Artykuły w czasopismach na temat „Time and Frequency Plot (TAFPLOT)”
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Peng, Fu Min, i Bin Fang. "Stabilizing Gain Regions of PID Controller for Time Delay Systems". Applied Mechanics and Materials 313-314 (marzec 2013): 432–37. http://dx.doi.org/10.4028/www.scientific.net/amm.313-314.432.
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Based on the inverse Nyquist plot, this paper proposes a method to determine stabilizing gain regions of PID controller for time delay systems. According to the frequency characteristic of the inverse Nyquist plot, it is confirmed that the frequency range is used for stability analysis, and the abscissas of two kind key points are obtained in this range. PID gain is divided into several regions by abscissas of key points. Using an inference and two theorems presented in the paper, the stabilizing PID gain regions are determined by the number of intersections of the inverse Nyquist plot and the vertical line in the frequency range. This method is simple and convenient. It can solve the problem of getting the stabilizing gain regions of PID controller for time delay system.
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Piedad, Eduardo Jr, Yu-Tung Chen, Hong-Chan Chang i Cheng-Chien Kuo. "Frequency Occurrence Plot-Based Convolutional Neural Network for Motor Fault Diagnosis". Electronics 9, nr 10 (18.10.2020): 1711. http://dx.doi.org/10.3390/electronics9101711.
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A novel motor fault diagnosis using only motor current signature is developed using a frequency occurrence plot-based convolutional neural network (FOP-CNN). In this study, a healthy motor and four identical motors with synthetically applied fault conditions—bearing axis deviation, stator coil inter-turn short circuiting, a broken rotor strip, and outer bearing ring damage—are tested. A set of 150 three-second sampling stator current signals from each motor fault condition are taken under five artificial coupling loads (0, 25%, 50%, 75% and 100%). The sampling signals are collected and processed into frequency occurrence plots (FOPs) which later serve as CNN inputs. This is done first by transforming the time series signals into its frequency spectra then convert these into two-dimensional FOPs. Fivefold stratified sampling cross-validation is performed. When motor load variations are considered as input labels, FOP-CNN predicts motor fault conditions with a 92.37% classification accuracy. It precisely classifies and recalls bearing axis deviation fault and healthy conditions with 99.92% and 96.13% f-scores, respectively. When motor loading variations are not used as input data labels, FOP-CNN still satisfactorily predicts motor condition with an 80.25% overall accuracy. FOP-CNN serves as a new feature extraction technique for time series input signals such as vibration sensors, thermocouples, and acoustics.
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Yusof, M. F. M., Mahadzir, Mohd Fairusham Ghazali i Mohd Rafiqul Islam. "Analysis of an Air Borne Acoustic Signatures from Welding Process Using Empirical Mode Decomposition". Advanced Materials Research 889-890 (luty 2014): 770–75. http://dx.doi.org/10.4028/www.scientific.net/amr.889-890.770.
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This work present the application of Empirical Mode Decomposition (EMD) to analyze the air borne acoustic signatures commenced during welding process. In order to achieve goals, bead-on plate welding was done onto the carbon steel specimen using Metal Inert Gas Welding. At the same moment, the microphone with operating frequency of 31.5 Hz to 8 kHz used to collect air borne acoustic signatures. In analysis part, Empirical Mode Decomposition has been applied to the acoustic signals and the selected Intrinsic Mode Function (IMF) was presented in frequency-distance plot using spectrogram. Based on the analysis results, there were 3 significant IMF has been found. Those were IMF mode 3, mode 5 and mode 8 which lie within the frequency of 1500 Hz to 4500 Hz, 200 Hz to 800 Hz, and 40 Hz to 80 Hz respectively. The frequency-distance plot from spectrogram of IMF mode 3 showed a significant pattern which can be related with the discontinuity of welding. The discontinuity appears wherever low amplitude power detected in the frequency-distance plot of IMF mode 3. Moreover, the frequency-distance plot of IMF mode 5 and mode 8 can be significantly related with the spatter and weld pool oscillation condition. High power amplitude in frequency-distance plot of IMF mode 8 can indicates the offset of weld pool oscillation frequency and cause the existence of higher amount of spatter which resulting the high power amplitude in frequency-distance plot of IMF mode 5. In summary, it can be conclude that the application of EMD in the analysis of air borne acoustic signatures allow the detection of several phenomena in welding process which might lead to defect once in a time. This was found to be significant in the process of developing the online welding quality monitoring.
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Carrasco, M. J. Gaitán, R. González, S. "Correlation among Poincare´plot indexes and time and frequency domain measures of heart rate variability". Journal of Medical Engineering & Technology 25, nr 6 (styczeń 2001): 240–48. http://dx.doi.org/10.1080/03091900110086651.
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Chen, Shih Tsung, Chia Yi Chou i Li Ho Tseng. "Recurrence Plot Analysis of HRV for Exposure to Low-Frequency Noise". Advanced Materials Research 1044-1045 (październik 2014): 1251–57. http://dx.doi.org/10.4028/www.scientific.net/amr.1044-1045.1251.
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Previous studies have indicated that the chronic effects of exposure to low-frequency noise causes annoyance. However, during the past two decades, most studies have employed questionnaires to characterize the effects of noise on psychosomatic responses. This study investigated cardiovascular activity changes in exposure to low-frequency noise for various noise intensities by using recurrence plot analysis of heart rate variability (HRV) estimation. The authors hypothesized that distinct noise intensities affect cardiovascular activity, which would be reflected in the HRV and recurrence quantification analysis (RQA) parameters. The test intensities of noises were no noise, 70-dBC, 80-dBC, and 90-dBC. Each noise level was sustained for 5 min, and the electrocardiogram (ECG) was recorded simultaneously. The cardiovascular responses were evaluated using RQA of the beat-to-beat (RR) intervals obtained from ECG signals. The results showed that the mean RR interval variability and mean blood pressure did not substantially change relative to the noise levels. However, the length of the longest diagonal line (Lmax) of the RQA of the background noise (no noise) condition was significantly lower than the 70-dBC, 80-dBC, and 90-dBC noise levels. The laminarity showed significant changes in the noise levels of various intensities. In conclusion, the RQA-based measures appear to be an effective tool for exposure to low-frequency noise, even in short-term HRV time series.
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Georgieva-Tsaneva, Galya, Evgeniya Gospodinova, Mitko Gospodinov i Krasimir Cheshmedzhiev. "Cardio-Diagnostic Assisting Computer System". Diagnostics 10, nr 5 (19.05.2020): 322. http://dx.doi.org/10.3390/diagnostics10050322.
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The mathematical analysis and the assessment of heart rate variability (HRV) based on computer systems can assist the diagnostic process with determining the cardiac status of patients. The new cardio-diagnostic assisting computer system created uses the classic Time-Domain, Frequency-Domain, and Time-Frequency analysis indices, as well as the nonlinear methods (Poincaré plot, Recurrence plot, Hurst R/S method, Detrended Fluctuation Analysis (DFA), Multi-Fractal DFA, Approximate Entropy and Sample Entropy). To test the feasibility of the software developed, 24-hour Holter recordings of four groups of people were analysed: healthy subjects and patients with arrhythmia, heart failure and syncope. Time-Domain (SDNN < 50 ms, SDANN < 100 ms, RMSSD < 17 ms) and Frequency-Domain (the spectrum of HRV in the LF < 550 ms2, and HF < 540 ms2) parameter values decreased in the cardiovascular disease groups compared to the control group as a result of lower HRV due to decreased parasympathetic and increased sympathetic activity. The results of the nonlinear analysis showed low values of (SD1 < 56 ms, SD2 < 110 ms) at Poincaré plot (Alpha < 90 ms) at DFA in patients with diseases. Significantly reducing these parameters are markers of cardiac dysfunction. The examined groups of patients showed an increase in the parameters (DET% > 95, REC% > 38, ENTR > 3.2) at the Recurrence plot. This is evidence of a pathological change in the regulation of heart rhythm. The system created can be useful in making the diagnosis by the cardiologist and in bringing greater accuracy and objectivity to the treatment.
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Brennan, Michael, Marimuthu Palaniswami i Peter Kamen. "Poincaré plot interpretation using a physiological model of HRV based on a network of oscillators". American Journal of Physiology-Heart and Circulatory Physiology 283, nr 5 (1.11.2002): H1873—H1886. http://dx.doi.org/10.1152/ajpheart.00405.2000.
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In this paper, we develop a physiological oscillator model of which the output mimics the shape of the R-R interval Poincaré plot. To validate the model, simulations of various nervous conditions are compared with heart rate variability (HRV) data obtained from subjects under each prescribed condition. For a variety of sympathovagal balances, our model generates Poincaréplots that undergo alterations strongly resembling those of actual R-R intervals. By exploiting the oscillator basis of our model, we detail the way that low- and high-frequency modulation of the sinus node translates into R-R interval Poincaré plot shape by way of simulations and analytic results. With the use of our model, we establish that the length and width of a Poincaré plot are a weighted combination of low- and high-frequency power. This provides a theoretical link between frequency-domain spectral analysis techniques and time-domain Poincaré plot analysis. We ascertain the degree to which these principles apply to real R-R intervals by testing the mathematical relationships on a set of data and establish that the principles are clearly evident in actual HRV records.
