Study on Microstructure and Mechanical Properties of the Al–25Cr–5Si (at%) Alloy Powder Using Gas-Atomization and SPS Process

Yong‑Ho Kim,Hyo‑Sang Yoo,Jeong‑Han Lee,Ik‑Hyun Oh,Hyun‑Kuk Park,Hyeon‑Taek Son 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.7

In order to investigate the microstructure and mechanical properties on Al–25Cr–5Si (at%) alloy, a mixed powder with pureelements and an alloy powder using a gas atomization process were used. Fine and high purity Al–25Cr–5Si (at%) alloypowder was successfully prepared by gas atomization and densified using a spark plasma sintering (SPS) process. The overallpowder size distribution of the mixed Al, Cr, and Si elemental powders was in the range of 10–15 μm. The atomized Al–Cr–Sialloy powder was fine and spherical in morphology and difficult to be formed by intermetallic formation. Densification wasclearly confirmed at 1000 °C, with almost isolated pores formed, by clear removal of pores between particles, deformationof particles, an increase in the number of contacts, and a change in size between particles. As a result of XRD analysis ofthe sintered compacts, single phase was observed using the mixed powder, but the compact using gas atomization remainedthe alloy phase even at the process temperature. The Vickers hardness of the compacts by mixed powder was observed at59.70 Hv and the compact using gas atomized powders on the temperature 1000 °C of the Vickers hardness increased to702.6 Hv. The compressive yield strength of the compact with mixed powder was 195.24 MPa and the compressive strengthof the compact with gas atomized powder increased to 802.07 MPa. It is considered not to be decomposed by the AlCrSi,Al13Cr4Si4and Al8Cr5phases sintering process, resulting from the improvement of mechanical properties.

외상성 대장 및 직장 손상

김익용,김상희,윤광수,김히욱 대한대장항문학회 1997 Annals of Coloproctolgy Vol.13 No.3

Disel 機關의 渦給性能에 關한 硏究

韓龍雲,金重燁,權純益 嶺南大學校 工業技術硏究所 1981 연구보고 Vol.9 No.2

The factors that effect the power output of diesel engine are intake temperature, intake pressure, compression ratio and so on, in constant revolution. Intake pressure and compression ratio of them are much more effective. If the compression ratio is raised, the thermal efficiency of engine increases, but silent driving is difficult for maximum combustion pressure. The durability of engine decreases also for vibration and mechanical strain of materials, and the weight of engine per horse power increases. In this paper an intake pressure in charge of negative effects to lower compression ratio is raised. The compression ratio is decreased through the gasket is replaced by thick copper plate between cylinder and cylinder head. The effect of supercharge is evaluated experimentally from measuring of an engine power output, fuel consumption, and intake air volume. As a result of a decreased compression ratio, it becomes the same as natural aspiration before change compression ratio to increase about 3% to supercharging-pressure change ratio per unit compression ratio in mean effective pressure. And it becomes also the same as natural aspiration before change compression ratio to the increase of supercharging pressure about 1.8% in thermal efficiency. In case the supercharging pressure is much greater than the former to increase intake air pressure, it will give better effects to lower compression ratio than higher compression ratio with natural aspiration.

지식기반 사회에서 중등학교 기술과 교사의 직무능력 관련변인 및 교육요구 분석

김용익 한국기술교육학회 2001 한국기술교육학회지 Vol.1 No.2

The purpose of this study were to find variables related to job competency needed by technology teachers in secondary schools, and to analyze educational needs for job competency in the base of difference between the importance of each job competency and their own performance with respect to the same which the technology teachers recognized. The population sample for the study constituted 458 completed questionnaires from systematic random sample of 720 technology teachers. The statistical techniques used in the study were mean, standard deviation, t-test, analysis of variance, multiple regression utilizing the SPSS PC. The major findings of this study were as follows. (1) Teachers in the metropolitan area, teachers at high schools, teachers graduated from vocational high schools, teachers with more practical work experience, and teachers with technical licences rated their job competency level more high and positive. Hiring policy and administrative support should be structured to facilitate the flow of these types of teachers into the profession. (2) Technology teachers showed highest educational needs with respect to some key job competency variables. That is to say, ‘diagraming and generalization of engineering skill or phenomena’, ‘understanding and using of information communication technology’, ‘unfolding of creative problem solving instruction’, etc. were found to be educational needs high. Therefore, such an items should be represented properly at in-service teacher education in near future.

安城市 都市·建築 保全方案

趙庸薰,金大翼 안성산업대학교 1998 論文集 Vol.30 No.2

During high speed economic growth period, our society has focused it's energy on the demolition and destruction of all our natural and man-made environment. In progress with that trend, our small cities a1so have just followed the metropolitan physical change and considered that imitation be the same meaning as "modernization". Therefore, our valuable urban and architectural heritages have been constantly destructed and that situation has been same in this small city, ANSUNG. But in spite of many environmental destruction and new development, ANSUNG has still more historic architectures and urban districts than other cities, i.e. PYONGTAEK or CHEONAN, because of comparatively low speed growth. By using this comparatively good condition, the execution of gradual development strategy with conservation method of urbanity and architecture should be carried immediately, and that strategy should be accompanied with the participation of citizens, local authority, and expert groups.

