scholarly journals Noise reduction, smoothing and time interval segmentation of noisy signals using an energy optimisation method

2006 ◽  
Vol 153 (2) ◽  
pp. 101 ◽  
Author(s):  
S. Mahmoodi ◽  
B.S. Sharif
Keyword(s):  
Noise Reduction ◽  
Time Interval ◽  
Noisy Signals ◽  
Energy Optimisation

Noise reduction by perfect-translation-invariant complex discrete wavelet transforms for fetal electrocardiography and magnetocardiography

2014 ◽  
Vol 12 (04) ◽  
pp. 1460008 ◽  
Author(s):  
Yasuhiro Ishikawa ◽  
Hitoshi Horigome ◽  
Akihiko Kandori ◽  
Hiroshi Toda ◽  
Zhong Zhang
Keyword(s):  
Noise Reduction ◽  
Wavelet Transforms ◽  
Body Movement ◽  
Internal Noise ◽  
P Wave ◽  
Time Interval ◽  
Discrete Wavelet ◽  
Translation Invariance ◽  
Qrs Complex ◽  
Fetal Electrocardiography

Echocardiography is widely used for the diagnosis of fetal cardiac arrhythmias. However, this method does not detect configurational changes in the electrocardiogram (ECG) such as life-threatening changes in QRS and the prolongation of the QT interval. Fetal magnetocardiography (fMCG) and fetal electrocardiography (fECG) are valuable tools for the detection of electrophysiological cardiac signals although both have certain limitations. Such techniques must deal with excess internal noise such as maternal respiratory movements, fetal movements, muscle contraction and fetal body movement and external noise (e.g., electromagnetic waves). Heart rate variability (HRV) is a well-known phenomenon with fluctuation in the time interval between heartbeats. The lack of translation invariance is a serious defect in the conventional wavelet transforms (discrete wavelet transform (DWT)). Fluctuation of the impulse response at each energy level is observed in the multi-resolution analysis (MRA). Configurational changes in the ECG waveforms are frequently observed after noise reduction by the conventional wavelet transforms. Both the lack of translation invariance of conventional wavelet transforms and HRV cause deformation of the ECG waveforms. We describe here the CDWTs with perfect translation invariance (PTI). Compared with conventional wavelets, PTI of the fECG and fMCG resulted in only minor configurational changes in the ECG waveforms. This technique yields persistently stable ECG waveforms, including P wave and QRS complex. First, an independent component analysis (ICA) was applied to fECG or fMCG data to remove noise. We provide an example to show that the morphological change in QRS complex is barely affected when PTI is applied to normal fECG. Examples of fetal arrhythmias, such as ventricular trigeminy, ventricular bigeminy and premature atrial contraction are demonstrated using this technique. The results lead us to the conclusion that ICA and noise reduction in fECG and fMCG by PTI are promising methods for the diagnosis of fetal arrhythmia.

Noise-canceling spike between pilot and main-pressure-rise peaks of multiple-injection diesel combustion

2019 ◽  
Vol 20 (7) ◽  
pp. 788-804 ◽  
Author(s):  
Takayuki Fuyuto ◽  
Masahiro Taki
Keyword(s):  
Heat Release ◽  
Noise Reduction ◽  
Pressure Rise ◽  
Noise Spectrum ◽  
Frequency Component ◽  
Combustion Noise ◽  
Time Interval ◽  
Diesel Combustion ◽  
Main Injection ◽  
Noise Canceling

