• Journal of Korean Society on Water Environment
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• v.30 no.2
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• pp.175-183
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• 2014

The influence of temperature on the treatment efficiency of chlorinated organic substances contained in groundwater by permeable reactive barrier which is composed of $Fe^{\circ}$ has been investigated by constructing the Pourbaix diagrams for Fe-$H_2O$ system at different temperatures based on thermodynamic estimation. In aerobic condition, the equilibrium potentials for $Fe^{\circ}/Fe^{2+}$ and $Fe^{2+}/Fe^{3+}$ were observed to increase, therefore, the dechlorination reaction for organic pollutants by $Fe^{\circ}$ was considered to decline with temperature due to the diminished oxidation of reactive barrier. The result for the variations of the ionization fraction of $Fe^{2+}$ and $Fe^{3+}$ ion in the pH range of 0 ~ 2.5 obtained by employing Visual MINTEQ program showed that the ionization fraction of $Fe^{2+}$ increased with pH, however, that of $Fe^{3+}$ decreased symmetrically and the extent of the variation of ionization fraction for both ions was raised as temperature rises. The equilibrium pH for $Fe^{3+}/Fe(OH)_3$ was examined to decrease with temperature so that the treatment efficiency of chlorinated organic substance was expected to decrease with temperature due to the enhanced formation of passivating film in aerobic condition. The change of the reactivity of a specific chemical species with temperature was defined quantitatively based on the area of its stable region in Pourbaix diagram and depending on this the reactivity of $Fe^{3+}$ was shown to decrease with temperature, however, that of $Fe(OH)_3$ was decreased monotonously as temperature is raised for $Fe^{3+}/Fe(OH)_3$ equilibrium system. In anaerobic condition, the equilibrium potential for $Fe^{\circ}/Fe^{2+}$ was observed to rise and the equilibrium pH for $Fe^{2+}/Fe(OH)_2$ were examined to decrease as temperature increases, therefore, similar to that for aerobic condition the efficiency of the dechlorination reaction for organic substances was considered to be diminished when temperature rises because of the reduced oxidation of $Fe^{\circ}$ and increased formation of $Fe(OH)_2$ passivating film.

• Journal of Korean Society of Water and Wastewater
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• v.37 no.6
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• pp.375-382
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• 2023

The binary oxide adsorbent using Fe and Mn (Fe-Mn) has been prepared by precipitation method to enhance the removal of phosphate. Different amounts of chitosan, a natural organic polymer, were used during preparation of Fe-Mn as a stabilizer to protect an aggregation of Fe-Mn particles. The optimal amount of chitosan has been determined considering the separation of the Fe-Mn particles by gravity from solution and highest removal efficiency of phosphate (Fe-Mn10). The application of Fe-Mn10 increased removal efficiency at least 15% compared to bare Fe-Mn. According to the Langmuir isotherm model, the maximum uptake (q_m) and affinity coefficient (b) were calculated to be 184 and 240 mg/g, and 4.28 and 7.30 L/mg for Fe-Mn and Fe-Mn10, respectively, indicating 30% and 70% increase. The effect of pH showed that the removal efficiency of phosphate was decrease with increase of pH regardless of type of adsorbent. The enhanced removal efficiency for Fe-Mn10 was maintained in entire range of pH. In the kinetics, both adsorbents obtained 70% removal efficiency within 5 min and 90% removal efficiency was achieved at 1 h. Pseudo second order (PSO) kinetic model showed higher correlation of determination (R²), suggesting chemisorption was the primary phosphate adsorption for both Fe-Mn and Fe-Mn10.

• Journal of the Korean Magnetics Society
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• v.4 no.2
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• pp.173-178
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• 1994

The water-based magnetic fluids were prepared with the synthesized ultra-fine magnetite, oleic acid and SDBS (sodium dodecyl benzene sulfonate) as surfactants. The dispersion of water-based magnetic fluids was about 90 % when the added amounts of oleic acid and SDBS for magnetite(27 g) were more than $2.66{\times}10^{-3}$ mol and 10 g respectively. As the solid content increased from o. 05 g/cc to 0.4 g/cc, saturation magnetization of magnetic fluids at 5 kOe increased from 1.98 emu/g to 9.63 emu/g at $Fe^{2+}/Fe^{3+}=0.5$ and from 2.7 emu/g to 14.63 emu/g at $Fe^{2+}/Fe^{3+}=1.0$, and the its viscosity increased from 1.3 cp to 4.4 cp at $Fe^{2+}/Fe^{3+}=0.5$. pH region of oleic acid and SDBS stabilized water-based mag¬netic fluids was stable was in the range of pH 3.0 to pH 11.0. Stability of Water-based magnetic fluids can be obtained by observation of magnetic memory patterns on the VCR tape.

