110,100 research outputs found

    On Two Ways of Enumerating Ordered Trees

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    The middle-levels graph MkM_k (0<kZ0<k\in\mathbb{Z}) has a dihedral quotient pseudograph RkR_k whose vertices are the kk-edge ordered trees TT, each TT encoded as a (2k+1)(2k+1)-string F(T)F(T) formed via \rightarrowDFS by: {\bf(i)} (\leftarrowBFS-assigned) Kierstead-Trotter lexical colors 0,,k0,\ldots,k for the descending nodes; {\bf(ii)} asterisks * for the kk ascending edges. Two ways of corresponding a restricted-growth kk-string α\alpha to each TT exist, namely one Stanley's way and a novel way that assigns F(T)F(T) to α\alpha via nested substring-swaps. These swaps permit to sort V(Rk)V(R_k) as an ordered tree that allows a lexical visualization of MkM_k as well as the Hamilton cycles of MkM_k constructed by P. Gregor, T. M\"utze and J. Nummenpalo.Comment: 26 pages, 8 figures, 10 table

    TreeWatch.net : a water and carbon monitoring and modeling network to assess instant tree hydraulics and carbon status

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    TreeWatch.net is an initiative that has been developed to watch trees grow and function in real-time. It is a water- and carbon-monitoring and modeling network, in which high quality measurements of sap flow and stem diameter variation are collected on individual trees. Automated data processing using a cloud service enables instant visualization of water movement and radial stem growth. This can be used to demonstrate the sensitivity of trees to changing weather conditions, such as drought, heat waves, or heavy rain showers. But TreeWatch.net's true innovation lies in its use of these high precision harmonized data to also parameterize process-based tree models in real-time, which makes displaying the much needed mechanisms underlying tree responses to climate change possible. Continuous simulation of turgor to describe growth processes and long-term time series of hydraulic resistance to assess drought-vulnerability in real-time are only a few of the opportunities our approach offers. TreeWatch.net has been developed with the view to be complementary to existing forest monitoring networks and with the aim to contribute to existing dynamic global vegetation models. It provides high-quality data and real-time simulations in order to advance research on the impact of climate change on the biological response of trees and forests. Besides its application in natural forests to answer climate-change related scientific and political questions, we also envision a broader societal application of TreeWatch.net by selecting trees in nature reserves, public areas, cities, university areas, schoolyards, and parks to teach youngsters and create public awareness on the effects of changing weather conditions on trees and forests in this era of climate change

    Task-based Augmented Contour Trees with Fibonacci Heaps

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    This paper presents a new algorithm for the fast, shared memory, multi-core computation of augmented contour trees on triangulations. In contrast to most existing parallel algorithms our technique computes augmented trees, enabling the full extent of contour tree based applications including data segmentation. Our approach completely revisits the traditional, sequential contour tree algorithm to re-formulate all the steps of the computation as a set of independent local tasks. This includes a new computation procedure based on Fibonacci heaps for the join and split trees, two intermediate data structures used to compute the contour tree, whose constructions are efficiently carried out concurrently thanks to the dynamic scheduling of task parallelism. We also introduce a new parallel algorithm for the combination of these two trees into the output global contour tree. Overall, this results in superior time performance in practice, both in sequential and in parallel thanks to the OpenMP task runtime. We report performance numbers that compare our approach to reference sequential and multi-threaded implementations for the computation of augmented merge and contour trees. These experiments demonstrate the run-time efficiency of our approach and its scalability on common workstations. We demonstrate the utility of our approach in data segmentation applications

    Mapping the Curricular Structure and Contents of Network Science Courses

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    As network science has matured as an established field of research, there are already a number of courses on this topic developed and offered at various higher education institutions, often at postgraduate levels. In those courses, instructors adopted different approaches with different focus areas and curricular designs. We collected information about 30 existing network science courses from various online sources, and analyzed the contents of their syllabi or course schedules. The topics and their curricular sequences were extracted from the course syllabi/schedules and represented as a directed weighted graph, which we call the topic network. Community detection in the topic network revealed seven topic clusters, which matched reasonably with the concept list previously generated by students and educators through the Network Literacy initiative. The minimum spanning tree of the topic network revealed typical flows of curricular contents, starting with examples of networks, moving onto random networks and small-world networks, then branching off to various subtopics from there. These results illustrate the current state of consensus formation (including variations and disagreements) among the network science community on what should be taught about networks and how, which may also be informative for K--12 education and informal education.Comment: 17 pages, 11 figures, 2 tables; to appear in Cramer, C. et al. (eds.), Network Science in Education -- Tools and Techniques for Transforming Teaching and Learning (Springer, 2017, in press

    Using the forest vegetation simulator as a teaching tool

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    The Forest Vegetation Simulator (FVS) is a tree-level, spatially non-explicit growth model. It is an outgrowth of the Stand Prognosis model that the U.S. Forest Service began developing in the late 1960s. Local variants of FVS now cover most of the forest types of the United States. Development of two complementary programs, Suppose and the Stand Visualization System (SVS), have opened the possibilities for using FVS as a teaching tool in forestry classes

    A visual analysis of the usage efficiency of library books

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    The monographic collections in academic libraries have undergone a period of tremendous growth in volume, in subject diversity, and in formats during the recent several decades. Readers may find it difficult to prioritize which book(s) should be borrowed for a specific purpose. The log data of book loan record may serve as a visible indicator for the more sought-after books by the readers. This paper describes our experimental efforts in works in a university library setting. The visual analysis is thought to provide an effective way to extract the book usage information, which may yield new insights into a host of other related technical as well as user behavior issues. Initial experiment has demonstrated that the proposed approach as articulated in this article can actually benefit end-users as well as library collection development personnel in their endeavor of book selections with effective measure.</p
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