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텍스쳐 정보를 이용한 VQ 기반의 내용 기반 영상 검색
신대규,김동훈 연세대학교 대학원 총학생회 2001 원우론집 Vol.34 No.-
This paper proposes a new method of retrieving images from large image databases. The method is based on VQ(Vector Quantization) of local texture information at interest points automatically detected in an image. The texture features are extracted by Gabor wavelet filter bank, and rearranged for rotation. These features are classified by VQ and then construct a pattern histogram. Retrievals are performed by just comparing pattern histograms between images. Experimental results have shown the robustness of the proposed VQ based retrieval method to image rotation, small scale change, noise addition and brightness change and also shown the possibility of the retrieval by a partial image.
Prediction Model of the Outer Radiation Belt Developed by Chungbuk National University
신대규,이대영,김진희,조정희 한국우주과학회 2014 Journal of Astronomy and Space Sciences Vol.31 No.4
The Earth’s outer radiation belt often suffers from drastic changes in the electron fluxes. Since the electrons can be apotential threat to satellites, efforts have long been made to model and predict electron flux variations. In this paper, wedescribe a prediction model for the outer belt electrons that we have recently developed at Chungbuk National University. The model is based on a one-dimensional radial diffusion equation with observationally determined specifications of afew major ingredients in the following way. First, the boundary condition of the outer edge of the outer belt is specified byempirical functions that we determine using the THEMIS satellite observations of energetic electrons near the boundary. Second, the plasmapause locations are specified by empirical functions that we determine using the electron density dataof THEMIS. Third, the model incorporates the local acceleration effect by chorus waves into the one-dimensional radialdiffusion equation. We determine this chorus acceleration effect by first obtaining an empirical formula of chorus intensityas a function of drift shell parameter L*, incorporating it as a source term in the one-dimensional diffusion equation, andlastly calibrating the term to best agree with observations of a certain interval. We present a comparison of the model runresults with and without the chorus acceleration effect, demonstrating that the chorus effect has been incorporated into themodel to a reasonable degree.
청각 모델을 이용한 Co-Channel 음성에서의 피치 추출에 관한 연구
신대규 연세대학교 대학원 2000 원우론집 Vol.- No.31
본 연구에서는 Robinson이 제안한 코클리어 청각 모델을 이용하여 noise 및 Co-Channel등의 환경에서 음성의 피치를 검출하는 방법을 제안한다. 제안된 피치 검출 방법은 noise가 존재하는 경우에서도 정확한 검출이 가능하였으며 특히 두 사람의 말이 동시에 들리는 Co-Channel 상에서 그 효과가 뛰어나다. 먼저 1인의 음성 발음에 대해서는 단순히 Robinson 모델의 신경 발화의 모양을 통해서 1차적으로 피치를 검출할 수 있다. 이 경우 피치의 길이 변화가 다소 있더라도 시간 축에서 결과를 보기 때문에 정확한 추정이 가능하다. 그러나 잡음이나 Co-Channel 상의 음성에 대해서는 청각 모델 출력에서 거짓된(spurious) peak가 많이 발생하기 때문에 발화 곡선을 autocorrelator와 결합하여 피치를 추정한다. 각각의 delay에 대해서 autocorrelator를 모두 사용할 경우 계산량이 많아지는 단점이 있으므로 본 연구에서는 energy가 밀집한 주파수 부분들의 값들에서만 autocorrelator를 사용하였다. 먼저 1인 화자에 대하여 제안된 algorithm을 적용해 보고, Co-Channel 상에서 기존의 autocorrelation 방법과 비교하여 성능을 보이도록 한다.
신대규,류도형,Shin, Dae-Kyu,Riu, Doh-Hyung 한국분말야금학회 2008 한국분말재료학회지 (KPMI) Vol.15 No.2
Nano magnetite particles have been prepared by two step reaction consisting of urea hydrolysis and ammonia addition at certain ranges of pH. Three different concentrations of aqueous solution of ferric ($Fe^{3+}$) and ferrous ($Fe^{2+}$) chloride (0.3 M-0.6 M, and 0.9 M) were mixed with 4 M urea solution and heated to induce the urea hydrolysis. Upon reaching at a certain pre-determined pH (around 4.7), 1 M ammonia solution were poured into the heated reaction vessels. In order to understand the relationship between the concentration of the starting solution and the final size of magnetite, in-situ pH measurements and quenching experiments were simultaneous conducted. The changes in the concentration of starting solution resulted in the difference of the threshold time for pH uprise, from I hour to 3 hours, during which the akaganeite (${\beta}$-FeOOH) particles nucleated and grew. Through the quenching experiment, it was confirmed that controlling the size of ${\beta}$-FeOOH and the attaining a proper driving force for the reaction of ${\beta}$-FeOOH and $Fe^{2+}$ ion to give $Fe_3O_4$ are important process variables for the synthesis of uniform magnetite nanoparticles.