Wavelet Analysis of Flexural Wave Fronts in Water/Slurry Hammer

2012 ◽  
Author(s):  
Kazuaki Inaba ◽  
Hiroto Takahashi ◽  
Yu Kurokawa ◽  
Kikuo Kishimoto
Keyword(s):  
Wavelet Analysis ◽  
Oscillation Frequency ◽  
Water Hammer ◽  
Flexural Wave ◽  
Hoop Strain ◽  
Wave Fronts ◽  
Transform Method ◽  
Time Frequency ◽  
Water Slurry ◽  
The Impact

The present study experimentally analyzes flexural wave fronts in water hammer and slurry hammer with polycarbonate tubes by wavelet analysis. The water/slurry hammer was initiated by the impact between the free-falling projectile and the water/slurry in the vertical mounting tube. We measured hoop strain histories of flexural wave fronts at several locations by strain gages and analyzed the histories, using the wavelet transform method. The wavelet power spectrum near the flexural wave fronts and dispersion behaviors in water/slurry hammer were examined. In the water hammer experiments, by tracing the dispersion curve from the time-frequency signal, it is revealed that the water hammer front have a dispersion tendency. Moreover, the measured frequencies indicate a reasonable agreement with the Skalak’s theory [1, 2]. As for slurry, we mixed water and alumina balls or polystyrene (PS) balls. Wave speeds with Alumina or PS balls were compared with theoretical estimations by Han et al. [3, 4]. It is confirmed that the particles enhance slurry hammer’s dispersion and the oscillation frequency of the slurry hammer becomes lower than that of the water hammer. Additionally, the oscillation frequency corresponds to the theoretical value estimated from wave speed assuming particles as rigid-body particles.

scholarly journals Identifying Risk Factors Of A(H7N9) Outbreak by Wavelet Analysis and Generalized Estimating Equation

2019 ◽  
Vol 16 (8) ◽  
pp. 1311
Author(s):  
Qinling Yan ◽  
Sanyi Tang ◽  
Zhen Jin ◽  
Yanni Xiao
Keyword(s):  
Risk Factors ◽  
Wavelet Analysis ◽  
Disease Transmission ◽  
Media Coverage ◽  
Meteorological Factors ◽  
Impact Factors ◽  
Observation Data ◽  
Time Frequency ◽  
The Impact ◽  
H7n9 Outbreak

Five epidemic waves of A(H7N9) occurred between March 2013 and May 2017 in China. However, the potential risk factors associated with disease transmission remain unclear. To address the spatial–temporal distribution of the reported A(H7N9) human cases (hereafter referred to as “cases”), statistical description and geographic information systems were employed. Based on long-term observation data, we found that males predominated the majority of A(H7N9)-infected individuals and that most males were middle-aged or elderly. Further, wavelet analysis was used to detect the variation in time-frequency between A(H7N9) cases and meteorological factors. Moreover, we formulated a Poisson regression model to explore the relationship among A(H7N9) cases and meteorological factors, the number of live poultry markets (LPMs), population density and media coverage. The main results revealed that the impact factors of A(H7N9) prevalence are manifold, and the number of LPMs has a significantly positive effect on reported A(H7N9) cases, while the effect of weekly average temperature is significantly negative. This confirms that the interaction of multiple factors could result in a serious A(H7N9) outbreak. Therefore, public health departments adopting the corresponding management measures based on both the number of LPMs and the forecast of meteorological conditions are crucial for mitigating A(H7N9) prevalence.

An improved method to estimate Q based on the logarithmic spectrum of moving peak points

2019 ◽  
Vol 7 (2) ◽  
pp. T255-T263 ◽  
Author(s):  
Yanli Liu ◽  
Zhenchun Li ◽  
Guoquan Yang ◽  
Qiang Liu
Keyword(s):  
Seismic Waves ◽  
Wave Attenuation ◽  
Real Data ◽  
Peak Frequency ◽  
Seismic Reflection Data ◽  
The Real ◽  
Time Frequency ◽  
Reflection Data ◽  
Text Filtering ◽  
The Impact

The quality factor ([Formula: see text]) is an important parameter for measuring the attenuation of seismic waves. Reliable [Formula: see text] estimation and stable inverse [Formula: see text] filtering are expected to improve the resolution of seismic data and deep-layer energy. Many methods of estimating [Formula: see text] are based on an individual wavelet. However, it is difficult to extract the individual wavelet precisely from seismic reflection data. To avoid this problem, we have developed a method of directly estimating [Formula: see text] from reflection data. The core of the methodology is selecting the peak-frequency points to linear fit their logarithmic spectrum and time-frequency product. Then, we calculated [Formula: see text] according to the relationship between [Formula: see text] and the optimized slope. First, to get the peak frequency points at different times, we use the generalized S transform to produce the 2D high-precision time-frequency spectrum. According to the seismic wave attenuation mechanism, the logarithmic spectrum attenuates linearly with the product of frequency and time. Thus, the second step of the method is transforming a 2D spectrum into 1D by variable substitution. In the process of transformation, we only selected the peak frequency points to participate in the fitting process, which can reduce the impact of the interference on the spectrum. Third, we obtain the optimized slope by least-squares fitting. To demonstrate the reliability of our method, we applied it to a constant [Formula: see text] model and the real data of a work area. For the real data, we calculated the [Formula: see text] curve of the seismic trace near a well and we get the high-resolution section by using stable inverse [Formula: see text] filtering. The model and real data indicate that our method is effective and reliable for estimating the [Formula: see text] value.

