Rough Correspondence Research Articles

Investigating the vertical distribution of the disk as a function of radial action: Results from simulations

Previous research has established a relationship between radial action and scale height in Galactic disks, unveiling a correlation between radial and vertical heating. This finding poses a challenge to our existing comprehension of heating theories and consequently encodes crucial insights into the formation and heating history of Galactic disks. In this study, we perform N-body simulations with the aim of verifying the existence of this correlation between radial action and scale height, thereby enhancing our comprehension of the heating history of Galactic disks. We conducted a simulation featuring a disk embedded within a static dark matter halo potential, and systematically analyzed the correlation between radial action and scale height across every snapshot. Furthermore, we augmented this simulation by incorporating massive, long-lasting particles to examine their impact on the aforementioned relationship. We find that the relationship between radial action and scale height in our simulations can be described by the same functional form observed in previous work. Furthermore, the relationships derived from our simulations align well with those of the Galactic thin disk. However, they do not coincide with the inner thick disk but exhibit a rough correspondence with the outer thick disk, suggesting the possibility that additional heating mechanisms may be required to explain the inner thick disk. We also find that the mean radial action and scale height undergo rapid increases during the initial stages of the simulation, yet remain relatively unchanged as the disk evolves further. By tracing example particles, we uncover a correlation between radial and vertical heating in our simulation: as a particle in the disk gains or loses radial action, its vertical motion tends to oscillate on a more or less extended orbit, accompanied by a tendency to migrate outward or inward, respectively. The massive, long-lasting particles in our simulation contribute to disk heating by solely enhancing the rate of increase in scale height with radial action, while maintaining the functional form that describes the relationship between these two variables. We have successfully replicated the functional form previously reported in research, thereby confirming a correlation between radial and vertical heating. This achievement enhances our understanding of heating theories in galactic disks.

Effects of structural zonation on fluids circulation of the Copahue geothermal system

The volcano-hosted geothermal system of Copahue is one of the most promising resources of renewable energy in Argentina. The associated geothermal field is bounded by a set of N60° trending normal faults to the north and by WNW-ESE trending faults to the south. This paper aims to review this first-order distribution of the structures, using previously published b-value data, and to explore the relationship between the local stress field, the superficial structural setting, the magmatic source, and the geothermal fluid flow paths related to the volcanic complex. The 2D dilation tendencies of the geomorphic lineaments is calculated, defining a structural domain with dilatant lineaments that agrees well with high b-values observed at shallow depths(2 km below the surface), and with the known extension of the geothermal field. A rough spatial correspondence is also observed between domains of unfavorable oriented to dilate lineaments and shallow low b-value areas, suggesting that these discontinuities inhibit the horizontal motion of fluids at the same structural level, and constraining the reservoir both to the northwest and to the southeast. b-value data unravels the potential magmatic plumbing system at depth, highlighting a major NW-elongated high b-value body centered at 5 km below surface, from Chancho-có hill towards the south of Maquinas fumaroles. It is coincident at surface with a high density of lineament intersections domain, which creates in depth an intense structural damage zone that may facilitate the ascent of magmatic fluids. The NW anomaly can be extrapolated to the western margin of the Caviahue lake, agreeing with the occurrence of volcano-tectonic seismic events and elevated heat flows reported in this area, and therefore suggesting the presence of the geothermal reservoir at depth. Vertical appendices branching from the b-value anomaly reach up to 3 km below Termas and Maquinitas fumaroles, outlining the possible bottom of the geothermal reservoir. The shallower one is interpreted as a blob of magma injected below the Copahue Village fault system, providing the main heat source. These findings contribute to the current understanding of the geothermal reservoir, its depth coverage and upflow zones, providing insights for future geophysical exploration stages.

