• 대한수학회지
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• 제55권1호
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• pp.43-58
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• 2018

In this paper, we study a delayed predator-prey system with Holling type IV functional response incorporating the effect of habitat complexity. The results show that there exist stability switches and Hopf bifurcation occurs while the delay crosses a set of critical values. The explicit formulas which determine the direction and stability of Hopf bifurcation are obtained by the normal form theory and the center manifold theorem.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제13권3호
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• pp.181-188
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• 2009

Hundreds of thousands of South Korean protesters staged candlelight vigils and demonstrations against US beef imports in 2008. The problems, however, went far beyond that of beef imports. The political party veterans, who lost the presidential election, exploited labor unions that were discontent with the economy and ideological student groups to weaken the majority party. In this study, an epidemiological model is constructed with a system of three nonlinear differential equations. The model seeks to examine the dynamics of the system through stability analysis. Two threshold conditions that spread the protests are identified and a sensitivity analysis on the conditions is performed to isolate the parameters to which the system is most responsive. The results are also explored by deterministic simulations. This model can be easily modified to apply to other protests that may occur in various circumstances.

• 한국콘텐츠학회논문지
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• 제8권5호
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• pp.276-286
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• 2008

본 논문에서는 컴퓨터 대수 시스템을 기반으로 하는 웹 저작 환경과 베이지언 추론망을 적용한 학습자 진단 환경이 포함된 이공계 수학용 적응적 이러닝 시스템 개발에 대하여 소개하였다. 본 시스템을 활용하면 교수자는 컴퓨터 대수 시스템을 수식처리 엔진으로 하며 웹을 인터페이스로 하는 이공계 수학용 웹 콘텐츠를 쉽게 생성할 수 있다. 구체적으로 선형대수, 미분방정식 및 이산수학의 영역에서 콘텐츠 개발의 예를 소개하였다. 또한 학습자의 지식 영역별 수준을 조건부 확률을 이용한 통계적 추론에 의해 진단하여 그 결과에 따라 피드백을 생성하는 적응적 이러닝 웹 콘텐츠를 만들 수 있다. 본 시스템을 사용하여 개발한 이공계 수학용 웹 콘텐츠를 평가하기 위하여 그 결과물을 대학 강의에 적용하였고, 설문지 조사를 통하여 콘텐츠 사용에 대한 학습자의 반응을 평가하였다.

• Journal of Information Processing Systems
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• 제13권1호
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• pp.152-173
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• 2017

Mobile phones are the most common communication devices in history. For this reason, the number of mobile subscribers will increase dramatically in the future. Therefore, the determining the location of a mobile station will become more and more difficult. The mobile station must be authenticated to inform the network of its current location even when the user switches it on or when its location is changed. The most basic weakness in the GSM authentication protocol is the unilateral authentication process where the customer is verified by the system, yet the system is not confirmed by the customer. This creates numerous security issues, including powerlessness against man-in-the-middle attacks, vast bandwidth consumption between VLR and HLR, storage space overhead in VLR, and computation costs in VLR and HLR. In this paper, we propose a secure authentication mechanism based new mobility management method to improve the location management in the GSM network, which suffers from a lot off drawbacks, such as transmission cost and database overload. Numerical analysis is done for both conventional and modified versions and compared together. The numerical results show that our protocol scheme is more secure and that it reduces mobility management costs the most in the GSM network.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권1호
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• pp.466-483
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• 2017

Zen Cart is an open-source online store management system. It is used all over the world because of its stability and safety. Today, Zen Cart's session security mechanism is mainly used to verify user agents and check IP addresses. However, the security in verifying the user agent is lower and checking the IP address can affect the user's experience. This paper, which is based on the idea of session protection as proposed by Ben Adida, takes advantage of the HTML5's sessionStorage property to store the shared keys that are used in HMAC-SHA256 encryption. Moreover, the request path, current timestamp, and parameter are encrypted by using HMAC-SHA256 in the client. The client then submits the result to the web server as per request. Finally, the web server recalculates the HMAC-SHA256 value to validate the request by comparing it with the submitted value. In this way, the Zen Cart's open-source system is reinforced. Owing to the security and integrity of the HMAC-SHA256 algorithm, it can effectively protect the session security. Analysis and experimental results show that this mechanism can effectively protect the session security of Zen Cart without affecting the original performance.

• 한국수학교육학회지시리즈E:수학교육논문집
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• 제24권3호
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• pp.525-541
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• 2010

P대학에서는 교양수학 교과에 대한 기초학력 부진학생들의 문제해결력 향상을 위하여, 대학 교육역량강화사업의 일환으로 수학카페 운영과 함께, 기초수학 특강, 개인지도 및 컴퓨터 활용학습 등을 시행하고 있다. 본 논문에서는 여름 및 겨울방학을 이용하여 기초수학 특강을 실시하고, 그 결과를 중심으로 수학에 대한 기초학력 부진학생들을 위한 효율적인 기초수학 학습지도 방안을 살펴보고자 한다.

