scholarly journals Dynamic Detection of Topological Information from Grid-Based Generalized Voronoi Diagrams

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
Long Qin ◽  
Quanjun Yin ◽  
Yabing Zha ◽  
Yong Peng
Keyword(s):  
Spatial Reasoning ◽  
Voronoi Diagrams ◽  
Dynamic Environments ◽  
Topological Information ◽  
Dynamic Topology ◽  
Order Of Magnitude ◽  
Generalized Voronoi Diagrams ◽  
High Level ◽  
Grid Based ◽  
Magnitude Improvement

In the context of robotics, the grid-based Generalized Voronoi Diagrams (GVDs) are widely used by mobile robots to represent their surrounding area. Current approaches for incrementally constructing GVDs mainly focus on providing metric skeletons of underlying grids, while the connectivity among GVD vertices and edges remains implicit, which makes high-level spatial reasoning tasks impractical. In this paper, we present an algorithm named Dynamic Topology Detector (DTD) for extracting a GVD with topological information from a grid map. Beyond the construction and reconstruction of a GVD on grids, DTD further extracts connectivity among the GVD edges and vertices. DTD also provides efficient repair mechanism to treat with local changes, making it work well in dynamic environments. Simulation tests in representative scenarios demonstrate that (1) compared with the static algorithms, DTD generally makes an order of magnitude improvement regarding computation times when working in dynamic environments; (2) with negligible extra computation, DTD detects topologies not computed by existing incremental algorithms. We also demonstrate the usefulness of the resulting topological information for high-level path planning tasks.

scholarly journals Incremental Construction of Generalized Voronoi Diagrams on Pointerless Quadtrees

2014 ◽  
Vol 2014 ◽  
pp. 1-14 ◽  
Author(s):  
Quanjun Yin ◽  
Long Qin ◽  
Xiaocheng Liu ◽  
Yabing Zha
Keyword(s):  
Voronoi Diagrams ◽  
Surrounding Area ◽  
Repair Mechanism ◽  
Local Repair ◽  
Order Of Magnitude ◽  
Generalized Voronoi Diagrams ◽  
Incremental Construction ◽  
Coarse To Fine ◽  
Multiple Granularities ◽  
Magnitude Improvement

In robotics, Generalized Voronoi Diagrams (GVDs) are widely used by mobile robots to represent the spatial topologies of their surrounding area. In this paper we consider the problem of constructing GVDs on discrete environments. Several algorithms that solve this problem exist in the literature, notably the Brushfire algorithm and its improved versions which possess local repair mechanism. However, when the area to be processed is very large or is of high resolution, the size of the metric matrices used by these algorithms to compute GVDs can be prohibitive. To address this issue, we propose an improvement on the current algorithms, using pointerless quadtrees in place of metric matrices to compute and maintain GVDs. Beyond the construction and reconstruction of a GVD, our algorithm further provides a method to approximate roadmaps in multiple granularities from the quadtree based GVD. Simulation tests in representative scenarios demonstrate that, compared with the current algorithms, our algorithm generally makes an order of magnitude improvement regarding memory cost when the area is larger than210×210. We also demonstrate the usefulness of the approximated roadmaps for coarse-to-fine pathfinding tasks.

scholarly journals Hexagon-Based Generalized Voronoi Diagrams Generation for Path Planning of Intelligent Agents

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Fen Tang ◽  
Xiong You ◽  
Xin Zhang ◽  
Kunwei Li
Keyword(s):  
Path Planning ◽  
Computer Games ◽  
Intelligent Agents ◽  
Voronoi Diagrams ◽  
Simulation Experiments ◽  
Square Grid ◽  
Surrounding Environment ◽  
Hexagonal Grids ◽  
Generalized Voronoi Diagrams ◽  
Grid Based

