• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.1
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• pp.123-144
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• 2014

Wireless sensor networks are generally deployed for specific applications to accomplish certain objectives over a period of time. To fulfill these objectives, it is crucial that the sensor network continues to function for a long time, even if some of its nodes become faulty. Energy efficiency and fault tolerance are undoubtedly the most crucial requirements for the design of an information extraction protocol for any sensor network application. However, most existing software agent based information extraction protocols are incapable of satisfying these requirements because of static agent itineraries and large agent sizes. This paper proposes an Information Extraction protocol based on Multiple software Agents with Dynamic Itineraries (IEMADI), where multiple software agents are dispatched in parallel to perform tasks based on the query assigned to them. IEMADI decides the itinerary for an agent dynamically at each hop using local information. Through mathematical analysis and simulation, we compare the performance of IEMADI with a well known static itinerary based protocol with respect to energy consumption and response time. The results show that IEMADI provides better performance than the static itinerary based protocols.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.10
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• pp.3789-3809
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• 2015

In this paper, we deal with the problem of M2M gateways' network selection for different types of M2M traffic in heterogeneous wireless networks. Based on the difference in traffic's quality of service (QoS) requirements, the M2M traffic produced by various applications is mainly classified as two categories: flexible traffic and rigid traffic. Then, game theory is adopted to solve the problem of network-channel selection with the coexistence of flexible and rigid traffic, named as flexible network access (FNA). We prove the formulated discrete game is a potential game. The existence and feasibility of the Nash equilibrium (NE) of the proposed game are also analyzed. Then, an iterative algorithm based on optimal reaction criterion and a distributed algorithm with limited feedback based on learning automata are presented to obtain the NE of the proposed game. In simulations, the proposed iterative algorithm can achieve a near optimal sum utility of whole network with low complexity compared to the exhaustive search. In addition, the simulation results show that our proposed algorithms outperform existing methods in terms of sum utility and load balance.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.10
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• pp.3867-3886
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• 2015

This article investigates the problem of opportunistic spectrum access in dynamic environment, in which the signal-to-noise ratio (SNR) is time-varying. Different from existing work on continuous feedback, we consider more practical scenarios in which the transmitter receives an Acknowledgment (ACK) if the received SNR is larger than the required threshold, and otherwise a Non-Acknowledgment (NACK). That is, the feedback is discrete. Several applications with different threshold values are also considered in this work. The channel selection problem is formulated as a non-cooperative game, and subsequently it is proved to be a potential game, which has at least one pure strategy Nash equilibrium. Following this, a multi-agent Q-learning algorithm is proposed to converge to Nash equilibria of the game. Furthermore, opportunistic spectrum access with multiple discrete feedbacks is also investigated. Finally, the simulation results verify that the proposed multi-agent Q-learning algorithm is applicable to both situations with binary feedback and multiple discrete feedbacks.

• Journal of Korea Multimedia Society
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• v.6 no.2
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• pp.309-318
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• 2003

XML documents are widely used for exchanging information in the distributed computing environment. Here, actual information contained in the document can only be interpreted with the provision of a proper DTD. However, XML documents collected from the web nay not always be accompanied by corresponding DTD, so that it may not be easy to extract information from such sources. In this study, we reverse construct a DTD from DTU-unknown XML sources. We then use the DTD to extract information from XML inputs and to store it into the underlying DB. The DTD construction module developed is designed in such a way that, it scans input XML files in 1-path, where most other implementations use 2-path approach. The information extraction module provides clean Java programming interfaces as well, so that it can be easily integrated with other web applications.

• Journal of KIISE:Computing Practices and Letters
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• v.5 no.6
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• pp.663-673
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• 1999

WWW에 있어서 데이타베이스 통로는 필수적이다. 데이타베이스를 이용한 대부분의 웹 서비스는 CGI를 통해서 이루어지고 있는데 본 논문에서는 CGI가 갖는 문제점을 근본적으로 해결하기 위한 프레임웍으로서 JAQS(JAva Query Stub)를 제안하고 있다. JAQS를 통하여 이루어지는 서비스는 HTTP의 비연결성(connectionless) 및 무상태성(stateless)을 극복함으로써 상태 및 트랜잭션 관리를 지원할 수 있음은 물론 자바언어로 구현되어 플랫폼 독립적인 구조와 다중쓰레드를 최대한 활용하고 있다. 또한 JAQS와 함께 제안하고 있는 JAQS 관리자를 이용하면 데이타베이스가 분산되어 있는 환경에서도 효율적으로 동작할 수 있는 구조로 이루어져있다.Abstract Database gateway is absolutely vital to web-based services. Most web-based services with DBMS are implemented using CGI(Common Gateway Interface). This paper proposes a framework, dubbed JAQS(JAva Query Stub), as a solution for problems of CGI. JAQS not only supports state/transaction management by overcoming the connectionless and stateless nature of HTTP, but also effectively guarantees platform/DBMS-independence and multi-threading abilities because JAQS is implemented using Java. Also, using the JAQS Manager additionally proposed in this paper, JAQS can operate efficiently even in distributed database environments.

• Journal of Information Processing Systems
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• v.16 no.4
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• pp.975-990
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• 2020

Nowadays, the Internet of Things (IoT) network, is increasingly becoming a ubiquitous connectivity between different advanced applications such as smart cities, smart homes, smart grids, and many others. The emerging network of smart devices and objects enables people to make smart decisions through machine to machine (M2M) communication. Most real-world security and IoT-related challenges are vulnerable to various attacks that pose numerous security and privacy challenges. Therefore, IoT offers efficient and effective solutions. intrusion detection system (IDS) is a solution to address security and privacy challenges with detecting different IoT attacks. To develop an attack detection and a stable network, this paper's main objective is to provide a comprehensive overview of existing intrusion detections system for IoT environment, cyber-security threats challenges, and transparent problems and concerns are analyzed and discussed. In this paper, we propose software-defined IDS based distributed cloud architecture, that provides a secure IoT environment. Experimental evaluation of proposed architecture shows that it has better detection and accuracy than traditional methods.

