• 공업화학
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• 제30권6호
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• pp.742-748
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• 2019

Influence of several experimental parameters (e.g., initial dye concentration, pH, distance between electrodes, applied voltage, electrical conductivity, current density, and reaction time) on the performance of electrocoagulation (EC) process for the removal of acid blue 25 (AB25) was studied. A bipolar batch reactor was used to test the impact of the parameters. The removal efficiency (RE) of AB25 dye was promoted by increasing the contact time, voltage, electrical conductivity, and applied current density. In contrast, RE of AB25 decreased with higher level of AB25 and the longer distance between electrodes. The removal efficiency increased consistently until pH 7, but decreased above pH 7. The maximum efficiency of AB25 removal above 90% was obtained at a voltage of 60 V, reaction time of 90 min, distance between electrodes of 0.5 cm, initial concentration of 25 mg/L, conductivity of 3,000 μS/cm and pH of 7. These results imply that the high RE of AB25 dye from the aqueous solution can be achieved by EC process.

• Parasites, Hosts and Diseases
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• 제39권4호
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• pp.293-299
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• 2001

The characteristics of vivax malaria epidemics along the demilitarized Bone (DMZ) in the Republic of Korea has been established by the early surveillance data. To further characterize the epidemic, data of civilian patients microscopically diagnosed with malaria from 1995 through 2000 were analyzed in Yonchon-gun (county) . Malaria incidence was greater in male civilians > 30 years of age (p < 0.05). The annual parasite index was significantly higher in those living in the administrative areas (Myeon) traversed by DMZ than those living in Myons not traversed by DMZ (p < 0.05). Analysis according to the distance (4 to 14 km) from DMZ showed that people living in villages close to DMZ had higher annual parasite indices than those living in villages remote from DMZ (p for trend < 0.05). Civilians living in Myeons with plains and located in northwestern part of the county had higher annual parasite indices than those living in hilly Myeons located in southeastern part of the county (p for trend f 0.05). These findings suggest that the contraction of vivax malaria is related with night-time outdoor activities, and that the distance from DMZ is a risk factor. In this area, the flying distance of infected vector mosquitos can explain the annually repeating occurrence of civilian cases.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제32권2호
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• pp.161-167
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• 2006

Objectives: Pericoronitis was the most common indication for mandibular third molar surgery and there are no universally acceptable predictive criteria for pericoronitis occurrence. This study was designed to analyze the correlation of the pericoronitis and the eruption state of the mandibular third molar using panoramic radiographs statistically. Materials and Methods: 218 patients whose chief complaint was the extraction of the mandibular third molar were examined. The presence and absence of pericoronitis, age, sex, position of extraction site, angulation, impaction degree, position to the anterior border of mandibular ramus, distance between distal cementoenamel junction of second molar and mesial cementoenamel junction of the mandibular third molar were assessed. Then the correlation of pericoronitis and the eruption state of the mandibular third molar were analyzed by Student's t-test and chi-square test. Results: There was no correlation between Pericoronitis and age, sex, position of the mandibular third molar. The angulation(P=0.005), impaction degree(P=0.043), relation with anterior border of mandibular ramus(P=0.003), distance between distal cementoenamel junction of second molar and mesial cementoenamel junction of the mandibular third molar(P<0.05) were correlated with pericoronitis. Conclusions: The occurrence of the pericoronitis can be predicted by the eruption state of the mandibular third molar such as angulation, impaction degree, relation with anterior border of mandibular ramus, distance between distal cementoenamel junction of second molar and mesial cementoenamel junction of third molar.

• 충청수학회지
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• 제12권1호
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• pp.169-177
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• 1999

In this paper, we shall define the usual fuzzy distance between two real fuzzy points, using the usual distance between two points in $\mathbb{R}$. We introduce the fuzzy sequence in the fuzzy real line and the notion of limit of fuzzy sequence in $F_p(\mathbb{R})$, and obtain uniformly fuzzy continuous in $F_p(\mathbb{R})$.

