SignificantPwave attenuation for a specific frequency range beneath Kirishima Volcano, Japan

1997 ◽  
Vol 24 (10) ◽  
pp. 1275-1278 ◽  
Author(s):  
K. Yamamoto ◽  
Y. Ida
Keyword(s):  
Frequency Range ◽  
Kirishima Volcano ◽  
Specific Frequency

scholarly journals A Novel Frequency Reconfigurable Microstrip Patch Antenna using Pin Diode

2020 ◽  
Vol 9 (5) ◽  
pp. 2013-2017
Keyword(s):  
Patch Antenna ◽  
Return Loss ◽  
Microstrip Patch Antenna ◽  
Pin Diode ◽  
Optimum Level ◽  
Frequency Range ◽  
Microstrip Patch ◽  
Single Antenna ◽  
Specific Frequency ◽  
Switching State

In recent study, in the growth of wireless technology single antenna that works with a specific frequency is becoming outdated. The antenna which is capable to work dynamically is encouraged. To make an antenna to work dynamically, modification in any of the antenna characteristics can be applied. In this proposed work, the antenna which can reconfigure its frequency is designed and analyzed. Microstrip patch antenna is most popular printed type antenna which is suitable for diverse applications. The antenna design consists of three PIN diodes which are placed in different positions on the patch. Depending upon the switching state of PIN diode the antenna can operate in different frequency ranges. The frequency range obtained ranges from 1.38 GHz to 3.24 GHz. Return loss value, VSWR obtained is of optimum level. The various gain of antenna is obtained in simulation. The analysis of the antenna is done in ANSYS HFSS software.

Vibroacoustic Optimization of Mechanical Structures: A Controlled Random Search Approach

2012 ◽  
Vol 622-623 ◽  
pp. 158-161 ◽  
Author(s):  
Mostafa Ranjbar ◽  
Steffen Marburg
Keyword(s):  
Random Search ◽  
Power Level ◽  
Search Method ◽  
Frequency Range ◽  
Controlled Random Search ◽  
Sound Power Level ◽  
Specific Frequency ◽  
Radiated Sound ◽  
Search Approach ◽  
Radiated Sound Power

A combination of controlled random search method and geometry modification concept is used to minimize the root mean square level of structure borne sound for a model. The structure is a rectangular plate made of steel. A specific frequency range for this porpuse is considered. The results show that this approach could produce significant reduction in the value of radiated sound power level of the structure within a limited time.

scholarly journals The blinking eye: A window into tinnitus

2021 ◽  
Author(s):  
Lars Rogenmoser
Keyword(s):  
Rhesus Monkeys ◽  
Cross Validation ◽  
Auditory Modality ◽  
Interference Effects ◽  
Frequency Range ◽  
Modulation Pattern ◽  
Specific Frequency ◽  
Fresh Impetus ◽  
Current Species ◽  
Underlying Pathophysiology

Tinnitus is a prevalent untreatable audiological disorder, charaterized by the perception of phantom sound. Despite longstanding research with animals, its underlying pathophysiology remains poorly understood. The obstacle in progressing in the field may lie in both the current species of choice and the available measurements of tinnitus for animals. To provide fresh impetus, we developed a novel tinnitus-verification technique applicable to rhesus monkeys. Tinnitus was induced via salicylate administration in two rhesus monkeys, and was confirmed by applying a specific eye-blinking procedure: Blinks, as monitored using EMG, were triggered via puffs of air towards the cheek, and their modulation was studied as a function of preceding tones with various frequency and intensity conditions. The advantage in using a tactile reflex-inducing stimulus lies in its non-auditory modality, bypassing potential confounding factors of hearing loss and hyperacusis. Interference effects on the blink modulation pattern was interpreted as tinnitus, and the interfering frequency of the preceding interfering tone as tinnitus frequency. A cross-validation in a sample of tinnitus patients revealed interfering effects of the preceding tone at the specific frequency range corresponding to their own tinnitus frequency, as independently determined by audiologists. This interference effect increased as a function of their individual tinnitus loudness. In conclusion, the present work demonstrates a considerable transferability of our newly established tinnitus-verification technique from non-human primates to human tinnitus patients.

