• Journal of Korean Society of Water and Wastewater
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• v.24 no.5
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• pp.537-548
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• 2010

Recently the Government has announced updated water quality standards for wastewater treatment effluent (become effective in 2012). That includes highly enforced regulations for T-P, BOD and COD, and a large budget, in particular for phosphorus removal, was set by the Ministry of environment. Chemical coagulation destabilizes colloidal particles so that particles grow to larger flocs, and solid particles are removed by solid-liquid separation. The efficiency of chemical coagulation depends on a various factors, including coagulant types and costs, construction and operation costs for the treatment facilities and so on. The proper selection should be based on the treatment efficiency of coagulants and underlying costs. The current research was to evaluate the treatment efficiencies of coagulants on a variety of wastewater influents and to develop saturation curves for several water quality parameters. Typical $Al_2(SO_4)_3$ and $FeCl_3$ were tested under a range of coagulant concentrations. The pollutant removal efficiencies of chemical treatment both for the $Al_2(SO_4)_3$ and $FeCl_3$ were especially high for T-P, followed by SS, BOD and COD. Correlation test also proved the highest relationship between SS and T-P.

• Korean Journal of Materials Research
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• v.27 no.1
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• pp.48-52
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• 2017

In this study, we used I-V spectroscopy, photoconductivity (PC) yield and internal photoemission (IPE) yield using IPE spectroscopy to characterize the Schottky barrier heights (SBH) at insulator-semiconductor interfaces of Pt/$HfO_2$/p-type Si metal-insulator-semiconductor (MIS) capacitors. The leakage current characteristics of the MIS capacitor were analyzed according to the J-V and C-V curves. The leakage current behavior of the capacitors, which depends on the applied electric field, can be described using the Poole-Frenkel (P-F) emission, trap assisted tunneling (TAT), and direct tunneling (DT) models. The leakage current transport mechanism is controlled by the trap level energy depth of $HfO_2$. In order to further study the SBH and the electronic tunneling mechanism, the internal photoemission (IPE) yield was measured and analyzed. We obtained the SBH values of the Pt/$HfO_2$/p-type Si for use in Fowler plots in the square and cubic root IPE yield spectra curves. At the Pt/$HfO_2$/p-type Si interface, the SBH difference, which depends on the electrical potential, is related to (1) the work function (WF) difference and between the Pt and p-type Si and (2) the sub-gap defect state features (density and energy) in the given dielectric.

• Journal of the Korean Vacuum Society
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• v.9 no.2
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• pp.136-143
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• 2000

$SrBi_2Ta_2O_9;(SBT)$ films were deposited on p-type Si(100) at room temperature by rf magnetron sputtering method to confirm the possibility of application of $Pt/SBT/Pt/Ti/SiO_2/Si$ structure (MFM) for destructive read out ferroelectric RAM (random access memory). Their structural characteristics with the various annealing times and Ar/$O_2$ gas flow ratios in sputtering were observed by XRD (X-ray diffractometer) and the surface morphologies were observed by FE-SEM (field emission scanning electron microscopy), and their electrical properties were observed by P-V (polarization-voltage measurement) and I-V (current-voltage measurement). The Ar/$O_2$ gas flow ratios of sputtering gas were changed from 1 : 4 to 4 : 1 and SBT thin films were deposited at room temperature. The films show (105), (110) peaks of SBT by XRD measurement. SBT thin films deposited at room temperature were crystallized by furnace annealing at 80$0^{\circ}C$ in oxygen atmosphere during either one hour or two hours. Among their electrical properties, P-V curves showed shaped hysteresis curves, but the SBT thin films showed the asymmetric ferroelectric properties in P-V curves. When Ar/$O_2$ gas flow ratios are 1 : 1, 2: 1, the leakage current density values of SBT thin films are good, those values of 3 V, 5 V, and 7 V are respectively $3.11\times10^{-8} \textrm{A/cm}^2$, $5\times10^{-8}\textrm{A/cm}^2$, $7\times10^{-8}\textrm{A/cm}^2$.After two hours of annealing time, their electrical properties and crystallization are improved.