• 한국산학기술학회논문지
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• 제22권3호
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• pp.527-535
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• 2021

전통적인 BI(Business Intelligence) 시스템은 제 시간에 더 나은 의사결정을 위한 도구로 널리 사용되어 왔다. 그러나 급증하는 데이터에 대한 효율적 분석을 위해 데이터 웨어하우스를 구축하는 일은 시간이 오래 걸리고 복잡하다. 특히, 데이터 웨어하우스 구축에 요구되는 ETL(Extract, Transform, Load) 프로세스는 BI 플랫폼이 클라우드 환경으로 전환되면서 훨씬 더 복잡해졌다. 이러한 ETL 이슈를 극복하기 위해 MongoDB와 같은 NoSQL 데이터베이스에 기반한 다양한 BI 솔루션들이 제안되었다. 한편, 의사 결정권자는 IT 부서나 BI 전문가 의 도움 없이 데이터에 쉽게 접근할 수 있기를 원한다. 최근, 이러한 BI 이슈들을 해결하기 위한 방안으로 셀프서비스 BI가 등장하였다. 본 논문에서는 귀농 귀촌인의 재배 작물 선택을 지원하기 위해 MongoDB 클라우드를 데이터 웨어하우스로 하는 농업 데이터 기반의 셀프서비스 BI 시스템을 제안한다. 제안 시스템은 의사 결정권자에게 통찰력을 제공하기 위해 MongoDB 차트를 이용한 데이터 시각화 기능, 고급 데이터 검색을 위한 리포팅 기능, 실시간 데이터 분석을 위한 모니터링 기능을 지원한다. 의사 결정권자는 다양한 방식으로 데이터에 직접 접근할 수 있고, 제안 시스템의 기능들을 활용하여 셀프서비스 방식으로 데이터를 분석할 수 있다.

• Journal of applied mathematics & informatics
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• 제14권1_2호
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• pp.461-471
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• 2004

In recent years, large volumes of data are transferred between a computer system and various subsystems through digital logic circuits and interconnected wires. And there always exist potential errors when data are transferred due to electrical noise, device malfunction, or even timing errors. In general, parity checking circuits are usually employed for detection of single-bit errors. However, it is not sufficient to enhance system reliability and availability for efficient error detection. It is necessary to detect and further correct errors up to a certain level within the affordable cost. In this paper, we report a generation of 3-distance code using the characteristic matrix of a PBCA.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권12호
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• pp.6069-6091
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• 2017

Augmented Reality (AR) overlays virtual information on real world data, such as displaying useful information on videos/images of a scene. This paper presents an Enhanced AR (EAR) system that displays useful statistical players' information on captured images of a sports game. We focus on the situation where the input image is degraded by strong sunlight. Proposed EAR system consists of an image enhancement technique to improve the accuracy of subsequent player and face detection. The image enhancement is followed by player and face detection, face recognition, and players' statistics display. First, an algorithm based on multi-scale retinex is proposed for image enhancement. Then, to detect players' and faces', we use adaptive boosting and Haar features for feature extraction and classification. The player face recognition algorithm uses boosted linear discriminant analysis to select features and nearest neighbor classifier for classification. The system can be adjusted to work in different types of sports where the input is an image and the desired output is display of information nearby the recognized players. Simulations are carried out on 2096 different images that contain players in diverse conditions. Proposed EAR system demonstrates the great potential of computer vision based approaches to develop AR applications.

• Journal of applied mathematics & informatics
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• 제28권1_2호
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• pp.163-173
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• 2010

We consider the system $$\{{{-{\Delta}_pu\;=\;{\lambda}f(\upsilon),\;\;\;x\;{\in}\;{\Omega}, \atop -{\Delta}_q{\upsilon}\;=\;{\mu}g(u),\;\;\;x\;{\in}\;{\Omega},} \atop u\;=\;\upsilon\;=\;0,\;\;\;x\;{\in}\;{\partial\Omega},}$$ where ${\Delta}_pu\;=\;div(|{\nabla}_u|^{p-2}{\nabla}_u)$, ${\Delta}_{q{\upsilon}}\;=\;div(|{\nabla}_{\upsilon}|^{q-2}{\nabla}_{\upsilon})$, p, $q\;{\geq}\;2$, $\Omega$ is a ball in $\mathbf{R}^N$ with a smooth boundary $\partial\Omega$, $N\;{\geq}\;1$, $\lambda$, $\mu$ are positive parameters, and f, g are smooth functions that are negative at the origin and f(x) ~ $x^m$ g(x) ~ $x^n$ for x large for some m, $n\;{\geq}\;0$ with mn < (p - 1)(q - 1). We establish the existence and uniqueness of positive radial solutions when the parameters $\lambda$ and $\mu$ are large.