Curvature Algorithm Research Articles

Seismic structure and texture analyses for fractured reservoir characterization: An integrated workflow

Fractured reservoir prediction is risky and challenging because of the variability in fracture characteristics and the lack of direct observational data in the subsurface. To reduce the risk and challenge, we have developed an integrated workflow to predict fractured reservoirs based on 3D seismic data. The workflow begins with reservoir structure analysis from seismic reflection geometry, which is referred to as seismic structure analysis, to define fracture intensity and fracture orientation using maximum curvature and maximum flexure algorithms. Next, the workflow proceeds with reservoir texture analysis from seismic amplitude signal, which is referred to as seismic texture analysis, to evaluate fracture scale and reservoir facies using waveform regression and calibration algorithms. The results from seismic structure and texture analyses are then used for modeling reservoir properties and fracture networks. Each algorithmic method in the workflow is tested in a siliciclastic tight-sand reservoir in the Teapot Dome oil field (Powder River Basin) and in a carbonate reservoir in the South Pars gas field (Persian Gulf Basin). The test results reveal the previously unknown reservoir heterogeneity and anisotropy that are interpreted to be attributable to the variability in fracture characteristics. It is concluded that the integrated workflow based on seismic structure and texture analyses could potentially contribute to reducing the risk and challenge in characterizing fractured reservoirs in the subsurface.

Flow rate impacts on capillary pressure and interface curvature of connected and disconnected fluid phases during multiphase flow in sandstone

We investigate capillary pressure-saturation (PC-S) relationships for drainage-imbibition experiments conducted with air (nonwetting phase) and brine (wetting phase) in Bentheimer sandstone cores. Three different flow rate conditions, ranging over three orders of magnitude, are investigated. X-ray micro-computed tomographic imaging is used to characterize the distribution and amount of fluids and their interfacial characteristics. Capillary pressure is measured via (1) bulk-phase pressure transducer measurements, and (2) image-based curvature measurements, calculated using a novel 3D curvature algorithm. We distinguish between connected (percolating) and disconnected air clusters: curvatures measured on the connected phase interfaces are used to validate the curvature algorithm and provide an indication of the equilibrium condition of the data; curvature and volume distributions of disconnected clusters provide insight to the snap-off processes occurring during drainage and imbibition under different flow rate conditions.

Two-dimensional Chebyshev pseudo spectral modal curvature and its application in damage detection for composite plates

To overcome the unstable problem in the classical modal curvature method, the two-dimensional Fourier spectral modal curvature method has been proposed in the former work of authors. The existences of the wrap-around effect and the Gibbs phenomenon in the Fourier spectrum-based method, however, necessitate the use of periodic extensions, which affects the efficiency of the modal curvature algorithm. To address the above problems, the two-dimensional Chebyshev pseudo spectral modal curvature is proposed in this work. The presented method inherits the spatial filtering capability and the spectral accuracy of the Fourier spectral modal curvature, and features an efficient modal curvature algorithm in absence of the periodic extension. Numerical and experimental validations are performed on composite structures. Validations show that the proposed method is accurate and effective in the damage detection for the two-dimensional composite structures.

Static and Dynamic Hand Gesture Recognition in Depth Data Using Dynamic Time Warping

This paper discusses the development of a natural gesture user interface that tracks and recognizes in real time hand gestures based on depth data collected by a Kinect sensor. The interest space corresponding to the hands is first segmented based on the assumption that the hand of the user is the closest object in the scene to the camera. A novel algorithm is proposed to improve the scanning time in order to identify the first pixel on the hand contour within this space. Starting from this pixel, a directional search algorithm allows for the identification of the entire hand contour. The $k$ -curvature algorithm is then employed to locate the fingertips over the contour, and dynamic time warping is used to select gesture candidates and also to recognize gestures by comparing an observed gesture with a series of prerecorded reference gestures. The comparison of results with state-of-the-art approaches shows that the proposed system outperforms most of the solutions for the static recognition of sign digits and is similar in terms of performance for the static and dynamic recognition of popular signs and for the sign language alphabet. The solution simultaneously deals with static and dynamic gestures as well as with multiple hands within the interest space. An average recognition rate of 92.4% is achieved over 55 static and dynamic gestures. Two possible applications of this work are discussed and evaluated: one for interpretation of sign digits and gestures for a friendlier human-machine interaction and the other one for the natural control of a software interface.

