Effect of Ti Addition on the Microstructure and High-Temperature Oxidation Property of AlCoCrFeNi High-Entropy Alloy

Gi‑Su Ham,Young‑Kyun Kim,Young Sang Na,Kee‑Ahn Lee 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.1

This study investigated the effect of Ti addition on microstructure and high-temperature oxidation property of AlCoCrFeNihigh-entropy alloy. Ti content was controlled at 0 at% and 1 at%. The two alloys were found to have BCC single phase, andthe average grain sizes of Ti0.0 and Ti1.0 were 47.3 μm and 49.7 μm, respectively, showing similarity. The EDS mappingof the inside of grains found that both alloys were characterized to be divided into Al-Ni element rich region and Cr–Feelement rich region. As a result of high-temperature oxidation test at 1100 °C, oxidation weight gains were measured atTi0.0: 0.75 mg/cm2 and Ti1.0: 0.17 mg/cm2, respectively. The results indicate that Ti addition largely improved high temperatureoxidation resistance of AlCoCrFeNi HEA. Ti1.0 alloy, in particular, showed remarkably more excellent 1100 °Chigh-temperature oxidation resistance than other previously reported major ones such as NiCrAl and FeCrAl. In the surfaceand cross-section observations after oxidation tests, both alloys were found to have Al2O3oxides mostly. While the Ti0.0material was observed to have Al2O3spallation macroscopically, the Ti1.0 alloy showed Al2O3spallation only in some localareas. In addition, a unique result was found in AlCoCrFeNiTix(x=0,1) alloy that BCC → FCC phase transformation was accelerated,and FCC phase layer was formed in the surficial area where Al element had been depleted due to high-temperatureoxidation. Moreover, as Ti was added, the thickness of FCC layer induced by high-temperature oxidation decreased. Basedon the results, it was also discussed on how to improve the high-temperature oxidation resistance of AlCoCrFeNiTixHEA.

능동소나에서 다중경로환경을 고려한 표적의 도플러 탐지

이수형,이철목,박상배,이평기 위덕대학교 산업기술연구소 2000 산업기술연구소 논문집 Vol.4 No.1

최근 능동 소나에서는 표적의 탐지 성능을 향상시키기 위하여 "높은 시간-대역폭곱"의 파형들을 사용한다. 표적까지의 거리와 표적의 속도를 추정하는 방법으로 FFT-기반 상관관계 기법이 많이 사용되고 있으나, 다중경로 환경에서는 운용자의 요구를 만족하기에 충분한 결과를 나타내지 못하고 있다. 본 논문에서는 다중경로 환경에서 직접경로 신호의 도플러 변이와 도달시간의 탐지 정확도를 높이기 위한 새로운 기법을 제안하였다. In modern active sonar, so-called "high time-bandwidth product" waveforms are used to obtain processing gain for improved detection performance. FFT-based correlation processing is used to detect doppler shift for velocity of target and arrival time, but obtained results are not enough to satisfy the operational needs in multipath environment. In this paper, the new algorithm is proposed in order to improve detection accuracy of doppler shift and arriving time of direct path in multipath environment. It is achieved since the replica is made with considering multipath.

건설현장 비계공사의 안전관리 실태 및 개성방안에 관한 연구 : 5층 이상의 건설현장을 중심으로 한 조사연구

이기한,김용수 중앙대학교 건설산업기술연구소 2000 건설산업기술연구소 논문집 Vol.1 No.-

The purpose of this study is to analyze safety management status and to suggest improvements of scffolding works. The study has been performed by using a check list and questionnaire survey in Seoul and Kyunggi province. The results of this study are as follows: 1. Safety facility side: Establishment of safety rules for the temporary stucture and development of new safety model ought to be performed. 2. Safety management side: Establishment of independent construction management policy and practical safety experience education should be realized. 3. Humanity side in safety: Imposing penalty to violation of safety rules in construction sites is required.

Rousseau 自然人의 敎育本質論的 理解

李元必,姜基洙 釜山敎育大學校 1995 부산교육대학 논문집 Vol.31 No.1

국제기구 및 외국에서 농산물중 농약잔류 허용기준의 설정절차

이미경,홍무기,박건상,최동미,임무혁,이서래 한국환경농학회 2005 한국환경농학회지 Vol.24 No.1

This study was undertaken to find out necessary measures to improve the tolerance setting system of pesticide residues on food crops in Korea which is scientifically reasonable and harmonizable with international standards. Information on tolerance setting systems of pesticide residues by Codex Alimentarius Commission, Joint FAO/WHO Meeting of Experts on Pesticide Residues, USA, EU, Japan and Taiwan was collected and analyzed. On the basis of information in the above countries, necessary actions to be taken by the Korean regulatory authorities were recommended with respect to priority setting, maximum residue limits (MRLs) setting based on field residue data, group MRLs, minor crop problems, quantitation limit and dietary intake assessment.

