• 상하수도학회지
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• 제34권5호
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• pp.311-321
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• 2020

In this study, a model to optimize residual chlorine concentrations in a water supply system was developed using a multi-objective genetic algorithm. Moreover, to quantify the effects of optimized residual chlorine concentration management and to consider customer service requirements, this study developed indices to quantify the spatial and temporal distributions of residual chlorine concentration. Based on the results, the most economical operational method to manage booster chlorination was derived, which would supply water that satisfies the service level required by consumers, as well as the cost-effectiveness and operation requirements relevant to the service providers. A simulation model was then created based on an actual water supply system (i.e., the Multi-regional Water Supply W in Korea). Simulated optimizations were successful, evidencing that it is possible to meet the residual chlorine concentration demanded by consumers at a low cost.

• 한국물환경학회지
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• 제29권5호
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• pp.618-624
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• 2013

This study was conducted to suggest the concentration distribution of organic matters in 348 tributaries of Nakdong River, and to review the validity of the conversion of organic matter indexes. The average concentration of organic matters in the tributaries was TOC 2.4 mgC/L, DOC 2.1 mgC/L, COD 1.0 mgC/L, respectively. DOC ratio to TOC is 87% and COD ratio is 44%. First tributaries shows higher organic pollution than second tributaries. The correlation between TOC and COD was relatively high as 0.796 (p < 0.01, n = 670). Based upon these results, a regression analysis was conducted. The results showed that TOC concentration was 2.5 times higher than COD concentration. In conclusion, it is appropriate to use TOC for the management of all organic matters. Furthermore, there is a need to build organic matter-related Databases for more rivers so as to establish TOC standards and manage the water quality.

• Transactions on Electrical and Electronic Materials
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• 제13권6호
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• pp.305-309
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• 2012

In this study, ZnO nanorods and $SnO_2$-CuO heterogeneous oxide were grown on membrane-type gas sensor platforms and the sensing characteristics for carbon monoxide (CO) were studied. Diaphragm-type gas sensor platforms with built-in Pt micro-heaters were made using a conventional bulk micromachining method. ZnO nanorods were grown from ZnO seed layers using the hydrothermal method, and the average diameter and length of the nanorods were adjusted by changing the concentration of the precursor. Thereafter, $SnO_2$-CuO heterogeneous oxide thin films were grown from evaporated Sn and Cu thin films. The average diameters of the ZnO nanorods obtained by changing the concentration of the precursor were between 30 and 200 nm and the ZnO nanorods showed a sensitivity value of 21% at a working temperature of $350^{\circ}C$ and a carbon monoxide concentration of 100 ppm. The $SnO_2$-CuO heterogeneous oxide thin films showed a sensitivity value of 18% at a working temperature of $200^{\circ}C$ and a carbon monoxide concentration of 100 ppm.

• 상하수도학회지
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• 제30권6호
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• pp.715-723
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• 2016

This study investigated the effect of high concentration of free ammonia on microalgal growth and substrate removal by applying real wastewater nitrogen ratio. To test of this, the conditions of free ammonia 1, 3, 6, 9, 12, 15 mg-N/L are compared. After 3 days of incubation, algal growth of Chlorella vulgaris and carbon removal rate are respectively lower in the reactors of FA 12, 15 mg-N/L compared to the others. This indicates that the high concentration of free ammonia, in this case, above 12 mg-N/L, has negative effect on algal growth and metabolic activity. Also, high concentration of free ammonia causes the proton imbalance, ammonium accumulation in algae and has toxicity for these reasons. So, we have to consider free ammonia in applying the microalgae to wastewater treatment system by the way of diluting wastewater or controlling pH and temperature.

• 한국환경과학회지
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• 제26권2호
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• pp.147-157
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• 2017

This study investigated the characteristics of variations in carbon dioxide concentration and air temperature with the vertical change of surface in a grassplot. Field observations were carried out at a grassplot in Gyeongnam Science High School, over four days in August and November, 2015. Continuous observation equipment (GMP343, VAISALA) was installed at the LP (0.1 m from the surface) and UP (1.1 m from the surface) points, and the carbon dioxide concentration and air temperature were measured simultaneously at 1-min intervals. To summarize the results of the observation, August had higher than average concentrations of carbon dioxide, while November showed average air temperatures. Moreover, the concentration of carbon dioxide was higher at the UP point, while the air temperature was higher at the LP point. The correlation coefficient of carbon dioxide concentration between the UP and LP points was 0.80 in August across all the four days, while it was higher in November at 0.58-0.95. The results of the regression analysis of carbon dioxide concentration with air temperature changes for both August and November showed a distinct change at the LP point (R2=0.36-0.76), as compared to the UP point (R2=0.1-0.57). Between the UP and LP points, the carbon dioxide concentration and air temperature regression analysis results indicated that an active exchange was taking place between the two points.

• 산업경영시스템학회지
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• 제16권27호
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• pp.27-34
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• 1993

It is requested to promote technology development and productivity that is way to conquer the competition of technology and quality and pressure of cost caused by a rise in prices. To pace up the market fluctution and the deepening of competion, there need a strategical thoughts of production management. Corporation's efforts concentrated in specific business field are desired to insure the initiative competion. In this paper, the concentration aimed at gaining higher competion is analized in the condition of equal enviornment and/or situation.

