• Analytical Science and Technology
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• v.7 no.4
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• pp.483-492
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• 1994

Direct solid analysis of various kinds of metal samples has been conducted by glow discharge. In this laboratory, the gas-jet assisted glow discharge(GJGD) device has been developed and characterized. The effect of changes in applied current, cell pressure and flow rate on atomic emission signals obtained from a jet-assisted cathodic sputtering was investigate. The emission intensities of Cu, Zn, and Ar were measured. They were increased with the current. But the intensities were decreased by increasing the flow rate of argon due to the diffusion and transportation of particles into plasma. By increasing the pressure of the cell, the intensities were greatly decreased because of enhancement of redeposition onto the surface of the sample.

• Journal of the Korean GEO-environmental Society
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• v.7 no.1
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• pp.41-53
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• 2006

In this study, estimation of nonlinear adsorption isotherms(Langmuir & Freundlich adsorption isotherm) and advection-dispersion model parameters was conducted using genetic algorithm(GA) for Zn and Cd adsorption. Estimated parameters of nonlinear adsorption isotherms, which were obtained from the optimization process using genetic algorithm(GA), are nearly same with the parameters obtained from a linearization process of the nonlinear isotherms. Estimated effective diffusion coefficients, which were obtained from a finite element analysis of the advection-dispersion model and an optimization procedure using the genetic algorithm, for the metals were approximately in the order of $10^{-7}cm^2/s$ which could be obtained based on the linear distribution coefficient. The effective diffusion coefficients based on the nonlinear retardation factors were in the range of $10^{-6}{\sim}10^{-5}cm^2/s$. As a result, the correlation coefficient obtained between the measured and calculated concentration was over 0.9 which means that the genetic algorithm should be successfully applied to estimate the unknown parameters of the nonlinear adsorption isotherms and advection-dispersion model.

• Applied Biological Chemistry
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• v.44 no.2
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• pp.103-108
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• 2001

The objectives of this study were to investigate the contamination of the soils around the major roadsides in Seoul and to accumulate base-line data. Fifty topsoils ($0{\sim}5$ cm) and 48 subsoils ($20{\sim}50$ cm) were collected from 50 sampling sites near Manguro in Chungnanggu. The samples were air-dried, passed through 2-mm sieves, and analyzed to determine the physicochemical properties and the contents of heavy metals (Cd, Cu, Pb, Zn) and anions (Cl, $NO_3$, $SO_4$). Soil textures of top- and subsoils were mainly loamy sand and sandy loam, respectively. Average $_PH$ of top- and subsoil was approximately 7.5, much higher than that of the forest soils in Seoul. Average heavy metal contents were lower than the levels allowed by the Soil Environment Conservation Act of Korea, whereas much higher than those of the forest soils. Contents of some heavy metals were higher than the maximum allowed levels. Anion concentrations were also much higher than those of the forest soils. A careful management to prevent the aggravation of the present contamination level and the diffusion of contaminants is recommended.

• Korean Journal of Materials Research
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• v.6 no.5
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• pp.483-488
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• 1996

InP 기판위에 InP와 격자정합된 undoped-InGaAs에서 zine의 확산 특성을 Electrochemical Capacitance-Voltage 법(polaron)과 Secondary Ion Mass Spectrometry(SIMS)로 조사하였다. Metallorganic Chemical Vapor Deposition (MOCVD)를 이용하여 undoped-InGaAs 층을 성장시켰으며 확산방법으로는 Zn3P2 확산원 박막과 Rapid Thermal Annealing (RTA)를 이용하였다. 450-55$0^{\circ}C$온도범위에서 30-300초 동안 확산을 수행한 결과 zinc의 확산계수는 D=Doexp(-$\Delta$E/kT)의 특성을 만족하였으며, Do와 $\Delta$E는 각각 1.3x105$\textrm{cm}^2$/sec와 2.3eV였다. 얻어진 확산계수는 다른 확산방법을 이용한 값들에 비해 매우 큰 값인데, 이것은 RTA 처리시 빠른 온도 증가에 의한 확산원 박막, 보호막, 그리고 InGaAs 에피층이 가지는 열팽창계수의 차이로인한 응력의 효과에 의한 것으로 생각되며, 이를 sealed-ampoule 법을 사용한 경우의 확산특성과 비교를 통하여 확인할 수 있었다.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.29 no.1
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• pp.169-184
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• 2003