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Alqamari, Muhammad, Chairani Hanum i Hamidah Hanum. "PERTUMBUHAN DAN HASIL TIGA VARIETAS CABAI MERAH (Capsicum annuum L.) DENGAN APLIKASI KALIUM SULFAT". Jurnal Pertanian Tropik 3, nr 3 (1.12.2016): 249–55. http://dx.doi.org/10.32734/jpt.v3i3.2984.
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This research was conducted in the experimental field of Agricultural Faculty of North Sumatra Muhammadiyah University with a height of ± 27 meters dpl, held in july - nov 2012. This study aims to determine the best dose frequency of k2so4 on growth and the result of red chili varieties. This research was conducted using the split plot design with two factors; the varieties factor as the main plot with 3 kinds of varieties, named, V1 = TM 999, V2 = Lado, V3 = Landung; and the dose and frequency factors of k2so4 as subplot with 10 stages of treatment which is: K0 = 0, dose = 1.5 g / liter frequency 6 x (K1), 9 x (K2) and 12 x (K3), dose = 3 grams / liter frequency 6 x (K4), 9 x (K5) and 12 x (K6), dose = 4.5 g / liter frequency 6 x (K7), 9 x (K8) and 12 x (K9). The fertilizing was cunducted in the morning at 06.30 am - 08.30 am. The measured variables are plant height, numbers of chlorophyll, age of flower, numbers of flower, the percentage of deciduous fruit, weight of fruit/plot. Varieties show significant differences in plant height, numbers of chlorophyll leaf, age of flower, numbers of flower, the percentage of deciduous fruit, numbers of fruit, weight of fruit, weight of fruit per plot, moisture content and storability. Dose and frequency treatment of potassium sulfate is significantly different from controls. The best dose and frequency of this research is K9 which is 4.5 g/liter k2so4 with 12 time frequency during the growing season in TM 999 and Landung while the varieties of Lado are at dose of 3 g/liter of water with 12 times in giving (K5).
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Marino, Stefano, i Arturo Alvino. "Detection of Spatial and Temporal Variability of Wheat Cultivars by High-Resolution Vegetation Indices". Agronomy 9, nr 5 (5.05.2019): 226. http://dx.doi.org/10.3390/agronomy9050226.
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An on-farm research study was carried out on two small-plots cultivated with two cultivars of durum wheat (Odisseo and Ariosto). The paper presents a theoretical approach for investigating frequency vegetation indices (VIs) in different areas of the experimental plot for early detection of agronomic spatial variability. Four flights were carried out with an unmanned aerial vehicle (UAV) to calculate high-resolution normalized difference vegetation index (NDVI) and optimized soil-adjusted vegetation index (OSAVI) images. Ground agronomic data (biomass, leaf area index (LAI), spikes, plant height, and yield) have been linked to the vegetation indices (VIs) at different growth stages. Regression coefficients of all samplings data were highly significant for both the cultivars and VIs at anthesis and tillering stage. At harvest, the whole plot (W) data were analyzed and compared with two sub-areas characterized by high agronomic performance (H) yield 20% higher than the whole plot, and low performances (L), about 20% lower of yield related to the whole plot). The whole plot and two sub-areas were analyzed backward in time comparing the VIs frequency curves. At anthesis, more than 75% of the surface of H sub-areas showed a VIs value higher than the L sub-plot. The differences were evident also at the tillering and seedling stages, when the 75% (third percentile) of VIs H data was over the 50% (second percentile) of the W curve and over the 25% (first percentile) of L sub-plot. The use of high-resolution images for analyzing the frequency value of VIs in different areas can be a useful approach for the detection of agronomic constraints for precision agriculture purposes.
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Zhan, Wen Lian, i Jing Fang Wang. "Voice Activity Detection Based on Nonlinear Processing Techniques". Applied Mechanics and Materials 198-199 (wrzesień 2012): 1560–66. http://dx.doi.org/10.4028/www.scientific.net/amm.198-199.1560.
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Hilbert-Huang transform is developed in recent years dealing with nonlinear, non-stationary signal analysis of the complete local time-frequency method, recurrence plot method is a recursive nonlinear dynamic behavior of time series method of reconstruction. In this paper, Hilbert-Huang Transform empirical mode decomposition (EMD) and the recurrence plot (RP) method, a new voice activity detection algorithm. Firstly, through the speech and noise based on the empirical mode decomposition and multi-scale features of the different intrinsic mode function (IMF) on a time scale filtering and nonlinear dynamic behavior of the recurrence plot method, quantitative Recursive analysis of statistical uncertainty for endpoint detection. Simulation results show that the method has a strong non-steady-state dynamic analysis capabilities, in low SNR environment more accurately than the traditional method to extract the start and end point of the speech signal, robustness.
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Şenol, Bilal, i Uğur Demiroğlu. "Fractional order proportional derivative control for first order plus time delay plants: achieving phase and gain specifications simultaneously". Transactions of the Institute of Measurement and Control 41, nr 15 (25.06.2019): 4358–69. http://dx.doi.org/10.1177/0142331219857397.
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The aim of the method in this paper is to achieve desired gain and phase specifications for robustness and performance of first order plus time delay plants. The previously proposed method “frequency frame”, implemented for tuning fractional order proportional integral controllers, is applied on such plants controlled with a fractional order proportional derivative controller. Four specifications of gain and phase are considered in the Bode plot inspired from an ideal system. The frame is drawn enclosing the magnitude and phase curves limited by gain and phase crossover frequencies. Then, the size of the frame is tuned to provide loop-shaping of the curves to meet desired properties. The iso-damping property is achieved by shaping the phase curve. Similarly, numerous studies in the literature work on robustness achievement by loop shaping the phase curve of the Bode plot. However, the “frequency frame” approach is a new perspective in controller tuning. Two examples are illustratively given to prove the proposed method. Plants in the examples are also considered to be due to load disturbances. Simulation results and effects of the method are clearly explained.
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Kamen, Peter Walter, Henry Krum i Andrew Maxwell Tonkin. "Poincaré Plot of Heart Rate Variability Allows Quantitative Display of Parasympathetic Nervous Activity in Humans". Clinical Science 91, nr 2 (1.08.1996): 201–8. http://dx.doi.org/10.1042/cs0910201.
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1. Time domain summary statistics and frequency domain parameters can be used to measure heart rate variability. More recently, qualitative methods including the Poincaré plot have been used to evaluate heart rate variability. The aim of this study was to validate a novel method of quantitative analysis of the Poincaré plot using conventional statistical techniques. 2. Beat-to-beat heart rate variability was measured over a relatively short period of time (10–20 min) in 12 healthy subjects aged between 20 and 40 years (mean 30 ± 7 years) during (i) supine rest, (ii) head-up tilt (sympathetic activation, parasympathetic nervous system activity withdrawal), (iii) intravenous infusion of atropine (parasympathetic nervous system activity withdrawal), and (iv) after overnight administration of low-dose transdermal scopolamine (parasympathetic nervous system augmentation). 3. The ‘width’ of the Poincaré plot, as quantified by SD delta R—R (the difference between successive R—R intervals), was determined at rest (median 48.9, quartile range 20 ms) and found to be significantly reduced during tilt (median 19.1, quartile range 13.7 ms, P < 0.01) and atropine administration (median 7.1, quartile range 5.7 ms, P < 0.01) and increased by scopolamine (median 79.3, quartile range 33 ms, P < 0.01). Furthermore, log variance of delta R—R intervals correlated almost perfectly with log high-frequency (0.15–0.4 Hz) power (r = 0.99, P < 0.01). 4. These findings strongly suggest that the ‘width’ of the Poincaré plot is a measure of parasympathetic nervous system activity. The Poincaré plot is therefore a quantitative visual tool which can be applied to the analysis of R—R interval data gathered over relatively short time periods.
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Wang, Lina, Chengdong Wang i Yong Chen. "A Fast Three-Dimensional Display Method for Time-Frequency Spectrogram Used in Embedded Fault Diagnosis Devices". Applied Sciences 8, nr 10 (15.10.2018): 1930. http://dx.doi.org/10.3390/app8101930.
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Time-frequency analysis is usually used to reveal the appearance of different frequency components varying with time, in signals, of which time-frequency spectrogram is an important visual tool to display the information. The Mesh Surface Generation (MSG) algorithm is widely used in three-dimensional (3D) modeling. Removing hidden lines from the mesh plot is an essential process that produces explicit depth information. In this paper, a fast and effective method has been proposed for a time-frequency Spectrogram Mesh Surface Generation (SMSG) display, especially, based on the painter’s algorithm. In addition, most portable fault diagnosis devices have little function to generate a 3D spectrogram, which generally needs a general computer to realize the complex time-frequency analysis algorithms and a 3D display. However, general computer is not portable and then not suitable for field test. Hence, the proposed SMSG algorithm is applied to an embedded fault diagnosis device, which is light, low-cost, and real-time. The experimental results show that this approach can realize a high degree of accuracy and save considerable time.
