2,716 research outputs found
Straight-line path following for asymmetric unmanned platform with disturbance estimation
The problem of straight-line path following for asymmetric unmanned platform exposed to unknown disturbances was addressed in this paper. The mathematical model of asymmetric unmanned platform was established and the inputs in sway and yaw directions were decoupled, which facilitated the establishment of control strategy of path following. The guidance law and the cross-track error were derived from the classical line-of-sight (LOS) guidance principle. And the equilibrium point of the cross-track error was proven to be uniformly semiglobally exponentially stable (USGES), which guaranteed the exponential convergence to zero. A new disturbance estimation law was developed by adding a linear item of the estimation error into the classical one, which improved the principleâs precision and sensitivity dramatically. The control strategy was developed based on the integrator backstepping technique and the new disturbance estimation law, which made the equilibrium system to be uniformly globally asymptotically stable (UGAS). Computer simulations were conducted to verify the effectiveness of the estimation and control laws during straight-line path following for asymmetric unmanned platform in the presence of unknown disturbances
ERNIE-ViL 2.0: Multi-view Contrastive Learning for Image-Text Pre-training
Recent Vision-Language Pre-trained (VLP) models based on dual encoder have
attracted extensive attention from academia and industry due to their superior
performance on various cross-modal tasks and high computational efficiency.
They attempt to learn cross-modal representation using contrastive learning on
image-text pairs, however, the built inter-modal correlations only rely on a
single view for each modality. Actually, an image or a text contains various
potential views, just as humans could capture a real-world scene via diverse
descriptions or photos. In this paper, we propose ERNIE-ViL 2.0, a Multi-View
Contrastive learning framework to build intra-modal and inter-modal
correlations between diverse views simultaneously, aiming at learning a more
robust cross-modal representation. Specifically, we construct multiple views
within each modality to learn the intra-modal correlation for enhancing the
single-modal representation. Besides the inherent visual/textual views, we
construct sequences of object tags as a special textual view to narrow the
cross-modal semantic gap on noisy image-text pairs. Pre-trained with 29M
publicly available datasets, ERNIE-ViL 2.0 achieves competitive results on
English cross-modal retrieval. Additionally, to generalize our method to
Chinese cross-modal tasks, we train ERNIE-ViL 2.0 through scaling up the
pre-training datasets to 1.5B Chinese image-text pairs, resulting in
significant improvements compared to previous SOTA results on Chinese
cross-modal retrieval. We release our pre-trained models in
https://github.com/PaddlePaddle/ERNIE.Comment: 14 pages, 6 figure
(E)-Benzaldehyde (2,4,6-trichloroÂphenÂyl)hydrazone
The title compound, C13H9Cl3N2, was obtained from a condensation reaction of benzaldehyde and 2,4,6-trichloroÂphenylÂhydrazine. The molÂecule assumes an E configuration with the phenyl ring and trichloroÂphenyl ring located on opposite sides of the C=N bond. The phenyl ring is oriented at a dihedral angle of 42.58â
(12)° with respect to the tricholorophenyl ring. In the crystal, the molÂecules are linked via NâHâŻN hydrogen bonds, forming supraÂmolecular chains running along the c axis. ÏâÏ stacking is present between parallel trichloroÂphenyl rings of adjacent molÂecules, the face-to-face and centroidâcentroid distances being 3.369â
(14) and 3.724â
(2)â
Ă
, respectively
Analysis of bacterial diversity in two oil blocks from two low-permeability reservoirs with high salinities
The community diversities of two oil reservoirs with low permeability of 1.81 x 10 \u273 and 2.29 x 10 \u273 1/4m 2 in Changqing, China, were investigated using a high throughput sequencing technique to analyze the influence of biostimulation with a nutrient activator on the bacterial communities. These two blocks differed significantly in salinity (average 17,500 vs 40,900 mg/L). A core simulation test was used to evaluate the effectiveness of indigenous microbial-enhanced oil recovery (MEOR). The results indicated that in the two high salinity oil reservoirs, one reservoir having relatively lower salinity level and a narrow salinity range had higher bacterial and phylogenetic diversity. The addition of the nutrient activator increased the diversity of the bacterial community structure and the diversity differences between the two blocks. The results of the core simulation test showed that the bacterial community in the reservoir with a salinity level of 17,500 mg/L did not show significant higher MEOR efficiency compared with the reservoir with 40,900 mg/L i.e. MEOR efficiency of 8.12% vs 6.56% (test p = 0.291 \u3e 0.05). Therefore, salinity levels affected the bacterial diversities in the two low permeability oil blocks remarkably. But the influence of salinity for the MEOR recovery was slightly
