scholarly journals Field Monitoring and Analysis of the Vibration of Stay Cables under Typhoon Conditions

Sensors ◽  
2020 ◽  
Vol 20 (16) ◽  
pp. 4520
Author(s):  
Jian Guo ◽  
Xujiang Zhu
Keyword(s):  
Wavelet Packet ◽  
Adaptive Method ◽  
Vibration Characteristics ◽  
Operational Conditions ◽  
Gust Factor ◽  
Stay Cables ◽  
Power Spectral ◽  
Health Monitoring Systems ◽  
And Performance ◽  
Fluctuating Wind

Structural health monitoring systems provide many advantages for full-scale measurements in bridge monitoring. In this study, a strong landing typhoon event recorded at the Jintang Bridge (Zhejiang Province, China) in 2019 was selected to study the nonstationary wind and cable vibration characteristics. To study the characteristics of the recorded typhoon, the time-varying mean wind was extracted based on the adaptive method of the wavelet-matrix transform. The nonstationary characteristics of Typhoon Lekima, including the turbulence intensity, gust factor, and fluctuating wind power spectral density, were analyzed and compared with the stationary model characteristics of a typhoon, and the typical characteristics and parameters were obtained. In addition, the measured vibration response of the cables was analyzed. The vibration characteristics of the cables and the energy distribution of the wind speed wavelet packet were investigated. The vibrations at different positions were compared. A power spectrum analysis and a wavelet packet energy analysis of the cable were performed. The results of this study can be used as a basis for wind-resistant design and performance evaluation of bridges under similar operational conditions.

Investigating the Effect of Prestress Force on Cross-Tensioned Concrete Pavement Vibration

2020 ◽  
Vol 2674 (8) ◽  
pp. 875-886
Author(s):  
Hongduo Zhao ◽  
Mengyuan Zeng ◽  
Hui Chen ◽  
Jianming Ling ◽  
Difei Wu
Keyword(s):  
Spectral Distribution ◽  
Field Testing ◽  
Dominant Frequency ◽  
Fe Analysis ◽  
Concrete Pavement ◽  
Vibration Characteristics ◽  
Dynamic Responses ◽  
Power Spectral ◽  
Force Monitoring ◽  
The Time Domain

Prestress force loss is crucial to the structural performance of cross-tensioned concrete pavement (CTCP). Severe loss in prestress force will reduce the constricting-cracking capacity of the CTCP, resulting in damage with load and temperature applied. Vibration-based methods are commonly used in prestress force monitoring, but few relative studies are reported into CTCP and the relationship between prestress force and CTCP vibration is still unclear. The purpose of this paper is to investigate the effect of prestress force on CTCP vibration. The vibration characteristics of CTCP subjected to different prestress forces were studied through field testing and finite element (FE) analysis. Impulse load was applied as excitation at the anchorage zone and dynamic responses were measured in the time domain. A signal processing method was employed to obtain short-time power spectral from original vibration signals, which was utilized to extract vibration characteristics in time and frequency. As shown in both the field testing and the FE analysis, the prestress force has a more significant effect on frequency spectral distribution, rather than the dominant frequency. Integrated frequency is proved to be a reliable index for describing frequency spectral distribution and has a good correlation with prestress force, which suggests it can be used to reflect the change in prestress force. Overall, these findings indicate that vibration testing has potential in prestress force monitoring in CTCP, though the practicality of this method requires further demonstration.

Investigation on an Adaptive Method for Tonal Vibration Suppression

2019 ◽  
Vol 142 (2) ◽  
Author(s):  
Xiling Xie ◽  
Mingke Ren ◽  
Zhiyi Zhang
Keyword(s):  
Convergence Rate ◽  
Dynamic Model ◽  
Adaptive Algorithm ◽  
Vibration Suppression ◽  
Mechanical Vibration ◽  
Adaptive Controller ◽  
Adaptive Method ◽  
In Series ◽  
Multiple Frequencies ◽  
And Performance

Abstract An adaptive method for suppressing mechanical vibration of multiple frequencies is investigated. The adaptive controller is reinforced with saturation alleviator to improve the convergence rate and performance of the adaptive algorithm. Tracking filters are used to extract harmonics of fluctuating frequencies and the anti-saturation unit works in series with the tracking filters to give constrained harmonic output. As a result, the controller is insensitive to abnormally large input that would otherwise induce saturation in actuators. A dynamic model is built for vibration suppression simulation and the numerical results indicate that the adaptive algorithm is effective in cases of multiple fluctuating frequencies and output saturation. Experiments were also conducted to test the performance of the adaptive method. Excitation with oscillating frequencies was applied, and the results have demonstrated that the harmonics can be suppressed effectively with the adaptive method.

scholarly journals Emission Characteristics and Effect of Battery Drain in “Budget” Curing Lights

