• Nuclear Engineering and Technology
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• 제25권4호
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• pp.515-528
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• 1993

피동형 원자력 발전소의 설계 특성상 소형 냉각재상실사고시 노심손상이 발생되지 않기 위해서는 자동감압계통의 성공적인 작동이 필수적으로 요구된다. 그러나 기수행된 연구들에서 자동감압계통의 비신뢰도가 소형 냉각재상실사고로부터 기인되는 노심손상빈도에 상당 부분을 기여하고 있음을 알 수 있다. 본 연구에서는 자동감압계통의 불능도에 기여하는 계통의 취약점을 파악함과 함께 계통의 신뢰도를 증대시키기 위한 설계개선 방안들을 제시하고 각 방안에 대한 신뢰도 분석과 함께 열수력학적 타당성 여부를 보기 위한 소형 냉각재상실사고 모의가 RELAP5/MOD3 전산 코드를 사용하여 수행되었다. 신뢰도 분석은 고장수목 기법을 이용하여 수행되어졌다.

• Nuclear Engineering and Technology
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• 제52권1호
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• pp.87-100
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• 2020

Performance shaping factors (PSFs) in a human reliability analysis (HRA) are one that may influence human performance in a task. Most currently applicable HRA methods for nuclear power plants (NPPs) use PSFs to highlight human error contributors and to adjust basic human error probabilities (HEPs) that assume nominal conditions of NPPs. Thus far, the effects of PSFs have been treated independently. However, many studies in the fields of psychology and human factors revealed that there may be relationships between PSFs. Therefore, the inter-relationships between PSFs need to be studied to better reflect their effects on operator errors. This study investigates these inter-relationships using two data sources and also suggests a context-based approach to treat the inter-relationships between PSFs. Correlation and factor analyses are performed to investigate the relationship between PSFs. The data sources are event reports of unexpected reactor trips in Korea and an experiment conducted in a simulator featuring a digital control room. Thereafter, context-based approaches based on the result of factor analysis are suggested and the feasibility of the grouped PSFs being treated as a new factor to estimate HEPs is examined using the experimental data.

• Structural Engineering and Mechanics
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• 제50권5호
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• pp.653-664
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• 2014

Wind fragility analysis provides a quantitative instrument for delineating the safety performance of civil structures under hazardous wind loading conditions such as cyclones and tornados. It has attracted and would be expected to continue to attract intensive research spotlight particularly in the nowadays worldwide context of adapting to the changing climate. One of the challenges encumbering efficacious assessment of the safety performance of existing civil structures is the possible incompleteness of the structural appraisal data. Addressing the issue of the data missingness, the study presented in this paper forms a first attempt to investigate the feasibility of using the expectation-maximization (EM) algorithm and Bayesian techniques to predict the wind fragilities of existing civil structures. Numerical examples of typical linear or hysteretic shear frames are introduced with the wind loads derived from a widely used power spectral density function. Specifically, the application of the maximum a posteriori estimates of the distribution parameters for the story stiffness is examined, and a surrogate model is developed and applied to facilitate the nonlinear response computation when studying the fragilities of the hysteretic shear frame involved.

• 한국태양에너지학회 논문집
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• 제31권4호
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• pp.66-71
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• 2011

This study focused on the application of the Passive Solar Chamber System (PSCS) as proposed by a previous study. The seasonal performance and sizing method for the system were investigated for a feasibility of the PSCS in Korean climate. For seasonal performance, heat and ventilation performances of the PSCS were analyzed for the months of January and August. This study proposed a simple configuration method in which the designer can decide on the system size at the preliminary design stage by using system efficiency, overall heat transfer coefficient transmission, monthly solar radiation, highest and lowest temperatures. During weeks that require heating, the system showed to acquire a daily average heat amount of $860.28Wh/m^2$ day. For cooling periods, the system was computed to supply a daily average natural ventilation of $1,360.2m^3/day$ to the room. Moreover, proposed sizing method and the overall computation results showed a 6.04~7.24% error of assessment.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2009년도 춘계학술대회 논문집 특별세미나,특별/일반세션
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• pp.641-646
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• 2009

Concrete tracks are superior to ballast tracks in the aspect of durability, maintenance and safety. However, deteriorated stiffness of railroad bed and settlement of soft ground induced by trapped or seepage water lead to problems in safety of train operation. In this research, characteristic stiffness of concrete tracks, which is determined from FRACTAL (Flexural-Rigidity Assessment of Concrete Tracks by Antisymmetric Lamb Waves) technique, was employed as an index of track displacement. The characteristic stiffness is defined using Poisson's ratio, moment of inertia and stiffness ratio of subgrade to slab. To verify validity and reliability of the proposed characteristic stiffness, experimental and theoretical researches were performed. Feasibility of the characteristic stiffness based on FRACTAL technique was proved at a real concrete track for Korean high-speed trains. Validity of the FRACTAL technique was also verified by comparing the results of impulse-response tests performed at the same measurement array and the results of SASW tests and DC resistivity survey performed at a shoulder nearby the track.

