• 상하수도학회지
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• 제26권6호
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• pp.825-831
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• 2012

The retrofitting of a thickening unit process is widely considered in municipal wastewater treatment plants in Korea to enhance the anaerobic digestion efficiency. The authors examined the effect of feed concentration (2-34.1 g VS/L) and feed to microorganism (F/M) ratio (0.50-1.35 g VS/g VS) on anaerobic batch digestion of sewage sludge. Methane yield over 90 mL $CH_4/g$ $VS_{feed}$ was found at a feed concentration in the range of 12-26 g VS/L and a F/M ratio below 0.6 g VS/g VS. A high F/M ratio decreased methane yield and rate with oragnic acid accumulation. As sudden increase of sewage sludge concentration prior to anaerobic digestion would jeopardize the digester performance due to the rasied F/M ratio, gradual increase of the sludge feed concentration or an additional biomass retention in the digester is recommended.

• 한국토양비료학회지
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• 제29권4호
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• pp.360-364
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• 1996

시설재배지(施設栽培地) 염류집적(鹽類集積)이 상추의 발아율 및 생육(生育)에 미치는 영향을 구명하기 위하여 토양(土壤)의 염류농도(鹽類濃度)(1.65, 3.50, 5.75. 7.15, 9.50, 13.57 dS/m)를 달리하여 폿트시험을 수행하였다. 1. 상추는 증류수 그리고 KCl로 조절한 EC: 2, 4, 6, 8, 10 dS/m의 농도(濃度)에서 각각 86.7, 86.7, 72.2, 42.2, 27.8 %의 발아율을 보였으며, 토양(土壤)의 EC 농도(濃度)별 입모율은 6dS/m이하의 토양에서는 60% 이상이었으나 7.15, 9.50, 13.57 dS/m의 토양에서는 각각 45, 32, 31%의 낮은 입모율(立毛率)을 보였다. 2. 상추의 생육(生育)은 EC가 낮은 토양(土壤)일수록 양호(良好)하였으며, 수량은 토양(土壤)의 EC 1.65 dS/m에 비하여 3.56 dS/m의 토양(土壤)에서 22% 증수된 반면, 토양EC가 5.75, 7.15, 9.50, 13.57 dS/m에서는 각각 3, 15, 60, 62% 감수(減收)하였다. 3. 토양의 EC와 상추의 입모율(立毛率)은 고도(高度)의 부의 상관(相關)($r=-0.9057^{**}$)이 있었으므로 염류집적지(鹽類集積地) 토양(土壤)에서 다음식 [Y=-4.313x + 82.95(Y : 입모율. x : 토양 EC)]으로 상추의 입모율(立毛率) 예측이 가능하며, 또한 상추의 입모율(立毛率)은 생체중(生體重)과 고도의 유의 상관($r=0.8396^{**}$)을 보였다.

• Journal of Biosystems Engineering
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• 제27권2호
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• pp.89-96
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• 2002

The trend of consumption of vegetable soybeans is increasing because they are recognized as the clean vegetable. The works requiring the most intensive labor are threshing and seperation ones, and they form about 80% of total labour for vegetable soybeans production. It is necessary to develop the vegetable soybeans-thresher for the sake of cost down of vegetable soybeans production. The purpose of this study is to acquire the basic informations to design of the vegetable soybeans-thresher. We make the experimental system which control the speed of threshing cylinder and the teeth gap and investigate the detachment forces. The result are as follows ; The ratio of un-threshed soybeans-pod to stem after threshing work is decreasing as the threshing cylinder speed increases: 0.0% and 2.8% at 55m/s and 18m/s of threshing cylinder speed respectively. Also the ratio of un-threshed soybeans-pod to stem is shown as 2.0% below in the condition of 64~160mm of teeth gap and over 28m/s of threshing cylinder speed. The damaged pod ratio of detached soybeans after threshing work is decreasing as the threshing cylinder speed increases: 4.8% and 1.3% at 55m/s and 18m/s of threshing cylinder speed respectively. The minimum damaged pod ratio of detached soybeans are shown as 1.0%, 1.5% and 1.9% at 18m/s, 28m/s and 37m/s of threshing cylinder speed respectively. The average detachment forces of pods are shown as 1.5kg$_{f}$ for 3 grains, 1.2kg$_{f}$ for 2 grains and 0.8kg$_{f}$ for 1 grain respectively. The maximum detachment force of pod is shown as 2.7kg$_{f}$ for 3 grains. grains.

