782 research outputs found
Improved Runtime Bounds for the Univariate Marginal Distribution Algorithm via Anti-Concentration
Unlike traditional evolutionary algorithms which produce offspring via
genetic operators, Estimation of Distribution Algorithms (EDAs) sample
solutions from probabilistic models which are learned from selected
individuals. It is hoped that EDAs may improve optimisation performance on
epistatic fitness landscapes by learning variable interactions. However, hardly
any rigorous results are available to support claims about the performance of
EDAs, even for fitness functions without epistasis. The expected runtime of the
Univariate Marginal Distribution Algorithm (UMDA) on OneMax was recently shown
to be in by Dang and Lehre
(GECCO 2015). Later, Krejca and Witt (FOGA 2017) proved the lower bound
via an involved drift analysis.
We prove a bound, given some restrictions
on the population size. This implies the tight bound when , matching the runtime
of classical EAs. Our analysis uses the level-based theorem and
anti-concentration properties of the Poisson-Binomial distribution. We expect
that these generic methods will facilitate further analysis of EDAs.Comment: 19 pages, 1 figur
The pathophysiology of diastolic heart failure
Whilst resting disturbances of both diastolic and long-axis systolic function are observed in patients with heart failure who have normal left ventricular ejection fraction, recent evidence suggests that dynamic disturbances in cardiac function occur during exercise. A paradoxical slowing of left ventricular active relaxation during exercise limits cardiac filling and therefore stroke volume and appears to be due to the combination of cardiac energetic impairment and disturbed ventricular-vascular coupling
Vietnam\u27s Entire People Ownership of Land: Theory and Practice
The Constitution of Vietnam declares that â[t]he Socialist Republic of Vietnam State is a socialist rule of law State of the People, by the People, and for the People.â It also states that land is âunder ownership by the entire people represented and uniformly managed by the State.â This means the entire people of Vietnam are collective landowners and the Vietnam State is their ârepresentative.â Given that, how might the public execute its real ownershipârather than treating âpeopleâs ownershipâ as just a slogan? This article analyzes the gaps in theory and practice in Vietnam, a country with a robust market economy where land user rights are marketable despite the lack of private land ownership rights. It reviews current Vietnamese land law and makes recommendations for reducing uncertainty about âentire people ownership,â and increasing the transparency and overall legitimacy of the legal regime governing private use of land. Specifically, the authors recommend that Vietnam grant lawful land users the status of âsecondary ownersâ of land, effectively as co-owners with the State and with protected property ownership rights
Maximum Power Extraction Method for a Doubly-fed Induction Generator Wind Turbine
This research presents a new scheme to extract the maximal available power from a wind turbine employing a doubly fed induction generator (DFIG). This scheme is developed from the wind turbineâs MPPT-curve. Furthermore, we propose control laws for the rotor and grid side-converters. The stability of the proposed maximum available power method and the control laws are proved mathematically upon Lyapunovâs stability criterion. Their efficiency is tested through the simulations of a DFIG wind turbine in Matlab/Simulink. Simulation results are analyzed and compared with that using a conventional scheme. Thanks to the suggested scheme, the wind turbine can track its maximum power point better and the electric energy output is higher comparing with that using the conventional scheme. Furthermore, by the suggested controllers, the rotor speed and current of the DFIG converged to their desired values. In other words, the wind turbine can achieve stable operations by the suggested control laws
Determine the source term of a two-dimensional heat equation
Let be a two-dimensional heat conduction body. We consider the
problem of determining the heat source with
be given inexactly and be unknown. The problem is nonlinear and ill-posed.
By a specific form of Fourier transforms, we shall show that the heat source is
determined uniquely by the minimum boundary condition and the temperature
distribution in at the initial time and at the final time .
Using the methods of Tikhonov's regularization and truncated integration, we
construct the regularized solutions. Numerical part is given.Comment: 18 page
Determination of the body force of a two-dimensional isotropic elastic body
Let represent a twodimensional isotropic elastic body. We
consider the problem of determining the body force whose form
with be given inexactly. The problem is
nonlinear and ill-posed. Using the Fourier transform, the methods of Tikhonov's
regularization and truncated integration, we construct a regularized solution
from the data given inexactly and derive the explicitly error estimate.
Numerical part is givenComment: 23 page
Performance of export-oriented small and medium-sized manufacturing enterprises in Viet Nam
The study recommends the formulation of policies that support the development of business linkages and networking, and which promote subcontracting arrangements between small and large enterprises or between domestic firms and foreign investment enterprises. It is also necessary to support and facilitate the direct involvement of SMMEs in exporting or indirectly through large manufacturing enterprises.Export-oriented, SME,SMME, Viet Nam
On the limitations of the univariate marginal distribution algorithm to deception and where bivariate EDAs might help
We introduce a new benchmark problem called Deceptive Leading Blocks (DLB) to
rigorously study the runtime of the Univariate Marginal Distribution Algorithm
(UMDA) in the presence of epistasis and deception. We show that simple
Evolutionary Algorithms (EAs) outperform the UMDA unless the selective pressure
is extremely high, where and are the parent and
offspring population sizes, respectively. More precisely, we show that the UMDA
with a parent population size of has an expected runtime
of on the DLB problem assuming any selective pressure
, as opposed to the expected runtime
of for the non-elitist
with . These results illustrate
inherent limitations of univariate EDAs against deception and epistasis, which
are common characteristics of real-world problems. In contrast, empirical
evidence reveals the efficiency of the bi-variate MIMIC algorithm on the DLB
problem. Our results suggest that one should consider EDAs with more complex
probabilistic models when optimising problems with some degree of epistasis and
deception.Comment: To appear in the 15th ACM/SIGEVO Workshop on Foundations of Genetic
Algorithms (FOGA XV), Potsdam, German
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