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1. Recreating Bat Behavior on Quad-Rotor UAVs—A Simulation Approach

   Tanveer, M. H. ; Thomas, A. ; Wu, X. ; Mueller, R. ; Tokekar, P. ; Zhu, H. ( January 2020 , The Thirty-Third International FLAIRS Conference (FLAIRS-33))

   We develop an effective computer model to simulate sensing environments that consist of natural trees. The simulated environments are random and contain full geometry of the tree foliage. While this simulated model can be used as a general platform for studying the sensing mechanism of different flying species, our ultimate goal is to build bat-inspired Quad-rotor UAVs—UAVs that can recreate bat’s flying behavior (e.g., obstacle avoidance, path planning) in dense vegetation. To this end, we also introduce an foliage echo simulator that can produce simulated echoes by mimicking bat’s biosonar. In our current model, a few realistic model choices ormore »assumptions are made. First, in order to create natural looking trees, the branching structures of trees are modeled by L-systems, whereas the detailed geometry of branches, subbranches and leaves is created by randomizing a reference tree in a CAD object file. Additionally, the foliage echo simulator is simplified so that no shading effect is considered. We demonstrate our developed model by simulating real-world scenarios with multiple trees and compute the corresponding impulse responses along a Quad-rotor trajectory.« less
2. Fast Simulation of Trees and Forests for Bat-inspired Sonar Sensing

   https://doi.org/10.1109/ICICT55905.2022.00041  

   Wahed, M. ; Islam, M. ; Wu, X. ; Zhu, H. ( May 2022 , 2022 5th International Conference on Information and Computer Technologies (ICICT))

   To study the sensing mechanism of bat's biosonar system, we propose a fast simulation algorithm to generate natural-looking trees and forest---the primary living habitat of bats. We adopt 3D Lindenmayer system to create the fractal geometry of the trees, and add additional parameters, both globally and locally, to enable random variations of the tree structures. Random forest is then formed by placing simulated trees at random locations of a field according to a spatial point process. By employing a single algorithmic model with different numeric parameters, we can rapidly simulate 3D virtual environments with a wide variety of trees, producingmore »detailed geometry of the foliage such as the leaf locations, sizes, and orientations. Written in C++ and visualized with openGL, our algorithm is fast to implement, easily parallable, and more adaptive to real-time visualization compared with existing alternative approaches. Our simulated environment can be used for general purposes such as studying new sensors or training remote sensing algorithms.« less
3. Echo interval and not echo intensity drives bat flight behavior in structured corridors

   https://doi.org/doi:10.1242/jeb.191155  

   Warnecke, M. ; Macias, S. ; Falk, B. ; Moss, C.F. ( October 2018 , Journal of experimental biology)

   To navigate in the natural environment, animals must adapt their locomotion in response to environmental stimuli. The echolocating bat relies on auditory processing of echo returns to represent its surroundings. Recent studies have shown that echo flow patterns influence bat navigation, but the acoustic basis for flight path selection remains unknown. To investigate this problem, we released bats in a flight corridor with walls constructed of adjacent individual wooden poles, which returned cascades of echoes to the flying bat. We manipulated the spacing and echo strength of the poles comprising each corridor side, and predicted that bats would adapt theirmore »flight paths to deviate toward the corridor side returning weaker echo cascades. Our results show that the bat’s trajectory through the corridor was not affected by the intensity of echo cascades. Instead, bats deviated toward the corridor wall with more sparsely spaced, highly reflective poles, suggesting that pole spacing, rather than echo intensity, influenced bat flight path selection. This result motivated investigation of the neural processing of echo cascades. We measured local evoked auditory responses in the bat inferior colliculus to echo playback recordings from corridor walls constructed of sparsely and densely spaced poles. We predicted that evoked neural responses would be discretely modulated by temporally distinct echoes recorded from the sparsely spaced pole corridor wall, but not by echoes from the more densely spaced corridor wall. The data confirm this prediction and suggest that the bat’s temporal resolution of echo cascades may drive its flight behavior in the corridor.« less
4. Simulate Forest Trees by Integrating L-System and 3D CAD Files

