• 한국환경과학회지
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• 제9권2호
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• pp.125-129
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• 2000

As one of the fundamental survey to evaluate purification capacity of pollutants at the tidal flat sediments, we studied vertical environmental characteristics in three tidal flat sediments, Chunjangdae, Eueunri and Gyewhado. These are dissmilar to external feature in each other. The results of this study may be summarized as followed; As the results of particle analysis, Eueunri tidal flat fediment located in Keum river estuary consists of 98.98% as silt & clay, Chunjangdae tidal flat sediment located in SeocheonGun consists of 97.99% as sand. And Gyewhado tidal flat sediment located in Saemankeum in Saemankeum area consists area consists of 32.81% as silt & clay and 67.19% as sand. The concentration of organic pollutants(I.L., COD, POC, PON) in Eueunri tidal flat sediment which highly content of silt & clay were 3~4 times higher than others. The concentration of organic pollutants at each layer were slightly increase goes with deepen layer. The linear correlation between I.L. and COD, POC, PON were obtained. Correlation coefficients were in range of 0.821~0.940. Also the correlation between pH and COD, POC, PON were high(>r=0.9). Filteration rate in Chunjangdae tidal flat sediment was 0.01584cm/s as mean value, but the other were almost nothing filtered off.

• 한국환경과학회지
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• 제10권5호
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• pp.315-321
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• 2001

This study was conducted to estimate the decomposition capacity for organic matter by microbe of tidal flat sediments (Hajae, Dongjin and Mankyung). The decomposition rate constants (K') have been determined by Thomas slope method and compared with the values of each tidal flats. The decomposition rates of organic matter by microbe were initially very slow, but at the end of 12 hours, very sharply increased. The values of decomposition rate constant for Dongjin, Mankyung and Hajae tidal flat sediment were 1.364$day^{-1}$/, 1.080d$day^{-1}$ and 0.735$day^{-1}$, respectively. The decomposition rate constant of Dongjin tidal flat sediment which affected by livestock wastewater was higher than others. The decomposition quantity (mg/g/day) of organic matter by microbe of tidal flat sediments was 0.4mg/g/day for Dongjin, 0.36mg/g/day for Mankyung and 0.36mg/g/day for Hajae. The average of decomposition quantity was 0.37mg/g/day. To calculate purification capacity (kg/ha) of organic matter by microbe, we applied to two assumption ; 1) biological action by microbe is occur within 0.1cm under surface 2) specific gravity of sediment are 2.5g/$\textrm{cm}^2$. The purification capacity of organic matter by microbe of tidal flat sediment was calculated to 9.25kg/ha. The relationships between decomposition rate constant (K') and ignition loss (I. L), chemical oxygen demand by sediment (CO $D_{sed}$), total carbon(TC), silt and clay as index of organic matter were a high positive($R^2$=0.97~1.00).

• 대한치과보철학회지
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• 제8권1호
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• pp.80-84
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• 1968

Observing the morphology of the incisal edges, the time of the loss of mamelon, the decrement rate of the mamelon and the increment rate of the flat edges in the lower incisors among 576 Korean from 7 to 16 years old, the author obtained the following results; 1) The morphology of the incisal edges of the lower incisors immediately after completing eruption is as follows; The lower central incisors show that three nodule is around 65%, flat edge is around 27%, two nodule is around 7% and the central prominence of the incisal edge is 2% The lower lateral incisors show that three nodule is around 23%, flat edge is 24.5%, two nodule is 4 to 12% and the central prominence of the incisal edges around 44%. 2) The loss of mamelon may start at the age of 10. 3) The decrement rate of the mamelon beyond 12 years old is above 80% in the lower central incisors and 70% in the lower lateral incisors. 4) The increment rate of the flat edges beyond 11 years old is above 170% in the lower central incisors and 30% in the lower lateral incisors. 5) None of significant differences are found between right and left sides.

