• 한국초등과학교육학회지:초등과학교육
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• 제19권1호
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• pp.145-156
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• 2000

Elementary school teachers' understandings about buoyancy were investigated through the questionnaire method. The questionnaire was composed of 4 questions on hydraulic pressure and 8 questions on buoyancy. The questions on buoyancy asked about the correlation of buoyancy with following basic concepts, density of liquid, volume of submerged object and so forth. 295 teachers on the 22 elementary schools in Busan, Yangsan and Gimhae were selected through random sampling method. The results of this study were summarized as follows: On the correlation of the magnitude and direction of hydraulic pressure with the depth of water, a large portion of the respondents had a scientific conception. But on the correlation of hydraulic pressure with density, the relatively small portion of them appeared to have a scientific conception. The respondents, on the whole, had a scientific conception about the correlation of buoyancy with density of liquid. But they seemed to have naive conceptions about the correlation of buoyancy with the volume of a submerged object and with the depth of water, the amount of water in container and the reduced amount of water by the object from container. We found that the respondents were context dependent and tended to search for solutions for the questions of buoyancy using the concept of pressure in the water. From above results, we suggested that in the would-be revised elementary science text book, the contents of pressure in the water should be introduced after the concept of weight in the water was gained.

• 조명전기설비학회논문지
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• 제29권3호
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• pp.54-60
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• 2015

There are 5 purification plants with the adopted advanced water purification treatment process in Korea. Annual operating costs were 8,990 million won including purchase cost of oxygen and power usage charges. We need research to optimize, in the future, when considering the direction of domestic water treatment continues to adopt advanced water treatment process. In this paper, calculate the optimal operating costs by injected the oxygen gas, used power cost. approximately 25% of the operating costs can be reduced when injected the ozone gas is 1.0ppm than 2.0ppm, the necessary amount of oxygen is increased then power is lower. so operating costs are decided according to oxygen costs. On the other hand, high ozone concentration 2.0ppm, the necessary power is increased then amount of oxygen is lower. Therefore, in the case of G purification plant, the controlling factor of the input ozone concentration 2ppm, PID control operation by setting the concentration of over 10Wt% is efficient. The installed capacity is the more little the more better when considering on Ozone injection rate in the process of water treatment.

• Asian-Australasian Journal of Animal Sciences
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• 제7권1호
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• pp.97-101
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• 1994

Two experiments were conducted to study the effect of ambient temperature and nicarbazin on SCWL adult roosters. In Experiment 1, the effects of nicarbazin supplementation (125 ppm) on the water metabolism, blood acid-base balance; and rectal temperature of 16 birds in normal ($21^{\circ}C$) and hot ($35-36^{\circ}C$) temperature were investigated. In Experiment 2, the evaporative water loss and $CO_2$ exhalation from 8 birds were measured individually with an open-circuit gravimetric respiration apparatus in normal ($21^{\circ}C$) and hot ($33.5-34^{\circ}C$) temperature. The amount of water intake and evaporative water loss increased in birds under heat stress (HS). Nicarbazin exacerbated these effect in hot temperature. Also, nicarbazin decreased the blood $pCO_2$ and increased pH of HS birds. The rectal temperature of birds increased in hot temperature, and nicarbazin worsened this effect. The evaporative water loss, measured directly with respiration apparatus (Experiment 2), was increased in hot temperature. HS decreased the amount of $CO_2$ exhalation. Nicarbazin did not exert ant effect on either of these measurements, probably due to the limited duration (2 h) of the trial. The decrease in $CO_2$ exhalation by HS birds could be explained by reduced metabolic rate, which helps homeothermy of birds in hot temperature.

• 한국토양비료학회지
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• 제48권5호
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• pp.477-484
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• 2015

