• Applied Chemistry for Engineering
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• v.26 no.1
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• pp.17-22
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• 2015

International interests in chemical warfare agents (CWAs) have been increased recently because of the use of sarin (GB) in Syrian civil war which caused around 1,300 casualties in 2013. After exposing to natural environments, CWAs undergo hydrolysis or photodegrade to non-toxic degradation byproducts. Generally, CWAs and their degradation byproducts are present at very low concentration (e.g. several ppb), thus pretreatment processes including separation, extraction and concentration are required prior to any analyses. Liquid-liquid extraction and solid-phase extraction (SPE) are common techniques to pretreat environmental samples. Recently, a novel pretreatment method, liquid phase miecoextraction (LPME), has been applied to CWAs analysis, which could reduce amounts of solvent used but promote analytical efficiencies. Fundamental backgrounds of LPME and its application to CWAs analysis were reviewed.

• 한국HCI학회:학술대회논문집
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• 2006.02a
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• pp.7-14
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• 2006

본 논문에서는 3D 복원과 카메라 측정과정 없이 정확하게 카메라 자세를 계산하고 가상객체를 비디오에 합성하기 위한 단일 프레임 기반의 고속 계산 기법을 제안한다. 객체의 로컬 좌표와 단일 이미지에서의 대응되는 이미지 좌표로부터 카메라 자세를 계산한다. 정사영 투영모델에서의 분해기법에 기반한 구조 계산 방법으로 카메라 자세의 고속 추정이 가능하다. 정사영 투영모델에 기반하기 때문에 참조점의 설정에 따라 정확도가 달라진다. 객체에 따라 참조점을 설정하여 정확한 카메라 자세를 계산하는 방법을 제안한다. 카메라 자세 및 물체의 형태는 단일 프레임 기반으로 수행되며 카메라 자세 추정 결과가 즉시 비디오 합성에 사용될 수 있도록 하였다. 제안하는 기법의 유효성 입증을 위해 실사 비디오에 기반한 증강현실시스템을 구현하고 카메라 자세 계산과 비디오 합성의 전체 과정을 단일 프레임에 기반하여 실험을 수행하고 제안 기법의 실용성을 보였다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.12 no.4
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• pp.681-690
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• 1999

본 논문에서는 요소를 사용하지 않은 수치해석기법인 무요소법 중에서 다중해상도(multi-resolution)특성이 내재되어 있는 Reproducing Kernel Particle Method (RKPM)의 이중스케일 분해기법을 사용하여 RKPM의 형상함수를 상단성분과 하단성분으로 분리하고 이를 3차원 선형탄성해석과정에 적용하여 von Mises 응력장의 상·하단성분을 유도하였다. 유도된 응력장의 상단성분을 이용하여 후처리과정을 거치지 않고도 응력의 고변화도 부위를 손쉽게 파악할 수 있는 기법을 개발하였으며 이를 이용한 효율적인 적응적 세분화기법의 적용가능성을 연구하였다. 대표적인 2차원 및 3차원 응력집중 문제에 적용하여 응력집중부위를 파악하고 간단한 적응적 세분화과정에 따른 절점추가를 통하여 해의 정도 향상을 파악해 본 결과, 본 연구에서 개발된 기법이 응력집중부위를 정확히 판정할 수 있었으며 효율적인 적응적 세분화기법의 유용한 도구로서 활용될 수 있음을 검증하였다.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.15 no.2
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• pp.65-72
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• 2005

Quite recently, Zhou, Lu and Cao proposed a proxy-protected signature scheme based on the RSA assumption and two proxy-protectcd schemes based on the hardness of integer factorization. Dey also provided a security proof for each signature scheme in the random oracle model. In this paper, we show that their schemes do not satisfy a security requirement necessary for proxy signature schemes. This results in generating proxy signature without fay Permission from an original signer.

