Improved Fourier terrain correction, Part I

Geophysics ◽  
1995 ◽  
Vol 60 (4) ◽  
pp. 1007-1017 ◽  
Author(s):  
Robert L. Parker
Keyword(s):  
Quadrature Rule ◽  
Observation Point ◽  
Terrain Correction ◽  
New Approach ◽  
Computational Speed ◽  
Marine Gravity ◽  
Numerical Effort ◽  
Local Contribution ◽  
Steep Terrain ◽  
Guadalupe Island

A description of a new Fourier technique is given for calculating the gravitational attraction of a layer with an irregular top surface for application in the terrain correction of marine gravity surveys in shallow water. An earlier Fourier‐based algorithm fails or becomes inaccurate when the peaks of the topography approach the sea surface too closely. The new approach divides the attraction into two parts: a local contribution from the material within a cylinder around each observation point and the attraction from the matter outside the cylinder. A special quadrature rule, optimized for the actual data distribution, evaluates the local contribution. The calculation of the exterior component represents the bulk of the numerical effort. Fortunately, the exterior integral possesses an expansion as a series of convolutions, and by evaluating these in the Fourier domain, the procedure can take advantage of the efficiency of the fast Fourier transform. Chebychev economization of the convolution series provides further significant improvements in computational speed. Two examples, one artificial and the other based on a survey around Guadalupe Island, illustrate the application of the new technique. Estimates of the errors from computation sources and from the inadequacies of the topographic model confirm the general accuracy of the approach, except in regions of very steep terrain.

scholarly journals Application of Asymmetrical Statistical Distributions for 1D Simulation of Solute Transport in Streams

Water ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 2145
Author(s):  
Sokáč ◽  
Velísková ◽  
Gualtieri
Keyword(s):  
Probability Distributions ◽  
New Approach ◽  
Dead Zones ◽  
Advection Dispersion ◽  
Small Streams ◽  
Computational Speed ◽  
Transient Storage Zones ◽  
The One ◽  
Published Research ◽  
Substance Transport

Analytical solutions of the one-dimensional (1D) advection–dispersion equations, describing the substance transport in streams, are often used because of their simplicity and computational speed. Practical computations, however, clearly show the limits and the inaccuracies of this approach. These are especially visible in cases where the streams deform concentration distribution of the transported substance due to hydraulic and morphological conditions, e.g., by transient storage zones (dead zones), vegetation, and irregularities in the stream hydromorphology. In this paper, a new approach to the simulation of 1D substance transport is presented, adapted, and tested on tracer experiments available in the published research, and carried out in three small streams in Slovakia with dead zones. Evaluation of the proposed methods, based on different probability distributions, confirmed that they approximate the measured concentrations significantly better than those based upon the commonly used Gaussian distribution. Finally, an example of the application of the proposed methods to an iterative (inverse) task is presented.

scholarly journals Direct Depth Domain Bayesian AVO Inversion

Geophysics ◽  
2021 ◽  
pp. 1-46
Author(s):  
Madhumita Sengupta ◽  
Houzhu Zhang ◽  
Yang Zhao ◽  
Mike Jervis ◽  
Dario Grana
Keyword(s):  
Reservoir Characterization ◽  
Time Window ◽  
Hybrid Approach ◽  
Spatial Location ◽  
Seismic Inversion ◽  
Reservoir Modeling ◽  
Model Parameters ◽  
New Approach ◽  
Avo Inversion ◽  
Computational Speed

