scholarly journals Noise Analysis of a Passive Resonant Laser Gyroscope

Sensors ◽  
2020 ◽  
Vol 20 (18) ◽  
pp. 5369
Author(s):  
Kui Liu ◽  
Fenglei Zhang ◽  
Zongyang Li ◽  
Xiaohua Feng ◽  
Ke Li ◽  
...  
Keyword(s):  
Large Scale ◽  
Free Spectral Range ◽  
Noise Analysis ◽  
Ring Cavity ◽  
Frequency Discrimination ◽  
Frequency Range ◽  
Noise Sources ◽  
Noise Transfer Function ◽  
Resonant Laser ◽  
Laser Gyroscope

Large-scale laser gyroscopes have found important applications in Earth sciences due to their self-sufficient property of measurement of the Earth’s rotation without any external references. In order to extend the relative rotation measurement accuracy to a better level so that it can be used for the determination of the Earth orientation parameters (EOP), we investigate the limitations in a passive resonant laser gyroscope (PRG) developed at Huazhong University of Science and Technology (HUST) to pave the way for future development. We identify the noise sources from the derived noise transfer function of the PRG. In the frequency range below 10−2Hz, the contribution of free-spectral-range (FSR) variation is the dominant limitation, which comes from the drift of the ring cavity length. In the 10−2 to 103Hz frequency range, the limitation is due to the noises of the frequency discrimination system, which mainly comes from the residual amplitude modulation (RAM) in the frequency range below 2 Hz. In addition, the noise contributed by the Mach–Zehnder-type beam combiner is also noticeable in the 0.01 to 2 Hz frequency range. Finally, possible schemes for future improvement are also discussed.

scholarly journals Suppression of amplitude modulation induced by polarization mode dispersion using a multi-degree-of-freedom fiber filter

2018 ◽  
Vol 6 ◽  
Author(s):  
Rao Li ◽  
Youen Jiang ◽  
Zhi Qiao ◽  
Canhong Huang ◽  
Wei Fan ◽  
...  
Keyword(s):  
High Power ◽  
Amplitude Modulation ◽  
Transmission Spectrum ◽  
High Speed ◽  
Large Scale ◽  
Modulation Depth ◽  
Free Spectral Range ◽  
Polarization Mode Dispersion ◽  
Polarization Mode ◽  
Mode Dispersion

Polarization mode dispersion (PMD) in fibers for high-power lasers can induce significant frequency modulation to amplitude modulation (FM-to-AM) conversion. However, existing techniques are not sufficiently flexible to achieve efficient compensation for such FM-to-AM conversion. By analyzing the nonuniform transmission spectrum caused by PMD, we found that the large-scale envelope of the transmission spectrum has more serious impacts on the amount of AM. In order to suppress the PMD-induced FM-to-AM conversion, we propose a novel tunable spectral filter with multiple degrees of freedom based on a half-wave plate, a nematic liquid crystal, and an axis-rotated polarization-maintaining fiber. Peak wavelength, free spectral range (FSR), and modulation depth of the filter are decoupled and can be controlled independently, which is verified through both simulations and experiments. The filter is utilized to compensate for the PMD-induced FM-to-AM conversion in the front end of a high-power laser facility. The results indicate that, for a pulse with phase-modulation frequency of 22.82 GHz, the FM-to-AM conversion could be reduced from 18% to 3.2% within a short time and maintained below 6.5% for 3 h. The proposed filter is also promising for other applications that require flexible spectral control such as high-speed channel selection in optical communication networks.

