• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.5
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• pp.60-69
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• 2013

An optimum configuration of the hybrid/dual swirl jet combustor for a micro-gas turbine was investigated experimentally. Location of pilot nozzle, angle and direction of swirler vane were varied systematically as main parameters under the conditions of constant thermal load. The results showed that the variation in locations of inner fuel nozzle and pilot burner resulted in significant change in flame shape and swirl intensity due to the changes in recirculating flow pattern and minimum flow area near burner exit, in particular, with the significant reduction of CO emission near lean-flammability limit. In addition, it was observed that the co-swirl configuration produced less CO and NOx emissions compared to the counter-swirl configuration.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.5
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• pp.325-331
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• 2016

This research developed a flood fragility curve of bridges considering the debris impacts. Damage and failures of civil infrastructure due to natural disasters can cause casualties as well as social and economic losses. Fragility analysis is an effective tool to help better understand the vulnerability of a structure to possible extreme events, such as earthquakes and floods. In particular, flood-induced failures of bridges are relatively common in Korea, because of the mountainous regions and summer concentrated rainfall. The main failure reasons during floods are reported to be debris impact and scour; however, research regarding debris impacts is considered challenging due to various uncertainties that affect the failure probability. This study introduces a fragility analysis methodology for evaluating the structural vulnerability due to debris impacts during floods. The proposed method describes how the essential components in fragility analysis are considered, including limit-state function, intensity measure of the debris impact, and finite element model. A numerical example of the proposed fragility analysis is presented using a bridge pier system under a debris impact.

• Atmosphere
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• v.32 no.4
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• pp.353-365
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• 2022

This paper evaluates precipitation forecast skill of Global/Regional Integrated Model system (GRIMs) over South Korea in a boreal winter from December 2013 to February 2014. Three types of precipitation are classified based on development mechanism: 1) convection type (C type), 2) low pressure type (L type), and 3) orographic type (O type), in which their frequencies are 44.4%, 25.0%, and 30.6%, respectively. It appears that the model significantly overestimates precipitation occurrence (0.1 mm d^-1) for all types of winter precipitation. Objective measured skill scores of GRIMs are comparably high for L type and O type. Except for precipitation occurrence, the model shows high predictability for L type precipitation with the most unbiased prediction. It is noted that Equitable Threat Score (ETS) is inappropriate for measuring rare events due to its high dependency on the sample size, as in the case of Critical Success Index as well. The Symmetric Extreme Dependency Score (SEDS) demonstrates less sensitivity on the number of samples. Thus, SEDS is used for the evaluation of prediction skill to supplement the limit of ETS. The evaluation via SEDS shows that the prediction skill score for L type is the highest in the range of 5.0, 10.0 mm d^-1 and the score for O type is the highest in the range of 1.0, 20.0 mm d^-1. C type has the lowest scores in overall range. The difference in precipitation forecast skill by precipitation type can be explained by the spatial distribution and intensity of precipitation in each representative case.

• Computers and Concrete
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• v.26 no.6
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• pp.483-495
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• 2020

Dams are vital infrastructures that are expected to maintain their stability during seismic excitations. Accordingly, cemented material dams are an emerging type, which are being increasingly used around the world owing to benefiting from advantages of both earth-fill and concrete gravity dams, which should be designed safely when subjected to strong ground motion. In the present paper, the seismic performance of a cemented sand and gravel (CSG) dam is assessed using incremental dynamic analysis (IDA) method by accounting for two failure modes of tension cracking and base joint sliding considering the dam-reservoir-foundation interactions. To take the seismic uncertainties into account, the dam is analyzed under a suite of ground motion records and then, the effect of friction angle for base sliding as well as deformability of the foundation are investigated on the response of dam. To carry out the analyses, the Cindere dam in Turkey is selected as a case study, and various limit states corresponding to seismic performance levels of the dam are determined aiming to estimate the seismic fragilities. Based on the results, sliding of the Cindere dam could be serious under the maximum credible earthquake (MCE). Besides, dam faces are mostly to be cracked under such level of intensity. Moreover, the results indicate that as friction angle increases, probability of sliding between dam and foundation is reduced whereas, increases tensile cracking. Lastly, it is observed that foundation stiffening increases the probability of dam sliding but, reduces the tensile damage in the dam body.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.12
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• pp.1013-1020
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• 2020

Spark-induced breakdown spectroscopy (SIBS) utilizes an electric spark to induce a strong plasma for collecting atomic emissions. This study analyses the potential for usinga compact SIBS instead of conventional laser-induced breakdown spectroscopy (LIBS) in discriminating rocks and soils for planetary missions. Targeting bulky solids using SIBS has not been successful in the past, and therefore a series of optimizations of electrode positioning and electrode materials were performed in this work. The limit of detection (LOD) was enhanced up to four times compared to when LIBS was used, showing a change from 78 to 20 ppm from LIBS to SIBS. Because of the higher energy of plasma generated, the signal intensity by SIBS was higher than LIBS in three orders of magnitude with the same spectrometer setup. Changing the electrode material and locating the optimum position of the electrodes were considered for optimizing the current SIBS setup being tested for samples of planetary origin.

