• Korean Journal of Remote Sensing
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• v.36 no.5_2
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• pp.975-988
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• 2020

Change detection is the process of identifying changes by observing the multi-temporal images at different times, and it is an important technique in remote sensing using satellite images. Among the change detection methods, the unsupervised change detection technique has the advantage of extracting rapidly the change area as a binary image. However, it is difficult to understand the changing pattern of land cover in binary images. This study used grid points generated from seamless digital map to evaluate the satellite image change detection results. The land cover change results were extracted using multi-temporal KOMPSAT-3A (K3A) data taken by Gimje Free Trade Zone and change detection algorithm used Spectral Angle Mapper (SAM). Change detection results were presented as binary images using the methods Otsu, Kittler, Kapur, and Tsai among the automated threshold selection algorithms. To consider the seasonal change of vegetation in the change detection process, we used the threshold of Differenced Normalized Difference Vegetation Index (dNDVI) through the probability density function. The experimental results showed the accuracy of the Otsu and Kapur was the highest at 58.16%, and the accuracy improved to 85.47% when the seasonal effects were removed through dNDVI. The algorithm generated based on this research is considered to be an effective method for accuracy assessment and identifying changes pattern when applied to unsupervised change detection.

• Journal of KIISE:Computer Systems and Theory
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• v.31 no.1_2
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• pp.41-50
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• 2004

Detecting races is important for debugging shared-memory Parallel programs, because races result in unintended nondeterministic executions of the programs. Particularly, the first races to occur in an execution of a program must be detected because they can potentially affect other races that occur later. Previous on-the-fly techniques that detect such first races based on candidate events that are likely to participate in the first races monitor access events in order to collect the candidate events during a program execution, and try to report the races only from determining the concurrency relationships of the candidates. Such races reported in this way. however, are not guaranteed to be first races, because they are not determined by taking into account how they are affected with each other. This paper presents a new post-mortem technique that analyzes, on each nesting level, candidate events collected from an execution of a shared-memory program with nested parallelism in order to report only first races. This technique is efficient, because it guarantees that first races reported by analyzing a nesting level are the races that occur first at the level, and does not require more analyses to the higher nesting levels than the current level. The Proposed technique facilitates more practical and effective debugging than the previous techniques, because it guarantees to detect first races if candidate events are collected from an execution instance of the program with nested parallelism.

• The KIPS Transactions:PartA
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• v.17A no.1
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• pp.9-18
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• 2010

Races that occur in shared-memory parallel programs such as OpenMP programs must be detected for debugging because of causing unintended non-deterministic results. Previous works which verify the existence of these races on-the-fly are limited to the programs without internal non-determinism. But in the programs with internal non-determinism, such works need at least N! execution instances for each critical section to verify the existence of races, where N is the degree of maximum parallelism. This paper presents a preprocessor that statically analyzes the locations of non-deterministic accesses using program slicing and can detect apparent races as well as potential races through single execution using the analyzed information. The suggested tool can deterministically monitor non-deterministic accesses to occur in OpenMP programs so that this tool can verify the existence of races even if it is used any race detection protocol which can apply to programs with critical section. To prove empirically this tool, we have experimented using a set of benchmark programs such as synthetic programs that involve non-deterministic accesses, OpenMP Microbenchmark, NAS Parallel Benchmark, and OpenMP application programs.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 1997.11a
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• pp.151-160
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• 1997

최근에 시스템의 불법적인 침입, 정보 유출 등의 보안 사고가 많아지면서 컴퓨터 보안을 위한 많은 방법들이 제시되고 있다. 그 중에서도 컴퓨터 시스템 자체에 존재하는 보안상의 결함을 막기 위한 노력들이 있어왔다. 그러나 시스템의 보안 결함은 기본적으로 운영체제나 어플리케이션 자체의 버그에 기인하므로 끊임없이 출현하는 실정이다. 따라서, 시스템 관리자가 이를 일일이 확인하여 보안 결함을 체크하고 대응하는 것은 상당히 힘든 일일 것이다. 본 논문에서는 HTTP 프로토콜을 이용하여 클라이언트 시스템의 보안 결함을 원격으로 점검해 주는 주문형 보안 결함 탐지 서버(Security On Demand)에 대해 설명한다. 주문형 보안 결함 탐지 서버(이하 SOD 서버)는 서버-클라이언트 모델로서 클라이언트가 원하면 보안 결함을 탐지하는 코드를 전송하여 클라이언트 측에서 실행되도록 한다. 그러므로 SOD서버 측에만 새로이 출현한 보안 결함 탐지코드를 추가하면 클라이언트는 최신의 보안 결함에 대한 점검이 가능하다. 또한 코드 자체가 클라이언트로 전송되어 수행되기 때문에 클라이언트측의 보안 결함 정보가 서버로 유출되지 않는 장점이 있다.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.535-538
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• 2004

마이크로폰을 이용하여 평면상에 직교형으로 배열된 음인 도래 방향 탐지 시스템을 구성하고, A/D 변환에 있어 일반저인 샘플링 기법과 spilt-beam형 어군 탐지 시스템에 적용된 4분 샘플링 기법을 이용하여 공기중에서의 음원의 토래 방향 탐지 성능에 관한 실험을 수행하였다. 일반 실내에서 단일 주파수의 음원에 대하여 직교형 마이크로폰 배열을 사용한 음인 토래 방향 탐지 시스템 및 4분 샘플링 기법의 적용이 유용함을 확인하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2018.05a
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• pp.424-427
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• 2018

