1,135 research outputs found
Phase diagram of Kondo-Heisenberg model on honeycomb lattice with geometrical frustration
We calculated the phase diagram of the Kondo-Heisenberg model on
two-dimensional honeycomb lattice with both nearest-neighbor and
next-nearest-neighbor antiferromagnetic spin exchanges, to investigate the
interplay between RKKY and Kondo interactions at presence of magnetic
frustration. Within a mean-field decoupling technology in slave-fermion
representation, we derived the zero-temperature phase diagram as a function of
Kondo coupling and frustration strength . The geometrical frustration
can destroy the magnetic order, driving the original antiferromagnetic (AF)
phase to non-magnetic valence bond state (VBS). In addition, we found two
distinct VBS. As is increased, a phase transition from AF to Kondo
paramagnetic (KP) phase occurs, without the intermediate phase coexisting AF
order with Kondo screening found in square lattice systems. In the KP phase,
the enhancement of frustration weakens the Kondo screening effect, resulting in
a phase transition from KP to VBS. We also found a process to recover the AF
order from VBS by increasing in a wide range of frustration strength. Our
work may provide deeper understanding for the phase transitions in
heavy-fermion materials, particularly for those exhibiting triangular
frustration
VibHead: An Authentication Scheme for Smart Headsets through Vibration
Recent years have witnessed the fast penetration of Virtual Reality (VR) and
Augmented Reality (AR) systems into our daily life, the security and privacy
issues of the VR/AR applications have been attracting considerable attention.
Most VR/AR systems adopt head-mounted devices (i.e., smart headsets) to
interact with users and the devices usually store the users' private data.
Hence, authentication schemes are desired for the head-mounted devices.
Traditional knowledge-based authentication schemes for general personal devices
have been proved vulnerable to shoulder-surfing attacks, especially considering
the headsets may block the sight of the users. Although the robustness of the
knowledge-based authentication can be improved by designing complicated secret
codes in virtual space, this approach induces a compromise of usability.
Another choice is to leverage the users' biometrics; however, it either relies
on highly advanced equipments which may not always be available in commercial
headsets or introduce heavy cognitive load to users.
In this paper, we propose a vibration-based authentication scheme, VibHead,
for smart headsets. Since the propagation of vibration signals through human
heads presents unique patterns for different individuals, VibHead employs a
CNN-based model to classify registered legitimate users based the features
extracted from the vibration signals. We also design a two-step authentication
scheme where the above user classifiers are utilized to distinguish the
legitimate user from illegitimate ones. We implement VibHead on a Microsoft
HoloLens equipped with a linear motor and an IMU sensor which are commonly used
in off-the-shelf personal smart devices. According to the results of our
extensive experiments, with short vibration signals (), VibHead has an
outstanding authentication accuracy; both FAR and FRR are around 5%
RefSelect: a reference sequence selection algorithm for planted (l, d) motif search
Background
The planted (l, d) motif search (PMS) is an important yet challenging problem in computational biology. Pattern-driven PMS algorithms usually use k out of t input sequences as reference sequences to generate candidate motifs, and they can find all the (l, d) motifs in the input sequences. However, most of them simply take the first k sequences in the input as reference sequences without elaborate selection processes, and thus they may exhibit sharp fluctuations in running time, especially for large alphabets.
Results
In this paper, we build the reference sequence selection problem and propose a method named RefSelect to quickly solve it by evaluating the number of candidate motifs for the reference sequences. RefSelect can bring a practical time improvement of the state-of-the-art pattern-driven PMS algorithms. Experimental results show that RefSelect (1) makes the tested algorithms solve the PMS problem steadily in an efficient way, (2) particularly, makes them achieve a speedup of up to about 100× on the protein data, and (3) is also suitable for large data sets which contain hundreds or more sequences.
Conclusions
The proposed algorithm RefSelect can be used to solve the problem that many pattern-driven PMS algorithms present execution time instability. RefSelect requires a small amount of storage space and is capable of selecting reference sequences efficiently and effectively. Also, the parallel version of RefSelect is provided for handling large data sets
(1R,1′S)-1,1′-Dihydroxy-1,1′-biisobenzofuran-3,3′(1H,1′H)-dione
In the title compound, C16H10O6, the complete molecule is generated by a crystallographic centre of symmetry. In the crystal, O—H⋯O hydrogen bonds link the molecules into (100) sheets and C—H⋯O links also occur
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