• Applied Microscopy
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• 제46권1호
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• pp.37-44
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• 2016

In this study $TiO_2$/reduced graphene oxide ($TiO_2/rGO$) bipyramid with tunable nanostructure was fabricated by two-step solvothermal process and subsequent heat-treatment in air. The as-synthesized anatase $TiO_2$ nanocrystals possessed morphological bipyramid with exposed dominantly by (101) facets. Polyethylenimine was utilized during the combination of $TiO_2$ and graphene oxide (GO) to tune the surface charge, hindering the restack of graphene during solvothermal process and resulting in 1 to 5 layers of rGO wrapped on $TiO_2$ surface. After a further calcination, a portion of carbon quantum dots (CQDs) with a diameter about 2 nm were produced owing to the oxidizing and cutting of rGO on $TiO_2$. The as-prepared $TiO_2/rGO$ hybrid showed a highly photocatalytic activity, which is about 3.2 and 7.7 times enhancement for photodegradation of methyl orange with compared to pure $TiO_2$ and P25, respectively. We assume that the improvement of photocatalysis is attributed to the chemical bonding between rGO/CQDs and $TiO_2$ that accelerates photogenerated electron-hole pair separation, as well as enhances light harvest.

• 한국정밀공학회지
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• 제31권4호
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• pp.359-364
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• 2014

This paper describes the development of needle type probe that measures temperature and injects medicine for both diagnosis and treatment of musculoskeletal pain syndrome (MPS). The size of trigger points is from several micrometers to millimeter. Therefore, it is required to develop a medical device that is capable of not only finding the trigger points by temperature measurement, but also injecting medicine at the exact location for treatment. To challenge these difficulties, thermocouple was fabricated on the surface of a needle using metal deposition process. Special type of stainless-constantan thermocouple was achieved from the stainless body of a needle itself and deposited constantan metal film. In particular, parylene coating enables to limit the temperature sensitive area to the end of the needle tip. Fabricated needle type probe produces $3.25mV/^{\circ}C$ of thermoelectric sensitivity and compared its performance with commercial T-type thermocouple in animal muscle sample.

• 정보저장시스템학회:학술대회논문집
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• 정보저장시스템학회 2005년도 추계학술대회 논문집
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• pp.185-189
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• 2005

We reported here nano-scale electrical phase-change recording in amorphous $Ge_2Sb_2Te_5$ media using an atomic force microscope (AFM) having conducting probes. In recording process, a pulse voltage is applied to the conductive probe that touches the media surface to change locally the electrical resistivity of a film. However, in contact operation, tip/media wear and contamination could major obstacles, which degraded SNR, reproducibility, and lifetime. In order to overcome tip/media wear and contamination in contact mode operation, we adopted the W incorporated diamond-like carbon (W-DLC) films as a protective layer. Optimized mutilayer media were prepared by a hybrid deposition system of PECVD and RF magnetron sputtering. When suitable electrical pulses were applied to media through the conducting probe, it was observed that data bits as small as 25 nm in diameter have been written and read with good reproducibility, which corresponds to a data density of $1 Tbit/inch^2$. We concluded that stable electrical phase-change recording was possible mainly due to W-DLC layer, which played a role not only capping layer but also resistive layer.

• Tribology and Lubricants
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• 제37권6호
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• pp.208-212
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• 2021

Chemical mechanical polishing (CMP) is a key technology used for the global planarization of thin films in semiconductor production and smoothing the surface of substrate materials. CMP is a type of hybrid process using a material removal mechanism that forms a chemically reacted layer on the surface of a material owing to chemical elements included in a slurry and mechanically removes the chemically reacted layer using abrasive particles. Sapphire is known as a material that requires considerable time to remove materials through CMP owing to its high hardness and chemical stability. This study introduces a technology using electrolytic ionization and ultraviolet (UV) light in sapphire CMP and compares it with the existing CMP method from the perspective of the material removal rate (MRR). The technology proposed in the study experimentally confirms that the MRR of sapphire CMP can be increased by approximately 29.9, which is judged as a result of the generation of hydroxyl radicals (·OH) in the slurry. In the future, studies from various perspectives, such as the material removal mechanism and surface chemical reaction analysis of CMP technology using electrolytic ionization and UV, are required, and a tribological approach is also required to understand the mechanical removal of chemically reacted layers.

