• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.2
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• pp.263-272
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• 2019

This study demonstrates the applicability of the FLO-2D for the influence analysis of the debris flow on expressway. To do this, the behavior of debris flow on the expressway was reproduced by applying the FLO-2D to actual generated debris flow. The study area is a part of the Deokyusan Service Area on the Daejon-Jinju Expressway, where traffic was blocked for 24 hours due to the debris flow in August 2005. Geographical analysis with GIS, hydrological analysis with HEC-HMS, and estimation of the amount of debris flow were carried out using field survey and soil property test data. Then, the optimum parameter combination of FLO-2D was selected through the parameter sensitivity analysis, and the behavior analysis of debris flow on expressway was applied. The comparison of the predictions with the observations shows the availability of FLO-2D for the behavior analysis of debris flow on the expressway.

• Nuclear Engineering and Technology
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• v.53 no.10
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• pp.3236-3246
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• 2021

Lessons learned from the Fukushima Daiichi nuclear power plant accident directed that multiple failures should be considered more seriously rather than single failure in the licensing bases and safety cases because attempts to take accident management measures could be unsuccessful under the high radiation environment aggravated by multiple failures, such as complete loss of electric power, uncontrollable loss of coolant inventory, failure of essential safety function recovery. In the case of the complete loss of electric power called station blackout (SBO), if there is no mitigation action for recovering safety functions, the reactor core would be overheated, and severe fuel damage could be anticipated due to the failure of the active heat sink. In such a transient condition at CANDU-6 plants, the seal failure of the primary heat transport (PHT) pumps can facilitate a consequent increase in the fuel sheath temperature and eventually lead to degradation of the fuel integrity. Therefore, it is necessary to specify the regulatory guidelines for multiple failures on a licensing basis so that licensees should prepare the accident management measures to prevent or mitigate accident conditions. In order to explore the efficiency of implementing accident management strategies for CANDU-6 plants, this study proposed a realistic accident analysis approach on the SBO transient with multiple-failure sequences such as seal failure of PHT pumps without operator's recovery actions. In this regard, a comparative study for two PHT pump seal failure modes with and without coolant seal leakage was conducted using a best-estimate code to precisely investigate the behaviors of thermal-hydraulic parameters during transient conditions. Moreover, a sensitivity analysis for different PHT pump seal leakage rates was also carried out to examine the effect of leakage rate on the system responses. This study is expected to provide the technical bases to the accident management strategy for unmitigated transient conditions with multiple failures.

• Journal of Microbiology and Biotechnology
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• v.29 no.10
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• pp.1522-1542
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• 2019

To adapt to environmental changes and to maintain cellular homeostasis, microorganisms adjust the intracellular concentrations of biochemical compounds, including metal ions; these are essential for the catalytic function of many enzymes in cells, but excessive amounts of essential metals and heavy metals cause cellular damage. Metal-responsive transcriptional regulators play pivotal roles in metal uptake, pumping out, sequestration, and oxidation or reduction to a less toxic status via regulating the expression of the detoxification-related genes. The sensory and regulatory functions of the metalloregulators have made them as attractive biological parts for synthetic biology, and the exceptional sensitivity and selectivity of metalloregulators toward metal ions have been used in heavy metal biosensors to cope with prevalent heavy metal contamination. Due to their importance, substantial efforts have been made to characterize heavy metal-responsive transcriptional regulators and to develop heavy metal-sensing biosensors. In this review, we summarize the biochemical data for the two major metalloregulator families, SmtB/ArsR and MerR, to describe their metal-binding sites, specific chelating chemistry, and conformational changes. Based on our understanding of the regulatory mechanisms, previously developed metal biosensors are examined to point out their limitations, such as high background noise and a lack of well-characterized biological parts. We discuss several strategies to improve the functionality of the metal biosensors, such as reducing the background noise and amplifying the output signal. From the perspective of making heavy metal biosensors, we suggest that the characterization of novel metalloregulators and the fabrication of exquisitely designed genetic circuits will be required.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.12
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• pp.1535-1541
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• 2019

To carry out safe and rapid decontamination in radiological accident areas, acquisition of various information on radiation sources is needed. In particular, to figure out the location and distribution of radiation sources is essential for rapid follow-up and removal of contaminants as well as minimizing worker damage. The radiation distribution detection device is used to obtain the position and distribution information of the radiation source. In the case of a radiation distribution detection device, a detection sensor unit is generally composed of a single sensor, and the detection range is limited due to the physical characteristics of the single sensor. We applied a calibration detector for controlling the detection sensitivity of a single sensor for radiation detection and improved the limited detection range of radiation dose rate. Also, gamma irradiation test confirmed the improvement of radiation distribution detection range.

