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Liu, Hao, Hongbo Qian, Ning Dai e Jianning Zhao. "Heuristic Initialization for Active Contour Models in CT/MRI Image Processing". International Journal of Image and Graphics 15, n.º 03 (11 de junho de 2015): 1550010. http://dx.doi.org/10.1142/s0219467815500102.
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It is an important segmentation approach of CT/MRI images to automatically extract contours in every slice using active contour models. The key point of the segmentation approach is to automatically construct initial contours for active contour models because any active contour model is sensitive to its initial contour. This paper presents an algorithm to construct such initial contours using a heuristic method. Assume that the contour in previous slice (previous contour) is accurate. The contour in the current slice (current contour) is constructed according to the previous contour using the way: Recognition and link of edge points of tissues according to the previous contour. The contour linking edge points is used as the initial contour of the distance regularized level set evolution (DRLSE) method and then an accurate contour can be extracted in the current slice.
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Xiao, Xiao, Yuhang Liu e Yanci Zhang. "Iterative Low-Poly Building Model Reconstruction from Mesh Soups Based on Contour". Remote Sensing 16, n.º 4 (16 de fevereiro de 2024): 695. http://dx.doi.org/10.3390/rs16040695.
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Existing contour-based building-reconstruction methods face the challenge of producing low-poly results. In this study, we introduce a novel iterative contour-based method to reconstruct low-poly meshes with only essential details from mesh soups. Our method focuses on two primary targets that determine the quality of the results: reduce the total number of contours, and generate compact surfaces between contours. Specifically, we implemented an iterative pipeline to gradually extract vital contours by loss and topological variance, and potential redundant contours will be removed in a post-processing procedure. Based on these vital contours, we extracted the planar primitives of buildings as references for contour refinement to obtain compact contours. The connection relationships between these contours are recovered for surface generation by a contour graph, which is constructed using multiple bipartite graphs. Then, a low-poly mesh can be generated from the contour graph using our contour-interpolation algorithm based on polyline splitting. The experiments demonstrated that our method produced satisfactory results and outperformed the previous methods.
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Ramli, Izzad, Nursuriati Jamil e Noraini Seman. "An Iterated Two-Step Sinusoidal Pitch Contour Formulation for Expressive Speech Synthesis". Journal of Information and Communication Technology 20, No.4 (27 de setembro de 2021): 489–510. http://dx.doi.org/10.32890/jict2021.20.4.2.
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Intonation generation in expressive speech such as storytelling is essential to produce high quality Malay language expressive speech synthesizer. Intonation generation, for instance explicit control, has shown good performance in terms of intelligibility with reasonably natural speech; thus, it was selected in this research. This approach modifies the prosodic features, such as pitch contour, intensity, and duration, to generate the intonation. However, modification of pitch contour remains a problem because the desired pitch contour is not achieved. This paper formulated an improved pitch contour algorithm to develop a modified pitch contour resembling the natural pitch contour. In this work, the syllable pitch contours of nine storytellers were extracted from their storytelling speeches to create an expressive speech syllable dataset called STORY_DATA. All the shapes of pitch contours from STORY_DATA were analyzed and clustered into the standard six main pitch contour clusters for storytelling. The clustering was performed using one minus the Pearson product moment correlation. Then, an improved iterative two-step sinusoidal pitch contour formulation was introduced to modify the pitch contours of a neutral speech into an expressive pitch contour of natural speeches. Overall, the improved pitch contour formulation was able to achieve 93 percent high correlated matches, indicating the high resemblance as compared to the previous pitch contour formulation at 15 percent. Therefore, the improved formula can be used in a text-to-speech (TTS) synthesizer to produce a more natural expressive speech. The paper also discovered unique expressive pitch contours in the Malay language that need further investigations in the future.
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Peng, Yan Jun, e Shuai Zhang. "A Novel Approach for Active Contour Initialization in 3D Medical Image Segmentation". Applied Mechanics and Materials 239-240 (dezembro de 2012): 1004–10. http://dx.doi.org/10.4028/www.scientific.net/amm.239-240.1004.
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Contour initialization is a big problem of the active contour model. Using the continuous features of the three-dimensional medical image, this paper proposes an initial contour prediction model. There are some changes in the boundary contours of the same object. We attribute these changes to continuous translation and similar deformation, and quantify into the centroid displacement and displacement of the point in the direction of Normal. The curve fitting method is used to predict the centroid displacement and the displacement of the points of the contours, which can provide more accurate prediction of changes in the contour. By predicting the initial contour, we have solved the contour initialization problem of the parametric active contour with external force using vector field convolution.
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Li, Wu, e Charles D. Gilbert. "Global Contour Saliency and Local Colinear Interactions". Journal of Neurophysiology 88, n.º 5 (1 de novembro de 2002): 2846–56. http://dx.doi.org/10.1152/jn.00289.2002.
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Our visual system can link components of contours and segregate contours from complex backgrounds based on geometric grouping rules. This is an important intermediate step in object recognition. The substrate for contour integration may be based on contextual interactions and intrinsic horizontal connections seen in primary visual cortex (V1). We examined the perceptual rules governing contour saliency to determine whether the spatial extents of contextual interactions and horizontal connections match those mediating saliency. To quantify these rules, we used stimuli composed of randomly oriented nonoverlapping line segments. Salient contours within this complex background were formed by colinear alignment of nearby segments. Contour detectability was measured using a 2-interval-forced-choice design. Contour detectability deteriorated with increasing spacing between contour elements and improved as the number of colinear line elements was increased. At short contour spacing, the detectability reached a plateau with alignment of a few line segments that together formed a contour subtending several visual degrees. At intermediate spacing, saliency built up progressively with a greater number of colinear lines, extending up to 30°. When contour spacing was beyond a critical range (about 2°), however, the detectability dropped to chance levels, regardless of the number of colinear lines. Contour detectability was found to be a function not only of the relative spacing of contour elements with respect to the noise elements but also of the average density of the overall pattern. Furthermore, training significantly improved contour detection, increasing the critical spacing of line elements beyond which contours were no longer detectable. Our data suggest that global contour integration is based on mechanisms of limited spatial extent, comparable to the interactions observed in V1. These interactions can cascade over larger distances provided the spacing of stimulus elements is kept within a limited range.
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Schmuckler, Mark A. "Testing Models of Melodic Contour Similarity". Music Perception 16, n.º 3 (1999): 295–326. http://dx.doi.org/10.2307/40285795.