Near-stability of a quasi-minimal surface indicated through a tested curvature algorithm

We decrease the rms mean curvature and area of a variable surface with a fixed boundary by iterating a few times through a curvature-based variational algorithm. For a boundary with a known minimal surface, starting with a deliberately chosen non-minimal surface, we achieve up to 65 percent of the total possible decrease in area. When we apply our algorithm to a bilinear interpolant bounded by four non-coplanar straight lines, the area decrease by the same algorithm is only 0.116179 percent of the original value. This relative stability suggests that the bilinear interpolant is already a quasi-minimal surface.

Performance Improvement of Collision Warning System on Curved Road Based on Intervehicle Communication

The vehicle on-board sensor based Advanced Driver Assistant System possesses limitations on a small road with a small radius of curvature because of the sensor’s inability to operate in nondetectable domains. This study suggests an Improved Cooperative Collision Warning System (ICCWS) that considers the curvature of the road and is based on intervehicle communication. To predict the radius of curvature of the road, the Arc Relative Distance (ARD), the real relative distance to a preceding vehicle on a curved road has been used. The risk of collision with the preceding vehicle is decided by calculating an index of the risk of collision on a curved road using the computed ARD. The effects of ICCWS, proposed through this simulation, have been reviewed, and the improvement in performance in following a preceding vehicle has been analyzed quantitatively via comparative analysis with the conventional forward collision warning system. Accordingly, if the estimating algorithm for curvature developed in this study is applied to a real system, the performance of following a preceding vehicle can be improved without any specific changes to the system.

Hand vein authentication using biometric graph matching

This study proposes an automatic dorsal hand vein verification system using a novel algorithm called biometric graph matching (BGM). The dorsal hand vein image is segmented using the K-means technique and the region of interest is extracted based on the morphological analysis operators and normalised using adaptive histogram equalisation. Veins are extracted using a maximum curvature algorithm. The locations and vascular connections between crossovers, bifurcations and terminations in a hand vein pattern define a hand vein graph. The matching performance of BGM for hand vein graphs is tested with two cost functions and compared with the matching performance of two standard point patterns matching algorithms, iterative closest point (ICP) and modified Hausdorff distance. Experiments are conducted on two public databases captured using far infrared and near infrared (NIR) cameras. BGM's matching performance is competitive with state-of-the-art algorithms on the databases despite using small and concise templates. For both databases, BGM performed at least as well as ICP. For the small sized graphs from the NIR database, BGM significantly outperformed point pattern matching. The size of the common subgraph of a pair of graphs is the most significant discriminating measure between genuine and imposter comparisons.

Contactless Palm Vein Recognition Using a Mutual Foreground-Based Local Binary Pattern

Local binary pattern (LBP) is popular for the texture representation owing to its discrimination ability and computational efficiency, but when used to describe the sparse texture in palm vein images, the discrimination ability is diluted, leading to lower performance, especially for contactless palm vein matching. In this paper, an improved mutual foreground LBP method is presented for achieving a better matching performance for contactless palm vein recognition. First, the normalized gradient-based maximal principal curvature algorithm and $k$ -means method are utilized for texture extraction, which can effectively suppress noise and improve accuracy and robustness. Then, an LBP matching strategy was adopted for similarity measurements on the basis of extracted palm veins and their neighborhoods, which include the vast majority of useful distinctive information for identification while eliminating interference by excluding the background. To further improve the LBP performance, the matched pixel ratio was adopted to determine the best matching region (BMR). Finally, the matching score obtained in the process of finding the BMR was fused with results of LBP matching at the score level to further improve the identification performance. A series of rigorous contrast experiments using the palm vein data set in the CASIA multispectral palmprint image database were conducted. The obtained low equal error rate (0.267%) and comparisons with the most state-of-the-art approaches demonstrate that our method is feasible and effective for contactless palm vein recognition.

