• Journal of Microbiology and Biotechnology
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• 제19권1호
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• pp.51-54
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• 2009

Myxobacteria, Gram-negative soil bacteria, are a well-known producer of bioactive secondary metabolites. Therefore, this study presents a methodological approach for the high-throughput screening of secondary metabolites from 4 wild-type Myxococcus xanthus strains. First, electrospray ionization mass spectrometry (ESI-MS) was performed using extracellular crude extracts. As a result, 22 metabolite peaks were detected, and the metabolite profiling was then conducted using the m/z value, retention time, and MS/MS fragmentation pattern analyses. Among the peaks, one unknown compound peak was identified as analogous to the myxalamid A, B, and C series. An analysis of the tandem mass spectrometric fragmentation patterns and HR-MS identified myxalamid K as a new compound derived from M. xanthus. In conclusion, LC-MS/MS-based chemical screening of diverse secondary metabolites would appear to be an effective approach for discovering unknown microbial secondary metabolites.

• 한국농공학회지
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• 제31권1호
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• pp.106-116
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• 1989

This study aims at scrutinizing the long4errn consolidation characteristics of peats sampled at three different regions of Chonbuk province. The standard consolidation test and the single load consolidation test were performed about these samples and especially in case of the latter the loading period was 350 days. The main condusions analyzed are as follows. 1. Void ratio showed much greater values than that of the general clay and was decresed greatly according to the increase of the load. 2. In case of the relationship between the sefflement and the long-term settlement time the rate of settlement increment became great according to the increase of the load step and the long4erm settlement became linely proportional to the logarithm of time alter 10 minutes. 3. The linear correlation was showed between the long4erm settlement time and the void ratio and therefore equations by regression analysis were derived in order to estimate the long-term settlement The slope of straight lines increased according th the increase of the load step and secondary consolidation coefficients ranged from 0.04-0.27. 4. The secondary consolidation coeffcient became linealy proportional to the compression index and the ratio of Ca to CC was 0.072. 5. The period required in ending the primary consolidation was about 10 minutes and alter that the secondary consolidation coefficient appeared to have constant value. Therefore the secondary consolidation coefficient was judged to be used as a significant factor in estimating the long4erm settlement. 6. In case of the single load consolidation test the secondary consolidation coefficient showed the tendancy increasing according to the increase of the consolidation pressure.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 추계학술대회 논문집 전력기술부문
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• pp.36-38
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• 2004

In many countries, including Korea, in order to transmit the more electric power, the higher transmission line voltage is inevitable. So, a rapid reclosing scheme is important for UHV transmission lines to ensure requirements for high reliability of main lines. But, because of the high voltage and long span of UHV lines, the secondary arc current flows across the fault point even after the interruption of the fault current. i.e. A critical aspect of reclosing operation is the extinction of the secondary arc since it must extinguish before successful reclosure can occur. In Korea transmission lines, it is scheduled to energize 765kV single transmission line(79km) between Sin-Ansung S/S and Sin-Gapyeong S/S at June 2006. Therefore this paper analyzes characteristics of the secondary arc extinction on 765kV single transmission line using EMTP. Simulation results shows that the average value of the secondary arc is $30A_{rms}$ and the auto-extinction time of it is longer at closer point to Sin-Gapyeong S/S.

• Corrosion Science and Technology
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• 제18권4호
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• pp.138-147
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• 2019

Pipes and components of the secondary system in the pressurized water reactor (PWR) are mainly comprised of manufactured carbon steel. Thus, the generated carbon steel corrosion products are transported into the steam generator and deposited, thereby deteriorating the integrity of the steam generator. Environmental condition in the secondary system of the PWRs differs across different locations. So, the corrosion rate and types of corrosion products depend on specific locations in the secondary system. In this study, the quantity and chemical compositions of corrosion products generated in various locations that vary in different temperatures and chemistry conditions were investigated. As a result of evaluating the PWR "Unit A" that is in current operation, the amount of corrosion products generated in the section of high temperature feedwater system was identified as the largest source in the secondary system. Major components of corrosion products were iron oxides such as magnetite, hematite, and lepidocrocite.

• Geomechanics and Engineering
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• 제24권1호
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• pp.43-55
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• 2021

Peatland is distributed in China widely, and organic matters in soil frequently induce problems in the construction and maintenance of highway engineering due to the high permeability and compressibility. In this paper, a selected site of Dali-Lijiang expressway was surveyed in China. A numerical model was built to predict the settlement of the foundation of the selected section employing the soft soil creep (SSC) model in PLAXIS 8.2. The model was subsequently verified by the result of field observance. Consequently, the parameters of 17 types of soils from different regions in China with organic contents varying from 1.1-74.9% were assigned to the numerical model to study the settlement characteristics. The calculated results showed that the duration of primary consolidation and proportion of primary settlement in the total settlement decreased with increasing organic content. Two empirical equations, for total consolidation settlement and secondary settlement, were proposed using multiple linear regression based on the calculated results from the numerical models. The analysis results of the significances of certain soil parameters demonstrated that the natural compression index, secondary compression index, cohesion and friction angle have significant linear relevance with both the total settlement and secondary settlement, while the initial coefficient of permeability exerts significant influence on the secondary settlement only.