• Water for future
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• v.13 no.3
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• pp.77-81
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• 1980

Probable Maximum Precipitation values for seven heavy stroms during the period from 1966 to 1976 are derived, using the manual for W.M.O P.M.P analysis of strom precipitation. The hydrometeoroogical and the statistical methods are consisted of the procedure of P.M.P. estimation in this study. It is possible to draw P.M.P curves from the view points of area and strom durations. A comparison has been made between the P.M.P values of Nakding River basin and the results of this paper. For a storm period of 24 hours, the P.M.P value at the maximum station is 762 mm and the moistrue maximization ratio are within the range 1.17 to 1.41 for the seven selected stroms.

• Polymer(Korea)
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• v.25 no.5
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• pp.649-656
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• 2001

Miscibility of poly(4-vinylpyridine) (P4VP) blends with poly(vinyl acetate-co-vinyl alcohol) (VAc-VAL copolymers) was investigated as a function of comonomer composition of VAc-VAL copolymers. Differential scanning calorimetry (DSC) and thermo-optical microscopic (TOM) analysis confirmed that P4VP is miscible with VAc-VAL copolymers containing more than 30 mole% VAL. Fourier transform inflated (FT-IR) spectroscopic analysis revealed that the strong intermolecular hydrongen bonding interaction between the vinylpyridine and VAL hydroxyl group was formed. Theoretical phase diagram was constructed by the calculation using the Association model, a thermodynamic model for hydrogen-bonded polymer blend systems developed by Coleman et al. The calculated theoretical binodal phase diagrams were in good agreement with the experimentally determined cloud point curves.

• Korean Journal of Community Nutrition
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• v.5 no.1
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• pp.109-119
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• 2000

The purpose of this study was to measure serum lipids concentrations by gender and age, and to investigated the relation of serum lipids levels to cigarette smoking alcohol intake exercise and menopausal status in Korean adults. The subjects consisted of 463 healthy adult(29- men and 173 women) volunteers who were visiting the health Promotion Center in the Asan Medical Center from July 1, 1994 to July 22, 1994 Subjects were ambulatory free-living people and aged 20- 80 years, Anthropometric measurement was performed and serum triglyceride(TG), HDL-cholesterol and total cholesterol(TChol) concentrations were measure by automatic system(Hitachi 736-40). Data on life styles were obtained using structured questionnaires issued by a trained interviewer, All data were statistically analyzed by PC-SAS(Version 6.04) Serum concentrations of triglyceride and total cholesterol was higher(p<0.05) in men than in women, and serum HDL-cholesterol was lower(p<0.05) in men than in women. The prevalence of hyperlipidemia(TG>170 mg/dL and TChol>220 mg /dL) was 12.5% in men and 4.1% in women. The levels of serum triglyceride, total cholesterol and BMI increased with age in women. The distribution curves of serum triglyceride, total cholesterol and LDL-cholesterol of women were located in lower increased more rapidly with aging than in men, The distribution curves of BMI of women increased with aging after the thirties, The BMI of women was located in higher levels than of men in their sixties. The serum concentration of triglyceride and total cholesterol of male current-smokers and non- smokers were significantly(p<0.05) higher than those of ex-smokers. The concentrations triglyceride the male current0drinkers were higher(p<0.05) than those of male non-drinkers. In non-smokers and non- drinkers, serum TG concentration were lower (p<0.05) than those of current-smokers and current-drinkers. In exercisers, the serum triglyceride concentration was significantly(p<0.05) lower than in non- exercisers. In postmenopausal woman BMI and serum concentrations of TChol, TG and LDL-Chol were significantly by age and gender and smoking alcohol drinking, exercise and menopausal staus might be a better indicator to predict serum lipids in both genders.

• The Journal of Korean Academy of Prosthodontics
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• v.32 no.2
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• pp.249-267
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• 1994