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In two experiments, descriptions of melodic contour structure and predictions of perceived similarity relations between pairs of contours produced by a number of different models are examined. Two of these models, based on the music- theoretic approaches of Friedmann (1985) and Marvin and Laprade (1987), characterize contours in terms of interval content or contour subset information. The remaining two approaches quantify the global shape of the contours, through the presence of cyclical information (assessed via Fourier analysis) and the amount of oscillation (e. g., reversals in direction, pitch deviations) in the contours. Theoretical predictions for contour similarity generated by these models were examined for 20th century, nontonal melodies (Experiment 1) and simplistic, tonal patterns (Experiment 2). These experiments demonstrated that similarity based on Fourier analysis procedures and oscillation measures predicted a derived measure of perceived similarity, with both variables contributing relatively independently; the music- theoretic models were inconsistent in their predictive power. These results suggest that listeners are sensitive to the presence of global shape information in melodic contour, with such information underlying the perception of contour structure and contour similarity.
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LIU, HAO, GUANHUA ZHU, JIANNING ZHAO, HONGBO QIAN e NING DAI. "RECOGNITION OF OCCLUSIONS IN CT IMAGES USING A CURVE-BASED PARAMETERIZATION METHOD". International Journal of Image and Graphics 13, n.º 04 (outubro de 2013): 1350018. http://dx.doi.org/10.1142/s0219467813500186.
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It is an important way for segmentations of CT images to extract contours of objects slice-by-slice. For such a way, an important idea is analogy. That is to say, correct the contour in current slice (current contour) according to the contour in previous slice (previous contour). The key to properly correct the current contour is the ability to recognize occlusions (or say leaking parts) in the current contour. We present a curve-based curve parameterization method to recognize occlusions. The previous contour is evolved to the current contour using line projections. In the process of evolution, the parameterization is realized, which includes two types of information for every point in the evolved contour: the arc length parameter on the previous contour, and distance moved from the initial position to the present position. Using these two parameters, we are able to recognize occlusions in the current contour. Many experiments indicate that the method can recognize all of the occlusions in a given contour. Consequently, the method is robust and can be used as a part of an algorithm to automatically extract contours for CT images.
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Yang, Shudi, Jiaxiong Wu e Zhipeng Feng. "Dual-Fusion Active Contour Model with Semantic Information for Saliency Target Extraction of Underwater Images". Applied Sciences 12, n.º 5 (28 de fevereiro de 2022): 2515. http://dx.doi.org/10.3390/app12052515.
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Underwater vision research is the foundation of marine-related disciplines. The target contour extraction is significant for target tracking and visual information mining. Aiming to resolve the problem that conventional active contour models cannot effectively extract the contours of salient targets in underwater images, we propose a dual-fusion active contour model with semantic information. First, the saliency images are introduced as semantic information and salient target contours are extracted by fusing Chan–Vese and local binary fitting models. Then, the original underwater images are used to supplement the missing contour information by using the local image fitting. Compared with state-of-the-art contour extraction methods, our dual-fusion active contour model can effectively filter out background information and accurately extract salient target contours. Moreover, the proposed model achieves the best results in the quantitative comparison of MAE (mean absolute error), ER (error rate), and DR (detection rate) indicators and provides reliable prior knowledge for target tracking and visual information mining.
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Wang, Ying, Zhi Xian Lin, Jian Guo Cao e Mao Qing Li. "Automatic MRI Brain Tumor Segmentation System Based on Localizing Active Contour Models". Advanced Materials Research 219-220 (março de 2011): 1342–46. http://dx.doi.org/10.4028/www.scientific.net/amr.219-220.1342.
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In this paper, an automatic segmentation system was developed for MRI brain tumor. Local region-based active contour models were suitable for heterogeneous features of brain MRI image. But the models are sensitive to initial contour, which generally requires manual setting. An automatic MRI brain tumor segmentation system were developed based on localized contour models, which can identify tumor-dominant slice, set initial contour automatically and segment tumor’s contours from all MRI slices autonomously. K-means clustering and grayscale analysis were combined to identify tumor-dominant slice. Multi-threshold algorithm with the aid of erosion and dilation operators was adopted to obtain an initial contour for the tumor-dominant slice. The segmentation contour from the local active contour models was applied as initial contours of two-side neighboring slices. MRI brain tumor data were applied to validate the automatic segmentation system.
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GEISLER, WILSON S., e JEFFREY S. PERRY. "Contour statistics in natural images: Grouping across occlusions". Visual Neuroscience 26, n.º 1 (janeiro de 2009): 109–21. http://dx.doi.org/10.1017/s0952523808080875.
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AbstractCorrectly interpreting a natural image requires dealing properly with the effects of occlusion, and hence, contour grouping across occlusions is a major component of many natural visual tasks. To better understand the mechanisms of contour grouping across occlusions, we (a) measured the pair-wise statistics of edge elements from contours in natural images, as a function of edge element geometry and contrast polarity, (b) derived the ideal Bayesian observer for a contour occlusion task where the stimuli were extracted directly from natural images, and then (c) measured human performance in the same contour occlusion task. In addition to discovering new statistical properties of natural contours, we found that naïve human observers closely parallel ideal performance in our contour occlusion task. In fact, there was no region of the four-dimensional stimulus space (three geometry dimensions and one contrast dimension) where humans did not closely parallel the performance of the ideal observer (i.e., efficiency was approximately constant over the entire space). These results reject many other contour grouping hypotheses and strongly suggest that the neural mechanisms of contour grouping are tightly related to the statistical properties of contours in natural images.
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MUKHERJEE, DIPTI PRASAD, e NILANJAN RAY. "CONTOUR INTERPOLATION USING LEVEL-SET ANALYSIS". International Journal of Image and Graphics 12, n.º 01 (janeiro de 2012): 1250004. http://dx.doi.org/10.1142/s0219467812500040.
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We propose a novel approach to generate intermediate contours given a sequence of object contours. The proposal unifies shape features through contour curvature analysis and motion between the contours through optic flow analysis. The major contribution of this work is in integrating this shape and image intensity-based contour interpolation scheme in a level-set framework. The interpolated contours between an initial and a target contour act as missing link and establish a path along which contour deformation has taken place. We have shown that for different application domains such as 3D organ visualization (the generation of contours between two spatially apart contours of 2D slice images of a 3D organ), the meteorological applications of tracing, and the path of a developing cyclone (when satellite images are taken at distant time points and the shape of cyclone in between two consecutive satellite images are of interest), the proposal has outperformed the competing approaches.
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Machilsen, B., M. Demeyer e J. Wagemans. "Peripheral contour integration favors convex contours". Journal of Vision 13, n.º 9 (25 de julho de 2013): 725. http://dx.doi.org/10.1167/13.9.725.
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Wang, Bei, e Jin Guo He. "Contour Reconstruction Based on Non-Closed Contours". Applied Mechanics and Materials 220-223 (novembro de 2012): 2313–18. http://dx.doi.org/10.4028/www.scientific.net/amm.220-223.2313.
