• 유기물자원화
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• 제4권1호
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• pp.13-21
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• 1996

고농도 황산염과 중금속을 함유한 피혁폐수를 처리하기 위하여, 반응조의 처리도, 황환원균과 메탄균 사이의 기질경쟁 및 크롬농도에 대한 메탄균의 활성을 평가하였다. COD는 $35^{\circ}C$의 반응조 온도에서 유기부하량 2.0 gCOD/l.day와 18시간의 수리학적 체류시간에서 70% 이상의 제거율을 얻을 수 있었다. 황환원균과 메탄균 사이의 기질경쟁에서 황환원균에 의해 이용된 COD는 운전초기 15%에서 실험종료시 43%까지 증가되었다. 이는 유기물 분해로부터 발생되는 대부분의 전자가 황환원균에 의해 이용되어 황산염 환원에 의한 황화물이 생성되므로 메탄균의 활성은 강력히 억제되었다. 전 실험기간 동안 크롬농도는 90% 이상 제거되었으며, 크롬농도의 높은 제거율에도 불구하고 반응조의 처리능력은 거의 감소되지 않았다. 이는 반응조내에서 제거된 3가 크롬이 미생물의 활성에 영향을 미치지 않은 점으로 볼 때 3가 크롬이 6가 크롬에 비해 미생물에 대한 독성영향이 심하지 않다고 볼 수 있다.

• Journal of Welding and Joining
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• 제13권2호
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• pp.96-105
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• 1995

본 연구에서는 종래의 미소피로균열 성장속도 해석방법에 대한 수정안을 제시하고 수정 후의 방 법에 의해서 계산한 값들과 S4SC 탄소강에 대한 Nisitani와 Goto의 실험결과를 비교하여 계산한 값과 실험데이터 사이에 양호한 일치가 있음을 보였다. 이미 제시된 피로균열성장속도 식에는 하한계수준과 피로한도를 연관시키는 재료상수와 탄소성 거동에 대한 수정 및 균열닫힘효과를 나타내는 방법이 포함되어 있다. 본 연구에서 행한 수정중의 하나는 기하학적인 상수대신에 퍼만(Forman)의 탄성응력 강도계수 범위식을 이용하는 것이고, 다른 하나는 균열이 성장함에 따라 편심형단면으로 되면서 모멘트에 기인해 발생되는 굽힘효과를 고려하는 것이다. 이 방 법을 수명예측에 사용하면 용접구조물은 물론 기계구조물의 보다 정확한 수명예측이 가능할 것 이다.

• Journal of Dairy Science and Biotechnology
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• 제22권2호
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• pp.131-141
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• 2004

The FTA(Free Trade Agreements) are loading the world trade liberalization. Entering into FTA with Chile on 1 Apr 2004, Korea is trying to tie with Singapore and Japan in FTA. It also has a long-term plan for free-trading with China, USA, ASEAN, Canada and India. The portion of the dairy products imported from Chile, Japan and Singapore is under 1% of total dairy product imports. However, in the long run the conclusion of FTA with dairy product exporting countries such as USA, Australia, New Zealand and Netherlands will give a big impact on the dairy industry with abrupt increment in dairy product imports. Especially, whole and skim milk powder imports which are imported on the high tariff rate expect to increase. Furthermore mixed milk powder(Food preparations of goods and other whey powders) imports which domestic price is higher than world market also will dramatically increase. The milk powder stocks have increased since 2002. That made the government carry out some policies. Those include slaughtering milking cow(2002) and terminating the dairy farm enterprise and decreasing in milk production(2003). Also the case of artificial insemination by a Hanwoo fertilized egg has increased with the rise of Hanwoo farm price in 2003. By those reason, it is forecasted that the downward trend in the number of cow will be continued in 2004. It is also forecasted that the raw milk production in 2004 will decrease 4.4% compared to last year due to decreasing in the number of milking cow and raw milk collecting quota.

