• Proceedings of the Korean Information Science Society Conference
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• 2011.06c
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• pp.88-91
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• 2011

NAND 플래시 메모리는 저전력과 빠른 접근 속도의 특징 때문에 차세대 저장장치로 주목 받고 있다. 특히 플래시 메모리로 만들어진 SSD(solid state disk)는 인터페이스가 기존의 하드디스크와 동일하고 대용량화 되고 있기 때문에 가까운 미래에 다양한 저장시스템의 저장장치로 사용될 것으로 예상된다. 그러나 NAND 플래시메모리 기반 저장장치는 쓰기 전 소거 구조와 같은 독특한 하드웨어 특징을 가지고 있기 때문에 특정 지역에 반복적인 쓰기 요청을 발생하는 B트리를 구축하는 것은 심각한 성능저하를 야기 할 것이다. 이러한 문제를 해결하기 위해 버퍼를 이용하여 B트리 구축 성능을 개선한 방법들이 제안되었다. 그러나 이러한 기법들은 갑작스러운 전원 차단 시 버퍼에 유지하고 있던 데이터를 모두 유실하기 때문에 고장회복을 위한 추가적인 방법이 필요하다. 따라서 본 논문에서는 버퍼를 이용한 방법 중 IBSF기법을 기반으로 NAND 플래시 메모리 기반 저장장치에서 고성능의B트리 구축 방법뿐만 아니라 전원 차단시 효율적인 고장회복을 할 수 있는 기법을 제안한다. 본 논문에서 제안하는 기법은 B트리 변경시 변경 된 정보를 로그에 저장하여 관리한다. 또한 루트노드가 변경될 때 검사점(checkpoint)을 수행한다. 마지막으로 다양한 실험을 통하여 본 논문의 고장회복 성능을 보여준다.

• The Journal of the Acoustical Society of Korea
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• v.32 no.2
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• pp.147-156
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• 2013

In this paper, a new speech endpoint detection method in noisy environments for moving robot platforms is proposed. In the conventional method, the endpoint of speech is obtained by applying an edge detection filter that finds abrupt changes in the feature domain. However, since the feature of the frame energy is unstable in such noisy environments, it is difficult to accurately find the endpoint of speech. Therefore, a novel feature extraction method based on the twice-iterated fast fourier transform (TIFFT) and statistical models of speech is proposed. The proposed feature extraction method was applied to an edge detection filter for effective detection of the endpoint of speech. Representative experiments claim that there was a substantial improvement over the conventional method.

• Proceedings of the Korean Information Science Society Conference
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• 2001.04a
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• pp.805-807
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• 2001

안전한 컴퓨터 시스템 평가기준인 TCSEC(Trusted Computer System Evaluation Criteria)[1] B1급 이상 시스템의 안전한 운영체제들은 강제접근통제(Mandatory Access Control : MAC) 메커니즘을 이용하여 정보의 흐름을 제어하고 있다. 하지만 아무리 정확하게 설계된 접근통제 메커니즘이라고 하더라도 시스템 관리자 또는 보안 관리자가 어떻게 시스템이 접근통제 메커니즘을 관리.운영하느냐에 따라 그 시스템의 안전성과 보안에 대한 신뢰도가 결정된다고 할 수 있다. 지금까지 연구되고 있는 대부분의 MAC을 적용한 안전한 운영체제는 접근통제메커니즘의 적용 및 관리.운영상의 보안문제점을 관리할 적당한 방법을 제시하고 있지 않다[4][5][6][7]. 본 논문은 MAC을 적용한 안전한 운영체제의 안전하고 효율적인 관리.운영을 위한 방법으로 LMACM(Log Manager for Access Control Mechanism)을 제안한다.

• Journal of Life Science
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• v.7 no.2
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• pp.73-78
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• 1997

Ion exchange performence to remove nitrate in water studied using commercially available strong vase anin exchange resin of $Cl^{-}$ type in the batch reactors. Anion exchange resin was more effective than activated carbon or zeolite. With large resin amount or high temperature or low initial concentration, nitrate removal characteristics for a typical gel-type resin was increased. The curves showed the generally accepted selectivity sequence as ${SO_4}^{2-}>{No_3}^->NO_{2-}>{HCO_3}^-$.

