• 한국재료학회지
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• 제31권9호
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• pp.511-518
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• 2021

An investigation is performed to clarify the manufacturing conditions of pure magnesium and AZ31 magnesium alloy thin plate using the melt drag method. By the melt drag method, suitable for magnesium molten metal, pure magnesium can be produced as a continuous thin plate with a thickness of 1.4 mm to 2.4 mm in the range of 5 m/min to 20 m/min of roll speed, and the width of the thin plate to the nozzle outlet width. AZ31 magnesium alloy is able to produce a continuous sheet of thickness in the range of 5 m/min to 30 m/min in roll circumferential speed, with a thickness of 0.6 mm to 1.6 mm and a width of the sheet matching the nozzle outlet width. In the magnesium melt drag method, the faster the circumferential speed of the roll, the shorter the contact time between the molten metal and the roll, and it is found that the thickness of the produced thin plate becomes thinner. The effect of the circumferential roll speed on the thickness of the thin plate is evident in the low roll circumferential region, where the circumferential speed is 30 m/min or less. The AZ31 thin plate manufactured by the melt drag method has a finer grain size as the thickness of the thin plate decreases, but it is currently judged that this is not the effect of cooling by the roll.

• 한국생산제조학회지
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• 제22권2호
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• pp.235-240
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• 2013

This paper presents a disposable microfluidic infusion pump using the restoring force of elastomeric membrane of Polydimethylsiloxane. Microfluidic infusion pump consists of hydraulic resistance control part, elastomeric blister actuator part, drug inlet and outlet. Expanded elastomeric blister actuator continuously pushes liquid in the chamber to outlet. At same time, microchannel diameter near the outlet was controlled by thin elastomeric membrane in hydraulic resistance control part. Eventually flow rate of infused liquid is controlled by air pressure. In experimental study, the amount of the filled liquid in the blister is precisely controlled by the height of the blister. Flow rate of infused liquid could be controlled, that is, controlled release of the drug over time was possible by adjusting hydraulic resistance and restoring pressure with the blister actuator.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2005년도 추계 학술대회논문집
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• pp.229-234
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• 2005

Following the recent trend in the automotive manufacturing technologies, the product design subject to the die casting becomes more and more complex. The requirement of the die design becomes more demanding than ever before. In some cases the product's shape can have multiple slender manifolds. In such cases, design of the inlet and outlet parts of the die is very important in the whole manufacturing process. The main issues required for the qualified products are to attain gentle and uniform flow of the molten liquid within the passages of the die. To satisfy such issues, the inlet cylinder ('bed cylinder' in this paper) must be as large as possible and simultaneously the outlet opening at the end of each passage must be as small as possible. However these in turn obviously bring additional manufacturing costs caused by re-melting of the bed cylinder and increased power due to the small outlet-openings. The purpose of this paper is to develop effective simulation methods of calculation for fluid flows in multiple columns, which mimic the actual complex design, and to get some useful information which can give some contributions to the die-casting industry. We have used a commercial code CFX in the numerical simulation. The primary parameter involved is the size of the air-vent. We will show how the very small opening of the outlet, i.e. the air-vent, can be treated with the aid of the porous model provided in the code. To check the validity of the numerical results we have also conducted a simple experiment by using water.

• Journal of Mechanical Science and Technology
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• 제20권10호
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• pp.1765-1772
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• 2006

High-pressure die casting such as thixocasting and rheocasting is an effective process in the manufacturing automotive parts. Following the recent trend in the automotive manufacturing technologies, the product design subject to the die casting becomes more and more complex. Simultaneously the injection speed is also designed to be very high to establish a short cycletime. Thus, the requirement of the die design becomes more demanding than ever before. In some cases the product's shape can have multiple slender manifolds. In such cases, design of the inlet and outlet parts of the die is very important in the whole manufacturing process. The main issues required for the qualified products are to attain gentle and uniform flow of the molten liquid within the passages of the die. To satisfy such issues, the inlet cylinder ('bed cylinder' in this paper) must be as large as possible and simultaneously the outlet opening at the end of each passage must be as small as possible. However these in turn obviously bring additional manufacturing costs caused by re-melting of the bed cylinder and increased power due to the small outlet-openings. The purpose of this paper is to develop effective simulation methods of calculation for fluid flows in multiple columns, which mimic the actual complex design, and to get some useful information which can give some contributions to the die-casting industry. We have used a commercial code CFX in the numerical simulation. The primary parameter involved is the size of the bed cylinder. We will show how the very small opening of the outlet can be treated with the aid of the porous model provided in the code. To check the validity of the numerical results we have also conducted a simple experiment by using water.

• 한국가시화정보학회지
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• 제17권2호
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• pp.58-66
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• 2019

This study investigated heat transfer and flow characteristics of a sweeping jet issued from a rectangular nozzle with a thin plate. A thin vertical aluminum plate was attached on outlet of fluidic oscillator to increase velocity of central area with Coanda effect and enhance heat transfer performance. From visualization and PIV experiments, sweeping jet with a thin plate has larger velocity distribution in center region than that of the normal sweeping jet while oscillating frequency is similar as the normal one. Thermographic phosphor thermometry method was used to visualize the temperature field and Nu distribution of plate with impinging sweeping jet with thin plate. Four Reynolds numbers and three jet-to-wall distances were selected as parameters. It is found that heat transfer performance in the low jet-to-wall spacing was enhanced as the cooled area was expanded. However, when the jet-to-wall spacing became greater than 8dh, heat transfer performance became similar due to reduced impinging velocity.