Exposure to industrial noise: impacts on cognitive performance

2021 ◽  
Vol 263 (4) ◽  
pp. 2590-2600
Author(s):  
Luiz Henrique Mesa Casa Pereira ◽  
Björn Knöfel ◽  
Jan Troge ◽  
Welf-Guntram Drossel ◽  
Marcel Klein ◽  
...  
Keyword(s):  
Cognitive Performance ◽  
Noise Analysis ◽  
Low Frequency ◽  
Cumulative Effect ◽  
Noise Sources ◽  
Industrial Noise ◽  
Sound Levels ◽  
Office Environments ◽  
High Sound ◽  
High Frequency Content

Research on the relation between exposure to noise and cognitive performance inside industrial environments is not as broad as on office environments. For a better understanding of the specific industrial noise problems, participants performed arithmetic tests inside a hemi anechoic room while they were exposed to sounds of five typical industrial noise sources. The subjects also classified how annoying they perceived the noise signals. The effect of noise on the arithmetic test's performance was larger on accuracy than on velocity, which was verified using a Student t-test. Spectral-temporal characteristics - especially high frequency content and strong low frequency modulation - appear to relate better with lower performance on the test than high sound levels. Subjects that evaluated noise as more annoying performed worse in a final arithmetic test (under silence) after being exposed to the noises, indicating a possible cumulative effect of noise on performance. The findings provide a better insight in the cognitive behavior of people who are exposed to industrial noise. Hence, the study will proceed with the specific noise analysis of single industrial workplaces.

scholarly journals Reducing the harmful effects of noise on the human environment. Sound insulation of industrial skeleton enclosures in the 10–40 kHz frequency range

2020 ◽  
Vol 18 (2) ◽  
pp. 1451-1463
Author(s):  
Witold Mikulski
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Sheet Steel ◽  
Pressure Level ◽  
Sound Insulation ◽  
Frequency Range ◽  
Noise Sources ◽  
Human Environment ◽  
Absorbing Material ◽  
Acoustic Enclosures

Abstract Purpose The purpose of the research is to work out a method for determining the sound insulation of acoustic enclosures for industrial sources emitting noise in the frequency range of 10–40 kHz and apply the method to measure the sound insulation of acoustic enclosures build of different materials. Methods The method is developed by appropriate adaptation of techniques applicable currently for sound frequencies of up to 10 kHz. The sound insulation of example enclosures is determined with the use of this newly developed method. Results The research results indicate that enclosures (made of polycarbonate, plexiglass, sheet aluminium, sheet steel, plywood, and composite materials) enable reducing the sound pressure level in the environment for the frequency of 10 kHz by 19–25 dB with the reduction increasing to 40–48 dB for the frequency of 40 Hz. The sound insulation of acoustic enclosures with a sound-absorbing material inside reaches about 38 dB for the frequency of 10 kHz and about 63 dB for the frequency of 40 kHz. Conclusion Some pieces of equipment installed in the work environment are sources of noise emitted in the 10–40 kHz frequency range with the intensity which can be high enough to be harmful to humans. The most effective technical reduction of the associated risks are acoustic enclosures for such noise sources. The sound pressure level reduction obtained after provision of an enclosure depends on its design (shape, size, material, and thickness of walls) and the noise source frequency spectrum. Realistically available noise reduction values may exceed 60 dB.

scholarly journals Solving Noise Pollution Issue Using Plenum Window with Perforated Thin Box

Crystals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 614
Author(s):  
Hsiao Mun Lee ◽  
Andi Haris ◽  
Kian Meng Lim ◽  
Jinlong Xie ◽  
Heow Pueh Lee
Keyword(s):  
White Noise ◽  
Traffic Noise ◽  
Noise Pollution ◽  
Experimental Results ◽  
Frequency Range ◽  
Noise Mitigation ◽  
Noise Sources ◽  
Acoustic Performance ◽  
Common Noise ◽  
The Common

In the present study, a conventional plenum window was incorporated with perforated thin box in order to enhance its performance at frequency range which centralized at 1000 Hz as most of the common noise sources at city nowadays are centralizing around this frequency. The entire studies were conducted in a reverberation room. The effectiveness of jagged flap on mitigating diffracted sound was also studied. Three types of noises were examined in the current study—white noise, traffic noise and construction noises. The experimental results showed that the plenum window with perforated thin box could reduce 8.4 dBA, 8.7 dBA and 6.9 dBA of white, traffic and construction noises, respectively. The jagged flaps did not have significant effect on the plenum window’s noise mitigation performance. When frequencies were ranging from 800 Hz to 1250 Hz, when compared with the case of without perforated thin box, it was found that the perforated thin box had good acoustic performance where it was able to reduce additional 1.6 dBA, 1.6 dBA and 1.2 dBA of white, construction and traffic noises, respectively.

