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.

Gliotoxin ameliorates TNBS-induced colitis through regulation of NF-kB, and up-regulation of HO-1

김상욱 ( Kim Sang Ug ),( Jay Min Oh ),( Yeon Hwa Kim ),( Jung Moo Hur ),( Kyo Sang Yoo ),( Yong Sung Kim ),( Joo Jin Yeom ),( Tae Hyeon Kim ),( Suck Chei Choi ),( Chang Duk Jun ),( Yong Ho Nah ) 대한소화기학회 2003 대한소화기학회 추계학술대회 Vol.2003 No.-

<Background & aims> During inflammation in colon, cells of the gut mucosa produce or express various inflammatory mediators, including IL-8, TNF-a and IL-1b, and intercellular adhesion molecule 1 (ICAM-1). These cytokines and chemokines have recently been

2006년 춘천지역 산사태 유발 강우와 사면의 기하 특성에 관한 연구

유남재,이용원,김호진 江原大學校 産業技術硏究所 2010 産業技術硏究 Vol.30 No.B

This paper is results of analyzing the characteristics of rainfall triggering landslides and geometry of slopes, caused by the heavy rainfall and antecedent precipitation by Typhoons Ewiniar and Bilis at Chuncheon area in Gangwondo around July in 2006. As results of analyzing the characteristics of rainfall, landslides in 131 sites were found to happen due to the heavy rainfall having the maximum intensity of rainfall in an hour during July 15 and antecedent precipitation during July 12 to 14 causing the ground to be weak by increasing the degree of saturation previously. From results of analyzing the geometrical characteristics of 131 slopes where landslides occurred, the slope width were in the range of 6~10m. The average slope length and angle were 46m and 51.8°, which was relatively steep slope, respectively. Landlises occurred in the elevation of 400 - 500 m with the most probable frequency.

오스테나이트계 304 스테인레스강과 Nd-YAG 레이저빔과의 상호작용

유영태,오용석,노경보,임인호 조선대학교 에너지.자원신기술연구소 2002 에너지·자원신기술연구소 논문지 Vol.24 No.1

Laser beam welding is increasingly being used in welding of structural steels. The laser welding process is one of the most advanced manufacturing technologies owing to its high speed and penetration. The thermal cycles associated with laser welding are generally much faster than those involved in conventional arc welding processes, leading to a rather small weld zone. The experiments are performed for 304 stainless steel plate applying variation of : laser power(600~2000W), welding speed (3~10m/min), shielding gas flow rate, presence of surface pollution, with fixed or variable gap and misalignment between the similar and dissimilar and plates, etc. The variation of brightness temperature versus modification of operational parameters is found, certain typical welding defects can be detected.

韓國行政體制 運營에 關한 考察

유호룡 대한신학교 1985 논문집 Vol.5 No.-

VCM을 이용한 마이크로 조립용 6자유도 정밀 정렬 장치의 설계

유용환,이수훈,송준엽,이창우,하태호,김정재,이문구 한국공작기계학회 2009 한국공작기계학회 춘계학술대회논문집 Vol.2009 No.-

This work will develop a 6-DOF precision aligner with small size and high resolution for assembling the micro parts for a mobile electronics. Here, VCM actuator that is precise and reliable will be applied to this aligner system. Arrangement of actuators will be a symmetrical based on kinematic design. This paper presents combining two modules of mechanism for the 6-DOF precision aligner. The first is a stage which can control XYθ_(z) motion, and the second can control Z motion, in other words, Z tilt motion. According to its specifications, it is expected to satisfy requirement of precision. Test of the first stage was presented to show the resolution and parasitic motion. For the test, PID algorithm was applied for feed-back control system.

