Design and numerical validation of quasi-zero-stiffness metamaterials for very low-frequency band gaps

2020 ◽  
Vol 236 ◽  
pp. 111862 ◽  
Author(s):  
Changqi Cai ◽  
Jiaxi Zhou ◽  
Linchao Wu ◽  
Kai Wang ◽  
Daolin Xu ◽  
...  
Keyword(s):  
Frequency Band ◽  
Low Frequency ◽  
Band Gaps ◽  
Very Low Frequency ◽  
Numerical Validation

Locally resonant periodic structures with low-frequency band gaps

2013 ◽  
Vol 114 (3) ◽  
pp. 033532 ◽  
Author(s):  
Zhibao Cheng ◽  
Zhifei Shi ◽  
Y. L. Mo ◽  
Hongjun Xiang
Keyword(s):  
Frequency Band ◽  
Periodic Structures ◽  
Low Frequency ◽  
Band Gaps

scholarly journals Accordion-like metamaterials with tunable ultra-wide low-frequency band gaps

2018 ◽  
Vol 20 (7) ◽  
pp. 073051 ◽  
Author(s):  
A O Krushynska ◽  
A Amendola ◽  
F Bosia ◽  
C Daraio ◽  
N M Pugno ◽  
...  
Keyword(s):  
Frequency Band ◽  
Low Frequency ◽  
Band Gaps

Low-frequency band gaps in a metamaterial rod by negative-stiffness mechanisms: Design and experimental validation

2019 ◽  
Vol 114 (25) ◽  
pp. 251902 ◽  
Author(s):  
Kai Wang ◽  
Jiaxi Zhou ◽  
Qiang Wang ◽  
Huajiang Ouyang ◽  
Daolin Xu
Keyword(s):  
Frequency Band ◽  
Experimental Validation ◽  
Low Frequency ◽  
Band Gaps ◽  
Negative Stiffness

Heart rate variability and dissociation in panic disorder

2011 ◽  
Vol 26 (S2) ◽  
pp. 147-147
Author(s):  
T. Diveky ◽  
D. Kamaradova ◽  
A. Grambal ◽  
K. Latalova ◽  
J. Prasko ◽  
...  
Keyword(s):  
Heart Rate ◽  
Heart Rate Variability ◽  
Panic Disorder ◽  
Frequency Band ◽  
High Frequency ◽  
Power Spectra ◽  
Low Frequency ◽  
Very Low Frequency ◽  
Significant Difference ◽  
Before And After

The aim of our study is to measure very low frequency band (VLF), low frequency band (LF) and high frequency band (HF) components of R-R interval during orthostatic experiment in panic disorder patients before and after treatment.MethodsWe assessed heart rate variability in 19 patients with panic disorder before and after 6-weeks treatment with antidepressants combined with CBT and 18 healthy controls. They were regularly assessed on the CGI, BAI and BDI. Heart rate variability was assessed during 5 min standing, 5 min supine and 5 min standing positions before and after the treatment. Power spectra were computed using a fast Fourier transformation for very low frequency - VLF (0.0033 - 0.04 Hz), low-frequency - LF (0.04-0.15 Hz) and high frequency - HF (0.15-0.40 Hz) powers.Results19 panic disorder patients entered a 6-week open-label treatment study with combination of SSRI and cognitive behavioral therapy. A combination of CBT and pharmacotherapy proved to be the effective treatment of patients. They significantly improved in all rating scales. There were highly statistical significant differences between panic patients and control group in all components of power spectral analysis in 2nd and in two component of 3rd (LF and HF in standing) positions. There was also statistically significant difference between these two groups in LF/HF ratio in supine position (2nd). During therapy there was tendency to increasing values in all three positions in components of HRV power spectra, but there was only statistically significant increasing in HF1 component.Supported by project IGA MZ ČR NS 10301-3/2009

scholarly journals SPECIAL PURPOSE PULSAR TELESCOPE FOR THE DETECTION OF COSMIC GRAVITATIONAL WAVES

2002 ◽  
Vol 11 (07) ◽  
pp. 1061-1065 ◽  
Author(s):  
Shou-Guan Wang ◽  
Zong-Hong Zhu ◽  
Zhen-Long Zou ◽  
Yuan-Zhong Zhang
Keyword(s):  
Gravitational Waves ◽  
Radio Telescope ◽  
Frequency Band ◽  
Low Frequency ◽  
Millisecond Pulsars ◽  
Very Low Frequency ◽  
Upper Limit ◽  
Stochastic Backgrounds

Pulsars can be used to search for stochastic backgrounds of gravitational waves of cosmological origin within the very low frequency band (VLF), 10-7 to 10-9 Hz. We propose to construct a special 50 m radio telescope. Regular timing measurements of about 10 strong millisecond pulsars will perhaps allow the detection of gravitational waves within VLF or at least will give a more stringent upper limit.

scholarly journals Vibration Attenuation Investigations on a Distributed Phononic Crystals Beam for Rubber Concrete Structures

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Chao Li ◽  
Sifeng Zhang ◽  
Liyong Gao ◽  
Wei Huang ◽  
Zhaoxin Liu
Keyword(s):  
Band Gap ◽  
Frequency Band ◽  
High Frequency ◽  
Concrete Beam ◽  
Vibration Isolation ◽  
Civil Engineering ◽  
Low Frequency ◽  
Band Gaps ◽  
Spring Force ◽  
Rubber Concrete

Locally resonant phononic crystals (LRPCs) beam is characterized by the band gaps; some frequency ranges within which flexural waves cannot propagate freely. So, the LRPCs beam can be used for noise or vibration isolation. In this paper, a LRPCs beam with distributed oscillators is proposed, and the general formula of band gaps and transmission spectrum are derived by the transfer matrix method (TMM) and spectrum element method (SEM). Subsequently, the parameter effects on band gaps are investigated in detail. Finally, a rubber concrete beam is designed to demonstrate the application of distributed LRPCs beam in civil engineering. Results reveal that the distributed LRPCs beam has multifrequency band gaps and the number of the band gaps is equal to that of the oscillators. Compared with others, the distributed LRPCs beam can reduce the stress concentration when subjected to vibration. The oscillator interval has no effect on the band gaps, which makes it more convenient to design structures. Individual changes of oscillator mass or stiffness affect the band gap location and width. When the resonance frequency of oscillator is fixed, the starting frequency of the band gap remains constant, and increasing oscillator mass of high-frequency band gap widens the high-frequency band gap, while increasing oscillator mass of low-frequency gap widens both high-frequency and low-frequency band gaps. External loads, such as the common uniform spring force provided by foundation in civil engineering, are conducive to the band gap, and when the spring force increases, all the band gaps are widened. Taken together, a configuration of LRPCs rubber concrete beam is designed, and it shows good isolation on the vibration induced by the railway. By the presented design flow chart, the research can serve as a reference for vibration isolation of LRPCs beams in civil engineering.

Multilayer-split-tube resonators with low-frequency band gaps in phononic crystals

2014 ◽  
Vol 116 (10) ◽  
pp. 103514 ◽  
Author(s):  
Li Jing ◽  
Jiu Hui Wu ◽  
Dong Guan ◽  
Nansha Gao
Keyword(s):  
Frequency Band ◽  
Low Frequency ◽  
Phononic Crystals ◽  
Band Gaps
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