ERNIE-UniX2: A Unified Cross-lingual Cross-modal Framework for Understanding and Generation
Recent cross-lingual cross-modal works attempt to extend Vision-Language
Pre-training (VLP) models to non-English inputs and achieve impressive
performance. However, these models focus only on understanding tasks utilizing
encoder-only architecture. In this paper, we propose ERNIE-UniX2, a unified
cross-lingual cross-modal pre-training framework for both generation and
understanding tasks. ERNIE-UniX2 integrates multiple pre-training paradigms
(e.g., contrastive learning and language modeling) based on encoder-decoder
architecture and attempts to learn a better joint representation across
languages and modalities. Furthermore, ERNIE-UniX2 can be seamlessly fine-tuned
for varieties of generation and understanding downstream tasks. Pre-trained on
both multilingual text-only and image-text datasets, ERNIE-UniX2 achieves SOTA
results on various cross-lingual cross-modal generation and understanding tasks
such as multimodal machine translation and multilingual visual question
answering.Comment: 13 pages, 2 figure
Trace amounts of copper induce neurotoxicity in the cholesterol-fed mice through apoptosis
AbstractEvidence has been gathered to suggest that trace amounts of copper induce neurotoxicity by interaction with elevated cholesterol in diet. Copper treatment alone showed no significant learning and memory impairments in behavioral tasks. However, copper-induced neurotoxicity was significantly increased in mice given elevated-cholesterol diet. Trace amounts of copper decreased the activity of SOD and increased the level of malondialdehyde (MDA) in the brain of cholesterol-fed mouse. Copper also caused an increase in amyloid precursor protein (APP) mRNA level and the activation of caspase-3 in the brain of cholesterol-fed mice. The apoptosis-induced nuclear DNA fragmentation was detected in the brain of those mice by terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end-labeling staining. These findings suggest that trace amounts of copper induce neurotoxicity in cholesterol-fed mice through apoptosis caused by oxidative stress
Bubble in the Whale: Identifying the Optical Counterparts and Extended Nebula for the Ultraluminous X-ray Sources in NGC 4631
We present a deep optical imaging campaign on the starburst galaxy NGC 4631
with CFHT/MegaCam. By supplementing the HST/ACS and Chandra/ACIS archival data,
we search for the optical counterpart candidates of the five brightest X-ray
sources in this galaxy, four of which are identified as ultraluminous X-ray
sources (ULXs). The stellar environments of the X-ray sources are analyzed
using the extinction-corrected color-magnitude diagrams and the isochrone
models. We discover a highly asymmetric bubble nebula around X4 which exhibits
different morphology in the H and [O III] images. The [O III]/H
ratio map shows that the H-bright bubble may be formed mainly via the
shock ionization by the one-sided jet/outflow, while the more compact [O III]
structure is photoionized by the ULX. We constrain the bubble expansion
velocity and interstellar medium density with the MAPPINGS V code, and hence
estimate the mechanical power injected to the bubble as erg s and the corresponding bubble age of yr. Relativistic jets are needed to provide such level of mechanical
power with a mass-loss rate of . Besides
the accretion, the black hole spin is likely an additional energy source for
the super-Eddington jet power.Comment: 17 pages, 10 figures, accepted by Ap
A controllable superconducting electromechanical oscillator with a suspended membrane
We fabricate a microscale electromechanical system, in which a suspended
superconducting membrane, treated as a mechanical oscillator, capacitively
couples to a superconducting microwave resonator. As the microwave driving
power increases, nonmonotonic dependence of the resonance frequency of the
mechanical oscillator on the driving power has been observed. We also
demonstrate the optical switching of the resonance frequency of the mechanical
oscillator. Theoretical models for qualitative understanding of our
experimental observations are presented. Our experiment may pave the way for
the application of a mechanical oscillator with its resonance frequency
controlled by the electromagnetic and/or optical fields, such as a
microwave-optical interface and a controllable element in a
superqubit-mechanical oscillator hybrid system.Comment: 8 pages,4 figure
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