• 상하수도학회지
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• 제35권3호
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• pp.197-204
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• 2021

In MBR, extracellular polymeric substance (EPS) is known as an important factor of fouling; soluble EPS (sEPS) affects internal contamination of membrane, and bound EPS (bEPS) affects the formation of the cake layer. The production of EPS changes according to the composition of influent, which affects fouling characteristics. Therefore, in this study, the effects of the F/M ratio on the sEPS concentration, bEPS content, and fouling were evaluated. The effects of F/M ratio on the amount and composition of EPS were confirmed by setting conditions that were very low or higher than the general F/M ratio of MBR, and the fouling occurrence characteristics were evaluated by filtration resistance distribution. As a result, it was found that the sEPS increased significantly with the increase of the F/M ratio. When the substrate was depleted, bEPS content decreased because bEPS was hydrolyzed into BAP and seemed to be used as a substrate. In contrast, when the substrate is sufficient, UAP (utilization-associated products) was rapidly generated in proportion with the consumption of the substrate. UAP has a relatively higher Protein/Carbohydrate ratio (P/C ratio) than BAP, and this means, it has a higher adhesive force to the membrane surface. As a result, UAP seems like causing fouling rather than BAP (biomass-associated products). Therefore, R_f (Resistance of internal contamination) increased rapidly with the increase of UAP, and R_c (Resistance of cake layer) increased with the accumulation of bEPS in proportion, and as a result, the fouling interval was shortened. According to this study, a high F/M ratio leads to an increment in UAP generation and accumulation of bEPS, and by these UAP and bEPS, membrane fouling is promoted.

• 한국농공학회:학술대회논문집
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• 한국농공학회 1998년도 학술발표회 발표논문집
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• pp.376-381
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• 1998

The large scaled field test by prefabricated vertical drains was performed to evaluate the superiority of vertical discharge capacity for drain materials through compare and analyze the time-settlement behavior with drain spacing and the compression index and consolidation coefficient obtained by laboratory experiments and field monitoring system 1. The relation of measurement settlement( $S_{m}$) versus design settlement( $S_{t}$) and measurement consolidation ratio( $U_{m}$) versus design consolidation ratio( $U_{t}$) were shown $S_{m}$=(1.0~l.1) $S_{t}$, $U_{m}$=(1.13~l.17) $U_{t}$, at 1.0m drain spacing and $S_{m}$=(0.7~0.8) $S_{t}$, $U_{m}$=(0.92~0.99) $U_{t}$ at 1.5m drain spacing, respectively. 2. The relation of field compression index( $C_{cfield}$) and virgin compression index( $V_{cclab}$) was shown $C_{cfield}$=(1.0~1.2) $V_{cclab}$, But it was nearly same value when considered the error with determination method of virgin compression index and prediction method of total settlement. 3. field consolidation coefficient was larger than laboratory consolidation coefficient, and the consolidation coefficient ratio( $C_{h}$/ $C_{v}$) were $C_{h}$=(2.4 ~ 3.0) $C_{v}$. $C_{h}$=(3.5 ~ 4.3) $C_{v}$ at 1.0m and 1.5m drain spacing and increased with increasing of drain spacingngasing of drain spacingng spacingng

• 대한환경공학회지
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• 제32권6호
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• pp.587-592
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• 2010

연소과정 중에 발생하는 질소산화물을 저감하는 기술인 MILD 연소에 대하여 공연비를 변화시키면서 나타나는 연소 특성을 수치해석을 통하여 연구하였다. 작은 크기의 공기분출속도(10 m/s)에서는 공기가 연소로 내 상부영역까지 침투하지 못한다. 반면에 공기분출속도가 30 m/s인 경우에는 공기유동이 연료유동을 억제하고 상부영역까지 흘러간다. 이론공기량에 해당하는 공기분출속도 18 m/s에서는 10 m/s 보다 상대적으로 상부영역까지 침투하였다. 이러한 유동 양상으로 공기분출속도가 작은 10 m/s에서는 연소반응대가 공기노즐 측에 치우쳐 나타나고 30 m/s에서는 연료노즐 측에 형성되었다. 공기분출속도 16, 18, 20 m/s에서는 공기노즐과 연료노즐 중간 영역에서 연소반응대가 형성되었다. 연소로 내 최대온도와 NOx 생성은 공기분출속도가 10 m/s, 30 m/s인 경우 보다 이론공기량이거나 이에 가까운 16, 18, 20 m/s에서 낮게 나타났다. 본 연구로부터 MILD 연소로에서 이론공기량 조건이 NOx를 저감하는 최적의 조건이라는 것을 밝혔다.

• 소음진동
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• 제10권2호
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• pp.325-330
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• 2000

A dynamic absorber is used to protect the primary vibration system under the steady-state harmonic disturbance. In a number of cases it appears expedient to install several absorbers of smaller masses instead of one. This may be due to the need of distribute the absorber's response along the construction, restrictions on the absorber's installation. So, we studied characteristics of the primary vibration system for the optimal natural frequency ratio and the optimal damping ratio of serial multi-dynamic absorber. Also we obtained the optimum values of the serial multi-dynamic absorber parameters using computer simulation for the damped primary vibration system. In designing multi-dynamic absorber, we presented for the optimal natural frequency and the optimal damping ratio of multi-dynamic absorbers.

