• 대한전기학회논문지:전력기술부문A
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• 제54권9호
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• pp.434-440
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• 2005

This paper describes an optimized Scheme of reactive-power compensation for the low short-circuit-ratio AC system interconnected with the HVDC system. An HVDC system interconnected with tile low SCR AC system is vulnerable to the ac voltage variation, which brings about the commutation failure of the converter. This problem can be solved using optimized compensation of reactive power. In this study, a benchmark system for HVDC system interconnected with low SCR AC system is derived using PSS/E simulation. Then an optimized srheme for reactive power compensation was derived using integer programming. The feasibility of proposed scheme was analyzed through silnulations with PSS/E and PSCAD/EMTDC. The proposed scheme can compensate the reactive power accurately and minimize the number of switching for harmonic filters and shunt reactors.

• 한국농공학회논문집
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• 제48권6호
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• pp.79-85
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• 2006

A simulation was done to analyze the seepage problems due to seawater intrusion through the embedded rock layers on heterogeneous layers of sea-dike. Numerical analysis with SAMTLE(developed by author) was done by taking various relative permeability $ratio(R_r/R_e)$. These results showed, when the sed-dike is newly designed, operated, and maintained considering the safety of sea-dike in seepage problems, these embankment materials are prudently chosen. The permeability of the soil materials, within the range of salinity management in freshwater, is comparatively high, however, the permeability of rock materials for bottom rock layer is low. Therefore, when the relative permeability $ratio(R_r/R_e)$ is bellow 10 it is safety in seepage problems of sea-dike.

• Communications for Statistical Applications and Methods
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• 제8권3호
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• pp.767-775
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• 2001

In this paper we propose a poll system using e-mail. This system expects to increase the response ratio because of including a questionnaire inner e-mail. Especially, this system automatically provides a general paper which is a result of categorical data analysis.

• Membrane and Water Treatment
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• 제2권1호
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• pp.63-74
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• 2011

A spiral wound nanofiltration (NF) membrane (GE Osmonics, DK 4040F) was used to remove pesticides from water. Several solutions of single pesticides and their mixtures were prepared. The pesticides initial concentration ranged from ca. 50 ng/L (single pesticide) to ca. 700 ng/L (as sum of 14 pesticides) and progressively increased with time since the NF experiments were carried out in a concentration mode up to a Volume Concentration Ratio, VCR = 10. Permeate flux and pesticides retention were evaluated as a function of the Volume Concentration Ratio. The permeate flux did not practically change by varying VCR. Pesticide retention was found to be around 97-98% both in the cases of single pesticide solutions and different mixtures of pollutants, and was not affected by the VCR. Pesticides concentration in permeate samples was found to be lower than the maximum concentration level fixed in European directive.

• 한국공작기계학회논문집
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• 제12권4호
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• pp.63-69
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• 2003

In discontinuous composite mechanics, shear lag theory is one of the most popular model because of its simplicity and accuracy. However, it does not provide sufficiently accurate strengthening predictions in elastic regime then the fiber aspect ratio is small. This is due to its neglect of stress transfer across the fiber ends and the stress concentrations that exist in the matrix regions near the fiber ends. To overcome this shortcoming, a more simplified shear lag model introducing the stress concentration factor which is a function of several variables, such as the modulus ratio, the fiber volume fraction, the fiber aspect ratio, is proposed. It is found that the modulus ratio($E_f$/$E_m$) is the essential variable among them. Thus, the stress concentration factor is expressed as a function of modulus ratio in the derivation. It is found that the proposed model gives a good agreement with finite element results and has the capability to correctly predict the values of interfacial shear stresses and local stress variations in the small fiber aspect ratio regime.

• 대한임상검사과학회지
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• 제48권4호
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• pp.394-400
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• 2016

B-type natriuretic peptide (BNP)와 심초음파는 심부전 진단과 예후를 판단하는 지표로써 수축 기능이상에 많은 연구를 했으나, 본 연구에서는 BNP 결과와 심초음파 이완 기능을 나타내는 항목의 상관관계를 알아보고자 한다. BNP 검사와 심초음파를 실시한 188명을 대상으로 BNP 결과에 따라 5그룹으로 분류하고, 심초음파의 좌심실 구혈률, 좌심방 크기, E velocity, A velocity, Deceleration time, E/A ratio, E', A', S', E/E'와의 상관관계를 조사하고, 그 중 심부전을 진단 받은 67명을 Relaxation abnormality (Grade I), Pseudonormalization (Grade II), Restrictive physiology (Grade III)로 등급을 분류하고 BNP 결과와 심초음파 항목을 비교한 결과 BNP 수치가 상승할수록 심초음파 항목 중 좌심실 구혈률, 좌심방 크기, E/A ratio, Deceleration time, A', S', E/E'와 유의한 상관관계가 있었다. 그룹간의 비교에서 E/E' 항목이 가장 좋은 유의성을 보여주었다. 심부전 환자의 등급 분류에 따른 BNP 결과는 $623.0{\pm}459.7pg/mL$, $1013.2{\pm}1155.1pg/mL$, $1693.4{\pm}1544.0pg/mL$로 유의성이 있었으며(p<0.01), 등급이 올라갈수록 심초음파 항목 중 좌심실 구혈률, 좌심방 크기, E velocity, A velocity, E/A ratio, Deceleration time, A', E/E' 와 상관관계가 있었다(p<0.001). BNP 결과가 상승할수록 심초음파 이완기 항목과 유의성이 있었고, 심초음파에서 Restrictive physiology 그룹의 BNP 결과가 가장 높았다.

