NORMAL‐MOVEOUT AND VELOCITY RELATIONS FOR FLAT AND DIPPING BEDS AND FOR LONG OFFSETS

Geophysics ◽  
1969 ◽  
Vol 34 (2) ◽  
pp. 180-195 ◽  
Author(s):  
Robert J. S. Brown
Keyword(s):  
Random Noise ◽  
Seismic Energy ◽  
Long Offset ◽  
Dominant Period ◽  
Exploration Seismology ◽  
Time Average ◽  
The Difference ◽  
Zero Offset ◽  
Velocity Averages ◽  
Velocity Average

Accurate relations between NMO and velocity are needed in modern exploration seismology, especially in long‐offset CDP work, where accurate NMO corrections must be made for stacking, and where several types of velocity averages may be computed with accuracy from NMO data. The velocity average associated with NMO is the time‐rms velocity [Formula: see text]. Even for long offsets the straight‐ray computation using [Formula: see text] is usually adequate, but a closer approximation for horizontal reflectors is obtained by reducing the NMO calculated from [Formula: see text] or reducing the value of [Formula: see text] calculated from NMO by the factor [Formula: see text], where σ is the rms deviation of the velocity from its mean, T is zero‐offset traveltime, and ΔT the NMO. The difference between time‐average and time‐rms velocities is often several percent. For the velocity function [Formula: see text] and for reflectors of arbitrary dip and strike, the NMO is shown to be [Formula: see text] where X is offset, α is emergence angle, and ψ is the angle between the offset direction and the reflector dip direction. The terms that contain angles can be used as a correction ΔΔT to the NMO value computed as if the seismic energy were reflected from a horizontal reflector, even for offset greater than those for which an NMO expression quadratic in offset is accurate. A further approximation gives [Formula: see text], where δT is dip moveout over a spread of length L, and [Formula: see text] is the angle between the receiver line and the dip direction, differing from ψ only if there is substantial perpendicular offset of the source point. An expression for the degradation of the stacked signals in CDP stacks because of NMO errors is given. It is shown that the criterion that the signal‐to‐random‐noise ratio could not be improved by dropping the longest‐offset trace(s) requires that the NMO error be not much larger than one‐quarter of a dominant period.

scholarly journals The reproducibility of subjective appetite scores

1995 ◽  
Vol 73 (4) ◽  
pp. 517-530 ◽  
Author(s):  
Anne Raben ◽  
ANNA TAGLIABUE ◽  
Arne Astrup
Keyword(s):  
Visual Analogue Scale ◽  
Food Consumption ◽  
Analogue Scale ◽  
Prior Experience ◽  
Random Noise ◽  
Normal Weight ◽  
Vas Scores ◽  
The Mean ◽  
The Difference ◽  
Mean Differences

Although subjective appetite scores are widely used, studies on the reproducibility of this method are scarce. In the present study nine healthy, normal weight, young men recorded their subjective appetite sensations before and during 5 h after two different test meals A and B. The subjects tested each meal twice and in randomized order. Visual analogue scale (VAS) scores, 10 cm in length, were used to assess hunger, satiety, fullness, prospective food consumption and palatability of the meals. Plasma glucose and lactate concentrations were determined concomitantly. The repeatability was investigated for fasting values, Δ-mean 5 h and mean 5 h values, Δ-peak/nadir and peak/nadir values. Although the profiles of the postprandial responses were similar, the coefficients of repeatability (CR = 2SD) on the mean differences were large, ranging from 2·86 to 5.24 cm for fasting scores, 1·36 to 1·88 cm for mean scores, 2·98 to 5·42 cm for Δ-mean scores, and 3·16 to 6·44 cm for peak and Δ-peak scores. For palatability ratings the CK values varied more, ranging from 2·38 (taste) to 8·70 cm (aftertaste). Part of the difference in satiety ratings could be explained by the differences in palatability ratings. However, the low reproducibility may also be caused by a conditioned satiation or hunger due to the subjects' prior experience of the meals and therefore not just be a reflection of random noise. It is likely, however, that the variation in appetite ratings is due both to methodological day-to-day variation and to biological day-to-day variation in subjective appetite sensations.

