• Journal of Korean Society of Water and Wastewater
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• v.21 no.4
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• pp.409-420
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• 2007

ASM No. 1 is a very useful model to analyze wastewater treatment system removing organic carbon and nitrogen material. But it isn't adequate to control the wastewater treatment system with real time since it has many material divisions and parameters. So, the purpose of this study is the simplification of ASM No. 1 to control the wastewater treatment system. ASM No. 1 was changed with the model which has 3 material divisions(COD, $NH_4{^+}$, $NO_3{^-}$) and two phases(Aerobic and Anoxic condition). SBR was running with two phases(Phase I and II). Phase II running 20 minutes with aerobic time was used for deciding model parameters and Phase I running 12 minutes with aerobic time was used for proving the simplified model. The simplified model was compared with ASM No. 1 using data of Phase I and II. As a result of model comparison, the simplified model has enough ability to express the variation of $NH_4{^+}$ compound.

• Journal of Korean Society of Water and Wastewater
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• v.22 no.1
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• pp.3-14
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• 2008

ASM No. 2(Activated sludge model No. 2) is very useful model to analyze the wastewater treatment which removes nitrogen and phosphorus. But, it is difficult to apply ASM No. 2 to control of wastewater treatment since it has 17 material divisions and 46 parameters. So the purpose of this study was the simplification of ASM No. 2 and the provement of simplification model. Firstly ASM No. 2 was simplified with 5 material division and three phases(Anaerobic, aerobic, anoxic phases). The simplified model was proved by R-square using track study data. As a result of provement, the values of R-square in ${NH_4}^+$ were 0.9815 in ASM No. 2 and 0.9250 in simplified model and in ${NO_3}^-$ were 0.8679 in ASM No. 2 and 0.7914 in simplified model and in ${PO_4}^{3-}$ are 0.9745 in ASM No. 2 and 0.9187 in the simplified model when the ability to express the material variation was compared by R-square. So, the simplified model has enough ability to express the variation of ${NH_4}^+$, ${NO_3}^-$ and ${PO_4}^{3-}$.

• Journal of Korean Society of Water and Wastewater
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• v.25 no.3
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• pp.349-357
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• 2011

This study has an objective to estimate effect on water-quality enhancement by removal of contaminated river-bed material using a two-dimensional numerical modeling in the Seonakdong River, the Pyunggang River and the Maekdo River. RMA2 and RMA4 models were used for flow and contaminant transport simulation, respectively. After the analysis of the effects of flow restoration plan for the Seonakdong River system made by Lee et al (2008), simulation have been performed about scenarios which contains operations of the Daejeo Gate, the Noksan Gate, the Makdo Gate (on planning), and the Noksan Pumping Station. Because there is no option for elution from bed sediment in the RMA4 model, a simple technique has been used for initial condition modification for elution. The analyses revealed that the effect on water quality improvement due to dredging of bed sediment seemed to be less than 10 % of the total effect. The most efficient measure for the water quality improvement of the river system was the linked operation of water-gates and pumping station.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.547-552
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• 2003

In mold machining, there are many concave machining regions where chatter and tool deflection occur since MRR (material removal rate) increases as curvature increases even though cutting speed and depth of cut are constant. Boolean operation between stock and tool model is widely used to compute MRR in NC milling simulation. In finish cutting, the side step is reduced to about 0.3mm and tool path length is sometimes over 300m. so Boolean operation takes long computation time and includes much error if the resolution of stock and tool model is larger than the side step. In this paper, curvature of CL(cutter location) surface and side step of tool path is used to compute the feedrate for constant MRR machining. The data structure of CL surface is Z-map generated from NC tool path. The algorithm to get local curvature from discrete data was developed and applied to compute local curvature of CL surface. The side step of tool path was computed by point density map which includes cutter location point density at each grid element. The feedrate computed from curvature and side step is inserted to new tool path to regulate MRR. The resultants wire applied to feedrate optimization system which generates new tool path with feedrate from NC codes for finish cutting. The system was applied to speaker mold machining. The finishing time was reduced to 12.6%. tool wear was reduced from 2mm to 1.1mm and chatter marks and over cut on corner were removed.

• Transactions on Electrical and Electronic Materials
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• v.8 no.2
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• pp.53-57
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• 2007

In this study, a novel slurry containing ceria as the abrasive particles was analyzed in terms of its frictional, thermal and kinetic attributes for interlayer dielectric (ILD) CMP application. The novel slurry was used to polish 200-mm blanket ILD wafers on an $IC1000_{TM}$ K-groove pad with in-situ conditioning. Polishing pressures ranged from 1 to 5 PSI and the sliding velocity ranged from 0.5 to 1.5 m/s. Shear force and pad temperature were measured in real time during the polishing process. The frictional analysis indicated that boundary lubrication was the dominant tribological mechanism. The measured average pad leading edge temperature increased from 26.4 to $38.4\;^{\circ}C$ with the increase in polishing power. The ILD removal rate also increased with the polishing power, ranging from 400 to 4000 A/min. The ILD removal rate deviated from Prestonian behavior at the highest $p{\times}V$ polishing condition and exhibited a strong correlation with the measured average pad leading edge temperature. A modified two-step Langmuir-Hinshelwood kinetic model was used to simulate the ILD removal rate. In this model, transient flash heating temperature is assumed to dominate the chemical reaction temperature. The model successfully captured the variable removal rate behavior at the highest $p{\times}V$ polishing condition and indicates that the polishing process was mechanical limited in the low $p{\times}V$ polishing region and became chemically and mechanically balanced with increasing polishing power.

