• 융합보안논문지
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• 제22권4호
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• pp.17-24
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• 2022

최근 머신러닝 기반의 사이버 공격 탐지 및 분류 연구가 활발히 이루어지고 있으며, 높은 수준의 탐지 정확도를 달성하고 있다. 그러나 저 사양 IoT 기기, 대규모의 네트워크 트래픽 등은 IoT 환경에서 머신러닝 기반의 탐지모델 적용을 어렵게 하고 있다. 따라서 본 논문에서는 국방분야에서도 활용되고 있는 MQTT(Message Queuing Telementry Transport) IoT 프로토콜 환경에서 수집된 데이터세트를 대상으로, 차원축소 기법인 PCA(Principal Component Analysis)와 LightGBM(Light Gradient Boosting Model)을 이용하여 IoT 공격을 효울적으로 탐지 및 분류하는 방안을 제안하였다. 실험을 통해 제안하는 분류모델의 성능을 확인한 결과 원본 데이터세트를 약 15%로 축소하였음에도 원본 전체를 모두 사용한 모델과 거의 유사한 성능을 나타냈으며, 본 논문에서 선정한 4가지 차원축소기법과의 비교 평가에서도 가장 우수한 성능을 나타냈다.

• Investigative Magnetic Resonance Imaging
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• 제8권1호
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• pp.1-8
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• 2004

목적: MRI를 촬영하면서 뇌전도 신호를 동시에 측정하는 것은 뇌기능 영상에 있어 매우 필요한 일이다. 그러나 MRI와 동시에 측정한 뇌전도 신호에는 많은 잡음이 유발되는데 이중 가장 심각한 영향을 주는 것은 경사자계에 의해서 유발되는 잡음이다. 경사자계 유발잡음을 ICA를 이용하여 효과적으로 제거하는 방법을 개발하고자 한다. 대상 및 방법: 29채널의 MR-compatible 뇌전도 측정시스템과 3.0 T MRI 시스템을 실험에 사용하였다. 3.0 T MRI 시스템 안에 뇌전도 캡을 쓴 피험자를 놓고 EPI 촬영을 하면서 뇌전도 신호를 측정하였다. 측정된 뇌전도 신호에 대하여 ICA를 적용해 경사자계 유발 잡음을 선택적으로 제거하였다. 제거한 결과를 평균화 방법과 PCA 방법을 사용해 얻은 결과와 비교하였다. 결과: ICA 방법, 평균화 방법 , PCA 방법 모두 경사자계 유발잡음 제거에 있어 일정 부분 효과가 있었다. 그러나 이들 방법들을 상호 비교하였을 때 잡음 제거 결과는 ICA 방법이 평균화 방법과 PCA 방법에 비해 우수하였다. 결론: ICA를 이용하여 경사자계 유발 잡음을 효과적으로 제거할 수 있었다. 잡음이 제거된 뇌전도 신호는 간질환자에 대한 뇌기능영상이나 뇌전도결합 fMRI 촬영에 활용될 수 있을 것이다.

• 대한기계학회논문집B
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• 제26권8호
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• pp.1191-1200
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• 2002

The measurements of velocity vectors are made in the near wake(X/d=5.0) of a circular cylinder with serrated fins. Velocity of fluid which flow through fins decreases as increasing fin height and freestream velocity and decreasing fin pitch. Therefore the velocity distribution at X/d=0.0 has lower gradient with increasing freestream velocity and fin height and decreasing fin pitch. The discontinuity of the streamwise velocity gradient is observed near the fin edge and causes significant changes in V-component velocity distribution in the near wake. This change attributes to the differences in Strouhal number and entraintment flow behavior. Increased turbulent intensity around a circular cylinder due to the serrated fins and entrainment flow are important factors for the recovery of velocity defect. The widths of velocity and turbulent intensity distribution of fin tubes are wider than those of a circular cylinder. The normalized velocity and turbulent intensity distributions with a hydraulic diameter which is proposed in this paper are in closer agreement with those of a circular cylinder.

• 전기학회논문지
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• 제64권7호
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• pp.1064-1073
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• 2015

In this study, we introduce the pedestrian detection system by using the feature of HOG-PCA and RBFNNs pattern classifier. HOG(Histogram of Oriented Gradient) feature is extracted from input image to identify and recognize a object. And a dimension is reduced for improving performance as well as processing speed by using PCA which is a typical dimensional reduction algorithm. So, the feature of HOG-PCA through the dimensional reduction by using PCA leads to the improvement of the detection rate. FCM clustering algorithm is used instead of gaussian function to apply the characteristic of input data as well and connection weight is used by polynomial expression such as constant, linear, quadratic and modified quadratic. Finally, INRIA person database known as one of the benchmark dataset used for pedestrian detection is applied for the performance evaluation of the proposed classifier. The experimental result of the proposed classifier are compared with those studied by Dalal.