• KIEAE Journal
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• 제13권6호
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• pp.93-98
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• 2013

The purpose of this study is to analyze the rate of opening windows that makes residents of a flat-type apartment feel pleasant in summer time. A few conditions were simulated on the wind flow that pass through internal and external spaces of the flat-type apartment, utilizing CFX program. The simulation was made with the criteria for the rates of opening window at 20%, 50%, 70% and 100%. When the rate of window opening was more 50%, the wind speed(more than 1m/s) that makes the residents feel pleasant was observed in more 60% of the internal space. When the all windows of the apartments were opened, the heat island phenomenon was almost disappeared and the pleasant wind flow was more evenly distributed in the external spaces. If residents of apartments recognize the result of this study and practice in agrement on opening windows in summer, it is expected to contribute to minimizing the energy consumption for air conditioning.

• 한국통신학회논문지
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• 제41권2호
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• pp.229-237
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• 2016

본 논문의 목적은 국내 이동통신시장에서 발생가능한 대표적인 인식편향(cognitive bias) 중 하나인 단위편향(unit bias) 현상의 발생 여부를 실증적으로 분석하고, 단위편향 발생을 최소화하기 위한 바람직한 요금제 개선방안을 제시하는 것이다. 분석 결과 이용자들은 정액요금제하에서 단위편향적 소비행태 발생에 따라 자신의 최적소비량보다 많은 통화량 혹은 데이터량을 사용함으로써 자신의 효용극대화를 위한 최적 통신비 지출보다 많은 통신비를 지출할 가능성이 높은 것으로 나타났다. 따라서 정액요금제의 요금구간을 보다 세분화함으로써 소비자들이 단위편향 발생에 따른 비합리적 소비를 최소화하고 자신의 효용함수에 따라 최적 소비량을 이용토록 마련하여 가계통신비 절감은 물론 소비자 후생을 극대화할 수 있도록 유도하는 것이 가능할 것으로 기대된다.

• 한국패류학회지
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• 제15권1호
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• pp.21-30
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• 1999

본 연구는 1994년 6월부터 1995년 7월까지 광양만의 조화조간대와 덕산조간대에 서식하는 바지락(Ruditapes philippinarum: Bivalvia)의 성장 양상을 알아보기 위하여 수행되었다. 조화조간대의 평균입도, 표층퇴적물내 유기물 함량, 저서미세조류의 엽록소-a 량은 각각 2.50-4.46 , 4.99-5.11%, 14.53-19.90 $\mu\textrm{g}$ $cm^{-3}$이었으며, 덕산조간대는 각각 0.83-1.66 , 2.22-2.34%, 6.20-6.90 $\mu\textrm{g}$ $cm^{-3}$이었다. 바지락의 각장은 봄-여름에 급격히 증가하였고, 가을로 가면서 서서히 둔화되다가, 겨울에 멈추었다. 반면에 육질부 중량은 봄과 가을에 증가하고, 여름과 겨울에 감소하였다. 상태지수 역시 육질부 중량과 동일한 경향을 보였다. 4개 연령군의 각장의 연성장은 von Bertalanffy 성장모델에 잘 적용되었고, 중량은 Gompertz 성장모델에 잘 적용되었다. 초기 각장 성장률 w, 최대 각장 성장률 AGR$_{max}$는 조화조간대가 덕산조간대보다 높았으며, 동일 조간대내에서는 하부조간대가 상부조간대보다 성장률이 높았다. 즉 개체군 서식밀도가 높은 조화조간대에서 이용가능한 잠재적 먹이량, 서식공간에 대한 경쟁이 심하여 개체 성장률이 낮았다.

• 대한기계학회논문집B
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• 제28권3호
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• pp.281-288
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• 2004

Combustion using oxygen enriched air is an energy saving technology that can increase thermal efficiency by improving the burning rate and by increasing the flame temperature. Flame figures, OH radical intensities, temperature distributions and emissions concentration were examined according to oxygen enriched concentration(OEC) in a turbulent diffusion flat flame. As long as the oxygen enriched concentration was increased, the length and volume of the flat flame was decreased while OH radical intensity was raised and the flame temperature was increased. However, RMS of the fluctuating temperature was decreased, and more homogeneous temperature field was formed. Thermal NO also was increased with increase of oxygen enriched concentration, but CO was decreased due to the increase of chemical reaction rate.