The purpose of this study was to compare the fatigue, physical properties, flexibility and surface roughness of titanium used in removable partial dentures with those of a type IV and alloy and a cobalt- chromium alloy. Fatigue testing subjected the test specimen to rapid cycling at a given stress until failure occurred by using a small-sized, electrodynamic type bending fatigue testing machine. The S-N curves for the framework materials were generated. For tensile testing, a tensile bar as described in the ADA Specification No.14 was subjected to tensile loading until failure occurred. Load-displacement curves were generated for 18 gauge round specimen and tapered half round specimen. Then the flexibilities were calculated. The surface roughnesses were compared by analyzer. Through analyses of the data, the following conclusions were obtained. 1. The fatigue property of titanium was higher than that of a type IV gold alloy$(p\leq0.05)$, but there was no significant difference between titanium and a cobalt-chromium alloy $(p\geq0.05)$. 2. The yield strength, the ultimate tensile strength and Victors hardness of titanium were higher than those of a type IV gold alloy but lower than those of a coalt-chromium alloy$(p\leq0.05)$. 3. The percentage of elongation and reduction of area of titanium were the highest $(p\leq0.05)$. 4. The surface roughness of titanium was the greatest$(p\leq0.05)$. 5. The flexibility of titanium was lower than that of a type IV gold alloy but higher than that of a cobalt-chromium alloy$(p\leq0.05)$.

• Journal of Environmental Science International
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• v.17 no.3
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• pp.275-285
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• 2008

The floc formation, breakage and reformation of humic acid by inorganic (alum and PAC) and organic coagulants (cationic polyelectrolytes) at several conditions (pH, ionic strength and floc breakage time) were examined and compared among the coagulants at different conditions using a continuous optical monitoring method, with controlled mixing and stirring conditions. For alum, the shapes of formation, breakage and reformation curves at different pH (5 and 7) were different, but the shapes and the sizes of initial floc and reformed floc were nearly the same in the absence and presence of electrolytes at pH 7. For PAC, similar shapes of the curves were obtained at different pH and ionic strength, but the sizes were different, except for those of reformed flocs at different pH. However, for these coagulants, reformed flocs after floc breakage, occurred irreversibly for all the conditions used in this study. For organic coagulants, the time to attain the initial plateau floc size, the extent of floc strength at high shear rate and reversibility of reformed floes were different, depending floc formation mechanism. Especially, for the cationic polyelectrolyte forming humic flocs by charge neutralization or electrostatic patch effect mechanism, reformed flocs occurred reversibly, regardless of pH and floc breakage time, but occurred irreversibly in the presence of electrolytes.

• Journal of Wetlands Research
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• v.19 no.3
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• pp.303-310
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• 2017

This paper is to understand the settling properties of cohesive sediments under effects of ions in turbulent flow. The experiments were conducted using a miniature annular flume(mini flume) with a free water surface. Silica was used as sediment of experiment. The suspended concentrations were measured by using a CCD-Camera. Settling of silica($SiO_2$) was allowed to occur under various shear stresses in a concentration of 7g/L. At condition of pH 4.2 and high NaCl concentration, the floc size D of silica was larger than D at condition of pH6.8 with the bed shear stress increasing. The settling velocity $W_s$ of silica was higher at condition of 10g NaCl/L than $W_s$ at condition of pH4.2. Comparison of measured concentration-time curves and concentration-time curves calculated by this study showed similar tendency in flow under effects of ions.

• Journal of Astronomy and Space Sciences
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• v.28 no.2
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• pp.109-116
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• 2011

The first presented BV light curves of BH UMa confirmed Krajci's (2005) result that BH UMa is an RR Lyr star that belongs to the RRc subgroup. The light curves showed a slight asymmetry of D = 0.453 with an amplitude of about $0.^m58$ in B, $0.^m47$ in V, and $0.^m11$ in B-V and with a small hump between $0.^p82$ and $0.^p86$. We determined nine new times of minimum light and eight times of maximum light. We also analyzed all of the available unanalyzed minimum timings and found for the first time that the period of BH UMa has varied dramatically in at least three independent sinusoidal ways superposed on a secularly downward parabola over 66 years. The secular period decreasing rate was obtained as $6.^d684{\times}10^{-8}y^{-1}$, corresponding to -0.58 s/century. The semi-amplitude and period for each of the three sinusoidal variations were ($0.^d058$, $14.^y44$), ($0.^d044$, $9.^y98$), and ($0.^d005$, $0.^y97$), respectively. It is uncertain whether the periodicity for the shortest period of $0.^y97$ is real or spurious. The secular period decrease, well consistent with those of the other RRc stars, could be considered as a natural result of the evolution of the BH UMa system. The two possible sinusoidal terms were interpreted as both two light-time effects due to two additional bodies orbiting BH UMa and combinations of random fluctuations in the pulsation period of BH UMa. Two interpretations were shortly discussed with related parameters.