Narrowband Spikes Observed During the 13 June 2012 Flare in the 800 – 2000 MHz Range

Narrowband (∼5 MHz) and short-lived (∼0.01 s) spikes with three different distributions in the 800 – 2000 MHz radio spectrum of the 13 June 2012 flare are detected and analyzed. We designate them as SB (spikes distributed in a broad band or bands), SZ (spikes distributed in zebra-like bands) and SBN (spikes distributed in broad and narrow bands). On analyzing AIA/SDO images of the active region NOAA 11504, a rough correspondence between groups of the spikes observed at 1000 MHz and peaks in the time profiles of AIA channels taken from the flare subarea close to the leading sunspot is found. Among the types of spikes the SZ type is the most interesting because it resembles zebras. Therefore, using autocorrelation and crosscorrelation methods we compare SZ and SBN spikes with the typical zebra observed in the same frequency range. While the ratio of SZ band frequencies with their frequency separation (220 MHz) is about 4, 5, and 6, in the zebra the frequency stripe separation is about 24 MHz and the ratio is around 50. Moreover, the bandwidth of SZ bands, which consists of clouds of narrowband spikes, is much broader than that of zebra stripes. This comparison indicates that SZ spikes are generated in a different way from the zebra, but in a similar way to SBN spikes. We successfully fit the SZ band frequencies by the Bernstein modes. Based on this fitting we interpret SZ and SBN spikes as those generated in the model of Bernstein modes. Thus, the magnetic field and plasma density in the SZ spike source are estimated to be about 79 G and 8.4 × 109 cm−3, respectively.

Magnon interactions in the frustrated pyrochlore ferromagnet Yb2Ti2O7

The frustrated rare-earth pyrochlore Yb$_2$Ti$_2$O$_7$ is remarkable among magnetic materials: despite a ferromagnetically ordered ground state it exhibits a broad, nearly gapless, continuum of excitations. This broad continuum connects smoothly to the sharp one-magnon excitations expected, and indeed observed, at high magnetic fields, raising the question: how does this picture of sharp magnons break down as the field is lowered? In this paper, we consider the effects of magnon interactions in Yb$_2$Ti$_2$O$_7$, showing that their inclusion greatly extends the reach of spin-wave theory. First, we show that magnon interactions shift the phase boundary between the (splayed) ferromagnet (SFM) and the antiferromagnetic $\Gamma_5$ phase so that Yb$_2$Ti$_2$O$_7$ lies very close to it. Next, we show how the high-field limit connects to lower fields; this includes corrections to the critical fields for the $[111]$ and $[1\bar{1}0]$ directions, bringing them closer to the observed experimental values, as well as accounting for the departures from linear spin wave theory that appear in $[001]$ applied fields below 3 T [Thompson et al., Phys. Rev. Lett. 119, 057203 (2017)]. Turning to low-fields, though the extent of the experimentally observed broadening is not quite reproduced, we find a rough correspondence between non-linear spin-wave theory and inelastic neutron scattering data on both a single-crystal sample, as well as on a powder sample [Pe\c{c}anha-Antonio et al., Phys. Rev. B, 96, 214415 (2017)]. We conclude with an outlook on implications for future experimental and theoretical work on Yb$_2$Ti$_2$O$_7$ and related materials, highlighting the importance of proximity to the splayed ferromagnet-$\Gamma_5$ phase boundary and its potential role in intrinsic or extrinsic explanations of the low-field physics of Yb$_2$Ti$_2$O$_7$.

Diffusion-based isometric depth correspondence

We propose an iterative isometric point correspondence method that relies on diffusion distance to handle challenges posed by commodity depth sensors which usually provide incomplete and noisy surface data exhibiting holes and gaps. We formulate the correspondence problem as finding an optimal partial mapping between two given point sets, that minimizes deviation from isometry. Our algorithm starts with an initial rough correspondence between keypoints, obtained via any point matching technique. This initial correspondence is then pruned and updated by iterating a perfect matching algorithm until convergence in order to find as many reliable correspondences as possible. The resulting set of sparse but reliable correspondences then serves as a base matching from which a dense correspondence set is estimated. We additionally provide a global intrinsic symmetry detection technique which clusters a point cloud into its symmetric sides. We incorporate this technique into our point-based correspondence method so as to address the symmetrical flip problem and to further improve the reliability of our matching results. Our symmetry-aware correspondence method is especially effective on human shapes with global reflectional symmetry. We hence conduct experiments on datasets comprising human shapes and show that our method provides state of the art performance over depth frames exhibiting occlusions, large deformations, and topological noise.