• Journal of Biosystems Engineering
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• 제18권4호
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• pp.371-381
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• 1993

Threshing operation is performed by impact, compression and friction forces inside the thresher. These values should be appropriate to the crop condition to enhance the threshing and separating efficiency and to decrease the grain damage. To analyze the threshing process inside the rasp-bar type thresher, impact, friction and compression forces were measured using transducers with strain gage circuits. To measure the impact forces and friction forces between the rasp-bar and crop, full bridge strain gage circuit was built on the rasp-bar holder. To measure the compression forces and circumferential friction forces between the concave and crop, two sets of full bridge strain gage circuits were built on the T-type concave transducer. Threshing work of wheat crop with 12% of moisture content was performed at 3 levels of compression ratio and with 3 replications. Each transducer could not measure the exact forces continuously because the transducer oscillates with the forces. However they could measure maximum forces and force distribution according to the time. Average friction coefficients between crop and concave was 0.61 not showing any significant difference according to the compression ratio. Average acceleration of the crop in the cylinder appeared from $70.6m/s^2$ to $140.8m/s^2$ according to the compression ratio. The velocity of the crop at the exit of the cylinder appeared from 10.7m/s to 15.0m/s according to the compression ratio.

• 대한임상검사과학회지
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• 제56권2호
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• pp.125-134
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• 2024

본 연구는 대한민국 성인을 대상으로 대사증후군(metabolic syndrome, MetS) 유·무에 따른 빈혈과 추정 사구체여과율(estimated glomerular filtration rate, eGFR) 및 요 미세 알부민/크레아티닌 비율(urine microalbumin/creatinine ratio, uACR)의 관련성을 평가하기 위하여 2012년 국민건강 영양조사(KNHNES V-3) 자료를 활용하여 20세 이상 성인 4,943명을 대상으로 데이터를 분석하였다. 본 연구에서 몇 가지 중요한 발견이 있었다. 첫째, 비 MetS 그룹에서는 정상군(eGFR≥60 mL/min/1.73 m² 및 uACR<30 mg/g)의 빈혈(남성, 헤모글로빈[hemoglobin, Hb]<13 g/dL; 여성, Hb<12 g/dL)의 발생률에 비하여 감소된 eGFR 그룹(eGFR<60 mL/min/1.73 m²; odds ratio [OR], 3.65; 95% confidence interval [CI], 1.90~7.00) 및 감소된 eGFR+증가된 uACR 그룹(eGFR<60 mL/min/1.73 m² 및 uACR≥30 mg/g, OR, 6.00; 95% CI, 2.61~13.80)의 빈혈 발생률이 높았다. 둘째, MetS 그룹에서는 정상군에 비하여 증가된 uACR 그룹(OR, 2.18; 95% CI, 1.11~4.27), 감소된 eGFR 그룹(OR, 3.73; 95% CI, 1.09~12.75) 및 감소된 eGFR+증가된 uACR 그룹(OR, 18.17; 95% CI, 6.16~53.63)의 빈혈 발생률이 높았다. 결론적으로, 비 MetS 그룹에서는 빈혈은 eGFR의 감소와 관련이 있었고, MetS 그룹에서는 빈혈은 eGFR 감소 및 uACR 증가와 관련이 있었다. 추가적으로, 비 MetS 그룹과 MetS 그룹 모두에서 eGFR의 감소 및 uACR의 증가가 동시에 나타날 때 빈혈의 발생률이 크게 증가하였다.

• 태양에너지
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• 제9권2호
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• pp.42-50
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• 1989

The Buoyant Jets were analysed experimentally changing flow rate (0.0291/s, 0.0371/s, 0.0451/s), ratio of nozzle tip area to throat area (aspect ratio ${\beta}$=0.4, 1.0, 1.9), and also the temperature difference (${\Delta}T=Ti-T{\infty}$) between the temperature of the inflow water into the storage tank ($1m{\times}1m{\times}3m$) and the mean temperature of the water in the storage tank were changed as $25^{\circ}C,\;35^{\circ}C$ and $45^{\circ}C$. The more aspect ratio decreased, the more the trajectories of Buoyant Jets center-line were decreased and not the more the trajectories of Buoyant Jets centerline were influenced by the increment of the difference of the temperature. The more aspect ratio decreased, the more the half widths and dilution ratio of Buoyant Jets were increased and not the more the half widths and dilution ratio of Buoyant Jets were influenced by the increment of the difference of the temperature. Fr number is the factor that can predict the flow pattern over the whole flow field. And yet for the consideration the near field of Buoyant Jets flow pattern is dominated by magnitude of momentum and buoyancy force.