• 농업과학연구
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• 제49권2호
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• pp.331-339
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• 2022

Deforestation and conservation of coniferous forest have been recognized as critical issues in Korea due to climate change. The main purpose of this research was to monitor changes of secondary metabolite contents and growth of Korean fir (Abies koreana) according to the temperature change in Mt. Halla. The Korean fir located at three different regions, Yeongsil, Witseoreum, and Jindallaebat, was monitored in April, July, and October from 2016 to 2018 and secondary metabolites, specifically lutein, α-carotenoid, and β-carotenoid, were analysed with high performance liquid chromatography. The results showed that average concentrations of lutein, α-carotenoid, and β-carotenoid were 0.82 - 23.30, 0.02 - 2.01, and 0.11 - 2.84 ㎍·g-1 and the highest concentration of secondary metabolite was observed in October compared to April and July. The average length and width of Korean fir in the three regions were 11.84 - 20.70 and 1.78 - 2.41 mm from 2016 - 2018. A correlation analysis showed that the concentrations of all three secondary metabolites were negatively correlated with temperature and a significant difference was observed between temperature and lutein concentration in Korean fir. Overall, growth and production of secondary metabolites in Korean fir highly depended on the temperature, and global warming thus might have an adverse effect on the growth and physiological changes of Korean fir in Mt. Halla.

• Geomechanics and Engineering
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• 제34권1호
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• pp.69-86
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• 2023

To overcome the dilemma of the [BQ] method's inability to predict mountain tunnel support loads, this study is based on the Hoek-Brown criterion and previous results to obtain the connection equations from GSI scores to each parameter of the Hoek-Brown criterion and the link between the [BQ] scores and the GSI system. The equations were embedded in the Hoek-Brown criterion of FLAC6.0 software to obtain tunnel construction forecasts without destroying the in-situ stratigraphy. The feasibility of the secondary development of the Hoek-Brown criterion was verified through comparative analysis with field engineering measurements. If GSI > 45 with a confining pressure of less than 10 MPa, GSI has little effect on the critical softening factor while we should pay attention to the parameter of confining pressure when GSI < 45. The design values for each parameter are closer to the FLAC3D simulation results and the secondary development of the Hoek-Brown criterion meets the design objectives. If the Class V surrounding rock is thinned with shotcrete or the secondary lining is installed earlier, the secondary lining may act as the main load-bearing structure. The study may provide ideas for rapid prediction of mountainous tunnels in China.

• 한국소음진동공학회논문집
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• 제13권4호
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• pp.266-273
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• 2003

The purpose of this study is to obtain the effects of the parameters of the suspension system in railway rolling-stock for KT-23 type Passenger vehicle. According to the analysis and the small scale model car test. optimal condition was obtained for the stiffness ratio of secondary spring to primary spring of the suspension system and the mass ratio of the bogie frame to the car body. The analysis of the study shows that if the car body mass is increased or secondary stiffness Is lowered, the vertical vibration level is reduced and the passenger comfort can be improved. Especially, strong peaks are occurred in the frequencies corresponding to the rotational speed of driving axle and vehicle wheel. Hence, in order to obtain the dynamic characteristics through the small scale model car, the driving method of the vehicle on the test bench, rotational characteristics of the wheel and the natural modes of vehicle should be investigated and be modified.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1991년도 춘계학술대회논문집; 한국해사기술연구소, 대전; 1 Jun. 1991
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• pp.153-158
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• 1991

Recently, demands on light weight, high strength, and low noise or vibration have led to the design of complicated structural systems. Although finite elements [1], mode synthesis [2], and statistical energy analysis [3] can be used to compute the dynamic response of such systems, the structural complexity has made the interpretation of the results of such analysis difficult. Many researchers in dynamic analysis have sought to further develop existing theories or develop alternate methods to obtain greater insight in the behavior of large massive primary systems (P systems) with connected light secondary systems (S systems). Some recent research includes work by Sackman and Kelly [4], Sackman et al.[5], Der Kiureghian et al.[6], and Igusa and Der Kiureghian [7-9] who have combined mode synthesis concepts, matrix algebraic theory, and perturbation methods for characterizing weakly-coupled structural systems. A major limitation of these works are that they are limited to lumped mass S systems. In this paper, the general ideas in the Refs.[4-9] are used to study continuous S systems and the method to reduce the complexity, studied in the works by Igusa, Achenbach, and Min [10,11], is developed into the frequency window method.

• 대한의용생체공학회:의공학회지
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• 제33권4호
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• pp.177-183
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• 2012

The inspiratory flow rate of a human is changed with the amount of the workload. The flow characteristic is affected by the inspiratory flow rate. In the flow field of airway, the both of turbulence intensity and secondary flow affect the deposition pattern of particles which is important for the drug-aerosol targeting. Thus the analysis of the flow characteristic in a human airway is important. The purpose of this study is to investigate the effects of the inspiratory flow rate on the flow characteristics in a human airway. The tubular airway is consistent with the oral cavity, pharynx, larynx and trachea. The relatively inspiratory flow rate is used at each case of human states regarding the workload. By the effect of geometric airway changes, transition to turbulent airflow after the larynx can occur with relaminarization further downstream. The low Reynolds number k-${\omega}$ turbulence model is used for analysis with flow regime. As the inspiratory flow rate is larger, the turbulence kinetic energy and secondary flow intensity increase in airway. On the other hand, the area of recirculation zone is smaller.