Performance analysis of freeware filtering algorithms for determining ground surface from airborne laser scanning data

Numerous filtering algorithms have been developed in order to distinguish the ground surface from nonground points acquired by airborne laser scanning. These algorithms automatically attempt to determine the ground points using various features such as predefined parameters and statistical analysis. Their efficiency also depends on landscape characteristics. The aim of this contribution is to test the performance of six common filtering algorithms embedded in three freeware programs. The algorithms’ adaptive TIN, elevation threshold with expand window, maximum local slope, progressive morphology, multiscale curvature, and linear prediction were tested on four relatively large (4 to 8 km2) and diverse landscape areas, which included steep sloped hills, urban areas, ridge-like eskers, and a river valley. The results show that in diverse test areas each algorithm yields various commission and omission errors. It appears that adaptive TIN is suitable in urban areas while the multiscale curvature algorithm is best suited in wooded areas. The multiscale curvature algorithm yielded the overall best results with average root-mean-square error values of 0.35 m.

A new algorithm for evaluating 3D curvature and curvature gradient for improved fracture detection

In 3D seismic interpretation, both curvature and curvature gradient are useful seismic attributes for structure characterization and fault detection in the subsurface. However, the existing algorithms are computationally intensive and limited by the lateral resolution for steeply-dipping formations. This study presents new and robust volume-based algorithms that evaluate both curvature and curvature gradient attributes more accurately and effectively. The algorithms first instantaneously fit a local surface to seismic data and then compute attributes using the spatial derivatives of the built surface. Specifically, the curvature algorithm constructs a quadratic surface by using a rectangle 9-node grid cell, whereas the curvature gradient algorithm builds a cubic surface by using a diamond 13-node grid cell. A dip-steering approach based on 3D complex seismic trace analysis is implemented to enhance the accuracy of surface construction and to reduce computational time. Applications to two 3D seismic surveys demonstrate the accuracy and efficiency of the new curvature and curvature gradient algorithms for characterizing faults and fractures in fractured reservoirs.

English

Super-resolution image reconstruction provides an effective way to increase image resolution from a single or multiple low resolution images. There exists various single image super-resolution based on different assumptions, amongst which edge adaptive algorithms are particularly used to improve the accuracy of the interpolation characterizing the edge features in a larger region. A recent algorithm for image iterative curvature based interpolation (ICBI) performs iterative procedure of the interpolated pixels obtained by the 2 nd order directional derivative of the image intensity. ICBI in comparison with bicubic interpolation and the other interpolation algorithm such as improved new edge directed interpolation (INEDI) provides notably higher values in terms of qualitative and quantitative analysis. Comparative analysis of these algorithms performed on number of test images on the basis of PSNR and RMSE metrics show effectiveness of edge based techniques.

Research on Algorithm of Gauss Curvature on Space Mesh Points of Battlefield Large-Scale Terrain and its Visualization

This paper discusses the calculation method of Gauss Curvature on space mesh points in simplified level-of-detail (LOD) model technique and how to program with C# language at the platform of .NET. Then, with this algorithm, get the curvature value of the mesh points, delete the center point of the small curvature and triangularize the cavity left so as to realize the simplification of the LOD model. In order to show the result of this algorithm, this paper visualizes the LOD model of the three-dimensional terrain model in full detail with Gauss Curvature Algorithm, puts forward the idea of carrying out error analysis on the algorithm with the geometric property of curvature, and compares the result with that with other algorithms. All the example and the error analysis show that this algorithm is not only of fast speed but also with good effect.

