1,175 research outputs found
Solvable 3-Lie algebras with a maximal hypo-nilpotent ideal N
This paper obtains all solvable 3-Lie algebras with the m-dimensional filiform 3-Lie algebra N (m >= 5) as a maximal hypo-nilpotent ideal, and proves that the m-dimensional filiform 3-Lie algebra N can't be as the nilradical of solvable non-nilpotent 3-Lie algebras. By means of one dimensional extension of Lie algebras to the 3-Lie algebras, we get some classes of solvable Lie algebras directly
LineMarkNet: Line Landmark Detection for Valet Parking
We aim for accurate and efficient line landmark detection for valet parking,
which is a long-standing yet unsolved problem in autonomous driving. To this
end, we present a deep line landmark detection system where we carefully design
the modules to be lightweight. Specifically, we first empirically design four
general line landmarks including three physical lines and one novel mental
line. The four line landmarks are effective for valet parking. We then develop
a deep network (LineMarkNet) to detect line landmarks from surround-view
cameras where we, via the pre-calibrated homography, fuse context from four
separate cameras into the unified bird-eye-view (BEV) space, specifically we
fuse the surroundview features and BEV features, then employ the multi-task
decoder to detect multiple line landmarks where we apply the center-based
strategy for object detection task, and design our graph transformer to enhance
the vision transformer with hierarchical level graph reasoning for semantic
segmentation task. At last, we further parameterize the detected line landmarks
(e.g., intercept-slope form) whereby a novel filtering backend incorporates
temporal and multi-view consistency to achieve smooth and stable detection.
Moreover, we annotate a large-scale dataset to validate our method.
Experimental results show that our framework achieves the enhanced performance
compared with several line detection methods and validate the multi-task
network's efficiency about the real-time line landmark detection on the
Qualcomm 820A platform while meantime keeps superior accuracy, with our deep
line landmark detection system.Comment: 29 pages, 12 figure
3-Lie algebras with an ideal N
AbstractWe define the hypo-nilpotent ideal in n-Lie algebras and obtain all solvable 3-Lie algebras with an m-dimensional simplest filiform 3-Lie algebra as a maximal hypo-nilpotent ideal. We prove that the dimension of such solvable 3-Lie algebras is at most m+2, and there is no solvable 3-Lie algebra with the simplest filiform 3-Lie algebra as the nilradical
Search for ultralight dark matter with a frequency adjustable diamagnetic levitated sensor
Among several dark matter candidates, bosonic ultralight (sub meV) dark
matter is well motivated because it could couple to the Standard Model (SM) and
induce new forces. Previous MICROSCOPE and Eot Wash torsion experiments have
achieved high accuracy in the sub-1 Hz region, but at higher frequencies there
is still a lack of relevant experimental research. We propose an experimental
scheme based on the diamagnetic levitated micromechanical oscillator, one of
the most sensitive sensors for acceleration sensitivity below the kilohertz
scale. In order to improve the measurement range, we used the sensor whose
resonance frequency could be adjusted from 0.1Hz to 100Hz. The limits of the
coupling constant are improved by more than 10 times compared to previous
reports, and it may be possible to achieve higher accuracy by using the array
of sensors in the future
Convex Hull-Based Multi-objective Genetic Programming for Maximizing ROC Performance
ROC is usually used to analyze the performance of classifiers in data mining.
ROC convex hull (ROCCH) is the least convex major-ant (LCM) of the empirical
ROC curve, and covers potential optima for the given set of classifiers.
Generally, ROC performance maximization could be considered to maximize the
ROCCH, which also means to maximize the true positive rate (tpr) and minimize
the false positive rate (fpr) for each classifier in the ROC space. However,
tpr and fpr are conflicting with each other in the ROCCH optimization process.
Though ROCCH maximization problem seems like a multi-objective optimization
problem (MOP), the special characters make it different from traditional MOP.
