerous phonological renditions. In addition to cognitive and other alphabetic tasks, 41 first graders were asked to spell 40 consistent words of medium-low frequency: 5 CV.CV (consonant, vowel. consonant, vowel) with well-articulated vowels; 10 C/ɨ/C.VC, the first vowel being a schwa, thereby creating potential phonological consonantal clusters, half legal (/fɨliʃ/, /fliʃ/), half illegal (/pɨdal/, /pdal/); 10 CV.C/ɨ/, the last vowel being a schwa, potentially creating phonological monosyllables half with a legal coda (/mɔlɨ/, /mɔl/) and half with an illegal coda (/n'avɨ/), (/nav/); in addition, the children spelt 15 CVC ending with /l/, /ɾ/ and /ʃ/, the only legal Portuguese codas. Participants were also asked to spell equivalent pseudowords at a second point in time. Our results show that children were sensitive to allowable letter patterns from the Time 1 assessment point. Although alphabetic spelling was not entirely mastered, children used <e> more in first syllables than at the end of the word, and more in illegal than in legal phonological consonantal clusters, although the pattern of significant differences did change over time. The results were similar for pseudowords. Also, children used <e> more at the CV.C/ɨ/ words whose last C was /l/, than in monosyllabic CVC words ending with /l/. This was not observed with pseudowords, where the grapheme <e> was used with a similar frequency in the two types of items. Overall, these results show that children's acquisition of this kind of context-conditioned orthographic knowledge occurs simultaneously with alphabetic letter-sound learning and depend largely on intuitive statistical learning reflecting the regularities of the written code to which they are exposed.

scholarly journals Territorial black-capped chickadee males respond faster to high- than to low-frequency songs in experimentally elevated noise conditions

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e3257 ◽  
Author(s):  
Stefanie E. LaZerte ◽  
Hans Slabbekoorn ◽  
Ken A. Otter
Keyword(s):  
High Frequency ◽  
Background Noise ◽  
Noise Exposure ◽  
Signal To Noise Ratio ◽  
Low Frequency ◽  
Trade Offs ◽  
Dependent Signal ◽  
Noisy Conditions ◽  
Carry Over ◽  
Free Ranging

Low-frequency urban noise can interfere with avian communication through masking. Some species are able to shift the frequency of their vocalizations upwards in noisy conditions, which may reduce the effects of masking. However, results from playback studies investigating whether or not such vocal changes improve audibility in noisy conditions are not clear; the responses of free-ranging individuals to shifted signals are potentially confounded by functional trade-offs between masking-related audibility and frequency-dependent signal quality. Black-capped chickadees (Poecile atricapillus) naturally sing their songs at several different frequencies as they pitch-shift to match conspecifics during song-matching contests. They are also known to switch to higher song frequencies in response to experimental noise exposure. Each male produces both high- and low-frequency songs and absolute frequency is not a signal of aggression or dominance, making this an interesting species in which to test whether higher-frequency songs are more audible than lower-frequency songs in noisy conditions. We conducted playback studies across southern and central British Columbia, Canada, using paired song stimuli (high- vs low-frequency songs, n = 24 pairs) embedded in synthetic background noise created to match typical urban sound profiles. Over the course of each playback, the signal-to-noise ratio of the song stimuli was gradually increased by raising the amplitude of the song stimuli while maintaining background noise at a constant amplitude. We evaluated variation in how quickly and aggressively territorial males reacted to each of the paired stimuli. We found that males responded more quickly to playbacks of high- than low-frequency songs when high-frequency songs were presented first, but not when low-frequency songs were first. This difference may be explained by high-frequency songs being more audible combined with a carry-over effect resulting in slower responses to the second stimulus due to habituation. We observed no difference in overall aggression between stimuli. These results suggest that high-frequency songs may be more audible under noisy conditions.

scholarly journals Good-enough production: Selecting easier words instead of more accurate ones

2021 ◽  
Author(s):  
Mark Koranda ◽  
Martin Zettersten ◽  
Maryellen MacDonald
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Word Meanings ◽  
Frequency Word ◽  
Trade Off ◽  
Word Use ◽  
Trade Offs ◽  
Language Communication ◽  
The Times ◽  
High Frequency Words

