• 한국농공학회논문집
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• 제52권5호
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• pp.87-95
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• 2010

The optimum volume of sediment settling pond is determined by the maximum rainfall and surface peak rate runoff from crop field. Based on analysis of measured rainfall and runoff data, it was found that rainfall intensity of 2 mm/min would result in peak rate runoff from the agricultural field of study area. Optimum pond volume under various slope scenarios were determined using the WEPP model calibrated with measured flow and sediment data for the study watershed. For the agricultural field with the slope of 7 % and area of $2,600\;m^2$ at the study area, at least $6.4\;m^3$ of sediment settling pond is needed as shown in this study. The results presented in this study could be used as a guide in designing appropriate volume of sediment settling pond at highland agricultural areas because both very detailed field measurement and calibrated WEPP model results are used in the analysis.

• 한국환경과학회지
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• 제11권8호
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• pp.793-800
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• 2002

Butyltin (BT) compounds were measured in seawater, sediment, sediment core, settling solids, and plankton from Gwangyang Bay in 2001, Tributyltin (TBT) was detected in seawater from 1 out of the 7 seawater sampling sites and in sediment from 18 out of the 35 sediment sampling sites. The highest concentration of TBT was found in the sediment from the site near Yeosu Harbor (53 ng Sn/g dry wt), acting as the point source for TBT The mean concentrations of TBT were in the order of plankton> settling solids> sediment. The degradation indexes ([DBT]+[MBT]/[TBT]) for the plankton were less than 1, indicating the possibility of recent inputs of TBT. The indexes for the sediment and settling solids ranged from 1.14 to 8.73. The composition of the BT compounds found in the settling solids was similar to that found in the sediment. The vertical profile of the total BT compounds in the sediment was characterized by an abrupt decline from the surface. However, no butyltin compounds appeared below a depth of 10 cm, corresponding to the 1980s. Accordingly, the current results demonstrated that the levels of all butyltin species in the environment of Gwangyang Bay were relatively lower than those in other polluted coastal areas. The vertical profile also suggested a fairly recent history for the down-core.

• 한국습지학회지
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• 제19권3호
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• pp.303-310
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• 2017

본 연구의 목적은 난류흐름에서 이온의 영향아래 점착성 유사의 침강특성을 이해하는데 있다. 실험연구는 자유수면을 가지는 소형 환형수조에서 실시하였다. 실험에서 유사 재료로써 실리카($SiO_2$)를 사용하였으며, 부유농도는 CCD-Camera로 측정하였다. 실리카의 침강실험은 7g/L의 농도일 경우 다양한 바닥전단응력을 부여해 실시되었다. 바닥전단응력이 증가하게 되면 실리카의 플럭(floc)입자 입경(D)은 pH6.8에서보다 pH4.2와 높은 NaCl 농도에서 더 크다. 실리카의 침강속도($W_s$)는 pH4.2에서보다 10g NaCl/L에서 더 높다. 본 연구에서 예측된 농도-시간 곡선은 실제 흐름에서 이온의 영향아래 실측된 농도-시간 곡선과 잘 일치하는 것으로 나타났다.

• 한국수처리학회지
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• 제26권6호
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• pp.73-80
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• 2018

In this study, the solids removal characteristics using T-P sludge generated from PACl coagulation were analyzed by laboratory scale and full scale experiment. As the amounts of T-P sludge injection into the raw sewage influent increased at the rate of 0, 1, 2, 3, 4 %, the suspended solids concentrations after 20 minutes setting test decreased to 210, 137, 91, 64, 43 mg/L, respectively. The filtration time required for dewatering test of the raw sewage influent decreased to 982, 728, 658, 581, 492 sec for 0, 1, 2, 3, 4% of T-P sludge injection, respectively. As the amounts of PACl coagulant into the effluent from final setting tank increased at 0, 10, 20, 30, 40 mg/L, the required filtration times for T-P sludge increased into 12.3, 41.7, 53.7, 67.2, 79.5 sec and the dewaterability of T-P sludge decreased. After T-P sludge returned into the primary settling tank on J-si sewage treatment plants, the effluent concentrations of COD, SS, T-N and T-P from primary settling tank into bioreactor decreased by 35.9, 27.9, 22.2, and 52.6% due to the coagulation effects of the T-P sludge. Finally, it was found that the return of T-P sludge into the primary settling tank could result into the sludge reduction having a lower water content of 3.03% p than in case of the only T-P sludge dehydration.

