• Computers and Concrete
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• 제5권6호
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• pp.559-572
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• 2008

The effects of fly ash and superplasticizer (SP) on workability of concrete are quite difficult to predict because they are dependent on other concrete ingredients. Because of high complexity of the relations between workability and concrete compositions, conventional regression analysis could be not sufficient to build an accurate model. In this study, a workability model has been built using artificial neural networks (ANN). In this model, the workability is a function of the content of all concrete ingredients, including cement, fly ash, blast furnace slag, water, superplasticizer, coarse aggregate, and fine aggregate. The effects of water/binder ratio (w/b), fly ash-binder ratio (fa/b), superplasticizer-binder ratio (SP/b), and water content on slump were explored by the trained ANN. This study led to the following conclusions: (1) ANN can build a more accurate workability model than polynomial regression. (2) Although the water content and SP/b were kept constant, a change in w/b and fa/b had a distinct effect on the workability properties. (3) An increasing content of fly ash decreased the workability, while raised the slump upper limit that can be obtained.

• 콘크리트학회논문집
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• 제29권3호
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• pp.275-281
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• 2017

본 연구는 물-결합재비(water-to-binder ratio, W/B) 및 인산염-결합재비(phosphate-to-binder ratio, P/B)가 마그네시아-인산칼륨 시멘트(magnesium-potassium phosphate cement, MKPC) 모르타르의 플로, 응결시간, 압축강도발현 및 pH 변화에 미치는 영향성에 대한 평가이다. MKPC 모르타르의 P/B가 0.3 및 0.5일 때 W/B 범위 20~40%에 대하여 10 배합의 모르타르 실험을 실시하였으며, X-선 회절 분석(X-ray diffraction, XRD), 전자현미경(scanning electron microscope, SEM) 및 수은압입법(mercury intrusion porosimetry, MIP) 분석을 위해 MKPC의 반응생성물 및 미세공극분포를 평가하였다. 실험결과, MKPC 모르타르의 플로 및 응결시간은 P/B의 증가에 따라 감소하였으며, P/B가 0.3에서 0.5로 증가함에 따라 종결시간은 약 24% 감소하였다. MKPC 모르타르의 초기 압축강도 발현 기울기의 경우 콘크리트 구조기준에서 제시하는 시멘트 콘크리트 대비 높은 수준에 있었다. 재령 28일의 압축강도 30 MPa 이상 및 pH 9.0 이하를 만족하기 위해 MKPC 모르타르의 P/B 및 W/B는 각각 0.5이상 및 30% 이하가 추천된다. MKPC의 반응생성물인 스트루바이트(struvite)-K의 결정은 MKPC의 P/B 및 W/B가 높을수록 증가하였는데, 이로 인해 거대 모세관 공극은 감소하였다.

• Journal of electromagnetic engineering and science
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• 제15권2호
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• pp.120-122
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• 2015

This study presents a new, simple method for improving the front-to-back (F/B) ratio of a microstrip patch antenna (MSA) based on surface wave suppression. The back radiation of the MSA is significantly reduced by using the meandered ground plane edges and placing split-ring resonators (SRRs) in the middle of the meandered slots. By loading SRRs near the center of the meandered ground plane edges, some parts of the diffracted back-lobe power density can be reduced further. Compared to the F/B ratio of a conventional MSA with a full ground plane of the same size, an improved F/B ratio of 18 dB has been achieved experimentally for our proposed MSA.

• 한국산업보건학회지
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• 제16권1호
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• pp.11-16
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• 2006

There are many counting rules for analyzing man-made mineral fibers. The representatives are the NIOSH Method 7400 A and B counting rules. The two rules have different rules of length-to-width ratio(aspect ratio) and diameter. The A rule counts only fibers $>5{\mu}m$ in length, and only fibers with aspect ratio >3:1. The B rule counts only ends of fibers $>5{\mu}m$ in length and $<3{\mu}m$ in diameter, and only fibers with aspect ratio ${\geq}5:1$. The A counting rule had been used before the B counting rule was introduced. The purpose of this study is to compare the A and B counting rules for airborne fibers from various man-made mineral fibers(glass wool fibers, rock wool fibers, refractory ceramic fibers, and continuous filament glass fibers) industries. There were significantly differences between the paired counts of A and B rules in all types of fibers(p<0.05). A rule counts/B rule counts(A/B ratios) were 1.52 for glass fibers, 1.53 for rock wool fibers, 1.19 for RCF, and 1.82 for continuous filament glass fibers. The counting results by A and B counting rules were highly correlated in glass wool fibers, rock wool fibers and refractory ceramic fibers(RCF) samples (r=0.96 for all types of fibers) except continuous filament glass fibers(r=0.82). Regression equations to correct for the differences between counting rules were presented in this paper.

