• Journal of Environmental Science International
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• v.20 no.6
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• pp.767-773
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• 2011

The objectives of this research are to investigate the proper coagulation conditions which are a type and doses of coagulants, mixing conditions (velocity gradients and mixing times), pH and so on through Jar-test, to evaluate the flux variations, permeate, backwashing according to characteristics of pretreatment of the wastewater by means of MF membranes for river maintenance water reuse. The effluent water from B-city K-sewage treatment plant are used for this research. Turbidity and suspended solids(SS) are 14.2 NTU and 10.4 mg/L respectively. This condition causes fouling for membrane process. The flux decline could be reduced when coagulation pretreatment was carried out. Optimal coagulations PAC which are commonly used in the sewage treatment plant was observed in this research. The results indicate that an optimal coagulation dose and pH are 80 ppm and pH of 7 respectively, but coagulation efficiency was lower at strong acid or strong base. Results showed that continuous and steady operations in membrane separation process by means of the effective removal of organic matter and turbidity with coagulation pretreatment of sewage secondary effluent were achieved.

• Journal of Sensor Science and Technology
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• v.20 no.6
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• pp.368-374
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• 2011

A microfluidic device for real-time monitoring of residual free chlorine and pH in water based on optical absorption is proposed. The device consists of a serpentine micromixer for mixing samples with a reagent, and a photodiode and light emitting diode(LED) for the detection of light absorbance at specific wavelengths, determined for specific reagent combinations. Spectral analyses of the samples mixed with N, N'-diethyl-p-phenylenediamine(DPD) reagent for chlorine determination and bromothymol blue(BTB) for pH measurement are performed, and the wavelengths providing the most useful linear changes in absorbance with chlorine concentration and pH are determined and used to select the combination of LED and photodiode wavelengths for each analyte. In tests using standard solutions, the device is shown to give highly reproducible results, demonstrating the feasibility of the device for the inexpensive and continuous monitoring of water quality parameters with very low reagent consumption.

• Journal of the Korean Chemical Society
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• v.15 no.4
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• pp.177-181
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• 1971

Free radicals of lysozyme produced by $Ti-H_2O_2$ system were studied in aqueous solution at room temperature using ESR with a continuous flow-mixing. The spectra, each consisting of a doublet with 5.5 G splitting and a broad resonance covering 80 G splitting are closely similar in shape to that for solid irradiated in vacuum at $77^{\circ}K$ and observed at room temperature immediately on warming. The result is assumed to indicate that the secondary protein radical components formed within 0.01 second, dead time of the mixing chamber, and initiated by hydrogen atom abstraction at ${\alpha}$-carbon atom of peptide chain in liquid solution at room temperature are identical to those resulting from the initial formation of a mixture of positive holes and negative ions by ionization processes as well as radical fragments by the rupture of chemical bonds in the solid during similar time at the same temperature. A broad resonance is observed with considerable amplitude on the high field side of the doublet, which is quite dissimilar to the spectra of irradiated solid lysozyme. This resonance was tentatively attributed to the polypeptide free radical in which unpaired electrons are localized on side chain.

• Journal of the Korean Ceramic Society
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• v.26 no.4
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• pp.575-582
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• 1989

The effects of raw material feeding procedures and gelation temperatures on zeolite synthesis are investigated. Thus, the synthesis of zeolite 4A from sodium aluminate and sodium silicate solutions is chosen as a model reaction, for which equi-molar hydrogelation is performed with variation of feeding procedures and gelation temperatures. The formation of crystal nuclei, often being referred to as precursors, is induced under different conditions, the variation being examined by means of viscosity and water contents. The final products of zeolite 4A are evaluated by XRD, SEM morphology, particle size analysis and cation exchange capacity. Evidence shows that the viscosity of the initial products and their water contents are markedly influenced by the feeding methods of the reactant materials and by the gelation temperature. Further, it is found that the gelation at an elevated temperatures near 7$0^{\circ}C$ can be made possible through modification of mixing procedures. This provides convenient means of controlling the particle size of the final products. In this regard, a continuous flow-type mixing technique is proposed, which is demonstrated to be superior to the conventional batch-type mixings. The significance of this finding may lie in savings of equipment as well as energy costs, especialy on a large scale commercialization of zeolite production.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.9 no.1
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• pp.43-54
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• 1997

This paper presents an approximate analytical solution to a two-region one-dimensional model for the charging process of stratified thermal storage tanks with variable inlet temperature in the presence of momentum-induced mixing. Based on the superposition principle, an arbitrary-varying inlet temperature is decomposed into inherent discontinuous steps and continuous intervals approximated as a finite number of piecewise linear functions. This approximation allows the temperature of the upper perfectly-mixed layer to be expressed in terms of constant, linear and exponential functions with respect to time. Applying the Laplace transform technique to the model equation for the lower thermocline layer subject to each of three representative interfacial conditions yields compact-form solutions, a linear combination of which constitutes the final temperature profile. A systematic method for deriving solutions to the plug-flow problem having polynomial-type boundary conditions is also established. The effect of adiabatic exit boundary on solution behaviors proves to be negligible under the actual working conditions, which justifies the assumption of semi-infinite domain introduced in the solution procedure. Finally, the approximate solution is validated by comparing it with an exact solution obtained for a specific variation of inlet temperature. Excellent agreements between them suffice to show the necessity and utility of this work.

