• Journal of the Earthquake Engineering Society of Korea
• /
• v.14 no.5
• /
• pp.1-12
• /
• 2010

This study presents a finite element analysis method that can accurately evaluate the nonlinear behaviour of structures affected by shallow soft subsoils and the soil-structure interaction. A two-dimensional finite element model that consists of a structure and shallow soft subsoil was used. The finite element model was used for a nonlinear time domain analysis of the OpenSees program. A parametric study was performed to investigate the effects of soil shear velocities, earthquake input motions, soft soil depth, and soil-structure interaction. The result of the proposed nonlinear finite element analysis method was compared with the result of an existing frequency domain analysis method, which is frequently used for addressing nonlinear soil behavior. The result showed that the frequency domain analysis, which uses equivalent secant soil stiffness and does not address the soil-structure interaction, significantly overestimated the response of the structures with short dynamic periods. The effect of the soil-structure interaction on the response spectrum did not significantly vary with the foundation dimensions and structure mass.

• The Korean Journal of Nuclear Medicine Technology
• /
• v.16 no.2
• /
• pp.35-43
• /
• 2012

Purpose : PET/CT performed CT-based attenuation correction generates the beam hardening artifact by metallic implant. The attenuation correction causes over or underestimate of the area adjacent to metallic hip prosthetic material and change of $^{18}F$-FDG uptake. Also, the image quality and the diagnosability on genitourinary disease are reduced. Therefore, this study will evaluate the usefulness of MAR (Metal Artifact Reduction) algorithm method to improve the image quality on PET/CT. Materials and Methods : PET/CT was performed by fixing hip prosthesis in SPECT/PET phantom. In PET images with and Without MAR algorithm, the Bright streak, Dark streak, Metal region and Background area that appeared on CT were confirmed, and the change of each SUV (standardized uptake value) was analyzed. Also, in 15 patients who underwent total hip arthroplasty, each MAR algorithm and Without MAR algorithm and non attenuation correction was evaluated. Results : In PET image Without MAR algorithm, SUV of Bright streak region was $0.98{\pm}0.48$ g/ml; Dark streak region was $0.88{\pm}0.02$ g/ml; Metal region was $0.24{\pm}0.16$ g/ml, Background area was $0.91{\pm}0.18$ g/ml. In SUV of PET image with MAR algorithm, Bright streak region was $0.88{\pm}0.49$ g/ml, Dark streak region was $0.63{\pm}0.21$ g/ml, Metal region was $0.06{\pm}0.07$ g/ml, Background was $0.90{\pm}0.02$ g/ml. SUV generally decreased when applying MAR algorithm. In PET image Without MAR algorithm, SUVs of Bright region were higher than those measured in the Background, and it was false positive uptake. But, in PET image with MAR algorithm, SUVs of Bright region were similar to the Background, and false positive uptake disappeared. Conclusion : MAR algorithm could reduce an increase of $^{18}F$-FDG uptake due to attenuation correction in the hip surrounding tissue. However, decrease of SUV in Dark streak region should be considered in the future. Therefore, this study propose that the diagnostic accuracy can be improved in genitourinary diseases adjacent to metallic hip prosthesis, if provided PET images with and Without MAR algorithm, and non attenuation correction images at the same time.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2008.05a
• /
• pp.1976-1980
• /
• 2008

본 연구에서는 만경강 점착성 퇴적물의 표본채취 및 실내실험을 통하여 만경강 점착성 퇴적물의 침강특성이 정량적으로 산정되었으며, 과거 타 지역 퇴적물의 침강특성 산정 결과들과 비교 검토 되었다. 또한 퇴적물의 기본 물리 화학적 특성과 침강특성간의 상관관계 해석을 통하여, 만경강 점착성 퇴적물의 침강특성결과의 타당성이 간접적으로 검토되었다. 침강실험 결과, 부유사 농도가 증가함에 따라 침강속도가 증가하는 응집침강 영역과, 역으로 침강속도가 감소하는 간섭침강 영역이 명확히 나타났으며, 만경강 퇴적물의 부유사농도값이 0.1$W_s$<1 mm/sec의 침강속도 값을 갖는 것으로 확인되었다. 또한 산정된 침강속도는 과거 타 지역과 비교하여 정량적으로 상당한 차이를 보였다.

• Journal of the Korean Society for Library and Information Science
• /
• v.39 no.1
• /
• pp.241-263
• /
• 2005

The purpose of this study is to investigate the description elements for the effective management of the special format archives. In this study, the existing description rules for data elements including that of both general archives and special format archives were analyzed in order to extract the core description elements for special format archives. The result of the study proposed overall description elements in accordance of the basic formats of ISAD(G).

