• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.196-196
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• 2012

Graphene, two-dimensional one-atom-thick planar sheet of carbon atoms densely packed in a honeycomb crystal lattice, has grabbled appreciable attention due to its extraordinary mechanical, thermal, electrical, and optical properties. Based on the graphene's high carrier mobility, high frequency graphene field effect transistors have been developed. Graphene is useful for photonic components as well as for the applications in electronic devices. Graphene's unique optical properties allowed us to develop ultra wide-bandwidth optical modulator, photo-detector, and broadband polarizer. Graphene can support SPP-like surface wave because it is considered as a two-dimensional metal-like systems. The SPPs are associated with the coupling between collective oscillation of free electrons in the metal and electromagnetic waves. The charged free carriers in the graphene contribute to support the surface waves at the graphene-dielectric interface by coupling to the electromagnetic wave. In addition, graphene can control the surface waves because its charge carrier density is tunable by means of a chemical doping method, varying the Fermi level by applying gate bias voltage, and/or applying magnetic field. As an extended application of graphene in photonics, we investigated the characteristics of the graphene-based plasmonic waveguide for optical signal transmission. The graphene strips embedded in a dielectric are served as a high-frequency optical signal guiding medium. The TM polarization wave is transmitted 6 mm-long graphene waveguide with the averaged extinction ratio of 19 dB at the telecom wavelength of $1.31{\mu}m$. 2.5 Gbps data transmission was successfully accomplished with the graphene waveguide. Based on these experimental results, we concluded that the graphene-based plasmonic waveguide can be exploited further for development of next-generation integrated photonic circuits on a chip.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.391-392
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• 2012

Graphene is a perfectly two-dimensional (2D) atomic crystal which consists of sp2 bonded carbon atoms like a honeycomb lattice. With its unique structure, graphene provides outstanding electrical, mechanical, and optical properties, thus enabling wide variety of applications including a strong potential to extend the technology beyond the conventional Si based electronic materials. Currently, the widespread application for electrostatically switchable devices is limited by its characteristic of zero-energy gap and complex process in its synthesis. Several groups have investigated nanoribbon, strained, or nanomeshed graphenes to induce a band gap. Among various techniques to synthesize graphene, chemical vapor deposition (CVD) is suited to make relatively large scale growth of graphene layers. Direct growth of graphene on hexagonal boron nitride (h-BN) using CVD has gained much attention as the atomically smooth surface, relatively small lattice mismatch (~1.7％) of h-BN provides good quality graphene with high mobility. In addition, induced band gap of graphene on h-BN has been demonstrated to a meaningful value about ~0.5 eV.[1] In this paper, we report the synthesis of grpahene / h-BN bilayer in a chemical vapor deposition (CVD) process by controlling the gas flux ratio and deposition rate with temperature. The h-BN (99.99％) substrate, pure Ar as carrier gas, and $CH_4$ are used to grow graphene. The number of graphene layer grown on the h-BN tends to be proportional to growth time and $CH_4$ gas flow rate. Epitaxially grown graphene on h-BN are characterized by scanning electron microscopy, atomic force microscopy, and Raman spectroscopy.

• 대한한방내과학회지
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• 제26권3호
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• pp.626-633
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• 2005

As age distributions of developed countries grow increasingly top-heavy with elderly, instances of bronchiectasis and pneumonia increase. An elderly patient was diagnosed with pneumonia by radiational examination, which showed pound glass opacity in the right middle lobe. Also, he was diagnosed with bronchiectasis in the honeycomb-like recticular area of the right lower lobe. He said that he was suffering from a cough, phlegm and general weakness. He was treated by oriental medicine treatment exclusively, through herbal medicine and acupuncture therapy. Yukmijihwabg-Tang(六味地黃湯), Gamijinhae-Tang(加味鎭咳湯), and Samchulbobi-Tang(參朮補脾湯) As a result, symptoms of cough phlegm and general weakness improved considerably. These results suggest that oriental medicine treatment is effective in improving quality of life fer chronic respiratory patients.

• 한국지열·수열에너지학회논문집
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• 제10권4호
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• pp.15-24
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• 2014

This study conducted a computational fluid dynamics(CFD) analysis to find an appropriate diameter or sectional area of air ducts and fluid pipes which have an electromagnetic pulse(EMP) shied to protect indoor electronic devices in special buildings like military fortifications. The result shows that the optimized outdoor air intake size can be defined with either the ratio of the maximum air velocity in the supply duct to the air intake size, or the shape ratio of indoor supply diffuser to the outdoor air intake. In the case of water channel, the fluid velocity at EMP shield with the identical size of the pipe, decreases by 25% in average due to the resistance of the shield. The enlargement of diameter at the shield, 2 step, improves the fluid flow. It illustrated that the diameter of downstream pipe size is 1step larger than the upstream for providing the design flow rate. The shield increases friction and resistance, in the case of oil pipe, so the average flow velocity at the middle of the shield increase by 50% in average. In consideration of the fluid viscosity, the oil pipe should be enlarged 4 or 5 step from the typical design configuration. Therefore, the fluid channel size for air, water, and oil, should be reconsidered by the engineering approach when EMP shield is placed in the middle of channel.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.630-630
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• 2013