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Shi, Ping, Ying Chen, Ming-Ming Guo i Hong-Liu Yu. "ACUTE EFFECTS OF ALCOHOL ON HEART RATE VARIABILITY: TIME-RELATED CHANGES AND GENDER DIFFERENCE". Biomedical Engineering: Applications, Basis and Communications 26, nr 03 (17.03.2014): 1450048. http://dx.doi.org/10.4015/s1016237214500483.
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Objectives: Alcohol consumption is associated with a broad array of physiologic and behavioral effects including changes in cardiac autonomic activity. In the present study, time-related acute effects of alcohol have been characterized and compared between genders. Methods: A total of 30 healthy subjects (15 males and 15 females) were enrolled in this study. The red wine was given to each subject at a dosage of 0.27 g of pure ethanol per kilogram of body weight. 5-min electrocardiograms (ECGs) were collected before (BR) and at 15 min (P15), 30 min (P30), 45 min (P45) and 60 min (P60) after alcohol intake. Time- and frequency-domain analysis of heart rate variability (HRV) was performed. The time-domain HRV indices include mean RR interval, pNN50, SDNN and RMSSD. The low- (LF: 0.04 to 0.15 Hz) and high-frequency (HF: 0.15 to 0.4 Hz) components along with LF/HF ratio were calculated for frequency-domain analysis of HRV. HRV was also analyzed by mathematical models, e.g. Poincaré plot, which uses a nonlinear geometric representation of change in interbeat heart rate. Poincaré plots indices, SD1, SD2, SD1/SD2 ratio and r RR , were applied in this study for HRV assessment. Results: Alcohol intake was associated with decreased HRV in both time and frequency domains. The lowest HRV was observed 30–40 min after the intake of alcohol. The alcohol intake also caused the decrease of Poincaré plots indices (SD1 and SD1/SD2 in P30, P40 and P60, and r RR in P45), accompanied with a narrower plot area. The changes of HRV indices differed by gender. The male subjects demonstrated a greater decrease of parameters measured in this study compared to the female subjects. Conclusion: Acute effects of alcohol ingestion resulted in reductions in HRV, indicating impaired cardiac autonomic nervous activity. Autonomic nervous activity in the females was less dampened by the alcohol compared to the males.
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Pitsik, Elena, i Nikita Frolov. "Recurrence plot structures reflect motor-related EEG pattern". Cybernetics and Physics, Volume 8, 2019, Number 4 (30.12.2019): 282–86. http://dx.doi.org/10.35470/2226-4116-2019-8-4-282-286.
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Detection and classification of motor-related brain patterns from non-invasive electroencephalograms (EEGs) is challenging due to their non-stationarity and low signal-to-noise ratio and requires using advanced mathematical approaches. Traditionally applied methods such as time-frequency analysis and spatial filtering allow to quantify the main attribute of the motor-related brain activity – contralateral desynchronization of mu-band oscillations (8-13 Hz) in sensorimotor cortex – by measuring EEG signal’s amplitude, power spectral density, location etc. However, these features suffer from strong inter- and intra-subject variability. So, special attention is paid to the finding of stable features. In present paper, we investigate application of the recurrence plots – robust mathematical tool for nonstationary data analysis – to explore properties of motor-related EEG samples. Our goal is to show that recurrence plots are sensitive to the changes in brain activity accessed from noninvasive EEG recordings and may provide us a new context for interpretation of motor-related pattern in EEG.
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NASRIN, RAHIMA, i A. H. BHUIYAN. "THERMAL AND AC ELECTRICAL PROPERTIES OF THIN FILMS PREPARED FROM n-BUTYL METHACRYLATE BY A CAPACITIVELY COUPLED PLASMA REACTOR". Surface Review and Letters 26, nr 02 (luty 2019): 1850146. http://dx.doi.org/10.1142/s0218625x18501469.
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Plasma-polymerized thin films of n-butyl methacrylate (PPnBMA) have been deposited on to glass substrate in an aluminium/PPnBMA/aluminium configuration by a capacitively coupled glow discharge reactor. The field emission scanning electron microscope and atomic force microscope images of PPnBMA thin films showed a flat, uniform and continuous surface. With increasing deposition time the root mean square roughness of the PPnBMA thin films increases. The differential thermal analysis and thermogravimetric analysis demonstrated that PPnBMA was thermally stable up to about 476 and 500[Formula: see text]K in air and N2 environments, respectively. The alternating current (AC) electrical conductivity ([Formula: see text]) and dielectric properties of the PPnBMA thin films of thickness 120[Formula: see text]nm were investigated in the frequency region from 102–106[Formula: see text]Hz at various temperatures. It was found that the mechanism dependable for the conduction process in PPnBMA is hopping. The trend of dielectric constant ascends with ascending temperature and descends with frequency. The dielectric loss tangent is seen to increase with frequency and attains a maximum loss peak at around 105[Formula: see text]Hz and above this frequency it decreases. The plot of relaxation time against the reciprocal of absolute temperature for PPnBMA thin film yields the activation energy for dielectric relaxation at 0.05[Formula: see text]eV. Cole–Cole plot exhibits little distorted semicircle which also indicates nearly Debye type relaxation process in this film.
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An, Li Qiong, D. S. Wang, Run Hua Fan i Li Hua Dong. "Dielectric and Conduction Properties of Lu3NbO7 Transparent Ceramic". Materials Science Forum 898 (czerwiec 2017): 1681–85. http://dx.doi.org/10.4028/www.scientific.net/msf.898.1681.
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The dielectric response and electrical conduction of Lu3NbO7 transparent ceramic produced by spark plasma sintering were investigated. Lu3NbO7 transparent ceramic exhibited low frequency dielectric dispersion and a peak in dielectric loss, shifting to higher frequency at high temperatures. This indicated space charge polarization and broad relaxation time, confirmed by impedance and modulus spectra. The Nyquist plot shows the dominant grain effect in the electrical conduction. The AC conductivity of Lu3NbO7 transparent ceramic is 4.18×10-2 S m-1 at 1073 K, with an activation energy of 1.30 eV.
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George, Fabian Parsia, Istiaque Mannafee Shaikat, Prommy Sultana Ferdawoos Hossain, Mohammad Zavid Parvez i Jia Uddin. "Recognition of emotional states using EEG signals based on time-frequency analysis and SVM classifier". International Journal of Electrical and Computer Engineering (IJECE) 9, nr 2 (1.04.2019): 1012. http://dx.doi.org/10.11591/ijece.v9i2.pp1012-1020.
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The recognition of emotions is a vast significance and a high developing field of research in the recent years. The applications of emotion recognition have left an exceptional mark in various fields including education and research. Traditional approaches used facial expressions or voice intonation to detect emotions, however, facial gestures and spoken language can lead to biased and ambiguous results. This is why, researchers have started to use electroencephalogram (EEG) technique which is well defined method for emotion recognition. Some approaches used standard and pre-defined methods of the signal processing area and some worked with either fewer channels or fewer subjects to record EEG signals for their research. This paper proposed an emotion detection method based on time-frequency domain statistical features. Box-and-whisker plot is used to select the optimal features, which are later feed to SVM classifier for training and testing the DEAP dataset, where 32 participants with different gender and age groups are considered. The experimental results show that the proposed method exhibits 92.36% accuracy for our tested dataset. In addition, the proposed method outperforms than the state-of-art methods by exhibiting higher accuracy.
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Yuhang, Hu. "Multi-scale Order Recurrence Plot based deterministic analysis on Heart Rate Variability in Congestive Heart Failure Assessment". E3S Web of Conferences 271 (2021): 03063. http://dx.doi.org/10.1051/e3sconf/202127103063.
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Congestive heart failure (CHF) is a cardiovascular disease associated with the abnormal autonomic nervous system (ANS). Heart rate variability analysis (HRV) is the main method for the quantitative evaluation of autonomic nervous function. Common analytical methods of HRV include time domain, frequency domain, and nonlinear methods. However, these methods generally ignore the short-term volatility of heart rate and autonomic ganglion law. Therefore, this study proposes a new parameter to analyze heart rate variability-determination of a multi-scale order recurrence plot (MSORP_DET). This method can analyze the HRV in patients with heart failure on multiple time scales. This study analyzed the R-R interval in 24-hour HRV data from 98 samples (54 normal subjects and 44 patients with CHF). The results showed that MSORP_DET could significantly distinguish CHF patients from normal subjects (p<0.001). Moreover, the accuracy rate of screening patients with CHF reached the maximum of 81.6% by using the combination of low frequency/high frequency (LF/HF) and MSORP_DET, compared with 78.6% when using LF/HF alone. Therefore, MSORP_DET can be used as a new index to screen patients with CHF and reveal that the rhythm of ANS in patients with heart failure is more complex than that in normal people.
