• 한국재료학회:학술대회논문집
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• 한국재료학회 2010년도 춘계학술발표대회
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• pp.37.1-37.1
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• 2010

The multi-component olivine cathode material, $LiMn_{1/3}Fe_{1/3}Co_{1/3}PO_4$, was prepared via a novel coprecipitation method of the mixed transition metal oxalate, $Mn_{1/3}Fe_{1/3}Co_{1/3}(C_2O_4){\cdot}2H_2O$. The stoichiometric ratio and distribution of transition metals in the oxalate, therefore, in the olivine product, was affected sensitively by the environments in the coprecipitation process, while they are the important factors in determining the electrochemical property of electrode materials with multiple transition metals. The effect of the pH, atmosphere, temperature, and aging time was investigated thoroughly with respect to the atomic ratio of transition metals, phase purity, and morphology of the mixed transition metal oxalate. The electrochemical activity of each transition metal in the olivine synthesized through this method clearly was enhanced as indicated in the cyclic voltammetry (CV) and galvanostatic charge/discharge measurement. Three distinctive contributions from Mn, Fe, and Co redox couples were detected reversibly in multiple charge and discharge processes. The first discharge capacity at the C/5 rate was $140.5\;mAh\;g^{-1}$ with good cycle retention. The rate capability test showed that the high capacity still is retained even at the 4C and 6C rates with 102 and $81\;mAh\;g^{-1}$, respectively.

• Journal of Welding and Joining
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• 제28권4호
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• pp.18-25
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• 2010

Super-duplex stainless steels (SDSS) have a good balance of mechanical property and corrosion resistance when they consist of approximately equal amount of austenite and ferrite. The SDSS needs to avoid the detrimental phases such as sigma(${\sigma}$), chi(${\chi}$), secondary austenite(${\gamma}2$), chromium carbide & nitride and to maintain the ratio of ferrite & austenite phase as well known. However, the effects of the subsequent weld thermal cycle were seldom experimentally studied on the micro-structural variation of weldment & pitting corrosion property. Therefore, the present study investigated the effect of the subsequent thermal cycle on the change of weld microstructure and pitting corrosion property at $40^{\circ}C$. The thermal history of root side was measured experimentally and the change of microstructure of weld root & the weight loss by pitting corrosion test were observed as a function of the thermal cycle of each weld layer. The ferrite contents of root weld were reduced with the subsequent weld thermal cycles. The pitting corrosion was occurred in the weld root region in case of the all pitted specimen & in the middle weld layer in some cases. And the weight loss by pitting corrosion was increased in proportional to the time exposed at high temperature of the root weld and also by the decrease of ferrite content. The subsequent weld thermal cycles destroy the phase balance of ferrite & austenite at the root weld. Conclusively, It is thought that as the more subsequent welds were added, the more the phase balance of ferrite & austenite was deviated from equality, therefore the pitting corrosion property was deteriorated by galvanic effect of the two phases and the increase of 2nd phases & grain boundary energy.

• 한국전기전자재료학회논문지
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• 제35권1호
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• pp.44-49
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• 2022

In this paper, we investigated current (I)- and voltage (V)-sweeping properties in a double-stack structure, Ge₂Sb₂Te₅/Ti/W-doped Ge₈Sb₂Te₁₁, a candidate medium for applications to multilevel phase-change memory. 200-nm-thick and W-doped Ge₂Sb₂Te₅ and W-doped Ge₈Sb₂Te₁₁ films were deposited on p-type Si(100) substrate using magnetron sputtering system, and the sheet resistance was measured using 4 point-probe method. The sheet resistance of amorphous-phase W-doped Ge₈Sb₂Te₁₁ film was about 1 order larger than that of Ge₂Sb₂Te₅ film. The I- and V-sweeping properties were measured using sourcemeter, pulse generator, and digital multimeter. The speed of amorphous-to-multilevel crystallization was evaluated from a graph of resistance vs. pulse duration (t) at a fixed applied voltage (12 V). All the double-stack cells exhibited a two-step phase change process with the multilevel memory states of high-middle-low resistance (HR-MR-LR). In particular, the stable MR state is required to guarantee the reliability of the multilevel phase-change memory. For the Ge₂Sb₂Te₅ (150 nm)/Ti (20 nm)/W-Ge₈Sb₂Te₁₁ (50 nm), the phase transformations of HR→MR and MR→LR were observed at t<30ns and t<65ns, respectively. We believe that a high speed and stable multilevel phase-change memory can be optimized by the double-stack structure of proper Ge-Sb-Te films separated by a barrier metal (Ti).