Environmental effect of water-saving irrigation on the emissions of greenhouse gases (GHGs) has not been well investigated. The objective of this study was to measure the effect of water-saving irrigation on GHGs as well as water use and rice production yield in paddy field condition in Korea. Four experimental runoff plots of 4x35 m in size were prepared at an existing paddy field. GHGs emission was measured during the 2012~2013 growing seasons while a Japonica rice variety was cultivated. Four different water management methods, 1) Continuous Flooding (CF), 2) Intermittent Drainage (ID), 3) Water Saving (WS), and 4) CF+WS, were used during a rice growing season to compare the effects of water management methods on GHGs emission. CF method is flooding all the time, ID method makes paddy water drained 40 days after transplanting for about two weeks, WS method maintains 2~3 cm water-level, which should be refilled when the water-level decreased to about 0 cm, and CF+WS method combines CF method before 30 days after transplanting (DAT) and WS method after 30 DAT. Regardless of water management methods, paddy field water was drained about 30 days before harvest. Amount of GHGs emission from WS plot was reduced by 69.3% compared to that from CF plot and by 59.0% compared to that from ID plot. Amount of GHGs emission from CF+WS plot was reduced by 60.7% compared to that from CF plot and by 47.5% compared to that from ID plot. Weed occurrence in CF+WS plots was reduced to 62.2% in comparison with the WS plot, implying that CF+WS plot showed the best effect to mitigation of the greenhouse gas emission in the atmosphere.

• 상하수도학회지
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• 제26권5호
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• pp.619-627
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• 2012

In order to determine reduction of greenhouse gas emissions (GHGs) when the submerged membrane bioreactor with granular sulfur (MBR-GS) is used in wastewater treatment plant (WTP), the amount of GHGs was compared and analyzed in the advanced treatment process of P wastewater treatment plant (WTP). The amount of GHGs was estimated by classifying as construction and operation phase in WTP. The amount of GHGs in construction phase was evaluated from multiplying raw materials by using carbon emission factors. Also the amount of GHGs in operating phase was calculated by using total electricity consumption and carbon emission factor. The construction of anoxic tank and secondary settling tank is unnecessary, because the MBR-GS conducts simultaneously the nitrification and denitrification in aeration tank and filtration by hollow fiber membrane. The amount of $CO_2$, $CH_4$, and $N_2O$ emitted by constructing the MBR-GS was 6.44E+06 kg, 8.16E+03 kg and 1.38E+01 kg, respectively. The result shows that the GHGs was reduced about 47 % as compared with the construction in the MLE process. In operating the MBR-GS, the electricity is not required in the biological reactor and secondary setting tank. Thus, the amount of $CO_2$, $CH_4$, and $N_2O$ emitted by operating in the MBR-GS was 7.39E+05 kg/yr, 5.80E+02 kg/yr and 2.44E+00 kg/yr, respectively. The result shows that the GHGs were reduced about 37 % as compared with the operation in the MLE process. Also, $LCCO_2$(Life Cycle $CO_2$) was compared and analyzed between MLE process and MBR-GS. The amount of $LCCO_2 $emitted from the MLE process and MBR-GS was 3.56E+04 ton $CO_2$ and 2.12E+04 ton $CO_2$, respectively. The result shows that the GHGs in MBR-GS were reduced to about 40 % as compared in the MLE process during life cycle. As a result, sulfur-utilizing autotrophic denitrification process (SADP) is expected to be utilized as the cost-effective advanced treatment process, owing to not only high nitrogen removal efficiency but also the GHGs reduction in construction and operation stage.

• Preventive Nutrition and Food Science
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• 제9권3호
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• pp.199-205
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• 2004

The effect of chitosan on enzymatic activities and on bioactive compounds was characterized during germination at $25^{\circ}C$ for 7 days to search for a method to produce a germinated black rice. The germination rate was reduced by the addition of lactate and chitosan. The rotting rate was greatly decreased by chitosan, suggesting that the addition of chitosan into a germination solution might be an effective method for controlling fungal contamination during the germination of cereals. The addition of 100 and 200 ppm chitosan increased $\alpha$-amylase activity after 7 days by up to 152 % and 197 %, respectively. The activities of $\beta$-amylase and $\beta$-glucosidase were lower with 200 ppm chitosan than in distilled water and 100 ppm lactate. The amount of total soluble phenolics and total flavonoids decreased rapidly for four days and thereafter remained constant until the seventh day. The antioxidant activity of germinated black rice, in terms of hydrogen-donating activity, increased slowly and did not correspond to the changes of total soluble phenolics and total flavonoids. The amount of phytic acid was reduced by the addition of 200 ppm chitosan compared to distilled water, indicating that chitosan could be used as an elicitor for the increase of phytase activity during the germination of black rice.