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Nguyen-Huu, Thien-An, Van Thang Nguyen, Kyeon Hur i Jae Woong Shim. "Coordinated Control of a Hybrid Energy Storage System for Improving the Capability of Frequency Regulation and State-of-Charge Management". Energies 13, nr 23 (29.11.2020): 6304. http://dx.doi.org/10.3390/en13236304.
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The paper proposes a coordinated operation method of two independent storages for managing state-of-charge (SOC) and for providing ancillary service concerning frequency regulation (FR); furthermore, this article also introduces the power allocation scheme between two storages in consideration of the coverage of the frequency band for each storage along with the SOC management scheme of the supercapacitor and battery. We also provide a guideline for the storage sizing on the basis of the smoothing time constant. Additionally, we verify the advantage of the HESS in extending the lifetime of the battery, which is estimated by a real-time state-of-health (SOH) calculation method. The Bode plot of the proposed method is analyzed to observe the power spectrum coverage in the frequency domain through the case studies using PSCAD/EMTDC and MATLAB.
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Köhler, P., H. Fischer, J. Schmitt i G. Munhoven. "On the application and interpretation of Keeling plots in paleo climate research – deciphering δ<sup>13</sup>C of atmospheric CO<sub>2</sub> measured in ice cores". Biogeosciences 3, nr 4 (15.11.2006): 539–56. http://dx.doi.org/10.5194/bg-3-539-2006.
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Abstract. The Keeling plot analysis is an interpretation method widely used in terrestrial carbon cycle research to quantify exchange processes of carbon between terrestrial reservoirs and the atmosphere. Here, we analyse measured data sets and artificial time series of the partial pressure of atmospheric carbon dioxide (pCO2) and of δ13C of CO2 over industrial and glacial/interglacial time scales and investigate to what extent the Keeling plot methodology can be applied to longer time scales. The artificial time series are simulation results of the global carbon cycle box model BICYCLE. The signals recorded in ice cores caused by abrupt terrestrial carbon uptake or release loose information due to air mixing in the firn before bubble enclosure and limited sampling frequency. Carbon uptake by the ocean cannot longer be neglected for less abrupt changes as occurring during glacial cycles. We introduce an equation for the calculation of long-term changes in the isotopic signature of atmospheric CO2 caused by an injection of terrestrial carbon to the atmosphere, in which the ocean is introduced as third reservoir. This is a paleo extension of the two reservoir mass balance equations of the Keeling plot approach. It gives an explanation for the bias between the isotopic signature of the terrestrial release and the signature deduced with the Keeling plot approach for long-term processes, in which the oceanic reservoir cannot be neglected. These deduced isotopic signatures are similar (−8.6‰) for steady state analyses of long-term changes in the terrestrial and marine biosphere which both perturb the atmospheric carbon reservoir. They are more positive than the δ13C signals of the sources, e.g. the terrestrial carbon pools themselves (−25‰). A distinction of specific processes acting on the global carbon cycle from the Keeling plot approach is not straightforward. In general, processes related to biogenic fixation or release of carbon have lower y-intercepts in the Keeling plot than changes in physical processes, however in many case they are indistinguishable (e.g. ocean circulation from biogenic carbon fixation).
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Lee, Si Hyeock, Il Sung Moon, Jae Soon Kang, Sang Chul Shin i Sang Gil Lee. "Rapid and accurate prediction of the frequencies of Bursaphelenchus xylophilus and B. mucronatus in mixed nematode samples using real-time species-specific PCR". Nematology 11, nr 2 (2009): 289–99. http://dx.doi.org/10.1163/156854109x429619.
Pełny tekst źródłaStreszczenie:
AbstractAccurate detection of Bursaphelenchus xylophilus and prediction of its frequency in crude nematode samples is often hindered by the coexistence of related nematode species, such as B. mucronatus, that are morphologically similar but non-pathogenic. To establish a detection system enabling determination of the relative frequencies of B. xylophilus and B. mucronatus from field nematode samples, we developed a real-time species-specific PCR (rtssPCR) protocol which targets the substantial sequence differences in the 5S rRNA marker gene between the two nematode species. Using standard DNA mixtures of B. xylophilus and B. mucronatus in various ratios, plots of percent species proportion vs cycle threshold value (Ct value) were generated for the prediction of species frequency. The rtssPCR protocol enables the detection of target nematode frequencies as low as 0.16% at the 95% confidence level. When nematode DNA samples were extracted from the mixed specimens of B. xylophilus and B. mucronatus in various ratios and analysed by rtssPCR, the semi-log plot was nearly identical to the plot generated from standard mixed DNA samples, demonstrating that field populations of the nematodes can be directly used for rtssPCR analysis. The rapid and accurate determination of B. xylophilus or B. mucronatus frequencies by this rtssPCR protocol makes it ideal for routine monitoring and quarantine of B. xylophilus in the field.
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Shin, Ki Hong. "A New Signal Processing Technique to Estimate Velocity Dependent Dynamic Friction Coefficient". Key Engineering Materials 321-323 (październik 2006): 1241–44. http://dx.doi.org/10.4028/www.scientific.net/kem.321-323.1241.
Pełny tekst źródłaStreszczenie:
In general, dynamic friction coefficient in a dry surface condition is dependent on the relative velocity between two sliding bodies. A conventional method of estimating the velocity dependent dynamic friction coefficient is time consuming and requires a special jig to measure the friction forces. In this paper, a new technique called the state space mapping method is proposed based on the nonlinear dynamics of a 1-DOF friction oscillator. One body is constructed as a single degree of freedom system and another body is formed as a moving base that may be built as a rotating disk or a horizontally oscillating plate. The resulting friction induced vibration system is used to estimate the dynamic friction coefficient. The measured vibration signals are utilized to construct a three dimensional plot of acceleration versus state variables. Then, the velocity dependent dynamic friction coefficient can be estimated from the plot. The natural frequency can also be estimated from the plot, which can be used to verify the quality of the results.
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Bourdim, Samia, Kamel Eddine Hemsas i Youcef Harbouche. "Intelligent Diagnostic of Induction Machine for Faults Detection and Classification Using Wavelet and Fuzzy Inference". Applied Mechanics and Materials 789-790 (wrzesień 2015): 597–603. http://dx.doi.org/10.4028/www.scientific.net/amm.789-790.597.
Pełny tekst źródłaStreszczenie:
An intelligent diagnostic method based on 3-D plot continuous wavelet transform (3-D plot CWT) and fuzzy inference system is presented to investigate the detectability and classification of rotor broken bars faults in induction machine (IM) and to overcome the limitation of classical Fourier Transform (FT). This approach is successfully used with Motor Current Signature Analysis (MCSA) and suitable developed model of IM in healthy and faulty mode using Matlab environment. As first step we performed new results using 3-D plot CWT to extract the discriminating features. The features extracted from the wavelet transformed signal are the second most predominant frequency, the time range at which it occurs and the corresponding wavelet coefficients .Then as second and last step a fuzzy Inference system is designed and implemented using Matlab software with these three features extracted from the wavelet transformed signal as inputs and generates an output that classifies the fault and no fault conditions. It is observed that the results are satisfactory.
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Bourdim, Samia, Kamel Eddine Hemsas, Youcef Harbouche i Rachid Abdssemed. "Intelligent Diagnostic of Induction Machine for Faults Detection and Classification Using Wavelet and Fuzzy Inference". Applied Mechanics and Materials 799-800 (październik 2015): 964–70. http://dx.doi.org/10.4028/www.scientific.net/amm.799-800.964.
Pełny tekst źródłaStreszczenie:
An intelligent diagnostic method based on 3-D plot continuous wavelet transform (3-D plot CWT) and fuzzy inference system is presented to investigate the detectability and classification of rotor broken bars faults in induction machine (IM) and to overcome the limitation of classical Fourier Transform (FT). This approach is successfully used with Motor Current Signature Analysis (MCSA) and suitable developed model of IM in healthy and faulty mode using Matlab environment. As first step we performed new results using 3-D plot CWT to extract the discriminating features. The features extracted from the wavelet transformed signal are the second most predominant frequency, the time range at which it occurs and the corresponding wavelet coefficients .Then as second and last step a fuzzy Inference system is designed and implemented using Matlab software with these three features extracted from the wavelet transformed signal as inputs and generates an output that classifies the fault and no fault conditions. It is observed that the results are satisfactory.
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Yu, Wenfei. "Probing the X-ray Variability of X-ray Binaries". Symposium - International Astronomical Union 214 (2003): 236–39. http://dx.doi.org/10.1017/s0074180900194483.
Pełny tekst źródłaStreszczenie:
Kilohertz quasi-periodic oscillations (kHz QPOs) has been regarded as representing the Keplerian frequency at the inner disk edge in the neutron star X-ray binaries. The so-called “parallel tracks” on the plot of the kHz QPO frequency vs. X-ray flux in neutron star X-ray binaries, on the other hand, show the correlation between the kHz QPO frequency and the X-ray flux on time scales from hours to days. This is suspected as caused by the variations of the mass accretion rate through the accretion disk surrounding the neutron star. We show here that by comparing the correlation between the kHz QPO frequency and the X-ray count rate on a certain QPO time scale observed approximately simultaneous in the Fourier power spectra of the X-ray light curve, we have found evidences that the X-ray flux of millihertz QPOs in neutron star X-ray binaries is generated inside the inner disk edge if adopting that the kilohertz QPO frequency is an orbital frequency at the inner disk edge.
