• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1018-1021
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• 2006

Powdered metal parts and components may be carburized successfully in a vacuum furnace by combining carburizing technology $VacCarb^{TM}$ with a hi-tech control system. This approach is different from traditional carburizing methods, because vacuum carburizing is a non-equilibrium process. It is not possible to set the carbon potential as in a traditional carburizing atmosphere and control its composition in order to obtain a desired carburized case. This paper presents test results that demonstrate that vacuum carburizing system $VacCarb^{TM}$ carburized P.M. materials faster than traditional steel with acceptable results. In the experiments conducted, PM samples with the lowest density and open porosity showed a dramatic increase in the surface carbon content up to 2.5%C and a 3 times deeper case. Currently the boost-diffusion technique is applied to control the surface carbon content and distribution in the case. In the first boost step, the flow of the carburizing gas has to be sufficient to saturate the austenite, while avoiding soot deposition and formation of massive carbides. To accomplish this goal, the proper gas flow rate has to be calculated. In the case of P.M. parts, more carbon can be absorbed by the part's surface because of the additional internal surface area created by pores present in the carburized case. This amount will depend on the density of the part, the densification grade of the surface layer and the stage of the surface. "as machined" or "as sintered". It is believed that enhanced gas diffusion after initial evacuation of the P.M. parts leads to faster carburization from within the pores, especially when pores are open . surface "as sintered" and interconnected . low density. A serious problem with vacuum carburizing is delivery of the carbon in a uniform manner to the work pieces. This led to the development of the different methods of carburizing gas circulation such as the pulse/pump method or the pulse/pause technique applied in SECO/WARWICK's $VacCarb^{TM}$ Technology. In both cases, each pressure change may deliver fresh carburizing atmosphere into the pores and leads to faster carburization from within the pores. Since today's control of vacuum carburizing is based largely on empirical results, presented experiments may lead to better understanding and improved control of the process.

• 한국결정성장학회지
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• 제21권2호
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• pp.82-86
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• 2011

인공경량 골재는 다결정질 소성체를 주 구성으로 하므로 골재 내부에 다량의 공극이 일정비율로 형성되는 것이 특징이다. 이러한 인공경량 골재는 조직 구조의 특성상 외부환경의 변화에 의해 수분이 비정상적인 이동을 보이는 경향이 있다. 다공질 재료의 수분 방출 특성은 일반적으로 기공률 및 기공크기 분포에 크게 좌우되지만, 인공적으로 소결 제조된 경우에는 표면에 생성된 치밀한 구조의 표피층에도 많은 영향을 받을 것으로 생각된다. 인공경량 골재 내부의 수분 이동에 미치는 요인은 골재내의 세공 및 공극의 분포와 형상, 크기, 그리고 프리웨팅 방법 등이 있으며 각 조건에 따라 상당한 차이를 보인다. 본 연구에서는 인공경량 골재를 제조하여 골재의 가압시 흡수 특성이나 침수시간에 대한 흡수율의 거동에 대한 명확한 규명을 함으로써 경량골재 펌프압송을 위한 기초적 자료를 제공하고자 하였다. 본 실험에 사용된 인공경량골재는 독일 'L'사의 상업용 인공경량골재와 본 연구팀이 제조한 2가지 조성의 인공경량골재를 사용하였으며, 골재 수분함침시간, 진공압력, 급냉조건을 변화시켜 골재의 흡수율을 측정하였다. 인공경량골재를 $300^{\circ}C$ 에서 급냉 하였을 경우 24시간 침수보다 높은 흡수율을 보였고, 진공압력에 따라 흡수율이 증가하는 경향이 있으며, -300 mmHg의 진공 압력시 24시간 침수보다 "L"사 골재는 54 %의 높은 증가를 보였으나 K622와 K73 골재는 비교적 적은 2 % 내외의 흡수율 증가양상을 보였다.

• Journal of Advanced Marine Engineering and Technology
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• 제29권5호
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• pp.488-494
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• 2005

The ejector is used to obtain a vacuum state, and it has been applied to a lot of industry field such as a heat engine, a fluid instrument power plant. a food industry, an environment industry etc., because there is no problem even it is mixed with any kind of liquid, gas. and solid. The flow characteristics in the ejector was investigated by a PIV and a CFD. The agreement between numerical analysis and experiment shows the validity of this study and the results of this study would be useful to the engineers who design for the flow systems for heating. ventilation. air conditioning and wastewater purification plants.

