Journal articles: 'Tree motion'

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Xing, Siyuan, and Albert C. J. Luo. "On a Global Sequential Scenario of Bifurcation Trees to Chaos in a First-Order, Periodically Excited, Time-Delayed System." International Journal of Bifurcation and Chaos 29, no. 10 (September 2019): 1950141. http://dx.doi.org/10.1142/s0218127419501414.

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In this paper, the global sequential scenario of bifurcation trees of periodic motions to chaos is studied for a first-order, time-delayed, nonlinear dynamical system with periodic excitation. The periodic motions of such a first-order time-delayed system is obtained semi-analytically, and the corresponding stability and bifurcations are determined by eigenvalue analysis. A global sequential scenario of bifurcation trees is given by [Formula: see text] where [Formula: see text] is a global bifurcation tree of an asymmetric period-[Formula: see text] motion to chaos, and [Formula: see text] is a global bifurcation tree of a symmetric period-[Formula: see text] motion to chaos. Each bifurcation tree of a specific periodic motion to chaos is presented in detail. Numerical simulations of periodic motions are performed from analytical predictions. From finite Fourier series, harmonic amplitudes and phases for periodic motions are obtained for frequency analysis. Through this study, the rich dynamics of the first-order, time-delayed, nonlinear dynamical system is presented.

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Xu, Yeyin, Zhaobo Chen, and Albert C. J. Luo. "Period-1 Motion to Chaos in a Nonlinear Flexible Rotor System." International Journal of Bifurcation and Chaos 30, no. 05 (April 2020): 2050077. http://dx.doi.org/10.1142/s0218127420500777.

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In this paper, a bifurcation tree of period-1 motion to chaos in a flexible nonlinear rotor system is presented through period-1 to period-8 motions. Stable and unstable periodic motions on the bifurcation tree in the flexible rotor system are achieved semi-analytically, and the corresponding stability and bifurcation of the periodic motions are analyzed by eigenvalue analysis. On the bifurcation tree, the appearance and vanishing of jumping phenomena of periodic motions are generated by saddle-node bifurcations, and quasi-periodic motions are induced by Neimark bifurcations. Period-doubling bifurcations of periodic motions are for developing cascaded bifurcation trees, however, the birth of new periodic motions are based on the saddle-node bifurcation. For a better understanding of periodic motions on the bifurcation tree, nonlinear harmonic amplitude characteristics of periodic motions are presented. Numerical simulations of periodic motions are performed for the verification of semi-analytical predictions. From such a study, nonlinear Jeffcott rotor possesses complex periodic motions. Such results can help one detect and control complex motions in rotor systems for industry.

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Liu, Feng, Yueting Zhuang, Fei Wu, and Yunhe Pan. "3D motion retrieval with motion index tree." Computer Vision and Image Understanding 92, no. 2-3 (November 2003): 265–84. http://dx.doi.org/10.1016/j.cviu.2003.06.001.

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Kale, Özkan, and Sinan Akkar. "A Ground-Motion Logic-Tree Scheme for Regional Seismic Hazard Studies." Earthquake Spectra 33, no. 3 (August 2017): 837–56. http://dx.doi.org/10.1193/051316eqs080m.

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We propose a methodology that can be useful to the hazard expert in building ground-motion logic trees to capture the center and range of ground-motion amplitudes. The methodology can be used to identify a logic-tree structure and weighting scheme that prevents the dominancy of a specific ground-motion model. This strategy can be useful for regional probabilistic seismic hazard since logic-trees biased by a specific ground-motion predictive model (GMPE) may cause disparities in the seismic hazard for regions represented by large number of sites with complex seismic features. The methodology first identifies a suit of candidate ground-motion prediction equations that can cover the center, body and range of estimated ground motions. The GMPE set is then used for establishing alternative logic-trees composed of different weighting schemes to identify the one(s) that would not be biased towards a particular GMPE due to its sensitivity to the weights. The proposed methodology utilizes visual and statistical tools to assess the ground motion distributions over large areas that makes it more practical for regional hazard studies.

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Jackson, Toby D., Sarab Sethi, Ebba Dellwik, Nikolas Angelou, Amanda Bunce, Tim van Emmerik, Marine Duperat, et al. "The motion of trees in the wind: a data synthesis." Biogeosciences 18, no. 13 (July 6, 2021): 4059–72. http://dx.doi.org/10.5194/bg-18-4059-2021.

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Abstract. Interactions between wind and trees control energy exchanges between the atmosphere and forest canopies. This energy exchange can lead to the widespread damage of trees, and wind is a key disturbance agent in many of the world's forests. However, most research on this topic has focused on conifer plantations, where risk management is economically important, rather than broadleaf forests, which dominate the forest carbon cycle. This study brings together tree motion time-series data to systematically evaluate the factors influencing tree responses to wind loading, including data from both broadleaf and coniferous trees in forests and open environments. We found that the two most descriptive features of tree motion were (a) the fundamental frequency, which is a measure of the speed at which a tree sways and is strongly related to tree height, and (b) the slope of the power spectrum, which is related to the efficiency of energy transfer from wind to trees. Intriguingly, the slope of the power spectrum was found to remain constant from medium to high wind speeds for all trees in this study. This suggests that, contrary to some predictions, damping or amplification mechanisms do not change dramatically at high wind speeds, and therefore wind damage risk is related, relatively simply, to wind speed. Conifers from forests were distinct from broadleaves in terms of their response to wind loading. Specifically, the fundamental frequency of forest conifers was related to their size according to the cantilever beam model (i.e. vertically distributed mass), whereas broadleaves were better approximated by the simple pendulum model (i.e. dominated by the crown). Forest conifers also had a steeper slope of the power spectrum. We interpret these finding as being strongly related to tree architecture; i.e. conifers generally have a simple shape due to their apical dominance, whereas broadleaves exhibit a much wider range of architectures with more dominant crowns.