• 천문학회지
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• 제40권1호
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• pp.9-16
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• 2007

We examine the morphology and luminosity distribution of a strongly warped spiral galaxy PGC 20348 by conducting a detailed BVI CCD surface photometry using BOAO 1.8m telescope. The radial surface brightness shows a break at warp radius $(r_{\omega})$ with a shallow gradient in the inner disk and a steeper gradient in the outer disk. The luminosity of east side of the disk is ${\sim}0.5$ mag fainter than the west side at r > $r_{\omega}$. The reason for the asymmetric luminosity distribution is thought to be the asymmetric flarings that result in the formation of a large diffuse region at the edge of the east disk and a smaller diffuse region at the west disk. The vertical luminosity profiles show a thick disk component whose scale heights increase with increasing galactocentric distances. The warp of PGC 20348 seems to be made by the tidal interactions with the two massive companion galaxies since the flarings and radial increase of disk scale heights are thought to be general properties of tidally perturbed disks. According to the colors of the two clumps inside the diffuse region at the edge of the east disk, they seem to be sites of active star formation triggered by tidal forces from the companion galaxies.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.295-295
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• 2008

This study introduced waste water treatment method applied superconductor HGMS(High Gradient Magnetic Separation). HGMS method treat high efficient method for various waste water. we have surveyed superconducting magnetic separation technology and reviewed the status of related industries using applied superconductivity. We fabricated the prototypes of magnetic matrix filter consisting of stainless steel mesh, which is a core component in the magnetic separation system. In our basic preliminary experiment using HGMS, it was made clear that the fine para-magnetic particles in the rolling colling wasted water obtained from rolling process of POSCO can be separated with high efficiency.

• 천문학회지
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• 제34권2호
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• pp.59-66
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• 2001

In this paper, we investigate the correlation between the radial ultraviolet color distribution and the shapes of the ultraviolet isophote for elliptical galaxies (M32, NGC 1399) and spiral bulges (of M31, M81) by using their archival UIT images. For M31, M81, and NGC 1399, the radial ultraviolet color distributions show a two-component trend; as the distance from the galactic center increase the color becomes redder in the inner region while it becomes bluer in the outer region. On the other hand, the color of M32 continues to become bluer with the increasing galactocentric distance. We also find, unlike the optical/IR images, significant variations of the position angle and the ellipticity in the ultraviolet isophotes of M31, M81, and NGC 1399 through the inner regions. For M32, the variation is significant in the outer region. Since these variation implies the triaxiality of their intrinsic shapes, we suggest that the early-type galaxies and spiral bulges with a radial color gradient in ultraviolet tend to have a triaxiality. On the other hand, the shape parameter characterized by the fourth order cosine Fourier coefficient of the isophote, a(4)/a, indicates that the systematic deviations of the ultraviolet isophotes of the four galaxies are smaller than $\~0.2\%$ in units of the semi-major axis. The latter result implies that the ultraviolet isophotes of the galaxies have a pure elliptical shape rather than the boxy or disky shapes. Therefore, there is no clear evidence of correlation between the radial ultra-violet color gradient and the boxy/disky shapes of isophotes.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2004년도 춘계종합학술대회
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• pp.599-602
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• 2004

본 논문에서는 로봇축구의 식별을 위한 초기 패치(patch)값 및 조명의 변화량에 따른 제어변수의 자동설정 방법을 연구하였다. 먼저 패치값 자동설정을 위해 찾고자하는 국부적인 패치영역을 획득하여 RCB값으로 표본화하고, 기울기 연산자를 적용하여 화소의 기울기 값을 얻는다. 그리고 기울기 값으로부터 유효 패치영역과 YUV값을 구한다. 또한 YUV 성분 중 휘도성분을 측정하여 조명의 변화량에 따른 제어변수를 설정한다. 제안된 방법을 로봇축구 영상에 적용하여 초기 패치값을 설정하였고 경기 중 조명의 변화에 적응적인 패치값 검출이 가능함을 보였다.

• Coupled systems mechanics
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• 제8권2호
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• pp.129-146
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• 2019

The main goal of this work is to develop a numerical simulator to study an isothermal single-phase two-component flow in a naturally fractured oil reservoir, taking into account advection and diffusion effects. We use the Peng-Robinson equation of state with a volume translation to evaluate the properties of the components, and the discretization of the governing partial differential equations is carried out using the Finite Difference Method, along with implicit and first-order upwind schemes. This process leads to a coupled non-linear algebraic system for the unknowns pressure and molar fractions. After a linearization and the use of an operator splitting, the Conjugate Gradient and Bi-conjugated Gradient Stabilized methods are then used to solve two algebraic subsystems, one for the pressure and another for the molar fraction. We studied the effects of fractures in both the flow field and mass transport, as well as in computing time, and the results show that the fractures affect, as expected, the flow creating a thin preferential path for the mass transport.

• 한국초전도ㆍ저온공학회논문지
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• 제11권4호
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• pp.8-11
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• 2009

This study introduced wastewater treatment method by High Gradient Magnetic Separation (HGMS). HGMS treatment was high efficient method for various industrial wastewaters. The system is currently research state, but we have surveyed commercialize the technology for industry. In rolling plate process, coolant wastewater was recycled by sedimentation and sand filter system. It needs several large reservoirs and long time to remove suspended solid (SS) like metal fines and iron oxide in hot rolling plate making process. If removing rate of suspended solid in rolling coolant wastewater is improved by using HGMS system, the productivity of working process can be increased and the area of reservoir can be reduced. We manufactured high temperature superconducting HGMS system that had a purpose to treatment of coolant wastewater in rolling plate process. We fabricated the prototypes of magnetic matrix filter consisting of stainless steel 430 mesh, which is a core component in the magnetic separation system, In our basic preliminary experiment using HGMS system, it has been clear that the fine paramagnetic particles in the coolant wastewater obtained from rolling plate process of POSCO can be separated with high efficiency.