We present a new approach to perform Bayesian linearized amplitude-versus-offset (AVO) inversion directly in the depth domain using non-stationary wavelets. Bayesian linearized AVO inversion, which is a hybrid approach combining physics-based models with statistical learning, has gained immense popularity in the past decade because of its superior computational speed and its ability to estimate uncertainties in the inverted model parameters. Bayesian linearized AVO inversion is typically performed on time-domain seismic data; therefore, depth-imaged seismic cannot be inverted directly using this method, and would require depth-to-time conversion before AVO inversion can be done. Subsequently, time-to-depth conversion of the inverted volumes would be required for reservoir modeling and well-placement. Domain-conversions introduce additional sources of uncertainty in the geophysical workflows. Another drawback of conventional AVO inversion techniques is that the seismic wavelet is assumed to be stationary, and this assumption leads to a restriction in the length of the time-window over which the inversion can be performed. Therefore, AVO inversion is usually restricted to a narrow time window around the target of interest, and in case multiple targets are present at different depths, multiple inversions have to be run on the same seismic volume if we use traditional AVO inversion. AVO inversion in the depth-domain using non-stationary wavelets (or point-spread functions) is a fairly recent development, and has been previously presented in an iterative formulation that is computationally intensive compared to Bayesian linearized AVO inversion. Implementing linearized Bayesian inversion directly in the depth-domain using non-stationary wavelets is a convenient new approach that takes advantage of superior computational speed and uncertainty quantification without compromising the accurate spatial location that depth imaging provides. Bringing these two schools of thought together creates a novel, unique, and powerful seismic inversion technique that can be useful for quantitative interpretation and reservoir characterization.

GRAVITY AND MAGNETIC FIELDS OF POLYGONAL PRISMS AND APPLICATION TO MAGNETIC TERRAIN CORRECTIONS

Geophysics ◽  
1976 ◽  
Vol 41 (4) ◽  
pp. 727-741 ◽  
Author(s):  
Donald Plouff
Keyword(s):  
Goodness Of Fit ◽  
Percent Level ◽  
Computer Programs ◽  
Exact Formula ◽  
Observation Point ◽  
Magnetic Effect ◽  
Terrain Correction ◽  
Coefficient Of Correlation ◽  
San Juan Mountains ◽  
Gravity And Magnetic

Computer programs based on the exact calculations of the gravity and magnetic anomalies of polygonal prisms are faster in operation and more accurate than previous programs based on the numerical integration of polygonal laminas. The prism programs also are of more general application than existing computer programs that are based on the exact gravity and magnetic effects of rectangular prisms. There are no restrictions on the use of the exact formula for the gravitational attraction of a polygonal prism, but the formulas for the magnetic effect are restricted in that demagnetization is not considered, and a finite answer is not obtained in the unrealistic circumstance where an observation point coincides with an edge of the prism. Least‐squares methods permit calculation of the gravity or magnetic effect of models without knowledge of the density or magnetization contrasts, respectively, by comparison of the observed anomalies with theoretical dimensionless values to determine contrasts as regression coefficients. The coefficient of correlation provides a goodness of fit estimate that helps model evaluation. After calculating a magnetic terrain correction for an outcrop of Quaternary dacite and andestite near Clear Lake, Calif., an improvement of the coefficient of correlation from 88 to the 92 percent level indicates that this volcanic unit probably extends at least 150 m beneath the surface. Application of a magnetic terrain correction to disconnected outcrops of Tertiary andesite, eliminates most of a prominent v-shaped magnetic anomaly south of the San Juan Mountains, Colo.

scholarly journals A new approach to distant solar system object detection in large survey data sets

2018 ◽  
Vol 615 ◽  
pp. A159 ◽  
Author(s):  
V. Perdelwitz ◽  
M. Völschow ◽  
H. M. Müller
Keyword(s):  
Solar System ◽  
Observation Point ◽  
Point Sources ◽  
Data Sets ◽  
Wide Field ◽  
Single Observation ◽  
New Approach ◽  
Long Time ◽  
Large Survey ◽  
Heliocentric Coordinates

Context. The recently postulated existence of a giant ninth planet in our solar system has sparked search efforts for distant solar system objects (SSOs) both via new observations and archival data analysis. Due to the likely faintness of the object in the optical and infrared regime, it has so far eluded detection. Aims. We set out to re-analyze data acquired by the Wide-Field Infrared Survey Explorer (WISE), an all-sky survey well suited for the detection of SSOs. Methods. We present a new approach to SSO detection via parallactic fitting. Using the heliocentric distance as a fit parameter, our code transforms groups of three or more single-observation point sources to heliocentric coordinates under the assumption that all data stem from an object. The fact that the orbit of a distant SSO is approximately linear in heliocentric coordinates over long time-scales can be utilized to produce candidates, which can then be confirmed with follow-up observations. Results. We demonstrate the feasibility of the approach by a posteriori detecting the outer SSO Makemake within WISE data. An all-sky search for Planet Nine yielded no detection. Conclusions. While the postulated Planet Nine eluded detection by our algorithm, we tentatively predict that this new approach to moving-object analysis will enable the discovery of new distant SSOs that cannot be discovered by other algorithms. Especially in cases of sparse data observed over long time spans, our approach is unique and robust due to the use of only one fit parameter.