• 환경위생공학
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• 제11권3호
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• pp.37-46
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• 1996

In this study, the effect of pH, Temp, dye concentration, distance of electrode, and the potential on the removal efficiency of dye-wastewater using electrochemical reaction were investigated. Optimum conditions for the electrochemical treatment of dye-wastewater were obtained that pH;7, 8V, electrode distance; 1cm and the reaction time for obtaining above 99% removal efficiency were 10 - 40min at each conditions, From this result, we can determine the instantaneous current efficiency and specific energy consumption, and we can provide the effective data for economical treatment of industrial dye-wastewater.

• 대한시과학회지
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• 제20권4호
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• pp.523-530
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• 2018

목적 : 본 연구는 근거리 동체시력(Dynamic visual acuity) 측정장치를 이용하여 측정된 근거리 동체시력과 원거리에서 측정된 동체시력과의 차이를 알아보고, 플러스렌즈 가입에 의한 조절자극의 변화가 동체시력에 미치는 영향을 알아보고자 하였다. 방법 : 대상은 전신질환 및 안질환이 없고, 시력이 1.0 이상인 성인 남 여 40명($22.84{\pm}2.43$세)으로 선정하였다. 원거리와 근거리 동체시력의 비교, 플러스렌즈 가입(+0.50D, +1.00D, +1.50D)으로 유도된 동체시력의 변화를 알아보았다. 결과 : 완전교정상태에서 원거리 동체시력과 근거리 동체시력은 각각 $78.86{\pm}19.46deg/sec$, $76.90{\pm}18.05deg/sec$로 원거리 동체시력이 약간 높게 나타났다(p=0.04). 원거리 동체시력이 높을수록 근거리 동체시력이 높은 양의 상관관계를 보여 원거리 동체시력이 우수한 사람이 근거리 동체시력도 우수한 것으로 나타났다(r=0.95, p=0.00, Fig. 4). 조절자극변화에 따른 근거리 동체시력은 완전교정상태에서 $75.95{\pm}18.85deg/sec$이었고 +0.50D 구면도수를 가입한 상태에서 동체시력은 $76.95{\pm}16.45deg/sec$로 통계적으로 유의한 차이가 없었으나(p>0.05), +1.00D를 가입한 상태는 $79.02{\pm}13.51deg/sec$로 약간 높게 나타났으며, +1.50D를 가입한 상태에서는 $84.28{\pm}18.96deg/sec$로 통계적으로 유의한 차이가 있었다(p<0.05). 결론 : 원거리와 근거리의 동체시력의 차이는 없지만 원거리 동체시력이 우수한 경우 근거리 동체시력도 우수하며, 조절자극 변화를 위해 플러스렌즈가 가입됨에 따라 동체시력이 증가함을 알 수 있었다.

• Journal of Electrical Engineering and Technology
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• 제3권3호
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• pp.363-372
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• 2008

In this paper, knowledge-based approach using Support Vector Machines (SVMs) are used for estimating the coordinated zonal settings of a distance relay. The approach depends on the detailed simulation studies of apparent impedance loci as seen by distance relay during disturbance, considering various operating conditions including fault resistance. In a distance relay, the impedance loci given at the relay location is obtained from extensive transient stability studies. SVMs are used as a pattern classifier for obtaining distance relay co-ordination. The scheme utilizes the apparent impedance values observed during a fault as inputs. An improved performance with the use of SVMs, keeping the reach when faced with different fault conditions as well as system power flow changes, are illustrated with an equivalent 265 bus system of a practical Indian Western Grid.

• 대한수학회보
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• 제54권2호
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• pp.507-519
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• 2017

We present an upper bound on the Cheeger constant of a distance-regular graph. Recently, the authors found an upper bound on the Cheeger constant of distance-regular graph under a certain restriction in their previous work. Our new bound in the current paper is much better than the previous bound, and it is a general bound with no restriction. We point out that our bound is explicitly computable by using the valencies and the intersection matrix of a distance-regular graph. As a major tool, we use the discrete Green's function, which is defined as the inverse of ${\beta}$-Laplacian for some positive real number ${\beta}$. We present some examples of distance-regular graphs, where we compute our upper bound on their Cheeger constants.

