• Economic and Environmental Geology
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• v.45 no.2
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• pp.105-119
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• 2012

Indigenous bacteria isolated from contaminated sites play important roles to remediate contaminated groundwater. Chromium has the most stable oxidation states. Cr(VI) is toxic, carcinogenic, and mobile, but Cr(III) is less toxic and immobile. In this study, indigenous microorganism (MMPH-0) was enriched from Cr(VI) contaminated groundwater, and identified by 16S rRNA gene analysis. Using MMPH-0, the effect of stimulating with e-donors (glucose, lactate, acetate, and no e-donor control), respiration conditions, biomass, tolerance, and geochemical changes on Cr(VI) reduction were investigated in batch experiments for 4 weeks. The changes of Cr(VI) concentration and geochemical conditions were monitored using UV-vis-spectrophotometer and Eh-pH meter. And the morphological and chemical characteristics of MMPH-0 and precipitates in the effluents were characterized by TEM-EDS and SEM-EDS analyses. MMPH-0 (Enterobacter aerogenes) was able to tolerate up to 2000 mg/L Cr(VI) and reduce Cr(VI) under aerobic and anaerobic conditions. MMPH-0 performed faster and higher efficiency of Cr(VI) reduction with electron donors (over 70% after 1 week with e-donor, 10-20% after 4 weeks without e-donor). The changes of Eh-pH in effluents showing the tendency from oxidizing to reducing condition and a bit of acidic change in pH due to microbial oxidation of organic matters donating electrons and protons suggested the roles of MMPH-0 on Cr(VI) in the contaminated water catalyzing to transit geochemical stable zone for more stable $Cr(OH)_3$ or Cr(III) precipitates. TEM/SEM-EDS analyses of MMPH-0 and precipitates indicate direct and indirect Cr(VI) reduction: extracellular polymers capturing Cr component outside cells. These results suggested diverse indigenous bacteria and their biogeochemical reactions might enhance more effective and feasible remediation technology of redox sensitive heavy metals in metal-contaminated in groundwater.

• Journal of Soil and Groundwater Environment
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• v.14 no.1
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• pp.29-35
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• 2009

In this study, the effect of pH and temperature on the adsorption behavior of acid mine drainage (AMD) on coal mine drainage sludge (CMDS) has been investigated during the treatment of coal mine drainage (CMD) by electrical purification method. The pH$_{zero\;point\;charge}$ (pH$_{zpc}$) of CMDS was 5. The removal ratio of copper, zinc, cadmium, iron were increased according to the increase of pH value. The adsorption amount of copper showed 0.64 mg g$^{-1}$ sludge. It was independent of pH value. The adsorption amount of the other metals showed l.l times when pH was 3. The adsorption amount of chromium was a little bit increased at the pH value higher than 7 due to a small amount of the chromium was eluted as $Cr(OH)_6^{3-}$. The amount of metals' absorption were decreased according to temperature was increase at pH value was 3. The selectivity order was Cd>Fe > Zn > Cu. The amount of absorption showed q$_{max}$ Cu 2.747 mg g$^{-1}$ andZn 2.525 mg g$^{-1}$ when pH value higher than 5. It was independent of temperature.

• Korean Journal of Soil Science and Fertilizer
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• v.27 no.3
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• pp.220-225
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• 1994

This study was conducted to investigate the influence of treatment of fly ash on heavy metal contents in the grain. Rice was cultivated on the two types of paddy field, clay loam and sandy loam soil, with 0, 4, 8, 12t/10a of anthracite fly ash and bituminous coal fly ash, respectively. And soybean was cultivated on the same types of upland field with those of 0, 3, 6, 9t/10a, respectively. Also. rice and soybean were cultivated the same types of paddy and upland field with those ashes of 0, 12ton/10a and 0, 9ton/10a, yearly for three years. At the harvest time, the heavy metal contents in rice and soybean were Investigated. The results were summarized as follows : 1. Amount of application. 1) The contents of Cd in brown rice increased in the clay loam soil. Cr and Ni increased sandy loam soil with the application of anthracite fly ash. 2) The contents of Zn in rice increased in the sandy loam soil with the application of bituminous coal fly ash. 3) The contents of Cu in soybean increased with the application of anthracite and bituminous coal fly ash, but Zn, Pb, Cr and Ni increased only with the bituminous. 2. Successive application. 1) The contents of Cd in brown rice increased in the clay and sandy loam soil, however Cu, Zn, Ni, Cr and Fe increased only in sandy loam soil with the anthracite fly ash. 2) The contents of Cr in soybean were increased in the clay and sandy loam soil, but Cu, Fe increased only sandy loam soil with anthracite fly ash. 3) The contents of Cd, Zn, and Cr in brown rice increased in the clay and sandy loam soil, but those of Cu, Mn increased only in the sandy loam soil with application of bituminous. 4) The contents of Cd, Pb, and Cr in soybean increased in the sandy loam soil with the application of bituminous coal fly ash.

