• Journal of Korean Society of Coastal and Ocean Engineers
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• v.18 no.3
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• pp.179-188
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• 2006

The purpose of this study is to quantitatively estimate the settling and erosional properties for cohesive sediments in Shihwa lake. Settling tests are conducted by multi-depth method using a specially designed 1.8 m tall settling column, and erosion tests are conducted with annular flume under the uniform bed condition. As result of settling tests, it is confirmed that the settling velocity of the cohesive sediments has the range of $0.002 for suspended sediments concentration of 0.1$0.19{\sim}0.55N/m^{2}$ for bed shear stress of $1.14{\sim}1.32g/cm^{3}$, and the erosion rate coefficient decreases with logarithmic function in a range of $18.4{\sim}3.9mg/cm^{2}{\cdot}hr$ with increase of bed shear stress.

• Journal of Ocean Engineering and Technology
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• v.19 no.4 s.65
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• pp.42-48
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• 2005

The sediment of Shihwa Lake contains an abundant quantity of cohesive sediments. The transport processes of the cohesive sediments are complex and difficult to predict, quantitatively. The cohesive sediments are the primary reason for the pollution of the environment and water quality in the coastal region. In this study, a column test has been performed. In order to quantify the settling velocities of sediment from Shihwa Lake, an experiment was conducted using a specially designed 1.8m tall settling column. A series of settling tests and physico-chemical property tests on Shihwa Lake cohesive sediments has been conducted to investigate the correlation between settling properties and their physico-chemical properties, which are represented as grain size distribution, mineralogical composition, and percentage oj organic contents. Experimental results of physico-chemical property tests show that Shihwa Lake sediments are relatively large in average grain $size(74\mu m)$ contain very small organic $material(6\%)$, and are dominantly composed of Quarts, which has relatively low cohesion. Thus, Shihwa Lake sediments might be specified as those whose settling properties are more influenced by gravity than cohesion. It is concluded that the magnitude of settling velocities of muddy sediments can be quite different, regionally, and it implies that field or laboratory experiments for settling velocity measurement should be preceded over the numerical modeling of muddy sediment transport, in order to obtain the reliable prediction results for a given specific site.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.60 no.3
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• pp.126-132
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• 2011

A conventional LDO(Low Dropout Regulator) uses one OPAMP and one signal path. This means that OPAMP's DC Gain and Bandwidth can't optimize simultaneously within usable power. This also appears that regulation property and settling time of LDO can't improve at the same time. Based on this idea, a proposed LDO uses two OPAMP and has two signal path. To improve regulation property, OPAMP where is used in the path which qualities DC gain on a large scale, bandwidth designed narrowly. To improve settling time, OPAMP where is used in the path which qualities DC gain small, bandwidth designed widely. A designed LDO used 0.5um 1P2M process and provided 200mA of output current. A line regulation and load regulation is 12.6mV/V, 0.25mV/mA, respectively. And measured settling time is 1.5us in 5V supply voltage.

• Journal of Ocean Engineering and Technology
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• v.16 no.5
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• pp.41-48
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• 2002

Numerical experiments are conducted using a three-dimensional baroclinic equation model and a Lagrangian method for clarifying the effect of th settling velocity on the suspended solids diffusion caused by the dredging and the reclamination works. Diffusion characteristics of the neutral particles and the weighting particles is experimented by the Lagrangian particles trajectory model, The results show that the diffusion characteristics of the suspended solids is effected by the settling velocity classified by the particles size in the density layered semi-closed bay. To estimate exactly the diffusion characteristics of the suspended solids and the contaminant with weight the three-dimensional baroclinic equation model and the three-dimensional Lagrangian particles trajectory model considering the settling velocity of the particle in the density layered semi-closed bay must be used.

