Al-1.0 % Mg2Si의 이원계합금의 G. P. Zone 형성과 시효석출에 미치는 Fe 첨가의 영향

조현기,윤병하,정인상 대한금속재료학회(대한금속학회) 1973 대한금속·재료학회지 Vol.11 No.1

Al-1.0% Mg₂Si 擬二元系合金에 微量(0.05∼0.16%)의 Fe를 첨가하여 G.P. zone형성과 각종 時效擧動을 硬度 및 電氣抵抗 測定에 의해서 檢討한 결과 다음과 같았다. (1) 低溫時效에서는 G.P. zone의 형성이 지연되었고 高溫時效에서는 G.P. zone의 형성 없이 析出反應만이 빠르게 일어났다. (2) G.P. zone의 臨界溫度는 208℃였고 Fe첨가에 의해 그 臨界溫度는 낮아져서 0.16% Fe 첨가시 160℃였다. (3) 時效初期의 硬度置는 Fe첨가에 의해 약간 증가되었다. 이상의 결과는 溶體化處理溫度에서도 용해되지 않은 一部의 Fe化合物이 有效 vacancy 농도와 有效 용질원자 농도를 감소시키고 析出物의 성장을 촉진시키기 때문이다. The effects of additional clement Fe in the range of 0.05-0.16% on G.P. zone formation and ageing phenomena in Al-1.0% Mg₂Si pseudo binary alloy were investigated by means of Vickers microhardness and electrical resistivity measurement. The results obtained were summarized as follows: (1) The G.P. zone formation was delayed in low temperature ageing and the rate of precipitation was increased without G.P. zone formation in high temperature ageing by the additional element Fe. (2) The critical temperature of G.P. zone was 208℃, and it was dropped down by the effect of additional element Fe as 160℃ at the 0.16% Fe content. (3) The hardness of specimens added element Fe were a little higher than that of matrix alloy in the initial ageing time. The above results can be explained by the facts that Fe compounds in the alloy undisolved even at solution treatment temperature decreases the concentration of effective vacancy and solute atom, and also accelerate the growth of precipitate in the alloy.

새로운 자동차 재료용 저농도 Al-Cu-Mg 합금의 시효석출현상

조현기,홍준균,이기대 대한금속재료학회(대한금속학회) 1978 대한금속·재료학회지 Vol.16 No.2

1. 緖論 종래 鐵合金위주로 사용하여오던 自動車用 材料가 최근에는 材料의 輕量化경향에 따라 Al合金을 위주로 한 輕合金材料와 複合材料로 대체되어 가고 있는 실정이다. 그중에서도 특히 Cu 및 Mg의 合金의 溶質濃度가 3.0wt%이하되는 Al-Cu-Mg系 低濃度合金은 最近 새로운 自動車用 材料로써 그 材料學的 性質이 대단히 우수하다는 것이 인정되어 注目받고 있으나 아직 이들 材料의 析出强化에 대한 연구는 거의 보고된 바 없다. 本 硏究에서는 최근 새로운 自動車用 材料로서 개발된 2036合金의 時效析出擧動을 밝혀내기 위하여 合金製造時 문제로 되어있는 Fe, Si, Mn 및 Ti의 時效析出現象에 미치는 영향을 電氣抵抗測定, 熱分析 및 電子顯微鏡組織 觀察등에 의하여 분석 검토 하였다. 2. 實驗方法 2.6wt% Cu 및 0.4wt% Mg을 함유하는 低濃度 純3元 Al合金과 미량의 Si, Fe, Mn 및 Ti을 단독 첨가한 合金을 각각 製造하여 각종 열처리를 한후, 각 실험을 위한 試料를 각종 가공에 의해서 제작하였다. 電子顯微鏡 觀察은 200kv의 透過電子顯微鏡에 의해서, 電氣抵抗 測定은 77°K에서 精密電位差 計法에 의해서, 熱分析은 自動記錄式 斷熱型比 熱測定裝置에 의해서 각각 행하였다. 3. 結論 1) G. P. B. zone의 形成은 Mn의 첨가에 의해서는 다소 促進되나, Ti첨가에 의해서는 현저하게 促進되었으며 Si 및 Fe의 첨가에 의해서는 현저하게 抑制되었다. 2) 各 添加元素는 G. P. B. zone의 復元을 위한 下限溫度에 의해 Tf가 상승하거나 혹은 降下함에 따라 달랐었다. 3) Si 및 Fe의 添加는 S' 및 S相의 形成을 현저히 抑制하였지만, 그중에서도 특히 S'中間相의 形成은 Si 첨가에 의해서, S 平衡相의 形成은 Fe첨가에 의해서 보다 더 많이 抑制되었다.

