3,497 research outputs found
On the spectral radius of weighted trees with fixed diameter and weight set
AbstractThe spectrum of weighted graphs are often used to solve the problems in the design of networks and electronic circuits. We first give some perturbational results on the spectral radius of weighted graphs when some weights of edges are modified, then we derive the weighted tree with the largest spectral radius in the set of all weighted trees with fixed diameter and weight set. Furthermore, an open problem of spectral radius on weighted paths is solved [H.Z. Yang, G.Z. Hu, Y. Hong, Bounds of spectral radii of weighted tree, Tsinghua Science and Technology 8 (2003) 517–520]
End-to-end Alternating Optimization for Real-World Blind Super Resolution
Blind Super-Resolution (SR) usually involves two sub-problems: 1) estimating
the degradation of the given low-resolution (LR) image; 2) super-resolving the
LR image to its high-resolution (HR) counterpart. Both problems are ill-posed
due to the information loss in the degrading process. Most previous methods try
to solve the two problems independently, but often fall into a dilemma: a good
super-resolved HR result requires an accurate degradation estimation, which
however, is difficult to be obtained without the help of original HR
information. To address this issue, instead of considering these two problems
independently, we adopt an alternating optimization algorithm, which can
estimate the degradation and restore the SR image in a single model.
Specifically, we design two convolutional neural modules, namely
\textit{Restorer} and \textit{Estimator}. \textit{Restorer} restores the SR
image based on the estimated degradation, and \textit{Estimator} estimates the
degradation with the help of the restored SR image. We alternate these two
modules repeatedly and unfold this process to form an end-to-end trainable
network. In this way, both \textit{Restorer} and \textit{Estimator} could get
benefited from the intermediate results of each other, and make each
sub-problem easier. Moreover, \textit{Restorer} and \textit{Estimator} are
optimized in an end-to-end manner, thus they could get more tolerant of the
estimation deviations of each other and cooperate better to achieve more robust
and accurate final results. Extensive experiments on both synthetic datasets
and real-world images show that the proposed method can largely outperform
state-of-the-art methods and produce more visually favorable results. The codes
are rleased at \url{https://github.com/greatlog/RealDAN.git}.Comment: Extension of our previous NeurIPS paper. Accepted to IJC
Multi-Label Image Classification via Knowledge Distillation from Weakly-Supervised Detection
Multi-label image classification is a fundamental but challenging task
towards general visual understanding. Existing methods found the region-level
cues (e.g., features from RoIs) can facilitate multi-label classification.
Nevertheless, such methods usually require laborious object-level annotations
(i.e., object labels and bounding boxes) for effective learning of the
object-level visual features. In this paper, we propose a novel and efficient
deep framework to boost multi-label classification by distilling knowledge from
weakly-supervised detection task without bounding box annotations.
