• Journal of Environmental Science International
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• v.23 no.4
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• pp.715-722
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• 2014

Effects of coagulation types on flocculation were investigated by using a photometric dispersion analyzer (PDA) as an on-line monitoring technique in this study. Nakdong River water were used and alum and ferric chloride were used as coagulants. The aim of this study is to compare the coagulation characteristics of alum and ferric chloride by a photometric dispersion analyzer (PDA). Floc growing rates ($R_v$) in three different water temperatures ($4^{\circ}C$, $16^{\circ}C$ and $30^{\circ}C$) and coagulants doses (0.15 mM, 0.20 mM and 0.25 mM as Al, Fe) were measured. The floc growing rate ($R_v$) by alum was 1.8~2.8 times higher than that of ferric chloride during rapid mixing period, however, for 0.15 mM~0.25 mM coagulant doses the floc growing rate ($R_v$) by ferric chloride was 1.1~2.3 times higher than that of alum in the slow mixing period at $16^{\circ}C$ water temperature. Reasonable coagulant doses of alum and ferric chloride for turbidity removal were 0.1 mM (as Al) and 0.2 mM (as Fe), respectively, and the removal efficiency of those coagulant doses showed 94% for alum and 97% for ferric chloride. The appropriate coagulant dose of alum and ferric chloride for removing dissolved organic carbon (DOC) showed about 0.3 mM (as Al, Fe) and at this dosage, DOC removal efficiencies were 36% and 44%, and ferric chloride was superior to the alum for removal of the DOC in water.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.13 no.1
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• pp.9-14
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• 1999

One of the IIDSt difficult problems in a tri-band fluorescent lamp manufacture is to search a desired color by an adequate mixing of tri-color phosphors. When a light spectrum of a phosphor is slightly changw or distorted due to process variable or when another spectrum such as from Ar, Kr or a iDosphor of calcium halo-phosphate as a first layer exist, it is even rrnre difficult to search a desired color. In this work, a rapid awuaching rrethod to a desired light color was studied. 1bree single-color fluorescent lamps and three-color-mixed fluorescent lamps with different mixing ratios were prepared and the spectra of these lamps were measured, from which the rrercury and the argon spectra were eliminatffl to obtain the rrndifiw color coordinates. From this rrndifiw color coordinate, h.lIlHl ratios of green and blue to red were correlatffl with their weight ratios. This correlation was awliw to the industrial line for single and double layer coating and proven to be valuable as a desired color matching procWure in tri-color fluorescent lamp manufacture.acture.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.46 no.5
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• pp.9-18
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• 2014

London Convention on the prevention of marine pollution by dumping of wastes and other matter prohibits the deliberate disposal of paper mill sludges at sea. In order to explore the alternative plan on the prohibition of sludge disposal at sea, the biodegradable seedling pot was developed by mixing the sludge with old newspaper (ONP) in appropriate mixing ratios. The C/N ratio of the mixed sludge was below 20, leading to rapid deterioration of the organic matters composing the seedling pot. The increased ONP contents in the seedling pot resulted in the increase of pot thickness and thereafter in the decrease of pot density. Cellulose fibers in ONP promoted water absorption of the pot but AKD addition helped the seedling pot to repel water during raising seedling. Breaking length and burst strength of the seedling pot were improved by addition of wet strength additives but air permeability was a little diminished. Biodegradable rate of the seedling pot in a soil was accelerated by the attack of soil microbes at the beginning, and finally the pot was completely degraded in 150 days in a soil.

