• 한국수자원학회논문집
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• 제42권8호
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• pp.659-671
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• 2009

본 연구에서는 레이더 강우량 자료의 편차보정에 사용되는 G/R비의 정확도를 향상시키기 위하여 fuzzy c-means 방법을 사용한 자료의 군집화를 적용하였다. 대상 레이더자료는 광덕산 레이더기지의 자료로서 유효범위 100km이내의 자료를 대상으로 지상관측망인 기상청의 AWS(Automatic Weather System) 지점에서 관측한 자료와의 비교를 통하여 G/R비를 구하였다. G/R비를 구하는데 있어서 전체 유효범위를 대상으로 동일한 방법을 사용한 경우와 레이더 자료의 군집화를 통해서 지형적인 효과를 고려한 경우를 비교하였으며, AWS 실측강우량과 G/R비를 통한 레이더 강우량 자료의 비교를 위하여 절대상대오차와 평균제곱근오차 등을 비교분석하였다. 그 결과 전체유효범위를 대상으로 동일하게 G/R비를 적용하여 구한 레이더 강우량에 비하여 군집분석을 이용하여 지형효과를 고려한 G/R비를 적용한 레이더 강우량의 오차가 더 적게 나타났다.

• 한국방재학회 논문집
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• 제11권3호
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• pp.17-28
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• 2011

본 연구에서는 초단기 예측강우의 편의(bias) 보정을 목적으로 G/R 비의 실시간 예측에 칼만 필터를 적용하였다. 초단기 예측강우로는 MAPLE 예측강우를 사용하였고, 강우의 임계치와 누적시간에 따른 G/R 비의 특성변화를 검토하여 G/R 비 산정방법도 개선하였다. 이러한 분석을 내륙, 산악, 해안 지역에 각기 적용하여 지역적 차이가 비교될 수 있도록 하였다. 결과적으로 강우의 임계치와 누적시간의 고려를 통해 안정화된 G/R 비의 산정이 가능하였으며, 이를 이용함으로서 예측 G/R 비의 정확성이 보다 향상되었다. 예측 G/R 비로 보정된 초단기 예측강우의 정도는 지역별로 내륙지역이 가장 우수한 것으로 나타난 반면에 해안지역에서 제일 열악한 것으로 나타났다.

• 한국물환경학회지
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• 제21권6호
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• pp.687-694
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• 2005

Lab-scale experiments have been carried out to investigate the effect of F/R ratio of ASBR (Anaerobic Sequencing Batch Reactor) process on the removal of the organic matters in ammonia stripped swine wastewater. Three ASBR inoculated with sludge mixed with granular sludge of UASB (Upflow Anaerobic Sludge Blanket) and anaerobic digested sludge of municipal wastewater treatment plant were operated. Ammonia stripped swine wastewater was used as influent. Prior to conducting the experiments with varied conditions, the effect of increasing organic loading rate from 2.34 to $5.79gTCOD_{Cr}/L$-day at a fixed F/R ratio of 0.1 on the organic removal efficiency has been studied during start-up period. As the result of the experiment, under the condition of varied organic loadings, less than $4.14gTCOD_{Cr}/L$-day, the removed efficiency $TCOD_{Cr}$ of the ASBR process is 83% resulted from the mean value of effluent $TCOD_{Cr}$, 9,125 mg/L during the start-up period. Then ASBRs were operated with F/R ratio of 0.024, 0.303 and 0.91 respectively. Organic loading rate was increased from 4.56 to $15.43gTCOD_{Cr}/L$-day to investigate the effects of F/R ratio and organic loading rate on the organic removal efficiency. As the result of the experiment, less than $6.23gTCOD_{Cr}/L$/L-day, F/R ratio haven't an effect on the organic removal efficiency and the mean removal efficiency of TSS, $TCOD_{Cr}$ and $SCOD_{Cr}$ was about 80%, 86% and 78% at the all of F/R ratio. But as organic loading rate was increased from 8.54 to $12.04gTCOD_{Cr}/L$-day at the F/R ratio of 0.024, the removal efficiency of $SCOD_{Cr}$ decreased from 71% to 63%. The range of decreased removal efficiency of $SCOD_{Cr}$ at the F/R ratio of 0.024 was much more higher than at the F/R ratio of 0.303, 0.91. Thus, as organic loading rate was increased, ASBRs were operated with high F/R ratio to obtain high removal efficiency.