Ge 완충층의 사용과 Ge 완충층의 in situ 열처리 온도의 변화에 대한 GaAs/Ge/Si 계면에서 전위의 거동

우용득,이해익 又石大學校 1998 論文集 Vol.20 No.-

Effect of in-situ annealing after the Ge buffer layer growth on the behavior of defects at the interfaces of GaAs/Ge/Si structure grown by molecular beam epitaxy(MBE) were investigated using transmission electron microscopy (TEM) technique. Results show that the threading dislocations toward the GaAs layers were blocked more efficiently at the Ge/GaAs interface, when an in situ thermal annealing at 750℃ for 10 minutes was performed after the Ge buffer layers Growth. It was also observed that dislocation density was independent on the thickness of Ge buffer layer. Neither stacking faults nor microtwins were observed in the samples studied. probably because surface morphology of the Ge buffer layer improved due to the in situ annealing and nucleation of the defects was suppressed a result.

수치모형실험을 통한 콘크리트 구조물의 결함탐지에 관한 연구

김용인,변중무,손권익,서백수 江原大學校 産業技術硏究所 2004 産業技術硏究 Vol.24 No.B

In this study, First, the results of travel-time inversion (first arrival inversion using the travel-time of the first arrival) were compared with those of full-wave inversion for numerical data. Numerical experiments to find key parameters other than initial velocity model showed that the frequency of source has a great effect on the result of full-wave inversion. Finally, this research presented the corrected full-wave inversion applying the correction term to the final result of full-wave inversion. The corrected full-wave inversion depicted cavities inside concretes even when the inversion started with 20% error in an initial velocity model for cavities. However, full-wave inversion did not reveal cavities.

濟州地方 마늘의 鱗片크기가 生育 및 鱗莖肥大에 미치는 影響

朴庸奉,張田益 제주대학교 1980 논문집 Vol.12 No.-

This experiment shows the influence that the seed clove size of garlic gives to the growth and the bulb formation of the garlic. The results of this investigation are as follows. 1. The growth of the top part continously increased until the middle of May, and then it decreased. The larger the size of seed cloves the more the number of leaves increased. Plant height, leaf lengths and the leaf widths also increased. 2. The larger the size of seed cloves the the more the bulb weight and bulb diameter of garlic increased. But there were no differences between bulb height and neck diameter. 3. When the bulb formation ratio was below 0.5 of an exponent, it was favorable regardless of the seed cloves size. 4. The number of seed cloves per bulb indicated that the number of seed cloves are more abundant in a inner layer, than in an outer layer. The number of primary seed cloves increased according to the size of the seed cloves, and the block of 3-4g increased more or less than any other block. 5. According to observations of a block of cut stalk, and a nuncut block, bulb diameter and bulb height increased in the block of cut stalk more than that in the block of nuncut stalk. However, the bulbformation ratio did not change.

F.A. Process에 의한 下水處理에 관한 硏究

姜龍太,柳在益,許宗文 東亞大學校 海洋資源硏究所 1989 硏究論文集 Vol.2 No.1

The purposes of this researches were to evaluate the effects of an advanced processes supplemented Conventional Activated Sludge Process and to invent the economical advanced process combined activated sludge process with FAC(Flocculation-Aeration-Clarification). Raw water used was synthetic wastewater. The primary treatment using the PAC process was effective in treating the wastewater with lower concentration. F.A process showed the removal rate of more than 90 percent without regard to variences of influent concentration.

한국인 양극성 장애와 5-HT_2A Receptor Gene Promoter-1438A/G Polymorphism과의 연관성 연구

오승용,지익성,이영호 대한신경정신의학회 2001 신경정신의학 Vol.40 No.1

연구목적: 최근 5-HT□수용체 유전자 promoter의 -1438A/G 다형성이 보고되었고, 이러한 -1438A/G 다형성이 기분장애와 연관이 있는지 알아보려는 연구가 시도되고 있다. 저자 등은 -1438A/G 다형성이 한국인 양극성 장애의 발병에 있어서 유전적 요인으로 작용하는지 알아보기 위하여 본 연구를 시행하였다. 방법: 양극성 장애 환자 120명과 정상 대조군 120명을 대상으로 중합효소 연쇄반응을 이용하여, 5-HT□ 수용체 유전자 promoter -1438A/G 다형성의 유전자형과 대립유전자의 빈도를 비교하였다. 결과: 1) 양극성 장애 환자군의 5-HT□수용체 유전자 promoter -1438A/G 다형성의 유전자형은 A/A 14(12%), A/G 66(55%), G/G 40(33%), 정상 대조군의 유전자형 A/A 30(25%), A/G 59(49%), G/G 31(26%)로 양군간에 유의한 차이가 있었다. 2) 대립유전자의 빈도는 양극성 장애 환자군에서 A 0.39, G 0.61, 정상대조군에서 A 0.49, G 0.51로 양군간에 유의한 차이가 있었다. 결론: 5-HT□ 수용체 유전자 promoter -1438A/G 다형성이 한국인 양극성 장애의 발병과 연관이 있을 수 있다는 가능성을 제시한다. Objectives : This study was designed to investigate the association between 5-HT□ receptor gene promoter -1438A/G polymorphism and bipolar disorder in a Korean population. Methods : 5-HT□ receptor gene promoter -1438A/G polymorphism were typed with Po-lymerase Chain Reaction in 120 patients with bipolar disorder and 120 normal controls. Results : The distributions of the genotype in the bipolar disorder with A/A, A/G, G/G were 14(12%), 66(55%), 40(33%), and in the controls were 30(25%), 59(49%), and 31(26%). The allele frequencies of the bipolar disorders with A and G were 94(39.2%), 146(60.8%), and in the controls were 119(49.6), and 121(50.4), respectively. There were significant differences in genotype distributions and allele frequencies of -1438A/G between patients with bipolar disorder and normal controls. Conclusion : These results suggest that 5-HT□ receptor gene promoter -1438A/G poly-morphism may be related to the development of bipolar disorder in a Korean population.