Fe-Ni-Al 합금의 석출강화에 미치는 Cu 의 영향

조현기,손유홍 대한금속재료학회(대한금속학회) 1987 대한금속·재료학회지 Vol.25 No.10

A detailed examination was carried out to clarify the effect of Cu on precipitation hardening of Fe-Ni-Al alloy by varying the amount of Cu and measuring the yield strength, hardness, and electric resistivity. Electolytically extracted residue was also analysed by transmission electron microscope. The absolute strength of Fe-XCu-3Ni-1Al alloy after aging at 500℃ increased and rapidly reached maximum strength with increasing Cu wt.% due to the increased Ni Al phase precipitated at intragranula. Intergranular precipitation of ε-Cu during aging increased with increasing Cu wt.% in Fe-XCu-3Ni-1Al alloy. It was found that ε-Cu precipitation promoted precipitation of the Ni Al phase by in-situ nucleation. The major strengthening mechanism during aging at 500℃ in Fe-XCu-3Ni-1Al alloy was attributed to the fine Ni Al-precipitates coherent with the ferrite matrix.

Glioblastoma in a Pekingese

조현기,유대영,강주연,이권영,황인구,최정훈,정진영 한국임상수의학회 2015 한국임상수의학회지 Vol.32 No.6

An 11-year-old, intact male Pekingese was brought to the Veterinary Teaching Hospital of Kangwon National University with a 10-day history of seizures. Fifteen days before coming to Kangwon National University, the dog had visited a local animal hospital for lameness, and non-steroidal anti-inflammatory drugs were prescribed to treat this symptom. However, 10 days before coming to our hospital, the dog experienced generalized seizures. Two days before his arrival, generalized ataxia and mental dullness also occurred. Our examinations revealed no remarkable findings on a routine blood test or X-ray. However, the neurological examinations confirmed mental dullness, generalized ataxia, and a lack of menace response and pupillary light reflexes. Nine hours later, dyspnea occurred, and 12 hours after that, the patient was euthanized per the client’s request. A necropsy of transverse sections confirmed the presence of a prominent midline shift due to extended tumor growth. On histopathological analyses, pseudopalisading necrosis of the glial cells and microvascular proliferation were observed. In immunohistochemical analysis, glial fibrillary acidic protein, proliferating cell nuclear antigens, and ionized calcium binding adaptor molecule 1 immunoreactive cells were observed in the tumor area. Based on the results, the tumor was confirmed to be a glioblastoma. Primary intracranial tumors are rare in the veterinary field. This case report describes the clinical and histopathological findings of glioblastoma in a Pekingese.

NiCrAl 합금 폼의 안정성 향상을 위해 코팅된 Nb-doped TiO₂의 효과

조현기,신동요,안효진,Jo, Hyun-Gi,Shin, Dong-Yo,Ahn, Hyo-Jin 한국재료학회 2019 한국재료학회지 Vol.29 No.5

Nb-doped $TiO_2$(NTO) coated NiCrAl alloy foam for hydrogen production is prepared using ultrasonic spray pyrolysis deposition(USPD) method. To optimize the size and distribution of NTO particles based on good physical and chemical stability, we synthesize particles by adjusting the weight ratio of the Nb precursor solution(5 wt%, 10 wt% and 15 wt%). The morphological, chemical bonding, and structural properties of the NTO coated NiCrAl alloy foam are investigated by X-ray diffraction(XRD), X-ray photo-electron spectroscopy(XPS), and Field-Emission Scanning Electron Microscopy(FESEM). As a result, the samples of controlled Nb weight ratio exhibit a common diffraction pattern at ${\sim}25.3^{\circ}$, corresponding to the(101) plane, and have chemical bonding(O-Nb=O) at 534 eV. The NTO particles with the optimum weight ratio of N (10 wt%) show a uniform distribution with a size of ~18.2-21.0 nm. In addition, they exhibit the highest corrosion resistance even in the electrochemical stability estimation. As a result, the introduction of NTO coated NiCrAl alloy foam by USPD improves the chemical stability of the NiCrAl alloy foam by protecting the direct electrochemical reaction between the foam and the electrolyte. Thus, the optimized NTO coating can be proposed for excellent protection of NiCrAl alloy foam for hydrocarbon-based steam methane reforming(SMR).