• Current Optics and Photonics
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• v.6 no.2
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• pp.143-150
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• 2022

Anti-resonant hollow-core photonic crystal fiber (AR-HCF) has unique advantages, such as low nonlinearity and high damage threshold, which make it a promising candidate for high-power laser delivery at distances of tens of meters. However, due to the special structure, optical properties such as mode-field profile and bending loss of hollow-core fibers are different from those of solid-core fibers. These differences have limited the widespread use of AR-HCF in practice. In this paper we conduct numerical analysis of AR-HCFs with different structural parameters, to analyze their influences on an AR-HCF's optical properties. The simulation results show that with a 23-㎛ air-core diameter, the fundamental mode profile of an AR-HCF can well match that of the widely used Nufern's 20/400 fiber, for nearly-single-mode power delivery applications. Moreover, with the ratio of cladding capillary diameter to air-core diameter ranging from 0.6 to 0.7, the AR-HCF shows excellent optical characteristics, including low bending sensitivity while maintaining single-mode transmission at the same time. We believe these results lay the foundation for the application of AR-HCFs in the power delivery of high power fiber laser systems.

• Smart Structures and Systems
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• v.29 no.3
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• pp.445-455
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• 2022

Steel anchor bolts are installed in concrete using a variety of methods. One of the most common methods of anchor bolt installation is using epoxy resin as an infill material injected into the drilled hole to act as a bonding material between the steel bolt and the surrounding concrete. Typical design standards assume uniform stress distribution along the length of the anchor bolt accompanied with single crack leading to pull-out failure. Experimental evidence has shown that the steel anchor bolts fail owing to the multiple failure patterns, hence these design assumptions are not realistic. In this regard, the presented research work details the analytical model that takes into consideration multiple micro cracks in the infill material induced via impact loading. The impact loading from the Schmidt hammer is used to evaluate the bond condition bond condition of anchor bolt and the epoxy material. The added advantage of the presented analytical model is that it is able to take into account the various type of end conditions of the anchor bolts such as bent or U-shaped anchors. Through sensitivity analysis the optimum stiffness and shear strength properties of the epoxy infill material is achieved, which have shown to achieve lower displacement coupled with reduced damage to the surrounding concrete. The accuracy of the presented model is confirmed by comparing the simulated deformational responses with the experimental evidence. From the comparison it was found that the model was successful in simulating the experimental results. The proposed model can be adopted by professionals interested in predicting and controlling the deformational response of anchor bolts.

• Restorative Dentistry and Endodontics
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• v.48 no.2
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• pp.12.1-12.11
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• 2023

Objectives: The present study evaluated the pulp response of human mandibular incisors subjected to in-office dental bleaching using gels with medium or high concentrations of hydrogen peroxide (HP). Materials and Methods: The following groups were compared: 35% HP (HP35; n = 5) or 20% HP (HP20; n = 4). In the control group (CONT; n = 2), no dental bleaching was performed. The color change (CC) was registered at baseline and after 2 days using the Vita Classical shade guide. Tooth sensitivity (TS) was also recorded for 2 days post-bleaching. The teeth were extracted 2 days after the clinical procedure and subjected to histological analysis. The CC and overall scores for histological evaluation were evaluated by the Kruskal-Wallis and Mann-Whitney tests. The percentage of patients with TS was evaluated by the Fisher exact test (α = 0.05). Results: The CC and TS of the HP35 group were significantly higher than those of the CONT group (p < 0.05) and the HP20 group showed an intermediate response, without significant differences from either the HP35 or CONT group (p > 0.05). In both experimental groups, the coronal pulp tissue exhibited partial necrosis associated with tertiary dentin deposition. Overall, the subjacent pulp tissue exhibited a mild inflammatory response. Conclusions: In-office bleaching therapies using bleaching gels with 20% or 35% HP caused similar pulp damage to the mandibular incisors, characterized by partial necrosis, tertiary dentin deposition, and mild inflammation.