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Cawley, P., i L. G. Rigner. "Rapid Measurement of Modal Properties Using FFT Analyzers With Random Excitation". Journal of Vibration and Acoustics 108, nr 4 (1.10.1986): 394–98. http://dx.doi.org/10.1115/1.3269361.
Pełny tekst źródłaStreszczenie:
The use of a Nyquist plot of the H2 (Syy/Sxy*) frequency response function estimates produced by an FFT based spectrum analyzer with random excitation to obtain modal amplitudes and hence modal constants has been investigated. It has been proved that, irrespective of the frequency resolution used, the H2 estimates always lie on the true modal circle so even at coarse frequency resolution, a circle fitted to these points gives accurate values of modal amplitude. The conventional H1 (Sxy/Sxx) estimates lie inside the true modal circle. Use of the H2 technique results in major savings in the testing time required for a modal survey, particularly when measurements are to be taken at many points on the test structure.
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Hommadi, Ali Hassan, i Sabah Anwer Almasraf. "Water Retention Techniques under Crop’s Root Zone a Tool to Enhance Water Use Efficiency and Economic Water Productivity for Zucchini". Journal of Engineering 25, nr 6 (31.05.2019): 44–52. http://dx.doi.org/10.31026/j.eng.2019.06.04.
Pełny tekst źródłaStreszczenie:
A new technique in cultivation by installing membrane sheet below the crop’s root zone was helped to save irrigation water in the root zone, less farm losses, increasing the field water use efficiency and water productivity. In this paper, the membrane sheet was installed below the root zone of zucchini during the summer growing season 2017 in open field. This research was carried out in a private field in Babil governorate at Sadat Al Hindiya Township reached 72 km from Baghdad. Surface trickle irrigation system was used for irrigation process. Two treatment plots were used, treatment plot T1 using membrane sheet and treatment plot T2 without using the membrane sheet. The applied irrigation water, time of irrigation, soil moisture contents before irrigation were calculated and recorded daily for the two treatments plots. Values of crop yield, Field water use Efficiency and economic water productivity were discussed and compared between the plots. The obtained results indicate that field water use efficiency for the two plots, T1 and T2 were: 6.04 and 4.64 kg/m3, respectively. The increasing value in field water use efficiency (FWUE) of plot T1 comparing with plot T2 was 30.2 %. Additionally, the value of economic water productivity of zucchini crop for plots T1 and T2 was: 20514.1 and 15031.7 ID/m3, respectively. The increasing value of the Economic water productivity (EWP) of plot T1 comparing with plot T2 was 36.5 %. The value of water saving in plot T1 was 16.7%. The reduction in frequency of irrigation at T1 was 12 %.
zucchini, water use efficiency, membrane sheet, and economic water productivity.
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Лесовой, Сергей, Sergey Lesovoi, Вероника Кобец i Veronika Kobets. "Simulating Siberian Radioheliograph response to the quiet Sun". Solar-Terrestrial Physics 4, nr 4 (21.12.2018): 82–87. http://dx.doi.org/10.12737/stp-44201811.
Pełny tekst źródłaStreszczenie:
The Siberian Radioheliograph (SRH) correlation plot is the time dependence of the sum of absolute values of complex correlations over all baselines. These plots are built for each operating frequency of SRH. The correlation is related not only to the spatial coherence of the incident microwave emission but also to antenna gains. That is why we have to consider real SRH antenna gains and shadowings. Correlation plots obtained by SRH are related to microwave flux density of the Sun and spatial features of microwave sources. Also the correlation plots show variability of SRH beam pattern in time with constant flux density and spatial structure of sources. The SRH beam pattern depends on position of the Sun with respect to SRH, which changes with time. This leads to variations of these plots, which can be confused, for example, with the quasi-harmonic oscillations of the microwave flux produced by sources located above sunspots. Because the solar disk is an extended source, the correlation plot variability is mostly due to the SRH response to the quiet Sun. The smaller is the microwave source, the smaller are the correlation plot variations caused by a change of the beam pattern. Relatively fast variations result from long baseline responses, so it is undesirable to exclude them from the plots. Moreover, the sensitivity of the plots is better when all baselines are taken in account. The impact of the correlation plot variations on the eruptive event response is especially strong because variations of microwave flux during such events are comparable with those of the correlation plots in magnitude and time. From the above it seems reasonable to simulate the SRH response to the quiet solar disk and correct the correlation plots.
In this work, we propose a method for simulating correlation plots, which allows us to correct their variations caused by time and frequency dependence of SRH response to the solar disk. The correlation plots are simulated either by summing all model antenna pair responses to the model solar disk or by summing the corresponding values of the solar disk visibility under the assumption that the visibility is ~J1(x)/x, where J1(x) is the Bessel function of the first kind. Also we consider the shadowing of antennas nearest to the center of the SRH antenna array.
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Лесовой, Сергей, Sergey Lesovoi, Вероника Кобец i Veronika Kobets. "Simulating Siberian Radioheliograph response to the quiet Sun". Solnechno-Zemnaya Fizika 4, nr 4 (20.12.2018): 106–13. http://dx.doi.org/10.12737/szf-44201811.
Pełny tekst źródłaStreszczenie:
The Siberian Radioheliograph (SRH) correlation plot is the time dependence of the sum of absolute values of complex correlations over all baselines. These plots are built for each operating frequency of SRH. The correlation is related not only to the spatial coherence of the incident microwave emission but also to antenna gains. That is why we have to consider real SRH antenna gains and shadowings. Correlation plots obtained by SRH are related to microwave flux density of the Sun and spatial features of microwave sources. Also the correlation plots show variability of SRH beam pattern in time with constant flux density and spatial structure of sources. The SRH beam pattern depends on position of the Sun with respect to SRH, which changes with time. This leads to variations of these plots, which can be confused, for example, with the quasi-harmonic oscillations of the microwave flux produced by sources located above sunspots. Because the solar disk is an extended source, the correlation plot variability is mostly due to the SRH response to the quiet Sun. The smaller is the microwave source, the smaller are the correlation plot variations caused by a change of the beam pattern. Relatively fast variations result from long baseline responses, so it is undesirable to exclude them from the plots. Moreover, the sensitivity of the plots is better when all baselines are taken in account. The impact of the correlation plot variations on the eruptive event response is especially strong because variations of microwave flux during such events are comparable with those of the correlation plots in magnitude and time. From the above it seems reasonable to simulate the SRH response to the quiet solar disk and correct the correlation plots.
In this work, we propose a method for simulating correlation plots, which allows us to correct their variations caused by time and frequency dependence of SRH response to the solar disk. The correlation plots are simulated either by summing all model antenna pair responses to the model solar disk or by summing the corresponding values of the solar disk visibility under the assumption that the visibility is ~J1(x)/x, where J1(x) is the Bessel function of the first kind. Also we consider the shadowing of antennas nearest to the center of the SRH antenna array.
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Köhler, P., J. Schmitt i H. Fischer. "On the application and interpretation of Keeling plots in paleo climate research – deciphering δ<sup>13</sup>C of atmospheric CO<sub>2</sub> measured in ice cores". Biogeosciences Discussions 3, nr 3 (14.06.2006): 513–73. http://dx.doi.org/10.5194/bgd-3-513-2006.
Pełny tekst źródłaStreszczenie:
Abstract. The Keeling plot analysis is an interpretation method widely used in terrestrial carbon cycle research to quantify exchange processes of carbon between terrestrial reservoirs and the atmosphere. Here, we analyse measured data sets and artificial time series of the partial pressure of atmospheric carbon dioxide (pCO2) and of δ13C of CO2 over industrial and glacial/interglacial time scales and investigate to what extent the Keeling plot methodology can be applied to longer time scales. The artificial time series are simulation results of the global carbon cycle box model BICYCLE. Our analysis shows that features seen in pCO2 and δ13C during the industrial period can be interpreted with respect to the Keeling plot. However, only a maximum of approximately half of the signal can be explained by this method. The signals recorded in ice cores caused by abrupt terrestrial carbon uptake or release loose information due to air mixing in the firn before bubble enclosure and limited sampling frequency. For less abrupt changes as occurring during glacial cycles carbon uptake by the ocean cannot longer be neglected. We introduce an equation for the calculation of the effective isotopic signature of long-term changes in the carbon cycle, in which the ocean is introduced as third reservoir. This is a paleo extention of the two reservoir mass balance equations of the Keeling plot approach. Steady state analyses of changes in the terrestrial and marine biosphere lead to similar effective isotopic signatures (−8.6 per mil) of the carbon fluxes perturbing the atmosphere. These signatures are more positive than the δ13C signals of the sources, e.g. the terrestrial carbon pools themselves (~−25 per mil). In all other cases the effective isotopic signatures are larger (−8.2 per mil to −0.7 per mil), and very often indistinguishable in the light of the uncertainties. Therefore, a back calculation from well distinct fluctuations in pCO2 and δ13C to identify their origin using the Keeling plot approach seems not possible.
