• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.125.2-125.2
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• 2016

Semiconductor nanowires are essential building blocks for various nanotechnologies including energy conversion, optoelectronics, and thermoelectric devices. Bottom-up synthetic approach utilizing metal catalyst and vapor phase precursor molecules (i.e., vapor - liquid - solid (VLS) method) is widely employed to grow semiconductor nanowires. Al has received attention as growth catalyst since it is free from contamination issue of Si nanowire leading to the deterioration of electrical properties. Al-catalyzed Si nanowire growth, however, unlike Au-Si system, has relatively narrow window for stable growth, showing highly tapered sidewall structure at high temperature condition. Although surface chemistry is generally known for its role on the crystal growth, it is still unclear how surface adsorbates such as hydrogen atoms and the nanowire sidewall morphology interrelate in VLS growth. Here, we use real-time in situ infrared spectroscopy to confirm the presence of surface hydrogen atoms chemisorbed on Si nanowire sidewalls grown from Al catalyst and demonstrate they are necessary to prevent unwanted tapering of nanowire. We analyze the surface coverage of hydrogen atoms quantitatively via comparison of Si-H vibration modes measured during growth with those obtained from postgrowth measurement. Our findings suggest that the surface adsorbed hydrogen plays a critical role in preventing nanowire sidewall tapering and provide new insights for the role of surface chemistry in VLS growth.

• 대한기계학회논문집B
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• 제28권9호
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• pp.1117-1123
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• 2004

The characteristics of soot near the soot inception point for an ethene-air flame was carried out in a WSR (well-stirred reactor). The new sampling tool like the temperature controlled filter system was introduced to minimize the condensation during sampling. The new analysis tools applied include the real time size distribution analysis with the Nano-DMA, particle size by transmission electron microscopy, C/H analysis, g filter analysis, and thermogravimetric analysis using both non-oxidative and oxidative pyrolysis. The WSR can generate young soot particles that can be collected and examined to gain insight into inception. For the current conditions, soot does not form for ${\Phi}$=1.9, inception occurs at or before ${\Phi}$=2.0, and inception combined with soot surface growth and/or coagulation occurs for ${\Phi}$=2.1. The filter samples for ${\Phi}$=1.9 are composed of volatile compounds that evolve at relatively low temperatures when heated in the presence or absence of O$_2$. The samples collected from the WSR at ${\Phi}$=2.0 and ${\Phi}$=2.1 are precursor-like in morphology and size. They have higher C/H ratios and lower organic percentages than precursor particles, but they are clearly not fully carbonized soot. The WSR PAH distribution is similar to that in young soot from inverse flames.

• Structural Engineering and Mechanics
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• 제47권6호
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• pp.791-818
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• 2013

The seismic performance of reinforced concrete (RC) frame structures with irregularities leading to soft first floor is studied using capacity assessment procedures. The soft first story effect is investigated for the cases: (i) slab-column connections without beams at the first floor, (ii) tall first story height and (iii) pilotis type building (open ground story). The effects of the first floor irregularity on the RC frame structure performance stages at global and local level (limit states) are investigated. Assessment based on the Capacity Spectrum Method (ATC-40) and on the Coefficient Method (FEMA 356) is also examined. Results in terms of failure modes, capacity curves, interstory drifts, ductility requirements and infills behaviour are presented. From the results it can be deduced that the global capacity of the structures is decreased due to the considered first floor morphology irregularities in comparison to the capacities of the regular structure. An increase of the demands for interstory drift is observed at the first floor level due to the considered irregularities while the open ground floor structure (pilotis type) led to even higher values of interstory drift demands at the first story. In the cases of tall first story and slab-column connections without beams soft-story mechanisms have also been observed at the first floor. Rotational criteria (EC8-part3) showed that the structure with slab-column connections without beams exhibited the most critical response.

• Journal of Korean Vacuum Science & Technology
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• 제1권1호
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• pp.24-29
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• 1997

Surface morphologies and fundamental characteristics of molybdenum nitride films deposited by reactive dc magnetron sputtering were studied for application to Cu diffusion barrier. A phase transformation from Mo to $\gamma$-Mo$_2$N phase at 0.5$N_2$ flow ratio.($N_2$/(Ar+$N_2$)) equal to and larger than 0.2, whereas a second phase transformation to $\gamma$-MoN phase at 0.5 N2 flow ratio, With the variation of the N2 ratio the surface morphologies of the films were generally smooth except the cases of 0.2 and 0.3$N_2$ gas rations, where build-up of film stresses occurred. $\gamma$-Mo$_2$N film was found to crystallize at the deposition temperature of 40$0^{\circ}C$. The surfaces of $\gamma$-Mo$_2$N films deposited up to 40$0^{\circ}C$ were smooth, but the film deposited at 50$0^{\circ}C$ had very rough surface morphology. It seems that this was due to the building-up of thermal stresses at the high deposition temperature, which might lead to hillock formation.

