• 상하수도학회지
• /
• 제24권5호
• /
• pp.537-548
• /
• 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.

• 한국재료학회지
• /
• 제27권1호
• /
• pp.48-52
• /
• 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.

• 한국진공학회지
• /
• 제9권2호
• /
• pp.136-143
• /
• 2000

RF magnetron sputtering법으로 $SrBi_2Ta_2O_9$ (SBT)박막을 상온에서 p-type Si(100) 기판위에 증착하여 DRO 강유전체 메모리(destructive read out ferroelectric random access memory)에 사용되는 강유전체막으로 Pt/SBT/Pt/Ti/$SiO_2$/Si (MFM)구조의 응용가능성을 확인하였다. 구조적인 특징들이 열처리 시간의 변화와 Ar/$O_2$의 가스 유량비의 변화에 따라서 XRD(x-ray diffractometer)에 의해 관찰되었으며 표면 특성은 FE-SEM(field emission scanning electron microscopy)에 의해서 관찰하고 박막의 전기적 특성들은 P-V(polarization-voltage measurement)와 I-V(current-voltage measurement)를 사용하여 관찰하였다. 스퍼터링 증착시 Ar/$O_2$의 가스 유량비는 1:4에서 4:1까지 변화 시켰고 SBT박막은 상온에서 증착시켰다. XRD 측정시 박막들은 SBT의 (105), (110) peak들을 나타내었다. 상온에서 증착시킨 박막은 1시간, 2시간 동안 산소 분위기에서 $800^{\circ}C$ 열처리를 하여 결정화 시켰다. SBT 박막의 P-V곡선은 이력 곡선의 모양을 갖추었으며 비대칭적인 강유전체 특성을 나타내었다. Ar/$O_2$ 가스유량비가 1 : 1, 2 : 1인 경우에 박막의 누설 전류밀도 값이 제일 좋았으며, 그 값은 3V 5V 7V에서 각각 $3.11\times10^{-8} \textrm{A/cm}^2$, $5\times10^{-8}\textrm{A/cm}^2$, $7\times10^{-8}\textrm{A/cm}^2$ 이었다. 열처리 시간을 2시간으로 증가시킨 후, 그들의 전기적 특성과 결정화특성이 개선됨을 확인하였다. AES 분석 및 EPMA분석으로 SBT박막의 깊이 분포 및 조성을 확인하였다.

• 물과 미래
• /
• 제13권3호
• /
• pp.77-81
• /
• 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.

• 폴리머
• /
• 제25권5호
• /
• pp.649-656
• /
• 2001

비닐아세테이트-비닐알핀을 (VAc-VAL) 공중합체의 조성에 따른 폴리(4-비닐피리딘)(P4VP)/VAc-VAL 공중합체 블렌드의 상용성을 조사하였다. 블렌드 시료의 시차 주사 열분석(DSC0 및 광학현미경에 의한 상분리온도 조사(TOM)를 통하여 P4VP는 VAL의 조성이 30 mole% 이상 함유된 VAc-VAL 공중합체들과 상용성이 있음이 확인되었다. 상용성 P4VP/Vac-VAL 공중합체 블렌드의 푸리에 변환 적외선(FT-IR) 분광 분석 결과 비닐피리딘과 비닐알코올 히드록실기 상에 강한 분자간 수소결합이 형성됨을 확인하였다. 성분 고분자 사이에 분자간 수소결합에 의해서 고분자 블렌드의 상용성이 유도되는 고분자 블렌드계의 열역학적 모델인 Association 모델을 이용하여 P4VP/VAc-VAL 공중합체 블렌드의 이론적인 상 그림을 구하였다. 이론적으로 계산된 binodal 곡선을 실험적으로 구한 흐림점 생성 곡서과 잘 일치하는 결과를 보였다.

• 대한지역사회영양학회지
• /
• 제5권1호
• /
• pp.109-119
• /
• 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.

• 대한치과보철학회지
• /
• 제32권2호
• /
• pp.249-267
• /
• 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$(p\leq0.05)$.

• 한국환경과학회지
• /
• 제17권3호
• /
• pp.275-285
• /
• 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.

• 한국습지학회지
• /
• 제19권3호
• /
• pp.303-310
• /
• 2017

본 연구의 목적은 난류흐름에서 이온의 영향아래 점착성 유사의 침강특성을 이해하는데 있다. 실험연구는 자유수면을 가지는 소형 환형수조에서 실시하였다. 실험에서 유사 재료로써 실리카($SiO_2$)를 사용하였으며, 부유농도는 CCD-Camera로 측정하였다. 실리카의 침강실험은 7g/L의 농도일 경우 다양한 바닥전단응력을 부여해 실시되었다. 바닥전단응력이 증가하게 되면 실리카의 플럭(floc)입자 입경(D)은 pH6.8에서보다 pH4.2와 높은 NaCl 농도에서 더 크다. 실리카의 침강속도($W_s$)는 pH4.2에서보다 10g NaCl/L에서 더 높다. 본 연구에서 예측된 농도-시간 곡선은 실제 흐름에서 이온의 영향아래 실측된 농도-시간 곡선과 잘 일치하는 것으로 나타났다.

• Journal of Astronomy and Space Sciences
• /
• 제28권2호
• /
• pp.109-116
• /
• 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.