Chan Yeol Park

Characterizing and Classifying Desktop Grid

Desktop Grid has recently received the strong attraction for executing high throughput applications as CPU, storage and network capacities improve and become cheaper. Desktop Grid is different from Grid in many respects, but there is no general survey or taxonomy for desktop Grid. Therefore, we propose a new comprehensive taxonomy and survey of desktop Grid in order to characterize and categorize desktop Grid.

Centroid-Based Movement Assisted Sensor Deployment Schemes in Wireless Sensor Networks

Efficient deployment of sensors is an important issue in wireless sensor networks. If we deploy sensors randomly by our hands or carriers only, some unlucky places are not covered forever. In this paper, we propose distributed self-deployment schemes of mobile sensors. At first, sensors are deployed randomly. They then calculate the next positions locally by utilizing the proposed schemes and move to them. The locations of the sensors are adjusted round by round so that the coverage is gradually improved. By using Voronoi diagram and centroid (geometric center), we design two schemes, named Centroid (centroid-based scheme) and Dual-Centroid (dual-centroid based scheme). We also measure the performance of the proposed schemes and the existing schemes, and show that the proposed schemes get better results.

Adaptive Result Verification Based on Fuzzy Inference Model in Desktop Grid Environments

A result verification procedure is required to guarantee the correctness of task results executed by any unspecified resources in desktop grids. Voting-based and trust-based schemes have typically been used for desktop grids. However, these schemes can encounter two problems: waste of resources, due to redundant replications of each task, and increased turnaround time, due to the inability to deal with a dynamic changeable execution environment. To overcome these problems, we propose an adaptive result verification scheme based on fuzzy inference that can determine the number of replications per task needed for result verification. Our scheme is based on the classification of resources according to the trusty degree and the result return probability. Using these two parameters, we develop the fuzzy inference model that allows correct task results to be returned by a task deadline for current desktop grid environments. Simulation results indicate that our scheme is superior to others in terms of turnaround time of entire tasks, quantity of resources consumed, and number of reallocations per task.

Lifetime Maximization Considering Connectivity and Overlapped Targets in Wireless Sensor Networks

A critical issue in wireless sensor networks is an energy-efficiency since the sensor batteries have limited energy power and, in most cases, are not rechargeable. The most practical manner relate to this issue is to use a node wake-up scheduling protocol that some sensor nodes stay active to provide sensing service, while the others are inactive for conserving their energy. Especially, CTC (Connected Target Coverage) problem has been considered as a representative energy-efficiency problem considering connectivity as well as target coverage. In this paper, we propose a new energy consumption model considering overlapped targets and create a new problem, OTCC (Overlapped Target and Connected Coverage) problem of which objective is to maximize the network lifetime based on the new energy consumption model. Also, we present SPT (Shortest Path based on Targets)-Greedy algorithm to solve the problem. Our simulation results show that SPT-Greedy algorithm performs much better than the previous algorithm in terms of the network lifetime.

A Community Detection Scheme in Delay-Tolerant Networks

Social analysis and community structure detection present a new angle of view in the design of data routing and dissemination in delay tolerant networks (DTNs). However, most community detection schemes developed in the context of sociology cannot be applied to DTNs since they have been designed without the consideration of the dynamic aspect of DTNs where the network topology changes and evolves over times. In this paper, we propose a new community detection algorithm which runs in a distributed and real-time manner and thus can be used in time-varying networks like DTNs. From the performance study, we show that our algorithm well adapts to dynamically changing networks.

Study on Relation between Social Circles and Communities in Facebook Ego Networks

Community detection is a core problem in social network analysis. Strictly speaking, however, the communities does not exactly correspond to the real group, well-known as social circles. In this paper, we study on 1) how close relation between the ground-truth social circles and communities exists and 2) whether the social circles can be detected by the classical community detection algorithm or not. We use the SNAP facebook dataset to reveal the correlation between the social circles and the detected communities. We listed up the community’s modularity values and the balanced accuracy values with the ground-truth circles per each level in the iterative process of divisive clustering. We analyzed the Spearman’s rank correlation between the paired data. The experimental results show that there is a strong correlation between the ground-truth social circles and the communities detected by classical method.

Failure Restoration for Location Server with User Movement Learning and Prediction

In this paper, we propose a restoration scheme from the location server failure using mobile users location pattern prediction. We consider each user has its own movement pattern with a day, a week, or a month. Whenever a mobile user registers or updates its location, the movement pattern is learned by a neuro-fuzzy inference system (NFS). When a failure occurs, the locations of mobile users are predicted by the NFS, and the predicted location is used to find the location where mobile user is. We classify several mobility patterns for individuals, and the performance of the NFS prediction and the restoration scheme is shown through simulation.

Tiger: Toward Object-Oriented Distributed and Parallel Programming in Global Environment

None of the current attempts to provide an Internet-wide global computing infrastructure presents well-defined programming constructs such as object distribution, dispatching, migration and concurrency with maximum portability and high transparency to a programmer. We propose a Web-based global computing infrastructure called Tiger, providing well-defined object-oriented programming constructs They allow a programmer to develop a well-composed, object-oriented distributed and parallel application using globally extended resources. We show the performance enhancement by conducting an experiment with a genetic-neuro-fuzzy algorithms.