영상이나 비디오에 담긴 장면을 이해하는 것은 컴퓨터 비전의 궁극적인 목표 중 하나이다. 본 논문에서는 입력 영상으로부터 장면을 구성하는 각 물체들과 그들 간의 공간 관계, 개별 물체들의 다양한 속성들을 탐지해, 지식 그래프를 생성해주는 심층 신경망 기반의 물체 속성 및 공간 관계 탐지 모델을 제안한다. 본 논문에서는 이러한 다양한 복합 시각 인식 작업을 동시에 수행하는 탐지 모델의 구성에 대해 설명하고, 대규모 벤치마크 데이터 집합인 CLEVR을 이용한 탐지 모델의 성능 분석 실험 결과를 소개한다.

• Review of KIISC
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• v.29 no.2
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• pp.29-35
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• 2019

CPS(Cyber Physical System)에 대한 사이버 공격이 다양해지고 고도화됨에 따라 시그니쳐에 기반한 악성행위 탐지는 한계가 있어 기계학습 기반의 정상행위 학습을 통한 비정상행위 탐지 기법이 많이 연구되고 있다. 그러나 CPS 보안 연구는 보안상의 이유로 CPS 데이터가 주로 외부에 공개되지 않으며 또한 실제 비정상행위를 가동 중인 CPS에 실험하는 것이 불가능하여 개발 기법의 검증이 어려운 문제가 있다. 이를 해결하기 위해 2015년 SUTD(Singapore University of Technology and Design)의 iTrust 연구소에서 SWaT(Secure Water Treatment) 테스트베드를 구성하고 36가지의 공격을 수행한 데이터셋을 공개하였다. 이후 국 내외에서 SWaT 테스트베드 데이터를 사용하여 다양한 보안 기법을 검증한 연구결과가 발표되고 있으며 CPS 보안에 기여하고 있다. 따라서 본 논문에서는 SWaT 테스트베드 데이터 및 SWaT 테스트베드 데이터에 기반한 비정상행위 탐지 연구를 분석한 내용을 설명하고, 이를 통해 CPS 비정상행위 탐지 설계의 주요 요소를 분석하여 제시하고자 한다.

• Convergence Security Journal
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• v.13 no.3
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• pp.33-38
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• 2013

Security between mobile nodes and efficient communication is one of the most important parts of the MANET. In particular, the wireless network is significantly higher for the attack threats because of collaborative structure for open communication media and communication. However, application of existing security mechanisms and intrusion detection system is not easy due to the characteristics of MANET. It is because collection and integration of adult data by the dynamic topology due to the mobility of nodes and many network sensors is difficult. In this study, we propose cooperative security system technique that can improve the reliability based on authentication assessing confidence about the whole nodes which joins to network and detect effectively this when intrusion occurs. Cluster head which manages the cluster performs CA role for the certificate issue and the gateway node performs role of intrusion detection system. Intrusion detection is performed by cooperating with neighboring nodes when attack is not detected in one intrusion detection node. The performance of the proposed method was confirmed through experiments comparing with the SRP technique.

• Korean Journal of Remote Sensing
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• v.36 no.5_1
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• pp.775-784
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• 2020

Recent global warming and anthropogenic activities have caused more frequent and massive wildfires with longer durations and more significant damages. MODIS has been monitoring global wildfires for almost 20 years, and GK2A and Himawari-8 are observing the wildfires in East Asia 144 times a day. However, the spatial resolution of 1 to 2 km is not sufficient for the detection of small and medium-size active fires, and therefore the studies on the active fire detection using high-resolution images are essential. However, there is no official product for the high-resolution active fire detection. Hence, we implemented the active fire detection algorithm of Landsat 8 and carried out a high-resolution-based detection of active fires in Australia in 2019, followed by the comparisons with the products of Himawari-8 and MODIS. Regarding the intense fires, the three satellites showed similar results, whereas the weak igniting and extinguishing fires or the fires in narrow areas were detected by only Landsat 8 with a 30m resolution. Small-sized fires, which are the majority in Korea, can be detected by the high-resolution satellites such as Landsat 8, Sentinel-2, Kompsat-3A, and the forthcoming Kompsat-7. Also, a comprehensive analysis together with the geostationary satellites in East Asia such as GK2A, Himawari-8, and Fengyun-3 will help the interoperability and the improvement of spatial and temporal resolutions.

• Journal of the Korea Society of Computer and Information
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• v.26 no.9
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• pp.1-12
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• 2021

In this paper, we propose a tool called ARCAV (Atomatic Recovery of CUDA Atomicity violation) to automatically repair atomicity violations in GPU (Graphics Processing Unit) program. ARCAV monitors information of every barrier and memory to make actual memory writes occur at the end of the barrier region or to make the program execute barrier region again. Existing methods do not repair atomicity violations but only detect the atomicity violations in GPU programs because GPU programs generally do not support lock and sleep instructions which are necessary for repairing the atomicity violations. Proposed ARCAV is designed for GPU execution model. ARCAV detects and repairs four patterns of atomicity violations which represent real-world cases. Moreover, ARCAV is independent of memory hierarchy and thread configuration. Our experiments show that the performance of ARCAV is stable regardless of the number of threads or blocks. The overhead of ARCAV is evaluated using four real-world kernels, and its slowdown is 2.1x, in average, of native execution time.