Deadman anchoring design for cable logging: a new approach

2019 ◽  
pp. 342-357
Author(s):  
Francisca Belart ◽  
Ben Leshchinsky ◽  
Jeff Wimer
Keyword(s):  
Pacific Northwest ◽  
Forest Operations ◽  
New Approach ◽  
High Productivity ◽  
Common System ◽  
Soil Failure ◽  
The Pacific ◽  
Bending Resistance ◽  
Cable Yarding ◽  
Steep Terrain

Cable yarding is still a common system for transporting wood in steep terrain. In the Pacific Northwest, United States, and other regions of high-productivity forestry, reduced rotation ages for harvest have resulted in a lack of large stumps to serve as anchors for cable-yarding systems. One of the most common anchoring alternatives to stumps is buried deadman anchors. Conventional design of this system has been limited to simplified charts that account for soil resistance, as well as both shear and bending resistance, of the deadman, which is typically a buried log. However, these charts are limited to larger deadman anchors of only Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), which are likely not readily available in modern operations. Thus, revised, simplified design charts are proposed that consider a variety of different soil failure mechanisms, as well as several different wood types and bending conditions. An updated approach provides a quantitative perspective towards safe anchoring in modern forest operations.

scholarly journals Traveling Wave Fault Location Using Layer Peeling

Energies ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 126 ◽  
Author(s):  
Stephen Robson ◽  
Abderrahmane Haddad ◽  
Huw Griffiths
Keyword(s):  
Simulation Model ◽  
Fault Location ◽  
Field Measurements ◽  
Distribution Networks ◽  
Observation Point ◽  
Electrical Network ◽  
New Approach ◽  
Real Network ◽  
Geometrical Information ◽  
Layer Peeling

Many fault-location algorithms rely on a simulation model incorporating network parameters which closely represent the real network. Estimations of the line parameters are usually based on limited geometrical information which do not reflect the complexity of a real network. In practice, obtaining an accurate model of the network is difficult without comprehensive field measurements of each constituent part of the network in question. Layer-peeling algorithms offer a solution to this problem by providing a fast “mapping” of the network based only on the response of a probing impulse. Starting with the classical “Schur” layer-peeling algorithm, this paper develops a new approach to map the reflection coefficients of an electrical network, then use this information post-fault to determine accurately and robustly the location of either permanent or incipient faults on overhead networks. The robustness of the method is derived from the similarity between the post-fault energy reaching the observation point and the predicted energy, which is based on real network observations rather than a simulation model. The method is shown to perform well for different noise levels and fault inception angles on the IEEE 13-bus network, indicating that the method is well suited to radial distribution networks.

The O–C diagrams of minor planets − a new approach to modelling the rotation

1999 ◽  
Vol 173 ◽  
pp. 185-188
Author(s):  
Gy. Szabó ◽  
K. Sárneczky ◽  
L.L. Kiss
Keyword(s):  
Error Analysis ◽  
Time Dependence ◽  
Theoretical Work ◽  
Minor Planet ◽  
Minor Planets ◽  
New Approach ◽  
Preliminary Results ◽  
Ccd Observations

AbstractA widely used tool in studying quasi-monoperiodic processes is the O–C diagram. This paper deals with the application of this diagram in minor planet studies. The main difference between our approach and the classical O–C diagram is that we transform the epoch (=time) dependence into the geocentric longitude domain. We outline a rotation modelling using this modified O–C and illustrate the abilities with detailed error analysis. The primary assumption, that the monotonity and the shape of this diagram is (almost) independent of the geometry of the asteroids is discussed and tested. The monotonity enables an unambiguous distinction between the prograde and retrograde rotation, thus the four-fold (or in some cases the two-fold) ambiguities can be avoided. This turned out to be the main advantage of the O–C examination. As an extension to the theoretical work, we present some preliminary results on 1727 Mette based on new CCD observations.