• 소성∙가공
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• 제8권3호
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• pp.271-271
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• 1999

A concentration change during grade transition operation in thin slab casting is investigated through computer simulation and the results are compared with experimental measurements. Fluid flow and mixing patterns in various tundish levers and flow rates were analysed by a three-dimensional mathematical model. Based on the contained results, a simple, efficient and accurate computational model is suggested to predict the concentration profile at the outlet of the tundish. Based on the model, mixing in and below the mold was analyzed considering electromagnetic braking force. The predicted concentration profiles show good agreements with the measured values. It is found that the lower vortices in the mold are suppressed by the electromagnetic field and a plug-like flow region develops, which decreases the intermixing of two different grades of steel and shortens the length of transition region.

• Tribology and Lubricants
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• 제23권6호
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• pp.298-300
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• 2007

Frictional characteristics of mesoporous $SiO_2$ thin films were evaluated with different pore sizes. The films were manufactured by sol-gel and self-assembly methods to have a porous structure. The pores on the surface may play as the outlet of wear particle and the storage of lubricant so that the surface interactions could be improved. The pores were exposed on the surface by chemical mechanical polishing (CMP) or plasma-etching after forming the porous films. The ball-on-disk tests with mesoporous $SiO_2$ thin films on glass specimen were conducted at sliding speed of 15 rpm and a load of 0.26 N. The results show considerable dependency of friction on pore size of mesoporous $SiO_2$ thin films. The friction coefficient decreased as increasing the pore size. CMP process was very useful to expose the pores on the surface.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• 제16권1호
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• pp.49-52
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• 2013

Antral web is a rare cause of gastric outlet obstruction in neonate. It is a 2-4 mm thin mucous membrane that can be found anywhere from 1 to 7 cm proximal to the pylorus. The baby was born at gestational age of $32^{+1}$ weeks with 1,880 g as 2nd baby of dizygotic twin. After birth, the baby had constant non-bilious vomiting without feeding while he didn't show abdominal distension or discoloration. The infantogram showed distended stomach with distal small bowel gas. Upper gastrointestinal series revealed that the antrum was abruptly narrowed at 1 cm proximal to pylorus. We performed laparotomy at the 10th day after birth and excised the 2 mm-thick web circumferentially. He began milk feeding after 6 days and discharged uneventfully at postoperative 35 days with corrected age of $38^{+4}$ weeks with body weight 2,420 g. The antral web should be considered in the case of non-bilious vomiting in neonate.

• Nuclear Engineering and Technology
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• 제54권11호
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• pp.4159-4169
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• 2022

Hydrogen mitigation using Passive Autocatalytic Recombiners (PARs) has been widely accepted methodology inside reactor containment of accident struck Nuclear Power Plants. They reduce hydrogen concentration inside reactor containment by recombining it with oxygen from containment air on catalyst surfaces at ambient temperatures. Exothermic heat of reaction drives the product steam upwards, establishing natural convection around PAR, thus invoking homogenisation inside containment. CFD models resolving individual catalyst plate channels of PAR provide good insight about temperature and hydrogen recombination. But very thin catalyst plates compared to large dimensions of the enclosures involved result in intensive calculations. Hence, empirical correlations specific to PARs being modelled are often used in integral containment studies. In this work, an experimentally validated CFD model of PAR has been employed for developing an empirical correlation for Indian PAR. For this purpose, detailed parametric study involving different gas mixture variables at PAR inlet has been performed. For each case, respective values of gas mixture variables at recombiner outlet have been tabulated. The obtained data matrix has then been processed using regression analysis to obtain a set of correlations between inlet and outlet variables. The empirical correlation thus developed, can be easily plugged into commercially available CFD software.

• 분석과학
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• 제26권1호
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• pp.34-41
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• 2013

SPLITT Fractionation (SF)는 콜로이드 입자 및 거대분자들을 둘 혹은 그 이상의 부분(fraction)으로 분획하는 기술이다. SF에서는 시료를 지속적으로 주입하므로 대용량 분획이 가능하다. 일반적으로, SF에서는 얇은 리본모양의 채널을 이용하는데, 채널의 입구와 출구부분에는 각각 flow stream splitter가 설치되어 있어서 채널의 입구와 출구가 위 아래로 두 개씩 존재한다. SF에는 두 가지 작동방법이 있는데, 하나는 conventional mode 이고 다른 하나는 전액 공급 모드(full feed mode, FFD)이다. FFD 모드에서의 분리도는 conventional mode 에 비해 떨어지지만, FFD 모드에는 몇 가지 독특한 장점이 있다. FFD 모드에서는 용매의 주입이 필요하지 않으므로 채널의 디자인 이나 작동이 더 간단하다. 따라서 입구 쪽에 flow stream splitter를 필요로 하지 않으며, 시료와 용매를 주입하기 위하여 두 개의 펌프가 필요한 conventional 모드와는 달리 한 개의 펌프만으로 작동이 가능하다. 또한 용매의 주입이 없으므로 시료가 희석되지 않는다. 이는 환경시료와 같이 콜로이드의 농도가 낮은 시료를 분획하고자 하는 경우 유리하다. 농도가 낮은 환경시료의 분획을 위해서는 종종 농축이 필요하다. 본 연구에서는 입구에는 물론 출구에도 splitter를 사용하지 않는 새로운 대용량 FFD 모드 SF 장치를 만들었다. Splitter가 없으므로 장치를 대형화 할 수 있어서 시료처리량(throughput, TP)을 크게 증가시킬 수 있었다. 산업용 폴리우레탄(polyurethane, PU) 라텍스 입자들을 이용하여 새로운 SF 장치를 테스트하였으며, 폴리아크릴레이트(polyacrylate, PA) 입자를 대상으로 새로운 SF 장치의 TP를 확인하기 위하여 유속 및 $d_c$에 따르는 TP의 변화를 조사하였다.