• Structural Engineering and Mechanics
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• v.32 no.2
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• pp.235-249
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• 2009

The response of concrete structures subjected to shock and blast load involves a rapid transient phase, during which material breach may take place. Such an effect could play a crucial role in determining the residual state of the structure and the possible dispersion of the fragments. Modelling of the transient phase response poses various challenges due to the complexities arising from the dynamic behaviour of the materials and the numerical difficulties associated with the evolving material discontinuity and large deformations. Typical modelling approaches include the traditional finite element method in conjunction with an element removal scheme, various meshfree methods such as the SPH, and the mesoscale model. This paper is intended to provide an overview of several alternative approaches and discuss their respective applicability. Representative concrete material models for high pressure and high rate applications are also commented. Several recent application studies are introduced to illustrate the pros and cons of different modelling options.

• Applied Chemistry for Engineering
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• v.31 no.5
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• pp.495-501
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• 2020

In this study, zirconium fumarate of metal-organic framework (MOF-801) was solvothermally synthesized at 130 ℃ and characterized through powder X-ray diffraction (PXRD) analyses and porosity measurements from N₂ sorption isotherms at 77 K. The ability of MOF-801 to act as an adsorbent for the phosphate removal from aqueous solutions at 25 ℃ was investigated. The phosphate removal efficiency (PRE) obtained by 0.05 g/L adsorbent dose at an initial phosphate concentration of 60 ppm after 3 h was 72.47%, whereas at 5 and 20 ppm, the PRE was determined to be 100% and 89.88%, respectively, after 30 min for the same adsorbent dose. Brunauer-Emmett-Teller (BET) surface area and pore volume of the bare MOF-801 sample were 478.25 ㎡/g and 0.52 ㎤/g, respectively, whereas after phosphate adsorption (at an initial concentration of 60 ppm, 3 h), the BET surface area and pore volume were reduced to 331.66 ㎡/g and 0.39 ㎤/g, respectively. The experimental data of kinetic (measured at initial concentrations of 5, 20 and 60 ppm) and isotherm measurements followed the pseudo-second-order kinetic equation and the Freundlich isotherm model, respectively. This study demonstrates that MOF-801 is a promising material for the removal of phosphate from aqueous solutions.

• Tribology and Lubricants
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• v.15 no.1
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• pp.46-51
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• 1999

An analytical model about lateral crack occurring in abrasive wear of brittle solids is developed. Stress field around the lateral crack and stress intensity factor at the crack tip are analytically modeled. Abrasive wear by abrasive particle is experimentally studied. In soda-lime glass, it is observed that chipping by lateral crack occurs and produces the greatest material removal when normal load applied by the abrasive particle is about 1.5∼3.0 N. The prediction of lateral crack length from the model is compared with the experimentally measured length in soda-lime glass.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.10a
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• pp.737-742
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• 1994

In this paper , we propose an incremental approach for recognizing a class of machining features from a featurebased design model as a part design proceeds, utilizing various information such as nominal geometry, design intents, and design feature characteristics. The proposed apptroach can handle complex intersecting features and protrusion features designed on oblique faces. The class of recognized volumetric machining features can be expressed as Material Removal Shape Element Volumes (MRSEVs), a PDES/STEP-based library of machining features.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.10
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• pp.154-160
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• 1996

The control of diamond turning is usually achieved through a laser-interferometer feedback of slide position. The limitation of this control scheme is that the feedback signal does not account for additional dynamics of the tool post and the material removal process. If the tool post is rigid and the material removal process is relatively static, then such a non-collocated position feedback control scheme may surfice. However, as the accuracy requirement gets tighter and desired surface cnotours become more complex, the need for a direct tool-tip sensing becomes inevitable. The physical constraints of the machining process prohibit any reasonable implementation of a tool-tip motion measurement. It is proposed that the measured force normal to the face of the workpiece can be filtered through an appropriate admittance transfer function to result in the estimated dapth of cut. This can be compared to the desired depth of cut to generate the adjustment control action in additn to position feedback control. In this work, the design methodology on the admittance model-based control with a conventional controller is presented. The recursive least-squares algorithm with forgetting factor is proposed to identify the parameters and update the cutting process in real time. The normal cutting forces are measured to identify the cutting dynamics in the real diamond turning process using the precision dynamoneter. Based on the parameter estimation of cutting dynamics and the admitance model-based nanodynamic control scheme, simulation results are shown.