• Korean Journal of Ecology and Environment
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• v.48 no.3
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• pp.168-175
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• 2015

This study was conducted in autumn to determine phosphorus (P) fraction in sediments of Daechung Lake, to elucidate controlling factors for sedimentary P, and to compare with the other areas. For this study, sediment samples were collected at 6 sites only once on November 2014 using ponar grab and analyzed for solid-phase P (Loosely adsorbed, Fe-bound, Al-bound, detrital apatite, and refractory organic P) by sequential extraction. Total phosphorus (TP) was relatively high in front of Daechung Dam and Hoinam where fish farm was run until 1997. The dominant sedimentary P form was Al-bound P, followed by Fe-bound P, which could be released from sediment to water column during suboxic state. Based on principal component analysis, Al-bound P, Fe-bound, and TP were controlled by grain size of sediments. Loosely adsorbed, detrital apatite, and refractory organic P were relatively highly accumulated at the mouth of major tributaries where suspended sediments were delivered. Sedimentary P concentrations in Daechung Lake sediments were not higher than in other lake sediments. Therefore, based on these results, major controlling factors were grain size and input of suspended sediments from tributaries.

• Asian-Australasian Journal of Animal Sciences
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• v.18 no.10
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• pp.1485-1491
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• 2005

This experiment was conducted to investigate the effects of iron from an amino acid complex (Availa-$Fe^{\circledR}$) on the iron status of neonatal and suckling piglets. A total of 24 gestating sows (Landrace${\times}$Large White) were randomly allocated to three dietary treatments. The control diet contained 80 mg $kg^{-1}$ Fe from ferrous sulfate heptahydrate ($FeSO_4$.$7H_2O$), while the two experimental diets were supplemented with an additional 120 mg $kg^{-1}$ Fe from Availa-$Fe^{(R)}$ or $FeSO_4$.$7H_2O$, respectively. The lactating sows remained the same iron treatments as gestating sows, while neonatal piglets of 24 litters born from the above sows were allotted to another three treatments. Piglets from the sows of the control treatment were fed basal diet with no supplemental Fe as control treatment, but were injected with 100 mg Fe as Fe dextran at birth. Piglets from the sows of Availa-$Fe^{(R)}$ or $FeSO_4$.$7H_2O$ treatments were supplemented with 120 mg $kg^{-1}$ iron from Availa-$Fe^{(R)}$ or $FeSO_4$.$7H_2O$, respectively. The total born alive and weaned, and the average piglets weight at birth and at weaning were not significantly affected by the sow' dietary treatments (p>0.05). Iron from Availa-$Fe^{(R)}$ did not demonstrate a statistically significant improvement in hemoglobin concentration, hematocrit and plasma iron of sows on day 90 and 105 of pregnancy and the milk iron of sows during lactation (p>0.05). Neonatal piglets in the Availa-$Fe^{(R)}$ treatment had a significantly higher hemoglobin concentration (p<0.05) and higher hematocrit and plasma iron (p>0.05) than those in the other two treatments, respectively. The hemoglobin of suckling piglets in the Availa-$Fe^{(R)}$ treatment was higher than that of piglets in $FeSO_4$.$7H_2O$ treatment on day 28 (p<0.05). The total iron binding capacity of piglets in Availa-$Fe^{(R)}$ treatment was lower than that of piglets in the control and $FeSO_4$.$7H_2O$ treatment on day 14 (p<0.05), but there was not a statistically significant difference among three treatments on day 28 (p>0.05). However, the hemoglobin and hematocrit of suckling piglets injected with Fe were higher than those of piglets in the other two treatments (p<0.05). This study indicated that the addition of 120 mg $kg^{-1}$ iron from amino acid complex into the diets improved iron status of neonatal and nursing piglets more effectively than the addition of 120 mg $kg^{-1}$ iron from $FeSO_4$.$7H_2O$, however, this improvement of the organic Fe was not sufficient to replace the Fe injection for prevention of iron-deficiency anemia.

• Journal of the Korean Magnetics Society
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• v.16 no.1
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• pp.18-22
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• 2006

Effects of V substitution of Fe on the magnetic properties of $Fe_3O_4$ have been investigated by x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), conversion electron Mossbauer spectroscopy (CEMS), and vibrating sample magnetometry (VSM) measurements on sol-gel-grown films. XRD data indicates that the $V_xFe_{3-x}O_4$ films maintain cubic structure up to x=1.0 with little change of the lattice constant. Analyses on V 2p and Fe 2p levels of the XPS data indicate that V exist as $V^{3+}$ mostly in the $V_xFe_{3-x}O_4$ films with the density of $V^{2+}$ ions increasing with increasing V content. Analyses on the CEMS data indicate that $V^{3+}$ ions substitute tetrahedral $Fe^{3+}$ sites mostly, while $V^{2+}$ ions octahedral $Fe^{2+}$ sites. Results of room-temperature VSM measurements on the films reveal that the saturation magnetization for the x=0.14 sample is larger than that of $Fe_3O_4$, while it becomes smaller than that of $Fe_3O_4$ for $x{\geq}0.5$. The coercivity of the $V_xFe_{3-x}O_4$ films is found to increase with x, attributed to the increase of anisotropy by the substitution of $V^{2+}(d^3)$ ions into the octahedral sites.

