• 한국정보통신설비학회:학술대회논문집
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• 2009.08a
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• pp.147-150
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• 2009

최근 새롭게 등장한 무선 센서 네트워크는 기존의 네트워크와는 다르게 통신 인프라가 없는 환경에서도 동작이 가능한 저전력 소출력의 무선 센서간의 네트워크를 형성하고 이들간의 정보 유통이 이루어진다. 무선 센서 네트워크는 열린 환경에서 배치되기 때문에 물리적 공격에 취약하다. 공격자는 손쉽게 노드들을 포획할 수 있으며 포획된 노드를 통해 허위 보고서를 네트워크에 주입할 수 있다. 허위 보고서 삽입 공격은 허위 경보를 유발할 뿐만 아니라 네트워크의 제한된 에너지를 고갈시킨다. 이러한 허위 보고서를 조기에 탐지 및 폐기하기 위하여 Yu와 Guan은 동적 여과 프로토골(dynamic on-route filtering scheme)를 제안하였다. 그러나 무선 센서 노드는 오직 제한된 진력자원으로 이루어져 있기 때문에 전력보존과 전력관리가 중요시 여겨진다. 본 논문에서는 동적 여과 프로토콜에서 허위 보고서 주입 공격에 대한 충분한 보안 강도 제공과 에너지 효율성을 위한 기법을 제안한다.

• Proceedings of the Korean Society of Computer Information Conference
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• 2015.07a
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• pp.71-72
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• 2015

WSN의 센서 노드는 제한된 자원으로 인해 보안상의 취약성을 가지며 공격자는 쉽게 임의의 데이터를 삽입하는 허위 데이터 주입 공격을 할 수 있다. WSN에서는 이러한 공격이 치명적이기 때문에 허위 데이터를 가능한 빨리 여과해야 한다. 허위 데이터 주입 공격을 탐지하는 기법으로 동적 여과 기법이 제안되었는데 이 기법은 초기 분배된 비밀키에 대한 재분배가 이루어지지 않아 같은 공격에 계속 노출될 경우 불필요한 에너지 소모가 발생한다. 본 논문에서 제안하는 기법은 효율적인 키 재분배를 통해 허위 데이터를 빨리 감지하고 에너지 효율성을 향상시킨다. 전달 노드에서 허위 데이터가 탐지되면 정의된 알람 메시지를 통해 베이스 스테이션에 보고되고 키 재분배를 수행하여 더 효율적으로 허위 데이터를 감지한다. 그러므로 제안 기법은 기존 기법과 비교하였을 때 허위 데이터를 조기에 감지하고 전체 네트워크의 에너지를 절약한다.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.14 no.1
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• pp.8-16
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• 2014

We consider the visual barcode recognition problem in a noisy video data setup. Unlike most existing single-frame recognizers that require considerable user effort to acquire clean, motionless and blur-free barcode signals, we eliminate such extra human efforts by proposing a robust video-based barcode recognition algorithm. We deal with a sequence of noisy blurred barcode image frames by posing it as an online filtering problem. In the proposed dynamic recognition model, at each frame we infer the blur level of the frame as well as the digit class label. In contrast to a frame-by-frame based approach with heuristic majority voting scheme, the class labels and frame-wise noise levels are propagated along the frame sequences in our model, and hence we exploit all cues from noisy frames that are potentially useful for predicting the barcode label in a probabilistically reasonable sense. We also suggest a visual barcode tracking approach that efficiently localizes barcode areas in video frames. The effectiveness of the proposed approaches is demonstrated empirically on both synthetic and real data setup.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.2 no.6
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• pp.280-298
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• 2008

For efficient content-based image retrieval, diverse visual features such as color, texture, and shape have been widely used. In the case of leaf images, further improvement can be achieved based on the following observations. Most plants have unique shape of leaves that consist of one or more blades. Hence, blade-based matching can be more efficient than whole shape-based matching since the number and shape of blades are very effective to filtering out dissimilar leaves. Guaranteeing rotational invariance is critical for matching accuracy. In this paper, we propose a new shape representation, indexing and matching scheme for leaf image retrieval. For leaf shape representation, we generated a distance curve that is a sequence of distances between the leaf’s center and all the contour points. For matching, we developed a blade-based matching algorithm called rotation invariant - partial dynamic time warping (RI-PDTW). To speed up the matching, we suggest two additional techniques: i) priority queue-based pruning of unnecessary blade sequences for rotational invariance, and ii) lower bound-based pruning of unnecessary partial dynamic time warping (PDTW) calculations. We implemented a prototype system on the GEMINI framework [1][2]. Using experimental results, we showed that our scheme achieves excellent performance compared to competitive schemes.