Recently, atomically smooth hexagonal boron nitride(h-BN) known as a white graphene has drawn great attention since the discovery of graphene. h-BN is a III-V compound and has a honeycomb structure very similar to graphene with smaller lattice mismatch. Because of strong covalent sp2bonds like graphene, h-BN provides a high thermal conductivity and mechanical strength as well as chemical stability of h-BN superior to graphene. While graphene has a high electrical conductivity, h-BN has a highly dielectric property as an insulator with optical band gap up to 6eV. Similar to the graphene, h-BN can be applied to a variety of field, such as gate dielectric layers/substrate, ultraviolet emitter, transparent membrane, and protective coatings. However, up until recently, obtaining and controlling good quality monolayer h-BN layers have been too difficult and challenging. In this work, we investigate the controlled synthesis of h-BN layers according to the growth condition, time, temperature, and gas partial pressure. h-BN is obtained by using chemical vapor deposition on Cu foil with ammonia borane (BH3NH3) as a source for h-BN. Scanning Transmission Electron Microscopy (STEM, JEOL-JEM-ARM200F) is used for imaging and structural analysis of h-BN layer. Sample's surface morphology is characterized by Field emission scanning electron microscopy (SEM, JEOL JSM-7100F). h-BN is analyzed by Raman spectroscopy (HORIBA, ARAMIS) and its topographic variations by Atomic force microscopy (AFM, Park Systems XE-100).

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.285-285
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• 2013

Recently, hexagonal boron nitride (h-BN), which is III-V compound of boron and nitride by strong covalent sp2 bonds has gained great interests as a 2 dimensional insulating material since it has honeycomb structure with like graphene with very small lattice mismatch (1.7%). Unlike graphene that is semi-metallic, h-BN has large band gap up to 6 eV while providing outstanding properties such as high thermal conductivity, mechanical strength, and good chemical stability. Because of these excellent properties, hBN can potentially be used for variety of applications such as dielectric layer, deep UV optoelectronic device, and protective transparent substrate. Low pressure and atmospheric pressure chemical vapor deposition (LPCVD and APCVD) methods have been investigated to synthesize h-BN by using ammonia borane as a precursor. Ammonia borane decomposes to polyiminoborane (BHNH), hydrogen, and borazine. The produced borazine gas is a key material that is a used for the synthesis of h-BN, therefore controlling the condition of decomposed products from ammonia borane is very important. In this paper, we optimize the decomposition of ammonia borane by investigating temperature, amount of precursor, and other parameters to fabricate high quality monolayer h-BN. Synthesized h-BN is characterized by Raman spectroscopy and its absorbance is measured with UV spectrophotometer. Topological variations of the samples are analyzed by atomic force microscopy. Scanning electron microscopy and Scanning transmission Electron microscopy are used for imaging and analysis of structures and surface morphologies.

• 디지털융복합연구
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• 제17권6호
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• pp.327-333
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• 2019

본 연구는 국민 채팅 앱으로 일컬을 수 있는 카카오톡을 부모들이 안심하고 초등학교 자녀들이 쓰게 할 수 있도록, 초등학생 자녀들도 안심하고 사용할 수 있도록, 양 대상자 간의 사용자 경험의 차이점을 조사한 후 카카오톡의 개선 영역을 제안하는 데 그 목적이 있다. 연구방법으로는 문헌연구를 통해 한국의 스마트폰 보급률을 조사하고, 키즈폰 출시와 한계점, 카카오톡의 사회적 문제에 대해 고찰하였으며, 카카오톡을 사용하는 부모 8명과 해당 자녀 8명을 대상으로 피터 모빌의 허니콤 모델을 기반으로 한 설문조사, 인터뷰를 진행하였다. 그 결과, 각 대상자의 카카오톡의 구체적인 사용 실태와 관점, 니즈를 파악하였고, 부모들은 신뢰성 부분에서 카카오톡을 신뢰하지 못하는 것을 알 수 있었다. 본 연구를 바탕으로 후속 연구를 통해 카카오톡 실제 개선까지 이루어져 부모와 자녀가 안심하고 쓸 수 있는 카카오톡이 되기를 기대한다.