• 한국통신학회논문지
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• 제25권4B호
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• pp.783-787
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• 2000

현재 사용되고 있는 개인용 컴퓨터의 중앙처리장치로서 주종을 이루고 있는 마이크로프로세서는 256KB, 혹은 512KB의 L2(Second Level) 캐쉬를 Direct Mapping, 32B 라인사이즈, 그리고 Write Allocation을 채택하지 않는 형태로 사용하고 있는데, 이러한 L2 캐쉬에서 Mapping 방식을 8-way Set Associative Mapping Procedure로 바꾸고, 라인사이즈를 늘려서 128B 이상으로 변경하고, 그리고 Write Allocation을 채택하였을 경우 그 적중률(Hit Ratio)이 약간의 하드웨어적 추가 비용만으로 2.5% 정도 개선됨을 확인하였다.

• 한국산림과학회지
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• 제101권1호
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• pp.46-52
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• 2012

본 연구의 목적은 구기자를 새로이 재배하고자 하는 사람들이나 재배면적을 늘이고자 하는 사람들에게 구기자의 경영실태 및 소득과 투자 수익성을 분석하여 투자에 대한 정보를 제공하고자 하는 것이다. 수익성 분석기법은 IRR, B/C Ratio, NPV를 이용하였다. 구기자 주산단지인 충남 청양, 전남 진도지역의 52가구의 구기자 재배농가를 대상으로 2009년 5월부터 9월까지 작업공정별 투입노동 및 자재비 등에 관해 면접방문조사를 실시하였다. 그 결과 현지판매가격과 투자수익성의 판단기준이 되는 가격을 기준으로 IRR, B/C Ratio, 조수익, 소득, 순수익, 소득율 등을 구하였다. 할인율 3%를 적용하였다. 최근 5년간 농가평균판매가격 kg당 15,000원은 B/C Ratio가 0.89로 나타나 투자수익성이 없는 것으로 나타났다. 적어도 수익성을 맞출려면 IRR=3.00%, B/C Ratio=1.00을 나타내는 구기자 판매가격이 16,800원/kg이상이 되어야 한다고 판단되며, 이때의 소득율은 21.75%인 것으로 나타났다.

• 한국전자파학회논문지
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• 제11권1호
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• pp.26-36
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• 2000

본 논문에서는 위성 통신에 이용될 수 있는 X-band원형 편파 마이크로스트립 $12\times12$배열 안테나를 설계하였다. 복사체는 대형배열에 적합한 개구면 결합형 마이크로스트립 환형 안테나를 사용하였으며, broadside 방향의 빔을 형성시키기 위해 소자간 간격은 $0.7\lambda_0$로 하였다. 또한 높은 이득과 좋은 원형 편파 특성을 위해 직-병렬 구조으1 sequential array 형태의 급전구조를 사용하였다. 제작된 안테나는 본 교의 compact range에서 측정하였 다 그 칠파 10,3 GHz에서 27.88 dB의 directivity에 대해 25.55 dB의 높은 gam을 가지며 이로써 60 %의 높은 효율을 가짐을 확인했다 또한 1.74 dB의 axial ratio와 - 13 dB의 side-lobe-level 특성을 가졌다. 그리고 VSWR 2 기준으로 볼 때 약 43 %의 넓은 반사 계수 대역폭플 가지며,16 %의 axial ratio 대역폭을 가짐을 알 수 있었다.

• 한국농림기상학회지
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• 제4권3호
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• pp.159-163
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• 2002