• 한국재료학회지
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• 제4권8호
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• pp.927-933
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• 1994

비구형 입자들의 크기와 형태에 따른 침강 특성의 영향을 검토하였다. 비구형입자를 포함하는 서스펜션의 침강에서 $log \mu_{c}$대 $log \varepsilon$로부터 얻은 기울기 지표n값은 형태와 크기가 다른 입자는 같은 부피 농도에서 흡착되는유체량이 달라져 입자크기가 감소하거나 불균일한 경우 증가하는 경향을 나타내었다. 실험결고 비구형입자를 포함하는 서스펜션의 침강에서 기울기 지표 $n_{i}$값에 대하여 $n_{i}=n(a+b/d_{v})$와 같은 식을 얻었으며 이때 a, b는 입자형태에 따른 상수이다.

• ETRI Journal
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• 제30권5호
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• pp.729-734
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• 2008

Wireless communication systems, such as WLAN or Bluetooth receivers, employ preamble data to estimate the channel characteristics, introducing stringent settling-time constraints. This makes the use of traditional closed-loop feedback automatic gain control (AGC) circuits impractical for these applications. In this paper, a compact feedforward AGC circuit is proposed to obtain a fast-settling response. The AGC has been implemented in a 0.35 ${\mu}m$ standard CMOS technology. Supplied at 1.8 V, it operates with a power consumption of 1.6 mW at frequencies as high as 100 MHz, while its gain ranges from 0 dB to 21 dB in 3 dB steps through a digital word. The settling time of the circuit is below 0.25 ${\mu}s$.

• Journal of Power Electronics
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• 제16권4호
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• pp.1367-1374
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• 2016

This paper presents a discrete-time version of voltage and current limited operation using an enhanced direct torque and flux control method for interior permanent magnet synchronous motor (IPMSM) drives. A command voltage vector for airgap torque and stator flux regulation can be uniquely determined by the finite-settling-step direct torque and flux control (FSS-DTFC) algorithm under physical constraints. The proposed command voltage vector trajectories can be developed to achieve the maximum inverter voltage utilization for the discrete-time current limit (DTCL)-based FSS-DTFC. The algorithm can produce adequate results over a number of the potential secondary upsets found in the steady-state current limit (SSCL)-based DTFC. The fast changes in the torque and stator flux linkage improve the dynamic responses significantly over a wide constant-power operating region. The control strategy was evaluated on a 900W IPMSM in both simulations and experiments.

• Ocean Systems Engineering
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• 제2권1호
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• pp.33-47
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• 2012

This study revealed the behavior of droplets formed through leak process in deep water. There was a threshold depth named the universal attraction depth (UAD). Droplets rose upward in the zone below the UAD called the rising zone, and settled down in the zone above the UAD called the settling zone. Three mass loss modes were identified and formulated: dissolution induced by mass transfer, condensation by heat transfer and phase separation by pressure decrease. The first two were active for the settling zone, and all the three were effective for the rising zone. In consequence, the life time of the droplets in the rising zone was far shorter than that of the droplets in the settling zone.

• 대한화학회지
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• 제9권1호
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• pp.49-54
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• 1965

One of the difficult and time consuming problems in the production of magnesia from sea water is a settling rate of magnesium hydroxide. In this experiments, authors attempted to accelerate its settling rate by addition of various sedimenting agents as C.M.C., Separan and Starch, and sought for optimum calcination temperature for domestic dolomite, as alkali source, mole ratio of dolomite milk to bittern. It is observed through experiments that the small amounts of sedimenting agents, C.M.C., Separan, starch, 20 mg/l, 40 mg/l, 400mg/l, respectively increase the settling rate of magnesium hydroxide by 8 times or more. The following conditions resulted in good yield of magnesium hydroxide from sea water with relatively tolerable calcium oxide contaminated for the magnesium clinker. Calcinating temperature, $1,100{\sim}1,200^{\circ}C$, mole ratio of 10% dolomite milk to magnesium salts in sea water or bittern, 1. 2 : 1.

• 한국세라믹학회지
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• 제31권2호
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• pp.161-170
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• 1994

For the preparation of short ceramic fibers of which average length might be in accordance with the opening size of sieve, e.g., 150${\mu}{\textrm}{m}$ or 300${\mu}{\textrm}{m}$, bulk fibers were grounded on sieve screen by applying both compressing and shearing force, and passed through the sieve screen. The grounded fibers were subjected to gravitational settling processes. The classified fibers were observed by scanning electron microscopy and the length of each fiber was measured to correlate the average length with the opening size of the sieve used for grinding bulk fibers. Theoretical analysis show that a free settling technique is ineffective for the classification of fibers by length compared with that of particles. The average lengths of classified fibers estimated by scanning electron microscopy were in good agreement with those obtained by relative packing volume of the fibers. Accordingly, it is confirmed that average fiber lengths can be determined from bulk volume data without photographing, counting and averaging results for hundreds of fibers.