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There are a lot of developments focused on 3D surface reconstruction based on 2D contours in recent decades, mostly based on closed contours. Due to the limitation of imperfect technology on material classification and edge extraction, it’s difficult to extract closed contours automatically, and this situation limits the application of 3D surface reconstruction based on contour. This paper designs a reconstruction algorithm based on non-closed contour, which not only provides a new viewpoint for research on 3D reconstruction, but also make 3D reconstruction based on contour more applicable.
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Humphreys, Glyn W., e Andrew Olson. "Separating effects of orthographic similarity and contour summation in the identification of masked letter strings". Quarterly Journal of Experimental Psychology Section A 54, n.º 4 (novembro de 2001): 1203–19. http://dx.doi.org/10.1080/713756017.
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We separated effects of contour summation and orthographic similarity under masking conditions, by comparing identification with simultaneous and sequentially presented letter strings, which either did or did not overlap spatially. With overlapping simultaneous stimuli, performance was better for strings with similar contours than for strings with the same letters (the orthographic similarity condition). This suggests that contour summation effects were strongest in the condition where stimuli had similar contours. With sequential presentations, performance in the similar contour and the orthographically similar conditions was equated when the stimuli were overlapping. However, effects of contour summation decreased when prime and target letters were spatially displaced, whereas performance in the orthographically similar condition was maintained. We conclude that effects of orthographic similarity can be distinguished from effects of contour summation, under masking conditions.
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Zheng, Yi, Ling Zhang, Eric Guilbert e Yi Long. "An improved spatial contour tree constructed method". Proceedings of the ICA 1 (16 de maio de 2018): 1–6. http://dx.doi.org/10.5194/ica-proc-1-128-2018.
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Contours are important data to delineate the landform on a map. A contour tree provides an object-oriented description of landforms and can be used to enrich the topological information. The traditional contour tree is used to store topological relationships between contours in a hierarchical structure and allows for the identification of eminences and depressions as sets of nested contours. This research proposes an improved contour tree so-called spatial contour tree that contains not only the topological but also the geometric information. It can be regarded as a terrain skeleton in 3-dimention, and it is established based on the spatial nodes of contours which have the latitude, longitude and elevation information. The spatial contour tree is built by connecting spatial nodes from low to high elevation for a positive landform, and from high to low elevation for a negative landform to form a hierarchical structure. The connection between two spatial nodes can provide the real distance and direction as a Euclidean vector in 3-dimention. In this paper, the construction method is tested in the experiment, and the results are discussed. The proposed hierarchical structure is in 3-demintion and can show the skeleton inside a terrain. The structure, where all nodes have geo-information, can be used to distinguish different landforms and applied for contour generalization with consideration of geographic characteristics.
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Poom, Leo. "Visual Inter-Attribute Contour Completion". Perception 30, n.º 7 (julho de 2001): 855–65. http://dx.doi.org/10.1068/p3222.
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A new visual phenomenon, inter-attribute illusory (completed) contours, is demonstrated. Contour completions are perceived between any combination of spatially separate pairs of inducing elements (Kanizsa-like ‘pacman’ figures) defined either by pictorial cues (luminance contrast or offset gratings), temporal contrast (motion, second-order-motion or ‘phantom’ contours), or binocular-disparity contrast. In a first experiment, observers reported the perceived occurrence of contour completion for all pair combinations of inducing elements. In a second experiment they rated the perceived clarity of the completed contours. Both methods generated similar results—contour completions were perceived even though the inducing elements were defined by different attributes. Ratings of inter-attribute clarity were no lower than in either of the two corresponding intra-attribute conditions and seem to be the average of these two ratings. The results provide evidence for the existence of attribute-invariant Gestalt processes, and on a mechanistic level indicate that the completion process operates on attribute-invariant contour detectors.
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Kim, Jehyeok, Junyoung Moon, Jaewook Ryu e Giuk Lee. "Bioinspired Divide-and-Conquer Design Methodology for a Multifunctional Contour of a Curved Lever". Applied Sciences 11, n.º 13 (28 de junho de 2021): 6015. http://dx.doi.org/10.3390/app11136015.
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In this study, we propose a bioinspired design methodology for a multifunctional lever based on the morphological principle of the lever mechanism in the Salvia pratensis flower. The proposed divide-and-conquer contour design methodology does not treat a lever contour as a single curve that satisfies multiple functions. Rather, the lever contour combines partial contours to achieve its assigned subfunction. This approach can simplify the complex multifunctional problem in lever design. We include a case study of a lever utilized in a compact variable gravity compensator (CVGC) to explain the methodology in more detail. In the case study, four partial contours were designed to satisfy three types of functional requirements. The final design for the lever contour was manufactured and verified with visual measurement experiments. The experimental result shows that each partial contour successfully achieved its subfunctions.
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Garrigan, Patrick. "The Effect of Contour Closure on Shape Recognition". Perception 41, n.º 2 (1 de janeiro de 2012): 221–35. http://dx.doi.org/10.1068/p7145.
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Recent research on the Gestalt principle of closure has focused on how the presence of closure affects the ability to detect contours hidden in cluttered visual arrays. Some of the earliest research on closure, however, dealt with encoding and recognizing closed and open shapes, rather than detection. This research re-addresses the relation between closure and shape memory, focusing on how contour closure affects the ability to learn to recognize novel contour shapes. Of particular interest is whether closed contour shapes are easier to learn to recognize and, if so, whether this benefit is due to better encoding of closed contour shapes or easier comparison of closed contour shapes to already learned shapes. The results show that closed contours are indeed easier to recognize and, further, that this advantage appears to be related to better encoding.
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Liu, Guang Shuai, e Bai Lin Li. "Auto-Identification of Symmetrical Contours on ICT Image in Reverse Engineering". Applied Mechanics and Materials 401-403 (setembro de 2013): 1341–46. http://dx.doi.org/10.4028/www.scientific.net/amm.401-403.1341.
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Through considering the symmetry constraint characteristics in mechanical product contours, an auto-identification method of two-dimensional symmetrical contour based on feature matching is presented in this paper. Firstly, the feature points are extracted based on contour cloud point data partition and by using offset method, the different distribution rules of axis-symmetrical and rotation-symmetrical images for judging the type of symmetry was studied. The feature description parameters of symmetrical contour were calculated by adopting rotational inertia method and periodic method, which is regarded as the parameters for solving overall constraint optimization of the contour. Examples show that the proposed method can effectively identify the symmetrical contours and their types, and accurately extract the symmetrical constraint features.
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Fang, Li Yong, Hui Li e Jin Ping Bai. "Defect Contour Matching Based on Similarity Measure for 3D Reconstruction". Advanced Materials Research 308-310 (agosto de 2011): 1656–61. http://dx.doi.org/10.4028/www.scientific.net/amr.308-310.1656.
