• Journal of the Korean Chemical Society
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• v.43 no.5
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• pp.522-526
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• 1999

2-Hydroxybenzaldehyde-5-nitro-pyridylhydrazone (2HB-5NPH) was synthesized and its application to the spectrophotometric determination of iron was studied. The reagent reacts with iron in the pH range 6.0-7.5 to form a yellow coIored 1:2 chelate which is very stable in methanol solution. Beer's law is obeyed in the concentration range 0.05∼2.0 ${\mu}gmL^{-1}$ iron and separation procedure using a short column filled with Amberlite XAD-7 nonionic chelating resin is proposed for the spectrophotometric determination of traces of iron. The influence of several ions as interference was discussed. The separation of Fe(III) ion from the mix-ture solution were carried out with the buffer solution (pH 5.0) and 0.25M HCl as eluents.

• Journal of the Korean Electrochemical Society
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• v.2 no.4
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• pp.195-201
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• 1999

The repassivation characteristics of Fe-Cr steels in deaerated 0.1 M $Na_2SO_4$ solution have been investigated with the variation of Cr content, applied potential and Cl- concentration. In the absence of chloride ion, abrading electrode test showed that, slope -n, of log i=k -n log t, a parameter of repassivation rate, approached to -1, regardless of Cr content but as Cr content increased, repassivation current density decreases with increasing Cr content. A.C. Impedance spectroscopy showed that the charge transfer resistance of passive film became higher as Cr content and applied potential increased. However, in the presence of chloride ion, it was observed that chloride ion suppressed the passive film formation, whose effect became greater with increasing applied potential.

• Proceedings of the Korea Society for Simulation Conference
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• 1999.10a
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• pp.70-74
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• 1999

발전소 시뮬레이션 시스템 기술은 종합적인 지식을 바탕으로 자료수집 및 분석, 소프트웨어 개발 환경, 수학적 모델, 전산기 구성, 각종 계기류 설계 및 구매 장착 등의 노하우를 알아야만 제작할 수 있는 종합적인 기술이다. 또 지시기반의 기술이며 부가가치가 높은 기술이기 때문에 선진 각국에서는 계측제어 시스템의 기술개발 및 시장 확대를 위하여 힘을 쓰는 동시에 타국으로의 기술정보 유출을 경계하는데 신경을 곤두세우고 있다. 현재 복잡화되어 가고 있는 산업 사회의 전력 수요에 대한 대폭적인 증가 추세에 따라 발전소에서는 보다 효율적이며 합리적이고 경제적인 전력 공급을 위해서 전력 생산에 대한 신뢰성 향상 및 안정성 확보는 물론, 효율성 높은 운전이 절실히 요구되고 있다. 한편, 국내의 시뮬레이션 시스템 분야 기술은 아직도 완벽한 수준에는 미치지 못하며, 이 분야의 기술력 확보 및 신기술 개발은 향후 미래의 모든 시스템산업의 성쇄를 판가름하는 아주 중요한 척도가 될 것이다. 이 중에서 접지 분야는 고전압 혼촉에 의한 저압측 선로의 전압상승 방지, 모선(Bus)이나 전력 기기의 절연보호 및 회로전압의 안정등으로 시스템 성능을 한층 증가 시켜줄 뿐아니라 기기의 오동작이나 낙뇌등으로 인명피해 발생을 없애주는 아주 중요한 분야임에도 불구하고 이 분야의 국내 관련법규등이 미비한 사항이다. 그래서 발전소 분산제어 시스템분야의 장기간 신뢰성 및 안정성을 가지고 있고, 국내에서 많이 사용하는 미국 Bailey의 infi-90 및 독일 ABB의 Procontrol-P를 비교 분석하여 발전소 시뮬레이션 시스템의 접지에 응용 하고져 한다.상호 발생기를 이용한 다양한 시스템 검증 및 분석에 이용할 수 있을 것이다. 본 논문은 가상호 발생기의 구조와 최대 용량 시험 방법을 소개하고, 더 나아가 호 Traffic에 대한 최대 용량 시험뿐 아니라 QoS를 향상시키기 위한 교환 시스템의 제반 성능 시험 및 분석에 이를 이용하기 위해 개선이 필요함을 서술하고자 한다.textrm{m}$~3.4$\mu\textrm{m}$ 범위에서의 투과 및 흡수 스펙트럼을 측정하였다. 결정 성장 결과 B3+, Er3+, Cr3+ 이온은 Ti4+ 이온과 이온의 크기 차이가 심하여 결정의 정상적인 성장을 방해하는 물성을 나타냈고, V5+, Cr3+ 이온은 흑색의 결정, Fe3+ 이온은 적갈색의 결정으로 성장되었다. Al3+, Zr4+, Al3+의 순서로 투과도가 높아지는 것이 관찰되었다. 불순이온의 농도에 따른 영향으로서 Al3+ 이온의 경우 주입농도가 높아질수록 low angle boundary와 oxygen deficiency가 감소하였고, 투과율은 조금 감소하거나 큰 차이가 없는 것으로 나타났다. 반면에 Cr3+ 이온을 주입한 경우 0.003 atomic%에서 최적의 물성을 보였으며, 주입농도가 높아질수록 결정성장이 어려워지고 광의 투과도가 급격히 저하되었다.은 1.3을 나타내었다.로 보인다.하면 수평축과 수직축의 분산 장벽의 비에 따라 cluster의 두께비가 달라지는 성장을 볼 수 있었고, 한 축 방향으로의 팔 넓이는 fcc(100) 표면의 경우 동일한 Ed+Ep값에 대응하는 팔 넓이와 거의 동일한 결과가 나타나는 것을 볼 수 있다. 따라서 이러한 비대칭적인

