428 research outputs found
Structural investigations of chloranilic acid pyrazine cocrystal and ferroelectric 2-methylbenzimidazole
The purpose of the project was to determine the crystal structures at variable temperatures and investigate the potential structural phase transitions in chloranilic acid pyrazine cocrystal and single-component ferroelectric 2-methylbenzimidazole. The crystal structure of chloranilic acid pyrazine at 120 K was triclinic, P-1, with a=4.7684(2) Å, b=5.8402(3) Å, c=10.6897(5) Å, α=82.038(4)°, β=81.568(4)°, γ=76.938(4)°. It undergoes a phase transition from monoclinic space group C2/m to triclinic space group P-1. We used ideas of rigid bodies and distortion-mode amplitudes to understand what drives the phase transition. The crystal structure of 2-methylbenzimidazole was explored by variable temperature powder and single crystal X-ray diffraction, as well as by variable temperature solid-state NMR and proton spectra calculations. The crystal structure did not change between 120 K and 400 K and was likely to be monoclinic space group Pn
VisFusion: Visibility-aware Online 3D Scene Reconstruction from Videos
We propose VisFusion, a visibility-aware online 3D scene reconstruction
approach from posed monocular videos. In particular, we aim to reconstruct the
scene from volumetric features. Unlike previous reconstruction methods which
aggregate features for each voxel from input views without considering its
visibility, we aim to improve the feature fusion by explicitly inferring its
visibility from a similarity matrix, computed from its projected features in
each image pair. Following previous works, our model is a coarse-to-fine
pipeline including a volume sparsification process. Different from their works
which sparsify voxels globally with a fixed occupancy threshold, we perform the
sparsification on a local feature volume along each visual ray to preserve at
least one voxel per ray for more fine details. The sparse local volume is then
fused with a global one for online reconstruction. We further propose to
predict TSDF in a coarse-to-fine manner by learning its residuals across scales
leading to better TSDF predictions. Experimental results on benchmarks show
that our method can achieve superior performance with more scene details. Code
is available at: https://github.com/huiyu-gao/VisFusionComment: CVPR 202
SIDE: Self-supervised Intermediate Domain Exploration for Source-free Domain Adaptation
Domain adaptation aims to alleviate the domain shift when transferring the
knowledge learned from the source domain to the target domain. Due to privacy
issues, source-free domain adaptation (SFDA), where source data is unavailable
during adaptation, has recently become very demanding yet challenging. Existing
SFDA methods focus on either self-supervised learning of target samples or
reconstruction of virtual source data. The former overlooks the transferable
knowledge in the source model, whilst the latter introduces even more
uncertainty. To address the above issues, this paper proposes self-supervised
intermediate domain exploration (SIDE) that effectively bridges the domain gap
with an intermediate domain, where samples are cyclically filtered out in a
self-supervised fashion. First, we propose cycle intermediate domain filtering
(CIDF) to cyclically select intermediate samples with similar distributions
over source and target domains. Second, with the aid of those intermediate
samples, an inter-domain gap transition (IDGT) module is developed to mitigate
possible distribution mismatches between the source and target data. Finally,
we introduce cross-view consistency learning (CVCL) to maintain the intrinsic
class discriminability whilst adapting the model to the target domain.
Extensive experiments on three popular benchmarks, i.e. Office-31, Office-Home
and VisDA-C, show that our proposed SIDE achieves competitive performance
against state-of-the-art methods.Comment: code at https://github.com/se111/SID
Nonlinear vibrations of beams with spring and damping delayed feedback control
The primary, subharmonic, and superharmonic resonances of an Euler–Bernoulli beam subjected to harmonic excitations are studied with damping and spring delayed-feedback controllers. By method of multiple scales, the non-linear governing partial differential equation is transformed into linear differential equations directly. Effects of the feedback gains and time-delays on the steady state responses are investigated. The velocity and displacement delayed-feedback controllers are employed to suppress the primary and superharmonic resonances of the forced nonlinear oscillator. The stable vibration regions of the feedback gains and time-delays are worked out based on stablility conditions of the resonances. It is found that proper selection of feedback gains and time-delays can enhance the control performance of beam’s nonlinear vibration. Position of the bifurcation point can be changed or the bifurcation can be eliminated
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