Grid-based Generalized Voronoi Diagrams (GVDs) are widely used to represent the surrounding environment of intelligent agents in the fields of robotics, computer games, and military simulations, which improve the efficiency of path planning of intelligent agents. Current studies mainly focus on square-grid-based GVD construction approaches, and little attention has been paid to constructing GVDs from hexagonal grids. In this paper, an algorithm named hexagon-based crystal growth (HCG) is presented to extract GVDs from hexagonal grids. In addition, two thinning patterns for obtaining one-cell-wide GVDs from rough hexagon-based GVDs are proposed. On the basis of the principles of a leading square-grid-based algorithm named Brushfire, a hexagon-based Brushfire algorithm is realized. A comparison of the HCG and the hexagon-based Brushfire algorithm shows that HCG is much more efficient. Further, the usefulness of hexagon-based GVDs for the path planning tasks of intelligent agents is demonstrated using several representative simulation experiments.

High-Density Memristor-CMOS Ternary Logic Family

2020 ◽  
Author(s):  
Xiaoyuan Wang ◽  
Pengfei Zhou ◽  
Jason Eshraghian ◽  
Chih-Yang Lin ◽  
Herbert Ho-Ching Iu ◽  
...  
Keyword(s):  
Indium Tin Oxide ◽  
Practical Implementation ◽  
Switching Speed ◽  
High Data ◽  
Fast Switching ◽  
Data Density ◽  
Order Of Magnitude ◽  
High Transconductance ◽  
Logic Functions ◽  
Magnitude Improvement

<div>This paper presents the first experimental demonstration</div><div>of a ternary memristor-CMOS logic family. We systematically</div><div>design, simulate and experimentally verify the primitive</div><div>logic functions: the ternary AND, OR and NOT gates. These are then used to build combinational ternary NAND, NOR, XOR and XNOR gates, as well as data handling ternary MAX and MIN gates. Our simulations are performed using a 50-nm process which are verified with in-house fabricated indium-tin-oxide memristors, optimized for fast switching, high transconductance, and low current leakage. We obtain close to an order of magnitude improvement in data density over conventional CMOS logic, and a reduction of switching speed by a factor of 13 over prior state-of-the-art ternary memristor results. We anticipate extensions of this work can realize practical implementation where high data density is of critical importance.</div>

scholarly journals A survey: which features are required for dynamic visual simultaneous localization and mapping?

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Zewen Xu ◽  
Zheng Rong ◽  
Yihong Wu
Keyword(s):  
Simultaneous Localization And Mapping ◽  
Dynamic Environments ◽  
Visual Features ◽  
Advantages And Disadvantages ◽  
Intelligent Robots ◽  
Localization And Mapping ◽  
High Level ◽  
Static World ◽  
Robotic Applications ◽  
Significant Attention

AbstractIn recent years, simultaneous localization and mapping in dynamic environments (dynamic SLAM) has attracted significant attention from both academia and industry. Some pioneering work on this technique has expanded the potential of robotic applications. Compared to standard SLAM under the static world assumption, dynamic SLAM divides features into static and dynamic categories and leverages each type of feature properly. Therefore, dynamic SLAM can provide more robust localization for intelligent robots that operate in complex dynamic environments. Additionally, to meet the demands of some high-level tasks, dynamic SLAM can be integrated with multiple object tracking. This article presents a survey on dynamic SLAM from the perspective of feature choices. A discussion of the advantages and disadvantages of different visual features is provided in this article.

Performance Assessment of a High-Level-Waste Repository in Clay

1988 ◽  
Vol 127 ◽  
Author(s):  
Jan L. Marivoet ◽  
Geert Volckaert ◽  
Arnold A. Bonne
Keyword(s):  
Performance Assessment ◽  
Maximum Dose ◽  
High Level Waste ◽  
Clay Layer ◽  
Geological Disposal ◽  
Dose Rates ◽  
Consequence Analysis ◽  
Calculated Dose ◽  
Order Of Magnitude ◽  
High Level

