• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.61.1-61.1
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• 2015

Nanoscale semiconductor plasma processing has become one of the most challenging issues due to the limits of physicochemical fabrication routes with its inherent complexity. The mission of future and emerging plasma processing for development of next generation semiconductor processing is to achieve the ideal nanostructures without abnormal profiles and damages, such as 3D NAND cell array with ultra-high aspect ratio, cylinder capacitors, shallow trench isolation, and 3D logic devices. In spite of significant contributions of research frontiers, these processes are still unveiled due to their inherent complexity of physicochemical behaviors, and gaps in academic research prevent their predictable simulation. To overcome these issues, a Korean plasma consortium began in 2009 with the principal aim to develop a realistic and ultrafast 3D topography simulator of semiconductor plasma processing coupled with zero-D bulk plasma models. In this work, aspects of this computational tool are introduced. The simulator was composed of a multiple 3D level-set based moving algorithm, zero-D bulk plasma module including pulsed plasma processing, a 3D ballistic transport module, and a surface reaction module. The main rate coefficients in bulk and surface reaction models were extracted by molecular simulations or fitting experimental data from several diagnostic tools in an inductively coupled fluorocarbon plasma system. Furthermore, it is well known that realistic ballistic transport is a simulation bottleneck due to the brute-force computation required. In this work, effective parallel computing using graphics processing units was applied to improve the computational performance drastically, so that computer-aided design of these processes is possible due to drastically reduced computational time. Finally, it is demonstrated that 3D feature profile simulations coupled with bulk plasma models can lead to better understanding of abnormal behaviors, such as necking, bowing, etch stops and twisting during high aspect ratio contact hole etch.

• 한국표면공학회지
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• 제38권1호
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• pp.21-27
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• 2005

Tensile properties and hardness of nickel electroform from chloride-free nickel sulfamate electrolyte at 50℃ and PH 4.5 were investigated. Current density varied from 20 to 60 mA/㎠. The deposit thicknesses were 360, 480 and 980 ㎛. It was found in 480 ㎛ thick electroform that highest tensile and yield strengths and hardness of 83.7 ksi, 53.6 ksi and 216 DPH, respectively were obtained at a current density of 40 mA/㎠ and they were slightly decreased at 20 and 60 mA/㎠. However the ductility was lowest of 7.9% at 40 mA/㎠. Such a high strength and low ductility at 40 mA/㎠ seems to be related to the narrower columnar structure than those of other current densities. All the deposits exhibited pronounced necking behavior. Tensile strength, yield strength and ductility increased as the nickel electroform thickens. Initial strong (200) texture developed on stainless steel mandrel decreased and (111) and (220) textures increased as deposit thickness increased, whereas (200) texture was preferred as the current density increased.

• 한국지반환경공학회 논문집
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• 제2권4호
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• pp.5-14
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• 2001

최근 구조물기초에 큰 변형 및 손상을 가하지 않고 안정성에 대한 정보를 비교적 쉽게 얻을 수 있는 비파괴시험(NDT, Non-Destructive Testing)기법이 큰 관심을 얻고 있다. 본 연구에서는 비파괴시험 중 검측공 기법(CSL, CT, PS)과 표면파 기법(SE, IR)을 현장타설말뚝의 건전도 평가에 이용하기 위한 적용성의 문제를 현장시험을 통하여 고찰하였다. 이를 위하여 결함이 없는 한 본의 정상말뚝과 연약선단, 단면축소 확대, 불량콘크리트 타설 등 현장에서 발생하기 쉬운 결함의 종류, 크기, 위치 등을 변화 조합한 9본의 현장타설말뚝(직경 0.4m, 길이 7.0m)을 시공하여 다양한 비파괴시험을 수행하였다. 시험을 통하여 각 기법을 현장타설말뚝의 건전도 평가에 적용할 때의 문제점과 각 기법의 합리적인 조합에 대하여 고찰하였다.

