• Corrosion Science and Technology
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• 제22권6호
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• pp.457-465
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• 2023

Irradiation-assisted stress corrosion cracking (IASCC) is one of the main degradation mechanisms of austenitic stainless steels, which are used as reactor internal materials. Slow strain rate testing (SSRT) has been widely applied to evaluate the IASCC initiation characteristics of proton-irradiated tensile specimens. Tensile specimens require low surface roughness for micro-crack observation, and electropolishing is the most important specimen pre-treatment process used for this. In this study, optimal electropolishing conditions were examined through analyzing results of polarization experiments and surface roughness measurements after electropolishing. Corrosion cell and electropolishing equipment were fabricated for polarization tests and electropolishing experiments using SSRT specimens. The experimental parameters were electropolishing time, current density, electrolyte temperature, and stirring speed. The optimal electropolishing conditions for SSRT tensile specimens made of type 316 stainless steel were evaluated as a polishing time of 180 seconds, a current density of 0.15 A/cm², an electrolyte temperature of 60 ℃, and a stirring speed of 200 RPM.

• 한국환경과학회지
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• 제4권2호
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• pp.139-150
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• 1995

한국남해 연안에 위치한 득량만에 있어서 하계의 태양복사, 바람, 조류에 의한 해양의 연적성층 및 연적혼합현상의 시간적 변동특성을 밝히기 위한 연구를 수행하였따. 이를 위하여 27개 정점에서 관측된 수온, 염분, 밀도값을 분석하였고. Simpson과 Hunter(1974)가 제안한 위치에너지 개념을 도입한 에너지 방정식을 이용하여 태양복사, 바람, 조류에너지를 각각 계산하였다. 그 결과 하계 득량만 해양의 연직 성층 및 혼합현상은 태양복사에너지가 일정하다고 할때 바람보다는 조류에 의해 크게 좌우됨을 알 수 있었고, 조류에너지에 의한 수괴의 연직합에너지이여율 $epsilon$의 값은 약 0.010 ~ 0.014사이를 나타내고 있었다.

• 대한기계학회논문집
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• 제15권2호
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• pp.584-595
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• 1991

In the direct rolling processes for the mushy state alloy, a mushy state material which simultaneously contains liquid-solid phase is obtained from the exit port of stirring apparatus with a given solid fraction. This solid fraction is dependent on the temperature of within the solid-liquid range which shows to be controlled accurately by the experimental conditions for a given stirring apparatus. Rolling conditions for fabrication the fine surface strip were obtained from direct rolling experiment with mushy state alloys of Sn-75%Pb and aluminum alloy. Influence of solid fraction, rolling speed and initial roller gap on the state of strip surface and solidified structure was observed. We proposed theoretical model for prediction of rolling force, and we compared calculation result and experimental value measured with load cell.

• The Journal of the Acoustical Society of Korea
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• 제25권4E호
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• pp.159-165
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• 2006

Human, horse and rat bloods in a cylindrical chamber where flow was controlled by a stirring magnet were used for studying red blood cell aggregation. Ultrasound backscattered powers from blood were obtained from the backscattered signals measured by a 5 MHz focused transducer in a pulse-echo setup. The experimental results showed the differences in red blood cell (RBC) aggregation tendency among the three mammalian species with an order of horse > human > rat. The ultrasound backscattered power decreased with stirring speed in human and horse blood, but no variations were observed in rat blood. Sudden flow stoppage led to the slow increase of the backscattered power for human and horse blood. There was no self-aggregation tendency in rat blood. The enveloped echo images showed the spatial and temporal variations of RBC aggregations in the cylindrical chamber. These observations from the different mammalian species may give a better understanding of the mechanism of RBC aggregation.

• 한국염색가공학회지
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• 제10권2호
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• pp.37-44
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• 1998

In this study, the polyurethane microcapsules containing disperse dye were prepared by in-situ polymerization method using hexamethylene diisocyanate (HDI, aliphatic type) and m-xylene diisocyanate(XDI, aromatic type) with ethylene glycol (EG) And the size, shape, particle size distribution, and breaking behavior of microcapsules prepared were investigated. The size and shape of microcapsule were observed by scanning electron microscope (SEM) . The particle size distribution was analyzed by image analyzer. The breaking behavior of microcapsule was checked by measuring the optical density of solution that the disperse dye was dissolved after the microcapsule was broken by constant pressure. The particle size was inversely proportional to the stirring speed, and the size of microcapsule prepared from HDI and EG was smaller than that of microcapsule prepared from XDI and EG. Aliphatic type microcapsule was broken easily, compared with aromatic type one. It was considered due to the difference of reactivity between HDI and XDI. And the microcapsule prepared by stirring strongly was broken easily.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.680-685
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• 2000