A previous study addressed combustion-noise reduction by optimizing the interval between two peaks in the pressure-rise rate (dP/dθ) of premixed charge combustion ignition with the split injection of fuel in diesel engines. Noise canceling occurs between two dP/dθ peaks, which reduces the overall combustion noise by lowering the maximum frequency component of the noise spectrum. The period of this frequency is twice the interval between the two dP/dθ peaks. We named this noise-reduction technique “noise-canceling spike” because it relies on the interference between a spike in the pressure rise and the preceding peak in the pressure rise. The time interval between the dP/dθ peaks must be controlled precisely to enable the utilization of the noise-canceling spike. In this article, the theory of the noise-canceling spike between the dP/dθ peak of the pilot injection and a single dP/dθ peak of the main injection is explained relatively simply, using experimental data analysis and zero-dimensional cycle simulations to prove that the noise-canceling spike is a universal phenomenon which occurs between the two dP/dθ peaks independently of the combustion (injection) strategy. Then, the theory of the noise-canceling spike is extended to those cases with three or more dP/dθ peaks, in which the noise-canceling spike can occur between every pair of dP/dθ peaks. Finally, we prove that the noise-canceling spike can occur between the dP/dθ peak of the pilot heat release and the multiple dP/dθ peaks of the main heat release in diesel combustion. The noise-canceling spike between the dP/dθ peak of the pilot combustion and the first dP/dθ peak of the main combustion becomes the dominating factor which reduces the overall combustion noise. In addition, the reasons why there have previously been no reports of the canceling and amplifying between the two dP/dθ peaks are discussed.

scholarly journals Improved Denoising Method for Ultrasonic Echo with Mother Wavelet Optimization and Best-Basis Selection

2016 ◽  
Vol 6 (6) ◽  
pp. 2742
Author(s):  
Mohammad Hossein Doost Mohammadi
Keyword(s):  
Feature Extraction ◽  
Noise Reduction ◽  
Discrete Wavelet ◽  
Mother Wavelet ◽  
Denoising Method ◽  
Signal Features ◽  
Error Ratio ◽  
Ultrasonic Echo ◽  
Noisy Signals ◽  
Best Basis Selection

<p>Weak features of ultrasonicnondestructive test signals are usually immersed in noisy signals. So, in this paper, we proposed an improved scheme for noise reduction and feature extraction based on discrete wavelet transform. The basis of the mother wavelet was selected to be matched to a given signal. Three different constraints were presented to minimize the error between the denoised and the given signal. It should be mentioned that such an optimum wavelet can represent the signal more compactly with a few large coefficients which can be considered as the signal features. Standard signals and simulated ultrasonic echo were used to evaluate the performance of the presented algorithms. Signal to error ratio was used to compare the designed wavelet performance with that of standard wavelets. Simulation results revealed that the proposed method outperformed the other presented methods and even standard wavelets. The results also has shown that the signal-based noise reduction algorithms make the feature extraction more reliable. Finally, the performance of the proposed algorithm was compared with other methods from different literatures.</p>

Improved Denoising Method for Ultrasonic Echo with Mother Wavelet Optimization and Best-Basis Selection

2016 ◽  
Vol 6 (6) ◽  
pp. 2742
Author(s):  
Mohammad Hossein Doost Mohammadi
Keyword(s):  
Feature Extraction ◽  
Noise Reduction ◽  
Discrete Wavelet ◽  
Mother Wavelet ◽  
Denoising Method ◽  
Signal Features ◽  
Error Ratio ◽  
Ultrasonic Echo ◽  
Noisy Signals ◽  
Best Basis Selection

<p>Weak features of ultrasonicnondestructive test signals are usually immersed in noisy signals. So, in this paper, we proposed an improved scheme for noise reduction and feature extraction based on discrete wavelet transform. The basis of the mother wavelet was selected to be matched to a given signal. Three different constraints were presented to minimize the error between the denoised and the given signal. It should be mentioned that such an optimum wavelet can represent the signal more compactly with a few large coefficients which can be considered as the signal features. Standard signals and simulated ultrasonic echo were used to evaluate the performance of the presented algorithms. Signal to error ratio was used to compare the designed wavelet performance with that of standard wavelets. Simulation results revealed that the proposed method outperformed the other presented methods and even standard wavelets. The results also has shown that the signal-based noise reduction algorithms make the feature extraction more reliable. Finally, the performance of the proposed algorithm was compared with other methods from different literatures.</p>