While many implicit decisions are the result of a trade-off, trade-offs in word use, such as whether a producer meant to convey a message more aligned with kitten despite saying a more accessible word like cat, are difficult to measure. To test the trade-off between message alignment and accessibility, we designed an artificial lexicon where word meanings corresponded to angles on a compass. In a novel language communication game, participants trained on some words more than others (high- vs low-frequency), and then earned points by producing words, often requiring an implicit decision between a high- vs low-frequency word. A trade-off was observed across four experiments, such that high-frequency words were produced even when less aligned with messages. Since high-frequency words are more accessible, these results suggest that implicit decisions between words are impacted by accessibility. Of all the times that people have said cat, many times they likely meant kitten.

scholarly journals How useful is eap vocabulary for esp? a corpus based case study

2020 ◽  
Author(s):  
C Sutarsyah ◽  
Paul Nation ◽  
G Kennedy
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Word List ◽  
Academic Vocabulary ◽  
Very High Frequency ◽  
Academic Texts ◽  
The University ◽  
General Service ◽  
Very High

This study compares the vocabulary of a single Economics text of almost 300,000 running words with the vocabulary of a corpus of similar length made up of a variety of academic texts. It was found that the general academic corpus used a very much larger vocabulary than the more focused Economics text. A small number of words that were closely related to the topic of the text occurred with very high frequency in the Economics text. The general academic corpus had a very large number of low frequency words. Beyond the words in West's General Service List and the University Word List, there was little overlap between the vocabulary of the two corpora. This indicates that as far as vocabulary is concerned, EAP courses that go beyond the high frequency academic vocabulary are of little value for learners with specific purposes. © 1994, Sage Publications. All rights reserved.

scholarly journals How useful is eap vocabulary for esp? a corpus based case study

2020 ◽  
Author(s):  
C Sutarsyah ◽  
Paul Nation ◽  
G Kennedy
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Word List ◽  
Academic Vocabulary ◽  
Very High Frequency ◽  
Academic Texts ◽  
The University ◽  
General Service ◽  
Very High

This study compares the vocabulary of a single Economics text of almost 300,000 running words with the vocabulary of a corpus of similar length made up of a variety of academic texts. It was found that the general academic corpus used a very much larger vocabulary than the more focused Economics text. A small number of words that were closely related to the topic of the text occurred with very high frequency in the Economics text. The general academic corpus had a very large number of low frequency words. Beyond the words in West's General Service List and the University Word List, there was little overlap between the vocabulary of the two corpora. This indicates that as far as vocabulary is concerned, EAP courses that go beyond the high frequency academic vocabulary are of little value for learners with specific purposes. © 1994, Sage Publications. All rights reserved.

scholarly journals GRAVITATIONAL WAVES, DARK ENERGY AND INFLATION

2010 ◽  
Vol 25 (11n12) ◽  
pp. 922-935 ◽  
Author(s):  
WEI-TOU NI
Keyword(s):  
Dark Energy ◽  
Gravitational Wave ◽  
Gravitational Waves ◽  
Frequency Band ◽  
High Frequency ◽  
Low Frequency ◽  
Big Bang ◽  
Complete Classification ◽  
High Frequency Band ◽  
Very High Frequency

In this paper we first present a complete classification of gravitational waves according to their frequencies: (i) Ultra high frequency band (above 1 THz); (ii) Very high frequency band (100 kHz–1 THz); (iii) High frequency band (10 Hz–100 kHz); (iv) Middle frequency band (0.1 Hz–10 Hz); (v) Low frequency band (100 nHz–0.1 Hz); (vi) Very low frequency band (300 pHz–100 nHz); (vii) Ultra low frequency band (10 fHz–300 pHz); (viii) Hubble (extremely low) frequency band (1 aHz–10 fHz); (ix) Infra-Hubble frequency band (below 1 aHz). After briefly discussing the method of detection for different frequency bands, we review the concept and status of space gravitational-wave missions — LISA, ASTROD, ASTROD-GW, Super-ASTROD, DECIGO and Big Bang Observer. We then address to the determination of dark energy equation, and probing the inflationary physics using space gravitational wave detectors.

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