Variation of Ionospheric Narrowband and Wideband Performance for a 12,760 km Transequatorial Link and Its Dependence on Solar and Ionospheric Activity

The ionosphere provides a channel that is able to propagate electromagnetic waves for long-haul communications, allowing Non-Line-Of-Sight (NLOS) radio communications in the high-frequency band (HF). Nonetheless, its performance as a communications channel mainly depends on solar activity, as Earth’s diurnal and seasonal cycles modify the ionospheric ionization by the sun and consequently the channel performance. La Salle and the Observatori de l’Ebre have conducted oblique soundings of a 12,760 km ionospheric channel from Livingston Island (South Shetland Archipelago—Antarctica −62.7∘S, 299.6∘E) to Cambrils (Spain −41.0∘N, 1.0∘E) to evaluate this evidence and analyze the characteristics of this particular channel. The final goal of the project is to establish a stable communications link to be used as a backup for low throughput data transmission from the various geomagnetic and meteorological sensors located in the Spanish Antarctic Station. The aim of this paper is to confirm the relationship between the channel availability of narrowband and wideband communications and the resulting channel parameters with the solar and ionospheric activity for four consecutive sounding campaigns.

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High-Frequency Electromagnetic Waves for Diesel Soot Oxidation Strategy

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.875-877.1382 ◽

2014 ◽

Vol 875-877 ◽

pp. 1382-1386 ◽

Cited By ~ 2

Author(s):

Zainal Ambri Abdul Karim ◽

Muhammad Abdul Halim Mohammad Mursal ◽

Mohd Hanafiah Mat Jamlus

Keyword(s):

Mild Steel ◽

High Frequency ◽

Electromagnetic Waves ◽

Soot Oxidation ◽

Reaction Chamber ◽

Diesel Soot ◽

Diesel Soot Oxidation ◽

Lower Melting Point ◽

The Relationship ◽

High Range

Results from an experimental investigation for diesel soot oxidation strategy using high-frequency electromagnetic waves in producing metal sparks is provided in this paper. It is envisaged that the micro plasma develop by metal when subjected to high-frequency electromagnetic waves, produces heat that enables soot oxidation process. The work attempts to investigate the relationship between spark inception of metals and micro plasma temperatures at different microwaves intensity. Various metal specimens were exposed to high-frequency electromagnetic waves at different power levels at a specific duration of time. The sparks temperatures or micro plasmas produced by the metals were measured using a high-range infrared thermometer. It was found that aluminum and brass have high spark temperatures when compared to mild steel at lower microwaves power levels. However, both aluminum and brass have lower melting point temperatures than mild steel. This makes the material unsuitable for prolong exposure to high-frequency electromagnetic waves. Mild steel was found the suitable metal to be used as the spark inceptor in the soot oxidation reaction chamber.

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Reliability of the Minimum Masking Level as Outcome Variable in Tinnitus Clinical Research

American Journal of Audiology ◽

10.1044/2020_aja-20-00047 ◽

2020 ◽

Vol 29 (3) ◽

pp. 429-435

Author(s):

Patricia C. Mancini ◽

Richard S. Tyler ◽

Hyung Jin Jun ◽

Tang-Chuan Wang ◽

Helena Ji ◽

...

Keyword(s):

Standard Deviation ◽

High Frequency ◽

Pearson Correlation ◽

Correlation Coefficients ◽

Outcome Variable ◽

Reliable Estimate ◽

Moderate Correlation ◽

Trained Subjects ◽

The Relationship ◽

Minimum Intensity

Purpose The minimum masking level (MML) is the minimum intensity of a stimulus required to just totally mask the tinnitus. Treatments aimed at reducing the tinnitus itself should attempt to measure the magnitude of the tinnitus. The objective of this study was to evaluate the reliability of the MML. Method Sample consisted of 59 tinnitus patients who reported stable tinnitus. We obtained MML measures on two visits, separated by about 2–3 weeks. We used two noise types: speech-shaped noise and high-frequency emphasis noise. We also investigated the relationship between the MML and tinnitus loudness estimates and the Tinnitus Handicap Questionnaire (THQ). Results There were differences across the different noise types. The within-session standard deviation averaged across subjects varied between 1.3 and 1.8 dB. Across the two sessions, the Pearson correlation coefficients, range was r = .84. There was a weak relationship between the dB SL MML and loudness, and between the MML and the THQ. A moderate correlation ( r = .44) was found between the THQ and loudness estimates. Conclusions We conclude that the dB SL MML can be a reliable estimate of tinnitus magnitude, with expected standard deviations in trained subjects of about 1.5 dB. It appears that the dB SL MML and loudness estimates are not closely related.