• Journal of Convergence for Information Technology
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• v.12 no.2
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• pp.134-141
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• 2022

To improve the performance of aluminum-air batteries, it is very important to understand the effect of electrolytes on the electrochemical properties of electrodes. In this study, the effects of electrolyte cations on the electrochemical redox reactions proceeding at the negative and positive electrodes were investigated using electrolytes having the same anion but different cations such as NaCl, LiCl, CaCl₂, and ZnCl₂. It was confirmed by discharge test, scanning electron microscopy and X-ray diffraction analysis that electrolyte cations affect the discharge potential and specific capacity of the electrode. Precipitates were formed on the surface of the positive electrode by Ca²⁺ and Zn²⁺ ions, resulting in degradation of the performance of the positive electrode. In addition, Ca²⁺ ions passivated the negative electrode and accelerated the performance degradation. This suggests that the positive ions of the electrolyte have different effects on the electrochemical performance of the positive and negative electrodes.

• Analytical Science and Technology
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• v.7 no.3
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• pp.1069-1084
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• 1994

수 MV급 탄뎀형 가속기와 정전형, 자장형 질량분석기를 결합함으로써 존재비가 극히 작은 동위원소 측정이 가능해진다. 수 MeV로 가속이 되면 분해에 방해가 되는 모든 분자이온들이 제거되며, 탄뎀형 가속기에서는 음이온으로부터 가속이 개시되므로 몇몇 음이온을 형성하지 못하는 동중원소의 간섭으로부터 자유로워지기 때문에 고감도분석이 실현될 수 있다. 이외에 음이온을 형성하는 동중원소들은 주로 이온함인 최종 검출기에서의 유효 전하에 따른 에너지손실 차이를 이용하여 효과적으로 제거할 수 있다. 현재는 주로 장반감기 방사성동위원소인 $^{10}Be$, $^{14}C$, $^{26}Al$, $^{36}Cl$과 $^{129}I$ 등의 측정법이 확립되어 천연시료 중에서 동위원소 존재비 $10^{-12}$에서 $10^{-15}$까지의 정량이 가능하며, 원자수로 환산한 검출하한을 $10^5$개가 된다. 또한 해당 원소를 기준으로 소요 시료량은 대부분 mg 정도로 충분하다. 지금까지는 불가능했던 이러한 특징으로 인해 지난 수년간 AMS(Accelerator Mass Spectrometry)가 활용되어 온 연구분야는 지구과학(기후학, 우주화학, 빙하학, 수문학, 해양학, 퇴적학, 화산학 및 광물탐사), 인류 및 고고학(연대측정), 그리고 물리학(천체물리, 핵 및 입자물리) 등으로 다양하다. 이외에 생의학 및 재료과학 분야에서도 AMS를 활용하고자 하는 노력이 계속되고 있다. 본 해설에서는 가속기질량분석기술의 특징, 원리, 장치 및 활용분야 등을 소개하고자 하며, 이로써 관련 분야의 연구 활성화에 기여하고자 한다.

• Journal of the Korean earth science society
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• v.24 no.5
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• pp.402-410
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• 2003

When the bivalve fossil microstructure is observed on a thin section, the growth lines of the older specimens are mostly erased by calcite recrystallization while those of the younger are well preserved in detail. During the fossil diagenesis, the shells tend to darken gradually since the valve-forming component Ca$^{2+}$ is the replaced by the surrounding materials Fe$^{2+}$, Mg$^{2+}$, and Mn$^{2+}$. Therefore, the metallic ratio against Ca component in fossil was increased during diagenesis. The UV-Visible spectrophotometry analysis shows that the reflecting degree is low level in Cretaceous bivalve fossils in contrast to the Tertiary and Recent ones. This result suggests that the dark color in older bivalve fossils is affected by the replacement of the metal ions.

• Journal of the Korean Chemical Society
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• v.17 no.2
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• pp.126-129
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• 1973

An amperometric method has been developed for the titration of silver with 2,5-dimercapto-1,3,4,-thiadiazole in ammonical solution (1N) using rotating platinum electrode as an indicator electrode and the mercury-mercury (II) iodide as reference electrode. Direct titration of milligram amount of silver (0.05-1.0mg) is possible in the presence of a number of foreign ions in ammonical solution containing ethylenediaminetetraacetic acid as masking agent under atmosphere. The interfering elements are gold and platinum. The milligram amount of silver can be determined by the proposed method within an error ${\pm}3{\%}$.