• 한국결정학회:학술대회논문집
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• 한국결정학회 2002년도 정기총회 및 추계학술연구발표회
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• pp.54-55
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• 2002

The fabrication, characterization and manipulation of nanoparticle system brings together physics, chemistry, materials science and biology in an unprecedented way. Phenomena occurring in such systems are fundamental to the workings of electronic devices, but also to living organisms. The ability to fabricate the surface of nanoparticles Is essential in the further development of functional devices that incorporate nanoscale features. Even more essential is the ability to introduce a wide range of chemical and materials flexibility into these structures to build up more complex nanostructures that can ultimately rival biological nanosystems. In this respect, polymers are potentially ideal nanoscale building blocks because of their length scale, well-defined architecture, controlled synthesis, ease of processing and wide range of chemical functionality that can be incorporated. In this presentation, we will look at a number of promising polymer-based nanoparticle fabrication strategies that have been developed recently, with an emphasis on those techniques that incorporate nanostructured polymeric particles into electronic devices or biomedical applications. And functional nanoparticles deliberately designed using several powerful process methods and their application will be discussed. Nanostructured nanoparticles, what we called, implies dispersed colloids with the size ranged from several nanometers to hundreds of nanometer. They have extremely large surface area, thus it is very important to control the morphology or surface functionality fitted for adequate objectives and properties. Their properties should be controlled for various kind of bio-related technologies, such as immunomagnetic cell separation, drug delivery systems, labeling and identification of lymphocyte populations, extracorporeal and hemoperfusion systems, etc. Well-defined polymeric nanoparticles can be considered as smart bomb or MEMS.

• 국제초고층학회논문집
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• 제6권2호
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• pp.139-147
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• 2017

Analyzing morphological evolution over a long period of time is deemed an effective way to identify problems occurring in the process of urban development, in addition to achieving a fundamental understanding of socio-cultural changes and growth rooted from the context. As far as the urban morphology is concerned, Hong Kong is characterized by its unique high-density and compact layout patterns, which have aroused the interest of a number of authors in the urban design domain. Whilst an increasing number of redevelopment projects in Hong Kong were criticized for ignoring and destroying the old urban fabric, there is a need for research to investigate the origins and changes of various urban patterns and their implications for society. By employing the theories and techniques of space syntax, this paper accordingly provides a morphological analysis based on the Wanchai District - a 'Segment-line' city, which particularly epitomizes various urban grids of Hong Kong and may have different implications for functional aspects. By axial-mapping the urban layouts of five stages of growth since 1842 and subsequently investigating their spatial and functional transformation over the past 170 years, this paper identifies a series of spatial characteristics underlying different grid patterns, as well as achieves a precise understanding of their ever changing relationship. Based on these understandings, this paper intends to provide valuable reference and guidance for upcoming spatial development in Hong Kong and other regions.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1298-1303
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• 2004

The characteristics of soot near the soot inception point for an ethene-air flame was carried out in a WSR (well-stirred reactor). The new sampling tool like the temperature controlled filter system was introduced to minimize the condensation during sampling. The new analysis tools applied include the real time size distribution analysis with the Nano-DMA, particle size by transmission electron microscopy, C/H analysis, g filter analysis, and thermogravimetric analysis using both non-oxidative and oxidative pyrolysis. The WSR can generate young soot particles that can be collected and examined to gain insight into inception. For the current conditions, soot does not form for ${\Phi}=1.9$, inception occurs at or before ${\Phi}=2.0$, and inception combined with soot surface growth and/or coagulation occurs for ${\Phi=2.1}$. The filter samples for ${\Phi}$=1.9 are composed of volatile compounds that evolve at relatively low temperatures when heated in the presence or absence of $O_2$. The samples collected from the WSR at ${\Phi}=2.0$ and ${\Phi}=2.1$ are precursor-like in morphology and size. They have higher C/H ratios and lower organic percentages than precursor particles, but they are clearly not fully carbonized soot. The WSR PAH distribution is similar to that in young soot from inverse flames.

