152 research outputs found
Online Alternating Direction Method
Online optimization has emerged as powerful tool in large scale optimization.
In this paper, we introduce efficient online algorithms based on the
alternating directions method (ADM). We introduce a new proof technique for ADM
in the batch setting, which yields the O(1/T) convergence rate of ADM and forms
the basis of regret analysis in the online setting. We consider two scenarios
in the online setting, based on whether the solution needs to lie in the
feasible set or not. In both settings, we establish regret bounds for both the
objective function as well as constraint violation for general and strongly
convex functions. Preliminary results are presented to illustrate the
performance of the proposed algorithms.Comment: Appears in Proceedings of the 29th International Conference on
Machine Learning (ICML 2012
Beef-derived mesoporous carbon as highly efficient support for PtRuIr electrocatalysts and their high activity for CO and methanol oxidation
In this work, a low-cost and nitrogen-containing carbon with mesoporous pores and high surface area was synthesized by
carbonizing a natural biomass precursor, i.e. beef. It is found that the prepared material has excellent textural properties such as
high specific surface areas and large pore diameters. TEM images showed that the PtRuIr nanoparticles were well dispersed on
the surface of carbonized beef (C-Beef). PtRuIr/C-Beef was highly active for methanol electro-oxidation. PtRuIr/C-Beef showed
superior catalytic activity to PtRuIr/C, i.e. lower onset potential and higher oxidation current density. Cyclic voltammograms
of CO electro-oxidation showed that PtRuIr/C-Beef catalyst was kinetically more active for CO electro-oxidation than PtRuIr
deposited on conventional carbon support. The highly porous structure and low cost of carbonized beef can be widely used as
support for highly dispersed metal nanoparticles to increase their electrochemical performance as electrocatalysts
Selenium-functionalized carbon as a support for platinum nanoparticles with improved electrochemical properties for the oxygen reduction reaction and CO tolerance
Using selenium-functionalized carbon as supports, platinum nanoparticles were uniformly dispersed on the carbon surface, and
showed improved electrochemical properties for the oxygen reduction reaction. At the same time the CO tolerance is improved. The
method provides a new route for functionalization of the carbon surface on which to disperse noble metal nanoparticles for use as
electrocatalysts in the oxygen reduction reaction.Web of Scienc
Parallel Direction Method of Multipliers
We consider the problem of minimizing block-separable convex functions
subject to linear constraints. While the Alternating Direction Method of
Multipliers (ADMM) for two-block linear constraints has been intensively
studied both theoretically and empirically, in spite of some preliminary work,
effective generalizations of ADMM to multiple blocks is still unclear. In this
paper, we propose a randomized block coordinate method named Parallel Direction
Method of Multipliers (PDMM) to solve the optimization problems with
multi-block linear constraints. PDMM randomly updates some primal and dual
blocks in parallel, behaving like parallel randomized block coordinate descent.
We establish the global convergence and the iteration complexity for PDMM with
constant step size. We also show that PDMM can do randomized block coordinate
descent on overlapping blocks. Experimental results show that PDMM performs
better than state-of-the-arts methods in two applications, robust principal
component analysis and overlapping group lasso.Comment: This paper has been withdrawn by the authors. There are errors in
Equations from 139-19
Selenium-functionalized carbon as a support for platinum nanoparticles with improved electrochemical properties for the oxygen reduction reaction and CO tolerance
Using selenium-functionalized carbon as supports, platinum nanoparticles were uniformly dispersed on the carbon surface, and
showed improved electrochemical properties for the oxygen reduction reaction. At the same time the CO tolerance is improved. The
method provides a new route for functionalization of the carbon surface on which to disperse noble metal nanoparticles for use as
electrocatalysts in the oxygen reduction reaction.Web of Scienc
Uplink Performance of Cell-Free Extremely Large-Scale MIMO Systems
In this paper, we investigate the uplink performance of cell-free (CF)
extremely large-scale multiple-input-multipleoutput (XL-MIMO) systems, which is
a promising technique for future wireless communications. More specifically, we
consider the practical scenario with multiple base stations (BSs) and multiple
user equipments (UEs). To this end, we derive exact achievable spectral
efficiency (SE) expressions for any combining scheme. It is worth noting that
we derive the closed-form SE expressions for the CF XL-MIMO with maximum ratio
(MR) combining. Numerical results show that the SE performance of the CF
XL-MIMO can be hugely improved compared with the small-cell XL-MIMO. It is
interesting that a smaller antenna spacing leads to a higher correlation level
among patch antennas. Finally, we prove that increasing the number of UE
antennas may decrease the SE performance with MR combining
Why cuckoos remove host eggs: Biting eggs facilitates faster parasitic eggālaying
Brood parasitism by cuckoos relies on manipulating hosts to raise their offspring and has evolved stunning adaptations to aid in their deception. The fact that cuckoos usually but not always, remove one or two host eggs while laying their eggs has been a longstanding focus of intensive research. However, the benefit of this behavior remains elusive. Moreover, the recently proposed help delivery hypothesis, predicting that egg removal by cuckoos may decrease the eggālaying duration in the parasitism process caused by biting action, lacks experimental verification. Therefore, in this study, we examined the effects of egg removal/biting on the eggālaying speed in the common cuckoo (Cuculus canorus) to experimentally test this hypothesis. We compared the duration of cuckoo eggālaying in empty nests, nests with host eggs, and nests with artificial blue stick models to test whether cuckoos biting an egg/stick can significantly hasten the eggālaying speed than no biting action. Our results showed that biting an egg or an object is associated with cuckoos laying approximately 37% faster than when they do not bite an egg or an object. This study provides the first experimental evidence for the help delivery hypothesis and demonstrates that when cuckoos bite eggs or other objects in the nest, they lay eggs more quickly and thereby avoid suffering the hosts' injurious attack
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