Crustal thickness and lithospheric thermal state beneath the Junggar Basin and adjacent Mountain Ranges, northwest China

In this paper, data of gravimetry, aeromagnetic survey, and surface heat flow are utilized in a combined manner to investigate the crustal thickness, Curie surface, and lithospheric thermal state beneath the Junggar Basin and adjacent Mountain Ranges. The Moho depth, Curie depth, and thermal lithospheric thickness are found to be 38–52 km, 32–50 km, and 120–260 km, respectively. The Moho and Curie surface present a rough inverse correspondence between each other. In the Tianshan and Altai Mountain Ranges, Moho interface is deep but Curie surface is shallow. In the Junggar Basin, Turpan Basin, and Yili Basin, the situation is in reverse. The uppermost mantle in the Central Depression and Eastern Uplift of the Junggar Basin, the Turpan Basin, the Yili Basin, as well as the north-west area off Fuhai is investigated to have been magnetized. The aeromagnetic anomalies and the Curie surface in the Junggar Basin surprisingly reveal that the northward subduction of the north Tarim block/slab under the Junggar Basin accompanied by the uplift of the Tianshan Mountain Range. Also, in response to the northward movement, the rigid Central Depression of the Junggar Basin extruded from its east and west sides. The westward extrusion is manifested by the West Uplift of the western Junggar Mountain Range.

Modality-Invariant Image-Text Embedding for Image-Sentence Matching

Performing direct matching among different modalities (like image and text) can benefit many tasks in computer vision, multimedia, information retrieval, and information fusion. Most of existing works focus on class-level image-text matching, called cross-modal retrieval , which attempts to propose a uniform model for matching images with all types of texts, for example, tags, sentences, and articles (long texts). Although cross-model retrieval alleviates the heterogeneous gap among visual and textual information, it can provide only a rough correspondence between two modalities. In this article, we propose a more precise image-text embedding method, image-sentence matching, which can provide heterogeneous matching in the instance level. The key issue for image-text embedding is how to make the distributions of the two modalities consistent in the embedding space. To address this problem, some previous works on the cross-model retrieval task have attempted to pull close their distributions by employing adversarial learning. However, the effectiveness of adversarial learning on image-sentence matching has not been proved and there is still not an effective method. Inspired by previous works, we propose to learn a modality-invariant image-text embedding for image-sentence matching by involving adversarial learning. On top of the triplet loss--based baseline, we design a modality classification network with an adversarial loss, which classifies an embedding into either the image or text modality. In addition, the multi-stage training procedure is carefully designed so that the proposed network not only imposes the image-text similarity constraints by ground-truth labels, but also enforces the image and text embedding distributions to be similar by adversarial learning. Experiments on two public datasets (Flickr30k and MSCOCO) demonstrate that our method yields stable accuracy improvement over the baseline model and that our results compare favorably to the state-of-the-art methods.

Using Expectation-Maximization for exposing image forgeries by revealing inconsistencies in shadow geometry

In this study, a new approach and mathematical framework are proposed for exposing image forgeries by detecting inconsistencies in the geometry of cast shadows. The main difficulty in detecting shadow inconsistencies is the precise establishment of correspondences between object points and their corresponding shadow points. To counter the problem, a mathematical framework is proposed to formulate the geometric transformation between the object points and their corresponding shadow points. We assume a rough correspondence between the object and shadow points and use Expectation-Maximization (EM) algorithm to simultaneously calculate the transformation parameters and categorize rough correspondences as inliers or outliers. To enhance the efficiency of the proposed algorithm, we extend the proposed algorithm to handle the ambiguity in initial correspondence by using the one-to-many correspondence strategy. Experimental results on the provided database comprising forged and authentic images showed the accuracy of 84% and 98% for one-to-one and one-to-many correspondence strategies, respectively.

In Communion with God’s Sparrow: Incorporating Animal Agency into the Environmental Vision of Laudato Sí

Although a conventional environmentalism focuses on the health of ecological systems, Pope Francis’s 2015 environmental encyclical Laudato Si invokes St. Francis of Assisi to emphasize God’s love for the individual organism, no matter how small. Decrying the tendency to regard other creatures as mere objects to be controlled and used, Pope Francis urges our enactment of a ‘universal communion’ governed by love. I suggest, however, that Laudato Si’s animal ethic, as focused on ordering human and animal need, is inadequate to its overarching vision of cross-species communion. This vision requires the sort of cross-species relational bridge implicit in Maurice Merleau-Ponty’s view of agency as an irreducibly ‘animate’ expression of choice and afforded further definition in Kenneth J. Shapiro’s conception of a ‘kinesthetic empathy.’ As the phenomenological epistemology underlying both discourses makes possible a rough correspondence, I put these in conversation to demonstrate that a Merleau-Pontyan and reciprocal agency is a constitutive aspect of the fullest sort of cross-species relation, such that recognition of this agency can both deepen our understanding of ‘universal communion’ and foster engagement in its practice.