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Wang, Jia-Jung, Shing-Hong Liu, Wei-Kung Tseng i Wenxi Chen. "Noninvasive Measurement of Time-Varying Arterial Wall Elastance Using a Single-Frequency Vibration Approach". Sensors 20, nr 22 (12.11.2020): 6463. http://dx.doi.org/10.3390/s20226463.
Pełny tekst źródłaStreszczenie:
The arterial wall elastance is an important indicator of arterial stiffness and a kind of manifestation associated with vessel-related disease. The time-varying arterial wall elastances can be measured using a multiple-frequency vibration approach according to the Voigt and Maxwell model. However, such a method needs extensive calculation time and its operating steps are very complex. Thus, the aim of this study is to propose a simple and easy method for assessing the time-varying arterial wall elastances with the single-frequency vibration approach. This method was developed according to the simplified Voigt and Maxwell model. Thus, the arterial wall elastance measured using this method was compared with the elastance measured using the multiple-frequency vibration approach. In the single-frequency vibration approach, a moving probe of a vibrator was induced with a radial displacement of 0.15 mm and a 40 Hz frequency. The tip of the probe directly contacted the wall of a superficial radial artery, resulting in the arterial wall moving 0.15 mm radially. A force sensor attached to the probe was used to detect the reactive force exerted by the radial arterial wall. According to Voigt and Maxwell model, the wall elastance (Esingle) was calculated from the ratio of the measured reactive force to the peak deflection of the displacement. The wall elastances (Emultiple) measured by the multiple-frequency vibration approach were used as the reference to validate the performance of the single-frequency approach. Twenty-eight healthy subjects were recruited in the study. Individual wall elastances of the radial artery were determined with the multiple-frequency and the single-frequency approaches at room temperature (25 °C), after 5 min of cold stress (4 °C), and after 5 min of hot stress (42 °C). We found that the time-varying Esingle curves were very close to the time-varying Emultiple curves. Meanwhile, there was a regression line (Esingle = 0.019 + 0.91 Emultiple, standard error of the estimate (SEE) = 0.0295, p < 0.0001) with a high correlation coefficient (0.995) between Esingle and Emultiple. Furthermore, from the Bland–Altman plot, good precision and agreement between the two approaches were demonstrated. In summary, the proposed approach with a single-frequency vibrator and a force sensor showed its feasibility for measuring time-varying wall elastances.
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Xin, Rui Hao, Chun Yang Wang, Xue Lian Liu, Ming Qiu Li i Duan Yuan Bai. "Robust Fractional Order Proportional Integral Control for Large Time-Delay System". Applied Mechanics and Materials 716-717 (grudzień 2014): 1614–19. http://dx.doi.org/10.4028/www.scientific.net/amm.716-717.1614.
Pełny tekst źródłaStreszczenie:
In this paper, a new control method for large time delay system is proposed. Firstly, the decreasing time delay controller is used to remodel large delay time plant into small delay time plant. Then, a fractional robust proportional-integral controller (FOPI) is designed, using the phase margin and cut-off frequency at a specified point in the Bode plot of flat robust conditions, to guarantee the desired control performance and the robustness of the high order system to the gain order system. For comparison between the fractional order proportional integral controller and the traditional integer order PID (IOPID) controller, the IOPID controller is also designed following the same proposed tuning specifications. The simulation results indicates that the both designed controllers work efficiently. Furthermore, the FOPI controller makes the large time-delay system get better control effect, the system has high robustness, adaptive ability and anti-jamming ability.
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Yan, Chang, Changchun Liu, Lianke Yao, Xinpei Wang, Jikuo Wang i Peng Li. "Short-Term Effect of Percutaneous Coronary Intervention on Heart Rate Variability in Patients with Coronary Artery Disease". Entropy 23, nr 5 (28.04.2021): 540. http://dx.doi.org/10.3390/e23050540.
Pełny tekst źródłaStreszczenie:
Myocardial ischemia in patients with coronary artery disease (CAD) leads to imbalanced autonomic control that increases the risk of morbidity and mortality. To systematically examine how autonomic function responds to percutaneous coronary intervention (PCI) treatment, we analyzed data of 27 CAD patients who had admitted for PCI in this pilot study. For each patient, five-minute resting electrocardiogram (ECG) signals were collected before and after the PCI procedure. The time intervals between ECG collection and PCI were both within 24 h. To assess autonomic function, normal sinus RR intervals were extracted and were analyzed quantitatively using traditional linear time- and frequency-domain measures [i.e., standard deviation of the normal-normal intervals (SDNN), the root mean square of successive differences (RMSSD), powers of low frequency (LF) and high frequency (HF) components, LF/HF] and nonlinear entropy measures [i.e., sample entropy (SampEn), distribution entropy (DistEn), and conditional entropy (CE)], as well as graphical metrics derived from Poincaré plot [i.e., Porta’s index (PI), Guzik’s index (GI), slope index (SI) and area index (AI)]. Results showed that after PCI, AI and PI decreased significantly (p < 0.002 and 0.015, respectively) with effect sizes of 0.88 and 0.70 as measured by Cohen’s d static. These changes were independent of sex. The results suggest that graphical AI and PI metrics derived from Poincaré plot of short-term ECG may be potential for sensing the beneficial effect of PCI on cardiovascular autonomic control. Further studies with bigger sample sizes are warranted to verify these observations.
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Qiao, Z.-G., L. Mørkrid i N. K. Vøllestad. "Characteristics of phase angle, extrapolated conductance and ion relaxation time in the low-frequency admittance locus plot of human palmar skin". Medical & Biological Engineering & Computing 32, nr 2 (marzec 1994): 161–67. http://dx.doi.org/10.1007/bf02518913.
Pełny tekst źródła
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Gilbert, Abigail L., Jungwha Lee, Madeleine Ma, Pamela A. Semanik, Loretta DiPietro, Dorothy D. Dunlop i Rowland W. Chang. "Comparison of Subjective and Objective Measures of Sedentary Behavior Using the Yale Physical Activity Survey and Accelerometry in Patients With Rheumatoid Arthritis". Journal of Physical Activity and Health 13, nr 4 (kwiecień 2016): 371–76. http://dx.doi.org/10.1123/jpah.2015-0176.
Pełny tekst źródłaStreszczenie:
Background:Sedentary behavior is associated with increased risk of functional decline and disability. Individuals with rheumatoid arthritis (RA) spend more time sedentary than healthy adults. Self-reported assessment of sedentary behavior has not been well-developed in this patient population.Methods:172 adults with RA wore an accelerometer for 7 days and completed a modified version of the Yale Physical Activity Survey (YPAS). YPAS-derived sedentary estimates included 1) daily sitting categories (<3, 3 to 6, 6 to 8, >8 hours/day), 2) continuous daily sedentary time calculated by subtracting hours spent sleeping or in physical activity from a 24-hour day, and 3) rank order of YPAS-derived continuous daily sedentary time. Each estimate was compared with objective accelerometer-derived sedentary time using linear regression and Bland-Altman analysis.Results:A significant relationship was observed between accelerometer-derived sedentary time and all 3 estimates. Bland-Altman plot demonstrated systematic bias, however Bland-Altman plot of rank-order demonstrated that the ranked YPAS-derived continuous estimate was an unbiased predictor of ranked accelerometer sedentary time though limits of agreement were wide.Conclusions:This patient-reported approach using the YPAS shows promise to be a useful tool to identify the most sedentary patients. Providing a practical and accurate tool may increase the frequency sedentary behavior is assessed by clinicians.
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Chakraborty, Sudhangshu. "Investigation on relaxation phenomenon on sodium silicate (Na2SiO3) using complex impedance spectroscopy". Journal of Micromechanics and Molecular Physics 02, nr 03 (wrzesień 2017): 1750012. http://dx.doi.org/10.1142/s2424913017500126.
Pełny tekst źródłaStreszczenie:
The relaxation property of sodium silicate [Formula: see text] (SS) was investigated by complex impedance spectroscopy (CIS) in a wide range of frequency (100[Formula: see text]kHz–5[Formula: see text]MHz) and temperature [Formula: see text]. Orthorhombic crystal phase was synthesized by a sintering process. The CIS study shows high complex impedance in low-frequency region due to strong dispersion and controls the relaxation mechanism of ions or cations in the crystal lattice. A decrease of the energy loss [Formula: see text] occurs with increasing frequency for all temperatures showing the normal behavior of SS. Relaxation time was calculated using the dielectric functions [Formula: see text] and [Formula: see text]. The temperature dependent relaxation plot follows the Arrhenius law, where the slope represents the activation energy.
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Tang, Qiansheng, Chaofeng Li i Bangchun Wen. "Analysis on Forced Vibration of Thin-Wall Cylindrical Shell with Nonlinear Boundary Condition". Shock and Vibration 2016 (2016): 1–22. http://dx.doi.org/10.1155/2016/8978932.