• 공업화학
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• 제25권3호
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• pp.318-323
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• 2014

랜덤 폴리프로필렌(random polypropylene, rPP)의 무수말레인산(maleic anhydride, MAH) 반응압출에 대한 MAH 함량 및 스티렌/MAH 몰비의 영향을 고찰하기 위해 이축압출기(twin screw extruder)를 이용하여 MAH가 그라프트된 rPP(MAH-g-rPP)를 제조하였다. MAH의 함량은 0.5, 1.0, 3.0, 5.0 phr이었고, 스티렌/MAH 몰비는 0, 1, 2로 하였으며, 개시제로는 dicumyl peroxide (DCP)가 사용되었다. MAH의 그라프트 정도는 FT-IR을 이용하여 $1700cm^{-1}$ 근처에서 나타나는 카르보닐기(C = O) 신축진동 피크의 존재 여부를 통해 확인하였으며, $3000cm^{-1}$ 근처의 C-H 신축진동을 기준으로 하여 정량한 결과 그라프트 반응이 MAH 함량이 3.0 phr까지 증가하는 경향을 보여주었고, 스티렌 몰비는 1.0일 때 최적을 나타내었다. MAH-g-rPP와 MAH-g-rPP가 5.0 phr 포함된 PP/MAH-g-rPP/pulp 복합체의 열적특성, 결정화 특성 등을 시차주사열용량분석기(DSC), 열중량분석기(TGA), X-선 회절분석(XRD), 편광현미경(POM) 등을 이용하여 관찰하였다. 비등온 결정화온도는 rPP-g-MAH가 첨가되었을 때 감소하는 경향을 나타내었고, PP/MAH-g-rPP/pulp 복합체의 인장특성과 인장시험 후 파단면의 SEM을 측정한 결과, MAH 함량 1.0 wt%, 스티렌/MAH 몰비 1.0일 때 상용화제로의 역할이 가장 우수한 것으로 나타났다. 복합체의 가공성 비교를 위해 복소 점도와 전단박하(shear thinning) 정도를 동적유변측정기를 이용하여 측정하였다. 상용화제를 가지는 복합체의 경우 낮은 멱수 법칙 지수(n)를 보여주었다.

• 대한토목학회논문집
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• 제31권5B호
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• pp.393-403
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• 2011

본 연구에서는 현재까지 경험적인 방법으로 적용되어 왔던 G/R 비를 선형 회귀선, 원점을 통과하는 선형 회귀선 및 원점과 관측자료의 무게중심을 지나는 추세선 등으로 구분하여 이론적으로 검토하였다. 이러한 검토에는 독립변수로 어떤 강우자료를 선택하느냐에 따른 문제와, 무강우 자료의 고려여부에 따른 영향 검토가 포함되었다. 이렇게 검토된 내용은 2003년에 발생한 태풍 매미 사상에 적용하여 평가하였다. 마지막으로 본 연구에서 유도된 회귀선 및 추세선을 이용한 레이더 강우의 보정결과와 관측된 우량계 강우 사이의 RMSE를 비교함으로서 최적의 G/R 비를 선정하였다. 그 결과는 다음과 같다. 먼저, 독립변수로 레이더 강우를 사용하는 것 보다는 우량계 강우를 사용하는 경우에 레이더 강우의 보정결과가 우수한 것으로 나타났다. 둘째, 무강우 자료의 영향은 레이더 및 우량계 자료의 구조에 따라 다르게 나타나는 것으로 확인되었다. 마지막으로 유도된 선형 회귀선 및 추세선의 평가 결과, 홍수 유출해석을 주목적으로 한 경우에는 독립변수에 우량계 자료를 적용하여 유도된 원점을 통과하는 선형 회귀선의 기울기를 G/R 비로 사용하는 것이 무난할 것으로 나타났다. 이 경우 무강우 자료의 영향은 상대적으로 미미한 것으로 나타났다.

• Journal of Information Technology Applications and Management
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• 제12권1호
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• pp.231-239
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• 2005

This paper describes a new algorithm for pixel-based skin color detection to differentiate human form in color images by the ratio of R to H. In order to detect skin color efficiently, we examine the distribution of the R, G and B color elements combining to constitute the skin color in various color images. It shows that R is located in a narrower area than G and B on the RGB color space. And skin color is more related to R than G and B. Meanwhile, when the color image is transformed to the HSI color space, the S is variously changed in accordance with skin colors. The I is changed in accordance with the quantity and angle of light. But the H is less influenced by other conditions except for color. On the basis of the aforementioned study, we propose that the threshold for skin color detection is decided by the ratio of R to H. The proposed method narrows down the range of threshold, detects more skin color and reduces mis-detection of skin color in comparison to detection by R or H. In experimentation. it shows that the proposed algorithm overcomes changes of brightness and color to detect skin color in color images.

