Doo-Soon Park

Large-Scale Middleware for Ubiquitous Sensor Networks

As our information society transitions from human-to object-oriented information, especially in ubiquitous-network environments, the advanced technologies developed for ubiquitous sensor networks (USNs) have received considerable attention. In addition, the prevalence of USN computing environments raises the issue of how applications can take full advantage of contextaware information. The main tasks of ubiquitous computing include generating new information from objects on the basis of data received from sensors, transmitting the newly generated information through wireless networks, analyzing the information received, and performing the specific tasks from that analysis. To establish a ubiquitous-computing environment, various fields (administration, medical, transportation, environment, disaster prevention, and so on) have incorporated USN technologies (such as sensor node hardware, sensor networks, and USN middleware) and USN application services (such as ecosystem forecasting, sniper countermeasures, health monitoring, environment observation, and surveillance to detect intruders).

Lifetime maximization considering target coverage and connectivity in directional image/video sensor networks

A directional sensor network consists of a large number of directional sensors (e.g., image/video sensors), which have a limited angle of sensing range due to technical constraints or cost considerations. In such directional sensor networks, the power saving issue is a challenging problem. In this paper, we address the Directional Cover and Transmission (DCT) problem of organizing the directional sensors into a group of non-disjoint subsets to extend the network lifetime. One subset in which the directional sensors cover all the targets and forward the sensed data to the sink is activated at one time, while the others sleep to conserve their energy. For the DCT problem proven to be the NP-complete problem, we present a heuristic algorithm called the Shortest Path from Target to Sink (SPTS)-greedy algorithm. To verify and evaluate the proposed algorithm, we conduct extensive simulations and show that it can contribute to extending the network lifetime to a reasonable extent.

Performance Improvement of a Movie Recommendation System based on Personal Propensity and Secure Collaborative Filtering

Abstract —There are many recommendation systems available to provide users with personalized services. Among them, the most frequently used in electronic commerce is ‘collaborative filtering’, which is a technique that provides a process of filtering customer information for the preparation of profiles and making recommendations of products that are expected to be preferred by other users, based on such information profiles. Collaborative filtering systems, however, have in their nature both technical issues such as sparsity, scalability, and transparency, as well as security issues in the collection of the information that becomes the basis for preparation of the profiles. In this paper, we suggest a movie recommendation system, based on the selection of optimal personal propensity variables and the utilization of a secure collaborating filtering system, in order to provide a solution to such sparsity and scalability issues. At the same time, we adopt ‘push attack’ principles to deal with the security vulnerability of collaborative filtering systems. Furthermore, we assess the system’s applicability by using the open database MovieLens, and present a personal propensity framework for improvement in the performance of recommender systems. We successfully come up with a movie recommendation system through the selection of optimal personalization factors and the embodiment of a safe collaborative filtering system

Proxy based seamless connection management method in mobile cloud computing

Nowadays, complex smartphone applications are developed that support gaming, navigation, video editing, augmented reality, and speech recognition which require considerable computational power and battery lifetime. The cloud computing provides a brand new opportunity for the development of mobile applications. Mobile Hosts (MHs) are provided with data storage and processing services on a cloud computing platform rather than on the MHs. To provide seamless connection and reliable cloud service, we are focused on communication. When the connection to cloud server is increased explosively, each MH connection quality has to be declined. It causes several problems: network delay, retransmission, and so on. In this paper, we propose proxy based architecture to improve link performance for each MH in mobile cloud computing. By proposed proxy, the MH need not keep connection of the cloud server because it just connected one of proxy in the same subnet. And we propose the optimal access network discovery algorithm to optimize bandwidth usage. When the MH changes its point of attachment, proposed discovery algorithm helps to connect the optimal access network for cloud service. By experiment result and analysis, the proposed connection management method has better performance than the 802.11 access method.

k-Cliques mining in dynamic social networks based on triadic formal concept analysis

Internet of Things (IoT), an emerging computing paradigm which interconnects various ubiquitous things is facilitating the advancement of computational intelligence. This paper aims at investigating the computation intelligence extraction approach with focus on the dynamic k-clique mining that is an important issue in social network analysis. The k-clique detection problem as one of the fundamental problems in computer science, can assist us to understand the organization style and behavioral patterns of users in social networks. However, real social networks usually evolve over time and it remains a challenge to efficiently detect the k-cliques from dynamic social networks. To address this challenge, this paper proposes an efficient k-clique dynamic detection theorem based on triadic formal concept analysis (TFCA) with completed mathematical proof. With this proposed detection theorem, we prove that the k-cliques detection problem is equivalent to finding the explicit k-cliques generated from k-triadic equiconcepts plus the implicit k-cliques derived from its high-order triadic equiconcepts. Theoretical analysis and experimental results illustrate that the proposed detection algorithm is efficient for finding the k-cliques and exploring the dynamic characteristics of the sub-structures in social networks.

Betweenness of Expanded Ego Networks in Sociality-Aware Delay Tolerant Networks

Recently, the consideration of social characteristics present a new angle of view in the design of data routing and dissemination in delay tolerant networks. Many social network studies have been undertaken using a ego network because it has the benefit of simplicity in data collection and gives statistically significant features about the entire network in many cases. In this paper, we newly define the expanded ego network by comprising the ego’s 2-hop neighbor nodes as well as the ego’s 1-hop ones. In delay tolerant networks, the expended ego network can be easily self-configured at a node and it can contain more network information than the ego network. Therefore, it is expected that the effectiveness of the expanded ego network will be higher than the one of the ego network in terms of data routing and dissemination. We examine that the relationship among the expanded ego betweenness, the ego betweenness, and the betweenness of the entire network for a node. By a simulation study, we show that the expanded ego betweenness is highly correlated with the betweenness of the entire network when the network is dense and its nodes are highly inter-related.

A Resource Management System for Fault Tolerance in Grid Computing

In Grid computing, resource management and fault tolerance services are important issues. The availability of the selected resources for job execution is a primary factor that determines the computing performance. The failure occurrence of resources in the grid computing is higher than in a tradition parallel computing. Since the failure of resources affects job execution fatally, fault tolerance service is essential in computational grids. And grid services are often expected to meet some minimum levels of quality of service (QoS) for desirable operation. However Globus toolkit does not provide fault tolerance service that supports fault detection service and management service and satisfies QoS requirement. Thus this paper proposes fault tolerance service to satisfy QoS requirement in computational grids. In order to provide fault tolerance service and satisfy QoS requirements, we expand the definition of failure, such as process failure, processor failure, and network failure. And we propose resource scheduling service, fault detection service and fault management service and show implement and experiment results.

Experimental study of the potential hazards of surgical smoke from powered instruments

Many surgical instruments have been replaced with powered devices in open gastrointestinal and laparoscopic surgery. The production of smoke as a result of vaporization of surgical tissue is inevitable, and exposure to surgical smoke is a long‐standing concern. These vapours are potentially hazardous to patients and surgical teams. The present research was designed to compare various surgical devices to determine whether viable cells exist in their surgical smoke.

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.

An instant messenger system for learner analysis in e-learning environment

In this paper, we present the idea of using an instant messenger system to collect and analysis information of learner in e-learning environment. For learner behavior analysis, we store data about the learners actions in log files by information gathering agent and perform basic analysis, process analysis and synthesis analysis by information analysis agent. Our instant messenger system can provide personalized feedback to learners about the quantity of quality of their learning.