scholarly journals Research progress of small low-frequency transmitting antenna

2020 ◽  
Vol 69 (20) ◽  
pp. 208401
Author(s):  
Yong Cui ◽  
Ming Wu ◽  
Xiao Song ◽  
Yu-Ping Huang ◽  
Qi Jia ◽  
...  
Keyword(s):  
Low Frequency ◽  
Research Progress ◽  
Transmitting Antenna

scholarly journals Research Progress of Locally Resonance Acoustic Metamaterials

2021 ◽  
Vol 248 ◽  
pp. 01041
Author(s):  
Du Zhehua
Keyword(s):  
Sound Wave ◽  
Negative Refraction ◽  
Low Frequency ◽  
Research Progress ◽  
Frequency Noise ◽  
Bragg Scattering ◽  
Acoustic Metamaterials ◽  
Low Frequency Noise ◽  
Phonon Crystal ◽  
Developed Surface

Bragg scattering phonon crystal and locally resonant acoustic metamaterials were introduced. In order to generate noise reduction, the lattice constant of Bragg scattering phonon crystal should be of the same order of magnitude as the wave length of the sound wave, therefore, its application field is limited. Locally resonant acoustic metamaterials consume sound energy by coupling its own resonant frequencies with those of sound waves at close range. Its size is two orders of magnitude smaller than the wavelength of sound wave; thus, the control of low-frequency noise by small-size acoustic metamaterials is realized. Locally resonant acoustic metamaterials have some extraordinary physical characteristic in the conventional medium for their special acoustic structural units, such as negative refraction and negative mass density. Especially in low frequency band, they have acoustic forbidden band in which the sound wave transmission is prohibited. Acoustic structural unit having resonant characteristics has been developed. Surface-mounted resonant element plate structures and thin film acoustic metamaterials are the normal types of locally resonant acoustic metamaterials. Their research and development provide a new method for low-frequency noise control.

scholarly journals Research progress on human feel test method of Substation low frequency noise

2020 ◽  
Vol 782 ◽  
pp. 032116
Author(s):  
Wei Chen ◽  
Sheng Hu ◽  
Wei Wen ◽  
Xiaowen Wu ◽  
Hao Cao ◽  
...  
Keyword(s):  
Low Frequency ◽  
Test Method ◽  
Research Progress ◽  
Frequency Noise ◽  
Low Frequency Noise

Wireless transmission monitoring in a geological disposal repository (II) Research and Development

2009 ◽  
Vol 1193 ◽  
Author(s):  
Hisashi Takamura ◽  
Hiroshi Shimbo ◽  
Kazuo Okutsu ◽  
Yasuhiro Suyama ◽  
Kazuhiro Aoki ◽  
...  
Keyword(s):  
Electromagnetic Wave ◽  
Low Frequency ◽  
Transmission System ◽  
Wireless Transmission ◽  
Wireless Data ◽  
Transmission Experiment ◽  
Geological Disposal ◽  
Transmission Distance ◽  
Wireless Data Transmission ◽  
Transmitting Antenna

AbstractThe development of the wireless transmission monitoring in the geological disposal repository, the underground laboratories, the test facilities and the demonstration area, will present an opportunity to provide greater flexibility and robustness to the confirmation of the barrier performance and therefore safety of repository [1]. So as to realize the wireless transmission monitoring especially in the betonite barrier, RWMC has been researching and developing the wireless data transmission system which uses the very low frequency (VLF: around 1 kHz) electromagnetic wave. In this system, transmitting and receiving is conducted through loop coil antennas. The overall transmission system is digitized and maximum 19 sensors can be connected to one transmitter. Transmission distance can be selected from several meters to several hundred meters.This paper firstly presents the behavior of VLF electromagnetic wave propagation in the rock mass and the underground facility revealed by the in-situ transmission experiment and the analytical method evaluating the behavior of the VLF electromagnetic field in various environments. Development results of the transmitting antenna and the improvement of the transmission performance are secondly shown. The technical feasibility and the future R&D plan of the wireless monitoring in the repository are also explained.

