For safeguarding dry storage facilities, a tomography system based on fast and thermal neutron detection was studied in Korea Institute of Nuclear Nonproliferation and Control. The study was conducted laboratory-scale experiments based on a custom built 1/10th scale model cask, He-4 gas scintillation detector array, and multiple 252Cf sources. A filtered back projection (FBP) was utilized to obtain the cask image via MATLAB. The Ram-Lak filter (ramp filter) was employed in FBP for improved the reconstructed image quality. The Ram-Lak filter is the increasing amplitude filter due to the increasing spatial frequency of the image. In spatial frequency, the frequency of brightness change in the low-frequency region is relatively low, and the frequency of brightness change in the highfrequency region is large. Thus, the high-frequency region in the neutron tomographic image is near the neutron sources and the cask, and the low-frequency region is outside of the cask and/or between the source and cask in the study. In order to apply the ramp filter, a Fourier transform is initially performed on projection data, and image reconstruction is performed with the corrected projection data. In this case, the filter is linearly changed. Therefore, a small filter value is applied at lower spatial frequencies to reduce the projection data, and a large filter value is applied at high spatial frequencies to reduce the projection data. The filter scale is a fraction of frequency amplitude, and the filter value applied to the projection data is determined according to the filter scale. This study was conducted for discussion of the image quality due to the effect of the filter scale used for image reconstruction of a neutron tomography system. The results show that in the experiment with one source, the source location was founded when we used the frequency scale of 0.5 and over. In the double or triple source experiment, the source locations and relative activities were found when we used a filter scale of 0.4 to 0.6. When the filter frequency scale of 0.7 to over, the relative activities are hard to know. It can be found that if the filter value is too large or too small, distortion may occur in the reconstruction results. Therefore, it seems reasonable to set a value between 0.4 and 0.6 as the scaling factor for the neutron tomography system. In the future, additional comparative studies will perform validation of the frequency scaling methods.

We introduce a depth scaling strategy to improve the accuracy of frequency-domain elastic full waveform inversion (FWI) using the new pseudo-Hessian matrix for seismic data without low-frequency components. The depth scaling strategy is based on the fact that the damping factor in the Levenberg-Marquardt method controls the energy concentration in the gradient. In other words, a large damping factor makes the Levenberg-Marquardt method similar to the steepest-descent method, by which shallow structures are mainly recovered. With a small damping factor, the Levenberg-Marquardt method becomes similar to the Gauss-Newton methods by which we can resolve deep structures as well as shallow structures. In our depth scaling strategy, a large damping factor is used in the early stage and then decreases automatically with the trend of error as the iteration goes on. With the depth scaling strategy, we can gradually move the parameter-searching region from shallow to deep parts. This flexible damping factor plays a role in retarding the model parameter update for shallow parts and mainly inverting deeper parts in the later stage of inversion. By doing so, we can improve deep parts in inversion results. The depth scaling strategy is applied to synthetic data without lowfrequency components for a modified version of the SEG/EAGE overthrust model. Numerical examples show that the flexible damping factor yields better results than the constant damping factor when reliable low-frequency components are missing.

This study was performed to investigate the effect of the health related factors on the preference and frequency of intake of coffee and traditional beverages among 280 university students (128 males and 152 females) who were residing in Incheon areas. The results were as follows; 1. Male students of over weight and obese were more than female students and female students of under weight were more than male students. Female students were interested in weight control and had an experience in weight control more than male students. 2. The group who was much interested in weight control preferred green tea, yuja tea and dunggulre tea. The group who was much interested in health when drink beverages preferred green tea, ginseng tea, dunggulre tea, vinegar drinks and water but didn’t prefer coffee. 3. The frequency of intake of green tea is high in the group who had an experience in weight control. And the frequency of intake of honey tea was high in the group who drank alcohol almost every day. Coffee intake was the highest among beverages in smokers and water intake was the highest among beverages in nonsmokers. In conclusion this study showed that as an interest in health is higher, the preference and frequency of intake of coffee was low whereas those who intake of traditional beverages was high in general.

고품위석회석의 품질 개념에서 특히 중요한 결정도 및 조직 관계는 계측상의 어려움 때문에 석회석 평가에서 그 동안 효과적으로 잘 적용될 수 없었다. 이를 극복하기 위해서 이 연구에서는 석회석 원광의 품질을 평가하는 방식으로서 영상분석시스템 하에서 결정의 형상계수 및 경계 빈도수의 측정법을 처음으로 적용하였다. 이 같은 석회석 원광 품질 평가방식을 국내산 소성용 석회석에 적용하여 광석별로 비교 검토하였다. 그 결과, 원광의 방해석 함량, 즉 품위와 그 결정 입도가 비슷하더라도 결정 형상계수와 경계빈도수에 의해서 생석회의 품질은 현격한 차이를 보인다. 즉, 원광의 결정 형상이 불규칙하고 경계 빈도수가 높을수록 이로부터 합성된 생석회는 소성율, 공극률, 반응성, 소결 정도 및 분화율과 같은 모든 품질 부문에서 우수한 특성을 보였다. 그렇지만 결정 형상계수와 경계빈도수가 상대적으로 너무 클 경우에는 쉽게 과소성되기 때문에 고품질의 생석회를 제조하는 데에는 가열처리 시간을 최소화하는 공정상의 기술이 요구된다. 석회석 산업에서 이같은 품질 평가 방식은 결정 입도는 물론 수치화할 수 없었던 결정 형상 및 조직적 사항들이 모두 고려되어 기존의 평균 입도 등에 의거한 평가보다 훨씬 합리적인 것으로 사료된다.