The 1983 Liege Earthquake: Damage Distribution and Site Effects

1990 ◽  
Vol 6 (4) ◽  
pp. 713-737 ◽  
Author(s):  
D. Jongmans ◽  
M. Campillo
Keyword(s):  
Site Effects ◽  
Large Scale ◽  
Site Response ◽  
Dominant Frequency ◽  
Small Scale ◽  
Eastern United States ◽  
Frequency Range ◽  
Damage Distribution ◽  
Damage Data ◽  
The City

On November 8, 1983, a moderate magnitude (Ml=4.9) earthquake struck Liege (Belgium). A damage study has shown that site effects at different scales have played an important role in amplifying ground motion. On a large scale, the damage distribution has been determined by the presence of a large Carboniferous syncline beneath the city as shown by 2D numerical modeling. On a small scale, the main damage concentrations can be correlated with local superficial deposits which have amplified ground motions in the frequency range of buildings. A geophysical survey was carried out to measure the shear wave velocity of the different formations. Site response computations were made at numerous sites in order to estimate the possible amplification and to compare the results with the damage. It was shown that the spectral amplifications computed in the dominant frequency range of the buildings are consistent with the damage data. In very affected areas, 1D amplifications of 4 to 6 were obtained and in some cases 2D effects may have occurred. The Liege earthquake, taking place in the intraplate region of Northwestern Europe, presents a significant interest to other similar areas as the eastern United States.

WAVELET-BASED POSTPROCESSING OF JET LES DATA FOR ACOUSTIC FAR-FIELD EXTRAPOLATIONS

2013 ◽  
Vol 21 (04) ◽  
pp. 1350017
Author(s):  
RAMIN KAVIANI ◽  
VAHID ESFAHANIAN ◽  
MOHAMMAD EBRAHIMI
Keyword(s):  
Large Scale ◽  
Stokes Equations ◽  
Near Field ◽  
Flow Simulation ◽  
Computational Time ◽  
Jet Flows ◽  
Small Scale ◽  
Frequency Noise ◽  
Far Field ◽  
Noise Sources

The affordable grid resolutions in conventional large-eddy simulations (LESs) of high Reynolds jet flows are unable to capture the sound generated by fluid motions near and beyond the grid cut-off scale. As a result, the frequency spectrum of the extrapolated sound field is artificially truncated at high frequencies. In this paper, a new method is proposed to account for the high frequency noise sources beyond the resolution of a compressible flow simulation. The large-scale turbulent structures as dominant radiators of sound are captured in LES, satisfying filtered Navier–Stokes equations, while for small-scale turbulence, a Kolmogorov's turbulence spectrum is imposed. The latter is performed via a wavelet-based extrapolation to add randomly generated small-scale noise sources to the LES near-field data. Further, the vorticity and instability waves are filtered out via a passive wavelet-based masking and the whole spectrum of filtered data are captured on a Ffowcs-Williams/Hawkings (FW-H) surface surrounding the near-field region and are projected to acoustic far-field. The algorithm can be implemented as a separate postprocessing stage and it is observed that the computational time is considerably reduced utilizing a hybrid of many-core and multi-core framework, i.e. MPI-CUDA programming. The comparison of the results obtained from this procedure and those from experiments for high subsonic and transonic jets, shows that the far-field noise spectrum agree well up to 2 times of the grid cut-off frequency.