Research Progress of Low-Frequency Vibration Cutting and Its Development Tendency

2010 ◽  
Vol 26-28 ◽  
pp. 648-652
Author(s):  
Qi Hong ◽  
Li Zhi Gu ◽  
Chun Jiang Xiang
Keyword(s):  
Manufacturing Process ◽  
Low Frequency ◽  
Research Progress ◽  
Advanced Manufacturing ◽  
Experiment Study ◽  
Vibration Cutting ◽  
Low Frequency Vibration ◽  
History Of ◽  
Cutting Operation ◽  
Development Tendency

Low-frequency vibration cutting is a new kind of advanced manufacturing process with several features of advantages, compared with conventional cutting operation. Based on the review of the history of low-frequency vibration cutting, its special technological effects and applications were discussed, and presented in detail the research progress in mechanism and experiment study on low-frequency vibration cutting. Three primary problems, lack of unified awareness of mechanism, establishment of a unified standard for the choice of certain parameters, application level, still in expertise for low-frequency vibration cutting were explored and the development tendency as well as the prospect of low-frequency vibration cutting in future was foreseen.

Data Visualization for Low-Frequency Inverse Synthetic Aperture Radar (ISAR)

2018 ◽  
Vol 10 (3) ◽  
pp. 1-8
Author(s):  
Giti Javidi ◽  
Ehsan Sheybani
Keyword(s):  
Time Delay ◽  
Synthetic Aperture Radar ◽  
Real Time ◽  
Data Visualization ◽  
Systematic Approach ◽  
Low Frequency ◽  
Synthetic Aperture ◽  
Receiving Antenna ◽  
Transmitting Antenna ◽  
The Relationship

The purpose of this article was to use ISAR to determine the distance between the receiving antenna and the transmitting antenna. Once a systematic approach has been determined, this article could be used on a spacecraft to locate debris in the path of the carrier. Using low frequency radar that has the transmitting pulse built within the converters, the authors transmitted the data and determined the distance between the two antennas according to the time delay of the radar. Using amplified signals, the relationship between the distance and the time delay for the radar were calculated for each case. Additionally, these results were used to visualize in real-time the data transpired between the receiver and transmitter.

scholarly journals Instruments and Methods: A Digital Low-Frequency, Surface-Profiling Ice-Radar System

1990 ◽  
Vol 36 (122) ◽  
pp. 112-121 ◽  
Author(s):  
David L. Wright ◽  
Steven M. Hodge ◽  
Jerry A. Bradley ◽  
Thomas P. Grover ◽  
Robert W. Jacobel
Keyword(s):  
Data Storage ◽  
High Speed ◽  
Short Pulse ◽  
Bottom Topography ◽  
Low Frequency ◽  
Time Profile ◽  
Radar System ◽  
Polar Regions ◽  
Internal Surfaces ◽  
Transmitting Antenna

AbstractA new short-pulse digital profiling radar system that operates at lower frequencies than most ice radars used in polar regions to date has been designed and built by the U.S. Geological Survey. The transmitter is an avalanche transistor pulser which drives a resistively loaded dipole transmitting antenna. A similar, but separate antenna is connected to the receiver. The receiver has adjustable sensitivity time control (STC) of as much as 60 dB to compensate for attenuation and geometric spreading factors. A fiber-optic cable is used to transmit both control signals and data. The data-acquisition and display system incorporates very high-speed digitizing and signal averaging, real-time profile display, and data storage on standard computer nine-track magnetic tape.The system was successfully used on Ice Stream B in West Antarctica at centre frequencies of 1, 2, 4, 8, and 12.5 MHz. Bottom-return signal-to-noise ratios of more than 40 dB were obtained at 2 MHz through 800 m of ice. Convoluted internal surfaces not related to present bottom topography were resolved within the ice streams and anomalous strong reflections or “bright spots” were identified near the base of the ice. At present, there is no satisfactory glaciological explanation for either of these observations.

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