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Contour matching is one of the important problems concerned in 3-D reconstruction field. According to the difficulties of defect contour matching in defect modeling, a method based on similarity measure is presented in this paper. In this method, the theory of similarity measure is introduced to quantitatively describe the similarity of two contours. And the value of similarity measure is set as the criterion to judge matching relation between two contours in consecutive slices. For reducing computational complexity and improving accuracy of contours matching, a candidate matching field of contour is proposed. The efficiency of this algorithm has been verified by a typical example and satisfying results have been obtained.
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Göbel, Alexander. "Additives pitching in: L*+H signals ordered Focus alternatives". Semantics and Linguistic Theory 29 (9 de dezembro de 2019): 279. http://dx.doi.org/10.3765/salt.v29i0.4612.
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Approaches to the meaning of intonational meaning differ in associatingeach subcomponent with a meaning that remains invariant across contours (e.g.Pierrehumbert & Hirschberg 1990) or treating a contour as contributing its meaningholistically (e.g. Goodhue et al. 2015). This paper argues for a common core ofthe L*+H pitch accent across two intonation contours, the Rise-Fall-Rise (RFR,e.g. Ward & Hirschberg 1985), and a novel contour coined the Downscale-Contour(DSC). Both contours are analyzed as indicating the presence of an alternative withrespect to a scale derived from the QUD, but differ in the relative strength of thisalternative, with the DSC indicating a weaker and the RFR a stronger one.
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Zhu, Shufeng, Lena L. N. Wong, Bin Wang e Fei Chen. "Assessing the Importance of Lexical Tone Contour to Sentence Perception in Mandarin-Speaking Children With Normal Hearing". Journal of Speech, Language, and Hearing Research 60, n.º 7 (12 de julho de 2017): 2116–23. http://dx.doi.org/10.1044/2017_jslhr-h-16-0272.
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Purpose The aim of the present study was to evaluate the influence of lexical tone contour and age on sentence perception in quiet and in noise conditions in Mandarin-speaking children ages 7 to 11 years with normal hearing. Method Test materials were synthesized Mandarin sentences, each word with a manipulated lexical contour, that is, normal contour, flat contour, or a tone contour randomly selected from the four Mandarin lexical tone contours. A convenience sample of 75 Mandarin-speaking participants with normal hearing, ages 7, 9, and 11 years (25 participants in each age group), was selected. Participants were asked to repeat the synthesized speech in quiet and in speech spectrum–shaped noise at 0 dB signal-to-noise ratio. Results In quiet, sentence recognition by the 11-year-old children was similar to that of adults, and misrepresented lexical tone contours did not have a detrimental effect. However, the performance of children ages 9 and 7 years was significantly poorer. The performance of all three age groups, especially the younger children, declined significantly in noise. Conclusions The present research suggests that lexical tone contour plays an important role in Mandarin sentence recognition, and misrepresented tone contours result in greater difficulty in sentence recognition in younger children. These results imply that maturation and/or language use experience play a role in the processing of tone contours for Mandarin speech understanding, particularly in noise.
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Shalaby, Abouzeid M. "Isomorphic Hilbert spaces associated with different complex contours of the $\mathcal{PT}$-symmetric (-x4) theory". International Journal of Modern Physics A 29, n.º 11n12 (25 de abril de 2014): 1450059. http://dx.doi.org/10.1142/s0217751x14500596.
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In this work, we stress the existence of isomorphisms which map complex contours from the upper half to contours in the lower half of the complex plane. The metric operator is found to depend on the chosen contour but the maps connecting different contours are norm-preserving. To elucidate these features, we parametrized the contour [Formula: see text] considered in Phys. Rev. D 73, 085002 (2006) for the study of wrong sign x4 theory. For the parametrized contour of the form [Formula: see text], we found that there exists an equivalent Hermitian Hamiltonian provided that a2c is taken to be real. The equivalent Hamiltonian is b-independent but the metric operator is found to depend on all the parameters a, b and c. Different values of these parameters generate different metric operators which define different Hilbert spaces. All these Hilbert spaces are isomorphic to each other even for the parameter values that define contours with ends in two adjacent wedges. As an example, we showed that the transition amplitudes associated with the contour [Formula: see text] are exactly the same as those calculated using the contour [Formula: see text], which is not [Formula: see text]-symmetric and has ends in two adjacent wedges in the complex plane.
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Zhang, Li Guo, Mei Jin, Ju Jin e Guo Hui Yu. "Research of ASM Object Tracking Method Combining Kalman Estimation". Advanced Materials Research 1049-1050 (outubro de 2014): 1595–98. http://dx.doi.org/10.4028/www.scientific.net/amr.1049-1050.1595.
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ASM is a statistical model applied to match contours of non-rigid object. The actual contour may much different from the initial contour and the result is likely to converge to an error contour. Kalman filter is adopted to track the current frame for the prediction and acts as the initial state of the ASM, and then applies the ASM to correct the contour of the object. Experimental results show that the method proposed in this paper allows the model to converge to the target contour quickly and accurately. It has good stability and robustness.
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Wang, Jingxue, Dongdong Zang, Jinzheng Yu e Xiao Xie. "Extraction of Building Roof Contours from Airborne LiDAR Point Clouds Based on Multidirectional Bands". Remote Sensing 16, n.º 1 (2 de janeiro de 2024): 190. http://dx.doi.org/10.3390/rs16010190.
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Because of the complex structure and different shapes of building contours, the uneven density distribution of airborne LiDAR point clouds, and occlusion, existing building contour extraction algorithms are subject to such problems as poor robustness, difficulty with setting parameters, and low extraction efficiency. To solve these problems, a building contour extraction algorithm based on multidirectional bands was proposed in this study. Firstly, the point clouds were divided into bands with the same width in one direction, the points within each band were vertically projected on the central axis in the band, the two projection points with the farthest distance were determined, and their corresponding original points were regarded as the roof contour points; given that the contour points obtained based on single-direction bands were sparse and discontinuous, different banding directions were selected to repeat the above contour point marking process, and the contour points extracted from the different banding directions were integrated as the initial contour points. Then, the initial contour points were sorted and connected according to the principle of joining the nearest points in the forward direction, and the edges with lengths greater than a given threshold were recognized as long edges, which remained to be further densified. Finally, each long edge was densified by selecting the noninitial contour point closest to the midpoint of the long edge, and the densification process was repeated for the updated long edge. In the end, a building roof contour line with complete details and topological relationships was obtained. In this study, three point cloud datasets of representative building roofs were chosen for experiments. The results show that the proposed algorithm can extract high-quality outer contours from point clouds with various boundary structures, accompanied by strong robustness for point clouds differing in density and density change. Moreover, the proposed algorithm is characterized by easily setting parameters and high efficiency for extracting outer contours. Specific to the experimental data selected for this study, the PoLiS values in the outer contour extraction results were always smaller than 0.2 m, and the RAE values were smaller than 7%. Hence, the proposed algorithm can provide high-precision outer contour information on buildings for applications such as 3D building model reconstruction.