Imaging the Nechako Basin, British Columbia, using ambient seismic noise1This article is one of a series of papers published in this Special Issue on the theme of New insights in Cordilleran Intermontane geoscience: reducing exploration risk in the mountain pine beetle-affected area, British Columbia.

2011 ◽  
Vol 48 (6) ◽  
pp. 1038-1049 ◽  
Author(s):  
O.A. Idowu ◽  
A.W. Frederiksen ◽  
J.F. Cassidy
Keyword(s):  
British Columbia ◽  
Surface Wave ◽  
Group Velocity ◽  
Large Scale ◽  
Green's Functions ◽  
Green’S Functions ◽  
Noise Analysis ◽  
Sedimentary Basins ◽  
Seismic Exploration ◽  
Velocity Models

The Nechako Basin in British Columbia, Canada is suspected to have hydrocarbon potential. However, it has been a difficult basin to explore because of the presence of Tertiary volcanic outcrop. The volcanic outcrop makes the use of conventional seismic exploration methods difficult owing to a strong velocity inversion at its base. An alternative is the passive source method known as ambient noise surface wave tomography. The method, which examines the high-frequency surface wave field that is obtained from noise analysis, is sensitive to large-scale crustal structure and has been successfully applied to measuring the depths of sedimentary basins. Station-to-station Green’s functions within the basin were estimated by cross-correlating the vertical components of the seismic noise data recorded by 12 POLARIS (Portable Observatories for Lithosphere Analysis and Research Investigating Seismicity) and CNSN (Canadian National Seismgraph Network) seismic stations between September 2006 and November 2007. The resulting Green’s functions were dominated by Rayleigh waves. The dispersion characteristics of the Rayleigh waveforms were measured within the microseismic band. Inversion of the dispersion curves produced 1-D and 2-D thickness models and 2-D group velocity models for the Nechako Basin and its surrounding region. The velocity models indicate two low group velocity structures within the basin that might represent sedimentary packages, and some pockets of high-velocity zones that show the presence of volcanic rocks within and on the basin. The thickness models indicated the presence of about six different velocity layers, in which the average thickness of the basin and the crust are ∼4.8 and 30–34 km, respectively.

Design and modeling of an ultra-wideband low-noise distributed amplifier in InP DHBT technology

2019 ◽  
Vol 11 (7) ◽  
pp. 635-644 ◽  
Author(s):  
T. Shivan ◽  
E. Kaule ◽  
M. Hossain ◽  
R. Doerner ◽  
T. Johansen ◽  
...  
Keyword(s):  
Noise Figure ◽  
Impedance Matching ◽  
Low Noise ◽  
Ultra Wideband ◽  
Frequency Range ◽  
Collector Current ◽  
Noise Sources ◽  
Distributed Amplifier ◽  
Double Heterojunction ◽  
High Bandwidth

AbstractThis paper reports on an ultra-wideband low-noise distributed amplifier (LNDA) in a transferred-substrate InP double heterojunction bipolar transistor (DHBT) technology which exhibits a uniform low-noise characteristic over a large frequency range. To obtain very high bandwidth, a distributed architecture has been chosen with cascode unit gain cells. Each unit cell consists of two cascode-connected transistors with 500 nm emitter length and ft/fmax of ~360/492 GHz, respectively. Due to optimum line-impedance matching, low common-base transistor capacitance, and low collector-current operation, the circuit exhibits a low-noise figure (NF) over a broad frequency range. A 3-dB bandwidth from 40 to 185 GHz is measured, with an NF of 8 dB within the frequency range between 75 and 105 GHz. Moreover, this circuit demonstrates the widest 3-dB bandwidth operation among all reported single-stage amplifiers with a cascode configuration. Additionally, this work has proposed that the noise sources of the InP DHBTs are largely uncorrelated. As a result, a reliable prediction can be done for the NF of ultra-wideband circuits beyond the frequency range of the measurement equipment.