덩굴식물 개머루, 계요등, 까마귀머루, 담쟁이덩굴, 댕댕이덩굴, 인동덩굴, 하늘타리 등 7수종과 덩굴식물이 아닌 쇠뜨기, 쑥 등 2수종을 이용하여 광색소 함량과 SOD활성에 대하여 분석한 결과는 다음과 같다. 100 ppb 처리구에서 볼 때 엽록소 a, 엽록소 b, 총 엽록소 함량, 카로테노이드에서 담쟁이덩굴이 가장 많이 증가하였으며, 엽록소 b와 a의 비에서는 쇠뜨기, 카로테노이드와 총 엽록소의 비에서는 계요 등에서 가장 많이 증가하였다. 덩굴식물과 덩굴식물이 아닌 쇠뜨기, 쑥의 비교에서는 엽록소 b와 엽록소 a의 비에서 확실한 차이를 보였다. 엽록소 a와 b의 비에서보면 엽록소 b보다 엽록소 a가 더 민감한 차이를 보였으며, 수종에서는 담쟁이덩굴, 덩굴식물과 덩굴식물이 아닌 쇠뜨기, 쑥의 비교에서는 덩굴식물이 민감한 것으로 나타났다. SOD 활성에서는 100 ppb 처리구에서 덩굴식물류 7수종과 쇠뜨기, 쑥의 처리전과 처리후의 차이는 쑥에서 3535.7 unit/g로 매우 크게 증가하였으며, 계요 등이 109.3 unit/g로 가장 적게 증가하였고, 개머루 한 수종에서 131.7 unit/g로 감소했다.

• 한국농공학회지
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• 제31권4호
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• pp.96-110
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• 1989

To suggest the fundamental data for the estimation of crop evaportranspiration by the ca- lculated coefficients for estimating the radiation suitable to the different regions of korea in application of Penman equcation, the daily data such as sc(skycover), n(actual sunshine hours), N(possible sunshine hours), Rs(horizontal solar radiation) and Ra(extraterrestial solar radiation) for 10 years (from 1977 to 1986) collected from 19 meteorological stations were analysed. The results are summarized as follows : 1. The coefficients a, b and c for estimating the radiation taken by the regression method with the daily and monthly mean data of the skycover and the ratio of Rs to Ra were shown as a=0.619, b= -0.0202, c= -0.0023 and a=0.64, b=0.0377 c=0.0001 in ave- rage respectively. 2. The coefficients a and b for estimating the radiation analysed by the regression and arithmetic method from the daily ratio of sunshine hours and Rs to Ra were shown as a= 0.157, b= 0.529, and a=0.119, b= 0.726 in average, respectively. 3. The coefficients a and b for estimating the radiation calculated by the regression me- thod based on the monthly ratio of sunshine hours and radiation were shown as a=0. 319 and b= 0.557 in average. 4. The values of a and b for estimating the radiation taken from the relationship between the daily ratio of sunshine hours and radiation showed high significance level. 5. The standard deviation and the coefficient of variance between the radiation calculated from the coefficients by the regression and arithmetic method with the daily data and the actual radiation were analysed and compared to the results by the coefficients of the modified Penman method (a=0.18, b=0.55) and by those of the F.A.O inodified Penman method(a=0.25, b=0.5). The standard deviation and the coefficient of varia- nce by the regression method in this study showed the lowest value. 6. From the above results, it is suggested that regression method using the coefficients taken from the relationship between the ratio of sunshine hours and the ratio of radia- tion based on the daily data has the highest accuracy in estimating the radiation. 7. The average reference crop evapotranspiration estimating by the modified Penman me- thod using the coefficients a and b derived by the regression method from the daily meterological data was closer to the actual evapotsranspiration of grass measured in Suwon area than the estimated evapotranspiration by the modified Penman method and the F.A.O modified Penman method.

• Journal of Mechanical Science and Technology
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• 제18권11호
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• pp.1932-1940
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• 2004

Although the previous researches evaluated the fatigue behavior of Al/GFRP laminates using the traditional fracture mechanism, their researches were not sufficient to do it : the damage zone of Al/GFRP laminates was occurred at the delamination zone instead of the crack-metallic damages. Thus, previous researches were not applicable to the fatigue behavior of Al/GFRP laminates. The major purpose of this study was to evaluate delamination behavior using the relationship between crack length (a) and delamination width (b) in Al/GFRP laminate. The details of investigation were as follows: 1) Relationship between the crack length (a) and the delamination width (b), 2) Relationship between the delamination aspect ratio (b/a) and the delamination area rate ((A$\_$D/)/subN// (A$\_$D/)$\_$All/), 3) The effect of delamination aspect ratio (b/a) on the delamination shape factor (f$\_$s/) and the delamination growth rate (dA$\_$D// da). As results, it was known that the delamination aspect ratio (b/a) was decreased and the delamination area rate ((A$\_$D/)$\_$N// (A$\_$D/)$\_$All/) was increased as the normalized crack size (a/W) was increased. And, the delamination shape factors (f$\_$s/) of the ellipse-II(f$\_$s3/) was greater than of the ellipse-I(f$\_$s2/) but that of the triangle (f$\_$s1/) was less than of the ellipse-I(f$\_$s2/).