건설공사의 재시공 현황에 대한 원인분석 및 개선안에 관한 연구 : 공동주택의 공조공사를 중심으로 한 조사 및 사례연구

이기한,유철종,김용수 중앙대학교 건설환경연구소 2000 環境科學硏究 Vol.11 No.2

This study aims to provide some efficient and effective ways to prevent reconstruction. For this study, the analysis on the current situation and various causes of reconstruction has been performed by using questionnaire survey and case studies from construction sites. The results of this study are as follows: 1.Causes of reconstruction occurrence through case studies show construction inability including technician' idleness(42.2%), misunderstanding of specification(26.7%) and imperfect specification(15.6%). 2.Influence of reconstruction on construction productivity is analysed as the following; increase of 3.8% in construction duration, increase of 5.7% in construction cost, and decrease of 4.4% in construction quality. 3.In order to prevent reconstruction, it is required to file and analyse reconstruction data, systemize construction management, train construction worders with systematic work procedural manual, and check design documents precisely. 4.Also it is necessary to develop new construction technology such as simplification, mechanization, dry-construction of work process.

악골결손 재건을 위한 탈회 및 비탈회 동결건조 동종골의 이용

이기혁,박인순,김영균,김수관,엄인웅,여환호,이병준 大韓顎顔面成形再建外科學會 1996 Maxillofacial Plastic Reconstructive Surgery Vol.18 No.3

Bone graft has been used to repair one defect caused by disease and trauma, congenital and acquired deformities. Graft materials are autogenous bone, allogenic bone, xenogenic bone, synthetics. Autogenous bone graft is the most superior to other materials for immunologic reaction, compatibility to host tissue, and revascularization. However, autogenous bone graft is required for additional operation and the amount of taking is limited. Autografts are obtained at own expense and also limited in size, shape. In order to compensate these problems, allogenic bone graft has been used increasingly. But allogenic bone graft encounters immunologic complications. Therefore, it has been used after freezing, lyophilization, or demineralization. Allogenic bone processed by only lyophilization includes potential antigenic properties on its surface, therefore it is demineralized to deplete immunologic reaction. Demineralized bone releases BMP and helps the mesenchymal cells transform to the chondroblast to produce cartilage and bone. This reaction is called osteoinducation. Many authors have reported that mineralized lyophilized bone had less antigenicity clinically and favorable bony consideration with host bone. In our department from 1995 to now, we have used banked allogenic bone graft that has been prepared from Wonkwang Bone Bank in 5 cases and mineralized lyophilized bone graft in 2 cases to reconstruct the maxillofacial bone defect after tumor resection and cyst enucleation and cleft alveolus. We will report with literature review that the result is favorable functionally and esthetically.

상악골에서 IMPLANT 매식을 위한 치조제 확대 골절단술

김수관,김영균,여환호,이기혁 大韓顎顔面成形再建外科學會 1997 Maxillofacial Plastic Reconstructive Surgery Vol.19 No.2

Ridge expansion osteotomy(REO) technique is a simple and more conservation method to widen a narrow alveolar ridge in the maxilla. This method is superior to drilling method in soft and narrow maxillary alveolar ridge and allows the surgeon to widen the ridge in routine office procedure. Therefore, it is the treatment of choice to implant the maxilla with narrow alveolar ridge. This article presents clinical cases and discusses the advantages, rationale and surgical protocol of REO technique.

진공플라즈마 용사법에 의한 Nickel Aluminides의 기계적 성질에 관한 연구

정용기,박수정,이현규 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.10

Nickel aluminides are a family of materials which offer the potential of improved high temperature performance over conventional nickel based superalloys. The synthesized material has been characterized by x-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy and selected area image analysis. The mechanical properties of the Ni₃Al/NiAl alloy have been determined as a function of temperature through compressive and four point flexural tests. The lamellar aluminide provides synergistic properties of each of the monolithic aluminides resulting in appreciable room temperature tensile ductility, reasonable room and elevated temperature fracture toughness and higher compressive yield strength than those of obtained in monolithic NiAl.

위암환자의 생존율에 관한 역학적 조사연구

김덕성,이태용,이영수,류기하 충남대학교 의과대학 지역사회의학연구소 1992 충남의대잡지 Vol.19 No.2

To find out the survival rates of stomach cancer patients, the author studied 288 stomach cancer patients who took operation at the Department of Surgery in Chungnam National University Hospital from January 1, 1985 to December 31, 1991. The results were as follows: 1. Of the total patients, 67.4% were male: but 32.6% were female. 2. 64.6% of patients lived in rural area and 35.4% urban;98.3% of those were married; 30.6% were farmers and 17.4% were commercial workers; 54.5% were smokers; 48.3% were alcohol drinkers. 3. By types of gastric cancer, 84.4% were progressive gastric cancer patients. Among these, type 2 patients were more than other type patients. 61.5% of those had metastasis to lymph node. 55.2% of those took operation by RSG with gastrojejunostomy; 97.6% of those knew that they had cancer; 19.1% of those had a family history that at least one of family members had cancer. 4. The gross 5 year survival rate of total patients was 47.2%. 5. The 5 year survival rate of male patients was 41.6% but that of female was 46.3%. The 5 year survival rates by residential area, chemotherapy, marital status, blood type, family history, smoking, and drinking were not significantly different. 6. The 5 year survival rate of type 2 progressive gastric cancer patients was the highest with the rate of 72.0%. Metastasis to lymph node and type of operation showed statistically significant difference in 5 year survival rates.