• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.292-292
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• 2008

The superconducting fault current limiter(SFCL) can be used to limit fault current level in electrical transmission line and power system. Up to now, there are several kinds of SFCL that have proposed and it is expects that they will be applied to appropriated position considering their own properties; initial fault current limiting instant and the current limiting characteristics. In this paper, we investigated the initial fault current limiting instant and the amplitude of initial fault current in the resistive type, the flux-lock type, the flux-coupling type and the transformer type SFCL. Experiment results show that the initial fault current limiting instant and the amplitude of initial fault current of the SFCLs are dependant on the ratio of inductance of primary and secondary coils.

• 조명전기설비학회논문지
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• 제22권8호
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• pp.26-30
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• 2008

본 논문에서는 본 저자가 제안한 직렬연결된 두 코일의 자기결합을 갖는 초전도 전류제한기의 사고전류제한 시뮬레이션과 실험을 수행하였다. 평상시에는 두 코일로부터 발생되는 자계는 상쇄되지만 사고가 발생되면 초전도 소자의 저항발생으로 더 이상 두 코일로부터 자계는 상쇄되지 않게 되고 제한기 임피던스 발생으로 고장전류가 제한된다. 제안한 자기결합을 이용한 초전도 전류제한기의 두 코일의 인덕턴스비를 조절함으로써 제한기의 동작전류와 임피던스는가 향상될 수 있음을 시뮬레이션과 실험을 통해 확인할 수 있었다.

• 한국전기전자재료학회논문지
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• 제36권6호
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• pp.614-619
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• 2023

The fault current limiting characteristics of three-phase transformer type superconducting fault current limiter (SFCL), which consisted of three-phase primary and secondary windings wound on E-I iron core, one high-TC superconducting (HTSC) element connected with the secondary winding of one phase and another HTSC element connected in parallel with other two secondary windings of two phases, were analyzed. Unlike other three-phase transformer type SFCLs with three HTSC elements, three-phase transformer type SFCL using double quench has the merit to perform fault current limiting operation for three-phase ground faults with two HTSC elements. To verify its proper three-phase ground fault current limiting operation, three-phase ground faults such as single-line ground, double-line ground and triple-line ground faults were generated in three-phase simulated power system installed with three-phase transformer type SFCL using double quench. From analysis of its fault current limiting characteristics based on tested results, three-phase transformer type SFCL using double quench was shown to be effectively operated for all three-phase ground faults.

• Membrane and Water Treatment
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• 제7권2호
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• pp.127-141
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• 2016

Electrodialysis (ED) is known to be a useful membrane process for desalination, concentration, separation, and purification in many fields. In this process, it is desirable to work at high current density in order to achieve fast desalination with the lowest possible effective membrane area. In practice, however, operating currents are restricted by the occurrence of concentration polarization phenomena. Many studies showed the occurrence of a limiting current density (LCD). The limiting current density in the electrodialysis process is an important parameter which determines the electrical resistance and the current utilization. Therefore, its reliable determination is required for designing an efficient electrodialysis plant. The purpose of this study is the development of a predictive model of the limiting current density in an electrodialysis process using response surface methodology (RSM). A two-factor central composite design (CCD) of RSM was used to analyze the effect of operation conditions (the initial salt concentration (C) and the linear flow velocity of solution to be treated (u)) on the limiting current density and to establish a regression model. All experiments were carried out on synthetic brackish water solutions using a laboratory scale electrodialysis cell. The limiting current density for each experiment was determined using the Cowan-Brown method. A suitable regression model for predicting LCD within the ranges of variables used was developed based on experimental results. The proposed mathematical quadratic model was simple. Its quality was evaluated by regression analysis and by the Analysis Of Variance, popularly known as the ANOVA.