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Greene, Ernest, e Marja Verloop. "Anomalous and Luminance Contours Produce Similar Angular Induction Effects". Perception 23, n.º 2 (fevereiro de 1994): 147–56. http://dx.doi.org/10.1068/p230147.
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One can shear a pattern of lines to produce an anomalous contour which has a perceptual influence similar to that of a straight line segment. Illusion effects have been found with configurations which contain these anomalous contours, as well as cross adaptation with respect to luminance contours. We have found that sheared-line contours will bias judgment of collinearity, ie perceived alignment, of a luminance contour. The angular induction effects are similar to those reported for interactions between luminance contours, and the same equation can be used to model both kinds of data. The results of this experiment support the neuroreductionist view that anomalous and luminance contours are processed at the same level of the nervous system. Additionally, we suggest that with both types of contour the perceptual system registers and responds to the alignment of local brightness differentials.
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Xi, Chuan Li, Xiao Rong Chen e Yuan Cong. "Halcon-Based Optical Fiber Geometry Parameters Measurement Algorithm". Advanced Materials Research 805-806 (setembro de 2013): 1929–32. http://dx.doi.org/10.4028/www.scientific.net/amr.805-806.1929.
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This paper presents an algorithm to measure geometric parameters of optical fibers based on Halcon. The algorithm enhances the contrast of the fiber image and uses canny edge detection operator to extract the contours of fiber cross section. In order to remove noise in the contour, this paper studies new methods, include setting the contour length range, whether each contour is circular or not and whether the center of the circular contour and the center of the fiber core is consistent or not. These methods remove most of the noise. Finally, the effective contours are merged and then approximated by circle and ellipse. According to the mathematical model, all parameters required can be obtained. Experiment results show that the algorithm accuracy meet the needs.
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Tatashev, Alexander G., e Marina V. Yashina. "Spectrum of continuous two-contours system". ITM Web of Conferences 24 (2019): 01014. http://dx.doi.org/10.1051/itmconf/20192401014.
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A deterministic continuous dynamical system is considered. This system contains two contours. The length of theith contour equalsci,i= 1, 2. There is a moving segment (cluster) on each contour. The length of the cluster, located on theith contour, equalsli,i= 1, 2. If a cluster moves without delays, then the velocity of the cluster is equal to 1. There is a common point (node) of the contours. Clusters cannot cross the node simultaneously, and therefore delays of clusters occur. A set of repeating system states is called a spectral cycle. Spectral cycles and values of average velocities of clusters have been found. The system belongs to a class of contour systems. This class of dynamical systems has been introduced and studied by A.P. Buslaev.
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Wallentinsen, Kristen. "Fuzzy Family Ties". Journal of Music Theory 66, n.º 1 (1 de abril de 2022): 93–128. http://dx.doi.org/10.1215/00222909-9534151.
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Abstract Melodic contour is one of a melody's defining characteristics. Music theorists such as Michael Friedmann, Robert Morris, Elizabeth West Marvin and Paul Laprade, and Ian Quinn have developed models for evaluating similarities between contours, but only a few compare similarities between pairs of contours with different lengths, and fewer still can measure shared characteristics among an entire family of contours. This article introduces a new method for evaluating familial similarities between related contours, even if the contours have different cardinalities. The model extends theories of contour transformation by using fuzzy set theory and probability, measuring a contour's degree of familial membership by examining the contour's transformational pathway and calculating the probability that each move in the pathway is shared by other family members. Through the potential of differing alignments along these pathways, the model allows for the possibility that pathways may be omitted or inserted within a contour that exhibits familial resemblance, despite its different cardinality. The analytical utility of the model is then demonstrated through an analysis of melodic possibility in phased portions of Steve Reich's The Desert Music. Integrating variable cardinality into contour similarity relations in this way more adequately accounts for familial relationships between contours and can provide new and valuable insights into one of music's most fundamental elements.
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Faghih, Behnam, e Joseph Timoney. "Smart-Median: A New Real-Time Algorithm for Smoothing Singing Pitch Contours". Applied Sciences 12, n.º 14 (12 de julho de 2022): 7026. http://dx.doi.org/10.3390/app12147026.
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Pitch detection is usually one of the fundamental steps in audio signal processing. However, it is common for pitch detectors to estimate a portion of the fundamental frequencies incorrectly, especially in real-time environments and when applied to singing. Therefore, the estimated pitch contour usually has errors. To remove these errors, a contour smoother algorithm should be employed. However, because none of the current contour-smoother algorithms has been explicitly designed to be applied to contours generated from singing, they are often unsuitable for this purpose. Therefore, this article aims to introduce a new smoother algorithm that rectifies this. The proposed smoother algorithm is compared with 15 other smoother algorithms over approximately 2700 pitch contours. Four metrics were used for the comparison. According to all the metrics, the proposed algorithm could smooth the contours more accurately than other algorithms. A distinct conclusion is that smoother algorithms should be designed according to the contour type and the result’s final applications.
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Al-Tamimi, Mohammed Sabbih Hamoud. "Hybrid Methodology for Image Segmentation Based on Active Contour Module and Alpha-Shape Theory". Modern Applied Science 10, n.º 11 (16 de julho de 2016): 30. http://dx.doi.org/10.5539/mas.v10n11p30.
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The concept of the active contour model has been extensively utilized in the segmentation and analysis of images. This technology has been effectively employed in identifying the contours in object recognition, computer graphics and vision, biomedical processing of images that is normal images or medical images such as Magnetic Resonance Images (MRI), X-rays, plus Ultrasound imaging. Three colleagues, Kass, Witkin and Terzopoulos developed this energy, lessening “Active Contour Models” (equally identified as Snake) back in 1987. Being curved in nature, snakes are characterized in an image field and are capable of being set in motion by external and internal forces within image data and the curve itself in that order. The present study proposes the use of a hybrid image segmentation technique to acquire precise segmentation outcomes, while engaging “Alpha Shape (α-Shape)” in supposition to derive the original contour, followed by a refining process through engaging a conventional active contour model. Empirical results show high potential in the suggested computational method. Trials indicate that the primary contour is capable of being precisely set next to the objective contour and effectively have these objective contours extracted, devoid of any contour instigation. Some of the benefits associated with the novel hybrid contour include minimized cost of computation, enhanced anti-jamming capability, as well as enlarged utilization array of snake model.
