• 상하수도학회지
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• 제29권1호
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• pp.33-38
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• 2015

In this study, flat-type photocatalytic reaction system is applied to reduce toxic hexavalent chromium (Cr(VI)) to trivalent chromium (Cr(III)) in aqueous solution under UV irradiation. To overcome the limitation of conventional photocatalysis, a novel approach toward photocatalytic system for reduction of hexavalent chromium including nanotubular $TiO_2$ (NTT) on two kinds of titanium substrates (foil and mesh) were established. In addition, modified Ti substrates were prepared by bending treatment to increase reaction efficiency of Cr(VI) in the flat-type photocatalytic reactor. For the fabrication of NTT on Ti substrates, Ti foil and mesh was anodized with mixed electrolytes ($NH_4F-H_2O-C_2H_6O_2$) and then annealed in ambient oxygen. The prepared NTT arrays were uniformly grown on two Ti substrates and surface property measurements were performed through SEM and XRD. Hydraulic retention time(HRT) and substrate type were significantly affected the Cr(VI) reduction. Hence, the photocatalytic Cr(VI) reduction was observed to be highest up to 95% at bended(modified) Ti mesh and lowest HRT. Especially, Ti mesh was more effective as NTT substrate in this research.

• Journal of Microbiology and Biotechnology
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• 제22권5호
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• pp.690-698
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• 2012

Cr-B2, a Gram-negative hexavalent chromium [Cr(VI)] reducing bacteria, was isolated from the aerator water of an activated sludge process in the wastewater treatment facility of a dye and pigment based chemical industry. Cr-B2 exhibited a resistance for 1,100 mg/l Cr(VI) and, similarly, resistance against other heavy metal ions such as $Ni^{2+}$ (800 mg/l), $Cu^{2+}$ (600 mg/l), $Pb^{2+}$ (1,100 mg/l), $Cd^{2+}$ (350 mg/l), $ZN^{2+}$ (700 mg/l), and $Fe^{3+}$ (1,000 mg/l), and against selected antibiotics. Cr-B2 was observed to efficiently reduce 200 mg/l Cr(VI) completely in both nutrient and LB media, and could convert Cr(VI) to Cr(III) aerobically. Cr(VI) reduction kinetics followed allosteric enzyme kinetics. The $K_m$ values were found to be 43.11 mg/l for nutrient media and 38.05 mg/l for LB media. $V_{max}$ values of 13.17 mg/l/h and 12.53 mg/l/h were obtained for nutrient media and LB media, respectively, and the cooperativity coefficients (n) were found to be 8.47 and 3.49, respectively, indicating positive cooperativity in both cases. SEM analysis showed the formation of wrinkles and depressions in the cells when exposed to 800 mg/l Cr(VI) concentration. The organism was seen to exhibit pleomorphic behavior. Cr-B2 was identified on the basis of morphological, biochemical, and partial 16S rRNA gene sequencing chracterizations and found to be Acinetobacter sp.

• 자원환경지질
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• 제43권3호
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• pp.223-233
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• 2010

세포외 중합체(EPS)의 존재 유무에 따라 Pseudomonas aeruginosa가 용존 비소, 크롬, 우라늄의 흡착 및 산화상태의 변화에 미치는 영향을 회분식 실험을 통해 조사하였다. 배양한 미생물의 표면을 세척한 것과 세척하지 않은 것으로 구분하여 무영양 상태에서 1.1 mg/L의 As(V)와 Cr(VI), 0.5 mg/L의 U(VI)와 반응시키며 시간에 따라 각각의 총 용존 함량과 산화상태 변화를 측정하였다. As(V)의 경우 EPS 존재 여부와 관계없이 흡착은 발생하지 않았으나 EPS가 보존된 박테리아는 As(V)의 약 60%를 As(III)로 환원하였다. 표면을 세척하지 않은 박테리아는 총 용존 크롬의 45%를 제거하였으며 잔류된 용존 크롬의 64%를 Cr(III)로 환원하였다. 우라늄의 경우, 박테리아 표면을 세척하지 않았을 때 U(VI)의 약 80% 이상이 용액으로부터 제거되었다. 이러한 원소 환원은 박테리아가 분비한 EPS 자체의 환원 능력 또는 EPS로부터 보호받아 생육성이 보존된 박테리아의 해독성 환원에 의한 것으로 여겨진다. 이 연구 결과는 자연 환경에서 대부분 바이오필름 상태로 존재하는 미생물이 비소, 크롬, 우라늄의 산화상태 및 이동도 조절에 지대한 영향을 미칠 수도 있음을 의미한다.