• KIPS Transactions on Computer and Communication Systems
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• v.8 no.1
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• pp.9-16
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• 2019

Smartphones are becoming a portable computer. As a result, even the most sensitive financial application services are now available anywhere on the smartphone. Compared to general PCs, smartphones communicate with external devices through various channels such as wireless internet, mobile communication network, Bluetooth, and NFC, and a wide variety of applications are provided. Therefore, if vulnerabilities exist, the possibility of attack damage increases. In this paper, we analyze the vulnerabilities of dynamic virtual keyboards used in login of banking apps of smartphones with various physical constraints and propose countermeasures.

• Convergence Security Journal
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• v.17 no.5
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• pp.71-76
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• 2017

Today, it is an information society where a large number of users access and view important data in a large number of information assets as needed. In this complexity, techniques related Identify Management are being applied, in order to verify authorized user access to important information assets and manage of history. But, the ability access to sensitive information using account has the disadvantage of being able to open the way for information to the attacker when it is hijacked. Thus, in this paper, we propose a secure Identify Management System that can control the use of accounts based on the attitude of the account holder, but also enhances the security and does not hinder the convenience.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.18 no.1
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• pp.103-114
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• 2008

Single Sign-On is an authentication scheme that enables a user to authenticate once and then to access to the resources of multiple software systems without re-authentication. As web services are being integrated into a single groupware, more web sites are adopting for user convenience. However, these Single Sign-On services are very dependent upon the cookies and thus, simple eavesdropping enables attackers to hiject the user's session. Even worse, the attacker who hijacked one session can move to another site through the Single Sign-On. In this paper, we show the vulnerabilities of the top ranked sites regarding this point of view and also propose a way to protect a user's session.

• The Journal of Korean Institute of Information Technology
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• v.17 no.12
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• pp.29-38
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• 2019

A path prediction method using lifelog requires a large amount of training data for accurate path prediction, and the path prediction performance is degraded when the training data is insufficient. The lack of training data can be solved using data of other users having similar user movement patterns. Therefore, this paper proposes a path prediction algorithm based on user similarity. The proposed algorithm learns the path in a triple grid pattern and measures the similarity between users using the cosine similarity technique. Then, it predicts the path with applying measured similarity to the learned model. For the evaluation, we measure and compare the path prediction accuracy of proposed method with the existing algorithms. As a result, the proposed method has 66.6% accuracy, and it is evaluated that its accuracy is 1.8% higher than other methods.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2022.10a
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• pp.333-336
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• 2022

With the development of IT technology, cybercrime is becoming sophisticated and intelligent. In particular, in the case of BackDoor, which is used in the APT attack (intelligent continuous attack), it is very important to detect malicious behavior and respond to infringement because it is often unaware that it has been damaged by an attacker. This paper aims to build an EDR platform that can monitor, analyze, and respond to malicious behavior in real time by collecting, storing, analyzing, and visualizing logs in an endpoint environment in real time using open source-based analysis solutions ELK Stack and Sysmon.

• The Journal of Engineering Geology
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• v.15 no.3
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• pp.245-255
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• 2005

Three dimensional Monte-Carlo simulations of non-ergodic transport of a non-reactive solute plume by steady-state groundwater flow under a uniform mean velocity in isotropic heterogeneous aquifers were conducted. The log-normally distributed hydraulic conductivity, K(x), is modeled as a random field. Significant efforts are made to reduce the simulation uncertainties. Ensemble averages of the second spatial moments of the plume, $$lt;S_{ij}'(t',l')$gt;$ and plume centroid variances, $$lt;R_{ij}'(t',l')$gt;$ were simulated with 3200 Monte Carlo runs for three variances of log K, $\omega^2_y1.0,,2.5,$ and 5.0, and three dimensionless lengths of line plume sources ( l=,5 and 10) normal to the mean velocity. The simulated second spatial moment and the plume centroid variance in longitudinal direction fit well to the first order theoretical results while the simulated transverse moments are not fit well with the first order results. The first order theoretical results definitely underestimated the simulated transverse second spatial moments for the aquifers of large u: and small initial plume sources. The ergodic condition for the second spatial moments is far from reaching, and the first order theoretical results of the transverse second spatial moment of the ergodic plume slightly underestimated the simulated moments.