• 대한기계학회논문집
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• 제9권6호
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• pp.777-787
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• 1985

본 논문에서는 스트레치 플랜징과 슈링크 플랜징에 대하여 각 공정에서의 성 형한계를 이론적으로 구하여 이를 실험과 비교검토함으로써 효과적인 성형한계예측 방 법을 개발하는데 주안점이 있다. 스트레치 플랜징의 경우는 Wang과 Wenner의 연구에 서 얻어진 결과를 이용하여 여기에 기본적인 네킹(Necking)이론을 적용하여 성형한계 를 구하도록 한다. 한편 슈링크 플랜징의 성형한계 해석을 위해서는 Wang과 Wenner 의 스트레치 플랜징에 대한 해석방법을 응용발전시켜 응력 및 변형도등을 계산하고 주 름현상해석을 위해서 Yu 및 Johnson이 도입했던 좌굴계수(Buckling Modulus)개념을 이 용하여 미소 각변위(angular displacement)동안 플랜지부에서 생기는 굽힘에너지와 소 성변형에너지를 비교하는 판별조건을 써서 슈링크 플랜징의 성형 한계를 해석하고자 한다.아울러 각 공정에서의 이론 해석결과들을 성형실험에서 얻어진 값들과 비교 검토하도록 한다.

• 한국재료학회지
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• 제17권6호
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• pp.318-322
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• 2007

Porous ${\beta}-tricalcium$ phosphate $({\beta}-TCP)$ bioceramic was fabricated by pressureless sintering using commercial HAp and different volume percentages of PMMA powders (30-60 vol.%). The range of spherical pore size was about $200-250\;{\mu}m$ in diameter. By increasing the PMMA content, the number of pores and their morphology were dramatically changed as well as decreased the material properties. In case of using 60 vol.% PMMA content, network-type pores were found, due to the necking of the PMMA powders. The values of relative density, elastic modulus, bending strength and hardness of the 60 vol.% PMMA content sample, sintered at $1500^{\circ}C$, were about 46%, 22.2 GPa, 5MPa and 182 Hv respectively. Human osteoblast-like MG-63 cells and osteoclast-like Raw 264.7 cells were well grown and fully covered all of the porous ${\beta}-TCP$ bodies sintered at $1500^{\circ}C$.

• Tribology and Lubricants
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• 제30권4호
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• pp.218-223
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• 2014

This paper presents a method of controlling the stiffness of a tungsten probe for an atomic force microscope (AFM) in order to provide high-quality phase contrast images in accordance with sample characteristics. While inducing sufficient deformation on sample surfaces with commercial Si or $Si_3N_4$ probes is difficult because of their low stiffness, a tungsten probe fabricated by electrochemical etching with appropriately high stiffness can generate relatively large elastic deformation without damaging sample surfaces. The fabrication of the tungsten probe involves two separate procedures. The first procedure involves immersing a tungsten wire with both ends bent parallel to the surface of an electrolyte and controlling the stiffness of the tungsten cantilever by decreasing its diameter using electrochemical etching in the direction of the central axis. The second procedure involves immersing the end of the etched tungsten cantilever in the direction perpendicular to the surface of the electrolyte and fabricating a tungsten tip with a tip radius of 20-50 nm via the necking phenomenon. The latter etching process applies pulse waves every 0.25 seconds to the manufactured tip to improve its yield. Finite element analysis (FEA) of the stiffness of the tungsten probe as a function of its diameter showed that the stiffness of the tungsten probes greatly varies from 56 N/m to 3501 N/m according to the cantilever diameters from $30{\mu}m$ to $100{\mu}m$, respectively. Thus, the proposed etching method is effective for producing a tungsten probe having specific stiffness for optimal use with an AFM and certain samples.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.281-292
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• 2008

Prefabricated Board Drains (PBDs) recently become more widely used than conventional sand drains in improving soft ground because the PBD is more time and cost effective. The performance of PBDs is affected by disturbance in the adjacent soil formation during inserting mandrels, the intrusion of fine particles into filter fabric, and necking of the drain by excessive lateral pressure especially occurring in very deep clay formation such as the Busan New Port site. In this study, the PBD with double-core is introduced, which seems to overcome the shortcomings of usual single-core PBDs. An in-situ test program was established in the Busan New Port site, in which a set of the double-core PBDs and the single-core PBDs was installed to compare the efficiency of each of the drains. The discharge capacity of the double-core and the single-core PBDs was compared for various confining pressures in the modified Delft test and the chamber test. A series of CRS consolidation tests was performed in order to obtain profiles of void ratio-effective stress and void ratio-permeability relationships in the Busan New Port site that are used as input date in performing a numerical program ILLICON. The numerically simulated settlements of ground surface in the test site are in good agreement with those of in-situ measurements. In addition, the performance of the double-core and single-core PBDs has been experimentally and numerically compared in this paper.