• Journal of the Korean Chemical Society
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• v.44 no.5
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• pp.422-428
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• 2000

Optimum analytical conditions of the aluminium ion were established by flow injection analysis. Eriochrome Cyanine R(ECR) dye reacts with the aluminium ion at pH 6.0 to form a complex that exhibits maximum absorption at 535 nm. Reaction conditions including the mixing and the reaction coil length, the concentration and the pH of the buffer solutio, temperature, and injection loop volume were optimized to intro-duce this reaction into flow injection analysis. The results were as follows. A mixing coil length of 0.5 m and a reaction coil length of 4.0 m, the pH 6.0 and 1M of acetate buffer solution, the ECR concentration of 0.56 mM, the reaction temperature of 40$^{\circ}C$, the injection loop volume of 300${\mu}L$ were chosen as optimum conditions. Under these conditions the detection limit of the aluminiumion was less than 0.05 mg/L and the repeatability was better than 1%. A sampling frequency of 24 times for an hour was achieved. Interfering ions such as $F^-$, HP$O_4^{2-}$, $Fe^{2+}$, $Fe^{3+}$, $Mn^{2+}$, and other anions were tested, interference did not occur up to 1,000mg/L of ion concentration and up to 2,CO0mg/L of sulfate ion con-centration. This method was applied for the determination of aluminium ion in tap water and ground water of Jeonju and the Gochang area. The results showed that the aluminium residual in tap water of the Jeonju area was at a mean of 0.478mg/L and that in tap water of the Gochang area was at a mean of 0.278mg/L. Aluminium ion residual of the tap waters in the Jeonju area was higher level than that in the Gochang area. Aluminium residual in the ground water of the Jeonju area was 0.386 mg/L and was lower compared to 0.564 mg/L for the Gochang area.

• Applied Chemistry for Engineering
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• v.10 no.1
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• pp.41-45
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• 1999

Simulated liquid waste containing 50 ppm cobalt ion was treated by precipitate flotation using the surfactant of sodium lauryl sulfate. The effects of initial cobalt ion concentration, pH, surfactant concentration, removal time, gas flow rate and foreign ions were estimated on removal efficiency. 35% $H_2O_2$ was added for pre-treatment stage before precipitate flotation. As the result of pre-treatment, optimum removal pH and the pH of treated water being discharged were lowed and optimum removal pH range was broadened. For the result of this experiment, 99.8% removal efficiency was obtained at the condition of 50ppm of initial cobalt ion concentration, pH 9.5, 70 mL/min of gas flow rate, and 30 min of removal time. Attraction between precipitate and surfactant was supposed to be influenced by solubility and chemical affinity among species in sloution as well as zeta potential. The influence of foreign ions such as, $NO_3{^-}$, ${SO_4}^{-2}$, $Na^+$, $Ca^{+2}$ on the removal efficiency was also observed. Removal efficiency by precipitate flotation containing 0.1 M of ${SO_4}^{-2}$ ion decreased to 90% due to the decrease of zeta potential and interruption of precipitation.

• Journal of the Mineralogical Society of Korea
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• v.15 no.3
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• pp.231-240
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• 2002

Microbial metal reduction influences the biogeochemical cycles of carbon and metals as well as plays an important role in the bioremediation of metals, radionuclides, and organic contaminants. The use of bacteria to facilitate the production of magnetite nanoparticles and the formation of carbonate minerals may provide new biotechnological processes for material synthesis and carbon sequestration. Metal-reducing bacteria were isolated from a variety of extreme environments, such as deep terrestrial subsurface, deep marine sediments, water near Hydrothemal vents, and alkaline ponds. Metal-reducing bacteria isolated from diverse extreme environments were able to reduce Fe(III), Mn(IV), Cr(VI), Co(III), and U(VI) using short chain fatty acids and/or hydrogen as the electron donors. These bacteria exhibited diverse mineral precipitation capabilities including the formation of magnetite ($Fe_3$$O_4$), siderite ($FeCO_3$), calcite ($CaCO_3$), rhodochrosite ($MnCO_3$), vivianite [$Fe_3$($PO_4$)$_2$ .$8H_2$O], and uraninite ($UO_2$). Geochemical and environmental factors such as atmospheres, chemical milieu, and species of bacteria affected the extent of Fe(III)-reduction as well as the mineralogy and morphology of the crystalline iron mineral phases. Thermophilic bacteria use amorphous Fe(III)-oxyhydroxide plus metals (Co, Cr, Ni) as an electron acceptor and organic carbon as an electron donor to synthesize metal-substituted magnetite. Metal reducing bacteria were capable of $CO_2$conversion Into sparingly soluble carbonate minerals, such as siderite and calcite using amorphous Fe(III)-oxyhydroxide or metal-rich fly ash. These results indicate that microbial Fe(III)-reduction may not only play important roles in iron and carbon biogeochemistry in natural environments, but also be potentially useful f3r the synthesis of submicron-sized ferromagnetic materials.