• Journal of electromagnetic engineering and science
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• 제11권1호
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• pp.11-15
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• 2011

Preserving high-order accuracy in high-order FDTD solutions across dielectric interfaces is very important for practical time-domain electromagnetic simulations. This paper presents a fourth-order accurate numerical boundary scheme for the planar dielectric interface to be used in the fourth-order FDTD method proposed earlier by the author. The interface scheme for the two-dimensional (2-D) transverse magnetic (TM) polarization case is derived and validated by monitoring the $L_2$ norm errors in the numerical solutions of a partially-filled cavity demonstrating its fourth-order convergence and long-time numerical stability in the presence of the planar dielectric interface.

• 융합보안논문지
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• 제2권1호
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• pp.35-47
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• 2002

본 논문에서는 동영상 워터마킹에 대한 전반적인 기술과 응용 분야에 대하여 고찰한다. 동영상 워터마킹 기술은 압축영역, 비압축 영역, 실시간 응용 분야 둥으로 나누어 질 수 있다. 동영상의 모든 프레임에 워터마크로 정한 시그네쳐(signature)를 삽입하여 실험한 결과를 보여준다. 워터 마크를 주파수 확산 방식으로 원 영상의 모든 프레임에 삽입하여 워터마크의 세기 변화에 따른 화질을 PSNR로 계산하였고 워터마크 검출은 DCT 계수 합의 부호로 삽입된 시그네쳐를 복원한다. 검출된 시그네쳐의 시각적 상태에 따른 평균 PSNR값의 변화를 보여준다.

• 한국산업융합학회 논문집
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• 제3권4호
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• pp.369-378
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• 2000

Conventional fractal image compression methods have many problems in searching time for matching domain block. Proposed method is an improved method of Fisher's Quadtree Decomposition in terms of time, compression ratio, and PSNR. This method determines range block in advance using QR algorithm. First, input image is partitioned to $4{\times}4$ range block and then recomposition is performed from bottom level to specified level. As a result, this proposed method achieves high encoding and decoding speed, high compression ratio, and high PSNR than Fisher's Quadtree Decomposition method.

• 대한수학회지
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• 제56권2호
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• pp.311-327
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• 2019

The aim of this paper is to extend the applicability of Gauss-Newton method for solving underdetermined nonlinear least squares problems in cases not covered before. The novelty of the paper is the introduction of a restricted convergence domain. We find a more precise location where the Gauss-Newton iterates lie than in earlier studies. Consequently the Lipschitz constants are at least as small as the ones used before. This way and under the same computational cost, we extend the local as well the semilocal convergence of Gauss-Newton method. The new developmentes are obtained under the same computational cost as in earlier studies, since the new Lipschitz constants are special cases of the constants used before. Numerical examples further justify the theoretical results.

• 한국항행학회논문지
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• 제28권1호
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• pp.155-158
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• 2024

Multipath, a major error source in urban GNSS positioning (global navigation satellite system), pose a challenge due to its site-dependent nature, varying with the user's signal reception environment. In our previous study, we introduced a technique generating GNSS multipath map in urban canyon. However, due to uncertainty in initial GNSS positions, applying multipath maps required generating multiple candidate positions. In this study, we present an efficient method for applying multipath maps by projecting the multipath correction in position domain. This approach effectively applies multipath maps, addressing the challenges posed by urban user position uncertainties.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2024년도 춘계학술발표대회
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• pp.337-340
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• 2024

Pretrained language models (PLMs) are extensively utilized to enhance the performance of log anomaly detection systems. Their effectiveness lies in their capacity to extract valuable semantic information from logs, thereby strengthening the detection performance. Nonetheless, challenges arise due to discrepancies in the distribution of log messages, hindering the development of robust and generalizable detection systems. This study investigates the structural and distributional variation across various log message datasets, underscoring the crucial role of domain-specific PLMs in overcoming the said challenge and devising robust and generalizable solutions.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2024년도 춘계학술발표대회
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• pp.196-198
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• 2024

DGA(Domain Generation Algorithms)로 생성된 도메인을 탐지하기 위한 다양한 연구 결과가 선행되었다. 기존 연구 상에서는 딥러닝 모델인 LSTM을 이용한 DGA 도메인 탐지가 가장 효과적인 방법으로 대두되었다. 하지만 본 논문 실험 결과, TCN 모델을 이용한 탐지 결과가 LSTM 모델보다 우수한 탐지 정확도를 나타내는 것을 확인하였다. 또한, 탐지 모델을 대규모 도메인 처리가 필요한 현업에서 사용될 것을 고려하여, LSTM과 TCN 모델보다 빠른 결과를 도출할 수 있는 XGBoost 모델을 확인하였다. TCN과 XGBoost 모델을 활용하여 현업에서 DGA 도메인을 탐지하는데 효과적으로 사용될 수 있을 것이다.

