7,038 research outputs found
Deep Cross-Modal Hashing
Due to its low storage cost and fast query speed, cross-modal hashing (CMH)
has been widely used for similarity search in multimedia retrieval
applications. However, almost all existing CMH methods are based on
hand-crafted features which might not be optimally compatible with the
hash-code learning procedure. As a result, existing CMH methods with
handcrafted features may not achieve satisfactory performance. In this paper,
we propose a novel cross-modal hashing method, called deep crossmodal hashing
(DCMH), by integrating feature learning and hash-code learning into the same
framework. DCMH is an end-to-end learning framework with deep neural networks,
one for each modality, to perform feature learning from scratch. Experiments on
two real datasets with text-image modalities show that DCMH can outperform
other baselines to achieve the state-of-the-art performance in cross-modal
retrieval applications.Comment: 12 page
Asymmetric Deep Supervised Hashing
Hashing has been widely used for large-scale approximate nearest neighbor
search because of its storage and search efficiency. Recent work has found that
deep supervised hashing can significantly outperform non-deep supervised
hashing in many applications. However, most existing deep supervised hashing
methods adopt a symmetric strategy to learn one deep hash function for both
query points and database (retrieval) points. The training of these symmetric
deep supervised hashing methods is typically time-consuming, which makes them
hard to effectively utilize the supervised information for cases with
large-scale database. In this paper, we propose a novel deep supervised hashing
method, called asymmetric deep supervised hashing (ADSH), for large-scale
nearest neighbor search. ADSH treats the query points and database points in an
asymmetric way. More specifically, ADSH learns a deep hash function only for
query points, while the hash codes for database points are directly learned.
The training of ADSH is much more efficient than that of traditional symmetric
deep supervised hashing methods. Experiments show that ADSH can achieve
state-of-the-art performance in real applications
Energy Efficient Downlink Transmission for Multi-cell Massive DAS with Pilot Contamination
In this paper, we study the energy efficiency (EE) of a downlink multi-cell
massive distributed antenna system (DAS) in the presence of pilot contamination
(PC), where the antennas are clustered on the remote radio heads (RRHs). We
employ a practical power consumption model by considering the transmit power,
the circuit power, and the backhaul power, in contrast to most of the existing
works which focus on co-located antenna systems (CAS) where the backhaul power
is negligible. For a given average user rate, we consider the problem of
maximizing the EE with respect to the number of each RRH antennas , the
number of RRHs , the number of users , and study the impact of system
parameters on the optimal , and . Specifically, by applying random
matrix theory, we derive the closed-form expressions of the optimal , and
find the solution of the optimal and , under a simplified channel model
with maximum ratio transmission. From the results, we find that to achieve the
optimal EE, a large number of antennas is needed for a given user rate and PC.
As the number of users increases, EE can be improved further by having more
RRHs and antennas. Moreover, if the backhauling power is not large, massive DAS
can be more energy efficient than massive CAS. These insights provide a useful
guide to practical deployment of massive DAS.Comment: 12 pages,10 figures. Accepted by the IEEE Transactions on Vehicular
Technolog
Size-Sensitive Young's modulus of Kinked Silicon Nanowires
We perform both classical molecular dynamics simulations and beam model
calculations to investigate the Young's modulus of kinked silicon nanowires
(KSiNWs). The Young's modulus is found to be highly sensitive to the arm length
of the kink and is essentially inversely proportional to the arm length. The
mechanism underlying the size dependence is found to be the interplay between
the kink angle potential and the arm length potential, where we obtain an
analytic relationship between the Young's modulus and the arm length of the
KSiNW. Our results provide insight into the application of this novel building
block in nanomechanical devices.Comment: Nanotechnology, accepted (2013
Deep Discrete Supervised Hashing
Hashing has been widely used for large-scale search due to its low storage
cost and fast query speed. By using supervised information, supervised hashing
can significantly outperform unsupervised hashing. Recently, discrete
supervised hashing and deep hashing are two representative progresses in
supervised hashing. On one hand, hashing is essentially a discrete optimization
problem. Hence, utilizing supervised information to directly guide discrete
(binary) coding procedure can avoid sub-optimal solution and improve the
accuracy. On the other hand, deep hashing, which integrates deep feature
learning and hash-code learning into an end-to-end architecture, can enhance
the feedback between feature learning and hash-code learning. The key in
discrete supervised hashing is to adopt supervised information to directly
guide the discrete coding procedure in hashing. The key in deep hashing is to
adopt the supervised information to directly guide the deep feature learning
procedure. However, there have not existed works which can use the supervised
information to directly guide both discrete coding procedure and deep feature
learning procedure in the same framework. In this paper, we propose a novel
deep hashing method, called deep discrete supervised hashing (DDSH), to address
this problem. DDSH is the first deep hashing method which can utilize
supervised information to directly guide both discrete coding procedure and
deep feature learning procedure, and thus enhance the feedback between these
two important procedures. Experiments on three real datasets show that DDSH can