• Fibers and Polymers
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• 제4권3호
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• pp.135-144
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• 2003

Permeability of the preform is one of key factors in design of RTM (Resin Transfer Molding) mold, determination of processing conditions, and modeling of flow in the mold. According to previous studies, permeability measured in the unsaturated fiber mats are higher than that in the saturated fiber mats by about 20% because of the capillary pressure. In this study, permeabilities of several fiber preforms are measured for both saturated and unsaturated flows. A saturated experiment of radial flow has been adopted to measure the permeability of anisotropic fiber preforms with high fiber content, i.e., circular braided preforms. In this method, four pressure transducers are used to measure the pressure distribution. Permeabilities in different directions are determined and the experimental results show a good agreement with the theory. Since permeability is affected by the capillary effect, permeability should be measured in the unsaturated condition for the textile composites to be manufactured under lower pressure as in the Vacuum Assisted Resin Transfer Molding (VARTM).

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.150.1-150.1
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• 2014

Showerhead is used as a main part in the semiconductor equipment. The face plate flatness should remain constant and the cleaning performance must be gained to keep the uniformity level of etching or deposition in chemical vapor deposition process. High operating temperature or long period of thermal loading could lead the showerhead to be deformed thermally. In some case, the thermal deformation appears very sensitive to showerhead performance. This paper describes the methods for robust design using computational fluid dynamics. To reveal the influence of the post distribution on flow pattern in the showerhead cavity, numerical simulation was performed for several post distributions. The flow structure appears similar to an impinging flow near a centered baffle in showerhead cavity. We took the structure as an index to estimate diffusion path. A robust design to reduce the thermal deformation of showerhead can be achieved using post number increase without ill effect on flow. To prevent the showerhead deformation by heat loading, its face plate thickness was determined additionally using numerical simulation. The face plate has thousands of impinging holes. The design key is to keep pressure drop distribution on the showerhead face plate with the holes. This study reads the methodology to apply to a showerhead hole design. A Hagen-Poiseuille equation gives the pressure drop in a fluid flowing through such hole. The assumptions of the equation are the fluid is viscous-incompressible and the flow is laminar fully developed in a through hole. An equation can be expressed with radius R and length L related to the volume flow rate Q from the Hagen-Poiseuille equation, $Q={\pi}R4{\Delta}p/8{\mu}L$, where ${\mu}$ is the viscosity and ${\Delta}p$ is the pressure drop. In present case, each hole has steps at both the inlet and the outlet, and the fluid appears compressible. So we simplify the equation as $Q=C(R,L){\Delta}p$. A series of performance curves for a through hole with geometric parameters were obtained using two-dimensional numerical simulation. We obtained a relation between the hole diameter and hole length from the test cases to determine hole diameter at fixed hole length. A numerical simulation has been performed as a tool for enhancing showerhead robust design from flow structure. Geometric parameters for the design were post distribution and face plate thickness. The reinforced showerhead has been installed and its effective deposition profile is being shown in factory.

• 한국유체기계학회 논문집
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• 제12권6호
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• pp.13-17
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• 2009

Ejector is an equipment devised for making use of the low pressure occurring from the fast fluid injection and it is a transportation equipment which can obtain vacuum using the kinetic energy of the fluid. This ejector system is, nowadays, widely used for construction machinery, heavy equipments, the cooling and ventilation of electronic devices and for the various fluid transportation and pumps. In this study, it is attempted to perform a numerical analysis and an experiment to find out the characteristics of fluid quantity, velocity and the pressure distribution of the induction pipe by changing the length and the radius ratio of the nozzle of ejector. From the results, it is investigated that the distributions of velocity and pressure of induction pipe attached are changing with the length and the radius ratio of the nozzle. In addition, it is shown that for the small and large ejector, the efficiency is the maximum when the length of the nozzle arrived to the neck of the ejector, however, if it is installed at below or above the neck the efficiency is rather decreased.

