• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.254-254
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• 2013

마그네트론 스퍼터링은 그 단순한 구조로 인하여 신뢰성과 확장성이 높은 기술이다, 이로 인해 DLC, ITO 등의 산업 분야에서 많이 사용하는 박막 공정 기술이다. 하지만 인듐과 같은 희토류 금속의 가격이 최근 상승함에 따라 나타난 낮은 타겟 효율성의 문제와 낮은 파워 밀도로 인한 기판의 추가적인 bias 추가에 따른 비용상승, 그리고 reactive 스퍼터링 시 낮은 증착률 등의 문제점들 또한 존재한다. 이러한 단점들을 해결하기 위해 많은 연구들이 이루어 졌으며, 높은 파워 밀도를 위해 High power Impulse Plasma Magnetron Sputtering (HIPIMS) 기술과 타겟 사용률을 높이기 위한 High Target Utilization Sputtering (HITUS) 등의 기술 등이 개발되었다. 본 연구에서는 직류 전원을 사용한 High density Plasma Sputtering System (HIPASS)이라 명하는 고밀도 원거리 플라즈마 소스를 이용한 스퍼터링 이용해 증착한 박막의 특성을 연구 하였다. Hollow cathode discharge에서 발생한 고밀도 플라즈마가 외부 유도 자장 코일에 의하여 타겟 표면까지 도달하게 되며, 스퍼터링 타겟의 고전압 bias에 의해 플라즈마 이온들이 가속이 이루어져 스퍼터링 공정이 이루어 지게 된다. 본 연구의 공정에서 타겟 사용 효율은 최대 90%까지 이며, 원거리 플라즈마 소스에서의 이온으로 스퍼터링을 실시함으로 인해 스퍼터링 전압과 전류의 독립적인 조절이 가능 하다. 본 연구에서 HIPASS을 이용하여 기판에 추가적인 전압 인가 없이 Ti 타겟과 아르곤/질소 혼합가스를 사용하여 TiN 박막을 증착 하였다. TiN의 증착률은 약 44 nm/min였으며, 이 박막의 XRD 분석 결과 TiN (111), (200), (220) 면들이 관찰이 되었다. 높은 스퍼터링 입자 에너지에서 증착 된 TiN 박막에서 우선적으로 나타나는(200)과 (220) 면들이, 본 실험에서는 기판에 추가적인 전압인가 없이도 우선방위 성장을 보였다. 이 박막의 micro-hardness 측정 결과 약 34.7 GPa이며, 이는 UBM 이나 HIPIMS에서 보여주는 결과에 준하거나 그 이상의 수치이다. 이와 같은 결과는 본 연구에서 사용한 HIPASS 증착 공정이 높은 스퍼터링 입자 에너지를 가지기에 고밀도의 TiN 박막이 증착 된 결과로 볼 수 있다.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2012.03a
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• pp.104-104
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• 2012

아웃도어용 스포츠웨어 의류분야는 소비자들의 욕구가 기능성, 착용감, 패션성을 매우 중시하는 고감성, 고기능성 제품특성을 요구하고 있으며 이를 가장 충족시킬 수 있는 패션 트랜드로서 보온, 경량화 제품이 가장 급부상하고 있는 아이템이다. 경량성의 쾌적 스포츠 웨어에 사용되는 주요 합섬소재인 PET, Nylon을 이용하여 소재의 세섬화, 중공 소재를 통한 제품 개발이 대부분으로 보온, 경량, 속건 등 의복에서의 쾌적 기능성을 개선하기 위하여 개발되는 소재 및 제품의 경량화, 보온 및 흡한속 건성 부여를 통한 기능 요소와 신질감 발현의 촉감요소를 통한 차별화 된 제품개발이 요구되고 있다. 보온 기능성을 부여하는 기술로써 가장 일반적인 기술은 섬유 내부에 중공을 형성하여 경량성과 보온성을 동시에 가지는 기능성 원사 제조 기술과 섬유 내에 열에너지를 흡수할 수 있는 물질을 넣어 외부의 태양광을 섬유내로 흡수하여 열에너지로 전환, 축적함으로서 보온성을 향상시키는 방식이 있다. 주로 경량 보온의 동시 발현을 위하여 중공 형성을 통한 보온 소재 개발이 활발하게 일어나고 있는 실정이다. 가장 많은 수요를 차지하고 있는 경량 보온성 중공사의 경우, 강도 저하, 염색 불량 등의 공정 애로점이 발생하며, 제직 및 가공 공정 시 원사 내 중공이 찌그러짐이 발생하므로 완제품 제조 후에는 중공의 기능이 제대로 발현되지 못하는 문제가 발생한다. 또한 알칼리 또는 용제를 사용하여 후용출 하는 중공사의 경우, 공정이 복잡함은 물론 환경에 유해한 공정이다. 특히, 감량 후 직물의 인열강도는 감량 전과 비교하여 감소하게 되는데 이는 이용성 polymer가 용출되면서 생긴 중공에 의해 섬도가 감소되어 강도가 저하됨을 알 수 있다. 따라서 Sheath 부분에 최대한 손상을 주지 않으면서 Core 부분을 완전 용출 시킬 수 있는 감량 조건을 확보할 필요가 있다. 이에 보온성, 경량성의 기능을 극대화시키고, 중공률 유지하는 최적 용출 가공 조건을 확립하고자 연구하였다.