• 대한치과재료학회지
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• 제45권4호
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• pp.275-286
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• 2018

본 연구에서는 근관 내의 주사침 말단의 위치, 근관 세척액의 주입 속도, 주사침 말단의 형상이 근관 세척 시 발생하는 치근단 압력에 미치는 영향을 평가하고자 하였다. 5개의 사람 하악 소구치에 근관 와동 형성 후 #35(0.06 taper) 니켈-티타늄 회전식 기구로 근관을 형성하였다. 주사침 말단의 형상에 따라 구분되는 notched, side-vented, flat 3가지 종류의 주사침을 근단 협착부로부터 치관 방향으로 1, 3, 5 mm 거리가 되는 지점(주사침 말단의 위치)에 위치시켰다. 각 군에 대하여 세척액 주입 속도는 0.05, 0.1, 0.2, 0.3 ml/s로 변화시키면서 치근단 압력을 측정하였다. 나머지 조건이 동일한 경우 주사침 말단의 위치가 감소할수록, 세척액 주입 속도가 증가할수록 치근단 압력은 유의하게 증가하였다(p<0.05). 주사침 말단의 위치와 세척액 주입 속도가 동일한 조건 하에서 side-vented 주사침이 가장 낮은 치근단 압력을 보였고, notched, flat 주사침 순서로 치근단 압력이 유의하게 증가하였다(p<0.05). 주사침 말단의 위치가 1 mm인 군 또는 세척액 주입 속도가 0.1 ml/s 이상인 군에서는 나머지 조건에 관계없이 모든 경우에서 중심정맥압(5.88mmHg)보다 높은 치근단 압력을 나타냈다. Flat 주사침은 세척액 주입 속도와 주사침 말단의 위치에 따른 치근단 압력의 급격한 증가로 인해 임상에서 사용이 추천되지 않으며, 안전하고 효율적인 근관 세척을 수행하기 위해서는 근단 협착부로부터 치관 방향으로 3 mm 떨어진 지점에 주사침 말단을 위치시키고 0.05 ml/s 이하의 세척액 주입 속도로 근관 세척액을 적용해야 할 것이다.

• 한국연초학회지
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• 제20권2호
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• pp.139-143
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• 1998

The occurrence and physico-chemical properties of flat leaves found in 1997 curing trial related to the prevention of occurrence of flat leaves at bulk curing of flue-cured tobacco were investigated and compared with those of normal leaves. Cured leaves of NC82 were separated into 4 classes of none, slight, fair and severe symptoms of flat leaf by the percentage of flattened parts to whole leaf area. The flat leaves were mostly found among the leaves of lower stalk position, and it was estimated that growth rate of lower leaves also influenced on the occurrence of flat leaves. In chromatic aberration of cured leaf, flat leaves showed remarkably lower b and L values than in those of normals but there was no difference in a value. On the other hand, in chemical analyses of flat leaf samples, nicotine, total sugar, ether extract and total nitrogen contents were decreased with the degree of flat symptoms. In physical properties, filling capacity of cured leaves was decreased with the degree of flat symptoms comparing with those of normal leaves, while shatter index was showed a reverse tendency, and then within the same leaf, flat parts were decreased in total sugar, ether extract and filling capacity compared with those of normal ones, but remarkably increased in shatter index, and there was no difference in nicotine and total nitrogen contents.

• 설비공학논문집
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• 제1권1호
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• pp.73-81
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• 1989

The purpose of this study is augmentation of heat transfer without additional power in a rectangular impinging air jet. As a method of passive heat transfer augmentation in a two-dimensional air jet, heat transfer surface of flat plate with rods is used. This study, particularly in the wall jet rigeon, investigates the effect of the clearance between the flat plate and rod. Mechanism of heat transfer enhancement is investigated by measuring the local heat transfer coefficient. It is concluded that the superposition of the effects of flow accelerlation through the clearance between the flat plate and the rod, and reattachment of the flow was the cause of the excellent performance. The overall heat transfer rate of flat plate with rods is about 1.5 times larger than that of flat plate without rods.