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Liu, Guang Shuai, e Bai Lin Li. "Extraction of Optimal Contour Dominant Points Based on ICT Images in Reverse Engineering". Applied Mechanics and Materials 423-426 (setembro de 2013): 2570–75. http://dx.doi.org/10.4028/www.scientific.net/amm.423-426.2570.
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How to effectively extract contour dominant points is one of key problems in process of industrial CT image, second extraction method was put forward. Second extraction method included two steps: rough extraction and accurate extraction. Firstly, discrete circular curvatures of contour points are calculated. Secondly, through rough extraction step, bad points and points which arent correlated with contour features were removed. At last, through accurate extraction step, contour dominant points were extracted by levels of detail. Experimental results show that contour dominant points can describe contours shape and redundant data are removed, the proposed method is simple and efficient.
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Yang, Yuhan, Shoujun Zhou, Peng Shang, En Qi, Shibin Wu e Yaoqin Xie. "Contour Propagation Using Feature-Based Deformable Registration for Lung Cancer". BioMed Research International 2013 (2013): 1–8. http://dx.doi.org/10.1155/2013/701514.
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Accurate target delineation of CT image is a critical step in radiotherapy treatment planning. This paper describes a novel strategy for automatic contour propagation, based on deformable registration, for CT images of lung cancer. The proposed strategy starts with a manual-delineated contour in one slice of a 3D CT image. By means of feature-based deformable registration, the initial contour in other slices of the image can be propagated automatically, and then refined by active contour approach. Three algorithms are employed in the strategy: the Speeded-Up Robust Features (SURF), Thin-Plate Spline (TPS), and an adapted active contour (Snake), used to refine and modify the initial contours. Five pulmonary cancer cases with about 400 slices and 1000 contours have been used to verify the proposed strategy. Experiments demonstrate that the proposed strategy can improve the segmentation performance in the pulmonary CT images. Jaccard similarity (JS) mean is about 0.88 and the maximum of Hausdorff distance (HD) is about 90%. In addition, delineation time has been considerably reduced. The proposed feature-based deformable registration method in the automatic contour propagation improves the delineation efficiency significantly.
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Shipley, Thomas F., e Philip J. Kellman. "Boundary Completion in Illusory Contours: Interpolation or Extrapolation?" Perception 32, n.º 8 (agosto de 2003): 985–99. http://dx.doi.org/10.1068/p3420.
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Most computational and neural-style models of contour completion (ie illusory and occluded contours) are based on interpolation: the filling in of an edge between two visible edges. The results of three experiments suggest an alternative conception, that units are formed as a result of extrapolation from visible edges. In three experiments, subjects reported illusory contours between standard illusory-contour inducing elements and forms that do not, by themselves, induce illusory contours. We suggest that these forms are not a special case of inducing elements but that they represent a different class— receiving elements. Receiving elements are forms that can receive an illusory contour but cannot generate one, and they can alter contour formation. In experiment 1, receiving elements increased the judged clarity of illusory contours. In experiment 2, illusory edges were seen to connect to corners, line ends, and even the edges of circles. Boundary formation in motion displays also appears to be based on extrapolation. In experiment 3, subjects reported that small moving dots altered the formation of spatiotemporally defined boundaries. Implications for higher-order operator and network models of boundary formation are discussed.
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Anderson, Barton L. "A Theory of Illusory Lightness and Transparency in Monocular and Binocular Images: The Role of Contour Junctions". Perception 26, n.º 4 (abril de 1997): 419–53. http://dx.doi.org/10.1068/p260419.
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A theory of illusory transparency and lightness is described for monocular and binocular images containing X-, T- and I-contour junctions. This theory asserts that the geometric and luminance relationships of contour junctions induce illusory transparency and lightness percepts by causing a phenomenal scission of a homogenous luminance into multiple contributions. Specifically, it is argued that a discontinuous change in contrast along aligned contours that preserve contrast polarity induces a scission of the lower contrast region into a near-transparent surface or an illumination change, and a more distant surface that continues behind this near layer. This scission is assumed to cause changes in perceived lightness and/or surface opacity. Discontinuous changes in contrast along contours also are assumed to induce end-cut illusory contours that run roughly perpendicular to the inducing orientation of the contour, both monocularly and binocularly. Binocular illusory contours are shown to be caused by the presence of unmatchable contour terminators. It is argued that the presented theory can provide a unified account of a variety of monocular and binocular illusions that induce uniform transformations in perceived lightness, including neon-color spreading, the Munker – White illusion, Benary's illusion, and illusory monocular and binocular transparency.
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Zhang, Tao, Yibo Ai e Weidong Zhang. "Hierarchical Tensor Decomposition of Module Partition for the Mechanical Simulation". Applied Sciences 13, n.º 4 (19 de fevereiro de 2023): 2684. http://dx.doi.org/10.3390/app13042684.
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The mechanical simulation experiment can provide guidelines for the structural design of materials, but the module partition of mechanical simulation experiments is still in its infancy. A mechanical simulation contour, e.g., strain and stress contour, has hierarchical characteristics. By analyzing the contour at different layers, the physical properties of the structure material can be improved. Current state-of-the-art methods cannot distinguish between simulation strain contours, as well as sparsely distributed spots of strain (stress concentrations) from simulation strain contour images, resulting in simulation data that does not accurately reflect real strain contours. In this paper, a Hierarchical Tensor Decomposition (HTD) method is proposed to extract hierarchical contours and stress concentrations from the simulation strain contours and then improve the mechanical simulation. HTD decomposes a tensor into three classes of components: the multi-smooth layers, the sparse spots layer, and the noise layer. The number of multismooth layers is determined by the scree plot, which is the difference between the smooth layers and the sparse spots layer. The proposed method is validated by several numerical examples, which demonstrate its effectiveness and efficiency. A further benefit of the module partition is the improvement of the mechanical structural properties.
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Wu, Yi-Cheng Daniel. "An Extension of the Minimally Divergent Contour Network: Considering Nonconsecutive Repeated Contour Pitches". Music Theory Spectrum 41, n.º 2 (2019): 341–62. http://dx.doi.org/10.1093/mts/mtz012.
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Abstract In a 2013 article, I partitioned all musical contours into fifteen types and arranged them in a network called the minimally divergent contour network (MDCN). Within the MDCN, we can examine the similarity between any two contour types by measuring the shortest path between them. However, despite the methodological efficiency, none of the fifteen types considers nonconsecutive repeated contour pitches. Prompted by this issue, this article extends the MDCN to include nonconsecutive repeated contour pitches. To demonstrate the analytic utility of the extended MDCN, I examine works by Bright Sheng and György Kurtág.
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Henderson, John M. "Transsaccadic Memory and Integration During Real-World Object Perception". Psychological Science 8, n.º 1 (janeiro de 1997): 51–55. http://dx.doi.org/10.1111/j.1467-9280.1997.tb00543.x.