• Nuclear Engineering and Technology
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• v.55 no.12
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• pp.4367-4381
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• 2023

Nuclear power plants are increasingly being equipped with digital I&C systems. Although some probabilistic safety assessment (PSA) models for the digital I&C of nuclear power plants have been constructed, there is currently no specific internationally agreed guidance for their modeling. This paper presents an initiative by the OECD Nuclear Energy Agency called "Digital I&C PSA - Comparative application of DIGital I&C Modelling Approaches for PSA (DIGMAP)", which aimed to advance the field towards practical and defendable modeling principles. The task, carried out in 2017-2021, used a simplified description of a plant focusing on the digital I&C systems important to safety, for which the participating organizations independently developed their own PSA models. Through comparison of the PSA models, sensitivity analyses as well as observations throughout the whole activity, both qualitative and quantitative lessons were learned. These include insights on failure behavior of digital I&C systems, experience from models with different levels of abstraction, benefits from benchmarking as well as major contributors to the core damage frequency and those with minor effect. The study also highlighted the challenges with modeling of large common cause component groups and the difficulties associated with estimation of key software and common cause failure parameters.

• The Korean Journal of Nuclear Medicine
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• v.33 no.5
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• pp.439-451
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• 1999

Purpose : It is important to differentiate malignant from benign lesions of intraocular masses in choosing therapeutic plan. Biopsy of intraocular tumor is not recommended due to the risk of visual damage. We evaluated the usefulness of F-18-FDG PET imaging in diagnosing intraocular neoplasms. Materials and Methods: F-18-FDG PET scan was performed in 13 patients (15 lesions) suspected to have malignant intraocular tumors. There were 3 benign lesions (retinal detachment, choroidal effusion and hemorrhage) and 10 patients with 12 malignant lesions (3 melanomas, 7 retinoblastomas and 2 metastatic cancers). Regional eye images ($256{\times}256$ and $128{\times}128$ matrices) were obtained with or without attenuation correction. Whole body scan was also performed in eight patients (3 benign and 6 malignant lesions). Results: All malignant lesions were visualized while all benign lesions were not visualized. The mean peak standardized uptake value (SUV) of malignant lesions was $2.64{\pm}0.57g/ml$. There was no correlations between peak SUV and tumor volume. Two large malignant lesions ($> 1000 mm^3$) showed hot uptake on whole body scan. But two medium-sized lesions ($100-1000mm^3$) looked faint and two small ($<100mm^3$) lesions were not visualized. The images reconstructed with $256{\times}256$ matrix showed lesions more clearly than those with $128{\times}128$ matrix Conclusion: F-18-FDG PET scan is highly sensitivity in detecting malignant intraocular tumor For the evaluation of small-sized intraocular lesions, whole body scan is not appropriate because of low sensitivity. A regional scan with sufficient acquisition time is recommended for that purpose. Image reconstruction in matrix size of $256{\times}256$ produced clearer images than the ones in $128{\times}128$, but it does not affect the diagnostic sensitivity.

• Pediatric Infection and Vaccine
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• v.11 no.1
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• pp.90-100
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• 2004

Objective : Urinary tract infection(UTI) is a frequent serious bacterial infection in young infants. The clinical presentation may be non-specific and variable, depends on factors such as the age and the level of infection. Children with renal involvement may be at risk of permanent renal damage. Experimental studies have shown that renal lesions caused by acute febrile UTI may be prevented or diminished by early diagnosis and treatment. Therefore, it is important to find a method that can permit early diagnosis and identification of patients who are at risk for progressive renal damage. We designed this study to identify related factors in culture positive UTI infants, and also to identify related factors in culture negative UTI infants, who are febrile with pyuria, by using renal imaging and functional studies including renal sonography, DMSA scan and VCUG. Methods : Retrospectively analyzed the medical records of 136 febrile infants with pyuria over 2 years(from January 2001 to February 2003). Urine culture was done in all cases, and regardless of urine culture findings, renal imaging study was done if symptomatic UTI suspected. Results : Total 57 organisms were isolated in 53 patients. E. coli was the most common organism(86%), followed by E. faecalis, M. morganii, Proteus species, P. aeruginosa, S. aureus and E. fergusonii. Most of the isolates had high sensitivity on cephalosporins or amikacin and had low sensitivities on aminopenicillins. Abnormal acute phase DMSA scan or VCUG findings were seen in both urine culture positive and negative group without statistical differences(P>0.05). In febrile infants with pyuria, fever over 48 hours, older age and high CRP related to abnormal acute phase DMSA scan findings regardless urine culture results. Conclusion : 1st or 3rd generation cephalosporins with amikacin could be the first choice of treatment for UTI. Febrile infants with positive urine culture dose mean urinary tract infection but not acute pyelonephritis which directly relates to cortical damage which could be confirmed by acute phase DMSA scan. Even cases with negative urine culture findings, acute pyelonephritis should be concerned in febrile infants with pyuria who are older than 3 months of age, has fever over 48 hours or high CRP level. And in such cases, acute phase DMSA scan and VCUG should be evaluated for early treatment and long term prognosis.