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We study a new class of visibility problems based on the notion of a-visibility. Given an angle α and a collection of line segments S in the plane, a segment t is said to be α-visible from a point p, if there exists an empty tri...
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We study a new class of visibility problems based on the notion of a-visibility. Given an angle α and a collection of line segments S in the plane, a segment t is said to be α-visible from a point p, if there exists an empty triangle with one vertex at p and the side opposite to p on t such that the angle at p is a. In this model of visibility, we study the classical variants of point visibility, weak and complete segment visibility, and the construction of the visibility graph. We also investigate the natural query versions of these problems, when a is either fixed or specified at query time.
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Supply chains need to be resilient to fight back the increasing environmental uncertainties. The current study complements the growing literature on resilience by exploring the influence of different visibility types on the develo...
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Supply chains need to be resilient to fight back the increasing environmental uncertainties. The current study complements the growing literature on resilience by exploring the influence of different visibility types on the development of supply chain resilience and how the same affects supply chain performance. Further, the current investigation explores the inter-relationship between different visibility types and their dominant role in the development of supply chain resilience. Further, our investigation has considered the moderating influence of internal integration on the proposed linkages between different visibility types and supply chain resilience. Survey-based data collected from 207 supply chain professionals largely support the proposed relationships. It has been observed that internal integration positively moderates the relationships between supply, market and demand visibility with supply chain resilience.
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The Ultraviolet and Visible Spectrometer Ultraviolet (UVIS UV) and Visible Spectrometer channel of the Nadir and Occultation for MArs Discovery spectrometer aboard the ExoMars Trace Gas Orbiter has made limb observations of the Ma...
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The Ultraviolet and Visible Spectrometer Ultraviolet (UVIS UV) and Visible Spectrometer channel of the Nadir and Occultation for MArs Discovery spectrometer aboard the ExoMars Trace Gas Orbiter has made limb observations of the Martian dayglow during more than a Martian year. Two pointing modes have been applied: (a) In the inertial mode, the spectrometer scans the atmosphere twice down to near the surface and provides altitude profiles of the dayglow; (b) in the tracking mode, the atmosphere is scanned at varying latitudes at a nearly constant altitude through the entire observation. We present a statistical study of the vertical and seasonal distribution of the recently discovered oxygen green and red lines at 557.7 nm and 630 nm. It indicates that the brightness of the green line emission responds to changes in the Lyman-α flux. The peak altitude of the green line emission increases seasonally when the Sun-Mars distance decreases. The lower peak of the green line statistically drops by 15-20 km between perihelion and aphelion at mid-to high altitude. The main lower peak intensity shows an asymmetry between the two hemispheres. It is significantly brighter and more pronounced in the southern hemisphere than in the north. This is a consequence of the stronger Lyman-α solar flux near perihelion. The second component of the oxygen red line at 636.4 nm is also detected for the first time in the Martian atmosphere. A photochemical model is used to simulate the variations of the green dayglow observed along limb tracking orbits.
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Visibility is one of the most important design elements in vehicle design because drivers perceive most driving-related information through vision. In this study, we redefine the area of vehicle forward visibility based on the dri...
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Visibility is one of the most important design elements in vehicle design because drivers perceive most driving-related information through vision. In this study, we redefine the area of vehicle forward visibility based on the driver visibility angle according to information susceptibility. In addition, we present a forward visibility assessment tool that employs the driver gaze ratio obtained from the tracking driver gaze and weighted value numbers. Experimental vehicles were selected from a group of domestic and foreign vehicles; those with similar characteristics were grouped together. Twenty-five adult subjects participated in this study. The vehicle forward visibility was assessed using the sensibility assessment method. It was then compared with results of the visibility assessment tool. The area of the forward visibility could be defined and classified into effective, optimal, inducible, and auxiliary visibility areas. Accordingly, the forward visibility assessment tool was developed. The results of this study demonstrate the high correlation and reliability between the results of the forward visibility assessment tool and subjective sensibility assessment. The proposed method of evaluating vehicle forward visibility is suggested for application to the vehicle design process.
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Visibility problems are central to many computer graphics applications. The most common examples include hidden-part removal for view computation, shadow boundaries, mutual visibility of objects for lighting simulation. In this pa...