scholarly journals Comparative analysis of conventional and new seismically isolated structure

2021 ◽  
Vol 64 (3) ◽  
pp. 185-193
Author(s):  
Jelena Ristić ◽  
Miloš Vučinić ◽  
Danilo Ristić ◽  
Milutin Vučinić
Keyword(s):  
Seismic Isolation ◽  
Low Cost ◽  
Seismic Energy ◽  
Seismic Excitation ◽  
Isolation System ◽  
Vibration Period ◽  
International Projects ◽  
Dominant Period ◽  
Efficient Protection ◽  
Seismically Isolated

Extensive analytical and experimental research has been done by the authors directed to mitigation of the effects of earthquakes on structures. The research results mainly represent parts of the realized several related international projects. A selected part of the analytical studies directed to comparison between conventional and seismically isolated frame structures is presented in this paper. The responses of the applied newely developed advanced seismic isolation system HC-RMS-GOSEB to the simulated input excitation of three representative earthquakes of intensity 0.50g, have shown that it is very effective for construction of vibro-isolated and seismically resistant buildings, providing activated multistage seismic response and globally optimized seismic energy balance. Its application achieves an increase in the vibration period of the structure, far enough from the dominant period of seismic excitation. The results of the research confirm that this system is a potential solution for achieving low-cost and highly efficient protection of buildings.

Lagrangian Mechanics

2019 ◽  
pp. 53-82
Author(s):  
David D. Nolte
Keyword(s):  
Dynamical Systems ◽  
Conservation Laws ◽  
Euler Equations ◽  
Virial Theorem ◽  
Variational Calculus ◽  
Mechanical Action ◽  
Lagrange Equations ◽  
Time Average ◽  
The Difference ◽  
Kinetic And Potential Energies

Dynamical systems follow trajectories for which the mechanical action integrated along the trajectory is an extremum. The action is defined as the time average of the difference between kinetic and potential energies, which is also the time average of the Lagrangian. Once a Lagrangian has been defined for a system, the Euler equations of variational calculus lead to the Euler–Lagrange equations of dynamics. This chapter explores applications of Lagrangians and the use of Lagrange’s undetermined multipliers. Conservation laws, central forces, and the virial theorem are developed and explained.

Pulmonary impedance in dogs measured by forced random noise with a retrograde catheter

1982 ◽  
Vol 52 (3) ◽  
pp. 725-733 ◽  
Author(s):  
J. M. Fullton ◽  
D. A. Hayes ◽  
R. L. Pimmel
Keyword(s):  
Endotracheal Tube ◽  
Airway Resistance ◽  
Random Noise ◽  
Peripheral Resistance ◽  
Base Line ◽  
The Mean ◽  
The Difference ◽  
Central Airway

Retrograde catheter and forced random noise techniques were combined to study the distribution of resistance and compliance in dogs following the inhalation of aerosols containing 2.5 and 5.0 mg/ml of histamine. Mean base-line peripheral resistance was 0.367 cmH2O . l'1 . s, agreeing with previous estimates. After correction for the endotracheal tube, the mean central airway resistance was 0.040 cmH2O . l'1 . s, considerably lower than previous estimates. This discrepancy was attributed to an overcorrection for the endotracheal tube resistance. The lower histamine dose caused a substantial increase in peripheral resistance, a relatively small increase in central resistance, and substantial decreases in total and peripheral compliance. After the higher histamine dose, changes in peripheral resistance and both compliances were similar to those obtained with the lower dose; however, the increase in central resistance was much larger than at the lower dose. The difference between total and peripheral compliance yielded estimates of airway compliance of 0.00306 l/cmH2O before and 0.00104 l/cmH2O after 2.5 mg/ml of histamine.

scholarly journals A New Method of Low Amplitude Signal Detection and Its Application in Acoustic Emission

2019 ◽  
Vol 10 (1) ◽  
pp. 73 ◽  
Author(s):  
Einar Agletdinov ◽  
Dmitry Merson ◽  
Alexei Vinogradov
Keyword(s):  
Time Series ◽  
Acoustic Emission ◽  
Logarithmic Derivative ◽  
Random Noise ◽  
Synthetic Data ◽  
Spectral Density Function ◽  
Integrity Assessment ◽  
Wide Range ◽  
Time Average ◽  
Low Amplitude