outperform other state-of-the-art baselines, including both discrete hashing
and deep hashing baselines, for image retrieval
Optical Variability of the Radio Source J 1128+5925
Very recently, J 1128+5925 was found to show strong intraday variability at
radio wavelengths and may be a new source with annual modulation of the
timescale of its radio variability. Therefore, its radio variability can be
best explained via interstellar scintillation. Here we present the properties
of its optical variability for the first time after a monitoring program in
2007 May. Our observations indicate that in this period J 1128+5925 only showed
trivial optical variability on internight timescale, and did not show any clear
intranight variability. This behavior is quite different from its strong radio
intraday variability. Either this object was in a quiescent state in optical in
this period, or it is intrinsically not so active in optical as it is in radio
regimes.Comment: 9 pages, 3 figure
On the Evaluation Metric for Hashing
Due to its low storage cost and fast query speed, hashing has been widely
used for large-scale approximate nearest neighbor (ANN) search. Bucket search,
also called hash lookup, can achieve fast query speed with a sub-linear time
cost based on the inverted index table constructed from hash codes. Many
metrics have been adopted to evaluate hashing algorithms. However, all existing
metrics are improper to evaluate the hash codes for bucket search. On one hand,
all existing metrics ignore the retrieval time cost which is an important
factor reflecting the performance of search. On the other hand, some of them,
such as mean average precision (MAP), suffer from the uncertainty problem as
the ranked list is based on integer-valued Hamming distance, and are
insensitive to Hamming radius as these metrics only depend on relative Hamming
distance. Other metrics, such as precision at Hamming radius R, fail to
evaluate global performance as these metrics only depend on one specific
Hamming radius. In this paper, we first point out the problems of existing
metrics which have been ignored by the hashing community, and then propose a
novel evaluation metric called radius aware mean average precision (RAMAP) to
evaluate hash codes for bucket search. Furthermore, two coding strategies are
also proposed to qualitatively show the problems of existing metrics.
Experiments demonstrate that our proposed RAMAP can provide more proper
evaluation than existing metrics
The Hidden Geometry of Attention Diffusion
We propose a geometric model to quantify the dynamics of attention in online
communities. Using clicks as a proxy of attention, we find that the diffusion
of collective attention in Web forums and news sharing sites forms
time-invariant "fields" whose density vary solely with distance from the center
of the fields that represents the input of attention from the physical world.
As time goes by, old information pieces are pushed farther from the center by
new pieces, receive fewer and fewer clicks, and eventually become invisible in
the virtual world. The discovered "attention fields" not only explain the fast
decay of attention to information pieces, but also predict the accelerating
growth of clicks against the active user population, which is a universal
pattern relevant to the economics of scales of online interactions.Comment: 12 pages, 4 figure
Deep Multi-Index Hashing for Person Re-Identification
Traditional person re-identification (ReID) methods typically represent
person images as real-valued features, which makes ReID inefficient when the
gallery set is extremely large. Recently, some hashing methods have been
proposed to make ReID more efficient. However, these hashing methods will
deteriorate the accuracy in general, and the efficiency of them is still not
high enough. In this paper, we propose a novel hashing method, called deep
multi-index hashing (DMIH), to improve both efficiency and accuracy for ReID.
DMIH seamlessly integrates multi-index hashing and multi-branch based networks
into the same framework. Furthermore, a novel block-wise multi-index hashing
table construction approach and a search-aware multi-index (SAMI) loss are
proposed in DMIH to improve the search efficiency. Experiments on three widely
used datasets show that DMIH can outperform other state-of-the-art baselines,
including both hashing methods and real-valued methods, in terms of both
efficiency and accuracy.Comment: 10 pages, 6 figures, 2 table
Heavy Quarkonium Production through the Semi-Exclusive Annihilation Channels around the Peak
Within the framework of the non-relativistic QCD, we present a detailed
discussion on the heavy quarkonium production at the leading order in
at a collider with the collision energy around the
peak. Quarkonia are produced through the semi-exclusive channels with or , where
indicates a heavy quark (respectively or ). It is noted that in addition
to the color-singlet 1S-level quarkonium states, the 2S and 1P color-singlet
states and the color-octet state also
provide sizable contributions. The heavy quarkonium transverse momentum and
rapidity distributions for the collision energy are
presented. For both charmonium and bottomonium production via the
propagator, there is approximate "spin degeneracy" between the spin-triplet and
spin-singlet quarkonium states. Uncertainties for the total cross sections are
estimated by taking GeV and GeV. Around
, due to the -boson resonance effect, total cross sections
for the channels via the -propagator become much larger than the channels
via the virtual photon propagator. We conclude that, in addition to the
factories as BaBar and Belle and the hadronic colliders as Tevatron and LHC,
such a super -factory will present an excellent platform for studying the
heavy quarkonium properties.Comment: 28 pages, 20 figures, 15 tables. to be published in Phys.Rev.D. We
are grateful for the anonymous referee's comments and suggestions that
substantially improve the manuscrip
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