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Long, Jie, and Michael D. Jones. "Reconstructing 3D Tree Models Using Motion Capture and Particle Flow." International Journal of Computer Games Technology 2013 (2013): 1–11. http://dx.doi.org/10.1155/2013/363160.

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Recovering tree shape from motion capture data is a first step toward efficient and accurate animation of trees in wind using motion capture data. Existing algorithms for generating models of tree branching structures for image synthesis in computer graphics are not adapted to the unique data set provided by motion capture. We present a method for tree shape reconstruction using particle flow on input data obtained from a passive optical motion capture system. Initial branch tip positions are estimated from averaged and smoothed motion capture data. Branch tips, as particles, are also generated within a bounding space defined by a stack of bounding boxes or a convex hull. The particle flow, starting at branch tips within the bounding volume under forces, creates tree branches. The forces are composed of gravity, internal force, and external force. The resulting shapes are realistic and similar to the original tree crown shape. Several tunable parameters provide control over branch shape and arrangement.

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Ao, Xuefeng, Zhongke Wu, and Mingquan Zhou. "Real Time Animation of Trees Based on BBSC in Computer Games." International Journal of Computer Games Technology 2009 (2009): 1–8. http://dx.doi.org/10.1155/2009/970617.

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That researchers in the field of computer games usually find it is difficult to simulate the motion of actual 3D model trees lies in the fact that the tree model itself has very complicated structure, and many sophisticated factors need to be considered during the simulation. Though there are some works on simulating 3D tree and its motion, few of them are used in computer games due to the high demand for real-time in computer games. In this paper, an approach of animating trees in computer games based on a novel tree model representation—Ball B-Spline Curves (BBSCs) are proposed. By taking advantage of the good features of the BBSC-based model, physical simulation of the motion of leafless trees with wind blowing becomes easier and more efficient. The method can generate realistic 3D tree animation in real-time, which meets the high requirement for real time in computer games.

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Luo, Albert C. J., and Jianzhe Huang. "Period-3 Motions to Chaos in a Softening Duffing Oscillator." International Journal of Bifurcation and Chaos 24, no. 03 (March 2014): 1430010. http://dx.doi.org/10.1142/s0218127414300109.

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In this paper, period-3 motions to chaos in the periodically forced, softening Duffing oscillator are investigated analytically. The analytical solutions for period-3 and period-6 motions are approximated through the generalized harmonic balance method. The bifurcation trees of period-3 motions to chaos are presented analytically. The symmetric and asymmetric period-3 motions are found. The symmetric to asymmetric period-3 motions experience the saddle-node bifurcation. From the Hopf bifurcation of the asymmetric period-3 motion, period-6 motions are determined analytically from the bifurcation tree of period-3 motions. Such an investigation provides a complete picture of period-3 motions to period-6 motions. With such bifurcation tree, the chaotic motions relative to period-3 motions in such a softening Duffing oscillator can be determined analytically. In a similar fashion, other bifurcation trees of period-m motions to chaos can be determined analytically.

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Merchant, Hugo, Alexandra Battaglia-Mayer, and Apostolos P. Georgopoulos. "Functional Organization of Parietal Neuronal Responses to Optic-Flow Stimuli." Journal of Neurophysiology 90, no. 2 (August 2003): 675–82. http://dx.doi.org/10.1152/jn.00331.2003.

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We analyzed the dissimilarity matrix of neuronal responses to moving visual stimuli using tree clustering and multidimensional scaling (MDS). Single-cell activity was recorded in area 7a while random dots moving coherently in eight different kinds of motion (right-, left-, up-, and downward, clockwise, counterclockwise, expansion, contraction) were presented to behaving monkeys with eyes fixated. Tree clustering analyses showed that the {rightward, leftward}, {upward, downward}, and {clockwise, counterclockwise]} motions were clustered in three separate branches (i.e., horizontal, vertical, and rotatory motion, respectively). In contrast, expansion was in a lone branch, whereas contraction was also separate but within a larger cluster. The distances among these clusters were then subjected to an MDS analysis to identify the dimensions underlying the tree clustering observed. This analysis revealed two major factors in operation. The first factor separated expansion from all other stimulus motions, which seems to reflect the prominence of expansion during the common activity of locomotion. In contrast, the second factor separated planar motions from motion in depth, which suggests that the latter may hold a special place in visual motion processing.

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Auletta, Vincenzo, and Pino Persiano. "Optimal Pebble Motion on a Tree." Information and Computation 165, no. 1 (February 2001): 42–68. http://dx.doi.org/10.1006/inco.2000.3005.

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11

Krebs, W. B. "Brownian motion on the continuum tree." Probability Theory and Related Fields 101, no. 3 (September 1995): 421–33. http://dx.doi.org/10.1007/bf01200505.

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Itakura, Kenta, and Fumiki Hosoi. "Automatic Tree Detection from Three-Dimensional Images Reconstructed from 360° Spherical Camera Using YOLO v2." Remote Sensing 12, no. 6 (March 19, 2020): 988. http://dx.doi.org/10.3390/rs12060988.

