241 research outputs found
LivePhoto: Real Image Animation with Text-guided Motion Control
Despite the recent progress in text-to-video generation, existing studies
usually overlook the issue that only spatial contents but not temporal motions
in synthesized videos are under the control of text. Towards such a challenge,
this work presents a practical system, named LivePhoto, which allows users to
animate an image of their interest with text descriptions. We first establish a
strong baseline that helps a well-learned text-to-image generator (i.e., Stable
Diffusion) take an image as a further input. We then equip the improved
generator with a motion module for temporal modeling and propose a carefully
designed training pipeline to better link texts and motions. In particular,
considering the facts that (1) text can only describe motions roughly (e.g.,
regardless of the moving speed) and (2) text may include both content and
motion descriptions, we introduce a motion intensity estimation module as well
as a text re-weighting module to reduce the ambiguity of text-to-motion
mapping. Empirical evidence suggests that our approach is capable of well
decoding motion-related textual instructions into videos, such as actions,
camera movements, or even conjuring new contents from thin air (e.g., pouring
water into an empty glass). Interestingly, thanks to the proposed intensity
learning mechanism, our system offers users an additional control signal (i.e.,
the motion intensity) besides text for video customization.Comment: Project page: https://xavierchen34.github.io/LivePhoto-Page
Legacy halogenated organic contaminants in urban-influenced waters using passive polyethylene samplers: Emerging evidence of anthropogenic land-use-based sources and ecological risks
Legacy halogenated organic pollutants, including organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs), remain ubiquitous in the environment and continue to pose potential (eco-)toxicological threats because of their ongoing releases from land-based sources. This study investigated the spatial trends of freely dissolved PCBs and OCPs by polyethylene passive samplers, and provided evidence of their land-use-based sources and ecological risk in an urbanized estuary area of Narragansett Bay. Dissolved Σ29PCB concentrations ranged from 0.01 to 1.37 ng L−1, and exhibited higher concentrations in the upper, more urban/built-up watershed, and in north coastal areas. Major inputs of PCBs were urban stormwater or treated wastewater that might carry past releases of Aroclors, pigment manufacturing byproducts, and volatilization-associated PCBs from ageing buildings from the Narragansett watershed to the bay. The dioxin toxicity equivalent values of Σ5PCBs were 8.6E-03 pg L−1 in water. Dissolved OCP concentrations had similar spatial trends to PCBs and were dominated by DDTs (average 230 pg L−1), followed by chlordanes (average 230 pg L−1), and HCB (average 22 pg L−1). Secondary sources of past usage and historic contamination were expected to re-enter the surface water via atmospheric transport and deposition. The risk quotients of DDE, DDD, DDT and α-Endosulfane showed medium to high ecological risks in the northern area, while chlordane, HCB, oxychlordane, and heptachlor epoxide showed low to negligible risks in all zones. This study presented new insights into the presence, sources and transport of legacy halogenated organic contaminants in an urban estuary\u27s watershed by combining passive samplers and geographic information system (GIS) technology. The approach is promising and could be extended to get better understand of terrestrial pollutant mobilization into estuaries affected by anthropogenic activities
Tetragonal Mexican-Hat Dispersion and Switchable Half-Metal State with Multiple Anisotropic Weyl Fermions in Penta-Graphene
In past decades, the ever-expanding library of 2D carbon allotropes has
yielded a broad range of exotic properties for the future carbon-based
electronics. However, the known allotropes are all intrinsic nonmagnetic due to
the paired valence electrons configuration. Based on the reported 2D carbon
structure database and first-principles calculations, herein we demonstrate
that inherent ferromagnetism can be obtained in the prominent allotrope,
penta-graphene, which has an unique Mexican-hat valence band edge, giving rise
to van Hove singularities and electronic instability. Induced by modest
hole-doping, being achievable in electrolyte gate, the semiconducting
pentagraphene can transform into different ferromagnetic half-metals with room