Specifically, given the image-level annotations, (1) we first develop a
weakly-supervised detection (WSD) model, and then (2) construct an end-to-end
multi-label image classification framework augmented by a knowledge
distillation module that guides the classification model by the WSD model
according to the class-level predictions for the whole image and the
object-level visual features for object RoIs. The WSD model is the teacher
model and the classification model is the student model. After this cross-task
knowledge distillation, the performance of the classification model is
significantly improved and the efficiency is maintained since the WSD model can
be safely discarded in the test phase. Extensive experiments on two large-scale
datasets (MS-COCO and NUS-WIDE) show that our framework achieves superior
performances over the state-of-the-art methods on both performance and
efficiency.Comment: accepted by ACM Multimedia 2018, 9 pages, 4 figures, 5 table
On the selection and design of proteins and peptide derivatives for the production of photoluminescent, red-emitting gold quantum clusters
Novel pathways of the synthesis of photoluminescent gold quantum clusters (AuQCs) using biomolecules as reactants provide biocompatible products for biological imaging techniques. In order to rationalize the rules for the preparation of red-emitting AuQCs in aqueous phase using proteins or peptides, the role of different organic structural units was investigated. Three systems were studied: proteins, peptides, and amino acid mixtures, respectively. We have found that cysteine and tyrosine are indispensable residues. The SH/S-S ratio in a single molecule is not a critical factor in the synthesis, but on the other hand, the stoichiometry of cysteine residues and the gold precursor is crucial. These observations indicate the importance of proper chemical behavior of all species in a wide size range extending from the atomic distances (in the AuI-S semi ring) to nanometer distances covering the larger sizes of proteins assuring the hierarchical structure of the whole self-assembled system
Hysteresis of Electronic Transport in Graphene Transistors
Graphene field effect transistors commonly comprise graphene flakes lying on
SiO2 surfaces. The gate-voltage dependent conductance shows hysteresis
depending on the gate sweeping rate/range. It is shown here that the
transistors exhibit two different kinds of hysteresis in their electrical
characteristics. Charge transfer causes a positive shift in the gate voltage of
the minimum conductance, while capacitive gating can cause the negative shift
of conductance with respect to gate voltage. The positive hysteretic phenomena
decay with an increase of the number of layers in graphene flakes. Self-heating
in helium atmosphere significantly removes adsorbates and reduces positive
hysteresis. We also observed negative hysteresis in graphene devices at low
temperature. It is also found that an ice layer on/under graphene has much
stronger dipole moment than a water layer does. Mobile ions in the electrolyte
gate and a polarity switch in the ferroelectric gate could also cause negative
hysteresis in graphene transistors. These findings improved our understanding
of the electrical response of graphene to its surroundings. The unique
sensitivity to environment and related phenomena in graphene deserve further
studies on nonvolatile memory, electrostatic detection and chemically driven
applications.Comment: 13 pages, 6 Figure
Joint population pharmacokinetic modeling of venlafaxine and O-desmethyl venlafaxine in healthy volunteers and patients to evaluate the impact of morbidity and concomitant medication
Introduction: Venlafaxine (VEN) is a widely used dual selective serotonin/noradrenaline reuptake inhibitor indicated for depression and anxiety. It undergoes first-pass metabolism to its active metabolite, O-desmethyl venlafaxine (ODV). The aim of the present study was to develop a joint population pharmacokinetic (PPK) model to characterize their pharmacokinetic characters simultaneously.Methods: Plasma concentrations with demographic and clinical data were derived from a bioequivalence study in 24 healthy subjects and a naturalistic TDM setting containing 127 psychiatric patients. A parent-metabolite PPK modeling was performed with NONMEM software using a non-linear mixed effect modeling approach. Goodness of fit plots and normalized prediction distribution error method were used for model validation.Results and conclusion: Concentrations of VEN and ODV were well described with a one-compartment model incorporating first-pass metabolism. The first-pass metabolism was modeled as a first-order conversion. The morbid state and concomitant amisulpride were identified as two significant covariates affecting the clearance of VEN and ODV, which may account for some of the variations in exposure. This model may contribute to the precision medication in clinical practice and may inspire other drugs with pre-system metabolism
Search for the Rare Decays J/Psi --> Ds- e+ nu_e, J/Psi --> D- e+ nu_e, and J/Psi --> D0bar e+ e-
We report on a search for the decays J/Psi --> Ds- e+ nu_e + c.c., J/Psi -->
D- e+ nu_e + c.c., and J/Psi --> D0bar e+ e- + c.c. in a sample of 5.8 * 10^7
J/Psi events collected with the BESII detector at the BEPC. No excess of signal
above background is observed, and 90% confidence level upper limits on the
branching fractions are set: B(J/Psi --> Ds- e+ nu_e + c.c.)<4.8*10^-5, B(J/Psi
--> D- e+ nu_e + c.c.) D0bar e+ e- + c.c.)<1.1*10^-5Comment: 10 pages, 4 figure
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