scholarly journals Fast high-energy X-ray imaging for Severe Accidents experiments on the future PLINIUS-2 platform

2018 ◽  
Vol 170 ◽  
pp. 08003
Author(s):  
L. Berge ◽  
N. Estre ◽  
D. Tisseur ◽  
E. Payan ◽  
D. Eck ◽  
...  
Keyword(s):  
Large Scale ◽  
Spot Size ◽  
High Energy ◽  
Simulation Software ◽  
Small Scale ◽  
Noise Sources ◽  
X Ray ◽  
X Ray Imaging ◽  
The Future ◽  
Set Up

The future PLINIUS-2 platform of CEA Cadarache will be dedicated to the study of corium interactions in severe nuclear accidents, and will host innovative large-scale experiments. The Nuclear Measurement Laboratory of CEA Cadarache is in charge of real-time high-energy X-ray imaging set-ups, for the study of the corium-water and corium-sodium interaction, and of the corium stratification process. Imaging such large and high-density objects requires a 15 MeV linear electron accelerator coupled to a tungsten target creating a high-energy Bremsstrahlung X-ray flux, with corresponding dose rate about 100 Gy/min at 1 m. The signal is detected by phosphor screens coupled to high-framerate scientific CMOS cameras. The imaging set-up is established using an experimentally-validated home-made simulation software (MODHERATO). The code computes quantitative radiographic signals from the description of the source, object geometry and composition, detector, and geometrical configuration (magnification factor, etc.). It accounts for several noise sources (photonic and electronic noises, swank and readout noise), and for image blur due to the source spot-size and to the detector unsharpness. In a view to PLINIUS-2, the simulation has been improved to account for the scattered flux, which is expected to be significant. The paper presents the scattered flux calculation using the MCNP transport code, and its integration into the MODHERATO simulation. Then the validation of the improved simulation is presented, through confrontation to real measurement images taken on a small-scale equivalent set-up on the PLINIUS platform. Excellent agreement is achieved. This improved simulation is therefore being used to design the PLINIUS-2 imaging set-ups (source, detectors, cameras, etc.).

scholarly journals Spontaneous otoacoustic emission recordings during contralateral pure-tone activation of medial olivocochlear reflex

2017 ◽  
Vol 104 (2) ◽  
pp. 171-182
Author(s):  
E Bulut ◽  
L Öztürk
Keyword(s):  
Pure Tone ◽  
Outer Hair Cell ◽  
Basilar Membrane ◽  
Otoacoustic Emission ◽  
Frequency Discrimination ◽  
Frequency Range ◽  
Unilateral Deafness ◽  
Transient Evoked Otoacoustic Emission ◽  
Medial Olivocochlear ◽  
Bilateral Deafness

We hypothesized that cochlear frequency discrimination occurs through medial olivocochlear efferent (MOCE)-induced alterations in outer hair cell (OHC) electromotility, which is independent from basilar membrane traveling waves. After obtaining informed consent, volunteers with normal hearing (n = 10; mean age: 20.6 ± 1.2 years) and patients with unilateral deafness (n = 10; mean age: 30.2 ± 17.9 years) or bilateral deafness (n = 8; mean age: 30.7 ± 13.8 years) underwent a complete physical and audiological examination, and audiological tests including transient evoked otoacoustic emission and spontaneous otoacoustic emission (TEOAE and SOAE, respectively). SOAE recordings were performed during contralateral pure-tone stimuli at 1 and 3 kHz. SOAE recordings in the presence of contralateral pure-tone stimuli showed frequency-specific activation out of the initial frequency range of SOAE responses. Basilar membrane motion during pure-tone stimulation results from OHC activation by means of MOCE neurons rather than from a traveling wave. Eventually, frequency-specific responses obtained from SOAEs suggested that OHC electromotility may be responsible for frequency discrimination of the cochlea independently from basilar membrane motion.

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