Introduction to Special Issue: African Artistic Practices and New Media: Intersections, Volatilities, Futures—Issue II

Introduction to Special Issue: African Artistic Practices and New Media: Intersections, Volatilities, Futures—Issue II Akin Adesokan The articles in the following pages constitute the second of the two special issues of Africa Today based on the interdisciplinary symposium held at the Indiana University European Gateway in Berlin, Germany, in June 2017. Since all the papers were presented together at the two-day symposium, there are no major conceptual differences between these articles and those published in the first special issue (Africa Today 64[4], Summer 2018). Rather, the symposium’s central concern with the intersections of various media, locations, and practices receives a catalyzing emphasis in the five articles published here, especially in relation to the volatilities of form, disciplinary knowledge, and institutions. Vincent Bouchard, in “Audiovisual Production in West Africa,” shows how digital shifts in production affect aspects of the cinematographic medium that were once viewed in specifically technical ways. From the artifacts of audiovisual broadcasting to the aesthetic expectations of audiences, important changes occur that necessitate what Bouchard characterizes as “the integration of new technical and aesthetic forms” with the language suited to the canon of film studies. In West Africa, this shift to the digital presents opportunities as well as challenges. Analyzing recent Francophone West African productions, Bouchard questions the aesthetic criteria applied to African cinema. He explores these new aesthetic paths and details how the aesthetic evolution presents challenges for African film studies in general and, more specifically, for audiovisual institutions in West Africa. Ivo Ritzer reframes African cinema along the lines of a philosophy of relationality in his contribution, “The Relational Politics of Media Culture in the Age of Post–Third Cinema.” His approach aligns questions of aesthetics with questions of politics. He eschews Third Cinema’s protocol of didactism and realism and posits Post–Third Cinema as an aesthetics of sensible intensities, moving toward a universal understanding of cinematographic art in the age of global media culture. Although he does not prioritize a digital shift as such, his analysis of “global media culture” draws on changes that occur [End Page vii] in both form and the location of production. Whether or not the protocols of Third Cinema are exhausted is a question still being debated by scholars, and Ritzer’s provocative argument is sure to add to the vibrancy of the debate. For her part, Nadine Siegert focuses on a particular process of imaging. In “Jesus, Che, Luaty: On the Relationship between a Digital Picture and an Iconic Image in Political Iconography in Angola,” she analyzes how images of the performer Luaty Beirão (a.k.a. Ikonoklasta a.k.a. Brigadeiro Mata Frakuxz) emerged in the context of a charged political moment in Angola. Luaty Beirão became internationally known as a political activist during his imprisonment in June 2015, when he was accused of challenging the Angolan state with a coup d’état. In analyzing the images of him that circulated at the time, Siegert suggests similarities with Christian iconography, which contributed to making Beirão into an iconic political figure. Politicized images of him, Siegert argues, met a demand for new imagery on behalf of the public opposed to the politics of the state. It is noteworthy that the process of circulation through which Beirão transcends the specifics of Angolan politics shares a rough correspondence with the idea of relationality that Ritzer analyzes in his article. This correspondence, accidental or not, is noteworthy because it is indicative of the theme of the symposium as generally prospective. In the roundtable that closed off the meeting at the end of the second day, participants discussed issues pertaining to future directions in research, especially in genres that are typically overlooked, and in disciplines not often considered feasible for representational or artistic purposes. The articles by Susanne Gehrmann and Ute Fendler take up two important themes in the first area, focusing on the creative use of new media in romance and superhero comics. In “Remediating Romance: Forms and Functions of New Media in Contemporary Love Stories from Togo and South Africa,” Gehrmann tackles new media’s impact on literature through an exploration of works—romance and chick lit—in which writers imagine new...

3D craniofacial registration using thin-plate spline transform and cylindrical surface projection.