Pełny tekst źródłaStreszczenie:
Forced vibration of thin-wall cylindrical shell under nonlinear boundary condition was discussed in this paper. The nonlinear boundary was modeled as supported clearance in one end of shell and the restraint was assumed as linearly elastic in the radial direction. Based on Sanders’ shell theory, Lagrange equation was utilized to derive the nonlinear governing equations of cylindrical shell. The displacements in three directions were represented by beam functions and trigonometric functions. In the study of nonlinear dynamic responses of thin-wall cylindrical shell with supported clearance under external loads, the Newmark method is used to obtain time history, frequency spectrum plot, phase portraits, Poincare section, bifurcation diagrams, and three-dimensional spectrum plot with different parameters. The effects of external loads, supported clearance, and support stiffness on nonlinear dynamics behaviors of cylindrical shell with nonlinear boundary condition were discussed.
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Cheng, Q., L. Li i L. Wang. "Characterization of peak flow events with local singularity method". Nonlinear Processes in Geophysics 16, nr 4 (22.07.2009): 503–13. http://dx.doi.org/10.5194/npg-16-503-2009.
Pełny tekst źródłaStreszczenie:
Abstract. Three methods, return period, power-law frequency plot (concentration-area) and local singularity index, are introduced in the paper for characterizing peak flow events from river flow data for the past 100 years from 1900 to 2000 recorded at 25 selected gauging stations on rivers in the Oak Ridges Moraine (ORM) area, Canada. First a traditional method, return period, was applied to the maximum annual river flow data. Whereas the Pearson III distribution generally fits the values, a power-law frequency plot (C-A) on the basis of self-similarity principle provides an effective mean for distinguishing "extremely" large flow events from the regular flow events. While the latter show a power-law distribution, about 10 large flow events manifest departure from the power-law distribution and these flow events can be classified into a separate group most of which are related to flood events. It is shown that the relation between the average water releases over a time period after flow peak and the time duration may follow a power-law distribution. The exponent of the power-law or singularity index estimated from this power-law relation may be used to characterize non-linearity of peak flow recessions. Viewing large peak flow events or floods as singular processes can anticipate the application of power-law models not only for characterizing the frequency distribution of peak flow events, for example, power-law relation between the number and size of floods, but also for describing local singularity of processes such as power-law relation between the amount of water released versus releasing time. With the introduction and validation of singularity of peak flow events, alternative power-law models can be used to depict the recession property as well as other types of non-linear properties.
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Wang, Xiang, i Yuan Zheng. "Application of Harmonic Wavelet Analysis to Rubbing Vibration Signals for Rotating Machinery Fault Diagnosis". Applied Mechanics and Materials 321-324 (czerwiec 2013): 1245–48. http://dx.doi.org/10.4028/www.scientific.net/amm.321-324.1245.
Pełny tekst źródłaStreszczenie:
Harmonic wavelet transform (HWT)and harmonic wavelet time-frequency profile plot (TFPP) is introduced firstly in practice to identify weak singularity in a signal with noise clearly. With TFPP method, emulational signal and vibration data of the rubbing of the large practical turbo-generator units are analyzed successfully, which prove that the method is effectively extract the rubbing signal feature which is can not gained by the other signal analysis methods, and the rubbing of the turbo-generator units is identified effectively.
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Vieira, Frederico Márcio C., Matheus Deniz, Edgar S. Vismara, Piotr Herbut, Jaqueline A. Pilatti, Maurício Zotti Sponchiado i Barbara de Oliveira Puretz. "Thermoregulatory and Behaviour Responses of Dairy Heifers Raised on a Silvopastoral System in a Subtropical Climate". Annals of Animal Science 20, nr 2 (1.04.2020): 613–27. http://dx.doi.org/10.2478/aoas-2019-0074.
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AbstractIn this study, we investigated the influence of a silvopastoral system on the thermal environment, behaviour and thermoregulation of dairy heifers in a subtropical climate. The experiment was conducted on a dairy farm in Southwest Paraná, Brazil, during the summer of 2014. Crossbred Holstein × Jersey dairy heifers (n = 10) were used in a split-plot design. The fixed effects in this study include time of day (9:00–10:00, 13:00–14:00, and 17:00–18:00 h) under silvopastoral or open pastures conditions, which were the main-plot and split-plot factors, respectively. To assess the environmental conditions in both systems, air temperature, relative humidity and wind speed were recorded. In addition, the temperature-humidity index was calculated based on the microcli-mate measurements. Respiratory rate and hair coat surface temperature of heifers were measured in both groups during time of day (30 days). Diurnal behaviour using focal observations with 0/1 sampling was observed. Data were analysed using Bayesian inference with a mixed effects model. The air temperature was higher (P<0.05) in open pasture conditions than the silvopasture system. Temperature-humidity index values for the silvopasture system were lower than open pasture during the hottest hours of the day. Regarding thermoregulation responses, there was an interaction between time of day and pasture environment (P<0.05). Heifers showed lower respiratory rates and hair coat surface temperature values (P<0.05) when access to shade was provided, mainly during the hottest periods in the afternoon. In addition, there was also an interaction between rumination and water intake (P<0.05), which indicates a higher rumination frequency for animals in the silvopasture system during the hottest period, as well as a higher water intake frequency for heifers in open pasture during midday. These findings imply that the arrangement of trees in a silvopasture system provides better thermal comfort conditions for dairy heifers raised in a subtropical climate.
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Tsitoglou, Kyriakos I., Yiannis Koutedakis i Petros C. Dinas. "Validation of the Polar RS800CX for assessing heart rate variability during rest, moderate cycling and post-exercise recovery". F1000Research 7 (20.09.2018): 1501. http://dx.doi.org/10.12688/f1000research.16130.1.
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Background: Heart rate variability (HRV) is an autonomic nervous system marker that provides reliable information for both disease prevention and diagnosis; it is also used in sport settings. We examined the validity of the Polar RS800CX heart rate monitor during rest, moderate cycling, and recovery in considering the total of 24 HRV indices. Method: A total of 32 healthy males (age=24.78±6.87 years, body mass index=24.48±3.13 kg/m2) completed a session comprised by three 20-minute time periods of resting, cycling at 60% of maximal heart rate, and recovery using a Polar RS800CX and an electrocardiogram (ECG) monitors. The HRV indices included time-domain, frequency-domain, Poincaré plot and recurrence plot. Bland–Altman plot analysis was used to estimate agreement between Polar RS800CX and ECG. Results: We detected significant associations (r>0.75, p<0.05) in all HRV indices, while five out of 24 HRV indices displayed significant mean differences (p<0.05) between Polar RS800CX and ECG during the resting period. However, for the exercise and recovery periods, we found significant mean differences (p<0.05) in 16/24 and 22/24 HRV indices between the two monitors, respectively. Conclusion: It is concluded that Polar RS800CX is a valid tool for monitoring HRV in individuals at resting conditions, but it displays inconsistency when used during exercise at 60% of maximal heart rate and recovery periods.
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Lian, Enyang, Yingyu Ren, Yunfeng Han, Weixin Liu, Ningde Jin i Junying Zhao. "Multi-Scale Morphological Analysis of Conductance Signals in Vertical Upward Gas–Liquid Two-Phase Flow". Zeitschrift für Naturforschung A 71, nr 11 (1.11.2016): 1031–52. http://dx.doi.org/10.1515/zna-2016-0235.
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AbstractThe multi-scale analysis is an important method for detecting nonlinear systems. In this study, we carry out experiments and measure the fluctuation signals from a rotating electric field conductance sensor with eight electrodes. We first use a recurrence plot to recognise flow patterns in vertical upward gas–liquid two-phase pipe flow from measured signals. Then we apply a multi-scale morphological analysis based on the first-order difference scatter plot to investigate the signals captured from the vertical upward gas–liquid two-phase flow loop test. We find that the invariant scaling exponent extracted from the multi-scale first-order difference scatter plot with the bisector of the second-fourth quadrant as the reference line is sensitive to the inhomogeneous distribution characteristics of the flow structure, and the variation trend of the exponent is helpful to understand the process of breakup and coalescence of the gas phase. In addition, we explore the dynamic mechanism influencing the inhomogeneous distribution of the gas phase in terms of adaptive optimal kernel time–frequency representation. The research indicates that the system energy is a factor influencing the distribution of the gas phase and the multi-scale morphological analysis based on the first-order difference scatter plot is an effective method for indicating the inhomogeneous distribution of the gas phase in gas–liquid two-phase flow.
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Bello, N., i K. O. Ogbeide. "Designing a Real-time Swept Spectrum Analyser with USRP B210". Nigerian Journal of Environmental Sciences and Technology 5, nr 2 (październik 2021): 329–39. http://dx.doi.org/10.36263/nijest.2021.02.0275.
