2,081 research outputs found

    An Econometric Analysis of Investment in Hungary

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    Input-output analysis has found widespread empirical application, in studies of how certain industrial sectors react to changes in national and international economic conditions and in static and dynamic investigations of the interrelationships between industries. Since 1979 IIASA has been consistently active in this field, primarily through extensive collaboration with the Inter-Industry Forecasting Program (INFORUM) coordinated at the University of Maryland by Clopper Almon and Douglas Nyhus. IIASA's aims have been to further the development of econometric input-output models, to assist in the linkage of national models, and to participate in and extend the international network of collaborating scientists. To date, eighteen national models have been installed at IIASA, the software package SLIMFORP has been distributed widely, and linked runs of some of the national models have been carried out. Furthermore, annual task force meetings on input-output modeling have served to bring together present and prospective members of the INFORUM-IIASA "family" to review progress and to exchange ideas for further work. Gerhard Fink (Vienna Institute for Comparative Economic Studies) and Andras Simon (Institute for Economic and Market Research, Budapest) are collaborating in the development of an INFORUM-type input-output model for Hungary. In this paper they describe a study of Hungarian investment policy over recent decades, dealing with both the sectoral allocation of total investment and the cyclical investment patterns observed. The results are being used in the construction of an econometric submodel of investment for the Hungarian INFORUM model

    Interdependence vs. dependence:: a network analysis of regional integration projects in Africa, America, Asia and Europe

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    "Integration theories usually either implicitly or explicitly assume that regional integration is driven by intraregional economic interdependence, which allows for the utilisation of economies of scale or comparative cost advantages within the region. However, following the new regionalism of the 1990s, it has become clear that regional integration may also be used by the respective member states to improve their standing in the global economy, to become more attractive for foreign direct investment and development aid, or to be more powerful in international trade negotiations. In this paper, we argue that the latter motive is more important for developing countries than the former two, because developing countries are more dependent on economic relationships with other regions than on those with their neighbours. Thus, in order to understand regional integration in the Southern hemisphere, integration theory needs to incorporate interregional relationships and the resulting positive feedback for regional integration projects among developing countries. To support this argument, we present network analyses of intraregional and interregional trade of the European Community (EC), the North American Free Trade Agreement (NAFTA), the Association of Southeast-Asian Nations (ASEAN), the Common Market of South America (MERCOSUR) and the Southern African Development Community (SADC)." (author's abstract

    How regulatory agencies use stakeholder consultations to craft their reputation

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    It is common for regulatory agencies to carry out consultations with relevant stakeholders. However, little is known about what agencies actually do with the information they receive during these consultations. Drawing on a new study, Simon Fink and Eva Ruffing shed some light on the process, illustrating how consultations are used by agencies as a tool to manage their reputation with stakeholders and the wider public

    Constrained Planarity in Practice -- Engineering the Synchronized Planarity Algorithm

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    In the constrained planarity setting, we ask whether a graph admits a planar drawing that additionally satisfies a given set of constraints. These constraints are often derived from very natural problems; prominent examples are Level Planarity, where vertices have to lie on given horizontal lines indicating a hierarchy, and Clustered Planarity, where we additionally draw the boundaries of clusters which recursively group the vertices in a crossing-free manner. Despite receiving significant amount of attention and substantial theoretical progress on these problems, only very few of the found solutions have been put into practice and evaluated experimentally. In this paper, we describe our implementation of the recent quadratic-time algorithm by Bl\"asius et al. [TALG Vol 19, No 4] for solving the problem Synchronized Planarity, which can be seen as a common generalization of several constrained planarity problems, including the aforementioned ones. Our experimental evaluation on an existing benchmark set shows that even our baseline implementation outperforms all competitors by at least an order of magnitude. We systematically investigate the degrees of freedom in the implementation of the Synchronized Planarity algorithm for larger instances and propose several modifications that further improve the performance. Altogether, this allows us to solve instances with up to 100 vertices in milliseconds and instances with up to 100 000 vertices within a few minutes.Comment: to appear in Proceedings of ALENEX 202

    Distinguishing wet from dry age-related macular degeneration using three-dimensional computer-automated threshold Amsler grid testing