• The KSFM Journal of Fluid Machinery
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• v.8 no.5 s.32
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• pp.29-34
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• 2005

In this study, the effect of flow settling means on the performance of fan tester were numerically investigated by using a computational fluid dynamics (CFD). The airflow rate was calculated from the pressure differential across a flow nozzle in the measuring plane and the flow settling means were generally installed in the chamber of the fan tester to provide proper airflow patterns ahead of the measuring plane. The predicted nozzle differential pressures with uniform inlet velocities were compared with the values of the ANSI/AMCA 210-99 to verify the performance of the commercial CFD code CFX 5.6. The influence of flow settling means on the measurement of airflow rate in a fan tester were discussed with various porosities and inlet jet velocities. The results obtained show that the proper band of porosities exist to meet the AMCA standard in a specified inlet jet velocity.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.12
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• pp.31-38
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• 2003

In this paper, we proposed a new structural AGC(Automatic Gain Control) circuit with extremely short settling time using high speed operation characteristics of a clipper. We investigated its operation characteristics in analysis. We also designed a burst-mode preamplifier for 1.25Gbps EPON systems using commercial foundry and investigated its characteristics by comparing the results of the designed and those of the analyzed. The characteristics of the designed circuit are in good agreement with those of the analyzed. As a result, it is shown that it is possible to realize extremely short settling time of under 1㎱.

• Journal of Korean Society on Water Environment
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• v.18 no.3
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• pp.313-319
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• 2002

Laboratory experiments using metal coagulants[alum, PAC(Poly Aluminum Chloride)] and polymer were conducted in this study to enhance dewatering and settling characteristics for swine wastewater. In this study, application of mixture of metal coagulants and polymer improved settling and dewatering characteristics for swine wastewater compared to using only metal coagulants. Also sludge volume was decreased when the mixture was applied. About 80-90% of settling velocity was increased and thickening ratio was increased as much as two times when adding 100mg/L of cationic polymers. Polymer was excellent for enhancing dewatering property among coagulants.

• The KSFM Journal of Fluid Machinery
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• v.9 no.4 s.37
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• pp.43-48
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• 2006

In this study, the effect of flow settling means on the performance of fan tester were numerically investigated by using a computational fluid dynamics(CFD). The airflow rate was calculated from the pressure differential across a flow nozzle in the measuring plane and the flow settling means were generally installed in the chamber of the fan tester to provide proper airflow patterns ahead of the measuring plane. The predicted nozzle differential pressures with uniform inlet velocities were compared with the values of the ANSI/AMCA 210-99 to verify the performance of the commercial CFD code CFX 5.6. The influence of flow settling means on the measurement of airflow rate in a fan tester were discussed with various porosities and inlet jet velocities. The results obtained show that the proper band of porosities exist to meet the AMCA standard in a specified inlet jet velocity.

• Journal of the Semiconductor & Display Technology
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• v.5 no.4 s.17
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• pp.1-4
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• 2006

Recently, with rapid development of digital media like semiconductor and large flat panel display, the manufacturing equipment is required to have high precision over large travel range. Moreover it should have high product throughput. To achieve high product throughput, a controller should perform fast point-to-point motion and high precision positioning after settling in spite of external disturbances or residual vibrations. We proposed a new mode switching control algorithm with an application to dual stage for long range and high precision positioning. The proposed algorithm uses a proximate time-optimal servomechanism for the fast settling and a time-delay controller for the high precision positioning. Experimental results show that the proposed method enables smooth mode switching and improves the settling time and the precision accuracy after settling by over than 33% and 45%, respectively.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.2
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• pp.265-272
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• 2006

While sludge settles down in a column, sludge settling characteristic is influenced by effect parameters, interparticle force, wall effect etc. As the height of a column changes, the settling velocity of sludge-water interface changes, too. At lower sludge concentration, particular effect was not observed by the difference of column height, however it was observed that settleability of sludge was greatly influenced by column height when sludge settling was poor or sludge concentration was high. It is therefore required to consider the effect of column height when the power model for sludge interface settling is established. In the tests, there was hardly any $SVI_{ts}$(SVI after "t" minutes) difference in each column after 10min at $1.5kg/m^3$ of sludge concentration. When sludge concentration was at $2.5kg/m^3$, $SVI_{ts}$ tended to be constant after 20min. At $3.5kg/m^3$, $SVI_{ts}$ increased to 30minuets. The purpose of this work is to establish the correction factor that is able to compensate the errors derived from each different height of column.