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Comparison of In-the-Ear and Over-the-Ear Hearing Aid Fittings

Journal of Speech and Hearing Disorders ◽

10.1044/jshd.5104.362 ◽

1986 ◽

Vol 51 (4) ◽

pp. 362-369 ◽

Cited By ~ 4

Author(s):

Donna M. Risberg ◽

Robyn M. Cox

Keyword(s):

Hearing Aids ◽

High Frequency ◽

Comparative Evaluation ◽

Speech Intelligibility ◽

Hearing Aid ◽

Hearing Aid Fitting ◽

The Difference ◽

Functional Gain ◽

The Relationship

A custom in-the-ear (ITE) hearing aid fitting was compared to two over-the-ear (OTE) hearing aid fittings for each of 9 subjects with mild to moderately severe hearing losses. Speech intelligibility via the three instruments was compared using the Speech Intelligibility Rating (SIR) test. The relationship between functional gain and coupler gain was compared for the ITE and the higher rated OTE instruments. The difference in input received at the microphone locations of the two types of hearing aids was measured for 10 different subjects and compared to the functional gain data. It was concluded that (a) for persons with mild to moderately severe hearing losses, appropriately adjusted custom ITE fittings typically yield speech intelligibility that is equal to the better OTE fitting identified in a comparative evaluation; and (b) gain prescriptions for ITE hearing aids should be adjusted to account for the high-frequency emphasis associated with in-the-concha microphone placement.

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Relationship of Semicircular Canal Size to Vestibular-Nerve Afferent Sensitivity in Mammals

Journal of Neurophysiology ◽

10.1152/jn.00798.2007 ◽

2007 ◽

Vol 98 (6) ◽

pp. 3197-3205 ◽

Cited By ~ 83

Author(s):

Aizhen Yang ◽

Timothy E. Hullar

Keyword(s):

Semicircular Canal ◽

High Frequency ◽

High Gain ◽

Vestibular Nerve ◽

Radius Of Curvature ◽

Horizontal Canal ◽

Vestibular Nerve Afferents ◽

The Relationship ◽

Irregular Afferents ◽

Anterior Canal

The relationship between semicircular canal radius of curvature and afferent sensitivity has not been experimentally determined. We characterized mouse semicircular canal afferent responses to sinusoidal head rotations to facilitate interspecies and intraspecies comparisons of canal size to sensitivity. The interspecies experiment compared the horizontal canal afferent responses among animals ranging in size from mouse to rhesus monkey. The intraspecies experiment compared afferent responses from the larger anterior canal to those from the smaller horizontal canal of mice. The responses of mouse vestibular-nerve afferents showed a low- and high-frequency phase lead and high-frequency gain enhancement. Regular horizontal-canal afferents showed a sensitivity to 0.5-Hz sinusoidal rotations of 0.10 ± 0.03 (SD) spike · s−1/deg · s−1 and high-gain irregular afferents showed a sensitivity of 0.25 ± 0.11 spike · s−1/deg · s−1. The interspecies comparison showed that the sensitivity of regular afferents was related to the radius of curvature R according to the formula Gr = 0.23R − 0.09 ( r2 = 0.86) and the sensitivity of irregular afferents was related to radius according to the formula Gi = 0.32R + 0.01 ( r2 = 0.67). The intraspecies comparison showed that regularly firing anterior canal afferents were significantly more sensitive than those from the relatively smaller horizontal canal, with Gr = 0.25R. This suggests that canal radius of curvature is closely related to afferent sensitivity both among and within species. If the relationship in humans is similar to that demonstrated here, the sensitivity of their regular vestibular-nerve afferents to 0.5-Hz rotations is likely to be about 0.67 spike · s−1/deg · s−1 and of their high-gain irregular afferents about 1.06 spikes · s−1/deg · s−1.

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Scattering of electromagnetic waves by hybrid waves in a two-electron-temperature plasma

Journal of Plasma Physics ◽

10.1017/s002237780001597x ◽

1991 ◽

Vol 46 (1) ◽

pp. 99-106 ◽

Cited By ~ 3

Author(s):

S. K. Sharma ◽

A. Sudarshan

Keyword(s):

Growth Rate ◽

Electron Temperature ◽

High Frequency ◽

Electromagnetic Waves ◽

Low Frequency ◽

Lower Hybrid ◽

Stimulated Scattering ◽

Coupled Modes ◽

Temperature Plasma ◽

Electrostatic Perturbation

In this paper, we use the hydrodynamic approach to study the stimulated scattering of high-frequency electromagnetic waves by a low-frequency electrostatic perturbation that is either an upper- or lower-hybrid wave in a two-electron-temperature plasma. Considering the four-wave interaction between a strong high-frequency pump and the low-frequency electrostatic perturbation (LHW or UHW), we obtain the dispersion relation for the scattered wave, which is then solved to obtain an explicit expression for the growth rate of the coupled modes. For a typical Q-machine plasma, results show that in both cases the growth rate increases with noh/noc. This is in contrast with the results of Guha & Asthana (1989), who predicted that, for scattering by a UHW perturbation, the growth rate should decrease with increasing noh/noc.

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