Craniofacial registration is used to establish the point-to-point correspondence in a unified coordinate system among human craniofacial models. It is the foundation of craniofacial reconstruction and other craniofacial statistical analysis research. In this paper, a non-rigid 3D craniofacial registration method using thin-plate spline transform and cylindrical surface projection is proposed. First, the gradient descent optimization is utilized to improve a cylindrical surface fitting (CSF) for the reference craniofacial model. Second, the thin-plate spline transform (TPST) is applied to deform a target craniofacial model to the reference model. Finally, the cylindrical surface projection (CSP) is used to derive the point correspondence between the reference and deformed target models. To accelerate the procedure, the iterative closest point ICP algorithm is used to obtain a rough correspondence, which can provide a possible intersection area of the CSP. Finally, the inverse TPST is used to map the obtained corresponding points from the deformed target craniofacial model to the original model, and it can be realized directly by the correspondence between the original target model and the deformed target model. Three types of registration, namely, reflexive, involutive and transitive registration, are carried out to verify the effectiveness of the proposed craniofacial registration algorithm. Comparison with the methods in the literature shows that the proposed method is more accurate.

Star Identification Algorithm Based on K–L Transformation and Star Walk Formation

For star sensors, the difficulty in realizing attitude determination lies in accurate and robust star identification algorithms. In this paper, an efficient star identification algorithm is described, which is fast, robust, and consumes small memory resources. It mainly involves two steps: the dedicated Karhunen–Loeve (K–L) transformation step and the star walk formation step. Once several pattern triangles for pole stars are built, the K–L transformation is performed to calculate the K–L values to match several rough correspondences from a predefined database. Star walks are then formed among the candidate stars using the neighboring star table, which indicates each star’s geometric distribution in the neighborhood, until a unique match is found. Our algorithm can also complete an efficient verification procedure based on a fast triangle algorithm, since stars’ surrounding information can be acquired from the neighboring star table. The simulation results compare favorably with two published algorithms, and the approach has been implemented on actual star images.

La visión artificial, un nuevo aliado para el análisis de imágenes artísticas

This paper analyzes the automatic classification of scenes that are the basis of the ideation and the designing of the sculptural production of the sculptor Miquel Planas. The main purpose is to evaluate the performance of the Bag-of-Features methods, in the challenging task of categorizing scenes when scenes differ in semantics rather than the objects they contain. We have employed a kernel-based recognition method that works by computing rough geometric correspondence on a global scale using the pyramid matching scheme introduced by Lazebnik, Schmid and Ponce in 2006. Results are promising, on average the score is about 70%. Experiments suggest that the automatic categorization of images based on computer vision methods can provide objective principles in cataloging images.

Counting Metaphors: What Does this Reveal about Language and Thought?

Counting metaphors has become quite fashionable in metaphor research. There are numerous attempts to reliably identify metaphors in discourse and count their frequencies. These studies aim to accurately assess the prominence of metaphor in language, but also provide insights into active metaphorical thinking. My evaluation of this research suggests that there may be rough correspondences between the frequency of metaphor and the richness of metaphorical thought. At the same time, even a single verbal metaphor can fundamentally structure an entire discourse, illustrating the power of metaphor to shape how we think about many abstract ideas and events. I also describe instances in which nonmetaphorical language can also enhance metaphorical thinking, and suggest the need for new ways of measuring metaphoricity in language and thought.

Robust <formula formulatype="inline"><tex Notation="TeX">$L_{2}E$</tex> </formula> Estimation of Transformation for Non-Rigid Registration

We introduce a new transformation estimation algorithm using the $L_{2}E$ estimator and apply it to non-rigid registration for building robust sparse and dense correspondences. In the sparse point case, our method iteratively recovers the point correspondence and estimates the transformation between two point sets. Feature descriptors such as shape context are used to establish rough correspondence. We then estimate the transformation using our robust algorithm. This enables us to deal with the noise and outliers which arise in the correspondence step. The transformation is specified in a functional space, more specifically a reproducing kernel Hilbert space. In the dense point case for nonrigid image registration, our approach consists of matching both sparsely and densely sampled SIFT features, and it has particular advantages in handling significant scale changes and rotations. The experimental results show that our approach greatly outperforms state-of-the-art methods, particularly when the data contains severe outliers.

