23 research outputs found
CoSDA: Continual Source-Free Domain Adaptation
Without access to the source data, source-free domain adaptation (SFDA)
transfers knowledge from a source-domain trained model to target domains.
Recently, SFDA has gained popularity due to the need to protect the data
privacy of the source domain, but it suffers from catastrophic forgetting on
the source domain due to the lack of data. To systematically investigate the
mechanism of catastrophic forgetting, we first reimplement previous SFDA
approaches within a unified framework and evaluate them on four benchmarks. We
observe that there is a trade-off between adaptation gain and forgetting loss,
which motivates us to design a consistency regularization to mitigate
forgetting. In particular, we propose a continual source-free domain adaptation
approach named CoSDA, which employs a dual-speed optimized teacher-student
model pair and is equipped with consistency learning capability. Our
experiments demonstrate that CoSDA outperforms state-of-the-art approaches in
continuous adaptation. Notably, our CoSDA can also be integrated with other
SFDA methods to alleviate forgetting.Comment: 15 pages, 6 figure
Rigid three-dimensional Ni3S4 nanosheet frames: Controlled synthesis and their enhanced electrochemical performance
Rigid three-dimensional (3D) NiS nanosheet frames assembled from ultrathin nanosheets are synthesized via a facile solvothermal method. Compared to flat NiS sheets, 3D NiS nanosheet frames have both a high free volume and high compressive strength. They can deliver a very high specific capacitance of 1213 F g with good rate performance. In addition, these 3D NiS nanosheet frames are stabilized by plastically deformed ridges. The stabilized nanosheet frames did not unfold or collapse during electrochemical tests, and thus showed enhanced cycling ability
Reversible Hydrogel–Solution System of Silk with High Beta-Sheet Content
Silkworm
silk has been widely used as a textile fiber, as biomaterials
and in optically functional materials due to its extraordinary properties.
The β-sheet-rich natural nanofiber units of about 10–50
nm in diameter are often considered the origin of these properties,
yet it remains unclear how silk self-assembles into these hierarchical
structures. A new system composed of β-sheet-rich silk nanofibers
about 10–20 nm in diameter is reported here, where these nanofibers
formed into “flowing hydrogels” at 0.5–2% solutions
and could be transformed back into the solution state at lower concentrations,
even with a high β-sheet content. This is in contrast with other
silk processed materials, where significant β-sheet content
negates reversibility between solution and solid states. These fibers
are formed by regulating the self-assembly process of silk in aqueous
solution, which changes the distribution of negative charges while
still supporting β-sheet formation in the structures. Mechanistically,
there appears to be a shift toward negative charges along the outside
of the silk nanofibers in our present study, resulting in a higher
zeta potential (above −50 mV) than previous silk materials
which tend to be below −30 mV. The higher negative charge on
silk nanofibers resulted in electrostatic repulsion strong enough
to negate further assembly of the nanofibers. Changing silk concentration
changed the balance between hydrophobic interactions and electrostatic
repulsion of β-sheet-rich silk nanofibers, resulting in reversible
hydrogel–solution transitions. Furthermore, the silk nanofibers
could be disassembled into shorter fibers and even nanoparticles upon
ultrasonic treatment following the transition from hydrogel to solution
due to the increased dispersion of hydrophobic smaller particles,
without the loss of β-sheet content, and with retention of the
ability to transition between hydrogel and solution states through
reversion to longer nanofibers during self-assembly. These reversible
solution-hydrogel transitions were tunable with ultrasonic intensity,
time, or temperature