• Journal of Powder Materials
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• v.10 no.6
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• pp.383-389
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• 2003

As in other areas of materials technology, the tendency towards light weight constructions becomes more and more important also for powder metallurgy. The development is mainly driven by the automotive industry looking for mass reduction of vehicles as a major factor for fuel economy. Powder metallurgy has to offer a number of interesting areas including the development of sintered materials of light metals. PM aluminium alloys with improved properties are on the way to replace ferrous pars. For high temperature applications in the engine, titanium aluminide based materials offer a great potential, e.g. for exhaust valves. The PM route using elemental powders and reactions sintering is considered to be a cost effective way for net shape parts production. Furthermore it is expected that lower costs for titanium raw materials coming from metallurgical activities will offer new chances for sintered parts with titanium alloys. The field of cellular metals expands with the hollow sphere technique, that can provide materials of many metals and alloys with a great flexibility in structure modifications. These structures are expected to be used in improving the safety (crash absoption) and noise reduction in cars in the near future and offer great potential for many other applications.

• Journal of Conservation Science
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• v.25 no.4
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• pp.411-420
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• 2009

A series of scientific analyses, including ICP-AES, microstructure, and TIMS, were carried out on 5 bronze spoons among 14 bronze artifacts excavated from the Ok-dong site in Andong, North Gyeongsang Province. The results of analysis showed that the bronze spoons were formed from an alloy of no more than 75% Cu and 21~23% Sn, placing it in the category of brassware, with trace elements such as Pb, Fe, and Zn. In particular, plumbum Pb contents of which traces of 0.04% were found, appears to have been added as an impurity during smelting. The microstructure of the bronze spoons suggests that the casting process involved using a spoon-shaped hollow mold, followed by an ropid-cooling process after the shape was perfected at approximately $586^{\circ}C$. After comparison of data measured from thermal ionization mass spectrometry (TIMS) of galena from Korea, China, and Japan, it appears that the raw materials for the bronze spoons included galena (lead sulfide) produced from the southern part of China.

• Journal of Conservation Science
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• v.26 no.1
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• pp.77-83
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• 2010

The damage from the underground termite cannot be discovered with peculiar appearance of building but hollow phenomenon will occur. But there is no case in Korea as a non-destructive measurement of termite activation. Therefore, this research constructs non-destructive diagnostic techniques for wooden cultural properties using microwave detector (Termatrac, Australia). Result of maximun distance were measured 16cm (Pine tree, sensitivity 5, 6), 17cm (Zelkova and Douglas fir, sensitivity 5, 6). These results are expected that can be applied in the field. Result of field test using microwave detector, 33.8% of the wooden cultural properties were damaged by termites, and until now 7.8% (18 buildings) are being damaged in nationwide (total 231 buildings). Based on the above results, microwave detector will be able to be utilized effectively for detecting termite, preventing intrusion in wooden structure, and making full use of monitoring system periodically. In addition, it could be of great worth in preventing insect and microorganism in wooden structure.

• Journal of Biomedical Engineering Research
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• v.26 no.5
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• pp.337-341
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• 2005

Blood pulsation has been reported to have an advantageous effect on extracorporeal blood circulation. However, the study of pulsatile blood flow in renal replacement therapy is very limited. The in-vitro experimental results of pulsatile blood flow on ultrafiltration, when compared with the conventional roller pump, are described in this paper. Methods: Blood flow rate (QB) and transmembrane pressure (TMP) were considered as regulating factors that have an influence on ultrafiltration. Experiments were performed under the condition of equal TMP and OB in both pulsatile and roller pump groups, Several kinds of hollow fiber dialyzers were tested using distilled water containing chemicals as a blood substitute. Mean TMP (mTMP) varied from 10 to 90mmHg while the QB was 200ml/min. Results: Ultrafiltration rate (QUF) was found to be linearly proportional to TMP, whereas QB had little influence on QUF. In addition, QUF was higher in the pulsatile group than the roller pump group at the identical TMP. Conclusion: In the controlled test, QUF increased solely as a consequence of blood pulsation, which implies that the pulse frequency represents an additional and important clinical variable during renal replacement therapy.