• 반도체디스플레이기술학회지
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• 제22권4호
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• pp.66-71
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• 2023

This paper describes a hybrid cleaning method of silicon wafer combining nano-bubble and ultrasound to remove sub-micron particles and contaminants with minimal damage to the wafer surface. In the megasonic cleaning process of semiconductor manufacturing, the cavitation induced by ultrasound can oscillate and collapse violently often with re-entrant jet formation leading to surface damage. The smaller size of cavitation bubbles leads to more stable oscillations with more thermal and viscous damping, thus to less erosive surface cleaning. In this study, ultrasonic energy was applied to the wafer surface in the DI water to excite nano-bubbles at resonance to remove contaminant particles from the surface. A patented nano-bubble generator was developed for the generation of nano-bubbles with concentration of 1×10⁹ bubbles/ml and nominal nano-bubble diameter of 150 nm. Ultrasonic nano-bubble technology improved a contaminant removal efficiency more than 97% for artificial nano-sized particles of alumina and Latex with significant reduction in cleaning time without damage to the wafer surface.

• 한국산업정보학회논문지
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• 제17권7호
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• pp.111-118
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• 2012

최근 기업은 시장 점유율을 높이기 위하여 고객의 다양한 요구를 반영한 제품을 지속적으로 출시하고 있다. 다양한 기능과 가격, 디자인의 제품이 시장에 출시됨에 따라 사용자는 여러 요인들을 고려하여 선택해야 하는 어려움이 있다. 특히 변화의 속도가 빠른 IT 기기의 경우에는 여러 가지 전문적인 지식까지 필요한 경우가 많아 더욱 더 선택을 어렵게 만든다. 디지털 카메라도 저변이 확대됨에 따라 다양한 종류의 카메라가 출시되고 있으며 카메라를 선택하는 소비자는 카메라의 기능과 가격, 디자인 등을 비교하기 위해 많은 시간과 노력을 투자해야 한다. 본 연구는 IT 기기에 익숙하지 않은 사용자들도 가장 적합한 기기를 추천받을 수 있도록 하기 위하여 다기준 의사결정(MCDM) 기법의 하나인 계층분석과정(AHP) 기법 및 내용기반 필터링과 협업 필터링 기법을 접목한 하이브리드 필터링 기법을 이용하여 개인화된 추천 시스템을 설계하고 구현하였다.

• Progress in Superconductivity
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• 제9권2호
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• pp.177-182
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• 2008

[ $MgB_2$ ] thin films were fabricated using hybrid physical-chemical vapor deposition (HPCVD) method on silicon substrates with buffers of alumina grown by using atomic layer deposition method. The growth war in a range of temperatures $500\;{\sim}\;600^{\circ}C$ and under the reactor pressures of $25\;{\sim}\;50\;Torr$. There are some interfacial reactions in the as-grown films with impurities of mostly $Mg_2Si$, $MgAl_2O_4$, and other phases. The $T_c$'s of $MgB_2$ films were observed to be as high as 39 K, but the transition widths were increased with growth temperatures. The magnetization was measured as a function of temperature down to the temperature of 5 K, but the complete Meissner effect was not observed, which shows that the granular nature of weak links is prevailing. The formation of mostly $Mg_2Si$ impurity in HPCVD process is discussed, considering the diffusion and reaction of Mg vapor with silicon substrates.

