High-resolution gathers by inverse Q filtering in the wavelet domain

Geophysics ◽  
2013 ◽  
Vol 78 (2) ◽  
pp. V53-V61 ◽  
Author(s):  
Igor L. S Braga ◽  
Fernando S. Moraes
Keyword(s):  
Synthetic Data ◽  
Structural Features ◽  
Natural Increase ◽  
Dispersive Media ◽  
Amplitude Variation With Offset ◽  
Time Frequency ◽  
Before And After ◽  
Text Filtering ◽  
Inverse Q Filtering ◽  
Definition Of

We have developed and applied an inverse [Formula: see text] filter formulation using the continuous wavelet transform (CWT), which provides a natural domain for time-variant operations, such as compensation for propagation in attenuating and dispersive media. The well-known linear attenuation model, given as a function of time and frequency, was applied very efficiently over wavelet coefficients in the time-frequency domain to correct for amplitude and phase distortions, as necessary. The inverse CWT yields the recovered trace with a broader bandwidth. The process works on a trace-by-trace basis, making no distinction if the data is pre- or poststack. Our motivation was to develop gather conditioning tools to enhance prestack interpretation techniques such as amplitude variation with offset (AVO) analysis and inversion — a technique that is often compromised by tuning and other propagation related issues that degrade seismic resolution. Thus, we investigated the AVO fidelity of our filter and the sensitivity of the results to incorrect values of [Formula: see text], using real and synthetic data. Our synthetic data experiments clearly showed that AVO anomalies are recovered and preserved in a stable manner, even with values of [Formula: see text] off by 50% of its correct value. The application in time-migrated gathers shows a very natural increase in the vertical definition of the events, especially due to the partial elimination of the tuning effect. The benefits for imaging are also evidenced by comparing stacked sections before and after inverse [Formula: see text] filtering. The higher resolution of seismic sections leads to a better definition of smaller scale stratigraphic and structural features.

Inverse Q filtering via synchrosqueezed wavelet transform

Geophysics ◽  
2019 ◽  
Vol 84 (2) ◽  
pp. V121-V132 ◽  
Author(s):  
Ya-Juan Xue ◽  
Jun-Xing Cao ◽  
Xing-Jian Wang
Keyword(s):  
Wavelet Transforms ◽  
Ambient Noise ◽  
Real Data ◽  
Dispersive Media ◽  
Time Frequency ◽  
Effective Components ◽  
Text Filtering ◽  
Inverse Q Filtering ◽  
The Time Domain ◽  
Amplitude Compensation

We have developed and applied an inverse [Formula: see text]-filter formulation using synchrosqueezed wavelet transforms for the compensation of attenuating and dispersive media. A damping criterion concerning the reconstruction of the effective components for controlling noise amplification and the separation of the noise and signal in the synchrosqueezed wavelet domain is generated. The proposed method provides stable attenuation compensation without decreasing the seismic vertical and lateral resolution. The best property of the proposed method, unlike conventional inverse [Formula: see text]-filtering methods, is that it carries out amplitude compensation for the effective components located at some time samples in the time-frequency domain. The spectral reconstruction contributes to the reconstruction of the trace in the time domain and suppresses the ambient noise located at high frequencies at later times, especially suppressing the ambient noise within the main frequency band. It is not a noise-level-dependent method. We validated our approach with synthetic and real data. The comparison of the proposed method with the conventional stabilized inverse [Formula: see text]-filtering method is also carried out to illustrate the particular features of the proposed method. The examples demonstrate that our proposed method can effectively compensate for the amplitude attenuation by suppressing the ambient noise and further provide seismic images at high resolution while highlighting the effective details. Furthermore, it is a robust and easily tunable algorithm.

scholarly journals Quaternion Processing Techniques for Color Synthesized NDT Thermography

2021 ◽  
Vol 11 (2) ◽  
pp. 790
Author(s):  
Pablo Venegas ◽  
Rubén Usamentiaga ◽  
Juan Perán ◽  
Idurre Sáez de Ocáriz
Keyword(s):  
Signal To Noise Ratio ◽  
High Capacity ◽  
Synthetic Data ◽  
Relevant Information ◽  
Color Images ◽  
Destructive Testing ◽  
Application Procedure ◽  
Definition Of ◽  
Characterization Procedure ◽  
Processing Techniques