• Archives of design research
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• v.19 no.1 s.63
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• pp.303-316
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• 2006

Eclecticism, fusing and mixing heterogeneous and contrasting elements to create a new awareness of beauty, is based on diversity and pluralism, and as such fits well with the demand of the contemporaries who pursue individualization and diversification, which explains the current vogue for Eclecticism. As a precondition to grasp eclectic styles that are expressed in modern textile design, this study looks into the characteristics of eclecticism in modern art and applies the insight so gained to textile design in an attempt to understand transformations of modern textile design by considering the aesthetic effects and plastic characteristics suggested by the new trend. The result of our research indicates that the trends that characterize modern textile design can be divided into three categories as follows: 1) Mixing of high culture and low culture through cultural fusion, 2) Fusion of differing sensitivities through blending of times, 3) Blending of regional characteristics through geographical mixing. Characteristics of textile designs as influenced by these trends can be summarized as: 1) a conversion in the way textile designs are viewed, 2) increasing emphasis on the playfulness of representation and 3) multi-cultural expressions. In short, eclecticism of textile design represents a phase of modern society that is increasingly oriented toward multifacetedness and points to a direction for a new possibility of future textile designs, necessitating a continuous research along this line.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.685-688
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• 2008

Concrete is strong on the compressive property, but weak on the tensile and flexural properties. To improve these problems, the reinforcing bar is used in concrete. But porous concrete with steel fiber has a weak point when exposed to air, because porous concrete has the vast continuous void on its inside and steel fiber is easily rusted by air. For these reasons, this study investigated the void ratio, compressive strength, bending strength and bending toughness as steel fiber mixing ratio and target void ratio. From test results, actual void ratio and strength properties increased as the mixing ratio of steel fiber increase. In case the mixing ratio of steel fiber over the fixed ratio, strength is decreased. And from the toughness evaluation, compared to the porous concrete which isn't mixed with steel fiber, the deflection variation efficiency is remarkably improved. Consequently we can confirm the possibility of porous concrete with steel fiber for the secondary product and pavement material to improve strength and bending resistance efficiency.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.8
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• pp.645-651
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• 2015

The objective of this study is to experimentally investigate the effect of design parameter on the mass ratio of a central-driven ejector. The design parameters are the primary nozzle area and distance ratios, diffuser exit-area ratio and mixing-tube length ratio. The experimental setup was an open-loop continuous circulation system which has a movable nozzle ejector, an electric motor-pump, a water tank, a control panel and high-speed camera unit. We calculated the mass ratio using the measured primary and suction-flow rates with the experimental parameter of primary water-flow rate or pressure. The results showed that the mass ratio increased with the primary nozzle distance ratio and mixing tube length ratio, while the mass ratio decreased with the primary nozzle-area ratio and diffuser exit-area ratio.

• Polymer(Korea)
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• v.38 no.3
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• pp.286-292
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• 2014

The rheology of highly concentrated polymer bonded explosive (PBX) simulant was studied. An energy material, polyethylene plastomer (Exact$^{TM}$) having similar properties to poly(BAMO-AMMO) was selected as a binder. Dechlorane with similar properties to RDX (Research Department eXplosive) was chosen as a filler. Mixing behavior in a batch melt mixer was investigated. During mixing a large amount of heat of viscous dissipation was generated and a continuous decrease in torque was observed when the filler content was above 70 v%. It was believed due to wall slip phenomena. From the SEM images, the fillers were well dispersed and the effect of mixing condition affected slightly on the dispersion. Owing to distinct shear thinning behavior of the suspensions, measuring viscosity of highly filled suspensions was possible in a high shear rate capillary rheometer though it was impossible even in a low shear rate plateplate rheometer.

• Nuclear Engineering and Technology
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• v.54 no.6
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• pp.2311-2320
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• 2022

The main outcomes of the experiments H2P6 performed in the thermal-hydraulics large-scale PANDA facility at PSI in the frame of the OECD/NEA HYMERES-2 project are presented in this article. The experiments of the H2P6 series consists of two PANDA tests characterized by the activation of three (H2P6_1) or one (H2P6_2) cooler(s) in an initially stratified and pressurized containment atmosphere. The initial stratification is defined by a helium-rich region located in the upper part of the vessel and a steam/air atmosphere in the lower part. The activation of the cooler(s) results i) in the condensation of the steam in the vicinity of the cooler(s), ii) the corresponding activation of large scale natural circulation currents in the vessel atmosphere, with the result of iii) the re-distribution and mixing of the Helium stratification initially located in the upper half of the vessel and iv) the continuous pressure decay. The initial helium layer represents hydrogen generated in a postulated severe accident. The main question to be answered by the experiments is whether or not the interaction of the different, localized cooler units would be important for the application of numerical methods. The paper describes the initial and boundary conditions and the experimental results of the H2P6 series with the suggestion of simple scaling laws for both experiments in terms of i) the temperature difference(s) across the cooler(s), ii) the transient steam and helium content and iii) the pressure decay in the vessel. The outcomes of this scaling indicate that the interaction between separate, closely localized units does not play a prominent role for the present experiments. It is therefore reasonable to model several units as one large component with equivalent heat transfer area and total water flow rate.