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It is important to grasp the number and location of trees, and measure tree structure attributes, such as tree trunk diameter and height. The accurate measurement of these parameters will lead to efficient forest resource utilization, maintenance of trees in urban cities, and feasible afforestation planning in the future. Recently, light detection and ranging (LiDAR) has been receiving considerable attention, compared with conventional manual measurement techniques. However, it is difficult to use LiDAR for widespread applications, mainly because of the costs. We propose a method for tree measurement using 360° spherical cameras, which takes omnidirectional images. For the structural measurement, the three-dimensional (3D) images were reconstructed using a photogrammetric approach called structure from motion. Moreover, an automatic tree detection method from the 3D images was presented. First, the trees included in the 360° spherical images were detected using YOLO v2. Then, these trees were detected with the tree information obtained from the 3D images reconstructed using structure from motion algorithm. As a result, the trunk diameter and height could be accurately estimated from the 3D images. The tree detection model had an F-measure value of 0.94. This method could automatically estimate some of the structural parameters of trees and contribute to more efficient tree measurement.

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Liu, Guoyang, and Junjie Li. "Research on the Effect of Tree Barriers on Rockfall Using a Three-Dimensional Discontinuous Deformation Analysis Method." International Journal of Computational Methods 17, no. 08 (May 31, 2019): 1950046. http://dx.doi.org/10.1142/s0219876219500464.

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On rockfall slopes, trees can play a natural and efficient protective role in preventing the occurrence of rockfall disasters. This paper presents a study on the tree barrier effect on rockfall based on a three-dimensional discontinuous deformation analysis (3D DDA) method. The tree barrier effect on rockfall is studied considering the 3D spatial effect of rockfall movement and the 3D spatial distribution of trees. The basic movement forms and collision modes of rockfall related to the tree barrier are classified, and the impact factors of tree arrangements on rockfall are proposed. The contact mechanism employed in the 3D DDA method is illustrated, and the accuracy of the 3D DDA rockfall simulation is verified by comparing with the results obtained from laboratory experiments. Numerical examples are conducted to study the effect of the tree barrier on rockfall, and general laws are derived by analyzing the variation of kinetic energies and motion trajectories of moving blocks. The results show that the 3D DDA method can effectively predict the 3D motion behaviors of rockfall and assess the tree barrier effect. Furthermore, a reasonable arrangement of trees or a combination of protective facilities and trees can prevent or mitigate the rockfall hazards.

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Croydon, D. A. "Scaling limits for simple random walks on random ordered graph trees." Advances in Applied Probability 42, no. 02 (June 2010): 528–58. http://dx.doi.org/10.1017/s0001867800004183.

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Consider a family of random ordered graph trees (Tn)n≥1, whereTnhasnvertices. It has previously been established that if the associated search-depth processes converge to the normalised Brownian excursion when rescaled appropriately asn→ ∞, then the simple random walks on the graph trees have the Brownian motion on the Brownian continuum random tree as their scaling limit. Here, this result is extended to demonstrate the existence of a diffusion scaling limit whenever the volume measure on the limiting real tree is nonatomic, supported on the leaves of the limiting tree, and satisfies a polynomial lower bound for the volume of balls. Furthermore, as an application of this generalisation, it is established that the simple random walks on a family of Galton-Watson trees with a critical infinite variance offspring distribution, conditioned on the total number of offspring, can be rescaled to converge to the Brownian motion on a related α-stable tree.

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Croydon, D. A. "Scaling limits for simple random walks on random ordered graph trees." Advances in Applied Probability 42, no. 2 (June 2010): 528–58. http://dx.doi.org/10.1239/aap/1275055241.

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Consider a family of random ordered graph trees (Tn)n≥1, where Tn has n vertices. It has previously been established that if the associated search-depth processes converge to the normalised Brownian excursion when rescaled appropriately as n → ∞, then the simple random walks on the graph trees have the Brownian motion on the Brownian continuum random tree as their scaling limit. Here, this result is extended to demonstrate the existence of a diffusion scaling limit whenever the volume measure on the limiting real tree is nonatomic, supported on the leaves of the limiting tree, and satisfies a polynomial lower bound for the volume of balls. Furthermore, as an application of this generalisation, it is established that the simple random walks on a family of Galton-Watson trees with a critical infinite variance offspring distribution, conditioned on the total number of offspring, can be rescaled to converge to the Brownian motion on a related α-stable tree.

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Bommer, Julian J., and Frank Scherbaum. "The Use and Misuse of Logic Trees in Probabilistic Seismic Hazard Analysis." Earthquake Spectra 24, no. 4 (November 2008): 997–1009. http://dx.doi.org/10.1193/1.2977755.

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Logic trees have become a standard feature of probabilistic seismic hazard analyses (PSHA) for determining design ground motions. A logic tree's purpose is to capture and quantify the epistemic uncertainty associated with the inputs to PSHA and thus enable estimation of the resulting uncertainty in the hazard. There are many potential pitfalls in setting up a logic tree for PSHA, mainly related to the fact that in practice, it is questionable that the requirements that the logic-tree branches be both mutually exclusive and collectively exhaustive can actually be met. Careful consideration is also required for making use of the output; in particular, in view of how PSHA is employed in current engineering design practice, it may be more rational to determine the mean ground motion at the selected design return period rather than to find the ground motion at the mean value of this return period.

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Frederickson, Greg N., and D. J. Guan. "Preemptive Ensemble Motion Planning on a Tree." SIAM Journal on Computing 21, no. 6 (December 1992): 1130–52. http://dx.doi.org/10.1137/0221066.