Ratcheting assessment of corroded elbow pipes subjected to internal pressure and cyclic bending moment

2021 ◽  
pp. 030932472198989
Author(s):  
Ali Salehi ◽  
Armin Rahmatfam ◽  
Mohammad Zehsaz
Keyword(s):  
Growth Rate ◽  
Stainless Steel ◽  
Internal Pressure ◽  
Bending Moment ◽  
Axial Direction ◽  
Hoop Strain ◽  
Cyclic Bending ◽  
High Fatigue ◽  
The Impact ◽  
Cyclic Bending Moment

The present study aimed to study ratcheting strains of corroded stainless steel 304LN elbow pipes subjected to internal pressure and cyclic bending moment. To this aim, spherical and cubical shapes corrosion are applied at two depths of 1 mm and 2 mm in the critical points of elbow pipe such as symmetry sites at intrados, extrados, and crown positions. Then, a Duplex 2205 stainless steel elbow pipe is considered as an alternative to studying the impact of the pipe materials, due to its high corrosion resistance and strength, toughness, and most importantly, the high fatigue strength and other mechanical properties than stainless steel 304LN. In order to perform numerical analyzes, the hardening coefficients of the materials were calculated. The results highlight a significant relationship between the destructive effects of corrosion and the depth and shape of corrosion, so that as corrosion increases, the resulting destructive effects increases as well, also, the ratcheting strains in cubic corrosions have a higher growth rate than spherical corrosions. In addition, the growth rate of the ratcheting strains in the hoop direction is much higher across the studied sample than the axial direction. The highest growth rate of hoop strain was observed at crown and the highest growth rate of axial strains occurred at intrados position. Altogether, Duplex 2205 material has a better performance than SS 304LN.

The Study of Quality Monitoring and Control for Laser Cutting Based on Pulse-Induced Acoustic Sound

2012 ◽  
Vol 182-183 ◽  
pp. 422-426 ◽  
Author(s):  
Hui Juan Hao ◽  
Guang He Cheng ◽  
Ji Yong Xu
Keyword(s):  
Adaptive Control ◽  
Laser Cutting ◽  
Cutting Speed ◽  
Processing Parameters ◽  
Wavelet Denoising ◽  
Quality Monitoring ◽  
Monitoring And Control ◽  
Time Frequency ◽  
And Control ◽  
The Impact

In this paper, the pulse-induced acoustic sound in laser cutting is collected, and the data processing is performed with wavelet denoising and time-frequncy analyzing. The impact of laser processing parameters on the acoustic signal is discussed; and further analysis of the effect of cutting speed is conducted. The corresponding relationship between the best velocity and the maximum time-frequency energy density is got; also the plan of adaptive control in laser cutting is designed. The results in this paper can provide important parameters for adaptive control of laser cutting.

Infrared Oscillators in Conventional Carbon Nanotube FET Technology

2015 ◽  
Vol 24 (04) ◽  
pp. 1550053
Author(s):  
Lobna I'msaddak ◽  
Dalenda Ben Issa ◽  
Abdennaceur Kachouri ◽  
Mounir Samet ◽  
Hekmet Samet
Keyword(s):  
Power Consumption ◽  
Response Time ◽  
Oscillation Frequency ◽  
Ring Oscillator ◽  
Propagation Time ◽  
Type C ◽  
P Type ◽  
Lc Tank ◽  
The Impact ◽  
Carbon Nanotube Fet

This paper presents the design of C-CNTFET oscillator's arrays for infrared 'IR' technology. These arrays are contained by both of the LC-tank and the voltage control 'coupled N- and P-type C-CNTFET LC-tank' oscillators. In this paper, the analysis of the impact of CNT diameter variations and the nonlinear capacitances (C GD and C GS ) were introduced, especially on propagation time, oscillation frequency and power consumption. The C-CNTFET inverter, ring oscillator, LC-tank and coupled N- and P-type C-CNTFET LC-tank oscillator structures were designed and their speeding and performances have been investigated with the proposed n-type of C-CNTFET model supplied by a 0.5 V power voltage. Simulation results show that the n- and p-types LC-tank oscillator circuit designs achieved an approximately equal oscillation frequency, response time and power consumption. Whereas the coupled N- and P-type C-CNTFET LC-tank oscillator has the lowest power consumption equal to 0.13 μW, the highest oscillation frequency (10.08 THz) and the fastest response time (1.81 ps).

scholarly journals ELIMINATION OF IMPACT WHEN CLOSING THE DISC VALVE ON THE DRAINAGE OF HORIZONTAL SEDIMENTS

2021 ◽  
Vol 11 (1) ◽  
pp. 56-62
Author(s):  
Sergej A. ANCIFEROV ◽  
Elena V. CHIRKOVA ◽  
Mariya N. KUCHERENKO
Keyword(s):  
Numerical Experiment ◽  
Low Pressure ◽  
Water Hammer ◽  
Pneumatic Actuator ◽  
Closed Space ◽  
Additional Energy ◽  
Before And After ◽  
Treatment Facilities ◽  
The Impact

The reasons for the occurrence of an impact when closing a butt erfl y valve installed on pipelines that discharge sludge water from horizontal sedimentation tanks of treatment facilities are considered. The assumption about the possibility of water hammer was experimentally refuted. It is hypothesized that the cause of the impact is the disruption of the fl uid fl ow when fl owing around a fl at plate at critical angles of att ack. A numerical experiment was carried out, which consists in modeling the movement of a water fl ow in a completely fi lled, closed space of a pipe. As a result of the experiment, it was revealed that the fl ow stall was caused by the formation of zones of high and low pressure, respectively, before and after the valve. This provides additional energy to increase the closing torque, comparable to the force of a pneumatic actuator, and results in an impact.

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