Experimental Research on the Impact Environment of Multiplate Cabinet

As an installation and protection device for electrical and electronic components, a shipboard cabinet is a typical multiplate structure. In order to study the impact environment distribution laws of such structures, impact testing was carried out on a shipboard cabinet under four working conditions in this paper. In addition, the impact response characteristics of such a multiplate structure were determined by numerical simulation and theoretical analysis. The impact environments of some pivotal points in cabinet were measured and some laws of dynamic response were found. The impact environment of central position was more severe on a single plate because of the first vibration modal. For different plates, the responses were usually similar at low-frequency band and a little different at high-frequency band. The theoretical analysis of the single degree of freedom oscillator was carried out, and the sensitivity of the response to the different characteristic frequencies was discussed based on the shock spectrum theory. A new method of calculating the response at a special frequency was proposed and verified.

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On the contamination of the global 21 cm signal from polarized foregrounds

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2425 ◽

2019 ◽

Cited By ~ 12

Author(s):

Marta Spinelli ◽

Gianni Bernardi ◽

Mario G Santos

Keyword(s):

Frequency Band ◽

Low Frequency ◽

Complex Frequency ◽

Gaussian Profile ◽

Reconstructed Signal ◽

Linearly Polarized ◽

Exotic Physics ◽

Single Polarization ◽

The Impact ◽

The Universe

Abstract Global (i.e. sky-averaged) 21 cm signal experiments can measure the evolution of the universe from the Cosmic Dawn to the Epoch of Reionization. These measurements are challenged by the presence of bright foreground emission that can be separated from the cosmological signal if its spectrum is smooth. This assumption fails in the case of single polarization antennas as they measure linearly polarized foreground emission - which is inevitably Faraday rotated through the interstellar medium. We investigate the impact of Galactic polarized foregrounds on the extraction of the global 21 cm signal through realistic sky and dipole simulations both in a low frequency band from 50 to 100 MHz, where a 21 cm absorption profile is expected, and in a higher frequency band (100 − 200 MHz). We find that the presence of a polarized contaminant with complex frequency structure can bias the amplitude and the shape of the reconstructed signal parameters in both bands. We investigate if polarized foregrounds can explain the unexpected 21 cm Cosmic Dawn signal recently reported by the EDGES collaboration. We find that unaccounted polarized foreground contamination can produce an enhanced and distorted 21 cm absorption trough similar to the anomalous profile reported by Bowman et al. (2018), and whose amplitude is in mild tension with the assumed input Gaussian profile (at ∼1.5σ level). Moreover, we note that, under the hypothesis of contamination from polarized foreground, the amplitude of the reconstructed EDGES signal can be overestimated by around 30%, mitigating the requirement for an explanation based on exotic physics.

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The Acoustic Behaviors of Dual Layered Nonwoven Absorbers: From Model Building to Experiment Verification

Journal of Computational Acoustics ◽

10.1142/s0218396x14500015 ◽

2014 ◽

Vol 22 (02) ◽

pp. 1450001

Author(s):

Jianli Liu ◽

Xinjin Liu ◽

Wei Bao ◽

Shuangshan Wang ◽

Longmin Chen ◽

...

Keyword(s):

Numerical Simulation ◽

Theoretical Analysis ◽

Sound Absorption ◽

Model Building ◽

Low Frequency ◽

Physical Structure ◽

Absorption Model ◽

Absorption Coefficients ◽

Experiment Verification ◽

The Impact

Nonwovens are ideal materials for use as noise control elements because of their unique physical structure and special acoustic behaviors, especially when their structures are complicatedly designed. In this paper, we first deduce a sound absorption model for dual-layered porous nonwovens by extending the Zwikker and Kosten theory. Then a theoretical analysis and a numerical simulation of the impact of thickness and porosity of outer and inner layers on the sound absorption coefficient are followed by an experiment designed to compare the calculated sound absorption coefficients and the measured ones. Experiment results indicate that the measured and the calculated sound absorption coefficients are very similar in trend with change of thickness, porosity and sound frequency, apart from the obvious difference at low frequency. Finally, the main reasons for the differences between the theoretic data and the experimental ones are also explored.

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Evaluation of Reduction Performance of Floor Impact Sound on Floor Covering in the Reverberation Chamber

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.851.685 ◽

2016 ◽

Vol 851 ◽

pp. 685-689

Author(s):

Jun Oh Yeon ◽

Hye Kyung Shin ◽

Kwan Seop Yang ◽

Kyoung Woo Kim

Keyword(s):

Frequency Band ◽

Low Frequency ◽

Floor Covering ◽

Reverberation Chamber ◽

Rubber Ball ◽

Floor Coverings ◽

Sound Reduction ◽

The Impact ◽

A Performance

In order to reduce floor impact sound in apartment houses, 30 types of floor coverings were chosen to evaluate a performance of reduction in impact sound in the reverberation chamber. In the test of performance of reduction in impact sound using bang machine, a performance of impact sound reduction can be ensured at a low frequency band of 63 Hz and 100 Hz. However, impact sound was amplified at a band of 80 Hz and 125 Hz except for some floor coverings. In the test of performance of reduction in impact sound using a rubber ball drop at a height of 100 cm, a performance of reduction in impact sound was improved from a band of 50 Hz up to 400 Hz. In the test of rubber ball drop at a height of 40 cm, which was similar to the impact of children's running, a performance of reduction in impact sound was improved from a band of 80 Hz and 160 Hz up to 400 Hz.