비타민 C(L-ascorbic acid)는 강한 항산화성, 피부에 대한 높은 안전성으로 인해 피부의 노화방지, 미백, 주름 개선 등의 기능성 화장품 원료로써 많은 관심이 있는 물질이지만, 화학적으로 매우 불안정하여 쉽게 산화, 분해되므로 화장품 제형으로 포함시키는데 곤란한 문제가 있다. 본 연구에서는 비타민 C 의 안정성에 대한 단점을 보완하기 위하여 생체 및 피부 친화성이 우수한 무기물을 사용하여 비타민 C 를 캡슐화(encapsulation)한 분말상의 유-무기 복합물질 Vitabrid-C 를 합성하고, 이를 함유하는 피부 미백용 트윈케익 파우더를 개발하였다. 우선 Vitabrid-C 는 수용액상에서 비타민 C 를 수화된 산화아연(ZnO)으로 1 차 캡슐화하여 나노입자를 형성시키고, 그 표면을 실리카(silica)나노 입자로 한번 더 코팅하여 표면의 껍질이 다공특성을 갖는 분말을 제조함으로써 완성하였다. 이렇게 제조된 Vitabrid-C는 순수 비타민 C 에 비해 우수한 안정성을 보였으며, 캡슐 내 비타민 C 가 서서히 방출되는 서방특성을 발휘하였다. 또한 Vitabrid-C는 입자의 크기가 미세하고 균일하여 트윈케익 처방에 용이하게 적용할 수 있었다. Vitabrid-C와 순수 비타민 C의 생화학적 동등성에 대한 평가는 tyrosinase 억제능(L-DOPA oxidase 억제) 및 DPPH항산화 실험을 통하여 비교하였다. 트윈 케익 처방에 적용된 Vitabrid-C 에서 비타민 C 의 피부 투과경향을 Franz diffusion cell 법을 이용하여 확인하였다 또한 Vitabrid-C가 포함된 트윈케익을 건강한 피부를 가진 25 세 이상되는 여성의 전박에 색소 침착을 유도한 후 피부색 개선 효과 평가를 통해 임상적 효능을 평가하였다.

• Journal of the Korean institute of surface engineering
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• v.45 no.3
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• pp.117-122
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• 2012

ZTO/GZO double layered films were prepared on unheated non-alkali glass substrates. ZTO films were deposited by RF/DC hybrid magnetron co-sputtering using ZnO (RF) target and $SnO_2$ (DC) targets, and then GZO films were deposited by DC magnetron sputtering using an GZO ($Ga_2O_3$:5.57 wt%) target. These films were post-annealed at temperature of 200, $300^{\circ}C$ in air and vacuum ambient for 30 min. In the case of post-annealing in air, ZTO/GZO double layer showed relatively low resistivity change, compared to GZO single layer. Furthermore, ZTO/GZO double layer revealed low WVTR, compared to GZO single layer. Therefore, it can be confirmed that ZTO film doing a role with barrier for water or oxygen diffusion.

• Membrane and Water Treatment
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• v.13 no.6
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• pp.291-301
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• 2022

In this study, cement/PVDF hollow-fiber hybrid membranes were prepared via a mixed process of diffusion-induced phase separation and hydration. The presence of X-ray diffraction peaks of Ca(OH)₂, an AFt phase, an AFm phase, and C-S-H phase confirmed the hydration reaction. Good hydrophilicity was obtained. The cross-sectional and surface morphologies of the hybrid membranes showed that an asymmetric pore structure was formed. Hydration products comprising parallel plates of Ca(OH)₂, fibrous ettringite AFt, and granulated particles AFm were obtained gradually. For the hybrid membranes cured for different time, the pore-size distribution was similar but the porosity decreased because of blocking of the hydration products. In addition, the water flux decreased with hydration time, and carbon retention was 90% after 5 h of rejection treatment. Almost all the Zn²⁺ ions were adsorbed by the hybrid membrane. The above results proved that the obtained membrane could be alternative as basement membrane for separation application.

• The Journal of Korean Academy of Prosthodontics
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• v.23 no.1
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• pp.39-59
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• 1985