A novel methodology is proposed to enhance the reliability of detection of low amplitude transients in a noisy time series. Such time series often arise in a wide range of practical situations where different sensors are used for condition monitoring of mechanical systems, integrity assessment of industrial facilities and/or microseismicity studies. In all these cases, the early and reliable detection of possible damage is of paramount importance and is practically limited by detectability of transient signals on the background of random noise. The proposed triggering algorithm is based on a logarithmic derivative of the power spectral density function. It was tested on the synthetic data, which mimics the actual ultrasonic acoustic emission signal recorded continuously with different signal-to-noise ratios (SNR). Considerable advantages of the proposed method over established fixed amplitude threshold and STA/LTA (Short Time Average / Long Time Average) techniques are demonstrated in comparative tests.

EXTRACTING SUB-SURFACE INFORMATION FROM LONG OFFSET P-WAVE DATA—A CHEAPER ALTERNATIVE TO MULTICOMPONENT OBC FOR EXPLORATION?

2002 ◽  
Vol 42 (1) ◽  
pp. 627
Author(s):  
R.G. Williams ◽  
G. Roberts ◽  
K. Hawkins
Keyword(s):  
Seismic Energy ◽  
Higher Order ◽  
P Wave ◽  
S Wave ◽  
Additional Information ◽  
Wave Data ◽  
Wave Velocities ◽  
Avo Inversion ◽  
Long Offset ◽  
Multicomponent Data

Seismic energy that has been mode converted from pwave to s-wave in the sub-surface may be recorded by multi-component surveys to obtain information about the elastic properties of the earth. Since the energy converted to s-wave is missing from the p-wave an alternative to recording OBC multi-component data is to examine p-wave data for the missing energy. Since pwave velocities are generally faster than s-wave velocities, then for a given reflection point the converted s-wave signal reaches the surface at a shorter offset than the equivalent p-wave information. Thus, it is necessary to record longer offsets for p-wave data than for multicomponent data in order to measure the same information.A non-linear, wide-angle (including post critical) AVO inversion has been developed that allows relative changes in p-wave velocities, s-wave velocities and density to be extracted from long offset p-wave data. To extract amplitudes at long offsets for this inversion it is necessary to image the data correctly, including correcting for higher order moveout and possibly anisotropy if it is present.The higher order moveout may itself be inverted to yield additional information about the anisotropy of the sub-surface.

scholarly journals From the Difference of Structures to the Structure of the Difference

Complexity ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Massimiliano Zanin ◽  
Ernestina Menasalvas ◽  
Xiaoqian Sun ◽  
Sebastian Wandelt
Keyword(s):  
Complex System ◽  
Network Theory ◽  
General Framework ◽  
Random Noise ◽  
Time Varying ◽  
Evolving Systems ◽  
Multiple Networks ◽  
Stochastic Fluctuations ◽  
Multidimensional Complex ◽  
The Difference

When dealing with evolving or multidimensional complex systems, network theory provides us with elegant ways of describing their constituting components, through, respectively, time-varying and multilayer complex networks. Nevertheless, the analysis of how these components are related is still an open problem. We here propose a general framework for analysing the evolution of a (complex) system, by describing the structure created by the difference between multiple networks by means of the Information Content metric. Differently from other approaches, which focus on assessing the magnitude of the change, the proposed one allows understanding if the observed changes are due to random noise or to structural (targeted) modifications; in other words, it allows describing the nature of the force driving the changes and discriminating between stochastic fluctuations and intentional modifications. We validate the framework by means of sets of synthetic networks, as well as networks representing real technological, social, and biological evolving systems. We further propose a way of reconstructing network correlograms, which allow converting the system’s evolution to the frequency domain.