• Steel and Composite Structures
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• v.29 no.1
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• pp.1-22
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• 2018

Multi-storey precast concrete skeletal structures are assembled from individual prefabricated components which are erected on-site using various types of connections. In the current design of these structures, beam-to-column connections are assumed to be pin jointed. Welded plate beam to-column connections have been used in the precast concrete industry for many years. They have many advantages over other jointing methods in component production, quality control, transportation and assembly. However, there is at present limited information concerning their detailed structural behaviour under bending and shear loadings. The experimental work has involved the determination of moment-rotation relationships for semi-rigid precast concrete connections in full scale connection tests. The study reported in this paper was undertaken to clarify the behaviour of such connections under symmetrical vertical loadings. A series of full-scale tests was performed on sample column for which the column geometry and weld arrangements conformed with successful commercial practice. Proprietary hollow core slabs were tied to the beams by tensile reinforcing bars, which also provide the in-plane continuity across the connections. The strength of the connections in the double sided tests was at least 0.84 times the predicted moment of resistance of the composite beam and slab. The secant stiffness of the connections ranged from 0.7 to 3.9 times the flexural stiffness of the attached beam. When the connections were tested without the floor slabs and tie steel, the reduced strength and stiffness were approximately a third and half respectively. This remarkable contribution of the floor strength and stiffness to the flexural capacity of the joint is currently neglected in the design process for precast concrete frames. In general, the double sided connections were found to be more suited to a semi-rigid design approach than the single sided ones. The behaviour of double sided welded plate connection test results are presented in this paper. The behaviour of single sided welded plate connection test results is the subject of another paper.

• Journal of Microbiology and Biotechnology
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• v.27 no.3
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• pp.552-560
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• 2017

Quorum quenching (QQ) bacteria entrapped in a polymeric composite hydrogel (QQ medium) have been successfully applied in membrane bioreactors (MBRs) for effective biofouling control. However, in order to bring QQ technology closer to practice, the physical strength and lifetime of QQ media should be improved. In this study, enforcement of physical strength, as well as an extension of the lifetime of a previously reported QQ bacteria entrapping hollow cylinder (QQ-HC), was sought by adding a dehydration procedure following the cross-linking of the polymeric hydrogel by inorganic compounds like $Ca^{2+}$ and boric acid. Such prepared medium demonstrated enhanced physical strength possibly through an increased degree of physical cross-linking. As a result, a longer lifetime of QQ-HCs was confirmed, which led to improved biofouling mitigation performance of QQ-HC in an MBR. Furthermore, QQ-HCs stored under dehydrated condition showed higher QQ activity when the storage time lasted more than 90 days owing to enhanced cell viability. In addition, the dormant QQ activity after the dehydration step could be easily restored through reactivation with real wastewater, and the reduced weight of the dehydrated media is expected to make handling and transportation of QQ media highly convenient and economical in practice.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.9
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• pp.5637-5643
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• 2014

This study examined the degree of life satisfaction and quality of life of elderly people living in abandoned mine regions as well as the life quality factors that affected their degree of life satisfaction. A structured survey was used to look at their degree of life satisfaction and quality of life. The subjects were 167 elderly people aged 60 or older residing in abandoned mine regions in Gangwon-do. Their quality of life and degree of life satisfaction was moderate and when they had worked for a mine for a long time, their current degree of life satisfaction was high. In addition, religion affected their degree of life satisfaction and the residential environment and pleasant environment were highly influential in their degree of life satisfaction. Therefore, to improve the degree of life satisfaction of elderly people living in abandoned mine regions, it is essential to recover their hollow areas and create a pleasant environment by organizing their residential areas and enhancing their environment.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.540-543
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• 2011

This work is devoted to an experimental investigation on conceptual design of dual consecutive stage micro plasma thruster (${\mu}PT$). Optimization study on the thruster configuration has been performed for various electrode gap distances from 1 mm to 2 mm and the hole diameter from 0.3 mm to 2 mm depending on desired operating conditions and corresponding nozzle design requirement. The operation of ${\mu}PT$ at low pressure from $10^{-1}$ Torr to $10^{-4}$ Torr and at various argon flow rates ranging from 5 sccm to 300 sccm has been studied to understand the physic of plasma and the gas dynamics in details. The specific impulse can reach up to 3000-4000 seconds at low power consumptions from 1 to 5 W. Image of exhaust plume from ${\mu}PT$ will be provided and electrical characteristics is also mentioned in this paper.