• 한국환경과학회지
• /
• 제4권3호
• /
• pp.259-267
• /
• 1995

This study was conducted to evaluate the effects of pressure and dissolved oxygen concentration on the activated slut비e and to determine the optimum depth of deep shaft process. Some results from this study were summarized as follows. 1. It is considered that low sludge product in the activated sludge system maintaining high dissolved oxygen concentration is attributed to the increase of endogeneous respiration rate caused by the increase of aerobic zone in the sludge floe. 2. The increase of dissolved oxygen concentration does not affect to the increase of organic removal efficiency greatly and therefore the limiting factor is the substrate transfer into the inner part of floe. 3. The yield coefficient, Y is decreased in proportion to the increase of oxygen concentration. In this study, Y values arre ranged from 0.70 to 0.41 according to the variation of dissolved oxygen concentration from 18.0mg/$\ell$ to 258 mg/$\ell$. 4. The optimum depth of deep shaft process should be determined within the limits of non-toxicity to the microorganism and it is about loom in this study.

• 한국실내디자인학회논문집
• /
• 제13권6호
• /
• pp.29-38
• /
• 2004

The purpose of this study is to provide design guidelines on office layouts to improve workers' concentration and communication behavior while supporting work processes. Among the present office types, benzene-type was preferred the most was providing better concentration. Regarding communication, link and benzene were preferred types. In present office types, workers were satisfied in communication more than concentration. To increase concentration level, acoustical privacy was indicated as the most important factor In conclusion, to support both concentration and communication in office, the team area should be divided into smaller sub-team areas. The sub-team areas may support interaction within a group while preventing unnecessary distraction. The major circulation of work process should be formed outside of the sub-team areas to provide concentration within the groups.

• The Korean Journal of Ecology
• /
• 제7권3호
• /
• pp.109-118
• /
• 1983

Near future dynamics of water qualities (nutrient concentration) of the Han River was predicted, based on a mathematical model representing the relationship between the nutrient concentration in th river wagter and environmental factors (population density, land-use types, rock compositions and nutrient accumulation) in the basin. The population density and land-use types were forecasted to change distinctly in the downstream area, especially in Seoul City area in 1985~1990 whereas any environmental factor was not expected to change its level significantly in both upstream and middle reaches areas. It was indicated by the model that the nutrients concentration in the up- and mid-streams would keep its level in future as it was, but it would increase drastially in the downstream area. For the preservation of the water qualities in the downstream at least to keep its level as it was in 1980, practical countermeasures were proposed, based on the assessment of the contribution of each environmental factor to the water qualities.

• 한국환경과학회지
• /
• 제23권5호
• /
• pp.793-800
• /
• 2014

This study was conducted to observe the influences of Crataegus pinnatifida BUNGE extract on lipid concentration in hypercholesterolemic rats (Sprague Dawley, male) fed the experimental diets for 5 weeks. Body weight gain was remarkably lower in the Crataegus pinnatifida BUNGE extract intake group than in the hypercholesterolemic rats. Total cholesterol concentration was remarkably lower in the extract of Crataegus pinnatifida BUNGE supplement in hypercholesterolemic rats than in the hypercholesterolemic model. Whereas, concentrations of HDL-cholesterol, ratio of HDL-cholesterol concentration to total cholesterol were remarkably higher in the extract of Crataegus pinnatifida BUNGE supplement in hypercholesterolemic rats than in the hypercholesterolemic model. Atherosclerotic index (AI), cardiac risk factor (CRF) were remarkably lower in the extract of Crataegus pinnatifida BUNGE supplement in hypercholesterolemic rats than in the hypercholesterolemic model. From the above research, Crataegus pinnatifida BUNGE extract was effective on the lipid concentrations in sera of dietary hypercholesterolemic rats.

• 한국환경보건학회지
• /
• 제32권4호
• /
• pp.292-303
• /
• 2006

The Volatile Organic Compounds(VOCs) are emitted from various sources and have lots of different form. Recently human are spending the many times at indoor area and indoor air pollution is issued the important social problem. The emission sources of indoor air pollutants are very various, also indoor building materials are composed of very complex chemical compounds, these indoor building materials discharge very much VOCs and other hazardous compounds. In this study, we performed the small chamber test to investigate the VOCs emission concentration and characteristics involving five kinds of the indoor building materials(furniture material, wooden floor, wall paper, paint and tile) under different conditions of four temperature and relative humidity as account of the air flow rate(AFR), air exchange rate(AER), loading factor and air velocity respectively. As the result, It was showed that building materials are emitted the highest VOCs concentration at the beginning of experiment and furniture material is emitted the highest VOCs concentration. Most of the materials were affected by temperature, but paint and tile material were affected by humidity.