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Mathew, Reji, and David S. Taubman. "Quad-Tree Motion Modeling With Leaf Merging." IEEE Transactions on Circuits and Systems for Video Technology 20, no. 10 (October 2010): 1331–45. http://dx.doi.org/10.1109/tcsvt.2010.2077480.

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Koike, Ryotaro, Kei Moritsugu, and Motonori Ota. "Description of Structural Changes by Motion Tree." Biophysical Journal 116, no. 3 (February 2019): 339a. http://dx.doi.org/10.1016/j.bpj.2018.11.1849.

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Frederickson, G. N., and D. J. Guan. "Nonpreemptive Ensemble Motion Planning on a Tree." Journal of Algorithms 15, no. 1 (July 1993): 29–60. http://dx.doi.org/10.1006/jagm.1993.1029.

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Kim, Beobkyoon, Terry Taewoong Um, Chansu Suh, and F. C. Park. "Tangent bundle RRT: A randomized algorithm for constrained motion planning." Robotica 34, no. 1 (May 28, 2014): 202–25. http://dx.doi.org/10.1017/s0263574714001234.

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SUMMARYThe Tangent Bundle Rapidly Exploring Random Tree (TB-RRT) is an algorithm for planning robot motions on curved configuration space manifolds, in which the key idea is to construct random trees not on the manifold itself, but on tangent bundle approximations to the manifold. Curvature-based methods are developed for constructing tangent bundle approximations, and procedures for random node generation and bidirectional tree extension are developed that significantly reduce the number of projections to the manifold. Extensive numerical experiments for a wide range of planning problems demonstrate the computational advantages of the TB-RRT algorithm over existing constrained path planning algorithms.

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Piermattei, Livia, Wilfried Karel, Di Wang, Martin Wieser, Martin Mokroš, Peter Surový, Milan Koreň, Julián Tomaštík, Norbert Pfeifer, and Markus Hollaus. "Terrestrial Structure from Motion Photogrammetry for Deriving Forest Inventory Data." Remote Sensing 11, no. 8 (April 20, 2019): 950. http://dx.doi.org/10.3390/rs11080950.

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The measurements of tree attributes required for forest monitoring and management planning, e.g., National Forest Inventories, are derived by rather time-consuming field measurements on sample plots, using calipers and measurement tapes. Therefore, forest managers and researchers are looking for alternative methods. Currently, terrestrial laser scanning (TLS) is the remote sensing method that provides the most accurate point clouds at the plot-level to derive these attributes from. However, the demand for even more efficient and effective solutions triggers further developments to lower the acquisition time, costs, and the expertise needed to acquire and process 3D point clouds, while maintaining the quality of extracted tree parameters. In this context, photogrammetry is considered a potential solution. Despite a variety of studies, much uncertainty still exists about the quality of photogrammetry-based methods for deriving plot-level forest attributes in natural forests. Therefore, the overall goal of this study is to evaluate the competitiveness of terrestrial photogrammetry based on structure from motion (SfM) and dense image matching for deriving tree positions, diameters at breast height (DBHs), and stem curves of forest plots by means of a consumer grade camera. We define an image capture method and we assess the accuracy of the photogrammetric results on four forest plots located in Austria and Slovakia, two in each country, selected to cover a wide range of conditions such as terrain slope, undergrowth vegetation, and tree density, age, and species. For each forest plot, the reference data of the forest parameters were obtained by conducting field surveys and TLS measurements almost simultaneously with the photogrammetric acquisitions. The TLS data were also used to estimate the accuracy of the photogrammetric ground height, which is a necessary product to derive DBHs and tree heights. For each plot, we automatically derived tree counts, tree positions, DBHs, and part of the stem curve from both TLS and SfM using a software developed at TU Wien (Forest Analysis and Inventory Tool, FAIT), and the results were compared. The images were oriented with errors of a few millimetres only, according to checkpoint residuals. The automatic tree detection rate for the SfM reconstruction ranges between 65% and 98%, where the missing trees have average DBHs of less than 12 cm. For each plot, the mean error of SfM and TLS DBH estimates is −1.13 cm and −0.77 cm with respect to the caliper measurements. The resulting stem curves show that the mean differences between SfM and TLS stem diameters is at maximum −2.45 cm up to 3 m above ground, which increases to almost +4 cm for higher elevations. This study shows that with the adopted image capture method, terrestrial SfM photogrammetry, is an accurate solution to support forest inventory for estimating the number of trees and their location, the DBHs and stem curve up to 3 m above ground.

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Koike, Ryotaro, and Motonori Ota. "All Atom Motion Tree detects side chain-related motions and their coupling with domain motion in proteins." Biophysics and Physicobiology 16 (2019): 280–86. http://dx.doi.org/10.2142/biophysico.16.0_280.

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Tinkham, Wade T., and Neal C. Swayze. "Influence of Agisoft Metashape Parameters on UAS Structure from Motion Individual Tree Detection from Canopy Height Models." Forests 12, no. 2 (February 22, 2021): 250. http://dx.doi.org/10.3390/f12020250.

