109 research outputs found
TaCA: Upgrading Your Visual Foundation Model with Task-agnostic Compatible Adapter
Visual foundation models like CLIP excel in learning feature representations
from extensive datasets through self-supervised methods, demonstrating
remarkable transfer learning and generalization capabilities. A growing number
of applications based on visual foundation models are emerging, including
innovative solutions such as BLIP-2. These applications employ pre-trained CLIP
models as upstream feature extractors and train various downstream modules to
accomplish diverse tasks. In situations involving system upgrades that require
updating the upstream foundation model, it becomes essential to re-train all
downstream modules to adapt to the new foundation model, which is inflexible
and inefficient. In this paper, we introduce a parameter-efficient and
task-agnostic adapter, dubbed TaCA, that facilitates compatibility across
distinct foundation models while ensuring enhanced performance for the new
models. TaCA allows downstream applications to seamlessly integrate
better-performing foundation models without necessitating retraining. We
conduct extensive experimental validation of TaCA using different scales of
models with up to one billion parameters on various tasks such as video-text
retrieval, video recognition, and visual question answering. The results
consistently demonstrate the emergent ability of TaCA on hot-plugging upgrades
for visual foundation models. Codes and models will be available at
https://github.com/TencentARC/TaCA
Extremely large magnetoresistance in topologically trivial semimetal -WP
Extremely large magnetoresistance (XMR) was recently discovered in many
non-magnetic materials, while its underlying mechanism remains poorly
understood due to the complex electronic structure of these materials. Here, we
report an investigation of the -phase WP, a topologically trivial
semimetal with monoclinic crystal structure (C2/m), which contrasts to the
recently discovered robust type-II Weyl semimetal phase in -WP. We
found that -WP exhibits almost all the characteristics of XMR
materials: the near-quadratic field dependence of MR, a field-induced up-turn
in resistivity following by a plateau at low temperature, which can be
understood by the compensation effect, and high mobility of carriers confirmed
by our Hall effect measurements. It was also found that the normalized MRs
under different magnetic fields has the same temperature dependence in
-WP, the Kohler scaling law can describe the MR data in a wide
temperature range, and there is no obvious change in the anisotropic parameter
value with temperature. The resistance polar diagram has a peanut
shape when field is rotated in plane, which can be understood by
the anisotropy of Fermi surface. These results indicate that both
field-induced-gap and temperature-induced Lifshitz transition are not the
origin of up-turn in resistivity in the -WP semimetal. Our findings
establish -WP as a new reference material for exploring the XMR
phenomena.Comment: 18 pages, 12 figure
Long-distance continuous-variable quantum key distribution over 202.81 km fiber
Quantum key distribution (QKD) provides secure keys resistant to code-breaking quantum computers. The continuous-variable version of QKD offers the advantages of higher secret key rates in metropolitan areas, as well as the use of standard telecom components that can operate at room temperature. However, the transmission distance of these systems (compared with discrete-variable systems) are currently limited and considered unsuitable for long-distance distribution. Herein, we report the experimental results of long distance continuous-variable QKD over 202.81 km of ultralow-loss optical fiber by suitably controlling the excess noise and employing highly-efficient reconciliation procedures. This record-breaking implementation of the continuous-variable QKD doubles the previous distance record and shows the road for long-distance and large-scale secure QKD using room-temperature standard telecom components
Stability of layer-by-layer nanofiltration membranes in highly saline streams
Layer-by-layer (LBL) assembly is an essential method for the preparation of nanofiltration (NF) membranes, offering tunable charge and pore size, high water permeability, and good anti-fouling properties, making them highly suitable for resource recovery, seawater desalination, and other fields. Despite their advantages, LBL NF membranes suffer from salinity instability, limiting their use in highly saline streams. This perspective review provides a summary of the fundamental physical and chemical principles of LBL assembly related to the salinity stability of LBL NF membranes. We critically analyze the driving force of LBL assembly, the binding strength of polyelectrolyte (PE) pairs, and the overcompensation of LBL membranes. We also discuss the factors affecting overcompensation level with respect to two different time scales. Furthermore, we examine the relationship between overcompensation level and salinity stability of LBL membranes, considering physical (osmotic pressure) and chemical (Le Chatelier's principle) aspects. Our analysis demonstrates that the salinity stability of LBL NF membranes in highly saline solutions can be improved by selecting PEs with stronger binding strength, increasing the overcompensation level, and chemical crosslinking. These methods not only enhance the salinity stability of LBL NF membranes but also offer greater potential for their future application in highly saline streams
Nematic Fluctuations in Iron-Oxychalcogenide Mott Insulators
Nematic fluctuations occur in a wide range of physical systems from liquid
crystals to biological molecules to solids such as exotic magnets, cuprates and
iron-based high- superconductors. Nematic fluctuations are thought to be
closely linked to the formation of Cooper-pairs in iron-based superconductors.
It is unclear whether the anisotropy inherent in this nematicity arises from
electronic spin or orbital degrees of freedom. We have studied the iron-based
Mott insulators LaOFeO = (S, Se) which are
structurally similar to the iron pnictide superconductors. They are also in
close electronic phase diagram proximity to the iron pnictides. Nuclear
magnetic resonance (NMR) revealed a critical slowing down of nematic
fluctuations as observed by the spin-lattice relaxation rate (). This is
complemented by the observation of a change of electrical field gradient over a
similar temperature range using M\"ossbauer spectroscopy. The neutron pair
distribution function technique applied to the nuclear structure reveals the
presence of local nematic fluctuations over a wide temperature range
while neutron diffraction indicates that global symmetry is preserved.
Theoretical modeling of a geometrically frustrated spin- Heisenberg model
with biquadratic and single-ion anisotropic terms provides the interpretation
of magnetic fluctuations in terms of hidden quadrupolar spin fluctuations.
Nematicity is closely linked to geometrically frustrated magnetism, which
emerges from orbital selectivity. The results highlight orbital order and spin
fluctuations in the emergence of nematicity in Fe-based oxychalcogenides. The
detection of nematic fluctuation within these Mott insulator expands the group
of iron-based materials that show short-range symmetry-breaking
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