• Bulletin of the Korean Chemical Society
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• 제30권9호
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• pp.2032-2038
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• 2009

The amount of phenol and NaOH for the colorimetric determination of ammonia in Korean standard methods (KSM) is found to be highly excessive compared to the standard methods of several other countries. The absorbance of indophenol formed by the Berthelot reaction for ammonia analysis was measured under the various reaction conditions classified in experiment groups 1, 2, 3, 4 and KSM and American standards methods (ASM), and the relationships between the absorbance of indophenol and concentration of ammonia were compared. The amount of phenol can be reduced to 10 g (current 25 g in KSM) and NaOH can be reduced to 1.76 g (current 11 g in KSM) for the preparation of 200 mL phenate solution, and the absorbance sensitivity increased. The concentration of the phenol and NaOH correlatively affect the pH of the solution, which is a critical variable in achieving the maximum sensitivity and rapid and stable color development.

• 상하수도학회지
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• 제22권5호
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• pp.517-522
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• 2008

This study aims at an assessment of the effectiveness of taste & odor removal and transmembrane pressure changes in a pilot membrane plant(500m3/day) by adding PAC to MF process, and at providing a basis for applying it to the advanced water treatment process. The transmembrane pressure showed, in low turbidity of raw water, a tendency to decrease when PAC was injected at the Flux of 1, $1.5m^3/m^2{\cdot}d$, while it increased in high Flux($1.5m^3/m^2{\cdot}d$) in high turbidity of raw water. in addtion, it is shown that the fouling could be reduced more when PAC is injected together with appropriate amount of coagulant, than when PAC is solely injected. Taste & Odor-causing 2-MIB may not be detected in membrane filtered water, if the amount of PAC injection is increased in accordance with the increasing concentration of 2-MIB. Hence, PAC injection, as a pre-treatment process in MF membrane filtering, is supposed to be a suitable process for reducing fouling as well as for improvement effectiveness of taste & odor treatment.

• Plant Resources
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• 제7권1호
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• pp.69-76
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• 2004

Lettuce (Lactuca sativa L.) is known to contain water-soluble substances that are biologically active. Aqueous or methanol extracts and residues from leaves of lettuce plants were assayed to determine their allelopathic effects, and the causative allelochemicals from fractions were quantified by means of HPLC analysis and bioassayed. Extracts from oven-dried leaf samples were more phytotoxic than those from freeze-dried samples. Leaf extracts of 40 g L$^{-1}$ were completely inhibitory on root growth of alfalfa (Medicago sativa L.), while root growths of barley (Hordeum vulgare L.) and soybean (Glycine max L.) were less sensitive. Early seedling growth of both alfalfa and barnyard grass (Echinochloa crus-galli) was significantly reduced by methanol leaf extracts. The major allelopathic substances analyzed by HPLC were coumarin, trans-cinnamic acid, o-coumaric acid, p-coumaric acid and chlorogenic acid. Of them p-coumaric acid was found as the greatest amount (8.9 mg 100 g$^{-1}$ ) in the EtOAc fraction; only coumarin was found in all the fractions. Hexane and EtOAc fractions of L. sativa reduced alfalfa root growth more than did BuOH and water fractions. These results suggest that lettuce had potent herbicidal activity, and that its activity differed depending on type and amount of causative compounds by fraction.

• 한국물환경학회지
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• 제27권1호
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• pp.36-43
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• 2011

This study is selected two points of combined sewer that occurred Fish Kill after first flush, that analyzed generation of pollutants and stream runoff generation of combined sewer overflows (CSOs) as fine weather and rainfall. In addition, this study was to analyze the relationship between CSOs and sediments, to propose measures to reduce the sediment relevant with CSOs and rainfall runoff from entering sewage treatment plants and measures for discharged directly into streams when indicate relatively good water quality after overflow. Sediments in combined sewer system was discharged about 50~80% as overflows during rainfall and we can reduce the amount of the CSOs at least 50% or more if the sewer does not exist in the sediments because of the amount of discharge about the amount of intercept has been investigated by 3~5 times. Because of velocity at sediment interval in sewer is very low, sewage velocity of about 3~5 times as much as it can increase the amount of sediment can be reduced if the separation wall is installed. Effective control of BOD overflow load is respectively 77.5%, 75.8% at first point, second point by the separation wall is installed. Drainage area greater than area in this study or many combined sewer overflows region is increased the more effective control of separation wall. Turbidity to measure changes in water quality of overflows can be used as an factor to control the intercept flows because the intercept flows(3Q) after the first flush has lowered removal efficiency and increases the operational load of sewage treatment plants. Sewage water quality after a overflow when the reasonable turbidity was measured at this point flows to excluded intercept flow(1Q) can be discharged to stream.