• 한국세라믹학회지
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• 제46권2호
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• pp.200-210
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• 2009

It is necessary to minimize the mismatch of sintering shrinkage between dielectric ceramic and Ni inner electrode layers for the purpose of developing the ultra high-capacity multi layered ceramic condenser(MLCC). Thus, low temperature sintering of dielectric $BaTiO_3$ ceramic should be precedently investigated. In this work, the influence of the milling condition on sintering behavior and electrical properties of $BaTiO_3$ ceramics was investigated in the $BaTiO_3$(BT)-Mg-Dy-Mn-Ba system with borosilicate glass as a sintering agent. As milling time increased, specific surface area(SSA) of the powder increased linearly, while both sinterability and dielectric property were found to be drastically decreased with an increasing SSA. It was also revealed that the sinterability of the excessively milled $BaTiO_3$ ceramics could be recovered by increasing Ba content, rather than increasing glass addition. These results suggest that the sintering behavior of $BaTiO_3$ ceramics under the high SSA was more strongly dependent on the transient liquid phase caused by Ba addition, than the liquid phase from additional glass.

• 한국가스학회지
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• 제21권2호
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• pp.32-40
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• 2017

SIS는 공정안전시스템 분야에서 폭넓게 활용될 수 있는 계장안전시스템이다. SIS는 유해화학물질 누출 사고로부터 인간, 물질적 자산 그리고 환경에 미치는 피해를 줄이기 위해 필수적이다. 현재 전기, 전자 그리고 프로그래밍 가능한 전자 (E / E/ PE) 장치가 기계, 공압 및 유압 시스템과 상호 작용하는 통합 안전 시스템은 IEC 61508과 같은 국제 안전 표준을 따르도록 되어있다. IEC 61508은 안전 수명주기의 모든 사항을 규정한다. SIS 지원 도구 없이 안전 수명주기에 따라 IEC 61508의 요구 사항을 충족시키는 것은 복잡한 일이다. 본 연구에서는, 사용자가 보다 쉽게 안전 수명주기의 설계 단계를 구현할 수 있도록 도움을 줄 수 있는 On-Line SIS 지원 도구를 제시하였다. On-Line SIS 지원 도구는 데이터 읽기 및 수정 시스템과 통합될 수 있는 안드로이드 응용 프로그램의 형태로 되어있다. 이 도구는 안전 수명주기의 설계 단계에서 소요되는 계산 시간을 줄이고 계산 과정에서 발생할 수 있는 오류를 줄인다. 또한 On-Line SIS 지원 도구는 비용 요소에 근거한 최적화 접근법을 제시할 수 있으며, multi-objective GA를 사용하여 최적의 솔루션 조합을 찾을 수 있도록 하였다.

• Carbon letters
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• 제13권2호
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• pp.126-129
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• 2012

Nanocomposite films were made by a simple solution casting method in which multi-walled carbon nanotubes (MWCNT) and magnetite nanoparticles ($Fe_3O_4$) were used as dopant materials to enhance the electrical conductivity of chitosan nanocomposite films. The films contained fixed CNT concentrations (5, 8, and 10 wt%) and varying $Fe_3O_4$ content. It was determined that a 1:1 ratio of CNT to $Fe_3O_4$ provided optimal conductivity according to dopant material loading. X-ray diffraction patterns for the nanocomposite films, were determined to investigate their chemical and phase composition, revealed that nanoparticle agglomeration occurred at high $Fe_3O_4$ loadings, which hindered the synergistic effect of the doping materials on the conductivity of the films.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2012년도 제38회 춘계학술대회논문집
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• pp.304-308
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• 2012

본 연구는 에틸렌-공기 혼합물로 채워져 있는 변형 가능한 구리 관에서의 초음속 화염 전파를 수치적으로 살펴보았다. 탄화수소의 화염 전파를 해석하기 위하여 지배방정식으로 Navier-Stokes 방정식과 Arrhenius 형태의 1단계 화학 반응식을 활용하였으며 변형 가능한 관을 해석하기 위하여 Inviscid Euler 방정식을 활용하였다. 또한, 두 물질 간 경계면 추적을 위하여 Level-set 기법을, 경계값 결정을 위하여 ghost fluid 기법을 사용하였다. 이러한 수치적 기법을 바탕으로 관의 변화에 따른 초음속 화염 내 팽창파의 전파 및 그에 따른 간섭 현상을 밀도 및 속도 변화를 통해 확인하였으며 초음속 화염 전파에도 안전성이 확보되는 최소 관 두께를 예측할 수 있는 수치적 기반을 마련하였다.