In this work, we will discuss the difference between them and propose convex
hull-based multi-objective genetic programming (CH-MOGP) to solve ROCCH
maximization problems. Convex hull-based sort is an indicator based selection
scheme that aims to maximize the area under convex hull, which serves as a
unary indicator for the performance of a set of points. A selection procedure
is described that can be efficiently implemented and follows similar design
principles than classical hyper-volume based optimization algorithms. It is
hypothesized that by using a tailored indicator-based selection scheme CH-MOGP
gets more efficient for ROC convex hull approximation than algorithms which
compute all Pareto optimal points. To test our hypothesis we compare the new
CH-MOGP to MOGP with classical selection schemes, including NSGA-II, MOEA/D)
and SMS-EMOA. Meanwhile, CH-MOGP is also compared with traditional machine
learning algorithms such as C4.5, Naive Bayes and Prie. Experimental results
based on 22 well-known UCI data sets show that CH-MOGP outperforms
significantly traditional EMOAs
Numerical analysis of underwater flow past columnar projectile with different cross-sections at high Reynolds numbers
Based on Detached Eddy Simulation (DES) technique, the flow around a columnar projectile with different cross-section shapes in the supercritical and extremely supercritical region is simulated by the Fluent. The cross-section of the projectile is regular polygon, which number of edges is 4, 6, 8, 10, 12, 24 and ∞, where ∞ means a circle. The vortex shedding pattern and flow field characteristics are analyzed at Reynolds number 2.5×105 to 2×107. Regarding circular cylinder projectile, when the flow velocity changes from 25 m/s to 200 m/s, the average drag coefficient decreases, and the St Number increases. Regarding regular polygon, when the number of edges for polygon changes from 4 to ∞ at flow velocity 50 m/s, the average drag coefficient decreases, and the St Number increases. The average lift coefficient is almost equal to zero and does not change with the flow velocity and the cross-section. The pressure coefficient Cp of 4-prism, 6-prism, 8-prism, 12-prism and 24-prism has multiple local minimum values at the polygon vertices of the cross section. According to the spectrum analysis, the vortex shedding frequency of 4-prism, 24-prism and cylindrical is single and fixed, so the projectile may cause resonance and deviates from a predetermined trajectory. But for the 6-prism and 8-prism and 12-prism, the cl and cd is multi-periodic vibration. So, considering the flow induced structural vibrations, drag, the power of shrapnel and manufacturing cost, the 8-prism are better choices for cluster warhead underwater in engineering design
3-[(2-HydroxyÂethyl)iminoÂmethÂyl]-1,1′-bi-2-naphthol
In the title compound, C23H19NO3, there is an intraÂmolecular O—H⋯N hydrogen bond, which forms a six-membered ring, and interÂmolecular O—H⋯O hydrogen bonds stabilize the crystal structure
PPD: A New Valet Parking Pedestrian Fisheye Dataset for Autonomous Driving
Pedestrian detection under valet parking scenarios is fundamental for
autonomous driving. However, the presence of pedestrians can be manifested in a
variety of ways and postures under imperfect ambient conditions, which can
adversely affect detection performance. Furthermore, models trained on
publicdatasets that include pedestrians generally provide suboptimal outcomes
for these valet parking scenarios. In this paper, wepresent the Parking
Pedestrian Dataset (PPD), a large-scale fisheye dataset to support research
dealing with real-world pedestrians, especially with occlusions and diverse
postures. PPD consists of several distinctive types of pedestrians captured
with fisheye cameras. Additionally, we present a pedestrian detection baseline
on PPD dataset, and introduce two data augmentation techniques to improve the
baseline by enhancing the diversity ofthe original dataset. Extensive
experiments validate the effectiveness of our novel data augmentation
approaches over baselinesand the dataset's exceptional generalizability.Comment: 9 pages, 6 figure
A review on hydrodynamics of free surface flows in emergent vegetated channels
YesThis review paper addresses the structure of the mean flow and key turbulence quantities in free-surface flows with emergent vegetation. Emergent vegetation in open channel flow affects turbulence, flow patterns, flow resistance, sediment transport, and morphological changes. The last 15 years have witnessed significant advances in field, laboratory, and numerical investigations of turbulent flows within reaches of different types of emergent vegetation, such as rigid stems, flexible stems, with foliage or without foliage, and combinations of these. The influence of stem diameter, volume fraction, frontal area of stems, staggered and non-staggered arrangements of stems, and arrangement of stems in patches on mean flow and turbulence has been quantified in different research contexts using different instrumentation and numerical strategies. In this paper, a summary of key findings on emergent vegetation flows is offered, with particular emphasis on: (1) vertical structure of flow field, (2) velocity distribution, 2nd order moments, and distribution of turbulent kinetic energy (TKE) in horizontal plane, (3) horizontal structures which includes wake and shear flows and, (4) drag effect of emergent vegetation on the flow. It can be concluded that the drag coefficient of an emergent vegetation patch is proportional to the solid volume fraction and average drag of an individual vegetation stem is a linear function of the stem Reynolds number. The distribution of TKE in a horizontal plane demonstrates that the production of TKE is mostly associated with vortex shedding from individual stems. Production and dissipation of TKE are not in equilibrium, resulting in strong fluxes of TKE directed outward the near wake of each stem. In addition to Kelvin–Helmholtz and von Kármán vortices, the ejections and sweeps have profound influence on sediment dynamics in the emergent vegetated flows
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