A New Approach to the Demonstration of Oxidase-Localization Using Tannic Acid Or Catechin

1973 ◽  
Vol 31 ◽  
pp. 698-699
Author(s):  
V. Mizuhira ◽  
Y. Futaesaku
Keyword(s):  
Cross Section ◽  
Tannic Acid ◽  
Elastic Fiber ◽  
The Other ◽  
New Approach ◽  
Tissue Block ◽  
Active Reaction ◽  
The Cross

Previously we reported that tannic acid is a very effective fixative for proteins including polypeptides. Especially, in the cross section of microtubules, thirteen submits in A-tubule and eleven in B-tubule could be observed very clearly. An elastic fiber could be demonstrated very clearly, as an electron opaque, homogeneous fiber. However, tannic acid did not penetrate into the deep portion of the tissue-block. So we tried Catechin. This shows almost the same chemical natures as that of proteins, as tannic acid. Moreover, we thought that catechin should have two active-reaction sites, one is phenol,and the other is catechole. Catechole site should react with osmium, to make Os- black. Phenol-site should react with peroxidase existing perhydroxide.

Bence-albee after 25 years: A new superior α-factor correction procedure for the quantitative analysis of oxides and silicates

1992 ◽  
Vol 50 (2) ◽  
pp. 1744-1745
Author(s):  
John T. Armstrong
Keyword(s):  
Quantitative Analysis ◽  
Electron Microprobe ◽  
Binary Systems ◽  
Correction Procedure ◽  
Geological Samples ◽  
The Past ◽  
Large Matrix ◽  
Computational Speed ◽  
Microprobe Data ◽  
Geological Sciences

One of the most cited papers in the geological sciences has been that of Albee and Bence on the use of empirical " α -factors" to correct quantitative electron microprobe data. During the past 25 years this method has remained the most commonly used correction for geological samples, despite the facts that few investigators have actually determined empirical α-factors, but instead employ tables of calculated α-factors using one of the conventional "ZAF" correction programs; a number of investigators have shown that the assumption that an α-factor is constant in binary systems where there are large matrix corrections is incorrect (e.g, 2-3); and the procedure’s desirability in terms of program size and computational speed is much less important today because of developments in computing capabilities. The question thus exists whether it is time to honorably retire the Bence-Albee procedure and turn to more modern, robust correction methods. This paper proposes that, although it is perhaps time to retire the original Bence-Albee procedure, it should be replaced by a similar method based on compositiondependent polynomial α-factor expressions.

Processing Immunoperoxidase Labeled Cell Monolayers and Cryostat Sesctions For Electron Microscopy

1985 ◽  
Vol 43 ◽  
pp. 714-715
Author(s):  
K. Chien ◽  
R. Van de Velde ◽  
I.P. Shintaku ◽  
A.F. Sassoon
Keyword(s):  
Cell Monolayer ◽  
Cell Types ◽  
Surface Antigens ◽  
Immunoperoxidase Method ◽  
Reaction Step ◽  
Hot Plate ◽  
Air Drying ◽  
New Approach ◽  
Cell Monolayers ◽  
Glass Slides

Immunoelectron microscopy of neoplastic lymphoma cells is valuable for precise localization of surface antigens and identification of cell types. We have developed a new approach in which the immunohistochemical staining can be evaluated prior to embedding for EM and desired area subsequently selected for ultrathin sectioning.A freshly prepared lymphoma cell suspension is spun onto polylysine hydrobromide- coated glass slides by cytocentrifugation and immediately fixed without air drying in polylysine paraformaldehyde (PLP) fixative. After rinsing in PBS, slides are stained by a 3-step immunoperoxidase method. Cell monolayer is then fixed in buffered 3% glutaraldehyde prior to DAB reaction. After the DAB reaction step, wet monolayers can be examined under LM for presence of brown reaction product and selected monolayers then processed by routine methods for EM and embedded with the Chien Re-embedding Mold. After the polymerization, the epoxy blocks are easily separated from the glass slides by heatingon a 100°C hot plate for 20 seconds.

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