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Cognitive radio has received considerable amount of attention as a promising technique to provide dynamic spectrum allocation. Spectrum sensing is one of the basic functions in the cognitive radio and is crucial to all other functions. Software- defined radios (SDRs) are considered due to its very high flexibility and have become a common platform for CR implementation replacing expensive spectrum analysers. The most popular among various SDR platforms is the universal software-defined radio peripheral (USRP). This paper presents a real-time swept spectrum sensing solution based on USRP B210. It also presents a detailed explanation of the concept of energy detection and the methodology for wide-band sensing. Finally, the performance of the proposed sensing solution is analysed through FFT graphs and spectrogram plot taken for 8 hours. The results showed that the proposed sensing solution was capable of achieving high resolution in the frequency domain of the wide band measured which implies that wide bands with heterogenous signals like the ISM band can be accurately resolved and analysed.
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Zeng, Ming, Zhan Xie Wu, Qing Hao Meng, Jing Hai Li i Shu Gen Ma. "Recurrence Characteristics Analysis of Near-Surface Wind Speed Signal with Different Sampling Frequencies". Applied Mechanics and Materials 599-601 (sierpień 2014): 1605–9. http://dx.doi.org/10.4028/www.scientific.net/amm.599-601.1605.
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The wind is the main factor to influence the propagation of gas in the atmosphere. Therefore, the wind signal obtained by anemometer will provide us valuable clues for searching gas leakage sources. In this paper, the Recurrence Plot (RP) and Recurrence Quantification Analysis (RQA) are applied to analyze the influence of recurrence characteristics of the wind speed time series under the condition of the same place, the same time period and with the sampling frequency of 1hz, 2hz, 4.2hz, 5hz, 8.3hz, 12.5hz and 16.7hz respectively. Research results show that when the sampling frequency is higher than 5hz, the trends of recurrence nature of different groups are basically unchanged. However, when the sampling frequency is set below 5hz, the original trend of recurrence nature is destroyed, because the recurrence characteristic curves obtained using different sampling frequencies appear cross or overlapping phenomena. The above results indicate that the anemometer will not be able to fully capture the detailed information in wind field when its sampling frequency is lower than 5hz. The recurrence characteristics analysis of the wind speed signals provides an important basis for the optimal selection of anemometer.
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Kotowski, Adam. "Cross-Correlation-Based Method vs. Classical Fft for Spectral Analysis of Impulse Response". Acta Mechanica et Automatica 8, nr 4 (1.12.2014): 219–22. http://dx.doi.org/10.2478/ama-2014-0040.
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Abstract The paper presents comparison of results of impulse response spectral analysis that has been obtained using a method based on cross-correlation with results obtained using classical FFT. The presented non-Fourier method is achieved by correlating the analyzed signal and reference single-harmonic signals and using Hilbert transform to obtain an envelope of cross-correlation. The envelope of crosscorrelation makes it possible to calculate appropriate indicator and make its plot in frequency domain as a spectrum. The spectrum obtained this way has its advantage over the FFT that the spectral resolution does not depend on duration of signal. At the same time, the spectral resolution can be much greater than spectral resolution resultant from FFT. Obtained results show that presented non-Fourier method gives frequency readout more accurate in comparison to FFT when the impulse response is a short-time signal e.g. few dozen of miliseconds lasting.
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Murayama, Norimitsu, Noriya Izu, Woosuck Shin i Ichiro Matsubara. "Application of Nano-Sized CeO2 Powder for Fast Response Oxygen Sensors". Key Engineering Materials 421-422 (grudzień 2009): 323–27. http://dx.doi.org/10.4028/www.scientific.net/kem.421-422.323.
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For resistive oxygen sensor elements of Ce1-xZrxO2 (x = 0.0, 0.05, 0.1, 0.2), grain diameter was varied in the range of 86 – 300 nm by changing sintering temperature or changing Zr content. The grain diameter decreased with increasing Zr content. The response time was approximately proportional to the square of the grain diameter. In the relationship between the amplitude of sensor output, An and the frequency, f of sine wave of variation in oxygen partial pressure, the gradient in the high-frequency region of a plot of log An vs. log f in was approximately –0.5. From these results, it was concluded that the sensor response was determined by the oxygen vacancy diffusion rate. The grain diameter of Ce0.8Zr0.2O2 element was 86 nm and the response time at 1073 K was 9 ms, which result opens the door to the technological development of independent control of engine cylinders.
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PREMALATHA, L., i P. VANAJARANJAN. "USE OF RECURRENCE PLOT ANALYSIS FOR DETECTING CHAOS AND NOISE IN NONLINEAR SWITCHING CIRCUITS". Journal of Circuits, Systems and Computers 15, nr 03 (czerwiec 2006): 409–36. http://dx.doi.org/10.1142/s0218126606003209.
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DC–DC converters controlled by naturally sampled, constant frequency pulse width modulation give rise to a wide range of bifurcation and chaos depending on the change in the system parameter values. Knowledge of transitions from regular to chaotic behavior is essential to understand the underlying dynamics of nonlinear switching circuits. While linear approaches are often insufficient to describe such processes, there are nonlinear methods available but requires long time observations. To overcome these difficulties, a newly developed pattern recognition method of nonlinear dynamics called Recurrence plot analysis method is proposed to detect transitions between periodic and chaotic states. The recurrence plot is a two-dimensional representation technique that brings out distance correlations in a time series and make it instantly apparent whether a system is periodic or chaotic. In this paper, the proposed method is applied to a nonlinear switching Buck converter, Boost converter, and Buck–Boost converters to analyze their period doubling route to chaos behavior and to distinguish chaos from noisy behavior. This may lead to a better understanding of the nonlinear switching systems, that may allow us to design stable, chaotic free switching circuits.
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Lodge, G. M. "Effects of cutting and grazing on newly sown plants of Phalaris aquatica cv. Sirosa at Tamworth, New South Wales". Australian Journal of Experimental Agriculture 47, nr 11 (2007): 1351. http://dx.doi.org/10.1071/ea06268.
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A field study was conducted (1994–97) to investigate defoliation time and frequency effects on a newly sown stand of phalaris (Phalaris aquatica cv. Sirosa). Defoliation treatments were applied from spring 1994 to autumn 1995 and effects on plant frequency and basal cover monitored until June 1997. The experimental design was a randomised split-plot in three replicates, with 45 main plots and 90 subplots. Main plots included three types of defoliation (two cutting heights or grazing with Merino sheep) applied at four different times (early stem elongation, anthesis, end of summer and end of autumn) and an undefoliated control. The main plots were divided into two subplots for frequency of defoliation (once only or cut every 8 weeks). In September 1995, none of the treatments had a significant effect on plant frequency, basal cover, green tiller weight and weight of individual tillers. However, there were significant (P < 0.05) effects of defoliation type on green tiller number, defoliation time on basal bud weight and water soluble carbohydrates and defoliation type and frequency on basal bud water soluble carbohydrates. In February and April 1996, there were significant effects of defoliation time on green tiller number and weight, basal bud weight and water soluble carbohydrates. In 1996, Sirosa phalaris plant frequency and basal cover values were generally higher (P < 0.05) in the undefoliated control compared with those defoliated at early stem elongation. However, despite fertiliser application and moderate grazing, Sirosa phalaris plant frequency had declined to a mean of 23.6% by February 1997 and to <10% by June 1997.
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Kamiyanagi, Ayuko, Yuka Sumita, Manabu Chikai, Kenta Kimura, Yoshikazu Seki, Shuichi Ino i Hisashi Taniguchi. "Evaluation of Swallowing Sound Using a Throat Microphone with an AE Sensor in Patients Wearing Palatal Augmentation Prosthesis". Journal of Advanced Computational Intelligence and Intelligent Informatics 21, nr 3 (19.05.2017): 573–80. http://dx.doi.org/10.20965/jaciii.2017.p0573.
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An increase in the population of dysphagia patients due to an aging population has led to increased attention on examination methods based on swallowing sound as simple methods of screening aspiration. However, an issue with the conventional method of cervical auscultation is that its accuracy varies based on the examiner. Previous studies examined the use of throat microphones and acceleration sensors to examine the acoustic characteristics of swallowing sound. Nevertheless, extant studies to date did not reach a level of clinical application. This study focused on using a throat microphone that is conventionally used to measure swallowing sound and an AE sensor to measurement a high-frequency range equal to and exceeding 20 kHz (upper limit 2 MHz). The study involved measuring the sounds of swallowing water of healthy subjects and patients wearing palatal augmentation prosthesis who had done surgical operation to treat head and neck cancer with the objective of using swallowing sound for screening aspiration. Acoustic characteristics of measured swallowing sound were analyzed using probability distributions using Quantile-Quantile (Q-Q) plots and spectral analysis based on wavelet transform. The findings indicated that with respect to patients with PAP, the duration time of the swallowing sound and the Q-Q plot departure rate were both significantly higher when compared with those in healthy subjects. The analysis based on wavelet transform indicated that the AE sensor allowed measurements of waveforms at a higher frequency range when compared to those in the case of the throat microphone. Additionally, an increased frequency of higher-frequency signals was associated with patients with PAP when compared to healthy subjects. The results revealed that it is possible to measure waveforms in the high-frequency range by using the AE sensor. The findings suggested the validity of analysis of the swallowing sound based on probability distributions using the Q-Q plot to evaluate the swallowing sound.