225 research outputs found
Distributed Lagrangian Methods for Network Resource Allocation
Motivated by a variety of applications in control engineering and information
sciences, we study network resource allocation problems where the goal is to
optimally allocate a fixed amount of resource over a network of nodes. In these
problems, due to the large scale of the network and complicated
inter-connections between nodes, any solution must be implemented in parallel
and based only on local data resulting in a need for distributed algorithms. In
this paper, we propose a novel distributed Lagrangian method, which requires
only local computation and communication. Our focus is to understand the
performance of this algorithm on the underlying network topology. Specifically,
we obtain an upper bound on the rate of convergence of the algorithm as a
function of the size and the topology of the underlying network. The
effectiveness and applicability of the proposed method is demonstrated by its
use in solving the important economic dispatch problem in power systems,
specifically on the benchmark IEEE-14 and IEEE-118 bus systems
On the convergence rate of distributed gradient methods for finite-sum optimization under communication delays
Motivated by applications in machine learning and statistics, we study
distributed optimization problems over a network of processors, where the goal
is to optimize a global objective composed of a sum of local functions. In
these problems, due to the large scale of the data sets, the data and
computation must be distributed over processors resulting in the need for
distributed algorithms. In this paper, we consider a popular distributed
gradient-based consensus algorithm, which only requires local computation and
communication. An important problem in this area is to analyze the convergence
rate of such algorithms in the presence of communication delays that are
inevitable in distributed systems. We prove the convergence of the
gradient-based consensus algorithm in the presence of uniform, but possibly
arbitrarily large, communication delays between the processors. Moreover, we
obtain an upper bound on the rate of convergence of the algorithm as a function
of the network size, topology, and the inter-processor communication delays
Qualitative analysis of solutions to mixed-order positive linear coupled systems with bounded or unbounded delays
This paper addresses the qualitative theory of mixed-order positive linear
coupled systems with bounded or unbounded delays. First, we introduce a general
result on the existence and uniqueness of solutions to mixed-order linear
coupled systems with time-varying delays. Next, we obtain the necessary and
sufficient criteria which characterize the positivity of a mixed-order delay
linear coupled system. Our main contribution is in Section 5. More precisely,
by using a smoothness property of solutions to fractional differential
equations and developing a new appropriated comparison principle for solutions
to mixed-order delayed positive systems, we prove the attractivity of
mixed-order non-homogeneous linear positive coupled systems with bounded or
unbounded delays. We also establish a necessary and sufficient condition to
characterize the stability of homogeneous systems. As a consequence of these
results, we show the smallest asymptotic bound of solutions to mixed-order
delay non-homogeneous linear positive coupled systems where disturbances are
continuous and bounded. Finally, we provide numerical simulations to illustrate
the proposed theoretical results
Direct measurements of DOCO isomers in the kinetics of OD+CO
Quantitative and mechanistically-detailed kinetics of the reaction of
hydroxyl radical (OH) with carbon monoxide (CO) have been a longstanding goal
of contemporary chemical kinetics. This fundamental prototype reaction plays an
important role in atmospheric and combustion chemistry, motivating studies for
accurate determination of the reaction rate coefficient and its pressure and
temperature dependence at thermal reaction conditions. This intricate
dependence can be traced directly to details of the underlying dynamics
(formation, isomerization, and dissociation) involving the reactive
intermediates cis- and trans-HOCO, which can only be observed transiently.
Using time-resolved frequency comb spectroscopy, comprehensive mechanistic
elucidation of the kinetics of the isotopic analogue deuteroxyl radical (OD)
with CO has been realized. By monitoring the concentrations of reactants,
intermediates, and products in real-time, the branching and isomerization
kinetics and absolute yields of all species in the OD+CO reaction are
quantified as a function of pressure and collision partner.Comment: 19 pages, 4 figure
Fluid Flows of Mixed Regimes in Porous Media
In porous media, there are three known regimes of fluid flows, namely,
pre-Darcy, Darcy and post-Darcy. Because of their different natures, these are
usually treated separately in literature. To study complex flows when all three
regimes may be present in different portions of a same domain, we use a single
equation of motion to unify them. Several scenarios and models are then
considered for slightly compressible fluids. A nonlinear parabolic equation for
the pressure is derived, which is degenerate when the pressure gradient is
either small or large. We estimate the pressure and its gradient for all time
in terms of initial and boundary data. We also obtain their particular bounds
for large time which depend on the asymptotic behavior of the boundary data but
not on the initial one. Moreover, the continuous dependence of the solutions on
initial and boundary data, and the structural stability for the equation are
established.Comment: 33 page
Postharvest loss in the supply chain for vegetables – The case of chili and tomato in Viet Nam
AVRDC Publication 06-685Christian Genova II, Katinka Weinberger, Hoang Bang An, Dang Dinh Dam, Nguyen Thi Tan Loc, Le Nhu Thinh, Nguyen Thi Thanh Thu
Temperature-dependent magnetic particle imaging with multi-harmonic lock-in detection
Advances in instrumentation and tracer materials are still required to enable
sensitive and accurate 3D temperature monitoring by magnetic particle imaging.
We have developed a magnetic particle imaging instrument to observe temperature
variations using MPI, and discuss resolution dependence on temperature and
harmonic number. Furthermore, we present a low noise approach using lock-in
detection for temperature measurement, and discuss implications for a new
detection modality of MPI.Comment: 26 pages, 17 figure
Application of internal transcribed spacer (ITS) sequences for identifying Anoectochilus setaceus Blume in Thanh Hoa, Vietnam
Background. The term “DNA barcode” is used extensively in molecular taxonomy. Basically, this technique is based on the use of a DNA sequence (about 400–800 bp) as a standard to identify and determine the species relation of organisms quickly and accurately. Therefore, DNA barcodes not only help taxonomists in classifying and identifying species, but also improve their ability to control, understand and utilize biodiversity. In this study, the authors conducted identification of samples of Anoectochilus setaceus Blume collected in Thanh Hoa through the isolated sequence of ITS gene regions.Materials and methods. Total DNA was extracted from young leaves of A. setaceus samples using CTAB method. The ITS gene segment was amplified by PCR and sequenced. This genetic sequence was analyzed, compared and used to establish a phylogenetic tree using BioEdit, BLAST and DNASTAR programs.Results and conclusion. We isolated 4 sequences of the ITS gene region in 4 A. setaceus samples collected at Xuan Lien and Pu Luong of Thanh Hoa province; the ITS gene region was 667 nucleotide long. The findings identified the samples as the same species and showed 99% similarity to the ITS gene sequence of A. roxburghii (Wall.) Lindl. published in GenBank, GQ328774. This study also demonstrates that the method employing internal transcribed spacer (ITS) sequences is an effective tool to identify A. setaceus taxa
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