• Archives of Plastic Surgery
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• 제42권6호
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• pp.721-728
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• 2015

Background We conducted this clinical study to compare the efficacy and safety between Neuramis Deep and Restylane in the correction of nasolabial folds. Methods In this phase III, randomized, multi-center, double-masked, matched-pairs, active-controlled trial (ClinicalTrials.gov Identifier: NCT01585220), we evaluated a total of 67 subjects (n=67). All the subjects underwent Neuramis Deep treatment on one side and Restylane on the contralateral side of the bilateral nasolabial folds at a ratio of 1:1. To compare the efficacy of Neuramis Deep and Restylane, we evaluated the Wrinkle Severity Rating Scale scores and those of the Global Aesthetic Improvement Scale. In addition, we compared the safety of Neuramis Deep and Restylane based on adverse events, physical examination, and clinical laboratory tests. Results Neuramis Deep was not inferior in improving the nasolabial folds as compared with Restylane. In addition, there was no significant difference in the efficacy between Neuramis Deep and Restylane. There were no significant differences in safety parameters between Neuramis Deep and Restylane. Conclusions In conclusion, our results indicate that Neuramis Deep may be a safe, effective material for improving the nasolabial folds. However, further studies are warranted to compare the tolerability of Neuramis Deep and Restylane based on histopathologic findings.

• 콘크리트학회논문집
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• 제17권6호
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• pp.939-946
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• 2005

비균질 재료인 콘크리트의 강성 특성과 성능저하 현상을 웨이블릿 변환을 이용한 다중해상도해석을 통해 각 관찰 규모에 따라 동질화 과정의 적용성 및 거시적 손상지수의 평가 등을 연구하였다. 연속적인 Haar 웨이블릿 변환은 기존 강성행렬의 특성을 연속적인 축소규모로의 복제를 통해 미세규모로부터 거시규모로의 축소 또는 복원 과정을 나타내었고 이는 선형구조계의 크기별 스펙트럼 특성의 보존, 즉 타원성, 철면성 그리고 양의 정부호성을 보존하여 각 규모별 해의 유효성을 확인하였다. 웨이블릿 계수를 이용한 기존 강성의 평균은 거시단계의 변형에너지와 상호관계를 가지고 아래 단계로의 축소, 윗 단계로의 복원을 자유롭게 할 수 있는 장점이 있다. 이러한 다중해상도해석의 예제로서 1차원 및 2차원 2상복합체를 가지고 유한요소해석을 통해 기존 이론의 검증과 최소고유치의 각 크기단계별 변화 과정, 원 축소 구조계의 해의 유일성 그리고 국부적 손상지수의 동질화 여부 등을 검사하였다. 이러한 동질화 축소 과정은 자유도가 큰 비선형 구조계로의 적용의 첫 단계를 제공하였다.

• 한국전기전자재료학회논문지
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• 제19권5호
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• pp.467-476
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• 2006

We fabricated the YBCO films on LAO substrate using the TFA-MOD method and evaluated the effects of heat treatment temperature and film thickness on the microstructure, degree of texture, and critical properties. The calcining and firing were peformed at the temperature range of $370^{\circ}C-460^{\circ}C\;and\;750^{\circ}C-800^{\circ}C$, respectively. For the films fired at $775^{\circ}C$ after calcining at $400^{\circ}C-430^{\circ}C$showed highest critical temperature (Tc-onset) of 89.5 K and critical current (Ic) of 40A/cm-width which corresponds to critical current density (Jc) of $1.8MA/cm^2$. The highest critical properties are probably attributed to the formation of purer YBCO phase, stronger biaxial texture, and higher oxygen content, according to the XRD, pole-figure, SEM, Raman analysis. From the multi-coated films, the Ic increased from 39 to 169 A/cm-width as the coating repeated to four times, while the corresponding Jc was measured from once to be in the range of $0.8-1.2MA/cm^2$. Both Ic and Jc degraded as the coating repeated further, indicating that the optimum thickness is in the range of $1.0{\mu}m-1.7{\mu}m$.