공동주택에 있어서 하자발생현황 및 보수책임기간에 관한 연구

유진호,김준환,김용수 중앙대학교 건설산업기술연구소 2001 건설산업기술연구소 논문집 Vol.2 No.-

The purpose of this study is to suggest a practical guarantee period in apartment buildings. The study has been performed by survey and interview for apartment buildings and managers in Seoul, Kyunggi and Chonnam provinces. The results of this study are as follows: 1. Practical guarantee periods of plastering, waterproofing, and tiling work are 2.3∼3.2, 3.5∼4.3, and 3∼4 years. 2. Rational guarantee periods of joiner's work, factory work, and paper hanging work are 2.7∼3.4, 2∼3, and 2.1∼2.6 years. 3. Rational guarantee periods of lighting work, water supply work, and water disposal work are 1.8∼2.4, 1.8∼3.4, and 2.6∼3.8 years. 4. Rational guarantee periods of sanitary fixture work, and kitchen facility work are 2.7∼2.9, and 1.8∼2.4 years.

연속파형 Nd:YAG SM45C 레이저 용접의 결함 감소연구

유영태,오용석,노경보,신호준 朝鮮大學校 機械技術硏究所 2003 機械技術硏究 Vol.6 No.1

본 연구에서는 Nd:YAG 연속파형 레이저를 이용하여 레이저 용접시 레이저빔의 출력에 대한 레이저범의 이송속도를 변화시켜 심입용접을 실시했다. 열처리를 하지 않고 용접을 실시했을 경우 매우 조대한 기공이 많이 발생하였지만 열처리 후 용접을 실시했을 때는 몇몇 미세한 기공만 발생하였다. Present investigation reports on the effect of incorporating pre-heating on the mechanical properties of laser weldi'ng joints. The Nd:YAG laser in combination with the optical fiber increase the automation and the flexibility of a whole industry. The Nd:YAG laser welding process is one of the most advenced menufacturing technologies owing to its high sped and penetration. This paper describes the weldability of Sh4456 carbon steel fox machine structural use by Nd:YAG laser. Optical microscopy SEM were performed to observe the micro structures and to determine the structures of welded zone. In addtion, mechanical propreties, were measured by tensile test to evaluate the formablity of the welded specimen. The results show that proper selection of the control parameters for per-heating technique can result the porosity and cracking of the welding significantly, and improve the welded joints mechanical properties, such as higher tensile strength and better durability.

경기 일부지역 육용 양돈작업장의 분진 및 내독소 농도

유동호,김형아,허용,성재혁,이한기,박용규 한국산업위생학회 2003 한국산업보건학회지 Vol.13 No.1

The aim of this study was to evaluate exposure to dust and endotoxin produced while working at swine confinement buildings. The dusts and endotoxin may cause adverse health effects on humans. Fourteen swine farms located at Yong-In, I-Cheon and Yeo-Ju of onggi-do were investigated. Husbandry workers form the farms were requested to wear personal sampler to measure respirable dust levels. Area samplings for total and respirable dust were also conducted at swine confinements buildings by season (summer under window open, winter under window close.) Gravimetric analyses and Limulus Amebocyte Lysate assay for measu- rement of dust level and endotoxin, respectively. The highest geometric mean (GM) concentration of airbome dusts was 7.47mg/㎡ for area respirable dust. and 10.35mg/㎡ for personal respirable dust. For respirable dust levels, seven farmers exceeded level of ACGIH, 3mg/㎥. The highest GM of endo- toxin was 5745.40 EU/㎥ for personal respirable dust. Significantly increased level of total dust (p〈0.001) and endotoxin in area total dust was observe with winter samples compared with those of summer. Area total dust and area respirable dust (r-0.622, p〈0.0001) was very significantly correlated in winter. Swine husbandry worker may have a considerable risk of ill health whenexposed to level of dust or endotoxin demonstrated at this study.

현행 민간아파트 리모델링사업의 수익성에 관한 인식조사 및 문제점 분석 : 동(棟)단위 리모델링사업을 중심으로

유진호,김용수 대한건축학회 2003 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.23 No.1

The purpose of this study are to survey the profitability and analyze problems for remodeling projects of apartment buildings. The research method of this study includes case studies and a questionnaire survey from remodeling teams of construction companies. The results of this study are as follows; 1) 60% of questionnaire responsers recognizes the project profitability as negative, and the contract sum is required to increase by 13~17%. 2) price increase after remodeling is expected to 8~10%, or 10~14% by cases. 3) problems related to remodeling project are analyzed as insufficient legal support, lacks of experience, and excessive competitions.