• 대한수의학회지
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• 제59권3호
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• pp.119-122
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• 2019

The goals of this study were, first, to evaluate the feasibility of inducing gastric perforation with 99% alcohol injection after electrocautery (EA-method), and, second, to observe "enhanced peritoneal stripe sign (EPSS)" and other lesions upon induction of gastric perforation. Six clinically normal beagle dogs were prepared for gastric perforation using endoscopy. After gastric perforation, EPSS and other lesions on ultrasonography were observed eventually (at 0 h, 3 h, day 1, day 2, day 3, day 4, day 5, and day 6). We graded the EPSS depending on its width and number. EPSS was observed until day 4 of the examination in all the 6 dogs. The grades of EPSS were the highest at 3 h and declined gradually. Peritoneal effusion was observed in all dogs at 3 h and on day 1. Regional bright mesenteric fat was confirmed in all dogs on days 3 and 4. In conclusion, gastric perforation can be induced by EA-method. EPSS and peritoneal effusion appear at a very early stage, and regional bright mesenteric fat was identified on days 3 and 4 in almost all dogs with gastric perforation.

• 한국자원식물학회지
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• 제32권3호
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• pp.244-253
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• 2019

In crop breeding program, information about genetic dissimilarity on breeding resources is very important to corroborate genealogical relationships and to predict the most heterozygotic hybrid combinations and inbred breeding. This study aimed to evaluate the genetic variation in Kenyan sunflower breeding lines based on simple sequence repeat (SSR). A total of 83 alleles were detected at 32 SSR loci. The allele number per locus ranged from 2 to 7 with an average of 2.7 alleles per locus detected from the 24 sunflower accessions and the average value of polymorphic information contents (PIC) were 0.384. A cluster analysis based on the genetic similarity coefficients was conducted and the 24 sunflower breeding resources were classified into three groups. The principal coordinates (PCoA) revealed 34% and 13.38% respectively, and 47.38% of total variation. It was found that the genetic diversity within the Kenyan sunflower breeding resources was narrower than that in other sunflower germplasm resources, suggesting the importance and feasibility of introducing elite genotypes from different origins for selection of breeding lines with broader genetic base in Kenyan sunflower breeding program.

• Nuclear Engineering and Technology
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• 제51권5호
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• pp.1333-1344
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• 2019

An integrated approach of model simplification for high burnup spent nuclear fuel is proposed based on material calibration using optimization. The spent fuel rods are simplified into a beam with a homogenous isotropic material. The proposed approach of model simplification is applied to fuel rods with two kinds of interfacial configurations between the fuel pellets and cladding. The differences among the generated models and the effects of interfacial bonding efficiency are discussed. The strategy of model simplification adopted in this work is to force the simplified beam model of spent fuel rods to possess the same compliance and failure characteristics under critical loads as those that result in the failure of detailed fuel rod models. It is envisioned that the simplified model would enable the assessment of fuel rod failure through an assembly-level analysis, without resorting to a refined model for an individual fuel rod. The effective material properties of the simplified beam model were successfully identified using the integrated optimization process. The feasibility of using the developed simplified beam models in dynamic impact simulations for a horizontal drop condition is examined, and discussions are provided.

• Current Optics and Photonics
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• 제3권1호
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• pp.54-65
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• 2019

To develop a biomarker predicting tumor treatment efficacy is helpful to reduce time, medical expenditure, and efforts in oncology therapy. In clinics, microvessel density using immunohistochemistry has been proposed as an indicator that correlates with both tumor size and metastasis of cancer. In the preclinical study, we hypothesized that vascular morphometrics using optical coherence tomography angiography (OCTA) could be potential indicators to estimate the treatment efficacy of breast cancer. To verify this hypothesis, a 13762-MAT-B-III rat breast tumor was grown in a dorsal skinfold window chamber which was applied to a nude mouse, and the change in vascular morphology was longitudinally monitored during tumor growth and metronomic cyclophosphamide treatment. Based on the daily OCTA maximum intensity projection map, multiple vessel parameters (vessel skeleton density, vessel diameter index, fractal dimension, and lacunarity) were compared with the tumor size in no tumor, treated tumor, and untreated tumor cases. Although each case has only one animal, we found that the vessel skeleton density (VSD), vessel diameter index and fractal dimension (FD) tended to be positively correlated with tumor size while lacunarity showed a partially negative correlation. Moreover, we observed that the changes in the VSD and FD are prior to the morphological change of the tumor. This feasibility study would be helpful in evaluating the tumor vascular response to treatment in preclinical settings.

• 한국지하수토양환경학회지:지하수토양환경
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• 제25권4호
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• pp.87-97
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• 2020

In this study, the applicability of the geostatistical evolution strategy as an inverse analysis method of estimating hydraulic properties of small-scale basin was tested. The geostatistical evolution strategy is a type of data assimilation method that can effectively estimate aquifer hydraulic conductivity by combining a global optimization model of the evolution strategy and a local optimization model of the ensemble Kalman filtering. In the applicability test, the geometry, hydraulic boundary conditions, and the distribution of groundwater monitoring wells of Hanlim-Eup were employed. On the other hand, a synthetic hydraulic conductivity distribution was generated and used as the reference property for ease of estimation quality assessment. In the estimations, two different cases were tested where, in Case I, both groundwater levels and hydraulic conductivity measurements were assumed to be available, and only the groundwater levels were available, in Case II. In both cases, the reference and estimated hydraulic conductivity fields were found to show reasonable similarity, even though the prior information for estimation was not accurate. The ability to estimate hydraulic conductivity without accurate prior information suggests that this method can be used effectively to estimate mathematical properties in real-world cases, many of which little prior information is available for the aquifer conditions.