4 research outputs found
Contour Context: Abstract Structural Distribution for 3D LiDAR Loop Detection and Metric Pose Estimation
This paper proposes \textit{Contour Context}, a simple, effective, and
efficient topological loop closure detection pipeline with accurate 3-DoF
metric pose estimation, targeting the urban utonomous driving scenario. We
interpret the Cartesian birds' eye view (BEV) image projected from 3D LiDAR
points as layered distribution of structures. To recover elevation information
from BEVs, we slice them at different heights, and connected pixels at each
level will form contours. Each contour is parameterized by abstract
information, e.g., pixel count, center position, covariance, and mean height.
The similarity of two BEVs is calculated in sequential discrete and continuous
steps. The first step considers the geometric consensus of graph-like
constellations formed by contours in particular localities. The second step
models the majority of contours as a 2.5D Gaussian mixture model, which is used
to calculate correlation and optimize relative transform in continuous space. A
retrieval key is designed to accelerate the search of a database indexed by
layered KD-trees. We validate the efficacy of our method by comparing it with
recent works on public datasets.Comment: 7 pages, 7 figures, accepted by ICRA 202
G3Reg: Pyramid Graph-based Global Registration using Gaussian Ellipsoid Model
This study introduces a novel framework, G3Reg, for fast and robust global
registration of LiDAR point clouds. In contrast to conventional complex
keypoints and descriptors, we extract fundamental geometric primitives
including planes, clusters, and lines (PCL) from the raw point cloud to obtain
low-level semantic segments. Each segment is formulated as a unified Gaussian
Ellipsoid Model (GEM) by employing a probability ellipsoid to ensure the ground
truth centers are encompassed with a certain degree of probability. Utilizing
these GEMs, we then present a distrust-and-verify scheme based on a Pyramid
Compatibility Graph for Global Registration (PAGOR). Specifically, we establish
an upper bound, which can be traversed based on the confidence level for
compatibility testing to construct the pyramid graph. Gradually, we solve
multiple maximum cliques (MAC) for each level of the graph, generating numerous
transformation candidates. In the verification phase, we adopt a precise and
efficient metric for point cloud alignment quality, founded on geometric
primitives, to identify the optimal candidate. The performance of the algorithm
is extensively validated on three publicly available datasets and a
self-collected multi-session dataset, without changing any parameter settings
in the experimental evaluation. The results exhibit superior robustness and
real-time performance of the G3Reg framework compared to state-of-the-art
methods. Furthermore, we demonstrate the potential for integrating individual
GEM and PAGOR components into other algorithmic frameworks to enhance their
efficacy. To advance further research and promote community understanding, we
have publicly shared the source code.Comment: Under revie
Optimizing protein and lipid levels in practical diet for juvenile northern snakehead fish (Channa argus)
A 3 × 3 factorial feeding trial was conducted to evaluate the production response of juvenile northern snakehead fish (Channa argus). Nine diets containing 3 protein levels (45%, 48% and 51%) and 3 lipid levels (9%, 12% and 15%) were formulated and fed to triplicate groups of juvenile northern snakehead (15.78 ± 0.09 g/fish) for 8 weeks. The formulated diets were named as P45L9, P45L12, P45L15, P48L9, P48L12, P48L15, P51L9, P51L12 and P51L15 (P-Protein, L-Lipid), respectively. Fish fed diets with the lowest protein and lipid combination (P45L9) had the lowest growth performance. Weight gains (WG) of fish fed the 4 diets P48L12, P48L15, P51L9, and P51L12 were not significantly different (P > 0.05), but significantly higher (P 0.05) by dietary treatments. Based on these results, the diet containing 48% protein with either 12% or 15% lipid is the optimal for supporting growth and feed utilization of juvenile northern snakehead under the current testing conditions