• Applied Chemistry for Engineering
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• v.27 no.2
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• pp.158-164
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• 2016

Spherical DADNE/AP (1,1-diamino-2,2-dinitroethylen/ammonium perchlorate) energetic composites were produced by drowning-out/agglomeration (D/A). The agglomeration of DADNE with AP particles was found to be affected by the amount of the bridging liquid, stirring velocity and residence time. The composites appeared to grow dramatically with the amount of bridging liquid which triggers agglomeration. As the stirring velocity and the residence time increased, the size of composites increased and then tended to decrease. Thermal gravimetric analysis showed that the addition of DADNE activates the low temperature decomposition (LTD) of AP. For the neat AP, the only about 30 wt% of AP was found to decompose at the LTD. On the other hand, it was found that 70 wt% of AP decomposed when DADNE was added by physical mixing and 90 wt% of AP decomposed when the DADNE/AP composites were prepared by the D/A method.

• The Journal of the Korea Contents Association
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• v.22 no.7
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• pp.46-54
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• 2022

The existing methods for determining influence in social networks do not accurately determine the influence of users because they do not delete or update existing relationships before they stop in the face of an increasing number of inactive users on social networks. In this paper, we propose a user influence detremination method using the temporal k-shell decomposition technique based on the creation date of users of social networks. To solve the problem of increasing influence of old users in social networks, we apply k-shell decomposition and age-specific order centrality as attenuation coefficients due to aging in neighbors. The age-decaying k-shell decomposition and age-specific order centrality are searched for influential users at the present time by applying the attenuation coefficient and age-dependent weights. Various performance evaluations are performed to show the superiority of the proposed method.

• Journal of Korea Water Resources Association
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• v.41 no.9
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• pp.959-967
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• 2008

Disaggregation techniques are widely used to transform observed daily rainfall values into hourly ones, which serve as important inputs for flood forecasting purposes. However, an important limitation with most of the existing disaggregation techniques is that they treat the rainfall process as a realization of a stochastic process, thus raising questions on the lack of connection between the structure of the models on one hand and the underlying physics of the rainfall process on the other. The present study introduces a nonlinear deterministic (and specifically chaotic) framework to study the dynamic characteristics of rainfall distributions across different temporal scales (i.e. weights between scales), and thus the possibility of rainfall disaggregation. Rainfall data from the Seoul station (recorded by the Korea Meteorological Administration) are considered for the present investigation, and weights between only successively doubled resolutions (i.e., 24-hr to 12-hr, 12-hr to 6-hr, 6-hr to 3-hr) are analyzed. The correlation dimension method is employed to investigate the presence of chaotic behavior in the time series of weights, and a local approximation technique is employed for rainfall disaggregation. The results indicate the presence of chaotic behavior in the dynamics of weights between the successively doubled scales studied. The modeled (disaggregated) rainfall values are found to be in good agreement with the observed ones in their overall matching (e.g. correlation coefficient and low mean square error). While the general trend (rainfall amount and time of occurrence) is clearly captured, an underestimation of the maximum values are found.

• Rubber Technology
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• v.22 no.2
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• pp.150-177
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• 2021

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.1
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• pp.80-87
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• 2017

This paper proposes a pre-processing algorithm to improve perceptual video coding efficiency which decomposes an input frame via a sub-band decomposition, and suppresses only high frequency band(s) having low visual sensitivity. First, we decompose the input frame into several frequency subbands by a linear sub-band decomposition. Next, high frequency subband(s) which is rarely recognized by human visual system (HVS) is suppressed by applying relatively small gain(s). Finally, the high frequency suppressed frame is compressed by a specific video encoder. We can find from the experimental results that if comparing before-use and after-use of the proposed pre-processing prior to the encoder, no visual difference is shown. Also, the proposed algorithm achieves bit-saving of 13.12% on average in a H.264 video encoder.

• The KIPS Transactions:PartB
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• v.13B no.5 s.108
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• pp.499-506
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• 2006

This Paper describes a fast and stable camera pose estimation method for real-time augmented reality systems. From the feature tracking results of a marker on a single frame, we estimate the camera rotation matrix and the translation vector. For the camera pose estimation, we use the shape factorization method based on the scaled orthographic Projection model. In the scaled orthographic factorization method, all feature points of an object are assumed roughly at the same distance from the camera, which means the selected reference point and the object shape affect the accuracy of the estimation. This paper proposes a flexible and stable selection method for the reference point. Based on the proposed method, we implemented a video augmentation system that inserts virtual 3D objects into the input video frames. Experimental results showed that the proposed camera pose estimation method is fast and robust relative to the previous methods and it is applicable to various augmented reality applications.