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Applications of unmanned aerial systems for forest monitoring are increasing and drive a need to understand how image processing workflows impact end-user products’ accuracy from tree detection methods. Increasing image overlap and making acquisitions at lower altitudes improve how structure from motion point clouds represents forest canopies. However, only limited testing has evaluated how image resolution and point cloud filtering impact the detection of individual tree locations and heights. We evaluate how Agisoft Metashape’s build dense cloud Quality (image resolution) and depth map filter settings influence tree detection from canopy height models in ponderosa pine forests. Finer resolution imagery with minimal filtering provided the best visual representation of vegetation detail for trees of all sizes. These same settings maximized tree detection F-score at >0.72 for overstory (>7 m tall) and >0.60 for understory trees. Additionally, overstory tree height bias and precision improve as image resolution becomes finer. Overstory and understory tree detection in open-canopy conifer systems might be optimized using the finest resolution imagery that computer hardware enables, while applying minimal point cloud filtering. The extended processing time and data storage demands of high-resolution imagery must be balanced against small reductions in tree detection performance when down-scaling image resolution to allow the processing of greater data extents.

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Creasy, Matthew B., Wade T. Tinkham, Chad M. Hoffman, and Jody C. Vogeler. "Potential for individual tree monitoring in ponderosa pine dominated forests using unmanned aerial system structure from motion point clouds." Canadian Journal of Forest Research 51, no. 8 (August 2021): 1093–105. http://dx.doi.org/10.1139/cjfr-2020-0433.

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Characterization of forest structure is important for management-related decision making, monitoring, and adaptive management. Increasingly, observations of forest structure are needed at both finer resolutions and across greater extents to support spatially explicit management planning. Unmanned aerial system (UAS) based photogrammetry provides an airborne method of forest structure data acquisition at a significantly lower cost and time commitment than existing methods such as airborne laser scanning (LiDAR). This study utilizes nearly 5000 stem-mapped trees in ponderosa pine (Pinus ponderosa Lawson & C. Lawson) dominated forests to evaluate several algorithms for detecting individual tree locations and characterizing crown area across tree sizes. Our results indicate that adaptive variable window detection methods with UAS-based canopy height models have greater tree detection rates compared with fixed window analysis across a range of tree sizes. Using the UAS approach, probability of detecting individual trees decreases from 97% for dominant overstory to 67% for suppressed understory trees. Additionally, crown radii were correctly determined within 0.5 m for approximately two-thirds of sampled trees. These findings highlight the potential for UAS photogrammetry to characterize forest structure through the detection of trees and tree groups in open-canopy ponderosa pine forests. Further work should investigate how these methods transfer to more diverse species compositions and forest structures.

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Li, Zhan Li, and Min Zhang. "Simulation of Tree Motion Based on Vega Prime." Key Engineering Materials 474-476 (April 2011): 1296–99. http://dx.doi.org/10.4028/www.scientific.net/kem.474-476.1296.

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Due to the high level complexity of the structure of trees, physical-based simulation of tree’s motion is a difficult task. Many visual simulation platforms and modeling tools are developed to simplify the process of simulation. In a variety of modeling tools, Creator is a simple and convenient modeling tool. It works with the visual simulation platform Vega Prime. They play an important role in the field of visualized simulation. Thus, a solution for simulating tree’s motion in the environment of Creator and Vega Prime is proposed. Each of branches around the tree’s 3D shape is built in Creator, and then is gradually merged together into a tree in Vega Prime. The Vega Prime APIs are used to realize the simulation of tree’s motion. The software development circle is shortened in the solution. The simulation of tree’s motion is accomplished faithfully. Experiment results show that the solution reduces the process of development and realizes the vivid simulation.

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Kurashige, Kentarou, Toshio Fukuda, and Haruo Hoshino. "Motion Planning for Six-Legged Locomotion Robot Based on Hierarchical Knowledge Using Genetic Programming." Journal of Robotics and Mechatronics 12, no. 4 (August 20, 2000): 459–65. http://dx.doi.org/10.20965/jrm.2000.p0459.

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Much research has been done on the motion planning problem. In this field, main research is to generate the motion for specific robot and task without previously acquired motions. We research the motion planning reusing knowledge. It is our objective to realize hierarchical knowledge with reuse. In this paper, we adopt tree-based representation for expressing the knowledge of the motion and adopt genetic programming as a learning method. We construct the motion planning system using hierarchical knowledge. We apply the proposed method to the six-legged locomotion robot to show its availability.

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Xu, Yeyin, and Albert C. J. Luo. "Independent Period-2 Motions to Chaos in a van der Pol–Duffing Oscillator." International Journal of Bifurcation and Chaos 30, no. 15 (December 9, 2020): 2030045. http://dx.doi.org/10.1142/s0218127420300451.

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In this paper, an independent bifurcation tree of period-2 motions to chaos coexisting with period-1 motions in a periodically driven van der Pol–Duffing oscillator is presented semi-analytically. Symmetric and asymmetric period-1 motions without period-doubling are obtained first, and a bifurcation tree of independent period-2 to period-8 motions is presented. The bifurcations and stability of the corresponding periodic motions on the bifurcation tree are determined through eigenvalue analysis. The symmetry breaks of symmetric period-1 motions is determined by the saddle-node bifurcations, and the appearance of the independent bifurcation tree of period-2 motions to chaos is also due to the saddle-node bifurcations. Period-doubling cascaded scenario of period-2 to period-8 motions are predicted analytically, and unstable periodic motions are also obtained. Numerical simulations are performed to illustrate motion complexity in such a van der Pol–Duffing oscillator. Such nonlinear systems can be applied in nonlinear circuit design and fluid-induced oscillations.

