• Journal of Radiation Protection and Research
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• v.10 no.2
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• pp.130-136
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• 1985

The activity measurement of a solution of $^{133}Ba$ which is an electron capture nuclide was carried out by the ${\beta}-{\gamma}$ coincidence method. The counting rates at the ${\beta}-,\;{\gamma}-$, and coincidence-channels were measured using a $4{\pi}$ proportional counter and two NaI(Tl) scintillation detectors. The specific activity of the solution calculated by the efficiency extrapolation was $(1151.01{\pm}2.99)kBqg^{-1}$ at the reference time(00h UT, 03-15-84). According to an international comparison of activity measurements organized by the Bureau International des Poids et Mesures, this result showed the difference of 0.94% to the mean value derived from the comparison.

• Journal of the Korean Society for information Management
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• v.16 no.2
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• pp.7-26
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• 1999

This experimental study examines informetric analysis of World Wide Web based upon cocitation analysis of Web pages and features of Web resources in the field of communication studies. Cocitation analysis is basically performed to examine the intellectual structure of the communication studies in reflecting link count on the Web. The selected Web resources in the field are mapped in two dimensions based upon the similarities of cocitation frequency, correlation matrix, mutidimensional scale and cluster analysis. Cocitation analysis methods using organizational homepage, personal homepage, or Web index, to Web produced clustering of Web resources that had topical similarities. So far, although informetric analysis of Web resources is in the preliminary stage, it shows that Web can be a new tool for indicating the intellectual structure of a specific research field. In addition, this study analyzes characteristics of printing resources and Web resources, and differences of research methods in applying cocitation analysis.

• Journal of Soil and Groundwater Environment
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• v.12 no.3
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• pp.36-43
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• 2007

In the case of single well pumping tests the storativities are generally overestimated. To compensate these errors, the effective wellbore radius should be introduced as a distance to an imaginary observation well in the time-drawdown analysis. Effective wellbore radius can be calculated through step drawdown tests or using skin factor equation. But both are of trial-and-error methods guessing real storativity values and, therefor, are difficult to apply to the field conditions. An equation was developed to estimate effective wellbore radius from storativity values obtained from pumping well data. For this study, a total of 136 time-drawdown data set were used to derive the equation. The effective wellbore radius were estimated first by changing them till the storativity values obtained from the pumping-well data match the ones based on the observation-well data. Then the equation was regressed from the relation between effective wellbore radius and the storativity values obtained from the pumping-well data. It is believed that the equation would be useful in estimating effective wellbore radius from the single well tests.

• The KIPS Transactions:PartB
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• v.9B no.5
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• pp.609-614
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• 2002

Watermarking is embedding a digital signal called as watermark into images to claim the ownership. In this paper, a new digital watermarking algorithm based on DCT (Discrete Cosine Transform) which enhances invisibility and robustness is proposed to improve contentional digital watermarking method using DCT. In the proposed method, it is possible to enhance invisibility and robustness using watermark reordering in which the relative significance of original DCT coefficients can be preserved in watermarked DCT coefficients, and the distortions of original DCT coefficients can be minimized. The experimental results show that the proposed method improves invisibility approximately 9～12[dB] and is more robust to various attacks than the conventional method.

• Proceedings of the IEEK Conference
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• 2001.09a
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• pp.499-502
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• 2001

본 연구에서는 화자에 따라 서로 다른 성도의 길이에 의해 발생하는 음성인식 시스템의 성능 저하를 줄이기 위하여, VTN(Vocal Tract Normalization)을 음성인식 시스템에 적용하고, 주소 인식 실험을 통하여 인식 성능을 평가하였다. 또, VTN을 CMN과 동시에 적용하여 인식 실험을 하였다. 실험에서는 화자간 성도길이의 차이를 반영하기 위하여 13개의 Warping 계수에 대해 필터 뱅크를 이용한 선형 Warping 방법을 적용하였다. 실험결과, Baseline 인식 시스템에 비하여 VTN을 적용하면, WER(Word Error Rate)이 1.24% 감소하였고, CMN과 VTN을 동시에 적용한 실험에서는 Baseline 인식 시스템과 비교하여 WER이 0.33% 감소 하였지만 VTN을 적용한 실험결과와 비교하면 오히려 0.91% 증가하였다.

• The Science & Technology
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• v.33 no.3 s.370
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• pp.76-77
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• 2000

한국의 우수두뇌유치 프로그램에 의해 지난해 2월부터 한국표준과학연구원에서 근무하고 있는 폴란드 과학자 리자드 브로다박사는 현재 베타방출핵종을 액체섬광계수방법으로 표준화하는 연구를 수행하고 있다. 그가 재직중인 폴란드방사성동위원소센터와 한국표준과학연구원 방사능그룹은 동시계수를 이용한 방사성 핵종의 표준화 등 비슷한 내용을 연구하고 있으므로 계측문제를 함께 풀어나가면서 훨씬 빠른 발전이 이루어질 것이라고 내다보았다.

