• Journal of Korean Society of Water and Wastewater
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• v.35 no.4
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• pp.285-292
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• 2021

Osmotic power is to produce electric power by using the chemical potential of two flows with the difference of salinity. Water permeates through a semipermeable membrane from a low concentration feed solution to a high concentration draw solution due to osmotic pressure. In a pressure retarded osmosis (PRO) process, river water and wastewater are commonly used as low salinity feed solution, whereas seawater and brine from the SWRO plant are employed as draw solution. During the PRO process using wastewater effluent as feed solution, PRO membrane fouling is usually caused by the convective or diffusive transport of PRO which is the most critical step of PRO membrane in order to prevent membrane fouling. The main objective of this study is to assess the PRO membrane fouling reduction by pretreatment to remove organic matter using coagulation-UF membrane process. The experimental results obtained from the pretreatment test showed that the optimum ferric chloride and PAC dosage for removal of organic matter applied for the coagulation and adsorption process was 50 mg/L as FeCl₃ (optimum pH 5.5). Coagulation-UF pretreatment process was higher removal efficiency of organic matter, as also resulting in the substantial improvement of water flux of PRO membrane.

• Journal of the Korean Chemical Society
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• v.32 no.3
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• pp.186-194
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• 1988

The electrochemical reduction of O,O-dimethyl-O-(3-methyl-4-nitrophenyl)-phosphorothioate (Fenitrothion) has been studied in acetonitrile solution containing surfactant micelle by direct current (DC)-differential pulse (DP) polarography, cyclic voltammetry (CV) and controlled potential coulometry (CPC). The partially reversible electron transfer-chemical reaction(EC, EC mechanism) of fenitrothion reduction proceeded by four electron transfer to form O,O-dimethyl-O-(3-methyl-4-hydroxyaminophenyl)-phosphorothioate which undergoes single bond of the phosphorus atom and phenoxy group cleaves to give p-amino-m-cresol and dimethyl thiophosphinic acid as major product by two electron transfer-protonation at higher negative potential. The polarograpic reduction waves shown to suppressed due to inhibitory effect of sodium lauryl sulfate micelle solution and split up on selectivity of anionic micelle effect in two step at the first reduction peak.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.1
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• pp.50-56
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• 2010

This paper presents a new design algorithm for piece-removing dynamical system, based on 6-Sigma DMADOV technique using ARIZ and Brainstorming. Our design target is the piece-removing system installed on a mobile platform of bead-grinding equipment. The 6-Sigma DMADOV technique guides us design process according to 6 steps, i.e., Define - Measure - Analyze - Design - Optimize - Verify. A Design strategy to reduce the weight of piece-removing dynamical system will be explored by using ARIZ, i.e.,(the abbreviation of Algorithm for Inventive Problem Solving in Russian). The ARIZ will result in a final solution that the height and angle control parts for a cutting tool should be replaced by a kinematical approach, rather than complicated mechatronic approach(using motors). The Optimize step is composed of two sub-steps: (i) Generating process for obtaining several ideas of piece-removing system by using Brainstorming technique, satisfying the final solution derived from the Design step using ARIZ, and (ii) Optimizing process for selecting the most optimal idea of piece-removing system by using Pugh's matrix from the viewpoints of weight, cost and accuracy. The laststep of Verify has shown that the final design obtained by the 6-Sigma DMADOV technique with ARIZ & Brainstormingcan improve an initial design with design requirements satisfied. In this paper, we have shown that ARIZ and Brainstorming can be cooperatively merged into 6-Sigma DMADOV to give us both a formulatedproblem-solving approach and diverse candidate solutions(or ideas) without trial-and-error efforts.

• Journal of Environmental Health Sciences
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• v.33 no.4
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• pp.317-324
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• 2007

The sewage treatment sludge disposal has become a serious environmental problem because of restricted direct land-filling and oceandumping in spite of their large amounts discharged. So the recycling of sewage treatment sludge is very useful alternative for waste management. Here, we studied the feasibility of zeolite synthesis in open system from the sewage treatment sludge incinerator fly ash by means of hydrothermal synthesis. We considered the concentration of NaOH, reaction time, reaction temperature and reaction step as synthesis variables. The phase of zeolite products was identified by X-ray diffractometer(XRD) and ammonium ion exchange test was performed for the raw fly ash and two zeolite products(Z-3 and Z-5). In leaching test of the raw fly ash, hazard metal is detected very low level compared with regulatory leaching test standard. But in total recoverable test, the total contents of the fly ash were very high in terms of the standard for waste-derived fertilizer. Through hydrothermal reaction, small amount of zeolite P was synthesied in 1 N of NaOH solution and relatively large amount of hydroxysodalite was synthesied in 3 N and 5 N of NaOH solution with similar peak intensity. Addition of an aging step in the synthesis didn't increase the amount of zeolite phase. Maximum $NE_4^+-N$ exchange capacity is 1.49 mg $NH_4^+-N/g$ in Z-3 and 1.38 mg $NH_4^+-N/g$ in Z-5. Most of the ammonium ion is exchanged in 30 minutes and disorption did not occur until 5 hours.