• 한국산학기술학회논문지
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• 제19권1호
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• pp.121-126
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• 2018

중환자실에 입원한 환자들의 구강위생은 매우 중요한 문제이다. 중환자들은 기본적으로 면역이 저하된 환자들로 각종 병원성 세균들에 의한 감염의 기회가 높기 때문이다. 구강문제는 감염의 1차 방어선인 구강이 감염의 우선적인 부위로 작용될 뿐 아니라 전신감염을 초래하기도 한다. 본 연구에서는 중증환자의 구강청소를 용이하게 하는 마우스 피스 형태의 새로운 진공 구강 세정기 설계에 관한 연구를 수행하였다. 이중 구조 방식의 세정기와 표준 치아 모델로써 3D CAD 모델링 및 유동해석 모델을 수립하고 압력 및 유동특성을 분석하였다. 세정기 내부의 압력은 거의 일정한 분포를 보였으나, 속력분포의 경우 치아 안쪽과 바깥쪽에서 큰 차이를 보였다. 치아 안쪽에서도 가운데 부분의 속도가 가장 높고 가운데에서 멀어질수록 속력이 감소하는 특성을 보였다. 세정기의 흡입관과 배출관을 바꾸어 해석한 결과 치아 바깥쪽 가운데 부분의 속도가 가장 높게 나타났다. 세정기의 효과를 높이기 위해서 흡입-배출을 교대로 바꾸는 교번식을 제안하고, 어금니 부위의 속력을 높이는 설계 보완이 요구된다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.59.2-59.2
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• 2015

Modification of film structure and properties in inductively-coupled plasma (ICP) assisted dc and pulsed dc sputtering has been reported by Oya and Kusano [1] and by Sakamoto, Kusano, and Matsuda [2], showing drastic changes in films structure and properties by the ICP assistance in particular to the pulsed dc discharge. Although mechanisms involved in the modification has been reported to be the increase in energy transferred to the substrate, details of effects of low-energy ion bombardment on the modification and origin of an anomalous increase in the ion quantity by the ICP assistance to the pulsed dc discharge have not been discussed. In this presentation, mechanisms involved in film structure and property modification in ICP assisted dc and pulsed dc sputtering, in which a number of low-energy ions are formed, will be discussed based on ion energy distribution as well as effectiveness of energy transfer to the substrate by low energy particles [3]. The results discussed in this presentation will emphasize the fact that the energetic particles playing an important role in the film structure modification are those to be deposited, but not those of inert gas, when their energies range in less than 100 eV in the pressure range of magnetron sputtering.

• 한국진공학회지
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• 제7권3호
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• pp.255-260
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• 1998

Ionized magnetron sputtering은 high density plasma를 사용하여 스퍼터된 입자의 이온화율을 기판에서의 플럭스 기준으로 80%이상까지 증대시킬 수 있는 방법으로 반도체 소자의 아주 작은 홀이나 via contact등을 채울 수 있는 아주 유용한 수단이나 가스의 압력 이 30mTorr 이상으로 상당히 높아야만 이온화율이 높게 유지되어 스퍼터 증착 속도가 느려 지고 중성입자의 각도 분포가 넓어지는 단점이 있다. 그 원인이 스퍼터된 입자들에 의한 전 자 온도의 급격한 감소와 타겟 주변에서의 가스 희귀화 현상에 있다고 보고 이를 보완하고 자 스퍼터 전력을 펄스화 하는 방법을 고안하여 실험하였다. 그 결과 펄스의 on/off time이 10ms/10ms, 100ms/100ms에서 가장 높은 이온화율을 가시광 분광 결과에서 보였으며 실제 로 Ag의 XRD결과 (111)에서 (200)으로 우선 방위의 현격한 변화가 관찰되었다. 이를 고전 력 스퍼터링에 의한 중성 가스 가열과 냉각의 측면에서 해석하였다.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 하계학술발표대회 논문집
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• pp.389-394
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• 2008

Nowadays Plate Heat Exchanger (PHE) is widely used in different industries such as chemical, food and pharmaceutical process and refrigeration due to the efficient heat transfer performance, extreme compact design and efficient use of the construction material. In present work, PHE is applied in the fresh water generator system. Fresh water generators or desalinators are installed in ship to convert seawater to fresh water using heat from engines. PHE is an important part of a condensing or evaporating system. Among many of factors which should be concentrated on, the heat transfer and pressure drop is most important parts during sizing and rating the performance of PHE. Flow maldistribution is common but it will significantly reduce the heat exchanger performance. In this paper provide a overview of PHE cover basic of theory and conduct a numerical approach for flow distribution in plate channel. An experimental study on the performance of fresh water generator system which developed by plate heat exchanger will presented in future research. Thus, extensive experiment and analysis is required to study the thermal and fluid flow characteristics of PHE.