• Computational Structural Engineering
• /
• v.10 no.3
• /
• pp.217-223
• /
• 1997

This paper deals with the basic concepts of sensitivity analysis in a time domain for the transient response of a lumped mass system. Sensitivity analysis methods in thme domain for determining the effects of parameter changes on the response of a dynamic system by external excitation are presented. The parametric sensitivity of a lumped mass system in time domain can be investigated using different types of sensitivity functions, including first order standard and percentage sensitivity functions. These sensitivity functions are determined as a function of partial derivatives of system variables taken with respect to system parameters. In addition, we compared the results of the analytical method by direct method and those of numerical methods.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.49 no.7
• /
• pp.601-608
• /
• 2021

Launch Acceptability Region of Air-to-Surface Guided Bomb is defined as the set of release points in order to reach a target successfully. LAR is consisted of fixed target area and moving target area whether the target maneuvers or not. In this paper, the computational algorithm of LAR is studied for fixed and moving target. First, multi-simulations are performed varying platform, target, and atmospheric environment to attain Min/Max DB. Second, the LAR functions are obtained using regression and classification algorithm. For operational suitability, the algorithm for display of LAR is studied to obtain appropriate LAR. In this progress, the results of LAR are suitable to apply air-to-ground guided bomb for moving target.

• Proceedings of the Korean Nuclear Society Conference
• /
• 1995.05b
• /
• pp.709-714
• /
• 1995

영광 3, 4호기에 사용되고 있는 원전 압력용기용 SA-508 IH 강의 미세구조 및 상온 피로균 열성장 특성을 고찰하였다. 본 강재의 미세구조, 석출물 분포 및 형상을 투과전자현미경을 통하여 관찰하였으며 임계영역에서의 거동 및 균열닫힘에 주목하여 피로균열성장 특성을 연구하였다. 다양한 형태의 (Fe, MR)$_3$C 세멘타이트 및 Mo$_2$C 석출물이 입계, 래스경계면 및 입내에 분포되고 있음을 확인하였다. Paris 영역에서의 피로균열성장 속도는 ASME 기준선과 유사하였으며, 임계 영역에서는 일반적인 저합금강의 경우보다 다소 낮게 나타났다. 파면조사 결과 입내 연성파괴현상이 전 $\Delta$K 영역에서 나타나고 있으며, $\Delta$K$_{th}$ 부터 $\Delta$K가 12 Mpa√m 영역에서는 입계파괴 및 입내 평활면이 관찰되었다.

• Journal of the Korean Society of Radiology
• /
• v.17 no.7
• /
• pp.1115-1122
• /
• 2023

This study aimed to present reasonable reception bandwidth application standards for the purpose of suppressing metal objects during MRI examinations. For this purpose, T2 contrast images were acquired using high-speed spin echo technology on a phantom made of screws for spinal surgery, and metal objects were detected. In addition, images were obtained by increasing the reception bandwidth from 100 Hz/PX to 800 Hz/PX by 100 Hz/PX. The metal artifacts were determined as the sum of the areas of the signal attenuation area and the signal accumulation area. In addition, Pearson correlation analysis was performed to analyze the pattern of metal artifacts according to imaging variables. As a result, the signal accumulation area did not change significantly as the reception bandwidth increased (p>0.05), but the signal loss area and the area of metal artifacts decreased as the reception bandwidth increased (p<0.05). Interestingly, the area of metal objects decreased to a maximum in the section where the reception bandwidth was increased from 100 Hz/PX to 200 Hz/PX, consistent with the section where the echo spacing was reduced to a maximum due to the increase in reception bandwidth. In addition, the correlation analysis results also showed that the eco spacing was more related to the signal attenuation area and the area of metal objects than to the reception bandwidth. Therefore, if the reception bandwidth is increased for the purpose of reducing metal objects, it is reasonable to set it based on a value that minimizes the echo spacing in consideration of image quality factors.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.22 no.1
• /
• pp.10-17
• /
• 2010

The interaction of oblique incident waves with a porous dual semi-cylindrical structure is investigated under the assumption of linear potential theory. The porous dual semi-cylindrical structure consists of two concentric bottom-mounted cylindrical structures that are porous in front half and transparent in back half. By changing porosity, gap, and wave characteristics(wave frequencies, incidence angle), the wave blocking performance as well as the wave loads and the wave run-up are obtained. As a convenient measure of overall wave blocking performance, the root mean square(R.M.S.) of the wave elevation in a sheltered region is used. It is found that the porous semi-cylindrical structure may significantly reduce the wave response in a sheltered region and the wave forces decrease largely compared to the impermeable structure. The dual structure is more effective in reducing the wave response in a sheltered region than the mono type in the region of high frequencies.

• 한국상하수도협회지
• /
• s.14
• /
• pp.2-5
• /
• 2006

환경부는 지난 2월 14일, 2015년까지 우리나라를 글로벌 물산업 강국으로 육성하기 위한 종합 추진계획을 국무회의에 보고하고, 물산업 육성을 정부 정책으로 확정하였다. 아직까지 물산업의 범위가 명확히 정립되었다고 보기는 어렵지만, 물을 최종적인 재화로 제공하거나 이를 위해 직접적으로 필요한 중간재 혹은 용역을 제공하는 산업을 ‘물산업’으로 보고자 한다. 일반적으로는 상수도, 하수도, 폐수, 생수, 정수기, 해수담수화 등을 주요 영역으로 보면 될 것이다.