Design of Broadband Acoustic Cloak Using Topology Optimization

2016 ◽  
Author(s):  
Weiyang Lin ◽  
James C. Newman ◽  
W. Kyle Anderson
Keyword(s):  
Topology Optimization ◽  
Acoustic Wave ◽  
Topological Optimization ◽  
Frequency Range ◽  
Acoustic Wave Propagation ◽  
Target Frequency ◽  
Scattering Field ◽  
Gradient Based ◽  
Specific Frequency ◽  
Improved Performance

A procedure for broadband topology optimization is applied to the design of acoustic cloaking. An acoustic cloak conceals a given object with arbitrary shapes. That is, the object can be made undetectable with respect to acoustic wave propagation in a specific frequency range. The guided acoustic wave in a given direction will re-attach in the incident direction, leading to a minimized norm of the scattering field. Gradient-based topological optimization is accomplished using a time-dependent adjoint formulation for sensitivity analysis. Results indicate that the current methodology produces improved cloaking performance for narrowband near a target frequency, and as expected less than optimal performance is observed away from this frequency. For topology optimization over a broadband, improved performance is realized over the entire frequency range, but not necessarily optimal at any given target frequency.

Development of an In Situ Tool Wear Monitoring System Using the Cutting Sound

2015 ◽  
Vol 1117 ◽  
pp. 277-280
Author(s):  
Haruka Takahashi ◽  
Katsuhiko Sakai ◽  
Hiroo Shizuka
Keyword(s):  
Tool Wear ◽  
Monitoring System ◽  
Sound Pressure ◽  
Tool Wear Monitoring ◽  
Frequency Range ◽  
Wear Monitoring ◽  
Specific Frequency ◽  
The Relationship ◽  
Fft Analysis

This paper discusses the development of an in-situ, real-time tool wear monitoring system using the cutting sound that occurs during machining. In this study, the turning of carbon steel was implemented to examine the relationship between tool wear and the waveform of the cutting sound. Characteristic waveforms were extracted by fast Fourier transform (FFT) analysis of the cutting sound. The results indicated that the sound pressure of a specific frequency range increased during the progress of cutting-tool wear. In addition, it was possible to monitor the progress of tool wear by measuring the spectrum of a specific frequency range, even if the shape of the tool rest and the shapes of the work material were different, under certain cutting conditions.

scholarly journals Frequency Analysis of Noise Generated by Pneumatic Wheels

2017 ◽  
Vol 42 (3) ◽  
pp. 459-467
Author(s):  
Jan Warczek ◽  
Rafał Burdzik ◽  
Łukasz Konieczny ◽  
Grzegorz Siwiec
Keyword(s):  
Acoustic Emission ◽  
Traffic Noise ◽  
Dominant Frequency ◽  
Frequency Range ◽  
Acoustic Emission Energy ◽  
Measuring Station ◽  
Source Data ◽  
Frequency Components ◽  
Specific Frequency

Abstract The dominant sources of traffic noise, which are linked directly to the vehicle, are dependent on the speed. In terms of speed of 50-120 km/h the dominant source of noise is pneumatic wheels. The aim of the research was chosen to develop a method and experimental determination of the dominant frequency components of noise generated by the car tire. For the purpose of the study and on the basis of the analysis of the source data it was assumed that there is a relationship between the vibration of the tread elements and emitted noise, especially for low and medium frequencies. Thus, the target was set on the basis of the own method of research in the built measuring station. Based on the survey and the obtained results it can be stated that in the spectrum of the noise emitted by the tires the frequency components are dominant. Non-directional tire structure includes more frequency components which at the speed adopted in the studies are located at a greater frequency range than it is for the directional tire. In the case of a tire with a directional tread, acoustic emission energy is more associated with specific frequency components. The developed method provides results independent from the influence of the type of road surface on the acoustic emission while driving.

scholarly journals Structural health monitoring of beams with moving oscillator: theory and laboratory