• Journal of Astronomy and Space Sciences
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• v.15 no.2
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• pp.341-358
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• 1998

The X-ray astronomy team of the Korea Astronomy Observatory(KAO) is planning to develop a multi-cell proportional counter, adopting an anti-coincidence method to reduce its internal background. We have developed a Monte Carlo code to determine the X-ray detection efficiency of the counter. As a check of our code, we successfully reproduced the detection efficiency of Ginga/LAC. In this paper, we report the simulation results for the counter being considered in KAO.

• Journal of the Korea Concrete Institute
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• v.13 no.3
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• pp.228-236
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• 2001

Even though numerous researches have been performed for the prediction of thermal stresses in mass concrete structures by both analytical and experimental means, the limitations exist for both approaches. In analytical approach, the fundamental limitation is derived from the difficulty of predicting concrete properties such as modulus of elasticity, coefficient of thermal expansion, etc.. In experimental approach, there are many uncertainties related to in-situ conditions, because a majority of researches have focused on measuring thermal stresses in actual and simulated structures. In this research, an experimental device measuring thermal stresses directly in a laboratory setting is developed. The equipment is located in a temperature chamber that follows the temperature history previously obtained from temperature distribution analysis. Thermal strains are measured continuously by a strain gauge in the device and the corresponding thermal stresses are calculated simply by force equilibrium condition. For the verification of the developed device, a traditional experiment measuring thermal strains from embedded strain gauges is performed simultaneously. The results show that the thermal strain values measured by the newly developed device agree well with the results from the benchmark experiment.

• Computational Structural Engineering
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• v.4 no.1
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• pp.20-27
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• 1991

본 논문에서는 유체-구조 상호작용해석의 일종의 3차원 접수구조물의 진동해석을 효과적으로 수행하기 위한 해석방법을 제시하기 위하여 동적재해석기법을 검토하였다. 접수구조물의 유한구조 상호작용해석 결과는 구조진동의 관심 주파수역에서는 3차원 연성 부가수질량으로 표현되는 관성력으로 나타난다. 따라서 구조질량행렬에 부가수질량 행렬이 더해져서 전체 관성력으로 표현된다. 이 부가수질량을 추가질량으로 보고 재해석기법을 응용하는 방법을 수치실험을 통해 검증하였다. 이 때 재해석기법이 갖추어야 할 조건은 원구조의 질량과 거의 같은 정도의 질량이 추가되고 또한 완전 연성질량이 추가된 경우에도 정확한 해를 주어야 한다는 것이다. 이를 검증하기 위해 직접재해석기법과 섭동법을 이용한 재해석기법으로 4질량 스프링지지구조에 대한 해석을 수행한 결과 직접재해석기법의 응용이 적합함을 쉽게 입증할 수 있었다. 접수구조물의 예로는 3차원 잠수주상체에 대해 접수진동해석을 수행하였으며 그 결과 선체진동해석에 전통적으로 이용되고 있는 2차원 부가수질량과 3차원 수정계수를 사용한 기준차수법에서는 수지모드와 수평-비틔 연성모드와 같이 서로 독립적인 모드에 대해서는 따로 진동해석을 수행해 주어야 하는 단점이 발견되었다. 이 단점을 보완한 각 모드의 3차원 수정계수행렬을 이용한 재해석기법을 도입하여 모드에 상관없이 동시에 해를 구할 수 있었다. 그러나, 이 방법은 3차원 수정계수가 구해져 있는 경우에 한해서만 적용가능하며 실제 선체진동의 경우에는 10Hz 미만의 저차 주선체 진동에 한해서만 적용가능한 방법이다. 고차의 진도옴드에는 3차원 수정계수를 구할 수 없기 때문에 유체-구조 상호작용 해석결과로부터 얻은 3차원 연성 부가수질량을 이용하게 되며 이 때 이 행렬이 접수구조 표면의 전 자유도와 연성되어 있기 때문에 방대한 방정식을 푸어야 하지만 직접재해석기법을 적용함으로써 정확한 해를 구할 수 있었다. 또한 3차원 부가수질량을 이용한 직접재해석기법은 종래의 2차원 부가수질량과 3차원 수정계수를 이용한 방법에 비해 해석시간 면에서도 전혀 불리한 점이 없는 경제적 방법임이 밝혀졌다. 앞으로 Slamming 혹은 수중폭파 등의 충격하중에 의한 천이 구조응답 해석을 위한 효과적인 방법에 대해서도 연구결과를 발표할 계획이다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.11
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• pp.625-636
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• 2014

In this paper, we propose a new embedded image compression scheme which uses rate-distortion optimized block coding of wavelet coefficients. Unlike to previous works in which set-partition or block-partition is performed according to the magnitude of wavelet coefficients, the proposed scheme achieves rate-distortion optimization by sorting wavelet coefficients or blocks according to their expected rate-distortion slope. At the same time, it performs the optimized block-partition coding using the expected rate-distortion slope of blocks. The proposed scheme also uses various relationship of wavelet coefficients for the entropy coding. Experimental results demonstrate that the proposed image compression scheme provides better overall performance than the existing embedded coding schemes such as SPIHT and EBCOT, in which the PSNR gains of the proposed scheme are about 0.11~1.16dB and -0.18~0.52dB, respectively.