ABSTRACTPerformance assessment studies have been undertaken on the geological disposal of high-level waste in a clay layer in the framework of the CEC project PAGIS. The methodology applied consists of two consecutive steps : a scenario and a consequence analysis. The scenario analysis has indicated that scenarios of normal evolution, of human intrusion, of climatic change, of secondary glaciation effects and of faulting should be evaluated. For the consequence analysis as well deterministic “best estimate” as stochastic calculations, including uncertainty, risk and sensitivity analyses, have been elaborated.The calculations performed show that most radionuclides decay to negligible levels within the first fewjneters of the clay barrier. Just a few radionuclides, 99Tc, 135Cs and 237Np with its daughter nuclides 233U and 229Th can eventually reach the biosphere. The maximum dose rates arising from the geological disposal of HLW, as evaluated by the “best-estimate” approach are about 10−11 Sv/y for river pathways. If the sinking of a water well into the 150 m deep aquifer layer in the vicinity of the repository is considered together with a climatic change, the maximum calculated dose rate rises to a value of 3×10−7 Sv/y. The maximum dose rates evaluated by stochastic calculations are about one order of magnitude higher due to the considerable uncertainties in the model parameters. In the case of the Boom clay the estimated consequences of a fault scenario are of the same order of magnitude as the results obtained for the normal evolution scenario. The maximum risk is estimated from the results obtained through stochastic calculations to be about 5×10−8 per year. The sensitivity analysis has shown that the effective thickness of the clay layer, the retention factors of Tc, Cs and Np, and the Darcy velocity in the aquifer are parameters which strongly influence the calculated dose rates.

Modelling spatial reasoning systems with shape algebras and formal logic

1997 ◽  
Vol 11 (4) ◽  
pp. 273-285 ◽  
Author(s):  
Scott C. Chase
Keyword(s):  
Spatial Reasoning ◽  
Predicate Logic ◽  
Spatial Relations ◽  
Large Set ◽  
First Order ◽  
Reasoning Systems ◽  
Geometric Objects ◽  
Small Set ◽  
Definition Of ◽  
High Level

AbstractThe combination of the paradigms of shape algebras and predicate logic representations, used in a new method for describing designs, is presented. First-order predicate logic provides a natural, intuitive way of representing shapes and spatial relations in the development of complete computer systems for reasoning about designs. Shape algebraic formalisms have advantages over more traditional representations of geometric objects. Here we illustrate the definition of a large set of high-level design relations from a small set of simple structures and spatial relations, with examples from the domains of geographic information systems and architecture.

scholarly journals The Array of Long Baseline Antennas for Taking Radio Observations from the Sub-Antarctic

2020 ◽  
Vol 09 (04) ◽  
pp. 2050019
Author(s):  
H. C. Chiang ◽  
T. Dyson ◽  
E. Egan ◽  
S. Eyono ◽  
N. Ghazi ◽  
...  
Keyword(s):  
Low Frequency ◽  
Neutral Hydrogen ◽  
Radio Frequency Interference ◽  
Marion Island ◽  
Radio Observations ◽  
Long Baseline ◽  
Galactic Emission ◽  
Operating Frequency Range ◽  
Order Of Magnitude ◽  
Magnitude Improvement

Measurements of redshifted 21[Formula: see text]cm emission of neutral hydrogen at [Formula: see text][Formula: see text]MHz have the potential to probe the cosmic “dark ages,” a period of the universe’s history that remains unobserved to date. Observations at these frequencies are exceptionally challenging because of bright Galactic foregrounds, ionospheric contamination, and terrestrial radio-frequency interference. Very few sky maps exist at [Formula: see text][Formula: see text]MHz, and most have modest resolution. We introduce the Array of Long Baseline Antennas for Taking Radio Observations from the Sub-Antarctic (ALBATROS), a new experiment that aims to image low-frequency Galactic emission with an order-of-magnitude improvement in resolution over existing data. The ALBATROS array will consist of antenna stations that operate autonomously, each recording baseband data that will be interferometrically combined offline. The array will be installed on Marion Island and will ultimately comprise 10 stations, with an operating frequency range of 1.2–125[Formula: see text]MHz and maximum baseline lengths of [Formula: see text][Formula: see text]km. We present the ALBATROS instrument design and discuss pathfinder observations that were taken from Marion Island during 2018–2019.

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