• Korean Chemical Engineering Research
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• v.45 no.6
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• pp.591-595
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• 2007

The membrane filter coated with nanostructured porous surface layer was made by heat treatment after depositing nanoparticles onto a conventional micron-fibrous metal filter as a substrate filter. The nanostructured porous layer membrane filter (NSPL-MF), whose the filtration performance was improved compared with the conventional metal membrane filters, was developed by coating the nanoparticle agglomerates of dendrite structure onto the micron-fibrous metal filter. Pressure drop of nanostructured porous layer membrane filter decreased with increasing the heat treatment temperature to make the nanostructured porous layer adhered on the filter surface because the nanoparticle agglomerates shrank, but filtration efficiency did not decrease clearly.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.8
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• pp.1337-1345
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• 2000

In spite of the advantages of lightweight, low profile, and mass productions, microstrip array antenna has inherently the scan blindness problems in case of wide angle scan. And this scan blindness can be overcome by using cavity-backed microstrip radiator. In this paper, we presented the algorithm of analyzing skewed cavity-backed microstrip array and verified the validity of the proposed numerical results with those of reference papers. Finally, we show the effect of cavity-backed and skewed grid array structure.

• Journal of the KSME
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• v.30 no.3
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• pp.246-251
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• 1990

마이크로폴라 탄성이론은 다른 마이크로연속체(microcontinuum) 이론에 비해 적용이 간단하며, 실제 많은 물리적인 현상을 규명하는 데 다양하게 이용할 수 있다. 특히 고전 탄성이론에 의해 적절하게 해결될 수 없는 덤벨(dumbell) 분자로 이루어진 물체, 액체 결정체(liquid crystals), 과립상(granular)의 분자로 구성된 물체와 복합 섬유재료(composite fibrous materials) 등은 마 이크로폴라 탄성이론에 의해 잘 해결될 수 있다. 또한 마이크로폴라 탄성이론은 고체 내에서의 파의 전파(propagation)와 분산(dispersion), 구멍 주위의 응력집중과 외부 하중을 받는 물체에 있어 균열끝에서의 응력 분포 등의 고체역학 문제들은 물론이고, 경계층(boundary layer), 난 류(turbulence), 유체 유동의 불안정(instability)과 표면장력 현상 등의 유체역학에서의 복잡한 문제들을 해결하는 데에도 이용할 수 있다. 마이크로폴라 탄성이론은 고전 탄성이론에 비해 상 대적으로 새롭고 미개척 분야이긴 하지만 이론의 기반이 확고하기 때문에 앞으로의 회전응력 측정장치의 개발을 통해 미소구조의 영향을 고려해야 하는 많은 문제들을 해결하는데 큰 기여를 할 것으로 전망된다.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.292-292
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• 2013

최근, 자연의 기능성 표면을 모사하여 우리 생활에 응용하기 위한 연구가 활발하다. 초-발수 특성을 가지는 대표적인 예인 연꽃잎은 마이크로-나노 크기의 거친 미세돌기(papillae)를 가지고 있으며 그 위에 낮은 표면 에너지를 가지는 왁스(wax)가 발달 되어 항상 깨끗한 상태를 유지한다. 본 실험에서는 이를 모사하여 RIE (Reactive Ion Etching)방법을 이용하여 기판인 Poly silicon wafer를 Sf6가스를 사용하여 Metal mash로 거칠기를 만들어 주었고, RF-magnetron sputtering 장치를 사용하여 $6{\times}10^{-3}$ Torr의 진공도에서 낮은 표면에너지를 가지는 PTFE (polytetrafluoroethylene)를 증착하여 표면 구조와 발수특성에 대하여 조사하였다. SSME(Surface shape measurement equipment)측정결과 0.24~0.36 um RSa 값이 측정되었고, 12 uL의 Di-water로 접촉각을 측정 한 결과 RIE 10분 처리를 한 기판 위에 PTFE를 3분 증착하였을 때 가장 높은 $153^{\circ}$의 초-발수 특성이 나타났으며, 4주의 시간이 지났을 때에도 접촉각이 유지가 되었다. XPS 측정결과 초-발수 표면에서 나타나는 CF2와 CF3 피크 값이 측정되었다. Reactive Ion Etching을 이용한 PTFE 발수 특성은 방수, 스마트 윈도우, 자가세정(Self-Cleaning), 디스플레이 표시장치, 김서림 방지(Anti-Fogging), 대전방지 코팅 등에 다각적으로 응용 가능할 것이라 사료된다.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.6
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• pp.577-585
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• 2015