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What is the nature of the information that is preserved and combined across saccadic eye movements during the visual analysis of real-world objects? The two experiments reported investigated transsaccadic memory and transsaccadic integration, respectively In the critical condition, participants were presented with one set of contours from an object during one fixation and with a complementary set of contours during the next fixation In Experiment 1, participants could at best inconsistently detect contour changes across the saccade In Experiment 2, a change in visible contour had no influence on object identification These results suggest that a veridical representation of object contour is neither consistently preserved nor integrated across a saccade
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Shkurat, Oksana. "SMOOTHED CONTOUR DETECTION METHOD FOR ARBITRARY SHAPE OBJECT OF IMAGES". Grail of Science, n.º 14-15 (10 de junho de 2022): 351–55. http://dx.doi.org/10.36074/grail-of-science.27.05.2022.062.
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Description of initial raster image objects by a set of contour vertices coordinates leads to increase efficiency of the retrieval, classification and recognition of graphical data in information systems. In this paper the smoothed contour detection method for objects of raster images is considered. The developed method is based on application of interpolation function for partial differential equation solutions and smoothed function for post-processing of detected contours. The accuracy of contour reproduction for raster image objects is increased on 4.87% by applying the developed method compared to the discrete method of contour detection.
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McDermott, Josh H., Andriana J. Lehr e Andrew J. Oxenham. "Is Relative Pitch Specific to Pitch?" Psychological Science 19, n.º 12 (dezembro de 2008): 1263–71. http://dx.doi.org/10.1111/j.1467-9280.2008.02235.x.
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Melodies, speech, and other stimuli that vary in pitch are processed largely in terms of the relative pitch differences between sounds. Relative representations permit recognition of pitch patterns despite variations in overall pitch level between instruments or speakers. A key component of relative pitch is the sequence of pitch increases and decreases from note to note, known as the melodic contour. Here we report that contour representations are also produced by patterns in loudness and brightness (an aspect of timbre). The representations of contours in different dimensions evidently have much in common, as contours in one dimension can be readily recognized in other dimensions. Moreover, contours in loudness and brightness are nearly as useful as pitch contours for recognizing familiar melodies that are normally conveyed via pitch. Our results indicate that relative representations via contour extraction are a general feature of the auditory system, and may have a common central locus.
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Wang, Quande, e Bugao Xu. "A coupled-contour model for effective segmentation of cotton cross-sections in wide-field microscopic images". Textile Research Journal 87, n.º 12 (24 de junho de 2016): 1509–21. http://dx.doi.org/10.1177/0040517516654113.
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Image analysis of a fiber cross-section can provide direct measurements for cotton maturity. Effective segmentation of fiber contours in a cross-sectional image is paramount for accurate fiber geometrical measurements. In a wide-field microscopic image, the adhesion, breakage, and ambiguity (low contrast or noise) of fiber contours make the segmentation rather challenging. This paper presents a new approach for contour segmentation that takes advantage of the shape features of the triple concentric contours, called the coupled-contour model (CCM), of a cross-section, and a CCM-based algorithm developed to locate, split, merge, and refine fiber contours based on the established rules concerning contour features. For a wide-field microscopic image (12 megapixels), this CCM-based algorithm could detect >500 fiber cross-sections with a recall rate of 93.53% and a precision rate of 98.13%, and reduced the errors in maturity measurements by 50%.
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Cheng, Xiaoqi, Junhua Sun e Fuqiang Zhou. "A Fully Convolutional Network-Based Tube Contour Detection Method Using Multi-Exposure Images". Sensors 21, n.º 12 (14 de junho de 2021): 4095. http://dx.doi.org/10.3390/s21124095.
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The tube contours in two-dimensional images are important cues for optical three-dimensional reconstruction. Aiming at the practical problems encountered in the application of tube contour detection under complex background, a fully convolutional network (FCN)-based tube contour detection method is proposed. Multi-exposure (ME) images are captured as the input of FCN in order to get information of tube contours in different dynamic ranges, and the U-Net type architecture is adopted by the FCN to achieve pixel-level dense classification. In addition, we propose a new loss function that can help eliminate the adverse effects caused by the positional deviation and jagged morphology of tube contour labels. Finally, we introduce a new dataset called multi-exposure tube contour dataset (METCD) and a new evaluation metric called dilate inaccuracy at optimal dataset scale (DIA-ODS) to reach an overall evaluation of our proposed method. The experimental results show that the proposed method can effectively improve the integrity and accuracy of tube contour detection in complex scenes.
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Liu, Guoqi, e Haifeng Li. "Robust Evolution Method of Active Contour Models and Application in Segmentation of Image Sequence". Journal of Electrical and Computer Engineering 2018 (2018): 1–11. http://dx.doi.org/10.1155/2018/3493070.
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Active contour models are widely used in image segmentation. In order to obtain ideal object boundary, researchers utilize various information to define new models for image segmentation. However, the models could not meet all scenes of image. In this paper, we propose a block evolution method to improve the robustness of contour evolution. A block matrix is consisted of contours of former iterations and contours of shape prior, and a nuclear norm of the matrix is a measure of the similarity of these shapes. The constraint of the nuclear norm minimization is imposed on the evolution of active contour models, which could avoid large deformation of the adjacent curves and keep the shape conformability of contour in the evolution. The shape prior can be integrated into the block evolution method, which is effective in dealing with missing features of images and noise. The proposed method can be applied to image sequence segmentation. Experiments demonstrate that the proposed method improves the robust performance of active contour models and can increase the flexibility of applications in image sequence segmentation.
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Alsamman, A., e M. Syed. "RGB-BASED DEEP SURFACE WATER CONTOUR DETECTION". International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLIII-B3-2022 (30 de maio de 2022): 827–32. http://dx.doi.org/10.5194/isprs-archives-xliii-b3-2022-827-2022.
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Abstract. The application of remote monitoring of surface water has focused primarily on the detection of water bodies using expensive multi-spectral IR sensors. However, critical information about surface water bodies, particularly the dynamic behavior, is better derived from water contours. We show that water body detection is inadequate in accurately capturing the contours. Furthermore, we argue that RGB-based detection should be sufficient for accurate water detection. We present a new global dataset of remote sensing images obtained from Sentinel-2 and Landsat-8 missions and contour labeled to assist in this effort. We propose a unique UNet-style contour detection system that utilizes multiscale filters to detect contours accurately. Comparisons between our proposed system, existing water detection, and other segmentation and contour detection systems show the system's effectiveness in detecting water.
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Sumi, Shigemasa. "Kinetic Contours in Rotating Objects". Perception 18, n.º 3 (junho de 1989): 293–302. http://dx.doi.org/10.1068/p180293.