• 한국안광학회지
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• 제12권3호
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• pp.39-48
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• 2007

엄밀한 조절자극과 폭주자극 값 그리고 프리즘 디옵터는 어떻게 정의되어야 하는지를 고찰하여 정리 하였다. 양안시기능 검사와 분석의 실무에서 조절자극과 폭주자극 값은 어떻게 처리되는지를 고찰하여 정리 했다. 그 결과 실무에서의 처리과정은 근거리를 렌즈면으로부터 40 cm로 하는 경우 평균 P.D가 64 mm일 때 안구의 회선점에서 시험렌즈까지 거리 $l_c$이 26.67 mm인 경우에 가장 적합하였다. 본 논문에서 이 값들을 사용하여 필요한 값들을 계산하였다. 그리고 실무에서 사용되는 (5)식의 조절자극 값이 지니는 오차를 눈의 물측 주점에서 시험렌즈까지 거리 $l_H$를 15.07 mm로 하여 계산했다. 굴절력이 $P_m$인 프리즘 가입에 의한 폭주자극 값의 변화량 P'을 순환 계산법으로 계산하였다. P'는 $P_m$, 회선점에서 프리즘까지의 거리 $p_c$, 프리즘을 가입하기 전의 폭주 값 $C_o$와 프리즘 재질의 굴절률 n에 따라 변한다. 그리고 순환 계산법과 필요한 수식들을 자세히 제시했다. P'를 증대시키는 요인에는 두 가지가 있다. 그 첫 번째는 주된 것으로서 폭주 값이 보통의 덧셈법에 따라 더해지지 않는 성질이다. 다른 하나는 영향력이 작은 것으로서 프리즘의 실제 굴절력이 빛의 입사각에 따라 다르게 되는 이유이다. 그리고 $p_c$와 $C_o$가 커짐에 따라 P'은 괄목할 만큼 작아진다. $P_m=20{\Delta}$, P.D=64 mm 그리고 n=1.7인 경우에 대해 $p_c$와 $C_o$값들에 따르는 $P^{\prime}/P_m$을 계산하여 그래프로 나타냈다. $P^{\prime}/P_m$의 굴절률 n에 대한 의존성은 무시 할만 큼 아주 작다(Fig. 6 참조). 가입 프리즘의 굴절력과 폭주자극 값의 변화량이 같게 되는 프리즘의 위치 값 $p_c$를 구했다(Table 1). 실무에서 약식으로 처리되는 조절자극과 폭주자극 값의 참 값을 구하였다. 이를 토대로 약식으로 처리된 조절자극과 폭주자극 값이 참 값의 위치에 표시 되게 하는 두 가지의 그래프 양식을 제시하였다. 하나는 기존의 것과 같은 형태(Fig. 9)이고 다른 하나는 프리즘 가입에 의한 폭주자극 값의 변화량만을 나타내는 형식이다(Fig. 11).

• 전기학회논문지P
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• 제64권2호
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• pp.67-73
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• 2015

Distance relay is widely used for the protection of long transmission line. Most of distance relay used to calculate line impedance by measuring voltage and current using DFT. So if there is a computation error due to the influence of phasor by DC offset component, due to excessive vibration by measuring line impedance, overreach or underreach can be occurs, and then abnormal and non-operation of distance relay can be issue. It is very important to implement the robust distance relaying that is not affected by DC offset component. This paper describes an enhanced distance relaying based on the DC offset elimination filter to minimize the effects of DC offset on a long transmission line. The proposed DC offset elimination filter has not need any prior information. The phase angle delay of the proposed DC offset filter did not occurred and the gain error was not found. The enhanced distance relay uses fault current as well as residual current. The behavior of the proposed distance relaying using off-line simulation has been verified using data about several fault conditions generated by the ATP simulation software.