• 대한화학회지
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• 제47권2호
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• pp.109-114
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• 2003

trans-$[CrX_2([15]aneN_4)]ClO_4 ([15]aneN_4=1,4,8,12-tetraazacyclopentadecane; X=F, Cl)$의 전자흡수 스펙트럼을 리간드장 이론으로 해석하였다. AOMX 프로그램을 사용하여 관측한 스핀허용 전이와 계산값을 최적화시켰다. 결정한 CFT 파라미터를 AOM, NSH 및 여러 가지 다른 파라미터와 관련시켜 구하고, 이를 화학적 견지에서 논의하였다. 리간드장 해석으로부터 이들 착물에서는 F 리간드가 강한${\sigma}-$ 및 ${\pi}-$주개인 반면에 Cl 원자는 Cr(III) 이온에 약한 ${\sigma}-$ 및 ${\pi}-$주개 성질이 있음을 확인할 수 있었다.

• Asian-Australasian Journal of Animal Sciences
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• 제22권11호
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• pp.1547-1554
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• 2009

This study was carried out to evaluate the effects of dietary supplementation of different sources of chromium on growth performance, blood profile and carcass trait in growing-finishing pigs. A total of 200 growing pigs (Landrace${\times}$Yorkshire)${\times}$Duroc, average initial weight 8.5 kg) were allotted to 5 treatments with 4 replicates per treatment and 10 pigs per replicate. Five treatments were designated as follows according to the source of chromium. i) Control (No chromium): corn-soybean meal based basal diet, ii) $CrCl_{3}$: control diet+200 ppb Cr as $CrCl_{3}$, iii) CrPic: control diet+200 ppb Cr as Cr picolinate, iv) CrMet-1: control diet+100 ppb Cr as Cr methionine, and v) CrMet-2: control diet+200 ppb Cr as Cr methionine. After the feeding trial, three pigs per replicate (12 pigs per treatment) were slaughtered for the evaluation of carcass traits. Average daily gain (ADG), average daily feed intake (ADFI), and feed: gain ratio (F/G) were not different (p>0.05) among dietary Cr sources. However, whole-period ADG of pigs fed CrPic, CrMet-1 and CrMet-2 diets was higher (p<0.05) than for the control diet. Nutrient digestibility was not different (p>0.05) among dietary Cr sources, but the nutrient digestibility of pigs fed CrPic, CrMet-1 and CrMet-2 diets was higher (p<0.05) than for the control diet. BUN level decreased with more magnitude (p<0.05) in pigs fed Cr during the 20 to 50 kg period. Although both serum cholesterol and triglyceride were different (p<0.05) among treatments, there was no consistent response that could be related to the dietary Cr sources regardless of growth phase. However, the overall data suggested that serum cholesterol level increased as BW of pigs increased. Blood total protein (TP) increased (p<0.05) in pigs fed Cr only during the 90-110 kg phase, and blood creatinine (Creat) level was higher in $CrCl_{3}$ and CrPic treatments than in the control only during the 90-110 kg phase. Backfat thickness was thinner (p<0.05) in pigs fed CrMet-2 than in the control treatment. Therefore, lean percentage was higher (p<0.05) in CrMet-2 than in control pigs. However, dressing percentage and Longissimus muscle area (LMA) were not different (p>0.05) among treatments. In conclusion, dietary supplementation of 200 ppb Cr, via either CrPic or CrMet, improved pig growth performance and nutrient digestibility. Moreover, dietary CrMet supplementation for the growing-finishing pig is evidently remarkable for improving both lean percentage of the carcass and backfat thickness.