• Nuclear Engineering and Technology
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• v.54 no.9
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• pp.3361-3379
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• 2022

A nuclear power plant (NPP) piping is designed against low-frequency earthquakes. However, earthquakes that can occur at NPP sites in the eastern part of the United States, northern Europe, and Korea are high-frequency earthquakes. Therefore, this study conducts bi-directional shaking table tests on actual-scale NPP piping and studies the response characteristics of low- and high-frequency earthquake motions. Such response characteristics are analyzed by comparing several responses that occur in the piping. Also, based on the test results, a piping numerical analysis model is developed and validated. The piping seismic performance under high-frequency earthquakes is derived. Consequently, the high-frequency excitation caused a large amplification in the measured peak acceleration responses compared to the low-frequency excitation. Conversely, concerning relative displacements, strains, and normal stresses, low-frequency excitation responses were larger than high-frequency excitation responses. Main peak relative displacements and peak normal stresses were 60%-69% and 24%-49% smaller in the high-frequency earthquake response than the low-frequency earthquake response. This phenomenon was noticeable when the earthquake motion intensity was large. The piping numerical model simulated the main natural frequencies and relative displacement responses well. Finally, for the stress limit state, the seismic performance for high-frequency earthquakes was about 2.7 times greater than for low-frequency earthquakes.

• Journal of Korea Entertainment Industry Association
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• v.13 no.4
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• pp.119-129
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• 2019

Traditional speech training in acting education focused on the technical aspects of expressing the lines such as finding long/short syllables in the word, exercising articulation of consonants and vowels, and practicing diction etc. There was a limit on this education to transform written words to vivid verbal words. The lines become live when the actor sees the concrete mental images hidden in the words while speaking the lines. I will bring the knowledge of cognitive brain science and NLP(Neural Linguistic Programming) to investigate what mental images are and why mental images are fundamental elements of thought and emotion. In addition to that, I will examine how the muscles of the body react in the process of visualization of delicate mental images (subordinate form) and how to use the responsive muscles to express speaking materials such as intensity, pause, pitch, intonation etc. Conclusion, I will enumerate the obstacles encountered by actors in the course of practicing mental images, and suggest 'activation of breathing' as a thesis of the follow-up paper to eliminate those obstacles. This process, I intend to make mental images to be the concrete and practical information that can be applied to speak the dialogue in the play.

• Korean Journal of Environmental Biology
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• v.40 no.3
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• pp.275-280
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• 2022

Suspended solids play an important role in the growth and survival of aquatic organisms. The marine zooplankton species tested in this study were Tigriopus west (Copepoda) and Haustorioides koreanus (Amphipoda) sampled from the intertidal zone, including Artemia nauplii(Branchiopoda) hatched from cysts. The study design included six concentrations (0, 50, 100, 250, 500, and 1,000mg L^-1) of the suspended test particles assayed in triplicate. Experimental cultures in 500 mL-round polycarbonate bottles were subsampled after 96 h to count dead zooplankton. The culture bottles were agitated at 4 RPM on a rotating wheel at 23℃ and 30 PSU. The survival rates of Artemia nauplii and T. west were not affected by suspended solid concentrations higher than 50.0 mg L^-1, whereas the survival rate of H. koreanus decreased with increasing concentrations (p<0.05). In conclusion, H. koreanus and T. west, which were continuously exposed to suspended solid concentrations higher than 50.0 mg L^-1, were affected by low-intensity ecological stress. However, in the case of H. koreanus, a concentration of 50.0 mg L^-1 may be considered to be the limit of tolerance to suspended solids, suggesting that the number of individuals who eventually die will increase if continuously exposed.

• Earthquakes and Structures
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• v.22 no.5
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• pp.503-515
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• 2022

This paper presents the development of seismic fragility curves for a precast reinforced concrete bridge instrumented with a structural health monitoring (SHM) system. The bridge is located near an active seismic fault in the Dominican Republic (DR) and provides the only access to several local communities in the aftermath of a potential damaging earthquake; moreover, the sample bridge was designed with outdated building codes and uses structural detailing not adequate for structures in seismic regions. The bridge was instrumented with an SHM system to extract information about its state of structural integrity and estimate its seismic performance. The data obtained from the SHM system is integrated with structural models to develop a set of fragility curves to be used as a quantitative measure of the expected damage; the fragility curves provide an estimate of the probability that the structure will exceed different damage limit states as a function of an earthquake intensity measure. To obtain the fragility curves a digital twin of the bridge is developed combining a computational finite element model and the information extracted from the SHM system. The digital twin is used as a response prediction tool that minimizes modeling uncertainty, significantly improving the predicting capability of the model and the accuracy of the fragility curves. The digital twin was used to perform a nonlinear incremental dynamic analysis (IDA) with selected ground motions that are consistent with the seismic fault and site characteristics. The fragility curves show that for the maximum expected acceleration (with a 2% probability of exceedance in 50 years) the structure has a 62% probability of undergoing extensive damage. This is the first study presenting fragility curves for civil infrastructure in the DR and the proposed methodology can be extended to other structures to support disaster mitigation and post-disaster decision-making strategies.

• Analytical Science and Technology
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• v.21 no.1
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• pp.20-24
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• 2008

A chemiluminescence method has been developed to determine vitamin $P_1$ in aqueous solution which is based on the enhancement of the intensity of lucigenin using lucigenin-$H_2O_2$ as chemiluminogenic system. The effects of experimental parameters such as concentrations of lucigenin, pH and concentrations of $H_2O_2$ were studied. The present method allows the determination of vitamin $P_1$ over the range $7.5{\times}10^{-6}{\sim}5.0{\times}10^{-4}mol/L$. The detection limit was $5.7{\times}10^{-7}mol/L$. The relative standard deviation was 0.75 % for 10 determinations of $7.5{\times}10^{-5}mol/L$ vitamin $P_1$. The correlation coefficient of the working curve was 0.9984 (S/N=3).