• 한국식품영양학회지
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• 제30권6호
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• pp.1222-1228
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• 2017

In the current study, we investigated the inhibitory activity of water soluble ${\beta}-glucan$ from oat (Avena sativa) against various digestive enzymes such as ${\alpha}-glucosidase$, sucrase, maltase and glucoamylase. Inhibition of these enzymes involved in the absorption of disaccharide can significantly decrease the post-prandial increase of blood glucose level after a mixed carbohydrate diet. The ${\beta}-glucan$ had the highest documented rate of small intestinal sucrase inhibitory activity (2.83 mg/mL, $IC_{50}$) relevant for potentially managing post-prandial hyperglycemia. Furthermore, we evaluated the effects of ${\beta}-glucan$ on the level of post-prandial blood glucose in animal model. The post-prandial blood glucose levels were tested two hours after sucrose/starch administration, with and without ${\beta}-glucan$ (100, and 500 mg/kg-body weight). The maximum blood glucose levels (Cmax) of ${\beta}-glucan$ administration group were decreased by about 23% (from $219.06{\pm}27.82$ to $190.44{\pm}13.18$, p<0.05) and 10% (from $182.44{\pm}13.77$ to $165.64{\pm}10.59$, p<0.01) in starch and sucrose loading test, respectively, when compared to control in pharmacodynamics study. The ${\beta}-Glucan$ administration significantly lowered the mean, maximum, and minimum level of post-prandial blood glucose at 30 min after meal. In view of the foregoing, it is felt that our findings suggest that ${\beta}-glucan$ from oat serves to reduce post-prandial blood glucose rise secondary to slower absorption of glucose in the small intestine, via carbohydrate hydrolyzing enzymes inhibition.

• 한국환경과학회지
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• 제1권2호
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• pp.125-136
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• 1992

Digestion of a municipal wastewater sludge by the anaerobic sequencing batch reactor (ASBR) was investigated to evaluate the performance of the ASBR process at a critical condition of high-solids-content fined. The reactors were operated at an HRT of 10 days with an equivalent loading rate of 0.8-1.5 gVS/L/d at 35$^{\circ}C$ The main conclusions drawn from this study were as follows: 1. Digestion of a municipal wastewater sludge was possible using the ASBR in spite of high concentration of settleable solids in the sludge. The ASBRS with 3- and 4-day cycle period showed almost identical high digestion performances. 2. No adverse effect on digestion stability was observed In the ASBRS in spite of withdrawal and replenishment of 30% or 40% of liquid contents. A conventional anaerobic digester could be easily converted to the ASBR without any stability problem. 3. Flotation thickening occurred in thicken step of the ASBRS throughout steady state, and floating bed volume at the end of thicken period occupied about 70% of the working volume of the reactor Efficiency of flotation thickening in the ASBRS could be comparable to that of additional gravity thickening of a completely mixed digester. 4. Solids were accumulated rapidly in the ASBR during start-up period. Solids concentrations in the ASBRS were 2.6 times higher than that in the completely mixed control reactor at steady state. Dehydrogenase activity had a strong correlation with the solids concentration. Dehydrogenase activity of the digested flu형e in the ASBR was 2.9 times higher than that of the flu형e in the control reactor, and about 25 times higher than that of the subnatant in the ASBR. 5. Remarkable increase in equivalent gas production of 52% was observed at the ASBRS compared with the control reactor in spite of similar quality of clarified effluent from the ASBRS and control reactor. The increase in gas production from the ASBRS was believed to be combined results of accumulation of microorganisms, higher driving force applied, and additional long-term degradation of organics continuously accumulated.