Source location with cross-coherence migration

Geophysics ◽  
2020 ◽  
Vol 85 (4) ◽  
pp. KS127-KS138 ◽  
Author(s):  
Yujin Liu ◽  
Yue Ma ◽  
Yi Luo
Keyword(s):  
Field Data ◽  
Random Noise ◽  
Synthetic Data ◽  
Seismic Energy ◽  
Seismic Source ◽  
Spectral Amplitude ◽  
Multiple Sources ◽  
Passive Seismic ◽  
Similar Images ◽  
Resolution Property

Locating microseismic source positions using seismic energy emitted from hydraulic fracturing is essential for choosing optimal fracking parameters and maximizing the fracturing effects in hydrocarbon exploitation. Interferometric crosscorrelation migration (ICCM) and zero-lag autocorrelation of time-reversal imaging (ATRI) are two important passive seismic source locating approaches that are proposed independently and seem to be substantially different. We have proven that these two methods are theoretically identical and produce very similar images. Moreover, we have developed cross-coherence that uses normalization by the spectral amplitude of each of the traces, rather than crosscorrelation or deconvolution, to improve the ICCM and ATRI methods. The adopted method enhances the spatial resolution of the source images and is particularly effective in the presence of highly variable and strong additive random noise. Synthetic and field data tests verify the equivalence of the conventional ICCM and ATRI and the equivalence of their improved versions. Compared with crosscorrelation- and deconvolution-based source locating methods, our approach shows a high-resolution property and antinoise capability in numerical tests using synthetic data with single and multiple sources, as well as field data.

Denoising seismic data using the nonlocal means algorithm

Geophysics ◽  
2012 ◽  
Vol 77 (1) ◽  
pp. A5-A8 ◽  
Author(s):  
David Bonar ◽  
Mauricio Sacchi
Keyword(s):  
Seismic Data ◽  
Random Noise ◽  
Seismic Energy ◽  
Real Data ◽  
Spatial Proximity ◽  
Data Sets ◽  
Noise Attenuation ◽  
Nonlocal Means ◽  
Reflection Seismic ◽  
Generally True

The nonlocal means algorithm is a noise attenuation filter that was originally developed for the purposes of image denoising. This algorithm denoises each sample or pixel within an image by utilizing other similar samples or pixels regardless of their spatial proximity, making the process nonlocal. Such a technique places no assumptions on the data except that structures within the data contain a degree of redundancy. Because this is generally true for reflection seismic data, we propose to adopt the nonlocal means algorithm to attenuate random noise in seismic data. Tests with synthetic and real data sets demonstrate that the nonlocal means algorithm does not smear seismic energy across sharp discontinuities or curved events when compared to seismic denoising methods such as f-x deconvolution.

scholarly journals The cost efficiency of Vietnamese banks – the difference between DEA and SFA

2020 ◽  
Vol 22 (2) ◽  
pp. 209-227
Author(s):  
Phong Hoang Nguyen ◽  
Duyen Thi Bich Pham
Keyword(s):  
Cost Efficiency ◽  
Stochastic Frontier Analysis ◽  
Random Noise ◽  
Stochastic Frontier ◽  
Time Consistency ◽  
Efficiency Frontier ◽  
Content Type ◽  
Frontier Analysis ◽  
The Difference ◽  
The Cost

PurposeThe paper aims to enrich previous findings for an emerging banking industry such as Vietnam, reporting the difference between the parametric and nonparametric methods when measuring cost efficiency. The purpose of the study is to assess the consistency in issuing policies to improve the cost efficiency of Vietnamese commercial banks.Design/methodology/approachThe cost efficiency of banks is assessed through the data envelopment analysis (DEA) and the stochastic frontier analysis (SFA). Next, five tests are conducted in succession to analyze the differences in cost efficiency measured by these two methods, including the distribution, the rankings, the identification of the best and worst banks, the time consistency and the determinants of efficiency frontier. The data are collected from the annual financial statements of Vietnamese banks during 2005–2017.FindingsThe results show that the cost efficiency obtained under the SFA models is more consistent than under the DEA models. However, the DEA-based efficiency scores are more similar in ranking order and stability over time. The inconsistency in efficiency characteristics under two different methods reminds policy makers and bank administrators to compare and select the appropriate efficiency frontier measure for each stage and specific economic conditions.Originality/valueThis paper shows the need to control for heterogeneity over banking groups and time as well as for random noise and outliers when measuring the cost efficiency.

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