256 research outputs found
Maximum approximate entropy and r threshold: A new approach for regularity changes detection
Approximate entropy (ApEn) has been widely used as an estimator of regularity
in many scientific fields. It has proved to be a useful tool because of its
ability to distinguish different system's dynamics when there is only available
short-length noisy data. Incorrect parameter selection (embedding dimension
, threshold and data length ) and the presence of noise in the signal
can undermine the ApEn discrimination capacity. In this work we show that
() can also be used as a feature to
discern between dynamics. Moreover, the combined use of and
allows a better discrimination capacity to be accomplished, even in
the presence of noise. We conducted our studies using real physiological time
series and simulated signals corresponding to both low- and high-dimensional
systems. When is incapable of discerning between different
dynamics because of the noise presence, our results suggest that
provides additional information that can be useful for classification purposes.
Based on cross-validation tests, we conclude that, for short length noisy
signals, the joint use of and can significantly decrease
the misclassification rate of a linear classifier in comparison with their
isolated use
The Work of Amnesty International and Human Rights Watch: Evidence from Colombia
We process the main written output of Amnesty International and Human Rights Watch on Colombia covering the period 1988-2004, recording all numerical conflict information and accounts of specific conflict events. We check for internal consistency and against a unique Colombian conflict database. We find that both organizations have substantive problems in their handling of quantitative information. Problems include failre to specify sources, unclear definitions, an erratic reporting template and a distorted portrayal of conflict dynamics. Accounts of individual events are fairly representative and much more useful and accurate than the statistical information. We disprove a common accusation that Amnesty International and Human Rights Watch rarely criticize the guerrillas, but do find some evidence of anti-government bias. The quantitative human rights and conflict information produced by these organizations for other countries must be viewed with scepticism along with cross-country and time series human rights data based on Amnesty International reports.
Characterizing the dynamical importance of network nodes and links
The largest eigenvalue of the adjacency matrix of the networks is a key
quantity determining several important dynamical processes on complex networks.
Based on this fact, we present a quantitative, objective characterization of
the dynamical importance of network nodes and links in terms of their effect on
the largest eigenvalue. We show how our characterization of the dynamical
importance of nodes can be affected by degree-degree correlations and network
community structure. We discuss how our characterization can be used to
optimize techniques for controlling certain network dynamical processes and
apply our results to real networks.Comment: 4 pages, 4 figure
Spatial patterns of desynchronization bursts in networks
We adapt a previous model and analysis method (the {\it master stability
function}), extensively used for studying the stability of the synchronous
state of networks of identical chaotic oscillators, to the case of oscillators
that are similar but not exactly identical. We find that bubbling induced
desynchronization bursts occur for some parameter values. These bursts have
spatial patterns, which can be predicted from the network connectivity matrix
and the unstable periodic orbits embedded in the attractor. We test the
analysis of bursts by comparison with numerical experiments. In the case that
no bursting occurs, we discuss the deviations from the exactly synchronous
state caused by the mismatch between oscillators
Caracterízación del sedimento de una laguna tropical rasa
Se presentan las características mecánicas y los contenidos de materia orgánica,humedad, fósforo y calcio del sedimento de la laguna del Parque Norte, un sistemaeutrófico tropical raso. El sedimento se ajusta al tipo orgánico (contenido medio demateria orgánica: 16.5%), se caracteriza desde el punto de vista mecánico comofranco arenoso, con alto contenido de agua (media = 84.4%). Como consecuencia delas altas temperaturas del agua, los valores de materia orgánica y fósforo halladosfueron mucho menores al ser comparados con los encontrados en ecosistemaslacustres de la zona templada. A pesar de su condición de ecosistema raso(profundidad media: 1.60 m) y su naturaleza cinética, el ‘metabolismo de corto circuito’afecta la velocidad de la descomposición y con esto los contenidos de materiaorgánica y nutrientes en el sedimento. La dinámica del sedimento es lenta y, por ello,su resuspensión es baja, a pesar del carácter polimíctico del cuerpo de agua
The Dynamics of the Colombian Civil Conflict:A New Data Set
Abstract We present a detailed, high-frequency data set on the civil conflict in Colombia during the period 1988–2002. We briefly introduce the Colombian case and the methodological issues that hinder data collection in civil wars, before presenting the pat-tern over time of conflict actions and intensity for all sides involved in the confrontation. We also describe the pattern of victimisation by group and the victimisation of civilians out of clashes. JEL Classification D74, C81, O5
Coastal subsidence increases vulnerability to sea level rise over twenty first century in Cartagena, Caribbean Colombia
Cartagena is subsiding at a higher rate compared to that of global climate-driven sea level rise. We investigate the relative sea level rise (RSLR) and the influence of vertical land movements in Cartagena through the integration of different datasets, including tide gauge records, GPS geodetic subsidence data, and Interferometric Synthetic Aperture Radar (InSAR) observations of vertical motions. Results reveal a long-term rate (\u3e 60 years) of RSLR of 5.98 ± 0.01 mm/yr. The last two decades exhibited an even greater rate of RSLR of 7.02 ± 0.06 mm/yr. GPS subsidence rates range between − 5.71 ± 2.18 and − 2.85 ± 0.84 mm/yr. InSAR data for the 2014–2020 period show cumulative subsidence rates of up to 72.3 mm. We find that geologically induced vertical motions represent 41% of the observed changes in RSLR and that subsidence poses a major threat to Cartagena’s preservation. The geodetic subsidence rates found would imply a further additional RSLR of 83 mm by 2050 and 225 mm by 2100. The Colombian government should plan for the future and serve as an example to similar cities across the Caribbean
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