2016 ◽  
Vol 41 (4) ◽  
pp. 397-408 ◽  
Author(s):  
MM AlShaafi ◽  
JE Harlow ◽  
HL Price ◽  
FA Rueggeberg ◽  
D Labrie ◽  
...  
Keyword(s):  
Light Emitting Diode ◽  
Medical Instrument ◽  
Light Output ◽  
The Internet ◽  
Spectral Emission ◽  
Light Emitting ◽  
Power Spectral ◽  
Radiant Power ◽  
And Performance ◽  
Emission Ratios

SUMMARY Recently, “budget” dental light-emitting diode (LED)–based light-curing units (LCUs) have become available over the Internet. These LCUs claim equal features and performance compared to LCUs from major manufacturers, but at a lower cost. This study examined radiant power, spectral emission, beam irradiance profiles, effective emission ratios, and the ability of LCUs to provide sustained output values during the lifetime of a single, fully charged battery. Three examples of each budget LCU were purchased over the Internet (KY-L029A and KY-L036A, Foshan Keyuan Medical Equipment Co, and the Woodpecker LED.B, Guilin Woodpecker Medical Instrument Co). Major dental manufacturers provided three models: Elipar S10 and Paradigm (3M ESPE) and the Bluephase G2 (Ivoclar Vivadent). Radiant power emissions were measured using a laboratory-grade thermopile system, and the spectral emission was captured using a spectroradiometer system. Irradiance profiles at the tip end were measured using a modified laser beam profiler, and the proportion of optical tip area that delivered in excess of 400 mW/cm2 (termed the effective emission ratio) was displayed using calibrated beam profile images. Emitted power was monitored over sequential exposures from each LCU starting at a fully charged battery state. The results indicated that there was less than a 100-mW/cm2 difference between manufacturer-stated average tip end irradiance and the measured output. All the budget lights had smaller optical tip areas, and two demonstrated lower effective emission ratios than did the units from the major manufacturers. The budget lights showed discontinuous values of irradiance over their tip ends. One unit delivered extremely high output levels near the center of the light tip. Two of the budget lights were unable to maintain sustained and stable light output as the battery charge decreased with use, whereas those lights from the major manufacturers all provided a sustained light output for at least 100 exposures as well as visual and audible indications that the units required recharging.

scholarly journals Effect of Temperature Variation on Vibration Monitoring of Prestressed Concrete Girders

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Thanh-Canh Huynh ◽  
Young-Hwan Park ◽  
Jae-Hyung Park ◽  
Dong-Soo Hong ◽  
Jeong-Tae Kim
Keyword(s):  
Spectral Density ◽  
Temperature Variation ◽  
Prestressed Concrete ◽  
Vibration Characteristics ◽  
Vibration Monitoring ◽  
Effect Of Temperature ◽  
Concrete Girders ◽  
Power Spectral ◽  
Coefficient Corrélation ◽  
Prestressed Concrete Girders

The effect of temperature variation on vibration monitoring of prestressed concrete (PSC) girders is experimentally analyzed. Firstly, vibration features such as autoregressive (AR) coefficient, correlation coefficient of power spectral density (CC of PSD), natural frequency, and mode shape are selected to estimate the effect of temperature variation on vibration characteristics of PSC girders. Secondly, vibration experiments on a lab-scale PSC girder are performed under the condition of temperature variation. Finally, the vibration features with respect to the temperature variation are analyzed to estimate the effect of temperature in vibration characteristics of the PSC girder.

scholarly journals EEG Based Demarcation of Yogic and Non-Yogic Sleep Patterns Using Power Spectral Analysis

2021 ◽  
Vol 12 (6) ◽  
pp. 0-0
Keyword(s):  
Sleep Stage ◽  
Power Spectral Analysis ◽  
Sleep Patterns ◽  
Power Spectral ◽  
Yoga Group ◽  
Eeg Recordings ◽  
And Performance ◽  
Sensitivity Specificity ◽  
And Behavior ◽  
Density Methods

Electroencephalogram (EEG) signals resulting from recordings of polysomnography play a significant role in determining the changes in physiology and behavior during sleep. This study aims at demarcating the sleep patterns of yogic and non-yogic subjects. Frequency domain features based on power spectral density methods were explored in this study. The EEG recordings were segmented into 1s and 0.5s. EEG patterns with four windowing scheme overlaps (0%, 50%, 60% and 75%) to ensure stationarity of the signal in order to investigate the effect of the pre-processing stage. In order to recognize the yoga and non-yoga group through N3 sleep stage, non-linear KNN classifier was introduced and performance was evaluated in terms of sensitivity and specificity. The experimental results show that modified covariance PSD estimate is the best method in classifying the sleep stage N3 of yogic and non-yogic subjects with 95% confidence interval, sensitivity, specificity and accuracy of 97.3%, 98% and 97%, respectively.