   Tanveer, M. H. ; Thomas, A. ; Wu, X. ; Zhu, H. ( January 2020 , 2020 3rd International Conference on Information and Computer Technologies (ICICT))

   In this article, we propose a new approach for simulating trees, including their branches, sub-branches, and leaves. This approach combines the theory of biological development, mathematical models, and computer graphics, producing simulated trees and forest with full geometry. Specifically, we adopt the Lindenmayer process to simulate the branching pattern of trees and modify the available measurements and dimensions of 3D CAD developed object files to create natural looking sub-branches and leaves. Randomization has been added to the placement of all branches, sub branches and leaves. To simulate a forest, we adopt Inhomogeneous Poisson process to generate random locations of trees.more »Our approach can be used to create complex structured 3D virtual environment for the purpose of testing new sensors and training robotic algorithms. We look forward to applying this approach to test biosonar sensors that mimick bats' fly in the simulated environment.« less
5. Diversity, taxonomic composition, and functional aspects of fungal communities in living, senesced, and fallen leaves at five sites across North America

   https://doi.org/10.7717/peerj.2768  

   U’Ren, Jana M. ; Arnold, A. Elizabeth ( December 2016 , PeerJ)

   Fungal endophytes inhabit symptomless, living tissues of all major plant lineages to form one of earth’s most prevalent groups of symbionts. Many reproduce from senesced and/or decomposing leaves and can produce extracellular leaf-degrading enzymes, blurring the line between symbiotrophy and saprotrophy. To better understand the endophyte–saprotroph continuum we compared fungal communities and functional traits of focal strains isolated from living leaves to those isolated from leaves after senescence and decomposition, with a focus on foliage of woody plants in five biogeographic provinces ranging from tundra to subtropical scrub forest.

   We cultured fungi from the interior of surface-sterilized leaves that weremore »living at the time of sampling (i.e., endophytes), leaves that were dead and were retained in plant canopies (dead leaf fungi, DLF), and fallen leaves (leaf litter fungi, LLF) from 3–4 species of woody plants in each of five sites in North America. Our sampling encompassed 18 plant species representing two families of Pinophyta and five families of Angiospermae. Diversity and composition of fungal communities within and among leaf life stages, hosts, and sites were compared using ITS-partial LSU rDNA data. We evaluated substrate use and enzyme activity by a subset of fungi isolated only from living tissues vs. fungi isolated only from non-living leaves.

   Across the diverse biomes and plant taxa surveyed here, culturable fungi from living leaves were isolated less frequently and were less diverse than those isolated from non-living leaves. Fungal communities in living leaves also differed detectably in composition from communities in dead leaves and leaf litter within focal sites and host taxa, regardless of differential weighting of rare and abundant fungi. All focal isolates grew on cellulose, lignin, and pectin as sole carbon sources, but none displayed ligninolytic or pectinolytic activityin vitro. Cellulolytic activity differed among fungal classes. Within Dothideomycetes, activity differed significantly between fungi from living vs. non-living leaves, but such differences were not observed in Sordariomycetes.

   Although some fungi with endophytic life stages clearly persist for periods of time in leaves after senescence and incorporation into leaf litter, our sampling across diverse biomes and host lineages detected consistent differences between fungal assemblages in living vs. non-living leaves, reflecting incursion by fungi from the leaf exterior after leaf death and as leaves begin to decompose. However, fungi found only in living leaves do not differ consistently in cellulolytic activity from those fungi detected thus far only in dead leaves. Future analyses should consider Basidiomycota in addition to the Ascomycota fungi evaluated here, and should explore more dimensions of functional traits and persistence to further define the endophytism-to-saprotrophy continuum.

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