• 한국게임학회 논문지
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• 제9권6호
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• pp.163-170
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• 2009

대부분의 온라인 게임서버 엔진에서의 Accept()사용한 Looping방식의 동적인 메모리 할당 방식의 사용은 다수의 클라이언트를 동시에 수용하고 진행해야하는 온라인 게임 상의 로그인 서버엔진에 많은 부하와 함께 병목현상을 유발하게 된다. 따라서 본 논문에서는 온라인상에서의 효율적인 게임서버를 위해 정적인 메모리 할당기법을 사용하여 메모리 단편화를 최소화하고, 클라이언트의 접속 시 세션연결 및 클라이언트 객체의 초기화를 위해 발생하는 부하를 최소화하기 위한 AcceptEx()를 사용한 풀링기법과 정적메모리를 생성하여 동적 할당처럼 포인터로 할당하는 메모리 풀링 기법을 합친 객체 풀링기법을 제안하고, 제안 기법을 적용한 게임엔진을 설계하여 구현한 후, 성능평가를 통해 제안한 기법의 효율성을 보였다.

• 폴리머
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• 제25권1호
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• pp.56-62
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• 2001

Polyethylene terephthalate(PET) 필름 시편을 약 0.5~500 mm/min의 속도까지 단계적으로 연신시켰을 때, 플라스틱 변형이 일어나는 동안에 투명 및 불투명 밴드들이 존재하는 넥킹영역이 형성되었다. 상기 시편의 응력-변형 곡선을 살펴보면, 응력 진동이 뚜렷하게 발생하였음을 확인할 수 있었다. 한편, 열처리된 시편의 응력-변형 곡선을 살펴보면, 응력 진동이 발생하지 않았음을 확인할 수 있었다. 시편들의 미세구조는 광학 현미경을 통하여 동적으로 관찰하였고, 시편들의 열적 특성은 시차 주사 열량기를 사용하여 10 ${\circ}C$/min의 승온 속도에서 측정하였다. 또한, 시편들의 배향화 및 결정화 정도는 단색-핀홀법을 이용하여 측정하였고, 시편들의 탄성계수는 동적 기계 분석기를 통하여 -150~70 ${\circ}C$의 온도 범위에서 1 Hz의 주파수 대에서 측정하였다. PET 펠렛을 전기로에서 약 83${\circ}C$에서 30분 동안 열처리하여 투명한 PET 제품을 제작하였다.

• 한국분말재료학회지
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• 제24권6호
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• pp.472-476
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• 2017

Porous W-10 wt% Ti alloys are prepared by freeze-drying a $WO_3-TiH_2$/camphene slurry, using a sintering process. X-ray diffraction analysis of the heat-treated powder in an argon atmosphere shows the $WO_3$ peak of the starting powder and reaction-phase peaks such as $WO_{2.9}$, $WO_2$, and $TiO_2$ peaks. In contrast, a powder mixture heated in a hydrogen atmosphere is composed of the W and TiW phases. The formation of reaction phases that are dependent on the atmosphere is explained by a thermodynamic consideration of the reduction behavior of $WO_3$ and the dehydrogenation reaction of $TiH_2$. To fabricate a porous W-Ti alloy, the camphene slurry is frozen at $-30^{\circ}C$, and pores are generated in the frozen specimens by the sublimation of camphene while drying in air. The green body is hydrogen-reduced and sintered at $1000^{\circ}C$ for 1 h. The sintered sample prepared by freeze-drying the camphene slurry shows large and aligned parallel pores in the camphene growth direction, and small pores in the internal walls of the large pores. The strut between large pores consists of very fine particles with partial necking between them.