• Geomechanics and Engineering
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• 제2권4호
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• pp.253-280
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• 2010

A new prediction model is derived for the uplift capacity of suction caissons using a hybrid method coupling genetic programming (GP) and simulated annealing (SA), called GP/SA. The predictor variables included in the analysis are the aspect ratio of caisson, shear strength of clayey soil, load point of application, load inclination angle, soil permeability, and loading rate. The proposed model is developed based on well established and widely dispersed experimental results gathered from the literature. To verify the applicability of the proposed model, it is employed to estimate the uplift capacity of parts of the test results that are not included in the modeling process. Traditional GP and multiple regression analyses are performed to benchmark the derived model. The external validation of the GP/SA and GP models was further verified using several statistical criteria recommended by researchers. Contributions of the parameters affecting the uplift capacity are evaluated through a sensitivity analysis. A subsequent parametric analysis is carried out and the obtained trends are confirmed with some previous studies. Based on the results, the GP/SA-based solution is effectively capable of estimating the horizontal, vertical and inclined uplift capacity of suction caissons. Furthermore, the GP/SA model provides a better prediction performance than the GP, regression and different models found in the literature. The proposed simplified formulation can reliably be employed for the pre-design of suction caissons. It may be also used as a quick check on solutions developed by more time consuming and in-depth deterministic analyses.

• 한국정보전자통신기술학회논문지
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• 제17권3호
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• pp.155-165
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• 2024

환원된 산화 그래핀(rGO)을 알루미늄, 티타늄, 스트론튬이 혼합된 졸-겔 용액에 혼합하여 브러시 코팅법을 이용하여 액정배향용 하이브리드 박막을 제조하였다. 160, 260, 및 360℃에서 어닐링한 후 산화 반응의 차이를 관찰하였다. 박막 제조 과정에서 생성된 졸-겔 용액은 브러시 모의 전단 응력에 의해 수축력을 발생시켜 미세홈 구조를 형성하였다. 이러한 구조는 주사 전자 현미경 분석을 통해 확인되었으며, rGO의 존재가 명확하게 보였다. 어닐링 온도가 증가함에 따라서 박막 표면의 산화 및 환원 반응이 더욱 활성화되어 표면 혼합물의 강도가 증가하였다. 또한 혼합물의 강도를 증가시킴으로써 전기광학적 특성이 안정화되고 개선되었다. 더불어 전압-정전용량 값도 크게 향상되었다. 최종적으로 투과율 측정 결과 액정디스플레이의 액정 배향막으로 적용하기에 적합한 것으로 나타났다.

• 디지털융복합연구
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• 제10권10호
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• pp.333-338
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• 2012

인적자원관리는 IT기술을 접목하여 다양한 변화를 가져오고 있다. 특히 HRM이 집단차원의 관리, 물리적 사업장, 근무시간의 제약, 개인적 접촉 등 비과학적 방법으로 이루어졌다면, 현재의 전자적 인적자원관리(e-HRM)는 개별 차원의 관리, 가상 작업 공간의 등장(예. 스마트워크센터, 홈워크 등), 근무시간의 유연화 및 탄력화, 컴퓨터 기반의 통계자료 및 과학적 방법에 의한 분석 및 관리를 근간으로 이루어지고 있다는 점에서 큰 차이가 있다. 따라서 환경의 변화에 따라 기업들은 보다 효율적이고 전략적인 인적자원 관리 체계를 구축하기 위하여 RFID 카드, 지문인식 근태관리 시스템 등 다양한 기술을 도입하고 있다. 본 논문에서는 효율적인 전사적 인적자원 관리를 위한 멀티 카메라를 이용하여 2D 및 3D 얼굴인식기술 기반의 근태관리, 출입통제관리 시스템을 개발하였다. 여기서는 기존 2D방식의 얼굴인식기술이 가지고 있는 문제점인 조명 및 자세에 따른 인식률 저하를 극복하여 90% 이상의 인식률을 확보하였다. 또한 3D 얼굴인식방식의 문제점인 많은 계산량을 개선하기 위하여 3D와 2D 인식기술을 병행하여 처리함으로써 하이브리드 영상인식 및 인식속도를 개선할 수 있었다.