• 대한화학회지
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• 제39권7호
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• pp.501-507
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• 1995

cis-$[Cr(cyclam)Cl_2]Cl$의 전자 구조를 77K의 방출 및 들뜬 상태 분광법을 비롯하여, 실온의 적외선과 가시선 분광법을 이용하여 연구하였다. 스핀-허용 및 스핀-금지에 해당하는 10개의 순수 전자전이의 성분을 배정하였다. 들뜬 상태 스펙트럼에서 0-0 띠는 $139\;cm^{-1}$로 분리되었으며, 이러한 갈라짐을 현대 리간드장 이론으로 재현할 수 있었다. 리간드장 해석의 결과에 의하면 cyclam의 N 원자는 Cr(III) 이온에 강한 ${\sigma}$-주개로 작용하는 반면에 Cl 리간드는 약한 ${\sigma}-$ 및 ${\pi}-$주개의 성질이 있음을 확인할 수 있었다.

• 대한수의학회지
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• 제39권3호
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• pp.501-512
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• 1999

We analyzed the contents of 12 types of minerals such as calcium in muscle from various species. Thereafter we observed changes of the concentrations according to age, part and sex in major domestic animals. The concentrations of calcium, iron, sodium, potassium, magnesium and zinc were high respectively whilst the content of cobalt, chromium, copper, manganese, molybdenum and nickel were low respectively in the muscle. The concentration of calcium was high in duck and dog but low in pig and horse. Also high level of sodium content was detected in dog and the content of potassium, iron showed high level in horse compared with the content in other animals. In 6 types of microminerals as cobalt, the level of muscle were no more than 1 ppm showing very low content in all animal, but $2.99{\pm}0.85$ppm of copper in duck was an exceptional case. According to the age some species showed small range of variation centering on macrominerals and there was no remarkable change in microminerals. Distribution of minerals was different according to the part and the variation was very diverse compared with other factors such as age and sex. Additionally, the content of minerals in muscle was higher in female than in male chicken and duck. In conclusion, the difference of the content of minerals according to the species was mainly focused on macrominerals.

• 대한화학회지
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• 제49권2호
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• pp.239-242
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• 2005

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2002년도 총회 및 춘계학술발표회
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• pp.233-236
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• 2002

다양한 산업활동에 의하여 발생하는 6가 크롬 (Cr(Ⅵ))은 대표적인 토양 및 지하수 오염물질이다. Cr(Ⅵ)은 3가크롬(Cr(III))로의 환원에 의한 침전반응으로 이동성이 저하된다고 알려져 있다. 본 연구에서는 기존의 고형화/안정화 공정에 환원.분해 반응을 추가한 2가철 기반 분해성 고형화/안정화(Degradative Solidification/Stabilization)공정에 의한 Cr(Ⅵ) 처리 특성을 고찰하였다. 회분식 실험결과 cemen/Fe(II) system내에 Cr(Ⅵ)은 환원반응 뿐만 아니라 cement에 의한 침전에 의해서도 제거됨이 밝혀졌다. Cr(Ⅵ)의 제거속도는 Fe(II)의 반응당량에 비례하는 것으로 보여진 반면, cement/solution ratio에 따른 Cr(Ⅵ) 제거동역학의 차이는 그다지 크지 않았다

• 대한치과기공학회지
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• 제8권1호
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• pp.45-50
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• 1986

This study investigated the effect of burnout temperature on the castability of some nickelchromium alloys for porcelain fused to metal system and the effect of beryllium on the castability. Four alloys were evaluated: two contained beryllium(rexillium III, Super I) and two nonberyllium(Unibond, NNB). five burnout temperature, ranging form 100$^{\circ}F$ to 1800$^{\circ}F$, were aet at 200$^{\circ}F$ intervals for this study. The results obtained were as follows: 1. Beryllium-containing alloys were more castable than nonberyllium-containing alloys. 2. There was an optimal burnout temperature of range from 1400$^{\circ}F$ to 1600$^{\circ}F$ for the berylliumcontaining alloys studied. 3. An optimal burnout temperature for the nonberyllium alloys was not established.