• Advances in concrete construction
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• v.14 no.3
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• pp.205-214
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• 2022

Due to seawater's physical and chemical deterioration effects on concrete structures, it is crucial to investigate the durability of these structures in marine environments. In some conditions, concrete structures are exposed to seawater from the first days of construction or because of the lack of potable water, part of the concrete curing stage is done with seawater. In this research, the effects of exposure to seawater after 7 days of curing in standard conditions were evaluated. To improve the durability of concrete, fly ash has been used as a substitute for a part of the cement in the mixing design. For this purpose, 5, 15, and 30% of the mixing design cement were replaced with type F fly ash, and the samples were examined after curing in seawater. The resistance of concrete against chloride ion penetration based on the rapid chloride penetration test (RCPT), water permeability based on the depth of water penetration under pressure, and water absorption test was done. The changes in the compressive strength of concrete in different curing conditions were also investigated. The results show that the curing in seawater has slightly reduced concrete resistance to chloride ion permeation. In the long-term, samples containing FA cured in seawater had up to 10% less resistance to chloride ion penetration. The amount of reduction in chloride ion penetration resistance was more for samples without FA. Whiles, for both curing conditions in the long-term up to 15%, FA improved the chloride ion penetration resistance up to 40%. Curing in seawater slightly increased the penetration depth of water under pressure in samples containing FA, while this increase was up to 12% for samples without FA. In the long-term the compressive strength of samples cured in seawater is not much different from the compressive strength of samples cured in plain water, while at the age of 28 days, due to seawater salts' accelerating effects the difference is more noticeable.

• Journal of Soil and Groundwater Environment
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• v.28 no.1
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• pp.15-24
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• 2023

A persulfate(PS)/sulfidated microscale zero-valent iron(S-mZVI) system was tested for treating a soil contaminated with phenol. Sulfidation of bare mZVI was conducted using a mechanochemical process utilizing a ball mill in order to improve persulfate activation capacity and stability of unmodified mZVI. The synthesized S-mZVI performed markedly better than the bare mZVI in activating PS. The optimum molar ratio of sulfur to mZVI was around 0.12. In the soil slurry experiments, a very rapid and complete removal of phenol was observed at the optimum molar ratios of PS to S-mZVI of 2:1 and PS to phenol of 16:1. The phenol removal efficiencies decreased as the water content of the slurries decreased. This was believed to be due to increased soil oxidant demand as the amount of soil was increased as relative to the water content. To evaluate the field applicability of the process, slurry experiments adopting high soil contents were carried out that simulated in-situ soil mixing conditions. These experiments resulted in substantially compromised degradation efficiencies of 54.3% and 43.8% within 4 hours. The current study generally shows that the PS/S-mZVI process has a potential to be developed into a remediation technology for soils contaminated with organics.

• Proceedings of the IEEK Conference
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• 2000.06b
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• pp.310-313
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• 2000

In this study, the Au/Ni and Au/Ni/Si/Ni layers prepared by electron beam evaporation were used to form ohmic contacts on p-type GaN. Before rapid thermal annealing, the current-voltage(I-V) characteristic of Au/Ni and Au/Ni/Si/Ni contact on p-type GaN film shows non-ohmic behavior. A Specific contact resistance as 3.4$\times$10$^{-4}$ Ω-$\textrm{cm}^2$ was obtained after 45$0^{\circ}C$-RTA. The Schottky barrier height reduction may be attributed to the presence of Ga-Ni and Ga-Au compounds, such as Ga$_4$Ni$_3$, Ga$_4$Ni$_3$, and GaAu$_2$ at the metal - semiconductor interface. The mixing behaviors of both Ni and Au have been studied by using X-ray photoelectron spectroscopy. In addition, X-ray diffraction measurements indicate that the Ni$_3$N, NiGa$_4$, Ni$_2$Si, and Ni$_3$Si$_2$ Compounds were formed at the metal-semiconductor interface.