• Proceedings of the Korean Fiber Society Conference
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• 2002.04a
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• pp.105-109
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• 2002

vinylidene fluoride(VDF)와 trifluoroethylene(TrFE)의 공중합체 인 P(VDF/TrFE)는 전기활성을 갖는 강유전성 결정이므로 압전성 및 초전성 재료로 PVDF와 더불어 널리 사용되고 있다. 그러나 P(VDF/TrFE)는 어떤 온도 이상에서는 all-trans conformation을 하는 강유전 결정상이 전기적으로 불활성으로 되면서 PVDP의 $\alpha$-결정의 사슬배좌(trans-gauche)와 유사한 상유전 결정상으로 전이하는 상승 Curie 전이 온도 (T$^{\uparrow}$ $_{c}$ )가 존재하기 때문에 P(VDF/TrFF)의 압전재료로서의 적용온도 범위가 넓지 못하다는 단점이 있다. (중략)

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.8
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• pp.698-703
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• 2009

We report the studies on the structrural properties of Langmuir Blodgett (LB) films fabricated from the copolymer of vinylidenefluoride (VDF) with trifluoroethylene(TrFE). The formation of nanomesas induced by thermal annealing at $135\;^{\circ}C$ for 1 hour was investigated with the atomic force microscope (AFM) and the X-ray diffractometer (XRD). From the result of surface morphology change in 30 monolayer LB film, we find that the annealing treatment on the P(VDF-TrFE) LB film result in the plastic deformation of crystalline polymer. The ${\beta}$ phase crytalline structure in annealed LB film was clearly confirmed from the XRD peak at $19.7^{\circ}$.

• Korean Journal of Soil Science and Fertilizer
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• v.37 no.4
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• pp.212-219
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• 2004

To minimize the danger of soil erosion and settle habitats earlier, afforestation, which vegetates bare slopes, is selected as an environmental recovering technology. Large portions of these areas often are suffered by a bad germination and growth inhibition of sprayed seeds. Afforested materials collected in the normal and damaged sites were not any big difference in chemical characteristics and biological response to ryegrass. But background soil of the damaged site has very low pH (3.6) and high contents of iron and aluminum compared with them of the normal sites. Both germination and root growth of ryegrass were inhibited severely in the water extracts of damaged soils, but not in the water extracts of normal sites. Groundwater collected nearby the damaged sites was very strong acidic (pH 33) and exhibited a high value of electrical conductivity and high contents of iron and aluminum. In the ground water, germinated ryegrass was scarcely grown. In Al standard solution, the root growth of ryegrass was inhibited over 50% in 0.5 mM in pH 3.5-4.5 and in 1.4 mM in pH 5.5, which seems to be related to $Al^{3+}$ activity in solution. In the ferric Fe ($Fe^{3+}$) standard solution, ryegrass growth was inhibited over 50% in the concentration of 14-19 mM in root and 23-25 mM in shoot. This strong tolerance of ryegrass to $Fe^{3+}$ might be concerned with the very low activity of $Fe^{3+}$ at pH 3.5-5.5. In contrast, ryegrass responded very sensitively to ferrous Fe ion ($Fe^{2+}$), especially in root growth: $Fe^{2+}$ concentrations corresponding to 50% growth reduction were 0.3-0.4 mM at pH 3.5-5.5 in roots. This high growth inhibition should be related to the high ion activity of $Fe^{2+}$ irrespective of different pH conditions. In conclusion, low pH and high contents of $Fe^{2+}$ and aluminum seem to be caused by pyrite and be closely related to the growth inhibition of ryegrass seeded in afforested area.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.29A no.4
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• pp.22-27
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• 1992

The cyclic voltammogram characteristics at the magnetized SrO${\cdot}6Fe_{2}O_{3}$ ceramics/(($10^{-3}$M KCI + p-Si powders) and /(($10^{-4}$M CsNO$_3$ + n-GaAs powders) suspension interfaces have been studied using the microelectrophoresis and the cyclic voltammetric method. The negatively charged ions are specifically absorbed on the virgin and the magnetized SrO${\cdot}6Fe_{2}O_{3}$ ceramics surfaces. The zeta potentials of the p-Si and n-GaAs colloidal semiconductors are + 41mV and -44.8mV, respectively. The magnetization effects act as potential barriers at the magnetized SrO${\cdot}6Fe_{2}O_{3}$ interfaces. The positivelely charged p-Si and the negatively charged n-GaAs colloidal semiconductors act as potential barriers at the virgin SrO${\cdot}6Fe_{2}O_{3}$ interfaces. On the other hand, the charged p-Si and n-GaAs colloidal semiconductors act as potential barrier scavengers at the magnetized SrO${\cdot}6Fe_{2}O_{3}$ interfaces. The magnetization effects and the charged colloidal semiconductor effects are irreversible and interdependent.