Satisfaction With Noise Reduction Circuits

1993 ◽  
Vol 2 (1) ◽  
pp. 51-53 ◽  
Author(s):  
Ruth A. Bentler
Keyword(s):  
Noise Reduction

Focusing of Visuospatial Attention

2001 ◽  
Vol 15 (4) ◽  
pp. 256-274 ◽  
Author(s):  
Caterina Pesce ◽  
Rainer Bösel
Keyword(s):  
Reaction Times ◽  
Visual Space ◽  
Spatial Relation ◽  
Stimulus Onset ◽  
Visuospatial Attention ◽  
Task Demands ◽  
Time Interval ◽  
Behavioral Studies ◽  
Task Conditions ◽  
Simple Rt

Abstract In the present study we explored the focusing of visuospatial attention in subjects practicing and not practicing activities with high attentional demands. Similar to the studies of Castiello and Umiltà (e. g., 1990) , our experimental procedure was a variation of Posner's (1980) basic paradigm for exploring covert orienting of visuospatial attention. In a simple RT-task, a peripheral cue of varying size was presented unilaterally or bilaterally from a central fixation point and followed by a target at different stimulus-onset-asynchronies (SOAs). The target could occur validly inside the cue or invalidly outside the cue with varying spatial relation to its boundary. Event-related brain potentials (ERPs) and reaction times (RTs) were recorded to target stimuli under the different task conditions. RT and ERP findings showed converging aspects as well as dissociations. Electrophysiological results revealed an amplitude modulation of the ERPs in the early and late Nd time interval at both anterior and posterior scalp sites, which seems to be related to the effects of peripheral informative cues as well as to the attentional expertise. Results were: (1) shorter latency effects confirm the positive-going amplitude enhancement elicited by unilateral peripheral cues and strengthen the criticism against the neutrality of spatially nonpredictive peripheral cueing of all possible target locations which is often presumed in behavioral studies. (2) Longer latency effects show that subjects with attentional expertise modulate the distribution of the attentional resources in the visual space differently than nonexperienced subjects. Skilled practice may lead to minimizing attentional costs by automatizing the use of a span of attention that is adapted to the most frequent task demands and endogenously increases the allocation of resources to cope with less usual attending conditions.

Attention Deficit and Disruptive Behavior Disorder Symptoms

2001 ◽  
Vol 17 (1) ◽  
pp. 25-35 ◽  
Author(s):  
G. Leonard Burns ◽  
James A. Walsh ◽  
David R. Patterson ◽  
Carol S. Holte ◽  
Rita Sommers-Flanagan ◽  
...  
Keyword(s):  
Attention Deficit ◽  
Rating Scales ◽  
Behavior Disorder ◽  
Disruptive Behavior Disorder ◽  
Subjective Rating ◽  
Time Interval ◽  
Assessment Procedure ◽  
Frequency Count ◽  
Hyperactivity Disorder ◽  
Oppositional Defiant

Summary: Rating scales are commonly used to measure the symptoms of attention deficit/hyperactivity disorder (ADHD), oppositional defiant disorder (ODD), and conduct disorder (CD). While these scales have positive psychometric properties, the scales share a potential weakness - the use of vague or subjective rating procedures to measure symptom occurrence (e. g., never, occasionally, often, and very often). Rating procedures based on frequency counts for a specific time interval (e. g., never, once, twice, once per month, once per week, once per day, more than once per day) are less subjective and provide a conceptually better assessment procedure for these symptoms. Such a frequency count procedure was used to obtain parent ratings on the ADHD, ODD, and CD symptoms in a normative (nonclinical) sample of 3,500 children and adolescents. Although the current study does not provide a direct comparison of the two types of rating procedures, the results suggest that the frequency count procedure provides a potentially more useful way to measure these symptoms. The implications of the results are noted for the construction of rating scales to measure the ADHD, ODD, and CD symptoms.

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