• Asian-Australasian Journal of Animal Sciences
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• 제20권2호
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• pp.252-256
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• 2007

This study was carried out to determine the effect of vitamin E and vitamin C on the performance of Japanese quails (Coturnix coturnix japonica) reared under heat stress during the growth and egg production period. A total of 810 seven-day-old Japanese quails were used in the trial. The birds received a diet with either three levels of vitamin E (DL-${\alpha}$Tocopheryl acetate) (60, 120 and 240 mg/kg of diet) and vitamin C (ROVIMIX STAY-C 35) (60, 120 and 240 mg/kg of diet). Live weight on day 35 and weight gain were the lowest in the group of chicks on a combination of 60 mg of vitamin E and 60 mg of vitamin C, whereas the highest live weight was demonstrated in chicks on a combination of 240 mg of vitamin E and 240 mg of vitamin C (p<0.01). The effects of treatments on cumulative feed consumption, feed conversion ratio, age at 5% lay, sexual maturity weight, rate of lay and mean egg weight values were found to be significant (p<0.01). The highest feed consumption, feed conversion ratio, age at 5% lay, sexual maturity weight, rate of lay and mean egg weight values were found in the group on a combination of 240 mg of vitamin E and 240 mg of vitamin C. The effect of treatments on the mortality ratio was found to be insignificant (p>0.01). The cost of supplementing diets with vitamin E and vitamin C is very low. Therefore such a combination of supplement can offer a potential protective management practice in preventing heat stress related losses in performance of Japanese quails.

• 한국응용곤충학회지
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• 제24권4호
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• pp.173-177
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• 1986

P.E. film으로 피복한 포장에서 숫검은밤나방 유충에 의한 담배 피해주율이 낮은 원인을 구명하기 위한 시험에서 다음과 같은 결과를 얻었다. 1. 피해주율은 무피복구(n)에 비해 P.E. film 피복구(m)에서 63% 감소하였다. 2. 피복한 휴(畦) 내의 일종 최고 토양온도(5cm 깊이)는 무피복구에 비해 조사기간중 평균 $5{\sim}7^{\circ}C$ 높았으며 6월 중순에는 $50^{\circ}C$까지 이르렀다. 3. 유충의 회수율, 토양내 잠복깊이 및 발육 정도 등에서 P.E. film 피복구와 무피복구간에 차이가 없었다. 4. m/n치와 5가지 변형된 피복방법의 결과에 비추어 P. E. film 자체에 의해 숫검은 밤나방유충의 이동 흑은 먹이탐색활동이 방해를 받는 것으로 생각되었다. 5. 숫검은밤나방유충의 사망율은 7월 하순과 8월하순 사이에 급격히 증가하는 것으로 나타났다.

• 지구물리
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• 제3권2호
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• pp.127-138
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• 2000

시멘트 모르타르 재료에 대한 동탄성계수와 정탄성계수의 차이를 고찰하고자 일곱 단계의 물시멘트 혼합비에 대해 다양한 길이의 시료를 제작, 시험하였다. 이들 시료의 동탄성계수 및 정탄성계수는 비중 측정, 초음파 전파 속도 측정 및 일축 압축 시험을 통해 결정되었으며, 시료에 대해 측정된 P파 및 S파 속도 분석은 기존의 아날로그 방식이 아닌 디지털 방식을 통해 수행되었다. 일련의 자료 처리 과정을 지친 디지털 방식 자료는, 초음파 전파 속도를 정밀하게 분석하는데 결정적인 역할을 할 수 있음이 확인되었으며, 복수 시료를 이용한 거리 변화에 따른 파의 지연 시간 변화를 이용한 속도 산정 방식이, 단일 시료 길이와 전파 시간을 이용한 기존 속도 산정 방식보다 더욱 정밀한 값을 보여주는 것으로 판명되었다. 밀도는 시료의 P파 및 5파 속도와 뚜렷한 양의 상관성을 보여주며, 일축 압축 강도 역시, 밀도와 뚜렷한 양의 상관성을 보여준다. 초음파 전파 속도를 통해 측정된 동탄성계수$(E_D)$와 일축 압축 시험을 통해 측정된 정탄성계수$(E_S)$의 비율$(E_D/E_S)$은 시료의 강도가 커질수록 함께 커지는 경향을 보여주었으며, 모든 시료에 대해 항상 동탄성계수가 정탄성계수보다 높게 평가됨이 확인되었다. 그러나 동포아송비$({\nu}_D)$와 정포아송비$({\nu}_S)$의 비율$({\nu}_D/{\nu}_S)$은 강도와 특별한 상관성을 보여주지 않았으며, 그 비율도 $69{\sim}122\;%$정도로 동포아송비와 정포아송비가 큰 차이를 보이지 않는 것으로 나타났다.

• 한국강구조학회 논문집
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• 제8권4호통권29호
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• pp.3-17
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• 1996

The purpose of this paper is to investigate experimentally and theoretically the strength and deformation of K-joints in welded Warren-type square hollow structural section truss. There are 2 types in K-joints in K-joints having one compression bracing member and one tension bracing member. One type is KP-series that brae members are rotated to $45^{\circ}$, another type is KS-series that are not rotated. Principal parameters are the ratio of the chord width to thickness (D/T=33.3, 25, 16.7), the ratio of brace width to chord width(d/D=0.4, 0.5, 0.67, 0.83, 1.0) and the ratio of eccenticity to chord height (e/D=0.25, 0.125, 0, -0.125, -0.25, -0.375, -0.5). The important results obtained from the experiments are as follow ; The strength of K-joints increase proportionally as the D/T ratio decreases, and the d/D ratio increases. But the e/D ratio has no correlation with the strength of K-joints. Generally the strength and ductility ratio of KP-series increase more than a current type(KS-series) in full ${\beta}$range.