• Archives of Pharmacal Research
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• 제17권2호
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• pp.76-79
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• 1994

The concentration of styrne in blood of the occupationally syrene-exposed workers was checked by gas chromatographic headspace analysis. Mandelic acd in urine, that is a major metabolite of styrene, and hippuric acid wre also analyzed by high performance liquid chromatography. For the biological monitoring of styrene-exposed workers, the routine method of the quantitative determination of styrene nad its metabolites in the biolgical samples were studied.

• 한국식품저장유통학회지
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• 제14권5호
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• pp.552-556
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• 2007

매실리큐르 제조시 사용되는 알코올 농도에 따른 숙성 중 매실 리큐르의 품질 변화를 비교 검토하였다. 산도의 경우, 알코올 농도 30%, 45% 처리구는 숙성 2개월까지는 농도에 관계없이 상승하는 경향을 보였으나, 그 이후 뚜렷한 변화는 관찰되지 않았으며, pH와 색상은 알코올 농도가 증가할수록 유의적으로 높은 경향을 나타내었다. 환원당 함량은 담금액의 알코올 농도가 증가할수록 증가하였다. 숙성 중 polyphenol 함량은 알코올 농도가 높아짐에 따라 증가하였으며, 각 처리구별 30%와 45% 처리구의 경우 숙성 3개월째 각각 630.6, 686.1 ppm 60% 처리구는 숙성 4개월째 791.1 ppm으로 가장 높은 함량을 나타내었다. 담금액중의 유리당은 fructose, glucose, sucrose, maltose가 검출되었으며, 알코올 농도에 관계없이 sucrose와 maltose에 비해 fructose와 glucose의 함량이 높았다. 매실 리큐르 숙성 중 총 유기산 함량은 알코올 농도가 증가함에 따라 증가하는 경향을 나타내었으며, 알코올 농도와 관계없이 citric, lactic, malic, succinic 및 acetic acid순으로 검출되었다. 고 알코올 매실리큐르의 제조용 주정의 농도는 45%가 적절할 것으로 판단되며, 숙성기간은 2개월이 가장 적절할 것으로 판단되었다

• 대한환경공학회지
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• 제30권10호
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• pp.1013-1020
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• 2008

시화호 인공습지의 오염물질 제거효율을 분석평가하고 수질정화기능의 저하원인을 파악하기 위하여 습지내 16개 지점에서 시공간적 수질분포에 대해 조사하였다. TN을 제외한 오염물질 제거효율은 조성 초기에 비해 낮아졌으며, 계절변동 또한 매우 큰 것으로 나타났다. 특히 BOD와 TP의 평균 제거효율이 각각 12.3%, -44.5%로 낮고, TN과 SS에 비해 계절변동이 큰 것으로 나타났다. 월평균 BOD의 제거효율은 습지 하류부에서 식물플랑크톤이 대량 증식하였던 4월과 7월에 처리효율이 나타나지 않았으며, TP의 경우는 4월부터 8월까지 제거효율이 지속적으로 감소하였으며 수온이 가장 높았던 8월에 -291%를 나타냈다. 폐쇄수역에서 SS 농도분포는 좌안과 우안에 비해 중앙지점에서 높은 것으로 나타났다. 또한 ANOVA test로부터 수평적으로 유의적인 차이(p = 0.013, 중앙 > 좌안 > 우안)를 보였다. 시화호 인공습지에서 오염물질 제거효율의 저하원인은 과도한 유기물 생산에 의한 습지의 혐기성환경과 이에 따른 습지 하류부에서 용출된 인과 대량 증식한 식물플랑크톤이 균등하지 못한 물 흐름에 의해 식생대를 거치지 않고 유출되었기 때문으로 유추된다.

• 에너지공학
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• 제26권3호
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• pp.78-89
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• 2017

미분탄화력발전소에서 사용되는 각종 발전연료의 탄화도에 따른 발열개시온도(CPT;Cross Point Temperature), 발화온도(IT; Ignition temperature) 및 발화온도 승온속도(CPS;Cross Point Slope)는 전기로 내부에 설치된 백금망에 $74{\mu}m$이하 입도의 시료를 넣고 공기분위기, $25^{\circ}C$에서 $600^{\circ}C$까지의 승온조건에서 평가하였다. 발열개시온도 및 발화온도는 탄화도에 대한 의존성이 크지 않은 반면, 발화온도 승온속도는 탄화도에 크게 의존하는 것으로 나타났다. 탄화도가 낮은 우드펠렛의 발화온도 승온속도는 $20.995^{\circ}C/min$으로 기장 높은 자연발화성을 가지며, 아역청 KIDECO탄은 $15.370^{\circ}C/min$인 반면, 가장 높은 탄화도를 가지는 석유코크스는 $20.950^{\circ}C/min$로 나타냈다. 자연발화 경향성은 석탄 표면의 산화반응에 주요한 변수로서 작용하는 휘발분 함량 및 산소관능기의 농도 뿐만 아니라 촤의 비표면적, 정압몰비열이 높을수록 증가하는 것으로 확인되었다.