The purpose of this study was to investigate how gap distances of 0.13mm, 0.15mm, 0.20mm, and 0.30mm affects solder joint strength from gold alloys and nickel-chromium base alloys and to examine the composition of solder gold, the solder joint of gold alloys and nickel-chromium base alloys. The tensile test specimens were prepared in the split stainless steel mold with a half dumbbell shape 2.5mm in diameter and l2mm in length. 6 pairs of specimens of each gap distance group of gold alloys and nickel-chromium base alloys were made and 48 pairs of all specimens were soldered with solder gold of 666 fineness. All soldered specimens were machined to a uniform diameter and then a tensile load was applied at a cross-head speed of 0.10mm/min using Instron Universal Testing Machine, Model 1115. The fractured specimens at solder gold of solder joint fracture with each gap distance of 0.13mm, 0.15mm, 0.20mm, and 0.30mm were examined under the Scanning Electron Microscope, JSM-35c and the composition of solder gold, the solder joint of gold alloys and nickel-chromium base alloys was analyzed by Electron Probe Micro Analyzer. The results of this study were obtained as follows: 1. In case of soldering of gold alloys, the tensile strength between gold alloys showed $37.33{\pm}2.52kg/mm^2$ at 0.13, $39.14{\pm}3.35kg/mm^2$ at 0.15mm, $43.76{\pm}2.97kg/mm^2$ at 0.20mm, and $49.18{\pm}4.60kg/mm^2$ at 0.30mm. There was statistically significant difference at each gap distance, and so the greater increase of gap distance showed the greater tensile strength. 2. In case of soldering of nickel-chromium base alloys, the tensile strength between nickel-chromium base alloys showed $34.84{\pm}4.26kg/mm^2$ at 0.13mm, $37.25{\pm}2.49kg/mm^2$ at 0.15mm, $42.91{\pm}4.32kg/mm^2$ at 0.20mm, and $46.93{\pm}4.21kg/mm^2$ at 0.30mm. There was not statistically significant difference only between 0.13mm and 0.15mm and bet ween 0.20 mm and 0.30mm, but generally the greater increase of gap distance showed the greater tensile strength. 3. The greater increase of gap distance shoed less porosities in solder gold at solder joint fracture. 4. In solder gold Au, Cu, Ag, Zn, and Sn were composed and Au and Cu were mostly distributed uniformly. 5. In solder joints of solder gold and gold alloys Au, Cu, Ag, Zn, and Sn were composed in solder gold and Au, Cu, Ag, Pt, and Pd were composed in gold alloys. Au and Cu of solder gold and gold alloys were mostly distributed uniformly and the diffusion of other elements except Pt and Pd around the solder joint was not almost found. In solder joints of solder gold and nickel-chromium base alloys Au, Cu, Ag, Zn, and Sn were composed in solder gold and Ni, Cr, and Al were composed in nickel-chromium base alloys. Au and Cu of solder gold and Ni and Cr of nickel-chromium base alloys were mostly distributed uniformly and the diffusion of other elements except Cr around the solder joint was not almost found.

• Analytical Science and Technology
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• v.25 no.6
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• pp.441-446
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• 2012

In this study, mercury, methylmercury and heavy metals in sediment from the lake Andong were analyzed, along with the estimation of mercury flux between sediments and water in the lake Andong. Average mercury concentrations in sediments sampled in 2009~2011 were $155.0{\pm}71.9$ ng/g, $211{\pm}62$ ng/g and $198{\pm}6.88$ ng/g, respectively. The average methylmercury concentration were $1.85{\pm}1.09$ ng/g (2009) and $3.49{\pm}1.79$ ng/g (2011), and %methylmercury, the fraction of methylmercury in total mercury were $1.17{\pm}0.39%$ and $1.77{\pm}0.94%$, respectively. Heavy metal (Zn, Cd, Pb, Cu) concentrations of the sediments exceeded ERL (Effect Range Low) level of US NOAA (National Oceanic and Atmospheric Administration)'s sediment quality criteria. Estimated mercury sedimentation flux was found to be 83.7 $ng/cm^2{\cdot}yr$ and mercury diffusion flux was estimated as 1.24 $ng/cm^2{\cdot}yr$.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.3
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• pp.293-301
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• 2005

We conducted several different leaching experiments for assessing the potential environmental risk when utilizing recycled concrete for stabilizing bridge pier. The methods include continuous batch leaching test (DIN 38414-S4), availability test (NEN 7341), pH-stat test (CEN/TC 292/WG6) and tank diffusion test (NEN 7345). The concentration ranges vary depending on the testing method. Nearly all the trace elements were low, some elements recording under detection limit. The maximum concentrations for trace elements leached throughout the whole tests are (as mg/L); Cd (0.029), Cu (0.437), Pb (0.14), Ni, Zn (0.95), Hg (0.005). Although the testing methods we used in this study are much more rigorous than other commonly adapted method including TCLP and domestic testing method for solid waste, the trace elemental concentrations are under the criteria for hazardous material set by the TCLP and domestic method. The result seems to suggest that applying the recycled concrete on stream water will be accepatable practice as for as trace elements are concerned. However, the influence of inorganics such as Ca, Mg, Ni and $SO_4^{2-}$ on aquatic ecology should be further examined.