• 국제초고층학회논문집
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• 제12권1호
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• pp.63-74
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• 2023

Large-capacity public transportation systems, represented by urban metro lines, are the key to alleviating the significant increase in urbanization and motorization in China. But to improve the agglomeration effect of metro stations in a more accurate and targeted way requires scientific evaluation and classification of the surrounding areas of metro stations. As spatial and functional design are the core factors for urban renewal design, this study took Beijing as an example, using multi-source data to evaluate the morphology and functional composition surrounding areas of metro stations, and the Boston Consulting Group (BCG) matrix was used to classify and characterize each type of surrounding areas from morphological-functional dimensions. It shows a negative correlation of the mix-use index with the floor area ratio, and only about 20% of the areas achieve the ideal situation of high construction intensity with high mix-use diversity. Hoping to provide a reference for city managers and designers in dealing with the surrounding metro stations with different construction intensities in a more precise way.

• ALGAE
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• 제39권2호
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• pp.59-74
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• 2024

Terrestrial cyanobacteria are extremely diverse. In urban areas, they can be found as black stains on the surface of building walls, stone monuments, or man-made structures. Many of the terrestrial cyanobacteria are still understudied. To expand knowledge of terrestrial cyanobacterial diversity, a polyphasic characterization was performed to identify 12 strains isolated from campus of University of the Ryukyus, Okinawa, Japan. Multigene phylogenetic analyses based on 16S rRNA gene and 16S-23S rRNA internal transcribed spacer (ITS) region showed that the isolated strains formed two independent subclades within Nodosilinea, and were distantly related to all described Nodosilinea species. The 16S-23S rRNA ITS secondary structures showed variations for D1-D1' and Box B domain, while V3 domain was almost identical among entire species of Nodosilinea, including the studied strains. In addition, a unique morphological character, i.e. forming nodule or spiral shape, was also observed in certain studied strains. According to polyphasic characterization, Nodosilinea coculeatus sp. nov. and Nodosilinea terrestrialis sp. nov., were proposed as two new species of terrestrial cyanobacteria from Okinawa.

• 한국지리정보학회지
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• 제25권4호
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• pp.136-150
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• 2022

본 연구는 하천 관리 및 홍수위 분석에 있어 필수적인 자료 중 하나인 하천 지형정보를 얻기 위해 RGB 영상을 활용하는 방법에 대한 비교 검토가 이루어졌다. 하천 구역의 지형정보를 얻는 데 있어 흐름 구간 즉 하도 지형정보를 얻는 것이 가장 어려운 분야 중 하나이기에 본 연구에서는 RGB 영상 기반으로 하도 지형정보를 추정하는 것에 집중하였다. 이를 위해 Acoustic Doppler Current Profiler(ADCP)와 RTK-GPS(Real Time Kinematic-GPS)를 이용하여 하도 지형을 직접 계측하였으며, 동시에 드론 촬영을 통해 획득한 고해상도 이미지를 이용하여 정사 영상을 생성하였다. 이후 수심 계측 결과와 RGB 정사 영상의 밴드 값들을 이용하여 수심 예측을 위한 기존에 개발된 회귀식들을 적용하였으며, 가장 뛰어난 예측력을 보여준 회귀식을 이용하여 연구 대상 지역의 하도 지형을 추정하였다. 흐름 구간 이외 지역의 경우 항공 라이다로부터 생성된 DEM을 이용하여 하천 구간 전체에 대한 지형정보를 구축하였다. 추가로 드론 촬영이 이루어진 동일한 시간 동안 직접 계측한 자료를 이용하여 생성된 지형정보와 드론 정사 영상 기반으로 생성된 하도 지형정보의 비교 검증을 수행하기 위해 CCHE2D 모형을 활용하여 흐름 모델링을 모의하였으며, 일부 구간에 대한 계측이 이루어지지 못한 직접 계측한 지형정보와 비교하여 영상 기반의 지형정보는 보다 나은 수심, 유속 모의 결과를 보여주었다. 본 연구 결과를 통해 RGB 영상으로부터 하도 지형정보를 획득할 수 있는 것을 확인하였으며, 추가적인 연구가 수행된다면 하천 관리를 위한 효율적인 하천 지형정보를 얻는 방법으로 활용할 가능성을 확인하였다.