We fabricated multi-scale such as macro-, micro-, and multi-scale wrinkles by using repetitive volume dividing (RVD) method and thermal curing process. Also wrinkle surface was modified with coating of a self-assembled monolayer (SAM). We measured the contact angle of each wrinkled surface, and observed the behavior of droplets on sloping surface. Through experimental study, we found out that the contact angle was much higher in case of multi-scale and SAM coated wrinkles. And micro-scale wrinkle showed a high contact angle comparing with that of macro-scale wrinkle. Dynamic behaviors of a water droplet like sliding velocity on diverse wrinkled surfaces were dependent on their static contact angles. These results showed that hydro-dynamic characteristics were changed depending on the wrinkle structure and the material forming the wrinkle. These dynamic characteristics can be utilized in bio-chip, microfluidics, and many others in order to control easily chemical reactivity.

• Membrane Journal
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• v.27 no.1
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• pp.1-42
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• 2017

Metal-organic frameworks (MOFs) are nanoporous materials that consist of organic and inorganic moieties, with well-defined crystalline lattices and pore structures. With a judicious choice of organic linkers present in the MOFs with different sizes and chemical groups, MOFs exhibit a wide variety of pore sizes and chemical/physical properties. This makes MOFs extremely attractive as novel membrane materials for gas separation applications. However, the synthesis of high-quality MOF thin films and membranes is quite challenging due to difficulties in controlling the heterogeneous nucleation/growth and achieving strong attachment of films on porous supports. Microwave-based synthesis technology has made tremendous progress in the last two decades and has been utilized to overcome some of these challenges associated with MOF membrane fabrication. The advantages of microwaves as opposed to conventional synthesis techniques for MOFs include shorter synthesis times, ability to achieve unique and complex structures and crystal size reductions. Here, we review the recent progress on the synthesis of MOF thin films and membranes with an emphasis on how microwaves have been utilized in the synthesis, improved properties achieved and gas separation performance of these films and membranes.

• Proceedings of the Korean Fiber Society Conference
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• 2001.10a
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• pp.368-370
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• 2001

폴리비닐알코올(poly(vinyl alcohol) (PVA))은 구조적인 단량체인 비닐알코올의 호변 이성질화 때문에 직접 중합에 의해서는 얻을 수 없으며, 아세트산 비닐 (vinyl acetate (VAc))이나 피발산 비닐 (vinyl pivalate (VPi))같은 비닐에스테르 계열 단량체를 사용하여 중합과 비누화 반응을 거쳐 제조되고 비누화 반응에서 모든 측쇄기가 효과적으로 제거되는 히드록시기 함유 선형 결정성 고분자이다[1-4]. (중략)

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.11a
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• pp.393-394
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• 2010

• Journal of Korean Association for Spatial Structures
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• v.7 no.6
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• pp.83-90
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• 2007

Today, many studies are progressed about source of vibration oscillator in reinforcement concrete structures. Source of vibration oscillator is load when it is happen from walking inhabitant. It is transmitted to another inhabitant through reinforcement concrete plate, and it is type of elastic wave. Those descriptions are ram wave and primary wave, secondary wave, and the are through the surface and inside plate. Analysis studies of those waves are used to piezoelectric materials. But, they are difficult to 3 axial type of transmitting elastic wave in concrete element. In this study, a fundamental study for source estimations of vibration oscillator using micro accelerometer are discussed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.10
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• pp.1041-1046
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• 2011

Micro shockwaves are induced in laser shock peening and their effect on metal samples is presented. Laser shock peening produces maximized internal compressive stress on metal surfaces. This research evaluated the effects of micro shockwaves from laser shock peening with a pulsed Nd:YAG laser on steel samples, through the analysis of the mechanical properties of the samples. In the experiments, a piezo material was applied to measure the micro shockwaves and the hardnesses and micro tensile strengths of the samples were evaluated.