• Bulletin of the Korean Chemical Society
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• v.26 no.12
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• pp.1981-1985
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• 2005

Kinetic studies have been performed for alkaline hydrolysis of a series of [(methoxy)(p-substituted styryl)carbene]pentacarbonyl chromium(0) complexes ($(CO)_5$Cr=$C(OCH_3)CH=CHC_6H_4X$, X = p-$OCH_3$, p-$CH_3$, H, p-Cl, p-$NO_2$). Second-order rate constants $(k_{{OH}^-})$ for the alkaline hydrolysis in 50% acetonitrile-water(v/v) were determined spectrophotometrically at various temperatures. At a low pH region (pH < 7.5), the observed rate constant $(k_{obs})$ remained constant with a small value, while in a high pH region (pH > 9.5), $k_{obs}$ increases linearly with increasing the pH of the medium. The second-order rate constants $(k_{{OH}^-})$ increase as the substituent X changes from a strong electron donating group to a strong electron withdrawing group. The Hammett plot obtained for the alkaline hydrolysis is consisted of two intersecting straight lines. The nonlinear Hammett plot might be interpreted as a change in the rate-determining step. However, the fact that the corresponding Yukawa-Tsuno plot is linear with $\rho$ and r values of 0.71 and 1.14, respectively indicates that the nonlinear Hammett plot is not due to a change in the rate-determing step but is due to ground-state stabilization through resonance interaction. The positive $\rho$ value suggests that nucleophilic attack by $OH^-$ to form a tetrahedral addition intermediate is the rate-determining step. The large negative ${\Delta}S^\neq$ value determined in the present system is consistent with the proposed mechanism.

• The Korean Journal of Nuclear Medicine
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• v.2 no.1
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• pp.27-41
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• 1968

The ferrokinetics and red cell life spans of the patients with chronic glomerulonephritis were investigated by the double tracing method using radioactive iron ($^{59}Fe$) and chromium ($^{51}Cr$). According to the serum NPN levels, the patients were subdivided into 3 groups: Group 1. 6 patients, had the levels below 40 mg/dl Group 2. 6 patients, had the levels between 41 mg/dl to 80 mg/dl Group 3. 10 patients, had the levels above 80 mg/dl The results were as follows: 1) Red blood cell-, hematocrit- and hemoglobin values were moderately reduced in patients with normal serum NPN levels, while markedly reduced in patients with elevated serum NPN levels. 2) The plasma volume was increased, while the red cell volume was decreased in patients with elevated serum NPN levels, hence, total blood volume was unchanged. 3) The serum iron level was slightly reduced h patients of groups 1 and 2, while was within the normal ranges in patients of group 3. 4) i) In patients with normal serum NPN levels, the plasma iron disappearance rate, red cell iron utilization rate, red cell iron turnover rate, daily red cell iron renewal rate, circulating red cell iron and red cell iron concentration were within the normal ranges, while the plasma iron turnover rate was slightly reduced. ii) In patients with elevated serum NPN levels, the plasma iron disappearance rate was delayed, while the plasma iron turnover rate was within the normal ranges. The red cell iron utilization rate, red cell iron turnover rate and circulating red cell iron were decreased and the period in which the red cell iron utilization rate reachd its peak was delayed in Group 3 patients. The daily red cell iron renewal rate and the red cell iron concentration were unchanged. iii) The mean red cell life span was within the normal ranges in patients with normal serum NPN levels, while was shortened in patients with elevated serum NPN levels.

• Bulletin of the Korean Chemical Society
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• v.18 no.10
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• pp.1061-1066
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• 1997

The complexes M(CO)4-1,2-(PPh2)2-1,2-C2B10H10 (M=Cr 2a, Mo 2b, W 2c) have been prepared in good yields from readily available bis-diphenylphosphino-o-carboranyl ligand, closo-1,2-(PPh2)2-1,2-C2B10H10 (1), by direct reaction with Group Ⅵ metal carbonyls. The infrared spectra of the complexes indicate that there is an octahedral disposition of chelate bis-diphenylphosphino-o-carboranyl ligand around the metal atom. The crystal structure of 2a was determined by X-ray diffraction. Complex 2a crystallizes in the monoclinic space group P21/n with cell parameters a = 12.2360(7), b = 17.156(1), c = 16.2040(6) Å, V = 3354.1(3) Å3, and Z =4. Of the reflections measured a total of 2514 unique reflections with F2 > 3σ(F2) was used during subsequent structure refinement. Refinement converged to R1 = 0.066 and R2 = 0.071. Structural studies showed that the chromium atom had a slightly distorted pseudo-octahedral configuration about the metal center with two phosphine groups of o-carborane occupying the equatorial plane cis-orientation to each other. These metal carbonyl complexes are rapidly converted to the corresponding metal carbene complexes, [(CO)3M=C(OCH3)(CH3)]-1,2-(PPh2)2-1,2-C2B10H10 (M= Cr 3a, Mo 3b, W 3c), via alkylation with methyllithium followed by O-methylation with CF3SO3CH3.