• 한국콘텐츠학회논문지
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• 제19권3호
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• pp.466-474
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• 2019

본 연구는 '교육방법 및 교육공학' 수업에서 중등예비교사에게 요구되는 창의역량 강화와 학업도전 변화를 확인하는데 목적이 있다. 이를 위해 중등예비교사 94명이 한 학기 동안 융합수업지도안 작성 및 수업시연으로 진행되는 프로젝트 학습에 참여하였다. 설문지는 지은림, 주언희(2012)가 개발한 창의적 인재 역량측정도구와 배상훈 외(2015)의 학부교육 실태조사(K-NSSE)의 학업도전 사전-사후 설문을 실시하였다. 데이터 분석은 IBM SPSS 18.0 프로그램을 이용하여 대응표본 t 검정을 수행하였다. 연구결과는 다음과 같다. 창의역량에서는 '고차적 사고력', '문제해결능력', '호기심', '감수성', '과제집착력', '사회 가치추구', '협동 및 배려'가 유의미하였다. 학업도전에서는 '고차원 학습'과 '학습전략'이 유의미하였다. 이를 바탕으로 융합교육, 융합수업을 일반화하여 수업하기 위해서는 다양한 융합수업설계, 지도안 작성, 실천연구와 반복적인 융합수업의 효과를 검증하며 수정 보완 과정의 필요성에 대한 시사점을 논의하였다.

• Coupled systems mechanics
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• 제4권3호
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• pp.263-277
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• 2015

This paper presents a coupled FEM-BEM strategy for the numerical analysis of elastodynamic problems where infinite-domain models and complex heterogeneous media are involved, rendering a configuration in which neither the Finite Element Method (FEM) nor the Boundary Element Method (BEM) is most appropriate for the numerical analysis. In this case, the coupling of these methodologies is recommended, allowing exploring their respective advantages. Here, frequency domain analyses are focused and an iterative FEM-BEM coupling technique is considered. In this iterative coupling, each sub-domain of the model is solved separately, and the variables at the common interfaces are iteratively updated, until convergence is achieved. A relaxation parameter is introduced into the coupling algorithm and an expression for its optimal value is deduced. The iterative FEM-BEM coupling technique allows independent discretizations to be efficiently employed for both finite and boundary element methods, without any requirement of matching nodes at the common interfaces. In addition, it leads to smaller and better-conditioned systems of equations (different solvers, suitable for each sub-domain, may be employed), which do not need to be treated (inverted, triangularized etc.) at each iterative step, providing an accurate and efficient methodology.

• Current Optics and Photonics
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• 제2권4호
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• pp.368-377
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• 2018

In this paper, we evaluate cryptographic properties of a double random phase encoding (DRPE) scheme in the discrete Gyrator domain with avalanche and bit independence criterions. DRPE in the discrete Gyrator domain is reported to have higher security than traditional DRPE in the Fourier domain because the rotation angle involved in the Gyrator transform is viewed as additional secret keys. However, our numerical experimental results demonstrate that the DRPE in the discrete Gyrator domain has an excellent bit independence feature but does not possess a good avalanche effect property and hence needs to be improved to satisfy with acceptable avalanche effect that would be robust against statistical-based cryptanalysis. We compare our results with the avalanche and bit independence criterion (BIC) performances of the conventional DRPE scheme, and improve the avalanche effect of DRPE in the discrete Gyrator domain by integrating a photon counting imaging technique. Although the Gyrator transform-based image cryptosystem has been studied, to the best of our knowledge, this is the first report on a cryptographic evaluation of discrete Gyrator transform with avalanche and bit independence criterions.