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Robinson, J. A., A. Druet, and N. Gosset. "Video compression with binary tree recursive motion estimation and binary tree residue coding." IEEE Transactions on Image Processing 9, no. 7 (July 2000): 1288–92. http://dx.doi.org/10.1109/83.847841.

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McMahon, James, and Erion Plaku. "Robot motion planning with task specifications via regular languages." Robotica 35, no. 1 (June 17, 2015): 26–49. http://dx.doi.org/10.1017/s0263574715000417.

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SUMMARYThis paper presents an efficient approach for planning collision-free and dynamically feasible trajectories that enable a mobile robot to carry out tasks specified as regular languages over workspace regions. A sampling-based tree search is conducted over the feasible motions and over an abstraction obtained by combining the automaton representing the regular language with a workspace decomposition. The abstraction is used to partition the motion tree into equivalence classes and estimate the feasibility of reaching accepting automaton states from these equivalence classes. The partition is continually refined to discover new ways to expand the search. Comparisons to related work show significant speedups.

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Yang, M., H. Cui, and K. Tang. "Efficient tree structured motion estimation using successive elimination." IEE Proceedings - Vision, Image, and Signal Processing 151, no. 5 (2004): 369. http://dx.doi.org/10.1049/ip-vis:20040720.

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MARTONEN, T. B., Y. YANG, Z. Q. XUE, and Z. ZHANG. "MOTION OF AIR WITHIN THE HUMAN TRACHEOBRONCHIAL TREE." Particulate Science and Technology 12, no. 2 (April 1994): 175–88. http://dx.doi.org/10.1080/02726359408906649.

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Plaku, Evis, Erion Plaku, and Patricio Simari. "Clearance-driven motion planning for mobile robots with differential constraints." Robotica 36, no. 7 (February 27, 2018): 971–93. http://dx.doi.org/10.1017/s0263574718000164.

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SUMMARYThis paper presents an approach that integrates the geometric notion of clearance (distance to the closest obstacle) into sampling-based motion planning to enable a robot to safely navigate in challenging environments. To reach the goal destination, the robot must obey geometric and differential constraints that arise from the underlying motion dynamics and the characteristics of the environment. To produce safe paths, the proposed approach expands a motion tree of collision-free and dynamically feasible motions while maintaining locally maximal clearance. In distinction from related work, rather than explicitly constructing the medial axis, the proposed approach imposes a grid or a triangular tessellation over the free space and uses the clearance information to construct a weighted graph where edges that connect regions with low clearance have high cost. Minimum-cost paths over this graph produce high-clearance routes that tend to follow the medial axis without requiring its explicit construction. A key aspect of the proposed approach is a route-following component which efficiently expands the motion tree to closely follow such high-clearance routes. When expansion along the current route becomes difficult, edges in the tessellation are penalized in order to promote motion-tree expansions along alternative high-clearance routes to the goal. Experiments using vehicle models with second-order dynamics demonstrate that the robot is able to successfully navigate in complex environments. Comparisons to the state-of-the-art show computational speedups of one or more orders of magnitude.

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Woo, T. C., and D. Dutta. "Automatic Disassembly and Total Ordering in Three Dimensions." Journal of Engineering for Industry 113, no. 2 (May 1, 1991): 207–13. http://dx.doi.org/10.1115/1.2899679.

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Generating a sequence of motions for removing components in a three-dimensional assembly, one at a time, is considered—the robot motion being strictly translational. We map the boundary representation of a given assembly to a tree structure called Disassembly Tree (DT). Traversing the DT in pre- and post-order yields a minimal sequence of operations for disassembly and assembly, respectively. In this paper, an assembly is classified by the logical complexity of its DT (an ordered graph whose nodes are components of the given assembly) and by the geometric complexity of the nodes in DT (in terms of the number of motions needed to remove a single component). Next, whether a component can be removed in one motion is described as a predicate. This predicate is then used in an algorithm for constructing the DT. For a class of assemblies that exhibit total ordering, the algorithm decides whether each component can be removed in a single motion, by constructing a DT in O(N log N) time, on the average, where N is the total number of mating faces in the assembly.

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Scherbaum, Frank, Nicolas M. Kuehn, Matthias Ohrnberger, and Andreas Koehler. "Exploring the Proximity of Ground-Motion Models Using High-Dimensional Visualization Techniques." Earthquake Spectra 26, no. 4 (November 2010): 1117–38. http://dx.doi.org/10.1193/1.3478697.

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Logic trees have become a popular tool to capture epistemic uncertainties in seismic hazard analysis. They are commonly used by assigning weights to models on a purely descriptive basis (nominal scale). This invites the creation of unintended inconsistencies regarding the weights on the corresponding hazard curves. On the other hand, for human experts it is difficult to confidently express degrees-of-beliefs in particular numerical values. Here we demonstrate for ground-motion models how the model and the value-based perspectives can be partially reconciled by using high-dimensional information-visualization techniques. For this purpose we use Sammon's (1969) mapping and self-organizing mapping to project ground-motion models onto a two-dimensional map (an ordered metric set). Here they can be evaluated jointly according to their proximity in predicting similar ground motions, potentially making the assignment of logic tree weights consistent with their ground motion characteristics without having to abandon the model-based perspective.

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Huang, Jianzhe, and Albert C. J. Luo. "Periodic Motions and Bifurcation Trees in a Buckled, Nonlinear Jeffcott Rotor System." International Journal of Bifurcation and Chaos 25, no. 01 (January 2015): 1550002. http://dx.doi.org/10.1142/s0218127415500029.