• Journal of Biosystems Engineering
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• 제30권1호
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• pp.45-55
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• 2005

Knowledge of the relationship between crop yield and yield-limiting factors is essential for precision farming. However, developing this knowledge is not easy because these yield-limiting factors are interrelated and affect crop yield in different ways. In this study, data for grain yield and yield-limiting factors, including crop chlorophyll content, soil chemical properties, and topography were collected for a small (0.3 ha) rice paddy field in Korea and a large (36 ha) upland corn field in the USA, and relationships were investigated with path analysis. Using this approach, the effects of limiting factors on crop yield could be separated into direct effects and indirect effects acting through other factors. Path analysis provided more insight into these complex relationships than did simple correlation or multiple linear regression analysis. Results of correlation analysis for the rice paddy field showed that EC, Ca, and $SiO_2$ had significant (P<0.1) correlations with rice yield, while pH, Ca, Mg, Na, $SiO_2,\;and\;P_2O_5$ had significant correlations with the SPAD chlorophyll reading. Path analysis provided additional information about the importance and contribution paths of soil variables to rice yield and growth. Ca had the highest direct effect (0.52) and indirect effect via Mg (-0.37) on rice yield. The indirect effect of Mg through Ca (0.51) was higher than the direct effect (-0.38). Path analysis also enabled more appropriate selection of important factors limiting crop yield by considering cause-and-effect relationships among predictor and response variables. For example, although pH showed a positive correlation (r=0.35) with SPAD readings, the correlation was mainly due to the indirect positive effects acting through Mg and $SiO_2$, while pH not only showed negative direct effects, but also negatively impacted indirect effects of other variables on SPAD readings. For the large upland Missouri corn field, two topographic factors, elevation and slope, had significant (P<0.1) direct effects on yield and highly significant (P<0.01) correlations with other limiting factors. Based on the correlation analysis alone, P and K were determined to be nutrients that would increase corn yield for this field. With the help of path analysis, however, increases in Mg could also be expected to increase corn yield in this case. In general, path analysis results were consistent with published optimum ranges of nutrients for rice and com production. We conclude that path analysis can be a useful tool to investigate interrelationships between crop yield and yield limiting factors on a site-specific basis.

• 한국과학교육학회지
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• 제36권6호
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• pp.935-946
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• 2016

이 연구의 목적은 과학교육과 관련된 인지편향을 확인하고 과학교육을 통하여 인지편향을 줄일 수 있는 방법을 확인하기 위하여 계획되었다. 문헌조사를 통하여 연구되어진 인지편향을 수집하였고, 과학학습의 관련성이 높은 인지편향을 과학교육전문가와의 토론을 통하여 추출하였다. 연구 결과 합리적 인과관계추론을 방해하는 인지편향, 다양한 정보와 결론 생성을 방해하는 인지편향, 자기반성적 학습을 방해하는 인지편향, 자기 주도적 의사결정을 방해하는 인지편향, 범주 제한적 사고를 조장하는 인지편향의 다섯 가지로 분류하였고, 총 29개의 인지편향들을 조사하였다. 합리적 인과관계추론의 방해하는 인지편향은 목적론적 사고, 가용성 편향, 착각적 상관, 클러스터 착각이었다. 문제해결에서 다양한 정보의 탐색을 방해하는 인지편향은 선택적 지각, 실험자 편향, 확증편향, 단순 사고 효과, 주의 편향, 신념편향, 실용 오류, 기능적 고착, 틀 효과가 있었다. 자기반성적 학습을 방해하는 인지편향은 과도한 자신감 편향, 우월성 편향, 계획 오류, 기본적 귀인 오류, 더닝-크루거 효과, 사후확신편향, 맹점편향을 확인하였다. 자기 주도적 의사결정을 방해하는 인지편향은 동조효과, 편승효과, 집단사고, 권위에 호소, 정보편향이 있다. 마지막으로 범주 제한적 사고를 조장하는 인지편향으로는 심리학적 본질주의, 고정관념, 의인화, 외집단 동질성 편향이 있었다. 연구된 인지편향에 대한 심리학적 특징들과 과학교수-학습방법들을 토대로 인지편향을 줄이고 역량을 향상시킬 수 있는 수업 방법에 대해서 논의한다.