• Journal of KSNVE
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• v.9 no.6
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• pp.1259-1266
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• 1999

The objective of this investigation is to develop a compliant track link model and apply this model to the multi-body dynamic analysis of high mobility tracked vehicles. Two major difficulties encountered in developing the compliant track models. The first one is that the integration step size must be kept small in order to maintain the numerical stability of the solution. This solution deals with high oscillatory signals resulting from the impulsive contact forces and stiff compliant elements to represent the joints between the track links. The second difficulty is due to the large number of the system equations of motion of the three dimensional multibody tracked vehicle model. This problem was sloved by decoupling the equations of motion of the chassis subsystem and the track subsystems. Recursive methods are used to obtain a minimum set of equations for the chassis subsystem. Several simulation scenarios were tested for the high mobility tracked vehicle including accelaeration, high speed cruising, braking, and turning motion in order to demonstrate the effectiveness and validity of the methods proposed in this investigation.

• Bulletin of the Society of Naval Architects of Korea
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• v.9 no.1
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• pp.7-14
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• 1972

Recently, the matrix method has become almost universal tool to solve various engineering problems in conjunction with the rapid development of high speed electronic computers. The method also has been introduced to ship structure analysis in past few years. This paper treats a method to obtain an approximate solution for stress distribution in a web frame of oil tankers. The method is designed to use relatively small computer. The procedure consists of two steps. In the first step, the web frame is idealized to a plane frame of slender members as shown in Fig. 2. Then, the plane frame is analyzed with a matrix method to determine forces and moments in each members. In the second step, the original shape of the web frame is restored and any portion of the frame, in which the stress distribution is desired, is isolated as shown in Fig. 3. Then, again, a finite element method is used to determine the stress distribution in the isolated portion. In this work, IBM 1130 computer in the computation center, SUN has been used. A numerical example with scantlings of an actual ship is worked out to prove the validity of this method.

• Journal of the Korean Chemical Society
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• v.15 no.2
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• pp.45-48
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• 1971

The various eluents have been used for the separations of alkaline earth metals by elutions through cation exchange resin column by many investigators. We find, the mixed solution of 1M HAc and 1M NaAc (pH 4.75) is the best eluent for this purpose, becouse the one step elution through 7cm Dowex 50w${\times}$8(100~200mesh) resin column with this eluent, gives the quantitative separation. When 2M NaAc is used as a eluent Sr(II) and Ba(II) is separated easily without any contamination of Mg(II) andCa(II). The Ca-Pb alloy which is composed of Cu, Ca, Sr, Ba and abundance of Pb metal is separated quantitatively into its components by the two step elution with 0.3M HAc + 0.3M NaAc(PH 4.75) and 0.5M HAc + 0.5M NaAc(PH 4.75) as eluents through 10cm resin column.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.11a
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• pp.71-78
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• 2004

Most of member parts have experienced severe springback problems because of their open shape Now it becomes imperative to develop an effective method, which can resolve these problems. However, there remain several obstacles to get accurate estimation of shape error. In analysis, we have to analyze the total process including forming, trimming and flanging. Furthermore, it is another challenge to compare the computed result with the real shape. In this study we developed an analysis program for the springback analysis. We could achive a big enhancement in computation time in springback analysis by using latest equation solving technique and could get a more robust solution conversence by contination method. We have approached this problem in two steps. In the first step, we analyzed forming stage to solve tearing and wrinkling problems. In the second step, we have analyzed full process and have done springback analysis with the same boundary condition as field measuring conditions. We have investigated the accuracy of springback analysis in terms of gap and flush used for insfection of real autobody panels. We found good and effective agreement with the observed results.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.111-111
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• 2016

Two step PEO ceramic coatings were formed on AZ91 magnesium alloy in $ZrO_2$ nanoparticles and $K_2ZrF_6$ based colloidal electrolyte solution for various voltages. Surface and layers tructure of the coatings was analyzed using SEM (ScanningElectronMicroscope). Structure analysis revealed that surface of the coating was transferred from individual pancake or craters-based structure to cluster-based structure with increasing the voltage of the secondary step process. Further, it was confirmed that the cluster zone was richin Zr-based complexes and formed due to high intensives parks. Increase in the Zr contents as discovered from the EDS analysis confirmed the rise in amorphous form of the Zr-based species, which justified the results of XRD where no increase in the intensity of Zr-based species was observed with increase in voltage. Potentiodynamic polarizariotion and impedance spectroscopy techniques were used to evaluate the corrosion performance of the coatings. The highest corrosion resistance was found for coatings prepared at 240V. The same specimen was found having highest and uniform vickers hardness ~1070.5 HV. The superior mechanical and electrochemical properties of the said coating can be attributed to the defect-less microstructure and the optimal role of $ZrO_2$ nanoparticles in the secondary PEO process at 240V.

• Nuclear Engineering and Technology
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• v.24 no.3
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• pp.252-262
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• 1992

The intent of this study is to develop an efficient calculation method which can be used to analyze the heterogeneous time-dependent reactor problems. By using the nodal theory one can not only reduce the calculational efforts, but accurately determine the group dependent flux densities averaged over the entire homogeneous nodes. This method uses correction factors(called“discontinuity factors”) in a rigorous manner to obtain the relationship between the node-averaged flux and the surface-averaged fluxes and currents. The discontinuity factors are calculated from the node-averaged fluxes, diffusion coefficients, and the discontinuity factors of the previous time step. The test results for two benchmark problems demonstrate the accuracy and efficiency of the method developed for the transient application in which assembly-size nodes can be used.