• 한국가정과학회지
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• 제4권1호
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• pp.36-45
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• 2001

This study was performed to determine the changes of maternal iron status during pregnancy cross sectionally, and to evaluate the appropriateness of the cut-off points of hemoglobin (Hb). hematocrit (Hct), serum transferrin receptor (sTfR) and sTfR : ferritin ratio for assessing iron deficiency status based on serum ferritin level (< 12${\mu}g$/L). Serum Hb concentrations in the first trimester were significantly higher (p < 0.05) than those in the second and third trimester. Serum levels of iron and ferritin in the third trimester were significantly lower (p < 0.05) than those in the first and second trimester. On the other hand, sTfR:ferritin ratios in the third trimester were significantly higher (p < 0.05) than those in the first and second trimester. sTfR concentrations did not change significantly during pregnancy. The appropriate cut-off points of Hb were 11.5g/dL for whole period of pregnancy. 12.0g/dL for 1st trimester. and 11.5g/dL for both 2nd and 3rd trimester. The good cut-off points of Hct were 34% for whole period of pregnancy. 36% for 1st trimester. and 34% for both 2nd and 3rd trimester The suitable cut-off points of TIBC were 400${\mu}g$/dL for whole period of pregnancy. 360${\mu}g$/dL for 1st trimester, and 400${\mu}g$/dL for both 2nd and 3rd trimester. Any cut-off point of sTfR could not be selected because of its low sensitivity and specificity. The proper cut-off point of sTfR : ferritin ratio was 600 or 650 for all the periods determined except the first trimester. In conclusion, there were no reliable cut-off levels of sTfR and those of sTfR : ferritin ratio showed low specificity. The cut-off values of Hb and Hct for assessing iron deficiency were slightly higher than the values used to evaluate anemia. Thus, if appropriate cut-off levels were applied, Hb. Hct, or TIBC might be useful indices for evaluating iron deficiency as well as anemia.

• 한국주조공학회지
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• 제25권1호
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• pp.30-35
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• 2005

The structures and mechanical property of the unidirectionally solidified Al-Co eutectic alloy were investigated. Al-Co eutectic alloy was unidirectionally solidified with growth rates(R) between I cm/hr and 10 cm/hr in the induction furnace maintaining the thermal gradient (G) at solid-liquid interface, $32^{\circ}C$/cm. The eutectic microstructure was varied with the growth condition(G/R ratio). When the G/R ratio was larger than $8.5{\times}10^{3}^{\circ}C/cm^{2}/sec$, a lamellar structure was formed, But the G/R ratio was smaller than $8.5{\times}10^{3}^{\circ}C/cm^{2}/sec$, a colony structure was formed. It was found that the interlamellar spacing(${\lambda}$) was dependent on the growth rate(R) with the relationship, ${\lambda}^{2}{\cdot}R=constant$. The microhardness of this eutectic alloy increased with increase in the growth rate.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1996년도 가을 학술발표회 논문집
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• pp.283-289
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• 1996

In this paper, the mix design of the super flowing concrete is described with respcet to basic concept, confined water ratio($\beta_p$), volume ratio of water-binder(w/b), volume ratio of fine aggregates($S_r$) and coarse aggregates($G_v$). The primary purposes of this study are to evaluate the effects of cementitious materials(fly ash, slag cement, portland cement), mixing factors ($\beta_p$, w/b, $S_r$, $G_v$)., and to propose the mix design method of the super flowing concrete. As results of this study, confined water ratio($\beta_p$) of cementitious materials is very high (0.99~1.1), and then the ranges of the optimum mixing factors to be satisfied with the super flowing concrete are $S_r$ 47$\ell$ 2%, $G_v$ 52$\ell$ 1%.

• 한국환경과학회지
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• 제5권1호
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• pp.93-102
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• 1996

Hydrodynamic characteristics such as gas holdup, liquid circulation velocity and bed expansion in a hexagonal inverse fluidized bed were investigated using air-water system by changing the ratio ($A_d$/$A_r$) of cross-sectional area between the riser and the downcomer, the liquid level($H_1$/H), and the superficial gas velocity($U_g$). The gas holdup and the liquid circulation velocity were steadily increased with the superficial gas velocity increasing, but at high superficial gas velocity, some of gas bubbles were carried over to a downcomer and circulated through the column. When the superficial gas velocity was high, the $A_d$/$A_r$ ratio in the range of 1 to 2.4 did not affect the liquid circulation velocity, but the maximum bed expansion was obtained at $A_d$/$A_r$ ratio of 1.25. The liquid circulation velocity was expressed as a model equation below with variables of the cross-sectional area ratio($A_d$/$A_r$) between riser to downcomer, the liquid level($H_1$/H), the superficial gas velocity($U_g$), the sparser height[(H-$H_s$)/H], and the draft Plate level($H_b$/H). $U_{ld}$ = 11.62U_g^{0.75}$${(\frac{H_1}{H})}^{10.30}$${(\frac{A_d}{A_r})}^{-0.52}$${(\frac({H-H_s}{H})}^{0.91}$${(\frac{H_b}{H})}^{0.13}$