• Journal of Microbiology and Biotechnology
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• 제11권4호
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• pp.607-613
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• 2001

The biodegradation rates of diesel oil by a selected diesel-degrading bacterium, Pseudomonas stutzeri strain Y2G1, and microbial consortia composed of combinations of 5 selected diesel-degrading bacterial were determined in liquid and soil systems. The diesel degradation rate by strain Y2G1 linearly increased $(R^2=0.98)$ as the diesel concentration increased up to 12%, and a degradation rate as high as 5.64 g/l/day was obtained. The diesel degradation by strain Y2G1 was significantly affected by several environmental factors, and the optimal conditions for pH, temperature, and moisture content were at pH8, $25^{\circ}C$, and 10%, respectively. In the batch soil microcosm tests, inoculation, especially in the form of a consortium, and the addition of nutrients both significantly enhanced the diesel degradation by a factor of 1.5 and 4, respectively. Aeration of the soil columns effectively accelerated the diesel degradation, and the initial degradation rate was obviously stimulated with the addition of inorganic nutrients. Based on these results, it was concluded that the major rate-limiting factors in the tested diesel-contaminated soil were the presence of inorganic nutrients, oxygen, and diesel-degrading microorganisms. To resolve these limiting parameters, bioremediation strategies were specifically designed for the tested soil, and the successful mitigation of the limiting parameters resulted in an enhancement of the bioremediation efficiency by a factor of 11.

• 한국지진공학회논문집
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• 제2권4호
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• pp.145-154
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• 1998

이동제한장치는 내진분리된 교량 또는 교각에 소서인지가 발생하는 다경간연속교에 있어서 지진에 의한 교축방향 최대변위 및 잔류변위를 제한함에 있어 매우 효과적이다 교축방향의 수평변위가 이동제한장치에 의해 제한되는 경우 상부구조의 최대변위를 예측하기 위해서 비선셩동적해석을 설계에 실무적으로 사용하기에는 시간소요 및 해석상 어려움이 있다 본 연구에서는 등가탄성해석방법과 가속도-변위 스펙트럼을 이용한 간단한 이동제한장치 설계절차를 제시하였다 여기서 제시된 방법은 이동제한 장치의 설치위치 및 이격거리를 결정함에 있어 매우 효율적으로 사용할 수 있을 것이다.

• 응용통계연구
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• 제23권6호
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• pp.1057-1065
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• 2010

In this paper we discuss some cautionary notes in using the Pearson chi-squared test statistic for the goodness-of-fit of the ordinal response model. If a model includes continuous type explanatory variables, the resulting table from the t of a model is not a regular one in the sense that the cell boundaries are not fixed but randomly determined by some other criteria. The chi-squared statistic from this kind of table does not have a limiting chi-square distribution in general and we need to be very cautious of the use of a chi-squared type goodness-of-t test. We also study the limiting distribution of the chi-squared type statistic for testing the goodness-of-t of cumulative logit models with ordinal responses. The regularity conditions necessary to the limiting distribution will be reformulated in the framework of the cumulative logit model by modifying those of Moore and Spruill (1975). Due to the complex limiting distribution, a parametric bootstrap testing procedure is a good alternative and we explained the suggested method through a practical example of an ordinal response dataset.

• 조명전기설비학회논문지
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• 제26권11호
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• pp.75-80
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• 2012

In this paper, the operational characteristics due to the introduction of the superconducting fault current limiter(SFCL) with a peak current limiting function were analyzed in the power distribution system. The parallel structure of the superconducting element can operate the peak current limiting function depending on the transient amplitude of fault current. We studied the operating characteristics of the introduction of the SFCL with a peak current limiting function in the power distribution system. Furthermore, we were analyzed between the SFCL with a peak current limiting function and the protection devices in the power distribution system, through the short circuit experiments.