• Journal of Biosystems Engineering
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• 제43권2호
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• pp.110-118
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• 2018

Purpose: In this study, the potential for biogas production, degradation rates, and lag-phase of diauxic growth of carbohydrate-based material, which is one of the proximate compositions, were investigated. Methods: This study was conducted using starch as a carbohydrate-based material. In experimental condition 1, the biogas potential of carbohydrate-based material was measured. In experimental condition 2, the effect of feed to microorganism ratio (F/M ratio) on lag-phase of diauxic growth from carbohydrate-based material was tested. Biochemical methane potential tests were performed at five different feed to microorganism ratios (0.2, 0.4, 0.6, 0.8, and 1.0) under mesophilic conditions. The biogas production patterns, lag-phase, total volatile fatty acids to total alkalinity ratio (TVFA/TA ratio), and time required for 90 percent biogas production were used to evaluate biogas production based on the biochemical methane potential tests. Results: In experimental condition 1, unlike previous studies, biogas was produced in the TVFA/TA ratio ranging from 1.131 to 2.029 (approximately 13-19 days). The methane content in the biogas produced from the digesters was 7% on day 9 and increased rapidly until approximately day 27 (approximately 72%). In experimental condition 2, biogas yield was improved when the feed to microorganism ratio exceeded 0.6, with an initial lag-phase. Conclusions: Even if the TVFA/TA ratio was greater than 1.0, the biogas production was processed continuously, and the $CO_2$ content of the biogas production was as high as 60%. The biogas yield was improved when the F/M ratio was increased more than 0.6, but the lag-phase of carbohydrate-based material digestion became longer starting with high organic loading rate. To clarify the problem of the initial lag-phase, our future study will examine the microbial mechanisms during anaerobic digestion.

• 한국산학기술학회논문지
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• 제1권2호
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• pp.57-62
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• 2000

Trichloroethvlene(TCE)의 수용액 내에서 광분해 반응을 연구하였다. 광촉매 TiO₂의 표면특성은 XRD, SEM 및 BET를 사용하여 선행연구[23]에서 고찰하였으며 Aldrich TiO₂는 100% anatase, Degussa 에서 제조한 P25-TiO₂는 75% anatase와 25% rutile의 혼합구조(structure)를 가짐을 알 수 있었다. 본 연구에서는 TCE 분해반응의 최적조건을 선정하기 위하여 광촉매의 사용량, 분해반응시 혼합용액의 순환유속, TCE의 초기농도 및 광촉매 TiO₂의 구조가 광분해 반응에 미치는 영향을 자세히 고찰하였다. 실험결과 증류수 1 L를 기준으로 무게비 0.1 wt%의 광촉매를 사용하여 증류수와 TCE의 혼합용액을 200 cc/min로 순환시켰을 때 분해활성이 가장 좋음을 알 수 있었으며 일반적으로 anatase 구조가 rutile구조를 가진 광촉매 보다 높은 활성을 보였다. 특히 anatase와 rutile의 혼합구조를 가진 Degussa P25-TiO₂가 가장 좋은 활성을 보였으며 이는 작은 입자크기와 큰 비표면적에 기인한 결과로 보인다.

• 한국환경보건학회지
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• 제24권1호
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• pp.62-69
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• 1998

It has been studied that the measurement of odor component emission at confectionery manufacture. The objects of this study were to investigate reduction of offensive odor. The survey effects of odorous materials are presented as follows. The countermeasure of operating process is to minimize sludge sediment in each unit facility. Especially, in summer, we have to clean the sludge frequently, because anaerobic decomposing is likely to occur easily. The sludge or scum from sedimentation tank pond, and floating tank should be treated quickly. We should avoid overloading operation. In the case of overloading, dissolved oxygen should be increased, the quality of wastewater input should be decreased. When dried cakes from condense tank or floating tank are left in treatment plant, we should cover, to prevent diffusion of smell with masking materials. The seasonal condition of operating should be fixed and the kind of coagulants should be changed because the wastewater in each season have different loading rates and organic materials. Odorous materials are very sensitive to the seasonal temperature variation. Especially, when the amount of rainfall is small and the high temperature of maintenance in long periods, air diffusion rate is large, so odorous materials can make great effect on surroundings comparision with other periods. To reduce odorous gas, as short term method, we had better take ceramic addition method. Especially, in summer we should take ceramic addition method. Also, as long term method, the size of wastewater treatment facility is the most important in the normal operating of wastewater treatment facility. But wastewater treatment facilities in this factory are too old, treatment process is old fashion, and the size is too small. So, large wastewater quantity to treat in summer. As results, the expansion of wastewater treatment facility and the process of improvement are required. Restriction level of odor was exceed. As it is overloaded in summer, the basis cause of odor is that the size of wastewater treatment facility is small. The prediction of air quality equilibrium density variation show that the odorous materials from working place are Amine materials whose smell strength is about 2.5(a little strong degree). We can suppose that in summer is sensitive to temperature variation, smell strength is larger as to reduce the origin of odor. We must expand wastewater treatment facility and improve the process A.S.A.P.