• Textile Coloration and Finishing
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• v.12 no.2
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• pp.129-137
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• 2000

Silk fabrics were dyed by Cochineal extracts after mordanted with various mordants and their properties of dyeing, fastness and change of surface color were investigated. Silk fabrics were mordanted with aluminum potassium sulfate, copper acetate, tin chloride, iron sulfate or chromium potassium sulfate at $60^\circ{C}$ for 30 minutes and subsequently dyed at $60^\circ{C}$ for 60 minutes unless mentioned otherwise. The dye-uptake of silk fabrics increased with the concentration of Cochineal extracts and mordants used. Maximum dye-uptake was obtained at pH 3.5-4, regardless of the type of mordants used. Surface color of silk fabrics changed from red purple to purple when mordanted with Al or Cu mordant, from purple to purple blue with Fe mordant and showed red purple with Sn or Cr mordant, respectively. It also changed according to pH of dyeing bath. Dyed silk fabrics showed poor light fastness but good dry-cleaning, perspiration and rubbing fastness.

• Bulletin of the Korean Chemical Society
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• v.32 no.2
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• pp.489-497
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• 2011

The proposed method for an effective assay of Cd, Cr and Pb in several polymer samples has been validated. The determination was carried out using ICP-OES after a high pressure asher (HPA) digestion at pressure and temperatures up to 13 MPa and $320^{\circ}C$, respectively. Polymer based materials were totally oxidized with nitric acid in a HPA chamber and determined by ICP-OES. Validation parameters such as linearity, matrix effect, limit of dectection (LOD), limit of quantitation (LOQ), accuracy and precision (repeatibility, intermediate precision and reproducibility) were assessed. The LOD and LOQ in the sample were ranged from 0.98 to 1.18 mg $kg^{-1}$ and 2.93 to 3.55 mg $kg^{-1}$, respectively, relying on the analyte. The proposed method had a good accuracy and precision for repeatability, intermediate precision with respect to days and analysts and reproducibility expressed as inter-laboratory study. The developed method was simple to use, suitable and applicable to various kinds of polymers.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.138-139
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• 2006

Sintered steels are materials characterized by residual porosity, whose dimension and morphology strongly affect the fatigue crack growth behaviour of the material. Prismatic specimens were pressed at $7.0\;g/cm^3$ from Astaloy CrM powder and sintered varying the sintering temperature and the cooling rate. Optical observations allowed to evaluate the dimensions and the morphology of the porosity and the microstructural characteristics. Fatigue tests were performed to investigate the threshold zone and to calculate the Paris law. Moreover $K_{Ic}$ tests were performed to complete the investigation. Both on fatigue and $K_{Ic}$ samples a fractographic analysis was carried out to investigate the crack path and the fracture surface features. The results show that the Paris law crack growth exponent is around 6.0 for $1120^{\circ}C$ sintered and around 4.7 for $1250^{\circ}C$ sintered materials. The same dependence to process parameters is not found for $K_{Ith}$.

• Korean Journal of Materials Research
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• v.6 no.4
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• pp.372-378
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• 1996

고크롬주철에 있어서 기지 및 탄화물의 조직제어는 내마모성의 향상을 위해 필수적이다. 특히 기지조직내의 잔류오스테나이트함량은 최적 내마모성을 얻기위해 반드시 조절되어야 한다. 본 연구에서는 3% C-18%(or 25%)Cr-Mo-Ni-Mn 고크롬주철을 80$0^{\circ}C$, 90$0^{\circ}C$, 100$0^{\circ}C$ 및 110$0^{\circ}C$의 질소분위기 하에서 각각 20분 불안정화열처리를 행한 후 공냉시켰다. 잔류오스테나이트의 함량은 Xtjs 회절시험을 통해 측정하였으며 회절 peak는 $\alpha$200, $\alpha$220, ${\gamma}$220그리고 ${\gamma}$311을 이용하였다. 화학조성, 불안정화열처리의 온도 및 시간, 그리고 잔류오스테니이트함량강의 관계식을 도출하였다.