The auto-geometric correction of multi-projector for cylindrical surface using Bézier patches

Geometric calibration to projection images is an indispensable operation for projection-based spatial display. In this paper, we propose a new method for correcting images generated in a computer onto a cylindrical surface accurately, which can project a high-resolution projection image with pixels matching avoiding too much manual operation. Images waiting to be projected are pre-warped according to the rough correspondence between projectors and physical surface. To solve the errors resulting from unexpected pixel shifts in overlap projection area, we fit the Bézier interpolation to the images and apply the optimization theory with added constraints to correct the projection image accurately. This optimization process, by taking the pixels with specific significance on the images as the basis of calculation, avoids the traditional ways of translating the control points of the Bézier surface directly. The final results achieve a completely accurate projection picture even if the projection surface shape is inaccurate and irregular. We present the details of the proposed accurate calibration algorithm and illustrate our method, which, with its scalability, can achieve perfect projection efficiently and accurately with experiments.

Non-rigid point set registration via coherent spatial mapping

Point set registration is essential for many computer vision technologies. In this paper, we proposed a new point set registration method based on coherent spatial mapping (CSM), whose solution is formulated as a maximum likelihood problem. Our algorithm iteratively recovers the point correspondence and estimates the transformation between two point sets. In the first step of the iteration, feature descriptors such as shape context are used to establish rough correspondence. In the second step, each training sample is associated with a latent variable which indicates whether it is an inlier, and then the thin-plate spline (TPS) is chosen to parameterize the CSM and Expectation Maximization (EM) algorithm is used to solve it. The registration experiments are undertaken on various synthetic and real data. The results demonstrate that the proposed approach is robust and accurate for scenes under deformation, noise, outlier, occlusion, and rotation and is superior to the state-of-the-art methods.

Extracting evolving pathologies via spectral clustering.

A bottleneck in the analysis of longitudinal MR scans with white matter brain lesions is the temporally consistent segmentation of the pathology. We identify pathologies in 3D+t(ime) within a spectral graph clustering framework. Our clustering approach simultaneously segments and tracks the evolving lesions by identifying characteristic image patterns at each time-point and voxel correspondences across time-points. For each 3D image, our method constructs a graph where weights between nodes capture the likeliness of two voxels belonging to the same region. Based on these weights, we then establish rough correspondences between graph nodes at different time-points along estimated pathology evolution directions. We combine the graphs by aligning the weights to a reference time-point, thus integrating temporal information across the 3D images, and formulate the 3D+t segmentation problem as a binary partitioning of this graph. The resulting segmentation is very robust to local intensity fluctuations and yields better results than segmentations generated for each time-point.

Contrast-preserved chroma enhancement technique using YCbCr color space

The YCbCr color space is widely used in image processing techniques. The preference for YCbCr is due to the rough correspondence between the YCbCr components and visual attributes. However, image contrast decreases as the chroma value increases owing to the nonorthogonality between YCbCr components. In this study, a contrast-preserved chroma enhancement algorithm using YCbCr signals is proposed by predicting the amounts of luma change needed to compensate for the lightness change induced by chroma enhancement. Numerical and psychophysical experimental results show that the proposed algorithm can effectively enhance the perceived image chroma and details.

Dating the fungus‐growing termites’ mutualism shows a mixture between ancient codiversification and recent symbiont dispersal across divergent hosts

The mutualistic symbiosis between fungus-growing termites and Termitomyces fungi originated in Africa and shows a moderate degree of interaction specificity. Here we estimate the age of the mutualism and test the hypothesis that the major splits have occurred simultaneously in the host and in the symbiont. We present a scenario where fungus-growing termites originated in the African rainforest just before the expansion of the savanna, about 31 Ma (19-49 Ma). Whereas rough age correspondence is observed for the four main clades of host and symbiont, the analysis reveals several recent events of host switching followed by dispersal of the symbiont throughout large areas and throughout different host genera. The most spectacular of these is a group of closely related fungi (the maximum age of which is estimated to be 2.4 Ma), shared between the divergent genera Microtermes, Ancistrotermes, Acanthotermes and Synacanthotermes (which diverged at least 16.7 Ma), and found throughout the African continent and on Madagascar. The lack of geographical differentiation of fungal symbionts shows that continuous exchange has occurred between regions and across host species.