• 한국환경과학회지
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• 제11권8호
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• pp.819-827
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• 2002

Laboratory scale experiments were conducted to evaluate the performance of a biofilter for eliminating dimethyl sulfide(DMS). A commercial compost/pine bark nugget mixture served as the biofilter material for the experiments. The gas flow rate and DMS concentration entering the filter were varied to study their effect on the biofilter efficiency. The operating parameters, such as the residence time, inlet concentration, pH, water content, and temperature, were all monitored throughout the filter operation. The kinetic dependence of the DMS removal along the column length was also studied to obtain a quantitative description of the DMS elimination. High DMS removal efficiencies(>95％) were obtained using the compost filter material seeded with activated sludge. DMS pollutant loading rates of up to 5.2 and 5.5 g-DMS/m$^3$/hr were effectively handled by the upflow and downflow biofilter columns, respectively. The macrokinetics of the DMS removal were found to be fractional-order diffusion-limited over the 9 to 25 ppm range of inlet concentrations tested. The upflow column had an average macrokinetic coefficient(K$\_$f/) of 0.0789 $\pm$ 0.0178 ppm$\^$$\sfrac{1}{2}$//sec, while the downflow column had an average coefficient of 0.0935 $\pm$ 0.0200 ppm$\^$$\sfrac{1}{2}$//sec. Shorter residence times resulted in a lower mass transfer of the pollutant from the gas phase to the aqueous liquid phase, thereby decreasing the efficiency.

• The Journal of Korean Physical Therapy
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• 제13권1호
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• pp.1-18
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• 2001

Aging has been recognized as the primary cause of disc degeneration. A biomechanical characteristics of disc degeneration has been demonstrated that intradiscal pressure is reduced. With the increasing population of elderly people, disc degeneration and associated problems of nerve entrapment are becoming more prevalent. Presently, research on reduced intradiscal pressure associated with degeneration is insufficient. In this study. we used the Finite Element Method (FEM) of computerized simulations to investigate the effects of variation in intradiscal pressure on mechanical behaviours of L4-5 intervertebral disc degeneration. Degeneration was classified using four grades based on initial intradiscal pressure; Normal (135 kPa), mild(107 kPa), moderate (47 kPa) and severe (15 kPa). The predicted results f3r bending loads were as follows; 1 . Range of motion increased progressively with severity of degeneration with flexion and lateral bending moments, but decreased with extension moments. 2. Discal bulging of posterolateral aspect was larger in lateral bending and extension moment. But bulging was increased with severity of degeneration in lateral bending and torsion(same side).3. The rate of increasing intradiscal pressure was decreased in all bending motions with severity of degeneration. In conclusion, lateral bending and extension moment yield greatest bulging in severe degeneration. In torsion, although bending load produces disc bulging, disc bulging was associated more strongly with severity of degeneration than increasing torsional moments. Clinical Implications: Discal bulging may produce nerve root impingement and irritation. The effect of loading and posture on the varying degrees of disc degeneration has important implications especially in the elderly. In the presence of disc degeneration, avoidance of end range postures, especially extension and lateral bending may help reduce discal bulging and in turn, nerve entrapment.