Infrared thermography is a widely used technology that has been successfully applied to many and varied applications. These applications include the use as a non-destructive testing tool to assess the integrity state of materials. The current level of development of this application is high and its effectiveness is widely verified. There are application protocols and methodologies that have demonstrated a high capacity to extract relevant information from the captured thermal signals and guarantee the detection of anomalies in the inspected materials. However, there is still room for improvement in certain aspects, such as the increase of the detection capacity and the definition of a detailed characterization procedure of indications, that must be investigated further to reduce uncertainties and optimize this technology. In this work, an innovative thermographic data analysis methodology is proposed that extracts a greater amount of information from the recorded sequences by applying advanced processing techniques to the results. The extracted information is synthesized into three channels that may be represented through real color images and processed by quaternion algebra techniques to improve the detection level and facilitate the classification of defects. To validate the proposed methodology, synthetic data and actual experimental sequences have been analyzed. Seven different definitions of signal-to-noise ratio (SNR) have been used to assess the increment in the detection capacity, and a generalized application procedure has been proposed to extend their use to color images. The results verify the capacity of this methodology, showing significant increments in the SNR compared to conventional processing techniques in thermographic NDT.

scholarly journals Method for designing multi-input system identification signals using a compact time-frequency representation

2021 ◽  
Author(s):  
Mathias Stefan Roeser ◽  
Nicolas Fezans
Keyword(s):  
System Identification ◽  
Design Method ◽  
Flight Test ◽  
Compact Representation ◽  
Time Frequency ◽  
Stability And Control ◽  
Frequency Representation ◽  
Aerodynamic Parameters ◽  
Definition Of ◽  
And Control

AbstractA flight test campaign for system identification is a costly and time-consuming task. Models derived from wind tunnel experiments and CFD calculations must be validated and/or updated with flight data to match the real aircraft stability and control characteristics. Classical maneuvers for system identification are mostly one-surface-at-a-time inputs and need to be performed several times at each flight condition. Various methods for defining very rich multi-axis maneuvers, for instance based on multisine/sum of sines signals, already exist. A new design method based on the wavelet transform allowing the definition of multi-axis inputs in the time-frequency domain has been developed. The compact representation chosen allows the user to define fairly complex maneuvers with very few parameters. This method is demonstrated using simulated flight test data from a high-quality Airbus A320 dynamic model. System identification is then performed with this data, and the results show that aerodynamic parameters can still be accurately estimated from these fairly simple multi-axis maneuvers.

scholarly journals Mediastinal anatomical landmarks, their variants and tips for video-assisted thoracoscopic navigation during oesophageal extirpation

2021 ◽  
Author(s):  
Sergey Dydykin ◽  
Friedrich Paulsen ◽  
Tatyana Khorobykh ◽  
Natalya Mishchenko ◽  
Marina Kapitonova ◽  
...  
Keyword(s):  
Prone Position ◽  
Anatomical Study ◽  
Structural Features ◽  
Posterior Mediastinum ◽  
Visual Navigation ◽  
Anatomical Landmarks ◽  
Video Assisted ◽  
Before And After ◽  
Human Cadavers ◽  
The Right

Abstract Purpose There is no systematic description of primary anatomical landmarks that allow a surgeon to reliably and safely navigate the superior and posterior mediastinum’s fat tissue spaces near large vessels and nerves during video-assisted endothoracoscopic interventions in the prone position of a patient. Our aim was to develop an algorithm of sequential visual navigation during thoracoscopic extirpation of the esophagus and determine the most permanent topographic and anatomical landmarks allowing safe thoracoscopic dissection of the esophagus in the prone position. Methods The anatomical study of the mediastinal structural features was carried out on 30 human cadavers before and after opening the right pleural cavity. Results For thoracoscopic extirpation of the esophagus in the prone position, anatomical landmarks are defined, their variants are assessed, and an algorithm for their selection is developed, allowing their direct visualization before and after opening the mediastinal pleura. Conclusion The proposed algorithm for topographic and anatomical navigation based on the key anatomical landmarks in the posterior mediastinum provides safe performance of the video-assisted thoracoscopic extirpation of the esophagus in the prone position.