Liquid flow in a stirring mixer driven by a six-blade turbine has been investigated experimentally. The flows were quantified by measurements of velocity characteristics. obtained by a Particle Image Velocimetry(PIV). for a blade rotational speed of 100r.p.m. and for two blade clearances from the bottom of the tank. The instantaneous flow fields show that the bulk flow consists of small scale vortices very complicately. However, the mean flow results show that the formation of ring vortices above and below the blade. which depend on the clearance.

• 패션비즈니스
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• 제15권4호
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• pp.110-121
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• 2011

As car seat is the closest part between driver and rider, the interest of the security and comfort of the seat is increasing. This research discovered the best condition for dyeing and finishing to produce a fabric for car seat and also developed the design of fabrication to give the feeling from such a finishing. The best condition of coating finishing solution is aqueous PU 65%, dye resist reagent 20%, water 12%, thicker 3%, and knife thickness 2mm, tenter temperature $170^{\circ}C$, tenter speed 35yard/min, viscosity 12,000cps and stirring time 100kg * 30min. According to the processing time of knife coating upon stirring the change of resin and the uneven of coating quantity was shown. This problems will be solved by means of automatic temperature control apparatus for resin and sealing device through a coming research.

• 한국분말재료학회지
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• 제11권3호
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• pp.224-232
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• 2004

Ni-diamond composite powders with nickel layer of round-top type on the surface of synthetic diamond (140/170 mesh) were prepared by the electroless plating method (EN) with semi-batch reactor. The effects of nickel concentration, feeding rates of reductant, temperature, reaction time and stirring speeds on the weight percentage and morphology of deposited Ni, mean particle size and specific surface area of the composite powders were investigated by Atomic Adsortion Spectrometer, SEM-EDX, PSA and BET. It was found that nucleated Ni-P islands, acted as catalytic sites for further deposition and grown into these relatively thick layers with nodule-type on the surface of diamond by a lateral growth mechanism. The weight percentage of Ni in the composite powder increased with reaction time, feeding rate of reductant and temperature, but decreased with stirring speed. The weight percentage of Ni in Ni-diamond composite powder was 55% at 150 min., 200 rpm and 7$0^{\circ}C$ .

• 한국결정성장학회지
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• 제27권6호
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• pp.289-294
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• 2017

원자층 두께의 2차원 나노쉬트(2 dimensional nanosheets)를 이용하여 제작한 필름은 나노쉬트 크기에 따라 다양한 물성을 나타낸다. 이는 필름의 물성이 쉬트와 쉬트 사이 계면물성에 의존하기 때문이다. 따라서 큰 나노쉬트의 합성은 필름의 계면물성 의존도를 줄일 수 있다는 점에서 매우 중요하다. 본 연구에서 단결정 성장된 출발물질과 화학적 박리법을 이용하여 마이크로미터 이상의 크기를 갖는 원자층 두께의 $TiO_x$ 나노쉬트를 제조하는데 성공하였다. 또한 제조 공정 중 유기물을 이용한 박리 단계 시 기계적 원심 교반속도가 나노쉬트 크기와 농도에 밀접히 연관되어 있음을 알 수 있었다.

• 소성∙가공
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• 제23권4호
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• pp.244-249
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• 2014

The thixoforming process has been applied to forming of a joint node for the aluminum frame of a low speed electric vehicle. A joint node should connect three aluminum extruded chassis showing different profiles. The MHS(magnetohydrodynamic stirring) A357 billet was selected because homogeneous globular grains are necessary as the billet materials for thixoforming. A careful design of joint node has been performed by the considerations of structural demands and the simulation results for the thixoforming process using the MAGMAsoft. Optimum heating temperature for the A357 billet was between 580 and $585^{\circ}C$ corresponding to the semi-solid temperatures showing 20-30% of liquid fraction. An injection speed of around 100mm/s and preheating of die at temperatures of $200^{\circ}C$ were also necessary conditions to obtain reasonable thixoformed parts.