• Composites Research
• /
• 제29권6호
• /
• pp.388-394
• /
• 2016

Fiber reinforced plastic (FRP) composites have drawn increasing attentions worldwide for decades due to its outstanding properties. Stress concentration factor (SCF) as an essential parameter in materials science are critically considered in structure design and application, strength assessment and failure prediction. However, investigation of stress concentration in FRP composites has been rarely reported so far. In this study, three resource-conserving analyses (Isotropic analysis, Orthotropic analysis and Finite element analysis) were introduced to plot the $K_T^A-d/W$ curve for E-glass/epoxy composite plate with the geometrical defect of circular hole placed centrally. The plates were loaded to uniaxial direction for simplification. Finite element analysis (FEA) was carried out via ACP (ANSYS composite prepost module). Based on the least squares method, a simple expression of fitting equation could be given based on the simulated results of a set of discrete points. Finally, all three achievable solutions were presented graphically for explicit comparison. In addition, the investigation into customized efficient SCFs has also been carried out for further reference.

• 공업화학
• /
• 제5권3호
• /
• pp.457-465
• /
• 1994

계면활성제 수용액과 액체오염간의 계면장력을 계산치와 실측치로 구분할 수 있다. 계산치로 구한 부착일(Wac)와 세정력과의 상관계수(r)는 계면활성제 수용액의 농도가 낮은 0.04%에서는 0.93으로 밀접한 연관성을 나타내었으나 높은 농도인 0.1%에서는 0.37로 상호관련이 없음을 나타내었다. 실측치로 구한 부착일(Wae)과 세정력과의 상관계수는 저농도(0.04%)에서 0.95이고, 고농도(0.1%)에서도 0.84로 세정력과 부착일과의 깊은 연관성이 있음을 나타내었다. 따라서 저농도에서는 어느 경우나 부착일과 세정력과의 상관관계가 크나, 고농도에서 계산치로 구한 부착일과 세정력과의 상관관계는 거의 없고 실측값은 밀접한 관계가 있음을 알 수 있었다.

• Biotechnology and Bioprocess Engineering:BBE
• /
• 제6권1호
• /
• pp.37-41
• /
• 2001

HPLC separation of ionic samples tends to be more complicated and difficult to understand than that of non-ionic compounds. On the other hand, band spacing is much more easily manipulated for ionic than for neutral samples. Ion-suppression RP-HPLC method was used with organic modifier and aqueous buffer solution. In this work, five mononucleotides of cytidine-5-monophosphate (5-CMP) disodium salt, uridine-5-monophosphate disodium salt (5-UMP), guanosine-5-monophosphate disodium salt (5-GMP), inosine-5-monophosphate disodium salt (5-IMP), and adenosine-5-monophosphate disodium salt (5-AMP) were examined. Acetic acid and sodium phosphate were used as buffers, and methanol as an organic modifier. A new relationship between the retention factor and the buffer concentration at a fixed modifier content (5% of methanol) could be expressed by following: K = (k(sub)-1 + k(sub)0 (k(sub)B/k(sub)S)/(1 + (k(sub)B/k(sub)S) C(sub)B(sup)a), where C(sub)B was the concentration of buffer. Using this relationship, the calculated values closely matched the experimental data. The derived relationship showed that as the buffer concentration increased, the retention factor approached a certain value, and this was buffer dependent.

• 한국식품영양학회지
• /
• 제25권2호
• /
• pp.317-323
• /
• 2012

We investigated the quality characteristics of cookies prepared after the addition of various concentration of used guava leaf powder(0%, 1%, 3%, 5%, all w/w) as a substitute for flour. In this study, as guava leaf powder concentration rose, there was a decrease in the water content level. In addition, color, spread factor, hardness and sensory evaluation of the cookies were examined. The results showed that with an increase in guava leaf powder concentration, the L value decreased significantly, while the values for a and b of cookies increased when more guava leaf power was added to cookies. The spread factor of cookies decreased, but the hardness of cookies increased significantly, as guava leaf powder concentration increased. Cookies containing 0% and 3% of guava leaf powder showed a similar sensory evaluation score in terms of color, taste and flavor of the cookies. In the case of texture and overall consumer acceptability, cookies with 3% of guava leaf powder showed the highest score.

• Nuclear Engineering and Technology
• /
• 제17권4호
• /
• pp.267-278
• /
• 1985

원자력발전소로부터 배출되는 방사성물질에 의한 피폭선량을 규제하는데 있어 몇 가지 종류들의 방식들이 적용되어 왔다. ICRP에 의해 권고된 일차 선량 당량 제한치가 가장 근본적인 것이다. 일차 제한치가 직접 적용될 수 없을 때 외부 피폭의 경우 선량당량 지표가 내부피폭의 경우 최대허용농도, 연섭취 제한치 흑은 유도대기 농도 및 최대 신체 부하량 등이 이용되어 왔다. 그러나 이 값들은 실제 배출량을 제어하는 견지에서 바로 사용할 수 없어 유도방출 기준치를 구하게 된다. 본 연구에선 월성 원자력발전소에 대해 고려되는 특정환경들 사이의 전달속도가 시간에 독립적인, 장기성 농축인자 방식으로 방출속도의 유도 제한치를 구하였다.