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Kinetic contours seen in rotating objects provide evidence about contour function in a kinetic condition. It was observed that (i) when an object with an arc-shaped edge in its outline is rotated, a kinetic contour arises from the rotating arc and bounds a ‘figure’; (ii) the kinetic contour not only protects the enclosed area of this figure from the destruction caused by motion, but also interrupts the continuity of the surroundings; (iii) kinetic contours are generally perceived to be organized into discs which appear as amodally completed forms in such a way that one object is hidden behind the other. The fact that oval or outline figures rarely produce kinetic contours is assumed to be due to figural self-sufficiency, which does not require perceptual completion through motion.
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Jiang, Ying, Jun Hong e Wei Wang. "Contour Features Based Comfort Evaluation Criterion on School Chair Surface". Applied Mechanics and Materials 34-35 (outubro de 2010): 1217–22. http://dx.doi.org/10.4028/www.scientific.net/amm.34-35.1217.
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The purpose of this paper is to establish a criterion for the school chair surface evaluation through analyzing the rules between contour features and the comfort base on experiments. In the paper, 5 basic contour feature parameters, which are buttocks plunging depth, thigh plunging depth, buttocks contour width, buttocks contour deep and thighs contour width, are proposed. Maximum peak stress (Pm) and contact area (S) are adopted as comfort indices. The participants are 50 Chinese high school students (29 boys, 21 girls) who grouped by body size. Through carrying out the experiments of body pressure distribution at different seat contours, all participants require expressing their feeling about sitting, the effect rules of the basic contour feature parameters on seated comfort are obtained. The results shows the different value of buttocks contour deep and thighs contour width leads to varying optimal comfort points corresponding to different somatotype people. According to BP neural network, a prediction model is established. Finally a kind of school chair surface evaluation criterion based on contour is put forward.
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Shen, J., W. L. Han, J. Ge, L. B. Zhang e H. Tan. "DIGITAL ELEVATION MODEL INTERPOLATION BY FUSION OF MORPHOLOGICAL RECONSTRUCTION AND DISTANCE TRANSFORMATION". ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-2/W7 (13 de setembro de 2017): 881–85. http://dx.doi.org/10.5194/isprs-archives-xlii-2-w7-881-2017.
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Interpolation methods have significant impacts on the accuracy of the digital elevation model (DEM) from contours which are one of frequently employed data sources. In this paper, an interpolation method is presented to build DEM from contour lines by fusion/integration of morphological reconstruction and distance transformation with obstacles. Particularly, morphological reconstruction is used to get the elevation values of the higher contour lines and the lower contour lines of any a spatial point between two contour lines, and distance transformation with obstacles is used to get the geodesic distances of the spatial point to the higher contour lines and the lower contour lines respectively. At last, linear interpolation along water flow line is used to get the elevation values of the pixels to be interpolated. The experiment demonstrates that feasibility of our proposed method.
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Chen chen e Daohui Bi. "A Motion Image Pose Contour Extraction Method Based on B-Spline Wavelet". International Journal of Antennas and Propagation 2021 (26 de outubro de 2021): 1–8. http://dx.doi.org/10.1155/2021/4553143.
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In order to improve the accuracy of traditional motion image pose contour extraction and shorten the extraction time, a motion image pose contour extraction method based on B-spline wavelet is proposed. Moving images are acquired through the visual system, the information fusion process is used to perform statistical analysis on the images containing motion information, the location of the motion area is determined, convolutional neural network technology is used to preprocess the initial motion image pose contour, and B-spline wavelet theory is used. The preprocessed motion image pose contour is detected, combined with the heuristic search method to obtain the pose contour points, and the motion image pose contour extraction is completed. The simulation results show that the proposed method has higher accuracy and shorter extraction time in extracting motion image pose contours.
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Eckert, Aubrey, Nevin Martin, Ryan G. Coe, Bibiana Seng, Zacharia Stuart e Zachary Morrell. "Development of a Comparison Framework for Evaluating Environmental Contours of Extreme Sea States". Journal of Marine Science and Engineering 9, n.º 1 (25 de dezembro de 2020): 16. http://dx.doi.org/10.3390/jmse9010016.
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Environmental contours of extreme sea states are often utilized for the purposes of reliability-based offshore design. Many methods have been proposed to estimate environmental contours of extreme sea states, including, but not limited to, the traditional inverse first-order reliability method (I-FORM) and subsequent modifications, copula methods, and Monte Carlo methods. These methods differ in terms of both the methodology selected for defining the joint distribution of sea state parameters and in the method used to construct the environmental contour from the joint distribution. It is often difficult to compare the results of proposed methods to determine which method should be used for a particular application or geographical region. The comparison of the predictions from various contour methods at a single site and across many sites is important to making environmental contours of extreme sea states useful in practice. The goal of this paper is to develop a comparison framework for evaluating methods for developing environmental contours of extreme sea states. This paper develops generalized metrics for comparing the performance of contour methods to one another across a collection of study sites, and applies these metrics and methods to develop conclusions about trends in the wave resource across geographic locations, as demonstrated for a pilot dataset. These proposed metrics and methods are intended to judge the environmental contours themselves relative to other contour methods, and are thus agnostic to a specific device, structure, or field of application. The metrics developed and applied in this paper include measures of predictive accuracy, physical validity, and aggregated temporal performance that can be used to both assess contour methods and provide recommendations for the use of certain methods in various geographical regions. The application and aggregation of the metrics proposed in this paper outline a comparison framework for environmental contour methods that can be applied to support design analysis workflows for offshore structures. This comparison framework could be extended in future work to include additional metrics of interest, potentially including those to address issues pertinent to a specific application area or analysis discipline, such as metrics related to structural response across contour methods or additional physics-based metrics based on wave dynamics.
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Li, Chengming, Xiaoli Liu, Wei Wu e Zhiwei Hao. "A Reconstruction Method for Broken Contour Lines Based on Similar Contours". ISPRS International Journal of Geo-Information 8, n.º 1 (26 de dezembro de 2018): 8. http://dx.doi.org/10.3390/ijgi8010008.
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The reconstruction of a broken contour line is a prerequisite for the automated processing of contour lines. When the situation with broken contour lines is severe or the terrain is more complex, incorrect and missing connections are most likely to occur using traditional methods. In this paper, a reconstruction method for broken contour lines based on similar and completely closed contours is proposed. First, node densification is conducted on broken contour lines to improve the identification accuracy of the reference line. Second, the discrete Fréchet distance is used to select a reference line and perform reconstruction. Finally, the actual data of Yunnan Province are utilized for verification. The results show that the method proposed in this paper can achieve better reconstruction of broken contour lines, especially for severe broken contour situations or complex terrains; the reconstruction accuracy is significantly improved over that of the traditional method, indicating good feasibility.