Effect of particle size and delignification on the rate of digestion of hemicellulose and cellulose by cellulase in mature pangola grass stems

1983 ◽  
Vol 34 (3) ◽  
pp. 241 ◽  
Author(s):  
CW Ford
Keyword(s):  
Particle Size ◽  
Cell Walls ◽  
Trichoderma Viride ◽  
Structural Features ◽  
Cell Wall Polysaccharides ◽  
Particle Size Reduction ◽  
Digitaria Decumbens ◽  
Hemicellulose Degradation ◽  
Before And After ◽  
The Difference

Stem cell walls of pangola grass (Digitaria decumbens) were ground to two particle sizes (c. 1 and 0.1 mm diameter), and incubated with cellulase (ex. Trichoderma viride) for varying times before and after delignification. Total cell walls finely ground (0.1 mm) with a Spex Shatterbox mill were initially degraded more rapidly (to 24 h) than delignified 1 mm particles. Thereafter the delignified material was solubilized to a greater extent. Subsequent specific determinations of cell wall polysaccharides indicated that delignification increased the rate of hemicellulose degradation to a greater extent than did particle size reduction, whereas the opposite was found for cellulose. The difference between delignified and Spex-ground residues, in terms of the amount of polysaccharide digested, was much greater for cellulose than hemicellulose. It is concluded that structural features play a more important role in limiting cellulase degradation of cellulose than does association with lignin, the reverse being so for hemicellulose.

scholarly journals Identification and inclusion of gender factors in retrospective cohort studies: the GOING-FWD framework

2021 ◽  
Vol 6 (4) ◽  
pp. e005413
Author(s):  
Valeria Raparelli ◽  
Colleen M. Norris ◽  
Uri Bender ◽  
Maria Trinidad Herrero ◽  
Alexandra Kautzky-Willer ◽  
...  
Keyword(s):  
Outcome Measurement ◽  
Meta Analysis ◽  
Synthetic Data ◽  
Well Being ◽  
Pooled Analysis ◽  
Research Network ◽  
Local Analysis ◽  
Related Factors ◽  
Measurement Framework ◽  
Definition Of

Gender refers to the socially constructed roles, behaviours, expressions and identities of girls, women, boys, men and gender diverse people. Gender-related factors are seldom assessed as determinants of health outcomes, despite their powerful contribution. The Gender Outcomes INternational Group: to Further Well-being Development (GOING-FWD) project developed a standard five-step methodology applicable to retrospectively identify gender-related factors and assess their relationship to outcomes across selected cohorts of non-communicable chronic diseases from Austria, Canada, Spain, Sweden. Step 1 (identification of gender-related variables): Based on the gender framework of the Women Health Research Network (ie, identity, role, relations and institutionalised gender), and available literature for a certain disease, an optimal ‘wish-list’ of gender-related variables was created and discussed by experts. Step 2 (definition of outcomes): Data dictionaries were screened for clinical and patient-relevant outcomes, using the International Consortium for Health Outcome Measurement framework. Step 3 (building of feasible final list): a cross-validation between variables per database and the ‘wish-list’ was performed. Step 4 (retrospective data harmonisation): The harmonisation potential of variables was evaluated. Step 5 (definition of data structure and analysis): The following analytic strategies were identified: (1) local analysis of data not transferable followed by a meta-analysis combining study-level estimates; (2) centrally performed federated analysis of data, with the individual-level participant data remaining on local servers; (3) synthesising the data locally and performing a pooled analysis on the synthetic data and (4) central analysis of pooled transferable data. The application of the GOING-FWD multistep approach can help guide investigators to analyse gender and its impact on outcomes in previously collected data.

