• Journal of the Society of Naval Architects of Korea
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• v.43 no.3 s.147
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• pp.322-330
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• 2006

Numerical calculations are carried out for flow past a circular cylinder forced oscillating normal to the free-stream flow at a fixed Reynolds number equal to 185. The cylinder oscillation frequency ranged from 0.8 to 1.2 of the natural vortex-shedding frequency, and the oscillation amplitude extended up to 20% of the cylinder diameter. IBM (Immersed Boundary Method) with direct momentum forcing was adopted to handle both of a stationary and an oscillating cylinder Present results such as time histories of drag and lift coefficients for both stationary and oscillating cases are in good agreement with previous numerical and experimental results. The instantaneous wake patterns of oscillating cylinder with different oscillating frequency ratios showed the synchronized wakes pattern in the lock-in region and vortex switching phenomenon at higher frequency ratio than the critical frequency ratio.

• Convergence Security Journal
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• v.14 no.5
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• pp.17-24
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• 2014

This study proposed LDP (Local Directional Pattern) as a new local micro pattern for facial expression recognition to solve noise sensitive problem of LBP (Local Binary Pattern). The proposed method extracts 8-directional components using $m{\times}m$ mask to solve LBP's problem and choose biggest k components, each chosen component marked with 1 as a bit, otherwise 0. Finally, generates a pattern code with bit sequence as 8-directional components. The result shows better performance of rotation and noise adaptation. Also, a new local facial feature can be developed to present both PFF (permanent Facial Feature) and TFF (Transient Facial Feature) based on the proposed method.

• Journal of KIISE:Computer Systems and Theory
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• v.28 no.10
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• pp.513-519
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• 2001

Home-based Lazy Release Consistency (HLRC) shows poor performance on lock based applications because of two reasons:(1) a whole page is fetched on a page fault while actual modification is much smaller , and(2) the home is at the fixed location while access pattern is migratory, In this paper we present an efficient lock protocol for HLRC. In this protocol, the pages that are expected to be used by acquirer selectively updated using diffs. The diff accumulation problem is minimized by limiting the size of diffs to be sent for each page. Our protocol reduces the number or page faults inside critical sections because pages can be updated by applying locally stored diffs . This reduction yields the reduction of average lock waiting time and the reduction of message amount. The experiment with five applications shows that our protocol archives 2%~40% speedup against base HLRC for four applications.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.2
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• pp.162-169
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• 2007

This study is focused on the comparison of a 3 dimensional numerical and hydraulic model experiment for the flow phenomenon when a lock gate is opened. The lock gate is designed to discharge the flood flow rate at $218m^3/s$ of Solicheon at the Kun Jang national industry complex. The three dimensional ${\kappa}-{\epsilon}$ turbulent model of ANSYS CFX-10 of the computational fluid dynamics(CFD) program was used. The characteristics of CFX-10 are able to be simulated effectively for turbulent flow, especially the flow separation of the boundary layer of the two phase interface of air and water. The velocity and the flow pattern of the numerical model was showed to be similar to the results of the hydraulic model experiment.

• Journal of the Korean Society for Nondestructive Testing
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• v.31 no.2
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• pp.139-143
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• 2011

The problem of delamination of composite tubes by impact has been acknowledged in aerospace and automobile industry. Non-destructive testing(NDT) methods in composite material structure are important to evaluate reliability of composite structure. There are many kinds of NDT methods which can detect the inside defect of the composite material such as Infrared Thermography(IRT). Infrared thermal imaging of object is different from that of a defect, in heated composite tubes with an internal defect, and then location and size of a defect can be measured by the analysis of thermal imaging pattern. In this study, Lock-in Infrared thermography detect internal defects of Impacted composite tubes by the inspection of infrared lay radiated from the surface of composite tubes.

