8,106 research outputs found
Tuning Co valence state in cobalt oxyhydrate superconductor by post reduction
We report a successful tuning of Co valence state in cobalt oxyhydrate
superconductor via a facile post reduction using NaOH as reducing agent. The
change in Co valence was precisely determined by measuring the volume of the
released oxygen. The possible hydronium-incorporation was greatly suppressed in
concentrated NaOH solution, making the absolute Co valence determinable. As a
result, an updated superconducting phase diagram was obtained, which shows that
the superconducting transition temperature increases monotonically with
increasing Co valence in a narrow range from +3.58 to +3.65.Comment: 17 pages, 5 figures and 1 table. Chem. Mat. in pres
The perfect spin injection in silicene FS/NS junction
We theoretically investigate the spin injection from a ferromagnetic silicene
to a normal silicene (FS/NS), where the magnetization in the FS is assumed from
the magnetic proximity effect. Based on a silicene lattice model, we
demonstrated that the pure spin injection could be obtained by tuning the Fermi
energy of two spin species, where one is in the spin orbit coupling gap and the
other one is outside the gap. Moreover, the valley polarity of the spin species
can be controlled by a perpendicular electric field in the FS region. Our
findings may shed light on making silicene-based spin and valley devices in the
spintronics and valleytronics field.Comment: 6 pages, 3 figure
Integer quantum Hall effect and topological phase transitions in silicene
We numerically investigate the effects of disorder on the quantum Hall effect
(QHE) and the quantum phase transitions in silicene based on a lattice model.
It is shown that for a clean sample, silicene exhibits an unconventional QHE
near the band center, with plateaus developing at and
a conventional QHE near the band edges. In the presence of disorder, the Hall
plateaus can be destroyed through the float-up of extended levels toward the
band center, in which higher plateaus disappear first. However, the center
Hall plateau is more sensitive to disorder and disappears at a
relatively weak disorder strength. Moreover, the combination of an electric
field and the intrinsic spin-orbit interaction (SOI) can lead to quantum phase
transitions from a topological insulator to a band insulator at the charge
neutrality point (CNP), accompanied by additional quantum Hall conductivity
plateaus.Comment: 7 pages, 4 figure
NNSplitter: An Active Defense Solution for DNN Model via Automated Weight Obfuscation
As a type of valuable intellectual property (IP), deep neural network (DNN)
models have been protected by techniques like watermarking. However, such
passive model protection cannot fully prevent model abuse. In this work, we
propose an active model IP protection scheme, namely NNSplitter, which actively
protects the model by splitting it into two parts: the obfuscated model that
performs poorly due to weight obfuscation, and the model secrets consisting of
the indexes and original values of the obfuscated weights, which can only be
accessed by authorized users with the support of the trusted execution
environment. Experimental results demonstrate the effectiveness of NNSplitter,
e.g., by only modifying 275 out of over 11 million (i.e., 0.002%) weights, the
accuracy of the obfuscated ResNet-18 model on CIFAR-10 can drop to 10%.
Moreover, NNSplitter is stealthy and resilient against norm clipping and
fine-tuning attacks, making it an appealing solution for DNN model protection.
The code is available at: https://github.com/Tongzhou0101/NNSplitter.Comment: To appear at ICML 202
PKUSEG: A Toolkit for Multi-Domain Chinese Word Segmentation
Chinese word segmentation (CWS) is a fundamental step of Chinese natural
language processing. In this paper, we build a new toolkit, named PKUSEG, for
multi-domain word segmentation. Unlike existing single-model toolkits, PKUSEG
targets multi-domain word segmentation and provides separate models for
different domains, such as web, medicine, and tourism. Besides, due to the lack
of labeled data in many domains, we propose a domain adaptation paradigm to
introduce cross-domain semantic knowledge via a translation system. Through
this method, we generate synthetic data using a large amount of unlabeled data
in the target domain and then obtain a word segmentation model for the target
domain. We also further refine the performance of the default model with the
help of synthetic data. Experiments show that PKUSEG achieves high performance
on multiple domains. The new toolkit also supports POS tagging and model
training to adapt to various application scenarios. The toolkit is now freely
and publicly available for the usage of research and industry
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