• Journal of the Korean Mathematical Society
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• v.60 no.2
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• pp.255-271
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• 2023

In this paper, we deal with random attractors for dynamical systems forced by a deterministic noise. These kind of systems are modeled as skew products where the dynamics of the forcing process are described by the base transformation. Here, we consider skew products over the Bernoulli shift with the unit interval fiber. We study the geometric structure of maximal attractors, the orbit stability and stability of mixing of these skew products under random perturbations of the fiber maps. We show that there exists an open set U in the space of such skew products so that any skew product belonging to this set admits an attractor which is either a continuous invariant graph or a bony graph attractor. These skew products have negative fiber Lyapunov exponents and their fiber maps are non-uniformly contracting, hence the non-uniform contraction rates are measured by Lyapnnov exponents. Furthermore, each skew product of U admits an invariant ergodic measure whose support is contained in that attractor. Additionally, we show that the invariant measure for the perturbed system is continuous in the Hutchinson metric.

• Journal of applied mathematics & informatics
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• v.41 no.6
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• pp.1341-1364
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• 2023

This article introduces a method for estimating the conditional hazard function of a real-valued response variable based on a functional variable. The method uses local linear estimation of the conditional density and cumulative distribution function and is applied to a functional stationary ergodic process where the explanatory variable is in a semi-metric space and the response is a scalar value. We also examine the uniform almost complete convergence of this estimation technique.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.8
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• pp.3551-3567
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• 2016

The Low Earth Orbit satellite network has the unique characteristics of the non-uniform and time-variant traffic load distribution, which often causes severe link congestion and thus results in poor performance for delay-sensitive flows, especially when the network is heavily loaded. To solve this problem, a novel adaptive routing algorithm, referred to as the delay-oriented adaptive routing algorithm (DOAR), is proposed. Different from current reactive schemes, DOAR employs Destination-Sequenced Distance-Vector (DSDV) routing algorithm, which is a proactive scheme. DSDV is extended to a multipath QoS version to generate alternative routes in active with real-time delay metric, which leads to two significant advantages. First, the flows can be timely and accurately detected for route adjustment. Second, it enables fast, flexible, and optimized QoS matching between the alternative routes and adjustment requiring flows and meanwhile avoids delay growth caused by increased hop number and diffused congestion range. In addition, a retrospective route adjustment requesting scheme is designed in DOAR to enlarge the alternative routes set in the severe congestion state in a large area. Simulation result suggests that DOAR performs better than typical adaptive routing algorithms in terms of the throughput and the delay in a variety of traffic intensity.

• Journal of the Korean Society for Library and Information Science
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• v.49 no.4
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• pp.241-264
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• 2015

Bibliometric analysis for research performance evaluation can generate erroneous assessments for various reasons. Application of the same evaluation metric to different domains, for instance, can produce unfair evaluation results, while analysis based on incomplete data can lead to incorrect conclusions. This study examines bibliometric data of library and information science (LIS) research in Korea to investigate whether research performance should be evaluated in a uniform manner in multi-disciplinary fields such as LIS and how data incompleteness can affect the bibliometric assessment outcomes. The initial analysis of our study data, which consisted of 4,350 citations to 1,986 domestic papers published between 2001 and 2010 by 163 LIS faculty members in Korea, showed an anomalous citation pattern caused by data incompleteness, which was addressed via data projection based on past citation trends. The subsequent analysis of augmented study data revealed ample evidence of bibliometric pattern differences across subject areas. In addition to highlighting the need for a subject-specific assessment of research performance, the study demonstrated the importance of rigorous analysis and careful interpretation of bibliometric data by identifying and compensating for deficiencies in the data source, examining per capita as well as overall statistics, and considering various facets of research in order to interpret what the numbers reflect rather than merely taking them at face value as quantitative measures of research performance.