215 research outputs found
Asynchronous Distributed ADMM for Large-Scale Optimization- Part I: Algorithm and Convergence Analysis
Aiming at solving large-scale learning problems, this paper studies
distributed optimization methods based on the alternating direction method of
multipliers (ADMM). By formulating the learning problem as a consensus problem,
the ADMM can be used to solve the consensus problem in a fully parallel fashion
over a computer network with a star topology. However, traditional synchronized
computation does not scale well with the problem size, as the speed of the
algorithm is limited by the slowest workers. This is particularly true in a
heterogeneous network where the computing nodes experience different
computation and communication delays. In this paper, we propose an asynchronous
distributed ADMM (AD-AMM) which can effectively improve the time efficiency of
distributed optimization. Our main interest lies in analyzing the convergence
conditions of the AD-ADMM, under the popular partially asynchronous model,
which is defined based on a maximum tolerable delay of the network.
Specifically, by considering general and possibly non-convex cost functions, we
show that the AD-ADMM is guaranteed to converge to the set of
Karush-Kuhn-Tucker (KKT) points as long as the algorithm parameters are chosen
appropriately according to the network delay. We further illustrate that the
asynchrony of the ADMM has to be handled with care, as slightly modifying the
implementation of the AD-ADMM can jeopardize the algorithm convergence, even
under a standard convex setting.Comment: 37 page
Effects of first-dose volume and exercise on the efficacy and tolerability of bowel preparations for colonoscopy in Chinese people
Enhanced interlayer neutral excitons and trions in trilayer van der Waals heterostructures
Vertically stacked van der Waals heterostructures constitute a promising
platform for providing tailored band alignment with enhanced excitonic systems.
Here we report observations of neutral and charged interlayer excitons in
trilayer WSe2-MoSe2-WSe2 van der Waals heterostructures and their dynamics. The
addition of a WSe2 layer in the trilayer leads to significantly higher
photoluminescence quantum yields and tunable spectral resonance compared to its
bilayer heterostructures at cryogenic temperatures. The observed enhancement in
the photoluminescence quantum yield is due to significantly larger
electron-hole overlap and higher light absorbance in the trilayer
heterostructure, supported via first-principle pseudopotential calculations
based on spin-polarized density functional theory. We further uncover the
temperature- and power-dependence, as well as time-resolved photoluminescence
of the trilayer heterostructure interlayer neutral excitons and trions. Our
study elucidates the prospects of manipulating light emission from interlayer
excitons and designing atomic heterostructures from first-principles for
optoelectronics.Comment: 25 pages, 5 figures(Maintext). 9 pages, 7 figures(Supplementary
Information). - Accepted for publication in npg: 2D materials and
applications and reformatted to its standard. - Updated co-authors and
references. - Title and abstract are modified for clarity. - Errors have been
corrected, npg: 2D materials and applications (2018
A Novel Positive Feedback Loop Between NTSR1 and Wnt/β-Catenin Contributes to Tumor Growth of Glioblastoma
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Possible Luttinger liquid behavior of edge transport in monolayer transition metal dichalcogenide crystals.
In atomically-thin two-dimensional (2D) semiconductors, the nonuniformity in current flow due to its edge states may alter and even dictate the charge transport properties of the entire device. However, the influence of the edge states on electrical transport in 2D materials has not been sufficiently explored to date. Here, we systematically quantify the edge state contribution to electrical transport in monolayer MoS2/WSe2 field-effect transistors, revealing that the charge transport at low temperature is dominated by the edge conduction with the nonlinear behavior. The metallic edge states are revealed by scanning probe microscopy, scanning Kelvin probe force microscopy and first-principle calculations. Further analyses demonstrate that the edge-state dominated nonlinear transport shows a universal power-law scaling relationship with both temperature and bias voltage, which can be well explained by the 1D Luttinger liquid theory. These findings demonstrate the Luttinger liquid behavior in 2D materials and offer important insights into designing 2D electronics
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