2021 ◽  
Vol 73 (07) ◽  
pp. 693-704
Keyword(s):  
Time History ◽  
Frequency Variation ◽  
Frequency Range ◽  
Variation Pattern ◽  
Fuzzy Genetic Algorithm ◽  
Specific Frequency ◽  
Fuzzy Genetic ◽  
Moving Oscillator ◽  
Emd Method ◽  
Oscillator Theory

In this paper, a new intelligent portable mechanical system is introduced experimentally and theoretically to detect damage employing the fuzzy-genetic algorithm and EMD. For this purpose, the acceleration-time history is obtained from three points of a simply-supported beam utilizing accelerometer sensors. The gained signal is decomposed into small components by using an EMD method. Each decomposed component contains a specific frequency range. Finally, the proposed algorithm is designed to find the location and severity of damage through the frequency variation pattern among the safe and the damaged beam.

An Improved Damage Index for Nondestructive Evaluation of a Disbond in Honeycomb Sandwich Structure Using Guided Waves

2020 ◽  
Vol 3 (3) ◽  
Author(s):  
Lifu Wang ◽  
Fei Gao ◽  
Yichi Zhang ◽  
Leonardo Araque ◽  
Steffen Tai ◽  
...  
Keyword(s):  
Nondestructive Evaluation ◽  
Large Scale ◽  
Experimental Studies ◽  
Damage Index ◽  
Ultrasonic Waves ◽  
Bottom Surface ◽  
Frequency Range ◽  
Great Loss ◽  
Honeycomb Sandwich ◽  
Specific Frequency

Abstract Honeycomb sandwich structures (HSS) are widely used in the aerospace industry due to their high strength-to-stiffness ratio. However, these materials are susceptible to damage during manufacturing or service that can cause great loss in the load bearing capacity or even failure. Thus, periodic or continuous nondestructive evaluation (NDE) of HSS is essential for safe operation. Development of effective NDE technique is challenging due to the geometric complexity of the honeycomb core. Guided ultrasonic waves are ideal for large-scale testing because of their large propagation range and high sensitivity to defects in their path. In this paper, an improved NDE method for detecting disbonds at the top and bottom interfaces between the core and facesheets is proposed based on experimental studies. By applying excitation signals at different frequencies, the responses at the top and bottom surface of plate-like HSS component are compared and analyzed. The response in a specific frequency range is further studied by introducing disbonds at the top interface. It is shown that some components of the recorded signal in a specific frequency range are more sensitive for detecting the disbond. In addition, an improvement of the conventional damage index based on the damage feature is proposed, and a systematic procedure for detecting damage inside HSS is conducted on an elevator section of an Airbus 330. The results show that the optimized damage index greatly improves the resolution and adaptability of damage detection in the structures.

scholarly journals Narrowband-to-Narrowband Frequency Reconfiguration with Harmonic Suppression Using Fractal Dipole Antenna

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
S. A. Hamzah ◽  
M. Esa ◽  
N. N. N. A. Malik ◽  
M. K. H. Ismail
Keyword(s):  
Dipole Antenna ◽  
Single Frequency ◽  
Harmonic Suppression ◽  
Frequency Range ◽  
Low Loss ◽  
Harmonic Frequency ◽  
Radiating Element ◽  
Measurement Results ◽  
Specific Frequency ◽  
Original Size

Harmonic suppressed fractal antenna with switches named TMFDB25 is developed to select desired frequency band from 400 MHz to 3.5 GHz. The radiating element length is changed to tune the operating frequency while the stub is used to eliminate the undesired harmonic frequency. The balun circuit is reduced by 75% from the original size. The antenna is built on a low loss material. It has the ability to select a single frequency out of fifteen different bands and maintain the omnidirectional radiation pattern properties. Furthermore, the antenna is designed, built, and tested. Simulation and measurement results show that the antenna operates well at the specific frequency range. Therefore, the antenna is suitable to be used for switching frequencies in the band of TV, GSM900/1800, 3G, ISM 2.4 GHz, and above.

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