2,254 research outputs found

    A methodology approach to delineate functional economic market areas: With an iterative three-step spatial clustering procedure

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    This paper proposes an iterative three-step spatial clustering procedure to define Functional Economic Market Areas (FEMAs) with an evolutionary computational approach using flow data on economic linkages. FEMAs are needed as basic observation units in disaggregated economic data analysis, since those have to be taken at the spatial level at which the markets operate. Only then can analyses provide accurate and consistent results and allow useful interpretations of variables and the measurement of spillover effects between markets. Therefore FEMAs should, besides their use as analysis regions, serve as basic areas for regional policy or coordination of these. Although functional markets are particularly used in regional science, the proposed concept with the spatial clustering procedure is transferable to other economic fields like business management and marketing research, network or competition analyses. The presented methodology approach is a generalized and ubiquitous, disjunctive and contiguous delineation extended application based on the suggestion in RUSCHE (2009) of a joint application of the AMOEBA clustering procedure by ALDSTADT/GETIS (2006) and an interaction indicator on flow data. The methodology will be illustrated with real-world applications on German commuting data. Also presented is a possible way of computation and illustration of fuzzy market borders (differentiated border densities) as an extension to the procedure

    A Perspective of the Qualified Plan Tax Subsidy

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    Measuring monopole and dipole polarizability of acoustic meta-atoms

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    We present a method to extract monopole and dipole polarizability from experimental measurements of two-dimensional acoustic meta-atoms. In contrast to extraction from numerical results, this enables all second-order effects and uncertainties in material properties to be accounted for. We apply the technique to 3D-printed labyrinthine meta-atoms of a variety of geometries. We show that the polarizability of structures with shorter acoustic path length agrees well with numerical results. However, those with longer path lengths suffer strong additional damping, which we attribute to the strong viscous and thermal losses in narrow channels

    Research and development of an air-puff excitation system for lightweight structures

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    © 2019 International Group of Operational Modal Analysis. Lightweight, thin-walled structures appear in numerous engineering and natural structures. Due to their sensitivity, vibration excitation by, now traditional, contacting techniques, such as modally-tuned impact hammers or electrodynamic shakers, to investigate their dynamics is challenging since it typically adds substantial mass and/or stiffness at the excitation location. The research presented in this article, therefore, is intended to yield a system for the non-contact excitation of thin-walled structures through small, controlled blasts of air. An air-puff system, consisting of two fast-acting solenoid-controlled valves, a small air outlet nozzle and bespoke control software with a programmable valve control sequence, is researched and developed. The excitation impulse characteristics are investigated experimentally and described in detail for varying input control parameters. Ultimately, suitability of the system for the excitation of thin-walled structures is explored, for both a 3D-printed micro-satellite panel and a natural bee honeycomb, with promising results when compared to that of an impact hammer

    Co-registration of Laser Altimeter Tracks with Digital Terrain Models and Applications in Planetary Science

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    We have derived algorithms and techniques to precisely co-register laser altimeter profiles with gridded Digital Terrain Models (DTMs), typically derived from stereo images. The algorithm consists of an initial grid search followed by a least-squares matching and yields the translation parameters at sub-pixel level needed to align the DTM and the laser profiles in 3D space. This software tool was primarily developed and tested for co-registration of laser profiles from the Lunar Orbiter Laser Altimeter (LOLA) with DTMs derived from the Lunar Reconnaissance Orbiter (LRO) Narrow Angle Camera (NAC) stereo images. Data sets can be co-registered with positional accuracy between 0.13 m and several meters depending on the pixel resolution and amount of laser shots, where rough surfaces typically result in more accurate co-registrations. Residual heights of the data sets are as small as 0.18 m. The software can be used to identify instrument misalignment, orbit errors, pointing jitter, or problems associated with reference frames being used. Also, assessments of DTM effective resolutions can be obtained. From the correct position between the two data sets, comparisons of surface morphology and roughness can be made at laser footprint- or DTM pixel-level. The precise co-registration allows us to carry out joint analysis of the data sets and ultimately to derive merged high-quality data products. Examples of matching other planetary data sets, like LOLA with LRO Wide Angle Camera (WAC) DTMs or Mars Orbiter Laser Altimeter (MOLA) with stereo models from the High Resolution Stereo Camera (HRSC) as well as Mercury Laser Altimeter (MLA) with Mercury Dual Imaging System (MDIS) are shown to demonstrate the broad science applications of the software tool
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