• Journal of the Korea institute for structural maintenance and inspection
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• v.3 no.3
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• pp.237-243
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• 1999

Recently, there has been considerable interest in the development of fiber-optic sensors based on fiber Bragg gratings (FBGs), which can be made into Ge-doped fiber's core by UV phase mask or holographic methods. A good sensitivity and small size of this sensor make it an ideal candidate for distributed sensing in smart structures or other structural monitoring applications. In this study, fiber optic Bragg grating sensor, which could be applied to measure the absolute strains, was constructed and the strain sensitivity of this sensor was investigated in order to apply to the structural health monitoring. Fiber Fabry-Perot (FFP) filter has been used to detect the optical signals instead of optical spectrum analyzer. It has been convenient to determine the structural strains from the output signal of FBGs. The fiber optic Bragg grating sensor was attached on the aluminum beam near the electrical strain gage to measure the same strain. The relationship between strain and fiber signal was linearly fitted. The strain sensitivity of the fiber optic Bragg grating sensor was determined as $l.57{\mu}{\varepsilon}/{\mu}sec$ from the aluminum beam test.

• Annual Conference of KIPS
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• 2000.04a
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• pp.356-361
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• 2000

이벤트 서비스는 멀티미디어 통신, 전자상거래 등과 같은 대용량의 분산 응용 시스템에서 발생하는 비동기적 이벤트의 전송을 제어하기 위한 서비스이다. 하지만 기존의 이벤트 서비스는 분산 환경의 실시간 응용 시스템을 지원하기 위해 필요한 실시간 지원 기능들이 결여되어 있어 이를 지원할 수 있는 실시간 이벤트 서비스 처리 방안이 요구된다. 본 논문에서 제안하는 RTEF(Real-Time Event Filtering) 서비스는 기존의 ORB 구조에 실시간 이벤트 필터링, 실시간 모니터 및 QoS 저장소를 포함시킨 실시간 이벤트 서비스 미들웨어이다. 특히, RTEF는 이벤트 사용자의 실시간 요구사항을 분산 실시간 응용시스템에 반영시키기 위하여 이벤트 필터링 기능을 실시간 처리에 맞게 강화 시켜 기존의 시스템에서 지원하지 못한 사용자의 실시간 요구사항을 지원하는데 중점을 두었다. 분산 실시간 응용시스템에 RTEF를 적용하면 사용자에게 자신이 원하는 실시간 요구조건에 맞게 필터링된 이벤트 처리결과를 제공하게 되므로 궁극적으로 보다 높은 서비스(QoS)를 제공하게 된다. 또한 이 과정을 통해 불필요한 이벤트가 필터링 됨으로써 전체적인 네트웍 트래픽(traffic)을 감소시키는 효과를 가져온다.

• Journal of Radiation Industry
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• v.5 no.4
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• pp.305-311
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• 2011

We introduced a novel sustainable slow-releasing agrochemical formulation, a biopolymer bound to silica, for controlling plant diseases. The formulation was obtained through the following process. Curdlan, sodium silicate ($Na_2SiO_3$) and isopropyl alcohol were dissolved in DDW (Deionized-distilled water). The resultant solution was then irradiated using a $^{60}Co$ ${\gamma}$-irradiator (150 TBq of capacity; ACEL, Canada) at KAERI. The resultant solution was treated with phosphorous acid ($H_3PO_3$). Finally, we obtained a novel biopolymer-silica microsized formulation containing phosphorous acid ($H_3PO_3$) from the solution. The morphology of the complex was characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). SEM and TEM images revealed that the curdlan-silica formulation has a particle size ranging from 1 to $3{\mu}m$ with high stability. We also detected that $H_3PO_3$ was distributed within the formulation through energy dispersive X-ray spectroscopy (EDX) analysis. $H_3PO_3$ was sustain-released from the formulation in water. Based on our results, it seems effectively that one or two applications of the formulation during a cropping season will assist in controlling various plant diseases.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.164-164
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• 2016

Radar rainfall estimates have been widely used in calculating rainfall amount approximately and predicting flood risks. The radar rainfall estimates have a number of error sources such as beam blockage and ground clutter hinder their applications to hydrological flood forecasting. Moreover, it has been reported in paper that those errors are inter-correlated spatially and temporally. Therefore, in the current study, we tested influence about spatio-temporal errors in radar rainfall estimates. Spatio-temporal errors were simulated through a stochastic simulation model, called Multivariate Autoregressive (MAR). For runoff simulation, the Nam River basin in South Korea was used with the distributed rainfall-runoff model, Vflo. The results indicated that spatio-temporal dependent errors caused much higher variations in peak discharge than spatial dependent errors. To further investigate the effect of the magnitude of time correlation among radar errors, different magnitudes of temporal correlations were employed during the rainfall-runoff simulation. The results indicated that strong correlation caused a higher variation in peak discharge. This concluded that the effects on reducing temporal and spatial correlation must be taken in addition to correcting the biases in radar rainfall estimates. Acknowledgements This research was supported by a grant from a Strategic Research Project (Development of Flood Warning and Snowfall Estimation Platform Using Hydrological Radars), which was funded by the Korea Institute of Construction Technology.