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    Background/aims: With the increased efficacy of current therapy for wet age-related macular degeneration (AMD), better ways to detect wet AMD are needed. This study was designed to test the ability of three-dimensional contrast threshold Amsler grid (3D-CTAG) testing to distinguish wet AMD from dry AMD. Methods: Conventional paper Amsler grid and 3D-CTAG tests were performed in 90 eyes: 63 with AMD (34 dry, 29 wet) and 27 controls. Qualitative comparisons were based upon the three-dimensional shapes of central visual field (VF) defects. Quantitative analyses considered the number and volume of the three-dimensional defects. Results: 25/34 (74%) dry AMD and 6/29 (21%) wet AMD eyes had no distortions on paper Amsler grid. Of these, 5/25 (20%) dry and 6/6 (100%) wet (p=0.03) AMD eyes exhibited central VF defects with 3D-CTAG. Wet AMD displayed stepped defects in 16/28 (57%) eyes, compared with only 2/34 (6%) of dry AMD eyes (p=0.002). All three volumetric indices of VF defects were two- to four-fold greater in wet than dry AMD (p<0.006). 3D-CTAG had 83.9% positive and 90.6% negative predictive values for wet AMD. Conclusions: 3D-CTAG has a higher likelihood of detecting central VF defects than conventional Amsler grid, especially in wet AMD. Wet AMD can be distinguished from dry AMD by qualitative and quantitative 3D-CTAG criteria. Thus, 3D-CTAG may be useful in screening for wet AMD, quantitating disease severity, and providing a quantitative outcome measure of therapy

    Experimental Comparison of PC-Trees and PQ-Trees

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    PQ-trees and PC-trees are data structures that represent sets of linear and circular orders, respectively, subject to constraints that specific subsets of elements have to be consecutive. While equivalent to each other, PC-trees are conceptually much simpler than PQ-trees; updating a PC-tree so that a set of elements becomes consecutive requires only a single operation, whereas PQ-trees use an update procedure that is described in terms of nine transformation templates that have to be recursively matched and applied. Despite these theoretical advantages, to date no practical PC-tree implementation is available. This might be due to the original description by Hsu and McConnell [Hsu et al., 2003] in some places only sketching the details of the implementation. In this paper, we describe two alternative implementations of PC-trees. For the first one, we follow the approach by Hsu and McConnell, filling in the necessary details and also proposing improvements on the original algorithm. For the second one, we use a different technique for efficiently representing the tree using a Union-Find data structure. In an extensive experimental evaluation we compare our implementations to a variety of other implementations of PQ-trees that are available on the web as part of academic and other software libraries. Our results show that both PC-tree implementations beat their closest fully correct competitor, the PQ-tree implementation from the OGDF library [Markus Chimani et al., 2014; Leipert, 1997], by a factor of 2 to 4, showing that PC-trees are not only conceptually simpler but also fast in practice. Moreover, we find the Union-Find-based implementation, while having a slightly worse asymptotic runtime, to be twice as fast as the one based on the description by Hsu and McConnell

    Parameterized Complexity of Simultaneous Planarity

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    Given kk input graphs G1,,GkG_1, \dots ,G_k, where each pair GiG_i, GjG_j with iji \neq j shares the same graph GG, the problem Simultaneous Embedding With Fixed Edges (SEFE) asks whether there exists a planar drawing for each input graph such that all drawings coincide on GG. While SEFE is still open for the case of two input graphs, the problem is NP-complete for k3k \geq 3 [Schaefer, JGAA 13]. In this work, we explore the parameterized complexity of SEFE. We show that SEFE is FPT with respect to kk plus the vertex cover number or the feedback edge set number of the the union graph G=G1GkG^\cup = G_1 \cup \dots \cup G_k. Regarding the shared graph GG, we show that SEFE is NP-complete, even if GG is a tree with maximum degree 4. Together with a known NP-hardness reduction [Angelini et al., TCS 15], this allows us to conclude that several parameters of GG, including the maximum degree, the maximum number of degree-1 neighbors, the vertex cover number, and the number of cutvertices are intractable. We also settle the tractability of all pairs of these parameters. We give FPT algorithms for the vertex cover number plus either of the first two parameters and for the number of cutvertices plus the maximum degree, whereas we prove all remaining combinations to be intractable.Comment: Appears in the Proceedings of the 31st International Symposium on Graph Drawing and Network Visualization (GD 2023

    Synchronized planarity with applications to constrained planarity problems

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    We introduce the problem Synchronized Planarity. Roughly speaking, its input is a loop-free multi-graph together with synchronization constraints that, e.g., match pairs of vertices of equal degree by providing a bijection between their edges. Synchronized Planarity then asks whether the graph admits a crossing-free embedding into the plane such that the orders of edges around synchronized vertices are consistent. We show, on the one hand, that Synchronized Planarity can be solved in quadratic time, and, on the other hand, that it serves as a powerful modeling language that lets us easily formulate several constrained planarity problems as instances of Synchronized Planarity. In particular, this lets us solve Clustered Planarity in quadratic time, where the most efficient previously known algorithm has an upper bound of O(n⁸)

    Probing the Top-Yukawa Coupling by Searching for Associated Higgs Boson Production with a Single Top Quark at the CMS Experiment

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    In this thesis the associated production of a single top quark with a Higgs boson is studied. This process is especially well suited for probing of the Top-Yukawa coupling, as the cross section of the tH process increases for couplings deviating from the Standard Model prediction. Upper exclusion limits are set on the tH production by analyzing the data recorded during Run-I and recorded in 2015 during Run-II of the LHC with the CMS detector
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