• Nuclear Engineering and Technology
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• 제52권1호
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• pp.14-18
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• 2020

Korea Atomic Energy Research Institute (KAERI) has carried out various neutronics experiments in the commissioning stage of the Jordan Research and Training Reactor (JRTR), and this paper introduces the results of first criticality prediction and experiment for the JRTR. The Monte Carlo Code for Advanced Reactor Design and analysis (McCARD) with the ENDF/B-VII.0 nuclear library was used for prediction calculations in the process of the first criticality approach, which was performed to provide reference for the first criticality experiment. In the experiment, fuel loading was carried out by measuring the inverse multiplication factor (1/M) to predict the number of fuel assemblies at the first criticality, and the first critical was reached on April 25, 2016. Comparing the first criticality prediction and experiment, the calculated and measured CAR (Control Absorber Rod) heights for the first criticality were 575 mm and 570.5 mm, respectively, that is, the difference between the two results was approximately 5 mm. From this result, it was confirmed that JRTR manufacturing and various experiments had successfully progressed as designed.

• 정보보호학회논문지
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• 제34권4호
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• pp.587-596
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• 2024

사이버 공격, 위협이 복잡해지고 빠르게 진화하면서, 4차 산업 혁명의 핵심 기술인 인공지능(AI)을 이용하여 사이버 위협 탐지 시스템 구축이 계속해서 주목받고 있다. 특히, 기업 및 정부 조직의 보안 운영 센터(Security Operations Center)에서는 보안 오케스트레이션, 자동화, 대응을 뜻하는 SOAR(Security Orchestration, Automation and Response) 솔루션 구현을 위해 AI를 활용하는 사례가 증가하고 있으며, 이는 향후 예견되는 근거를 바탕으로 한 지식인 사이버 위협 인텔리전스(Cyber Threat Intelligence, CTI) 구축 및 공유를 목적으로 한다. 본 논문에서는 네트워크 트래픽, 웹 방화벽(WAF) 로그 데이터를 대상으로 한 사이버 위협 탐지 기술 동향을 소개하고, TF-IDF(Term Frequency-Inverse Document Frequency) 기술과 자동화된 머신러닝(AutoML)을 이용하여 웹 트래픽 로그 공격 유형을 분류하는 방법을 제시한다.

• 대한조선학회논문집
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• 제31권4호
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• pp.51-57
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• 1994

본 연구는 실선 내파성시험 분석시 시험해역의 파랑을 다방향파로 분석하여 신뢰성 있는 주파수 전달함수를 도출하는 기법에 관한 연구이다. 다방향파에서의 주파수 전달함수를 도출하기 위하여 다방향 수조 모형시험 분석에서 적용하는 Takezawa의 역추정법을 도입하였으며, 실선 상황에 적합하도록 주파수 영역을 3영역으로 구분하여 취급함으로써 추파 범위에서도 주파수 전달함수의 도출이 가능하도록 하였다. 본 연구의 타당성을 검증하기 위하여 수치 시뮬레이션을 수행한 결과, 다방향파 해상에서의 선박운동 응답을 이용한 주파수 전달함수 도출시 단방향파 분석방법보다 다방향파 분석방법이 보다 더 신뢰성 있는 결과를 획득할 수 있음을 확인하였다.

• 한국산업융합학회 논문집
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• 제6권1호
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• pp.23-29
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• 2003

This paper proposes an efficient feature extraction of the images by using independent component analysis(ICA) based on neural networks of the hybrid learning algorithm. The proposed learning algorithm is the fixed point(FP) algorithm based on Newton method and moment. The Newton method, which uses to the tangent line for estimating the root of function, is applied for fast updating the inverse mixing matrix. The moment is also applied for getting the better speed-up by restraining an oscillation due to compute the tangent line. The proposed algorithm has been applied to the 10,000 image patches of $12{\times}12$-pixel that are extracted from 13 natural images. The 144 features of $12{\times}12$-pixel and the 160 features of $16{\times}16$-pixel have been extracted from all patches, respectively. The simulation results show that the extracted features have a localized characteristics being included in the images in space, as well as in frequency and orientation. And the proposed algorithm has better performances of the learning speed than those using the conventional FP algorithm based on Newton method.