Estimates of surface normal and curvature, reconstruction of continuum surface force model, and elimination of spurious currents

SUMMARYA reconstructed continuum surface force (CSF) model is presented for the volume‐of‐fluid (VOF) method in numerical simulations of surface tension‐driven flow. The gradient of VOF function yielded by the one‐direction difference (ODD) algorithm has second‐order accuracy in one direction and exhibits unit pulse function in the other direction. Use of our ODD algorithm for surface normal and curvature improves the accuracy of surface tension force estimate and meets the necessary condition of a circular droplet free of spurious currents. The immersed length, a physical depth of grid cell center introduced in this paper, is computed from VOF function and surface orientation. It is chosen instead of VOF function as weight parameters in the evaluations of density and volumetric surface tension force between interfacial grid cells. Grid cells and control cells are classified into interfacial, sublayer, and interior cells according to their distances to interface. Surface tension is thus constructed within interfacial or sublayer cells. The numerical approach is modified so that flow pressure solutions are sought only at those immersed grid cell centers. The transitional region from one fluid to the other is compressed. Spurious currents by no means grow on free surface in the numerical simulations using our algorithms and reconstructed CSF model. The simulation results agree with the Laplace pressure jump across a static circular free surface or experimental observations. Copyright © 2014 John Wiley & Sons, Ltd.

3A1-H06 粘弾性チューブ内超音波伝搬を利用した安全確認型接触センサの開発 : チューブ曲率を考慮した伝搬特性推定及び自己診断アルゴリズム(安全・安心なRT構築を目指して)

3A1-H06 粘弾性チューブ内超音波伝搬を利用した安全確認型接触センサの開発 : チューブ曲率を考慮した伝搬特性推定及び自己診断アルゴリズム(安全・安心なRT構築を目指して)

Integrating 3D seismic curvature and curvature gradient attributes for fracture characterization: Methodologies and interpretational implications

In 3D seismic interpretation, curvature is a popular attribute that depicts the geometry of seismic reflectors and has been widely used to detect faults in the subsurface; however, it provides only part of the solutions to subsurface structure analysis. This study extends the curvature algorithm to a new curvature gradient algorithm and integrates both algorithms for fracture detection using a 3D seismic test data set over Teapot Dome (Wyoming). In fractured reservoirs at Teapot Dome formed by tectonic folding and faulting, curvature helps define the crestal portion of reservoirs that is associated with strong seismic amplitude and high oil productivity. In contrast, curvature gradient helps define the regional northwest-trending and the cross-regional northeast-trending lineaments that are associated with weak seismic amplitude and low oil productivity. In concert with previous reports from image logs, cores, and outcrops, an integrated seismic curvature and curvature gradient analysis suggests that curvature might help define areas of enhanced potential to form tensile fractures, whereas curvature gradient might help define zones of enhanced potential to develop shear fractures. In fractured reservoirs at Teapot Dome where faulting and fault-related folding contribute dominantly to the formation and evolution of fractures, curvature and curvature gradient attributes can be potentially applied to differentiate fracture mode, to predict fracture intensity and orientation, to evaluate fracture volume and connectivity, and to model fracture networks.

Multi-resolution morpho-bathymetric survey results at the Pozzuoli–Baia underwater archaeological site (Naples, Italy)

Here we show the results of two morpho-bathymetric surveys carried out on the underwater archaeological area of the Pozzuoli Bay (Naples, Italy). Such area is enclosed in the Campi Flegrei active volcanic complex, where bradyseism and recent volcanic activity strongly influenced the coastline shape over the last 2 Ka. The Digital Elevation Model (DTM) of the seafloor allowed to draw the main archaeological features of the Bay, that also include the military complex of Portus Iulius and the ancient thermal and villa complex of Baianus Lacus. The extraction of archaeological features from DTM was achieved thanks to the use of a GIS-derived tool based on the profile curvature algorithm. Thus, the Villa dei Pisoni (1st Century B.C.) and the thermal complex of Secca delle Fumose were investigated by using ultra-high resolution DTMs, that show the presence of Roman pilae for the protection of coastal buildings and also the inner planimetry of the Villa dei Pisoni complex. The observation of coastal engineering structures give also the opportunity to formulate some hypothesis on the evolution of morphology and of the sedimentary pattern of the area, while depth of archaeological remains allowed a rough computation of the rate of subsidence, resulted to be 2.55 (±0.5) mm/y for the Eastern sector (Pozzuoli) and 2.90 (±0.5) mm/y for the western (Baia).

