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홍채 표현 공격 탐지(Iris PAD)에 강인한 위조 홍채인식 방어 시스템에 관한 연구
백영현 대한전자공학회 2023 전자공학회논문지 Vol.60 No.1
Iris presentation attack detection (PAD) technology plays an important role in enhancing the security of access control systems that use iris recognition among biometric access authentication facilities. This study examines a fake iris recognition defense system that provides a strong defense against fake iris recognition attacks. Accurate pupil region detection through preprocessing is required to reduce errors when implementing PAD for identifying a fake iris. Iris PAD was designed to analyze whether instructions were implemented according to random blink attempts by an administrator and to determine the number of blinks and the presence or absence of the pupil in a given period. In a simulation, the pupil region of the iris of 100 was accurately detected in an external light environment. The experimental results showed that the proposed method accurately detected a fake iris.
백영현,변오성,문성룡 대한전자공학회 2007 電子工學會論文誌-SP (Signal processing) Vol.44 No.1
In most electronic imaging applications, image with high resolution(HR) are desired. HR means that pixel density within an image is high, and therefore HR image can offer more details that may be critical in various applications. Digital images that are captured by CCD and CMOS cameras usually have a very low resolution, which significantly limits the performance of image recognition systems. Image super-resolution techniques can be applied to overcome the limits of these imaging systems. Super-resolution techniques have been proposed to increase the resolution by combining information from multiple images. To techniques were consisted of the registration algorithm for estimation and shift, the nearest neighbor interpolation using weight of acquired frames and presented frames. In this paper, it is proposed the image interpolation techniques using the wavelet base function. This is applied to embody a correct edge image and natural image when expend part of the still image by applying the wavelet base function coefficient to the conventional Super-Resolution interpolation method. And the proposal algorithm in this paper is confirmed to improve the image applying the nearest neighbor interpolation algorithm, bilinear interpolation algorithm.,bicubic interpolation algorithm through the computer simulation. 모든 전자 영상응용에는 고해상도 영상이 요구된다. 고해상도는 영상 안에 픽셀의 밀집도가 높음을 나타내며, 이로 인해 더 세밀하고 중요한 정보를 얻어 다양한 응용에 사용된다. 하지만 CCD 나 CMOS 카메라로 획득된 디지털 영상들은 영상인식 시스템 구현 시 많은 저해상도영상을 가지게 된다. 초해상도 기술은 이와 같은 한계를 넘어서서 영상인식시스템에 적용이 가능하다. 초해상도 기술은 다수의 영상으로부터 정보를 결합하여 해상도를 증가시키는 것으로써, 이 기술은 추정과 이동을 위한 정합알고리즘과 획득된 프레임과 현재 프레임의 가중치를 이용한 최소거리 이웃보간법으로 되어있다. 본 논문에서는 초해상도에 웨이브렛 변환 기저 함수 계수를 이용한 영상 보간 기법을 제안하고자 한다. 기존 초해상도 보간 방식 대신 웨이브렛 기저 계수를 적용한 B-스플라인 보간 함수를 이용하여, 움직이는 영상의 한 부분을 확대할 때 정확한 영상과 자연스러운 영상을 구현하기 위하여 적용하였다. 제안된 보간 알고리즘은 최소거리 이웃보간 알고리즘, bilinear 보간 알고리즘, bicubic 보간 알고리즘 적용한 확대 영상보다 우수한 결과를 얻었음을 모의실험을 통하여 확인하였다.
뷔스타이트의 분해속도와 산세효율에 미치는 제 3 원소의 영향
백영현,남상욱,양재웅 대한금속재료학회(대한금속학회) 1989 대한금속·재료학회지 Vol.27 No.10
Effects of dopants on the decomposition of synthetic wu¨stite and it's pickling efficiency were throughly investigated. Chemicals, such as Li₂O, CaO and Al₂O₃ at a concentration of 0.8 wt.% were used as dopants. The isothermal decomposition temperature adopted in this study ranged from 380℃ to 530℃. The decomposition rate of wu¨stite at 460℃ was found to be significantly greaser than that at 380℃ and 530℃. The decomposition rate was increased with the addition of A1₂O₃ due to an increase in the vacancy concentration of wustite, whereas the rate was, decreased with the addition of Li₂O or CaO. Scales doped at two levels 3.23×10^(-4)g/㎠ and 5.38×10^(-4)g/㎠ were used for the pickling tests. The pickling rate of the scale was increased with the addition of either Li₂O or CaO to wu¨stite substrate, whereas decreased with the A1₂O₃ addition. It was also observed that those effects were enlarged with increasing the dopant concentration.
황산용액중에서 함철유화아연광의 용해에 관한 속도론적 고찰
백영현,김희동 대한금속재료학회(대한금속학회) 1975 대한금속·재료학회지 Vol.13 No.3
철의 함량을 달리하는 3종의 sphalerite(Fe 13.96%, 0.33%, 0.11%)들에 대한 용해속도를 황산용액중에서 조사하였다. 사용된 황산의 농도 및 온도의 범위는 각기 0.1N∼10N과 20℃∼90℃였다. 소극제가 존재하지 않는 실험조건하에서 sphalerite의 용해속도는 계면의 S-atom과 H^+ ion을 포함하는 계면화학반응에 의하여 설명되며 초기 반응에 대하여 시료의 spherical geometry를 적용할 수 있다. 용해반응에 대한 activation energy는 철분의 함량에 무관하게 11㎉/mole이었다. 자연산 sphalerite의 용해속도를 증가시키는 요인은 함유철분의 영향보다는 Galvanic effect로 설명된다. Rates of dissolution reaction of natural sphalerite with aqueous sulfuric acid were studied in the concentration range of 0.1N to 10N and over a temperature range of 20℃ to 90℃. The effect of iron on the dissolution rate wes investigated by using three sphalerites at the different iron levels of Fe 13.96%, 0.33% and 0.11%. In the absence of depolarizer, the dissolution reaction a controlled by the surface reaction, and the rate could be expressed in terms of the spherical geometry for the initial stage of the reaction; 1-(1-R)^(◎)=kt An activation energy for tine dissolution reaction was found to be 11 ㎉ regardless of the iron level in sphalerite. A quantitative picture of the reaction mechanism was given based on rate studies and etching tests. Galvanic dissolution may be an important factor affecting the reaction rate of natural sphalerite.