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

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

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

A case for multiple views of function in design based on a common definition

2013 ◽  
Vol 27 (3) ◽  
pp. 271-279 ◽  
Author(s):  
Amaresh Chakrabarti ◽  
V. Srinivasan ◽  
B.S.C. Ranjan ◽  
Udo Lindemann
Keyword(s):  
State Change ◽  
Multiple Views ◽  
System Environment ◽  
Common Definition ◽  
Effect Model ◽  
Before And After ◽  
Definition Of

AbstractFunctions are important in designing. However, several issues hinder progress with the understanding and usage of functions: lack of a clear and overarching definition of function, lack of overall justifications for the inevitability of the multiple views of function, and scarcity of systematic attempts to relate these views with one another. To help resolve these, the objectives of this research are to propose a common definition of function that underlies the multiple views in literature and to identify and validate the views of function that are logically justified to be present in designing. Function is defined as a change intended by designers between two scenarios: before and after the introduction of the design. A framework is proposed that comprises the above definition of function and an empirically validated model of designing, extended generate, evaluate, modify, and select of state-change, and an action, part, phenomenon, input, organ, and effect model of causality (Known as GEMS of SAPPhIRE), comprising the views of activity, outcome, requirement–solution–information, and system–environment. The framework is used to identify the logically possible views of function in the context of designing and is validated by comparing these with the views of function in the literature. Describing the different views of function using the proposed framework should enable comparisons and determine relationships among the various views, leading to better understanding and usage of functions in designing.

The Meaning of Pain and the Pain of Meaning: A Bio-Hermeneutical Inquiry

2021 ◽  
Vol 90 ◽  
pp. 215-234
Author(s):  
Teodora Manea
Keyword(s):  
The Body ◽  
Main Interest ◽  
Main Approach ◽  
Memento Mori ◽  
Finding Meaning ◽  
Pace Of Life ◽  
Before And After ◽  
Definition Of

AbstractMy main interest here is to look at pain as a sign of the body that something is wrong. I will argue that there is a meaning of pain before and after an illness is diagnosed. An illness contains its own semantic paradigm, but the pain before the diagnosis affects the pace of life, not only by limiting our interactions, but also as a struggle with its meaning and a reminder of mortality.My main approach is what I call bio-hermeneutics, an extension of medical hermeneutics branching out from the Continental hermeneutical tradition. As such, I will explore the connection between pain and language, temporality, dialectics, and ontology. Given the centrality of language in constructing the meaning of pain, my analysis is informed by the semantics (looking at pain metaphors), syntax (pain as incoherence), and pragmatics (pain as companion) of expressing pain.The last section explores the meaning of pain in connection with death, as memento mori. Revisiting an old definition of philosophy as melete thanatou, or ‘rehearsal of death’, I will reflect on the difficulty of finding meaning not only for pain, but also for death as cessation of all existential possibilities.

scholarly journals Computer Modeling of Barrel-Vaulted Sanctuary Exhibiting Flutter Echo with Comparison to Measurements

Acoustics ◽  
2020 ◽  
Vol 2 (1) ◽  
pp. 87-109
Author(s):  
Heather Lai ◽  
Brian Hamilton
Keyword(s):  
Computer Modeling ◽  
Architectural Design ◽  
Impulse Responses ◽  
Time Frequency ◽  
Geometrical Acoustics ◽  
Decay Times ◽  
Before And After ◽  
Show Evidence ◽  
Architectural Planning ◽  
The Cost

Computer modeling in acoustics allows for the prediction of acoustical defects and the evaluation of potential remediations. In this article, computer modeling is applied to the case of a barrel-vaulted sanctuary whose architectural design and construction led to severe flutter echoes along the main aisle, which was later mitigated through acoustical remediations. State-of-the-art geometrical acoustics and wave-based simulations are carried out to analyze the acoustics of this space, with a particular focus on the flutter echoes along the main aisle, before and after remediations. Multi-resolution wavelet and spectrogram analyses are carried out to isolate and characterize flutter echoes within measurements and computer-simulated room impulse responses. Comparisons of simulated responses to measurements are also made in terms of decay times and curves. Simulated room impulse responses from both geometrical acoustics and wave-based methods show evidence of flutter echoes matching measurements, to varying degrees. Time-frequency analyses isolating flutter echoes demonstrate better matches to measurements from wave-based simulated responses, at the cost of longer simulation times than geometrical acoustics simulations. This case study highlights the importance of computer modeling of acoustics in early design phases of architectural planning of worship spaces.

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