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이상 유동에서 영상 복원을 위한 EIT system 회로의 안정성 평가
이보안,현종관,이헌주,김신,김경연 제주대학교 산업기술연구소 2001 尖端技術硏究所論文集 Vol.12 No.1
The EIT(Electrical Impedance Tomography) system is one of the methods for tomography technologies. The EIT measurement is less expensive than other methods because the system is relatively simple and easy to construct compared to other methods. In this study, the real voltage values were compared to theoretical values. The rmse(root mean square error) of measured data was 2.99%. So that, this EIT system circuit was a accuracy circuit for a reconstruction algorithm.
이상 유동에서 영상 복원을 위한 EIT system 회로의 안정성 평가
이보안,현종관,이헌주,김신,김경연 濟州大學校 産業技術硏究所 2001 산업기술연구소논문집 Vol.12 No.1
The EIT(Electrical Impedance Tomography) system is one of the methods for tomographv technologies. The EIT measurement is less expensive than other methods because the system is relatively simple and easy to construct compared to other methods. In this study. the real voltage values were compared to theoretical values. The rmse(root mean square error) of measured data was 2.99%. So that. this EIT system circuit was a accuracy circuit for a reconstruction algorithm.
PEO가 첨가된 원형관 난류유동에서의 마찰저항 감소 측정
이보안,이동원,김신,현명택,천원기 濟州大學校 産業技術硏究所 1998 산업기술연구소논문집 Vol.9 No.2
The drag reduction by polymer additive is a well-known phenomenon and has been widely studied due to its high usefulness. In this study, in order to obtain the fundamental data on the drag reduction by polymer additive. we measured the friction factors in the polymer added turbulent flow through a circular pipe for Reynolds number ranging 10000-50000. As polymer additive, PEO (polyethylene oxide: molecular weight 4 x l0^(6)) was used. We also performed the experiments varying the concentration of PEO from 3 to 24 wppm to investigate the effect of the PEO concentration on the drag reduction. We observed more than 25% drag reduction under the above experimental conditions and the most effective drag reduction was found at 6 wppm (31% drag reduction).
이보안,김봉석,고민석,김경연,김신 한국원자력학회 2014 Nuclear Engineering and Technology Vol.46 No.1
An electrical resistance tomography (ERT) technique combining the particle swarm optimization (PSO) algorithm withthe Gauss-Newton method is applied to the visualization of two-phase flows. In the ERT, the electrical conductivitydistribution, namely the conductivity values of pixels (numerical meshes) comprising the domain in the context of anumerical image reconstruction algorithm, is estimated with the known injected currents through the electrodes attached onthe domain boundary and the measured potentials on those electrodes. In spite of many favorable characteristics of ERT suchas no radiation, low cost, and high temporal resolution compared to other tomography techniques, one of the majordrawbacks of ERT is low spatial resolution due to the inherent ill-posedness of conventional image reconstructionalgorithms. In fact, the number of known data is much less than that of the unknowns (meshes). Recalling that binarymixtures like two-phase flows consist of only two substances with distinct electrical conductivities, this work adopts the PSOalgorithm for mesh grouping to reduce the number of unknowns. In order to verify the enhanced performance of theproposed method, several numerical tests are performed. The comparison between the proposed algorithm and conventionalGauss-Newton method shows significant improvements in the quality of reconstructed images
Fingerprint Spoof Detection Using Quality Features
보안공학연구지원센터(IJSIA) 보안공학연구지원센터 2015 International Journal of Security and Its Applicat Vol.9 No.10
Biometrics refers to automated recognition of individuals based on their biological and behavioral characteristics. Biometric systems are widely used for security. They are used in forensic and commercial applications. Among all biometric techniques, fingerprint recognition is the most widely used for personal identification systems due to its permanence and uniqueness. But biometric systems are vulnerable to certain type of attacks. Spoofing refers to the fraudulent action by an unauthorized person into biometric systems using fake input that reproduces one of the authorized person’s biometric input. Spoof detection provides extra level of authentication to biometrics. It is used to prevent forgeries. The fingerprint spoof detection is performed by measuring the following quality features of fingerprint. They are Spatial Coherence, Clustering Factor, Gabor Features, Uniformity of Frequency field, Ridge frequency, Direction map and Contrast map. This approach is based on fingerprint image quality. This technique is software based as it requires no external hardware. This approach is inexpensive.
보안공학연구지원센터(IJSIA) 보안공학연구지원센터 2015 International Journal of Security and Its Applicat Vol.9 No.10
Extended three-particle GHZ state decoy is introduced in controlled quantum secure direct communication to improve eavesdropping detection probability and prevent correlation-elicitation (CE) attack. Each particle of extended three-particle GHZ state decoy is inserted into sending particles to detect eavesdroppers, which reaches 63% eavesdropping detection probability. And decoy particles prevent the receiver from obtaining the correct correlation between particle 1 and particle 2 before the sender coding on them, so that he can not get any secret information without the controller's permission. In the security analysis, the maximum amount of information that a qubit contains is obtained by introducing the entropy theory method, and two decoy strategies are compared quantitatively. If the eavesdroppers intend to eavesdrop on secret information, the per qubit detection rate of using only two particles of extended three-particle GHZ state as decoy is 58%;while the presented protocol using three particles of extended three-particle GHZ state as decoy reaches per qubit 63%.
Study on the System for Prevention of Harmful Invasion with Access from Wireless LAN Access Point
보안공학연구지원센터(IJSIA) 보안공학연구지원센터 2015 International Journal of Security and Its Applicat Vol.9 No.10
Due to a recent increase of usage of Internet and users of smart devices, there has been an increasing trend of wireless networks that can be conveniently used. However, wireless network is exposed to a weaker security than wire network. Because of such a security-related issue, users are exposed to the crime and also financial damage as well. In addition, there is an issue that using the AP of wireless network makes it feasible for a party to break into an internal network. This study is intended to suggest a system for prevention of harmful invasion with access from wireless LAN Access Point. In order to verify the function of invasion prevention system, tools used in the penetration testing were utilized preparing for a scenario that made an attempt of attack on wireless network.