• 전자공학회논문지
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• 제52권8호
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• pp.148-155
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• 2015

Levenberg-Marquardt은 최소자승법 문제의 풀이법으로 잘 알려져 있다. 하지만 이전의 표적기동분석(TMA)의 추적필터의 경우 대부분 Gauss-Newton방법을 사용하고 있으며 Gauss-Newton은 역행열 연산이 요구되어 시스템을 불안정하게 만드는 문제점이 있다. 본 논문에서는 Gauss-Newton의 수치적 불안정성을 해결하기 위해 TMA에 Levenberg-Marquardt을 적용하여 Levenberg-Marquardt이 적용된 표적기동분석 알고리즘의 안정성을 실험으로 보인다. 이를 위해 실험에서는 Monte-Calro 시물레이션을 3개 시나리오에 대하여 수행하였으며 그 결과 Levenberg-Marquardt이 Gauss-Newton에 비하여 표적기동분석 결과인 거리, 침로, 속력의 수렴되는 시간이 빨라졌으며 행렬의 발산빈도가 저하되어 표적기동분석 결과가 안정화되었다.

• 소성∙가공
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• 제29권5호
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• pp.265-271
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• 2020

The purpose of this paper is to analyze the numerical simulation accuracy according to the CFRP modeling method in the CFRP-Al alloy SPR (Self-Piercing Rivet) joint process. The mechanical properties of the CFRP, aluminum sheet are precisely obtained from the tensile test according to the loading direction. Additionally, the hardening curve of rivet was calculated from the inverse analysis of the machined rivet-ring compression test. For the CFRP-Al alloy SPR simulation, two kinds of the CFRP modeling methods were established based on the continuum and layer-by-layer approaches. The simulation results showed that the CFRP layer-by-layer modeling method can provide more reliable prediction shape of the fractured sheets and deformed rivet. This simulation technique can be used in evaluating the CFRP-Metal SPR performance and designing the SPR process conditions.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2004년도 봄 학술발표회 논문집
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• pp.1-8
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• 2004

For the linearized differential algebraic equation of the nonlinear constrained system, exact initial values of the acceleration are needed to solve itself. It may be very troublesome to perform the inverse operation for obtaining the incremental quantities since the mass matrix contains the zero element in the diagonal. This fact makes the mass matrix impossible to be positive definite. To overcome this singularity phenomenon the mass matrix needs to be modified to allow the feasible application of predictor and corrector in the iterative computation. In this paper the proposed numerical algorithm based on the modified mass matrix combines the conventional implicit algorithm, Newton-Raphson method and Newmark method. The numerical example presents reliabilities for the proposed algorithm via comparisons of the 4th order Runge-kutta method. The proposed algorithm seems to be satisfactory even though the acceleration, Lagrange multiplier, and energy show unstable behaviour. Correspondingly, it provides one important clue to another algorithm for the enhancement of the numerical results.

• Journal of Mechanical Science and Technology
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• 제18권9호
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• pp.1529-1536
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• 2004

A structure is broken down into a number of substructures by means of the finite element method and the substructures are synthesized for the complete structure. The divided substructures take two types: fixed-free and free-free elements. The flexibility and stiffness matrices of the free-free elements are the Moore-Penrose inverse of each other. Thus, it is not easy to determine the equilibrium equations of the complete structure composed of two mixed types of substructures. This study provides the general form of equilibrium equation of the entire structure through the process of assembling the equilibrium equations of substructures with end conditions of mixed types. Applications demonstrate that the proposed method is effective in the structural analysis of geometrically complicated structures.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.263-266
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• 2002

An optical method for surface roughness estimation based on statistical analysis of the light intensity of a scattered laser beam pattern. The method is very simple but has a disadvantage that no more information than the averaged roughness is estimated. In this study a new try was conducted to derive more advanced surface information from the details of the light intensity distribution. Some periodic ripples among the light intensity distribution being assumed to relate with scratch left on the machined surface, a corresponding surface profile is estimated from the ripples using FFT and IFFT algorithm. IFFT technique is used to extract some dominant signal components among the intensity distribution. Compared to the measured profiles by a stylus type surf-tester, the profiles obtained through the proposed method are probably acceptable in a sense of the profile shape. Calibration of the amplitude needs more works in the future.

• 한국공간구조학회논문집
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• 제2권1호
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• pp.67-73
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• 2002

Measurement of fluctuating pressure by tube system is carefully designed due to the organ-pipe resonance. It is necessary to correct the pressure before analysis. The three method for correction the distortion fluctuation pressure short tube length and the frequency response functions and insert a restrictor in the tube to increase the damping. The first method is useful when the tube length is short. In second method, the distorted signal through the tubing transformed into the frequency domain, dividing by transfer function and inverse fourier transforming back into the time domain gives the required pressure signal. In this paper three types of tubing which have different length of 100cm, 150cm, 200cm were experimented the distorted signal and correct the distortion signal