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In this paper, analytical solutions for period-m motions in a buckled, nonlinear Jeffcott rotor system are obtained. This nonlinear Jeffcott rotor system with two-degrees of freedom is excited periodically from the rotor eccentricity. The analytical solutions of period-m solutions are developed, and the corresponding stability and bifurcation are also analyzed by eigenvalue analysis. Analytical bifurcation trees of period-1 motions to chaos are presented. The Hopf bifurcations of periodic motions cause not only the bifurcation tree but quasi-periodic motions. The quasi-periodic motion can be stable or unstable. Displacement orbits of periodic motions in the buckled, nonlinear Jeffcott rotor systems are illustrated, and harmonic amplitude spectrums are presented for harmonic effects on periodic motions of the nonlinear rotor. Coexisting periodic motions exist in such a buckled nonlinear Jeffcott rotor.

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Sakai, Toru, Emiru Birhane, Buruh Abebe, and Destaalem Gebremeskel. "Applicability of Structure-from-Motion Photogrammetry on Forest Measurement in the Northern Ethiopian Highlands." Sustainability 13, no. 9 (May 9, 2021): 5282. http://dx.doi.org/10.3390/su13095282.

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Ethiopia is one of the countries with the most degraded forest resources. Information on tree structure is needed at some points in the process to assess the appropriateness of forest management. The objectives are to examine whether the Structure from Motion (SfM)-based photogrammetry can be used to derive the forest structural parameters, and how the tree structural parameters can vary by location. In this study, the possible applicability of low-cost SfM-based photogrammetry was evaluated for forest management and conservation purposes in the Adi Zaboy watershed of the Northern Ethiopian highlands. In the watershed, dwarf Acacia etbaica was sparsely distributed. Consequently, the full three-dimensional point clouds of the individual trees were generated, which provided a wide variety of tree structural parameters in a non-destructive manner. The R2 values for tree height, canopy width, and stump diameter were 0.936, 0.891, and 0.808, respectively, and the corresponding RMSE values were 0.128 m, 0.331 m, and 0.886 cm. In addition, differences in forest structure and composition were caused by differences in the environment. The SfM-based photogrammetry would provide fundamental information to meet the demand of sustainable forest management from a morphological point of view, especially in forests of Ethiopian highlands.

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Guerra-Hernandez, Juan, Eduardo Gonzalez-Ferreiro, Alexandre Sarmento, João Silva, Alexandra Nunes, Alexandra Cristina Correia, Luis Fontes, Margarida Tomé, and Ramon Diaz-Varela. "Short Communication. Using high resolution UAV imagery to estimate tree variables in Pinus pinea plantation in Portugal." Forest Systems 25, no. 2 (July 20, 2016): eSC09. http://dx.doi.org/10.5424/fs/2016252-08895.

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Aim of study: The study aims to analyse the potential use of low‑cost unmanned aerial vehicle (UAV) imagery for the estimation of Pinus pinea L. variables at the individual tree level (position, tree height and crown diameter).Area of study: This study was conducted under the PINEA project focused on 16 ha of umbrella pine afforestation (Portugal) subjected to different treatments.Material and methods: The workflow involved: a) image acquisition with consumer‑grade cameras on board an UAV; b) orthomosaic and digital surface model (DSM) generation using structure-from-motion (SfM) image reconstruction; and c) automatic individual tree segmentation by using a mixed pixel‑ and region‑based based algorithm.Main results: The results of individual tree segmentation (position, height and crown diameter) were validated using field measurements from 3 inventory plots in the study area. All the trees of the plots were correctly detected. The RMSE values for the predicted heights and crown widths were 0.45 m and 0.63 m, respectively.Research highlights: The results demonstrate that tree variables can be automatically extracted from high resolution imagery. We highlight the use of UAV systems as a fast, reliable and cost‑effective technique for small scale applications.Keywords: Unmanned aerial systems (UAS); forest inventory; tree crown variables; 3D image modelling; canopy height model (CHM); object‑based image analysis (OBIA), structure‑from‑motion (SfM).

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Gülerce, Zeynep, N. A. Alipour, and M. A. Sandikkaya. "Ground Motion Characterization for Vertical Ground Motions in Turkey—Part 2: Vertical Ground Motion Models and the Final Logic Tree." Pure and Applied Geophysics 177, no. 5 (November 6, 2019): 2105–23. http://dx.doi.org/10.1007/s00024-019-02353-7.

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Armstrong, W. W., T. A. Marsland, M. Olafsson, and J. Schaeffer. "Solving Equations of Motion on a Virtual Tree Machine." SIAM Journal on Scientific and Statistical Computing 8, no. 1 (January 1987): s59—s72. http://dx.doi.org/10.1137/0908013.

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Lam, Tin Lun, and Yangsheng Xu. "Motion planning for tree climbing with inchworm-like robots." Journal of Field Robotics 30, no. 1 (July 3, 2012): 87–101. http://dx.doi.org/10.1002/rob.21431.

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Dupont, Sylvain, Pauline Défossez, Jean-Marc Bonnefond, Mark R. Irvine, and Didier Garrigou. "How stand tree motion impacts wind dynamics during windstorms." Agricultural and Forest Meteorology 262 (November 2018): 42–58. http://dx.doi.org/10.1016/j.agrformet.2018.06.022.

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Gvili, Yaniv, Aner Tal, Moty Amar, Yael Hallak, Brian Wansink, Michael Giblin, and Colombe Bommelaer. "Fresh from the tree: Implied motion improves food evaluation." Food Quality and Preference 46 (December 2015): 160–65. http://dx.doi.org/10.1016/j.foodqual.2015.07.015.