scholarly journals ECG Based Biometric uing Wavelet Packet Decomposition

2019 ◽  
Vol 9 (1) ◽  
pp. 2178-2183 ◽  
Keyword(s):  
Discriminant Analysis ◽  
Wavelet Packet ◽  
Support Vector ◽  
Frequency Noise ◽  
Wavelet Packet Decomposition ◽  
Linear Discriminant ◽  
Biometric Technology ◽  
Vector Machines ◽  
And Performance ◽  
Electrocardiogram Ecg

Biometric technology has been commonly used for authentication. Fingerprint or iris become one of the biometrics that is widely applied. However, this type of biometrics tends to be easily falsified and damaged. So it is misused for manipulating actions and even crime. Therefore a new biometric method is needed to overcome this problem. One potential modality is biometrics based on an electrocardiogram (ECG) signal. This research simulates a one-lead ECG waveform for person authentication. ECG waves were taken from eleven healthy adult volunteers with a length of 60 seconds. ECG waves from each person are segmented into 10 sections so that a total of 110 ECG waves are used for person authentication simulations. All noise of the ECG waves was removed using a bandpass filter to reduce artifacts and high-frequency noise. Wavelet packet decomposition (3 Level) was applied to decompose the signal in several intrinsic parts so that typical wave information can be retrieved. Entropy-based feature extraction applied to all decomposed signals. A total of 14 entropy features have been calculated and used as predictors in the classification process. Validation and performance tests are carried out by cross-validation combined with linear discriminant analysis and support vector machines with five scenarios. The proposed method provides the highest accuracy of 71.8% using discriminant analysis and cubic support vector machine. The best accuracy value was achieved if all entropy features from all wavelet decomposition levels are used as predictors in the classification process. This research is expected to be a reference that ECG has the potential to become a future biometric modality

scholarly journals Correlation Between Physiological and Performance-Based Metrics to Estimate Pilots' Cognitive Workload

2021 ◽  
Vol 12 ◽  
Author(s):  
P. Archana Hebbar ◽  
Kausik Bhattacharya ◽  
Gowdham Prabhakar ◽  
Abhay A. Pashilkar ◽  
Pradipta Biswas
Keyword(s):  
Invasive Technique ◽  
Cognitive Workload ◽  
L1 Norm ◽  
Pilot Performance ◽  
Non Invasive ◽  
Quantitative Metrics ◽  
Power Spectral ◽  
Beta Frequency Band ◽  
And Performance ◽  
Beta Frequency

This paper discusses the utilization of pilots' physiological indications such as electroencephalographic (EEG) signals, ocular parameters, and pilot performance-based quantitative metrics to estimate cognitive workload. The study aims to derive a non-invasive technique to estimate pilot's cognitive workload and study their correlation with standard physiological parameters. Initially, we conducted a set of user trials using well-established psychometric tests for evaluating the effectiveness of pupil and gaze-based ocular metrics for estimating cognitive workload at different levels of task difficulty and lighting conditions. Later, we conducted user trials with the NALSim flight simulator using a business class Learjet aircraft model. We analyzed participants' ocular parameters, power levels of different EEG frequency bands, and flight parameters for estimating variations in cognitive workload. Results indicate that introduction of secondary task increases pilot's cognitive workload significantly. The beta frequency band of EEG, nearest neighborhood index specifying distribution of gaze fixation, L1 Norm of power spectral density of pupil diameter, and the duty cycle metric indicated variations in cognitive workload.

Microscopic and enzymatic investigations on biofilms of wastewater treatment systems

1997 ◽  
Vol 36 (1) ◽  
pp. 21-30 ◽  
Author(s):  
Tanja Gschlößl ◽  
Ingrid Michel ◽  
Marion Heiter ◽  
Christian Nerger ◽  
Verena Rehbein
Keyword(s):  
Wastewater Treatment ◽  
Activated Sludge ◽  
Wastewater Treatment Plants ◽  
Biological Properties ◽  
Organic Substances ◽  
Operational Conditions ◽  
Sludge Flocs ◽  
And Performance ◽  
The Stability

In biological wastewater treatment inorganic and organic substances are fixed and metabolized by mixed populations of microorganisms forming either activated sludge flocs or biofilms. Not only the type of wastewater but also the operational conditions promote the development of an adapted biocenosis of microorganisms with specialized enzymatic functions. Understanding the biological properties of the microorganisms, it is possible to assess the prevailing conditions in their natural environment. Regular microscopic and enzymatic investigations of activated sludge and biofilms thus improve the assessment of the stability of the processes and support troubleshooting in wastewater treatment plants. While the role of bacteria is often discussed, the importance of ciliated protozoes and metazoes for the maintenance of the stability of biofilm systems is rarely mentioned. In this paper we intend to show some new results of direct microscopic observations in different sorts of biofilm systems focussing upon ciliated protozoes and metazoes. Practical results will demonstrate the relation between enzymatic analysis, microscopic investigations and performance of biofilm systems.

Sign in / Sign up

Export Citation Format

Share Document