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Dynamic Response of Seismic Dangerous Rock Based on PFC and Dynamics

Advances in Civil Engineering ◽

10.1155/2020/8846130 ◽

2020 ◽

Vol 2020 ◽

pp. 1-19

Author(s):

Yun Tian ◽

Linfeng Wang ◽

Honghua Jin ◽

Biao Zeng

Keyword(s):

Dynamic Response ◽

Low Frequency ◽

Peak Stress ◽

Slope Instability ◽

Dynamic Responses ◽

Distribution Model ◽

Distribution Models ◽

Response Characteristics ◽

Crack Propagation Process ◽

The Impact

Rock slope instability by earthquakes results in substantial economic and property losses. The calculation method of interlayer load and stability coefficient of horizontal complex layered rock slopes in high-intensity areas is established from material mechanics, fracture mechanics, and dynamics. The stability of horizontal layered dangerous rock is calculated after combining it with PFC simulation technology to verify the rationality of the calculation in the Wenchuan area of Sichuan Province. The dynamic response characteristics of dangerous rocks under different weathering degrees are also analyzed. The results show that both methods have an excellent early warning effect on earthquake dangerous rocks. Among the PGA amplification factors, Model 1 has a relatively uniform distribution, Model 2 has a zigzag distribution, Models 3 and 4 have a “U”-shaped distribution, and the most severe acceleration dynamic responses are 4-1 and 4-2 rock blocks. The dynamic acceleration response of mudstone is affected by the crack propagation process of the upper sandstone and exhibits a particular elevation amplification effect. The peak stress gradually decreases with the increase in weathering and elevation. The stress change of the inner chain No. 2 in the horizontal x and y directions is severe, and the stress response of the outer chain No. 1 in the vertical z-direction is severe. It recommends that earthquake disaster protection projects should pay attention to the impact of low-frequency (0–10 Hz) and high-frequency (250 Hz) earthquakes on slope stability.

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Design And Experimental Investigation Of Single Plate Clutch

International Journal of Mechanical Engineering ◽

10.14445/23488360/ijme-v7i3p104 ◽

2020 ◽

Vol 7 (3) ◽

pp. 30-34

Author(s):

Mr. Kannan ◽

Saravanan P ◽

Srinivasaperumal K P

Keyword(s):

High Performance ◽

Low Cost ◽

Impact Testing ◽

Material Strength ◽

Plate Material ◽

Disk Interface ◽

Single Plate ◽

Research Material ◽

The Cost ◽

The Impact

The Clutch Disk or plate is a part of the manual transmission system for your vehicle that delivers power from the engine to the transmission. It is mounted b/w the pressure plate & the flywheel. For high performance automobiles it is constructed from highly durable steel or sometimes other material. Performance of Vehicle Clutch plates on pad-to-disk interface touch conditions. The purpose of this study is to evaluate the impact on the friction & wear of Clutch Plate material from different material composition. If we use the composite material the cost instead of the traditional material, weight can be reduced and the life of the brake material can be extended at low cost. In our research, material strength is experimentally investigated to predict compression, tensile & impact testing in both materials (E-glass & Jute fiber) to choose the better material of single plate clutch

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Interdigitated Sensor Optimization for Blood Sample Analysis

Biosensors ◽

10.3390/bios10120208 ◽

2020 ◽

Vol 10 (12) ◽

pp. 208

Author(s):

Julien Claudel ◽

Thanh-Tuan Ngo ◽

Djilali Kourtiche ◽

Mustapha Nadi

Keyword(s):

Frequency Band ◽

Low Frequency ◽

Fast Method ◽

Bioimpedance Analysis ◽

Sample Analysis ◽

Electrode Size ◽

Sensor Optimization ◽

Sensor Model ◽

Layer Effect ◽

The Impact

Interdigitated (ITD) sensors are specially adapted for the bioimpedance analysis (BIA) of low-volume (microliter scale) biological samples. Impedance spectroscopy is a fast method involving simple and easy biological sample preparation. The geometry of an ITD sensor makes it easier to deposit a sample at the microscopic scale of the electrodes. At this scale, the electrode size induces an increase in the double-layer effect, which may completely limit interesting bandwidths in the impedance measurements. This work focuses on ITD sensor frequency band optimization via an original study of the impact of the metalization ratio α. An electrical sensor model was studied to determine the best α ratio. A ratio of 0.6 was able to improve the low-frequency cutoff by a factor of up to 2.5. This theoretical approach was confirmed by measurements of blood samples with three sensors. The optimized sensor was able to extract the intrinsic electrical properties of blood in the frequency band of interest.

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