• Composites Research
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• 제33권6호
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• pp.408-414
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• 2020

샌드위치 구조는 우수한 강도와 경량성을 동시에 만족하는 구조물로써 다양한 분야에서 널리 사용되고 있다. 스킨은 주로 고강도의 섬유가, 코어는 경량화에 유리한 허니콤 구조 및 발사(balsa) 나무가 주로 사용되고 있으나, 내부의 공기층 및 난연처리의 어려움으로 인하여 화재에 취약하는 것이 단점이다. 본 연구에서는 대나무 섬유의 난연처리 연구를 통하여 친환경적인 소재를 이용한 난연처리 조건을 제시하였다. 또한 대나무 섬유를 이용하여 천연섬유 샌드위치 복합재료를 제조하고 기계적 특성평가를 수행하였다. 난연성이 향상된 천연섬유를 이용하여 샌드위치 구조의 복합재료를 제조한다면 새로운 유형의 복합재료가 될 수 있을 것으로 기대된다.

• 대한세포병리학회지
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• 제4권2호
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• pp.105-110
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• 1993

갑상선의 세침흡인 세포학적 검사에서 가장 문제가 되는 점은 여포상 종양의 진단이다. 세포학적 소견만으로는 증식성 결절성 갑상선종, 여포성 선종 및 분화가 잘 된 여포상 암종 간의 감별 진단이 매우 어려운 경우가 많다. 저자들은 최근 4년 5개월 간에 조직학적으로 확진된 여포상 종양 중 수술 전에 적합한 세포학적 검사가 시행된 15예를 대상으로 그 세포학적 소견을 재검토하였다. 여포상 선종 6예의 흡인 도말은 공 모양 또는 합포체를 형성하는 다량의 여포성 세포를 함유하고 있었고, 경도의 핵 다형성 및 작은 핵소체가 각각 2예에서 관찰되었다. 배경은 출혈성으로 교질 성분은 매우 적거나 없었다. 여포상 암종 9예도 기본적으로 선종과 유사한 세포학적 소견을 보였는데, 세포밀도가 좀더 높고, 세포집단의 모양이 더 크고 불규칙하였으며, 흩어진 개별 종양세포가 많은 것이 차이점이었다. 핵의 다형성 및 눈에 띄는 핵소체가 선종에서 보다 많은 6예 및 5예에서 각각 관찰되었으나 그 정도는 심하지 않았다. 대부분의 암종과 1예의 선종에서 종양세포 집단에 밀착한 혈관 내피세포가 관찰되었다. 전반적으로 여포상 선종 및 암종은 미미한 차이를 보여서 세포학적으로 확실히 구별하기는 어려웠으나, 많은 수의 개별 세포와 종양세포 간에 포착된 혈관내피세포의 존재는 양성보다는 악성을 시사하는 소견으로 생각되었다. 여포상 종양의 세포학에 좀더 관심을 가짐으로써 그 발견율을 현저히 높일 수 있다고 생각된다.

• Asian-Australasian Journal of Animal Sciences
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• 제20권6호
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• pp.994-1001
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• 2007

Changes in shear force value, transverse sections, myofibrils and intramuscular connective tissue of bovine skeletal muscle exposed to the combination of high-pressure up to 400 MPa and heat (30 and $60^{\circ}C$) were studied. The shear force value decreased by pressure-heat treatment up to 200 MPa at 30 and $60^{\circ}C$, and then slightly increased over 200 MPa at $30^{\circ}C$. Shear force values of treated muscles were lower than those of untreated ones. Gaps between muscle fibers in the untreated muscle were a little clear, and then they became very clear in the treated muscles up to 200 MPa at 30 and $60^{\circ}C$. However, the gaps reduced significantly over 200 MPa at $30^{\circ}C$. The remarkable rupture of I-band and loss of M-line materials progressed in the myofibrils with increasing pressure applied. However, degradation and loss of the Z-line in myofibrils observed in the muscle treated at $60^{\circ}C$ was not apparent in the muscle treated at $30^{\circ}C$. The length of the sarcomere initially contracted by pressure-heat treatment of 100 MPa at $30^{\circ}C$ seemed to have recovered with increase of the pressure up to 400 MPa. In the muscle treated at $60^{\circ}C$, the length of sarcomere gradually decreased with increase of the pressure up to 400 MPa. In the treated muscles, changes in the honeycomb-like structure of endomysium were observed and accelerated with increase of the pressure. A wavy appearance clearly observed at the inside surface of endomysium in the untreated muscles gradually decreased in the treated muscles with increase of the pressure. Tearing of the membrane was observed in the muscles treated over 150 MPa at $30^{\circ}C$, as observed in the sample pressurized at 100 MPa at $60^{\circ}C$. The roughening, disruption and fraying of the membrane were observed over 200 MPa at $60^{\circ}C$. From the results obtained, the combination of high-pressure and heat treatments seems to be effective to tenderize tough meat. The shear force value may have some relationship with deformation of intramuscular connective tissue and myofibrils.