• The KIPS Transactions:PartA
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• v.12A no.1 s.91
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• pp.41-52
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• 2005

Memory reference instruction caused by cache miss is the critical factor that limits the processing power of processor. Cache prefetching technique is an effective way to reduce the latency due to memory access. However, excessively aggressive prefetch leads to cache pollution and finally to cancel out the advantage of prefetch. In this study, an active prefetch filtering scheme is introduced which dynamically decides whether to commence prefetching after referring a filtering table to reduce the cache pollution due to unnecessary prefetches. For the precision filtering, an evicted address referencing scheme has been proposed where the filter directly compares the current prefetch address with previous unnecessary prefetch addresses stored in filtering table. Moreover, a small sized exclusive prefetch cache has been introduced to increase the amount of eviction of unnecessarily prefetched addresses to enhance the accuracy of dynamic filtering. The exclusive prefetch cache also prevents useful demand data from being pushed out by prefetched data, while the evicted address direct referencing scheme enables the prefetch cache to keep most of useful prefetch data within its small size. Experimental results from commonly used general and multimedia benchmarks show that the average cache miss ratio has been decreased by $13.3{\%}$ by virtue of enhanced filtering accuracy compared with conventional schemes.

• 한국정보통신설비학회:학술대회논문집
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• 2008.08a
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• pp.197-200
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• 2008

In most sensor networks, nodes can be easily compromised by adversaries due to hostile environments. Adversaries may use compromised nodes to inject false reports into the sensor networks. Such false report attacks will cause false alarms that can waste real-world response effort, and draining the finite amount of energy resource in the battery-powered network. A dynamic enroute scheme proposed by Yu and Guan can detect and drop such false reports during the forwarding phase. In this scheme, choosing a threshold value is very important, as it trades off between security power and energy consumption. In this paper, we propose a threshold determining method which uses the fuzzy rule-based system. The base station periodically determines a threshold value though the fuzzy rule-based system. The number of cluster nodes, the value of the key dissemination limit, and the remaining energy of nodes are used to determine the threshold value.

• Journal of Mechanical Science and Technology
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• v.14 no.4
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• pp.369-379
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• 2000

In industrial production-distribution systems, production and purchasing rates, associated inventories, and sales are very critical for the profits of each component in the system. The objective of this study is to investigate an effective information control scheme for a production -distribution system by automatic feedback control techniques. In this work, a dynamic control scheme that has an integrated -error with state-feedback and filtering (ISFF) is proposed as a new algorithm for a dynamic controller. Generalized formulations of the dynamic control are proposed in the continuous-time and discrete-time cases. A methodology for an evaluation of ISFF controller gains using the eigen structure property is presented. When an upper-limit is imposed on the production capability by available factory space and capital equipment, supervisory control is provided to avoid integrator-windup and deterioration of system performance.

• Journal of Broadcast Engineering
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• v.14 no.2
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• pp.238-252
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• 2009

Due to the rapid increase of available contents via the convergence of broadcasting and internet, the efficient access to personally preferred contents has become an important issue. In this paper, for recommendation scheme for TV programs using a collaborative filtering technique is studied. For recommendation of user preferred TV programs, our proposed recommendation scheme consists of offline and online computation. About offline computation, we propose reasoning implicitly each user's preference in TV programs in terms of program contents, genres and channels, and propose clustering users based on each user's preferences in terms of genres and channels by dynamic fuzzy clustering method. After an active user logs in, to recommend TV programs to the user with high accuracy, the online computation includes pulling similar users to an active user by similarity measure based on the standard preference list of active user and filtering-out of the watched TV programs of the similar users, which do not exist in EPG and ranking of the remaining TV programs by proposed rank model. Especially, in this paper, the BM (Best Match) algorithm is extended to make the recommended TV programs be ranked by taking into account user's preferences. The experimental results show that the proposed scheme with the extended BM model yields 62.1% of prediction accuracy in top five recommendations for the TV watching history of 2,441 people.

• Proceedings of the Korean Society of Computer Information Conference
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• 2013.07a
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• pp.11-13
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• 2013

무선 센서 네트워크는 개방된 환경에서 무작위로 배치되어 악의적인 공격자들에게 쉽게 노출된다. 센서 노드는 한정된 에너지 자원과 손쉽게 훼손된다는 단점을 통해 허위 보고서와 투표 삽입 공격이 발생한다. Li와 Wu는 두 공격을 대응하기 위해 확률적 투표기반 여과기법을 제안하였다. 확률적 투표기반 여과기법은 고정적인 검증 경로를 결정하기 때문에 특정 노드의 에너지 자원고갈 위험이 있다. 본 논문에서는 센서 네트워크에서 보고서 여과 확률 향상을 위하여 퍼지 시스템을 기반으로 다음 노드 선택을 약 6% 효율적인 경로 선택 방법을 제안한다. 제안 기법은 전달 경로 상의 노드 중 상태정보가 높은 노드를 검증 노드로 선택하고, 선택된 검증 노드는 허용 범위 경계 값을 기준으로 공격 유형을 판별하고 여과한다. 실험결과를 통해 제안기법은 기존기법과 비교하였을 때 에너지 효율이 향상되었다.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.803-807
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• 2001

This paper presents a new control scheme for a DVR (Dynamic Voltage Restorer) system consisting of series voltage source PWM converters. To control the negative sequence components of the source, it is necessary to detect the negative sequence components. Generally, a filtering process is used which has some undesirable effects. This paper suggests a new method for separating positive and negative sequences components. This control system is designed using differential controllers and digital filters. The positive and negative sequences are extracted and controlled individually. The performance of the presented controller and scheme are confirmed through simulation and actual experiment with a 2.5kVA prototype DVR system.