temperature stability and switchable spin directions. In particular, multiple
anisotropic Weyl states, including type-I and type-II Weyl cones and hybrid
quasi Weyl nodal loop, can be found in a sizable energy window of spin-down
half-metal under proper strains. These findings not only identify a promising
carbon allotrope to obtain the inherent magnetism for carbon-based spintronic
devices, but highlight the possibility to realize different Weyl states by
combining the electronic and mechanical means as well
Size-dependent bandwidth of semipolar (1122) light-emitting-diodes
The limited modulation bandwidth of commercial light-emitting diodes (LEDs) is one of the critical bottlenecks for visible light communications. Possible approaches to increase the bandwidth include the use of micron sized LEDs, which can withstand higher current densities, as well as the use of LED structures that are grown on different crystal planes to the conventional polar c-plane. We compare c-plane InGaN/GaN LEDs with semipolar ( 112¯¯¯2 ) LEDs containing a 4- and 8-nm single quantum well. The modulation bandwidth of semipolar LEDs with active areas varying from 200×200 to 30×30μm2 is shown to be governed by both current density and size. A small signal bandwidth of over 800 MHz for a relatively low applied current density of 385 A/cm2 is reported for 30×30μm2 LEDs with 8-nm thick quantum well. An optical link using an easy non-return-to-zero ON–OFF keying modulation scheme with a data rate of 1.5 Gb/s is demonstrated
Visualizing the Zhang-Rice singlet, molecular orbitals and pair formation in cuprate
The parent compound of cuprates is a charge-transfer-type Mott insulator with
strong hybridization between the Cu and O orbitals.
A key question concerning the pairing mechanism is the behavior of doped holes
in the antiferromagnetic (AF) Mott insulator background, which is a
prototypical quantum many-body problem. It was proposed that doped hole on the
O site tends to form a singlet, known as Zhang-Rice singlet (ZRS), with the
unpaired Cu spin. But experimentally little is known about the properties of a
single hole and the interplay between them that leads to superconductivity.
Here we use scanning tunneling microscopy to visualize the electronic states in
hole-doped , aiming to establish the atomic-scale local
basis for pair formation. A single doped hole is shown to have an in-gap state
and a clover-shaped spatial distribution that can be attributed to a localized
ZRS. When the dopants are close enough, they develop delocalized molecular
orbitals with characteristic stripe- and ladder-shaped patterns, accompanied by
the opening of a small gap around the Fermi level (). With
increasing doping, the molecular orbitals proliferate in space and gradually
form densely packed plaquettes, but the stripe and ladder patterns remain
nearly the same. The low-energy electronic states of the molecular orbitals are
intimately related to the local pairing properties, thus play a vitally
important role in the emergence of superconductivity. We propose that the
Cooper pair is formed by two holes occupying the stripe-like molecular orbital,
while the attractive interaction is mediated by the AF spin background
Improved sliding mode direct power control for low-carbon oriented MMC-HVDC of asymmetric offshore wind power flexible systems
The modular multilevel converter based high voltage direct current (MMC-HVDC) is a dynamic power balancing system. The control system of MMC generally adopts a dual closed-loop vector control strategy based on the traditional instantaneous power model under asymmetric grid state, which has complex control structure and low control accuracy. This paper introduces a flexible instantaneous power model and establishes a general power equation with active power and new reactive power as control objects. Based on this, an improved sliding-mode MMC-HVDC direct power control strategy based on the new instantaneous power model is proposed which combines the flexible instantaneous power model and the improved sliding-mode control method to eliminate the twice grid-frequency ripples in both active and reactive power under asymmetric grid states. Furthermore, it omits the inner-loop controller and power compensation terms while optimizing the control structure. Simulation results show that the proposed method has better dynamic responsiveness, control accuracy and robustness under operating conditions such as asymmetric grid state and parameter perturbation which can better exploit the advantages of the flexible instantaneous power model
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