전기 이중층 커패시터를 위한 다공성 탄소나노섬유의 메조 기공 제어 효과

조현기,신동요,안효진,Jo, Hyun-Gi,Shin, Dong-Yo,Ahn, Hyo-Jin 한국재료학회 2019 한국재료학회지 Vol.29 No.3

To improve the performance of carbon nanofibers as electrode material in electrical double-layer capacitors (EDLCs), we prepare three types of samples with different pore control by electrospinning. The speciments display different surface structures, melting behavior, and electrochemical performance according to the process. Carbon nanofibers with two complex treatment processes show improved performance over the other samples. The mesoporous carbon nanofibers (sample C), which have the optimal conditions, have a high sepecific surface area of $696m^2g^{-1}$, a high average pore diameter of 6.28 nm, and a high mesopore volume ratio of 87.1%. In addition, the electrochemical properties have a high specific capacitance of $110.1F\;g^{-1}$ at a current density of $0.1A\;g^{-1}$ and an excellent cycling stability of 84.8% after 3,000 cycles at a current density of $0.1A\;g^{-1}$. Thus, we explain the improved electrochemical performance by the higher reaction area due to an increased surface area and a faster diffusion path due to the increased volume fraction of the mesopores. Consequently, the mesoporous carbon nanofibers are demonstrated to be a very promising material for use as electrode materials of high-performance EDLCs.

[국방연구개발 50주년, 미래를 기획하라! ⑴] 자주국방 50년을 이끈 국방 R&D! 미래도전기술개발로 변화를 꿈꾼다. - 제도 도입 1년의 운영 성과와 향후 운영방안에 대하여-

조현기,김중수,이승훈 한국방위산업진흥회 2020 國防과 技術 Vol.- No.495

공리적설계/AHP를 이용한 해외무기체계 구매사업 제안서 평가지표 개발에 관한 연구

조현기,김우제,Cho, Hyun-Ki,Kim, Woo-Je 한국군사과학기술학회 2011 한국군사과학기술학회지 Vol.14 No.3

In this study, the axiomatic design(AD) method is applied to construct the hierarchical structure of evaluation criteria and the AHP method is used to calculate the weights of criteria in order to develop the proposal evaluation index for the overseas weapon system purchasing projects. The common evaluation items as main categories are selected through the review of evaluation criteria from the previous works and projects, relevant regulations and defense policy, and the design matrix using fuzzy concept is established and evaluated by the expert group in each design phase to determine the independency, that is the satisfaction of decoupled or uncoupled design, for each criteria in the same hierarchy when they are derived from the main categories. The establishment of decoupled or uncoupled design matrix provides mutually exclusiveness of how small number of DPs can be accounted for FRs within the same hierarchy. The proposal evaluation index developed in this study will be used as a general proposal evaluation index for the overseas weapon system purchasing projects which there are no systematically established evaluation tools.

라켓종목 복식선수를 위한 파트너 상호작용 척도 개발 및 타당화

조현기,황재욱 한국사회체육학회 2020 한국사회체육학회지 Vol.0 No.81

Purpose: The purpose of the present study is to develop and verify thvea lidation of the partner interaction inventory for the racket event doubles athletes. Method: 699 doubles athletes of ping-pong, tennis and badminton eventp articipated in this study. The qualitative data were categorized according to the qualitative analysis procedure, and the collected quantitative data were analyzed through SPSS 18.0 Version and AMOS 20.0 Version. Results: The results of the study were as follows. Firstly, the results revealed that the four general dimensions were identified such as productive conversation, inducement, belief, and recognition. Secondly, result of exploratory factor analysis indicated that factors of partner niteraction were four which named as productive conversation, inducement, belief, recognition and result of confirmatory factor analysis indicated that partner interaction was structured 4 factor and 20 items including, goodness of fit index was satisfied value. Thirdly, convergent validity and discriminant validity were demonstrated through the external validity. Conclusion: The structural/external validity of the developed partner interaction inventory is verified, therefore the possibility of field application can be expected.

문화와 교실의 연결 ― 한일 국제 공동수업의 교사 경험 사례 연구 ―

조현기 한국일본학회 2024 한국일본학회 학술대회 Vol.2024 No.08