190 research outputs found
Time-Dependent Density Matrix Renormalization Group Algorithms for Nearly Exact Absorption and Fluorescence Spectra of Molecular Aggregates at Both Zero and Finite Temperature
We implement and apply time-dependent density matrix renormalization group
(TD-DMRG) algorithms at zero and finite temperature to compute the linear
absorption and fluorescence spectra of molecular aggregates. Our implementation
is within a matrix product state/operator framework with an explicit treatment
of the excitonic and vibrational degrees of freedom, and uses the locality of
the Hamiltonian in the zero-exciton space to improve the efficiency and
accuracy of the calculations. We demonstrate the power of the method by
calculations on several molecular aggregate models, comparing our results
against those from multi-layer multiconfiguration time- dependent Hartree and
n-particle approximations. We find that TD-DMRG provides an accurate and
efficient route to calculate the spectrum of molecular aggregates.Comment: 10 figure
Different phase leads to different transport behavior in PbCu(PO)O compounds
The recent claimed room-temperature superconductivity in Cu-doped lead
apatite at ambient pressure are under highly debate. To identify its physical
origin, we studied the crystal structures, energy band structures, lattice
dynamics and magnetic properties of the parent Pb(PO)O compound,
in which two different phases of the LK-99 compound are analyzed in detail. Our
results show that the Pb(PO)O compound is an indirect band gap
semiconductor, where Cu doping at the 4 site of Pb leads to a semiconducting
to half-metallic transition. Two half-filled flat bands spanning the Fermi
energy levels are present in the 4-phase of LK-99, which are mainly formed
by hybridization of the and orbitals of Cu with the 2
orbitals of O. In addition, 6-phase of LK-99 always has spin polarity at the
bottom of the conduction band and at the top of the valence band, making the
material a bipolar magnetic semiconductor. Our results are basically consistent
with the recent experimental transport properties of LK-99 posted on
arXiv:2308.05778.Comment: 6 pages and 4 figure
Intention-Aware Planner for Robust and Safe Aerial Tracking
The intention of the target can help us to estimate its future motion state
more accurately. This paper proposes an intention-aware planner to enhance
safety and robustness in aerial tracking applications. Firstly, we utilize the
Mediapipe framework to estimate target's pose. A risk assessment function and a
state observation function are designed to predict the target intention.
Afterwards, an intention-driven hybrid A* method is proposed for target motion
prediction, ensuring that the target's future positions align with its
intention. Finally, an intention-aware optimization approach, in conjunction
with particular penalty formulations, is designed to generate a
spatial-temporal optimal trajectory. Benchmark comparisons validate the
superior performance of our proposed methodology across diverse scenarios. This
is attributed to the integration of the target intention into the planner
through coupled formulations.Comment: 7 pages, 10 figures, submitted to 2024 IEEE International Conference
on Robotics and Automation (ICRA
Object-based attention mechanism for color calibration of UAV remote sensing images in precision agriculture.
Color calibration is a critical step for unmanned aerial vehicle (UAV) remote sensing, especially in precision agriculture, which relies mainly on correlating color changes to specific quality attributes, e.g. plant health, disease, and pest stresses. In UAV remote sensing, the exemplar-based color transfer is popularly used for color calibration, where the automatic search for the semantic correspondences is the key to ensuring the color transfer accuracy. However, the existing attention mechanisms encounter difficulties in building the precise semantic correspondences between the reference image and the target one, in which the normalized cross correlation is often computed for feature reassembling. As a result, the color transfer accuracy is inevitably decreased by the disturbance from the semantically unrelated pixels, leading to semantic mismatch due to the absence of semantic correspondences. In this article, we proposed an unsupervised object-based attention mechanism (OBAM) to suppress the disturbance of the semantically unrelated pixels, along with a further introduced weight-adjusted Adaptive Instance Normalization (AdaIN) (WAA) method to tackle the challenges caused by the absence of semantic correspondences. By embedding the proposed modules into a photorealistic style transfer method with progressive stylization, the color transfer accuracy can be improved while better preserving the structural details. We evaluated our approach on the UAV data of different crop types including rice, beans, and cotton. Extensive experiments demonstrate that our proposed method outperforms several state-of-the-art methods. As our approach requires no annotated labels, it can be easily embedded into the off-the-shelf color transfer approaches. Relevant codes and configurations will be available at https://github.com/huanghsheng/object-based-attention-mechanis
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