OPERATIONAL CHARACTERISTICS OF SMALL-SIZED ANTENNA DEVICES OF THE MEDIUM FREQUENCY RANGE IN MINES

2021 ◽  
Author(s):  
А.В. КОЛЕСНИКОВ
Keyword(s):  
Input Power ◽  
Frequency Range ◽  
Medium Frequency ◽  
Radio Stations ◽  
Portable Radio ◽  
Operational Characteristics ◽  
Impedance Characteristics ◽  
Near Zone ◽  
The Stability ◽  
Medium Frequency Range

Представлены результаты исследования трех малогабаритных антенн (электрического,магнитного и магнитоэлектрического типов)СВ-диапазона с целью определения особенностей их эксплуатации в рудниках и шахтах,т.е. в диспергирующих средах. Рассмотрены импедансные характеристики и изменение частотных зависимостей коэффициента стоячей волны в ближней зоне антенн, обусловленное непостоянством электрических характеристик горных пород при перемещении антенн вдоль горной выработки. Проведена оценка стабильности работы портативных радиостанций при подводимой к малогабаритной антенне мощности 1 Вт с учетом времени,характерного для сеансов связи. Даны рекомендации по эксплуатации антенн в условиях рудников и шахт. The article investigates three main types of small antennas (electric, magnetic and magnetoelectric) of the medium frequency range in order to determine the features of their operation in mines, i.e. in dispersing media. The impedance characteristics and the change in the frequency dependences of the standing wave ratio are considered when the situation in the near zone changes. An assessment of the stability of the operation of portable radio stations at an input power of 1 W has been carried out, taking into account the time characteristic of communication sessions. Recommendations for the operation of antennas in mines are given.

Topographic Analysis of Steady-State Visual Evoked Potentials (SVEPs) in The Medium Frequency Range in Migraine With and Without Aura

Cephalalgia ◽  
1992 ◽  
Vol 12 (4) ◽  
pp. 244-249 ◽  
Author(s):  
Franco M Puca ◽  
Marina de Tommaso ◽  
Maria A Savarese ◽  
Sergio Genco ◽  
Addolorata Prudenzano
Keyword(s):  
Steady State ◽  
Frequency Range ◽  
Medium Frequency ◽  
Topographic Analysis ◽  
Absolute Power ◽  
Interhemispheric Coherence ◽  
The Mean ◽  
Student’S T ◽  
Medium Frequency Range ◽  
Student’S T Test

Topographic analysis of SVEPs in the medium frequencies range was performed in 30 migraineurs without aura, 20 migraineurs with aura and in 20 control subjects. The mean absolute power values of the fundamental component F1, the subharmonic F1/2 and the first harmonic F2, corrected by logarithmic transformation, were computed in each group and then compared using Student's t-test. The interhemispheric coherence of the F1 component was also evaluated. The 18, 21 and 27 Hz F1 components were increased in both migraineurs with and without aura, particularly in the temporo-parietal regions. The 24 Hz F1 component was augmented only in migraineurs without aura in the parieto-occipital regions in comparison with migraineurs with aura and controls. Migraine with aura patients had a reduced interhemispheric coherence mostly of 12 Hz and 15 Hz F1 components in frontal and temporo-parietal regions. Results of the study confirm abnormalities of SVEPs in migraineurs with and without aura. These consist of widespread increases of F1 components in the medium frequency range over the temporo-parietal regions.

Measurements of the Surface Elasticity in Medium Frequency Range Using the Oscillating Bubble Method

1998 ◽  
Vol 208 (1) ◽  
pp. 34-48 ◽  
Author(s):  
Klaus-Dieter Wantke ◽  
Horst Fruhner ◽  
Jiping Fang ◽  
Klaus Lunkenheimer
Keyword(s):  
Surface Elasticity ◽  
Frequency Range ◽  
Medium Frequency ◽  
Medium Frequency Range

Analysis of Medium-Frequency Vibrations in a Frequency Range

2003 ◽  
Vol 11 (02) ◽  
pp. 255-283 ◽  
Author(s):  
P. Ladevèze ◽  
P. Rouch ◽  
H. Riou ◽  
X. Bohineust
Keyword(s):  
Frequency Range ◽  
Variational Theory ◽  
Elastic Structures ◽  
Medium Frequency ◽  
New Approach ◽  
Numerical Examples ◽  
Vibrational Response ◽  
Complex Rays ◽  
Medium Frequency Range

A new approach called the ''Variational Theory of Complex Rays'' (VTCR) is being developed in order to calculate the vibrations of slightly damped elastic structures in the medium-frequency range. Here, the emphasis is put on the extension of this theory to analysis across a range of frequencies. Numerical examples show the capability of the VTCR to predict the vibrational response of a structure in a frequency range.

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