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Scheffler, C., K. H. Scheffler, and C. W. Omlin. "Articulated tree structure from motion—A matrix factorisation approach." SAIEE Africa Research Journal 96, no. 2 (June 2005): 93–98. http://dx.doi.org/10.23919/saiee.2005.9488090.

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Ali, Ahmad, and Ji Yeong Lee. "Integrated Motion Planning for Assembly Task with Part Manipulation Using Re-Grasping." Applied Sciences 10, no. 3 (January 21, 2020): 749. http://dx.doi.org/10.3390/app10030749.

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This paper presents an integrated planner based on rapidly exploring random tree (RRT) for an assembly task with possible re-grasping. Given multiple grasp poses for the part to assemble, the planner chooses candidate grasp poses considering the environment (including the partially finished assembly) in addition to the initial and final poses of the part. Orientation graph search based re-grasping approach is proposed for part manipulation which is needed when there is no feasible grasp solution for a part between its initial and final poses. Orientation graph search helps finding a series of the intermediate poses of the part needed between its initial and final poses so that robot can grasp and assemble it without interfering the pre-assembled parts. Then while extending the tree, the algorithm tries to connect the tree to a robot configuration with a chosen candidate grasp pose. Also, since the task space undergoes changes at each step of the assembly task, a node or edge in the tree can become in collision during the assembly of later parts, making the node in collision and its descendant nodes disconnected from the whole tree. To handle this, Two stage extended RRT strategy is proposed. The disconnected parts of the main tree are put into forest, and attempts are made to re-connect the tree in the forest to main tree while extending the main tree, thus making it possible to use the disconnected part again. The algorithm is implemented in Linux based system using C++. The proposed algorithm is demonstrated experimentally using UR5e robot manipulator by assembling the soma puzzle pieces in different 3D formations.

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Bartelt, Perry, Peter Bebi, Thomas Feistl, Othmar Buser, and Andrin Caviezel. "Dynamic magnification factors for tree blow-down by powder snow avalanche air blasts." Natural Hazards and Earth System Sciences 18, no. 3 (March 7, 2018): 759–64. http://dx.doi.org/10.5194/nhess-18-759-2018.

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Abstract. We study how short duration powder avalanche blasts can break and overturn tall trees. Tree blow-down is often used to back-calculate avalanche pressure and therefore constrain avalanche flow velocity and motion. We find that tall trees are susceptible to avalanche air blasts because the duration of the air blast is near to the period of vibration of tall trees, both in bending and root-plate overturning. Dynamic magnification factors for bending and overturning failures should therefore be considered when back-calculating avalanche impact pressures.

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Detwiler, Paul W., Christina B. Spetzler, Sara B. Taylor, Neil R. Crawford, Randall W. Porter, and Volker K. H. Sonntag. "Biomechanical comparison of facet-sparing laminectomy and Christmas tree laminectomy." Journal of Neurosurgery: Spine 99, no. 2 (September 2003): 214–20. http://dx.doi.org/10.3171/spi.2003.99.2.0214.

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Object. The authors compared differences in biomechanical stability between two decompressive laminectomy techniques for treating lumbar stenosis. A Christmas tree laminectomy (CTL), in which bilateral facetectomies and foraminotomies are performed, was compared with facet-sparing laminectomy (FSL), in which the facets are undercut but not resected. Spinal instability was assessed immediately postoperatively and again after discectomy to model long-term degeneration. Methods. Sixteen motion segments obtained from five human cadaveric lumbar specimens were studied in vitro by conducting nondestructive flexibility tests. Specimens were tested intact, after FSL or CTL, and again after discectomy. Nonconstraining torques (≤ 5 Nm) were applied to induce flexion, extension, axial rotation, and lateral bending; strings and pulleys were used while vertebral angles were measured. Anteroposterior translation in response to shear loading (≤ 100 N) was also measured. Angular motion, shear motion, and sagittal-plane axes of rotation were compared to evaluate stability. Compared with the intact condition, CTL-treated specimens had significantly larger increases in angular motion during flexion, lateral bending, and axial rotation than their FSL-treated counterparts (p < 0.05, nonpaired Student t-tests). Subsequent discectomy caused greater increases in motion in the CTL group. Axes of rotation shifted less from their normal positions after FSL than after CTL. Conclusions. This study provides objective evidence that the treatment of lumbar stenosis with FSL induces less biomechanical instability and alters kinematics less than FSL. These findings support the use of the FSL in treating lumbar stenosis.

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KOIKE, Ryotaro, and Motonori OTA. "Hierarchical Description of Complicated Structural Change in Protein with Motion Tree." Seibutsu Butsuri 55, no. 3 (2015): 142–44. http://dx.doi.org/10.2142/biophys.55.142.

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Hu, Xiao-yi, Wei-ming Tao, and Yi-mu Guo. "Using FEM to predict tree motion in a wind field." Journal of Zhejiang University-SCIENCE A 9, no. 7 (July 2008): 907–15. http://dx.doi.org/10.1631/jzus.a0720035.

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Le Gall, Jean-François, and Céline Abraham. "Excursion theory for Brownian motion indexed by the Brownian tree." Journal of the European Mathematical Society 20, no. 12 (September 12, 2018): 2951–3016. http://dx.doi.org/10.4171/jems/827.

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Journal articles on the topic 'Tree motion'

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