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Visibility problems are central to many computer graphics applications. The most common examples include hidden-part removal for view computation, shadow boundaries, mutual visibility of objects for lighting simulation. In this paper, we present a theoretical study of 3D visibility properties for scenes of smooth convex objects. We work in the space of light rays, or more precisely, of maximal free segments. We group segments that "see" the same object; this defines the 3D visibility complex. The boundaries of these groups of segments correspond to the visual events of the scene (limits of shadows, disappearance of an object when the viewpoint is moved, etc.). We provide a worst case analysis of the complexity of the visibility complex of 3D scenes, as well as a probabilistic study under a simple assumption for "normal" scenes. We extend the visibility complex to handle temporal visibility. We give an output-sensitive construction algorithm and present applications of our approach.
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Least visible path analysis is a basic function in terrain visibility analysis. However, current least visible path planning is constrained to least-cost path computing on a cost surface obtained from visibility information of all...
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Least visible path analysis is a basic function in terrain visibility analysis. However, current least visible path planning is constrained to least-cost path computing on a cost surface obtained from visibility information of all the terrain points on digital elevation models. This kind of method ignores the visibility correlation caused by the overlapped part of the adjacent points' reverse viewsheds. With regard to such a correlation, this paper proposes a new method using the amalgamation of reverse viewsheds to find an optimal path with the minimal visibility dominance. Both methods are implemented using C + + programming, and the experimental results show that the new method produces more accurate least visible paths than the traditional one does.
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Analytic visibility algorithms, for example methods which compute a subdivided mesh to represent shadows, are notoriously unrobust and hard to use in practice. We present a new method based on a generalized definition of extremal ...
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Analytic visibility algorithms, for example methods which compute a subdivided mesh to represent shadows, are notoriously unrobust and hard to use in practice. We present a new method based on a generalized definition of extremal stabbing lines, which are the extremities of shadow boundaries. We treat scenes containing multiple edges or vertices in degenerate configurations, (e.g., collinear or coplanar). We introduce a robust ε method to determine whether each generalized extremal stabbing line is blocked, or is touched by these scene elements, and thus added to the line's generators. We develop robust blocker predicates for polygons which are smaller than ε. For larger ε values, small shadow features merge and eventually disappear. We can thus robustly connect generalized extremal stabbing lines in degenerate scenes to form shadow boundaries. We show that our approach is consistent, and that shadow boundary connectivity is preserved when features merge. We have implemented our algorithm, and show that we can robustly compute analytic shadow boundaries to the precision of our chosen ε threshold for non-trivial models, containing numerous degeneracies.
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A bar visibility representation of a graph G is a collection of horizontal bars in the plane corresponding to the vertices of G such that two vertices are adjacent if and only if the corresponding bars can be joined by an unobstru...
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A bar visibility representation of a graph G is a collection of horizontal bars in the plane corresponding to the vertices of G such that two vertices are adjacent if and only if the corresponding bars can be joined by an unobstructed vertical line segmen
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Estimating atmospheric visibility is a critical task in our current time, particularly in the
safety of aviation, navigation, and highway traffic, because it measures the quality of the
atmosphere’s transparency. Poor visibilit...
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Estimating atmospheric visibility is a critical task in our current time, particularly in the
safety of aviation, navigation, and highway traffic, because it measures the quality of the
atmosphere’s transparency. Poor visibility caused by climatic factors such as fog, haze,
and clouds makes driving difficult and can lead to serious road accidents. Therefore, the
researchers proposed several Deep Learning (DL) approaches to facilitate visibility estimation
instead of using meteorological equipment, which is very expensive. This paper aims
to give an overview of the DL systems used in previous studies to estimate atmospheric
visibility. These systems are categorized based on the input data type, with some based on
tabular data and others on image data. The methodologies, datasets, and Deep Neural Network
(DNN) architectures used in the reviewed studies are thoroughly discussed. The evaluation
metrics are also compared. Finally, the common limitations of the proposed approaches are
highlighted, as well as potential future trends in this research field.
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Given a simple polygon P in the plane, we present new data structures for computing the weak visibility polygon from any query line segment in P. We build a data structure in O(n) time and space that can compute the visibility pol...
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Given a simple polygon P in the plane, we present new data structures for computing the weak visibility polygon from any query line segment in P. We build a data structure in O(n) time and space that can compute the visibility polygon for any query line segment s in O(k logn) time, where k is the size of the visibility polygon of s and n is the number of vertices of P. Alternatively, we build a data structure in O(n(3)) time and space that can compute the visibility polygon for any query line segment in O(k + logn) time. In order to develop these data structures, we obtain many other results that may be interesting in their own right (C) 2015 Elsevier B.V. All rights reserved.
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