Analysis on Using Average Curvature Algorithm to Simplify the Mapping of Large-Scale Battlefield Terrain Space Grids with LOD and its Errors

When mapping large-scale battlefield terrain, in order to make a real-time show it on the computer it is required to keep the vector data (points, lines, areas) at the high curvature and delete the vector data at the low curvature as much as possible. This article puts forward a simplified algorithm to calculate the average curvature of the space mesh points with level of detail (LOD) model technique as well as the visualization implementation of this algorithm. Then according to this algorithm, work out the curvature value of the mesh points, delete the center points of the low curvature and triangularize the cavity left so as to simplify LOD model and reduce dramatically the number of the vector data (points, lines, areas) in the field of view of the large-scale battlefield terrain. Experiments show the average curvature algorithm put forward in this article can better solve the contradiction between the big vector data and the limited real-time processing capacity of the computer. As a result, it can meet the requirements of mapping great number of real-time data of the large-scale battlefield terrain by 3 D visualization.

Application of Different Algorithms to Predict the Faults and Fractures in Carbonate Formation

The application of coherent cube and volume curvature algorithm to analyze and process the three-dimensional seismic data of Ordovician carbonate rocks in the Tazhong area of Tarim Basin, and to predict the faults and fractures development. After the comparison, coherent cube algorithm is fit for prediction of main faults development with the clear result in oilfield exploration stage , volume curvature algorithm is fit for prediction of faults and fractures development with the abundant information in oilfield development stage. Therefore, according to different purposes of exploration and development, different algorithms could be applied to prediction of faults and fractures. This would be useful to guide the oilfield exploration and development.

Mean-shifted surface curvature algorithm for automatic bone shape segmentation in orthopedic surgery planning: a sensitivity analysis

The results of recent studies concerning statistical bone atlases and automated shape analysis are promising with a view to widening the use of surface models in orthopedic clinical practice, both in pre-operative planning and in the intra-operative stages. In this domain, automatic shape analysis is strongly advocated because it offers the opportunity to detect morphological and clinical landmarks with superior repeatability in comparison to human operators. Surface curvatures have been proposed extensively for segmentation and labeling of image and surface regions based on their appearance and shape. The surface curvature is an invariant that can be exploited for reliable detection of geometric features. In this paper, we investigate the potentiality of the algorithm termed mean-shift (MS), as applied to a non-linear combination of the minimum and maximum curvatures of a surface. We exploited a sensitivity analysis of the algorithm parameters across increasing surface resolutions. Results obtained with femur and pelvic bone surface data, reconstructed from cadaveric CT scans, demonstrated that the information content derived by the MS non-linear curvature overcomes both the mean and the Gaussian curvatures and the original non-linear curvature. By applying a threshold-based clustering algorithm to the curvature distribution, we found that the number of clusters yielded by the MS non-linear curvature is significantly lower (by a factor of up to 6) than that obtained by using the original non-linear curvature. In conclusion, this study provides valuable insights into the use of surface curvature for automatic shape analysis.

Hydromorphological Mapping and Analysis for Characterizing Darfur Paleolake, NW Sudan Using Remote Sensing and GIS

The north-western part of Sudan, which is the driest region on earth has revealed newly surface and near surface paleodrainage network underneath sand sheets indicating the possibilities for economic groundwater reservoirs. Advanced Space-born Thermal Radiometer (ASTER), the Shuttle Radar Topography Mission (SRTM ~90 m) DEMs and Quickbird images corroborate the presence of surface and near surface paleodrainage network. Bivariate quadratic surfaces with moving window size of 3 × 3 were fitted to the SRTM DEM. The second derivative surface curvature was calculated to reveal landform classes that may receive most of fossil water. The results showed that the new unnamed depression which recharges by a longitudinal paleodrainage network may receive vast amount of groundwater during humid phases. The results demonstrate that the D8 and curvature algorithms are very efficient tools for revealing and characterizing hydrological elements in arid and semi-arid regions and they provide information for hydrological exploration in remote deserts over large scale prior to geophysical survey.