• The Korean Journal of Physiology
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• v.28 no.2
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• pp.203-214
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• 1994

Using the methods of stopped-flow and epifluorescence microscopy with entrapped fluorophore, membrane permeability of $NH_3$ and weak acids in liposomes, renal brush border (BBMV) and basolateral membrane vesicles (BLMV), and primary culture cells from renal proximal tubule was measured. Permeability coefficient (cm/sec) of $NH_3$ was $(2.9{\times}10^{-2}$ in phosphatidylcholine liposome $25^{\circ}C)$, $5.9{\times}10^{-2}$ in renal proximal tubule cell $(37^{\circ}C)$, $4.0{\times}10^{-2}\;and\;2.4{\times}10^{-2}$ in BBMV and BLMV $(25^{\circ}C)$, respectively. Formic acid has the highest permeability coefficient among the weak acids tested, which was $4.9{\times}10^{-3}$ in liposome, $5.0{\times}10^{-3}$ in renal proximal tubule cell, $9.1{\times}10^{-3}$ in BBMV and $3.8{\times}10^{-3}$ in BLMV. There was a linear relationship between external concentration of nonionized formic acid and initial rate of flux of formic acid in liposome, and the slope coincided with the value of permeability coefficient of formic acid measured in pH 7.0. These results show that techniques of stopped-flow and epifluorescence microscopy with entrapped fluorophore provide the precise method of measurement of very rapid transport of nonelectrolytes through membranes with the advantages of instantaneous mixing effect, good resolution time and easy manipulation.

• Resources Recycling
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• v.24 no.3
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• pp.66-75
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• 2015

The flexural performance of amorphous steel fibers having environmental and economy benefits due to relatively short manufacturing process were evaluated as well as that of hooked steel fibers by varing fiber length and volume fraction. Fiber lengths were 10 mm, 20 mm, 30 mm and fiber volume fractions were varied from 0.3% to 1.2%. Test results with flexural performance showed that mixing design needs to be careful because of relatively high volume of amorphous steel fiber compared to hooked steel fibers. High flexural strength was obtained from both longer fiber length and higher volume fraction. Residual strength and toughness of amorphous steel fiber were similar to that of hooked steel fiber, even though rapid dropping of applied load right after concrete matrix breaking. It can be judged that relatively high ability of energy dissipation around first cracking area relatively overcome rapid dropping of loading.

• Atmosphere
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• v.26 no.1
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• pp.141-158
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• 2016

The objective of this study is to examine the impact of urban canopy and the horizontal resolution on simulated meteorological variables such as 10-m wind speed, 2-m temperature and precipitation using WRF model for a local, convective rainfall case. We performed four sensitivity tests by varying the use of urban canopy model (UCM) and the horizontal resolution, then compared the model results with observations of AWS network. The focus of our study is over the Seoul metropolitan area for a convective rainfall that occurred on 16 August 16 2015. The analysis shows that mean diurnal variation of temperature is better simulated by the model runs with UCM before the convective rainfall. However, after rainfall, model shows significant difference in air temperature among sensitivity tests depending on the simulated rainfall amount. The rainfall amount is significantly underestimated in 0.5 km resolution model run compared to 1.5 km resolution, particularly over the urban areas. This is due to earlier occurrence of light rainfall in 0.5 km resolution model. Earlier light rainfall in the afternoon eliminates convective instability significantly, which prevents occurrence of rainfall later in the evening. The use of UCM results in a higher maximum rainfall in the domain, which is due to higher temperature in model runs with urban canopy. Earlier occurrence of rainfall in 0.5 km resolution model is related to rapid growth of PBL. Enhanced mixing and higher temperature result in rapid growth of PBL, which provides more favorable conditions for convection in the 0.5 km resolution run with urban canopy. All sensitivity tests show dry bias, which also contributes to the occurrence of light precipitation throughout the simulation period.

• Journal of Adhesion and Interface
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• v.14 no.3
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• pp.128-134
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• 2013

This study investigated the natural adhesives for ceramics conservation that can be used as a substitution for synthetic resins. Samples were prepared by mixing lacquer with animal glue and the structure and adhesion properties of the samples were analyzed. The structure analysis with FT-IR showed that carbonyl (C=O), amine (N-H) and aromatic (C=C) bonds are increased by adding animal glue on lacquer. Comparing to the viscosity and tensile strength of the sample to the Paraloid B-72 and Araldite rapid type, these natural adhesives can be a substitution for the synthetic resins. Through methodical and intensive study, we expect practical uses of this eco-friendly natural adhesives for ceramics conservation.