1,720,958 research outputs found
Robot motion planning: configuration space exploration and estimation
Full text linkSubmission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2025-10-20 without embargo termsThe student, Stav Ashur, accepted the attached license on 2025-06-24 at 14:18.The student, Stav Ashur, submitted this Dissertation for approval on 2025-06-24 at 14:18.This Dissertation was approved for publication on 2025-06-25 at 15:55.DSpace SAF Submission Ingestion Package generated from Vireo submission #22361 on 2025-10-20 at 20:14:51Fully or semi-autonomous machines, such as robots, are increasingly present in every domain of human society. Cleaning robots, self-driving cars, assembly machines in factories, and exploration vessels for deep sea and space. One of the core challenges when designing and deploying these robots is motion planning, which encompasses almost every action of the robot that requires the operation of a motor -- traveling by land, water, or air, grasping, pushing, or pulling objects, and positioning and utilizing tools, all require motion planning capabilities. Motion planning is frustratingly easy for people -- consider tasks such as assembling a LEGO set or cutting a vegetable into equal parts. Meanwhile, these tasks are quite difficult to automate. The conceived easiness of the task is misleading - young children cannot perform these actions, and years of ``training'' are required to develop the prerequisite set of skills. These tasks require precise motions using a large number of muscles operating in coordination, happening in some space significantly more complicated than the 3D physical workspace, all done by technology that took hundreds of millions of years to emerge via evolution. In this dissertation, we present research on robot motion planning performed in the robot configuration space, a space that captures the complexity of motions problems, striving to improve and utilize methods that efficiently search the space for solutions. We use novel techniques to improve the speed of motion planning algorithms, by modifying the exploration strategies, and the representations of the search space they use. Two of our methods can be easily incorporated in many motion planning algorithms, improving their performance, as measured by runtime, sampling efficiency, or length of the solution. Significantly, these improvements are also present in highly constrained scenarios where motion planning is difficult. We show that these techniques are beneficial when used with various types of robots, suggesting they are widely applicable. We also present a method to update quickly motion planning roadmaps, enabling planning in the presence of changing environments. This method out-performs the state of the art dynamic roadmap, and thus leads to faster planning. We also show the applicability of the new dynamic data-structure to another task planning problem, in which the robot is required to rearrange objects
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Local Spanners Revisited
Full text linkFor a set P ⊆ ℝ² of points and a family ℱ of regions, a local t-spanner of P is a sparse graph G over P, such that for any region r ∈ ℱ the subgraph restricted to r, denoted by G ∩ r, is a t-spanner for all the points of r ∩ P.
We present algorithms for the construction of local spanners with respect to several families of regions such as homothets of a convex region. Unfortunately, the number of edges in the resulting graph depends logarithmically on the spread of the input point set. We prove that this dependency cannot be removed, thus settling an open problem raised by Abam and Borouny. We also show improved constructions (with no dependency on the spread) of local spanners for fat triangles, and regular k-gons. In particular, this improves over the known construction for axis-parallel squares.
We also study notions of weaker local spanners where one is allowed to shrink the region a "bit". Surprisingly, we show a near linear-size construction of a weak spanner for axis-parallel rectangles, where the shrinkage is multiplicative. Any spanner is a weak local spanner if the shrinking is proportional to the diameter of the region
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
On the Rectangles Induced by Points
Full text link \newcommand{\Re}{\mathbb{R}} \newcommand{\reals}{\mathbb{R}}
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\newcommand{\VorX}[1]{\mathcal{V} \pth{#1}} \newcommand{\Polygon}{\mathsf{P}}
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{#1} - {#2} \right\|} \newcommand{\ptq}{q} \newcommand{\pts}{s} A set of
points in the plane, induces a set of Delaunay-type axis-parallel
rectangles , potentially of quadratic size, where an axis-parallel
rectangle is in , if it has two points of as corners, and no
other point of in it. We study various algorithmic problems related to this
set of rectangles, including how to compute it, in near linear time, and handle
various algorithmic tasks on it, such as computing its union and depth. The set
of rectangles induces the rectangle influence graph , which we also study. Potentially our most interesting result
is showing that this graph can be described as the union of bicliques,
where the total weight of the bicliques is . Here, the weight of
a bicliques is the cardinality of its vertices
On Undecided LP, Clustering and Active Learning
Full text linkWe study colored coverage and clustering problems. Here, we are given a colored point set, where the points are covered by k (unknown) clusters, which are monochromatic (i.e., all the points covered by the same cluster have the same color). The access to the colors of the points (or even the points themselves) is provided indirectly via various oracle queries (such as nearest neighbor, or separation queries). We show that one can correctly deduce the color of all the points (i.e., compute a monochromatic clustering of the points) using a polylogarithmic number of queries, if the number of clusters is a constant.
We investigate several variants of this problem, including Undecided Linear Programming and covering of points by k monochromatic balls
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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