• Journal of Oral Medicine and Pain
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• v.16 no.1
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• pp.113-120
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• 1991

The authors examined the patterns and various ranges of mandibular movements in TMJ lock closed patients in the frontal, sagittal and horizontal plane pre-end post-treatment. And the author obtained the following results. 1. In the frontal plane, the patterns and ranges of mandibular movement of the patients were very irregular and small before treatment. But after the treatment, the patterns were similar to the typical shield shape of the normal subjects. And the velocity of opening and closing was improved after the treatment. 2. In the sagittal plane, the mean amount of maximum mouth opening was 27.0±4.0mm before treatment and 44.0±5.4mm after treatment. And there was statistically significant improvement(p<0.005). The patterns of the movement were very irregular and small before treatment, but were similar to the shape of "Posselt's envelope of motion" after the treatment. The velocity of opening and closing was improved after the treatment 3. In the horizontal plane, the mean amount of maximum laterotrusion was 8l2±2.5mm in the affected side and 6.7±2.2mm in the non-affected side before treatment. There was a significant difference between the sides(p<0.05). After the treatment, the mean was 10.4±2.6mm in the affected side and 8.9±2.3mm in the non-affected side and there was no significant difference between the sides(p>0.05). There was no significant difference in the mean amount of maximum protrusion between the before and aftertreatment(p>0.05), but the patterns of the movements were improved.

• Convergence Security Journal
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• v.22 no.1
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• pp.29-38
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• 2022

The importance of prevention of epidemics is increasing due to the serious spread of infectious diseases. For prevention of epidemics, we need to focus on the non-contact industry. Therefore, in this paper, a face recognition door lock that controls access through non-contact is designed and developed. First very simple features are combined to find objects and face recognition is performed using Haar-based cascade algorithm. Then the texture of the image is binarized to find features using LBPH. An non-contact door lock system which composed of Raspberry PI 3B+ board, an ultrasonic sensor, a camera module, a motor, etc. are suggested. To verify actual performance and ascertain the impact of light sources, various experiment were conducted. As experimental results, the maximum value of the recognition rate was about 85.7%.

• Structural Monitoring and Maintenance
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• v.9 no.2
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• pp.201-220
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• 2022

Lateral vibrations of footbridges may induce synchronization between pedestrians and structure itself, resulting in amplification of such vibrations, a phenomenon identified by lock-in. However, investigations about accelerations and frequencies of the structural movement that are related to the occurrence of synchronization are still incipient. The aim of this paper is to investigate conditions that could lead to avoidance of synchronization among pedestrians themselves and footbridge, expressed in terms of peak acceleration. The focus is on the low acceleration range, employed in some guidelines as a criterion to avoid synchronization. An experimental campaign was carried out, employing a prototype footbridge that was set into oscillatory motion through a pneumatic exciter controlled by a fuzzy system, with controlled frequency and amplitude. Test subjects were then asked to cross the oscillating structure, and accelerations were simultaneously recorded at the structure and at the subject's waist. Pattern and phase differences between these signals were analysed. The results showed that test subjects tended to keep their walking patterns without synchronization induced by the vibration of the structure, for structural peak acceleration values up to 0.18 m/s², when frequencies of oscillation were around 0.8 to 0.9 Hz. On the other hand, for frequencies of oscillation below 0.7 Hz, structural peak accelerations up to 0.30 m/s² did not induce synchronization.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.28 no.2
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• pp.369-383
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• 2018

User authentication using PIN input or lock pattern is widely used as a user authentication method of smartphones. However, it is vulnerable to shoulder surfing attacks and because of low complexity of PIN and lock pattern, it has low security. To complement these problems, keystroke dynamics have been used as an authentication method for complex authentication and researches on this have been in progress. However, many studies have used imposter data in classifier training and validation. When keystroke dynamics authentications are actually applied in reality, it is realistic to use only legitimate user data for training, and using other people's data as imposter training data may result in problems such as leakage of authentication data and invasion of privacy. In response, in this paper, we experiment and obtain the optimal ratio of the thresholds for distance based classification. By suggesting the optimal ratio, we try to contribute to the real applications of keystroke authentications.

• Proceedings of the Korea Information Processing Society Conference
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• 2015.10a
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• pp.441-443
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• 2015

본 논문에서는 스마트폰 보안방식중 하나인 잠금패턴 방식에서 사용자가 즐겨 사용하는 프로그램을 설정한 후 바로가기가 가능하도록 하며 휴대폰을 사용하기 어려운 상황에 간단한 문자메시지를 보낼 수 있는 앱을 개발한다. 이 앱의 특징은 잠금화면 상태에서 위젯 및 앱 실행이 가능하며, 기존 보안패턴방식의 보안성을 유지하고 사용자가 스마트폰을 더 빠르게 사용 할 수 있게 한 것이 특징이다.